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Mass-Stiffness Templates for Cubic Structural Elements Dedicated to Professor Karl Stark Pister for his 95th birthday

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Computer Modeling in Engineering & Sciences 2021年第12期129卷 1209-1241页

作者： carlos A.Felippa Department of Aerospace Engineering Sciences and Aerospace Mechanics Research Center University of Colorado at BoulderBoulderCO 80309-0429USA

1 This paper considers Lagrangian finite elements for structural dynamics constructed with cubic displacement shape *** method of templates is used to investigate the construction of accurate mass-stiffness *** method introduces free parameters that can be adjusted to customize elements according to accuracy and rank-sufficiency ***-and two-dimensional Lagrangian cubic elements with only translational degrees of freedom(DOF)carry two additional nodes on each side,herein called side nodes or *** usually placed at the third-points,the SN location may be adjusted within geometric *** adjustment effect is studied in detail using symbolic computations for a bar *** best SN location is taken to be that producing accurate approximation to the lowest natural frequencies of the continuum *** is investigated through Fourier analysis of the propagation of plane waves over a regular infinite lattice of bar *** is placed on the acoustic branch of the frequency-vs.-wavenumber dispersion *** is found that dispersion results using the fully integrated consistent mass matrix(CMM)are independent of the SN location whereas its lowfrequency accuracy order is O(κ8),whereκis the dimensionless wave *** the diagonally lumped mass matrix(DLMM)constructed through the HRZ scheme,two optimal SN locations are identified,both away from third-points and of accuracy order O(κ8).That with the smallest error coefficient corresponds to the Lobatto 4-point integration rule.A special linear combination of CMM and DLMM with nodes at the Lobatto points yields an accuracy of O(κ10)without any increase in the computational effort over *** effect of reduced integration(RI)on both mass and stiffness matrices is also *** is shown that singular mass matrices can be constructed with 2-and 3-point RI rules that display the same optimal accuracy of the exactly integrated case,at the cost of introducing spurious modes

关键词： Structural dynamics Lagrangian elements finite elements cubic shape functions bar plane stress mass stiffness vibration wave propagation Fourier analysis dispersion templates

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Stability analysis of the fluttering and autorotation of flow-induced rotation of a hinged flat plate

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Journal of Hydrodynamics 2013年第5期25卷 755-762页

作者： MIRZAEISEFAT Sina FERNANDES Antonio carlos Department of Naval Architecture and Marine Engineering University of Michigan COPPE/UFRJ Federal University of Rio de Janeiro

This work describes investigations performed on the interaction of uniform current and freely rotating plate about a fixed vertical axis. Fluttering and autorotation are two different motions that may occur during the flow induced rotation. The dimensional analysis proves that the motion in flow induced rotation motion is governed essentially by the dimensionless moment of inertia and Reynolds number. Certain combinations define the stability boundaries between fluttering and autorotation. Fluttering is oscillation of body about a vertical axis and the autorotation is a name given to the case when the body turns continuously about the vertical axis First, the loads and moment coefficients are calculated by experiments and streamline theory for different angles of attack for a fixed fiat plate. Then for dynamic case, a bifurcation diagram is presented based on experiments to classify different motion states of flow induced rotation. Finally, a dynamical model is proposed for stability analysis of flow induced rotation of a flat plate.

关键词： flow-induced rotation autorotation fluttering stability analysis

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Phenomenological model for torsional galloping of an elastic flat plate due to hydrodynamic loads

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Journal of Hydrodynamics 2014年第1期26卷 57-65页

作者： FERNANDES Antonio carlos ARMANDEI Mohammadmehdi Department of Naval and Ocean Engineering COPPE/UFRJ

This study investigates the torsional galloping phenomenon, an instability type flow-induced oscillation, in an elastic stru-cture due to hydrodynamic loads into the water current. The structure applied here is a rectangular flat plate with an elastic axis in its mid-chord length. The elasticity is provided by torsion spring. The flat plate has only one degree of freedom which is rotation in pure yaw about its axis. It is observed that as the current speed is higher than a critical velocity, the flat plate becomes unstable. The instability leads to torsional galloping occurrence, as a result of which the flat plate begins to yaw about the elastic axis. By testing two different chord lengths each with several torsion spring rates, the flat plate behavior is investigated and three different responses are recognized. Then, a phenomenological model is developed with the original kernel in the form of the van der Pol-Duffing equa-tion. The model explains these three responses observed experimentally.

