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Full-Text Articles in Physical Sciences and Mathematics

Mobile Unity: A Language And Logic For Concurrent Mobile Systems, Peter J. Mccann, Gruia-Catalin Roman Jan 1997

Mobile Unity: A Language And Logic For Concurrent Mobile Systems, Peter J. Mccann, Gruia-Catalin Roman

All Computer Science and Engineering Research

Traditionally, a distributed system has been viewed as a collection of fixed computational elements connected by a static network. Prompted by recent advances in wireless communications rechnology, the emerging field of mobile computing is challenging these assumptions by providing mobile hosts with connectivity that may change over time, raising the possibility that hosts may be called upon to operate while only weakly connected to or while completely disconnected from other hosts. We define a concurrent mobile system as one where independently executing coponents may migrate through some space during the course of the computation, and where the pattern of connectivity …

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Reasoning About Code Mobility With Mobile Unity, Gian Pietro Picco, Gruia-Catalin Roman, Peter J. Mccann Jan 1997

Reasoning About Code Mobility With Mobile Unity, Gian Pietro Picco, Gruia-Catalin Roman, Peter J. Mccann

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Advancements in network technology have led to the emergence of new computing paradigms that challenge established programming practices by employing weak forms of consistency and dynamic forms of binding. Code mobility, for instance, allows for invocation-time binding between a code fragment and the location where it executes. Similarly, mobile computing allows hosts (and the software they execute) to alter their physical location. Despite apparent similarities, the two paradigms are distinct in their treatment of location and movement. This paper seeks to uncover a common foundation for the two paradigms by exploring the manner in which stereotypical forms of code mobility …

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Sequence Assembly Validation By Restriction Digest Fingerprint Comparison, Eric C. Rouchka, David J. States Jan 1997

Sequence Assembly Validation By Restriction Digest Fingerprint Comparison, Eric C. Rouchka, David J. States

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DNA sequence analysis depends on the accurate assembly of fragment reads for the determination of a consensus sequence. Genomic sequences frequently contain repeat elements that may confound the fragment assembly process, and errors in fragment assembly, and errors in fragment assembly may seriously impact the biological interpretation of the sequence data. Validating the fidelity of sequence assembly by experimental means is desirable. This report examines the use of restriction digest analysis as a method for testing the fidelity of sequence assembly. Restriction digest fingerprint matching is an established technology for high resolution physical map construction, but the requirements for assembly …

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End-User Visualization And Manipulation Of Aggregate Data, T. Paul Mccartney, Kenneth J. Goldman Jan 1997

End-User Visualization And Manipulation Of Aggregate Data, T. Paul Mccartney, Kenneth J. Goldman

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Aggregate visualization and manipulation enables the viewing and interaction of dynamically changing data sets in a graphically meaningful way. However, off-the-shelf applications generally provide only limited ways to view aggregates. To be truly effective to the end-user, an aggregate visualization should be customizable to suit the individual's needs. This paper describes a software system that empowers end-users to create interactive aggregate visualizations through direct manipulation. Included are mechanisms for specifying how aggregate data is processed from multiple sources, providing functionality similar to project, select, join, and cross product of relational databases. Visualization of distributed data sets is emphasized.

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Compositional Programming Abstractions For Mobile Computing, Peter J. Mccann, Gruia-Catalin Roman Jan 1997

Compositional Programming Abstractions For Mobile Computing, Peter J. Mccann, Gruia-Catalin Roman

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Recent advances in wireless networking technology and the increasing demand for ubiquitous, mobile connectivity demonstrate the importance of providing reliable systems for managing reconfiguration and disconnection of components. Design of such systems requires tools and techniques appropriate to the task. Many formal models of computation, including UNITY, are not adequate for expressing reconfiguration and disconnection and are therefore inappropriate vehicles for investigating the impact of mobility on the construction of modular and composable systems. Algebraic formalisms such as the pi-calculus have been proposed for modeling mobility. This paper addresses the question of whether UNITY, a state-based formalism with a foundation …

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An Introduction To Mobile Unity, Gruia-Catalin Roman, Peter J. Mccann Jan 1997

An Introduction To Mobile Unity, Gruia-Catalin Roman, Peter J. Mccann

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Traditionally, a distributed system has been viewed as a collection of fixed computational elements connected by a static network. Prompted by recent advances in wireless communications rechnology, the emerging field of mobile computing is challenging these assumptions by providing mobile hosts with connectivity that may change over time, raising the possibility that hosts may be called upon to operate while only weakly connected to or while completely disconnected from other hosts. We define a concurrent mobile system as one where independently executing coponents may migrate through some space during the course of the computation, and where the pattern of connectivity …

