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Does the Compelled Cooperation Determine the Structure of a Complex Network?
XUAN Qi, LI Yan-Jun, WU Tie-Jun
Chin. Phys. Lett. 2008, 25 (2):
363-366
.
Cooperation among individuals is considered to play an important role in the evolution of complex networked systems in physical, biological, economical and even epidemiological worlds, but its effects on the development of the
systems is not so clear. We consider a specific kind of primal cooperation in a group of individuals, i.e., an individual never cooperates with others except when compelled to do so. The lowest level of compelled cooperation, in which cooperators share no message or resources, is investigated in the background of complex networks driven by the simple game rock--paper--scissors. Simulation results show that with the evolution of the systems, the cooperation will spread all over the networks, and finally results in systems with modular structures and a scale-free property.
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Spatiotemporal Characteristic of Epidemic Spreading in Mobile Individuals
HE Min-Hua, ZHANG Duan-Ming, PAN Gui-Jun, YIN Yan-Ping, TAN Xin-Yu
Chin. Phys. Lett. 2008, 25 (2):
393-396
.
We numerical simulate the propagation behaviour and people distribution trait of epidemic spreading in mobile individuals by using cellular automaton
method. The simulation results show that there exists a critical value of infected rate fluctuating amplitude, above which the epidemic can spread in whole population. Moreover, with the value of infected rate fluctuating amplitude increasing, the spatial distribution of infected population exhibits the spontaneous formation of irregular spiral waves and convergence phenomena, at the same time, the density of different populations will oscillate automatically with time. What is more, the traits of dynamic grow
clearly and stably when the time and the value of infected rate fluctuating amplitude increasing. It is also found that the maximal proportion of infected individuals is independent of the value of fluctuating amplitude rate, but increases linearly with the population density.
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Fuzzy Impulsive Control of Permanent Magnet Synchronous Motors
LI Dong, WANG Shi-Long, ZHANG Xiao-Hong, YANG Dan, WANG Hui
Chin. Phys. Lett. 2008, 25 (2):
401-404
.
The permanent magnet synchronous motors (PMSMs) may experience chaotic behaviours with systemic parameters falling into a certain area or under certain working conditions, which threaten the secure and stable operation of motor-driven. Hence, it is important to study the methods of controlling or
suppressing chaos in PMSMs. In this work, the Takagi--Sugeno (T-S) fuzzy impulsive control model for PMSMs is established via the T-S modelling methodology and impulsive technology. Based on the new model, the control conditions of asymptotical stability and exponential stability for PMSMs have been derived by the Lyapunov method. Finally, an illustrated example is also given to show the effectiveness of the obtained results.
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Comparison of Phase Synchronizability of Several Regular Networks for Non-Phase-Coherent Attractors
ZHAO Jun-Chan, LU Jun-An, DING Chun
Chin. Phys. Lett. 2008, 25 (2):
417-420
.
Though applying master stability function method to analyse network omplete synchronization has been well studied in chaotic dynamical systems, it does not work well for phase synchronization. Moreover, it is difficult to identify phase synchronization with the angle of rotation for non-phase-coherent attractors. We employ the recurrences plot method to detect phase synchronization for several regular networks with non-phase-coherent attractors. It is found that the coupling strength μ is different for different coupled networks. The coupling strength μ is reduced as completed coupled network scale enlarges, the coupling strength μ of star coupled network is
irrelevant to network scale, and these two regular networks are easier to achieve phase synchronization. However, for ring and chain coupled networks, the larger the phase synchronization couple strength μ is, the larger the network scale is, and it is more difficult to achieve phase synchronization. For same scale network, once ring coupled structure becomes a chain coupled structure, phase synchronization becomes much more difficult.
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Inverse Scattering Transform for the Derivative Nonlinear Schrodinger Equation
YANG Chun-Nuan, YU Jia-Lu, CAI Hao, HUANG Nian-Ning
Chin. Phys. Lett. 2008, 25 (2):
421-424
.
