ACCURATE MEASUREMENT OF ROTARY MACHINE AXIS CENTER TRACE

Four methods aiming at measuring rotary machine axis center trace arediscussed in detail. The comparative analysis is made on some aspects such as measurement accuracy,on-machine characteristics, feasibility, practical operation convenience and the integrity ofmeasurement information. In order to simplify measurement, the axis profile error is ignored intraditional condition, while the measurement accuracy will be reduced. The 3-point method that theaxis profile error is firstly separated has better real time character, at the same time, not onlythe axis motion error but also the axis profile error can be measured. All of those information canbe used to diagnose the fault origin. The analysis result is proved to be correct by the experiment.

Sustainable Development and Transition of Traditional Retailing Centers in Beijing from Consumers' Perspective

Based on the consumer questionnaires of the three traditional retailing centers,Qianmen,Wangfujing and Xidan in Beijing,this article analyzes the present features of consumer composition in the three retailing centers.What is more,the evolution course and function transition of traditional retailing centers is revealed based on the changing of consumer composition in different times.Lastly,the renewal method and development trends of traditional retailing centers are discussed based on the evaluation results in consumers'perspective.

High-Precision Nonsingular Integrator of Guiding-Center Orbit Close to Magnetic Axis in Tokamak Equilibrium Configuration

Equations of guiding-center motion without the coordinate singularity at the magnetic axis have been derived from the guiding-center Lagrangian.The poloidal magnetic flux is suggested to be included as one of the nonsingular coordinates for the computation of the guidingcenter orbit.The numerical results based on different nonsingular coordinates are verified using the GCM code which is based on canonical variables.A comparison of numerical performance among these nonsingular coordinates and canonical coordinates has been carried out by checking the conservation of energy and toroidal canonical momentum.It is found that by using the poloidal magnetic flux in the nonsingular coordinate system,the numerical performance of nonsingular coordinates can be greatly improved and is comparable to that of canonical variables in long-time simulations.

Imaging the mantle transition zone beneath eastern and central China with CEArray receiver functions

We analyzed a total of 37 427 receiver-function data recorded by national and regional broadband seismic networks of the China Earthquake Administration to study the mantle transition zone beneath eastern and central China. Significant topography on both the 410-km and 660-km discontinuities was clearly imaged in the 3D volume of CCP （common-conversion-point） stacked images that cover an area of 102.5°F-122.5°E and 22.0°N-42.0°N. 3D crustal and mantle velocity models were used in computing the Ps time moveouts to better image the absolute depths of the two discontinuities. We found that the 660-km discontinuity is depressed up to 25 km along the east coast of China, indicating the presence of the subducted Pacific slab in the region. More interestingly, a double 660-km was observed beneath the Huanghai Sea, which was not seen from the 410-km discontinuity. We found a strong and localized anomaly beneath the Quaternary Datong volcano located at the northeastern edge of the Ordos Plateau in North China. The 410-km is depressed by as much as 15 km beneath the volcano. If the amount of the depression is caused by unmodeled low velocity anomaly in the upper mantle, it requires either a strong （4%-8%） localized low velocity anomaly near the lithosphere-asthenosphere boundary or -1.5% low velocity column across the entire upper mantle above the 410-km. The latter could suggest a deep origin of the Datong volcano, although it was usually attributed to edge-driven convection by most of the literatures.

Healthy axis: Towards an integrated view of the gut-brain health

Despite the lack of precise mechanisms of action, a growing number of studies suggests that gut microbiota is involved in a great number of physiological functions of the human organism. In fact, the composition and the relations of intestinal microbial populations play a role, either directly or indirectly, to both the onset and development of various pathologies. In particular, the gastrointestinal tract and nervous system are closely connected by the so-called gut–brain axis, a complex bidirectional system in which the central and enteric nervous system interact with each other, also engaging endocrine, immune and neuronal circuits. This allows us to put forward new working hypotheses on the origin of some multifactorial diseases: from eating to neuropsychiatric disorders (such as autism spectrum disorders and depression) up to diabetes and tumors (such as colorectal cancer). This scenario reinforces the idea that the microbiota and its composition represent a factor, which is no longer negligible, not only in preserving what we call “health” but also in defining and thus determining it. Therefore, we propose to consider the gut-brain axis as the focus of new scientific and clinical investigation as long as the locus of possible systemic therapeutic interventions.

