An integrated simulation for the whole forming process of the picture tube panel

An integrated model for the whole forming operation of the picture tube panel is developed in this paper, which couples the behaviors of glass and mold. The molten glass is modeled by an incompressible Newtonian liquid undergoing flow. And a three-dimensional finite element method is used to perform the simulation of the fluid and heat flow. A local one-dimensional transient analysis in the thickness direction is adopted for the part cooling stage after pressing, which employs the finite-difference method. The mold heat transfer is established by boundary conditions analysis and its numerical implementation is a three-dimensional boundary element method. The glass and mold simulations are coupled by matching the temperature and heat flux on the glass-mold interface. For residual stresses analysis, a thermo-rheologically simple viscoelastic material model is introduced to consider the stresses relaxation effect and to describe the mechanical behavior according to the temperature change. The shrinkage of formed parts induced by the residual stresses is calculated based on the theory of shells, represented as an assembly of flat elements formed by combining the constant strain and the discrete Kirchhoff triangular elements. A thermoelastic model is presented to predict the deformation of the mold blocks during pressing, which is based on the steady mold temperature field and thermoelastic boundary element method.     

高压开关柜触头温度场的数值仿真分析

为验证光纤温度传感器用于高压开关柜触头温度检测的可行性,调研了高压开关柜触头的几何结构,利用多物理场耦合分析软件COMSOL Multiphysics,结合传热学相关理论进行了触头的温度场数值仿真分析。计算了额定电流和短路电流2种情况下的触头温度分布情况,结果表明:触指为触头温度检测的最佳位置;短路电流通过时,触头温度最高可达564℃。在此基础上,在安装、量程、应变干扰三方面对光纤温度传感器进行了分析,证实光纤温度传感器可用于触头温度的检测。     

0～100mV精密电压源的设计与仿真

基于16bit高精度D/A转换器AD5422和高精度放大器LM2902设计了以AT89S51单片机为主控芯片的0～100mV精密电压源。输出电压的反馈控制采用16bitA/D转换器LTC1865,显示器为1602LCD;系统的控制软件采用C语言设计。结果表明,系统的输出信号偏移量ΔUomax≤0.02mV,最大输出驱动电流可达20mA,设计成本和体积相比传统设计显著降低,可很好地满足使用要求。     

基于JSTAMP/NV的汽车外覆盖件表面缺陷仿真

随着汽车制造水平的不断进步,汽车覆盖件的成形质量已经越来越被汽车制造商所重视。表面缺陷是汽车覆盖件冲压成形过程中常见的缺陷之一,消除该缺陷传统的办法主要依靠经验,在制造过程需要反复修模,导致产品制造成本昂贵。本文简述了汽车外覆件件产生表面缺陷的原因及其基于数值模拟技术的仿真机理。最后,应用JSTAMP/NV软件提供的解决方案对某汽车门外板进行油石仿真分析,并将该仿真结果与试模结果进行比较,结果表明仿真结果与试模结果吻合良好。     

手机触摸屏抗跌落仿真分析

跌落试验是手机产品可靠性试验的一个重要测试项目,一般在产品开发后期进行.采用有限元仿真分析可以大大降低开发成本,缩短开发周期,提高产品开发速度.利用Abaqus对处于开发阶段的手机触摸屏抗跌落性能进行数值仿真分析,研究跌落过程中触摸屏的受力情况,为造型设计师和结构工程师提供相应的设计参考.     

JSTAMP/NV在汽车管材液压成形数值模拟中的应用

为有效预测管材液压成形过程中存在的制品在外侧过度减薄和内侧起皱等问题,用JSTAMP/NV对汽车副车架成形的弯曲、预成形和管材液压成形工序分别进行有限元分析,得出各工序的成形极限云图和壁厚分布.应用逆向求解器HYSTAMP仅需直接指定管坯的尺寸参数、材料和弯曲工艺参数即可自动执行弯曲仿真并可在几秒内获取弯曲仿真的结果.设定液压成形工序的液压加载曲线和方向以及轴向进给位移,应用LS-DYNA执行预成形和液压成形工序仿真.JSTAMP/NV能有效模拟管材液压成形工艺过程,并预测和消除成形过程中在变形区出现的屈曲、起皱和破裂等缺陷.     

