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Articles 841 - 870 of 1103

Full-Text Articles in Computer Sciences

Mobile Agents And The Future Of The Internet, David Kotz, Robert S. Gray Aug 1999

Mobile Agents And The Future Of The Internet, David Kotz, Robert S. Gray

Dartmouth Scholarship

Use of the Internet has exploded in recent years with the appearance of the World-Wide Web. In this paper, we show how current technological trends may lead to a system based substantially on mobile code, and in many cases, mobile agents. We discuss several technical and non-technical hurdles along the path to that eventuality. It seems likely that, within a few years, nearly all major Internet sites will be capable of hosting and willing to host some form of mobile code or mobile agents.

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Existence Theorems For Scheduling To Meet Two Objectives, April M. Rasala Jun 1999

Existence Theorems For Scheduling To Meet Two Objectives, April M. Rasala

Dartmouth College Undergraduate Theses

We will look at the existence of schedules which are simultaneously near-optimal for two criteria. First, we will present some techniques for proving existence theorems, in a very general setting, for bicriterion scheduling problems. We will then use these techniques to prove existence theorems for a large class of problems. We will consider the relationship between objective functions based on completion time, flow time, lateness and the number of on-time jobs. We will also present negative results first for the problem of simultaneously minimizing the maximum flow time and average weighted flow time and second for minimizing the maximum flow …

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Computers, Art And Smart Rooms: A Smart Picture Frame That Senses The Weather And Genetically Evolves Images, Marisa E. Kolodny Jun 1999

Computers, Art And Smart Rooms: A Smart Picture Frame That Senses The Weather And Genetically Evolves Images, Marisa E. Kolodny

Dartmouth College Undergraduate Theses

By using sensors to sense the environment and genetic programming to evolve images, this thesis explores two methods for developing smart pictures that can be integrated with a living space. The system presented senses the weather and indoor conditions, displays current weather and forecast information retrieved from the web, and displays genetically evolved images. Sensing the weather not only provides the user with information they might find useful, but also allows the computer to gain a better understanding of the user which in turn allows the computer to respond more accurately. Genetic programming allows the computer to better respond to …

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A Two Dimensional Crystalline Atomic Unit Modular Self-Reconfigurable Robot, Marsette Arthur Vona Iii Jun 1999

A Two Dimensional Crystalline Atomic Unit Modular Self-Reconfigurable Robot, Marsette Arthur Vona Iii

Dartmouth College Undergraduate Theses

Self-reconfigurable robots are designed so that they can change their external shape without human intervention. One general way to achieve such functionality is to build a robot composed of multiple, identical unit modules. If the modules are designed so that they can be assembled into rigid structures, and so that individual units within such structures can be relocated within and about the structure, then self-reconfiguration is possible. We propose the Crystalline Atomic unit modular self-reconfigurable robot, where each unit is called an Atom. In two dimensions, an Atom is square. Connectors at the faces of each Atom support structure formation …

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An Application Of Word Sense Disambiguation To Information Retrieval, Jason M. Whaley Jun 1999

An Application Of Word Sense Disambiguation To Information Retrieval, Jason M. Whaley

Dartmouth College Undergraduate Theses

The problems of word sense disambiguation and document indexing for information retrieval have been extensively studied. It has been observed that indexing using disambiguated meanings, rather than word stems, should improve information retrieval results. We present a new corpus-based algorithm for performing word sense disambiguation. The algorithm does not need to train on many senses of each word; it uses instead the probability that certain concepts will occur together. That algorithm is then used to index several corpa of documents. Our indexing algorithm does not generally outperform the traditional stem-based tf.idf model.

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The Implementation Of Dassf Otcl Apis, Hongxia Quan Jun 1999

The Implementation Of Dassf Otcl Apis, Hongxia Quan

Dartmouth College Undergraduate Theses

As an extension of Tcl, Otcl provides basic functionality for object-oriented programming in scripting language Tcl. We implemented the Otcl APIs for DaSSF (a parallel simulator software written in C++ at Dartmouth College) using Tclcl software package written in University of California at Berkeley. This document discussed the issues involved in the implementation, especially the communications between C++ objects and Otcl objects required by DaSSF and the naming problems.

