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排序方式: 共有783条查询结果,搜索用时 15 毫秒
1.
A 55-year-old woman with primary (granulomatous) angiitis of the central nervous system in association with non-Hodgkin's lymphoma (mucosa-associated lymphoid tissue type) presented with an acute spinal subdural hemorrhage secondary to rupture of one of several fusiform inflammatory aneurysms of the spinal cord radicular arteries. The literature on hemorrhagic complications, aneurysms, and spinal cord involvement in granulomatous angiitis is reviewed. Recognition of granulomatous angiitis is important, as the condition may be responsive to immunosuppressive therapy. 相似文献
2.
The influence of liquid penetration at grain boundary regions on the rate of advance of the solid-liquid interface during
isothermal solidification of transient liquid phase (TLP) brazed nickel joints has been examined. The test samples used in
this study were Ohno-cast nickel with a grain size of >4 mm and a fine-grained nickel with a grain size of around 40 μm. Both
Ni-base materials had the same chemical composition. The rate of isothermal solidification was greater when fine-grained nickel
was employed during TLP brazing using Ni-11 wt pct P filler metal at 1200 °C. Liquid penetration at grain boundaries accelerates
the isothermal solidification process by increasing the effective solid-liquid interfacial area and increasing the rate of
solute diffusion into the base material. An analysis of electron channeling patterns has confirmed that random high-angle
boundaries have a greater influence on the rate of isothermal solidification than ordered boundaries including small-angle
or twin boundaries.
Formerly Visiting Scientist, Department of Metallurgy and Materials Science, University of Toronto.
Formerly Postdoctoral Fellow, Department of Metallurgy and Materials Science, University of Toronto 相似文献
3.
钻井技术水平的不断提高和PDC钻头的广泛使用给现场录井作业带来了新问题。与传统的三牙轮钻头相比,PDC钻头突出的特点是产生的岩屑稀少、细小甚至失真,给地质录井的岩屑采集、鉴定、识别以及油气层级别的判定、解释、评价带来了一系列困难。为此,结合PDC钻头在新疆塔河、松辽盆地、鄂尔多斯等地油田的使用及录井经验,从PDC钻头条件下岩屑特征和岩性特征的分析入手,阐述使用PDC钻头对气测录井、荧光录井的影响,总结了在PDC钻头条件下搞好录井作业的应对措施,并列举了提高录井技术水平的可行途径。 相似文献
4.
Peter Su Adrian Gerlich Motomichi Yamamoto Thomas H. North 《Journal of Materials Science》2007,42(24):9954-9965
The formation of local melted films during friction stir spot welding of as-cast AZ91D and thixomolded AZ91 material is investigated.
The average temperatures close to the tip of the rotating pin vary from 438 to 454 °C during the dwell period in friction
stir spot welding. These measured temperature values are higher than the melting temperature of α-Mg + Mg17Al12 eutectic (437 °C). It is suggested that the temperature in the stir zone during the dwell period is determined by the relative
proportions of α-Mg and (α-Mg + Mg17Al12) eutectic material, which are incorporated during friction stir spot welding. Based on the stir zone temperature measurements
and a detailed examination of material located at the root of the pin thread it is suggested that material is moved downwards
via the pin thread and into the stir zone during the dwell period in friction stir spot welding. Evidence of local melted
film formation is observed in the stir zone of AZ91 spot welds. It is suggested that melted films are retained since their
dissolution rate is much slower in the high temperature stir zone than it is when melted films is formed in the stir zone
during Al 7075-T6 friction stir spot welding. The spontaneous melting temperature, solute diffusion rate and the thermodynamic
driving force for droplet dissolution are much higher during Al 7075-T6 friction stir spot welding. 相似文献
5.
