使用CAXA与Pro/E的渐开线椭圆齿轮三维建模与运动仿真

根据椭圆齿轮传动理论,分析了轮齿在节曲线上分布的特点,依据齿形折算法原理,以一个实例阐述了联合应用CAXA与Pro/E对椭圆齿轮进行三维实体建模.在此基础上构建了椭圆齿轮副运动仿真模型,实现了椭圆齿轮三维传动仿真,为进一步建立高速插秧机行星椭圆轮系分插机构仿真模型奠定了基础.     

非圆齿轮三维造型设计系统的开发

基于非圆形节曲线的非圆齿轮设计和计算要比圆齿轮复杂得多。由于非圆齿轮各轮齿的形状不尽相同,因此无法使用阵列、镜像等方法进行建模。目前的三维机械CAD软件还不能直接进行非圆齿轮实体建模。文章利用Visual Basic语言对三维软件SolidEdge进行二次开发,实现了齿轮的根切校验、凸性校验、压力角计算等功能,建立了非圆齿轮的三维建模系统,为非圆齿轮三维建模参数化设计提供了一种方法。生成的齿轮三维实体可用于装配设计、运动仿真及计算机辅助教学中。     

SolidWorks中的非圆齿轮实体建模方法研究

非圆齿轮因其节曲线为非圆形,目前的三维CAD软件还无法直接进行实体建模.研究了非圆齿轮轮齿设计方法及计算方程,采用Visual Basic语言进行SolidWorks二次开发,论述了系统开发的具体过程.以常用的椭圆齿轮为例实现了参数化实体建模.     

三维环境下高阶椭圆齿轮副的运动仿真

依据非圆齿轮传动特性,确定啮合齿轮在非圆节曲线上的位置及传动关系式,给出了非圆齿轮三维建模设计方法。利用Visual Basic语言对三维软件Solid Edge进行二次开发,实现了三维环境下椭圆齿轮参数化设计及运动仿真,能直观的观察到齿轮副的啮合状况。系统运行效果良好,为非圆齿轮传动三维设计提供了一种方法。     

非圆齿轮系啮合传动的计算机辅助设计

基于自由节曲线的非圆齿轮可实现非匀速比传动,但其设计复杂、制造成本高.利用动画技术实现非圆齿轮传动的计算机辅助设计,可增强非圆齿轮设计的可预见性,降低成本.依据非圆齿轮啮合原理,确定轮齿在节曲线上的对应位置,推导了轮齿的齿廓、齿顶、齿根的曲线方程.给出了齿形设计的计算方法及啮合传动的模拟程序.最后,通过实例验证了方法的可行性.     

非圆齿轮的应用与动力学分析

目的为了验证某自动包装机传动系统的动态特性,结合某自动包装机的特定需求,文中设计一种新型的非圆齿轮系统,并对其进行动力学特性研究。方法首先介绍非圆齿轮的特点,建立非圆齿轮的数学模型,并进行推导和分析,得到其动力学方程;然后利用UG软件建立非圆齿轮的三维模型,运用Adams开展动力学仿真研究,并对比在相同中心距下非圆齿轮和圆形齿轮的动力学特性。结果新设计的这种非圆齿轮比圆形齿轮的啮合力大500 N左右,主动齿轮的加速度是其10倍左右。结论通过对比非圆齿轮和传统齿轮发现,非圆齿轮具有变传动比、传动装置空间布局灵活等优点,由于非圆齿轮无法制成斜齿,故传动性能要略低于圆形齿轮。     

基于圆柱螺线法的偏置机构控制算法仿真及实验研究

偏置机构芯轴偏心位移的精确控制是实现导向钻进的核心问题.针对一种新型静态指向式偏置机构,首先介绍了其结构组成以及轨迹控制原理;其次,建立基于圆柱螺线法的井眼轨迹控制算法数学模型,并以三维多目标井眼轨迹为例,讨论了如何通过该机构实现井眼轨迹的控制,并基于SolidWorks和ADAMS进行机构虚拟模型的建立和运动仿真,得到偏置机构运动情况曲线;最后,建立基于LabVIEW的实验平台对偏置机构样机的导向性能进行验证.通过仿真结果、实验值和理论值的比较,确定该算法产生较好的控制效果,证明了实现机构导向控制的可行性,从而为旋转导向钻井工具实际轨迹控制算法设计与优化奠定理论基础.     

