Página 32 dos resultados de 2566 itens digitais encontrados em 0.048 segundos

Aspectual separation of feature dependencies for flexible feature composition

Lee, Kwanwoo; Botterweck, Goetz; Thiel, Steffen
Fonte: IEEE Computer Society Publicador: IEEE Computer Society
Tipo: Conference item; all_ul_research; ul_published_reviewed; none
Português
Relevância na Pesquisa
36.69903%
non-peer-reviewed; Aspect-oriented programming (AOP) provides effective mechanisms for improving the modularity of feature implementations. However, as features in general are not independent of each other, changes in the implementation of one feature may cause changes to or side effects in the implementation of other features. We address this challenge by separating feature dependencies from feature implementations using AOP techniques. Specifically, this paper contributes by providing aspect-oriented implementation patterns for feature dependencies (e.g., modification dependency and activation dependency). With the resulting clear separation of dependencies, this approach makes each feature implementation easier to understand and reuse. A product line of scientific calculator applications is used to demonstrate and evaluate the proposed approach.

Detecting Events From Twitter In Real-Time

Zhao, Siqi
Fonte: Universidade Rice Publicador: Universidade Rice
Português
Relevância na Pesquisa
36.69903%
Twitter is one of the most popular online social networking sites. It provides a unique and novel venue of publishing: it has over 500 million active users around the globe; tweets are brief, limited to 140 characters, an ideal way for people to publish spontaneously. As a result, Twitter has the short delays in reflecting what its users perceive, compared to other venues such as blogs and product reviews. We design and implement SportSense, which exploits Twitter users as human sensors of the physical world to detect major events in real-time. Using the National Football League (NFL) games as a targeted domain, we report in-depth studies of the delay and trend of tweets, and their dependence on other properties. We present event detection method based on these findings, and demonstrate that it can effectively and accurately extract major game events using open access Twitter data. SportSense has been evolving during the 2010-11 and 2011-12 NFL seasons and it has been collecting hundreds of millions tweets. We provide SportSense API for developers to use our system to create Twitter-enabled applications.

A person-tracking mobile robot using an ultrasonic positioning system

Yang, Chuan-Hao
Fonte: Monterey California. Naval Postgraduate School Publicador: Monterey California. Naval Postgraduate School
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
36.69903%
It is desirable in many applications that a mobile robot is able to track and follow a person. There have been various efforts in literature to create person-tracking robots. However, current person-tracking robots are not capable of operating in unstructured environments. The problem of creating a person-tracking mobile robot has been studied by many researchers in literature. There are two main issues associated with this problem. The first issue is to equip a robot with proper sensory devices so that it is able to identify and locate the target person in a crowd in real time. Various approaches have been investigated, including vision, infrared sensors, ultrasonic sensors, and other approaches. The second issue is to control and navigate the robot so that it follows the target person within a certain distance. This seems to be simple, but in reality it is a fairly difficult task. For example, if the target person is in a busy corridor with many people standing and walking, the robot has to constantly avoid other people while following the target. There is still no reported evidence that a person-tracking robot has been implemented that is able to track a person in arbitrary environmental conditions. In this research, by using an innovative RF/ultrasonic sensor system...

A performance analysis of routing protocols for adhoc networks

Pore, Ghee Lye.
Fonte: Monterey California. Naval Postgraduate School Publicador: Monterey California. Naval Postgraduate School
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
36.69903%
A mobile ad-hoc network (MANET) is an autonomous system of mobile nodes connected by wireless links. The performance of MANET is related to the efficiency of the routing protocols in adapting to frequently changing network topology and link status. This thesis addresses the issue by comparing the relative performance of three key ad-hoc routing protocols: Destination-sequenced Distance Vector (DSDV), Ad-hoc On-demand Distance Vector (AODV) and Optimized Link State Routing (OLSR). The protocols are tested based on two scenarios, namely, tactical networks for ships and sensor-based network nodes. The objective is to validate the scalability and effectiveness of the protocols. Four performance metrics were measured by varying the maximum speed of mobile hosts, network size and traffic load, to assess the routing capability and protocol efficiency. The simulation results indicate that AODV performs better than OSLR and DSDV in the first scenario. Although OLSR also performed relatively well, the associated high routing overhead is the dominant reason for not choosing it. On the other hand, OLSR emerged as the protocol of choice for sensor networks, where the high routing overhead is counteracted by consistently better performance in all other metrics. Due to the slow evolution of the sensor network topology...