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Noise-Tolerant Parallel Learning Of Geometric Concepts, Nader H. Bshouty, Sally A. Goldman, H. David Mathias Jan 1997

Noise-Tolerant Parallel Learning Of Geometric Concepts, Nader H. Bshouty, Sally A. Goldman, H. David Mathias

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We present several efficient parallel algorithms for PAC-learning geometric concepts in a constant-dimensional space. The algorithms are robust even against malicious classification noise of any rate less than 1/2. We first give an efficient noise-tolerant parallel algorithm to PAC-learn the class of geometric concepts defined by a polynomial number of (d-1)-dimensional hyperplanes against an arbitrary distribution where each hyperplane has a slope from a set of known slopes. We then describe how boosting techniques can be used so that our algorithms' dependence on {GREEK LETTER} and {DELTA} does not depend on d. Next we give an efficient noise-tolerant parallel algorithm …

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Noise-Tolerant Distribution-Free Learning Of General Geometric Concepts, Nader H. Bshouty, Sally A. Goldman, H. David Mathias, Subhash Suri, Hisao Tamaki Jan 1997

Noise-Tolerant Distribution-Free Learning Of General Geometric Concepts, Nader H. Bshouty, Sally A. Goldman, H. David Mathias, Subhash Suri, Hisao Tamaki

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We present an efficient algorithm for PAC-learning a very general class of geometric concepts over Rd for fixed d. More specifically, let T be any set of s halfspaces. Let x = (x1,...,xd) be an arbitrary point in Rd. With each t Є T we associate a boolean indicator function It(x) which is 1 if and only if x is in the halfspace t. The concept class Cds that we study consists of all concepts formed by any boolean function over It1, ...Its for ti Є T. This class is much more general than any geometric concept class known to …

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An Error Control Scheme For Large-Scale Multicast Applications, Christos Papadopoulos, Guru Parulkar, George Varghese Jan 1997

An Error Control Scheme For Large-Scale Multicast Applications, Christos Papadopoulos, Guru Parulkar, George Varghese

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Retransmission based error control for large scale multicast applications is difficult because of two main problems: request implosion and lack of local recovery. Existing schemes (SRM, RMTP, TMTP, LBRRM) have good solutions to request implosion, but only approximate solutions (e.g., based on scoped multicast) for the local recovery problem. Our scheme achieves finer grain fault recovery by exploiting new forwarding services that allow us to create a dynamic hierarchy of receivers. We use a new paradigm, where routers provide a more refined form of multicasting (that may be useful to other applications), that enables local recovery. The new services, however, …

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Reducing Web Latencies Using Precomputed Hints, Girish P. Chandranmenon, George Varghese Jan 1997

Reducing Web Latencies Using Precomputed Hints, Girish P. Chandranmenon, George Varghese

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Current network technology is bandwidth-rich but latency-poor; thus round-trip delays will dominate access latency for web traffic. We describe four new techniques that reduce the round-trips needed for web accesses. The techniques are based on the paradigm of preprocessing a web page to collect information about links and inline data in the page. Stored Address Binding almost always eliminates the DNS lookup (which can cost seconds) at the start of a transaction. In Informed Server Proxying, a server tells its client that it has cached pages referenced in a page the client just retrieved; this allows the client to retrieve …

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An Architecture For Monitoring Visualization And Control Of Gigabit Networks, Guru Parulkar, Douglas Schmidt, Eileen Kraemer, Jonathan Turner, Anshul Kantawala Jan 1997

An Architecture For Monitoring Visualization And Control Of Gigabit Networks, Guru Parulkar, Douglas Schmidt, Eileen Kraemer, Jonathan Turner, Anshul Kantawala

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We propose a network monitoring, visualization and control system (NMVC) that ensures adequate quality of service to network users while maintaining high network resource utilization. The main components of our system are a network probe, an endsystem probe, software network management agents that provide extensible multi-attribute event filtering for highly scalable data/event collection, network operation centers (NOCs) which can remotely install and (re)configure these agents, efficient online event ordering algorithms that can help synthesize and display a consistent view of network health, status and performance and a View Choreographer that allows management applications and administrators to specify the mapping of …

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Euphoria Reference Manual, T. Paul Mccartney, Kenneth J. Goldman Jan 1997

Euphoria Reference Manual, T. Paul Mccartney, Kenneth J. Goldman

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EUPHORIA is a user interface management system that enables end-users to create direct manipulation graphical user interfaces (GUIs) through interactive drawing. Used in conjunction with The Programmers' Playground, a distributed programming environment, end-users can dynamically create and associate GUI components with an underlying application without programming, This document describes EUPHORIA's functionality.

