1,190 research outputs found
Experimental investigation of scalar dispersion in indoor spaces
No full textThe scalar dispersion from point sources in indoor spaces is experimentally investigated using simultaneous particle–image velocimetry and planar laser-induced fluorescence techniques in a 20:1 and a 60:1 full-to-model scale room model. The ventilation inlets dominate turbulence production, with magnitudes of the velocities and Reynolds stresses observed to increase with air changes per hour (ACH). Mean concentration maps show a dependence on the ACH and source location which is attributed to the flow field at the near-source region. The peak-to-mean concentration shows a weak dependence on the mean concentration and concentration variance maps, indicating risk for toxic chemicals may be underpredicted if based only on these information. The concentration PDFs are generally well-described by exponential distributions with C
99/c
rms
′ values never exceeding 5.0. The magnitudes of the advective and turbulent scalar fluxes are strongly dependent on the ACH and source location, neither of which are able to dominate the other by more than an order of magnitude. The eddy diffusivity tensor was measured and a conditional-averaging based method is proposed to approximate it to an isotropic eddy diffusion coefficient, K. For real applications where K is used to estimate magnitudes of the turbulent scalar flux using the gradient transport model, the assumption of isotropic turbulence can introduce an uncertainty of around 17.8%.</p
On the effects of walking speed, crowd density and human-to-source distance on pollutant dispersion in indoor spaces
No full textThe effects of walking speed, crowd density and human-to-source distance on pollutant dispersion in two scaled room models are investigated using simultaneous planar laser-induced fluorescence and particle-image velocimetry techniques. For a small 3 m high room, where the length-scales of the people and room are comparable, the walking motions significantly influenced the macro room mean flow patterns. This has a strong effect on the scalar dispersion properties as the magnitudes of the advective scalar fluxes are often comparable or larger than the turbulent scalar fluxes. As such, the scalar dispersion properties are case specific. For a large 9 m high room, the walking motion influenced only the local mean flow field. The increase in walking speed and crowd density improves the efficiency in which the scalar is transported and mixed with fresh ambient fluid out of the measurement plane (i.e. along the direction of the motion), leading to scalar-free zones observed on the opposite side of the room from the ventilation outlet. The area of the scalar-free zone increases with an increase in the walking speed and crowd density. The advective scalar fluxes are more sensitive to the human motion than the turbulent components, and as the mixing efficiency improves, the advective fluxes show a greater weakening with increased distance from source. The concentration PDFs in the near-source region can be described by the exponential function where the expected value at the 99% percentile can be derived as C
99/c
rms
′=4.61, which agreed well with the experimental measurements of 4.1 to 5.9.</p
Technical note: A new method for the evaluation of puff dispersion field experiments for the validation of time-resolved dispersion simulations
No full textWe present a new method for the evaluation of field measurements of atmospheric dispersion at the smallest resolvable time scales. Our method has its origins in the distance-neighbour functions defined by Richardson as well as the auto correlations, spatial correlations and cross correlations commonly used in the turbulence community. We show that a robust quantification of the puff duration can be achieved, which is comparable to the puff duration derived by a dosage-based approach. The new method gives reasonable results without the need to apply thresholds when the concentration measurement is very noisy, which is very advantageous in the context of field measurements.</p
2000 Commencement Address: G. Timothy Johnson, M.D.
No full textTimothy Johnson, M.D., medical editor for ABC News will deliver the principal address and receive an honorary degree at the 154th commencement exercises at the College of the Holy Cross on Friday, May 26, beginning at 10:30 a.m. at Fitton Field.
Johnson, one of the nation’s leading medical communicators of health care information, has provided commentary on medical problems and answers for viewers since 1975. In addition to commentary on Good Morning America, Johnson provides on-air analysis of medical news for World News Tonight, Nightline and 20/20. He consults with ABC News regardingcoverage of medical news. He is also medical editor for WCVB-TV, Channel 5 in Boston.
Johnson holds joint positions in medicine at Harvard University and Massachusetts General Hospital in Boston. He is the founding editor of the Harvard Medical School Health Letter and co-editor of the Harvard Medical School Health Letter Book. He is also coeditor of the book, “Your Good Health,” published by Harvard Press, as well as co-author with former US Surgeon General Dr. C. Everett Koop of the book, “Let’s Talk,” published by Zondervan in 1992.
