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On the study of ricochet and penetration in sand,water and gelatin by spheres,7.62 mm APM2,and 25 mm projectiles

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Defence Technology（防务技术） 2016年第2期12卷 159-170页

作者： john f.moxnes ∅yvind fR∅YLAND Stian SKRIUDALEN Anne K.PRYTZ Jan A.TELAND Eva fRIIS Gard ∅DEGARDSTUEN Land Systems Division Norwegian Defence Research EstablishmentP.O.Box 25N0-2027 KjellerNorway Nammo Raufoss AS P.O.Box 162N0-2831 RaufossNorway

We examine the ricochet and penetration behavior in sand, water and gelatin by steel spheres, 7.62 mm APM2 and 25 mm projectiles. A threshold impact angle(critical angle) exists beyond which ricochet cannot occur. The Autodyn simulation code with the smooth particle hydrodynamic(SPH) method and Impetus Afea Solver with the corpuscular model are used and the results are compared with experimental and analytical results. The resistance force in sand for spheres was proportional to a term quadratic in velocity plus a term linear in velocity. The drag coefficient for the quadratic term was 0.65. The Autodyn and Impetus Afea codes simulate too large penetration due to the lack of a linear velocity resistance force. Critical ricochet angles were consistent with analytical results in the literature. In ballistic gelatin at velocities of 50–850 m/s a drag coefficient of 0.30 fits the high speed camera recordings if a linear velocity resistance term is included. However, only a quadratic velocity resistance force with drag coefficient that varies with the Reynolds number also fits the measurements. The simulation of a sphere in water with Autodyn showed too large drag coefficient. The 7.62 mm APM2 core simulations in sand fit reasonable well for both codes. The 25 mm projectile ricochet simulations in sand show consistency with the high speed camera recordings. Computer time was reduced by one to two orders of magnitudes when applying the Impetus Afea Solver compared to Autodyn code due to the use of the graphics processing units(GPU).

关键词：明胶微球渗透行为炮弹光滑粒子流体动力学阻力系数模拟显示高速摄像机砂

Strain rate dependency and fragmentation pattern of expanding warheads

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Defence Technology（防务技术） 2015年第1期11卷 1-9页

作者： john f.moxnes Anne K.PRYTZ Фyvind fR?YLAND Stian SKRIUDALEN Steinar BФRVE Gard ФDEGARDSTUEN Land Systems Division Norwegian Defence Research Establishment (FFI) P.O.Box 25 NO-2027 Kjeller Norway Nammo Raufoss AS P.O.Box 162 NO-2831 Raufoss Norway

for the characterization of the behaviors of a metal material in events like expanding warheads, it is necessary to know its strength and ductility at high strain rates, around 104e105/s. The flyer plate impact testing produces the uniform stress and strain rates but the testing is expensive. The Taylor test is relatively inexpensive but produces non-uniform stress and strain fields, and the results are not so easily inferred for material modeling. In the split-Hopkinson bar(SHB), which may be used in compression, tension and torsion testing, the strain rates never exceeds 103/s. In the present work, we use the expanding ring test where the strain rate is 104e105/s. A streak camera is used to examine the expanding ring velocity, and a water tank is used to collect the fragments. The experimental results are compared with the numerical simulations using the hydrocodes AUTODYN, IMPETUS Afea and a regularized smooth particle(RSPH) software. The number of fragments increases with the increase in the expansion velocity of the rings. The number of fragments is similar to the experimental results. The RSPH software shows much the same results as the AUTODYN where the Lagrangian solver is used for the ring. The IMPETUS Afea solver shows a somewhat different fragmentation characteristic due to the node splitting algorithm that induces pronounced tensile splitting.

关键词： Warhead fragmentation Simulation fracture model Expanding ring

Experimental and numerical study of the fragmentation of expanding warhead casings by using different numerical codes and solution techniques

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Defence Technology（防务技术） 2014年第2期10卷 161-176页

作者： john f.moxnes Anne K.PRYTZ Фyvind fRФYLAND Siri KLOKKEHAUG Stian SKRIUDALEN Eva fRIIS Jan A.TELAND Cato DФRUM Gard ФDEGARDSTUEN Land Systems Division.Norwegian Defence Research Establishment P.O.Box 25 Nammo Raufoss AS.P.O.Box 162

