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On Thermodynamics of AdS Black Holes in Arbitrary Dimensions
A. Belhaj, M. Chabab, H. El Moumni, M. B. Sedra
Chin. Phys. Lett. 2012, 29 (10):
100401
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DOI: 10.1088/0256-307X/29/10/100401
Considering the cosmological constant Λ as a thermodynamic pressure and its conjugate quantity as a thermodynamic volume as proposed by Kubiznak and Mann [ J. High Energy Phys. 1207 (2012) 033], we discuss the critical behavior of charged AdS black hole in arbitrary dimensions d. In particular, we present a comparative study in terms of the spacetime dimension d and the displacement of critical points controlling the transition between the small and the large black holes. Such behaviors vary nicely in terms of d. Our result shows that the equation of state for a charged Reissner–Nordstrom AdS black hole predicts an universal number given by (2 d?5)/(4 d?8). The three-dimensional solution is also discussed.
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Quark Stars Investigated using an Improved Quasi-Particle Model
YAN Yan, CAO Jing, LUO Xin-Lian, SUN Wei-Min, ZONG Hong-Shi
Chin. Phys. Lett. 2012, 29 (10):
101201
.
DOI: 10.1088/0256-307X/29/10/101201
The equation of state (EOS) of cold and dense strongly interacting matter is crucial for better research of compact stars, i.e., neutron stars and quark stars. We generalize our improved quasi-particle model from finite temperature and zero chemical potential [ Phys. Lett. B 711 (2012) 65] to the case of zero temperature and finite chemical potential to obtain an EOS of our improved quasi-particle model and then apply this EOS to study the structure of a quark star. The results are consistent with the most recent astronomical observational data.
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Inelastic Scattering of 32Mg at 190 MeV/Nucleon from a Thick Proton Target
LI Kuo-Ang, YE Yan-Lin, Heiko SCHEIT, Pieter DOORNENBAL, Satoshi TAKEUCHI, Nori AOI, Masafumi MATSUSHITA, Eri TAKESHITA, Tohru MOTOBAYASHI, Hiroyoshi SAKURAI, PANG Dan-Yang
Chin. Phys. Lett. 2012, 29 (10):
102301
.
DOI: 10.1088/0256-307X/29/10/102301
The first excited 2+ state (885 keV) of 32Mg and its corresponding deformation parameter β2 are studied with proton inelastic scattering at 190 MeV/nucleon using in-beam γ technology with a thick target. Angular distributions of the inelastic scattering cross sections are analyzed with coupled-channel calculations. The deformation parameter β2=0.41(3) obtained in this work agrees with the earlier experimental results obtained at lower beam energies. Our work demonstrates that the structure of unstable nuclei can be studied with proton inelastic scattering at high incident energies in the vicinity of 200 MeV/nucleon using thick targets.
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The Radiative and Auger Decay Properties of K-Shell Ionized Np Ions
WANG Xiang-Li, DONG Chen-Zhong, XIE Lu-You, SHI Ying-Long, SABER Ismail Abdalla, ZHOU Wei-Dong
Chin. Phys. Lett. 2012, 29 (10):
103201
.
DOI: 10.1088/0256-307X/29/10/103201
The radiative and Auger decay processes of K-shell ionized Np ions are studied theoretically using the flexible atomic code (FAC). Relativistic effects, Breit interaction, QED corrections and nuclear finite mass and volume effects are considered systematically. The resulting calculated K x-rays and Auger spectra of Np are compared with the measured spectra emitted after the electron-capture (EC)-decay of mass-separated 237Pu. The general consistency between theory and experiment is good; the relative intensities and relative positions of the peaks in the measured spectra are reproduced with good accuracy, in spite of the existence of different ways to produce the primary K-shell vacancy, enabling identification of the observed structure in the experimental spectra. We find that most of the radiative transition rates are greater than the Auger transition rates, and the latter decrease rapidly with the transfer of initial vacancies to the outer shell.
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Stable and High OSNR Compound Linear-Cavity Single-Longitudinal-Mode Erbium-Doped Silica Fiber Laser Based on an Asymmetric Four-Cavity Structure
FENG Ting, YAN Feng-Ping, LI Qi, PENG Wan-Jing, FENG Su-Chun, WEN Xiao-Dong, LIU Peng, TAN Si-Yu
Chin. Phys. Lett. 2012, 29 (10):
104205
.
