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.
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......This work deals with the mathematical modelling of multibody systems interconnected via thin fluid films. The dynamics of the fluid films can be actively controlled by means of different types of actuators, allowing significant vibration reduction of the system components. In this framework...... to the rotor via a thin fluid film, where the hydrodynamic pressure is described by the Reynolds equation, which is modified to accommodate the controllable lubrication conditions. The fluid film forces are coupled to the set of nonlinear equations that describes the dynamics of the reciprocating linear...
Three-dimensional formulation of rigid-flexible multibody systems with flexible beam elements
International Nuclear Information System (INIS)
Garcia-Vallejo, D.; Mayo, J.; Escalona, J. L.; Dominguez, J.
2008-01-01
Multibody systems generally contain solids with appreciable deformations and which decisively influence the dynamics of the system. These solids have to be modeled by means of special formulations for flexible solids. At the same time, other solids are of such a high stiffness that they may be considered rigid, which simplifies their modeling. For these reasons, for a rigid-flexible multibody system, two types of formulations coexist in the equations of the system. Among the different possibilities provided in the literature on the material, the formulation in natural coordinates and the formulation in absolute nodal coordinates are utilized in this paper to model the rigid and flexible solids, respectively. This paper contains a mixed formulation based on the possibility of sharing coordinates between a rigid solid and a flexible solid. The global mass matrix of the system is shown to be constant and, in addition, many of the constraint equations obtained upon utilizing these formulations are linear and can be eliminated
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....
Simulating coupled dynamics of a rigid-flexible multibody system and compressible fluid
Hu, Wei; Tian, Qiang; Hu, HaiYan
2018-04-01
As a subsequent work of previous studies of authors, a new parallel computation approach is proposed to simulate the coupled dynamics of a rigid-flexible multibody system and compressible fluid. In this approach, the smoothed particle hydrodynamics (SPH) method is used to model the compressible fluid, the natural coordinate formulation (NCF) and absolute nodal coordinate formulation (ANCF) are used to model the rigid and flexible bodies, respectively. In order to model the compressible fluid properly and efficiently via SPH method, three measures are taken as follows. The first is to use the Riemann solver to cope with the fluid compressibility, the second is to define virtual particles of SPH to model the dynamic interaction between the fluid and the multibody system, and the third is to impose the boundary conditions of periodical inflow and outflow to reduce the number of SPH particles involved in the computation process. Afterwards, a parallel computation strategy is proposed based on the graphics processing unit (GPU) to detect the neighboring SPH particles and to solve the dynamic equations of SPH particles in order to improve the computation efficiency. Meanwhile, the generalized-alpha algorithm is used to solve the dynamic equations of the multibody system. Finally, four case studies are given to validate the proposed parallel computation approach.
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.
Fijany, Amir
1993-01-01
In this paper, parallel O(log n) algorithms for computation of rigid multibody dynamics are developed. These parallel algorithms are derived by parallelization of new O(n) algorithms for the problem. The underlying feature of these O(n) algorithms is a drastically different strategy for decomposition of interbody force which leads to a new factorization of the mass matrix (M). Specifically, it is shown that a factorization of the inverse of the mass matrix in the form of the Schur Complement is derived as M(exp -1) = C - B(exp *)A(exp -1)B, wherein matrices C, A, and B are block tridiagonal matrices. The new O(n) algorithm is then derived as a recursive implementation of this factorization of M(exp -1). For the closed-chain systems, similar factorizations and O(n) algorithms for computation of Operational Space Mass Matrix lambda and its inverse lambda(exp -1) are also derived. It is shown that these O(n) algorithms are strictly parallel, that is, they are less efficient than other algorithms for serial computation of the problem. But, to our knowledge, they are the only known algorithms that can be parallelized and that lead to both time- and processor-optimal parallel algorithms for the problem, i.e., parallel O(log n) algorithms with O(n) processors. The developed parallel algorithms, in addition to their theoretical significance, are also practical from an implementation point of view due to their simple architectural requirements.
Dynamics of underactuated multibody systems modeling, control and optimal design
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.
Multibody system dynamics, robotics and control
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.
A multibody motorcycle model with rigid-ring tyres: formulation and validation
Leonelli, Luca; Mancinelli, Nicolò
2015-06-01
The aim of this paper is the development and validation of a three-dimensional multibody motorcycle model including a rigid-ring tyre model, taking into account both the slopes and elevation of the road surface. In order to achieve accurate assessment of ride and handling performances of a road racing motorcycle, a tyre model capable of reproducing the dynamic response to actual road excitation is required. While a number of vehicle models with such feature are available for car application, the extension to the motorcycle modelling has not been addressed yet. To do so, a novel parametrisation for the general motorcycle kinematics is proposed, using a mixed reference point and relative coordinates approach. The resulting description, developed in terms of dependent coordinates, makes it possible to include the rigid-ring kinematics as well as road elevation and slopes, without affecting computational efficiency. The equations of motion for the whole multibody system are derived symbolically and the constraint equations arising from the dependent coordinate formulation are handled using the position and velocity vector projection technique. The resulting system of equations is integrated in time domain using a standard ordinary differential equation (ODE) algorithm. Finally, the model is validated with respect to experimentally measured data in both time and frequency domains.
Flexible Multibody Systems Models Using Composite Materials Components
International Nuclear Information System (INIS)
Neto, Maria Augusta; Ambr'osio, Jorge A. C.; Leal, Rog'erio Pereira
2004-01-01
The use of a multibody methodology to describe the large motion of complex systems that experience structural deformations enables to represent the complete system motion, the relative kinematics between the components involved, the deformation of the structural members and the inertia coupling between the large rigid body motion and the system elastodynamics. In this work, the flexible multibody dynamics formulations of complex models are extended to include elastic components made of composite materials, which may be laminated and anisotropic. The deformation of any structural member must be elastic and linear, when described in a coordinate frame fixed to one or more material points of its domain, regardless of the complexity of its geometry. To achieve the proposed flexible multibody formulation, a finite element model for each flexible body is used. For the beam composite material elements, the sections properties are found using an asymptotic procedure that involves a two-dimensional finite element analysis of their cross-section. The equations of motion of the flexible multibody system are solved using an augmented Lagrangian formulation and the accelerations and velocities are integrated in time using a multi-step multi-order integration algorithm based on the Gear method
Planar reorientation maneuvers of space multibody systems using internal controls
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.
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 this paper the system reduction in nonlinear multibody dynamics of wind turbines is investigated for various updating schemes of the moving frame of reference. In one case, the moving frame of reference is updated to a stiff body, relative to which the elastic deformations are fixed at one end....... In the other case, the stiff body motion is defined as the chord line connecting the end points of the beam, and the elastic deformations are simply supported at the end points. The system reduction is performed by discretizing the spatial motion into a set of rigid body modes and linear elastic eigenmodes...
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.
Developments of multibody system dynamics: computer simulations and experiments
International Nuclear Information System (INIS)
Yoo, Wan-Suk; Kim, Kee-Nam; Kim, Hyun-Woo; Sohn, Jeong-Hyun
2007-01-01
It is an exceptional success when multibody dynamics researchers Multibody System Dynamics journal one of the most highly ranked journals in the last 10 years. In the inaugural issue, Professor Schiehlen wrote an interesting article explaining the roots and perspectives of multibody system dynamics. Professor Shabana also wrote an interesting article to review developments in flexible multibody dynamics. The application possibilities of multibody system dynamics have grown wider and deeper, with many application examples being introduced with multibody techniques in the past 10 years. In this paper, the development of multibody dynamics is briefly reviewed and several applications of multibody dynamics are described according to the author's research results. Simulation examples are compared to physical experiments, which show reasonableness and accuracy of the multibody formulation applied to real problems. Computer simulations using the absolute nodal coordinate formulation (ANCF) were also compared to physical experiments; therefore, the validity of ANCF for large-displacement and large-deformation problems was shown. Physical experiments for large deformation problems include beam, plate, chain, and strip. Other research topics currently being carried out in the author's laboratory are also briefly explained
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.)
Constraint Embedding Technique for Multibody System Dynamics
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
Applications of Lie Group Theory to the Modeling and Control of Multibody Systems
International Nuclear Information System (INIS)
Mladenova, Clementina D.
1999-01-01
This paper reviews our research activities concerning the modeling and control of rigid and elastic joint multibody mechanical systems, including some investigations into nonholonomic systems. Bearing in mind the different parameterizations of the rotation group in three-dimensional space SO(3), and the fact that the properties of the parameterization more or less influence the efficiency of the dynamics model, here the so-called vector parameter is used for parallel considerations of rigid body motion and of rigid and elastic joint multibody mechanical systems. Besides the fundamental role of this study, the vector-parameter approach is efficient in its computational aspect and quite convenient for real time simulation and control. The consideration of the mechanical system on the configuration space of pure vector parameters with a group structure opens the possibilities for the Lie group theory to be applied in problems of dynamics and control
Dynamic Behavior of Wind Turbine by a Mixed Flexible-Rigid Multi-Body Model
Wang, Jianhong; Qin, Datong; Ding, Yi
A mixed flexible-rigid multi-body model is presented to study the dynamic behavior of a horizontal axis wind turbine. The special attention is given to flexible body: flexible rotor is modeled by a newly developed blade finite element, support bearing elasticities, variations in the number of teeth in contact as well as contact tooth's elasticities are mainly flexible components in the power train. The couple conditions between different subsystems are established by constraint equations. The wind turbine model is generated by coupling models of rotor, power train and generator with constraint equations together. Based on this model, an eigenproblem analysis is carried out to show the mode shape of rotor and power train at a few natural frequencies. The dynamic responses and contact forces among gears under constant wind speed and fixed pitch angle are analyzed.
System Reduction in Multibody Dynamics of Wind Turbines
DEFF Research Database (Denmark)
Holm-Jørgensen, Kristian; Nielsen, Søren R.K.
2009-01-01
Abstract A system reduction scheme is devised related to a multibody formulation from which the dynamic response of a wind turbine is determined. In this formulation each substructure is described in its own frame of reference, which is moving freely in the vicinity of the moving substructure....... 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...... in the expansion via a quasi-static correction. The results show that by using the derived reduction scheme it is only necessary with 2 dynamical modes for the blade substructure when the remaining modes are treated as quasi-static. Moreover, it is shown that it has little to none effect if the gyroscopic...
