The network current harmonics were very high in conventional uncontrolled rectifier, the network side power factor was low and the dynamic response was slow in closed loop control in thyristor phase-controlled rectifier, a three-phase voltage source rectifier adopting the PWM technology was proposed aiming at the above problems in this paper. Simulation experiments were performed on the three-phase VSR based on the design of the double closed-loop control system of it, the obtained simulation results indicate that, compared with the uncontrolled or phase rectifier circuit, the harmonics of the input current is greatly reduced, the electric energy can flow in both directions in the three-phase VSR, it can realize the unit power factor operation in the rectification and inverter state, and can better suppress the DC side voltage fluctuation during the load mutation, so as to significantly improve the resisting disturbance ability of the system, and truly realize the high combination of green environmental protection with high efficiency and energy saving.
运用非奇异M-矩阵和矩阵Schur积的定义及性质,结合矩阵的特征值包含域定理和不等式放缩技巧,对非奇异M-矩阵和M-矩阵的逆矩阵的Schur积的最小特征值下界做进一步研究,给出其在不同情况下的几个新不等式.新不等式在某些条件下改进了现有文献中的结论,计算简单且更精确,具有一定的优越性.
Starting from the "right to explanation" which is related to students′vital interests and needs, this paper proposes that the premise of "right to explanation" of intelligent learning space is the unequal relationship between students and intelligent learning space, and illustrates the essence of intelligent learning space from the connotation and attributes of intelligent learning space, and puts forward that the realization path of "right to explanation" of intelligent learning space is the 4W model constructed by learning community.
人工智能技术的革新为高校思政课教师提升教学技能增添了新亮点和新活力,赋予其教学思维灵活化、教学服务多样化、教学工具新颖化与教学实践智能化的发展契机,但也相伴而生了教师自主创新性弱化、教学积极性降低、评价权威性消解和职业危机性加剧等四重挑战.面对新的契机与挑战,应着重从提高自主创新能力、打造双师教学模式、构建综合评价体系、提升智能教学素养等方面发力,有效增强高校思政课教师提升教学技能的应然性与实然性.
长三角地区居民食物消费整体向高碳的动物性食物消费转变,给全社会实现"双碳"目标带来极大的挑战.利用2010-2019年长三角地区城乡居民7大类食物消费数据,采用结构分解法对居民食物消费碳排放变化进行测算.研究表明:长三角地区城乡居民食物消费碳排放呈现二元性和趋同性特征,人均食物消费总量变化与食物消费结构变化是长三角地区居民食物消费碳排放增加的主要因素,控制肉禽类和粮食类消费是减少食物消费碳排放的主要突破口.未来应着力推动长三角地区居民膳食结构调整,实现居民膳食平衡和环境可持续发展双赢.
