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Sample records for accommodate multibody dynamics

  1. Modelling Hermetic Compressors Using Different Constraint Equations to Accommodate Multibody Dynamics and Hydrodynamic Lubrication

    DEFF Research Database (Denmark)

    Estupinan, Edgar Alberto; Santos, Ilmar

    2009-01-01

    In this work, the steps involved for the modelling of a reciprocating linear compressor are described in detail. The dynamics of the mechanical components are described with the help of multibody dynamics (rigid components) and finite elements method (flexible components). Some of the mechanical ...... forces among machine components, looking for the optimization and application of active lubrication towards vibration reduction....

  2. Conference on Multibody Dynamics

    CERN Document Server

    Multibody Dynamics : Computational Methods and Applications

    2014-01-01

    By having its origin in analytical and continuum mechanics, as well as in computer science and applied mathematics, multibody dynamics provides a basis for analysis and virtual prototyping of innovative applications in many fields of contemporary engineering. With the utilization of computational models and algorithms that classically belonged to different fields of applied science, multibody dynamics delivers reliable simulation platforms for diverse highly-developed industrial products such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, smart structures, biomechanical applications and nano-technologies. The chapters of this volume are based on the revised and extended versions of the selected scientific papers from amongst 255 original contributions that have been accepted to be presented within the program of the distinguished international ECCOMAS conference. It reflects state-of-the-art in the advances of multibody dynamics, providing excellent insight in the recen...

  3. Substructured multibody molecular dynamics.

    Energy Technology Data Exchange (ETDEWEB)

    Grest, Gary Stephen; Stevens, Mark Jackson; Plimpton, Steven James; Woolf, Thomas B. (Johns Hopkins University, Baltimore, MD); Lehoucq, Richard B.; Crozier, Paul Stewart; Ismail, Ahmed E.; Mukherjee, Rudranarayan M. (Rensselaer Polytechnic Institute, Troy, NY); Draganescu, Andrei I.

    2006-11-01

    We have enhanced our parallel molecular dynamics (MD) simulation software LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator, lammps.sandia.gov) to include many new features for accelerated simulation including articulated rigid body dynamics via coupling to the Rensselaer Polytechnic Institute code POEMS (Parallelizable Open-source Efficient Multibody Software). We use new features of the LAMMPS software package to investigate rhodopsin photoisomerization, and water model surface tension and capillary waves at the vapor-liquid interface. Finally, we motivate the recipes of MD for practitioners and researchers in numerical analysis and computational mechanics.

  4. Multibody dynamics with unilateral contacts

    CERN Document Server

    Pfeiffer, Friedrich

    2008-01-01

    As mechanical systems become more complex so do the mathematical models and simulations used to describe the interactions of their parts. One area of multibody theory that has received a great deal of attention in recent years is the dynamics of multiple contact situations occurring in continuous joints and couplings. Despite the rapid gains in our understanding of what occurs when continuous joints and couplings interact, until now there were no books devoted exclusively to this intriguing phenomenon. Focusing on the concerns of practicing engineers, Multibody Dynamics with Unilateral Contact

  5. Multibody dynamic simulation of knee contact mechanics.

    Science.gov (United States)

    Bei, Yanhong; Fregly, Benjamin J

    2004-11-01

    Multibody dynamic musculoskeletal models capable of predicting muscle forces and joint contact pressures simultaneously would be valuable for studying clinical issues related to knee joint degeneration and restoration. Current three-dimensional multibody knee models are either quasi-static with deformable contact or dynamic with rigid contact. This study proposes a computationally efficient methodology for combining multibody dynamic simulation methods with a deformable contact knee model. The methodology requires preparation of the articular surface geometry, development of efficient methods to calculate distances between contact surfaces, implementation of an efficient contact solver that accounts for the unique characteristics of human joints, and specification of an application programming interface for integration with any multibody dynamic simulation environment. The current implementation accommodates natural or artificial tibiofemoral joint models, small or large strain contact models, and linear or nonlinear material models. Applications are presented for static analysis (via dynamic simulation) of a natural knee model created from MRI and CT data and dynamic simulation of an artificial knee model produced from manufacturer's CAD data. Small and large strain natural knee static analyses required 1 min of CPU time and predicted similar contact conditions except for peak pressure, which was higher for the large strain model. Linear and nonlinear artificial knee dynamic simulations required 10 min of CPU time and predicted similar contact force and torque but different contact pressures, which were lower for the nonlinear model due to increased contact area. This methodology provides an important step toward the realization of dynamic musculoskeletal models that can predict in vivo knee joint motion and loading simultaneously.

  6. Multibody system dynamics, robotics and control

    CERN Document Server

    Gerstmayr, Johannes

    2013-01-01

    The volume contains 19 contributions by international experts in the field of multibody system dynamics, robotics and control. The book aims to bridge the gap between the modeling of mechanical systems by means of multibody dynamics formulations and robotics. In the classical approach, a multibody dynamics model contains a very high level of detail, however, the application of such models to robotics or control is usually limited. The papers aim to connect the different scientific communities in multibody dynamics, robotics and control. Main topics are flexible multibody systems, humanoid robots, elastic robots, nonlinear control, optimal path planning, and identification.

  7. Multibody systems and robot dynamics

    OpenAIRE

    Schiehlen, Werner

    1990-01-01

    The method of multibody system has been developed during the last two decades with application to various engineering topics, including robotics and walking machines. On the other hand, special algorithms for robot dynamics are available featuring the high computational efficiency required for control purposes. This paper shows the close relation between both approaches. Essential criteria for the effeciency of dynamics software are the numbers of coordinates used, which should be minimal. Fo...

  8. Numerical methods in multibody dynamics

    CERN Document Server

    Eich-Soellner, Edda

    1998-01-01

    Today computers play an important role in the development of complex mechanical systems, such as cars, railway vehicles or machines. Efficient simulation of these systems is only possible when based on methods that explore the strong link between numerics and computational mechanics. This book gives insight into modern techniques of numerical mathematics in the light of an interesting field of applications: multibody dynamics. The important interaction between modeling and solution techniques is demonstrated by using a simplified multibody model of a truck. Different versions of this mechanical model illustrate all key concepts in static and dynamic analysis as well as in parameter identification. The book focuses in particular on constrained mechanical systems. Their formulation in terms of differential-algebraic equations is the backbone of nearly all chapters. The book is written for students and teachers in numerical analysis and mechanical engineering as well as for engineers in industrial research labor...

  9. ECCOMAS Thematic Conference on Multibody Dynamics

    CERN Document Server

    Multibody Dynamics : Computational Methods and Applications

    2016-01-01

    This book includes selected papers from the ECCOMAS Thematic Conference on Multibody Dynamics, that took place in Barcelona, Spain, from June 29 to July 2, 2015. By having its origin in analytical and continuum mechanics, as well as in computer science and applied mathematics, multibody dynamics provides a basis for analysis and virtual prototyping of innovative applications in many fields of contemporary engineering. With the utilization of computational models and algorithms that classically belonged to different fields of applied science, multibody dynamics delivers reliable simulation platforms for diverse highly-developed industrial products such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, smart structures, biomechanical systems,and nanotechnologies.

  10. Contact force models for multibody dynamics

    CERN Document Server

    Flores, Paulo

    2016-01-01

    This book analyzes several compliant contact force models within the context of multibody dynamics, while also revisiting the main issues associated with fundamental contact mechanics. In particular, it presents various contact force models, from linear to nonlinear, from purely elastic to dissipative, and describes their parameters. Addressing the different numerical methods and algorithms for contact problems in multibody systems, the book describes the gross motion of multibody systems by using a two-dimensional formulation based on the absolute coordinates and employs different contact models to represent contact-impact events. Results for selected planar multibody mechanical systems are presented and utilized to discuss the main assumptions and procedures adopted throughout this work. The material provided here indicates that the prediction of the dynamic behavior of mechanical systems involving contact-impact strongly depends on the choice of contact force model. In short, the book provides a comprehens...

  11. Earth system multi-body restriction dynamics model research

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Qingxian; BI; Siwen; GONG; Huili

    2006-01-01

    Research provides a theoretical basis for an Earth system multi-body mechanics model and its dynamics, including the Earth system multi-body restriction function and its power, Earth system multi-body restriction under decreasing generalized velocity and decreasing partial palstance, the Earth system multi-body decreasing generalized force, a moving mechanics function, and the Earth system multi-body restriction's wattful and wattless forces.

  12. Dynamics and control of underactuated multibody spacecraft

    Science.gov (United States)

    Cho, Sangbum

    In this dissertation, we develop equations of motion for a class of multibody spacecraft consisting of a rigid base body and multiple rigid appendages connected to the base body. There has been much prior research on this topic; however, much of this research is not appropriate for nonlinear control design purposes. The motion of a multibody spacecraft is described by the position and attitude of a base body in an inertial frame and by the relative position and attitude of the attached bodies with respect to the base body; these latter quantities define the shape of the multibody spacecraft. Our aim is to develop equations of motion that reveal important nonlinear coupling effects between the translation, rotation and shape dynamics, but are simple enough for control design purposes. A rotation matrix is used to represent the attitude of the spacecraft. This allows us to avoid complexity related to the use of parameter representations such as Euler angles. Hamilton's variational principle gives three sets of nonlinear equations of motion. The latter part of this dissertation presents results of control problems for several underactuated multibody spacecraft examples. These include spacecraft with an unactuated internal sliding mass, spacecraft with unactuated fuel slosh dynamics, tethered spacecraft with attachment point actuation and the triaxial attitude control testbed with two proof mass actuation devices. These examples illustrate important features related to the dynamics and control of various underactuated multibody spacecraft. Differences in geometries of the spacecraft and gravitational assumptions require adoption of different types of control schemes. We use the multibody equations in this dissertation to formulate control equations for the models and to construct feedback controllers that achieves asymptotic stability (or convergence) to the desired (relative) equilibrium manifolds. Computer simulations demonstrate the effectiveness of the controllers.

  13. ECCOMAS Thematic Conference on Multibody Dynamics

    CERN Document Server

    Fisette, Paul; Multibody Dynamics : Computational Methods and Applications

    2013-01-01

    This volume provides the international multibody dynamics community with an up-to-date view on the state of the art in this rapidly growing field of research which now plays a central role in the modeling, analysis, simulation and optimization of mechanical systems in a variety of fields and for a wide range of industrial applications. This book contains selected contributions delivered at the ECCOMAS Thematic Conference on Multibody Dynamics, which was held in Brussels, Belgium and organized by the Université catholique de Louvain, from 4th to 7th July 2011.  Each paper reflects the State-of-Art in the application of Multibody Dynamics to different areas of engineering. They are enlarged and revised versions of the communications, which were enhanced in terms of self-containment and tutorial quality by the authors. The result is a comprehensive text that constitutes a valuable reference for researchers and design engineers which helps to appraise the potential for the application of multibody dynamics meth...

  14. Planar multibody dynamics formulation, programming and applications

    CERN Document Server

    Nikravesh, Parviz E

    2007-01-01

    Introduction Multibody Mechanical Systems Types of Analyses Methods of Formulation Computer Programming Application Examples Unit System Remarks Preliminaries Reference Axes Scalars and Vectors Matrices Vector, Array, and Matrix Differentiation Equations and Expressions Remarks Problems Fundamentals of Kinematics A Particle Kinematics of a Rigid Body Definitions Remarks Problems Fundamentals of Dynamics Newton's Laws of Motion Dynamics of a Body Force Elements Applied Forces Reaction Force Remarks Problems Point-Coordinates: Kinematics Multipoint

  15. NONLINEAR DYNAMIC ANALYSIS OF FLEXIBLE MULTIBODY SYSTEM

    Institute of Scientific and Technical Information of China (English)

    A.Y.T.Leung; WuGuorong; ZhongWeifang

    2004-01-01

    The nonlinear dynamic equations of a multibody system composed of flexible beams are derived by using the Lagrange multiplier method. The nonlinear Euler beam theory with inclusion of axial deformation effect is employed and its deformation field is described by exact vibration modes. A numerical procedure for solving the dynamic equations is presented based on the Newmark direct integration method combined with Newton-Raphson iterative method. The results of numerical examples prove the correctness and efficiency of the method proposed.

  16. Flexible joints in structural and multibody dynamics

    OpenAIRE

    O. A. Bauchau; Han, S.

    2013-01-01

    Flexible joints, sometimes called bushing elements or force elements, are found in all structural and multibody dynamics codes. In their simplest form, flexible joints simply consist of sets of three linear and three torsional springs placed between two nodes of the model. For infinitesimal deformations, the selection of the lumped spring constants is an easy task, which can be based on a numerical simulation of the joint or on experimental measurements. If the joint undergoes finite deformat...

  17. Elastic Multibody Dynamics A Direct Ritz Approach

    CERN Document Server

    Bremer, H

    2008-01-01

    This textbook is an introduction to and exploration of a number of core topics in the field of applied mechanics: On the basis of Lagrange's Principle, a Central Equation of Dynamics is presented which yields a unified view on existing methods. From these, the Projection Equation is selected for the derivation of the motion equations of holonomic and of non-holonomic systems. The method is applied to rigid multibody systems where the rigid body is defined such that, by relaxation of the rigidity constraints, one can directly proceed to elastic bodies. A decomposition into subsystems leads to a minimal representation and to a recursive representation, respectively, of the equations of motion. Applied to elastic multibody systems one obtains, along with the use of spatial operators, a straight-on procedure for the interconnected partial and ordinary differential equations and the corresponding boundary conditions. The spatial operators are eventually applied to a RITZ series for approximation. The resulting equ...

  18. Constraint Embedding Technique for Multibody System Dynamics

    Science.gov (United States)

    Woo, Simon S.; Cheng, Michael K.

    2011-01-01

    Multibody dynamics play a critical role in simulation testbeds for space missions. There has been a considerable interest in the development of efficient computational algorithms for solving the dynamics of multibody systems. Mass matrix factorization and inversion techniques and the O(N) class of forward dynamics algorithms developed using a spatial operator algebra stand out as important breakthrough on this front. Techniques such as these provide the efficient algorithms and methods for the application and implementation of such multibody dynamics models. However, these methods are limited only to tree-topology multibody systems. Closed-chain topology systems require different techniques that are not as efficient or as broad as those for tree-topology systems. The closed-chain forward dynamics approach consists of treating the closed-chain topology as a tree-topology system subject to additional closure constraints. The resulting forward dynamics solution consists of: (a) ignoring the closure constraints and using the O(N) algorithm to solve for the free unconstrained accelerations for the system; (b) using the tree-topology solution to compute a correction force to enforce the closure constraints; and (c) correcting the unconstrained accelerations with correction accelerations resulting from the correction forces. This constraint-embedding technique shows how to use direct embedding to eliminate local closure-loops in the system and effectively convert the system back to a tree-topology system. At this point, standard tree-topology techniques can be brought to bear on the problem. The approach uses a spatial operator algebra approach to formulating the equations of motion. The operators are block-partitioned around the local body subgroups to convert them into aggregate bodies. Mass matrix operator factorization and inversion techniques are applied to the reformulated tree-topology system. Thus in essence, the new technique allows conversion of a system with

  19. An Earth multi-body system elasticity and plasticity dynamics model

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qingxian; BI Siwen; GONG Huili

    2006-01-01

    Research on the elasticity and plasticity dynamics of the Earth multi-body system, including the Earth multi-body system stratum-block's equivalent inertia force system and generalized inertia force, the Earth multi-body system stratum-block's equivalent inertia force system expressed with partial velocity and partial palstance, and Earth multi-body system generalized inertia force expressed with partial velocity and partial palstance. This research provides a theoretical foundation for further investigation of Earth multi-body dynamics.

  20. Multibody system dynamics and mechatronics. Plenary lecture

    Energy Technology Data Exchange (ETDEWEB)

    Hiller, M.H.; Hirsch, K. [Duisburg-Essen Univ., Duisburg (Germany). Faculty of Engineering

    2006-02-15

    Mechatronics as an interdisciplinary combination of domains of mechanical engineering, electrical engineering, electronics, and computer science has developed in industry and universities since the eighties of the last century, and it is meanwhile fully established in many technical areas. The main focus of the mechatronic approach is to extend and to complete the design process of mechanical and more general engineering systems by incorporating from the very beginning sensors and controllers - which includes also the required information processing - and thus being able to generate partly intelligent products. The components and modules of such systems originate from mechanical engineering, from electrical engineering or from other engineering domains. Methods for describing and designing these components and modules are based in the fields of applied mechanics, electrical engineering, system theory, control and automation theory, and information processing. In particular, in mechatronic systems like robots, manipulation systems, machine tools, or all kinds of vehicles, the multibody systems approach offers a powerful tool to model the mechanical properties of the system in an appropriate manner. In this paper, methodologies for the development of formalisms and software for modeling and simulation of multibody and mechatronic systems will be presented and illustrated by examples from automotive systems and robotics. (orig.)

  1. Isogeometric shell discretizations for flexible multibody dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Goyal, Anmol, E-mail: goyal@mathematik.uni-kl.de; Doerfel, Michael R., E-mail: michael.doerfel@web.de; Simeon, Bernd, E-mail: simeon@mathematik.uni-kl.de; Vuong, Anh-Vu, E-mail: vuong@mathematik.uni-kl.de [Technische Universitaet Kaiserslautern, Felix Klein Zentrum fuer Mathematik, FB Mathematik (Germany)

    2013-08-01

    This work aims at including nonlinear elastic shell models in a multibody framework. We focus our attention to Kirchhoff-Love shells and explore the benefits of an isogeometric approach, the latest development in finite element methods, within a multibody system. Isogeometric analysis extends isoparameteric finite elements to more general functions such as B-splines and NURBS (Non-Uniform Rational B-Splines) and works on exact geometry representations even at the coarsest level of discretizations. Using NURBS as basis functions, high regularity requirements of the shell model, which are difficult to achieve with standard finite elements, are easily fulfilled. A particular advantage is the promise of simplifying the mesh generation step, and mesh refinement is easily performed by eliminating the need for communication with the geometry representation in a CAD (Computer-Aided Design) tool. Target applications are wind turbine blades and twist beam rear suspensions. First numerical examples demonstrate an impressive convergence behavior of the isogeometric approach even for a coarse mesh, while offering substantial savings with respect to the number of degrees of freedom.

  2. Screw-matrix method in dynamics of multibody systems

    Science.gov (United States)

    Yanzhu, Liu

    1988-05-01

    In the present paper the concept of screw in classical mechanics is expressed in matrix form, in order to formulate the dynamical equations of the multibody systems. The mentioned method can retain the advantages of the screw theory and avoid the shortcomings of the dual number notation. Combining the screw-matrix method with the tool of graph theory in Roberson/Wittenberg formalism. We can expand the application of the screw theory to the general case of multibody systems. For a tree system, the dynamical equations for each j-th subsystem, composed of all the outboard bodies connected by j-th joint can be formulated without the constraint reaction forces in the joints. For a nontree system, the dynamical equations of subsystems and the kinematical consistency conditions of the joints can be derived using the loop matrix. The whole process of calculation is unified in matrix form. A three-segment manipulator is discussed as an example.

  3. Inverse and forward dynamics: models of multi-body systems.

    Science.gov (United States)

    Otten, E

    2003-01-01

    Connected multi-body systems exhibit notoriously complex behaviour when driven by external and internal forces and torques. The problem of reconstructing the internal forces and/or torques from the movements and known external forces is called the 'inverse dynamics problem', whereas calculating motion from known internal forces and/or torques and resulting reaction forces is called the 'forward dynamics problem'. When stepping forward to cross the street, people use muscle forces that generate angular accelerations of their body segments and, by virtue of reaction forces from the street, a forward acceleration of the centre of mass of their body. Inverse dynamics calculations applied to a set of motion data from such an event can teach us how temporal patterns of joint torques were responsible for the observed motion. In forward dynamics calculations we may attempt to create motion from such temporal patterns, which is extremely difficult, because of the complex mechanical linkage along the chains forming the multi-body system. To understand, predict and sometimes control multi-body systems, we may want to have mathematical expressions for them. The Newton-Euler, Lagrangian and Featherstone approaches have their advantages and disadvantages. The simulation of collisions and the inclusion of muscle forces or other internal forces are discussed. Also, the possibility to perform a mixed inverse and forward dynamics calculation are dealt with. The use and limitations of these approaches form the conclusion. PMID:14561340

  4. Rigid multibody system dynamics with uncertain rigid bodies

    Energy Technology Data Exchange (ETDEWEB)

    Batou, A., E-mail: anas.batou@univ-paris-est.fr; Soize, C., E-mail: christian.soize@univ-paris-est.fr [Universite Paris-Est, Laboratoire Modelisation et Simulation Multi Echelle, MSME UMR 8208 CNRS (France)

    2012-03-15

    This paper is devoted to the construction of a probabilistic model of uncertain rigid bodies for multibody system dynamics. We first construct a stochastic model of an uncertain rigid body by replacing the mass, the center of mass, and the tensor of inertia by random variables. The prior probability distributions of the stochastic model are constructed using the maximum entropy principle under the constraints defined by the available information. The generators of independent realizations corresponding to the prior probability distribution of these random quantities are further developed. Then several uncertain rigid bodies can be linked to each other in order to calculate the random response of a multibody dynamical system. An application is proposed to illustrate the theoretical development.

  5. Roller-chain Drives Mechanics using Multibody Dynamics Tools

    DEFF Research Database (Denmark)

    Ambrosio, Jorge A. C.; Hansen, John Michael

    1999-01-01

    An integrated model for the simulation of roller-chain drives based on a multibody dynamics methodology is presented here in order to describeits complex dynamic behavior. The chain is modeled by masses lumped at the roller locations and connected by translational spring-damper elements in order...... to take into account the elastic flexibility of the chain and the energy dissipation at the joints. The driver and driven sprockets are modeled as rigid bodies that can be repositioned during the analysis in order to simulate automatic tensioners or out-of-balanceshafts. The problem of the rollers...

  6. Numerical Solution for Stiff Dynamic Equations of Flexible Multibody System

    Institute of Scientific and Technical Information of China (English)

    L(U) Yan-ping; WU Guo-rong

    2008-01-01

    A nonlinear numerical integration method, based on forward and backward Euler integration methods, is proposed for solving the stiff dynamic equations of a flexible multibody system, which are transformed from the second order to the first order by adop- ring state variables. This method is of A0 stability and infinity stability. The numerical solutions violating the constraint equations are corrected by Blajer's modification approach. Simulation results of a slider-crank mechanism by the proposed method are in good a- greement with ones from other literature.

  7. General background and approach to multibody dynamics for space applications

    Science.gov (United States)

    Santini, Paolo; Gasbarri, Paolo

    2009-06-01

    Multibody dynamics for space applications is dictated by space environment such as space-varying gravity forces, orbital and attitude perturbations, control forces if any. Several methods and formulations devoted to the modeling of flexible bodies undergoing large overall motions were developed in recent years. Most of these different formulations were aimed to face one of the main problems concerning the analysis of spacecraft dynamics namely the reduction of computer simulation time. By virtue of this, the use of symbolic manipulation, recursive formulation and parallel processing algorithms were proposed. All these approaches fall into two categories, the one based on Newton/Euler methods and the one based on Lagrangian methods; both of them have their advantages and disadvantages although in general, Newtonian approaches lend to a better understanding of the physics of problems and in particular of the magnitude of the reactions and of the corresponding structural stresses. Another important issue which must be addressed carefully in multibody space dynamics is relevant to a correct choice of kinematics variables. In fact, when dealing with flexible multibody system the resulting equations include two different types of state variables, the ones associated with large (rigid) displacements and the ones associated with elastic deformations. These two sets of variables have generally two different time scales if we think of the attitude motion of a satellite whose period of oscillation, due to the gravity gradient effects, is of the same order of magnitude as the orbital period, which is much bigger than the one associated with the structural vibration of the satellite itself. Therefore, the numerical integration of the equations of the system represents a challenging problem. This was the abstract and some of the arguments that Professor Paolo Santini intended to present for the Breakwell Lecture; unfortunately a deadly disease attacked him and shortly took him

  8. Dynamics of Multibody Systems Near Lagrangian Points

    Science.gov (United States)

    Wong, Brian

    This thesis examines the dynamics of a physically connected multi-spacecraft system in the vicinity of the Lagrangian points of a Circular Restricted Three-Body System. The spacecraft system is arranged in a wheel-spoke configuration with smaller and less massive satellites connected to a central hub using truss/beams or tether connectors. The kinematics of the system is first defined, and the kinetic, gravitational potential energy and elastic potential energy of the system are derived. The Assumed Modes Method is used to discretize the continuous variables of the system, and a general set of ordinary differential equations describing the dynamics of the connectors and the central hub are obtained using the Lagrangian method. The flexible body dynamics of the tethered and truss connected systems are examined using numerical simulations. The results show that these systems experienced only small elastic deflections when they are naturally librating or rotating at moderate angular velocities, and these deflections have relatively small effect on the attitude dynamics of the systems. Based on these results, it is determined that the connectors can be modeled as rigid when only the attitude dynamics of the system is of interest. The equations of motion of rigid satellites stationed at the Lagrangian points are linearized, and the stability conditions of the satellite are obtained from the linear equations. The required conditions are shown to be similar to those of geocentric satellites. Study of the linear equations also revealed the resonant conditions of rigid Lagrangian point satellites, when a librational natural frequency of the satellite matches the frequency of its station-keeping orbit leading to large attitude motions. For tethered satellites, the linear analysis shows that the tethers are in stable equilibrium when they lie along a line joining the two primary celestial bodies of the Three-Body System. Numerical simulations are used to study the long term

  9. Decoupling Kinematic Loops for Real-Time Multibody Dynamic Simulations

    Directory of Open Access Journals (Sweden)

    Omar Mohamed

    2016-01-01

    Full Text Available Earth moving equipment are typically equipped with hydraulic cylinder actuators to perform the designated tasks. Multibody modelling of such systems results in models with kinematic loops that couples the motion variables of the loop bodies. Iterative solutions will be needed to satisfy the loop constraints and the applied constraints, which require evaluation of the constraint Jacobean matrix. The size of the Jacobean matrix and the associated projections depends on the number of motion variables in each kinematic loop. Consequently, the computational cost significantly increases as the number of variables in the kinematic loop increases. Real-time control and hybrid hardware-in-the-loop systems both require efficient and fast computational algorithms. Eliminating the kinematic loops can improve the computational efficiency and effectiveness of the control algorithms. This paper presents an efficient approach to eliminate the coupling due to the cylinder-rod connections and consequently the kinematic loops in the multibody models leading to efficient simulation. The proposed approach calculates the spatial accelerations and inertia forces of the actuator bodies and the interaction forces with other components. The actuator forces are then projected onto the connecting bodies leading to exact dynamics of the system.

  10. A Modelling Approach to Multibody Dynamics of Fluid Power Machinery with Hydrodynamic Lubrication

    DEFF Research Database (Denmark)

    Johansen, Per; Rømer, Daniel; Andersen, Torben Ole

    2013-01-01

    The efficiency potential of the digital displacement technology and the increasing interest in hydraulic transmissions in wind and wave energy applications has created an incentive for development of high efficiency fluid power machinery. Modelling and analysis of fluid power machinery loss...... to be coupled with multibody dynamics models. The focus of the current paper is an approach where the transient pressure field in hydrodynamic lubricated joint clearances are modelled by a set of control volumes and coupled with the fluid power machinery mechanics....... mechanisms is necessary in order to accommodate this demand. At present fully coupled thermo-elastic models for various tribological interfaces has been presented. However, in order to analyse the interaction between tribological interfaces in fluid power pumps and motors, these interface models needs...

  11. Spatially recursive filtering and smoothing for multibody dynamics

    Science.gov (United States)

    Rodriguez, G.

    1988-01-01

    Methods developed recently by the author to solve the problem of forward dynamics for nonlinear joint-connected multibody systems are summarized. Solution of this problem is of interest in such application areas as robotics, deploying structures, ground vehicles, and pointing of antennas and instrumented platforms. The problem is solved by the recursive filtering and smoothing techniques of state estimation theory. The filtering stage takes the applied joint moments as inputs to produce a sequence of spatial constraint forces acting at the joints of the system. The smoothing stage takes the innovations process resulting from the filter as an input and produces a set of spatial accelerations and a corresponding set of joint-angle accelerations.

  12. DYNAMIC MODELLING OF BAR-GEAR MIXED MULTIBODY SYSTEMS USING A SPECIFIC FINITE ELEMENT METHOD

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    A new dynamic model for mixed, flexible bar and gear multibody systems is developed based on a specific finite element method, and a new gear-element is proposed. The gear-element can take into account the time variant stiffness, the gear errors and mass unbalance. The model for geared multibody systems can couple the gear meshing and the flexibility of all contained components. The kinematic and dynamic analyses of the geared multibody systems are expounded and illustrated on an example composed of three gears, two bars and one slider.

  13. Dynamics of underactuated multibody systems modeling, control and optimal design

    CERN Document Server

    Seifried, Robert

    2014-01-01

    Underactuated multibody systems are intriguing mechatronic systems, as they possess fewer control inputs than degrees of freedom. Some examples are modern light-weight flexible robots and articulated manipulators with passive joints. This book investigates such underactuated multibody systems from an integrated perspective. This includes all major steps from the modeling of rigid and flexible multibody systems, through nonlinear control theory, to optimal system design. The underlying theories and techniques from these different fields are presented using a self-contained and unified approach and notation system. Subsequently, the book focuses on applications to large multibody systems with multiple degrees of freedom, which require a combination of symbolical and numerical procedures. Finally, an integrated, optimization-based design procedure is proposed, whereby both structural and control design are considered concurrently. Each chapter is supplemented by illustrated examples.

  14. Modeling friction phenomena and elastomeric dampers in multibody dynamics analysis

    Science.gov (United States)

    Ju, Changkuan

    The first part of this dissertation focuses on the development, implementation and validation of models that capture the behavior of joints in a realistic manner. These models are presented within the framework of finite element based, nonlinear multibody dynamics formulations that ensure unconditional nonlinear stability of the computation for complex systems of arbitrary topology. The proposed approach can be divided into three parts. First, the joint configuration: this purely kinematic part deals with the description of the configuration of the joint and the evaluation of the relative distance and relative tangential velocity between the contacting bodies. Second, the contact conditions: in most cases, contact at the joint is of an intermittent nature. The enforcement of the unilateral contact condition is a critical aspect of the computational procedure. And finally, the contact forces: this last part deals with the evaluation of the forces that arise at the interface between contacting bodies. The advantage of the proposed approach is that the three parts of the problem can be formulated and implemented independently. Many articulated rotor helicopters use hydraulic dampers, which provide high levels of damping but are also associated with high maintenance costs and difficulties in evaluating their conditions due to the presence of seals, lubricants and numerous moving parts, all operating in a rotating frame. To avoid problems associated with hydraulic dampers, the industry is now switching to elastomeric lead-lag dampers that feature simpler mechanical design, lower part count, and result in "dry" rotors. However, the design of robust elastomeric dampers is hampered by the lack of reliable analytical tools that can be used to predict their damping behavior in the presence of large multi-frequency motions experienced by the rotor and thus the damper. The second part of this dissertation focuses on the development of an elastomeric damper model which predicts

  15. DYNAMIC CHARACTERISTICS ON PRECISION NC LATHE BASED ON MULTI-BODY SYSTEM THEORY

    Institute of Scientific and Technical Information of China (English)

    Wu Nanxing; Sun Qinghong; Zhang Yonghong; Yu Dongling

    2005-01-01

    Based on multi-body system theory and the mainshaft system of precision NC lathe as object investigated, it is treated as a coupled rigid-flexible multi-body system which is made up of some rigid and elastic bodies in an especial linking mode. And a dynamic model is established. The problems of computing vibration characteristics are resolved by using multi-body system transfer matrix method. Results show that the mainshaft system of NC lathe is in the stable and reliable working area all the time. The method is simple and easy, the idea is clear. In addition, the method can be easily used and popularized in the other multi-body system.

  16. Structure-preserving integrators in nonlinear structural dynamics and flexible multibody dynamics

    CERN Document Server

    2016-01-01

    This book focuses on structure-preserving numerical methods for flexible multibody dynamics, including nonlinear elastodynamics and geometrically exact models for beams and shells. It also deals with the newly emerging class of variational integrators as well as Lie-group integrators. It discusses two alternative approaches to the discretization in space of nonlinear beams and shells. Firstly, geometrically exact formulations, which are typically used in the finite element community and, secondly, the absolute nodal coordinate formulation, which is popular in the multibody dynamics community. Concerning the discretization in time, the energy-momentum method and its energy-decaying variants are discussed. It also addresses a number of issues that have arisen in the wake of the structure-preserving discretization in space. Among them are the parameterization of finite rotations, the incorporation of algebraic constraints and the computer implementation of the various numerical methods. The practical application...

  17. STUDY ON DYNAMICS, STABILITY AND CONTROL OF MULTI-BODY FLEXIBLE STRUCTURE SYSTEM IN FUNCTIONAL SPACE

    Institute of Scientific and Technical Information of China (English)

    徐建国; 贾军国

    2001-01-01

    The dynamics, stability and control problem of a kind of infinite dimensional system are studied in the functional space with the method of modern mathematics. First,the dynamical control model of the distributed parameter system with multi-body flexible and multi-topological structure was established which has damping, gyroscopic parts and constrained damping. Secondly, the necessary and sufficient condition of controllability and observability, the stability theory and asymptotic property of the system were obtained.These results expand the theory of the field about the dynamics and control of the system with multi-body flexible structure, and have important engineering significance.

  18. Multibody Dynamics of a Fluid Power Radial Piston Motor Including Transient Hydrodynamic Pressure Models of Lubricating Gaps

    DEFF Research Database (Denmark)

    Johansen, Per; Rømer, Daniel; Andersen, Torben Ole

    2014-01-01

    The increasing interest in hydraulic transmissions in wind and wave energy applications has created an incentive for the development of high efficiency fluid power machinery. Modeling and analysis of fluid power machinery loss mechanisms are necessary in order to accommodate this demand. At present...... is a multibody dynamics model of a radial piston fluid power motor, which connects the rigid bodies through models of the transient hydrodynamic lubrication pressure in the joint clearance. A finite volume approach is used to model the pressure dynamics of the fluid film lubrication. The model structure...... fully coupled thermo-elastic models has been used to simulate and study loss mechanisms in various tribological interfaces. Consequently, a reasonable focus of further development is to couple the interface models and the rigid body mechanics of fluid power machinery. The focus of the current paper...

  19. Evolution of the DeNOC-based dynamic modelling for multibody systems

    Directory of Open Access Journals (Sweden)

    S. K. Saha

    2013-01-01

    Full Text Available Dynamic modelling of a multibody system plays very essential role in its analyses. As a result, several methods for dynamic modelling have evolved over the years that allow one to analyse multibody systems in a very efficient manner. One such method of dynamic modelling is based on the concept of the Decoupled Natural Orthogonal Complement (DeNOC matrices. The DeNOC-based methodology for dynamics modelling, since its introduction in 1995, has been applied to a variety of multibody systems such as serial, parallel, general closed-loop, flexible, legged, cam-follower, and space robots. The methodology has also proven useful for modelling of proteins and hyper-degree-of-freedom systems like ropes, chains, etc. This paper captures the evolution of the DeNOC-based dynamic modelling applied to different type of systems, and its benefits over other existing methodologies. It is shown that the DeNOC-based modelling provides deeper understanding of the dynamics of a multibody system. The power of the DeNOC-based modelling has been illustrated using several numerical examples.

  20. Research on the Earth system multi-body force system dynamical model

    Institute of Scientific and Technical Information of China (English)

    CHEN; Xiaofei; BI; Siwen; WU; Fei; DONG; Qianlin

    2006-01-01

    This paper presents an overview of the binding force and freedom force of Earth system, and describes force moment to point and line and force system in the Earth system. It introduces the force theory of the Earth system multi-body force system from special or equivalent force system of Earth system mechanics, general force and no-power force of Earth system. Finally it describes the force and moment of nodes of Earth system and provides basic model for the research of the Earth system multi-body dynamics.

  1. Multibody systems handbook

    Energy Technology Data Exchange (ETDEWEB)

    Schiehlen, W. (Univ. Stuttgart (DE))

    1990-01-01

    Dynamics of multibody systems is of importance in the fields of robotics, biomechanics, spacecraft control, road and rail vehicle design, and dynamics of machinery. Many research problems have been solved and a considerable number of computer codes based on multibody formalisms is now available. This book reports on software systems for multibody system dynamics which are established and have found acceptance in the users community.

  2. A Component Mode Synthesis Algorithm for Multibody Dynamics of Wind Turbines

    DEFF Research Database (Denmark)

    Holm-Jørgensen, Kristian; Nielsen, Søren R.K.

    2009-01-01

    A system reduction scheme related to a multibody formulation of wind turbine dynamics is devised. Each substructure is described in its own frame of reference, which is moving freely in the vicinity of the moving substructure, in principle without any constraints to the rigid body part of the mot...

  3. A computational procedure for multibody systems including flexible beam dynamics

    Science.gov (United States)

    Downer, J. D.; Park, K. C.; Chiou, J. C.

    1990-01-01

    A computational procedure suitable for the solution of equations of motions for flexible multibody systems has been developed. The flexible beams are modeled using a fully nonlinear theory which accounts for both finite rotations and large deformations. The present formulation incorporates physical measures of conjugate Cauchy stress and covariant strain increments. As a consequence, the beam model can easily be interfaced with real-time strain measurements and feedback control systems. A distinct feature of the present work is the computational preservation of total energy for undamped systems; this is obtained via an objective strain increment/stress update procedure combined with an energy-conserving time integration algorithm which contains an accurate update of angular orientations. The procedure is demonstrated via several example problems.

  4. A New Application of Multi-Body System Dynamics in Vehicle-Road Interaction Simulation

    Institute of Scientific and Technical Information of China (English)

    RenWei-qun; ZhangYun-qing; JinGuo-dong

    2003-01-01

    In vehicle-road interaction simulation, multibody system (MBS) dynamics as well as the corresponding software ADAMS has been employed to model the nonlinear vehicle in more detail. The simulation method has been validated by the test data, and been compared to the former simple models. This method can be used for estimating the effects of dynamic tire forces and other vehicle features on road damage so that the “road-friendliness” can be assessed in vehicle design process.

  5. Multi-Body Dynamics and Modal Analysis of Compliant Gear Bodies

    Science.gov (United States)

    Vinayak, H.; Singh, R.

    1998-02-01

    This paper extends the multi-body dynamics modelling strategy for rigid gears to include compliant gear bodies in multi-mesh transmissions. Only external, fixed center, helical or spur gears are considered. This formulation combines distributed gear mesh stiffness and gear blank compliance models in a multi-body dynamics framework resulting in a set of non-linear differential equations with time-varying coefficients. Linearization and other simplifications are applied to yield the resulting linear time-invariant equations of motion. Several solution techniques are then used to determine eigensolutions and forced harmonic responses. The resulting normal mode solutions are compared to those obtained by the finite element analysis for several examples of transmission containing flexible gears. These include ring-gears and bodies with discontinuities. A parametric study has been performed to assess the effect of gear orientation on the dynamics of transmissions. Finally analytical predictions are compared to the results of a laboratory experiment.

  6. Articulated Lifting System Modeling Based on Dynamics of Flexible Multi-Body Systems

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In lifting sub-system of deep-sea mining system, spherical joint is used to connect lifting pipes to replace fixed joint. Based on Dynamics of Flexible Multi-body systems, the mechanics model of articulated lifting system is established. Under the four-grade and six-grade oceanic condition, dynamic responses of lifting system are simulated and experiment verified. The simulation results are consistent with experimental ones. The maximum moment of flexion is 322 kN-m on the first pipe under six-grade sea condition. It is seen that the articulated connection can reduce the moment of flexion. The bending deformation of pipe center is researched, and the maximum is 0.000479 m on the first pipe. Deformation has a little effect on the motion of system. It is feasible to analyze articulated lifting system by applying the theory of flexible multi-body dynamics. The articulated lifting system is obviously better than the fixed one.

  7. Multibody system dynamics for bio-inspired locomotion: from geometric structures to computational aspects.

    Science.gov (United States)

    Boyer, Frédéric; Porez, Mathieu

    2015-03-26

    This article presents a set of generic tools for multibody system dynamics devoted to the study of bio-inspired locomotion in robotics. First, archetypal examples from the field of bio-inspired robot locomotion are presented to prepare the ground for further discussion. The general problem of locomotion is then stated. In considering this problem, we progressively draw a unified geometric picture of locomotion dynamics. For that purpose, we start from the model of discrete mobile multibody systems (MMSs) that we progressively extend to the case of continuous and finally soft systems. Beyond these theoretical aspects, we address the practical problem of the efficient computation of these models by proposing a Newton-Euler-based approach to efficient locomotion dynamics with a few illustrations of creeping, swimming, and flying.

  8. Flight Loads Prediction of High Aspect Ratio Wing Aircraft Using Multibody Dynamics

    Directory of Open Access Journals (Sweden)

    Michele Castellani

    2016-01-01

    Full Text Available A framework based on multibody dynamics has been developed for the static and dynamic aeroelastic analyses of flexible high aspect ratio wing aircraft subject to structural geometric nonlinearities. Multibody dynamics allows kinematic nonlinearities and nonlinear relationships in the forces definition and is an efficient and promising methodology to model high aspect ratio wings, which are known to be prone to structural nonlinear effects because of the high deflections in flight. The multibody dynamics framework developed employs quasi-steady aerodynamics strip theory and discretizes the wing as a series of rigid bodies interconnected by beam elements, representative of the stiffness distribution, which can undergo arbitrarily large displacements and rotations. The method is applied to a flexible high aspect ratio wing commercial aircraft and both trim and gust response analyses are performed in order to calculate flight loads. These results are then compared to those obtained with the standard linear aeroelastic approach provided by the Finite Element Solver Nastran. Nonlinear effects come into play mainly because of the need of taking into account the large deflections of the wing for flight loads computation and of considering the aerodynamic forces as follower forces.

  9. Recursive linearization of multibody dynamics equations of motion

    Science.gov (United States)

    Lin, Tsung-Chieh; Yae, K. Harold

    1989-01-01

    The equations of motion of a multibody system are nonlinear in nature, and thus pose a difficult problem in linear control design. One approach is to have a first-order approximation through the numerical perturbations at a given configuration, and to design a control law based on the linearized model. Here, a linearized model is generated analytically by following the footsteps of the recursive derivation of the equations of motion. The equations of motion are first written in a Newton-Euler form, which is systematic and easy to construct; then, they are transformed into a relative coordinate representation, which is more efficient in computation. A new computational method for linearization is obtained by applying a series of first-order analytical approximations to the recursive kinematic relationships. The method has proved to be computationally more efficient because of its recursive nature. It has also turned out to be more accurate because of the fact that analytical perturbation circumvents numerical differentiation and other associated numerical operations that may accumulate computational error, thus requiring only analytical operations of matrices and vectors. The power of the proposed linearization algorithm is demonstrated, in comparison to a numerical perturbation method, with a two-link manipulator and a seven degrees of freedom robotic manipulator. Its application to control design is also demonstrated.

  10. Experimental validation of flexible multibody dynamics beam formulations

    Energy Technology Data Exchange (ETDEWEB)

    Bauchau, Olivier A., E-mail: olivier.bauchau@sjtu.edu.cn; Han, Shilei [University of Michigan-Shanghai Jiao Tong University Joint Institute (China); Mikkola, Aki; Matikainen, Marko K. [Lappeenranta University of Technology, Department of Mechanical Engineering (Finland); Gruber, Peter [Austrian Center of Competence in Mechatronics GmbH (Austria)

    2015-08-15

    In this paper, the accuracies of the geometrically exact beam and absolute nodal coordinate formulations are studied by comparing their predictions against an experimental data set referred to as the “Princeton beam experiment.” The experiment deals with a cantilevered beam experiencing coupled flap, lag, and twist deformations. In the absolute nodal coordinate formulation, two different beam elements are used. The first is based on a shear deformable approach in which the element kinematics is described using two nodes. The second is based on a recently proposed approach featuring three nodes. The numerical results for the geometrically exact beam formulation and the recently proposed three-node absolute nodal coordinate formulation agree well with the experimental data. The two-node beam element predictions are similar to those of linear beam theory. This study suggests that a careful and thorough evaluation of beam elements must be carried out to assess their ability to deal with the three-dimensional deformations typically found in flexible multibody systems.

  11. Dynamic Analysis of Flexible Multibody Systems for High-Rise Building Window Cleaning Gondola

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    A virtual prototype of high-rise building window cleaning gondola based on multibody system dynamics software MSC.ADAMS is presented. The rigid bodies are modeled by CAD software and flexible bodies are modeled by discrete beam method. The whole machine's natural characteristics are analyzed and changed to frequency field. According to the results, the dangerous frequencies are avoided and the design can be optimized and the performance can be improved.

  12. Rapid maneuvering of multi-body dynamic systems with optimal motion compensation

    Science.gov (United States)

    Bishop, B.; Gargano, R.; Sears, A.; Karpenko, M.

    2015-12-01

    Rapid maneuvering of multi-body dynamical systems is an important, yet challenging, problem in many applications. Even in the case of rigid bodies, it can be difficult to maintain precise control over nominally stationary links if it is required to move some of the other links quickly because of the various nonlinearities and coupled interactions that occur between the bodies. Typical control concepts treat the multi-body motion control problem in two-stages. First, the nonlinear and coupling terms are treated as disturbances and a trajectory tracking control law is designed in order to attenuate their effects. Next, motion profiles are designed, based on kinematics parameterizations, and these are used as inputs to the closed loop system to move the links. This paper describes an approach for rapid maneuvering of multi-body systems that uses optimal control theory to account for dynamic nonlinearities and coupling as part of the motion trajectory design. Incorporating appropriate operational constraints automatically compensates for these multi-body effects so that motion time can be reduced while simultaneously achieving other objectives such as reducing the excitation of selected links. Since the compensatory effect is embedded within the optimal motion trajectories, the performance improvement can be obtained even when using simple closed-loop architectures for maneuver implementation. Simulation results for minimum time control of a two-axis gimbal system and for rapid maneuvering of a TDRS single-access antenna, wherein it is desired to limit the excitation of the satellite body to which the antenna is attached, are presented to illustrate the concepts.

  13. Partition method for impact dynamics of flexible multibody systems based on contact constraint

    Institute of Scientific and Technical Information of China (English)

    段玥晨; 章定国; 洪嘉振

    2013-01-01

    The impact dynamics of a flexible multibody system is investigated. By using a partition method, the system is divided into two parts, the local impact region and the region away from the impact. The two parts are connected by specific boundary conditions, and the system after partition is equivalent to the original system. According to the rigid-flexible coupling dynamic theory of multibody system, system’s rigid-flexible coupling dynamic equations without impact are derived. A local impulse method for establishing the initial impact conditions is proposed. It satisfies the compatibility con-ditions for contact constraints and the actual physical situation of the impact process of flexible bodies. Based on the contact constraint method, system’s impact dynamic equa-tions are derived in a differential-algebraic form. The contact/separation criterion and the algorithm are given. An impact dynamic simulation is given. The results show that system’s dynamic behaviors including the energy, the deformations, the displacements, and the impact force during the impact process change dramatically. The impact makes great effects on the global dynamics of the system during and after impact.

  14. Applied dynamics with applications to multibody and mechatronic systems

    CERN Document Server

    Moon, Francis C

    1998-01-01

    Applied Dynamics provides a modern and thorough examination of dynamics with specific emphasis on physical examples and applications such as: robotic systems, magnetic bearings, aerospace dynamics, and microelectromagnetic machines. Also includes the development of the method of virtual velocities based on the principle of virtual power

  15. Evolution of Flexible Multibody Dynamics for Simulation Applications Supporting Human Spaceflight

    Science.gov (United States)

    Huynh, An; Brain, Thomas A.; MacLean, John R.; Quiocho, Leslie J.

    2016-01-01

    During the course of transition from the Space Shuttle and International Space Station programs to the Orion and Journey to Mars exploration programs, a generic flexible multibody dynamics formulation and associated software implementation has evolved to meet an ever changing set of requirements at the NASA Johnson Space Center (JSC). Challenging problems related to large transitional topologies and robotic free-flyer vehicle capture/ release, contact dynamics, and exploration missions concept evaluation through simulation (e.g., asteroid surface operations) have driven this continued development. Coupled with this need is the requirement to oftentimes support human spaceflight operations in real-time. Moreover, it has been desirable to allow even more rapid prototyping of on-orbit manipulator and spacecraft systems, to support less complex infrastructure software for massively integrated simulations, to yield further computational efficiencies, and to take advantage of recent advances and availability of multi-core computing platforms. Since engineering analysis, procedures development, and crew familiarity/training for human spaceflight is fundamental to JSC's charter, there is also a strong desire to share and reuse models in both the non-realtime and real-time domains, with the goal of retaining as much multibody dynamics fidelity as possible. Three specific enhancements are reviewed here: (1) linked list organization to address large transitional topologies, (2) body level model order reduction, and (3) parallel formulation/implementation. This paper provides a detailed overview of these primary updates to JSC's flexible multibody dynamics algorithms as well as a comparison of numerical results to previous formulations and associated software.

  16. Brownian dynamics simulations of a flexible polymer chain which includes continuous resistance and multibody hydrodynamic interactions

    Science.gov (United States)

    Butler, Jason E.; Shaqfeh, Eric S. G.

    2005-01-01

    Using methods adapted from the simulation of suspension dynamics, we have developed a Brownian dynamics algorithm with multibody hydrodynamic interactions for simulating the dynamics of polymer molecules. The polymer molecule is modeled as a chain composed of a series of inextensible, rigid rods with constraints at each joint to ensure continuity of the chain. The linear and rotational velocities of each segment of the polymer chain are described by the slender-body theory of Batchelor [J. Fluid Mech. 44, 419 (1970)]. To include hydrodynamic interactions between the segments of the chain, the line distribution of forces on each segment is approximated by making a Legendre polynomial expansion of the disturbance velocity on the segment, where the first two terms of the expansion are retained in the calculation. Thus, the resulting linear force distribution is specified by a center of mass force, couple, and stresslet on each segment. This method for calculating the hydrodynamic interactions has been successfully used to simulate the dynamics of noncolloidal suspensions of rigid fibers [O. G. Harlen, R. R. Sundararajakumar, and D. L. Koch, J. Fluid Mech. 388, 355 (1999); J. E. Butler and E. S. G. Shaqfeh, J. Fluid Mech. 468, 204 (2002)]. The longest relaxation time and center of mass diffusivity are among the quantities calculated with the simulation technique. Comparisons are made for different levels of approximation of the hydrodynamic interactions, including multibody interactions, two-body interactions, and the "freely draining" case with no interactions. For the short polymer chains studied in this paper, the results indicate a difference in the apparent scaling of diffusivity with polymer length for the multibody versus two-body level of approximation for the hydrodynamic interactions.

  17. Multibody Systems

    DEFF Research Database (Denmark)

    Wagner, Falko Jens

    1999-01-01

    Multibody Systems is one area, in which methods for solving DAEs are of special interst. This chapter is about multibody systems, why they result in DAE systems and what kind of problems that can arise when dealing with multibody systems and formulating their corresponding DAE system....

  18. Multibody Dynamic Stress Simulation of Rigid-Flexible Shovel Crawler Shoes

    Directory of Open Access Journals (Sweden)

    Samuel Frimpong

    2016-06-01

    Full Text Available Electric shovels are used in surface mining operations to achieve economic production capacities. The capital investments and operating costs associated with the shovels deployed in the Athabasca oil sands formation are high due to the abrasive conditions. The shovel crawler shoes interact with sharp and abrasive sand particles, and, thus, are subjected to high transient dynamic stresses. These high stresses cause wear and tear leading to crack initiation, propagation and premature fatigue failure. The objective of this paper is to develop a model to characterize the crawler stresses and deformation for the P&H 4100C BOSS during propel and loading using rigid-flexible multi-body dynamic theory. A 3-D virtual prototype model of the rigid-flexible crawler track assembly and its interactions with oil sand formation is simulated to capture the model dynamics within multibody dynamics software MSC ADAMS. The modal and stress shapes and modal loads due to machine weight for each flexible crawler shoes are generated from finite element analysis (FEA. The modal coordinates from the simulation are combined with mode and stress shapes using modal superposition method to calculate real-time stresses and deformation of flexible crawler shoes. The results show a maximum von Mises stress value of 170 MPa occurring in the driving crawler shoe during the propel motion. This study provides a foundation for the subsequent fatigue life analysis of crawler shoes for extending crawler service life.

  19. System Reduction in Multibody Dynamics of Wind Turbines

    DEFF Research Database (Denmark)

    Holm-Jørgensen, Kristian; Nielsen, Søren R.K.

    2009-01-01

    . The Ritz bases spanning the reduced system comprises of rigid body modes and some dynamic low-frequency elastic eigenmodes compatible to the kinematic constraints of the related substructure. The high-frequency elastic modes are presumed to cause merely quasi-static displacements, and thus are included...

  20. Dynamic multibody protein interactions suggest versatile pathways for copper trafficking.

    Science.gov (United States)

    Keller, Aaron M; Benítez, Jaime J; Klarin, Derek; Zhong, Linghao; Goldfogel, Matthew; Yang, Feng; Chen, Tai-Yen; Chen, Peng

    2012-05-30

    As part of intracellular copper trafficking pathways, the human copper chaperone Hah1 delivers Cu(+) to the Wilson's Disease Protein (WDP) via weak and dynamic protein-protein interactions. WDP contains six homologous metal binding domains (MBDs) connected by flexible linkers, and these MBDs all can receive Cu(+) from Hah1. The functional roles of the MBD multiplicity in Cu(+) trafficking are not well understood. Building on our previous study of the dynamic interactions between Hah1 and the isolated fourth MBD of WDP, here we study how Hah1 interacts with MBD34, a double-domain WDP construct, using single-molecule fluorescence resonance energy transfer (smFRET) combined with vesicle trapping. By alternating the positions of the smFRET donor and acceptor, we systematically probed Hah1-MBD3, Hah1-MBD4, and MBD3-MBD4 interaction dynamics within the multidomain system. We found that the two interconverting interaction geometries were conserved in both intermolecular Hah1-MBD and intramolecular MBD-MBD interactions. The Hah1-MBD interactions within MBD34 are stabilized by an order of magnitude relative to the isolated single-MBDs, and thermodynamic and kinetic evidence suggest that Hah1 can interact with both MBDs simultaneously. The enhanced interaction stability of Hah1 with the multi-MBD system, the dynamic intramolecular MBD-MBD interactions, and the ability of Hah1 to interact with multiple MBDs simultaneously suggest an efficient and versatile mechanism for the Hah1-to-WDP pathway to transport Cu(+).

  1. On the effect of linear algebra implementations in real-time multibody system dynamics

    Science.gov (United States)

    González, Manuel; González, Francisco; Dopico, Daniel; Luaces, Alberto

    2008-03-01

    This paper compares the efficiency of multibody system (MBS) dynamic simulation codes that rely on different implementations of linear algebra operations. The dynamics of an N-loop four-bar mechanism has been solved with an index-3 augmented Lagrangian formulation combined with the trapezoidal rule as numerical integrator. Different implementations for this method, both dense and sparse, have been developed, using a number of linear algebra software libraries (including sparse linear equation solvers) and optimized sparse matrix computation strategies. Numerical experiments have been performed in order to measure their performance, as a function of problem size and matrix filling. Results show that optimal implementations can increase the simulation efficiency in a factor of 2 3, compared with our starting classical implementations, and in some topics they disagree with widespread beliefs in MBS dynamics. Finally, advices are provided to select the implementation which delivers the best performance for a certain MBS dynamic simulation.

  2. A multibody approach for 6-DOF flight dynamics and stability analysis of the hawkmoth Manduca sexta.

    Science.gov (United States)

    Kim, Joong-Kwan; Han, Jae-Hung

    2014-03-01

    This paper investigates the six degrees of freedom (6-DOF) flight dynamics and stability of the hawkmoth Manduca sexta using a multibody dynamics approach that encompasses the effects of the time varying inertia tensor of all the body segments including two wings. The quasi-steady translational and unsteady rotational aerodynamics of the flapping wings are modeled with the blade element theory with aerodynamic coefficients derived from relevant experimental studies. The aerodynamics is given instantaneously at each integration time step without wingbeat-cycle-averaging. With the multibody dynamic model and the aerodynamic model for the hawkmoth, a direct time integration of the fully coupled 6-DOF nonlinear multibody dynamics equations of motion is performed. First, the passive damping magnitude of each single DOF is quantitatively examined with the measure of the time taken to half the initial velocity (thalf). The results show that the sideslip translation is less damped approximately three times than the other two translational DOFs, and the pitch rotation is less damped approximately five times than the other two rotational DOFs; each DOF has the value of (unit in wingbeat strokes): thalf,forward/backward = 7.10, thalf,sideslip = 17.95, thalf,ascending = 7.13, thalf,descending = 5.77, thalf,roll = 0.68, thalf,pitch = 2.39, and thalf,yaw = 0.25. Second, the natural modes of motion, with the hovering flight as a reference equilibrium condition, are examined by analyzing fully coupled 6-DOF dynamic responses induced by multiple sets of force and moment disturbance combinations. The given disturbance combinations are set to excite the dynamic modes identified in relevant eigenmode analysis studies. The 6-DOF dynamic responses obtained from this study are compared with eigenmode analysis results in the relevant studies. The longitudinal modes of motion showed dynamic modal characteristics similar to the eigenmode analysis results from the relevant literature

  3. Multi-body dynamic system simulation of carrier-based aircraft ski-jump takeoff

    Institute of Scientific and Technical Information of China (English)

    Wang Yangang; Wang Weijun; Qu Xiangju

    2013-01-01

    The flight safety is threatened by the special flight conditions and the low speed of carrier-based aircraft ski-jump takeoff.The aircraft carrier motion,aircraft dynamics,landing gears and wind field of sea state are comprehensively considered to dispose this multidiscipline intersection problem.According to the particular naval operating environment of the carrier-based aircraft ski-jump takeoff,the integrated dynamic simulation models of multi-body system are developed,which involves the movement entities of the carrier,the aircraft and the landing gears,and involves takeoff instruction,control system and the deck wind disturbance.Based on Matlab/Simulink environment,the multi-body system simulation is realized.The validity of the model and the rationality of the result are verified by an example simulation of carrier-based aircraft ski-jump takeoff.The simulation model and the software are suitable for the study of the multidiscipline intersection problems which are involved in the performance,flight quality and safety of carrier-based aircraft takeoff,the effects of landing gear loads,parameters of carrier deck,etc.

