Physical Sciences and Mathematics Commons^™

The Changing Usage Of A Mature Campus-Wide Wireless Network, Tristan Henderson, David Kotz, Ilya Abyzov

Dartmouth Scholarship

Wireless Local Area Networks (WLANs) are now commonplace on many academic and corporate campuses. As “Wi-Fi” technology becomes ubiquitous, it is increasingly important to understand trends in the usage of these networks. \par This paper analyzes an extensive network trace from a mature 802.11 WLAN, including more than 550 access points and 7000 users over seventeen weeks. We employ several measurement techniques, including syslogs, telephone records, SNMP polling and tcpdump packet sniffing. This is the largest WLAN study to date, and the first to look at a large, mature WLAN and consider geographic mobility. We compare this trace to a …

Visual Unified Modeling Language For The Composition Of Scenarios In Modeling And Simulation Systems, Daniel E. Swayne

Theses and Dissertations

The Department of Defense uses modeling and simulation systems in many various roles, from research and training to modeling likely outcomes of command decisions. Simulation systems have been increasing in complexity with the increased capability of low-cost computer systems to support these DOD requirements. The demand for scenarios is also increasing, but the complexity of the simulation systems has caused a bottleneck in scenario development due to the limited number of individuals with knowledge of the arcane simulator languages in which these scenarios are written. This research combines the results of previous AFIT efforts in visual modeling languages to create …

Sclope: An Algorithm For Clustering Data Streams Of Categorical Attributes, Kok-Leong Ong, Wenyuan Li, Wee-Keong Ng, Ee Peng Lim

Research Collection School Of Computing and Information Systems

Clustering is a difficult problem especially when we consider the task in the context of a data stream of categorical attributes. In this paper, we propose SCLOPE, a novel algorithm based on CLOPE's intuitive observation about cluster histograms. Unlike CLOPE however, our algorithm is very fast and operates within the constraints of a data stream environment. In particular, we designed SCLOPE according to the recent CluStream framework. Our evaluation of SCLOPE shows very promising results. It consistently outperforms CLOPE in speed and scalability tests on our data sets while maintaining high cluster purity; it also supports cluster analysis that other …

Shared-Storage Auction Ensures Data Availability, Hady W. Lauw, Siu-Cheung Hui, Edmund M. K. Lai

Research Collection School Of Computing and Information Systems

Most current e-auction systems are based on the client-server architecture. Such centralized systems provide a single point of failure and control. In contrast, peer-to-peer systems permit distributed control and minimize individual node and link failures' impact on the system. The shared-storage-based auction model described decentralizes services among peers to share the required processing load and aggregates peers' resources for common use. The model is based on the principles of local computation at each peer, direct inter-peer communication, and a shared storage space.

Robust Classification Of Event-Related Potential For Brain-Computer Interface, Manoj Thulasidas

Research Collection School Of Computing and Information Systems

We report the implementation of a text input application (speller) based on the P300 event related potential. We obtain high accuracies by using an SVM classifier and a novel feature. These techniques enable us to maintain fast performance without sacrificing the accuracy, thus making the speller usable in an online mode. In order to further improve the usability, we perform various studies on the data with a view to minimizing the training time required. We present data collected from nine healthy subjects, along with the high accuracies (of the order of 95% or more) measured online. We show that the …

Quantifying Initial Condition And Parametric Uncertainties In A Nonlinear Aeroelastic System With An Efficient Stochastic Algorithm, Daniel R. Millman

Theses and Dissertations

There is a growing interest in understanding how uncertainties in flight conditions and structural parameters affect the character of a limit cycle oscillation (LCO) response, leading to failure of an aeroelastic system. Uncertainty quantification of a stochastic system (parametric uncertainty) with stochastic inputs (initial condition uncertainty) has traditionally been analyzed with Monte Carlo simulations (MCS). Probability density functions (PDF) of the LCO response are obtained from the MCS to estimate the probability of failure. A candidate approach to efficiently estimate the PDF of an LCO response is the stochastic projection method. The objective of this research is to extend the …

A Nonparametric Method For Separating Photosynthesis And Respiration Components In Co2 Flux Measurements, Chuixiang Yi, Runze Li, Peter S. Backwin, Ankur Desai, Daniel M. Ricciuto, Sean P. Burns, Andrew A. Turnipseed, Steven C. Wofsy, J. William Munger, Kell Wilson, Russell K. Monson

