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151.
H.264视频编解码标准的算法复杂度高,不能满足视频监控和无线传输中要求的高压缩比、低码率和实时性的要求,通过分析可知运算量最大的是运动估计模块,本文对该模块的算法进行优化。在ARPS算法的基础上结合预测的初始点和自适应调节臂长的搜索策略的优点,采用可变阈值的早期终止策略和简单的搜索模板的算法。实验表明该算法在有效减少搜索点数的情况下并不会对图像质量产生较大的影响,提高了运动估计算法的搜索速率和鲁棒性。 相似文献
152.
《Journal of the European Ceramic Society》2006,26(10-11):1957-1960
The structure evolution, sintering behavior and microwave dielectric properties of La(2−x)/3Nax(Mg1/2W1/2)O3 (x = 0–0.5) were investigated in this paper. The X-ray diffraction (XRD) results show that all samples exhibit single phase, and the structure changed from orthorhombic when 0 ≤ x < 0.3 to monoclinic phase when 0.3 ≤ x ≤ 0.5. The size and ordering degree of A/B-site domains decrease with the increase in x value. The sintering temperature of the Na-doped samples increased compared to the pure La2/3(Mg1/2W1/2)O3 (LMW) due to the estimated decrease in the concentration of A-site vacancies. The addition of Na+ ion does not affect the dielectric permittivity greatly. The Q × f value decreases with the increase in x value, although the estimated concentration of A-site vacancies decreases with increasing x, which may be ascribed to the decrease of A/B-site ordering and domain size with the increase in x. The temperature coefficient of resonant frequency changed from negative values into positive values with the increase in x value. 相似文献
153.
由氯化钙制备纳米碳酸钙研究 总被引:1,自引:0,他引:1
随着国民经济的发展,对纳米碳酸钙的需求量越来越大.基于化工生产中大量副产氯化钙,以氯化钙和碳酸铵为原料,对制备纳米碳酸钙进行了研究.实验研究了添加剂、反应温度和反应物浓度等工艺条件对产物粒径的影响,并采用XRD和TEM对产物进行了初步分析.实验结果表明:不同的添加剂对产物粒径以及形貌具有一定的影响,当氯化钙和碳酸铵配料比为1.0:1.0 mol/mol、反应温度为15℃和氯化钙浓度为0.3 mol/L时,以有机醇A和磷酸系化合物G为添加剂制备的产物为方解石型球状碳酸钙,粒径在50 nm左右. 相似文献
154.
We have observed, for the first time, that when the initial chain conformation changed from coil to globule, the association of linear poly(N-vinylcaprolactam-co-sodium acrylate) chains could gradually change from a reaction limited to diffusion limited process, reflected in a change of the fractal dimension of the resultant aggregates from ∼2.5 to ∼1.6. Such an influence of the initial chain conformation has been overlooked in past studies of the formation of the mesoglobule phase in a dilute heteropolymer solution. 相似文献
155.
By analyzing the extended X-ray absorption fine structure (EXAFS) of the Mo K-absorption edge, structural information for both oxidic and sulfided K-MoO3/-Al2O3 catalysts with different potassium content was obtained. The oxidic samples show two backscatterer peaks in the radial distribution function (RDF), which correspond to the Mo-O coordinations in the nearest Mo-O shell. The nearest oxygen atoms are present with large configurational disorder. The RDF for the K/Mo = 0 sample is significantly different from that for crystalline MoO3 and ammonium heptamolybdate. The RDFs for potassium promoted samples are, in some extent, similar to that for ammonium heptamolybdate. The sample with K/Mo = 0.8 and that with K/Mo=1.5 do not show obvious difference in their local Mo-O structures. The EXAFS results support the earlier conclusions from Raman spectroscopy studies on identical samples [7]. When the samples are sulfided, a rearrangement of the local neighbors around Mo atoms takes place, to form small MoS2-like crystallites. The Mo-S and Mo-Mo coordination distances on these catalysts are the same as those in crystalline MoS2, but the coordination numbers are significantly lower than in MoS2. The EXAFS results indicate that Mo species on the K/Mo=0 catalyst mainly consist of Mo-S-Mo units (the basic building units of MoS2), which are highly dispersed and show a higher level of disorder than in MoS2. With the modification by the potassium promoter, Mo species are significantly aggregated and their local neighbors are more similar to those in MoS2, but the Mo species still exist in a state of high dispersion. 相似文献
156.
