bluuebunny/crossref_metadata_2025 huggingface dataset:
Research on large dynamic range streak camera based on electron-bombarded CCD
Authors: Zhu Min  , Tian Jin-Shou  , Wen Wen-Long  , Wang Jun-Feng  , Cao Xi-Bin  , Lu Yu  , Xu Xiang-Yan  , Sai Xiao-Feng  , Liu Hu-Lin  , Wang Xing  , Li Wei-Hua  ,   State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an 710119, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

In order to detect the weaker on greater span of light signals, the dynamic range, spatial resolution, and the signal to noise ratio of the streak camera need to be improved to meet further diagnostic requireflents in scientific area of materials, biology, information, semiconductor physics and energy, etc. Therefore, we design a streak camera with a larger dynamic range based on electron-bombarded CCD. Using the rectangle-framed electrode and electric quadruple lens in the streak camera can reduce its space charge effect and shorten the space charge interaction time by improving electron accelerating voltage to minimize the electron transit time. Using a back-illuminated CCD, which is based on the electron bombardment readout technology as image device to replace the traditional intensified CCD can shorten the chain of image conversion and greatly reduce the image degradation in the conversion of ultrafast diagnostic equipment. The signal to noise ratio, spatial resolution and dynamic range of the streak camera may gain improvement. Experimental results show that the static spatial resolution is better than 35 lp/mm and the dynamic spatial resolution is up to 20 lp/mm. Deflection sensitivity is 60.76 mm/kV and dynamic range reaches 2094: 1. Nonlinear scanning speed is 5.04%. EBS gain of the streak camera can be over 3000.
X-ray focusing optics and its application in X-ray communication system
Authors: Liu Duo  , Qiang Peng-Fei  , Li Lin-Sen  , Su Tong  , Sheng Li-Zhi  , Liu Yong-An  , Zhao Bao-Sheng  ,   State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Science, Xi'an 710119, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

X-ray communication, which was first introduced by Keith Gendreau in 2007, is potential to compete with conventional communication methods, such as microware and laser communication, against space surroundings. Researchers have spent much time and effort on the mission making the initial idea into reality in recent years. Eventually, the X-ray communication demonstration system based on the grid-controlled X-ray source and single-photon detection technique can deliver both audio and video information in a 6-meter vacuum tunnel, and the bit-error-rate performance of the communication system is analyzed. But it is difficult to implement applications in industries. The point is to find a way to reduce the signal divergence geometrical attenuation and increase the distance of the communication which can be regarded as an important foundation of future deep-space X-ray communication applications. Therefore, it is urgent to study the X-ray communication system. By using a nested X-ray focusing optics as transmitting and receiving antennas of the communication system, the signal gain and the distance of X-ray communication can be greatly improved. Specifically, the nested X-ray focusing optics is similar to the Wolter type I telescope, which is widely used in the field of X-ray astronomy. The difference between them is that the Wolter type I optics is originally proposed based on a paraboloid mirror and a hyperboloid mirror, but X-ray focusing optics, the simplified Wolter type I optics, provides a single reflection by a conical approximation mirror, and it is more suitable for X-ray communication. In this paper, aiming at the future demand of X-ray communication, the optimization and analysis of the nested X-ray focusing optics are carried out, and the recurrence relations between the layers of mirrors are derived. Reasonable initial structural parameters and structure of the optics are designed. In addition, the theoretical effective collection area is calculated. Feasibility of using the X-ray focusing optics as transmitting and receiving antennas is analyzed, and the theory and structural design of the X-ray focusing optical are discussed. Signal divergence of transmitting antenna, effective area of receiving antenna, the focal spot size, and the signal gain properties are preliminary studied. The results show that the signal divergence is about 3 mrad, and the transmit gain is 23 dB; the effective area of receiving antenna is 5700 mm2 at 1.5 keV. Moreover, the focal spot diameter and the receive gain are 4.5 mm and 25 dB, respectively, and the total gain of this communication system can reach up to 48 dB.
First-principles study on the electronic structures and optical properties of Cu, Fe doped LiNbO_3 crystals
Authors: Zhao Bai-Qiang  , Zhang Yun  , Qiu Xiao-Yan  , Wang Xue-Wei  ,   School of Physical Science and Technology, Southwest University, Chongqing 400715, China
Published: December 2020

