检索结果-内蒙古大学图书馆

Complexity and approximability of double digest

Journal of Bioinformatics and Computational Biology 2005年第2期3卷 207-223页

作者： Cieliebak, Mark Eidenbenz, Stephan Woeginger, Gerhard J. Inst. of Theoretical Computer Sci. ETH Zurich 8092 Zurich Switzerland Basic and Applied Simulation Science Los Alamos National Laboratory Los Alamos NM 87545 P.O. Box 1663 United States Faculty of Electrical Engineering Mathematics/Computer Science University of Twente 7500 AE Enschede P.O. Box 217 Netherlands

We revisit the DOUBLE DIGEST problem, which occurs in sequencing of large DNA strings and consists of reconstructing the relative positions of cut sites from two different enzymes. We first show that DOUBLE DIGEST is strongly NP-complete, improving upon previous results that only showed weak NP-completeness. Even the (experimentally more meaningful) variation in which we disallow coincident cut sites turns out to be strongly NP-complete. In the second part, we model errors in data as they occur in real-life experiments: we propose several optimization variations of DOUBLE DIGEST that model partial cleavage errors. We then show that most of these variations are hard to approximate. In the third part, we investigate variations with the additional restriction that coincident cut sites are disallowed, and we show that it is NP-hard to even find feasible solutions in this case, thus making it impossible to guarantee any approximation ratio at all. © Imperial College Press.

关键词： Approximability Complexity DNA physical mapping Double digest

来源：评论

学校读者我要写书评

暂无评论

Into the twilight zone: How does WIPL-D perform in quasistatics

Into the twilight zone: How does WIPL-D perform in quasistat...

引用

2005 IEEE/ACES International Conference on Wireless Communications and Applied Computational Electromagnetics

作者： Sihvola, Ari Sarkar, Tapan K. Kolundžija, Branko Electromagnetics Laboratory Helsinki University of Technology P.O. Box 3000 FIN-02015 HUT Finland College of Engineering and Computer Science Syracuse University 121 Link Hall Syracuse NY 13244-1240 United States Faculty of Electrical Engineering University of Belgrade Bulevar kralja Aleksandra 73 11120 Belgrade Yugoslavia

ISBN: (纸本)0780390687

We focus on the question how well WIPL-D, a numerical code designed to tackle dynamical electromagnetic problems, can be applied to solving very low-frequency problems. In particular, the problem of the static polarizability of a dielectric sphere is calculated. This is done by enumerating the monostatic radar cross section of the object and taking the low-frequency limit. Peeling away the strong frequency dependence of the radar cross section, the remaining coefficient is proportional to the square of the static polarizability. The results show that there is around two decades of frequency range where the code works well and the situation is clearly in the quasistatic regime. In the example of a sphere of one-meter radius and relative permittivity 10, the low-frequency breakdown happens at around 10 kHz. © 2005 ACES.

关键词： Codes (symbols)

来源：评论

学校读者我要写书评

暂无评论

Real-time simulation to study the impact of renewable energy in power systems

Real-time simulation to study the impact of renewable energy...

引用

International Conference on Future Power Systems

作者： I.J. van Vliet A.M. van Voorden P.H. Schavemaker G.C. Paap L. van der Sluis Faculty of Electrical Engineering Mathematics & Computer ScienceElectrical Power System Laboratory (EPS) Delft University슠of슠Technology Delft Netherlands

A real-time simulation tool, in our case a real-time digital simulator (RTDS), gives the opportunity to study the impact of renewable energy in power systems on a real-time base, driven by actual solar and wind data. In the first part of this paper, the real-time digital simulator (RTDS) is briefly introduced. The application of this analyzing tool is first demonstrated on a detailed model of a wind energy conversion system (WECS) whereas secondly the application on an autonomous power system is shown. Both applications demonstrate the capabilities of this simulator and the added value for power system analysis

关键词： Power system simulation Real time systems Renewable energy resources Power system modeling Power system analysis computing Induction generators Computational modeling Wind energy Distributed power generation Power generation

来源：评论

学校读者我要写书评

暂无评论

A delay filter for an ir-UWB front-end

A delay filter for an ir-UWB front-end

引用

ICU 2005: 2005 IEEE International Conference on Ultra-Wideband

作者： Bagga, Sumit Haddad, Sandro A. P. Serdijn, Wouter A. Long, John R. Busking, Erik B. Electronics Research Laboratory Faculty of Electrical Engineering Mathematics and Computer Science Delft University of Technology Mekelweg 4 2628CD Delft Netherlands TNO Defence Security and Safety P.O. Box 96864 2509JG The Hague Netherlands

ISBN: (纸本)078039397X

A continuous-time analog delay is designed as a requirement for the autocorrelation function in the Quadrature Downconversion Autocorrelation Receiver (QDAR) [1]. An eight-order Padé approximation of its transfer function is selected to implement this delay. Subsequently, the orthonormal form [1] is adopted, which is intrinsically semi-optimized for dynamic range, has low sensitivity to component mismatch, high sparsity and whose coefficients can be physically implemented. Each coefficient in the state-space description of the orthonormal ladder filter is implemented at circuit level using a novel 2-stage gm cell employing negative feedback. Simulation results in IBM's Bi-CMOS 0.12 μm technology show that this delay filter requires a total current of 70 mA at a 1.6 V power supply. The 1-dB compression point of the delay is at 565 mV and the SNR is 47.5 dB. On performing a Monte Carlo simulation it becomes evident that the response of the frequency selective analog delay does not suffer drastically from neither process variations nor component mismatch.

