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Development of readout electronics for bunch arrival-time monitor system at SXFEL

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Nuclear Science and Techniques 2019年第5期30卷 113-121页

作者： jin-Guo Wang bo Liu Shanghai Institute of Applied Physics Chinese Academy of Science University of the Chinese Academy of Science

A bunch arrival-time monitor(BAM) system,based on electro-optical intensity modulation scheme, is under study at Shanghai Soft X-ray Free Electron *** aim of the study is to achieve high-precision time measurement for minimizing bunch fluctuations. A readout electronics is developed to fulfill the requirements of the BAM system. The readout electronics is mainly composed of a signal conditioning circuit, field-programmable gate array(FPGA), mezzanine card(FMC150), and powerful FPGA carrier board. The signal conditioning circuit converts the laser pulses into electrical pulse signals using a photodiode. Thereafter, it performs splitting and low-noise amplification to achieve the best voltage sampling performance of the dual-channel analog-to-digital converter(ADC) in FMC150. The FMC150 ADC daughter card includes a 14-bit 250 Msps dual-channel high-speed ADC,a clock configuration, and a management module. The powerful FPGA carrier board is a commercial high-performance Xilinx Kintex-7 FPGA evaluation board. To achieve clock and data alignment for ADC data capture at a high sampling rate, we used ISERDES, IDELAY, and dedicated carry-in resources in the Kintex-7 FPGA. This paper presents a detailed development of the readout electronics in the BAM system and its performance.

关键词： Bunch arrival-time monitor (BAM) Shanghai Soft X-ray Free Electron Laser (SXFEL) Fieldprogrammable gate array (FPGA) Signal conditioning High-speed analog-to-digital converter (ADC)

Classification of Positive Solutions to a Divergent Equation on the Upper Half Space

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Acta Mathematica Sinica,English Series 2022年第3期38卷 499-509页

作者： jin Ge YAO jing bo DOU School of Mathematics and Statistics Shaanxi Normal UniversityXi’an710119P.R.China

In this paper we classify the positive solutions of the divergent equation with Neumann boundary on the upper half space{-div(t^(α)∇u)=t^(β)f(u),(y,t)∈R^(n+1)_(+),lim t→0^(+)t^(α)■u/■t=0 by the method of moving spheres and Kelvin transformations,where n≥1,α>0,β>−1,n−1/n+1β≤αbolev inequality involving divergent operator div(t^(α)∇u)on the upper half space.

关键词： Divergent operator Liouville theorem Neumann boundary method of moving spheres Kelvin transformation

Forced Decadal Changes in Summer Precipitation Characteristics over China:The Roles of Greenhouse Gases and Anthropogenic Aerosols

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Journal of Meteorological Research 2020年第6期34卷 1226-1241页

作者： bo ZHANG Buwen DONG Ronghua jin National Meteorological Center China Meteorological AdministrationBeijing 100081China National Centre for Atmospheric Science-Climate Department of MeteorologyUniversity of ReadingReading RG66URUK

We investigated the decadal changes in the different types of summer mean precipitation over China across the mid-1990 s based on observational *** spatial variations in the observed decadal changes were estimated by comparing the present day(PD)time period of 1994–2011 with an earlier period of 1964–*** summer total precipitation increased in southern China and decreased in northern China from the early period to the *** increases of precipitation in southern China were due to increases in the frequency of heavy and moderate rainfall,whereas the decreases over northern China were mainly due to decreases in the frequency of moderate and light *** on a set of numerical experiments using an atmospheric general circulation model coupled with a multilevel mixed-layer ocean model,we found that the increase of precipitation frequency forced by greenhouse gases is the main reason of increasing precipitation over southern and northeastern China,while the decrease of frequency caused by anthropogenic aerosol(AA)induces the decreasing precipitation over northern *** water vapor flux convergence and water vapor flux strengthen in southern China and northeastern China by anthropogenic greenhouse *** distribution is also conducive to precipitation in most of southern China and northeastern *** the control of weakened southwesterly winds and 850-h Pa divergence,precipitation decreases over northern and southwestern China by AA.