The binding energies, electronic structures and optical properties of LiNbO3 and Cu/Fe doped LiNbO3 crystals are investigated by first principles based on the density functional theory in this paper. The supersell structures of crystals are established each with 60 atoms, including five models: pure LiNbO3, LN1 (Cu2+ occupy Li+ site), LN2 (Fe3+ occupy Li+ site), LN3 (Cu2+ occupy Li+site and Fe3+ occupy Li+ site) and LN4 (Cu2+ occupy Li+ site and Fe3+ occupy Nb5+ site). The optimized results show that the total energies of all models can achieve certain stable values, which means that the models accord with the actual crystal structures. The impurity energy levels of Cu and Fe doped LiNbO3 crystals appear within the band gaps, which are contributed by Cu 3d orbital, Fe 3d orbital and O 2p orbital; in co-doped LiNbO3, Cu offers deep energy level and Fe offers shallow energy level within the band gaps. There are two wide absorption peaks appearing respectively at 445 nm and 630 nm in co-doped LiNbO3 crystal, which correspond to the electron transitions from Eg orbital of Cu to Nb 4d orbital and T2g orbital of Fe to Nb 4d orbital respectively; the absorption edge of Cu, Fe mono and co-doped LiNbO3 crystals are red-shift successively, which coincides with the variation of band gape. The light absorption intensity of co-doped LiNbO3 crystal is stronger than that of mono-doped LiNbO3 crystal. The co-doped sample light absorption property is related to Fe site occupation. In this paper, it is suggested that the co-doped sample with Fe at Nb site is more competitive than that with Fe at Li site in optical volume holographic storage applications, and that reducing properly [Fe2+]/[Fe3+] value may be conducible to the formation of this advantage.
Experimental study of clustering behaviors in granular gases
Authors: Wang Hua  , Chen Qiong  , Wang Wen-Guang  , Hou Mei-Ying  ,   School of Physics, Beijing Institute of Technology, Beijing 100081, China;,   Key Laboratory of Soft Matter Physics, Beijing National Laboratory for Condense Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

Granular materials are widely spread in nature and in industry. Owing to the inelastic collisions between particles and frictions among particles, granular systems are dissipative in nature. This intrinsic dissipative nature causes local clustering in granular gas systems. This is a unique phenomenon compared with the molecular gases. Understanding and predicting the condition and parameter values when this phenomenon happens will be helpful for us to gain knowledge of the conditions of clustering or pattern formations in non-equilibrium complex systems. The clustering phenomenon in granular gas is analyzed using phase-separation modeling of van der Waals-like molecules. The results from the model are verified by molecular dynamics numerical simulations. However, due to the influence of the gravity, experimental verification is difficult in laboratory. In this work, we perform an experiment in micro-gravity environment provided by the drop tower of National Microgravity Laboratory Chinese Academy of Science. In the experiment we for the first time observe the phase-separation clustering phenomenon. Comparing the observation condition with the model prediction, we are able to indirectly obtain the restitution coefficients of particles used in the experiment. A model calculation for the spinodal regime under experimental conditions is performed for possible particle restitution coefficients, and a comparison with the experimental observation allows us to justify the values of the restitution coefficients. It is found that the coefficient is larger for bigger particles. For d=2.5mm titanium particles, the restitution coefficient is higher than 0.8; for d=1mm titanium particles, the restitution coefficient is about 0.8, and for d=0.5mm titanium particles, the restitution coefficient is between 0.6 and 0.8. This useful result can be essential for comparing experimental observation with the theoretical and the numerical results, and is crucial to the success in the SJ-10 satellite experiments.
Dynamic properties of a small-size streak tube
Authors: Hui Dan-Dan  , Tian Jin-Shou  , Wang Jun-Feng  , Lu Yu  , Wen Wen-Long  , Xu Xiang-Yan  ,   Key Laboratory of Ultra-fast Photoelectric Diagnostics Technology, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an 710119, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Scannerless (flash) lidar system based on streak camera is able to realize three-dimensional (3D) multi-spectral fluorescence imaging and 3D imaging polarimetry. Compared with conventional lidar system, the flash lidar system overcomes image distortions caused by the motion between the target and the sensor platform. Other advantages of the flash lidar system are higher image update rates and the potential for creating a miniaturized lidar system. To meet the requirements for developing this new technology, a super small-sized, large photocathode area and meshless streak tube with spherical cathode and screen is designed with the aid of computer simulation technology (CST) software. The tube with nearly 28 mm wide photocathode work area contains two electrostatic focusing lens, a pair of deflection plates, and a 50 mm diameter output screen. The external dimension of the tube is merely 50 mm100 mm. And its electromagnetic fields are calculated in the CST Particle Studio based on the finite integration theory. Some dynamic properties of the tube are analyzed via observing different electron trajectories launched from a number of different points on the cathode. The influences of the deflector position on deflection sensitivity and spatial resolution are analyzed. Increasing the distance between the deflector and the anode pin hole leads to a worse deflection sensitivity but a better spatial resolution. As for the temporal resolution, three electron pulses separated by 30 ps can be well resolved by the streak tube in the dynamic mode. Thus, the dynamic temporal resolution of the streak tube is better than 30 ps. And a 10 lp/mm spatial resolution across the 28 mm long slit on the photocathode can be obtained by estimating modulation transfer functions of the electron trajectories. Temporal distortions at the entire photocathode working area are evaluated, and the data reveal that the larger the photocathode working area, the bigger the temporal distortions are. Also, the temporal distortion is present mainly in the photocathode-to-deflection plates region. In addition, the slit image of the streak tube working in the dynamic mode is simulated and presented. The phenomenon that the slit image is curved due to the temporal distortion is analyzed. Two rectangular electron pulses separated by 50 ps are well resolved by the streak tube. Therefore, the temporal resolution of this small-size steak tube is better than 50 ps with a rectangular slit dimension of 30 mm50 m on the photocathode, and its electron-optic magnification is 1.2.
Applications of Yangian algebra in the entanglement and the decay channels of the mixed meson state
Authors: Qin Li-Guo  , Tian Li-Jun  , Wu Shi-Chao  ,   Jiading Campus, Shanghai Open University, Shanghai 201800, China;,   Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China;,   Department of Physics, Shanghai University, Shanghai 200444, China
Published: December 2020

