78 resultados para Armor.


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"Literatur über Griechisch-römische Geschütze": p. 86-88.

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"Appendix, no. X. A general and compleat list-military of every commission-officer ... of England ... London, N. Brooks, 1684" (v. 2. p. [1]-22 [3d series of numbering]) has special t.p.

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Added t.-p., illus.

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"October 1991."

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Mode of access: Internet.

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At head of title: H. M. Office of works.

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Mode of access: Internet.

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"Qunito anno--decima-terceira serie."

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"Aus den Abhandlungen der Königl. Akademie der wissenschaften zu Berlin, 1874."

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"A select bibliography on the country church" : p. 287.

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This dissertation explores the role of artillery forward observation teams during the battle of Okinawa (April–June 1945). It addresses a variety of questions associated with this front line artillery support. First, it examines the role of artillery itself in the American victory over the Japanese on Okinawa. Second, it traces the history of the forward observer in the three decades before the end of World War II. Third, it defines the specific role of the forward observation teams during the battle: what they did and how they did it during this three-month duel. Fourth, it deals with the particular problems of the forward observer. These included coordination with the local infantry commander, adjusting to the periodic rotation between the front lines and the artillery battery behind the line of battle, responding to occasional problems with "friendly fire" (American artillery falling on American ground forces), dealing with personnel turnover in the teams (due to death, wounds, and illness), and finally, developing a more informal relationship between officers and enlisted men to accommodate the reality of this recently created combat assignment. Fifth, it explores the experiences of a select group of men who served on (or in proximity to) forward observation teams on Okinawa. Previous scholars and popular historians of the battle have emphasized the role of Marines, infantrymen, and flame-throwing armor. This work offers a different perspective on the battle and it uses new sources as well. A pre-existing archive of interviews with Okinawan campaign forward observer team members conducted in the 1990s forms the core of the oral history component of this research project. The verbal accounts were checked against and supplemented by a review of unit reports obtained from the U.S. National Archives and various secondary sources. The dissertation concludes that an understanding of American artillery observation is critical to a more complete comprehension of the battle of Okinawa. These mid-ranking (and largely middle class) soldiers proved capable of adjusting to the demands of combat conditions. They provide a unique and understudied perspective of the entire battle.

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The focus of this work is to develop and employ numerical methods that provide characterization of granular microstructures, dynamic fragmentation of brittle materials, and dynamic fracture of three-dimensional bodies.

We first propose the fabric tensor formalism to describe the structure and evolution of lithium-ion electrode microstructure during the calendaring process. Fabric tensors are directional measures of particulate assemblies based on inter-particle connectivity, relating to the structural and transport properties of the electrode. Applying this technique to X-ray computed tomography of cathode microstructure, we show that fabric tensors capture the evolution of the inter-particle contact distribution and are therefore good measures for the internal state of and electronic transport within the electrode.

We then shift focus to the development and analysis of fracture models within finite element simulations. A difficult problem to characterize in the realm of fracture modeling is that of fragmentation, wherein brittle materials subjected to a uniform tensile loading break apart into a large number of smaller pieces. We explore the effect of numerical precision in the results of dynamic fragmentation simulations using the cohesive element approach on a one-dimensional domain. By introducing random and non-random field variations, we discern that round-off error plays a significant role in establishing a mesh-convergent solution for uniform fragmentation problems. Further, by using differing magnitudes of randomized material properties and mesh discretizations, we find that employing randomness can improve convergence behavior and provide a computational savings.

The Thick Level-Set model is implemented to describe brittle media undergoing dynamic fragmentation as an alternative to the cohesive element approach. This non-local damage model features a level-set function that defines the extent and severity of degradation and uses a length scale to limit the damage gradient. In terms of energy dissipated by fracture and mean fragment size, we find that the proposed model reproduces the rate-dependent observations of analytical approaches, cohesive element simulations, and experimental studies.

Lastly, the Thick Level-Set model is implemented in three dimensions to describe the dynamic failure of brittle media, such as the active material particles in the battery cathode during manufacturing. The proposed model matches expected behavior from physical experiments, analytical approaches, and numerical models, and mesh convergence is established. We find that the use of an asymmetrical damage model to represent tensile damage is important to producing the expected results for brittle fracture problems.

The impact of this work is that designers of lithium-ion battery components can employ the numerical methods presented herein to analyze the evolving electrode microstructure during manufacturing, operational, and extraordinary loadings. This allows for enhanced designs and manufacturing methods that advance the state of battery technology. Further, these numerical tools have applicability in a broad range of fields, from geotechnical analysis to ice-sheet modeling to armor design to hydraulic fracturing.