1,514 research outputs found
Graphical Simulation Tool from Logical Token-based Distributed Mutual Exclusion Algorithms�
Computer Science
User Profile and Workload Analysis for Local Area Networks
Performance analysis tools for computer networks need accurate and comprehensive estimates of user workload. An approach is presented that estimates network impact for a wide variety of end user types and applications that are typical on local area networks. Fourteen user types and nine generic application types are defined, and data is collected to determine the average network bandwidth needed to accommodate the output of individual and aggregate user/application combinations. Workload is estimated using a combination of data obtained from live test experiments, and data collected from the literature. Finally, the implementation of this data in a highly interactive network modeling tool (NetMod) is illustrated with screen images generated during tool execution.http://deepblue.lib.umich.edu/bitstream/2027.42/107870/1/citi-tr-90-3.pd
When is a Network a Network? Multi-Order Graphical Model Selection in Pathways and Temporal Networks
We introduce a framework for the modeling of sequential data capturing
pathways of varying lengths observed in a network. Such data are important,
e.g., when studying click streams in information networks, travel patterns in
transportation systems, information cascades in social networks, biological
pathways or time-stamped social interactions. While it is common to apply graph
analytics and network analysis to such data, recent works have shown that
temporal correlations can invalidate the results of such methods. This raises a
fundamental question: when is a network abstraction of sequential data
justified? Addressing this open question, we propose a framework which combines
Markov chains of multiple, higher orders into a multi-layer graphical model
that captures temporal correlations in pathways at multiple length scales
simultaneously. We develop a model selection technique to infer the optimal
number of layers of such a model and show that it outperforms previously used
Markov order detection techniques. An application to eight real-world data sets
on pathways and temporal networks shows that it allows to infer graphical
models which capture both topological and temporal characteristics of such
data. Our work highlights fallacies of network abstractions and provides a
principled answer to the open question when they are justified. Generalizing
network representations to multi-order graphical models, it opens perspectives
for new data mining and knowledge discovery algorithms.Comment: 10 pages, 4 figures, 1 table, companion python package pathpy
available on gitHu
MGSim - Simulation tools for multi-core processor architectures
MGSim is an open source discrete event simulator for on-chip hardware
components, developed at the University of Amsterdam. It is intended to be a
research and teaching vehicle to study the fine-grained hardware/software
interactions on many-core and hardware multithreaded processors. It includes
support for core models with different instruction sets, a configurable
multi-core interconnect, multiple configurable cache and memory models, a
dedicated I/O subsystem, and comprehensive monitoring and interaction
facilities. The default model configuration shipped with MGSim implements
Microgrids, a many-core architecture with hardware concurrency management.
MGSim is furthermore written mostly in C++ and uses object classes to represent
chip components. It is optimized for architecture models that can be described
as process networks.Comment: 33 pages, 22 figures, 4 listings, 2 table
NetMod: A Design Tool for Large-Scale Heterogeneous Campus Networks
The Network Modeling Tool (NetMod) uses simple analytical models to provide the designers of large interconnected local area networks with an in-depth analysis of the potential performance of these systems. This tool can be used in either a university, industrial, or governmental campus networking environment consisting of thousands of computer sites. NetMod is implemented with a combination of the easy-to-use Macintosh software packages HyperCard and Excel. The objectives of NetMod, the analytical models, and the user interface are described in detail along with its application to an actual campus-wide network.http://deepblue.lib.umich.edu/bitstream/2027.42/107971/1/citi-tr-90-1.pd
Effect of real video streaming over virtual MANET environment
Wireless Ad hoc Network is promising in solving many challenging real-world communication problems. Examples of these are: military field operation, emergency response system, and oil drilling and mining operation. However, the wide deployment of this type of network is still a challenging task. It is very difficult to manage quality of services for real time applications like video transmission over mobile nodes. Mobile ad hoc networks are not so resilient and reliable because of their dynamic topology due to the mobile nodes and impact of environmental circumstances. However, it provides multiple routes from the source to the destination, which gives extra redundancy for video and data transmission. In this research work, I will analyze the effect of real video streaming in virtual simulation environment using mobile ad hoc network, terrain modeling module and the System-in-the-loop modules from the OPNET modeling tool
