By making use of the φ-mapping topological current theory, this
paper shows that the Gauss--Bonnet--Chern density (the
Euler--Poincaré characteristic χ(M) density) can be
expressed in terms of a smooth vector field φ and take
the form of δ(φ), which means that only the zeros of
φ contribute to χ(M). This is the elementary fact of
the Hopf theorem. Furthermore, it presents that a new topological
tensor current of \tilde {p}-branes can be derived from the
Gauss--Bonnet--Chern density. Using this topological current, it
obtains the generalized Nambu action for multi \tilde p-branes.

We study the effect of incubation period on epidemic spreading in
the Barabasi--Albert scale-free network and the Watts--Strogatz
small world network by using a
Suspectable-Incubated-Infected-Suspectable model. Our analytical
investigations show that the epidemic threshold is independent of
incubation period in both networks, which is verified by our
large-scale simulation results. We also investigate the effect of
incubation period on the epidemic dynamics in a supercritical
regime. It is found that with the increase of incubation period
Ω , a damped oscillation evolution of ρ_{T}(the
ratio of persons in incubated state) appears and the time needed to
reach a saturation value increases. Moreover, the steady value of
ρ_{T} increases and approaches to an asymptotic constant with
the value of {\it\Omega} increasing. As a result, the infected
ratio ρ_{I} decreases with the increase of Ω
according to a power law.

This paper studies a new conserved quantity which can be called
generalized Mei conserved quantity and directly deduced by Mei
symmetry of Birkhoff system. The conditions under which the Mei
symmetry can directly lead to generalized Mei conserved quantity and
the form of generalized Mei conserved quantity are given. An example
is given to illustrate the application of the results.

The propagation of coupled flexural-torsional vibration in the
periodic beam including warping effect is investigated with the
transfer matrix theory. The band structures of the periodic beam,
both including warping effect and ignoring warping effect, are
obtained. The frequency response function of the finite periodic
beams is simulated with finite element method, which shows large
vibration attenuation in the frequency range of the gap as expected.
The effect of warping stiffness on the band structure is studied and
it is concluded that substantial error can be produced in high
frequency range if the effect is ignored. The result including
warping effect agrees quite well with the simulated result.

This paper proposes two lattice traffic models by taking into
account the drivers' delay in response. The lattice versions of the
hydrodynamic model are described by the differential-difference
equation and difference-difference equation, respectively. The
stability conditions for the two models are obtained by using the
linear stability theory. The modified KdV equation near the critical
point is derived to describe the traffic jam by using the reductive
perturbation method, and the kink--antikink soliton solutions related
to the traffic density waves are obtained. The results show that the
drivers' delay in sensing headway plays an important role in jamming
transition.

This paper introduces two types of two-mode excited entangled
coherent states (TMEECSs) |Ψ_{±}(α,m,n)>, studies
their entanglement characteristics, and investigates the influence
of photon excitations on quantum entanglement. It shows that for the
state |Ψ_{+}(α,m,m)> the two-mode photon excitations
affect seriously entanglement character while the state
|Ψ_{-}(α,m,m)> is always a maximally entangled state,
and shows how such states can be produced by using cavity quantum
electrodynamics and quantum measurements. It finds that the
entanglement amount of the TMEECSs is larger than that of the
single-mode excited entangled coherent states with the same photon
excitation number.

The security of quantum secret sharing based on entanglement
swapping is revisited and a participant attack is presented. In this
attack two dishonest agents together can illegally recover the
secret quantum state without the help of any other controller, and
it will not be detected by any other users. Furthermore, by
modifying the distribution process of particles and adding a
detection step after each distribution process, we propose an
improved protocol which can resist this kind of attack.

This paper investigates bipartite entanglement of a two-qubit system
with anisotropic couplings under an inhomogeneous magnetic field.
This work is mainly to investigate the characteristics of a
Heisenberg XYZ chain and obtains some meaningful results. By the
concept of negativity, it finds that the inhomogeneity of magnetic
field may induce entanglement and the critical magnetic field is
independent of J_{z}. The inhomogeneous magnetic field can
increase the value of critical magnetic field B_{c}. It also finds
that the magnetic field not only suppresses the entanglement but
also can induce it to revival for some time.

This paper reconsiders carefully the possibility of using the
Smolin bound entangled states as the carrier for sharing quantum
secret. It finds that the process of quantum secret sharing based on
Smolin states has insecurity though the Smolin state was reported to
violate maximally the two-setting Bell-inequality. The general proof
is given.

Motivated by the wise idea of entanglement witness (EW), we present
an inequivalent entanglement witness (IEEW) that can analogously
classify certain eigenstates entangled in inequivalent ways under
stochastic local operations and classical communication (SLOCC) in
the Heisenberg spin chain. Since the IEEW is the absolute value of
magnetization | M| that is a macroscopically
measurable quantity, our conclusions provide a macroscopic method to
detect inequivalent entanglement between microscopic spins, on the
one hand, and clearly show that inequivalent entanglement can yield
different macroscopic effects, on the other hand.

In the system with two two-level ions confined in a linear trap,
this paper presents a simple scheme to realize the quantum phase
gate (QPG) and the swap gate beyond the Lamb--Dicke (LD) limit.
These two-qubit quantum logic gates only involve the internal states
of two trapped ions. The scheme does not use the vibrational mode as
the data bus and only requires a single resonant interaction of the
ions with the lasers. Neither the LD approximation nor the auxiliary
atomic level is needed in the proposed scheme. Thus the scheme is
simple and the interaction time is very short, which is important in
view of decoherence. The experimental feasibility for achieving this
scheme is also discussed.

This paper investigates the change of entanglement for transmitting
an arbitrarily entangled two-qubit pure state via one of three
typical kinds of noisy quantum channels: amplitude damping
quantum channel, phase damping quantum channel and depolarizing
quantum channel. It finds, in all these three cases, that the output
distant entanglement (measured by concurrence) reduces
proportionately with respect to its initial amount, and the decaying
ratio is determined only by the noisy characteristics of quantum
channels and independent of the form of initial input state.