There has been increasing interest in numerical simulations of fragmentation of expanding warheads in *** there is a pressure on developers of leading commercial codes,such as *** and IMPETUS *** implement the reliable fracture models and the efficient solution *** applicability of the johnson—Cook strength and fracture model is evaluated by comparing the fracture behaviour of an expanding steel casing of a warhead with *** numerical codes and different numerical solution techniques,such as Eulerian,*** particle hydrodynamics(SPH).and the corpuscular models recently implemented in IMPETUS Afea are *** the same solution techniques and material models we find that the codes give similar *** SPH technique and the corpuscular technique are superior to the Eulerian technique and the Lagrangian technique(with erosion) when it is applied to materials that have fluid like behaviour such as the explosive and the *** Eulerian technique gives much larger calculation time and both the Lagrangian and Eulerian techniques seem to give less agreement with our *** more correctly simulate the fracture behaviours of the expanding steel casing,we applied that ductility decreases with strain *** phenomena may be explained by the realization of adiabatic shear *** implemented node splitting algorithm in IMPETUS Afea seems very promising.

关键词：技术试验数字代码数值模拟弹头光滑粒子流体动力学 LS-DYNA 外壳数值求解方法

Human development across the lifespan john S. Dacey, john f. Travers.

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Projected area and drag coefficient of high velocity irregular fragments that rotate or tumble

2002年

作者： john S. Dacey john f. Travers.

来源：畅想之星图书光盘版（南... 评论

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Defence Technology（防务技术） 2017年第4期13卷 269-280页

作者： john f. moxnes 0yvind fr0 yland Ivar J. 0ye Tom I. Brate Eva friis Gard 0degardstuen Tallak H. Risdal Norwegian Defence Research Establishment Land Systems Division P.O. Box 25 2027 Kjeller Norway Nammo Raufoss AS P.O. Box 162 2831 Raufoss Norway HPVisTech AS Bj0rnstadgutua 21 2092 Minnesund Norway

3 degrees of freedom(DOf)exterior ballistic computer models are used in fragment studies to calculate individual trajectories of each fragment based on drag coefficient and the projected(presented)area in the direction of velocity of center of *** expectation of a randomly distributed projected area is commonly used for fragments that tumble(random rotation)during *** forecast a model where the expected drag coefficient is dependent of shape and Mach *** or tumbling only affects the expected projected *** of projected areas during tumbling and rotation are *** examination of the data by Mc Cleskey(1988)indicates that the volume of the fragment to the power of2/3 is a better parameter to characterize the drag coefficient of the fragments than the maximum projected *** simulations are used to verify results and to study projected area and drag coefficient of fragments.

关键词： fragments form factor Mach number Drag coefficient Cauchy area Tumbling

Synchronous formation of the‘forearc’Bay of Islands ophiolite and its basal high-temperature metamorphic sole constrained by U-Pb zircon ages

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Geoscience frontiers 2023年第6期14卷 234-272页

作者： Weiyao Yan john f.Casey Department of Earth and Atmospheric Sciences University of HoustonHoustonTXUSA

The welded metamorphic sole at the base of the Bay of Islands Ophiolite Complex(BOIC)in the Northern Appalachians of Newfoundland shows a typical inverted pressure-temperature(P-T)metamorphic gradient from HT-MP granulite to LT-LP greenschist *** incorporates mafic volcanic/plutonic protoliths mixed with pelagic,hemi-pelagic and coarser epiclastic sedimentary *** LA-ICP-MS U–Pb concordia ages,trace elements,and Ti-in-zircon geothermometry for -250 zircon analyses from three metabasites of the upper HT sole amphibolites with N-MORB-like protoliths are *** samples collected within meters of the ophiolite peridotite-sole contact of the Blow Me Down Mountain and North Arm Mountain massifs yielded the oldest comparable concordia ages of 487.7±2.6 Ma and 489.1±3.1 Ma,respectively,that are both within error of the igneous age of 488.3±1.5 Ma of the directly overlying BOIC ophiolite,which formed at a supra-subduction zone(SSZ)forearc spreading center.A third slightly younger age of 484.2±2.4 Ma was obtained for an upper HT amphibolite sample with similar phase assemblages but collected30 m below the peridotite contact of the Table Mountain *** crystals analyzed have similar size and morphologies,subparallel rare earth element(REE)variation patterns,and steep heavy REE-enrichments((Lu/Gd)_(cn)>20),significant positive Ce anomalies(dominantly>5)and slight positive to dominantly negative Eu anomalies(1.2–0.4).Zircon shows Th/U mean values of 0.37–0.48 with little to no rim to core *** Ti-in-zircon mean crystallization temperatures range from764–787℃.These neocrystallized zircon crystals appear to be derived from thin leucosomes within the three *** other samples also from the upper HT sole show evidence of inherited detrital zircon with core dates spanning the Cambrian Notre Dame Arc through older Laurentian-like basement and rift age *** of the sole took place below a hot forearc asthenospheric wed

