101 results on '"Xinbo He"'
Search Results
2. Analysis of coupling characteristics of whip antenna on aircraft carrier under incident electromagnetic pulse of high-altitude nuclear electromagnetic pulse
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Meng CHEN, Bing WEI, and Xinbo HE
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finite different time domain ,high-altitude nuclear electromagnetic pulse ,half space plus source ,thin wire algorithm ,antenna ,aircraft carrier ,Naval architecture. Shipbuilding. Marine engineering ,VM1-989 - Abstract
ObjectivesUnder the condition of considering the influence of the sea surface, the relationships between the induced current of a whip antenna on a large ship under the incidence of high-altitude nuclear electromagnetic pulse (HEMP) and the incident angle of the pulse and antenna position are studied.Methods The half-space finite different time domain (FDTD) method is used to consider the influence of the sea surface; the thin wire algorithm is used to solve the problems of huge computational grid and low efficiency caused by the fine structure; the lumped element FDTD method is used to consider the influence of the load behind the antenna on the induced current; and a parallel algorithm based on MPI is used to speed up the calculation.ResultsThe results show that the induced current on the whip antenna of an aircraft carrier model is related to the antenna position and incident angle in the HEMP incident case. The peak value of the induced current at the antenna port is 5.6 A in typical cases.ConclusionsThe analysis shows that the magnitude of the induced current at the antenna port mainly depends on the antenna position and has little relationship with the incident angle of the pulse. The research provides an algorithm basis for the calculation and analysis of induced current in the case of the incident pulse electromagnetic wave of large ships, and the research results provide a theoretical support for the analysis of ship electromagnetic compatibility problems.
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- 2023
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3. Microstructure and performance of carbon fiber reinforced aluminum matrix composites with molybdenum carbide coating on carbon fibers
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Tingting Liu, Xinbo He, Lin Zhang, Shubin Ren, and Xuanhui Qu
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carbon fibers ,aluminum matrix composites ,molybdenum carbide coating ,interfaces ,Materials of engineering and construction. Mechanics of materials ,TA401-492 ,Chemical technology ,TP1-1185 - Abstract
In this work, a molybdenum carbide coating on the surface of short carbon fibers prepared using molten salt method was proposed to ameliorate the interfacial bonding and improve the performance of carbon fiber/Al composites. The carbon fiber/Al composites were produced using vacuum hot pressing. The characteristics of molybdenum carbide coating were analyzed. Besides, the microstructures, bending strength and thermal properties of the carbon fiber/Al composites were explored. Furthermore, the interfacial thermal resistance of the composites was investigated in relation to theoretical evaluations derived from the combined Maxwell-Garnett effective medium approach and acoustic mismatch model schemes. The results indicated that a homogeneous Mo _2 C coating with a thickness of 0.5 μ m was obtained by proper molar ratio of carbon fibers, MoO _3 and chloride salts mixture and heated at 1000 °C for 60 min. The Mo _2 C coating greatly enhanced the bond between the aluminum matrix and carbon fiber, leading to improvements in the densification behavior and bending strength of the coated composites. The enhanced thermal properties including improved thermal conductivity and reduced coefficient of thermal expansion (CTE) were also achieved by the Mo _2 C coating. The in-plane thermal conductivity of 60 vol.% Mo _2 C-coated carbon fiber/Al composite was 221 W·m ^−1 ·K ^−1 enhanced by 92% compared to that of uncoated composite and the CTE was 6.0 × 10 ^–6 K ^−1 which was suitable for electronic packaging materials.
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- 2024
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4. Investigation on the Attainment of High-Density 316L Stainless Steel with Selective Laser Sintering
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Pengfei Zhu, Xinbo He, Hongda Guan, Zijian Zhang, Tao Zhang, and Xuanhui Qu
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selective laser sintering ,additive manufacturing ,316L stainless steel ,sintering atmosphere ,mechanical property ,Technology ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Microscopy ,QH201-278.5 ,Descriptive and experimental mechanics ,QC120-168.85 - Abstract
Due to the low density of the green part produced by selective laser sintering (SLS), previous reports mainly improve the sample’s density through the infiltration of low-melting metals or using isostatic pressing technology. In this study, the feasibility of preparing high-density 316L stainless steel using 316L and epoxy resin E-12 as raw materials for SLS combined with debinding and sintering was investigated. The results indicated that in an argon atmosphere, high carbon and oxygen contents, along with the uneven distribution of oxygen, led to the formation of impurity phases such as metal oxides, including Cr2O3 and FeO, preventing the effective densification of the sintered samples. Hydrogen-sintered samples can achieve a high relative density exceeding 98% without losing their original design shape. This can be attributed to hydrogen’s strong reducibility (effectively reducing the carbon and oxygen contents in the samples, improving their distribution uniformity, and eliminating impurity phases) and hydrogen’s higher thermal conductivity (about 10 times that of argon, reducing temperature gradients in the sintered samples and promoting better sintering). The microstructure of the hydrogen-sintered samples consisted of equiaxed austenite and ferrite phases. The samples exhibited the highest values of tensile strength, yield strength, and elongation at 1440 °C, reaching 513.5 MPa, 187.4 MPa, and 76.1%, respectively.
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- 2023
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5. A novel fractional grey forecasting model with variable weighted buffer operator and its application in forecasting China's crude oil consumption
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Yong Wang, Yuyang Zhang, Rui Nie, Pei Chi, Xinbo He, and Lei Zhang
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Grey forecasting model ,Variable weighted buffer operator ,Particle swarm optimization ,Oil consumption forecast ,Petroleum refining. Petroleum products ,TP690-692.5 ,Engineering geology. Rock mechanics. Soil mechanics. Underground construction ,TA703-712 - Abstract
Oil is an important strategic material and civil energy. Accurate prediction of oil consumption can provide basis for relevant departments to reasonably arrange crude oil production, oil import and export, and optimize the allocation of social resources. Therefore, a new grey model FENBGM(1,1) is proposed to predict oil consumption in China. Firstly, the grey effect of the traditional GM(1,1) model was transformed into a quadratic equation. Four different parameters were introduced to improve the accuracy of the model, and the new initial conditions were designed by optimizing the initial values by weighted buffer operator. Combined with the reprocessing of the original data, the scheme eliminates the random disturbance effect, improves the stability of the system sequence, and can effectively extract the potential pattern of future development. Secondly, the cumulative order of the new model was optimized by fractional cumulative generation operation. At the same time, the smoothness rate quasi-smoothness condition was introduced to verify the stability of the model, and the particle swarm optimization algorithm (PSO) was used to search the optimal parameters of the model to enhance the adaptability of the model. Based on the above improvements, the new combination prediction model overcomes the limitation of the traditional grey model and obtains more accurate and robust prediction results. Then, taking the petroleum consumption of China's manufacturing industry and transportation, storage and postal industry as an example, this paper verifies the validity of FENBGM(1,1) model, analyzes and forecasts China's crude oil consumption with several commonly used forecasting models, and uses FENBGM(1,1) model to forecast China's oil consumption in the next four years. The results show that FENBGM(1,1) model performs best in all cases. Finally, based on the prediction results of FENBGM(1,1) model, some reasonable suggestions are put forward for China's oil consumption planning.
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- 2022
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6. FDTD Complex Terrain Modeling Method Based on Papery Contour Map
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Meng Chen, Bing Wei, and Xinbo He
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Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Cellular telephone services industry. Wireless telephone industry ,HE9713-9715 - Abstract
This study aims to develop a finite difference time-domain (FDTD) modeling method for complex terrain using a paper contour map. First, the image preprocessing technology is employed to segment, denoise, and number the drawing area to arrive at independent figures and curve matrices. Subsequently, the support vector machine (SVM) classifier is implemented to identify the number and obtain the elevation value pertinent to the curve in the figure. Finally, the scattered points in the curve matrix are meshed by the Delaunay triangulation algorithm, and a three-dimensional triangular mesh model is established according to the recognition results. The FDTD calculation model is established by the method of intersection of Yee cell grid lines and triangle projection. The simulation results reveal that the recognition rate of the SVM classification model in this study is close to 100% for printed numerals. This approach is capable of quickly and accurately establishing the FDTD-based calculation model for complex terrain on the basis of the paper contour map.
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- 2023
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7. Hybrid FDTD algorithm for electromagnetic analysis of fine structures
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Sihan Zhao, Bing Wei, Xinbo He, Yiwen Li, and Xiaolong Wei
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Finite-Difference Time-Domain (FDTD) ,Unconditionally stable ,Explicit ,Hybrid FDTD ,Unstable modes ,Physics ,QC1-999 - Abstract
A new hybrid Finite-Difference Time-Domain (hybrid FDTD) algorithm is proposed in this paper. This hybrid FDTD method combines the superiorities of explicit unconditionally stable FDTD (US-FDTD) and traditional FDTD methods to achieve unconditional stability and high calculation efficiency. US-FDTD is used in fine grids and the adjacent coarse grids subdomain and it breaks the Courant-Friedrich-Levy (CFL) condition. Traditional FDTD is used in the remaining coarse grids subdomain and it is a matrix free method. A compensation scheme is used on the subdomain boundary without compromising accuracy. Hybrid FDTD makes the explicit time marching with a uniform time step determined by the size of coarse grid in whole domain, which reduces the iteration time. In addition, because US-FDTD is only used in one of the subdomains, compared with global US-FDTD method, the matrix dimension of hybrid FDTD is reduced, which saves the time for eigenvalue solution. Numerical results show high efficiency and accuracy of the proposed method.