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Parallel Dassf Discrete-Event Simulation Without Shared Memory, James D. Chalfant Jun 1999

Parallel Dassf Discrete-Event Simulation Without Shared Memory, James D. Chalfant

Dartmouth College Undergraduate Theses

The Dartmouth implementation of the Scalable Simulation Framework (DaSSF) is a discrete-event simulator used primarily in the simulation of networks. It achieves high performance through parallel processing. DaSSF 1.22 requires shared memory between all processors in order to operate. This limits the number of processors available and the hardware platforms that can exploit parallelism. We are interested in extending parallel DaSSF operation to architectures without shared memory. We explore the requirements of this by implementing parallel DaSSF using MPI as the sole form of interaction between processors. The approaches used to achieve this can be abstracted and applied to the …

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Two Algorithms For Performing Multidimensional, Multiprocessor, Out-Of-Core Ffts, Lauren M. Baptist Jun 1999

Two Algorithms For Performing Multidimensional, Multiprocessor, Out-Of-Core Ffts, Lauren M. Baptist

Dartmouth College Undergraduate Theses

We show two algorithms for computing multidimensional Fast Fourier Transforms (FFTs) on a multiprocessor system with distributed memory when problem sizes are so large that the data do not fit in the memory of the entire system. Instead, data reside on a parallel disk system and are brought into memory in sections. We use the Parallel Disk Model for implementation and analysis. The first method is a straightforward out-of-core variant of a well-known method for in-core, multidimensional FFTs. It performs 1-dimensional FFT computations on each dimension in turn. This method is easy to generalize to any number of dimensions, and …

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Improved Computer Detection And Mapping Of Cerebral Oxygenation, David H. Kung Jun 1999

Improved Computer Detection And Mapping Of Cerebral Oxygenation, David H. Kung

Dartmouth College Undergraduate Theses

Near-infrared (NIR) optical image reconstruction that incorporates blood oxygen level dependant (BOLD) magnetic resonance imaging has the potential to improve both quantifiable measurement of oxygenation and the spatial resolution involved in such mapping. My thesis continues some preliminary work in this area through development of an analytic diffusion parameter estimation algorithm for use with a NIR imaging array and development of a finite element mesh utility to read a priori BOLD images and tag them with property elements for NIR image resolution improvement.

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Investigating Measures For Pairwise Document Similarity, Jeffrey D. Isaacs Jun 1999

Investigating Measures For Pairwise Document Similarity, Jeffrey D. Isaacs

Dartmouth College Undergraduate Theses

The need for a more effective similarity measure is growing as a result of the astonishing amount of information being placed online. Most existing similarity measures are defined by empirically derived formulas and cannot easily be extended to new applications. We present a pairwise document similarity measure based on Information Theory, and present corpus dependent and independent applications of this measure. When ranked with existing similarity measures over TREC FBIS data, our corpus dependent information theoretic similarity measure ranked first.

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Fast Out-Of-Core Sorting On Parallel Disk Systems, Matthew D. Pearson Jun 1999

Fast Out-Of-Core Sorting On Parallel Disk Systems, Matthew D. Pearson

Dartmouth College Undergraduate Theses

This paper discusses our implementation of Rajasekaran's (l,m)-mergesort algorithm (LMM) for sorting on parallel disks. LMM is asymptotically optimal for large problems and has the additional advantage of a low constant in its I/O complexity. Our implementation is written in C using the ViC* I/O API for parallel disk systems. We compare the performance of LMM to that of the C library function qsort on a DEC Alpha server. qsort makes a good benchmark because it is fast and performs comparatively well under demand paging. Since qsort fails when the swap disk fills up, we can only compare these algorithms …

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An Environment For The Facilitation Of Robotic Programming, Artem Lifschitz Jun 1999

An Environment For The Facilitation Of Robotic Programming, Artem Lifschitz

Computer Science Technical Reports

I have developed, tested, and evaluated a robot programming environment organized as a library of flexible data structures to facilitate the creation of robotics programs. Abstractions are the basis of all of the achievements of Computer Science, and if it were possible to create a truly flexible, generic abstraction for the programming of robots -- the science of robotics could advance at a faster pace. For this reason, I have attempted to implement the abstraction of low-level commands, and the assembling of them into hierarchies of higher-level actions. My libraries provide mechanisms for the manipulation and queuing of actions, as …

