The development of MHD cold wall channels in the oil-fired condition

The durability of a cold wall MHD generator consisting of metal electrodes and alumina-coated peg insulators was experimentally examined in the oil-fired MHD condition with the additive of SO₂ corresponding to S = 0.54 wt%. The structure of the electrode wall and various anode and cathode materials were tested, with particular reference to developing long-life electrodes. It was clarified that Pt, SHOMAC (28.8 Cr−1.9 Mo) and SUS-304 as anodes and W---Cu (70 W−30 Cu) and WC---Ag (60 WC−40 Ag) alloys as cathodes were promising for durability and that the structure of an anode divided into two elements connected to each other with an SnO₂ resistor was very useful for uniformity of the anode corrosion pattern and the inter-anode voltages. It is reasonable to expect, from the test results, that the lifetime of a cold wall MHD generator in an oil-fired commercial plant will be over 4000 h, and therefore, a foundation for its commercial use has been established.     

微机在应变测量中的应用

微机在应变测量中的应用，采用上位机和下位机组合方式．上位机为一台ＩＢＭ－ＰＣ／ＸＴ微机，用于对数据进行后处理．下位机以Ｚ８０－ＣＰＵ为控制器，由传感器、转换器、接口及外设等组成数据采集器，实施对应变、压力和位移等参数的采集、显示和打印（即数据的预处理）．上位机和下位机之间的数据传输，采用串行的方式，通过ＲＳ－２３２接口完成．本文主要以应变的采集处理为例，介绍系统功能、硬件配置及软件设计．     

小麦、玉米控制灌溉技术研究

198 6～ 1998年 ,在山东省的 3个灌溉试验站 ,对冬小麦、秋玉米进行了控制灌溉试验 ,对农作物的多个生育阶段 ,按高产的要求 ,分别给予适时、适量的灌溉水 ,来控制作物不同生长期的根层土壤含水量 ,从而控制作物不同生长期根系对水分的吸收 ,培植农作物的“丰产群体结构”和与之相适应的“高产理想株型” ,适当降低无效的蒸腾量 ,使农作物能在高产的基础上再增产 .该项控制灌溉技术获得了明显的节水、增产效果 ,灌溉水的生产效率超过了 10kg/m3,产量超过了 8t/hm2 .     

国产CN—31催化剂与ICI65—2催化剂工业应用的比较

国产轻油预转化催化剂与进口催化剂相比,具有性能相当、价格低廉、供应方便等优势。国产预转化催化剂需在较高的液空速、温度较低的条件下实现烃类转化反应,生成含甲烷60%以上的富气。采用国产催化剂能明显反映性能价格比。文章对两种催化剂进行了工业应用比较和分析。     

数字视频混合系统的设计

介绍了利用Philips的一款视频芯片SAA71 99B实现的数字视频混合系统.该系统可以将一路PAL制彩色复合视频信号编码进入另一路PAL制彩色复合视频信号中,以取代第二路视频中用户指定的颜色,从而实现了两路视频的混合.另外还介绍了如何利用单片机的I/O口模拟I 2C总线以及如何利用单片机进行彩色空间变换的算法.     

Application of SiC-Si functionally gradient material to thermoelectric energy conversion device

Because of its high–temperature chemical stability, SiC ceramic is a promising material for high-temperature device applications such as thermoelectric energy converters. However, the electrical conductivity of SiC ceramic is too low for it to be used as a thermoelectric energy converter at the cold junction. Therefore, we propose a SiC-Si functionally gradient material (FGM) in order to improve the electrical conductivity of the SiC ceramic at the cold junction. An SiC rod was fired in a temperature gradient furnace. One end of the SiC rod was maintained at 2473 K and the other end was maintained at 1973 K for 30 min. After firing, the porous SiC edge fired at 1973 K was dipped into molten Si in order to infiltrate molten Si into the porous SiC. The microstructure of the FGM is classified into three regions: the SiC-Si composite material; the porous SiC ceramic; and the densified SiC ceramic. The electrical conductivity, the Seebeck coefficient and the thermal conductivity for each region of SiC-Si FGM was measured at 300 K; a figure of merit was calculated. The figure of merit of the SiC-Si FGM at the cold junction, at room temperature, was 10⁸ times higher than that of a nongradient SiC ceramic.     