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- 2021
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8. The Optimization of Ti Gradient Porous Structure Involves the Finite Element Simulation Analysis
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Bowen Liu, Wei Xu, Xin Lu, Maryam Tamaddon, Mingying Chen, Jiaqi Dong, Yitong Liu, Lijia Guo, Jiazhen Zhang, Xuanhui Qu, Xinbo He, and Chaozong Liu
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titanium ,gradient porosity ,oral implants ,three-dimensional finite element simulation ,bone stress ,Technology - Abstract
Titanium (Ti) and its alloys are attracting special attention in the field of dentistry and orthopedic bioengineering because of their mechanical adaptability and biological compatibility with the natural bone. The dental implant is subjected to masticatory forces in the oral environment and transfers these forces to the surrounding bone tissue. Therefore, by simulating the mechanical behavior of implants and surrounding bone tissue we can assess the effects of implants on bone growth quite accurately. In this study, dental implants with different gradient pore structures that consisted of simple cubic (structure a), body centered cubic (structure b) and side centered cubic (structure c) were designed, respectively. The strength of the designed gradient porous implant in the oral environment was simulated by three-dimensional finite element simulation technique to assess the mechanical adaptation by the stress-strain distribution within the surrounding bone tissue and by examining the fretting of the implant-bone interface. The results show that the maximum equivalent stress and strain in the surrounding bone tissue increase with the increase of porosity. The stress distribution of the gradient implant with a smaller difference between outer and inner pore structure is more uniform. So, a-b type porous implant exhibited less stress concentration. For a-b structure, when the porosity is between 40 and 47%, the stress and strain of bone tissue are in the range of normal growth. When subject to lingual and buccal stresses, an implant with higher porosity can achieve more uniform stress distribution in the surrounding cancellous bone than that of low porosity implant. Based on the simulated results, to achieve an improved mechanical fixation of the implant, the optimum gradient porous structure parameters should be: average porosity 46% with an inner porosity of 13% (b structure) and outer porosity of 59% (a structure), and outer pore sized 500 μm. With this optimized structure, the bone can achieve optimal ingrowth into the gradient porous structure, thus provide stable mechanical fixation of the implant. The maximum equivalent stress achieved 99 MPa, which is far below the simulation yield strength of 299 MPa.
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- 2021
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9. Preparation of W-Plated Diamond and Improvement of Thermal Conductivity of Diamond-WC-Cu Composite
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Xulei Wang, Xinbo He, Zhiyang Xu, and Xuanhui Qu
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diamond-WC-Cu composite ,cyclic vacuum pressure infiltration ,thermal conductivity ,interface thermal resistance ,Mining engineering. Metallurgy ,TN1-997 - Abstract
The tungsten (W)-plated diamond process was explored and optimized. A dense and uniform tungsten coating with a thickness of 900 nm was successfully prepared by the powder covering sintering method. The Diamond-WC-Cu composite with high density and high thermal conductivity were successfully prepared by cyclic vacuum pressure infiltration. The microstructure and composition of the W-plated diamond particles were analyzed. The effect of tungsten coating on the microstructure and thermal conductivity of the Diamond-WC-Cu composite was investigated. After calculation, the interface thermal resistance of the composite forming the tungsten carbide transition layer is 2.11 × 10−8 m2∙K∙W−1. The thermal conductivity average value of the Diamond-WC-Cu composite with a diamond volume fraction of 60% reaches 874 W∙m−1∙K−1, which is close to the theoretical prediction value of Hasselman-Johnson (H-J) model and differential effective medium (DEM) model. Moreover, the Maxwell-Eucken (M-E) model, H-J model, and DEM model were used to evaluate the thermal conductivity of the Diamond-WC-Cu composite.
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- 2021
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10. Mesporous 3C-SiC Hollow Fibers
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Yangwen Liu, Huilin Hou, Xinbo He, and Weiyou Yang
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Medicine ,Science - Abstract
Abstract In the present work, for the first time, we reported the exploration of mesoporous 3C-SiC hollow fibers via single-spinneret electrospinning of polyureasilazane (PSN) and polyvinylpyrrolidone (PVP) solution followed by high-temperature pyrolysis treatment. The resultant products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and N2 adsorption. The as-prepared hollow fibers with totally mesoporous walls were uniformly sized in diameter and high purity in morphology. They were composed of single-crystalline 3C-SiC nanoparticles with a surface area of 21.75 m2/g and average pore diameter of ~34 nm. The PSN concentration played a determined role on the formation of hollow fibers rather than the conventional solid counterparts, enabling their growth in a tunable manner. A possible mechanism was proposed for the formation of mesoporous SiC hollow fiber.
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- 2017
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11. Investigation on Sub-Solvus Recrystallization Mechanisms in an Advanced γ-γ’ Nickel-Based Superalloy GH4151
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Shaomin Lv, Jinbin Chen, Xinbo He, Chonglin Jia, Kang Wei, and Xuanhui Qu
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GH4151 superalloy ,dynamic recrystallization ,gamma prime precipitates ,heteroepitaxial dynamic recrystallization ,step-shaped structures ,Technology ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Microscopy ,QH201-278.5 ,Descriptive and experimental mechanics ,QC120-168.85 - Abstract
Sub-solvus dynamic recrystallization (DRX) mechanisms in an advanced γ-γ’ nickel-based superalloy GH4151 were investigated by isothermal compression experiments at 1040 °C with a strain rate of 0.1 s−1 and various true strain of 0.1, 0.3, 0.5, and 0.7, respectively. This has not been reported in literature before. The electron backscatter diffraction (EBSD) and transmission electron microscope (TEM) technology were used for the observation of microstructure evolution and the confirmation of DRX mechanisms. The results indicate that a new dynamic recrystallization mechanism occurs during hot deformation of the hot-extruded GH4151 alloy. The nucleation mechanism can be described as such a feature, that is a primary γ’ (Ni3(Al, Ti, Nb)) precipitate embedded in a recrystallized grain existed the same crystallographic orientation, which is defined as heteroepitaxial dynamic recrystallization (HDRX). Meanwhile, the conventional DRX mechanisms, such as the discontinuous dynamic recrystallization (DDRX) characterized by bulging grain boundary and continuous dynamic recrystallization (CDRX) operated through progressive sub-grain merging and rotation, also take place during the hot deformation of the hot-extruded GH4151 alloy. In addition, the step-shaped structures can be observed at grain boundaries, which ensure the low-energy surface state during the DRX process.
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- 2020
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12. Superplastic Deformation and Dynamic Recrystallization of a Novel Disc Superalloy GH4151
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Shaomin Lv, Chonglin Jia, Xinbo He, Zhipeng Wan, Xinxu Li, and Xuanhui Qu
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gh4151 alloy ,superplastic deformation ,activation energy ,dynamic recrystallization ,Technology ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Microscopy ,QH201-278.5 ,Descriptive and experimental mechanics ,QC120-168.85 - Abstract
The superplastic deformation of a hot-extruded GH4151 billet was investigated by means of tensile tests with the strain rates of 10−4 s−1, 5 × 10−4 s−1 and 10−3 s−1 and at temperatures at 1060 °C, 1080 °C and 1100 °C. The superplastic deformation of the GH4151 alloy was reported here for the first time. The results reveal that the uniform fine-grained GH4151 alloy exhibited an excellent superplasticity and high strain rate sensitivity (exceeded 0.5) under all experimental conditions. It was found that the increase of strain rate resulted in an increased average activation energy for superplastic deformation. A maximum elongation of 760.4% was determined at a temperature of 1080 °C and strain rate of 10−3 s−1. The average activation energy under different conditions suggested that the superplastic deformation with 1 × 10−4 s−1 in this experiment is mainly deemed as the grain boundary sliding controlled by grain boundary diffusion. However, with a higher stain rate of 5 × 10−4 s−1 and 1 × 10−3 s−1, the superplastic deformation is considered to be grain boundary sliding controlled by lattice diffusion. Based on the systematically microstructural examination using optical microscope (OM), SEM, electron backscatter diffraction (EBSD) and TEM techniques, the failure and dynamic recrystallization (DRX) nucleation mechanisms were proposed. The dominant nucleation mechanism of dynamic recrystallization (DRX) is the bulging of original grain boundaries, which is the typical feature of discontinuous dynamic recrystallization (DDRX), and continuous dynamic recrystallization (CDRX) is merely an assistant mechanism of DRX. The main contributions of DRX on superplasticity elongation were derived from its grain refinement process.
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- 2019
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13. Time-Domain Analytical Expression for Near Fields of Arbitrarily Oriented Electric Dipole and Its Application
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Qian Yang, Bing Wei, Xinbo He, and Minghao Gong
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Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Cellular telephone services industry. Wireless telephone industry ,HE9713-9715 - Abstract
The near fields of electric dipole are commonly used in wide-band analysis of complex electromagnetic problems. In this paper, we propose new near field time-domain expressions for electric dipole. The analytical expressions for the frequency-domain of arbitrarily oriented electric dipole are given at first; next we give the time-domain expressions by time-frequency transformation. The proposed expressions are used in hybrid TDIE/DGTD method for analysis of circular antenna with radome. The accuracy of the proposed algorithm is verified by numerical examples.
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- 2017
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14. Improvement in Mechanical and Thermal Properties of Graphite Flake/Cu Composites by Introducing TiC Coating on Graphite Flake Surface
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Ren Zhang, Xinbo He, Qian Liu, and Xuanhui Qu
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graphite flake ,composites ,interface ,thermal properties ,Mining engineering. Metallurgy ,TN1-997 - Abstract
In this work, TiC coating was successfully deposited on a graphite flake surface via molten salt technique, for the purpose of promoting the interfacial connection between Cu and graphite flake. Vacuum hot pressing was then employed to prepare TiC-coated graphite flake/Cu composite. The results indicate that introducing TiC coating on graphite flake surface can evidently reduce the pores and gaps at the interface, resulting in a significant improvement on the bending strength. When the TiC-coated graphite flake content is 60 vol%, the bending strength is increased by 58% compared with the uncoated one. The coefficient of thermal expansion dropped from 6.0 ppm·K−1 to 4.4 ppm·K−1, with the corresponding thermal conductivity as high as 571 W·m−1·K−1. The outstanding thermal conductivity, apposite coefficient of thermal expansion, as well as superior processability, make TiC-coated graphite flake/Cu composite a satisfactory electronic packaging material with vast prospect utilized in microelectronic industry.
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- 2019
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15. Improvement of ZrC/Zr Coating on the Interface Combination and Physical Properties of Diamond-Copper Composites Fabricated by Spark Plasma Sintering
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Yanpeng Pan, Xinbo He, Shubin Ren, Mao Wu, and Xuanhui Qu
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diamond-copper ,composites ,coating ,sintering ,physical properties ,Technology ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Microscopy ,QH201-278.5 ,Descriptive and experimental mechanics ,QC120-168.85 - Abstract
In this study, diamond-copper composites were prepared with ZrC/Zr-coated diamond powders by spark plasma sintering. The magnetron sputtering technique was employed to coat the diamond particles with a zirconium layer. After heat treatment, most of the zirconium reacted with the surface of diamond and was transformed into zirconium carbide. The remaining zirconium on the zirconium carbide surface formed the outer layer. Owing to the method used to produce the ZrC/Zr-coated diamond in this study, the maximum thermal conductivity (TC) of 609 W·m−1·K−1 was obtained for 60 vol. % diamond-copper composites and the corresponding coefficient of thermal expansion (CTE) reached as low as 6.75 × 10−6 K−1. The bending strength of 40 vol. % ZrC/Zr-coated diamond-copper composites reached 255.95 MPa. The thermal and mechanical properties of ZrC/Zr-coated diamond-copper composites were substantially superior to those of uncoated diamond particles. Excellent properties can be attributed to the strengthening of the interfacial combination and the decrease in the interfacial thermal resistance due to the improvement associated with the ZrC/Zr coating. Theoretical analysis was also proposed to compare the thermal conductivities and CTE of diamond-copper composites fabricated with these two kinds of diamond powders.
