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2010

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Articles 151 - 180 of 8620

Full-Text Articles in Physical Sciences and Mathematics

Chemical Vapor Deposition Of Silanes And Patterning On Silicon, Feng Zhang Dec 2010

Chemical Vapor Deposition Of Silanes And Patterning On Silicon, Feng Zhang

Theses and Dissertations

Self assembled monolayers (SAMs) are widely used for surface modification. Alkylsilane monolayers are one of the most widely deposited and studied SAMs. My work focuses on the preparation, patterning, and application of alkysilane monolayers. 3-aminopropyltriethoxysilane (APTES) is one of the most popular silanes used to make active surfaces for surface modification. To possibly improve the surface physical properties and increase options for processing this material, I prepared and studied a series of amino silane surfaces on silicon/silicon dioxide from APTES and two other related silanes by chemical vapor deposition (CVD). I also explored CVD of 3-mercaptopropyltrimethoxysilane on silicon and quartz. …

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Conjugated Quantum Dots Inhibit The Amyloid Β (1–42) Fibrillation Process, Garima Thakur, Miodrag Micic, Yuehai Yang, Wenzhi Li, Dania Movia, Silvia Giordani, Hongzhou Zhou, Roger M. Levlanc Dec 2010

Conjugated Quantum Dots Inhibit The Amyloid Β (1–42) Fibrillation Process, Garima Thakur, Miodrag Micic, Yuehai Yang, Wenzhi Li, Dania Movia, Silvia Giordani, Hongzhou Zhou, Roger M. Levlanc

Department of Physics

Nanoparticles have enormous potential in diagnostic and therapeutic studies. We have demonstrated that the amyloid beta mixed with and conjugated to dihydrolipoic acid- (DHLA) capped CdSe/ZnS quantum dots (QDs) of size approximately 2.5 nm can be used to reduce the fibrillation process. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) were used as tools for analysis of fibrillation. There is a significant change in morphology of fibrils when amyloid β (1–42) (Aβ (1–42)) is mixed or conjugated to the QDs. The length and the width of the fibrils vary under modified conditions. Thioflavin T (ThT) fluorescence supports the decrease …

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Respecting Tutorial Instructors’ Beliefs And Experiences: A Case Study Of A Physics Teaching Assistant, Renee Michelle Goertzen, Rachel E. Scherr, Andrew Elby Dec 2010

Respecting Tutorial Instructors’ Beliefs And Experiences: A Case Study Of A Physics Teaching Assistant, Renee Michelle Goertzen, Rachel E. Scherr, Andrew Elby

Department of Physics

Effective physics instruction benefits from respecting the physics ideas that introductory students bring into the classroom. We argue that it is similarly beneficial to respect the teaching ideas that novice physics instructors bring to their classrooms. We present a case study of a tutorial teaching assistant TA, Alan. When we first examined Alan’s teaching, we focused our attention on the mismatch between his actions and those advocated by the TA instructors. Further study showed us that Alan cared about helping his students and that his teaching was well integrated with his beliefs about how students learn physics and how teachers …

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The Effects Of High Density Septic Systems On Surface Water Quality In Gwinnett County, Georgia, John R. Anderson Ii Dec 2010

The Effects Of High Density Septic Systems On Surface Water Quality In Gwinnett County, Georgia, John R. Anderson Ii

Geosciences Theses

Gwinnett County, Georgia experienced rapid growth in the 1970’s without the infrastructure so septic systems were installed for residential homes. The number of septic systems grew to over 85,000 with a density of 487 septic systems per square mile. This study mapped the distribution of septic systems to determine regions of potential pathogen surface water. This study addressed what potential health risks do high density septic systems have on surface water quality and how can the history of Gwinnett County assist in future development in the Metropolitan Atlanta area? It was found that the density of septic systems has reduced …

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Descending Central Series Of Free Pro-P-Groups, German A. Combariza Dec 2010