偏心齿轮变速输纸机构优化设计

将优化设计概念引入偏心齿轮变速输纸机构设计,建立了纸张到达前规时的速度作为目标函数优化设计的数学模型,分析和讨论了其求解方法。使基于传统分析的设计方法成为基于综合的设计,避免了具有较大盲目性的参数试凑和反复校验过程,提高了该机构传动设计的科学性和一次成功率。优化结果表明,采用偏心齿轮变速输纸机构,可以在满足各方面约束条件下,得到最佳的设计方案,其较未采用偏心齿轮变速机构输纸,速度可降低61%,实现变速输纸的目的。     

基于COSMOSMotion的偏心齿轮机构运动仿真

介绍了三维机械设计软件SolidWorks及其二次开发,并基于SolidWorks建立了偏心齿轮变速机构的实体模型,运用COSMOSMotion对其进行了运动仿真,得出相应的运动曲线,将以电子表格形式存放的动画模拟数据和理论分析数据做了一定的对比和分析,提高机构设计的直观性.     

椭圆类齿轮参数化设计与运动仿真系统的开发

非圆齿轮因其节曲线为非圆形,计算复杂,设计困难,目前的三维设计软件都无法直接进行实体建模。根据非圆齿轮的设计理论,利用Visual Basic 6.0良好的界面设计功能和计算能力对SolidWorks进行二次开发,设计出椭圆类齿轮参数化设计与运动仿真系统,实现了椭圆类齿轮的三维参数化建模与运动仿真。论述了系统的开发过程,运行实例表明系统界面友好,设计正确。解决了椭圆类齿轮设计中的复杂计算和三维实体造型难的问题,可提高设计精度、缩短产品开发周期,保证产品质量。     

凝固科学技术与材料

从凝固科学与实践发展的角度介绍了当前凝固材料体系的基本框架和凝固科学主要发展阶段的基本理论。作为材料科学与工程的基本组成，凝固科学技术正在现代科学理论的基础上针对传统材料的改性提高和新材料的发展需求，以控形、控构、控性为目标开展优质铸件的定向、晶体生长、快凝、深过冷及各种新型和超常领域凝固过程的研究，并介绍了其中某些方面和展望了可能的发展趋势。     

Development and challenges of planning and scheduling for petroleum and petrochemical production

Production planning and scheduling are becoming the core of production management, which support the decision of a petrochemical company. The optimization of production planning and scheduling is attempted by every refinery because it gains additional profit and stabilizes the daily production. The optimization problem considered in industry and academic research is of different levels of realism and complexity, thus increasing the gap. Operation research with mathematical programming is a conventional approach used to address the planning and scheduling problem. Additionally, modeling the processes, objectives, and constraints and developing the optimization algorithms are significant for industry and research. This paper introduces the perspective of production planning and scheduling from the development viewpoint.     

The Candela and Photometric and Radiometric Measurements

The national measurement system for photometric and radiometric quantities is presently based upon techniques that make these quantities traceable to a high-accuracy cryogenic radiometer. The redefinition of the candela in 1979 provided the opportunity for national measurement laboratories to base their photometric measurements on optical detector technology rather than on the emission from high-temperature blackbody optical sources. The ensuing technical developments of the past 20 years, including the significant improvements in cryogenic radiometer performance, have provided the opportunity to place the fundamental maintenance of photometric quantities upon absolute detector based technology as was allowed by the 1979 redefinition. Additionally, the development of improved photodetectors has had a significant impact on the methodology in most of the radiometric measurement areas. This paper will review the status of the NIST implementation of the technical changes mandated by the 1979 redefinition of the candela and its effect upon the maintenance and dissemination of optical radiation measurements.     

