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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

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

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

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

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

On a Strategy to Develop Robust and Simple Tariffs from Motor Vehicle Insurance Data

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Acta Mathematicae Applicatae Sinica 2005年第2期21卷 193-208页

作者： andreas Christmann Department of Statistics University of Dortmund D-44221 Dortmund Germany

Abstract The goals of this paper are twofold: we describe common features in data sets from motor vehicle insurance companies and we investigate a general strategy which exploits the knowledge of such features. The results of the strategy are a basis to develop insurance tariffs. We use a nonparametric approach based on a combination of kernel logistic regression and e-support vector regression which both have good robustness properties. The strategy is applied to a data set from motor vehicle insurance companies.

关键词： Data mining kernel logistic regression robustness statistical machine learning support vector regression

Autonomous vehicles wheel wander: Structural impact on flexible pavements

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Journal of Traffic and Transportation Engineering(English Edition) 2021年第3期8卷 388-398页

作者： Konstantina Georgouli Christina Plati andreas Loizos Department of Transportation Planning and Engineering School of Civil EngineeringNational Technical University of AthensZografou 15773Greece

Autonomous vehicles(AVs), including trucks, are already available and their adoption is coming at a rapid pace. Despite the fact that this new transportation technology will travel on existing pavement infrastructure assets, the study and investigation of the AVs structural impact on pavements has not reached the same level of attention and maturity as other related research areas. Considering the extensive investment on pavement construction and maintenance, the necessity to fully understand these impacts in the long term, is becoming evident. The present paper presents and discusses currently published relevant research and findings on the quantification of the wheel wander potential impact,both negative and positive, offering potential insightful future areas of enquiry to help mold and shape future research for this emerging field. The paper focuses on the impact of the AVs zero lateral wheel wander on both new flexible pavement design and the damage accumulation within existing flexible pavement structures. Other wheel wander distributions(normal, uniform, etc.) are investigated as well. The outcome and findings are that the AVs zero lateral wheel wander has a definable negative structural impact on flexible pavement structures in comparison to current human-driven(non-autonomous) vehicles that tend to follow a normal lateral wheel wander distribution. However, under certain defined conditions(optimal wheel wander distribution), the pavement service life can be potentially extended.

关键词： Road engineering Autonomous vehicles Wheel wander Pavement design Pavement performance

Stop-and-go waves induced by correlated noise in pedestrian models without inertia

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Journal of Traffic and Transportation Engineering(English Edition) 2020年第1期7卷 52-60页

作者： Antoine Tordeux andreas Schadschneider Sylvain Lassarre School of Mechanical Engineering and Safety Engineering University of WuppertalWuppertal 42119Germany Institute for Theoretical Physics University of CologneCologne 50937Germany Engineering of Surface Transportation Networks and Advanced Computing Laboratory French Institute of Science and Technology for TransportDevelopment and NetworksMarne La Vallee E-77447France

Stop-and-go waves are commonly observed in traffic and pedestrian *** most microscopic traffic models,they occur through a phase transition and instability of the homogeneous solution after fine tuning of *** effects are believed to play an important role in this *** this article,we present a novel explanation for stop-and-go waves based on stochastic effects in the absence of *** model used is a first order optimal velocity(OV)model including an additive stochastic noise.A power spectral analysis for single-file pedestrian trajectories highlights the existence of Brownian speed *** use the Ornstein-Uhlenbeck process to describe such a correlated *** introduction of this specific colored noise in the first order OV model allows describing realistic stop-and-go behavior without requiring instabilities or phase transitions,the homogeneous configurations being systematically stochastically *** compare the stochastic model to deterministic unstable OV models and analyze individual speed autocorrelation to describe the nature of the waves in stationary *** apply the approach to pedestrian single-file motion and compare simulation results to real pedestrian *** simulation results are quantitatively very similar to the real *** discuss plausible values for the model parameters and their meaning.

关键词： Transportation engineering Pedestrian single-file motion Stop-and-go dynamics First order microscopic model Brownian noise Simulation

Between plaza and peak: a montological perspective on verticality and urbanization in highland Peru

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Journal of Mountain Science 2023年第10期20卷 2783-2803页

作者： andreas HALLER Domenico BRANCA Deyvis CANO Institute for Interdisciplinary Mountain Research Austrian Academy of SciencesInnsbruck 6020Austria Department of Humanities and Social Sciences University of SassariSassari 07100Italy Programa Académico de Ingeniería Ambiental Universidad de HuánucoHudnuco 10001Peru

Under the influence of concentrated and extended urbanization,Andean cities and the different altitudinal zones of their“hinterlands”are experiencing profound changes in land cover—from the central plazas up to the highest *** complex regional-geographic characteristics of these socioecological systems,such as the vertical complementarity of land use,require a montological perspective on verticality and urbanization:it transcends disciplinary approaches and can be crucial to properly interpret the trajectories of land cover change and formulate hypotheses for future practiceoriented *** trajectories of land cover change characterized altitudinal zones of Andean cities and their surroundings over the last three decades?Are there similarities that allow for the formulation of more general hypotheses?Using the Peruvian cases of Cusco and Huaraz,and combining a traditional altitudinal zonation model of land use in Peru with direct field observations and GIS-based analyses of remotely sensed data from 1991,2001,2011,and 2021,this study identifies the main trajectories of land cover change in the Quechua(>2300–3500 m),Suni(>3500–4000 m),and Puna(>4000–4800 m)regions—and finds insightful similarities between Cusco and Huaraz:(1)an impressive area of built-up land substitutes grassland in the Quechua,which,following regional altitudinal zonation models,is characterized by irrigated and rain-fed cropland;(2)an unexpected expansion of irrigated cropland takes place in the Suni,which,in theory,often lacks irrigation infrastructure and is mostly used for rain-fed tuber cultivation;and(3)a clear change from“other land”to grassland occurs in the Puna—where grassland is thought to predominate,anyway,since pre-Hispanic *** that these changes reflect the interplay between speculative fallow,agricultural intensification,and ecological restoration,the results can be read as vertically complementary,local manifestations of concentrated and extended urba

关键词： Mountain cities Mountain agriculture Land use change Land cover change Rural-urban linkages Montology