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Search Results: 1 - 10 of 285220 matches for " Gray G.T. "
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Influence of sweeping detonation-wave loading on shock hardening and damage evolution during spallation loading in tantalum
Gray G.T.,Hull L.M.,Livescu V.,Faulkner J.R.
EPJ Web of Conferences , 2012, DOI: 10.1051/epjconf/20122602004
Abstract: Widespread research over the past five decades has provided a wealth of experimental data and insight concerning the shock hardening, damage evolution, and the spallation response of materials subjected to square-topped shock-wave loading profiles. However, fewer quantitative studies have been conducted on the effect of direct, in-contact, high explosive (HE)-driven Taylor wave (unsupported shocks) loading on the shock hardening, damage evolution, or spallation response of materials. Systematic studies quantifying the effect of sweeping-detonation wave loading are yet sparser. In this study, the shock hardening and spallation response of Ta is shown to be critically dependent on the peak shock stress and the shock obliquity during sweeping-detonation-wave shock loading. Sweeping-wave loading is observed to: a) yield a lower spall strength than previously documented for 1-D supported-shock-wave loading, b) exhibit increased shock hardening as a function of increasing obliquity, and c) lead to an increased incidence of deformation twin formation with increasing shock obliquity.
The effect of shockwave profile shape on dynamic brittle failure
Brown E.N.,Escobedo J.P.,Trujillo C.P.,Gray G.T.
EPJ Web of Conferences , 2012, DOI: 10.1051/epjconf/20122602010
Abstract: The role of shock wave loading profile is investigated for the failure processes in a brittle material. The dynamic damage response of ductile metals has been demonstrated to be critically dependent on the shockwave profile and the stress-state of the shock. Changing from a square to triangular (Taylor) profile with an identical peak compressive stress has been reported to increase the “spall strength” by over a factor of two and suppress damage mechanisms. The spall strength of tungsten heavy alloy (WHA) based on plate impact square-wave loading has been extensively reported in the literature. Here a triangular wave loading profile is achieved with a composite flyer plate of graded density in contrast to the square-wave loading. Counter to the strong dependence in wave profile in ductile metals, for WHA, both square and triangle wave profiles the failure is by brittle cleavage fracture with additional energy dissipation through crack branching in the more brittle tungsten particles, largely indistinguishable between wave profiles. The time for crack nucleation is negligible compared to the duration of the experiment and the crack propagation rate is limited to the sound speed as defined by the shock velocity.
Characterization of shocked beryllium
Cady C.M.,Adams C.D.,Hull L.M.,Gray G.T.
EPJ Web of Conferences , 2012, DOI: 10.1051/epjconf/20122601009
Abstract: While numerous studies have investigated the low-strain-rate constitutive response of beryllium, the combined influence of high strain rate and temperature on the mechanical behavior and microstructure of beryllium has received limited attention over the last 40 years. In the current work, high strain rate tests were conducted using both explosive drive and a gas gun to accelerate the material. Prior studies have focused on tensile loading behavior, or limited conditions of dynamic strain rate and/or temperature. Two constitutive strength (plasticity) models, the Preston-Tonks-Wallace (PTW) and Mechanical Threshold Stress (MTS) models, were calibrated using common quasi-static and Hopkinson bar data. However, simulations with the two models give noticeably different results when compared with the measured experimental wave profiles. The experimental results indicate that, even if fractured by the initial shock loading, the Be remains sufficiently intact to support a shear stress following partial release and subsequent shock re-loading. Additional “arrested” drive shots were designed and tested to minimize the reflected tensile pulse in the sample. These tests were done to both validate the model and to put large shock induced compressive loads into the beryllium sample.
Promoting a Culture of Reading and Research: Challenges for Efficiency and Effectiveness in Schools as Learning and Teaching Institutions
G.T. Tsayang
Pakistan Journal of Social Sciences , 2012,
Abstract: This study is theoretical and aims at exploring the possible strategies to use in promoting a culture of reading and research in order to strive towards efficiency and effectiveness in school institutions. The study starts off by defining reading and research. It goes on to explain the role of reading and research in the improvement of both the management of schools and the learning and teaching processes. It also suggests examples of strategies which can be adopted by schools in order to improve the culture of Reading and Research in the school management teams, teachers and students. Overall the study can be viewed as food for thought because Reading and Research, though affords one the opportunity to discover new things, in most cases it simply makes one aware of obvious things or facts around oneself that are often taken for granted. This awareness of what could be regarded as the obvious is important because once one is aware of what is around them, one can apply for improvement of the quality of same and hence improve efficiency and effectiveness.
Golden Research Thoughts , 2013, DOI: 10.9780/22315063
Abstract: The word 'Gazetteer' comes from the Latin term 'Gazeta' which means a small coin or the cost of an early news sheet. In earlier days, it was used in narrow sense. But today this word has a broader meaning. After geographical discoveries various attempts to prepare Gazetteers of various regions. As a result of establishment of imperialism and colonialism, preparation of Gazetteers began. In the same way the British who came to India to establish their Supremacy became interested in the study of the regions of India which came under their rule. Mainly there was self interest in this matter. There was a plan by the British to establish their colonial subjugation and political hegemony over the regions through a study and acquaintance.
