铸造车间噪声控制

铸造车间噪声控制李大勇编译产品的性质和铸造车间的生产特点，使我们很难有一个安静的工作环境。铸件是＂坚硬＂的物体，当这些坚硬的物体互相碰撞或与其它坚硬表面如输送器、斜槽和储料斗等相互振动时，便会产生噪声。瞬间的冲击产生高强度高频率的噪声，这些噪声恰好在...     

唐僧与经理

以历史或文学作品中的人物来谈现代的管理问题似乎是一种时尚，但是这种脱离实际的演绎性观点其实并没有多大的理论价值，更谈不上实际价值，反而给人一种“黔驴技穷”的感觉。     

基于RLS自适应滤波算法的广义互相关时延估计方法研究

为了提高低信噪比环境下信号传输时间延迟的估计性能,将RLS自适应滤波算法与广义互相关时延估计算法相结合,提出了一种基于RLS自适应滤波的广义互相关时延估计(RLS-GCC)方法。该方法先对信号进行滤波预处理以提高信噪比,然后通过广义互相关运算实现时延估计。通过改变RLS自适应滤波算法中的参数大小,分析了RLS自适应滤波算法中滤波阶数、遗传因子等参数对RLS-GCC算法的影响,并通过与广义互相关算法、二次相关算法的对比时延实验,研究了RLS-GCC的时延估计性能。仿真结果表明,在低信噪比环境下,RLS-GCC方法比广义互相关算法和二次相关算法具有更高的时延估计准确率和更低的估计误差。     

唐僧与经理

以历史或文学作品中的人物来谈现代的管理问题似乎是一种时尚，但是这种脱离实际的演绎性观点其实并没有多大的理论价值，更谈不上实际价值，反而给人一种“黔驴技穷”的感觉。     

如何减少铝材氟碳漆喷涂中的"大龟裂"缺陷

氟碳漆是由聚偏二氟乙烯树脂、颜料、改性剂等组成，在实际生产过程中，涂层会产生类似干枯河床的线状或格状裂纹，这种现象称为“大龟裂”。“大龟裂”通常是由于喷涂后的漆膜在烘烤过程中溶解时，溶剂不足而造成的。以下几种情况可加重此现象：     

铜锌铁硒与癫痫病

<正> 癫痫病俗称羊羔风,是一种古老的严重危害人体健康的神经系统疾病;在祖国医学的典籍中记载繁多,属“痰饮”范畴,与先天遗传或惊吓、外伤和神志有关。脑电图证实:脑部兴奋性过高的某些神经元突然、过度的重复放电,引起突然的脑功能短暂异常;由于过度放电神经元的部位不同,临床上出现短暂的感觉障碍、肢体抽搐、意识丧失、行为障碍和自主神经功能异常。单独、多种障碍同时发作,重     

浅谈机床电气实用诊断方法的应用

依靠维修电工的工作经验和感觉器官，对机床电气进行问、看、听、触、闻等的诊断，称之为机床电气“实用诊断方法”。笔者结合自己的维修实践，浅谈其应用体会。1．问：询问机床故障发生的经过。（1）故障发生在开车前、开车后，还是发生在运行中？是运行中自行停车，还是发生异常情况后由操作者停下来的；（2）故障发生在什么工作顺序，按动了哪个按钮，扳动了哪个开关；（3）故障发生后，设备有无异常现象（如响声、气味、冒烟或冒火等）；（4）以前是否发生过类似的故障，是怎样处理的等。2．看：直观机床电器真实现象并进行分析处理。例…     

管道漏磁检测系统中自适应滤波器设计

利用MATLAB仿真工具比较了自适应滤波器的常用自适应算法LMS算法和RLS算法，论述了基于变步长、正则LMS算法自适应滤波器原理，并针对漏磁检测的缺陷信号和噪声特点，设计了一种适于漏磁信号除噪的自适应滤波器。通过MATLAB程序仿真，试验结果表明该滤波器具有较快的收敛特性和较小的失调量，可满足漏磁检测系统除噪要求。     

