The steady-state and dynamic simulation of cascade distillation system for the production of oxygen-18 isotope from water

Accurate simulation of water distillation system for oxygen-18(18O) isotope separation is necessary to guide industrial practice, since both deuterium(D) and oxygen-18 isotope get enriched and interfere with each other. In the present work, steady-state and dynamic distillation models are established based on a classic method and a cascade distillation system with 5 towers is introduced to test the models. The theoretical expressions of separation factor αH/Dfor protium/deuterium and separation factor α^(16)O/^(18) O.for oxygen-16/oxygen-18 were derived,with the existence of deuterium and oxygen-18, respectively. The results of the steady-state simulation by the classical method proposed in the present work agreed well with the results of the lumping method. The dynamic process could be divided into 5 stages. Impressively, a peak value of product withdraw was observed before the final steady state, which was resulted from the change of ^(16)O/^(18) O separation factor and isotope distribution. An interesting low concentration zone in the towers of T2–T5 existed at the beginning of the dynamic process and it required industrial evidence.

Elastic-plastic finite element simulation for diamond turning process

Using general commercial software, a coupled thermo-mechanical plane strain larger deformation orthogonal cutting model is developed on the basis of updated Lagrangian formulation in this paper. The workpiece is oxygen free high conductivity copper (OFHC copper), its flow stress is considered as a function of strain, strain rate and temperature to reflect its realistic changes in physical properties. In order to take into account the cutting edge radius effects of the single crystal diamond tool, rezoning technology is introduced into this simulation model. Diamond turning process is simulated from the initial stage to the steady stage of chip formation, and the distribution of temperature, equivalent stress, residual stress, strain rate and shear angle are obtained. The simulated principal force is compared with published experiment data and they are found to be in good agreement with each other, but poor for thrust force due to no consideration of elastic recovery for machined surface in the elastic-plastic material model.

Simulation of Steady-State and Dynamic Behaviour of a Plate Heat Exchanger

The present paper deals with both the steady-state and dynamic simulation of a plate heat exchanger, in counter-flow arrangement. A CFD （computational fluid dynamics） program FLUENT has been used to predict the temperature distribution in steady-state conditions in plate heat exchanger as well as fluid temperatures at exit of flow channels in transient condition. The results are presented for the heat exchanger, which is simulated according to the configuration of the plate heat exchanger used in the experiment. The simulated results obtained by the CFD model have been compared with the experimental data from the literature, which shows that the CFD model developed in this study is capable of predicting the steady-state and transient performance of the plate heat exchangers satisfactorily.

Development and Experimental Evaluation of a Steady-state Model for the Step-feed Biological Nitrogen Removal Process

In this article,a steady-state mathematical model was developed and experimentally evaluated to inves- tigate the effect of influent flow distribution and volume ratios of anoxic and aerobic zones in each stage on the to- tal nitrogen concentration of the effluent in the step-feed biological nitrogen removal process.Unlike the previous modeling methods,this model can be used to calculate the removal rates of ammonia and nitrate in each stage and thereby predict the concentrations of ammonia,nitrate,and total nitrogen in the effluent.To verify the simulation results,pilot-scale experimental studies were carried out in a four-stage step feed process.Good correlations were achieved between the measured data and the simulation results,which proved the validity of the developed model. The sensitivity of the model predictions was analyzed.After verification of the validity,the step feed process was optimally operated for five months using the model and the criteria developed for the design and operation.During the pilot-scale experimental period,the effluent total nitrogen concentrations were all below 5mg·L -1 ,with more than 90%removal efficiency.

Simulation study of plane motion of air cushion vehicle

This research is on horizontal plane motion equations of Air Cushion Vehicle (ACV) and its simulation. To investigate this, a lot of simulation study including ACV's voyage and turning performance has been done. It was found that the voyage simulation results were accorded with ACV own characteristic and turning simulation results were accorded with USA ACV's movement characteristic basically.

Finite Element Simulation of Processes Involving Moving Heat Sources. Application to Welding and Surface Treatment

A wide range of welding and surface treatment processes involve the use of a heat source which is moving at a constant speed over the component. The numerical simulation of such processes implies a transient analysis using a very refined mesh in order to follow properly the path of the heat source. The 3D-mesh size can be very large if one consider the welds length or the heat-treated surface size in industrial components. To reduce the computational time to acceptable values, several techniques have been investigated. The first type is to use analytical methods such as Rosenthal equations. The second type of solutions consists in performing a transient analysis using adaptive meshing. But, for a large proportion of the involved processes, practical experience demonstrates the existence of quasi steady state conditions over the major part of the heat source path. Numerical algorithms have therefore been developed to directly compute the steady temperature, metallurgical phase proportion and stress distributions. This paper gives a general overview of the different numerical methods used to simulate welding and surface treatment processes with a special emphasis on the steady state calculation. The benefits and limitations of each of them are discussed and applications are presented.

