bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Chemical-looping Gasification Characteristics of Chinese Western Coals with Hematite-CuO Oxygen Carrier
Authors: An Mei , Yuan Nini , Sun Xiunan , Guo Qingjie
Published: December 2020

In order to realize highly efficient conversion of Chinese western bituminous coals into syngas, a series of chemical-looping gasification experiments was conducted with hematite-CuO oxygen carrier in a laboratory-scale fluidized-bed reactor. The results indicated that the gasification rate of Chinese western bituminous increased by 2-3 times after addition of a hematite-CuO oxygen carrier. Meanwhile, the syngas yields of Chinese western bituminous ranged from 1.84–2.04 m3/kg, three times higher than that of lignite. This shows that the combination of chemical-looping technology and gasification of coal can achieve efficient conversion of Chinese/western bituminous coals. The temperature and the supply oxygen coefficient (O/C) all demonstrated a clear effect on the gasification rates and the gas yields. 10 cycles of redox experiments indicated that the hematite-CuO oxygen carriers have good recycled reaction characteristics. Those results provide theoretical guidance for the efficient conversion of Chinese western bituminous coals into syngas via chemical-looping gasification.
A productivity prediction method for condensate gas reservoir
Authors: Huang Quan Hua , Ding Hong Jun , Lin Xing Yu
Published: December 2020

At present, multiphase flow productivity calculation requires many parameters, and most of them only consider oil and gas two-phase flow, which is complicated and limited. Therefore, a reasonable productivity formula of condensate gas reservoir with producing water is needed. The three-zone model of condensate gas reservoirs is generally applied to the physical model for inferring productivity. On this basis, an improved model is established, which includes that different seepage characteristics are considered for different zones. Moreover, the effects of inclined angle and water production on gas wells are regarded as pseudo-skin factors and additional-skin factors. In addition, Zone I considers the effects of high-speed nonDarcy effect(HSND), starting pressure gradient, stress sensitivity, inclined angle and water production; Zone II is the same way excepting starting pressure gradient and stress sensitivity ; Zone III only considers the effects of inclined angle and water production. As a result, a productivity equation with multiple factors for condensate gas wells is established. Through analysing cases and influences in H gas reservoir X1 well, the HSND, starting pressure gradient, stress sensitivity and water production have a negative impact on gas well productivity, but the inclined angle is opposite. Founded that the starting pressure gradient impacts on productivity is less than the HSND because of the limited radius of Zone I; the impact of the HSND on productivity increases with the decreasing of bottom hole pressure; the impact of water production on gas well productivity is much higher. When the angle is over 60°, the effect of gas
S, N co-doped pitch-based composite carbon nanofibers with enlarged interlayer distance as a superior potassium ion batteries anode
Authors: Liu Chang , Song Ze , Ma Tianyi , Qiu Jieshan
Published: December 2020

Potassium ion batteries (PIBs), an alternative to traditional lithium ion batteries to large-scale energy storage device, have attracted tremendous attention, due to abundant reserves of potassium resources and low cost. However, it still remains challenge to fabricate suitable anode materials with high K storage capabilities. In this work, facile S/N co-doped pitch based composite carbon nanofibers has been fabricated by electrospinning of coal tar pitch and polyacrylonitrile, and followed by carbonization under H2S/Ar atmosphere. The formation of -C-S-Cbond effectively increased S utilization, and enlarged carbon interlayer distance to some degree. As anode for PIBs, the S/N co-doped carbon displayed enhancement of capacity, rate capability and cycle stability. This work would shed a light on the fabrication of S/N co-doped materials for both battery, supercapacitor and electrocatalytic electrodes.
Optimal operation of regional integrated energy system based on demand-side load response
Authors: Fang Peng , Mao Cui , Chen Yuping , Zhou Shan , You Rui , Chen Siqi
Published: December 2020

The integrated energy system (IES) has the advantage of improving energy utilization and promoting energy flexibility. From the perspective of demand-side load response, this paper establishes demand-side power, thermal load response, and natural gas demand response models, and then constructs the objective function of the lowest operating cost of the regional IES for combined electric heating and gas supply, using Cplex to perform optimization. Finally, a typical northern park is taken as an example to analyze and verify the feasibility of the model and algorithm. The analysis of the case shows that considering the electric heating gas demand side response will be better than not considering or considering only the single and both responses, not only can reduce operating costs, achieve peak reduction and valley filling, but also reduce abandonment of wind and energy, and increase energy utilization rate.
Corrosion Failure Cause Analysis of Buried Pipelines in Oil and Gas Stations
Authors: Su Bihuang , Zhang Yanjun , Huang Guibai , Wang Zhitao , Liu Ran
Published: December 2020

Objective: To explore the failure cause of buried pipelines in an oil and gas station. Method: The chemical elements and metallographic structure of the failed pipes were analyzed to evaluate whether the pipe body meets the requirements of relevant standards; the morphology and composition of the corrosion products were analyzed to discover the cause of corrosion. Result: The metal surface was rough and full of pitting pits with severe localized corrosion, and no crack of the metallic matrix was found. The corrosion products mainly contain Fe3O4 and a small amount of FeCO3, wherein Fe3O4 is the secondary corrosion product formed in the air, and FeCO3 is the corrosion product of CO2 in an oil and gas environment. The surface of the corroded product is loose in structure and easy to peel off, leading to further corrosion of the metallic matrix. Conclusion: The pipeline corrosion failure was caused by CO2-induced corrosion failure in the medium.
Modification Methods and Applications of CNTs/WPU Composite Material
Authors: Gao Yunong
Published: December 2020

