Physical Sciences and Mathematics Commons^™

Inter- And Intra-Annual Variability Of Vegetation In The Northern Hemisphere And Its Association With Precursory Meteorological Factors, Boksoon Myoung, Yong-Sang Choi, Seungbum Hong, Seon Ki Park

Mathematics, Physics, and Computer Science Faculty Articles and Research

Determination of phenological variation is one of the most critical challenges in dynamic vegetation modeling, given the lack of a strong theoretical framework. Previous studies generally focused on the timing of a phenological event (e.g., bud-burst or onset of growing season) and its atmospheric prompts, but not on the interactive variations across phenological stages. This study, therefore, investigated the inter- and intra-annual variability existing in all the phenological stages and the relations of the variability with four meteorological variables (surface temperature (Ts), shortwave radiation (SW ), vapor pressure deficit (VPD), and precipitation (PRCP)) using a 25-year (1982-2006) dataset of leaf …

Topological Convolution Algebras, Daniel Alpay, Guy Salomon

Mathematics, Physics, and Computer Science Faculty Articles and Research

In this paper we introduce a new family of topological convolution algebras of the form ⋃p∈NL2(S,μp), where S is a Borel semi-group in a locally compact group G, which carries an inequality of the type ∥f∗g∥p≤Ap,q∥f∥q∥g∥p for p>q+d where d pre-assigned, and Ap,q is a constant. We give a sufficient condition on the measures μp for such an inequality to hold. We study the functional calculus and the spectrum of the elements of these algebras, and present two examples, one in the setting of non commutative stochastic distributions, and the other related to Dirichlet series.

Fuel Efficient Computation In Passive Self-Assembly, Robert Schweller, Michael Sherman

Computer Science Faculty Publications and Presentations

In this paper we show that passive self-assembly in the context of the tile self-assembly model is capable of performing fuel efficient, universal computation. The tile self-assembly model is a premiere model of self-assembly in which particles are modeled by four-sided squares with glue types assigned to each tile edge. The assembly process is driven by positive and negative force interactions between glue types, allowing for tile assemblies floating in the plane to combine and break apart over time. We refer to this type of assembly model as passive in that the constituent parts remain unchanged throughout the assembly process …

The Road To Deterministic Matrices With The Restricted Isometry Property, Afonso S. Bandeira, Matthew C. Fickus, Dustin G. Mixon, Percy Wong

Faculty Publications

The restricted isometry property (RIP) is a well-known matrix condition that provides state-of-the-art reconstruction guarantees for compressed sensing. While random matrices are known to satisfy this property with high probability, deterministic constructions have found less success. In this paper, we consider various techniques for demonstrating RIP deterministically, some popular and some novel, and we evaluate their performance. In evaluating some techniques, we apply random matrix theory and inadvertently find a simple alternative proof that certain random matrices are RIP. Later, we propose a particular class of matrices as candidates for being RIP, namely, equiangular tight frames (ETFs). Using the known …

Versatile Rb Vapor Cells With Long Lifetimes, John F. Hulbert, Matthieu Giraud-Carrier, Tom Wall, Aaron R. Hawkins, Scott D. Bergeson, Jennifer Black, Holger Schmidt

Faculty Publications

The authors report on an approach to the construction of long-lasting rubidium atomic vapor cells. The method uses pinch-off copper cold-welds, low temperature solders, and electroplated copper to create long-lasting hermetic seals between containment chambers of dissimilar geometries and materials. High temperature epoxy, eutectic lead/tin solder, and indium solder were considered as sealing materials. These seals were analyzed using accelerated lifetime testing techniques. Vapor cells with epoxy and bare metal solder seals had a decrease in the rubidium atomic density within days after being heated to elevated temperatures. They also exhibited broadened spectra as a result of rubidium reacting with …

Can The Causeway In The Great Salt Lake Be Used To Manage Salinity, Sarah E. Null, Wayne A. Wurtsbaugh, Craig Miller

Wayne A. Wurtsbaugh

No abstract provided.

Fair Cost Sharing Auction Mechanisms In Last Mile Ridesharing, Duc Thien Nguyen

Dissertations and Theses Collection (Open Access)

With rapid growth of transportation demands in urban cities, one major challenge is to provide efficient and effective door-to-door service to passengers using the public transportation system. This is commonly known as the Last Mile problem. In this thesis, we consider a dynamic and demand responsive mechanism for Ridesharing on a non-dedicated commercial fleet (such as taxis). This problem is addressed as two sub-problems, the first of which is a special type of vehicle routing problems (VRP). The second sub-problem, which is more challenging, is to allocate the cost (i.e. total fare) fairly among passengers. We propose auction mechanisms where …

Impact Of Multimedia In Sina Weibo, Xun Zhao

Dissertations and Theses Collection (Open Access)