On the design of cost-tables for realizing multiple-valued circuits

Schueller, Kriss A.; Butler, Jon T.
Fonte: Escola de Pós-Graduação Naval Publicador: Escola de Pós-Graduação Naval
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.69903%
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. As such, it is in the public domain, and under the provisions of Title 17, United States Code, Section 105, it may not be copyrighted.; IEEE Transactions on Computers, Vol. 41, No. 2, February 1992, pp. 178-189; We propose a heuristic for finding minimal cost- tables for use in the design of multiple-valued logic circuits. It is an iterative approach, in which a good table of size t is composed of a good table of size t - 1, etc. We analyze its performance, comparing it with three other heuristics. The importance of finding good cost-tables is demonstrated by an analysis that shows there is a wide variation in both cost-table performance and in the performance of heuristics for generating cost-tables. We study linear cost, a general cost function of which two previously studied cost functions are special cases. It is shown that the minimal cost-table using one of the (infinitely many) linear cost functions is identical to a minimal cost-table using any other linear cost function. Thus, a heuristic for finding the minimal cost-table using the linear cost function is independent of the specific cost function parameters. This result and our observation of well-studied nonlinear cost functions indicate that cost-table design is only marginally dependent on the cost function. We show two additional results on cost-table design. First...

Application of the constrained implicants set concept to the minimization of binary functions

Ozkan, Ugur
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
36.69903%
Approved for public release; distribution in unlimited.; Several heuristics and algorithms have been developed to find minimal sum-of-products expressions in binary logic. Most of them use prime implicants during minimization process. An efficient search strategy has been developed for finding minimal sum-of-products expressions for multiple-valued logic (MVL) functions by using the constrained implicants set concept. The search space can be considerably reduced over the only other known exact minimization technique and exhaustive search. The primary goals of this research are to: (1) examine whether the constrained implicant set concept can be efficiently used in binary logic, and; (2) develop a heuristic called the constrained implicant set heuristic (CISH). The general idea of the CISH is to select the minterm with the least implicant cover size and find the implicant with the largest minterm coverage that covers a selected minterm. In this research, the implementation of the CISH is presented, the performance analysis of the CISH is shown by comparing with other heuristics (Maximum Implicant Heuristic, Espresso II) with respect to the average number of the product terms, the average computation time, and the average memory usage.

A Comparison of Optimized Link State Routing with Traditional Ad-hoc Routing Protocols

Lye, Pore Ghee; McEachen, John C.
Fonte: Escola de Pós-Graduação Naval Publicador: Escola de Pós-Graduação Naval
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.69903%
The performance of mobile ad-hoc networks (MANET) is related to the efficiency of the routing protocols in adapting to frequently changing network topology and link status. This paper addresses the issue by comparing the relative performance of three key ad-hoc routing protocols: Destination-sequenced Distance Vector (DSDV), Ad-hoc Ondemand Distance Vector (AODV) and Optimized Link State Routing (OLSR). The protocols are tested based on two scenarios, namely, tactical networks for ships and sensor-based network nodes. Four performance metrics were measured by varying the maximum speed of mobile hosts, network size and traffic load, to assess the routing capability and protocol efficiency. The simulation results indicate that AODV performs better than OSLR and DSDV in the first scenario. Although OLSR also performed relatively well, the associated high routing overhead is the dominant reason for not choosing it. On the other hand, OLSR emerged as the protocol of choice for sensor networks, where the high routing overhead is counteracted by consistently better performance in all other metrics. Due to the slow evolution of the sensor network topology, OLSR performed satisfactorily for best effort traffic but needed subtle adjustments to balance between latency and bandwidth to meet the requirements of delay-sensitive applications.

A hybrid time synchronization algorithm based on broadcast sequencing for wireless sensor networks

Park, Sung C.
Fonte: Monterey, California: Naval Postgraduate School Publicador: Monterey, California: Naval Postgraduate School
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
36.69903%
Approved for public release; distribution is unlimited; In recent years, time synchronization has emerged as an essential research topic for wireless sensor networks. Numerous wireless network applications require a common reference time for collaborative data fusion and communications. Other time synchronization protocols have been proposed over the years, but none have eliminated the possibility of collisions associated with wireless packet transmissions while maintaining a precise level of synchronization for any given topology. In this thesis, we present a new hybrid time synchronization scheme that provides a high degree of network-wide synchronization and eliminates the possibility of collisions when transmitting timestamp messages. We propose an algorithm that allows a network to determine a broadcast sequence by which nodes transmit and forward messages and then conducts a network-wide synchronization based on received timestamp information. The proposed hybrid time synchronization scheme utilizes two existing protocols, namely relative referenceless receiver/receiver synchronization and ratio-based synchronization protocol, that provide a high degree of precision. We implement our broadcast sequencing algorithm in simulations and demonstrate its effective performance for a series of network topologies. We also present results demonstrating an improvement in network-wide synchronization using our hybrid scheme over other time synchronization protocols.

