bluuebunny/crossref_metadata_2025 huggingface dataset:
Interpretation of XENON1T excess with MeV boosted dark matter *
Authors: Jia Lian-Bao , Li Tong
Published: May 2022

The XENON1T excess of keV electron recoil events may be induced by the scattering of electrons and long-lived particles with an MeV mass and high speed. We consider a tangible model composed of two scalar MeV dark matter (DM) particles,

and

, to interpret the XENON1T keV excess via boosted

. A small mass splitting

is introduced, and the boosted

can be produced using the dark annihilation process of

via a resonant scalar ϕ.

electron scattering is intermediated by a vector boson X. Although the constraints from Big Bang nucleosynthesis, cosmic microwave background (CMB), and low-energy experiments set the

mediated

electron scattering cross section to be

, the MeV scale DM with a resonance enhanced dark annihilation today can still provide sufficient boosted

and induce the XENON1T keV excess. The relic density of

is significantly reduced by the s-wave process

, which is permitted by the constraints from CMB and 21-cm absorption. A very small relic fraction of

is compatible with the stringent bounds on un-boosted

-electron scattering in DM direct detection, and the

-electron scattering is also allowed.
CFD simulation of shockwave-boundary layer interaction induced oscillation in NACA SC2-0714 transonic airfoil
Authors: Zhang Zhi , Hirahara Anna , Xue Yaohua , Uchiyama Naoki
Published: May 2022

To develop an advanced way of designing transonic airfoils for industry, a reliable and user-friendly mesh generator and a robust CFD solver are necessary. Especially, the prediction of unsteady shock buffet phenomenon is always a focus for the CFD simulation of transonic airfoils. In this study, BOXERmesh (an automatic mesh generator) and NEWT (a robust CFD solver), which are developed by CFS (Cambridge Flow Solutions) in collaboration with MHI (Mitsubishi Heavy Industries), are used to perform the CFD simulation of NACA SC2-0714 transonic airfoil. CFD simulation is conducted at two different attack angles with Mach number as 0.74 and Reynold number as 1.5×107 (non-buffet: α=2°; shock buffet: α=3°). A hexahedral dominant mesh is generated by BOXERmesh with the cell number as 5.52 million. Both unsteady RANS (URANS) and LES are performed using the CFD solver NEWT. Specifically, the governing equation is discretized by central differencing scheme with 2nd order accuracy in space by applying Swanson and Turkel type artificial viscosity, and the Adams-Bashford time integration with the dual-time stepping method is applied for temporal discretization in the density-based solver. Results show CFD simulation could reproduce the time averaged chordwise distribution of pressure coefficient at the two conditions. Both URANS and LES successfully capture the unsteady shock buffet phenomenon when increasing attack angle from 2° to 3°. However, the calculated peak oscillation location and the shock buffet frequency are different between URANS and LES. Applying the same mesh resolution, URANS performances better than LES, with the deviation of the shock buffet frequency less than 6% (Exp.: 69 Hz; URANS: 73 Hz). The reason is considered as the wall-normal mesh refinement near the airfoil surface (y+∼66) being not enough for LES to accurately resolve the turbulence scale and capture the boundary layer separation behavior. On the other hand, URANS is thought to be enough to reproduce the periodic moving of the onset of boundary separation and to predict the main characteristics of the shock buffet phenomenon.
Cavitating flow investigation in low specific speed axial flow waterjet pumps
Authors: Wang Zhe , Zhang Ruizhi , Zhou Jiajian , Luo Xianwu
Published: May 2022

In this paper, the cavitating flow in low specific speed axial flow waterjet pumps are treated at different cavitation conditions. In order to analyze the cavitating turbulent flow comprehensively, three axial flow waterjet pumps with the specific speed less than 650 min-1·m3s-1·m are chosen to compare the internal flow phenomenon. The investigations are conducted by numerical simulation, where RANS method is applied with k-ω SST turbulence model and homogeneous cavitation model. The results show that there are several types of cavitation such as tip leakage vortex cavitation, sheet cavitation attached on blade suction surface, and shedding cavity in the pumps. The vortex structure in the low specific speed waterjet pump contains tip leakage vortex, shedding vortex downstream of the sheet cavitation and perpendicular cavitation vortex. It is noted that the cavity firstly occurs at the leading edge near blade tip, and the sheet cavity covering the blade suction surface extends from leading edge to the middle part, while the tip leakage vortex cavitation develops with the decreasing cavitation number. Further analysis using relative vortex transport equation depicts that the vortex stretching term is the main contributor for the vorticity production in the pump, and the vortex dilation and baroclinic torque occur at the interface between cavity and water.
Airfoil optimization using a machine learning-based optimization algorithm
Authors: Song Xueyi , Wang Lin , Luo Xianwu
Published: May 2022

