Concept modeling of tapered thin-walled tubes     

Yu-cheng Liu  Michael L. Dag 《浙江大学学报(A卷英文版)》2009,10(1):44-53

This paper presents a method to create concept models for the tapered thin-walled tubes using beam elements and spring elements. Developed concept tapered beam models with different taper angles and cross sections are compared with those detailed models through impact analyses. Important crash results are recorded and compared, and the relatively good agreement is achieved between these analyses. Concept modeling steps are illustrated in detail, and a general concept modeling method for such thin-walled tubes is summarized and presented.  相似文献   

The vibrational mode structure of a golf ball     

John D. Axe  K. Brown  Kevin Shannon 《Journal of sports sciences》2013,31(8):623-627

In this paper, we report the discrete frequencies at which golf balls can vibrate, the mode patterns of these vibrations and how these modes can be excited. There are two broad classes of modes: those that radiate sound waves and those that do not. Both silent and acoustic modes are excited by tangential (i.e. spin-producing) impact forces; only acoustic modes are excited by radial impact forces. Exact analytical results for a homogeneous ball core are compared with finite element numerical results for both a core and a model two-piece ball. Correspondences are readily established for the important low-frequency modes, and the good agreement suggests the validity of these results for real golf balls. The results potentially provide the basis for a rapid, simple and non-destructive method of measuring the effective high-frequency elastic shear modulae of balls (and ball cores) as well as a method for 'tuning' the performance of balls for specific clubs. Some of these aspects are explored further in our companion paper in this issue.  相似文献   

Development and use of one-dimensional models of a golf ball     

Alastair J. Cochran 《Journal of sports sciences》2013,31(8):635-641

One-dimensional models of a golf ball are useful in modelling near-normal (90°) impact. The model described here has two masses connected by a non-linear spring in parallel with a non-linear damper. The behaviour of this system in collision with an infinite rigid mass is compared with the results of tests involving real golf balls. Values of the four unknown constants are found by fitting the model results, over a range of impact speeds from zero to 50 m· s -1 , to the coefficient of restitution and duration of contact found in the tests. The simplest model (Model 1) was a good fit for duration of contact over the whole range of impact speeds, but for the coefficient of restitution only at high speed (above 20 m· s -1 ). However, when used with a similar model of a flexible faced club, the simple model predicted the coefficient of restitution of the club-ball combination, determined by direct testing, quite well and as such is a useful screening tool. More complicated Models 2 and 3 fitted the rigid target coefficients of restitution better at low speed than Model 1. However, Models 2 and 3 have other disadvantages and are no better than Model 1 for high-speed impact with flexible faced clubs.  相似文献   

征收碳税对中国经济影响评估的差异因素研究——基于Meta分析     

栾昊  杨军  黄季焜  姜晔 《资源科学》2013,35(5):958-965

作为减缓气候变化的重要调控工具之一,征收碳税在减少CO2排放的同时也将给国家经济发展带来一定负面影响.由于所采用的分析模型、数据以及情景假设等不同,在征收碳税对中国经济(GDP)影响幅度上,国内现有研究结论存在较大差异.本文利用Meta方法对导致评估结果差异的各种因素进行分析,研究结果表明模型选择和碳税税率的设定是导致评估差异的主要原因.其中,模型选择是造成研究结论差异的主要原因,可以解释结论差异的74％左右;如果考虑模型选择与碳税税率的交叉影响,其解释效力可进一步提高到87％;而征税方式与碳税使用方式对研究结论差异没有显著影响.相比于其他模型,CGE模型与MARKAL-MACRO模型的评估结果比较稳定,影响幅度居中并较为接近,更为适用于评估实施碳税对GDP的影响程度.基于研究结果,提出在分析征收碳税对中国经济影响的研究上亟需方法论创新,需要特别注重研究方法的科学性.  相似文献   

中英工程领域合作的文献计量学研究"     

田汇宝  方若冰  周萍 《情报杂志》2013,(1):98-104

以Web of Science收录论文数据为研究对象,多角度分析中国与英国在工程领域的国际合作状况。着重比较中国与美国、德国、日本以及印度的合作状况。评价论文影响力时,采用Loet Leydesdorff提出的综合影响指标(Integrated Impact Indicator:I3)。20世纪以来,中国在该领域的研究进入快速发展期;中国的国际合作产出呈指数性增长,主要合作伙伴包括美国、英国、加拿大、新加坡、日本、澳大利亚等;中英合作对于英国论文产量的贡献率快速增长,而对中国的贡献率则增长极为缓慢;中国在工程领域影响力增长显著,国际合作对于提升中国或英国在该领域的影响力均具有很大促进作用。  相似文献   