Constraint Embedding for Multibody System Dynamics
Jain, Abhinandan
2009-01-01
This paper describes a constraint embedding approach for the handling of local closure constraints in multibody system dynamics. The approach uses spatial operator techniques to eliminate local-loop constraints from the system and effectively convert the system into tree-topology systems. This approach allows the direct derivation of recursive O(N) techniques for solving the system dynamics and avoiding the expensive steps that would otherwise be required for handling the closedchain dynamics. The approach is very effective for systems where the constraints are confined to small-subgraphs within the system topology. The paper provides background on the spatial operator O(N) algorithms, the extensions for handling embedded constraints, and concludes with some examples of such constraints.
Nonlinear dynamic analysis of flexible multibody systems
Bauchau, Olivier A.; Kang, Nam Kook
1991-01-01
Two approaches are developed to analyze the dynamic behavior of flexible multibody systems. In the first approach each body is modeled with a modal methodology in a local non-inertial frame of reference, whereas in the second approach, each body is modeled with a finite element methodology in the inertial frame. In both cases, the interaction among the various elastic bodies is represented by constraint equations. The two approaches were compared for accuracy and efficiency: the first approach is preferable when the nonlinearities are not too strong but it becomes cumbersome and expensive to use when many modes must be used. The second approach is more general and easier to implement but could result in high computation costs for a large system. The constraints should be enforced in a time derivative fashion for better accuracy and stability.
Dynamics of Multibody Systems Near Lagrangian Points
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
System Theory Aspects of Multi-Body Dynamics.
1978-08-18
systems are described from a system theory point of view. Various system theory concepts and research topics which have applicability to this class of...systems are identified and briefly described. The subject of multi-body dynamics is presented in a vector space setting and is related to system theory concepts. (Author)
International Nuclear Information System (INIS)
Leyendecker, Sigrid; Betsch, Peter; Steinmann, Paul
2008-01-01
In the present work, the unified framework for the computational treatment of rigid bodies and nonlinear beams developed by Betsch and Steinmann (Multibody Syst. Dyn. 8, 367-391, 2002) is extended to the realm of nonlinear shells. In particular, a specific constrained formulation of shells is proposed which leads to the semi-discrete equations of motion characterized by a set of differential-algebraic equations (DAEs). The DAEs provide a uniform description for rigid bodies, semi-discrete beams and shells and, consequently, flexible multibody systems. The constraints may be divided into two classes: (i) internal constraints which are intimately connected with the assumption of rigidity of the bodies, and (ii) external constraints related to the presence of joints in a multibody framework. The present approach thus circumvents the use of rotational variables throughout the whole time discretization, facilitating the design of energy-momentum methods for flexible multibody dynamics. After the discretization has been completed a size-reduction of the discrete system is performed by eliminating the constraint forces. Numerical examples dealing with a spatial slider-crank mechanism and with intersecting shells illustrate the performance of the proposed method
A new version of transfer matrix method for multibody systems
Energy Technology Data Exchange (ETDEWEB)
Rui, Xiaoting, E-mail: ruixt@163.net [Nanjing University of Science and Technology, Institute of Launch Dynamics (China); Bestle, Dieter, E-mail: bestle@b-tu.de [Brandenburg University of Technology, Engineering Mechanics and Vehicle Dynamics (Germany); Zhang, Jianshu, E-mail: zhangdracpa@sina.com; Zhou, Qinbo, E-mail: zqb912-new@163.com [Nanjing University of Science and Technology, Institute of Launch Dynamics (China)
2016-10-15
In order to avoid the global dynamics equations and increase the computational efficiency for multibody system dynamics (MSD), the transfer matrix method of multibody system (MSTMM) has been developed and applied very widely in research and engineering in recent 20 years. It differs from ordinary methods in multibody system dynamics with respect to the feature that there is no need for a global dynamics equation, and it uses low-order matrices for high computational efficiency. For linear systems, MSTMM is exact even if continuous elements like beams are involved. The discrete time MSTMM, however, has to use local linearization. In order to release the method from such approximations, a new version of MSTMM is presented in this paper where translational and angular accelerations, on the one hand, and internal forces and moments, on the other hand, are used as state variables. Already linear relationships among these quantities are utilized, which results in new element transfer matrices and algorithms making the study of multibody systems as simple as the study of single bodies. The proposed approach also allows combining MSTMM with any general numerical integration procedure. Some numerical examples of MSD are given to demonstrate the proposed method.
Attitude coordination of multi-HUG formation based on multibody system theory
Xue, Dong-yang; Wu, Zhi-liang; Qi, Er-mai; Wang, Yan-hui; Wang, Shu-xin
2017-04-01
Application of multiple hybrid underwater gliders (HUGs) is a promising method for large scale, long-term ocean survey. Attitude coordination has become a requisite for task execution of multi-HUG formation. In this paper, a multibody model is presented for attitude coordination among agents in the HUG formation. The HUG formation is regarded as a multi-rigid body system. The interaction between agents in the formation is described by artificial potential field (APF) approach. Attitude control torque is composed of a conservative torque generated by orientation potential field and a dissipative term related with angular velocity. Dynamic modeling of the multibody system is presented to analyze the dynamic process of the HUG formation. Numerical calculation is carried out to simulate attitude synchronization with two kinds of formation topologies. Results show that attitude synchronization can be fulfilled based on the multibody method described in this paper. It is also indicated that different topologies affect attitude control quality with respect to energy consumption and adjusting time. Low level topology should be adopted during formation control scheme design to achieve a better control effect.
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.
Analysis of Large Flexible Body Deformation in Multibody Systems Using Absolute Coordinates
International Nuclear Information System (INIS)
Dombrowski, Stefan von
2002-01-01
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
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.
Dynamic analysis of multibody system immersed in a fluid medium
International Nuclear Information System (INIS)
Wu, R.W.; Liu, L.K.; Levy, S.
1977-01-01
This paper is concerned primarily with the development and evaluation of an analysis method for the reponse prediction of immersed systems to seismic and other dynamic excitations. For immersed multibody systems, the hydrodynamic interaction causes coupled motion among the solid bodies. Also, under intense external excitations, impact between bodies may occur. The complex character of such systems inhibit the use of conventional analytical solutions in closed form. Therefore, approximate numerical schemes have been devised. For an incompressible, inviscid fluid, the hydrodynamic forces exerted by the fluid on solid bodies are determined to be linearly proportional to the acceleration of the vibrating solid bodies; i.e., the presence of the fluid only affects the inertia of the solid body system. A finite element computer program has been developed for computing this hydrodynamic (or added) mass effect. This program can be used to determine the hydrodynamic mass of a two-dimensional fluid field with solid bodies of arbitrary geometry. Triangular elements and linear pressure interpolation function are used to discretize the fluid region. The component element method is used to determine the dynamic response of the multibody system to externally applied mechanical loading or support excitation. The present analysis method for predicting the dynamic response of submerged multibody system is quite general and pertains to any number of solid bodies. However in this paper, its application is demonstrated only for 4 and 25 body systems. (Auth.)
Modeling multibody systems with uncertainties. Part II: Numerical applications
International Nuclear Information System (INIS)
Sandu, Corina; Sandu, Adrian; Ahmadian, Mehdi
2006-01-01
This study applies generalized polynomial chaos theory to model complex nonlinear multibody dynamic systems operating in the presence of parametric and external uncertainty. Theoretical and computational aspects of this methodology are discussed in the companion paper 'Modeling Multibody Dynamic Systems With Uncertainties. Part I: Theoretical and Computational Aspects .In this paper we illustrate the methodology on selected test cases. The combined effects of parametric and forcing uncertainties are studied for a quarter car model. The uncertainty distributions in the system response in both time and frequency domains are validated against Monte-Carlo simulations. Results indicate that polynomial chaos is more efficient than Monte Carlo and more accurate than statistical linearization. The results of the direct collocation approach are similar to the ones obtained with the Galerkin approach. A stochastic terrain model is constructed using a truncated Karhunen-Loeve expansion. The application of polynomial chaos to differential-algebraic systems is illustrated using the constrained pendulum problem. Limitations of the polynomial chaos approach are studied on two different test problems, one with multiple attractor points, and the second with a chaotic evolution and a nonlinear attractor set. The overall conclusion is that, despite its limitations, generalized polynomial chaos is a powerful approach for the simulation of multibody dynamic systems with uncertainties
Modeling multibody systems with uncertainties. Part II: Numerical applications
Energy Technology Data Exchange (ETDEWEB)
Sandu, Corina, E-mail: csandu@vt.edu; Sandu, Adrian; Ahmadian, Mehdi [Virginia Polytechnic Institute and State University, Mechanical Engineering Department (United States)
2006-04-15
This study applies generalized polynomial chaos theory to model complex nonlinear multibody dynamic systems operating in the presence of parametric and external uncertainty. Theoretical and computational aspects of this methodology are discussed in the companion paper 'Modeling Multibody Dynamic Systems With Uncertainties. Part I: Theoretical and Computational Aspects .In this paper we illustrate the methodology on selected test cases. The combined effects of parametric and forcing uncertainties are studied for a quarter car model. The uncertainty distributions in the system response in both time and frequency domains are validated against Monte-Carlo simulations. Results indicate that polynomial chaos is more efficient than Monte Carlo and more accurate than statistical linearization. The results of the direct collocation approach are similar to the ones obtained with the Galerkin approach. A stochastic terrain model is constructed using a truncated Karhunen-Loeve expansion. The application of polynomial chaos to differential-algebraic systems is illustrated using the constrained pendulum problem. Limitations of the polynomial chaos approach are studied on two different test problems, one with multiple attractor points, and the second with a chaotic evolution and a nonlinear attractor set. The overall conclusion is that, despite its limitations, generalized polynomial chaos is a powerful approach for the simulation of multibody dynamic systems with uncertainties.
