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Dynamics of Open Systems with Affine Maps
ZHANG Da-Jian, LIU Chong-Long, TONG Dian-Min
Chin. Phys. Lett. 2015, 32 (4):
040302
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DOI: 10.1088/0256-307X/32/4/040302
Many quantum systems of interest are initially correlated with their environments and the reduced dynamics of open systems are an interesting while challenging topic. Affine maps, as an extension of completely positive maps, are a useful tool to describe the reduced dynamics of open systems with initial correlations. However, it is unclear what kind of initial state shares an affine map. In this study, we give a sufficient condition of initial states, in which the reduced dynamics can always be described by an affine map. Our result shows that if the initial states of the combined system constitute a convex set, and if the correspondence between the initial states of the open system and those of the combined system, defined by taking the partial trace, is a bijection, then the reduced dynamics of the open system can be described by an affine map.
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Propagation and Interaction of Edge Dislocation (Kink) in the Square Lattice
JIA Li-Ping, Jasmina Tekić, DUAN Wen-Shan
Chin. Phys. Lett. 2015, 32 (4):
040501
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DOI: 10.1088/0256-307X/32/4/040501
The propagation of kink or edge dislocations in the underdamped generalized two-dimensional Frenkel–Kontorova model with harmonic interaction is studied with numerical simulations. The obtained results show that exactly one line of atoms can be inserted into the lattice, which remains at standstill. However, if more than one line of atoms are inserted into the lattice, then they will split into several lines with α=1, where α presents the atoms inserted. In other words, only the kink with α=1 is stable, while the other kinks are unstable, and will split into α=1 kinks, which remain at standstill.
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Residual Nuclides Induced in Cu Target by a 250 MeV Proton Beam
ZHANG Hong-Bin, ZHANG Xue-Ying, MA Fei, JU Yong-Qin, GE Hong-Lin, CHEN Liang, ZHANG Yan-Bin, WEI Ji-Fang, LI Yan-Yan, LUO Peng, WANG Jian-Guo, WAN Bo, XU Xiao-Wei, ZHOU Bin
Chin. Phys. Lett. 2015, 32 (4):
042501
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DOI: 10.1088/0256-307X/32/4/042501
Residual nuclide production is studied experimentally by bombarding a Cu target with a 250 MeV proton beam. The data are measured by the off-line γ-spectroscopy method. Six nuclides are identified and their cross sections are determined. The corresponding calculated results by the MCNPX and GEANT4 codes are compared with the experimental data to check the validity of the codes. A comparison shows that the MCNPX simulation has a better agreement with the experiment. The energy dependence of residual nuclide production is studied with the aid of MCNPX simulation, and it is found that the mass yields for the nuclides in the light mass region increase significantly with the proton energy.
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Laser-Induced Graphite Plasma Kinetic Spectroscopy under Different Ambient Pressures
K. Chaudhary, S. Rosalan, M. S. Aziz, M. Bohadoran, J Ali, P. P. Yupapin, N. Bidin, Saktioto
Chin. Phys. Lett. 2015, 32 (4):
043201
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DOI: 10.1088/0256-307X/32/4/043201
The laser induced plasma dynamics of graphite material are investigated by optical emission spectroscopy. Ablation and excitation of the graphite material is performed by using an 1064 nm Nd:YAG laser in different ambient pressures. Characteristics of graphite spectra as line intensity variations and signal-to-noise ratio are presented with a main focus on the influence of the ambient pressure on the interaction of laser-induced graphite plasma with an ambient environment. Atomic emission lines are utilized to investigate the dynamical behavior of plasma, such as the excitation temperature and electron density, to describe emission differences under different ambient conditions. The excitation temperature and plasma electron density are the primary factors which contribute to the differences among the atomic carbon emission at different ambient pressures. Reactions between the plasma species and ambient gas, and the total molecular number are the main factors influencing molecular carbon emission. The influence of laser energy on the plasma interaction with environment is also investigated to demonstrate the dynamical behavior of carbon species so that it can be utilized to optimize plasma fluctuations.