Yangian, as an algebra beyond the Lie algebra, is an infinite dimensional algebra and a powerful mathematical method for inVestigating the new symmetry of quantum systems which are nonlinear and integrable. Based on the su(3) symmetry of the quarK-flaVor in the meson states and the transition property of the generators in Yangian algebra, we study the applications of Yangian algebra Y(su(3)) in the decay of three mixed meson states(, K and Ki0) composed of the three positiVe and negatiVe meson states (, K, K0 and K0). As the transition operators, the eight generators (Ī, Ŭ, V, Ī3 and Ī8) of Yangian algebra Y(su(3)) are acting on the three mixed meson states, respectiVely. Then, the possible decay channels and the changes of the entanglement are studied. Results show: (i) Under the effects of Ī3 and Ī8 within the Lie algebra on the three mixed meson states, the compositions of the final states after decays of the three mixed meson states are not changed as compared with the initial state. The entanglement is not changed for the decay of the mixed meson state with the effect of Ī^8, and the others are changed. (ii) Under the effects of the other six generators (Ī, Ŭ and V) beyond the Lie algebra on the three mixed meson states, the compositions of the final states after the decay are changed compared
with the initial state. In the six possible decay channels, the two final states become single states without entanglement; two decay channels are absent; and the entanglements of the final states in the remaining two decays are changed. In addition, the entanglement of the final meson states in the possible six decay channels of the two types K mixed meson states, the charged (K+, K-) and neutral (K0, K0) meson states, are the same two by two. (iii) The three mixed meson states can be circularly transferred by the operators Ī, Ŭ and V, implying the obVious symmetry. In this paper the Yangian method is presented to study the possible decay channels of the mixed meson states and may be used to present a possible interpretation of the new unKnown or Known particle in the decay of the mixed meson.
Acoustic detection and nonlinear response of granular materials under vertical vibrations
Authors: Zhang Pan  , Zhao Xue-Dan  , Zhang Guo-Hua  , Zhang Qi  , Sun Qi-Cheng  , Hou Zhi-Jian  , Dong Jun-Jun  ,   Department of physics, University of Science and Technology Beijing, Beijing 100083, China;,   College of Mechanics, Taiyuan University of Technology, Taiyuan 030024, China;,   State Key Laboratory for Hydroscience and Engineering, Tsinghua University, Beijing 100084, China
Published: December 2020

Owing to their efficient penetration into elastic media, the measurement of sound waves can provide a sensitive probe of both the structural and mechanical properties of the materials through which they propagate. In this work, we first investigate the transversal and longitudinal wave velocities in granular assemblies composed of glass beads under uniaxial load by the time-of-flight method. Then the ratio G/B, (G is the shear modulus and B is the bulk modulus) as a function of pressure is analyzed, based on the theory of classical elasticity. Experimental results show that, with the pressure increasing from 10 to 100 kPa, i) the velocity of longitudinal wave (cL ) is obviously faster than that of transversal one (cT ) in the granular system(the ratio cL/cT is about 1.6), and the cL and cT of the system show power law scaling, i.e. cL p0.3817, cT p0.2809; ii) the ratio G/B decreases in the low pressure range for glass beads packing, i.e. G/B p-0.4539. It is found that the power-law exponent of G/B with pressure is very close to -1/2 (the prediction in 2015 Phys. Rev. Lett. 114 035502), suggesting that the granular system lies in glass L state within the pressure range in our experiment. Furthermore, the fast Fourier transform method is used to study the variation of acoustic attenuation and nonlinear characteristics in granular materials. Our results reveal that the acoustic attenuation coefficient () and the ratio of the second harmonic amplitude ( 2 ) to the square of fundamental amplitude ( 1 ) at the receiving end in the granular system, 2/12, both decrease in power law with the increase of pressure, i.e. p-0.1879, 2/12 p-0.866, respectively.
Influence of atomic potential on the generation of high harmonic generation from the atoms irradiated by mid-infrared laser pulses
Authors: Liu Yan  , Jia Cheng  , Guo Fu-Ming  , Yang Yu-Jun  ,   College of Sciences, Jilin Institute of Chemical Technology, Jilin 132022, China;,   Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China;,   Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy (Jilin University), Changchun 130012, China
Published: December 2020

