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Experimental and numerical investigations in ballistic applications have predominantly focused on determining the ballistic limit of target plates for various projectile shapes. However, limited attention has been given to the influence of projectile nose shapes at high impact velocities. To address this gap, 3D FE simulations were carried out on a 1 mm thin target plate using J-C material model, the Gruneisen equation of state (EOS), an erosion contact algorithm, and the explicit FE code LS-DYNA. The simulations involved impact of fragments of equal mass but different nose shapes. The results revealed a significant influence of fragment shape on both the ballistic limit and overall plastic deformation of the target plate. Particularly, the target plate impacted by a hexagonal pyramid fragment shape exhibited the highest ballistic limit and global plastic deformation. Further, it was also observed that at higher impact velocities, the former fragment shape caused the maximum damage to the target plate, while at lower impact velocities, the cubical fragment shape demonstrated the highest lethality. This difference in target damage is known to be governed by the energy required to erode the target and fragment material. The results from the current study offers valuable insights into how different fragment shapes influence the damage inflicted on target plates in ballistic scenarios. The findings presented in this study also offer guidance on selecting suitable fragment shapes for future use in Fragment Generator Warheads (FGW) in order to maximize the damage or lethality inflicted on targets. [ABSTRACT FROM AUTHOR]

The detonation wave–aiming warhead can effectively enhance the lethality efficiency. In the past, rules for casing rupture and velocity distribution under asymmetrical initiations were not adequately investigated. In this study, X-ray photography and numerical modelling are used to examine the casing expansions under centre point, asymmetrical one-point, and asymmetrical two-point (with central angles of 45° and 90°) initiations. The results indicate that early casing ruptures are caused by local high pressures, induced by the initiation, detonation wave interaction, and Mach wave onset. The fragment shapes are controlled by the impact angle of the detonation wave. The fragment velocity distributions differ under different initiation types, and the end rarefaction waves can affect the velocity distribution. This study can serve as a reference for the design and optimization of high-efficiency warheads.

Variation in species richness and density of native birds in urban parks and greenspaces ("parks") is often substantial. Understanding why differences exist, and whether all migratory guilds are equally affected, is poorly known. We surveyed breeding bird communities in 48 undeveloped forested parks in Portland, Oregon, USA, to determine the contributions of park area, shape, connectivity, landscape composition surrounding parks, and differences in structure/composition of local habitat to variation in richness and density of residents, long-distance migrants, and short-distance/partial migrants. Migratory guilds responded differently to environmental factors. Richness and density of long-distance migrants increased with park area and abundance of small (< 10 cm DBH), mostly native, tree species. Resident richness also increased with the abundance of small trees. However, resident and short-distance/partial migrant richness was independent of park area, and resident density declined with increasing area. Park shape, connectivity, and landscape composition did not influence richness or density of any migratory guilds, possibly because of relatively high tree cover in Portland's landscape. Separate analyses of forest-dependent species of all migratory guilds revealed that area was the primary contributor to variation in density of residents and long-distance migrants, structural habitat features contributed to variation in density of residents but not long-distance migrants, and that density of long-distance migrants declined with elongated park shape. Few forest-dependent species existed in parks below 10 ha, and their minimum area requirements for maintaining populations were estimated to be 30 to 40 ha. Without such parks most long-distance migrants would likely disappear from Portland's landscape. [ABSTRACT FROM AUTHOR]

Explosion models based on Finite Element Analysis (FEA) can be used to simulate how a warhead fragments. However their execution times are extensive. Active protection systems need to make very fast predictions, before a fast attacking weapon hits the target. Fast execution times are also needed in real time simulations where the impact of many different computer models is being assessed. Hence, FEA explosion models are not appropriate for these real-time systems. The research presented in this paper delivers a fast simulation model based on Mott’s equation that calculates the number and weight of fragments created by an explosion. In addition, the size and shape of fragments, unavailable in Mott’s equation, are calculated using photographic evidence and a distribution of a fragment’s length to its width. The model also identifies the origin of fragments on the warhead’s casing. The results are verified against experimental data and a fast execution time is achieved using uncomplicated simulation steps. The developed model then can be made available for real-time simulation and fast computation.