关键词： decadal changes in precipitation frequency and intensity numerical experiments China

CFD simulation of bubbly turbulent Tayor–Couette flow

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Chinese Journal of Chemical Engineering 2016年第6期24卷 719-727页

作者： Xi gao bo Kong R.Dennis Vigil Department of Chemical & Biological Engineering 2114 Sweeney Hall Iowa State University

Bubbly gas-liquid Taylor-Couette vortex flow has been the subject of several recent investigations both because of interest in bubble-induced drag reduction and because such devices have potential applications to a variety of chemical and biochemical processing problems. In order to quantitatively describe the hydrodynamics of highly turbulent two phase Taylor-Couette flow, a rigorous two-fluid computational fluid dynamics （CFD） model was developed and compared with previously published experimental data. This model includes a comprehensive description of the constitutive closure for inter-phase forces and turbulence was simulated using both the k- and k-to models. In addition, the mechanism by which the dispersed fluid attains a non-uniform radial and axial distribution is analyzed and the relative importance of various interphase forces is discussed. Lastly the model was validated by comparison of simulation predictions with experimental data, and it is shown that the CFD model correctly predicts phase velocity, velocity fluctuation, and gas distribution, and may provide guidance for reactor design and scale-up.

关键词： Taylor-Couette flowTwo-phase flowBubbleCFD

Nonequilibrium molecular dynamics for accelerated computation of ion–ion correlated conductivity beyond Nernst–Einstein limitation

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npj Computational Materials 2023年第1期9卷 1796-1803页

作者： Ryoma Sasaki bo gao Taro Hitosugi Yoshitaka Tateyama School of Materials and Chemical Technology Tokyo Institute of Technology2-12-1 OokayamaMeguroTokyo 152-8552Japan Center for Green Research on Energy and Environmental Materials National Institute for Material Science1-1 NamikiTsukubaIbaraki 305-0044Japan Department of Chemistry The University of Tokyo7-3-1 HongoBunkyoTokyo 113-0033Japan

Condensed matters with high ionic conductivities are crucial in various solid devices such as solid-state batteries. The conduction ischaracterized by the cooperative ionic motion associated with the high carrier density. However, the high cost of computingcorrelated ionic conductivities has forced almost all ab initio molecular dynamics (MD) to rely on the Nernst–Einstein dilute-solutionapproximation, which ignores the cross-correlation effect. Here we develop a chemical color-diffusion nonequilibrium MD (CCD-NEMD) method, which enables to calculate the correlated conductivities with fewer sampling steps than the conventional MD. ThisCCD-NEMD is demonstrated to well evaluate the conductivities in the representative solid electrolyte bulk Li10GeP2S12 andLi_(7)La_(3)Zr_(2)O_(12). We also applied CCD-NEMD to the grain boundary of Li_(7)La_(3)Zr_(2)O_(12) and demonstrated its applicability for calculatinginterfacial local conductivities, which is essential for investigating grain boundaries and composite electrolytes. CCD-NEMD canprovide further accurate understanding of ionics with ionic correlations and promote developing solid devices.

关键词： dynamics Nernst steps

Influence of laser scanning speed on Cu-Zr-Al composite coatings on Mg alloys

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International Journal of Minerals,Metallurgy and Materials 2013年第6期20卷 568-573页

作者： Ya-li gao Meng Jie Hai-bo Zhang School of Mechanical Engineering Northeast Dianli University School of Mechanical and Electrical Engineering Jilin Institute of Chemical Technology

To improve the surface properties of magnesium alloys, a study was conducted on Cu-Zr-A1 composite coatings on AZ91HP magnesium alloy by laser cladding. The influence of laser scanning speed on the microstructures and properties of the coatings was discussed. The coatings consist of amorphous phase, CusZr3, and Cul0ZrT. With the increase of laser scanning speed, the amorphous phase content of the coatings increases and reaches 60.56wt% with the laser scanning speed of 2.0 m/min. Because of the influence of laser scanning speed on the amorphous and crystal phases, the coatings show the maximum elastic modulus, hardness, and wear resistance at the laser scanning speed of 1.0 m/min. At the laser scanning speed of 2.0 m/min, the coatings have the best corrosion resistance.

关键词： magnesium alloys composite coatings amorphous laser cladding speed

Friction and Wear Study on Friction Pairs with a Biomimetic Non-smooth Surface of 316L Relative to CF/PEEK under a Seawater Lubricated Condition

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Chinese Journal of Mechanical Engineering 2019年第4期32卷 47-60页

作者： Yingna Liang Dianrong gao bo Chen Jianhua Zhao School of Mechanical Engineering Yanshan University Qinhuangdao 066004China Liren College Yanshan University Qinhuangdao 066004 China Heibei Provincial Key Laboratory of Heavy Machinery Fluid Power Transmission and Control Yanshan University Qinhuangdao 066004 China

