Lateral static and dynamic characteristics of thin-walled box girder

To analyze the static and dynamic behaviors of the thin-walled box girder in its lateral webs in consideration of shear lag effect and shear deformation, an approach based on the minimum potential principle is introduced in this paper. Both static and dynamic response equations as well as the corresponding natural boundary conditions of the box girder are deduced. Meanwhile, three generalized displacement functions： w （x） , U（x） and O（x） are employed and their differences in the calculus of variation are quantitatively investigated. The comparison of finite shell element results with analytical results of calculation examples validates the feasibility of the proposed approach.

Finite Deformation, Finite Strain Nonlinear Dynamics and Dynamic Bifurcation in TVE Solids

This paper presents the mathematical model consisting of conservation and balance laws (CBL) of classical continuum mechanics (CCM) and the constitutive theories derived using entropy inequality and representation theorem for thermoviscoelastic solids (TVES) matter without memory. The CBL and the constitutive theories take into account finite deformation and finite strain deformation physics. This mathematical model is thermodynamically and mathematically consistent and is ideally suited to study nonlinear dynamics of TVES and dynamic bifurcation and is used in the work presented in this paper. The finite element formulations are constructed for obtaining the solution of the initial value problems (IVPs) described by the mathematical models. Both space-time coupled as well as space-time decoupled finite element methods are considered for obtaining solutions of the IVPs. Space-time coupled finite element formulations based on space-time residual functional (STRF) that yield space-time variationally consistent space-time integral forms are considered. This approach ensures unconditional stability of the computations during the entire evolution. In the space-time decoupled finite element method based on Galerkin method with weak form for spatial discretization, the solutions of nonlinear ODEs in time resulting from the decoupling of space and time are obtained using Newmark linear acceleration method. Newton’s linear method is used to obtain converged solution for the nonlinear system of algebraic equations at each time step in the Newmark method. The different aspects of the deformation physics leading to the factors that influence nonlinear dynamic response and dynamic bifurcation are established using the proposed mathematical model, the solution method and their validity is demonstrated through model problem studies presented in this paper. Energy methods and superposition techniques in any form including those used in obtaining solutions are neither advocated nor used in the present work as these are not supported by calculus of variations and mathematical classification of differential operators appearing in nonlinear dynamics. The primary focus of the paper is to address various aspects of the deformation physics in nonlinear dynamics and their influence on dynamic bifurcation phenomenon using mathematical models strictly based on CBL of CCM using reliable unconditionally stable space-time coupled solution methods, which ensure solution accuracy or errors in the calculated solution are always identified. Many model problem studies are presented to further substantiate the concepts presented and discussed in the paper. Investigations presented in this paper are also compared with published works when appropriate.

THE DESIGN AND ANALYSIS OF VIBRATION STRUCTURE OF VERTICAL DYNAMIC BALANCING MACHINE

A new type of vibration structure (i.e. supporting system, called swing frame cus- tomarily) of vertical dynamic balancing machine has been designed, which is based on an analysis for the swing frame of a traditional double-plane vertical dynamic balancing machine. The static unbalance and couple unbalance can be e?ectively separated by using the new dynamic balancing machine with the new swing frame. By building the dynamics model, the advantages of the new structure are discussed in detail. The modal and harmonic response are analyzed by using the ANSYS7.0. By comparing the ?nite element modal analysis with the experimental modal analy- sis, the natural frequencies and vibration modes are found. There are many spring boards in the new swing frame. Their sti?nesses are di?erent and assorted with each other. Furthermore, there are three sensors on the measuring points. Therefore, the new dynamic balancing machine can measure static unbalance and coupling unbalance directly, and the interaction between them is faint. The result shows that the new vertical dynamic balancing machine is suitable for inertial measurement of ?ying objects, and can overcome the shortcomings of traditional double-plane vertical dynamic balancing machines, which the e?ect of plane-separation is inferior. The vertical dynamic balancing machine with the new vibration structure can ?nd wide application in the future. The modelling and analysis of the new vibration structure will provide theoretical basis and practical experience for designing new-type vertical dynamic balancing machines.