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- 2019
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16. Improved FDTD Method for Coupling Analysis of a Dielectric-Coated Wire Above Rough Soil Surface Under HPEM Pulse
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Wei Tian, Bing Wei, and Xinbo He
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Electrical and Electronic Engineering ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics - Published
- 2022
17. A Subgridding Unconditionally Stable FETD Method Based on Local Eigenvalue Solution
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Xinbo He, Kaihang Fan, and Bing Wei
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Physics::Fluid Dynamics ,Matrix (mathematics) ,Computer science ,Applied mathematics ,Symmetric matrix ,Electrical and Electronic Engineering ,Temporal discretization ,Multiscale modeling ,Finite element method ,Eigenvalues and eigenvectors ,Eigendecomposition of a matrix ,Matrix decomposition - Abstract
A subgridding unconditionally stable finite-element time-domain method based on local eigenvalue solution (SUSL-FETD) is proposed to solve multiscale modeling. In this method, subgridding elements are used to discrete a multiscale computational domain, and the explicit central-difference method is applied for temporal discretization. Compared with traditional elements, the subgridding elements have a more complex distribution of edges and nodes. Therefore, an efficient subgridding scheme is given to form the element matrix for each subgridding element. Such system matrices assembled by all element matrices are symmetric. The subgridding FETD (S-FETD) is then further developed into the subgridding unconditionally stable FETD (SUS-FETD) by filtering spatial unstable modes. It is time-consuming to obtain the unstable modes by global eigenvalue decomposition. In this article, the local eigenvalue decomposition is proposed to get the unstable modes, which further reduces the memory storage and computing time. Numerical examples certify that the proposed SUSL-FETD has high accuracy and efficiency.
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- 2021
18. Exploring the relationship between lattice distortion and phase stability in a multi-principal element alloy system based on machine learning method
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Jiaxin Huang, Wei Fang, Congcong Xue, Tiexu Peng, Haoyang Yu, Jia Li, Liying Sun, Xinbo He, Baoxi Liu, Yong Yang, and Fuxing Yin
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Computational Mathematics ,General Computer Science ,Mechanics of Materials ,General Physics and Astronomy ,General Materials Science ,General Chemistry - Published
- 2023
19. Ultrahigh-energy photons up to 1.4 petaelectronvolts from 12 γ-ray Galactic sources
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Alejandro Sáiz, Y. H. Yao, W. X. Wu, P. P. Zhang, Zhuo Li, R. Liu, Pak-Hin Thomas Tam, H. C. Li, Liang Chen, J. C. Wang, Y. L. Xin, L. Chen, M. J. Chen, Hong-Guang Wang, Y. J. Wei, S. Hu, Junjie Mao, Y. Q. Guo, J. Y. Liu, V. Rulev, P. F. Zhang, L. Xue, H. B. Hu, H. Liu, Rui Zhang, Linbin Yang, C. F. Feng, F. Ji, Xiaofei Zhang, F. Zheng, V. I. Stepanov, Ping Zhou, Q. H. Chen, H. R. Wu, Warit Mitthumsiri, X. C. Chang, Z. K. Zeng, C. D. Gao, Bin Zhou, W. L. Li, S. Z. Chen, M. M. Ge, Lei Zhao, Y. Z. Li, Y. Y. Guo, Y. J. Bi, Zhe Cao, Y. K. Hor, Xuejiao Li, H. D. Liu, S. H. Feng, B. Liu, Y. D. Cheng, Bo Zhang, H. K. Lv, H. M. Zhang, K. Levochkin, Y. J. Wang, L. X. Bai, Jixia Li, T. Montaruli, Duo Yan, Hefan Li, Ying Zhang, Bingshui Gao, Q. An, H. B. Xiao, J. R. Shi, X. D. Sheng, Z. X. Liu, W. H. Huang, M. L. Chen, Jianeng Zhou, Q. Gao, Minghao Qi, W. Zeng, Li-Sheng Geng, J. Chen, B. M. Chen, T. Wen, S. W. Cui, Z. X. Wang, Chiming Jin, S. B. Yang, L. Z. Zhao, C. W. Yang, J. B. Zhao, D.A. Kuleshov, Y. M. Xing, L. P. Wang, E. W. Liang, X. F. Wu, Zhe Li, B. Y. Pang, B. B. Li, X. Zuo, Cong Li, S. Q. Xi, Kun Fang, W. Gao, B. Z. Dai, Z. H. Wang, H. Cai, Jun Liu, Zhen Wang, J. C. He, Houdun Zeng, J. Fang, G. C. Xiao, Y. C. Nan, Z. G. Yao, Z. Y. Pei, Jun-Hui Fan, X. X. Zhou, Q. Yuan, H. B. Li, Shi-Qi Hu, G. G. Xin, J. F. Chang, Xufang Li, Oleg Shchegolev, G. M. Xiang, S. P. Zhao, W. Liu, X. L. Ji, M. J. Yang, H. H. He, R. Lu, Zhengguo Cao, Felix Aharonian, J. W. Zhang, H. C. Song, Yongchun Wang, Yugang Zhang, Wenwu Tian, He Zhang, Bai Yibing, S. L. He, Donglian Xu, Y. L. Feng, Zebo Tang, X. L. Guo, Y. D. Cui, X. J. Dong, Zheng Wang, Jun-Jie Wei, Q. B. Gou, Qizhi Huang, H. N. He, K. J. Zhu, M. Zha, B. D. Wang, Ruizhi Yang, X. N. Sun, Y. P. Wang, Z. C. Huang, H. L. Dai, H. Wang, Xiang Zhang, Xing-Yuan Hou, Yunchao Liu, H. Y. Jia, D. M. Wei, Z. G. Dai, Rong Xu, Fan Yang, A. Masood, F. Y. Li, Xinbo He, Youping Li, X. T. Huang, L. Y. Wang, X. R. Li, J. J. Xia, K. Jiang, Binyu Zhao, X. J. Hu, Yun-Feng Liang, W. Wang, Y. A. Han, J. G. Guo, Yu. V. Stenkin, Lang Shao, J.W. Xia, P. Pattarakijwanich, X. H. You, S.H. Chen, S. R. Zhang, C. Hou, Shuibin Lin, Lu Zhang, L. Feng, Xuelong Wang, S. Wu, X. X. Zhai, Xuliang Chen, C. X. Liu, L. L. Ma, Y. He, Z. X. Fan, Z. Y. You, F. R. Zhu, Y. W. Bao, Qie Sun, Yi Chen, X. G. Wang, Yi Zhang, Xiang-Yu Wang, D. H. Huang, R. Zhou, Hao Zhou, H. Zhu, X. J. Bi, D. della Volpe, Tao Zeng, T. L. Chen, Bin Ma, J. S. Wang, Cunguo Wang, L. X. Zhang, Shujuan Liu, N. Yin, N. Cheng, D. Bastieri, X. H. Cui, Cheng Li, W. J. Long, Shengxue Zhang, Axikegu, Li Zhang, G. H. Gong, Danzengluobu, M. H. Gu, Y. H. Yu, Jie Zhang, Y. Z. Fan, Dong Liu, C. Y. Wu, J. T. Cai, Long Chen, Y. Zheng, L. Q. Yin, Y. M. Ye, J. Y. Yang, B D Ettorre Piazzoli, David Ruffolo, Z. B. Sun, Cheng Guang Zhu, X. H. Ma, M. Heller, K. Li, Z. J. Jiang, J. Liu, Yong Zhang, Minghui Liu, R. N. Wang, and Jinyao Liu
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Physics ,Multidisciplinary ,Photon ,COSMIC cancer database ,Proton ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Electron ,Astrophysics ,01 natural sciences ,Galaxy ,Supernova ,Crab Nebula ,Pulsar ,0103 physical sciences ,010306 general physics ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
The extension of the cosmic-ray spectrum beyond 1 petaelectronvolt (PeV; 1015 electronvolts) indicates the existence of the so-called PeVatrons—cosmic-ray factories that accelerate particles to PeV energies. We need to locate and identify such objects to find the origin of Galactic cosmic rays1. The principal signature of both electron and proton PeVatrons is ultrahigh-energy (exceeding 100 TeV) γ radiation. Evidence of the presence of a proton PeVatron has been found in the Galactic Centre, according to the detection of a hard-spectrum radiation extending to 0.04 PeV (ref. 2). Although γ-rays with energies slightly higher than 0.1 PeV have been reported from a few objects in the Galactic plane3–6, unbiased identification and in-depth exploration of PeVatrons requires detection of γ-rays with energies well above 0.1 PeV. Here we report the detection of more than 530 photons at energies above 100 teraelectronvolts and up to 1.4 PeV from 12 ultrahigh-energy γ-ray sources with a statistical significance greater than seven standard deviations. Despite having several potential counterparts in their proximity, including pulsar wind nebulae, supernova remnants and star-forming regions, the PeVatrons responsible for the ultrahigh-energy γ-rays have not yet been firmly localized and identified (except for the Crab Nebula), leaving open the origin of these extreme accelerators. Observations of γ-rays with energies up to 1.4 PeV find that 12 sources in the Galaxy are PeVatrons, one of which is the Crab Nebula.