Carbon nanotubes have lots of good properties, and occupy a great position in the field of science today. However, they also have some disadvantages, such as the existence of Van der Waals forces between the nanotubes bundle, which can result the attraction between the bundles and finally will cause more serious agglomeration. So researchers make the CNTs and WPU into the composite via solution blending, melt blending and in situ polymerization, in order to give play to the excellent properties of the two materials. This paper is aimed at summarizing various modification methods of CNTs/WPU composite material in the current research status and show the effects after each modification method. Finally, it can be concluded that there were differences between composites and the results of modification methods were affected.
Research on coordinated controller design method based on fault early warning model
Authors: Xu Jian , Jia Shaokun , Bai Jie , Zhao Kunpeng , Wu Minglei , Ding Qiang
Published: December 2020

With increasing degree of power electronics in power system, the interaction between controllers of different FACTS devices poses a greater threat to security and stability of the system. In this paper, a linearized state space model with SVC and STATCOM was established, and the negative interaction mechanism of FACTS device in transient process was analyzed and summarized considering control characteristics, operation mode and setting principle of PI controllers. A model predictive control (MPC) is proposed to replace traditional PI link to establish a coordination controller to overcome the difficulties of PI control parameter setting and global optimization.
Experimental verification of a CFD model for the closed plant factory under artificial lighting
Authors: Lu Wei , Hu Yiwen , Zhou Shenghan , Zhang Xin , Yuan Quan , Zhou Xiaoting , Liu Houcheng , Hu Jiangtao , Yang Qichang , Zheng Yinjian , Zheng Yangxia
Published: December 2020

A computational fluid dynamics (CFD) model for the closed plant factory under artificial lighting has been developed in this study, the experimental verification of CFD model with the air velocity value was compared with the measured air temperature value. The results showed that the mean relative error of validation with the air velocity was 15%, and comparable with experimentally observed air temperature profile inside the plant factory with RMSE of 3% which show the utility of CFD to study plant factory microclimatic parameters.
Study on the Different Method of Extraction of Star Anise Oil
Authors: Cheng Haidi , Sun Tianmin
Published: December 2020

The three reagents of anhydrous ethanol, petroleum ether and ethyl acetate were selected by soxlet extraction, steam distillation and ultrasonic extraction to extract the star anise oil from the fine anise powder. Three kinds of methods for extracting star anise oil were studied on different pattern organic solvent. The result of the different volume fractions of ethanol is that the highest extraction rate is 99.7% ethanol. It can be seen that the extraction rate are: ethanol > petroleum ether > acetic acid ethyl ester. The different methods of extracting the star anise oil shows that the extraction rate are: soxhlet extraction method > ultrasonic extraction method > steam distillation extraction method. In summary, it can be seen by soxhlet extraction method and the best solvent is 99.7% ethanol.
Thermal performance of biosourced materials on Buildings: The case of Typha Australis
Authors: Ba Labouda , El Abbassi Ikram , Kane Cheikh S.E , Darcherif A-M , Ndongo Mamoudou
Published: December 2020

Developing countries are facing population growth, which leads, on the one hand, to increased requirements for buildings and, on the other hand, to the depletion of fossil fuels along with exposure, of people living in those areas, to some detrimental consequences of climate change. Because of these factors, we propose approaches to control energy consumption in buildings. In some countries, the architectures adopted are not adequate to the environment and climate, resulting in discomfort in those buildings, in such circumstances, residents resort to the use of energy systems, such as heating, ventilation, and air conditioning, which leads to exorbitant electricity bills. Housing consumes 40% of the world's energy and is responsible for a third of greenhouse gas emissions. Optimizing energy needs in buildings is a solution to overcome these problems. For this purpose, there are solutions such as: the design of the building characterized by its shape and envelope, while using less energy-consuming equipment. For several years, the building materials sector has been developing with a particular focus on bio-source materials, which are generally materials with good thermal performance. In order to highlight the thermal performance of bio-source materials, we will study the case of Typha Australis which is a plant of the Typhaceae family that grows abundantly in an aquatic environment mainly in the Senegal River valley.Recent studies showed that Typha Australis has good thermal insulation properties. In order to determine the impact of Typha Australis on a building, a dynamic thermal simulation was carried out using the Trnsys software according to specific scenarios, the Typha was mixed with other local materials and used as a wall insulation panel, the result of the study shows that this fiber has allowed us to optimize energy consumption in a building. Mixing Typha with other materials (e. g. clay) is a promising solution for energy efficiency in buildings.
Modelling and simulation of a cold storage room driven by a continuous adsorption refrigerator
Authors: Missaoui Kolthoum , Gabsi Slimane , Frikha Nader , Kheiri Abdelhamid , El Ganaoui Mohammed
Published: December 2020