DOI: 10.1088/0256-307X/29/10/104205
We propose a stable and high optical signal-to-noise ratio (OSNR) compound linear-cavity single-longitudinal-mode (SLM) erbium-doped silica fiber laser. It consists of three uniform fiber Bragg gratings (FBGs) and two fiber couplers to form a simple asymmetric four-cavity structure to select the longitudinal mode. The stable SLM operation at the wavelength of 1544.053 nm with a 3 dB bandwidth of 0.014 nm and an OSNR of ~60 dB was verified experimentally. Under laboratory conditions, a power fluctuation performance of less than 0.05 dB for 5 h and wavelength variation of less than 0.01 nm for about 150 min is demonstrated. Finally, the characteristic of laser output power as a function of pump power is investigated. The proposed system provides a simple and cost-effective approach to realize a stable SLM fiber laser.
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Widely Wavelength-Tunable Blue-Shifted Dispersive Waves for Broadband Visible Wavelength Generation in a Photonic Crystal Fiber Cladding
YUAN Jin-Hui, SANG Xin-Zhu, YU Chong-Xiu, SHEN Xiang-Wei, WANG Kui-Ru, YAN Bin-Bin, HAN Ying, ZHOU Gui-Yao, HOU Lan-Tian
Chin. Phys. Lett. 2012, 29 (10):
104207
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DOI: 10.1088/0256-307X/29/10/104207
Blue-shifted dispersive waves (DWs) are efficiently generated from the red-shifted solitons by coupling the 120 fs pulses into the fundamental mode of the multi-knots of a photonic crystal fiber cladding. When the femtosecond pulses at the wavelength of 825 nm and the average power of 300 mW are coupled into knots 1–3, the conversion efficiency ηDW of 32% and bandwidth BDW of 50 nm are obtained. The ultrashort pulses generated by the DWs can be tunable over the whole visible wavelength by adjusting the wavelengths of the pump pulses coupled into different knots. It can be believed that this widely wavelength-tunable ultrashort visible pulse source has important applications in ultrafast photonics and resonant Raman scattering.
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Sound Propagation in a Wedge with a Rigid Bottom
LUO Wen-Yu, YANG Chun-Mei, QIN Ji-Xing, ZHANG Ren-He
Chin. Phys. Lett. 2012, 29 (10):
104303
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DOI: 10.1088/0256-307X/29/10/104303
Sound propagation in a wedge with perfectly reflecting boundaries is one of the few range-dependent problems with an analytical solution. Since sound propagation towards the wedge apex will be completely backscattered due to the perfectly reflecting boundaries, this test problem is an ideal benchmark for a full two-way solution to the wave equation. An analytical solution for sound propagation in a wedge with a pressure-release sea surface and a pressure-release bottom was presented by Buckingham et al. [ J. Acoust. Soc. Am. 87 (1990) 1511]. The ideal wedge problem with a rigid bottom is also of great importance in underwater acoustics. We present an analytical solution to the problem with a wedge bounded above by a pressure-release sea surface and below by a rigid bottom, which may be used to provide informative means of investigating the sound field in depth-varying channels, and to establish the accuracy of numerical propagation models for which it is difficult to treat problems with a pressure-release bottom. A comparison of the analytical solution and the numerical solution recently proposed by Luo et al. [ Chin. Phys. Lett. 29 (2012) 014302] is also presented, indicating that this numerical propagation model provides high accuracy.
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Cooperative Car-Following Model of Traffic Flow and Numerical Simulation
LIU You-Jun, ZHANG Hai-Lin, HE Li
Chin. Phys. Lett. 2012, 29 (10):
104502
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DOI: 10.1088/0256-307X/29/10/104502
Based on the impact of a desired following speed and safe distance on driving behaviour, we establish a cooperative car-following model (CCFM). The dynamics analysis results indicate that no unrealistic deceleration or collision occurs in the CCFM. Also, this model can describe the kinetic property in the processes of starting and braking. In addition, evolution of a small perturbation can be reproduced in a numerical simulation. Compared to the full velocity difference model (FVDM), the CCFM has a wider range of stability and a much smaller blocking region width. Meanwhile, the CCFM averts negative velocity, and is accordingly advanced compared with the comprehensive optimal velocity model (COVM). Moreover, the CCFM describes the deceleration process more smoothly than both the FVDM and COVM.