- Published
- 2021
20. 3D gel printing of VC reinforced high vanadium high-speed steel
- Author
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Fang Yang, Qian Qin, Sun Haixia, Zhimeng Guo, Cunguang Chen, and Xinbo He
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Materials science ,Metals and Alloys ,General Engineering ,Vanadium ,chemistry.chemical_element ,Microstructure ,Flexural strength ,Machining ,chemistry ,Slurry ,Surface roughness ,Relative density ,Composite material ,High-speed steel - Abstract
Due to their high hardness and high strength, VC reinforced hard materials such as high vanadium high-speed steel (HVHSS) are not suitable for machining to obtain complex shape with low cost. Therefore, 3D gel printing (3DGP) was employed to print HVHSS parts, using highly loaded slurry with 60% solid content as printing slurry. After printing parameters optimization, the printing sample had good surface quality, and obvious printing lines were observed. The extruded filament was in-situ cured, thus enough to maintain the designed shape. Uniform sintering shrinkage with a shrinkage rate of about 15% was obtained in the as-sintered sample with relative density of 99%. The surface roughness decreased from 6.5 µm to 3.8 µm. Fine carbides (
- Published
- 2021
21. A novel fractional structural adaptive grey Chebyshev polynomial Bernoulli model and its application in forecasting renewable energy production of China
- Author
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Yong Wang, Rui Nie, Pei Chi, Xin Ma, Wenqing Wu, Binhong Guo, Xinbo He, Lei Zhang, and Yuyang Zhang
- Subjects
Artificial Intelligence ,General Engineering ,Computer Science Applications - Published
- 2022
22. Searching for an additional high-energy component in Fermi-LAT GRB afterglows
- Author
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Yong Zhang, Guang-Bo Long, Xinbo He, Pak-Hin Thomas Tam, Li-Jun Zhang, and Partha Sarathi Pal
- Subjects
High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,High energy ,Photon ,Component (thermodynamics) ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Spectral line ,Afterglow ,Space and Planetary Science ,Gamma-ray burst ,Astrophysics - High Energy Astrophysical Phenomena ,Fermi Gamma-ray Space Telescope ,Energy component - Abstract
The VHE component from at least two GRBs, i.e., GRB180720B and GRB190114C, has been detected in the afterglow phase. We systematically analyzed 199 GRBs detected by Fermi-LAT during 2008-2019. If an additional high-energy component exists in the afterglows of Fermi-LAT GRBs, the best-fit spectral model could be a broken power-law (BPL) model with an upturn above a break energy. We compare the afterglow spectra using PL and BPL representations. Out of the 30 GRBs with >10GeV photons that arrived after T90, 25 GRBs are tentatively or significantly detected at 0.1-200 GeV after 2*T90. The spectrum of GRB131231A shows an upturn above a break of 1.6+-0.8~GeV, supporting the BPL model. For GRB131231A, we performed a modeling of its X-ray and gamma-ray spectra, and found that the SSC model can explain the upturn with acceptable parameter values. In the cases of GRBs 190114C, 171210A, 150902A, 130907A, 130427A, and 090902B, the improvement of the BPL fit compared to the PL fit is tentative or marginal. There is no conclusive evidence that an additional higher energy component commonly exists in Fermi-LAT GRB afterglows, except for a group of Fermi-LAT GRBs mentioned above. Such an additional high-energy component may be explained by the synchrotron self-Compton mechanism. Current and future VHE observations will provide important constraints on the issue., A\&A in press. arXiv admin note: substantial text overlap with arXiv:2002.08734
- Published
- 2021
23. A novel structure adaptive new information priority discrete grey prediction model and its application in renewable energy generation forecasting
- Author
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Xinbo He, Yong Wang, Yuyang Zhang, Xin Ma, Wenqing Wu, and Lei Zhang
- Subjects
General Energy ,Mechanical Engineering ,Building and Construction ,Management, Monitoring, Policy and Law - Published
- 2022
24. A novel structure adaptive fractional discrete grey forecasting model and its application in China’s crude oil production prediction
- Author
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Yong Wang, Lingling Ye, Zhongsen Yang, Xin Ma, Wenqing Wu, Li Wang, Xinbo He, Lei Zhang, Yuyang Zhang, Ying Zhou, and Yongxian Luo
- Subjects
Artificial Intelligence ,General Engineering ,Computer Science Applications - Published
- 2022
25. A novel self-adaptive fractional multivariable grey model and its application in forecasting energy production and conversion of China
- Author
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Yong Wang, Li Wang, Lingling Ye, Xin Ma, Wenqing Wu, Zhongsen Yang, Xinbo He, Lei Zhang, Yuyang Zhang, Ying Zhou, and Yongxian Luo
- Subjects
Artificial Intelligence ,Control and Systems Engineering ,Electrical and Electronic Engineering - Published
- 2022
26. Discovery of a new $\gamma$-ray source LHAASO J0341+5258 with emission up to 200TeV
- Author
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Zhengguo Cao, L. Feng, Xufang Li, Zebo Tang, Jun-Jie Wei, C. Y. Wu, Jia Zhang, L. X. Bai, Yi Zhang, H. K. Lv, Jixia Li, L. L. Yang, Z. X. Wang, M. Zha, Y. M. Ye, X. H. Ma, L. P. Wang, X. G. Wang, Donglian Xu, X. L. Guo, Y. A. Han, Binyu Zhao, Yun-Feng Liang, Houdun Zeng, Zhe Li, Y. Su, B. Z. Dai, Z. G. Dai, Jinmei Liu, B. D'Ettorre Piazzoli, Z. G. Yao, Y. Zheng, W. X. Wu, M. L. Chen, Jianeng Zhou, Hefan Li, W. Wang, P. Pattarakijwanich, Rong Xu, J. J. Xia, X. X. Zhai, J. Fang, F. R. Zhu, Qie Sun, Yi Chen, H. B. Li, G. M. Xiang, W. Liu, B. Y. Pang, S. Wu, X. L. Ji, R. Lu, K. Li, Y. J. Bi, H. D. Liu, Y. D. Cheng, Bo Zhang, L. Q. Yin, Hanzhong Zhang, C. X. Liu, D. della Volpe, Y. D. Cui, Kun Fang, Yugang Zhang, E. W. Liang, Ping Zhou, Z. J. Jiang, Y. J. Wei, J. Liu, Yong Zhang, Duo Yan, Yu. V. Stenkin, S. L. He, Y. P. Wang, Z. X. Liu, D. H. Huang, R. N. Wang, S. M. Liu, F. Ji, V. Rulev, Y. Z. Li, H. H. He, H. Zhu, C. Hou, Zheng Wang, B. Q. Ma, Y. C. Nan, L. Xue, Jun Liu, Lu Zhang, H. Y. Jia, D. M. Wei, V. I. Stepanov, E. S. Chen, Sina Chen, K. J. Zhu, Y. Q. Qi, Fulai Guo, J. Y. Shi, Minghui Liu, Yi Liu, J. B. Zhao, H. Wang, X. F. Wu, Zhen Wang, Z. X. Fan, Z. Y. You, Shi-Qi Hu, J. Y. Yang, N. Cheng, Z. K. Zeng, C. D. Gao, X. H. You, Long Gao, H. C. Song, Lei Zhao, D.A. Kuleshov, X. X. Zhou, Q. Yuan, B. M. Chen, Ruizhi Yang, X. N. Sun, Shengxue Zhang, Danzengluobu, J. F. Chang, S. P. Zhao, H. Liu, J.W. Xia, W. Gao, G. C. Xiao, Felix Aharonian, Xinbo He, K. Jiang, Pak-Hin Thomas Tam, H. C. Li, Y. Wang, Y. Z. Fan, Dong Liu, Y. W. Bao, P. F. Zhang, X. J. Bi, H. N. He, T. L. Chen, L. Z. Zhao, X. J. Hu, R. Zhou, Ying Zhang, Oleg Shchegolev, Junjie Mao, Y. Q. Guo, F. Y. Li, K. Levochkin, J. T. Cai, X. D. Sheng, Cong Li, X. Zuo, B. B. Li, Long Chen, Yunchao Liu, H. L. Dai, T. Wen, S. W. Cui, S. Z. Chen, David Ruffolo, Y. M. Xing, H. R. Wu, Liang Chen, Xiang-Kun Dong, S. Hu, J. Y. Liu, X. Y. Huang, P. P. Zhang, X. H. Cui, Minghao Qi, Z. B. Sun, Y. Bai, Z. Y. Pei, Cheng Guang Zhu, Yuan-Hao Wang, Zhuo Li, Warit Mitthumsiri, H. M. Zhang, Q. An, Y. H. Yao, W. H. Huang, H. Zhou, W. J. Long, Binbin Zhou, Li-Sheng Geng, R. Liu, Xiang Zhang, J. G. Guo, J. W. Zhang, S. R. Zhang, Wenwu Tian, L. L. Ma, Q. Gao, C. F. Feng, Jiangang He, J. S. Wang, Cunguo Wang, Y. L. Xin, Z. C. Huang, H. B. Hu, N. Yin, B. Q. Qiao, Xin Li, Cheng Li, Jiajun Qin, M. H. Gu, Boyang Wang, Rui Zhang, H. B. Xiao, W. Zeng, L. X. Zhang, S. H. Feng, M. M. Ge, Axikegu, Yonggang Wang, M. J. Chen, Zhao-Qi Wang, Y. Y. Guo, Li Zhang, G. H. Gong, Zhe Cao, Y. K. Hor, Y. H. Yu, T. Montaruli, Jian Wang, Chiming Jin, Z. Min, Xuelong Wang, G. G. Xin, Kai-Kai Duan, D. Bastieri, Y. L. Feng, T. Ke, S. J. Lin, X. T. Huang, L. Y. Wang, B. Liu, Jingzhi Yan, Bingshui Gao, Xiang-Yu Wang, Yulong Li, Tao Zeng, Xuliang Chen, Y. He, C. W. Yang, Jun-Hui Fan, Q. B. Gou, W. L. Li, D. X. Xiao, Qizhi Huang, J. Chen, Xiao-Hu Zhang, H. Cai, M. J. Yang, S. Q. Xi, Hong-Guang Wang, Alejandro Sáiz, Q. H. Chen, S. B. Yang, Fan Yang, A. Masood, F. Zheng, Lang Shao, and M. Heller
- Subjects
Physics ,Astrophysics::High Energy Astrophysical Phenomena ,Hadron ,Gamma ray ,Flux ,Astronomy and Astrophysics ,Astrophysics ,Galactic plane ,Crab Nebula ,Pulsar ,Space and Planetary Science ,Angular diameter ,High Energy Physics::Experiment ,Supernova remnant ,Astrophysics - High Energy Astrophysical Phenomena ,Astrophysics::Galaxy Astrophysics - Abstract
We report the discovery of a new unidentified extended $\gamma$-ray source in the Galactic plane named LHAASO J0341+5258 with a pre-trial significance of 8.2 standard deviations above 25 TeV. The best fit position is R.A.$=55.34^{\circ}\pm0.11^{\circ}$ and Dec$=52.97^{\circ}\pm0.07^{\circ}$. The angular size of LHAASO J0341+5258 is $0.29^\circ \pm 0.06^\circ_{stat} \pm0.02^\circ_{sys}$. The flux above 25 TeV is about $20\%$ of the flux of Crab Nebula. Although a power-law fit of the spectrum from 10 TeV to 200 TeV with the photon index $\alpha=2.98 \pm 0.19_{stat} \pm 0.02_{sys}$ is not excluded, the LHAASO data together with the flux upper limit at 10 GeV set by the Fermi LAT observation, indicate a noticeable steepening of an initially hard power-law spectrum %($\alpha \leq 1.75$) spectrum with a cutoff at $\approx 50$ TeV. We briefly discuss the origin of UHE gamma-rays. The lack of an energetic pulsar and a young SNR inside or in the vicinity of LHAASO J0341+5258 challenge, but do not exclude both the leptonic and hadronic scenarios of gamma-ray production., Comment: Accepted by APJL
- Published
- 2021
27. The Optimization of Ti Gradient Porous Structure Involves the Finite Element Simulation Analysis
- Author
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Xuanhui Qu, Lijia Guo, Mingying Chen, Jiaqi Dong, Chaozong Liu, Yitong Liu, Zhang Jiazhen, Maryam Tamaddon, Wei Xu, Xin Lu, Xinbo He, and Liu Bowen
- Subjects
