检索结果-内蒙古大学图书馆

High speed directional relaying algorithm based on the fundamental frequency positive sequence superimposed components

引用

IET GENERATION TRANSMISSION & DISTRIBUTION 2014年第7期8卷 1211-1220页

作者： Gu, Bin Tan, Jiancheng Wei, Hua Guangxi Univ Guangxi Power Syst Optimizat & Energy Saving Tech Nanning 530004 Peoples R China Shaoxing Univ Shaoxing Peoples R China

The conventional travelling wave protection is susceptible to the high frequency transient quantities, which can reduce the protection reliability. A directional-relay algorithm based on positive sequence superimposed components is proposed in this study. In microprocessor relays, the extraction of fundamental frequency voltages and currents is, conventionally, provided by phasor estimation methods such as the Fourier algorithm. The common required time for fault detection in these relays is approximately one to two cycles. This study presents a high-speed algorithm for the extraction of fundamental frequency positive sequence voltages and currents superimposed components based on Park transformation. In the meantime, specially designed high speed algorithms to solve the difficult problems that exist in a real system are proposed. Extensive simulations are performed to evaluate the performance of the proposed algorithm. The results show that the algorithm is fast and reliable for power transmission line protections. Also it is immune to fault resistances and system condition.

关键词： ALGORITHMS BROADBAND communication systems superimposed coding ELECTRIC potential FOURIER analysis

来源：评论

学校读者我要写书评

暂无评论

A method for improving full text search using signature files

引用

INTERNATIONAL JOURNAL OF COMPUTER MATHEMATICS 2001年第1期77卷 73-88页

作者： Yamakawa, Y Fuketa, M Morita, K Aoe, J Univ Tokushima Fac Engn Dept Informat Sci & Intelligent Syst Tokushima 770 Japan

Efficiency of full text retrieval using signatures depends on the number of filtering and the reduction of the original text, but there has been no discussion how a signature is constructed keeping the worst-case filtering ratio. In order to consider this problem, we present a technique of constructing signatures by using an appearance probability of strings in a textual data. It enables us to retrieve any keywords in expected worst-case searching time. A partial appearance probability is proposed because the overall probability for the whole text takes a lot of time building signatures. From the simulation result, it turns can't that the worst-case filtering ratio of the presented method can keep the expected ratio while that of the traditional method degrades zero.

关键词： text retrieval signature file superimposed coding appearance probability worst-case filtering ratio

来源：评论

学校读者我要写书评

暂无评论

Sampling-Based Correlation Estimation for Distributed Source coding Under Rate and Complexity Constraints

引用

IEEE TRANSACTIONS ON IMAGE PROCESSING 2008年第11期17卷 2122-2137页

作者： Cheung, Ngai-Man Wang, Huisheng Ortega, Antonio Hong Kong Univ Sci & Technol Dept Elect & Comp Engn Hong Kong Hong Kong Peoples R China Google Inc Mountain View CA 94043 USA Univ So Calif Dept Elect Engn Inst Signal & Image Proc Los Angeles CA 90089 USA

In many practical distributed source coding (DSC) applications, correlation information has to be estimated at the encoder in order to determine the encoding rate. coding efficiency depends strongly on the accuracy of this correlation estimation. While error in estimation is inevitable, the impact of estimation error on compression efficiency has not been sufficiently studied for the DSC problem. In this paper, we study correlation estimation subject to rate and complexity constraints, and its impact on coding efficiency in a DSC framework for practical distributed image and video applications. We focus on, in particular, applications where binary correlation models are exploited for Slepian-Wolf coding and sampling techniques are used to estimate the correlation, while extensions to other correlation models would also be briefly discussed. In the first part of this paper, we investigate the compression of binary data. We first propose a model to characterize the relationship between the number of samples used in estimation and the coding rate penalty, in the case of encoding of a single binary source. The model is then extended to scenarios where multiple binary sources are compressed, and based on the model we propose an algorithm to determine the number of samples allocated to different sources so that the overall rate penalty can be minimized, subject to a constraint on the total number of samples. The second part of this paper studies compression of continuous-valued data. We propose a model-based estimation for the particular but important situations where binary bit-planes are extracted from a continuous-valued input source, and each bit-plane is compressed using DSC. The proposed model-based method first estimates the source and correlation noise models using continuous-valued samples, and then uses the models to derive the bit-plane statistics analytically. We also extend the model-based estimation to the cases when bit-planes are extracted based on the sig

关键词： DATA transmission systems coding theory CORRELATORS DATA compression (Telecommunication) IMAGE compression superimposed coding