Novel Models and Algorithms of Load Balancing for Variable-structured Collaborative Simulation under HLA/RTI

High level architecture(HLA) is the open standard in the collaborative simulation field. Scholars have been paying close attention to theoretical research on and engineering applications of collaborative simulation based on HLA/RTI, which extends HLA in various aspects like functionality and efficiency. However, related study on the load balancing problem of HLA collaborative simulation is insufficient. Without load balancing, collaborative simulation under HLA/RTI may encounter performance reduction or even fatal errors. In this paper, load balancing is further divided into static problems and dynamic problems. A multi-objective model is established and the randomness of model parameters is taken into consideration for static load balancing, which makes the model more credible. The Monte Carlo based optimization algorithm(MCOA) is excogitated to gain static load balance. For dynamic load balancing, a new type of dynamic load balancing problem is put forward with regards to the variable-structured collaborative simulation under HLA/RTI. In order to minimize the influence against the running collaborative simulation, the ordinal optimization based algorithm(OOA) is devised to shorten the optimization time. Furthermore, the two algorithms are adopted in simulation experiments of different scenarios, which demonstrate their effectiveness and efficiency. An engineering experiment about collaborative simulation under HLA/RTI of high speed electricity multiple units(EMU) is also conducted to indentify credibility of the proposed models and supportive utility of MCOA and OOA to practical engineering systems. The proposed research ensures compatibility of traditional HLA, enhances the ability for assigning simulation loads onto computing units both statically and dynamically, improves the performance of collaborative simulation system and makes full use of the hardware resources.

MDSLB:A new static load balancing method for parallel molecular dynamics simulations

Large-scale parallelization of molecular dynamics simulations is facing challenges which seriously affect the simula- tion efficiency, among which the load imbalance problem is the most critical. In this paper, we propose, a new molecular dynamics static load balancing method （MDSLB）. By analyzing the characteristics of the short-range force of molecular dynamics programs running in parallel, we divide the short-range force into three kinds of force models, and then pack- age the computations of each force model into many tiny computational units called ＂cell loads＂, which provide the basic data structures for our load balancing method. In MDSLB, the spatial region is separated into sub-regions called ＂local domains＂, and the cell loads of each local domain are allocated to every processor in turn. Compared with the dynamic load balancing method, MDSLB can guarantee load balance by executing the algorithm only once at program startup without migrating the loads dynamically. We implement MDSLB in OpenFOAM software and test it on TianHe-lA supercomputer with 16 to 512 processors. Experimental results show that MDSLB can save 34%-64% time for the load imbalanced cases.

NEW TYPE OF VIBRATION STRUCTURE OF VERTICAL DYNAMIC BALANCING MACHINE

A new type of vibration structure of vertical dynamic balancing machine isdesigned, which is based on the analysis for swing frame of a traditional vertical dynamic balancingmachine. The static unbalance and couple unbalance can be separated effectively by using the newmachine with the new swing frame. By building the dynamics model, the advantages of the newstructure are discussed in detail. The modal and harmonic response are analyzed by using theANSYS7.0. By comparing the finite element modal analysis with the experimental modal analysis, thenatural frequencies and vibration modes are found out. There are many spring boards in the new swingframe. Their stiffness is different and assort with each other. Furthermore, there are threesensors on the measurement points. Therefore, the new dynamic balancing machine can measure thestatic unbalance and couple unbalance directly, and the influence between them is faint. The newstructure has the function of belt-strain compensation to improve the measurement precision. Thepractical result indicates that the new vertical dynamic balancing machine is suitable for inertialmeasurement of flying objects, and can overcome the shortcomings of traditional double-planevertical dynamic balancing machines. The vertical dynamic balancing machine with the new vibrationstructure can be widely used in the future applications. The modeling and analysis of the newvibration structure provide theoretic instruction and practical experience for designing new type ofvertical dynamic balancing machines. Based on the design principles such as stiffness-matching,frequency-adjacence and strain-compensation and so on, various new type of vibration structures canbe designed.

