NAS: The first year

Discussed are the capabilities of NASA's Numerical Aerodynamic Simulation (NAS) Program and its application as an advanced supercomputing system for computational fluid dynamics (CFD) research. First, the paper describes the NAS computational system, called the NAS Processing System Network, and the advanced computational capabilities it offers as a consequence of carrying out the NAS pathfinder objective. Second, it presents examples of pioneering CFD research accomplished during NAS's first operational year. Examples are included which illustrate CFD applications for predicting fluid phenomena, complementing and supplementing experimentation, and aiding in design. Finally, pacing elements and future directions for CFD and NAS are discussed

Some examples of the behaviour of conformal geodesics

With the aid of concrete examples, we consider the question of whether, in the presence of conformal curvature, a conformal geodesic can become trapped in smaller and smaller sets, or phrased informally: are spirals possible? We do not arrive at a definitive answer, but we are able to find situations where this behaviour is ruled out, including a reduction of the conformal-geodesic equations to quadratures in a specific non-conformally flat metric.Comment: 19 pages; to appear in Jour.Geom.Phy

Efficient detection of a CW signal with a linear frequency drift

An efficient method is presented for the detection of a continuous wave (CW) signal with a frequency drift that is linear in time. Signals of this type occur in transmissions between any two locations that are accelerating relative to one another, e.g., transmissions from the Voyager spacecraft. We assume that both the frequency and the drift are unknown. We also assume that the signal is weak compared to the Gaussian noise. The signal is partitioned into subsequences whose discrete Fourier transforms provide a sequence of instantaneous spectra at equal time intervals. These spectra are then accumulated with a shift that is proportional to time. When the shift is equal to the frequency drift, the signal to noise ratio increases and detection occurs. Here, we show how to compute these accumulations for many shifts in an efficient manner using a variety of Fast Fourier Transformations (FFT). Computing time is proportional to L log L where L is the length of the time series

Oral History Interview: Paul Bailey

This interview is one of a series conducted concerning the history of various businesses in West Virginia. Paul Bailey, the resident golf professional of the Guyan Golf and Country Club, discusses the services and recreation which the club offers both its members and the general public. He discusses the golf club\u27s financial operations, as well as the history of the country club as a whole. The interview closes with Bailey\u27s comments concerning the future of the golf club.https://mds.marshall.edu/oral_history/1288/thumbnail.jp

From Family to Care: Issues for the Child

It is still widely held that the traditional or conventional nuclear family is the only suitable environment in which children can grow up and that any deviation from this norm puts children at a considerable disadvantage (Kahan, 1989). The vulnerability of children and young people coming into residential care in Ireland due to their dysfunctional family experiences, and how coming into residential care and their subsequent experience therein can sometimes further increase this level of vulnerability for the adolescent child has been well documented. This paper discusses the question: What can we, as residential child care workers and agencies, do to reduce the anxiety level of the vulnerable child coming into care, or at the very least, to ensure that this level of anxiety is not increased, during their admission and subsequent stay in care? Before I attempt to answer this question, it is important to point out that there are many aspects of residential care which can effect the vulnerable child. It is not possible in this short paper to consider all those aspects. However, I concentrate on those issues which I, as a social care practitioner, feel to be important. I discuss what I term influencing factors or macro issues. These factors can have an adverse affect on good residential child care practice. Next I critically analyse current practices issues in residential care based on my own personal experiences and on discussions with child care workers and students in a variety of settings. The views expressed are not intended to offend but rather to encourage selfevaluation and debate in order to improve our professional practice (see McElwee, 1998). I will conclude with suggestions and recommendations as to how we can endeavour to provide a better service for the vulnerable child in our care

The acute effects of static-stretching, dynamic exercise and combined warm-up protocols on the speed, agility and muscular power of trained youth rugby union players

Several minutes of low intensity aerobic exercise followed by static stretching is typically administered and considered the norm for youth performers. While the active aerobic component of a warm-up has been demonstrated to improve short term, intermediate and long term performance, scientific evidence supporting the performance attributes of warm ups including static stretching are sparse. As a result there has been a growing interest in warm-up procedures that involve dynamic exercise. Consequently, the purpose of this study was to examine the differing acute effects of a dynamic exercise warm-up with that of a static stretching warm up and a combination warm up (static and dynamic) on the sports specific actions of youth rugby union players; namely speed, agility and muscular power. 20 male youth (age 12-13) rugby union players participated in a Vertical Jump, ‘L run’ and 20 meters sprint after three different warm-up protocols. All sessions were administered in a random order with at least 3 days apart. Before testing, participants performed 5 min of walking/jogging followed by one of the following warm-up protocols: a) six static stretches (2 × 15 s) designed to replicate a typical youth team procedure, or b) ten low to high-intensity dynamic movements (2 × 15 meters), or c) 5 low to high-intensity dynamic movements (2 × 15 meters) interspersed with 5 static stretches for the major muscle groups (2 × 15 s). After each warm-up routine, participants performed the selected tests designed to measure muscular power, speed, and agility. Each subject completed all test with each warm up protocol within 21 days. Statistical analysis of the data revealed that on all tests, except 20 meters sprint , the dynamic exercise warm-up significantly (p <0.017) improved performance over the static stretching and combination protocols. Performance on the 20 meters sprint was significantly improved after the dynamic protocol than after the static but not the combination protocol.The results of this study indicate that pre-event dynamic exercise might be more beneficial than both pre-event static stretching and combination warm up protocols for preparing for performance in youth rugby union players and youth sports of a similar nature

