恒定轴压力下Q690高性能钢管抗弯性能的试验研究

为研究国家电网输电塔中高强钢焊接中厚板圆管压弯稳定相关性,考虑长细比30、45和60,径厚比(D0/t)为31.25、50.00和58.33,以壁厚为6,8 mm国产Q690高性能钢板制作了5组15根焊接圆管试件,并对其进行恒定轴压力下的抗弯性能试验。记录各试件加载过程中变形现象,得到了试件的弯矩-轴向变形曲线。根据试验结果分析试件的承载力、失稳破坏模式和破坏状态等力学性能,并采用中国及美国相关行业规范公式对压弯承载力进行验算对比。结果显示:失稳破坏类型主要取决于钢管试件径厚比和长细比,随长细比减小或径厚比增大,构件破坏类型由整体失稳转化为局部失稳;失稳状态关键在于径厚比,随径厚比减小,破坏状态由弹性转化为弹塑性;所有规范设计公式均偏于保守,验证了相关规范压弯设计公式和稳定系数取值用于指导工程设计的可行性和合理性。     

LDMOS在正常开关工作下的瞬态热效应

利用热等效电路对外加连续脉冲产生的热效应中晶格温度的上升及下降作了研究并与实验进行了比较.结果表明,若高频脉冲的延迟时间大于降温驰豫时间,则器件处于热安全工作区.对热阻为3.5K/W,热容为5μs·W/K的LDMOS,如脉冲频率小于7.14kHz且占空比为0.5,或脉冲频率为10kHz且占空比小于0.3,则该器件工作在热安全区.文中还给出了功率器件热安全工作区的判据.     

一种无线传感器网络跨层能量模型及能耗计算

首先提出了一种基于无线传感器网络数据链路层的跨层能量模型。该能量模型考虑了网络层、物理层以及信道对能量损耗的影响。然后通过NS2仿真确定了模型中的重要因素对能耗的影响,并在此基础上推导了计算能耗的数学模型。最后通过对仿真结果的拟和得出模型中的参数,从而获得了能耗的计算公式。     

Evaluation of suspended load transport rate using transport formulas and artificial neural network models （Case study： Chelchay Catchment）＊

Accurate estimation of sediment load or transport rate is very important to a wide range of water resources projects. This study was undertaken to determine the most appropriate model to predict suspended load in the Chelchay Watershed, northeast of Iran. In total, 59 data series were collected from four gravel bed-rivers and a sand bed river and two depth integrating suspended load samplers to evaluate nine suspended load formulas and feed forward backpropagation Artificial Neural Network (ANN) structures. Although the Chang formula with higher correlation coefficient (r = 0.69) and lower Root Mean Square Error (RMSE = 0.013) is the best suspended load predictor among the nine studied formulas, the ANN models significantly outperform traditional suspended load formulas and show their superior performance for all statistical parameters. Among different ANN structures two models including 4 inputs, 4 hidden and one output neurons, and 4 inputs, 4 and one hidden and one output neurons provide the best simulation with the RMSE values of 0.0009 and 0.001, respectively.     

Adjustments to the correction for attenuation.

With respect to the often-present covariance between error terms of correlated variables, D. W. Zimmerman and R. H. Williams's (1977) adjusted correction for attenuation estimates the strength of the pairwise correlation between true scores without assuming independence of error scores. This article focuses on the derivation and analysis of formulas that perform the same function for partial and part correlation coefficients. Values produced by these formulas lie closer to the actual true-score coefficient than do the observed-score coefficients or those obtained by using C. Spearman's (1904) correction for attenuation. The new versions of the formulas thus allow analysts to use hypothetical values for error-score correlations to estimate values for the partial and part correlations between true scores while disregarding the independence-of-errors assumption. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

乳化炸药连续乳化生产工艺安全性浅析

文章从实践出发，对国内乳化炸药代表性生产工艺的诸方面进行了分析对比后认为，若保证安全生产，应当根据自身的情况，指定出合理的生产工艺。否则，无论何种生产工艺，都不可能万无一失。     

用电子表格软件建立动态仿真模型

本文描术了用于船舶操纵的动态仿真模型的电子表格开发环境，文中用自引用公式对动态方程进行了编程，该技术不需要电子表格的宏指令。文中还讨论了电子表格用于动态仿真建模的利弊。     

R型可调文氏管流通面积计算公式的简化

本文通过推导演算，对Ｒ型可调文氏管翻板在不同角度下流通面积计算公式作了进一步简化。     

Some remarks concerning B-splines

As examples of application of the de Boor-Fix dual functionals, alternative proofs are given for the recurrence formula of discrete B-splines (Oslo algorithm [Cohen et al. '80]), as well as the de Boor-Cox recurrence formula and the derivative formula of B-splines.