For the design of wind turbines, airfoil optimization is widely required as the operation efficiency of wind turbines is closely dependent on the airfoil aerodynamic performance, where the accuracy of the optimization method is of great importance. In this paper, a machine learning-based optimization algorithm is proposed to improve the airfoil performance. A low-speed airfoil of NACA0012 is selected as the original airfoil for the optimization. The class-shape-transformation (CST) method is used to construct the geometry for the airfoil, and the aerodynamic performance is calculated using the panel code XFOIL. The validation of the simulation is carried out by comparing the predicted aerodynamic performance with the experimental data. In order to improve aerodynamic performance of the airfoil, maximizing the lift-to-drag ratio is selected as the main objective of the optimization problem while maintaining the lift coefficient not smaller than the original values. The results show that the present machine learning-based algorithm has fairly good convergence, and can obtain much higher lift-to-drag ratio for the optimized airfoil compared with the original one. Compared with the traditional genetic algorithm method, the machine learning based method can achieve much better aerodynamic performance and much shorter simulation time for the same airfoil optimization problem. In the future, the machine learning-based method is very promising for fluid machinery design optimization.
Experimental study on fiber suspension in a centrifugal pump by PIV
Authors: Zhang Qihua , Xie Zhiang , Kang Shun , Zhang Weidong
Published: May 2022

To study the influence of fiber particles on the flow field within the passages of an open impeller centrifugal pump, an experiment was performed. The hair fiber was used as solid particle phase in this experiment. After measuring the performance characteristic and PIV data, the flow field in impeller was measured and analyzed. It was shown that at the concentration of 0.1%, a varied distribution of relative velocity from different flow channels was observed. The outlet velocity of the impeller in the second flow channel was obviously higher than that in the first flow channel. The variation of the relative velocity near the hub tended to be consistent at the position of the front plane and the middle plane of the impeller. At 0.2% concentration, the relative velocity at the suction surface of the two channels changes more sharply than the other positions. Within the second channel, it was found that the relative velocity under low flow condition was obviously higher than that under rated and large flow rates. Under different concentrations, the increase of the relative velocity at low flow rate changed intensely compared with the other two conditions. The low velocity zone will be formed near the middle part of the suction surface of the flow channel which gradually decreases with the increase of the flow rate. The external characteristic test shows that the efficiency of the pump and the drag reducing feature increase with the increase of concentration.
Visualization of rotating cavitation in a centrifugal pump
Authors: Yokoi T , Kang D , Nohmi M , Tsuneda T , Okajima J , Iga Y
Published: May 2022

In this study, unsteady cavitation in a centrifugal pump that had 3 blades was visualized in experiments. Cavitation behavior was photographed by using a high-speed camera from the axial direction. To observe rotating cavitation, its aspects were visualized using a high-speed camera. The experiment was performed at rotational speed of 825 rpm with a centrifugal pump under reduced pressure. Rotating cavitation occurred on the suction side of blades under the condition of flow rates lower than the best efficiency point. In addition, observed rotating cavitation was super-synchronous rotating cavitation, which rotates at a faster speed than the impeller in absolute coordinate form. As a result of frequency analysis of the brightness value on the channel, propagation velocity ratios, which is the ratio of the propagation velocity of the cavity to the rotational velocity of the impeller were 1.2 - 1.3. It was confirmed that the propagation velocity ratio of rotating cavitation in the centrifugal pump is close to that of rotating cavitation in the inducer even when the specific speed and Reynolds number are different.
Nonlinear and dissipation effects of pressure waves in water flows containing translational bubbles with a drag force
Authors: Arai S , Kanagawa T , Ayukai T , Yatabe T
Published: May 2022

Weakly nonlinear (i.e., finite but small amplitude) propagation of plane progressive pressure waves in compressible water flows uniformly containing many spherical bubbles is theoretically studied. Drag force acting bubbles and translation of bubbles are newly considered by introducing in momentum conservation equations in a two fluid model and the bubble dynamics equation for volumetric oscillations, respectively. Although these assumptions are the same as our previous paper, in this study, the energy conservation equation for each bubble describing a thermal conduction inside bubble is introduced. By using the method of multiple scales, the Korteweg–de Vries–Burgers equation for low-frequency long wave was derived from the set of basic equations in the two-fluid model. As a result, the dissipation effect was described by two types of terms, i.e., one was the second-order partial derivative owing to the liquid compressibility and the other was the term without differentiation owing to the drag force and the thermal conduction. Finally, we clarified that the dissipation owing to the drag force was smaller than that owing to the thermal conduction.
Flow visualization of non-contacting mechanical seals with bidirectional rotation
Authors: Sato Y , Ochiai M
Published: May 2022

Non-contacting mechanical seals are used as a shaft seal in a turbomachinery. A few micrometers thin lubrication film is formed by grooves on the seals. Various groove shapes were presented, and most of these grooves were designed for unidirectional rotation. However, reverse rotation occurs accidentally in the turbomachinery. In this study, the performance of two type unidirectional grooves was investigated by measuring the pressure in a chamber which means sealed fluid pressure and visualizing the flow in the lubrication film with bidirectional rotation. The measurement results of pressure under forward rotation showed that the pressures fluctuated as rotational speeds increased by hydrodynamic pressure. By contrast, under reverse rotation, the amount of fluctuation was smaller and almost not changed with increasing rotational speeds. In addition, the flow visualization results showed the increase of pressure drop areas and occurrence of gas phase. This indicates the decrease in load capacity and film stiffness. In contrast, the discharging flow from inner to outer side or the breakage of the film were confirmed and prevented fluid leaking. In summary, the results showed the degradation of lubrication characteristics though the no degradation of a sealing performance.
Effect of balanced edge cutting configurations on the aeroacoustics of high-speed turbomachinery
Authors: Song Ji-Hun , Jang Seungsoo , Kim Youn-Jea
Published: May 2022

