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Dileptons from a Chemically Equilibrating Quark--Gluon Plasma at Finite Baryon Density
GUAN Na-Na, HE Ze-Jun, LONG Jia-Li, CAI Xiang-Zhou
Chin. Phys. Lett. 2008, 25 (11):
3916-3919
.
We perform a complete calculation for the dilepton production from the processes qq-→ll-, Compton-like (qg→qll-, q-g→q-ll-),qq-→gll-, gluon fusion gg-→cc-, annihilation qq-→cc- as well as multiple scattering of quarks in a chemically equilibrating quark--gluon plasma system at finite baryon density. It is found that quark-antiquark annihilation, Compton-like, gluon fusion and multiple scattering of quarks give important contribution. Moreover, the increase of the quark phase life-time with increasing initial quark chemical potential makes the dilepton yield as an increasing function of the initial quark chemical potential.
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Ultrahigh Spin Structures in 157,158,159Er
MA Hai-Liang, DONG Bao-Guo, YAN Yu-Liang
Chin. Phys. Lett. 2008, 25 (11):
3928-3931
.
Rotational structures at ultrahigh spin in 157,158,159Er have been investigated with the configuration-dependent cranked Nilsson--Strutinsky approach. Configurations of observed bands are assigned and the corresponding deformations are given theoretically. The calculations suggest that one of ultrahigh spin bands in 158Er is triaxial highly deformed and the other is normal-deformed, while both ultrahigh spin bands in 157Er are suggested to be triaxial highly deformed. The possible ultrahigh spin bands in 159Er are predicted to be triaxial highly deformed and have shape coexistence in the same configuration. The configurations with two neutron holes in the Nosc=4 orbitals and two neutron holes in the h11/2 orbitals in 159Er are favoured for ultrahigh spin states but unfavoured for band termination, which is similar to ultrahigh spin bands in 157,158Er.
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The First Nine-Cell TESLA Cavity Made in China
LU Xiang-Yang, QUAN Sheng-Wen, ZHANG Bao-Cheng, HAO Jian-Kui, ZHU Feng, LIN Lin, XU Wen-Can, WANG Er-Dong, WANG Fang, JIN Song, XIN Tian-Mu, YAO Zhong-Yuan, CHEN Jia-Er, ZHAO Kui
Chin. Phys. Lett. 2008, 25 (11):
3940-3941
.
A totally home-made 9-cell TESLA type superconducting cavity is made at Peking University. The cavity fabrication is according to DESY specification. The cavity is made of high purity niobium from OTIC, Ningxia. The electron beam welding is carried out at Harbin Institute of Technology, Harbin. By the cooperation, the cavity is tested at Thomas Jefferson National Accelerator Facility, USA. The preliminary result shows the acceleration gradient Eacc is 23MV/m without quench and has potential for improvement.
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Accurate One-Centre Method for Hydrogen Molecule Ions in Strong Magnetic Field
ZHANG Yue-Xia, KANG Shuai, SHI Ting-Yun
Chin. Phys. Lett. 2008, 25 (11):
3946-3949
.
An accurate one-centre method for the hydrogen molecule ion is tested. The slow convergence and singularities at the nuclear positions that are problems in the general one-centre method are solved well by employing the optimal radial and angular B-spline basis. Therefore, the accuracy of the one-centre method is improved observably. For the ground state of the H2+ in the free field, 7×10-8 accuracy is obtained, which rivals the best one-centre calculation before. As a test, the nuclear distances and the total energies of the 1σg,u, 1πu, 1δg,u and 2σg states of the H2+ for the magnetic field strength B=1a.u. are also obtained. Compared to other results, five-digit accuracy at least can be arrived even for the antibonding states 1σu and 1δu, whose equilibrium distances R is very large
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An Artificially Garnet Crystal Materials Using In Terahertz Waveguide
YANG Qing-Hui, ZHANG Huai-Wu, LIU Ying-Li, WEN Qi-Ye, ZHA Jie
Chin. Phys. Lett. 2008, 25 (11):
3957-3960
.
