情景模拟式教学法在教学中的应用

摘要：情景模拟式教学法是一种虚拟的实践性教学方法，其类型可以包括模拟辩论法、模拟考试法、模拟任务法、模拟程序法等。本文结合教学中的实践，重点介绍了情景模拟式教学法在教学中应用时的步骤，即课前准备、任务设计、课堂总结和课下补充。同时指出在场景、身份的范围、任务的设计和参与的程度等方面容易出现的问题及应对策略。     

Kinetic Isotope Effect as a Tool To Investigate the Oxygen Reduction Reaction on Pt-based Electrocatalysts – Part I: High-loading Pt/C and Pt Extended Surface

Kinetic isotope effect (KIE) was used to study the rate-determining step for oxygen reduction reaction (ORR) on dispersed Pt/C electrocatalyst and polycrystalline Pt (Pt-poly). KIE is defined as the ratio of the kinetic current measured in protonated electrolyte versus deuterated electrolyte, with KIE values larger than one indicating proton participation in the rate-determining step. The effect of poisoning anions on the platinum rate determining step is investigated by assessing the KIE in perchloric (non-poisoning) and sulfuric acid-based electrolytes. The kinetics currents were calculated using the Koutechy-Levich and Tafel analysis. A KIE of 1 was observed for Pt/C (with a 40 wt.% Pt loading) and Pt-poly, thus indicating that, on 40 wt. % Pt/C and Pt-poly, the rate determining step is proton independent.     

Synthesis of hydroxyl‐bearing polyurethanes from naturally occurring myo‐inositol

A route from naturally occurring myo‐inositol to hydroxyl‐bearing polyurethanes has been developed. The diol prepared from the bis‐acetalization of myo‐inositol with 1,1‐dimethoxycyclohexane was reacted with a rigid diisocyanate, 1,3‐bis(isocyanatomethyl)cyclohexane to afford the corresponding polyurethane, of which glass transition temperature (T_g) was quite high as 192 °C. The polyurethane contains side chains inherited from the acetal moieties of the diol monomer and was treated with trifluoroacetic acid to hydrolyze the acetal moieties and afford the target polyurethane functionalized with hydroxyl groups. The presence of many hydroxyl groups in the side chains, which can form hydrogen bonds with each other, resulted in a high T_g, 186 °C. In addition, the hydroxyl groups were reacted with isocyanates to achieve further side‐chain modifications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1358–1364     

A new sequence isomer of AB‐polybenzimidazole for high‐temperature PEM fuel cells

A new sequence isomer of AB‐polybenzimidazole (AB‐PBI) was developed as a candidate for high‐temperature polymer electrolyte membrane fuel cells. A diacid monomer, 2,2′‐bisbenzimidazole‐5,5′‐dicarboxylic acid, was synthesized and polymerized with 3,3′,4,4′‐tetraaminobiphenyl to prepare a polymer that was composed of repeating 2,5‐benzimidazole units. In contrast to previously prepared AB‐PBI, which contains only head‐to‐tail benzimidazole sequences, the new polymer also contains head‐to‐head and tail‐to‐tail benzimidazole sequences. The polymer was prepared in polyphosphoric acid (PPA) and cast into membranes using the sol–gel PPA process. Membranes formed from the new AB‐PBI were found to be mechanically stronger, possessed higher acid doping levels, and showed improved fuel cell performance, when compared to the previously known AB‐PBI. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

脉冲调制高压电源高频化改造的仿真分析与实验

对HL-2A 装置原有的高压电源进行了高频化改造，改造后的单元电源采用脉冲步进阶梯调制(PSM)技术，采用24 个不可控整流电源模块与4 个调节电源模块串联输出，通过控制各模块的投入切出，使输出电压范围在0~20kV 可调，模块开关频率最高可以达到20kHz。通过仿真和实验测试结果表明，该电源运行参数可以达到20kV/200A，开关频率最高达到了20kHz，能够满足系统的实验需求。     

Descent Direction Stochastic Approximation Algorithm with Adaptive Step Sizes

A stochastic approximation (SA) algorithm with new adaptive step sizes for solving unconstrained minimization problems in noisy environment is proposed. New adaptive step size scheme uses ordered statistics of fixed number of previous noisy function values as a criterion for accepting good and rejecting bad steps. The scheme allows the algorithm to move in bigger steps and avoid steps proportional to $1/k$ when it is expected that larger steps will improve the performance. An algorithm with the new adaptive scheme is defined for a general descent direction. The almost sure convergence is established. The performance of new algorithm is tested on a set of standard test problems and compared with relevant algorithms. Numerical results support theoretical expectations and verify efficiency of the algorithm regardless of chosen search direction and noise level. Numerical results on problems arising in machine learning are also presented. Linear regression problem is considered using real data set. The results suggest that the proposed algorithm shows promise.     

