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为了将高纯锗(HPGe)探测器用于快定时的物理实验中,本实验研究厂影响高纯锗探测器定时谱仪时间性能的各种因素,找出了获得谱仪最小时间分辨的各种最佳参数。并建立了分辨时间为4.19ns,能量分辨率为20keV,微分非线性好于±2.0%,计效率可承受120×10 ̄3s ̄(-1)的时间微分扰动角关联谱仪。利用此谱仪,以 ̄(204)Bi为探针核,研究了Bi系高温超导的微观机理,取得了较好的结果。 相似文献
23.
本文介绍的接杆锚杆护顶技术和上向眼大孔距多排微差爆破落矿技术,解决了逐昌金矿全面留矿法采矿工艺中存在的采场顶盘围在面积冒落和采场落矿爆破效果差、效率低这两个问题。 相似文献
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The electron spin resonance (ESR) spectra of end‐group spin labelled poly(ethylene oxide) (SLPEO) using 2,2,6,6‐tetramethyl‐piperdine‐1‐oxyl nitroxide and its blends with poly(styrene‐co‐4‐vinylphenol) (STVPhs) of different hydroxyl contents were recorded over a wide temperature range. For a blend of SLPEO and pure polystyrene (PS), the ESR spectrum was composed of a single motion component, indicating that PS was immiscible with PEO. For blends composed of SLPEO and different‐hydroxyl‐content STVPhs, two spectral components with different motion rates were observed over a certain temperature range. The difference between the motion rates should be attributed to micro‐heterogeneity in the blends, with the faster rate corresponding to a nitroxide radical motion trapped in the PEO‐rich domain and the slower rate corresponding to a nitroxide radical motion trapped in the STVPh‐rich domain. Variations in the values of a number of the ESR parameters (Ta, Td and T50G) and the apparent activation energy (Ea) with hydroxyl content in the blends indicated that the miscibility of the blends increased with increasing hydrogen‐bonding density due to specific interactions between the hydroxyl groups in STVPh and the ether oxygens in PEO. Copyright © 2004 Society of Chemical Industry 相似文献
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Yanhan Shen Rongrong Qi Qiaochu Liu Yanling Wang Yapeng Mao Juan Yu 《应用聚合物科学杂志》2008,110(4):2261-2266
The grafting of a polymer can lead to the improvement and modification of the polymer and thus expand its applications. Grafting methods include solution grafting in organic solvents, melt grafting at high temperatures, and light grafting with radioactive sources. These methods have their advantages and disadvantages. The disadvantages include waste treatment, consumption of energy, and so on. In this study, a hydrothermal process which is called the green approach, was developed to prepare graft copolymers. The effect of various factors on the grafting degree was investigated in detail. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
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Novel calix[4]arene‐poly(ethylene glycol) crosslinked polymer (CCP) has been synthesized by the polycondensation reaction between a p‐tert‐butylcalix[4]arene derivative and dihydroxyl capped poly(ethylene glycol) (DHPEG, Mn = 1000) catalyzed by neodymium tosylate. The hydrogel, consisted of 66.9% water and 33.1% CCP, can selectively extract aromatic organic molecules from aqueous solution according to the diameter of the guest molecules, which infers that the diameter of the calix[4]arene cavity is about 5.4 Å and the conformation of calix[4]arene units altered from cone conformation to 1,3‐alternate conformation during the polycondensation reaction. Furthermore, CCP can also adsorb naphthalene from gas phase, showing much higher capacity than active carbon does, which may have some potential applications in the field of separation and environment protection. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
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ROI-based Watermarking Scheme for JPEG 2000 总被引:1,自引:0,他引:1
Yu-Cheng Fan Arvin Chiang Jan-Hung Shen 《Circuits, Systems, and Signal Processing》2008,27(5):763-774
A new region of interest (ROI)-based watermarking method for JPEG 2000 is presented. The watermark is embedded into the host
image based on the characteristics of the ROI to protect rights to the images. This scheme integrates the watermarking process
with JPEG 2000 compression procedures. Experimental results have demonstrated that the proposed watermark technique successfully
survives JPEG 2000 compression, progressive transmission, and principal attacks. 相似文献
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