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2018年, 第27卷, 第10期　刊出日期：2018-10-05 上一期    下一期

SPECIAL TOPIC—Recent advances in thermoelectric materials and devices

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Some studies of the interaction between two two-level atoms and SU(1, 1) quantum systems T M El-Shahat, M Kh Ismail 2018 (10):  100201-100201.  doi: 10.1088/1674-1056/27/10/100201 摘要 ( 526 )   HTML ( 0 )   PDF(7637KB) ( 181 )   Herein, we present an approach to look for the best phenomenon to measure quantum correlation. The system of two isolated qubits each interacting with a single-mode cavity was theoretically created to study the quantum correlation. Some of the phenomena, such as the quantum discord and concurrence, were generated through such a system. The influences of initial state purity, qubit motion, and detuning parameters were discussed for the phenomena. These parameters for a specific value show that the behavior of phenomena are analogous. It is interesting to mention that some values of detuning undergo a sudden death of phenomena, and the quantum discord still captures the qubits quantum correlation. We predict that the quantum discord may be a better measure of quantum correlation than concurrence. 参考文献 | 相关文章 | 计量指标

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Truncated series solutions to the (2+1)-dimensional perturbed Boussinesq equation by using the approximate symmetry method 焦小玉 2018 (10):  100202-100202.  doi: 10.1088/1674-1056/27/10/100202 摘要 ( 591 )   HTML ( 0 )   PDF(1642KB) ( 143 )   In this paper, the (2+1)-dimensional perturbed Boussinesq equation is transformed into a series of two-dimensional (2D) similarity reduction equations by using the approximate symmetry method. A step-by-step procedure is used to acquire Jacobi elliptic function solutions to these similarity equations, which generate the truncated series solutions to the original perturbed Boussinesq equation. Aside from some singular area, the series solutions are convergent when the perturbation parameter is diminished. 参考文献 | 相关文章 | 计量指标

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Factorization method for inverse obstacle scattering problem in three-dimensional planar acoustic waveguides 秦雪 2018 (10):  100203-100203.  doi: 10.1088/1674-1056/27/10/100203 摘要 ( 573 )   HTML ( 0 )   PDF(369KB) ( 170 )   In this paper, we consider the inverse scattering problem of reconstructing a bounded obstacle in a three-dimensional planar waveguide from the scattered near-field data measured on a finite cylindrical surface containing the obstacle and corresponding to infinitely many incident point sources also placed on the measurement surface. The obstacle is allowed to be an impenetrable scatterer or a penetrable scatterer. We establish the validity of the factorization method with the near-field data to characterize the obstacle in the planar waveguide by constructing an outgoing-to-incoming operator which is an integral operator defined on the measurement surface with the kernel given in terms of an infinite series. 参考文献 | 相关文章 | 计量指标

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Hybrid sub-gridding ADE-FDTD method of modeling periodic metallic nanoparticle arrays 梁图禄, 邵维, 魏晓琨, 梁木生 2018 (10):  100204-100204.  doi: 10.1088/1674-1056/27/10/100204 摘要 ( 684 )   HTML ( 0 )   PDF(1282KB) ( 183 )   In this paper, a modified sub-gridding scheme that hybridizes the conventional finite-difference time-domain (FDTD) method and the unconditionally stable locally one-dimensional (LOD) FDTD is developed for analyzing the periodic metallic nanoparticle arrays. The dispersion of the metal, caused by the evanescent wave propagating along the metal-dielectric interface, is expressed by the Drude model and solved with a generalized auxiliary differential equation (ADE) technique. In the sub-gridding scheme, the ADE-FDTD is applied to the global coarse grids while the ADE-LOD-FDTD is applied to the local fine grids. The time step sizes in the fine-grid region and coarse-grid region can be synchronized, and thus obviating the temporal interpolation of the fields in the time-marching process. Numerical examples about extraordinary optical transmission through the periodic metallic nanoparticle array are provided to show the accuracy and efficiency of the proposed method. 参考文献 | 相关文章 | 计量指标

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Decoherence of macroscopic objects from relativistic effect 董国慧, 马宇翰, 陈劲夫, 王欣, 孙昌璞 2018 (10):  100301-100301.  doi: 10.1088/1674-1056/27/10/100301 摘要 ( 1008 )   HTML ( 0 )   PDF(2005KB) ( 269 )   We study how the decoherence of macroscopic objects originates intrinsically from the relativistic effect. With the degree of freedom of the center of mass (CM) characterizing the collective quantum state of a macroscopic object (MO), it is found that an MO consisting of N particles can decohere with a time scale of no more than √N-1. Here, the special relativity can induce the coupling of the collective motion mode and the relative motion modes in an order of 1/c2, which intrinsically results in the above minimum decoherence. 参考文献 | 相关文章 | 计量指标

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Controlling of entropic uncertainty in open quantum system via proper placement of quantum register 嵇英华, 柯强, 胡菊菊 2018 (10):  100302-100302.  doi: 10.1088/1674-1056/27/10/100302 摘要 ( 887 )   HTML ( 0 )   PDF(945KB) ( 158 )   We investigate the dynamical behaviors of quantum-memory-assisted entropic uncertainty and its lower bound in the amplitude-damping channel. The influences of different placement positions of the quantum register on the dynamics of quantum coherence, quantum entanglement, and quantum discord are analyzed in detail. The numerical simulation results show that the quantum register should be placed in the channel of the non-Markovian effect. This option is beneficial to reduce the entropic uncertainty and its lower bound. We also find that this choice does not change the evolution of the quantum coherence and quantum entanglement, but changes the dynamical process of the quantum discord of the system. These results show that quantum coherence, quantum entanglement, and quantum discord are different quantum resources with unique characteristics and properties, and quantum discord can play a key role in reducing the uncertainty of quantum systems. 参考文献 | 相关文章 | 计量指标

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Extended Bell inequality and maximum violation 古燕, 张海峰, 宋志刚, 梁九卿, 韦联福 2018 (10):  100303-100303.  doi: 10.1088/1674-1056/27/10/100303 摘要 ( 759 )   HTML ( 0 )   PDF(351KB) ( 166 )   The original formula of Bell inequality (BI) in terms of two-spin singlet has to be modified for the entangled-state with parallel spin polarization. Based on classical statistics of the particle-number correlation, we prove in this paper an extended BI, which is valid for two-spin entangled states with both parallel and antiparallel polarizations. The BI and its violation can be formulated in a unified formalism based on the spin coherent-state quantum probability statistics with the state-density operator, which is separated to the local and non-local parts. The local part gives rise to the BI, while the violation is a direct result of the non-local quantum interference between two components of entangled state. The Bell measuring outcome correlation denoted by PB is always less than or at most equal to one for the local realistic model (PBlc ≤ 1) regardless of the specific superposition coefficients of entangled state. Including the non-local quantum interference the maximum violation of BI is found as PBmax=2, which, however depends on state parameters and three measuring directions as well. Our result is suitable for entangled photon pairs. 参考文献 | 相关文章 | 计量指标

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Ultra-thin and light-weight spoof surface plasmon polariton coupler achieved by broadside coupled split ring resonators 范亚, 王甲富, 马华, 李勇峰, 冯明德, 屈绍波 2018 (10):  100304-100304.  doi: 10.1088/1674-1056/27/10/100304 摘要 ( 524 )   HTML ( 0 )   PDF(5978KB) ( 148 )   Low profile and light weight are very important for practical applications of a spoof surface plasmon polariton (SSPP) coupler, especially at low frequencies. In this paper, we propose and design an ultra-thin, light-weight SSPP coupler based on broadside coupled split ring resonators (BC-SRRs). The size of BC-SRR can be far less than λ/100 and can extremely well control the reflective phases within a subwavelength thickness. Due to the broadside capacitive coupling, the electrical size of BC-SRR is dramatically reduced to guarantee the ultra-thin thickness of the SSPP coupler. The weight of the SSPP coupler is reduced by a low occupation ratio of BC-SRR in the unit cell volume. As an example, a C-band SSPP coupler composed of phase gradient BC-SRRs is designed, fabricated, and measured. Due to the ultra-small size and low occupation ratio of BC-SRRs, the thickness of the coupler is λ/12 and the surface density is only 0.98 kg/m2. Both simulation and experiment results verify that the coupler can achieve high-efficiency SPP coupling at 5.27 GHz under normal incidence. 参考文献 | 相关文章 | 计量指标

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Non-Gaussianity dynamics of two-mode squeezed number states subject to different types of noise based on cumulant theory 向少华, 朱喜香, 宋克慧 2018 (10):  100305-100305.  doi: 10.1088/1674-1056/27/10/100305 摘要 ( 712 )   HTML ( 0 )   PDF(484KB) ( 157 )   We provide a measure to characterize the non-Gaussianity of phase-space function of bosonic quantum states based on the cumulant theory. We study the non-Gaussianity dynamics of two-mode squeezed number states by analyzing the phase-averaged kurtosis for two different models of decoherence:amplitude damping model and phase damping model. For the amplitude damping model, the non-Gaussianity is very fragile and completely vanishes at a finite time. For the phase damping model, such states exhibit rich non-Gaussian characters. In particular, we obtain a transition time that such states can transform from sub-Gaussianity into super-Gaussianity during the evolution. Finally, we compare our measure with the existing measures of non-Gaussianity under the independent dephasing environment. 参考文献 | 相关文章 | 计量指标

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Two-qubit pure state tomography by five product orthonormal bases 王宇, 尚云 2018 (10):  100306-100306.  doi: 10.1088/1674-1056/27/10/100306 摘要 ( 691 )   HTML ( 1 )   PDF(352KB) ( 157 )   In this paper, we focus on two-qubit pure state tomography. For an arbitrary unknown two-qubit pure state, separable or entangled, it has been found that the measurement probabilities of 16 projections onto the tensor products of Pauli eigenstates are enough to uniquely determine the state. Moreover, these corresponding product states are arranged into five orthonormal bases. We design five quantum circuits, which are decomposed into the common gates in universal quantum computation, to simulate the five projective measurements onto these bases. At the end of each circuit, we measure each qubit with the projective measurement {|0><0|,|1><1|}. Then, we consider the open problem whether three orthonormal bases are enough to distinguish all two-qubit pure states. A necessary condition is given. Suppose that there are three orthonormal bases B1,B2,B3. Denote the unitary transition matrices from B1 to B2,B3 as U1 and U2. All 32 elements of matrices U1 and U2 should not be zero. If not, these three bases cannot distinguish all two-qubit pure states. 参考文献 | 相关文章 | 计量指标

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Implementation of quantum phase gate between two atoms via Rydberg antiblockade and adiabatic passage 谭曦, 吴金雷, 邓灿, 毛伟建, 王海涛, 计新 2018 (10):  100307-100307.  doi: 10.1088/1674-1056/27/10/100307 摘要 ( 814 )   HTML ( 0 )   PDF(682KB) ( 185 )   Combining adiabatic passage and Rydberg antiblockade, we propose a scheme to implement a two-qubit phase gate between two Rydberg atoms. Detuning parameters between frequencies of atomic transitions and those of the corresponding driving lasers are carefully chosen to offset the blockade effect of two Rydberg atoms, so that an effective Hamiltonian, representing a single-photon detuning Λ-type three-level system and concluding the quantum state of two Rydberg atoms excited simultaneously, is obtained. The adiabatic-passage technique, based on the effective Hamiltonian, is adopted to implement a two-atom phase gate by using two time-dependent Rabi frequencies. Numerical simulations indicate that a high-fidelity two-qubit π-phase gate is constructed and its operation time does not have to be controlled accurately. Besides, owing to the long coherence time of the Rydberg state, the phase gate is robust against atomic spontaneous emission. 参考文献 | 相关文章 | 计量指标

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Coherent attacks on a practical quantum oblivious transfer protocol 何广平 2018 (10):  100308-100308.  doi: 10.1088/1674-1056/27/10/100308 摘要 ( 879 )   HTML ( 0 )   PDF(337KB) ( 150 )   In a recent quantum oblivious transfer protocol proposed by Nagy et al., it was proven that attacks based on individual measurements and 2-qubit entanglement can all be defeated. Later we found that 5-body entanglement-based attacks can break the protocol. Here we further tighten the security bound, by showing that the protocol is insecure against 4-body entanglement-based attacks, while being immune to 3-body entanglement-based attacks. Also, increasing the number of qubits in the protocol is useless for improving its security. 参考文献 | 相关文章 | 计量指标