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Costs Of Constraint Based Networks On A Sphere, Hongzhou Ma, Jonathan Turner Jan 1997

Costs Of Constraint Based Networks On A Sphere, Hongzhou Ma, Jonathan Turner

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This paper estimates the link costs of constraint based nonblocking ATM networks on a sphere. Analytical results are obtained when switches are uniformly distributed on the surface of a unit sphere and every switch has source and sink capacity of one, and the results are compared with simulations.

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An Algorithm For Message Delivery In A Micromobility Environment, Amy L. Murphy, Gruia-Catalin Roman, George Varghese Jan 1997

An Algorithm For Message Delivery In A Micromobility Environment, Amy L. Murphy, Gruia-Catalin Roman, George Varghese

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With recent advances in wireless communication and the ubiquity of laptops, mobile computing has become an important research area. An essential problem in mobile computing is the delivery of a message from a source to either a single mobile node, unicast, or to a group of mobile nodes, multicast. Standard solutions proposed for macromobility (Mobile IP) and micromobility (cellular phones) for the unicast problem rely on tracking the mobile node. Tracking solutions scale badly when mobile nodes move frequently, and do not generalize well to multicast delivery. Our paper proposes a new message delivery algorithm for micromobility based on a …

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Symmetrical Routes And Reverse Path Congestion Control, Rajib Ghosh, George Varghese Jan 1997

Symmetrical Routes And Reverse Path Congestion Control, Rajib Ghosh, George Varghese

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We describe new mechanisms to deal with asymmetries that arise in routing protocols. We show how to avoid route asymmetries (due to non-unique shortest paths) by adding random integer link costs. We show in detail how RIP can be modified to avoid route asymmetry with high probability, without affecting either its efficiency or performance metrics such as convergence time. Symmetrical intra-domain routing also makes possible a new form of congestion control that we call Reverse Path Congestion Control (RPCC). We show, using simulations, that RPCC can augment existing TCP congestion control mechanisms to improve start up behavior and to avoid …

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Enhancements To 4.4 Bsd Unix For Efficient Networked Multimedia In Project Mars, Milind M. Buddhikot, Xin Jane Chen, Dakang Wu, Guru M. Parulkar Jan 1997

Enhancements To 4.4 Bsd Unix For Efficient Networked Multimedia In Project Mars, Milind M. Buddhikot, Xin Jane Chen, Dakang Wu, Guru M. Parulkar

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Cluster based architectures that employ high performance inexpensive Personal Computers (PCs) interconnected by high speed commodity interconnect have been recognized as a cost-effective way of building high performance scalable Multimedia-On-Demand (MOD) storage servers [4, 5, 7, 9]. Typically, the PCs in these architectures run operating systems such as UNIX that have traditionally been optimized for interactive computing. They do not provide fast disk-to-network data paths and guaranteed CPU and storage access. This paper reports enhancements to the 4.4 BSD UNIX system carried out to rectify these limitations in the context of our Project Massively-parallel And Real-time Storage (MARS) [7]. We …

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End-User Visualization And Manipulation Of Distributed Aggregate Data, T. Paul Mccartney, Kenneth J. Goldman Jan 1997

End-User Visualization And Manipulation Of Distributed Aggregate Data, T. Paul Mccartney, Kenneth J. Goldman

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Aggregate visualization and manipulation enables the viewing and interaction of dynamically changing data sets in a graphically meaningful way. However, off-the-shelf applications typically provide only limited ways to view static aggregates and generally to not support manipulation of aggregate data through the resulting visualization. To be fully dynamic, an aggregate visualization should be customizable to suit the individual's needs and should allow end-users to modify the data through direct manipulation. This paper describes a software system that empowers end-users to create interactive aggregate visualizations through a visual language interface. Included are mechanisms for specifying how aggregate data is processed from …

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Replication Of The First Controlled Experiment On The Usefulness Of Design Patterns: Detailed Description And Evaluation, Lutz Prechelt, Barbara Unger, Douglas Schmidt Jan 1997

Replication Of The First Controlled Experiment On The Usefulness Of Design Patterns: Detailed Description And Evaluation, Lutz Prechelt, Barbara Unger, Douglas Schmidt

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Advocates of software design patterns claim that using design patterns improves communication between software developers. The controled experiment that we describe in this report tests the hypothesis that software maintainers of well-structured, well-documented software containing design patterns can make changes (1) faster and (2) with less errors if the use of patterns is explicitly documented in the software. The experiment was performed with 22 participants of a university course on C++ and design patterns; it is similar to a previous experiment performed in Karlsruhe. For one of the two experiment tasks the experiment finds that both hypotheses appear to be …

