Physical Sciences and Mathematics Commons^™

Crevasse Patterns And The Strain-Rate Tensor: A High-Resolution Comparison, Joel T. Harper, Neil Humphrey, W. Tad Pfeffer

Geosciences Faculty Publications

Values of the strain-rate tensor represented at a 20 m length scale are found to explain the pattern and orientation of crevasses in a 0.13 km² reach of Worthington Glacier, Alaska, U.S.A. The flow field of the reach is constructed from surveyed displacements of 110 markers spaced 20-30 m apart. A velocity gradient method is then used to calculate values of the principal strain-rate axes at the nodes of a 20 m x 20 m orthogonal grid. Crevasses in the study reach are of two types, splaying and transverse, and are everywhere normal to the trajectories of greatest (most …

Frequency Modulated Excitation Of A Two-Level Atom, Michael W. Noel, W. M. Griffith, T. F. Gallagher

Physics Faculty Research and Scholarship

We present a detailed experimental study of the frequency-modulated excitation of a two-level atom, using a microwave field to drive transitions between two Rydberg Stark states of potassium. In the absence of a modulation the interaction is the standard model of the Rabi problem, producing sinusoidal oscillations of the population between the two states. In the presence of a frequency modulation of the interacting field, however, the time evolution of the system is significantly modified, producing square wave oscillations of the popula- tion, sinusoidal oscillations at a different frequency, or even sinusoidal oscillations built up in a series of stair …

Phase And Risetime Dependence Using Rf Pulses In Multiphoton Processes, W. M. Griffith, Michael W. Noel, T. F. Gallagher

Physics Faculty Research and Scholarship

With this experiment we demonstrate that excitation of a two-state system with radio-frequency fields differing in phase by 90° produces nonintuitively different results, even for very long pulses. In addition, we show how the phase dependence of the transition probability of long pulses can be easily understood by using the single cycle time propagator. Finally, we have found surprising results for real pulses in the strong-field regime, i.e., pulses having appreciable rise and fall times.

A Longitudinal Study Of Engineering Student Performance And Retention. V. Comparisons With Traditionally-Taught Students, Richard M. Felder, Gary Felder, E. Jacquelin Dietz

Physics: Faculty Publications

In a longitudinal study at North Carolina State University, a cohort of students took five chemical engineering courses taught by the same instructor in five consecutive semesters. The courses made extensive use of active and cooperative learning and a variety of other techniques designed to address a broad spectrum of learning styles. Previous reports on the study summarized the instructional methods used in the experimental course sequence, described the performance of the cohort in the introductory chemical engineering course, and examined performance and attitude differences between students from rural and urban backgrounds and between male and female students.1–4 This paper …

Generalized Inverse Estimator And Comparison With Least Squares Estimator, S. Sakallıoğlu, F. Akdeniz

Turkish Journal of Mathematics

Trenkler [13] described an iteration estimator. This estimator is defined as follows: for $0 < \gamma < 1/\lambda_i \max$ \[ \hat{\beta}_{m, \gamma} = \gamma \sum^m_{i=0} (1-\gamma X'X)^i X'y , \] where $\lambda_i$ are eigenvalues of $X'X$. In this paper a new estimator (generalized inverse estimator) is introduced based on the results of Tewarson [11]. A sufficient condition for the difference of mean square error matrices of least squares estimator and generalized inverse estimator to be positive definite (p.d.) is derived.

Uniform Lipschitz Continuity Of Best L(P)-Approximations By Polyhedral Sets, Martina Finzel, Wu Li

Mathematics & Statistics Faculty Publications

In this paper we prove that the metric projection Π_{k, p} onto a polyhedral subset K of ℝⁿ, endowed with the p-norm, is uniformly Lipschitz continuous with respect to p,1 , p , ∞. As a consequence the strict best approximation and the natural best approximation are Lipschitz continuous selections for the metric projections Π_k, _∞ and Π_k,1, respectively. This extends a recent analogous result in Berens et al. [J.Math. Anal. Appl. 213 1997, 183-201] on linear subspaces.

Cyclic Cutwidth Of Three Dimensional Cubes, Ray N. Gregory

Theses Digitization Project

No abstract provided.

The Eigenfunctions Of A Certain Composition Operator, Valentin Matache

Mathematics Faculty Publications

The composition operator on the classical Hardy space H2, induced by a hyperbolic disk automorphism is considered. It is investigated when a H2-function induces under the given operator a minimal invariant cyclic subspace. Theorems where we use the behaviour of this function in the neighbourhood of the fixed points of the hyperbolic automorphism in order to decide if the cyclic subspace mentioned above is minimal invariant or not, are obtained. The inner eigenfunctions of the operator under consideration are characterized.