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Passive round-robin differential-quadrature-phase-shift quantum key distribution scheme with untrusted detectors 刘宏伟, 屈文秀, 窦天琦, 王吉鹏, 张勇, 马海强 2018 (10):  100309-100309.  doi: 10.1088/1674-1056/27/10/100309 摘要 ( 765 )   HTML ( 0 )   PDF(1274KB) ( 221 )   In this paper, we proposed the scheme for a passive round-robin differential-phase-shift quantum key distribution (RRDPS-QKD) set-up based on the principle of Hong-Ou-Mandel interference. Our scheme requires two legitimate parties to prepare their signal state with two different non-orthogonal bases instead of single in original protocol. Incorporating this characteristic, we establish the level of security of our protocol under the intercept-resend attack and demonstrate its detector-flaw-immune feature. Furthermore, we show that our scheme not only inherits the merit of better tolerance of bit errors and finite-sized-key effects but can be implemented using hardware similar to the measurement device independent QKD (MDI-QKD). This ensures good compatibility with the current commonly used quantum system. 参考文献 | 相关文章 | 计量指标

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Fabrication of Al air-bridge on coplanar waveguide 金震川, 吴海腾, 于海峰, 于扬 2018 (10):  100310-100310.  doi: 10.1088/1674-1056/27/10/100310 摘要 ( 1023 )   HTML ( 0 )   PDF(930KB) ( 357 )   Superconducting coplanar waveguide (CPW) can be widely used as two-dimensional (2D) resonator, transmission line or feedline, providing an important component for superconducting quantum circuit which is a promising candidate for quantum information processing. Due to the discontinuities and asymmetries in the ground planes, CPW usually exhibits the spurious resonance, which is a common source of decoherence in circuit quantum electrodynamics experiments. To mitigate the spurious resonance, we fabricated superconducting aluminum air-bridges on Nb CPW. The fabricated air-bridges are approximately 3 μ high and up to 120 μ long. Compared with other methods, the fabrication procedures of our air-bridges are simpler, and the air-bridge can withstand strong ultrasound. 参考文献 | 相关文章 | 计量指标

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The stabilizer for n-qubit symmetric states 石现 2018 (10):  100311-100311.  doi: 10.1088/1674-1056/27/10/100311 摘要 ( 525 )   HTML ( 0 )   PDF(544KB) ( 137 )   The stabilizer group for an n-qubit state|φ> is the set of all invertible local operators (ILO) g=g1⊗ g2⊗ …⊗ gn, gi∈ GL(2,C) such that|φ>=g|φ>. Recently, Gour et al.[Gour G, Kraus B and Wallach N R 2017 J. Math. Phys. 58 092204] presented that almost all n-qubit states|Ψ〉 own a trivial stabilizer group when n ≥ 5. In this article, we consider the case when the stabilizer group of an n-qubit symmetric pure state|Ψ> is trivial. First we show that the stabilizer group for an n-qubit symmetric pure state|φ> is nontrivial when n ≤ 4. Then we present a class of n-qubit symmetric states|φ> with a trivial stabilizer group when n ≥ 5. Finally, we propose a conjecture and prove that an n-qubit symmetric pure state owns a trivial stabilizer group when its diversity number is bigger than 5 under the conjecture we make, which confirms the main result of Gour et al. partly. 参考文献 | 相关文章 | 计量指标

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Sonic horizon dynamics of ultracold Fermi system under elongated harmonic potential 王颖, 周蜀渝 2018 (10):  100312-100312.  doi: 10.1088/1674-1056/27/10/100312 摘要 ( 569 )   HTML ( 0 )   PDF(304KB) ( 115 )   We study the phenomena of the sonic horizon in an ultracold atomic Fermi system in an elongated harmonic trap. Based on the one-dimensional Gross-Pitaevskii equation model and variational method combined with exact derivation approach, we derive an analytical formula which describes the occurrence of the sonic horizon and the associated Hawking radiation temperature. Using a pictorial demonstration of the key physical quantities we identify the features reported in prior numerical studies of a three-dimensional (3D) ultracold atomic system, proving the applicability of the theoretical model presented here. 参考文献 | 相关文章 | 计量指标

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A new four-dimensional hyperjerk system with stable equilibrium point, circuit implementation, and its synchronization by using an adaptive integrator backstepping control J P Singh, V T Pham, T Hayat, S Jafari, F E Alsaadi, B K Roy 2018 (10):  100501-100501.  doi: 10.1088/1674-1056/27/10/100501 摘要 ( 1032 )   HTML ( 0 )   PDF(8078KB) ( 195 )   This paper reports a new simple four-dimensional (4D) hyperjerk chaotic system. The proposed system has only one stable equilibrium point. Hence, its strange attractor belongs to the category of hidden attractors. The proposed system exhibits various dynamical behaviors including chaotic, periodic, stable nature, and coexistence of various attractors. Numerous theoretical and numerical methods are used for the analyses of this system. The chaotic behavior of the new system is validated using circuit implementation. Further, the synchronization of the proposed systems is shown by designing an adaptive integrator backstepping controller. Numerical simulation validates the synchronization strategy. 参考文献 | 相关文章 | 计量指标

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Phase order in one-dimensional piecewise linear discontinuous map 杜如海, 王圣军, 金涛, 屈世显 2018 (10):  100502-100502.  doi: 10.1088/1674-1056/27/10/100502 摘要 ( 677 )   HTML ( 0 )   PDF(5443KB) ( 118 )   The phase order in a one-dimensional (1D) piecewise linear discontinuous map is investigated. The striking feature is that the phase order may be ordered or disordered in multi-band chaotic regimes, in contrast to the ordered phase in continuous systems. We carried out an analysis to illuminate the underlying mechanism for the emergence of the disordered phase in multi-band chaotic regimes, and proved that the phase order is sensitive to the density distribution of the trajectories of the attractors. The scaling behavior of the net direction phase at a transition point is observed. The analytical proof of this scaling relation is obtained. Both the numerical and analytical results show that the exponent is 1, which is controlled by the feature of the map independent on whether the system is continuous or discontinuous. It extends the universality of the scaling behavior to systems with discontinuity. The result in this work is important to understanding the property of chaotic motion in discontinuous systems. 参考文献 | 相关文章 | 计量指标

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Intra-layer synchronization in duplex networks 沈洁, 汤龙坤 2018 (10):  100503-100503.  doi: 10.1088/1674-1056/27/10/100503 摘要 ( 737 )   HTML ( 0 )   PDF(10290KB) ( 362 )   This paper explores the intra-layer synchronization in duplex networks with different topologies within layers and different inner coupling patterns between, within, and across layers. Based on the Lyapunov stability method, we prove theoretically that the duplex network can achieve intra-layer synchronization under some appropriate conditions, and give the thresholds of coupling strength within layers for different types of inner coupling matrices across layers. Interestingly, for a certain class of coupling matrices across layers, it needs larger coupling strength within layers to ensure the intra-layer synchronization when the coupling strength across layers become larger, intuitively opposing the fact that the intra-layer synchronization is seemly independent of the coupling strength across layers. Finally, numerical simulations further verify the theoretical results. 参考文献 | 相关文章 | 计量指标

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Detecting overlapping communities based on vital nodes in complex networks 王兴元, 王宇, 秦小蒙, 李睿, Justine Eustace 2018 (10):  100504-100504.  doi: 10.1088/1674-1056/27/10/100504 摘要 ( 733 )   HTML ( 0 )   PDF(3329KB) ( 209 )   Detection of community structures in the complex networks is significant to understand the network structures and analyze the network properties. However, it is still a problem on how to select initial seeds as well as to determine the number of communities. In this paper, we proposed the detecting overlapping communities based on vital nodes algorithm (DOCBVA), an algorithm based on vital nodes and initial seeds to detect overlapping communities. First, through some screening method, we find the vital nodes and then the seed communities through the pretreatment of vital nodes. This process differs from most existing methods, and the speed is faster. Then the seeds will be extended. We also adopt a new parameter of attribution degree to extend the seeds and find the overlapping communities. Finally, the remaining nodes that have not been processed in the first two steps will be reprocessed. The number of communities is likely to change until the end of algorithm. The experimental results using some real-world network data and artificial network data are satisfactory and can prove the superiority of the DOCBVA algorithm. 参考文献 | 相关文章 | 计量指标

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Absolute density measurement of nitrogen dioxide with cavity-enhanced laser-induced fluorescence 杨正海, 杨永成, 邓联忠, 印建平 2018 (10):  100601-100601.  doi: 10.1088/1674-1056/27/10/100601 摘要 ( 713 )   HTML ( 0 )   PDF(680KB) ( 153 )   The absolute number density of nitrogen dioxide (NO2) seeded in argon is measured with cavity-enhanced laser-induced fluorescence (CELIF) through using a pulsed laser beam for the first time. The cavity ring down (CRD) signal is acquired simultaneously and used for normalizing the LIF signal and determining the relationship between the measured CELIF signal and the NO2 number density. The minimum detectable NO2 density down to (3.6±0.1)×108 cm-3 is measured in 60 s of acquisition time by the CELIF method. The minimum absorption coefficient is measured to be (2.0±0.1)×10-10 cm-1, corresponding to a noise equivalent absorption sensitivity of (2.2±0.1)×10-9 cm-1·Hz-1/2. The experimental system demonstrated here can be further improved in its sensitivity and used for environmental monitoring of outdoor NO2 pollution. 参考文献 | 相关文章 | 计量指标

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Development of a 170-mm hollow corner cube retroreflector for the future lunar laser ranging 何芸, 刘祺, 何静静, 黎明, 段会宗, 叶贤基, 罗俊 2018 (10):  100701-100701.  doi: 10.1088/1674-1056/27/10/100701 摘要 ( 824 )   HTML ( 1 )   PDF(1231KB) ( 277 )   Over the past 50 years, lunar laser ranging has made great contributions to the understanding of the Earth-Moon system and the tests of general relativity. However, because of the lunar libration, the Apollo and Lunokhod corner-cube retroreflector (CCR) arrays placed on the Moon currently limit the ranging precision to a few centimeters for a single photon received. Therefore, it is necessary to deploy a new retroreflector with a single and large aperture to improve the ranging precision by at least one order of magnitude. Here we present a hollow retroreflector with a 170-mm aperture fabricated using hydroxide-catalysis bonding technology. The precisions of the two dihedral angles are achieved by the mirror processing with a sub-arc-second precision perpendicularity, and the remaining one is adjusted utilizing an auxiliary optical configuration including two autocollimators. The achieved precisions of the three dihedral angles are 0.10 arc-second, 0.30 arc-second, and 0.24 arc-second, indicating the 68.5% return signal intensity of ideal Apollo 11/14 based on the far field diffraction pattern simulation. We anticipate that this hollow CCR can be applied in the new generation of lunar laser ranging. 参考文献 | 相关文章 | 计量指标

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A rapid and convenient experimental method of absolutely calibrating transmission of x-ray flat-response filter 余建, 候立飞, 王静, 张文海, 陈铭, 周保充, 肖沙里, 刘慎业 2018 (10):  100702-100702.  doi: 10.1088/1674-1056/27/10/100702 摘要 ( 669 )   HTML ( 0 )   PDF(771KB) ( 104 )   We develop a rapid and convenient experimental method of absolutely calibrating the transmission of an x-ray flat-response filter. The calibration experiment is performed on a small laser-target facility, and a set of high resolution holographic flat-field grating spectrometers is used as a discrimination system of the laser-produced x-ray source. Given that the holographic flat-field grating has a relatively large width, the grating is divided into two regions for use in that direction, where one region has the filter added and the other region does not. The filter transmission is determined by dividing the x-ray signal counts detected when the filter is in the line of sight by those detected when the filter is out of the line of sight. We find that the calibration results of this experiment agree with the calibration results using a synchrotron radiation source, as well as simulation results. Our method is not only highly reliable but also rapid and convenient. 参考文献 | 相关文章 | 计量指标