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Mobile-Agent Planning In A Market-Oriented Environment, Jonathan Bredin, David Kotz, Daniela Rus May 1999

Mobile-Agent Planning In A Market-Oriented Environment, Jonathan Bredin, David Kotz, Daniela Rus

Computer Science Technical Reports

We propose a method for increasing incentives for sites to host arbitrary mobile agents in which mobile agents purchase their computing needs from host sites. We present a scalable market-based CPU allocation policy and an on-line algorithm that plans a mobile agent's expenditure over a multihop ordered itinerary. The algorithm chooses a set of sites at which to execute and computational priorities at each site to minimize execution time while preserving a prespecified budget constraint. We present simulation results of our algorithm to show that our allocation policy and planning algorithm scale well as more agents are added to the …

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Using Haptic Vector Fields For Animation Motion Control, Bruce Randall Donald, Frederick Henle May 1999

Using Haptic Vector Fields For Animation Motion Control, Bruce Randall Donald, Frederick Henle

Computer Science Technical Reports

We are exploring techniques for animation authoring and editing using a haptic force-feedback device. In our system, a family of animations is encoded by a bundle of trajectories. This bundle in turn defines a time-varying, higher-order vector field on a configuration space for the animation. A haptic input device provides a low-dimensional parameterization of the resulting dynamical system, and the haptic force feedback permits browsing and editing of the space of animations, by allowing the user to experience the vector field as physical forces.

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Mobile Code: The Future Of The Internet, David Kotz, Robert S. Gray May 1999

Mobile Code: The Future Of The Internet, David Kotz, Robert S. Gray

Dartmouth Scholarship

Use of the Internet has exploded in recent years with the appearance of the World-Wide Web. In this paper, we show how current technological trends necessarily lead to a system based substantially on mobile code, and in many cases, mobile agents. We discuss several technical and non-technical hurdles along the path to that eventuality. Finally, we predict that, within five years, nearly all major Internet sites will be capable of hosting and willing to host some form of mobile agents.

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Economic Markets As A Means Of Open Mobile-Agent Systems, Jonathan Bredin, David Kotz, Daniela Rus May 1999

Economic Markets As A Means Of Open Mobile-Agent Systems, Jonathan Bredin, David Kotz, Daniela Rus

Dartmouth Scholarship

Mobile-agent systems have gained popularity in use because they ease the application design process by giving software engineers greater flexibility. Although the value of any network is dependent on both the number of users and the number of sites participating in the network, there is little motivation for systems to donate resources to arbitrary agents. We propose to remedy the problem by imposing an economic market on mobile-agent systems where agents purchase resources from host sites and sell services to users and other agents. Host sites accumulate revenues, which are distributed to users to be used to launch more agents. …

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Greedy Approximation Algorithms For K-Medians By Randomized Rounding, Neal E. Young Mar 1999

Greedy Approximation Algorithms For K-Medians By Randomized Rounding, Neal E. Young

Computer Science Technical Reports

We give an improved approximation algorithm for the general k-medians problem. Given any \epsilon>0, the algorithm finds a solution of total distance at most D(1+\epsilon) using at most k ln(n+n/\epsilon) medians (a.k.a. sites), provided some solution of total distance D using k medians exists. This improves over the best previous bound (w.r.t. the number of medians) by a factor of \Omega(1/\epsilon) provided 1/\epsilon=n^O(1). The algorithm is a greedy algorithm, derived using the method of oblivious randomized rounding. It requires at most k ln(n+n/\epsilon) linear-time iterations. We also derive algorithms for fractional and weighted variants of the problem.

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Hey, You Got Your Language In My Operating System!, Jon Howell, Mark Montague Dec 1998

Hey, You Got Your Language In My Operating System!, Jon Howell, Mark Montague

Computer Science Technical Reports

Several projects in the operating systems research community suggest a trend of convergence among features once divided between operating systems and languages. We describe how partial evaluation and transformational programming systems apply to this trend by providing a general framework for application support, from compilation to run-time services. We contend that the community will no longer think of implementing a static collection of services and calling it an operating system; instead, this general framework will allow applications to be flexibly configured, and the ``operating system'' will simply be the application support that is supplied at run-time.