The present work proposes a continuous solar adsorption refrigerator for a positive cold storage room of 231 m3 used for fruits and vegetables preservation and installed in the south of Tunisia. After the estimation of the storage room cooling load, which is equal to 13 kW, a parametric study, aims to improve, the performance of the chiller is done in order to achieve the storage room need and to estimate the required heat in the refrigerator generator. A theoretical model, based on the thermodynamics of the adsorption process, heat and mass transfer within the porous medium and energy balance in the system components, is developed and a simulation with Matlab/Simulink, is carried out. The model was established and validated with the literature experimental data. A maximum coefficient of performance of 0.52 and cooling load of 22 kW are reached at cycle time of 800 seconds, the inlet temperatures of heating, cooling and chilled water are 85°C, 22°C and 15°C, respectively.
Characterization of a sustainable mortar based on mineral additions and prepared sand
Authors: Bellalmi Khemissi , Belagraa Larbi , Taallah Bachir , Bakir Nassima , Briki Lila
Published: December 2020

The present study is to investigate the physical and mechanical properties of the prepared sand mortars, mainly based on the local Oued Souf sand region south of Algeria, this in accordance with standard sand grading. The principal aim of the research is to replace the restricted fine part between (0.08and 0.16 mm) which is of the order 15% and to substitute it with additions active slag (S) and inert glass powder(GP) with dosages of 5, 10 and 15 % and maintain the rest of the granular fractions of the sand studied fixed. Thus, to see and analyze the influence of these additions on the physical properties and in regards the mechanical performances of confected prepared sand mortars. The results showed the advantageous effect of replacing the said prepared sand with two additions (slag and glass powder) on physical, mechanical properties mortars based on this local sand by improving the performance of these cement products, especially at an optimal percentage of 10%.
Clinical and radiological results after Internal Brace suture versus the all-inside reconstruction technique in anterior cruciate ligament tears 12 to 18 months after index surgery
Authors: Mattiassich Georg , Ortmaier Reinhold , Kindermann Harald , Barthofer Jürgen , Vasvary Imre , Kulnik Stefan Tino , Katzensteiner Klaus , Leister Iris
Published: December 2020

Background Anterior cruciate ligament (ACL) injury can lead to reduced function, meniscal lesions, and early joint degeneration. Preservation of a torn ACL using the Internal Brace technique might re-establish normal knee kinematics, avoid donor-site morbidity due to tendon harvesting, and potentially maintain proprioception of the knee.

Methods Fifty subjects were recruited for this study between December 2015 and October 2016. Two groups of individuals who sustained a unilateral ACL rupture were included: those who underwent surgery with preservation of the injured ACL (Internal Brace technique; IB) and those who underwent ACL reconstruction using a hamstring tendon graft (all-inside technique; AI). Subjective self-administered scores were used: the German version of the IKDC Subjective Knee Form (International Knee Documentation Committee), the German version of the WOMAC (Western Ontario and McMaster Universities Arthritis Index), SF-36 (short form), the German version of the KOOS (Knee Osteoarthritis Outcome Score), and the German version of themodified Lysholm Score by Lysholm and Gillquist. Anterior tibial translation was assessed using the KT-1000 Arthrometer (KT-1000 Knee Ligament Arthrometer, MEDmetric Corp., San Diego, CA, USA). Magnetic resonance evaluation was performed in all cases.

Results Twenty-three subjects (46 %) were men, and the mean age was 34.7 years. The objective IKDC scores were “normal” in 15 and 14 patients, “nearly normal” in 11 and 7 patients, and “abnormal” in 1 and 2 patients, in the IB and AI groups, respectively. KT-1000 assessment showed a sideto-side difference of more than 3 mm on maximum manual testing in 11 (44 %) and 6 subjects (28.6 %) in the IB and AI groups, respectively. In the postoperative MRI, 20 (74 %) and 22 subjects (96 %) in the IB and AI groups had an intact ACL. Anterior tibial translation was significantly higher in the IB group compared with the AI group in the manual maximum test.

Conclusions Preservation of the native ACL with the Internal Brace primary repair technique can achieve comparable results to ACL reconstruction using Hamstring autografts over a short term. Clinically relevant limitations such as a higher incidence of pathologic laxity, with patients more prone to pivot-shift phenomenon were observed during the study period.
Transoral outlet reduction: could additional sutures cause more harm?
Authors: Farha Jad , Gebran Selim , Itani Mohamad I. , Simsek Cem , Abbarh Shahem , Lopez Ariana , Haq Zadid , Koller Kristen , Dunlap Margo , Adam Atif , Khashab Mouen A. , Oberbach Andreas , Schweitzer Michael , Badurdeen Dilhana , Kumbhari Vivek
Published: December 2020

Background The double purse-string pattern (DPSP) of transoral outlet reduction (TORe) should conceivably result in a more robust scaffolding for the gastrojejunal anastomosis (GJA). However, there is a paucity of literature pertaining to post-TORe stenosis as an adverse event. Our aim was to determine the rate of stenosis, its potential predictors, and other complications of DPSP TORe.

Methods We performed a retrospective analysis of a prospectively maintained database of 129 consecutive patients who underwent DPSP TORe between December 2015 and August 2019.