关键词： torsional galloping flow-induced oscillation phenomenological model van der Pol-Duffing equation

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Optimal Positioning Strategy for Multi-Camera Zooming Drones

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IEEE/CAA Journal of Automatica Sinica 2024年第8期11卷 1802-1818页

作者： Manuel Vargas carlos Vivas Teodoro Alamo Department of System Engineering and Automation University of SevilleSeville 41092Spain

In the context of multiple-target tracking and surveillance applications,this paper investigates the challenge of determining the optimal positioning of a single autonomous aerial vehicle or agent equipped with multiple independently-steerable zooming cameras to effectively monitor a set of targets of *** camera is dedicated to tracking a specific target or cluster of *** key innovation of this study,in comparison to existing approaches,lies in incorporating the zooming factor for the onboard cameras into the optimization *** enhancement offers greater flexibility during mission execution by allowing the autonomous agent to adjust the focal lengths of the onboard cameras,in exchange for varying real-world distances to the corresponding targets,thereby providing additional degrees of freedom to the optimization *** proposed optimization framework aims to strike a balance among various factors,including distance to the targets,verticality of viewpoints,and the required focal length for each *** primary focus of this paper is to establish the theoretical groundwork for addressing the non-convex nature of the optimization problem arising from these *** this end,we develop an original convex approximation *** paper also includes simulations of diverse scenarios,featuring varying numbers of onboard tracking cameras and target motion profiles,to validate the effectiveness of the proposed approach.

关键词： Convex optimization projective transformation unmanned aerial vehicle visual object tracking visual surveillance.

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Bresse Beam with Damping and Logarithmic Source

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Chinese Annals of Mathematics,Series B 2024年第5期45卷 685-702页

作者： Sebastiao CORDEIRO carlos BALDEZ carlos RAPOSO Ducival PEREIRA Octavio VERA Department of Mathematics Federal University of ParaAbaetetubaParaBrazil Department of Mathematics Federal University of ParaBragancaParaBrazil Department of Mathematics Federal University of ParaSalinopolisParaBrazil Department of Mathematics State University of ParaBelemParaBrazil Department of Mathematics University of TarapacaAricaChile

This paper investigates the stabilization of a Bresse system with internal damping and logarithmic *** authors use the potential well *** initial data in the stability set created by the Nehari surface,the existence of a global solution is proved by using Faedo-Galerkin's *** Nakao theorem gives the exponential decay.A numerical approach is presented to illustrate the results obtained.

关键词： Bresse beam Logarithmic source Global solution Exponential decay Numerical approach

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Air Pollution, Government Pollution Regulation, and Industrial Production in China

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Journal of Systems Science & Complexity 2020年第4期33卷 1064-1079页

作者： CAO Dong RAMIREZ carlos D. School of Economics and Management Xidian UniversityXi’an 710071China Department of Economics George Mason UniversityFairfaxVAUnited States

Over the last four decades,a severe deterioration in air quality has accompanied China’s rapid *** a result,the Chinese government has implemented stricter policies and regulation to control air *** this paper,the authors create a measure of government policies on air pollution by tracking all pollution-related government announcements in Chinese *** authors then use this variable,along with measures of actual pollution,to investigate how air pollution,industrial production,and government policies on air pollution are *** authors conduct this investigation nationwide,as well as in five large cities in China.A vector autoregression model suggests that,nationwide,government policies seem to decrease air pollution without significantly affecting industrial ***,the effect appears to be short-lived,dissipating after a few *** addition,the authors find that the dynamic relationship among these variables differs by *** instance,following an adverse air quality shock in Beijing,government efforts to control pollution seem to have an ameliorating city-wide effect,decreasing local air pollution in subsequent *** Shanghai and Guangzhou,while the local government reacts to adverse air pollution shocks,the ameliorating effects are not statistically *** Chengdu and Shenyang,the authors detect no significant local government reaction to adverse air pollution ***,in these cities,local government policies do not impart a statistically measurable effect on air pollution.

关键词： pollution. pollution nationwide

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Shaping digital earth applications through open innovation - setting the scene for a digital earth living lab

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International Journal of Digital Earth 2014年第7期7卷 594-612页

作者： Sven Schade carlos Granell European Commission Joint Research CentreInstitute for Environment and SustainabilityIspraItaly

Science and policy increasingly request for sustainable development and ***,Digital Earth undergoes a paradigm shift to an open platform that actively supports user *** the public becomes able to contribute new content,we recognize a gap in user-driven validation,feedback and requirements capture,and innovative application *** than defining Digital Earth applications top down,we see a need for methods and tools that will help building applications bottom up and driven by community *** should include a technology toolbox of geospatial and environ-mental enablers,which allow to access functional building blocks and content in multiple ways,but-equally important-enable the collaboration within partially unknown stakeholder *** validation and testing in real-life scenarios will be a central requirement when approaching the Digital Earth 2020 goals,which were articulated *** particularly argue to follow a Living Lab approach for co-creation and awareness rising in relation to environmental and geospatial *** explain why and how such a Digital Earth Living Lab could lead to a sustainable approach for developing,deploying,and using Digital Earth applications and suggest a paradigm shift for Virtual Globes becoming forums for research and innovation.