Surrogaatmiddelen en –medicijnen
G.T. Haneveld
Tijdschrift voor de Geschiedenis der Geneeskunde, Natuurwetenschappen, Wiskunde en Techniek , 1991,
Abstract: Surrogate cure and medicine In contrast to the many food surrogates — tulip bulbs! — 'Ersatz' pharmaceuticals or alternative healing methods never reached a large scale in the Netherlands during the second world war. Nevertheless some 50.000 people died in the winter 1944-'45, due to a severe shortage of medicines. In the former Dutch East Indies all western inhabitants were sent into prisoncamps where medicines deliberately were withheld. This led to all kinds of individual efforts to find alternative ways for wound treatment and to make ingenious surrogate yeast- and vitamin preparations.
Medische aspecten van de slag bij Doggersbank
G.T. Haneveld
Tijdschrift voor de Geschiedenis der Geneeskunde, Natuurwetenschappen, Wiskunde en Techniek , 1982,
Abstract: The Naval Battle at Doggersbank The outcome of the encounter near Doggersbank (5 August 1781) between 7 Dutch and 7 British heavily armed men-of-war is remembered as a remarkable Dutch victory. Losses however were heavy: 104 dead and 3.39 wounded in the British fleet, 140 dead and 404 wounded in the Dutch. Dutch medical information on this naval battle is very scarce. 24 Amputations were performed at sea; only 4 died from tetanus. The wounded were transported to the municipal hospital at Amsterdam which was brought in readiness hastily. In the Hospital Archives one only finds the names of the victims and the location of their wounds; no details about the treatment. Next to fractures, dislocations and wounds from bullets and flying wood one encounters severe burns: all typical hazards of the war at sea. One sailor with a devastating injury of his upper jaw and face, due to a cannonball, survived for 16 years. His deformed skull is on exhibit in the Leyden Pathological Institute. As a result of the generous financial contributions for the survivors of this naval battle or their next of kin a national foundation was created to stimulate interest for the navy. In 1784 a nautical college was inaugurated which still exists.
Extensión noroccidental de la cuenca paleozoica de Claromecó, provincia de Buenos Aires Northwestern extension of the Claromecó Paleozoic Basin, province of Buenos Aires
G.T. Alvarez
Revista de la Asociación Geológica Argentina , 2007,
Abstract: El área de estudio se encuentra ubicada en el sector norte y oriental de las Sierras Australes de la provincia de Buenos Aires. Se realizaron 700 observaciones geofísicas de gravedad y magnetismo calculándose las anomalías de esos campos potenciales con el fin de elaborar mapas gravimétricos a escala 1: 200.000 de las hojas Tornquist, Pigüé, Guaminí y Coronel Suárez. Se modelaron las anomalías de Bouguer por medio de prismas de densidad conocida. Para conocer el desarrollo de los sedimentos en profundidad se realizaron dos perfiles gravimétricos según las direcciones E-O y NE-SO. De esa forma, se pudo dimensionar la cuenca paleozoica que tiene 6.000 metros de espesor de sedimentos y una extensión de 5.200 kilómetros cuadrados. Su geometría en el sector oeste de la cuenca de Claromecó es de forma alargada en dirección NO con un ancho aproximado de 48 km y una longitud de 145 km. Se observan anomalías magnéticas con expresiones de poca magnitud, indicando la presencia de sedimentos en profundidad con moderado contenido de minerales magnéticos. La existencia de disparos de sísmica de refracción realizados por YPF y el DYMAS en los alrededores de Carhué indican con precisión los espesores de los sedimentos terciarios y por lo tanto el techo de las formaciones sedimentarias paleozoicas. The study area extends to the north and western of Sierras Australes. It has been surveyed 700 stations for gravimetry and magnetometry and the calculated anomalies were positioned in the Tornquist, Pigüé, Guaminí and Coronel Suárez map sheets. The survey was done at 1: 200,000 scale. Gravimetric sections were made in W-E and SW-NE directions in order to get an estimation of the sediment thickness. Based on these date the extension of the Paleozoic was determined. The thickness reaches up to 6,000 m and 5,200 square kilometers. The Claromecó basin extends to the NW in the western side by 145 km with a width of 48 km. The observed magnetic anomalies of the total field magnetic map are small pointing out the presence of moderate magnetic minerals. The existence of refraction seismic lines provided by Y.P.F. and DYMAS for the neighboring areas of Carhué allows a precise thickness of the Tertiary sediments.
Indian Streams Research Journal , 2013,
Abstract: B.L Rice was well known epigraphist, Historian, Educationist and Editor of literary works. He rendered Yeoman's service in erstwhile Mysore state for six decades. After he served Headmaster of the central school, he was appointed as school inspector, then director of public instruction in erstwhile Mysore state and Coorg. During this period he introduced many important reforms in the field of education. He prepared a comprehensive scheme called 'Hobli-Schools Scheme'. He gave great importance to education of girls. He played a significant role in the preparation of the 'Hunter Report'. This report recommended reforms at all India level in the field of education.
Dating recent peat profiles using spheroidal carbonaceous particles (SCPs)
G.T. Swindles
Mires and Peat , 2010,
Abstract: This article provides a brief overview of spheroidal carbonaceous particles (SCPs) as age-equivalent stratigraphic markers in recent peat profiles. A detailed method for the extraction and analysis of SCPs is provided and specific limitations of the technique are discussed.
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