On the constraints violation in forward dynamics of multibody systems
Energy Technology Data Exchange (ETDEWEB)
Marques, Filipe [University of Minho, Department of Mechanical Engineering (Portugal); Souto, António P. [University of Minho, Department of Textile Engineering (Portugal); Flores, Paulo, E-mail: pflores@dem.uminho.pt [University of Minho, Department of Mechanical Engineering (Portugal)
2017-04-15
It is known that the dynamic equations of motion for constrained mechanical multibody systems are frequently formulated using the Newton–Euler’s approach, which is augmented with the acceleration constraint equations. This formulation results in the establishment of a mixed set of partial differential and algebraic equations, which are solved in order to predict the dynamic behavior of general multibody systems. The classical solution of the equations of motion is highly prone to constraints violation because the position and velocity constraint equations are not fulfilled. In this work, a general and comprehensive methodology to eliminate the constraints violation at the position and velocity levels is offered. The basic idea of the described approach is to add corrective terms to the position and velocity vectors with the intent to satisfy the corresponding kinematic constraint equations. These corrective terms are evaluated as a function of the Moore–Penrose generalized inverse of the Jacobian matrix and of the kinematic constraint equations. The described methodology is embedded in the standard method to solve the equations of motion based on the technique of Lagrange multipliers. Finally, the effectiveness of the described methodology is demonstrated through the dynamic modeling and simulation of different planar and spatial multibody systems. The outcomes in terms of constraints violation at the position and velocity levels, conservation of the total energy and computational efficiency are analyzed and compared with those obtained with the standard Lagrange multipliers method, the Baumgarte stabilization method, the augmented Lagrangian formulation, the index-1 augmented Lagrangian, and the coordinate partitioning method.
Comparison and Implementation of a Rigid and a Flexible Multibody Planetary Gearbox Model
DEFF Research Database (Denmark)
Jørgensen, Martin Felix; Pedersen, Niels Leergaard; Sørensen, Jens Nørkær
2014-01-01
We propose algorithms for developing (1) a rigid (constrained) and (2) a flexible planetary gearbox model. The two methods are compared against each other and advantages/disadvantages of each method are discussed. The rigid model (1) has gear tooth reaction forces expressed by Lagrange multipliers...... between one and two gear teeth in mesh. The final results are from modelling the planetary gearbox in a 500 kW wind turbine which we also described in Jørgensen et al. (2013)........ The flexible approach (2) is being compared with the gear tooth forces from the rigid approach, first without damping and second the influence of damping is examined. Variable stiffness as a function of base circle arc length is implemented in the flexible approach such that it handles the realistic switch...
Directory of Open Access Journals (Sweden)
Wenguang Yang
2016-01-01
Full Text Available This paper proposes an improved rigid multibody model for the dynamic analysis of the planetary gearbox in a wind turbine. The improvements mainly include choosing the inertia frame as the reference frame of the carrier, the ring, and the sun and adding a new degree of freedom for each planet. An element assembly method is introduced to build the model, and a time-varying mesh stiffness model is presented. A planetary gear study case is employed to verify the validity of the improved model. Comparisons between the improvement model and the traditional model show that the natural characteristics are very close; the improved model can obtain the right equivalent moment of inertia of the planetary gear in the transient simulation, and all the rotation speeds satisfy the transmission relationships well; harmonic resonance and resonance modulation phenomena can be found in their vibration signals. The improved model is applied in a multistage gearbox dynamics analysis to reveal the prospects of the model. Modal analysis and transient analysis with and without time-varying mesh stiffness considered are conducted. The rotation speeds from the transient analysis are consistent with the theory, and resonance modulation can be found in the vibration signals.
A 3D Finite Element Method for Flexible Multibody Systems
International Nuclear Information System (INIS)
Gerstmayr, Johannes; Schoeberl, Joachim
2006-01-01
An efficient finite element (FE) formulation for the simulation of multibody systems is derived from Hamilton's principle. According to the classical assumptions of multibody systems, a large rotation formulation has been chosen, where large rotations and large displacements, but only small deformations of the single bodies are taken into account. The strain tensor is linearized with respect to a co-rotated frame. The present approach uses absolute coordinates for the degrees of freedom and forms an alternative to the floating frame of reference formulation that is based on relative coordinates and describes deformation with respect to a co-rotated frame. Due to the modified strain tensor, the present formulation distinguishes significantly from standard nodal based nonlinear FE methods. Constraints are defined in integral form for every pair of surfaces of two bodies. This leads to a small number of constraint equations and avoids artificial stress singularities. The resulting mass and stiffness matrices are constant apart from a transformation based on a single rotation matrix for each body. The particular structure of this transformation allows to prevent from the usually expensive factorization of the system Jacobian within implicit time--integration methods. The present method has been implemented and tested with the FE-package NGSolve and specific 3D examples are verified with a standard beam formulation
Dynamic Multi-Rigid-Body Systems with Concurrent Distributed Contacts: Theory and Examples
International Nuclear Information System (INIS)
TRINKLE, JEFFREY C.; TZITZOURIS, J.A.; PANG, J.S.
2001-01-01
Consider a system of rigid bodies with multiple concurrent contacts. The multi-rigid-body contact problem is to predict the accelerations of the bodies and the normal friction loads acting at the contacts. This paper presents theoretical results for the multi-rigid-body contact problem under the assumptions that one or more contacts occur over locally planar, finite regions and that friction forces are consistent with the maximum work inequality. Existence and uniqueness results are presented for this problem under mild assumptions on the system inputs. In addition, the performance of two different time-stepping methods for integrating the dynamics are compared on two simple multi-body systems
Evaluation of constraint stabilization procedures for multibody dynamical systems
Park, K. C.; Chiou, J. C.
1987-01-01
Comparative numerical studies of four constraint treatment techniques for the simulation of general multibody dynamic systems are presented, and results are presented for the example of a classical crank mechanism and for a simplified version of the seven-link manipulator deployment problem. The staggered stabilization technique (Park, 1986) is found to yield improved accuracy and robustness over Baumgarte's (1972) technique, the singular decomposition technique (Walton and Steeves, 1969), and the penalty technique (Lotstedt, 1979). Furthermore, the staggered stabilization technique offers software modularity, and the only data each solution module needs to exchange with the other is a set of vectors plus a common module to generate the gradient matrix of the constraints, B.
Fu, Yao; Song, Jeong-Hoon
2014-08-01
Hardy stress definition has been restricted to pair potentials and embedded-atom method potentials due to the basic assumptions in the derivation of a symmetric microscopic stress tensor. Force decomposition required in the Hardy stress expression becomes obscure for multi-body potentials. In this work, we demonstrate the invariance of the Hardy stress expression for a polymer system modeled with multi-body interatomic potentials including up to four atoms interaction, by applying central force decomposition of the atomic force. The balance of momentum has been demonstrated to be valid theoretically and tested under various numerical simulation conditions. The validity of momentum conservation justifies the extension of Hardy stress expression to multi-body potential systems. Computed Hardy stress has been observed to converge to the virial stress of the system with increasing spatial averaging volume. This work provides a feasible and reliable linkage between the atomistic and continuum scales for multi-body potential systems.
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.
Modeling Multibody Systems with Uncertainties. Part I: Theoretical and Computational Aspects
International Nuclear Information System (INIS)
Sandu, Adrian; Sandu, Corina; Ahmadian, Mehdi
2006-01-01
This study explores the use of generalized polynomial chaos theory for modeling complex nonlinear multibody dynamic systems in the presence of parametric and external uncertainty. The polynomial chaos framework has been chosen because it offers an efficient computational approach for the large, nonlinear multibody models of engineering systems of interest, where the number of uncertain parameters is relatively small, while the magnitude of uncertainties can be very large (e.g., vehicle-soil interaction). The proposed methodology allows the quantification of uncertainty distributions in both time and frequency domains, and enables the simulations of multibody systems to produce results with 'error bars'. The first part of this study presents the theoretical and computational aspects of the polynomial chaos methodology. Both unconstrained and constrained formulations of multibody dynamics are considered. Direct stochastic collocation is proposed as less expensive alternative to the traditional Galerkin approach. It is established that stochastic collocation is equivalent to a stochastic response surface approach. We show that multi-dimensional basis functions are constructed as tensor products of one-dimensional basis functions and discuss the treatment of polynomial and trigonometric nonlinearities. Parametric uncertainties are modeled by finite-support probability densities. Stochastic forcings are discretized using truncated Karhunen-Loeve expansions. The companion paper 'Modeling Multibody Dynamic Systems With Uncertainties. Part II: Numerical Applications' illustrates the use of the proposed methodology on a selected set of test problems. The overall conclusion is that despite its limitations, polynomial chaos is a powerful approach for the simulation of multibody systems with uncertainties
Efficient methodology for multibody simulations with discontinuous changes in system definition
International Nuclear Information System (INIS)
Mukherjee, Rudranarayan M.; Anderson, Kurt S.
2007-01-01
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
International Nuclear Information System (INIS)
Pi Ting; Zhang Yunqing; Chen Liping
2012-01-01
Design sensitivity analysis of flexible multibody systems is important in optimizing the performance of mechanical systems. The choice of coordinates to describe the motion of multibody systems has a great influence on the efficiency and accuracy of both the dynamic and sensitivity analysis. In the flexible multibody system dynamics, both the floating frame of reference formulation (FFRF) and absolute nodal coordinate formulation (ANCF) are frequently utilized to describe flexibility, however, only the former has been used in design sensitivity analysis. In this article, ANCF, which has been recently developed and focuses on modeling of beams and plates in large deformation problems, is extended into design sensitivity analysis of flexible multibody systems. The Motion equations of a constrained flexible multibody system are expressed as a set of index-3 differential algebraic equations (DAEs), in which the element elastic forces are defined using nonlinear strain-displacement relations. Both the direct differentiation method and adjoint variable method are performed to do sensitivity analysis and the related dynamic and sensitivity equations are integrated with HHT-I3 algorithm. In this paper, a new method to deduce system sensitivity equations is proposed. With this approach, the system sensitivity equations are constructed by assembling the element sensitivity equations with the help of invariant matrices, which results in the advantage that the complex symbolic differentiation of the dynamic equations is avoided when the flexible multibody system model is changed. Besides that, the dynamic and sensitivity equations formed with the proposed method can be efficiently integrated using HHT-I3 method, which makes the efficiency of the direct differentiation method comparable to that of the adjoint variable method when the number of design variables is not extremely large. All these improvements greatly enhance the application value of the direct differentiation
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.
Elastic Multibody Dynamics A Direct Ritz Approach
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...
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.
Active vibration control of spatial flexible multibody systems
International Nuclear Information System (INIS)
Neto, Maria Augusta; Ambrósio, Jorge A. C.; Roseiro, Luis M.; Amaro, A.; Vasques, C. M. A.
2013-01-01
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.