The Dynamic Simulation of Rotary Inertia on Light vehicle-Slope I

According to formula we can simulate their driven force and acceleration on the slope.The mechanical formula is used to obtain force and theoretical dynamics in the slope.The driven force decreases when rotation increases.When power increases the acceleration increases.it reduces when its weight raises.It is found that the a will decrease as slope becomes high from 5 to 11°to 22°,which fit the formula too.Meantime as the radius is high from 0.3m to 0.4m to 0.47m a will be low.The needed force will increase as the slope decline becomes big at the same power.

基于AutoTURN的车库环形坡道平曲线与小型车行驶空间适应性分析

为明确JGJ 100—2015《车库建筑设计规范》给出的曲线单行环形坡道最小尺寸能否适应长车身小型车的转弯空间需求,论文采用模拟法(以AutoTURN软件为例)及传统的公式法,选取7款车型进行了测试。结果表明:两种方法结论一致;最小尺寸坡道能够满足车长5000 mm的小型车顺利通过;如需经常服务车长超过5000 mm的小型车,坡道宽度宜相应加大。

基于MATLAB/Simulink再生车削颤振仿真研究

首先建立了再生型外圆车削颤振模型,对该模型进行了理论分析,阐明了含重合度不为1的条件下颤振瓣图的绘制过程。随后通过锤击法对某型号数控机床的刀具系统进行模态测试,获得其刀具系统在进给及吃刀方向的传递函数,并获得其模态参数作为仿真参数,借助与MATLAB/Simulink对颤振模型进行数值仿真。仿真结果表明,随着进给量的降低,重合度随之增大,再生效应即增大,导致稳定极限切深减小。同时,颤振仿真是在机床主轴转速较高的条件下进行的,忽略了过程阻尼的影响。仿真结果对于颤振的预测、监测研究具有一定参考意义。

基于RecurDyn和Matlab/Simulink的一种小型轮式平台的联合仿真

为了验证后轮为万向轮时平台的转向性能,提出了一种基于RecurDyn与Simulink的联合仿真策略;在SolidWorks建立了一种小型轮式平台,平台前轮为主动轮,后轮为万向轮,两个主动轮分别由两个电机独立驱动;将三维模型导入到RecurDyn中,添加相应的约束,设定相应的参数,验证模型的准确性,建立相应的接口;在Simulink中搭建无刷直流电机的模型,并且搭建相应的调速系统,同时验证模型的正确性;将两个电机的转速作为输出,通过接口输入到RecurDyn中作为两主动轮的驱动,通过对电机的控制,从而完成平台的直行、转弯、中心转向等动作;仿真结果表明这种轮式平台有良好的转向性能,搭建的电机模型能够实现相应的功能,电机的控制策略也是可行的;本研究对平台的实物研制及实验具有重要意义。

A theoretical and deep learning hybrid model for predicting surface roughness of diamond-turned polycrystalline materials

Polycrystalline materials are extensively employed in industry.Its surface roughness significantly affects the working performance.Material defects,particularly grain boundaries,have a great impact on the achieved surface roughness of polycrystalline materials.However,it is difficult to establish a purely theoretical model for surface roughness with consideration of the grain boundary effect using conventional analytical methods.In this work,a theoretical and deep learning hybrid model for predicting the surface roughness of diamond-turned polycrystalline materials is proposed.The kinematic–dynamic roughness component in relation to the tool profile duplication effect,work material plastic side flow,relative vibration between the diamond tool and workpiece,etc,is theoretically calculated.The material-defect roughness component is modeled with a cascade forward neural network.In the neural network,the ratio of maximum undeformed chip thickness to cutting edge radius RT S,work material properties(misorientation angle θ_(g) and grain size d_(g)),and spindle rotation speed n s are configured as input variables.The material-defect roughness component is set as the output variable.To validate the developed model,polycrystalline copper with a gradient distribution of grains prepared by friction stir processing is machined with various processing parameters and different diamond tools.Compared with the previously developed model,obvious improvement in the prediction accuracy is observed with this hybrid prediction model.Based on this model,the influences of different factors on the surface roughness of polycrystalline materials are discussed.The influencing mechanism of the misorientation angle and grain size is quantitatively analyzed.Two fracture modes,including transcrystalline and intercrystalline fractures at different RTS values,are observed.Meanwhile,optimal processing parameters are obtained with a simulated annealing algorithm.Cutting experiments are performed with the optimal parameters,and a flat surface finish with Sa 1.314 nm is finally achieved.The developed model and corresponding new findings in this work are beneficial for accurately predicting the surface roughness of polycrystalline materials and understanding the impacting mechanism of material defects in diamond turning.