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Laser cooling of CH molecule: Insights from ab initio study 崔洁, 徐建刚, 祁建霞, 窦戈, 张云光 2018 (10):  103101-103101.  doi: 10.1088/1674-1056/27/10/103101 摘要 ( 811 )   HTML ( 0 )   PDF(597KB) ( 247 )   The feasibility of laser cooling a CH molecule is investigated theoretically by employing the ab initio method. The potential energy curves for the five Λ-S states and eight Ω states of CH are determined by the multi-reference configuration interaction with the Davidson corrections (MRCI+Q) level of theory. The results agree well with the available experimental data and other theoretical values. Also, the permanent dipole moments and transition dipole moments of the CH molecule are calculated at the multi-reference configuration interaction (MRCI) level. We find highly diagonally distributed Franck-Condon factors (f00=0.9950 and 0.9998) and branching ratios (R00=0.983 and 0.993) for the A2Δ→X2Π and C2Σ+→X2Π transitions. Moreover, the values of suitable radiative lifetime τ of the A2Δ and C2Σ+ states are evaluated to be 9.64×10-7 s and 2.02×10-7 s, respectively, for rapid laser cooling. A scheme for laser cooling the CH molecule is designed. In the proposed cooling scheme, three wavelengths for A2Δ→X2Π and C2Σ+→X2Π transitions are used, and the main pump lasers are λ00=430.86 nm and 313.45 nm, respectively. The feasibility of laser cooling the CH molecules is demonstrated for each of these schemes, and this study offers a theoretical basis for experimental research into preparation of cold CH molecules. 参考文献 | 相关文章 | 计量指标

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Interpulse interference of electron emission from an atom irradiated by sinusoidally phase-modulated pulse 袁海颖, 郭福明, 张頔玉, 王俊, 陈基根, 杨玉军 2018 (10):  103201-103201.  doi: 10.1088/1674-1056/27/10/103201 摘要 ( 671 )   HTML ( 0 )   PDF(752KB) ( 182 )   We theoretically investigate the photoelectron emission from an atom irradiated by an amplitude modulated sinusoidally phase-modulated pulse through solving the time-dependent Schrödinger equation in the momentum space. By controlling the phase amplitude of the pulse in the frequency domain, it can be found that the photoelectron spectra appear as explicit interference phenomena, which originated from the interference between the directly ionized electron and the ionization of the pre-excited atom from different subpulses. 参考文献 | 相关文章 | 计量指标

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Backward rescattered photoelectron holography in strong-field ionization 陈富军, 姚汝贤, 罗江华, 王长清 2018 (10):  103202-103202.  doi: 10.1088/1674-1056/27/10/103202 摘要 ( 858 )   HTML ( 0 )   PDF(2207KB) ( 201 )   By numerically solving the time-dependent Schrödinger equation, we observe a remarkable strong-field interference pattern in the photoelectron momentum distribution of a hydrogen atom ionized by a few-cycles laser pulse. This interference pattern is joined together with the familiar near-forward strong-field photoelectron holographic interference. By applying the strong-field approximation theory, we investigate the formation of this interference pattern, which arises from the interference between the backward rescattered part and the direct part of the tunneling ionized electron wave packet. We demonstrate that this backward rescattered photoelectron holographic interference can also be observed in a more realistic parallel two-color laser field. These results pave a new way to look into the atomic and molecular structure with ultrafast timescale. 参考文献 | 相关文章 | 计量指标

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Isomerism and coordination mode effects on two-photon absorption of tris(picolyl)amine-based fluorescent probes for zinc ions 赵珂, 宋军, 朱美玉, 张瀚, 王传奎 2018 (10):  103301-103301.  doi: 10.1088/1674-1056/27/10/103301 摘要 ( 714 )   HTML ( 0 )   PDF(1532KB) ( 170 )   One-photon absorption and two-photon absorption (TPA) properties of three tris(picolyl)amine-based zinc ion sensors are investigated by employing the density functional response theory in combination with the polarizable continuum model. The different isomer and coordination geometry of each probe are taken into account. Special emphasis is placed on the effects of isomerism and the coordination mode on the optical properties. The intra-molecular charge transfer (ICT) properties are specified by natural bond orbital charge analysis. It is shown that the isomerism has non-negligible effects on TPA properties of free ligands. It is found that both the TPA wavelength and the cross section are highly dependent on the coordination mode. When the zinc ion connects with the picolyl unit in the middle of a ligand, the zinc complex has a large TPA intensity in a long wavelength range due to the increased ICT mechanism. 参考文献 | 相关文章 | 计量指标

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS

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Shim coil design for Halbach magnet by equivalent magnetic dipole method 吴嘉敏, 徐征, 郭盼, 戚金凤, 贺玉成 2018 (10):  104101-104101.  doi: 10.1088/1674-1056/27/10/104101 摘要 ( 640 )   HTML ( 0 )   PDF(1839KB) ( 271 )   Low-field nuclear magnetic resonance magnet (2 MHz) is required for rock core analysis. However, due to its low field strength, it is hard to achieve a high uniform B0 field only by using the passive shimming. Therefore, active shimming is necessarily used to further improve uniformity for Halbach magnet. In this work, an equivalent magnetic dipole method is presented for designing shim coils. The minimization of the coil power dissipation is considered as an optimal object to minimize coil heating effect, and the deviation from the target field is selected as a penalty function term. The lsqnonlin optimization toolbox of MATLAB is used to solve the optimization problem. Eight shim coils are obtained in accordance with the contour of the stream function. We simulate each shim coil by ANSYS Maxwell software to verify the validity of the designed coils. Measurement results of the field distribution of these coils are consistent with those of the target fields. The uniformity of the B0 field is improved from 114.2 ppm to 26.9 ppm after using these shim coils. 参考文献 | 相关文章 | 计量指标

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Design of multi-band metasurface antenna array with low RCS performance 王思铭, 高军, 曹祥玉, 郑月军, 李桐, 兰俊祥, 吉地辽日 2018 (10):  104102-104102.  doi: 10.1088/1674-1056/27/10/104102 摘要 ( 828 )   HTML ( 0 )   PDF(2062KB) ( 268 )   In this paper, a multi-band metasurface (MS) antenna array with low radar cross section (RCS) performance is proposed and measured. Firstly, a 4×4 antenna array is composed of four 2×2 Jerusalem cross structure antenna arrays working at different frequency bands, which is aimed at enhancing the bandwidth effectively. Then, each antenna can be seen as a unit of MS in spite of adding the feeding structure. Based on phase cancellation principle, the MS is arranged into a chessboard configuration in order to realize wideband RCS reduction. Thus, excellent radiation and scattering characteristics are obtained simultaneously. Simulated and measured results indicate that this work provides a novel method to achieve bandwidth expansion as well as wideband RCS reduction of the antenna array. 参考文献 | 相关文章 | 计量指标

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Nonparaxial propagation properties of the chirped Airy Gaussian vortex beams in uniaxial crystals orthogonal to the optical axis 陈奕佐, 赵官文, 叶峰, 许创杰, 邓冬梅 2018 (10):  104201-104201.  doi: 10.1088/1674-1056/27/10/104201 摘要 ( 828 )   HTML ( 0 )   PDF(1935KB) ( 193 )   In this article, we investigate the nonparaxial propagation properties of the chirped Airy Gaussian vortex (CAiGV) beams in uniaxial crystals orthogonal to the optical axis analytically and numerically. We discuss how the linear chirp parameters, the quadratic chirp parameters, and the Gaussian factors influence the nonparaxial propagation dynamics of the CAiGV beams. The intensity, the energy flow, the beam center, and the angular momentum of the CAiGV beams are deeply investigated. It is shown that the Gaussian factors have a great effect on the intensity and the centroid positions of the CAiGV beams. With the Gaussian factors increasing, the intensity of CAiGV beams decreases rapidly. The main lobes of the transverse intensity distribution of the CAiGV beams are similar to triangles. 参考文献 | 相关文章 | 计量指标

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Speckle reduction by selective spatial-domain mask in digital holography 梁明大, 陈丽, 胡义华, 林伟涛, 陈永昊 2018 (10):  104202-104202.  doi: 10.1088/1674-1056/27/10/104202 摘要 ( 745 )   HTML ( 0 )   PDF(1459KB) ( 133 )   An improved method of using a selective spatial-domain mask to reduce speckle noise in digital holography is proposed. The sub-holograms are obtained from the original hologram filtered by the binary masks including a shifting aperture for being reconstructed. Normally, the speckle patterns of these sub-reconstructed images are different. The speckle intensity of the final reconstructed image is suppressed by averaging the favorable sub-reconstructed images which are selected based on the most optimal pixel intensity sub-range in the sub-holograms. Compared with the conventional spatial-domain mask method, the proposed method not only reduces the speckle noise more effectively with fewer sub-reconstructed images, but also reduces the redundant information used in the reconstruction process. 参考文献 | 相关文章 | 计量指标

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Tunneling exits of H2+ in strong laser fields 张兆涵, 何峰 2018 (10):  104203-104203.  doi: 10.1088/1674-1056/27/10/104203 摘要 ( 747 )   HTML ( 0 )   PDF(748KB) ( 168 )   Different from atoms, the multicenter of the Coulombic potentials in molecules makes the tunneling ionization complex, and the electron tunnels out the laser-dressed Coulomb potential with a complex structure. We study tunneling exits of H2+ at large internuclear distance in strong laser fields by numerically simulating the time-dependent Schrödinger equation plus a classical backward propagation of the ionized wave packet. This study strengthens the understanding of molecular tunneling ionization in strong laser fields. 参考文献 | 相关文章 | 计量指标

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Generation of few-cycle radially-polarized infrared pulses in a gas-filled hollow-core fiber 赵睿睿, 黄志远, 王丁, 赵钰, 冷雨欣, 李儒新 2018 (10):  104204-104204.  doi: 10.1088/1674-1056/27/10/104204 摘要 ( 655 )   HTML ( 0 )   PDF(1233KB) ( 163 )   We perform a numerical study for temporally compressing radially-polarized (RP) infrared pulses in a gas-filled hollow-core fiber (HCF). The dynamic transmission and nonlinear compression of RP pulses centered at wavelengths of 0.8 μ, 1.8 μ, 3.1 μ, and 5.0 μ in HCFs are simulated. By comparing the propagation of pulses with the same optical cycles and intensity, we find that under proper conditions these pulses can be compressed down to 2-3 cycles. In the transverse direction, the spatiotemporal beam profile ameliorates from 0.8-μ to 1.8-μ and 3.1-μ pulses before the appearance of high-order dispersion. These results show an alternative method of scaling generation for delivering RP infrared pulses in gas-filled HCFs, which can obtain energetic few-cycle pulses, and will be beneficial for relevant researches in the infrared scope. 参考文献 | 相关文章 | 计量指标

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Scanning the energy dissipation process of energetic materials based on excited state relaxation and vibration-vibration coupling 王文岩, 隋宁, 张里荃, 王英惠, 王琳, 王权, 王娇, 康智慧, 杨延强, 周强, 张汉壮 2018 (10):  104205-104205.  doi: 10.1088/1674-1056/27/10/104205 摘要 ( 908 )   HTML ( 0 )   PDF(1155KB) ( 161 )   The energy dissipation mechanism of energetic materials (EMs) is very important for keeping safety. We choose nitrobenzene as a model of EM and employ transient absorption (TA) spectroscopy and time-resolved coherent anti-stokes Raman scattering (CARS) to clarify its energy dissipation mechanism. The TA data confirms that the excited nitrobenzene spends about 16 ps finishing the twist intramolecular charge transfer from benzene to nitro group, and dissipates its energy through the rapid vibration relaxation in the initial excited state. And then the dynamics of vibrational modes (VMs) in the ground state of nitrobenzene, which are located at 682 cm-1 (v1), 854 cm-1 (v2), 1006 cm-1 (v3), and 1023 cm-1 (v4), is scanned by CARS. It exhibits that the excess energy of nitrobenzene on the ground state would further dissipate through intramolecular vibrational redistribution based on the vibrational cooling of v1 and v2 modes, v1 and v4 modes, and v3 and v4 modes. Moreover, the vibration-vibration coupling depends not only on the energy levels of VMs, but also on the spatial position of chemical bonds relative to the VM. 参考文献 | 相关文章 | 计量指标