铸造车间噪声控制

铸造车间噪声控制产品的性质和铸造车间的生产特点，使我们很难有一个安静的工作环境。铸件是“坚硬”的物体，当这些坚硬的物体互相碰撞或与其它坚硬表面如输送器、斜槽和储料斗等相互振动时，便会产生噪声。瞬间的冲击产生高强度高频率的噪声，这些噪声恰好在人的听力最敏感频率范围内。铸造车间的许多操作都会导致坚硬物体间的冲击。振动输送器传送原料进炉，在每一次方向改变时，原料都将下落一英尺或者更大的高度。运输器输送铸件也会产生噪声。型砂和型芯的落砂是另一个噪声来源，在直浇道和横浇道的清理过程中，废料被扔进斜槽而铸件…     

《华尔街日报》专栏撰稿人观点：2009年中国和世界的十大逆转

世界经济在2009年体验了一把坐过山车的感觉，从年初时的六神无主，到年底时的峰回路转，2009年不折不扣是个逆转之年。以下是笔者眼中年内十大逆转事件：     

Stewart型并联机床伸缩杆伸长量误差在线测量

标定作为提高Stewart型并联机床静态精度的有效方法，包括建模、测量、参数识别和补偿等环节。其中伸缩杆伸长量误差的测量准确性直接影响标定效果。本文提出间接方法准确测量其值。首先选择激光跟踪系统精确测量并联机床不同位姿对应的伸缩杆绝对伸长量，再辅以符号运算，最终达到测量机床伸缩杆伸长量误差的目的。     

Development and evaluation of ferrocement legs for a lathe

The feasibility of using ferrocement as a replacement material for cast iron in the fabrication of supporting legs (columns) for a centre lathe has been investigated in this project. These machine tool structures were designed with the aid of a finite element package so as to have static stiffnesses at least equal to those of the corresponding cast iron legs. Tests were carried out to evaluate the performance of the ferrocement legs with reference to the traditional cast iron legs. The highly improved dynamic performance as exhibited by the ferrocement legs indicates that this new construction materials has a great potential in the machine tool industry.     

6UPS并联机构杆长误差标定及其对动平台运动的影响分析

分析了不同误差对并联机构的影响,尤其是杆长误差对动平台姿态误差的影响.建立了采用并联机构运动学反解模型的矢量法误差求解模型;针对6UPS并联刀具机构的结构特点,使用支链分析方法,对由杆长误差引起的动平台误差变化趋势及变化的敏感性方向进行了分析.使用激光干涉仪完成了误差测量实验,使用多组姿态数据的不同组合进行误差计算,获得了优化的杆长误差数据.完成了杆长误差对动平台误差变化影响的数值分析与矢量合成两种方法的验证.     

反应堆压力容器检查机支撑腿的设计及可靠性研究

反应堆压力容器检查机的支撑腿结构起定位和支撑作用,其结构的合理性对反应堆压力容器检查机的定位精度和可靠性具有重要影响。针对第三代核电站EPR堆型核反应堆压力容器结构,设计了具有自动定心功能的支撑腿结构。采用有限元方法分析了支撑腿结构的可靠性,并进行了验证力学试验。试验结果印证了相关理论分析结果,证明该支撑腿结构的设计是合理可行的。     

两栖复合腿机器人运动仿真及能耗分析

对水陆两栖复合腿机器人进行运动仿真及能耗分析。设计一种弧形腿与桨结合的两栖六足机器人,研究其地面三角步态行走机制,提取腿部转动关节运动模型。分析机器人能源消耗组成部分,简化得到其单周期能耗计算模型。构建9种不同腿长参数的机器人三维模型,在ADAMS软件中设置规划的转动关节轨迹,实现运动仿真。提取仿真后的电机力矩,计算一周期的能耗并进行分析。结果表明：适当减小机器人腿长参数可提高能源利用效率,这对提升腿式机器人整体性能具有一定的参考意义。     