Scalable mobile ad hoc network (MANET) to enhance situational awareness in distributed small unit operations

Driesslein, Jonathan Clarke
Fonte: Monterey, California: Naval Postgraduate School Publicador: Monterey, California: Naval Postgraduate School
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
36.69903%
Approved for public release; distribution is unlimited; Platforms throughout the military and other government agencies (such as FEEMA and police departments) have become more networked; the last link in each network chain, however, has always been the individuals themselves. This structure requires a network that can process large amounts of data in order to provide the individuals with succinct and actionable information. Information, such as individual positions, weapons orientation, and friendly positions, serve to greatly enhance the situational awareness and improve the likelihood of mission success. The goal of this research is to use networking to improve the infantry’s situational awareness. The Robotic Operating System (ROS) is the foundation of a prototype network investigated in this thesis. It enables rapid prototyping of components and functionality through an open-source library with multi-language and multi-platform support. The network was constructed with software and hardware modules consisting of wearable sensors and various computational platforms. Future development will include linking the network to autonomous units and other assets with simplified controls. The deliverable is a mobile ad-hoc network (MANET) with hardware designed to be operational for infantry squads and software designed to deliver contextual situational awareness to all of its members. The data distribution is handled through a brokered publish and subscribe network implemented via ROS.; ; Ensign...

The use of commercial Low Earth Orbit satellite systems to support DoD communications; Use of commercial Low Earth Orbit satellite systems to support Department of Defense communications

Stelianos, Haralambos.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: xii, 99 p.: ill.
Português
Relevância na Pesquisa
36.69903%
Approved for public release; distribution is unlimited; Within the next five years there will be a proliferation of commercial Low Earth Orbit (LEO) satellite systems providing voice/data services to anywhere in the world. Instead of investing heavily in new satellite systems, the military services can use these forthcoming commercial satellite shyster to enhance their existing satellite-based systems. An in-depth study and detailed summary is provided in this thesis for each of the following four commercial LEO satellite systems: Iridium, Teledesic, Odyssey, and Globalstar. Then, a comparison of these systems is performed from the military point of view by using criteria such as antijam protection, security, mobility, flexibility, interoperability, coverage, and capacity. It is shown that an architecture consisting of Globalstar and Odyssey has the potential to provide communications support for DoD's less critical needs which include administration, logistics, and other support functions. Finally , other military applications of these systems are given.; http://archive.org/details/useofcommerciall00stel; Captain, Hellenic Army

Solution of the Lloyd-Max quantizer parameters by the method of successive substitution

Moose, Paul H.; Bassiouni, A-A. M.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Relatório Formato: 35 p. ; 28 cm.
Português
Relevância na Pesquisa
36.69903%
The method of successive substitution is shown applicable to solve for the classical minimum distortion quantizer parameters. The method is self converging and parameters can be calculated to any desired accuracy. The minimum distortion quantizer parameters, as well as parameters based on other criterion such as quantizers for signal detection, minimum risk quantizers and quantizers for LMMS estimation can be solved by Max's trial and error technique. There are also many other approximation methods to calculate the quantizer parameters. This report applies the method of successive substitution and its modifications to solve for the Lloyd-Max quantizer parameters. It is more accurate and computationally more efficient than the previously reported methods. It is shown to easily generate 7 bit (128 level) optimum quantization. The Lloyd-Max minimum mean square distortion quantizer problem deals with transforming a random variable X of differentiable probability density function f(x) into the N-level discrete random variable Y; http://archive.org/details/solutionoflloydm00moos; NA

