考虑陀螺效应的面齿轮振动特性分析

为提高面齿轮传动系统的动力学特性,建立考虑陀螺效应、包含时变啮合刚度、啮合阻尼、齿侧间隙、支撑刚度和阻尼等参数的非线性动力学模型。采用欧拉单步法对非线性动力学方程进行求解,分析模型计算结果的准确性和合理性。分析面齿轮传动系统啮合线位移、啮合力以及面齿轮和圆柱齿轮振动位移与时变啮合刚度幅值系数变化之间的关系,并通过两齿轮质心坐标平面相图得到两齿轮质心的振动情况。     

高精度光纤陀螺信号的在线建模与滤波

针对高精度光纤陀螺随机误差,在分析其一般时间序列模型的基础上,提出了一种改进型二阶自回归AR(2)模型,可以在线建立光纤陀螺随机误差模型.根据该模型,采用卡尔曼滤波算法,实现了光纤陀螺惯导系统在对准与导航过程中光纤陀螺随机误差的实时滤波.滤波结果和Allan方差分析证明,光纤陀螺信号中角随机游走、零偏不稳定性、速率随机游走、速率斜坡和量化噪声五项噪声源误差系数都小于滤波前的二分之一,有效减小了光纤陀螺随机误差,提高了光纤陀螺精度.     

鲁棒Kalman滤波陀螺随机噪声AR快速/实时建模

针对传统陀螺随机噪声的AR建模方法收敛速度慢、所需样本多等问题,提出新的基于鲁棒Kalman滤波的陀螺随机噪声AR建模方法。该方法将AR模型参数作为系统的状态量,采用未知时变的噪声统计估值器估计观测噪声的均值和方差,通过Kalman滤波估计出AR模型参数。实验结果表明:这种AR建模方法具有收敛速度快,时间开销少的优点。当有新的噪声数据到来时,还能使建立的AR模型得到及时更新,提高建模准确度,适用于快速建模或陀螺随机噪声具有强时变性的工程场合。     

前后向时间序列模型联合估计的时变结构模态参数辨识

为提高时变结构模态参数辨识精度和抗噪声能力,提出一种前后向泛函向量时变自回归滑动平均（FS-VTARMA）时间序列模型联合估计的模态参数辨识方法。首先建立前后向FS-VTARMA模型联合估计的均方误差形式的费用函数,其次引入非平稳信号中前向模型和后向模型估计系数的近似共轭关系,再利用两步最小二乘法（2SLS）得到时变模型系数,最后把时变模型特征方程转换为广义特征值问题提取出模态参数。利用时变刚度系统非平稳振动信号验证该方法,结果表明：能有效地克服前向模型估计中模态参数一步延迟以及起始时刻无法准确获得,以及后向模型估计中模态参数一步超前以及终止时刻无法准确获得的缺点,具有更高的模态参数辨识精度和更强的抗噪声能力。     

基于小波变换与子结构法的多层剪切结构时变参数识别

对于多层剪切时变结构,利用子结构技术将发生时变的局部结构提取出来作为子结构,将交界面上的内力当做外荷载施加给子结构,建立子结构振动微分方程,通过小波变换将子结构的时变参数用小波展开系数来表示,将子结构微分方程转变为线性方程组,将时变参数识别问题转换为时不变小波系数求解问题。各时变参数的分解层数通过Akaike信息准则来确定。由求解得到的小波系数进行重构得到待识别的时变参数。最后,对一个多层剪切时变结构模型进行了数值分析。分析结果表明,提出的方法可以只用局部子结构的响应数据对时变参数进行识别,方法具有一定的抗噪性。     

光纤陀螺IMU的六位置旋转现场标定新方法

针对光纤陀螺惯性测量单元(Inertial Measurement Unit,IMU)的误差系数随时间推移而变化的问题,本文提出一种光纤陀螺IMU的六位置旋转现场高精度标定新方法,该方法在使用现场将光纤陀螺IMU在六个位置上进行十二次旋转,然后根据光纤陀螺IMU的误差模型建立42个非线性输入输出方程,通过旋转积分和对称位置误差相消,消除方程中的非线性项,最终求解出陀螺标度因数、陀螺常值漂移、陀螺安装误差和加速度计常值偏置等15个误差系数.实验结果表明,该方法可在没有精密转台的现场实现光纤陀螺IMU的精确标定,其标定精度与基于精密转台的标定精度相当.     

功率四分支齿轮传动弯扭耦合动力学特性研究

建立了功率四分支齿轮传动系统的动力学模型和32个自由度的振动方程,提出了基于时变啮合线方程的齿轮啮合刚度计算方法,研究了在时变刚度激励下不同安装角对传动系统的动载系数和均载系数的影响规律,得出系统第二级、第三级齿轮副的均载系数随着安装角的增大而增大,当安装角等于120°时,最大均载系数分别为1.288和1.291。继续增大安装角,各齿轮副均载系数将不再有明显变化。     

硅微陀螺信号处理方法——基于前向线性预测小波变换方法

为补偿漂移误差对硅微陀螺的测量精度造成的损失,针对漂移误差易受外部环境噪声影响的特点,提出了一种基于前向线性预测（FLP）的小波变换（WT）处理方法——DWT-FLP算法,并通过硅微陀螺试验对其进行了验证。该方法利用快速小波变换算法进行信号的小波分解和小波重构,并将FLP方法用于小波分解系数的重构,比较显著地提高了重构信号的精度。对于4尺度的db4小波变换,40阶FLP的滤波方法可以将硅微陀螺静态漂移的标准差提高4.8倍,动态测量过程信噪比可以提高6.5dB,并且该算法的实时性也可以满足实际工程的需要。     

光纤陀螺“死区”测试分析与建模

针对采用方波偏置调制、阶梯波反馈调制方案的全数字闭环光纤陀螺"死区"现象的机理进行了实验和仿真研究.为了考察闭环检测反馈环节对干扰的影响,在开环检测的状态下,叠加了长周期固定台阶高度的数字阶梯波,得到阶梯波总高度和开环输出之间的相关性,建立了含干扰通道的光纤陀螺开环检测模型.根据形成数字阶梯波电压大小的等价性,将上述开环模型转换为闭环模型,对闭环简化模型进行了理论分析和仿真计算,并与闭环"死区"测量曲线进行了对比.实验样机阶梯波电压和开环输出线性相关系数为0.97,根据开环测得的耦合系数仿真出的闭环"死区"范围与实验值相差6.7%.结果表明:干扰随阶梯波电压线性变化是闭环光纤陀螺"死区"产生的机理之一.     

基于BP神经网络的光纤陀螺仪温度建模研究

目前光纤陀螺应用广泛，但是其性能容易受到环境温度影响，从而影响到惯性导航系统的性能．光纤陀螺的温度特性具有非常复杂的非线性特点，而BP神经网络具有良好的逼近复杂非线性函数能力。使用BP神经网络建立光纤陀螺温度特性的黑箱模型，不对零漂和标度因子进行补偿，而直接对陀螺输出进行校正．经实际数据检验，该建模补偿方法比未经补偿和经过传统工程补偿方法的精度提高了两个数量级．与传统的线性模型相比较，本文基于BP神经网络建立的光纤陀螺温度模型具有补偿方法简单，精度高，通用性好等优点．     

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.……     

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.     

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.     

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 ...