车用尾气催化剂工作性能的模拟与分析方法

本文建立了包含催化剂温度特性、空燃比特性和空速特性在内的车用尾气催化剂工作性能模型,给出了载体的开口率、内部表面积、排气阻力等性能参数的计算公式,并介绍了在实际应用中对催化剂催化性能,耐久性能及失效原因的分析方法。     

一种长寿命高稳定的电化学传感器

本文以超精细还原法制得电极催化剂和电极,以这种催化剂和电极形成电化学传感器具有非常高的稳定性和可靠性。标志着传感器性能稳定可靠的主要技术指标:温度特性、线性、基线性能和长寿命稳定性都取得非常可靠数据,这表明了它处于国内领先水平。     

车用尾气催化剂催化特性的模拟

为研究车用尾气催化剂在实际使用中的工作性能,本文建立了用于模拟车用尾气催化剂的转化率－温度特性模型,以及空速对转化率影响的计算模型,利用上述模型可根据不同车辆行驶工况下催化剂的人口温度以及空速情况,计算出相应工况下的催化转化率,这样还可为催化剂的设计提供指导。此外,本文还讨论了所建模型的限制之外。     

软件与驱动

ATI的催化剂5.6在没正式发布前就已放出风声,其更新的重点就是在性能和功能方面会有相当大的改进。由5.6版驱动开始,ATI的催化剂驱动将正式支持Mobility系列芯片组,也就是说ATMobility系列显卡的笔记本用户也能每月按时更新新版驱动(不过目前5.6版驱动仅支持MobilitX700/X800显卡,其余型号会在今后的版本中陆续加入)。新驱动改善了催化剂控制中心的性能,改进了催化剂控制中心的用户界面并在系统托盘中加入一项新功能,能让用户更方便快捷地进行系统配置。此外,它在控制中心里还加入全新的视频特性。在性能方面,新驱动可使ATI显卡在DO…     

驱动程序更新与推荐

ATi发布催化剂8．5支持WinXP SP3 拥有一块A卡的你．是不是已经把WinXP操作系统升级到SP3了呢？如果是的话．那这款最新发布的催化剂你就绝对不能错过了。虽然它并不能带来为显卡性能的提升带来太多帮助．但是却加入了对WinXP SP3的支持。当然除了这点之外．催化剂8．5还有其他的新特性和新功能,像支持1080p HDTV自定义模式就是之前没有过的哦!     

掺Rh对纳米SnO2的气敏性能的影响

以无机试剂为前驱物,采用溶胶—凝胶法合成了纳米级 SnO_2,以此为基材掺入不同量 Rh 作为气敏材料制成气敏元件。测试了它们的阻温特性和气敏性能。通过比较它们对还原性气体的灵敏度和选择性,讨论了掺入 Rh 催化剂对纳米 SnO_2的阻温特性和气敏性能的影响。结果表明,纳米 SnO_2具有特征的阻温曲线。随着 Rh 催化剂掺入,不仅引起电阻增大,同时掺杂 Rh 占据表面活性位,使纳米 SnO_2对表面氧吸附时的物种类型相互转换的影响体现不出来。不过,在工作温度为300℃时。掺入0.2%Rh 催化剂使得纳米级 SnO_2对 C_2H_5OH 和 petrol、H_2的灵敏度提高了10倍以上,而且使其对 petrol 与 C_4H_(10)的选择性检测性提高了3倍以上,对 C_2H_5OH 与 CO 的选择性检测性提高2倍以上。     

氧化物半导体甲烷敏感元件研究进展

介绍了氧化物半导体甲烷气体敏感元件的工作机理,论述了改善氧化物半导体甲烷气敏传感器性能的几种途径.采用加入催化剂、控制材料的微细结构、利用新制备工艺和表面修饰等新方法、新技术可提高氧化物半导体甲烷气敏元件的灵敏度、选择性、响应和恢复特性、稳定性.     