来源：评论

学校读者我要写书评

暂无评论

Phase Behavior of Magnetic Nanocolloids of Different Sizes Suspended in an Apolar Solvent

引用

LANGMUIR 2017年第42期33卷 11366-11376页

作者： Wandrei, Stefanie M. McCarthy, Dannielle G. Schoen, Martin Tech Univ Berlin Stranski Lab Phys & Theoret Chem Fak Math & Nat Wissensch Str 17 Juni 115 D-10623 Berlin Germany Stanford Univ Dept Chem 333 Campus Dr Stanford CA 94305 USA North Carolina State Univ Dept Chem & Biomol Engn Engn Bldg 1Box 7905911 Partners Way Raleigh NC 27695 USA

We employ classical density functional theory (DFT) to investigate the phase behavior and composition of binary mixtures;each compound consists of hard spheres of different sizes with superimposed dispersion attraction. In addition to the dispersion attraction, molecules of one component carry an additional three-dimensional magnetic "spin" where the orientation-dependent spin spin interaction is accounted for by the Heisenberg model. We are treating the excess free energy using a modified mean-field approximation (second virial coefficient) for the orientation-dependent pair correlation function. Depending on the concentration of the magnetic particles, the strength of the spin spin coupling, and the size ratio of the particles, the model predicts the formation of ordered (polar) phases in addition to the more conventional gas and isotropic liquid phases. Key features of our model are a particle-size dependent shift of the gas liquid critical point (critical temperature and density) and a change in the width of the phase diagram. In the near-critical region, the latter can be analyzed quantitativly in terms of an effective critical exponent beta(eff) that may differ from the classical critical exponent beta = 1/2;the classical value is attained in the immediate vicinity of the critical point as it must. The deviation between beta(eff) and beta can be linked to nontrivial composition effects along the phase boundaries.

关键词： COLLOIDS SOLVENTS DENSITY functional theory superimposed coding BINARY mixtures HEISENBERG model

来源：评论

学校读者我要写书评

暂无评论

Magnetotransport along a boundary: from coherent electron focusing to edge channel transport

引用

NEW JOURNAL OF PHYSICS 2013年第11期15卷 1-12页

作者： Stegmann, T. Wolf, D. E. Lorke, A. Univ Duisburg Essen Dept Phys D-47048 Duisburg Germany CENIDE D-47048 Duisburg Germany

We study theoretically how electrons, coherently injected at one point on the boundary of a two-dimensional electron system, are focused by a perpendicular magnetic field B onto another point on the boundary. Using the non-equilibrium Green's function approach, we calculate the generalized four-point Hall resistance R-xy as a function of B. In weak fields, R-xy shows the characteristic equidistant peaks observed in the experiment and explained by classical cyclotron motion along the boundary. In strong fields, R-xy shows a single extended plateau reflecting the quantum Hall effect. In intermediate fields, we find superimposed upon the lower Hall plateaus anomalous oscillations, which are neither periodic in 1/B (quantum Hall effect) nor in B (classical cyclotron motion). The oscillations are explained by the interference between the occupied edge channels, which causes beatings in R-xy. In the case of two occupied edge channels, these beatings constitute a new commensurability between the magnetic flux enclosed within the edge channels and the flux quantum. Introducing decoherence and a partially specular boundary shows that this new effect is quite robust.

关键词： NON-equilibrium reactions MAGNETOMETERS QUANTUM Hall effect MAGNETIC flux superimposed coding

来源：评论

学校读者我要写书评

暂无评论

GENERALIZED PARTITIONING SCHEME OF SIGNATURE FILE FOR INFORMATION-RETRIEVAL

引用

IEICE TRANSACTIONS ON INFORMATION AND SYSTEMS 1993年第2期E76D卷 189-198页

作者： KWON, YM PARK, YJ KIST Seoul South Korea

Compared to multi-level signature file techniques, PSF (Partitioned Signature File) technique has less processing overhead by its characteristics of a simple file organization. In a multi-processor environment, the PSF technique also has an advantage that queries can be processed in parallel effectively by allocating one or more partitions to each processor. Main point of the PSF technique is a partitioning scheme based on a key selection. In this paper, an n-BFK (n-Bounded Floating Key) partitioning scheme is proposed, in which the number of segments for a key selection is bounded by n. The cost model is developed for the performance evaluation of the proposed scheme. By performance comparison with the existing schemes, the efficiencies of the proposed scheme are shown with respect to a disk access cost, a signature reduction ratio, and an uniformity of workload.

