bluuebunny/crossref_metadata_2025 huggingface dataset:
A novel organic light-emitting diode by utilizing double hole injection layer
Authors: Liu Bai-Quan  , Lan Lin-Feng  , Zou Jian-Hua  , Peng Jun-Biao  ,   Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou 510640, China;,   State Key Laboratory of Luminescent Materials and Devices, Guangzhou 510640, China
Published: December 2020

Highly efficient organic light-emitting diode is fabricated with a novel double hole injection layer consisting of MeO-TPD/CuPc. We observe that the insertion of such a double hole injection layer leads to a striking enhancement in the electrical property:higher luminance, power efficiency and lower driving voltage. It has the configuration of ITO/MeO-TPD (15 nm)/CuPc(15 nm)/NPB(15 nm)/Alq3 (50 nm)/LiF(1 nm)/Al(120 nm). Its turn-on voltage is 3.2 V, which is 2, 0.3 and 0.1 V lower than those of the device without hole injection layer (device A) and the devices using MeO-TPD (device B), CuPc (device C) as hole injection layer, respctively. The highest luminance of the novel device reaches 23893 cd/m2 at a drving voltage of 10 V. The maximum power efficiency of the novel decive is 1.91 lm/W, which is 43% (1.34 lm/W), 22% (1.57 lm/W) and 7% (1.79 lm/W) higher than those of devices A, B and C, respectively. The improvement is ascribed to its high hole injection and transport ability. The results are verified by using the J-V curves of "hole-only" devices.
Characteristics and applications of line defect modes in two-dimensional magnonic crystals
Authors: Cao Yong-Jun  , Jiang Xin  ,   Inner Mongolia Key Laboratory of Physics and Chemistry of Functional Materials, College of Physics and Electronic Information, Inner Mongolia Normal University, Huhhot 010022, China
Published: December 2020

In this paper, band structures and defect modes of two-dimensional magnonic crystals with line defect are calculated by using the plane-wave expansion method under supercell approximation. The obtained results show that line defect modes can be produced in the band gap by introducing the line defect bodies into the two-dimensional magnonic crystal. The presence of the line defect modes leads to the spin waves propagating along the direction of the line defects in these structures. Utilizing the wave-guide characteristic of line defect modes, two-dimensional magnonic crystals can be used as the materials for fabricating spin-wave waveguides.
Investigation on relaxation loss mechanism of CaCu3Ti4O12 ceramic
Authors: Wang Hui  , Lin Chun-Jiang  , Li Sheng-Tao  , Li Jian-Ying  ,   State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an 710049, China
Published: December 2020

The dielectric loss of the CaCu3Ti4O12 ceramic is high, and the mechanism of the loss is not clear, which restricts its application. The CaCu3Ti4O12 ceramic samples are synthesised by solid state reaction method and coprecipitation method. The electronic relaxation of deep bulk traps at the depletion layer edge, carrier relaxation and the dielectric loss of CaCu3Ti4O12 ceramic are investigated. Both perfect double Schottky barrier and low impurity density can reduce the DC conductivity, thus reducing the low-frequency dielectric loss. High-frequency dielectric loss is controlled by deep bulk trap density, especially in the one whose activation energy is 0.12 eV. At room temperature, when the frequency is 1 kHz, the dielectric constant and loss of CaCu3Ti4O12 ceramic prepared by coprecipitation method are 1.4× 104 and 0.037, indicating a good improvement.
Research of metamaterial absorbers and their rectangular waveguide matching terminal applications based on the electric resonators
Authors: Li Jian  , Wen Guang-Jun  , Huang Yong-Jun  , Wang Ping  , Sun Yuan-Hua  ,   Key Laboratory of Broadband Optical Fiber Transmission and Communication Networks, School of Communication and Information Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
Published: December 2020

To cope with the high complex properties and high costs of measuring the metamaterial absorber in the free space, in this paper we experimentally discuss the absorption characteristics of four kinds of metamaterial absorbers based on different electric resonators in a closed X-band (8-12 GHz) rectangular waveguide. The measured results indicate that the four metamaterial absorbers exhibite similar absorption characteristics and mechanisms in comparison with the results obtained from free space. Further, in this paper we also discuss the rectangular wave matching terminal applications based on the proposed four metamaterial absorbers. And the results show that these new rectangular waveguide matching terminals can possess the advantages including the compact dimensional size, flexible controllability of the operating frequencies, and low costs. Moreover, the matching frequency bands of the novel terminals can be realized by designing the broadband metamaterial absorbers.
Double spectrum analysis of photoacoustic signal
Authors: Jiao Yang  , Jian Xiao-Hua  , Xiang Yong-Jia  , Cui Yao-Yao  ,   Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, China
Published: December 2020