  4. Numerical Simulation of the Spreading Dynamic Responses of the Multibody System with a Floating Base

    Institute of Scientific and Technical Information of China (English)

    Zhaobing Jiang; Luzhong Shao; Fei Shao

    2015-01-01

    To simulate the dynamic responses of the multibody system with a floating base when the upper parts spread with a certain sequence and relative speed, the homogeneous matrix method is employed to model and simulate a four-body system with a floating base and the motions are analyzed when the upper parts are spread sequentially or synchronously. The rolling, swaying and heaving temporal variations are obtained when the multibody system is under the conditions of the static water along with the wave loads and the mean wind loads or the single pulse wind loads, respectively. The moment variations of each joint under the single pulse wind load are also gained. The numerical results showed that the swaying of the floating base is almost not influenced by the spreading time or form when the upper parts spread sequentially or synchronously, while the rolling and the heaving mainly depend on the spreading time and forms. The swaying and heaving motions are influenced significantly by the mean wind loads. The single pulse wind load also has influences on the dynamic responses. The torque of joint 3 and joint 4 in the single pulse wind environment may be twice that in the windless environment when the system spreads with 60 s duration.

  5. A Coupled Helicopter Rotor/Fuselage Dynamics Model Using Finite Element Multi-body

    Directory of Open Access Journals (Sweden)

    Cheng Qi-you

    2016-01-01

    Full Text Available To develop a coupled rotor/flexible fuselage model for vibration reduction studies, the equation of coupled rotor-fuselage is set up based on the theory of multi-body dynamics, and the dynamic analysis model is established with the software MSC.ADMAS and MSC.NASTRAN. The frequencies and vibration acceleration responses of the system are calculated with the model of coupled rotor-fuselage, and the results are compared with those of uncoupled modeling method. Analysis results showed that compared with uncoupled model, the dynamic characteristic obtained by the model of coupled rotor-fuselage are some different. The intrinsic frequency of rotor is increased with the increase of rotational velocities. The results also show that the flying speed has obvious influence on the vibration acceleration responses of the fuselage. The vibration acceleration response in the vertical direction is much higher at the low speed and high speed flight conditions.

  6. The bond graph model of planar flexible multibody mechanical systems and its dynamic principle

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In order to increase the efficiency and reliability of the dynamic analysis for flexible planar linkage containing the coupling of multi-energy domains, a method based on bond graph is introduced. From the viewpoint of power conservation, the peculiar property of bond graph multiport element MTF is discussed. The procedure of modeling planar flexible multibody mechanical systems by bond graphs and its dynamic principle are described. To overcome the algebraic difficulty brought by differential causality and nonlinear junction structure, the constraint forces at joints can be considered as unknown effort sources and added to the corresponding O-junctions of system bond graph model. As a result, the automatic modeling on a computer is realized. The validity of the procedure is illustrated by a practical example.

  7. Virtual design software for mechanical system dynamics using transfer matrix method of multibody system and its application

    Directory of Open Access Journals (Sweden)

    Hai-gen Yang

    2015-09-01

    Full Text Available The complex mechanical systems such as high-speed trains, multiple launch rocket system, self-propelled artillery, and industrial robots are becoming increasingly larger in scale and more complicated in structure. Designing these products often requires complex model design, multibody system dynamics calculation, and analysis of large amounts of data repeatedly. In recent 20 years, the transfer matrix method of multibody system has been widely applied in engineering fields and welcomed at home and in abroad for the following features: without global dynamic equations of the system, low orders of involved system matrices, high computational efficiency, and high programming. In order to realize the rapid and visual simulation for complex mechanical system virtual design using transfer matrix method of multibody system, a virtual design software named MSTMMSim is designed and implemented. In the MSTMMSim, the transfer matrix method of multibody system is used as the solver for dynamic modeling and calculation; the Open CASCADE is used for solid geometry modeling. Various auxiliary analytical tools such as curve plot and animation display are provided in the post-processor to analyze and process the simulation results. Two numerical examples are given to verify the validity and accuracy of the software, and a multiple launch rocket system engineering example is given at the end of this article to show that the software provides a powerful platform for complex mechanical systems simulation and virtual design.

  8. Multi-Body Dynamics Analysis and Low Noise Optimization of X6170ZC Diesel

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The multi-body dynamics model of the X6170ZC diesel is established to analyze vibration and acoustic noise. The high quality finite element and simulation models are developed, and nonlinear springs are used to imitate the joints of engine components. The acoustic behavior of the structure is evaluated by the velocity of surface vibration. The noise level is reduced by improving the structure of the engine. The result shows that the surface vibration velocity level is decreased about 3.7 dB (A) at 1 600 Hz after the optimization. Based on the contrast between the two structures, it is concluded that through structure design the combined noise can be reduced, and the virtual design mode of diesel engines is feasible.

  9. Improved Multibody Dynamics for Investigating Energy Dissipation in Train Collisions Based on Scaling Laws

    Directory of Open Access Journals (Sweden)

    Heng Shao

    2016-01-01

    Full Text Available This study aimed to investigate energy dissipation in train collisions. A 1/8 scaled train model, about one-dimensional in longitudinal direction, was used to carry out a scaled train collision test. Corresponding multibody dynamic simulations were conducted using traditional and improved method model (IMM in ADAMS. In IMM, the connection between two adjacent cars was expressed by a nonlinear spring and energy absorbing structures were equivalently represented by separate forces, instead of one force. IMM was able to simulate the motion of each car and displayed the deformation of structures at both ends of the cars. IMM showed larger deformations and energy absorption of structures in moving cars than those in stationary cars. Moreover, the asymmetry in deformation proportion in main energy absorbing structures decreased with increasing collision speed. The asymmetry decreased from 11.69% to 3.60% when the collision speed increased from 10 km/h to 36 km/h.

  10. Newton-Euler Dynamic Equations of Motion for a Multi-body Spacecraft

    Science.gov (United States)

    Stoneking, Eric

    2007-01-01

    The Magnetospheric MultiScale (MMS) mission employs a formation of spinning spacecraft with several flexible appendages and thruster-based control. To understand the complex dynamic interaction of thruster actuation, appendage motion, and spin dynamics, each spacecraft is modeled as a tree of rigid bodies connected by spherical or gimballed joints. The method presented facilitates assembling by inspection the exact, nonlinear dynamic equations of motion for a multibody spacecraft suitable for solution by numerical integration. The building block equations are derived by applying Newton's and Euler's equations of motion to an "element" consisting of two bodies and one joint (spherical and gimballed joints are considered separately). Patterns in the "mass" and L'force" matrices guide assembly by inspection of a general N-body tree-topology system. Straightforward linear algebra operations are employed to eliminate extraneous constraint equations, resulting in a minimum-dimension system of equations to solve. This method thus combines a straightforward, easily-extendable, easily-mechanized formulation with an efficient computer implementation.

  11. Aeroelastic deployable wing simulation considering rotation hinge joint based on flexible multibody dynamics

    Science.gov (United States)

    Otsuka, Keisuke; Makihara, Kanjuro

    2016-05-01

    Morphing wings have been developed by several organizations for a variety of applications including the changing of flight ability while in the air and reducing the amount of space required to store an aircraft. One such example of morphing wings is the deployable wing that is expected to be used for Mars exploration. When designing wings, aeroelastic simulation is important to prevent the occurrence of destructive phenomena while the wing is in use. Flutter and divergence are typical issues to be addressed. However, it has been difficult to simulate the aeroelastic motion of deployable wings because of the significant differences between these deployable wings and conventional designs. The most apparent difference is the kinematic constraints of deployment, typically a hinge joint. These constraints lead not only to deformation but also to rigid body rotation. This research provides a novel method of overcoming the difficulties associated with handling these kinematic constraints. The proposed method utilizes flexible multibody dynamics and absolute nodal coordinate formulation to describe the dynamic motion of a deployable wing. This paper presents the simulation of the rigid body rotation around the kinematic constraints as induced by the aeroelasticity. The practicality of the proposed method is confirmed.

  12. Analysis of Free Pendulum Vibration Absorber Using Flexible Multi-Body Dynamics

    Directory of Open Access Journals (Sweden)

    Emrah Gumus

    2016-01-01

    Full Text Available Structures which are commonly used in our infrastructures are becoming lighter with progress in material science. These structures due to their light weight and low stiffness have shown potential problem of wind-induced vibrations, a direct outcome of which is fatigue failure. In particular, if the structure is long and flexible, failure by fatigue will be inevitable if not designed properly. The main objective of this paper is to perform theoretical analysis for a novel free pendulum device as a passive vibration absorber. In this paper, the beam-tip mass-free pendulum structure is treated as a flexible multibody dynamic system and the ANCF formulation is used to demonstrate the coupled nonlinear dynamics of a large deflection of a beam with an appendage consisting of a mass-ball system. It is also aimed at showing the complete energy transfer between two modes occurring when the beam frequency is twice the ball frequency, which is known as autoparametric vibration absorption. Results are discussed and compared with findings of MSC ADAMS. This novel free pendulum device is practical and feasible passive vibration absorber in the mitigation of large amplitude wind-induced vibrations in traffic signal structures.

  13. An Explicit Formulation of Singularity-Free Dynamic Equations of Mechanical Systems in Lagrangian Form---Part Two: Multibody Systems

    Directory of Open Access Journals (Sweden)

    Pål Johan From

    2012-04-01

    Full Text Available This paper presents the explicit dynamic equations of multibody mechanical systems. This is the second paper on this topic. In the first paper the dynamics of a single rigid body from the Boltzmann--Hamel equations were derived. In this paper these results are extended to also include multibody systems. We show that when quasi-velocities are used, the part of the dynamic equations that appear from the partial derivatives of the system kinematics are identical to the single rigid body case, but in addition we get terms that come from the partial derivatives of the inertia matrix, which are not present in the single rigid body case. We present for the first time the complete and correct derivation of multibody systems based on the Boltzmann--Hamel formulation of the dynamics in Lagrangian form where local position and velocity variables are used in the derivation to obtain the singularity-free dynamic equations. The final equations are written in global variables for both position and velocity. The main motivation of these papers is to allow practitioners not familiar with differential geometry to implement the dynamic equations of rigid bodies without the presence of singularities. Presenting the explicit dynamic equations also allows for more insight into the dynamic structure of the system. Another motivation is to correct some errors commonly found in the literature. Unfortunately, the formulation of the Boltzmann-Hamel equations used here are presented incorrectly. This has been corrected by the authors, but we present here, for the first time, the detailed mathematical details on how to arrive at the correct equations. We also show through examples that using the equations presented here, the dynamics of a single rigid body is reduced to the standard equations on a Lagrangian form, for example Euler's equations for rotational motion and Euler--Lagrange equations for free motion.

  14. A joint-space numerical model of metabolic energy expenditure for human multibody dynamic system.

    Science.gov (United States)

    Kim, Joo H; Roberts, Dustyn

    2015-09-01

    Metabolic energy expenditure (MEE) is a critical performance measure of human motion. In this study, a general joint-space numerical model of MEE is derived by integrating the laws of thermodynamics and principles of multibody system dynamics, which can evaluate MEE without the limitations inherent in experimental measurements (phase delays, steady state and task restrictions, and limited range of motion) or muscle-space models (complexities and indeterminacies from excessive DOFs, contacts and wrapping interactions, and reliance on in vitro parameters). Muscle energetic components are mapped to the joint space, in which the MEE model is formulated. A constrained multi-objective optimization algorithm is established to estimate the model parameters from experimental walking data also used for initial validation. The joint-space parameters estimated directly from active subjects provide reliable MEE estimates with a mean absolute error of 3.6 ± 3.6% relative to validation values, which can be used to evaluate MEE for complex non-periodic tasks that may not be experimentally verifiable. This model also enables real-time calculations of instantaneous MEE rate as a function of time for transient evaluations. Although experimental measurements may not be completely replaced by model evaluations, predicted quantities can be used as strong complements to increase reliability of the results and yield unique insights for various applications.

  15. SMA actuator material model with self-sensing and sliding-mode control; experiment and multibody dynamics model

    Science.gov (United States)

    Lambert, Tyler Ross; Gurley, Austin; Beale, David

    2017-03-01

    Shape memory alloys (SMA) can be used to create actuators that are simple, high strength, and inexpensive. These benefits come at the cost of low electrical efficiency, moderate lifetime, and complex mechanical behavior that makes them difficult to design into new applications and products. To improve the integration of SMA actuators—in particular thin SMA wires heated by passing electric current through them—into modern mechanical applications, we have created tools for modeling SMA mechanical and thermal behavior in dynamic systems and under feedback controls. Thermo-electro-mechanical constitutive models are implemented in a multibody dynamics software where they are easily applied to an actuator emplaced in a multibody dynamic system. Mechanical behavior is modeled with 1D constitutive equations. The material state determines the electrical resistivity of the material which drives ohmic heating, while thermal cooling is based on a heat transfer analysis of thin cylinders. These models contain states which are very difficult to measure experimentally (such as crystal phase fraction) and thus provide insight into the material behavior and design that experimental results cannot offer. This thermomechanical model is used in conjunction with sliding mode control—historically difficult to simulate in numerically integrated models—to develop a working ball-on-a-beam setup in which the ball position is controlled via current passed through an SMA wire and with application of an original self-sensing method. The constitutive model is developed in the multibody dynamics software MSC ADAMS and validated through the simulation of the same system.

  16. Lagrangian Dynamics of Open Multibody Systems with Generalized Holonomic and Nonholonomic Joints

    NARCIS (Netherlands)

    Duindam, Vincent; Stramigioli, Stefano

    2007-01-01

    Standard methods to model multibody systems are aimed at systems with configuration spaces isomorphic to Rn. This limitation leads to singularities and other artifacts in case the configuration space has a different topology, for example in the case of ball joints or a free-floating mechanism. This

  17. Multibody dynamics modelling and system identification of a quarter-car test rig with McPherson strut suspension

    Science.gov (United States)

    Sandu, Corina; Andersen, Erik R.; Southward, Steve

    2011-02-01

    In this paper, we develop a multibody dynamics model of a quarter-car test-rig equipped with a McPherson strut suspension and we apply a system identification technique on it. Constrained equations of motion in the Lagrange multiplier form are derived and employed to characterise the dynamic behaviour of the test rig modelled once as a linear system and once as a non-linear system. The system of differential algebraic equations is integrated using a Hilber-Hughes-Taylor integrator. The responses of both models (linear and non-linear) to a given displacement input are obtained and compared with the experimental response recorded using the physical quarter-car test rig equipped with a McPherson strut suspension. The system identification is performed for control purposes. The results, as well as the performance and area of applicability of the test rig models derived, are discussed.

  18. Comparison of Selected Formulations for Multibody System Dynamics with Redundant Constraints

    Directory of Open Access Journals (Sweden)

    Pękal Marcin

    2016-03-01

    Full Text Available This paper compares selected optimization-based methods for the analysis of multibody systems with redundant constraints. The following numerical schemes are examined: direct integration method, Udwadia-Kalaba formulation, two types of least-squares block solution method and Udwadia-Phohomsiri formulation. In order to compare efficiency of the algorithms, a series of simulations is performed on two exemplary McPherson struts. In the first variant, the mechanism has no redundant constraints whereas the other is overconstrained. Three constraint stabilization schemes are also compared in terms of integration errors.

  19. Prediction of in vivo joint mechanics of an artificial knee implant using rigid multi-body dynamics with elastic contacts.

    Science.gov (United States)

    Chen, Zhenxian; Zhang, Xuan; Ardestani, Marzieh M; Wang, Ling; Liu, Yaxiong; Lian, Qin; He, Jiankang; Li, Dichen; Jin, Zhongmin

    2014-06-01

    Lower extremity musculoskeletal computational models play an important role in predicting joint forces and muscle activation simultaneously and are valuable for investigating functional outcomes of the implants. However, current computational musculoskeletal models of total knee replacement rarely consider the bearing surface geometry of the implant. Therefore, these models lack detailed information about the contact loading and joint motion which are important factors for evaluating clinical performances. This study extended a rigid multi-body dynamics simulation of a lower extremity musculoskeletal model to incorporate an artificial knee joint, based upon a novel force-dependent kinematics method, and to characterize the in vivo joint contact mechanics during gait. The developed musculoskeletal total knee replacement model integrated the rigid skeleton multi-body dynamics and the flexible contact mechanics of the tibiofemoral and patellofemoral joints. The predicted contact forces and muscle activations are compared against those in vivo measurements obtained from a single patient with good agreements for the medial contact force (root-mean-square error = 215 N, ρ = 0.96) and lateral contact force (root-mean-square error = 179 N, ρ = 0.75). Moreover, the developed model also predicted the motion of the tibiofemoral joint in all degrees of freedom. This new model provides an important step toward the development of a realistic dynamic musculoskeletal total knee replacement model to predict in vivo knee joint motion and loading simultaneously. This could offer a better opportunity to establish a robust virtual modeling platform for future pre-clinical assessment of knee prosthesis designs, surgical procedures and post-operation rehabilitation.

  20. Convergence of a class of semi-implicit time-stepping schemes for nonsmooth rigid multibody dynamics.

    Energy Technology Data Exchange (ETDEWEB)

    Gavrea, B. I.; Anitescu, M.; Potra, F. A.; Mathematics and Computer Science; Univ. of Pennsylvania; Univ. of Maryland

    2008-01-01

    In this work we present a framework for the convergence analysis in a measure differential inclusion sense of a class of time-stepping schemes for multibody dynamics with contacts, joints, and friction. This class of methods solves one linear complementarity problem per step and contains the semi-implicit Euler method, as well as trapezoidal-like methods for which second-order convergence was recently proved under certain conditions. By using the concept of a reduced friction cone, the analysis includes, for the first time, a convergence result for the case that includes joints. An unexpected intermediary result is that we are able to define a discrete velocity function of bounded variation, although the natural discrete velocity function produced by our algorithm may have unbounded variation.

  1. A multibody dynamics model of contact between the drillstring and the wellbore and the rock penetration process

    Directory of Open Access Journals (Sweden)

    Ningyu Wang

    2015-05-01

    Full Text Available This article models the contact between the drillstring with large slenderness ratio and the extending rigid wellbore based on the multibody dynamics method. The drillstring is modeled as absolute nodal coordinate formulation beams with contact detection points. An algorithm is developed to locate the contact points and calculate the contact forces when the drillstring is sliding and rotating in the wellbore. This provides support force and friction for the moving drillstring and effectively confines it inside the wellbore. A rock penetration model is established based on the rock-breaking velocity equation. The governing equation for the full-hole drilling system including the drillstring and the contact model is established and solved. A rock penetration correction method is proposed to stabilize the computation and to model and simulate the slide drilling process. A field drilling process is modeled and simulated. The simulation result fits the experimental result well.

  2. Development of Constraint Force Equation Methodology for Application to Multi-Body Dynamics Including Launch Vehicle Stage Seperation

    Science.gov (United States)

    Pamadi, Bandu N.; Toniolo, Matthew D.; Tartabini, Paul V.; Roithmayr, Carlos M.; Albertson, Cindy W.; Karlgaard, Christopher D.

    2016-01-01

    The objective of this report is to develop and implement a physics based method for analysis and simulation of multi-body dynamics including launch vehicle stage separation. The constraint force equation (CFE) methodology discussed in this report provides such a framework for modeling constraint forces and moments acting at joints when the vehicles are still connected. Several stand-alone test cases involving various types of joints were developed to validate the CFE methodology. The results were compared with ADAMS(Registered Trademark) and Autolev, two different industry standard benchmark codes for multi-body dynamic analysis and simulations. However, these two codes are not designed for aerospace flight trajectory simulations. After this validation exercise, the CFE algorithm was implemented in Program to Optimize Simulated Trajectories II (POST2) to provide a capability to simulate end-to-end trajectories of launch vehicles including stage separation. The POST2/CFE methodology was applied to the STS-1 Space Shuttle solid rocket booster (SRB) separation and Hyper-X Research Vehicle (HXRV) separation from the Pegasus booster as a further test and validation for its application to launch vehicle stage separation problems. Finally, to demonstrate end-to-end simulation capability, POST2/CFE was applied to the ascent, orbit insertion, and booster return of a reusable two-stage-to-orbit (TSTO) vehicle concept. With these validation exercises, POST2/CFE software can be used for performing conceptual level end-to-end simulations, including launch vehicle stage separation, for problems similar to those discussed in this report.

  3. Numerical methods for multibody systems

    Science.gov (United States)

    Glowinski, Roland; Nasser, Mahmoud G.

    1994-01-01

    This article gives a brief summary of some results obtained by Nasser on modeling and simulation of inequality problems in multibody dynamics. In particular, the augmented Lagrangian method discussed here is applied to a constrained motion problem with impulsive inequality constraints. A fundamental characteristic of the multibody dynamics problem is the lack of global convexity of its Lagrangian. The problem is transformed into a convex analysis problem by localization (piecewise linearization), where the augmented Lagrangian has been successfully used. A model test problem is considered and a set of numerical experiments is presented.

  4. Application of stabilization techniques in the dynamic analysis of multibody systems

    Directory of Open Access Journals (Sweden)

    Hajžman M.

    2007-11-01

    Full Text Available This paper is intended to the discussion of possible methods for the solution of the motion equations of constrained multibody systems. They can be formulated in the form of differential-algebraic equations and their numerical solution brings the problems of constraint violation and numerical stability. Therefore special methods were proposed to handle these problems. Various approaches for the numerical solution of equations are briefly reviewed and the application of the Baumgarte’s stabilization method on testing examples is shown. The paper was motivated by the effort to find the suitable solution methods for the equations of motion in the form of differentialalgebraic equations using the MATLAB standard computational system.

  5. Dynamic analysis of multibodies system with a floating base for rolling of ro-ro ship caused by wave and slip of heavy load

    Institute of Scientific and Technical Information of China (English)

    SHEN Qing; LI Yue; CHEN Xu-jun

    2003-01-01

    Common effect of wave and slip of internal heavy load will make rolling of the roll-on ship serious. This is one of the important reasons for overturn of ro-ro ships. The multibodies System with a floating base is composed of ro-ro ship and slipping heavy load. This paper takes the rolling angle of the ship and the transverse displacement of the heavy load on desk as two freedoms. Making use of analysis of apparent gravitation and apparent buoyancy, the wave rolling moment is derived. By use of dynamic method of multibodies system with a floating base, dynamic equations of the system are established. Taking a certain channel ferry as an example, a set of numerical calculation have been carried out for rolling response of the ship and displacement response of the slipping heavy load under common effect of synchro-slipping heavy loads and wave.

  6. Analysis for the Deployment of Single-Point Mooring Buoy System Based on Multi-Body Dynamics Method

    Institute of Scientific and Technical Information of China (English)

    CHANG Zong-yu; TANG Yuan-guang; LI Hua-jun; YANG Jian-ming; WANG Lei

    2012-01-01

    Deployment of buoy systems is one of the most important procedures for the operation of buoy system.In the present study,a single-point mooring buoy system which contains surface buoy,cable segments with components,anchor and so on is modeled by applying multi-body dynamics method.The motion equations are developed in discrete node description and fully Cartesian coordinates.Then numerical method is used to solve the ordinary differential equations and dynamics simulations are achieved while anchor is casting from board.The trajectories and velocities of different nodes without current and with current in buoy system are obtained.The transient tension force of each part of the cable is analyzed in the process of deployment.Numerical results indicate that the transient payload increases to a peak value when the anchor is touching the seabed and the maximum tension force will vary with different floating configuration.This work is helpful for design and deployment planning of buoy system.

  7. Discrete time transfer matrix method for dynamics of multibody system with flexible beams moving in space

    Institute of Scientific and Technical Information of China (English)

    Xiao-Ting Rui; Edwin Kreuzer; Bao Rong; Bin He

    2012-01-01

    In this paper,by defining new state vectors and developing new transfer matrices of various elements moving in space,the discrete time transfer matrix method of multi-rigid-flexible-body system is expanded to study the dynamics of muhibody system with flexible beams moving in space.Formulations and numerical example of a rigidflexible-body three pendulums system moving in space are given to validate the method. Using the new method to study the dynamics of multi-rigid-flexible-body system mov ing in space,the global dynamics equations of system are not needed,the orders of involved matrices of the system are very low and the computational speed is high,irrespective of the size of the system.The new method is simple,straightforward,practical,and provides a powerful tool for multi-rigid-flexible-body system dynamics.

  8. Gain in computational efficiency by vectorization in the dynamic simulation of multi-body systems

    Science.gov (United States)

    Amirouche, F. M. L.; Shareef, N. H.

    1991-01-01

    An improved technique for the identification and extraction of the exact quantities associated with the degrees of freedom at the element as well as the flexible body level is presented. It is implemented in the dynamic equations of motions based on the recursive formulation of Kane et al. (1987) and presented in a matrix form, integrating the concepts of strain energy, the finite-element approach, modal analysis, and reduction of equations. This technique eliminates the CPU intensive matrix multiplication operations in the code's hot spots for the dynamic simulation of the interconnected rigid and flexible bodies. A study of a simple robot with flexible links is presented by comparing the execution times on a scalar machine and a vector-processor with and without vector options. Performance figures demonstrating the substantial gains achieved by the technique are plotted.

  9. Varying parameter models to accommodate dynamic promotion effects

    NARCIS (Netherlands)

    Foekens, E.W.; Leeflang, P.S.H.; Wittink, D.R.

    1999-01-01

    The purpose of this paper is to examine the dynamic effects of sales promotions. We create dynamic brand sales models (for weekly store-level scanner data) by relating store intercepts and a brand's own price elasticity to a measure of the cumulated previous price discounts - amount and time - for t

  10. Spatial multibody modeling and vehicle dynamics analysis of advanced vehicle technologies

    Science.gov (United States)

    Letherwood, Michael D.; Gunter, David D.; Gorsich, David J.; Udvare, Thomas B.

    2004-08-01

    The US Army vision, announced in October of 1999, encompasses people, readiness, and transformation. The goal of the Army vision is to transition the entire Army into a force that is strategically responsive and dominant at every point of the spectrum of operations. The transformation component will be accomplished in three ways: the Objective Force, the Legacy (current) Force, and the Interim Force. The objective force is not platform driven, but rather the focus is on achieving capabilities that will operate as a "system of systems." As part of the Objective Force, the US Army plans to begin production of the Future Combat System (FCS) in FY08 and field the first unit by FY10 as currently defined in the FCS solicitation(1). As part of the FCS program, the Future Tactical Truck System (FTTS) encompasses all US Army tactical wheeled vehicles and its initial efforts will focus only on the heavy class. The National Automotive Center (NAC) is using modeling and simulation to demonstrate the feasibility and operational potential of advanced commercial and military technologies with application to new and existing tactical vehicles and to describe potential future vehicle capabilities. This document will present the results of computer-based, vehicle dynamics performance assessments of FTTS concepts with such features as hybrid power sources, active suspensions, skid steering, and in-hub electric drive motors. Fully three-dimensional FTTS models are being created using commercially available modeling and simulation methodologies such as ADAMS and DADS and limited vehicle dynamics validation studies are will be performed.

  11. Dynamic distance direct ophthalmoscopy, a novel technique to assess accommodation in children

    Directory of Open Access Journals (Sweden)

    Mihir Kothari

    2012-01-01

    Full Text Available Aim: To describe and compare dynamic distance direct ophthalmoscopy (DDDO with dynamic retinoscopy (DR in assessment of accommodation in children. Materials and Methods: This prospective observational study had four components. Component 1: to understand the characteristic digital images of DDDO. Component 2: to compare DDDO with DR for detection of accommodative defects in children (1-16 years. Component 3: to compare DDDO with DR for the detection of completeness of pharmacologically induced cycloplegia in children (5-16 years and Component 4: to assess which one of the two techniques was more sensitive to detect onset of cycloplegia after instillation of 1% cyclopentolate eye drops. Results: Component 1: image analysis of DDDO on two subjects (7 years and 35 years demonstrated superior pupillary crescent that progressively disappeared with increasing accommodation. Concurrently an inferior crescent appeared that became bigger in size with increasing accommodation. Component 2: the prevalence of defects in accommodation was 3.3% (33/1000 children. Three had unilateral accommodation failure. Sensitivity of DDDO was 94%, specificity 100%, positive predictive value 100%, negative predictive value 99%, and clinical agreement (kappa 0.97. Component 3: in the detection of completeness of pharmacologically induced cycloplegia (n=30, the sensitivity of DDDO was 94%, specificity 96%, positive predictive value 97%, negative predictive value 93% and kappa 0.9. DR had two false positives. DDDO had one false negative. Component 4: DDDO detected onset of pharmacologically induced cycloplegia 5 min earlier than DR (n=5. Conclusion: DDDO is a novel, simple, clinical and reliable method to assess accommodation in young children. This test can assess the accommodative response of both eyes simultaneously.

  12. Dynamic performance of accommodating intraocular lenses in a negative feedback control system: a simulation-based study.

    Science.gov (United States)

    Schor, Clifton M; Bharadwaj, Shrikant R; Burns, Christopher D

    2007-07-01

    A dynamic model of ocular accommodation is used to simulate the stability and dynamic performance of accommodating intraocular lenses (A-IOLs) that replace the hardened natural ocular lens that is unable to change focus. Accommodation simulations of an older eye with A-IOL materials having biomechanical properties of a younger eye illustrate overshoots and oscillations resulting from decreased visco-elasticity of the A-IOL. Stable dynamics of an A-IOL are restored by adaptation of phasic and tonic neural-control properties of accommodation. Simulations indicate that neural control must be recalibrated to avoid unstable dynamic accommodation with A-IOLs. An interactive web-model of A-IOL illustrating these properties is available at http://schorlab.berkeley.edu.

  13. 爆破拆除科技发展及多体-离散体动力学%Scientific Development of Explosive Demolition and Multibody-discretebody Dynamics

    Institute of Scientific and Technical Information of China (English)

    魏晓林

    2015-01-01

    多体—离散体动力学是爆破拆除科技理论发展的新阶段。研究描述了建筑物爆破拆除科技的发展历程,定义了建筑物倒塌动力学及包含的多体—离散体动力学,突出了与传统多体的不同特点,建立了动力学方程,列举出典型拆除动力学方程实例,求取其解析解和近似解,提出动力学方程的相似性及无量纲规整应用,实现了变拓扑多体—离散体动力学的全局仿真,阐明了与方程运算参数有关的破损材料力学和混凝土构件冲击动力学。应用多体动力学,可简便地将拆除模型导出各类建筑结构各种倒塌方式的切口尺寸、爆堆形态、后坐下坐、起爆次序和分段时差等无量纲表达,为高大建(构)筑物选择合理的倒塌方式、拆除措施和切口参数提供了完整理论和简单实用算法,实现了对爆破拆除的精确控制。%The multi-discrete body dynamics was new scientific idea in explosive demolition. The building explo-sive demolition was described. The dynamics behavior of building toppling down and multi-discrete body dynamics was defined. The dynamic characteristic was different from traditional multi-body system. The dynamic equations and the representative equations of demolition were erected and enumerated,finally the approximate solutions were put forward. The dynamic equations comparability and applications of complete dimensionless were given. The complete chessboard emulating of variable topological multi-discrete body dynamics were performed. The parameters of material mechanics and impact dynamics of concrete component concerning the equation computing were clarified. With the multi-body dynamics,the demolition model was simply educed such as the dimensionless expression of cutting size, shape of muck pile,back and down sitting,firing order and delay time of collapse types of different buildings. In order to choose reasonable collapse scheme

  14. Multibody simulation of adhesion pili

    CERN Document Server

    Zakrisson, Johan; Servin, Martin; Axner, Ove; Lacoursiere, Claude; Andersson, Magnus

    2014-01-01

    We present a coarse grained rigid multibody model of a subunit assembled helix-like polymer, e.g., adhesion pili expressed by bacteria, that is capable of describing the polymers force-extension response. With building blocks representing individual subunits the model appropriately describes the complex behavior of pili expressed by the gram-negative uropathogenic Escherichia coli bacteria under the action of an external force. Numerical simulations show that the dynamics of the model, which include both the effects of unwinding and rewinding, are in good quantitative agreement with the characteristic force-extension response as observed experimentally for type 1 and P pili. By tuning the model, it is also possible to reproduce the force-extension response in the presence of anti-shaft antibodies, which dramatically changes the mechanical properties. Thus, the model and the results in this work give enhanced understanding of how a pilus unwinds under action of external forces and provide new perspective of th...

  15. 斜齿行星传动多体动力学建模与分析%Multibody dynamic modeling and analysis for a helical planetary gear train

    Institute of Scientific and Technical Information of China (English)

    张俊; 刘先增

    2014-01-01

    A multibody dynamic model for a helical planetary gear train (HPGT)was proposed and the dynamic performance of the HPGT system was analyzed.Its free vibration characteristics,steady-state dynamic responses and the effects of design parameters on the system dynamic behavior were investigated with numerical simulations.The free vibration of the HGPT was classified into 3 categories according to modal properties,such as,eigenvalue multiplies, modal coordinates of central components and coordinate ratios of planets.The classified vibration modes were axial translational and torsional mode (AT mode ),radial translational and rotational mode (RR mode )and planet mode (P mode).The characteristics of each category were presented.The simulation results agreed well with those using the previous discretized model neglecting the component flexibilities to validate the correctness of the proposed multibody dynamic model.The steady-state dynamic responses indicated that the dynamic meshing forces fluctuate about the average static values and the time-varying meshing stiffness is the major excitation of the system.The parametric sensitivity analysis showed that the floating sun gear and the reduction of circumferential assembly error of planets are effective to suppress the vibration of the HGPT.%建立了斜齿行星传动的多体动力学模型,对其进行了动态特性仿真,获知了该类系统的自由振动特性、稳态动力响应以及部分设计参数对系统动态特性的影响规律。根据系统特征值的重根数、中心构件的振型坐标及各行星轮间振型坐标的比例,将斜齿行星轮系的自由振动归结为3类典型振动模式,即:轴向平移-扭转振动模式、径向平移-扭摆振动模式和行星轮振动模式,并进一步给出了各类模式的特点。当不考虑构件自身柔性时,基于多体动力学模型的自由振动特性与前人的集中参数模型的仿真结果完全一致,表明了本文

  16. Study on movement inertia in the Earth multi-body system

    Institute of Scientific and Technical Information of China (English)

    CHEN; Xiaofei; BI; Siwen; GONG; Huili

    2006-01-01

    This paper summarizes the first movement and mass centre of stratum-block movement inertia in the Earth multi-body system and introduces its application. It also elaborates the moment of inertia and the products of inertia: the inertia dyadic transformation of reference system and the parallel axis theorem of stratum-block movement inertia of the Earth multi-body system. It provides an academic foundation for research on the dynamic model of Earth multi-body system.

  17. Parallel computing studies of flexible multibody system dynamics using OpenMP and Pardiso%基于OpenMP和Pardiso的柔性多体系统动力学并行计算

    Institute of Scientific and Technical Information of China (English)

    曹大志; 强洪夫; 任革学

    2012-01-01

    Parallel algorithms were developed for multibody dynamic systems to accelerate the speed of dynamic simulations of large complex flexible multibody systems. The main computational loads during the numerical solution of the differential algebraic equations (DAEs) were analyzed with OpenMP then used to compute the system tangent matrix and residual vector in parallel and with a parallel sparse linear equation solver, Pardiso, used for the linear equations. Both of the parallel strategies were implemented in an in-house multibody algorithm for parallel analyses of multibody dynamic systems. The parallel speedup and the computational efficiency of the algorithm are quite good so the simulation speeds of multibody dynamic analyses are increased substantially.%为加快大型、复杂柔性多体系统的动力学仿真的速度,对多体系统动力学的并行算法进行研究。首先分析了微分代数方程(differentialalgebraicequations,DAEs)在数值计算求解过程中主要的计算量。据此,提出采用OpenMP并行计算系统的刚度矩阵、右端项和采用并行的稀疏线性方程组求解器Pardiso对线性方程组进行求解的并行策略。将这两种并行策略应用到自主开发的柔性多体系统动力学软件THUS01ver中,实现了对多体系统动力学的并行计算。通过两个工程算例的仿真得到并行的加速比和计算效率,结果表明:采用的两种并行策略都有很高的计算效率,能大幅提高多体系统动力学仿真的速度。

  18. Dynamics and control for Constrained Multibody Systems modeled with Maggi's equation: Application to Differential Mobile Robots Partll

    Science.gov (United States)

    Amengonu, Yawo H.; Kakad, Yogendra P.

    2014-07-01

    Quasivelocity techniques were applied to derive the dynamics of a Differential Wheeled Mobile Robot (DWMR) in the companion paper. The present paper formulates a control system design for trajectory tracking of this class of robots. The method develops a feedback linearization technique for the nonlinear system using dynamic extension algorithm. The effectiveness of the nonlinear controller is illustrated with simulation example.

  19. A computational procedure for the dynamics of flexible beams within multibody systems. Ph.D. Thesis Final Technical Report

    Science.gov (United States)

    Downer, Janice Diane

    1990-01-01

    The dynamic analysis of three dimensional elastic beams which experience large rotational and large deformational motions are examined. The beam motion is modeled using an inertial reference for the translational displacements and a body-fixed reference for the rotational quantities. Finite strain rod theories are then defined in conjunction with the beam kinematic description which accounts for the effects of stretching, bending, torsion, and transverse shear deformations. A convected coordinate representation of the Cauchy stress tensor and a conjugate strain definition is introduced to model the beam deformation. To treat the beam dynamics, a two-stage modification of the central difference algorithm is presented to integrate the translational coordinates and the angular velocity vector. The angular orientation is then obtained from the application of an implicit integration algorithm to the Euler parameter/angular velocity kinematical relation. The combined developments of the objective internal force computation with the dynamic solution procedures result in the computational preservation of total energy for undamped systems. The present methodology is also extended to model the dynamics of deployment/retrieval of the flexible members. A moving spatial grid corresponding to the configuration of a deployed rigid beam is employed as a reference for the dynamic variables. A transient integration scheme which accurately accounts for the deforming spatial grid is derived from a space-time finite element discretization of a Hamiltonian variational statement. The computational results of this general deforming finite element beam formulation are compared to reported results for a planar inverse-spaghetti problem.

  20. Dynamics and Control of Constrained Multibody Systems modeled with Maggi's equation: Application to Differential Mobile Robots Part I

    Science.gov (United States)

    Amengonu, Yawo H.; Kakad, Yogendra P.

    2014-07-01

    Quasivelocity techniques such as Maggi's and Boltzmann-Hamel's equations eliminate Lagrange multipliers from the beginning as opposed to the Euler-Lagrange method where one has to solve for the n configuration variables and the multipliers as functions of time when there are m nonholonomic constraints. Maggi's equation produces n second-order differential equations of which (n-m) are derived using (n-m) independent quasivelocities and the time derivative of the m kinematic constraints which add the remaining m second order differential equations. This technique is applied to derive the dynamics of a differential mobile robot and a controller which takes into account these dynamics is developed.

  1. Linking rigid multibody systems via controllable thin fluid films

    DEFF Research Database (Denmark)

    Estupinan, Edgar Alberto; Santos, Ilmar

    2009-01-01

    , this paper gives a theoretical contribution to the combined fields of fluid–structure interaction and vibration control. The methodology is applied to a reciprocating linear compressor, where the dynamics of the mechanical components are described with help of multibody dynamics. The crank is linked...... of the journal orbits, maximum fluid film pressure and minimum fluid film thickness....

  2. DAE-LCP MIXED METHOD FOR MULTIBODY SYSTEM DYNAMICS WITH FRICTIONAL CONTACTS%多体系统摩擦接触问题的DAE-LCP方法

    Institute of Scientific and Technical Information of China (English)

    富立; 岳凤桐

    2011-01-01

    当多体系统的约束全部是摩擦接触时,其动力学问题可归结为一个常微分方程(ordinary differential equation,ODE)与线性互补问题(linear complementarity problem,LCP)的混合动力学问题.如果除了摩擦接触之外还增加了光滑的双边约束,则需要将ODE-LCP混合动力学模型推广为微分代数方程(differential algebra equation,DAE)与LCP的混合动力学模型.该文采用DAE与LCP混合动力学方法求解不考虑碰撞但同时含有持续摩擦接触及光滑等式约束的多体系统动力学问题.在建立系统动力学模型时,首先将含摩擦的约束从系统中移去得到基本动力学系统.由于基本系统中带有等式约束,所以基本系统的动力学方程为一组DAE.结合基本系统的DAE与约束的互补条件便可以得到DAE-LCP混合动力学模型.数值计算采用基于DAE与LCP的步进(time-stepping)算法,将系统动力学方程及其约束离散化并转化为一个混合LCP进行求解.该算法无需进行滞-滑状态检测,避免了事件检测导致的繁复计算.利用所提方法对典型机构的非光滑非线性特征进行了数值分析,验证了该文方法的正确有效性.%Presently, dynamics of nonsmooth multibody systems is a hot research topic. The usual approach in treating such systems is to derive basic system from the original system by removing the nonsmooth constraints firstly. The Lagrange equations of the second kind of basic system combine with the complementarity condition of the nonsmooth constraints to set up at each discrete moment in time a Linear Complementarity Problem (LCP).This article focuses on the problem of dynamic modeling and numerical simulating of multibody systems with friction contacts. By neglecting the clearance and the effect of impact between rigid bodies and constraints,the state variables in the differential equations are continuous. Due to the set-value mapping characteristic of dry friction forces, the

  3. Development of New Generation of Multibody System Computer Codes

    Science.gov (United States)

    2012-11-02

    Book ,” 2nd edn. Springer , New York. 12. Roberson, R.E., and Schwertassek, R., 1988, Dynamics of Multibody Systems, Springer Verlag, Berlin, Germany...vehicle, machine, aerospace, biomechanics , and biological system components such as tires, belt drives, rubber chains, soil, cables, ligaments, soft

  4. Active vibration control of spatial flexible multibody systems

    Energy Technology Data Exchange (ETDEWEB)

    Neto, Maria Augusta, E-mail: augusta.neto@dem.uc.pt [Universidade de Coimbra (Polo II), Departamento de Engenharia Mecanica, Faculdade de Ciencia e Tecnologia (Portugal); Ambrosio, Jorge A. C., E-mail: jorge@dem.ist.utl.pt [Instituto Superior Tecnico, Instituto de Engenharia Mecanica (Portugal); Roseiro, Luis M., E-mail: lroseiro@isec.pt [Instituto Superior de Engenharia de Coimbra, Departamento de Engenharia Mecanica (Portugal); Amaro, A., E-mail: ana.amaro@dem.uc.pt [Universidade de Coimbra (Polo II), Departamento de Engenharia Mecanica, Faculdade de Ciencia e Tecnologia (Portugal); Vasques, C. M. A., E-mail: cvasques@inegi.up.pt [Universidade do Porto, INEGI-Instituto de Engenharia Mecanica e Gestao Industrial (Portugal)

    2013-06-15

    In this work a flexible multibody dynamics formulation of complex models including elastic components made of composite materials is extended to include piezoelectric sensors and actuators. The only limitation for the deformation of a structural member is that they must remain elastic and linear when described in a coordinate frame fixed to a material point or region of its domain. The flexible finite-element model of each flexible body is obtained referring the flexible body nodal coordinates to the body fixed frame and using a diagonalized mass description of the inertia in the mass matrix and on the gyroscopic force vector. The modal superposition technique is used to reduce the number of generalized coordinates to a reasonable dimension for complex shaped structural models of flexible bodies. The active vibration control of the flexible multibody components is implemented using an asymmetric collocated piezoelectric sensor/actuator pair. An electromechanically coupled model is taken into account to properly consider the surface-bonded piezoelectric transducers and their effects on the time and spatial response of the flexible multibody components. The electromechanical effects are introduced in the flexible multibody equations of motion by the use of beam and plate/shell elements, developed to this purpose. A comparative study between the classical control strategies, constant gain and amplitude velocity feedback, and optimal control strategy, linear quadratic regulator (LQR), is performed in order to investigate their effectiveness to suppress vibrations in structures with piezoelectric sensing and actuating patches.

  5. 某型转管机枪刚柔耦合多体发射动力学仿真%Simulation of Coupled Rigid and Flexible Multi-body Dynamics on Gatling Gun

    Institute of Scientific and Technical Information of China (English)

    李涛; 王瑞林; 张军挪; 蔡伟

    2013-01-01

    以某型转管机枪为对象,研究了将CAD软件中复杂实体模型导入到ADAMS软件中的方法;考虑转管机枪实际射击条件下土壤本构关系和射手边界问题,建立了驻锄—土壤参数模型与人—枪参数模型;以多刚体动力学和柔性多体动力学理论为基础,采用ADAMS/Flex柔性体模块,建立了某型转管机枪刚柔耦合的虚拟样机仿真模型.通过对所建立的模型构件之间添加相互作用力,并进行多体发射动力学仿真和分析,获得了自动机运动过程中各主要部件的动力学特性.选取机枪自动机的速度和位移为校验指标,通过与试验数据中枪口响应位移比较,证明建立的刚柔耦合模型科学合理、准确有效,为该枪后期的结构优化与改进提供了模拟试验平台.%The method of translation complex model from CAD to ADAMS was studied on the object of Gatling gun; considering the soil constitutive relationship and the striker boundary problem in the actual shooting condition,spade-soil system and Parameter models of man-gun system were built; based on rigid multi-body dynamics and flexible body dynamics theories,the coupled rigid and flexible ADAMS model of the Gatling gun was established by using ADAMS/Flex module.The whole gun's kinematics circumstances and a series of dynamic curves were obtained during the course of simulation and analysis of coupled rigid and flexible multi-body dynamics.The Model was testified rational,accuracy and effective by comparing simulating results with the experimental data of the velocity and displacement of muzzle,which has laid the foundation for further simulation and structural optimization.

  6. Analysis of servo-constraint problems for underactuated multibody systems

    Directory of Open Access Journals (Sweden)

    R. Seifried

    2013-02-01

    Full Text Available Underactuated multibody systems have fewer control inputs than degrees of freedom. In trajectory tracking control of such systems an accurate and efficient feedforward control is often necessary. For multibody systems feedforward control by model inversion can be designed using servo-constraints. So far servo-constraints have been mostly applied to differentially flat underactuated mechanical systems. Differentially flat systems can be inverted purely by algebraic manipulations and using a finite number of differentiations of the desired output trajectory. However, such algebraic solutions are often hard to find and therefore the servo-constraint approach provides an efficient and practical solution method. Recently first results on servo-constraint problems of non-flat underactuated multibody systems have been reported. Hereby additional dynamics arise, so-called internal dynamics, yielding a dynamical system as inverse model. In this paper the servo-constraint problem is analyzed for both, differentially flat and non-flat systems. Different arising important phenomena are demonstrated using two illustrative examples. Also strategies for the numerical solution of servo-constraint problems are discussed.

  7. Static analysis of large-scale multibody system using joint coordinates and spatial algebra operator.

    Science.gov (United States)

    Omar, Mohamed A

    2014-01-01

    Initial transient oscillations inhibited in the dynamic simulations responses of multibody systems can lead to inaccurate results, unrealistic load prediction, or simulation failure. These transients could result from incompatible initial conditions, initial constraints violation, and inadequate kinematic assembly. Performing static equilibrium analysis before the dynamic simulation can eliminate these transients and lead to stable simulation. Most exiting multibody formulations determine the static equilibrium position by minimizing the system potential energy. This paper presents a new general purpose approach for solving the static equilibrium in large-scale articulated multibody. The proposed approach introduces an energy drainage mechanism based on Baumgarte constraint stabilization approach to determine the static equilibrium position. The spatial algebra operator is used to express the kinematic and dynamic equations of the closed-loop multibody system. The proposed multibody system formulation utilizes the joint coordinates and modal elastic coordinates as the system generalized coordinates. The recursive nonlinear equations of motion are formulated using the Cartesian coordinates and the joint coordinates to form an augmented set of differential algebraic equations. Then system connectivity matrix is derived from the system topological relations and used to project the Cartesian quantities into the joint subspace leading to minimum set of differential equations.

  8. Multi-body system dynamics analysis and finite element simulation on marine power transmission system%船舶传动装置多体动力学和有限元仿真技术

    Institute of Scientific and Technical Information of China (English)

    马炳杰; 周文建; 童宗鹏; 沈建平

    2011-01-01

    目前,传动装置振动计算多采用集中参数法,未将轴系振动(扭转振动、横向振动与纵向振动)以及结构振动进行综合分析,与实际情况有一定的差别.本文以典型双机并车装置传动(包括柴油机、高弹性联轴器、万向轴、传动齿轮、主轴与输出负载)为研究对象,应用多体系统动力学理论对其激励特性进行研究,为传动装置有限元动力学响应分析提供输入条件.在完成传动装置多体动力学仿真分析的基础上建立传动装置有限元分析模型,然后对传动装置进行轴系振动和结构振动有限元动力学响应分析,并进行试验验证.同时,讨论转速和隔振刚度对传动装置结构振动的影响规律.最后,通过总结,初步形成船舶传动装置基于多体动力学和有限元仿真的振动特性预估方法,以完善和充实传动装置的研究方法和理论.%The lumped parameter method is widely adopted in the vibration calculation of the transmission system currently. The aggregate analysis of the torsional vibration of the shafting, the transverse vibration,the extensional vibration and the structural vibration are not undertaken. In this thesis,the drive characteristics are researched applied the theory of the multi-body dynamics and the input conditions are supplied to the dynamic response analysis of the finite element model based on typical two-engined joint operating device ( include diesel engine, the elasticity coupling, cardan shaft, driving gear, main shaft and output load). Through the dynamic simulation with transmission system,the finite element analysis model of the transmission shafting is established, and the dynamic responses of the shafting vibration and structural vibration are analyzed, and the experimental verification was proceeded. Meanwhile, the transmission characteristics of the structure vibration about transmission system are revealed. The influence regulations about the parameters of the

  9. Influence of Amplitude, Starting Point, and Age on First- and Second-Order Dynamics of Edinger-Westphal–Stimulated Accommodation in Rhesus Monkeys

    OpenAIRE

    Baumeister, Martin; Wendt, Mark; Glasser, Adrian

    2010-01-01

    First- and second-order dynamics of Edinger-Westphal–stimulated accommodation in rhesus monkeys depend on the amplitude but not on the starting point of the response. The disaccommodative peak velocity for a given amplitude is lower in older than in younger monkeys.

  10. Structure overset grid method and its applications to simulation of multi-body separation

    Science.gov (United States)

    Zhang, HaiRui; Fan, JingJing; Yuan, Wu; Zhang, WeiHua

    2015-09-01

    This paper proposes an automatic structure overset grid method, which utilizes the hole-surface optimization with one-step searching, wall-surface grid oversetting, and dynamic overset grid approaches to achieve the high adaptability of overset grids for complex multi-body aircrafts. Specifically, based on the automatic structure overset grids, the method first solves the coupling of Navier-Stokes (N-S) unsteady flow equation and 6DOF motion equation, and establishes the multi-body collision model. Then, the numerical simulation of unsteady flow for complex aircrafts' multi-body separation, the simulation of multi-body separating trajectory and the separation safety analysis are accomplished. Thus, the method can properly handle practical engineering problems including the wing/drop tank separation, aircraft/mount separation, and cluster bomb projection. Experiments show that our numerical results match well with experimental results, which demonstrates the effectiveness of our methods in solving the multi-body separation problem for aircrafts with complex shapes.

  11. Optimal design method for force in vibration control of multi-body system with quick startup and brake

    Institute of Scientific and Technical Information of China (English)

    TANG Hua-ping; PENG Ya-qing

    2005-01-01

    A kind of active vibration control method was presented through optimal design of driving load of multi-body system with quick startup and brake. Dynamical equation of multi-body system with quick startup and brake was built, and mathematical model of representing vibration control was also set up according to the moving process from startup to brake. Then optimization vibration control model of system driving load was founded by applying theory of optimization control, which takes rigid body moving variable of braking moment as the known condition, and vibration control equation of multi-body system with quick startup and brake was converted into boundary value problem of differential equation. The transient control algorithm of vibration was put forward, which is the analysis basis for the further research. Theoretical analysis and calculation of numerical examples show that the optimal design method for the multi-body system driving load can decrease the vibration of system with duplication.

  12. Finite element approach for transient analysis of multibody systems

    Science.gov (United States)

    Wu, Shih-Chin; Chang, Che-Wei; Housner, Jerrold M.

    1992-01-01

    A three-dimensional, finite element based formulation for the transient dynamics of constrained multibody systems with trusslike configurations is presented. A convected coordinate system is used to define the rigid-body motion of individual elements in the system. Deformation of each element is defined relative to its convected coordinate system. The formulation is oriented toward joint-dominated structures. Through a series of sequential transformations, the joint degree of freedom is built into the equations of motion of the element to reduce geometric constraints. Based on the derivation, a general-purpose code has been developed. Two examples are presented to illustrate the application of the code.

  13. An Efficient Method for Synthesis of Planar Multibody Systems including Shape of Bodies as Design Variables

    DEFF Research Database (Denmark)

    Hansen, Michael R.; Hansen, John Michael

    1998-01-01

    A point contact joint has been developed and implemented in a joint coordinate based planar multibody dynamics analysis program that also supports revolute and translational joints. Further, a segment library for the definition of the contours of the point contact joints has been integrated...... in the code and as a result any desired contour shape may be defined. The sensitivities of the basic physical variables of a multibody system, i.e. the positions, velocities, accelerations, and reactions of the system with respect to the automatically identified independent design variables may be determined...

  14. Estimating the largest Lyapunov exponent in a multibody system with dry friction by using chaos synchronization

    Institute of Scientific and Technical Information of China (English)

    Shihui Fu; Qi Wang

    2006-01-01

    Using the properties of chaos synchronization. the method for estimating the largest Lyapunov exponent in a multibody system with dry friction is presented in this paper. The Lagrange equations with multipliers of the systems are given in matrix form. which is adequate for numerical calculation. The approach for calculating the generalized velocity and acceleration of the slider is given to determine slipping or sticking of the slider in the systems. For slip-slip and stick-slip multibody systems, their largest Lyapunov exponents are calculated to characterize their dynamics.

  15. 大变形复合材料薄板多体系统动力学建模%Dynamic modeling of composite thin-plate multibody systems with large deformation

    Institute of Scientific and Technical Information of China (English)

    张炜华; 刘锦阳

    2016-01-01

    Dynamic modeling theory of composite thin-plate multibody systems with large deformation was investigated.Based on Kirchhoff's assumption that the normal vector is always perpendicular to the central surface,the relation among in-plane strains,curvatures,absolute nodal coordinates and absolute gradients were derived according to the definition of Green strain,and the generalized elastic-force vector and its differentiation with respect to the generalized coordinates were derived.Equations of motion of the composite thin-plate multibody systems with large deformation were derived based on absolute nodal-coordinate formulation.Generalized method and the Newton-Raphson method were used to solve the differential-algebraic equations.Simulation of a composite thin plate applied with an external force was conducted.Comparison of the present simulation results with those obtained by ANSYS software verifies the accuracy and effectiveness of the formulation.Finally,the proposed formulation is used for numerical simulation of composite solar-array deployment mechanisms.The vibration characteristics of the driving force and constraint forces are analyzed in case of different panel layers.%对大变形复合材料薄板的多体系统动力学建模方法进行研究。基于 Kirchhoff 假设,法线与中面保持垂直,从格林应变的表达式出发,建立了面内应变和曲率与绝对位置坐标和斜率的关系,在此基础上推导了广义弹性力阵和弹性力阵对广义坐标的导数阵,用绝对节点坐标方法建立了大变形复合材料薄板多体系统的动力学方程,用广义α法和和牛顿迭代法求解微分-代数混合方程。对外载荷作用下的复合材料薄板进行数值仿真,通过与 ANSYS 的仿真结果进行对比,验证了该建模方法的准确性和快速收敛性。最后,将建模方法应用于复合材料太阳帆板展开机构的数值仿真,分析了不同铺层情况下驱动力和约束力的振动特性。

  16. Multibody interactions of actuated magnetic particles used as fluid drivers in microchannels

    NARCIS (Netherlands)

    Derks, R.J.S.; Frijns, A.J.H.; Prins, M.W.J.; Dietzel, A.H.

    2010-01-01

    The forced motion of superparamagnetic particles and their multibody interactions are studied in view of the application as integrated fluid drivers in microchannel systems. Previous studies on particle manipulation in open fluid volumes serve as our starting point for the analysis of particle dynam

  17. On validation of multibody musculoskeletal models

    DEFF Research Database (Denmark)

    Lund, Morten Enemark; de Zee, Mark; Andersen, Michael Skipper;

    2012-01-01

    This paper reviews the opportunities to validate multibody musculoskeletal models in view of the current transition of musculoskeletal modelling from a research topic to a practical simulation tool in product design, healthcare and other important applications. This transition creates a new need...... for improvement of the validation of multibody musculoskeletal models are pointed out and directions for future research in the field are proposed. It is our hope that a more structured approach to model validation can help to improve the credibility of musculoskeletal models....