关键词： Wave filters

来源：评论

学校读者我要写书评

暂无评论

A quantized analog delay for an ir-UWB quadrature downconversion autocorrelation receiver

A quantized analog delay for an ir-UWB quadrature downconver...

引用

ICU 2005: 2005 IEEE International Conference on Ultra-Wideband

作者： Bagga, Sumit Zhang, Lujun Serdijn, Wouter A. Long, John R. Busking, Erik B. Electronics Research Laboratory Faculty of Electrical Engineering Mathematics and Computer Science Delft University of Technology Mekelweg 4 2628CD Delft Netherlands TNO Defence Security and Safety P.O. Box 96864 2509JG The Hague Netherlands

ISBN: (纸本)078039397X

A quantized analog delay is designed as a requirement for the autocorrelation function in the Quadrature Downconversion Autocorrelation Receiver (QDAR) [1]. The quantized analog delay is comprised of a quantizer, multiple binary delay lines and an adder circuit. Being the foremost element, the quantizer consists of a series of comparators, each one comparing the input signal to a unique reference voltage. The comparator outputs connect to binary delay lines, which are a cascade of synchronized D-latches. The outputs available at each line are linked together to reconstruct the incoming signal using an adder circuit. For a delay time of 550 ps, simulation results in IBM's CMOS 0.12 μm technology show that the quantized analog delay requires a total current of 36.7 mA at a 1.6 V power supply. Furthermore, delays in the range of several nanoseconds are feasible at the expense of power. After a Monte Carlo simulation it becomes evident that the response of the quantized analog delay does not suffer drastically from neither process nor component mismatch variations.

关键词： Signal filtering and prediction

来源：评论

学校读者我要写书评

暂无评论

Probabilistic power flow methodology for the modeling of horizontally-operated power systems

Probabilistic power flow methodology for the modeling of hor...

引用

International Conference on Future Power Systems

作者： G. Papaefthymiou A. Tsanakas D. Kurowicka P.H. Schavemaker L. van der Sluis Electrical Power System Laboratory (EPS) Faculty of Electrical Engineering Mathematics & Computer Science Delft University of Technnology Delft Netherlands Lloyďs of London London UK Institute for Applied Mathematics Faculty of Electrical Engineering Mathematics & Computer Science Delft University of Technnology Delft Netherlands

Stochastic generation is expected to take a large share of the energy production in future power systems. Two basic features of this type of generation distinguish it from the traditional centralized, conventional generation: it is highly distributed (large number of small-scale generators) and non-dispatchable (use of an uncontrolled prime mover). The incorporation of such power sources in the lower system levels leads to a new horizontal structure of the power system, where the distribution networks contain both uncertain stochastic generation and load. For the analysis of such systems, the use of a probabilistic approach is necessary. There are two basic problems with the probabilistic formulation of this problem: the large number of random variables involved in the analysis and the presence of complex dependencies between the system inputs. In this contribution, a two-step method is presented for the stochastic modeling of the system: first, clusters of positively correlated variables are defined and modeled based on the concepts of perfect correlation (comonotonicity), and then the exact correlations between these clusters are modeled based on a new proposed technique, the joint normal transform methodology. This powerful computational method can be easily applied to large systems with a high number of stochastic generators. The proposed method has been implemented and applied for the 5-bus/7-branch test system (Hale network) with a high penetration of wind generation. The results are presented in the paper

关键词： Power system modeling Load flow Stochastic systems Power generation Distributed power generation Wind energy generation Production systems Power system analysis computing Random variables System testing

来源：评论

学校读者我要写书评

暂无评论

An application of MAP-MRF to change detection in image sequence based on mean field theory

An application of MAP-MRF to change detection in image seque...

引用

作者： Liu, Qiang Sclabassi, Robert J. Li, Ching-Chung Sun, Mingui Laboratory for Computational Neuroscience Departments of Neurological Surgery and Electrical Engineering University of Pittsburgh Pittsburgh PA 15213 United States University of Pittsburgh Pittsburgh United States Dept. of Neurol. Surg. Elec. Eng. Neurosci. Mech. Eng. Psychiatry and Biomedical Engineering University of Pittsburgh Department of Electrical Engineering and Computer Science University of Pittsburgh Pittsburgh PA Center for Clinical Neurophysiology Department of Neurological Surgery University of Pittsburgh Research at Computational Diagnostics Inc.

