基于真实情境彰显学科价值*——初中 “化学与社会发展”复习课

在分析了“化学与社会发展”主题内容和教学现状的基础上,针对目前课堂教学中过分强调学科知识而淡化学科价值的渗透,过分注重知识体系的完整而忽视真实情境下利用学科知识解决问题,过分注重习题的反复操练而忽视化学实验的真实体验等值得关注和改进的问题,以“阳光动力2号”为主题情境,通过分析材料、能源和环境的过去和现在,畅想材料、能源和环境的未来,促进学生重构材料、能源、环保的知识体系,体悟化学学科的本体价值及对生活、社会和生命的价值。     

Adaptive control of MEMS gyroscope using global fast terminal sliding mode control and fuzzy-neural-network

An adaptive control of MEMS gyroscope using global fast terminal sliding mode control (GTSMC) and fuzzy-neural-network (FNN) is presented for micro-electro-mechanical systems (MEMS) vibratory gyroscopes in this paper. This approach gives a new global fast terminal sliding surface, which will guarantee that the designed control system can reach the sliding surface and converge to equilibrium point in a shorter finite time from any initial state. In addition, the proposed adaptive global fast terminal sliding mode controller can real-time estimate the angular velocity and the damping and stiffness coefficients. Moreover, the main feature of this scheme is that an adaptive fuzzy-neural-network is employed to learn the upper bound of model uncertainties and external disturbances, so the prior knowledge of the upper bound of the system uncertainties is not required. All adaptive laws in the control system are derived in the same Lyapunov framework, which can guarantee the globally asymptotical stability of the closed-loop system. Numerical simulations for a MEMS gyroscope are investigated to demonstrate the validity of the proposed control approaches.     

Finite-time chaos control via nonsingular terminal sliding mode control

This paper considers the nonsingular terminal sliding mode control for chaotic systems with uncertain parameters or disturbances. The switching surface is designed technically to realize fast convergence. The controller derived from such switching surface is nonsingular and it can stabilize the chaotic systems in a finite time. Besides the second-order system and the triangular system, the proposed method can also be applied to a general class of uncertain nonlinear system. Finally, simulation results are presented to illustrate the effectiveness of the design.     

南方某河水质荧光指纹特征及污染溯源

基于三维荧光光谱随荧光有机物的种类和浓度的不同与水体或污染排放源呈现对应关系的特性,水质荧光指纹溯源技术能够通过水体的三维荧光信号追溯污染排放源。以我国南方C市地表水A河为主要研究对象,利用水质荧光指纹溯源技术对A河及其上游来水方向J河进行了水质荧光指纹特征解析和污染排放源溯源。A河水质荧光指纹主要包括三个特征荧光峰,其[激发波长,发射波长]分别为[280, 320],[235, 345]和[255, 460] nm,其上、中、下游水质指纹之间相似度均大于99%,具有典型的印染废水污染特征。A河上游由J河分流汇入,J河水质荧光指纹与A河相似度低于60%,且强度不超过A河的40%。J河对A河水质荧光指纹形成过程的影响较小,A河的荧光强度主要由A河上游区域贡献。溯源结果表明,A河河水与A河上游印染纺织工业园区的印染废水水质荧光指纹相似度为94%,A河污染很可能来自其上游未经处理的印染废水的排放。A河和J河河水水质荧光指纹各荧光峰强度与高锰酸盐指数的线性相关系数R2分别达到0.956 4,0.937 5和0.985 4,而水质荧光指纹法感知污染的灵敏度更高。与其他三维荧光光谱相似度算法的结果对比表明,水质荧光指纹溯源技术是一种可靠的水环境监管技术,能够为进一步实现污染源头治理和环境精细化管理提供有力的技术支撑。     

加速溶剂萃取-在线凝胶渗透色谱-气相色谱-质谱联用法快速测定蔬菜和水果中多农药残留

建立了加速溶剂萃取-在线凝胶渗透色谱-气相色谱-质谱联用(GPC-GC-MS)快速测定蔬菜、水果中代表性农药残留的检测方法。样品经二氯甲烷-丙酮(1:1, v/v)加速溶剂提取,活性炭柱-氨基柱串联净化,氮吹至干,残留物用环己烷-丙酮(7:3, v/v)溶解后经GPC-GC-MS系统以选择离子监测(SIM)模式测定。结果表明,22种农药在各自的线性范围内线性关系良好(相关系数不低于0.9981),检出限(以信噪比(S/N)为3计算)为0.3～1.8 μg/kg,定量限（S/N=10）为1~6 μg/kg。在2种基质(大白菜、苹果)中3个添加水平下的回收率为70.5%～107.5%,相对标准偏差为2.1%～8.7%。该方法提取效率高,定性定量准确、灵敏,可实现对蔬菜、水果中多农药残留的快速检测。     

基于RCWA的太阳能电池抗反射膜分析研究

利用严格耦合波分析法（RCWA）分别计算了五种不同形貌的亚波长浮雕结构的太阳能电池抗反射膜性能,分别从占空比、光栅高度和周期等结构参数以及入射光角度进行模拟。研究结果表明：周期为200rim,高度为400nm,占空比为1的金字塔型浮雕结构的抗反射效果令人满意,且平均反射率低于1％;光波的入射角对光栅的反射率影响较大,光波在光栅法线的角度控制在40°以下合适。通过对亚波长浮雕结构的反射特性模拟和分析,为太阳能电池抗反射膜设计与制作提供理论支持。     

Homogenization of a nonlinear degenerate parabolic differential equation

This paper is devoted to the homogenization of a nonlinear degenerate parabolic problem ɑtu∈-div(D(x/∈, u∈,▽u∈)+ K(x/∈, u∈))= f(x) with Dirichlet boundary condition. Here the operator D(y, s,s) is periodic in y and degenerated in ▽s. In the paper, under the two-scale convergence theory, we obtain the limit equation as ∈→ 0 and also prove the corrector results of ▽u∈ to strong convergence.     

Persistence of invariant torus in Hamiltonian systems with two-degree of freedom

In this paper with the KAM iteration we prove a KAM theorem for nearly integrable Hamiltonian systems with two degrees of freedom without any non-degeneracy condition.     

无限流体中孔隙介质圆柱周向导波的传播特性

为研究无限大流体约束的孔隙圆柱中周向导波的传播规律,分析孔隙参数对导波传播特性的影响,建立了无限流体中孔隙介质圆柱的理论模型,利用孔隙介质弹性波动理论,建立了周向导波频散方程,通过数值模拟计算得到无限流体中孔隙介质圆柱的频散曲线,探讨了圆柱半径和孔隙参数对导波传播特性的影响,并对导波的衰减特性进行了分析;通过数值计算,得到了周向导波的时域波形,讨论了孔隙参数对波形的影响.结果表明,孔隙介质圆柱半径的改变影响圆柱尺度,孔隙度的改变影响孔隙介质中体声波的波速,都对周向导波频散曲线产生一定的影响,所得到的频散曲线特征及衰减曲线与时域波形吻合.研究结果对开展无限流体中孔隙介质圆柱的超声无损评价提供了一定的理论参考.