13 research outputs found
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Experimental and computational studies of rod-deployment mechanisms
We describe experimental measurements and hydrocode simulations of two tests in which long (L/D=12), steel rods were accelerated laterally with charges of Detasheet-C high explosive (HE). In each test configuration, 84 rods were initially aligned parallel to one another in an array of four concentric rings. The first test had a central core of HE that dispersed the rods isotropically. The second test had a narrow, 180 degree strip of HE on one side of the assembly that focused the rods directionally. Using radiographic data taken at several milliseconds after HE initiation, we measured the dynamic distributions of the rods, and their translational velocities and tumble rates. To compare with the data, we also modeled the experiments with our smooth particle hydrocode SPHINX. Within the context of our numerical model, the hydrocode results agree satisfactorily with the test data. We include in our discussion many of the inferences and insights that our results provide to the phenomenology and performance of multimode, rod-deployment mechanisms
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MESA 3-D calculations of armor penetration by projectiles with combined obliquity and yaw
We introduce and briefly describe MESA, a new 3-D hydrodynamic code, developed specifically for simulations of armor and anti-armor systems. The code's current capabilities an its planned model improvements and additions are discussed. An Eulerian code using state-of-the-art numerical methods, MESA runs faster and is less affected by spurious numerical diffusion than older codes. It models hydrodynamic flow and the dynamic deformation of solid materials. It uses simple elastic-perfectly plastic material strength models as well as models with strain and strainrate hardening and thermal softening. Future versions will incorporate advanced fracture models. It treats detonations in explosives using a programmed burn. The code's current capabilities are illustrated with simulations of experiments on yawed rods obliquely impacting armor plates at 1.29 km/s. 12 refs., 14 figs
Toward an Approach to Generate Forward-Looking Theories Using Systems Concepts
Part 2: Section 1: How the Future and the Past Are Connected and Inter-relatedInternational audienceThe need to generate original theory about information systems phenom ena and ensure that such outputs are forward looking is an important concern. The paper gives examples of how IS project management practice and theories remain underpinned by concepts which do not map to experienced realities. The paper makes the case to use systems thinking approaches to unearth new theories to offer better explanations. In the pursuit of this goal, the paper first provides insight into the as-lived condition that makes human beings prone to being imprisoned by theories of yesteryear. This is done by discussing the role of language in cognition and theory development. In the IS literature, such discussions are limited despite the consid erable attention to on types of theories and anatomies of theories. The paper claims and demonstrates why debate on theory cannot take place without explicit attention to aspects of cognition and as-lived existence. In the context of these discussions, the paper puts forward the suggestion that theoretical contributions rooted in systems concepts could allow for the emergence of forward-looking theory about IS phenomena. As a means of illuminating how to go about developing such theories, the paper provides a brief overview of how soft systems methodology and work systems method concepts can be used in a theorizing framework to achieve this. The main contributions to knowledge are two-fold. First, there is the inter-contextual coherence which is established by creating coherence between as-lived human experience, embodied cognition, theory, and language. Second, within such a con text, we are able to demonstrate a pragmatic approach to generate better explanations about IS phenomena using systems concepts