Technology ,Materials science ,Materials Science (miscellaneous) ,medicine.medical_treatment ,0206 medical engineering ,chemistry.chemical_element ,oral implants ,02 engineering and technology ,Bone tissue ,bone stress ,medicine ,titanium ,Composite material ,Dental implant ,Porosity ,Stress concentration ,Bone growth ,three-dimensional finite element simulation ,Stress–strain curve ,021001 nanoscience & nanotechnology ,020601 biomedical engineering ,medicine.anatomical_structure ,chemistry ,Implant ,gradient porosity ,0210 nano-technology ,Titanium - Abstract
Titanium (Ti) and its alloys are attracting special attention in the field of dentistry and orthopedic bioengineering because of their mechanical adaptability and biological compatibility with the natural bone. The dental implant is subjected to masticatory forces in the oral environment and transfers these forces to the surrounding bone tissue. Therefore, by simulating the mechanical behavior of implants and surrounding bone tissue we can assess the effects of implants on bone growth quite accurately. In this study, dental implants with different gradient pore structures that consisted of simple cubic (structure a), body centered cubic (structure b) and side centered cubic (structure c) were designed, respectively. The strength of the designed gradient porous implant in the oral environment was simulated by three-dimensional finite element simulation technique to assess the mechanical adaptation by the stress-strain distribution within the surrounding bone tissue and by examining the fretting of the implant-bone interface. The results show that the maximum equivalent stress and strain in the surrounding bone tissue increase with the increase of porosity. The stress distribution of the gradient implant with a smaller difference between outer and inner pore structure is more uniform. So, a-b type porous implant exhibited less stress concentration. For a-b structure, when the porosity is between 40 and 47%, the stress and strain of bone tissue are in the range of normal growth. When subject to lingual and buccal stresses, an implant with higher porosity can achieve more uniform stress distribution in the surrounding cancellous bone than that of low porosity implant. Based on the simulated results, to achieve an improved mechanical fixation of the implant, the optimum gradient porous structure parameters should be: average porosity 46% with an inner porosity of 13% (b structure) and outer porosity of 59% (a structure), and outer pore sized 500 μm. With this optimized structure, the bone can achieve optimal ingrowth into the gradient porous structure, thus provide stable mechanical fixation of the implant. The maximum equivalent stress achieved 99 MPa, which is far below the simulation yield strength of 299 MPa.
- Published
- 2021
28. Preparation of W-Plated Diamond and Improvement of Thermal Conductivity of Diamond-WC-Cu Composite
- Author
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Zhiyang Xu, Wang Xulei, Xuanhui Qu, and Xinbo He
- Subjects
lcsh:TN1-997 ,Materials science ,Thermal resistance ,Composite number ,Sintering ,chemistry.chemical_element ,02 engineering and technology ,diamond-WC-Cu composite ,engineering.material ,Tungsten ,010402 general chemistry ,01 natural sciences ,chemistry.chemical_compound ,Thermal conductivity ,Tungsten carbide ,General Materials Science ,thermal conductivity ,Composite material ,cyclic vacuum pressure infiltration ,lcsh:Mining engineering. Metallurgy ,Metals and Alloys ,Diamond ,021001 nanoscience & nanotechnology ,Microstructure ,0104 chemical sciences ,chemistry ,interface thermal resistance ,engineering ,0210 nano-technology - Abstract
The tungsten (W)-plated diamond process was explored and optimized. A dense and uniform tungsten coating with a thickness of 900 nm was successfully prepared by the powder covering sintering method. The Diamond-WC-Cu composite with high density and high thermal conductivity were successfully prepared by cyclic vacuum pressure infiltration. The microstructure and composition of the W-plated diamond particles were analyzed. The effect of tungsten coating on the microstructure and thermal conductivity of the Diamond-WC-Cu composite was investigated. After calculation, the interface thermal resistance of the composite forming the tungsten carbide transition layer is 2.11 × 10−8 m2∙K∙W−1. The thermal conductivity average value of the Diamond-WC-Cu composite with a diamond volume fraction of 60% reaches 874 W∙m−1∙K−1, which is close to the theoretical prediction value of Hasselman-Johnson (H-J) model and differential effective medium (DEM) model. Moreover, the Maxwell-Eucken (M-E) model, H-J model, and DEM model were used to evaluate the thermal conductivity of the Diamond-WC-Cu composite.
- Published
- 2021
29. GRID: a student project to monitor the transient gamma-ray sky in the multi-messenger astronomy era
- Author
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Yuchong Zhang, Siyao Li, Chi-Pui Tang, Shiyu Zheng, Yuehan Xia, Xuewen Liu, Hongbing Chen, Ke Li, Xuelin Tan, Huan Yu, Xiaolong Zhou, He Gao, Bin-Bin Zhang, Bing Zhang, Junling Hu, Mingming Kang, Xuefeng Huang, Xinbo He, Changyu Chen, Can Xu, Xutao Zheng, Chang Liu, Di'an Lu, Yi-Zhong Fan, Ruining Zhao, Wei Deng, Jing Shu, Qiaoya Wu, Yiying Han, Hui Sun, Aiqiang Zhang, Jirong Cang, Fan Hu, Yi-Si Yang, Jianjun Wang, Hangci Du, Xiangyun Long, Shaolin Xiong, Gengyuan Shi, Hang Yang, Yang Tian, LJ Chen, Tianyu Liu, Rui Xu, Yu An, Lian Duan, C. X. Liu, Wenqing Ding, Zongqing Zhao, Yuanhang Ma, Jianfeng Wu, Yue Wang, Xinhao He, Dacheng Xu, Yinong Liu, Yuchen Jiang, Xuanyi Wu, Shude Mao, Yurong Li, Wenfei Yu, Enwei Liang, Shen Zhang, Zigao Dai, Wanqiang Liu, Fayin Wang, Xuefeng Wu, Yu Zou, Yunwei Yu, Litao Deng, Bo Huang, Hongbang Liu, Zhi Zeng, Rui Liu, Shengyu Yan, Dongxin Yang, Zhiyong Lu, Maoxing Zhang, Quan Gan, Liang Huang, Yifan Yang, Qiyuan Nie, Sizheng Ma, Zhiying Gao, Yanshan Mo, Lin Lin, Mingrui Tao, Qianru Zhao, Tianliang Zhang, Weiming Song, Ming Zeng, Rongfeng Shen, Jiaxing Wen, Lixin Li, B. Q. Wang, Wei Lin, Zhuo Li, Bingtao Zhang, Qianqian Lin, Shuiyin Qu, Zonghong Zhu, Hengyuan Xiao, Hua Feng, Yingjie Cheng, Shihai Jia, Rong Zhou, Xiang Lu, Xiaoqing Mao, Runyu Zhu, Dongyang Huang, Xiyu Luo, Haoguang Yang, Zhigang Sun, Meng Su, Yifei Jin, Songsong Tang, Wenbin Han, Yifu Cai, Ziyun Chen, Wenjin Xie, Zhonghai Wang, Tai Gao, Zhiang Wang, Wei Wang, Jiandong Yu, Jianwei Liang, Xiaolong Shan, Pak-Hin Thomas Tam, Changqing Feng, Lei Yao, Gang Liu, Peng An, Lixuan Zhang, Qianjun Chen, Yuepeng Che, Long Hou, Weili Xu, Mengyuan Liu, Zhengyang Cai, Longbiao Yan, Peiyibin Lu, Yuanyuan Liang, and Yangyi Yu
- Subjects
High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,010308 nuclear & particles physics ,Gravitational wave ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Astrophysics::Instrumentation and Methods for Astrophysics ,FOS: Physical sciences ,Astronomy ,Astronomy and Astrophysics ,Grid ,01 natural sciences ,Occultation ,LIGO ,Space and Planetary Science ,Sky ,0103 physical sciences ,CubeSat ,Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena ,Gamma-ray burst ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,010303 astronomy & astrophysics ,Geocentric orbit ,media_common - Abstract
The Gamma-Ray Integrated Detectors (GRID) is a space mission concept dedicated to monitoring the transient gamma-ray sky in the energy range from 10 keV to 2 MeV using scintillation detectors onboard CubeSats in low Earth orbits. The primary targets of GRID are the gamma-ray bursts (GRBs) in the local universe. The scientific goal of GRID is, in synergy with ground-based gravitational wave (GW) detectors such as LIGO and VIRGO, to accumulate a sample of GRBs associated with the merger of two compact stars and study jets and related physics of those objects. It also involves observing and studying other gamma-ray transients such as long GRBs, soft gamma-ray repeaters, terrestrial gamma-ray flashes, and solar flares. With multiple CubeSats in various orbits, GRID is unaffected by the Earth occultation and serves as a full-time and all-sky monitor. Assuming a horizon of 200 Mpc for ground-based GW detectors, we expect to see a few associated GW-GRB events per year. With about 10 CubeSats in operation, GRID is capable of localizing a faint GRB like 170817A with a 90% error radius of about 10 degrees, through triangulation and flux modulation. GRID is proposed and developed by students, with considerable contribution from undergraduate students, and will remain operated as a student project in the future. The current GRID collaboration involves more than 20 institutes and keeps growing. On August 29th, the first GRID detector onboard a CubeSat was launched into a Sun-synchronous orbit and is currently under test., accepted for publication in Experimental Astronomy
- Published
- 2019
30. Preparation of refractory metal diboride powder by reducing refractory metal oxide with calcium hexaboride
- Author
-
Baijun Yan, Xinbo He, Guo-Hua Zhang, and Yu Wang
- Subjects
010302 applied physics ,Materials science ,Reducing agent ,Process Chemistry and Technology ,Oxide ,Refractory metals ,chemistry.chemical_element ,02 engineering and technology ,Calcium ,021001 nanoscience & nanotechnology ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,chemistry ,Boride ,0103 physical sciences ,Materials Chemistry ,Ceramics and Composites ,Leaching (metallurgy) ,Particle size ,Calcium hexaboride ,0210 nano-technology ,Nuclear chemistry - Abstract
This paper provides a new method for preparing refractory metal diboride by reducing refractory metal oxide with Calcium hexaboride (CaB6), which is prepared using B4C and calcium as raw materials. For refractory metal powders (M = Ti, Zr, Hf, V, Nb, Ta, Cr) which are expensive and hard to be produced by a simple route, it is more cost-effective to directly use refractory metal oxide to prepare its boride. After reacting at 1473 K for 4 h, CaB6 and refractory metal oxide could completely react to form MB2, CaO and B2O3. The single-phase product with the particle size of sub-micron was obtained after acidic leaching, filtration and drying. CaB6 could be used as a universal reducing agent to prepare metal boride.
