基于质点-弹簧模型的布模拟方法

布的计算机模拟是服装 CAD和计算机图形学中的一个重要研究课题 ,该文提出了一种基于质点 -弹簧模型的布模拟方法。在质点 -弹簧模型的布模拟方法中 ,布被视为由许多质点和弹簧组成 ,在力的作用下 ,布产生变形 ,最后采用欧拉方法 ,求解布的运动方程。实验结果表明 ,该模型可以得到逼真的模拟效果 。

布模拟算法在机载雷达点云滤波中的研究

点云就是用物体表面大量的点将现实三维世界的物体离散化表示,所谓的点云滤波,就是指要区分开哪些点云属于地面(称为地面点),哪些点云属于高出地面的地物(如建筑物、树木、车辆等),点云滤波是后续点云数据处理的关键步骤。文章将介绍布模拟滤波(Filtering Method Based on Cloth Simulation)算法原理,基于美国国际摄影测量与遥感协会提供的数据来做滤波,实验表明在大多数地形下,相比传统的点云滤波算法,布模拟算法滤波效果比较好。

基于布模拟算法与三角形插值的稀疏点云处理方法

为了提高深度学习模型对样本的训练以及后续的分割效果,需要实现一种快速高效的点云插值方法。基于三角形内部线性插值,并结合三角网的面积以及边长权重进行插值,对室外复杂场景实测点云使用布模拟算法进行多次不同分类阈值下的滤波后,分别对地面点和非地面点进行插值。以ModelNet10点云数据集与郑州市高新技术开发区的一处机载LiDAR点云为例进行插值实验,插值效果理想。

基于布模拟滤波和支持向量机的隧道三维点云提取算法

针对传统隧道点云提取方法存在先验条件要求较高、参数依赖性较强、通用性较差的问题,提出基于布模拟滤波和支持向量机的隧道三维点云提取算法。介绍隧道三维点云提取算法流程,分析点云数据获取与下采样算法、基于布模拟滤波算法的地面滤波,以及基于支持向量机的隧道点云提取算法,并开展现场验证试验。试验结果表明,基于布模拟滤波和支持向量机的隧道三维点云提取算法,可准确剔除与隧道点云特征不一致的非隧道点云,隧道点云提取具有处理速度快、准确率高、通用性强的特点。但如果隧道中出现大量距离隧道非常接近的物体,且体积较小,该算法会出现较多误判。减少误判是该隧道三维点云提取算法今后的研究方向。

基于布模拟算法在LiDAR点云中生成数字高程模型

机载激光雷达(LiDAR)能获得高精度的三维点云数据,可透过林叶到达地表面,快速准确反映出研究区域连续起伏的地形特征,有利于建立高分辨率数字高程模型(DEM)。用布模拟滤波(CSF)算法对机载LiDAR点云数据进行滤波,通过设置算法的布粒子生成个数和地面点分类阈值,从6组不同地势条件的点云数据中提取地面点云,用交叉表法计算出分类的Kappa系数在0.851~0.954之间。用CSF算法提取的地面点生成1 m×1 m的DEM,并与研究区域提供的DEM进行线性拟合,实验结果表明,两者的回归直线拟合优度系数R^2大于0.99,均方根误差在0.10451~0.30387之间。布模拟算法在提取点云地面点方面设置参数少、适用地形广,且基于该算法生成的高分辨率DEM能很好地表达该地区连续起伏的地表变化和地形特征。

基于线网分类的模拟电路自动布线器

提出一种基于线网分类的模拟电路自动布线方法,并设计实现了一种基于线网分类的模拟电路布线器NCARouter.基于模拟电路性能要求,布线器中的线网被分为关键线网、普通线网和电源/地线网3种类型.同时,模拟电路的性能约束被转化为线网的属性描述,包括几何约束(如对称)、电学约束(如匹配)、寄生参数描述等.此外,针对不同类型的线网,该布线器使用了不同的布线算法,以满足总体性能约束.实验结果表明,该布线器不仅能很好地完成布线,还能确保满足模拟电路各种性能要求.

Molecular simulation study of the microstructures and properties of pyridinium ionic liquid[HPy][BF_(4)]mixed with acetonitrile

The microstructures and thermodynamic properties of mixed systems comprising pyridinium ionic liquid[HPy][BF_(4)]and acetonitrile at different mole fractions were studied using molecular dynamics simulation in this work.The following properties were determined:density,self-diffusion coefficient,excess molar volume,and radial distribution function.The results show that with an increase in the mole fraction of[HPy][BF_(4)],the self-diffusion coefficient decreases.Additionally,the excess molar volume initially decreases,reaches a minimum,and then increases.The rules of radial distribution functions(RDFs)of characteristic atoms are different.With increasing the mole fraction of[HPy][BF_(4)],the first peak of the RDFs of HA1-F decreases,while that of CT6-CT6 rises at first and then decreases.This indicates that the solvent molecules affect the polar and non-polar regions of[HPy][BF_(4)]differently.