  18. X-37 separation from a B-52H: application of multi-body dynamics and closed-loop feedback using overset CFD

    Energy Technology Data Exchange (ETDEWEB)

    Jolly, B.; Rizk, M. [Jacobs Sverdrup Tech., TEAS Group, Elgin AFB, Florida (United States)]. Email: jollyb@eglin.af.mil; Moran, R. [United States Air Force, Elgin AFB, Florida (United States)

    2005-07-01

    The Air Force SEEK EAGLE Office (AFSEO) provided independent aerodynamic data, which was key in the separation analysis for the X-37 Approach and Landing Test Vehicle (ALTV). To ensure the best aerodynamic B-52H interference database would be generated for the analysis, NASA contracted both NASA Johnson Space Center (JSC) and the AFSEO via the 412th Flight Test Squadron (Edwards AFB CA) to run independent Computational Fluid Dynamics (CFD) studies. These data were then compared to the existing database from Boeing to establish confidence and determine areas of uncertainty. NASA requested CFD data from the AFSEO primarily for static and carriage solutions of the X-37 at various positions under the B-52H. In addition, several dynamic simulations of X-37 trajectories used rate feedback control to deflect the control surfaces to stabilize the X-37. The AFSEO CFD team calculated 140 static, unsteady solutions and 9 dynamic time-accurate trajectory simulations between April 2003 and June 2004 to support the NASA X-37 ALTV program. The computational models used structured adjacent and overlapping grids with the total computational domain consisting of 25 million points in 315 grids. The rate-control autopilot commanded both yaw and roll in four control surfaces; pitch commands were preset. The results show significant increase in stability of the X-37 trajectory from the B-52H. (author)

  19. 汽车-行人碰撞多体动力学仿真与抛距模型研究%Simulation of Car-Pedestrian Collision Multi-body Dynamics and Study of Throwing Distance Model

    Institute of Scientific and Technical Information of China (English)

    谢州凯; 王秋成; 刘卫国; 宁晓斌

    2012-01-01

    汽车与行人碰撞是我国道路交通事故的主要类型之一,该类事故在所有事故中致死率最高且与人们的安全出行密切相关,受到民众的广泛关注.然而传统的事故分析方法在此类事故的处理上存在较大困难.文章以多体动力学理论为基础,以PC-CRASH为平台,建立了多刚体数字化行人模型,通过设定代表身体各部分的属性(外形、质量、刚度、摩擦系数等)来定义行人特征.并将模型与国外某实车碰撞试验对比验证其可靠性.通过对仿真结果的回归分析得出了车速-抛距模型,为该类交通事故处理提供了数据参考.%Vehicle-pedestrian collision is a major type traffic accident in China. Because of its high fatality rate and closely related with people's travelling, people pay close attention to this type of accident. However, it is difficult to handle such kind of accident with common use "accident analyzing method". Based on multi-body dynamic theory, the paper built a numerical multi-rigid-body pedestrian model as a platform for PC-CRASH to simulate the collision between vehicle and pedestrian. Through setting rigid-body characters of different parts of the pedestrian (appearance , mass, rigid, friction factor) , the characters of pedestrian can be defined. The model was validated by comparing with a real car collision experiment abroad. The speed throwing distance was obtained through the regression analysis of simulation results. It provides numerical reference for such vehicle-pedestrian traffic accident. [Ch,5 fig. 3 tab. 13 ref.

  20. Multi-body Dynamic Modeling and Mobility Simulation Analysis of Deep Ocean Tracked Miner%深海履带式集矿机多体动力学建模与行走性能仿真分析

    Institute of Scientific and Technical Information of China (English)

    张滔; 戴瑜; 刘少军; 陈君; 黄中华

    2015-01-01

    Deep seafloor extremely soft cohesive sediment is completely different from land surface soils, which need high requirements for structure design and mobility performance of the seafloor operated machine. According to the physical and mechanical properties of the seafloor sediment, laboratory simulated sediment is prepared. Based on the theory of terramechanics, mechanics experiments on the simulated tracks and simulated sediment interactions are performed. The normal pressure-sinkage and horizontal shear stress-shear displacement mathematical relationships are obtained. According to the detailed structure design parameters of the deep seafloor tracked miner, its multi-body dynamic model is built by the dynamic modeling and simulation code RecurDyn/Track. Application of the mechanics relationships of the seafloor sediment obtained from experiments, user-written subroutines are compiled with C language. Based on the secondary development for RecurDyn/Track, the development of the deep seafloor sediment mechanics model in the RecurDyn/Track is realized. Various dynamic simulations of the tracked miner on the seafloor special sediment are carried out. The mobility performance of the miner are analyzed and evaluated, which lay the foundations for the structure design optimization, mobility performance evaluation and moving control of the practical deep seafloor tracked miner.%深海底极稀软底质是一种完全不同于陆地表面的特殊底质,对海底作业机器的结构设计及其行走性能提出高要求。根据海底底质物理力学特性,配制实验室模拟底质,基于车辆地面力学理论,开展模拟履带板与模拟底质相互作用力学特性试验,分别获得法向压力-沉陷、水平切应力-剪切位移函数关系式。根据深海底履带式集矿机详细结构设计参数,采用动力学建模与仿真程序 RecurDyn/Track 构建海底履带式集矿机多体动力学模型。应用实验室模拟试验获得

  1. Natural Frequency Analysis of Wind Turbines Based on Flexible Multi-body Dynamics%基于柔性多体动力学的风力发电机固有振动频率研究

    Institute of Scientific and Technical Information of China (English)

    张丰豪; 何榕

    2014-01-01

    The horizontal axis wind turbine has a tendency of being larger and more flexible, which results in the linear dynamic models based on small deflection assumption inappropriate. The coupled vibration of flexible blades and tower become more important in large wind turbine. Hence, it is necessary to analyze the stability of wind turbine using a global model. Based on the theory of flexible multi-body dynamics, a global structural dynamic model of wind turbine was developed using the rigid finite element method. The model could be used in both small and large deflection situations and could be used to analyze the vibration of wind turbine in different cases. Results of the model were compared with other programs, and it was approved that our model was more accurate than other models based on modal method. Natural frequencies of wind turbine were studied under the coupled and uncoupled vibration conditions of blades and tower. Results show that some higher natural frequencies of blades and tower in the whole system have changed and there are some new frequencies created in coupled vibration. The results mean that it is not reliable to analyze the wind turbine vibration using the natural frequencies of the separate tower or blades. The global model should be used for the large wind turbine.%水平轴风力发电机大型化、柔性化的发展趋势使得基于小变形假设的线性分析方法不再合理。大型风力机柔性叶片和塔架的耦合振动加剧,需采用整机模型对其进行分析。基于柔性多体动力学理论,采用刚体有限元方法建立了风力发电机的整机结构动力学模型,该模型不受几何变形量大小限制,能够对风力机在各种情况下的整机振动进行分析。模型结果与其他程序进行了对比,证实该文模型的精度比模态方法更高。研究了叶片和塔架在耦合与非耦合状态下整机的固有振动频率,结果表明:在整机状态下塔架和叶片的部

  2. Active vibration control of multibody system with quick startup and brake based on active damping

    Institute of Scientific and Technical Information of China (English)

    TANG Hua-ping; TANG Yun-jun; TAO Gong-an

    2006-01-01

    A kind of active vibration control method was presented based on active damping and optimization design for driving load of multibody system with quick startup and brake. Dynamical equation of multibody system with quick startup and brake and piezoelectric actuators intelligent structure was built. The optimum driving load was calculated by applying the presented method. The self-sensing and self-tuning closed-loop active vibration control in quick startup and brake process was realized. The control algorithm, using local velocity negative feedback, i.e. the output of a sensor only affects the output of the actuator collocated, can induce damping effectively to actively suppress the system vibration. Based on the optimization design for driving load of multibody system with quick startup and bake, the active damping of piezoelectric actuators intelligent structure was used to farther suppress the vibration of system. Theoretical analysis and calculation of numerical show that the proposed method makes the vibration of system decrease more than the optimal design method for driving load of multibody system.

  3. Nonlinear Multibody Dynamics of Wind Turbines

    DEFF Research Database (Denmark)

    Holm-Jørgensen, Kristian

    The continuing development of wind turbines aim at higher effect production and reducing the purchase and maintenance costs for the customers. This demands that the components in the wind turbine are optimized closer to the limit than previously. In order to determine the design loads it is neces......The continuing development of wind turbines aim at higher effect production and reducing the purchase and maintenance costs for the customers. This demands that the components in the wind turbine are optimized closer to the limit than previously. In order to determine the design loads...... is investigated. I the first method a Ritz basis is used, which contains rigid body modes and a number of elastic eigenmodes compatible to the kinematical boundary conditions. By use of very few elastic eigenmodes to model a blade it has shown convenient to use a quasi-static term for the truncated elastic...

  4. KEY TECHNIQUES OF MULTI-BODY MODELING OF OCCUPANT RESTRAINT SYSTEM OF VEHICLE SIDE IMPACT

    Institute of Scientific and Technical Information of China (English)

    ZHANG Junyuan; ZHANG Min; DING Rufang; QIU Shaobo; ZHANG Yu; LI Hongjian

    2006-01-01

    Based on multi-body dynamics, the simulation models of auto-side structures and occupant's dynamic responses are set up, using the occupant injury simulation software MADYMO3D. These models include auto-body structure, impact barrier, seat and dummy. Definitions of multi-body and joints and dynamics properties of joints based on FE combination models, of model setup are introduced. Kelvin element of MADYMO is introduced to show the force action between non-adjoining rigid bodies, too. Then all examples of the methods mentioned are given. By the comparison of simulation and real test, the contract curves between simulation and real test for main structures and biology mechanics properties of dummy are obtained. The result shows the accuracy and validity of the models.

  5. Engine Multi-Body with Flexible Crankshaft Modeling and Numerical Simulation

    Institute of Scientific and Technical Information of China (English)

    LIU Yong-hong; WANG Hong; GU Hong-liang; ZHANG You-yun

    2005-01-01

    A multi-body model of engine system with flexible crankshaft was presented in this paper to analyze the dynamic behavior of an internal combustion engine. The flexible crankshaft structural dynamics was coupled with the main bearing hydrodynamic lubrication in this model by a system approach. An application of an I4 engine was given to show this sophisticated simulation model and to predict the loads and the orbit plots in the journal bearings by the dynamic response of the multi-body engine system with flexible crankshaft. The numerical results show the capabilities and significance of the flexible crankshaft in this system. The objective of the research is to provide the scientific guidance for design and maintenance of the internal combustion engine.

  6. Multi-body coalescence in Pickering emulsions

    Science.gov (United States)

    Wu, Tong; Wang, Haitao; Jing, Benxin; Liu, Fang; Burns, Peter C.; Na, Chongzheng

    2015-01-01

    Particle-stabilized Pickering emulsions have shown unusual behaviours such as the formation of non-spherical droplets and the sudden halt of coalescence between individual droplets. Here we report another unusual behaviour of Pickering emulsions—the simultaneous coalescence of multiple droplets in a single event. Using latex particles, silica particles and carbon nanotubes as model stabilizers, we show that multi-body coalescence can occur in both water-in-oil and oil-in-water emulsions. The number of droplets involved in the nth coalscence event equals four times the corresponding number of the tetrahedral sequence in close packing. Furthermore, coalescence is promoted by repulsive latex and silica particles but inhibited by attractive carbon nanotubes. The revelation of multi-body coalescence is expected to help better understand Pickering emulsions in natural systems and improve their designs in engineering applications.

  7. Controllability of a multibody mobile robot

    Energy Technology Data Exchange (ETDEWEB)

    Laumond, J.P. (LAAS/CNRS, Toulouse (France))

    1993-12-01

    This paper presents a proof of controllability for a multibody mobile robot (e.g., a car pulling and pushing trailers like a luggage carrier in an airport). Such systems appear as canonical systems to illustrate the tools from differential geometric control theory required by nonholonomic motion planning. Three modeling steps are considered: geometric, differential, and control steps. The author derives the kinematic equations for four distinct multibody mobile robot systems: a convoy driven by (1) a unicycle, (2) a two-driving wheels vehicle, (3) a real and (4) the first two bodies. He shows that these four control systems correspond to the same differential model, which is then used to give the same proof of controllability. Previous work proved the controllability of two-body systems and three body systems. The main result of this paper is proving the controllability for a general n-body system.

  8. Nonlinear MPC and MHE for Mechanical Multi-Body Systems with Application to Fast Tethered Airplanes

    OpenAIRE

    2012-01-01

    International audience; Mechanical applications often require a high control frequency to cope with fast dynamics. The control frequency of a nonlinear model predictive controller depends strongly on the symbolic complexity of the equations modeling the system. The symbolic complexity of the model equations for multi-body mechanical systems can often be dramatically reduced by using representations based on non-minimal coordinates, which result in index-3 differential-algebraic equations (DAE...

  9. Multi-Body Analysis of a Tiltrotor Configuration

    Science.gov (United States)

    Ghiringhelli, G. L.; Masarati, P.; Mantegazza, P.; Nixon, M. W.

    1997-01-01

    The paper describes the aeroelastic analysis of a tiltrotor configuration. The 1/5 scale wind tunnel semispan model of the V-22 tiltrotor aircraft is considered. The analysis is performed by means of a multi-body code, based on an original formulation. The differential equilibrium problem is stated in terms of first order differential equations. The equilibrium equations of every rigid body are written, together with the definitions of the momenta. The bodies are connected by kinematic constraints, applied in form of Lagrangian multipliers. Deformable components are mainly modelled by means of beam elements, based on an original finite volume formulation. Multi-disciplinar problems can be solved by adding user-defined differential equations. In the presented analysis the equations related to the control of the swash-plate of the model are considered. Advantages of a multi-body aeroelastic code over existing comprehensive rotorcraft codes include the exact modelling of the kinematics of the hub, the detailed modelling of the flexibility of critical hub components, and the possibility to simulate steady flight conditions as well as wind-up and maneuvers. The simulations described in the paper include: 1) the analysis of the aeroelastic stability, with particular regard to the proprotor/pylon instability that is peculiar to tiltrotors, 2) the determination of the dynamic behavior of the system and of the loads due to typical maneuvers, with particular regard to the conversion from helicopter to airplane mode, and 3) the stress evaluation in critical components, such as the pitch links and the conversion downstop spring.

  10. DAEs and PDEs in elastic multibody systems

    Science.gov (United States)

    Simeon, B.

    1998-12-01

    Elastic multibody systems arise in the simulation of vehicles, robots, air- and spacecrafts. They feature a mixed structure with differential-algebraic equations (DAEs) governing the gross motion and partial differential equations (PDEs) describing the elastic deformation of particular bodies. We introduce a general modelling framework for this new application field and discuss numerical simulation techniques from several points of view. Due to different time scales, singular perturbation theory and model reduction play an important role. A slider crank mechanism with a 2D FE grid for the elastic connecting rod illustrates the techniques.

  11. 基于多刚体动力学模型的漂浮式拦污排的平衡形状和张力%Space Equilibrium Configuration and Tensile Forces of Drift Trash Barrier Based on Multi-Body Dynamic

    Institute of Scientific and Technical Information of China (English)

    徐远杰; 夏明锬; 楚锡华

    2013-01-01

    漂浮式拦污排为多个浮箱通过铰接组成的多体系统.将浮箱模型简化为刚性杆件,基于多体动力学理论,建立了漂浮式拦污排的运动控制方程,并给出了相应的数值求解方案.模型试验表明了数值模型及求解方案的有效性.数值算例结果表明,传统的悬链线假设得到的结果误差较大.此外还讨论了平衡状态下拦污排发生“自锁”状态的判断方法及水面下降时的张力演化过程.%Drift trash barrier was a kind of multibody system made up of float boxes and hin-ges. The float boxes were simplified to rigid bars, and the governing equations for them were established based on the multi-body dynamics theory. An iteration strategy was also proposed to obtain a numerical solution. To validate the proposed model and solution, a scaled model test was designed and the test results illustrated the validation of the model and the solution. Numerical example compared the results given by the proposed model and classical model. In addition, a judge method of the self-locking state of the drift trash barrier and the change process of tensile force were presented when the water level fell.

  12. Optimization of actuator/sensor position of multi-body system with quick startup and brake

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A new method was put forward to optimize the position of actuator/sensor of multi-body system with quick startup and brake. Dynamical equation was established for the system with intelligent structure of piezoelectric actuators. According to the property of the modes varying with time, the performance index function was developed based on the optimal configuration principle of energy maximal dissipation, and the relevant optimal model was obtained. According to its characteristic, a float-encoding genetic algorithm, which is efficient, simple and excellent for solving the global-optimal solution of this problem, was adopted. Taking the plane manipulator as an example, the result of numerical calculation shows that, after the actuator/sensor position being optimized,the vibration amplitude of the multi-body system is reduced by 35% compared with that without optimization.

  13. A minimum state multibody/FEM approach for modeling flexible orbiting space systems

    Science.gov (United States)

    Pisculli, A.; Gasbarri, P.

    2015-05-01

    In the past the deployment of space structures has widely been analyzed by using multibody formulations. The two leading approaches are usually based on the Newton-Euler (NE) formulation and Euler-Lagrange (EL) formulation. Both of them present advantages and drawbacks. The ideal approach for describing multi-body systems can be represented by a combination between NE and EL formulations. This can be obtained by considering the NE formulation for assembling the equation of motion and then by defining the ODE governing equations with the use of a minimum set of variables. In this paper the authors present a mixed NE/EL formulation suitable for synthesizing optimal control strategies during the deploying maneuvers of robotic arms or solar arrays. The proposed method has two main characteristics: (i) the reference frame, which all the bodies motions are referred to, is a floating reference frame attached to the orbiting base platform body; (ii) it leads to a more organic formulation which makes a shifting from the NE to the EL formulations possible, through the use of a Jacobian matrix. In the present work this mixed formulation is derived to describe a fully elastic multi-body spacecraft. Furthermore the presented formulation, complemented with gravity, gravity gradient and generalized gravitational modal forces, will be used to study the dynamic behavior of an orbiting manipulator with flexible appendages. Finally a Reaction Null/Jacobian Transpose control strategy will be applied to control and deploy the robotic arms to grasp an orbiting flexible spacecraft.

  14. Integrating Multibody Simulation and CFD: toward Complex Multidisciplinary Design Optimization

    Science.gov (United States)

    Pieri, Stefano; Poloni, Carlo; Mühlmeier, Martin

    This paper describes the use of integrated multidisciplinary analysis and optimization of a race car model on a predefined circuit. The objective is the definition of the most efficient geometric configuration that can guarantee the lowest lap time. In order to carry out this study it has been necessary to interface the design optimization software modeFRONTIER with the following softwares: CATIA v5, a three dimensional CAD software, used for the definition of the parametric geometry; A.D.A.M.S./Motorsport, a multi-body dynamic simulation software; IcemCFD, a mesh generator, for the automatic generation of the CFD grid; CFX, a Navier-Stokes code, for the fluid-dynamic forces prediction. The process integration gives the possibility to compute, for each geometrical configuration, a set of aerodynamic coefficients that are then used in the multiboby simulation for the computation of the lap time. Finally an automatic optimization procedure is started and the lap-time minimized. The whole process is executed on a Linux cluster running CFD simulations in parallel.

  15. Criteria of benchmark selection for efficient flexible multibody system formalisms

    Directory of Open Access Journals (Sweden)

    Valášek M.

    2007-10-01

    Full Text Available The paper deals with the selection process of benchmarks for testing and comparing efficient flexible multibody formalisms. The existing benchmarks are briefly summarized. The purposes for benchmark selection are investigated. The result of this analysis is the formulation of the criteria of benchmark selection for flexible multibody formalisms. Based on them the initial set of suitable benchmarks is described. Besides that the evaluation measures are revised and extended.

  16. ROBOTRAN: a powerful symbolic gnerator of multibody models

    Directory of Open Access Journals (Sweden)

    N. Docquier

    2013-05-01

    Full Text Available The computational efficiency of symbolic generation was at the root of the emergence of symbolic multibody programs in the eighties. At present, it remains an attractive feature of it since the exponential increase in modern computer performances naturally provides the opportunity to investigate larger systems and more sophisticated models for which real-time computation is a real asset. Nowadays, in the context of mechatronic multibody systems, another interesting feature of the symbolic approach appears when dealing with enlarged multibody models, i.e. including electrical actuators, hydraulic devices, pneumatic suspensions, etc. and requiring specific analyses like control and optimization. Indeed, since symbolic multibody programs clearly distinguish the modeling phase from the analysis process, extracting the symbolic model, as well as some precious ingredients like analytical sensitivities, in order to export it towards any suitable environment (for control or optimization purposes is quite straightforward. Symbolic multibody model portability is thus very attractive for the analysis of mechatronic applications. In this context, the main features and recent developments of the ROBOTRAN software developed at the Université catholique de Louvain (Belgium are reviewed in this paper and illustrated via three multibody applications which highlight its capabilities for dealing with very large systems and coping with multiphysics issues.

  17. [Techniques for measuring phakic and pseudophakic accommodation. Methodology for distinguishing between neurological and mechanical accommodative insufficiency].

    Science.gov (United States)

    Roche, O; Roumes, C; Parsa, C

    2007-11-01

    The methods available for studying accommodation are evaluated: Donder's "push-up" method, dynamic retinoscopy, infrared optometry using the Scheiner principle, and wavefront analysis are each discussed with their inherent advantages and limitations. Based on the methodology described, one can also distinguish between causes of accommodative insufficiency. Dioptric insufficiency (accommodative lag) that remains equal at various testing distances from the subject indicates a sensory/neurologic (afferent), defect, whereas accommodative insufficiency changing with distance indicates a mechanical/restrictive (efferent) defect, such as in presbyopia. Determining accommodative insufficiency and the cause can be particularly useful when examining patients with a variety of diseases associated with reduced accommodative ability (e.g., Down syndrome and cerebral palsy) as well as in evaluating the effectiveness of various potentially accommodating intraocular lens designs.

  18. Model updating in flexible-link multibody systems

    Science.gov (United States)

    Belotti, R.; Caneva, G.; Palomba, I.; Richiedei, D.; Trevisani, A.

    2016-09-01

    The dynamic response of flexible-link multibody systems (FLMSs) can be predicted through nonlinear models based on finite elements, to describe the coupling between rigid- body and elastic behaviour. Their accuracy should be as high as possible to synthesize controllers and observers. Model updating based on experimental measurements is hence necessary. By taking advantage of the experimental modal analysis, this work proposes a model updating procedure for FLMSs and applies it experimentally to a planar robot. Indeed, several peculiarities of the model of FLMS should be carefully tackled. On the one hand, nonlinear models of a FLMS should be linearized about static equilibrium configurations. On the other, the experimental mode shapes should be corrected to be consistent with the elastic displacements represented in the model, which are defined with respect to a fictitious moving reference (the equivalent rigid link system). Then, since rotational degrees of freedom are also represented in the model, interpolation of the experimental data should be performed to match the model displacement vector. Model updating has been finally cast as an optimization problem in the presence of bounds on the feasible values, by also adopting methods to improve the numerical conditioning and to compute meaningful updated inertial and elastic parameters.

  19. Accommodating Translational Research

    Science.gov (United States)

    Giles, Howard

    2008-01-01

    This is an article in a series illustrating the way scholars in communication have pursued translating their research into practice. The translational nature of communication accommodation theory and examples of its application are the focus of this contribution.

  20. Multibody charmless b-hadron decays

    CERN Document Server

    Dujany, Giulio

    2016-01-01

    Multibody charmless b-hadron decays are a unique laboratory to probe CP violation, to look for effects of new physics and to provide insights into the hadronisation mechanism. The decay modes $\\Lambda_b^0 \\to \\Lambda K^+ K^-$, $\\Lambda_b^0 \\to \\Lambda K^+ \\pi^-$, $\\Lambda_b^0 \\to \\Lambda \\phi$ and $B_s^0 \\to K_{\\rm S}^0 K^*$ are observed for the first time by LHCb and their branching fractions are measured. Evidence is seen for the $\\Lambda_b^0 \\to \\Lambda \\pi^+ \\pi^-$ decay and limits are set for the decays $\\Xi_b^0\\to \\Lambda h^+ h^{(\\prime)-}$ and $B^0 \\to K_{\\rm S}^0 K^*$ . The phase-space integrated CP asymmetry parameters are measured for $\\Lambda_b^0 \\to \\Lambda K^+ K^-$ and $\\Lambda_b^0 \\to \\Lambda K^+ \\pi^-$ while several triple-product asymmetries are measured for $\\Lambda_b^0 \\to \\Lambda \\phi$. All these asymmetries are found to be compatible with zero.

  1. Real and Pseudoaccommodation in Accommodative Lenses

    Directory of Open Access Journals (Sweden)

    Ioannis G. Pallikaris

    2011-01-01

    Full Text Available In the attempt to manage presbyopia, different intraocular lens designs have been proposed such as monofocal IOLs with monovision or multifocal IOLs. Even though the lenses mentioned offer satisfactory visual results, contemporary ophthalmology has not completely answered the presbyopic dilemma by simulating the accommodative properties of the crystalline lens itself. Accommodative IOLs were designed to fill this gap and provide satisfactory vision for all distances by restoring some degree of “pseudoaccommodation.” Pseudo accommodative capability can be linked to monofocal IOL’s as well but the results are not satisfactory enough to fully support unaided near vision. Pseudoaccommodation is a complex phenomenon that can be attributed to several static (i.e., pupil size, against-the-rule cylindrical refractive error, multifocality of the cornea and dynamic (i.e., anterior movement of the implant itself factors. Objective measurement of the accommodative capability offered by the accommodative IOLs is extremely difficult to obtain, and different methods such as autorefractometers, retinoscopy, and ultrasound imaging during accommodative effort, ray tracing, or pharmacological stimulation have been developed but the results are sometimes inconsistent. Despite the difficulties in measuring accommodation, accommodative IOLs represent the future in the attempt to successfully “cure” presbyopia.

  2. Intraocular lens with accommodation capacity

    OpenAIRE

    Dorronsoro, Carlos; Alejandre, Nicolás; Bekesi, Nandor; Marcos, Susana

    2014-01-01

    Intraocular lens with accommodation capacity comprising a first optical member (1) having a dynamic optical power, to which a second optical member (2) with a fixed optical power is affixed, in such a manner that at least a central part of each of one of one of the curved surfaces (2a, 2b) of the second optical member (2) and of at least one of the surfaces (1a, 1b) of the first optical member (1) are in contact with each other, the second optical member (2) and the first optical member (1) p...

  3. Application of Periapse Maps for the Design of Trajectories Near the Smaller Primary in Multi-Body Regimes

    Directory of Open Access Journals (Sweden)

    Kathleen C. Howell

    2012-01-01

    Full Text Available The success of the Genesis spacecraft, as well as the current Artemis mission, continue to generate interest in expanding the trajectory options for future science and exploration goals throughout the solar system. Incorporating multi-body dynamics into the preliminary design can potentially offer flexibility and influence the maneuver costs to achieve certain objectives. In the current analysis, attention is focused on the development and application of design tools to facilitate preliminary trajectory design in a multi-body environment. Within the context of the circular restricted three-body problem, the evolution of a trajectory in the vicinity of the smaller primary is investigated. Introduced previously, periapse Poincaré maps have emerged as a valuable resource to predict both short- and long-term trajectory behaviors. By characterizing the trajectories in terms of radius and periapse orientation relative to the 1-2 line, useful trajectories with a particular set of desired characteristics can be identified and computed.

  4. Development of Three-dimensional Grid-free Solver and its Applications to Multi-body Aerospace Vehicles

    Directory of Open Access Journals (Sweden)

    K. Anandhanarayanan

    2010-10-01

    Full Text Available Grid-free solver has the ability to solve complex multi-body industrial problems with minimal effort. Grid-free Euler solver has been applied to number of multi-body aerospace vehicles using Chimera clouds of points including flight vehicle with fin deflection, nose fairing separation of hypersonic launch vehicle. A preprocessor has been developed to generate connectivity for multi-bodies using overlapped grids. Surface transpiration boundary condition has been implemented to model aerodynamic damping and to impose the relative velocity of moving components. Dynamic derivatives are estimated with reasonable accuracy and less effort using the grid-free Euler solver with the transpiration boundary condition. Further, the grid-free Euler solver has been integrated with six-degrees of freedom (6-DOF equations of motion to form store separation dynamics suite which has been applied to obtain the trajectory of a rail launch air-to-air-missile from a complex fighter aircraft.Defence Science Journal, 2010, 60(6, pp.653-662, DOI:http://dx.doi.org/10.14429/dsj.60.583

  5. Optimization of a tuned vibration absorber in a multibody system by operational analysis

    Science.gov (United States)

    Infante, F.; Perfetto, S.; Mayer, D.; Herold, S.

    2016-09-01

    Mechanical vibration in a drive-train can affect the operation of the system and must be kept below structural thresholds. For this reason tuned vibration absorbers (TVA) are usually employed. They are optimally designed for a single degree of freedom system using the Den Hartog technique. On the other hand, vibrations can be used to produce electrical energy exploitable locally avoiding the issues to transfer it from stationary devices to rating parts. Thus, the design of an integrated device for energy harvesting and vibration reduction is proposed to be employed in the drive-train. By investigation of the dynamic torque in the system under real operation, the accuracy of a numerical model for the multibody is evaluated. In this study, this model is initially used for the definition of the TVA. An energetic procedure is applied in order to reduce the multibody in an equivalent single degree of freedom system for a particular natural mode. Hence, the design parameters of the absorber are obtained. Furthermore, the introduction of the TVA in the model is considered to evaluate the vibration reduction. Finally, an evaluation of the power generated by the piezo transducer and its feedback on the dynamic of the drive-train is performed.

  6. Accommodating Different Learning Styles

    DEFF Research Database (Denmark)

    Ovesen, Nis

    2014-01-01

    Design engineering educations often struggle to accommodate a highly diverse group of students as it combines an equally diverse range of topics in one education. This paper investigates how a specific course, Mathematics and Form, integrates two distinct areas into one course with the aim of fac...

  7. Accommodating Picky Palates

    Science.gov (United States)

    Lum, Lydia

    2007-01-01

    Healthy gourmet offerings are fast becoming the norm at college dining halls around the country. At a time when the children of Baby Boomers are hitting higher education in record numbers, college officials have scrambled to accommodate their picky palates and their insistence for healthier meals than were served to past generations. At the same…

  8. Reduced accommodation in children with cerebral palsy.

    Science.gov (United States)

    Leat, S J

    1996-09-01

    Accommodation in 43 subjects with cerebral palsy was measured objectively using a dynamic retinoscopy technique, which has already been shown to be reliable and repeatable. The subject's ages ranged from 3 to 35 years. Of these, 42% were found to have an accommodative response pattern which was different from the normal control group for his/her age. Nearly 29% had an estimated amplitude of accommodation of 4 D or less. The presence of reduced accommodation was found to be associated with reduced visual acuity, but was not associated with cognitive or communication ability, refractive error or age. The prevalence of other ocular disorders in this group is also high. These findings have developmental and educational implications.

  9. Multibody simulation of vehicles equipped with an automatic transmission

    Science.gov (United States)

    Olivier, B.; Kouroussis, G.

    2016-09-01

    Nowadays automotive vehicles remain as one of the most used modes of transportation. Furthermore automatic transmissions are increasingly used to provide a better driving comfort and a potential optimization of the engine performances (by placing the gear shifts at specific engine and vehicle speeds). This paper presents an effective modeling of the vehicle using the multibody methodology (numerically computed under EasyDyn, an open source and in-house library dedicated to multibody simulations). However, the transmission part of the vehicle is described by the usual equations of motion computed using a systematic matrix approach: del Castillo's methodology for planetary gear trains. By coupling the analytic equations of the transmission and the equations computed by the multibody methodology, the performances of any vehicle can be obtained if the characteristics of each element in the vehicle are known. The multibody methodology offers the possibilities to develop the vehicle modeling from 1D-motion to 3D-motion by taking into account the rotations and implementing tire models. The modeling presented in this paper remains very efficient and provides an easy and quick vehicle simulation tool which could be used in order to calibrate the automatic transmission.

  10. Trajectory evolution in the multi-body problem with applications in the Saturnian system

    Science.gov (United States)

    Craig Davis, Diane; Howell, Kathleen C.

    2011-12-01

    Recent discoveries by the Cassini spacecraft have generated interest in future missions to further explore the moons of Saturn as well as other small bodies in the solar system. Incorporating multi-body dynamics into the preliminary design can aid the design process and potentially reduce the cost of maneuvers that are required to achieve certain objectives. The focus in this investigation is the development and application of additional design tools to facilitate preliminary trajectory design in a multi-body environment where the gravitational influence of both primaries is quite significant. Within the context of the circular restricted 3-body problem, then, the evolution of trajectories in the vicinity of the smaller primary (P 2) that are strongly influenced by the distant larger primary (P 1) is investigated. By parameterizing the orbits in terms of radius and periapse orientation relative to the P 1-P 2 line, the short- and long-term behaviors of the trajectories are predictable. Initial conditions that yield a trajectory with a particular set of desired characteristics are easily selected from periapsis Poincaré maps for both short- and long-term orbits. Analysis in the Sun-Saturn and Saturn-Titan systems serves as the basis for examples of mission design applications.

  11. Analysis of Large Flexible Body Deformation in Multibody Systems Using Absolute Coordinates

    Energy Technology Data Exchange (ETDEWEB)

    Dombrowski, Stefan von [Institute of Robotics and Mechatronics, German Aerospace Center (DLR) (Germany)], E-mail: stefan.von.dombrowski@dlr.de

    2002-11-15

    To consider large deformation problems in multibody system simulations a finite element approach, called absolute nodal coordinate.formulation,has been proposed. In this formulation absolute nodal coordinates and their material derivatives are applied to represent both deformation and rigid body motion. The choice of nodal variables allows a fully nonlinear representation of rigid body motion and can provide the exact rigid body inertia in the case of large rotations. The methodology is especially suited for but not limited to modeling of beams, cables and shells in multibody dynamics.This paper summarizes the absolute nodal coordinate formulation for a 3D Euler-Bernoulli beam model, in particular the definition of nodal variables, corresponding generalized elastic and inertia forces and equations of motion. The element stiffness matrix is a nonlinear function of the nodal variables even in the case of linearized strain/displacement relations. Nonlinear strain/displacement relations can be calculated from the global displacements using quadrature formulae.Computational examples are given which demonstrate the capabilities of the applied methodology. Consequences of the choice of shape.functions on the representation of internal forces are discussed. Linearized strain/displacement modeling is compared to the nonlinear approach and significant advantages of the latter, when using the absolute nodal coordinate formulation, are outlined.

  12. Bridging as Coercive Accommodation

    CERN Document Server

    Bos, J W; Mineur, A M; Bos, Johan; Buitelaar, Paul; Mineur, Anne-Marie

    1995-01-01

    In this paper we discuss the notion of "bridging" in Discourse Representation Theory as a tool to account for discourse referents that have only been established implicitly, through the lexical semantics of other referents. In doing so, we use ideas from Generative Lexicon theory, to introduce antecedents for anaphoric expressions that cannot be "linked" to a proper antecedent, but that do not need to be "accommodated" because they have some connection to the network of discourse referents that is already established.

  13. Accommodation and Catering

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In the first five months, retail sales of the accommodation and catering sector reached 412.77 billion yuan, contributing 13.6 percent to total retail sales of consumer goods, said the Ministry of Commerce. Their year-on-year growth of 15 percent, or 53.78 billion yuan, was 1.78 percentage points higher than the overall increase of retail sales of consumer goods.

  14. Multiphysics modelling of multibody systems: application to car semi-active suspensions

    Science.gov (United States)

    Docquier, N.; Poncelet, A.; Delannoy, M.; Fisette, P.

    2010-12-01

    The goal of the present article is to analyse the performances of a modern vehicle equipped with a novel suspension system linking front, rear, right and left cylinders via a semi-active hydraulic circuit, developed by the Tenneco Automotive company. In addition to improving the vehicle's vertical performances (in terms of comfort), both the stiff roll motion of the carbody and the soft wrap motion of the rear/front wheel-axle units can be obtained and tuned via eight electrovalves. The proposed system avoids the use of classical anti-roll bars, which would be incompatible with the wrap performance. A major problem of the project is to produce a realistic and efficient 3D multibody dynamic model of an Audi A6 coupled, at the equational level, with an hydraulic model of the suspension including cylinders, accumulators, valve characteristics, oil compressibility and pipe dynamics. As regards the hydraulic submodel, a particular attention is paid to assemble resistive components properly without resorting to the use of artificial volumes, as proposed by some software dealing with the dynamics of hydraulic systems. According to Tenneco Automotive requirements, this model must be produced in a Matlab/Simulink form, in particular for control purposes. Thanks to the symbolic approach underlying our multibody program; a unified hybrid model can be obtained as a unique plant dynamic block to be real-time integrated in the Simulink environment on a standard computer. Simulation results highlight the advantages of this new suspension system, in particular regarding the behaviour of the car which can remain stiff in roll for curve negotiation, while maintaining a soft wrap behaviour on uneven surfaces.

  15. [Spasm of accommodation].

    Science.gov (United States)

    Lindberg, Laura

    2014-01-01

    Spasm of accommodation refers to prolonged contraction of the ciliary muscle, most commonly causing pseudomyopia to varying degrees in both eyes by keeping the lens in a state of short sightedness. It may also be manifested as inability to allow the adaptation spasticity prevailing in the ciliary muscle relax without measurable myopia. As a rule, this is a functional ailment triggered by prolonged near work and stress. The most common symptoms include blurring of distance vision, varying visual acuity as well as pains in the orbital region and the head, progressing into a chronic state. Cycloplegic eye drops are used as the treatment.

  16. Planar reorientation maneuvers of space multibody systems using internal controls

    Science.gov (United States)

    Reyhanoglu, Mahmut; Mcclamroch, N. H.

    1992-01-01

    In this paper a reorientation maneuvering strategy for an interconnection of planar rigid bodies in space is developed. It is assumed that there are no exogeneous torques, and torques generated by joint motors are used as means of control so that the total angular momentum of the multibody system is a constant, assumed to be zero in this paper. The maneuver strategy uses the nonintegrability of the expression for the angular momentum. We demonstrate that large-angle maneuvers can be designed to achieve an arbitrary reorientation of the multibody system with respect to an inertial frame. The theoretical background for carrying out the required maneuvers is briefly summarized. Specifications and computer simulations of a specific reorientation maneuver, and the corresponding control strategies, are described.

  17. 大型水平轴风力机多体系统的动力学分析与仿生设计%Dynamic Analysis and Bionic Design of Multi-Body System of Large-Scale Horizontal-Axis Wind Turbine

    Institute of Scientific and Technical Information of China (English)

    刘旺玉; 张勇; 陈龙

    2011-01-01

    In this paper, a dynamic model of the multi-body system of a 1.5MW direct-drive wind turbine is established with the finite element software ANSYS. Then, the natural frequency of the wind turbine is calculated, and the resonance and the stability of the system are analyzed. Moreover, the transient response of each component of the system under extreme operation gusts is discussed. The results indicate that, the tower is flexible; the system is stable and safe at normal working rotational velocity; and that, due to the difference in stiffness of the components, the variation of the tip of the wind turbine blade, which is induced by the coupling of the elastic deformations of three blades and the tower under wind loading, is more complex than that of other components. The flexible structure of the plant trunk is applied to the design of the wind turbine tower, and the feasibility of this bionic design is finally proved.%采用ANSYS建立了1.5 MW直驱风力机多体系统的动力学模型,计算了系统的固有频率,对系统的共振性和稳定性进行了分析,并探讨了在极端运行阵风下风力机系统各部件的瞬态响应振动.分析结果表明:塔架为柔塔,在正常工作转速下风力机能够安全、稳定运转;由于各个部件刚度不同,使得叶片叶尖振动较其它部件复杂,叶尖的振动是受风栽作用的三叶片与塔架弹性变形相互耦合作用的结果.最后将植物树干柔性结构应用于风力机塔架的结构设计中,说明了风力机塔架仿生设计的可行性.

  18. Multi-Body Analysis of the 1/5 Scale Wind Tunnel Model of the V-22 Tiltrotor

    Science.gov (United States)

    Ghiringhelli, G. L.; Masarati, P.; Mantegazza, P.; Nixon, M. W.

    1999-01-01

    The paper presents a multi-body analysis of the 1/5 scale wind tunnel model of the V-22 tiltrotor, the Wing and Rotor Aeroelastic Testing System (WRATS), currently tested at NASA Langley Research Center. An original multi-body formulation has been developed at the Dipartimento di Ingegneria Aerospaziale of the Politecnico di Milano, Italy. It is based on the direct writing of the equilibrium equations of independent rigid bodies, connected by kinematic constraints that result in the addition of algebraic constraint equations, and by dynamic constraints, that directly contribute to the equilibrium equations. The formulation has been extended to the simultaneous solution of interdisciplinary problems by modeling electric and hydraulic networks, for aeroservoelastic problems. The code has been tailored to the modeling of rotorcrafts while preserving a complete generality. A family of aerodynamic elements has been introduced to model high aspect aerodynamic surfaces, based on the strip theory, with quasi-steady aerodynamic coefficients, compressibility, post-stall interpolation of experimental data, dynamic stall modeling, and radial flow drag. Different models for the induced velocity of the rotor can be used, from uniform velocity to dynamic in flow. A complete dynamic and aeroelastic analysis of the model of the V-22 tiltrotor has been performed, to assess the validity of the formulation and to exploit the unique features of multi-body analysis with respect to conventional comprehensive rotorcraft codes; These are the ability to model the exact kinematics of mechanical systems, and the possibility to simulate unusual maneuvers and unusual flight conditions, that are particular to the tiltrotor, e.g. the conversion maneuver. A complete modal validation of the analytical model has been performed, to assess the ability to reproduce the correct dynamics of the system with a relatively coarse beam model of the semispan wing, pylon and rotor. Particular care has been used

  19. Multibody Modeling and Simulation for the Mars Phoenix Lander Entry, Descent and Landing

    Science.gov (United States)

    Queen, Eric M.; Prince, Jill L.; Desai, Prasun N.

    2008-01-01

    A multi-body flight simulation for the Phoenix Mars Lander has been developed that includes high fidelity six degree-of-freedom rigid-body models for the parachute and lander system. The simulation provides attitude and rate history predictions of all bodies throughout the flight, as well as loads on each of the connecting lines. In so doing, a realistic behavior of the descending parachute/lander system dynamics can be simulated that allows assessment of the Phoenix descent performance and identification of potential sensitivities for landing. This simulation provides a complete end-to-end capability of modeling the entire entry, descent, and landing sequence for the mission. Time histories of the parachute and lander aerodynamic angles are presented. The response of the lander system to various wind models and wind shears is shown to be acceptable. Monte Carlo simulation results are also presented.

  20. Optimal Disturbance Accommodation with Limited Model Information

    CERN Document Server

    Farokhi, F; Johansson, K H

    2011-01-01

    The design of optimal dynamic disturbance-accommodation controller with limited model information is considered. We adapt the family of limited model information control design strategies, defined earlier by the authors, to handle dynamic-controllers. This family of limited model information design strategies construct subcontrollers distributively by accessing only local plant model information. The closed-loop performance of the dynamic-controllers that they can produce are studied using a performance metric called the competitive ratio which is the worst case ratio of the cost a control design strategy to the cost of the optimal control design with full model information.

  1. Mutual Orbits of Transneptunian Multibody Systems

    Science.gov (United States)

    Grundy, William

    2014-08-01

    We propose to use LGS AO with NIRC2 during stellar appulses to measure relative astrometry of the large sample of transneptunian binaries for which mutual orbits remain unknown. Our long-term goal is to determine as many of their orbits as possible. These orbits provide a crucial constraint on dynamical conditions in outer parts of the protoplanetary nebula, as well as subsequent outer solar system history. They provide system masses and thus bulk densities, as well as enabling constraint of tidal dissipation parameters, scheduling of mutual event seasons, and revealing possible unresolved n>2 systems.

  2. Sensitivity analysis approach to multibody systems described by natural coordinates

    Science.gov (United States)

    Li, Xiufeng; Wang, Yabin

    2014-03-01

    The classical natural coordinate modeling method which removes the Euler angles and Euler parameters from the governing equations is particularly suitable for the sensitivity analysis and optimization of multibody systems. However, the formulation has so many principles in choosing the generalized coordinates that it hinders the implementation of modeling automation. A first order direct sensitivity analysis approach to multibody systems formulated with novel natural coordinates is presented. Firstly, a new selection method for natural coordinate is developed. The method introduces 12 coordinates to describe the position and orientation of a spatial object. On the basis of the proposed natural coordinates, rigid constraint conditions, the basic constraint elements as well as the initial conditions for the governing equations are derived. Considering the characteristics of the governing equations, the newly proposed generalized-α integration method is used and the corresponding algorithm flowchart is discussed. The objective function, the detailed analysis process of first order direct sensitivity analysis and related solving strategy are provided based on the previous modeling system. Finally, in order to verify the validity and accuracy of the method presented, the sensitivity analysis of a planar spinner-slider mechanism and a spatial crank-slider mechanism are conducted. The test results agree well with that of the finite difference method, and the maximum absolute deviation of the results is less than 3%. The proposed approach is not only convenient for automatic modeling, but also helpful for the reduction of the complexity of sensitivity analysis, which provides a practical and effective way to obtain sensitivity for the optimization problems of multibody systems.

  3. System Reduction in Nonlinear Multibody Dynamics of Wind Turbines

    DEFF Research Database (Denmark)

    Holm-Jørgensen, Kristian; Nielsen, Søren R.K.; Rubak, Rune

    2007-01-01

    in the deformed state. To illustrate the method a numerical example of a wind turbine blade with a length of 45m attached to a rotor shaft supported by two bearings is used. The reduced model based on a truncated modal expansion has been compared with the full FE model in both linear and nonlinear analyses...

  4. Substructuring of multibody systems for numerical transfer path analysis in internal combustion engines

    Science.gov (United States)

    Acri, Antonio; Offner, Guenter; Nijman, Eugene; Rejlek, Jan

    2016-10-01

    Noise legislations and the increasing customer demands determine the Noise Vibration and Harshness (NVH) development of modern commercial vehicles. In order to meet the stringent legislative requirements for the vehicle noise emission, exact knowledge of all vehicle noise sources and their acoustic behavior is required. Transfer path analysis (TPA) is a fairly well established technique for estimating and ranking individual low-frequency noise or vibration contributions via the different transmission paths. Transmission paths from different sources to target points of interest and their contributions can be analyzed by applying TPA. This technique is applied on test measurements, which can only be available on prototypes, at the end of the designing process. In order to overcome the limits of TPA, a numerical transfer path analysis methodology based on the substructuring of a multibody system is proposed in this paper. Being based on numerical simulation, this methodology can be performed starting from the first steps of the designing process. The main target of the proposed methodology is to get information of noise sources contributions of a dynamic system considering the possibility to have multiple forces contemporary acting on the system. The contributions of these forces are investigated with particular focus on distribute or moving forces. In this paper, the mathematical basics of the proposed methodology and its advantages in comparison with TPA will be discussed. Then, a dynamic system is investigated with a combination of two methods. Being based on the dynamic substructuring (DS) of the investigated model, the methodology proposed requires the evaluation of the contact forces at interfaces, which are computed with a flexible multi-body dynamic (FMBD) simulation. Then, the structure-borne noise paths are computed with the wave based method (WBM). As an example application a 4-cylinder engine is investigated and the proposed methodology is applied on the

  5. Impact behaviors of human knee joint during triple-jump based on multi-body dynamics and finite element analysis%基于多体动力学和有限元方法的三级跳运动人体膝关节冲击损伤分析研究

    Institute of Scientific and Technical Information of China (English)

    刘同众; 朱林; 程曦; 彭双双; 戚银银; 秦义先; 尹成龙; 章文峰; 朱德泉

    2015-01-01

    In order to better understand the effects of triple-jump movement on jumpers,impact behaviors of left knee joint of a healthy man athlete were studied.Based on CT and MRI scanning pictures of the jumper’s knee joint,a three-dimensional model was built,including complete femur,tibia,fibular,patellar,cartilages and main ligaments of the knee joint.Then,a method combining finite element analysis (FEA)and multi-body dynamic analysis (MDA)was used to simulate a real human triple-jump.Finally,the loading data,such as,muscle force and joint reaction obtained from an MDA were impulted into a finite element model to compute stress,strain and displacement variations of the knee joint under impact conditions.The numerical simulation results showed that the stress,stain and the displacement of medical cartilage are larger than those of lateral cartilage;the contact force and contact areas increase with increase in load,consequently,this can incur severer wear contours of the knee joint and badly injure the jumper.The computation results matched reasonably the research results in the published literatures.The results demonstrated the importance of performing MDA as a preliminary step to FEA in biomechanical fields,and the proposed method had a potential to generate a better understanding of injury mechanisms of jumpers.%为了研究三级跳训练、竞赛对运动员膝关节冲击损伤影响程度,以1名健康男性运动员左膝关节为研究对象,利用膝部 CT 扫描和磁共振(MRI)相结合的方法,建立了包括股骨、胫骨、腓骨、髌骨以及膝部各主要软骨、韧带在内完整的三维膝关节立体模型;采用多体动力学(MDA)与有限元分析(FEA)相结合的方法,计算出三级跳起跑、跳跃、落地全过程运动员膝关节处冲击状态下的应力、应变及位移变化状况。计算显示:在三级跳运动过程中,膝关节胫骨外侧接触区域受到的载荷,

  6. Distributed digital signal processors for multi-body flexible structures

    Science.gov (United States)

    Lee, Gordon K. F.

    1992-01-01

    Multi-body flexible structures, such as those currently under investigation in spacecraft design, are large scale (high-order) dimensional systems. Controlling and filtering such structures is a computationally complex problem. This is particularly important when many sensors and actuators are located along the structure and need to be processed in real time. This report summarizes research activity focused on solving the signal processing (that is, information processing) issues of multi-body structures. A distributed architecture is developed in which single loop processors are employed for local filtering and control. By implementing such a philosophy with an embedded controller configuration, a supervising controller may be used to process global data and make global decisions as the local devices are processing local information. A hardware testbed, a position controller system for a servo motor, is employed to illustrate the capabilities of the embedded controller structure. Several filtering and control structures which can be modeled as rational functions can be implemented on the system developed in this research effort. Thus the results of the study provide a support tool for many Control/Structure Interaction (CSI) NASA testbeds such as the Evolutionary model and the nine-bay truss structure.

  7. Anthropometric accommodation in USAF cockpits

    Science.gov (United States)

    Zehner, Gregory F.

    1994-01-01

    Over the past three years, a new set of methodologies has been developed to specify and evaluate anthropometric accommodation in USAF crewstation designs. These techniques are used to improve the ability of the pilot to reach controls, to safely escape the aircraft, to achieve adequate mobility and comfort, and to assure full access to the visual field both inside and outside the aircraft. This paper summarized commonly encountered aircraft accommodation problems, explains the failure of the traditional 'percentile man' design concept to resolve these difficulties, and suggests an alternative approach for improving cockpit design to better accommodate today's more heterogeneous flying population.

  8. Biomechanical investigation of thoracolumbar spine in different postures during ejection using a combined finite element and multi-body approach.

    Science.gov (United States)

    Du, Chengfei; Mo, Zhongjun; Tian, Shan; Wang, Lizhen; Fan, Jie; Liu, Songyang; Fan, Yubo

    2014-11-01

    The aim of this study is to investigate the dynamic response of a multi-segment model of the thoracolumbar spine and determine how the sitting posture affects the response under the impact of ejection. A nonlinear finite element model of the thoracolumbar-pelvis complex (T9-S1) was developed and validated. A multi-body dynamic model of a pilot was also constructed so an ejection seat restraint system could be incorporated into the finite element model. The distribution of trunk mass on each vertebra was also considered in the model. Dynamics analysis showed that ejection impact induced obvious axial compression and anterior flexion of the spine, which may contribute to spinal injuries. Compared with a normal posture, the relaxed posture led to an increase in stress on the cortical wall, endplate, and intradiscal pressure of 43%, 10%, 13%, respectively, and accordingly increased the risk of inducing spinal injuries.

  9. A new subregion mesh method for the investigation of the elastic-plastic impact in flexible multibody systems

    Science.gov (United States)

    Chen, Peng; Liu, Jin-Yang; Lu, Guang-Can

    2017-02-01

    Impact processes between flexible bodies often lead to local stress concentration and wave propagation of high frequency. Therefore, the modeling of flexible multibody systems involving impact should consider the local plastic deformation and the strict requirements of the spatial discretization. Owing to the nonlinearity of the stiffness matrix, the reduction of the element number is extremely important. For the contact-impact problem, since different regions have different requirements regarding the element size, a new subregion mesh method is proposed to reduce the number of the unnecessary elements. A dynamic model for flexible multibody systems with elastic-plastic contact impact is established based on a floating frame of reference formulation and complete Lagrange incremental nonlinear finite-element method to investigate the effect of the elastic-plastic deformation as well as spatial discretization. Experiments on the impact between two bodies are carried out to validate the correctness of the elastic-plastic model. The proposed formulation is applied to a slider-crank system with elastic-plastic impact.

  10. A simple probabilistic model of multibody interactions in proteins

    DEFF Research Database (Denmark)

    Johansson, Kristoffer Enøe; Hamelryck, Thomas

    2013-01-01

    predictions. Our coarse-grained model is compared to state-of-art methods that use full atomic detail. This article illustrates how the use of simple probabilistic models can lead to new opportunities in the treatment of nonlocal interactions in knowledge-based protein structure prediction and design....... beyond pairwise interactions have been described, the formulation of a general multibody potential is seen as intractable due to the perceived limited amount of data. In this article, we show that it is possible to formulate a probabilistic model of higher order interactions in proteins, without...... arbitrarily limiting the number of contacts. The success of this approach is based on replacing a naive table-based approach with a simple hierarchical model involving suitable probability distributions and conditional independence assumptions. The model captures the joint probability distribution of an amino...

  11. Study of the railway vehicle suspension using the multibody method

    Directory of Open Access Journals (Sweden)

    Gheorghe GHITA

    2011-12-01

    Full Text Available The article presents a mathematical model for the study of a passenger coach hunting motion using the multibody approach. The model comprises the lateral displacement, rolling and yawing motions for the main constitutive elements: axles, bogies and case. The equation system is written applying energetic methods. The forced vibrations determined by the irregular profile of the tracks are considered. The wheel – rail contact forces are expressed using the creepage coefficients established according to Kalker's linear theory. The equations system is solved through numeric methods using specialized calculus programs. The response of the system – passenger coach on a tangent track, the critical speed and the influence of the constructive characteristics of the coach on its performances are determined.

  12. A Multi-Leveled Coordinate for Multibody Mechanics

    Directory of Open Access Journals (Sweden)

    Shen Fan

    2016-01-01

    Full Text Available For a proper way of modelling and simulation, as well as the precise and completeness, and a new multi-level method named homogeneous tensor coordinate(HTC was developed by improving the absolute nodal coordinate formulation(ANCF and the homogeneous coordinates(HC. In HTC, a new form of 2×2 matrix was employed instead of angles, when the capacity of expression and calculation was increased at the same time. HTC has good performance in traditional rigid body mechanics, which especially suitable for multibody modelling. Therefore, the robotic engineering may benefit from this finding, and a new formulation for scientific research may also affect the physics although some mathematical problems are raised in matrix theory.

  13. CP violation in multibody decays of beauty baryons

    CERN Document Server

    Durieux, Gauthier

    2016-01-01

    Beauty baryons are being observed in large number in the LHCb detector. The rich kinematics of their multibody decays are therefore becoming accessible and provide us with new opportunities to search for CP violation. We analyse the angular distributions of some three- and four-body decays of spin-$1/2$ baryons using the Jacob-Wick helicity formalism. The asymmetries that provide access to small differences of CP-odd phases between decay amplitudes of identical CP-even phases are notably discussed. The understanding gained on processes featuring specific resonant intermediate states allows us to establish which asymmetries are relevant for what purpose. It is for instance shown that some CP-odd angular asymmetries measured by the LHCb collaboration in the $\\Lambda_b \\to \\Lambda\\,\\varphi \\to p\\,\\pi\\, K^+ K^-$ decay are expected to vanish identically.

  14. CP violation in multibody decays of beauty baryons

    Science.gov (United States)

    Durieux, Gauthier

    2016-10-01

    Beauty baryons are being observed in large numbers in the LHCb detector. The rich kinematic distributions of their multibody decays are therefore becoming accessible and provide us with new opportunities to search for CP violation. We analyse the angular distributions of some three- and four-body decays of spin-1/2 baryons using the Jacob-Wick helicity formalism. The asymmetries that provide access to small differences of CP-odd phases between decay amplitudes of identical CP-even phases are notably discussed. The understanding gained on processes featuring specific resonant intermediate states allows us to establish which asymmetries are relevant for what purpose. It is for instance shown that some CP-odd angular asymmetries measured by the LHCb collaboration in the Λ b → Λ φ → p π K + K - decay are expected to vanish identically.

  15. Prediction of elbow joint contact mechanics in the multibody framework.

    Science.gov (United States)

    Rahman, Munsur; Cil, Akin; Stylianou, Antonis P

    2016-03-01

    Computational multibody musculoskeletal models of the elbow joint that are capable of simultaneous and accurate predictions of muscle and ligament forces, along with cartilage contact mechanics can be immensely useful in clinical practice. As a step towards producing a musculoskeletal model that includes the interaction between cartilage and muscle loading, the goal of this study was to develop subject-specific multibody models of the elbow joint with discretized humerus cartilage representation interacting with the radius and ulna cartilages through deformable contacts. The contact parameters for the compliant contact law were derived using simplified elastic foundation contact theory. The models were then validated by placing the model in a virtual mechanical tester for flexion-extension motion similar to a cadaver experiment, and the resulting kinematics were compared. Two cadaveric upper limbs were used in this study. The humeral heads were subjected to axial motion in a mechanical tester and the resulting kinematics from three bones were recorded for model validation. The maximum RMS error between the predicted and measured kinematics during the complete testing cycle was 2.7 mm medial-lateral translation and 9.7° varus-valgus rotation of radius relative to humerus (for elbow 2). After model validation, a lateral ulnar collateral ligament (LUCL) deficient condition was simulated and, contact pressures and kinematics were compared to the intact elbow model. A noticeable difference in kinematics, contact area, and contact pressure were observed for LUCL deficient condition. LUCL deficiency induced higher internal rotations for both the radius and ulna during flexion and an associated medial shift of the articular contact area.

  16. On the Formulation of Flexible Multibody Systems with Constant Mass Matrix

    DEFF Research Database (Denmark)

    Pedersen, Niels Leergaard

    1997-01-01

    A flexible body in a multibody system isdescribed only by the position of the nodes in theinertial frame. With this description we can formulatethe mass matrix of the flexible multibody as aconstant matrix. This matrix can be inverted in apreprocessing stage which yields a more efficientaccelerat...... of this formulation is that neither thecentrifugal nor the Coriolis forces appear in theequations due to the description of the flexible body....