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Synthetic Turbulence Constructed by Self-Learning Fractal Interpolation
WANG Yan-Zhi, ZHANG Zhi-Xiong, SHI Yi-Peng, SHE Zhen-Su
Chin. Phys. Lett. 2012, 29 (10):
104705
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DOI: 10.1088/0256-307X/29/10/104705
A self-learning fractal interpolation algorithm to construct synthetic fields with statistical properties close to real turbulence is proposed. Different from our previous work [ Phys. Rev. E 84 (2011) 026328, 82 (2010) 036311], the position mapping and stretching factors between the adjacent large and small scales are learned from the initial information. Using this method, a turbulence-like field with K41 spectra and without dissipation is constructed well through a coarse grid velocity signal from one experiment's data. After filtering the interpolated signal appropriately, the probability distribution of velocity, velocity structure functions and the anomalous scaling law of the synthetic field are close to those of the original signal.
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Snowflake Divertor Simulation for an HL-2M Conceptual Design
ZHENG Guo-Yao, PAN Yu-Dong, FENG Kai-Ming, HE Hong-Da, CUI Xue-Wu
Chin. Phys. Lett. 2012, 29 (10):
105202
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DOI: 10.1088/0256-307X/29/10/105202
A conceptual design study of the HL-2M facility has shown that one can create not only a standard single-null divertor configuration on it, but also a second-order null (snowflake (SF)) configuration. For the SF divertor, the magnetic flux expansion closes to the separatrix and exceeds that of the standard configuration by more than a factor of 4 at the outer divertor. The heat load at the divertor targets of this innovative configuration has been investigated by using B2.5-Eirene. It is shown that the heat load it targets is different from that of the standard configuration. As a result of the magnetic flux expansion, the peak heat load reduces and does not concentrate on a small area near the separatrix. The heat load profile becomes flat as compared to the standard divertor. When the upstream density is 2.0×1019/m3 with 10 MW heating power flowing into the SOL/divertor regions, the peak load at the outer divertor is 1.64 MW/m2 for the SF divertor, but it is 3.2 MW/m2 for the standard divertor, so the SF divertor can mitigate the heat load at the divertor targets when HL-2M operates at low plasma density and high heating power.
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Germanium Nitride as a Buffer Layer for Phase Change Memory
ZHANG Xu, LIU Bo, PENG Cheng, RAO Feng, ZHOU Xi-Lin, SONG San-Nian, WANG Liang-Yong, CHENG Yan, WU Liang-Cai, YAO Dong-Ning, SONG Zhi-Tang, FENG Song-Lin
Chin. Phys. Lett. 2012, 29 (10):
107201
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DOI: 10.1088/0256-307X/29/10/107201
The results of adhesion improvement and SET-RESET operation voltage reduction for the GeN buffer layer are presented. It is found that the adhesive strength between the Ge2Sb2Te5(GST) layer and the layer below could be increased at least 20 times, which is beneficial for solving the phase change material peeling issue in the fabrication process of phase change memory (PCM). Meanwhile, the RESET voltage of the PCM cell with a 3-nm-thick GeN buffer layer can be reduced from 3.5 V to 2.2 V. The GeN buffer layer will play an important role in high density and low power consumption PCM applications.
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Properties of p-NiO/n-GaN Diodes Fabricated by Magnetron Sputtering
WANG Hui, ZHANG Bao-Lin, WU Guo-Guang, WU Chao, SHI Zhi-Feng, ZHAO Yang, WANG Jin, MA Yan, DU Guo-Tong , DONG Xin
Chin. Phys. Lett. 2012, 29 (10):
107304
.
DOI: 10.1088/0256-307X/29/10/107304
The p-NiO thin film is prepared by radio frequency magnetron sputtering on the n-GaN/sapphire substrate to form p-NiO/n-GaN heterojunction diodes. The structural, optical and electrical properties of the p-NiO thin film are investigated. The results indicate that the NiO film has good crystal qualities and stable p-type conductivities. The current-voltage measurement of the p-NiO/n-GaN diode exhibits typical rectifying behaviour with a turn-on voltage of about 2.2 V. Under forward bias, a prominent ultraviolet emission centered at 375 nm is observed at room temperature. Furthermore, the mechanism of the light emission is discussed in terms of the band diagrams of the heterojunction in detail.
