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81.
The maximum entropy principle (MEP) is used to generate a natural probability distribution among the many possible that have
the same moment conditions. The MEP can accommodate higher order moment information and therefore facilitate a higher quality
PDF model. The performance of the MEP for PDF estimation is studied by using more than four moments. For the case with four
moments, the results are compared with those by the Pearson system. It is observed that as accommodating higher order moment,
the estimated PDF converges to the original one. A sensitivity analysis formulation of the failure probability based on the
MEP is derived for reliability-based design optimization (RBDO) and the accuracy is compared with that by finite difference
method (FDM). Two RBDO examples including a realistic three-dimensional wing design are solved by using the derived sensitivity
formula and the MEP-based moment method. The results are compared with other methods such as TR-SQP, FAMM + Pearson system,
FFMM + Pearson system in terms of accuracy and efficiency. It is also shown that an improvement in the accuracy by including
more moment terms can increase numerical efficiency of optimization for the three-dimensional wing design. The moment method
equipped with the MEP is found flexible and well adoptable for reliability analysis and design. 相似文献
82.
83.
陆曼 《西华大学学报(自然科学版)》1994,(3)
对基准物“最好具有较大当量”更改为“最好具有较大摩尔质量”是否完全等效及当前所提出的两种求证方法进行了论证、比较。指出两法得到相同结论实属巧合之例;另举例说明在比较基准物摩尔质量大小以说明称量误差大小时,只有选用完全一致的比较标准才能使基准物“最好具有较大当量”或“最好具有较大摩尔质量”的两提法完全等效,并适用于任何情况。 相似文献
84.
针对PMSM传统直接转矩控制存在开关频率不规则、开关噪声的频率范围太宽和死区补偿算法复杂等问题,本文提出了一种基于优化脉宽调制(PWM)和死区补偿的PMSM预测直接转矩控制(DTC)方法。该方法首先在已知零电压矢量的基础上,根据预测转矩和磁通误差来选择两个其他有效电压矢量,与此同时,也考虑反电动势和磁通-转矩耦合器;接着,利用零电压矢量和两个其他有效电压矢量预测每个采样周期的转矩和磁通变化量,其中,三个电压矢量的开关周期由转矩和磁通误差以及在上一步中计算出的预测转矩和磁通变化共同决定;然后,采用死区补偿算法和改进的PWM来减小死区效应,以提高预测效果;最后,通过仿真和实验验证了所提方法的有效性和优越性,研究结果表明,所提方法在转矩控制和磁通控制效果要明显优于其他方法,且极大降低了开关损耗。 相似文献
85.
由低维InAs材料和其他二维层状材料堆叠而成的垂直范德华异质结构在纳米电子、光电子和量子信息等新兴领域中应用广泛。探索跨结界面的电荷转移机制对于全面理解该类器件的非凡特性至关重要。第一性原理计算在揭示界面电荷转移特性与各种能量稳定型InAs基范德华异质结的电、光、磁等原理物理特性和器件性能变化之间的内在关系方面发挥着不可比拟的作用。文中梳理、总结和探讨了近年来InAs基范德华异质结间界面电荷转移特性的理论研究工作与潜在的功能应用,提出在理论方法和计算精度方面大力发展第一性原理计算的几个途径,为更好地开展InAs基范德华异质结的基础科学研究和应用器件设计提供可借鉴的量化研究基础。 相似文献
86.
稀Bi半导体InPBi的光致发光(Photoluminescence, PL)主要来自缺陷能级跃迁过程,具有红外长波长、大线宽和高辐射强度等特点,因而引发广泛兴趣。针对InPBi的红外发光效率问题,本文研究了不同Bi组分InPBi的激发功率依赖红外PL光谱演化规律。实验发现,随着Bi组分增大,PL线型发生显著变化,导致发光波长总体红移;同时激发功率依赖的PL积分强度演化分析表明,发光效率随Bi组分先增大然后下降,在0.5%组分时发光效率达到峰值。发光效率增大一方面归因于Bi捕获空穴降低非辐射复合,另一方面来自Bi的表面活性剂效应;而高Bi组分引入过多缺陷从而抑制了Bi的优势,导致发光效率下降。这些结果或有助于理解InPBi的红外发射性能,表明InPBi具有红外光电子应用前景。 相似文献
87.
