石英音叉陀螺振动特性有限元仿真

石英音叉陀螺是一种新型的振动陀螺.在设计阶段必须对其性能进行分析仿真,以便为微型石英陀螺的设计提供依据,缩短开发周期.利用耦合场有限元对石英音叉陀螺的振动特性进行了仿真,确定了最佳激励信号频率和影响陀螺灵敏度的因素,并且给出了调节驱动模态与检测模态的频率差值的方法.     

密闭式炼胶（塑）机若干结构改善

本文主要阐述了密闭式炼胶（塑）机的主要功能、结构组成及其工作特点,并从装配和维修角度提出了几点结构改善建议,以实现整个设备合理、便捷、可靠的装拆性,最终强调了做为设备维护人员必须考虑的几项问题。     

20CrNiMo钢拨叉热处理工艺试验

采用正交试验法,研究了温度、碳势、氨流量和保温时间对拨叉表面硬度、有效硬化层深度及表层组织的影响。优选的20CrNiMo钢拨叉的热处理工艺参数为：840℃保温30 min,碳势1.0%,氨流量10 L/min。     

基于微石英晶振的动态非接触静电力显微测量(EFM)技术

在一台基于微晶振的原子力显微镜的基础上，通过在针式传感器前端细小针尖加入可调交流偏压，获得高分辨率动态非接触静电力显微镜。此装置可以分别利用微小针尖与样品间的范德华力与附加的可调整电力信号，同时获得样品表面微观形貌特征和表面电特性，如表面电荷分布，表面电势等。     

Performance evaluation of a multi-product system under CONWIP control

Analytical models of multi-product manufacturing systems operating under CONWIP control are composed of closed queuing networks with synchronization stations. Under general assumptions, these queuing networks are hard to analyze exactly and therefore approximation methods must be used for performance evaluation. This research proposes a new approach based on parametric decomposition. Two-moment approximations are used to estimate the performance measures at individual stations. Subsequently, the traffic process parameters at the different stations are linked using stochastic transformation equations. The resulting set of non-linear equations is solved using an iterative algorithm to obtain estimates of key performance measures such as throughput, and mean queue lengths. Numerical studies indicate that the proposed method is computationally efficient and yields fairly accurate results when compared to simulation.     

基于ProCAST的拨叉件熔模精密铸造工艺优化

拨叉件是汽车变速器上的重要零件,一般采用熔模精密铸造工艺进行生产,热裂是拨叉件生产中常见的铸造缺陷。本文通过分析热裂产生的机理,采用相当热节计算法设计浇注系统,并进行数值模拟,计算了铸件的流场、温度场和应力场,模拟结果准确性得到了实验验证。     

卡群电站压力前池防冰塞设计与试验研究

通过卡群电站工程实例,研究讨论了引水式电站冬季输排冰运行的条件和电站前池布局的合理性,对引水式电站前池的各关键部位,提出了具体防冰塞措施,并对SL 211-2006水工建筑物抗冰冻设计规范中的若干问题进行了讨论,供设计、研究人员参考。     

Test for measuring the stretchability of melted cheese

A test for measuring the stretchability of cheese was developed by adapting a texture-profile analyzer to pull strands of cheese upwards from a reservoir of melted cheese. Seven different cheeses were analyzed using the Utah State University stretch test. The cheeses were also analyzed for apparent viscosity with a helical viscometer, for meltability using a tube melt test, and for stretch using the pizza-fork test. Cheese was placed into a stainless steel cup and tempered in a water bath at 60, 70, 80, or 90 degrees C for 30 min before analysis. The cup was then placed in a water-jacketed holder mounted on the base of the instrument. A three-pronged hook-shaped probe was lowered into the melted cheese and then pulled vertically until all cheese strands broke or 30 cm was reached. This produced a stretch profile as the probe was lifted through the reservoir of melted cheese and then pulled strands of cheese upwards. Three parameters were defined to characterize the stretchability of the cheese. The maximum load, obtained as the probe was lifted through the cheese, was defined as melt strength (F(M)). The distance to which cheese strands were lifted was defined as stretch length (SL). The load exerted on the probe as the strands of cheese were being stretched was defined as stretch quality (SQ). There was a correlation between F(M) and apparent viscosity. There was also some correlation between SL measured by the fork test and SL when the cheese was tested at 90 degrees C, but no correlation occurred at lower temperatures.     

前叉下管铸件的铸造工艺设计

介绍了前叉下管铸件的结构及技术要求,详细阐述了其铸造工艺设计:采取垂直分型,膨润土湿型砂造型;采用底注式浇注系统,圆锥形直浇道的截面面积为972 mm2,横浇道与直浇道、内浇道相连接,横浇道为截面积1 200 mm2的标准梯形浇道,内浇道的截面面积为420mm2,选用六角形浇口杯,浇注速度为8.12kg/s,浇注时间为5s,浇注温度为1580℃;采用12个尺寸为30mm×60mm×75mm的冷铁,选用腰形暗冒口,尺寸为a=50 mm,b=100 mm,h=100 mm;选择扁形出气孔。模拟结果显示,整个铸件未发现有缩孔、缩松等铸造缺陷,而且工艺出品率也达到了76.53%。     

GaAs-based tuning fork microresonators: A first step towards a GaAs-based coriolis 3-axis Micro-Vibrating Rate Gyro (GaAs 3-axis μCVG)

This paper presents the design of a piezoelectric MEMS Coriolis Vibrating Gyroscope (CVG) based on a single gallium arsenide vibrating structure allowing the measurement of rotation rate along 3 orthogonal sensitive axes. Based on a theoretical and FEM study, we demonstrate that the achieved sensitivities reached for each axis is about 1.6 × 10⁻¹⁶ C/(°/s). We then demonstrate the feasibility of the realization of simple MEMS structures from C-doped Gallium Arsenide (GaAs) using standard micromachining processes. Finally, we show the fabrication and characterization of GaAs-based tuning fork microresonators as a first step towards a complete 3-axis GaAs MEMS CVG. These resonators show a resonance frequency of 42 350 Hz, a quality factor of 122 000 and a frequency temperature coefficient of 24 ppm/°K, validating the high potential of GaAs as a structural material for 3-axis MEMS CVGs.