关键词： sustainable development open innovation stakeholder engagement living laboratories governance methodologies virtual globes

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Flow near a model spur dike with a fixed scoured bed

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International Journal of Sediment Research 2013年第3期28卷 349-357页

作者： Roger KUHNLE carlos ALONSO National Sedimentation Laboratory U.S.Department of AgricultureAgricultural Research Service

Three-dimensional flow velocities were measured using an acoustic Doppler velocimeter at a closely spaced grid over a fixed scoured bed with a submerged spur ***-dimensional flow velocities were measured at 3,484 positions around the trapezoidal shaped submerged model spur *** velocity distributions and detailed near field flow structures were revealed by the *** differences were revealed between flow over fixed flat and scoured *** lateral flows were the dominant cause of the observed local *** stresses were higher for the scoured bed than in the flat bed *** rates of scour as the scour hole developed were attributed to increases in critical shear stress in the scour holes caused by the increase in the length and magnitude of adverse slopes associated with the two main scour holes.

关键词： Submerged spur dike 3-dimensional flow Velocity measurements Free surface flow Hydraulic structure

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Successful liver transplantation for acute sickle cell intrahepatic cholestasis: A case report and review of the literature

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World Journal of Hepatology 2020年第3期12卷 108-115页

作者： Motasem Alkhayyat Mohannad Abou Saleh Mohammad Zmaili Vedha Sanghi Tavankit Singh Carol Rouphael C Roberto Simons-linares carlos Romero-Marrero William D Carey Christina C Lindenmeyer Department of Internal Medicine Cleveland ClinicClevelandOH 44195United States Digestive Disease&Surgery Institute Department of GastroenterologyHepatology&NutritionCleveland ClinicClevelandOH 44195United States

BACKGROUND Sickle cell hepatopathy(SCH)is an inclusive term referring to any liver dysfunction among patients with sickle cell *** sickle cell intrahepatic cholestasis is one of the rarest and most fatal presentations of *** present the 23rd reported case of liver transplantation(LT)for SCH;a rare case of acute sickle cell intrahepatic cholestasis managed with LT from a hepatitis C virus(HCV)nucleic acid amplification test positive *** SUMMARY A 29-year-old male with a past medical history of sickle cell disease presented with vaso-occlusive pain *** examination,he had jaundice and a soft,nontender *** he was alert and fully oriented;within 24 h he developed new-onset *** evaluation was notable for hyperbilirubinemia,leukocytosis,anemia,thrombocytopenia,acute kidney injury and elevated international normalized ratio(INR).Imaging by ultrasound and computed tomography scan suggested a cirrhotic liver morphology with no evidence of biliary ductal *** patient was diagnosed with acute sickle cell intrahepatic cholestasis after excluding competing etiologies of acute liver *** underwent LT from an HCV nucleic acid amplification test positive donor 9 d after initial *** liver explant was notable for widespread sinusoidal dilatation with innumerable clusters of sickled red blood cells and *** postoperative day 3,HCV RNA was detectable in the patient's peripheral blood and anti-HCV therapy with glecaprevir/pibrentasvir was initiated on postoperative day *** subsequently achieved sustained virologic response after completing 3 mo of therapy and has been followed clinically for 12 mo *** This case highlights the utility of LT as a viable treatment option for acute sickle cell intrahepatic cholestasis.

关键词： Case report Sickle cell hepatopathy Acute intrahepatic cholestasis Liver transplant Hepatitis C virus Post-operative surveillance

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Modeling the effect of wetting on the mechanical behavior of crushable granular materials

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Geoscience Frontiers 2020年第2期11卷 487-494页

作者： carlos Ovalle Pierre-Yves Hicher Research Institute of Mining and Environment(RIME UQAT-Polytechnique) Department of CivilGeological and Mining EngineeringPolytechnique MontrealQuebecCanada GeM UMR CNRS 6183 Ecole Centrale de NantesFrance

It is well known that the compressibility of crushable granular materials increases with the moisture content,due to the decrease of particle strength in a humid *** existing approach to take into account the effect of grain breakage in constitutive modeling consists in linking the evolution of the grain size distribution to the plastic *** how the material humidity can affect this relationship is not clear,and experimental evidence is quite *** on compression tests on dry and saturated crushable sand recently reported by the present authors,a new non-linear relationship is proposed between the amount of particle breakage and the plastic *** expression contains two parameters:(1)a material constant dependent on the grain characteristics and(2)a constant depending on the wetting condition(in this study,dry or saturated).A key finding is that the relationship does not depend on the stress path and,for a given wetting condition,only one set of parameters is necessary to reproduce the results of isotropic,oedometric,and triaxial compression *** relationship has been introduced into an elastoplastic constitutive model based on the critical state concept with a double yield surface for plastic sliding and *** breakage ratio is introduced into the expression of the elastic stiffness,the critical state line and the hardening compression *** stress-strain computations with the model allow the plastic work to be calculated and,therefore,the evolution of particle crushing can be predicted through the proposed non-linear relationship and reintroduced into the constitutive *** predictions of the experimental results in terms of both stress-strain relationships and breakage ratio were obtained.

关键词： Grain crushing Wetting Constitutive modeling

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