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排序方式: 共有8841条查询结果,搜索用时 276 毫秒
31.
Christos C. Agrafiotis Chrysoula Pagkoura Souzana Lorentzou Margaritis Kostoglou Athanasios G. Konstandopoulos 《Catalysis Today》2007,127(1-4):265-277
The present work summarizes the recent activities of our laboratory in the field of solar-aided hydrogen production with structured monolithic solar reactors. This reactor concept, “transferred” from the well-known automobile exhaust catalytic after-treatment systems, employs ceramic supports optimized to absorb effectively solar radiation and develop sufficiently high temperatures, that are coated with active materials capable to perform/catalyze a variety of “solar-aided” reactions for the production of hydrogen such as water splitting or natural gas reforming. Our work evolves in an integrated approach starting from the synthesis of active powders tailored to particular hydrogen production reactions, their deposition upon porous absorbers, testing of relevant properties of merit such as thermomechanical stability and hydrogen yield and finally to the design, operation simulation and performance optimization of structured monolithic solar hydrogen production reactors. This approach, among other things, has culminated to the world's first closed, solar-thermochemical cycle in operation that is capable of continuous hydrogen production employing entirely renewable and abundant energy sources and raw materials – solar energy and water, respectively – without any CO2 emissions and holds, thus, a significant potential for large-scale, emissions-free hydrogen production, particularly for regions of the world that lack indigenous resources but are endowed with ample solar energy. 相似文献
32.
R. Kaji S. Adachi H. Sasakura S. Muto H. Kumano I. Suemune 《Journal of Superconductivity and Novel Magnetism》2007,20(6):447-451
We investigated optical pumping of nuclear spin polarizations in a single self-assembled In0.75Al0.25As/Al0.3Ga0.7As quantum dot. The nuclear spin polarization exhibits the abrupt jump and hysteresis in the excitation power dependence at
a particular excitation polarization. Measurement of circular polarization rate of the photoluminescence reveals that the
abrupt change of the nuclear spin polarization is created mainly by the spin flip-flop process between nuclei and an electron
of a positive charged exciton in this single quantum dot. Model calculation explains well the experimentally observed bistable
behavior in InAlAs quantum dot. By using this abrupt change, the sign and magnitude of electron and hole g-factors in z-direction are verified.
相似文献
33.
Marie-Claude Druguet David E. Zeitoun 《Computers & Fluids》2003,32(4):515-533
Numerical simulations are investigated to describe precisely the shock wave reflections in supersonic steady air flow field. The main objectives are to study the influence of the wedge trailing edge corner angle, of the numerical methods and of the viscous effects on the shock wave reflections and on the hysteresis behavior. The computations are done with different MUSCL-TVD finite volume schemes and the corresponding results are compared. The flow viscosity is also taken into account and comparisons are made between inviscid and viscous flow simulations. The results display the non-negligible influence of the numerical scheme accuracy on the results, mainly on the position and height of the Mach stem, and the relatively weak influence of the flow viscosity on these parameters. Comparisons between numerical results and experimental data have also been done and a good agreement is only observed for small wedge angles mainly due to the three-dimensional effects in the experimental setup. 相似文献
34.
An Interval Fuzzy Multiobjective Watershed Management Model for the Lake Qionghai Watershed, China 总被引:4,自引:0,他引:4
Lijing Wang Wei Meng Huaicheng Guo Zhenxing Zhang Yong Liu Yingying Fan 《Water Resources Management》2006,20(5):701-721
Integrated watershed management is required to ensure the reasonable use of resources and reconcile interactions among natural and human systems. In the present study, an interval fuzzy multiobjective programming (IFMOP) method was used to solve an integrated watershed management problem. Based on system analysis, an IFMOP model suitable for a lake watershed system {IFMOPLWS} was developed and applied to the Lake Qionghai watershed in China. Scenario analysis and an interactive approach were used in the solution process. In this manner, various system components were incorporated into one framework for holistic consideration and optimization. Integrality and uncertainty, as well as the multiobjective and dynamic characteristics of the watershed system, were well addressed. Using two scenarios, two planning schemes were generated. Agriculture, tourism, macroeconomics, cropland use, water supply, forest coverage, soil erosion, and water pollution were fully interpreted and compared to identify a preferable planning alternative for local agencies. This study showed that the IFMOPLWS is a powerful tool for integrated watershed management planning and can provide a solid base for sustainable watershed management. 相似文献
35.
36.
利用地震属性钻前预测井壁稳定性 总被引:4,自引:2,他引:2
钻前准确预测井壁稳定性是防止钻进过程中井壁失稳的有效手段。声波时差和地层密度是井壁稳定分析的两个关键参数。根据地震记录与地层声波时差及密度之间存在的非线性关系,提出了利用地震属性钻前预测井壁稳定性的方法。从井旁地震记录中提取地震属性,通过RBF神经网络在已钻井段的地震属性与声波时差及密度之间建立起映射模型,以此为基础预测待钻地层的声波时差和密度。运用预测结果结合井壁稳定力学模型,确定岩石力学参数和地应力状态,计算井壁坍塌压力和破裂压力,确定安全钻井液密度窗口,实现钻前井壁稳定预测。该方法在塔里木油田的应用中取得了良好的预测效果。 相似文献
37.
We present some sufficient and necessary conditions for convergent splitting of a non-Hermitian indefinite matrix. Some sufficient
conditions to determinate a matrix with a (strongly) dominant symmetric part for a class of boundary value problem are also
obtained. These results are applicable to identify the convergence of iterative methods for solving large sparse systems of
linear equations. 相似文献
38.
RLL码的计算机辅助设计 总被引:1,自引:1,他引:0
本文着重讨论计算机辅助设计RLL码的具体实现问题.该过程首先根据RLL码两个参数d,k确定一个编码率p/q,然后构造出RLL码的高阶状态转换-输出符号矩阵并求相应的近似特征向量.最后通过状态分裂和状态归并过程,即可得到一个满足d,k约束的编码输出表.其中状态转换-输出符号矩阵为实现计算机辅助设计RLL码提供了有效的数据结构,而且要优化RLL码编码器,就必须有选择地进行状态分裂. 相似文献
39.
一、概述核电厂压水堆的初始过剩反应性是通过控制捧、固体可燃毒物和溶解在主回路冷却剂中的硼酸等三种方式联合控制的。随着反应堆的燃耗和裂变毒物的积累,堆的过剩反应性不断减少,需要通过化容系统,控制硼酸的浓度来进行补偿。如果化容系统发生故障或操作员误操作,就会给回路注入无硼或低于规定浓度的补给水,给反应堆引入正反应性,造成硼稀释事故。按核安全法规的要求,应对换料、冷停堆、热停堆和启动等工况进行计算,并要求在这些 相似文献
40.
区间系统在反馈控制情况下的性能鲁棒性 总被引:1,自引:0,他引:1
本文讨论含区间对象的反馈控制系统性能鲁棒性问题,给出了检验区间系统性能鲁棒性的充要条件.当补偿器满足某种假设条件时,给出了闭环系统性能鲁棒性的有限检验结果。在有限检验的前提下,给出了补偿器在系数空间中所应满足的制约条件。 相似文献