DEFF Research Database (Denmark)
Chen, Shanshin; Tortorelli, Daniel A.; Hansen, John Michael
1999-01-01
of ordinary diffferential equations is employed to avoid the instabilities associated with the direct integrations of differential-algebraic equations. To extend the unconditional stability of the implicit Newmark method to nonlinear dynamic systems, a discrete energy balance is enforced. This constraint......Advances in computer hardware and improved algorithms for multibody dynamics over the past decade have generated widespread interest in real-time simulations of multibody mechanics systems. At the heart of the widely used algorithms for multibody dynamics are a choice of coordinates which define...... the kinmatics of the system, and a choice of time integrations algorithms. The current approach uses a non-dissipative implict Newmark method to integrate the equations of motion defined in terms of the independent joint coordinates of the system. The reduction of the equations of motion to a minimal set...
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.
Planar multibody dynamics formulation, programming and applications
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
Hard real-time multibody simulations using ARM-based embedded systems
Energy Technology Data Exchange (ETDEWEB)
Pastorino, Roland, E-mail: roland.pastorino@kuleuven.be, E-mail: rpastorino@udc.es; Cosco, Francesco, E-mail: francesco.cosco@kuleuven.be; Naets, Frank, E-mail: frank.naets@kuleuven.be; Desmet, Wim, E-mail: wim.desmet@kuleuven.be [KU Leuven, PMA division, Department of Mechanical Engineering (Belgium); Cuadrado, Javier, E-mail: javicuad@cdf.udc.es [Universidad de La Coruña, Laboratorio de Ingeniería Mecánica (Spain)
2016-05-15
The real-time simulation of multibody models on embedded systems is of particular interest for controllers and observers such as model predictive controllers and state observers, which rely on a dynamic model of the process and are customarily executed in electronic control units. This work first identifies the software techniques and tools required to easily write efficient code for multibody models to be simulated on ARM-based embedded systems. Automatic Programming and Source Code Translation are the two techniques that were chosen to generate source code for multibody models in different programming languages. Automatic Programming is used to generate procedural code in an intermediate representation from an object-oriented library and Source Code Translation is used to translate the intermediate representation automatically to an interpreted language or to a compiled language for efficiency purposes. An implementation of these techniques is proposed. It is based on a Python template engine and AST tree walkers for Source Code Generation and on a model-driven translator for the Source Code Translation. The code is translated from a metalanguage to any of the following four programming languages: Python-Numpy, Matlab, C++-Armadillo, C++-Eigen. Two examples of multibody models were simulated: a four-bar linkage with multiple loops and a 3D vehicle steering system. The code for these examples has been generated and executed on two ARM-based single-board computers. Using compiled languages, both models could be simulated faster than real-time despite the low resources and performance of these embedded systems. Finally, the real-time performance of both models was evaluated when executed in hard real-time on Xenomai for both embedded systems. This work shows through measurements that Automatic Programming and Source Code Translation are valuable techniques to develop real-time multibody models to be used in embedded observers and controllers.
Hard real-time multibody simulations using ARM-based embedded systems
International Nuclear Information System (INIS)
Pastorino, Roland; Cosco, Francesco; Naets, Frank; Desmet, Wim; Cuadrado, Javier
2016-01-01
The real-time simulation of multibody models on embedded systems is of particular interest for controllers and observers such as model predictive controllers and state observers, which rely on a dynamic model of the process and are customarily executed in electronic control units. This work first identifies the software techniques and tools required to easily write efficient code for multibody models to be simulated on ARM-based embedded systems. Automatic Programming and Source Code Translation are the two techniques that were chosen to generate source code for multibody models in different programming languages. Automatic Programming is used to generate procedural code in an intermediate representation from an object-oriented library and Source Code Translation is used to translate the intermediate representation automatically to an interpreted language or to a compiled language for efficiency purposes. An implementation of these techniques is proposed. It is based on a Python template engine and AST tree walkers for Source Code Generation and on a model-driven translator for the Source Code Translation. The code is translated from a metalanguage to any of the following four programming languages: Python-Numpy, Matlab, C++-Armadillo, C++-Eigen. Two examples of multibody models were simulated: a four-bar linkage with multiple loops and a 3D vehicle steering system. The code for these examples has been generated and executed on two ARM-based single-board computers. Using compiled languages, both models could be simulated faster than real-time despite the low resources and performance of these embedded systems. Finally, the real-time performance of both models was evaluated when executed in hard real-time on Xenomai for both embedded systems. This work shows through measurements that Automatic Programming and Source Code Translation are valuable techniques to develop real-time multibody models to be used in embedded observers and controllers.
Parallel Evolutionary Optimization of Multibody Systems with Application to Railway Dynamics
Energy Technology Data Exchange (ETDEWEB)
Eberhard, Peter [University of Erlangen-Nuremberg, Institute of Applied Mechanics (Germany)], E-mail: eberhard@ltm.uni-erlangen.de; Dignath, Florian [University of Stuttgart, Institute B of Mechanics (Germany)], E-mail: fd@mechb.uni-stuttgart.de; Kuebler, Lars [University of Erlangen-Nuremberg, Institute of Applied Mechanics (Germany)], E-mail: kuebler@ltm.uni-erlangen.de
2003-03-15
The optimization of multibody systems usually requires many costly criteria computations since the equations of motion must be evaluated by numerical time integration for each considered design. For actively controlled or flexible multibody systems additional difficulties arise as the criteria may contain non-differentiable points or many local minima. Therefore, in this paper a stochastic evolution strategy is used in combination with parallel computing in order to reduce the computation times whilst keeping the inherent robustness. For the parallelization a master-slave approach is used in a heterogeneous workstation/PC cluster. The pool-of-tasks concept is applied in order to deal with the frequently changing workloads of different machines in the cluster. In order to analyze the performance of the parallel optimization method, the suspension of an ICE passenger coach, modeled as an elastic multibody system, is optimized simultaneously with regard to several criteria including vibration damping and a criterion related to safety against derailment. The iterative and interactive nature of a typical optimization process for technical systems is emphasized.
Parallel Evolutionary Optimization of Multibody Systems with Application to Railway Dynamics
International Nuclear Information System (INIS)
Eberhard, Peter; Dignath, Florian; Kuebler, Lars
2003-01-01
The optimization of multibody systems usually requires many costly criteria computations since the equations of motion must be evaluated by numerical time integration for each considered design. For actively controlled or flexible multibody systems additional difficulties arise as the criteria may contain non-differentiable points or many local minima. Therefore, in this paper a stochastic evolution strategy is used in combination with parallel computing in order to reduce the computation times whilst keeping the inherent robustness. For the parallelization a master-slave approach is used in a heterogeneous workstation/PC cluster. The pool-of-tasks concept is applied in order to deal with the frequently changing workloads of different machines in the cluster. In order to analyze the performance of the parallel optimization method, the suspension of an ICE passenger coach, modeled as an elastic multibody system, is optimized simultaneously with regard to several criteria including vibration damping and a criterion related to safety against derailment. The iterative and interactive nature of a typical optimization process for technical systems is emphasized
Directory of Open Access Journals (Sweden)
José Elias Tomazini
2012-12-01
Full Text Available Vários sistemas podem ser tratados com formalismos multicorpos: mecanismos de máquinas em geral, robôs industriais e manipuladores, estruturas espaciais, motores e, ainda, sistemas biomecânicos. A locomoção ou marcha humana e animal podem ser estudadas através de formalismos multicorpos.Nos últimos anos, diversos trabalhos relacionados à biomecânica, e utilizando formalismos multicorpos, têm sido apresentados. Muitos estudos in vitro e in vivo têm sido realizados, objetivando descrever o potencial de sobrecarga nas articulações do corpo humano e de modelos animais. O objetivo desta revisão foi apresentar estudos envolvendo o modelamento matemático aplicado à bioengenharia, biomecânica e engenharia biomédica. Conclui-se que o modelamento matemático é uma ferramenta muito útil, barata e não invasiva que vem contribuir nos estudos envolvendo o sistema multicorpo mecânico e complexo, que é o corpo humano. Several systems can be treated with multibody formalisms: mechanisms of general machinery, industrial robots and manipulators, space structures, engines, and also biomechanical systems. The locomotion or human gait can be studied using multibody formalisms. Several studies related to biomechanics, and using multibody formalisms, have been presented in recent years. Many studies in vitro and in vivo have been carried out, aiming to describe the potential overload in the joints of the human body and animal models. The aim of this review was to present studies involving mathematical modeling applied to bioengineering, biomechanics and biomedical engineering. We have concluded that mathematical modeling is a useful, inexpensive and noninvasive tool which comes to contribute in studies involving the mechanical and complex multibody system which is the human body.
Partition method and experimental validation for impact dynamics of flexible multibody system
Wang, J. Y.; Liu, Z. Y.; Hong, J. Z.
2018-06-01
The impact problem of a flexible multibody system is a non-smooth, high-transient, and strong-nonlinear dynamic process with variable boundary. How to model the contact/impact process accurately and efficiently is one of the main difficulties in many engineering applications. The numerical approaches being used widely in impact analysis are mainly from two fields: multibody system dynamics (MBS) and computational solid mechanics (CSM). Approaches based on MBS provide a more efficient yet less accurate analysis of the contact/impact problems, while approaches based on CSM are well suited for particularly high accuracy needs, yet require very high computational effort. To bridge the gap between accuracy and efficiency in the dynamic simulation of a flexible multibody system with contacts/impacts, a partition method is presented considering that the contact body is divided into two parts, an impact region and a non-impact region. The impact region is modeled using the finite element method to guarantee the local accuracy, while the non-impact region is modeled using the modal reduction approach to raise the global efficiency. A three-dimensional rod-plate impact experiment is designed and performed to validate the numerical results. The principle for how to partition the contact bodies is proposed: the maximum radius of the impact region can be estimated by an analytical method, and the modal truncation orders of the non-impact region can be estimated by the highest frequency of the signal measured. The simulation results using the presented method are in good agreement with the experimental results. It shows that this method is an effective formulation considering both accuracy and efficiency. Moreover, a more complicated multibody impact problem of a crank slider mechanism is investigated to strengthen this conclusion.
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.
Energy Technology Data Exchange (ETDEWEB)
Fu, Yao, E-mail: Yao.Fu@colorado.edu; Song, Jeong-Hoon, E-mail: JH.Song@colorado.edu
2015-08-01
Heat flux expressions are derived for multibody potential systems by extending the original Hardy's methodology and modifying Admal & Tadmor's formulas. The continuum thermomechanical quantities obtained from these two approaches are easy to compute from molecular dynamics (MD) results, and have been tested for a constant heat flux model in two distinctive systems: crystalline iron and polyethylene (PE) polymer. The convergence criteria and affecting parameters, i.e. spatial and temporal window size, and specific forms of localization function are found to be different between the two systems. The conservation of mass, momentum, and energy are discussed and validated within this atomistic–continuum bridging.