顺北油气田断溶体油藏产量预测模型研究及应用

Arps递减曲线方程是油气田开发初期产量预测中应用较为普遍的方法,基本是参考类似油藏拟合参数以定压差生产为开发政策指导进行产量预测,对于顺北断溶体油藏地层压力下降明显,且储集层在地饱压差内的非线性流动特征明显,存在唯一的非线性惯性阻力,无法通过描述线性流动特征的采油指数来表征,存在误差较大、产量预测结果单一的缺点。通过分析顺北油气田产量递减特征,基于物质平衡原理,构建动态储量模型,结合顺北油气田通用产能方程和产能评价指标成果,形成了新的断溶体油藏弹性驱产量预测方法,用于指导断溶体油藏弹性驱开发阶段的生产管理,有更高的适应性和准确率,也为断溶体油藏开展产能建设方案经济评价优化、指导油井开发政策奠定了基础、提供多开发政策方案决策支撑。

长期体育锻炼对青年人不同认知任务干扰时平衡能力的影响

目的:探索青年人在不同认知任务干扰时的平衡表现,以及长期体育锻炼的调节效应。方法:测试有体育锻炼习惯组和无体育锻炼习惯组的健康青年人在不同认知任务干扰时的静态、动态平衡,并以分组变量(group)为主体间变量、多次平衡测试结果(task)为主体内变量进行单因素重复测量方差分析。结果:长期体育锻炼对计算、唱歌、书写干扰时的静态平衡、书写干扰时的静态左右对称平衡、唱歌干扰时的静态前后对称平衡以及计算干扰时的动态平衡具有积极的调节效应(P<0.05),且能够明显降低青年人受到相应认知任务干扰时的双任务成本(P<0.05),但是对计算干扰时的静态左右对称平衡、朗读干扰时的静态前后对称平衡以及计算和唱歌干扰时的动态左右对称平衡具有消极的调节效应(P<0.05)。结论:长期体育锻炼对青年人在不同认知任务干扰时的动态和静态平衡表现都具有显著的调节效应。

静动力边界转换及其合理性验证方法的研究

繁琐复杂的静动力边界转换处理是进行静动力耦合模拟的关键步骤,为了研究黏弹性边界条件下传统静动力边界转换的合理性及其验证方法的适用性,本文首先根据弹性叠加原理提出了一种验证静动力耦合模拟分析中静动力边界转换合理性的方法(参考解法);然后基于有限元软件ABAQUS,并结合自行研发的适用于成层介质的黏弹性边界施加和等效节点力计算程序VBEA2.0,对多土层自由场静动力耦合模型和土-地下结构静动力耦合模型进行了地震反应分析,对参考解法的适用性进行了探究;最后使用本文提出的参考解法,对一种典型的未进行合理静动力边界转换的自由场模型进行了分析,探讨了静动力边界转换产生振荡的原因和机理。研究结果表明:用于验证静动力边界转换合理性的参考解法,既适用于多土层自由场静动力耦合计算模型,又适用于土-结构相互作用的静动力耦合模型;静动力边界转换后产?生的振荡是静动力耦合计算模型静力不平衡所导致,一般是因为未合理施加边界反力或单元应力。

新型车轮平衡机振动系统分析设计

通过对现有转子支撑系统的分析,确定了车轮动平衡机的支撑类型;建立了传统硬支撑立式平衡机振动模型,并对其质心运动方程进行解算,根据解算结果分析其静偶分离效果不佳的原因以及误差的来源;在此基础之上,提出了一种新型车轮平衡机振动系统模型,给出了此振动系统下的运动微分方程,并对其进行详细的解算分析研究,从误差来源上解决了静偶分离不佳的问题。实验结果表明,采用此振动系统解算分析方法,改善了车轮动平衡机的静偶分离性能,提高了不平衡量测量的稳定性与精度。

直流配电网交错串联式固态断路器

鉴于有源直流配电网的故障特性,能够快速有效切除故障电流的固态直流断路器对提高直流配电网的供电可靠性意义重大。为此,提出一种交错串联式固态断路器,其拓扑将多个内层单元串联交错以提高整体耐压能力,每个内层单元由多个串联的常通型SiC JFET开关管组成,电路拓扑具有极强的可扩展性。通过双层均压网络实现串联开关的快速响应、动静态电压平衡。基于LTspice软件构建4.5 kV/20 A固态断路器仿真,仿真结果表明额定工况下该断路器关断时间仅为80 ns,验证了所提交错串联式固态断路器拓扑可行性。