Since the Jost solutions of the derivative nonlinear Schrodinger equation do not tend to the free Jost solutions, when the spectral parameter tends to
infinity(|λ| → ∞), the usual inverse scattering transform (IST) must be revised. If we take the parameter k=λ-1 as the basic parameter, the Jost solutions in
the limit of |k → ∞), do tend to the free Jost solutions, hence the usual procedure to construct the equations of IST in k-plane remains effective. After we derive the equation of IST in terms of k, we can obtain the equation of
IST in λ-plane by the simple change of parameters λ=kappa-1. The procedure to derive the equation of IST is reasonable, and attention is never paid to the function W(x) introduced by the revisions of Kaup and Newell. Therefore, the
revision of Kaup and Newell can be avoided.
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Fragmentation Cross Sections of 12C on Different Targets at Beam Energies from 50 to 100MeV/Nucleon
BIAN Bao-An, ZHANG Feng-Shou, , ZHOU Hong-Yu,
Chin. Phys. Lett. 2008, 25 (2):
451-454
.
The fragmentation cross sections of reactions 12C + 2H, 12C, 14N, 16O at beam energies from 50 to 100 MeV/nucleon are investigated using the
isospin-dependent Boltzmann--Langevin equation model. It is found that fragment species increase approximately with the increasing target mass. The fragment species and some fragments production cross sections in reactions of 12C + 12C, 14N, 16O show an obvious variation at the beam energies from 50 to 80MeV/nucleon. However the calculated fragment production cross sections do not change much when the incident energy increases from 80 to
100MeV/nucleon.
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Measurement of Angular Distribution for the 8Li(p,d)7Li Reaction
LI Yun-Ju, LI Zhi-Hong, GUO Bing, WANG You-Bao, BAI Xi-Xiang, SU Jun, LIAN Gang, ZENG Sheng, WANG Bao-Xiang, QIN Xing, JIANGChao, LIU Wei-Ping, ZHAO Wei-Juan
Chin. Phys. Lett. 2008, 25 (2):
455-457
.
The 8Li(p,d)7Li reaction plays an important role in the inhomogeneous Big Bang nucleosynthesis and in the seed-nuclide production phase for the r-process. For the first time, its angular distribution at backward angles was measured in inverse kinematics at Ec.m.=4.0MeV by using an 8Li secondary beam. The result of measurement includes the contributions of 8Li(p, d0)7Li and 8Li(p, d1)7Li. The 8Li(p, d0)7Li component is estimated to be 40~58% in the mixture angular distribution by analysing the measured result.
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K0 Condensation in Hyperonic Neutron Star Matter
DING Wen-Bo, LIU Guang-Zhou, ZHU Ming-Feng, YU Zi, ZHAO En-Guang
Chin. Phys. Lett. 2008, 25 (2):
458-461
.
In the framework of the relativistic mean field theory, we investigate K0 condensation along with K- condensation in neutron star matter including the baryon octet. The results show that both K0 and K- condensations can occur well in the core of the maximum mass stars for relatively shallow optical potentials of K in the range of -100MeV~ -160MeV. With the increasing optical potential of K, the critical densities of K decrease and the species of baryons appearing in neutron stars become fewer. The main role of K0 condensation is to make the abundances of particles become identical leading to isospin saturated symmetric matter including antikaons, nucleons and hyperons. K-
condensation is chiefly responsible for the softening of the corresponding equation of state, which leads to a large reduction in the maximum masses of neutron stars. In the core of massive neutron stars, neutron star matter including rich particle species, such as antikaons, nucleons and hyperons, may exist.
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Growth of C30 and C31 Clusters: Structures, Energetics and Dynamics
GONG Xiu-Fang, WANG Yin, NING Xi-Jing
Chin. Phys. Lett. 2008, 25 (2):
468-471
.