Results The adverse event rate of TORe was 17.1 % (n = 22), with a 13.3 % (n = 17) rate of stenosis. Stenosis was not significantly associated with any baseline characteristics. GJA diameter pre- and post-TORe, the difference between these values, and procedure duration were not predictive of stenosis. Of patients who developed stenosis, 10 (58.8 %) responded to endoscopic balloon dilation and 7 (41.2 %) required stent placement.

Conclusion As the DPSP technique is a challenging procedure, with high complication rate and limited benefit, it should not be used for TORe.
Particle-in-cell simulation of surface plasmon polaritons excited by external introduction of electron density
Authors: Wang Kaiyue , Wang Hongguang , Wang Yue , Chen Kun , Liu Chunliang
Published: December 2020

Plasmonic devices work at visible and near-infrared frequencies, where a large number of bound electrons (polarization) in metals are excited. However, the existing particle-in-cell (PIC) software cannot take into account these bound electrons. In this paper, a new PIC simulation method is developed to study plasmonic devices, which has the ability to model both free electrons and bound electrons in metals. In this study, surface plasmon polaritons (SPPs) are excited by depositing excess electrons at one end of the metal film of thickness 140 nm (surrounded by air), thus initiating nonequilibrium in the electron density to start the oscillations. The spectrum, mode size, and propagation length of SPPs are calculated to confirm the electrical excitation of SPPs and characterize their properties. The excited SPPs are of a broad range of frequencies. Unlike SPPs excited by inelastic electron tunneling, the spectrum of SPPs excited in this way is not determined by eVbias but only by the properties of metals and dielectrics, and therefore the excited SPPs are intrinsic. The mode sizes of the intrinsic SPPs in the Ag–air geometry are 30 nm in Ag and 120 nm in air. The propagation length is ∼730 nm. The excited SPPs are converted into radiation modes by a sub-wavelength slit etched on the back side of the film to enable the detection of the radiation modes.
Robust short-term prediction of wind turbine power based on combined neural networks
Authors: Etemadi Mostafa , Abdollahi Amir , Rashidinejad Masoud , Aalami Habib Allah
Published: December 2020

This paper proposes a powerful and accurate prediction method for modeling wind turbine output power considering uncertainty effects. It develops a probabilistic prediction method to make intervals around the forecast point samples. Due to the instable nature of the neural networks, several models with different classes are first trained, and then a combinatorial interval is constructed based on all their results. Through this idea, some lower and upper bounds are produced which can capture the uncertainty effects. In order to train the neural networks and adjust their setting parameters, a new optimization method based on the social spider optimization search (SOS) algorithm is presented which is equipped with some modification methods for increasing its capabilities. This increases the training robustness, thus resulting in stable but accurate algorithms. The experimental results of some wind turbines are used to assess the performance of the proposed method.
Preferential acceleration of positrons by a filamentation instability between an electron–proton beam and a pair plasma beam
Authors: Dieckmann M. E. , Spencer S. J. , Falk M. , Rowlands G.
Published: December 2020

Particle-in-cell simulations of jets of electrons and positrons in an ambient electron–proton plasma have revealed an acceleration of positrons at the expense of electron kinetic energy. We show that a filamentation instability, between an unmagnetized ambient electron–proton plasma at rest and a beam of pair plasma that moves through it at a non-relativistic speed, indeed results in preferential positron acceleration. Filaments form that are filled predominantly with particles with the same direction of their electric current vector. Positron filaments are separated by electromagnetic fields from beam electron filaments. Some particles can cross the field boundary and enter the filament of the other species. Positron filaments can neutralize their net charge by collecting the electrons of the ambient plasma, while protons cannot easily follow the beam electron filaments. Positron filaments can thus be compressed to a higher density and temperature than the beam electron filaments. Filament mergers, which take place after the exponential growth phase of the instability has ended, lead to an expansion of the beam electron filaments, which amplifies the magnetic field they generate and induces an electric field in this filament. Beam electrons lose a substantial fraction of their kinetic energy to the electric field. Some positrons in the beam electron filament are accelerated by the induced electric field to almost twice their initial speed. The simulations show that a weaker electric field is induced in the positron filament and particles in this filament hardly change their speed.
Empty electron states in cobalt-intercalated graphene
Authors: Calloni Alberto , Bussetti Gianlorenzo , Avvisati Giulia , Jagadeesh Madan S. , Pacilè Daniela , Ferretti Andrea , Varsano Daniele , Cardoso Claudia , Duò Lamberto , Ciccacci Franco , Betti Maria Grazia
Published: December 2020

The dispersion of the electronic states of epitaxial graphene (Gr) depends significantly on the strength of the bonding with the underlying substrate. We report on empty electron states in cobalt-intercalated Gr grown on Ir(111), studied by angle-resolved inverse photoemission spectroscopy and x-ray absorption spectroscopy, complemented with density functional theory calculations. The weakly bonded Gr on Ir preserves the peculiar spectroscopic features of the Gr band structure, and the empty spectral densities are almost unperturbed. Upon intercalation of a Co layer, the electronic response of the interface changes, with an intermixing of the Gr π* bands and Co d states, which breaks the symmetry of π/σ states, and a downshift of the upper part of the Gr Dirac cone. Similarly, the image potential of Ir(111) is unaltered by the Gr layer, while a downward shift is induced upon Co intercalation, as unveiled by the image state energy dispersion mapped in a large region of the surface Brillouin zone.
Non-contact imaging detection of thermal Hall effect signature by periodic heating method using lock-in thermography
Authors: Tomioka Kota , Uchida Ken-ichi , Iguchi Ryo , Nagano Hosei
Published: December 2020

