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Concurrent multi-scale design optimization of composite frame structures using the Heaviside penalization of discrete material model

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Acta Mechanica Sinica 2016年第3期32卷 430-441页

作者： Jun Yan Zunyi Duan erik Lund Guozhong Zhao Dalian University of Technology Dalian 116024 China Aalborg University 9220 Aalborg Denmark

This paper deals with the concurrent multi-scale optimization design of frame structure composed of glass or carbon fiber reinforced polymer laminates. In the composite frame structure, the fiber winding angle at the micro-material scale and the geometrical parameter of components of the frame in the macro-structural scale are introduced as the independent variables on the two geometrical scales. Considering manufacturing requirements, discrete fiber winding angles are specified for the micro design variable. The improved Heaviside penalization discrete material optimization interpolation scheme has been applied to achieve the discrete optimization design of the fiber winding angle. An optimization model based on the minimum structural compliance and the specified fiber material volume constraint has been established. The sensitivity information about the two geometrical scales design variables are also deduced considering the characteristics of discrete fiber winding angles. The optimization results of the fiber winding angle or the macro structural topology on the two single geometrical scales, together with the concurrent two-scale optimization, is separately studied and compared in the paper. Numerical examples in the paper show that the concurrent multi-scale optimization can further explore the coupling effect between the macro-structure and micro-material of the composite to achieve an ultralight design of the composite frame structure. The novel two geometrical scales optimization model provides a new opportunity for the design of composite structure in aerospace and other industries.

关键词： Composite frame structure Multi-scale optimization Topology optimization Fiber winding angle Structural compliance

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Determination of coefficients of friction for laminated veneer lumber on steel under high pressure loads

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Friction 2021年第2期9卷 367-379页

作者： Michael DORN Karolína HABROVÁ Radek KOUBEK erik SERRANO Department of Building Technology Linnaeus UniversityVäxjö35252Sweden Czech University of Life Sciences Prague-Department of Materials and Engineering Technology Prague 16521Czech Republic Daikin UK The HeightsBrooklandsWeybridgeKT130NYUnited Kingdom Division of Structural Mechanics Lund UniversityLund 22100Sweden

In this study,static coefficients of friction for laminated veneer lumber on steel surfaces were determined *** focus was on the frictional behaviors at different pressure levels,which were studied in combination with other influencing parameters:fiber orientation,moisture content,and surface *** of friction were obtained as 0.10–0.30 for a smooth steel surface and as high as 0.80 for a rough steel *** influenced the measured coefficients of friction,and lower normal pressures yielded higher *** influence of fiber angle was observed to be moderate,although clearly detectable,thereby resulting in a higher coefficient of friction when sliding perpendicular rather than parallel to the *** specimens contained higher coefficients of friction than oven-dry *** results provide realistic values for practical applications,particularly for use as input parameters of numerical simulations where the role of friction is often wrongfully considered.

关键词： laminated veneer lumber(LVL) wood static friction high pressure angle-to-grain moisture content

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MISCIBILITY BEHAVIOR AND PRESSURE DEPENDENCE OF THE SYSTEMS POLYSTYRENE/CYCLOPENTANE AND POLYSTYRENE/1-PHENYLDECANE ACCORDING TO A MODIFIED HOLE THEORY

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Journal of China Textile University(English Edition) 1993年第3期10卷 42-46页

作者：谢涵坤 erik Nies Department of Basic Sciences Center for Polymers and Composites Eindhoven University of TechnologyThe Netherlands

The influence of pressure on miscibility behavior of the systems polystyrene/cyclopentan(?)and polystyrene/1-phenyldecane is studied with a modified hole *** is found that the pres-sure dependence of excess volume is responsible for the different kinds of behavior of these two ***,the excess volume is decomposed into two separatc parts,one from the contri-bution of cell volume expansion and the other from the change of hole fraction,and their relation-ship with pressure dependence of the miscibility behavior is analysed.

关键词： miscibility pressure dependence polystyrene cyclopentane hole theory phenyldecane excess volume.

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Transcriptional Regulation of Nutrient Exchange in Arbuscular Mycorrhizal Symbiosis

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Molecular Plant 2018年第12期11卷 1421-1423页

作者： erik Limpens Rene Geurts Laboratory of Molecular Biology Department of Plant SciencesWageningen UniversityWageningen 6708PBThe Netherlands

Most land plants rely on the symbiosis with arbuscular mycor- rhizal (AM)fungi to acquire sufficient mineral nutrients from soils. Plants host AM fungi inside root cortex cells,where the fungus forms highly branched structures called *** are surrounded by a specialized host membrane across which nutrients are exchanged in a cooperative *** return for mineral nutrients,the fungus obtains sugars and fatty acids from the plant (Luginbuehl and Oldroyd,2017).