Change detection is one of the most important problems in video segmentation. In conventional methods, predetermined thresholds are utilized to test the variation between frames. Although certain reasonings about the thresholds are provided, appropriate determination of these parameters is still problematic. We present a new approach to change detection from an optimization point of view. We model the video frames and the change detection map (CDM) as Markov random fields (MRFs), and formulate change detection into a problem of seeking the optimal configuration of the CDM. Under the MRP assumption, the optimal solution, in the sense of maximum a posteriori (MAP), is obtained by minimizing the energy function associated with the MRF which is designed by utilizing the prior knowledge of noise and contextual constraints on the video frames. An algorithm that computes the potentials and optimizes the solution is constructed by applying the mean field theory (MFT). The experimental results show that the new method detects changes accurately and is robust to noise. © 2005 Hindawi Publishing Corporation.

关键词： Image segmentation

来源：评论

学校读者我要写书评

暂无评论

Abstractions of Stochastic Hybrid Systems

Abstractions of Stochastic Hybrid Systems

引用

IEEE Conference on Decision and Control

作者： M.L. Bujorianu M.C. Bujorianu J. Lygeros Faculty of Computer Science University of Twente Enschede Netherlands Computing Laboratory University of Kent Canterbury UK Department of Electrical and Computer Engineering University of Patras Patras Greece

Many control systems have large, infinite state space that can not be easily abstracted. One method to analyse and verify these systems is reachability analysis. It is frequently used for air traffic control and power plants. Because of lack of complete information about the environment or unpredicted changes, the stochastic approach is a viable alternative. In this paper, different ways of introducing rechability under uncertainty are presented. A new concept of stochastic bisimulation is introduced and its connection with the reachability analysis is established. The work is mainly motivated by safety critical situations in air traffic control (like collision detection and avoidance) and formal tools are based on stochastic analysis.

关键词： Stochastic systems Stochastic processes Reachability analysis Air traffic control Control systems State-space methods Power generation Uncertainty Air safety Road accidents

来源：评论

学校读者我要写书评

暂无评论

Into the twilight zone: how does WIPL-D perform in quasistatics?

Into the twilight zone: how does WIPL-D perform in quasistat...

引用

IEEE/ACES International Conference on Wireless Communications and Applied Computational Electromagnetics

作者： A. Sihvola T.K. Sakar B. Kolundzija Electromagnetics Laboratory Helsinki University of Technology Finland College of Engineering and Computer Science Syracuse University Syracuse New York USA Faculty of Electrical Engineering University of Belgrade Belgrade Yugoslavia

We focus on the question how well WLPL-D, a numerical code designed to tackle dynamical electromagnetic problems, can be applied to solving very low-frequency problems. In particular, the problem of the static polarizability of a dielectric sphere is calculated. This is done by enumerating the monostatic radar cross section of the object and taking the low-frequency limit. Peeling away the strong frequency dependence of the radar cross section, the remaining coefficient is proportional to the square of the static polarizability. The results show that there is around two decades of frequency range where the code works well and the situation is clearly in the quasistatic regime. In the example of a sphere of one-meter radius and relative permittivity 10, the low-frequency breakdown happens at around 10 kHz.

关键词： Radar cross section Electromagnetic scattering Frequency Dielectrics Radar scattering Electromagnetic wave polarization Permittivity Electric breakdown Electromagnetic fields Electrostatics

来源：评论

学校读者我要写书评

暂无评论

A delay filter for an ir-UWB front-end

A delay filter for an ir-UWB front-end

引用

IEEE International Conference on Ubiquitous Wireless Broadband (ICUWB)

作者： S. Bagga S.A.P. Haddad W.A. Serdijn J.R. Long E.B. Busking Electronics Research Laboratory Faculty of Electrical Engineering Mathematics and Computer Science Delft University of Technnology Netherlands TNO Defence Safety and Security The Hague Netherlands

A continuous-time analog delay is designed as a requirement for the autocorrelation function in the quadrature downconversion autocorrelation receiver (QDAR). An eight-order Fade approximation of its transfer function is selected to implement this delay. Subsequently, the orthonormal form is adopted, which is intrinsically semi-optimized for dynamic range, has low sensitivity to component mismatch, high sparsity and whose coefficients can be physically implemented. Each coefficient in the state-space description of the orthonormal ladder filter is implemented at circuit level using a novel 2-stage gm cell employing negative feedback. Simulation results in IBM's Bi-CMOS 0.12 /spl mu/m technology show that this delay filter requires a total current of 70 mA at a 1.6 V power supply. The 1-dB compression point of the delay is at 565 mV and the SNR is 47.5 dB. On performing a Monte Carlo simulation it becomes evident that the response of the frequency selective analog delay does not suffer drastically from neither process variations nor component mismatch.

关键词： Delay Filters Autocorrelation Transfer functions Dynamic range Feedback circuits Negative feedback Circuit simulation Power supplies Frequency

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：