Multimedia contents such as images and videos are widely used in social network sites nowadays. Sina Weibo, a Chinese microblogging service, is one of the first microblog platforms to incorporate multimedia content sharing features. This thesis provides statistical analysis on how multimedia contents are produced, consumed, and propagated in Sina Weibo. Based on 230 million tweets and 1.8 million user profiles in Sina Weibo, we study the impact of multimedia contents on the popularity of both users and tweets as well as tweet life span. In addition to consider the multimedia impact on popularity, we also compare the user influence …

A Study Of The Imitation, Collection And Usability Issues Of Keystroke Biometrics, Chee Meng Tey

Dissertations and Theses Collection (Open Access)

The majority of authentication systems used today involves passwords, where a user is required to remember and key in the correct password to login. Keystroke biometrics is an alternative approach whereby users are identified by one or more features such as (a) the timing between keystrokes, (b) how long users hold each key and (c) how hard users press each key. It is being assumed in prior research that the way one user types a password/word is different from the way another user types the same password and this characteristic remains stable over time. Existing literature however left open three …

Let's Get In The Mood: An Exploration Of Data Mining Techniques To Predict Mood Based On Musical Properties Of Songs, Sarah Smith-Polderman

Senior Independent Study Theses

This thesis explores the possibility of predicting the mood a song will evoke in a person based on certain musical properties that the song exhibits. First, I introduce the topic of data mining and establish its significant relevance in this day and age. Next, I explore the several tasks that data mining can accomplish, and I identify classification and clustering as the two most relevant tasks for mood prediction based on musical properties of songs. Chapter 3 introduces in detail two specific classification techniques: Naive Bayes Classification and k-Nearest Neighbor Classification. Similarly, Chapter 4 introduces two specific clustering techniques: …

Becoming Aware Of Mathematical Gaps In New Curricular Materials: A Resource-Based Analysis Of Teaching Practice, José Guzman, Carolyn Kieran

The Mathematics Enthusiast

The study featured in this article, with its central focus on resources-in-use, draws upon salient aspects of the documentational approach of didactics. It includes an a priori analysis of the curricular resources being used by a teacher for the first time, followed by detailed in situ observations of the unfolding of her teaching practice involving these resources. The central mathematical problem of the lesson being analyzed deals with families of polynomial functions. The analysis highlights the teacher’s growing awareness of the mathematical gaps in the resources she is using, which we conjecture to be a first step for her in …

Two-Step Arithmetic Word Problems, Enrique Castro-Martínez, Antonio Frías-Zorilla

The Mathematics Enthusiast

This study uses the perspective of schemes to analyze characteristics of arithmetic word problems that can influence the process of translation from the verbal statement to an arithmetical representation. One characteristic that we have detected in the two-step word problems is the presence of one or two connections (nodes) in schemes that represent them, and this paper explores whether the number of nodes affects the activation of the associated schemas. With students from the 5th and 6th grades of elementary school (11 and 12 years of age), we analyze the written productions and would stress that the number of connections …

Trajectory Of A Problem: A Study In Teacher Training, Alain Kuzniak, Bernard Parzysz, Laurent Vivier

The Mathematics Enthusiast

Problems are frequently used in mathematics to introduce and convey new notions and skills. Hence, teachers transform and adjust those problems to their students' level. The present study focuses on this transformation process on the particular case of a geometric problem posed by two teacher educators in one French Institute for Teacher Training. The whole process is described as a trajectory of the problem through various institutions from training center to secondary school and back. Before presenting the notion of trajectory of the problem, some elements about a general theoretical frame which refers to didactics of mathematics are presented.

Bacillus Thuringiensis: Transgenic Crops, Julie A. Peterson, John J. Obrycki, James D. Harwood

Department of Entomology: Faculty Publications

Bacillus thuringiensis (Bt) crops, genetically modified to express insecticidal toxins that target key pests of corn, cotton, rice, potato, and other crops, have been rapidly adopted and have become dominant fixtures in agroecosystems throughout the world. Due to the constitutive nature of Bt toxin expression, insecticidal proteins may be found in nearly all plant tissues, presenting multiple sources for Bt toxins to enter the environment, thus creating complex direct and indirect pathways for non-target organisms to be exposed to insecticidal proteins. The environmental impacts of Bt crops have been widely debated, although both benefits and risks do exist. Benefits of …

Concept Drift Datasets, Patrick Lindstrom

Doctoral

This zip file contains the datasets used in the PhD thesis:

Lindstrom, P., 2013. Handling Concept Drift in the Context of Expensive Labels. Technological University Dublin. For more information about the datasets please see the README file and the aforementioned thesis.