A hypothesis is brought forward that the materials with low propagation loss in both optical and microwave band may exhibit good performance in terahertz (THz) band because THz wave band interspaces those two wave bands. For the purpose of exploring a kind of low-loss material for THz waveguide, Lu2.1Bi0.9Fe5O12(LuBiIG) garnet films are prepared by liquid phase epitaxy (LPE) method on a gadolinium~gallium~garnet (GGG) substrate from lead-free flux because of the good properties in both optical and microwave bands. In microwave band, the ferromagnetic resonance (FMR) linewidth of the film 28710;H=2.8-5.1Oe; in optical band, the optical absorption coefficient is 600cm-1 at visible range and about 100-170cm-1 when the wavelength is longer than 800nm. In THz range, our hypothesis is well confirmed by a THz-TDS measurement which shows that the absorbance of the film for THz wave is 0.05-0.3cm-1 and the minimum value appears at 2.3THz. This artificial ferromagnetic material holds a great promise for magnetic field tunable THz devices such as waveguide, modulator or switch.
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Simultaneous Generation of Multi-Wavelength Laser from Nd:YAG Crystals in a Cruciform Cavity
CHEN Xiu-Yan, REN Zhao-Yu, ZHANG Hao-Lei, LI Xiu, ZHENG Xin-Liang, CHEN Hao-Wei, BAI Jin-Tao,
Chin. Phys. Lett. 2008, 25 (11):
3984-3987
.
A cruciform cavity is presented for multi-wavelength laser generation. On the basis of considering the optimal power ratio and good spatial overlap of the two fundamental beams, the maximum output power of 589nm laser reaches 3.5W when the pumping power of Nd:YAG A and Nd:YAG B are 311.5W and 261.8W, respectively. At the same time, the other wavelength lasers are also obtained with the output power distribution of 2.5W at 660nm, 15W at 532nm, 100mW at 1319nm and 240mW at 1064nm. The corresponding beam quality factors are Mx2=4.93, My2=5.01 at 589nm, Mx2=4.51, My2=4.85 at 660nm, and Mx2=4.12, My2=3.96 at 532nm, respectively. The instabilities of the three visible lights are measured, which are also less than 2% within three hours.
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Highly Efficient Diode-Side-Pumped Six-Rod Nd:YAG Laser
CUI Qian-Jin, PENG Qin-Jun, ZHANG Hong-Bo, YANG Xiao-Dong, BO Yong, GUO Xin-Jun, ZHOU Yong, LU Yuan-Fu, CUI Da-Fu, XU Zu-Yan
Chin. Phys. Lett. 2008, 25 (11):
3991-3994
.
We have demonstrated a highly efficient, high average output power laser based on the optimized resonator made up of multiple Nd:YAG rods. The laser consists of three groups, each of which contains two rods with one quartz 90° rotator between them. By a desirable design of the resonator, the average output power of 1906W at 1064nm is reached with repetition rate of 1.1kHz. The optical to optical conversion efficiency is up to 50.8% with the pulse width 224μs and it is the highest conversion efficiency of six rods resonator.
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Microchip Laser Feedback Interferometer with an Optical Path Multiplier
REN Zhou, TAN Yi-Dong, WAN Xin-Jun, LI Duo, ZHANG Shu-Lian
Chin. Phys. Lett. 2008, 25 (11):
3995-3998
.
We present a microchip laser feedback interferometer with an optical path multiplier to enhance the resolution of traditional laser feedback interferometers (LFI). The optical path multiplier has a unique device, i.e. diffusive reflector. As class B microchip lasers have extremely high sensitivity to laser feedback, the diffusive reflector can easily reflect or diffuse back the laser beam without much manual adjustment to the optical system, which ensures the system's easy-adjustment and practical feature. The optical path multiplier is a two-mirror system which enables the laser beam to reflect between the two mirrors by N times. When the target shifts a distance of 8710;d, the variation of the optical path will be about (4N×8710;d). Thus the system's resolution is about 4N times as high as the traditional LFI. Under typical room conditions, the optical path multiplier can effectively enhance the system's resolution by more than 26 times as high as a traditional LFI system and even to the level of 0.1nm.