Photoacoustic spectroscopy based on the photoacoustic effect is the combination of optical imaging and acoustical imaging, which has become a powerful medical diagnosis tool to distinguish different tissues and components with several different wavelength photoacoustic images. But photoacoustic spectroscopy is limited by the scanning speed, system stability and signal accuracy. To solve these limitation problems, in this paper we propose a new method called photoacoustic double spectrum analysis which can greatly improve the image contrast and identification capability with quantitative analysis of the detected photoacoustic signal frequency. The final experimental results indicate that this method has the feasibility to distinguish different tissues quickly and easily with better contrast, which will be helpful for improving the applications of photoacoustic imaging in various branches of physics, biology, engineering, medicine, etc. We also expect the theoretical and experimental research proposed in this paper to establish the foundation and method for photoacoustic frequency imaging.
Synthesis and photoluminescence of AlON:Ce3+ phosphors
Authors: Zhong Hong-Mei  , Liu Qian  , Zhou Yao  , Zhuang Jian-Dong  , Zhou Hu  ,   State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China
Published: December 2020

In this paper, AlON phosphors doped with Ce3+ are prepared by solid-state reaction method. Phases, microstructures and optical properties of the synthesized phosphors are characterized by X-ray diffraction and scanning electron microscopy and photoluminescence. The results indicate that AlON3+:Ce phosphors emit the blue light centered at 390 nm under the excitation of 305 nm. The emission intensity of AlON:Ce3+ at 150 ℃ is about 86% of that measured at room temperature. It demonstrates that the AlON:Ce3+ has a great potential in applications of high-density white light-emitting diodes.
Characteristic spectra of single-bubble sonoluminescence in the rare-earth salt aqueous solutions
Authors: Zhou Chao  , Chen Wei-Zhong  , Cui Wei-Cheng  ,   Key Laboratory of Modern Acoustics of Ministry of Education, Institute of Acoustics, Nanjing University, Nanjing 210093, China
Published: December 2020

The single-bubble sonoluminescence spectra of the terbium chloride aqueous solutions dissolved with the noble gas Ar are studied in this paper. Under the condition of fixed driving ultrasonic frequency and different sound pressures, a series of line spectra is identified as emissions from the transitions of OH radical vibrational levels from the first excited state A2∑+ to the ground state X2Π, including (0, 0) transition at 307 nm, (0, 1) transition at 335 nm and (1, 0) transition at 276 nm and so on. The experimental results show that higher sound pressure is conducive to the appearance of the line spectrum at 276 nm while lower sound pressure is favorable for the appearance of the line spectra at 307 nm and 335 nm. The relative intensity of the line spectrum in the total spectrum is expressed quantificationally by defining an intensity ratio of the line spectrum to the continuous spectrum. In addition, the effects of the driving sound pressure on the intensity ratios of different line spectra are given.
Review of the ultrashort echo time magnetic resonance imaging of cortical bone
Authors: Bao Shang-Lian  , Du Jiang  , Gao Song  ,   Beijing Key Laboratory of Medical Physics and Engineering, School of Physics, Peking University, Beijing 100871, China;,   Department of Radiology, University of California, San Diego, CA 92103-8226, USA;,   Medical Imaging Physics Laboratory, HSC of Peking University, Beijing 100191, China
Published: December 2020

The evaluation of bone quality, especially cortical bone, is very important for diagnosing and treating the bone diseases. Because of the rapidly aging population of the global society, noninvasively, precisely and feasibly evaluating the bone quality has become a hot topic in the contemporary medical physics studies. Among the several available methods of evaluation, the bone mineral density (BMD) measured with dual-energy X-ray absorptiometry is currently considered to be the gold standard in clinical applications. However, the BMD is limited by its incapability of assessing the organic matrix, microstructure, porosity and perfusion of bone. In addition, the BMD can neither provide a definite diagnose of osteoporosis nor predict fractures precisely. Cortical bone shows near zero signal with all conventional clinical magnetic resonance imaging (MRI) sequences, because of the rapid decay of the magnetic resonance signal in the bone. Due to the recently developed theories, methods and hardware, ultrashort time echo (UTE) sequences with nominal TE of less than 100 s have aroused the increasing research interest. In this paper an introduction to the basic physics of UTE MRI of cortical bone is presented. The newly proposed qualitative and quantitative UTE MRI methods are reviewed with an introduction to the research work in the authors laboratory. The features, application scopes and limitations of those methods are also summarized. Finally, the authors point out the directions and steps of further studies. The paper will be helpful for understanding theoretical research and the clinical applications of UTE imaging of cortical bone.
New three-soliton solutions to (2+1)-dimensional Nizhnik-Novikov-Vesselov equations with variable coefficients
Authors: Xu Lan-Lan  , Chen Huai-Tang  ,   School of Science, Linyi University, Linyi 276005, China;,   Department of Mathematics, Shandong Normal University, Jinan 250014, China
Published: December 2020

In this paper, in order to obtain new solutions to nonlinear evolution equations, the auxiliary equation method and (G'/G)-expansion method are studied and extended. By using the method, many new exact solutions of the nonlinear (2+1)-dimensional Nizhnik-Novikov-Vesselov equations with variable coefficients are obtained. The interaction new solutions include Jacobi elliptic function, hyperbolic function, triangular function and rational function.
A new detecting method for periodic weak signals based on fractional order stopping oscillation system
Authors: Zhou Xue-Xue  , Lai Li  , Luo Mao-Kang  ,   Department of Mathematics, Sichuan University, Chengdu 610065, China
Published: December 2020