基于Simulink的翻抛装置液压系统控制策略研究

针对传统翻抛机翻抛装置能量损耗高、响应迟缓等问题,对翻抛装置液压系统进行了优化,并建立了翻抛装置液压系统泵控马达的数学模型,为后续仿真分析提供理论基础。基于Simulink对翻抛装置液压系统及控制器进行建模及仿真分析,以了解系统在不同输入曲线、负载干扰下的动态特性。仿真结果表明:模糊PID控制比PID控制抗负载干扰能力更强,动态响应更快。课题组对翻抛装置液压系统控制策略进行研究,实现了翻抛装置的无级调速,使其更适合翻抛机的工作环境,提高了翻抛机的工作效率,对以后翻抛装置液压系统的设计及性能优化具有指导意义。

Assessing the Effects of Indirect Left Turn on a Signalized Intersection Performance: A Case Study for the Tehran Metropolitan Area

Many signalized intersections are characterized with frequent left-turn moves. Vehicles waiting for a protected left turn may form long queues, which will increase the intersection delay and negatively impact the network performance. Researchers and practitioners across various countries underline that access management leads to a smoother traffic flow. One way of access management at intersections is to eliminate the direct left-turn maneuver. This study aims to evaluate how the traffic conditions will be affected from replacing the direct left turn with the right-turn U-turn maneuver at intersections. In case of the right-turn U-turn maneuver, a vehicle turns right instead of making the left turn and travels either to the median opening or to the next intersection to make a U-turn. Two simulation models are built using the Synchro Studio and Aimsun simulation software packages based on the data, collected from one of the busiest intersections in Tehran (Iran), to quantify the effects of replacing the direct left turn with the right-turn U-turn maneuver on the intersection and network performance. Results of a comprehensive simulation analysis indicate that the proposed access management treatment not only significantly reduces the total vehicle queue length and the total delay at the considered intersection, but also decreases the total network delay and the total travel time. Furthermore, elimination of the direct left turn increases the number of vehicles entering the network.

基于模拟驾驶的借道左转驾驶人视觉特性研究

借道左转是一种缓解左转车流压力的新型交通组织方法,通过信号灯时空调配借用对向车道为左转待行区,提高相位内左转车辆通行能力。笔者运用驾驶模拟平台,建立城市道路交叉口借道左转仿真场景;结合眼动追踪系统,获取驾驶人借道左转过程中视觉特性参数的变化;通过瞳孔变化和眼动行为,分析驾驶人心理紧张程度及其与行车风险的关联。结果表明:识读借道左转标识及分隔带开口、到达分隔带开口和到达借用车道停车线几个位置,是驾驶人瞳孔面积变化和持续注视时间、注视兴趣区域变化以及扫视频率骤增的集中点,反映出相应位置驾驶人风险感知强、心理负荷大;借道左转短期注视行为较多,注视时长差距较大,表明该过程驾驶人关注目标多、摄取信息密集且处理难度悬殊,需要进行高强度的信息处理;累计扫视时间占比高于普通左转,且以5°以下小角度扫视为主,反映出借道左转过程环境信息复杂、行车风险较大,驾驶人搜索、对比分析的需求更高,扫视主要是为了捕捉关注目标和补充注视信息。

Drivers’ Reaction of Warning Messages in Work Zone Termination Areas with Left Turn

Work-zone crashes have always drawn public attention. A number of fatalities are recorded every year nationwide within work zone areas. Most existing countermeasures have been dedicated more to the advance warning areas, transition areas, and activity areas of work zone, than the termination areas, where drivers might play less attention to safety threats. In this study, the vehicle-to-vehicle communication based left turn warning system was applied at a work zone termination area, which is immediately followed by a T-intersection. The work-zone is located on the minor road side, while left turn vehicles will be appearing from the major street through the said T-intersection. A smart phone application was designed using Android coding system to provide several types of warning messages to drivers. Corresponding scenarios were designed in a driving simulator, and 20 subjects were recruited to participate in the simulation test followed by a questionnaire survey. The subjects received a warning message when driving to the termination area of a work zone on the coming left turn vehicles. Twenty test drivers’ driving speed, acceleration rates, and break reaction distance to the warning messages were studied in four different scenarios. Results show that the smartphone application has a great impact on driving behaviors, especially the female voice and the beep tone warning, which are recommended for possible field tests. Besides, the developed smartphone applications can be further updated for practical applications of similar needs.