阶跃Q开关激光器输出光脉冲波形的研究

用数值积分法计算阶跃Q开关激光器输出光脉冲波形,并由计算得出的数据与模拟实验结果基本相吻.最后分析出四能级系统激光器中存在严重的差瓶颈效应,此导致了图形中的上升阶段初始时间内的差异,和下降阶段末端时间内的差异.     

Facile design of degradable poly(β‐thioester)s with tunable structure and functionality

The synthesis of a range of linear biodegradable poly(β‐thioester)s, PBTs, via hexylamine‐catalyzed thiol‐ene Micheal additions between a variety of diacrylate and dithiol monomers is described. Molecular weights up to 12,000 g mol^?1 are obtained for this new class of polymer materials. PBTs featuring very different chemical and mechanical behavior are obtained on the basis of seven diacrylate and three dithiol monomers. Polar PBTs are synthesized based on ethylene glycol‐containing monomers in an environmentally friendly solvent. Furthermore, PBTs containing urethane units in the main chain are obtained, providing access to an isocyanate‐free polyurethane polymerization method. The thiol‐ene addition approach can also be used to couple polystyrene oligomers synthesized from a bifunctional trithiocarbonate reversible addition fragmentation transfer agent. In this way, PBTs featuring polystyrene segments as well as diacrylate segments are produced. In general for these step‐growth polymerizations, by tuning the stoichiometric monomer ratio, a desired end group functionality can be quantitatively introduced into the PBT, which is demonstrated via soft ionization mass spectrometry analysis. As an example, alkyne end groups have been built in, giving access to use these materials in modular polymer design strategies. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 178–187     

基于STM32的接种分离装置控制系统

为实现高效、精确、自动化的接种分离，设计了一种以ARM系列STM32F407型单片机为核心，配备相应传感器、执行器的全自动控制系统。该系统可控制接种分离装置中的各个执行部分的动作，并与外部扫码器、RFID射频读卡器、触摸屏以及PC机进行数据交换处理，以实现样本采集、细菌培养、实验数据存储以及授权扣费等功能。本仪器取代了传统的人工操作，真正实现无菌操作，减少了医务人员感染病毒的几率，填补了目前国内技术空白。     

Transient kinetic studies and microkinetic modeling of primary olefin formation from dimethyl ether over ZSM-5 catalysts

The formation of primary olefins from dimethyl ether (DME) was studied over ZSM-5 catalysts at 300°C using a novel step response methodology in a temporal analysis of products (TAP) reactor. For the first time, the TAP reactor framework was used to conduct single- and multiple-step response cycles of DME (balance argon) over a shallow bed with the continuous flow panel. Propylene is the major primary olefin and portrays an S-shaped profile with a preceding induction period when it is not observed in the gas phase. Methanol and water portray overshoot profiles due to their different rates of generation and consumption. DME effluent shows a rapid rise halfway to its steady-state value leading to a slow rise thereafter because of its high desorption rates followed by subsequent reactions involving DME in further steps during the induction period. To analyze the experimental data quantitatively, nine reaction schemes were compared, and kinetic parameters were obtained by solving a transient plug flow reactor model with coupled dispersion, convection, adsorption, desorption, and reaction steps. The methoxymethyl pathway involving dimethoxyethane and methyl propenyl ether gives the closest match to experimental data in agreement with recent density functional theory studies. Gaseous dispersion coefficients of ca. 10⁻⁹ m² s⁻¹ were obtained in the TAP reactor. The novel experimental data validated against the transient kinetic model suggests that after the formation of initial species, the bottleneck in propylene formation is the transformation of the initial C–C bond, that is dimethoxyethane formed initially from DME and methoxymethyl groups. DME adsorption on ZSM-5 catalyst generates surface methoxy groups, which further react with the feed to give methoxymethyl groups. These methoxymethyl groups are regenerated through a series of reactions involving intermediates such as dimethoxymethane and methyl propenyl ether before propylene formation.