Two mathematical models are developed in this paper to study the effectiveness of system administration efforts on the improvement of system availability, based on the assumption that there exists a transitional state...Two mathematical models are developed in this paper to study the effectiveness of system administration efforts on the improvement of system availability, based on the assumption that there exists a transitional state for a computer system in operation before it is brought down by some hardware or software problems and with intensified system administration efforts, it is possible to discover and fix the problems in time to bring the system back to normal state before it is down. Markov chain is used to simulate the transition of system states. A conclusion is made that increasing system administration efforts may be a cost-effective way to meet the requirements for moderate improvement on system availability, but higher demand on this aspect still has to be met by advanced technologies.展开更多
为了研究苹果片的热风干燥特性,考察了切片厚度、热风温度和装样量对苹果片热风干燥过程的影响,比较了6种数学模型在苹果片热风干燥中的适用性.结果表明:切片厚度、热风温度和装样量均对苹果片的热风干燥过程影响较大,苹果片切片厚度越...为了研究苹果片的热风干燥特性,考察了切片厚度、热风温度和装样量对苹果片热风干燥过程的影响,比较了6种数学模型在苹果片热风干燥中的适用性.结果表明:切片厚度、热风温度和装样量均对苹果片的热风干燥过程影响较大,苹果片切片厚度越小,热风温度越高,热风干燥速率越大,装样量对干燥速率的影响呈现先增大后减小的趋势;苹果片的热风干燥过程可分为升速干燥阶段及降速干燥阶段,没有恒速阶段;Midilli-Kucuk模型对实验数据的拟合度最高,优于Page模型和Modified Page模型;热风温度从50℃增加到70℃,其有效水分扩散系数由1.10×10^(-9)m^2/s增加到1.83×10^(-9)m^2/s,苹果片的干燥活化能为13.58 k J/mol.展开更多
基金This project was supported by the National Key program of Science and Technology(99-A29-0101).
文摘Two mathematical models are developed in this paper to study the effectiveness of system administration efforts on the improvement of system availability, based on the assumption that there exists a transitional state for a computer system in operation before it is brought down by some hardware or software problems and with intensified system administration efforts, it is possible to discover and fix the problems in time to bring the system back to normal state before it is down. Markov chain is used to simulate the transition of system states. A conclusion is made that increasing system administration efforts may be a cost-effective way to meet the requirements for moderate improvement on system availability, but higher demand on this aspect still has to be met by advanced technologies.
文摘为了研究苹果片的热风干燥特性,考察了切片厚度、热风温度和装样量对苹果片热风干燥过程的影响,比较了6种数学模型在苹果片热风干燥中的适用性.结果表明:切片厚度、热风温度和装样量均对苹果片的热风干燥过程影响较大,苹果片切片厚度越小,热风温度越高,热风干燥速率越大,装样量对干燥速率的影响呈现先增大后减小的趋势;苹果片的热风干燥过程可分为升速干燥阶段及降速干燥阶段,没有恒速阶段;Midilli-Kucuk模型对实验数据的拟合度最高,优于Page模型和Modified Page模型;热风温度从50℃增加到70℃,其有效水分扩散系数由1.10×10^(-9)m^2/s增加到1.83×10^(-9)m^2/s,苹果片的干燥活化能为13.58 k J/mol.