Multiple off-axis acoustic vortices generated by dual coaxial vortex beams

As a kind of special acoustic field, the helical wavefront of an acoustic vortex（AV） beam is demonstrated to have a pressure zero with phase singularity at the center in the transverse plane. The orbital angular momentum of AVs can be applied to the field of particle manipulation, which attracts more and more attention in acoustic researches. In this paper,by using the simplified circular array of point sources, dual coaxial AV beams are excited by the even-and odd-numbered sources with the topological charges of l_E and l_O based on the phase-coded approach, and the composite acoustic field with an on-axis center-AV and multiple off-axis sub-AVs can be generated by the superimposition of the AV beams for｜l_E｜ ≠ ｜l_O｜. The generation of edge phase dislocation is theoretically derived and numerically analyzed for l_E=-l_O. The numbers and the topological charges as well as the locations of the center-AV and sub-AVs are demonstrated, which are proved to be determined by the topological charges of the coaxial AV beams. The proposed approach breaks through the limit of only one on-axis AV with a single topological charge along the beam axis, and also provides the feasibility of off-axis particle trapping with multiple AVs in object manipulation.

Vibrational transition spectra of H_2^+ in a strong magnetic field

Vibrational transition spectra of H2＋ in an ultra-strong magnetic field are determined. The validity of Born- Oppenheimer approximation is analyzed based on one-center method and B-spline basis sets. It is shown that Born- Oppenheimer approximation is reliable for the investigation on the ground state and low excited states of H2＋ subjected to the strong magnetic field. Furthermore, it is found that the vibrational transition spectra from lσg, lπu, and 1δg states lie in infrared, visible, and ultraviolet ranges with increasing magnetic field strength.

基于CT影像儿童枢椎正常发育与变异的解剖特征

背景:枢椎发育演变过程复杂,研究报道较少。CT成像可以显示枢椎的正常发育过程、解剖结构、发育变异与畸形,明确枢椎骨化中心出现与骺板闭合时间及其演变过程和规律具有重要的临床价值。目的:基于CT影像展示儿童枢椎正常发育与变异的解剖结构。方法:回顾性分析2016年6月至2019年11月行颈部扫描的732例0-15岁儿童CT图像。观察指标包括枢椎齿状突、双侧椎弓、椎体骨化中心,齿突尖部二次骨化中心,椎弓、齿突基底部及后正中骺板,以及枢椎发育变异或畸形。分析与比较各项指标在不同年龄下的变化情况,并利用SPSS 17.0统计学软件包进行数据分类处理及统计学分析。结果与结论:(1)732例研究对象包括枢椎正常发育718例(98.1%),畸形或发育异常14例(1.9%);(2)枢椎5个骨化中心,其中双侧椎弓及齿突、椎体骨化中心在出生时已出现;齿突尖部二次骨化中心出现的中位年龄是5.7岁,年龄四分位差(IQR)是4.1-7岁,最早出现的为8个月22 d,最迟未出现的为12岁10个月;(3)齿突尖骺板融合的中位年龄是6岁,IQR是5-8岁,未融合最大年龄是8岁9个月,融合的最小年龄是4岁3个月;(4)双侧椎弓骺板闭合的中位年龄约3.8岁,IQR约2.9-4.6岁,闭合的最小年龄是2岁3个月,未闭合的最大年龄是6岁;(5)齿突基底部骺板闭合的中位数5.2岁,IQR为3.5-6.8岁,闭合最小年龄是2岁6个月,最晚未闭合年龄是9岁6个月;(6)后正中骺板闭合年龄中位数为1.5岁,IQR为1.0-2.1岁,最晚未闭合2例分别为2岁5个月、14岁,最早闭合为6个月20 d;(7)枢椎畸形或发育异常,包括出现副骨化中心及副骺板7例、枢椎游离骨化小骨3例、后正中骺板不闭合2例、无齿突尖部二次骨化中心2例及枢椎齿突骨化中心未出现1例;(8)提示多层螺旋CT扫描、结合多平面重组技术可以完整显示枢椎的解剖结构,评估其正常发育变异及畸形。