  17. A Study on the Dynamic Analysis of A Tracked Vehicle for Ocean Mining on the Deep Seabed

    Institute of Scientific and Technical Information of China (English)

    Hyung-suk HAN

    2003-01-01

    A study is presented on the dynamic analysis of a tracked vehicle for mining on the deep seabed of very soft soil. Equations for the interaction between the track and extremely soft seabed are employed to develop a track/soil interaction module called TVAS. The vehicle is modeled as a multibody dynamic system by the use of a multibody dynamic analysis program. The module developed is cooperated with the multibody dynamic analysis program with a user-defined subroutine. The dynamic behavior and the conceptual design of the mining vehicle on the deep seabed are investigated.

  18. Are high lags of accommodation in myopic children due to motor deficits?

    Science.gov (United States)

    Labhishetty, Vivek; Bobier, William R

    2017-01-01

    Children with a progressing myopia exhibit an abnormal pattern of high accommodative lags coupled with high accommodative convergence (AC/A) and high accommodative adaptation. This is not predicted by the current models of accommodation and vergence. Reduced accommodative plant gain and reduced sensitivity to blur have been suggested as potential causes for this abnormal behavior. These etiologies were tested by altering parameters (sensory, controller and plant gains) in the Simulink model of accommodation. Predictions were then compared to the static and dynamic blur accommodation (BA) measures taken using a Badal optical system on 12 children (6 emmetropes and 6 myopes, 8-13years) and 6 adults (20-35years). Other critical parameters such as CA/C, AC/A, and accommodative adaptation were also measured. Usable BA responses were classified as either typical or atypical. Typical accommodation data confirmed the abnormal pattern of myopia along with an unchanged CA/C. Main sequence relationship remained invariant between myopic and nonmyopic children. An overall reduction was noted in the response dynamics such as peak velocity and acceleration with age. Neither a reduced plant gain nor reduced blur sensitivity could predict the abnormal accommodative behavior. A model adjustment reflecting a reduced accommodative sensory gain (ASG) coupled with an increased AC cross-link gain and reduced vergence adaptive gain does predict the empirical findings. Empirical measures also showed a greater frequency of errors in accommodative response generation (atypical responses) in both myopic and control children compared to adults.

  19. Reasonable Accommodation in Training Safety.

    Science.gov (United States)

    Sandoz, Jeff

    A pictograph and icon-driven training program has been specifically designed for educators who are responsible for teaching the developmentally disabled regarding the safe use of hazardous chemicals. In alignment with the Americans with Disabilities Act, it offers "reasonable accommodation" by those who educate and train this special…

  20. A centre for accommodative vergence motor control

    Science.gov (United States)

    Wilson, D.

    1973-01-01

    Latencies in accommodation, accommodative-vergence, and pupil-diameter responses to changing accommodation stimuli, as well as latencies in pupil response to light-intensity changes were measured. From the information obtained, a block diagram has been derived that uses the least number of blocks for representing the accommodation, accommodative-vergence, and pupil systems. The signal transmission delays over the various circuits of the model have been determined and compared to known experimental physiological-delay data. The results suggest the existence of a motor center that controls the accommodative vergence and is completely independent of the accommodation system.

  1. 模拟生理调节状态下人眼高阶像差的波动%The dynamic characteristics of ocular wavefront aberrations with the physiological accommodation in human eyes

    Institute of Scientific and Technical Information of China (English)

    熊瑛; 万修华; 余翔; 薛丽霞; 李靖; 李树宁; 卿国平; 凌宁; 王宁利

    2011-01-01

    Objective To investigate the dynamic characteristics of ocular wavefront aberrations and discuss the relationship between aberrations and pupil size, as well as the relationships between aberrations and accommodation under simulated physiological conditions. Design Prospective comperative study. Participants Normal eyes (21 cases) and the simulated eye. Methods The condition of ocular accommodation was controlled by the moving visual target when the value of the wavefront aberrations was collected by Hart-mann-Shark aberrometry. The simulated eye was used as the control. Main Outcome Measures The root mean square of total wave- front aberration (t-RMS) and high-order aberration (h-RMS) from normal eyes and the simulated eye and their coefficient of variance. Results In normal eye, the mean t-RMS was 0.46±0.18μm; the mean h-RMS was 0.27±0.14μm, the coefficient of variance was 40.37% and 36.34%, respectively. As a control, the mean t-RMS and coefficient of variance of the simulated eye' s was 0.39±0.00μm and 0.47% respectively. The h-RMS of normal eyes was correlated with pupil sizes and accommodation. The regression equation could be expressed as: h-RMS= 0.111 x pupil diameter (mm) -0.015 x dioptre (D) - 0.313(P<0.001 ,R2=0.458). Conclusion The ocular wavefront aberrations could change significantly under physiological conditions. The pupil size is the main factor.%目的 模拟生理调节状态下随着眼调节和瞳孔直径的变化人眼高阶像差的波动特点.设计 前瞻性比较性研究.研究对象 21例正常人眼与模拟眼.方法 通过控制视路上移动视标的位置诱发人眼调节,在调节过程中,不人为控制瞳孔直径,使其处于自然收缩舒张状态,实时用哈特曼波前传感器(Hartman-Shark)采集人眼波前像差.模拟眼作为对照.主要指标 人眼与模拟眼的总波前像差的均方根(t-RMS)和高阶像差的均方根(h-RMS)及其变异系数.结果 生理调节状态下,人眼的t-RMS为(0.46±0

  2. Treatment of Partly Accommodative Esotropia With a High Accommodative Convergence-Accommodation Ratio

    NARCIS (Netherlands)

    H.J. Simonsz (Huib)

    1988-01-01

    textabstractIn the June 1987 issue of the Archives, the results were published of a study by Kushner et al1 on the treatment of accommodative convergence excess, with bilateral medial rectus recessions or recessions with 14-mm posterior fixation sutures. Posterior fixation surgery was considered an

  3. FDI and Accommodation Using NN Based Techniques

    Science.gov (United States)

    Garcia, Ramon Ferreiro; de Miguel Catoira, Alberto; Sanz, Beatriz Ferreiro

    Massive application of dynamic backpropagation neural networks is used on closed loop control FDI (fault detection and isolation) tasks. The process dynamics is mapped by means of a trained backpropagation NN to be applied on residual generation. Process supervision is then applied to discriminate faults on process sensors, and process plant parameters. A rule based expert system is used to implement the decision making task and the corresponding solution in terms of faults accommodation and/or reconfiguration. Results show an efficient and robust FDI system which could be used as the core of an SCADA or alternatively as a complement supervision tool operating in parallel with the SCADA when applied on a heat exchanger.

  4. A simple probabilistic model of multibody interactions in proteins.

    Science.gov (United States)

    Johansson, Kristoffer Enøe; Hamelryck, Thomas

    2013-08-01

    Protein structure prediction methods typically use statistical potentials, which rely on statistics derived from a database of know protein structures. In the vast majority of cases, these potentials involve pairwise distances or contacts between amino acids or atoms. Although some potentials beyond pairwise interactions have been described, the formulation of a general multibody potential is seen as intractable due to the perceived limited amount of data. In this article, we show that it is possible to formulate a probabilistic model of higher order interactions in proteins, without arbitrarily limiting the number of contacts. The success of this approach is based on replacing a naive table-based approach with a simple hierarchical model involving suitable probability distributions and conditional independence assumptions. The model captures the joint probability distribution of an amino acid and its neighbors, local structure and solvent exposure. We show that this model can be used to approximate the conditional probability distribution of an amino acid sequence given a structure using a pseudo-likelihood approach. We verify the model by decoy recognition and site-specific amino acid predictions. Our coarse-grained model is compared to state-of-art methods that use full atomic detail. This article illustrates how the use of simple probabilistic models can lead to new opportunities in the treatment of nonlocal interactions in knowledge-based protein structure prediction and design.

  5. FATIGUE LIFE EVALUATION OF SUSPENSION KNUCKLE USING MULTIBODY SIMULATION TECHNIQUE

    Directory of Open Access Journals (Sweden)

    A.G.A. Rahman

    2012-12-01

    Full Text Available Suspension is part of automotive systems, providing both vehicle control and passenger comfort. The knuckle is an important part within the suspension system, constantly encountering the cyclic loads subjecting it to fatigue failure. This paper presents an evaluation of the fatigue characteristics of a knuckle using multibody simulation (MBS techniques. Load time history extracted from the MBS is used for stress analysis. An actual road profile of road bumps was used as the input to MBS. The stress fluctuations for fatigue simulations are considered with the road profile. The strain-life method is utilized to assess the fatigue life. The instantaneous stress distributions and maximum principal stress are used for fatigue life predictions. Mesh sensitivity analysis has been performed. The results show that the steering link in the knuckle is found to be the most susceptible region for fatigue failure. The number of times the knuckle can manage a road bump at 40 km/hr is determined to be approximately 371 times with a 50% certainty of survival. The proposed method of using the loading time history extracted from MBS simulation for fatigue life estimation is found to be very promising for the accurate evaluation of the performance of suspension system components.

  6. Charles F. Prentice award lecture 2008: surgical correction of presbyopia with intraocular lenses designed to accommodate.

    Science.gov (United States)

    Schor, Clifton M

    2009-09-01

    Surgical restoration of accommodation with accommodating intra-ocular lenses (A-IOLs) presents a complex set of problems involving the design of the prosthetic mechanism. A variety of designs are currently employed that either translate the A-IOL toward the cornea along the sagittal axis, shear two lens components laterally, or deform lens shape to change dioptric power of the eye during attempts to accommodate. Effective biomechanical properties (elasticity and viscosity) of these lenses depend on both material properties and structural design of the A-IOL. Inevitable mismatches between the neuromuscular control of accommodation and the effective biomechanical properties of the prosthetic lens could lead to either unstable oscillations or sluggishness of dynamic accommodation; however, optimal dynamic responses may possibly be restored by neural recalibration. A model of dynamic accommodation is used to predict the consequences of these mismatches on dynamic accommodation, and reverse engineering is used to test the feasibility of neuromuscular recalibration. Empirical measures verify that neuromuscular adaptation of dynamic accommodation is possible in response to optically simulated increases and decreases of ocular-lens stiffness. Other design issues for A-IOLs include stability of optical properties, aberrations and image quality, and interactions of restored accommodation with binocular eye alignment (the near response).

  7. Feasibility Assessment of an ISS Artificial Gravity Conditioning Facility by Means of Multi-Body Approach

    Science.gov (United States)

    Toso, Mario; Baldesi, Gianluigi; Moratto, Claudio; De Wilde, Don; Bureo Dacal, Rafael; Castellsaguer, Joaquim

    2012-07-01

    Even though human exploration of Mars is a distant objective, it is well understood that, for human space voyages of several years duration, crews would be at risk of catastrophic consequences should any of the systems that provide adequate air, water, food, or thermal protection fail. Moreover, crews will face serious health and/or safety risks resulting from severe physiologic deconditioning associated with prolonged weightlessness. The principal ones are related to physical and functional deterioration of the regulation of the blood circulation, decreased aerobic capacity, impaired musculo-skeletal systems, and altered sensory- motor system performance. As the reliance of future space programmes on virtual modelling, simulation and justification has substantially grown together with the proto-flight hardware development approach, a range of simulation capabilities have become increasingly important in the requirements specification, design, verification, testing, launch and operation of new space systems. In this frame, multibody software is a key tool in providing a more coordinated and consistent approach from the preliminary development phases of the most complex systems. From a scientific prospective, an artificial gravity facility, such as the one evaluated in this paper, would be the first in-flight testing of the effectiveness and acceptability of short radius centrifuge as a countermeasure to human deconditioning on orbit. The ISS represents a unique opportunity to perform this research. From an engineering point of view, the preliminary assessment described in this paper, highlights the difficult engineering challenges of such a facility. The outcome proves that a human can be accommodated in the available volume, while respecting the human ergonomic basic requirements and preserving the global structural integrity of the hosting ISS module. In particular, analysis shows that, although the load capacity of the structural interfaces imposes a very low

  8. Accommodation and pupil responses to random-dot stereograms.

    Science.gov (United States)

    Suryakumar, Rajaraman; Allison, Robert

    2016-01-01

    We investigated the dynamics of accommodative and pupillary responses to random-dot stereograms presented in crossed and uncrossed disparity in six visually normal young adult subjects (mean age=25.8±3.1 years). Accommodation and pupil measures were monitored monocularly with a custom built photorefraction system while subjects fixated at the center of a random-dot stereogram. On each trial, the stereogram initially depicted a flat plane and then changed to depict a sinusoidal corrugation in depth while fixation remained constant. Increase in disparity specified depth resulted in pupil constriction during both crossed and uncrossed disparity presentations. The change in pupil size between crossed and uncrossed disparity conditions was not significantly different (p>0.05). The change in pupil size was also accompanied by a small concomitant increase in accommodation. In addition, the dynamic properties of pupil responses varied as a function of their initial (starting) diameter. The finding that accommodation and pupil responses increased with disparity regardless of the sign of retinal disparity suggests that these responses were driven by apparent depth rather than shifts in mean simulated distance of the stimulus. Presumably the need for the increased depth of focus when viewing stimuli extended in depth results in pupil constriction which also results in a concomitant change in accommodation. Starting position effects in pupil response confirm the non-linearity in the operating range of the pupil.

  9. Accommodative spasm in siblings: A unique finding

    Directory of Open Access Journals (Sweden)

    Rutstein Robert

    2010-01-01

    Full Text Available Accommodative spasm is a rare condition occurring in children, adolescents, and young adults. A familial tendency for this binocular vision disorder has not been reported. I describe accommodative spasm occurring in a brother and sister. Both children presented on the same day with complaints of headaches and blurred vision. Treatment included cycloplegia drops and bifocals. Siblings of patients having accommodative spasm should receive a detailed eye exam with emphasis on recognition of accommodative spasm.

  10. Ski Control Model for Parallel Turn Using Multibody System

    Science.gov (United States)

    Kawai, Shigehiro; Yamaguchi, Keishi; Sakata, Toshiyuki

    Now, it is possible to discuss qualitatively the effects of skis, skier’s ski control and slope on a ski turn by simulation. The reliability of a simulation depends on the accuracy of the models used in the simulation. In the present study, we attempt to develop a new ski control model for a “parallel turn” using a computer graphics technique. The “ski control” necessary for the simulation is the relative motion of the skier’s center of gravity to the ski and the force acting on the ski from the skier. The developed procedure is as follows. First, the skier is modeled using a multibody system consisting of body parts. Second, various postures of the skier during the “parallel turn” are drawn using a 3D-CAD (three dimensional computer aided design) system referring to the pictures videotaped on a slope. The position of the skier’s center of gravity is estimated from the produced posture. Third, the skier’s ski control is obtained by arranging these postures in a time schedule. One can watch the ski control on a TV. Last, the three types of forces acting on the ski from the skier are estimated from the gravity force and the three relative types of inertia forces acting on the skier. Consequently, one can obtain accurate ski control for the simulation of the “parallel turn”, that is, the relative motion of the skier’s center of gravity to the ski and the force acting on the ski from the skier. Furthermore, it follows that one can numerically estimate the edging angle from the ski control model.

  11. Validation of Multibody Program to Optimize Simulated Trajectories II Parachute Simulation with Interacting Forces

    Science.gov (United States)

    Raiszadeh, Behzad; Queen, Eric M.; Hotchko, Nathaniel J.

    2009-01-01

    A capability to simulate trajectories of multiple interacting rigid bodies has been developed, tested and validated. This capability uses the Program to Optimize Simulated Trajectories II (POST 2). The standard version of POST 2 allows trajectory simulation of multiple bodies without force interaction. In the current implementation, the force interaction between the parachute and the suspended bodies has been modeled using flexible lines, allowing accurate trajectory simulation of the individual bodies in flight. The POST 2 multibody capability is intended to be general purpose and applicable to any parachute entry trajectory simulation. This research paper explains the motivation for multibody parachute simulation, discusses implementation methods, and presents validation of this capability.

  12. 46 CFR 108.143 - Accommodation space.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Accommodation space. 108.143 Section 108.143 Shipping... EQUIPMENT Construction and Arrangement Structural Fire Protection § 108.143 Accommodation space. (a) Each corridor bulkhead in an accommodation space must be an A class or B class bulkhead except if an A...

  13. Pupil movements to light and accommodative stimulation - A comparative study.

    Science.gov (United States)

    Semmlow, J.; Stark, L.

    1973-01-01

    Isolation and definition of specific response components in pupil reflexes through comparison of the dynamic features of light-induced and accommodation-induced pupil movements. A quantitative analysis of the behavior of the complex nonlinear pupil responses reveals the presence of two independent nonlinear characteristics: a range-dependent gain and a direction dependence or movement asymmetry. These nonlinear properties are attributed to motor processes because they are observable in pupil responses to both light and accommodation stimuli. The possible mechanisms and consequences of these pupil response characteristics are quantitatively defined and discussed.

  14. Accommodating environmental variation in population models: metaphysiological biomass loss accounting.

    Science.gov (United States)

    Owen-Smith, Norman

    2011-07-01

    1. There is a pressing need for population models that can reliably predict responses to changing environmental conditions and diagnose the causes of variation in abundance in space as well as through time. In this 'how to' article, it is outlined how standard population models can be modified to accommodate environmental variation in a heuristically conducive way. This approach is based on metaphysiological modelling concepts linking populations within food web contexts and underlying behaviour governing resource selection. Using population biomass as the currency, population changes can be considered at fine temporal scales taking into account seasonal variation. Density feedbacks are generated through the seasonal depression of resources even in the absence of interference competition. 2. Examples described include (i) metaphysiological modifications of Lotka-Volterra equations for coupled consumer-resource dynamics, accommodating seasonal variation in resource quality as well as availability, resource-dependent mortality and additive predation, (ii) spatial variation in habitat suitability evident from the population abundance attained, taking into account resource heterogeneity and consumer choice using empirical data, (iii) accommodating population structure through the variable sensitivity of life-history stages to resource deficiencies, affecting susceptibility to oscillatory dynamics and (iv) expansion of density-dependent equations to accommodate various biomass losses reducing population growth rate below its potential, including reductions in reproductive outputs. Supporting computational code and parameter values are provided. 3. The essential features of metaphysiological population models include (i) the biomass currency enabling within-year dynamics to be represented appropriately, (ii) distinguishing various processes reducing population growth below its potential, (iii) structural consistency in the representation of interacting populations and

  15. Summary of the 2015 LHCb workshop on multi-body decays of D and B mesons

    CERN Document Server

    Amato, Sandra; Baesso, Clarissa; Haim, Eli Ben; Bigi, Ikaros; Boito, Diogo; Brodzicka, Jolanta; Reis, Alberto Correa dos; Craik, Daniel Charles; Torres, Melissa Maria Cruz; Dalseno, Jeremy; Hickman, Ignacio de Bediaga; Vieira, Daniel Evangelho; Rodrigues, Fernando Luiz Ferreira; Gershon, Timothy; Göbel, Carla; Greenwald, Daniel; Harnew, Samuel Thomas; Henry, Louis; Hicheur, Adlene; Latham, Thomas Edward; Loiseau, Benoit; London, David; Lopes, Helder; Magalhães, Patricia; de Miranda, Jussara Marques; Tostes, Danielle Martins; Rodrigues, Andre Massafferri; Mathad, Abhijit; Meadows, Brian; Carreno, Diego Milanes; Rodriguez, Josue Danilo Molina; Moraes, Danielle; Nasteva, Irina; Nielsen, Marina; Nogueira, Jorge; O'Hanlon, Daniel Patrick; Oset, Eulogio; Rodrigues, Bruno Osorio; Goicochea, Juan Martin Otalora; Paul, Stephan; Polycarpo, Erica; Prouvé, Claire; Quagliani, Renato; Rademacker, Jonas; Robilotta, Manoel; Rodriguez, Jairo Alexis; Coutinho, Rafael Silva; Skwarnicki, Tomasz; Sun, Liang; Szczepaniak, Adam; Aoude, Rafael Tourinho; Wallace, Charlotte; Whitehead, Mark

    2016-01-01

    This document contains a summary of the LHCb workshop on multi-body decays of D and B mesons, held at CBPF, Rio de Janeiro, in July 2015. The workshop was focused on issues related to amplitude analysis of three- and four-body hadronic decays. In addition to selected LHCb results, contributions from guest theorists are included.

  16. Experimental and analytical investigation of inertial propulsion mechanisms and motion simulation of rigid multi-body mechanical systems

    Science.gov (United States)

    Almesallmy, Mohammed

    Methodologies are developed for dynamic analysis of mechanical systems with emphasis on inertial propulsion systems. This work adopted the Lagrangian methodology. Lagrangian methodology is the most efficient classical computational technique, which we call Equations of Motion Code (EOMC). The EOMC is applied to several simple dynamic mechanical systems for easier understanding of the method and to aid other investigators in developing equations of motion of any dynamic system. In addition, it is applied to a rigid multibody system, such as Thomson IPS [Thomson 1986]. Furthermore, a simple symbolic algorithm is developed using Maple software, which can be used to convert any nonlinear n-order ordinary differential equation (ODE) systems into 1st-order ODE system in ready format to be used in Matlab software. A side issue, but equally important, we have started corresponding with the U.S. Patent office to persuade them that patent applications, claiming gross linear motion based on inertial propulsion systems should be automatically rejected. The precedent is rejection of patent applications involving perpetual motion machines.

  17. Evaluating relative accommodations in general binocular dysfunctions

    OpenAIRE

    García Muñoz, Ángel; Cacho Martínez, Pilar; Lara Lacarcel, Francisco

    2001-01-01

    Purpose. To examine the relationship between relative accommodation and general binocular disorders and to establish their importance in the diagnosis of these anomalies. Methods. We analyzed data of negative relative accommodation (NRA) and positive relative accommodation (PRA) in 69 patients with nonstrabismic binocular anomalies. Results. Statistical analysis showed that low values of NRA and PRA were not associated with any particular disorder. High values of PRA (>3.50 D) were related to...

  18. Uniformity of accommodation across the visual field.

    Science.gov (United States)

    Liu, Tao; Sreenivasan, Vidhyapriya; Thibos, Larry N

    2016-01-01

    We asked the question: Does accommodation change the eye's focusing power equally over the central visual field in emmetropic and myopic adult eyes? To answer this question we modified our laboratory scanning wavefront aberrometer to rapidly measure ocular refractive state over the central 30° diameter of visual field as a function of foveal accommodative demand. On average, ocular refractive state changed uniformly over the central visual field as the eye accommodated up to 6 D. Visual field maps of accommodative error (relative to a spherical target surface of constant vergence) reveal subtle patterns of deviation on the order of ± 0.5 D that are unique to the individual and relatively invariant to changes in accommodative state. Population mean maps for accommodative error are remarkably uniform across the central visual field, indicating the retina of the hypothetical "average eye" is conjugate to a sphere of constant target vergence for all states of accommodation, even though individual eyes might deviate from the mean due to random variations. No systematic difference between emmetropic and myopic eyes was evident. Since accuracy of accommodation across the central visual field is similar to that measured in the fovea, loss of image quality due to accommodative errors, which potentially drives myopia and may affect many aspects of visual function, will be similar across the central retina.

  19. Accommodative response and cortical activity during sustained attention.

    Science.gov (United States)

    Poltavski, Dmitri V; Biberdorf, David; Petros, Thomas V

    2012-06-15

    Greater accommodative lag and vergence deficits have been linked to attentional deficits similar to those observed in Attention Deficit Hyperactivity Disorder (ADHD). The purpose of the present study was to assess the effect of accommodative-vergence stress on a measure of sustained attention (Conners CPT) used in the diagnosis of ADHD. Twenty-seven normal non-ADHD adults completed the Conners CPT twice: wearing -2.00 D lenses and normally (without the -2.00 D lenses) in a counterbalanced order with at least 24 h between the sessions. Simultaneous recording of participants' dynamic accommodative responses was performed from the right eye using the Grand Seiko WAM-5500 auto-refractor and electroencephalographic activity (EEG) in the left prefrontal region using the Neurosky Mindset headset. The results demonstrated a significantly greater accommodative lag in the -2.00 D stress condition and a significantly poorer performance on the Conners CPT as indexed by slower reaction time, greater standard error of hit reaction time, grater response variability, poorer stimulus detectability and a greater number of perseverations. No differences were observed on measures of EEG in the theta (4-7 Hz), alpha (8-12 Hz), and beta (12-20 Hz) bands. Moreover, when directly juxtaposed with each EEG band in multiple linear regression analyses, greater accommodative lag in the stress condition was significantly associated with a greater probability of clinical classification on the Conners CPT, and was also marginally predictive of the number of omissions recorded in the stress condition. The results demonstrated that sustained attention can be influenced by such factors as accommodative-vergence stress and suggest that bottom-up processes can contribute to and potentially exacerbate attentional problems in individuals with ADHD. The study also showed that cortical dysfunction (while sufficient) may not be a necessary condition for attentional deficits.

  20. Adherence Evaluation of a MacPherson Suspension under EuSAMA Norm in a Mathematical Model and one Multibody

    Directory of Open Access Journals (Sweden)

    Juan J. Arbeláez-Toro

    2013-11-01

    Full Text Available A computational simulation is Implemented, in order to response to a problem of dynamics associated With The assessment of adherence in suspension systems. The process begins with the lifting of the most representative geometries of a MacPherson system of a Nissan Sentra B13, where each of the devices is created and assembled into a CAD software to give a dynamic solution on a CAE multibody package. Afterwards a mathematical model was created whose differential equations are generated substantiated on Newton's second law and this are resolved using Matlab-Simulink applications. Once the model developing process is over, the variables are fed with accurate information of the studied vehicle to obtain the graphs that give an answer to EuSAMA (European Shock Absorber Manufacturers Association test protocol for the adherence analysis. The results presented show the reliability of the developed models when compared with the experimental test; furthermore, it demonstrates that the decrease of the damping coefficient compromises the vehicle´s adherence on the track, affecting its stability and maneuverability.

  1. Decentralized Disturbance Accommodation with Limited Plant Model Information

    CERN Document Server

    Farokhi, F; Johansson, K H

    2011-01-01

    The design of optimal disturbance accommodation and servomechanism controllers with limited plant model information is considered in this paper. Their closed-loop performance are compared using a performance metric called competitive ratio which is the worst-case ratio of the cost of a given control design strategy to the cost of the optimal control design with full model information. It was recently shown that when it comes to designing optimal centralized or partially structured decentralized state-feedback controllers with limited model information, the best control design strategy in terms of competitive ratio is a static one. This is true even though the optimal structured decentralized state-feedback controller with full model information is dynamic. In this paper, we show that, in contrast, the best limited model information control design strategy for the disturbance accommodation problem gives a dynamic controller. We find an explicit minimizer of the competitive ratio and we show that it is undomina...

  2. Bearing-Mounting Concept Accommodates Thermal Expansion

    Science.gov (United States)

    Nespodzany, Robert; Davis, Toren S.

    1995-01-01

    Pins or splines allow radial expansion without slippage. Design concept for mounting rotary bearing accommodates differential thermal expansion between bearing and any structure(s) to which bearing connected. Prevents buildup of thermal stresses by allowing thermal expansion to occur freely but accommodating expansion in such way not to introduce looseness. Pin-in-slot configuration also maintains concentricity.

  3. BRANDING ORIENTATION IN THE ACCOMMODATION INDUSTRY

    Directory of Open Access Journals (Sweden)

    Melissa Li Sa Liow

    2015-04-01

    Full Text Available This paper starts by clarifying the role of branding orientation (BO among academic studies. It shortly introduces the development of the BO concepts. The empirical part consists of a search for and analysing of academic articles using a meta-analysis that consider BO in the accommodation industry. According to the results, significant appraisal of the branding building activities among higher star rating and luxury accommodation businesses are taking place due to the increasingly demanding guests. Thus, there is an upward pressure on small and medium accommodation businesses to survive or perform well. This paper recommends that scholars study the owners-managers, employees, and customer perspectives altogether, to better comprehend how large accommodation businesses displaying BO can generate superior performance. For the small and medium accommodation businesses, the emphasis is the owners-managers perceptions since they are the main decision-makers, and due to infancy of the small and medium enterprise (SME branding application.

  4. Analysis of truck platoon dynamics

    NARCIS (Netherlands)

    Verhoeff, L.; Zuurbier, J.; Lupker, H.A.

    1999-01-01

    This paper presents the analysis of truck platoon dynamics using a simulation environment. In this case the platoon consists of a number of trucks following each other using driver algorithms. MADYMO (a multibody and FE software package) and MATLAB/SIMULINK are coupled to allow for these driver algo

  5. Recursive Filtering And Smoothing In Robot Dynamics

    Science.gov (United States)

    Rodriguez, Guillermo

    1992-01-01

    Techniques developed originally for electronic systems also useful for multibody mechanical systems. Report summarizes methods developed to solve nonlinear forward-dynamics problem for robot of multiple-link arms connected by joints. Primary objective to show equivalence between recursive methods of dynamical analysis and some filtering and smoothing techniques from state-estimation theory.

  6. A Large-Scale Multibody Manipulator Soft Sensor Model and Experiment Validation

    Directory of Open Access Journals (Sweden)

    Wu Ren

    2014-01-01

    Full Text Available Stress signal is difficult to obtain in the health monitoring of multibody manipulator. In order to solve this problem, a soft sensor method is presented. In the method, stress signal is considered as dominant variable and angle signal is regarded as auxiliary variable. By establishing the mathematical relationship between them, a soft sensor model is proposed. In the model, the stress information can be deduced by angle information which can be easily measured for such structures by experiments. Finally, test of ground and wall working conditions is done on a multibody manipulator test rig. The results show that the stress calculated by the proposed method is closed to the test one. Thus, the stress signal is easier to get than the traditional method. All of these prove that the model is correct and the method is feasible.

  7. An exact nonlinear hybrid-coordinate formulation for flexible multibody systems

    Institute of Scientific and Technical Information of China (English)

    Jinyang Liu; Jiazhen Hong; Lin Cui

    2007-01-01

    The previous low-order approximate nonlinear formulations succeeded in capturing the stiffening terms,but failed in simulation of mechanical systems with large deformation due to the neglect of the high-order deforma-tion terms. In this paper, a new hybrid-coordinate formu-lation is proposed, which is suitable for flexible multibody systems with large deformation. On the basis of exact strain-displacement relation, equations of motion for flexible multi-body system are derived by using virtual work principle. A matrix separation method is put forward to improve the efficiency of the calculation. Agreement of the present results with those obtained by absolute nodal coordinate formula-tion (ANCF) verifies the correctness of the proposed formu-lation. Furthermore, the present results are compared with those obtained by use of the linear model and the low-order approximate nonlinear model to show the suitability of the proposed models.

  8. Concurrent multibody and Finite Element analysis of the lower-limb during amputee running.

    Science.gov (United States)

    Rigney, Stacey M; Simmons, Anne; Kark, Lauren

    2015-01-01

    Lower-limb amputee athletes use Carbon fiber Energy Storage and Return (ESAR) prostheses during high impact activities such as running. The advantage provided to amputee athletes due to the energy-storing properties of ESAR prostheses is as yet uncertain. Conventional energy analysis methods for prostheses rely upon multibody models with articulating joints. Alternatively, Finite Element (FE) analysis treats bodies as a deforming continuum and can therefore calculate the energy stored without using these rigid-body mechanics assumptions. This paper presents a concurrent multibody and FE model of the femur, tibia, socket and ESAR prosthesis of a transtibial amputee athlete during sprinting. Gait analysis spatial data was used to conduct an offline simulation of the affected leg's stance phase in COMSOL Multiphysics. The calculated peak elastic strain energy of the prosthesis was 80J, with an overall RMSE of simulated marker displacement of 4.19 mm. This concurrent model presents a novel method for analyzing in vivo ESAR prosthesis behavior.

  9. Multibody Model for Planetary Gearbox of 500 kW Wind Turbine

    DEFF Research Database (Denmark)

    Jørgensen, Martin Felix; Pedersen, Niels Leergaard; Sørensen, Jens Nørkær

    The aim of the work is to simulate the loadings in a planetary gearbox of a wind turbine using a multibody program. A realistic wind turbine gearbox of a 500 kW wind turbine is examined using turbulent inflow data. An aeroelastic model of the wind turbine has been set up using the FLEX5-code...... (industrial standard software). The FLEX5 model as well as the developed multibody code has been verified from strain gauge measurements, giving e.g. the main shaft torque, and met mast wind data measurements. The realistic measurements on both input and output variables form an excellent base for studying...... the gearbox fatigue loads, the effect of wind turbulence on the power production/output torque on the highspeed shaft and for calibration and verification of the gearbox model....

  10. Parameter identification of multi-body railway vehicle models - Application of the adjoint state approach

    Science.gov (United States)

    Kraft, S.; Puel, G.; Aubry, D.; Funfschilling, C.

    2016-12-01

    For the calibration of multi-body models of railway vehicles, the identification of the model parameters from on-track measurement is required. This involves the solution of an inverse problem by minimising the misfit function which describes the distance between model and measurement using optimisation methods. The application of gradient-based optimisation methods is advantageous but necessitates an efficient approach for the computation of the gradients considering the large number of model parameters and the costly evaluation of the forward model. This work shows that the application of the adjoint state approach to the nonlinear vehicle-track multi-body system is suitable, reducing on the one hand the computational cost and increasing on the other hand the precision of the gradients. Gradients from the adjoint state method are computed for vehicle models and validated taking into account measurement noise.

  11. Multi-body simulation of a canine hind limb: model development, experimental validation and calculation of ground reaction forces

    Directory of Open Access Journals (Sweden)

    Wefstaedt Patrick

    2009-11-01

    Full Text Available Abstract Background Among other causes the long-term result of hip prostheses in dogs is determined by aseptic loosening. A prevention of prosthesis complications can be achieved by an optimization of the tribological system which finally results in improved implant duration. In this context a computerized model for the calculation of hip joint loadings during different motions would be of benefit. In a first step in the development of such an inverse dynamic multi-body simulation (MBS- model we here present the setup of a canine hind limb model applicable for the calculation of ground reaction forces. Methods The anatomical geometries of the MBS-model have been established using computer tomography- (CT- and magnetic resonance imaging- (MRI- data. The CT-data were collected from the pelvis, femora, tibiae and pads of a mixed-breed adult dog. Geometric information about 22 muscles of the pelvic extremity of 4 mixed-breed adult dogs was determined using MRI. Kinematic and kinetic data obtained by motion analysis of a clinically healthy dog during a gait cycle (1 m/s on an instrumented treadmill were used to drive the model in the multi-body simulation. Results and Discussion As a result the vertical ground reaction forces (z-direction calculated by the MBS-system show a maximum deviation of 1.75%BW for the left and 4.65%BW for the right hind limb from the treadmill measurements. The calculated peak ground reaction forces in z- and y-direction were found to be comparable to the treadmill measurements, whereas the curve characteristics of the forces in y-direction were not in complete alignment. Conclusion In conclusion, it could be demonstrated that the developed MBS-model is suitable for simulating ground reaction forces of dogs during walking. In forthcoming investigations the model will be developed further for the calculation of forces and moments acting on the hip joint during different movements, which can be of help in context with the in

  12. Accommodation of workers with chronic neurologic disorders.

    Science.gov (United States)

    Bleecker, Margit L; Barnes, Sheryl K

    2015-01-01

    The ability to work is important to those with chronic neurologic disorders (CND) and to the aging workforce. Many signs and symptoms are similar in those with CND and normal aging, but may interfere with the ability to work if not appropriately accommodated. This requires the healthcare provider to recognize the specific features of the CND that interferes with work and how it can be accommodated. Review of the American with Disabilities Act and the subsequent amendment informs the healthcare provider as to what is covered under the law and how the disability can be accommodated. Overall employers want to retain qualified employees and therefore accommodating workers is beneficial to both the employee with CND and the employer.

  13. Dynamics Modeling of Heavy Special Driving Simulator

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Based on the dynamical characteristic parameters of the real vehicle, the modeling approach and procedure of dynamics of vehicles are expatiated. The layout of vehicle dynamics is proposed, and the sub-models of the diesel engine, drivetrain system and vehicle multi-body dynamics are introduced. Finally, the running characteristic data of the virtual and real vehicles are compared, which shows that the dynamics model is similar closely to the real vehicle system.

  14. Relationship of ocular accommodation and motor skills performance in developmental coordination disorder.

    Science.gov (United States)

    Rafique, Sara A; Northway, Nadia

    2015-08-01

    Ocular accommodation provides a well-focussed image, feedback for accurate eye movement control, and cues for depth perception. To accurately perform visually guided motor tasks, integration of ocular motor systems is essential. Children with motor coordination impairment are established to be at higher risk of accommodation anomalies. The aim of the present study was to examine the relationship between ocular accommodation and motor tasks, which are often overlooked, in order to better understand the problems experienced by children with motor coordination impairment. Visual function, gross and fine motor skills were assessed in children with developmental coordination disorder (DCD) and typically developing control children. Children with DCD had significantly poorer accommodation facility and amplitude dynamics compared to controls. Results indicate a relationship between impaired accommodation and motor skills. Specifically, accommodation anomalies correlated with visual motor, upper limb and fine dexterity task performance. Consequently, we argue accommodation anomalies influence the ineffective coordination of action and perception in DCD. Furthermore, reading disabilities were related to poorer motor performance. We postulate the role of the fastigial nucleus as a common pathway for accommodation and motor deficits. Implications of the findings and recommended visual screening protocols are discussed.

  15. Adaptive Locomotion of Multibody Snake-like Robot

    CERN Document Server

    Meister, Eugen; Kernbach, Serge

    2011-01-01

    This paper represents an adaptive rhythmic control for a snake-like robot with 25 degrees of freedom. The adaptive gait control is implemented in algorithmic way in simulation and on a real robot. We investigated behavioral and energetic properties of this control and a dynamics of different body segments. It turned out that despite using homogeneous generators, physical constraints have an inhomogeneous impact on neighbor body segments. By analytical modeling of such dynamics, it may result in heterogeneous coupling of oscillators for a rhythmic control and impact scalability and synchronization effects of gait pattern generators.

  16. Variable universe fractal control of flexible multi-body spacecraft for large angle attitude maneuver%柔性航天器大角度姿态机动的变论域分形控制

    Institute of Scientific and Technical Information of China (English)

    杨思亮; 徐世杰

    2011-01-01

    The dynamic model of flexible multi-body spacecraft with topological tree configuration has been established based on the Lagrange's equations in terms of quasi-coordinates. The kinematics of the spacecraft is described by Modified Rodrigues Parameters (MRPs). For this time-varing uncertainty flexible multi-body spacecraft dynamic system, a modified fractal controller via variable universe of discourse was designed and the numerical simulation was done. The results show that this control scheme avoids the flaw caused by real-time calculating of shrinkable factors, realizes the effective control of flexible multi-body spacecraft for large angte attitude maneuver, and assures the vibration suppression of the spacecraft flexible appendages at the same time%针对具有开环树状拓扑结构的柔性多体航天器,基于真一伪坐标形式的拉格朗日方程,建立柔性多体航天器的动力学模型,充分考虑了柔性航天器的时变与不确定性的动力学特征,设计了改进的变论域分形模糊控制器,并对该系统进行了仿真验证.仿真结果表明,该方案回避了实时计算收缩因子所导致的论域范围实时收缩的缺点,实现了对柔性多体航天器大角度姿态机动的有效控制,同时保证了航天器柔性附件振动的有效抑制.

  17. Complex treatment of accommodation disturbances in students

    Directory of Open Access Journals (Sweden)

    O. G. Pozdeeva

    2013-01-01

    Full Text Available Purpose: Assessment of the effectiveness of different methods of treatment accommodation disturbances in patients 18‑23 years old.Methods: Determination of refraction and the size of the absolute accommodation and reserves of the relative accommodationbefore and after the treatment with Midrimax and Irifrin 2.5 % in combination with the course of electrostimulation.Results: The clinical effect was obtained in all patients. The maximum improvement of visual functions with a lower degree of myopia (1.0‑3.0 D, increase of absolute accommodation (by 2.5‑3,.D and reserves of the relative accommodation (up to age norms were observed in the younger age group of patients, wich had received the treatment with Midrimax, especially when combined with electrostimulation.Conclusion: Instillation of Midrimax in the treatment of violations of accommodation contribute to the effective reduction in the degree of myopia and improve of accomodation in patients 18‑23 years old. The combination of this therapy with functional methods of treatment increase its effectiveness.

  18. Complex treatment of accommodation disturbances in students

    Directory of Open Access Journals (Sweden)

    O. G. Pozdeeva

    2014-07-01

    Full Text Available Purpose: Assessment of the effectiveness of different methods of treatment accommodation disturbances in patients 18‑23 years old.Methods: Determination of refraction and the size of the absolute accommodation and reserves of the relative accommodationbefore and after the treatment with Midrimax and Irifrin 2.5 % in combination with the course of electrostimulation.Results: The clinical effect was obtained in all patients. The maximum improvement of visual functions with a lower degree of myopia (1.0‑3.0 D, increase of absolute accommodation (by 2.5‑3,.D and reserves of the relative accommodation (up to age norms were observed in the younger age group of patients, wich had received the treatment with Midrimax, especially when combined with electrostimulation.Conclusion: Instillation of Midrimax in the treatment of violations of accommodation contribute to the effective reduction in the degree of myopia and improve of accomodation in patients 18‑23 years old. The combination of this therapy with functional methods of treatment increase its effectiveness.

  19. Prediction of anthropometric accommodation in aircraft cockpits

    Science.gov (United States)

    Zehner, Gregory Franklin

    Designing aircraft cockpits to accommodate the wide range of body sizes existing in the U.S. population has always been a difficult problem for Crewstation Engineers. The approach taken in the design of military aircraft has been to restrict the range of body sizes allowed into flight training, and then to develop standards and specifications to ensure that the majority of the pilots are accommodated. Accommodation in this instance is defined as the ability to: (1) Adequately see, reach, and actuate controls; (2) Have external visual fields so that the pilot can see to land, clear for other aircraft, and perform a wide variety of missions (ground support/attack or air to air combat); and (3) Finally, if problems arise, the pilot has to be able to escape safely. Each of these areas is directly affected by the body size of the pilot. Unfortunately, accommodation problems persist and may get worse. Currently the USAF is considering relaxing body size entrance requirements so that smaller and larger people could become pilots. This will make existing accommodation problems much worse. This dissertation describes a methodology for correcting this problem and demonstrates the method by predicting pilot fit and performance in the USAF T-38A aircraft based on anthropometric data. The methods described can be applied to a variety of design applications where fitting the human operator into a system is a major concern. A systematic approach is described which includes: defining the user population, setting functional requirements that operators must be able to perform, testing the ability of the user population to perform the functional requirements, and developing predictive equations for selecting future users of the system. Also described is a process for the development of new anthropometric design criteria and cockpit design methods that assure body size accommodation is improved in the future.

  20. Aerobrake assembly with minimum Space Station accommodation

    Science.gov (United States)

    Katzberg, Steven J.; Butler, David H.; Doggett, William R.; Russell, James W.; Hurban, Theresa

    1991-01-01

    The minimum Space Station Freedom accommodations required for initial assembly, repair, and refurbishment of the Lunar aerobrake were investigated. Baseline Space Station Freedom support services were assumed, as well as reasonable earth-to-orbit possibilities. A set of three aerobrake configurations representative of the major themes in aerobraking were developed. Structural assembly concepts, along with on-orbit assembly and refurbishment scenarios were created. The scenarios were exercised to identify required Space Station Freedom accommodations. Finally, important areas for follow-on study were also identified.

  1. Gear fatigue damage for a 500 kW wind turbine exposed to increasing turbulence using a flexible multibody model

    DEFF Research Database (Denmark)

    Jørgensen, Martin Felix; Pedersen, Niels Leergaard; Sørensen, Jens Nørkær

    2014-01-01

    This paper investigates gear tooth fatigue damage in a 500 kW wind turbine using FLEX5 and own multibody code. FLEX5 provides the physical wind eld, rotor and generator torque and the multibody code is used for obtaining gear tooth reaction forces in the planetary gearbox. Dierent turbulence levels...... and therefore increased fatigue damage levels. This article contributes to a better understanding of gear fatigue damage when turbulence is increased (e.g. in the center of large wind farms or at places where turbulence is pronounced)....

  2. Effects of viewing distance on accommodative and pupillary responses following a three-dimensional task.

    Science.gov (United States)

    Iwasaki, Tsuneto; Tawara, Akihiko

    2002-03-01

    We have investigated accommodation and pupil responses after viewing stereoscopic images related to the resting position of accommodation. After a 10-min visual task viewing stereoscopic three-dimensional images, measurements of dynamic accommodation and pupil response were made using an infrared optometer and a pupil analyser. Four conditions were given for the viewing distance: 0.4 m (closer than the subjects' resting position), 1 m (approximating to their resting state), and 1.5 and 3 m (farther than the resting position). For the 0.4- and 1-m groups, a delay in the accommodation response for near-to-far movement was shown after the task, from 817 to 1120 ms and from 830 to 898 ms, respectively, but there was no change in the pupillary response. In the 1.5- and 3-m groups, on the other hand, a significant delay in the accommodation response for far-to-near movement was shown, from 827 to 912 ms and from 857 to 1150 ms, respectively, and greater miosis was found, from 7.2 to 9.2 mm2 and from 8.0 to 10.4 mm2. The data reveal that there are different after-effects on accommodation and pupillary functions when subjects perform the task within their accommodative resting position, than when the task is performed outside the resting position.

  3. 22 CFR 142.12 - Reasonable accommodation.

    Science.gov (United States)

    2010-04-01

    ..., acquisition or modification of equipment or devices, the provision of readers or interpreters, and other... facilities, and size of budget; (2) Job restructuring, part-time or modified work schedules, acquisition and... sign language, when appropriate. (3) The nature and cost of the accommodation needed. (d) A...

  4. 34 CFR 104.12 - Reasonable accommodation.

    Science.gov (United States)

    2010-07-01

    ... 34 Education 1 2010-07-01 2010-07-01 false Reasonable accommodation. 104.12 Section 104.12 Education Regulations of the Offices of the Department of Education OFFICE FOR CIVIL RIGHTS, DEPARTMENT OF EDUCATION NONDISCRIMINATION ON THE BASIS OF HANDICAP IN PROGRAMS OR ACTIVITIES RECEIVING FEDERAL...

  5. Accommodating Faculty Members Who Have Disabilities. Report

    Science.gov (United States)

    American Association of University Professors, 2012

    2012-01-01

    In recent years the rights and responsibilities of students who have disabilities have received considerable attention. Professors routinely accommodate students with a front-row seat in class or extended time on an examination. Faculty members who have disabilities have received far less attention. This report from a subcommittee of Committee A…

  6. Robot response behaviors to accommodate hearing problems

    NARCIS (Netherlands)

    Vroon, Jered; Kim, Jaebok; Koster, Raphaël

    2015-01-01

    One requirement that arises for a social (semi-autonomous telepresence) robot aimed at conversations with the elderly, is to accommodate hearing problems. In this paper we compare two approaches to this requirement; (1) moving closer, mimicking the leaning behavior commonly observed in elderly with

  7. Anthropometric Accommodation in Space Suit Design

    Science.gov (United States)

    Rajulu, Sudhakar; Thaxton, Sherry

    2007-01-01

    Design requirements for next generation hardware are in process at NASA. Anthropometry requirements are given in terms of minimum and maximum sizes for critical dimensions that hardware must accommodate. These dimensions drive vehicle design and suit design, and implicitly have an effect on crew selection and participation. At this stage in the process, stakeholders such as cockpit and suit designers were asked to provide lists of dimensions that will be critical for their design. In addition, they were asked to provide technically feasible minimum and maximum ranges for these dimensions. Using an adjusted 1988 Anthropometric Survey of U.S. Army (ANSUR) database to represent a future astronaut population, the accommodation ranges provided by the suit critical dimensions were calculated. This project involved participation from the Anthropometry and Biomechanics facility (ABF) as well as suit designers, with suit designers providing expertise about feasible hardware dimensions and the ABF providing accommodation analysis. The initial analysis provided the suit design team with the accommodation levels associated with the critical dimensions provided early in the study. Additional outcomes will include a comparison of principal components analysis as an alternate method for anthropometric analysis.

  8. Simulation of Moving Loads in Elastic Multibody Systems With Parametric Model Reduction Techniques

    Directory of Open Access Journals (Sweden)

    Fischer Michael

    2014-08-01

    Full Text Available In elastic multibody systems, one considers large nonlinear rigid body motion and small elastic deformations. In a rising number of applications, e.g. automotive engineering, turning and milling processes, the position of acting forces on the elastic body varies. The necessary model order reduction to enable efficient simulations requires the determination of ansatz functions, which depend on the moving force position. For a large number of possible interaction points, the size of the reduced system would increase drastically in the classical Component Mode Synthesis framework. If many nodes are potentially loaded, or the contact area is not known a-priori and only a small number of nodes is loaded simultaneously, the system is described in this contribution with the parameter-dependent force position. This enables the application of parametric model order reduction methods. Here, two techniques based on matrix interpolation are described which transform individually reduced systems and allow the interpolation of the reduced system matrices to determine reduced systems for any force position. The online-offline decomposition and description of the force distribution onto the reduced elastic body are presented in this contribution. The proposed framework enables the simulation of elastic multibody systems with moving loads efficiently because it solely depends on the size of the reduced system. Results in frequency and time domain for the simulation of a thin-walled cylinder with a moving load illustrate the applicability of the proposed method.

  9. New Computational Framework for the Treatment of Joint Constraints and Connectivity Conditions in Finite Element/Multibody System Algorithms

    Science.gov (United States)

    2014-03-21

    NEW COMPUTATIONAL FRAMEWORK FOR THE TREATMENT OF JOINT CONSTRAINTS AND CONNECTIVITY CONDITIONS IN FINITE ELEMENT/MULTIBODY SYSTEM ALGORITMS Ahmed... ALGORITMS 5a. CONTRACT NUMBER W56hzv-13-c-0032 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Ahmed Shabana; Paramsothy Jayakumar; Michael

  10. A geometrically non-linear formulation of a three-dimensional beam element for solving large deflection multibody system problems

    NARCIS (Netherlands)

    Jonker, J.B.; Meijaard, J.P.

    2013-01-01

    A beam finite element formulation for large deflection problems in the analysis of flexible multibody systems has been proposed. In this formulation, a set of independent discrete deformation modes are defined for each element which are related to conventional small deflection beam theory in a co-ro

  11. Moving beyond misperceptions: the provision of workplace accommodations.

    Science.gov (United States)

    Hernandez, Brigida; McDonald, Katherine; Lepera, Nicole; Shahna, Monna; Wang, T Arthur; Levy, Joel M

    2009-01-01

    This mixed-methods study examined the provision of workplace accommodations in the health care, hospitality, and retail sectors. First, focus groups with administrators from each sector revealed that accommodations costs were viewed as minimal (although frontline managers were perceived as having misperceptions). Second, the provision of accommodations as documented through human resources records for health care and hospitality indicated that accommodations were infrequent, not costly, and provided to employees with disabilities. Finally, retail employees (irrespective of disability status) reported many more accommodations than health care and hospitality workers. To dispel misperceptions related to accommodations, education is critical and social workers are well-positioned for this role.

  12. Combined finite element and multibody musculoskeletal investigation of a fractured clavicle with reconstruction plate

    DEFF Research Database (Denmark)

    Cronskar, Marie; Rasmussen, John; Tinnsten, Mats

    2015-01-01

    This paper addresses the various treatment options for clavicle fractures by means of computational models, more precisely cases with a need for internal fixation: non-unions and certain complex fractures. The motivation for the work is that treatment can be enhanced by a better understanding...... of the loading of the clavicle and fixation device. This study aimed to develop a method for realistic simulation of stresses in the bone and fixation device in the case of a fractured clavicle. A finite element (FE) mesh of the clavicle geometry was created from computer tomography (CT) data and imported...... into the FE solver where the model was subjected to muscle forces and other boundary conditions from a multibody musculoskeletal model performing a typical activity of daily life. A reconstruction plate and screws were also imported into the model. The combination models returned stresses and displacements...

  13. Sub-discretized surface model with application to contact mechanics in multi-body simulation

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, S; Williams, J

    2008-02-28

    The mechanics of contact between rough and imperfectly spherical adhesive powder grains are often complicated by a variety of factors, including several which vary over sub-grain length scales. These include several traction factors that vary spatially over the surface of the individual grains, including high energy electron and acceptor sites (electrostatic), hydrophobic and hydrophilic sites (electrostatic and capillary), surface energy (general adhesion), geometry (van der Waals and mechanical), and elasto-plastic deformation (mechanical). For mechanical deformation and reaction, coupled motions, such as twisting with bending and sliding, as well as surface roughness add an asymmetry to the contact force which invalidates assumptions for popular models of contact, such as the Hertzian and its derivatives, for the non-adhesive case, and the JKR and DMT models for adhesive contacts. Though several contact laws have been offered to ameliorate these drawbacks, they are often constrained to particular loading paths (most often normal loading) and are relatively complicated for computational implementation. This paper offers a simple and general computational method for augmenting contact law predictions in multi-body simulations through characterization of the contact surfaces using a hierarchically-defined surface sub-discretization. For the case of adhesive contact between powder grains in low stress regimes, this technique can allow a variety of existing contact laws to be resolved across scales, allowing for moments and torques about the contact area as well as normal and tangential tractions to be resolved. This is especially useful for multi-body simulation applications where the modeler desires statistical distributions and calibration for parameters in contact laws commonly used for resolving near-surface contact mechanics. The approach is verified against analytical results for the case of rough, elastic spheres.

  14. Assessment of excitation mechanisms and structural flexibility influence in excitation propagation in multi-megawatt wind turbine gearboxes: Experiments and flexible multibody model optimization

    Science.gov (United States)

    Helsen, Jan; Marrant, Ben; Vanhollebeke, Frederik; De Coninck, Filip; Berckmans, Dries; Vandepitte, Dirk; Desmet, Wim

    2013-10-01

    Reliable gearbox design calculations require sufficient insight in gearbox dynamics, which is determined by the interaction between the different excitation mechanisms and the gearbox modal behavior. Both external gearbox excitation originating from the wind turbine drive train and internal gearbox excitation are important. Moreover with regard to the modal behavior the different gearbox structural components: planet carrier, shafts and housing are of influence. The main objective of this article is the experimental investigation of the interaction between the different excitation mechanisms and the gearbox modal behavior. The insights gathered are used to prove the need for accurate gear mesh representation and structural flexibility within the corresponding flexible multibody gearbox simulation model. Experiments are conducted on a dynamic 13.2 MW test facility on which two multi-megawatt wind turbine gearboxes are placed back to back and subjected to a speed run-up. Measurement sensors consist of bearing displacement sensors, torque sensors, encoders and accelerometers distributed over the gearbox. Excitation order amplitudes on different locations in the gearbox are determined by means of a Time Varying Discrete Fourier Transform (TVDFT) order tracking on the measured sensor signals. Moreover the propagation of this excitation throughout the gearbox is assessed. Relating the orders to the corresponding excitation source allows the definition of order influence regions within the gearbox. The interaction between the gear mesh order excitation and structural flexibility is shown.

  15. Simultaneous refraction measurement and OCT axial biometry of the eye during accommodation (Conference Presentation)

    Science.gov (United States)

    De Freitas, Carolina; Hernandez, Victor M.; Ruggeri, Marco; Durkee, Heather A.; Williams, Siobhan; Gregori, Giovanni; Ho, Arthur; Manns, Fabrice; Parel, Jean-Marie

    2016-03-01

    The purpose of this project is to design and evaluate a system that will enable objective assessment of the optical accommodative response in real-time while acquiring axial biometric information. The system combines three sub-systems which were integrated and mounted on a joystick x-y-z adjustable modified slit-lamp base to facilitate alignment and data acquisition: (1) a Shack-Hartmann wavefront sensor for dynamic refraction measurement, provided software calculates sphere, cylinder and axis values, (2) an extended-depth Optical Coherence Tomography (OCT) system using an optical switch records high-resolution cross-sectional images across the length of the eye, from which, dynamic axial biometry (corneal thickness, anterior chamber depth, crystalline lens thickness and vitreous depth) can be extracted, and (3) a modified dual-channel accommodation stimulus unit based on the Badal optometer for providing a step change in accommodative stimulus. The prototypal system is capable of taking simultaneous measurements of both the optical and the mechanical response of lens accommodation. These measurements can provide insight into correlating changes in lens shape with changes in lens power and ocular refraction and ultimately provide a more comprehensive understanding of accommodation, presbyopia and an objective assessment of presbyopia correction techniques.

  16. Simulations and Measurements of Human Middle Ear Vibrations Using Multi-Body Systems and Laser-Doppler Vibrometry with the Floating Mass Transducer

    OpenAIRE

    Tobias Strenger; Stefan Lehner; Frank Böhnke; Theodor Bretan

    2013-01-01

    The transfer characteristic of the human middle ear with an applied middle ear implant (floating mass transducer) is examined computationally with a Multi-body System approach and compared with experimental results. For this purpose, the geometry of the middle ear was reconstructed from μ-computer tomography slice data and prepared for a Multi-body System simulation. The transfer function of the floating mass transducer, which is the ratio of the input voltage and the generated force, is deri...

  17. THE IMPACTS OF PRIVATE ACCOMMODATION ATTRIBUTES ON TOURISM DEMAND

    OpenAIRE

    Portolan, Ana

    2013-01-01

    The private tourism accommodation concept has not been largely represented in the scientific research. It started appearing on the margins of the actual research in the past ten years, namely with a hotel as the most analyzed form of tourism accommodation. In the structure of tourism accommodation in Croatia in 2011 private accommodation participated with 465 000 beds which represents 49,8 percent of the total capacity and therefore demands more attention. Using the main marketing postulate w...

  18. Dynamics of flexible multi-body mechanisms and manipulators. Part 1: An overview

    Science.gov (United States)

    Dubowsky, Steven

    1989-01-01

    Flexibility can be a major limitation to the performance of high performance conventional machine systems. The current status of robotic manipulators is limited by the effects of system flexibility. The status of current commercial robots, anticipated development in 5 and 10 years is outlined.