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Study on polarization properties of graphene coated D-shaped fiber 刘学静, 杨禄文, 马敬云, 李彩丽, 金娃, 毕卫红 2018 (10):  104206-104206.  doi: 10.1088/1674-1056/27/10/104206 摘要 ( 758 )   HTML ( 0 )   PDF(518KB) ( 221 )   The optical properties of graphene coated D-shaped single mode fiber and photonic crystal fiber are numerically analyzed. Enhancement of the graphene-light interaction is found in graphene coated D-shaped photonic crystal fiber, which introduces a tunable polarization of the D-shaped fiber by changing the chemical potential of the coated graphene. An optimal polarizer model is demonstrated with the extinction ratio of 66.26 dB/mm and the insertion loss of 9.4 dB/mm. The modulator extinction ratios of the TE mode and TM mode are 11.5 dB and 5 dB, respectively, with a device length of 100 μ m. This paper provides a theoretical reference for the optical property research of the graphene fiber. 参考文献 | 相关文章 | 计量指标

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Total ionizing dose effects in pinned photodiode complementary metal-oxide-semiconductor transistor active pixel sensor 马林东, 李豫东, 文林, 冯婕, 张翔, 王田珲, 蔡毓龙, 王志铭, 郭旗 2018 (10):  104207-104207.  doi: 10.1088/1674-1056/27/10/104207 摘要 ( 747 )   HTML ( 0 )   PDF(604KB) ( 239 )   A pinned photodiode complementary metal-oxide-semiconductor transistor (CMOS) active pixel sensor is exposed to 60Co to evaluate the performance for space applications. The sample is irradiated with a dose rate of 50 rad (SiO2)/s and a total dose of 100 krad (SiO2), and the photodiode is kept unbiased. The degradation of dark current, full well capacity, and quantum efficiency induced by the total ionizing dose damage effect are investigated. It is found that the dark current increases mainly from the shallow trench isolation (STI) surrounding the pinned photodiode. Further results suggests that the decreasing of full well capacity due to the increase in the density, is induced by the total ionizing dose (TID) effect, of the trap interface, which also leads to the degradation of quantum efficiency at shorter wavelengths. 参考文献 | 相关文章 | 计量指标

SPECIAL TOPIC—Recent advances in thermoelectric materials and devices

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Silicon nanophotonics for on-chip light manipulation 郭敬书, 戴道锌 2018 (10):  104208-104208.  doi: 10.1088/1674-1056/27/10/104208 摘要 ( 1063 )   HTML ( 0 )   PDF(2920KB) ( 664 )   The field of silicon nanophotonics has attracted considerable attention in the past decade because of its unique advantages, including complementary metal-oxide-semiconductor (CMOS) compatibility and the ability to achieve an ultra-high integration density. In particular, silicon nanophotonic integrated devices for on-chip light manipulation have been developed successfully and have played very import roles in various applications. In this paper, we review the recent progress of silicon nanophotonic devices for on-chip light manipulation, including the static type and the dynamic type. Static on-chip light manipulation focuses on polarization/mode manipulation, as well as light nanofocusing, while dynamic on-chip light manipulation focuses on optical modulation/switching. The challenges and prospects of high-performance silicon nanophotonic integrated devices for on-chip light manipulation are discussed. 参考文献 | 相关文章 | 计量指标

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS

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Optical power limiting of ultrashort hyper-Gaussian pulses in cascade three-level system 刘纪彩, 郭芬芬, 赵亚男, 李兴哲 2018 (10):  104209-104209.  doi: 10.1088/1674-1056/27/10/104209 摘要 ( 940 )   HTML ( 0 )   PDF(381KB) ( 150 )   Propagation of strong femtosecond hyper-Gaussian pulses in a cascade three-level molecular system is studied by solving numerically the Maxwell-Bloch equations by the iterative predictor-corrector finite-difference time-domain method. Optical power limiting behavior induced by strong nonlinear two-photon absorption is observed for different orders of the femtosecond hyper-Gaussian pulses. Pulses of a higher order temporal profile are found to have a wider power range of optical limiting but a larger output saturation intensity. Both the output saturation value and the damage threshold of optical power limiting decrease with pulse duration increasing. The decrease of the pulse area along the pulse propagation is much slower than that obtained from the two-photon area theorem due to invalidity of the slowly varying amplitude approximation and the monochromatic field hypothesis. 参考文献 | 相关文章 | 计量指标

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Theoretical analysis of optical force density distribution inside subwavelength-diameter optical fibers 张运原, 虞华康, 王向珂, 吴婉玲, 谷付星, 李志远 2018 (10):  104210-104210.  doi: 10.1088/1674-1056/27/10/104210 摘要 ( 772 )   HTML ( 0 )   PDF(1735KB) ( 209 )   We investigate the microscopic optical force density distributions respectively inside a subwavelength-diameter (SD) fiber with flat endface and inside one with oblique endface by using a finite-difference time-domain (FDTD) method. Optical force density distributions at the fiber endfaces can now be readily available. The complete knowledge of optical force density distributions not only reveal features regarding the microscopic near-field optomechanical interaction, but also provide straightforward explanations for the sideway deflections and other mechanical motions. Our results can provide a useful reference for better understanding the mechanical influence when light transports in a microscale or nanoscale structure and for developing future highly-sensitive optomechanical devices. 参考文献 | 相关文章 | 计量指标

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Radiation from finite cylindrical shell with irregular-shaped acoustic enclosure 杨德森, 张睿, 时胜国 2018 (10):  104301-104301.  doi: 10.1088/1674-1056/27/10/104301 摘要 ( 752 )   HTML ( 0 )   PDF(693KB) ( 174 )   In practical situations, large machinery is usually placed in an underwater vessel and changes the acoustic enclosure shape into an irregular one. The existence of machinery causes the difficulties in expressing sound transmission and radiation analytically. In this study, the sound radiation of a cylindrical shell excited by an internal acoustic source is modeled and analyzed. The cylindrical shell contains a machine modeled as a rectangular object, which is attached to a shell with a spring-mass system. The acoustic field of the cavity is computed by the integro-modal approach. The effect of object size on the coupling between acoustic mode and structural mode is investigated. The relationship between object volume and sound radiation is also studied. Numerical results show that the existence of objects inside vessels leads to a more effective coupling between the structure and acoustic enclosure than the existence of no objects in a regular-shaped cavity (i.e. empty vessel). 参考文献 | 相关文章 | 计量指标

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Simulation research on effect of magnetic nanoparticles on physical process of magneto-acoustic tomography with magnetic induction 闫孝姮, 张莹, 刘国强 2018 (10):  104302-104302.  doi: 10.1088/1674-1056/27/10/104302 摘要 ( 866 )   HTML ( 1 )   PDF(3217KB) ( 188 )   Magneto-acoustic tomography with magnetic induction (MAT-MI) is a multiphysics coupled imaging technique that is combined with electrical impedance tomography and ultrasound imaging. In order to study the influence of adding magnetic nanoparticles as a contrast agent for MAT-MI on its physical process, firstly, we analyze and compare the electromagnetic and acoustical properties of MAT-MI theoretically before and after adding magnetic nanoparticles, and then construct a two-dimensional (2D) planar model. Under the guidance of space-time separation theory, we determine the reasonable simulation conditions and solve the electromagnetic field and sound field physical processes in the two modes by using the finite element method. The magnetic flux density, sound pressure distribution, and related one-dimensional (1D), 2D, and three-dimensional(3D) images are obtained. Finally, we make a qualitative and quantitative analysis based on the theoretical and simulation results. The research results show that the peak time of the time item separated from the sound source has a corresponding relationship with the peak time of the sound pressure signal. At this moment, MAMPT-MI produces larger sound pressure signals, and the sound pressure distribution of the MAMPT-MI is more uniform, which facilitates the detection and completion of sound source reconstruction. The research results may lay the foundation for the MAT-MI of magnetically responsive nanoparticle in subsequent experiments and even clinical applications. 参考文献 | 相关文章 | 计量指标

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Influence of particle packing structure on sound velocity 赵闯, 李成波, 鲍琳 2018 (10):  104501-104501.  doi: 10.1088/1674-1056/27/10/104501 摘要 ( 691 )   HTML ( 1 )   PDF(1624KB) ( 175 )   The anisotropy in the particle systems of different packing structures affects the sound velocity. The acoustic propagation process in four kinds of packing structures (denoted as S45, H60, S90, and D) of two-dimensional granular system is simulated by the discrete element method. The velocity vtof obtained by the time of flight method and the velocity vc obtained from the stiffness tensor of the system are compared. Different sound velocities reflect various packing structures and force distributions within the system. The compression wave velocities of H60 and S90 are nearly the same, and transmit faster than that of D packing structure, while the sound velocity of S45 is the smallest. The shear wave velocities of S45 and H60 are nearly the same, and transmit faster than that of D packing structure. The compression wave velocity is sensitive to the volume fraction of the structure, however, the shear wave velocity is more sensitive to the geometrical structure itself. As the normal stress p is larger than 1 MPa, vtof and vc are almost equal, and the stiffness tensors of various structures explain the difference of sound velocities. When the normal stress is less than 1 MPa, with the coordination number unchanged, the law vtof∝ p1/4 still exists. This demonstrates that apart from different power laws between force and deformation as well as the change of the coordination number under different stresses, there are other complicated causes of vtof∝ p1/4, and an explanation of the deviation from vtof∝ p1/6 is given from the perspective of dissipation. 参考文献 | 相关文章 | 计量指标

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Coherent structures over riblets in turbulent boundary layer studied by combining time-resolved particle image velocimetry (TRPIV), proper orthogonal decomposition (POD), and finite-time Lyapunov exponent (FTLE) 李山, 姜楠, 杨绍琼, 黄永祥, 吴彦华 2018 (10):  104701-104701.  doi: 10.1088/1674-1056/27/10/104701 摘要 ( 708 )   HTML ( 0 )   PDF(3378KB) ( 281 )   Time-resolved particle image velocimetry (TRPIV) experiments are performed to investigate the coherent structure's performance of riblets in a turbulent boundary layer (TBL) at a friction Reynolds number of 185. To visualize the energetic large-scale coherent structures (CSs) over a smooth surface and riblets, the proper orthogonal decomposition (POD) and finite-time Lyapunov exponent (FTLE) are used to identify the CSs in the TBL. Spatial-temporal correlation is implemented to obtain the characters and transport properties of typical CSs in the FTLE fields. The results demonstrate that the generic flow structures, such as hairpin-like vortices, are also observed in the boundary layer flow over the riblets, consistent with its smooth counterpart. Low-order POD modes are more sensitive to the riblets in comparison with the high-order ones, and the wall-normal movement of the most energy-containing structures are suppressed over riblets. The spatial correlation analysis of the FTLE fields indicates that the evolution process of the hairpin vortex over riblets are inhibited. An apparent decrease of the convection velocity over riblets is noted, which is believed to reduce the ejection/sweep motions associated with high shear stress from the viscous sublayer. These reductions exhibit inhibition of momentum transfer among the structures near the wall in the TBL flows. 参考文献 | 相关文章 | 计量指标

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Numerical study of heat-transfer in two-and quasi-two-dimensional Rayleigh-Bénard convection 高振源, 罗嘉辉, 包芸 2018 (10):  104702-104702.  doi: 10.1088/1674-1056/27/10/104702 摘要 ( 805 )   HTML ( 0 )   PDF(2011KB) ( 167 )   A detailed comparative numerical study between the two-dimensional (2D) and quasi-two-dimensional (quasi-2D) turbulent Rayleigh-Bénard (RB) convection on flow state, heat transfer, and thermal dissipation rate (TDR) is made. The Rayleigh number (Ra) in our simulations ranges up to 5×1010 and Prandtl number (Pr) is fixed to be 0.7. Our simulations are conducted on the Tianhe-2 supercomputer. We use an in-house code with high parallelization efficiency, based on the extended PDM-DNS scheme. The comparison shows that after a certain Ra, plumes with round shape, which is called the “temperature islands”, develop and gradually dominate the flow field in the 2D case. On the other hand, in quasi-2D cases, plumes remain mushroom-like. This difference in morphology becomes more significant as Ra increases, as with the motion of plumes near the top and bottom plates. The exponents of the power-law relation between the Nusselt number (Nu) and Ra are 0.3 for both two cases, and the fitting pre-factors are 0.099 and 0.133 for 2D and quasi-2D respectively, indicating a clear difference in magnitude of the heat transfer rate between two cases. To understand this difference in the magnitude of Nu, we compare the vertical profile of the horizontally averaged TDR for both two cases. It is found that the profiles of both cases are nearly the same in the bulk, but they vary near boundaries. Comparing the bifurcation height zb with the thermal boundary layer thickness δθ, it shows that zb < δθ(3D) < δθ(2D) and all three heights obey a universal power-law relation z~Ra-0.30. In order to quantify the difference further, we separate the domain by zb, i.e., define the area between two zb (near top and bottom plates respectively) as the “mid region” and the rest as the “side region”, and integrate TDR in corresponding regions. By comparing the integral it is found that most of the difference in TDR between two cases, which is connected to the heat transfer rate, occurs within the thermal boundary layers. We also compare the ratio of contributions to total heat transfer in BL-bulk separation and side-mid separation. 参考文献 | 相关文章 | 计量指标