A Monte Carlo Simulation of a Monomer Dimer CO-O2 Catalytic Reaction on the Surface and Subsurface of a Face-centered Cubic Lattice

The presence of oxygen in the subsurface in monomer-dimer reactions(CO-O_(2)and NO-CO)is observed experimentally.The effect of subsurface oxygen on a CO-O_(2)catalytic reaction on a face-centered cubic(FCC)lattice is studied using Monte Carlo simulation.The effect of adding subsurface neighbours on the phase diagram is also extensively explored.It is observed that the subsurface oxygen totally eliminates the typical second order phase transition.It is also shown that the introduction of the diffusion of O atoms and the subsurface of the FCC lattice shifts the single transition point towards the stoichiometric ratio.

COMPLETE STREETS&LIVABLE CENTERSWhy Location Matters

INTRODUCTION In recent years,Houston has made great strides in green building,moving into the top ten nationally on both LEED certified and Energy Star rated structures.At the same time,fewer steps have been taken to address transportation,which accounts for one third of U.S.greenhouse gas emissions.3 To achieve greater sustainability,architects,planners,and developers must take the space between buildings into greater account.

Three-Center Configuration with Four,Three, and Two Electrons for Carbon,Boron, Hydrogen, and Halogen Exchange. A Model and Theoretical Study with Experimental Evidence

The introduction of specific sites in organic frames for accommodation of various modes of bonding has been focused on reaction types which are described by using different theoretical models with or without a definite experimental proof. In this study three-center four-, three-, and two-electron systems based on carbon-, boron-, hydrogen-, and halogen exchange are under consideration. Based on the number of electrons in the transition state or transition complex it is shown that all transfer or exchange reactions share the same ratio numbers expressed as the quotient of the transitional bond distance under investigation and its normal bond length. With X-ray data of model systems it was even possible to give the ratio numbers for a three-center four-electron configuration experimental support with additional ab initio data. Furthermore a novel model type of substitution in organic chemistry is introduced through electrophilic insertion, informative for enzyme-substrate interactions based on the lock-and-key model. Reactions based on a three-center two-electron configuration mostly follow a nonlinear transition. In this alignment there will be a pursuit of cyclization for stabilization via homoaromaticity as homocyclopropenyl cation. The molecular dynamics of such a process is discussed based on recent X-ray crystallographic data of the symmetrically bridged, nonclassical geometry of the 2-norbornyl cation. In the present paper the focus is aimed at the transition intermediate of the (classical) 2-norbornyl cation involved in the isomerization into the nonclassical geometry. This model description is compared with a simple molecular rearrangement of the 1-propyl cation into the corner-protonated cyclopropane using the ab initio data. The exclusivity of the former isomerization compared with the latter one could be unambiguously demonstrated by the invention that theintramolecularelectron shift can be expressed in a linear relationship between the concerned electron-donating and accepting bond lengths. Finally, the fluor transitions as divalent atoms in a three-center two-electron configuration are described. The role of fluor in comparison with the other halogens is striking. The attention was focused on an excellent correspondence between the recent chemical and theoretical evidence for a symmetrical fluoronium ionin solution. Simple dialkylfluoroniumions in contrast to the other halonium ions are not present in solution. Although the geometry of the fluoronium ion theoretically can be described as a real minimum, the C-F-C angle of 120° is apparently the borderline transition for dissociation in C+ and F-C.

