金属型型内球化法生产球墨铸铁

本文介绍了一种球墨铸铁金属型型内球化法的研制过程。反应室内放置孕育剂芯,可得到全部铁素体的无白口的铸态球铁。但为了获得无浮渣缺陷的球墨铸铁件,其化学成分必须严格控制。     

Critical Comparison of Novel and Conventional Processing for Dual-Phase Steels

The final properties of an industrial product depend on the processing route of the material. Hence there is an impetus to study different processing routes to obtain the most desirable final properties. In the present study, low carbon steels have been subjected to the novel deformation induced ferrite transformation (DIFT) technique to produce dual-phase microstructures that are composed of ultra-fine ferrite with martensite and/or bainite as a second transformation product. In this thermomechanical processing technique, the steels have been rapidly cooled from the austenitization temperature to the deformation temperature (which is at least 25°C above the Ar₃ temperature) to produce highly undercooled austenite, followed by heavy deformation, and subsequently rapidly cooled thereby facilitating transformation to fine grained ferrite. Comparing the final microstructures obtained by this route with those attained by conventional thermo-mechanical processing, it can be concluded that significant ferrite grain refinement is attainable by the novel DIFT technique thereby emphasizing its potential to achieve improved mechanical properties.     

Design of rock support system under rockburst condition

As mining and civil tunneling progresses to depth, excavation-induced seismicity and rockburst problems increase and cannot be prevented. As an important line of defense, ground control measures and burst-resistant rock support are used to prevent or minimize damage to excavations and thus to enhance workplace safety. Rock support in burst-prone ground differs from conventional rock support where controlling gravity-induced rockfalls and managing shallow zones of loose rock are the main target. Rock support in burst-prone ground needs to resist dynamic loads and large rock dilation due to violent rock failure. After reviewing the rockburst phenomenon, types of rockbursts, damage mechanisms, and rockburst support design principles and acceptability criteria, this paper describes that the support selection process in burst-prone ground is iterative, requiring design verification and modification based on field observations. An interactive design tool for conducting rockburst support design in underground tunnels is introduced to facilitate cost-effective design.     

Wellbuilt for wellbeing: Controlling relative humidity in the workplace matters for our health

This study offers a new perspective on the role of relative humidity in strategies to improve the health and wellbeing of office workers. A lack of studies of sufficient participant size and diversity relating relative humidity (RH) to measured health outcomes has been a driving factor in relaxing thermal comfort standards for RH and removing a lower limit for dry air. We examined the association between RH and objectively measured stress responses, physical activity (PA), and sleep quality. A diverse group of office workers (n = 134) from four well-functioning federal buildings wore chest-mounted heart rate variability monitors for three consecutive days, while at the same time, RH and temperature (T) were measured in their workplaces. Those who spent the majority of their time at the office in conditions of 30%-60% RH experienced 25% less stress at the office than those who spent the majority of their time in drier conditions. Further, a correlational study of our stress response suggests optimal values for RH may exist within an even narrower range around 45%. Finally, we found an indirect effect of objectively measured poorer sleep quality, mediated by stress responses, for those outside this range.     

Parenteral calcium gluconate supplementation: efficacious or potentially disastrous?

A new instrument is described for use in the sagittal ramus split osteotomy by Obwegeser. This modified channel retractor simplifies the sagittal ramus osteotomy procedure, allows clear vision and easy access, and protects adjacent tissues.     

无线接入——广泛提供基本电话业务的有效方法

本文综述了无线接入的技术要求，无线／蜂窝移动通信的演变，以及针对大范围电话业务采取的无线接入的技术可行性和所遇到的设计挑战。     

油砂沥青改质产品中甲苯不溶物的表征

油砂沥青及其衍生产品中含有悬浮的甲苯不溶物如粘土和碳质固体颗粒，会导致后续加工过程中的结垢、催化剂失活和床层堵塞。笔者从油砂沥青衍生产品中分离出甲苯不溶物并进行了分析表征。研究发现，油砂沥青渣油中的甲苯不溶物主要是超细的硅铝酸盐粘土颗粒，结合了部分干酪根成分；焦化渣油和焦化瓦斯油储罐中沉积的甲苯不溶物类似焦炭；焦化瓦斯油中的甲苯不溶物主要是碳质有机物颗粒，但氮、氧含量相对丰富，并含少量矿物质和粘土颗粒，含氮的杂环化合物如吡咯类物质的存在可能是导致焦化瓦斯油中甲苯不溶物生成的主要因素。     

标准三脚复位监控器的手动复位

为设计增加手动复位时一般采用一只带手动复位输入的新器件.但是,只要增加几只小电阻,一个标准的三脚复位监控器就足以应付多数应用.     

23号花园 丰盈的花粉

花粉的重大意义……为了想象花园的未来,我们不可避免地要回顾它的过去。过去我们丰富多样的作物源于植物无穷的多样性。它们是我们的食物和生存之所在,还是百余种甚至百万种与我们错综复杂的生活方式相交织的各种生物的本源。现代农业倾向于标准化和植物种类的减少。这个花园旨在探索风媒花园的遗产①。