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991.
Yang Xiaoli Chen Nuofu Yin Zhigang Zhang Xingwang Li Yang You Jingbi Wang Yu Dong Jingjing Cui Min Gao Yun Huang Tianmao Chen Xiaofeng Wang Yanshuo 《半导体学报》2010,31(9)
Zinc oxide (ZnO) thin films were grown on n-GaN/sapphire substrates by radio-frequency (RF) magnetron sputtering. The films were grown at substrate temperatures ranging from 400 to 700 ℃ for 1 h at a RF power of 80 W in pure Ar gas ambient. The effect of the substrate temperature on the structural and optical properties of these films was investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and photoluminescence (PL) spectra. XRD results indicated that ZnO films exhibited wurtzite symmetry and c-axis orientation when grown epitaxially on n-GaN/sapphire. The best crystalline quality of the ZnO film is obtained at a growth temperature of 600 ℃. AFM results indicate that the growth mode and degree of epitaxy strongly depend on the substrate temperature. In PL measurement, the intensity of ultraviolet emission increased initially with the rise of the substrate temperature, and then decreased with the temperature. The highest UV intensity is obtained for the film grown at 600 ℃ with best crystallization. 相似文献
992.
A fast automatic power control (APC) circuit for a laser diode driver (LDD) has been implemented in a 0.6-μm BiCMOS process. The APC circuit adopts double-loops and variable-bandwidth techniques to achieve a turn-on time of < 400 μs for most kinds of TOSAs. Thus, it meets the small form-factor pluggable (SFP) agreement. Such techniques make a good tradeoffbetween stability, accuracy, turn-on time, noise and convenience. The measured results indicate that the APC circuit is suitable for SFP LDD. 相似文献
993.
可靠性较高的数据网格多采用双副本容灾可以保证节点在灾难发生时进行有效恢复,但由于节点数据存储量较大,当节点发生灾难时,从一个节点进行数据恢复速度较慢,导致在数据恢复期备份节点发生失效的概率较大。针对这些问题,本文给出一个容灾存储模型,基于该模型推导出一个数据失效模型,理论证明该失效模型的数据失效概率明显小于双副本容灾方式的数据失效概率,同时在灾难发生时又能达到较快的恢复速度。设计了仿真实验,将模型的数据失效概率与双副本失效概率进行了比较,实验结果与理论推导一致,证明了存储模型和数据失效模型的正确性和有效性。最后给出进一步研究思路。 相似文献
994.
水凝胶是最常用的生物材料之一。它们在化学和结构上的多样性使其能够在广泛的场景中使用,目前 水凝胶材料在生物医药领域主要用于药物输送、癌症治疗和伤口愈合等。聚合物网络是水凝胶的核心组成部分,赋予水凝胶最独特的功能和性质。在分子层面上可以控制水凝胶的连接方式和聚合物的网络结构。因此,在材料研发的初期,了解聚合物网络的连接方式、结构、功能和特性,选择合适的聚合物对于制备特定功能的水凝胶至关重要。本文首先概述了水凝胶的凝胶机理和影响凝胶的因素,在分子层面上可以控制聚合物网络的形成,从而制备临床上需要的水凝胶。最后介绍了水凝胶在临床医学上的应用,展望了水凝胶材料的未来发展趋势。 相似文献
995.
A least-squares (LS) method for identifying alias components of discrete linear periodically time-varying (LPTV) systems is proposed.The authors apply a periodic input signal to a finite impulse response (FIR)--LPTV system and measure the noise-contaminated output.The output of this LPTV system has the same period as the input when the period of the input signal is amultiple of the period of the LPTV system.The authors show that the input and the output can be related by using the discrete Fourier transform. In the frequency domain, an LS method can be used to identify the alias components. A lower bound on the mean square error (MSE) of the estimated alias components is given for FIR--LPTV systems.The optimal training signal achieving this lower MSE bound is designed subsequently. The algorithm is extended to the identification of infinite impulse response (IIR)--LPTV systems as well. Simulation results show the accuracy of the estimation and the efficiency of the optimal training signal design. 相似文献
996.
997.
Hong-Yan Zhu Xiang-Ying Meng Yong-Li Bao Chun-Lei Yu Yin Wu Yu-Xin Li 《Chromatographia》2010,71(7-8):617-622
A novel, simple and specific normal-phase liquid chromatography (NPLC) method has been developed for simultaneous determination of the four lathyrane diterpenoids, lathyrol-5,15-diacetate-3-benzoate (1, L3), lathyrol-5,15-diacetate-3,7-dibenzoate (2, L2), Δ6,17-epoxide-5,15-diacetate-3-phenylacetate (3, L1), lathyrol-5,15-diacetate-3-nicotinate (4, L8) in the hexane extract of the seeds of Euphorbia lathyris and “ZI-JIN-DING” pastille. The method showed good linearity for the four analytes (r 2 > 0.99), the intra-day and inter-day variations (RSD) were less than 3%, and the recoveries ranged from 99.4 to 100.6%. This method was successfully used to determine the four lathyrane diterpenoids in the seeds of Euphorbia lathyris and “ZI-JIN-DING” pastille, and could be applied for their quality control. 相似文献
998.
Lian-Hong Yin Li-Na Xu Xiao-Na Wang Bi-Nan Lu Yue-Tao Liu Jin-Yong Peng 《Chromatographia》2010,71(1-2):15-23
An economical method for isolation of dioscin from Dioscorea nipponica Makino by high-speed counter-current chromatography (HSCCC) was successfully developed by using a UNIFAC mathematical model coupled with computer-aided counter-current chromatography solvent-selection software (CCC-SSS) for separate preparation of the components of the solvent system (i.e., the stationary and mobile phases). The solvent system n-hexane–ethyl acetate–ethanol–water 2:5:2:5 (v/v) was selected to demonstrate the feasibility of the approach. A comparative study was also carried out on different methods for preparation of the solvent system, namely conventional preparation of the mobile and stationary phases together in the same vessel and the method developed for separate preparation of the phases. The results indicated that purity and recovery of dioscin were no different when solvent systems prepared by the different methods were used for HSCCC separation. Much less n-hexane, ethyl acetate, and ethanol was used when the mobile and stationary phases were prepared separately, however. This was not only environmentally sensible, but also enabled conservation of resources. Use of the UNIFAC mathematical model combined with the CCC-SSS technique for separate preparation of the components of the solvent system in HSCCC is reported and explained. It is a simple and economical means of isolating pure dioscin from Dioscorea nipponica Makino. 相似文献
999.
Shipeng Sun Li Dong Jianhua Guo Zhenming Yin 《Journal of chemical crystallography》2010,40(12):1142-1145
Abstract
A new compound, 1,3-bis[2-(pyrrol-2-carbonyloxy)ethoxy]benzene (1), was synthesized and characterized by X-ray diffraction. The crystal is monoclinic, space group P21/c with a = 6.3571(7), b = 11.0416(11), c = 28.156(3) ?, b = 92.821(2), V = 1974.0(4) ?3, Z = 4, Dc = 1.293 g/cm3, F(000) = 808, μ = 0.097 mm−1. The final R = 0.0395 and wR = 0.0927 for 3478 observed reflections with I > 2 σ(I), and R = 0.0660 and wR = 0.1058 for all reflections. The title compound assembles into 2-D structure through a catemer type N–H⋯O hydrogen bonding motif and further forms 3-D structure through C–H···O hydrogen bonds. 相似文献1000.