Flow-noise corresponding to the balanced edge cutting configurations on the compressor wheel of a turbocharger is investigated in this study. The turbocharger is a type of high-speed turbomachinery that rotates at up to 2.0×105 RPM. Microscopic air bubbles are generated inside the compressor wheel due to inaccuracies in the cast introduced in the production process. These bubbles cause a mass-unbalance phenomenon when operated at high rotational speeds, which even leads to breakage in severe cases. To prevent theses problems, cutting configurations are utilized at various locations on the rear of the wheel. However, the cutting shapes rather produce severe vortices from a flow perspective, which has a significant effect on the flow noise. Therefore, after calculating the steady-state shear stress transport k-ω based on the Reynolds-averaged Navier-Stokes equation model, transient large eddy simulation was conducted from initial values using the commercial computational fluid dynamics software, ANSYS FLUENT V20.2. The flow-noise was calculated based on unsteady analysis data with the Ffowcs-Williams and Hawkings equation. The flow-noise of the balanced edge cutting configurations of turbocharger compressor wheels was calculated according to various receiver points, and rotational velocities. Results show that various noise characteristics occur depending on the rotational speeds and the receivers depending on the cutting configurations.
Noise prediction of a box fan by RANS simulation
Authors: Kitamura Masashi , An Byungjin , Nohmi Motohiko
Published: May 2022

The characteristics of aerodynamic performance and aerodynamic noise of a box fan were evaluated to investigate the industrial applicability of computational fluid dynamics (CFD) with Reynolds averaged numerical simulation (RANS) model for fan design. In the case of unsteady RANS, the characteristic of the static pressure rise for flow rates was in good agreement with the experimental results. Aerodynamic noise performance at the design flow rate and low flow rate is well predicted using acoustic/viscous splitting technique based on unsteady RANS with multiple reference frame (MRF). As a result, it was able to evaluate the overall sound characteristic of each fan design relatively. The results suggest that the acoustic/viscous splitting technique based on RANS with MRF simulation has potential as a useful design tool.
Two-dimensional numerical simulation of the performance of orthopter-type wind turbine with S-shaped arc blades
Authors: Shima Takuma , Kiwata Takahiro , Kono Takaaki
Published: May 2022

This paper evaluates the performance of an orthopter-type wind turbine with S-shaped arc blades using two-dimensional numerical simulations. For this variable-pitch vertical-axis wind turbine, each blade rotates on its own axis while all blades rotate on the main axis. This configuration ensures that the blades rotate around their own axes by 360° for every two-full revolutions of the main rotor. The central angle φ of an S-shaped arc blade was set to 60°, 90°, 120°, or 150°. The power coefficient Cp
for a normal S-shaped arc blade is larger than that for an inverse S-shaped arc blade. The maximum power coefficient Cpmax
for the normal S-shaped arc blade with φ = 90°-120° is suitable for an orthopter-type wind turbine. The inlet angle of the wind turbine θP
was set 0°, ±5°, ±15°, or ±30°. The maximum power coefficient Cpmax
was large for θP
values of –15° to +5°. This wind turbine can achieve passive yaw control by means of a tail vane installed on the sprocket of main axis.
Preliminary flow measurements of a small-scale, vertical axis wind turbine for the analysis of blockage influence in wind tunnels
Authors: Santamaría Luis , Díaz Katia María Argüelles , Pereiras Bruno , Vega Mónica Galdo , Pérez José González , Velarde-Suáréz Sandra , Oro Jesús Manuel Fernández
Published: May 2022

The development of competitive lift vertical axis wind turbines (VAWTs) is yet a challenge in wind power research. New designs typically require wind tunnel testing before in site implementation. One of the major problems at the laboratory stage is the appearance of a significant flow blockage for small scale models, which affects the performance of the tested wind turbines and prevents the direct extrapolation of results to open field conditions without previous correction. Unfortunately, a suitable blockage correction for lift VAWTs has not been achieved yet, so more studies are needed in this research field to fill the gap. As part of preliminary work with this aim, a small scale VAWT prototype has been designed, constructed, and tested in a 1.15×1 m2 test section wind tunnel with a semi-closed chamber, featuring a blockage ratio of 0.37. Preliminary aerodynamic measurements were performed for different tip speed ratios on the downstream near wake using a special 3-hole pressure probe. Results show that the wake velocity profiles present a velocity increase around the prototype with a low velocity region in the windward quadrant of the turbine, indicating an important influence of the tunnel boundaries. These preliminary measurements have given an initial insight on the aerodynamic relationships between turbine performance and flow patterns. Additionally, they will help to devise an appropriate strategy for the following experiments, with the final objective of developing a blockage correction for small scaled VAWTs.
Casing treatment using oblique slots for a single-stage transonic axial compressor
Authors: Vuong Tien-Dung , Kim Kwang-Yong
Published: May 2022

