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51.
52.
Haoshu SHEN Yuxin WU Minmin ZHOU Hai ZHANG Guangxi YUE Junfu LYU 《Frontiers in Energy》2021,15(1):124
Large eddy simulation (LES) has become a promising tool for pulverized coal combustion with the development of computational fluid dynamics (CFD) technologies in recent years. LES can better capture the unsteady features and turbulent structures of coal jet flame than Reynolds averaged Navier Stokes (RANS). The coal-fired power plants in China are now required to be operated in a wide load range and quickly respond to the electric grid. The boiler performance of variable loads should be evaluated in terms of flow, heat transfer, and combustion processes. In this paper, LES was applied to simulate a 660 MW ultra-supercritical boiler under BMCR (boiler maximum continue rate), 75%THA-100, and 50%THA-100 conditions. The predicted gas velocities agree well with the thermal calculation and the temperature error is less than 130 K. The simulation results show that the operation load has significant effects on the boiler performance. It is also proved that LES can provide guidance for the design and operation of advanced coal-fired boilers. 相似文献
53.
Lingfeng Zhou Zhipeng Zeng Michael P. Brady Donovan N. Leonard Harry M. Meyer Yukinori Yamamoto Wenyuan Li Greg Collins Xingbo Liu 《International Journal of Hydrogen Energy》2021,46(41):21619-21633
The chromium (Cr) evaporation behavior of several different types of iron (Fe)-based AFA alloys and benchmark Cr2O3-forming Fe-based 310 and Ni-based 625 alloys was investigated for 500 h exposures at 800 °C to 900 °C in air with 10% H2O. The Cr evaporation rates from alumina-forming austenitic (AFA) alloys were ~5 to 35 times lower than that of the Cr2O3-forming alloys depending on alloy and temperature. The Cr evaporation behavior was correlated with extensive characterization of the chemistry and microstructure of the oxide scales, which also revealed a degree of quartz tube Si contamination during the test. Long-term oxidation kinetics were also assessed at 800 to 1000 °C for up to 10,000 h in air with 10% H2O to provide further guidance for SOFC BOP component alloy selection. 相似文献
54.
Kaihui Ma Junyi Deng Gang Wang Qi Zhou Jian Xu 《International Journal of Hydrogen Energy》2021,46(52):26646-26664
Hydrogen (H2) energy is a promising candidate to replace carbon monoxide (CO) as a reductant for iron oxide reduction in revolutionary ironmaking industrial processes, and numerous studies have been conducted to intensively study the utilization and impact of H2 in ironmaking processes. Therefore, this review first collects and compares the H2-assisted reduction mechanism and kinetics. The impacts of H2 on the reduction accompanying behaviors, such as the disintegration, swelling, sticking, softening, and melting of iron ores, are then summarized. Third, the performance of H2 predicted by either mass and heat balance models or numerical simulation models in various ironmaking processes is highlighted. Finally, the different applications of hydrogen-rich materials in blast furnace and non-blast furnace ironmaking processes are further compared to illuminate H2 utilization before our outlook on the use of H2 in the ironmaking industry. 相似文献
55.
56.
为了保证无线传感器网络(Wireless Sensor Networks,WSNs)中的源节点位置隐私安全,同时实现安全性能和网络能耗的均衡,提出了WSNs中规避攻击者的源节点位置隐私路由协议,该协议假设节点具有检测攻击者的能力,通过发出危险警告消息使路由路径上的节点采取路由改变策略,使攻击者无法回溯到源节点,延长了源节点保持位置隐私的安全时间。理论分析和仿真实验表明,该协议在消耗较少的通信开销的情况下保证了源节点位置的高度隐私。 相似文献
57.
锥束计算机断层扫描(Cone-Beam Computed Tomography,CBCT)具有采集速度快和空间分辨率高等特点,被生物医学等领域广泛关注。然而通过CPU串行处理CBCT重建中海量投影数据非常耗时,难以满足实时性的需求。GPU的发展为CBCT重建的并行加速提供了条件。根据三角函数周期性的特点对FDK算法进行了改进,并利用GPU实现了12幅投影数据同时并行计算。实验结果表明,相比于传统基于CPU的重建算法,基于GPU的CBCT重建算法在保证图像质量的前提下,将重建速度提高了超过310倍。 相似文献
58.
变分自编码器(VAE)作为深度隐空间生成模型的一种,近年来其表现性能取得了极大的成功,尤其是在图像生成方面。变分自编码器模型作为无监督式特征学习的重要工具之一,可以通过学习隐编码空间与数据生成空间的特征映射,进而在输出端重构生成输入数据。梳理了传统变分自编码器模型及其衍生变体模型的发展与研究现状,并就此做了总结和对比,最后分析了变分自编码器模型存在的问题与挑战,并就可能的发展趋势做了展望。 相似文献
59.
In this work we propose an optimal back plane biasing (OBB) scheme to be used in a UTBB FD SOI technology that minimizes the energy per operation consumption of sub threshold digital CMOS circuits. By using this OBB scheme, simulations show that more than 30% energy savings can be obtained with low threshold voltage (LVT) devices in comparison with classic symmetric back plane biasing (SBB) schemes. Additionally, this OBB scheme allows to adjust the performance of the circuit with very small energy penalties. A very simple and intuitive model, for sub threshold digital CMOS circuits, was developed to justify the benefits obtained by OBB. The results predicted by the model are confirmed with extensive simulation results. We show that the OBB approach can be applied easily to a given circuit just based on the information provided by a logic simulation of the circuit (or even an analysis of its structure) and simple electrical simulations of the pMOS and nMOS transistors. Finally, we show that the variability in the energy consumption is improved by using OBB and suggests that new sizing methodologies must be studied to fully benefit from the wide back plane voltage range available in UTBB FD SOI technology for the design of robust energy efficient digital circuits. 相似文献
60.
戴敏 《计算机工程与应用》2019,55(19):134-140
Web缓存是用来解决网络访问延迟和网络拥塞问题,缓存替换策略直接影响缓存的命中率。为此,提出一种朴素贝叶斯(NB)分类器重访概率预测的Web缓存替换策略;根据用户之前访问日志,通过分区操作提取多项特征来表示每次访问的对象,并构建特征数据集;训练NB分类器,用来确定缓存中对象被再次访问的概率,为对象分配权重;结合LRU策略来合理删除一些对象。仿真结果表明,提出的策略在保证较高命中率的同时有效降低了执行时间。 相似文献