为了准确评估堆场存储能力和合理选择疏浚泥处理工艺,以泥沙运动学为理论基础,将疏浚泥颗粒分为d0.005 mm、0.005 mm≤d≤0.01 mm和d0.01 mm 3个粒组,分析了各粒组相对含量的沿程变化规律,明确了堆场疏浚泥分选的主要原因是d0.01 mm粒组与0.005 mm≤d≤0.01 mm粒组的相对运动;以分选系数量化堆场疏浚泥分选的显著程度,以偏离系数量化原泥颗粒组成对堆场疏浚泥分选的影响,分析了分选系数、偏离系数分布与堆场疏浚泥土性分布的关系,提出了堆场疏浚泥分选特性的初步量化方法。研究结果表明:随着离吹填口距离的增大,分选系数沿程减小,呈幂函数分布,堆场疏浚泥分选性沿程减弱,吹填口附近分选系数最大,颗粒分选显著,粒度差异大,退水口附近分选系数趋近于零,分选不明显,颗粒分布均匀;偏离系数沿程先减小后增大,呈勺形分布,反映堆场前、后段疏浚泥土性与原泥相差较大,而堆场中段疏浚泥土性与原泥接近;分选系数、偏离系数的沿程分布与堆场疏浚泥土性分区具有良好的相关性。 相似文献
157.
158.
Image clustering methods are efficient tools for applications such as content-based image retrieval and image annotation. Recently, graph based manifold learning methods have shown promising performance in extracting features for image clustering. Typical manifold learning methods adopt appropriate neighborhood size to construct the neighborhood graph, which captures local geometry of data distribution. Because the density of data points’ distribution may be different in different regions of the manifold, a fixed neighborhood size may be inappropriate in building the manifold. In this paper, we propose a novel algorithm, named sparse patch alignment framework, for the embedding of data lying in multiple manifolds. Specifically, we assume that for each data point there exists a small neighborhood in which only the points that come from the same manifold lie approximately in a low-dimensional affine subspace. Based on the patch alignment framework, we propose an optimization strategy for constructing local patches, which adopt sparse representation to select a few neighbors of each data point that span a low-dimensional affine subspace passing near that point. After that, the whole alignment strategy is utilized to build the manifold. Experiments are conducted on four real-world datasets, and the results demonstrate the effectiveness of the proposed method. 相似文献
159.
Optimal performance of vehicle occupant restraint system (ORS) requires an accurate assessment of occupant injury values including head, neck and chest responses, etc. To provide a feasible framework for incorporating occupant injury characteristics into the ORS design schemes, this paper presents a reliability-based robust approach for the development of the ORS. The uncertainties of design variables are addressed and the general formulations of reliable and robust design are given in the optimization process. The ORS optimization is a highly nonlinear and large scale problem. In order to save the computational cost, an optimal sampling strategy is applied to generate sample points at the stage of design of experiment (DOE). Further, to efficiently obtain a robust approximation, the support vector regression (SVR) is suggested to construct the surrogate model in the vehicle ORS design process. The multiobjective particle swarm optimization (MPSO) algorithm is used for obtaining the Pareto optimal set with emphasis on resolving conflicting requirements from some of the objectives and the Monte Carlo simulation (MCS) method is applied to perform the reliability and robustness analysis. The differences of three different Pareto fronts of the deterministic, reliable and robust multiobjective optimization designs are compared and analyzed in this study. Finally, the reliability-based robust optimization result is verified by using sled system test. The result shows that the proposed reliability-based robust optimization design is efficient in solving ORS design optimization problems. 相似文献
160.
Users are inclined to share sensitive data in a remote server if no strong security mechanism is in place. Searchable encryption satisfies the need of users to execute a search encrypted data. Previous searchable encryption methods such as “public key encryption with keyword search (PEKS)” restricted the data access to certain users, because only the assigned users were able to search the encrypted data. In this paper we will discuss the relation between Attribute Based Encryption (ABE) and searchable encryption and define a weak anonymity of the ABE scheme, named “attribute privacy”. With this weak anonymity, we propose a general transformation from ABE to Attribute Based Encryption with Keyword Search (ABEKS) and a concrete attribute private key-policy ABE (KP-ABE) scheme. We present an ABEKS scheme based on this KP-ABE scheme and permit multi-users to execute a flexible search on the remote encrypted data. 相似文献