This work presents a casing treatment design using oblique slots to improve the stability of a single-stage transonic axial compressor, NASA Stage 37. 36 individual slots are distributed uniformly on the rotors’ shroud. Numerical simulations were performed to find the effects of the casing treatment on the compressor’s stability as well as the adiabatic efficiency and pressure ratio. The oblique slots were found to effectively alleviate the negative influence of the tip leakage flow on the compressor’s performance, thus increasing the stall margin without significant sacrifices in efficiency and pressure rise. Three geometric parameters of the casing treatment were examined. The results showed that, with the oblique slots, the highest stall margin reached 13.59% - a 37% increase from the smooth casing case, with about 0.17% and 0.09% reductions in the peak efficiency and maximum pressure ratio, respectively.
Effect of side-wall ribs on heat transfer and flow characteristics in internal cooling passage of gas turbine blade
Authors: Matsuura Kensuke , Yoshida Tetsuya , Hata Daisuke , Miyabe Masahiro
Published: May 2022

The effect of the side-wall ribs on the heat transfer and flow characteristics in the blade internal cooling passage was conducted by both experiments and CFD calculations, and its optimal shape, arrangement and further development were investigated. It is necessary for the side-wall ribs to optimize the shape for the purpose of not increasing the total pressure loss as much as possible. In this study, Λ and V shaped side-wall ribs with aspect ratio of 1.0 were numerically and experimentally investigated. In addition, with the aim of reducing the total pressure loss, the side-wall ribs with slit which were modified by removing the central part of the Λ and V shaped ribs and those combinations were investigated. As a result, it was confirmed that the combination of V and V shaped with slit were promising and multi-objective optimization using a genetic algorithm was conducted for it. The design parameters were the angle of attack (AoA) for both V shaped with slit and V shaped side-wall ribs, the slit width of V shaped and the height of ribs. The objective functions were Nusselt number, total pressure loss coefficient and thermal performance. The optimized shape has the highest thermal performance, although there exists a strong trade-off relationship between heat transfer coefficient and total pressure loss coefficient. Moreover, the effect of aspect ratio was investigated with considering the vortices distributions in the three-dimensional space. In this study, two kinds of aspect ratio, W/H=0.5 and 2.0 were numerically investigated. As a result, it was found that W/H=0.5 is the best with respect to thermal performance due to pressure loss reduction because the interaction of vortices were suppressed. In conclusion, the side-wall ribs promote the reattachment of separated cooling air flow and the high heat transfer coefficient region can be expanded and the thermal performance can be improved.
Trajectory analysis of air-entrainment vortex in a suction sump
Authors: Noguchi T , Komatsu K , Hirata K
Published: May 2022

We attempt to develop the algorithm that identify the trajectory of the air strings from the image data. As a result, we reveal the behaviour of the vortex. Furthermore, we extract the air string with the longest life, and reveal its trajectory with poor regularity. In some cases, the air string tends to turn back and to attract to the pipe. But in some cases, the air string tends to move linearly and to have the trajectory that moves away from the pipe. In addition, the air string sometimes takes the trajectory that wraps around the wake along the pipe.
Nature inspired design modification of fluidic diode for wave energy harvesting device
Authors: Hithasih Doddamani , Samad Abdus , Takao Manabu
Published: May 2022

A fluidic diode (FD) coupled with the unidirectional turbine (UT) can improve its flow rectification operating in a bi-directional airflow. However, the shape of the FD is not standardized like other fluidic components, and they are usually problem-specific. The performance of the FD is given by diodicity, which is the ratio of pressure drop for the reverse to forward direction. This article aims to improve the performance of the FD proposed for wave energy application by modifying its shape, which is inspired by the bud of the lotus flower. The modified model is numerically studied by solving three-dimensional steady-state Reynolds Averaged Navier Stokes equations using the commercial computational fluid dynamics software ANSYS FLUENT 16.2. The proposed modification had a lesser pressure drop in both directions compared to the base model. The detailed flow physics and performance analysis of the modified FD are presented.
Effect of blade skew, endplate and casing groove on the aerodynamic performance of Wells turbine for OWC: a review
Authors: Kumar Amit , Das Tapas K. , Samad Abdus
Published: May 2022

The geometry modification of a bidirectional flow Wells turbine used in a wave energy converter can assist in overcoming the mammoth stall triggered by tip leakage, secondary flow on the blade surface, corner vortex, passage vortex, tip scrubbing, tip trailing edge vortex, boundary layer formation on hub and casing, and combination of all the listed making it a complex 3D flow. As the flow varies almost sinusoidally in each wave cycle in the ocean, it is inevitable to get a turbine having a higher operating range and average power output. Skewing a blade reduces the radial flow on the blade suction surface. A casing groove and endplate reduce tip leakage flow. These modifications give a significant improvement in the turbine performance. There are several design alternatives reported in the articles, and they have shown different results. In this article, the modifications and their effects are discussed in detail and concluded for future recommendations.
Research on Target Imaging Scene Simulation for Photoelectronic Tracking
Authors: Jiang Kai , Mao Zheng
Published: May 2022