Deep Space Network information system architecture study
The purpose of this article is to describe an architecture for the Deep Space Network (DSN) information system in the years 2000-2010 and to provide guidelines for its evolution during the 1990s. The study scope is defined to be from the front-end areas at the antennas to the end users (spacecraft teams, principal investigators, archival storage systems, and non-NASA partners). The architectural vision provides guidance for major DSN implementation efforts during the next decade. A strong motivation for the study is an expected dramatic improvement in information-systems technologies, such as the following: computer processing, automation technology (including knowledge-based systems), networking and data transport, software and hardware engineering, and human-interface technology. The proposed Ground Information System has the following major features: unified architecture from the front-end area to the end user; open-systems standards to achieve interoperability; DSN production of level 0 data; delivery of level 0 data from the Deep Space Communications Complex, if desired; dedicated telemetry processors for each receiver; security against unauthorized access and errors; and highly automated monitor and control
Petri net based development of globally-asynchronous locally-synchronous distributed embedded systems
Dissertação para obtenção do Grau de Doutor em Engenharia Electrotécnica e de ComputadoresA model-based development approach (MBDA) for Globally-Asynchronous Locally-
Synchronous (GALS) Distributed Embedded Systems (DESs) is proposed. This approach
relies on the GALS-DESs specification through (low- or high-level) Petri net classes, which
ensure that the created models are GALS, locally deterministic, distributable, networkindependent,
and platform-independent and support their simulation, verification, and
implementation (using simulation, model-checking, and code generation tools). The use
of network- and platform-independent models enable the use of heterogeneous communication
networks to support the distributed components interaction and enable the use
of heterogeneous platforms to support the components and the communication nodes
implementation. To enable the proposed MBDA, Petri nets are extended with a set of the
concepts, most notably time-domains and asynchronous-channels. Algorithms to support
the verification of GALS-DES models and their decomposition into implementable
sub-models are also proposed. A tool chain framework (IOPT-tools) was extended with
this work proposals, supporting their validation and the GALS-DESs development.Fundação para a Ciência e a Tecnologia - grant ref. SFRH/BD/62171/200
Tangible user interfaces : past, present and future directions
In the last two decades, Tangible User Interfaces (TUIs) have emerged as a new interface type that interlinks the digital and physical worlds. Drawing upon users' knowledge and skills of interaction with the real non-digital world, TUIs show a potential to enhance the way in which people interact with and leverage digital information. However, TUI research is still in its infancy and extensive research is required in or- der to fully understand the implications of tangible user interfaces, to develop technologies that further bridge the digital and the physical, and to guide TUI design with empirical knowledge. This paper examines the existing body of work on Tangible User In- terfaces. We start by sketching the history of tangible user interfaces, examining the intellectual origins of this field. We then present TUIs in a broader context, survey application domains, and review frame- works and taxonomies. We also discuss conceptual foundations of TUIs including perspectives from cognitive sciences, phycology, and philoso- phy. Methods and technologies for designing, building, and evaluating TUIs are also addressed. Finally, we discuss the strengths and limita- tions of TUIs and chart directions for future research
WebFlow - A Visual Programming Paradigm for Web/Java Based Coarse Grain Distributed Computing
We present here the recent work at NPAC aimed at developing WebFlow---a general purpose Web based visual interactive programming environment for coarse grain distributed computing. We follow the 3-tier architecture with the central control and integration WebVM layer in tier-2, interacting with the visual graph editor applets in tier-1 (front-end) and the legacy systems in tier-3. WebVM is given by a mesh of Java Web servers such as Jeeves from JavaSoft or Jigsaw from MIT/W3C. All system control structures are implemented as URL-addressable servlets which enable Web browser-based authoring, monitoring, publication, documentation and software distribution tools for distributed computing. We view WebFlow/WEbVM as a promising programming paradigm and coordination model for the exploding volume of Web/Java software, and we illustrate it in a set of ongoing application development activities
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