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The Application of Permanent Magnet Synchronous Motor with Small Electrical Time Constant in Fiber Positioner

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Research in Astronomy and Astrophysics 2024年第1期24卷 212-222页

作者： Shaoxiong guo Yan Yang Yanbin Yin Yihu Tang Yang Tian Chao Zhai Department of Precision Machinery and Precision Instrumentation University of Science and Technology of ChinaHefei 230026China School of Biomedical Engineering Division of Life Sciences and MedicineUniversity of Science and Technology of ChinaHefei 230026China Experiment Center of Engineering and Material Science University of Science and Technology of ChinaHefei 230026China

With the development of cutting-edge multi-object spectrographs,fiber positioners located in the focal plane are being scaled down in size,and miniature hollow-cup Permanent Magnet motors are now being considered as a suitable replacement for Faulhaber Precistep stepper ***,the small electrical time constant of such coreless motors poses a challenge,as the problem of severe commutation torque ripple in a fiber positioner running a position loop has been *** overcome this challenge,it is advised to increase the Pulse Width Modulation(PWM)frequency as much as possible to mitigate the effects of the current *** must be done while ensuring adequate resolution of the PWM *** employing a voltage open-loop field-oriented control based on a modulation frequency of 1 MHz,the drive current only costs 25 m A under a 3.3 V power *** sine degree of phase current is immaculate,and the repeat positioning accuracy can reach 2μ***,it is possible to further shrink the bill of devices and the layout area of the Printed Circuit Board,especially in sizesensitive *** device has been developed under the new generation of The Large Sky Area MultiObject Fiber Spectroscopic Telescope.

关键词： instrumentation:adaptive optics instrumentation:spectrographs proper motions reference systems

Design and analyses of open-ended pipe piles in cohesionless soils

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Frontiers of Structural and Civil Engineering 2016年第1期10卷 22-29页

作者： Yuan guo Xiong (bill) YU Department of Civil Engineering Case Western Reserve University 2104 Adelbert Road Bingham 260 Cleveland OH 44106-7201USA

Large open-ended pipe pile has been found to be advantageous for use in transportation projects. The current design method, however, is not adequately developed. To close this practice gap, this paper first summarized different design methods for open-ended pipe piles in sandy soils. A major factor for all the design codes is to properly account for the formation and effects of soil plug. The comparison indicates that there is a large variation in the base capacity evaluation among different methods due to the complex behaviors of soil plug. To close the knowledge gap, discrete element method （DEM） was used to simulate the soil plugging process and provide insight on the plugging mechanism. The simulation results show that the arching effect significantly increases the internal unit shear resistance along pipe piles. The porosity distribution and particle contact force distribution from DEM model indicate a large stress concentration occurs at the bottom of the soil plug. Besides, nearly 90% of the plug resistance is provided by the bottom half portion of the soil column. The soil-pile friction coefficient has a significant effect on the magnitude of plug resistance, with the major transition occurred for friction coefficient between 0.3 and 0.4.

关键词： open-ended pipe pile soil plug DEM base capacity

Influence of particle shape on the erodibility of non-cohesive soil： Insights from coupled CFD-DEM simulations

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Particuology 2018年第4期16卷 12-24页

作者： Yuan guo Yang Yang Xiong (bill) Yu Department of Civil Engineering Case Western Reserve University 2104 Adelbert Road Bingharn 269 Cleveland OH 44106-7201 USA Department of Electrical Engineering and Computer Science Case Western Reserve University 2104 Adelbert Road Bingharn 203D Cleveland OH 44106-7201 USA Departrnent of Civil Engineering Case Western Reserve University 2104 Adelbert Road Bingharn 206 Cleveland OH 44106- 7201 USA

Soil erosion is a critical process that is being studied in soil science, hydraulic engineering, and geotech- nical engineering. Among many societal and environmental impacts, soil erosion is a major cause for the failures of bridges. The erodibility of soil is determined by its physical and geochemical properties and is also affected by surrounding biological activities. In most of the current models for soil erosion, erodibility of non-cohesive soil is characterized by its median grain size （Dso）, density, and porosity. The contribution to erodibility of the irregular shape of soil grains, which plays an important role in the mechanical and hydraulic properties of coarse-grained soils, is generally ignored. In this paper, a coupled computational fluid dynamics and discrete element method model is developed to analyze the influence of the shape of sand grain on soil erodibility. A numerical model for the drag force on spherical and non-spherical particles is verified by using the results from physical free settling experiments. Erosion of sand grains of different shapes is simulated in a virtual erosion function apparatus, a laboratory device used to mea- sure soil erodibility. The simulation results indicate that the grain shape has major effects on erodibility. Spherical particles do not show a critical velocity because of their low rolling resistance, but a critical velocity does exist for angular particles owing to grain interlocking. The erosion rate is proportional to the flow velocity for both spherical and non-spherical particles. The simulation result for angular particle erosion is fairly consistent with the experimental observations, implying that grain shape is an important factor affecting the erodibility of non-cohesive soils.