Acoustic image models for navigation with forward-looking sonars

Masek, Theodore
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: xiv, 53 p. : ill. (some col.) ;
Português
Relevância na Pesquisa
36.76748%
Cost and miniaturization of autonomous unmanned vehicles (AUV) drive component reuse and better sensor data analysis. One such component is the forward looking sonar (FLS) which can be used for obstacle avoidance and to extract vehicle state information. However, autonomous feature extraction of images from the FLS is difficult due to the noise inherent in the sensor and the sensor's susceptibility to interference from other acoustic devices. This thesis investigated techniques to detect and classify common acoustic noise artifacts and common objects in a single frame. Other techniques require three or more frames to filter objects from other noise sources. A combination of probabilistic and template-based models were used to successfully detect and classify acoustic noise and objects. One common noise source is the micro modem which was detected 100% of the time with 1% false positives. Objects such as the ocean floor were correctly classified more than 93% of the time in most sites. Due to the short development time frame, the software was developed with a two-stage approach. First, a high level scripting language was used for rapid prototyping of different classification techniques. In order to meet the time-constrained requirements of the target software...

A Robust Missing Value Imputation Method MifImpute For Incomplete Molecular Descriptor Data And Comparative Analysis With Other Missing Value Imputation Methods

Doreswamy; Vastrad, Chanabasayya . M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 10/12/2013 Português
Relevância na Pesquisa
36.76748%
Missing data imputation is an important research topic in data mining. Large-scale Molecular descriptor data may contains missing values (MVs). However, some methods for downstream analyses, including some prediction tools, require a complete descriptor data matrix. We propose and evaluate an iterative imputation method MiFoImpute based on a random forest. By averaging over many unpruned regression trees, random forest intrinsically constitutes a multiple imputation scheme. Using the NRMSE and NMAE estimates of random forest, we are able to estimate the imputation error. Evaluation is performed on two molecular descriptor datasets generated from a diverse selection of pharmaceutical fields with artificially introduced missing values ranging from 10% to 30%. The experimental result demonstrates that missing values has a great impact on the effectiveness of imputation techniques and our method MiFoImpute is more robust to missing value than the other ten imputation methods used as benchmark. Additionally, MiFoImpute exhibits attractive computational efficiency and can cope with high-dimensional data.; Comment: arXiv admin note: text overlap with arXiv:1105.0828 by other authors without attribution

Architectures for Memristor-based Storage Structures

Liu, Yang
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2011 Português
Relevância na Pesquisa
36.776929%

Rapid data growth nowadays makes it more critical to reduce search time to improve the performance of search-intensive applications. However, huge data size makes it more difficult to efficiently perform search operations. Representative conventional approaches to reduce search time, such as CAM and in-memory databases, are no longer efficient because of the data explosion: CMOS-based CAM has low capacity which cannot be increased through CMOS scaling, and in-memory databases have performance degradation as data size increases. As a result, we have to exploit emerging nanotechnologies to accelerate search.

Among emerging nanotechnologies, memristors have become promising candidates to build storage structures because of high capacity, short switching time and low power consumption. However, the benefit we can obtain from these storage structures is limited by low endurance of memristors. In order to utilize the computation ability of memristors and deal with the endurance problem, we explore the design space of memristor-based storage structures.

We first propose MemCAM/MemTCAM, a configurable memristor-based CAM/TCAM design, in which we use memristors as both memory latches and logic gates. Computation ability of memristors makes it possible to perform range search and high density of memristors provides an opportunity to build MemCAM/MemTCAM with large capacity and small area. We use SPICE to model the memristor and analyze power and performance at different temperatures. The results show that it is feasible to build MemCAM and MemTCAM which have high capacity and can reduce total search time and energy consumption for search-intensive applications with huge data size.

We then propose four hybrid memristor-based storage structures...

Simulation of a morphological image processor using VHDL - Part I: Mathematical Components

Chen, Wei-chun
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
36.776929%
Very high speed integrated circuit Hardware Description Language (VHDL) is utilized in this project to model a Morphological Image Processor (MIP) Array. Both behavioral and structural models have been established at the system level, and the simulation results from both models are consistent with each other. The successful implementation of the models accomplishes our original goal to document the MIP with VHDL. It is observed from the project that VHDL is a powerful language. It is flexible since it can be used to model any level of a system independent of the technology.

