Timothy Urness - research and publications

Generating Interest in Computer Science Through Middle-School Android Summer Camps
Consortium for Computing Sciences in Colleges
Journal of Computing Sciences in Colleges, Volume 28 Issue 5
Timothy Urness and Eric Manley

We conducted a week-long summer camp to promote interest in computer science among middle-school students. The camp primarily used self-paced video tutorials to teach programming concepts using the App Inventor for Android programming environment. Based on strong interest from students and parents as well as positive survey feedback, we conclude that the camp was very successful.

Building a Thriving CS Program at a Small Liberal Arts College
Consortium for Computing Sciences in Colleges
Journal of Computing Sciences in Colleges, Volume 26 Issue 5
Timothy Urness and Eric Manley

In this paper we describe several techniques that have helped increase enrollment in the computer science program from 23 computer science majors in 2008 to 42 computer science majors in 2010 — an increase of 82.6% We discuss issues related to curriculum, programming assignments, and professor-student interactions that have made the discipline more attractive and manageable to a variety of students within the setting of a small liberal arts college.

Multivariate Visualization of Chromatographic Systems
Visualization and Data Analysis 2011
Proceedings of SPIE-IS&T Electronic Imaging, SPIE Vol. 7868-11
Timothy Urness, Thomas Marrinan, Andrew R. Johnson, and Mark F. Vitha

Chromatography is a technique used to separate and quantify the components in a complex chemical mixture. We have created a 3D visualization system capable of comparing the chemical properties of chromatographic systems. The visualization system combines scatter plots, parallel coordinates, and specialized glyphs to assist in the analysis of chromatographic data and comparisons of multiple systems. Using this tool, numerous separation systems can be readily compared simultaneously — greatly facilitating the ability to select systems that are likely to produce desired separations during method development.
software available here

Understanding and Interpreting Multivalued Astronomical Data
IEEE Computer Graphics and Applications, September/October 2010
Thomas Marrinan, Timothy Urness, Charles Nelson, Kory Kreimeyer, and Jordan Mirocha

This article discusses how data visualization can help astronomers understand the kinematics of ionized gas in the nuclear regions of Seyfert galaxies, the most common active galactic nuclei. The goal is to compare spectroscopic-analysis results with the expectations from various gas flow models to determine the dominant acceleration mechanism.

System Selectivity Cube: A 3D Visualization Tool for Comparing the Selectivity of Gas Chromatography, Supercritical-Fluid Chromatography, High-Pressure Liquid Chromatography, and Micellar Electrokinetic Capillary Chromatography Systems
Analytical Chemistry, Volume 82, Issue 14
Andrew R. Johnson, Mark F. Vitha, Timothy Urness and Thomas Marrinan

A three-dimensional visualization tool termed the system selectivity cube (SSC) has been developed to aid in the selection of chromatography systems. The most effective way to change the resolution of a complex mixture is to change the selectivity of the separation. The SSC allows efficient identification of systems of differing selectivity. The SSC groups those systems which provide little or no difference in selectivity and those systems which do differ in their selectivities. We anticipate that this approach will be useful for selecting replacement columns, systems that may offer better results for difficult separations, and orthogonal phases for 2D gas chromatography (GC) and reversed phase liquid chromatography (RPLC) separations.
software available here

How Bob Barker Would (Probably) Teach Discrete Mathematics
PRIMUS: Problems, Resources, and Issues in Mathematics Undergraduate Studies, Volume 20, Issue 6
Timothy Urness

This paper proposes a discrete mathematics course in which games from The Price Is Right are used to engage students in a deeper, practical study of discrete mathematics. The games themselves are not the focus of the course; rather, the mathematical principles of the games give motivation for the concepts being taught. The game examples are designed to be an alternative to traditional textbook problems and used as active exercises throughout the course.


