我国中小企业融资问题简论

融资困难是不同时期各国中小企业普遍面临的重要问题之一.本文通过中小企业与国有企业融资的对比分析,考察了我国中小企业融资困难的原因和相应策略.作者认为,中小企业自身发展的特点、融资渠道与融资风险、金融机构和社会服务体系等的综合作用是造成中小企业融资难的根本原因,而破解中小企业融资难的基本思路就在于政府、市场和中介组织的共同创新与发展.     

插电式混合动力汽车等效燃油消耗最小能量管理策略研究

对某插电式混合动力汽车电量保持(CS)阶段的能量管理策略进行了设计和优化研究。首先基于等效燃油消耗最小策略(ECMS)设计了汽车的能量管理策略,然后针对传统遗传算法(SGA)在运行过程中存在的收敛速度慢、种群进化动力不足问题进行了算法改进,并使用改进的遗传算法(IGA)优化燃油等效因子。硬件在环仿真试验结果表明:在电量保持阶段电池荷电状态允许的偏差内,该方法可以获得更高的燃油经济性。     

Electronic Structure and Stability of Lead-free Hybrid Halide Perovskites: A Density Functional Theory Study

The most commonly used and studied hybrid halide perovskite is ABX_3, where A usually stands for CH_3NH_3, B for Pb, and X for I. A lead-free perovskite with high stability and ideal electronic band structure would be of essence, especially considering the toxicity of lead. In this work, we have considered 11 metal elements for the B site and three halide elements(Cl, Br, and I) including various combinations among the three halides for the X site. A total number of 99 hybrid perovskites are studied to understand how the crystal structure, band gap and stability can be tuned by the chemistry modification, i.e., the replacement of toxic element, Pb in the original MAPbX_3, with non-toxic metal elements. We find that the favorable substitutes for Pb in MAPbI_3 are Ge and Sn.