This paper presents a new exact inflationary solution to the
non-minimally coupled scalar field. The inflation is driven by the
evolution of a scalar field with inflation potential V(φ ) =
(λ/ 4)φ^{4}+ b_{1} φ^{2}+ b_{2} + b_{3} φ^{-2}
+ b_{4} φ^{-4}. The spectral index of the scalar density
fluctuations n_{s} is consistent with the result of WMAP3
(Wilkinson Microwave Anisotropy Probe 3) for λCDM
(Lambda-Cold Dark Matter). This model relaxes the constraint to the
quartic coupling constant. And it can enter smoothly into a
radiation-dominated stage when inflation ends.

The chirality-asymmetry macroscopic force mediated by light
pseudoscalar particles between α -quartz and some achiral
matter is studied. If this force between achiral source mass and
α -quartz with some chirality is attractive, it will become
repulsive when the chirality of the α -quartz crystal is
changed. According to the tested limits of the coupling constant
g_{s} g_{p} /\hbar c< 1.5× 10^{-24} at the
Compton wavelength λ = 10^{-3} m, the force (F) between
a 0.08× 0.08× 0.002 m^{3} block of α -quartz
and a 0.08× 0.08× 0.01 m^{3} copper block with a
separation being 0.5× 10^{-3} \mbox{m} in between, is
estimated from the published data at less than 4.64× 10^{-24} N, i.e. F < 4.64× 10^{-24} N.

In the study of complex networks (systems), the scaling phenomenon
of flow fluctuations refers to a certain power-law between the mean
flux (activity) < F_{i}> of the i-th node and its
variance σ_{i} as F_{i ∝ <Fiα. Such scaling laws are found to be prevalent both in
natural and man-made network systems, but the understanding of their
origins still remains limited. This paper proposes a non-stationary
Poisson process model to give an analytical explanation of the
non-universal scaling phenomenon: the exponent α varies
between 1/2 and 1 depending on the size of sampling time window
and the relative strength of the external/internal driven forces of
the systems. The crossover behaviour and the relation of fluctuation
scaling with pseudo long range dependence are also accounted for by
the model. Numerical experiments show that the proposed model can
recover the multi-scaling phenomenon.}

The thermostatistic properties of a q-generalized Fermi system
trapped in a generic power-law potential are studied, based on the
generalized statistic distribution derived from the Tsallis entropy.
The total number of particles, the total energy, and the heat
capacity at constant volume of the system are derived. The
thermostatistic characteristics of the system are discussed in
detail. It is found that the thermostatistic properties of such a
system depend closely on parameter q, dimensional number of the
space, kinetic characteristics of particles and shapes of the
external potential, and the external potential has a great influence
on the thermostatistic properties of the system. Moreover, it is
shown that the results obtained here are very general and can be
used to unify the description of the nonextensive and extensive
thermostatistic properties of a class of Fermi systems trapped in
different external potentials so that the important conclusions of
many typical Fermi systems in the literature may be directly derived
from the present paper.

This paper investigates the phenomenon of stochastic resonance in a
single-mode laser driven by quadratic pump noise and
amplitude-modulated signal. A new linear approximation approach is
advanced to calculate the signal-to-noise ratio. In the linear
approximation only the drift term is linearized, the multiplicative
noise term is unchangeable. It is found that there appears not only
the standard form of stochastic resonance but also the broad sense
of stochastic resonance, especially stochastic multiresonance
appears in the curve of signal-to-noise ratio as a function of
coupling strength λ between the real and imaginary parts of
the pump noise.

This paper reports a new hyperchaotic system evolved from the
three-dimensional Lü chaotic system. The Lyapunov exponents
spectrum and the bifurcation diagram of this new hyperchaotic system
are obtained. Hyperchaotic attractor, periodic orbit and chaotic
attractor are obtained by computer simulation. A circuit is designed
to realize this new hyperchaotic system by electronic workbench.

This paper reports that the performance of permanent magnet
synchronous motor (PMSM) degrades due to chaos when its systemic
parameters fall into a certain area. To control the undesirable
chaos in PMSM, a nonlinear controller, which is simple and easy to
be constructed, is presented to achieve finite-time chaos control
based on the finite-time stability theory. Computer simulation
results show that the proposed controller is very effective. The
obtained results may help to maintain the industrial servo driven
system's security operation.

By using the well-known Ikeda model as the node dynamics, this paper
studies synchronization of time-delay systems on small-world
networks where the connections between units involve time delays. It
shows that, in contrast with the undelayed case, networks with
delays can actually synchronize more easily. Specifically, for
randomly distributed delays, time-delayed mutual coupling suppresses
the chaotic behaviour by stabilizing a fixed point that is unstable
for the uncoupled dynamical system.

This paper reports that two identical external-cavity-diode-laser
(ECDL) based spectrometers are constructed at 634 nm referencing on
the hyperfine B-X transition R(80)8-4 of ^{127}I_{2}. The lasers
are stabilized on the Doppler-free absorption signals using the
third-harmonic detection technique. The instability of the
stabilized laser is measured to be 2.8×10^{-12} (after
1000 s) by counting the beat note between the two lasers. The
absolute optical frequency of the transition is, for the first time,
determined to be 472851936189.5 kHz by using an optical frequency
comb referenced on the microwave caesium atomic clock. The
uncertainty of the measurement is less than 4.9 kHz.

The improved version of Los Alamos model with the multi-modal fission approach is used to analyse the prompt fission neutron spectrum and multiplicity for the neutron-induced fission of ^{237}Np. The spectra of neutrons emitted from fragments for the three most dominant fission modes (standard I, standard II and superlong) are calculated separately and the total spectrum is synthesized. The multi-modal parameters contained in the spectrum model are determined on the basis of experimental data of fission fragment mass distributions. The calculated total prompt fission neutron spectrum and multiplicity are better agreement with the experimental data than those obtained from the conventional treatment of the Los Alamos model.