Ionization of Atomic Hydrogen in Strong Infrared Laser Fields
Physical Review A, Volume 81, Issue 4
Alexei N. Grum-Grzhimailo, Brant Abeln, Klaus Bartschat, Daniel Weflen, and Timothy Urness

We have used the matrix iteration method of Nurhuda and Faisal [Phys. Rev. A 60, 3125 (1999)] to treat ionization of atomic hydrogen by a strong laser pulse. After testing our predictions against a variety of previous calculations, we present ejected-electron spectra as well as angular distributions for few-cycle infrared laser pulses with peak intensities of up to 1015 W/cm2. It is shown that the convergence of the results with the number of partial waves is a serious issue, which can be managed in a satisfactory way by using the velocity form of the electric dipole operator in connection with an efficient time-propagation scheme.

GPU Programming for Mathematical and Scientific Computing
Midwest Instruction and Computing Symposium
Proceedings of MICS 2010
Ethan Kerzner and Timothy Urness
Received Award for Best Student Paper

Graphical processing units used for mathematical and scientific computing are known as general purpose graphical processing units (GPGPUs). This paper is an introduction to the most popular GPGPU technology, NVIDIA's Compute Unified Device Architecture (CUDA). We approach CUDA from the perspective of a software developer, discussing the structure and organization of programs to explain the function of the GPU. We propose a potential application of GPGPU programming, the parallel analysis of a Hidden Markov Model, and discuss arithmetic error on the graphical processing unit.

Discrete Logarithms and Elliptic Curves in Cryptography
Midwest Instruction and Computing Symposium
Proceedings of MICS 2010
Derek Olson and Timothy Urness

This paper surveys the mathematical foundations, shortcomings, and novel variants of the first public key cryptosystem envisioned by Whitfield Diffie, Martin Hellman, and Ralph Merkle in 1976. The system they developed, Diffie-Hellman key exchange, relied on the difficulty of taking discrete logarithms in finite fields. While relatively secure, methods known as the index calculus exist to crack Diffie-Hellman key exchange in less than exponential running time. This has led to the use of elliptic curves in analogous cryptosystems. The basic theory underlying these elliptic curve cryptosystems is presented as well as a comparison of these systems with standard RSA encryption.

Assessment using Peer Evaluations, Random Pair Assignment, and Collaborative Programming in CS1
Consortium for Computing Sciences in Colleges
Journal of Computing Sciences in Colleges, Volume 25 Issue 1
Timothy Urness

A common concern of professors implementing collaborative (pair) programming is the potential for a student to not actively participate in the programming process. In this paper I describe a technique for student assessment that uses peer evaluation and random pair assignment in collaborative programming assignments in CS1. The results showed that the assignment quality greatly increased and exam scores were comparable compared to previous course offerings when assignments were completed individually.

Using Daily Student Presentations to Address Attitudes and Communication Skills in CS1
SIGCSE: ACM Special Interest Group on Computer Science Education
Proceedings of SIGCSE 2009
Chris Bennett and Timothy Urness

Many CS1 courses lack a breadth in coverage of computing related topics and fail to help students develop oral communication skills. In this paper, we describe our experience with addressing these issues in CS1 at two different institutions through the use of brief, daily student presentations. We also describe the results of a survey students take before and after the course to evaluate how participating in the course can affect attitudes and beliefs about computer science.

Using Recycled Computers to Construct a Beowulf Cluster for Molecular Modeling
Midwest Instruction and Computing Symposium
Proceedings of MICS 2009
Creston Flemming, Timothy Urness, and Maria Bohorquez

We describe the process of using recycled computers to construct a Beowulf cluster to simulate the molecular dynamics of a chemical system. The cluster was assembled using computers taken out of service due to upgrades and would have otherwise been discarded. When assembled in a cluster, the computers performed the numerically-intensive process of molecular modeling roughly four times faster than a current machine.