“动—静”结合视角下黄河中下游粮食生产全周期碳平衡测度及分区

研究目的:构建粮食生产全周期碳收支体系,基于“动—静”结合视角测算黄河中下游粮食生产碳平衡水平,针对不同碳平衡水平分区提出差异化调控策略,可为全面反映粮食生产碳平衡水平、协同推进粮食绿色生产提供支持与参考。研究方法:生命周期评价法,碳转化系数法,经验公式法,静态平衡指数,动态平衡指数,信息熵模型。研究结果:(1)黄河中下游粮食生产碳排放和碳吸收均为增长趋势,空间上均呈“西北低,东南高”态势。(2)黄河中下游粮食生产碳收支静态平衡指数呈“西北低,东南高”分布,地区均值波动下降,各地市存在直升型、直降型、U型和倒U型4种演变趋势,粮食生产碳收支动态平衡指数具有显著时空异质性。(3)黄河中下游粮食生产碳平衡水平分区呈“西北失衡,东南平衡”分布,格局结构有序性历经“较有序—较无序—有序—无序”波动。研究结论:贡献度视角下黄河中下游部分地市粮食生产碳收支仍存在失衡情况,需进一步施行针对性和差异性的粮食绿色生产策略。

民事庭外作证方式的体系构造

民事庭外作证方式的扩张表现为两种基本模式:庭外作证方式多样化、庭外作证条件低阶化。由此使庭外作证手段呈现繁复多变的色彩。欲厘定具体庭外作证方式选择所应遵从的程序法理与规则,须准确透视复杂庭外作证现象下的体系构造。以单一基准衡量,各庭外作证方式与直接言词原则的距离呈现远近分层的静态构造;以双重基准衡量,直接言词原则与成本衡量决定各庭外作证方式分层呈现模糊性、相对性的动态构造。静态构造与动态构造均对庭外作证方式选择发挥规范与引导作用,法官在两种构造的价值取向之间保持平衡,保证庭外作证运用的妥当性与可接受性。

基于自适应平衡静动态联合网络的公交客流预测

为解决现有公交客流预测方法多数利用预定义的图结构进行空间建模,对交通状况变化所引起客流波动考虑不充分,无法捕捉短时动态的空间依赖关系问题,提出一种自适应平衡静动态联合网络(ASDNet)模型。首先,利用时间卷积网络捕获序列的时间相关性;其次,利用图卷积捕捉站点之间整体空间信息,采用动态图同构网络捕捉相邻时隙动态图之间隐藏的动态依赖关系;最后,通过自适应平衡机制自适应地调节静动态联合网络之间的信息传递。在广州市真实公交数据集上进行了实验,结果表明,与多个基准模型相比,该模型在MAE、RMSE和MAPE预测误差指标上平均降低了12.2%、9.9%和15%,R2精确度指标上平均提高了6.3%。表明该模型能够有效地捕捉客流数据的时空变化规律,可为公交运营管理提供技术参考。

TBR轮胎胎体帘线稀并线原因分析与对策

分析TBR轮胎胎体帘布稀并线异常的产生原因,并提出相应解决方案。胶料流动性、工艺工装磨损、帘布渗胶质量、压延张力波动、胶部件接头缺陷、帘布局部拉伸等因素均会造成胎体帘线间距排列异常,通过优化混炼工艺、工艺工装精细管理、提升帘布渗胶质量、稳定钢丝压延张力、严控压延机积胶均一性与部件接头质量等措施,可有效解决胎体稀并线异常问题。

机轮组件的机械平衡研究

针对使用传统工艺校正的机轮组件在飞机上时有振动与抖动的问题,介绍了对开式机轮组件动平衡和先进静平衡等技术,以提升轮毂、轮缘式机轮组件平衡精度与效率。文中指出,航空机轮的平衡将由现在的机轮组件和轮胎两家生产商各自平衡最终走向机轮组件配装轮胎后的整体平衡。

