Application of piece‐wise linear weight functions for 2D 8‐node quadrilateral element in contact problems

The present study is a continuation of our previous work with the aim to reduce problems caused by standard higher order elements in contact problems. The difficulties can be attributed to the inherent property of the Galerkin method which gives uneven distributions of nodal forces resulting in oscillating contact pressures. The proposed remedy is use of piece‐wise linear weight functions. The methods to establish stiffness and/or mass matrix for 8‐node quadrilateral element in 2D are presented, i.e. the condensing and direct procedures. The energy and nodal displacement error norms are also checked to establish the convergence ratio. Interpretation of calculated contact pressures is discussed. Two new 2D 8‐node quadrilateral elements, QUAD8C and QUAD8D, are derived and tested in many examples, which show their good performance in contact problems. Copyright © 2004 John Wiley & Sons, Ltd.     

Restoration of small lakes through cooperative management: A suitable strategy for poverty‐laden areas in developing countries?

Lake Rupa is a small, subtropical, shallow lake with a surface area of 100 ha situated 600 m a.s.l. in Central Himalaya, Nepal. This degraded lake was studied between 2000 and 2006, with the goal of determining whether or not it could be restored by a community‐based cooperative of local people living in its catchment. Main threats to the lake, its aquatic life and its very existence include encroachment by excessive aquatic vegetation, sedimentation, and low in‐lake concentrations of dissolved oxygen (DO). Small lakes (≤ 500 ha) are relatively prone to the process of ‘succession and climax’, although they also can be of social, environmental and ecological importance. Thus, their disappearance could spark social chaos and disorder in areas already having to cope with other rapid environmental changes. This means that credible mechanisms for revitalizing or protecting small lakes are an important goal. Accordingly, a lake cooperative of 329 households living in close vicinity to Lake Rupa was formed in 2002, by prioritizing traditional fishers, women and other deprived community members with the goals of respecting the citizenry and equity. Following the cooperative's campaigns directed at weed removal and fish stocking, encroachment of vegetation on the lake margins was halted, its aquatic weeds became under control, and its fisheries improved. In addition to the cooperative's restoration activities, several water quality parameters, including water transparency and DO and chlorophyll‐a concentrations, were monitored on a monthly basis. The measured water transparency was inconsistent, exhibiting large variations between 2000 and 2003. Relatively low, but consistent, values, however, were measured after 2004. The results imply that the removal of weeds, and sufficient nutrients and solar radiation are subsequently available to the lake's phytoplankton communities. Supporting this notion is that the chlorophyll‐a concentration spiked to 205 µg L⁻¹ in November 2006, the water transparency became consistent, and the DO concentration increased to >3.8 mg L⁻¹ during the critical months (March–May) after 2004. These water quality indicators indicated improvement in the degraded Lake Rupa, suggesting that the establishment of cooperatives such as that highlighted in this study could be a powerful and sustainable mechanism for restoring degraded lakes in similar socioeconomic settings by maintaining equity, by connecting communities with their resources, and by facilitating integrity, equity, citizenry and social justice.     

A well‐conditioned and optimally convergent XFEM for 3D linear elastic fracture

A variation of the extended finite element method for three‐dimensional fracture mechanics is proposed. It utilizes a novel form of enrichment and point‐wise and integral matching of displacements of the standard and enriched elements in order to achieve higher accuracy, optimal convergence rates, and improved conditioning for two‐dimensional and three‐dimensional crack problems. A bespoke benchmark problem is introduced to determine the method's accuracy in the general three‐dimensional case where it is demonstrated that the proposed approach improves the accuracy and reduces the number of iterations required for the iterative solution of the resulting system of equations by 40% for moderately refined meshes and topological enrichment. Moreover, when a fixed enrichment volume is used, the number of iterations required grows at a rate which is reduced by a factor of 2 compared with standard extended finite element method, diminishing the number of iterations by almost one order of magnitude. Copyright © 2015 John Wiley & Sons, Ltd.     

企业慈善——新时期我国企业与社会的双赢选择

企业慈善是企业与社会的双赢选择。企业慈善可促进慈善事业的发展，达到整合社区资源、促进社区发展的目的，在更为广阔的社会系统中表达一种“关爱与和谐”的理想与信念。同时，企业慈善有利于提升企业自身形象，增进企业内部凝聚力，培养优秀的企业文化。当前我国企业慈善的发展现状不容乐观。我国企业应该大力参与慈善事业，开创社会主义和谐社会下企业与社会的双赢局面。     

连铸小方坯表面横裂的控制

根据安钢第一炼轧厂近几年的连铸生产实践，系统分析了连铸小方坯发生横裂的原因，其影响因素主要有振动参数，二次冷却、拉速、保护渣的性能及操作因素。通过采取相应的措施，使方坯横裂废品率降到较低水平。     

需求引领空间设计提升价值——以上海市宝山区体育中心设计为例

马斯洛需求层次理论把人类需求分成生理、安全、社交、尊重和自我实现五类,依次由较低层次到较高层次。据此理论,不同的空间形态及相互组合能够满足不同层次的心理需求,进而促进不同类型活动的发生及商业业态的发展,最终形成城市综合体育中心“以馆养馆”“以商养体”的局面,推动并保持项目的持续发展。     

基于委托代理模型的发电权交易模式

从发电权特性角度,针对“弃水”现象,剖析现有发电权交易中存在的问题。基于委托代理理论,提出了非对称信息条件下,无交易中心参与和交易中心以承包形式参与的发电权委托代理模型。通过分析激励合同中关键参数设定及其对交易各方风险分担份额、努力水平等的影响,分别比较了2种模式下采用不同激励合同的各方收益。算例分析表明,文中设计的激励合同可以在引导参与发电权交易各方获得最优收益的同时,使电力系统资源得到更有效的配置,提高社会总体效用,实现交易各方多赢。     

校企合作模式实践研究

校企合作是高职专业教育发展的基础。只有让企业走进高职院校,让学生与教师走进企业,才能实现共同获利。让高职教学质量提高,学生轻松就业,企业拥有优秀的人才。但是校企合作不能表面化。高职院校要真正实现校企合作,要为企业展现合作将给企业带来的效益。要进行看得见摸得着的,切实可行的合作方案。本文主要就如何实现校企之间的合作,把校企合作落实到实处进行了研究。     

工业锅炉行业应对变局的创新思维和实践

2020年,新冠疫情、中美对战和低碳能源革命的大变局叠加锅炉技术自身之变局将深刻影响工业锅炉行业和企业的未来.笔者根据多年从事锅炉技术及产学研合作的深切体会,建议工业锅炉行业从业者一定要转变思维方式,用一种学习和实践的态度重新认识自己、认识世界,重新审视低碳能源革命将给自己带来的前所未有的挑战和机会,谨慎选择,以有重点...     

基于K-奇异值分解和层次化分块正交匹配算法的滚动轴承故障诊断

利用层次化分块正交匹配算法（HBW-OOMP）的高稀疏性和运算速度快等优点,提出了一种基于K-奇异值分解（K-SVD）字典和HBW-OOMP算法的故障轴承诊断方法。首先利用K-SVD自学习训练方法得到包含冲击成分的冗余字典,克服了固定结构字典适应性不强的缺点。然后采用基于分块思想的HBW-OOMP算法进行原子的选取和稀疏系数的求解,以重构信号包络谱峭度最大为终止条件,自适应确定分解次数。最后应用所提方法对仿真信号和故障轴承实验信号进行故障特征提取,结果表明该方法能够有效提取强背景噪声下故障特征成分,具有一定的应用前景。