Persistence in Mathematics by Underrepresented Students: Experiences of a Math Excel Program

Success in mathematics by underrepresented and nontraditional college students is measured not only by academic performance (grades), but also by the continued participation and persistence of these students in mathematics coursework. The Math Excel program at Oregon State University attempts to build learning communities with a sharp academic focus in support of students concurrently taking introductory level mathematics courses. The Math Excel program is based heavily on Uri Treisman\u27s Emerging Scholars Workshop model of collaborative problem solving. In this article, we examine the experience of minority students in the Educational Opportunities Program participating in the Math Excel program. While the program had appeared successful in terms of improving academic performance in the concurrent mathematics course, the continued participation and persistence of these students in mathematics was disappointing. On a trial basis, structural changes were made to build a much stronger identification of the Math Excel learning community with a section of College Algebra. In the next term, there was a much higher incidence of participation in the subsequent Precalculus using the same Math Excel structure. While the collaborative problem solving activity provided in Math Excel was crucial to students\u27 successful academic performance, these results suggest that subtle issues related to students\u27 recognition of and identification with a learning community may be critically important to underrepresented and nontraditional students\u27 continued persistence in mathematics

Strengths of sulfur-basalt concretes

Sulfur used in bonding high strength basalt aggregates to form sulfur-basalt concrete

Description of a computer simulation of an orbital SAR system

In order to predict the performance of a synthetic aperture radar for a wide variety of system and environmental parameters a computer simulation of the SAR system was developed. This model is a detailed description of the SAR imaging process on a pulse-by-pulse basis. The simulation is implemented as seven computer programs for a CDC Cyber 171 digital computer

Improving QC Relaxations of OPF Problems via Voltage Magnitude Difference Constraints and Envelopes for Trilinear Monomials

AC optimal power flow (AC~OPF) is a challenging non-convex optimization problem that plays a crucial role in power system operation and control. Recently developed convex relaxation techniques provide new insights regarding the global optimality of AC~OPF solutions. The quadratic convex (QC) relaxation is one promising approach that constructs convex envelopes around the trigonometric and product terms in the polar representation of the power flow equations. This paper proposes two methods for tightening the QC relaxation. The first method introduces new variables that represent the voltage magnitude differences between connected buses. Using "bound tightening" techniques, the bounds on the voltage magnitude difference variables can be significantly smaller than the bounds on the voltage magnitudes themselves, so constraints based on voltage magnitude differences can tighten the relaxation. Second, rather than a potentially weaker "nested McCormick" formulation, this paper applies "Meyer and Floudas" envelopes that yield the convex hull of the trilinear monomials formed by the product of the voltage magnitudes and trignometric terms in the polar form of the power flow equations. Comparison to a state-of-the-art QC implementation demonstrates the advantages of these improvements via smaller optimality gaps.Comment: 8 pages, 1 figur

Temperature dependence of the phonon entropy of vanadium

The phonon density-of-states (DOS) of elemental vanadium was measured at elevated temperatures by inelastic neutron scattering. The phonon softening predicted by thermal expansion against the bulk modulus is much larger than the measured shifts in phonon energies. We conclude that the phonon anharmonicities associated with thermal expansion are largely canceled by effects from phonon-phonon scattering. Prior measurements of the heat capacity and calculations of the electronic entropy of vanadium are assessed, and consistency requires an explicit temperature dependence of the phonon DOS. Using data from the literature, similar results are found for chromium, niobium, titanium, and zirconium

Anderson localization vs. Mott-Hubbard metal-insulator transition in disordered, interacting lattice fermion systems

We review recent progress in our theoretical understanding of strongly correlated fermion systems in the presence of disorder. Results were obtained by the application of a powerful nonperturbative approach, the Dynamical Mean-Field Theory (DMFT), to interacting disordered lattice fermions. In particular, we demonstrate that DMFT combined with geometric averaging over disorder can capture Anderson localization and Mott insulating phases on the level of one-particle correlation functions. Results are presented for the ground-state phase diagram of the Anderson-Hubbard model at half filling, both in the paramagnetic phase and in the presence of antiferromagnetic order. We find a new antiferromagnetic metal which is stabilized by disorder. Possible realizations of these quantum phases with ultracold fermions in optical lattices are discussed.Comment: 25 pages, 5 figures, typos corrected, references update

Tests of Modulated Intensity Small Angle Scattering in time of flight mode

We report results of tests of the MISANS technique at the CG-1D beamline at High Flux Isotope Reactor (HFIR), Oak Ridge National Laboratory (ORNL). A chopper at 40 Hz simulated a pulsed neutron source at the beamline. A compact turn-key MISANS module operating with the pulsed beam was installed and a well characterised MnSi sample was tested. The feasibility of application of high magnetic fields at the sample position was also explored. These tests demonstrate the great potential of this technique, in particular for examining magnetic and depolarizing samples, under extreme sample environments at pulsed sources, such as the Spallation Neutron Source (SNS) or the planned European Spallation Source (ESS).Comment: 5 pages, 5 figure

A Comparison of Job Satisfaction among Women in Computing and a More Traditional Female Occupation

Despite the economic slowdown of the early 2000s, Information Technology (IT) workers are likely to remain in high demand in the U.S. for the next decade. One of the problems faced in meeting this demand is the gender discrepancy in choosing IT employment; men are far more likely to engage in IT careers than women. Although there are many potential reasons for this discrepancy, satisfaction in one’s job is likely to be an influence in career choice. This study compares the satisfaction of women in a professional computing career to those in a more traditionally female career—elementary school teachers

A Review of Shark Control in Hawaii with Recommendations for Future Research

In an attempt to allay public fears and to reduce the risk of shark attack, the state government of Hawaii spent over $300,000 on shark control programs between 1959 and 1976. Six control programs of various intensity resulted in the killing of 4,668 sharks at an average cost of$182 per shark. The programs furnished information on diet, reproduction, and distribution of sharks in Hawaii, but research efforts of the programs had a number of shortcomings. Analysis of the biological data gathered was not directed toward the tiger shark, Galeocerdo cuvier (Peron & LeSueur), which is responsible for most attacks in Hawaii. Reliable estimates of shark populations in Hawaii cannot be made based on catch data from control programs because of sampling biases. Most of the information gained from the control programs was not published in reviewed journals and is not readily available to the scientific community. The ability of the control programs to reduce shark populations and to remove large sharks from coastal waters appears to have been stated with more confidence than is warranted, considering seasonal changes observed in shark abundance and variable fishing effort. Shark control programs do not appear to have had measurable effects on the rate of shark attacks in Hawaiian waters. Implementation of large-scale control programs in the future in Hawaii may not be appropriate. Increased understanding of the behavior and biology of target species is necessary for evaluation of the effectiveness of small-scale control efforts, such as selective fishing after an attack. Acoustic telemetry, conventional tagging, and studies on population dynamics concentrating primarily on the tiger shark may be used to obtain data about activity patterns, distribution, and population parameters, providing information useful for reducing the risk of shark attack in Hawaii and elsewhere