By numerically solving the time dependent Schrodinger equation, the harmonic spectra generated from the atoms are obtained. The atomic potentials are modeled by a short-range potential and a long-range soft Coulomb potential, respectively. It is found that using the same laser parameters, the intensity of harmonic spectrum from the short-range atom is lower than the one from the long-range atom. However, in a high energy (near the cutoff) region of harmonic spectra, their conversion efficiencies are almost the same. The differences in emission intensity among harmonic spectra decrease as the harmonic energy increases. We calculate the time dependent probabilities of the ground state and ionization. It is found that the ionization probability of the long-range potential is larger than that of the short-range potential. There is no large difference in ground probability between the potentials of two models. The high harmonic generation is a stimulated process, and its intensity is proportional to the product between the amplitude for ground state and the amplitude of the continuum state. Thus the product of the long-range atom is larger than that of the short-range atom, and the emission spectrum presents a similar character. In order to analyze the mechanism of the intensity difference between two models, we perform a time-frequency analysis of the harmonic emission spectrum. The analysis is selected of the wavelet of the time dependent dipole moment. From the emission profile of the harmonic analysis, we find that the harmonic generated from long orbit plays a dominant role for the short-range atom. The amplitudes of electric field are large for the long orbit harmonic emission, thus the ionization mechanism of the atom is the tunnel ionization. For the short orbit, the instant field for the ionization is weak. Thus the short orbit plays a small role in the harmonic emission from the short-range atom. Using this feature of the short-range atom, we generate an isolated attosecond pulse. The short model atom is widely used to study the ionization of the plasma. Thus this work will contribute to the research on the high-order harmonic generation from the plasma.
Element area analysis of chaotic morphology of verical gas-liquid two-phase flow
Authors: Chen Ping  , Du Ya-Wei  , Xue You-Lin  ,   School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072, China;,   Beijing Pingguozhi Technology Co., Ltd, Beijing 100124, China;,   Engineering Research Center of Seawater Utilization Technology of Ministry of Education, School of Marine Science and Engineering, Hebei University of Technology, Tianjin 300130, China;,   College of Light Industry, Liaoning University, Shenyang 110036, China
Published: December 2020

In order to better understand the variation of flow structure with delay time, we propose the element area (EA) of attractor morphology parameter in this paper. First, the conductance fluctuating signals and adaptive optimal kernel time-frequency representations of different gas-liquid flows are shown, we can find that flow pattern evolution is always accompanied by the numerical and frequency changes of large amplitude fluctuation (LAF). Then three kinds of signals, i. e., rossler signal, white noise and sinusoidal signal with multi-components, are used for analyzing the simulations, and the results indicate that the greater the frequency of LAF, the smaller the delay time of first crest of EA( peak ) is, and that the more the LAF, the bigger the peak value of first crest of EA(hpeak) is. Additionally, we use the above rule to analyze the conductance fluctuating signals measured from upward gas-liquid two-phase flow experiments and the signal length is selected to be 10 s for analysis. When the water superficial velocity is fixed to be 0.1138 m/s and the gas superficial velocity is gradually increased, we find that the peak is constant and hpeak changes up and down at bubble flow. When the flow pattern evolves into bubble-slug transition flow, the peak begins to turn bigger, and when the flow pattern evolves into slug flow, the peak becomes constant again while the hpeak increases monotonically with the gas flow rate increasing. The peak begins to become smaller as the flow pattern evolves from slug flow into churn flow, and we can find that the peak and hpeak of transition flow are alike. The peak and hpeak of bubble flow and churn flow are also alike because their dynamical mechanisms are similar but the downward trend of bubble flow is more gently than that of churn flow. When the water superficial velocity is fixed to be 0.2719 m/s, we can find similar variations of peak and hpeak to the above. Finally we determine the fall ratio (Rf) which is the ratio of the difference between the first crest and the first trough of EA and the hpeak, and then quantitatively distinguish three typical flow patterns, i.e., bubble flow, slug flow and churn flow by the Rf - peak distribution.
Effect of wall secondary electron distribution function on the characteristics of stable sheath near a dielectric wall
Authors: Qing Shao-Wei  , Li Mei  , Li Meng-Jie  , Zhou Rui  , Wang Lei  ,   Institute of Power Engineering, Chongqing University, Chongqing 400044, China
Published: December 2020