In this paper, the 3D visual display and generation of target in optoelectronic tracking are researched by simulation. 3ds max software is used to model the target, the target model is converted into code files by Deep Exploration and added into the system model. The key point is to associate the target model track and size ratio with the actual target to approach the real battlefield environment. The image data provided by the scene building is tracked by the internal image processing algorithm of photoelectric tracking such as the Canny-based edge tracking. The experiment will compare the tracking of the same target in same algorithm but different backgrounds, and the same backgrounds but different algorithm. Result can see that through the experimental data, the application of the simulated sky background, and the proportion relationship between real target and target in simulation scene, provides a high authenticity data support for the image processing algorithm of self-propelled gun photoelectric tracking system.
The ECAP Process Simulation and Experiments with Different Back Pressures for Magnesium Alloy
Authors: Quang P
Published: May 2022

According to this study, the ECAP process with different BP is performed on the engineering magnesium alloy (AZ31). The effect of BP on the strain condition and flow paths may differ as the statically deformed portion of the sample passes through the strain zone. The BP application of 25, 50 and 100 MPa brings about the forward typical shear rotation of structural components in the horizontal direction. The complex (20 x 20 x 200) mm3
ECAP engine is applied with movable outer walls and specially designed sliding bottoms for low friction (moving die). The flow model is made by a cubic flow net of the DEFORM software tool on the workpiece. Structural features and initial micro-hardness measurements made on the x and y planes of the workpiece also received a special attention. Since BP leads to increased density the micro-hardness could be improved and ascribed to the change in texture.
Three-Dimensional Modeling and Simulation of Normal Knee Joint Motion
Authors: Alemayehu Dereje Gobena , Zhang Zhi , Tahir Elena , Gateau Djovensky , Ma Xing
Published: May 2022

Three-dimensional (3D) modeling and simulation have important applications in orthopedic surgery. This technology can be used to create a 3D model of anatomic structures that can be used as a template to perform surgical simulations preoperatively. This study was aimed to apply 3D modeling to simulate flexion of a human knee based on the normal knee joint motion that includes tibial internal rotation and femoral rollback under high degree knee flexion. A 3D knee joint model was constructed from a two-dimensional computed tomography image of a normal knee joint. Based on the reconstructed 3D model of the knee joint, simulation of knee joint flexion at 90,100,110,120,130, and 140 degrees was conducted while replicating the normal knee joint motion. The rotation, translation, and tilt wizards allow the simulation of a complex motion that happens at the human knee joint. Simulation of knee joint motion allows replication of the complex motion during a gait cycle and can offer an alternative option to in vivo experiments to simulate surgical techniques, analyse knee implants and conduct biomechanical studies. This study has demonstrated that 3D modeling and simulation technology is an important tool to study the relationship between the degree of knee flexion and femoral tunnel orientation in anterior cruciate ligament (ACL) reconstruction. Accordingly, the joint flexion angle, and the sagittal and axial drill angles should be taken into consideration in ACL reconstruction.
Bifurcation Analysis and Travelling Wave Solution for a Generalized Time Fractional KdV Equation
Authors: Wang Yan , Yang Wei , Yang Liu , Wang Nan , Yan Yongsheng , Wang Meng , Li Lingfei
Published: May 2022

By using bifurcation theory of planar dynamic system to a generalized time fractional KdV equation, a large number of solutions including irrational function solution, Jacobian elliptic function solution, trigonometric function solution, solitary solution as well as compacton solution are derived. Under different parametric selection, various kinds of sufficient conditions and numerical simulations are demonstrated to visualize their mechanism.
Effective Ship Domains Considering Ship Encounter Situations and Speeds
Authors: Yang Shujie , Sun Wei
Published: May 2022

Ship domain is an important concept in assessing navigation situation and planning collision avoidance manoeuvres of a ship. For purpose of improving the precision and adaptability of the ship domains, effective ship domains are proposed for ships with different speeds in a variety of encounter situations in this work. Firstly, the COLREGs-based division of encounter types and corresponding collision avoidance actions are further optimized. Therefore, the problem of unclear division of responsibilities caused by the intersection of relative position and relative heading is resolved. On this basis, ship domains are determined by the encounter situations and the target ship’s speed. More specifically, the ship domain is approximated to a circle, and the dependence of the domain size on the encounter situation and the target ship’s speed has been analysed and described, that enable us to determine effective ships domains for ships varying in speeds and encounter situations. The simulation results show that ships can make effective collision-avoidance actions in different encounter scenarios based on the optimized COLREGs-based division of encounter types and effective ship domains.
Design Methods for the Lethality of Fragmentation Warhead based on a Multi-Objective Optimization Algorithm
Authors: Li Xiangyu , Li Fugang , Liang Minzu , Zhang Kefan
Published: May 2022

