基于细分粒子的刚体破裂动画

为了模拟固体在外力作用下产生的破裂现象,提出一种采用细分粒子的刚体破裂的模拟算法.该算法首先将固体的四面体网格绑定到一系列离散的粒子上;再利用光滑粒子流体动力学（SPH）对线弹性力学方程进行离散求解;并采用粒子细分的算法来进行开裂面的生成和延展.最后实现了多个固体现象的模拟,如砖块碎落、砖墙受力倒塌等.文中算法可适用于刚体脆性破碎的动画应用.     

基于随机骨料模型的EPS混凝土粒子尺寸效应分析

建立基于随机分布的EPS混凝土细观力学模型,对EPS混凝土的受压损伤破坏过程进行数值模拟,分析EPS混凝土的损伤破坏过程。研究表明,EPS混凝土的损伤破坏有两种形态,即延性破坏和脆性破坏。延性破坏与EPS颗粒的面积占有率、断裂过程区长度有关;脆性破坏与EPS颗粒的面积占有率、粒径大小以及颗粒间距有关。在EPS颗粒面积占有率较低的情况下,EPS混凝土的粒子尺寸效应对混凝土力学性能的影响较明显,在较高面积占有率的情况下,粒子尺寸效应对其影响较小。随着EPS颗粒面积占有率的增加,EPS混凝土损伤破坏由脆性破坏向延性破坏转变。建立基于损伤力学与断裂力学的粒子尺寸效应数学模型,用数值模拟进行验证,发现两者吻合较好。     

剪切场作用下短纤维复合材料纤维取向的耗散粒子动力学研究

为了描述短纤维复合材料注射充模过程的介观结构生成、演化规律,借鉴硬棒模型和粒子模型,建立了一种修正的耗散粒子动力学模型,采用修正的Verlet算法对剪切场作用下短纤维复合材料熔体纤维取向进行研究,模拟结果与实际基本符合.     

基于高斯粒子滤波的当前统计模型跟踪算法

对于非线性系统估计问题,高斯粒子滤波器可以获得近似最优解,与粒子滤波器相比其优点是不需要重采样步骤和不存在粒子退化现象.采用高斯粒子滤波代替当前模型自适应跟踪算法中的卡尔曼滤波,将高斯粒子滤波与当前统计模型的优点相结合,提出了一种新的当前统计模型自适应跟踪算法,用于非线性非高斯系统的机动目标跟踪.MonteCarlo仿真表明,该算法跟踪精度优于标准的交互多模型算法和当前统计模型自适应跟踪算法,实时性好于交互多模型粒子滤波算法.     

基于均值移动确定性漂移的改进CONDENSATION人脸跟踪

针对视频序列目标跟踪粒子滤波经典CONDENSATION算法用先验转移概率,即采用一阶或二阶AR模型难以有效进行粒子传播的问题,提出了一种改进的CONDENSATION人脸跟踪算法.首先利用高效的均值移动跟踪器以低廉的计算成本初步进行人脸目标跟踪定位,并用此初步跟踪结果来确定CONDENSATION粒子动态传播模型中的确定性漂移部分,然后只需加入一个较小的随机扩散噪声来完成粒子的传播.由于这样所得的粒子点能较为集中地分布在状态的真实区域附近,因而大大提高了粒子的利用效率.人脸跟踪实验表明,该改进算法的性能明显优于原CONDENSATION方法.     

A particle filter algorithm based on gray forecast

针对标准粒子滤波(SPF)算法在目标机动时跟踪滤波性能不高的问题,引入灰色预测理论,提出了一种基于灰色预测的粒子滤波(PFGF)算法,给出了算法的具体描述和运算流程.当预先建立的状态模型不再适用于目标的真实运动状态时,该方法具有良好的预估性能,减少了对事先假定目标状态模型的依赖性.与SPF方法进行了蒙特卡洛仿真比较分析,实验结果证明,PFGF算法在不增加计算复杂度的情况下,提高了跟踪精度,能够很好地克服粒子退化现象.     

粒子群算法在超声三维坐标测量中的应用

提出一种基于粒子群算法的三维坐标反演模型,实现了超声波三坐标测量中三维坐标的高精度反演,提高了坐标反演迭代过程的鲁棒性.同时介绍了超声波测距系统的原理,推导了三维坐标反演的目标函数,建立了基于粒子群算法的反演模型,并进行了实验研究.通过软件仿真,对粒子群算法在超声波三维测量上的可行性和鲁棒性进行了验证,并搭建超声波三维定位平台,在1m×1m×2m空间中进行了测量实验.结果表明,测量的绝对误差小于10mm,具有较高的反演精度.     

摇摆结构刚体模型研究综述

合理的理论模型对于结构分析至关重要,摇摆结构理论研究中应用最为广泛的模型是摇摆刚体模型。该文对摇摆结构刚体模型进行了较为系统考察与总结,对摇摆刚体模型的研究起源与研究现状进行了介绍,针对经典摇摆刚体模型、其他典型摇摆刚体模型、相关试验研究、有限元模拟及其在结构体系中的应用进行了探讨,指出了已有模型的优点与局限性,提出摇摆结构刚体模型未来研究的关键问题,为建立更完善实用的摇摆结构刚体模型及应用于摇摆结构分析提供了参考。     

AgOx薄膜的形貌、光谱以及激光烧蚀研究

制备了不同氧分压比的AgOx薄膜,对其进行了原子力(AFM)形貌观察,发现分压比0.4时,薄膜的粗糙度最小,均匀性也最好.光谱性质表明:随着分压比的增加,存在着金属向半导体的转变;经过热处理后的共振吸收峰和扫描电(SEM)表明了金属银粒子的析出.不同激光功率下的烧蚀实验表明:在激光照射下存在着两记录(烧蚀)形态,一种是银粒子散布在其间的气泡型;另一种是形成中间烧蚀孔,银粒子在孔附近密集的破裂气泡型.     

基于粒子群优化算法和BP神经网络的变频压缩机功率预测

本文针对变频压缩机的功率测量困难,测量误差大等问题,提出了一种仿真测量模型。利用粒子群算法寻找全局最优粒子,用它初始化BP神经网络的阈值和权值,测量变频压缩机的功率。本文共建立了3种仿真模进行对比,分别为BP神经网络模型、GA-BP神经网络模型和PSO-BP神经网络模型,然后分别通过3种模型的内插、蒸发温度外推和冷凝温度外推的测试方法对变频压缩机进行功率测量,对比分析其预测结果的平均相对误差和拟合程度。结果表明:基于粒子群算法优化的BP神经网络模型明显优于其他两个模型,特别是在冷凝温度外推测试中,较其他两个神经网络相对误差降低了1. 11%、2. 64%,3种测试方法下的平均相对误差均小于1%,拟合程度在0. 9以上,表明基于粒子群算法优化的BP神经网络模型对变频压缩机功率有较好的测量能力,而且有较强的泛化能力。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...