正交加边法在条件平差中的应用

在用经典的方法进行条件平差时,往往是按多余观测值的个数列立条件方程式,把多余的条件式,即非独立的条件式予以去掉进行平差.而实际上这些多余(非独立)的条件式是有意义的.如图     

简易平差法在隧道施工控制测量中的应用

通过建立导线测量简易平差法的计算方程式,把抽象的平差理论变成一种易操作的实用计算方法,为导线测量简易平差法提供了一个较好的学习空间,对隧道施工控制测量具有指导意义和实用价值.     

简易平差法在隧道施工控制测量中的应用

通过建立导线测量简易平差法的计算方程式，把抽象的平差理论变成一种易操作的实用计算方法，为导线测量简易平差法提供了一个较好的学习空间，对隧道施工控制测量具有指导意义和实用价值。     

SOR迭代法在测量平差中的应用

测量平差中经常会遇到方程组的求解,大规模的方程组求解计算量大,只能利用程序求解。可以将数值分析中的线性方程组的SOR迭代法运用到测量学中,利用Matlab软件,建立模块程序,从而简化计算过程。以水准测量中的高差计算为例,可以采用条件平差法,通过建立数学模型,在Matlab中编程实现解算。     

刚体绕定轴转动方程的矢量推导

在目前常用的力学教材中,推导刚体绕定轴转动方程时,一般都采用如下方法,即由刚体是不变质点系出发,对刚体中每一质点应用牛顿第二定律列出动力学方程式(标量式),再计算每一质点所受的力矩,将所有这些方程式相加,导出转动方程(标量形式),最后指出M、β都是矢量,     

特殊条件下的离子方程式的书写

许多离子反应由于反应条件不同,可发生不同的离子反应.因此,在书写有些离子反应方程式时,除遵循一般离子方程式的书写要求外,还要考虑特殊条件,如反应物的用量,反应的浓度、温度,反应的介质的性质等.     

求轨迹方程的列式技巧

根据已知条件求出点的轨迹方程，是解析几何的两个主要问题之一，而根据曲线上的点所满足的条件列出等式，则是求点的轨迹方程的关键步骤．有时候我们可根据条件直接列出式子，但运算较繁，这就需要我们深入挖掘题中条件中隐含的等量关系，以得到比较简捷的解法，下面举一道例题说明列式的技巧．     

应用伯努利方程式解题的技巧

在“流体的流动与输送”一章中,伯努利方程式是一个非常重要的计算公式。它可以用来确定管道中流体的流速、流量、压强或压强差、设备间的相对位置和输送机械的有效功率。式中的物理量可分为两类：一类是要用伯努利方程式计算的对象,即待求量;另一类是在用该方程式计算前需要确定的数据,即代入量。在应用伯努利方程式解题时,如何利用其它关系式求出代入量,可从以广诸方面考虑：1、求位能zZ值是指截面中心点与基准水平面的会在距离。通常取基准水平面通过衡算系统两个截面中的任一个截面,如该截面与地面平行,则二者重合,该截面上的…     

化学反应中的能量变化考点例析

化学反应中的能量变化考点主要有判断热化学方程式是否正确．或给出已知条件正确书写热化学方程式．或比较不同状态时热量的大小、反应热的计算等．     

用方程解应用题的窍门

用方程解应用题和用算术方法解应用题是两种截然不同的思路。要学好用方程解应用题，关键是先要把问题和条件联系起来思考，看它们之间存在什么样的数量关系，再确定等量关系，然后列出程式，最后求出方程的解。 用方程解应用题一般有两种解法。这是因为任何三者数量之间的关系都可以写成三个不同的等式，其中两个可构成方程式，另一个是算术关系式。 如：路程、速度、时间三者之间可写成下列关系式： （1）速度×时间=路程 （2）路程÷时间=速度 （3）路程÷速度=时间 假如求时间，则（1）（2）式为方程式，（3）式…     

词法分析程序的一种高效实现

经典的词法分析程序实现中,输入输出缓冲区使用定长内存块,程序主体使用许多条件跳转,它们都需要执行大量判断,这种实现效率不高。对此提出一种新的实现方法,使用内存映射和异常处理替代定长输入输出缓冲区,使用函数数组索引跳转来替代条件跳转,它们能显著减少判断次数,提升词法分析程序的效率。     

Balancing chemical equations: The role of developmental level and mental capacity

Why are some students able to learn to use the trial and error method to balance chemical equations while others are not? To test the hypothesis that formal reasoning is required to balance even simple one-step equations, while formal reasoning and a sufficiently large mental capacity are required to balance more complex many-step equations, a sample of science students was tested to determine level of intellectual development, mental capacity, and degree of field dependence/field independence. Students were then given classroom instruction in using trial and error to balance equations. As predicted, a posttest revealed significant correlations between developmental level and equation balancing ability for both simple and complex equations. Also, as predicted, mental capacity correlated significantly with complex equations but not with simple equations. Field dependence/field independence played no significant role in performance. Educational implications are drawn.     

