Optimization of epicardial electrode size and implant site for reduced sequential pulse defibrillation thresholds

The influence of epicardial electrode surface area and implant site on sequential pulse defibrillation threshold was investigated in four isolated heart preparations. Electrodes with surface areas of 2.5, 5.0, and 10.0 cm2 were each sutured, in random order, to the epicardial surface of the isolated heart at each of four sites: mid-ventral left ventricle (LV); mid-dorsal LV; lateral-apical LV; and lateral-basal LV. The epicardial electrode is one of the electrodes in a three-electrode, two-current pathway, sequential pulse system. The first two electrodes, which are catheter-mounted, are located in the right ventricular apex (RVA) and superior vena cava (SVC). In sequential pulse defibrillation, one shock is delivered from the SVC to the RVA, followed 1 msec later by a second shock delivered from the third electrode to the RVA. Sequential pulse defibrillation threshold was obtained with each epicardial electrode used at each site. A single-pulse (SVC to RVA) catheter threshold was also obtained in each heart. The overall mean sequential pulse threshold was 47 per cent less than the mean single-pulse threshold (P less than 0.001). Increasing patch size reduced sequential pulse threshold (P less than 0.03), but no significant effect of patch location could be demonstrated. It is concluded that sequential pulse defibrillation is superior to single-pulse catheter defibrillation and that increasing epicardial patch size is advantageous, although patch location does not influence thresholds in the isolated heart.     

Relationship between liquidity index and stabilized strength of local subgrade materials in a tropical area

This paper presents the effect of soil liquidity index and cement stabilizer on strength properties for the usage of low traffic volume subgrade roads. Three types of soil were used to represent a different soil based on liquid limit value. Standard proctor tests have been conducted to determine the Optimum Moisture Content (OMC) and Maximum Dry Density (MDD) of stabilized soils with 0%, 7%, and 13% Ordinary Portland Cement (OPC). In order to study the effect of the soil Liquidity Index, various moisture contents are used based on the OMC value from the compaction test (0.9, 1.0, and 1.1 from OMC). The California Bearing Ratio (CBR) and Unconfined Compressive Strength (UCS) tests were conducted to determine the strength of all soil samples at optimum moisture content after 7 days curing period. It has been observed that the CBR and UCS values increased by increasing the percentage of cement content. This study found that 7% of cement content was the optimum percentage of cement content to be added to all tested soils to achieve the minimum required strength of 0.8 MPa and 80% CBR for low traffic volume roads. The presented results could provide a guideline for engineers as regards the property changes of the local subgrade materials in a tropical area due to the addition of cement content.     

大面积液浮平面电极稳定性分析

电致化学抛光是一种超光滑超平整表面的无应力加工方法,加工工具是大面积液浮平面电极,其稳定性是影响加工质量的最关键因素。研究电极稳定性对于提高加工质量具有重要意义。基于静压支撑原理,设计了电极结构,采用COMSOL仿真研究了液压腔数目,倾斜方向对电极法向刚度和倾覆力矩的影响。结果显示法向刚度大小与液压腔数目成正相关,增加液压腔数目可以有效提高电极抗倾覆能力和弱化其异向性,表明了增加液压腔数目可以有效提高电极稳定性能。     

Relationship between cavitation structures and cavitation damage

A study of visual and erosion effects of cavitation on simple single hydrofoil configurations in a cavitation tunnel was made. A two-dimensional hydrofoil with circular leading edge was used for the experiments. In addition, the hydrofoil geometry was modified to obtain some three-dimensional cavitation effects. A thin copper foil, applied to the surface of the hydrofoil, was used as an erosion sensor. Cavitation phenomenon above hydrofoils at different flow conditions (system pressure, water gas content) was observed. Images of vapour cavities from above and from side view were taken. A statistical evaluation of cavitation structures was made. Images of damaged copper coated hydrofoil surface were taken under sufficient magnification. A pit-count method, based on computer-aided image processing, was used for direct measurement of the cavitation erosion by evaluating the damage of the surface of the hydrofoil. A relation between characteristics of cavitation structures and cavitation damage was established.     

