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Deformation,fragmentation and acceleration of a controlled fragmentation charge casing

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

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A Method for the Determination of Turbulence Intensity by Means of a Fast Response Pressure Probe and its Application in a LP Turbine

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Journal of Thermal Science 2012年第1期21卷 21-31页

作者： Davide Lengani Berardo Paradiso andreas Marn Inst. f. Thermal Turbomachinery and Machine Dynamics Graz University of Technology

This paper describes the measurements and the post-processing procedure adopted for the determination of the turbulence intensity in a low pressure turbine (LPT) by means of a single sensor fast response aerodynamic pressure probe. The rig was designed in cooperation with MTU Aero Engines and considerable efforts were put into the adjustment of all relevant model parameters. Blade count ratio, airfoil aspect ratio, reduced massflow, reduced speed, inlet turbulence intensity and Reynolds numbers were chosen to reproduce the full scale LP turbine. Measurements were performed adopting a phase-locked acquisition technique in order to provide the time resolved flow field downstream of the turbine rotor. The total pressure random fluctuations are obtained by selectively filtering, in the frequency domain, the deterministic unsteadiness due to the rotor blades and coherent structures. The turbulence intensity is derived from the inverse Fourier transform and the correlations between total pressure and velocity fluctuations. The determination of the turbulence intensity allows the discussion of the interaction processes between the stator and rotor for engine-representative operating conditions of the turbine.

关键词： Turbulence fast response aerodynamic pressure probe low pressure turbine.

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Evolution and future of laparoscopic colorectal surgery

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World Journal of Gastroenterology 2014年第41期20卷 15119-15124页

作者： andreas M Kaiser Department of Colorectal Surgery Keck School of MedicineUniversity of Southern California

The advances of laparoscopic surgery since the early 1990 s have caused one of the largest technical revolutions in medicine since the detection of antibiotics(1922,Flemming),the discovery of DNA structure(1953,Watson and Crick),and solid organ transplantation(1954,Murray).Perseverance through a rocky start and increased familiarity with the chop-stick surgery in conjunction with technical refinements has resulted in a rapid expansion of the indications for minimally invasive ***-related factors initially contributed to this success and included the improved postoperative recovery and cosmesis,fewer wound complications,lower risk for incisional hernias and for subsequent adhesionrelated small bowel obstructions; the major breakthrough however came with favorable long-term outcomes data on oncological *** future will have to determine the specific role of various technical approaches,define prognostic factors of success and true progress,and consider directing further innovation while potentially limiting approaches that do not add to patient outcomes.

关键词： Laparoscopic Laparoscopy Open surgery Colorectal surgery Colectomy Robot

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Accurate large-scale simulations of siliceous zeolites by neural network potentials

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npj Computational Materials 2022年第1期8卷 1662-1673页

作者： andreas Erlebach Petr Nachtigall LukášGrajciar Department of Physical and Macromolecular Chemistry Charles UniversityHlavova 812800Prague 2Czech Republic

The computational discovery and design of zeolites is a crucial part of the chemical *** highly accurate while computational feasible protocol for identification of hypothetical siliceous frameworks that could be targeted experimentally is a great *** tackle this challenge,we trained neural network potentials(NNP)with the SchNet architecture on a structurally diverse database of density functional theory(DFT)*** database was iteratively extended by active learning to cover not only low-energy equilibrium configurations but also high-energy transition *** demonstrate that the resulting reactive NNPs retain DFT accuracy for thermodynamic stabilities,vibrational properties,as well as reactive and non-reactive phase *** a showcase,we screened an existing zeolite database and revealed>20k additional hypothetical frameworks in the thermodynamically accessible range of zeolite ***,our NNPs are expected to be essential for future high-throughput studies on the structure and reactivity of siliceous zeolites.

