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1.
Abstract. In this paper the problems of parameter estimation and order determination of an exponential (EX) model are studied in the time domain. In order to estimate the parameters, the parameter equations of an EX model are given in terms of the autocorrelation function, which is similar to the Yule-Walker equations of an autoregressive moving-average model. Estimates of parameters are obtained with the aid of the parameter equations and theorems are proved relating the convergence rate and asymptotic distribution of the estimates. We present two kinds of methods for estimating the order and prove that the estimates of the order are consistent. 相似文献
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Qiansheng Cheng Rong Chen Ta-Hsin Li 《Geoscience and Remote Sensing, IEEE Transactions on》1996,34(2):377-384
The problem of simultaneous wavelet estimation and deconvolution is investigated with a Bayesian approach under the assumption that the reflectivity obeys a Bernoulli-Gaussian distribution. Unknown quantities, including the seismic wavelet, the reflection sequence, and the statistical parameters of reflection sequence and noise are all treated as realizations of random variables endowed with suitable prior distributions. Instead of deterministic procedures that can be quite computationally burdensome, a simple Monte Carlo method, called Gibbs sampler, is employed to produce random samples iteratively from the joint posterior distribution of the unknowns. Modifications are made in the Gibbs sampler to overcome the ambiguity problems inherent in seismic deconvolution. Simple averages of the random samples are used to approximate the minimum mean-squared error (MMSE) estimates of the unknowns. Numerical examples are given to demonstrate the performance of the method 相似文献
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以柠檬酸和尿素分别为碳源和氮源,微波法合成含氮掺杂碳点N-CDs。以异氟尔酮二异氰酸酯(IPDI)、聚氧化丙烯(PPG-2000)为主要原料,加入不同量的N-CDs制备一系列碳点水性聚氨酯复合材料 (N-CDs/WPU)。通过FTIR、TEM、XPS、UV-vis、荧光光谱和力学性能测试等对复合材料结构和性能进行表征。测试结果表明N-CDs主要由碳氮氧元素组成,表面具有胺基、羟基等活性基团,N-CDs的加入,提高了复合胶膜的力学性能,赋予了胶膜荧光性能。当N-CDs质量分数为0.6%时胶膜拉伸强度达到最大35.00MPa,加入量质量分数为0.8%时荧光强度最佳。 相似文献
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钻井液处理剂及体系对聚合醇JLXI浊点的影响 总被引:5,自引:7,他引:5
聚合醇类水基防塌钻井液体系(简称 PEM)作为适应环境保护要求的一种新型钻井液体系应用越来越广泛。PEM 的核心处理剂为聚合醇类水基防塌润滑剂 JLX,JLX是一种非离子型低分子量聚合物,其作用机理是具有浊点特性。研究了钻井液体系及常用处理剂对两种聚合醇 JLX1 和JLX2 浊点的影响。实验结果表明,无机处理剂如 KCl 对 JLX浊点有显著的影响;而有机高分子处理剂的影响则较复杂,低浓度时能使 JLX 浊点上升,高浓度时则使 JLX 浊点下降;体系也能降低 JLX 浊点,并且对低浓度的无机处理剂如 KCl有一定的缓冲作用。 相似文献
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With the rapid development of deepwater drilling operations,more and more complex technical challenges have to be faced due to the rigorous conditions encountered.One of these challenges is that the drilling fluid used must had good rheological properties at low temperatures and high ability to inhibit hydrate formation.Synthetic drilling fluid has been widely applied to deepwater drilling operations due to its high penetration rate,excellent rheological properties,good ability to prevent hydrate formation,and high biodegradability.A synthetic drilling fluid formulation was developed in our laboratory.The rheological properties of this drilling fluid at low temperatures (0-20 °C) were tested with a 6-speed viscometer and its ability to inhibit hydrate formation was evaluated at 20 MPa CH 4 gas and 0 °C by differential scanning calorimetry (DSC).Several factors influencing the low temperature rheological properties of this synthetic drilling fluid were studied in this paper.These included the viscosity of the base fluid,the amount of CEMU and organic clay,and the water volume fraction. 相似文献
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Effective and efficient dimensionality reduction for large-scale and streaming data preprocessing 总被引:3,自引:0,他引:3
Jun Yan Benyu Zhang Ning Liu Shuicheng Yan Qiansheng Cheng Fan W. Qiang Yang Xi W. Zheng Chen 《Knowledge and Data Engineering, IEEE Transactions on》2006,18(3):320-333
Dimensionality reduction is an essential data preprocessing technique for large-scale and streaming data classification tasks. It can be used to improve both the efficiency and the effectiveness of classifiers. Traditional dimensionality reduction approaches fall into two categories: feature extraction and feature selection. Techniques in the feature extraction category are typically more effective than those in feature selection category. However, they may break down when processing large-scale data sets or data streams due to their high computational complexities. Similarly, the solutions provided by the feature selection approaches are mostly solved by greedy strategies and, hence, are not ensured to be optimal according to optimized criteria. In this paper, we give an overview of the popularly used feature extraction and selection algorithms under a unified framework. Moreover, we propose two novel dimensionality reduction algorithms based on the orthogonal centroid algorithm (OC). The first is an incremental OC (IOC) algorithm for feature extraction. The second algorithm is an orthogonal centroid feature selection (OCFS) method which can provide optimal solutions according to the OC criterion. Both are designed under the same optimization criterion. Experiments on Reuters Corpus Volume-1 data set and some public large-scale text data sets indicate that the two algorithms are favorable in terms of their effectiveness and efficiency when compared with other state-of-the-art algorithms. 相似文献
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本文论述了一种适合风机类负载6/8极变极电机的新型带调整线圈的3Y/3Y绕组,该绕组采用换相法原理设计,保证了电机在两上极下都有较高的分布系数,并可以相对独立地设计两个极下的性能。与2Y/Y、2Y/△接法绕组相比,明显提高了低速级的力能指标,达到高效节能的目的。 相似文献
10.
覆盖是无线传感网络中最重要的问题之一,随机覆盖是目前研究的主流。基于Voronoi图的随机覆盖算法是无线传感网络领域的研究热点。目前研究中采用的Voronoi图,主要采用基于距离的Voronoi边赋权值模型,存在两个主要问题,即模型粗糙和监测节点不全。以实测的分段概率传感模型为基础,从多传感协同监测的角度构造一种概率Voronoi模型,试图解决以上问题。并且用基于概率Voronoi模型的最大突破路径算法验证了模型有效性。就掌握的文献来看,该模型是首次提出,具有较好的实用推广价值。 相似文献