关键词： Transcriptional Regulation Nutrient Exchange

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Hybrid High‑Order Methods for the Acoustic Wave Equation in the Time Domain

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Communications on Applied Mathematics and Computation 2022年第2期4卷 597-633页

作者： erik Burman Omar Duran Alexandre Ern Department of Mathematics University College LondonLondon WC1E 6BTUK CERMICS Ecole des Ponts77455 Marne la Vallée Cedex 2France INRIA Paris 75589 ParisFrance

We devise hybrid high-order(HHO)methods for the acoustic wave equation in the time *** frst consider the second-order formulation in *** the Newmark scheme for the temporal discretization,we show that the resulting HHO-Newmark scheme is energy-conservative,and this scheme is also amenable to static condensation at each time *** then consider the formulation of the acoustic wave equation as a frst-order system together with singly-diagonally implicit and explicit Runge-Kutta(SDIRK and ERK)***-SDIRK schemes are amenable to static condensation at each time *** HHO-ERK schemes,the use of the mixed-order formulation,where the polynomial degree of the cell unknowns is one order higher than that of the face unknowns,is key to beneft from the explicit structure of the *** results on test cases with analytical solutions show that the methods can deliver optimal convergence rates for smooth solutions of order O(hk+1)in the H1-norm and of order O(h^(k+2))in the L^(2)-***,test cases on wave propagation in heterogeneous media indicate the benefts of using high-order methods.

关键词： Hybrid high-order methods Wave equation Newmark scheme Runge-Kutta scheme

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Approved HIV reverse transcriptase inhibitors in the past decade

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Acta Pharmaceutica Sinica B 2022年第4期12卷 1567-1590页

作者： Guangdi Li Yali Wang erik De Clercq Hunan Provincial Key Laboratory of Clinical Epidemiology Xiangya School of Public HealthCentral South UniversityChangsha 410078China Rega Institute for Medical Research Department of MicrobiologyImmunology and TransplantationKU LeuvenLeuven B-3000Belgium

HIV reverse transcriptase(RT)inhibitors are the important components of highly active antiretroviral therapies(HAARTs)for anti-HIV treatment and pre-exposure prophylaxis in clinical *** RT inhibitors and their combination regimens have been approved in the past ten years,but a review on their drug discovery,pharmacology,and clinical efficacy is ***,we provide a comprehensive review of RT inhibitors(tenofovir alafenamide,rilpivirine,doravirine,dapivirine,azvudine and elsulfavirine)approved in the past decade,regarding their drug discovery,pharmacology,and clinical efficacy in randomized controlled *** RT inhibitors such as islatravir,MK-8504,MK-8507,MK8583,IQP-0528,and MIV-150 will be also *** development may focus on the new generation of novel antiretroviral inhibitors with higher bioavailability,longer elimination half-life,more favorable side-effect profiles,fewer drug–drug interactions,and higher activities against circulating drug-resistant strains.

关键词： HIV treatment HAART NRTI NNRTI Clinical efficacy

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Proximal Methods with Bregman Distances to Solve VIP on Hadamard Manifolds with Null Sectional Curvature

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Journal of the Operations Research Society of China 2021年第3期9卷 499-523页

作者： erik Alex Papa Quiroz Paulo Roberto Oliveira Universidad Nacional Mayor de San Marcos Universidad Privada del NorteLimaPeru PESC-COPPE Federal University of Rio de JaneiroRio de Janeiro CEP 21941-972Brazil

We present an extension of the proximal point method with Bregman distances to solve variational inequality problems(VIP)on Hadamard manifolds with null sectional *** some natural assumptions,as for example,the existence of solutions of the VIP and the monotonicity of the multivalued vector field,we prove that the sequence of the iterates given by the method converges to a solution of the ***,this convergence is linear or superlinear with respect to the Bregman distance.