Quantifying rock weathering processes, especially in ways of nondisturbance and on-site investigation, is one of the most critical tasks in predicting rocks erosion rates and understanding the sediment transportation. We proposed a more reproducible approach to test how image analysis can quantify the changes in the size and shape of fragments during the weathering process. Four artificial models were designed to select suitable metrics among over 20 parameters. To validate the efficiency of image analysis, we analyzed rocks from badlands in Nanxiong Basin, Southeast China, under three different ranges of temperature differences (TD) during cyclic wetting and drying (WD). Our results show that TDs can accelerate the disintegration rate, and even if there is only a 20°C difference in the range of TDs, an apparent difference in fragment size was observed. Moreover, the shape of fragments became more round as the increasing number of cyclic treatments, and for samples that went through the same number of treatments, the larger the temperature difference, the more round the shape became. All that serves as another evidence for landscape evolution response to climatic warming. [ABSTRACT FROM AUTHOR]

Explosion models based on Finite Element Analysis (FEA) can be used to simulate how a warhead fragments. However their execution times are extensive. Active protection systems need to make very fast predictions, before a fast attacking weapon hits the target. Fast execution times are also needed in real time simulations where the impact of many different computer models is being assessed. Hence, FEA explosion models are not appropriate for these real-time systems. The research presented in this paper delivers a fast simulation model based on Mott's equation that calculates the number and weight of fragments created by an explosion. In addition, the size and shape of fragments, unavailable in Mott's equation, are calculated using photographic evidence and a distribution of a fragment's length to its width. The model also identifies the origin of fragments on the warhead's casing. The results are verified against experimental data and a fast execution time is achieved using uncomplicated simulation steps. The developed model then can be made available for real-time simulation and fast computation. [ABSTRACT FROM AUTHOR]

Context: Mediterranean forests have been fragmented intensively over time, thereby yielding small and isolated forest remnants. They host a rich variety of epiphytes, which may be affected by landscape structure. Previous studies have analyzed the influence of habitat quality on these epiphytic communities, but there is little knowledge of the effects of other fragment features. Objectives: We evaluated the impacts of forest loss and fragmentation on epiphytic communities (lichens and bryophytes) at plot and fragment scales after controlling the variation in forest structure and management. Methods: We considered 40 fragments of dense oak forests in a human-modified landscape. We quantified their spatial attributes (size and shape), the quality of the surrounding matrix and the forest stand structure. We modeled community traits, and the presence and abundance of species at fragment and plot scales. Results: Fragment size, shape, and the quality of the surrounding matrix were key factors that affected epiphytic richness and diversity. Larger and more regularly shaped fragments hosted the richest and most diverse communities, possibly offering a larger core area and thus favoring the entry of typical forest species. A high-contrast matrix was only favorable in small fragments, probably allowing the arrival of propagules. The species-level response was highly variable. Conclusions: Landscape structure provides powerful explanations of the richness and diversity losses among epiphytes. Forest management should ensure the retention of the largest possible continuous forests. The management strategy of the matrix will depend on the conservation goal, since we observed different effects related with quality and fragment size. [ABSTRACT FROM AUTHOR]

Habitat fragmentation affects species and their interactions through intertwined mechanisms that include changes to fragment area, shape, connectivity and distance to edge. Disentangling these pathways is a fundamental challenge of landscape ecology and will help identify ecological processes important for management of rare species or restoration of fragmented habitats. In a landscape experiment that manipulated connectivity, fragment shape, and distance to edge while holding fragment area constant, we examined how fragmentation impacts herbivory and growth of nine plant species in longleaf pine savanna. Probability of herbivory in open habitat was strongly dependent on proximity to forest edge for every species, increasing with distance to edge in six species (primarily grasses and annual forbs) and decreasing in three species (perennial forbs and a shrub). In the two species of perennial forbs, these edge effects were dependent on fragment shape; herbivory strongly decreased with distance to edge in fragments of two shapes, but not in a third shape. For most species, however, probability of herbivory was unrelated to connectivity or fragment shape. Growth was generally determined more strongly by leaf herbivory than by distance to edge, fragment shape, or connectivity. Taken together, these results demonstrate consistently strong edge effects on herbivory, one of the most important biotic factors determining plant growth and demography. Our results contrast with the generally inconsistent results of observational studies, likely because our experimental approach enabled us to tease apart landscape processes that are typically confounded. [ABSTRACT FROM AUTHOR]