It is widely known that the energy distribution of secondary electrons induced by a single-energy electron beam presents typical bimodal configuration. However, the total velocity distribution of secondary electrons induced by a Maxwellian plasma electron group has not been revealed clearly, due to the lack of detailed theoretical calculation and calculation and experiment result. Therefore, researchers usually function satisfies single-energy distribution ( 0), half-Maxwellian distribution and so on, in order to study the characteristics of stable fluid sheath near a dielectric wall. For this reason, using the Monte Carlo method to simulate the wall secondary electron emission events based on a detailed probabilistic model of secondary electron emission induced by single-energy incident electron beam, we found that, when the incident electron follows an isotropic Maxwellian distribution, the total perpendicular-to-wall velocity distribution of the secondary electrons emitted from dielectric wall follows a three-temperature Maxwellian distribution. In the simulation, the incident angle of the plasma electrons and the emergence angle of the secondary electrons are considered, so the Monte Carlo method can discriminate whether the secondary electron velocity is perpendicular to or parallel to the wall surface. Then, a one-dimensional stable fluid sheath model is established under the wall boundary condition that the secondary electrons obey the three-temperature Maxwellian distribution; and some contrastive studies are made in order to reveal the effect of wall total secondary electron distribution functions such as single-energy distribution, half-Maxwellian distribution, and three-temperature Maxwellian distribution with the sheath characteristics. It is found that the total secondary electron distribution function can significantly influence the ion energy at the sheath interface, the wall surface potential, the potential and electron/ion-density distributions, and so on. Both the ion energy at sheath interface and the wall surface potential increase monotonously with the increase of wall total secondary electron emission coefficient. But the values of three-temperature Maxwellian distribution differ much from that of half-Maxwellian distribution and single-energy distribution. When the total secondary electron follows a three-temperature Maxwellian distribution, the critical space charge saturated sheath has no solution, indicating that with the increase of the wall total secondary electron emission coefficient, the sheath will directly transit from the classic sheath structure to the anti-sheath one. In the future work, a kinetic, static sheath model will be developed in order to study the characteristics of anti-sheath and space charge saturated sheath near a dielectric wall
Fabrication and excellent formaldehyde Gas sensing properties of Yb-doped In2O3 nanotubes
Authors: Wang Xue-Song  , Wang Guo-Guang  , Li Hai-Ying  , Wang Lian-Yuan  , Liu Li  , Guo Xue-Xin  , Wang Han  , Lian Hong-Wei  ,   State Key Laboratory of Superhard Materials, College of Pysics, Jilin University, Changchun 130012, China
Published: December 2020

Pure and Yb-doped In2O3 nanotubes have been successfully fabricated by using the single-capillary electrospinning method, followed by calcination. The morphological and structural characteristics of the as-synthesized nanotubes are investigated by scanning electron microscope (SEM) and X-ray powder diffraction (XRD). The SEM images reveal that all the pure and Yb-doped In2O3 nanotubes are distributed evenly, and the average diameter of the as-synthesized nanotubes is about 200 nm. The XRD analysis results show that the as-prepared samples are well-crystallized, and the diffraction peaks can be indexed according to cubic In2O3. Gas sensors based on pure and Yb-doped In2O3 nanotubes have been fabricated and investigated for formaldehyde detection in detail. As shown in the experimental results, Yb-doped In2O3 nanotubes exhibit enhanced formaldehyde sensing properties compared with pure In2O3 nanotubes. At the optimum operating temperature of 230 ℃, the response of the gas sensors based on pure In2O3 nanotubes to 100 ppm formaldehyde is 18.4, while the response of gas sensors based on Yb-doped In2O3 nanotubes is 69.8 in the same working condition, which is 3.8 times larger than that of pure In2O3 nanotubes. The improvement of Yb-doped In2O3 nanotubes gas-sensing property may be due to the formation of the heterojunction structure at the interface between the two different semiconducting oxides. The response and recovery times of Yb-doped In2O3 nanotubes to 100 ppm formaldehyde are about 4 s and 84 s respectively, indicating the fast response speed of Yb-doped In2O3 nanotubes. Moreover, even at 100 ppb of formaldehyde a detectable response can be observed and the value is 2.5. The low limit of formaldehyde detection shows that the as-synthesized Yb-doped In2O3 nanotube gas sensors can be used for the detection of dilute formaldehyde. Furthermore, the Yb-doped In2O3 nanotube gas sensors have excellent selectivity towards formaldehyde. In this experiment, acetone has the highest sensitivity in a variety of common interfering gases and the response value is 22 to 100 ppm at 230 ℃, which is less than one-third of the sensitivity of formaldehyde. Carbon monoxide has the lowest response value of 1.7, which is much lower than that of formaldehyde. In addition, the responses of gas sensors to different concentrations of formaldehyde almost unchanged during the test (50 days), indicating that the Yb-doped In2O3 nanotubes possess good repeatability and long-term stability. The excellent formaldehyde gas-sensing properties of Yb-doped In2O3 nanotubes indicate that the as-synthesized nanomaterials can be used as a promising candidate to detect formaldehyde in practical applications.
Collapse and evolution of wave field based on a generalized nonlinear Schrdinger equation
Authors: Cui Shao-Yan  , Lü Xin-Xin  , Xin Jie  ,   School of Mathematics and Statistics Science, Ludong University, Yantai 264025, China
Published: December 2020

