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961.
The magnitude and activation energy of electrical conductivity in nanocrystalline cerium oxide exhibit a clear grain size dependence. Experimental results compiled from the literature were analyzed using a space charge model, which takes into account the deviation of point defect concentrations from their bulk values in the vicinity of grain boundaries. The consequences on conductivity arising from such space charge layers were calculated using the brick-layer model (BLM) for grain sizes L large compared to the screening length . The obtained results were supplemented by the calculated conductivity in the flat-band limit for L . This combination allowed for a quantitative comparison with experimental values, which were obtained in the mesoscopic regime of grain sizes from 10–40 nm. The analysis yielded a value for the space charge potential in cerium oxide of 0.55 V. This space charge potential is caused by a reduced standard chemical potential of oxygen vacancies in the grain boundary core as compared to the bulk phase. 相似文献
962.
基于随机算法的三相异步电动机全局优化 总被引:7,自引:3,他引:4
以效率为目标函数的铸铝转子异步电机全局优化是一种个复杂的非凸、非线性规划问题。首先使用TABU算法将这一高维问题降维分解并缩步搜索域,一局寻优。验证结果表明,该方法充分了长期积累的经验知识,与单独使用TABU算法或遗传算法相比,计算量较为合理,结果满意度较高,基本满足了高效电机设计的要求。 相似文献
963.
Junping Wang Binggang Cao Quanshi Chen Feng Wang 《Control Engineering Practice》2007,15(12):1569-1576
Ah counting is not a satisfactory method for the estimation of the state of charge (SOC) of a battery, as the initial SOC and coulomb efficiency are difficult to measure. To address this issue, an equivalent coulomb efficiency is defined and a new SOC estimation method, denoted as “KalmanAh”, is proposed. This method uses the Kalman filtering method to correct for the initial value used in the Ah counting method. A Ni/MH battery test, consisting of 8.08 continuous federal urban driving schedule (FUDS) cycles, is carried out to verify the method. The SOC estimation error is 2.5% when compared with the real SOC obtained from a discharge test. This compares favorably with an estimation error of 11.4% when using Ah counting. 相似文献
964.
针对充电过程的复杂情况,采用模糊智能技术进行蓄电池的充电系统控制。以C5042EM-44单片机为控制单元,应用温度、电流、电压等参数的采样技术和用户界面技术以及主电路的设计中的工频整流滤波、DC—DC变换、二次斩波,对充放电的过程参数进行了控制.实现了其控制和报警功能。 相似文献
965.
Clinicians' drug regimen decision making is critical, particularly when involving high-alert medications. In this study, we use decision-tree induction C4.5 and a backpropagation neural network to construct decision support systems for predicting the regimen adequacy of vancomycin, a glycopeptide antimicrobial antibiotic effective for Gram-positive bacterial infections. We comparatively evaluate the respective systems using a total of 987 clinical vancomycin cases collected from a major tertiary medical center in southern Taiwan. We supplement each system using Bagging and then examine the predictive power of the extended system. Overall, our evaluation results show the overall accuracy of the decision support system based on C4.5 or the neural network to be significantly higher than that of the benchmark one-compartment pharmacokinetic model. Use of Bagging can considerably improve the effectiveness of each system across different performance measures, particularly for cases of decision classes in which the base systems (i.e., without Bagging) perform modestly. Taken together, our evaluation results seem to favor the use of Bagging to enhance the performance of decision support systems constructed using decision-tree induction C4.5. 相似文献
966.
XPATH在Web信息提取中起重要作用,但是这些XPATH规则通常要人工生成。文中讨论了在XPATH与基于文本上下文规则的信息提取方法结合的系统中如何归纳学习XPATH规则。生成的XPATH规则结构简单,可以为基于文本上下文的信息提取系统提供较为准确的信息定位。 相似文献
967.
将蓄电池恒流充电和恒压充电比较,对不同的电池采用低压恒压充电和恒压限流充电方法的优点、可靠性及充电终了的判定进行介绍。 相似文献
968.
969.
A simple and feasible method for the production of high nitrogen austenitic stainless steels involves nitrogen gas alloying and adding nitrided ferroalloys under normal atmospheric conditions. Alloying by nitrogen gas bubbling in Fe Cr Mn Mo series alloys was carried out in MoSi2 resistance furnace and air induction furnace under normal atmospheric conditions. The results showed that nitrogen alloying could be accelerated by increasing nitrogen gas flow rate, prolonging residence time of bubbles, increasing gas/molten steel interfaces, and decreasing the sulphur and oxygen contents in molten steel. Nitrogen content of 069% in 18Cr18Mn was obtained using air induction furnace by bubbling of nitrogen gas from porous plug. In addition, the nickel free, high nitrogen austenitic stainless steels with sound and compact macrostructure had been produced in the laboratory using vacuum induction furnace and electroslag remelting furnace under nitrogen atmosphere by the addition of nitrided alloy with the maximum nitrogen content of 081%. Pores were observed in the ingots obtained by melting and casting in vacuum induction furnace with the addition of nitrided ferroalloys and under nitrogen atmosphere. After electroslag remelting of the cast ingots, they were all sound and were free of pores. The yield of nitrogen increased with the decrease of melting rate in the ESR process. Due to electroslag remelting under nitrogen atmosphere and the consequential addition of aluminum as deoxidizer to the slag, the loss of manganese decreased obviously. There existed mainly irregular Al2O3 inclusions and MnS inclusions in ESR ingots, and the size of most of the inclusions was less than 5 μm. After homogenization of the hot rolled plate at 1 150 ℃×1 h followed by water quenching, the microstructure consisted of homogeneous austenite. 相似文献
970.
梁旗 《数字社区&智能家居》2007,3(14):404-1858
在分析锁相环基本原理和线性化模型的基础上,给出了基于锁相环系统环路带宽和相位裕度的环路滤波器参数的计算公式.结合具体的参数计算,给出系统参数,然后用ADS工具对系统进行仿真,结果表明利用给出的方法来设定锁相环的参数,通过反复几次的调节能得到一组很好的系统参数,仿真结果于预期的相吻合,对三阶电荷泵锁相环的系统设计和仿真有一定的指导意义. 相似文献