Fragmentation warhead is the main weapon used to damage personnel and light armored objectives, with the lethal parameters primarily consisting of the number and velocity of fragments. Increasing the lethality of fragmentation warhead is currently the most important development direction for fragmentation warhead. The formation process of natural fragment is complicated and there are several factors that affect the properties of fragment, so there are still many techniques of developing the lethality of fragmentation warhead. In this paper, our object is to focus on the optimization design for the lethality of fragmentation warhead, based on the optimal Latin hypercube test design method and the radial basis function neural network surrogate modelling, taking the number of effective fragments per unit mass and the average kinetic energy of the effective fragments as the optimization objectives, and the explosive charge, the fragment material, the overall structure and initiation method are considered, respectively. The Pareto optimal solution sets under different design variables are obtained, and the optimal matching of multiple design parameters is realized, establishing the integration design method for “explosive - material-structure” of the fragmentation warhead. The research results can provide technical support for the structural optimization design of the fragmentation warhead.
Improved Migratory Bird Migration Algorithm for Flexible Job Shop Scheduling
Authors: Shen Liezheng , Zhen Guohui , Zhu Haiping
Published: May 2022

For flexible job shop scheduling, an improved migratory bird migration algorithm is proposed to minimize the maximum completion time. Firstly, global, local and random selection methods were used to initialize the population, which improved the quality of the initial solution; The structure of migratory bird group was changed by increasing leading birds, and the crossover and mutation operators were introduced to enhance the global optimization ability. And different variable neighborhood search algorithms on critical path were introduced among different bird groups, which improved the local optimization ability of and the diversity of migratory bird groups; The jumping and competition mechanisms were proposed to improve the ability of the algorithm to jump out of the local optimal solution and convergence. Finally, the simulation results of the benchmarks verified the algorithm’s searching ability and stability of the algorithm.
An Floyd-Warshall Evolution Relations Algorithm Based on Social Networks Key Groups
Authors: Gao Zhan , He Junjiang , Li Tao , Chen Yang , Fang Wenbo , Li Zhiyong
Published: May 2022

With the development of the society, people increasingly frequent application in social network, the formation of social networking groups become important step in people’s life. How to analyze the evolution of social network group relations become very important. In this paper, an Floyd-Warshall evolution relations algorithm based on social networks key groups is proposed. Mainly includes four parts, initial construction of social network group relations, social big data acquisition, network group relations weighting, and group relations reconstruction. Experimental results show that, by analyzing group communication frequency, group membership relationship and the number of social group members, the evolution map of social network group relationship can be obtained, which can make a more intuitive analysis and expression of the development process of social network group and the evolution of social network group relationship.
Nonlinear Spectral Unmixing of Hyperspectral Imagery Based on Hapke Model and Relevance Vector Regression Algorithm
Authors: Sun Cheng , Xing Feng , Liu Donghao , Han Jieguo , Yang Bei
Published: May 2022

This paper put forward a nonlinear hyperspectral imagery unmixing method based on Hapke nonlinear spectral mixture model and the relevance vector regression. This paper presents a method of relevance vector regression algorithm for unmixing of hyperspectral images. The spectrum was mixed to train the relevance vector regression algorithm according to Hapke non-linear mixing model. This method made our training process coincident with the physical feature of non-linear spectral mixing process. The experiments of smiulated data and hyperspectral imagery are conducted to validate the methods. The smiulated data and hyperspectral image was used for accuracy assessment. Results show that relevance vector regression algorithm can provide better result as compared with linear spectral unmixing model and support vector regression method. And our method provides better result with relative less relevant vector. The proposed algorithm reduced computational complexity of the spectral unmixing problem.
Modeling of Feature Selection Based on Random Forest Algorithm and Pearson Correlation Coefficient
Authors: Mei Kai , Tan Meifang , Yang Zhihui , Shi Shaoyue
Published: May 2022

This paper establishes a feature selection model to selects 20 molecular descriptors of compounds with the most significant influence on biological activity. Random forest algorithm was used to calculate the correlation between molecular descriptors and pIC50 values of biological activity. In this way, the top 26 molecular descriptors with high correlation were screened out. The Pearson correlation coefficient was used to analyze the 26 molecular descriptors just selected and eliminate the variables with high correlation between the independent variables. By consulting literature, the parameters such as MlogP, XlogP and TopoPSA in the selected molecular descriptors were found that had a prominent effect on the biological activity, indicating that the screening methods and results of the 20 molecular descriptors were reasonable.
Improved ALS Recommendation Algorithm Based on Interest-Value Model
Authors: Wang Zhaoyang , Huang Jianjun , Sun Hongyuan
Published: May 2022