In this paper, a new detecting method for weak periodic signals with unknown periods and unknown forms, the so-called fractional stopping oscillation method, is presented. This new detecting method, which is based on the research of some dissipative system of single degree of freedom, is sensitive to periodic signal—even with unknown period and unknown form—and insensitive to noise. Compared with the known chaotic detections in which a built-in signal must be pre-set with the same frequency and the same form as the detected periodic signal, the fractional stopping oscillation method can not only be used even at lower SNR than chaotic detection, but also has some other notable advantages as follows: (1) it need not get the period and the form of detected signal before hand or pre-estimate them; (2) it need not pre-calculate the chaotic threshold value; (3) the existence of periodic signal in system input can be reliably and quantitatively judged by volatility index function, designed in this paper, for stopping oscillation method; (4) a more sensitive detection method can be achieved by the fractionalization of the detection system, especially, the detection threshold can reach -182 dB when the background noise is colored Gaussian noise.
A side-leakage photonic crystal fiber torsion sensor for measuring torsion angle and determining torsion direction simultaneously
Authors: Lou Shu-Qin  , Lu Wen-Liang  , Wang Xin  ,   School of Electronic and Information Engineer, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

A highly sensitive torsion sensor, which can measure the torsion angle and determine the torsion direction simultaneously, is proposed and experimentally demonstrated by using side-leakage photonic crystal fiber (SLPCF) based Sagnac loop. When the SLPCF is turned in the clockwise direction, the transmission spectra of the torsion sensor shift towards the shorter wavelength side; whereas the transmission spectra of the torsion sensor shift towards the longer wavelength side when the SLPCF is turned in anticlockwise direction. Experimental results demonstrate that the length of the SLPCF inserted into Sagnac loop plays an important role for determining the torsion sensitivity and the torsion angle range. For the SLPCF with shorter length, the torsion sensor has the larger torsion sensitivity, but the torsion angle measuring range would be decreased. The opposite situation takes place for the SLPCF with longer length used in the torsion sensor. When the length of SLPCF is 14.85 cm, the torsion sensitivity of the sensor is up to 0.9354 nm/(°) and the torsion angle range from -90° to +90°; When we increase the length of SLPCF to 32 cm, the torsion sensitivity of the sensor gets down to 0.2132 nm/(°), but the torsion angle range can be expanded as from -180° to +180°. To eliminate the perturbation of environmental temperature, we adopt a two-dimensional measuring matrix to achieve simultaneous measurements of the torsion angle and temperature. In other words, using two-dimensional measuring matrix can also eliminate the perturbation of the environmental temperature to the measured result of torsion angle.
State transfer of ultracold nS Rydberg atoms
Authors: Wang Yong  , Zhang Hao  , Chen Jie  , Wang Li-Mei  , Zhang Lin-Jie  , Li Chang-Yong  , Zhao Jian-Ming  , Jia Suo-Tang  ,   State Key Laboratory of Quantum Optics and Quantum Optics Devices, Lab for Laser Spectroscopy, Shanxi University, Taiyuan 030006, China
Published: December 2020

The state transfer of nS Rydberg atoms induced by external pulsed electric field has been investigated. Cold nS Rydberg atoms are prepared by the two-photon transition and the selective field-ionization method is used to detect the Rydberg atoms and "P" state due to the state mixing. The avoided crossing of nS and (n-4) manifold is studied and the dependence of the state transfer rate on the strength of pulsed field is obtained. Experimental result is interpreted by using Stark effect of electric field and it shows consistency between experiment and calculation.
High-order generalized extended Born approximation algorithm for 3D electromagnetic responses modeling in anisotropic medium
Authors: Chen Gui-Bo  , Bi Juan  , Zhang Ye  , Li Zong-Wen  ,   School of Science, Changchun University of Science and Technology, Changchun 130022, China
Published: December 2020

In this paper, we present a high-order generalized extended Born approximation (Ho-GEBA) algorithm for modeling 3D electromagnetic responses of an arbitrary anisotropic body in transverse anisotropic background medium based on integral equation method. First, generalized series solutions of the integral equation are obtained by successive iterative technique, and a contraction operator is introduced for the anisotropic medium based on the iterative dissipation principle to guarantee the convergence of high-order series. Then, we derive the Ho-GEBA solutions of 3D electromagnetic responses in the anisotropic medium using the abnormal body domain decomposition method combining with the extended Born approximation. Analytical solutions of dyadic Green's functions in the transverse isotropic medium are used, which can improve the efficiency of the algorithm greatly. Numerical results show the validity of the algorithm by comparing it with the full integral equation method and the classical Born approximation.
Investigation on partially coherent Airy beams and their propagation
Authors: Cui Sheng-Wei  , Chen Zi-Yang  , Hu Ke-Lei  , Pu Ji-Xiong  ,   Department of Information Science & Engineering, Huaqiao University, Xiamen 361021, China
Published: December 2020

Based on the cross-spectral density function of Gaussian Shell-Model and Huygens integral, the expression of partially coherent Airy beam was derived. The non-diffraction and acceleration characteristics of partially coherent Airy beam were theoretically studied and experimentally observed. The experimental observation was consistent with the theoretical prediction. Furthermore, the non-diffraction distance and the transversal acceleration decrease with decreasing coherent length.
The production mechanism of image periodicity in digital holography and its application in zero-order noise suppression
Authors: Lu Ming-Feng  , Wu Jian  , Zheng Ming  ,   Department of Applied Physics, Beihang University, Beijing 100191, China
Published: December 2020

