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Automatic tuning method for the design of supplementary damping controllers for flexible alternating current transmission system devices

OLIVEIRA, R. V. de; KUIAVA, R.; RAMOS, R. A.; BRETAS, N. G.
Fonte: INST ENGINEERING TECHNOLOGY-IET Publicador: INST ENGINEERING TECHNOLOGY-IET
Tipo: Artigo de Revista Científica
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The design of supplementary damping controllers to mitigate the effects of electromechanical oscillations in power systems is a highly complex and time-consuming process, which requires a significant amount of knowledge from the part of the designer. In this study, the authors propose an automatic technique that takes the burden of tuning the controller parameters away from the power engineer and places it on the computer. Unlike other approaches that do the same based on robust control theories or evolutionary computing techniques, our proposed procedure uses an optimisation algorithm that works over a formulation of the classical tuning problem in terms of bilinear matrix inequalities. Using this formulation, it is possible to apply linear matrix inequality solvers to find a solution to the tuning problem via an iterative process, with the advantage that these solvers are widely available and have well-known convergence properties. The proposed algorithm is applied to tune the parameters of supplementary controllers for thyristor controlled series capacitors placed in the New England/New York benchmark test system, aiming at the improvement of the damping factor of inter-area modes, under several different operating conditions. The results of the linear analysis are validated by non-linear simulation and demonstrate the effectiveness of the proposed procedure.; FAPESP[2004/04672-4]; FAPESP[2006/05191-5]

Comparing finite state machine test coverage criteria

SIMAO, A.; PETRENKO, A.; MALDONADO, J. C.
Fonte: INST ENGINEERING TECHNOLOGY-IET Publicador: INST ENGINEERING TECHNOLOGY-IET
Tipo: Artigo de Revista Científica
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To plan testing activities, testers face the challenge of determining a strategy, including a test coverage criterion that offers an acceptable compromise between the available resources and test goals. Known theoretical properties of coverage criteria do not always help and, thus, empirical data are needed. The results of an experimental evaluation of several coverage criteria for finite state machines (FSMs) are presented, namely, state and transition coverage; initialisation fault and transition fault coverage. The first two criteria focus on FSM structure, whereas the other two on potential faults in FSM implementations. The authors elaborate a comparison approach that includes random generation of FSM, construction of an adequate test suite and test minimisation for each criterion to ensure that tests are obtained in a uniform way. The last step uses an improved greedy algorithm.

Class-based OSPF traffic engineering inspired on evolutionary computation

Sousa, Pedro; Rocha, Miguel; Rio, Miguel; Cortez, Paulo
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Conferência ou Objeto de Conferência
Publicado em /05/2007 Português
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This paper proposes a novel traffic engineering framework able to automatically provide near-optimal OSPF routing configurations for QoS constrained scenarios. Within this purpose, this work defines a mathematical model able to measure the QoS compliance in a class-based networking domain. Based on such model, the NP-hard optimization problem of OSPF weight setting is faced resorting to Evolutionary Algorithms. The presented results show that, independently of other QoS aware mechanisms that might be in place, the proposed framework is able to improve the QoS level of a given domain only taking into account the direct influence of the routing component of the network. The devised optimization tool is able to optimize OSPF weight configurations in scenarios either considering a single level of link weights or using multiple levels of weights (one for each class) in multi-topology routing scenarios.

Specifying and detecting meaningful changes in programs

Yu, Yijun; Tun, Thein Than; Nuseibeh, Bashar
Fonte: IEEE Computer Society Publicador: IEEE Computer Society
Tipo: Conference item; all_ul_research; ul_published_reviewed; none
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non-peer-reviewed; Software developers are often interested in particular changes in programs that are relevant to their current tasks: not all changes to evolving software are equally important. However, most existing differencing tools, such as diff, notify developers of more changes than they wish to see. In this paper, we propose a technique to specify and automatically detect only those changes in programs deemed meaningful, or relevant, to a particular development task. Using four elementary annotations on the grammar of any programming language, namely Ignore, Order, Prefer and Scope, developers can specify, with limited effort, the type of change they wish to detect. Our algorithms use these annotations to transform the input programs into a normalised form, and to remove clones across different normalised programs in order to detect non-trivial and relevant differences. We evaluate our tool on a benchmark of programs to demonstrate its improved precision compared to other differencing approaches.

