PowerPoint电子讲义的"迷航"问题及其解决策略

PowerPoint电子讲义(下简称PPT)是如今学校课堂教学中非常常用的媒体形式和教学资源整合工具,许多学科教师的教学从某种程度上已十分依赖这一软件工具,但其对教学内容以页面为单位的呈现方式,却容易使学生在听讲过程中出现"迷航"现象.本文结合自身的教学实践,对PPT制作和使用中的"迷航"问题提出了几种解决策略和实用的建议.     

并行设计中冲突的协商解决研究

针对并行设计中冲突协商策略的选取和优化解的非唯一性问题,给出了冲突的数学描述形式以及冲突原因的数学解释,证明了合作策略的优越性,研究了基于Nash定理的冲突协商解的存在性和唯一性,并给出一种协商模型以及具体应用实例.     

溶液统计热力学模型的计算机模拟

溶液统计热力学中涉及到许多模型和抽象的概念,很难用传统的教学手段加以清晰地描述,成为教学中的难点。3DS MAX提供了能将这些概念和理论以三维空间清晰地叙述和形象地模拟的有力工具。本文利用3DS MAX动画制作技术（造型制作、材质设计、变色动画）模拟了S－正规溶液理论中二元理想固溶体的形成过程,并形象化地表达了二元理想固溶体中粒子在系统中NA＋NB个晶格位上随机分布的构型数（混合位形配分函数）。充分发挥了3DS动画制作技术的优势,制作成高质量的溶液统计热力学MCAI课件,突破了教学中的难点。     

根际环境因子对马铃薯块茎生长发育影响的研究进展

根际环境因子对马铃薯块茎生长发育具有重要影响。马铃薯根际环境因子包括光照、温度、水分、空气、营养以及重力等,从生态学的角度综述了根际环境因子对马铃薯块茎生长发育的影响,并对存在的问题及其研究进展进行了讨论。     

非乘积解随机Petri网的乘积形式近似求解

讨论了非乘积解随机Petri网的近似求解问题。将Marie方法引入到随机Petri网的近似分析中,利用随机Petri网中已有的结论将该方法中的分解原则推广到更一般的情形,使其应用范围更广,利用运算分析法对这些分解原则作了形式化描述,在此基础上,给出了有关结论的数学证明。最后,对这种近似方法作了误差分析,找出了产生误差的原因。实验数据表明本文所给的近似方法应用广且有效。     

Time-dependent soil-water distribution under a circular trickle source

Soil-water distribution in homogeneous soil profiles of Yolo clay loam and Yolo sand (Typic xerorthents) irrigated from a circular source of water, was measured several times after the initiation of irrigation. The effect of trickle discharge rates and soil type on the locations of the wetting front and soil-water distribution was considered. Soil-water tension and hydraulic conductivity, as functions of soil-water content, were also measured. The theories of time-dependent, linearized infiltration from a circular source and a finite-element solution of the two-dimensional transient soil-water equation were compared with the experimental results. In general, for both soils the computer horizontal and vertical advances of the wetting front were closely related to those observed. With both theories, a better prediction of the wetting front position for the clay loam soil than for the sandy soil is shown. The calculated and measured horizontal vertical advances did not agree over long periods of time. With the linearized solution, overestimated and underestimated vertical advances for the clay and sandy soils, respectively, were shown. The finite-element model approximate in a better way the vertical advances than the linearized solution, while an opposite tendency for the horizontal advances indicated, especially in sandy soil.Notation k constant (dK/d) - K hydraulic conductivity - K ₀ saturated hydraulic conductivity - J ₀,J ₁ Bessel functions of the first kind - h soil water tension - q Q/r ₀ ² - Q discharge rate - r cylindrical coordinate; also horizontal distance in soil surface - R dimensionless quantity forr - r ₀ constant pond radius - R ₀ dimensionless quantity forr ₀ - t time - T dimensionless quantity fort - x, y Cartesian coordinates - z vertical coordinate; also vertical distance along thez axis chosen positively downward - Z dimensionless quantity forz - empirical soil characteristic constant - dummy variable of integration - volumetric soil water content - matrix flux potential - dimensionless quantity for      

Evidence for transient composition variations at GaAs/Ga1−xAlxAs heterostructure interfaces prepared by metal-organic chemical vapour deposition

The composition profiles of GaAs/Ga_1?xAl_xAs heterostructures prepared in two different Metal-Organic Chemical Vapour Deposition (MOCVD) reactors have been studied. Transmission electron microscopy (TEM). and Auger and secondary ion mass spectrometry (SIMS) sputter profiling results are in good agreement and interface widths below 20 å have been achieved. Significant new results on transient phenomena have been obtained. showing that large and sometimes very sharp excursions in composition can be associated with valve switching actions. Direct evidence is presented that gas pressure or flow transients can occur during valve operations. and it is suggested that such instabilities are the cause of the effects observed.     

新型无毒无味卡尔.费休试剂的研制

对原卡尔．费休试剂进行了改进。以无毒无味的咪唑代替了原试剂中的吡啶，并以乙醇代替了试剂中的甲醇，制成了无毒无味的卡氏试剂。对由卡尔．费休试剂组成的电解液进行了改进，用碘化物代替碘，解决了长期储存和问题。     

添加剂和亚磷酸对Ni^2＋,Fe^2＋电化学行为的影响

在Ｎｉ－Ｆｅ－Ｐ非晶态合金电镀工艺研究中，采用循环伏安法研究了某些有机酸和亚磷酸对Ｎｉ２＋、Ｆｅ２＋在铂电极上的电化学行为的影响。结果认为，甘氨酸、抗坏血酸和丁二酸等均能不同程度地增大Ｎｉ２＋、Ｆｅ２＋的阴极极化，亚磷酸能促进Ｎｉ２＋的还原析出，但阻止Ｆｅ的成核和生长过程。     

海盐水溶液渗透压计算的探讨

在反渗透脱盐装置的设计中,渗透压是必不可少的设计参数。考虑在水处理过程中遇到的混合电解质水溶液绝大多数的离子强度都不高,据此作者提出一近似计算公式。在盐溶液浓度为1000～50000 ppm 范围内,用该式计算所得渗透压值与实测值及Stoughton 式计算值相比,相对误差在2.5%以内。