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Generation of Linear Isolated Sub-60 Attosecond Pulses by Combining a Circularly Polarized Pulse with an Elliptically Polarized Pulse
XIA Chang-Long, MIAO Xiang-Yang
Chin. Phys. Lett. 2015, 32 (4):
043202
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DOI: 10.1088/0256-307X/32/4/043202
The two-color circularly polarized pulses scheme was proposed to generate isolated attosecond pulses in our previous work [ Phys. Rev. A 87 (2013) 043406], while the polarization of the attosecond pulse was not investigated. We show a supplementary explanation of this scheme and present another scheme to generate linear isolated attosecond pulses by combining a circularly polarized pulse with an elliptically polarized pulse. High-order harmonic generation and quantum path control are investigated to compare these two schemes. Both schemes can obtain supercontinuum spectra plateau from about 200 eV to 550 eV, which belong to the water window region. It is found that the latter scheme can clearly eliminate the short quantum path and extend the harmonic plateau. A linear isolated attosecond pulse with a duration of sub-60 as can be generated by superposing a bandwidth of 70 eV.
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Microwave Absorption Properties of Polyester Composites Incorporated with Heterostructure Nanofillers with Carbon Nanotubes as Carriers
LIU Hai-Tao, LIU Yang, WANG Bin-Song, LI Chen-Sha
Chin. Phys. Lett. 2015, 32 (4):
044102
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DOI: 10.1088/0256-307X/32/4/044102
Carbonaceous nanomaterials such as carbon nanotubes (CNTs), magnetic metal nanomaterials and semiconductor nanomaterials are superior candidates for microwave absorbers. Taking full advantage of the features of CNTs, nanophase cobalt and nanophase zinc oxide, whose main microwave absorption mechanisms are based on resistance loss, magnetic loss and dielectric loss, we fabricate CNT/Co and CNT/ZnO heterostructure nanocomposites, respectively. By using the CNTs, CNT/Co nanocomposites and CNT/ZnO nanocomposites as nanofillers, composites with polyester as matrix are prepared by in situ polymerization, and their microwave absorption performance is studied. It is indicated that the synergetic effects of the physic properties of different components in nano-heterostructures result in greatly enhanced microwave absorption performance in a wide frequency range. The absorption peak is increased, the absorption bandwidth is broadened, and the maximum peak shifts to a lower frequency.
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Low-Temperature Deposition of nc-SiOx:H below 400°C Using Magnetron Sputtering
LI Yun, YIN Chen-Chen, JI Yun, SHI Zhen-Liang, JIN Cong-Hui, YU Wei, LI Xiao-Wei
Chin. Phys. Lett. 2015, 32 (4):
046802
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DOI: 10.1088/0256-307X/32/4/046802
Silicon oxide films containing nanocrystalline silicon (nc-SiOx:H) are deposited by co-sputtering technology at low temperatures (<400°C) that are much lower than the typical growth temperature of nc-Si in SiO2. The microstructures and bonding properties are characterized by Raman and FTIR. It is proven that an optimum range of substrate temperatures for the deposition of nc-SiOx:H films is 200–400°C, in which the ratio of transition crystalline silicon decreases, the crystalline fraction is higher, and the hydrogen content is lower. The underlying mechanism is explained by a competitive process between nc-Si Wolmer–Weber growth and oxidation reaction, both of which achieve a balance in the range of 200–400°C. We further implement this technique in the fabrication of multilayered nc-SiOx:H/a-SiOx:H films, which exhibit controllable nc-Si sizes with high crystallization quality.
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Fabrication and Characterization of a Single Electron Transistor Based on a Silicon-on-Insulator
SU Li-Na, LV Li, LI Xin-Xing, QIN Hua, GU Xiao-Feng
Chin. Phys. Lett. 2015, 32 (4):
047301
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DOI: 10.1088/0256-307X/32/4/047301
A single electron transistor based on a silicon-on-insulator is successfully fabricated with electron-beam nanolithography, inductively coupled plasma etching, thermal oxidation and other techniques. The unique design of the pattern inversion is used, and the pattern is transferred to be negative in the electron-beam lithography step. The oxidation process is used to form the silicon oxide tunneling barriers, and to further reduce the effective size of the quantum dot. Combinations of these methods offer advantages of good size controllability and accuracy, high reproducibility, low cost, large-area contacts, allowing batch fabrication of single electron transistors and good integration with a radio-frequency tank circuit. The fabricated single electron transistor with a quantum dot about 50 nm in diameter is demonstrated to operate at temperatures up to 70 K. The charging energy of the Coulomb island is about 12.5 meV.
