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泡沫金属——高分子聚合物的复合体机械阻尼性能研究 总被引:8,自引:1,他引:8
本文研究了泡沫金属和同分子聚合物形成的复合体机械阻尼性能,结果表明它是一种内耗值Q^-1极高的阻尼材料,其阻尼特征表现为与应变振幅密切相关而与频率无显著关系的非线性内耗。同时研究了泡沫金属孔隙结构对复合体内耗值的影响关系,并对实验结果进行了讨论。 相似文献
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用X射线漫散射研究了中子辐照GaAs中的缺陷,结果表明:中子辐照产生点缺陷团,辐照剂量为10^19m^-2和10^21m^-2时,缺陷团的平均半径分别为387nm和455nm,这可能高剂量辐照下损伤区域交叠的结果,平均半径随退火温度的升高而减小是间隙原子与空位复合造成的。 相似文献
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OH^—和氧离子杂质在BaF2晶体辐照损伤的影响 总被引:2,自引:1,他引:1
从理论和实验两方面研究OH^-和氧离子杂质为BaF2晶体辐照损伤的影响,并对其机理进行讨论,理论上用HFS-DVM-Xα)局域密度离散变分法计算OH^-和氧离子杂质心在BaF2中的电子结构,得到OH^-,Hs^-(U心),Os^-,Os^2-和(Os^2--F^+)都可能是引起辐照损伤的源泉。实验发现,BaF2晶体水解处理后,OH^-和氧离子杂质很容易进入BaF2,在晶体中的存在形式主要是:OH^ 相似文献
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在空间质子辐照下甲基硅橡胶的破坏模型 总被引:2,自引:0,他引:2
利用空间辐照环境地面模拟设备研究了质子辐照对甲基硅橡胶的破坏,建立了甲基硅橡胶的破坏模型.结果表明,在辐照能量为180 keV,辐照剂量为1016cm-2的条件下,被质子辐照后,硅橡胶生成CH3SiOCH3气体产物;量子化学计算表明,在H 直接进攻硅橡胶高分子链中的O导致高分子链断裂的过程中要放热655.34 kJ/mol,是唯一的放热反应通道.这一过程不会形成稳定的过渡态和中间体,而是直接形成断键产物.计算结果与质子辐照生成的气体产物CH3SiOCH3一致. 相似文献
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为探讨空间高能质子模拟试验方法,用基于蒙特卡罗方法的SRIM程序计算了质子在石英玻璃基银膜反射镜中的射程和能量损失分布,试验研究了不同能量质子辐照对反射镜光学性能的影响.能量低于160keV时,50%以上的质子能量损失在表面膜中,随着能量的增大,质子在膜系中的能量损失逐渐减小;在1016/cm2注量条件下,100keV质子辐照引起350~500nm波段反射率明显下降,而0.5MeV和1MeV质子辐照对光谱的影响很小;计算与试验结果表明,低能质子辐照对反射镜的膜系损伤起主要作用,在进行空间质子辐照模拟试验时,能量选取应低于200keV. 相似文献
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紫外辐照聚丙烯与绢英粉共混增容作用的研究 总被引:4,自引:0,他引:4
聚丙烯在室温,空气下,通过低能,短时间的紫外光辐照,在其分子链上引入了含氧的极限基团,通过DSC,TG,DMTA等的测试分析发现,经过紫外辐照的聚丙烯在聚丙烯/绢英粉填充体系中具有增容作用。紫外辐照聚丙烯填充体系的结晶度下降,热稳定性提高,动态内耗下降,内耗峰移向高温,绢英粉在紫外辐照聚丙烯基体中的均匀分布,而在未辐照的聚丙烯基体中,明显可见分散不均匀的绢英粉颗粒。 相似文献
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PMN—PNN—PZ—PT四元系铁电陶瓷的电疲劳特性 总被引:2,自引:1,他引:1
本文研究了PMN-PNN-PZ-PT四元系铁电陶瓷的电疲劳特性。在反复的交变电场作用下,经过约10^7 ̄10^8次循环后,材料的极化强度减小,而矫顽场强也减小。但经过一段时间的放置的,材料疲劳的性能逐渐恢复。这种现象与通常我电陶瓷疲劳特性不同,可能的疲劳机制是电荷的钉轧。 相似文献
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《工程(英文)》2017,3(4):504-511
The stability of pump-turbines is of great importance to the operation of pumped storage power (PSP) stations. Both hydraulic instabilities and operational instabilities have been reported in PSP stations in China. In order to provide a reference to the engineers and scientists working on pump-turbines, this paper summarizes the hydraulic instabilities and performance characteristics that promote the operational instabilities encountered in pump-turbine operations in China. Definitions, analytical methods, numerical and experimental studies, and main results are clarified. Precautions and countermeasures are also provided based on a literature review. The gaps between present studies and the need for engineering practice are pointed out. 相似文献
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Chinedu Nweke Erika Martin Todd Gehr Donald Brophy Daniel Carl 《Hemodialysis international. International Symposium on Home Hemodialysis》2015,19(2):323-329
Arteriovenous graft (AVG) thrombosis is a frequent cause of graft failure. We evaluated coagulation protein concentrations, platelet function, and viscoelasticity factors in 20 hemodialysis (HD) patients with AVGs. The goal was to determine whether significant differences in protein concentrations, platelet function, and viscoelasticity factors exist among dialysis patients requiring frequent AVG declot procedures vs. those who do not. Twenty HD patients were enrolled: 10 frequent clotters (>3 declots in the previous year) and 10 were nonclotters. Patients on antiplatelets or chronic anticoagulation were excluded. Laboratories were drawn pretreatment and heparinase was added to counteract any potential heparin effect. Coagulation protein concentrations