We demonstrate non-contact imaging detection of the thermal Hall effect by means of the lock-in thermography with rotationally asymmetric periodic heating. In the lock-in thermography measurements, we applied periodic laser heating in an elliptical pattern to a sample and measured the temperature modulation oscillating at the same frequency as the heating under a magnetic field. From the magnetic field dependence of the elliptical heating pattern, the temperature modulation due to the thermal Hall effect can be extracted. We confirm the validity of this method by detecting a signature pattern specific to the thermal Hall effect in a Bi slab at room temperature.
Shear strain bandgap tuning of monolayer MoS2
Authors: Choudhary Meenakshi , Shital Shilpi , Ya'akobovitz Assaf , Niv Avi
Published: December 2020

Bandgap tuning is an attractive property of two-dimensional semiconductors and monolayer MoS2, in particular. We report here the bandgap tuning of monolayer MoS2. This was achieved by growing monolayer MoS2 on optical fibers that were then subjected to torsion, such that pure shear was transferred to MoS2. The effect of shear was inferred from the observed photoluminescence spectrum, after which a blue shift of ∼10 meV/% emerged. Detailed analysis revealed that this shift is mainly due to the trion luminescence and less due to the excitons. This observation experimentally uncovers the behavior of MoS2 under a yet uncharted pure shear deformation, which may enable the development of devices, such as tunable electronic components and high-precision sensors.
Direction inversion of spin-polarization current and exceptional tunnel magnetoresistance
Authors: Xue NaiTao , Guo Yajing , Wang Qiang , Wang ZhiMei , Bai XueMin
Published: December 2020

By the rate equation method in sequential and cotunneling regimes, we study the transport current and tunnel magnetoresistance through a single molecule magnet asymmetrically coupled to two collinear ferromagnetic electrodes. It is observed that the direction of spin-polarization current can be inversed by spin bias voltage and the adjacent magnetic field changed with left lead’s polarization. As a consequence, the tunnel magnetoresistance can reach exceptional values beyond the usual restriction of −1 to +1. Moreover, since charge current can be zero in parallel configuration and spin current stays positive, the pure spin current appears. Thus, the system may act as a spin-valve device.
Production of pulsed high-energy neutron bursts from beam–target interaction using a 15 MeV HERMES III ion beam
Authors: Renk T. J. , Ottinger P. F. , Durrer R. E.
Published: December 2020

Intense pulsed neutron fluences are generated by a high-energy (>10 MeV) proton beam using the beam-target method on the HERMES III facility at Sandia National Laboratories [J. J. Ramirez et al., in Proceedings of the 7th International Conference on High Power Particle Beams (Kernforschungszentrum, Karlsruhe GmbH, Karlsruhe, Germany, 1988), p. 148]. In order to generate the high-energy proton beam, a radial ion diode previously developed and fielded at the 6-MeV level in negative polarity was extended in performance to the 15-MeV level. This performance increase is described along with the development of a more durable hardware set to withstand the much more potent 15-MeV proton beam. An extensive series of simulations is developed to characterize the neutrons produced by the proton–target interaction. Particle-in-cell simulations describe the electron and ion dynamics, while Monte Carlo simulations characterize the neutron output. Due to differing estimates of proton beam voltage and current between the respective simulations, we make an approximate estimate of 13.5-MeV to 15-MeV and 120-kA ion beams at peak power in a 40 ns FWHM pulse. Simulations indicate that a total of 1.7 × 1013 neutrons are generated into 4π. Comparison of the neutron output predictions with a limited set of neutron flux measurements suggests a flux level of ∼1 × 1010 neutrons/cm2 to 10 × 1010 neutrons/cm2 over an approximately few tens of cm2 area at the relevant application location. This effort also contributes to physics understanding of the use of inductive voltage adder platforms to drive ion-beam diode loads.
First-principles study of resistive random access memory based on single-layer black phosphorous resistive layer
Authors: Dai Yuehua , Gao Jianhua , Huang Lihua , Ding Renjie , Wang Peng , Yang Fei
Published: December 2020

In this work, Ti3C2/single-layer black phosphorus (BP)/Ti3C2 resistive random access memory (RRAM) was studied based on the first-principles theory. First, after determining the size of the material, the Ti3C2/BP(100) interface was built. By studying the electrostatic potential of the interface, it was found that there was a Schottky barrier at the interface, and the barrier height was obtained by calculating the work function and the band structure of the interface. Next, a Ti3C2/BP(100)/Ti3C2 RRAM device was designed based on the mechanism of the Schottky barrier at the interface. The bipolar switching characteristics were confirmed after calculating the I–V curve of the device, in which the turn-on threshold voltage is about 1.5 V, the turn-off threshold voltage is about 0.5 V, and the switch ratio is greater than 105. However, there are still shortcomings such as insufficient drive current. So, in the end, the optimization program is determined through a series of studies of device doping and vacancy, and it is found that after a certain concentration of Mg atoms are adsorbed, the conductivity of the resistive switching layer can be increased, the interface barrier can be adjusted, and the device performance such as the turn-on voltage, drive current, and switching ratio can be improved. This work may have guiding significance and value for the experimental research of manufacturing a new two-dimensional material RRAM.
Leakage current analysis of silicon diode with anode activated by furnace annealing or laser annealing using deep level transient spectroscopy
Authors: Wakimoto Hiroki , Matsumoto Takashi , Yano Koji , Muranaka Tsutomu
Published: December 2020