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Influence of Temperature on Stimulated Raman Scattering in Single-Mode Silica Fibre
MEN Zhi-Wei, FANG Wen-Hui, SUN Xiu-Ping, LI Zuo-Wei, YI Han-Wei, WANG Zhao-Min, GAO Shu-Qin, LU Guo-Hui
Chin. Phys. Lett. 2008, 25 (11):
3999-4002
.
One piece of single-mode silica fibre is used to study of temperature characteristics of stimulated Raman scattering (SRS), additional peaks (double-humped) are observed at both sides of pump light and 1st-order Stokes light in the experiment. The frequency shift of the double-humped is calculated by stimulated Four--Photon mixing (SFPM) phase matching theory, the result is consistent with the frequency shift of this experiment. Simultaneously, the experimental conditions accord with the theoretical calculation of effective coherence length. We indicate that the double-humped phenomenon is caused by SFPM. The intensity of double-humped is first increased, then decreased and finally disappeared as the temperature increases. This phenomenon has been explained theoretically.
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Broadband Third-Harmonic Generation with a Composite KD*P Crystal
HAN Wei, ZHENG Wan-Guo, YUAN Peng, QIAN Lie-Jia, WANG Fang, YANG Yi-Sheng, FENG Bin, XIANG Yong, LI Ke-Yu, LI Fu-Quan
Chin. Phys. Lett. 2008, 25 (11):
4003-4005
.
We predict that broadband efficient third-harmonic generation (THG) can be achieved with a frequency-doubling crystal and a novel composite KD*P tripler. The composite KD*P tripler is made of two partially deuterated KDP crystals with different deuteration levels by using the thermal bonding technique. The deuteration level of a partially deuterated KDP crystal is used as a degree of freedom to alter the phase-matching (PM) wavelength. Simulations show that the composite KD*P tripler can improve third-harmonic conversion efficiencies over a very wide band of input fundamental frequencies. In terms of robustness, alignment and stability, this THG scheme should be more promising than other broadband THG approaches because the composite KD*P tripler is a monolithic device.
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Distinguishing Structure Change of Cells Based on Analysis of Light Scattering Patterns
JIN Yong-Long, YANG Fang, WANG Meng, ZHANG Yu, GU Ning
Chin. Phys. Lett. 2008, 25 (11):
4013-4015
.
We develop a new method to distinguish structural change of cells based on light scattering and Fourier spectra analysis. The light scattering detection system is composed of a laser source, an optical microscope, a CCD with high resolution and low distortion. After the scattering patterns of cells are recorded by the CCD, the Fourier spectra are obtained by the intensity distribution of scattered light. In the experiment, the change of cell structure is designed by sonication treatment. It is found that different typical peaks can be shown in the Fourier spectra of MCF7 cells with and without sonication treatment, which indicates that this method can be used to distinguish the structural change of cells.
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Efficient Pumping Scheme by Direct Excitation of Upper Laser Level in Nd:CNGG
CAO Ning, LI Qi-Nan, ZHAO Yan-Ying, XU Chang-Wen, WEI Zhi-Yi, FENG Bao-Hua, ZHANG Zhi-Guo, ZHANG Huai-Jin, WANG Ji-Yang, HE Kun-Na, GAO Chun-Qing
Chin. Phys. Lett. 2008, 25 (11):
4016-4018
.
We report an efficient pumping scheme which involves a direct excitation of the upper lasing level of a four-level laser in a Nd-doped Ca3(NbGa)2-xGa3O12 (Nd:CNGG) by using a tunable Ti:sapphire, 700-920nm, cw pump source. The slope efficiency is improved from 10.5% of the traditional band pumping at 808nm to 21.8% of the direct pumping at 882nm. The influence of pumping wavelength on lasing is discussed. We present a scheme of double pumping for lasing.
