基于分形和小波的几何型面加工误差综合分析

对几何型面加工误差提出并建立了基于分形和小波的综合分析方法，可以精细分析几何型面加工误差的微细成分，并重构出型面轮廓加工误差曲线，以便进行公差与性能关系分析以及加工过程质量监控等相关工作。应用实例表明，该方法是非常有效的。     

基于周期分解的机床主轴回转误差预报模型

随着精密机械、惯性技术和宇宙科学等学科的发展 ,超高精密零件在这些领域有着重要用途。但是其制造以及测量均受到主轴回转误差的限制。当今加工预测补偿控制已成为精密加工技术的一个发展研究方向。依靠传统的主轴回转误差预测模型仅仅能补偿掉误差成分中可表达的重复误差。本文对主轴回转误差采用了基于周期分解的组合建模方法 ,建立了更有效的预测模型。仿真实验结果表明该模型提高了回转误差的预报精度 ,为预测补偿精密加工技术奠定了基础     

加工中心的几何误差和热误差综合补偿模型

本将剂次坐标变换理论结合刀具与工件联结链矢量概念建立了加工中心误差运动综合偿模型。此模型不但包了三轴加工中心的几何误差而且还饮食了热误差的共计35个误差元素,使用此模型的补偿加工大幅度地提高了加工中心的加工精度。该方法可对多轴设备和机器人的非网体误差运动进行描述。     

雨量预报方法优劣的评价模型

本文通过5种不同的插值方法得到所有观测站点的预报值：再从不同角度建立了评价预报方法两个模型。模型Ⅰ是基于预报值与实测值的误差平方和的。模型Ⅱ是基于公众对预报准确度的感受差异的。该模型考虑了公众对预报等级误差感受的不对称性以及不同时段的预报误差对公众行动的影响度差异，建立了公众不满意度指标。两种模型评价的结果是第一种预报方法要优于第二种预报方法。     

基于机床体误差模型的加工面形误差预测

零件面形精度满足要求是超精密装备实现其关键功能的重要保证.影响工件加工面形精度的因素很多,机床体误差是其中最关键的因素.通过构建机床误差元与加工面形误差之间的直接关系来进行面形误差预测研究.提出了一种基于机床体误差模型的频域多尺度面形误差预测方法,该方法可结合机床体误差模型、工艺参数、加工轨迹等进行频域多尺度面形误差预测,可为加工路径规划、机床设计等提供理论参考,从而提高加工精度.进行了低频PV面形误差预测的实例研究,采用的机床为一台五轴联动超精密机床,加工表面为凹形截圆锥台锥面.通过实验与理论分别获得PV面形误差,其相对误差为17.3%,证明基于机床体误差模型的低频PV面形误差预测是可行的.     

船体梁在近距爆炸冲击波作用下动态响应的相似律研究

以船体梁在爆炸冲击波作用下发生整体塑性运动响应的理论方法为基础,首先确定了影响梁整体结构最终塑性变形的相关物理量,利用定律对该问题进行相似性分析,给出相似参数和准确相似条件。研究了考虑结构应变率强化效应造成的相似畸变问题,分析了模型缩比尺度、模型应变率大小以及不同结构材料对相似误差的影响。研究发现:随着缩比尺度的减小,或结构应变率响应值的增大,预报误差将增大;所用结构材料的应变率敏感度越高,模型预报原型的误差越大。结论可用于指导船体梁在水下爆炸冲击波作用下动态响应的模型试验设计。     

全自动激光切割法加工板材试样

研制了一项兼备冷轧板、热轧板、酸洗板试样加工能力的全自动激光切割加工技术,实现了板材的自动上样、自动打标、自动生成切割模型并切割试样、自动分拣、自动精加工等全流程的自动激光切割加工。将该技术与传统加工工艺进行对比分析,研究了全自动激光切割法加工板材试样的优势。研究结果可为提高冶金行业板材试样的加工效率、加工质量提供理论基础。     

