Calculations of plastic collapse load of pressure vessel using FEA     

Peng-fei Liu  Jin-yang Zheng  Li Ma  Cun-jian Miao  Lin-lin Wu 《浙江大学学报(A卷英文版)》2008,9(7):900-906

This paper proposes a theoretical method using finite element analysis （FEA） to calculate the plastic collapse loads of pressure vessels under internal pressure, and compares the analytical methods according to three criteria stated in the ASME Boiler Pressure Vessel Code. First, a finite element technique using the arc-length algorithm and the restart analysis is developed to conduct the plastic collapse analysis of vessels, which includes the material and geometry non-linear properties of vessels. Second, as the mechanical properties of vessels are assumed to be elastic-perfectly plastic, the limit load analysis is performed by employing the Newton-Raphson algorithm, while the limit pressure of vessels is obtained by the twice-elastic-slope method and the tangent intersection method respectively to avoid excessive deformation. Finally, the elastic stress analysis under working pressure is conducted and the stress strength of vessels is checked by sorting the stress results. The results are compared with those obtained by experiments and other existing models. This work provides a reference for the selection of the failure criteria and the calculation of the plastic collapse load.  相似文献   

煤矿机械中齿轮的失效形式及改进方法   总被引：1，自引：0，他引：1  

涂杰 《宁波职业技术学院学报》2008,12(2):98-101

煤矿机械具有工作负荷大、环境差的特点,通过对煤矿机械中齿轮失效形式的分析,阐述了造成传动齿轮失效的原因,从而提出了一些能够提高煤矿机械齿轮传动质量,延长煤矿机械齿轮使用寿命的改进途径。  相似文献   

Effects of instructional aids on the acquisition of dynamic decision-making skills     

Christian FrederiksenE. James Kehoe  Robert Wood 《Learning and Instruction》2011,21(5):601-613

This study tested the effects of two instructional aids in a complex, dynamic environment, specifically, a business simulation. Participants studied (1) a “causal map,” which depicted key variables in an interconnected network, (2) a textual outline of the same relationships, or (3) no-aid. With the relevant aid still available, the participants ran the simulation three times. Then, the aid was removed, and the participants ran another three simulations. Both when the aid was available and later when removed, the group receiving the causal map gained a greater market share than the other two groups, which failed to differ. With respect to profits, however, a cross-over interaction appeared. When the aid was available, the causal map group showed lower profits than the other two groups, but, without the aid, the causal map group showed greater profits. The results are discussed in the context of information processing theories of instructional design.  相似文献   

Effects of presentation modes on mobile-assisted vocabulary learning and cognitive load     

Chih-Cheng Lin  Ya-Chuan Yu 《Interactive Learning Environments》2017,25(4):528-542

Previous studies of multimedia presentations have determined the effects of the combination of text and pictures on vocabulary learning, but not those of the sound of new words. This study was intended to confirm those previous findings from the integration of mobile technologies and the approach of cognitive load. It adopted a within-subjects design and recruited 32 eighth graders in central Taiwan to participate in a vocabulary learning program on mobile phones. During the program the participants needed to learn four sets of target words in four different weeks. Each set was presented in one of the four modes: text mode, text-picture mode, text-sound mode, and text-picture-sound mode. Immediately after learning each set, all participants took a vocabulary test and completed a cognitive load questionnaire; and, two weeks later, they took the vocabulary test again. Their perceptions of the vocabulary learning program were also collected in a post-program questionnaire. The findings were that audio input helped our participants recall new words’ meanings after two weeks; and, it reduced their cognitive load of learning new words. Our participants also provided positive feedback on the mobile-assisted vocabulary learning program featuring multimedia presentations.  相似文献   

Getting the point: Tracing worked examples enhances learning     

《Learning and Instruction》2015

Embodied cognition and evolutionary educational psychology perspectives suggest pointing and tracing gestures may enhance learning. Across two experiments, we examine whether explicit instructions to trace out elements of geometry worked examples with the index finger enhance learning processes and outcomes. In Experiment 1, the tracing group solved more test questions than the non-tracing group, solved them more quickly, made fewer errors, and reported lower levels of test difficulty. Experiment 2 replicated and extended the findings of Experiment 1, providing evidence for a performance gradient across conditions, such that students who traced on the paper outperformed those who traced above the paper, who in turn outperformed those who simply studied by reading. These results are consistent with the activation of an increasing number of working memory channels (visual, kinaesthetic and tactile) for learning-related processing.  相似文献   