关键词： CFD-DEM Soil erosion Grain shape Erodibility of coarse-grained soil Erosion function apparatus mode

A holistic computational model for prediction of clay suspension structure

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International Journal of Sediment Research 2019年第4期34卷 345-354页

作者： Yuan guo Xiong (bill) Yu Department of Civil Engineering Case Western Reserve University

The formation of clay suspensions involves complex interactions among clay particles subjected to the geochemical environment during the sedimentation process. The structural characteristics have a major influence on the physical and mechanical behavior of the suspension. A modeling framework involving a Discrete Element Method(DEM) model with customized particle mechanical interactions is proposed in this paper for the holistic prediction of the physical structure of clay suspensions. The particle interaction force model is based on the Derjaguin, Landau, Verwey, and Overbeek(DLVO) theory that accounts for electrostatic repulsion, van der Waals attraction, contact repulsion, etc. Kaolinite is used as the model clay to demonstrate the model performance. The surface charge density of kaolinite is obtained through Atomic Force Microscope(AFM) force measurement and is implemented in the particle interaction force model in the subsequent simulations. Influencing factors, such as centrifugal acceleration, ionic concentration, platy structure of particles, and particle size, on the formation of kaolinite suspensions are studied with the numerical model and compare favorably well with the experimental data. This work lays down a unique framework consisting of computational modeling and microscale characterization of clay particles to holistically predict the characteristics of clay suspensions, which paves the basis to model and predict their bulk physical and mechanical behavior.

关键词： Clay suspension Discrete element method DLVO theory Atomic force microscope Kaolinite Surface potential

Understanding the microscopic moisture migration in pore space using DEM simulation

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Journal of Rock Mechanics and Geotechnical Engineering 2015年第2期7卷 171-177页

作者： Yuan guo Xiong(bill) Yu Department of Civil Engineering Case Western Reserve University

The deformation of soil skeleton and migration of pore fluid are the major factors relevant to the triggeringof and damages by liquefaction. The influence of pore fluid migration during earthquake has beendemonstrated from recent model experiments and field case studies. Most of the current liquefactionassessment models are based on testing of isotropic liquefiable materials. However the recent NewZealand earthquake shows much severer damages than those predicted by existing models. A fundamentalcause has been contributed to the embedded layers of low permeability silts. The existence ofthese silt layers inhibits water migration under seismic loads, which accelerated liquefaction and causeda much larger settlement than that predicted by existing theories. This study intends to understand theprocess of moisture migration in the pore space of sand using discrete element method （DEM） *** were conducted on consolidated undrained triaxial testing of sand where a cylindersample of sand was built and subjected to a constant confining pressure and axial loading. The porositydistribution was monitored during the axial loading process. The spatial distribution of porosity changewas determined, which had a direct relationship with the distribution of excess pore water pressure. Thenon-uniform distribution of excess pore water pressure causes moisture migration. From this, themigration of pore water during the loading process can be estimated. The results of DEM simulationshow a few important observations：（1） External forces are mainly carried and transmitted by the particlechains of the soil sample; （2） Porosity distribution during loading is not uniform due to nonhomogeneoussoil fabric （i.e. the initial particle arrangement and existence of particle chains）; （3）Excess pore water pressure develops differently at different loading stages. At the early stage of loading,zones with a high initial porosity feature higher porosity changes under the influence of e

关键词： Moisture migration Consolidated undrained triaxial test Particle chains Porosity distribution Pore water pressure

1963年伯明翰运动与肯尼迪政府民权法案的出台

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史学集刊 2024年第4期 126-144页

作者：谢国荣华东师范大学历史学系上海200241

自1960年入座运动开展以来,美国民权运动在直接行动阶段取得了一系列丰硕成果,但这种非暴力斗争在奥尔巴尼运动中却遭到重大挫败。为避免重蹈覆辙并防止民权运动进入“冷却期”,马丁·路德·金和南方基督教领导大会周密筹划,特意选择在... 详细信息

自1960年入座运动开展以来,美国民权运动在直接行动阶段取得了一系列丰硕成果,但这种非暴力斗争在奥尔巴尼运动中却遭到重大挫败。为避免重蹈覆辙并防止民权运动进入“冷却期”,马丁·路德·金和南方基督教领导大会周密筹划,特意选择在种族隔离十分严重且容易激起种族暴力的伯明翰市开展民权运动。金不仅公开发表《伯明翰狱中来信》,而且把黑人学童带到民权运动的现场。伯明翰运动促使美国民权运动走向激进化。伯明翰警察局长康纳下令用高压水龙头和警犬对付非暴力的示威民众,甚至连黑人学童亦不例外。这一幕给美国的国家形象、声誉和外交造成巨大伤害,威胁到美国在冷战中对20世纪60年代大量新兴的非洲独立国家的争夺。伯明翰运动唤起了美国社会具有同情心和正义感的白人民众的支持,而且迫使肯尼迪政府从冷战成败的高度出台了民权法案。美国民权运动由此进入民权立法的黄金时代。