Habitat loss is a critical threat to tropical biodiversity and its quantification constitutes a central conservation issue. Typically, assessments have been based on deforestation rates statistics. However, this overlooks the effects brought about by the spatial reconfiguration of the remaining habitat: fragmentation. We present an analysis of fragmentation in a Neotropical site aimed at: (a) devising a protocol for its quantification, (b) using such protocol to provide insights on the ecological consequences of fragmentation, (c) exploring its applicability to address the hypothesis that forest size-inequality decreases with elevation, an indicator of habitat accessibility. We applied the Gini coefficient (G) and the Lorenz curve to analyze fragment-size variation using a satellite-generated map. We also estimated edge effect, fragment shape and isolation. Remaining forest includes 1,005 fragments, ranging from 0.5 to 9.356 ha (median = 0.89). Size inequality was very high (G = 0.928), producing a flattened Lorenz curve. Forty percent of the fragments did not maintain an area free of a 30-m edge effect, and larger fragments showed a marked deviation from ideal circular forms. Eighty-four percent of the fragments lay further than 500 m from the largest forest tract and their size decreased with distance. Fragment size distribution changed with altitude: the Gini coefficient was lowest and forest coverage was greatest at the highest altitude, but inequality peaked at an intermediate elevation. Given the current pace of habitat deterioration, application of similar analyses may improve global assessments of tropical ecosystems and their perspectives for biodiversity conservationLa destrucción del hábitat es la principal amenaza para la biodiversidad tropical, por lo que su cuantificación constituye un aspecto central para la biología de la conservación. Usualmente, esta cuantificación se basa en el cálculo de las tasas de deforestación, ignorando los efectos derivados de la reconfiguración espacial del hábitat remanente postdeforestación: la fragmentación. Aquí presentamos un análisis de la fragmentación en un sitio Neotropical para: (a) proponer un protocolo para su cuantificación; (b) utilizar tal protocolo para explorar las consecuencias ecológicas de la fragmentación; y (c) explorar su aplicación para evaluar la hipótesis de que la heterogeneidad de tamaños de los fragmentos disminuye con la elevación (indicativo de la accesibilidad del hábitat). Calculamos el coeficiente de Gini y la curva de Lorenz para analizar la desigualdad de tamaños de los fragmentos, utilizando un mapa generado con una imagen de satélite; además evaluamos el efecto de borde, la forma de los fragmentos y su grado de aislamiento. Encontramos que el bosque remanente incluye 1.005 fragmentos entre 0,5 y 9,356 ha (mediana = 0,89). La desigualdad de tamaños fue considerable (G= 0,928), con una curva de Lorenz muy abatida. El 40% de los fragmentos no tuvo un área libre de un efecto de borde de 30 m de ancho; los fragmentos más grandes mostraron un desvío considerable con respecto a la forma circular ideal. El 84 % de los fragmentos estuvo aislado, ubicándose más allá de 500 m de distancia del parche más grande de bosque y su tamaño disminuyó con la distancia. La distribución de tamaños de los fragmentos varió con la elevación: el coeficiente de Gini fue menor y la cobertura relativa de bosque fue mayor en la elevación más grande, pero la desigualdad fue máxima en una elevación intermedia. Proponemos que, en vista de los ritmos actuales de deterioro del hábitat, la aplicación de análisis similares puede mejorar nuestras evaluaciones del estado de conservación de los ecosistemas tropicales y las perspectivas para la conservación de la biodiversidad