An interesting fact in digital holography is that the reconstruction process of the hologram recorded by the color camera may result in some periodic distribution of images in the image plane. In this paper we describe the production mechanism, characteristics and application of image periodicity in digital hologram reconstruction. Our study shows that the image distribution characteristics in the hologram reconstruction are strongly dependent on the option of RGB sampling mode due to a color filter array being used in the CCD camera, and the relevant demosaicing process of the sampling array reconstruction. The image and the dc noise from the hologram reconstruction may be of different distribution patterns due to the modulation function in the inverse Fourier transform of a full monochromatic sampling array (MSA) with demosaicing. Thus, this work reveals the potential relationship between the demosaicing algorithm for a full MSA reconstruction, the sampling frequency in the hologram recording, and the image periodicity in the hologram reconstruction. Finally the application of the image periodicity in zero-order noise suppression is discussed.
A long ring regenerative cavity for high energy chirped pulse amplification
Authors: Liu Cheng  , Wang Zhao-Hua  , Shen Zhong-Wei  , Zhang Wei  , Teng Hao  , Wei Zhi-Yi  ,   Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

We demonstrate a novel regenerative amplifier with a long ring cavity. Calculation on cavity parameters supports a large mode size. Based on the simulation with the cavity design software, we successfully established a 12 m ring regenerative amplifier. The amplified laser energy up to 20 mJ was obtained under 150 mJ green pump laser at a repetition rate of 10 Hz, corresponding to 13.3% conversion efficiency. The spectral bandwidth of the output pulse was 30 nm, which could support a sub 30 fs pulse duration. After seed injection, the ASE of the amplifier was effectively suppressed.
Analysis of stress-etching quality based on nanosecond pulse laser electrochemical machining
Authors: Zhang Zhao-Yang  , Li Zhong-Yang  , Qin Chang-Liang  , Yin Jie  , Zhang Chang-Tao  , Mao Wei-Ping  , Feng Qin-Yu  ,   Institute of Laser Technology, School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013, China
Published: December 2020

Nanosecond pulse laser electrochemical etching can remove the electrolytic products of laser irradiated region and so improve the processing stability and processing efficiency. The stress-etching characteristics and the material removal mechanism for aluminum alloy workpiece were investigated theoretically and experimentally by the use of a laser electrochemical machining system. For comparison of processing topography between laser direct etching in air and laser electrochemical machining, the scanning electron microscopy and the optical profilometry were used to detect and analyze etching morphological characteristics of machining areas. Based on the principle of mechanics and electrochemistry, stress-etching principles of laser electrochemical machining were studied. In this study, the effects of processing parameters and machining method on machining quality were explored, and a complex microstructure was processed successfully with reasonable processing parameters. The results show that laser electrochemical machining with better stability can reduce surface roughness and improve machining quality effectively.
Ultra-short laser pulse compression by using the group-velocity-matched cascaded quadratic nonlinearity
Authors: Ye Rong  , Zhang Bin  , Li Ke-Yu  ,   College of Electronics and Information Engineering, Sichuan University, Chengdu 610064, China;,   China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

A new method for compressing ultra-short laser pulse has been proposed in which cascaded quadratic nonlinearity with tilt pulse is used. The pulse compression scheme with group velocity matching between fundamental harmonic (FH) and second harmonic (SH) pulses in a single BBO crystal has been analyzed theoretically. The compressed results have been investigated and compared between the cases of group velocity matching and mismatching. Furthermore, the influences of the phase mismatching between the FH and SH pulses, the length of the nonlinear crystal, the initial peak intensity and pulse-duration of the FH pulse on the pulse-duration compression have been analyzed and simulated. The results show that the matched group velocity between FH and SH pulses can improve significantly both the temporal profile and the spectrum distribution of the compressed pulse. High quality compression can be achieved by optimizing and selecting the parameters such as phase mismatch, length of the nonlinear crystal, initial intensity and so on. For the fundamental pulse with 800 nm central wavelength, 100 fs duration and 50 GW/cm2 peak intensity, the 20fs output FH pulse has been achieved, and at the same time the 14 fs SH pulse has also been generated in 25 mm-long BBO crystal with Δk=60 mm-1 (1.98° detuning angle) and external tilt angle γ0=74°.
Impact of boundary on the surface soliton in (1+1)-dimensional nonlocal nonlinear media
Authors: Zhao Can  , Ma Xue-Kai  , Wang Jing  , Lu Da-Quan  , Hu Wei  ,   Laboratory of Photonic Information Technology, South China Normal University, Guangzhou 510631, China
Published: December 2020

