基于“系统化”理论和MATLAB的自动控制原理课程的教学改革

目前"自动控制原理"课程教学中存在知识点多、数学公式多、课时少等问题.为解决这些问题,在教学过程中,一方面将知识点系统化,另一方面在教学中通过MATLAB软件进行教学改革.教学实践表明,教学改革大大提高了课堂教学效率,效果良好.     

在高职《Protel99se》课程中实施项目教学研究

将《Protel99se》课程按知识点分解为七个项目,同时将项目对应于课程"会用""精通""熟练"三个阶段,通过不同项目的学习,使学生对知识点的掌握逐步深入,以此激发学生的学习兴趣,提高教学效果.     

面向初等数学的知识点关系提取研究

随着互联网技术的发展,在线教育已经改变了学生的学习方式.但由于缺乏完整的知识体系,在线教育存在着智能化程度低和"信息迷航"的问题.因此,构建知识体系成为在线教育平台的核心技术.知识点间的关系提取是知识体系构建的主要任务之一,目前比较高效的关系提取算法主要是监督式的.但是这类方法受限于文本质量低、语料稀缺、标签数据难获取、特征工程效率低、难以提取有向关系等挑战.为此,基于百科语料和远程监督思想,研究了知识点间的关系提取算法.提出了基于关系表示的注意力机制,该方法能够提取知识点间的有向关系信息.结合了GCN和LSTM的优势,提出了GCLSTM,该模型更好地提取了句子中的多点信息.基于Transformer架构和关系表示的注意力机制,提出了适用于有向关系提取的BTRE模型,降低了模型的复杂度.设计并实现了知识点关系提取系统.通过设计3组对比实验,验证了模型的性能和效率.     

"通信原理"易混淆知识点浅析

"通信原理"是电子信息类专业课程中的一门重要课程。本文通过图文结合的方式将"通信原理"教学中学生容易混淆的9对知识点逐一进行比较分析,阐述彼此之间的区别和联系。通过对带通滤波与低通滤波等9对知识点的讨论,引导学生理解这些知识点在通信系统中的作用,提高学生学习"通信原理"的兴趣和积极性。     

"C程序设计"上机实验题目精选

介绍了几个精心编选的"C程序设计"上机实验题目,内容涵盖C的核心知识点,并兼顾知识性和趣味性,可供教学同行参考.     

知识点网络下的知识评估和学习路径选择

学习者在认知过程中可能掌握了某些知识点，但自身的知识状态并未改变，因此，为了提高学习效率并对学习者进行知识评估，在知识点网络下运用形式概念分析方法讨论如何对学习者进行知识评估和学习路径选择问题.首先，给出了知识点网络的构造方法、有效知识点组合的概念及知识点网络下题库的构造方法；其次，通过知识点网络诱导知识点背景，在已知学习者知识状态的情况下对学习者掌握的知识点进行评估，并给出知识点网络下的学习路径图及其算法；最后，通过实验验证了提出的算法的有效性和可行性.研究发现，由知识点网络诱导的知识点背景确定的知识点结构满足良级性.     

寓教于乐话积分

把高等数学中各种类型积分的相关知识点用"顺口溜"的形式给出了,给抽象难以理解的知识点以具体化,以便容易理解,达到寓教于乐的目的。     

"信息系统项目管理"课程多种案例教学模式分析

信息系统项目管理是一门知识点多,技术性、综合性、实践性的课程,为提高课程的教学质量,通常采用案例教学.本文讨论了案例教学中,采用"教师案例+学生案例"教学模式对教学过程的影响,并分析了教学的效果.     

普通生物学课程互动拓展式教学方法改革探索

普通生物学作为生物学相关专业的基础课,涵盖了诸多生命科学领域,旨在帮助学生了解生命科学全貌,打下坚实基础.然而在教学实际中,课程内容广泛且松散,部分知识点高中生物已涉猎,传统"填鸭式"教学无法提升低年级学生的学习兴趣,以致影响对该课程甚至后续其他专业课程的学习.为了解决这些问题,采用互动拓展式教学对"普通生物学"课程进行了改革尝试,引入BBC科学纪录片、诺贝尔奖案例和科学动画等辅助知识点教学,增加翻转课堂、微课视频、第二实践课堂等互动和拓展方式来丰富课堂教学.改革实践表明,互动拓展式教学方法能够提升学生兴趣并且培养学生思维,为后续其他专业课程的学习以及高素质生物学人才的培养打下坚实基础.     