等式约束条件极值存在的必要条件及其应用

从拉格朗日乘子法出发,考虑多元函数在等式约束条件下的极值问题.由线性方程组理论得到多元函数在一个或多个等式约束条件下极值点存在的必要条件.并进一步考虑该条件在优化理论中的应用,通过将不等式约束转化为等式约束,运用等约束条件下极值存在的必要条件获得最优解.     

扁球面网壳在动静荷载作用下的非线性稳定性

根据薄壳非线性动力学理论和拟壳法的思想,给出了扁球面网壳在动、静荷载协同作用下的非线性动力学控制方程.然后利用扁球面网壳的非线性动力学变分方程和协调方程,在夹紧固定的边界条件下,通过Galerkin作用得到一个含二次和三次的非线性动力学微分方程.用Floquet指数方法研究了系统的分岔问题,讨论了平衡点（奇点）邻域的稳定性问题.指出了系统在纯动态作用和在动静荷载协同作用下其平衡位置的变化情况.     

Conditional Standard Error of Measurement in Prediction

Previous methods for estimating the conditional standard error of measurement (CSEM) at specific score or ability levels are critically discussed, and a brief summary of prior empirical results is given. A new method is developed that avoids theoretical problems inherent in some prior methods, is easy to implement, and estimates not only a quantity analogous to the CSEM at each score but also the conditional standard error of prediction (CSEP) at each score and the conditional true score standard deviation (CTSSD) at each score, The new method differs from previous methods in that previous methods have concentrated on attempting to estimate error variance conditional on a fixed value of true score, whereas the new method considers the variance of observed scores conditional on a fixed value of an observed parallel measurement and decomposes these conditional observed score variances into true and error parts. The new method and several older methods are applied to a variety of tests, and representative results are graphically displayed. The CSEM-Iike estimates produced by the new method are called conditional standard error of measurement in prediction (CSEMP) estimates and are similar to those produced by older methods, but the CSEP estimates produced by the new method offer an alternative interpretation of the accuracy of a test at different scores. Finally, evidence is presented that shows that previous methods can produce dissimilar results and that the shape of the score distribution may influence the way in which the CSEM varies across the score scale.     

Optimization of time-delayed feedback control of seismically excited building structures

An optimization method for time-delayed feedback control of partially observable linear building structures subjected to seismic excitation is proposed. A time-delayed control problem of partially observable linear building structure under horizontal ground acceleration excitation is formulated and converted into that of completely observable linear structure by using separation principle. The time-delayed control forces are approximately expressed in terms of control forces without time delay. The control system is then governed by Itoe stochastic differential equations for the conditional means of system states and then transformed into those for the conditional means of modal energies by using the stochastic averaging method for quasi-Hamiltonian systems. The control law is assumed to be modal velocity feedback control with time delay and the unknown control gains are determined by the modal performance indices. A three-storey building structure is taken as example to illustrate the proposal method and the numerical results are confirmed by using Monte Carlo simulation.     

基于有限差分法的一维输运方程定解问题

许多物理方程的定解问题,如波动方程、输运方程等,或由于其泛定方程比较复杂,或由于边界形状比较复杂,或由于其它原因,往往不具有解析解,或者其解析解不易计算,所以要采用可行的数值解法。有限差分方法就是一种数值解法,它把表示变量连续变化关系的偏微分方程离散为有限个代数方程,然后利用电子计算机求解此线性代数方程组。     

A study of the effect of HyperCard and pen-paper performance assessment methods on expert-novice chemistry problem solving

This study investigated HyperCard as a tool for assessment in science education and determined whether or not a HyperCard assessment instrument could differentiate between expert and novice student performance (balancing stoichiometric equations) in science education. Five chemical equations were presented by traditional pen-paper and by a HyperCard (Hyperequation) program. Thirty honors (expert) and 30 regular (novice) chemistry students were randomly divided into HyperCard and traditional pen-paper groups of 15 students each. Scoring was based on five dependent variables: performance scores, number of attempts, rate of attempts, time on task, and correctness. Correlation results indicated that students with high performance scores correctly balanced more equations, required fewer attempts to balance equations, and required less time per attempt than did students with low performance scores. MANOVA results showed that performance scores and correctness scores for both experts and novice were significantly higher on HyperCard compared to pen-paper assessment; the novice scores on HyperCard nearly equaled the expert pen-paper assessment scores. Significant interactions were found for time on task and for correctness. The results suggest that HyperCard can be a suitable tool for assessment in science education and that such an instrument can differentiate between expert and novice student performance.     

Increasing the Validity of Angoff Standards Through Analysis of Judge-Level Internal Consistency

The purpose of the present study was to extend past work with the Angoff method for setting standards by examining judgments at the judge level rather than the panel level. The focus was on investigating the relationship between observed Angoff standard setting judgments and empirical conditional probabilities. This relationship has been used as a measure of internal consistency by previous researchers. Results indicated that judges varied in the degree to which they were able to produce internally consistent ratings; some judges produced ratings that were highly correlated with empirical conditional probabilities and other judges’ ratings had essentially no correlation with the conditional probabilities. The results also showed that weighting procedures applied to individual judgments both increased panel-level internal consistency and produced convergence across panels.