A generalized nonlinear Schrdinger equation is numerically studied using the split-step Fourier method. For a fixed external potential field and an initial pulse disturbance, the effects of the complex coefficients p and q in the nonlinear Schrdinger equation on the evolution of the wave field are investigated. From a large number of simulations, it is found that the evolution of the wave field remains similar for different signs of the real parts of p and q, and different values of the real part of p. The initial pulse consisting of the longest wavelength modes (in the smallest-|k| corner of the phase space) of the spectrum first suffers modulational instability. Collapse begins at t～0.1, followed by inverse cascade of the shortest wavelength modes to longer wavelength ones, so that the whole k space becomes turbulent. For p = 1+0.04i, and q = 1+0.6i, it is found that first modulational instability occurs in the longer wavelength regime and the wave energy is transferred to the larger |k| modes. Then the wave collapse appears with increasing wave energy. Next, the large-|k| modes condense into a smaller-|k| mode by inverse cascade before spreading to the center of the phase space, until a turbulent state occurs there. Finally, most of the wave energy is condensed to the neighborhoods of three modes.
Auto-adjust lag particle filter smoothing algorithm for non-linear state estimation
Authors: Yang Wei-Ming  , Zhao Mei-Rong  ,   State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China;,   College of Electronic Information and Automation, Tianjin University of Science & Technology, Tianjin 300222, China
Published: December 2020

A novel particle filter smoothing algorithm for non-linear state estimation is proposed. The key point of this algorithm is that the length of the interval of the particle filter smoothing can be dynamically computed by the difference between the particle and the signal observations, which effectively suppress the phenomenon of increasing error of the system state estimation caused by the particles' weight redistribution when using the fixed smoothing interval method. By considering the signal and the heat bath as an abstract universe based on the particle filter/resampling, a physical analogy is made between the particle filter and the abstract universe, which obeys the second law of thermodynamics. That is to say, when there is no new observation, no matter where the initial state is from, the entropy of the whole system will increase. However, with the coming of the observations this law can be violated. The particle filter behaves like a Maxwellian demon in this physical analogy, returning energy to the heat bath which thus causes entropy to decrease. This is possible due to the steady supply of new information. Then the length of the smoothing interval can be dynamically corrected based on the change of the entropy, so the weight assignments of the particles is optimized, and the performance of the particle filter can be improved. The estimation accuracy of the approach which is verified by simulations is better than the traditional smoothing methods with an affordable computation burden.
Broadband acoustic focusing effect based on temperature gradient distribution
Authors: Liu Chen  , Sun Hong-Xiang  , Yuan Shou-Qi  , Xia Jian-Ping  ,   Faculty of Science, Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang 212013, China;,   State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

Acoustic focusing effect with broad bandwidth based on the temperature gradient distribution is studied. The propagation paths of the acoustic waves can be controlled by the temperature gradient distribution generated by two heat sources, which is adopted to realize the acoustic focusing effect. This focusing effect arises from the continuous change of the acoustic refractive index induced by the change of temperature, and has no reflection energy loss. Therefore, the acoustic focusing effect has the advantages of broad bandwidth and high focusing performance. In addition, we have investigated the influences of the factors (incident frequency, temperature of heat source, spatial distribution of interface, position of heat source, attenuation coefficient of the medium, and asymmetric distribution of heat source temperature) on the acoustic focusing effect in detail, and verified the feasibility of the acoustic focusing system by using aerogel based on temperature gradient distribution in single medium.
Sauna-like process prepared periodic molybdenum metal catalytic electrodes and their applications in water reduction
Authors: He Rui-Xia  , Liu Bo-Fei  , Liang Jun-Hui  , Gao Hai-Bo  , Wang Ning  , Zhang Qi-Xing  , Zhang De-Kun  , Wei Chang-Chun  , Xu Sheng-Zhi  , Wang Guang-Cai  , Zhao Ying  , Zhang Xiao-Dan  ,   Institute of Photoelectronic thin Film Devices and Technology of Nankai University, Key Laboratory of Photoelectronic Thin Film Devices and Technology, Tianjin 300071, China
Published: December 2020

To verify that the molybdenum metals exhibit similar catalysis characteristics as the related molybdenum compounds, i.e. molybdenum selenide (MoSe2) and molybdenum sulfide (MoS2) which have been well known as the high-performing catalysts for hydrogen evolution reactions, we may thus seek a low-cost, process-simplified, scalable, and highly-catalytic counterpart. We have grown periodic molybdenum (Mo) metal catalytic electrodes by employing self-assembled polystyrene (PS) spheres prepared by a sauna-like method as templates, followed by a reactive ion etching (RIE) process with oxygen gas and a double-layer deposition by low-temperature magnetron sputtering. By controlling the etching time of oxygen gas on PS spheres during the RIE process, the lateral and vertical feature sizes of Mo catalytic electrodes can be efficiently controlled, thereby having various surface area ratios. According to surface morphologies from atomic force microscopy, electrochemical linear sweep voltammetry, Tafel, and impendency measurements, we have found that the surface roughness and surface area ratios of Mo metal catalytic electrodes can be enhanced by prolonging the etching times of PS spheres, thereby reducing the charge transfer resistances and Tafel slopes, and then improving the hydrogen evolution reactions at the catalysts/electrolyte interfaces. We attribute this improvement to the fact that the Mo metal catalytic electrodes can efficiently form beneficial Schottky junctions with the electrolyte to enhance the carrier transportation, and the increased surface area ratios can improve the effective area of the Schottky junctions, thereby enhancing the carrier transportation at the catalysts/electrolyte interfaces. Tafel slope of the periodic molybdenum (Mo) metal catalytic electrodes in our work is as low as about 53.9 mV/dec, equivalent to highly catalytic materials MoS2 (55 mV/dec) and MoSe2 (105-120 mV/dec). The proposed periodic Mo catalytic electrodes, which combine a simple sauna-like self-assembly process with a double-layer Mo architecture is scalable and simple; and the surface area of periodic molybdenum (Mo) metal catalytic electrodes can also be flexibly controlled, so that the low-temperature magnetron sputtered Mo metal catalytic electrodes are cost-effective and highly compatible with various photovoltaic devices, highlighting the great potential to form high efficient monolithic solar-water-splitting devices.
Interface performance of PbTe-based thermoelectric joints
Authors: Wang Ya-Ning , Chen Shao-Ping , Fan Wen-Hao , Guo Jing-Yun , Wu Yu-Cheng , Wang Wen-Xian ,   College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China,   College of Physics and Optoelectronic Engineering, Taiyuan University of Technology, Taiyuan 030024, China
Published: December 2020

