期刊：
Materials Science in Semiconductor Processing,2021年121:105439 ISSN：1369-8001
通讯作者：
Guo, Jian
作者机构：
[Guo, Jian; Wang, Yongqiang] Univ South China, Sch Mech Engn, Hengyang 421001, Hunan, Peoples R China.
通讯机构：
[Guo, Jian] U;Univ South China, Sch Mech Engn, Hengyang 421001, Hunan, Peoples R China.
关键词：
GaN single Crystal;Nano abrasive machining;Abrasive size;Molecular dynamics
摘要：
Molecular dynamics simulations were used to explore the effect of abrasive size on the nano abrasive machining for wurtzite gallium nitride (GaN) single crystal. The deformation behaviours, varied with the abrasive size, were systematically analysed. The simulation results show that increasing the abrasive size results in more severe plastic deformation and machining-induced hardening, which consequently cause an increase in atomic tem-perature, strain, stress, and cutting forces. The use of larger abrasive produces greater compression, thus boosts the elastic recovery and damages the subsurface of GaN single crystal much heavily, with the enhancement of the nucleation and emission of dislocation, and the local phase transition from B4 to B3 structure or even to fivefold hexagonal structure. The development of pile-up and amorphization is impressively inhibited by increasing abrasive size, suggesting that the cutting effect could be impaired using a larger abrasive under a given depth of cut.
通讯机构：
[Min Liu] C;Cooperative Innovation Center for Nuclear Fuel Cycle Technology and Equipment, University of South China, Hengyang, Hunan 421001, P. R. China
摘要：
Multiferroic nanocrystalline Bi 1−xSr xFeO3 ( x=0, 0.05, 0.1) samples were synthesized using the sol–gel method and characterized by powder X-ray diffraction, Mössbauer spectroscopy and SQUID system. The small-angle X-ray diffraction analysis showed that the sample underwent phase transition from rhombohedral to pseudo-cubic structure with the enhancement of Sr content. In addition, impurity peaks gradually diminished, indicating that content of impurities of samples reduced. Furthermore, it can be determined that there is only Fe 3+ in all the samples and impurity phase that existed in the samples was Bi 25FeO 40 by fitting Mössbauer spectra. It is further confirmed that Bi 1−x Sr xFeO3 samples were generated by oxygen vacancy equilibrium valence state when Sr 2+ ions replaced Bi 3+ ions. The change of quadrupole splitting indicated that a low concentration of Sr 2+ ions diffused homogeneously in the sample. Magnetization measurement showed that the magnetization of the sample increased gradually with the substitution of Bi 3+ by nonequivalent Sr 2+ ions, which can be ascribed to the decrease of grain size and the increase of oxygen vacancy and specific surface in the samples.
作者：
Zhang, H. Q.;Wang, Z. M.;Luo, F. J.;Yang, A. B.;Wu, D. R.;...
期刊：
Journal of Instrumentation,2021年16(8):T08009 ISSN：1748-0221
作者机构：
[Heng, Y. K.; Yang, A. B.; Chen, H. S.; Wang, Y. F.; Wu, D. R.; Zhang, H. Q.; Yang, C. G.] Univ Chinese Acad Sci, 19A Yuquan Rd, Beijing, Peoples R China.;[Li, Y. C.; Heng, Y. K.; Wang, Z. M.; Yang, A. B.; Chen, H. S.; Wang, Y. F.; Wu, D. R.; Zhang, H. Q.; Yang, C. G.; Qin, Z. H.] Chinese Acad Sci, Inst High Energy Phys, 19B Yuquan Rd, Beijing, Peoples R China.;[Li, Y. C.; Heng, Y. K.; Wang, Z. M.; Yang, A. B.; Chen, H. S.; Wang, Y. F.; Wu, D. R.; Zhang, H. Q.; Yang, C. G.; Qin, Z. H.] State Key Lab Particle Detect & Elect, 19B Yuquan Rd, Beijing, Peoples R China.;[Chen, H. S.] Key Lab Particle Astrophys, 19B Yuquan Rd, Beijing, Peoples R China.;[Luo, F. J.] Univ South China, Sch Nucl Sci & Technol, 28 Changsheng West Rd, Hengyang, Hunan, Peoples R China.