关键词： SIGNATURE FILE superimposed coding INFORMATION RETRIEVAL PARTITIONED SIGNATURE FILE TECHNIQUE PARTITIONING SCHEME OF SIGNATURE FILE

来源：评论

学校读者我要写书评

暂无评论

Declustering of key-based partitioned signature files

引用

ACM TRANSACTIONS ON DATABASE SYSTEMS 1996年第3期21卷 295-338页

作者： Ciaccia, P Tiberio, P Zezula, P TECH UNIV BRNO BRNO 60200CZECH REPUBLIC

Access methods based on signature files can largely benefit from possibilities offered by parallel environments. To this end, an effective. declustering strategy that would distribute signatures over a set of parallel independent disks has to be combined with a synergic clustering which is employed to avoid searching the whole signature file while executing a query. This-article proposes two parallel signature file organizations, Hamming Filter (HF) and Hamming(+) Filter (H+F), whose common declustering strategy is based on error correcting codes, and where clustering is achieved by organizing signatures into fixed-size buckets, each containing signatures sharing the same hey value. HF allocates signatures on disks in a static way and works well if a correct relationship holds between the parameters of the code and the size of the file. H+F is a generalization of HF suitable to manage highly dynamic files. It uses a dynamic declustering, obtained through a sequence of codes, and organizes a smooth migration of signatures between disks so that high performance levels are retained regardless of current file size. Theoretical analysis characterizes the best-case, expected, and worst-case behaviors of these organizations. Analytical results are verified by experiments on prototype systems.

关键词： design performance error correcting codes information retrieval parallel independent disks partial match queries performance evaluation superimposed coding

来源：评论

学校读者我要写书评

暂无评论

THE OPTIMAL SIZE OF A SIGNATURE

引用

MATHEMATICAL AND COMPUTER MODELLING 1995年第4期21卷 67-75页

作者： SUNG, SY HSU, WJ NANYANG TECHNOL UNIV SCH APPL SCISINGAPORE 2263SINGAPORE

Signature file has been shown to be a fairly good filtering mechanism to reduce the amount of data that need to be retrieved for a query. Previous work in signature construction has emphasized on determining the optimal signature weight to minimize the false drop probability. In this paper, we present a method to determine the optimal signature size to a block according to its bit probability and the number of objects in that block. The scheme is optimal for both uniform and nonuniform block accessing frequencies.

关键词： DATABASE INFORMATION RETRIEVAL PERFORMANCE EVALUATION SIGNATURE FILE superimposed coding

来源：评论

学校读者我要写书评

暂无评论

EFFICIENT SIGNATURE FILE METHODS FOR TEXT RETRIEVAL

引用

IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING 1995年第3期7卷 423-435页

作者： LEE, DL KIM, YM PATEL, G MITSUBISHI MAT CORP OMIYASAITAMAJAPAN

Signature files have been studied extensively as an access method for textual databases. Many approaches have been proposed for searching signatures files efficiently. However, different methods make different assumptions and use different performance measures, making it difficult to compare their performance. In this paper, we study three basic methods proposed in the literature, namely, the indexed descriptor file, the two-level superimposed coding scheme, and the partitioned signature file approach. The contribution of this paper is two-fold. First, we present a uniform analytical performance model so that the methods can be compared fairly and consistently. The analysis shows that the two-level superimposed coding scheme, if stored in a transposed file, has the best performance. Second, we extend the two-level superimposed coding method into a multilevel superimposed coding method, we obtain the optimal number of levels for the multilevel method and show that for databases with reasonable size the optimal value is much larger than 2, which is assumed in the two-level method. The accuracy of the analytical formula is demonstrated by simulation.

关键词： ACCESS METHODS TEXT RETRIEVAL PERFORMANCE ANALYSIS superimposed coding

来源：评论

学校读者我要写书评

暂无评论

PROBABILISTIC PERCEPTRONS

引用

NEURAL NETWORKS 1995年第4期8卷 513-523页

作者： FALKOWSKI, BJ Volkartstraβe 43 80636 München Germany

A probabilistic perceptron is a device that computes a representation of a predicate ICI as a linear threshold function. In contrast to the classical perceptron, this representation will only be correct with probability close to 1. For the construction of this device the method of superimposed coding is used. The resulting advantages in comparison to the original perceptron may be summarized as follows: there is a trivial learning theorem;the size of the coefficients remains small;the condition of linear separability is not required. It is argued that the advantages mentioned outweigh the disadvantages. To support this claim, experimental work concerning full text retrieval is presented. En passant a qualitative comparison between several information retrieval methods is obtained.

关键词： PERCEPTRONS superimposed coding FULL TEXT RETRIEVAL

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：