Problem Solving In The Primary School (K-2), Richard Lesh, Lyn English, Chanda Riggs, Serife Sevis

The Mathematics Enthusiast

This article focuses on problem solving activities in a first grade classroom in a typical small community and school in Indiana. But, the teacher and the activities in this class were not at all typical of what goes on in most comparable classrooms; and, the issues that will be addressed are relevant and important for students from kindergarten through college. Can children really solve problems that involve concepts (or skills) that they have not yet been taught? Can children really create important mathematical concepts on their own – without a lot of guidance from teachers? What is the relationship between …

Young Children Investigating Advanced Mathematical Concepts With Haptic Technologies: Future Design Perspectives, Stephen Hegedus

The Mathematics Enthusiast

In this chapter, we focus on how new technologies can be used with young children to investigate mathematical ideas and concepts that would normally be introduced at a later age. In particular, we focus on haptic technologies that allow learners to touch and feel objects through force feedback in addition to visual images on a screen. The main purpose of this paper is to describe how these technologies can be used to enable young learners to construct meaning about geometric shapes and surfaces as well as attributes of particular mathematical constructions in multiple dimensions (particularly 2D and 3D for purposes …

Cognitive Processes Developed By Students When Solving Mathematical Problems Within Technological Environments, Fernando Barrera-Mora, Aarón Reyes-Rodríguez

The Mathematics Enthusiast

In this paper we document and discuss how the use of digital technologies in problem solving activities can help students to develop mathematical competences; particularly, we analyze the characteristics of reasoning that students develop as a result of using Cabri Geometry software in problem solving. We argue that the dynamical nature of representations constructed with Cabri, and the availability of measure tools integrated to it are important elements that enhance students’ ability to think mathematically and foster the implementation of several heuristic strategies in problem solving processes.

Thoughts About Research On Mathematical Problem- Solving Instruction, Frank K. Lester Jr.

The Mathematics Enthusiast

In this article, the author, who has written extensively about mathematical problem solving over the past 40 years, discusses some of his current thinking about the nature of problem-solving and its relation to other forms of mathematical activity. He also suggests several proficiencies teachers should acquire in order for them to be successful in helping students become better problem solvers and presents a framework for research on problem-solving instruction. He closes the article with a list of principles about problem-solving instruction that have emerged since the early 1970s.

Contribution Of The Pacific Decadal Oscillation To Global Mean Sea Level Trends, B. D. Hamlington, R. R. Leben, M. W. Strassburg, R. S. Nerem, K-Y. Kim

CCPO Publications

Understanding and explaining the trend in global mean sea level (GMSL) have important implications for future projections of sea level rise. While measurements from satellite altimetry have provided accurate estimates of GMSL, the modern altimetry record has only now reached 20 years in length, making it difficult to assess the contribution of decadal to multidecadal climate signals to the global trend. Here, we use a sea level reconstruction to study the 20 year trends in sea level since 1950. In particular, we show that the Pacific Decadal Oscillation (PDO) contributes significantly to the 20 year trends in GMSL. We estimate …

Editorial-The 4th International Workshop On Modeling The Ocean (Iwmo 2012), Lie-Yauw Oey, Yasumasa Miyazawa, Hidenori Aiki, Yukio Masumoto, Tal Ezer, Takuji Waseda

CCPO Publications

The 4th International Workshop on Modeling the Ocean (IWMO; http://www.jamstec.go.jp/frcgc/jcope/htdocs/e/ iwmo2012.html) was held on May 21–24, 2012 in the vibrant city of Yokohama on the Tokyo Bay, Japan. The Workshop was hosted by Japan Agency for Marine-Earth Science and Technology (JAMSTEC)—the home of the famous “Earth Simulator”—one of the world's most powerful supercomputers dedicated for simulating the complex interactive processes of the earth and its environment.

A Population Density Domain Model For Calcium-Inactivation Of L-Type Calcium Channels, Kiah Hardcastle, Seth H. Weinberg, Gregory D. Smith

Arts & Sciences Articles

No abstract provided.

Simulation Studying Effects Of Multiple Primary Aberrations On Donut-Shaped Gaussian Beam, Chen Zhang, K. Wang, J. Bai, Y. Liu, Guiren Wang

Faculty Publications

In this paper, we demonstrate the variation of donut-shaped depletion pattern which influenced by multiple primary aberrations. The simulation is base on a common stimulation emission of depletion (STED) system composed by Gaussian laser and vortex phase plate. The simulation results are helpful guidelines for analyzing the aberration of depletion patterns in real situations.