We obtain the isomer spectra of C30 and C31 clusters by time-going-backward quasi-dynamics method and perform molecular dynamics simulations of the cluster growth from isolated atoms in He buffer gas at 2500K. The
geometrical structures of the isomers of C30 and C31 can be classified into closed cages, open cages, bowls, sheets and other irregular shapes, where closed cages are found to have the lowest potential energies. However, dynamics simulations show that the sheet structures of C30 and C31 are the dominant outcome at the simulation temperature. Compared with relevant experimental results, we propose a different view in interpreting the
experimental data and a research procedure to predict isomers that would be formed most probably under specific experimental conditions.
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Cavity-Induced Enhancement of Squeezing in Resonance Fluorescence of a V-Type Three-Level Atom
ZHOU Lu, , LI Gao-Xiang, ZHAN Ming-Sheng,
Chin. Phys. Lett. 2008, 25 (2):
497-500
.
The quadrature squeezing spectra in the resonance fluorescence of a V-type three-level atom driven by a coherent field and coupled to a single-mode cavity is investigated. For weak excitation, the fluorescence field exhibit squeezing in the out-of-phase quadrature. The coupling between the atom and the cavity mode can greatly enhance the squeezing centred at the laser frequency. More importantly, for strong excitation, under the effect of the cavity-atom coupling, the in-phase quadrature of fluorescence can exhibit two-mode squeezing at the two inner sideband frequencies. By working in the dressed-state representation and hiring secular approximation, we give an analytical explanation for the effect. The result shows, under appropriate conditions, the squeezing can be greatly enhanced by appropriately tuning the cavity resonant frequency.
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Single-Photon Emission from a Single InAs Quantum Dot
DOU Xiu-Ming, SUN Bao-Quan, HUANG She-Song, NI Hai-Qiao, NIU Zhi-Chuan
Chin. Phys. Lett. 2008, 25 (2):
501-504
.
Excitation power-dependent micro-photoluminescence spectra and photon-correlation measurement are used to study the optical properties and photon statistics of single InAs quantum dots. Exciton and biexciton emissions, whose photoluminescence intensities have linear and quadratic excitation power dependences, respectively, are identified. Under pulsed laser excitation, the zero time delay peak of second order correlation function corresponding to exciton emission is well suppressed, which is a clear evidence of single photon emission.
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Competition between Dispersion and Absorption of Doubly-Dressed Four-Wave Mixing and Dressed Six-Wave Mixing
SHEN Lei-Jian, LI Chuang-She, DU Yi-Gang, ZUO Cui-Cui, NIE Zhi-Qiang, ZHANG Yan-Peng, GAN Chen-Li, LI Yuan-Yuan, LU Ke-Qing
Chin. Phys. Lett. 2008, 25 (2):
509-512
.
We study the competition between dispersion and absorption of doubly-dressed four-wave mixing (DDFWM) and dressed six-wave mixing. In the case of weak coupling fields limit, we find DDFWM signal is affected by destructive interference between four-wave mixing(FWM) and six-wave mixing as well as constructive interference between FWM and eight-wave mixing. By analysing the difference between two kinds of doubly dressing mechanisms (parallel cascade and nested cascade) in this opening five-level system, we can further understand the generated high-order nonlinear optical signal dressed by multi-fields.
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Structural, Electronic Properties and Chemical Bonding of Borate Li4CaB2O6 under High Pressure: an Ab Initio Investigation
ZHANG Hong, TANG Jin, CHENG Xin-Lu
Chin. Phys. Lett. 2008, 25 (2):
552-555
.
We calculate structural, electronic properties and chemical bonding of borate Li4CaB2O6 under high pressure by means of the local density-functional
pseudopotential approach. The equilibrium lattice constants, density of states, Mulliken population, bond lengths, bond angles as well as the pressure dependence of the band gap are presented. Analysis of the simulated high pressure band structure suggests that borate Li4CaB2O6 can be used as the semi-conductor optical material. Based on the Mulliken population analysis, it is found that the electron transfer of the Li atom is very different from that of other atoms in the studied range of high pressures. The charge populations of the Li atom decrease with the pressure up to 60GPa,
then increase with the pressure.
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Phonon Dispersion in Equiatomic Li-Based Binary Alloys
Aditya M. Vora
Chin. Phys. Lett. 2008, 25 (2):
654-657
.