关键词：非暴力斗争伯明翰运动《伯明翰狱中来信》冷战民权法案

供应链关联与中小企业融资——基于供应链金融与商业信用视角

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经济学（季刊） 2024年第4期24卷 1173-1190页

作者：郭晔姚若琪厦门大学经济学院厦门大学大数据金融交叉实验室中南大学商学院

利用改进的企业名称匹配方法,本文发现供应链关联可以通过增信效应和供应链金融改善中小企业融资。具体而言,受上市公司增信的应收账款将提高上游中小企业保理和票据贴现的能力,但所获得的部分资金将被上市公司通过商业信用的方式吸收... 详细信息

利用改进的企业名称匹配方法,本文发现供应链关联可以通过增信效应和供应链金融改善中小企业融资。具体而言,受上市公司增信的应收账款将提高上游中小企业保理和票据贴现的能力,但所获得的部分资金将被上市公司通过商业信用的方式吸收。此外,当中小企业的市场力量更强时,将提供更少的商业信用并获得更多的融资,此时中小企业资金从总量和结构上都将得到优化。本文为引导供应链金融充分发挥“稳链固链”作用,提供了经验启示。

关键词：供应链金融商业信用中小企业融资

运用STOMP数值模拟器进行多空介质中尿素水解以及方解石沉淀数值模拟(英文)

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地学前缘 2010年第6期17卷 117-133页

作者：郭娈靖 bill X.Hu Idaho National Laboratory Idaho Falls China University of Geosciences(Beijing) Florida State University Tallahassee

遍布于美国能源部所辖野外场地的地下放射性核素和痕量金属污染对美国能源部的长期监管职能提出了最严峻的挑战。目前较有前景的一个原地固化污染物方法是利用尿素酶催化尿素水解,进而推动方解石沉淀及与之共同沉淀。运用STOMP数值模拟... 详细信息

遍布于美国能源部所辖野外场地的地下放射性核素和痕量金属污染对美国能源部的长期监管职能提出了最严峻的挑战。目前较有前景的一个原地固化污染物方法是利用尿素酶催化尿素水解,进而推动方解石沉淀及与之共同沉淀。运用STOMP数值模拟器实施一系列反应性溶质数值模拟来研究系统中水流、运移、反应与反应导致的介质性质变化之间的紧密的非线性耦合,并在研究中系统性增加反应系统的复杂度和物理-化学的非均质性以考察模拟效果。通过调整反应速率表达式中尿素酶浓度和沉淀反应常数,对尿素水解和方解石沉淀速率进行了敏感度分析。结果显示:尿素水解速率是矿物沉淀总量的决定性因素,沉淀物的空间分布既取决于水解速率也取决于沉淀速率;在一维水流柱6个空隙体积的时间段模拟中,观察到了5%的最大空隙度减少;当二维模拟中考虑一个低渗透性包裹体时,被改变的流场重新对生成的沉淀组成物进行了分布,形成了扭曲的反应锋面。模拟结果也显示沉淀在低渗透性区域边界上形成,这说明位于这个区域里面的污染物可能被囊裹而从流线中被隔离起来。

关键词：数值模拟原地污染治理尿素水解方解石沉淀 STOMP

欧盟碳边境调节机制的探析及其对中国的影响和应对

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中国标准化 2024年第3期 241-245页

作者：付国印陈晓丽广东外语外贸大学南国商学院广东贸促国际商事认证中心中国科学院广州能源研究所

欧盟碳边境调节机制(CBAM)本质上是一种新型的技术性贸易壁垒,是欧盟针对部分进口商品的碳排放向企业征收税费,该法案的实施有助于欧盟恢复经济并抢占全球气候治理的话语权及“碳排放”权的定价权,防止欧盟内部企业向排放成本更低的国... 详细信息

欧盟碳边境调节机制(CBAM)本质上是一种新型的技术性贸易壁垒,是欧盟针对部分进口商品的碳排放向企业征收税费,该法案的实施有助于欧盟恢复经济并抢占全球气候治理的话语权及“碳排放”权的定价权,防止欧盟内部企业向排放成本更低的国家进行转移,从而避免“碳泄露”。文章阐述了CBAM出台的背景、进展及意义,对CBAM实施可能对我国相关产业产生不同程度影响进行分析,建议应紧抓挑战和机遇,构建企业欧盟碳关税信息披露相关技术指南,推进可再生能源和碳交易市场机制建设。

关键词：碳边境调节机制欧盟碳关税碳泄露气候政策

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