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Influence of Temperature on the Conductivity of Multi-walled Carbon Nanotube Interconnects
LU Qi-Jun, ZHU Zhang-Ming, YANG Yin-Tang, DING Rui-Xue
Chin. Phys. Lett. 2015, 32 (4):
047305
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DOI: 10.1088/0256-307X/32/4/047305
We propose a new conductivity model of multi-walled carbon nanotube (MWCNT) interconnects considering the influence of temperature. For each shell of MWCNT interconnects, it may present the property of ballistic transport or may suffer from acoustic photo and optical phonon (OP) scattering depending on their mean free paths (MFPs) and the wire length. Furthermore, since the MFPs are proportional to the shell diameter, five regions exist in the wire length in which the factors influencing the conductivity are determined. Thus the conductivity is modeled in five cases according to their lengths, and the final obtained model is a 5-piecewise function. By using this model, the influence of temperature on the conductivity is examined and analyzed. It is shown that the conductivity demonstrates different, changing behaviors with the increase of temperature in the five cases. Additionally, the influence of OP scattering on the conductivity does not need to be taken into account at room temperatures, whereas this influence will produce a decline region in the conductivity at high temperatures.
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Dependence of Switching Current Distribution of a Current-Biased Josephson Junction on Microwave Frequency
ZHAI Ji-Quan, LI Yong-Chao, SHI Jian-Xin, ZHOU Yu, LI Xiao-Hu, XU Wei-Wei, SUN Guo-Zhu, WU Pei-Heng
Chin. Phys. Lett. 2015, 32 (4):
047402
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DOI: 10.1088/0256-307X/32/4/047402
We investigate the distribution of the switching current of a current-biased Josephson junction (CBJJ) and its dependence on the microwave frequency using two theoretical methods, one of which is the quantum trajectory method and the other is the master equation method. Both the methods show that the distribution of the switching current of CBJJ will exhibit double peaks in a certain range of microwave frequency if proper microwave power is given, and the gap between the two peaks will increase with the microwave frequency. The obtained results can be used to identify the energy difference of the ground and first excited states in a Josephson junction for any bias current.
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Doping Effect of Co at Ag Sites in Antiperovskite Mn3AgN Compounds
CHU Li-Hua, WANG Cong, SUN Ying, LI Mei-Cheng, WAN Zi-Pei, WANG Yu, DOU Shang-Yi, CHU Yue
Chin. Phys. Lett. 2015, 32 (4):
047501
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DOI: 10.1088/0256-307X/32/4/047501
Antiperovskite compounds Mn3Ag1?xCoxN (x=0.2, 0.5 and 0.8) are synthesized and the doping effect of the magnetic element Co at the Ag site is investigated. The crystal structure is not changed by the introduction of Co. However, with the increase of the content of Co, the spin reorientation gradually disappears and the antiferromagnetic transition changes to the ferromagnetic transition at the elevated temperature when x=0.8. In addition, all of the magnetic phase transitions at the elevated temperature are always accompanied by the abnormal thermal expansion behaviors and an entropy change. Moreover, when x=0.8, the coefficient of linear expansion is ?1.89×10?6 K?1 (290–310 K, ΔT=20 K), which is generally considered as the low thermal expansion.