驱动热报

热门驱动热辣评本期热评焦点:ATi显示卡催化剂驱动5.6版如果说ATi每月发布的催化剂驱动都是大家关注的焦点的话,那么本次的5.6版驱动则可以说是焦点中的焦点。原因就在于前几个版本的催化剂驱动仅是做一些修正BUG的工作,在新功能和性能方面没有大的变化,而本次的5.6在没正式发布前就已经放出风声,其更新的重点就是在性能和功能方面大做文章。现在ATi官方终于把最新催化剂驱动5.6-8.14-6.14.10.6542官方正式完整版驱动送到我们面前。这款驱动在新特性方面更新如下:1.由5.6版驱动开始,ATi的催化剂驱动将正式支持Mobility移动系列芯片组。…     

汽车三效催化转化器劣化机理分析与仿真研究

在三效催化转化器特性的研究中,为解决发动机台架实验的断油劣化、周期长、成本高等缺点,并为开发高效长寿低排放的汽车TWC,缩短开发周期,节省开发费用,提出在分析TWC劣化机理的基础上,运用数值仿真技术,建立了包含劣化过程化学反应、储放氧反应、催化剂颗粒直径、反应速率、烧结速率及转化率的TWC劣化特性数学模型,对影响TWC的劣化的排气温度场、浓度场及表征劣化性能的Pt颗粒直径、失活因子及转化效率等参数进行了仿真与分析.研究表明可为预测TWC劣化特性的变化,提高TWC抗劣化性能与制定TWC抗劣化对策提供依据,具有很大的实际应用价值.     

基于催化剂表面修饰改善催化传感器性能

研究了催化剂载体孔径、比表面积与催化传感器工作性能关系和催化剂表面的酸性或碱性修饰对催化传感器工作性能的影响。得出了经高温焙烧的载体以及对载体预先进行表面的酸性或碱性处理有利于催化传感器性能提高的结论。     

基于传热理论的热电能量转换系统集成分析

热电能量转换系统可实现热能和电能的直接转换。在一个完整的热电系统中,热电器件与冷热端换热器组成热阻网络,该热阻网络与冷热源之间的换热对系统性能具有决定性影响。该文从网络节点间的耦合传热关系出发,分析了外部换热对系统内部温度分布的影响,得到了实际热环境中热电系统输出性能的近似理论表达式。在此基础上,该文建立了外部换热条件与系统峰值输出功率的直接关系,并提出一套热电能量转换系统设计策略,可用于热电发电系统的快速设计。     

Relativistic theory of mode conversion at plasma frequency – the finite difference time domain simulation

The equations governing the mode conversion between an electromagnetic wave and a plasma wave are derived from the fluid equations for the nonrelativistic case, and from the Vlasov equation for the relativistic case. They are further reduced to involve only two electric field components. Both cases show that the mode conversion has similar magnitude in conversion efficiency and becomes insignificant beyond 45° of incident angle. The finite difference time domain simulation measuring the wave packet of the electromagnetic wave with and without the mode conversion indicates that while the mode efficiency improves with plasma temperature in the nonrelativistic case, it saturates in the relativistic case.     

Electrochemomechanical energy conversion efficiency in silica nanochannels

The electrochemomechanical energy conversion efficiency has been investigated using a new theoretical and numerical framework for modeling the multiphysiochemical transport in long silica nanochannels. Both the chemical dissociation effects on surface charge boundary conditions and the bulk concentration enrichment caused by double layer interactions are considered in the framework. The results show that the energy conversion efficiency decreases monotonically with the increasing ionic concentration at pH = 8. For a given ionic concentration, there is an optimal channel height for the highest efficiency. The efficiency does not increase with the pH value monotonically, and there is an optimal pH value for the maximum energy conversion efficiency as the other conditions are given. The energy conversion efficiency increases with the environmental temperature. The present results may guide the design and optimization of nanofluidic devices for energy conversion.     

Experimental Studies of Shift-Work III: Stabilized 12-hour Shift Systems

Twenty-two subjects took part in an experiment to determine whether the relationship botween efficiency at mental tasks and the circadian rhythm of body temperature observed in two earlier studios was affected by an increase in the length of the duty spoil from S to 12 hours. Subjects wore assignod either to a control ‘ day ‘ shift (0800-2000) or a ‘ night‘ shift (2000-0800), and woro tested for a period of 12 consecutive days on the same shift. Some signs of fatigue duo to the oxeessive length of the duty-spell wero observed, but an underlying relationship between temperature and performance remained in evidence in some scores throughout the trial period. Adaptation of temperature rhythm to work on the night shift was only partial, and less marked than in a previously studied ' night ' work situation; the partial adaptation was nevertheless relatively closely reflected in the recorded performance trends. It was concluded that the rosults obtained in the present and previous studies in this series demonstrated that, within certain limits, the relationship between temperature and efficiency was sufficiently marked to warrant further research into its generality.     

