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Structural metamaterials with negative mechanical/thermomechanical indices: A review

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Progress in Natural Science:Materials International 2021年第6期31卷 801-808页

作者： Jo?o o.Cardoso Jo?o Paulo Borges Alexandre Velhinho CENIMAT/i3N Departamento de Ciência dos Materiais Faculdade de Ciências e Tecnologia Universidade Nova de Lisboa

Structural metamaterials presenting negative values of one or more mechanical and thermomechanical indices–namely the Poisson's ratio, the linear compressibility, and the coefficient of thermal expansion – are the promising candidates to the applications in many fields, ranging from precision mechanics to biomedical devices or energy absorption. Although scattered mentions may be found in the literature since the late eighties of 20th century, the systematic research efforts concerning these materials became effective much later. The present work is to review the main scientific contributions to the topic in the last five years. This paper first deals with those metamaterials showing a single negative index, and then proceeds to analyze the much less frequent instances of coupled negative indices, with emphasis on the so-called anepectic case, which exhibits an unusual thermomechanical response.

关键词： Mechanical and thermomechanical metamaterials Auxetic Anepectic Negative Poisson's ratio Negative thermal expansion Negative linear compressibility

Theoretical and Experimental Investigation of Driver Noncooperative-Game Steering Control Behavior

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IEEE/CAA Journal of Automatica Sinica 2021年第1期8卷 189-205页

作者： Xiaoxiang Na david Cole the Department of Engineering University of CambridgeCambridge CB21PZUK

This paper investigates two noncooperative-game strategies which may be used to represent a human driver's steering control behavior in response to vehicle automated steering *** first strategy,namely the Nash strategy is derived based on the assumption that a Nash equilibrium is reached in a noncooperative game of vehicle path-following control involving a driver and a vehicle automated steering *** second one,namely the Stackelberg strategy is derived based on the assumption that a Stackelberg equilibrium is reached in a similar context.A simulation study is performed to study the differences between the two proposed noncooperativegame *** experiment using a fixed-base driving simulator is carried out to measure six test drivers'steering behavior in response to vehicle automated steering *** Nash strategy is then fitted to measured driver steering wheel angles following a model identification *** weight parameters involved in the Nash strategy are *** is found that the proposed Nash strategy with the identified control weights is capable of representing the trend of measured driver steering behavior and vehicle lateral *** is also found that the proposed Nash strategy is superior to the classic driver steering control strategy which has widely been used for modeling driver steering control over the past.A discussion on improving automated steering control using the gained knowledge of driver noncooperative-game steering control behavior was made.

关键词： Driver experiment model identification noncooperative game steering control strategy vehicle

Use of tree species by three species of Magicicada(Hemiptera:Cicadidae)in an Appalachian forest

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Journal of Forestry Research 2023年第6期34卷 2051-2063页

作者： Cindy Perkovich david Ward Department of Biology and Toxicology Ashland UniversityAshlandOH 44805USA Department of Biological Sciences Kent State UniversityKentOH 44242USA

Periodical cicadas(Magicicada spp.)are endemic to deciduous forests in the eastern United *** successional forests,they must partition resources such as host trees to *** measured tree size,emergence holes,oviposition scar bundles,and chorusing center abundances of Magicicada species on 12 common tree species in a deciduous forest to understand host-tree *** predicted that the abundance of periodical cicadas and use of specific host-tree species would change depending on the Magicicada species and tree life *** considered the size of the tree(diameter at breast height)as a covariate to control for tree size and collected eggs for a greenhouse experiment to assess whether nymphs prefer to feed on Quercus rubra or Acer *** emergence holes were found below Quercus species than any other tree *** abundance of periodical cicadas on host trees used for chorusing centers varied depending on the Magicicada species,but were most abundant on Quercus *** scar bundles were also more frequent on *** nymphs were found on Quercus than Acer in the nymph preference *** periodical cicadas used Quercus hosts more than other tree species,their abundances on different host tree sizes and species differed *** cicada species may use specific host species and life stages as a way to partition resources and minimize competition among the Magicicada species during emergence years.

