Stability of mixing layers

The research program for the first year of this project (see the original research proposal) consists of developing an explicit marching scheme for solving the parabolized stability equations (PSE). Performing mathematical analysis of the computational algorithm including numerical stability analysis and the determination of the proper boundary conditions needed at the boundary of the computation domain are implicit in the task. Before one can solve the parabolized stability equations for high-speed mixing layers, the mean flow must first be found. In the past, instability analysis of high-speed mixing layer has mostly been performed on mean flow profiles calculated by the boundary layer equations. In carrying out this project, it is believed that the boundary layer equations might not give an accurate enough nonparallel, nonlinear mean flow needed for parabolized stability analysis. A more accurate mean flow can, however, be found by solving the parabolized Navier-Stokes equations. The advantage of the parabolized Navier-Stokes equations is that its accuracy is consistent with the PSE method. Furthermore, the method of solution is similar. Hence, the major part of the effort of the work of this year has been devoted to the development of an explicit numerical marching scheme for the solution of the Parabolized Navier-Stokes equation as applied to the high-seed mixing layer problem

Student user preferences for features of next-generation OPACs: a case study of University of Sheffield international students

Purpose. The purpose of this study is to identity the features that international student users prefer for next generation OPACs. Design/ methodology/ approach. 16 international students of the University of Sheffield were interviewed in July 2008 to explore their preferences among potential features in next generation OPACs. A semi-structured interview schedule with images of mock-up screens was used. Findings. The results of the interviews were broadly consistent with previous studies. In general, students expect features in next generation OPACs should be save their time, easy to use and relevant to their search. This study found that recommender features and features that can provide better navigation of search results are desired by users. However, Web 2.0 features, such as RSS feeds and those features which involved user participation were among the most popular. Practical implications. This paper produces findings of relevance to any academic library seeking to implement a next-generation OPAC. Originality/value. There have been no previous published research studies of users’ preferences among possible features of next-generation OPACs

A Closer Look at Long Run Money Demand

We study annual United States data from 1869 or 1900 to 1999. We find evidence for a well-specified and stable model of money demand with data from 1946 to 1999. We carry out diagnostic and stability tests, including nonlinearity tests. A linear cointegration model with the monetary base performs better than a model with M1. A specification with M2 is not supported. We use real GNP as the scale variable and a short term interest rate as the opportunity cost measure. We estimate an income elasticity of .86 and an interest rate elasticity of -.44 for the monetary base.

Numerical analysis of flow and heat transfer in the VAFB LOX storage Dewar tank

The present report describes numerical simulation of three-dimensional transient distributions of velocity and temperature of liquid oxygen (LOX) in the LOX Dewar tank of Vendenberg Air Force Base (VAFB). The present analyses cover the replenish time period only. Four test cases have been considered. For all four cases, the input boundary conditions are comprised of LOX facility heat loads, drain flow rates, recirculation flow rates and dewar heating. All the quantities are prescribed as functions of time. The first two test cases considered sensitivity of results to the computational grid. In Case 3, system heat load was changed, while in Case 4, a lower LOX level was specified. Cases 1 and 2 showed that the temperatures were not sensitive to the grid refinement. This provided a basic check on the numerical model. Cases 3 and 4 showed that the thermal boundary layer motion near the tank surface becomes more significant at the late time, e.g., 5 1/2 hours from replenish start. Comparison between results of Cases 3 and 4 showed, as expected, that the smaller initial LOX volume given in Case 4, results in higher temperature level. All calculated velocity and temperature distributions were found to be plausible

A Structural VAR Approach to Estimating Budget Balance Targets

The Fiscal Responsibility Act 1994 states that, as a principle of responsible fiscal management, a New Zealand government should ensure total Crown debt is at a prudent level by ensuring total operating expenses do not exceed total operating revenues. In this paper a structural VAR model is estimated to evaluate the impact on the government's cash operating surplus (or budget balance) of four independent disturbances: supply, fiscal, real private demand, and nominal disturbances. Based on the distribution of these disturbances, stochastic simulations are undertaken to derive the level of the ex ante cash budget balance needed to achieve an actual cash budget balance, at a given level of probability, at some future time horizon.Budget target; Fiscal policy; Fiscal Responsibility Act; Structural VAR; Stochastic Simulation

Rocket injector anomalies study. Volume 1: Description of the mathematical model and solution procedure

The capability of simulating three dimensional two phase reactive flows with combustion in the liquid fuelled rocket engines is demonstrated. This was accomplished by modifying an existing three dimensional computer program (REFLAN3D) with Eulerian Lagrangian approach to simulate two phase spray flow, evaporation and combustion. The modified code is referred as REFLAN3D-SPRAY. The mathematical formulation of the fluid flow, heat transfer, combustion and two phase flow interaction of the numerical solution procedure, boundary conditions and their treatment are described

Incidence of Guillain-Barre syndrome among patients with Campylobacter infection: A general practice research database study

The association between Campylobacter infection and subsequent Guillain-Barre syndrome (GBS) has been well documented. To date, however, there exists no direct estimate of the incidence of GBS among patients with Campylobacter infection. Using the General Practice Research Database, we estimate the incidence of GBS in a cohort of patients presenting with Campylobacter enteritis to be 1.17/1000 person-years, a rate 77 times greater than that in the general population. The probability that an individual who develops Campylobacter enteritis will also develop GBS during the subsequent 2-month period is < 2/10,000

Axion Dark Matter and Cosmological Parameters

We observe that photon cooling after big bang nucleosynthesis (BBN) but before recombination can remove the conflict between the observed and theoretically predicted value of the primordial abundance of $^7$Li. Such cooling is ordinarily difficult to achieve. However, the recent realization that dark matter axions form a Bose-Einstein condensate (BEC) provides a possible mechanism, because the much colder axions may reach thermal contact with the photons. This proposal predicts a high effective number of neutrinos as measured by the cosmic microwave anisotropy spectrum.Comment: 4 pages, one figure. Version to appear in Phys. Rev. Lett., incorporating useful comments by the referees and emphasizing that photon cooling by axion BEC is a possibility, not a certaint

On-the-fly Table Generation

Many information needs revolve around entities, which would be better answered by summarizing results in a tabular format, rather than presenting them as a ranked list. Unlike previous work, which is limited to retrieving existing tables, we aim to answer queries by automatically compiling a table in response to a query. We introduce and address the task of on-the-fly table generation: given a query, generate a relational table that contains relevant entities (as rows) along with their key properties (as columns). This problem is decomposed into three specific subtasks: (i) core column entity ranking, (ii) schema determination, and (iii) value lookup. We employ a feature-based approach for entity ranking and schema determination, combining deep semantic features with task-specific signals. We further show that these two subtasks are not independent of each other and can assist each other in an iterative manner. For value lookup, we combine information from existing tables and a knowledge base. Using two sets of entity-oriented queries, we evaluate our approach both on the component level and on the end-to-end table generation task.Comment: The 41st International ACM SIGIR Conference on Research and Development in Information Retrieva