- Published
- 2019
31. Tailored synthesis of amorphous SiCNO mesoporous fibers through combining a facile electrospinning process and microwave-assisted pyrolysis
- Author
-
Huilin Hou, Weiyou Yang, Xinbo He, and Yangwen Liu
- Subjects
010302 applied physics ,Materials science ,Process Chemistry and Technology ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electrospinning ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,symbols.namesake ,Chemical engineering ,Transmission electron microscopy ,Specific surface area ,0103 physical sciences ,Materials Chemistry ,Ceramics and Composites ,symbols ,Fourier transform infrared spectroscopy ,0210 nano-technology ,Mesoporous material ,High-resolution transmission electron microscopy ,Raman spectroscopy ,Pyrolysis - Abstract
In the current work, we first reported the fabrication of mesoporous SiCNO fibers by electrospun polyureasilazane and polyvinylpyrrolidone precursor followed with a microwave-assisted pyrolysis process. The resulting product was characterized by field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), nitrogen adsorption-desorption, X-ray diffraction (XRD), Raman spectrometer (Raman) and Fourier Transform infrared spectroscopy (FTIR). The as-prepared SiCNO fibers have uniform diameter and high morphological purity. It is found that the elemental compositions and BET specific surface area in the resulted SiCNO fibers could be controlled by adjustment the pyrolysis temperature.
- Published
- 2019
32. Effects of Ball-milling on the microstructure and properties of W Ti alloy gasket
- Author
-
Haiyang Lu, Chaosheng Wu, Tao Lin, Xinbo He, Jian Xu, and Jin Zhongling
- Subjects
Materials science ,Scanning electron microscope ,020502 materials ,Alloy ,02 engineering and technology ,engineering.material ,Microstructure ,Grain size ,0205 materials engineering ,Powder metallurgy ,Phase (matter) ,engineering ,Composite material ,Ball mill ,Eutectic system - Abstract
W Ti alloy, which is a candidate of the gasket material used for the neutron high pressure diffraction, was proposed and fabricated by the powder metallurgy method in this paper. The laser particle size analyzer, scanning electron microscope, and transmission electron microscope were used to study the effects of milling time on the particle size distribution and the microstructure. The results show that with the extension of milling time, the particle size of the milled powders decreases, and the grain size of the sintered alloys also decreases. However, the oxygen content increases, and the αTi phase gradually appears and its amount increases with the increase of the milling time. The microstructure is composed of the W-rich (βTi,W) phase, the αTi phase and the eutectic phase before the milling time of 2 h, and after that the eutectic phase disappears. Oxygen coming from the milling gets rich in titanium so that it makes more and stable αTi phase. This is because, with the extension of milling time, the oxygen content is so high that the αTi phase can be very stable and the diffusion of W into Ti at the high temperature is suppressed. Moreover after 0.5 h ball milling, the maximum strength of the alloy is 3323 MPa due to the uniform microstructure.
- Published
- 2019
33. Effect of alloying element Zr on the microstructure and properties of graphite flake/Cu composites fabricated by vacuum hot pressing
- Author
-
Xuanhui Qu, Ren Zhang, Haitian Chen, and Xinbo He
- Subjects
Materials science ,Mechanical Engineering ,Flake ,Metals and Alloys ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Hot pressing ,Microstructure ,01 natural sciences ,0104 chemical sciences ,Carbide ,Thermal conductivity ,Flexural strength ,Mechanics of Materials ,Materials Chemistry ,Graphite ,Composite material ,0210 nano-technology ,Layer (electronics) - Abstract
Graphite flake/Cu composites with Zr element introduced into the matrix were successfully fabricated by vacuum hot pressing. The influence of Zr addition on the phase composition, microstructure and properties were investigated. The results indicate that the bending strength in X-Y plane gradually rises with the Zr content increasing from 0 to 2.0 wt%, nearly doubled from 50 MPa to 95 MPa. The thermal conductivity in X-Y plane initially increases and then decreases, yielding a maximum of 640 W m−1 K−1 at 1.0 wt% Zr. This improvement is ascribed to the formation of carbide interfacial layer at the graphite flake/Cu interface. Due to the simple preparation process and excellent thermal conductivity, the graphite flake/Cu composites with moderate Zr addition can be a highly promising candidate for thermal management materials.
- Published
- 2019
34. A novel fractional time-delayed grey Bernoulli forecasting model and its application for the energy production and consumption prediction
- Author
-
Yong Wang, Xinbo He, Lei Zhang, Xin Ma, Wenqing Wu, Rui Nie, Pei Chi, and Yuyang Zhang
- Subjects
Artificial Intelligence ,Control and Systems Engineering ,Electrical and Electronic Engineering - Published
- 2022
35. Spatially Decomposed γ-Ray Features Surrounding Supernova Remnant Kes 79 and PSR J1853+0056
- Author
-
Xinbo He, Yudong Cui, Paul K. H. Yeung, P. H. Thomas Tam, Yong Zhang, and Yang Chen
- Subjects
Space and Planetary Science ,Astrophysics::High Energy Astrophysical Phenomena ,Astronomy and Astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
There have been substantial improvements on Fermi Large Area Telescope (LAT) data and analysis tools since the last analysis by Auchettl et al. on the intermediate-aged supernova remnant (SNR) Kes 79. Recent multiwavelength studies confirmed its interaction with molecular clouds. About 0.°36 north from Kes 79, a powerful pulsar, PSR J1853+0056, also deserves our attention. In this work, we analyze the 11.5 yr Fermi-LAT data to investigate the γ-ray feature in/around this complex region. Our result shows a more significant detection (∼34.8σ in 0.1–50 GeV) for this region. With ≥5 GeV data, we detect two extended sources: Src-N (the brighter one; radius ≈0.°31) concentrated at the north of the SNR while enclosing PSR J1853+0056, and Src-S (radius ≈0.°58) concentrated at the south of the SNR. Their spectra have distinct peak energies (∼1.0 GeV for Src-N and ≲0.5 GeV for Src-S), suggesting different origins for them. In our hadronic model that includes the leaked cosmic rays (CRs) from the shock-cloud collision, even with extreme values of parameters, SNR Kes 79 can by no means provide enough CRs reaching clouds at Src-N to explain the local GeV spectrum. We propose that the Src-N emission could be predominantly reproduced by a putative pulsar wind nebula powered by PSR J1853+0056. On the other hand, our same hadronic model can reproduce a majority of the GeV emission at Src-S with typical values of parameters, while the three known pulsars inside Src-S release a total power that is too low to account for half of its γ-ray emission.
- Published
- 2022
36. Fabrication of CdS-decorated mesoporous SiC hollow nanofibers for efficient visible-light-driven photocatalytic hydrogen production
- Author
-
Xinbo He, Yangwen Liu, Lin Wang, Weiyou Yang, Huilin Hou, and Fengmei Gao
- Subjects
010302 applied physics ,Materials science ,Nanoparticle ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Electrospinning ,Electronic, Optical and Magnetic Materials ,Chemical engineering ,Transmission electron microscopy ,Nanofiber ,0103 physical sciences ,Photocatalysis ,Electrical and Electronic Engineering ,High-resolution transmission electron microscopy ,Mesoporous material ,Visible spectrum - Abstract
In the present work, we reported the fabrication of CdS decorated mesoporous SiC hollow nanofibers for efficient visible-light-driven photocatalytic hydrogen production. The mesoporous SiC hollow nanofibers were firstly fabricated by electrospinning, followed by hydrothermal treatment to introduce the CdS nanoparticles decorated on the preformed fiber matrix, The resultant CdS/SiC hybrid photocatalysts were systematically characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and N2 adsorption. The as-fabricated CdS/SiC hybrids exhibited a robust stability with a release rate up to ~ 124.65 µmol h−1 g−1 for photocatalytic H2 evolution driven by visible light, which was profoundly enhanced for more than 16 times to that of pristine SiC counterparts, and comparable to the state-of-the-art one of SiC-based photocatalysts.