关键词：
Photon detectors for UV, visible and IR photons (vacuum) (photomultipliers, HPDs, others);Neutrino detectors;Detectors for UV, visible and IR photons
摘要：
JUNO is a 20-kton liquid scintillator detector aiming to determine the neutrino mass ordering, precisely measure the oscillation parameters, detect the astrophysical neutrinos and search for exotic physics. It is designed to reach an energy resolution of 3% at 1 MeV with the highest ever PMT coverage, using two types of 20" phototubes: MCP-PMT from NNVT and dynode-PMT from Hamamatsu. In this article, the gain and charge response of the MCP and dynode PMTs are investigated with the study of JUNO Central Detector prototype. The linearity of the MCP-PMT charge output is measured too to check the effect of a long tail on its charge spectrum.
作者机构：
[Guan, W.; Hu, J.; Xiong, X.] Univ South China, Sch Mech Engn, Hengyang 421001, Peoples R China.;[Long, H.] Xiangtan Univ, Sch Mat Sci & Engn, Xiangtan 411105, Peoples R China.
通讯机构：
[J. Hu] S;School of Mechanical Engineering, University of South China, Hengyang, 421001, China
关键词：
Solar cell;Long-term stability;Charge transport layer;Photovoltaic performance
摘要：
Organic/inorganic hybrid perovskite architectures have shown tremendous potential in the photovoltaic (PV) device community owing to the remarkable performance and concise solution-synthesized scheme. In the past decade, the perovskite solar cells (PSCs) achieved a significant improvement in the photo-voltaic performances from a modest 3.81% to the recently certified highest values surpassing 24%. Nevertheless, issues constraining long-term stability and large-scale production still hinder the commercialization process of PSCs. Carbon nanomaterials, scoping from carbon-based quantum dots (QDs) to the two-dimensional graphene materials, have been widely utilized in perovskite device structures to enhance both the efficiency and stability of PSCs due to their outstanding chemical, elec-trical, and mechanical characteristics. In particular, the water-resistance property of specific carbon nanomaterials has significantly prevented the degradation of various function layers through impeding ambient moisture ingress, subsequently improving the long-term stability for PSCs. All of those unique properties have made nanocarbon one of the most potential materials to construct excellent photovoltaic performance PSCs with long-term stability. In this review, we conducted a comprehensive overview of extraordinary and notable efforts in implementing different carbon materials into individual function layers of perovskite device structure to simultaneously enhance their device efficiency and operating stability. Finally, we outline the prospects with a perspective on facing challenges and research directions of utilizing carbon materials in efficient and stable PSCs. (C) 2021 Elsevier Ltd. All rights reserved.
摘要：
Low-grade uranium ore, which was challenging to be treated economically by conventional methods, can be treated by uranium leaching by bacteria. However, high uranium concentration will lead to the death of bacteria. This work researched the oxidative leaching performance of bacteria (Acidithiobacillus ferrivorans with uranium resistance) under different iron valence conditions. Oxidative leaching of UO2 by bacteria from energy substrates with varying states of the valence of iron ions was studied through an Acidithiobacillus ferrivorans oxidation model. The results showed that the probability of pyrite being oxidized by the Acidithiobacillus ferrivorans system was 98.05% under the condition of Fe2+, while it was 87.30% exposed to Fe3+. In addition, the leaching rate of UO2 by the Acidithiobacillus ferrivorans & Fe2+ system was 94.70%. Under the same conditions, while adding 1 g/L pyrite, the leaching rate of UO2 increased to 99.96%. This study revealed the oxidative leaching mechanism of UO2 and provided a new theoretical basis for the bacterial leaching of uranium.
期刊：
International Journal of Advanced Manufacturing Technology,2021年116(5-6):1691-1706 ISSN：0268-3768
通讯作者：
Li, F.;Liu, Z.
作者机构：
[Sun, Kaibo; Liu, Zhiwen; Li, Fazhi; Wang, Xi] Univ South China, Sch Mech Engn, Hengyang 421001, Peoples R China.;[Li, Shikang; Li, Luoxing] Hunan Univ, State Key Lab Adv Design & Manufacture Vehicle Bo, Changsha 410082, Peoples R China.