The computations of the phonon dispersion curves (PDC) of four equiatomic Li-based binary alloys, namely Li0.5Na0.5, Li0.5K0.5, Li0.5Rb0.5 and Li0.5Cs0.5, to second order in the local model potential is discussed in terms of the real-space sum of Born von Karman central force constants. Instead of the concentration average of the force constants of metallic Li, Na, K, Rb and Cs, the pseudo-alloy atom (PAA) is adopted to compute directly the force constants of four equiatomic Li-based binary alloys. The exchange and correlation functions due to Hartree (H) and Ichimaru--Utsumi (IU) are used to investigate the influence of screening effects. The phonon frequencies of four equiatomic Li-based binary alloys in the longitudinal branch are more sensitive to the exchange and correlation effects in comparison with the transverse branches. However, the frequencies in the longitudinal branch are suppressed due to IU-screening function than the frequencies due to static
H-screening function.
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Specific Heat of Rhombohedral Polymeric C60 in Temperature Range 300--2K
CUI Guang-Lei, GU Min, YU Yao, XU Xi-Bin, WANG Li-Hang, CHENXiao, FENG Duan, TANG Tong Bor
Chin. Phys. Lett. 2008, 25 (2):
658-660
.
Polymerization of C60 is realized under high temperature and high pressure. X-ray diffraction reveals a rhombohedral lattice structure in the product, and
solid-state 13C nuclear magnetic resonance spectroscopy confirms the formation of sp3 bonds between C60 molecules. Specific heat is then measured over the temperature range of 300--2K. It is found that its specific heat values are significantly less than those in fullerite within the region of
80--2K, and this huge reduction is attributed to the suppression of intermolecular librational modes in polymerized C60. An excellent fit to the experimental data over the entire temperature range is provided by a model, which needs to include only three-dimensional and two-dimensional translational modes in various contributions at different temperatures.
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Low Density Self-Assembled InAs/GaAs Quantum Dots Grown by Metal Organic Chemical Vapour Deposition
LI Lin, LIU Guo-Jun, WANG Xiao-Hua, LI Mei, LI Zhan-Guo, WAN Chun-Ming
Chin. Phys. Lett. 2008, 25 (2):
667-670
.
The self-assembled InAs quantum dots (QDs) on GaAs substrates with low density (5×108cm-2) are achieved using relatively higher growth temperature and low InAs coverage by low-pressure metal-organic chemical vapour deposition. The macro-PL spectra exhibit three emission peaks at 1361, 1280 and 1204nm, corresponding to the ground level (GS), the first excited state (ES1) and the second excited state (ES2) of the QDs, respectively, which are obtained when the GaAs capping layer is grown using triethylgallium and tertiallybutylarsine. As a result of micro-PL, only a few peaks from individual dots have been observed. The exciton--biexciton behaviour was clearly observed at low temperature.
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Solid Dye Lasers Based on 2-Hydroxypropyl Methacrylate and Methyl Methacrylate Copolymers
FAN Rong-Wei, LI Xiao-Hui, YUE Sai-Sai, JIANG Yu-Gang, XIA Yuan-Qin, CHEN De-Ying
Chin. Phys. Lett. 2008, 25 (2):
700-702
.
Polymers are a kind of attractive hosts for laser dyes because of their superior optical homogeneity, and high transparency in pumping and lasing range. Copolymers usually have higher damage threshold and better photostability than mono-polymers. Solid dye samples based on copolymer of methyl methacrylate (MMA) with 2-hydroxypropyl methacrylate (HPMA) doped
with 1-, 3-, 5-, 7-, 8-pentamethyl-2, 6-diethylpyrromethene-BF2 (PM567) are prepared. Spectra and lasing properties of the samples are studied. Compared to the samples based on monopolymer polymethyl methacrylate (PMMA), enhanced slope efficiency and photostability are obtained in the copolymers. The highest slope efficiency is 45.1%, and nearly one-fold increase of photostability is obtained. The longest useful lifetime of 4390 pumping pulses is presented with the pump energy as high as 183mJ per pulse at repetition rate of 10Hz. The results indicate that the laser performances of solid dye mediums can be greatly increased using copolymer of MMA with HPMA as host.