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The Magnetic Anisotropy and Complete Phase Diagram of CuFeO2 Measured in a Pulsed High Magnetic Field up to 75 T
ZUO Hua-Kun, SHI Li-Ran, XIA Zheng-Cai, HUANG Jun-Wei, CHEN Bo-Rong, JIN Zhao, WEI Meng, OUYANG Zhong-Wen, CHENG Gang
Chin. Phys. Lett. 2015, 32 (4):
047502
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DOI: 10.1088/0256-307X/32/4/047502
The magnetization behavior of a CuFeO2 single crystal grown by the floating zone technique is investigated with a pulsed high magnetic field. We observe a series of field-induced multi-step-like transitions with hysteresis, of which the critical magnetic fields are temperature-dependent and show anisotropy. By using a pulsed high magnetic field up to 75 T, the magnetization behavior shows that the critical transition magnetic fields of spin-flip/flop shift to lower field regions with an increase in temperature. According to the magnetization curves, a complete magnetic phase diagram is depicted.
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Temperature Dependence of Raman Scattering in 4H-SiC Films under Different Growth Conditions
WANG Hong-Chao, HE Yi-Ting, SUN Hua-Yang, QIU Zhi-Ren, XIE Deng, MEI Ting, Tin C. C., FENG Zhe-Chuan
Chin. Phys. Lett. 2015, 32 (4):
047801
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DOI: 10.1088/0256-307X/32/4/047801
The microRaman scattering of 4H-SiC films, fabricated by low pressure chemical vapor deposition under different growth conditions, is investigated at temperatures ranging from 80 K to 550 K. The effects of growth conditions on E2(TO), E1(TO) and A1(LO) phonon mode frequencies are negligible. The temperature dependences of phonon linewidth and lifetime of E2(TO) modes are analyzed in terms of an anharmonic damping effect induced by thermal and growth conditions. The results show that the lifetime of E2(TO) mode increases when the quality of the sample improves. Unlike other phone modes, Raman shift of A1 (longitudinal optical plasma coupling (LOPC)) mode does not decrease monotonously when the temperature increases, but tends to blueshift at low temperatures and to redshift at relatively high temperatures. Theoretical analyses are given for the abnormal phenomena of A1(LOPC) mode in 4H-SiC.
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Numerical Investigation on the Propagation Mechanism of Steady Cellular Detonations in Curved Channels
LI Jian, NING Jian-Guo, ZHAO Hui, HAO Li, WANG Cheng
Chin. Phys. Lett. 2015, 32 (4):
048202
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DOI: 10.1088/0256-307X/32/4/048202
The propagation mechanism of steady cellular detonations in curved channels is investigated numerically with a detailed chemical reaction mechanism. The numerical results demonstrate that as the radius of the curvature decreases, detonation fails near the inner wall due to the strong expansion effect. As the radius of the curvature increases, the detonation front near the inner wall can sustain an underdriven detonation. In the case where detonation fails, a transverse detonation downstream forms and re-initiates the quenched detonation as it propagates toward the inner wall. Two kinds of propagation modes exist as the detonation is propagating in the curved channel. One is that the detonation fails first, and then a following transverse detonation initiates the quenched detonation and this process repeats itself. The other one is that without detonation failure and re-initiation, a steady detonation exists which consists of an underdriven detonation front near the inner wall subject to the diffraction and an overdriven detonation near the outer wall subject to the compression.
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Spectroscopic Characterization of Staphylococcal Nuclease Mutants with Tryptophan at Internal Sites
GAO Guang-Yu, LI Yu, WANG Wei, ZHONG Dong-Ping, WANG Shu-Feng, GONG Qi-Huang
Chin. Phys. Lett. 2015, 32 (4):
048701
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DOI: 10.1088/0256-307X/32/4/048701
Tryptophan (Trp) is an intrinsic fluorescent probe for detecting the site-specified dynamics inside/outside protein. It is found that the Trp can easily be inserted in desired sites of protein, which affects the integrity of the overall structure. To evaluate this effect, we design thirteen double point mutants of staphylococcal nuclease, each of which has a single Trp residue planted at an internal site. The studies on Trp fluorescence, ANS-binding fluorescence, far- and near-UV CD spectra, and enzymatic activity are carried out. It is found that the mutation at the hydrophobic core of protein generates molten globular state conformation, which is a loose structure compared to their original compactness in wild type (WT). Its enzyme activity and surface hydrophobicity are also affected. The studies show that by proper site designing and external binding, Trp mutagenesis is a suitable method for carrying out the study on site specified dynamics of proteins.
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38 articles
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