Exploring Cache Optimization for Bioinformatics Applications
Midwest Instruction and Computing Symposium
Proceedings of MICS 2009
Shannon Dybvig, Megan Bailey, and Timothy Urness

Bioinformatics is one of the fastest growing fields due to its long-term medical and genetic implications. This paper explores the benefits of splitting cache and creating an optimal split in cache for bioinformatics applications.

Visualization of Energy Minimization in Ferromagnetic Systems
Midwest Instruction and Computing Symposium
Proceedings of MICS 2008
Zachary Oler and Timothy Urness
Received Award for Best Student Paper

Many different studies of magnetism models have presented theories on energy minimization. These studies, however, do not give a visual confirmation of what is occurring during minimization. In this paper, we describe a model and visualization system designed to illustrate the principles of energy minimization in magnetic systems.

Teaching File Input/Output, Loops, and If-Statements via a Red Eye Reduction Assignment
Consortium for Computing Sciences in Colleges
Journal of Computing Sciences in Colleges, Volume 23 Issue 4
Timothy Urness

This paper describes a "nifty" programming assignment that requires students to use files, loops, and if-statements to implement an algorithm that will remove the red-eye artifact from an image. The assignment is most suitable for a CS1 course, but could be altered to accommodate a CS0 or CS2 course.

Streamline Visualization of Multiple 2D Vector Fields
Visualization and Data Analysis 2008
Proceedings of SPIE-IS&T Electronic Imaging, SPIE Vol. 6809-9
Timothy Urness and Victoria Interrante

The analysis of data that consists of multiple vector fields can be greatly facilitated by the simultaneous visualization of the vector fields. An effective visualization must accurately reflect the key physical structures of the fields in a way that does not allow for an unintended bias towards one distribution. While there are several effective techniques to visualize a single vector field through equally-spaced streamlines, applying these techniques to individual vector fields and combining them in a single image yields several undesirable artifacts. In this paper, we present strategies for the effective visualization of two vector fields through the use of streamlines.

Teaching Computer Organization/Architecture by Building a Computer
2007 Workshop on Computer Architecture Education
Timothy Urness

This paper describes a series of exercises and assignments suggested for an introductory computer organization or computer architecture course. The primary objective of these exercises is to engage a class of students by introducing the practical, hands-on application of assembling a computer by selecting and purchasing individual components.

FieldVis: A Tool for Visualizing Astrophysical Magnetohydrodynamic Flow
IEEE Computer Graphics and Applications, January/February 2007
Blayne Field, Sean O'Neill, Timothy Urness, Victoria Interrante, and Thomas W. Jones

Our group is involved in magnetohydrodynamic simulations that track the time and space evolution of the full 3D velocity and magnetic vector fields, plus fundamental scalar fields such as density and pressure. To accomplish the complex visualization of these jets, we developed FieldVis, a simulation tool that focuses primarily on representing 3D vector and scalar fields.

Directional Enhancement in Texture-based Vector Field Visualization
Graphite 2006
Francesca Taponecco, Timothy Urness, and Victoria Interrante

The use of textures provides a rich and diverse set of possibilities for the visualization of flow data. We present methods designed to produce oriented and controlled textures that accurately reflect the complex patterns that occur in vector field visualizations.

Strategies for the Visualization of Multiple 2D Vector Fields
IEEE Computer Graphics and Applications, July/August 2006
Timothy Urness, Victoria Interrante, Ellen Longmire, Ivan Marusic, Sean O'Neill, and Thomas W. Jones

Strategies for effectively visualizing co-located 2D vector fields enable understanding of key physical structures of one vector field within the context of a related vector field. We describe the range of effects possible by combining several existing flow visualization techniques for analyzing multiple vector fields.

Texture-Based Visualization of Multi-Field Flow Data
Ph.D. Dissertation, May 2006
University of Minnesota
Department of Computer Science and Engineering
Timothy Urness

The goal through this work is to enable researchers to obtain a succinct, meaningful visual summary of the contents of a dataset that consists of multiple, coincident variables. This is accomplished through providing techniques that allow the creation of an image in which the important features of multiple scalar or vector fields can be understood both independently and in the context of the other fields.