In the era of big data, all kinds of information around, how to effectively get the information others want and achieve recommendation is the original purpose of recommendation algorithm, traditional recommendation has collaborative filtering, content-based, model-based recommendation algorithm. Matrix factorization recommendation algorithm solves the problems of data sparsity and low space utilization brought by dimensional explosion. ALS(Alternating Least Squares) algorithm is one of the matrix factorization and the only one recommendation algorithm implemented in Spark, which is in line with the computation method of big data distributed computing. However, in the traditional ALS, there are still some shortcomings: the determination of the number of Implicit features does not give a clear definition, the information factor is lost after matrix factorization, which leads to the poor interpretability of the decomposed matrix, and the performance parameters of the ALS model are not optimal in terms of performance. Based on the above shortcomings, the IVM-ALS(ALS Based on Interest-Value Model) based on interest-value is proposed, an interest-value model is introduced, a solution to solve the Implicit feature number is introduced, and the feasibility of the feature matrix of the subdivided item is enhanced, so as to meet the actual requirements., And improve the algorithm performance than traditional ALS.
Metamorphic Relations Recognition Method Based on Node Features and Path Features
Authors: Zhang Tongtong , Liu Jie , Yang Xiaohua , Yan Shiyu , Li Meng
Published: May 2022

The classification model of the metamorphic relations of the scientific computing program has four categories, of which the code model occupies an important position. We redefine a metamorphic relations, which is single-line metamorphic relations and it exists in the nuclear power program. And it is more comprehensive compared to other metamorphic relations to reflect the internal logic of the program, while node features and path features can maximize the logical structure of the programs. Based on the above situation, we started from the code layer to study the metamorphic relations, put the control flow chart as the bridge of the code and metamorphic relations, extract node features and path features control flowchart and transform the identification problem of metamorphic relations into the problem of predictive model classification. Apply the identified single-line metamorphic relations to the nuclear power field and detect the effectiveness of the software program. The results show that the method is used to enrich the study of the metamorphic relations with the code level, and further improve the degree of automation of metamorphic tests.
Er-doped fiber laser with regular and random distributed feedback
Authors: Skvortsov M.I. , Wolf A.A. , Fomiryakov E.A. , Treshchikov V.N. , Nikitin S.P. , Vlasov A.A. , Dostovalov A.V. , Babin S.A.
Published: May 2022

Using a point-by-point fs inscription technology, a Rayleigh reflector with unique characteristics has been designed and fabricated. The reflection coefficient of the structure with a length of 5 cm amounts to 0,03%, which corresponds to the reflection of 6-km SMF-28e+ fiber spool. The designed artificial Rayleigh scattering fiber in combination with distributed feedback (DFB) erbium-doped fiber laser allows to narrow the linewidth. A similar effect was observed in configuration with 25-km SMF-28e+ fiber spool, where it was used as an additional spectral filter. In both cases, an identical narrowing of the linewidth by an order of magnitude was observed at times less than 0,1 msec.
Precision laser diagnostics for LUXE
Authors: Prasad Rajendra
Published: May 2022

Strong field QED is an active research frontier. The investigation of fundamental phenomena such as pair creation, photon-photon and photon-electron interactions in the nonlinear QED regime are a formidable challenge both experimentally and theoretically. Several experiments around the world are being planned or in preparation to probe this strong field regime.

LUXE (Laser Und XFEL Experiment) is an experimental platform which envisages the collision of the high quality 16.5 GeV electron beam from the European XFEL accelerator with a 100 TW class high power laser. One of the unique features of LUXE is to measure the key observables such as pair rates (e
+
e
−) with unprecedented accuracy in the characterization of both beams together with ample statistics. The state-of-art detector technologies for high energy particle/photon detection enable percent level precision. The state-of-art high power lasers offer high quality laser beams, however, the residual shot-to-shot fluctuations coupled with the large nonlinearity of the processes under investigation form a particular challenge. An uncertainty of 5% on the absolute laser intensity already leads to a very large ( about 40%) uncertainty in the pair rate. Hence it becomes essential to control the laser parameters precisely.

To mitigate this issue a full suite of laser diagnostics is being currently developed at the JETI 40 laser in Jena with the aim of tagging the shot intensity to < 1%. In this presentation, details of the laser and the diagnostics suit for the single shot tagging of all the laser parameters will be presented. Moreover, results from an ongoing campaign to properly relay image the beam without significant distortion of the laser beam parameters for post-diagnosis will be discussed.
Depolymerization Performance of Pd/Al2O3 on Ether Biomass Model Molecules under Continuous Flow Reaction
Authors: Xu Jinyun , Li Ming , Ma Chao , Sun Yu , Li Minjing , Zhong Guoqiang , Zhao Di , Hu Xudong , Su Han , Yan Zhangyong , Cao Jingran , Xu Chao , Zheng Chunming , Sun Xiaohong
Published: May 2022

The ether model molecules BPE (phenylbenzyl ether), diphenyl ether (DPE) and phenoxyethylbenzene (PPE) of lignin were used as degradation raw materials, and Pd-Al2O3 was used as catalyst to react in batch reactor and continuous reactor, respectively. Pd-Al2O3 showed good degradation performance in batch reaction. The catalytic performance of three substances was compared in a flow reactor. The reasons of catalyst deactivation and the products adsorbed on the surface during the hydrogenolysis of BPE were studied.
Research on Cyber Physical Fusion Modeling of Photovoltaic System
Authors: Wang Chuanrui , Zhang Liting , Yang Yongwen , Li Qifen , Song Lifei
Published: May 2022