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Synthesis and Band Gap Control in Three-Dimensional Polystyrene Opal Photonic Crystals
LIU Ye, ZHENG Zhong-Yu, QIN Fei, ZHOU Fei, ZHOU Chang-Zhu, ZHANG Dao-Zhong, MENG Qing-Bo, LI Zhi-Yuan
Chin. Phys. Lett. 2008, 25 (11):
4019-4022
.
High-quality three-dimensional polystyrene opal photonic crystals are fabricated by vertical deposition method. The transmission properties with different incident angles and different composite refractive index contrasts are experimentally and theoretically studied. Good agreement between the experiment and theory is achieved. We find that with the increasing incident angle, the gap position shifts to the short wavelength (blue shift) and the gap becomes shallower; and with the increase of refractive index of the opal void materials and decrease the contrast of refractive index, the gap position shifts to the long wavelength (red shift). At the same time, we observe the swelling effects when the sample is immerged in the solutions with different refractive indices, which make the microsphere diameter in solution become larger than that in air. The understanding of band gap shift behaviour may be helpful in designing optical sensors and tunable photonic crystal ultrafast optical switches.
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Multi-Bifurcation Effect of Blood Flow by Lattice Boltzmann Method
RAO Yong, NI Yu-Shan, LIU Chao-Feng
Chin. Phys. Lett. 2008, 25 (11):
4038-4041
.
The multi-bifurcation effect of blood flow is investigated by lattice Boltzmann method at Re=200 with six different bifurcation angles α, which are 22.5°, 25°, 28°, 30°, 33°, 35°, respectively. The velocities and ratios of average velocity at various bifurcations are discussed. It is indicated that the maximum velocity at the section near the first divider increases and shifts towards the walls of branch with the increase of α. At the first bifurcation, the average horizontal velocities increase with the increase of α. The average horizontal velocities of outer branches at the secondary bifurcation decrease at 22.5°≤ α≤30° and increase at 30°≤α≤ 35°, whereas those of inner branches at the secondary bifurcation have the opposite variation, as the same as the above variations of the ratios of average horizontal velocities at various bifurcations. The ratios of average vertical velocities of branch at first bifurcation to that of outer branches at the secondary bifurcation increase at 22.5°≤α≤30° and decrease at 30°≤ α ≤ 35°, whereas the ratios of average vertical velocities of branch at first bifurcation to that of inner branches at the secondary bifurcation always decrease.
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Effect of Silane Flow Rate on Structure and Corrosion Resistance of Ti-Si-N Thin Films Deposited by a Hybrid Cathodic Arc and Chemical Vapour Process
YIN Long-Cheng, LUAN Sen, LV Guo-Hua, WANG Xing-Quan, HUANG Jun, JIN Hui, FENG Ke-Cheng, YANG Si-Ze
Chin. Phys. Lett. 2008, 25 (11):
4072-4075
.
Ti--Si--N thin films with different silicon contents are deposited by a cathodic arc technique in an Ar+N2+SiH4 mixture atmosphere. With the increase of silane flow rate, the content of silicon in the Ti--Si--N films varies from 2.0at.% to 12.2at.%. Meanwhile, the cross-sectional morphology of these films changes from an apparent columnar microstructure to a dense fine-grained structure. The x-ray diffractometer (XRD) and x-ray photoelectron spectroscopy (XPS) results show that the Ti--Si--N film consists of TiN crystallites and SiNx amorphous phase. The corrosion resistance is improved with the increase of silane flow rate. Growth defects in the films produced play a key role in the corrosion process, especially for the local corrosion. The porosity of the films decreases from 0.13% to 0.00032% by introducing silane at the flow rate of 14sccm.