Dynamics At A Janus Interface, M. Von Domaros, D. Bratko, B. Kirchner, A. Luzar

Chemistry Publications

Electric field effects on water interfacial properties abound, ranging from electrochemical cells to nanofluidic devices to membrane ion channels. On the nanoscale, spontaneous orientational polarization of water couples with field alignment, resulting in an asymmetric wetting behavior of opposing surfacesa field-induced analogue of a chemically generated Janus interface. Using atomistic simulations, we uncover a new and significant field polarity (sign) dependence of the dipolar- orientation polarization dynamics in the hydration layer. Applying electric fields across a nanoparticle, or a nanopore, can lead to close to 2 orders of magnitude difference in response times of water polarization at opposite surfaces. Typical …

Tunable Thermal Quenching Of Photoluminescence In Mg-Doped P-Type Gan, Michael A. Reshchikov, J. D. Mcnamara, S. Fernández-Garrido, R. Calarco

Physics Publications

We have studied the thermal quenching of the ultraviolet luminescence band with a maximum at about 3.25 eV in p-type Mg-doped GaN. The characteristic temperature of the thermal quenching of photoluminescence (PL) gradually shifted to higher temperatures with increasing excitation intensity. This effect is explained by a population inversion of charge carriers at low temperatures, which suddenly converts into a quasiequilibrium population as the temperature increases above the characteristic value. Tunable quenching of PL has been observed only in some of the GaN:Mg samples. The absence of the tunable quenching of PL in another group of GaN:Mg samples is preliminarily …

The Effect Of Sulfur Covalent Bonding On The Electronic Shells Of Silver Clusters, Anthony F. Pedicini, Arthur C. Reber, Shiv N. Khanna

Physics Publications

The nature of the bonding in Ag n S m ^0/− clusters, n = 1–7; m = 1–4, has been analyzed to understand its effect on the electronic shell structure of silver clusters. First-principle investigations reveal that the sulfur atoms prefer 2 or 3-coordinate sites around a silver core, and that the addition of sulfur makes the planar structures compact. Molecular orbital analysisfinds that the 3p orbitals of sulfur form a bonding orbital and two weakly bonding lone pairs withsilver. We examine the electronic shell structures of Ag 6Sm, which are two electrons deficient of a spherical closed electronic shell …

Magnetic Hollow Cages With Colossal Moments, Menghao Wu, Puru Jena

Physics Publications

A comprehensive study of the interaction of transition metal clusters with B, C, N, O, and Si reveal novel structure and properties: Co12C6, Mn12C6, and Mn24C18 clusters form stable ferromagnetic hollow cages with total magnetic moments of 14 μB, 38 μB, and 70 μB, respectively. Replacement of C with B, N, O, or Si has significant impact on their structure and magnetic properties. For example, Mn20Si12 cluster forms a ferrimagnetic dodecahedral hollow cage with a total magnetic moment of 36 μB while Mn12N6, X12C6 (X = Ni, Cu, Pd, Pt), and Cu12O6 possess no magnetic moment, although they retain hollow …

Unusually Large Spin Polarization And Magnetoresistance In A Femg8-Femg8 Superatomic Dimer, Lin Zhu, Meichun Qian, Shiv N. Khanna

Physics Publications

Electronic transport across a FeMg8 magnetic superatom and its dimer has been investigated using a density functional theory combined with Keldysh nonequilibrium Green's-function formalism. For a single cluster, our studies for the cluster supported in various orientations on a Au(100) surface show that the transport is sensitive to the contact geometry. Investigations covering the cases where the axes of Mg square antiprism are 45°, perpendicular, and parallel to the transport direction, show that the equilibrium conductance, transferred charge, and currentpolarizations can all change significantly with orientation. Our studies on the transport across a magnetic superatom dimer FeMg8–FeMg8 focus on the …

Quantification Of Biomass And Cell Motion In Human Pluripotent Stem Cell Colonies, Thomas A. Zangle, Jennifer Chun, Jin Zhang, Jason C. Reed, Michael A. Teitell

Physics Publications

Abstract

Somatic cell reprogramming to pluripotency requires an immediate increase in cell proliferation and reduction in cell size. It is unknown whether proliferation and biomass controls are similarly coordinated with early events during the differentiation of pluripotent stem cells (PSCs). This impasse exists because PSCs grow in tight clusters or colonies, precluding most quantifying approaches. Here, we investigate live cell interferometry as an approach to quantify the biomass and growth of HSF1 human PSC colonies before and during retinoic acid-induced differentiation. We also provide an approach for measuring the rate and coordination of intracolony mass redistribution in HSF1 clusters using …

Blue Luminescence And Zn Acceptor In Gan, Denis Demchenko, Michael A. Reshchikov

Physics Publications

In this paper, we present a comparison of exchange-tuned hybrid density functional calculations with experimental data obtained for the Zn acceptor in GaN. Since this acceptor is one of the few reliably identified defects in GaN, we use Zn-doped GaN as a test case for the widely used HSE06 hybrid functional method of calculations of defect properties in semiconductors. Here, we present the experimental results of luminescence measurements in Zn-doped GaN from which we obtain Zn acceptor defect levels. They are compared with theoretically calculated defect thermodynamic and optical transition levels as well as the zero-phonon line associated with this …