Physical Sciences and Mathematics Commons^™

Bismuth-Based Oxide Semiconductors: Mild Synthesis And Practical Applications, Hari Krishna Timmaji

Earth & Environmental Sciences Dissertations

In this dissertation study, bismuth based oxide semiconductors were prepared using 'mild' synthesis techniques - electrodepostion and solution combustion synthesis. Potential environmental remediation and solar energy applications of the prepared oxides were evaluated. Bismuth vanadate (BiVO₄) was prepared by electrodeposition and solution combustion synthesis. A two step electrosynthesis strategy was developed and demonstrated for the first time. In the first step, a Bi film was first electrodeposited on a Pt substrate from an acidic BiCl₃ medium. Then, this film was anodically stripped in a medium containing hydrolyzed vanadium precursor, to generate Bi3+, and subsequent BiVO₄ formation by in situ precipitation. …

A Unit Test Approach For Database Schema Evolution, Katarina Grolinger, Miriam A M Capretz

Electrical and Computer Engineering Publications

Context: The constant changes in today’s business requirements demand continuous database revisions. Hence, database structures, not unlike software applications, deteriorate during their lifespan and thus require refactoring in order to achieve a longer life span. Although unit tests support changes to application programs and refactoring, there is currently a lack of testing strategies for database schema evolution.

Objective: This work examines the challenges for database schema evolution and explores the possibility of using various testing strategies to assist with schema evolution. Specifically, the work proposes a novel unit test approach for the application code that accesses databases with the objective …

Some Problems Of Integral Geometry In Advanced Imaging, Rim Gouia

Mathematics Dissertations

During the past decade, our society has become dependent on advanced mathematics for many of our daily needs. Mathematics is at the heart of the 21st century technologies and more specifically the emerging imaging technologies from thermoacoustic tomography (TAT) and ultrasound computed tomography (UCT) to non-destructive testing (NDT). All of these applications reconstruct the internal structure of an object from external measurements without damaging the entity under investigation. The basic mathematical idea common to such reconstruction problems is often based upon Radon integral transform.The Radon integral transform Rf puts into correspondence to agiven function f its integrals over certain subsets. …

On The Existence Of Totally Reflexive Modules, Kristen Ann Beck

Mathematics Dissertations

In this manuscript, we investigate the existence of non-free totally reflexive modules over two classes of commutative local (Noetherian) rings.First, we demonstrate existence over a class of local rings which are defined by a Gorenstein homomorphism. Among the corollaries to this result, we recover a theorem of Avramov, Gasharov, and Peeva (1997) concerning the existence of non-free totally reflexive modules over local rings with embedded deformations. We also give a general construction for a class of local rings which satisfy the hypotheses of our theorem, and we show it is able to produce rings without embedded deformations.The second focus of …

High Order Compact Scheme For Discontinuous Differential Equations, James Louis Thompson

Mathematics Dissertations

A high order implicit second derivative compact method is given which is similar the Adams-Moulton method, but requiring only two steps for sixth order. This method is used in both predictor-corrector and Newton's method formulations, and although the compact scheme is not A-stable or stiffly stable, it's region of stability is over six times greater than the Sixth order Adams-Moulton method. This compact method has a small truncation error coefficient, and is more accurate than Enright's method within the region of stability. Fourth and sixth order explicit compact methods are derived as well, and the three step sixth order explicit …

Assessing Measurement Invariance In The Presence Of Testlets, Luis Andres Alvarado

Open Access Theses & Dissertations

Dealing with measurement invariance has been an issue of concern in confirmatory factor analysis for many years. It is important to establish measurement invariance across groups so that instruments may be validly used in multiple groups for comparison of the mean or summative scores. Throughout the years, many studies have considered testing for measurement invariance in factor models. However, there have been no studies that assess measurement invariance when so-called testlets should be modeled in the factor analytic model. Testlets add nuisance covariation to the model which can interfere when trying to detect measurement invariance. In the past, models have …

The Influence Of Pressure Relaxation On The Structure Of An Axial Vortex, Robert L. Ash, Irfan Zardadkhan, Allan J. Zuckerwar

Mechanical & Aerospace Engineering Faculty Publications

Governing equations including the effects of pressure relaxation have been utilized to study an incompressible, steady-state viscous axial vortex with specified far-field circulation. When sound generation is attributed to a velocity gradient tensor-pressure gradient product, the modified conservation of momentum equations that result yield an exact solution for a steady, incompressible axial vortex. The vortex velocity profile has been shown to closely approximate experimental vortex measurements in air and water over a wide range of circulation-based Reynolds numbers. The influence of temperature and humidity on the pressure relaxation coefficient in air has been examined using theoretical and empirical approaches, and …