In this paper, the impacts of boundary on the surface bright soliton in (1+1)-dimensional nonlocal nonlinear media are investigated First the solution of the surface soliton under the given boundary conditions in a normalized system is derived, and then, the critical power and the balance position of the surface soliton are obtained. Next, in the numerical simulation, due to the impact of boundary, it is difficult to form stable solitons when the width of the sample is too small. And the impact of the boundary on the soliton can be ignored only if the width of the sample is large enough; then the stable soliton can exist, which is similar to the analytical results. In addition, the impact of the boundary on the surface soliton when beams do not input from its equilibrium position is also investigated. In this case, the beam will propagate oscillating periodically about the stationary position, which is equivalent to the interaction of two out-of-phase solitons in nonlocal bulk media. Both the oscillating trajectory and period dovetail coinsde nicely with each other.
Experimental study on supercontinuum generation in zero-dispersion wavelength decreasing photonic crystal fiber
Authors: Zhu Xian  , Zhang Xin-Ben  , Xiang Chen  , Peng Jing-Gang  , Dai Neng-Li  , Li Hai-Qing  , Li Jin-Yan  ,   Wuhan National Laboratory for Optoelectronics, College Optoelectronic Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
Published: December 2020

We have carried out experimentally the supercontinuum generation in GeO2-doped-core uniform photonic crystal fiber and zero-dispersion wavelength-decreasing photonic crystal fiber with pump pulses 1.8 ps operating at 1040 nm. Dispersion and nonlinear effects such as cross-phase modulation, four-wave mixing, modulation instability play a crucial role as they extend the supercontinuum towards short wavelength side. Zero-dispersion wavelength-decreasing photonic crystal fiber can improve group-velocity matching between solitons and dispersive waves deduced from numerical simulation of the evolution of spectra generated in a taper and uniform fiber. We obtained experimentally a spectrum expanding to the blue side and the power variation is indeed of 10 dB over a spectral range of 165.7 nm (between 4061 and 6718 nm) in the taper fiber.
Determination and model construction of microbes' complex refractive index in far infrared band
Authors: Sun Du-Juan  , Hu Yi-Hua  , Gu You-Lin  , Wang Yong  , Li Le  ,   State Key Laboratory of Pulsed Power Laser Technology (Electronic Engineering Institute, Hefei 230037, China;,   Anhui Province Key Laboratory of Electronic Restriction Technology, Hefei 230037, China
Published: December 2020

Bacillus subtilis, Aspergillus niger spore and Aspergillus niger mycelium are chosen for samples preparation. The above three samples' reflection spectra in 2.5—15 μm band are recorded by using infrared microscopic spectrometer. From Kramers-Kronig (K-K) relationship, microbe samples' complex refractive indexes in 6—14 μm band are calculated. According to the microbe samples' absorption spectra, their water contents are calculated using the absorption characteristics of water, protein and nucleic acid. Based on the above three microbe samples' water contents and complex refractive indexes in far infrared band, biologic particle's complex refractive index model in 6—14 μm band are constructed and the model's reliability is analyzed. The construction of biologic particle's complex refractive index model has important significance in the development of rapid analysis and identification method of biologic samples, and the detection and identification technologies of biologic aerosol.
Effect of cooling of electron-hole plasma in electrically pumped graphene layer structures with split gates
Authors: Zhang Yu-Ping  , Liu Ling-Yu  , Chen Qi  , Feng Zhi-Hong  , Wang Jun-Long  , Zhang Xiao  , Zhang Hong-Yan  , Zhang Hui-Yun  ,   Qingdao Key Laboratory of Terahertz Technology, College of Science,Shandong University of Science and Technology, Qingdao 266510, China;,   Institute of Electronic Engineering, China Academy of Engineering Physics, Mianyang Sichuan 621900, China;,   Science and Technology on ASIC Labarotary, Shijiazhuang 050051, China
Published: December 2020

We have studied the effect of population inversion associated with the electron and hole injection in graphene layer n-i-p structures with split gates at room temperature. Considering the transverse electric field screening of the n-section, we calculated the dependence of the electron-hole effective temperature and optical phonon effective temperature on the gate-voltage. It is shown that the injection can lead to cooling of the electron-hole plasma in n-section to the temperatures lower than the lattice temperature. The current-voltage characteristics, and the frequency-dependent dynamic conductivity are calculated, the frequency-dependent dynamic conductivity can be negative in the terahertz frequency range at a certain applied voltage. The study demonstrates that electron-hole plasma cooling can enhance the negative dynamic conductivity effect and improve the feasibility of terahertz lasing.
Preparation and thermoelectric properties of Ag-ZnO nanocomposites synthesized by means of sol-gel
Authors: Wu Zi-Hua  , Xie Hua-Qing  , Zeng Qing-Feng  ,   School of Urban Development and Environmental Engineering, Shanghai Second Polytechnic University, Shanghai 201209, China
Published: December 2020