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Electronic Band Structure and Optical Parameters of Spinel SnMg2O4 by Modified Becke–Johnson Potential
Masood Yousaf, M. A. Saeed, Ahmad Radzi Mat Isa, Amiruddin Shaari, H. A. Rahnamaye Aliabad
Chin. Phys. Lett. 2012, 29 (10):
107401
.
DOI: 10.1088/0256-307X/29/10/107401
The electronic band structure and optical parameters of SnMg2O4 are investigated by the first-principles technique based on a new potential approximation known as modified Becke–Johnson (mBJ). The direct band gap values by LDA, GGA and EV-GGA are underestimated significantly as compared to mBJ-GGA, which generally provides the results comparable to the experimental values. Similarly, the present band gap value (4.85 eV) using mBJ-GGA is greatly enhanced to the previous value by EV-GGA (2.823 eV). The optical parametric quantities (dielectric constant, index of refraction, reflectivity, optical conductivity and absorption coefficient) relying on the band structure are presented and examined. The first critical point (optical absorption's edge) in SnMg2O4 occurs at about 4.85 eV. A strong absorption region is observed, extending between 5.4 eV to 25.0 eV. For SnMg2O4, static dielectric constant ε1(0), static refractive index n(0), and the magnitude of the coefficient of reflectivity at zero frequency R(0) are 2.296, 1.515 and 0.0419, respectively. The optoelectronic properties indicate that this material can be successfully used in optical devices.
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A New Bipolar Type Transistor Created Based on Interface Effects of Integrated All Perovskite Oxides
XIA Feng-Jin, WU Hao, FU Yue-Ju, XU Bo, YUAN Jie, ZHU Bei-Yi, QIU Xiang-Gang, CAO Li-Xin, LI Jun-Jie, JIN Ai-Zi, WANG Yu-Mei, LI Fang-Hua, LIU Bao-Ting, XIE Zhong, ZHAO Bai-Ru
Chin. Phys. Lett. 2012, 29 (10):
107402
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DOI: 10.1088/0256-307X/29/10/107402
Oxide transistor is the basic device to construct the oxide electronic circuit that is the backing to develop integrated oxide electronics with high efficiency and low power consumption. By growing the perovskite oxide integrated layers and tailoring them to lead semiconducting functions at their interfaces, the development of oxide transistors may be able to perform. We realize a kind of p-i-n type integrated layers consisting of an n-type cuprate superconductor, p-type colossal magnetoresistance manganite, and a ferroelectric barrier (i). From this, bipolar transistors were fabricated at the back-to-back p-i-n junctions, for which the Schottky emission and p-n junction barriers, as well as the ferroelectric polarization, were integrated into the interfaces to control the transport properties; a preliminary but distinct current gain greater than 1.6 at input current of microampers order was observed. These results present a real possibility to date for developing bipolar all perovskite oxide transistors.
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Time-Domain Frequency Correction Method for Averaging Low-Field NMR Signals Acquired in Urban Laboratory Environment
QIU Long-Qing, LIU Chao, DONG Hui, XU Lu, ZHANG Yi, Hans-Joachim Krause, XIE Xiao-Ming, Andreas Offenhäusser
Chin. Phys. Lett. 2012, 29 (10):
107601
.
DOI: 10.1088/0256-307X/29/10/107601
Using a second-order helium-cooled superconducting quantum interference device gradiometer as the detector, ultra-low-field nuclear magnetic resonance (ULF-NMR) signals of protons are recorded in an urban environment without magnetic shielding. The homogeneity and stability of the measurement field are investigated. NMR signals of protons are studied at night and during working hours. The Larmor frequency variation caused by the fluctuation of the external magnetic field during daytime reaches around 5 Hz when performing multiple measurements for about 10 min, which seriously affects the results of averaging. In order to improve the performance of the averaged data, we suggest the use of a data processor, i.e. the so-called time-domain frequency correction (TFC). For a 50-times averaged signal spectrum, the signal-to-noise ratio is enhanced from 30 to 120 when applying TFC while preserving the NMR spectrum linewidth. The TFC is also applied successfully to the measurement data of the hetero-nuclear J-coupling in 2,2,2-trifluoroethanol.