A Cell Electrofusion Microfluidic Device Integrated With 3d Thin-Film Microelectrode Arrays, Ning Hu, Jun Yang, Shizhi Qian, Sang W. Joo, Xiaolin Zheng

Mechanical & Aerospace Engineering Faculty Publications

A microfluidic device integrated with 3D thin film microelectrode arrays wrapped around serpentine-shaped microchannel walls has been designed, fabricated and tested for cell electrofusion. Each microelectrode array has 1015 discrete microelectrodes patterned on each side wall, and the adjacent microelectrodes are separated by coplanar dielectric channel wall. The device was tested to electrofuse K562 cells under a relatively low voltage. Under an AC electric field applied between the pair of the microelectrode arrays, cells are paired at the edge of each discrete microelectrode due to the induced positive dielectrophoresis. Subsequently, electric pulse signals are sequentially applied between the microelectrode arrays …

Parametric Study On Instabilities In A Two-Layer Electromagnetohydrodynamic Channel Flow Confined Between Two Parallel Electrodes, P. Dinesh Sankar Reddy, Dipankar Bandyopadhyay, Sang Woo Joo, Ashutosh Sharma, Shizhi Qian

Mechanical & Aerospace Engineering Faculty Publications

Instabilities in a two-phase electromagnetohydrodynamic (EMHD) flow between a pair of parallel electrodes are explored. A linear stability analysis has been performed based on a coupled Orr-Sommerfeld system generated from the conservation laws. The study shows the presence of a finite-wave-number EMHD mode of instability in addition to the two commonly observed instability modes in the pressure-driven two-layer flows, namely, the long-wave interfacial mode arising from the viscosity or density stratification and the finite-wave-number shear flow mode engendered by the Reynolds stresses. This extra EMHD mode originates from the additional stresses generated by the Lorenz force acting at the liquid …

Drag Reduction Of A Modern Straight Truck, Drew Landman, Matthew Cragun, Mike Mccormick, Richard Wood

Mechanical & Aerospace Engineering Faculty Publications

A wind tunnel test program was conducted at the Langley Full Scale Tunnel (LFST) to evaluate the performance of five passive drag reduction configurations on a modern straight truck at full scale. Configurations were tested in a build-up fashion with results representing a cumulative effect. Tested configurations include a front valance, a front box fairing, a boat-tail, an ideal side-skirt, and a practical side-skirt. Configurations were evaluated over a nominal 9 degree yaw sweep to establish wind averaged drag coefficients using SAE J1252. Genuine replicate yaw sweeps were used in an uncertainty analysis. Results show up to 28% improvement in …

Uranyl Reactions With Dithionite, L-Ascorbic Acid, And Supported Nanosized Zero-Valent Iron, Shanna Estes

All Theses

This work examined several reductants for remediation of low pH aqueous uranium contamination by reductive precipitation. Reductants included sodium dithionite, L-ascorbic acid, and nanosized zero-valent iron (nZVI). Additionally, the reductive capacity of nZVI successfully entrapped within a silicate matrix (cryogel) was also examined. This supported nZVI is expected to increase nZVI stability in the subsurface, and to provide a convenient in situ delivery mechanism for other remediation systems which may combine entrapped reductant and catalyst.
Fluorescence and absorbance spectroscopy were used to investigate the interaction between hexavalent uranium (U(VI), uranyl) and both sodium dithionite and L-ascorbic acid at pH 2. …

The Behavior Of Nanothermite Reaction Based On Bi2o3/Al, L. Wang, D. Luss, Karen S. Martirosyan

Physics and Astronomy Faculty Publications and Presentations

We studied the impact of aluminum particle size and the thickness of surrounding alumina layer on the dynamic pressure discharge of nanothermite reactions in the Bi2O3/Al system. A pressure discharge from 9 to 13 MPa was generated using as-synthesized Bi2O3 nano-particles produced by combustion synthesis and Al nanoparticles with size from 3 μm to 100 nm. The maximum reaction temperature was measured to be ∼2700 °C. The estimated activation energy of the reaction was 45 kJ/mol. A very large (several orders of magnitude) difference existed between the rate of the pressure pulse release by nanothermite reactions and by thermite …

It’S Growing Season For Maine’S Food System, Deborah Felder

Maine Policy Review

In the introduction to this special issue, guest editor Deb Felder lays out the elements of a sustainable food system. She notes that the increased interest in more ecologically sustainable, safe, humane, and economical community-supported food systems has “put Maine in the forefront of the food movement.”