Descending Central Series Of Free Pro-P-Groups, German A. Combariza

Electronic Thesis and Dissertation Repository

In this thesis, we study the first three cohomology groups of the quotients of the descending central series of a free pro-p-group. We analyse the Lyndon-Hochschild- Serre spectral sequence up to degree three and develop what we believe is a new technique to compute the third cohomology group. Using Fox-Calculus we express the cocycles of a finite p-group G with coefficients on a certain module M as the kernel of a matrix composed by the derivatives of the relations of a minimal presentation for G. We also show a relation between free groups and finite fields, this is a new …

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Evaluation Of A Novel Two-Step Server Selection Metric, Katrina M. Hanna, Nandini Natarajan, Brian Neil Levine Dec 2010

Evaluation Of A Novel Two-Step Server Selection Metric, Katrina M. Hanna, Nandini Natarajan, Brian Neil Levine

Brian Levine

Choosing the best-performing server for a particular client from a group of replicated proxies is a difficult task. We offer a novel, two-step technique for server selection that chooses a small subset of five servers, and isolates testing to that subset for ten days. We present an empirical evaluation of both our method and previously proposed metrics based on traces to 193 commercial proxies. We show that our technique performs better than any of the other metrics we studied — often one to two seconds better for a one-megabyte file — while requiring considerably less work over time. Metrics such …

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Dtn Routing As A Resource Allocation Problem, Aruna Balasubramanian, Brian Neil Levine, Arun Venkataramani Dec 2010

Dtn Routing As A Resource Allocation Problem, Aruna Balasubramanian, Brian Neil Levine, Arun Venkataramani

Brian Levine

Routing protocols for disruption-tolerant networks (DTNs) use a variety of mechanisms, including discovering the meeting probabilities among nodes, packet replication, and network coding. The primary focus of these mechanisms is to increase the likelihood of finding a path with limited information, and so these approaches have only an incidental effect on routing such metrics as maximum or average delivery delay. In this paper, we present rapid, an intentional DTN routing protocol that can optimize a specific routing metric such as the worst-case delivery delay or the fraction of packets that are delivered within a deadline. The key insight is to …

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Mv Routing And Capacity Building In Disruption Tolerant Networks, Brendan Burns, Oliver Brock, Brian Neil Levine Dec 2010

Mv Routing And Capacity Building In Disruption Tolerant Networks, Brendan Burns, Oliver Brock, Brian Neil Levine

Brian Levine

Disruption Tolerant Networks (DTNs) require routing algorithms that are different from those designed for ad hoc networks. In DTNs, transport of data through the network is achieved through the physical movement of the participants in the network. We address two fundamental problems of routing in DTNs: routing algorithms with robust delivery rates, and management of networks where demand for routes does not match with the movement of peers. For the first problem, we propose the MV algorithm, which is based on observed meetings between peers and visits of peers to geographic locations. We show that our approach can achieve robust …

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Interactive Wifi Connectivity For Moving Vehicles, Aruna Balasubramanian, Ratul Mahajan, Arun Venkataramani, Brian Neil Levine, John Zahorjan Dec 2010

Interactive Wifi Connectivity For Moving Vehicles, Aruna Balasubramanian, Ratul Mahajan, Arun Venkataramani, Brian Neil Levine, John Zahorjan

Brian Levine

We ask if the ubiquity of WiFi can be leveraged to provide cheap connectivity from moving vehicles for common applications such as Web browsing and VoIP. Driven by this question, we conduct a study of connection quality available to vehicular WiFi clients based on measurements from testbeds in two different cities. We find that current WiFi handoff methods, in which clients communicate with one basestation at a time, lead to frequent disruptions in connectivity. We also find that clients can overcome many disruptions by communicating with multiple basestations simultaneously. These findings lead us to develop ViFi, a protocol that opportunistically …

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Mobile Distributed Information Retrieval For Highly-Partitioned Networks, Katrina M. Hanna, Brian Neil Levine, R. Manmatha Dec 2010

Mobile Distributed Information Retrieval For Highly-Partitioned Networks, Katrina M. Hanna, Brian Neil Levine, R. Manmatha