VHITS: Vertical handoff initiation and target selection in a heterogeneous wireless network

Kaleem, Faisal
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica
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Global connectivity, for anyone, at anyplace, at anytime, to provide high-speed, high-quality, and reliable communication channels for mobile devices, is now becoming a reality. The credit mainly goes to the recent technological advances in wireless communications comprised of a wide range of technologies, services, and applications to fulfill the particular needs of end-users in different deployment scenarios (Wi-Fi, WiMAX, and 3G/4G cellular systems). In such a heterogeneous wireless environment, one of the key ingredients to provide efficient ubiquitous computing with guaranteed quality and continuity of service is the design of intelligent handoff algorithms. ^ Traditional single-metric handoff decision algorithms, such as Received Signal Strength (RSS) based, are not efficient and intelligent enough to minimize the number of unnecessary handoffs, decision delays, and call-dropping and/or blocking probabilities. ^ This research presented a novel approach for the design and implementation of a multi-criteria vertical handoff algorithm for heterogeneous wireless networks. Several parallel Fuzzy Logic Controllers were utilized in combination with different types of ranking algorithms and metric weighting schemes to implement two major modules: the first module estimated the necessity of handoff...

Evanescent Wave Coupling in Terahertz Waveguide Arrays

Reichel, Kimberly
Fonte: Universidade Rice Publicador: Universidade Rice
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At optical frequencies, evanescent wave coupling in waveguides is an important concept underlying key technologies such as optical fiber splitters and combiners. At terahertz (THz) frequencies, there is a lack of such devices. In order to fill this gap, we investigate evanescent wave coupling at THz frequencies in an array of narrow-width parallel-plate waveguides (PPWGs). Although researchers have studied THz wave coupling between two adjacent wire waveguides, evanescent coupling in an array of PPWGs has not previously been considered. Metal PPWGs are ideal THz waveguide platforms since they offer low losses and negligible dispersion in the TEM waveguide mode. Additionally, PPWGs can exhibit energy leakage when the plates are narrow and the plate separation is large, indicating that an array of narrow-width PPWGs is a convenient platform for studying THz energy coupling between waveguides. By using the presented design of an array of identical narrow-width PPWGs in close proximity with their unconfined sides facing each other, we have demonstrated evidence of evanescent wave coupling in THz PPWG arrays. Thereby, we observed stronger coupling with larger waveguide plate separations and longer propagation paths. We confirmed these results through THz time-domain spectroscopy (THz-TDS) experiments and finite-element method (FEM) simulations. Based on evanescent wave coupling...

Implementation of New Strategies in Multidimensional Compressive Imaging

Xu, Lina
Fonte: Universidade Rice Publicador: Universidade Rice
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Since 2004, compressive sensing (CS) has attracted considerable attentions due to its virtue of being able to reconstruct a signal when being sampled at sub-Nyquist rate. Building on the mathematical breakthroughs of CS, we previously developed a unique imaging hardware platform, named single pixel camera (SPC), which incorporates a spatial light modulator and a single detector. We have exploited this to construct the infrared, hyperspectral, and low-light imaging systems that have greatly reduced cost in power, space, and/or expense compared to their traditional counterparts. However, previous imaging applications based on these systems are constrained to static images and fail for time-varying scenes (videos). There are also several drawbacks to the SPC system. One of which is the use of the digital micromirror device (DMD) as the light modulator. While this modulator has a broad spectral response from the ultraviolet through the visible and across the mid-infrared, it does not operate in the terahertz or other portions of the spectrum. Additionally, the binary nature and limited twelve degree of tilt of the micromirrors reduces the eld of view and presents optical design challenges in certain con gurations. To surmount the static scene limitation...

Automatic target recognition statistical feature selection of non-Gaussian distributed target classes

Wilder, Matthew J.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado
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Target and pattern recognition systems are in widespread use. Efforts have been made in all areas of pattern recognition to increase the performance of these systems. Feature extraction, feature selection, and classification are the major aspects of a target recognition system. This research proposes algorithms for selecting useful statistical features in pattern/target classification problems in which the features are non-Gaussian distributed. In engineering practice, it is common to either not perform any feature selection procedure or to use a feature selection algorithm that assumes the features are Gaussian distributed. These results can be far from optimal if the features are non-Gaussian distributed, as they often are. This research has the goal of mitigating that problem by creating algorithms that are useful in practice. This work focuses on the performance of three common feature selection algorithms: the Branch and Bound, the Sequential Forward Selection, and Exhaustive Search algorithms. Ordinarily, the performance index used to measure the class separation in feature space involves assuming the data are Gaussian and deriving tractable performance indices that can be calculated without estimating the probability density functions of the class data. The advantage of this approach is that it produces feature selection algorithms that have low computational complexity and do not require knowledge of the data densities. The disadvantage is that these algorithms may not perform reasonably when the data are non-Gaussian. This research examines the use of information-theoretic class separability measures that can deal with the non-Gaussian case. In particular...