International Nuclear Information System (INIS)
Fu, Yao; Song, Jeong-Hoon
2015-01-01
Heat flux expressions are derived for multibody potential systems by extending the original Hardy's methodology and modifying Admal & Tadmor's formulas. The continuum thermomechanical quantities obtained from these two approaches are easy to compute from molecular dynamics (MD) results, and have been tested for a constant heat flux model in two distinctive systems: crystalline iron and polyethylene (PE) polymer. The convergence criteria and affecting parameters, i.e. spatial and temporal window size, and specific forms of localization function are found to be different between the two systems. The conservation of mass, momentum, and energy are discussed and validated within this atomistic–continuum bridging
Entropic Measure of Epistemic Uncertainties in Multibody System Models by Axiomatic Design
Directory of Open Access Journals (Sweden)
Francesco Villecco
2017-06-01
Full Text Available In this paper, the use of the MaxInf Principle in real optimization problems is investigated for engineering applications, where the current design solution is actually an engineering approximation. In industrial manufacturing, multibody system simulations can be used to develop new machines and mechanisms by using virtual prototyping, where an axiomatic design can be employed to analyze the independence of elements and the complexity of connections forming a general mechanical system. In the classic theories of Fisher and Wiener-Shannon, the idea of information is a measure of only probabilistic and repetitive events. However, this idea is broader than the probability alone field. Thus, the Wiener-Shannon’s axioms can be extended to non-probabilistic events and it is possible to introduce a theory of information for non-repetitive events as a measure of the reliability of data for complex mechanical systems. To this end, one can devise engineering solutions consistent with the values of the design constraints analyzing the complexity of the relation matrix and using the idea of information in the metric space. The final solution gives the entropic measure of epistemic uncertainties which can be used in multibody system models, analyzed with an axiomatic design.
Virtual Nonlinear Multibody Systems, NATO Advanced Study Institute. Volume 2
National Research Council Canada - National Science Library
Schiehlen, W. O
2002-01-01
.... The virtual prototyping and dynamic modeling of such systems are, from an economical point of view, perspective fields of scientific investigations having in mind the huge expenses for their design...
Conference on Multibody Dynamics
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...
Applied dynamics with applications to multibody and mechatronic systems
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
Gravitational equilibrium of a multi-body fluid system
International Nuclear Information System (INIS)
Eriguchi, Yoshiharu; Hachisu, Izumi.
1983-01-01
We have computed gravitational equilibrium sequences for systems consisting of N incompressible fluid bodies (N = 3, 4, 5). The component fluids are assumed congruent. The system seems to become a lobe-like shape for N = 3 case and a ring-like shape for N>=4 cases according as the fluid bodies come nearer to each other. For every sequence there is a critical equilibrium whose dimensionless angular momentum has the minimum value of the sequence. As the final outcome is nearly in equilibrium in the computation of a collapsing gas cloud, we can apply the present results to the interpretation of these dynamical calculations. For instance, the gas cloud can never fissure into any N-body equilibrium when its dimensionless angular momentum is below the critical value of the N-body sequence. (author)
Heading Control System for a Multi-body Vehicle with a Virtual Test Driver
Directory of Open Access Journals (Sweden)
POSTALCIOGLU OZGEN, S.
2010-08-01
Full Text Available This paper includes a Heading Control (HC system for a multi-body vehicle. HC system helps reducing the required torque from the driver and improves the lane keeping efficiency. HC system is important for safety and driver comfort in traffic. The controller performance is examined on a virtual test drive platform. The optimal control theory is applied to HC system and examined on a curved path and under a side wind disturbance. Different assistance levels are applied to see the characteristics of the controller with different virtual test drivers. The results are analyzed based on three performance indices; lane keeping performance (LKP index, assist torque performance (ATP index and driver torque performance (DTP index. As seen from the results while using HC system the lateral displacement decreases as the lane keeping performance increases and the driver torque performance decreases as the assist torque performance increases.
Null Space Integration Method for Constrained Multibody Systems with No Constraint Violation
International Nuclear Information System (INIS)
Terze, Zdravko; Lefeber, Dirk; Muftic, Osman
2001-01-01
A method for integrating equations of motion of constrained multibody systems with no constraint violation is presented. A mathematical model, shaped as a differential-algebraic system of index 1, is transformed into a system of ordinary differential equations using the null-space projection method. Equations of motion are set in a non-minimal form. During integration, violations of constraints are corrected by solving constraint equations at the position and velocity level, utilizing the metric of the system's configuration space, and projective criterion to the coordinate partitioning method. The method is applied to dynamic simulation of 3D constrained biomechanical system. The simulation results are evaluated by comparing them to the values of characteristic parameters obtained by kinematics analysis of analyzed motion based unmeasured kinematics data
Rapid Onboard Trajectory Design for Autonomous Spacecraft in Multibody Systems
Trumbauer, Eric Michael
This research develops automated, on-board trajectory planning algorithms in order to support current and new mission concepts. These include orbiter missions to Phobos or Deimos, Outer Planet Moon orbiters, and robotic and crewed missions to small bodies. The challenges stem from the limited on-board computing resources which restrict full trajectory optimization with guaranteed convergence in complex dynamical environments. The approach taken consists of leveraging pre-mission computations to create a large database of pre-computed orbits and arcs. Such a database is used to generate a discrete representation of the dynamics in the form of a directed graph, which acts to index these arcs. This allows the use of graph search algorithms on-board in order to provide good approximate solutions to the path planning problem. Coupled with robust differential correction and optimization techniques, this enables the determination of an efficient path between any boundary conditions with very little time and computing effort. Furthermore, the optimization methods developed here based on sequential convex programming are shown to have provable convergence properties, as well as generating feasible major iterates in case of a system interrupt -- a key requirement for on-board application. The outcome of this project is thus the development of an algorithmic framework which allows the deployment of this approach in a variety of specific mission contexts. Test cases related to missions of interest to NASA and JPL such as a Phobos orbiter and a Near Earth Asteroid interceptor are demonstrated, including the results of an implementation on the RAD750 flight processor. This method fills a gap in the toolbox being developed to create fully autonomous space exploration systems.
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.
Simulating Dynamics of the System of Articulated Rigid Bodies with Joint Friction
Directory of Open Access Journals (Sweden)
M. V. Michaylyuk
2016-01-01
Full Text Available The subject of the work is to simulate dynamics of the system of articulated rigid bodies in the virtual environment complexes. The work aim is to develop algorithms and methods to simulate the multi-body system dynamics with joint friction to ensure all calculations in real time in line with visual realistic behavior of objects in a scene.The paper describes the multibody system based on a maximal set of coordinates, and to simulate the joint friction is used a Coulomb's law of dry friction. Joints are described using the holonomic constraints and their derivatives that specify the constraints on velocities of joined bodies. Based on The Coulomb’s law a correlation for the friction impulse values has been derived as an inequality. If the friction impulse performs a constraint that is a lack of relative motion of two joint-joined bodies, there is a static friction in the joint. Otherwise, there is a dynamic friction in the joint. Using a semi-implicit Euler method allows us to describe dynamics of articulated rigid bodies with joint friction as a system of linear algebraic equations and inequalities for the unknown velocities and impulse values.To solve the obtained system of equations and inequalities is used an iterative method of sequential impulses, which sequentially processes constraints for each joint with impulse calculation and its application to the joined bodies rather than considers the entire system. To improve the method convergence, at each iteration the calculated impulses are accumulated for their further using as an initial approximation at the next step of simulation.The proposed algorithms and methods have been implemented in the training complex dynamics subsystem, developed in SRISA RAS. Evaluation of these methods and algorithms has demonstrated their full adequacy to requirements for virtual environment systems and training complexes.
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.
Linked-List-Based Multibody Dynamics (MBDyn) Engine
MacLean, John; Brain, Thomas; Wuiocho, Leslie; Huynh, An; Ghosh, Tushar
2012-01-01
This new release of MBDyn is a software engine that calculates the dynamics states of kinematic, rigid, or flexible multibody systems. An MBDyn multibody system may consist of multiple groups of articulated chains, trees, or closed-loop topologies. Transient topologies are handled through conservation of energy and momentum. The solution for rigid-body systems is exact, and several configurable levels of nonlinear term fidelity are available for flexible dynamics systems. The algorithms have been optimized for efficiency and can be used for both non-real-time (NRT) and real-time (RT) simulations. Interfaces are currently compatible with NASA's Trick Simulation Environment. This new release represents a significant advance in capability and ease of use. The two most significant new additions are an application programming interface (API) that clarifies and simplifies use of MBDyn, and a link-list infrastructure that allows a single MBDyn instance to propagate an arbitrary number of interacting groups of multibody top ologies. MBDyn calculates state and state derivative vectors for integration using an external integration routine. A Trickcompatible interface is provided for initialization, data logging, integration, and input/output.
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
Directory of Open Access Journals (Sweden)
Gangli Chen
2013-01-01
Full Text Available The dynamic test precision of the strapdown inertial measurement unit (SIMU is the basis of estimating accurate motion of various vehicles such as warships, airplanes, spacecrafts, and missiles. So, it is paid great attention in the above fields to increase the dynamic precision of SIMU by decreasing the vibration of the vehicles acting on the SIMU. In this paper, based on the transfer matrix method for multibody system (MSTMM, the multibody system dynamics model of laser gyro strapdown inertial measurement unit (LGSIMU is developed; the overall transfer equation of the system is deduced automatically. The computational results show that the frequency response function of the LGSIMU got by the proposed method and Newton-Euler method have good agreements. Further, the vibration reduction performance and the attitude error responses under harmonic and random excitations are analyzed. The proposed method provides a powerful technique for studying dynamics of LGSIMU because of using MSTMM and its following features: without the global dynamics equations of the system, high programming, low order of system matrix, and high computational speed.