Brian Levine

We propose and evaluate a mobile, peer-to-peer Information Retrieval system. Such a system can, for example, support medical care in a disaster by allowing access to a large collections of medical literature. In our system, documents in a collection are replicated in an overlapping manner at mobile peers. This provides resilience in the face of node failures, malicious attacks, and network partitions. We show that our design manages the randomness of node mobility. Although nodes contact only direct neighbors (who change frequently) and do not use any ad hoc routing, the system maintains good IR performance. This makes our design …

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Proto-Transfer Learning In Markov Decision Processes Using Spectral Methods, Kimberly Ferguson, Sridhar Mahadevan Dec 2010

Proto-Transfer Learning In Markov Decision Processes Using Spectral Methods, Kimberly Ferguson, Sridhar Mahadevan

Sridhar Mahadevan

In this paper we introduce proto-transfer leaning, a new framework for transfer learning. We explore solutions to transfer learning within reinforcement learning through the use of spectral methods. Proto-value functions (PVFs) are basis functions computed from a spectral analysis of random walks on the state space graph. They naturally lead to the ability to transfer knowledge and representation between related tasks or domains. We investigate task transfer by using the same PVFs in Markov decision processes (MDPs) with different rewards functions. Additionally, our experiments in domain transfer explore applying the Nyström method for interpolation of PVFs between MDPs of different …

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Learning To Communicate And Act Using Hierarchical Reinforcement Learning, Mohammad Ghavamzadeh, Sridhar Mahadevan Dec 2010

Learning To Communicate And Act Using Hierarchical Reinforcement Learning, Mohammad Ghavamzadeh, Sridhar Mahadevan

Sridhar Mahadevan

In this paper, we address the issue of rational communication behavior among autonomous agents. The goal is for agents to learn a policy to optimize the communication needed for proper coordination, given the communication cost. We extend our previously reported cooperative hierarchical reinforcement learning (HRL) algorithm to include communication decisions and propose a new multiagent HRL algorithm, called COM-Cooperative HRL. In this algorithm, we define cooperative subtasks to be those subtasks in which coordination among agents significantly improves the performance of the overall task. Those levels of the hierarchy which include cooperative subtasks are called cooperation levels. Coordination skills among …

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Hierarchical Policy Gradient Algorithms, Mohammad Ghavamzadeh, Sridhar Mahadevan Dec 2010

Hierarchical Policy Gradient Algorithms, Mohammad Ghavamzadeh, Sridhar Mahadevan

Sridhar Mahadevan

Hierarchical reinforcement learning is a general framework which attempts to accelerate policy learning in large domains. On the other hand, policy gradient reinforcement learning (PGRL) methods have received recent attention as a means to solve problems with continuous state spaces. However, they su#11;er from slow convergence. In this paper, we combine these two approaches and propose a family of hierarchical policy gradi- ent algorithms for problems with continuous state and/or action spaces. We also introduce a class of hierarchical hybrid algorithms, in which a group of subtasks, usually at the higher-levels of the hierarchy, are formulated as value function-based RL …

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Manifold Alignment Using Procrustes Analysis, Chang Wang, Sridhar Mahadevan Dec 2010

Manifold Alignment Using Procrustes Analysis, Chang Wang, Sridhar Mahadevan

Sridhar Mahadevan

In this paper we introduce a novel approach to manifold alignment, based on Procrustes analysis. Our approach di®ers from \semi- supervised alignment" in that it results in a mapping that is de¯ned everywhere { when used with a suitable dimensionality reduction method { rather than just on the training data points. We describe and evaluate our approach both theoretically and experimen- tally, providing results showing useful knowl- edge transfer from one domain to another. Novel applications of our method including cross-lingual information retrieval and trans- fer learning in Markov decision processes are presented.

