Experimental Study of Microstructure Evolution during Tempering of Quenched Steel and Its Application

LARGE-SIZED FORGINGS are usually intensivelyquenched to obtain the desired microstructuredistribution,high strength and hardness.Becauseresidual stresses are high in quenched large-sizedforgings,tempering processes follow quenchingprocesses to reduce the residual stress and obtain goodmechanical properties.Several differentmicrostructures are generated in quenched steelforgings,such as martensite,bainite and retainedaustenite.Modeling of microstructure evolution inquenched steel during …     

鋁电解工艺的现状

历史資料在第二次世界大战之前,彼施涅公司的鋁厂装备的是3～5万安培的預焙阳极电解槽和2～3万安培的側部导电自焙阳极电解槽。电解槽的技术指标列于表1。     

设计电解槽阳极时应考虑的因素

序言铝工业趋向采用低电流密度的大型多爪头阳极,所以考虑对使用中阳极有影响的起作用的机械应力和热应力的设计因素变得更加重要。设计时应该使合成应力不超过碳块的机械强度极限,同时要使钢爪和碳块间的接触电压降为最小。     

W-Ni-Cr系高比重合金

研究了W-Ni-Cr系高比重合金的硬度和机械性能。这些合金的硬度较一般合金高得多(Hv值高达600,而W-Ni-Fe合金的Hv值为310)。该合金系的机械性能,按合金成分可分为截然不同的二类:一类是铬镍比(Cr:Ni)低的——塑性较好,硬度略高;另一类是铬镍比高的——硬度高,抗张强度低,几乎没有塑性。为了解释W-Ni-Cr系合金的这种性质,本文确定了该合金系相图的1250℃截面图,证明了三元σ脆性相的存在。延性-脆性转变界限与有σ相的相区边界相对应。对σ相稳定性的研究表明,不可能用简单的热处理消除σ相。在高硬度的合金中,添加第四组元不能阻止σ相生成。     

Note: The intermodulation lockin analyzer

Nonlinear systems can be probed by driving them with two or more pure tones while measuring the intermodulation products of the drive tones in the response. We describe a digital lockin analyzer which is designed explicitly for this purpose. The analyzer is implemented on a field-programmable gate array, providing speed in analysis, real-time feedback, and stability in operation. The use of the analyzer is demonstrated for intermodulation atomic force microscopy. A generalization of the intermodulation spectral technique to arbitrary drive waveforms is discussed.     

Strategies for processing diffraction data from randomly oriented particles

The high intensity of free-electron X-ray light sources may enable structure determinations of viruses or even individual proteins without the encumbrance of first forming crystals. This note compares two schemes of non-crystalline diffraction data collection that have been proposed: serial single-shot data from individual particles, and averaged cross-correlation data from particle ensembles. The information content of these schemes is easily compared and we show that the single-shot approach, although experimentally more challenging, is always superior in this respect. In fact, for 3D structure determination a constraint counting argument shows that the cross-correlation scheme suffers from data deficiency.     

Computer-aided methods in bespoke breast prosthesis design and fabrication

This case study presents a method of utilizing computer-aided design technologies to provide bespoke, external breast prostheses. The technique is illustrated through a case study of a mastectomy patient. Photogrammetry methods were used to capture the breast form when supported by a brassiere and the unsupported breast and defect side. Computer-aided design techniques were used to generate a digital prosthesis based upon the supported breast shape and with a fitting surface that matched the defect side. Furthermore, a two-part mould was designed and fabricated using rapid prototyping methods. A colour-matched prosthesis was then fabricated in a gel-based, platinum-cured silicone.     

Spatial and functional relationships between air conduits and blood capillaries in the pulmonary gas exchange tissue of adult and developing chickens

The documented data regarding the three-dimensional structure of the air capillaries (ACs), the ultimate sites of gas exchange in the avian lung is contradictory. Further, the mode of gas exchange, described as cross-current has not been clearly elucidated. We studied the temporal and spatial arrangement of the terminal air conduits of the chicken lung and their relationship with the blood capillaries (BCs) in embryos as well as the definitive architecture in adults. Several visualization techniques that included corrosion casting, light microscopy as well as scanning and transmission electron microscopy were used. Two to six infundibulae extend from each atrium and give rise to numerous ACs that spread centrifugally. Majority of the ACs are tubular structures that give off branches, which anastomose with their neighboring cognates. Some ACs have globular shapes and a few are blind-ending tapering tubes. During inauguration, the luminal aspects of the ACs are characterized by numerous microvillus-like microplicae, which are formed during the complex processes of cell attenuation and canalization of the ACs. The parabronchial exchange BCs, initially inaugurated as disorganized meshworks, are reoriented via pillar formation to lie predominantly orthogonal to the long axes of the ACs. The remodeling of the retiform meshworks by intussusceptive angiogenesis essentially accomplishes a cross-current system at the gas exchange interface in the adults, where BCs form ring-like patterns around the ACs, thus establishing a cross-current system. Our findings clarify the mode of gas exchange in the parabronchial mantle and illuminate the basis for the functional efficiency of the avian lung.     

抽水蓄能技术的优势

抽水蓄能除了其常规效益外,相比其他蓄能技术更具优势,并可以解决可再生能源的间歇性问题,为此世界上许多国家都计划大力发展抽水蓄能。简要介绍了环球数据中心有关抽水蓄能的最新报告、西班牙抽水蓄能的发展情况及全球发展趋势。最后指出,在快速发展的可再生能源技术中,抽水蓄能将会得到越来越多的关注。