Prediction of distortions and pattern allowances during sand casting of a steel bracket

Mechanical interactions between the casting and mould generate unwanted distortions and lead to dimensional inaccuracies. In this study, the effects of mould expansion and mould restraint are investigated through sand casting experiments involving a U-shaped steel bracket. Distortions are quantified by in situ measurements of the evolution of the gap opening between the bracket legs. Mould expansion is observed immediately after filling. Outer mould restraint prevents distortions in the bracket legs until the time of mould fracture, after which the legs are pushed outward. The experiments are simulated using a sequential thermo-mechanical coupling. The steel and bonded sand are modelled using previously calibrated elasto-visco-plastic and Drucker–Prager Cap constitutive laws, respectively. Excellent agreement between measured and predicted pattern allowances (PA) is obtained. Distortions are greatly under-predicted unless mould fracture is considered. Variations in the packing density of the moulds are also shown to have an impact on PA.     

原发性下肢浅静脉曲张氧自由基损伤及AescuvenForte的拮抗作用

目的 探讨下肢浅静脉曲张患者氧自由基损伤及强力脉痔灵(AescuvenForte)对其损伤指标—血清过氧化氢酶(SOD),谷胱甘肽还原酶(GSH)及过氧化脂质(LPO)水平的影响。方法 利用放射免疫测定法、DTNB直接法和TBA荧光法对60例原发性下肢浅静脉曲张患者进行用药前后血清SOD、GSH、LPO测定。结果 本病患者血清中存在高水平的LPO及低水平的SOD、GSH,应用Aescuven Forte可有效地纠正血清SOD、GSH、LPO水平。结论 测定SOD、GSH、LPO水平可用于了解治疗效果、指导临床用药;本研究提示拮抗自由基损伤可能是Aecuven Forte治疗下肢浅静脉曲张及其并发症的机制之一。     

Catalyst-free synthesis, growth mechanism and optical properties of multipod ZnO with nanonail-like legs

Multipod ZnO with nanonail-like legs was synthesized successfully by a facile combustion oxidation method at 880 °C without any catalysts. The morphologies of three samples obtained from three growth stages, namely sprout, growing and multipod with nanonail-like legs, were investigated. The possible growth mechanism was discussed in detail. Compared with the other two structures, the multipod with nanonail-like legs exhibited a significant enhancement in the green emission region. Its unique structure together with its good optical properties suggest that it is a promising candidate for the fabrication of optical nanodevices.     

The effect of a surface-active medium on the mechanical stability and damageability of a solid surface. Review

This review considers the regularities of manifestations of the Rebinder effect in surface damageability. The general physico-chemical fundamentals of such surface phenomena (predominantly, in contact interactions) are stated, and examples of versatility and specifics of their manifestations in nature and technology are given for minerals, ionic structures, metals, and catalysts.     

Thermoelectric Device Fabrication Using Thermal Spray and Laser Micromachining

Thermoelectric generators (TEGs) are solid-state devices that convert heat directly into electricity. They are used in many engineering applications such as vehicle and industrial waste-heat recovery systems to provide electrical power, improve operating efficiency and reduce costs. State-of-art TEG manufacturing is based on prefabricated materials and a labor-intensive process involving soldering, epoxy bonding, and mechanical clamping for assembly. This reduces their durability and raises costs. Additive manufacturing technologies, such as thermal spray, present opportunities to overcome these challenges. In this work, TEGs have been fabricated for the first time using thermal spray technology and laser micromachining. The TEGs are fabricated directly onto engineering component surfaces. First, current fabrication techniques of TEGs are presented. Next, the steps required to fabricate a thermal spray-based TEG module, including the formation of the metallic interconnect layers and the thermoelectric legs are presented. A technique for bridging the air gap between two adjacent thermoelectric elements for the top layer using a sacrificial filler material is also demonstrated. A flat 50.8 mm × 50.8 mm TEG module is fabricated using this method and its performance is experimentally characterized and found to be in agreement with expected values of open-circuit voltage based on the materials used.