Techniques for Visualizing Multi-Valued Flow Data
Eurographics/IEEE TCVG Symposium on Visualization 2004
Timothy Urness, Victoria Interrante, Ellen Longmire, Ivan Marusic, and Bharathram Ganapathisubramani

We discuss several techniques to display scalar distributions within an image depicting a 2D flow field. We address how contrast and luminance can effectively be used, present modifications to an algorithm that uses dense streamlines to represent flow direction, and present a new technique, based on embossing, to encode the out-of-plane component of a 3D vector field over a 2D domain.

Animations
mpeg movie and interactive java applet
Timothy Urness, 2003

The vector field in any visualization is dependent on the relative velocity of the observer. Traditionally, the average value of the streamwise component of the global vector field is calculated and subtracted from each vector. However, the resulting LIC image, critical points, and vector field features are greatly influenced by the magnitude of the value subtracted from the streamwise velocity. Examples of this phenomenon are shown here.

Effectively Visualizing Multi-Valued Flow Data Using Color and Texture
IEEE Visualization 2003
Timothy Urness, Victoria Interrante, Ivan Marusic, Ellen Longmire, and Bharathram Ganapathisubramani

In this paper we offer several new insights and techniques for effectively using color and texture to simultaneously convey information about multiple 2D scalar and vector distributions, in a way that facilitates allowing each distribution to be understood both individually and in the context of one or more of the other distributions.

Effective Visualization of Stereo PIV Vector Fields of a Turbulent Boundary Layer
Journal of Turbulence, Article 23, Volume 4, 2003.
E. K. Longmire, B Ganapathisubramani, I Marusic, T Urness, and V Interrante

Stereo PIV datasets contain three dimensional information over a plane from which multiple quantities can be derived at each point. The task of visualizing these different parameters simultaneously is challenging and this inhibits our ability to analyze and derive firm conclusions about the physics of the flow. In this paper, we discuss several different ways in which the primary quantities can be viewed simultaneously in the same image.

Techniques for Visualizing Multi-Valued Flow Data
Master of Science Thesis, May 2003
University of Minnesota
Department of Computer Science and Engineering
Timothy Urness

We present several techniques to effectively visualize multi-valued flow data using contrast, color, 3D visualization, and texture. The ultimate goal through this work is to enable researchers to obtain a succinct, meaningful visual summary of the contents of a dataset through providing techniques that allow the creation of images in which the important features of multiple scalar distributions can be understood both independently and in the context of multiple other distributions.

Structure Identification and Analysis in Turbulent Boundary Layers by Stereo PIV
4th International Symposium on Particle Image Velocimetry, 2001
E. K. Longmire, B. Ganapathisubramani, I. Marusic, T. Urness

The objective of this study is to apply Stereo PIV in streamwise-spanwise planes to measure three-dimensional velocity fields and to develop methods for the identification of typical flow structures. These methods can then be applied to quantify the strength, size, and frequency of various structures and therefore to examine the existence, nature, and symmetry of hairpin-like vortices and vortex packets.

Analyzing Industrial Furnace Efficiency Using Comparative Visualization in a Virtual Reality Environment
Proceedings of the 1999 ASME International Mechanical Engineering Congress and Exposition, pages 191-199.
Lori Frietag and Tim Urness

We describe an interactive toolkit used to perform comparative analysis of two or more data sets arising from numerical simulations. An industrial application aimed at designing an efficient, low-NOx burner for industrial furnaces is used. Critical insights are obtained by interactively adjusted color maps, data culling, and data manipulation. New paradigms for scaling small values in the data comparison technique are described. The display device used for this application was the CAVE virtual reality theater, and we describe the user interface to the visualization toolkit and the benefits of immersive 3D visualization for comparative analysis.