Zinc oxide (ZnO) has attracted increasing attention as one of the most promising n-type thermoelectric materials. Although ZnO has been screened for high power factor, the ZT results were discouraging for its high thermal conductivity. Preparing nanocomposite is an effective way to reduce the thermal conductivity. The Ag-ZnO nanocomposites were synthesized by means of sol-gel method and their thermoelectric properties were investigated. Their XRD pattern and SEM miro graphs show that Ag nanoparticles are mainly lecated at the grain boundary of ZnO. Increasing Ag content leads to a significant decrease in absolute value of Seebeck coefficient (|S|). The electrical conductivity increases with increasing Ag content, while the thermal conductivity of Ag-ZnO nanocomposites is much lower than the bulk ZnO sample. The highest ZT (0.062) is found for 7.5 mol% Ag@ZnO nanocomposite at 750 K, thirty-five times of that of bulk ZnO. Since the Ag-ZnO junction leads to charge redistribution, the deflexed energy band obtained for ZnO should facilitate the electron transfer across the interface and thus accelerates the mobility of charge carriers. Thus increasing mobility of charge carriers would lead to the increase in electrical conductivity and a decrease in Seebeck coefficient. The difference of thermal conductivity comes from the lattice thermal conductivity. Due to the high density of interfaces and grain boundaries present in the nanocomposites, the scattering of phonons across a broad wavelength spectrum is enhanced. This suppresses the lattice thermal conductivity of the nanocomposites significantly.
Exchange bias in BiFeO3/Ni81Fe19 magnetic films and its thermal stability
Authors: Zhou Guang-Hong  , Pan Xuan  , Zhu Yu-Fu  ,   Jiangsu Provincial Key Laboratory for Interventional Medical Devices, Huaiyin Institute of Technology, Huaian 223003, China;,   School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China
Published: December 2020

This paper deals with the exchange bias and its thermal stability in magnetic BiFeO3/Ni81Fe19 bilayer sputtered under an electromagnetic field. The results show that the BiFeO3/Ni18Fe19 bilayer presents an in-plane uniaxial magnetic anisotropy and a significant exchange bias effect, however the exchange bias field Hex in the BiFeO3/Ni18Fe19 bilayer does not show a visible training effect. The forward and recoil loop shifts towards positive fields, while holding the film in a negative saturation field. Hex decreases monotonously with the increase in the holding time (tsat), whereas Hc is almost the same. With increasing temperature Tm, Hex will not alter significantly, which means that Hex is not sensitive to the temperature, showing a good thermal stability. However, Hc may reduce rapidly with the increase in temperature. We believe that the good thermal stability may result from the coupling between ferroelectric and antiferromagnetic moments in BiFeO3.
Effects of Dy and Co co-substitution on the magnetic properties and TC of BiFeO3 ceramics
Authors: Song Gui-Lin  , Luo Yan-Ping  , Su Jian  , Zhou Xiao-Hui  , Chang Fang-Gao  ,   College of Physics & Information Engineering, Henan Normal University, Xinxiang 453007, China;,   Henan Key laboratory of photovoltail Materials, Xinxiang 453007, China
Published: December 2020

Multiferroic Bi0.95Dy0.05Fe1-xCoxO3 (x=0, 0.05, 0.1, 0.15) ceramics were prepared by rapid liquid phase sintering method. We studied the effect of (Dy+Co) doping on the structure, electrical and ferromagnetism properties of BiFeO3 ceramics. The structure and morphology of BiFeO3 ceramics were characterized by X-ray diffraction (XRD) and scanning electron microscopey (SEM). The results showed that all the peaks for Bi0.95Dy0.05Fe1-xCoxO3 samples can be indexed based on the crystal structure of pure BiFeO3. And XRD analysis revealed a phase transition in (Dy+Co) co-doped BiFeO3 when x was larger than 0.1 and grain sizes changed from 1 to 5 μm. Magnetic hysteresis loops were clearly observed in co-substituted specimens and magnetization was greatly improved. Magnetic measurements showed that all samples possess strong ferromagnetism at room temperature expect BiFeO3 and Bi0.95Dy0.05FeO3, which are weakly ferromagnetic. The M'rs, of Bi0.95Dy0.05Fe1-xCoxO3 with x=0.05, 0.01 and 0.15 are 0.43, 0.489, 0.973 emu/g and the M'rs of them are 0.77, 1.65, 3.08 emu/g, respectively. The magnetic moment of BiFeO3 and B0.95Dy0.05Fe1-xCoxO3 ceramics varies with temperature from 300 to 900 K at an applied field of 5 kOe. It shows that the TN of BiFeO3 from 644 to 648 K with different content of Dy3+ can be changed by crystal structures and exchanges between Dy3+-Fe3+. The phase transition temperature of Bi0.95Dy0.05Fe1-xCoxO3 shifted to lower temperatures from 870 K to 780 K demonstrate that Co3+ doping causes a drop of TC as compared with BiFeO3. The change of TC of Bi0.95Dy0.05Fe1-xCoxO3 depends mainly on the Fe-O-Fe super-exchange strength and the relative stability of magnetic structure.
Effect of synthesis temperature on preparation and field emission property of Ce-doped SiC nanowires
Authors: Li Zhen-Jian  , Li Wei-Dong  ,   College of Electromechanical Engineering, Qingdao University of Science and Technology, Qingdao 266061, China
Published: December 2020

In this paper, Ce doped-SiC nanowires were prepared by chemical vapor reaction technique at the different synthesis temperatures, and the field emission (FE) properties of the nanowires were measured. The products were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD). The results suggested that the products were β-SiC, the nanowires become bending and the content of Ce reduces with increasing temperature; the values of the turn-on and threshold field increase at first and then decrease. When the synthesis temperature is 1250 ℃, the content of Ce is 0.27 at%, the turn-on and threshold fields of the product are 2.5 V/μm and 5.2 V/μm.
The lithium intercalation properties of SnSb/MCMB core-shell composite as the anode material for lithium ion battery
Authors: Li Juan  , Ru Qiang  , Sun Da-Wei  , Zhang Bei-Bei  , Hu She-Jun  , Hou Xian-Hua  ,   Engineering Research Center of Materials and Technology for Electrochemical Energy Storage (Ministry of Education), Guangzhou 510006, China;,   Engineering Research Center of Materials and Technology for Electrochemical Energy Storage (Ministry of Education), Guangzhou 510006, China
Published: December 2020