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Framework For Analyzing Garbage Collection, Matthew Hertz, Neil Immerman, J. Eliot B. Moss Dec 2010

Framework For Analyzing Garbage Collection, Matthew Hertz, Neil Immerman, J. Eliot B. Moss

Neil Immerman

While the design of garbage collection algorithms has come of age, the analysis of these algorithms is still in its infancy. Current analyses are limited to merely documenting costs of individual collector executions; conclusive results, measuring across entire programs, require a theoretical foundation from which proofs can be offered. A theoretical foundation also allows abstract examination of garbage collection, enabling new designs without worrying about implementation details. We propose a theoretical framework for analyzing garbage collection algorithms and show how our framework could compute the ef#2;ciency (time cost) of garbage collectors. The central novelty of our proposed framework is its …

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A Control Architecture Formulti-Modal Sensory Integration, Luiz M. G. Gonçalves, Roderic A. Grupen, Antonio A. F. Oliveira Dec 2010

A Control Architecture Formulti-Modal Sensory Integration, Luiz M. G. Gonçalves, Roderic A. Grupen, Antonio A. F. Oliveira

Roderic Grupen

This work describes the architecture of an integrated multi-modal sensory (vision and touch) computational system. We propose to use an approach based on robotics control theory that is motivated by biology and developmental psychology, in order to integrate the haptic and visual information processing. We show some results carried out in simulation and discuss the implementation of this system using a platform consisting on an articulated stereo-head and an arm, which is currently under development.

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Capturing Data Uncertainty In Highvolume Stream Processing, Yanlei Diao, Boduo Li, Anna Liu, Liping Peng, Charles Sutton, Thanh Tran, Michael Zink Dec 2010

Capturing Data Uncertainty In Highvolume Stream Processing, Yanlei Diao, Boduo Li, Anna Liu, Liping Peng, Charles Sutton, Thanh Tran, Michael Zink

Yanlei Diao

We present the design and development of a data stream system that captures data uncertainty from data collection to query processing to final result generation. Our system focuses on data that is naturally modeled as continuous random variables such as many types of sensor data. To provide an end-to-end solution, our system employs probabilistic modeling and inference to generate uncertainty description for raw data, and then a suite of statistical techniques to capture changes of uncertainty as data propagates through query operators. To cope with high-volume streams, we explore advanced approximation techniques for both space and time efficiency. We are …

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Flux: A Language For Programming High-Performance Servers, Brendan Burns, Kevin Grimaldi, Alexander Kostadinov, Emery D. Berger, Mark D. Corner Dec 2010

Flux: A Language For Programming High-Performance Servers, Brendan Burns, Kevin Grimaldi, Alexander Kostadinov, Emery D. Berger, Mark D. Corner

Mark Corner

Programming high-performance server applications is challenging: it is both complicated and error-prone to write the concurrent code required to deliver high performance and scalability. Server performance bottlenecks are difficult to identify and correct. Finally, it is difficult to predict server performance prior to deployment. This paper presents Flux, a language that dramatically simplifies the construction of scalable high-performance server applications. Flux lets programmers compose offthe- shelf, sequential C or C++ functions into concurrent servers. Flux programs are type-checked and guaranteed to be deadlock-free. We have built a number of servers in Flux, including a web server with PHP support, an …

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Improving The Accuracy Of Petri Net-Based Analysis Of Concurrent Programs, A. T. Chamillard, Lori A. Clarke Dec 2010

Improving The Accuracy Of Petri Net-Based Analysis Of Concurrent Programs, A. T. Chamillard, Lori A. Clarke

Lori Clarke

Spurious results are an inherent problem of most static analysis methods. These methods, in an effort to produce conservative results, overestimate the executable behavior of a program. Infeasible paths and imprecise alias resolution are the two causes of such inaccuracies. In this paper we present an approach for improving the accuracy of Petri net-based analysis of concurrent programs by including additional program state information in the Petri net. We present empirical results that demonstrate the improvements in accuracy and, in some cases, the reduction in the search space that result from applying this approach to concurrent Ada programs.