A novel laboratory bench for practical evaluation of catalysts useful for simultaneous conversion of NOx and soot in diesel exhaust

This study deals with the development of a laboratory bench for the practical evaluation of catalysts that are useful for the direct conversion of NO_x and soot in the exhaust of diesel engines. The employed model exhaust is generated by using a diffusion burner with additionally dosing some gaseous components to the burner gas to obtain a realistic feed composition. The produced soot is extensively characterized by employing thermogravimetry, transmission electron microscopy, N₂ physisorption and temperature programmed techniques. The results of the different characterization methods show that the present soot is suitable for the intended catalytic investigations. The simultaneous conversion of NO_x and soot is examined like in practice, i.e. the soot is separated from the tail gas by a diesel particulate filter (DPF) that is coated with the catalyst. The deposited soot is then catalytically converted by NO_x and O₂ to form N₂ and CO₂. The conversions of NO_x and soot are measured by exclusively applying gas analysers, whereby a special experimental procedure is developed to determine the soot removal. Hence, additional soot related analytics are not required. To show the suitability of the constructed bench a Pt/Fe₂O₃/β-zeolite sample is taken as test catalyst that is reported to be very active in NO_x/soot reaction. The measurements performed with and without catalyst clearly show the effect of the used sample in simultaneous NO_x/soot conversion. We therefore consider the constructed laboratory bench to be a useful tool for testing and ranking catalytic materials.     

地理环境与先秦南北饮食文化

先秦时期是我国饮食文化的形成时期，受地理环境的强烈影响，逐渐形成了以秦岭-淮河一线为界的南北两个主要的饮食文化区域：黄河中下游地区为中心的北方饮食文化区，是以旱地粮食作物黍、稷、粟等为主食，陆地动物为辅食，烧、烤、炸为主要烹饪方法的北方饮食风味；长江中下游地区为中心的南方饮食文化区，是以水田粮食作物稻米为主食，陆地动物和水产动植物为辅食，蒸、炖、煎为主要烹饪方法的南方饮食风味。     

A New Variable Diffusion Drying Model for the Second Falling Rate Period of Paddy Dried in a Rapid Bin Dryer

The objectives of this article is to propose a new drying model for the second falling rate period known as the variable diffusion controlled period that follows after the first falling rate period and to propose a new method to determine the second critical moisture content that separates these two periods. Experimental work on paddy drying at minimum fluidization velocity was carried out in a rapid bin dryer. The effects of operating temperatures (60-120°C) and bed depths (2-6 cm) on the paddy drying characteristics were investigated. It was found that the normalized drying rate of paddy was proportional to the normalized moisture content in the first falling rate period but in the second falling rate period, the normalized drying rate of the material varies exponentially with the normalized moisture content. The different relationship between the normalized drying rate and the normalized moisture content in the first and second falling rate periods indicate that two different mechanism of moisture transport are at work. The new exponential model of the second falling rate period and the linear model of the first falling rate period were found to fit the experimental data very well. Derivation from variable diffusion equation shows that the linear model is the result of constant diffusion coefficient whereas the new exponential model is the result of linear diffusion coefficient. This also implies that the first falling rate period is a constant diffusion controlled period and the second falling rate period is a variable diffusion controlled period. In addition, drying kinetics data of a drying process that fits the exponential model over a very slow drying period will show that the drying process is under the effect of a linear diffusion coefficient. It was also found that the proposed new method to determine the second critical moisture content that distinguishes between the first and second falling rate periods by using a sudden change in the value of the drying rate gradient to a much lower value at that point is more rigorous and yet simpler than the method of determining the specific location of the receding drying boundary since it is based on the behavior of the actual drying kinetic data.     

舰船导航信号发生器虚拟化设计

介绍了基于PC总线的便携式舰船导航信号发生器虚拟化设计，着重叙述该仪器硬件设计、基于虚拟仪器开发平台LabWindows／CVI的软件设计。