  19. A dynamic model with substructures for contact-impact analysis of flexible multibody systems

    Institute of Scientific and Technical Information of China (English)

    GUO; Anping(郭安萍); HONG; Jiazhen(洪嘉振); YANG; Hui(杨辉)

    2003-01-01

    Using a substructure synthesis method this paper studies the longitudinal compressive impact of a flexible bar with a rigid body. The crucial variable affecting the validity of the method is derived theoretically. By computational simulation tests, excellent agreement has been found between the solution of this model and the exact solution when the variable is chosen suitably. Considering both the computational efficiency and the accuracy of solutions obtained on the model in different engineering problems, several optimum values of the variable are suggested.

  20. Physics-Based Robot Motion Planning in Dynamic Multi-Body Environments

    Science.gov (United States)

    2010-05-10

    replanning interval results in an agressive growth of collision rates. 132 0 0.2 0.4 0.6 0.8 1 0 1 2 3 4 5 6 P er fo rm a n ce LOD Time-Horizon (s...Hierarchy of Reactive Behaviors Handles Complexity. Balancing Reactivity and Social Deliberation in Multi-Agent Systems: From Robocup to Real-World

  1. Robust Stability and Control of Multi-Body Ground Vehicles with Uncertain Dynamics and Failures

    Science.gov (United States)

    2010-01-01

    Modeling for Heavy Articulated Tractor Semi- Trailer Vehicle 2.2.3.1 Rollover Index (RI) for A single Unit Vehicle 2.2.3.2...increasing complexity to capture Roll Over phenomenon and Other Performance and Ride Quality requirements. In this connection, first simple ` Bicycle ...methodology to a specific heavy articulated vehicle with tractor semi- trailer shows that a single active anti-roll bar system at the trailer unit gives

  2. A Multibody Formulation for Three Dimensional Brick Finite Element Based Parallel and Scalable Rotor Dynamic Analysis

    Science.gov (United States)

    2010-05-01

    ers of bricks. Different element groups can be prescribed different material properties (e.g. spar, skin , and honey - comb). The component merger can...ensures that computations of the same complexity are compared and that the speed-up is not contaminated with the benefits of substructuring itself

  3. Novel coordinates for nonlinear multibody motion with applications to spacecraft dynamics and control

    Science.gov (United States)

    Schaub, Hanspeter

    1998-12-01

    Novel sets of attitude coordinates called the Stereographic Parameters (SPs) and configuration quasivelocity coordinates called the Eigenfactor Quasivelocities (EQVs) are discussed. The SPs are generated through stereographic projections of the Euler parameter constraint hypersphere onto hyperplanes. SP sets are non-unique and have distinct alternate sets referred to as shadow sets. They abide by the same differential kinematic equation, but generally display a different singular behavior. Explicit expressions are developed that map the original SP set to the shadow set and thus avoid any singularities. Both symmetric SPs such as the classical and Modified Rodrigues Parameters (MRPs), as well as asymmetric SPs are discussed. A globally asymptotically stable MRP feedback law which tracks any reference trajectory is presented. Both unsaturated and saturated control cases are discussed. Further, an MRP costate switching condition is developed that allows both original and shadow MRPs to be used simultaneously in optimal control problems. The Lagrange equations of motion in terms of the n-dimensional EQV vector are developed. The EQV formulation has an identity mass matrix which results in no matrix inverse being taken in numerical simulations. An explicit expression is presented that incorporates Pfaffian non-holonomic constraints into the EQV formulation without increasing the system order. Unfortunately, the use of EQV in numerical simulations only proved beneficial in selected cases. Generally the computational burden proved too high. However, the EQVs are found to be valuable when used as velocity feedback coordinates. EQV feedback laws have an exponentially decaying kinetic energy, superior performance to traditional state velocity feedback laws and are found to decouple the motion of multi-link robotic systems. The equations of motion and steering laws of spacecraft containing Variable Speed Control Moment Gyroscopes (VSCMGs) are developed. Contrary to classical CMG steering laws, VSCMG steering laws derived herein do not encounter singularities. Both gimbal angle velocity and acceleration based steering laws are presented. Since gimbaling is more efficient energy consumption wise, the steering law presented only utilizes reaction wheel modes close to classical CMG singularities. The reaction wheel mode also assists in driving the gimbals to preferred angles using null motion.

  4. Reimbursement of education fees / accommodation fees

    CERN Multimedia

    2003-01-01

    Your attention is drawn to the 20 km distance limit set in Article R A 8.01 of the Staff Regulations, namely, that only accommodation fees of students attending an educational establishment which is more than 20 km from the place of residence and the duty station of the member of the personnel are reimbursed by the Organization, subject to the percentage rate and maximum amounts set out in this article and in Administrative Circular N° 12. Human Resources Division Tel: 72862 / 74474

  5. Reminder : Reimbursement of education fees / accommodation fees

    CERN Multimedia

    2003-01-01

    Your attention is drawn to the 20 km distance limit set in Article R A 8.01 of the Staff Regulations, namely, that only accommodation fees of students attending an educational establishment which is more than 20 km from the place of residence and the duty station of the member of the personnel are reimbursed by the Organization, subject to the percentage rate and maximum amounts set out in this article and in Administrative Circular N° 12. Human Resources Division Tel : 72862 / 74474

  6. Vehicle dynamics modeling and simulation

    CERN Document Server

    Schramm, Dieter; Bardini, Roberto

    2014-01-01

    The authors examine in detail the fundamentals and mathematical descriptions of the dynamics of automobiles. In this context different levels of complexity will be presented, starting with basic single-track models up to complex three-dimensional multi-body models. A particular focus is on the process of establishing mathematical models on the basis of real cars and the validation of simulation results. The methods presented are explained in detail by means of selected application scenarios.

  7. 46 CFR 108.197 - Construction of accommodation spaces.

    Science.gov (United States)

    2010-10-01

    ... accommodation spaces. (a) Each sleeping, mess, recreational, or hospital space that is adjacent to or... deckheads of each accommodation space must be a light color. (e) Each accommodation space in which water may... readily enter any sleeping, mess, recreational, or hospital space....

  8. Accommodation-Amplitudes following an Accommodative Lens Refilling Procedure — an in vivo Update

    Science.gov (United States)

    Nishi, Okihiro; Nishi, Yutaro; Chang, S.; Nishi, Kayo

    2014-01-01

    Purpose To investigate whether a newly developed lens refilling procedure can provide some accommodation in monkey eyes and to evaluate the difference in accommodation with different degrees of capsular bag refilling. Setting Jinshikai Medical Foundation, Nishi Eye Hospital, Osaka, Japan. Design Experimental monkey study. Methods Following a central 3–4 mm continuous curvilinear capsulorhexis, phacoemulsification was performed in the usual manner. A novel accommodative membrane intraocular lens for sealing capsular opening was implanted into the capsular bag. Silicone polymers were injected beneath the intraocular lens into the capsular bag through the delivery hole. In three study groups, each with six monkey eyes, the lens capsule was refilled with 0.08 ml corresponding to 65% bag volume, 0.1 ml corresponding to 80% bag volume, and 0.125 ml of silicone polymers corresponding to 100% bag volume, respectively. To calculate the accommodation-amplitudes achieved, automated refractometry was performed before and 1 hour after the topical 4% pilocarpine application before and four weeks after surgery. Results The refilling technique was successful in all monkeys without polymer leakage. Accommodation-amplitudes attained were 2.56 ± 0.74 dioptries (D), 2.42 ± 1.00D, and 2.71 ± 0.63D, respectively, 4 weeks after surgery in the three study groups. Conclusions Using the technique, some accommodation could be obtained in the young monkey eyes. Leakage of the injectable silicone polymer and anterior capsular opacification at least in the visual axis could be avoided. The results suggest that this lens refilling procedure warrants further studies for a possible clinical application. PMID:24461501

  9. Objective Assessment of Vergence and Accommodation After Vision Therapy for Convergence Insufficiency in a Child: A Case Report

    Directory of Open Access Journals (Sweden)

    Mitchell Scheiman, OD

    2014-01-01

    Full Text Available Background: To evaluate objective changes in vergence and accommodation after treatment of symptomatic convergence insufficiency (CI with office-based optometric vision therapy in a pediatric patient. Case Report: A 10-year, 10-month-old child with symptomatic CI was treated with 16 visits of office-based vision therapy with home reinforcement. Pre- and post-therapy testing included both traditional clinical measures and objective laboratory measures of vergence and accommodation. The main clinical outcome measures were the CI Symptom Survey (CISS, near point of convergence (NPC, positive fusional vergence range at near (PFV, accommodative amplitude, and accommodative facility. The objective vergence range outcome measures were peak velocity, time constant, total response time, and steady-state response variability as assessed with the Power Refractor II. The objective accommodative outcome measures were peak velocity, time constant, total response time, steady-state response variability, and steady-state level, as assessed with the Grand Seiko WAM-5500. Most accommodative and vergence objective laboratory parameters improved/normalized following the vision therapy. Gains were greater for vergence than for accommodation. These objective measures confirmed the concurrent improvements in the clinical tests and markedly reduced symptom levels. Conclusions: This is the first study to document, objectively, improvements in laboratory-based dynamic measures of both accommodation and vergence following conventional office-based optometric vision therapy for CI in a child. Objective oculomotor measures can and should be performed in similar future studies in children, as well as in adults

  10. [Dissociated near reflex and accommodative convergence excess].

    Science.gov (United States)

    Gräf, M; Becker, R; Kloss, S

    2004-10-01

    We report on an 8-year-old boy whose near reflex could be elicited exclusively when the left eye was fixing (LF) but not when the right eye was fixing (RF). With RE +1.25/-1.25/169 degrees and LE +1.0/-0.75/24 degrees, the visual acuity was 1.0 OU at 5 m and RE 0.5, LE 1.0 at 0.3 m improving to 1.0 OU by a near addition of 3.0 D. Stereopsis was 100 degrees (Titmus test). The prism and cover test revealed an esophoria of 4 degrees at 5 m. At 3 m there was an esophoria of 6 degrees (RF) and an esotropia of 28 degrees (LF), compensating to an esophoria of 3 degrees (RF/LF) with a near addition of 3.0 D. Accommodation and the pupillary near reaction (OU) were hardly elicitable during RF. During LF, retinoscopy revealed an accommodation of 8 D (OU) and the pupils constricted normally. Correction by bifocal glasses yielded orthotropia with random dot stereopsis at near.

  11. Gear fatigue damage for a 500 kW wind turbine exposed to increasing turbulence using a flexible multibody model

    Directory of Open Access Journals (Sweden)

    Martin Felix Jørgensen

    2014-04-01

    Full Text Available This paper investigates gear tooth fatigue damage in a 500 kW wind turbine using FLEX5 and own multibody code. FLEX5 provides the physical wind field, rotor and generator torque and the multibody code is used for obtaining gear tooth reaction forces in the planetary gearbox. Different turbulence levels are considered and the accumulated fatigue damage levels are compared. An example where the turbulence/fatigue sensitivity could be important, is in the middle of a big wind farm. Interior wind turbines in large wind farms will always operate in the wake of other wind turbines, causing increased turbulence and therefore increased fatigue damage levels. This article contributes to a better understanding of gear fatigue damage when turbulence is increased (e.g. in the center of large wind farms or at places where turbulence is pronounced.

  12. Knee Kinematics Estimation Using Multi-Body Optimisation Embedding a Knee Joint Stiffness Matrix: A Feasibility Study

    OpenAIRE

    Richard, V.; Lamberto, G.; Lu, T.W.; Cappozzo, A.; Dumas, R

    2016-01-01

    The use of multi-body optimisation (MBO) to estimate joint kinematics from stereophotogrammetric data while compensating for soft tissue artefact is still open to debate. Presently used joint models embedded in MBO, such as mechanical linkages, constitute a considerable simplification of joint function, preventing a detailed understanding of it. The present study proposes a knee joint model where femur and tibia are represented as rigid bodies connected through an elastic element the behaviou...

  13. Applied dynamics

    CERN Document Server

    Schiehlen, Werner

    2014-01-01

    Applied Dynamics is an important branch of engineering mechanics widely applied to mechanical and automotive engineering, aerospace and biomechanics as well as control engineering and mechatronics. The computational methods presented are based on common fundamentals. For this purpose analytical mechanics turns out to be very useful where D’Alembert’s principle in the Lagrangian formulation proves to be most efficient. The method of multibody systems, finite element systems and continuous systems are treated consistently. Thus, students get a much better understanding of dynamical phenomena, and engineers in design and development departments using computer codes may check the results more easily by choosing models of different complexity for vibration and stress analysis.

  14. Near-unity mass accommodation coefficient of organic molecules of varying structure.

    Science.gov (United States)

    Julin, Jan; Winkler, Paul M; Donahue, Neil M; Wagner, Paul E; Riipinen, Ilona

    2014-10-21

    Atmospheric aerosol particles have a significant effect on global climate, air quality, and consequently human health. Condensation of organic vapors is a key process in the growth of nanometer-sized particles to climate relevant sizes. This growth is very sensitive to the mass accommodation coefficient α, a quantity describing the vapor uptake ability of the particles, but knowledge on α of atmospheric organics is lacking. In this work, we have determined α for four organic molecules with diverse structural properties: adipic acid, succinic acid, naphthalene, and nonane. The coefficients are studied using molecular dynamics simulations, complemented with expansion chamber measurements. Our results are consistent with α = 1 (indicating nearly perfect accommodation), regardless of the molecular structural properties, the phase state of the bulk condensed phase, or surface curvature. The results highlight the need for experimental techniques capable of resolving the internal structure of nanoparticles to better constrain the accommodation of atmospheric organics.

  15. Exact solutions for generalized variable-coefficients Ginzburg-Landau equation: Application to Bose-Einstein condensates with multi-body interatomic interactions

    Science.gov (United States)

    Kengne, E.; Lakhssassi, A.; Vaillancourt, R.; Liu, Wu-Ming

    2012-12-01

    We present a double-mapping method (D-MM), a natural combination of a similarity with F-expansion methods, for obtaining general solvable nonlinear evolution equations. We focus on variable-coefficients complex Ginzburg-Landau equations (VCCGLE) with multi-body interactions. We show that it is easy by this method to find a large class of exact solutions of Gross-Pitaevskii and Gross-Pitaevskii-Ginzburg equations. We apply the D-MM to investigate the dynamics of Bose-Einstein condensation with two- and three-body interactions. As a surprising result, we obtained that it is very easy to use the built D-MM to obtain a large class of exact solutions of VCCGLE with two-body interactions via a generalized VCCGLE with two- and three-body interactions containing cubic-derivative terms. The results show that the proposed method is direct, concise, elementary, and effective, and can be a very effective and powerful mathematical tool for solving many other nonlinear evolution equations in physics.

  16. A Synchronous Multi-Body Sensor Platform in a Wireless Body Sensor Network: Design and Implementation

    Directory of Open Access Journals (Sweden)

    Jungtae Lee

    2012-07-01

    Full Text Available Background: Human life can be further improved if diseases and disorders can be predicted before they become dangerous, by correctly recognizing signals from the human body, so in order to make disease detection more precise, various body-signals need to be measured simultaneously in a synchronized manner. Object: This research aims at developing an integrated system for measuring four signals (EEG, ECG, respiration, and PPG and simultaneously producing synchronous signals on a Wireless Body Sensor Network. Design: We designed and implemented a platform for multiple bio-signals using Bluetooth communication. Results: First, we developed a prototype board and verified the signals from the sensor platform using frequency responses and quantities. Next, we designed and implemented a lightweight, ultra-compact, low cost, low power-consumption Printed Circuit Board. Conclusion: A synchronous multi-body sensor platform is expected to be very useful in telemedicine and emergency rescue scenarios. Furthermore, this system is expected to be able to analyze the mutual effects among body signals.

  17. Efficient methodology for multibody simulations with discontinuous changes in system definition

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, Rudranarayan M., E-mail: rudranarayan.m.mukherjee@jpl.nasa.gov; Anderson, Kurt S. [Rensselaer Polytechnic Institute, Department of Mechanical, Aeronautical, and Nuclear Engineering (United States)], E-mail: anderk5@rpi.edu

    2007-09-15

    A new method is presented for accurately and efficiently simulating multi-scale multibody systems with discontinuous changes in system definitions as encountered in adaptive switching between models with different resolutions as well as models with different system topologies. An example of model resolution change is a transition of a system from a discrete particle model to a reduced order articulated multi-rigid body model. The discontinuous changes in system definition may be viewed as an instantaneous change (release or impulsive application of) the system constraints. The method uses a spatial impulse-momentum formulation in a divide and conquer scheme. The approach utilizes a hierarchic assembly-disassembly process by traversing the system topology in a binary tree map to solve for the jumps in the system generalized speeds and the constraint impulsive loads in linear and logarithmic cost in serial and parallel implementations, respectively. The method is applicable for systems in serial chain as well as kinematical loop topologies. The coupling between the unilateral and bilateral constraints is handled efficiently through the use of kinematic joint definitions. The equations of motion for the system are produced in a hierarchic sub-structured form. This has the advantage that changes in sub-structure definitions/models results in a change to the system equations only within the associated sub-structure. This allows for significant changes in model types and definitions without having to reformulate the equations for the whole system.

  18. Stress and heat flux for arbitrary multi-body potentials: A unified framework

    CERN Document Server

    Admal, Nikhil Chandra

    2015-01-01

    A two-step unified framework for the evaluation of continuum field expressions from molecular simulations for arbitrary interatomic potentials is presented. First, pointwise continuum fields are obtained using a generalization of the Irving-Kirkwood procedure to arbitrary multi-body potentials. Two ambiguities associated with the original Irving-Kirkwood procedure (which was limited to pair potential interactions) are addressed in its generalization. The first ambiguity is due to the non-uniqueness of the decomposition of the force on an atom as a sum of central forces, which is a result of the non-uniqueness of the potential energy representation in terms of distances between the particles. This is in turn related to the shape space of the system. The second ambiguity is due to the non-uniqueness of the energy decomposition between particles. The latter can be completely avoided through an alternate derivation for the energy balance. It is found that the expressions for the specific internal energy and the h...

  19. Effect of various upper limb multibody models on soft tissue artefact correction: A case study.

    Science.gov (United States)

    Naaim, Alexandre; Moissenet, Florent; Duprey, Sonia; Begon, Mickaël; Chèze, Laurence

    2017-01-31

    Soft tissue artefacts (STA) introduce errors in joint kinematics when using cutaneous markers, especially on the scapula. Both segmental optimisation and multibody kinematics optimisation (MKO) algorithms have been developed to improve kinematics estimates. MKO based on a chain model with joint constraints avoids apparent joint dislocation but is sensitive to the biofidelity of chosen joint constraints. Since no recommendation exists for the scapula, our objective was to determine the best models to accurately estimate its kinematics. One participant was equipped with skin markers and with an intracortical pin screwed in the scapula. Segmental optimisation and MKO for 24-chain models (including four variations of the scapulothoracic joint) were compared against the pin-derived kinematics using root mean square error (RMSE) on Cardan angles. Segmental optimisation led to an accurate scapula kinematics (1.1°≤RMSE≤3.3°) even for high arm elevation angles. When MKO was applied, no clinically significant difference was found between the different scapulothoracic models (0.9°≤RMSE≤4.1°) except when a free scapulothoracic joint was modelled (1.9°≤RMSE≤9.6°). To conclude, using MKO as a STA correction method was not more accurate than segmental optimisation for estimating scapula kinematics.

  20. Feasibility of Applying Controllable Lubrication to Dynamically Loaded Journal Bearings

    DEFF Research Database (Denmark)

    Estupinan, Edgar Alberto; Santos, Ilmar

    2009-01-01

    levels, wear and power losses of the system components. From the point of view of actively controlled lubrication and specifically for the case of dynamically loaded journal bearings, the injection pressure should be controlled in time domain. However, taking into account that the gas pressure......A multibody dynamic model of the main mechanical components of a hermetic reciprocating compressor is presented in this work. Considering that some of the mechanical elements are interconnected via thin fluid films, the multibody dynamic model is coupled to the equations from the dynamics...... of the upper and lower bearings of the crankshaft, when the system operates under passive and active lubrication conditions. It is thought that the dynamics of the fluid films can be passively or actively controlled by means of different types of actuators, allowing significant reduction in the vibration...

  1. Can Partial Structures Accommodate Inconsistent Science?

    Directory of Open Access Journals (Sweden)

    Peter Vickers

    2009-08-01

    Full Text Available The semantic approach to scientific representation is now long established as a favourite amongst philosophers of science. One of the foremost strains of this approach—the model-theoretic approach (MTA—is to represent scientific theories as families of models, all of which satisfy or ‘make true’ a given set of constraints. However some authors (Brown 2002, Frisch 2005 have criticised the approach on the grounds that certain scientific theories are logically inconsistent, and there can be no models of an inconsistent set of constraints. Thus it would seem that the MTA fails to represent inconsistent scientific theories at all, and this raises concerns about the way it represents in general. In a series of papers (1990, 1993, 1995 and a recent book (2003 da Costa and French have developed a variant of the MTA approach which they call ‘partial structures’, and which they claim can accommodate inconsistent theories. I assess this claim, looking to two theories which have been called ‘inconsistent’: Bohr’s theory of the atom and classical electrodynamics.

  2. Effect of Vision Therapy on Accommodation in Myopic Chinese Children

    Directory of Open Access Journals (Sweden)

    Martin Ming-Leung Ma

    2016-01-01

    Full Text Available Introduction. We evaluated the effectiveness of office-based accommodative/vergence therapy (OBAVT with home reinforcement to improve accommodative function in myopic children with poor accommodative response. Methods. This was a prospective unmasked pilot study. 14 Chinese myopic children aged 8 to 12 years with at least 1 D of lag of accommodation were enrolled. All subjects received 12 weeks of 60-minute office-based accommodative/vergence therapy (OBAVT with home reinforcement. Primary outcome measure was the change in monocular lag of accommodation from baseline visit to 12-week visit measured by Shinnipon open-field autorefractor. Secondary outcome measures were the changes in accommodative amplitude and monocular accommodative facility. Results. All participants completed the study. The lag of accommodation at baseline visit was 1.29 ± 0.21 D and it was reduced to 0.84 ± 0.19 D at 12-week visit. This difference (−0.46 ± 0.22 D; 95% confidence interval: −0.33 to −0.58 D is statistically significant (p<0.0001. OBAVT also increased the amplitude and facility by 3.66 ± 3.36 D (p=0.0013; 95% confidence interval: 1.72 to 5.60 D and 10.9 ± 4.8 cpm (p<0.0001; 95% confidence interval: 8.1 to 13.6 cpm, respectively. Conclusion. Standardized 12 weeks of OBAVT with home reinforcement is able to significantly reduce monocular lag of accommodation and increase monocular accommodative amplitude and facility. A randomized clinical trial designed to investigate the effect of vision therapy on myopia progression is warranted.

  3. ATHENA: system studies and optics accommodation

    Science.gov (United States)

    Ayre, M.; Bavdaz, M.; Ferreira, I.; Wille, E.; Fransen, S.; Stefanescu, A.; Linder, M.

    2016-07-01

    ATHENA is currently in Phase A, with a view to adoption upon a successful Mission Adoption Review in 2019/2020. After a brief presentation of the reference spacecraft (SC) design, this paper will focus on the functional and environmental requirements, the thermo-mechanical design and the Assembly, Integration, Verification & Test (AIVT) considerations related to housing the Silicon Pore Optics (SPO) Mirror Modules (MM) in the very large Mirror Assembly Module (MAM). Initially functional requirements on the MM accommodation are presented, with the Effective Area and Half Energy Width (HEW) requirements leading to a MAM comprising (depending on final mirror size selected) between 700-1000 MMs, co-aligned with exquisite accuracy to provide a common focus. A preliminary HEW budget allocated across the main error-contributors is presented, and this is then used as a reference to derive subsequent requirements and engineering considerations, including: The procedures and technologies for MM-integration into the Mirror Structure (MS) to achieve the required alignment accuracies in a timely manner; stiffness requirements and handling scheme required to constrain deformation under gravity during x-ray testing; temperature control to constrain thermo-elastic deformation during flight; and the role of the Instrument Switching Mechanism (ISM) in constraining HEW and Effective Area errors. Next, we present the key environmental requirements of the MMs, and the need to minimise shock-loading of the MMs is stressed. Methods to achieve this Ø are presented, including: Selection of a large clamp-band launch vehicle interface (LV I/F); lengthening of the shock-path from the LV I/F to the MAM I/F; modal-tuning of the MAM to act as a low-pass filter during launch shock events; use of low-shock HDRMs for the MAM; and the possibility to deploy a passive vibration solution at the LV I/F to reduce loads.

  4. School Boarding Accommodation. A Design Guide. Building Bulletin 84.

    Science.gov (United States)

    Wilson, Jeremy; Lloyd-Jones, Liz; Carden, Tom; Daniels, Richard; Fitzgerald, Brian; Maddick, Jenny

    This bulletin contains on-statutory guidance describing good practice and its implications for boarding accommodation to assist those responsible for briefing and designing boarding accommodations across all school sectors. It offers practical advice and illustrates examples that reflect changes in provision which are thought to be acceptable and…

  5. Accommodating World Englishes in Developing EFL Learners' Oral Communication

    Science.gov (United States)

    Mukminatien, Nur

    2012-01-01

    This article aims to discuss issues of World Englishes (WEs) and the implications in ELT. It explores the extent to which WEs are taken into account as emerging English varieties different from inner circle varieties, how WEs should be accommodated by English teachers, and which standard to adopt to accommodate learner's linguistic needs for…

  6. Privately Provided Accommodation Service Quality and Customer Satisfaction

    Directory of Open Access Journals (Sweden)

    Joshua Mugambwa

    2016-04-01

    Full Text Available Privately provided accommodation is a growing service in Uganda’s higher education sector due to education liberalization and demand for education. This research took a case study of Nsamizi Training Institute of Social Development (NTISD to determine the relationship between privately provided accommodation service quality and customer satisfaction. Specifically, the objectives of the study were (a to find out the relationship between security and NTISD students’ satisfaction with privately provided accommodation, and (b to find out the hierarchical level of importance of NTISD student satisfaction of the three service quality dimensions (reliability, security, and tangibles with privately provided accommodation. Using quantitative and qualitative modes of data analysis and a sample of 300 students from 20 private hostels, this study established a strong positive significant relationship between security and satisfaction regarding privately provided accommodation. This implies that accommodation service providers should increase the quality of security so as to increase the satisfaction of students regarding privately provided accommodation. The study established the hierarchical order of importance from the most important service quality dimension, respectively, as follows: reliability, security, and tangibles. Therefore, private accommodation service managers should pay extra attention to the dimensions in the same order.

  7. The Evolution of the Number of Tourists accommodated in Arad

    Directory of Open Access Journals (Sweden)

    Sergiu Rusu

    2014-12-01

    Full Text Available The paper analyses the evolution of the number of tourists accommodated in Arad between January 2006 and September 2009. For this purpose we have used the statistics data from the official sites. As variables we chose: X – independent variable - Total tourist arrival and accommodated in Arad, Y - dependent variable - Tourists staying in hotels.

  8. Regional Sign Language Varieties in Contact: Investigating Patterns of Accommodation

    Science.gov (United States)

    Stamp, Rose; Schembri, Adam; Evans, Bronwen G.; Cormier, Kearsy

    2016-01-01

    Short-term linguistic accommodation has been observed in a number of spoken language studies. The first of its kind in sign language research, this study aims to investigate the effects of regional varieties in contact and lexical accommodation in British Sign Language (BSL). Twenty-five participants were recruited from Belfast, Glasgow,…

  9. Making Accommodations: The Legal World of Students with Disabilities.

    Science.gov (United States)

    Grossman, Paul D.

    2001-01-01

    Describes the legal requirements with which institutions of higher education must comply regarding students with disabilities. Addresses the topics of equal access, degree of deference toward institutions' accommodations decisions, documentation, types of accommodation, and benefits to the academic community from inclusion of people with…

  10. Dynamic Characteristics Analysis of the Coupled Lateral-Torsional Vibration with Spur Gear System

    OpenAIRE

    Shihua Zhou; Zhaohui Ren; Guiqiu Song; Bangchun Wen

    2015-01-01

    A sixteen-degree-of-freedom (16-DOF) lumped parameter dynamic model taking into account the gravity, eccentricity, bearing clearance, transmission error, and coupled lateral-torsional vibration is established. Based on the dynamical equation, the dynamic behaviors of the spur gear rotor bearing system are investigated by using Runge-Kutta method. The research focuses on the effect of rotational speed, eccentricity, and bearing clearance and nonlinear response of the coupled multibody dynamics...

  11. Application of parallel computing to robot dynamics

    OpenAIRE

    Schäfer, Peter; Schiehlen, Werner

    1993-01-01

    In this paper an approach for the application of parallel processing to the dynamic analysis of robots based on the multibody system method is presented. The inherent structure of the symbolic equations of motion is used for partitioning those into independent modules for concurrent evaluation. The applied strategies for parallelization include the parallel evaluation of subsystem equations and the parallel computation of the inertia matrix along with its factorization, and of the force vecto...

  12. Digital Elevation Map Reconstruction for Port-based Dynamic Simulation of Contacts on Irregular Surfaces

    NARCIS (Netherlands)

    Wassink, Martin; Carloni, Raffaella; Poulakis, Pantelis; Stramigioli, Stefano

    2009-01-01

    This paper presents a method to utilize a port-based multibody contact model for simulating dynamic interaction between irregular surfaces. The existing compliant contact model requires an analytic parametrization of the surfaces involved in the interaction, the definition of a Gauss frame in each o

  13. Kinematic and Dynamic Analysis of New Polar Positioning System Dedicated to Mechatronic Laser Glass Engraving System

    Directory of Open Access Journals (Sweden)

    Trochimczuk R.

    2014-11-01

    Full Text Available Analytical formulas describing the kinematics and dynamics of a multibody system of a new polar positioning system dedicated to mechatronic laser glass or other transparent dielectrics engraving system will be presented in this work. The analytical results will become in the later stages of the research the basis of numerical simulations. They will optimize the proposed solution of the positioning system.

  14. Age-related changes in ocular aberrations with accommodation.

    Science.gov (United States)

    Radhakrishnan, Hema; Charman, W Neil

    2007-05-30

    This study investigates the changes in aberrations with monocular accommodation as a function of age. Second-order and higher order wavefront aberrations and pupil size were measured as a function of accommodation demand over the range of 0-4 D in the right eyes of 47 normal subjects with ages between 17 and 56 years. Higher order ocular Zernike aberrations were analyzed for the natural pupil size in terms of their equivalent defocus and were also determined for fixed pupil diameters of 4.5 mm in the unaccommodated eyes and 2.5 mm in the accommodating eyes. With relaxed accommodation (0 D accommodation stimulus), the major change with age was in the value of C4(0), which increased in positive value over the age range studied, although the total higher order RMS wavefront aberration did not increase. When the data were analyzed for natural pupils, spherical aberration was again found to change systematically in the positive direction with age. The equivalent defocus of total higher order RMS error for natural pupils showed no significant correlation with age (p > .05). With active accommodation, spherical aberration was found to decrease and become negative as the accommodative response increased in the younger subjects (40 years), the spherical aberration showed only small changes, some of which were positive, within the limited amplitude of accommodation available. Other higher order aberrations and the RMS of higher order aberrations did not appear to change systematically with accommodation, except in the oldest subjects. The change with age in the relationship between aberration and accommodation is interpreted in terms of the changing gradients of refractive index and surface curvatures of the crystalline lens.

  15. Structural optimization of wind turbine rotor blades by multilevel sectional/multibody/3D-FEM analysis

    DEFF Research Database (Denmark)

    Bottasso, C. L.; Campagnolo, F.; Croce, A.;

    2014-01-01

    model fully-populated cross sectional stiffness matrices. Next, a "fine"-level 3D FEM model is used for the refinement of the coarse-level solution. Improved results obtained at the level of the 3D model are utilized at the following coarse-level iteration through a heuristic modification of the design...... level. At first, a "coarse"-level constrained design optimization is performed by using a 1D spatial geometrically exact beam model for aero-servo-elastic multibody analysis and load calculation, integrated with a 2D FEM cross sectional model for stress/strain analysis, and the evaluation of the 1D...

  16. A phase-field model for incoherent martensitic transformations including plastic accommodation processes in the austenite

    Science.gov (United States)

    Kundin, J.; Raabe, D.; Emmerich, H.

    2011-10-01

    If alloys undergo an incoherent martensitic transformation, then plastic accommodation and relaxation accompany the transformation. To capture these mechanisms we develop an improved 3D microelastic-plastic phase-field model. It is based on the classical concepts of phase-field modeling of microelastic problems (Chen, L.Q., Wang Y., Khachaturyan, A.G., 1992. Philos. Mag. Lett. 65, 15-23). In addition to these it takes into account the incoherent formation of accommodation dislocations in the austenitic matrix, as well as their inheritance into the martensitic plates based on the crystallography of the martensitic transformation. We apply this new phase-field approach to the butterfly-type martensitic transformation in a Fe-30 wt%Ni alloy in direct comparison to recent experimental data (Sato, H., Zaefferer, S., 2009. Acta Mater. 57, 1931-1937). It is shown that the therein proposed mechanisms of plastic accommodation during the transformation can indeed explain the experimentally observed morphology of the martensitic plates as well as the orientation between martensitic plates and the austenitic matrix. The developed phase-field model constitutes a general simulations approach for different kinds of phase transformation phenomena that inherently include dislocation based accommodation processes. The approach does not only predict the final equilibrium topology, misfit, size, crystallography, and aspect ratio of martensite-austenite ensembles resulting from a transformation, but it also resolves the associated dislocation dynamics and the distribution, and the size of the crystals itself.

  17. Failure Accommodation Tested in Magnetic Suspension Systems for Rotating Machinery

    Science.gov (United States)

    Provenza, Andy J.

    2000-01-01

    The NASA Glenn Research Center at Lewis Field and Texas A&M University are developing techniques for accommodating certain types of failures in magnetic suspension systems used in rotating machinery. In recent years, magnetic bearings have become a viable alternative to rolling element bearings for many applications. For example, industrial machinery such as machine tool spindles and turbomolecular pumps can today be bought off the shelf with magnetically supported rotating components. Nova Gas Transmission Ltd. has large gas compressors in Canada that have been running flawlessly for years on magnetic bearings. To help mature this technology and quiet concerns over the reliability of magnetic bearings, NASA researchers have been investigating ways of making the bearing system tolerant to faults. Since the potential benefits from an oil-free, actively controlled bearing system are so attractive, research that is focused on assuring system reliability and safety is justifiable. With support from the Fast Quiet Engine program, Glenn's Structural Mechanics and Dynamics Branch is working to demonstrate fault-tolerant magnetic suspension systems targeted for aerospace engine applications. The Flywheel Energy Storage Program is also helping to fund this research.

  18. A multibody approach applied to the study of driver injuries due to a narrow-track wheeled tractor rollover

    Directory of Open Access Journals (Sweden)

    Simone Pascuzzi

    2015-10-01

    Full Text Available This paper proposes the use of the multibody approach to evaluate the severity of the injuries to the driver associated with rollover of an agricultural tractor. A simple rollover accident of a narrow-track wheeled tractor was simulated in the multibody-FEM Madymo environment and the biomechanical damage to the operator with and without 2-point pelvic restraint was analysed. The structure of the tractor was considered to be unbendable, whereas i infinitely rigid, ii clay-based and iii sand-based soils have been studied. The obtained results highlight the important role played by the seat belt in confining the farm operator within the safety volume maintained by the rollover protective structure (ROPS of the tractor so that the injuries are reduced. The deformation of the soil produces lower acceleration and velocity values than those obtained with a rigid soil. On the other hand, as soil plastic deformations increase, the penetration of ROPS into the soil also increases, thus reducing the safety volume of the tractor and increasing the probability of interactions between the operator and the soil.

  19. Model Order Reduction of Large-Scale Finite Element Systems in an MPI Parallelized Environment for Usage in Multibody Simulation

    Directory of Open Access Journals (Sweden)

    Volzer Thomas

    2016-12-01

    Full Text Available The use of elastic bodies within a multibody simulation became more and more important within the last years. To include the elastic bodies, described as a finite element model in multibody simulations, the dimension of the system of ordinary differential equations must be reduced by projection. For this purpose, in this work, the modal reduction method, a component mode synthesis based method and a moment-matching method are used. Due to the always increasing size of the non-reduced systems, the calculation of the projection matrix leads to a large demand of computational resources and cannot be done on usual serial computers with available memory. In this paper, the model reduction software Morembs++ is presented using a parallelization concept based on the message passing interface to satisfy the need of memory and reduce the runtime of the model reduction process. Additionally, the behaviour of the Block-Krylov-Schur eigensolver, implemented in the Anasazi package of the Trilinos project, is analysed with regard to the choice of the size of the Krylov base, the block size and the number of blocks. Besides, an iterative solver is considered within the CMS-based method.

  20. On cloud modelling and the mass accommodation coefficient of water

    Directory of Open Access Journals (Sweden)

    A. Laaksonen

    2004-11-01

    Full Text Available The mass accommodation coefficient of water is a quantity for which different experimental techniques have yielded conflicting values in the range 0.04–1. From the viewpoint of cloud modelling, this is an unfortunate situation, since the value of the mass accommodation coefficient affects the model results, e.g. the number concentration of activated cloud droplets. In this paper we argue that a mass accommodation coefficient of unity should be used in cloud modelling, since this value has been obtained in experimental studies of water droplet growth rates, a quantity which is explicitly described in cloud models. In contrast, mass accommodation coefficient values below unity have been derived from experimental results which are analyzed with different theoretical expressions than those included in cloud models.

  1. Occlusal accommodation and mouthguards for prevention of orofacial trauma.

    LENUS (Irish Health Repository)

    Geary, Julian Lindsay

    2009-01-01

    The aim of this study was to investigate the effect of two types of occlusal accommodation on the arch separation in centric and eccentric arch positions and to assess the opposing tooth contacts in professionally made, thermoformed sports mouthguards.

  2. Opto-mechanical artificial eye with accommodative ability.

    Science.gov (United States)

    Esteve-Taboada, José J; Del Águila-Carrasco, Antonio J; Marín-Franch, Iván; Bernal-Molina, Paula; Montés-Micó, Robert; López-Gil, Norberto

    2015-07-27

    The purpose of this study was to describe the design and characterization of a new opto-mechanical artificial eye (OMAE) with accommodative ability. The OMAE design is based on a second-pass configuration where a small source of light is used at the artificial retina plane. A lens whose focal length can be changed electronically was used to add the accommodation capability. The changes in the OMAE's aberrations with the lens focal length, which effectively changes the accommodative state of the OMAE, were measured with a commercial aberrometer. Changes in power and aberrations with room temperature were also measured. The OMAE's higher-order aberrations (HOAs) were similar to the ones of the human eye, including the rate at which fourth-order spherical aberration decreased with accommodation. The OMAE design proposed here is simple, and it can be implemented in an optical system to mimic the optics of the human eye.

  3. Amplitude of Accommodation and its Relation to Refractive Errors

    Directory of Open Access Journals (Sweden)

    Abraham Lekha

    2005-01-01

    Full Text Available Aims: To evaluate the relationship between amplitude of accommodation and refractive errors in the peri-presbyopic age group. Materials and Methods: Three hundred and sixteen right eyes of 316 consecutive patients in the age group 35-50 years who attended our outpatient clinic were studied. Emmetropes, hypermetropes and myopes with best-corrected visual acuity of 6/6 J1 in both eyes were included. The amplitude of accommodation (AA was calculated by measuring the near point of accommodation (NPA. In patients with more than ± 2 diopter sphere correction for distance, the NPA was also measured using appropriate soft contact lenses. Results: There was a statistically significant difference in AA between myopes and hypermetropes ( P P P P P P >0.5. Conclusion: Our study showed higher amplitude of accommodation among myopes between 35 and 44 years compared to emmetropes and hypermetropes

  4. Rigid MATLAB drivetrain model of a 500 kW wind turbine for predicting maximum gear tooth stresses in a planetary gearbox using multibody gear constraints

    DEFF Research Database (Denmark)

    Jørgensen, Martin Felix; Pedersen, Niels Leergaard; Sørensen, Jens Nørkær

    2014-01-01

    The aeroelastic FLEX 5 code and a semi-advanced rigid multibody model has been utilized for simulating drivetrain forces and moments in a real 500 kW wind turbine. Experimental validation is carried out with results based on known physical properties of the blades, tower, hub, gearbox, shaft and ...

  5. Numerical Algorithm for Calculating Lyapunov Exponents of Multibody Hamilton Systems with Topological Tree Configuration%树形多体Hamilton系统的Lyapunov指数计算方法

    Institute of Scientific and Technical Information of China (English)

    金俐; 王琪; 陆启韶

    2001-01-01

    A numerical algorithm for calculating Lyapunov exponents of Hamiltonian multibody systems with topological tree configuration is studied. The algorithms for Lyapunov exponents of Hamiltonian multibody systems using the canonical equations of the system and symplectic algorithm for ordinary differential equations are presented, which are used to study the stability of the Hamiltonian multibody systems. An example is given to analyze the stability of a typical Hamiltonian multibody system, including periodic solution and chaos.%研究了树形多体Hamilton系统Lyapunov指数的数值方法.利用多体Hamilton系统的正则方程和辛算法, 给出了多体Hamilton系统Lyapunov指数的计算方法,该算法具有较好的计算精度和通用性.利用该算法可对系统的运动稳定性进行分析.最后用算例说明了该算法的有效性.

  6. Visual Accommodation, the Mandelbaum Effect, and Apparent Size.

    Science.gov (United States)

    1979-11-01

    monkeys were awakened, accommodation immediately went to a far distance, followed by accurate accommodation to the - ambient stimuli. Similarly... ambient stimulation is present. Morgan (1957) proposes - two possible conditions in which visual stimuli are reduced to the minimum--in complete darkness...oj Physiology, 1941, 12, 720-733. Otero, J. M. and Duran, Continuacion del estudio de la miopia nocturna. Anales de i y Quimica , 1942, 38, 236-248

  7. An application of SODA methodology in student accommodation problems

    OpenAIRE

    E. Teimoury; H. Gitinavard; Mousavi, S. M.

    2014-01-01

    The one of the main problems that students have faced with are the accommodation problems. In this paper, we review problems that may occur in university systems. Also, we use strategic options development and analysis method (SODA) to represent the accommodation problems and to create an agreement between student and staff. This method can help us with achieving goals; because in the same situation, there are different viewpoints for various reasons. By plotting the cognitive maps of involve...

  8. Quasi-variational principles of single flexible body dynamics and their applications

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The reasons for studying single flexible body dynamics are that on one hand,it is the basis of flexible multi-body dynamics.If the theory of the single flexible body dynamics has been deeply studied,the theory of flexible multi-body dynamics will be researched easily.On the other hand,it has its unique and important applications.Quasi-variational principle of non-conservative single flexible body dynamics is established under the cross-link of particle rigid body mechanics and deformable body mechanics.Taking the interceptor as an example,this paper has explained the physical meaning of the quasi-stationary value condition of the quasi-variational principle in non-conservative single flexible body dynamics.Taking the launch of rocket as an example,it has illustrated the features of"one force for two effects"in a single flexible body dynamics.With an example of the extending flexible beam coupled with the spacecraft attitude,it has shown the transition from the single flexible body dynamics to the flexible multi-body dynamics.Finally,a number of related problems are discussed.

  9. Quasi-variational principles of single flexible body dynamics and their applications

    Institute of Scientific and Technical Information of China (English)

    LIANG LiFu; LIU ShiQuan; ZHOU JianSheng

    2009-01-01

    The reasons for studying single flexible body dynamics are that on one hand, it is the basis of flexible multi-body dynamics. If the theory of the single flexible body dynamics has been deeply studied, the theory of flexible multi-body dynamics will be researched easily. On the other hand, it has its unique and important applications. Quasi-variational principle of non-conservative single flexible body dynamics is established under the cross-link of particle rigid body mechanics and deformable body mechanics. Taking the interceptor as an example, this paper has explained the physical meaning of the quasi-stationary value condition of the quasi-variational principle in non-conservative single flexible body dynamics. Taking the launch of rocket as an example, it has illustrated the features of "one force for two effects" in s single flexible body dynamics. With an example of the extending flexible beam coupled with the spacecraft attitude, it has shown the transition from the single flexible body dynamics to the flexible multi-body dynamics. Finally, a number of related problems are discussed.

  10. Towards electricity markets accommodating uncertain offers

    DEFF Research Database (Denmark)

    Papakonstantinou, Athanasios; Pinson, Pierre

    2014-01-01

    The use of renewable energy sources of energy and in particular wind and solar has been on the rise over the last decades with plans to increase it even more. Such developments introduce significant challenges in existing power systems and can result in high electricity prices and costly infrastr......The use of renewable energy sources of energy and in particular wind and solar has been on the rise over the last decades with plans to increase it even more. Such developments introduce significant challenges in existing power systems and can result in high electricity prices and costly...... infrastructure investments. In this paper we propose a new electricity market mechanism whereby the uncertain and dynamic nature of wind power and other stochastic sources is embedded in the market mechanism itself, by modelling producers’ bids as probabilistic estimates. An extension on the bilevel programming...... formulation of an electricity market, based on the Continuous Ranked Probability Score (CRPS) reduces the impact of poor estimates for both the stochastic producers and the system operator. We introduce a simulation setting which first demonstrates that impact and then proceed to illustrate the main features...

  11. Perturbation Dynamics and Its Application for Parachute-Munition System

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The nine-degree-freedom dynamic model of the parachute-munition system is developed by the theories and the analysis methods of parachute dynamics and multibody dynamics. On the basis of the above model, a linear five-degree-offreedom dynamic model is developed by linearization at the steady state. A new algorithm, which can be fused with submunition kinematics and used in target identification, is developed by the principle of parachute dynamics. The simulation program is developed and used to remove the influence of wind gust on hitting accuracy. The successful airdrop test demonstrates that the new method can be used in the guidance of smart munition.

  12. Advanced Dynamics Analytical and Numerical Calculations with MATLAB

    CERN Document Server

    Marghitu, Dan B

    2012-01-01

    Advanced Dynamics: Analytical and Numerical Calculations with MATLAB provides a thorough, rigorous presentation of kinematics and dynamics while using MATLAB as an integrated tool to solve problems. Topics presented are explained thoroughly and directly, allowing fundamental principles to emerge through applications from areas such as multibody systems, robotics, spacecraft and design of complex mechanical devices. This book differs from others in that it uses symbolic MATLAB for both theory and applications. Special attention is given to solutions that are solved analytically and numerically using MATLAB. The illustrations and figures generated with MATLAB reinforce visual learning while an abundance of examples offer additional support. This book also: Provides solutions analytically and numerically using MATLAB Illustrations and graphs generated with MATLAB reinforce visual learning for students as they study Covers modern technical advancements in areas like multibody systems, robotics, spacecraft and des...

  13. Interaction between Accommodation and Vergence on Distance Perception

    Directory of Open Access Journals (Sweden)

    Tomoyuki Daijogo

    2011-05-01

    Full Text Available Fisher and Ciuffreda (1988 and Mon-Williams and Tresilian (1999 reported that, without vergence cue, diopter change in accommodation induced change in apparent distance. Meanwhile, there is conflicting evidence about the relative roles of accommodation and vergence in distance perception (Richards & Miller, 1969; von Holst, 1973. In the current study, we investigated interaction between accommodation and vergence on distance perception. The perceived distance from integration of vergence evoked by a fixation target and accommodation by a pair of concave or convex lenses in front of eyes is measured with a mirror stereoscope. The stimulus was a white square with a black cross-shaped fixation on a black background. In dark surroundings, subjects were asked to commit the apparent distance of the target to memory, and then without the lenses, re-create the distance by changing distance of another fixation target. The apparent size of the target through lenses were equivalent to the size without lenses. The results showed that not only vergence but accommodation affect the apparent distance, and they were summed linearly.

  14. Short-term induction of assimilation and accommodation.

    Science.gov (United States)

    Leipold, Bernhard; Bermeitinger, Christina; Greve, Werner; Meyer, Birgit; Arnold, Manuel; Pielniok, Marianna

    2014-01-01

    The dual-process model of developmental regulation distinguishes two processes of self-regulation (assimilation = tenacious goal pursuit, and accommodation = flexible goal adjustment) that depend on differing conditions, but both contribute to successful development. Four experiments were conducted to investigate whether assimilation and accommodation can be induced or at least shifted by sensorimotor and cognitive manipulations. Experiment 1 investigated the relation between body manipulation and self-regulation. It was shown that assimilation could be triggered when participants were asked to hold on to golf balls as compared to being asked to drop them. Experiment 2 showed that a semantic priming of "let go" or "hold on" via instructions influenced the processes of self-regulation. Experiment 3 and Experiment 4 investigated the role of cognitive sets (divergent thinking) and motivational processes (thinking about one's action resources) in enhancing accommodation or assimilation. As expected, accommodation was triggered by an intervention activating divergent thought, and participants were more assimilative when they thought about their action resources. In sum, the results indicate that assimilation and accommodation can be induced experimentally; they were systematically dependent on physical, cognitive, and motivational states. The implications of the findings were discussed in the light of the dual-process model.

  15. Relative Importance of Student Accommodation Quality in Higher Education

    Directory of Open Access Journals (Sweden)

    Simon Gyasi Nimako

    2013-07-01

    Full Text Available This study, which was part of a large study, empirically examinesthe importance students attach to different dimensions of Student Accommodation Quality (SAQ delivered by Student Accommodation Providers (SAP in two tertiary (higher education institutions in Ghana. The study involved a cross-sectional survey that used a structured questionnaire administered to 700 tertiary students in residential and non-residential accommodation. The survey yielded a usable 66.6% response rate for analysis. The findings indicate that utility facility quality is the most important SAQ dimension to the students, followed by the overall impression of hostel, security, physical environment, toilet, distance to lecture, bedroom, bath room, accommodation fee, among others. Moreover, it was found that kitchen facility, access to transport and entertainment facility are less important SAQ items while the least important is garage facility. Few differences were found in the priority for SAQ items between COLTEK and K-Poly respondents and between residential and non-residential respondents. Implications for theory and recommendations to management of the two higher education institutions and SAP have been discussed. The study contributes to the body of knowledge in student affairs and managing student accommodation quality in higher education.

  16. A model of job activity description for workplace accommodation assessment.

    Science.gov (United States)

    Sevilla, Joaquin; Sanford, Jon A

    2013-01-01

    Workplace accommodations to enable employees with disabilities to perform essential job tasks are an important strategy ways for increasing the presence of people with disabilities in the labor market. However, assessments, which are crucial to identifying necessary accommodations, are typically conducted using a variety of methods that lack consistent procedures and comprehensiveness of information. This can lead to the rediscovery of the same solutions over and over, inability to replicate assessments and a failure to effectively meet all of an individual's accommodation needs. To address standardize assessment tools and processes, a taxonomy of demand-producing activity factors is needed to complement the taxonomies of demand-producing person and environment factors already available in the International Classification of Functioning, Disability and Health (ICF). The purpose of this article is to propose a hierarchical model of accommodation assessment based on level of specificity of job activity. While the proposed model is neither a taxonomy nor an assessment process, the seven-level hierarchical model provides a conceptual framework of job activity that is the first step toward such a taxonomy as well as providing a common language that can bridge the many approaches to assessment. The model was designed and refined through testing against various job examples. Different levels of activity are defined to be easily linked to different accommodation strategies. Finally, the levels can be cross-walked to the ICF, which enhances its acceptability, utility and universality.

  17. The role of short-wavelength sensitive cones and chromatic aberration in the response to stationary and step accommodation stimuli.

    Science.gov (United States)

    Rucker, Frances J; Kruger, Philip B

    2004-01-01

    The aim of the experiment was to test for a contribution from short-wavelength sensitive cones to the static and step accommodation response, to compare responses from short and long- plus middle-wavelength sensitive cone types, and to examine the contribution of a signal from longitudinal chromatic aberration to the accommodation response. Accommodation was monitored continuously (eight subjects) to a square-wave grating (2.2 c/d; 0.57 contrast) in a Badal optometer. The grating stepped (1.00 D) randomly towards or away from the eye from a starting position of 2.00 D. Five illumination conditions were used to isolate cone responses, and combine them with or without longitudinal chromatic aberration. Accuracy of the response before the step, step amplitude, latencies and time-constants, were compared between conditions using single factor ANOVA and t-test comparisons. Both S-cones and LM-cones mediated static and step accommodation responses. S-cone contrast drives "static" accommodation for near, but the S-cone response is too slow to influence step dynamics when LM-cones participate.

  18. A Multibody Knee Model Corroborates Subject-Specific Experimental Measurements of Low Ligament Forces and Kinematic Coupling During Passive Flexion.

    Science.gov (United States)

    Kia, Mohammad; Schafer, Kevin; Lipman, Joseph; Cross, Michael; Mayman, David; Pearle, Andrew; Wickiewicz, Thomas; Imhauser, Carl

    2016-05-01

    A multibody model of the knee was developed and the predicted ligament forces and kinematics during passive flexion corroborated subject-specific measurements obtained from a human cadaveric knee that was tested using a robotic manipulator. The model incorporated a novel strategy to estimate the slack length of ligament fibers based on experimentally measured ligament forces at full extension and included multifiber representations for the cruciates. The model captured experimentally measured ligament forces (≤ 5.7 N root mean square (RMS) difference), coupled internal rotation (≤ 1.6 deg RMS difference), and coupled anterior translation (≤ 0.4 mm RMS difference) through 130 deg of passive flexion. This integrated framework of model and experiment improves our understanding of how passive structures, such as ligaments and articular geometries, interact to generate knee kinematics and ligament forces.

  19. Accommodation with and without short-wavelength-sensitive cones and chromatic aberration.

    Science.gov (United States)

    Kruger, Philip B; Rucker, Frances J; Hu, Caitlin; Rutman, Hadassa; Schmidt, Nathan W; Roditis, Vasilios

    2005-05-01

    Accommodation was monitored while observers (23) viewed a square-wave grating (2.2 cycles/deg; 0.53 contrast) in a Badal optometer. The grating moved sinusoidally (0.2 Hz) to provide a stimulus between -1.00 D and -3.00 D during trials lasting 40.96 s. There were three illumination conditions: 1. Monochromatic 550 nm light to stimulate long-wavelength-sensitive cones (L-cones) and medium-wavelength-sensitive cones (M-cones) without chromatic aberration; 2. Monochromatic 550 nm light+420 nm light to stimulate long-, medium- and short-wavelength-sensitive cones (S-cones) with longitudinal chromatic aberration (LCA); 3. Monochromatic 550 nm light+420 nm light to stimulate L-, M- and S-cones viewed through an achromatizing lens. In the presence of LCA mean dynamic gain decreased (p=0.0003; ANOVA) and mean accommodation level was reduced (p=0.001; ANOVA). The reduction in gain and increased lag of accommodation in the presence of LCA could result from a blue-yellow chromatic signal or from a larger depth-of-focus.

  20. Simulation of diatomic gas-wall interaction and accommodation coefficients for negative ion sources and accelerators

    Science.gov (United States)

    Sartori, E.; Brescaccin, L.; Serianni, G.

    2016-02-01

    Particle-wall interactions determine in different ways the operating conditions of plasma sources, ion accelerators, and beams operating in vacuum. For instance, a contribution to gas heating is given by ion neutralization at walls; beam losses and stray particle production—detrimental for high current negative ion systems such as beam sources for fusion—are caused by collisional processes with residual gas, with the gas density profile that is determined by the scattering of neutral particles at the walls. This paper shows that Molecular Dynamics (MD) studies at the nano-scale can provide accommodation parameters for gas-wall interactions, such as the momentum accommodation coefficient and energy accommodation coefficient: in non-isothermal flows (such as the neutral gas in the accelerator, coming from the plasma source), these affect the gas density gradients and influence efficiency and losses in particular of negative ion accelerators. For ideal surfaces, the computation also provides the angular distribution of scattered particles. Classical MD method has been applied to the case of diatomic hydrogen molecules. Single collision events, against a frozen wall or a fully thermal lattice, have been simulated by using probe molecules. Different modelling approximations are compared.

  1. Mark My Words! Linguistic Style Accommodation in Social Media

    CERN Document Server

    Danescu-Niculescu-Mizil, Cristian; Dumais, Susan; 10.1145/1963405.1963509

    2011-01-01

    The psycholinguistic theory of communication accommodation accounts for the general observation that participants in conversations tend to converge to one another's communicative behavior: they coordinate in a variety of dimensions including choice of words, syntax, utterance length, pitch and gestures. In its almost forty years of existence, this theory has been empirically supported exclusively through small-scale or controlled laboratory studies. Here we address this phenomenon in the context of Twitter conversations. Undoubtedly, this setting is unlike any other in which accommodation was observed and, thus, challenging to the theory. Its novelty comes not only from its size, but also from the non real-time nature of conversations, from the 140 character length restriction, from the wide variety of social relation types, and from a design that was initially not geared towards conversation at all. Given such constraints, it is not clear a priori whether accommodation is robust enough to occur given the con...

  2. EVALUATION OF SERVICES’ QUALITY IN UPPER SILESIA ACCOMMODATION FACILITIES

    Directory of Open Access Journals (Sweden)

    Iwona Cieślik

    2013-12-01

    Full Text Available This paper presents the results of study about impact of accommodation services’ quality, particularly quality of work and qualifications of staff, on the guests’ opinion, and thus promoting the accommodation facilities, and making a choice of a hotel in the Upper Silesia. The study involved 200 people, taking into account their gender, age, place of residence, education and occupational status. The research tool was a survey questionnaire. The results indicate close correlation between the quality of staff services (individual approach, aesthetics, discretion, understanding and the customer is satisfaction. Particular attention was paid to the quality of service by the guests with high professional status, and higher education.

  3. Technology needs for the development of the accommodative intraocular lens

    Science.gov (United States)

    Nishi, Okihiro

    2010-02-01

    Refilling the lens capsule while preserving capsular integrity offers the potential to restore ocular accommodation. There are two persisting problems in capsular bag refilling for possible clinical application: Leakage of the injectable material through the capsular opening and capsular opacification. Numerous attempts for solving these cardinal problems have not been proven to be clinically applicable. Recently, we developed a novel capsular bag refilling procedure using a novel accommodative intraocular lens that serves as an optic as well as a plug for sealing the capsular opening. The procedure and the results of monkey experiments will be presented.

