bluuebunny/crossref_metadata_2025 huggingface dataset:
An evaluation criterion of infrared image complexity based on background optimal filter scale
Authors: Hou Wang  , Mei Feng-Hua  , Cheng Guo-Jun  , Deng Xi-Wen  ,   Naval Academy of Armament, Shanghai 200436, China
Published: December 2020

An evaluation of infrared image complexity is proposed based on the background optimal filtering to solve the problem that the traditional methods have given poor results in the background evaluation. Meanwhile, the optimal filtering scale for infrared image filtering can be given by this method, it will provide a guidance for optimal infrared image filtering. First, we generate the Gaussian simulated target and fuse it to the infrared image to obtain the real infrared image with the simulated target. Then, this image is filtered in different scales and the signal-to-noise ratio of the target after filtering is calculated. Finally, the maximal value of signal-to-noise ratio of the target is used as the background optimal filter scale, to evaluate the infrared image complexity. Besides, the infrared filtering scale is deduced by establishing the mathematic model, and then the mathematical expression of optimal filtering scale is obtained. A lot of experiments indicate that: 1) The mathematical expression of optimal filtering scale agrees with the experimental results. 2) The result of our method is better than that of the traditional methods based on information entropy. Because the optimal filtering scale is obtained by using our method, we can use this scale to filter the infrared image to effectively detect a small target. 3) When the scale of simulated target increases, the optimal filtering scale increases accordingly. So, when we calculate the infrared image complexity, the scale of simulated target must be the same. We can compare the infrared image complexity between different images. Moreover, the optimal filtering scale is independent of the intensity of simulated target. 4) The effect of Gaussian and Butterworth high-pass filter is better than that of the ideal high-pass filter in the proposed method. 5) The infrared image complexity can be analyzed by the proposed method effectively. Moreover, changes of different image contents can be analyzed by using the optimal filtering scale.
Preparation and characterization of the superlattice (Sm-doped ceria/yttria-stabilized zirconia)N electrolyte film
Authors: Liu Hua-Yan  , Fan Yue  , Kang Zhen-Feng  , Xu Yan-Bin  , Bo Qing-Rui  , Ding Tie-Zhu  ,   School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021, China
Published: December 2020

As is well known, a solid oxide fuel cell(SOFC) is a device that can convert chemical energy directly into electrical energy. The possibility to grow thin films of oxide materials is of great importance in the development of SOFC. Recently, it is expected that oxide heterostructures, with almost ideal interfaces, should lead to the interesting artificial materials with some novel properties. So we have prepared superlattice electrolyte thin films.On the MgO single-crystal substrates, multilayer epitaxial thin-film heterostructures of 20 mol% samarium-oxide-doped ceria (Ce0.8Sm0.2O2-, SDC) and 8 mol% yttria-stabilized zirconia (Y2O3: ZrO2YSZ) have been deposited in turn, using the pulsed laser deposition (PLD) technique. Five different superlattices (SDC/YSZ)N (N=3, 5, 10, 20, 30) films are fabricated, keeping the total thickness constant (300 nm), but with a different number of hetero-interfaces. The choice of coupling SDC and YSZ aims to have both layers in the superlattices made of oxygen-ion conductors with compatible crystallographic features. On one hand, we have to remove any potential contribution of the deposition substrate to the total conductivity, and the superlattices may be grown on 110-oriented MgO single-crystalline wafers. On the other hand, the YSZ electrolyte film requires that the temperature should be higher, and SDC as the electrolyte leakage; both should be combined with each other, so as to have complementary advantages. In this way, not only the temperature of SOFCs is reduced, but also the leakage avoided. Because YSZ and SDC both belong to cubic fluorite structure and have similar lattice parameters, the lattice constant of YSZ is 5.14 , and the lattice constant of SDC is 5.44 . Compatible crystal properties, oxygen ion conductivity, and great matching defects can lead to a semi-coherent interface between the ZrO2 and CeO2 layers. The interface effect is obvious. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM) and AC impedance mearurements are used to characterize the surface morphology, phase structure and electrical properties of the electrolyte film. Results show that the superlattice (SDC/YSZ)N electrolyte films will form obviously interface and better superlattice structure. This kind of thin films do not show crack, with no element diffusion at the interfaces, growing uniformly, densely and smoothly. Electrochemical measurements show a sizable increase in conductivity with increasing number of SDC/YSZ interfaces. So it is an ideal low-temperature fuel cell electrolyte materials.
Control of chaos in a semiconductor laser using the Faraday effect
Authors: Yan Sen-Lin  ,   School of Electronic Engineering, Nanjing Xiaozhuang University, Nanjing 211171, China
Published: December 2020