多硝基芳香化合物撞击感度的理论研究   总被引：2，自引：0，他引：2  

黄新旺  曾荣英  邝代治  杨英辉  蒋丽平 《衡阳师范学院学报》2004,25(6):62-65

采用密度泛函的方法，在3—21G基组水平上，对五种多硝基芳香化合物TNA(Ⅰ)、2，3．4，6-四硝基苯胺(Ⅱ)、五硝基苯胺(Ⅲ)、DATB(Ⅳ)、TATB(Ⅴ)炸药的撞击感度进行了理论研究，探讨苯环上引入氨基和硝基对该类炸药撞击敏感度的影响。结果表明，利用Mulliken键级可以很好的解释分子的撞击感度，氨基引入苯环后，炸药的撞击感度减小，硝基引入苯环后，撞击感度也发生了变化，其撞击敏感度顺序为：Ⅰ＞Ⅲ＞Ⅱ＞Ⅳ＞Ⅴ。  相似文献   

An Empirical Examination of Factors Affecting Group Effectiveness in Information Systems Projects     

Bassam Hasan  Jafar Ali 《Decision Sciences Journal of Innovative Education》2007,5(2):229-243

Although group project concepts and skills have become a major component in most information systems (IS) academic programs, very little research has attempted to examine factors that may improve or undermine effectiveness of IS group projects. Accordingly, based on relevant literatures, this study develops and empirically tests a model of factors affecting IS group project effectiveness. The research model posits that group cohesion and group efficacy will have positive effects on group effectiveness (project success and expected impact), whereas perceived loafing is expected to have a negative effect on IS group effectiveness. Data collected from 104 students working in 29 groups to complete semester‐long projects in two IS courses revealed that group efficacy had positive impact on group effectiveness and perceived loafing demonstrated a partial effect. Contrary to expectations, the impact of group cohesion was nonsignificant. These results could be useful in evaluating groups' potential for success and creating conditions conducive to enhancing effectiveness and success of IS student group projects.  相似文献   

环境影响评价中的公众参与     

张丽华 《三明学院学报》2003,20(2):40-44

通过对环境影响评价的公众参与发展的介绍 ,分析了我国环境影响评价中公众参与的含义、方式、内容及程序等 ,并对公众参与在我国环境影响评价中的重要性及意义作了有益探讨。  相似文献   

编制集中供热项目环境影响报告书的常见问题探讨     

杨芳 《辽宁科技学院学报》2016,18(3)

根据集中供热项目的特点,对该类项目环境影响评价中存在的问题进行探讨,明确了集中供热项目环评类别、资质要求以及评价的重点内容,从而为这类项目的环境影响评价工作提供参考,也为环境保护行政主管部门的审批提供依据。  相似文献   

How Europe Shapes Academic Research: insights from participation in European Union Framework Programmes     

Emilia Primeri  Emanuela Reale 《European Journal of Education》2012,47(1):104-121

This article describes the effects of participating in European Union Framework Programmes (EUFPs) at the level of research units and researchers. We consider EUFPs as policy instruments that contribute to the Europeanisation of academic research and study the changes they produce with respect to: 1) the organisation and activities of Departments, 2) the type of knowledge produced, and 3) the ways of doing research. The analysis is based on a case study of the Sapienza University in Rome. We also discuss the extent to which EUFPs produce different effects at the level of scientific fields. This pilot study analyses changes driven by EUFPs from an institutional perspective and uses the concept of institutionalisation to explain how these changes are translated into rules and practices by research units and researchers. Our preliminary investigation supports the idea that EUFPs do not trigger a process of Europeanisation and lead, within academic institutions, to highly diversified institutional responses by scientific fields rather than to undifferentiated ones. They strengthen leading research groups and Departments, already competitive at the EU level, by enhancing existing international behaviours and practices. However, they do not support and, at times, even decrease competition opportunities for less experienced participants and they do not promote the participation of new groups. Moreover, the absence of relevant organisational changes at the University level and the lack of incentives for EUFP participation seem to strengthen these trends. What emerges is the need for decisions at the University level, taking into account differences across scientific groups.  相似文献