SnSb/MCMB composite material was prepared by multi-step synthesis methods. Mesocarbon Microbeads (MCMB) powders were modified by acid treatment firstly, and then SnSb nano particles were deposited on the surface of MCMB through chemical reduction method forming a core-shell composite structure. To characterize the phase and morphology of the composites material, X-ray diffraction (XRD), scanning electron microscope (SEM) were used. The constant current charge and discharge (CD) and cyclic volt ampere (CV) methods were also used to test the electrochemical performance of SnSb/MCMB. The results demonstrated that SnSb/MCMB presents a multiphase system of nanocrystalline and amorphous structure. The capacity attenuation of SnSb alloy is faster than that of SnSb/MCMB. For the SnSb/MCMB composite, the tiny alloy particles were dispersed on the surface of MCMB powders, preventing from the serious agglomeration of nano particles. At the same time, the inner core MCMB can also buffering the volume effect of the alloy compoites to improve the elecrtochemical cycling stability. The composite material was a first discharge specific capacity of 936.161 mAh/g and the first Coulomb efficiency 80.3%. The specific capacity was still up to 498.221 mAh/g after 50 cycles.
Study of a selective averaging method for magnetocardiography-based noise suppression
Authors: Liu Ming  , Zhang Shu-Lin  , Li Hua  , Qiu Yang  , Zeng Jia  , Zhang Guo-Feng  , Wang Yong-Liang  , Kong Xiang-Yan  , Xie Xiao-Ming  ,   Electronic Science and Technology Department, University of Science and Technology of China, Hefei 230027, China;,   State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
Published: December 2020

Noise suppression is a key technique in retrieving weak magnetic signal from human heart. In order to improve the signal-to-noise ratio (SNR) of magnetocardiography (MCG) signals, signal average method is widely used. However, due to the existence of local environmental interference, averaging the whole section data would unavoidable bring distortion to the average signal. In this paper, the authors proposed a kind of selective average method by using the template matching. The results showed that this method can effectively eliminate the data section with interference such as low frequency fluctuation, pulse burr etc. Thus averaging MCG signal with high SNR and fidelity will be obtained.
A 2D semi-analytical model for the potential distribution of ultra-short channel MOSFET
Authors: Han Ming-Jun  , Ke Dao-Ming  , Chi Xiao-Li  , Wang Min  , Wang Bao-Tong  ,   Institute of Electronics and Information, Anhui University, Hefei 230601, China;,   Department of Electronics and Information, Wuhu Institute of Technology, Wuhu 241000, China
Published: December 2020

Based on the principle of ultra-short channel MOSFET, a definite solution of potential is proposed by introducing two rectangular sources between the insulated gate and the space-charge region. By using the semi-analytical method and the spectral method, the 2D semi-analytical solution has been obtained for the first time as faras we know. The solution is a special function for the infinite series expressions. The most advantage of this model is that it can not only be calculated directly without numerical analysis but also keep the same accuracy as that of numerical solution. In addition, this model, which can be directly used in circuit simulation, has the characteristics that in its expression there is no adapter parameter with small calculating amount. The potential, surface potential and threshold of 45—22 nm MOSFET have been calculated in the frame of this model. It is shown that the calculated results are identical with Medici.
Energy balance analysis over Loess Plateau and the consequences for carbon dioxide flux
Authors: Liang Jie-Ning  , Zhang Lei  , Zhang Wu  , Shi Jin-Sen  ,   Key Laboratory for Semi-Arid Climate Change of the Ministry of Education, College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China
Published: December 2020

This paper examines the surface energy imbalance status over the semi-arid areas of the Loess Plateau, using the data collected by eddy covariance (EC) and boundary layer meteorological measurement systems at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL). The energy balance ratio is about 0.80 during the daytime in all seasons, while that is only about 0.20 in the night. For the observation time with no local circulation, the energy balance ratio is improved to more than 85% in the daytime. Even in the night of spring, summer or autumn, the energy balance ratio is also improved to 70%. However, the ratio in nighttime of winter is only 29.4%. After taking into consideration all the energy budget items, the surface energy is still not closed, which means that the eddy covariance system underestimated the turbulent heat flux. And the observation error changes with seasons, with maximum in winter and minimum in spring. The errors of sensible heat flux and latent heat flux may impact CO2 flux through the WPL correction, and cause the uncertainty of long term net ecosystem exchange (NEE), and the NEE throughout the year can be overestimated by 41.2%.
The experiments of transseasonal prediction by combining together the dynamical and statistical methods of the geopotential height fields on the blocking high in the Eurasia mid-high latitudes
Authors: Zhao Jun-Hu  , Yang Jie  , Gong Zhi-Qiang  , Zhi Rong  ,   College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China;,   Laboratory for Climate Studies, National Climate Center, China Meteorological Administration, Beijing 100081, China
Published: December 2020