We present a novel laser system with an external cavity delay feedback semiconductor laser under the control of Faraday effect. To study the chaos-control and chaos-anti-control of the laser system, we construct two types of optical path structures as two control systems of the negative feedback and the ring cavity by using the combination of the Faraday effect controller, the polarizer and the mirror. We give a physical model of laser dynamics with the delayed negative feedback or the delayed positive feedback under the control of Faraday effect. Using the Faraday effect principle of magnetic rotation and the characteristics of the system, we can achieve the double parameter control of the laser. We can shift the optical rotation angle by operating Faraday effect controller and modulate the optical delay time by performing the mirror to vary the double parameter. The laser can be controlled to a double-cycle, a tri-cycle, a multi-cycle, and beat phenomenon by using the control system of the negative feedback, etc. The periodic laser can be anti-controlled to chaos by using the control system of the ring cavity. Some control and anti-control areas formed with the distribution of magnetic rotation angular are found in the laser. For the negative feedback system under the some control cases, the chaotic laser can be controlled to some tri-cycle states between π/14 and π/9. By shifting the control parameters, the chaotic laser can be controlled to some cycle-7 states between 10π/133 and 10π/108 and another tri-cycle region is found from 10π/96 to π/8. Under other control parameters, the chaotic laser can be controlled to some cycle-8 or cycle-9 states. For the ring cavity system under the some control cases, the dual-cycle region is between π/10 and π/30, the cycle-6 region is between π/4 and π/5, the cycle-13 region is found to be from π/6 to 10π/76. In another control case, the large chaos-anti-control region is found to exist between 0 and π/12. Dynamic controls of the chaotic laser and the periodic laser are also studied while the transformation and evolution of laser states are discussed. It is found that it takes about 10 ns for one state to change into another state when the control operation is applied to the laser. The control method is very useful for studying chaos-control, new laser system and its application.
Neutron holography simulation based on different sample rotations
Authors: Tang Bin  , Cao Chao  , Yin Wei  , Sun Yong  , Liu Bin  ,   Insitute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

Neutron holography is a new imaging technique based on the recording of the interference pattern of two coherent waves emitted by the same source, which allows observing the spatial order of microscopic objects like molecules or atoms in crystal sample. Two approaches can be used in neutron holography measurements. One is called inside-source holography, in which both the reference wave and object wave come from embedded atoms in the sample and propagate toward the detector outside the sample. The second approach called inside-detector holography is the inverse method of inside-source holography, in this case the reference wave is the initial neutron beam coming from a distant source outside the sample, while the atoms embedded in the sample act as detectors. In an ideal inside-source holography experiment, the sample should be fixed and the detector moves on a sphere, which is not practical because the detector system is usually heavy and far from the sample. In order to minimize the operation space, the detector always moves on a circle around sample or is located at a fixed position, while the sample rotates in an appropriate way to imitate the motion of the detector in a sphere. However, the orientation of the sample relative to the incident neutron beam is changed during sample rotation, and part of the inverse hologram is recorded together with the inside-detector hologram, which can cause distortion in the holographic reconstruction. In this paper, we simulate neutron holograms and reconstructions based on three different sample/detector rotations. In the first case, the detector moves on a circle, while the sample rotates about an axis perpendicular to the detector moving surface. In the second case, the detector is fixed, while the sample rotates around two perpendicular axes, the θ axis rotating the sample through πradians is perpendicular to the incident beam-detector plane, while the θ axis rotating the sample through 2πradians moves on a circle parallel to the incident beam-detector plane, this rotation can be carried out on a 3-axis spectrometry. In the third case, the detector is also fixed and the sample rotates around two perpendicular axes, but the θ axis is parallel to the sample-detector direction, while the θ axis moves on a circle perpendicular to the incident beam-detector plane, this rotation can be carried out on a 4-cycle spectrometry. The distortions and corresponding correcting methods of three kinds of rotations are discussed. The result shows that most distortions can be corrected by using special measurement or reconstruction techniques. Furthermore, pure sample rotation based on 3-axis spectrometer can achieve the best reconstruction result, so this rotation approach is preferred if conditions permit.
Atomical simulations of structural changes of a melted TiAl alloy particle on TiAl (001) substrate
Authors: Qian Ze-Yu  , Zhang Lin  ,   Institute of Material Physics and Chemistry, College of Science, Northeastern University, Shenyang 110004, China
Published: December 2020