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Acoustic characteristics of pulse detonation engine with ellipsoidal reflector 康杨, 李宁, 翁春生, 王传位 2018 (10):  104703-104703.  doi: 10.1088/1674-1056/27/10/104703 摘要 ( 578 )   HTML ( 0 )   PDF(2578KB) ( 286 )   Acoustic characteristics of a pulse detonation engine (PDE) with and without an ellipsoidal reflector are numerically and experimentally investigated. A two-dimensional (2D) non-splitting unstructured triangular mesh Euler solver based on the space-time conservation element and solution element (CE/SE) method is employed to simulate the flow field of a PDE. The numerical results clearly demonstrate the external flow field of the PDE. The effect of an ellipsoidal reflector on the flow field characteristic near the PDE exit is investigated. The formation process of reflected shock wave and reflected jet shock are reported in detail. An acoustic measurement system is established for the PDE acoustic testing. The experimental results show that the ellipsoidal reflector changes the sound waveform and directivity of PDE sound. The reflected shock wave and reflected jet shock result in two more positive pressure peaks in the sound waveform. The ellipsoidal reflector changes the directivity of PDE sound from 20° to 0°. It is found that the peak sound pressure level (PSPL) and overall sound pressure level (OASPL) each obtain an increment when the PDE is installed with a reflector. The maximum relative increase ratio of PSPL and OASPL are obtained at the focus point F2, whose values are 6.1% and 6.84% respectively. The results of the duration of the PDE sound indicate that the reflecting and focusing wave generated by the reflector result in the increment of A duration and B duration before and near focus point F2. Results show that the ellipsoidal reflector has a great influence on the acoustic characteristic of PDE sound. The research is helpful for understanding the influence of an ellipsoidal reflector on the formation and propagation process of PDE sound. 参考文献 | 相关文章 | 计量指标

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Ion population fraction calculations using improved screened hydrogenic model with l-splitting Amjad Ali, G Shabbir Naz, Rukhsana Kouser, Ghazala Tasneem, M Saleem Shahzad, Aman-ur-Rehman, M H Nasim 2018 (10):  105201-105201.  doi: 10.1088/1674-1056/27/10/105201 摘要 ( 641 )   HTML ( 0 )   PDF(2671KB) ( 230 )   Ion population fraction (IPF) calculations are very important to understand the radiative spectrum emitted from the hot dense matter. IPF calculations require detailed knowledge of all the ions and correlation interactions between the electrons of an ion which are present in a plasma environment. The average atom models, e.g., screened hydrogenic model with l-splitting (SHML), now have the capabilities for such calculations and are becoming more popular for in line plasma calculations. In our previous work[Ali A, Shabbir Naz G, Shahzad M S, Kouser R, Rehman A and Nasim M H 2018 High Energy Density Phys. 26 48], we have improved the continuum lowering model and included the exchange and correlation effects in SHML. This study presents the calculation of IPF using classical theory of fluctuation for our improved screened hydrogenic model with l-splitting (I-SHML) under local thermodynamic equilibrium conditions for iron and aluminum plasma over a wide range of densities and temperatures. We have compared our results with other models and have found a very good agreement among them. 参考文献 | 相关文章 | 计量指标

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Dense pair plasma generation and its modulation dynamics in counter-propagating laser field 刘维媛, 罗文, 袁韬, 余继晔, 陈民 2018 (10):  105202-105202.  doi: 10.1088/1674-1056/27/10/105202 摘要 ( 707 )   HTML ( 0 )   PDF(2163KB) ( 183 )   With two-dimensional quantum electrodynamics (QED) particle-in-cell simulations, a dense electron-positron (e-e+) pair generation from laser-solid interactions is demonstrated. When the interaction of two linearly polarized laser pulses with a thin target enters into the relativistic transparency regime, a stable standing wave (SW) field can be formed by the overlap of the two counter-propagating laser pulses directly. The present study aims to clarify the effects of the SW field on the dynamics of e-e+ pair plasmas. Our results indicate that under the combined effect of the SW field and radiation reaction (RR) effect, the created e-e+ pairs can be trapped into the electric field nodes when the field strength is strong. The trapping effect contributes to the generation of γAV ≥ 400 and ultra-dense pair plasmas in the two-side irradiation scheme. Despite different laser intensities, these pair plasmas have a Maxwellian spectral distribution with a peak energy of 150 MeV. Besides, the periodical modulation of the average energy, spatial, phase-space, and angular patterns of the e-e+ pair plasmas can be triggered. In the angular patterns, as long as the SW field exists, pair plasmas can be pinched along the laser polarization direction. These results may offer a better understanding of the laser-solid interactions in the experiments when 10-PW laser facilities come into operation in the future. 参考文献 | 相关文章 | 计量指标

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Tunneling dynamics of bosons in the diamond lattice chain 常娜娜, 薛具奎 2018 (10):  105203-105203.  doi: 10.1088/1674-1056/27/10/105203 摘要 ( 681 )   HTML ( 0 )   PDF(5419KB) ( 198 )   We analyze the effect of tilting and artificial magnetic flux, on the energy bands structure for the system and the corresponding tunneling dynamics for bosons with various initial configurations in the diamond lattice chain, where intriguing and significant phenomena occur, including Landau-Zener tunneling, Bloch oscillations, and localization phenomenon. Both vertical tilting and artificial magnetic flux may alter the structure of energy levels (dispersion structure or flat band), and enforce the occurrence of Landau-Zener tunneling, which scans the whole of the Bloch bands. We find that, transitions among Landau-Zener tunneling, Bloch oscillations, and localization phenomenon, are not only closely related to the energy bands structure, but also depends on the initial configuration of bosons in the diamond lattice chain. As a consequence, Landau-Zener tunneling, Bloch oscillations, and localization phenonmenon of bosons always counteract and are complementary with each other in the diamond lattice chain. 参考文献 | 相关文章 | 计量指标

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Small amplitude double layers in an electronegative dusty plasma with q-distributed electrons 李中正, 韩娟芳, 郜东宁, 段文山 2018 (10):  105204-105204.  doi: 10.1088/1674-1056/27/10/105204 摘要 ( 606 )   HTML ( 0 )   PDF(390KB) ( 181 )   The small amplitude dust ion-acoustic double layers in a collisionless four-component unmagnetized dusty plasma system containing nonextensive electrons, inertial negative ions, Maxwellian positive ions, and negatively charged static dust grains are investigated theoretically. Using the pseudo-potential approach and reductive perturbation method, an energy integral equation for the system has been derived and its solution in the form of double layers is obtained. The results appear that the existence regime of the double layer is very sensitive to the plasma parameters, e.g., electron nonextensivity, negative-to-positive ion number density ratio etc. It has been observed that for the selected set of parameters, the system supports rarefactive, (compressive) double layers depending upon the degree of nonextensivity of electrons. 参考文献 | 相关文章 | 计量指标

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UAV flight test of plasma slats and ailerons with microsecond dielectric barrier discharge 苏志, 李军, 梁华, 郑博睿, 魏彪, 陈杰, 谢理科 2018 (10):  105205-105205.  doi: 10.1088/1674-1056/27/10/105205 摘要 ( 739 )   HTML ( 0 )   PDF(4934KB) ( 389 )   Plasma flow control (PFC) is a promising active flow control method with its unique advantages including the absence of moving components, fast response, easy implementation, and stable operation. The effectiveness of plasma flow control by microsecond dielectric barrier discharge (μs-DBD), and by nanosecond dielectric barrier discharge (NS-DBD) are compared through the wind tunnel tests, showing a similar performance between μs-DBD and NS-DBD. Furthermore, the μs-DBD is implemented on an unmanned aerial vehicle (UAV), which is a scaled model of a newly developed amphibious plane. The wingspan of the model is 2.87m, and the airspeed is no less than 30m/s. The flight data, static pressure data, and Tufts images are recorded and analyzed in detail. Results of the flight test show that the μs-DBD works well on board without affecting the normal operation of the UAV model. When the actuators are turned on, the stall angle and maximum lift coefficient can be improved by 1.3° and 10.4%, and the static pressure at the leading edge of the wing can be reduced effectively in a proper range of angle of attack, which shows the ability of μs-DBD to act as plasma slats. The rolling moment produced by left-side μs-DBD actuation is greater than that produced by the maximum deflection of ailerons, which indicates the potential of μs-DBD to act as plasma ailerons. The results verify the feasibility and efficacy of μs-DBD plasma flow control in a real flight and lay the foundation for the full-sized airplane application. 参考文献 | 相关文章 | 计量指标

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On the dielectric response function and dispersion relation in strongly coupled magnetized dusty plasmas M Shahmansouri, N Khodabakhshi 2018 (10):  105206-105206.  doi: 10.1088/1674-1056/27/10/105206 摘要 ( 668 )   HTML ( 0 )   PDF(304KB) ( 244 )   Using the generalized viscoelastic fluid model, we derive the dielectric response function in a strongly coupled dusty magnetoplasma which reveals two different dust acoustic (DA) wave modes in the hydrodynamic and kinetic limits. The effects of the strong interaction of dust grains and the external magnetic on these DA modes, as well as on the shear wave are examined. It is found that both the real and imaginary parts of DA waves are significantly modified in strongly coupled dusty magnetoplasmas. The implications of our results to space and laboratory dusty plasmas are briefly discussed. 参考文献 | 相关文章 | 计量指标

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Nonlinear ion-acoustic solitary waves in an electron-positron-ion plasma with relativistic positron beam Ridip Sarma, Amar P Misra, Nirab C Adhikary 2018 (10):  105207-105207.  doi: 10.1088/1674-1056/27/10/105207 摘要 ( 696 )   HTML ( 1 )   PDF(383KB) ( 307 )   The propagation characteristics of nonlinear ion-acoustic (IA) solitary waves (SWs) are studied in thermal electron-positron-ion plasma considering the effect of relativistic positron beam. Starting from a set of fluid equations and using the reductive perturbation technique, we derive a Korteweg-de Vries (KdV) equation which governs the evolution of weakly nonlinear IA SWs in relativistic beam driven plasmas. The properties of the IA soliton are studied, and it is shown that the presence of relativistic positron beam significantly modifies the characteristics of IA solitons. 参考文献 | 相关文章 | 计量指标

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Practical 2.45-GHz microwave-driven Cs-free H- ion source developed at Peking University 张滔, 彭士香, 武文斌, 任海涛, 张景丰, 温佳美, 马腾昊, 蒋耀湘, 孙江, 郭之虞, 陈佳洱 2018 (10):  105208-105208.  doi: 10.1088/1674-1056/27/10/105208 摘要 ( 731 )   HTML ( 0 )   PDF(2671KB) ( 213 )   A practical 2.45-GHz microwave-driven Cs-free H- source was improved based on the experimental H- source at Peking University (PKU). Several structural improvements were implemented to meet the practical requirements of Xi'an Proton Application Facility (XiPaf). Firstly, the plasma chamber size was optimized to enhance the plasma intensity and stability. Secondly, the filter magnetic field and electron deflecting magnetic field were enhanced to reduce co-extracted electrons. Thirdly, a new two-electrode extraction system with farther electrode gap and enhanced water cooling ability to diminish spark and sputter during beam extraction was applied. At last, the direct H- current measuring method was adopted by the arrangement of a new pair of bending magnets before Faraday cup (FC) to remove residual electrons. With these improvements, electron cyclotron resonance (ECR) magnetic field optimization experiments and operation parameter variation experiments were carried out on the H- ion source and a maximum 8.5-mA pure H- beam was extracted at 50 kV with the time structure of 100 Hz/0.3 ms. The root-mean-square (RMS) emittance of the beam is 0.25π·mm·mrad. This improved H- source and extraction system were maintenance-free for more than 200 hours in operation. 参考文献 | 相关文章 | 计量指标