高考中的能级问题

在原子物理部分高考也考查能的转化和守恒定律,本文就"能级"这一知识点在近几年高考中出现的情况加以总结,并对2009年高考相关内容做出预测.     

盾构机密封舱渣土非线性本构模型参数识别

根据密封舱改性渣土的三轴压缩实验数据,建立了基于优化方法的Duncan-Chang双曲线本构模型参数反演方法。为了解决参数识别反问题解的不稳定性问题,在Gauss-Newton优化迭代算法的基础上,提出了正则化参数反演方法。实际应用结果表明,所提出的反演方法具有较快的收敛速度和较强的鲁棒性,预测的实验模型变形与实验值吻合较好。     

Electrochemical properties of LiNi<Subscript>0.5</Subscript>Mn<Subscript>1.3</Subscript>Ti<Subscript>0.2</Subscript>O<Subscript>4</Subscript>/Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> cells

Spinel compounds LiNi_0.5Mn_1.3Ti_0.2O₄ (LNMTO) and Li₄Ti₅O₁₂ (LTO) were synthesized by different methods. The particle sizes of LNMTO and LTO are 0.5–2 and 0.5–0.8 μm, respectively. The LNMTO/LTO cell exhibits better electrochemical properties at both a low current rate of 0.2C and a high current rate of 1C. When the specific capacity was determined based on the mass of the LNMTO cathode, the LNMTO/LTO cell delivered 137 mA·h·g⁻¹ at 0.2C and 118.2 mA·h·g⁻¹ at 1C, and the corresponding capacity retentions after 30 cycles are 88.5% and 92.4%, respectively.     

Preparation of Al<Subscript>72</Subscript>Ni<Subscript>8</Subscript>Ti<Subscript>8</Subscript>Zr<Subscript>6</Subscript>Nb<Subscript>3</Subscript>Y<Subscript>3</Subscript> amorphous powders and bulk materials

Amorphous Al₇₂Ni₈Ti₈Zr₆Nb₃Y₃ powders were successfully fabricated by mechanical alloying. The microstructure, glass-forming ability, and crystallization behavior of amorphous Al₇₂Ni₈Ti₈Zr₆Nb₃Y₃ powders were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). The isothermal crystallization kinetics was analyzed by the Johnson–Mehl–Avrami equation. In the results, the supercooled liquid region of the amorphous alloy is as high as 81 K, as determined by non-isothermal DSC curves. The activation energy for crystallization is as high as 312.6 kJ·mol?1 obtained by Kissinger and Ozawa analyses. The values of Avrami exponent (n) imply that the crystallization is dominated by interface-controlled three-dimensional growth in the early stage and the end stage and by diffusion-controlled two- or three-dimensional growth in the middle stage. In addition, the amorphous Al₇₂Ni₈Ti₈Zr₆Nb₃Y₃ powders were sintered under 2 GPa at temperatures of 673 K and 723 K. The results show that the Vickers hardness of the compacted powders is as high as Hv 1215.     

Kinetic parameters of oscillating reaction of amino acid- BrO3^——Mn^2＋-H2SO4-acetone system

In the previous papers[1—3], the oscillating reactionusing amino acids as organic substrates was studied. Inorder to obtain information about the kinetic parameters ofoscillating reaction of amino acids in amino acid- BrO3 - ?Mn2 -H2SO4-acetone sy…     

Acid etching process for fabrication of Bi2Sr2CaCu2O8＋x stack

We adopted a new method, acid etching process, to fabricate the intrinsic Josephson junctions based on the Bi2Sr2CaCu2O8 x single crystals. By soaking the crystals into the dilute hydrochloric acid, we fabricated a junction stack successfully, and meantime made the surrounding area insulated. A certain concentration of hydrochloric acid was used to maintain the roughness of the modified layer. The cur-rent-voltage characteristic was achieved through the four terminal measurement. We could control the junctions' number by changing the concentration and the soaking time. We also found that the thick-ness of the stack was equal to the average height of the insulation layer. Such a simple, convenient and controllable fabrication method with a high yield might widen the applications of the intrinsic Joseph-son junctions.     