High-Power Diffusion Cooling Planar Waveguide Co_{2} Laser, E. Taal, M. S. Kiliçkaya

Turkish Journal of Physics

A diffusion-cooled CO_{2} laser using a coaxial waveguide is investigated theoretically. The resonator extracting the laser beam consits of two annular plane mirrors enclosing the two ends of the waveguide. A theoretical resonator model based on the vector modes of propagation in a dielectric coaxial waveguide is described.

Automatic Granularity Control For Load Balancing Of Concurrent Particle Simulations, Marc Rieffel, Stephen Taylor, Jerrell Watts

Electrical Engineering and Computer Science - All Scholarship

This paper demonstrates the use of automatic granularity control as part of dynamic load balancing for irregular, particle-based simulations. Performance optimization techniques are considered in the context of a concurrent Direct Simulation Monte Carlo method used to study the rarefied gas flow inside three-dimensional plasma reactors. Several computational techniques are used to reduce the overall time to deliver realistic threedimensional results. The effectiveness of dynamic load balancing and granularity control are presented for large-scale simulations on distributed-memory multicomputers.

Magnetospheric Response Times Following Southward Imf Turnings, Niescja E. Turner, D N. Baker, T I. Pulkkinen, H J. Singer, F Mozer

Physics and Astronomy Faculty Research

We analyze the response times of various regions of the magnetosphere-ionosphere system to sudden southward turnings of the IMF. Our data set consists of 26 events during which the IMP B_Z component was observed by WIND to change from a stea northward field to a southward field, which subsequently led to a substorm. The magnetospheric response to such IMF southward turnings is examined using data from the POLAR EFI experiment, the GOES 9 magnetometer, and ground magnetometers. The POLAR/EFI was used to investigate changes in the polar cap electric field which occurred in response to the changing interplanetary electric …

Ab Initio Study Of Formazan And 3-Nitroformazan, G. Buemi, F. Zuccarello, P. Venuvanalingam, M. Ramalingam, Salai Cheettu Ammal

Faculty Publications

Formazan and 3-nitroformazan have been investigated at abinitio level (MP2/6-31G** and B3LYP/6-31G**) in all their possible conformations, for studying the various possibilities of intramolecular hydrogen bonding formation. The trans-syn-s-cis (TSSC), known also asyellowform, has been found to be the most stable conformer (at least in the gas phase) in both compounds. This particular structure is strongly stabilized by a N–H···N hydrogen bridge, which gives rise to a hexatomic chelate ring, with the possibility of a proton transfer process.This closely resembles that of malondialdehyde, previously studied, in the evolution of the …

Quartzite Fabric Transition In A Cordilleran Metamorphic Core Complex, Allen J. Mcgrew, Martin Casey

Department of Earth, Environment and Sustainability Faculty Publications

Photomicrographs 143A-143F record fabric variations in quartzite with increasing structural depth in a > 1 km thick, amphibolite-facies, normal-sense shear zone in the East Humboldt metamorphic core complex, Nevada (Figure 143.1). This shear zone and the overlying detachment system unroofed an infrastructure of high-grade, migmatitic gneiss during Oligocene to early Miocene extension (Dallmeyer and others, 1986; Wright and Snoke, 1993; McGrew and Snee, 1994). Thermobarometric constraints from near the base of the mylonitic zone record deformation conditions of 550°- 620°C and 300-400 MPa (Hurlow and others, 1991). Sample WBC6 (l43A and 143B) characterizes the mylonitic zone, whereas sample 8706-1 (143C and …

Quadratic Convergence Of Approximate Solutions Of Two-Point Boundary Value Problems With Impulse, Vidya Doddaballapur, Paul W. Eloe, Yongzhi Zhang

Mathematics Faculty Publications

The method of quasilinearization, coupled with the method of upper and lower solutions, is applied to a boundary value problem for an ordinary differential equation with impulse that has a unique solution. The method generates sequences of approximate solutions which converge monotonically and quadratically to the unique solution. In this work, we allow nonlinear terms with respect to velocity; in particular, Nagumo conditions are employed.

Mea Culpa: Formal Education And The Dis-Integrated World., Brian P. Coppola, Douglas S. Daniels

Chemistry Faculty Publications

Formal education has removed itself so far from any truly integrated view of the Natural World that fragmentation and certainty are prevailing ethics. Technological progress has resulted in increased specialization within academic disciplines and their concurrent separation from each other. Knowledge is extracted from a fully integrated world, but is examined and defined by the 'dis-integrated' objectives.