Silicon P-i-N diodes with a p+ region in the anode—where boron atoms are implanted and activated with relatively low-temperature furnace annealing (FA) or high-temperature laser annealing (LA)—show a large difference between the leakage currents of the diode samples activated using FA and LA. In this paper, in order to clarify the cause of the difference in leakage current, the generation current and diffusion current are verified. For estimating the generation current, the trap level was analyzed by deep level transient spectroscopy (DLTS) in a wide bias range of +0.3 V to −160 V, which corresponds to a depletion region width of 0 µm–37 µm, and trap density depth profiles are analyzed using DLTS. The DLTS analysis shows that the trap density is relatively uniform in the FA sample; however, the LA sample has a lower trap density near the p+ region of the anode. The leakage current of the diodes is calculated using the trap density profiles based on the leakage current model that includes generation and diffusion currents. The calculated and measured leakage currents are compared, and the relationship between the trap density and the leakage current is investigated. The reverse bias dependence of the calculated leakage current corresponds with the measured value for the LA sample, which implies that the trap density in the n-substrate obtained by DLTS can explain the measured leakage current well. For the FA sample, the measured leakage current is larger than the calculated value in the high reverse bias region. This suggests that there are large amounts of inactivated boron in the p+ region of the anode of the FA sample because of the low activation temperature. Only a few parts of the inactivated boron are believed to form a deep energy level trap that increases the generation leakage current. In order to reduce the leakage current of the P-i-N diode, it is effective to increase the activation rate of boron in the anode p+ region. By applying the LA method to a reverse-blocking insulated gate bipolar transistor with a built-in P-i-N diode on the collector side, the reverse leakage current can be reduced, and the operating temperature can be improved.
Extended Solov'ev type equilibria for rotating plasmas with positive and negative triangularity
Authors: Farengo R.
Published: December 2020

The Solov'ev ansatz is employed to solve the equilibrium equation for plasmas rotating in the toroidal direction. The plasma shape can be controlled by fixing the values of the aspect ratio, elongation, triangularity, and curvature at the equatorial points. In addition, it is possible to set the values of the plasma current, total β, and Mach number. Analytic expressions for the shape coefficients and examples of equilibria with positive and negative triangularity are presented.
GaN ultraviolet photodetector with petal-like β-Ga2O3 microcrystalline layer
Authors: Su Xilin , Li Yufeng , Zhang Minyan , Hu Peng , Guo Maofeng , Li Aixing , Zhang Ye , Li Qiang , Yun Feng
Published: December 2020

A GaN ultraviolet photodetector with a petal-like β-Ga2O3 microcrystalline layer was prepared on the GaN template using electrochemical anodizing and annealing processes. The petal-like β-Ga2O3 microcrystalline layer was found to enhance the absorption of ultraviolet light and suppress the dark current, and a high responsivity from 230 nm (responsivity 8.5 A/W) to 400 nm (responsivity 0.1 A/W) was achieved by the photodetector. The rejection ratio of ultraviolet–visible light is greater than three orders of magnitude representing a high selectivity of ultraviolet light detection. The responsivity slopes of the photodetector under different biases were found to be strongly correlated with the wavelength of light, and the responsivity is much higher than that of conventional metal/insulator/metal wavelength identification photodetectors. This effective method of synthesizing β-Ga2O3 crystallites on GaN can be used to enhance the ultraviolet absorption of GaN photodetectors and improve the detection performance.
A computational investigation of the interstitial oxidation thermodynamics of a Mo-Nb-Ta-W high entropy alloy beyond the dilute regime
Authors: Samin Adib J.
Published: December 2020

High entropy alloys (HEAs) are promising candidates for high-temperature structural material applications. Oxidation is a major factor that must be accounted for when designing such materials and it is thus important to study the oxidation behavior of HEAs to enable the optimum design of next generation materials. In this study, the thermodynamic behavior of interstitial oxygen in a Mo-Nb-Ta-W high entropy alloy was explored beyond the dilute limit. This was accomplished by sampling configurations of the HEA and HEA-oxygen systems from an isothermal–isobaric ensemble using a series of first-principle-based Monte Carlo simulations. It was found that the interstitial oxygen had comparable stability at tetrahedral (T) sites and octahedral (O) sites. The stability of the interstitial oxygen was correlated with the composition of the surrounding local metallic environment. The O-site interstitial oxygen was further found to arrange in ordered clusters and was associated with enhanced mechanical properties as demonstrated by an increase in the bulk modulus with increasing oxygen content. Finally, the solubility of the interstitial oxygen in the alloy was found to decrease with temperature.
Chasing chaos by improved identification of suitable embedding dimensions and lags
Authors: Perinelli Alessio , Ricci Leonardo
Published: December 2020