关键词： Ecological succession Habitat partitioning Periodical cicadas Successional forests

on CAP Representations for Even orthogonal Groups I:A Correspondence of Unramified Representations

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Chinese Annals of Mathematics,Series B 2015年第4期36卷 485-522页

作者： david GINZBURG Dihua JIANG david SoUDRY School of Mathematical Sciences Sackler Faculty of Exact Sciences Tel-Aviv University School of Mathematics University of Minnesota

The authors prove the local unramified correspondence for a new type of construction of CAP representations of even orthogonal groups by a generalized automorphic descent method. This method is expected to work for al... 详细信息

关键词： Automorphic representations Fourier coefficients Satake parametertransfer

A methodological framework for improving air quality monitoring network *** to environment management

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Journal of Environmental Sciences 2021年第4期33卷 138-147页

作者： david Galán-Madruga Department of Atmospheric Pollution National Center for Environment HealthHealth Institute Carlos IIICtra.Majadahonda a Pozuelo km 2228220 MadridSpain

This work aims to provide a methodology framework which allows to improve the performance and efficiency of an air quality monitoring network(AQMN).It requires to be constituted by a minimum and reliable number of measurement ***,the AQMN efficiency should be assessed over time,as a consequence of the possible emergence of new emission sources of air pollutants,which could lead to variations on their spatial distribution within the target ***_(10)particles data monitored by the Community of Madrid's(Spain)AQMN between 2008 and 2017 were used to develop a methodology to optimize the AQMN *** annual spatial distribution of average PM_(10)levels over the studied period monitored by all current stations vs those more representative was provided by a geographic information system(GIS),and the percentage of similarity between both postulates was quantified using simple linear regression(>95%).As one innovative tool of this study,the practical application of the proposed methodology was validated using PM_(10)particles data measured by AQMN during 2007 and 2018,reaching a similitude degree higher than 95%.The influence of temporal variation on the proposed methodological framework was around 20%.The proposed methodology sets criteria for identifying non-redundant stations within AQMN,it is also able to appropriately assess the representativeness of fixed monitoring sites within an AQMN and it complements the guidelines set by European legislation on air pollutants monitoring at fixed stations,which could help to tackle efforts to improve the air quality management.

关键词： Air quality Ambient air monitoring network PM_(10)particles Redundant stations optimization Environment management

on Inherent Irreversibility in a Reactive Hydromagnetic Channel Flow

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Journal of Thermal Science 2010年第1期19卷 72-79页

作者： o.D.Makinde o.Anwar Bég Faculty of Engineering Cape Peninsula University of TechnologyP.O.Box 1906Bellville 7535South Africa. Mechanical Engineering Department Harmer BuildingSheffield Hallam UniversitySheffieldS1 1WB EnglandUK.

This study is devoted to investigate the inherent irreversibility and thermal stability in a reactive electrically conducting fluid flowing steadily through a channel with isothermal walls under the influence of a transversely imposed magnetic *** a perturbation method coupled with a special type of Hermite-Pade' approximation technique,the simplified governing non-linear equation is solved and the important properties of overall flow structure including velocity field,temperature field and thermal criticality conditions are derived which essentially expedite to obtain expressions for volumetric entropy generation numbers,irreversibility distribution ratio and the Bejan number in the flow field.