通讯机构：
[Zhiwen Liu; Fazhi Li] S;School of Mechanical Engineering, University of South China, Hengyang, China<&wdkj&>School of Mechanical Engineering, University of South China, Hengyang, China
摘要：
The structure type of porthole die has a crucial impact on metal flow balance in die cavities, strength of seam weld, and die strength. At present, there was little industrial case for the application of protection-type porthole die. In this study, a novel combined porthole die which includes protection, upper, and lower dies was designed to manufacture a multi-cavity and thin-walled profile. The plastic deformation behavior and flow velocity distribution of metal in die cavities were examined by numerical simulation. Seam weld strength and porthole die strength were quantitatively analyzed. In order to eliminate extrusion defects, multiple structure modifications for protection-type porthole die were proposed to balance metal flow and improve seam weld strength. Extrusion experiments were carried out on the horizontal extruder to validate the accuracy of numerical model and the rationality of modified dies. The research results showed that the relative velocity difference at die exit corresponding to the theoretical flow velocity for the designed die is at the range of −54.96 ~ 5.86 mm/s. The weld strength at the outer edges of profile is larger than that at the connecting edges of profile. The comprehensive effect of above factors that leads to an uneven front end, bending defect and seam weld cracking in extruded profile. After optimization, the relative exit velocity difference is decreased to at the range of −1.478 ~ 1.641 mm/s. The welding pressures on the concerned welding planes are obviously improved. The maximum stresses on the optimized porthole dies are both far less than the yield strength of H13 tool steel. The simulated front end shape for extruded profile agrees well with experimental one as well as the grain size and distribution on different observation positions are relatively uniform, which validate the rationality of design method for protection-type porthole die.
作者机构：
[Li, Xiao-Hua; Pan, Xiao; Liu, Hong-Ming; Zou, You-Tian] Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.;[Wu, Xi-Jun] Univ South China, Sch Math & Phys, Hengyang 421001, Peoples R China.;[He, Biao] Cent South Univ, Coll Phys & Elect, Changsha 410083, Peoples R China.;[Li, Xiao-Hua] Univ South China, Collaborat Nucl Energy & Nucl Safety, Natl Exemplary Base Int Sci & Tech, Hengyang 421001, Peoples R China.;[Li, Xiao-Hua] Univ South China, Cooperat Innovat Ctr Nucl Fuel Cycle Technol & Eq, Hengyang 421001, Peoples R China.
关键词：
half-lives;alpha decay;neptunium isotopes
摘要：
In the present work, we systematically study the alpha decay half-lives of neptunium (Z = 93) isotopes within a one-parameter model (OPM). The calculated results are in reasonable agreement with the experimental data. Noticeably, the recently measured alpha decay half-life value of 380(-110)(+260)ns for Np-222 [Phys. Rev. Lett. 125, 032 502 (2020)] has been fairly reproduced by the OPM as 780 ns within a factor of approximate to 2. In addition, we extend this model to predict alpha decay half-lives of neptunium isotopes whose alpha decay is energetically allowed or observed but not yet quantified in NUBASE2016. Meanwhile, it is found that the half-life between the neutron number N = 126 and N = 128 in Np drop sharply, this result shows that the N = 126 shell closure is still very robust at Z = 93. At last, alpha particle preformation probability P-alpha(extd) are extracted in two cases with alpha transition orbital angular momentum l = 0 and l = 1, we find a amazing phenomenon that the P-alpha(extd) are basically the same for alpha transition with the same orbital angular momentum l.
作者机构：
[Zhang, Zhen] Sun Yat Sen Univ, Sino French Inst Nucl Engn & Technol, Zhuhai 519082, Peoples R China.;[Liu, He; Zhang, Xiao-Min; Chu, Peng-Cheng] Qingdao Univ Technol, Res Ctr Theoret Phys, Sci Sch, Qingdao 266033, Peoples R China.;[Li, Xiao-Hua] Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.;[Li, Xiao-Hua] Univ South China, Cooperat Innovat Ctr Nucl Fuel Cycle Technol & Eq, Hengyang 421001, Peoples R China.
摘要：
We investigate the properties of the equation of state of strange-quark matter and u−d quark matter, the sound velocity of quark matter, the stability region for star matter, the maximum mass of quark stars (QSs), and the tidal deformability for QSs by using a quark quasiparticle model. Our results indicate that the recently discovered heavy compact stars PSR J0348+ 0432 , MSR J0740+6620 , and PSR J2215+5135 , and especially the GW190814s secondary component m2 can be well described as QSs within the quasiparticle model.