The blocking high in Eurasia mid-high latitudes (EMHBH) is one of the leading members of East Asian summer monsoon circulation system, which also has a crucial influence on the summer flood/drought in China, especially in the region of Yangtze River. However, the objective quantitative prediction of EMHBH is an urgent issue we are facing and also a complicated problem in the current short-term climate prediction. This paper, by using the dynamical and statistical prediction (DSP) methods and based on the forecast data of the numerical modal(CGCM) and the abundant historical observations, has carried out prediction experiments of the above three blocking high regions in the summer averaged 500 hPa geopotential height fields. The results show that the DSP methods can diminish the prediction errors to some extent, which is also suitable for operational application. In addition, sensitivity tests show that the selection of the number of similar targets or similar yeas has significant influences on the prediction results.
Mechanism of rapid-charging events for international space station
Authors: Huang Jian-Guo  , Yi Zhong  , Meng Li-Fei  , Zhao Hua  , Liu Ye-Nan  ,   Science and Technology on Reliability and Environmental Engineering Laboratory, Beijing 100094, China
Published: December 2020

The high negative amplitude rapid-charging events (RCEs), which were observed by the floating potential measurement unit (FPMU) on the International Space Station (ISS) and occurred at the eclipse exit, have attracted a lot of attention recently and are not yet understood. The RCEs are most serious of all types of ISS charging phenomena. Compared with the normal-charging events (NCEs) which occurred on morning sector, the RCEs are characteristic of rapid rise time (<10 seconds) and higher amplitude (30—70 V). In particular, their occurrence at the morning terminator indicates that they are related to the solar panel excitation process at the moment of receiving solar illumination. In this paper, an electric circuit model for the charging of the ISS structure and solar panel is established, based on which a differential equation is developed, with the different charging mechanisms included and also the way of solar panel excitation considered. The calculation results for the RCEs agree well with the typical waveforms.
Memristive chaotic circuit based on modified SC-CNNs
Authors: Li Zhi-Jun  , Zeng Yi-Cheng  , Li Zhi-Bin  ,   College of Information Engineering, Xiangtan University, Xiangtan 411105, China;,   Dept. of Optoelectronic Engineering, Xiangtan University, Xiangtan 411105, China;,   College of Energy Engineering, Xiangtan University, Xiangtan 411105, China
Published: December 2020

Memristor, as a fundamental nonlinear circuit element, is very suitable for realizing new nonlinear circuits that are able to exhibit complex dynamical behaviors. A modified state-controlled cellular nonlinear network (SC-CNN) cell containing memristors, the output nonlinear function of which is implemented with the intrinsic nonlinearity of memristor, is presented in this paper. By using appropriate connection of four modified SC-CNN cells, a SC-CNN based memristive chaotic circuit is developed. In particular, an imitative memristive circuit is developed to experimentally investigate its dynamical behaviors. The resemblance of experimental results with those of numerical simulations shows that the memristive chaotic circuit can be efficiently implemented in terms of SC-CNN scheme.
A sectioned method to correct spectral imaging data degraded by satellite vibrations
Authors: Nan Yi-Bing  , Tang Yi  , Zhang Li-Jun  , Chang Yue-E  , Chen Ting-Ai  ,   Key Laboratory of Photoelectronic Imaging Technology and System School of Photoelectricity, Beijing Institute of Technology, Beijing 100081, China
Published: December 2020

The quality of spectral imaging data will be degraded by the vibrations of satellite platform. We study the methods to correct degraded spectral imaging data in this paper. First, the vibration patterns of satellites and the degradation mechanism of the motion imaging of dispersion imaging spectrometer are introduced. Considering the problems of traditional two-dimensional deconvolution algorithms, and the speciality of push-sweeping mechanism, a sectioned correction method is presented, in which are combined image dividing, dimension rising, and gradual splicing. And the motion deblurring algorithm based on natural image statistics is applied in the correction of degraded spectral imaging data. We implement degradation and correction experiments for various data. Results show that the qualities of spectral imaging data are significantly improved for both the spatials and spectrals. Our method is better than the traditional deconvolution algorithms.
Improvement of the output power of optical pumping THz lasers based on the theory of vibrational relaxation
Authors: Zhang Hui-Yun  , Liu Meng  , Zhang Yu-Ping  , He Zhi-Hong  , Shen Duan-Long  , Wu Zhi-Xin  , Yin Yi-Heng  , Li De-Hua  ,   Qingdao Key Laboratory of Terahertz Technology, College of Science, Shandong University of Science and Technology, Qingdao 266510, China;,   Department of Electronic Engineering, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China
Published: December 2020

Based on the semiclassical density matrix theory and vibrational relaxation theory, the present paper studies the influences on optical pumping THz lasers output power due to adding an appropriate proportion of buffer gas and appropriately reducing the waveguide core diameter. Results prove that adding appropriate proportion of buffer gas or appropriately reducing the waveguide core diameter can increase the output of light intensity of THz laser. Optimizing the two parameters at the same time can further improve the efficiency of pumping laser energy into THz laser energy, extend the effective activation area of the working cavity, put off the appearance of the pumping saturation effect, and increase the output power of the THz lasers. This research may have a guiding significance for the THz optical pumping laser in improving energy conversion efficiency, and increasing the output power so as to bring about the miniaturization of THz optical pumping laser.