The astrophysical reaction rate of ^{12}C(α, γ)^{16}O plays a key role in massive star evolution. However, this reaction rate and its uncertainties have not been well determined yet, especially at T_{9}=0.2. The existing results even disagree with each other to a certain extent. In this paper, the E1, E2 and total (E1+E2) ^{12}C(α,γ)^{16}O reaction rates are calculated in the temperature range from T_{9}=0.3 to 2 according to all the available cross section data. A new analytic expression of the ^{12}C(α,γ)^{16}O reaction rate is brought forward based on the reaction mechanism. In this expression, each part embodies the underlying physics of the reaction. Unlike previous works, some physical parameters are chosen from experimental results directly, instead of all the parameters obtained from fitting. These parameters in the new expression, with their 3∑gma fit errors, are obtained from fit to our calculated reaction rate from T_{9}=0.3 to 2. Using the fit results, the analytic expression of ^{12}C(α,γ)^{16}O reaction rate is extrapolated down to T_{9}=0.05 based on the underlying physics. The ^{12}C(α,γ)^{16}O reaction rate at T_{9}=0.2 is (8.78\pm1.52)×10^{15} cm^{3}s^{-1}mol^{-1}. Some comparisons and discussions about our new ^{12}C(α, γ)^{16}O reaction rate are presented, and the contributions of the reaction rate correspond to the different part of reaction mechanism are given. The agreements of the reaction rate below T_{9}=2 between our results and previous works indicate that our results are reliable, and they could be included in the astrophysical reaction rate network. Furthermore, we believe our method to investigate the ^{12}C(α,γ)^{16}O reaction rate is reasonable, and this method can also be employed to study the reaction rate of other astrophysical reactions. Finally, a new constraint of the supernovae production factor of some isotopes are illustrated according to our ^{12}C(α,γ)^{16}O reaction rates.

This paper reports on an experiment for testing natural nuclear fusion at low temperature searching for evidence of the origin of ^{3}He from natural nuclear fusion in deep Earth. The experiment was carried out using deuterium-loaded titanium foil samples and powder sample. Detection of charged particle was carried out using a low-level charged particle spectrometer. An Al foil was used as an energy absorber for identification of charged particle. Although the counting rate is very low in the experiment, the emission of energetic particle from the sample is observed and the particle is identified as a proton having energy about 2.8 MeV after exiting the titanium sample. This work provides a positive result for the emission of charged particle in the deuterium-loaded titanium foil samples at low temperature, but a negative result for the deuterium-loaded titanium powder sample. The average reaction yield is deduced to be (0.46±0.08) protons/h for the foil samples. With the suggestion that the proton originates from d--d reaction, we calculate the reaction rate for d--d reaction, and the obtained result is 1.4× 10^{-24} fusion/d--d\cdot sec. The negative result of the deuterium-loaded titanium powder sample suggests that the reaction yield might be correlated with the density or microscopic variables of deuterium-loaded titanium materials. The negative result also indicates that d--d reaction catalysed by μ-meson from cosmic ray can be excluded in the samples in this experiment.

This paper obtains the lowest-energy geometric structures and the
electronic and magnetic properties of small CuNi_{N} clusters by
using all-electron density functional theory. The calculated results
reveal that the Cu atom prefers to occupy the apical site when N
≤ 9 and for the clusters with N=10, the Cu atom starts to
encapsulate in the cage. The CuNi_{7}} and CuNi_{9} are magic
clusters. The magnetism correlates closely with the symmetry of the
clusters. For these clusters, the charge tends to transfer from the
nickel atoms to the copper atoms. It finds that the doping of Cu
atom decreases the stability of pure Ni_{N} clusters.

Song Zhang-Yong, Yang Zhi-Hu, Shao Jian-Xiong, Cui Ying, Zhang Hong-Qiang, Ruan Fang-Fang, Du Juan, Gao Zhi-Min, Yu De-Yang, Chen Xi-Meng, Cai Xiao-Hong

Chin. Phys. B 2009, 18 (4): 01443; doi: 10.1088/1674-1056/18/4/026
Full Text: PDF (197KB) (
626
)

This paper reports that the K x-ray spectra of the thin target
_{47}Ag, _{48}Cd, _{49}In and _{50}Sn were measured by an
HPGe semi-conductor detector in collisions with 84.5~MeV _{6}C^{4+} ions. Our experiment revealed the Kα x-ray energy
shifts were not obvious and the Kβ_{1} x-ray energy shifts were
about 90～110~eV. The simple model of Burch \emph{et al} has
been previously used to calculate the K x-ray energy shifts due to an
additional vacancy in 2p orbit. The present work extends the
model of Burch to calculate the x-ray energy shifts of multiple
ionized atoms induced by heavy ions with kinetic energy of MeV/u. In
addition to our experimental results, many other experimental
results are compared with the calculated values by using the model.

The influence of the local-field on the photoabsorption cross
section of the atomic silver is studied in detail by using the
Clausius--Mossotti (CM) model and the Onsager model separately. The
variations of the photoabsorption cross section of atomic silver
with number density and radius of the environmental interaction
cavity are studied systematically by using more general expressions
for the photoabsorption cross sections, proposed by Sun et
al recently. It has proved to be reasonable to model the optical
response properties of bulky material by coupling the property of
isolated atom with the environmental effects in the present work.