Well Characteristics Influencing Microscopic Particulate Analysis Risk Index, Robert Christopher Sharek

Retrospective Theses and Dissertations

Cryptosporidium parvum is a common surface water contaminant that can cause illness in human beings. The presence of this etiological agent in groundwater identifies the groundwater as under the direct influence (GWUDI) of surface water. Currently the determination of GWUDI water sources requires an expensive, labor-intensive laboratory procedure called the Microscopic Particulate Analysis (MPA). The results of the MPA provide a risk index that rates the degree of surface water contamination. The objective of this study is to identify other methods of identifying GWUDI of surface waters, such as well characteristics and hydrogeologic factors which may contribute to higher MPA …

Requirement Elicitation For Environmental Life Cycle Processes, Mariam Y. Burmawalla

Theses

To develop a user-satisfying product the most essential ingredient is to understand user's needs and expectations from the system. Lack of communication between the user and the developer results in an unsatifying output from the user's point of view. Thus proper understanding between the stakeholder and the developer is the most important requirement during the development of any system.

Requirement elicitation process is one such means of expressing wants and requirements from the system by both the parties. Based on Software Engineering Institute's model, requirement elicitation is a web-based application that allows all the people involved in the system to …

Energy Requirements For Certified Organic Farms In New Jersey : A Survey And Analysis Of Tomato Production, Cecilia Kelnhofer-Feeley

Theses

The focus of this thesis is to document the fossil fuel and electrical energy consumption required to grow certified organic tomatoes in the State of New Jersey. First, in order to evaluate the energy requirement for agriculture, a literature review of energy changes during the twentieth century is discussed. Secondly, an in-depth look at energy requirements for all farming types is evaluated. Third, previous studies of the energy requirements in agriculture are examined; this includes both analyzing organic and conventional farming practices. A survey was generated from the information gathered. The survey was conducted via face-to-face interviews. When all the …

Performing Cooperative Work And Conferencing On An Intranet Using Java, Thaveeporn Limpanyalers

Theses: Doctorates and Masters

The process of organising, preparing and conducting a meeting is a time consuming one. Additionally, geographic separation compounds the amount of effort required. Within this study, an electronic conferencing system in an Intranet environment is designed and implemented, thus enabling employees in the same organisation to meet up electronically without the dual constraints of time and space. Specifically, the study investigates incorporation of facial expressions and an ongoing polling system. The results demonstrate that a presence of facial expressions helps users to better engage in on-line discussion and that users find an ongoing poll to be useful in determining direction …

Stackguard: Automatic Adaptive Detection And Prevention Of Buffer-Overflow Attacks, Crispin Cowan, Calton Pu, David Maier, Heather Hinton, Jonathan Walpole, Peat Bakke, Steve Beattie, Aaron Grier, Perry Wagle, Qian Zhang

Computer Science Faculty Publications and Presentations

This paper presents a systematic solution to the persistent problem of buffer overflow attacks. Buffer overflow attacks gained notoriety in 1988 as part of the Morris Worm incident on the Internet. While it is fairly simple to fix individual buffer overflow vulnerabilities, buffer overflow attacks continue to this day. Hundreds of attacks have been discovered, and while most of the obvious vulnerabilities have now been patched, more sophisticated buffer overflow attacks continue to emerge.

We describe StackGuard: a simple compiler technique that virtually eliminates buffer overflow vulnerabilities with only modest performance penalties. Privileged programs that are recompiled with the StackGuard …

Statistical Dynamics Of The Royal Road Genetic Algorithm, Erik Van Nimwegen, James P. Crutchfield, Melanie Mitchell

Computer Science Faculty Publications and Presentations

Metastability is a common phenomenon. Many evolutionary processes, both natural and artificial, alternate between periods of stasis and brief periods of rapid change in their behavior. In this paper an analytical model for the dynamics of a mutation-only genetic algorithm (GA) is introduced that identifies a new and general mechanism causing metastability in evolutionary dynamics. The GA’s population dynamics is described in terms of flows in the space of fitness distributions. The trajectories through fitness distribution space are derived in closed form in the limit of infinite populations. We then show how finite populations induce metastability, even in regions where …

On C^1 Robust Singular Transitive Sets For Three-Dimensional Flows, Carlos Arnoldo Morales, Maria José Pacífico, Enrique Ramiro Pujals

Publications and Research

Abstract:

The main goal of this paper is to study robust invariant transitive sets containing singularities for C¹ flows on three-dimensional compact boundaryless manifolds:they are partially hyperbolic with volume expanding central direction. Moreover, they are either attractors or repellers. Robust here means that this property cannot be destroyed by small C¹-perturbations of the flow.