通讯机构：
[Haibo Liu] H;Hunan Vanguard Group Corporation Limited, Changsha 410100, PR China<&wdkj&>Hunan Provincial Key Laboratory of Health Maintenance for Mechanical Equipment, Hunan University of Science and Technology, Xiangtan 411201, PR China
摘要：
In the response analysis of uncertain structural models with limited information, probability-boxes can be effectively employed to address the aleatory and epistemic uncertainty together. This paper presents a copula-based uncertainty propagation method which can accurately perform uncertainty propagation analysis with correlated parametric probability-boxes. Firstly, the parameter estimation and Akaike information criterion analysis are utilized to select an optimal copula based on available samples, by which the joint cumulative distribution function is constructed for the correlated input variables. Then, using the obtained joint cumulative distribution function, the correlated parametric probability-boxes are transformed into independent normal variables, and an efficient method based on sparse grid numerical integration is proposed to calculate the bounds on statistical moments of a response function. Finally, numerical examples and an engineering application are provided to verify the effectiveness of the presented method. (C) 2021 Elsevier Inc. All rights reserved.
作者机构：
[Yi, Jie; Zeng, Wen-qi] Hunan Ind Polytech, Sch Mech Engn, Changsha 410208, Peoples R China.;[Liu, Zhi-wen] Univ South China, Sch Mech Engn, Hengyang 421001, Peoples R China.
关键词：
isothermal control;extrusion speed curve;porthole die extrusion;PID control;heat balance
摘要：
The isothermal extrusion process of hollow aluminium profile was investigated using incremental proportional-integral-derivative (PID) control algorithm and finite element simulations. The range of extrusion speed was determined by considering the maximum extrusion load and production efficiency. By taking the optimal solution temperature of the secondary phase as the target temperature, the extrusion speed-stroke curve for realizing the isothermal extrusion of the aluminium profile was obtained. Results show that in the traditional constant extrusion speed process, the average temperature of the cross-section of the aluminium profile at the die exit rapidly increases and then slowly rises with the increase in ram displacement. As the extrusion speed increases, the temperature difference at the die exit of the profile along the extrusion direction increases. The exit temperature difference between the front and back ends of the extrudate along the extrusion direction obtained by adopting isothermal extrusion is about 6.9 degrees C. Furthermore, the heat generated by plastic deformation and friction during extrusion is balanced with the heat transfer from the workpiece to the container, porthole die and external environment.
摘要：
We report on an electro-optically Q-switched Tb:LiYF4 green laser pumped by a frequency-doubled optically pumped semiconductor blue laser. The electro-optically Q-switched characteristics were studied under a wide range of repetition rates from 200 Hz to 50 kHz using a KD2PO4 Q-switch. Up to 198 mu J of pulse energy was obtained with a pulse width of 248 ns at a repetition rate of 200 Hz, corresponding to a peak power of 797 W at 544 nm. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
摘要：
Small Modular Reactors (SMRs) are attracting wide attention due to their outstanding performance, extensive studies have been carried out for lead-based fast reactors (LFRs) that cooled with Lead or Lead-bismuth (LBE), and small modular natural circulation LFR is one of the promising candidates for SMRs and LFRs development. One of the challenges for the design small modular natural circulation LFR is to master the natural circulation thermal-hydraulic performance in the reactor primary circuit, while the natural circulation characteristics is a coupled thermal-hydraulic problem of the core thermal power, the primary loop layout and the operating state of secondary cooling system etc. Thus, accurate predicting the natural circulation LFRs thermal-hydraulic features are highly required for conducting reactor operating condition evaluate and Thermal hydraulic design optimization. In this study, a thermal-hydraulic analysis code is developed for small modular natural circulation LFRs, which is based on several mathematical models for natural circulation originally. A small modular natural circulation LBE cooled fast reactor named URANUS developed by Korea is chosen to assess the code's capability. Comparisons are performed to demonstrate the accuracy of the code by the calculation results of MARS, and the key thermal-hydraulic parameters agree fairly well with the MARS ones. As a typical application case, steady-state analyses were conducted to have an assessment of thermal-hydraulic behavior under nominal condition, and several parameters affecting natural circulation were evaluated. What's more, two characteristics parameters that used to analyze natural circulation LFRs natural circulation capacity were established. The analyses show that the core thermal power, thermal center difference and flow resistance is the main factors affecting the reactor natural circulation. Improving the core thermal power, increasing the thermal center difference and decreasing the flow resistance can significantly increase the reactor mass flow rate. Characteristics parameters can be used to quickly evaluate the natural circulation capacity of natural circulation LFR under normal operating conditions.
