4,089 research outputs found
Quantum effects in the Alcubierre warp drive spacetime
The expectation value of the stress-energy tensor of a free conformally
invariant scalar field is computed in a two-dimensional reduction of the
Alcubierre ``warp drive'' spacetime. The stress-energy is found to diverge if
the apparent velocity of the spaceship exceeds the speed of light. If such
behavior occurs in four dimensions, then it appears implausible that ``warp
drive'' behavior in a spacetime could be engineered, even by an arbitrarily
advanced civilization.Comment: 9 pages, ReVTe
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Toward a Science of Sustainability
This report presents an overview of research horizons in sustainability science. Its motivation is to help harness science and technology to foster a transition toward sustainability – toward patterns of development that promote human well-being while conserving the life-support systems of the planet. It builds on but does not explicitly address the vast range of relevant sector-specific and cross-sectoral problem-solving work now underway in fields ranging from green technologies in energy and manufacturing to urban design to agriculture and natural resources. It focuses on the narrower but essential task of characterizing the needs for fundamental work on the core concepts, methods, models, and measurements that, if successful, would support work across all of those sectoral applications by advancing fundamental understanding of the science of sustainability. The report sets forth the workshop’s findings and recommendations on six fundamental questions now facing scholars seeking to harness science and technology to foster sustainability: 1. What are the principal tradeoffs between human well-being and the natural environment, and how are those tradeoffs mediated by the ways in which people use nature? 2. What determines the adaptability of coupled human-environment systems and, more broadly, their vulnerability and robustness/resilience in the face of external shocks and internal dynamics? 3. What shapes the long term trends and transitions that set the stage on which humanenvironment interactions are played out? 4. How can theory and models be formulated that better account for the variation in types or trends of human-environment interactions? 5. How can society most effectively guide or manage human-environment systems toward a sustainability transition? 6. How can the “sustainability” of alternative trajectories of human-environment interactions be usefully and rigorously evaluated
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Climate Change and the Integrity of Science
We are deeply disturbed by the recent escalation of political assaults on scientists in general and on climate scientists in particular. All citizens should understand some basic scientific facts. There is always some uncertainty associated with scientific conclusions; science never absolutely proves anything. When someone says that society should wait until scientists are absolutely certain before taking any action, it is the same as saying society should never take action. For a problem as potentially catastrophic as climate change, taking no action poses a dangerous risk for our planet
My mother : (was the greatest gift that Daddy gave to me)
https://digitalcommons.library.umaine.edu/mmb-vp/2214/thumbnail.jp
12-An Archaeological Survey of the Thornapple River Basin in Hastings and Castleton Townships, Barry County, Michigan
When the Thornapple Basin Survey program commenced in 1979, the Barry County site files indicated the presence of only 64 archaeological sites in this area of the state. However, it was also quite apparent from the available data in the site files as well as from information provided by the Michigan History Division that no program of systematic archaeological research had ever been conducted in the county. And, clearly, this was a situation that the MHD desired to have remedied.
Aside from the interest expressed by the State Archaeologist, Dr. John Halsey, and his staff in having a program of systematic site location survey initiated in the Thornapple River Basin, the senior author, Dr. William Cremin of Western Michigan University, also was anxious to expand WMU\u27s survey activities beyond the nearby Kalamazoo River Basin. After four years of systematic survey in portions of this drainage, Cremin recognized the need for creating a data set for comparison with the growing body of information generated by the Kalamazoo Basin Survey a need which has only increased with the recent completion of this survey program. Now, with a data set derived from more than 350 prehistoric sites occurring in 135 km of the basin surveyed, it has become absolutely essential that comparative information from other drainages in southern Lower Michigan be made available in order that predictive models of prehistoric settlement and subsistence behavior emerging for this universe (and other areas in this portion of the state) might be rigorously tested.
With this thought in mind, and responding to the request of MHD that a proposal be submitted for initiating site survey in the Thornapple River Valley, Cremin and his associates began a literature/documents search and examination of the Barry County site files, evaluated the available information, and established a series of research objectives to guide TBS Phase I activities in 1979 as well as to provide a basis for long term systematic survey in this universe in future years
Letter from John C. Calhoun & William Clark to George Sibley. September 5, 1818
Transcript of Letter from John C. Calhoun & William Clark to George Sibley. September 5, 1818. Calhoun discusses how to address claims made by Native American and U.S. citizens
Development of a management practicum in a clinical psychology program
Some clinical psychology programs are developing training in management in response to both the recognition that management is a major professional role for many psychologists (Clements, Rickard, & Kleinot, 1986) and the National Council of Schools of Professional Psychology’s (NCSPP) inclusion of “supervision and management” as one of six competency areas for the core curriculum in professional psychology (Peterson, R. L., McHolland, J. D., Bent, R. J., Davis-Russell, E., Edwall, G. E., Polite, K., Singer, D. L., & Stricker, G., 1991). At the Graduate School of Clinical Psychology at George Fox University (Newberg, OR), we developed a management practicum to facilitate specific and advanced training of selected doctoral students in this competency area. In this article, we compare and contrast our program with the one developed at West Virginia University (WVU), described in a previous article in this journal
Prediction of Undsteady Flows in Turbomachinery Using the Linearized Euler Equations on Deforming Grids
A linearized Euler solver for calculating unsteady flows in turbomachinery blade rows due to both incident gusts and blade motion is presented. The model accounts for blade loading, blade geometry, shock motion, and wake motion. Assuming that the unsteadiness in the flow is small relative to the nonlinear mean solution, the unsteady Euler equations can be linearized about the mean flow. This yields a set of linear variable coefficient equations that describe the small amplitude harmonic motion of the fluid. These linear equations are then discretized on a computational grid and solved using standard numerical techniques. For transonic flows, however, one must use a linear discretization which is a conservative linearization of the non-linear discretized Euler equations to ensure that shock impulse loads are accurately captured. Other important features of this analysis include a continuously deforming grid which eliminates extrapolation errors and hence, increases accuracy, and a new numerically exact, nonreflecting far-field boundary condition treatment based on an eigenanalysis of the discretized equations. Computational results are presented which demonstrate the computational accuracy and efficiency of the method and demonstrate the effectiveness of the deforming grid, far-field nonreflecting boundary conditions, and shock capturing techniques. A comparison of the present unsteady flow predictions to other numerical, semi-analytical, and experimental methods shows excellent agreement. In addition, the linearized Euler method presented requires one or two orders-of-magnitude less computational time than traditional time marching techniques making the present method a viable design tool for aeroelastic analyses
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