This paper studies the harmonic generation of the hydrogen atom
subjected to a collinear bichromatic laser field by numerically
solving the time-dependent Schr?dinger equation using the
split-operator pseudo-spectral method. By adding a frequency
variation to the additional field, the contributions of different
pathways to particular order harmonic generation can be isolated.
The quantum interference pattern between harmonic pathways, which
influences the harmonic intensity, is found to be either
constructive or destructive with respect to different relative phase
of the two field components. Detailed description of up to the
35th-order harmonics and the harmonic pathways for a wide range of
field parameters is presented.

This paper demonstrates the femtosecond time-resolved coherent
anti-Stokes Raman scattering by using folded BOXCARS geometry where
an ultrashort broadband coherent white light continuum was used as
Stokes pulse, and carries out the non-contact detection at long
distance. The CARS signal is so easy to be detected that it can be
seen even by nude eye. The C--H bonds of chloroform or PMMA were
detected and the vibration modes belonging to the side chain and the
main chain in PMMA were also compared. Their vibrational
characteristics involved decay process and quantum beating were
discussed. This modified CARS experimental technique could make up
the deficiency of traditional CARS technique.

This paper reports that the tunable self-phase-stabilized infrared
laser pulses have been generated from a two-stage optical parametric
amplifier. With an 800 nm pump source, the output idler pulses are
tunable from 1.3 μm to 2.3 μm, and the maximum output
energy of the idler pulses is higher than 1 mJ at 1.6 μm by
using 6 mJ pump laser. A carrier-envelope phase fluctuation of
～ 0.15 rad (rms) for the idler pulses is measured for longer
than one hour by using a home build f-to-2f interferometer.

The photoelectron energy spectra (PESs) excited by narrow bandwidth
attosecond x-ray pulses in the presence of a few-cycle laser are
quantum-mechanically calculated. Transfer equations are used to
reconstruct the detailed temporal structure of an attosecond x-ray
pulse directly from a measured PES. Theoretical analysis shows that
the temporal uncertainties of the pulse reconstruction depend on the
x-ray bandwidth. The procedure of pulse reconstruction is direct and
simple without making any previous pulse assumption, data fitting
analysis and time-resolved measurement of PESs. The temporal
measurement range is half of a laser optical cycle.

This paper reports that the (2+1) resonance enhanced multi-photon
ionization spectra of SH radical in external fields are simulated
using the split-operator scheme of time-dependent wave-packet
method. Two ionic states, i.e.~a^{1}Δ and b^{1}∑^{+}, are
involved in the simulation. It gives the simulated photoelectron
spectra, the population in each electronic state, as well as the
projection of the wave-packet in each electronic state on different
vibrational states. These results show that the so-called four-state
model can represent the experimental results well.

This paper firstly reports a theoretical study of elastic scattering
properties in a mixture of ^{23}Na and ^{7}Li atoms at cold and
ultracold temperatures in detail. Based on the new constructed
accurate singlet X^{1}∑_{g}^{+} and the triplet a^{3}∑_{u}^{+}
states interatomic potentials for ^{23}Na^{7}Li mixture, it
calculates the scattering lengths and the effective ranges by three
computational methods, and obtains good agreements. Using the mass
scaling method, it also calculates ^{23}Na^{6}Li scattering
lengths and s-wave and total elastic cross sections, whose rich
resonance structures were found and interpreted in terms of
quasibound diatomic levels trapped behind a centrifugal barrier.

The ground-state configurations of the Nb_{n} (n= 2--11)
clusters are studied through the first-principles calculations. It
is found that niobium clusters (n= 2--11) tend to form compact
structures with low symmetry. The clusters with 4, 8 and 10 atoms
are found to be magic and have relatively large highest
occupied--lowest unoccupied molecular orbital (HOMO-LUMO) gaps. The
Nb_{n} clusters possess low magnetic moments, which exhibit an
odd-even oscillational character. The analyses of calculated
electronic density and population of the lowest-energy niobium
clusters for n= 2, 3, 5, 7, 9, 11 show that the total magnetic
moments of Nb_{n} originate mainly from a few Nb atoms with longer
spacings between them in most cases, while they are located on two
Nb atoms for n= 2, 3, 5. The total magnetic moments come mainly
from the 4d local moments but with the exception of the Nb_{5}
cluster.

This paper reports that a one-colour fs pump--probe measurement has
been carried out for studying photoionization/photodissociation of
cyclohexanone (C_{6}H_{10}O) in intense laser field. Two of the
fragments from cyclohexanone, C_{2}H_{3}^{+} and
C_{3}}H_{3}^{+}, are studied under 800 nm laser pump--probe and
the results obtained show similar time evolutions. It proposes a
feasible model for analysing the experimental observations of the
one-colour {fs} pump--probe measurement. The results demonstrate
that as an intermediate product, the excited molecular parent ions
play a very important role in photionization/photodissociation
processes in intense laser field.

A current based hybrid method (HM) is proposed which combines the method
of moment (MOM) with the Kirchhoff approximation (KA) for the analysis
of scattering interaction between a two-dimensional (2D) infinitely
long conducting target with arbitrary cross section and a
one-dimensional (1D) Gaussian rough surface. The electromagnetic
scattering region in the HM is split into KA region and MOM region.
The electric field integral equation (EFIE) in MOM region (target)
is derived, the computational time of the HM depends mainly on the
number of unknowns of the target. The bistatic scattering
coefficient for the infinitely long cylinder above the rough surface
with Gaussian roughness spectrum is calculated, and the numerical
results are compared and verified with those obtained by the
conventional MOM, which shows the high efficiency of the HM.
Finally, the influence of the size, location of the target, the rms
height and correlation length of the rough surface on the bistatic
scattering coefficient with different polarizations is discussed in
detail.

Based on the fact that a two-mode squeezed number state is a
two-variable Hermite polynomial excitation of the two-mode squeezed
vacuum state, the result of one-mode l-photon measurement for the
two-mode squeezed number state S_{2}| m,n>
is discussed. It is found that a remaining field-mode simultaneously
collapses into a number state | n-m+l> with
the coefficient being a Jacobi polynomial of n,m
and l, which manifestly exhibits the entanglement
between the two modes, i.e. it depends on the number-difference
between the two modes. The second mode collapses into an excited
coherent state when the first mode is measured as a coherent state.