including tissue factor (TF), thrombin/antithrombin III complex (TAT), and prothrombin fragment 1 + 2 (F1+2) were assayed. The time to clot onset was measured by force onset time (FOT). Platelet contractile force (PCF) measured the force produced by platelets during clot retraction, whereas clot rigidity was measured as clot elastic modulus (CEM). FOT, CEM, and PCF were measured by Hemodyne. Both groups had upregulation of the TF pathway, as TF, TAT, and F1+2 levels were similarly increased over baseline levels. Hemodialysis patients with frequent AVG clotting had higher levels of both PCF and CEM compared with nonclotters. Additionally, the frequent clotters had a lower FOT relative to nonclotters, although both were considered in the normal range. Our study suggests that HD patients with recurrent AVG thrombotic events form clots with higher tensile strength compared with HD patients without recurrent graft thrombosis. 相似文献
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Ward Vanlaar Robyn Robertson Kyla Marcoux Daniel Mayhew Steve Brown Paul Boase 《Accident; analysis and prevention》2012
While a general decreasing trend in the number of persons killed in a traffic crash involving a drinking driver has occurred in Canada since the 1980s, it is evident that much of this decrease occurred in the 1990s. Since 2002, less progress has been made as the number of persons killed in crashes involving drinking drivers remains high. To better understand the current situation, this paper describes trends in drinking and driving in Canada from 1998 to 2011 using multiple indicators based on data collected for the Traffic Injury Research Foundation's (TIRF) Road Safety Monitor (RSM), the National Opinion Poll on Drinking and Driving, and trends in alcohol-related crashes based on data collected for TIRF's national Fatality Database in Canada. There has been a continued and consistent decrease in the number of fatalities involving a drinking driver in Canada. This remains true when looking at the number of fatalities involving a drinking driver per 100,000 population and per 100,000 licensed drivers. This decreasing trend is also still apparent when considering the percentage of persons killed in a traffic crash in Canada involving a drinking driver although less pronounced. Data from the RSM further show that the percentage of those who reported driving after they thought they were over the legal limit has also declined. However, regardless of the apparent decreasing trend in drinking driving fatalities and behaviour, reductions have been relatively modest, and fatalities in crashes involving drivers who have consumed alcohol remain high at unacceptable levels. 相似文献
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Kamlesh Goel 《Scientometrics》2002,55(2):243-258
An analysis of gender differences in psychology in India provides quantitative and qualitative assessment of R&D output contributed by psychologists with the indication of the trend of growth, skewness, relatedness, co-authorship pattern of productivity. 相似文献
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References: 《中国标准化(英文版)》2007,(3):22-27
China has begun its standardization process in the cultural heritage since 1960.The standards contributed a lot to the development of the heritage conservation practices. In this paper, the author summaries the existing condition of standardization in the cultural heritages and museums field in China, and presents Standards for the Classification of Collected Cultural Heritages. Also this paper points out the problems which exist in the standardization in the cultural heritage, and gives the advice to solve these problems. 相似文献