土木工程专业钢结构课程教学改革探讨

对土木工程专业结构类主干课程之一的钢结构课程特点、目前教学现状和存在问题进行了分析,从课时分配不合理,对学生力学基础要求高,教学方法单一等方面进行了论述,提出了优化教学内容、改进教学方法、加强钢结构实践教学等措施,以期培养出合格的钢结构人才。     

顶煤动态分析及放煤参数的确定

对综采放顶煤开采的顶煤移动、顶煤破碎、顶煤放出等动态过程进行了分析；研究探讨了放煤步距、放煤顺序、顶煤厚度等主要放煤参数及其对顶煤回采率的影响。     

预采顶分层放顶煤开采利于安全生产

本文根据矿山压力理论，对预采顶分层放顶煤开采工作面释放瓦斯、减缓矿山压力显现、提高回采率及防止采空区自然发火等方面作了分析，认为采用预采顶分层放顶煤开采是一种安全、有效的方法。     

预采预分层放顶煤开采利于安全生产

本文根据矿山压力理论，对预采顶分层放顶煤开采工作面释放瓦斯、减缓矿山压力显现、提高回采率及防止采空区自然发火等方面作了分析，认为采用预采顶分层放顶煤开采是一种安全、有效的方法。     

自膨胀封隔器的技术现状和发展趋势

自膨胀封隔器是油气井固井、完井、找水、堵水等工艺新的井下工具,其优良的性能已成为当今研究的热点。本文介绍了自膨胀封隔器的基本结构及工作原理,总结了国内外自膨胀封隔器的技术现状;通过对比分析传统封隔器与自膨胀封隔器的优点和不足,以及技术现状,研究认为自膨胀封隔器能有效解决现代井下作业安全难题,降低作业成本,节约施工时间,建议今后加大对自膨胀封隔器中膨胀比、高温高压差、系统化等方面的研究。     

双中心节点的网络软RAID系统的设计与实现

随着计算机技术与网络技术的快速发展,基于网络的分布式存储逐渐成为研究的重点,通过网络提供方便、可靠与大容量的存储服务成为可能。该文设计并实现了双中心节点的网络软RAID系统,并对系统结构、工作原理和技术要点进行了详细介绍。     

对等结构的分布式存储系统设计与研究

随着计算机技术与网络技术的快速发展,网络分布式存储逐渐成为存储技术研究的重点。文章设计并实现了对等结构的分布式存储系统—NDSS,它可以提供大容量、高性能、高可靠性与灵活扩展的存储服务。介绍了NDSS的系统结构、工作原理与关键技术,并提供了对系统访问性能的实验测试结果。     

茅台仍将在价格和产能之间平衡

今年旺季之前的价格上扬,让茅台方面的心情显得颇为复杂。茅台酒股份有限公司副总经理杜光义在接受记者采访时说：“价格涨这么高我们也很无奈,从心底来说,我并不希望茅台的价格无限制涨下去。现在因为茅台的供应量有限,     

Fracture toughness of frozen meat

The fracture toughness and dynamic mechanical moduli of frozen beef M. semitendinosus were investigated at various sub-zero temperatures using several different test geometries. Traditional fracture mechanics methods were considered inapplicable to frozen meat, since considerable plastic flow occurs in addition to elastic deformation and fracture. Graphical work area methods still apply, based on calculating areas under load-deflection diagrams to measure the energy used up to fracture. Total work to fracture was found to vary both with temperature and geometry, with a peak occurring between -10°C and -15°C. It was shown that it is possible to separate out the components of fracture and flow using two methods: microtome cutting and compact tension. In microtome cutting, the cutting energy was found to depend on the thickness of cut, increasing linearly from 50 μm to 500 μm. This variation is attributed to a dependence of the volume of the plastic zone size at the cutting tip on the thickness. By extrapolation to zero thickness, an essential value of fracture energy of approximately 100J/m(2) was determined, assuming the absence of large-scale plastic yielding. It was also possible to determine a value for the essential work of fracture using graphical work area methods in compact tension, obtaining values between 100 and 200 J/m(2). Dynamic mechanical testing showed loss peaks in mechanical damping occurring between -5°C and -10°C, with both temperature and magnitude of these peaks varying with frequency. Cryo-scanning electronic microscopy showed evidence of the nature of the fracture transition within frozen meat, indicating ductile deformation at higher temperatures (above -15°C), and brittle fracture at lower temperatures (below -15°C).