In this paper, we investigate the entropy squeezing for a two-level
atom interacting with two quantized fields through Raman coupling.
We obtain the dynamical evolution of the total system under the
influence of intrinsic decoherence when the two quantized fields are
prepared in a two-mode squeezing vacuum state initially. The effects
of the field squeezing factor, the two-level atomic transition
frequency, the second field frequency and the intrinsic decoherence
on the entropy squeezing are discussed. Without intrinsic
decoherence, the increase of field squeezing factor can break the
entropy squeezing. The two-level atomic transition frequency changes
only the period of oscillation but not the strength of entropy
squeezing. The influence of the second field frequency is
complicated. With the intrinsic decoherence taken into
consideration, the results show that the stronger the intrinsic
decoherence is, the more quickly the entropy squeezing will
disappear. The increase of the atomic transition frequency can
hasten the disappearance of entropy squeezing.

This paper investigates the nonlinear evolution of the pulse probe
field in an asymmetric coupled-quantum well driven coherently by a
pulse probe field and two controlled fields. This study shows that,
by choosing appropriate physical parameters, self-modulation can
precisely balance group velocity dispersion in the investigated
system, leading to the formation of ultraslow optical solitons of
the probe field. The proposed scheme may lead to the development of
the controlled technique of optical buffers and optical delay lines.

In this paper by virtue of the technique of integration within an
ordered product (IWOP) of operators and the intermediate
coordinate-momentum representation in quantum optics, we derive the
normal ordering and antinormal ordering products of the operator
( fQ+gP)^{n} when n is an arbitrary integer. These
products are very useful in calculating their matrix elements and
expectation values and obtaining some useful mathematical formulae.
Finally, the applications of some new identities are given.

The parametric optimization of the Ne--CuBr UV laser excited by
longitudinal pulsed discharge is analysed by using a self-consistent
kinetic model. Consistent characteristics of the optimization
process are obtained by comparing with the experimental results.
Simulation results show that neon ions come into being along with
considerable depletion of the ground-state copper atoms. And the
optimization of the discharge tube diameter is the tradeoff between
the specific output photon density and the total active volume. Both
the optimal neon gas pressure and the optimal reservoir temperature
result from the balance between the neon ion density and the
ground-state copper atom density to arrive at a maximum of their
product.

This paper investigates the temperature field distribution and
thermal focal length within a laser diode array (LDA) end-pumped
YVO_{4}/Nd:YVO_{4} rectangular composite crystal. A general
expression of the temperature field distribution within the
Nd:YVO_{4} rectangular crystal was obtained by analysing the
characteristics of the Nd:YVO_{4} crystal and solving the Poisson
equation with boundary conditions. The temperature field
distributions in the Nd:YVO_{4} rectangular crystal for the
YVO4/Nd:YVO_{4} composite crystal and the Nd:YVO_{4} single
crystal are researched respectively. Calculating the thermal focal
length within the Nd:YVO_{4} rectangular crystal was done by an
analysis of the additional optical path differences (OPD) caused by
heat, which was very identical with experimental results in this
paper. Research results show that the maximum relative temperature
on the rear face of the Nd:YVO_{4} crystal in the composite
crystal is 150 K and the thermal focal length is 35.7 mm when the
output power of the LDA is 22 W. In the same circumstances, the
experimental value of the thermal focal length is 37.4 mm. So the
relative error between the theoretical analysis and the experimental
result is only 4.5%. With the same conditions, the thermal focal
length of the Nd:YVO_{4} single crystal is 18.5 mm. So the
relative rate of the thermal focal length between the
YVO4/Nd:YVO_{4} crystal and the Nd:YVO_{4} crystal is 93%.
So, the thermal stability of the output power and the beam quality
of the YVO_{4}/Nd:YVO_{4} laser is more advantageous than the
laser with Nd:YVO_{4} single crystal.

Asymmetric tree-like branched networks are explored by geometric
algorithms. Based on the network, an analysis of the thermal
conductivity is presented. The relationship between effective
thermal conductivity and geometric structures is obtained by using
the thermal-electrical analogy technique. In all studied cases, a
clear behaviour is observed, where angle (δ ,θ ) among
parent branching extended lines, branches and parameter of the
geometric structures have stronger effects on the effective thermal
conductivity. When the angle δ is fixed, the optical
diameter ratio β^{*} is dependent on angle θ .
Moreover, γ and m are not related to β ^{*} . The
longer the branch is, the smaller the effective thermal conductivity
will be. It is also found that when the angle θ < δ / 2,
the higher the iteration m is, the lower the thermal conductivity
will be and it tends to zero, otherwise, it is bigger than zero.
When the diameter ratio β _{1}< 0.707 and angle δ is
bigger, the optimal k of the perfect ratio increases with the
increase of the angle δ ; when β _{1}> 0.707, the
optimal k decreases. In addition, the effective thermal
conductivity is always less than that of single channel material.
The present results also show that the effective thermal
conductivity of the asymmetric tree-like branched networks does not
obey Murray's law.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

Hybrid nematic films have been studied by Monte Carlo simulations
using a lattice spin model, in which the pair potential is spatially
anisotropic and dependent on elastic constants of liquid crystals.
We confirm in the thin hybrid nematic film the existence of a
biaxially nonbent structure and the structure transition from the
biaxial to the bent-director structure, which is similar to the
result obtained using the Lebwohl--Lasher model. However, the
step-like director's profile, characteristic for the biaxial
structure, is spatially asymmetric in the film because the pair
potential leads to K_{1} ≠ K_{3}. We estimate the upper cell
thickness to be 69 spin layers, in which the biaxial structure can
be found.