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Snowflake: Spanning Administrative Domains, Jon Howell, David Kotz Dec 1998

Snowflake: Spanning Administrative Domains, Jon Howell, David Kotz

Computer Science Technical Reports

Many distributed systems provide a ``single-system image'' to their users, so the user has the illusion that they are using a single system when in fact they are using many distributed resources. It is a powerful abstraction that helps users to manage the complexity of using distributed resources. The goal of the Snowflake project is to discover how single-system images can be made to span administrative domains. Our current prototype organizes resources in namespaces and distributes them using Java Remote Method Invocation. Challenging issues include how much flexibility should be built into the namespace interface, and how transparent the network …

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Utility Driven Mobile-Agent Scheduling, Jonathan Bredin, David Kotz, Daniela Rus Oct 1998

Utility Driven Mobile-Agent Scheduling, Jonathan Bredin, David Kotz, Daniela Rus

Computer Science Technical Reports

Mobile agents are programs capable of migrating from one host machine to another. We propose that mobile agents purchase resource access rights from host machines thereby establishing a market for computational resources and giving agents a metric to evenly distribute themselves throughout the network. Market participation requires quantitative information about resource consumption to define demand and calculate utility. We create a formal utility model to derive user-demand functions, allowing agents to efficiently plan expenditure and deal with price fluctuations. By quantifying demand and utility, resource owners can precisely set a value for a good. We simulate our model in a …

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Abstractions For Simplifying Planning In Self-Reconfigurable Robotic Systems, Craig Mcgray, Daniela Rus Oct 1998

Abstractions For Simplifying Planning In Self-Reconfigurable Robotic Systems, Craig Mcgray, Daniela Rus

Computer Science Technical Reports

In [KVRM], we described a three-dimensional self-reconfiguring robot module called the Molecule Robot. In this paper, we provide a system of abstractions for modules in self-reconfigurable robotic systems, and show how this system can be used to simplify the motion planning of the Molecule Robot system.

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Applications Of Parallel I/O, Ron Oldfield, David Kotz Aug 1998

Applications Of Parallel I/O, Ron Oldfield, David Kotz

Computer Science Technical Reports

Scientific applications are increasingly being implemented on massively parallel supercomputers. Many of these applications have intense I/O demands, as well as massive computational requirements. This paper is essentially an annotated bibliography of papers and other sources of information about scientific applications using parallel I/O. It will be updated periodically.

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Multiple Media Correlation: Theory And Applications, Charles B. Owen Jun 1998

Multiple Media Correlation: Theory And Applications, Charles B. Owen

Dartmouth College Ph.D Dissertations

This thesis introduces multiple media correlation, a new technology for the automatic alignment of multiple media objects such as text, audio, and video. This research began with the question: what can be learned when multiple multimedia components are analyzed simultaneously? Most ongoing research in computational multimedia has focused on queries, indexing, and retrieval within a single media type. Video is compressed and searched independently of audio, text is indexed without regard to temporal relationships it may have to other media data. Multiple media correlation provides a framework for locating and exploiting correlations between multiple, potentially heterogeneous, media streams. The goal …

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Boosting A Simple Weak Learner For Classifying Handwritten Digits, Matthew P. Carter Jun 1998

Boosting A Simple Weak Learner For Classifying Handwritten Digits, Matthew P. Carter

Dartmouth College Undergraduate Theses

A weak PAC learner is one which takes labeled training examples and produces a classifier which can label test examples more accurately than random guessing. A strong learner (also known as a PAC learner), on the other hand, is one which takes labeled training examples and produces a classifier which can label test examples arbitrarily accurately. Schapire has constructively proved that a strong PAC learner can be derived from a weak PAC learner. A performance boosting algorithm takes a set of training examples and a weak PAC learning algorithm and generates a strong PAC learner. Our research attempts to solve …