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In-Plane Optical Anisotropy of a-Plane GaN Film on r-Plane Sapphire Grown by Metal Organic Chemical vapour Deposition
DING Yu, LIU Bin, TAO Tao, LI Yi, ZHANG Zhao, ZHANG Rong, XIE Zi-Li, ZHAO Hong, GU Shu-Lin, LV Peng, ZHU Shi-Ning, ZHENG You-Dou
Chin. Phys. Lett. 2012, 29 (10):
107801
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DOI: 10.1088/0256-307X/29/10/107801
The in-plane optical anisotropic properties of the non-polar a-plane GaN films grown by metal organic chemical vapour deposition are investigated by using polarised photoluminescence (PL), optical transmission and Raman scattering measurements. Through polarised PL and transmission spectra, the in-plane optical anisotropic properties of a-plane GaN film are found, which are attributed to the topmost valance band (at Γ point) split into three sub-bands under anisotropic strain. The PL spectra also exhibit that the light hole band moves up more rapidly than the spin-orbit crystal-field spilt-off hole band with the increasing in-plane anisotropic compressive strain. Raman scattering spectra under different configurations further indicate the in-plane anisotropy and the hexagonal crystalline structure of these a-plane GaN films.
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Effects of WO3 Particle Size in WO3/Epoxy Resin Radiation Shielding Material
DONG Yu, CHANG Shu-Quan, ZHANG Hong-Xu, REN Chao, KANG Bin, DAI Ming-Zhu, DAI Yao-Dong
Chin. Phys. Lett. 2012, 29 (10):
108102
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DOI: 10.1088/0256-307X/29/10/108102
To verify the influence of the functional elements particular size for the radiation attenuation coefficients and mechanical properties radiation shielding material based on epoxy resin, we prepare two WO3/E44 samples with different particular sizes of WO3 by a solidified forming approach. The linear attenuation coefficients of these samples are measured for γ-ray photo energies of 59.6, 121.8, and 344.1 keV, etc. using narrow beam transmission geometry. It is found that the linear attenuation coefficients would increase with the decreasing particle size of the WO3 in the epoxy resin based radiation shielding material. The theoretical values of the linear attenuation coefficients and mass attenuation are calculated using WinXcom, and good agreements between the experimental data and the theoretical values are observed. From the studies of the obtained results, it is reported that from the shielding point of view the nano-WO3 is more effective than micro-WO3 in the epoxy resin based radiation shielding material.
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Crystallization Behavior of Fe50?xCr15Mo14C15B6Mx (x=0, 2 and M = Y, Gd) Bulk Metallic Glasses and Ribbons by in situ High Temperature X-Ray Diffraction
Badis Bendjemil, Abderrezak Bouchareb, Ahmed Belbah, Jamel Bougdira, Rafael Piccin, Marcello Baricco
Chin. Phys. Lett. 2012, 29 (10):
108103
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DOI: 10.1088/0256-307X/29/10/108103
The effect of rare earth addition on thermal stability of Fe50?xCr15Mo14C15B6Mx (x=0, 2 and M=Y, Gd) is studied. Thermal and structural properties are measured using differential scanning calorimetry and x-ray diffraction, respectively. The microstructure is observed by using a scanning electron microscope, and chemical composition is checked by energy dispersive spectroscopy analysis. The effect of high temperature on the isothermal crystallization of Fe50?xCr15Mo14C15B6Mx (x=0, 2 and M=Y, Gd) bulk metallic glass and ribbons is investigated by high-temperature x-ray diffraction. It is found that the crystallization behavior of Fe50?xCr15Mo14C15B6Mx(x=0, 2 and M=Y, Gd) bulk metallic glass strongly depends on the annealing temperature. The different crystallization behavior is believed to be due to the different structures that the metallic glass possesses at different temperatures.
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Violation of the First Law of Thermodynamics in f(R,T) Gravity
Mubasher Jamil, D. Momeni, Ratbay Myrzakulov
Chin. Phys. Lett. 2012, 29 (10):
109801
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DOI: 10.1088/0256-307X/29/10/109801
We derive the first law of thermodynamics using the method proposed by Wald. Treating the entropy as Noether charge and comparing with the usual first law of thermodynamics, we obtain explicitly the expression of entropy which contains infinitely many non-local terms (i.e. the integral terms). We have proved, in general, that the first law of black hole thermodynamics is violated for f(R,T) gravity. However, there might exist some special cases in which the first law for f(R,T) gravity is recovered.
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69 articles
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