Resonant Absorption as Mode Conversion? II. Temporal Ray Bundle

A fast-wave pulse in a simple, cold, inhomogeneous MHD model plasma is constructed by Fourier superposition over frequency of harmonic waves that are singular at their respective Alfven resonances. The pulse partially reflects before reaching the resonance layer, but also partially tunnels through to it to mode convert to an Alfven wave. The exact absorption/conversion coefficient for the pulse is shown to be given precisely by a function of transverse wavenumber tabulated in Paper I of this sequence, and to be independent of frequency and pulse width.Comment: 6 pages, 4 figures, accepted (15 Nov 2010) by Solar Physics. Ancillary file (animation) attache

Fast C-V method to mitigate effects of deep levels in CIGS doping profiles

In this work, methods to determine more accurate doping profiles in semiconductors is explored where trap-induced artifacts such as hysteresis and doping artifacts are observed. Specifically in CIGS, it is shown that this fast capacitance-voltage (C-V) approach presented here allows for accurate doping profile measurement even at room temperature, which is typically not possible due to the large ratio of trap concentration to doping. Using deep level transient spectroscopy (DLTS) measurement, the deep trap responsible for the abnormal C-V measurement above 200 K is identified. Importantly, this fast C-V can be used for fast evaluation on the production line to monitor the true doping concentration, and even estimate the trap concentration. Additionally, the influence of high conductance on the apparent doping profile at different temperature is investigated

Auction Design and the Market for Sulfur Dioxide Emissions

Title IV of the Clean Air Act Amendments of 1990 created a market for electric utility emissions of sulfur dioxide (SO2). Recent papers have argued that flaws in the design of the auctions that are part of this market have adversely affected its performance. These papers incorrectly assume that trade can only occur at auctions, however. Our empirical analysis of the SO2 emissions market shows that the auctions have become a small part of a relatively efficient market and that the auction design problems that have attracted the most attention have had no effect on actual market prices

DETERMINANTS OF COLLEGE GRADE POINT AVERAGES

Chapter 2: The Role of Class Difficulty in College Grade Point Averages. Grade Point Averages (GPAs) are widely used as a measure of college students' ability. Low GPAs can remove a students from eligibility for scholarships, and even continued enrollment at a university. However, GPAs are determined not only by student ability but also by the difficulty of the classes the students take. When class difficulty is correlated with student ability, GPAs are biased estimates of students' abilities. Using a fixed effects model on eight years of transcript data from one university with one fixed effect for student ability and another for class difficulty, I decompose grades at the individual student-class level to find that GPAs are largely not biased. Eighty percent of the variation in GPAs is explained by student ability, while only three percent of the variation in GPAs is explained by class difficulty. This estimation is carried out using an ordered logit estimator to account for the ordered but non-cardinal nature of grades. Chapter 3: Are Low Income Students Diamonds in the Rough? Consider two students who earn the same SAT score, one from a lower-income household and the other from a higher-income household. Since educational expense is a normal good, the lower income student will, on average, have had a less well-resourced primary and secondary education. The lower income student may therefore be stronger than their higher income counterpart because they have earned an equally high SAT score despite a lower quality pre-collegiate environment. If this is the case, once the two students start attending the same college---and school spending becomes more similar---the lower income student's in-college performance should be relatively higher. I test this theory by using eight years of data from one university to compare the grade point averages of students from various family income levels. Results show that lower income students appear to be "diamonds in the rough": lower income students have surprisingly high outcomes, conditional on their SAT scores. However, unconditional on SAT score, the lower income students also outperform their higher income counterparts. This suggests that a single university's data is inappropriate for answering this question. I also develop how this type of regression might give insight into the production function of human capital. Specifically, a common assumption made in the economics of education literature is that first differenced human capital accumulation rates are independent of ability because ability is already represented in the test used as a base period. A &ldquo;diamonds in the rough&rdquo; result would contradict that assumption, and show that SAT is not a perfect measure of underlying ability. Chapter 4: Estimation of Large Ordered Multinomial Models. Decomposing grades data into class fixed effects and student fixed effects is difficult and the estimator's accuracy is unknown. I describe the successful application of the L-BFGS algorithm for fitting these data and propose a new convergence criterion. I also show that when the number of classes is about 32 (slightly fewer than is typical at the University of Maryland), the estimator performs well at estimating correlations and the non-parametric statistics used in Chapter 2 of this dissertation. Some issues with significance testing the sets of fixed effects are also considered and I show that when the number of classes is 32, the significance tests are not sufficiently protective against false rejection of the null hypothesis. The jackknifed likelihood ratio test is shown to be only modestly biased towards false rejection regardless of the number of classes per student