Publications and Research

Future climate change is expected to affect ecosystem-atmosphere CO₂ exchange, particularly through the influence of temperature. To date, however, few studies have shown that differences in the response of net ecosystem CO₂ exchange (NEE) to temperature among ecosystems can be explained by differences in the photosynthetic and respiratory processes that compose NEE. Using a new nonparametric statistical model, we analyzed data from four forest ecosystems. We observed that differences among forests in their ability to assimilate CO₂ as a function of temperature were attributable to consistent differences in the temperature dependence of photosynthesis and respiration. This observation …

Breakup Of H₂ In Singly Ionizing Collisions With Fast Protons: Channel-Selective Low-Energy Electron Spectra, Christina Dimopoulou, Robert Moshammer, Daniel Fischer, C. Hohr, Alexander Dorn, Pablo Daniel Fainstein, Jose R. Crespo Lopez-Urrutia, Claus Dieter Schroter, Holger Kollmus, Rido Mann, Siegbert Hagmann, Joachim Hermann Ullrich

Physics Faculty Research & Creative Works

The dissociation of H₂ in singly ionizing collisions with fast protons was analyzed using channel-selective low-energy electron spectra. Dissociative and nondissociative single ionization of H₂ by 6MeV proton impact was described in a kinematically by determining momentum vectors of electron and H⁺ fragment of H₂⁺ target ion, respectively. The electron spectra exhibited role of autoionization of doubly and singly excited states of H₂. The doubly and singly excited states of H₂ involve coupling between electronic and nuclear motion of molecule.

Book Review: Sky Vistas: Astronomy For Binoculars And Richestfield Telescopes, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Sky Vistas : Astronomy for Binoculars and Richestfield Telescopes by Craig Crossen and Gerald Rhemann Springer, 2004 279p, 3211008519 $69.95

Technical Assessment Of Natural Resource Management Threats And Options In The Northern Agricultural Region Of Western Australia, Lorinda Hunt, G Patterson, Northern Agricultural Catchments Council (Wa)

Resource management technical reports

Analysis of the risk of soil, land and water degradation within the Northern Agricultural Region of Western Australia. Natural resource issues discussed include: acid groundwater, acid sulfate soils, climate change, dryland salinity, flooding, herbicide resistance, non-wetting (water repellence), nutrient loss and eutrophication, remnant vegetation decline, soil acidity, soil fertility decline, soil structure decline, subsurface compaction, waterlogging, wind erosion and soil contamination.

Every Polynomial-Time 1-Degree Collapses If And Only If P=Pspace, Stephen A. Fenner, Stuart A. Kurtz, James S. Royer

Faculty Publications

No abstract provided.

Probing Cation Antisite Disorder In Gd2ti2o7 Pyrochlore By Site-Specific Nexafs And Xps, Ponnusamy Nachimuthu, S. Thevuthasan, Mark H. Engelhard, W. J. Weber, D. K. Shuh, N. M. Hamdan, B. S. Mun, E. M. Adams, D. E. Mccready, V. Shutthanandan, Dennis W. Lindle, G. Balakrishnan, R. C. Ewing

Chemistry and Biochemistry Faculty Research

Disorder in Gd₂Ti₂O₇ is investigated by near-edge x-ray-absorption fine structure (NEXAFS) and x-ray photoelectron spectroscopy (XPS). NEXAFS shows Ti⁴⁺ ions occupy octahedral sites with a tetragonal distortion induced by vacant oxygen sites. O 1s XPS spectra obtained with a charge neutralization system from Gd₂Ti₂O₇(100) and the Gd₂Ti₂O₇ pyrochlore used by Chen et al. [Phys. Rev. Lett. 88, 105901 (2002)], both yielded a single peak, unlike the previous result on the latter that found two peaks. The current results give no evidence for …

Mechanical Properties Of Carbon Nanotubes Composites, David Hui, Mircea Chipara, Jagannathan Sankar, K. T. Lau

Physics and Astronomy Faculty Publications and Presentations

A critical review of theoretical models aiming to explain the physical properties of composites based on polymeric matrices reinforced with carbon nanotubes is presented. Attention is paid to descriptions based on molecular dynamics, continuum mechanics, and finite element analysis. It is shown that both the continuum mechanics approximation and the finite size element analyses fail to describe composites with very thin interfaces, while the performances of molecular dynamics simulations are still restricted by computer's performances. The limitations of the continuum mechanics approximation are analyzed in detail.

