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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

Transformer for the Design of Automatic Control Systems with Prefilters

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World Journal of Engineering and Technology 2024年第3期12卷 575-586页

作者： Isaac Hughes john f. O’Brien Department of Electrical Engineering and Computer Science University of Wyoming Laramie USA

A machine learning model, using the transformer architecture, is used to design a feedback compensator and prefilter for various simulated plants. The output of the transformer is a sequence of compensator and prefilter parameters. The compensator and prefilter are linear models, preserving the ability to analyze the system with linear control theory. The input to the network is a window of recent reference and output samples. The goal of the transformer is to minimize tracking error at each time step. The plants under consideration range from simple to challenging. The more difficult plants contain closely spaced, lightly damped, complex conjugate pairs of poles and zeros. Results are compared to PID controllers tuned for a similar crossover frequency and optimal phase margin. for simple plants, the transformer converges to solutions which overly rely on the prefilter, neglecting the maximization of negative feedback. for more complex plants, the transformer designs a compensator and prefilter with more desirable qualities. In all cases, the transformer can start with random model parameters and modify them to minimize tracking error on the step reference.

关键词： feedback Machine Learning Compensator Design

Endoscopic ultrasound-guided portal pressure gradient identifies patients with previously undiagnosed clinically significant portal hypertension

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Portal Hypertension & Cirrhosis 2024年第2期3卷 67-74页

作者： Jerome C.Edelson Scott f.D.Edelson john G.Quiles Cyrus V.Edelson Eric M.Montminy Christian L.Horn john P.Magulick Don C.Rockey Department of Gastroenterology and Hepatology Brooke Army Medical CenterFort Sam HoustonTexasUSA Department of Medicine Uniformed Services University of the Health SciencesBethesdaMarylandUSA Department of Medicine Brooke Army Medical CenterFort Sam HoustonTexasUSA john H.Stroger Jr.Hospital of Cook County ChicagoIllinoisUSA Digestive Disease Research Center Medical University of South CarolinaCharlestonSouth CarolinaUSA

Aims:Portal hypertension(PH)is a complication of cirrhosis that leads to hepatic *** the portal pressure gradient(PPG)provides valuable information for disease assessment,staging,and *** this study,we aimed to report the utilization of endoscopic ultrasound(EUS)-guided PPG(EUS-PPG)measurements in a real-world ***:This retrospective analysis included patients at a tertiary care center who underwent EUS-PPG between february 2021 and May *** most common indication was to establish or exclude the diagnosis of cirrhosis,followed by an assessment of surgical risk in the setting of suspected *** demographic and clinical data were collected,and statistical analysis was performed using the Student's t ***:Eighteen patients underwent *** success was achieved in 17 of the 18 *** complications were *** mean scores of Child-Pugh,Model for End-Stage Liver Disease-Sodium,and fibrosis-4 scores were 5.1±0.5,9.0±3.0,and 3.7±4.5,*** the 18 patients,two presented with esophageal varices and six with portal hypertensive *** mean PPG was 5.8±4.5 mmHg,and five patients exhibited clinically significant PH(CSPH).Of the 18 patients,15 underwent concurrent EUS-liver biopsy,which was 100%successful and provided diagnostic histology for all *** PPG data led to changes in the clinical management of 17 ***:EUS-PPG is safe and technically *** Child-Pugh score did not correlate well with the presence of CSPH;however,PPG measurements resulted in changes in the management of almost all *** studies correlating EUS-PPG with other assessments of liver diseases are required.

关键词： EUS portal hypertension portal pressure gradient

Artificial light at night(ALAN) pollution alters bat lunar chronobiology:insights from broad-scale long-term acoustic monitoring

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Ecological Processes 2024年第01期13卷 176-187页

作者： Han Li Pauline Allen Saige Boris Samantha Lagrama Jade Lyons Christina Mills Pauline Moussi Casey Nichols Carter Tacosik Mc Kenzie Tsaousis Nyzaya Livingston Wilson john f.Grider Kevin A.Parker Matina C.Kalcounis-Rueppell Department of Biology University of Nebraska Omaha Department of Biology University of North Carolina Greensboro Colorado Parks and Wild-life Parker Ecology LLC Department of Biological Sciences University of Alberta

Background The timing of behavior and habitat use of nocturnal animals can be influenced by the lunar cycle in nature. The prevalence of artificial light at night(ALAN) has been recognized as a source of environmental pol-lution. The interaction between ALAN and the lunar cycle on bat behavior is important for understanding anthro-pogenic effects on bats. We utilized a decade(2012–2022) of acoustic monitoring data collected in North Carolina, United States, to investigate the relationship between bat activity, lunar cycle, and light pollution. We examined whether the amount of lunar illumination affected species-specific nightly activity and whether hourly bat activity patterns varied between nights with different moon phases. We further investigated if the relationship between bat activity and the lunar cycle might be altered by light *** We found that seven bat species showed activity variation across nights in relation to the amount of moon illumination when ALAN was absent. In general, bats were less active on full moon nights compared to new moon nights. Light pollution interacted with the bat–lunar relationship in five of the seven species, masking the effect of the lunar cycle. We identified delayed bat activity patterns on nights with a full or waxing moon in seven species, and light pollution altered that pattern in four species. Overall, ALAN was associated with decreased bat activity inde-pendent of lunar cycle *** Our study demonstrated that at a broad spatial scale, ALAN negatively affected many North American temperate bat species and altered their lunar chronobiology. As light pollution is spreading to historically dark areas and habitats, ALAN might couple with other threats, such as the white-nose syndrome or climate change, to cause cascading damage in the environment that depends on ecosystem services such as pest control provided by bats. We argue that further research and conservation actions are needed to mitigate