Semantics of roundoff error propagation in finite precision calculations

We introduce a concrete semantics for floating-point operations which describes the propagation of roundoff errors throughout a calculation. This semantics is used to assert the correctness of a static analysis which can be straightforwardly derived from it. In our model, every elementary operation introduces a new first order error term, which is later propagated and combined with other error terms, yielding higher order error terms. The semantics is parameterized by the maximal order of error to be examined and verifies whether higher order errors actually are negligible. We consider also coarser semantics computing the contribution, to the final error, of the errors due to some intermediate computations. As a result, we obtain a family of semantics and we show that the less precise ones are abstractions of the more precise ones.     

内置转子换热管强化传热数值模拟

为分析内置转子换热管的传热效果,建立光管和内置转子换热管的三维模型,对换热管内流场、温度场、压力场以及传热过程进行模拟,得到管内流体的阻力特性和传热特性.模拟结果表明:内置转子换热管内的三维流动比较复杂,转子与管壁之间缝隙内的流体有明显的环绕流动,切向速度和径向速度也增大到一定范围;相同雷诺数条件下,内置转子换热管压降...     

光伏电池板输出特性的仿真及检验

依据太阳能电池的工程数学模型,使用Matlab软件包中的Simulation标准模块直接建立太阳能电池的仿真模型。在仿真中对模型本身的参数变化条件下的输出特性进行了研究,得出了太阳能电池输出特性变化的一般规律曲线。最后根据实际搭建的实验平台对所用的京瓷电池板的输出特性进行仿真,给出了测量曲线和分析。     

测量造型技术在汽车覆盖件成形数值模拟中的应用

汽车覆盖件冲压成形数值模拟需要有精确的曲面CAD模型来划分有限元网格。利用测量造型技术从覆盖件产品的原模型获得CAD模型,并在此基础上建立成形数值模拟所需有限元模型的全过程,讨论了其中的关键技术和难点。     

铝合金整体壁板填料滚弯成型有限元仿真

提出整体壁板填料滚弯成型工艺,建立填料滚弯成型过程的有限元模型.仿真分析填料和工艺参数对滚弯成型壁板的等效应力、剪切应力、等效应变和回弹等的影响规律.结果表明：壁板滚弯成型时纵向筋条的等效应力和应变最大,填料填充滚弯提高壁板等效应力和塑性应变的均匀性,改善壁板弯曲半径的均匀性,提高弯曲件的几何精度;随着压下量的增大,壁板回弹率减小.     

高频系统电子管功率放大电路的建模与仿真

根据四极电子管4CW10000B用户手册提供的电气参数和性能测试曲线,利用ADS软件建立仿真模型。结合华中科技大学研发的回旋加速器(CYCHU-10)高频(RF)系统的功率放大要求,利用电子管设计一个输出功率为10kW的功率放大器(PA),同时考虑到了无源网络匹配问题。对101 MHz RF系统中电子管功率放大器进行了仿真,仿真结果符合预期设计指标。     

Development and evaluation of the problem identification picture cards method

In this paper the development and assessment of a new formative evaluation method called the problem identification picture cards (PIPC) method is described. This method enables young children to express both usability and fun problems while playing a computer game. The method combines the traditional thinking-aloud method with picture cards that children can place in a box to indicate that there is a certain type of problem. An experiment to assess this method shows that children may express more problems (verbally, or with a picture card, or with a combination of a picture card and a verbalisation) with the PIPC method than without this method (in which they can only indicate problems verbally). Children in the experiment did not just replace verbalisations by using the provided picture cards and some children preferred to use the PIPC method during the test instead of the standard thinking-aloud method. The PIPC method or some aspects of the method could be a good instrument to increase the amount of information expressed by young children during an evaluation.     

On the use of binary and gray code schemes for continuous-tone picture representation

The paper discusses the idea of iterating the conversion of a continuous-tone picture from binary to Gray code representation. A simple recursive function is defined by means of which the value of the ith bit representing a picture point's grey level after the mth iteration is determined. The resulting rearrangement of grey levels as well as that of the bits throughout the planes is discussed next. The iteration is shown to repeat after 2″ steps, where n is the number of bit planes representing the picture. A data compression scheme is developed on the basis that prior to exact repetition, approximate repetitions take place during the iterations, and the resulting picture is almost the same as the original.     