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Experimental and numerical investigation of a Hall thruster with a chamfered channel wall 李鸿, 夏国俊, 毛威, 刘金文, 丁永杰, 于达仁, 王晓钢 2018 (10):  105209-105209.  doi: 10.1088/1674-1056/27/10/105209 摘要 ( 657 )   HTML ( 0 )   PDF(3287KB) ( 194 )   A discharge channel with a chamfered wall not only has application in the design of modern Hall thrusters, but also exists where the channel wall is eroded, and so is a common status for these units. In this paper, the laws and mechanisms that govern the effect of the chamfered wall on the performance of a Hall thruster are investigated. By applying both experimental measurement and particle-in-cell simulation, it is determined that there is a moderate chamfer angle that can further improve the optimal performance obtained with a straight channel. This is because the chamfering of the wall near the channel exit can enhance ion acceleration and effectively reduce ion recombination on the wall, which is favorable to the promotion of the thrust and efficiency. However, the chamfer angle should not be too large; otherwise, both the density of the propellant gas and the distribution of the plasma potential in the channel are influenced, which is undesirable for efficient propellant utilization and beam concentration. Therefore, it is suggested that the chamfer shape of the channel wall is an important factor that must be carefully considered in the design of Hall thrusters. 参考文献 | 相关文章 | 计量指标

SPECIAL TOPIC—Recent advances in thermoelectric materials and devices

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Recent progress on magnetic-field studies on quantum-spin-liquid candidates 马祯, 冉柯静, 王靖珲, 鲍嵩, 蔡正蔚, 李世超, 温锦生 2018 (10):  106101-106101.  doi: 10.1088/1674-1056/27/10/106101 摘要 ( 806 )   HTML ( 0 )   PDF(3850KB) ( 485 )   Quantum spin liquids (QSLs) represent a novel state of matter in which quantum fluctuations prevent the conventional magnetic order from being established, and the spins remain disordered even at zero temperature. There have been many theoretical developments proposing various QSL states. On the other hand, experimental movement was relatively slow largely due to limitations on the candidate materials and difficulties in the measurements. In recent years, the experimental progress has been accelerated. In this topical review, we give a brief summary of experiments on the QSL candidates under magnetic fields. We arrange our discussions by two categories:i) Geometrically-frustrated systems, including triangular-lattice compounds YbMgGaO4 and YbZnGaO4, κ-(BEDT-TTF)2Cu2(CN)3, and EtMe3Sb[Pd(dmit)2]2, and the kagomé system ZnCu3(OH)6Cl2; ii) the Kitaev material α-RuCl3. Among these, we will pay special attention to α-RuCl3, which has been intensively studied by ours and other groups recently. We will present evidence that both supports and rejects the QSL ground state for these materials, based on which we give several perspectives to stimulate further research activities. 参考文献 | 相关文章 | 计量指标

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Effects of Al component content on optoelectronic properties of AlxGa1-xN 纪延俊, 王俊平, 刘友文 2018 (10):  106102-106102.  doi: 10.1088/1674-1056/27/10/106102 摘要 ( 821 )   HTML ( 0 )   PDF(961KB) ( 216 )   Using density functional theory, the electronic structures, lattice constants, formation energies, and optical properties of AlxGa1-xN are determined with Al component content x in a range from 0 to 1. As x increases, the lattice constants decrease in e-exponential form, and the band gap increases with a band bending parameter b=0.3954. The N-Al interaction force in the (0001) direction is greater than the N-Ga interaction force, while the N-Al interaction force is less than the N-Ga interaction force in the (1010) direction. The formation energies under different Al component content are negative and increase with Al component content increasing. The static dielectric function decreases, the absorption edge has a blue shift, and the energy loss spectrum moves to high energy with the Al component content increasing. 参考文献 | 相关文章 | 计量指标

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Unusual softening behavior of yield strength in niobium at high pressures 敬秋民, 何强, 张毅, 李守瑞, 柳雷, 侯琪玥, 耿华运, 毕延, 俞宇颖, 吴强 2018 (10):  106201-106201.  doi: 10.1088/1674-1056/27/10/106201 摘要 ( 682 )   HTML ( 0 )   PDF(1164KB) ( 224 )   In situ synchrotron angle-dispersive x-ray diffraction experiments on niobium powders have been conducted at pressures up to 61 GPa and room temperature using the diamond anvil cell technique. From the full width at half maximum of the measured diffraction lines, the yield strength was derived with the line-width analysis theory. The niobium powder sample was found to be compressed more packed firstly and then yielded at ~14 GPa-18 GPa. Following an initial increase in the yield strength with pressure, an obvious decrease was observed occurring at ~42 GPa-47 GPa accompanying with a typical pressure dependence above 47 GPa. The experimentally observed anomalous softening of the yield strength in niobium surprisingly follows the trend of the predicted unusual softening in the shear modulus by the recent theoretical investigations. The possible mechanisms, applicable to interpret the yield strength softening of materials at high pressure, were also discussed in detail. 参考文献 | 相关文章 | 计量指标

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The affection on the nature of percolation by concentration of pentagon-heptagon defects in graphene lattice 杨宇明, 滕保华 2018 (10):  106401-106401.  doi: 10.1088/1674-1056/27/10/106401 摘要 ( 771 )   HTML ( 0 )   PDF(732KB) ( 180 )   In this paper the percolation behavior with a specific concentration of the defects was discussed on the two-dimensional graphene lattice. The percolation threshold is determined by a numerical method with a high degree of accuracy. This method is also suitable for locating the percolation critical point on other crystalline structures. Through investigating the evolution of the largest cluster size and the cluster sizes distribution, we find that under various lattice sizes and concentrations of pentagon-heptagon defects there is no apparent change for the percolation properties in graphene lattice. 参考文献 | 相关文章 | 计量指标

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Study on the phase transition of the fractal scale-free networks 孟庆宽, 冯东太, 孙玉萍, 周爱萍, 孙艳, 谭树刚, 高绪团 2018 (10):  106402-106402.  doi: 10.1088/1674-1056/27/10/106402 摘要 ( 723 )   HTML ( 0 )   PDF(454KB) ( 155 )   Based on the Ising spin, the phase transition on fractal scale-free networks with tree-like skeletons is studied, where the loops are generated by local links. The degree distribution of the tree-like skeleton satisfies the power-law form P(k)~k-δ. It is found that when δ ≥ 3, the renormalized scale-free network will have the same degree distribution as the original network. For a special case of δ=4.5, a ferromagnetic to paramagnetic transition is found and the critical temperature is determined by the box-covering renormalization method. By keeping the structure of the fractal scale-free network constant, the numerical relationship between the critical temperature and the network size is found, which is the form of power law. 参考文献 | 相关文章 | 计量指标

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Elastocaloric effect and mechanical behavior for NiTi shape memory alloys 周敏, 李玉霜, 张晨, 李来风 2018 (10):  106501-106501.  doi: 10.1088/1674-1056/27/10/106501 摘要 ( 667 )   HTML ( 1 )   PDF(963KB) ( 214 )   The NiTi shape memory alloy exhibits excellent superelastic property and elastocaloric effect. The large temperature change (ΔT) value of 30 K upon loading and -19 K upon unloading are obtained at room temperature, which are higher than those of the other NiTi-based materials and among the highest values reported in the elastocaloric materials. The asymmetry of the measured ΔT values between the loading and unloading process is ascribed to the friction dissipation. The large temperature change originates from the large entropy change during the stress-induced martensite transformation (MT) and the reverse MT. A large coefficient-of-performance of the material is obtained to be 11.7 at ε=1%, which decreases with increasing the applied strain. These results are very attractive in the present solid-state cooling, which potentially could replace the vapor compression refrigeration technologies. 参考文献 | 相关文章 | 计量指标

SPECIAL TOPIC—Recent advances in thermoelectric materials and devices

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Spin detection and manipulation with scanning tunneling microscopy 高春雷 2018 (10):  106701-106701.  doi: 10.1088/1674-1056/27/10/106701 摘要 ( 948 )   HTML ( 1 )   PDF(2275KB) ( 340 )   Over the past few decades, spin detection and manipulation at the atomic scale using scanning tunneling microcopy has matured, which has opened the possibility of realizing spin-based functional devices with single atoms and molecules. This article reviews the principle of spin polarized scanning tunneling microscopy and inelastic tunneling spectroscopy, which are used to measure the static spin structure and dynamic spin excitation, respectively. Recent progress will be presented, including complex spin structure, magnetization of single atoms and molecules, as well as spin excitation of single atoms, clusters, and molecules. Finally, progress in the use of spin polarized tunneling current to manipulate an atomic magnet is discussed. 参考文献 | 相关文章 | 计量指标

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Adsorption and diffusion of F2 molecules on pristine graphene 杨勇, 刘富池, 川添良幸 2018 (10):  106801-106801.  doi: 10.1088/1674-1056/27/10/106801 摘要 ( 848 )   HTML ( 0 )   PDF(1082KB) ( 239 )   The adsorption and diffusion of F2 molecules on pristine graphene are studied by using first-principles calculations. For the diffusion of F2 from molecular state in gas phase to the dissociative adsorption state on graphene surface, a kinetic barrier is identified, which explains the inertness of graphene in molecular F2 at room temperature, and its reactivity with F2 at higher temperatures. Study of the diffusion of F2 molecules on graphene surface determines the energy barrier along the optimal diffusion pathway, which conduces to the understanding of the high stability of fluorographene. 参考文献 | 相关文章 | 计量指标

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Evolutionary algorithm for optimization of multilayer coatings Mahdi Ebrahimi, Mohsen Ghasemi, Zeinab Sajjadi 2018 (10):  106802-106802.  doi: 10.1088/1674-1056/27/10/106802 摘要 ( 612 )   HTML ( 0 )   PDF(1719KB) ( 194 )   In this paper, a new evolutionary algorithm, the well-known imperialist competition algorithm, is proposed for optimizing the optical thin-films. In this method, the process is modeled of the competition between countries as imperialists and their colonizing of others as colonies. This algorithm could be an appropriate alternative to some of the more popular algorithms for optimizing the optical thin-films for good performance. The polarizer and edge filter for example are designed by using the imperialist competition algorithm method and the results are compared with those from two optimization high-performance methods:the genetic algorithm and differential evolutionary algorithm. Based on these results, the performance of the imperialist competition algorithm method shows that this algorithm is not sensitive to the change of its parameters and it can be an important advantage for quickly achieving a global optimal point. On the other hand the results show a better ratio of P-polarization transmittance to S-polarization transmittance in the design of a 1540-nm polarizer, which is more appropriate than the results from the other two methods. In the second design, an edge filter with a lower number of layers and more uniform bandpass spectrum than the counterparts of those methods is obtained. These results indicate that the imperialist competition algorithm is a robust method for optical thin-film designs. 参考文献 | 相关文章 | 计量指标

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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Effect of Mn doping on mechanical properties and electronic structure of WCoB ternary boride by first-principles calculations 张桐, 尹海清, 张聪, 曲选辉, 郑清军 2018 (10):  107101-107101.  doi: 10.1088/1674-1056/27/10/107101 摘要 ( 641 )   HTML ( 2 )   PDF(2244KB) ( 246 )   The first-principles calculations are performed to investigate the structural, mechanical property, hardness, and electronic structure of WCoB with 0, 8.33, 16.67, 25, and 33.33 at.% Mn doping content and W2CoB2 with 0, 10, and 20 at.% Mn doping content. The cohesive energy and formation energy indicate that all the structures can retain good structural stability. According to the calculated elastic constants, Mn is responsible for the increase of ductility and Poisson's ratio and the decrease of Young's modulus, shear modulus, and bulk modulus. By using the population analysis and mechanical properties, the hardness is characterized through using the five hardness models and is found to decrease with the Mn doping content increasing. The calculated electronic structure indicates that the formation of a B-Mn covalent bond and a W-Mn metallic bond contribute to the decreasing of the mechanical properties. 参考文献 | 相关文章 | 计量指标