Farms And The Working Landscape, John Piotti

Maine Policy Review

After years of losing farms and farmers, Maine is seeing an increase in the number of acres being farmed, due partly to a resurgence of interest in farming and new tools that help preserve working landscapes. These tools include agricul­tural easements such as those offered by the Land for Maine’s Future, the Buy/Protect/Sell program at Maine Farmland Trust, local ordinances, and several federal programs

Building A Sustainable Seafood System For Maine, Robin Alden

Maine Policy Review

In this article, Robin Alden notes that Maine could have one of the premier marine food systems in the world. However, that means adequate steward­ship of the Gulf of Maine ecosystem and diversifying the fishing industry beyond lobster by creating innovative public policy and a food system that supports community fishing.

Adrift In A Sea Of Information About Sustainable Seafood: The Maine Consumer Perspective, Catherine V. Schmitt

Maine Policy Review

The desire for a sustainable seafood industry that protects the environment and the future of fishing is certainly of interest to consumers, but even here there are conflicting standards, as Catherine Schmitt explores in this article.

Historical Perspectives On Resource Use In Food Systems, John Jemison, Amanda Beal

Maine Policy Review

No one would deny that industrial agriculture and fishing have been highly productive—but at what cost? This article explores the historical development and contemporary impact of food production on the environment, availability of water and other resources, energy, food safety, and even our waistlines

Resource, Environment And Energy Considerations For Maine Food Security In 2050 And Beyond, Amanda Beal, John Jemison

Maine Policy Review

This article discusses some of the expensive “externalities” produced by industrial agriculture and fishing. These include impaired watershed quality, soil degradation, pollution, reduction in biodiversity, and impacts on human health. The article also includes a discussion of transgenic crops and how these relate to sustainable agriculture

Mathematics In The Age Of Technology: There Is A Place For Technology In The Mathematics Classroom, Helen Crompton

Teaching & Learning Faculty Publications

In today’s world of ubiquitous computing there are a number of technologies available to K-12 educators for teaching and learning mathematics. However, Koehler and Mishra (2008) have described how teaching and learning with such technologies presents a “wicked problem,” as it can involve a number of variables, independent of each other and contextually bound, that need to be brought together. This article highlights the advantages technology offers for mathematics education and looks at some of the reasons behind the poor uptake, such as teacher beliefs and lack of training. A number of solutions are offered to address these issues, including …

Feeling The Ambiance: Using Smart Ambiance To Increase Contextual Awareness In Game Agents, Colm Sloan, John D. Kelleher, Brian Mac Namee

Conference papers

The behaviour of non-player character game agents can be made more interesting and believable through the use of increased contextual awareness. In this paper, we present smart ambiance which allows information about the am- biance of an environment (determined by the environment itself, objects in the environment and recent events) to be used in agent plan generation. We demonstrate how this leads to contextually in uenced action selection and, in turn, more interesting and believable character behaviour.

Epoxi: Comet 103p/Hartley 2 Observations From A Worldwide Campaign ; Astrophysical Journal Letters, K. Meech, M. A'Hearn, J. Adams, P. Bacci, J. Bai, L. Barrera, M. Battelino, J. Bauer, E. Becklin, B. Bhatt, N. Biver, D. Bockelee-Morvan, D. Bodewits, H. Bohnhardt, J. Boissier, B. Bonev, W. Borghini, J. Brucato, E. Bryssinck, M. Buie, H. Canovas, D. Castellano, S. Charnley, W. Chen, P. Chiang, Y. Choi, D. Christian, Y. Chuang, Anita Cochran, P. Colom, M. Combi, I. Coulson, J. Crovisier, N. Russo, K. Dennerl, K. Dewahl, M. Disanti, M. Facchini, T. Farnham, Y. Fernandez, H. Floren, U. Frisk, T. Fujiyoshi, R. Furusho, T. Fuse, G. Galli, D. Garcia-Hernandez, A. Gersch, Z. Getu

Physics Faculty Works

Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was ~16.4 hr. Starting in 2010 August the period changed from 16.6 hr to near 19 hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope …

Computational Studies Of New Materials Ii: From Ultrafast Processes And Nanostructures To Optoelectronics, Energy Storage And Nanomedicine, Thomas George, D. Jelski, R. Letfullin, G. Zhang

Chemistry & Biochemistry Faculty Works

No abstract provided.