The detection of an underlying chaotic behavior in experimental recordings is a longstanding issue in the field of nonlinear time series analysis. Conventional approaches require the assessment of a suitable dimension and lag pair to embed a given input sequence and, thereupon, the estimation of dynamical invariants to characterize the underlying source. In this work, we propose an alternative approach to the problem of identifying chaos, which is built upon an improved method for optimal embedding. The core of the new approach is the analysis of an input sequence on a lattice of embedding pairs whose results provide, if any, evidence of a finite-dimensional, chaotic source generating the sequence and, if such evidence is present, yield a set of equivalently suitable embedding pairs to embed the sequence. The application of this approach to two experimental case studies, namely, an electronic circuit and magnetoencephalographic recordings of the human brain, highlights how it can make up a powerful tool to detect chaos in complex systems.
Maximum volume simplex method for automatic selection and classification of atomic environments and environment descriptor compression
Authors: Parsaeifard Behnam , Tomerini Daniele , De Deb Sankar , Goedecker Stefan
Published: December 2020

Fingerprint distances, which measure the similarity of atomic environments, are commonly calculated from atomic environment fingerprint vectors. In this work, we present the simplex method that can perform the inverse operation, i.e., calculating fingerprint vectors from fingerprint distances. The fingerprint vectors found in this way point to the corners of a simplex. For a large dataset of fingerprints, we can find a particular largest simplex, whose dimension gives the effective dimension of the fingerprint vector space. We show that the corners of this simplex correspond to landmark environments that can be used in a fully automatic way to analyze structures. In this way, we can, for instance, detect atoms in grain boundaries or on edges of carbon flakes without any human input about the expected environment. By projecting fingerprints on the largest simplex, we can also obtain fingerprint vectors that are considerably shorter than the original ones but whose information content is not significantly reduced.
An assessment of theories modeling vortex breakdown as a transition between cylindrical flow states
Authors: Moise Pradeep
Published: December 2020

This study assesses the validity of two theories proposed to explain vortex breakdown occurring in swirling flows in pipes [Benjamin, J. Fluid Mech. 14, 593–629 (1962) and Wang and Rusak, J. Fluid Mech. 340, 177–223 (1997)]. Both model vortex breakdown as a steady, inviscid, streamwise transition between axisymmetric, cylindrical (streamwise-invariant) flow states, with the downstream “conjugate” state predicted differently by each based on the upstream inflow state. In this study, these conjugate solutions are computed for three distinct swirling inflow profiles by solving the Bragg–Hawthorne equation based on the inflow conditions. It is first shown that the “adjacent” conjugate solution proposed by Benjamin exhibits stronger flow reversal when the inflow swirl strength is decreased. This is in direct contradiction to trends observed in experiments, indicating that this aspect of the theory is invalid. Following this, the “global minimizer” conjugate solution proposed by Wang and Rusak is examined. In addition to numerical computations, an analytic expression for this conjugate solution is derived for the case of a Rankine vortex as the inflow. For various inflow profiles, it is shown that these conjugate solutions exhibit many trends similar to those observed in experiments. However, the results also indicate that the stagnation zone associated with these solutions expands radially in an unbounded fashion in the absence of confinement effects, implying that viscous effects might play a crucial role in limiting the radial expansion of the flow. Finally, based on these results and the inverse relationship between the swirl parameter and Mach number, it is argued that modeling vortex breakdown as directly analogous to a gasdynamic normal shock wave is erroneous.
Exploring a near-Hartree–Fock–Kohn–Sham approach to study electronic properties of azobenzene in interaction with gold: From clusters to the Au(111) surface
Authors: Martins Gabriel F. , de P. Cardoso Bernardo , Galamba Nuno , Cabral Benedito J. C.
Published: December 2020

The electronic properties of azobenzene (AB) in interaction with gold clusters and adsorbed on the Au(111) surface are investigated by adopting a near-Hartree–Fock–Kohn–Sham (HFKS) scheme. This scheme relies on a hybrid Perdew–Burke–Ernzerhof functional, in which the exact non-local HF exchange contribution to the energy is taken as 3/4. Ionization energies and electron affinities for gas phase AB are in very good agreement with experimental data and outer valence Green’s function) calculations. The presence of C—H⋯Au interactions in AB–Aun complexes illustrates the role played by weak interactions between molecular systems and Au nanoparticles, which is in line with recent works on Au–H bonding. In AB–Aun complexes, the frontier orbitals are mainly localized on the gold platform when n ≥ 10, which indicates the transition from a molecular to a semiconducting regime. In the latter regime, the electronic density reorganization in AB–Aun clusters is characterized by significant polarization effects on the Au platform. The accuracy of the near-HFKS scheme for predicting adsorption energies of AB on Au(111) and the interest of combining exact non-local HF exchange with a non-local representation of the dispersion energy are discussed. Taking into account the significant computational cost of the exact non-local HF exchange contribution, calculations for the adsorption energies and density of states for AB adsorbed on Au(111) were carried out by using a quantum mechanics/molecular mechanics approach. The results strongly support near-HFKS as a promising methodology for predicting the electronic properties of hybrid organic–metal systems.
Offcut-related step-flow and growth rate enhancement during (100)
β
-Ga2O3 homoepitaxy by metal-exchange catalyzed molecular beam epitaxy (MEXCAT-MBE)
Authors: Mazzolini Piero , Falkenstein Andreas , Galazka Zbigniew , Martin Manfred , Bierwagen Oliver
Published: December 2020

