Memristance controlling approach based on modification of linear M–q curve

The memristor has broad application prospects in many fields, while in many cases, those fields require accurate impedance control. The nonlinear model is of great importance for realizing memristance control accurately, but the im- plementing complexity caused by iteration has limited the actual application of this model. Considering the approximate linear characteristics at the middle region of the memristance-charge （M-q） curve of the nonlinear model, this paper pro- poses a memristance controlling approach, which is achieved by linearizing the middle region of the M-q curve of the nonlinear memristor, and establishes the linear relationship between memristances M and input excitations so that it can realize impedance control precisely by only adjusting input signals briefly. First, it analyzes the feasibility for linearizing the middle part of the M-q curve of the memristor with a nonlinear model from the qualitative perspective. Then, the lin- earization equations of the middle region of the M-q curve is constructed by using the shift method, and under a sinusoidal excitation case, the analytical relation between the memristance M and the charge time t is derived through the Taylor series expansions. At last, the performance of the proposed approach is demonstrated, including the linearizing capability for the middle part of the M-q curve of the nonlinear model memristor, the controlling ability for memristance M, and the influence of input excitation on linearization errors.     

谈谈学生课程学业成绩的评价

目前考试，绝大多数采用统一的闭卷形式，在有限的二、三个小时内要检查出学生对该课程的学习状况，显然不妥，例如，《实变函数》课程，任何一个数学专业的人都知道，实变函数中任何一个较复杂的题是要花较多时间的，有的甚至要一、二天时间．因此，无论是期末考试，还是研究生入学考试，其试题都不好出，只能出些非常简单、甚至是书上现成的定理、例题要考生来做，这显然不能检验出学生的水平来．纵观历史，中国自古以来采取科举考试，就实行了阅卷考试这一形式，不用否定，在过去，阅卷这一形式确实发挥了它应有的巨大作用，但这一作用发…