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Improved Blue-Green Electrophosphorescence from a Tuning Iridium Complex with Benzyl Group in Polymer Light-Emitting Devices
MA Xiao-Yun, ZHU Ke-Ming, WANG Lei, XIAO Fang-Liang, WEN Zhong-Lin, ZHU Mei-Xiang, ZHU Wei-Guo,
Chin. Phys. Lett. 2008, 25 (2):
711-714
.
Electroluminescence performances from a tuning biscyclometlated iridium complex with benzyl group are demonstrated in double-layered polymer light-emitting devices (PLEDs) using a blend of poly(9,9-dioctylfluorene) and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole as a host matrix. Blue-green electrophosphorescent emission with a peak at 521nm and a shoulder at 492nm was observed. The highest luminance efficiency of 4.8cd/A at current density of 0.56mA/cm2 and a maximum luminance of 1944cd/m2 at 217.6mA/cm2 were achieved in the devices at the dopant concentration of 8%. The luminous performance of the devices becomes better with increasing dopant concentrations from 1% → 8%. This implies that the concentration quenching of this iridium complex with benzyl group can be efficiently inhibited
in the devices.
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Near-Infrared Emission from Organic Light-Emitting Diodes Based on Copper Phthalocyanine with a Periodically Arranged Alq3:CuPc/DCM Multilayer structure
GUO Zhen-Giang, CHENG Chuan-Hui, FAN Zhao-Qi, HE Wei, YU Shu-Kun, CHANG Yu-Chun, DU Xi-Guang, WANG Xu, DU Guo-Tong,
Chin. Phys. Lett. 2008, 25 (2):
715-718
.
We demonstrate near-infrared organic light-emitting devices with a periodically arranged tris(8-quinolinolato)alumi-num (Alq3):copper phthalocyanine (CuPc)/4-(dicyanomethylene)-2-methyl% -6-(4-dimethylaminost-yry)-4H-pyran (DCM) multilayer structure. DCM and Alq3 doped with CuPc were periodically deposited. Room-temperature electrophosphorescence was observed at about 1.1μm due to transitions from the first excited triplet state to the singlet ground state (T1-S0) of CuPc. In this device, we utilize the overlap between the Q band π-π* at about 625nm of the absorption spectra of CuPc and the PL spectra of the DCM. The near-infrared emission intensity of the CuPc-doped Alq3 device with DCM increases about 2.5 times larger than that of the device without DCM. We attribute the efficiency enhancement to the better overlap between the PL spectra of DCM and the absorption spectra of CuPc.
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Organic Light-Emitting Diodes with Magnesium Doped CuPc as an Efficient Electron Injection Layer
CAO Jun-Song, GUAN Min, CAO Guo-Hua, ZENG Yi-Ping, LI Jin-Min, QIN Da-Shan
Chin. Phys. Lett. 2008, 25 (2):
719-721
.
Bright organic electroluminescent devices are developed using a metal-doped organic layer intervening between the cathode and the emitting layer. The typical device structure is a glass substrate/indium-tin oxide (ITO)/copper
phthalocyanine (CuPc)/N,N'-bis-(1-naphthl)-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB)/Tris(8-quinolinolato) alu\-minum(Alq3)/Mg-doped CuPc/Ag. At a driving voltage of 11V, the device with a layer of Mg-doped CuPc (1:2 in weight) shows a brightness of 4312cd/m2 and a current efficiency of 2.52cd/A, while the reference device exhibits 514cd/m2 and 1.25cd/A.
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Flexible Cu(In, Ga)Se2 Thin-Film Solar Cells on Polyimide Substrate by Low-Temperature Deposition Process
ZHANG Li, HE Qing, JIANG Wei-Long, LI Chang-Jian, SUN Yun
Chin. Phys. Lett. 2008, 25 (2):
734-736
.