- Published
- 2018
37. Investigation on Sub-Solvus Recrystallization Mechanisms in an Advanced γ-γ’ Nickel-Based Superalloy GH4151
- Author
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Chonglin Jia, Jinbin Chen, Xinbo He, Xuanhui Qu, Kang Wei, and Shaomin Lv
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Materials science ,Nucleation ,lcsh:Technology ,Article ,dynamic recrystallization ,GH4151 superalloy ,General Materials Science ,Solvus ,Composite material ,lcsh:Microscopy ,lcsh:QC120-168.85 ,lcsh:QH201-278.5 ,lcsh:T ,Recrystallization (metallurgy) ,Microstructure ,Superalloy ,lcsh:TA1-2040 ,heteroepitaxial dynamic recrystallization ,Dynamic recrystallization ,step-shaped structures ,Grain boundary ,lcsh:Descriptive and experimental mechanics ,lcsh:Electrical engineering. Electronics. Nuclear engineering ,lcsh:Engineering (General). Civil engineering (General) ,lcsh:TK1-9971 ,gamma prime precipitates ,Electron backscatter diffraction - Abstract
Sub-solvus dynamic recrystallization (DRX) mechanisms in an advanced &gamma, &gamma, &rsquo, nickel-based superalloy GH4151 were investigated by isothermal compression experiments at 1040 °, C with a strain rate of 0.1 s&minus, 1 and various true strain of 0.1, 0.3, 0.5, and 0.7, respectively. This has not been reported in literature before. The electron backscatter diffraction (EBSD) and transmission electron microscope (TEM) technology were used for the observation of microstructure evolution and the confirmation of DRX mechanisms. The results indicate that a new dynamic recrystallization mechanism occurs during hot deformation of the hot-extruded GH4151 alloy. The nucleation mechanism can be described as such a feature, that is a primary &gamma, (Ni3(Al, Ti, Nb)) precipitate embedded in a recrystallized grain existed the same crystallographic orientation, which is defined as heteroepitaxial dynamic recrystallization (HDRX). Meanwhile, the conventional DRX mechanisms, such as the discontinuous dynamic recrystallization (DDRX) characterized by bulging grain boundary and continuous dynamic recrystallization (CDRX) operated through progressive sub-grain merging and rotation, also take place during the hot deformation of the hot-extruded GH4151 alloy. In addition, the step-shaped structures can be observed at grain boundaries, which ensure the low-energy surface state during the DRX process.
- Published
- 2020
- Full Text
- View/download PDF
38. Reconciling low and high redshift GRB luminosity correlations
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Xinbo He, Lu Huang, Xiaolin Luo, Zhiqi Huang, and YuHong Fang
- Subjects
J.2 ,Cold dark matter ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,General Relativity and Quantum Cosmology (gr-qc) ,Lambda ,01 natural sciences ,Cosmology ,Spectral line ,General Relativity and Quantum Cosmology ,Luminosity ,High Energy Physics - Phenomenology (hep-ph) ,0103 physical sciences ,010306 general physics ,83F05 ,Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,010308 nuclear & particles physics ,Redshift ,High Energy Physics - Phenomenology ,Gamma-ray burst ,Astrophysics - High Energy Astrophysical Phenomena ,Energy (signal processing) ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
The correlation between the peak spectra energy ($E_p$) and the equivalent isotropic energy ($E_{\rm iso}$) of long gamma-ray bursts (GRBs), the so-called Amati relation, is often used to constrain the high-redshift Hubble diagram. Assuming Lambda cold dark matter ($\Lambda$CDM) cosmology, Wang et al. found a $\gtrsim 3\sigma$ tension in the data-calibrated Amati coefficients between low- and high-redshift GRB samples. To reduce the impact of fiducial cosmology, we use the Parameterization based on cosmic Age (PAge), an almost model-independent framework to trace the cosmological expansion history. We find that the low- and high-redshift tension in Amati coefficients stays almost the same for the broad class of models covered by PAge, indicating that the cosmological assumption is not the dominant driver of the redshift evolution of GRB luminosity correlation. Next, we analyze the selection effect due to flux limits in observations. We find Amati relation evolves much more significantly across energy scales of $E_{\rm iso}$. We debias the GRB data by selectively discarding samples to match low-$z$ and high-$z$ $E_{\rm iso}$ distributions. After debiasing, the Amati coefficients agree well between low-$z$ and high-$z$ data groups, whereas the evidence of $E_{\rm iso}$-dependence of Amati relation remains to be strong. Thus, the redshift evolution of GRB luminosity correlation can be fully interpreted as a selection bias, and does not imply cosmological evolution of GRBs., Comment: 5 pages, 4 figures; significant modification
- Published
- 2020
- Full Text
- View/download PDF
39. A multi-wavelength study of the gamma-ray binary candidate HESS J1832-093
- Author
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Partha Sarathi Pal, C. P. Hu, Xinbo He, Vlad Tudor, Pak-Hin Thomas Tam, Albert K. H. Kong, K. K. Lee, Y. D. Cui, and K. L. Li
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Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Absorption spectroscopy ,Binary number ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Spectral line ,Stars ,Wavelength ,Space and Planetary Science ,Binary star ,Astrophysics - High Energy Astrophysical Phenomena ,Spectroscopy - Abstract
We investigate the nature of the unidentified very-high-energy (VHE) gamma-ray object, HESS J1832-093, in a multi-wavelength context. Based on X-ray variability and spectral index ($\Gamma_X\sim\,1.5$), and its broad-band spectrum (which was remarkably similar to HESS J0632+057, a confirmed gamma-ray binary), HESS J1832-093 has been considered to be a strong gamma-ray binary candidate in previous works. In this work, we provide further evidence for this scenario. We obtained a spectrum of its IR counterpart using Gemini/Flamingo, finding absorption lines that are usually seen in massive stars, in particular O stars. We also obtained a rather steep ATCA spectrum ($\alpha=-1.18^{+1.04}_{-0.88}$) which prefers a gamma-ray binary over an AGN scenario. Based on spatial-spectral analysis and variability search, we found that 4FGL J1832.9-0913 is possible to be associated with SNR G22.7-0.2 rather than with HESS J1832-093 only., Comment: 9 pages, 5 figures, submitted
- Published
- 2020
- Full Text
- View/download PDF
40. Effects of chromium and carbon content on microstructure and properties of TiC-steel composites
- Author
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You Guo, Li Feihong, Haiyang Lu, Tao Lin, Xinbo He, Huiping Shao, and Zhi Wang
- Subjects
010302 applied physics ,Materials science ,Scanning electron microscope ,Alloy steel ,technology, industry, and agriculture ,Sintering ,chemistry.chemical_element ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Chromium ,chemistry ,Powder metallurgy ,0103 physical sciences ,engineering ,Composite material ,0210 nano-technology ,Porosity ,Carbon - Abstract
The composite of low alloy steel reinforced with TiC particles (36 wt%) was prepared by the powder metallurgy (PM) process in this paper. The effects of the chromium content and the total carbon content on the composites were studied. The scanning electron microscopy (SEM) was used to observe the microstructure and such properties as porosity, hardness, transverse rupture strength (TRS) and fracture morphology of the samples were tested. The results show that the optimum sintering temperature decreases with the increase of chromium content. The porosity of sintered samples decreases with increasing the total carbon content, and increases with increasing the chromium content. The TRS and hardness of samples increase with the increase of the carbon content. With the increase of the chromium content, the TRS of the sample gradually decreases, and the hardness firstly increases and then decreases a little. This results from the combined effects of the martensite amount and the shape, size and composition of precipitated chromium carbides in the steel matrix.
- Published
- 2018
41. High thermal conductivity of diamond/copper composites produced with Cu–ZrC double-layer coated diamond particles
- Author
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Pan Yanpeng, Shubin Ren, Xinbo He, Mao Wu, and Xuanhui Qu
- Subjects
010302 applied physics ,Materials science ,Mechanical Engineering ,Composite number ,chemistry.chemical_element ,Diamond ,02 engineering and technology ,engineering.material ,Sputter deposition ,021001 nanoscience & nanotechnology ,01 natural sciences ,Copper ,Thermal expansion ,Zirconium carbide ,chemistry.chemical_compound ,Thermal conductivity ,chemistry ,Mechanics of Materials ,0103 physical sciences ,engineering ,General Materials Science ,Composite material ,0210 nano-technology ,Layer (electronics) - Abstract
A new method was proposed to fabricate diamond/Cu composites. Double-layer diamond particles were directly compressed at ultra-high pressure to prepare the preform and then sintered in a vacuum equipment for densification. The raw diamond particles were coated with zirconium carbide by magnetron sputtering for the inner layer and then deposited with copper by chemical method for the outer layer. Prepared with these particles, the composites had good interface bonding and homogeneously distributed particles in the copper matrix. The thermal conductivity of 65 vol% diamond/Cu composite was as high as 720 W m−1 K−1. When the diamond content increased to 70 vol%, the coefficient of thermal expansion was extremely low (4.33 × 10−6/K). With superb thermal–physical performance, diamond/Cu composites are potentially applicable to electronic packaging.
- Published
- 2018
42. Powder injection molding of Ti–6Al–4V alloy
- Author
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Shibo, Guo, Xuanhui, Qu, Xinbo, He, Ting, Zhou, and Bohua, Duan
- Published
- 2006
- Full Text
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43. Influence of total pressure on the microstructures and growth mechanism of ZrC coatings prepared by chemical vapor deposition from the Zr-Br2-C3H6-H2-Ar system
- Author
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Yong Li, Guangde Li, Xinbo He, Xuanhui Qu, X.Q. Ma, Min Mei, Haifeng Hu, and Si'an Chen
- Subjects
010302 applied physics ,Supersaturation ,Materials science ,Process Chemistry and Technology ,Diffusion ,Nucleation ,Crystal growth ,02 engineering and technology ,Chemical vapor deposition ,021001 nanoscience & nanotechnology ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Zirconium carbide ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,0103 physical sciences ,Materials Chemistry ,Ceramics and Composites ,Deposition (phase transition) ,Total pressure ,0210 nano-technology - Abstract
Zirconium carbide (ZrC) coatings were deposited on graphite substrates by chemical vapor deposition from the Zr-Br 2 -C 3 H 6 -H 2 -Ar system. The influence of total pressure on the growth of ZrC was investigated in the range of 5–60 kPa. As the total pressure increased, the deposition rate increased evidently, and the preferential orientation of ZrC coatings changed from the (200) plane to the (220) plane. The growth mechanism changed from a mass transport reaction to a surface reaction at the total pressure of 20–40 kPa. At the total pressure below 20 kPa, the deposition was dominated by crystal growth, so the coatings were composed of well-faceted pyramidal-shaped crystals growing along the direction. At the total pressure above 60 kPa, the growth of ZrC coatings was controlled by the nucleation mechanism, so the coatings were cluster-like crystals rapidly growing along the direction. In addition, low pressure was conducive to the formation of near-stoichiometric ZrC without free carbon. These variations of ZrC coatings can mainly be attributed to gas supersaturation and remarkably changed transport diffusion coefficients with increasing total pressure.