Almost Poisson integration of rigid body systems
International Nuclear Information System (INIS)
Austin, M.A.; Krishnaprasad, P.S.; Li-Sheng Wang
1993-01-01
In this paper we discuss the numerical integration of Lie-Poisson systems using the mid-point rule. Since such systems result from the reduction of hamiltonian systems with symmetry by lie group actions, we also present examples of reconstruction rules for the full dynamics. A primary motivation is to preserve in the integration process, various conserved quantities of the original dynamics. A main result of this paper is an O(h 3 ) error estimate for the Lie-Poisson structure, where h is the integration step-size. We note that Lie-Poisson systems appear naturally in many areas of physical science and engineering, including theoretical mechanics of fluids and plasmas, satellite dynamics, and polarization dynamics. In the present paper we consider a series of progressively complicated examples related to rigid body systems. We also consider a dissipative example associated to a Lie-Poisson system. The behavior of the mid-point rule and an associated reconstruction rule is numerically explored. 24 refs., 9 figs
On the identifiability of inertia parameters of planar Multi-Body Space Systems
Nabavi-Chashmi, Seyed Yaser; Malaek, Seyed Mohammad-Bagher
2018-04-01
This work describes a new formulation to study the identifiability characteristics of Serially Linked Multi-body Space Systems (SLMBSS). The process exploits the so called "Lagrange Formulation" to develop a linear form of Equations of Motion w.r.t the system Inertia Parameters (IPs). Having developed a specific form of regressor matrix, we aim to expedite the identification process. The new approach allows analytical as well as numerical identification and identifiability analysis for different SLMBSSs' configurations. Moreover, the explicit forms of SLMBSSs identifiable parameters are derived by analyzing the identifiability characteristics of the robot. We further show that any SLMBSS designed with Variable Configurations Joint allows all IPs to be identifiable through comparing two successive identification outcomes. This feature paves the way to design new class of SLMBSS for which accurate identification of all IPs is at hand. Different case studies reveal that proposed formulation provides fast and accurate results, as required by the space applications. Further studies might be necessary for cases where planar-body assumption becomes inaccurate.
A joint-space numerical model of metabolic energy expenditure for human multibody dynamic system.
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. Copyright © 2015 John Wiley & Sons, Ltd.
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...
DEFF Research Database (Denmark)
Kim, Taeseong; Hansen, Anders Melchior; Branner, Kim
2013-01-01
In this paper a new anisotropic beam finite element for composite wind turbine blades is developed and implemented into the aeroelastic nonlinear multibody code, HAWC2, intended to be used to investigate if use of anisotropic material layups in wind turbine blades can be tailored for improved...
Energy Technology Data Exchange (ETDEWEB)
Papadopoulos, Alessandro Vittorio, E-mail: alessandro.papadopoulos@control.lth.se [Lund University, Department of Automatic Control (Sweden); Leva, Alberto, E-mail: alberto.leva@polimi.it [Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria (Italy)
2015-06-15
The presence of different time scales in a dynamic model significantly hampers the efficiency of its simulation. In multibody systems the fact is particularly relevant, as the mentioned time scales may be very different, due, for example, to the coexistence of mechanical components controled by electronic drive units, and may also appear in conjunction with significant nonlinearities. This paper proposes a systematic technique, based on the principles of dynamic decoupling, to partition a model based on the time scales that are relevant for the particular simulation studies to be performed and as transparently as possible for the user. In accordance with said purpose, peculiar to the technique is its neat separation into two parts: a structural analysis of the model, which is general with respect to any possible simulation scenario, and a subsequent decoupled integration, which can conversely be (easily) tailored to the study at hand. Also, since the technique does not aim at reducing but rather at partitioning the model, the state space and the physical interpretation of the dynamic variables are inherently preserved. Moreover, the proposed analysis allows us to define some novel indices relative to the separability of the system, thereby extending the idea of “stiffness” in a way that is particularly keen to its use for the improvement of simulation efficiency, be the envisaged integration scheme monolithic, parallel, or even based on cosimulation. Finally, thanks to the way the analysis phase is conceived, the technique is naturally applicable to both linear and nonlinear models. The paper contains a methodological presentation of the proposed technique, which is related to alternatives available in the literature so as to evidence the peculiarities just sketched, and some application examples illustrating the achieved advantages and motivating the major design choice from an operational viewpoint.
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......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 motion of the substructure. The system reduction is based on a component mode synthesis method, where the response of the internal degrees of freedom of the substructure is described as the quasi-static response induced by the boundary degrees of freedom via the constraint modes superimposed...
DEFF Research Database (Denmark)
Sun, Jialiang; Tian, Qiang; Hu, Haiyan
2018-01-01
Recent years have witnessed the application of topology optimization to flexible multibody systems (FMBS) so as to enhance their dynamic performances. In this study, an explicit topology optimization approach is proposed for an FMBS with variable-length bodies via the moving morphable components...... (MMC). Using the arbitrary Lagrangian–Eulerian (ALE) formulation, the thin plate elements of the absolute nodal coordinate formulation (ANCF) are used to describe the platelike bodies with variable length. For the thin plate element of ALE–ANCF, the elastic force and additional inertial force, as well...
International Nuclear Information System (INIS)
Zhang Hongkun; Cen Song; Wang Haitao; Cheng Huanyu
2012-01-01
An efficient 3D approach is proposed for simulating the complicated responses of the multi-body structure in reactor core under seismic loading. By utilizing the rigid-body and connector functions of the software Abaqus, the multi-body structure of the reactor core is simplified as a mass-point system interlinked by spring-dashpot connectors. And reasonable schemes are used for determining various connector coefficients. Furthermore, a scripting program is also complied for the 3D parametric modeling. Numerical examples show that, the proposed method can not only produce the results which satisfy the engineering requirements, but also improve the computational efficiency more than 100 times. (authors)
Online Kinematic and Dynamic-State Estimation for Constrained Multibody Systems Based on IMUs
Directory of Open Access Journals (Sweden)
José Luis Torres-Moreno
2016-03-01
Full Text Available This article addresses the problems of online estimations of kinematic and dynamic states of a mechanism from a sequence of noisy measurements. In particular, we focus on a planar four-bar linkage equipped with inertial measurement units (IMUs. Firstly, we describe how the position, velocity, and acceleration of all parts of the mechanism can be derived from IMU signals by means of multibody kinematics. Next, we propose the novel idea of integrating the generic multibody dynamic equations into two variants of Kalman filtering, i.e., the extended Kalman filter (EKF and the unscented Kalman filter (UKF, in a way that enables us to handle closed-loop, constrained mechanisms, whose state space variables are not independent and would normally prevent the direct use of such estimators. The proposal in this work is to apply those estimators over the manifolds of allowed positions and velocities, by means of estimating a subset of independent coordinates only. The proposed techniques are experimentally validated on a testbed equipped with encoders as a means of establishing the ground-truth. Estimators are run online in real-time, a feature not matched by any previous procedure of those reported in the literature on multibody dynamics.
Online Kinematic and Dynamic-State Estimation for Constrained Multibody Systems Based on IMUs
Torres-Moreno, José Luis; Blanco-Claraco, José Luis; Giménez-Fernández, Antonio; Sanjurjo, Emilio; Naya, Miguel Ángel
2016-01-01
This article addresses the problems of online estimations of kinematic and dynamic states of a mechanism from a sequence of noisy measurements. In particular, we focus on a planar four-bar linkage equipped with inertial measurement units (IMUs). Firstly, we describe how the position, velocity, and acceleration of all parts of the mechanism can be derived from IMU signals by means of multibody kinematics. Next, we propose the novel idea of integrating the generic multibody dynamic equations into two variants of Kalman filtering, i.e., the extended Kalman filter (EKF) and the unscented Kalman filter (UKF), in a way that enables us to handle closed-loop, constrained mechanisms, whose state space variables are not independent and would normally prevent the direct use of such estimators. The proposal in this work is to apply those estimators over the manifolds of allowed positions and velocities, by means of estimating a subset of independent coordinates only. The proposed techniques are experimentally validated on a testbed equipped with encoders as a means of establishing the ground-truth. Estimators are run online in real-time, a feature not matched by any previous procedure of those reported in the literature on multibody dynamics. PMID:26959027
ECCOMAS Thematic Conference on Multibody Dynamics
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.
Meng, Luming; Sheong, Fu Kit; Zeng, Xiangze; Zhu, Lizhe; Huang, Xuhui
2017-07-01
Constructing Markov state models from large-scale molecular dynamics simulation trajectories is a promising approach to dissect the kinetic mechanisms of complex chemical and biological processes. Combined with transition path theory, Markov state models can be applied to identify all pathways connecting any conformational states of interest. However, the identified pathways can be too complex to comprehend, especially for multi-body processes where numerous parallel pathways with comparable flux probability often coexist. Here, we have developed a path lumping method to group these parallel pathways into metastable path channels for analysis. We define the similarity between two pathways as the intercrossing flux between them and then apply the spectral clustering algorithm to lump these pathways into groups. We demonstrate the power of our method by applying it to two systems: a 2D-potential consisting of four metastable energy channels and the hydrophobic collapse process of two hydrophobic molecules. In both cases, our algorithm successfully reveals the metastable path channels. We expect this path lumping algorithm to be a promising tool for revealing unprecedented insights into the kinetic mechanisms of complex multi-body processes.
Rong, Bao; Rui, Xiaoting; Lu, Kun; Tao, Ling; Wang, Guoping; Ni, Xiaojun
2018-05-01
In this paper, an efficient method of dynamics modeling and vibration control design of a linear hybrid multibody system (MS) is studied based on the transfer matrix method. The natural vibration characteristics of a linear hybrid MS are solved by using low-order transfer equations. Then, by constructing the brand-new body dynamics equation, augmented operator and augmented eigenvector, the orthogonality of augmented eigenvector of a linear hybrid MS is satisfied, and its state space model expressed in each independent model space is obtained easily. According to this dynamics model, a robust independent modal space-fuzzy controller is designed for vibration control of a general MS, and the genetic optimization of some critical control parameters of fuzzy tuners is also presented. Two illustrative examples are performed, which results show that this method is computationally efficient and with perfect control performance.