混凝土楼板早拆后受力分析     

耿午龙  梁为民  王永贵 《洛阳工业高等专科学校学报》2015,(2)

楼板进行早拆时处于混凝土早龄期,此时混凝土强度处于高速发展阶段,需要对其进行早拆使其承受荷载,必须对其安全性进行充足的验算,否则将会造成安全隐患甚至酿成安全事故。理论分析部分采用两种模型基于开裂荷载进行验算并将结果对比分析。在理论分析的基础上利用 ANSYS 进行数值模拟,并将其结果与理论分析进行对比分析。  相似文献   

A time sequence-oriented concept map approach to developing educational computer games for history courses     

Hui-Chun Chu  Kai-Hsiang Yang  Jing-Hong Chen 《Interactive Learning Environments》2015,23(2):212-229

Concept maps have been recognized as an effective tool for students to organize their knowledge; however, in history courses, it is important for students to learn and organize historical events according to the time of their occurrence. Therefore, in this study, a time sequence-oriented concept map approach is proposed for developing a game-based environment to facilitate students' learning of historical events and their organization during the gaming process. With this approach, students can easily learn the precedence relationships among the historical events that occurred in different time periods with the time sequence-oriented concept map. To evaluate the effectiveness of the proposed approach, a historical role-playing game has been developed for an elementary school history course to examine the students' performance in terms of learning motivation, self-efficacy and learning achievements. A subject unit, the “Siege of Fort Zeelandia by Zheng Cheng-Gong,” was chosen as the history topic. The results show that the proposed approach can significantly enhance the students' learning achievement, but did not affect their learning motivation or self-efficacy for the history course. As a consequence, it is concluded that students can benefit from concept maps in terms of enhancing their learning achievement, but they do not necessarily enjoy using concept maps in game-based learning activities.  相似文献   

雅鲁河大桥静动载试验及分析     

葛贝德 《鸡西大学学报》2015,(7)

对黑龙江省碾景公路雅鲁河大桥进行静载试验和动载试验,根据主梁静载试验、墩台静载试验以及桥梁动载试验测试数据,对桥梁结构的承载能力和刚度作出评估,测试结果表明该桥的强度储备较弱,甚至出现承载力不足的情况,并据此对该桥的后期维修加固提出了可行的建议,可为同类型的工程提供参考。  相似文献   

A six-year monitoring case study of a top-10 cycling Grand Tour finisher     

Julien Pinot  Frederic Grappe 《Journal of sports sciences》2015,33(9):907-914

This study analysed the evolution of the physical potential of a twice top-10 Grand Tour cycling finisher (Tour de France and Vuelta a España) whose training was monitored between the ages of 18 and 23 years. The world-class cyclist’s power output (PO) data and training indices were analysed over six years to determine the evolution of his record power profile and training load (TL), which were estimated by using the session rating of perceived exertion (RPE) method. The total annual duration and TL increased through six seasons by 79% and 83%, respectively. The record POs in all exercise intensity zones improved over the six years. The increases in TL, monotony (+34%) and strain (+162%) from the junior category to the world-class level significantly correlated with an improvement in his aerobic potential, which was characterised by an increase in the record POs between 5 min and 4 h. This case study of the performance level and training parameters of a world-class cyclist provides comprehensive insight into the evolution of a cyclist to the top level. Furthermore, determining the record power profile of this athlete over six competitive seasons illuminates the maturation of the physical potential of a top-10 Grand Tour finisher.  相似文献   

不同社会文化对企业技术创新方式选择的影响     

高展军  李垣  雷宏振 《科学学与科学技术管理》2005,26(11):69-73,78

持续的技术创新和对不同社会文化的适应已经成为全球激烈竞争中企业取得成功的两个关键因素，然而有关不同社会文化类型对企业技术创新方式选择的影响关系仍然不很清楚。以Hofstede的社会文化理论为基础，分析了四个社会文化维度对渐进创新与突变创新的不同影响，期望为企业跨国经营中依据不同社会文化背景进行技术创新方式选择提供理论依据。  相似文献