Cyber-Physical System (CPS) is a system that closely integrates physical computing, communication, and control for optimal regulation. At present, the interaction channel between the physical model and information model has not been opened up directly, so it is difficult to realize the optimal regulation of the energy internet. The key to solving this problem is to study the Fusion Modeling Technology of the two. Based on the concept of CPS, this paper proposed a fusion modeling method of the cyber-physical system after analyzing the interaction mechanism of the physical flow and information flow in CPS. The fusion of the information model and physical model was realized by corresponding with each other, which made the fusion model more accurate and reliable. A cyber-physical model of the photovoltaic system was simulated and analyzed to verify the superiority of proposed fusion modeling method. The simulation results showed that the PV output fluctuation of PV system with the cyber-physical model is much more smaller, and the output of the cyber-physical model is increased by 8.6%-10.2% compared to the physical model. It shows the influence of the information model on the system and the effectiveness of the cyber-physical model.
Theoretical study of spin-orbit coupling in Janus monolayer MA2Z4
Authors: Wu Liang , Zhou Wenzhe , Zhang Dehe , Ouyang Fangping
Published: May 2022

In this paper, based on first-principles calculations, we investigate the energy valley and spin-orbit coupling properties of Janus monolayer MA2Z4. The stability of different structures is illustrated. Due to the breaking of mirror symmetry, Rashba splitting occurs at the Γ point in the band structures of Janus monolayers WSiGeN4 and WSi2(NP)2. The relationship between Rashba spin-orbit coupling strength and potential energy gradient and d-orbital composition is explored. Janus monolayer WSi2(NP)2 has stronger Rashba effect than WSiGeN4 due to the strong asymmetry of the d orbital of W atom. These results help to promote the application of two-dimensional materials in spintronics and valleytronics.
Oxidation behavior of Mg-Gd binary alloys at elevated temperatures and the effect on corrosion property
Authors: Yu Xiaowen , Li Jing , Chen Sanxing , Wang Xiaodong , Huang Xiaoping
Published: May 2022

The oxidation behavior of magnesium alloy in air at the temperature of 500 ° C to 650 ° C was evaluated abstractly. Increasing Gd content in the alloy is beneficial for the enhanced of oxidation resistance. After Mg-1.5Gd and Mg-3.5Gd alloys were oxidized in air at 500 °C for 6h, dense and smooth oxide films dominated by MgO and Gd2O3 were formed on their surfaces. Gd2O3 content in the oxide films increased with increasing Gd content in the alloy. The oxidized alloys with high content of Gd (1.5 wt.% and 3.5 wt. %) exhibited good corrosion resistance when immersed in salt solution for 100 h.
Research progress on surface modification and application status of UHMWPE fiber
Authors: Wang Yixuan , Hou Ruixiang
Published: May 2022

Ultrahigh molecular weight polyethylene (UHMWPE) fiber is a high-performance material with superior properties of high strength and modulus, low density, wear resistance and corrosion resistance. But the development of UHMWPE fiber reinforced polymers is hindered due to its inert inactive surface and poor interfacial adhesion with polymer matrix. This work presents the research progress on surface modification techniques, including ‘dry’ treatment, strong oxidant treatment, chemical grafting and coating, of UHMWPE fiber and the mechanisms of the improvement on surface properties and interfacial adhesion strength between the UHMWPE fiber and the polymer matrix. Application status of UHMWPE fiber such as aerospace, ocean engineering and individual protection is introduced.
Preparation of porous silicon/metal composite negative electrode materials and their application in high-energy lithium batteries
Authors: Zhang Baoguo , Tong Ling , Wu Lin , Yang Xiaoyu , Liao Zhiyuan , Zhou Yilai , Hu Ya , Fang Hailiang
Published: May 2022

Porous silicon/metal composites have huge specific surface area, rich pore structure, tough framework system and low SEI film formation rate, and have great application prospects in the field of high-energy lithium batteries. Porous silicon/metal composites have abundant pore structure, which can greatly alleviate the volume effect of silicon during charging and discharging. The introduction of metal can increase the conduction rate and reduce the formation rate of SEI film. However, the development of a facile and rapid method to synthesize porous silicon/metal composites remains a challenge for current research. Based on the current research progress of porous silicon/metal composites and related literatures, in this paper, the preparation methods of porous silicon/metal composites in recent years are reviewed in detail, with a focus on their applications in the field of high-energy lithium batteries. Finally, the future development direction of porous silicon/metal composites is further prospected.
Study on the coupling properties of hydrogen PEMFC and air source heat pump
Authors: Ma Zhenxi , Cai Liang
Published: May 2022

A steady-state model for the coupling of a proton exchange membrane fuel cell and an air source heat pump (PEMFC–ASHP) is established in this paper. The influence of reaction pressure and relative humidity on the polarization curve and operating characteristics of PEMFC, as well as the influence of ambient temperature and compressor speed on the system performance are investigated. The results show that the increase of reaction pressure and relative humidity is conducive to the improvement of fuel cell output voltage and efficiency, and the influence of reactant gas relative humidity is more obvious. As the increase of ambient temperature and compressor speed, the heat pump efficiency and system efficiency decrease. The research results can provide theoretical guidance for the design and operation of the PEMFC–ASHP system.