Current studies of a seawater axial piston pump mainly solve the problems of corrosion and wear in a slipper pair by selecting materials with corrosion resistance, self-lubrication, and wear resistance. In addition, an appropriate biomimetic non-smooth surface design for the slipper pair can further improve the tribological behavior. In this paper, 316 L stainless steel and CF/PEEK were selected to process the upper and bottom specimens, and the biomimetic non-smooth surface was introduced into the interface between the friction pair. The friction and wear tests were performed on a MMD-5 A tester at a rotation speed of 1000 r/min and load of 200 N under seawater lubricated condition. The results indicate that the main friction form of the smooth surface friction pair corresponds to abrasive wear and adhesive wear and that it exhibits a friction coe cient of 0.05–0.07, a specimen temperature of 56 ℃, a high wear rate, and surface roughness. Pits on the non-smooth surface friction pairs produced hydrodynamic lubrication and reduced abrasive wear, and thus the plowing e ect is their main friction form. The non-smooth surface friction pairs exhibit a friction coe cient of 0.03–0.04, a specimen temperature of 48 ℃, a low wear rate, and surface roughness. The study has important theoretical significance for enriching the lubrication, friction, and wear theory of a seawater axial piston pump, and economic significance and military significance for promoting the marine development and the national defense military.

关键词： Biomimetic non-smooth surface 316L CF/PEEK Seawater lubrication Friction and wear

Experimental Study on Influence of Dimples on Lubrication Performance of Glass Fiber-epoxy Resin Composite under Natural Seawater Lubrication

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Chinese Journal of Mechanical Engineering 2017年第1期30卷 110-117页

作者： WU Shaofeng gao Dianrong LIANG Yingna CHEN bo School of Mechanical Engineering Yanshan UniversityQinhuangdao 066004China Heibei Provincial Key Laboratory of Heavy Machinery Fluid Power Transmission and Control Yanshan UniversityQinhuangdao 066004China Liren College Yanshan UniversityQinhuangdao 066004China

Bionic non-smooth surface is widely applied in metal and ceramics materials. In order to introduce this technology to high pressure seawater pump, the influence of bionic non-smooth surface on the engineering plastics used in pump should be investigated. The comparative tests are carried out with a ring-on-disc configuration under 800, 1000, 1200 and 1400 r/min in order to research the influence of the bionic non-smooth surface on glass fiber-epoxy resin composite（GF/EPR） under natural seawater lubrication. The disc surfaces are textured with five kinds of pits, which are semi-spherical, conical, cone-cylinder combined, cylindrical pits and through holes, respectively. A smooth surface is tested as reference. The results show that the lubrication performance of dimpled GF/EPR sample is much better than that of the smooth sample under all rotational speeds. The semi-spherical pits surface has more obvious friction reduction than the others, which shows that the least reduction is approximately 43.29% of smooth surface under 1200 r/rain. However, the wear level is only marginally influenced by dimples. The surface morphology investigations disclose severe modifications caused by abrasive wear primarily. The results are helpful to vary friction properties of GF/EPR by non-smooth surface, or provide references to the design of non-smooth surfaces under certain condition.

关键词： !bionic non-smooth surface seawater lubrication friction coefficient glass fiber-epoxy resin composite stainless steel 316L

Experiment and Numerical Simulation of Free Water Jet by a Central-body Nozzle

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Chinese Journal of Mechanical Engineering 2010年第6期23卷 797-804页

作者： YANG Minguan ZHANG Feng KANG Can gao bo School of Energy and Power Engineering Jiangsu University Zhenjiang 212013 China

The recent research about cavitation jet mainly focuses on the organ-pipe nozzle and triangular nozzle. The research content mainly includes the optimized design about the structure of nozzles, the observation and flow analysis about the cavitation jet in the water, and the theory of rock attacked by the cavitation jet, while the energy characteristic of the free jet is not studied yet. In China, the research about the central-body nozzle is almost empty. For the purpose of studying the energy characteristic and the structure of free water jet discharged from central-body nozzle, an experiment with phase Doppler particle anemometry（PDPA） technology is carried out to measure the free water jet flow, which is produced by a central-body nozzle under the jet pressure of 15 MPa. While five sections with different axial distances from the nozzle outlet are selected for data process and analysis, the axial and radial velocity and the droplets of the particle size are studied. Meanwhile, numerical calculation of corresponding flow field is conducted by using volume of fluid（VOF） multiphase model, and the jet flow feature is discussed. The experimental and calculating results show that the axial velocity of high speed jet flow dissipates slowly in the air, and the core area and diffused area are discovered. The diameter of droplet in the core area is small, and jet energy is concentrated, while in the diffusion area, water is mingled with ambient air and radial velocity is relatively large. Obvious low-pressure area exists behind the central body and potential cavitation may occur in that area. The proposed research reveals the energy characteristic of free jet discharged from central-body nozzle, provides the theoretical basis for preestimating erosion feature of the central-body nozzle and also the theoretical foundation for revealing the mechanism of erosion.

关键词： central-body nozzle free water jet phase Doppler particle anemometry(PDPA) energy characteristic VOF model