气溶胶细粒子与能见度的相关性

为了分析气溶胶粒子特别是细粒子(PM2.5)对能见度的影响,从理论上建立了气溶胶细粒子与能见度的关系,分析了谱分布的变化对PM2.5/PM10和细粒子消光所占总消光比重的影响.对测量数据与理论计算结果进行了对比分析,结果表明:所建立的气溶胶细粒子与能见度的关系是合理的,理论计算的误差小于30%,这对治理污染和提高城市能见度具有指导意义.     

浅述氧传感器与废气净化的关系

本文阐述了氧传感器对减少汽车废气污染的重要作用及其结构和工作原理。介绍了氧传感的故障症状、失效原因和检查方法。实践证明:保持氧传感的正常工作是确保发动机工况良好和排放达标的重要途经之一。     

基准位移与加工要求的关系

在一般情况下,工件在夹具中的定位误差ΔＤ由基准位移误差ΔＹ和基准不重合误差ΔＢ两部分组成,并且在计算时一般是先求出ΔＹ和ΔＢ,再根据具体情况按公式ΔＤ＝ΔＹ±ΔＢ进行合成。就基准位移误差而言,有关文献均给出了各种定位情况下的计算方法和公式。通常认为,当基准位移方向与加工要求方向一致时,基准位移误差应等于定位基准的最大位移量,但实际情况并非如此。本文以平面定位为例,分析当基准位移方向与加工要求方向一致时基准位移对加工要求的影响,以此来确定基准位移误差的计算方法。１－定位基准位移全部影响工序加工要求…     

校园网与现代教育的关系

明确指出了校园网与现代教育的关系,说明了建设校园网的几个误区,最后对目前一些著名的网络教育软件进行了简单分析,希望能给校园网和现代教育技术的发展有所帮助。     

信息技术和企业竞争力的关系研究

按外生视角-内生视角-集成视角的演进过程,介绍了信息技术与企业竞争力中的基于竞争优势、经济学、资源观、互补资源、能力观、核心能力、动态能力、集成观八种相关理论.重点比较了这八种理论的分析对象、论题、分析因素、局限和可能的应用等,指出了目前该领域研究的主要热点和趋势,提出了从信息技术应用能力角度研究信息技术与企业竞争力的关系.     

智慧制造与智慧城市的关系研究

基于新一代信息技术和IBM智慧地球的思想,我国许多地方正在开展智慧城市建设,但只有很少的智慧城市建设方案中考虑了智慧制造.针对该问题全面分析研究了智慧制造与智慧城市的关系,剖析了智慧城市对智慧制造的各种需求,明确了智慧制造的发展方向和意义,分析了智慧制造与智慧城市其他建设内容的关系.智慧制造对智慧城市的影响很重要,同时又是长期的、大范围的和模糊的,这是智慧制造有别于智慧城市其他建设内容的主要特征.     

人际关系与现代企业管理

简述现代企业管理中人际关系的涵义和影响人际关系建立的因素等内容，并提出了改善人际关系应注意的问题。     

方向公差带与基准的关系

机械零件上不可避免地存在加工误差,这些加工误差超过一定范围。就会影响其使用性能．因此要对这些加工误差加以限制．即对其规定相应的几何公差。以保证产品的使用性能及互换性。对于设计者而言。其设计要求需通过图样标注等方式表达。而图样标注必须符合有关标准的规定。这就需要对相应标准的进行认真分析和准确解读。以达到正确标注的目的。     

气溶胶细粒子与能见度的相关性研究

为了分析气溶胶粒子特别是细粒子（PM2.5）对能见度的影响,本文从理论上建立了气溶胶细粒子与能见度的关系,分析了谱分布、PM2.5/PM10和细粒子消光所占总消光比重的关系。利用2004年8月在北京的测量数据与理论计算对比表明：建立的气溶胶细粒子与能见度的关系是合理的。这对治理污染提高城市能见度是很有指导意义的。     

