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101.
A test has been devised that allows one to determine the work of adhesion and wettability in a system composed of aluminum nitride ceramics with a liquid metal without the need for experimental examination. A correlation is examined between the work of adhesion on the one hand and that criteria or others on the other that have been proposed by various researchers. Forecasts are made for the work of adhesion and wetting angle for a series of metals that have not been examined previously. An experimental check has been made on the forecast adhesion activity for some elements. 相似文献
102.
103.
104.
金属PTC陶瓷复合材料结构及其导电机理 总被引:2,自引:0,他引:2
研究了金属PTC陶瓷复合材料的电学性能和其材料组分。结果表明,掺入金属的PTC陶瓷材料经氮气中烧结,然后在空气中进行热处理,材料表面形成高势垒层,金属PTC陶瓷复合材料的室温电阻较PTC的陶瓷高。样品之中存在大量不同类型的极化,在低温时样品电阻较高,温度增加后,大量各种类型离子极化出现,在变价金属铁的变价导电作用下,削弱表面势垒,使金属PTC陶瓷复合材料电阻降低,表现出NTC现象。在电场作用下,正负电荷、晶粒畸变和空位缺陷等产生空间电荷极化使金属PTC陶瓷复合材料有较高介电常数。介电损耗(tgδ)频谱和介电δ温度谱上都出现一个介电峰,其主要原因是跃迁极化,金属阳离子由一个位置跃迁到另一个位置,在介电损耗所对应的频率和温度时出现跃迁极化率最大 相似文献
105.
热释电系数的测量方法 总被引:2,自引:0,他引:2
描述热释电系数的两种测量方法。其一为电荷积分法,测试系统简单,测量数据准确,且能满足零电场条件下的测量。其二为动态电流法,采用调制热源技术,研究在特定温度条件下热释电材料的动态热释电响应。 相似文献
106.
本文介绍了以各种中药材为主要原料 ,配以茶叶为辅料 ,运用先进的处理方法制备降脂减肥果茶的生产工艺、质量标准 ,并对确定生产工艺的几个主要问题进行了探讨 相似文献
107.
M P Vaquero M Veldhuizen W van Dokkum C J A van den Hamer G Schaafsma 《Journal of the science of food and agriculture》1994,64(4):475-481
The influence of drinking tea on copper bioavailability is unclear, particularly when tea is consumed with food. A breakfast meal containing white bread, margarine, strawberry jam, cheese and tea, with or without milk, was digested in; vitro and the dialysis of copper investigated. Reference breakfasts were prepared with water and water with milk. Copper dialysability (percentage of copper dialysed) was markedly increased by tea. The influence of adding milk to tea was not significant. A second study was carried out in rats using the breakfasts containing tea and water. They were spiked with 64Cu and given orally to the animals in a single dose. Whole-body 64Cu retention was measured over a 4-day period after administration. In order to determine the true absorption of 64Cu a control group of rats received the dose intraperitioneally. The results in vivo indicate a tendency to higher absorption and retention of 64Cu with tea. Liver 64Cu retention was significantly elevated by tea. Therefore, the presence of tea in a breakfast meal favours the formation of soluble low-molecular-weight ligands which can be absorbed and retained by rats. The concomitant increase in liver copper retetition may be associated with higher bioavailability and/or lower copper mobilisation. 相似文献
108.
电致伸缩陶瓷微位移器非线性的数值方法补偿 总被引:7,自引:1,他引:6
本文通过对电致伸缩陶瓷材料的非线性进行分析。找到了补偿电致伸缩陶瓷非线性的数值方法,并对不同回程大小的电滞回线进行了分段处理,使补偿结果更为精确。 相似文献
109.
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. 相似文献
110.
G. Dong 《Annals of Mathematics and Artificial Intelligence》1993,7(1-4):107-127
LDL is one of the recently proposed logical query languages, which incorporate set, for data and knowledge base systems. Since LDL programs can simulate negation, they are not monotonic in general. On the other hand, there are monotonic LDL programs. This paper addresses the natural question of “When are the generally nonmonotonic LDL programs monotonic?” and investigates related topics such as useful applications for monotonicity. We discuss four kinds of monotonicity, and examine two of them in depth. The first of the two, called “ω-monotonicity”, is shown to be undecidable even when limited to single-stratum programs. The second, called “uniform monotonicity”, is shown to implyω-monotonicity. We characterize the uniform monotonicity of a program (i) by a relationship between its Bancilhon-Khoshafian semantics and its LDL semantics, and (ii) with a useful property called subset completion independence. Characterization (ii) implies that uniformly monotonie programs can be evaluated more efficiently by discarding dominated facts. Finally, we provide some necessary and/or sufficient, syntactic conditions for uniform monotonicity. The conditions pinpoint (a) enumerated set terms, (b) negations of membership and inclusion, and (c) sharing of set terms as the main source for nonuniform monotonicity. 相似文献