Atomic packing structures of a melted TiAl alloy nanoparticle on TiAl(001) substrate at different temperatures are investigated by molecular dynamic simulation within the framework of embedded atom method. In order to obtain a melted TiAl alloy nanoparticle, a larger TiAl alloy bulk in nano-size is initially constructed, subsequently it is heated up to 1500 K and finally melted. A smaller sphere is extracted from the center of the melted bulk to serve as the melted nanoparticle. Periodic boundary conditions are employed in the x and y directions when constructing the sheet-like TiAl alloy substrate. In this simulation, the melted nanoparticle at 1500 K is laid on a TiAl(001) substrate, separately, at 1100, 1000, 900, …, 200 and 100 K as integral systems, and then they experience rapid solidification process. With the analysis of atomic arrangements of the nanoparticle and substrate surface layer by layer, it is found that temperature greatly affects the atomic packing structure of the nanoparticle. When the temperature of the substrate is 1100 K, most atoms in the nanoparticle disorderly pack, indicating that the nanoparticle is still melted at this temperature. At 1000 K, nearly all the atoms in the nanoparticle occupy TiAl lattice points, indicating that the nanoparticle is already solidified at this temperature. With the substrate temperature decreasing, most atoms in the nanoparticle are still of orderly pack. Meanwhile, a pyramid-like inner region, which takes TiAl(001) crystallographic plane as undersurface and TiAl [101], [101], [011], and [01 1] crystallographic axis as edges, abruptly emerges in the nanoparticle. Different atomic packing structures are observed inside and outside this region. Atomic layers composed of atoms inside this region are parallel to the (001) crystallographic plane of TiAl alloy substrate while atomic layers composed of atoms outside this region arranges along other different directions, which therefore leads to four interfaces separating the inner region from other parts of the nanoparticle. At low temperatures, this inner region still exists but its volume decreases with temperature decreasing. Besides, more and more atoms in the upper part of the nanoparticle gradually pack disorderly, which makes it more difficult to distinguish the inner region. In addition, the melted nanoparticle has very limited influences on the central and bottom parts of the substrate. However, thermal motion of atoms of substrate surface which touches the nanoparticle is intensified, thus leading to more obvious lattice distortion.
Experimental optimal design of the Er3+/Yb3+ codoped BaGd2ZnO5 phosphor and its upconversion luminescence properties
Authors: Sun Jia-Shi  , Li Shu-Wei  , Shi Lin-Lin  , Zhou Tian-Min  , Li Xiang-Ping  , Zhang Jin-Su  , Cheng Li-Hong  , Chen Bao-Jiu  ,   Department of Physics, Dalian Maritime University, Dalian 116026, China
Published: December 2020

In order to obtain the Er3+/Yb3+ co-doped BaGd2ZnO5 up-conversion phosphor which has the maximum green and red emission intensity, firstly, the method of homogeneous design rooted in the experimental optimal design is employed to search optimum Er3+/Yb3+doping concentration preliminarily. Next, the quadratic general rotary unitized design is adopted to further optimize the experiment, and the regression equation in green and red emission intensity is established as a function of the doping concentration of Er3+/Yb3+. Finally, the optimal solution, that is, the doping concentration of Er3+/Yb3+ corresponding to the maximum emission intensity, is calculated by genetic algorithm. The optimal Er3+/Yb3+co-doped BaGd2ZnO5 phosphor is synthesized by the conventional high temperature solid state method. The crystal structure of as-prepared products is characterized by X-ray diffraction (XRD), and the results show that all the Er3+/Yb3+co-doped BaGd2ZnO5 phosphors we synthesized are of pure phase. The steady-state up-conversion (UC) emission spectra of products are measured under the excitation of a continuous 980 nm laser diode at different working currents. From the UC luminescent spectra of Er3+/Yb3+co-doped BaGd2ZnO5 phosphor, we can see a red emission centered at 662 nm, two green emissions centered at 551 nm and 527 nm, which are assigned to 4F9/2→4I15/2, 4S3/2→4I15/2 and 2H11/2→$4I15/2 transitions of Er3+ ion, respectively. The dependences of green and red UC emission intensities of optimal samples on working current are investigated, indicating that the red emission and green emission of optimal samples both originate from two-photon process. From the normalized green UC emission spectra, it can be concluded that the experimental laser working current induced temperature variation of samples can be omitted. According to Boltzmann distribution law and the thermal equilibrium existing between the levels of 2H11/2 and 4S3/2, the relationship between green emission and temperature in the optimal green UC emission sample is discussed in depth, and the energy level gap between 2H11/2 level and 4S3/2 level is calculated to be 926.11 cm-1. Through the study of the temperature effect on the optimal green UC emission sample, we find that the emission intensity decreases with the increasing of the temperature, owing to the thermal quenching effect. Furthermore, we calculate the activation energies of the samples, the activation energies of the green emission, red emission, and the overall emission are deduced to be 0.45, 0.46, and 0.45 eV, respectively.
Generation and three-dimensional characterization of complex nondiffracting optical beams
Authors: Yu Xiang-Hua  , Yao Bao-Li  , Lei Ming  , Yan Shao-Hui  , Yang Yan-Long  , Li Run-Ze  , Cai Ya-Nan  ,   State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an 710119, China
Published: December 2020