Is The Initial Mass Function Of Low Surface Brightness Galaxies Dominated By Low-Mass Stars?, Hyun Chul Lee, Brad K. Gibson, Chris Flynn, Daisuke Kawata, Michael A. Beasley

Physics and Astronomy Faculty Publications and Presentations

The rotation curves of low surface brightness (LSB) galaxies suggest that they possess significantly higher mass-to-light (M/L) ratios than their high surface brightness counterparts, indicating that LSB galaxies may be dark matter dominated. This interpretation is hampered by the difficulty of disentangling the disc and dark halo contributions from the disc dynamics of LSB galaxies. Recently, Fuchs has attempted such a disentanglement using spiral arm density wave and swing amplification theory, allowing an independent measurement of the disc mass; this work suggests that LSB discs are significantly more massive than previously believed. This would considerably reduce the amount of matter …

Towards Personalised Web Intelligence, Ah-Hwee Tan, Hwee-Leng Ong, Hong Pan, Jamie Ng, Qiu-Xiang Li

Research Collection School Of Computing and Information Systems

The Flexible Organizer for Competitive Intelligence (FOCI) is a personalised web intelligence system that provides an integrated platform for gathering, organising, tracking, and disseminating competitive information on the web. FOCI builds personalised information portfolios through a novel method called User-Configurable Clustering, which allows a user to personalise his/her portfolios in terms of the content as well as the organisational structure. This paper outlines the key challenges we face in personalised information management and gives a detailed account of FOCI’s underlying personalisation mechanism. For a quantitative evaluation of the system’s performance, we propose a set of performance indices based on information …

Security Analysis Of Two Signcryption Schemes, Guilin Wang, Robert H. Deng, Dongjin Kwak, Sangjae Moon

Research Collection School Of Computing and Information Systems

Signcryption is a new cryptographic primitive that performs signing and encryption simultaneously, at a cost significantly lower than that required by the traditional signature-then-encryption approach. In this paper, we present a security analysis of two such schemes: the Huang-Chang convertible signcryption scheme, and the Kwak-Moon group signcryption scheme. Our results show that both schemes are insecure. Specifically, the Huang-Chang scheme fails to provide confidentiality, while the Kwak-Moon scheme does not satisfy the properties of unforgeability, coalition-resistance, and traceability.

On The Security Of The Lee-Hwang Group-Oriented Undeniable Signature Schemes, Guilin Wang, Jianying Zhou, Robert H. Deng

Research Collection School Of Computing and Information Systems

Undeniable signature is an intriguing concept introduced by Chaum and van Antwerpen at Crypto89. In 1999, Lee and Hwang presented two group-oriented undeniable signature schemes with a trusted center. Their schemes are natural generalizations of Chaums zero knowledge undeniable signature scheme proposed in 1990. However, we find that the Lee-Hwang schemes are insecure. In this paper, we demonstrate five effective attacks on their schemes: four of them are insider universal forgeries, in which one dishonest member (maybe colluding with a verifier) can get a valid signature on any chosen massage, and another attack allows a dishonest member to prevent honest …

Proxy Signature Scheme With Multiple Original Signers For Wireless E-Commerce Applications, Guilin Wang, Feng Bao, Jianying Zhou, Robert H. Deng

Research Collection School Of Computing and Information Systems

In a proxy signature scheme, a user delegates his/her signing capability to another user in such a way that the latter can sign messages on behalf of the former. We propose an efficient and secure proxy signature scheme with multiple original signers. Our scheme is suitable for wireless electronic commerce applications, since the overheads of computation and communication are low. As an example, we present an electronic air ticket booking scheme for wireless customers.

Every Polynomial-Time 1-Degree Collapses If And Only If P=Pspace, Stephen A. Fenner, Stuart A. Kurtz, James S. Royer

Faculty Publications

No abstract provided.

Condylar Remodeling After Distraction Osteogenesis And Bilateral Sagittal Split Osteotomy, Robert Barker Hoffman

Loma Linda University Electronic Theses, Dissertations & Projects

The present pilot study is a histological evaluation of mandibular condyles taken from minipigs that underwent either traditional mandibular advancement (bilateral sagittal split osteotomy), or a distraction osteogenesis procedure to advance the mandible. One pig received a bilateral sagittal split osteotomy with an immediate mandibular advancement of 14 mm, while another pig underwent distraction osteogenesis consisting of a gradual advancement of 2 mm per day to advance the mandible the same distance. The control animal received no surgery.