误差齿面下直齿轮副内部激励及动态特性分析

基于齿轮加工、安装误差的分布规律,建立了渐开线直齿轮的误差齿面模型,提出了适用于该误差齿面模型的齿轮承载接触分析算法,研究了不同误差对直齿轮副内部激励的影响规律;建立了直齿轮副弯扭耦合动力学模型,分析了不同误差下齿轮系统的动态特性。研究表明：加工误差中,齿距偏差是齿轮副内部激励的主要影响因素;齿距偏差作用下,综合啮合误差呈阶跃变化,当阶跃值超过一定范围后时变啮合刚度发生突变;安装误差影响下,综合啮合误差为一定值,时变啮合刚度随中心距和轴线倾斜误差的增加而减小;为减小齿轮系统动态传递误差的峰峰值,齿距偏差应根据载荷大小合理分配,同时应避免由轴线倾斜误差导致的偏载现象发生。     

基于贝叶斯模型的动态误差实时修正方法研究

应用贝叶斯动态模型理论,探讨了非平稳动态测量误差贝叶斯建模原理及实时修正的方法.由多项式模型、季节模型、回归模型和噪声模型等模型分量组合的贝叶斯动态模型,较好地描述了各种系统误差和随机误差的综合特征,客观反映了动态测量误差的变化规律.利用贝叶斯递推算法和标准信号插入,适时对动态误差模型参数进行调整,以适应非平稳动态误差的时变性,有效控制了动态模型预报精度损失,提高了动态误差实时修正的精度.通过长光栅动态测量系统实时误差修正实例,验证了该方法正确可行,误差修正效果显著,具有较高的应用价值.     

双线性时间序列模型的参数辨识

导出了双线性时间序列模型参数预报误差估计的递推算法，采用伴随常微分方程的稳定性分析方法分析了双线性模型的ｍ－可逆性对可预报误差估计算法收敛性的影响，并给出了相应的仿真示例。     

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.     

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.……     

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.     

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.     

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 ...     

Effect of Oxide Assisted Metal Nanoparticles on Microstructure and Morphology of Gallium oxide Nanowires

Several researches have been reported about the characteristic of β-Ga2O3 nanowires which was synthesized on nickel oxide particle. But indeed, recent researches about synthesis of β-Ga2O3 nanowires on oxide-assisted transition metal are limited to nickel or cobalt oxide catalyst. In this work, Gallium oxide (β-Ga2O3 ) nanowires were synthesized by a simple thermal evaporation method from gallium powder in the range of 700 - 1000℃ using the iron, nickel, copper, cobalt and zinc oxide as a catalyst, respectively. The β-Ga2O3 nanowires with single crystalline without defects were successfully synthesized at the reaction temperature of 850, 900 and 950℃ in all the catalysts. But optimum experimental condition in synthesis of nanowires varied with the kind of catalyst. As increasing synthesis temperature,the morphology of gallium oxide nanowires changed from nanowires to nanorods, and its diameter increased. From these results, we could be proposed that the growth mechanism of β-Ga2O3 nanowires was changed with synthesis temperature of nanowires. Microstructure and morphology of Synthesized nanowire was characterized by HR-TEM, FE-SEM, EDX and XRD.     

The Influence of Nitrogen and Boron Implant into Silicon Substrate on the Phase and Internal Stress of c-BN Films

Cubic boron nitride(c-BN) film was deposited on a Si (100) substrate by the RF-magnetron sputtering.The mainly problems for fabrication of c-BN films are the low purity and high intrinsic compressive stress. In order to solve the two problems, the c-BN film with the buffer interlayer was deposited on the substrate which had been implanted with nitrogen and/or boron ions. The results show: the implantation of nitrogen ions can obviously increase c-BN content and reduce the internal stress slightly; while the implantation of boron shows no obvious improvement to the content of c-BN, which can reduce the internal stress in the film obviously. In addition, it is suggested that the implantation of nitrogen and boron shows the best result, which not only can increase the content of c-BN, but also reduce the internal stress in the c-BN film obviously.