Development of a multi-body nonlinear model for a seat-occupant system
Azizi, Yousof
-degree of freedom foam-mass model which is also the simplest model of seat-occupant systems. The steady-state response of the system when it is subjected to harmonic base excitation was studied using the incremental harmonic balance method. The incremental harmonic balance method was used to reduce the time required to generate the steady-state response of the system. The incremental harmonic balance method was used to reduce the time required to generate the steady-state response of the system. Experiments are conducted on a single-degree of freedom foam-mass system subjected to harmonic base excitation. Initially, the simulated response predictions were found to deviate from the experimental results. The foam-mass model was then modified to incorporate rate dependency of foam parameters resulting in response predictions that were in good agreement with experimental results. In the second part of this research, the dynamic response of a seat-occupant system was examined through a more realistic planar multi-body seat-occupant model. A constraint Lagrangian formulation was used to derive the governing equations for the seat-occupant model. First, the governing equations were solved numerically to obtain the occupant transient response, the occupant's H-Point location and the interfacial pressure distribution. Variations in the H-Point location and the seat-occupant pressure distribution with changes in the seat-occupant parameters, including the seat geometry and the occupant's characteristics, were studied. The estimated pressure was also investigated experimentally and was found to match with the results obtained using the seat-occupant model. Next, the incremental harmonic balance method was modified and used to obtain the occupant's steady-state response when the seat-occupant system was subjected to harmonic base excitation at different frequencies. The system frequency response and mode shapes at different frequencies were also obtained and compared to the previously
Multibody dynamic analysis using a rotation-free shell element with corotational frame
Shi, Jiabei; Liu, Zhuyong; Hong, Jiazhen
2018-03-01
Rotation-free shell formulation is a simple and effective method to model a shell with large deformation. Moreover, it can be compatible with the existing theories of finite element method. However, a rotation-free shell is seldom employed in multibody systems. Using a derivative of rigid body motion, an efficient nonlinear shell model is proposed based on the rotation-free shell element and corotational frame. The bending and membrane strains of the shell have been simplified by isolating deformational displacements from the detailed description of rigid body motion. The consistent stiffness matrix can be obtained easily in this form of shell model. To model the multibody system consisting of the presented shells, joint kinematic constraints including translational and rotational constraints are deduced in the context of geometric nonlinear rotation-free element. A simple node-to-surface contact discretization and penalty method are adopted for contacts between shells. A series of analyses for multibody system dynamics are presented to validate the proposed formulation. Furthermore, the deployment of a large scaled solar array is presented to verify the comprehensive performance of the nonlinear shell model.
Numerical methods in multibody dynamics
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...
Directory of Open Access Journals (Sweden)
Jianguo Ding
2014-11-01
Full Text Available Portal frame structures are widely used in industrial building design but unfortunately are often damaged during an earthquake. As a result, a study on the seismic response of this type of structure is important to both human safety and future building designs. Traditionally, finite element methods such as the ANSYS and MIDAS have been used as the primary methods of computing the response of such a structure during an earthquake; however, these methods yield low calculation efficiencies. In this paper, the mechanical model of a single-story portal frame structure with two spans is constructed based on the transfer matrix method of multibody system (MS-TMM; both the transfer matrix of the components in the model and the total transfer matrix equation of the structure are derived, and the corresponding MATLAB program is compiled to determine the natural period and seismic response of the structure. The results show that the results based on the MS-TMM are similar to those obtained by ANSYS, but the calculation time of the MS-TMM method is only 1/20 of that of the ANSYS method. Additionally, it is shown that the MS-TMM method greatly increases the calculation efficiency while maintaining accuracy.
General background and approach to multibody dynamics for space applications
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
Gain in computational efficiency by vectorization in the dynamic simulation of multi-body systems
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.
Collisions of Constrained Rigid Body Systems with Friction
Directory of Open Access Journals (Sweden)
Haijun Shen
1998-01-01
Full Text Available A new approach is developed for the general collision problem of two rigid body systems with constraints (e.g., articulated systems, such as massy linkages in which the relative tangential velocity at the point of contact and the associated friction force can change direction during the collision. This is beyond the framework of conventional methods, which can give significant and very obvious errors for this problem, and both extends and consolidates recent work. A new parameterization and theory characterize if, when and how the relative tangential velocity changes direction during contact. Elastic and dissipative phenomena and different values for static and kinetic friction coefficients are included. The method is based on the explicitly physical analysis of events at the point of contact. Using this method, Example 1 resolves (and corrects a paradox (in the literature of the collision of a double pendulum with the ground. The method fundamentally subsumes other recent models and the collision of rigid bodies; it yields the same results as conventional methods when they would apply (Example 2. The new method reformulates and extends recent approaches in a completely physical context.
Efficiency Analysis of a Wave Power Generation System by Using Multibody Dynamics
International Nuclear Information System (INIS)
Kim, Min Soo; Sohn, Jeong Hyun; Kim, Jung Hee; Sung, Yong Jun
2016-01-01
The energy absorption efficiency of a wave power generation system is calculated as the ratio of the wave power to the power of the system. Because absorption efficiency depends on the dynamic behavior of the wave power generation system, a dynamic analysis of the wave power generation system is required to estimate the energy absorption efficiency of the system. In this study, a dynamic analysis of the wave power generation system under wave loads is performed to estimate the energy absorption efficiency. RecurDyn is employed to carry out the dynamic analysis of the system, and the Morison equation is used for the wave load model. According to the results, the lower the wave height and the shorter the period, the higher is the absorption efficiency of the system
Efficiency Analysis of a Wave Power Generation System by Using Multibody Dynamics
Energy Technology Data Exchange (ETDEWEB)
Kim, Min Soo; Sohn, Jeong Hyun [Pukyong National Univ., Busan (Korea, Republic of); Kim, Jung Hee; Sung, Yong Jun [INGINE Inc., Seoul (Korea, Republic of)
2016-06-15
The energy absorption efficiency of a wave power generation system is calculated as the ratio of the wave power to the power of the system. Because absorption efficiency depends on the dynamic behavior of the wave power generation system, a dynamic analysis of the wave power generation system is required to estimate the energy absorption efficiency of the system. In this study, a dynamic analysis of the wave power generation system under wave loads is performed to estimate the energy absorption efficiency. RecurDyn is employed to carry out the dynamic analysis of the system, and the Morison equation is used for the wave load model. According to the results, the lower the wave height and the shorter the period, the higher is the absorption efficiency of the system.
Toledo Fuentes, A.; Kipfmueller, M.; José Prieto, M. A.
2017-10-01
Mobile manipulators are becoming a key instrument to increase the flexibility in industrial processes. Some of their requirements include handling of objects with different weights and sizes and their “fast” transportation, without jeopardizing production workers and machines. The compensation of forces affecting the system dynamic is therefore needed to avoid unwanted oscillations and tilting by sudden accelerations and decelerations. One general solution may be the implementation of external positioning elements to active stabilize the system. To accomplish the approach, the dynamic behavior of a robotic arm and a mobile platform was investigated to develop the stabilization mechanism using multibody simulations. The methodology used was divided into two phases for each subsystem: their natural frequencies and modal shapes were obtained using experimental modal analyses. Then, based on these experimental results, multibody simulation models (MBS) were set up and its dynamical parameters adjusted. Their modal shapes together with their obtained natural frequencies allowed a quantitative and qualitative analysis. In summary, the MBS models were successfully validated with the real subsystems, with a maximal percentage error of 15%. These models will serve as the basis for future steps in the design of the external actuators and its control strategy using a co-simulation tool.
ECCOMAS Thematic Conference on Multibody Dynamics
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...
Dynamical analysis of an orbiting three-rigid-body system
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Pagnozzi, Daniele, E-mail: daniele.pagnozzi@strath.ac.uk, E-mail: james.biggs@strath.ac.uk; Biggs, James D., E-mail: daniele.pagnozzi@strath.ac.uk, E-mail: james.biggs@strath.ac.uk [Department of Mechanical and Aerospace Engineering, University of Strathclyde, Glasgow, Scotland (United Kingdom)
2014-12-10
The development of multi-joint-spacecraft mission concepts calls for a deeper understanding of their nonlinear dynamics to inform and enhance system design. This paper presents a study of a three-finite-shape rigid-body system under the action of an ideal central gravitational field. The aim of this paper is to gain an insight into the natural dynamics of this system. The Hamiltonian dynamics is derived and used to identify relative attitude equilibria of the system with respect to the orbital reference frame. Then a numerical investigation of the behaviour far from the equilibria is provided using tools from modern dynamical systems theory such as energy methods, phase portraits and Poincarè maps. Results reveal a complex structure of the dynamics as well as the existence of connections between some of the equilibria. Stable equilibrium configurations appear to be surrounded by very narrow regions of regular and quasi-regular motions. Trajectories evolve on chaotic motions in the rest of the domain.
Directory of Open Access Journals (Sweden)
Yufei Liu
2015-01-01
Full Text Available This paper investigates the dynamic of a flexible robotic manipulator (FRM which consists of rigid driving base, flexible links, and flexible joints. With considering the motion fluctuations caused by the coupling effect, such as the motor parameters and mechanism inertias, as harmonic disturbances, the system investigated in this paper remains a parametrically excited system. An elastic restraint model of the FRM with elastic joints (FRMEJ is proposed, which considers the elastic properties of the connecting joints between the flexible arm and the driving base, as well as the harmonic disturbances aroused by the electromechanical coupling effect. As a consequence, the FRMEJ accordingly remains a flexible multibody system which conveys the effects of rigid-flexible couple and electromechanical couple. The Lagrangian function and Hamilton’s principle are used to establish the dynamic model of the FRMEJ. Based on the dynamic model proposed, the vibration power flow is introduced to show the vibration energy distribution. Numerical simulations are conducted to investigate the effect of the joint elasticities and the disturbance excitations, and the influences of the structure parameters and motion parameters on the vibration power flow are studied. The results obtained in this paper contribute to the structure design, motion optimization, and vibration control of FRMs.
Reaction Null Space of a multibody system with applications in robotics
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D. N. Nenchev
2013-02-01
Full Text Available This paper provides an overview of implementation examples based on the Reaction Null Space formalism, developed initially to tackle the problem of satellite-base disturbance of a free-floating space robot, when the robot arm is activated. The method has been applied throughout the years to other unfixed-base systems, e.g. flexible-base and macro/mini robot systems, as well as to the balance control problem of humanoid robots. The paper also includes most recent results about complete dynamical decoupling of the end-link of a fixed-base robot, wherein the end-link is regarded as the unfixed-base. This interpretation is shown to be useful with regard to motion/force control scenarios. Respective implementation results are provided.
The discrete adjoint method for parameter identification in multibody system dynamics.
Lauß, Thomas; Oberpeilsteiner, Stefan; Steiner, Wolfgang; Nachbagauer, Karin
2018-01-01
The adjoint method is an elegant approach for the computation of the gradient of a cost function to identify a set of parameters. An additional set of differential equations has to be solved to compute the adjoint variables, which are further used for the gradient computation. However, the accuracy of the numerical solution of the adjoint differential equation has a great impact on the gradient. Hence, an alternative approach is the discrete adjoint method , where the adjoint differential equations are replaced by algebraic equations. Therefore, a finite difference scheme is constructed for the adjoint system directly from the numerical time integration method. The method provides the exact gradient of the discretized cost function subjected to the discretized equations of motion.