关键词： Proximal point methods Hadamard manifolds Bregman distances Variational inequality problems Monotone vector field

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Transition Modelling with the k-Ω Turbulence Model and an Intermittency Transport Equation

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Journal of Thermal Science 2004年第3期13卷 220-225页

作者： Koen LODEFIER Bart MERCI Chris De LANGHE erik DICK Ghent University Dept. of Flow Heat and Combustion Mechanics Sint-Pietersnieuwstraat 41 B-9000 Gent BelgiumGhent University Dept. of Flow Heat and Combustion Mechanics Sint-Pietersnieuwstraat 41 B-9000 Gent BelgiumGhent University Dept. of Flow Heat and Combustion Mechanics Sint-Pietersnieuwstraat 41 B-9000 Gent BelgiumGhent University Dept. of Flow Heat and Combustion Mechanics Sint-Pietersnieuwstraat 41 B-9000 Gent Belgium

In gas turbine engines, laminar-turbulent transition occurs. However, generally, the turbulence models to describe such transition results in too early and too short transition. Combining a turbulence model with a description of intermittency, i.e. the fraction of time the flow is turbulent during the transition phase, can improve it. By letting grow the intermittency from zero to unity, start and evolution of transition can be imposed. In this paper, a method where a dynamic equation of intermittency combining with a two-equation k-ωturbulence model is described. This intermittency factor is a premultiplicator of the turbulent viscosity computed by the turbulence model. Following a suggestion by Menter et al.[1], the start of transition is computed based on local variables.

关键词： bypass transition intermittency SST turbulence model.

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Adaptive Walking Control of Biped Robots Using Online Trajectory Genera- tion Method Based on Neural Oscillators

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Journal of Bionic Engineering 2016年第4期13卷 572-584页

作者： Chengju Liu Danwei Wang erik David Goodman Qijun Chen School of Electronics and Information Engineering Tongji University Shanghai 201804 China School of Electrical and Electronic Engineering Nanyang Technological University Manyang Avenue 639798 Singapore BEACON Center for the Study of Evolution in Action Michigan State University East Lansing 48824 USA

This work concerns biped adaptive walking control on irregular terrains with online trajectory generation. A new trajectory generation method is proposed based on two neural networks. One oscillatory network is designed to generate foot trajectory, and another set of neural oscillators can generate the trajectory of Center of Mass （CoM） online. Using a motion engine, the characteristics of the workspace are mapped to the joint space. The entraining property of the neural oscillators is exploited for adaptive walking in the absence of a priori knowledge of walking conditions. Sensory feedback is applied to modify the gen- erated trajectories online to improve the walking quality. Furthermore, a staged evolutionary algorithm is developed to tune system parameters to improve walking performance. The developed control strategy is tested using a humanoid robot on ir- regular terrains. The experiments verify the success of the presented strategy. The biped robot can walk on irregular terrains with varying slopes, unknown bumps and stairs through autonomous adjustment of its walking patterns.

关键词： biped robot adaptive walking neural oscillator trajectory generation staged evolution algorithm

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Aquatic community structure and stream habitat in a karst agricultural landscape

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Ecological Processes 2022年第1期11卷 155-170页

作者： Neal D.Mundahl erik D.Mundahl Department of Biology and Southeastern Minnesota Water Resources Center Winona State UniversityWinonaMN 55987USA Mundahl Nordic Services Glennallen/McCarthyP.O.Box MXYAlaska 99588USA

Background:Watersheds dominated by agriculture often have significant,negative impacts on local stream habitats and *** study examined stream biota and habitats within an entire stream in a karst agricultural landscape to determine if several decades of watershed conservation and management had reversed the severe degradation caused by poor land use and catastrophic soil erosion during the 1920s and ***:Fish communities and stream habitats were degraded at over half of the 22 stream sites examined,and benthic macroinvertebrate communities were mostly poor throughout the entire *** fish communities were associated with missing or narrow riparian buffers,high percent fine sediments,high embeddedness of coarse sub-strates,and homogeneous run *** communities were dominated by filter-feeding taxa and those adapted to life on or within fine *** sites with wide buffers and influenced by groundwater springs had higher fish community integrity and good to excellent instream ***:Our results suggest that wide riparian buffers and karstic springs may have allowed recovery of some stream reaches,but more extensive buffers and additional soil conservation practices in upland areas likely are necessary to protect most stream segments and their biota from on-going agricultural *** state stream buffer laws instituted after this study resulted in establishment of vegetated buffers at all study sites,which may lead to improved stream habitat and biotic communities in future *** invertebrate community improvement also may require translocation of sensitive taxa from nearby watersheds due to limited dispersal abilities of many species currently absent from the study *** frequency and intensity of storm events and flooding may hinder future recovery of stream habitats and biota.

关键词： Agricultural stream Fish Macroinvertebrates Stream habitats Karst

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