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61.
铸膜液的溶剂体系(溶剂和非溶剂)对不对称膜形态的形成有重要作用。为了探索溶剂和透气性间的关系,本文考虑到了制备BCA梯度密度不对称膜的各种溶剂的一系列物理参数,得到了一些定性结果,并指出了更全面、明确、解释两者关系的研究方向。 相似文献
62.
本文简要介绍了军用光电侦察装备在现代军事侦察中的作用和地位,几种主要军用光电侦察装备的发展趋势,提出了应该采取的技术对策和重点研究的课题。 相似文献
63.
低密度聚乙烯光引发交联机理——Ⅱ.BNB自旋捕捉ESR研究 总被引:2,自引:4,他引:2
在光引发剂二苯甲酮(BP)存在下,紫外光辐照低密度聚乙烯(LDPE)所形成的自由基中间体已被自旋捕捉剂2,4,6-三特丁基亚硝基苯(BNB)所捕捉,其自旋加合物自由基已为电子自旋共振(ESR)所特征。现已检测和鉴定到二种自旋加合物:一种是叔碳自由基;另一种是仲碳自由基。它们分别是由BP的激发三重态从LDPE链的支化点和亚甲基团上夺氢所形成的自由基中间体同自旋捕捉剂BNB反应生成的。上述的证据表明:LDPE的光引发交联点主要发生在叔碳和仲碳原子上,且H-型交联点占主导地位。 相似文献
64.
Time‐resolved coherent anti‐Stokes Raman scattering (CARS) impulsively excited by a supercontinuum (SC) is investigated. We show that it is critical to optimize the temporal overlapping of the constituent solitons of a SC in order to impulsively excite vibrational modes over a broad frequency range. The cross‐correlation frequency‐resolved optical gating technique is utilized to retrieve the optical response function of molecules under SC impulsive excitation, and background‐free CARS with spectral resolution significantly better than the bandwidth of the probe pulses is achieved. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
65.
XiGuang Cao Xun Chen YunHua Chen XiangYi Cui DeQing Fang ChangBo Fu Karl L. Giboni HaoWei Gong GuoDong Guo Ming He Jie Hu XingTao Huang XiangDong Ji YongLin Ju ShaoLi Li Qing Lin HuaXuan Liu JiangLai Liu Xiang Liu Wolfgang Lorenzon YuGang Ma YaJun Mao KaiXuan Ni Kirill Pushkin XiangXiang Ren Michael Schubnell ManBing Shen YuJie Shi Scott Stephenson AnDi Tan Greg Tarlé HongWei Wang JiMing Wang Meng Wang XuMing Wang Zhou Wang YueHuan Wei ShiYong Wu MengJiao Xiao Xiang Xiao PengWei Xie Tao Ye YingHui You XiongHui Zen Hua Zhang Tao Zhang HaiYing Zhao Li Zhao XiaoPeng Zhou ZhongHua Zhu 《中国科学:物理学 力学 天文学(英文版)》2014,57(8):1476-1494
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Nonlinear contrast imaging modes such as second harmonic imaging (HI) and subharmonic imaging (SHI) are increasingly important for clinical applications. However, the performance of currently available transducers for HI and SHI is significantly constrained by their limited bandwidth. To bypass this constraint, a novel transducer concept termed multi-frequency harmonic transducer arrays (MFHA's) has been designed and a preliminary evaluation has been conducted. The MFHA may ultimately be used for broadband contrast enhanced HI and SHI with high dynamic range and consists of three multi-element piezo-composite sub-arrays (A-C) constructed so the center frequencies are 4f(A) = 2f(B) = f(C) (specifically 2.5/5.0/10.0 MHz and 1.75/3.5/7.0 MHz). In principle this enables SHI by transmitting on sub-array C receiving on B and, similarly, from B to A as well as HI by transmitting on A receiving on B and, likewise, from B to C. Initially transmit and receive pressure levels of the arrays were measured with the elements of each sub-array wired in parallel. Following contrast administration, preliminary in vitro HI and SHI signal-to-noise ratios of up to 40 dB were obtained. In conclusion, initial design and in vitro characterization of two MFHA's have been performed. They have an overall broad frequency bandwidth of at least two octaves. Due to the special design of the array assembly, the SNR for HI and SHI was comparable to that of regular B-mode and better than commercially available HI systems. However, further research on multi-element MFHA's is required before their potential for in vivo nonlinear contrast imaging can be assessed. 相似文献
70.
A novel optical element, axilens, proposed by Davidson et al., for achieving extended focal length is introduced. We propose a method to design the binary axilens which has high diffraction efficiency. Using computer numerical simulation, we designed 4 axilenses each has different parameters. In this paper we present our results and make comparison with that in ref. [1]. The properties of binary axilens such as the focal depth, the lateral resolution and the intensity distribution along axis is discussed. 相似文献