关键词： synthesis zeolite zeolites

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Tribology of self-lubricating high performance ATSP,PI,and PEEK-based polymer composites up to 300℃

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Friction 2023年第1期11卷 141-153页

作者： Kian BASHANDEH Pixiang LAN andreas A.POLYCARPOU Department of Mechanical Engineering Texas A&M UniversityCollege StationTexas 77843USA ATSP Innovations Inc.Texas 77055USA

High-performance polymers(HPPs)are increasingly used in different industrial machinery components,particularly for rubbing parts that demand reliable and durable operation at extreme sliding conditions such as elevated temperature environments,where the use of conventional lubricants is not *** current study investigates the role of environmental temperature on the tribological properties of three advanced HPPs,namely aromatic thermosetting copolyester(ATSP),polyimide(PI),and polyether ether ketone(PEEK)based polymer *** experiments were carried out at different environmental temperatures from room temperature up to 300℃,and under dry sliding *** attention was given to the role of temperature on the development of transfer films and its subsequent effect on the tribological *** ATSP composite was recommended as the best performing material,based on the overall tribological performance at all examined operating temperatures.

关键词： aromatic thermosetting copolyester(ATSP) polyimide(PI) polyether ether ketone(PEEK) high temperature tribology transfer film

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Configuration-dependent stretchable all-solid-state supercapacitors and hybrid supercapacitors

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Carbon Energy 2023年第5期5卷 1-47页

作者： Ahmad Amiri Ashley Bruno andreas A.Polycarpou J.Mike Walker’66 Mechanical Engineering Department Texas A&M UniversityCollege StationTexasUSA

Given the rise in the popularity of wearable electronics that are able to deform into desirable configurations while maintaining electrochemical functionality,stretchable and flexible(hybrid)supercapacitors(SCs)have become increasingly of interest as innovative energy storage *** outstanding power density,long lifetime with low capacitance loss,and appropriate energy density,in particular in hybrid cases make them ideal candidates for flexible *** aim of this review paper is to provide an in-depth discussion of these stretchable and flexible SCs ranging from fabrication to electro-mechanical *** review paper begins with a short overview of the fundamentals of charge storage mechanisms and different types of multivalent metal-ion hybrid *** research methods leading up to the current state of these stretchable and flexible SCs are then *** is followed by an in-depth presentation of the challenges associated with the fabrication methods for different *** novel strategies to maximize the elastic and electrochemical properties of stretchable/flexible or quasi-solid-state SCs are classified and the pros and cons associated with each are *** advances in mechanical properties and the expected advancements for the future of these SCs are discussed in the last section.

关键词： 1D fiber-like SCs 2D planar supercapacitors 3D sponge and textile structures flexible/stretchable supercapacitors kirigami/origami-inspired structures

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Dynamic multimedia stream adaptation and rate control for heterogeneous networks

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2006年第z1期7卷 63-69页

作者： SZWABE Andrzej SCHORR andreas HAUCK Franz J. KASSLER andreas J. Poznan University of Technology Poznan 60-965 Poland University of Ulm Ulm 89069 Germany University of Karlstad Karlstad SE-65188 Sweden

Dynamic adaptation of multimedia content is seen as an important feature of next generation networks and pervasive systems enabling terminals and applications to adapt to changes in e.g. context, access network, and available Quality-of-Service(QoS) due to mobility of users, devices or sessions. We present the architecture of a multimedia stream adaptation service which enables communication between terminals having heterogeneous hardware and software capabilities and served by heterogeneous networks. The service runs on special content adaptation nodes which can be placed at any location within the network. The flexible structure of our architecture allows using a variety of different adaptation engines. A generic transcoding engine is used to change the codec of streams. An MPEG-21 Digital Item Adaptation (DIA) based transformation engine allows adjusting the data rate of scalable media streams. An intelligent decision-taking engine implements adaptive flow control which takes into account current network QoS parameters and congestion information. Measurements demonstrate the quality gains achieved through adaptive congestion control mechanisms under conditions typical for a heterogeneous network.