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First principles study of stability, mechanical, and electronic properties of chromium silicides 任博, 卢德宏, 周荣, 姬德朋, 胡明钰, 冯晶 2018 (10):  107102-107102.  doi: 10.1088/1674-1056/27/10/107102 摘要 ( 690 )   HTML ( 1 )   PDF(3358KB) ( 275 )   Through the first principles calculations, the chemical stability, mechanical, and electronic properties of chromium silicides are predicted. Estimating enthalpies and binding energies, density state density and electron density distribution are combined to analyse the thermodynamic stability and physical properties of chrome-silicon binary compounds. The chromium silicide includes Cr3Si, Cr5Si3, CrSi, and CrSi2. The chemical stability and the information about electronic structure, mechanical properties, Debye temperature, and anisotropy properties are obtained by density functional theory and Debye quasi-harmonic approximation. Meanwhile, the calculation of elastic modulus shows that Cr3Si has the highest body modulus value (251 GPa) and CrSi2 possesses the highest shear modulus (169.5 GPa) and Young's modulus (394.9 GPa). In addition, the Debye temperature and the speed of sound of these Cr-Si compounds are also calculated. Since the calculated bulk modulus is different from Young's modulus anisotropy index, and also different from Young's modulus of a three-dimensional surface shape, the different mechanical anisotropies of all the compounds are obtained. 参考文献 | 相关文章 | 计量指标

SPECIAL TOPIC—Recent advances in thermoelectric materials and devices

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Spin switching in antiferromagnets using Néel-order spin-orbit torques P Wadley, K W Edmonds 2018 (10):  107201-107201.  doi: 10.1088/1674-1056/27/10/107201 摘要 ( 776 )   HTML ( 2 )   PDF(2916KB) ( 325 )   Antiferromagnets offer considerable potential for electronic device applications. This article reviews recent demonstrations of spin manipulation in antiferromagnetic devices using applied electrical currents. Due to spin-orbit coupling in environments with particular crystalline or structural symmetries, the electric current can induce an effective magnetic field with a sign that alternates on the lengthscale of the unit cell. The staggered effective field provides an efficient mechanism for switching antiferromagnetic domains and moving antiferromagnetic domain walls, with writing speeds in the terahertz regime. 参考文献 | 相关文章 | 计量指标

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Recent spinterfacial studies targeted to spin manipulation in molecular spintronic devices 谷现荣, 郭立丹, 孙向南 2018 (10):  107202-107202.  doi: 10.1088/1674-1056/27/10/107202 摘要 ( 580 )   HTML ( 1 )   PDF(3526KB) ( 374 )   Molecular spintronics is an emerging field which evoked wide research attention since the first molecule-based spintronic device has been reported at 2002. Due to the active study over the last few years, it is found that the interfaces in spintronic device, so called spinterface, is of critical importance for many key issues in molecular spintronics, such as enhancing spin injection, lengthening spin transport distance, as well as manipulating spin signals in molecular spintronic devices. Here in this review, recent studies regarding spinterface in molecular devices, especially those impressive efforts devoted on spin manipulation, have been systematically summarized and discussed. 参考文献 | 相关文章 | 计量指标

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Superconductivity with peculiar upper critical fields in quasi-one-dimensional Cr-based pnictides 曹光旱, 朱增伟 2018 (10):  107401-107401.  doi: 10.1088/1674-1056/27/10/107401 摘要 ( 741 )   HTML ( 0 )   PDF(5950KB) ( 446 )   The discovery of superconductivity in quasi-one-dimensional Cr-based pnictides A2Cr3As3 (A=alkali metals) has generated considerable research interest, primarily owing to their reduced dimensionality, significant electron correlations, and possible unconventional superconductivity. The upper critical field (Hc2) provides important information on the superconducting pairing. In this paper, we first briefly overview the latest research progress on the Cr-based superconductors. Then, we introduce typical Hc2(T) behaviors of type-Ⅱ superconductors in relation with the pair-breaking mechanisms. After a description of the measurement method for Hc2, we focus on the analysis of Hc2 data, especially for the temperature and angle dependence, in K2Cr3As3 crystals. The result indicates (i) an absence of Pauli-paramagnetic pair breaking for field perpendicular to the Cr3As3 chains, and (ii) a unique threefold modulation for the in-plane Hc2(φ) profile. Finally we conclude with remarks on the possible unconventional superconducting pairing symmetry. 参考文献 | 相关文章 | 计量指标

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Electron transport in Dirac and Weyl semimetals 王慧超, 王健 2018 (10):  107402-107402.  doi: 10.1088/1674-1056/27/10/107402 摘要 ( 872 )   HTML ( 0 )   PDF(6382KB) ( 740 )   Recently, the Dirac and Weyl semimetals have attracted extensive attention in condensed matter physics due to both the fundamental interest and the potential application of a new generation of electronic devices. Here we review the exotic electrical transport phenomena in Dirac and Weyl semimetals. Section 1 is a brief introduction to the topological semimetals (TSMs). In Section 2 and Section 3, the intriguing transport phenomena in Dirac semimetals (DSMs) and Weyl semimetals (WSMs) are reviewed, respectively. The most widely studied Cd3As2 and the TaAs family are selected as representatives to show the typical properties of DSMs and WSMs, respectively. Beyond these systems, the advances in other TSM materials, such as ZrTe5 and the MoTe2 family, are also introduced. In Section 4, we provide perspectives on the study of TSMs especially on the magnetotransport investigations. 参考文献 | 相关文章 | 计量指标

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Ultrasensitive nanosensors based on localized surface plasmon resonances: From theory to applications 陈文, 胡华天, 姜巍, 徐宇浩, 张顺平, 徐红星 2018 (10):  107403-107403.  doi: 10.1088/1674-1056/27/10/107403 摘要 ( 1216 )   HTML ( 0 )   PDF(9311KB) ( 473 )   The subwavelength confinement feature of localized surface plasmon resonance (LSPR) allows plasmonic nanostructures to be functionalized as powerful platforms for detecting various molecular analytes as well as weak processes with nanoscale spatial resolution. One of the main goals of this field of research is to lower the absolute limit-of-detection (LOD) of LSPR-based sensors. This involves the improvement of (i) the figure-of-merit associated with structural parameters such as the size, shape and interparticle arrangement and, (ii) the spectral resolution. The latter involves advanced target identification and noise reduction techniques. By highlighting the strategies for improving the LOD, this review introduces the fundamental principles and recent progress of LSPR sensing based on different schemes including 1) refractometric sensing realized by observing target-induced refractive index changes, 2) plasmon rulers based on target-induced relative displacement of coupled plasmonic structures, 3) other relevant LSPR-based sensing schemes including chiral plasmonics, nanoparticle growth, and optomechanics. The ultimate LOD and the future trends of these LSPR-based sensing are also discussed. 参考文献 | 相关文章 | 计量指标

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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Structural, Mössbauer spectroscopy, magnetic properties, and thermal measurements of Y3-xDyxFe5O12 Mahdi Lataifeh, Qassem I Mohaidat, Sami H Mahmood, Ibrahim Bsoul, Mufeed Awawdeh, Ibrahim Abu-Aljarayesh, Mu'ath Altheeba 2018 (10):  107501-107501.  doi: 10.1088/1674-1056/27/10/107501 摘要 ( 668 )   HTML ( 0 )   PDF(3727KB) ( 278 )   Yttrium iron garnet powder samples (Y3-xDyxFe5O12), where part of yttrium ions are substituted by dysprosium ions with different concentrations are prepared by the solid state reaction method. The properties of the prepared samples are examined by different methods such as x-ray diffraction (XRD), Mössbauer spectroscopy, macroscopic magnetization measurements, and thermal measurements. The XRD measurements show that all the samples reveal the presence of a single garnet phase with a BCC structure. Room temperature Mössbauer spectra indicate that iron ions occupy three magnetic sites, i.e., two octahedral sites and one tetrahedral site. The saturation magnetization and the initial magnetic susceptibility decrease with the increase of Dy3+ substitution. The Curie temperature obtained from the thermal measurements seems to be independent of Dy3+ substitution. 参考文献 | 相关文章 | 计量指标

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Ferromagnetism and magnetostructural coupling in V-doped MnNiGe alloys 杨慧, 刘俊, 李超, 王广龙, 龚元元, 徐锋 2018 (10):  107502-107502.  doi: 10.1088/1674-1056/27/10/107502 摘要 ( 818 )   HTML ( 0 )   PDF(906KB) ( 183 )   The magnetostructural coupling between magnetic and structure transitions plays an important role in the multifunctional applications of magentocaloric materials. In this work, ferromagnetism and magnetostructural transformation are achieved in nonmagnetic V-doped MnNiGe alloys. With simultaneously reducing the transformation temperature and converting antiferromagnetic martensite to ferromagnetic state, the magnetostructural transformation between ferromagnetic orthorhombic phase and paramagnetic hexagonal phase is established in a temperature region as large as 130 K. The magnetic-field-induced magnetostructural transformation is accompanied by considerable magnetocaloric effect. 参考文献 | 相关文章 | 计量指标

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Electro-optical properties and (E, T) phase diagram of fluorinated chiral smectic liquid crystals R Zgueb, H Dhaouadi, T Othman 2018 (10):  107701-107701.  doi: 10.1088/1674-1056/27/10/107701 摘要 ( 622 )   HTML ( 0 )   PDF(3494KB) ( 138 )   Fluorinated smectic liquid crystals each with a biphenyl benzoate rigid core are investigated. Molecular structures of the studied compounds have difference only in fluorine position and the length of the carbon chain. Dielectric relaxation study and electro-optical measurements are carried out with the classical SSFLC geometry. The field-induced phase transitions are studied and the (E,T) phase diagram is established. 参考文献 | 相关文章 | 计量指标

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Low-temperature green synthesis of boron carbide using aloe vera H V SarithaDevi, M S Swapna, G Ambadas, S Sankararaman 2018 (10):  107702-107702.  doi: 10.1088/1674-1056/27/10/107702 摘要 ( 660 )   HTML ( 1 )   PDF(1229KB) ( 210 )   The unique structural and physical properties of boron carbide, which make it suitable for a wide range of applications, demands the development of low-cost and green synthesis method. In the present work, the commonly available leaves of aloe vera are hydrothermally treated to form the carbon precursor for the synthesis of boron carbide. The morphological characterization reveals the porous nature of the precursor turning into a tubular structure upon boron carbide formation. The structural characterization by x-ray diffraction and other spectroscopic techniques such as Fourier transform infrared, Raman, photoluminescence and uv-visible near-infrared spectroscopy confirm the formation of boron carbide. The thermogravimetric analysis of the sample is found to exhibit good thermal stability above 500℃. When the sample is annealed to 600℃, boron carbide with phase purity is obtained, which is confirmed through XRD and FTIR analyses. The optical emission properties of the sample are studied through CIE plot and power spectrum. Compared with other natural precursors for boron carbide, the aloe vera is found to give a good yield above 50%. 参考文献 | 相关文章 | 计量指标

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Improvement of electro-optic performances in white organic light emitting diodes with color stability by buffer layer and multiple dopants structure 寇志起, 唐宇, 杨丽萍, 杨飞宇, 郭文军 2018 (10):  107801-107801.  doi: 10.1088/1674-1056/27/10/107801 摘要 ( 740 )   HTML ( 0 )   PDF(498KB) ( 163 )   A series of white phosphorescent OLED devices with buffer layer and multiple dopant structure is investigated in order to obtain better electro-optic performances and color stability. The color coordinate and color stability are related to the location of multiple dopants layer, and the optimized location can compensate for the change of the blue emission intensity under a high voltage and stabilize the spectrum. The electro-optic performances and color stability can be further improved by changing the composition and thickness of the buffer layer between the emitting layer and the electron transport layer. In device B2, the distance from multiple dopant layer to buffer layer is 2 nm and the thickness of buffer layer is 5 nm, the maximum luminance, current density, and power efficiency can reach 9091 cd/m2, 364.5 mA/cm2, and 26.74 lm/W, respectively. The variation of international commission on the illumination (CIE) coordinate of device B2 with voltage increasing from 4 V to 7 V is only (0.006, 0.004). 参考文献 | 相关文章 | 计量指标

