389 research outputs found
#413 The H-Bomb and the Future.
No full textParticipants include: Mr. James R. Shepley, Co-Author of The Hydrogen Bomb Mr. Clay Blair Jr., Co-Author of Mr. Ramsay D. Potts, Former Administrative Asst. to Senator Stuart Symington; Author of articles on Military and Policy Implications of Atomic Weapons Developmen
A numerical investigation into key factors controlling hard rock excavation via electropulse stimulation
No full textElectropulse stimulation provides an energy-efficient means of excavating hard rocks through repeated application of high voltage pulses to the rock surface. As such, it has the potential to confer significant advantages to mining and drilling operations for mineral and energy resources. Nevertheless, before these benefits can be realized, a better understanding of these processes is required to improve their deployment in the field. In this paper, we employ a recently developed model of the grain-scale processes involved in electropulse stimulation to examine excavation of hard rock under realistic operating conditions. To that end, we investigate the maximum applied voltage within ranges of 120–600 kV, to observe the onset of rock fragmentation. We further study the effect of grain size on rock breakage, by comparing fine (granodiorite) and coarse grained (granite) rocks. Lastly, the pore fluid salinity is investigated, since the electric conductivity of the pore fluid is shown to be a governing factor for the electrical conductivity of the modeled system. This study demonstrates that all investigated factors are crucial to the efficiency of rock fragmentation by electropulsing.</p
Epigrafía maya: Tabasco
No full textLa información de esta miniguía está basada en los trabajos de M. Coe, N. Grove, S. Guenter, S. Martín, P. Mathews, Linda Schele, D. Stuart y M. U. Zender.Cuatro de las grandes culturas desarrolladas en Mesoamérica poseían un sistema propio de escritura: zapoteca, maya, mixteca y náhuatl. La escritura maya fue el sistema más complejo y el que más correspondencia tuvo con la lengua hablada. Parece haber surgido alrededor del 100 o 200 d.C., y según la mitología fue el dios ltzamná quien la inventó. Sus últimas expresiones se sitúan alrededor de 1696. Los mayas utilizaron diferentes soportes para plasmar la escritura y su historia escrita, como códices de papel vasijas de barro, textiles, pieles, estelas y altares de piedra, dinteles y cajas de madera, pendientes de hueso y hasta finas puntas de cola de mantarraya, entre otros.</p
An Efficient and Robust Method for Lagrangian Magnetic Particle Tracking in Fluid Flow Simulations on Unstructured Grids
No full textIn this paper we report on a newly developed particle tracking scheme for fluid flow simulations on 3D unstructured grids, aiming to provide detailed insights in the particle behaviour in complex geometries. A possible field of applications is the Magnetic Drug Targeting (MDT) technique, on which this paper will be focused. MDT is a promising medical technique that uses locally applied magnetic fields to capture magnetic drug carriers at the desired locations in the human body, strongly increasing the efficiency of medical drugs. The new particle tracking scheme combines the advantages of existing methods and is easy for implementation in a generic numerical code. The scheme is tested and validated for simple MDT cases that include effects of a non-homogeneous magnetic field on deposition of magnetic particles in laminar flow. The first test case is a validation study of the magnetic particle trajectories released in a horizontal circular pipe flow with a current-carrying wire parallel to the flow, for which analytical solutions are reported in literature. The second test case involves particle capture efficiencies in a 90o bent tube for different configurations of the imposed magnetic field. This configuration corresponds more closely to the conditions inside blood vessels, because of the presence of secondary motions. These results are compared with numerical studies from literature too. The obtained results demonstrate that the developed particle tracking scheme is a very robust, efficient and accurate method, which can give detailed insights in particle behaviour in complex geometries. As such it is a good candidate for future applications and optimisations of MDT technique for loco-regional cancer treatment or treatment of cardiovascular diseases.Multi-Scale PhysicsApplied Science
More Employers, More Jobs, More Money: An Empirical Analysis of Local Economic Development Policy Impacts in U.S. Cities
No full textLocal government leaders in the U.S. employ a multitude of programs and policies in the name of economic development to increase the number of firms, employment, wages, and, of course, the tax base. The past few decades have seen a surge in local economic development policies, yet research analyzing their effectiveness is sparse. This study analyzes the relationship between local economic development policy and economic growth in a data set of 412 U.S. cities. Results indicate that policy has only has a weak correlation with economic growth, suggesting that growth is determined more by market conditions rather than government intervention. The article concludes with an entrepreneurial policy approach this author believes may yield development results in an era of limited policy effectiveness.Economic development, Cities, Attraction, Retention, Incentives
A numerical investigation into key factors controlling hard rock excavation via electropulse stimulation
No full textISSN:1674-7755ISSN:2589-0417ISSN:2589-041
The JPS Pathfinding System in 3D
No full textThe ability to quickly compute shortest paths in 3D grids is a technological enabler for several applications such as pipe routing and computer video games. The main challenge is how to deal with the many symmetric permutations of each shortest path. We tackle this problem by adapting Jump Point Search (JPS), a well-known symmetry breaking technique developed for fast pathfinding in 2D grids. We give a rigorous reformulation of the JPS pathfinding system into 3D and we prove that our new algorithm, JPS-3D, is optimality preserving. We also develop a novel method for limiting scan depth during jump operations, which can further reduce search time. Experimental results show significant improvements versus online A* search and previous attempts at generalising JPS. We demonstrate that searching with adaptive scan limits can yield additional speedups of over an order of magnitude
Assessment of two-phase flow on the chemical alteration and sealing of leakage pathways in cemented wellbores
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