PSD和PWELCH函数的分析改进及应用

针对MATLAB中两个内建功率谱密度计算函数psd()和pwelch()计算结果迥异的现象,在功率谱密度估计理论的基础上,根据经典的周期图理论和Welch平均周期图方法,通过详细分析源程序,解析计算方法,发现psd()计算的并不是工程单边功率谱密度,而是采样信号双边谱,故与pwelch()结果迥异,另外pwelch()不能对分段信号数据进行预处理。就上述不足提出了相应的改进措施,比较验证表明改进措施行之有效。     

江澳两地高校文创设计的协同研究与商业实践

目的 探索江门世遗文化的传承、发展和转化的新思路,践行国家在《粤港澳大湾区发展规划》纲要中要求江门承担与港澳地区文化创意合作与开发任务的分工。方法 与澳门高校紧密合作,开展专业培训课程,以开平碉楼为例,从人文视角开展设计研究,梳理开平碉楼的文化脉络,把世遗文化的元素和其背后的文化融入文创产品中,提升文创产品的附加值,推动当地文创产业结构的变革。结果 两地高校构建了稳定的科研团队,开设长期有效的设计培训课程,与景区建立了研究协作关系,帮助景区构建了一套产销研的商业模式。结论 以跨区域高校合作为平台,以文创产品为抓手,依托江澳两地的资源优势,可以构建江门世遗文化全新的品牌形象,最终推动开平世遗文化的活化。     

Creation and motion of dislocations and fracture in metal and silicon crystals

By making a step on one surface ( ) of a rectangular small paralellepiped copper crystal, dislocations could be created by the molecular dynamic method. The dislocation created was not a complete edge dislocation but a pair of Heidenreich-Shockley partial dislocations. Each time a dislocation was created, the stress on the surface was released. Small copper crystals having a notch were pulled (until fracture), compressed and buckled by use of the molecular dynamic method. An embedded atom potential was used to represent the interaction between atoms. Dislocations were created near the tip of the notch. A very sharp yield stress was observed. The results of high speed deformations of pure silicon small crystals using the molecular dynamics are presented. The results suggest that plastic deformation may be possible for the silicon with a high speed deformation even at room temperature. Another small size single crystal, the same size and the same surfaces, was compressed using molecular dynamic method. The surfaces are {110}, {112} and {111}. The compressed direction was [111]. It was found that silicon crystals are possible to be compressed with a high speed deformation. This may suggest that silicon may be plastically deformed with high speed deformation.     

Error and uncertainty in modeling and simulation

This article develops a general framework for identifying error and uncertainty in computational simulations that deal with the numerical solution of a set of partial differential equations (PDEs). A comprehensive, new view of the general phases of modeling and simulation is proposed, consisting of the following phases: conceptual modeling of the physical system, mathematical modeling of the conceptual model, discretization and algorithm selection for the mathematical model, computer programming of the discrete model, numerical solution of the computer program model, and representation of the numerical solution. Our view incorporates the modeling and simulation phases that are recognized in the systems engineering and operations research communities, but it adds phases that are specific to the numerical solution of PDEs. In each of these phases, general sources of uncertainty, both aleatory and epistemic, and error are identified. Our general framework is applicable to any numerical discretization procedure for solving ODEs or PDEs. To demonstrate this framework, we describe a system-level example: the flight of an unguided, rocket-boosted, aircraft-launched missile. This example is discussed in detail at each of the six phases of modeling and simulation. Two alternative models of the flight dynamics are considered, along with aleatory uncertainty of the initial mass of the missile and epistemic uncertainty in the thrust of the rocket motor. We also investigate the interaction of modeling uncertainties and numerical integration error in the solution of the ordinary differential equations for the flight dynamics.     

Miniature and MEMS-type vacuum sensors and pumps

In the paper, the observable trends of the actual research and development of selected types of miniature and MEMS-type vacuum sensors are presented. Some information about the new types of active vacuum gauges, which are offered by the leading manufacturers of the vacuum measurement instruments, is given. Next, the list of MEMS devices that need vacuum for proper operation is presented. Some aspects of vacuum-encapsulation of MEMS devices, on wafer level and package level are shown. The new conceptions of obtaining and maintenance of high and ultra-high vacuum in MEMS devices are described. They concern the conception of integration of a miniature orbitron pump on-chip with MEMS-type device or with vacuum part of the portable advanced instruments such as electron microscope, ion mass spectrometer, and free electron laser.