Nondiffracting optical beams play an important role in contemporary optics due to their special propagation characteristics, i.e., nondiffracting in a diffraction-free zone, shape recovering behind obstacles or self-healing property. Liquid crystal spatial light modulators (LC-SLM) are widely used for generating nondiffracting optical beams in virtue of programmable and dynamic features. In this paper, we propose a complex amplitude modulation technique that can encode any scalar complex fields for generating the complex nondiffracting beams. Before experiment, the phase modulation curve of the phase-only LC-SLM is optimized into being linear in a range of 0-2πby gamma correction in the way of variable binary phase gratings. Then, we experimentally generate the nonaccelerating beams, e.g., two zero-order Bessel beams with variable intensity distributions, and the nondiffracting petal-like beams generated by interfering with two coaxial Bessel beams. By scanning a reflection mirror near the focal region along the optical axis, a stack of two-dimensional images is acquired, and then a three-dimensional intensity profile of the beam is reconstructed with a software. We also experimentally demonstrate a new kind of multi-main-lobe accelerating beam with parabolic accelerating trajectory by modifying the spatial spectrum of classical Airy beam. Compared with the so-called vectorial accelerating beam with multiple main lobes in spheroidal coordinates, our generated two-main-lobe accelerating beam has a very high energy efficiency. The self-healing property of the two-main-lobe accelerating beam is also demonstrated. The presented technique can generate a variety of complex nondiffracting optical beams rapidly and obtain their three-dimensional intensity distributions accurately, which has potential applications in the fields of optical microscope, optical date storage, optical trapping, optical micromachining, etc.
Electromagnetically induced transparency of Rydberg atoms in modulated laser fields
Authors: Yang Zhi-Wei  , Jiao Yue-Chun  , Han Xiao-Xuan  , Zhao Jian-Ming  , Jia Suo-Tang  ,   State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan 030006, China
Published: December 2020

Rydberg atoms, with large principal quantum number n, have been widely investigated in recent years due to their peculiar properties, such as big sizes, long lifetimes and strong interactions with fields and other Rydberg atoms. Rydberg atoms are very sensitive to external fields due to their large polarizabilities scaling as n7.These make Rydberg atoms an ideal candidate for the quantum information, the many-body interaction, etc.In this work, we investigate the Rydberg atoms using electromagneticlly induced transparency (EIT) in a ladder three-level system. The EIT is a quantum interference effect between two excitation path-ways driven by two laser fields. The main idea is performed in a room temperature cesium vapor cell, where the probe laser frequency is modulated. The ground state (6P1/2), excited state (6P3/2), and Rydberg state (nS1/2) constitute a Rydberg three-level system, in which the probe laser is fixed to the 6S1/2 (F = 4)6P3/2 (F = 5) transition by saturated absorption spectrum technique, whereas the coupling laser is scanned across the 6P3/249S1/2 transition. We detect the demodulated EIT signal with the lock-in amplifier (SR830). The modulated EIT signal shows a two-peak structure. The measured spacing between two peaks increases with the frequency detuning, caused by the modulation amplitude, and half the spacing between the peak-to-peak is nearly 1.67 times the modulation amplitude of the probe laser; the measured result shows that the splitting is independent of the modulation frequency. The experimental results are in agreement with the theoretical calculations. The results in our work can be used for real-time monitoring of the laser-line profiles and the fluctuation of laser frequency.
Effects of thermal annealing, laser and electron beam on the fabrication of nanosilicon and the emission properties of its localized states
Authors: Wu Xue-Ke  , Huang Wei-Qi  , Dong Tai-Ge  , Wang Gang  , Liu Shi-Rong  , Qin Chao-Jie  ,   College of Big Data and Information Engineering, Guizhou University, Guiyang 550025, China;,   Institute of Nanophotonic Physics, Guizhou University, Guiyang 550025, China;,   State Key Laboratory of Ore Deposit Geochemistry Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550003, China;,   College of Physics and Electronic Engineering, Kaili University, Kaili 556011, China
Published: December 2020

In the process of preparing nanosilicon, the crystallization process is an important part to influence and improve the efficiency of nanosilicon luminescence. Thermal annealing, laser annealing, and electron beam irradiation are different ways of crystallizing the nanosilicon. Different photoluminescence (PL) spectra and structures of nanocrystalline silicon are observed for different treatment time of crystallization. The experimental results show that choosing an appropriate crystallization method and parameters is very important for preparing the nanosilicon crystalline structures. High luminous efficiency can be obtained by controlling the parameters properly in the processes of preparing silicon quantum dots (QDs) and quantum surface, especially. It is discovered experimentally that better nanosilicon crystalline structure such as nanosilicon QD structure, better PL luminescence, and the doped localized state luminescence of nanocrystalline silicon can be obtained when the crystallization time is about 20 min. According to the nanosilicon crystallization process under thermal annealing, laser annealing and electron beam irradiation, a physical model of the effect of crystallization time on the nanosilicon localized state luminescence is established in this paper, which can explain the effect of crystallization time on the localized state luminescence of the nanosilicon.
Atomic scale piezoelectricity and giant piezoelectric resistance effect in gallium nitride tunnel junctions under compressive strain
Authors: Zhang Geng-Hong  , Zhu Jia  , Jiang Ge-Lei  , Wang Biao  , Zheng Yue  ,   Micro-Nano Physics and Mechanics Research Laboratory, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, China;,   State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, China;,   Institute Franco-Chinois de l’Energie Nucléaire, Sun Yat-sen University, Zhuhai 519082, China
Published: December 2020