内燃机试验对曲轴轴心轨迹影响的研究

内燃机台架试验时需要与测试设备连接,其中连接时的对中精度和连接方式直接影响试验质量。本文研究了不同对中精度对内燃机轴心轨迹的影响,确定了对中精度控制范围,通过试验过程振动与转速的对应关系测量,确认保养和连接方式影响,为内燃机开发试验过程的对中精度、保养和连接方案制定提供了参考依据。研究表明:对中精度超过0.5mm时可能会引起轴心轨迹偏离;试验过程定期保养可减少对中劣化的影响;高速内燃机应监测主轴承的振动情况,根据测量结果制定连接方案。

马扎克五轴加工中心后处理研究及验证

在制造业飞速发展的今天,产品对零件的结构及精度要求越来越高。传统三轴加工中心无法满足零件加工要求,而五轴联动机床能很好适应复杂零件的加工工艺。然而,机床厂家并不会免费提供该设备的专用后处理,这给机床使用人员带来了极大困难,同时也浪费了人力成本和时间成本。这里针对马扎克五轴加工中心,运用Tcl脚本语言在UG/Post环境中编制适合该机床的后处理系统。该系统能有效读取刀位文件,并且按照机床要求生成相应加工程序,该程序能安全有效地运行于马扎克VARIAXIS j-500/5X机床。最后通过加工检测五轴联动机床的S试件证明了该后处理系统的有效性和安全性。

盾构隧道缓和曲线段管片组合轴线拟合计算方法

盾构隧道在缓和曲线部分存在管片拼装问题,因缓和曲线线型复杂,管片拼装点位多变,一直是施工过程中的一个难题。基于错缝拼装要求与楔形管片特点,提出一种在平面范围内,利用循环计算与误差控制的条件判定,综合比选标准环与楔形环组合,完成每环管片拼装施工,最终拟合出既满足规范与控制指标,又可保证线型较为均匀的管片拼装轴线的管片施工设计方法与验证方法。并根据实际工程需要,提出最大允许偏差控制方法和缓圆点附近的管片拼装优化措施,结合珠海市珠机线湾仔北站—湾仔站区间盾构隧道实例,证明了此方法的准确性与适用性,为缓和曲线上控制管片拼装质量提供理论依据。

基于Isight的可变角度主轴刀柄机构设计与优化

为实现基于三轴数控加工中心的四轴数控加工功能,文中提出了一种可变角度主轴刀柄机构,其具有低成本的多轴化数控功能升级技术优势。首先,完成可变角度主轴刀柄机构的结构设计,并建立该机构的运动学模型;其次,基于ADAMS∕View建立可变角度主轴刀柄机构的参数化模型,并通过Isight平台搭建多目标优化设计流程,以主动臂平均扭矩、主动臂转角及连杆总长度为优化目标,采用NSGA-Ⅱ算法进行多目标优化设计。数值算例的结果表明:相较于原始方案,优化后主动臂平均扭矩减小了15.5%,连杆总长度减小了11.3%,且机构内各部件在运动中不发生结构干涉。因此,基于Isight平台对可变角度主轴刀柄机构进行多目标优化设计的方法是可行的,优化后的机构具有更加合理的尺寸参数,可最大限度地发挥可变角度主轴刀柄机构的动力性和经济性。