The use of an electronic analog computer in the determination of the normal modes of lateral vibration of non-uniform beams

Erickson, Whitney Adoulphe; Parrett, Gaylord Swayne
Fonte: Ann Arbor, Michigan; University of Michigan Publicador: Ann Arbor, Michigan; University of Michigan
Tipo: Tese de Doutorado
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This thesis document was issued under the authority of another institution, not NPS. At the time it was written, a copy was added to the NPS Library collection for reasons not now known. It has been included in the digital archive for its historical value to NPS. Not believed to be a CIVINS (Civilian Institutions) title.; It is the purpose of this paper to describe an investigation of the normal modes of lateral vibration of a free-free beam having variable stiffness and mass considering the effects of bending and shear deflections and rotary inertia, by mean of an electronic system. A practical engineering problem of this type is found in the vibrations of an aircraft wing, or, as in the case of this investigation, the normal modes of vibrations of a naval vessel for which data and solutions by other methods were readily accessible.

Communications network design, simulation, and analysis for an autonomous unmanned vehicle system

Matson, Nathan C.
Fonte: Monterey California. Naval Postgraduate School Publicador: Monterey California. Naval Postgraduate School
Tipo: Tese de Doutorado
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Approved for public release; distribution is unlimited.; In this thesis, we designed, simulated, and analyzed a wireless communications system for an autonomous unmanned vehicle system. The system used for the design context is the Unmanned Vehicle (UV) Sentry, which is a system of autonomous unmanned vehicles that can be tasked for a variety of missions that involve the patrolling and protecting of a geographical region. Accordingly, the communications network needs to allow for flexibility of the vehicle topography to enable large amounts of delay intolerant sensor data to be transmitted between nodes and a capability that allows vehicles to act as relays for other vehicles. To meet these requirements, a medium access control (MAC) relay protocol based on the IEEE 802.16 standard was developed. To evaluate the performance of the protocol, Simulink was used to model the performance of the protocol as it was implemented in a specific UV Sentry scenario. Several network parameters were chosen as factors for the model, and these factors were systematically varied to yield a full factorial design of experiments. The network quality of service parameters for the tests were then analyzed to determine the best communication network configuration for the UV Sentry scenario and to illuminate the tradeoffs between the factors.

Linking combat systems capabilities and ship design through modeling and computer simulation

Pisani, Christopher R.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado
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Approved for public release; distribution is unlimited; When designing combat vessels, the traditional approach has been to configure weapons and other operational systems around the hull. Such thinking may have been rooted in the idea that hull design is the highest priority, since it can translate into a speedier and more seaworthy vessel, thereby allowing the vessel to reach its destination and complete its mission on a timelier basis. The traditional approach, however, has its shortcomings; once the ship is built, modifications to meet changing operational requirements can be costly and difficult to implement. Ship designers have long sought a methodology to identify such shortcomings by linking mission requirements with naval requirements in the early stages of ship design. The ongoing challenge has been to devise a synthesizing and modeling tool that enables designers to assess the trade-offs that may occur as design modifications are proposed. The Naval Postgraduate School has taken on this challenge through its design concept using Model-Based Systems Engineering (MBSE). This thesis considers how MBSE might extend its use of simulation and modeling to better link architectural ship designs to combat system requirements. This thesis considers such linking and identifies a synthesizing tool that may facilitate the synthesizing and modeling process.

The design and implementation of a multimedia storage server tosupport video-on-demand applications

Molano, Anastasio; García-Martínez, Alberto; Viña, Ángel
Fonte: IEEE Computer Society Press Publicador: IEEE Computer Society Press
Tipo: Conferência ou Objeto de Conferência Formato: application/pdf
Publicado em /09/1996 Português
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In this paper we present the design and implementation of a client/server based multimedia architecture for supporting video-on-demand applications. We describe in detail the software architecture of the implementation along with the adopted buffering mechanism. The proposed multithreaded architecture obtains, on one hand, a high degree of parallelism at the server side, allowing both the disk controller and the network card controller work in parallel. On the other hand; at the client side, it achieves the synchronized playback of the video stream at its precise rate, decoupling this process from the reception of data through the network. Additionally, we have derived, under an engineering perspective, some services that a real-time operating system should offer to satisfy the requirements found in video-on-demand applications.; This research has been supported by the Regional Research Plan of the Autonomus Community of Madrid under an F.P.I. research grant.