聚合酶链式反应微流控生物芯片的数值模拟

微通道内具有一定流速的DNA反应混和物能否达到聚合酶链式反应(PCR)指定的温度PCR微流控芯片研究的关键问题.本文应用有限体元法(FEV)数值模拟该芯片上3个恒温区的直型、弯型、逶迤型三类微通道内,微流体的温度场和速度场.结果表明:对于宽100 μm深50μm的微通道,速度在0.002 m/s～0.02 m/s范围内,180.的弯道以及温度场、温度梯度的存在对其速度场分布无影响,微流体仍旱现为层流;微流体大约经过60μm的距离,其温度场达到稳态,其速度场充分发展为层流;采用宽4 mm深2 mm的空气隔热槽能起到隔热的效果.     

抗冲击性能要求下一种新型夹心板的设计研究

防护板在舰船上的应用非常广泛,它对于提高舰船抵抗水下爆炸冲击波载荷性能、抗碰撞冲击性能等都具有重要作用.文中利用薄壁圆管的吸能特性设计了离散型和紧密型圆管夹心板,使用大型非线性有限元软件MSC.Dytran建立水域、炸药及防护板的三维有限元模型,并进行水下爆炸数值仿真计算,从板的吸能能力、加速度响应、变形量三个方面分析了两种夹心板和普通平板在水下爆炸载荷作用下的抗冲击性能,仿真计算结果表明离散型夹心板的抗爆性能优于紧密型夹心板和普通平板.     

精准施药动态仿真无线信息采集系统的设计

为对精准施药进行深入研究,设计了精准施药动态仿真无线信息采集系统.该系统由上位管理机、多个信息采集终端、专用数控系统及RF模块等组成,能够对精准施药动态仿真系统中的各相关因素进行精确,同步测定.多个信息采集终端组成了信息采集网络,为便于网络中信息的传输,采用了信息无线传输技术.软件设计中通过定义传输协议,提高了信息传输的准确可靠性.为便于数控系统与上位管理机的连接,数控系统设计中增设了USB转换接口.现场大量实验表明,该系统性能可靠,配置灵活,信息采集精度高,具有较高的推广价值.     

Modeling and Monte Carlo simulation of photon transmission in glass-packaged WLEDs

Luminous efficiency is a key factor affecting the luminous performance of white light-emitting diodes (WLEDs). However, the mechanism and photon transport process in WLEDs encapsulated with multilayer films have not been elucidated. In this work, the effect of five different encapsulated inorganic glasses on the luminescence efficiency of WLEDs was investigated by using the Monte Carlo method. Compared with the conformal coating method, the away-from-coating method is more beneficial to improve the light output of WLEDs. The results show that the optical property of WLEDs is closely related to the concentration of phosphor and the thickness of the fluorescent glass. In addition, compared with other fluorescent glasses, fluorophosphate fluorescent glass has higher blue and yellow light transmittance and lower yellow light loss rate, which is suitable to be used as packaging materials to effectively improve the light output efficiency of WLEDs.     

消电管中集流放电针截面形状对消电效果影响的研究

本文对消电管中集流放电针的形状与消电效果之间的关系进行了研究。采用FEM的方法,对同一尺度的三种不同截面的集流放电针在空间中形成的静电场进行了仿真。分析了两个特定方向上的电场强度分布,并对电场强度与消电效果之间的关系进行了讨论。结果表明,其中截面为三角形的集流放电针在几个特定方向上电场强度的平均值最高,对静电的消除效果最好。     

Discrete simulation of NC machining

We describe a method for simulating and verifying the correctness of Numerical Control (NC) programs. NC programs contain the sequence of cutting tool movements which machine raw stock into a finished object. Our method is based on a discrete approximation of the object by a set of points. A vector is passed through each of the points and machining is simulated by finding the intersections of tool movements with these vectors. We present a point-selection method and an analysis that shows that the error introduced by the approximation can be made as small as desired. The run time is inversely proportional to the allowable error and the size of the cutting tool, and directly proportional to the distance that the cutting tool moves.This research was supported in part by the National Science Foundation under Contract No. DMC 8512621 and by the Ford Motor Company.