人民日报社报刊综合业务楼制冷机房设备及管线排布深化设计

介绍了人民日报社报刊综合业务楼机房概况、制冷机房设备布局深化的重要性,决定对制冷机房设备及管线排布进行深化设计,具体设计内容包括深化前图纸问题分析、机房设备区域划分排布、设置排水沟、管线细化排布、管道阀部件预先模拟排布、大管径管道支架设置等方面。

在系统可编程模拟电路及其编程实现

ispPAC的出现 ,改变了传统的模拟电路的设计思想 ,它具有在系统可编程的特点 ,无需外围元器件可以灵活地实现信号放大、滤波、D/A转换 .利用它设计电路方便、快捷 ,一片ispPAC芯片可以反复使用 10 0 0 0次 ,同时还可以将设计的电路加密保护 .

OPTIMIZATION FOR COMBAT CONFIGURATION OF AIR DEFENSE WEAPON SYSTEMS

At evaluating the combat effectiveness of the defense system, target′s probability to penetrate the defended area is a primary care taking index. In this paper, stochastic model to compete the probability that target penetrates the defended area along any flight path is established by the state analysis and statistical equilibrium analysis of stochastic service system theory. The simulated annealing algorithm is an enlightening random search method based on Monte Carlo recursion, and it can find global optimal solution by simulating annealing process. Combining stochastic model to compete the probability and simulated annealing algorithm, this paper establishes the method to solve problem quantitatively about combat configuration optimization of weapon systems. The calculated result shows that the perfect configuration for fire cells of the weapon is fast found by using this method, and this quantificational method for combat configuration is faster and more scientific than previous one based on principle via map fire field.

MARS:A General Multilayer Area Router

Based on a ripped-up and rerouted methodology,a multilayer area detailed router is presented by using simulated evolution technique.A modified maze algorithm is also performed for the single net.

Local structure of calcium silicate melts from classical molecular dynamics simulation and a newly constructed thermodynamic model

The distributions of local structural units of calcium silicate melts were quantified by means of classical molecular dynamics simulation and a newly constructed structural thermodynamic model. The distribution of five kinds of Si-O tetrahedra Qi from these two methods was compared with each other and also with the experimental Raman spectra, an excellent agreement was achieved. These not only displayed the panorama distribution of microstructural units in the whole composition range, but also proved that the thermodynamic model is suitable for the utilization as the subsequent application model of spectral experiments for the thermodynamic calculation. Meanwhile, the five refined regions mastered by different disproportionating reactions were obtained. Finally, the distributions of two kinds of connections between Qi were obtained, denoted as Qi-Ca-Qj and Qi-[Ob]-Qj, from the thermodynamic model, and a theoretical verification was given that the dominant connections for any composition are equivalent connections.

Molecular Dynamics Study on Configuration Energy and Radial Distribution Functions of Ammonium Dihydrogen Phosphates Solution

Molecular dynamics simulations were carried out to study the configuration energy and radial distribution functions of mmonium dihydrogen phosphate solution at different temperatures. The dihydrogen phosphate ion was treated as a seven-site model and the ammonium ion was regarded as a five-site model, while a simple-point-charge model for water molecule. An unusually local particle number density fluctuation was observed in the system at saturation temperature. It can be found that the potential energy increases slowly with the temperature from 373 K to 404 K, which indicates that the ammonium dihydrogen phosphate has partly decomposed. The radial distribution function between the hydrogen atom of ammonium cation and the oxygen atom of dihydrogen phosphate ion at three different temperatures shows obvious difference, which indicates that the average H-bond number changes obviously with the temperature. The temperature has an influence on the combination between hydrogen atoms and phosphorus atoms of dihydrogen phosphate ion and there are much more growth units at saturated solutions.

Numerical study of pressure drop for a new fibrous media model

An open-source computational fluid dynamics（CFD）code named OpenFOAM is used to validate the flow field characteristics（flow patterns and pressure drop）around a single cylinder.Results show that OpenFOAM is suitable for simulating the low Reynolds number flow and Shaw＇s analytical expression is one of the solutions to Stokes＇ paradox.Experiments are performed on fibrous media and OpenFOAM simulation is carried out using the Tronville-Rivers two-dimensional random fiber model in terms of the characteristics of pressure drop.It is shown that the Kuwabara model predicts the pressure drop of fibrous filter media more accurately than the Happel model,and the experimental pressure drop is between simulated pressure drops with both non-slip and full-slip boundaries on fiber surfaces.