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Expressing Code Mobility In Mobile Unity, Gian Pietro Picco, Gruia-Catalin Roman, Peter J. Mccann Jan 1997

Expressing Code Mobility In Mobile Unity, Gian Pietro Picco, Gruia-Catalin Roman, Peter J. Mccann

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Advancements in network technology have led to the emergence of new computing paradigms that challenge established programming practices by employing weak forms of consistency and dynamic forms of binding. Code mobility, for instance, allows for invocation-time binding between a code fragment and the location where it executes. Similarly, mobile computing allows hosts (and the software they execute) to alter their physical location. Despite apparent similarities, the two paradigms are distinct in their treatment of location and movement. This paper seeks to uncover a common foundation for the two paradigms by exploring the manner in which stereotypical forms of code mobility …

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Eliding The Arguments Of Cases, Ronald P. Loui, Jeff Norman Jan 1997

Eliding The Arguments Of Cases, Ronald P. Loui, Jeff Norman

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No abstract provided.

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Dynamic Flow Switching: A New Communication Service For Atm Networks, Qiyong Bian, Kohei Shimoto, Jonathan Turner Jan 1997

Dynamic Flow Switching: A New Communication Service For Atm Networks, Qiyong Bian, Kohei Shimoto, Jonathan Turner

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This paper presents a new communication service for ATM networks that provides one-way, adjustable rate, on-demand communication channels. The proposed dynamic flow service is designed to operate within a multi-service cell switched network that supports both conventional switched virtual circuits and IP packet routing and is designed to complement those services. It is particularly well suited to applications that transmit substantial amounts of data (a few tens of kilobytes or more) in fairly short time periods (up to a few seconds). Much of the current world-wide web traffic falls within this domain. Like IP packet networks, the new service permits …

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Balancing Consistency And Lag In Transaction-Based Computational Steering, Eileen Kraemer, Delbert Hart, Gruia-Catalin Roman Jan 1997

Balancing Consistency And Lag In Transaction-Based Computational Steering, Eileen Kraemer, Delbert Hart, Gruia-Catalin Roman

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Computational steering, the interactive adjustment of application parameters and allocation of resources, is a promising technique for higher-productivity simulation, finer-grained optimization of dynamically varying algorithms, and greater understanding of program behavior and the characteristics of data sets and solution spaces. Tools for computational steering must provide monitoring, visualization, and interaction facilities. In addition, these tools must address issues related to the consistency, latency, and scalability at each of these phases, and must consider the perturbation that results. In this paper we describe transaction-based components for a computational steering system and present an approach that guarantees consistent monitoring and displays, supports …

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The Programmers' Playground Application Management System User Guide, William M. Shapiro, T. Paul Mccartney, E.F. Berkley Shands Jan 1997

The Programmers' Playground Application Management System User Guide, William M. Shapiro, T. Paul Mccartney, E.F. Berkley Shands

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Application Management permits the advertising, launching, and configuring of distributed applications created using the Programmers' Playground. Applications can be documented and made available to end-users through the use of application pages on the World Wide Web. The launching and configuring of applications is performed by a brokerage system consisting of an applicatoin broker and one or more hierarchies of module launchers. This document describes how to setup and use the components of the Application Management system.

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Design And Implementation Of A New Connection Admission Control Algorithm Using A Multistate Traffic Source Model, Robert Engel Jan 1997

Design And Implementation Of A New Connection Admission Control Algorithm Using A Multistate Traffic Source Model, Robert Engel

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This report develops a practical method for connection admission control in ATM networks. The method is based on a virtual cell loss probability criterion, is designed to handle heterogeneous traffic types and allows each traffic source to be described by an individual finite-state model with as many states as are needed to describe the source traffic. To make connection admission decisions with respect to individual links, an aggregate finite state model is computed from the individual models and used to estimate the virtual cell loss probabilities. To reduce the computational requirements for maintaining the aggregate traffic model, the aggregate model …

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Principles For Developing And Measuring High-Performance Web Servers Over Atm, James C. Hu, Sumedh Mungee, Douglas C. Schmidt Jan 1997

Principles For Developing And Measuring High-Performance Web Servers Over Atm, James C. Hu, Sumedh Mungee, Douglas C. Schmidt