It is an urgent and significant issue to investigate the influence factors of functional devices and then improve, modify or control their performances, which has important significance for the practical application and electronic industry. Based on first principle and quantum transport calculations, the effects of compressive strain on the current transport and relative electrical properties (such as the electrostatic potential energy, built-in electric field, charge density and polarization, etc.) in gallium nitride (GaN) tunnel junctions are investigated. It is found that there are potential energy drop, built-in electric field and spontaneous polarization in the GaN barrier of the tunnel junction due to the non-centrosymmetric structure of GaN. Furthermore, results also show that all these electrical properties can be adjusted by compressive strain. With the increase of the applied in-plane compressive strain, the piezocharge density in the GaN barrier of the tunnel junction gradually increases. Accordingly, the potential energy drop throughout the GaN barrier gradually flattens and the built-in electric field decreases. Meanwhile, the average polarization of the barrier is weakened and even reversed. These strain-dependent evolutions of the electric properties also provide an atomic level insight into the microscopic piezoelectricity of the GaN tunnel junction. In addition, it is inspiring to see that the current transport as well as the tunneling resistance of the GaN tunnel junction can be well tuned by the compressive strain. When the applied compressive strain decreases, the tunneling current of the junction increases and the tunneling resistance decreases. This strain control ability on the tunnel junctions current and resistance becomes more powerful at large bias voltages. At a bias voltage of -1.0 V, the tunneling resistance can increase up to 4 times by a -5% compressive strain, which also reveals the intrinsic giant piezoelectric resistance effect in the GaN tunnel junction. This study exhibits the potential applications of GaN tunnel junctions in tunable electronic devices and also implies the promising prospect of strain engineering in the field of exploiting tunable devices.
High-order harmonic generation of O2 molecules with different nuclear axis orientations
Authors: Yuan Zhong  , Guo Ying-Chun  , Wang Bing-Bing  ,   School of Physics and Materials Science, East China Normal University, Shanghai 200241, China;,   Laboratory of Optical Physics, Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

High-order harmonic generation (HHG) is one of the hottest topics in strong field atomic and molecular physics. In this paper, frequency domain theory which is based on formal scattering theory is extended to study the HHG of O2 molecules under a linearly polarized single mode laser field. The dependence of HHG on the angle 0 between the laser polarization direction and nuclear axis is investigated. In our calculation, we only consider the contribution of highest occupied molecular orbital (HOMO) and use the single electron approximation. The HOMO is obtained from quantum chemical software Molpro. The intensity of the laser is 5.181014 W/cm2 and the wavelength is 800 nm. On the one hand, in the case that the nuclear axis lies in the plane perpendicular to the laser propagation direction, we find that the yields of all order harmonics increase with 0 increasing until the yields reach the maximum values when 0 is equal to about 45. Then the yields decrease with 0 increasing and have the minimum values when 0 is equal to about 90. The analysis shows that the yield of HHG is dominated by the density of electrons in HOMO along the laser polarizing direction in momentum space. On the other hand, in the case that the nuclear axis lies in the plane parallel to laser propagation direction, the dependence of HHG on 0 is the same as that when the nuclear axis is in the plane perpendicular to laser propagation direction. The reasons for the same results for the two cases lie in the following fact. The HOMO of O2 molecule has g symmetry which is not rotationally symmetric around nuclear axis. So HHG yield relies on the g extension orientation. Since the g extension orientation cannot be fixed, the HHG of O2 should be averaged over the contributions to HHG at all possible g extension orientations. This average is equivalent to that the electron density is rotationally symmetric around the nuclear axis and hence leads to the fact that the HHG yield of O2 depends on 0 rather than the plane that the nuclear axis lies in.
Thermal stability of compound stucture of silicon nanowire encapsulated in carbon nanotubes
Authors: Lu Shun-Shun  , Zhang Jin-Min  , Guo Xiao-Tian  , Gao Ting-Hong  , Tian Ze-An  , He Fan  , He Xiao-Jin  , Wu Hong-Xian  , Xie Quan  ,   Institute of New Optoelectronic Materials and Technology, College of Electronic Information, Guizhou University, Guiyang 550025, China
Published: December 2020