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Growth and Characterization of a Kind of Nitrogen-Rich Niobium Nitride for Bolometer Applications at Terahertz Frequencies
LU Xue-Hui, KANG Lin, ZHOU Lei, CHEN Jian, JI Zheng-Ming, CAO Chun-Hai, JIN Biao-Bing, XU Wei-Wei, WU Pei-Heng, WANG Xiao-Shu
Chin. Phys. Lett. 2008, 25 (11):
4076-4078
.
Niobium is sputtered onto a single crystalline silicon substrate in N2:Ar=4:1 gas mixture at the total pressure of 2Pa. The temperature coefficient of resistance of the sample is about 0.5% at 300K, and up to 7% at 77K, indicating the possibility of using it to make room-temperature bolometers with performances better than those based on Pt, Bi, or Nb. For a 60-nm-thick sample, the rms surface roughness is 0.45nm over an area of 2μm×2μm. Analyses based on x-ray diffraction and x-ray photoelectronic spectroscopy indicate that the samples are Nb5N6 thin films in which there is a combination of Nb3+ and Nb5+, or Nb4+.
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High-Temperature Characteristics of Ti/Al/Ni/Au Ohmic Contacts to n-GaN
ZHANG Yue-Zong, FENG Shi-Wei, GUO Chun-Sheng, ZHANG Guang-Chen, ZHUANG Si-Xiang, SU Rong, BAI Yun-Xia, LU Chang-Zhi
Chin. Phys. Lett. 2008, 25 (11):
4083-4085
.
We present the high-temperature characteristics of Ti/Al/Ni/Au(15nm/220nm/40nm/50nm) multiplayer contacts to n-type GaN (Nd=3.7×1017cm-3, Nd=3.0×1018cm-3). The contact resistivity increases with the measurement temperature. Furthermore, the increasing tendency is related to doping concentration. The higher the doped, the slower the contact resistivity with decreasing measurement temperature. Ti/Al/Ni/Au ohmic contact to heavy doping n-GaN takes on better high temperature reliability. According to the analyses of XRD and AES for the n-GaN/Ti/Al/Ni/Au, the Au atoms permeate through the Ni layer which is not thick enough into the Al layer even the Ti layer.
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Structural, Elastic and Electronic Properties of ReO2
LI Yan-Ling, , ZENG Zhi
Chin. Phys. Lett. 2008, 25 (11):
4086-4089
.
Structural, elastic and electronic properties of ReO2 are investigated by first-principles calculations based on density functional theory. The ground state of ReO2 has an orthorhombic symmetry which belongs to space group Pbcn with a=4.7868Å b=5.5736Å, and c=4.5322Å. The calculated bulk moduli are 322GPa, 353GPa, and 345GPa for orthorhombic, tetragonal, and monoclinic ReO2, respectively, indicating that ReO2 has a strong incompressibility. ReO2 is a metal ductile solid and presents large elastic anisotropy. The obtained Debye temperatures are 850K for orthorhombic, 785K for tetragonal, and 791K for monoclinic ReO2.
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Noise Characteristics of Optocouplers on Neutron Radiation
LI Ying-Hui, CHEN Chun-Xia, LIU Yong-Zhi, JIANG Cheng, ZOU Ze-Ya, OU Yi, LI Zu-An
Chin. Phys. Lett. 2008, 25 (11):
4093-4096
.
Neutron dose radiation experiment is designed to study the optocoupler's displacement effects and the noise characteristics. The burst noise is introduced in optocouplers on neutron radiation, which is indicated from experiments. With the increasing neutron radiation the displacement defects in space-charge region increase, the scattering enhances and the noise signal mutations increase. All these represent the noise time series mutations, the random pulses and the increasing noise complexity. The burst noise becomes evident, and the power spectrum density, the characteristic frequency and the fractal dimension of time series of noise greatly increase.
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Degradation of Ultra-Thin Gate Oxide NMOSFETs under CVDT and SHE Stresses
HU Shi-Gang, CAO Yan-Rong, HAO Yue, MA Xiao-Hua, CHEN Chi, WU Xiao-Feng, ZHOU Qing-Jun
Chin. Phys. Lett. 2008, 25 (11):
4109-4112
.