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Model-Based Motion Planning, Brendan Burns, Oliver Brock Dec 2010

Model-Based Motion Planning, Brendan Burns, Oliver Brock

Oliver Brock

Robotic motion planning requires configuration space exploration. In high-dimensional configuration spaces, a complete exploration is computationally intractable. To devise practical motion planning algorithms in such high-dimensional spaces, computational resources have to be expended in proportion to the local complexity of a configuration space region. We propose a novel motion planning approach that addresses this problem by building an incremental, approximate model of configuration space. The information contained in this model is used to direct computational resources to difficult regions. This effectively addresses the narrow passage problem by adapting the sampling density to the complexity of that region. Each sample of …

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Mv Routing And Capacity Building In Disruption Tolerant Networks, Brendan Burns, Oliver Brock, Brian Neil Levine Dec 2010

Mv Routing And Capacity Building In Disruption Tolerant Networks, Brendan Burns, Oliver Brock, Brian Neil Levine

Oliver Brock

Disruption Tolerant Networks (DTNs) require routing algorithms that are different from those designed for ad hoc networks. In DTNs, transport of data through the network is achieved through the physical movement of the participants in the network. We address two fundamental problems of routing in DTNs: routing algorithms with robust delivery rates, and management of networks where demand for routes does not match with the movement of peers. For the first problem, we propose the MV algorithm, which is based on observed meetings between peers and visits of peers to geographic locations. We show that our approach can achieve robust …

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Sampling-Based Motion Planning Using Predictive Models, Brendan Burns, Oliver Brock Dec 2010

Sampling-Based Motion Planning Using Predictive Models, Brendan Burns, Oliver Brock

Oliver Brock

Robotic motion planning requires configuration space exploration. In high-dimensional configuration spaces, a complete exploration is computationally intractable. Practical motion planning algorithms for such high-dimensional spaces must expend computational resources in proportion to the local complexity of configuration space regions. We propose a novel motion planning approach that addresses this problem by building an incremental, approximate model of configuration space. The information contained in this model is used to direct computational resources to difficult regions, effectively addressing the narrow passage problem by adapting the sampling density to the complexity of that region. In addition, the expressiveness of the model permits predictive …

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Flux: A Language For Programming High-Performance Servers, Brendan Burns, Kevin Grimaldi, Alexander Kostadinov, Emery D. Berger, Mark D. Corner Dec 2010

Flux: A Language For Programming High-Performance Servers, Brendan Burns, Kevin Grimaldi, Alexander Kostadinov, Emery D. Berger, Mark D. Corner

Emery Berger

Programming high-performance server applications is challenging: it is both complicated and error-prone to write the concurrent code required to deliver high performance and scalability. Server performance bottlenecks are difficult to identify and correct. Finally, it is difficult to predict server performance prior to deployment. This paper presents Flux, a language that dramatically simplifies the construction of scalable high-performance server applications. Flux lets programmers compose offthe- shelf, sequential C or C++ functions into concurrent servers. Flux programs are type-checked and guaranteed to be deadlock-free. We have built a number of servers in Flux, including a web server with PHP support, an …

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Diehard: Probabilistic Memory Safety For Unsafe Languages, Emery D. Berger Dec 2010

Diehard: Probabilistic Memory Safety For Unsafe Languages, Emery D. Berger

Emery Berger

Applications written in unsafe languages like C and C++ are vulnerable to memory errors such as buffer overflows, dangling pointers, and reads of uninitialized data. Such errors can lead to program crashes, security vulnerabilities, and unpredictable behavior. We present DieHard, a runtime system that tolerates these errors while probabilistically maintaining soundness. DieHard uses randomization and replication to achieve probabilistic memory safety by approximating an infinite-sized heap. DieHard’s memory manager randomizes the location of objects in a heap that is at least twice as large as required. This algorithm prevents heap corruption and provides a probabilistic guarantee of avoiding memory errors. …

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Umass At Trec 2004: Novelty And Hard, Nasreen Abdul-Jaleel, James Allan, W. Bruce Croft, Fernando Diaz, Leah Larkey, Xiaoyan Li, Mark D. Smucker, Courtney Wade Dec 2010

Umass At Trec 2004: Novelty And Hard, Nasreen Abdul-Jaleel, James Allan, W. Bruce Croft, Fernando Diaz, Leah Larkey, Xiaoyan Li, Mark D. Smucker, Courtney Wade