To guide the experiment research, the thermal stability of composite silicon nanowire encapsulated in carbon nanotubes is investigated by computer simulation. The cubic-diamond-structured silicon nanowires with the same diameter and [111] orientationt are filled in some armchaired single-walled carbon nanotubes. The heat process of compound structure of silicon nanowire encapsulated in carbon nanotubes is simulated by classical molecular dynamic method. Through the visualization and energy analysis method, the thermal stability of composite structure is studied. The changes in the thermal stability of silicon nanowires and carbon nanotubes are explained by the relationship between carbon nanotube space constraint and van der Waals force. It is found that the diameter of the carbon nanotubes is closely related to the thermal stability of silicon nanowires inside. When the nanotube diameter is small, thermal stability of silicon nanowires increases; when the nanotube diameter increases up to a certain size, the thermal stability of silicon nanowires will suddenly drop significantly: until the distance between silicon nanowires and the wall of carbon nanotube is greater than 1 nm, the thermal stability of silicon nanowires will be restored. On the other hand, silicon nanowires filled into the carbon nanotubes have an effect of reducing the thermal stability of carbon nanotubes.
Magnetic device properties for a heterojunction based on functionalized armchair-edged graphene nanoribbons
Authors: Zhu Zhen  , Li Chun-Xian  , Zhang Zhen-Hua  ,   School of Physics and Electronic Science, Changsha University of Science and Technology, Changsha 410114, China
Published: December 2020

Graphene is predicted to hold a promising use for developing future miniaturized electronic devices. However, the magnetic transport properties based on the armchair-edged graphene nanoribbons (AGNRs) is less studied in currently existing work. So in this work the special chemical modified nanoribbons based on the edge of the AGNR bridged by the transition metal Mn atom and passivated subsequently by two F atoms or two H atoms (AGNR-Mn-F2 or AGNR-Mn-H2) are proposed theoretically. Our calculations from first-principle method based on the spin-polarized density functional theory combined with the non-equilibrium Green's function technique show that the heterojunction F2-AGNR-Mn-H2 consisting of such two types of nanoribbons possesses the excellent magnetic device features, namely, the spin polarization is able to reach almost 100% in a very large bias region, and under P magnetic configuration (the external magnetic fields applied perpendicularly to two electrodes are set to point to the same direction), the single spin filtering effects can be realized, while under the AP configuration (the external magnetic fields applied perpendicularly to two electrodes are set to point to the opposite directions), the dual spin filtering effects can be realized. It is also found that such a heterojunction features dual diode-like effect, and its rectification ratio is up to be 108. Additionally, changing the direction of switching magnetic field, namely, changing the magnetic configurations from one kind of case to another, would lead to an obvious spin valve effect, and the giant magnetoresistace approaches to 108%. These findings suggest that the excellent spin polarization, dual diode-like effect, and giant magnetoresistace effect can be realized simultaneously for this heterojunction, therefore, it holds good promise in developing spintronic devices.
Modulating catalytic capacities of room-temperature synthetized amorphous molybdenum trisulfide hydrogen evolving catalysts and their applications to in series solar water splitting devices in series
Authors: Jin Zhong-Hua  , Liu Bo-Fei  , Liang Jun-Hui  , Wang Ning  , Zhang Qi-Xing  , Liu Cai-Chi  , Zhao Ying  , Zhang Xiao-Dan  ,   School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China;,   Institute of Photo Electronics thin Film Devices and Technology of Nankai University, Key Laboratory of Photoelectronic Thin Film Devices and Technology, Tianjin 300071, China
Published: December 2020

Highly-catalytic, cost-effective, well process-compatible, and highly-stable hydrogen-evolving catalysts are increasingly becoming key catalysts in realizing monolithic electrochemical solar water-splitting devices. However, the typical noble metallic catalysts seriously restrict the industrialization of electrochemical solar water-splitting devices on account of their poor storages and high costs. Low-cost, high-catalytic and non-metallic catalysts pave the promising way for the industrialization process. Molybdenum sulfide has emerged as a type of potential catalyst with high-activity and stability for the hydrogen-evolving reaction (HER) in the acidic condition, nowadays gradually becoming a research hotspot in solar-water-splitting. The process preparation of high-efficient molybdenum sulfide catalyst is consequently extremely important for enhancing the solar-to-hydrogen efficiency. In this paper, we synthesize highly-catalytic, low-cost, and highly-compatible non-metallic amorphous molybdenum trisulfide catalyst based on a simple wet chemical approach at room temperature for hydrogen-evolving reaction, followed by extensive studies of the effects of the mass loading of catalyst on the catalytic capacity and the solar-to-hydrogen performance of solar-water-splitting devices in series. When the mass loading is 0.5 mgcm-2, the MoS3 catalyst exhibits the promising HER activity. the surface of catalyst appears to be rough, porous, nano-sized architecture and the thickness is around 2.0 m, which simultaneously enlarges the electrochemically active area and reduces charge transfer impedance, accelerating the electron transport to electrochemically active site and improving the interfacial charge transfer. Besides, the HER catalytic activity is illustrated in a wired solar-water-splitting device. The current density can achieve the maximum values of 7.51 and 3.28 mA/cm2 corresponding to 0 and 0.8 V vs. RHE, and the onset potential is 1.83 V, comparable to the open circuit voltage (1.90 V) of two amorphous silcon cells in series. Therefore, we conclude that for amorphous molybdenum trisulfide catalyst there exists an optimized mass loading, with which an optimized catalytic capacity (260 mV vs. RHE at 10 mA/cm2 and tafel slope of 68 mV/dec) can be achieved. Further, by using the catalyst as a cathode for the solar-water-splitting devices in series, the catalyst can efficiently reduce the overpotential and improve the current output for the device, thereby potentially achieving a higher solar-to-hydrogen efficiency.
Voice over quantum IP routing based on least relay node constrained optimization strategy
Authors: Nie Min  , Liu Guang-Teng  , Yang Guang  , Pei Chang-Xing  ,   School of Communication and Information Engineering, Xi'an University of Posts and Telecommunication, Xi'an 710121, China;,   School of Electronics and Information, Northwestern Polytechnical University, Xi'an 710072, China;,   State Key Laboratory of Integrated Service Networks, Xi'an University of Electronic Science and Technology, Xi'an 710071, China
Published: December 2020