Degradation of device under substrate hot-electron (SHE) and constant voltage direct-tunnelling (CVDT)stresses are studied using NMOSFET with 1.4- nm gate oxides. The degradation of device parameters and the degradation of the stress induced leakage current (SILC) under these two stresses are reported. The emphasis of this paper is on SILC and breakdown of ultra-thin-gate-oxide under these two stresses. SILC increases with stress time and several soft breakdown events occur during direct-tunnelling (DT) stress. During SHE stress, SILC firstly decreases with stress time and suddenly jumps to a high level, and no soft breakdown event is observed. For DT injection, the positive hole trapped in the oxide and hole direct-tunnelling play important roles in the breakdown. For SHE injection, it is because injected hot electrons accelerate the formation of defects and these defects formed by hot electrons induce breakdown.
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Electromechanical Properties of Microcantilever Actuated by Enhanced Piezoelectric PZT Thick Film
LIU Hong-Mei, ZHAO Quan-Liang, CAO Mao-Sheng, YUAN Jie, DUAN Zhong-Xia, QIU Cheng-Jun,
Chin. Phys. Lett. 2008, 25 (11):
4128-4130
.
Pb(Zr0.53,Ti0.47)O3 (PZT) films with thicknesses of 0.8μm, 2μm and 4μm are prepared by a sol-gel method and their longitudinal piezoelectric coefficients are analysed. The results show that the PZT thick films, whose density is closer to bulk PZT, has the better crystallization, with d33 and density much larger than those of PZT thin films. A piezoelectric microcantilever actuated by a 4-μm-thick PZT film is fabricated and its displacement is measured in different frequencies and voltages. The displacement increases linearly with the increasing bias, and the maximum displacement of 0.544μm is observed at 30kHz for 5V bias. The resonant frequency obtained in the experiment matches quite well with the theoretical result, and it is shown that the resonant frequency of PZT microcantilever could be controlled and predicated.
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Strong Green Light Emission from Low-Temperature Grown a-SiNx:H Film after Different Oxidation Routes
DONG Heng-Ping, HUANG Rui, WANG Dan-Qing, CHEN Kun-Ji, LI Wei, MAZhong-Yuan, XU Jun, HUANG Xin-Fan
Chin. Phys. Lett. 2008, 25 (11):
4147-4150
.
Room-temperature deposited amorphous silicon nitride (a-SiNx:H) films exhibit intense green light emission after post-treated by plasma oxidation, thermal oxidation and natural oxidation, respectively. All the photoluminescence (PL) spectra are peaked at around 500nm, independent of oxidation method and excitation wavelength. Compared with the PL results from oxidized a-Si:H and as-deposited a-SiNx:H samples, it is indicated that not only oxygen but also nitrogen is of an important role in enhancing light emission from the oxidized a-SiNx:H. Combining the PL results with the analyses of the bonding configurations as well as chemical compositions of the films, the strong green light emission is suggested to be from radiative recombination in luminescent centres related to N--Si--O bonds.
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Parameter Study on Far-Field Sub-Diffraction-Limited Hyperlens
HU Ji-Gang, , CAO Yong, WANG Pei, LU Yong-Hua, MING Hai,
Chin. Phys. Lett. 2008, 25 (11):
4151-4153
.
Influence of hyperlens structure parameters, such as curvature radius and layer number, and incident wavelength on the beam propagation is numerically investigated by FDTD. It is found that the intensity and the full width at half maximum (FWHM) of the output beam can be controlled by the structure parameters and operating wavelength. The optimized structure parameters and operating wavelength are obtained, which will be of great significance in design and fabrication of optical hyperlens with high resolution.
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Fabrication and Characterization of Mg-Doped GaN Nanowires
ZHANG Dong-Dong, XUE Cheng-Shan, ZHUANG Hui-Zhao, HUANG Ying-Long, WANG Zou-Ping, WANG Ying, GUO Yong-Fu
Chin. Phys. Lett. 2008, 25 (11):
4158-4161
.
