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991.
992.
鉴于用户对目前数据库接入技术要求的提高,一种基于XML技术对数据库接入进行优化的技术出现了。这种技术利用了基于XML传输时的可扩展、高度结构化等特性,在JavaBean,JDBC,Apache,Tomcat等设计组件及Linux体系结构的配合使用下.为用户提供了一个安全、高效、可扩展且访问灵活的数据库接入方式。 相似文献
993.
迭加与量化水印嵌入方案的比较及量化参数优化 总被引:3,自引:0,他引:3
分别研究了迭加法和量化法的隐蔽性和稳健性,并且提出了量化调制水印方案中的参数优化方法。对两类方法的分析比较表明,迭加法适用于在高频分量嵌入水印,而量化法适用于在低频分量嵌入水印。并以实验验证了这一结论。 相似文献
994.
With video compression standards such as MPEG‐4, a transmission error happens in a video‐packet basis, rather than in a macroblock basis. In this context, we propose a semantic error prioritization method that determines the size of a video packet based on the importance of its contents. A video packet length is made to be short for an important area such as a facial area in order to reduce the possibility of error accumulation. To facilitate the semantic error prioritization, an efficient hardware algorithm for face tracking is proposed. The increase of hardware complexity is minimal because a motion estimation engine is efficiently re‐used for face tracking. Experimental results demonstrate that the facial area is well protected with the proposed scheme. 相似文献
995.
胡志勇 《电子工业专用设备》2003,32(3):83-86
叙述了先进再流焊接技术的新发展,描述了提高BGA再流焊接效果的工艺要点,优化倒装芯片再流焊接和固化的新方法。最后,讲述了先进的降低氮消耗量的方法即:通过最大限度地提高潜在收益,以促进再流焊接技术的发展,以此来满足装配厂商的需要。 相似文献
996.
997.
This paper derives the admissible decompositions for a time series dynamic linear model, assuming only that the model is observable. The decompositions depend on factorizations of the characteristic polynomial of the state evolution matrix G into relatively prime factors. This generalizes the method of West (1997 ) which considers one decomposition in the particular case where G is diagonalizable. Conditions are derived for a decomposition to be independent. These results show that no autoregressive process of order d has an independent decomposition for any integer d . Two illustrations of this procedure are discussed in detail. 相似文献
998.
J.K.J. vanDuren X. Yang J. Loos C.W.T. Bulle‐Lieuwma A.B. Sieval J.C. Hummelen R.A.J. Janssen 《Advanced functional materials》2004,14(5):425-434
The performance of bulk‐heterojunction solar cells based on a phase‐separated mixture of donor and acceptor materials is known to be critically dependent on the morphology of the active layer. Here we use a combination of techniques to resolve the morphology of spin cast films of poly(p‐phenylene vinylene)/methanofullerene blends in three dimensions on a nanometer scale and relate the results to the performance of the corresponding solar cells. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and depth profiling using dynamic time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) clearly show that for the two materials used in this study, 1‐(3‐methoxycarbonyl)propyl‐1‐phenyl‐[6,6]‐methanofullerene (PCBM) and poly[2‐methoxy‐5‐(3′,7′‐dimethyloctyloxy)‐1,4‐phenylene vinylene] (MDMO‐PPV), phase separation is not observed up to 50 wt.‐% PCBM. Nanoscale phase separation throughout the film sets in for concentrations of more than 67 wt.‐% PCBM, to give domains of rather pure PCBM in a homogenous matrix of 50:50 wt.‐% MDMO‐PPV/PCBM. Electrical characterization, under illumination and in the dark, of the corresponding photovoltaic devices revealed a strong increase of power conversion efficiency when the phase‐separated network develops, with a sharp increase of the photocurrent and fill factor between 50 and 67 wt.‐% PCBM. As the phase separation sets in, enhanced electron transport and a reduction of bimolecular charge recombination provide the conditions for improved performance. The results are interpreted in terms of a model that proposes a hierarchical build up of two cooperative interpenetrating networks at different length scales. 相似文献
999.
N‐vinylcarbazole (NVC) was polymerized by 13X zeolite alone in melt (65°C) or in toluene (110°C) and a poly(N‐vinylcarbazole) (PNVC)‐13X composite was isolated. Composites of polypyrrole (PPY) and polyaniline(PANI) with 13X zeolite were prepared via polymerization of the respective monomers in the presence of dispersion of 13X zeolite in water (CuCl2 oxidant) and in CHCl3 (FeCl3 oxidant) at an ambient temperature. The composites were characterized by Fourier transform infrared analyses. Scanning electron microscopic analyses of various composites indicated the formation of lumpy aggregates of irregular sizes distinct from the morphology of unmodified 13X zeolite. X‐ray diffraction analysis revealed some typical differences between the various composites, depending upon the nature of the polymer incorporated. Thermogravimetric analyses revealed the stability order as: 13X‐zeolite > polymer‐13X‐zeolite > polymer. PNVC‐13X composite was essentially a nonconductor, while PPY‐13X and PANI‐13X composites showed direct current conductivity in the order of 10?4 S/cm in either system. However, the conductivity of PNVC‐ 13X composite could be improved to 10?5 and 10?6 S/cm by loading PPY and PANI, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 913–921, 2006 相似文献
1000.
Hot electrons emitted from thin oxide film-coated heavily doped silicon electrodes by cathodic pulse polarization can induce electrochemiluminescence from luminophores. The intensity of electrochemiluminescence produced at the electrode surface is dependent on the features of thin oxide films formed by thermal oxidation. As a preliminary study, we investigated the effect of thermal oxide growth conditions on the intensity of electrochemiluminescence produced at these electrodes, such as oxidation atmospheres, oxidation temperature, oxidation time and pre-treatment of wafers, using ruthenium(II) tris-(2,2′-bipyridine) chelate as a model luminophore. Optimal oxidation conditions of heavily doped silicon electrodes were obtained for the generation of intense electrochemiluminescence at this kind of silicon electrodes. 相似文献