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Open cell steel foams were successfully fabricated through the powder metallurgy route using urea granules as the water leachable space holder in the present study. The influence of different amounts of phosphorus (0, 0.5wt%, 1wt%, 2wt%, and 4wt%) was investigated on the cell morphology, porosity, microstructure of cell walls, and mechanical properties of steel foams. The cell morphology and microstructure of the cell walls were evaluated using an optical microscope equipped with image processing software and a scanning electron microscope equipped with an energy dispersive X-ray spectrometer. In addition, the compression tests were conducted on the steel foams using a universal testing machine. Based on microscopic images, the porous structure consists of spherical cells and irregularly shaped pores that are distributed in the cell walls. The results indicated that by increasing the phosphorus content, the porosity increases from 71.9% to 83.2%. The partially distributed ferrite and fine pearlite was observed in the microstructure of the cell walls, and α-Fe and Fe3P eutectic extended between the boundaries of agglomerated iron particles. Furthermore, elastic and long saw-toothed plateau regions were observed before fracture in the compressional stress–strain curves. According to the results, by increasing the phosphorus content from 0 to 4wt%, the plateau region of the stress–strain curves shifts to the right and upward. Therefore, increasing phosphorus content causes improvement in the mechanical properties of steel foams. 相似文献
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Cooper GM Coe BP Girirajan S Rosenfeld JA Vu TH Baker C Williams C Stalker H Hamid R Hannig V Abdel-Hamid H Bader P McCracken E Niyazov D Leppig K Thiese H Hummel M Alexander N Gorski J Kussmann J Shashi V Johnson K Rehder C Ballif BC Shaffer LG Eichler EE 《Nature genetics》2011,43(9):838-846
To understand the genetic heterogeneity underlying developmental delay, we compared copy number variants (CNVs) in 15,767 children with intellectual disability and various congenital defects (cases) to CNVs in 8,329 unaffected adult controls. We estimate that ~14.2% of disease in these children is caused by CNVs >400 kb. We observed a greater enrichment of CNVs in individuals with craniofacial anomalies and cardiovascular defects compared to those with epilepsy or autism. We identified 59 pathogenic CNVs, including 14 new or previously weakly supported candidates, refined the critical interval for several genomic disorders, such as the 17q21.31 microdeletion syndrome, and identified 940 candidate dosage-sensitive genes. We also developed methods to opportunistically discover small, disruptive CNVs within the large and growing diagnostic array datasets. This evolving CNV morbidity map, combined with exome and genome sequencing, will be critical for deciphering the genetic basis of developmental delay, intellectual disability and autism spectrum disorders. 相似文献
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Effects of copper content on the shell characteristics of hollow steel spheres manufactured using an advanced powder metallurgy technique 下载免费PDF全文
Metallic hollow spheres are used as base materials in the manufacture of hollow sphere structures and metallic foams. In this study, steel hollow spheres were successfully manufactured using an advanced powder metallurgy technique. The spheres’ shells were characterized by optical microscopy in conjunction with microstructural image analysis software, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The microscopic evaluations revealed that the shells consist of sintered iron powder, sintered copper powder, sodium silicate, and porosity regions. In addition, the effects of copper content on various parameters such as shell defects, microcracks, thickness, and porosities were investigated. The results indicated that increasing the copper content results in decreases in the surface fraction of shell porosities and the number of microcracks and an increase in shell thickness. 相似文献
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Yajing Lei Wenhui Liu Lizheng Fang Muhammad Sajid Hamid Akash Kanwal Rehman Hua Narenmandura Weixing Shi Weixian Lu Yingchun Xu Shuqing Chen 《科学通报(英文版)》2014,59(13):1386-1391
Environmental tobacco smoke (ETS) is a well- known reason of many adverse health consequences in pregnant women. Exposure of ETS during pregnancy may increase the risk of some fetal diseases in pregnant women and/or birth defects in neonates. Many countries have implemented laws to control smoking and free of second hand smoke in all enclosed workplaces. In China, anti- smoking law was enforced in March 2010. We aimed to assess the exposure of pregnant women to cotinine after anti-smoking law was implemented in China. The urine samples were collected from 2,100 volunteers from Zhejiang Province, China and urinary concentration of cotinine was measured using gas chromatography and mass spectrometry. Cotinine was detected in 87 % of the pregnant women. The GM and 95th percentile concentration in pregnant women were 4.28 and 44.00 μg/L, respectively. Similarly, the GM and 95th concentration of cotinine were significantly higher in smoking group than in non-smoking group (P 〈 0.0001). Our results indicate that pregnant women in China are at the high risk of exposure ETS. Further attempts are required to make strategies to find out the sources of ETS exposure and prevent smoking at public places especially during pregnancy. 相似文献
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提出了一种形式方法用于验证TLM-2.0的设计方案.该方法中TLM-2.0设计方案将被转换成定时自动机形式模型.定义若干种属性,验证将根据这些属性执行,并引入一种模拟事务级设计方案差错的故障模型来评估这些属性.然后这些属性通过使用形式UPPAAL验证工具在系统的定时自动机表示上针对这些故障被验证.最后通过一个实例研究说明该方法的有效性. 相似文献