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Multiscouting: Guiding Distributed Manipulation With Multiple Mobile Sensors, Michael G. Ross Jun 1998

Multiscouting: Guiding Distributed Manipulation With Multiple Mobile Sensors, Michael G. Ross

Dartmouth College Undergraduate Theses

This thesis investigates the use of multiple mobile sensors to guide the motion of a distributed manipulation system. In our system, multiple robots cooperatively place a large object at a goal in a dynamic, unstructured, unmapped environment. We take the system developed in [Rus, Kabir, Kotay, Soutter 1996], which employs a single mobile sensor for navigational tasks, and extend it to allow the use of multiple mobile sensors. This allows the system to perform successful manipulations in a larger class of spaces than was possible in the single scout model. We focus on the development of a negotiation protocol that …

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Distributed Route Planning Using Partial Map Building, Christine J. Alvarado Jun 1998

Distributed Route Planning Using Partial Map Building, Christine J. Alvarado

Dartmouth College Undergraduate Theses

Our goal is to manipulate and guide an object across an unknown environment toward a goal in a known location in space. Our tools include a system of manipulation robots, which are "blind" and one mobile scout robot who relies on a series of sonar sensors for information about the environment. Previous solutions to this problem have taken a simultaneous guiding and manipulating approach, moving the whole system under the scout's guidance. My approach, however, presents a separate scouting algorithm that can return a series of coordinates through which the manipulation system can safely pass to reach the goal in …

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An Implementation Of External-Memory Depth-First Search, Christopher S. Leon Jun 1998

An Implementation Of External-Memory Depth-First Search, Christopher S. Leon

Dartmouth College Undergraduate Theses

In many different areas of computing, problems can arise which are too large to fit in main memory. For these problems, the I/O cost of moving data between main memory and secondary storage (for example, disks) becomes a significant bottleneck affecting the performance of the program. Since most algorithms do not take into account the size of main memory, new algorithms have been developed to optimize the number of I/O's performed. This paper details the implementation of one such algorithm, for external-memory depth-first search. Depth-first search is a basic tool for solving many problems in graph theory, and since graph …

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The Effects Of Singular Value Decomposition On Collaborative Filtering, Michael H. Pryor Jun 1998

The Effects Of Singular Value Decomposition On Collaborative Filtering, Michael H. Pryor

Dartmouth College Undergraduate Theses

As the information on the web increases exponentially, so do the efforts to automatically filter out useless content and to search for interesting content. Through both explicit and implicit actions, users define where their interests lie. Recent efforts have tried to group similar users together in order to better use this data to provide the best overall filtering capabilities to everyone. This thesis discusses ways in which linear algebra, specifically the singular value decomposition, can be used to augment these filtering capabilities to provide better user feedback. The goal is to modify the way users are compared with one another, …

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Avoiding Conflicts Dynamically In Direct Mapped Caches With Minimal Hardware Support, Peter N. Desantis Jun 1998

Avoiding Conflicts Dynamically In Direct Mapped Caches With Minimal Hardware Support, Peter N. Desantis

Dartmouth College Undergraduate Theses

The memory system is often the weakest link in the performance of today's computers. Cache design has received increasing attention in recent years as increases in CPU performance continues to outpace decreases in memory latency. Bershad et al. proposed a hardware modification called the Cache Miss Lookaside buffer which attempts to dynamically identify data which is conflicting in the cache and remap pages to avoid future conflicts. In a follow-up paper, Bershad et al. tried to modify this idea to work with standard hardware but had less success than with their dedicated hardware. In this thesis, we focus on a …

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C Compiler Targeting The Java Virtual Machine, Jack Pien May 1998

C Compiler Targeting The Java Virtual Machine, Jack Pien

Dartmouth College Undergraduate Theses

One of the major drawbacks in the field of computer software development has been the inability for applications to compile once and execute across many different platforms. With the emergence of the Internet and the networking of many different platforms, the Java programming language and the Java Platform was created by Sun Microsystems to address this "Write Once, Run Anywhere" problem. What sets a compiled Java program apart from programs compiled from other high level languages is the ability of a Java Virtual Machine to execute the compiled Java program on any platform, as long as the Java Virtual Machine …

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