A software assurance framework for mitigating the risks of malicious software in embedded systems used in aircraft

Ginn, Robert C.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: xviii, 99 p.
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Approved for public release; distribution is unlimited.; techniques that can be used to detect malicious code in individual aircraft Weapons Replaceable Assemblies (WRAs); risks and mitigation strategies related to a generic aircraft software development process; system level techniques to prevent embedded malicious software from causing harm in aircraft; and a technique for documenting Software Assurance (SwA) arguments being made about the system and the individual WRAs.; Malicious software represents a significant and growing threat to Defense systems. Threats to airborne systems in particular can be characterized not by system vulnerability to Internet based exploits but rather by the risk posed by malicious code already present in the system's software. Although there are software techniques to detect and prevent certain types of attacks, a Systems Engineer has access to system level information and system design techniques that can quantify and in many cases mitigate the risks posed by potential malicious code present in the system. These techniques are especially applicable to malicious code in embedded airborne system although they can be applied to other systems that share certain traits. This thesis provides an overview of the types of threat involved

Design, Implementation and Characterization of a Cooperative Communications System

Murphy, Patrick O.
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Thesis; Text Formato: 227 p.; application/pdf
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Cooperative communications is a class of techniques which seek to improve reliability and throughput in wireless systems by pooling the resources of distributed nodes. While cooperation can occur at different network layers and time scales, physical layer cooperation at symbol time scales offers the largest benefit. However, symbol level cooperation poses significant implementation challenges, especially in the context of a network of distributed nodes. We first present the design and implementation of a complete cooperative physical layer transceiver, built from scratch on the Wireless Open-Access Research Platform (WARP). In our implementation fully distributed nodes employ physical layer cooperation at symbol time scales without requiring a central synchronization source. Our design supports per-packet selection of non-cooperative or cooperative communication, with cooperative links utilizing either amplify-and-forward or decode-and-forward relaying. A single design implements transmission, reception and relaying, allowing each node to assume the role of source, destination or relay per packet. We also present experimental methodologies for evaluating our design and extensive experimental results of our transceiver's performance under a variety of topologies and propagation conditions. Our methods are designed to test both overall performance and to isolate and understand the underlying causes of performance limitations. Our results clearly demonstrate significant performance gains (more than 50× improvement in PER in some topologies) provided by physical layer cooperation even when subject to the constraints of a real-time implementation. As with all our work on WARP...

Delay-sensitive service request scheduling for cloud computing

Liu, Shuo
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica
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Cloud computing realizes the long-held dream of converting computing capability into a type of utility. It has the potential to fundamentally change the landscape of the IT industry and our way of life. However, as cloud computing expanding substantially in both scale and scope, ensuring its sustainable growth is a critical problem. Service providers have long been suffering from high operational costs. Especially the costs associated with the skyrocketing power consumption of large data centers. In the meantime, while efficient power/energy utilization is indispensable for the sustainable growth of cloud computing, service providers must also satisfy a user's quality of service (QoS) requirements. This problem becomes even more challenging considering the increasingly stringent power/energy and QoS constraints, as well as other factors such as the highly dynamic, heterogeneous, and distributed nature of the computing infrastructures, etc. ^ In this dissertation, we study the problem of delay-sensitive cloud service scheduling for the sustainable development of cloud computing. We first focus our research on the development of scheduling methods for delay-sensitive cloud services on a single server with the goal of maximizing a service provider's profit. We then extend our study to scheduling cloud services in distributed environments. In particular...