A detailed experimental investigation on the dynamic fracture of a cylindrical shell with internal and external grooves subjected to internal explosive loading was carried out. Distributions of fragment velocities and fragment masses were measured and analyzed for specimens with different depths of the external grooves and different explosive materials, with the internal grooves of a fixed rectangular shape. Based on the experimental results, corresponding numerical simulations using the commercial software LS-DYNA were undertaken. By inspecting the fragments recovered from the experiments and the numerical results, the dynamic fracture of the casing led to fragments of approximately three shapes: a large cuboid fragment, a small cuboid fragment, and two irregular fragments formed by three classical fracture trajectories. The formation mechanism of fragment shapes was analyzed using the fracture trajectories. A good agreement has been obtained between the numerical and experimental results. Finally, a parametric study for the casing thickness, grid patterns of the grooves and explosive materials was carried out in order to investigate the effects of fracture. The results showed that grid patterns of grooves and explosive materials had significant effects on the fracture mechanism of the casing. The numerical technique was used to predict the dynamic fracture of casing with internal and external grooves under internal explosive loading and for structural design in order to achieve desirable fragments with controlled shapes. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we revisit the 1995 Kaman database of the SOCIT4 fragment characteristics with added analysis of a subset of the cataloged fragments from the test. This database was compiled from the last of a series of four hypervelocity impact tests conducted under a U.S. Department of Defense program in 1991–1992. This test targeted a flight-ready, U.S. Transit navigation satellite, yielding collision fragments in the size regime of sub-millimeter through tens of centimeters. Results in this database were used in the 1998 NASA Standard Breakup Model to represent characteristic length (size) and area-to-mass distributions of fragments smaller than 10cm. In this analysis we explore, in detail, the tabulated fragment material and shape. What emerges is a clear distinction in fragment area-to-mass ratio between primarily metal and primarily non-metal fragments. Metal fragments, which are dominated by aluminum, follow the characteristic curve of increasing area-to-mass ratio with decreasing characteristic length: objects move from the character of large irregular bent shards to that of small solid spheroids. Non-metal fragments, dominated by phenolic/plastic, do not appear to move towards solid spheroids as easily as metals. Also unlike the metals, their area-to-mass ratio curve plateaus in the midsize region (smaller than 1cm), coinciding with a peak in plate-like, non-metal fragments. The internal structure of the Transit payload, with its phenolic surface skin and packed arrays of plastic circuit boards, certainly governs this plateau behavior. In the small fragment regime (smaller than 4mm) phenolic/plastic ellipsoidal ‘Nuggets’ dominate the population. They outnumber aluminum ‘Nuggets’ by over four to one. Through this study we gain a more detailed understanding of the collisional-breakup process of this particular payload, but also have begun to determine how these data may apply to other breakups. Our long-term goal is to apply this new understanding to future upgrades of the NASA Standard Breakup Model. [Copyright &y& Elsevier]

Purpose: Tibial tubercle osteotomy (TTO) is a surgical technique used in the management of severe fractures of the knee joint and revision total knee arthroplasty. Limited research discusses the performance of the osteotomy and fixation of the TTO with screws. Therefore, this study investigated the effects of fragment shape and screw configuration on the mechanical behavior in the fixation of the TTO using the finite element (FE) method., Methods: FE TTO models with three fragment shapes and three screw configurations were developed. The three fragment shapes were a step cut, bevel cut, and straight cut. The screw configurations were two parallel horizontal and downward screws and two trapezoidal screws. A 1654-N upward tension force was applied on the tibia tubercle, and the distal end of the tibia was completely fixed., Results: The results indicated that the step cut resulted in higher stability than the bevel and straight cut, but the stress was higher as well. Among the screw configurations, two parallel downward screws resulted in the highest stability, given the same fragment shape. In the horizontal configuration, the step cut tibia developed the largest contact force to achieve stability of the bone fragment under loading., Conclusion: The fragment shape with a step cut and fixation with two parallel horizontal or downward screws are suggested for TTO, while the trapezoidal screw configuration is not suggested. Furthermore, the downward screw configuration is a suitable strategy to reduce bone stress.