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本文报道的钴铁尖晶石多孔湿敏陶瓷,具有电阻率低,电阻和相对湿度呈线性关系的特点。该材料制成的湿敏元件不需要加热清洗,性能稳定。以石墨粉为造孔剂制成多孔湿敏陶瓷,可以提高湿敏元件的湿度灵敏度,并且有利于改进湿敏元件的长期稳定性。最后,讨论了石墨的钝化作用。 相似文献
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采用水热腐蚀铁钝化法在单晶硅片上生长铁钝化多孔硅(IPS)薄膜,以IPS为感湿介质制成湿敏元件。在不同湿度环境以及测试频率下,测出其电容值,得到了IPS的湿敏特性曲线。研究发现,当相对湿度从11%RH逐渐增加到95%RH的过程中,在测试频率为100Hz时,IPS湿敏元件的电容值增大幅度达1500%,电容响应时间在升湿过程和脱湿过程分别为15s和5s,并且IPS湿敏元件的温度系数在15℃到35℃的范围内较小。结果表明:IPS湿敏元件的特性包括灵敏度、响应时间以及温度系数等均优于多孔硅(PS)湿敏元件的特性。 相似文献
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<正> 一、前言 响应时间是湿敏元件重要参数之一,评价一种湿敏元件,总是比较关心这种湿敏元件的响应时间。 测定响应时间必须规定湿度变化率及选择合适的湿度源。对陶瓷等电阻式湿敏元件,常规定达到63%湿度变化量所需的时间为响应时间。对电容式高分子湿敏元件,常规定达到湿度变化量的90%时所用的时间为响应时间。至于测定响应时间时所选择的标准湿度源,没有统一规定,通常 相似文献
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本文报道了用TiO_2/SnO_2陶瓷制成的实芯园盘湿敏元件的阻值稳定性与水吸附性质的关系的研究。研究了由于水的化学吸附形成的羟基团使湿敏的阻值增加与陶瓷微观结构间的相互关系;陶瓷的微观结构是通过分析扫描电镜,粉末法X射线衍射的数据和通过在充满水气的真空中使湿敏阻值变化的试验的方法得到的。此外,还让湿敏元件在大气中,外加100Hz交流脉冲的情况下,进行了3000小时的寿命试验。最后,通过介绍陶瓷湿敏元件的简化等效电路的方法,讨论了未加热的湿敏元件实际应用的可能性。 相似文献
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In this note a fast and efficient formulation is presented for the eighteen degrees of freedom high precision plate bending element. Two basic matrices are presented explicitly and by pre and post multiplying one with the other, the element stiffness matrix is obtained. The element with both uniform and linearly varying thickness is considered. Fortran subroutines are presented to ease implementation of the method. It is believed that this formulation is almost an order of magnitude faster than those presented previously. 相似文献
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大展弦比复合材料机翼动力学分析 总被引:1,自引:0,他引:1
针对结构非线性对大展弦比机翼动力学特性影响很大的问题,使用MSC Patran和MSC Nastran软件进行有限元建模及分析,将大展弦比机翼建成薄壁盒型梁模型.研究大变形对机翼动力学特性的影响,比较复合材料盒型梁模型和金属盒型梁模型的计算结果,并讨论复合材料铺层顺序的改变对机翼动力学特性的影响.研究表明:复合材料机翼的各阶固有频率明显高于铝合金机翼;铺层顺序会影响复合材料机翼的固有频率. 相似文献
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A fine grid finite element computation of two-dimensional high Reynolds number flows 总被引:2,自引:0,他引:2
Sang-Wook Kim 《Computers & Fluids》1988,16(4):429-444
A velocity—pressure integrated, mixed interpolation, Galerkin finite element computation of the Navier-Stokes equations using fine grids, is presented. In the method, the velocity variables were interpolated using complete quadratic shape functions: and the pressure was interpolated using linear shape functions defined on a triangular element, which is contained inside the quadratic element for velocity variables. Comprehensive computational results for a cavity flow for Reynolds number of 400 through 10,000 and a laminar backward-facing step flow for Reynolds number of 100 through 900 are presented in this paper. Many high Reynolds number flows involve convection dominated motion as well as diffusion dominated motion (such as the fluid motion inside the subtle pressure driven recirculation zones where the local Reynolds number may become vanishingly small) in the flow domain. The computational results for both of the fluid motions compared favorably with the high accuracy finite difference computational results and/or experimental data available. 相似文献
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设计了光电型高精度周期测定装置,从原理上消除了人为误差,从而可以对多周期信号进行自动的精确测量,很好地提高了物理实验的精度和效率。从理论上分析了测量误差的组成并给出了实测结果。 相似文献
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Moshe Eisenberger 《Computers & Structures》2003,81(3):147-152
This work gives the exact stiffness coefficients for an high order isotropic beam element. The terms are found directly from the solutions of the differential equations that describe the deformations of the cross-section according to the high order theory, which include cubic variation of the axial displacements over the cross-section of the beam. The model has six degrees of freedom at the two ends, one transverse displacement and two rotations, and the end forces are a shear force and two end moments. Also given are the equivalent end forces and moments for several cases of loading along the member. The components of the end moments are investigated, and are found for exact results. Comparison is made with the Bernoulli-Euler and Timoshenko beam models. 相似文献
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Explicit formulation for a high precision triangular laminated anisotropic thin plate finite element
An efficient formulation of the stiffness matrix is presented for a high precision triangular laminated anisotropic thin plate finite element. The formulation is based on the classical lamination theory which is reviewed briefly. The stiffness matrix is obtained simply by pre and post multiplication of a few basic matrices, which are presented explicitly. It is believed that this formulation is almost an order of magnitude faster than those available for similar order elements. In addition, the present element formulation is readily applicable as a thin flat shell element. A complete listing of FORTRAN subroutines is presented for the users, to ease implementation of the algorithm. 相似文献
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高效XML验证技术的实现 总被引:1,自引:0,他引:1
XML解析器是分析、处理XML文档的基础软件.对XML解析器的高效验证技术进行了研究,实现了支持StAX接口的验证型解析器OnceStAXParser2.0.该解析器采用了多项性能优化措施,包括属性验证的高效实现、元素验证自动机的优化、基于统计的预测算法等.性能测试表明,在进行验证的条件下,OnceStAXParser2.0具有出色的解析性能. 相似文献
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研制了一种宽带、高频压电复合材料圆环阵水声换能器.该换能器的宽带结果是通过采用降低压电材料机械品质因数Qm值和多模耦合振动两种方法实现的.通过径向切割压电陶瓷圆环、灌注环氧树脂得到压电复合材料圆环,再将不同壁厚的压电复合材料圆环轴向叠堆而成敏感元件,对敏感元件进行模具封装,引出电极引线,得到换能器.利用ANSYS软件对结构进行仿真,得到敏感元件谐振频率和带宽随压电陶瓷圆环厚度、高度和平均半径的变化规律,并根据仿真结果确定了换能器敏感元件的最优设计方案.将由最优参数得到的两个压电复合材料圆环轴向叠堆,制作了双圆环叠堆复合材料换能器.经测试,该换能器形成了明显的双模耦合振动,该换能器谐振频率为375 kHz,其-3 dBd工作带宽为90 kHz,最大发送电压响应达148 dB.实现了换能器的高频、宽带、水平全向发射声波的设计目标. 相似文献