关键词： Ophiolite metamorphic sole U-Pb zircon ages Hot subduction interface Supra-subduction forearc spreading center Arc-continent collision Taconic Orogeny

Xylose: absorption, fermentation, and post-absorptive metabolism in the pig

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Journal of Animal Science and Biotechnology 2018年第1期9卷 1-9页

作者： Nichole f.Huntley john f.Patience Department of Animal Science 213 Kildee HallIowa State University Department of Animal Science 201B Kildee HallIowa State University

Xylose, as β-1,4-linked xylan, makes up much of the hemicel ulose in cel wal s of cereal carbohydrates fed to pigs. As inclusion of fibrous ingredients in swine diets continues to increase, supplementation of carbohydrases, such as xylanase,is of interest. However, much progress is warranted to achieve consistent enzyme efficacy, including an improved understanding of the utilization and energetic contribution of xylanase hydrolysis product（i.e. xylooligosaccharides or monomeric xylose）. This review examines reports on xylose absorption and metabolism in the pig and identifies gaps in this knowledge that are essential to understanding the value of carbohydrase hydrolysis products in the nutrition of the pig. Xylose research in pigs was first reported in 1954, with only sporadic contributions since. Therefore, this review also discusses relevant xylose research in other monogastric species, including humans. In both pigs and poultry, increasing purified D-xylose inclusion general y results in linear decreases in performance, efficiency, and diet digestibility. However,supplementation levels studied thus far have ranged from 5% to 40%, while theoretical xylose release due to xylanase supplementation would be less than 4%. More than 95% of ingested D-xylose disappears before the terminal ileum but mechanisms of absorption have yet to be ful y elucidated. Some data support the hypothesis that mechanisms exist to handle low xylose concentrations but become overwhelmed as luminal concentrations increase. Very little is known about xylose metabolic utilization in vertebrates but it is wel recognized that a large proportion of dietary xylose appears in the urine and significantly decreases the metabolizable energy available from the diet. Nevertheless, evidence of labeled D-xylose-1-^（14）C appearing as expired^（14）CO_2 in both humans and guinea pigs suggests that there is potential,although small, for xylose oxidation. It is yet to be determined if pigs develop increased xy

关键词： Pentose utilization Swine Threitol Xylose absorption Xylose metabolism

Calcium-mediated paired pulse depression in juvenile rat dorsal striatum

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Neural Regeneration Research 2012年第10期7卷 772-777页

作者： Yufeng Xie Michael f. Jackson john f. MacDonald Robarts Research Institute University of Western Ontario London Ontario Canada Department of Physiology and Pharmacology University of Western Ontario London Ontario Canada Department of Anatomy and Cell Biology University of Westem Ontario London Ontario Canada

As the major division of the basal ganglia, neostriatum forms mutual connections with multiple brain areas and is critically involved in motor control and learning/memory. Long-term synaptic plasticity has been widely studied in different species recently. However, there are rare reports about the short-term synaptic plasticity in neostratium. In the present study, using field excitatory postsynaptic potentials recording, we reported one form of short-term synaptic plasticity that is paired pulse depression in juvenile rat dorsal striatum slices induced by stimuli of the white matter. The field excitatory postsynaptic potentials could be abolished by α-amino-3-hydroxy-5-methylizoxazole-4-propionic acid receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione, but not by gamma-aminobutyric acid type A receptor antagonist bicuculline or dopamine D1 receptor antagonist SKf-81297. The paired pulse depression in the corticostratial pathway was different from paired pulse facilitation in the hippocampal CA1 synapse. In addition, the paired pulse depression was not affected by bath application of gamma-aminobutyric acid type A receptor antagonist or dopamine D1 receptor antagonist. However, low calcium and high magnesium could attenuate the paired pulse depression. These findings suggest a more complicated plasticity form in the dorsal striatum of juvenile rats that is different from that in the hippocampus, which is related with extracellular calcium.

关键词： paired pulses depression dorsal striatum calcium juvenile rats

Business, government, and society : a managerial perspective : text and cases / George A. Steiner, john f. Steiner. 9th ed.

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