Quantum communication is the interdisciplinary science of quantum mechanics and telecommunication theory. It has advantages of perfect information security and high efficiency in transmission. In recent years, the theoretical and experimental results show that quantum communication systems have the superiority over the traditional communication systems. Quantum communication systems are hopeful for solving the information security problems that everyone is facing today, therefore, they possess broad application prospects and are forming a research hotspot of the telecommunications field currently. On the other hand, Voice over Internet Protocol (VoIP) is the method to transmit the digitized packet voice in Internet around the world. The advantages of VoIP are that it can carry voice, data, video, telephone conference, electronic commerce, and electronic mail economically. VoIP can realize the information storage and retransmission easily and flexibly. However, VoIP also encounters the problem of information security. We are trying to combine the quantum communications network and the VoIP system together and build a brand new network named quantum VoIP network which combines the advantages of both quantum communications and VoIP. The data packets may be delayed and lost in a queue up with a router due to the congestion and link failure during the transmission of quantum information. In order to ensure the performance of quantum VoIP system, the routing optimization strategies are proposed in the paper. The relay technology based on entanglement swapping is adopted. The multiuse quantum communications are realized by giving priority to the quantum channels with the least relay nodes. Theoretical analysis and simulation results show that when the data transmission links are fail to work properly and routers are in congestion, adopting the routing optimization strategies in M/M/m queuing system with the bit error rate (BER) of quantum bit setting to be 0.2 and the number of common channels increasing from 4 to 8,, the percentage of call failure in quantum communication network decreases from 0.25 to 0.024, and the maximum throughput of quantum networks increases from 64 kbps to 132 kbps. In comparison, when the number of common channels is set to be 4 andthe BER of the quantum bit is from 0.3 to 0.1, the maximum throughput of quantum networks increases from 41 kbps to 140 kbps. Thus it can be concluded that the routing optimization strategies proposed in this paper can improve the performance of quantum VoIP system significantly.
A parameter inversion method of film based on thermal effects induced by laser irradiation
Authors: Chen Gui-Bo  , Zhang Jia-Jia  , Wang Chao-Qun  , Bi Juan  ,   School of Science, Changchun University of Science and Technology, Changchun 130022, China
Published: December 2020

In this paper, we present an inversion estimation method of thin film parameters based on thermal effects induced by laser irradiation. Firstly, the theoretical model of classical Fourier heat conduction of thin film irradiated by laser is established, and the analytical solutions of temperature fields are obtained by using Laplace transform. Then, the inversion model and the iteration algorithm are established based on the nonlinear conjugate gradient method on condition that the thermal conductivities of the film and the substrate are selected as inversion parameters and the temperature fields of the thin film surface in different irradiation times are selected as measured data. In view of the fact that the sensitivity coefficient plays a decisive role in determining the accuracy and efficiency of the nonlinear conjugate gradient iteration inversion algorithm, we derive the closed form expressions of the sensitivity coefficients for the thermal conductivities of the film and the substrate based on the above analytical solutions of the temperature fields, and this closed form expressions can improve the accuracy and efficiency of the thin film parameter inversion significantly. Taking four kinds of metal films (aluminum, silver, copper and gold) with glass substrate for example, the accuracies of the analytical solutions of temperature fields are verified by comparing with the numerical results from the finite element method in the existing literature, and it can ensure the accuracies of the sensitivity coefficients in the process of iteration inversion. Finally, the thermal conductivities of the above four kinds of thin films are estimated by using the presented iteration inversion method. The accuracy and efficiency of the parameter inversion are verified by investigating and analyzing the inversion results of the parameters for different random noises and different iterative initial values. The inversion results show that this method has a high accuracy and efficiency, and it only needs less than 20 iteration times to convergence when the iteration stop error is 10-7. The smaller random noise is added in the measured data, and the less iteration times to convergence are needed. It can achieve higher convergence efficiency even in the iterative initial values from the inversion results that differ greatly for the case of 5% random noise. This inversion method of thin film parameters is not only applicable to the inversion of the thermal conductivity, but can also be used to inverse the parameters such as the reflection coefficient or the absorption coefficient. The presented method has a certain guiding significance for the parameters inversion and the parameters optimization in the process of the laser processing or the laser damage.
First-principle studies of half-metallicities and magnetisms of the semi-Heusler alloys CoCrTe and CoCrSb
Authors: Yao Zhong-Yu  , Sun Li  , Pan Meng-Mei  , Sun Shu-Juan  ,   School of Physics and Electronic Engineering, Hainan Normal University, Haikou 571158, China
Published: December 2020