Zhang Man Zhou Yong Liu Bing Zhao Jiaqi Yao Rui Shao Zhiwen Zhu Hancheng Chen Hao 《Pattern Analysis & Applications》2023,26(2):669-677
Pattern Analysis and Applications - The designed method aims to perform image classification tasks efficiently and accurately. Different from the traditional CNN-based image classification methods,... 相似文献
88.
Hu Youhao Wang Hai Yazdani Amirmehdi Man Zhihong 《Neural computing & applications》2022,34(7):5241-5253
Neural Computing and Applications - This paper proposes a novel extreme learning machine (ELM)-based fixed time adaptive trajectory control for electronic throttle valve system with uncertain... 相似文献
89.
In Situ Observation of Crystallization of Methylammonium Lead Iodide Perovskite from Microdroplets 下载免费PDF全文
Yahui Li Zhenhao Zhao Feng Lin Xiaobing Cao Xian Cui Jinquan Wei 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(26)
It is of great importance to investigate the crystallization of organometallic perovskite from solution for enhancing performance of perovskite solar cells. Here, this study develops a facile method for in situ observation of crystallization and growth of the methylammonium lead iodide (MAPbI3) perovskite from microdroplets ejected by an alternating viscous and inertial force jetting method. It is found that there are two crystallization modes when MAPbI3 grows from the CH3NH3I (MAI)/PbI2/N,N‐dimethylformamide (DMF) solution: needle precursors and granular perovskites. Generally, needle Lewis adduct of MAPbI3·DMF tends to nucleate and grow from the solution due to low solubility of PbI2. The growth of MAPbI3·DMF depends on both the concentration of MAI and temperature. It tends to form large perovskite domains on substrates at high temperature. The MAPbI3·DMF coverts to nanocrystalline perovskite due to lattice shrinkage when DMF molecules escape from the Lewis adduct. Granular perovskite can also directly nucleate from the solution at high concentration of MAI due to compositional segregation. 相似文献
90.
Flexible Nonvolatile Transistor Memory with Solution‐Processed Transition Metal Dichalcogenides 下载免费PDF全文
Richard Hahnkee Kim Jinseong Lee Kang Lib Kim Suk Man Cho Dong Ha Kim Cheolmin Park 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(20)
Nonvolatile field‐effect transistor (FET) memories containing transition metal dichalcogenide (TMD) nanosheets have been recently developed with great interest by utilizing some of the intriguing photoelectronic properties of TMDs. The TMD nanosheets are, however, employed as semiconducting channels in most of the memories, and only a few works address their function as floating gates. Here, a floating‐gate organic‐FET memory with an all‐in‐one floating‐gate/tunneling layer of the solution‐processed TMD nanosheets is demonstrated. Molybdenum disulfide (MoS2) is efficiently liquid‐exfoliated by amine‐terminated polystyrene with a controlled amount of MoS2 nanosheets in an all‐in‐one floating‐gate/tunneling layer, allowing for systematic investigation of concentration‐dependent charge‐trapping and detrapping properties of MoS2 nanosheets. At an optimized condition, the nonvolatile memory exhibits memory performances with an ON/OFF ratio greater than 104, a program/erase endurance cycle over 400 times, and data retention longer than 7 × 103 s. All‐in‐one floating‐gate/tunneling layers containing molybdenum diselenide and tungsten disulfide are also developed. Furthermore, a mechanically‐flexible TMD memory on a plastic substrate shows a performance comparable with that on a hard substrate, and the memory properties are rarely altered after outer‐bending events over 500 times at the bending radius of 4.0 mm. 相似文献