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Modelling ballistic impact on military helmets:The relevance of projectile plasticity

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Defence Technology（防务技术） 2021年第5期17卷 1699-1711页

作者： A.Caçoilo R.Mourao F.Teixeira-Dias A.Azevedo F.Coghe R.A.F.Valente School of Engineering The University of EdinburghEdinburghEH93FGUK dept.weapon systems and ballistics Royal Military AcademyBrusselsBelgium Centre for Mechanical Technology and Automation Department of Mechanical EngineeringUniversity of AveiroPortugal

The need to develop armour systems to protect against attacks from various sources is increasingly a matter of personal,social and national *** develop innovative armour systems it is necessary to monitor developments being made on the type,technology and performance of the threats(weapons,projectiles,explosives,etc.) Specifically,the use of high protection level helmets on the battlefield is *** development of evaluation methods that can predict injuries and trauma is therefore of major ***,the risk of injuries or trauma that can arise from induced accelerations is an additional *** develop new materials and layouts for helmets it is necessary to study the effects caused by ballistic impacts in the human head on various *** use of numerical simulation is a fundamental tool in this *** work here presented focuses on the use of numerical simulation(finite elements analysis) to predict the consequences of bullet impacts on military helmets on human *** main objectives are to assess the level and probability of head trauma using the Head Injury Criterion,caused by the impact of a 9 mm NATO projectile on a PASGT helmet and to quantify the relevance of projectile plasticity on the whole modelling *** accelerations derived from the impact phenomenon and the deformations caused on the helmet are evaluated using fully three-dimensional models of the helmet,head,neck and *** studies are done at impact angles ranging from 0 to 75°.Results are presented and discussed in terms of HIC and probability of acceleration induced trauma *** comparison analyses are done using a rigid and a deformable projectile and it is observed that plastic deformation of the projectile is a significant energy dissipation mechanism in the whole impact process.

关键词： Ballistic impact Helmet impact Plasticity Finite element analysis Injury Trauma HIC

Towards reconstructing the Shakespeare’s first Globe Theatre: A virtual model for research and development

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Frontiers of Architectural Research 2022年第6期11卷 1104-1120页

作者： Paolo Croce Francesco Leccese Mirko Mordagà Giacomo Salvadori dept.of Energy SystemsTerritory and Construction Engineering(DESTeC)School of EngineeringUniversity of PisaPisaItaly dept.of Civil and Industrial Engineering(DICI) School of EngineeringUniversity of PisaPisaItaly

Shakespeare’s first Globe Theatre(early 17th century)is considered one of the most iconic theatres in English history,despite lasting less than twenty years and having little information directly attributable to its shape and *** building,part of a wide variety of Elizabethan theatres found in London during a fertile period in the history of entertainment,has fascinated historians and scholars for *** in Globe Theatre has led to several attempts at reconstruction around the world in recent decades,very few of which are historically reliable due to a lack of accurate sources and the need to adapt a historic building,burnt down in a fire in 1613,to modern safety ***,with the increasing evolution of modelling systems in a virtual environment,it is now possible to analyse the theatre in a spatially and historically more consistent way with surviving *** aim of this paper is to provide a historically and constructively valid virtual model that can reopen the debate on the shapes and dimensions of Shakespeare’s first Globe *** model has been created by collecting the main hypotheses proposed by *** were used to create the basic scheme,the plans,and then the whole ***,the model was made available to encourage its use in future research and development.

关键词： Globe Theatre Historical reconstruction Virtual model Outdoor playhouses Vernacular architecture Timber-framed

赛德西港用于船舶减排的陆上可再生能源供电评估

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哈尔滨工程大学学报（英文版） 2024年第2期23卷 506-524页

作者： Merna Makram Ameen M.Bassam Adel A.Tawfik Waleed Yehia Naval Architecture and Marine Eng.dept. Faculty of EngineeringPort Said UniversityPort Fuad 42526Egypt

Air pollution from shipping is becoming a critical issue,particularly in dense hub port *** proposed solution to minimize ship-based emissions at ports is the implementation of an Onshore Power Supply(OPS)*** allows ships to shut off their auxiliary engines and instead connect to the port *** there have been numerous studies conducted on ports in Europe and the United States,little research has been done on Egyptian ***,this paper aims to investigate the feasibility of implementing OPS at Port Said West Port in Egypt,aligning with Egypt Vision 2030’s goals for addressing climate *** research primarily focuses on analyzing data collected from calling ships to generate socio-economic and cost-effectiveness analyses of *** further enhance the environmental benefits of OPS,the paper proposes the use of solar energy as the OPS electricity *** findings of the study revealed that by relying on the national grid,emissions can be reduced by 28%.Moreover,it is predicted that this reduction could reach 100%if electricity generation is solely based on solar ***,the economic analysis demonstrates promising profitability,with a payback period of approximately two years.