He originally intended to join the ministry and graduated from the North Park Seminary in 1963. Two years later he decided to enter medicine. Johnson, who is a Phi Beta Kappa graduate of Augustana College, graduated summa cum laude from Albany Medical College and holds a master’s degree in public health from Harvard University. Johnson served as an assisting minister at the Community Covenant Church in West Peabody, Mass.https://crossworks.holycross.edu/commence_address/1012/thumbnail.jp
Dataset for "Experimental investigation of scalar dispersion in indoor spaces"
No full textData supports: H.D. Lim, Timothy G. Foat, Simon T. Parker, Christina Vanderwel, Experimental investigation of scalar dispersion in indoor spaces, Building and Environment, 2024, 111167, ISSN 0360-1323,
https://doi.org/10.1016/j.buildenv.2024.111167
(https://www.sciencedirect.com/science/article/pii/S036013232400009X)
This dataset contains PIV-PLIF experimental data in the folder. Readme files are provided in the zip folder explaining the data fields and how to interpret them. The data files are in .mat format. </span
Evaluating Research Impact through Open Access to Scholarly Communication
No full textScientific research is a competitive business – in order to secure funding, promotion and tenure researchers must demonstrate their work has impact in their field. To maximise impact researchers undertake high priority research, aim to get results first, and publish in the highest impact journals. The Internet now presents a new opportunity to the scholarly author seeking higher impact: s/he can now make their work instantly accessible on the Web through author self-archiving. This growing body of open access literature (coupled with new publishing models that make journals available for-free to the reader) maximises research impact by maximising the number of people who can read it, and making it available sooner. Open access also provides a new opportunity for bibliometric research. This thesis describes the relatively recent phenomenon of open access to research literature, tools that were built to collect and analyse that literature, and the results of analyses of the effect of open access and its effect on author behaviour. It shows that articles self-archived by authors receive between 50-250% more citations, that rapid pre-printing on the Web has dramatically reduced the peak citation rate from over a year to virtually instant and how citation-impact – now widely used for evaluation – can be expanded to include a new web metric of download impact
Dataset for "On the effects of walking speed, crowd density and human-to-source distance on pollutant dispersion in indoor spaces"
No full textData supports: H.D. Lim, Timothy G. Foat, Simon T. Parker, Christina Vanderwel, On the effects of walking speed, crowd density and human-to-source distance on pollutant dispersion in indoor spaces, Building and Environment, 2024, 111649, ISSN 0360-1323,
https://doi.org/10.1016/j.buildenv.2024.111649
(https://www.sciencedirect.com/science/article/pii/S0360132324004918)
This dataset contains PIV-PLIF experimental data in the folder. Readme files are provided in the zip folder explaining the data fields and how to interpret them. The data files are in .mat format. </span
Book Review: Sun Tzu in Space: What International Relations, History, and Science Fiction Teach Us About Our Future
No full textAuthor: Gregory D. Miller
Reviewed by: Lieutenant Colonel Timothy S. Martin, director, Defense Strategy Course, US Army War College, and Captain Stephanie St. Louis, strategic planner, Office of the Chief of Army Reserve, Fort Belvoir
Sun Tzu in Space combines an examination of history and science fiction to assess what humanity’s future in space could look like through an international relations lens. The reviewer sees it as “a pulse check on the potential for violent future conflicts” and recommends it for policymakers and science fiction enthusiasts alike.
©2025 Timothy G. Martin and Stephanie St. Louishttps://press.armywarcollege.edu/parameters_bookshelf/1108/thumbnail.jp
Analysis of watersheds and river systems: short course
No full textShort course: Analysis of Watersheds and River Systems, Session I and II, held on May 28-June 1, 1979 and June 4-June 8, 1979 at Colorado State University, Fort Collins, Colorado.Speakers: Dr. E. V. Richardson, Dr. David Duttweiller, Mr. Lee Mulkey, Dr. Stanley A. Schumm, Dr. Daryl B. Simons, Dr. Ross Carder.Includes bibliographical references.This short course is designed for individuals dealing with the analysis of watersheds and rivers. Practical applications concerning physical processes will be emphasized.Chapter 1. General introduction / Daryl B. Simons and Ruh-Ming Li -- Chapter 2. Introduction to watershed and river analysis / Daryl B. Simons and Ruh-Ming Li -- Chapter 3. Physical processes governing response of watersheds and rivers / Daryl B. Simons, Timothy J. Ward and Ruh-Ming Li -- Chapter 4. Sediment transport / H. W. Shen -- Chapter 5. Alluvial bed roughness / H. W. Shen -- Chapter 6. Overview of flood routing methods / Ruh-Ming Li and V. Miguel Ponce -- Chapter 7. Water routing and yield from watersheds, Part I and II / Ruh-Ming Li, Daryl B. Simons, and Kenneth G. Eggert -- Chapter 8. Water routing in rivers / Yung-Hai Chen -- Chapter 9. Stage discharge relations / Robert K. Simons, Ruh-Ming Li, and Daryl B. Simons -- Chapter 10. Watershed sediment yield / Ruh-Ming Li, Daryl B. Simons, and Timothy J. Ward -- Chapter 11. Unsteady sediment routing models in rivers / Yung-Hai Chen and Daryl B. Simons -- Chapter 12. Known discharge sediment routing / Glenn O. Brown and Ruh-Ming Li -- Chapter 13. Landslide potential delineation / Timothy J. Ward, Ruh-Ming Li, and Daryl B. Simons -- Chapter 14. Application of Kalman filtering in watershed and river analysis / Nguyen Duong -- Chapter 15. Handheld calculator programs for analysis / Kenneth G. Eggert, Ruh-Ming Li, and Daryl B. Simons -- Chapter 16. Overview of case studies and data management / Daryl B. Simons, Ruh-Ming Li, and Nguyen Duong -- Chapter 17. Canal and channel design and river response analysis / Daryl B. Simons, Ruh-Ming Li, and Yung-Hai Chen -- Chapter 18. Degradation and aggradation analysis / Ruh-Ming Li and Daryl B. Simons -- Chapter 19. Watershed best management analysis / Ruh-Ming Li, Timothy J. Ward, and Daryl B. Simons -- Chapter 20. Large river basin analysis: Yazoo River Sedimentation Study / Daryl B. Simons and Ruh-Ming Li
Increasing Distributed Generation Penetration using Soft Normally-Open Points
No full textThis paper considers the effects of various voltage control solutions on facilitating an increase in allowable levels of distributed generation installation before voltage violations occur. In particular, the voltage control solution that is focused on is the implementation of `soft' normally-open points (SNOPs), a term which refers to power electronic devices installed in place of a normally-open point in a medium-voltage distribution network which allows for control of real and reactive power flows between each end point of its installation sites. While other benefits of SNOP installation are discussed, the intent of this paper is to determine whether SNOPs are a viable alternative to other voltage control strategies for this particular application. As such, the SNOPs ability to affect the voltage profile along feeders within a distribution system is focused on with other voltage control options used for comparative purposes. Results from studies on multiple network models with varying topologies are presented and a case study which considers economic benefits of increasing feasible DG penetration is also given
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