  4. Analysis on the accommodation of renewable energy in northeast China

    Science.gov (United States)

    Liu, Jun; Zhang, Jinfang; Tian, Feng; Mi, Zhe

    2017-01-01

    The accommodation and curtailment of renewable energy in northeast China have attracted much attention with the rapid growth of wind and solar power generation. Large amount of wind power has been curtailed or abandoned in northeast China due to several reasons, such as, the redundancy of power supplies, inadequate power demands, imperfect power structure with less flexibility and limited cross-regional transmission capacity. In this paper, we use multi-area production simulation to analyse the accommodation of renewable energy in northeast China by 2020. Furthermore, we suggest the measures that could be adopted in generation, grid and load side to reduce curtailment of renewables.

  5. Against the accommodation of subjective healthcare provider beliefs in medicine: counteracting supporters of conscientious objector accommodation arguments.

    Science.gov (United States)

    Smalling, Ricardo; Schuklenk, Udo

    2017-04-01

    We respond in this paper to various counter arguments advanced against our stance on conscientious objection accommodation. Contra Maclure and Dumont, we show that it is impossible to develop reliable tests for conscientious objectors' claims with regard to the reasonableness of the ideological basis of their convictions, and, indeed, with regard to whether they actually hold they views they claim to hold. We demonstrate furthermore that, within the Canadian legal context, the refusal to accommodate conscientious objectors would not constitute undue hardship for such objectors. We reject concerns that refusing to accommodate conscientious objectors would limit the equality of opportunity for budding professionals holding particular ideological positions. We also clarify various misrepresentations of our views by respondents Symons, Glick and Jotkowitz, and Lyus.

  6. Cooperating or competing in three languages : Cultural accommodation or alienation?

    NARCIS (Netherlands)

    Gargalianou, Vasiliki; Urbig, D.; van Witteloostuijn, Arjen

    2017-01-01

    Purpose The purpose of this paper is to study the effect of using foreign languages on cooperative behavior in a prisoner’s dilemma setting. The cultural accommodation hypothesis suggests that people are less cooperative in English, associated with the Anglophone cultural cluster, than in French, wh

  7. Accommodating Students with Disabilities in Soil Science Activities

    Science.gov (United States)

    Langley-Turnbaugh, S. J.; Murphy, Kate; Levin, E.

    2004-01-01

    Soil science education is lacking in terms of accommodations for persons with disabilities. Individuals with disabilities are often excluded from soil science activities in school, and from soil science careers. GLOBE (Global Learning Observations to Benefit the Environment) is a worldwide, hands-on primary and secondary school-based education and…

  8. Development of a ciliary muscle-driven accommodating intraocular lens

    NARCIS (Netherlands)

    Hermans, Erik A.; Terwee, Thom T.; Koopmans, Steven A.; Dubbelman, Michiel; van der Heijde, Rob G. L.; Heethaar, Rob M.

    2008-01-01

    PURPOSE: To develop a ciliary muscle-driven accommodating intraocular lens (IOL) that has a large and predictable range of variable power as a step toward spectacle independence. SETTING: Department of Physics and Medical Technology, VU University Medical Center, Amsterdam, The Netherlands. METHODS:

  9. The accommodative ciliary muscle function is preserved in older humans

    Science.gov (United States)

    Tabernero, Juan; Chirre, Emmanuel; Hervella, Lucia; Prieto, Pedro; Artal, Pablo

    2016-05-01

    Presbyopia, the loss of the eye’s accommodation capability, affects all humans aged above 45–50 years old. The two main reasons for this to happen are a hardening of the crystalline lens and a reduction of the ciliary muscle functionality with age. While there seems to be at least some partial accommodating functionality of the ciliary muscle at early presbyopic ages, it is not yet clear whether the muscle is still active at more advanced ages. Previous techniques used to visualize the accommodation mechanism of the ciliary muscle are complicated to apply in the older subjects, as they typically require fixation stability during long measurement times and/or to have an ultrasound probe directly in contact with the eye. Instead, we used our own developed method based on high-speed recording of lens wobbling to study the ciliary muscle activity in a small group of pseudophakic subjects (around 80 years old). There was a significant activity of the muscle, clearly able to contract under binocular stimulation of accommodation. This supports a purely lenticular-based theory of presbyopia and it might stimulate the search for new solutions to presbyopia by making use of the remaining contraction force still presented in the aging eye.

  10. Accommodations in Homeschool Settings for Children with Special Education Needs

    Science.gov (United States)

    Stoudt, Patricia Koelsch

    2012-01-01

    This qualitative study was designed to examine how homeschooling parents in Pennsylvania make the determination to engage with public school districts to accommodate the special education needs (SEN) of their children. This phenomenological study used direct interviews with 30 Pennsylvania families who are homeschooling children with SEN. Data…

  11. Teaching Disability Employment Discrimination Law: Accommodating Physical and Mental Disabilities

    Science.gov (United States)

    Kulow, Marianne DelPo

    2012-01-01

    Disability employment discrimination is often treated summarily in legal environment courses. This is actually a topic with significant practical application in the workplace since managers are often those who are confronted with accommodation requests. It is therefore desirable to include a class with hands-on exercises for students to begin to…

  12. Development of the Reasonable Accommodation Factor Survey: Results and Implications

    Science.gov (United States)

    Dong, Shengli; MacDonald-Wilson, Kim L.; Fabian, Ellen

    2010-01-01

    The purpose of this study was (a) to explore the latent factors in the "Reasonable Accommodation Factor Survey" (RAFS) instrument and (b) to compare scores on the latent factors of the RAFS by participant's role. Eight latent factors were identified through an exploratory factor analysis with orthogonal rotation. The reliability tests…

  13. Language Shift and Language Accommodation across Family Generations in Taiwan

    Science.gov (United States)

    Sandel, Todd L.; Chao, Wen-Yu; Liang, Chung-Hui

    2006-01-01

    This study explored language shift and accommodation among bilingual Mandarin and Tai-gi (also called Hokkien, Holo, Tai-gu, Taiwan Min, Taiwanese) families in Taiwan. From the 1940s until the 1980s the Chinese Nationalist Party (KMT) on Taiwan promoted Mandarin Chinese. Recent years have witnessed a shift in policy: since 2001 elementary schools…

  14. Translation Accommodations Framework for Testing English Language Learners in Mathematics

    Science.gov (United States)

    Solano-Flores, Guillermo

    2012-01-01

    The present framework is developed under contract with the Smarter Balanced Assessment Consortium (SBAC) as a conceptual and methodological tool for guiding the reasonings and actions of contractors in charge of developing and providing test translation accommodations for English language learners. The framework addresses important challenges in…

  15. The relationship between anemia and accommodative esotropia in children

    Directory of Open Access Journals (Sweden)

    Fethiye Gulden Turgut

    2013-01-01

    Full Text Available Background: Refraction problems, motor disorders, sensorial disorders, physical and psychic traumas of eye may be responsible for development of strabismus. Anemia may cause sensory-neural disorders in children. We investigated the relationship between anemia and accommodative esotropia in children. Materials and Methods: Sixty-four patients with accommodative esotropia were evaluated. This group was identified as patient group (group 1. Eighty-three pediatric patients, who were not esotropia and only had refraction problems, were identified as control group (group 2. The difference between the groups was statistically analyzed evaluating patients for anemia. Results: 33 of 64 patients with accommodative esotropia in group 1 were male, as 43 of 83 patients with refractive error in group 2 were male. The mean age of patients in group 1 and 2 were 6 ΁ 3.92 and 6.37 ΁ 2.74 (P > 0.05 respectively. There was significant difference between two groups, when mean hemoglobin value of those was compared (P < 0.05. Conclusion: Hb level may affects the accommodative esotropia.

  16. 36 CFR 910.34 - Accommodations for the physically handicapped.

    Science.gov (United States)

    2010-07-01

    ... physically handicapped. 910.34 Section 910.34 Parks, Forests, and Public Property PENNSYLVANIA AVENUE... § 910.34 Accommodations for the physically handicapped. (a) Every development shall incorporate features which will make the development accessible by the physically handicapped. The standards in the...

  17. Mechanically implementable accommodation matrices for passive force control

    Energy Technology Data Exchange (ETDEWEB)

    Goswami, A. [Univ. of Pennsylvania, Philadelphia, PA (United States). Center for Human Modeling and Simulation; Peshkin, M. [Northwestern Univ., Evanston, IL (United States). Dept. of Mechanical Engineering

    1999-08-01

    Robot force control implemented by means of passive mechanical devices has inherent advantages over active implementations with regard to stability, response rapidity, and physical robustness. The class of devices considered in this paper consists of a Stewart platform-type mechanism interconnected with a network of adjustable mechanical elements such as springs and dampers. The control law repertoire of such a device, imagined as a robot wrist, is given by the range of admittance matrices that it may be programmed to possess. This paper focuses on wrists incorporating damper networks for which the admittance matrices reduce to accommodation or inverse-damping matrices. The authors show that a hydraulic network of fully adjustable damper elements may attain any diagonally dominant accommodation matrix. They describe the technique of selecting the individual damping coefficients to design a desired matrix. They identify the set of dominant matrices as a polyhedral convex cone in the space of matrix entries, and show that each dominant matrix can be composed of a positive linear combination of a fixed set of basis matrices. The overall wrist-accommodation matrix is obtained by projecting the accommodation matrix of the damper network through the wrist kinematics. The linear combination of the dominant basis matrices projected through the wrist kinematics generates the entire space of mechanically implementable force-control laws. The authors quantify the versatility of mechanically implementable force-control laws by comparing this space to the space of all matrices.

  18. Knowledge Transfer and Accommodation Effects in Multinational Corporations

    DEFF Research Database (Denmark)

    Geisler Asmussen, Christian; Foss, Nicolai J.; Pedersen, Torben

    2013-01-01

    Foreign subsidiaries in multinational corporations (MNCs) possess knowledge that has different sources (e.g., the firm itself or various sources in the environment). How such sources influence knowledge transfer is not well understood. Drawing on the "accommodation effect" from cognitive psychology...

  19. Solutions to Efficient Provision of Accommodations for Universities in China

    Institute of Scientific and Technical Information of China (English)

    ZHANGSiping

    2002-01-01

    Chinese universities are facing a series of challenges in their accommodations,of which a pr\\edominant one is how to provide both students and staff with enough accommodations of a large scope and good quality in good time and with limited budgets,In order to find applicable approaches to solve this problem,the current situations of the Chinese higher education reform and the resulted rapid growth of student numbers whereby the requirement of lodgings is greatly incresed are discussed.It is elucidated that in providing enough accommodations for staff and students,Chinese universities are confronted with difficulties including demand too big,lack of funding support,time limitation and incapability in both project management and facilities management.Industrialized building approach is demonstrated to be a desirable access to build large quantities of accommodations of good quality in limited time.and Private Fuinancial Initiative(PFI) appears to be a prosperous solution to the fund shortage,Regarding project and facilities management,qualified professionals are available by either employing exterior consultants or training related staff of universities for such occupations.

  20. Hydrogels for an accommodating intraocular lens. An explorative study

    NARCIS (Netherlands)

    de Groot, JH; Spaans, CJ; van Calck, RV; van Beijma, FJ; Norrby, S; Pennings, AJ

    2003-01-01

    In this study it was investigated whether hydrogels could be used for an accommodating lens. The requirements of such a hydrogels are a low modulus, high refractive index, transparency, and strength. Since conventional hydrogels do not possess this combination of properties, a novel preparation meth

  1. Accommodation, Cafes and Restaurants. Industry Training Monograph No. 8.

    Science.gov (United States)

    Dumbrell, Tom

    Australia's accommodation, cafes, and restaurants industry represents more than half of the nation's total tourism and hospitality employment. It accounts for roughly 4.5% of all jobs in Australia (400,000 workers). Since 1987, the number of jobs in the sector has risen from about 257,000 to about 372,000. Approximately 57% of employees are…

  2. ACCOMMODATION INFRASTRUCTURE AND TOURISM FLOWS ON FELEACU HILL (CLUJ COUNTY

    Directory of Open Access Journals (Sweden)

    DANIELA-LIVIA GHEORGHIEȘ

    2016-06-01

    Full Text Available Accommodation Infrastructure and Tourism Flows on Feleacu Hill (Cluj County. Feleacu Hill experienced tourism development between 2001 and 2015. The INS data indicates that the number of accommodation units increased from one (2001 to four (2015 and there are a few more which are not registered in the INS database. The accommodation capacity increases, as many guesthouses are expanding their premises to receive more tourists and new accommodation units emerge, such as Hotel Premier in Vâlcele (Feleacu commune. Tourism flows also registered a highly positive trend. The number of arrivals increased from 95 tourists in 2002 to 7791 tourists in 2015. However, there was a downturn between 2009 and 2012, due to the economic crisis and the opening of the Turda – Gilău motorway (A3, which redirected transit routes outside the region and led to the closure of Paradis Hotel in 2012. Since 2012, the number of arrivals and overnight stays increased steadily due to the development of new forms of tourism – rural tourism, agrotourism, extreme tourism and complex tourism, materialized in growing numbers of tourists at the two guesthouses in Ciurila commune (“La Mesteceni” and “Domeniul Regilor”. Tourism brings obvious benefits to the rural communities on Feleacu Hill, even if the average duration of stay is still low.

  3. Structure and thermodynamics of a mixture of patchy and spherical colloids: a multi-body association theory with complete reference fluid information

    CERN Document Server

    Bansal, Artee; Cox, Kenneth R; Chapman, Walter G

    2016-01-01

    A mixture of solvent particles with short-range, directional interactions and solute particles with short-range, isotropic interactions that can bond multiple times is of fundamental interest in understanding liquids and colloidal mixtures. Because of multi-body correlations predicting the structure and thermodynamics of such systems remains a challenge. Earlier Marshall and Chapman developed a theory wherein association effects due to interactions multiply the partition function for clustering of particles in a reference hard-sphere system. The multi-body effects are incorporated in the clustering process, which in their work was obtained in the absence of the bulk medium. The bulk solvent effects were then modeled approximately within a second order perturbation approach. However, their approach is inadequate at high densities and for large association strengths. Based on the idea that the clustering of solvent in a defined coordination volume around the solute is related to occupancy statistics in that def...

  4. Simulations and Measurements of Human Middle Ear Vibrations Using Multi-Body Systems and Laser-Doppler Vibrometry with the Floating Mass Transducer

    Directory of Open Access Journals (Sweden)

    Tobias Strenger

    2013-10-01

    Full Text Available The transfer characteristic of the human middle ear with an applied middle ear implant (floating mass transducer is examined computationally with a Multi-body System approach and compared with experimental results. For this purpose, the geometry of the middle ear was reconstructed from μ-computer tomography slice data and prepared for a Multi-body System simulation. The transfer function of the floating mass transducer, which is the ratio of the input voltage and the generated force, is derived based on a physical context. The numerical results obtained with the Multi-body System approach are compared with experimental results by Laser Doppler measurements of the stapes footplate velocities of five different specimens. Although slightly differing anatomical structures were used for the calculation and the measurement, a high correspondence with respect to the course of stapes footplate displacement along the frequency was found. Notably, a notch at frequencies just below 1 kHz occurred. Additionally, phase courses of stapes footplate displacements were determined computationally if possible and compared with experimental results. The examinations were undertaken to quantify stapes footplate displacements in the clinical practice of middle ear implants and, also, to develop fitting strategies on a physical basis for hearing impaired patients aided with middle ear implants.

  5. An Efficient Optimal Design Methodology for Nonlinear Multibody Dynamics Systems with Application to Vehicle Occupant Restraint Systems

    Science.gov (United States)

    2011-04-01

    initial vehicle longitudinal velocity is 17 m/s, and the road profile is a sinusoid function with magnitude of 0.05 m and wave length of 8 m...Position and Stiffness of Human Elbow Joint, Biological Cybernetics, Vol. 96, No. 3, pp. 341–350. 36...Comparison between Numerical and Experimental Results on Mine Blast Attenuating Seating, Paper Presented at the 77th Shock & Vibration Symposium

  6. Implicit gas-kinetic unified algorithm based on multi-block docking grid for multi-body reentry flows covering all flow regimes

    Science.gov (United States)

    Peng, Ao-Ping; Li, Zhi-Hui; Wu, Jun-Lin; Jiang, Xin-Yu

    2016-12-01

    Based on the previous researches of the Gas-Kinetic Unified Algorithm (GKUA) for flows from highly rarefied free-molecule transition to continuum, a new implicit scheme of cell-centered finite volume method is presented for directly solving the unified Boltzmann model equation covering various flow regimes. In view of the difficulty in generating the single-block grid system with high quality for complex irregular bodies, a multi-block docking grid generation method is designed on the basis of data transmission between blocks, and the data structure is constructed for processing arbitrary connection relations between blocks with high efficiency and reliability. As a result, the gas-kinetic unified algorithm with the implicit scheme and multi-block docking grid has been firstly established and used to solve the reentry flow problems around the multi-bodies covering all flow regimes with the whole range of Knudsen numbers from 10 to 3.7E-6. The implicit and explicit schemes are applied to computing and analyzing the supersonic flows in near-continuum and continuum regimes around a circular cylinder with careful comparison each other. It is shown that the present algorithm and modelling possess much higher computational efficiency and faster converging properties. The flow problems including two and three side-by-side cylinders are simulated from highly rarefied to near-continuum flow regimes, and the present computed results are found in good agreement with the related DSMC simulation and theoretical analysis solutions, which verify the good accuracy and reliability of the present method. It is observed that the spacing of the multi-body is smaller, the cylindrical throat obstruction is greater with the flow field of single-body asymmetrical more obviously and the normal force coefficient bigger. While in the near-continuum transitional flow regime of near-space flying surroundings, the spacing of the multi-body increases to six times of the diameter of the single

  7. CHOA concussion consensus: establishing a uniform policy for academic accommodations.

    Science.gov (United States)

    Popoli, David Michael; Burns, Thomas G; Meehan, William P; Reisner, Andrew

    2014-03-01

    Concussion research generally centers on physical challenges, though aspects such as social functioning and returning to school also warrant attention in pediatric populations. Restoring academic performance postconcussion remains a challenge. Here we provide recommendations addressing a uniform policy for pediatric concussion patients in academic institutions. Tools that may minimize difficulty with academic re-entry include independent educational evaluations, individualized educational programs (IEPs), student support teams (SSTs), letters of academic accommodation, time off, and 504 Plans. Recognition and treatment is crucial for symptom relief and prevention of functional disruption, as is specialist referral during the acute window. We recommend early intervention with a letter of academic accommodation and SST and suggest that 504 Plans and IEPs be reserved for protracted or medically complicated cases. Students with concussion should be observed for anxiety and depression because these symptoms can lead to prolonged recovery, decreased quality of life, and other social challenges.

  8. Accommodating MOOCs into HEI: is blended-learning the solution?

    OpenAIRE

    Martínez, Juan Antonio; Campuzano, Joaquim

    2015-01-01

    MOOCs are without discussion one of the key changers in education, and in particular in higher education. They affect both on-Campus universities and on-line. Advisory boards in Universities face the need to accommodate a new player in the learning process arena. The MOOC tsunami affects Universities, forcing them to offer MOOCs assuming costs. On the other side, MOOC platform managers need to convince Universities that creating and offering MOOCs is a must, generating revenues at the same ti...

  9. Linguistic Simplification: A Promising Test Accommodation for LEP Students?

    Directory of Open Access Journals (Sweden)

    Charles W. Stansfield

    2002-07-01

    Full Text Available This article is a synopsis of an experimental study of the effects of linguistic simplification, a test accommodation..designed for LEP students. Conducted as part of Delaware's statewide assessment program, this study examined the..effects of linguistic simplification of fourth- and sixth-grade science test items and specifically looked at score..comparability between LEP and non-LEP examinees.

  10. Digital electronic engine control fault detection and accommodation flight evaluation

    Science.gov (United States)

    Baer-Ruedhart, J. L.

    1984-01-01

    The capabilities and performance of various fault detection and accommodation (FDA) schemes in existing and projected engine control systems were investigated. Flight tests of the digital electronic engine control (DEEC) in an F-15 aircraft show discrepancies between flight results and predictions based on simulation and altitude testing. The FDA methodology and logic in the DEEC system, and the results of the flight failures which occurred to date are described.

  11. Bimatoprost (0.03%)-induced accommodative spasm and pseudomyopia.

    Science.gov (United States)

    Padhy, Debananda; Rao, Aparna

    2015-11-23

    Bimatoprost is a prostaglandin analogue used topically in the treatment of glaucoma. Commonly known side effects include eyelash growth, iris pigmentation and conjunctival hyperemia. While pseudomyopia is reported to be caused by parasympathomimetics, such an effect precipitated by bimatoprost has not yet been reported. We report a case demonstrating pseudomyopia and accommodative spasm caused after starting bimatoprost 0.03% in a young patient with glaucoma.

  12. Recent Religious Accommodations: Have We Gone Too Far Too Fast?

    Science.gov (United States)

    2012-03-12

    length of head hair for both men and women , making certain allowances for women to wear longer hairstyles. The regulation prohibits the wear of beards...exceptions in order to further religious sensitivity. 10 Review of Canada, United Kingdom, and Netherlands Policy on Head and Facial Hair Some...militaries have religious accommodations for males who maintain facial and head hair for religious purposes. In addition, one nation allows soldiers to

  13. Kinematic and ground reaction force accommodation during weighted walking.

    Science.gov (United States)

    James, C Roger; Atkins, Lee T; Yang, Hyung Suk; Dufek, Janet S; Bates, Barry T

    2015-12-01

    Weighted walking is a functional activity common in daily life and can influence risks for musculoskeletal loading, injury and falling. Much information exists about weighted walking during military, occupational and recreational tasks, but less is known about strategies used to accommodate to weight carriage typical in daily life. The purposes of the study were to examine the effects of weight carriage on kinematics and peak ground reaction force (GRF) during walking, and explore relationships between these variables. Twenty subjects walked on a treadmill while carrying 0, 44.5 and 89 N weights in front of the body. Peak GRF, sagittal plane joint/segment angular kinematics, stride length and center of mass (COM) vertical displacement were measured. Changes in peak GRF and displacement variables between weight conditions represented accommodation. Effects of weight carriage were tested using analysis of variance. Relationships between peak GRF and kinematic accommodation variables were examined using correlation and regression. Subjects were classified into sub-groups based on peak GRF responses and the correlation analysis was repeated. Weight carriage increased peak GRF by an amount greater than the weight carried, decreased stride length, increased vertical COM displacement, and resulted in a more extended and upright posture, with less hip and trunk displacement during weight acceptance. A GRF increase was associated with decreases in hip extension (|r|=.53, p=.020) and thigh anterior rotation (|r|=.57, p=.009) displacements, and an increase in foot anterior rotation displacement (|r|=.58, p=.008). Sub-group analysis revealed that greater GRF increases were associated with changes at multiple sites, while lesser GRF increases were associated with changes in foot and trunk displacement. Weight carriage affected walking kinematics and revealed different accommodation strategies that could have implications for loading and stability.

  14. Employers’ Perspectives on Hiring and Accommodating Workers With Mental Illness

    Directory of Open Access Journals (Sweden)

    Janki Shankar

    2014-08-01

    Full Text Available Many individuals with mental illness want to return to work and stay in employment. Yet, there is little research that has examined the perspectives of employers on hiring and accommodating these workers and the kinds of supports employers need to facilitate their reintegration into the workforce. The aim of the current research was to explore the challenges employers face and the support they need to hire and accommodate workers with mental illness (WWMI. A qualitative research design guided by a grounded theory approach was used. In-depth interviews were conducted with 28 employers selected from a wide range of industries in and around Edmonton, Canada. The employers were a mix of frontline managers, disability consultants, and human resource managers who had direct experience with hiring and supervising WWMI. Data were analyzed using the principles of grounded theory. The findings highlight several challenges that employers face when dealing with mental health issues of workers in the workplace. These challenges can act as barriers to hiring and accommodating WWMI.

  15. ABOUT GENERAL INFRASTRUCTURE AND ACCOMMODATION SYSTEM IN ROMANIAN BALNEOLOGY

    Directory of Open Access Journals (Sweden)

    ILIE ROTARIU

    2013-12-01

    Full Text Available A strong infrastructure is a precondition for the development of balneology. On this base new tourism might build the modern services that supply the experiences. The key factor is the labor force: an EU project about labor force in Romania and Bulgaria in balneology allow us to present the preliminary findings focusing on general infrastructure and accommodation which allow the development of the balneology as well as the additional conditions as the existence of a social pact, easy access facilities etc. Our paper gives more details about the accommodation facilities in Romania insisting about the results of the transition and privatization of the former socialist facilities and the transformation of the property into private ones and the consequences of this. It also present the capability of new developed accommodation units built after 1990 and how they might compete in an international competition. The findings force us to conclude that the actual facilities do not allow the balneology resorts to compete in the international competition and might fill only a poor and low demanding tourists

  16. Analysis and modeling of error of spiral bevel gear grinder based on multi-body system theory

    Institute of Scientific and Technical Information of China (English)

    CHEN Shu-han; YAN Hong-zhi; MING Xing-zu

    2008-01-01

    Six-axis numerical control spiral bevel gear grinder was taken as the object, multi-body system theory and Denavit-Hartenberg homogeneous transformed matrix (HTM) were utilized to establish the grinder synthesis error model, and the validity of model was confirmed by the experiment. Additionally, in grinding wheel tool point coordinate system, the errors of six degrees of freedom were simulated when the grinding wheel revolving around C-axis, moving along X-axis and Y-axis. The influence of these six errors on teeth space, helix angle, pitch, teeth profile was discussed. The simulation results show that the angle error is in the range from -0.1484 rad to -0.2419 rad when grinding wheel moving along X, Y-axis; the translation error is in the range from 0.8660 μm to 3.6053 μm when grinding wheel moving along X-axis. These angle and translation errors have a great influence on the helix angle, pitch, teeth thickness and tooth socket.

  17. Validation of multi-body modelling methodology for reconfigurable underwater robots

    DEFF Research Database (Denmark)

    Nielsen, M.C.; Eidsvik, O. A.; Blanke, Mogens;

    2016-01-01

    This paper investigates the problem of employing reconfigurable robots in an underwater setting. The main results presented is the experimental validation of a modelling methodology for a system consisting of N dynamically connected robots with heterogeneous dynamics. Two distinct types....... The purpose of the model is to enable design of control strategies for cooperative reconfigurable underwater systems....... of experiments are performed, a series of hydrostatic free-decay tests and a series of open-loop trajectory tests. The results are compared to a simulation based on the modelling methodology. The modelling methodology shows promising results for usage with systems composed of reconfigurable underwater modules...

  18. Indirect Inverse Substructuring Method for Multibody Product Transport System with Rigid and Flexible Coupling

    Directory of Open Access Journals (Sweden)

    Jun Wang

    2015-01-01

    Full Text Available The aim of this paper is to develop a new frequency response function- (FRF- based indirect inverse substructuring method without measuring system-level FRFs in the coupling DOFs for the analysis of the dynamic characteristics of a three-substructure coupled product transport system with rigid and flexible coupling. By enforcing the dynamic equilibrium conditions at the coupling coordinates and the displacement compatibility conditions, a closed-form analytical solution to inverse substructuring analysis of multisubstructure coupled product transport system is derived based on the relationship of easy-to-monitor component-level FRFs and the system-level FRFs at the coupling coordinates. The proposed method is validated by a lumped mass-spring-damper model, and the predicted coupling dynamic stiffness is compared with the direct computation, showing exact agreement. The method developed offers an approach to predict the unknown coupling dynamic stiffness from measured FRFs purely. The suggested method may help to obtain the main controlling factors and contributions from the various structure-borne paths for product transport system.

  19. LA DINÁMICA DE LA ALTERNANCIA ENTRE TÚ, VOS Y USTED EN MEDELLÍN (COLOMBIA DESDE LA TEORÍA DE LA ACOMODACIÓN COMUNICATIVA THE DYNAMICS OF ALTERNATION BETWEEN TÚ, VOS Y USTED IN MEDELLIN (COLOMBIA FROM THE COMMUNICATION ACCOMMODATION THEORY

    Directory of Open Access Journals (Sweden)

    Ji Son Jang

    2012-01-01

    Full Text Available En el presente artículo se presentan algunos casos en los que se observa la alternancia pronominal en los hablantes de la ciudad de Medellín, con base en la teoría de la acomodación lingüística y especialmente relacionado con la noción de convergencia. Los hablantes de la comunidad de Medellín realizan la estrategia de la convergencia a través del ajustamiento al tratamiento pronominal que es empleado por su interlocutor cuando interactúan con: 1 los extranjeros no hispanohablantes; 2 los españoles que no son voseantes; 3 los colombianos no voseantes; 4 los habitantes de otras zonas de Antioquia y 5 las personas que pertenecen a un diferente estrato socio-económico de Medellín.In this article, we present some cases in which we observe the pronominal alternation on the Medellin speakers, based on the Communication Accommodation Theory and specially related to the notion of convergence. The speakers of the Medellin community practice the convergence strategy throught the ajustement to the pronominal treatment used by their speaker when they interact with: 1 the foreigners not spanish speakers; 2 the spanish speakers not using "vos"; 3 the colombians not using "vos"; 4 the inhabitants coming from another Antioquia zone and 5 the persons from Medellin belonging to a different socio-economical status.

  20. Mechanism design and dynamic analysis of a large-scale spatial deployable structure for space mission

    Science.gov (United States)

    Xu, Yanling; Lin, Qiuhong; Wang, Xingze; Li, Lin; Cong, Qiang; Pan, Bo

    2017-01-01

    The deployable structure is critical to the overall success of the space mission. This paper introduces a large-scale spatial deployable structure (SDS), which is developed to deploy and support the payload panels in a precise configuration once on the track. And segmental researching in the design, kinematics and dynamics analysis of SDS's prototyping system are presented. Geometric construction method and Bar-groups method are adopted to analysis the dimensions and coordinates of the SDS, which finally construct an well-determined mathematical model to raise the productivity and efficiency during optimization and analysis work. Be reasoned with the large-scale of the truss structures, flexible multibody dynamic simulations are developed, which present much more authentic stress transfer and kinematics behaviors. According to the deployment experiments of SDS's prototyping system, the correctness and validity of the flexible multibody simulation work are well proved.

  1. Symmetry and lattice mismatch induced strain accommodation near and away from correlated perovskite interfaces

    Science.gov (United States)

    Vailionis, A.; Boschker, H.; Liao, Z.; Smit, J. R. A.; Rijnders, G.; Huijben, M.; Koster, G.

    2014-09-01

    Distinct MnO6 octahedral distortions near and away from the La0.67Sr0.33MnO3/SrTiO3(001) (LSMO/STO) interface are quantified using synchrotron x-ray diffraction and dynamical x-ray diffraction simulations. Three structural regions of stress accommodation throughout the film thickness were resolved: near the LSMO/STO interface, intermediate region farther from the interface, and the main layer away from the interface. The results show that within the first two unit cells stress is accommodated by the suppression of octahedral rotations in the film, leading to the expansion of the c-axis lattice parameter. Farther from the interface film structure acquires octahedral tilts similar to thicker perovskite films under tensile stress, leading to a reduced c-axis parameter. We demonstrate that these regions are related to two different strain coupling mechanisms: symmetry mismatch at the interface and lattice mismatch in the rest of the film. The findings suggest new routes for strain engineering in correlated perovskite heterostructures.

  2. Symmetry and lattice mismatch induced strain accommodation near and away from correlated perovskite interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Vailionis, A. [Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305 (United States); Boschker, H. [MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede (Netherlands); Max Planck Institute for Solid State Research, 70569 Stuttgart (Germany); Liao, Z.; Smit, J. R. A.; Rijnders, G.; Huijben, M.; Koster, G. [MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede (Netherlands)

    2014-09-29

    Distinct MnO{sub 6} octahedral distortions near and away from the La{sub 0.67}Sr{sub 0.33}MnO{sub 3}/SrTiO{sub 3}(001) (LSMO/STO) interface are quantified using synchrotron x-ray diffraction and dynamical x-ray diffraction simulations. Three structural regions of stress accommodation throughout the film thickness were resolved: near the LSMO/STO interface, intermediate region farther from the interface, and the main layer away from the interface. The results show that within the first two unit cells stress is accommodated by the suppression of octahedral rotations in the film, leading to the expansion of the c-axis lattice parameter. Farther from the interface film structure acquires octahedral tilts similar to thicker perovskite films under tensile stress, leading to a reduced c-axis parameter. We demonstrate that these regions are related to two different strain coupling mechanisms: symmetry mismatch at the interface and lattice mismatch in the rest of the film. The findings suggest new routes for strain engineering in correlated perovskite heterostructures.

  3. 49 CFR 595.7 - Requirements for vehicle modifications to accommodate people with disabilities.

    Science.gov (United States)

    2010-10-01

    ... accommodate people with disabilities. 595.7 Section 595.7 Transportation Other Regulations Relating to Transportation (Continued) NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) MAKE INOPERATIVE EXEMPTIONS Vehicle Modifications To Accommodate People With Disabilities §...

  4. Analysis of internal drive train dynamics in a wind turbine

    Science.gov (United States)

    Peeters, Joris L. M.; Vandepitte, Dirk; Sas, Paul

    2006-01-01

    Three types of multibody models are presented for the investigation of the internal dynamics of a drive train in a wind turbine. The first approach is limited to the analysis of torsional vibrations only. Then a rigid multibody model is presented with special focus on the representation of the bearings and gears in the drive train. The generic model implementation can be used for parallel as well as planetary gear stages with both helical and spur gears. Examples for different gear stages describe the use of the presented formulations. Furthermore, the influence of the helix angle and the flexibility of the bearings on the results of eigenmode calculations are discussed. The eigenmodes of a planetary stage are classified as rotational, translational or out-of-plane modes. Thirdly, the extension to a flexible multibody model is presented as a method to include directly the drive train components' flexibilities. Finally, a comparison of two different modelling techniques is discussed for a wind turbine's drive train with a helical parallel gear stage and two planetary gear stages. In addition, the response calculation for a torque input at the generator demonstrates which eigenmodes can be excited through this path. Copyright

  5. Multi-body coupling numerical algorithms for free variable-pitch vertical axis tidal turbine%垂直轴自由变偏角水轮机的多体耦合数值求解方法

    Institute of Scientific and Technical Information of China (English)

    张学伟; 张亮; 李志川; 盛其虎; 王树齐

    2013-01-01

    A structural dynamics model for free variable-pitch vertical axis tidal turbine was established based on D'Alembert principle.Combining this model with viscous CFD method,a multi-body coupling numerical method for analyzing the hydrodynamics of free variable-pitch vertical axis tidal turbine was developed.Coupling algorithms results were compared with experiment results and non-coupling algorithms results,and the effect of self-starting,flow velocity,and load on the performance of the turbine were investigated.Studies have shown that:the developed algorithms can simulate the kinematical characteristics and dynamic characteristics of free variable-pitch vertical axis tidal turbine effectively in all kinds of unsteady process.%基于达朗伯原理建立了自由变偏角水轮机结构动力学模型,并结合粘性CFD方法,形成了一种用于分析自由变偏角潮流能水轮机水动力特性的多体耦合数值计算方法.将该方法与试验及非耦合算法进行了对比分析,并研究了自启动、流速变化和负载变化对水轮机性能的影响规律.研究表明:本文建立的数值计算方法能够有效模拟自由变偏角水轮机在各种非定常过程中的运动特性和动力特性.

  6. Progressive Fault Accommodation for Time-delay Systems with Parametric Faults

    Institute of Scientific and Technical Information of China (English)

    WU Jun-sheng; WENG Zheng-xin; TIAN Zuo-hua

    2009-01-01

    The fault accommodation problem for time-delay system is studied in this paper. The progressive accommodation strategy based on the Newton-Raphson scheme is proposed to solve this problem. This accommodation scheme can significantly reduces the loss of performance and risk associated with system instability which results from the time-delay needed by fault accommodation aigorithms to provide a solution. Simulation results are given to illustrate the efficiency of the provided method.

  7. ACCOMMODATING WORLD ENGLISHES IN DEVELOPING EFL LEARNERS’ ORAL COMMUNICATION

    Directory of Open Access Journals (Sweden)

    Nur Mukminatien

    2012-07-01

    Full Text Available This article aims to discuss issues of World Englishes (WEs and the implications in ELT. It explores the extent to which WEs are taken into account as emerging English varieties different from inner circle varieties, how WEs should be accomodated by English teachers, and which standard to adopt to accommodate learner’s linguistic needs for international communication. It would help ELT practitioners adjust their current practices through the inclusion of varieties of WEs in developing learners’ oral communication. This offers relevant pedagogical movement to argue that changes should be made about the way English is valued and taught.

  8. Functionalised polysiloxanes as injectable, in situ curable accommodating intraocular lenses.

    Science.gov (United States)

    Hao, Xiaojuan; Jeffery, Justine L; Wilkie, John S; Meijs, Gordon F; Clayton, Anthony B; Watling, Jason D; Ho, Arthur; Fernandez, Viviana; Acosta, Carolina; Yamamoto, Hideo; Aly, Mohamed G M; Parel, Jean-Marie; Hughes, Timothy C

    2010-11-01

    The aged eye's ability to change focus (accommodation) may be restored by replacing the hardened natural lens with a soft gel. Functionalised polysiloxane macromonomers, designed for application as an injectable, in situ curable accommodating intraocular lens (A-IOL), were prepared via a two-step synthesis. Prepolymers were synthesised via ring opening polymerisation (ROP) of octamethylcyclotetrasiloxane (D(4)) and 2,4,6,8-tetramethylcyclotetrasiloxane (D(4)(H)) in toluene using trifluoromethanesulfonic acid (TfOH) as catalyst. Hexaethyldisiloxane (HEDS) was used as the end group to control the molecular weight of the prepolymers, which were then converted to macromonomers by hydrosilylation of the SiH groups with allyl methacrylate (AM) to introduce polymerisable groups. The resulting macromonomers had an injectable consistency and thus, were able to be injected into and refill the empty lens capsular bag. The macromonomers also contained a low ratio of polymerisable groups so that they may be cured on demand, in situ, under irradiation of blue light, in the presence of a photo-initiator, to form a soft polysiloxane gel (an intraocular lens) in the eye. The pre-cure viscosity and post-cure modulus of the polysiloxanes, which are crucial factors for an injectable, in situ curable A-IOL application, were controlled by adjusting the end group and D(4)(H) concentrations, respectively, in the ROP. The macromonomers were fully cured within 5 min under light irradiation, as shown by the rapid change in modulus monitored by photo-rheology. Ex vivo primate lens stretching experiments on an Ex Vivo Accommodation Simulator (EVAS) showed that the polysiloxane gel refilled lenses achieved over 60% of the accommodation amplitude of the natural lens. An in vivo biocompatibility study in rabbits using the lens refilling (Phaco-Ersatz) procedure demonstrated that the soft gels had good biocompatibility with the ocular tissue. The polysiloxane macromonomers meet the targeted

  9. Submerged discontent and patterns of accommodation: a case study of doctors' pay in two public hospitals in China.

    Science.gov (United States)

    Cao, Xuebing

    2014-01-01

    The article evaluates submerged discontent among Chinese public hospital doctors (Note1) regarding their pay and patterns of accommodation, including doctors' responses through formal and informal actions in the context of health service marketization. On the basis of a case study of two public hospitals, the article illustrates the dynamical impact of marketization on Chinese doctors' pay-related dissatisfaction and health service employment relationship. Because of the authoritarian management and compliant trade unions, the conflict between doctors and hospitals is unable to be accommodated through collective methods. Instead, doctors' discontent is often channelled through informal, individual and subtle activities. Meanwhile, doctors' professional society is gradually influential, showing its potential of developing doctors' group identity and protecting members' interests in future.

  10. 41 CFR 301-10.160 - What classes of train accommodations are available?

    Science.gov (United States)

    2010-07-01

    ... business-class. (1) First-class—Includes bedrooms, roomettes, club service, parlor car accommodations or other premium accommodations. (2) Business-class—A class of extra fare train service that is offered... only has two classes of accommodations available, i.e., first and business class, then the...

  11. Teaching Adolescent Students with Learning Disabilities to Self-Advocate for Accommodations

    Science.gov (United States)

    Prater, Mary Anne; Redman, Ashleigh Smith; Anderson, Darlene; Gibb, Gordon S.

    2014-01-01

    In the general education classroom students with learning disabilities (LD) often need academic accommodations to be successful. These accommodations are typically selected and implemented by their general education teachers, not by the students themselves. High school students with LD were taught to recognize when an accommodation was needed,…

  12. Predictive Validity of Accommodated LSAT Scores. Technical Report. LSAC Research Report Series.

    Science.gov (United States)

    Thornton, Andrea E.; Reese, Lynda M.; Pashley, Peter J.; Dalessandro, Susan P.

    This study was undertaken to evaluate the predictive validity of the Law School Admission Test (LSAT) earned under accommodated testing conditions. Of special interest was the validity of scores obtained by test takers who were accommodated under nonstandard time conditions (i.e., accommodations that included extra testing time). Separate…

  13. The Use of Computer Technology in Designing Appropriate Test Accommodations for English Language Learners

    Science.gov (United States)

    Abedi, Jamal

    2014-01-01

    Among the several forms of accommodations used in the assessment of English language learners (ELLs), language-based accommodations are the most effective in making assessments linguistically accessible to these students. However, there are significant challenges associated with the implementation of many of these accommodations. This article…

  14. 46 CFR 30.10-2 - Accommodation space-TB/ALL.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 1 2010-10-01 2010-10-01 false Accommodation space-TB/ALL. 30.10-2 Section 30.10-2... Accommodation space—TB/ALL. The term accommodation space means any public space such as a hall, dining room... that contains no cooking appliances, and a similar space open to the passengers and crew....

  15. Partial and total actuator faults accommodation for input-affine nonlinear process plants.

    Science.gov (United States)

    Mihankhah, Amin; Salmasi, Farzad R; Salahshoor, Karim

    2013-05-01

    In this paper, a new fault-tolerant control system is proposed for input-affine nonlinear plants based on Model Reference Adaptive System (MRAS) structure. The proposed method has the capability to accommodate both partial and total actuator failures along with bounded external disturbances. In this methodology, the conventional MRAS control law is modified by augmenting two compensating terms. One of these terms is added to eliminate the nonlinear dynamic, while the other is reinforced to compensate the distractive effects of the total actuator faults and external disturbances. In addition, no Fault Detection and Diagnosis (FDD) unit is needed in the proposed method. Moreover, the control structure has good robustness capability against the parameter variation. The performance of this scheme is evaluated using a CSTR system and the results were satisfactory.

  16. Knee Kinematics Estimation Using Multi-Body Optimisation Embedding a Knee Joint Stiffness Matrix: A Feasibility Study.

    Science.gov (United States)

    Richard, Vincent; Lamberto, Giuliano; Lu, Tung-Wu; Cappozzo, Aurelio; Dumas, Raphaël

    2016-01-01

    The use of multi-body optimisation (MBO) to estimate joint kinematics from stereophotogrammetric data while compensating for soft tissue artefact is still open to debate. Presently used joint models embedded in MBO, such as mechanical linkages, constitute a considerable simplification of joint function, preventing a detailed understanding of it. The present study proposes a knee joint model where femur and tibia are represented as rigid bodies connected through an elastic element the behaviour of which is described by a single stiffness matrix. The deformation energy, computed from the stiffness matrix and joint angles and displacements, is minimised within the MBO. Implemented as a "soft" constraint using a penalty-based method, this elastic joint description challenges the strictness of "hard" constraints. In this study, estimates of knee kinematics obtained using MBO embedding four different knee joint models (i.e., no constraints, spherical joint, parallel mechanism, and elastic joint) were compared against reference kinematics measured using bi-planar fluoroscopy on two healthy subjects ascending stairs. Bland-Altman analysis and sensitivity analysis investigating the influence of variations in the stiffness matrix terms on the estimated kinematics substantiate the conclusions. The difference between the reference knee joint angles and displacements and the corresponding estimates obtained using MBO embedding the stiffness matrix showed an average bias and standard deviation for kinematics of 0.9±3.2° and 1.6±2.3 mm. These values were lower than when no joint constraints (1.1±3.8°, 2.4±4.1 mm) or a parallel mechanism (7.7±3.6°, 1.6±1.7 mm) were used and were comparable to the values obtained with a spherical joint (1.0±3.2°, 1.3±1.9 mm). The study demonstrated the feasibility of substituting an elastic joint for more classic joint constraints in MBO.

  17. Knee Kinematics Estimation Using Multi-Body Optimisation Embedding a Knee Joint Stiffness Matrix: A Feasibility Study.

    Directory of Open Access Journals (Sweden)

    Vincent Richard

    Full Text Available The use of multi-body optimisation (MBO to estimate joint kinematics from stereophotogrammetric data while compensating for soft tissue artefact is still open to debate. Presently used joint models embedded in MBO, such as mechanical linkages, constitute a considerable simplification of joint function, preventing a detailed understanding of it. The present study proposes a knee joint model where femur and tibia are represented as rigid bodies connected through an elastic element the behaviour of which is described by a single stiffness matrix. The deformation energy, computed from the stiffness matrix and joint angles and displacements, is minimised within the MBO. Implemented as a "soft" constraint using a penalty-based method, this elastic joint description challenges the strictness of "hard" constraints. In this study, estimates of knee kinematics obtained using MBO embedding four different knee joint models (i.e., no constraints, spherical joint, parallel mechanism, and elastic joint were compared against reference kinematics measured using bi-planar fluoroscopy on two healthy subjects ascending stairs. Bland-Altman analysis and sensitivity analysis investigating the influence of variations in the stiffness matrix terms on the estimated kinematics substantiate the conclusions. The difference between the reference knee joint angles and displacements and the corresponding estimates obtained using MBO embedding the stiffness matrix showed an average bias and standard deviation for kinematics of 0.9±3.2° and 1.6±2.3 mm. These values were lower than when no joint constraints (1.1±3.8°, 2.4±4.1 mm or a parallel mechanism (7.7±3.6°, 1.6±1.7 mm were used and were comparable to the values obtained with a spherical joint (1.0±3.2°, 1.3±1.9 mm. The study demonstrated the feasibility of substituting an elastic joint for more classic joint constraints in MBO.

  18. A flexible multi-body approach for frictional contact in spur gears

    Science.gov (United States)

    Lundvall, O.; Strömberg, N.; Klarbring, A.

    2004-12-01

    In the present paper, a large rotational approach for dynamic contact problems with friction is proposed. The approach is used for modelling a spur gear pair with shafts and bearings. The model is obtained by superposing small displacement elasticity on rigid-body motions, and postulating tribological laws on the gear flanks. The finite element method is used to model the elastic properties of the gear pair. Shafts and bearings are represented by linear springs. The tribological laws of the contact interface are Signorini's contact law and Coulomb's law of friction. An important feature of the approach is that the difficulties of impacting mass nodes are avoided. The governing equations of the model are numerically treated by use of the augmented Lagrangian approach. In such manner the geometry of the gear flanks are well represented in the numerical simulations. It is possible to study accurately the consequences of different types of profile modifications as well as flank errors. In this work, the dynamic transmission error is studied. For instance, it turns out that the effect from profile modification is less significant for the transmission error when frictional effects are included.

  19. Can mergers-in-progress be unmerged in speech accommodation?

    Directory of Open Access Journals (Sweden)

    Molly eBabel

    2013-09-01

    Full Text Available This study examines spontaneous phonetic accommodation of a dialect with distinct categories by speakers who are in the process of merging those categories. We focus on the merger of the NEAR and SQUARE lexical sets in New Zealand English, presenting New Zealand participants with an unmerged speaker of Australian English. Mergers-in-progress are a uniquely interesting sound change as they showcase the asymmetry between speech perception and production. Yet, we examine mergers using spontaneous phonetic imitation, which is phenomenon that is necessarily a behavior where perceptual input influences speech production. Phonetic imitation is quantified by a perceptual measure and an acoustic calculation of mergedness using a Pillai-Bartlett trace. The results from both analyses indicate spontaneous phonetic imitation is moderated by extra-linguistic factors such as the valence of assigned conditions and social bias. We also find evidence for a decrease in the degree of mergedness in post-exposure productions. Taken together, our results suggest that under the appropriate conditions New Zealanders phonetically accommodate to Australian English and that in the process of speech imitation, mergers-in-progress can, but do not consistently, become less merged.

  20. Validation of a nonrigid registration framework that accommodates tissue resection

    Science.gov (United States)

    Risholm, Petter; Samset, Eigil; Wells, William, III

    2010-03-01

    We present a 3D extension and validation of an intra-operative registration framework that accommodates tissue resection. The framework is based on the bijective Demons method, but instead of regularizing with the traditional Gaussian smoother, we apply an anisotropic diffusion filter with the resection modeled as a diffusion sink. The diffusion sink prevents unwanted Demon forces that originates from the resected area from diffusing into the surrounding area. Another attractive property of the diffusion sink is the resulting continuous deformation field across the diffusion sink boundary, which allows us to move the boundary of the diffusion sink without changing values in the deformation field. The area of resection is estimated by a level-set method evolving in the space of image intensity disagreements in the intra-operative image domain. A product of using the bijective Demons method is that we can also provide an accurate estimate of the resected tissue in the preoperative image space. Validation of the proposed method was performed on a set of 25 synthetic images. Our experiments show a significant improvement in accommodating resection using the proposed method compared to two other Demons based methods.

  1. Accommodation coefficient of HOBr on deliquescent sodium bromide aerosol particles

    Directory of Open Access Journals (Sweden)

    M. Wachsmuth

    2002-01-01

    Full Text Available Uptake of HOBr on sea salt aerosol, sea salt brine or ice is believed to be a key process providing a source of photolabile bromine (Br2 and sustaining ozone depletion cycles in the Arctic troposphere. In the present study, uptake of HOBr on sodium bromide (NaBr aerosol particles was investigated at an extremely low HOBr concentration of 300 cm-3 using the short-lived radioactive isotopes 83-86Br. Under these conditions, at maximum one HOBr molecule was taken up per particle. The rate of uptake was clearly limited by the mass accommodation coefficient, which was calculated to be 0.6 ± 0.2. This value is a factor of 10 larger than estimates used in earlier models. The atmospheric implications are discussed using the box model "MOCCA'', showing that the increase of the accommodation coefficient of HOBr by a factor of 10 only slightly affects net ozone loss, but significantly increases chlorine release.

  2. H2S, a novel gasotransmitter, involves in gastric accommodation.

    Science.gov (United States)

    Xiao, Ailin; Wang, Hongjuan; Lu, Xin; Zhu, Jianchun; Huang, Di; Xu, Tonghui; Guo, Jianqiang; Liu, Chuanyong; Li, Jingxin

    2015-11-04

    H2S is produced mainly by two enzymes:cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE), using L-cysteine (L-Cys) as the substrate. In this study, we investigated the role of H2S in gastric accommodation using CBS(+/-) mice, immunohistochemistry, immunoblot, methylene blue assay, intragastric pressure (IGP) recording and electrical field stimulation (EFS). Mouse gastric fundus expressed H2S-generating enzymes (CBS and CSE) and generated detectable amounts of H2S. The H2S donor, NaHS or L-Cys, caused a relaxation in either gastric fundus or body. The gastric compliance was significantly increased in the presence of L-Cys (1 mM). On the contrary, AOAA, an inhibitor for CBS, largely inhibited gastric compliance. Consistently, CBS(+/-) mice shows a lower gastric compliance. However, PAG, a CSE inhibitor, had no effect on gastric compliances. L-Cys enhances the non-adrenergic, non-cholinergic (NANC) relaxation of fundus strips, but AOAA reduces the magnitude of relaxations to EFS. Notably, the expression level of CBS but not CSE protein was elevated after feeding. Consistently, the production of H2S was also increased after feeding in mice gastric fundus. In addition, AOAA largely reduced food intake and body weight in mice. Furthermore, a metabolic aberration of H2S was found in patients with functional dyspepsia (FD). In conclusion, endogenous H2S, a novel gasotransmitter, involves in gastric accommodation.

  3. Science Language Accommodation in Elementary School Read-Alouds

    Science.gov (United States)

    Glass, Rory; Oliveira, Alandeom W.

    2014-03-01

    This study examines the pedagogical functions of accommodation (i.e. provision of simplified science speech) in science read-aloud sessions facilitated by five elementary teachers. We conceive of read-alouds as communicative events wherein teachers, faced with the task of orally delivering a science text of relatively high linguistic complexity, open up an alternate channel of communication, namely oral discussion. By doing so, teachers grant students access to a simplified linguistic input, a strategy designed to promote student comprehension of the textual contents of children's science books. It was found that nearly half (46%) of the read-aloud time was allotted to discussions with an increased percentage of less sophisticated words and reduced use of more sophisticated vocabulary than found in the books through communicative strategies such as simplified rewording, simplified definition, and simplified questioning. Further, aloud reading of more linguistically complex books required longer periods of discussion and an increased degree of teacher oral input and accommodation. We also found evidence of reversed simplification (i.e. sophistication), leading to student uptake of scientific language. The main significance of this study is that it reveals that teacher talk serves two often competing pedagogical functions (accessible communication of scientific information to students and promotion of student acquisition of the specialized language of science). It also underscores the importance of giving analytical consideration to the simplification-sophistication dimension of science classroom discourse as well as the potential of computer-based analysis of classroom discourse to inform science teaching.

  4. The Effects of Branding on Purchasing Preferences of Tourists at Accommodation Enterprises: An Implementation at Chain Accommodation Enterprises in Antalya

    Directory of Open Access Journals (Sweden)

    Banu Yıldız

    2013-09-01

    Full Text Available The aim of this study is to determine the effect of branding on the purchasing preferences of tourists at accommodation enterprises. Towards this end questionnaire technique was used and 398 questionnaires were considered to be evaluated. The data, gathered, analyzed by using statistical methods. As a result it is revealed that branding (brad awareness, perceived quality, brand image, brand trust, brand attitude and brand loyalty parameters has a positive effect on purchasing preferences of tourists and a negative effect on the volume of perceived risk. Factors contributing to more on purchasing preferences of tourists, respectively, brand attitude, brand loyalty and brand awareness.

  5. Dynamic Analysis of Offshore Oil Pipe Installation Using the Absolute Nodal Coordinate Formulation

    DEFF Research Database (Denmark)

    Nielsen, Jimmy D; Madsen, Søren B; Hyldahl, Per Christian;

    2013-01-01

    centrifugal and Coriolis forces [12]. This makes the method attractive for multibody dynamics implementation. The focus in this paper is the application of ANCF beam elements and their performance on large deformation dynamic analysis. Large dynamic deformation is characteristic for the installation process...... of offshore submerged oil pipes using oceangoing vessels. In this investigation such an oil pipe is modeled using ANCF beam elements to simulate the dynamic behavior of the pipe during the installation process. Multiple physical effects such as gravity, buoyancy, seabed contact, and fluid damping...

  6. Multi-Scale Dynamics, Control, and Simulation of Granular Spacecraft

    Science.gov (United States)

    Quadrelli, Marco B.; Basinger, Scott; Swartzlander, Grover

    2013-01-01

    In this paper, we present some ideas regarding the modeling, dynamics and control aspects of granular spacecraft. Granular spacecraft are complex multibody systems composed of a spatially disordered distribution of a large number of elements, for instance a cloud of grains in orbit. An example of application is a spaceborne observatory for exoplanet imaging, where the primary aperture is a cloud instead of a monolithic aperture. A model is proposed of a multi-scale dynamics of the grains and cloud in orbit, as well as a control approach for cloud shape maintenance and alignment, and preliminary simulation studies are carried out for the representative imaging system.

  7. Dynamic Analysis of The Intelligent Sprayer Boom

    DEFF Research Database (Denmark)

    Wiggers, Sine Leergaard; Maagaard, Jørgen; Terp, Christian Istjord

    and not the surroundings. However this requires that the boom movements are predictable and based on data from field tests. At field tests a first version of the newly developed camera system was tested in 2010. At the field test it was found that the vertical boom movements where too big for the camera weed prediction...... system to work properly. At the University of Southern Denmark (SDU) a patent for an active damping system of the sprayer boom has been obtained. The subject of this paper is analysis of the dynamics of the Sprayer boom. The analysis is based on a Multibody Dynamics model of the sprayer boom and is made...... in Matlab. The model is made in order to analyse the boom movements. The purpose of the model is to support the development of the patented active damping system for the sprayer boom. The Multibody Dynamics model has been made based on data retrieved from a CAD model and a Finite Element model...

  8. The effect of proximity on open-loop accommodation responses measured with pinholes.

    Science.gov (United States)

    Morrison, K A; Seidel, D; Strang, N C; Gray, L S

    2010-07-01

    Open-loop accommodation levels were measured in 41 healthy, young subjects using a Shin-Nippon SRW-5000 autorefractor in the three viewing conditions: a small physical pinhole pupil (SP), an optically projected pinhole in Maxwellian view (MV) and in the dark (DF). The target viewed through the pinholes was a high-contrast letter presented at 0 D vergence in a +5 D Badal lens system. Overall, results showed that SP open-loop accommodation levels were significantly higher than MV and DF levels. Subjects could be divided into two distinct subgroups according to their response behaviour: responders to the proximal effect of the small physical pinhole (SP accommodation > MV accommodation) and non-responders to the proximal effect of the small physical pinhole (SP accommodation approximately MV accommodation). Correlation analysis demonstrated that open-loop accommodation for both pinhole conditions was correlated with DF for the responders, while for the non-responders SP and MV accommodation were correlated, but were not related to DF accommodation. This suggests that under open-loop conditions some individuals' accommodation levels are mainly affected by proximal and cognitive factors (responders) while others are guided primarily by the presence of the more distal target (non-responders). In conclusion, MV reduces the proximal effect of the physical pinhole and produces open-loop accommodation responses which are more consistent than SP and DF responses.

  9. Sensory outcome with nonsurgical management of esotropia with convergence excess (a high accommodative convergence/accommodation ratio).

