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101.
102.
Dr.-Ing. Dr.-Ing. E.h. Karl-Eugen Kurrer 《Beton- und Stahlbetonbau》2020,115(1):62-80
Kurt Beyer's contribution to theory of structures Heinrich Müller-Breslau (1851–1925) is regarded as having completed classical theory of structures in the final quarter of the 19th century. The step up to the next level on a disciplinary scale was taken by Kurt Beyer (1881–1952) with his monograph Die Statik im Eisenbetonbau (statics of reinforced concrete construction), which appeared in the second half of the consolidation period of theory of structures (1900–1950). Beyer's theory of structures book is a scientific synthesis of the very highest order. It advanced to become the unrivalled reference book for this fundamental engineering science discipline during its invention phase (1925–1950), and was still having an effect well into the innovation phase (1950–1975). Kurt Beyer can therefore be regarded as having completed the classical modern movement in theory of structures, which is taken here as being an integral part of the classical modern movement in civil and structural engineering. Based on archival material, this evolutionary process is described and analysed from the point of view of the biographical and history of science and history of engineering perspectives. 相似文献
103.
求取静态电压稳定极限的改进连续潮流法 总被引：27，自引：1，他引：27
连续潮流法是求取静态电压稳定极限的一种有效的方法。根据预测和校正过程的不同,连续潮流法具有不同的形式。提出了改进的连续潮流法,使用PQ分解法求解潮流,预测过程使用Lagrange二次插值技术,校正过程采用局部参数法求解修正方程。与传统的使用基于极坐标形式的牛顿一拉夫逊法的连续潮流法相比,所提的改进连续潮流法计算速度快、占用内存少、准确度高。 相似文献
104.
电压稳定性在很大程度上受负荷特性的影响。本文分析了采用ZIP负荷模型改变了潮流方程,继而影响了电压的稳定性,通过IEEE30节点系统的仿真分析了ZIP负荷的不同比重对最大负荷因子、临界电压及相对应负荷功率变化情况的影响,得出临界电压值和相对应的功率不是单调的变化。说明了采用ZPI负荷模型相对于恒功率负荷而言,负荷的静态... 相似文献
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The use of the life history calendar (LHC) or the event history calendar as tools for collecting retrospective data has received increasing attention in many fields of social science and medicine. However, little research has examined the use of this method with web-based surveys. In this study, we adapted this method to an on-line setting to collect information about young adults' life histories, sexual behaviors, and substance use. We hypothesized that the LHC method would help respondents to date sensitive and non-sensitive events more precisely than when using a conventional questionnaire. We conducted an experimental design study comparing university students' responses to an on-line LHC and a conventional on-line question list. A test-retest design in which the respondents completed the survey again two weeks later was also applied to test the precision and reliability of the participants' dating of events. The results showed that whereas the numbers of sensitive and non-sensitive events were generally similar for the two on-line questionnaires, the responses obtained with the LHC were more consistent across the two administrations. Analyses of the respondents' on-line behavior while completing the LHC confirmed that respondents used the LHC's graphic interface to correct and reedit previous answers, thus decreasing data errors. 相似文献
108.
Large-scale strongly nonlinear and nonconvex mixed-integer nonlinear programming (MINLP) models frequently appear in optimization-based process synthesis, integration, intensification, and process control. However, they are usually difficult to solve by existing algorithms within acceptable time. In this study, we propose two robust homotopy continuation enhanced branch and bound (HCBB) algorithms (denoted as HCBB-FP and HCBB-RB) where the homotopy continuation method is employed to gradually approach the optimum of the NLP subproblem at a node from the solution at its parent node. A variable step length is adapted to effectively balance feasibility and computational efficiency. The computational results from solving four existing process synthesis problems demonstrate that the proposed HCBB algorithms can find the same optimal solution from different initial points, while the existing MINLP algorithms fail or find much worse solutions. In addition, HCBB-RB is superior to HCBB-FP due to much lower computational effort required for the same locally optimal solution. 相似文献
109.
针对百度百科词条收集百科特色词条以及普通词条的编辑历史数据,从整体编辑历史时间间隔和用户编辑历史时间间隔两方面对两组词条分析其分布.通过最大似然估计法计算参数以及似然比检验法对结果进行检验,结果显示特色词条的整体编辑历史时间间隔分布服从双幂律分布,前半段的参数近似等于1.1,后半段参数均大于2;用户编辑历史时间间隔服从... 相似文献
110.
Lukáš Kolek Vít Šisler Patrícia Martinková Cyril Brom 《Journal of Computer Assisted Learning》2021,37(5):1348-1369
This study investigates a video game's effects on implicit and explicit attitudes towards depicted historical events in the short- and long-term on a sample of 148 young adults. We used, as an intervention tool, a serious game Czechoslovakia 38–89: Borderlands that deals with the expulsion of the Sudeten Germans from the former Czechoslovakia after the WWII. Results showed more negative pretest-posttest explicit attitude changes towards the expulsion on a general level (d = −0.34) and a specific level (d = −0.53) compared to the control group. Over the long-term, group differences in attitude change remained significant for the specific level (d = −0.44), but not for general one (d = −0.16). Exploratory analysis on the item level indicated that especially attitudes towards the expulsion's (un)fairness were affected by the game. However, no significant changes were found in implicit attitudes in the experimental group. This study is the first of such scale to empirically investigate video games' effects on a society's historical awareness. 相似文献