关键词： Hydromagnetic channel flow Entropy analysis Thermal criticality Arrhenius kinetics Hermite-Pade approximants

Numerical analysis for the prediction of bump prone conditions:A southern Appalachian pillar coal bump case study

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International Journal of Mining Science and Technology 2021年第1期31卷 75-81页

作者： Christopher Newman david Newman Appalachian Mining&Engineering Inc.LexingtonKY 40503USA

Two miners were fatally injured when a pillar bump occurred during retreat mining in a southern West Virginia coal *** mine was operating in the Eagle seam with overmining in the No.2 Gas and Powellton seams.A coal bump is defined as a sudden and violent failure of coal caused by the release of stored strain energy in the *** significant strides have been made by academia,industry,and regulatory agencies to better understand bump conditions and mitigation techniques,coal bumps represent a long standing,highly site-specific engineering problem in which the exact failure mechanism is not clearly *** this case history,a cut-by-cut analysis of retreat mining operations was conducted on the 4 East Main leading up to the pillar bump *** input parameters were derived from site-specific geologic information and mine geometry for the analysis of pillar stress conditions and energy release using *** overview of stress conditions in the panel was presented including a precursor event that occurred two crosscuts inby the bump *** methodology presented in the paper for the evaluation of the fatal bump event can be used for the identification of bump prone conditions prior to development and retreat of a mining area.

关键词： Bump Burst Coal Energy release rate LaModel Numerical modeling

Meta-analysis reveals that reproductive strategies are associated with sexual differences in oxidative balance across vertebrates

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Current Zoology 2018年第1期64卷 1-11页

作者： david CoSTANTINI UMR 7221 Museum National d'Histoire Naturelle 7 rue Cuvier 75231 Paris Cedex 05 France Department of Evolutionary Ecology Leibniz Institute for Zoo and Wildlife Research Alfred-Kowalke-Str. 17 Berlin 10315 Germany Behavioural Ecology & Ecophysiology Group Department of Biology University of Antwerp Universiteitsplein 1 Wilrijk 2610 Belgium

oxidative stress is a key physiological mechanism underlying life-history tradeoffs. Here, I use meta-analytic techniques to test whether sexual differences in oxidative balance are common in vertebrates and to identify which factors are associated with such differences. The dataset included 732 effect size estimates from 100 articles （82 species）. Larger unsigned effect size （meaning larger sexual differences in a given marker） occurred in： reptiles and fish; those species that do not pro- vide parental care; and oviparous species. Estimates of signed effect size （positive values meaning higher oxidative stress in males） indicated that females were less resistant to oxidative stress than males in： reptiles while males and females were similar in fish, birds, and mammals; those species that do not provide parental care; and oviparous species. There was no evidence for a significant sexual differentiation in oxidative balance in fish, birds, and mammals. Effect size was not associ- ated with： the number of offspring; whether the experimental animals were reproducing or not; biomarker （oxidative damage, non-enzymatic, or enzymatic antioxidant）, the species body mass; the strain （wild vs. domestic）; or the study environment （wild vs. captivity）. oxidative stress tended to be higher in females than males across most of the tissues analyzed. Levels of residual heterogeneity were high in all models tested. The findings of this meta-analysis indicate that diversification of reproductive strategies might be associated with sexual differences in oxidative balance. This explorative meta-analysis offers a starting platform for future research to investigate the rela-tionship between sex and oxidative balance further.

关键词： antioxidants oviparity oxidative damage parental care vertebrates viviparity.

The Two Hyperplane Conjecture

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Acta Mathematica Sinica,English Series 2019年第6期35卷 728-748页

作者： david JERISoN Department of Mathematics Massachusetts Institute of Technology

We introduce a conjecture that we call the Two Hyperplane Conjecture, saying that an isoperimetric surface that divides a convex body in half by volume is trapped between parallel hyperplanes. The conjecture is motivated by an approach we propose to the Hots Spots Conjecture of J. Rauch using deformation and Lipschitz bounds for level sets of eigenfunctions. We will relate this approach to quantitative connectivity properties of level sets of solutions to elliptic variational problems, including isoperimetric inequalities, Poincar′e inequalities, Harnack inequalities, and NTA(non-tangentially accessibility). This paper mostly asks questions rather than answering them, while recasting known results in a new light. Its main theme is that the level sets of least energy solutions to scalar variational problems should be as simple as possible.

关键词： Minimal surfaces isoperimetric elliptic variational problems hot spots conjecture