Shielding effect and emission criterion of a screw dislocation near
an interfacial blunt crack are dealt with in this paper. Utilizing
the conformal mapping technique, the closed-form solutions are
derived for complex potentials and stress fields due to a screw
dislocation located near the interfacial blunt crack. The stress
intensity factor on the crack tips and the critical stress intensity
factor for dislocation emission are also calculated. The influence
of the orientation of the dislocation and the morphology of the
blunt crack as well as the material elastic dissimilarity on the
shielding effect and the emission criterion is discussed in detail.
The results show that positive screw dislocations can reduce the
stress intensity factor of the interfacial blunt crack tip
(shielding effect). The shielding effect increases with the increase
of the shear modulus of the lower half-plane, but it decreases with
the increase of the dislocation azimuth angle. The critical loads at
infinity for dislocation emission increases with the increase of
emission angle and curvature radius of blunt crack tip, and the most
probable angle for screw dislocation emission is zero. The present
solutions contain previous results as special cases.

This paper reports that amorphous silicon nitride (a-SiN_{x})
overcoats were deposited at room temperature by microwave ECR plasma
enhanced unbalanced magnetron sputtering. The 2 nm a-SiN_{x}
overcoat has better anti-corrosion properties than that of reference
a-CN_{x} overcoats (2--4.5 nm). The superior anti-corrosion
performance is attributed to its stoichiometric bond structure,
where 94.8% Si atoms form Si--N asymmetric stretching vibration
bonds. The N/Si ratio is 1.33 as in the stoichiometry of
Si_{3}N_{4} and corresponds to the highest hardness of
25.0 GPa. The surface is atomically smooth with RMS <0.2 nm. The
ultra-thin a-SiN_{x} overcoats are promising for hard disks and
read/write heads protective coatings.

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

In this paper the first-principles calculations within local spin
density approximation (LSDA)+U
show that BiFeO_{3} experiences a mixed phase state with P4mm structure being
the intermediate phase before the pressure of phase transition is reached.
The critical pressure for the insulator--metal transition (IMT) is found to be
about 50 GPa. A pressure induced crossover of high-spin states
and low-spin states is observed close to the IMT pressure in R3c
structure. The LSDA+U calculations account well for the mechanism
of the IMT and crossover of spin states predicted in recent
experiment (Ref.[1]).

In this work, the effects of quantum confinement on the ground state
energy of a correlated electron--hole pair in a spherical and in a
disc-like quantum dot have been investigated as a function of
quantum dot size. Under parabolic confinement potential and within
effective mass approximation Ritz's variational method is applied to
Hylleraas-like trial wavefunction. An efficient method for reducing
the main effort of the calculation of terms like r_{eh}^{k}exp{(-λ r_{eh})} is introduced. The main
contribution of the present work is the introduction of integral
transforms which provide the calculation of expectation value of
energy and the related matrix elements to be done analytically over
single-particle coordinates instead of Hylleraas coordinates.

By simulating the electron paramagnetic resonance (EPR) and optical
spectra on the basis of the 120× 120 complete energy matrix,
this paper determines the local lattice structure parameters R_{1}
and R_{2} for MCl:V^{2+} (M=Na, K, Rb) systems at 77 K, 195 K
and RT (room temperature 295 K or 302 K), respectively. The
theoretical results indicate that there exists a compressed
distortion in MCl:V^{2+} systems. Meanwhile, it finds that the
structure parameters R_{1} , R_{2} and |Δ R |(= R_{1} - R_{2} ) increase with the rising temperature.
Subsequently, from the analysis it concludes that the relation of
EPR parameter D vs. Δ R is approximately linear. Finally,
the effects of orbital reduction factor k on the g factors for
the three systems have been discussed.

This paper reports that a novel type of suspended ZnO nanowire field-effect
transistors (FETs) were successfully fabricated using a
photolithography process, and their electrical properties were
characterized by I--V measurements. Single-crystalline ZnO
nanowires were synthesized by a hydrothermal method, they were used
as a suspended ZnO nanowire channel of back-gate field-effect
transistors (FET). The fabricated suspended nanowire FETs showed a
p-channel depletion mode, exhibited high on--off current ratio of
～10^{5}. When V_{DS}=2.5 V, the peak transconductances
of the suspended FETs were 0.396 μS, the oxide capacitance was
found to be 1.547 fF, the pinch-off voltage V_{TH} was about
0.6 V, the electron mobility was on average 50.17 cm^{2}/Vs. The
resistivity of the ZnO nanowire channel was estimated to be
0.96× 10^{2}Ω cm at V_{GS} = 0 V. These
characteristics revealed that the suspended nanowire FET fabricated
by the photolithography process had excellent performance. Better
contacts between the ZnO nanowire and metal electrodes could be
improved through annealing and metal deposition using a focused ion
beam.

Frequency selective surface (FSS) is a two-dimensional periodic
structure which has prominent characteristics of bandpass or
bandblock when interacting with electromagnetic waves. In this
paper, the thickness, the dielectric constant, the element graph and
the arrangement periodicity of an FSS medium are investigated by
Genetic Algorithm (GA) when an electromagnetic wave is incident on
the FSS at a wide angle, and an optimized FSS structure and
transmission characteristics are obtained. The results show that the
optimized structure has better stability in relation to incident
angle of electromagnetic wave and preserves the stability of centre
frequency even at an incident angle as large as 80°, thereby
laying the foundation for the application of FSS to curved surfaces
at wide angles.