高阶代码消除性能比较框架的设计与实现

函数式语言编译中,闭包变换和函数消除是广泛采用的高阶代码消除方法。为了提高函数式语言的运行效率,针对函数式语言编译阶段的高阶代码消除过程对目标代码效率的影响,设计并实现了一种函数式语言编译框架。该框架采用了菱形的架构,平行地使用了闭包变换与函数消除两种高阶代码消除方法。设计了一种具有代表性的函数式语言——FUN语言,并以FUN语言为基础,给出了比较框架的一个完整实现。通过该系统,对闭包变换与函数消除的效率影响进行对比实验,选取具有典型特征的测试例,分别从生成代码的规模和运行效率方面对闭包变换与函数消除两种方法的结果进行比较。实验结果表明,与闭包变换相比,使用函数消除方式所得的目标代码量更少,最多可减少33.76%的目标代码量;并且运行效率更高,最多可提高69.51%。     

环境模拟风洞高压动力系统设计研究

为实现环境模拟风洞风速性能指标,对动力系统进行了设计;介绍了环境模拟风洞的气动轮廓构型,阐述了动力系统的工作原理,包括主驱动回路、散热辅助系统和控制系统,给出了10 kV 4 MW动力电机的计算选型过程并分析了电机特性曲线;采用高压变频器实现了动力系统的调速驱动,通过48脉冲整流完美无谐波矢量变频实现高品质的电能利用;通过基于Modbus TCP现场总线协议,实现了主控计算机、本地控制系统的实时通讯和数据交互,给出了控制系统软件工作流程;通过不同构型风洞喷口试验,分析研究了最大风速和极端温度负荷工况条件下,轴功率随试验温度的变化关系、电机温升特性以及稀油站供油压力与轴升的关系;实验测试结果表明,本系统对于环境模拟风洞有较好的风速、温度匹配性能,对于开展相关实验具有优良环境适应性.     

Efficiency analysis of information technology and online social networks management: An integrated DEA-model assessment

This paper analyses the relationship between productive efficiency and online-social-networks (OSN) in Spanish telecommunications firms. A data-envelopment-analysis (DEA) is used and several indicators of business “social Media” activities are incorporated. A super-efficiency analysis and bootstrapping techniques are performed to increase the model's robustness and accuracy. Then, a logistic regression model is applied to characterise factors and drivers of good performance in OSN. Results reveal the company's ability to absorb and utilise OSNs as a key factor in improving the productive efficiency. This paper presents a model for assessing the strategic performance of the presence and activity in OSN.     

基于Voronoi图的工程数据格式转换研究

根据工程软件数据格式间的转换关系,构建一个以软件和数据格式为节点的网络图。利用常用工程软件的数据格式,确定软件和数据格式节点在二维空间中的位置分布,并基于Voronoi图实现网络图的可视化。实验结果表明,该方法能够有效地分析软件和数据格式间的复杂关系,提高信息移存的效率。     

Theoretical limits of rectifying efficiency for low‐power wireless power transfer

The theoretical limits of power conversion efficiency for near‐field wireless power transfer were derived in recent years, but the maximum achievable efficiency for low‐power and far‐field powering has not yet been characterized. In this paper, we derive the performance limits of rectifiers using diodes for input power ranging from ?20 dBm to 0 dBm. These theoretical limits are verified via measurement and simulation, and experimental performance data from the literature are extracted to validate the established maximum efficiency. Moreover, we propose design guidelines to achieve such performance limits, clarifying the method for optimizing the rectifier circuitry and the associated parameters. We further show potential approaches for the enhancement of maximum conversion efficiency via analyzing the loss parameters of Schottky diodes. This work thus establishes the performance benchmark of low‐power rectifiers and provides useful guidelines for future rectenna development.