The electrical and structural properties of polycrystalline Cu(In,Ga)Se2 films grown on polyimide (PI) substrates below 400°C via one-stage and three-stage co-evaporation process have been investigated by x-ray diffraction spectra (XRD), scanning electron microscopy (SEM) and Hall effect measurement. As shown by XRD spectra, the stoichiometric CIGS films obtained by one-stage process exhibit the characteristic diffraction peaks of the (In0.68Ga0.32)2Se3 and Cu(In0.7Ga0.3)2Se. It is also found that the film
structures indicate more columnar and compact than the three-stage process films from SEM images. The stoichiometric CIGS films obtained by three-stage process exhibit the coexistence of the secondary phase of (In0.68Ga0.32)2Se3, Cu2-xSe and Cu(In0.7Ga0.3)2Se. High net carrier concentration and
sheet conductivity are also observed for this kind of film, related to the presence of Cu2-xSe phase. As a result, when the CIGS film growth temperature is below 400°C, the three-stage process is inefficient for solar cells. By using the one-stage co-evaporation process, the flexible CIGS solar cell on a PI substrate with the best conversion efficiency of 6.38% is
demonstrated (active area 0.16cm2).
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An All-Thin-Film Electrochromic Device Composed of MoO3--LiBSO--NiOx Multilayer Structure
YANG Hai-Gang, WANG Cong, ZHU Kai-Gui, DIAO Xun-Gang, WANG Huai-Yi, CUIYi, WANG Tian-Min
Chin. Phys. Lett. 2008, 25 (2):
740-742
.
An all-thin-film (ATF) electrochromic device for modulating the optical
transmittance is manufactured using magnetron sputtering. The devices
consists of MoO3 as the main electrochromic layer, LiBO2+Li2SO4(LiBSO) as the ion conductor layer, and NiOx as the complementary electrochromic layer. Glass covered with indium tin oxide (ITO) is used as the substrate and the ITO film is used as the bottom electrode. The ITO film deposited on the top of the devices is used as the other electrode. The structure and morphology of
the films are characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM). The devices exhibit good optical properties with low transmittance values in the coloured state, and the optical modulation is measured by spectrophotometer in the wavelength range from 400 to 800nm. The average visible light transmittance reaches 50.2% and 3.7% in bleached and coloured state, respectively. The results indicate that such a monolithic system has great potential to be applied in smart windows.
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Determination of Thickness and Optical Constants of ZnO Thin Films Prepared by Filtered Cathode Vacuum Arc Deposition
WANG Ming-Dong, ZHU Dao-Yun, LIU Yi, ZHANG Lin, ZHENG Chang-Xi, HE Zhen-Hui, CHEN Di-Hu, WEN Li-Shi
Chin. Phys. Lett. 2008, 25 (2):
743-746
.
ZnO thin films are prepared on glass substrates by filtered cathode vacuum arc (FCVA) deposition technique. A new method is demonstrated to extract the refractive index, thickness and optical band gap of ZnO thin films from the
transmission spectrum alone. The refractive index is calculated from the extremes of the interference fingers. The transmission spectrum is divided into two terms, non-interference term and interference effect term. The thickness of thin films is calculated by simulating the interference term, and the non-interference term is used to calculate optical band gap with the gained thickness. The results are compared with measurements by using an ellipsometry and a scanning electron microscope.
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Superhydrophobicity of LaMnO3 Coatings with Hierarchical Microstructures
CHEN Jie-Fei, XIAO Wen-Jia, LI Da, YANG Yang-Yi, HE Zhen-Hui,
Chin. Phys. Lett. 2008, 25 (2):
747-750
.
As proposed by Herminghaus, a hierarchical structure could render any surface nonwettable as long as the roughness amplitude at small scales is sufficient to suspend a free liquid surface. Recently we reported that the wettability of La0.7Sr0.3MnO3, an intrinsic hydrophilic oxide, can be tuned from superhydrophilicity to superhydrophobicity by hierarchical microstructures generated by annealing the coatings of La0.7Sr0.3MnO3 powder in nanometric scale at different temperatures. Here we further demonstrate the similar phenomenon observed on LaMnO3 coatings, which conforms THAT the surface
geometrical structure is a key factor to determine the wettability.