关键词： Stream adaptation, Quality-of-Service (QoS), Heterogeneous networks, Rate control, MPEG-21 DIA

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Discontinuous Galerkin Methods for a Class of Nonvariational Problems

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Communications on Applied Mathematics and Computation 2022年第2期4卷 634-656页

作者： andreas Dedner Tristan Pryer Mathematics Institute University of WarwickCoventry CV47ALUK Department of Mathematical Sciences University of BathBath BA27AYUK

We extend the fnite element method introduced by Lakkis and Pryer(SIAM ***.33(2):786–801,2011)to approximate the solution of second-order elliptic problems in nonvariational form to incorporate the discontinuous Galerkin(DG)*** is done by viewing the“fnite element Hessian”as an auxiliary variable in the *** the fnite element Hessian in a discontinuous setting yields a linear system of the same size and having the same sparsity pattern of the compact DG methods for variational elliptic ***,the system matrix is very easy to assemble;thus,this approach greatly reduces the computational complexity of the discretisation compared to the continuous *** conduct a stability and consistency analysis making use of the unifed frameworkset out in Arnold et al.(SIAM ***.39(5):1749–1779,2001/2002).We also give an a posteriori analysis of the method in the case where the problem has a strong *** analysis applies to any consistent representation of the fnite element Hessian,and thus is applicable to the previous works making use of continuous Galerkin *** evidence is presented showing that the method works well also in a more general setting.

关键词： Nonvariational problems Discontinuous Galerkin Error estimates Adaptivity

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The break-up tendency of long rod projectiles

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Defence Technology（防务技术） 2016年第2期12卷 177-187页

作者： Ewa LIDéN andreas HELTE FOI Swedish Defence Research Agency

A model for the tendency of fragmentation of a long rod projectile subjected to armour components in add-on armours such as reactive armour and active protection systems is presented. The model is based on studies of the interaction between a cylindrical streamlined projectile and moving thin plates(backwards moving like the front plate in a reactive armour panel and forwards moving like the rear plate in a reactive armour panel).The assumption behind the model is that the sliding force, with velocity vslidebetween the projectile and the plate, gives rise to a transverse velocity vtransof the projectile segment it passes, which will deflect the projectile segment. This deflection is assumed to be a major reason for the fractures that can emerge along the projectile. The velocity, geometry and material of the projectile and the plate are of importance for the fragmentation of the projectile and the dimensionless parameterδ? = v trans vslideexpresses how these parameters influence the break-up tendency. Experiments and simulations have verified that the identifiedδ?-parameter predicts an increased amount of fragmentation of the projectile with increasing value of this parameter.

关键词：长杆弹破裂反应装甲趋势模型主动防护系统横向速度无量纲参数附加装甲

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Epithelial restitution and wound healing in inflammatory bowel disease

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World Journal of Gastroenterology 2008年第3期14卷 348-353页

作者： andreas Sturm Axel U Dignass Department of Gastroenterology and Hepatology Charité-Campus Virchow Clinic Berlin Germany Department of Gastroenterology Hepatology Oncology and Metabolic Diseases Markus-Krankenhaus Frankfurt/Main Germany

Inflammatory bowel disease is characterized by a chronic inflammation of the intestinal mucosa. The mucosal epithelium of the alimentary tract constitutes a key element of the mucosal barrier to a broad spectrum of deleterious substances present within the intestinal lumen including bacterial microorganisms, various dietary factors, gastrointestinal secretory products and drugs. In addition, this mucosal barrier can be disturbed in the course of various intestinal disorders including inflammatory bowel diseases. Fortunately, the integrity of the gastrointestinal surface epithelium is rapidly reestablished even after extensive destruction. Rapid resealing of the epithelial barrier following injuries is accomplished by a process termed epithelial restitution, followed by more delayed mechanisms of epithelial wound healing including increased epithelial cell proliferation and epithelial cell differentiation. Restitution of the intestinal surface epithelium is modulated by a range of highly divergent factors among them a broad spectrum of structurally distinct regulatory peptides, variously described as growth factors or cytokines. Several regulatory peptide factors act from the basolateral site of the epithelial surface and enhance epithelial cell restitution through TGF-13-dependent pathways. In contrast, members of the trefoil factor family （TFF peptides） appear to stimulate epithelial restitution in conjunction with mucin glycoproteins through a TGF-13-independent mechanism from the apical site of the intestinal epithelium. In addition, a number of other peptide molecules like extracellular matrix factors and blood clotting factors and also non- peptide molecules including phospholipids~ short-chain fatty acids （SCFA）, adenine nucleotides, trace elements and pharmacological agents modulate intestinal epithelial repair mechanisms. Repeated damage and injury of the intestinal surface are key features of various intestinal disorders including inflammatory bowel disease

关键词： Intestines Wound healing Inflammation Restitution

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