摘要：
This study demonstrates a simple hydrothermal method while can be generalized for controllable synthesis of noble metallic carbonaceous nanostructures (e.g., Au@C, Ag@C) under mild conditions (180-200 degrees C), which also provides a unique approach for fabricating hollow carbonaceous structures by removal of cores (e.g., silver) via a redox etching process. The microstructure and composition of the as-achieved nanoparticles have been characterized using various microscopic and spectroscopic techniques. Cetyltrimethylammonium bromide (CTAB), serving as a surfactant in the reaction system, plays a key role in the formation of Ag@C, Au@C nanocables, and their corresponding hollow carbonaceous nanotubes in this work. The dynamic growth and formation mechanism of carbonaceous nanostructures was discussed in detail. And finally, laser-induced photothermal property of Au@C nanocomposites was examined. The results may be useful for designing and constructing carbonaceous metal(s) or metal oxide(s) nanostructures with potential applications in the areas of electrochemical catalysis, energy storage, adsorbents, and biomedicine. This study demonstrate a facile hydrothermal synthesis of noble metal carbonaceous nanocomposites (e.g., Au@C) with simple procedures under mild conditions, which can be25expanded as a general method for preparing diverse carbonaceous core-shell nanoparticles. The Au@C carbonaceous nanostructures exhibit interesting UV-Vis properties dependent upon shell thickness.
摘要：
The process of changing the attachment of a demolition robot is a complex operation and requires a high docking accuracy, so it is hard for operators to control this process remotely through the camera’s perspective. To solve this problem, this paper studies trajectory planning for changing a demolition robot attachment. This paper establishes a link parameter model of the demolition robot; the position and attitude of the attachment are obtained through a camera, the optimal docking point is calculated to minimize the distance error during angle alignment for attachment change, the inverse kinemics of the demolition robot are solved, the trajectory planning algorithm and visualization program are programmed, and then the trajectory planning for the demolition robot attachment changing method is proposed. The results of calculations and experiments show that the method in this paper can meet the accuracy, efficiency, and safety requirements of demolition robot attachment changing, and it has promising application prospects in the decommissioning and dismantling of nuclear facilities and other radioactive environments.
关键词：
High temperature oxidation;Cr-coated Zr-4;Al-coated Zr-4;Diffusion layer;Accident tolerant fuel
摘要：
Y Cr and Al coating were respectively deposited on Zr-4 alloy by magnetron sputtering and high temperature oxidation (HTO) tests were conducted in air environment at 1200 degrees C for 3 h for Cr-coated and Al-coated specimens. The morphology and phase composition of the specimens were detected by SEM, EDS and XRD. The adhesion properties were characterized by scratch test. The XRD results revealed that the two coatings were crystalline with preferred orientation. The results of scratch testing showed that critical load of Cr coating was higher than that of Al coating. After HTO test, the Cr-coated specimen was intact without cracking and spalling off, only the outermost layer of Cr coating was oxidized to a Cr2O3 layer of about 4 mu m thick with a residual Cr layer of about 4 mu m thick, and the internal zirconium alloy was not oxidized. For Al-coated specimen, besides the complete oxidation of the Al coating, there were also about 500 mu m Zr-4 alloy oxidized on each side, and there were a lot of voids and cracks in the specimen. The EDS results indicated that a thickness of about 5 mu m Cr-Zr diffusion layer developed at the interface between Cr coating and Zr-4 alloy for the Cr-coated Zr-4 specimen. While, for the Al-coated Zr-4 specimen, Al diffused into the specimen to a depth of about 100 mu m, and Zr diffused almost to the outermost layer. Moreover, Sn in the Zr-4 alloy is concentrated at the interface between the residual Zr-4 alloy and ZrO2 layer. The obtained results manifested that Cr coating shows better oxidation resistance than Al coating.