The conversion efficiency of thermoelectric material PbTe is high. A high-quality and high-conversion-efficiency PbTe thermoelectric connector is investigated systematically. Excess Pb in composition can increase the carrier concentration and improve the thermoelectric performance of PbTe. The composite electrode can improve the interface barrier and reduce the contact resistance. Traditional processes of making contacts onto bulk crystalline PbTe-based materials do not work for reducing the contact resistance by inhibiting element diffusion and increasing the shear strength at the same time. In this study, we consider a composite electrode which can form an intermediate layer to suppress the diffusion of the Pb element on the PbTe side. This work not only reduces the contact resistance, but also increases the shear strength. The sample Pb50.01Te49.99 is obtained by adjusting the stoichiometric ratio of PbTe; Te and Pb are mixed in the Fe electrode. The composite electrode and Pb50.01Te49.99 are hot-pressed and sintered in one step to obtain the required PbTe thermoelectric electrode joint. We find that the contact resistance of the composite electrode is reduced by nearly 75% compared with that of metallization layer (Fe) connection. The smallest value is 26.610 μΩ·cm2 which is closer to the lowest 10 μΩ·cm2 reported in the literature than the counterpart of pure Fe electrode, and the shear strength is also greatly improved simultaneously. This work provides a new idea for obtaining PbTe thermoelectric connectors with excellent performance.
First-principles study of atomic bond nature of one-dimensional carbyne chain under different strains
Authors: Hou Lu , Tong Xin , Ouyang Gang ,   Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education, Key Laboratory for Matter Microstructure and Function of Hunan Province, School of Physics and Electronics, Hunan Normal University, Changsha 410006, China
Published: December 2020

One-dimensional (1D) carbyne chain has the potential applications in the nanoelectronic devices due to its unique properties. Although some progress of the mechanical and thermal properties of 1D carbyne chain has been made, the physical mechanism of the strain modulation of atomic bond nature remains unclear. In order to explore the strain effects on the mechanical and related physical properties of 1D carbyne chain, we systematically investigate the strain-dependent bond nature of 1D carbyne chain based on the first-principles calculations of density functional theory and generalized gradient approximation. It is found that when the compressive strain is 16%, the bonding nature of 1D carbyne chain is changed, and the bond length alternation of single and triple bonds in 1D carbyne chain tends to zero, which originates from the difference in bond strength between single bond and triple bond. Moreover, 1D carbyne chain can change from semiconductor into metal when the compressive strain is 16% indicated by analyzing the band structure and related differential charge density. When the strain is 17%, the phonon spectrum has an imaginary frequency. Besides, when the ambient temperature is less than 510 K, the heat capacity of 1D carbyne chain decreases with strain increasing. However, more phonon modes will be activated at larger strains when the temperature is higher than 510 K, and the heat capacity is enhanced gradually with strain increasing. Also, the stiffness coefficient of 1D carbyne chain is larger than that of graphene and carbon nanotube. These results conduce to the fundamental understanding of atomic bond nature in 1D carbyne chain under different strains.
Invited Editorial: Effectiveness of Surgical and Cotton Masks in Blocking COVID-19 Spread
Authors: Richard Seidu A.
Published: December 2020

The use of cloth mask or cotton mask by health care works or the general public in infection prevention has been cautions in a large sampled cluster randomized trial of cloth masks compared with medical masks. The study concluded that medical or surgical mask was potent in preventing infection in the hospital setting. A new study however detected greater contamination of COVID-19 on the outer surfaces both surgical mask and cotton or cloth mask than the inner mask surfaces. This study goes contrary to the early studies on the use of surgical mask for infection prevention. This currently study is misleading and distorting the literature on the use of surgical mask in infection prevention. In the current COVID-19 outbreak, it is most anticipate that hospital as well as community prevention of the spread of the disease involves the use of medical mask and not cloth mask.
Children’s development of humour in everyday interactions: two case-studies in French and Brazilian Portuguese
Authors: Del Ré Alessandra , Dodane Christelle , Morgenstern Aliyah , Vieira Alessandra Jacqueline
Published: December 2020