Self-Similarity in a multi-stage queueing ATM switch fabric

Lange-Pearson, Adam
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
36.776929%
Recent studies of digital network traffic have shown that arrival processes in such an environment are more accurately modeled as a statistically self-similar process, rather than as a Poisson-based one. We present a simulation of a combination sharedoutput queueing ATM switch fabric, sourced by two models of self-similar input. The effect of self-similarity on the average queue length and cell loss probability for this multi-stage queue is examined for varying load, buffer size, and internal speedup. The results using two self-similar input models, Pareto-distributed interarrival times and a Poisson-Zeta ON-OFF model, are compared with each other and with results using Poisson interarrival times and an ON-OFF bursty traffic source with Ge ometrically distributed burst lengths. The results show that at a high utilization and at a high degree of self-similarity, switch performance improves slowly with increasing buffer size and speedup, as compared to the improvement using Poisson-based traffic.

Analysis and hardware implementation of color map inversion algorithms

Martin, Michael
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
36.776929%
The purpose of this thesis is to investigate several algorithms that are used to compute the inverse of a forward printer map. The forward printer map models the printer by mapping points in the printer's input color space to points in the printer's output color space. The inverse of this forward map is required to convert input color specifications in a device-independent color space to a color in the printer's device-dependent color space before being presented to the print engine. The accuracy of the inverse printer map directly affects the accuracy of the reproduced colors. Therefore, any measured change in the forward printer map requires re-computation of the inverse map if accurate and consistent color reproduction is to be maintained. An efficient and accurate method of computing the inverse map could be used in an automatic color correction system. Three algorithms for computing the inverse of the forward printer map are studied in this thesis project. These are the Shepard's, Moving Matrix, and Iteratively Clustered Interpolation (ICI) algorithms. The algorithms are implemented in C and simulated in order to benchmark their relative accuracy, speed, and complexity. The simulations show the ICI algorithm to be the fastest and most accurate at computing the inverse map...

Simulation of a morphological image processor using VHDL - Part II: Control Mechanism

Chen, Hao
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
36.776929%
Very high speed integrated circuit Hardware Description Language (VHDL) is utilized in this project to model a Morphological Image Processor (MIP) Array. Both behavioral and structural models have been established at the system level, and the simulation results from both models are consistent with each other. The successful implementation of the models accomplishes our original goal to document the MIP with VHDL. It is observed from the project that VHDL is a powerful language. It is flexible since it can be used to model any level of a system independent of the technology.

Soft error propagation in floating-point programs

Li, Sha
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
36.776929%
Li, Xiaoming; As technology scales, VLSI performance has experienced an exponential growth. As feature sizes shrink, however, we will face new challenges such as soft errors (singleevent upsets) to maintain the reliability of circuits. Recent studies have tried to address soft errors with error detection and correction techniques such as error-correcting codes or redundant execution. However, these techniques come at a cost of additional storage or lower performance. We present a different approach to address soft errors. We start from building a quantitative understanding of the error propagation in software and propose a systematic evaluation of the impact of bit flip caused by soft errors on floating-point operations. Furthermore, we introduce a novel model to deal with soft errors. More specifically, we assume soft errors have occurred in memory and try to know how the errors will manifest in the results of programs. Therefore, some soft errors can be tolerated if the error in result is smaller than the intrinsic inaccuracy of floating-point representations or within a predefined range. We focus on analyzing error propagation for floating-point arithmetic operations. Our approach is motivated by interval analysis. We model the rounding effect of floating-point numbers...

Exploring Hidden Coherent Feature Groups and Temporal Semantics for Multimedia Big Data Analysis

Yang, Yimin
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: text Formato: application/pdf
Português
Relevância na Pesquisa
36.776929%
Thanks to the advanced technologies and social networks that allow the data to be widely shared among the Internet, there is an explosion of pervasive multimedia data, generating high demands of multimedia services and applications in various areas for people to easily access and manage multimedia data. Towards such demands, multimedia big data analysis has become an emerging hot topic in both industry and academia, which ranges from basic infrastructure, management, search, and mining to security, privacy, and applications. Within the scope of this dissertation, a multimedia big data analysis framework is proposed for semantic information management and retrieval with a focus on rare event detection in videos. The proposed framework is able to explore hidden semantic feature groups in multimedia data and incorporate temporal semantics, especially for video event detection. First, a hierarchical semantic data representation is presented to alleviate the semantic gap issue, and the Hidden Coherent Feature Group (HCFG) analysis method is proposed to capture the correlation between features and separate the original feature set into semantic groups, seamlessly integrating multimedia data in multiple modalities. Next, an Importance Factor based Temporal Multiple Correspondence Analysis (i.e....