AlGaN/GaN high electron mobility transistors (HEMTs) are fabricated by employing SiN passivation, this paper investigates the degradation due to the high-electric-field stress. After the stress, a recoverable degradation has been found, consisting of the decrease of saturation drain current I_{Dsat}, maximal transconductance g_{m}, and the positive shift of threshold voltage V_{TH} at high drain-source voltage V_{DS}. The high-electric-field stress degrades the electric characteristics of AlGaN/GaN HEMTs because the high field increases the electron trapping at the surface and in AlGaN barrier layer. The SiN passivation of AlGaN/GaN HEMTs decreases the surface trapping and 2DEG depletion a little during the high-electric-field stress. After the hot carrier stress with V_{DS}=20 V and V_{GS}=0 V applied to the device for 10^{4} sec, the SiN passivation decreases the stress-induced degradation of I_{Dsat} from
36% to 30%. Both on-state and pulse-state stresses produce comparative decrease of I_{Dsat}, which shows that although the passivation is effective in suppressing electron trapping in surface states, it does not protect the device from high-electric-field degradation in nature. So passivation in conjunction with other technological solutions like cap layer, prepassivation surface treatments, or field-plate gate to weaken high-electric-field degradation should be adopted.

A flattened elliptic ring containing an electron is studied. The
emphasis is placed on clarifying the effect of the flattening. The
localized states are classified into four types according to their
inherent nodes. When the ring becomes more flattened, the total
probability of dipole absorption of each state is found to be
reduced. Furthermore, each spectral line of absorption is found to
shift towards red and may split into a few lines, and these lines as
a whole become more diffusive.

This paper investigates the behaviour of the reverse-bias leakage
current of the Schottky diode with a thin Al inserting layer
inserted between Al_{0.245}Ga_{0.755}N/GaN heterostructure and
Ni/Au Schottky contact in the temperature range of
25--350 °C. It compares with the Schottky diode without
Aluminium inserting layer. The experimental results show that in the
Schottky diode with Al layer the minimum point of I--V curve
drifts to the minus voltage, and with the increase of temperature
increasing, the minimum point of I--V curve returns the 0 point.
The temperature dependence of gate-leakage currents in the novelty
diode and the traditional diode are studied. The results show that
the Al inserting layer introduces interface states between metal and
Al_{0.245}Ga_{0.755}N. Aluminium reacted with oxygen formed
Al_{2}O_{3} insulator layer which suppresses the trap tunnelling
current and the trend of thermionic field emission current. The
reliability of the diode at the high temperature is improved by
inserting a thin Al layer.

Recently GaN-based high electron mobility transistors (HEMTs) have
revealed the superior properties of a high breakdown field and high
electron saturation velocity. Reduction of the gate leakage current
is one of the key issues to be solved for their further improvement.
This paper reports that an Al layer as thin as 3 nm was inserted
between the conventional Ni/Au Schottky contact and n-GaN epilayers,
and the Schottky behaviour of Al/Ni/Au contact was investigated
under various annealing conditions by current--voltage (I--V)
measurements. A non-linear fitting method was used to extract the
contact parameters from the I--V characteristic curves.
Experimental results indicate that reduction of the gate leakage
current by as much as four orders of magnitude was successfully
recorded by thermal annealing. And high quality Schottky contact
with a barrier height of 0.875 eV and the lowest reverse-bias
leakage current, respectively, can be obtained under 12 min
annealing at 450°C in N_{2} ambience.

The molecular thin films of Rose Bengal (RB) embedded in polymethyl
methacrylate matrix are fabricated by using the spin-coating
technique. The macroscopic current--voltage (I--V) characterization
of the film shows that the RB molecule has two conductance switching
states with a high ON/OFF ratio in ambient conditions. The infrared
spectra indicate that intermolecular hydrogen bonds can form in the
RB thin films after their hydrolysis in air. With the
first-principles calculations, we demonstrate that the hydrogen
bonds will be destroyed in concomitance with the conformational
change when the RB molecule switches to its high-conductance state
after applying a voltage.

A numerical model of multilayer organic light-emitting devices is
presented in this article. This model is based on the
drift-diffusion equations which include charge injection, transport,
space charge effects, trapping, heterojunction interface and
recombination process. The device structure in the simulation is
ITO/CuPc (20 nm)/NPD (40 nm)/Alq3 (60 nm)/LiF/Al. There are two
heterojunctions which should be dealt with in the simulation. The
I--V characteristics, carrier distribution and recombination
rate of a device are calculated. The simulation results and measured
data are in good agreement.

This paper systematically investigates the intermediate phases of
YBa_{2}Cu_{3}O_{7-x} (YBCO) film prepared by metalorganic
deposition method using trifluoroacetates (TFA-MOD). According to
x-ray diffraction and Raman analyses, the precursor film decomposed
in a mixture of BaF_{2}, Y_{2}O_{3} and CuO after the
pyrolysis process. Then these intermediate phases converted into
tetragonal YBa_{2}Cu_{3}O_{6.5} at about 725 °C. The
influence of water vapour pressure on the YBa_{2}Cu_{3}O_{7-x}
film growth on LaAlO_{3} single-crystal substrates was also
studied. The films prepared at low water vapour pressures
(40--140 hPa) showed poor electrical performance due to the
a-axis grain structure and impurity phases. However, the films
prepared at 190 hPa exhibited the highest critical temperature of
90 K and the highest J_{c} of 3.8 MA/cm^{2}, which was
attributed to the formation of a purer YBCO phase and stronger
biaxial texture.

This paper reports that the Raman spectra have been recorded on the
metal-organic chemical vapour deposition epitaxially grown GaN
before and after the Mn ions implanted. Several Raman defect modes
have emerged from the implanted samples. The structures around
182 cm^{-1} modes are attributed to the disorder-activated Raman scattering, whereas the 361 cm^{-1} and 660 cm^{-1} peaks are assigned to nitrogen vacancy-related defect scattering. One additional peak at 280 cm^{-1} is attributed to the vibrational mode of gallium vacancy-related defects and/or to disorder activated Raman scattering. A Raman-scattering study of lattice recovery is also presented by rapid thermal annealing at
different temperatures between 700 °C and 1050 °C on Mn implanted GaN epilayers. The behaviour of peak-shape change and
full width at half maximum (FWHM) of the A_{1}(LO) (733 cm^{-1}) and E^{H}_{2} (566 cm^{-1}) Raman modes are explained on the basis of implantation-induced lattice damage in GaN epilayers.