    Science.gov (United States)

    Pratt-Johnson, J A; Tillson, G

    1984-08-01

    Twenty-seven patients with esotropia and convergence excess (a high accommodative convergence/accommodation [AC/A] ratio) managed nonsurgically underwent a final standardized evaluation of their sensory and motor status after a follow-up period of at least 8 years. All had a deviation with distance fixation of less than 10 prism dioptres (PD) of esotropia with full optical correction both initially and throughout the follow-up period. The average spherical-equivalent refractive error was +2.3 D. The AC/A ratio had tended to decrease with age, and most patients had fusion, although only a small proportion had central fusion and stereopsis. Approximately half of the patients had been treated with bifocals, but their sensory outcome did not differ from that of the other patients. Miotics had not been used for more than a few months in any patient, as they were ineffective in reducing the deviation with near fixation to less than 10 PD of esotropia. A study, possibly a multicentre one, involving larger numbers of patients should be designed to find out whether bifocal therapy offers an advantage in the final sensory outcome of such patients.

  10. Symptomatic accommodative disorders and asthenopia: Prevalence and association in Ghanaian children

    Directory of Open Access Journals (Sweden)

    Charles Darko-Takyi

    2016-03-01

    Full Text Available Background: There is a scarcity of data on asthenopia and accommodative disorders in children in Ghana as optometrists sometimes fail to carry out comprehensive assessments because of the lack of appropriate instruments.Aim: To establish the prevalence of asthenopic symptoms and symptomatic accommodative disorders among Junior High School children in Cape Coast metropolis (in their habitual vision state and to investigate if there are any associations between asthenopic symptoms and the disorders.Method: A prospective cross-sectional school-based study using a multistage sample of 627 participants aged 12–17 years from Junior High Schools in Cape Coast metropolis, Ghana, was conducted. Participants completed a reliable asthenopic symptoms questionnaire (Cronbach’s α = 0.866, and 220 participants who expressed two or more severe or very severe symptoms were selected for comprehensive accommodative system assessment over their habitual vision state.Results: The prevalence of symptoms of asthenopia (two or more severe or very severe and symptomatic accommodative disorders were 35.1% and 17.4% respectively. For specific symptomatic accommodative disorders, the prevalence was as follows: 7.7% accommodative insufficiency, 4.5% accommodative infacility, 1.4% accommodative excess and 3.8% accommodative fatigue. There were significant associations between some specific accommodative disorders and some specific asthenopic symptoms even though these asthenopic symptoms overlapped in other accommodative disorders.Conclusion: Specific asthenopic symptoms do not discriminate between the presences of specific types of accommodative disorders. A comprehensive accommodative system assessment with appropriate instruments is relevant to the diagnosis and management of accommodative disorders to relieve asthenopic symptoms.

  11. From time series analysis to a biomechanical multibody model of the human eye

    Energy Technology Data Exchange (ETDEWEB)

    Pascolo, P. [Dipartimento di Ingegneria Civile, Universita di Udine, Udine (Italy); Dipartimento di Bioingegneria, CISM, Udine (Italy)], E-mail: paolo.pascolo@uniud.it; Carniel, R. [Dipartimento di Georisorse e Territorio, Universita di Udine, Udine (Italy)], E-mail: roberto.carniel@uniud.it

    2009-04-30

    A mechanical model of the human eye is presented aimed at estimating the level of muscular activation. The applicability of the model in the biomedical field is discussed. Human eye movements studied in the laboratory are compared with the ones produced by a virtual eye described in kinematical terms and subject to the dynamics of six actuators, as many as the muscular systems devoted to the eye motion control. The definition of an error function between the experimental and the numerical response and the application of a suitable law that links activation and muscular force are at the base of the proposed methodology. The aim is the definition of a simple conceptual tool that could help the specialist in the diagnosis of potential physiological disturbances of saccadic and nystagmic movements but can also be extended in a second phase when more sophisticated data become available. The work is part of a collaboration between the Functional Mechanics Laboratory of the University and the Neurophysiopatology Laboratory of the 'S. Maria della Misericordia' Hospital in Udine, Italy.

  12. Disturbance Accommodating Adaptive Control with Application to Wind Turbines

    Science.gov (United States)

    Frost, Susan

    2012-01-01

    Adaptive control techniques are well suited to applications that have unknown modeling parameters and poorly known operating conditions. Many physical systems experience external disturbances that are persistent or continually recurring. Flexible structures and systems with compliance between components often form a class of systems that fail to meet standard requirements for adaptive control. For these classes of systems, a residual mode filter can restore the ability of the adaptive controller to perform in a stable manner. New theory will be presented that enables adaptive control with accommodation of persistent disturbances using residual mode filters. After a short introduction to some of the control challenges of large utility-scale wind turbines, this theory will be applied to a high-fidelity simulation of a wind turbine.

  13. Automation for Accommodating Fuel-Efficient Descents in Constrained Airspace

    Science.gov (United States)

    Coopenbarger, Richard A.

    2010-01-01

    Continuous descents at low engine power are desired to reduce fuel consumption, emissions and noise during arrival operations. The challenge is to allow airplanes to fly these types of efficient descents without interruption during busy traffic conditions. During busy conditions today, airplanes are commonly forced to fly inefficient, step-down descents as airtraffic controllers work to ensure separation and maximize throughput. NASA in collaboration with government and industry partners is developing new automation to help controllers accommodate continuous descents in the presence of complex traffic and airspace constraints. This automation relies on accurate trajectory predictions to compute strategic maneuver advisories. The talk will describe the concept behind this new automation and provide an overview of the simulations and flight testing used to develop and refine its underlying technology.

  14. Method for compensating bellows pressure loads while accommodating thermal deformations

    Energy Technology Data Exchange (ETDEWEB)

    Woodle, M.H.

    1985-01-01

    Many metal bellows are used on storage ring vacuum chambers. They allow the ring to accommodate deformations associated with alignment, mechanical assembly and thermal expansion. The NSLS has two such electron storage rings, the vuv ring and the x-ray ring. Both rings utilize a number of welded metal bellows within the ring and at every beam port. There are provisions for 16 beam ports on the vuv and 28 ports in the x-ray ring. At each of these locations the bellows are acted on by an external pressure of 1 atmosphere, which causes a 520 lb reaction at the vacuum chamber beam port and at the beamline flange downstream of the bellows. The use of rigid tie rods across the bellows flanges to support this load is troublesome because most storage ring vacuum chambers are baked in situ to achieve high internal vacuum. Significant forces can develop on components if thermal deformation is restrained and damage could occur.

  15. Communication accommodation and managing musculoskeletal disorders: doctors' and patients' perspectives.

    Science.gov (United States)

    Baker, Susan C; Gallois, Cindy; Driedger, S Michelle; Santesso, Nancy

    2011-06-01

    This study examined the ways in which health care providers (general practitioners and specialists) and patients communicate with each other about managing musculoskeletal (MSK) disorders, a major cause of long-term pain and physical disability. In managing their illness, patients must interact closely with health care providers, who play a large role in transferring knowledge to them. In-depth interviews with patients, general practitioners, and specialist rheumatologists in Australia and Canada were analyzed using Leximancer (a text-mining tool). Results indicated that, in their communication, doctors subtly emphasized accepting and adjusting to the illness ("new normal"), whereas patients emphasized pain relief and getting "back to normal." These results suggest that doctors and patients should accommodate in their communication across subtle and often unexpressed differences in the priorities of provider and patient, or they are likely to be at cross purposes and thus less effective.

  16. Baudoinia, a new genus to accommodate Torula compniacensis.

    Science.gov (United States)

    Scott, James A; Untereiner, Wendy A; Ewaze, Juliet O; Wong, Bess; Doyle, David

    2007-01-01

    Baudoinia gen. nov. is described to accommodate Torula compniacensis. Reported originally from the walls of buildings near brandy maturation warehouses in Cognac, France, species of Baudoinia are cosmopolitan colonists of exposed surfaces subjected to large diurnal temperature shifts, episodic high relative humidity and wetting, and ambient airborne ethanol. Morphologically B. compniacensis resembles some anamorphic Mycosphaerellaceae in possessing dark brown, nonseptate or uniseptate conidia with coarsely roughened walls that are borne acropetally in unbranched chains and released by schizolytic dehiscence. Analysis of partial nuclear rDNA SSU sequences positions B. compniacensis in the order Capnodiales and reveals that it is most closely related to the microcolonial genus Friedmanniomyces. Heat resistance is induced by brief sublethal temperature exposure.

  17. Dynamics

    CERN Document Server

    Goodman, Lawrence E

    2001-01-01

    Beginning text presents complete theoretical treatment of mechanical model systems and deals with technological applications. Topics include introduction to calculus of vectors, particle motion, dynamics of particle systems and plane rigid bodies, technical applications in plane motions, theory of mechanical vibrations, and more. Exercises and answers appear in each chapter.

  18. Effect of interfacial turbulence and accommodation coefficient on CFD predictions of pressurization and pressure control in cryogenic storage tank

    Science.gov (United States)

    Kassemi, Mohammad; Kartuzova, Olga

    2016-03-01

    Pressurization and pressure control in cryogenic storage tanks are to a large extent affected by heat and mass transport across the liquid-vapor interface. These mechanisms are, in turn, controlled by the kinetics of the phase change process and the dynamics of the turbulent recirculating flows in the liquid and vapor phases. In this paper, the effects of accommodation coefficient and interfacial turbulence on tank pressurization and pressure control simulations are examined. Comparison between numerical predictions and ground-based measurements in two large liquid hydrogen tank experiments, performed in the K-site facility at NASA Glenn Research Center (GRC) and the Multi-purpose Hydrogen Test Bed (MHTB) facility at NASA Marshall Space Flight Center (MSFC), are used to show the impact of accommodation coefficient and interfacial and vapor phase turbulence on evolution of pressure and temperatures in the cryogenic storage tanks. In particular, the self-pressurization comparisons indicate that: (1) numerical predictions are essentially independent of the magnitude of the accommodation coefficient; and (2) surprisingly, laminar models sometimes provide results that are in better agreement with experimental self-pressurization rates, even in parametric ranges where the bulk flow is deemed fully turbulent. In this light, shortcomings of the present CFD models, especially, numerical treatments of interfacial mass transfer and turbulence, as coupled to the Volume-of-Fluid (VOF) interface capturing scheme, are underscored and discussed.

  19. Dynamic Simulation for Missile Erection System

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In order to study the dynamic characteristics of the missile erection system, it can be considered as a rigid-flexible coupling multi-body system. Firstly, the actual system is abstracted as an equal and simplified one and then the forces applied to it are analyzed. Secondly, the rigid-flexible coupling dynamic simulation for erection system is accomplished by use of the system simulation software, for example Pro/E, ADAMS, ANSYS, MATLAB/Simulink, etc. Finally, having the aid of simulation results, the kinetic and dynamic characteristics of the flexible bodies in erection system are analyzed.The simulation considering the erection system as a rigid-flexible coupling system can provide valuable results to the research of its kinetic, dynamic and vibrational characteristics.

  20. Structure and thermodynamics of a mixture of patchy and spherical colloids: A multi-body association theory with complete reference fluid information.

    Science.gov (United States)

    Bansal, Artee; Asthagiri, D; Cox, Kenneth R; Chapman, Walter G

    2016-08-21

    A mixture of solvent particles with short-range, directional interactions and solute particles with short-range, isotropic interactions that can bond multiple times is of fundamental interest in understanding liquids and colloidal mixtures. Because of multi-body correlations, predicting the structure and thermodynamics of such systems remains a challenge. Earlier Marshall and Chapman [J. Chem. Phys. 139, 104904 (2013)] developed a theory wherein association effects due to interactions multiply the partition function for clustering of particles in a reference hard-sphere system. The multi-body effects are incorporated in the clustering process, which in their work was obtained in the absence of the bulk medium. The bulk solvent effects were then modeled approximately within a second order perturbation approach. However, their approach is inadequate at high densities and for large association strengths. Based on the idea that the clustering of solvent in a defined coordination volume around the solute is related to occupancy statistics in that defined coordination volume, we develop an approach to incorporate the complete information about hard-sphere clustering in a bulk solvent at the density of interest. The occupancy probabilities are obtained from enhanced sampling simulations but we also develop a concise parametric form to model these probabilities using the quasichemical theory of solutions. We show that incorporating the complete reference information results in an approach that can predict the bonding state and thermodynamics of the colloidal solute for a wide range of system conditions.

  1. Structure and thermodynamics of a mixture of patchy and spherical colloids: A multi-body association theory with complete reference fluid information

    Science.gov (United States)

    Bansal, Artee; Asthagiri, D.; Cox, Kenneth R.; Chapman, Walter G.

    2016-08-01

    A mixture of solvent particles with short-range, directional interactions and solute particles with short-range, isotropic interactions that can bond multiple times is of fundamental interest in understanding liquids and colloidal mixtures. Because of multi-body correlations, predicting the structure and thermodynamics of such systems remains a challenge. Earlier Marshall and Chapman [J. Chem. Phys. 139, 104904 (2013)] developed a theory wherein association effects due to interactions multiply the partition function for clustering of particles in a reference hard-sphere system. The multi-body effects are incorporated in the clustering process, which in their work was obtained in the absence of the bulk medium. The bulk solvent effects were then modeled approximately within a second order perturbation approach. However, their approach is inadequate at high densities and for large association strengths. Based on the idea that the clustering of solvent in a defined coordination volume around the solute is related to occupancy statistics in that defined coordination volume, we develop an approach to incorporate the complete information about hard-sphere clustering in a bulk solvent at the density of interest. The occupancy probabilities are obtained from enhanced sampling simulations but we also develop a concise parametric form to model these probabilities using the quasichemical theory of solutions. We show that incorporating the complete reference information results in an approach that can predict the bonding state and thermodynamics of the colloidal solute for a wide range of system conditions.

  2. Real-space finite-difference approach for multi-body systems: path-integral renormalization group method and direct energy minimization method.

    Science.gov (United States)

    Sasaki, Akira; Kojo, Masashi; Hirose, Kikuji; Goto, Hidekazu

    2011-11-02

    The path-integral renormalization group and direct energy minimization method of practical first-principles electronic structure calculations for multi-body systems within the framework of the real-space finite-difference scheme are introduced. These two methods can handle higher dimensional systems with consideration of the correlation effect. Furthermore, they can be easily extended to the multicomponent quantum systems which contain more than two kinds of quantum particles. The key to the present methods is employing linear combinations of nonorthogonal Slater determinants (SDs) as multi-body wavefunctions. As one of the noticeable results, the same accuracy as the variational Monte Carlo method is achieved with a few SDs. This enables us to study the entire ground state consisting of electrons and nuclei without the need to use the Born-Oppenheimer approximation. Recent activities on methodological developments aiming towards practical calculations such as the implementation of auxiliary field for Coulombic interaction, the treatment of the kinetic operator in imaginary-time evolutions, the time-saving double-grid technique for bare-Coulomb atomic potentials and the optimization scheme for minimizing the total-energy functional are also introduced. As test examples, the total energy of the hydrogen molecule, the atomic configuration of the methylene and the electronic structures of two-dimensional quantum dots are calculated, and the accuracy, availability and possibility of the present methods are demonstrated.

  3. Optimal secondary coil design for inductive powering of the Artificial Accommodation System.

    Science.gov (United States)

    Nagel, J A; Krug, M; Gengenbach, U; Guth, H; Bretthauer, G; Guthoff, R F

    2011-01-01

    Age-related ailments like presbyopia and cataract are increasing concerns in the aging society. Both go along with a loss of ability to accommodate. A new approach to restore the patients' ability to accommodate is the Artificial Accommodation System. This micro mechatronic system will be implanted into the capsular bag to replace the human crystalline lens. Depending on the patients' actual need for accommodation, the Artificial Accommodation System autonomously adapts the refractive power of its integrated optical element in a way that the projection on the patients' retina results in a sharp image. As the Artificial Accommodation System is an active implant, its subsystems have to be supplied with electrical energy. Evolving technologies, like energy harvesting, which can potentially be used to power an implant like the Artificial Accommodation System are at the current state of art not sufficient to power the Artificial Accommodation System autonomously [1]. In the near future, therefore an inductive power supply system will be developed which includes an energy storage to power the Artificial Accommodation System autonomously over a period of 24 h and can be recharged wirelessly. This Paper describes a new possibility to optimize the secondary coil design in a solely analytical way, based on a new figure of merit. Within this paper the developed figure of merit is applied to optimize the secondary coil design for the Artificial Accommodation System.

  4. The Assessment of Accommodation and Convergence System in the Bank Employees

    Directory of Open Access Journals (Sweden)

    Monireh Mahjoob

    2013-02-01

    Full Text Available Background: Regarding the high outbreak rate of the eye disorders and problems particularly accommodation disorders and convergence insufficiency in computer users, the study tries to determine the convergence, accommodation system, condition, fusion reserves and vision dimension in bank employees (who work with computers and the control group (who are not computer users and then to compare the mentioned parameters in the two groups. Materials and Methods: In this cross-sectional and observational study a total of 44 bank employees and 44 people as the control group members were selected randomly. Initially, refractive problems were reformed, and then accommodation, convergence and vision dimension evaluative tests were conducted. The test included measuring the near point of convergence, jump convergence, phoria, accommodation range (one eye, both eyes, ease of accommodation (one eye, both eyes, positive and negative related accommodation, near fusion versions and TNO.Results: Our results showed that there was a not significant difference among the near point of convergence, jump convergence, near phoria, accommodation range (one eye and both eyes, ease of accommodation (one eye, both eyes, positive and negative related accommodation in bank employees and control group.Conclusion: Regarding the studies, the outbreak rate of accommodation and convergence disorders is higher in bank employees than the control group which would be due to over working with computer within a fixed interval.

  5. The rate of change of vergence-accommodation conflict affects visual discomfort.

    Science.gov (United States)

    Kim, Joohwan; Kane, David; Banks, Martin S

    2014-12-01

    Stereoscopic (S3D) displays create conflicts between the distance to which the eyes must converge and the distance to which the eyes must accommodate. Such conflicts require the viewer to overcome the normal coupling between vergence and accommodation, and this effort appears to cause viewer discomfort. Vergence-accommodation coupling is driven by the phasic components of the underlying control systems, and those components respond to relatively fast changes in vergence and accommodative stimuli. Given the relationship between phasic changes and vergence-accommodation coupling, we examined how the rate of change in the vergence-accommodation conflict affects viewer discomfort. We used a stereoscopic display that allows independent manipulation of the stimuli to vergence and accommodation. We presented stimuli that simulate natural viewing (i.e., vergence and accommodative stimuli changed together) and stimuli that simulate S3D viewing (i.e., vergence stimulus changes but accommodative stimulus remains fixed). The changes occurred at 0.01, 0.05, or 0.25 Hz. The lowest rate is too slow to stimulate the phasic components while the highest rate is well within the phasic range. The results were consistent with our expectation: somewhat greater discomfort was experienced when stimulus distance changed rapidly, particularly in S3D viewing when the vergence stimulus changed but the accommodative stimulus did not. These results may help in the generation of guidelines for the creation and viewing of stereo content with acceptable viewer comfort.

  6. Breakdown of accommodation in nerve: a possible role for persistent sodium current

    Directory of Open Access Journals (Sweden)

    Andersen Ole K

    2005-04-01

    Full Text Available Abstract Background Accommodation and breakdown of accommodation are important elements of information processing in nerve fibers, as they determine how nerve fibers react to natural slowly changing stimuli or electrical stimulation. The aim of the present study was to elucidate the biophysical mechanism of breakdown of accommodation, which at present is unknown. Results A model of a space-clamped motor nerve fiber was developed. It was found that this new model could reproduce breakdown of accommodation when it included a low-threshold, rapidly activating, persistent sodium current. However, the phenomenon was not reproduced when the persistent sodium current did not have fast activation kinetics or a low activation threshold. Conclusion The present modeling study suggests that persistent, low-threshold, rapidly activating sodium currents have a key role in breakdown of accommodation, and that breakdown of accommodation can be used as a tool for studying persistent sodium current under normal and pathological conditions.

  7. A slide rule for calculating the ocular accommodation of an ametrope corrected with a spectacle lens.

    Science.gov (United States)

    Wang, Guang-Ji

    2007-07-01

    A slide rule has been designed to calculate the ocular accommodation of an ametrope corrected with a spectacle lens. The slide rule makes the calculation itself easier to perform than with traditional methods and is easily applicable in a clinical setting. In the slide rule, there are 3 scales indicating the power of the spectacle lens, the viewing distance, and the ocular accommodation. The most accurate accommodative unit was used to design the slide rule. The ocular accommodation is the product of the accommodative unit and the dioptric viewing distance. The calculating results are accurate from +21 diopters to all minus powers of the spectacle lens. In a clinical setting, the patients can be advised how much accommodation they exert before and after the refractive surgeries.

  8. The Effect of Child Distress on Accommodation of Anxiety: Relations With Maternal Beliefs, Empathy, and Anxiety.

    Science.gov (United States)

    Settipani, Cara A; Kendall, Philip C

    2015-12-16

    Little is known about the influence of child behaviors on accommodation of anxiety and how accommodation relates to other parent factors. The present study examined the comparative effect of high and low levels of child distress on mother-reported accommodation, mother factors in relation to accommodation, and moderators of the relation between accommodation and child distress. Maternal perceptions of accommodation were measured by vignettes depicting youth exhibiting high or low levels of distress in anxiety-provoking situations that elicited social anxiety, generalized anxiety, or separation anxiety in a sample of 7- to 17-year-old youth with anxiety disorders (N = 70, M = 11.66, 47.1% male). Findings indicated an effect of child distress on mother-reported accommodation of youth anxiety, such that mothers reported more overall accommodation under conditions of high child distress; situation-level analyses revealed this effect for social and generalized anxiety situations. Furthermore, an association was found between greater mother-reported accommodation and more negative beliefs about their child's experience of anxiety, which held across situations. Maternal empathy moderated the relation between overall accommodation and child distress. Maternal anxiety also moderated the relation between accommodation and child distress, with results varying based on situation type. Findings, consistent with theory, indicate a relation between child distress and mother-reported accommodation and suggest that maternal beliefs about anxiety are an important treatment target. High maternal empathy may be related to a greater degree of adaptability in response to child behaviors, whereas maternal anxiety may be linked with less adaptive responses to child behaviors.

  9. Maximising the local development potential of Nature Tourism accommodation establishments in South Africa

    OpenAIRE

    Jayne M. Rogerson

    2016-01-01

    Abstract: Within extant scholarship on tourism and local development one knowledge gap concerns the role of the accommodation sector as a base for tourism-led local development in rural areas and small towns. The focus is upon nature tourism accommodation establishments which cluster mainly in geographically marginal areas in South Africa where poverty levels are high and the imperative exists for new drivers of economic and social development. A national audit of nature tourism accommodation...

  10. A framework for providing telecommuting as a reasonable accommodation: some considerations on a comparative case study.

    Science.gov (United States)

    Kaplan, Shelley; Weiss, Sally; Moon, Nathan W; Baker, Paul

    2006-01-01

    Telecommuting, whether full time, part time, or over short periods when the need arises, can be an important accommodation for employees with disabilities. Indeed, telecommuting may be the only form of accommodation that offers employees whose disabilities fluctuate a means to stay consistently and gainfully employed. This article describes one employer's experience in considering a request for telecommuting as a reasonable accommodation for a particular employee. Drawing on real-life examples, both positive and negative, this article provides a win/win framework for decision-making that can help employers evaluate the use of telecommuting as a possible accommodation and facilitates open and ongoing communication between employer and employee.

  11. An Intelligent Hierarchical Approach to Actuator Fault Diagnosis and Accommodation Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal presents a novel intelligent hierarchical approach to detection, isolation, and accommodation of primary aerodynamic actuator failures. The proposed...

  12. Phenomenology and clinical correlates of family accommodation in pediatric anxiety disorders.

    Science.gov (United States)

    Storch, Eric A; Salloum, Alison; Johnco, Carly; Dane, Brittney F; Crawford, Erika A; King, Morgan A; McBride, Nicole M; Lewin, Adam B

    2015-10-01

    Despite evidence documenting high prevalence of family accommodation in pediatric obsessive-compulsive disorder, examination in other pediatric anxiety disorders is limited. Preliminary evidence suggests that family accommodation is common amongst children with anxiety disorders; however, the impact on clinical presentation and functional impairment has not been addressed. This study assessed the nature and clinical correlates of family accommodation in pediatric anxiety, as well as validating a mechanistic model. Participants included 112 anxious youth and their parents who were administered a diagnostic clinical interview and measure of anxiety severity, as well as questionnaires assessing internalizing and externalizing symptoms, family accommodation and functional impairment. Some form of accommodation was present in all families. Family accommodation was associated with increased anxiety severity and externalizing behaviors, having a diagnosis of separation anxiety, and increased functional impairment. Family accommodation partially mediated the relationship between anxiety severity and functional impairment, as well as externalizing behaviors and functional impairment. Family accommodation is common in pediatric anxiety disorders, and is associated with more severe clinical presentations and functional impairment. These findings highlight the importance of parental involvement in treatment and the need to specifically target accommodation practices during interventions to mitigate negative outcomes in anxious youth. Further studies utilizing longitudinal data are needed to validate mechanistic models.

  13. The online potential for the development of eco-certified accommodation units in Romania

    Directory of Open Access Journals (Sweden)

    Codruţa Adina BĂLTESCU

    2015-12-01

    Full Text Available The Internet and electronic communication have generated significant changes in the marketing strategies of accommodation units. On the other hand, sustainable development is a goal which requires concrete actions and changed mentalities. In Romania operates a number of eco-certified accommodation units. The online tools allow them to communicate the advantages and benefits of the sustainable services, and also to obtain a quick feedback from the consumers. This paper highlights the extent to which eco-certified accommodation units in our country offer relevant information to potential consumers and analyzes the online reviews regarding the eco-certified accommodation services

  14. Big brake singularity is accommodated as an exotic quintessence field

    CERN Document Server

    Chimento, Luis P

    2015-01-01

    We describe a big brake singularity in terms of a modified Chaplygin gas equation of state $p=(\\ga_{m}-1)\\rho+\\al\\ga_{m}\\rho^{-n}$, accommodate this late-time event as an exotic quintessence model obtained from an energy-momentum tensor, and focus on the cosmological behaviour of the exotic field, its kinetic energy and the potential energy. At background level, the exotic field does not blow-up whereas its kinetic energy and potential both grow without limit near the future singularity. We evaluate the classical stability of this background solution by examining the scalar perturbations of the metric along with the inclusion of entropy perturbation in the perturbed pressure. Within the Newtonian gauge, the gravitational field approaches to a constant near the singularity plus additional regular terms. When the perturbed exotic field is associated with $\\al>0$, the perturbed pressure and contrast density both diverge whereas the perturbed exotic field and the divergence of exotic field's velocity go to zero e...

  15. Accommodating Thickness in Origami-Based Deployable Arrays

    Science.gov (United States)

    Zirbel, Shannon A.; Magleby, Spencer P.; Howell, Larry L.; Lang, Robert J.; Thomson, Mark W.; Sigel, Deborah A.; Walkemeyer, Phillip E.; Trease, Brian P.

    2013-01-01

    The purpose of this work is to create deployment systems with a large ratio of stowed-to-deployed diameter. Deployment from a compact form to a final flat state can be achieved through origami-inspired folding of panels. There are many models capable of this motion when folded in a material with negligible thickness; however, when the application requires the folding of thick, rigid panels, attention must be paid to the effect of material thickness not only on the final folded state, but also during the folding motion (i.e., the panels must not be required to flex to attain the final folded form). The objective is to develop new methods for deployment from a compact folded form to a large circular array (or other final form). This paper describes a mathematical model for modifying the pattern to accommodate material thickness in the context of the design, modeling, and testing of a deployable system inspired by an origami six-sided flasher model. The model is demonstrated in hardware as a 1/20th scale prototype of a deployable solar array for space applications. The resulting prototype has a ratio of stowed-to-deployed diameter of 9.2 (or 1.25 m deployed outer diameter to 0.136 m stowed outer diameter).

  16. Development of an Accommodation-Dependent Eye Model and Studying the Effects of Accommodation on Electron and Proton Dose Conversion Coefficients

    Directory of Open Access Journals (Sweden)

    Alireza Vejdani-Noghreiyan

    2016-06-01

    Full Text Available Introduction International Commission on Radiological Protection (ICRP has provided a comprehensive discussion on threshold dose for radiation-induced cataract in ICRP publication 116. Accordingly, various parts of the eye lens have different radio-sensitivities. Recently, some studies have been performed to develop a realistic eye model with the aim of providing accurate estimation of fluence-to-dose conversion coefficients for different parts of the eye. However, the effect of accommodation, which changes the lens shape and pupil size, on dose conversion coefficients has not been considered yet. In this study, we purport to develop an accommodation-dependent eye model and to study the effects of accommodation on the electron and proton fluence-to-dose conversion coefficients. Materials and Methods Herein, a modified eye model was developed by considering the effects of accommodation on the lens shape and pupil size. In addition, MCNPX 2.6 Monte Carlo transport code was used to calculate the effects of  eye lens accommodation on electron and proton fluence-to-dose conversion coefficients. Results Calculation of dose conversion coefficients demonstrated that the accommodation causes up to 40% discrepancy for fluence-to-dose conversion coefficients of electrons in the range of 600 to 800 keV, which is due to the change of eye lens shape during the accommodation of the eye. Conclusion Since the accommodation of the eye change the lens shape and pupil size, it has considerable effect on fluence-to-dose conversion coefficients of electrons at some ranges of incident particle energies that should be considered in simulation. However, the fluctuation of dose conversion coefficients of protons is negligible.

  17. An initial study of family accommodation in children and adolescents with chronic tic disorders.

    Science.gov (United States)

    Storch, Eric A; Johnco, Carly; McGuire, Joseph F; Wu, Monica S; McBride, Nicole M; Lewin, Adam B; Murphy, Tanya K

    2017-01-01

    This initial study examined the nature, incidence, and clinical correlates of family accommodation in youth with tic disorders, and validated a brief self-report measure of tic-related family accommodation, the Tic Family Accommodation Scale (TFAS). Seventy-five youth aged 6-18 who were diagnosed with a tic disorder and their parent completed a diagnostic clinical interview, and clinician and parent-report measures of tic severity, depressive symptoms, anxiety symptoms, behavioral problems, family accommodation and impairment. An exploratory factor analysis of the TFAS showed a two-factor structure, with good internal consistency for the Total score, Modification of Child Environment and Modification of Parent Environment subscales (α = 0.88, 0.86, and 0.81, respectively). Family accommodation was not associated with tic severity. Family accommodation was associated with increased anxiety and depressive symptoms, higher externalizing, rule breaking, aggressive behaviors and social problems, and with greater tic-related functional impairment. Anxiety and externalizing problems (but not depressive symptoms) predicted family accommodation when controlling for tic severity. Family accommodation predicted high levels of functional impairment over and above the effect of tic severity, anxiety, depression and externalizing problems. Family accommodation is a common phenomenon for youth with tic disorders, with modifications typically encompassing changes to the child and/or parent environments. Accommodation was not associated with tic severity, but was related to higher levels of anxiety, depressive symptoms, externalizing symptoms, aggression, and rule breaking behaviors. Results suggest that other emotional symptoms are more likely to drive accommodation practices than the tic symptoms per se.

  18. Stabilization of computational procedures for constrained dynamical systems

    Science.gov (United States)

    Park, K. C.; Chiou, J. C.

    1988-01-01

    A new stabilization method of treating constraints in multibody dynamical systems is presented. By tailoring a penalty form of the constraint equations, the method achieves stabilization without artificial damping and yields a companion matrix differential equation for the constraint forces; hence, the constraint forces are obtained by integrating the companion differential equation for the constraint forces in time. A principal feature of the method is that the errors committed in each constraint condition decay with its corresponding characteristic time scale associated with its constraint force. Numerical experiments indicate that the method yields a marked improvement over existing techniques.

  19. Disturbance Accommodating Control Design for Wind Turbines Using Solvability Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Na [National Renewable Energy Laboratory,15013 Denver West Parkway,Golden, CO 80401e-mail: na.wang@nrel.gov; Wright, Alan D. [National Renewable Energy Laboratory,15013 Denver West Parkway,Golden, CO 80401e-mail: alan.wright@nrel.gov; Balas, Mark J. [ProfessorFellow ASMEAerospace Engineering Department,Embry-Riddle Aeronautical University,Daytona Beach, FL 32114e-mail: balasm@erau.edu

    2017-02-07

    In this paper, solvability conditions for disturbance accommodating control (DAC) have been discussed and applied on wind turbine controller design in above-rated wind speed to regulate rotor speed and to mitigate turbine structural loads. DAC incorporates a predetermined waveform model and uses it as part of the state-space formulation, which is known as the internal model principle to reduce or minimize the wind disturbance effects on the outputs of the wind turbine. An asymptotically stabilizing DAC controller with disturbance impact on the wind turbine being totally canceled out can be found if certain conditions are fulfilled. Designing a rotor speed regulation controller without steady-state error is important for applying linear control methodology such as DAC on wind turbines. Therefore, solvability conditions of DAC without steady-state error are attractive and can be taken as examples when designing a multitask turbine controller. DAC controllers solved via Moore-Penrose Pseudoinverse and the Kronecker product are discussed, and solvability conditions of using them are given. Additionally, a new solvability condition based on inverting the feed-through D term is proposed for the sake of reducing computational burden in the Kronecker product. Applications of designing collective pitch and independent pitch controllers based on DAC are presented. Recommendations of designing a DAC-based wind turbine controller are given. A DAC controller motivated by the proposed solvability condition that utilizes the inverse of feed-through D term is developed to mitigate the blade flapwise once-per-revolution bending moment together with a standard proportional integral controller in the control loop to assist rotor speed regulation. Simulation studies verify the discussed solvability conditions of DAC and show the effectiveness of the proposed DAC control design methodology.

  20. Study of thread grinding based on the multi-body system theory%基于多体系统理论的螺纹磨削研究

    Institute of Scientific and Technical Information of China (English)

    范晋伟; 金爱韦; 宁堃; 梅钦; 李海涌

    2012-01-01

    将多体系统运动建模方法应用到数控螺纹磨床建模中,建立机床、工件和砂轮的运动关系,推导出多线砂轮磨削螺纹的加工方程.开发螺纹磨削仿真软件,获得螺纹磨削加工G代码,在磨削螺纹的生产中取得了很好的效果.%Applying the multi-body system modeling theory to CNC thread grinder modeling. Deriving multi-line grinding wheel thread processing equation based on movement relationship of machine tool, workpiece and grinding wheel. A thread grinding simulation software is developed, and the generating thread grinding G-code achieves good results in the production of thread grinding.

  1. Classroom Use of Test Accommodations: Issues of Access, Equity, and Conflation

    Science.gov (United States)

    Schissel, Jamie L.

    2014-01-01

    Test accommodations are changes to test administration, responses, or the test itself that are offered to emergent bilingual students for standardized tests and also for classroom assessments in some states in the USA. Currently there is a lack of research examining the use of test accommodations as a pedagogical practice. This paper presents a…

  2. A Structural Equation Analysis of Family Accommodation in Pediatric Obsessive-Compulsive Disorder

    Science.gov (United States)

    Caporino, Nicole E.; Morgan, Jessica; Beckstead, Jason; Phares, Vicky; Murphy, Tanya K.; Storch, Eric A.

    2012-01-01

    Family accommodation of symptoms is counter to the primary goals of cognitive-behavioral therapy for pediatric obsessive-compulsive disorder (OCD) and can pose an obstacle to positive treatment outcomes. Although increased attention has been given to family accommodation in pediatric OCD, relatively little is known about associated child and…

  3. 41 CFR 301-10.122 - What class of airline accommodations must I use?

    Science.gov (United States)

    2010-07-01

    ... 41 Public Contracts and Property Management 4 2010-07-01 2010-07-01 false What class of airline accommodations must I use? 301-10.122 Section 301-10.122 Public Contracts and Property Management Federal Travel... Common Carrier Transportation Airline Accommodations § 301-10.122 What class of airline...

  4. An Analysis of Accommodations Issues from the Standards and Assessments Peer Review. Technical Report 51

    Science.gov (United States)

    Thurlow, Martha; Christensen, Laurene; Lail, Kathryn E.

    2008-01-01

    To meet the assessment requirements of the No Child Left Behind Act (NCLB) and the Individuals with Disabilities Education Act (IDEA), states must ensure the inclusion of students with disabilities, as well as provide for the appropriate use of assessment accommodations. Accommodations have been defined in a number of ways. In the Council of Chief…

  5. Recognizing and Accommodating Employees with PTSD: The Intersection of Human Resource Development, Rehabilitation, and Psychology

    Science.gov (United States)

    Hughes, Claretha; Lusk, Stephanie L.; Strause, Stephanie

    2016-01-01

    All employees within the workplace must be treated fairly and equitably including those with disabilities who may require accommodations that serve to increase access to and maintenance of competitive employment. Human Resource Development (HRD) researchers and practitioners have experience in accommodating employees with disabilities but are now…

  6. Computer Testing as a Form of Accommodation for English Language Learners

    Science.gov (United States)

    Abedi, Jamal

    2009-01-01

    This study compared performance of both English language learners (ELLs) and non-ELL students in Grades 4 and 8 under accommodated and nonaccommodated testing conditions. The accommodations used in this study included a computerized administration of a math test with a pop-up glossary, a customized English dictionary, extra testing time, and…

  7. Polymer refilling of presbyopic human lenses in vitro restores the ability to undergo accommodative changes

    NARCIS (Netherlands)

    Koopmans, SA; Terwee, B; Haitjema, HJ; Kooijman, AC; Barkhof, J

    2003-01-01

    PURPOSE. Because presbyopia is thought to be accompanied by increased lens sclerosis this study was conducted to investigate whether refilling the capsule of the presbyopic human lens with a soft polymer would restore the ability of the lens to undergo accommodative changes. METHODS. Accommodative f

  8. Being an Elbow: A Phenomenological Autoethnography of Faculty-Student Collaboration for Accommodations

    Science.gov (United States)

    Aguirre, Regina T. P.; Duncan, Chad

    2013-01-01

    Hybrid and online courses and advances in assistive technologies make accommodating students with disabilities ever-changing, requiring innovation. This reality, coupled with students' reluctance to disclose disabilities, points toward a need for replacing accommodations directed at those with disabilities with universal design whereby they…

  9. Visual discomfort and the temporal properties of the vergence-accommodation conflict

    Science.gov (United States)

    Kim, Joohwan; Kane, David; Banks, Martin S.

    2012-03-01

    The vergence-accommodation conflict associated with viewing stereoscopic 3D (S3D) content can cause visual discomfort. Previous studies of vergence and accommodation have shown that the coupling between the two responses is driven by a fast, phasic component. We investigated how the temporal properties of vergence-accommodation conflicts affect discomfort. Using a unique volumetric display, we manipulated the stimulus to vergence and the stimulus to accommodation independently. There were two experimental conditions: 1) natural viewing in which the stimulus to vergence was perfectly correlated with the stimulus to accommodation; and 2) conflict viewing in which the stimulus to vergence varied while the stimulus to accommodation remained constant (thereby mimicking S3D viewing). The stimulus to vergence (and accommodation in natural viewing) varied at one of three temporal frequencies in those conditions. The magnitude of the conflict was the same for all three frequencies. The young adult subjects reported more visual discomfort when vergence changes were faster, particularly in the conflict condition. Thus, the temporal properties of the vergence-accommodation conflict in S3D media affect visual discomfort. The results can help content creators minimize discomfort by making conflict changes sufficiently slow.

  10. Computer-Based Signing Accommodations: Comparing a Recorded Human with an Avatar

    Science.gov (United States)

    Russell, Michael; Kavanaugh, Maureen; Masters, Jessica; Higgins, Jennifer; Hoffmann, Thomas

    2009-01-01

    Many students who are deaf or hard-of-hearing are eligible for a signing accommodation for state and other standardized tests. The signing accommodation, however, presents several challenges for testing programs that attempt to administer tests under standardized conditions. One potential solution for many of these challenges is the use of…

  11. Disentangling Mathematics Target and Access Skills: Implications for Accommodation Assignment Practices

    Science.gov (United States)

    Ketterlin-Geller, Leanne R.; Jamgochian, Elisa M.; Nelson-Walker, Nancy J.; Geller, Joshua P.

    2012-01-01

    Appropriate assignment of accommodations is predicated on a clear distinction between target skills and access skills. In this study, we examine the agreement between test developer/researchers' and educators' classification of target and access skills as a possible explanatory mechanism for assigning accommodations. Findings indicate that…

  12. Electrical properties of Lupinus angustifolius L. stem. II. Accommodation and anode break excitation

    Directory of Open Access Journals (Sweden)

    Tadeusz Zawadzki

    2015-01-01

    Full Text Available Under electrical stimulation of Lupinus stem phenomena of accommodation and anode break excitation appear. Their characteristic is the same as in the axon or nerve. Only their duration is about 103-104 longer in plants. The constant characterizing the rate of accommodation was calculated. A limiting threshold value was found beyond which excitation occurs, irrespective of the rate of stimulus rise (voltage gradient. The accommodation rate is approximately constant, whereas the range of accommodation varies and is dependent on the difference between the rheobase value and the limiting threshold value. Hence plants with a low rheobase are characterized by a wider range of accommodation. It is suggested that the changes in potential (including AP recorded on the stem surface are connected with changes of the potential on cell membranes (Sibaoka, 1962.

  13. Social accommodation and energy efficiency dossier; Dossier habitat social et efficacite energetique

    Energy Technology Data Exchange (ETDEWEB)

    Despretz, H. [Agence de l' Environnement et de la Maitrise de l' Energie, ADEME, 75 - Paris (France); Morlot, R. [Centre Scientifique et Technique du Batiment, (CSTB), 75 - Paris (France); Gibert, M. [OPAC 38, Grenoble (France); Marichez, J.M. [CDHR 62 - Arras (France); Bouchardeau, Ph. [ADIL 26 (France); Sidler, O. [Enertech, 26 - Felines sur Rimandoule (France); Hamadou, H. [Mouvement pour les Villages d' Enfants, MVE (France)

    2001-09-01

    This dossier takes stock of the experiences and programs in progress in some French regions about the enforcement of the new thermal regulation from June 2001 in social accommodations: recall of the principles of the new regulation, practices and needs for renewable energy uses in accommodations for underprivileged people; campaign of sensitization to water, electricity and heat saving; the energy policy of the OPAC 38, a social accommodation organization of Grenoble (SE France); the energy mastery in Northern France rural accommodations; the social stake of energy mastery, its impact on standard of living, health and public finances; the first lessons gained from the scheduled operations of improvement of accommodations (rehabilitation of private buildings) in Drome region (SE France); the electricity mastery action of Montreuil-Vincennes Energie organization for the evaluation of the different specific uses of electricity in common and private parts of social apartment buildings. (J.S.)

  14. Assessing the accommodation response after near visual tasks using different handheld electronic devices

    Directory of Open Access Journals (Sweden)

    Aikaterini I. Moulakaki

    Full Text Available ABSTRACT Purpose: To assess the accommodation response after short reading periods using a tablet and a smartphone as well as determine potential differences in the accommodation response at various stimulus vergences using a Hartmann- Shack aberrometer. Methods: Eighteen healthy subjects with astigmatism of less than 1 D, corrected visual acuity of 20/20 or better, and normal findings in an ophthalmic examination were enrolled. Accommodation responses were obtained under three different conditions: accommodation system of the eye relaxed and visually stressed with a tablet and an smartphone for 10 min, at a distance of 0.25 m from the subject's eyes. Three measurements of accommodation response were monocularly acquired at stimulus vergences ranging from 0 to 4 D (1-D step. Results: No statistically significant differences were found in the accommodation responses among the conditions. A moderate but gradually increasing root mean square, coma-like aberration was found for every condition. Conversely, the spherical aberration decreased as stimulus vergences increased. These outcomes were identified in comparison to the one-to-one ideal accommodation response, implying that a certain lag value was present in all stimulus vergences different from 0 D. Conclusions: The results support the hypothesis that the difference between the ideal and real accommodation responses is mainly attributed to parameters associated with the accommodation process, such as the near visual acuity, depth of focus, pupil diameter, and wavefront aberrations. The wavefront aberrations were dependent on the 3-mm pupil size selected in this study. The accommoda tion response was not dependent on the electronic device employed in each condition, and it was mainly associated with young age and level of amplitude of accommodation of the subjects.

  15. Generalization Aspect of Neural Networks on Upgrading Assimilation Structure into Accommodating Scheme

    Directory of Open Access Journals (Sweden)

    Waleed

    2009-01-01

    Full Text Available Problem statement: Generalization feature enhancement of neural networks, especially feed forward structural model has limited progress. The major reason behind such limitation is attributed to the principal definition and the inability to interpret it into convenient structure. Traditional schemes, unfortunately have regarded generalization as an innate outcome of the simple association, referred to by Pavlov and had been modeled by piaget as the basis of assimilating conduct. Approach: A new generalization approach based on the addition of a supportive layer to the traditional neural network scheme (atomic scheme was presented. This approach extended the signal propagation of the whole net in order to generate the output in two modes, one deals with the required output of trained patterns with predefined settings, while the other tolerates output generation dynamically with tuning capability for any newly applied input. Results: Experiments and analysis showed that the new approach is not only simpler and easier, but also is very effective as the proportions promoting the generalization ability of neural networks have reached over 90% for some cases. Conclusion: Expanding neuron as the generalization essential construction denoted the accommodating capabilities involving all the innate structures in conjugation with Intelligence abilities and with the needs of further advanced learning phases. Cogent results were attained in comparison with that of the traditional schemes.

  16. Independent Blade Pitch Controller Design for a Three-Bladed Turbine Using Disturbance Accommodating Control

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Na; Wright, Alan D.; Johnson, Kathryn E.

    2016-08-01

    Two independent pitch controllers (IPCs) based on the disturbance accommodating control (DAC) algorithm are designed for the three-bladed Controls Advanced Research Turbine to regulate rotor speed and to mitigate blade root flapwise bending loads in above-rated wind speed. One of the DAC-based IPCs is designed based on a transformed symmetrical-asymmetrical (TSA) turbine model, with wind disturbances being modeled as a collective horizontal component and an asymmetrical linear shear component. Another DAC-based IPC is designed based on a multiblade coordinate (MBC) transformed turbine model, with a horizontal component and a vertical shear component being modeled as step waveform disturbance. Both of the DAC-based IPCs are found via a regulation equation solved by Kronecker product. Actuator dynamics are considered in the design processes to compensate for actuator phase delay. The simulation study shows the effectiveness of the proposed DAC-based IPCs compared to a proportional-integral (PI) collective pitch controller (CPC). Improvement on rotor speed regulation and once-per-revolution and twice-per-revolution load reductions has been observed in the proposed IPC designs.

  17. Independent Blade Pitch Controller Design for a Three-Bladed Turbine Using Disturbance Accommodating Control: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Na; Wright, Alan D.; Johnson, Kathryn E.

    2016-07-29

    Two independent pitch controllers (IPCs) based on the disturbance accommodating control (DAC) algorithm are designed for the three-bladed Controls Advanced Research Turbine to regulate rotor speed and to mitigate blade root flapwise bending loads in above-rated wind speed. One of the DAC-based IPCs is designed based on a transformed symmetrical-asymmetrical (TSA) turbine model, with wind disturbances being modeled as a collective horizontal component and an asymmetrical linear shear component. Another DAC-based IPC is designed based on a multiblade coordinate (MBC) transformed turbine model, with a horizontal component and a vertical shear component being modeled as step waveform disturbance. Both of the DAC-based IPCs are found via a regulation equation solved by Kronecker product. Actuator dynamics are considered in the design processes to compensate for actuator phase delay. The simulation study shows the effectiveness of the proposed DAC-based IPCs compared to a proportional-integral (PI) collective pitch controller (CPC). Improvement on rotor speed regulation and once-per-revolution and twice-per-revolution load reductions has been observed in the proposed IPC designs.

  18. Extending the COVAD toolbox to accommodate system non-linearities

    NARCIS (Netherlands)

    Bucco, D.; Weiss, M.

    2009-01-01

    The COVAD toolbox is a MATLAB/Simulink based tool conceived and developed for the rapid analysis and simulation of stochastically driven dynamic systems. In addition to a generic Monte Carlo capability, the toolbox is also supported by traditional analytical techniques such as the adjoint and covari

  19. Dynamic response analysis of single-span guideway caused by high speed maglev train

    OpenAIRE

    2011-01-01

    High speed maglev is one of the most important reformations in the ground transportation systems because of its no physical contact nature. This paper intends to study the dynamic response of the single-span guideway induced by moving maglev train. The dynamic model of the maglev train-guideway system is established. In this model, a maglev train consists of three vehicles and each vehicle is regarded as a multibody system with 34 degrees-of-freedom. The guideway is modeled as a simply suppor...

  20. A New Application of Multi- Body System Dynamics in Vehicle- Road Interaction Simulation

    Institute of Scientific and Technical Information of China (English)

    Ren Wei-qun; Zhang Yun-qing; Jin Guo-dong

    2003-01-01

    In vehicle-road interaction simulation, multi-body system (MBS) dynamics as well as the corresponding software ADAMS has been employed to model the nonlinear vehicle in more detail. The simulation method has been vali-dated by the test data, and been compared to the former sim-ple models. This method can be used for estimating the effects of dynamic tire forces and other vehicle features on road damage so that the "road- friend liness" can be assessed in vehicle design process.

  1. Motorcycle state estimation for lateral dynamics

    Science.gov (United States)

    Teerhuis, A. P.; Jansen, S. T. H.

    2012-08-01

    The motorcycle lean (or roll) angle development is one of the main characteristics of motorcycle lateral dynamics. Control of motorcycle motions requires an accurate assessment of this quantity and for safety applications also the risk of sliding needs to be considered. Direct measurement of the roll angle and tyre slip is not available; therefore, a method of model-based estimation is developed to estimate the state of a motorcycle. This paper investigates the feasibility of such a motorcycle state estimator (MCSE). A simplified analytic model of a motorcycle is developed by comparison to an extended multi-body model of the motorcycle, designed in Matlab/SimMechanics. The analytic model is used inside an extended Kalman filter. Experimental results of an instrumented Yamaha FJR1300 motorcycle show that the MCSE is a feasible concept for obtaining signals related to the lateral dynamics of the motorcycle.

  2. Family Accommodation in Obsessive-Compulsive Disorder: A Study on Associated Variables

    Directory of Open Access Journals (Sweden)

    Teresa Cosentino

    2015-10-01

    Full Text Available The present study aimed to examine family accommodation in relatives of obsessive-compulsive disease (OCD patients. Accommodation was assessed in a sample of 31 relatives of OCD patients by means of the Family Accommodation Scale. Other variables measured as predictors of accommodation were the tendency of a family member to feel guilty, sensitivity to guilt, anxiety sensitivity and the prevalence of a passive communication style. Accommodation was found to be rather widespread in the family members who took part in our study, and they tended to show more accommodation the greater their sensitivity to guilt and the stable tendency to experience this emotion as well as anxiety sensitivity and a passive communication style. Multiple linear regression analyses showed that, among the variables considered, the family member’s sensitivity to guilt is the only factor which can predict accommodation with regard to the patient’s demands for involvement. On the other hand, the small number of family members in the sample and the lack of clinical data on patients (such as the severity, typology and duration of their obsessive-compulsive disorder pose limits to the generalizability of the results and point to the need for further research.

  3. An influenza outbreak among pilgrims sleeping at a school without purpose built overnight accommodation facilities.

    Science.gov (United States)

    Staff, Michael; Torres, Maria I

    2011-03-01

    This report describes a respiratory illness outbreak amongst a group of over 700 World Youth Day 2008 pilgrims staying at a basic accommodation venue for 1 week in July 2008. At this venue, 1 group of pilgrims was accommodated as a large group in a gymnasium and another group was sub-divided into smaller groups and accommodated in classrooms. Following confirmation of an influenza B outbreak by influenza point of care testing, control measures were promptly implemented. Isolation of cases, improved hand, respiratory and general hygiene, establishment of a mobile tent health facility at the accommodation venue, and the use of oseltamivir for the treatment of cases and prophylaxis of high risk contacts were implemented and the outbreak was brought under control within the week. Overall, 20% of pilgrims met the case definition for an influenza-like illness and 36% had an onset prior to arrival at the venue. The attack rate for those with onset while at the venue was significantly higher amongst pilgrims accommodated in the gymnasium than those staying in the classrooms. Findings from this study highlight the importance of early detection, the rapid implementation of control measures and appropriate prescribing of antivirals to manage influenza outbreaks. The findings also highlight the benefits of accommodating individuals in smaller groups within basic accommodation venues in the context of mass gatherings.

  4. Accommodation-induced variations in retinal thickness measured by spectral domain optical coherence tomography

    Science.gov (United States)

    Fan, Shanhui; Sun, Yong; Dai, Cuixia; Zheng, Haihua; Ren, Qiushi; Jiao, Shuliang; Zhou, Chuanqing

    2014-09-01

    To research retinal stretching or distortion with accommodation, accommodation-induced changes in retinal thickness (RT) in the macular area were investigated in a population of young adults (n=23) by using a dual-channel spectral domain optical coherence tomography (SD-OCT) system manufactured in-house for this study. This dual-channel SD-OCT is capable of imaging the cornea and retina simultaneously with an imaging speed of 24 kHz A-line scan rate, which can provide the anatomical dimensions of the eye, including the RT and axial length. Thus, the modification of the RT with accommodation can be calculated. A significant decrease in the RT (13.50±1.25 μm) was observed during maximum accommodation. In the 4 mm×4 mm macular area centered at the fovea, we did not find a significant quadrant-dependent difference in retinal volume change, which indicates that neither retinal stretching nor distortion was quadrant-dependent during accommodation. We speculate that the changes in RT with maximum accommodation resulted from accommodation-induced ciliary muscle contractions.

  5. Comparative reference of accommodation tension in schoolchildren of junior classes depending on emotional state

    Directory of Open Access Journals (Sweden)

    L. E. Fedorischeva

    2014-07-01

    Full Text Available Purpose: to study the change of adaptation mechanisms in children of junior classes during working on close distance depending on their psychoemotional state.Methods: 52 children of the second classes of grammar school were included into the study. There were allocated 30 emotional labile schoolchildren with choleric temperament. The children were examined by pediatrician, neurologist and in laboratory. Standard ophthalmic examination was performed. Accommodation was examined by subjective (reserve of relative accommodation and objective (familiar tone of accommodation methods.Results: All children had low reserve of relative accommodation (RRA and high familiar tone of accommodation (FTA in the end of educational week especially in emotional labile children. After course of treatment (hygiene of visual activity; restoration of accommodation and therapy of visual tiredness; gymnastics for cervical spine; preparations with microelements, vitamins C,E, B-carotene; fenibute RRA was increased and FTA was decreased even in emotional labile children.Conclusion: There is correlation between refractive-accommodative apparatus and psychoemotional state in schoolchildren ofjunior classes.

  6. Quantifying interactions between accommodation and vergence in a binocularly normal population.

    Science.gov (United States)

    Sweeney, Laura E; Seidel, Dirk; Day, Mhairi; Gray, Lyle S

    2014-12-01

    Stimulation of the accommodation system results in a response in the vergence system via accommodative vergence cross-link interactions, and stimulation of the vergence system results in an accommodation response via vergence accommodation cross-link interactions. Cross-link interactions are necessary in order to ensure simultaneous responses in the accommodation and vergence systems. The crosslink interactions are represented most comprehensively by the response AC/A (accommodative vergence) and CA/C (vergence accommodation) ratios, although the stimulus AC/A ratio is measured clinically, and the stimulus CA/C ratio is seldom measured in clinical practice. The present study aims to quantify both stimulus and response AC/A and CA/C ratios in a binocularly normal population, and determine the relationship between them. 25 Subjects (mean ± SD age 21.0 ± 1.9 years) were recruited from the university population. A significant linear relationship was found between the stimulus and response ratios, for both AC/A (r² = 0.96, p values, and lower than response ratios at high values (95% CI -0.46 to 0.42 D/MA). Agreement between stimulus and response CA/C ratios is poorer than that found for AC/A ratios due to increased variability in vergence responses when viewing the Gaussian blurred target. This study has shown that more work is needed to refine the methodology of CA/C ratio measurement.

  7. The flexibility of conceptual pacts: referring expressions dynamically shift to accommodate new conceptualizations

    Directory of Open Access Journals (Sweden)

    Alyssa eIbarra

    2016-04-01

    Full Text Available In a classic paper, Brennan and Clark argued that when interlocutors agree on a name for an object, they are forming a temporary agreement on how to conceptualize that object; that is, they are forming a conceptual pact. The literature on conceptual pacts has largely focused on the costs and benefits of breaking and maintaining lexical precedents, and the degree to which they might be partner-specific. The research presented here focuses on a question about conceptual pacts that has been largely neglected in the literature: To what extent are conceptual pacts specific to the local context of the interaction? If conceptual pacts are indeed temporary, then when the local context changes in ways that are accessible to participants, we would expect participants to seamlessly shift to referential expressions that reflect novel conceptualizations. Two experiments examined how referential forms change across context in collaborative, task-oriented dialogue between naïve participants. In Experiment 1, names for parts of an unknown object were established in an item identification stage (e.g., a shape that looked like a wrench was called the wrench. In a second build stage, that name was often supplanted by an object-oriented name, e.g., the leg. These changes happened abruptly and without negotiation. In Experiment 2, interlocutors manipulated clip art and more abstract tangram pictures in a slider puzzle to arrange the objects into a target configuration. On some trials moving an object revealed a picture that could be construed as a contrast competitor, e.g., a clip art picture of a camel after the camel had been negotiated as a name for a tangram shape, or vice versa. As would be expected, modification rates increased when a potential contrast was revealed. More strikingly, the degree to which a name had been negotiated or the frequency with which it had been used did not affect the likelihood that the revealed shape would be considered as a potential contrast. We find little evidence that names that are introduced as part of a conceptual pact persist when either the task goals or informational needs change. Rather, conceptual pacts are fluid temporary agreements.