- Published
- 2017
44. Is the SNR HESS J1731-347 colliding with molecular clouds?
- Author
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P. H. Thomas Tam, G. Pühlhofer, Y. D. Cui, Ruizhi Yang, and Xinbo He
- Subjects
Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Space and Planetary Science ,Molecular cloud ,Astrophysics::High Energy Astrophysical Phenomena ,Gamma ray ,FOS: Physical sciences ,Astronomy and Astrophysics ,Cosmic ray ,High Energy Physics::Experiment ,Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena ,Astrophysics::Galaxy Astrophysics - Abstract
The supernova remnant (SNR) HESS J1731-347 is a young SNR which displays a non-thermal X-ray and TeV shell structure. A molecular cloud at a distance of 3.2 kpc is spatially coincident with the western part of the SNR, and it is likely hit by the SNR. The X-ray emission from this part of the shell is much lower than from the rest of the SNR. Moreover, a compact GeV emission region coincident with the cloud has been detected with a soft spectrum. These observations seem to imply a shock-cloud collision scenario at this area, where the stalled shock can no longer accelerate super-TeV electrons or maintain strong magnetic turbulence downstream, while the GeV cosmic rays (CRs) are released through this stalled shock. To test this hypothesis, we have performed a detailed Fermi-LAT reanalysis of the HESS J1731-347 region with over 9 years of data. We find that the compact GeV emission region displays a spectral power-law index of -2.4, whereas the GeV emission from the rest of the SNR (excluding the cloud region) has an index of -1.8. A hadronic model involving a shock-cloud collision scenario is built to explain the -ray emission from this area. It consists of three CR sources: run-away super-TeV CRs that have escaped from the fast shock, leaked GeV CRs from the stalled shock, and the local CR sea. The X-ray and -ray emission of the SNR excluding the shock-cloud interaction region is explained in a one-zone leptonic model. Our shock-cloud collision model explains well the GeV-TeV observations from both cloud regions around HESS J1731-347, i.e. from the cloud in contact with the SNR and from the more distant cloud which is coincident with the nearby TeV source HESS J1729-345. We find however that the leaked GeV CRs from the shock-cloud collision do not necessarily dominate the GeV emission from the clouds, due to a comparable contribution from the local CR sea., Comment: 20 pages
- Published
- 2019
- Full Text
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45. MAGICal GRB 190114C: Implications of cutoff in the spectrum at sub-$GeV$ energies
- Author
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Ankush Banerjee, Vidushi Sharma, Partha Sarathi Pal, Xinbo He, Pak-Hin Thomas Tam, and Vikas Chand
- Subjects
Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,010504 meteorology & atmospheric sciences ,High-energy astronomy ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Astronomy and Astrophysics ,Cosmic ray ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Redshift ,Spectral line ,Afterglow ,Pair production ,Space and Planetary Science ,0103 physical sciences ,Gamma-ray burst ,Astrophysics - High Energy Astrophysical Phenomena ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences ,Fermi Gamma-ray Space Telescope - Abstract
GRB 190114C is an unusual gamma-ray burst (GRB) due to its detection at sub-$TeV$ energies by MAGIC, seen at redshift z = 0.42. This burst is one of the brightest GRB detected by \fermi. A joint GBM-LAT analysis of the prompt emission reveals the presence of sub-$GeV$ spectral cutoff when the LAT \emph{low-energy events} (LLE) data is also examined. A similar high-energy cutoff was likewise reported in GRB 160509A and GRB 100724B earlier, as well as handful of other sources. The cutoff can be explained by the intrinsic opacity due to pair production within the emitting region. GRB 190114C shows a transition from non-thermal to a quasi-thermal-like spectrum and a radiation component that can be attributed to afterglow. Based on spectral analysis, we constrain the site of the prompt emission and $Lorentz$ factor. Knowing that sub-$TeV$ photons are detected in MAGIC, we perceive that the observed spectrum is indeed an overlap from two emission sites, where the emission observed in \fermi is more consistent with prompt emission produced via photospheric dissipation along with a concurrent component from the external shock., Comment: Revised and accepted for publication in the ApJ
- Published
- 2019
- Full Text
- View/download PDF
46. Fabrication and properties of the TiC reinforced high-strength steel matrix composite
- Author
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Zhi Wang, Tao Lin, Xuanhui Qu, Bo Tang, Xinbo He, and Huiping Shao
- Subjects
010302 applied physics ,Materials science ,Annealing (metallurgy) ,Scanning electron microscope ,Metallurgy ,Composite number ,Sintering ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Flexural strength ,Powder metallurgy ,0103 physical sciences ,Relative density ,Tempering ,Composite material ,0210 nano-technology - Abstract
The composite of 35CrMo high-strength steel matrix reinforced with TiC reinforcement (50 wt.%) has been produced by conventional powder metallurgy (PM). The sintering temperature and process for heating treatment were discussed. The scanning electron microscopy (SEM) revealed the morphology and distribution of the reinforcement phase. Density, hardness, and transverse rupture strength (TRS) of the samples were analyzed. The results showed that the optimal sintering process for the composite is sintering at 1430 °C for 1 h and heat treatment process is annealing at 850 °C/30 min, quenching at 880 °C/30 min and then tempering at 560 °C/60 min. The composite after heat treatment has excellent mechanical properties with a relative density of 99.7%, hardness of 65 HRC, TRS of 1850 ± 20 MPa, respectively, and will be used as refractory moulds, cold work moulds and some gaskets, etc.
- Published
- 2016
47. Effect of (0–40) wt. % Si addition to Al on the thermal conductivity and thermal expansion of diamond/Al composites by pressure infiltration
- Author
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Caiyu Guo, Xuanhui Qu, Xinbo He, and Shubin Ren
- Subjects
Materials science ,Mechanical Engineering ,Composite number ,Metals and Alloys ,Diamond ,02 engineering and technology ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Thermal expansion ,0104 chemical sciences ,Matrix (chemical analysis) ,Infiltration (hydrology) ,Thermal conductivity ,Mechanics of Materials ,Materials Chemistry ,engineering ,Composite material ,0210 nano-technology - Abstract
•Si addition to Al matrix can reduce the unwanted reactions of Al4C3.•12 wt.% Si addition to Al matrix between diamond and Al can form SiC with a high TC.•The diamond/Al–12.2Si composite has a high TC (558 W/mK) and a low CTE (8.9 × 10−6/K).•The diamond/Al–40Si composite has a very low CTE of 4.5 × 10−6/K.•The mixing of the diamond powders can enhance the TC and reduce the CTE.
- Published
- 2016
48. Fabrication and characterization of porous Ti–4Mo alloy for biomedical applications
- Author
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Xinbo He, Meiping Wu, Fangxia Xie, Jinghu Yu, Xueming He, and Xuanhui Qu
- Subjects
Materials science ,Mechanical Engineering ,Metallurgy ,Alloy ,02 engineering and technology ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,0104 chemical sciences ,Corrosion ,law.invention ,Selective laser sintering ,Mechanics of Materials ,law ,engineering ,Relative density ,General Materials Science ,Composite material ,0210 nano-technology ,Porosity ,Polarization (electrochemistry) ,Elastic modulus - Abstract
Porous Ti–4Mo alloy was prepared by indirect selective laser sintering and investigated with focuses on its porous structure, microstructural characteristic, mechanical properties and corrosion behavior. The results indicate that as the porous alloy is sintered from 1000 to 1200 °C, the pore morphology changes gradually from interconnected to closed pores, meanwhile the porosity level and pore size reduce in the ranges 54–20 % and 103–35 μm, respectively. A laminar microstructure composed of dominant α and minor β phases is observed in pore walls together with slight α precipitations. Elastic modulus and yield strength increase with decreased porosity in the ranges 2.56–10.8 GPa and 47.0–162.4 MPa, respectively. The relationship between the relative mechanical properties and relative density obeys a power law relation. All the polarization curves exhibit an obvious passive characteristic despite different pore features, and the passive film could protect the porous alloy against corrosion in simulated body fluids. Overall, the porous Ti–4Mo alloy may be a potential candidate material for biomedical implants.
- Published
- 2016
49. Microstructure and tensile properties optimization of MIM418 superalloy by heat treatment
- Author
-
Xuanhui Qu, Mingli Qin, Xinbo He, Lin Zhang, Dan Li, and Zhou Li
- Subjects
010302 applied physics ,Ostwald ripening ,Materials science ,Precipitation (chemistry) ,Metallurgy ,Metals and Alloys ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Indentation hardness ,Industrial and Manufacturing Engineering ,Computer Science Applications ,Superalloy ,symbols.namesake ,Precipitation hardening ,Modeling and Simulation ,Critical resolved shear stress ,0103 physical sciences ,Ultimate tensile strength ,Ceramics and Composites ,symbols ,0210 nano-technology - Abstract
Solution plus ageing leads to the precipitation of finer and more homogeneous γ′ precipitates in comparison to direct ageing. Solution treatment at 1220 °C eliminates the large primary γ′ phase and replaces them with homogeneous secondary γ′ precipitates. Coarsening of γ′ particles according to Ostwald ripening mechanism is confirmed. An increase of the critical resolved shear stress (CRSS) is observed for the under-aged specimens, followed by a maximum of CRSS at γ′ particle size of around 100 nm and a decrease of CRSS for the over-aged specimen. This result agrees well with the highest yield strength and microhardness of the 750 °C × 24 h aged specimens.
- Published
- 2016
50. The influence of matrix alloy on the microstructure and properties of (flake graphite + diamond)/Cu composites by hot pressing
- Author
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Jianhao Chen, Hong Qingnan, Xinbo He, Shubin Ren, and Xuanhui Qu
- Subjects
Pressing ,Fabrication ,Materials science ,Mechanical Engineering ,Alloy ,Metals and Alloys ,Diamond ,engineering.material ,Hot pressing ,Microstructure ,Thermal conductivity ,Mechanics of Materials ,Materials Chemistry ,engineering ,Particle size ,Composite material - Abstract
Cu matrix composites reinforced with flake graphite and diamond particles were prepared by a powder hot pressing process. In this paper, we assess the influence of particle size and the powder composition of the raw material on the microstructure and thermal properties of (Gf + Diamond)/Cu composites. Our results show that Cu powders with small particle sizes that are close to the size of the diamond beneficially increase the performance of prepared composites because their improved flowability allows parallel arrangement of the flake graphite during pressing. The optimum Cu powder composition has an equal volume of the matrix alloy to the combined volume of diamond and flake graphite. Additionally, we compared the experimentally determined thermal conductivity with the theoretically calculated value.
- Published
- 2015
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