Balance Performance in Female Collegiate Athletes

Proper balance is essential for athletes during competition and training as sport places different balance requirements on the human body. The purpose of the study was to analyze balance performance among female athletes using COP （center of pressure） sway parameters. Twenty one NCAA （National Collegiate Athletic Association） division I female athletes （soccer, volleyball and dance） completed the study. Static balance was assessed using UST （unilateral stance test） and dynamic balance was assessed using MCT （motor control test） on the NeuroCom Equitest. Sway velocities, root mean square sway and reaction time latencies were used to quantify balance. A one-way between subjects ANOVA （analysis of variance） was performed to analyze these balance parameters. Significant （p 〈 0.05） differences between groups were found and post hoc comparisons revealed that the volleyball and dance groups had better static balance compared to soccer players, while both soccer and volleyball groups had better dynamic balance compared to the dance group. The results from the study indicate two points： first, differences in balance performance among female athletes in different sporting discipline; second, there is no relationship between static and dynamic balance. This indicates that it may be more beneficial to assess and train for static and dynamic balance individually.

Exact Computation of Parallel Robot's Generalized Inertia Matrix

According to the definition of the new hypothetical states which have obvious physical significance and are termed as no-gravity static and accelerated states, a method for exact computation of the parallel robot＇s generalized inertia matrix is presented. Based on the matrix theory, the generalized inertia matrix of the parallel robot can be computed on the assumption that the robot is in these new hypothetical states respectively. The approach is demonstrated by the Delta robot as an example. Based on the principle of the virtual work, the inverse dynamics model of the robot is formulized after the kinematics analysis. Finally, a numerical example is given and the element distribution of the Delta robot＇s inertia matrix in the workspace is studied. The method has computationa＇, advantage of numerical accuracy for the Delta robot and can be parallelized easily.

基于音乐节律性刺激疗法联合动静态平衡训练对帕金森病患者平衡及步行功能影响的临床观察

目的:观察基于音乐节律性刺激疗法联合动静态平衡仪训练对帕金森病患者平衡功能及步行功能的影响。方法:筛选2020年1月—2022年12月于我院治疗的符合纳入标准的66例帕金森病患者随机分为试验组(33例)和对照组(33例)。对照组接受常规的康复训练及动静态平衡仪训练,试验组在对照组的基础上给予基于音乐的节律性刺激治疗,共治疗8周。两组在治疗前、治疗8周后均进行Berg平衡量表(BBS)、计时起立-行走测试(TUGT)、改良Barthel指数(MBI)、帕金森病生活质量问卷(PDQ-39)评定及满意度调查,以组内和组间比较治疗前后平衡功能、步行功能及PDQ-39的变化,并对两组患者的康复训练满意度进行分析比较。结果:与治疗前比较,经过8周治疗后试验组和对照组的BBS、TUGT、MBI、PDQ-39及满意度均有所改善(P<0.05),而试验组的BBS、TUGT、MBI、PDQ-39及满意度均显著优于对照组(P<0.05)。结论:基于音乐节律性刺激疗法联合动静态平衡训练能够提高帕金森病患者的平衡功能及步行功能,具有一定的临床推广价值。

数控连杆机构式机器人的平衡特性及优化

为了提升数控连杆机构式机器人的平衡特性,以一种数控连杆机构式机器人机构为研究对象,首先计算总质心坐标,采用倾覆力矩和惯性力作为机器人静态及动态平衡性评价指标;其次构建去除支链的传统机器人,将该机器人与数控连杆式机器人进行对比,对比结果表明,数控连杆机构式机器人的平均倾覆力矩比传统串联机器人减小了96.31%;在负载为10 kg的情况下,x方向和y方向的惯性力比传统机器人分别减少了20.76%、34.88%;为进一步提升机器人平衡性,以支链杆长为设计变量,总惯性力最小为目标函数,支链杆长之和为约束条件,运用遗传算法,求出其杆长最优解。优化结果表明,优化后的机器人总惯性力相比优化前减小21.67%,从而验证了杆件优化的有效性。