基于碰撞问题及应用算法的优化

碰撞问题很早就引起了人们的关注，为了提高动画的质量和计算时间，解决完全碰撞时间和反映脉冲，本文提出了优化方法来解决碰撞问题，并在具体实例中阐述了如何使用该优化方法。

CFD-supported optimization of flow distribution in quench tank for heat treatment of A357 alloy large complicated components

The flow distribution in quench tank for heat treatment of A357 alloy large complicated components was simulated using FLUENT computational fluid dynamics（CFD） software.The flow velocity and the uniformity of flow field in two types of quench tanks（with or without agitation system） were calculated.The results show that the flow field in the quench tank without agitation system has not evident regularity.While as for the quench tank with agitation system,the flow fields in different parameters have certain regularity.The agitation tanks have a distinct advantage over the system without agitation.Proper process parameters were also obtained.Finally,the tank model established in this work was testified by an example from publication.This model with high accuracy is able to optimize the tank structures and can be helpful for industrial production and theoretical investigation in the fields of heat treatment of large complicated components.

Molecular Dynamic Simulation of Melting Points of Trans-1,4,5,8- tetranitro-1,4,5,8-tetraazadacalin （TNAD） with Some Propellants

Molecular dynamic simulation was employed to predict the melting points Tm of TNAD/HMX, TNAD/RDX, TNAD/DINA, and TNAD/DNP systems （tans-1,4,5,8- tetranitro-1,4,5,8-tetraazadacalin （TNAD）, dinitropiperazine （DNP）, cyclotetramethylenetetranitroamine （HMX）, cyclotrimethylenetrinitramine （RDX）, and N-nitrodihydroxyethylaminedinitrate （DINA））. Tm was determined from the inflexion point on the curve of mean specific volume vs. temperature. The result shows that the Tm values of TNAD/HMX, TNAD/RDX, and TNAD/DINA systems are 500, 536, and 488 K, respectively. The TNAD/DNP system has no obvious Tm value, which shows the system is insoluble. Using Tm, the solubility of the four systems was analyzed. The radial distribution functions of the four systems were analyzed and the main intermolecular forces between TNAD and other energetic components are short-range interactions. The better the solubility is, the stronger the intermoleenlar interaction is. In addition, the force field energy at different temperature was also analyzed to predict Tm of the four systems.

SIMULATION OF MICROSTRUCTURE AND RHEOGICAL PROPERTIES OF SURFACTANT SOLUTION

The Brownian dynamics （BD） simulation of a dilute surfactant solution is conducted in a steady shear flow. The rodlike micelle is assumed as a rigid rod composed of lined-up beads. A novel intercluster potential model is introduced for describing the interactions between, micelles. In the model, the Lennard-Jones and the soft-sphere potentials are used as inter-bead potentials for end-end and interior-interior beads, respectively. The micelles are combined at their ends to form a network structure at lower shear rates and are disconnected to become more and more parallel to the shear flow direction with increasing shear rate. The change of micellar microstructures with the variation of the shear rate results in shear thinning characteristics of the computed shear viscosities and first normal stress difference coefficients. The effects of surfactant solution concentration on the micellar structures and rheological properties are also investigated. Results show that the shear viscosities and the first normal stress difference coefficients increase with increasing the viscosity of the surfactant solution.

Atomistic simulation of thermal effects and defect structures during nanomachining of copper

Molecular dynamics （MD） simulations of monocrystalline copper （100） surface during nanomachining process were performed based on a new 3D simulation model. The material removal mechanism and system temperature distribution were discussed. The simulation results indicate that the system temperature distribution presents a roughly concentric shape, a steep temperature gradient is observed in diamond cutting tool, and the highest temperature is located in chip. Centrosymmetry parameter method was used to monitor defect structures. Dislocations and vacancies are the two principal types of defect structures. Residual defect structures impose a major change on the workpiece physical properties and machined surface quality. The defect structures in workpiece are temperature dependent. As the temperature increases, the dislocations are mainly mediated from the workpiece surface, while the others are dissociated into point defects. The relatively high cutting speed used in nanomachining results in less defect structures, beneficial to obtain highly machined surface quality.

Novel hybrid optimal algorithm for broad-band Raman amplifier

A hybrid optimal algorithm, named the SAA-PA in brief, based on the simulated annealing algorithm （SAA） and the Powell algorithm （PA） is proposed. The proposed algorithm puts the random search strategy of the SAA into the PA, which can prevent optimizing courses from trapping in local optima. The SAA-PA can effectively solve multimodal optimization in the distributed multi-pump Raman amplifier （DMRA）. Optimal results show that, under the conditions of the on-off gain of 10 dB, the gain bandwidth of larger than 80 nm and the fiber length of 80 km, the gain ripple of less than 1.25 dB can be designed from the DMRA with only four backward pumps after the optimization of the proposed SAA-PA. Compared with the pure SAA, the SAA-PA can attain a lower gain ripple with the same number of pumps. Also, the relationship between the optimal signal bandwidth and the number of pumps can be simulated numerically with the SAA-PA.