关键词： Onshore power supply Port sustainability Shipping emissions inventory Solar energy Photovoltaic systems

The relationship between controllability, optimal testing resource allocation, and incubation-latent period mismatch as revealed by COVID-19

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Infectious Disease Modelling 2023年第2期8卷 514-538页

作者： Jeffery Demers William F.Fagan Sriya Potluri Justin M.Calabrese Center for Advanced systems Understanding(CASUS) Helmholtz-Zentrum Dresden-Rosendorf(HZDR)G€orlitzGermany dept.of Biology University of MarylandCollege ParkMDUSA dept.of Ecological Modelling Helmholtz Centre for Environmental Research-UFZLeipzigGermany

The severe shortfall in testing supplies during the initial COVID-19 outbreak and ensuing struggle to manage the pandemic have affirmed the critical importance of optimal supplyconstrained resource allocation strategies for controlling novel disease *** address the challenge of constrained resource optimization for managing diseases with complications like pre-and asymptomatic transmission,we develop an integro partial differential equation compartmental disease model which incorporates realistic latent,incubation,and infectious period distributions along with limited testing supplies for identifying and quarantining infected *** model overcomes the limitations of typical ordinary differential equation compartmental models by decoupling symptom status from model compartments to allow a more realistic representation of symptom onset and presymptomatic *** analyze the influence of these realistic features on disease controllability,we find optimal strategies for reducing total infection sizes that allocate limited testing resources between‘clinical’testing,which targets symptomatic individuals,and‘non-clinical’testing,which targets non-symptomatic *** apply our model not only to the original,delta,and omicron COVID-19 variants,but also to generically parameterized disease systems with varying mismatches between latent and incubation period distributions,which permit varying degrees of presymptomatic transmission or symptom onset before *** find that factors that decrease controllability generally call for reduced levels of non-clinical testing in optimal strategies,while the relationship between incubation-latent mismatch,controllability,and optimal strategies is *** particular,though greater degrees of presymptomatic transmission reduce disease controllability,they may increase or decrease the role of nonclinical testing in optimal strategies depending on other disease factors like transmissibility

关键词： Testing quarantine control Optimal resource allocation Presymptomatic transmission Latent period Incubation period Age of infection

Target Capturing in an Ellipsoidal Region for a Swarm of Double Integrator Agents

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IEEE/CAA Journal of Automatica Sinica 2022年第5期9卷 801-811页

作者： Antonio Bono Luigi D'Alfonso Giuseppe Fedele Veysel Gazi IEEE Department of Informatics ModelingElectronics and Systems EngineeringUniversity of CalabriaRende 87036Italy dept.Electrical and Electronics Eng. Faculty of EngineeringMarmara UniversityIstanbul 34722 Department of Control and Automation Engineering Faculty of Electrical and Electronics EngineeringYildiz Technical UniversityEsenler 34220Turkey

In this paper we focus on the target capturing problem for a swarm of agents modelled as double integrators in any finite space *** agent knows the relative position of the target and has only an estimation of its velocity and *** that the estimation errors are bounded by some known values,it is possible to design a control law that ensures that agents enter a user-defined ellipsoidal ring around the moving *** know the relative position of the other members whose distance is smaller than a common detection ***,in the case of no uncertainty about target data and homogeneous agents,we show how the swarm can reach a static configuration around the moving *** simulations are reported to show the effectiveness of the proposed strategy.

关键词： Agents-based systems cooperative control swarms target-capturing

Control of exterior ballistic properties of spin-stabilized bullet by optimizing internal mass distribution

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Defence Technology（防务技术） 2019年第1期15卷 38-50页

作者： Janne Lahti Timo Sailaranta Mikko Harju Kai Virtanen systems Analysis Laboratory Department of Mathematics and Systems AnalysisAalto University Aero RD Ltd systems Analysis Laboratory Department of Mathematics and Systems AnalysisAalto Universit Department of Military Technology National Defence University of Finland

This paper introduces a novel approach for controlling the exterior ballistic properties of spin-stabilized bullets by optimizing their internal mass distributions. Specifically, the properties of interest are the bullets’ stability characteristics that are examined through dynamic and gyroscopic stability *** analytical expressions for aerodynamic quantities are also derived to address the compressibility of air. These expressions are utilized in a bullet model that enables efficient computation of the stability parameters for a given mass distribution. The bullet model is used in the formulation of nonlinear optimization problems that provide optimal mass distributions with respect to given goals, i.e., desired stability characteristics. The bullet types investigated in this paper are a long range bullet and a limited range training bullet. In the optimization of the mass distribution of the long range bullet, the goal is that the bullet stays stable for as long as possible. The mass distribution of the training bullet is optimized such that the bullet is stable at launch but becomes unstable shortly afterwards. The global optimal solutions obtained with the new approach fulfill the desired stability characteristics better than currently used uniformly filled bullets. Overall, the optimization approach reveals a new goal focused philosophy for bullet design compared to current trial and error design practices.

