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141.
金属快速凝固方法的数学模型 总被引:1,自引:1,他引:0
本文综述了与几种典型的快速凝固方法相应的数学模型,并对每种模型作了相应的分析和评价。文中重点介绍了“活塞-砧法”,“双辊法”,“单辊法”和“雾化沉积法”数学模型的理论基础,建模过程,理论优缺点及实用局限性。 相似文献
142.
Yin He-Jun Lu Bao-Wei Song Wen-Miao Yin Yuan-Zhao 《Journal of Infrared, Millimeter and Terahertz Waves》1994,15(8):1421-1431
In this paper, we put forward a new version of Cantor fractal multilayers, which are nonlinear medium, and investigate its properties of reflection and transmission when a plane wave is obliquely incident upon it. A new exact self-similarity algorithm that make use of the self -similarity of these structure are developed. The results for different stages of fractal growth within the first-order nonlinear approximation are found. Compared with the traditional chain-matrix approach, the scheme provides the reflection and transmission coefficients for any stage (S) with much less calculation time on a personal computer. 相似文献
143.
144.
本文报道了1985年鄱阳湖湖底沉积物放射性水平的调查结果。沉积物中 U、Th、~(226)Ra、~(40)(?)和~(137)Cs 的比活度分别为64.8、67.9,58.9、676.1和3.5Bq/kg;用~(137)Cs 测龄方法作了沉积物泥芯垂直深度的年代定位,由此得知1985—1958年对应深度沉积物中 U、Th、~(226)Ra 和~(40)K 的比活度与1957—1930年对应深度沉积物比较无显著性差异;U、Th 和~(226)Ra 的浓集因予分别为5.2×10~413.9×10~4和4.8×10~4L/kg。 相似文献
145.
本文在已有成果资料的基础上,为组合拱式管桥的设计建立了常规设计表达式,并研制出组合拱式管桥计算机模拟的程序软件CAPBD。该软件具有以下计算功能:(1)计算组合管拱的几何特征参数;(2)计算组合管拱自重和组合拱式管桥的竖向荷载及其材料费用;(3)分析和计算各种载荷作用下组合拱式管桥的内力;(4)组合拱式管桥各控制截面强度校核、稳定性验算以及拱支墩稳定性验算和地基承载力强度校核。 相似文献
146.
用EVA复配物改善高含蜡原油低温流动性的研究 总被引:4,自引:0,他引:4
本文研究了采用化学处理剂改善南海高含蜡原油的低温流动性,结果表明,添加150ppm EVA复合化学处理剂,原油低温流动性得到明显改善,凝固点由32℃降至11.5℃,表观粘度降低86.9%,1;℃时屈服值降低98%。同时考察了添加温度,冷却速度以及化学处理剂的化学组成和结构对改善原油低温流动性的影响。根据南海高含蜡原油中蜡的组成和正构烷烃的碳数分布及其对不同结构的EVA的感受性,讨论了化学处理剂改善原油低温流动性的机理,指出,EVA中乙烯链长与原油中正构烷烃链长相近时才能形成共晶,起到改变原油中蜡的结晶形态的作用,达到降凝减粘效果。 相似文献
147.
A study of dislocation configurations in superconducting oxide BiSrCaCuO has been made by transmission electron microscopy. Evidence was found for the presence of dislocation pairs composed of two parallel single dislocations holding together with the same Burgers vectors. The pair can further dissociate into partials, giving rise to a four-fold ribbon. Networks consisting of dislocation pairs were also observed. These phenomena are attributed to the possible ordering of strontium and calcium ions and the existence of some oxygen sheet of the Aurivillius type in the oxide crystal. Schemes to illustrate the configurations are suggested and discussed. 相似文献
148.
149.
Beliefs about human nature, adult education, adult learners, and moral commitment are at the heart of the educator-learner agreement. In continuing nursing education, it is the point where professional values, morals, and ethical principles meet. Using Husteds' bioethical decision-making model, the values, beliefs, and actions within the educator-learning agreement are identified and organized by the bioethical standards. By relating the bioethical standards to practice, continuing nurse educators can find their own basis for practice and work toward attaining a consistent professional ethical orientation. 相似文献
150.
DK Song HW Suh SO Huh JS Jung BM Ihn IG Choi YH Kim 《Canadian Metallurgical Quarterly》1998,287(1):144-149
The development of control strategies for loiasis is of crucial importance in endemic areas and depends heavily on the accurate identification of occult-infected individuals. A polymerase chain reaction (PCR) and nested polymerase chain reaction (nested PCR) were developed and based on sequences of the repeat 3 region (15r3) of the gene encoding a Loa loa 15-kD protein. The assays was performed on 20 blood samples from occult-infected subjects and 30 from field-collected amicrofilaremic individuals. The size of the initial PCR product was 396 basepairs (bp). When this initial amplification using primers 15r3(1) and 15r3(2) was carried out for 30 cycles, the PCR products from three of the 20 occult-infected and five of the 30 amicrofilaremic individuals were visualized after electrophoresis by staining the gel with ethidium bromide. Subsequent Southern blotting and hybridization with the specific probe revealed hybridization in 19 of 20 occult-infected and 23 of 30 amicrofilaremic samples but only after two days of exposure of the blot to the x-ray film. When the nested PCR was carried out (product size = 366 bp, primers 15r3(3) and 15r3(4)), 19 of 20 occult-infected and 23 of 30 amicrofilaremic samples that were positive by Southern hybridization of the initial PCR products were strongly positive by staining with ethidium bromide. Qualitative Southern blotting of the nested PCR products using the same probe previously described confirmed the ethidium bromide staining results after a very short exposure time of 4 hr. These results demonstrate that the nested PCR amplification product is specific and that its sensitivity in detecting occult loiasis is 95%. This approach has significant promise for the screening of large human populations for active loiasis without the requirement for blotting and hybridization of the PCR products. 相似文献