Optimal Summer Camp Layout, Anthony Bonifonte

Honors Papers

Convex optimization is an important branch of operations research. It generalizes linear programming and offers powerful tools for modelling problems and discovering optimal solutions to real world problems. Mathematically it is an interesting topic because it ties together many branches: linear algebra, multivariable calculus, and numerical analysis, to name a few. Modelling a problem as a convex optimization problem can be challenging but offers many benefits. Algorithm design is critically important to ensure precision of solutions that solve with minimal computation power. From an engineering perspective it is also incredibly useful, since many more situations can be modeled than with …

Review: The Mathematics Of Sex: How Biology And Society Conspire To Limit Talented Women And Girls, Susan Jane Colley

Faculty & Staff Scholarship

No abstract provided.

Haskell For The Cloud, Andrew P. Black

Computer Science Faculty Publications and Presentations

We present Cloud Haskell, a domain specific language for developing programs for a distributed-memory computing environment. Implemented as a shallow embedding in Haskell, it provides a message-passing communication model, inspired by Erlang, without introducing incompatibility with Haskell's established sharedmemory concurrency. A key contribution is a method for serializing function closures for transmission across the network. Cloud Haskell has been implemented; we present example code and some preliminary performance measurements.

Finding Haystacks With Needles: Ranked Search For Data Using Geospatial And Temporal Characteristics, Veronika Margaret Megler, David Maier

Computer Science Faculty Publications and Presentations

The past decade has seen an explosion in the number and types of environmental sensors deployed, many of which provide a continuous stream of observations. Each individual observation consists of one or more sensor measurements, a geographic location, and a time. With billions of historical observations stored in diverse databases and in thousands of datasets, scientists have difficulty finding relevant observations. We present an approach that creates consistent geospatial-temporal metadata from large repositories of diverse data by blending curated and automated extracts. We describe a novel query method over this metadata that returns ranked search results to a query with …

Can Transportation Researchers Reuse Project Datasets And Programs?, Tyler Hayes, Lois Delcambre, Leonard Shapiro

Computer Science Faculty Publications and Presentations

Data users involved in research and analysis typically invest a lot of eort cleaning and manipu- lating their data as they work. Based on this observation, we have investigated two hypotheses: 1) reuse of datasets and procedures is difficult, and 2) the inability to reuse datasets and procedures is primarily due to a lack of documentation. To test these hypotheses we conducted structured interviews with data users asking questions regarding the struggles in their work pertaining to data, their documentation habits, and the importance of documentation. The interviews revealed that the data users rarely reused data or procedures, frequently encountered …

Bipartite Density Of Generalized Petersen Graphs, Lisa Jordan Ewell

Electronic Theses and Dissertations

The bipartite density b(G) of a graph G with m edges is the maximum ratio [special characters omitted] where m0 is the number of edges in a bipartitesubgraph of G. In this study we determine the bipartite density of several classes of Generalized Petersen Graphs. These graphs are denoted by P(n, k), where n ≥ 3 and 1 ≤ k < n with n ≠ 2k. The Generalized Petersen Graph P(n, k) has vertices [special characters omitted] and edges [special characters omitted] where subscript addition is modulo n. We define subgraphs P'(n, k) of P( n, k) by deleting the edge vn –1v0 and the edges w iwi+k for n – k ≤ i ≤ n – 1. For P'(n, k) and many classes of P(n, k), we determine the exact number of edges which must be removed from P( n, k) to reduce it to a bipartite subgraph. In many classes of Generalized Petersen Graphs the exact bipartite density is derived. For example: b(P(n, k)) = 1 for n even, k odd; b(P(n, k)) = 1 – [special characters omitted] for n and k odd and n > k²; b(P( n, k)) is asymptotically 1 – [special characters omitted] for n odd, k even.

Covering Systems Of Polynomial Rings Over Finite Fields, Michael Wayne Azlin

Electronic Theses and Dissertations

In 1950 Paul Erdos observed that every integer belonged to a certain system of congruences with distinct moduli. He called such systems of congruences covering systems. Utilizing his covering system, he disproved a conjecture of de Polignac asking, “for every odd k, is there a prime of the form 2n + k?” Examples of covering systems of the integers are presented along with some brief history and a sketch of the disproof by Erd?s. Open conjectures concerning covering systems and best known results of attempts to prove these conjectures are given. Analogies are drawn between the integers and Fq[x], and …

Relativistic Red-Black Trees, Philip William Howard, Jonathan Walpole

Computer Science Faculty Publications and Presentations

Operating system performance and scalability on sharedmemory many-core systems depends critically on efficient access to shared data structures. Scalability has proven difficult to achieve for many data structures. In this paper we present a novel and highly scalable concurrent red-black tree. Red-black trees are widely used in operating systems, but typically exhibit poor scalability. Our red-black tree has linear read scalability, uncontended read performance that is at least 25% faster than other known approaches, and deterministic lookup times for a given tree size, making it suitable for realtime applications.