关键词： Artificial light at night ALAN Bats Chiroptera Chronobiology Light pollution Lunar cycle Moonlight

Managerial perspectives of scaling up robotic-assisted surgery in healthcare systems:A systematic literature review

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Laparoscopic, Endoscopic and Robotic Surgery 2024年第3期7卷 113-122页

作者： Ravichandran Anitha Komattu Chacko john Gnanadhas Jabarethina Sri Ramachandra faculty of Management Sciences Sri Ramachandra Institute of Higher Education and Research(Category-I Deemed to be University)ChennaiIndia

Objectives Robotic-assisted surgery(RAS)is a minimally invasive technique practiced in multiple *** training is essential for the acquisition of RAS *** cost of RAS is considered to be high,which makes it a burden for institutes and unaffordable for *** systematic literature review(SLR)focused on the various RAS training methods applied in different surgical specialties,as well as the cost elements of RAS,and was to summarize the opportunities and challenges associated with scaling up *** An SLR was carried out based on the Preferred Reporting Items for Systematic reviews and Meta-Analyses reporting *** PubMed,EBSCO,and Scopus databases were searched for reports from January 2018 through January ***-text reviews and research articles in the English language from Asia-Pacific countries were *** that outlined training and costs associated with RAS were *** The most common training system is the da Vinci *** simulation technique,which includes dry-lab,wet-lab,and virtual reality training,was found to be a common and important *** cost of RAS encompasses the installation and maintenance costs of the robotic system,the operation theatre rent,personnel cost,surgical instrument and material cost,and other miscellaneous *** synthesis of SLR revealed the challenges and opportunities regarding RAS training and *** The results of this SLR will help stakeholders such as decision-makers,influencers,and end users of RAS to understand the significance of training and cost in scaling up RAS from a managerial *** any healthcare innovation to reach a vast population,cost-effectiveness and standard training are crucial.

关键词： da Vinci system Healthcare Robotic-assisted surgery Robotic surgery Robotic training Robotic surgery cost

What diameter?What height?Influence of measures of average tree size on area-based allometric volume relationships

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forest Ecosystems 2024年第1期11卷 100-109页

作者： Yilin Wang john A.Kershaw Mark J.Ducey Yuan Sun James B.McCarter Integrated forest Mensuration and Systems Analysis Laboratory Faculty of Forestry and Environmental ManagementUniversity of New BrunswickFrederictonNBCanada Department of Natural Resources and the Environment University of New HampshireDurhamNHUSA College of forestry Nanjing Forestry UniversityNanjing210037China Scientific Programmer RayonierYuleeFLUSA

Volume is an important attribute used in many forest management *** from 83 fixed-area plots located in central New Brunswick,Canada,are used to examine how different measures of stand-level diameter and height influence volume prediction using a stand-level variant of Honer's(1967)volume *** density was included in the models(Volume=f(Diameter,Height,Density))choice of diameter measure was more important than choice of height *** density was not included(Volume=f(Diameter,Height)),the opposite was *** models with density included,moment-based estimators of stand diameter and height performed better than all other *** models without density,largest tree estimators of stand diameter and height performed better than other *** overall best equation used quadratic mean diameter,Lorey's height,and density(root mean square error=5.26 m^3·ha^(-1);1.9%relative error).The best equation without density used mean diameter of the largest trees needed to calculate a stand density index of 400 and the mean height of the tallest 400 trees per ha(root mean square error=32.08 m^(3)·ha^(-1);11.8%relative error).The results of this study have some important implications for height subsampling and LiDAR-derived forest inventory analyses.

关键词： Allometric relationships Stand structure Volume estimation Stand-level attributes

Effect of cinnamaldehyde on Rhizopus stolonifer and on the conservation of sweet potato

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food Quality and Safety 2024年第1期8卷 212-225页

作者：陈晨薛智超 Penta Pristijono john B.Golding 陈刚李永新杨虎清 College of food and Health Zhejiang A&F UniversityHangzhouChina Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine Zhejiang A&F UniversityHangzhouChina School of Environmental and Life Sciences University of NewcastleOurimbahNSWAustralia NSW Department of Primary Industries OurimbahNSWAustralia

Objectives:Rhizopus stolonifer,which causes soft rot of sweet potato,has resulted in substantial loss of economy *** and Methods:The antifungal effect and mechanism of cinnamaldehyde(CIN)against *** were explored by biochemical analysis and RNA-sequencing in this research,and the edible quality of CIN-treated sweet potato was ***:The results showed that CIN inhibited the growth of *** and reduced the incidence of soft rot in sweet potato at a minimum inhibitory concentration of 1000μL/*** damage of the cell walls of *** by CIN was associated with the upregulation of *** leakage and malondialdehyde content increased following CIN-treatment,which was correlated with increased reactive oxygen species levels and decreased catalase *** of ERG genes and oxidative stress-related genes following CIN treatment was associated with impaired cell membrane *** mitochondrial structure of *** was damaged by CIN treatment resulting in decreased respiration rates and ATP production,which was correlated with lower expression levels of IDH1,COX4,and ***:Our research suggests that the inhibition of CIN on *** was related to the disruption of its normal gene expression network,and CIN maintained the nutritional and edible quality of sweet *** study provides valuable insights into the antifungal mechanism of CIN on *** and the maintenance of root quality,which contributes to the effcient use of CIN for controlling soft rot in sweet potato.

关键词： Ipomoea batatas soft rot cinnamaldehyde antifungal mechanism transcriptome