Rolling-induced microstructure change in Zr_（65）Al_（7.5）Ni_（10）Cu_（12.5）Ag_5 bulk metallic glass

The microstructures and free-volume evolutions of as-cast and pre-annealed Zr65Al7.5Ni10Cu12.5Ag5 bulk metallic glasses during rolling deformation have been investigated. No phase transformation is detected in the as-cast/rolled specimen. However,the structural stability of the glass against plastic deformation is worse after pre-annealing,indicated by nanocrystallization in preannealed/rolled specimens with large deformation degrees. Moreover,with increasing deformation degree,the free-volume content in a pre-annealed/rolled specimen increases at a lower average rate than that in an as-cast/rolled specimen.     

基于遗传算法的带附加气室空气悬架多目标优化

以带附加气室的空气弹簧悬架为研究对象,按照物理模型建立带附加气室空气弹簧的数学模型,考虑到空气弹簧刚度的非线性,将该模型以空气弹簧非线性力的形式直接引入到1/4车辆模型。以提高车辆平顺性、行驶安全性及操纵稳定性的综合性能为目标,以附加气室容积为优化变量,设计带附加气室空气悬架的多目标优化模型;考虑到悬架性能各指标量在量纲与量级上的差异,对各指标量进行统一化处理,并采用线性加权和法将多目标函数转化为单目标评价函数。在MAT-LAB/Simulink中搭建系统仿真模型,采用遗传优化算法对典型工况下的最优附加气室容积进行寻优。优化结果表明,优化附加气室容积能有效提高悬架的综合性能,降低车身加速度、悬架动行程,但轮胎动载荷有所增加。     

Synthesis, Characterization and Calorimetry of Ni（C4H8N2O3）2Cl2

A coordination complex was synthesized from NiCl2 and dipeptide glycylglycine（GG）. It was characterized by element analysis, NMR and TG methods, and then was determined to be Ni（C4HsN2O3）2Cl2. Using an isoperibolic reaction calorimeter, the standard molar enthalpy of formation of Ni（GG）2Cl2（solid） has been determined to be -（1 674.66±2.02） kJ · mol^-1 at 298.15 K.     

Work toughening effect in Zr_（41）Ti_（14）Cu_（12.5）Ni_（10）Be_（22.5） bulk metallic glass

Work hardening is a well-known phenomenon occurring in crystalline metals during deformation,which has been widely used to increase the strength of metals although their ductility is usually reduced simultaneously. Here we report that the plastic strain of Zr41Ti14Cu12.5Ni10Be22.5 (at.%) bulk metallic glasses has been increased from 0.3% for the as-cast sample to 2.5%-8.0% for samples that have experienced pre-deformation under constrained conditions. The pre-deformed glassy alloys possess more free volume and abundant introduced shear bands,which are believed to promote the activation of shear bands in post-deformation and result in an increase in plasticity. The orientation of the pre-introduced shear bands relative to the loading direction will affect the deformation behavior of pre-deformed samples. The present results show that pre-deformation of this glassy alloy will result in work toughening. This work toughening effect can be removed by isothermal annealing at a sub-Tg (glass transition) temperature,which causes annihilation of free volume and healing of shear bands.     

Mutagenesis of Ser24 of Cytochrome b559 α Subunit Affects PSII Acitivies in Chlamydomonas reinhardtii

In order to study the functions of cytochrome b559 (Cyt b559) in photosystem two (PSII) activity, mutant S24F of Chlamydomonas reinhardtii was constructed using site directed mutagenesis, in which Serine24 (Ser24) locating downstream of Histidine23 (His23) in α subunit of Cyt b559 was replaced by Phenylalanine (Phe). Physiological and biochemical analysis showed that mutant S24F could be grown photoautotrophically or photoheterotrophically. However, their growth rate was slower either on HSM or TAP medium than that of the control; Analysis of PSII activity revealed that its oxygen evolution was about 71% of wild type (WT); The Photochemical efficiency of PSII (Fv/Fm) of S24F was reduced 0.23 compared with WT; S24F was more sensitive to strong light irradiance than the wild type; Furthermore, SDS-PAGE and Western-blotting analysis indicated that the expression levels of α subunit of Cyt b559, LHCII and PsbO of S24F were a little less than those of the wild type. Overall, these data suggests that Ser24 plays a significant role in making Cyt b559 structure maintain PSII complex activity of oxygen evolution although it is not directly bound to heme group.