Mg-doped GaN nanowires have been synthesized by ammoniating Ga2O3 films doped with Mg under flowing ammonia atmosphere at 850°C. The Mg-doped GaN nanowires are characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscopy (HRTEM) and photoluminescence (PL). The results demonstrate that the nanowires are single crystalline with hexagonal wurzite structure. The diameters of the nanowires are 20-30nm and the lengths are 50-100μm. The GaN nanowires show three emission bands with well-defined PL peak at 3.45eV, 3.26eV, 2.95eV, respectively. The large distinct blueshift of the bandgap emission can be attributed to the Burstein--Moss effect. The peak at 3.26eV represents the transition from the conduction-band edge to the acceptor level AM (acceptor Mg). The growth mechanism of crystalline GaN nanowires is discussed briefly.
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Improvement of Plasticity of Ti-Based Bulk Metallic Glasses by Addition of Nb
SHAN Sheng-Feng, ZHAN Zai-Ji, FAN Chang-Zeng, JIA Yuan-Zhi, ZHANG Bao-Qing, LIU Ri-Ping, WANG Wen-Kui
Chin. Phys. Lett. 2008, 25 (11):
4165-4167
.
Ti-based bulk metallic glasses (Ti40Zr25Cu9Ni8Be18)100-xNbx with x=0 to 5at.% are prepared by copper-mold casting. The glass formation ability is almost unchanged by addition of Nb. The compression plasticity is, however, apparently changed, from 3% at x=0 to 13% at x=3, about 330% increases at the strain rate of 1×10-4s-1. The increment of the plasticity can be attributed to the segregation of Nb in the area of shear bands during the compression processing. An effective way to increase the plasticity of Ti-based bulk metallic glasses is thus proposed.
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Network Entropy Based on Topology Configuration and Its Computation to Random Networks
LI Ji, WANG Bing-Hong, WANG Wen-Xu, ZHOU Tao
Chin. Phys. Lett. 2008, 25 (11):
4177-4180
.
A definition of network entropy is presented, and as an example, the relationship between the value of network entropy of ER network model and the connect probability p as well as the total nodes N is discussed. The theoretical result and the simulation result based on the network entropy of the ER network are in agreement well with each other. The result indicated that different from the other network entropy reported before, the network entropy defined here has an obvious difference from different type of random networks or networks having different total nodes. Thus, this network entropy may portray the characters of complex networks better. It is also pointed out that, with the aid of network entropy defined, the concept of equilibrium networks and the concept of non-equilibrium networks may be introduced, and a quantitative measurement to describe the deviation to equilibrium state of a complex network is carried out.
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Node Weight Distribution and Disparity of Some Collaboration--Competition Networks
FU Chun-Hua, XU Xiu-Lian, LIU Ai-Fen, WU Yong-Ping, SHEN Dan, LIU Shui-Jing, QIAN Xia, FENG Ya-Chao, WEI Cheng-Liang, HE Da-Ren
Chin. Phys. Lett. 2008, 25 (11):
4181-4184
.
We present an empirical investigation of 14 real world networks, which can be described by bipartite graphs. We show that the basic elements (the actor nodes) in all the networks cooperate and compete in some acts (activities, organizations, or events). Each node is assigned by a `node weight', which denotes the obtained competition result. We are interested in the distribution and disparity of the node weight and propose three parameters for the description. Firstly, empirically we observe that the total node weight distributions of all the systems may be fitted by the so-called `shifted power law' function form. The key parameters of the function, α and γ, can be used to describe the disparity. Secondly, a `node weight disparity', Y, is defined for the same purpose. The empirical relationships among the parameters Y, α and γ, are obtained. From the relationships between Y and α as well as Y and γ, one can deduce the relationship between α and γ, which is in a good agreement with the empirically obtained relationship. The results show that the node weight distribution is very uneven.
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95 articles
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