An Experimental Comparison of PMSPrune and Other Algorithms for Motif Search

Sharma, Dolly; Rajasekaran, Sanguthevar; Dinh, Hieu
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 25/08/2011 Português
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Extracting meaningful patterns from voluminous amount of biological data is a very big challenge. Motifs are biological patterns of great interest to biologists. Many different versions of the motif finding problem have been identified by researchers. Examples include the Planted $(l, d)$ Motif version, those based on position-specific score matrices, etc. A comparative study of the various motif search algorithms is very important for several reasons. For example, we could identify the strengths and weaknesses of each. As a result, we might be able to devise hybrids that will perform better than the individual components. In this paper we (either directly or indirectly) compare the performance of PMSprune (an algorithm based on the $(l, d)$ motif model) and several other algorithms in terms of seven measures and using well established benchmarks In this paper, we (directly or indirectly) compare the quality of motifs predicted by PMSprune and 14 other algorithms. We have employed several benchmark datasets including the one used by Tompa, et.al. These comparisons show that the performance of PMSprune is competitive when compared to the other 14 algorithms tested. We have compared (directly or indirectly) the performance of PMSprune and 14 other algorithms using the Benchmark dataset provided by Tompa...

Contributions of PDM Systems in Organizational Technical Data Management

Ahmed, Zeeshan; Gerhard, Detlef
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 07/08/2010 Português
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Product Data Management (PDM) claims of producing desktop and web based systems to maintain the organizational data to increase the quality of products by improving the process of development, business process flows, change management, product structure management, project tracking and resource planning. Moreover PDM helps in reducing the cost and effort required in engineering. This paper discusses PDM desktop and web based system, needed information and important guidelines for PDM system development, functional requirements, basic components in detail and some already implemented PDM Sys-tems. In the end paper investigates and briefly concludes major currently faced challenges to Product Data Management (PDM) community.; Comment: In the proceedings of The First IEEE International Conference On Computer, Control & Communication (IEEE-IC4 2007), 12-13 November 2007

Data Transfer between Two USB Flash SCSI Disks using a Touch Screen

Chakravorty, Anurag A.; Suryawanshi, Raghwendra J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/07/2014 Português
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Under normal circumstances, as an intermediate device, if we want to move or copy data from one mass storage device to another, we use a computer in the form of desktops, laptops, etc. We need a device which can be used as an intermediate device, also which is a complete blend of hardware & software. This device is a gadget that can be used to transfer data between two flash SCSI devices via a touch screen. This is a user friendly device which uses the most popular bus USB (Universal Serial Bus) with Type-A connector. It is governed by the USB 2.0 Protocol. One of the major advantage of this device is its portability.; Comment: 5 pages, 7 figures, Published with International Journal of Engineering Trends and Technology (IJETT)

Investigation of a simultaneous multithreaded architecture

Torrant, Marc
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
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Many enhancements have been made to the traditional general purpose load-store computer architectures. Among the enhancements are memory hierarchy improvements, branch prediction, and multiple issue processors. A major problem that exists with current microprocessor design is the disparity in the much larger increase in speed of the CPU versus the moderate increase in speed accessing main memory. The simultaneous multithreaded architecture is an extension of the single-threaded architecture that helps hide the performance penalty created by long-latency instructions, branch mispredictions, and memory accesses. Simultaneous multithreaded architectures use a more flexible parallelism, which takes advantage of both instruction-level, and thread-level parallelism. The goal of this project was to design, simulate, and analyze a model of a simultaneous multithreaded architecture in order to evaluate design alternatives. The simulator was created by modifying a version of the Simple Scalar toolset, developed at the University of Wisconsin. The simulations provide documentation for an overall system performance improvement of a simulta neous multithreaded architecture. In early simulation results, performed with the same number of functional units...

Tapestry: weaving execution and synchronization models

Landwehr, Joshua
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
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Gao, Guang R.; With the advent of the many-core era of computing, finding parallelism has become a key battleground to the performance of computer algorithms. Traditional methods focused on providing users with synchronization primitives, standard threading models, and shared memory models. However, it was clear that these models were limited in performance. Thus, many new forms of synchronization and parallel models were designed focusing on the big three types of parallelism: data, task, and dataflow. Nevertheless, all these models (1) only solve a particular subset of problems, (2) provide limited extendability for addressing new forms of parallelism, (3) and require a new languages with poor fine-grain performance. As an approach to find a unified solution to these problems, Tapestry is an easily extendable portable compiler-free runtime. It is designed to quickly explore new or traditional synchronization and execution models for multi-core and many-core architectures by separating synchronization and threading models. The main contributions of this thesis are: 1. Design of the Tapestry runtime and model to explore synchronization features or execution models that supports the mixing of all of the big three types of parallelism. 2. Proposal of extendable threaded dependency model of execution that expands traditional threads...