双输入Buck变换器的单周期控制

在可再生能源联合发电系统中,采用单个多输入直流变换器(MIC)代替原有的多个单输入直流变换器,可以简化电路结构,降低系统成本。MIC通常需要进行能量管理以实现可再生能源的优先利用,因此采用MIC构成的可再生能源联合发电系统是一个典型的多输入-多输出的耦合系统,其闭环设计复杂。因此本文针对双输入Buck变换器,提出单周期控制方式来消除环路之间的耦合。同时本文还提出了模式切换电路以实现各个模式之间的平滑切换,并推导了双输入Buck变换器在不同工作模式下的单周期控制小信号模型。由该小信号模型可知,采用单周期控制无需电流调节器,而且电压调节器在不同工作模式下的设计条件相同,因此调节器的设计大大简化。最后本文设计制作了一台800W的实验样机,实验结果验证了所提出单周期控制方法的有效性。     

Physico-chemical properties and microstructure of hydroxyapatite-316L stainless steel biomaterials

Sintering shrinkage, compressive strength, bending strength, metallurgical morphology, microstructure and chemical composition diffusion of hydroxyapatite-316L stainless steel(HA-316L SS) composites were investiga-ted. The results show that the sintering shrinkage of HA-316L SS composites decreases from 27.38O/6o to 8.87% for cylinder sample or from 27.18% to 8.62% for cuboid sample with decreasing the volume ratio of HA to 316L SS,which leads to higher sintering activity of HA compared with that of 316L SS. The compressive strength of HA-316L SS composites changes just like parabolic curve (245.3→126.3→202.8 MPa) with reducing the volume ratio of HA to 316L SS. Bending strength increases from 86.3MPa to 124. 2 MPa with increasing the content of 316L SS. Furthermore, comprehensive mechanical properties of 1.0：3.0 (volume ratio of HA to 316L SS) composite are optimal with compressive strength and bending strength equal to 202. 8 MPa and 124. 2 MPa, respectively. The microstructure and metallurgical structure vary regularly with the volume ratio of HA to 316L SS. Some chemical reaction takes place at the interface of the composites during sintering.     

改进残差χ~2检验法在组合导航故障检测中应用

在组合导航系统故障检测中,针对残差χ2检验法对于检测缓变故障的不足,提出了用基于卡尔曼滤波模型的速度检测模块的输出值辅助残差χ2检验,并采用模糊逻辑和加权平均来处理检验阈值,从而更有效地检测缓变故障,并在GPS/JTIDS/IFDL/INS组合导航系统中各个子滤波器中进行仿真验证,在加入不同大小的缓变故障时与残差χ2检验法进行了比较。仿真结果表明,该方法有效缩短了检测延迟,提高了故障检测的灵敏度,并且此优势在故障越小时,体现越明显。因此,改进残差χ2检验法提高了组合导航系统对于缓变故障的检测效率,使系统的可靠性得到了改善。     

基于神经网络的最短路算法及其应用

提出一种基于递归神经网络的最短路算法,降低了神经元之间的连接复杂度,能稳定收敛到准最优解。并将其应用于基于流量的动态分布式路由。仿真表明,该处上敛稳定。     

Crystallographically-oriented nanoassembly by ZnS tricrystals and subsequent three-dimensional epitaxy

Chemistry gives us the ability to manipulate atoms and molecules into nanometer and micrometer scale building blocks, while the science of crystallography is concerned with the spatial arrangement of atoms, ions, and molecules and thus the morphology and structures of materials. Complex three-dimensional ZnS nanostructures have been fabricated via step-by-step crystallographically-controlled chemical processes. Tricrystals of ZnS whiskers were prepared via a controlled thermal evaporation process, and then the tricrystals were thermally treated in an atmosphere formed by evaporating B-N-O precursors into N₂/NH₃ to afford BN-coated arrays of nanobranches. The ZnS nanobranches grew epitaxially on the ternary facets and extended in three [0001] directions forming ordered nanostructures. Meanwhile, the protecting insulating sheath of BN formed on the ZnS nanostructures confined the growth of the nanospines and enhanced their stability. The method may be extended to fabricate other semiconductor nanomaterials with novel structures.      

Sandwich Photothermal Membrane with Confined Hierarchical Carbon Cells Enabling High‐Efficiency Solar Steam Generation

Solar‐driven vaporization is a sustainable solution to water and energy scarcity. However, most of the present evaporators are still suffering from inefficient utilization of converted thermal energy. Herein, a universal sandwich membrane strategy is demonstrated by confining the hierarchical porous carbon cells in two energy barriers to obtain a high‐efficiency evaporator with a rapid water evaporation rate of 1.87 kg m^?2 h^?1 under 1 sun illumination, which is among the highest performance for carbon‐based and wood‐based evaporators. The significantly enhanced evaporation rate is mainly attributed to the inherently optimized porous evaporation mode derived from the hierarchical hollow structures of pollen carbon cells, and the synergistically regulated water transporting and thermal management performance of the sandwich membrane. Moreover, the constructed sandwich membrane also exhibits excellent self‐regenerating performance in simulated seawater and high salinity water. The developed device can maintain an average evaporation rate of 4.3 L m^?2 day^?1 in a 25 day consecutive outdoor test.     

偏微分方程约束下基于动态大小模块的图像修复模型

提出一种保持图像线性特征和纹理信息、并能应用于存在较大规模缺失信息区域的图像修复模型.该模型根据图像局部纹理特征强度动态地选择匹配模块的大小,使用切向等照度线强度数据项约束修复顺序.几何特征作用下的切向等照度线偏微分方程在边缘宽度约束下扩散,具有很好的线性特征保持性能;它具有形态学不变性,可以真实地修复自然场景图像.根据基于模块的修复模型的特点,使用欧氏距离作为模块相似度测量函数.针对模型引起的模块接缝效应,使用散度约束下总体变分插值法对修复结果进行无接缝效应处理,使得最终结果平滑.理论和实验证明了该模型在图像修复中的有效性.     

基于共轭梯度的布谷鸟搜索算法

布谷鸟搜索算法(Cuckoo Search,CS)是基于群体智能的新型随机全局优化算法,具有控制参数少、搜索路径优和全局寻优能力强等优点,但也存在局部搜索能力较弱、收敛速度偏慢和收敛精度不够高等缺点。为了克服CS算法的缺点,提出一种基于共轭梯度的布谷鸟搜索算法(CGCS),使经过Levy飞行机制和淘汰机制进化后的布谷鸟种群沿着相互共轭的方向迅速下降.从而在保持算法的强大全局寻优能力的基础上大幅提高算法的收敛能力。用4个典型测试函数分别对CGCS算法和CS算法进行性能测试,结果表明,CGCS算法比CS算法具有更快的收敛速度、更高的收敛精度和更稳定的优化结果。CGCS算法同时具有很强的全局寻优能力、收敛能力和鲁棒性,特别适合多峰及高维函数的优化。