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81.
82.
一个正在建设的位于韩国Y2L地下实验室的低能暗物质探测实验中, 采用了CsI(Tl)晶体反符合探测器作为主动屏蔽体. 本工作对CsI(Tl)晶体反符合探测器的实验性能进行了研究. 通过FADC系统记录的脉冲波形数据, 研究了探测器的能量分辨率和波形甄别的能力; 研究相同能量γ射线入射到反符合探测器不同位置的相对光输出将有助于选择探测器的工作参数; 为了解晶体自身放射性对暗物质测量的影响, 利用低本底HPGe探测器对CsI(Tl)晶体内部的放射性进行了测量, 得到晶体内部Cs同位素的放射性活度. 探测器系统进行了约18d的试运行取数. 实验数据表明, CsI(Tl)晶体探测器的反符合效率约为31% HPGe探测器的本底计数率水平约为133cpd. 为了进行暗物质探测研究, 需要采取有效的方法进一步降低探测器的本底水平. 相似文献
83.
可紫外光固化的聚乙烯基硅氮烷合成与表征 总被引:1,自引:0,他引:1
采用带丙烯酸酯基团的烯丙基溴化合物(4-溴丁烯酸乙酯)和聚乙烯基硅氮烷发生取代反应,实现了丙烯酸酯基团在聚乙烯基硅氮烷主链上的链接.采用质子核磁共振谱(1H-NMR)和二维质子核磁共振谱(2D-1H-1H-NMR)对分子结构进行了表征,采用光学差热分析仪(Photo-DSC)和傅立叶转换红外光谱仪(FT-IR)测试了改性高分子的光敏性能,用热重分析仪(TGA)分析了产物在高纯氮气氛围下的陶瓷收率.结果表明,通过分子改性,交联固化时间从改性前的20min减少到1min之内,功能化的聚乙烯基硅氮烷可以在光刻蚀工艺中作为负性光刻胶使用. 相似文献
84.
ESTIMATES OF LOWER CRITICAL MAGNETIC FIELD AND VORTEX PINNING BY INHOMOGENEITIES IN TYPE Ⅱ SUPERCONDUCTORS 下载免费PDF全文
The effect of an applied magnetic field on an inhomogeneous superconductor is studied and the value of the lower critical magnetic field Hc1 at which superconducting vortices appear is estimated. In addition, the authors locate the vortices of local minimizers, which depends on the inhomogeneous term a(x). 相似文献
85.
We prove the Bochner–Schwartz type theorem for conditionally positive definite Fourier hyperfunctions which generalizes the result of Gelfand-Vilenkin in their treatise Generalized functions, vol. IV for distributions. 相似文献
86.
87.
I. KIM 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(2):293-304
ABSTRACT Sequential NMR-scale reactions have been carried out in order to generate cationic methylzirconium complexes by the reaction of rac-(EBI)Zr(NMe2)2 (rac- 1 , EBI = Et(indenyl)2) with methylaluminoxane (MAO) or various anionic compounds. By reacting 40 equiv. of MAO with rac- 1 in an NMR tube containing CD 2CI2 as a solvent at room temperature, rac- 1 is completely activated to give stable cationic methylzirconium complexes, [(EBI)ZrMe]+[MAO]? which polymerize propylene to isotactic polypropylene (iPP). The formation of the cationic species is achieved after rac- 1 is methylated to form rac-(EBI)ZrMe2 (rac- 2 ) by MAO and/or free Al2Me6 contained in MAO. The same sequential reaction has been performed by using rac(EBI)ZrCl2 (rac- 3 ) for the comparison. MAO cannot generate the cationic species at the same reaction conditions in the reaction of rac- 3 and MAO, mainly due to the difficulties of methylation of rac- 3. Ansa ziconocene amide rac- 1 is stoichiometrically methylated by 2 equiv. of Al2Me6 to give rac- 2. Introduction of 1 equiv. of noncoordinating to the solution mixture of rac- 1 and 2 equiv. of Al2Me6 leads to the formation of stable cationic methylzirconium species, [rac-(EBI)Zr(μ-Me)2AlMe2]+. NMR-scale polymerizations have been carried out by adding a small amount of liquid propylene to these cationic species. The meso pentad values of iPP isolated in these polymerizations are in the range of 80.2–84.7%. By changing the order of sequential reaction, i.e., by reacting rac- 1 with noncoordinating anions prior to methylation by Al2Me6, the yield to give cationic methylzirconium species is decreased. Coordinative anions such as [HNMe2Ph][BPh4] and [HNBu3][BP4] are less effective for the generation of the active zirconium cations than noncoordinating anions. The amount of MAO needed to activate rac- 1 can be decreased by the pre-methylation of rac- 1 by Al2Me6. 相似文献
88.
Hyun Jung KIM Kwang Ho KIM Seung Hwan YEOM Min Kee KIM Jae Geul SHIM Hyun Woo LIM Min Won LEE 《中国化学快报》2005,16(10):1337-1340
A new diarylheptanoid glycoside, 1,7-bis-(3,4-dihydroxyphenyl)-5-hydroxyheptane- 3-O-β-D-xylopyranoside (1), together with nine known diarylheptanoids (2-10) were isolated from the fresh bark of Alnus japonica which is a species of the genus Alnus species, growing throughout Korea. 相似文献
89.
ANALYSIS OF SOUND TRANSMISSION THROUGH PERIODICALLY STIFFENED PANELS BY SPACE-HARMONIC EXPANSION METHOD 总被引:1,自引:0,他引:1
J.-H. LEEJ. KIM 《Journal of sound and vibration》2002,251(2):349-366
An analysis method is developed to study sound transmission characteristics of a thin plate stiffened by equally spaced line stiffeners. The dynamic equation that describes the vibro-acoustic response of the system is derived by expanding the structural and acoustic responses in terms of the space harmonics and by using the virtual energy method. The series solution can be considered as the exact solution because the structural and acoustic-structural coupling effects in the system are fully considered and the solution converges. Parameter studies are conducted for major design parameters to understand the characteristics of the system. 相似文献
90.
H.-Y. KIM 《Journal of sound and vibration》2003,259(5):1131-1146
This work aims to establish a vibration-based damage identification method for fiber-reinforced laminated composites and their sandwich construction. This new on-line structural damage identification technique uses the structural dynamic system reconstruction method exploiting the frequency response functions (FRFs) of a damaged structure. To verify the effectiveness of this damage identification method, the frequency responses obtained by vibration testing of fatigue-damaged laminated composites and honeycomb sandwich beams with debonding are examined according to the extent of the damage via the fatigue-damage load cycle for laminated composites, and via the debonding extent for honeycomb sandwich beams. The changes of the peaks and valley of the FRFs according to the debonding extent and the fatigue load cycles are examined, and the area changes in the FRFs are also discussed as the damage index. The residual FRFs or the difference between intact and damaged FRFs are newly defined for application of the on-line damage identification method. Finally, the delamination extent for the sandwich beams and the fatigue damage level for the laminated composites can be easily identified in terms of the changes in natural frequencies and damping ratios of the reconstructed FRFs for these damaged composite structures. 相似文献