浅谈初中生化学计算能力的培养

初中化学计算的学习不仅是初中化学教学的重要内容,还是初中化学教学的主要难点。本文主要从学生对化学计算的兴趣、学生对化学计算各个知识点的掌握情况、教师对化学计算知识的教学方法等方面,对影响初中生化学计算能力的因素进行综合分析,并提出改进措施,以培养初中生的化学计算能力。

初中生化学计算能力现状及对策

化学计算是初中化学试题必不可少的题型之一,能考查学生思维的逻辑性、发散性和创造性,也能考查学生知识网络的建构情况。而现阶段学生的化学实际计算能力欠缺,得分率低,对化学计算涵义不明确,计算方式单一,有效训练不足等问题,本文对初中生的化学计算能力现状进行介绍,并提出了提升化学计算能力的教学对策。

基于学习进阶的初中化学计算习题与内蒙古中考计算题的比较分析

化学计算是以化学概念、原理为基础,贯穿了各种化学知识的综合应用,在化学知识体系中占有重要地位。基于学习进阶理论,将初中学生的化学计算能力分为识别、应用、建构三个水平,作为分析教科书课后计算习题和近五年内蒙古不同地区中考化学计算题的依据。研究发现,教科书课后习题主要考查学生识别和应用两个水平的计算能力,而中考重在考查应用或建构水平的化学计算能力。由此,对初中化学计算的教学提出几点建议,以期对初中化学一线教师提供帮助。

Insight into Capture of Greenhouse Gas （CO2） based on Guanidinium Ionic Liquids

Quantum mechanics and molecular dynamics are used to simulate guanidinium ionic liquids. Results show that the stronger interaction exists between guanidine cation and chlorine anion with interaction energy about 109.216 kcal/mol. There are two types of spatial distribution for the title system： middle and top. Middle mode is a more stable conformation according to energy and geometric distribution. It is also verified by radial distribution function. The continuous increase of carbon dioxide （CO2） does not affect the structure of ionic liquids, but CO2 molecules are always captured by the cavity of ionic liquids.

Recent advances in micro-alloyed wrought magnesium alloys:Theory and design

Micro-alloying design of wrought magnesium(Mg) alloys is an important strategy to achieve high mechanical properties at a low cost. In the last two decades, significant progress has been made from both theory and experiment. In the present review, we try to summarize recent advances in micro-alloying design of wrought Mg alloys from both theoretical and pragmatic perspectives, and provide fundamental data required for establishing the relationship between chemical composition and mechanical properties of Mg alloys. We start with theoretical attempts for understanding the mechanical properties of Mg alloys at different scales, by involving first principle calculations,molecular dynamics, cellular automata, and crystal plasticity. Then, the role of alloying elements is discussed for a series of promising Mg alloys such as Mg-Al, Mg-Zn, Mg-RE(rare-earth element), Mg-Sn, and Mg-Ca families.Potential challenges in the micro-alloying design of Mg alloys are highlighted at the end. The review is expected to provide helpful guidance for the intelligent design of novel wrought Mg alloys and inspire more innovative ideas in this field.

Environmental capacity of chemical oxygen demand in the Bohai Sea: modeling and calculation

A three-dimensional advection-diffusion model coupled with the degradation process is established for describing the transport of chemical oxygen demand (COD). Comparison of the simulated distribution of COD at the surface in the Bohai Sea in August, 2001 with field observations, shows that the model simulates the dataset reasonably well. The Laizhou Bay, Bohai Bay, and Liaodong Bay were contaminated heavily near shore. Based on the optimal discharge flux method, the Environmental Capacity (EC) and allocated capacities of COD in the Bohai Sea are calculated. For seawater of Grades I to IV of the Chinese National Standard, the ECs of COD in the Bohai Sea were 77×104 t/a, 116×104 t/a, 154×104 t/a and 193×104 t/a, respectively. The Huanghe (Yellow) River pollutant discharge accounted for the largest percentage of COD at 14.3%, followed by that of from the Liugu River (11.5%), and other nine local rivers below 10%. The COD level in 2005 was worse than that of Grade II seawater and was beyond the environmental capacity. In average, 35% COD reduction is called to meet the standard of Grade I seawater.

Semi-empirical modeling of volumetric efficiency in engines equipped with variable valve timing system

Volumetric efficiency and air charge estimation is one of the most demanding tasks in control of today's internal combustion engines.Specifically,using three-way catalytic converter involves strict control of the air/fuel ratio around the stoichiometric point and hence requires an accurate model for air charge estimation.However,high degrees of complexity and nonlinearity of the gas flow in the internal combustion engine make air charge estimation a challenging task.This is more obvious in engines with variable valve timing systems in which gas flow is more complex and depends on more functional variables.This results in models that are either quite empirical(such as look-up tables),not having interpretability and extrapolation capability,or physically based models which are not appropriate for onboard applications.Solving these problems,a novel semi-empirical model was proposed in this work which only needed engine speed,load,and valves timings for volumetric efficiency prediction.The accuracy and generalizability of the model is shown by its test on numerical and experimental data from three distinct engines.Normalized test errors are 0.0316,0.0152 and 0.24 for the three engines,respectively.Also the performance and complexity of the model were compared with neural networks as typical black box models.While the complexity of the model is less than half of the complexity of neural networks,and its computational cost is approximately 0.12 of that of neural networks and its prediction capability in the considered case studies is usually more.These results show the superiority of the proposed model over conventional black box models such as neural networks in terms of accuracy,generalizability and computational cost.

Artificial intelligence in drug design

Thanks to the fast improvement of the computing power and the rapid development of the computational chemistry and biology,the computer-aided drug design techniques have been successfully applied in almost every stage of the drug discovery and development pipeline to speed up the process of research and reduce the cost and risk related to preclinical and clinical trials.Owing to the development of machine learning theory and the accumulation of pharmacological data, the artificial intelligence(AI) technology, as a powerful data mining tool, has cut a figure in various fields of the drug design, such as virtual screening,activity scoring, quantitative structure-activity relationship(QSAR) analysis, de novo drug design, and in silico evaluation of absorption, distribution, metabolism, excretion and toxicity(ADME/T) properties. Although it is still challenging to provide a physical explanation of the AI-based models, it indeed has been acting as a great power to help manipulating the drug discovery through the versatile frameworks. Recently, due to the strong generalization ability and powerful feature extraction capability,deep learning methods have been employed in predicting the molecular properties as well as generating the desired molecules,which will further promote the application of AI technologies in the field of drug design.

Exploration in Optimal Design of an Airfoil with a Leading Edge Rotating Cylinder

Based on the theory of moving surface boundary layer control(MSBC),a concept of an airfoil having a rotating cylinder at the leading edge has been developed and experimentally proven to have good aerodynamic performance even at large angles of attack.Thus,this research aims to give guidance on optimizing the design of this kind of airfoil with high lift coefficients.Using computational fluid dynamics(CFD)technique,the CFD simulation results have been compared with the experimental results available in the literature,and then the SST two-equation model is selected as the appropriate turbulence model.At a given cylinder surface velocity ratio,the cylinder diameter d,the drop height of trailing edgeδand the curvatures of the pressure and suction surfaces of the airfoil are regarded as the optimal design parameters and the airfoil lift coefficient is considered as the optimization objective function.Therefore,using orthogonal optimization method,we herein develop a new design of airfoil favorable for having a rotating leading edge.It has been numerically proven that the resulting airfoil has good capability of achieving a substantially superior performance when compared to the airfoils of the prior art.