关键词： Aerodynamics Bullet Exterior ballistics Mass properties Optimization Stability

Structural ensemble dynamics based closure model for wall-bounded turbulent flow

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Acta Mechanica Sinica 2009年第5期25卷 731-736页

作者： Zhen-Su She Ning Hu You Wu State Key Laboratory for Turbulence and Complex systems and dept Mechanical and Aerospace Engineering,College of Engineering, Peking University,100871 Beijing, China State Key Laboratory for Turbulence and Complex systems and dept Mechanical and Aerospace Engineering College of Engineering Peking University Beijing China

Wall-bounded turbulent flow involves the development of multi-scale turbulent eddies, as well as a sharply varying boundary layer. Its theoretical descriptions are yet phenomenological. We present here a new framework called structural ensemble dynamics （SED）, which aims at using systematically all relevant statistical properties of turbulent structures for a quantitative description of ensemble means. A new set of closure equations based on the SED approach for a turbulent channel flow is presented. SED order functions are defined, and numerically determined from data of direct numerical simulations （DNS）. Computational results show that the new closure model reproduces accurately the solution of the original Navier-Stokes simulation, including the mean velocity profile, the kinetic energy of the streamwise velocity component, and every term in the energy budget equation. It is suggested that the SED-based studies of turbulent structure builds a bridge between the studies of physical mechanisms of turbulence and the development of accurate model equations for engineering predictions.

关键词： Turbulence Closure equation Channel flow Structural ensemble dynamics

Improved world-based language model

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Journal of Harbin Institute of Technology(New Series) 2004年第1期11卷 114-120页

作者：陈勇 CHAN Kwok-ping dept. of Computer Science and Information systems University of Hong Kong Hong KongChina

In order to construct a good language model used in the postprocessing phase of a recognition system. A smoothing technique must be used to solve the data sparseness problem. In the past, many smoothing techniques have been proposed. Among them, Katz’s smoothing technique is well known. However, we found that a weakness with the Katz’s smoothing technique. We improved this approach by incorporating one kind of special Chinese language information and Chinese word class information into the language model. We tested the new smoothing technique with a Chinese character recognition system. The experimental result showed that a better performance can be achieved.

关键词：汉字识别机器语言语言模型 LM 平滑技术

Deformation,fragmentation and acceleration of a controlled fragmentation charge casing

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Defence Technology（防务技术） 2019年第5期15卷 786-795页

作者： Andreas Helte Olof Andersson Patrik Lundberg FOI Defence and SecuritySystems and Technology

Two different finite element software,LS-DYNA and Impetus,have been evaluated to test their ability to predict the deformation,fragmentation and acceleration of a controlled fragmentation charge *** general-purpose program LS-DYNA was used with a multi-material ALE formulation and a masspreserving erosion criterion coupled to a Johnson-Cook fracture *** the Impetus simulations,a third order Lagrangian element formulation was used for the casing and a node-splitting element erosion treatment coupled to a Cockcroft-Latham failure criterion was used to describe casing *** high-explosive gases were described by a discrete particle *** order to acquire data to validate our computational tools and constitutive models,a series of experiments have been performed using a laboratory charge with an internal grooved *** the test series,the charge geometry was fixed except that the groove depth were varied from very shallow to very deep resulting in different deformation patterns,fracture modes and terminal *** diagnostic tools captured the different stages of the expansion and fragmentation of the casing.A high-speed framing camera depicted the deformation pattern before fragmentation and was used to determine the moment when the casing *** different complementary techniques were used to follow the acceleration of the fragments;a Photon Doppler velocimetry to determine the initial acceleration of the casing,double exposed radiographs to estimate the fragment velocity after break-up and a high-speed video to determine the terminal velocity of the fragment after leaving the *** addition,the fragments were soft recovered in a set of sawdust pit tests and their final shape and weight were measured.A SEM was used to characterise the fracture surfaces and to determine the modus of fracture(tensile or shear failure).Comparisons to experiments show that both software can predict the change in deformation behaviour

关键词： Controlled fragmentation Fracture mechanics LS-DYNA Impetus