In the present study, the mandibular condyles of the three pigs (2 control, 2 bilateral sagittal split osteotomy, and 2 distraction osteogenesis) …

Prevalence Of Degenerative Joint Disease In A Pre-Orthodontic Adolescent Sample, Marie Mansour

Loma Linda University Electronic Theses, Dissertations & Projects

The purpose of this research was to determine a prevalence of degenerative joint disease in our pre-orthodontic adolescent patients age ten through seventeen. The prevalence was assessed according to gender. Severity of DJD was established for each patient and a "red flag" for diagnosis was identified. The purpose was also to establish norms for joint space for patients with and without degenerative joint disease. Correlations to distal condyle position and angle classification were described. 123 consecutive patients, 77 female and 46 male T1 NewTom records were reviewed. Severity of DJD was classified according to none, mild, moderate, and severe. Sagittal …

Report On The Oregon Ballast Water Management Program In 2004, Kiirsten Flynn, Mark Sytsma

Center for Lakes and Reservoirs Publications and Presentations

This report was prepared for the Oregon legislature pursuant to HB 3620, which was passed during the 2003 session of the Oregon legislature to address management of ballast water discharged from ships. The bill removed sediment from the definition of ballast water, allowed discharge of treated ballast water, created a task force on ballast water management, and required this report. Includes List of Acronyms, charts, graphs and maps.

Heterogeneous Self-Reconfiguring Robotics, Robert Charles Fitch

Dartmouth College Ph.D Dissertations

Self-reconfiguring (SR) robots are modular systems that can autonomously change shape, or reconfigure, for increased versatility and adaptability in unknown environments. In this thesis, we investigate planning and control for systems of non-identical modules, known as heterogeneous SR robots. Although previous approaches rely on module homogeneity as a critical property, we show that the planning complexity of fundamental algorithmic problems in the heterogeneous case is equivalent to that of systems with identical modules. Primarily, we study the problem of how to plan shape changes while considering the placement of specific modules within the structure. We characterize this key challenge in …

A Visual Language For Animating Sketches, Richard C. Davis, James A. Landay

Research Collection School Of Computing and Information Systems

We present our research into visual languages for animating sketches. Animation is a rich mode of communication that is currently accessible to few. Simple animation systems exist, but severely restrict the types of motion that can be represented. Our field studies are demonstrating that would-be animators need to coordinate many objects moving in a variety of ways. The visual language described here allows a variety of motions to be defined with hand gestures, and gives visual feedback for coordination of events. This may open up computerized communication to users who think in dynamic visual images.

A Development Framework For Rapid Metaheuristics Hybridization, Hoong Chuin Lau, M. K. Lim, W. C. Wan, S. Halim

Research Collection School Of Computing and Information Systems

While meta-heuristics are effective for solving large-scale combinatorial optimization problems, they result from time-consuming trial-and-error algorithm design tailored to specific problems. For this reason, a software tool for rapid prototyping of algorithms would save considerable resources. This work presents a generic software framework that reduces development time through abstract classes and software reuse, and more importantly, aids design with support of user-defined strategies and hybridization of meta-heuristics. Most interestingly, we propose a novel way of redefining hybridization with the use of the "request and response" metaphor, which form an abstract concept for hybridization. Different hybridization schemes can now be formed …

A Two-Level Framework For Coalition Formation Via Optimization And Agent Negotiation, Hoong Chuin Lau, Lei Zhang

Research Collection School Of Computing and Information Systems

We present a two-level coalition formation approach based on a centralized optimization model on the upper level, and a distributed agent-negotiation model on the lower level. This approach allows us to balance agent self-interests against a high joint utility. Experimental results show that the two-level coalition formation mechanism will increase not only the overall utility of the coalition, but also the individual utility of most participating agents. The results also suggest it is better for the agents to be partially cooperative rather than either fully cooperative or self-interested in our setting.

Ws-Trustworthy: A Framework For Web Services Centered Trustworthy Computing, Jia Zhang, Liang-Jie Zhang, Jen-Yao Chung

Jia Zhang

No abstract provided.

An Approach To Help Select Trustworthy Web Services, Jia Zhang, Liang-Jie Zhang, Jen-Yao Chung

Jia Zhang

No abstract provided.

A Uniform Meta-Model For Mediating Formal Electronic Conferences, Jia Zhang, Carl Chang, Jeffrey Voas

Jia Zhang

No abstract provided.

How A Mirage Is Formed, Christopher Roman

Christopher N. Roman

Article that appeared in Sail magazine (ISSN: 0036-2700).