Résumé:

Le but de ce travail est d'étudier des ensembles invariants robustes ayant des singularités pour des flots C¹ sur des variétés tridimensionelles : ce sont des ensembles hyperboliques singuliers. << Robuste >> veut dire ici que cette propriété ne peut être détruite par des …

Adaptive Prefetching For Device-Independent File I/O, Dan Revel, Dylan Mcnamee, David Steere, Jonathan Walpole

Computer Science Faculty Publications and Presentations

Device independent I/O has been a holy grail to operating system designers since the early days of UNIX. Unfortunately, existing operating systems fall short of this goal for multimedia applications. Techniques such as caching and sequential read-ahead can help mask I/O latency in some cases, but in others they increase latency and add substantial jitter. Multimedia applications, such as video players, are sensitive to vagaries in performance since I/O latency and jitter affect the quality of presentation. Our solution uses adaptive prefetching to reduce both latency and jitter. Applications submit file access plans to the prefetcher, which then generates I/O …

4. Grain-Size Distribution And Significance Of Clay And Clay-Sized Minerals In Eocene To Holocene Sediments From Sites 918 And 919 In The Irminger Basin, Kraig Heiden, Mary Anne Holmes

Department of Earth and Atmospheric Sciences: Faculty Publications

Published by the Ocean Drilling Program, Texas A & M University, in cooperation with the National Science Foundation and Joint Oceanographic Institutions, Inc."

Dissociation Constants Of Oxalic Acid In Aqueous Sodium Chloride And Sodium Trifluoromethanesulfonate Media To 175 °C, Richard Kettler, David J. Wesolowski, Donald A. Palmer

Department of Earth and Atmospheric Sciences: Faculty Publications

The first and second molal dissociation constants of oxalic acid were measured potentiometrically in a concentration cell fitted with hydrogen electrodes. Measurements were made at six temperatures ranging from 5 °C to 125 °C at four ionic strengths ranging from 0.1 mol•kg^-1 to 1.0 mol•kg^-1 (NaCl and NaCF₃-SO₃). The second molal dissociation constant was measured in NaCF₃SO₃ media only. The data obtained in this study were combined with the corresponding literature values, including a number of recalculated Harned cell and concentration cell measurements and previous results from this laboratory. Data for …

Mesozoic Biostratigraphic, Paleoenvironmental, And Paleobiogeographic Synthesis, Equatorial Atlantic, M. Moullade, David K. Watkins, F. E. Oboh-Ikuenobe, J.-P. Bellier, E. Masure, A. E.L. Holbourn, J. Erbacher, W. Kuhnt, T. Pletsch, M. A. Kaminski, R. Rauscher, S. Shafik, O. Yepes, J. Dejax, J. M. Gregg, Im Chul Shin, M. Schuler

Department of Earth and Atmospheric Sciences: Faculty Publications

Cretaceous sediments from Ocean Drilling Program Leg 159 on the Côte d’Ivoire-Ghana Marginal Ridge (CIGMR), eastern equatorial Atlantic, are characterized by distinct stratigraphic changes in sedimentary facies associated with changes in the composition of the clayey and organic fractions, as well as of the calcareous nannofossil, radiolarian, foraminiferal, and palynomorph assemblages. In the absence of reliable magnetostratigraphic information, an integrated biostratigraphy provides the only means used to calibrate the geologic history of the Leg 159 area.

The existence of marine depositional environments as early as the late Aptian to early Albian close to the Leg 159 drill sites puts constraints …

กิจกรรมสิ่งแวดล้อม

Thai Environment

No abstract provided.

สรุปข่าวสิ่งแวดล้อม : สถานการณ์สิ่งแวดล้อมในรอบปี่ พ.ศ. 2540, อุษณีย์ ศิริสุนทรไพบูลย์

Thai Environment

No abstract provided.

ไฟไหม้ป่าอินโดนีเซีย เกิดจากปรากฏการณ์ "เอล นิโน" หรือ?, พันธวัส สัมพันธ์พานิช

Thai Environment

No abstract provided.

เขื่อนพัง : ใครรับผิดชอบ, บุญล้อม

Thai Environment

No abstract provided.