基于“脑-肠-菌”轴探讨健脾益气自拟方对老年慢传输型便秘的影响

目的基于“脑-肠-菌”轴理论,探究健脾益气自拟方对老年慢传输型便秘的临床疗效及作用机制。方法回顾性选取湖南中医药大学第一附属医院胃肠外科门诊2021年1月至2023年12月的128例气虚型老年慢传输型便秘患者,随机分为空白组(17例)、对照组(48例)和观察组(63例)。空白组仅进行饮食、生活调整;对照组在空白组基础上口服枸橼酸莫沙必利分散片(5 mg/次,3次/d);观察组在空白组基础上予健脾益气自拟方干预,每日1剂,水煎服,分两次服用。3组均干预6周,对比各组血清脑肠肽[血管活性肠肽(vasoactive intestinal peptide,VIP)、血清5-羟色胺(5-hydroxytryptamine,5-HT)、P物质(substance P,SP)]水平、肠道菌群丰度、结肠传输功能、完全自主排便次数(complete spontaneous bowel movements,CSBM)、便秘患者生存质量自评量表(Patient Assessment of Constipation-Quality of Life,PAC-QOL)评分及临床疗效。结果与治疗前比较,治疗后3组乳酸杆菌菌群数量均升高(P<0.05,P<0.01),血清VIP水平及PAC-QOL评分降低(P<0.05,P<0.01)。与空白组比较,对照组和观察组双歧杆菌、类杆菌数量、血清5-HT、血清SP水平均升高(P<0.01),肠杆菌、梭杆菌数量、血清VIP水平、PAC-QOL评分均降低(P<0.05,P<0.01)。与对照组比较,观察组双歧杆菌、乳酸杆菌、类杆菌数量、血清5-HT、血清SP、CSBM水平均升高(P<0.01);肠杆菌、梭杆菌数量、血清VIP水平、PAC-QOL评分均降低(P<0.05,P<0.01),72 h标记物残留粒数减少(P<0.01)。与空白组比较,对照组和观察组总有效率升高(P<0.05,P<0.01);与对照组比较,观察组总有效率升高(P<0.01)。结论健脾益气自拟方可通过调节“脑-肠-菌”轴,有效改善老年气虚慢传输型便秘患者血清脑肠肽水平,促进肠道菌群平衡,增强结肠传输功能,缓解临床症状,具有临床推广价值。

基于Bezier曲线的二维振镜扫描系统轨迹过渡

二维振镜扫描投影系统是新兴的研究领域,通过在目标面上投影出CAD图形来辅助生产制造,有效提高生产效率和制造精度。以往通过设置跳转延时保证跳转过程中扫描图形的精度,未考虑电机的运行情况。为解决扫描过程中存在的电机振动冲击问题,基于Bezier曲线为扫描轨迹跳转自由段加入轨迹过渡,结合二维振镜系统对扫描图形进行等距离散的工作特点,得出扫描轨迹交接处平滑过渡的Bezier曲线控制点位置条件。随后依照平滑过渡条件为扫描图形加入轨迹过渡,并依照轨迹最大曲率进行迭代择优。最后基于典型的音圈电机模型对轨迹过渡的优化效果进行仿真验证。结果表明,对于二维振镜扫描式激光投影系统而言,使用Bezier曲线进行轨迹过渡简单高效,有效消除电机运行过程中的速度与加速度突变,减少了运行过程中的振动冲击,同时保证了扫描图形的精度。

高速立式五轴加工中心滑枕结构设计与优化

以高速立式五轴加工中心滑枕为研究对象,阐述了其初始结构设计原理,并基于静动态分析理论,采用有限元分析方法针对其进行静态和模态分析,为了进一步提高其动态特性,利用拓扑优化方法对滑枕结构进行轻量化设计,并对优化前后结构做对比分析。最终优化后的滑枕质量减轻了31%,一阶固有频率增长了22.4%。既提升了机床滑枕部件的动态性能,又实现了滑枕部件的轻量化设计。该方法为该类机床其他关键零部件及至整机优化设计奠定了基础。

基于雷尼绍5轴加工中心丝杆螺距误差检测与补偿研究

实验采用雷尼绍XL-80激光干涉仪检测各线性轴精度及反向间隙,对各轴丝杆螺距误差及反向间隙进行补偿,保证各轴定位精度和重复定位精度,通过雷尼绍激光干涉仪对沈阳机床VMU635轴立式加工中心丝杆螺距误差检测与补偿实验,机床线性轴定位精度提高显著,这对该型号机床后续零件加工精度控制方面提供有力保障,研究结论对该设备在机床加工精度调试领域中的应用具有一定的参考价值。

卧式加工中心转台回转夹具定位销连线的数学建模及实例应用研究分析

卧式加工中心转台回转夹具的典型结构是通过在卧式加工中心工作台上配置转台、尾座和夹具体,进而构成摇篮式转台,该种方式可以使加工工序集中化,进一步提高零件的加工质量和加工效率。在基于摇篮式转台回转夹具构成型式分析的基础上,以定位销连线为研究对象,通过讨论定位销连线与转台回转轴线及机床坐标系三者之间平行关系的几种情况,进而建立数学模型,并通过实例的方式解决生产过程中遇到的实际问题。