基于多位置振动融合的精整车削表面形貌仿真

针对高精度加工工件表面粗糙度及表面形貌精确预测的难题,提出根据多位置振动信号融合,并结合刀具轮廓轨迹合成的形貌仿真模型。首先建立刀具轮廓轨迹方程,然后通过主成分分析法分析表面精整车削主要影响振动部位对表面粗糙度的贡献度,将不同部位的振动信号进行融合,最后将以上两部分进行叠加得到表面粗糙度表面形貌仿真模型。根据振动信号的来源方式不同,分别建立了刀具轮廓轨迹-振动仿真模型(PTS)和刀具轮廓轨迹-振动实测模型(PTM)两种模型进行研究。其中PTS模型中振动信号为根据车削动力学模型求解得到的振动位移,PTM模型中的振动信号为切削实验中实际采集的振动位移信号。通过仿真与试验结果的对比,表明PTM模型较PTS模型精确度更高,同时两种模型表面形貌仿真模型都具有较高的准确性,均可为实际加工生产提供参考。

木片集装箱翻转机设计与试验

木片集装箱翻转机械作为重要装卸转运机械,是木片输送链的核心设备,能够简化木片装卸工艺流程、提升装卸效率。为此,研制一款木片集装箱翻转机,能够实现集装箱转运、举升、装载和翻转等作业。阐述整机结构工作原理,对集装箱装载作业、翻转作业和关键零件进行力学分析,综合Hypermesh、ANSYS、Adams软件建立机器有限元模型和动力学仿真模型,分析机器装载作业和翻转作业得到,集装箱翻转角为γ∈[0°,85°]、支撑轴最大作用力为4331 kN、最小直径为65 mm、翻转液压缸最大负载力为59.4 kN,小于机器相关设计参数,满足设计要求。以自行研制的集装箱翻转机展开相关试验研究,计算分析试验数据与仿真结果高度拟合,利用与试验数据高度拟合的仿真模型分析机器关键零部件可缩短机器研制开发周期、降低加工制造成本。该研制的木片集装箱翻转机满足设计要求,具有一定的应用潜力。

基于DDPG的振动台控制参数整定方法

三参量控制是地震模拟振动台的底层控制算法,其参数整定过程中涉及的参数多,传统的参数整定方法存在效率低、过程繁琐等问题。为了提高整定效率和准确性,提出一种基于确定性策略梯度(DDPG)算法的振动台三参量控制参数整定算法。此方法通过将振动台三参量控制系统作为强化学习环境,利用DDPG算法对系统的状态-动作-奖励数据进行学习和训练;训练好的智能体则可以输出最优的控制参数,然后将整定完成的控制参数放在实际振动台系统模型中进行测试。结果表明:DDPG算法可以有效优化振动台控制性能,提高试验结果的准确性和可靠性,具有实际应用价值。

智能魔方仓库出入库作业虚拟仿真实验系统建设

智能魔方仓库具有存储密度大、集成度高等优点,在小件订单拣选领域发展迅速,但因其特殊的堆存形式使得出入库较之传统仓库多出一个翻箱的环节。为了直观展示出入库作业过程,在研究出入库、翻箱规则及机器小车调度策略的基础上,基于Unity 3D开发了智能魔方仓库出入库作业虚拟仿真实验系统。学生通过交互操作实现不同仓库规模、存储水平及订单数的出入库调度,对智能魔方仓库运作有更深切的认识。该系统可为仓储系统、机器小车调度等课程开展提供虚拟仿真实验环境,也是对现有仓储仿真软件的有效拓展。

单口轮放策略下借道左转交叉口优化设计

针对高峰时段交叉口左转车流大、部分相位空放及部分出口道闲置问题,从相位优化和出口道资源最大化利用出发,分析单口轮放预信号设置时间和交通流不对称性,研究交叉口应用单口轮放—借道左转优化方案和不同信号配时方案后,交叉口车均延误、排队长度改善情况。以兰州市天水路—东岗西路交叉口为例,通过VISSIM仿真建模,比较优化前后交叉口各项指标优劣。结果表明:设置优化方案后,高峰时段该交叉口车辆平均延误、平均排队长度分别减少了44.91%、50.61%,平峰时段车辆平均延误、平均排队长度分别降低了40.91%、48.42%;采取Webster配时方法和多目标信号配时优化方法皆可优化信号配时方案,多目标信号配时优化方法优于Webster配时方法。在交通流不对称性明显的交叉口,单口轮放策略优于对称放行。研究成果为城市道路交叉口交通管理和控制提供一定的设计参考。