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Charge compensation and capacity fading in LiCoO2 at high voltage investigated by soft x-ray absorption spectroscopy 龙兴辉, 吴颜如, 张念, 于鹏飞, 冯雪飞, 郑顺, 傅佳敏, 刘啸嵩, 柳娜, 王梦, 徐磊敏, 陈锦明, 李振民 2018 (10):  107802-107802.  doi: 10.1088/1674-1056/27/10/107802 摘要 ( 773 )   HTML ( 0 )   PDF(1328KB) ( 245 )   In order to obtain an in-depth insight into the mechanism of charge compensation and capacity fading in LiCoO2, the evolution of electronic structure of LiCoO2 at different cutoff voltages and after different cycles are studied by soft x-ray absorption spectroscopy in total electron (TEY) and fluorescence (TFY) detection modes, which provide surface and bulk information, respectively. The spectra of Co L2,3-edge indicate that Co contributes to charge compensation below 4.4 V. Combining with the spectra of O K-edge, it manifests that only O contributes to electron compensation above 4.4 V with the formation of local O 2p holes both on the surface and in the bulk, where the surficial O evolves more remarkably. The evolution of the O 2p holes gives an explanation to the origin of O2- or even O2. A comparison between the TEY and TFY of O K-edge spectra of LiCoO2 cycled in a range from 3 V to 4.6 V indicates both the structural change in the bulk and aggregation of lithium salts on the electrode surface are responsible for the capacity fading. However, the latter is found to play a more important role after many cycles. 参考文献 | 相关文章 | 计量指标

SPECIAL TOPIC—Recent advances in thermoelectric materials and devices

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Transport properties of doped Bi2Se3 and Bi2Te3 topological insulators and heterostructures 王振华, 高翾, 张志东 2018 (10):  107901-107901.  doi: 10.1088/1674-1056/27/10/107901 摘要 ( 810 )   HTML ( 0 )   PDF(2709KB) ( 826 )   In this review article, the recent experimental and theoretical research progress in Bi2Se3- and Bi2Te3-based topological insulators is presented, with a focus on the transport properties and modulation of the transport properties by doping with nonmagnetic and magnetic elements. The electrical transport properties are discussed for a few different types of topological insulator heterostructures, such as heterostructures formed by Bi2Se3- and Bi2Te3-based binary/ternary/quaternary compounds and superconductors, nonmagnetic and magnetic metals, or semiconductors. 参考文献 | 相关文章 | 计量指标

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Efficient thermal analysis method for large scale compound semiconductor integrated circuits based on heterojunction bipolar transistor 杨施政, 吕红亮, 张玉明, 张义门, 芦宾, 严思璐 2018 (10):  108101-108101.  doi: 10.1088/1674-1056/27/10/108101 摘要 ( 617 )   HTML ( 0 )   PDF(2105KB) ( 193 )   In this paper, an efficient thermal analysis method is presented for large scale compound semiconductor integrated circuits based on a heterojunction bipolar transistor with considering the change of thermal conductivity with temperature. The influence caused by the thermal conductivity can be equivalent to the increment of the local temperature surrounding the individual device. The junction temperature for each device can be efficiently calculated by the combination of the semi-analytic temperature distribution function and the iteration of local temperature with high accuracy, providing a temperature distribution for a full chip. Applying this method to the InP frequency divider chip and the GaAs analog to digital converter chip, the computational results well agree with the results from the simulator COMSOL and the infrared thermal imager respectively. The proposed method can also be applied to thermal analysis in various kinds of semiconductor integrated circuits. 参考文献 | 相关文章 | 计量指标

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Performance of n-type silicon/silver composite anode material in lithium ion batteries: A study on effect of work function matching degree 徐国军, 金晨鑫, 孔凯捷, 杨西西, 岳之浩, 李晓敏, 孙福根, 黄海宾, 周浪 2018 (10):  108201-108201.  doi: 10.1088/1674-1056/27/10/108201 摘要 ( 674 )   HTML ( 0 )   PDF(1979KB) ( 162 )   In this paper, two types of silicon (Si) particles ball-milled from n-type Si wafers, respectively, with resistivity values of 1 Ω·cm and 0.001 Ω·cm are deposited with silver (Ag). The Ag-deposited n-type 1-Ω·cm Si particles (n1-Ag) and Ag-deposited n-type 0.001-Ω·cm Si particles (n0.001-Ag) are separately used as an anode material to assemble coin cells, of which the electrochemical performances are investigated. For the matching of work function between n-type 1-Ω·cm Si (n1) and Ag, n1-Ag shows discharge specific capacity of up to 683 mAh·g-1 at a current density of 8.4 A·g-1, which is 40% higher than that of n0.001-Ag. Furthermore, the resistivity of n1-Ag is lower than half that of n0.001-Ag. Due to the mismatch of work function between n-type 0.001-Ω·cm Si (n0.001) and Ag, the discharge specific capacity of n0.001-Ag is 250.2 mAh·g-1 lower than that of n1-Ag after 100 cycles. 参考文献 | 相关文章 | 计量指标

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Synergistic effect of total ionizing dose on single event effect induced by pulsed laser microbeam on SiGe heterojunction bipolar transistor 张晋新, 郭红霞, 潘霄宇, 郭旗, 张凤祁, 冯娟, 王信, 魏莹, 吴宪祥 2018 (10):  108501-108501.  doi: 10.1088/1674-1056/27/10/108501 摘要 ( 692 )   HTML ( 0 )   PDF(1529KB) ( 203 )   The synergistic effect of total ionizing dose (TID) on single event effect (SEE) in SiGe heterojunction bipolar transistor (HBT) is investigated in a series of experiments. The SiGe HBTs after being exposed to 60Co γ irradiation are struck by pulsed laser to simulate SEE. The SEE transient currents and collected charges of the un-irradiated device are compared with those of the devices which are irradiated at high and low dose rate with various biases. The results show that the SEE damage to un-irradiated device is more serious than that to irradiated SiGe HBT at a low applied voltage of laser test. In addition, the γ irradiations at forward and all-grounded bias have an obvious influence on SEE in the SiGe HBT, but the synergistic effect after cutting off the γ irradiation is not significant. The influence of positive oxide-trap charges induced by TID on the distortion of electric field in SEE is the major factor of the synergistic effect. Moreover, the recombination of interface traps also plays a role in charge collection. 参考文献 | 相关文章 | 计量指标

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Shortening turn-on delay of SiC light triggered thyristor by 7-shaped thin n-base doping profile 王曦, 蒲红斌, 刘青, 安丽琪 2018 (10):  108502-108502.  doi: 10.1088/1674-1056/27/10/108502 摘要 ( 766 )   HTML ( 0 )   PDF(741KB) ( 174 )   A new 4H-SiC light triggered thyristor (LTT) with 7-shaped thin n-base doping profile is proposed and simulated using a two-dimensional numerical method. In this new structure, the bottom region of the thin n-base has a graded doping profile to induce an accelerating electric field and compensate for the shortcoming of the double-layer thin n-base structure in transmitting injected holes. In addition, the accelerating electric field can also speed up the transmission of photon-generated carriers during light triggering. As a result, the current gain of the top pnp transistor of the SiC LTT is further increased. According to the TCAD simulations, the turn-on delay time of the SiC LTT decreases by about 91.5% compared with that of previous double-layer thin n-base SiC LTT. The minimum turn-on delay time of the SiC LTT is only 828 ns, when triggered by 100 mW/cm2 ultraviolet light. Meanwhile, there is only a slight degradation in the forward blocking characteristic. 参考文献 | 相关文章 | 计量指标

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Phase transition and charge transport through a triple dot device beyond the Kondo regime 熊永臣, 朱占武, 贺泽东 2018 (10):  108503-108503.  doi: 10.1088/1674-1056/27/10/108503 摘要 ( 688 )   HTML ( 0 )   PDF(400KB) ( 199 )   Semiconductor quantum dot structure provides a promising basis for quantum information processing, within which to reveal the quantum phase and charge transport is one of the most important issues. In this paper, by means of the numerical renormalization group technique, we study the quantum phase transition and the charge transport for a parallel triple dot device in the strongly correlated limit, focusing on the effect of inter-dot hopping t beyond the Kondo regime. We find the quantum behaviors depend closely on the initial electron number on the dots, and the present model may map to single, double, and side-coupled impurity models in different parameter spaces. An orbital spin-1/2 Kondo effect between the conduction leads and the bonding orbital, and several magnetic-frustration phases are demonstrated when t is adjusted to different regimes. To understand these phenomena, a canonical transformation of the energy levels is given, and important physical quantities with respect to increasing t and necessary theoretical discussions are shown. 参考文献 | 相关文章 | 计量指标

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Effects of edge hydrogenation and Si doping on spin-dependent electronic transport properties of armchair boron-phosphorous nanoribbons 赵虹, 彭丹丹, 何军, 李新梅, 龙孟秋 2018 (10):  108504-108504.  doi: 10.1088/1674-1056/27/10/108504 摘要 ( 636 )   HTML ( 0 )   PDF(1350KB) ( 259 )   In this article, the spin-dependent electronic and transport properties of the armchair boron-phosphorous nanoribbons (ABPNRs) are mainly studied by using the non-equilibrium Green function method combined with the spin-polarized density function theory. Our calculated electronic structures indicate that the edge hydrogenated ABPNRs exhibit a ferromagnetic bipolar magnetic semiconductor property, and that the Si atom doping can make ABPNRs convert into up-spin dominated half metal. The spin-resolved transport property results show that the doped devices can realize 100% spin-filtering function, and that the interesting negative differential resistance phenomenon can be observed. Our calculations suggest that the ABPNRs can be constructed as a spin heterojunction by introducing Si doping partially, and it would be used as a spin-diode for nano-spintronics in future. 参考文献 | 相关文章 | 计量指标

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Controllability of heterogeneous interdependent group systems under undirected and directed topology 裴惠琴, 陈世明 2018 (10):  108901-108901.  doi: 10.1088/1674-1056/27/10/108901 摘要 ( 609 )   HTML ( 0 )   PDF(1608KB) ( 191 )   The controllability problem of heterogeneous interdependent group systems with undirected and directed topology is investigated in this paper. First, the interdependent model of the heterogeneous system is set up according to the difference of individual characteristics. An extended distributed protocol with the external sliding-mode control is designed, under which it is shown that a heterogeneous interdependent group system is controllable when the corresponding communication topology is controllable. Then, using the network eigenvalue method, the driving individuals are determined for a heterogeneous system with undirected topology. Under directed topology, the maximum match method is utilized to confirm the driving individuals. Some sufficient and necessary conditions are presented to assure that the heterogeneous interdependent group system is structurally controllable. Via theoretical analysis, the controllability of heterogeneous interdependent systems is related to the interdependent manner and the structure of the heterogeneous system. Numerical simulations are provided to demonstrate the effectiveness of the theoretical results. 参考文献 | 相关文章 | 计量指标

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Synchronization performance in time-delayed random networks induced by diversity in system parameter 钱郁, 高红艳, 姚成贵, 崔晓华, 马军 2018 (10):  108902-108902.  doi: 10.1088/1674-1056/27/10/108902 摘要 ( 622 )   HTML ( 0 )   PDF(5940KB) ( 247 )   Synchronization rhythm and oscillating in biological systems can give clues to understanding the cooperation and competition between cells under appropriate biological and physical conditions. As a result, the network setting is appreciated to detect the stability and transition of collective behaviors in a network with different connection types. In this paper, the synchronization performance in time-delayed excitable homogeneous random networks (EHRNs) induced by diversity in system parameters is investigated by calculating the synchronization parameter and plotting the spatiotemporal evolution pattern, and distinct impacts induced by parameter-diversity are detected by setting different time delays. It is found that diversity has no distinct effect on the synchronization performance in EHRNs with small time delay being considered. When time delay is increased greatly, the synchronization performance of EHRN degenerates remarkably as diversity is increased. Surprisingly, by setting a moderate time delay, appropriate parameter-diversity can promote the synchronization performance in EHRNs, and can induce the synchronization transition from the asynchronous state to the weak synchronization. Moreover, the bistability phenomenon, which contains the states of asynchronous state and weak synchronization, is observed. Particularly, it is confirmed that the parameter-diversity promoted synchronization performance in time-delayed EHRN is manifested in the enhancement of the synchronization performance of individual oscillation and the increase of the number of synchronization transitions from the asynchronous state to the weak synchronization. Finally, we have revealed that this kind of parameter-diversity promoted synchronization performance is a robust phenomenon. 参考文献 | 相关文章 | 计量指标