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High-performance Web servers are essential to meet the growing demands of the Internet. Satisfying these demands requires a thorough understanding of the key factors that affect Web server performance. This paper provides three contributions to the design, implementation, and evaluation of high-performance Web servers. First, we report the results of a comprehensive empirical study of popular high-performance Web servers (such as Apache, Netscape Enterprise, PHTTPD, and Zeus) over high-speed ATM networks. This study illustrates their relative performance and identifies their performance bottlenecks. To measure performance accurately, we developed a new benchmarking technique that subjects Web servers to varying connection frequencies. …

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Optimizing The Performance Of The Corba Internet Inter-Orb Protocol Over Atm, Aniruddha Gokhale, Douglas C. Schmidt Jan 1997

Optimizing The Performance Of The Corba Internet Inter-Orb Protocol Over Atm, Aniruddha Gokhale, Douglas C. Schmidt

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The Internet Inter-ORB Protocol (IIOP) enables heterogeneous CORBA-compliant Object Request Brokers (ORBs) to interoperate over TCP/IP networks. The IIOP uses the Common Data Representation (CDR) transfer syntax to map CORBA Interface Definition Langauge (IDL) data types into a bi-canonical wire format. Due to the excessive marshaling/demarshaling overhead, data copying, and high-levels of function call overhead, conventional implementation of IIOP protocols yield poor performance over high-speed networks. To meet the demands of emerging distributed multimedia applications, CORBA-compliant ORBs must support both interoperable and highly efficient IIOP implementations. This paper provides two contributions to the study and design of high performance CORBA …

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Using Snapshot Streams To Support Visual Exploration, Delbert Hart, Eileen Kraemer, Gruia-Catalin Roman Jan 1997

Using Snapshot Streams To Support Visual Exploration, Delbert Hart, Eileen Kraemer, Gruia-Catalin Roman

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The non-determinism, complexity, and size of distributed software systems present significant difficulties for designers and maintainers. Visualization can help alleviate these difficulties through interactive exploratory tools that allow both novice and experienced users to investigate a distributed computation using a common tool set. Essential to the success of a visual exploration tool is the ability to provide accurate representations of global states. This paper is concerned with the use of snapshots in support of interactive visual exploration of distributed computations. The nature of the visualization process requires snapshots that (1) are consecutive, thus facilitating smooth animation of state changes, (2) …

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Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 13, Number 1, January 1997, College Of Engineering And Computer Science, Wright State University Jan 1997

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 13, Number 1, January 1997, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

A twelve page newsletter created by the Wright State University College of Engineering and Computer Science that addresses the current affairs of the college.

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Measurement Of The Spectral Functions Of Vector Current Hadronic Tau Decays, R. Barate, M. Thulasidas Jan 1997

Measurement Of The Spectral Functions Of Vector Current Hadronic Tau Decays, R. Barate, M. Thulasidas

Research Collection School Of Computing and Information Systems

A measurement of the spectral functions of non-strange τ vector current final states is presented, using 124 358 τ pairs recorded by the ALEPH detector at LEP during the years 1991 to 1994. The spectral functions of the dominant two- and four-pion τ decay channels are compared to published results of e + e - annihilation experiments via isospin rotation. A combined fit of the pion form factor from τ decays and e + e - data is performed using different parametrizations. The mass and the width of the ρ ±(770) and the ρ 0(770) are separately determined in order …

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A Study Of Τ Decays Involving Η And Ω Mesons, D. Buskulic, M. Thulasidas Jan 1997

A Study Of Τ Decays Involving Η And Ω Mesons, D. Buskulic, M. Thulasidas

Research Collection School Of Computing and Information Systems

The 132 pbt - 1 of data collected by ALEPH from 1991 to 1994 have been used to analyze η and ω production in τ decays. The following branching fractions have been measured: B(τ−→ντωh−)=(1.91±0.07±0.06)×10−2,B(τ−→ντωh−)=(1.91±0.07±0.06)×10−2, B(τ−→ντωh−π0)=(4.3±0.6±0.5)×10−3,B(τ−→ντωh−π0)=(4.3±0.6±0.5)×10−3, B(τ−→ντηK−)=(2.9+1.3−1.2±0.7)×10−4,B(τ−→ντηK−)=(2.9−1.2+1.3±0.7)×10−4, B(τ−→ντηh−π0)=(1.8±0.4±0.2)×10−3B(τ−→ντηh−π0)=(1.8±0.4±0.2)×10−3 and the 95% C.L. limit B(τ− → ντηπt -) t - 4 has been obtained. The ωπt- and ηπt -π0 rates and dynamics are found in agreement with the predictions made from e+e∼ - annihilation data with the help of isospin invariance (CVC).

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