Homoepitaxial β-Ga2O3 layers grown via molecular beam epitaxy (MBE) have exhibited prohibitively low growth rates on (100) oriented substrates in the past. In this work, we investigate the possibility to employ indium-assisted metal exchange catalyzed (MEXCAT) MBE to overcome this limit. We demonstrate that the fine tuning of the MEXCAT growth parameters and the choice of a proper substrate offcut allow for the deposition of thin films with high structural quality via the step-flow growth mechanism at relatively high growth rates for β-Ga2O3 homoepitaxy (i.e., around 1.5 nm/min, ≈ 45% incorporation of the incoming Ga flux), making MBE growth in this orientation feasible. Moreover, through the employment of the four investigated different (100) substrate offcuts along the [001¯] direction (i.e., 0°, 2°, 4°, and 6°), we give experimental evidence on the fundamental role of the (2¯01) step edges as nucleation sites in the growth of (100)-oriented Ga2O3 films by MBE.
Computational phonogram archiving
Authors: Blaß Michael , Fischer Jost Leonhardt , Plath Niko
Published: December 2020

A general approach to analyzing audio files makes it possible to re-create the sound of ancient instruments, identify cross-cultural musical properties, and more.
Generation of high-power few-cycle femtosecond IR pulses by double-chirp parametric amplification
Authors: Frolov S.A. , Trunov V.I.
Published: December 2020

We present an energy scalable configuration for the generation of high-power few-cycle femtosecond IR pulses based on the sequential parametric amplification of chirped radiation pulses at the idler (0.86 μm) and signal (1.39 μm) wavelengths from the multi-terawatt femtosecond laser system made at the Institute of Laser Physics, Siberian Branch of the Russian Academy of Sciences (ILP SB RAS). The configuration under consideration involves the sequential production of radiation pulses with centre wavelengths of 2.24, 3.56, and 7.25 μm. The conditions are determined for the generation of few-cycle pulses with a terawatt peak power in the 3.56 μm (15.8 fs, 1.5 cycles) and 7.25 μm (17.2 fs, shorter than one cycle) domains. The phase transfer between signal and idler waves in the double-chirp parametric amplification is investigated for the first time.
Adaptive system for wavefront correction of the PEARL laser facility
Authors: Soloviev A.A. , Kotov A.V. , Perevalov S.E. , Esyunin M.V. , Starodubtsev M.V. , Alexandrov A.G. , Galaktionov I.V. , Samarkin V.V. , Kudryashov A.V. , Ginzburg V.N. , Korobeynikova A.P. , Kochetkov A.A. , Kuzmin A.A. , Shaykin A.A. , Yakovlev I.V. , Khazanov E.A.
Published: December 2020

The results of the operation of a wavefront correction system based on a deformable bimorph mirror of the PEARL subpetawatt laser facility are presented. An improvement in the quality of focusing of laser radiation, which led to an increase in the Strehl ratio from 0.3 to 0.6, is demonstrated. The features of the compensation for phase distortions of the wavefront in the case of a low pulse repetition rate, as well as the correct allowance for the noise of the CCD camera when calculating the Strehl ratio are investigated.
AlGaInAs/InP semiconductor lasers with an ultra-narrow waveguide and an increased electron barrier
Authors: Svetogorov V.N. , Ryaboshtan Yu.L. , Ladugin M.A. , Padalitsa A.A. , Volkov N.A. , Marmalyuk A.A. , Slipchenko S.O. , Lyutetskii A.V. , Veselov D.A. , Pikhtin N.A.
Published: December 2020

Semiconductor lasers based on AlGaInAs/InP heterostructures with an ultra-narrow waveguide and an increased electron barrier layer are developed. It is shown that the use of this waveguide in conjunction with profiled doping ensures a balance between internal optical losses and heat resistance. Additional use of strained wide-bandgap layers as blocking barriers limiting electron leakage from the active region makes it possible to increase the output power at the same pump current. The developed lasers with a stripe contact 100 μm wide demonstrate at room temperature an output optical power of 4.0 – 4.4 W (pump current 14 A) in a continuous-wave regime and 15 – 17 W (100 A) in a pulsed regime (100 ns, 1 kHz) at wavelengths of 1450 – 1500 nm.
A goal-driven modular neural network predicts parietofrontal neural dynamics during grasping
Authors: Michaels Jonathan A. , Schaffelhofer Stefan , Agudelo-Toro Andres , Scherberger Hansjörg
Published: December 2020

Significance

Grasping objects is something primates do effortlessly, but how does our brain coordinate such a complex task? Multiple brain areas across the parietal and frontal cortices of macaque monkeys are essential for shaping the hand during grasping, but we lack a comprehensive model of grasping from vision to action. In this work, we show that multiarea neural networks trained to reproduce the arm and hand control required for grasping using the visual features of objects also reproduced neural dynamics in grasping regions and the relationships between areas, outperforming alternative models. Simulated lesion experiments revealed unique deficits paralleling lesions to specific areas in the grasping circuit, providing a model of how these areas work together to drive behavior.