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排序方式: 共有454条查询结果,搜索用时 15 毫秒
81.
82.
Energy bandgaps are observed to increase with decreasing diameter due to quantum confinement in quasi-one-dimensional semiconductor nanostructures or nanowires. A similar effect is observed in semimetal nanowires for sufficiently small wire diameters: A bandgap is induced, and the semimetal nanowire becomes a semiconductor. We demonstrate that on the length scale on which the semimetal-semiconductor transition occurs, this enables the use of bandgap engineering to form a field-effect transistor near atomic dimensions and eliminates the need for doping in the transistor's source, channel, or drain. By removing the requirement to supply free carriers by introducing dopant impurities, quantum confinement allows for a materials engineering to overcome the primary obstacle to fabricating sub-5 nm transistors, enabling aggressive scaling to near atomic limits. 相似文献
83.
利用激光烧结技术制备316不锈钢/MCrAlY复合多孔金属材料。利用扫描电镜及轮廓仪表征了激光烧结试样的形貌, 研究了在激光作用下聚苯乙烯空心球造孔剂的造孔机制。同时对烧结试样的力学性能及高温抗氧化性能进行了测试。结果表明: 成形孔洞平均分布在20 μm左右, 孔隙率为61%, 孔洞与孔洞之间有序的排布, 孔壁之间连接较好, 贯通性良好, 聚苯乙烯空心球造孔剂起到了重要的作用。烧结试样压缩强度达到4.78 MPa; 在900℃下氧化50 h增重仅为3.49 mg/cm2。 相似文献
84.
借助于结构导向集总方法,建立了延迟焦化过程的分子动力学模型。该模型用7004种分子集总来代表原料渣油的分子组成,用92条反应规则来模拟延迟焦化反应行为,实现了对延迟焦化产物分布的预测。经小试试验验证,该模型的预测精度较高。 相似文献
85.
Alice Ying Jörg Reimann Lorenzo Boccaccini Mikio Enoeda Marc Kamlah Regina Knitter Yixiang Gan Jaap G. van der Laan Lida Magielsen P.A. Di Maio G. Dell’Orco Ratna Kumar Annabattula Jon T. Van Lew Hisashi Tanigawa Sander van Til 《Fusion Engineering and Design》2012,87(7-8):1130-1137
Among the international fusion solid breeder blanket community, there exists steady progress on the experimental, phenomenological, and numerical characterizations of the pebble bed effective thermo physical and mechanical properties, and of thermomechanic state of the bed under prototypical operating conditions. This paper summarizes recent achievements in pebble bed thermomechanics that were carried out by members of the IEA Fusion Nuclear Technology Subtask I Solid Breeding Blanket. A major goal is on developing predictive capability while identifying a pre-conditioned equilibrium stress state that would warrant pebble bed integrity during operations. The paper reviews and synthesizes existing computational modeling approaches for pebble bed thermomechanics prediction, and differentiating points of convergence/divergence among existing approaches. The progress toward modeling benchmark is also discussed. These advancements have led to a framework to help navigate future research. 相似文献
86.
Aluminum 7075 is a functional aerospace alloy that has high strength and low formability during room temperature deep drawing. Therefore, to avoid warm forming process and relative difficulties, careful control in the process design is needed to enhance quality of drawn part and improve die life. In the present work, an attempt was made to experimentally and numerically study the effect of hydrodynamic deep drawing process such as die geometry and fluid pressure on thinning ratio and punch force. Statistical analysis based on response surface methodology was carried out to correlate empirical relationship between die corner radius, punch corner radius and die fluid pressure as process factors and maximum thinning ratio and punch force as responses. Sensitivity analysis was also performed to find out the factor having greatest impact on aforementioned responses. Further, optimization was carried out by using desirability approach to find out optimal parameter setting to attain minimum thinning and forming force simultaneously. Results indicated that punch and die corner radius followed by fluid had significant effect on the process quality characteristics. Moreover, setting of 9.3 mm punch corner radius, 2 mm die corner radius and 26 MPa fluid pressure resulted in 71% desirability incorporating 31% thinning and 175 MPa punch force. The obtained optimal results were then verified through both FE simulation and confirmatory experiment. 相似文献
87.
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89.
Urea–formaldehyde (UF) capsules were synthesized in micro and nano sizes, containing linseed oil (LO). The micro- and nanocapsules were incorporated through epoxy coatings and the coatings were applied on C-steel panels. Then the self-healing performance of the coatings was investigated. The corrosion resistance, adhesion strength and its retaining after immersion of nanocapsule incorporated coatings were compared with the optimum microcapsule incorporated ones. 相似文献
90.
采用22个结构向量描述渣油分子,构建了7 004种渣油分子集总,结合模拟退火算法提出了一种模拟计算渣油分子组成的方法。制定了92条反应规则用以描述渣油延迟焦化分子反应行为。在对工业延迟焦化工艺进行一定程度简化和假设的基础上,建立了一个用以预测延迟焦化产物分布的结构导向集总模型。通过模型预测结果和小试试验结果对比发现,该模型在不同延迟焦化工艺条件下对不同原料得到的产物分布均具有较好的预测可靠性。利用该模型计算了不同原料渣油掺炼以及渣油掺炼回收废道路沥青共焦化对延迟焦化液体收率的影响。计算结果表明:这两种方案都能有效提高延迟焦化液体收率。计算结果经小型试验得到了证实。 相似文献