  8. Formal-language-theoretic Optimal Path Planning For Accommodation of Amortized Uncertainties and Dynamic Effects

    CERN Document Server

    Chattopadhyay, Ishanu; Ray, Asok

    2010-01-01

    We report a globally-optimal approach to robotic path planning under uncertainty, based on the theory of quantitative measures of formal languages. A significant generalization to the language-measure-theoretic path planning algorithm $\

  9. The impact of regulatory approaches targeting collaborative economy in the tourism accommodation sector:

    DEFF Research Database (Denmark)

    Dredge, Dianne; Gyimóthy, Szilvia; Birkbak, Andreas

    economy peer-to-peer accommodation sector has significant impacts for traditional tourism industry structures and relationships. The growth of the collaborative economy peer-to-peer accommodation market has led to a diversification of accommodation stock, it has led to increased competition, and it has...... stimulated a range of ancillary services offered by small and micro-entrepreneurs. However, incumbent industry actors (such as hotels, apartment hotels, bed and breakfasts, hostels and vacation rentals) are concerned about the uneven regulatory landscape and the unfair competition this may create. Municipal...

  10. Sustainable development of the today accommodation; Developpement durable de l'habitat existant

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2003-07-01

    This first colloquium deals with the energy mastership and the greenhouse gases reduction in the today accommodation. The accommodation represent u=indeed the main part of the energy consumption in front of the industry, the transports, the ternary buildings and the agricultural. This document proposes six papers presented during this day: the importance of the accommodation improvement market; the energy performance of buildings and the main requirements of the french directive; the energy performance of buildings and the german regulations in existing buildings; the energy performance standards in existing buildings in UK; the example of the danish certification; the home energy conservation Act (HECA) in United Kingdom. (A.L.B.)

  11. Accommodating Conscientious Objection in Medicine-Private Ideological Convictions Must Not Trump Professional Obligations.

    Science.gov (United States)

    Schuklenk, Udo

    2016-01-01

    The opinion of the American Medical Association (AMA) Council on Ethical and Judicial Affairs (CEJA) on the accommodation of conscientious objectors among medical doctors aims to balance fairly patients' rights of access to care and accommodating doctors' deeply held personal beliefs. Like similar documents, it fails. Patients will not find it persuasive, and neither should they. The lines drawn aim at a reasonable compromise between positions that are not amenable to compromise. They are also largely arbitrary. This article explains why that is the case. The view that conscientious objection accommodation has no place in modern medicine is defended.

  12. DYNAMIC ANALYSIS OF FLEXIBLE BODY WITH DEFINITE MOVING ATTITUTE

    Institute of Scientific and Technical Information of China (English)

    YANG Yuan-ming; ZHANG Wei; SONG Tian-xia; CHEN Chuan-yao

    2006-01-01

    The nonlinear dynamic control equation of a flexible multi-body system with definite moving attitude is discussed. The motion of the aircraft in space is regarded as known and the influence of the flexible structural members in the aircraft on the motion and attitude of the aircraft is analyzed. By means of a hypothetical mode, the deformation of flexible members is regarded as composed of the line element vibration in the axial direction of rectangular coordinates in space. According to Kane's method in dynamics, a dynamic equation is established, which contains the structural stiffness matrix that represents the elastic deformation and the geometric stiffness matrix that represents the nonlinear deformation of the deformed body. Through simplification the dynamic equation of the influence of the planar flexible body with a windsurfboard structure on the spacecraft motion is obtained. The numerical solution for this kind of equation can be realized by a computer.

  13. Morphology and Accommodative Function of the Vitreous Zonule in Human and Monkey Eyes

    OpenAIRE

    Lütjen-Drecoll, Elke; Kaufman, Paul L.; Wasielewski, Rainer; Ting-Li, Lin; Croft, Mary Ann

    2010-01-01

    The vitreous zonule may be a therapeutic target for presbyopia. The age-related changes in the vitreous zonular system and the correlation with loss of accommodative forward movement of the ciliary body are reported.

  14. THE ROLE OF ECONOMIC EFFICIENCY OF ACCOMMODATION UNITS IN DETERMINATION OF PURCHASE INTENTIONS OF TOURIST SERVICES

    Directory of Open Access Journals (Sweden)

    Simona Cristina Martin

    2014-11-01

    Full Text Available The indicators of demand distribution for various types of accommodation provide information regarding changing tourist preferences for different ways of tourist accommodation. Appreciation of economic efficiency for hotels activity is done through quantitative results obtained in accommodation units. For this purpose it uses, currently, a partial or synthetic indicators system. Taking into account the fact that, in appreciation of hotel business, it must start from the premise that it may not be fully reflected only in terms of economic results, but also through social results, appear obvious the need to maintain costs at a level that satisfies both requirements at the same time. Achieving superior social-financial indicators, remains one of the main goals also in hotel activities, but do not be overlooked the fact that it is necessary that these indicators must be obtained by ensuring a higher level of satisfaction of consumers requirements. Only simultaneous achievement of these two objectives can provide raising efficiency in accommodation sector.

  15. Best Sensor Configuration and Accommodation Rule Based on Navigation Performance for INS with Seven Inertial Sensors

    Directory of Open Access Journals (Sweden)

    Cheol-Kwan Yang

    2009-10-01

    Full Text Available This paper considers the best sensor configuration and fault accommodation problem for inertial navigation systems which use seven inertial sensors such as gyroscopes and accelerometers. We prove that when six inertial sensors are used, the isolation of a double fault cannot be achieved for some combinations of fault magnitudes, whereas when seven inertial sensors are used, the isolation of any double fault can be achieved. There are many configurations which provide the minimum position errors. This paper proposes four configurations which show the best navigation performance and compares their FDI performances. Considering the FDI performance and the complexity of the accommodation rule, we choose one sensor configuration and provide accommodation rules for double faults. A Monte Carlo simulation is performed to show that the accommodation rules work well.

  16. Accommodations quality for students who are d/Deaf or hard of hearing.

    Science.gov (United States)

    Cawthon, Stephanie W; Leppo, Rachel

    2013-01-01

    Students who are d/Deaf or hard of hearing often receive accommodations that are intended to increase access to the educational environment. The authors provide the results of a large national study of accommodations use in secondary and postsecondary settings. The article focuses on three aspects of accommodations use: access, quality, and consistency. The participants were 1,350 professionals working with a diverse group of students who were d/Deaf or hard of hearing in a variety of roles, including educators, administrators, interpreters, vocational rehabilitation agency staff, and allied service providers. Data were collected from both a national survey and a series of focus groups conducted over a 1-year period. The authors discuss the results in light of the crucial nature of accommodations during the transition into a variety of educational, training, and employment options.

  17. 75 FR 36414 - Federal Travel Regulation (FTR); Directions for Reporting Other Than Coach-Class Accommodations...

    Science.gov (United States)

    2010-06-25

    ... From the Federal Register Online via the Government Publishing Office GENERAL SERVICES ADMINISTRATION Federal Travel Regulation (FTR); Directions for Reporting Other Than Coach-Class Accommodations for Employees on Official Travel AGENCY: Office of Governmentwide Policy, General...

  18. Decoupled crust-mantle accommodation of Africa-Eurasia convergence in the NW Moroccan margin

    OpenAIRE

    Jiménez-Munt, Ivone; Fernandez, Manel; Vergés, Jaume; García-Castellanos, Daniel; Fullea, J.; M. Pérez-Gussinyé; Afonso, Juan Carlos

    2011-01-01

    The extent of the area accommodating convergence between the African and Iberian plates, how this convergence is partitioned between crust and mantle, and the role of the plate boundary in accommodating deformation are not well-understood subjects. We calculate the structure of the lithosphere derived from its density distribution along a profile running from the Tagus Abyssal Plain to the Sahara Platform and crossing the Gorringe Bank, the NW Moroccan margin, and the Atlas Mountains. The mod...

  19. Ocular accommodation and cognitive demand: An additional indicator besides pupil size and cardiovascular measures?

    Directory of Open Access Journals (Sweden)

    Jaschinski Wolfgang

    2008-08-01

    Full Text Available Abstract Background The aim of the present study was to assess accommodation as a possible indicator of changes in the autonomic balance caused by altered cognitive demand. Accounting for accommodative responses from a human factors perspective may be motivated by the interest of designing virtual image displays or by establishing an autonomic indicator that allows for remote measurement at the human eye. Heart period, pulse transit time, and the pupillary response were considered as reference for possible closed-loop accommodative effects. Cognitive demand was varied by presenting monocularly numbers at a viewing distance of 5 D (20 cm which had to be read, added or multiplied; further, letters were presented in a "n-back" task. Results Cardiovascular parameters and pupil size indicated a change in autonomic balance, while error rates and reaction time confirmed the increased cognitive demand during task processing. An observed decrease in accommodation could not be attributed to the cognitive demand itself for two reasons: (1 the cognitive demand induced a shift in gaze direction which, for methodological reasons, accounted for a substantial part of the observed accommodative changes. (2 Remaining effects disappeared when the correctness of task processing was taken into account. Conclusion Although the expectation of accommodation as possible autonomic indicator of cognitive demand was not confirmed, the present results are informative for the field of applied psychophysiology noting that it seems not to be worthwhile to include closed-loop accommodation in future studies. From a human factors perspective, expected changes of accommodation due to cognitive demand are of minor importance for design specifications – of, for example, complex visual displays.

  20. A Model of Supervisor Decision-Making in the Accommodation of Workers with Low Back Pain.

    Science.gov (United States)

    Williams-Whitt, Kelly; Kristman, Vicki; Shaw, William S; Soklaridis, Sophie; Reguly, Paula

    2016-09-01

    Purpose To explore supervisors' perspectives and decision-making processes in the accommodation of back injured workers. Methods Twenty-three semi-structured, in-depth interviews were conducted with supervisors from eleven Canadian organizations about their role in providing job accommodations. Supervisors were identified through an on-line survey and interviews were recorded, transcribed and entered into NVivo software. The initial analyses identified common units of meaning, which were used to develop a coding guide. Interviews were coded, and a model of supervisor decision-making was developed based on the themes, categories and connecting ideas identified in the data. Results The decision-making model includes a process element that is described as iterative "trial and error" decision-making. Medical restrictions are compared to job demands, employee abilities and available alternatives. A feasible modification is identified through brainstorming and then implemented by the supervisor. Resources used for brainstorming include information, supervisor experience and autonomy, and organizational supports. The model also incorporates the experience of accommodation as a job demand that causes strain for the supervisor. Accommodation demands affect the supervisor's attitude, brainstorming and monitoring effort, and communication with returning employees. Resources and demands have a combined effect on accommodation decision complexity, which in turn affects the quality of the accommodation option selected. If the employee is unable to complete the tasks or is reinjured during the accommodation, the decision cycle repeats. More frequent iteration through the trial and error process reduces the likelihood of return to work success. Conclusion A series of propositions is developed to illustrate the relationships among categories in the model. The model and propositions show: (a) the iterative, problem solving nature of the RTW process; (b) decision resources necessary

  1. 41 CFR 301-10.123 - When may I use other than coach-class airline accommodations?

    Science.gov (United States)

    2010-07-01

    ... than coach-class airline accommodations? 301-10.123 Section 301-10.123 Public Contracts and Property... 10-TRANSPORTATION EXPENSES Common Carrier Transportation Airline Accommodations § 301-10.123 When may I use other than coach-class airline accommodations? Government travelers are required to...

  2. Flexibility of PCNA-protein interface accommodates differential binding partners.

    Directory of Open Access Journals (Sweden)

    Anthony M Pedley

    Full Text Available The expanding roles of PCNA in functional assembly of DNA replication and repair complexes motivated investigation of the structural and dynamic properties guiding specificity of PCNA-protein interactions. A series of biochemical and computational analyses were combined to evaluate the PIP Box recognition features impacting complex formation. The results indicate subtle differences in topological and molecular descriptors distinguishing both affinity and stoichiometry of binding among PCNA-peptide complexes through cooperative effects. These features were validated using peptide mimics of p85α and Akt, two previously unreported PCNA binding partners. This study characterizes for the first time a reverse PIP Box interaction with PCNA. Small molecule ligand binding at the PIP Box interaction site confirmed the adaptive nature of the protein in dictating overall shape and implicates allosterism in transmitting biological effects.

  3. Water accommodation on ice and organic surfaces: insights from environmental molecular beam experiments.

    Science.gov (United States)

    Kong, Xiangrui; Thomson, Erik S; Papagiannakopoulos, Panos; Johansson, Sofia M; Pettersson, Jan B C

    2014-11-26

    Water uptake on aerosol and cloud particles in the atmosphere modifies their chemistry and microphysics with important implications for climate on Earth. Here, we apply an environmental molecular beam (EMB) method to characterize water accommodation on ice and organic surfaces. The adsorption of surface-active compounds including short-chain alcohols, nitric acid, and acetic acid significantly affects accommodation of D2O on ice. n-Hexanol and n-butanol adlayers reduce water uptake by facilitating rapid desorption and function as inefficient barriers for accommodation as well as desorption of water, while the effect of adsorbed methanol is small. Water accommodation is close to unity on nitric-acid- and acetic-acid-covered ice, and accommodation is significantly more efficient than that on the bare ice surface. Water uptake is inefficient on solid alcohols and acetic acid but strongly enhanced on liquid phases including a quasi-liquid layer on solid n-butanol. The EMB method provides unique information on accommodation and rapid kinetics on volatile surfaces, and these studies suggest that adsorbed organic and acidic compounds need to be taken into account when describing water at environmental interfaces.

  4. Comparison between carbachol iontophoresis and intravenous pilocarpine stimulated accommodation in anesthetized rhesus monkeys.

    Science.gov (United States)

    Wendt, Mark; He, Lin; Glasser, Adrian

    2013-10-01

    Rhesus monkeys are an animal model for human accommodation and presbyopia and consistent and repeatable methods are needed to stimulate and measure accommodation in anesthetized rhesus monkeys. Accommodation has typically been pharmacologically stimulated with topical pilocarpine or carbachol iontophoresis. Intravenous (i.v.) pilocarpine has recently been shown to produce more natural, rapid and reproducible accommodative responses compared to topical pilocarpine. Here, i.v. pilocarpine was compared to carbachol iontophoresis stimulated accommodation. Experiments were performed under anaesthesia on five previously iridectomized monkeys aged 10-16 years. In three monkeys, accommodation was stimulated with carbachol iontophoresis in five successive experiments and refraction measured with a Hartinger coincidence refractometer. In separate experiments, accommodation was stimulated using a 5 mg/kg bolus of i.v. pilocarpine given over 30 s followed by a continuous infusion of 20 mg/kg/hr for 5.5 min in three successive experiments with the same monkeys as well as in single experiments with two additional monkeys. Refraction was measured continuously using photorefraction with baseline and accommodated refraction also measured with the Hartinger. In subsequent i.v. pilocarpine experiments with each monkey, accommodative changes in lens equatorial diameter were measured in real-time with video-image analysis. Maximum accommodation of three monkeys with carbachol iontophoresis (five repeats) was (mean ± SD; range) 14.0 ± 3.5; 9.9-20.3 D and with i.v. pilocarpine stimulation (three repeats) was 11.1 ± 1.1; 9.9-13.0 D. The average of the standard deviations of maximum accommodation from each monkey was 0.8 ± 0.3 D from carbachol iontophoresis and 0.3 ± 0.2 from i.v. pilocarpine. The average latency to the start of the response after carbachol iontophoresis was 2.5 ± 3.9; 0.0-12.0 min with a time constant of 12.7 ± 9.5; 2.3-29.2 min. The average

  5. Home Stay Accommodation for Tourism Development in East Coast Economic Region

    Directory of Open Access Journals (Sweden)

    Md. Anowar Hossain Bhuiyan

    2012-01-01

    Full Text Available Problem statement: Home stay program provided tourists multi ethnic life condition with cultural experiences and economic well beings for the local people. Malaysian home stay program differed from the other commercial home stay in the world. Home stay accommodation can create a scope to the local communities for active participation in tourism activities. Home stay accommodation might be a potential economic activity in the East Coast Economic Region (ECER. The study examined the potentialities of home stay accommodation for tourism development in ECER. The aim of the study was to analyze the overall situations of home stay accommodation in ECER from the perception of operators. Approach: The data of this study perceived from both the primary and secondary sources. A structured questionnaire had been used for data collection. In 2006, home stay accommodation was remaining 31 villages and in the year 2008 it spreads in 38 villages of ECER. Within this period, there were 482 and 648 home stay operators in this region. The necessary requirements for home stay operations are located; basic facilities; hygiene; safety and security. Results: There were some potentialities are remaining in ECER for establishing home stay in this region. These were low charging, hospitality, motivation for young generation, women entrepreneurship, profitable investment, easy access and satisfactory income. Some initiatives such as government support, capacity building, develop facilities, appropriate act, Community involvement, loan facilities and infrastructure development might be taken for the home stay accommodations in ECER. Conclusion: Research initiatives, various services for customer satisfaction, sustainable marketing and proper policy in management had been considered for home stay development in ECER. Home stay accommodations would be ensured the economic advancement in this region as well as sustainable regional development.

  6. Amplitude, facility and accuracy of accommodation in a primary school population

    Directory of Open Access Journals (Sweden)

    V. R. Moodley

    2008-01-01

    Full Text Available Vision screening at an early age in children is important as it can identify aspects in the visual system that may need to be managed to enable a child to function optimally at school.  The National School Vision Screening Programme was discontinued in many provinces of South Africa, often due to a lack of financial resources or adequately trained personnel. This action has resulted in the majority of children not having a visual examination during their school career.  In a few instances where vision screenings are performed, these are usually limited to visual acuity (VA evaluation alone; an endeavour that may miss many significant visual problems.  The purpose of this article is to highlight the need for vision screening to be conducted in schools and for the screening protocols to include the various accommodative tests. A retrospective analysis of the amplitudes of accommodation, accommodative facility and accuracy of accommodation findingsfrom a primary school vision screening of 264 children between 6 and 13 years was undertaken in this study.  Data was captured and analysed with Microsoft Excel. The ages of the children ranged from 6 to 13 years with a mean of 9.38 years (SD = 1.85.  One hundred and thirty eight (52.3% were males and 126 (47.7% females.  A significant number of the children failed the monocular accommodative amplitude tests (24%, binocular accommodative amplitude test (26%, the accommodative facility (30% and the MEM test (27%.  These results highlight the need for a more comprehensive vision screening exercise rather than VA alone as this approach would have  missed more than a quarter of the children who had other visual problems that could impact on their ability to perform optimally at school.

  7. Composite modeling method in dynamics of planar mechanical system

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    This paper presents a composite modeling method of the forward dynamics in general planar mechanical system. In the modeling process, the system dynamic model is generated by assembling the model units which are kinematical determinate in planar mechanisms rather than the body/joint units in multi-body system. A state space formulation is employed to model both the unit and system models. The validation and feasibility of the method are illustrated by a case study of a four-bar mechanism. The advantage of this method is that the models are easier to reuse and the system is easier to reconfigure. The formulation reveals the relationship between the topology and dynamics of the planar mechanism to some extent.

  8. Composite modeling method in dynamics of planar mechanical system

    Institute of Scientific and Technical Information of China (English)

    WANG Hao; LIN ZhongQin; LAI XinMin

    2008-01-01

    This paper presents a composite modeling method of the forward dynamics in general planar mechanical system.In the modeling process,the system dynamic model is generated by assembling the model units which are kinematical determi-nate in planar mechanisms rather than the body/joint units in multi-body system.A state space formulation is employed to model both the unit and system models.The validation and feasibility of the method are illustrated by a case study of a four-bar mechanism.The advantage of this method is that the models are easier to reuse and the system is easier to reconfigure.The formulation reveals the rela-tionship between the topology and dynamics of the planar mechanism to some extent.

  9. Accommodations Use Patterns in High School and Postsecondary Settings for Students Who Are d/Deaf or Hard of Hearing.

    Science.gov (United States)

    Cawthon, Stephanie W; Leppo, Rachel; Ge, Jin Jin; Bond, Mark

    2015-01-01

    Using data from the second National Longitudinal Transition Study (Newman et al., 2011), the authors investigated longitudinal patterns of educational accommodations use in secondary and, later, postsecondary settings by students who are d/Deaf or hard of hearing (SDHH). The study focused on language and communication (LC) accommodations used primarily by SDHH, plus non-LC accommodations typically used by a broad range of students. Both LC accommodations for standardized testing and instruction showed decreased use in postsecondary settings compared with high school. After student demographic characteristics were controlled for, no relationships were found between types of accommodations students used in high school and those they later used in postsecondary settings. Student accommodations use in postsecondary settings was not significantly predictive of retention or degree completion. However, several student- and parent-level demographic characteristics were predictive of accommodations use in postsecondary settings. Implications and future research directions are discussed.

  10. Dynamics and Habitability in Binary Star Systems

    CERN Document Server

    Eggl, Siegfried; Pilat-Lohinger, Elke

    2014-01-01

    Determining planetary habitability is a complex matter, as the interplay between a planet's physical and atmospheric properties with stellar insolation has to be studied in a self consistent manner. Standardized atmospheric models for Earth-like planets exist and are commonly accepted as a reference for estimates of Habitable Zones. In order to define Habitable Zone boundaries, circular orbital configurations around main sequence stars are generally assumed. In gravitationally interacting multibody systems, such as double stars, however, planetary orbits are forcibly becoming non circular with time. Especially in binary star systems even relatively small changes in a planet's orbit can have a large impact on habitability. Hence, we argue that a minimum model for calculating Habitable Zones in binary star systems has to include dynamical interactions.

  11. Contact dynamics of elasto-plastic thin beams simulated via absolute nodal coordinate formulation

    Institute of Scientific and Technical Information of China (English)

    Qing-Tao Wang; Qiang Tian; Hai-Yan Hu

    2016-01-01

    Under the frame of multibody dynamics, the contact dynamics of elasto-plastic spatial thin beams is numerically studied by using the spatial thin beam elements of absolute nodal coordinate formulation (ANCF). The inter-nal force of the elasto-plastic spatial thin beam element is derived under the assumption that the plastic strain of the beam element depends only on its longitudinal deformation. A new body-fixed local coordinate system is introduced into the spatial thin beam element of ANCF for efficient con-tact detection in the contact dynamics simulation. The linear isotropic hardening constitutive law is used to describe the elasto-plastic deformation of beam material, and the classical return mapping algorithm is adopted to evaluate the plastic strains. A multi-zone contact approach of thin beams previ-ously proposed by the authors is also introduced to detect the multiple contact zones of beams accurately, and the penalty method is used to compute the normal contact force of thin beams in contact. Four numerical examples are given to demonstrate the applicability and effectiveness of the pro-posed elasto-plastic spatial thin beam element of ANCF for flexible multibody system dynamics.

  12. Managing Guest as an Asset: a Conceptual Review in the Context of Accommodation Services

    Directory of Open Access Journals (Sweden)

    Dwi Suhartanto

    2015-10-01

    Full Text Available This article discusses the concept of a customer as an asset of business in the accommodation industry. The purpose of this article is to examine the value of guests as a firm asset and to propose a model for managing guests as an asset in the context of accommodation services. A guest is considered an asset due to its role in providing revenue to the accommodation firm. Because of this role, the accommodation guest needs to be managed appropriately. This article argues that guest service evaluation (i.e. service quality, perceived value, and guest satisfaction and service loyalty are important factors in the development of guest lifetime value. The proposed model of managing guests as an asset consists of marketing instruments, service evaluation, guest loyalty, and financial outcomes provides a comprehensive guide on how accommodation firms can manage the lifetime value of their guests. Finally, as there are limited studies examining this issue, future research should test the proposed model.

  13. Evaluation of lightning accommodation systems for wind-driven turbine rotors

    Energy Technology Data Exchange (ETDEWEB)

    Bankaitis, H

    1982-03-01

    Several concepts of lightning accommodation systems for wind-driven turbine rotor blades were evaluated by submitting them to simulated lightning tests. Test samples representative of epoxy-fiberglass and wood-epoxy composite structural materials were submitted to a series of high-voltage and high-current damage tests. The high-voltage tests were designed to determine the strike points and current paths through the sample and the need for, and the most proper type of, lightning accommodation. The high-current damage tests were designed to determine the capability of the potential lightning accommodation system to sustain the 200-kA lightning current without causing damage to the composite structure. The observations and data obtained in the series of tests of lightning accommodation systems clearly led to the conclusions that composite-structural-material rotor blades require a lightning accommodation system; that the concepts tested prevent internal streamering; and that keeping discharge currents on the blade surface precludes structure penetration. Induced voltage effects or any secondary effects on the integral components of the total system could not be addressed. Further studies should be carried out to encompass effects on the total system design.

  14. Salivary oxytocin in clinically anxious youth: Associations with separation anxiety and family accommodation.

    Science.gov (United States)

    Lebowitz, Eli R; Leckman, James F; Feldman, Ruth; Zagoory-Sharon, Orna; McDonald, Nicole; Silverman, Wendy K

    2016-03-01

    Clinical anxiety disorders in youth are common and associated with interpersonal behaviors including reliance on parents for family accommodation, or changes that parents make to their own behaviors to help the youth avoid anxiety related distress. The neuropeptide oxytocin is associated with the regulation of anxiety and of close interpersonal behavior leading to the hypothesis that oxytocinergic functioning plays a role in youth anxiety and its disorders, and the resulting family accommodation. To test this hypothesis salivary OT from 50 youth with primary DSM-5 anxiety disorders was assayed. A multi-source/multi-method anxiety assessment including semistructured interviews with youth and mothers, rating scales, and behavioral observations was used to assess anxiety disorders and symptoms, and family accommodation. Youth with separation anxiety disorder had significantly lower salivary OT levels than clinically anxious youth not diagnosed with separation anxiety disorder. Salivary OT levels were significantly negatively correlated with separation anxiety symptoms based on both youth- and mother-ratings. Anxious behavior displayed by youth during interactions with their mothers was associated with lower salivary OT levels in youth. Maternal ratings of family accommodation were negatively associated with salivary OT levels in youth. Results support the role of the oxytocinergic system in youth anxiety and its disorders and in parental involvement in youth anxiety through family accommodation. OT may be particularly important for diagnoses and symptoms of separation anxiety, which is inherently interpersonal in nature. Findings have potentially important implications for assessment and treatment of anxiety in youth.

  15. Development of a Dynamic Biomechanical Model for Load Carriage: Phase 1 Part A: Equipment Upgrades to Accommodate Dynamic Biomechanical Modeling

    Science.gov (United States)

    2005-08-01

    mannequin. For the first objective, a combination of MatLab (a numerical computation and data visualization program) and Microsoft Excel macros was...modifications bidimensionnelles ont été apportées à l’appareil; la fonction tridimensionnelle sera ajoutée plus tard. Les changements apportés au...système automatisé programmable de commande des mouvements ont donné accès à des fonctions qui n’existaient pas dans le système précédent, notamment : 1

  16. Development of an Offshore Direct-Drive Wind Turbine Model by Using a Flexible Multibody Simulation (Poster)

    Energy Technology Data Exchange (ETDEWEB)

    Bergua, R.; Jove, J.; Campbell, J.; Guo, Y.; Van Dam, J.

    2014-05-01

    Modern wind turbines are complex, highly-coupled systems. The dynamic interaction between various components is especially pronounced for multi-megawatt wind turbines. As a result, design process is generally split in several phases. First step consists of creating a global aero-elastic model that includes essential dynamics of structural components using the minimum-possible number of degrees of freedom (d.o.f.). The most important simplifications concern drivetrain and rotor-nacelle assembly (RNA). This approach has been shown valid for several wind turbine configurations. Nevertheless, with increasing size of wind turbines, any simplified design approach must be validated. The present work deals with the comparison and validation of the two modeling approaches for directdrive offshore wind turbines. ARNA/drivetrain model idealized as collection of lumped masses and springs is compared to a detailed Finite Element Method (FEM) based model. The comparison between models focuses on dynamic loads concerning drivetrain system. The comparison is performed in several operational conditions in order to explore the range of validity of the simplified model. Finally, the paper proposes a numerical-based workflow to assess the validity of simplified models of RNA/drivetrain in an aero-elastic global WT model.

  17. Monocular accommodation condition in 3D display types through geometrical optics

    Science.gov (United States)

    Kim, Sung-Kyu; Kim, Dong-Wook; Park, Min-Chul; Son, Jung-Young

    2007-09-01

    Eye fatigue or strain phenomenon in 3D display environment is a significant problem for 3D display commercialization. The 3D display systems like eyeglasses type stereoscopic or auto-stereoscopic multiview, Super Multi-View (SMV), and Multi-Focus (MF) displays are considered for detail calculation about satisfaction level of monocular accommodation by geometrical optics calculation means. A lens with fixed focal length is used for experimental verification about numerical calculation of monocular defocus effect caused by accommodation at three different depths. And the simulation and experiment results consistently show relatively high level satisfaction about monocular accommodation at MF display condition. Additionally, possibility of monocular depth perception, 3D effect, at monocular MF display is discussed.

  18. Analysis of source-grid-load contribution to wind power accommodation

    Science.gov (United States)

    Li, Nan; Zhang, Jinfang; Zhang, Fuqiang

    2017-01-01

    In recent years, China’s wind power is developing rapidly, but wind electricity curtailment becomes a serious problem. This paper evaluates wind power penetration limit from peak regulation, analyses relevant technical elements that impact wind power accommodation, coving the source side, the transmission side and the load side. By taking certain measures around the three aspects, for example, reducing the minimum technical output of conventional units, increasing outbound transmission capacity, or increasing the valley load, wind electricity curtailment will be effectively reduced. This paper quantitatively analyses wind power penetration limit under certain conditions and the source-grid-load contribution to wind power accommodation, and explores the important technical factors that affect wind power accommodation.

  19. SIBIU EUROPEAN CULTURAL CAPITAL PROGRAM: MEASURING THE IMPACT ON THE ACCOMMODATION SYSTEM

    Directory of Open Access Journals (Sweden)

    Rotariu Ilie

    2010-07-01

    Full Text Available The Sibiu 2007 European Cultural Capital (ECOC was monitored in order to highlight the long-term impacts of the event. Preliminary findings on the tourism impacts are presented based on field research among visitors and statistics and field inventory. The most visible as well as the most significant impact on the city is the growth of accommodation supply. Not only did the number of licensed units and room grow substantially, but there was also considerable growth in the informal accommodation sector. Not only the city of Sibiu, but also the surrounding region benefited from the ECOC opportunity. The research shows that although the informal sector was able to respond fastest to the growth in accommodation demand, the greatest economic impact came from the development of large commercial hotels in the city itself.

  20. Prevalence of Accommodative and Non-Strabismic Binocular Anomalies in a Puerto Rican Pediatric Population

    Directory of Open Access Journals (Sweden)

    Stefania M. Paniccia, OD, MS

    2015-06-01

    Full Text Available Background: There exists a considerable void in the literature of studies that examine the prevalence of non-strabismic binocular and accommodative disorders in the pediatric population of Puerto Rico. The purpose of this retrospective study was to fill this void by performing a comprehensive record review of the pediatric clinical population of the InterAmerican University College of Optometry satellite clinics. Methods: This study was performed using a random selection of 593 existing health records of patients between the ages of 5 and 20 years. Patients had participated in a complete optometric assessment between the years 2004 and 2012. The criteria for selection were the absence of strabismus, amblyopia, nystagmus, vertical deviation, corneal pathology, retinal pathology, lens pathology, or any other parameter outside of population requirements. Results: Statistical analysis was performed using the IBM SPSS program. Results of this study indicate that the most common non-strabismic and accommodative anomalies in the studied population are accommodative insufficiency (39.0%, convergence insufficiency (12.6%, convergence excess (9.1%, and accommodative infacility (7.6%. Conclusions: Accommodative and non-strabismic binocular vision problems are prevalent in the pediatric population of the InterAmerican satellite clinics. This is the first epidemiologic study about the prevalence of these conditions in Puerto Rico. Due to the possibility of these non-strabismic and accommodative anomalies resulting in a reduced quality of life for children and affecting school performance, sports performance, and play activities, an appropriate vision evaluation, diagnosis, and treatment is important. Lastly, further comprehensive studies should be conducted in Puerto Rico using this study as a base for data collection and analysis.

  1. Steering Dynamic Performance of an Electric Transmission Tracked Vehicle Based on Rotating Speed Control

    Institute of Scientific and Technical Information of China (English)

    SUN Feng-chun; CHEN Shu-yong; ZHANG Cheng-ning

    2006-01-01

    In order to analyze steering dynamic performance of an electric transmission tracked vehicle exactly, modern design theory and methodology-collaborative simulation and virtual prototype are applied. The 3-D multi-body dynamic model of full vehicle running gears and control system model are built based on the simulation platform on dynamic analysis software known as RecurDyn/Track-HM and control system analysis software known as Matlab/Simulink. Theory analysis and collaborative simulation of turning kinematic/dynamic performance in different velocity and turning radius are made. Comparing the test result with theory computation validates the correctness of the model. The method has instructional significance of solving the existent modeling problem, comprehension of turning performance and test debugging strategy,and also forms a new idea of research on dynamic characteristics for the electric transmission tracked vehicle's electric propulsion system.

  2. Simulation Study of AC Contactor Dynamic Contacts Contact Pressure Based on ADAMS

    Directory of Open Access Journals (Sweden)

    Gu Yungao

    2015-01-01

    Full Text Available A multi-body dynamics simulation model of CJ20-25 AC contactor was established with Pro/E(Pro/Engineerin this paper. A coupling simulation with machine, electric, magnetic on the contactor has been achieved in this model. Dynamic parameters which were called use the secondary development technology of ADAMS. The dynamic contact pressure signal of an AC contactor was obtained with ADAMS’s own simultaneous solution such as electromagnetic suction, kinematics and dynamics equations. The simulation results and actual measurement of contactor contact pressure signals are very similar. However, the complexity of the measured contacts vibration is greater than the simulation results because the actual working condition is more complex. This result provides a theoretical foundation to the dynamic contacts contact pressure test.

  3. Riccati Discrete Time Transfer Matrix Method for Multibody System Dynamics%多体系统动力学Riccati离散时间传递矩阵法

    Institute of Scientific and Technical Information of China (English)

    何斌; 芮筱亭; 陆毓琪

    2006-01-01

    多体系统离散时间传递矩阵法是近年发展的多体系统动力学方法,因无须建立系统动力学方程、相关矩阵阶次低、计算速度快、建模程式化程度高等特点而倍受重视.为提高多体系统离散时间传递矩阵法的计算稳定性,本文将其与Riccati变换相结合,形成多体系统Riccati离散时间传递矩阵法,使空间传递两点边值问题化为初值问题、矩阵阶次降低.在Riccati变换时,选择了不同于振动力学Riccati传递矩阵法的合适中间变量,不扩大存储量的前提下进一步减小了计算时间.与多体系统离散时间传递矩阵法相比,提出的方法改善空间传递数值稳定性的同时不仅节省了计算时间,也提高了时间迭代计算稳定性.数值算例证明该方法对自由度十万的大系统有效、稳定性好,具有一定工程应用价值.

  4. Development of High Fidelity Mobility Simulation of an Autonomous Vehicle in an Off-Road Scenario Using Integrated Sensor, Controller, and Multi-Body Dynamics

    Science.gov (United States)

    2011-08-01

    intervene in the control of the vehicle. The software can be used to develop IV systems based on sensor technologies such as radar, laser, camera, GPS , and...traffic scenarios using a database of road sections, infrastructure components (trees, buildings, traffic signs) and road users (cars, trucks, cyclists ...a GPS navigation device. Weather conditions (rain, snow, fog) and light circumstances can also be specified. Modeling sensors is done by filling

  5. 多体系统发射动力学及其应用%Launch dynamics of multibody system and its applications

    Institute of Scientific and Technical Information of China (English)

    芮筱亭

    2011-01-01

    射击精度差、试验用弹量大、发射不安全是制约现代火箭、火炮武器发展的三大技术难题.武器系统精度和发射安全性取决于武器系统动力学规律,发射动力学作为研究武器系统发射过程中受力和运动规律的一门新兴综合工程学科,在国际上已成为提高火箭和火炮武器系统射击精度和发射安全性的新技术突破口,为射击精度和发射安全性设计与试验提供新理论与技术.文章研究多体系统发射动力学理论与技术及其在火箭和火炮武器射击精度和安全性设计与试验中的应用.%To review the marine radioactive-pollution monitoring and assessment technology, the sources and components of marine radioactivity were introduced; the development on the methods of marine radioactivity analysis and the technology of monitoring network were appreciated, and the possibility and importance on building the methodologies of non-human species radiation protection and assessment were discussed, including the assessment of marine radioactive-pollution. Some advice for developing marine radio-monitoring technology in China was proposed at last.

  6. Seven rules to live by: accommodations in social work education and the field.

    Science.gov (United States)

    Neely-Barnes, Susan Louise; McCabe, Heather A; Barnes, Craig P

    2014-01-01

    Students with disabilities are a growing population in higher education (National Center for Education Statistics, 2009 ). Providing accommodations for students with disabilities can raise ethical and social justice questions and pose challenges for social work faculty, administrators, and field instructors. Social work educators must balance the legal mandates for nondiscrimination and reasonable accommodation against ethical obligations around protection of clients and preparation for practice. This article presents case examples in the context of legal analysis to help social work educators make difficult decisions about student academic performance.

  7. Fault detection and accommodation via neural network and variable structure control

    Institute of Scientific and Technical Information of China (English)

    Hao YANG; Bin JIANG

    2007-01-01

    This paper proposes a novel idea that classifies faults into two different kinds: serious faults and small faults,and treats them with different strategies respectively. A kind of artificial neural network (ANN) is proposed for detecting serious faults, and variable structure (VS) model-following control is constructed for accommodating small faults. The proposed framework takes both advantages of qualitative way and quantitative way of fault detection and accommodation.Moreover, the uncertainty case is investigated and the VS controller is modified. Simulation results of a remotely piloted aircraft with control actuator failures illustrate the performance of the developed algorithm.

  8. The effects of emotional intelligence on human resources selection: A research on managers of accommodation enterprises

    Directory of Open Access Journals (Sweden)

    Mahmut Demir

    2010-04-01

    Full Text Available The purpose of this study is to determine the effect of emotional intelligence characteristics of managers on human resources selection in the accommodation enterprises. Previously questionnaire was developed from MSCEIT. Data were gathered from hotel managers with the help of a questionnaire which is conducted face to face. Data was tested with factor analysis and regression analysis on SPSS. The results of the study show that emotional intelligence characteristics of managers in the accommodation enterprises, effect on their decision of human resources selection

  9. FORMATION OF CONSUMER ACCOMMODATION MODELS WITH DUE ACCOUNT OF POPULATION INVESTMENT POTENTIAL

    Directory of Open Access Journals (Sweden)

    I. Shaniukevich

    2013-01-01

    Full Text Available The paper considers a theme of typological urban housing diversity  which is relevant for a modern residential real estate market. Analyzed Quantitative and qualitative characteristics of the existing urban residential accommodation, new  house building have been analyzed in the paper. The paper presents author’s calculations of differentiation extent and changes in economic opportunities of the population. Differentiation of  potential consumer accommodation models with specific standardized characteristics has been made in terms of the population economic prosperity.  The paper substantiates proposals on accountability and implementation of typological differences in the government housing policy.

  10. Design of Multi-body Straw Biomass Gasifier%多体式秸秆生物质气化炉的设计

    Institute of Scientific and Technical Information of China (English)

    鲍振博; 刘长安; 解光传; 彭锦星; 靳登超; 刘玉乐

    2017-01-01

    Biomass energy is a kind of clean and renewable energy, the development and application of straw biomass en-ergy has broad prospects, gasification combustion is a form of straw biomass utilization. For the problems in use of small household biomass gasifier, such as the more tar and ash in gasification gas, materials continuous addition process com-plexity, and materials intermittent supply inconvenience and so on, the overall structure of multi-body straw biomass gasi-fier has designed. Through the structure designs of three gasification combustion furnaces and removable inner furnace, air gasification agent preheat and uniform supply, and secondary purification disposals of tar and dust impurities, which can make the biomass material loading conditions meet the needs of home cooking, ensure process requirements of gasification reaction, and effective removal of tar and dust impurities in gasification gas. The using promotion of multi-body straw bio-mass gasifier can promote the realization of the effective use of straw biomass, while help to solve the problems of straw bi-omass resource waste and pollution.%生物质能是一种清洁、可再生的能源,秸秆生物质能的开发、应用具有广阔前景,而气化燃烧是秸秆生物质能利用的一种形式。针对小型家用生物质气化炉在使用中存在气化气中焦油、灰分含量多,物料连续添加工艺复杂,而物料间断供给使用不便等问题,提出一种多体式秸秆生物质气化炉的设计。通过3个气化燃烧炉体且内炉体可拆卸,空气气化剂预热、均布供给,焦油及灰尘杂质二级净化处置等结构设计,可使得生物质物料装填工况满足家用炊事需求、保证气化反应工艺要求、有效去除气化气中焦油及灰尘杂质。多体式秸秆生物质气化炉的使用推广,可实现对秸秆生物质能源有效利用,也有助于解决秸秆生物质资源浪费及污染问题。

  11. Work Accommodations and Natural Supports for Employees with Severe Mental Illness in Social Businesses: An International Comparison.

    Science.gov (United States)

    Villotti, Patrizia; Corbière, Marc; Fossey, Ellie; Fraccaroli, Franco; Lecomte, Tania; Harvey, Carol

    2016-12-03

    Little is known about the types of work accommodations and natural supports that are useful for people experiencing severe mental illness working in social businesses. We conducted an exploratory, descriptive and cross-sectional investigation in Australia, Canada and Italy to study the nature of work accommodations and natural supports available in social businesses. Study findings are drawn from survey responses of a convenience sample of 90 employees with self-reported psychiatric disabilities. Results showed that, regardless of the country, social businesses provide many work accommodations and natural supports, especially those linked to schedule flexibility and support, while work accommodations related to training and schedule flexibility were linked to longer job tenure. Overall, this study advances our knowledge about the spectrum of work accommodations and natural supports that are available in social businesses for people with severe mental illness. Also, it highlights the type of work accommodations that are likely to support this population to sustain employment.

  12. Dislocation-accommodated grain boundary sliding as the major deformation mechanism of olivine in the Earth's upper mantle.

    Science.gov (United States)

    Ohuchi, Tomohiro; Kawazoe, Takaaki; Higo, Yuji; Funakoshi, Ken-Ichi; Suzuki, Akio; Kikegawa, Takumi; Irifune, Tetsuo

    2015-10-01

    Understanding the deformation mechanisms of olivine is important for addressing the dynamic processes in Earth's upper mantle. It has been thought that dislocation creep is the dominant mechanism because of extrapolated laboratory data on the plasticity of olivine at pressures below 0.5 GPa. However, we found that dislocation-accommodated grain boundary sliding (DisGBS), rather than dislocation creep, dominates the deformation of olivine under middle and deep upper mantle conditions. We used a deformation-DIA apparatus combined with synchrotron in situ x-ray observations to study the plasticity of olivine aggregates at pressures up to 6.7 GPa (that is, ~200-km depth) and at temperatures between 1273 and 1473 K, which is equivalent to the conditions in the middle region of the upper mantle. The creep strength of olivine deforming by DisGBS is apparently less sensitive to pressure because of the competing pressure-hardening effect of the activation volume and pressure-softening effect of water fugacity. The estimated viscosity of olivine controlled by DisGBS is independent of depth and ranges from 10(19.6) to 10(20.7) Pa·s throughout the asthenospheric upper mantle with a representative water content (50 to 1000 parts per million H/Si), which is consistent with geophysical viscosity profiles. Because DisGBS is a grain size-sensitive creep mechanism, the evolution of the grain size of olivine is an important process controlling the dynamics of the upper mantle.

  13. Linear dynamic analysis of multi-mesh transmissions containing external, rigid gears

    Science.gov (United States)

    Vinayak, H.; Singh, R.; Padmanabhan, C.

    1995-08-01

    This paper extends the multi-body dynamics modeling strategy for a gear pair [6] to multi-mesh transmissions with external, fixed center, helical or spur gears. Each gear is modeled as a rigid body with six degrees of freedom. A multi-dimensional, position-dependent formulation is used to describe the gear mesh stiffness which is assumed to be distributed along the line of action. A simplified model of the shaft-bearing subsystems is included since the focus of this study is on the gear dynamics. Excitation to the system is considered in the form of either external torque pulsation or internal static transmission error. The governing equations are linearized to yield a formulation with position or time-varying coefficients (LTV). Subsequently, three examples of linearized time-invariant (LTI) transmission systems are solved, and eigensolution predictions of the multi-body dynamics model compare very well with finite element calculations. Then the periodic response of a non-unity gear pair system is studied in depth. New results including a comparison between LTI and LTV models are presented. It has been demonstrated that both time and frequency domain solutions can be efficiently and accurately constructed by using the multi-term harmonic balance method, provided that several shaft and gear mesh harmonics are included.

  14. Cultural accommodation and language priming : Competitive versus cooperative behavior in a prisoner's dilemma game

    NARCIS (Netherlands)

    Akkermans, D.H.M.; Harzing, A.W.; van Witteloostuijn, A.

    2010-01-01

    This paper explores three arguments. First, cultural accommodation by living in another culture for a while may have a long-lasting but partially dormant influence on behavior. Second, foreign language is a prime, activating behavior associated with this language. Third, a foreign language is expect

  15. Performance Measurement and Accommodation: Students with Visual Impairments on Pennsylvania's Alternate Assessment

    Science.gov (United States)

    Zebehazy, Kim T.; Zigmond, Naomi; Zimmerman, George J.

    2012-01-01

    Introduction: This study investigated the use of accommodations and the performance of students with visual impairments and severe cognitive disabilities on the Pennsylvania Alternate System of Assessment (PASA)yCoan alternate performance-based assessment. Methods: Differences in test scores on the most basic level (level A) of the PASA of 286…

  16. Developing Testing Accommodations for English Language Learners: Illustrations as Visual Supports for Item Accessibility

    Science.gov (United States)

    Solano-Flores, Guillermo; Wang, Chao; Kachchaf, Rachel; Soltero-Gonzalez, Lucinda; Nguyen-Le, Khanh

    2014-01-01

    We address valid testing for English language learners (ELLs)--students in the United States who are schooled in English while they are still acquiring English as a second language. Also, we address the need for procedures for systematically developing ELL testing accommodations--changes in tests intended to support ELLs to gain access to the…

  17. Comparing Audio-Supported Text and Explicit Instruction on Students' Knowledge of Accommodations, Rights, and Responsibilities

    Science.gov (United States)

    Wood, Charles L.; Kelley, Kelly R.; Test, David W.; Fowler, Catherine H.

    2010-01-01

    With increasing numbers of students with disabilities entering postsecondary education, it is important to teach students with disabilities their rights and responsibilities governed by civil rights acts (i.e., Section 504 of the Rehabilitation Act of 1973, Americans With Disabilities Act) for requesting accommodations in postsecondary education.…

  18. 34 CFR 79.10 - How does the Secretary make efforts to accommodate intergovernmental concerns?

    Science.gov (United States)

    2010-07-01

    ... 34 Education 1 2010-07-01 2010-07-01 false How does the Secretary make efforts to accommodate intergovernmental concerns? 79.10 Section 79.10 Education Office of the Secretary, Department of Education INTERGOVERNMENTAL REVIEW OF DEPARTMENT OF EDUCATION PROGRAMS AND ACTIVITIES § 79.10 How does the Secretary...

  19. 75 FR 65261 - Virginia Graeme Baker Pool and Spa Safety Act; Public Accommodation

    Science.gov (United States)

    2010-10-22

    ... main drain other than an unblockable drain be equipped with certain secondary anti-entrapment systems...) (condominium complex does not constitute a place of public accommodation, assuming it does not offer such short... Hotel Condominium Ass'n, 2005 U.S. Dist. LEXIS 41601 (November 22, 2005) (condominium buildings may...

  20. The Effect of Visual-Chunking-Representation Accommodation on Geometry Testing for Students with Math Disabilities

    Science.gov (United States)

    Zhang, Dake; Ding, Yi; Stegall, Joanna; Mo, Lei

    2012-01-01

    Students who struggle with learning mathematics often have difficulties with geometry problem solving, which requires strong visual imagery skills. These difficulties have been correlated with deficiencies in visual working memory. Cognitive psychology has shown that chunking of visual items accommodates students' working memory deficits. This…

  1. Implementation of the Eco-label for Tourist Accommodation Units in Arad

    Directory of Open Access Journals (Sweden)

    F. S. Barbu

    2013-12-01

    Full Text Available This study examines tourist accommodation managers' attitude towards implementing the eco-labeling scheme; and, also, the degree of awareness regarding the necessity of directing businesses towards sustainable development by adopting the following: limited water and energy consumption, reduced waste production, the use of renewable resources and low-environmental impact substances, the promotion of the environmental protection education.

  2. Implementation of the Eco-label for Tourist Accommodation Units in Arad

    OpenAIRE

    F. S. Barbu

    2013-01-01

    This study examines tourist accommodation managers' attitude towards implementing the eco-labeling scheme; and, also, the degree of awareness regarding the necessity of directing businesses towards sustainable development by adopting the following: limited water and energy consumption, reduced waste production, the use of renewable resources and low-environmental impact substances, the promotion of the environmental protection education.

  3. End-of-Life Care Policies in Flemish Residential Care Facilities Accommodating Persons with Intellectual Disabilities

    Science.gov (United States)

    D'Haene, I.; Pasman, H. R. W.; Deliens, L.; Bilsen, J.; Mortier, F.; Stichele, R. Vander

    2010-01-01

    Objective: This article aims to describe the presence, content and implementation strategies of written policies on end-of-life decisions in Flemish residential care facilities (RCFs) accommodating persons with intellectual disabilities (ID), and to describe training, education and quality assessments of end-of-life care. Methods: A…

  4. Voice Onset Time in Consonant Cluster Errors: Can Phonetic Accommodation Differentiate Cognitive from Motor Errors?

    Science.gov (United States)

    Pouplier, Marianne; Marin, Stefania; Waltl, Susanne

    2014-01-01

    Purpose: Phonetic accommodation in speech errors has traditionally been used to identify the processing level at which an error has occurred. Recent studies have challenged the view that noncanonical productions may solely be due to phonetic, not phonological, processing irregularities, as previously assumed. The authors of the present study…

  5. Robust observer-based fault estimation and accommodation of discrete-time piecewise linear systems

    DEFF Research Database (Denmark)

    Tabatabaeipour, Mojtaba; Bak, Thomas

    2013-01-01

    In this paper a new integrated observer-based fault estimation and accommodation strategy for discrete-time piecewise linear (PWL) systems subject to actuator faults is proposed. A robust estimator is designed to simultaneously estimate the state of the system and the actuator fault. Then, the es...

  6. The Effect of a Noise Reducing Test Accommodation on Elementary Students with Learning Disabilities

    Science.gov (United States)

    Smith, Gregory W.; Riccomini, Paul J.

    2013-01-01

    Researchers in the fields of cognitive psychology and education have been studying the negative effects of noise on human performance for almost a century. A new empirical study that builds upon past relevant research on (1) test accommodations and (2) auditory distraction and academic performance was conducted with elementary age students.…

  7. The Effects of Vocalics and Nonverbal Sensitivity on Compliance: A Speech Accommodation Theory Explanation.

    Science.gov (United States)

    Buller, David B.; Aune, R. Kelly

    1988-01-01

    Explains a speech accommodation theory for the interaction between a receiver's decoding ability and a speaker's voice tone on compliance with requests for help. Good decoders complied more with the fast request, whereas poor decoders complied more with the slow request. (RAE)

  8. Optical method for measuring thermal accommodation coefficients using a whispering-gallery microresonator

    Science.gov (United States)

    Ganta, D.; Dale, E. B.; Rezac, J. P.; Rosenberger, A. T.

    2011-08-01

    A novel optical method has been developed for the measurement of thermal accommodation coefficients in the temperature-jump regime. The temperature dependence of the resonant frequency of a fused-silica microresonator's whispering-gallery mode is used to measure the rate at which the microresonator comes into thermal equilibrium with the ambient gas. The thermal relaxation time is related to the thermal conductivity of the gas under some simplifying assumptions and measuring this time as a function of gas pressure determines the thermal accommodation coefficient. Using a low-power tunable diode laser of wavelength around 1570 nm to probe a microsphere's whispering-gallery mode through tapered-fiber coupling, we have measured the accommodation coefficients of air, helium, and nitrogen on fused silica at room temperature. In addition, by applying thin-film coatings to the microsphere's surface, we have demonstrated that accommodation coefficients can be measured for various gases on a wide range of modified surfaces using this method.

  9. Culture Change from Tobacco Accommodation to Intolerance: Time to Connect the Dots

    Science.gov (United States)

    Livingood, William C., Jr.; Allegrante, John P.; Green, Lawrence W.

    2016-01-01

    Broad changes in normative health behavior are critical to overcoming many of the contemporary challenges to public health. Reduction in tobacco use during the last third of the 20th century--one of the greatest improvements in public health--illustrates such change. The culture change from accommodation to intolerance of smoking is irrefutable.…

  10. Prevention of capsular opacification after accommodative lens refilling surgery in rabbits

    NARCIS (Netherlands)

    Koopmans, Steven A.; Terwee, Thom; van Kooten, Theo G.

    2011-01-01

    Silicone gel-like polymers have been proposed to replace the cataractous lens and therewith restore both vision and accommodation. Lens replacement is associated with opacification of the capsular bag due to the lens epithelial cell response. In this study, the in vivo effectiveness of a 5 min treat

  11. Contextual and Mathematics Accommodation Test Effects for English-Language Learners.

    Science.gov (United States)

    Hofstetter, Carolyn Huie

    2003-01-01

    Examined selected contextual variables, their impact on test performance, and how the variables interact with the type of test accommodation that a student received. Data from 849 eighth graders suggest that numerous student and classroom-level variables are associated with mathematics test performance, English reading proficiency in particular.…

  12. The Failure to Construct Proof Based on Assimilation and Accommodation Framework from Piaget

    Science.gov (United States)

    Netti, Syukma; Nusantara, Toto; Subanji; Abadyo; Anwar, Lathiful

    2016-01-01

    The purpose of this article is to describe the process of a proof construction. It is more specific on the failure of the process. Piaget's frameworks, assimilation and accommodation, were used to analyze it. Method of this research was qualitative method. Data were collected by asking five students working on problems of proof using think aloud…

  13. Math Learning Model That Accommodates Cognitive Style to Build Problem-Solving Skills

    Science.gov (United States)

    Warli; Fadiana, Mu'jizatin

    2015-01-01

    The purpose of this research is to develop mathematical learning models that accommodate the cognitive styles reflective vs. impulsive students to build problem-solving skills, quality (valid, practical, and effective). To achieve the target would do research development (development research) and method development that consists of five stages,…

  14. 13 CFR 113.3-2 - Accommodations to religious observance and practice.

    Science.gov (United States)

    2010-01-01

    ..., at least the following factors should be considered: (a) Business necessity, (b) financial costs and... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Accommodations to religious observance and practice. 113.3-2 Section 113.3-2 Business Credit and Assistance SMALL BUSINESS...

  15. Students' Thinking Process in Solving Combination Problems Considered from Assimilation and Accommodation Framework

    Science.gov (United States)

    Jalan, Sukoriyanto; Nusantara, Toto; Subanji, Subanji; Chandra, Tjang Daniel

    2016-01-01

    This study aims to explain the thinking process of students in solving combination problems considered from assimilation and accommodation frameworks. This research used a case study approach by classifying students into three categories of capabilities namely high, medium and low capabilities. From each of the ability categories, one student was…

  16. A formal translation of the Assimilation-Accommodation Coping Scale from German to Dutch

    NARCIS (Netherlands)

    L. Aben (Laurien); J.J. van Busschbach (Jan)

    2009-01-01

    textabstractThe Assimilation-Accommodation Coping Scale was developed in Germany by Brandtstädter and Renner and applied in the UK and the Netherlands. A formal translation was never reported. Such formal translation was warranted as we found ambivalent language and atypical sentences in the Dutch t

  17. OSHA and ADA: "Reasonable Accommodation" in Training Persons with Developmental Disabilities.

    Science.gov (United States)

    Sandoz, Charles J.

    This paper documents an approach to meeting the training requirements of the Occupational Safety and Health Act (OSHA) and the "reasonable accommodation" requirements of the Americans with Disabilities Act (ADA) for individuals with developmental disabilities. It describes a training program used with three adult workers with mild mental…

  18. IDENTIFYING TOURISTS INTERESTED IN ECO-CERTIFIED ACCOMMODATION UNITS FROM BRASOV, ROMANIA

    Directory of Open Access Journals (Sweden)

    Cristinel Petrisor Constantin

    2014-02-01

    Full Text Available Ecolabels are key instruments for a sustainable tourism development and implementation of environmental certification of tourist accommodation facilities and services. The present paper aimes to analyze whether eco-certification is considered by tourists in the choice of accommodation in Romanian destinations. We have chosen as a case study the city of Brasov in order to evaluate if certification as a sustainability policy tool is needed for accommodation facilities. A survey was conducted among 940 tourists from the analyzed destination. Data collected in the survey was analyzed using the Statistical Package for Social Sciences (SPSS and several statistical methods have been used: descriptive analysis, crosstabs, Cluster Analysis. The results of the research outline the necessity for Brasov’s accommodation managers to consider the eco-certification of their businesses. However, since some tourists remain unaware regarding the existence of tourism certification programs and far fewer understand their meaning, they would have to consider educating tourists with respect to the utility and scope of tourism ecolabels alongside efforts towards creating or adopting tourism ecolabeling programs.

  19. 77 FR 16163 - Nondiscrimination on the Basis of Disability by Public Accommodations and in Commercial...

    Science.gov (United States)

    2012-03-20

    ... Parts 35 and 36 RIN 1190-AA68 Nondiscrimination on the Basis of Disability by Public Accommodations and in Commercial Facilities; Swimming Pools AGENCY: Civil Rights Division, Department of Justice. ACTION... certain requirements in the 2010 Americans with Disabilities Act (ADA) Standards for Accessible...

  20. "What's in It for Me?" A Study on Students' Accommodation or Resistance during Group Work

    Science.gov (United States)

    Forslund Frykedal, Karin; Samuelsson, Marcus

    2016-01-01

    This article explores students' accommodation and resistance while participating in group work. The data collected are from fieldwork observations in several classrooms over the course of four terms in different secondary school classes in Sweden, and also from interviews with the students. Through this data analysis, we report that the students…