摩擦焊接缺陷与工艺参数的关系

1　引言杆类刀具采用高速钢与碳结构钢焊接法制坯 ,可节约高速钢材料 ,降低生产成本。焊接方式有摩擦焊和闪光焊。摩擦焊与闪光焊相比焊件质量更高 ,性能更稳定 ,因此在焊接加工中应用日益广泛。在刀具焊接过程中 ,由于柄、刃部材质不同 ,采用摩擦法焊接时所产生的预热效果也不相同。如果焊接工艺参数选择不当 ,就会产生焊接缺陷 ,影响刀具的使用效果。本文根据生产实践经验 ,分析摩擦焊接缺陷的种类和产生原因 ,并提出改进焊接质量的技术措施。　　2 摩擦焊接缺陷种类及产生原因( 1 )接头不牢特征 :①飞边小 ;②焊缝横断面上机械挖掘的环…     

螺旋锥齿轮磨齿机砂轮位置误差与齿轮齿面误差的关系

研究砂轮主轴偏心误差及垂直度误差对齿面误差的影响规律,目的是研究它们之间的定量关系.基于展成法加工大轮,由啮合原理建立无误差砂轮与有误差砂轮情况下的大轮齿面方程,通过理论齿面与误差齿面的差曲面得到实际齿面的法向误差.提出主轴偏心误差及垂直度误差的误差敏感方向概念和确定误差敏感方向的计算方法,得到误差敏感方向上砂轮位置度误差量与齿面误差的关联规律,以及发生砂轮位置度误差时齿面误差的分布规律.研究内容与方法有助于螺旋锥齿轮齿面误差溯源与齿面加工反调.     

跳动公差之间的关系及在实际中的应用

研究跳动公差各项目之间及与其它形位公差项目之间的关系和相互替代作用，对机械设计工作具有实用价值。     

物流管理与车间生产管理

阐述物流管理给车间生产带来的好处.采用缺件管理系统可以减少人员工作量,减少漏项,及早发现问题,促进生产.     

地表水TOC和CODMn相关关系研究

总有机碳TOC和高锰酸盐指数CODMn是反映水体受有机物质污染程度的重要指标,两个参数可能具有一定的相关关系,要对水体受有机物质污染程度做更加全面的评价,进行TOC和CODMn相关关系研究非常必要。天津市果河桥断面是国家重点水质监控断面,水质好坏关系着天津的饮用水安全。通过对不同季节、不同输水环境时TOC和COD”。相关关系进行的研究分析结果可以看出：在水质基质基本保持稳定时,TOC和COD”。之间显著线性相关;在水体基质发生变化时,TOC和CODmn之间没有相关性。     

Permittivity measurements using adjustable microscale electrode gaps between millimeter-sized spherical electrodes

This paper presents a technique for measuring the electrical permittivity of liquids and gases using millimeter-sized spherical electrodes with adjustable microscale separation. This technique eliminates the need for wet calibration by using the precise adjustment of electrode separation to remove the inherent errors of parasitic capacitance and electrode polarization. The spherical electrode geometry also eliminates the need for precise parallel adjustment of electrode separation, and enables small-volume, small-electrode-gap measurements where the applied electric field is constrained in a region of well-defined geometry. By further leveraging the fact that spherical electrodes can be obtained with extremely high diametrical accuracy, absolute permittivity measurement accuracies within 1% of the established values has been demonstrated. Finally, the apparatus also enables the creation of nanometer electrode gaps between macroscopic electrodes with precisely controlled separation, which can be used to study the electrical properties of liquids in highly confined states. The electrode gaps created in this manner can be adjusted from 20 nm to 50 microm, in increments of 0.25 nm.     

稳压器喷雾阀阀芯倒角尺寸对流动的影响

V型旋转式阀芯具有流阻小,切断性能好,调节精度较高的特点。为了减小阀芯旋转时流体在阀芯和阀座棱边上剪切力以及阀门形阻系数,通常在阀芯的棱边上加工倒角来达到此目的,研究稳压器喷雾阀V型阀芯棱边不同倒角尺寸时,阀内流体流动时在阀芯与阀座上的产生的剪切力大小,以及阀芯棱边取不同倒角尺寸时对流动的各参数的影响。采用CFD软件fluent,基于RANS方程,采用有限体积法进行空间离散,使用K-ε湍流模型和SIMPLE算法,针对阀芯不同的倒角尺寸,计算稳压器喷雾阀V型阀芯在关闭时阀门的体积流量,湍流参数,壁面剪切力,形阻系数等各种参数。得到阀芯倒角对流动参数的影响规律。