In order to understand how children learn to recognize and use humor in their own cultural environment, we have chosen to study their production in two different languages and cultures. We studied a French-speaking monolingual child and a Brazilian Portuguese-speaking child, video-recorded once a month up to seven years old. The detailed multimodal linguistic coding of our data enabled us to draw the multimodal paths the two children followed from the first instances of shared amusement initiated by the adult, expressed mainly through reactive behavior such as laughing, to the children’s own verbal production of successful humor in dialogue. Our study demonstrates that the production of children’s humor is closely linked to the family input (their micro-culture), and to children’s multimodal linguistic and meta-cognitive development. We did not observe important differences between the two children at the macro-cultural level, but there were noticeable inter-individual differences.
Humour expression at the crossroads of deaf and hearing cultures: the case of the Oral Deaf fitted with cochlear implants
Authors: Vincent-Durroux Laurence
Published: December 2020

In deaf people who use sign languages, humour expression has been looked at extensively, examining the preferred means and topics in deaf humour (Cancio-Bello 2015; Sutton-Spence & Napoli 2009). Humour expression remained to be further examined in deaf people with cochlear implants, which give access to the sounds of speech, and facilitate speech production and interaction. In this paper, we address these questions: is delayed linguistic input an obstacle on their way to using humour expression in their target spoken language? To what extent do profoundly deaf cochlear implants recipients access and share the means and topics of hearing people? How do they stand culture-wise? We analyze French and English data collected from 18 profoundly deaf cochlear implant recipients, aged two to 15, with ages at implantation varying from one to 7, and filmed in interaction with an adult. For the youngest children, the main sources of humour are the gestures they make, the objects they build, and onomatopoeia. Older children use formal speech in order to make the adult laugh, either by taking up the adult’s speech, or by speaking to / for the objects they have built. The children tend to grow out of deaf experience jokes and visual jokes. They already evidence some of the trends of humour in their respective target language (e.g. third-party target in French, discursive strategies in English), although the French participants do not use linguistic play as much as would be expected, and the English participants do not use much recipient-oriented humour. We discuss the growing ability of cochlear implant recipients to access speech-based, co-constructed humour, even though such high-level linguistic processes have been shown to be impacted in deaf children (Arfé et al. 2015; Bourdin 2015) with deafness itself and limited linguistic input as possible causes accounting for their preference for discursive strategies over play-on-words in humour expression.
USHEERA (Vetiveria zizanioides Linn. Nash): A DRUG REVIEW
Authors: J Keerthana , Hegde Prakash L , Javagal Vijay
Published: December 2020

Usheera (Vetiveria zizanioides Linn. Nash) possesses a great therapeutic value in the traditional Ayurvedic medicine and is widely distributed in India. Apart from the medicinal value, the culms are used for sweeping, scenting clothes and also as soil binders. In Ayurvedic literature, the plant has been mentioned from Veda Kala to Nighantu Kala. Hence in a view of immense medicinal importance of the plant this review is therefore compile all the information related to Usheera.
A REVIEW ON THE HAMMAM: A REGIMEN FROM ASCLEPIONS
Authors: Ansari Md Khursid Alam , Rahman Azizur , Bashir Tabish
Published: December 2020

The bathing was almost universally followed practice in antiquity. It was of religious, cultural as well as therapeutic values. Before scientific medicine, Asclepions were the healing temples, which were always built near a river or spring and worked as today's clinic and hospitals, where water was used for therapeutic purposes. Hippocrates also described the different kinds of water as well as the therapeutic property of bathing. In the Roman and Arabic periods, Hammam was too popular and it was social practice. The bathing Houses were highly sophisticated building. The physicians of medieval age also considered hammam as one of the important resigns in the art of healing. They were described as the different kind of Hammam and their therapeutic importance.
Highly Efficient Metasurface Quarter‐Wave Plate with Wave Front Engineering
Authors: Chen Chen , Gao Shenglun , Xiao Xingjian , Ye Xin , Wu Shengjie , Song Wange , Li Hanmeng , Zhu Shining , Li Tao
Published: December 2020

Metasurfaces with local phase tuning by subwavelength elements promise unprecedented possibilities for ultrathin and multifunctional optical devices in which geometric phase design is widely used due to its resonant‐free and large tolerance in fabrications. By arranging the orientations of anisotropic nanoantennas, the geometric phase‐based metasurfaces can convert the incident spin light to its orthogonal state, and enable flexible wave front engineering together with the function of a half‐wave plate. Herein, by incorporating the propagation phase, another important optical device of quarter‐wave plate together with the wave front engineering as well, which is implemented by controlling both the cross‐ and copolarized light simultaneously with a singlet metasurface, is realized. Highly efficient conversion of the spin light to a variety of linearly polarized light is obtained for meta‐holograms, metalens focusing and imaging in the blue light region. This work provides a new strategy for efficient metasurfaces with both phase and polarization control, and enriches the functionalities of metasurface devices for wider application scenarios.