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排序方式: 共有168条查询结果,搜索用时 31 毫秒
41.
Sung Won Youn Ho Kyun Kim Hong Tae Kim Sung Mi Han Jin Kuk Do Young Rok Do Hui Joong Lee Jongmin Lee Jae Hong Lim 《Journal of synchrotron radiation》2014,21(1):215-222
Phase‐contrast synchrotron X‐ray microtomography (pcSyncX) based on the highly coherent X‐ray beam has previously been used to visualize the microstructures of biologic specimens, but it has never been used to evaluate embolic debris adherent on a cerebral protection device (CPD). The purpose of this study was to demonstrate the feasibility of pcSyncX for evaluating embolic debris during carotid artery stenting (CAS). Five patients (four males, age range 67–77 years) with severe carotid artery stenosis underwent CAS. The retrieved CPD was exposed to synchrotron radiation and 1000 pcSyncX projection images were obtained by rotating the CPD through 180°. An X‐ray shadow of a CPD was converted into a visual image by the scintillator. After microtomographic reconstruction, the three‐dimensionally reconstructed images were further segmented into the embolic debris and CPD. The total volume of emboli was calculated by summing the volume at each scanning level. The number of membrane pores covered by emboli as seen from the outer surface was counted and the percentage of covered area was calculated. Embolic debris was clearly demonstrated not only on the inner surface and within pores but also on the outer surface of the CPD. The mean total volume of embolic debris was 0.538 × 10–6 mm3 (range 0.225–0.965 × 10–6 mm3). Most (61.5%) of the debris was located at the apical one‐third of the CPD and 20.8% of the pore area was covered by debris. 相似文献
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高温高密度等离子体辐射源产生脉冲X射线的同时还产生等离子体碎片,飞散速度分布在0.1~10km/s。研制电磁驱动超高速机械快门,有效通光孔径为40mm×50mm,利用45mm×60mm×100μm的铝膜作为快门叶片,在放电电压20kV、驱动电流80kA、放电周期18μs条件下,获得的快门关门时间小于180μs。将快门放置在距离等离子体X射线源2m处,X射线通过后在180μs时间内关闭光学通道,以阻挡高温高密度等离子体产生的碎片,保护X射线精密探测系统和样品,同时实现等离子体参数的精密测量。 相似文献
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安凯 《数学的实践与认识》2014,(18)
借助碎片云粒子对靶板的毁伤程度与粒子的速度成正比,与靶板的厚度成反比的理论和实验结果,提出一种用于评价航天器内部电子仪器设备遭受二次碎片粒子撞击毁伤程度的毁伤指标.针对六面体外壳的仪器设备,提出两种在航天器内部的安放姿态.通过计算这两种姿态毁伤指标的最大值,并与两个面与航天器速度垂直的安放姿态毁伤指标的最大值进行了比较,得到了当碎片粒子速度不超过航天器速度2倍时两种安放姿态毁伤指标至少分别降低9.76%和14.09%的结论.采用这两种安放姿态,既不改变仪器设备的设计,也不增加重量和体积,就能达到增强仪器设备防护性能的目的,对提高航天器在碎片环境中的生存能力具有重要意义. 相似文献
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对太空轨道碎片清理的商业运营模式和是否存在商机问题建模进行研究。首先,提出了太空轨道碎片清理公司的商业运营模式,即以清理公司、保险公司和卫星公司为主体的三位一体的系统运营模式;其次,给出私营清理公司商机的定义,通过对运营系统资金费用的分析,定量建立系统正常运营的保险公司最低保单价格和卫星公司最高保险价格求解的模型,并分析了模型的可计算性,给出了商机存在的条件以及商机大小的计算方法;最后,借助于清除效率,建立3种不同轨道碎片清除模式下清除成本的模型,给出了计算不同清除方式下保险公司最低保单价格和卫星公司最高保险价格的模型,验证了定义的商机是合理的并可计算的。 相似文献
46.
The analysis of fire debris evidence might offer crucial information to a forensic investigation, when for instance, there is suspicion of the intentional use of ignitable liquids to initiate a fire. Although the evidence analysis in the laboratory is mainly conducted by a handful of well-established methodologies, during the last eight years several authors proposed noteworthy improvements on these methodologies, suggesting new interesting approaches. This review critically outlines the most up-to-date and suitable tools for the analysis and interpretation of fire debris evidence. The survey about analytical tools covers works published in the 2008–2015 period. It includes sources of consensus-classified reference samples, current standard procedures, new proposals for sample extraction and analysis, and the most novel statistical tools. In addition, this review provides relevant knowledge on the distortion effects of the ignitable liquid chemical fingerprints, which have to be considered during interpretation of results. 相似文献
47.
Electrocatalytic Activities of Chemically Reduced Graphene Are Essentially Dominated by the Adhered Carbonaceous Debris 下载免费PDF全文
Xiaomeng Li Danyang Ma Prof. Liande Zhu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(48):17239-17244
Due to its simple, scalable, and facile qualities, the chemical reduction of graphene oxide seems to be the most popular approach to prepare graphene. We show that such prepared graphene is strongly adhered with carbonaceous debris that has been produced during the synthesis of graphene oxide by the chemical exfoliation of graphite and still remain on graphene sheets through the chemical reduction steps. Interestingly, the presence of the carbonaceous debris causes a significant impact on the electrochemical behavior of the chemical reduced graphene. Herein, we demonstrate that the electrocatalytical activities of the graphene are greatly boosted by the adhered carbonaceous debris. After the removal of the carbonaceous debris, the electrocatalysis of graphene is not superior to conventional graphite. 相似文献
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低地球轨道的各类航天器易受到微流星体及空间碎片的超高速撞击。这些撞击损伤航天器飞行的关键系统,进而导致航天器发生灾难性失效。为了保证航天员的安全及航天器的正常运行,微流星体及空间碎片防护结构设计是航天器设计的一个重要问题。采用AUTODYN软件进行了弹丸超高速正撞击及斜撞击防护屏所产生碎片云的SPH法数值模拟,给出了二维及三维模拟结果;研究了防护屏厚度、弹丸形状、撞击速度以及材料模型等对碎片云的影响。模拟结果同高质量实验研究的结果进行了比较,模拟的碎片云形状和碎片云特征点的速度同实验相吻合。验证了数值模拟方法的有效性。 相似文献