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Opinion Spreading with Mobility on Scale-Free Networks
GUO Qiang, LIU Jian-Guo, WANG Bing-Hong, ZHOU Tao, CHEN Xing-Wen, YAO Yu-Hua
Chin. Phys. Lett. 2008, 25 (2):
773-775
.
A continuum opinion dynamic model is presented based on two rules. The first one considers the mobilities of the individuals, the second one supposes that the individuals update their opinions independently. The results of the model indicate that the bounded confidence εc, separating consensus and incoherent states, of a scale-free network is much smaller than the one of a lattice. If the system can reach the consensus state, the sum of all individuals' opinion change Oc(t) quickly decreases in an exponential form, while if it reaches the incoherent state finally, Oc(t) decreases slowly and has the punctuated equilibrium characteristic.
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In Situ Raman Spectroscopy Study on Dissociation of Methane at High Temperatures and at High Pressures
CHEN Jin-Yang, JIN Lu-Jiang, DONG Jun-Ping, ZHENG Hai-Fei
Chin. Phys. Lett. 2008, 25 (2):
780-782
.
We investigate the stability and dissociation of methane, which is the most abundant organic molecule in the universe, using diamond anvil cell (DAC) with in situ Raman spectroscopy up to 903K and 21GPa. At the temperatures of 793 and 723K and the corresponding pressures of 16.15 and 20.30GPa,
methane dissociates to form carbon `soot' and heavier hydrocarbons
involving C=C and C≡C bonds. However, if the pressure is not very high, methane remains stability up to the highest temperature of 903K of the work. The four symmetric C--H bonds of methane split at high temperatures and at high pressures, and there is at least one phase transition of crystalline symmetry from face centred cubic (fcc) to hexagonal close packed (hcp) before dissociation.
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Dynamical Evolution of Modified Chaplygin Gas
FU Ming-Hui, WU Ya-Bo, HE Jing
Chin. Phys. Lett. 2008, 25 (2):
798-801
.
Based our previous work [Mod. Phys. Lett. A 22(2007)783, Gen. Relat. Grav. 39(2007)653], some properties of modified Chaplygin gas (MCG) as a dark energy model continue to be studied mainly in two aspects: one is the change
rates of the energy density and energy transfer, and the other is the evolution of the growth index. It is pointed that the density of dark energy undergoes the change from decrease to increase no matter whether the interaction between dark energy and dark matter exists or not, but the corresponding transformation points are different from each other. urthermore, it is stressed that the MCG model even supports the existence of interaction between dark energy and dark matter, and the energy of transfer flows from dark energy to dark matter. The evolution of the interaction term with an ansatz Hc2ρ is discussed with the MCG model. Moreover, the evolution of the growth index f in the MCG model without interaction is illustrated, from which we find that the evolutionary trajectory of f overlaps with that of the λ CDM model when a>0.7 and its theoretical value f≈0.566 given by us at z = 0.15 is consistent with the observations.
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Constraints on Deceleration Parameter of a 5D Bounce Cosmological Model from Recent Cosmic Observations
LI Jie-Chao, XU Li-Xin, Lü Jian-Bo, CHANG Bao-Rong, LIU Hong-Ya
Chin. Phys. Lett. 2008, 25 (2):
802-804
.
We study the constraint on deceleration parameter q from the recent
SNeIa Gold dataset and observational Hubble data by using a model-independent deceleration parameter q(z)=1/2-a/(1+z)b under the five-dimensional bounce cosmological model. For the cases of SNeIa Gold dataset, Hubble data, and their combination, the present results show that the constraints on transition redshift zT are 0.35+0.14-0.07, 0.68+1.47-0.58, and 0.55+0.18-0.09 with 1σ errors, respectively.
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122 articles
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