Influence of Ni Interlayers on the Mechanical Properties of Ti6Al4V/(WC-Co) Friction Welds 总被引:2,自引:0,他引:2
M. Shamanian M. Salehi A. Saatchi T. H. North 《Materials and Manufacturing Processes》2003,18(4):581-598
Ni interlayers were introduced prior to dissimilar friction welding of Ti6Al4V base material to three cemented carbide substrates. The fracture strength of Ti6Al4V/(WC-6 wt% Co) welds were poor and were markedly improved when 20-µm thick Ni interlayers were introduced prior to dissimilar friction welding. These results were only produced when the (WC-6 wt% Co) cermet was electroplated prior to friction welding. When the Ti6Al4V alloy was electroplated prior to friction welding, fractured WC particles and cracking were observed in the (WC-Co) carbide substrate. The fracture strengths of Ti6Al4V/(WC-11 wt% Co) and Ti6Al4V/(WC-24 wt% Co) welds were not improved when 20-µm thick Ni interlayers were introduced prior to friction welding. During mechanical testing, the Ni layer retained at the dissimilar joint interface created a region of weakness. 相似文献
6.
The influence of tie-layer Melt Flow Index on the lap-shear strength of ultrasonic welds in oriented polypropylene (OPP) has been evaluated. The tie-layer Melt Flow Index was varied from 0.03 dg/min to 2600 dg/min; the highest lap-shear strength properties were obtained using tie-layers that had melt flow index values between 30 and 100 dg/min. When using low Melt Flow Index tie-layers, hot spot formation and concomitant changes in fusion zone and heat-affected-zone dimensions produced stress concentrations that promoted failure in oriented polypropylene material away from the bondline region. When very high Melt Flow Index (2600 dg/min) tie-layers were used, the mode of failure during lap-shear testing was a mix of cohesive, in oriented polypropylene, and adhesive failure. The molecular weight of material at the bondline was not markedly affected by the thermal cycle produced during ultrasonic welding. Only the flash ejected when using low Melt Flow Index tie-layers exhibited any evidence of degradation; it is suggested that the ejected flash may have been degraded because of a combination of thermal, cavitation, and thermo-oxidative processes. 相似文献
7.
空冷发电厂的热力设计与分析 总被引:1,自引:1,他引:0
张鸿坚 《中国电机工程学报》1992,12(4):57-61
本文对热力发电厂的汽轮机排汽冷却系统进行了评估。作者编制了计算机程序,并对海勒式空冷系统做了计算,结果显示了塔高、水流速与空气流量、冷却塔与散热器投资以及经济效益的关系。 相似文献
8.
9.
塔巴庙区块气藏属于低压、低渗气藏,储集层物性差异大、含气级别高,但含气非均质性强,录井解释评价困难。针对这一问题,开展了综合判断储集层物性和含气性方面的研究,分别探讨了钻时与全烃、钻井液性能与全烃、钻井液粘度与全烃、气测显示与测井参数和烃组分与气显示之间的关系,分析了其相关性及其在塔巴庙区块气层解释评价中的意义及作用。通过相关性研究,不但摸索出定性解释评价气层的方法,同时为今后深入研究录井相关参数关系,探索其内在规律,为实现准确解释评价储集层奠定了基础。 相似文献
10.
致密砂岩储集层裂缝综合录井识别技术研究 总被引:6,自引:0,他引:6
四川盆地油气勘探结果表明,盆地油气储集层普遍为致密砂岩非常规储集层,有效性主要取决于孔、洞、缝发育程度,因此在油气钻井中如何识别致密储集层的孔、洞、缝并确定其所在井段尤其重要。针对综合录井仪的0.1m钻时及相关参数的资料采集技术要求,通过对大量录井数据资料的统计和演算,建立起储集层裂缝发育程度及裂缝发育位置的3种储集层裂缝识别模型,即直接识别模型、地层可钻性(A值)识别模型、钻时回归(RWSR)值识别模型。系统阐述了致密砂岩储集层裂缝综合录井识别技术方法原理,详细介绍了致密砂岩储集层裂缝识别的3个模型在实际生产中的应用情况。该技术方法的研究在国内尚属首次,为油气勘探中储集层评价提供了一个新的方法和手段,可最大限度地发挥现代录井技术在油气勘探开发过程中的作用。 相似文献