Half-metallic ferromagnet, in which the electrons with one spin band are metallic and the electrons with another spin band are semiconducting, is believed to be the most promising spin-injector material for spintronic devices, such as spin valves, spin filters, spin diodes, and magnetic tunnel junctions. The main advantages of half-metallic Heusler alloy over other half-metallic systems are their relatively high Curie temperatures and structural similarity to important binary semiconductors that are widely utilized in the industry. Thus far, half-metallicity has been predicted theoretically or confirmed experimentally in a limited number of Heusler alloys. Exploring new half-metallic Heusler alloys is necessary. In this study, the full-potential linearized augmented plane wave (FP_LAPW) method under density functional theory is utilized to investigate the electronic structures and magnetisms of semi-Heusler alloys CoCrTe and CoCrSb. In the calculations, the generalized gradient approximation (GGA) in the scheme of Perdew-Bueke-Ernzerhof is adopted to treat the exchange-correlation potential. The cutoff parameter is set to be Rmt Kmax =9, where Rmt is the smallest atomic sphere radius and Kmax is the maximum value of the reciprocal lattice vector. Meshes (131313 k-points) are used in the first Brillouin zone integration. Self-consistent calculations are considered to be convergent only when the integrated charge difference between the last two iterations is less than 110-4 e/cell. Spin-polarized calculations of the electronic structure for the semi-Heusler alloys CoCrTe and CoCrSb are performed. The calculations reveal that CoCrTe and CoCrSb at their equilibrium lattice constants are half-metallic ferromagnets with half-metallic gaps of 0.28 and 0.22 eV and total magnetic moments of 3.00 and 2.00 B per formula unit, respectively. The calculated integer total magnetic moments (in B) are consistent with the Slater-Pauling rule, Mt = Zt-18, where Zt denotes the total number of valence electrons and Mt means the total magnetic moment (in B) per formula unit. Moreover, the spin moment of the Cr atom is obviously larger than those of the Co, Te, and Sb atoms. Co, Te and Sb are all antiferromagnetically coupled to Cr for CoCrTe and CoCrSb. The electronic structures of CoCrTe and CoCrSb are also calculated as their lattice constants change from -13% to +13% relative to the equilibrium lattice constant. The calculated results indicate that CoCrTe and CoCrSb can maintain their half-metallicities and retain their total magnetic moments of 3.00 and 2.00 B per formula unit even as their lattice constants change from -11.4% to 9.0% and from -11.2% to 2.0%, respectively. The semi-Heusler alloys CoCrTe and CoCrSb should be useful in spintronics and other applications.
Application of transfer matrix method to calculating the effect of multiple internal reflections on the small signal gain ripple of TWT
Authors: Yi Hong-Xia  , Xiao Liu  , Su Xiao-Bao  ,   Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

The low-signal-gain versus frequency slope is often a highly desirable property of traveling wave tube (TWT) used in a communication system. The gain ripple is usually caused by internal reflexions of forward and backward waves in the TWT. Random fabrication error may have a detrimental effect on the performance of TWT. The quartic equation including backward wave models the effect of reflection to analyze the effect of Gain ripple from many small circuit errors in a TWT operating under small-signal condition. We present a transfer matrix method (TMM) to correctly calculate the transmission and reflection of the wave incident respectively from left and right at a single isolated joint. The TMM, which links the input signal to output signal that includes the feedback signal from the reflections at multiple joints to the output end, can calculate the gain ripple of multiple internal reflections. Appling this method to several numerical examples, we look at how small signal gain is affected by a single isolated discontinuity and many small randomly distributed discontinuities. In particular, we investigate the effects of random perturbations of Pierce velocity detuning parameter b and Pierce gain parameter C on the small signal gain at different values of space charge 4QC. The computed result agrees with that from Chernin's model. We find that reflections may significantly increase the statistical effects on the gain. A further conclusion is that the standard deviation of gain, dgain, increases with b gradually, but the ratio of the backward wave power to the forward wave power at x=0 decreases with b when standard deviation of pierce velocity detuning parameter, b, is more than 1.5. In another example, the effects of two discontinuities of pitch distribution and many small random pitch errors on gain ripple are reported for a G-band TWT. We find that larger pitch error and longer distance for the discontinuities may produce a larger ripple in the small-signal-gain versus frequency. Many small discontinuities may produce a large gain ripple, and the gain ripple grows as the level of pitch error increases. These effects of random fabrication errors become increasingly important for very high frequencies, such as 1 THz, at which TWTs are currently being designed and built.