This paper reports that longitudinally oriented CoCrPt thin films with Cr_{85}W_{15} underlayer and CoCr intermediate layer for use of giant magnetoresistance heads were fabricated by magnetron sputtering. Without CoCr intermediate layer, CoCrPt layer deposited directly on Cr_{85}W_{15} underlayer which has a dominant (200) texture exhibits unexpected (10\bar {1}1) texture. After introducing CoCr intermediate layer, the CoCrPt layer shifts into (11\bar {2}0) texture. This article studies the crystallographic hetero-epitaxy relationship between magnetic layer and underlayer in order to understand the appearance of CoCrPt (10\bar {1}1) texture on (200) textured Cr underlayer and the influence of CoCr intermediate layer on the inducement of CoCrPt (11\bar {2}0) texture. The CoCr intermediate layer plays a crucial role in controlling the microstructure and consequently the magnetic properties of the overlying magnetic layer.

This paper investigates the electronic structure and
magnetocrystalline anisotropy of Fe--Ga magnetostrictive material by
means of the full potential-linearized augmented plane-wave method
within the generalized gradient approximation. The 3d-orbit
splitting of Fe atoms in D0_{3}, B2-like and L1_{2} crystalline
structures of Fe--Ga is calculated with consideration of the crystal
field as well as the spin--orbit coupling effect. Because of the
frozen orbital angular momenta of the 3d-orbit for Fe atoms in Fe--Ga
magnetostrictive alloys and the spin--orbit coupling, the
distribution of the electron cloud is not isotropic, which leads to
the anisotropy of exchange interaction between the different atoms.
A method on estimating the magnetocrystalline anisotropy of Fe--Ga
alloys by means of calculating orbit-projected density of states for
Fe atoms is performed. The anisotropic distribution of the electron
cloud of Fe atoms in these three crystalline structures of Fe--Ga is
studied based on the above method showing the highest magnetic
anisotropy for B2-like structure. This qualitative method comes
closer to physical reality with a vivid physical view, which can
evaluate the anisotropy of electron cloud for 3d transition atoms
directly. The calculated results are in good agreement with both the
previous theoretical computation and the tested value on the
magnetic anisotropy constant, which confirms that the electron cloud
anisotropy of Fe atoms could well characterize the
magnetocrystalline anisotropy of Fe--Ga magnetostrictive material.

This paper reports on experimental study of the microwave
properties of a composite material consisting of ferrite and
copper wires. It finds that the slim ferrite rods can modify the
magnetic field distribution through their anisotropy, so that the
ferrite's negative influence on the copper wires' plasma will be
reduced. Left-handed properties are observed even in the specimen
with close stuck ferrite rods and copper wires.

Within the framework of modified Ginzburg--Landau--Devonshire
phenomenological theory, a ferroelectric bilayer film with a
transition layer within each constituent film and an interfacial
coupling between two materials has been studied. Properties
including the Curie temperature and the spontaneous polarization of
a bilayer film composed of two equally thick ferroelectric
constituent films are discussed. The results show that the combined
effect of the transition layer and the interfacial coupling plays an
important role in explaining the interesting behaviour of
ferroelectric multilayer structures consisting of two ferroelectric
materials.

This paper proposes a scheme based on the Potts and Ising models for
simulating polarization switching of polycrystalline ferroelectrics
using the Monte Carlo method. The polycrystalline texture with
different average grain size is produced from the Potts model. Then
Ising model is implemented in the polycrystalline texture to produce
the domain pattern and hysteresis loop. The domain patterns and
hysteresis loops have been obtained for polycrystalline texture with
different average grain size. From the results of domain pattern
evolution process under an applied electric field using this scheme,
an extended domain, which covers more than one grain with
polarization aligned roughly in the same direction, has been
observed during the polarization reversal. This scheme can well
reproduce the basic properties of polycrystalline ferroelectrics and
is a valuable tool for exploring the physical properties of
polycrystalline ferroelectrics.

8000 CROSSDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

In the gravitational field of central mass with electric and
magnetic charges and magnetic moment (CM space-time), this paper
calculates the interference phase of mass neutrino along geodesic in
the radial direction, and discusses the contribution of the electric
and magnetic charges and magnetic moment of the central mass to the
phase.

In the framework of a five-dimensional (5D) bounce cosmological model, a useful function f(z) is obtained by giving a concrete expression of deceleration parameter q(z)=q_{1}+{q_{2}}/{1+ln (1+ z)}. Then using the obtained Hubble parameter H(z) according to the function f(z), we constrain the accelerating universe from
recent cosmic observations: the 192 ESSENCE SNe Ia and the 9 observational H(z) data. The best fitting values of transition redshift z_{T} and current deceleration parameter q_{0} are given as z_{T}= 0.65_{-0.12}^{0.25} and q_{0} = - 0.76_{-0.15}^{+0.15} (1σ). Furthermore, in the 5D bounce model it can be seen that the evolution of equation of state (EOS) for dark energy w_{de} can cross over -1 at about z=0.23 and the current
value w_{0de}= - 1.15<- 1. On the other hand, by giving a concrete expression of model-independent EOS of dark energy w_{de}, in the 5D bounce model we obtain the best fitting values z_{T}= 0.66_{0.08}^{+0.11} and q_{0} = - 0.69_{0.10}^{+0.10} (1σ) from the recently observed data: the 192 ESSENCE SNe Ia, the observational H(z) data, the 3-year Wilkinson Microwave Anisotropy Probe (WMAP), the Sloan Digital Sky Survey (SDSS) baryon acoustic peak and the x-ray gas mass fraction in clusters.

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