Reynolds-averaged Navier-Stokes simulation of turbulent flow in a circular pipe using OpenFOAM®

A RANS simulation of flow through a pipe is performed and validated against experimental data and previous DNS results. A mesh refinement study is performed to illustrate the near wall mesh size needed to correctly predict mean flow characteristics. In addition, aspects of the model are changed to study their impact on the results as well as the computational requirements. Comparisons are made between a two-dimensional analysis with axisymmetric boundary conditions, a one-eighth axisymmetric model, a one-fourth axisymmetric model, and a full three-dimensional pipe. The two-dimensional model provides the best match to past data; however, it is noted that the model may not be well tuned for a three-dimensional mesh. The simulation is also performed using three different turbulence models and the results of each model are compared. The purpose of the model is to create a tool that can be used for design iterations. While the model does not fully capture the complexities of turbulent flow, it is able to predict the mean flow accurately enough to be useful in a design setting. The goal of this work is to create a foundation upon which further studies of pipe flow with internal obstructions can build. The overall results show the model is able to predict the mean flow well for the validation case. However, the model does not perform well when certain aspects are changed. Increasing the robustness of the model and the determination of more usable boundary conditions remains a subject for future studies

The Business Case for Quality: Ending Business as Usual in American Health Care

Examines some of the reasons why establishing a business case for improving health care is so difficult, and considers possible solutions. Includes comments on quality provisions of the Medicare Prescription Drug Improvement and Modernization Act of 2003

Identifying music documents in a collection of images

Digital libraries and search engines are now well-equipped to find images of documents based on queries. Many images of music scores are now available, often mixed up with textual documents and images. For example, using the Google “images” search feature, a search for “Beethoven” will return a number of scores and manuscripts as well as pictures of the composer. In this paper we report on an investigation into methods to mechanically determine if a particular document is indeed a score, so that the user can specify that only musical scores should be returned. The goal is to find a minimal set of features that can be used as a quick test that will be applied to large numbers of documents. A variety of filters were considered, and two promising ones (run-length ratios and Hough transform) were evaluated. We found that a method based around run-lengths in vertical scans (RL) that out-performs a comparable algorithm using the Hough transform (HT). On a test set of 1030 images, RL achieved recall and precision of 97.8% and 88.4% respectively while HT achieved 97.8% and 73.5%. In terms of processor time, RL was more than five times as fast as HT

Summary of Gateway Power and Propulsion Element (PPE) Studies

NASA's Power and Propulsion Element (PPE) is based on a joint industry/NASA demonstration of an advanced solar electric propulsion powered spacecraft to meet commercial and NASA objectives. The PPE can establish the initial presence in cislunar space for the Gateway through initial operations and the subsequent deployment of additional partner-provided elements for the cislunar platform. Five commercial vendors were selected to conduct PPE studies which addressed key drivers for PPE development and support for the Gateway concept formulation. The study vendors focused on their performance trades and assessing their strategic capabilities, leveraging their existing and planned capabilities for PPE development. The industry studies examined differences between prior Solar Electric Propulsion (SEP) mission concepts, expected industry capabilities, and potential needs supporting NASA's Gateway concept. These studies provided data on commercial capabilities relevant to NASA's exploration needs and reduced risk for a new, powerful, and efficient SEP-based PPE spacecraft

Zeroes of partial sums of the zeta-function

This article considers the positive integers $N$ for which $\zeta_{N}(s) = \sum_{n=1}^{N} n^{-s}$ has zeroes in the half-plane $\Re(s)>1$. Building on earlier results, we show that there are no zeroes for $1\leq N\leq 18$ and for $N=20, 21, 28$. For all other $N$ there are infinitely many zeroes.Comment: 5 Pages - Final Version will appear in LMS JC

Sudden Stops and Liability Dollarization: Evidence from East Asian Financial Intermediaries

Before the currency crisis of 1997-1998, East Asian financial intermediaries borrowed heavily in international markets. During the crisis, the intermediaries’ stock market value declined sharply, and a sizable fraction of the institutions were closed or nationalized. We find that 1) the stocks of intermediaries with large international debt exposure performed poorly during the crisis; 2) more short-term international debt outstanding was associated with a higher probability of bankruptcy; 3) among those intermediaries that survived, more long-term international debt was associated with a lower equity return; and 4) higher international debt, especially short-term international debt, was associated with a more severe contraction in the assets and liabilities of the intermediaries. This evidence supports the “sudden stop†and “liability dollarization†theories of emerging market financial crises. It indicates that both the sudden withdrawal of funds by international creditors and the foreign currency nature of international debt damage the financial system, and exacerbate the decline in the financing of investment.Stops, Liability Dollarization, Financial Intermediaries, Asian Financial Crisis.