James Allan

For the TREC 2004 Novelty track, UMass participated in all four tasks. Although finding relevant sentences was harder this year than last, we continue to show marked improvements over the baseline of calling all sentences relevant, with a variant of tfidf being the most successful approach. We achieve 5–9%improvements over the baseline in locating novel sentences, primarily by looking at the similarity of a sentence to earlier sentences and focusing on named entities. For the High Accuracy Retrieval from Documents (HARD) track, we investigated the use of clarification forms, fixed- and variable-length passage retrieval, and the use of metadata. Clarification …

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Strategy-Based Interactive Cluster Visualization For Information Retrieval, Anton Leuski, James Allan Dec 2010

Strategy-Based Interactive Cluster Visualization For Information Retrieval, Anton Leuski, James Allan

James Allan

In this paper we investigate a general purpose interactive information organization system. The system organizes documents by placing them into 1-, 2-, or 3- dimensional space based on their similarity and a springembedding algorithm. We begin by developing a method for estimating the quality of the organization when it is applied to a set of documents returned in response to a query. We show how the relevant documents tend to clump together in space. We proceed by presenting amethod for measuring the amount of structure in the organization and explain how this knowledge can be used to refine the system. …

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Find-Similar: Similarity Browsing As A Search Tool, Mark D. Smucker, James Allan Dec 2010

Find-Similar: Similarity Browsing As A Search Tool, Mark D. Smucker, James Allan

James Allan

Search systems have for some time provided users with the ability to request documents similar to a given document. Interfaces provide this feature via a link or button for each document in the search results. We call this feature findsimilar or similarity browsing. We examined find-similar as a search tool, like relevance feedback, for improving retrieval performance. Our investigation focused on find-similar’s document-to-document similarity, the reexamination of documents during a search, and the user’s browsing pattern. Find-similar with a query-biased similarity, avoiding the reexamination of documents, and a breadth-like browsing pattern achieved a 23% increase in the arithmetic mean average …

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Dynamic Composition Of Information Retrieval Techniques, Andrew Arnt, Shlomo Zilberstein, James Allan Dec 2010

Dynamic Composition Of Information Retrieval Techniques, Andrew Arnt, Shlomo Zilberstein, James Allan

James Allan

This paper presents a new approach to information retrieval (IR) based on run-time selection of the best set of techniques to respond to a given query. A technique is selected based on its projected effectiveness with respect to the specific query, the load on the system, and a time-dependent utility function. The paper examines two fundamental questions: (1) can the selection of the best IR techniques be performed at run-time with minimal computational overhead? and (2) is it possible to construct a reliable probabilistic model of the performance of an IR technique that is conditioned on the characteristics of the …

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Incremental Test Collections, Ben Carterette, James Allan Dec 2010

Incremental Test Collections, Ben Carterette, James Allan

James Allan

Corpora and topics are readily available for information retrieval research. Relevance judgments, which are necessary for system evaluation, are expensive; the cost of obtaining them prohibits in-house evaluation of retrieval systems on new corpora or new topics. We present an algorithm for cheaply constructing sets of relevance judgments. Our method intelligently selects documents to be judged and decides when to stop in such a way that with very little work there can be a high degree of con#12;dence in the result of the evaluation. We demonstrate the algorithm's e#11;ectiveness by showing that it produces small sets of relevance judgments that …

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Evaluating Combinations Of Ranked Lists And Visualizations Of Inter-Document Similarity, James Allan Dec 2010

Evaluating Combinations Of Ranked Lists And Visualizations Of Inter-Document Similarity, James Allan

James Allan

We are interested in how ideas from document clustering can be used to improve the retrieval accuracy of ranked lists in interactive systems. In particular, we are interested in ways to evaluate the e€ectiveness of such systems to decide how they might best be constructed. In this study, we construct and evaluate systems that present the user with ranked lists and a visualization of inter-document similarities. We ®rst carry out a user study to evaluate the clustering/ranked list combination on instance-oriented retrieval, the task of the TREC-6 Interactive Track. We ®nd that although users generally prefer the combination, they are …

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