Comparative multibody dynamics analysis of falls from playground climbing frames
Forero Rueda, Manuel A.; Gilchrist, M. D.
2009-01-01
This paper shows the utility of multibody dynamics in evaluating changes in injury related parameters of the head and lower limbs of children following falls from playground climbing frames. A particular fall case was used as a starting point to analyze the influence of surface properties, posture of the body at impact, and intermediate collisions against the climbing frame before impacting the ground. Simulations were made using the 6-year-old pedestrian MADYMO rigid body model and scaled he...
Nonlinear Multibody Dynamics of Wind Turbines
DEFF Research Database (Denmark)
Holm-Jørgensen, Kristian
individually and next couple them by use of joints. This gives a high level of modelling flexibility, where parts of the structure with relative ease can be interchanged to analyze other possibilities in a design process, or if a higher detail level is wanted for some components. In a multibody formulation...... turbine blade with large nonlinear displacements it has shown most favorable to use the end points in the substructure for updating the moving frames. For speeding up dynamical simulations for use in e.g. active control or parameter studies, system reduction of substructures in the multibody formulation...... element parameters also can determine e.g. torsional stiffness and the position of the shear center. The method makes use of three node triangular elements where the different material layers in the blade profile are taken into consideration. The results are compared to a similar tool which makes use...
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.
Biomimetic model systems of rigid hair beds: Part II - Experiment
Jammalamadaka, Mani S. S.; Hood, Kaitlyn; Hosoi, Anette
2017-11-01
Crustaceans - such as lobsters, crabs and stomapods - have hairy appendages that they use to recognize and track odorants in the surrounding fluid. An array of rigid hairs impedes flow at different rates depending on the spacing between hairs and the Reynolds number, Re. At larger Reynolds number (Re>1), fluid travels through the hairs rather than around them, a phenomenon called leakiness. Crustaceans flick their appendages at different speeds in order to manipulate the leakiness between the hairs, allowing the hairs to either detect the odors in a sample of fluid or collect a new sample. Theoretical and numerical studies predict that there is a fast flow region near the hairs that moves closer to the hairs as Re increases. Here, we test this theory experimentally. We 3D printed rigid hairs with an aspect ratio of 30:1 in rectangular arrays with different hair packing fractions. We custom built an experimental setup which establishes poiseuille flow at intermediate Re, Re <=200. We track the flow dynamics through the hair beds using tracer particles and Particle Imaging Velocimetry. We will then compare the modelling predictions with the experimental outcomes.
Composite Sliding Mode Control for a Free-Floating Space Rigid-Flexible Coupling Manipulator System
Congqing, Wang; Pengfei, Wu; Xin, Zhou; Xiwu, Pei
2013-01-01
The flexible space manipulator is a highly nonlinear and coupled dynamic system. This paper proposes a novel composite sliding mode control to deal with the vibration suppression and trajectory tracking of a free-floating space rigid-flexible coupling manipulator with a rigid payload. First, the dynamic equations of this system are established by using Lagrange and assumed mode methods and in the meantime this dynamic modelling allows consideration of the modelling errors, the external distur...
Directory of Open Access Journals (Sweden)
Pål Johan From
2012-04-01
Full Text Available This paper presents the explicit dynamic equations of a mechanical system. The equations are presented so that they can easily be implemented in a simulation software or controller environment and are also well suited for system and controller analysis. The dynamics of a general mechanical system consisting of one or more rigid bodies can be derived from the Lagrangian. We can then use several well known properties of Lie groups to guarantee that these equations are well defined. This will, however, often lead to rather abstract formulation of the dynamic equations that cannot be implemented in a simulation software directly. In this paper we close this gap and show what the explicit dynamic equations look like. These equations can then be implemented directly in a simulation software and no background knowledge on Lie theory and differential geometry on the practitioner's side is required. This is the first of two papers on this topic. In this paper we derive the dynamics for single rigid bodies, while in the second part we study multibody systems. In addition to making the equations more accessible to practitioners, a motivation behind the papers is to correct a few errors commonly found in literature. For the first time, we show the detailed derivations and how to arrive at the correct set of equations. We also show through some simple examples that these correspond with the classical formulations found from Lagrange's equations. The dynamics is derived from the Boltzmann--Hamel equations of motion in terms of local position and velocity variables and the mapping to the corresponding quasi-velocities. Finally we present a new theorem which states that the Boltzmann--Hamel formulation of the dynamics is valid for all transformations with a Lie group topology. This has previously only been indicated through examples, but here we also present the formal proof. The main motivation of these papers is to allow practitioners not familiar with
Constraint elimination in dynamical systems
Singh, R. P.; Likins, P. W.
1989-01-01
Large space structures (LSSs) and other dynamical systems of current interest are often extremely complex assemblies of rigid and flexible bodies subjected to kinematical constraints. A formulation is presented for the governing equations of constrained multibody systems via the application of singular value decomposition (SVD). The resulting equations of motion are shown to be of minimum dimension.
Research on The Construction of Flexible Multi-body Dynamics Model based on Virtual Components
Dong, Z. H.; Ye, X.; Yang, F.
2018-05-01
Focus on the harsh operation condition of space manipulator, which cannot afford relative large collision momentum, this paper proposes a new concept and technology, called soft-contact technology. In order to solve the problem of collision dynamics of flexible multi-body system caused by this technology, this paper also proposes the concepts of virtual components and virtual hinges, and constructs flexible dynamic model based on virtual components, and also studies on its solutions. On this basis, this paper uses NX to carry out model and comparison simulation for space manipulator in 3 different modes. The results show that using the model of multi-rigid body + flexible body hinge + controllable damping can make effective control on amplitude for the force and torque caused by target satellite collision.
Biomimetic model systems of rigid hair beds: Part I - Theory
Hood, Kaitlyn; Jammalamadaka, Mani S. S.; Hosoi, Anette
2017-11-01
Crustaceans - such as lobsters, crabs, and stomapods - have hairy appendages that they use to recognize and track odorants in the surrounding fluid. An array of rigid hairs impedes flow at different rates depending on the spacing between hairs and the Reynolds number, Re. At larger Reynolds numbers (Re >1), fluid travels through the hairs rather than around them, a phenomenon called leakiness. Crustaceans flick their appendages at different speeds in order to manipulate the leakiness between the hairs, allowing the hairs to either detect odors in a sample of fluid or collect a new sample. A single hair can be represented as a slender body attached at one end to a wall. Using both slender body theory and numerical methods, we observe that there is a region of flow around the hair that speeds up relative to the unobstructed flow. As the Reynolds number increases, this fast flow region moves closer to the hair. Using this model, we predict that an array of hairs can be engineered to have a desired leakiness profile.
Bernier, Caroline; Gazzola, Mattia; Ronsse, Renaud; Chatelain, Philippe
2017-11-01
We present a 2D fluid-structure interaction simulation method with a specific focus on articulated and actuated structures. The proposed algorithm combines a viscous Vortex Particle-Mesh (VPM) method based on a penalization technique and a Multi-Body System (MBS) solver. The hydrodynamic forces and moments acting on the structure parts are not computed explicitly from the surface stresses; they are rather recovered from the projection and penalization steps within the VPM method. The MBS solver accounts for the body dynamics via the Euler-Lagrange formalism. The deformations of the structure are dictated by the hydrodynamic efforts and actuation torques. Here, we focus on simplified swimming structures composed of neutrally buoyant ellipses connected by virtual joints. The joints are actuated through a simple controller in order to reproduce the swimming patterns of an eel-like swimmer. The method enables to recover the histories of torques applied on each hinge along the body. The method is verified on several benchmarks: an impulsively started elastically mounted cylinder and free swimming articulated fish-like structures. Validation will be performed by means of an experimental swimming robot that reproduces the 2D articulated ellipses.
High precision NC lathe feeding system rigid-flexible coupling model reduction technology
Xuan, He; Hua, Qingsong; Cheng, Lianjun; Zhang, Hongxin; Zhao, Qinghai; Mao, Xinkai
2017-08-01
This paper proposes the use of dynamic substructure method of reduction of order to achieve effective reduction of feed system for high precision NC lathe feeding system rigid-flexible coupling model, namely the use of ADAMS to establish the rigid flexible coupling simulation model of high precision NC lathe, and then the vibration simulation of the period by using the FD 3D damper is very effective for feed system of bolt connection reduction of multi degree of freedom model. The vibration simulation calculation is more accurate, more quickly.
International Nuclear Information System (INIS)
Ahn, Byungseong; Kim, Suh In; Kim, Yoon Young
2016-01-01
When a system consisting of rigid and flexible bodies is optimized to improve its dynamic characteristics, its eigenfrequencies are typically maximized. While topology optimization formulations dealing with simultaneous design of a system of rigid and flexible bodies are available, studies on eigenvalue maximization of the system are rare. In particular, no work has solved for the case when the target frequency becomes one of the repeated eigenfrequencies. The problem involving repeated eigenfrequencies is solved in this study, and a topology optimization formulation and sensitivity analysis are presented. Further, several numerical case studies are considered to demonstrate the validity of the proposed formulation
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.
Rheology of multiphase polymer systems using novel "melt rigidity" evaluation approach
Kracalik, Milan
2015-04-01
Multiphase polymer systems like blends, composites and nanocomposites exhibit complex rheological behaviour due to physical and also possibly chemical interactions between individual phases. Up to now, rheology of heterogeneous polymer systems has been usually described by evaluation of viscosity curve (shear thinning phenomenon), storage modulus curve (formation of secondary plateau) or plotting information about damping behaviour (e.g. Van Gurp-Palmen-plot). On the contrary to evaluation of damping behaviour, "melt rigidity" approach has been introduced for description of physical network of rigid particles in polymer matrix as relation of ∫G'/∫G" over specific frequency range. This approach has been experimentally proved for polymer nanocomposites in order to compare shear flow characteristics with elongational flow field. In this contribution, LDPE-clay nanocomposites with different dispersion grades (physical networks) have been prepared and characterized by both conventional as well as novel "melt rigidity" approach.
Hamiltonian Dynamics of Spider-Type Multirotor Rigid Bodies Systems
International Nuclear Information System (INIS)
Doroshin, Anton V.
2010-01-01
This paper sets out to develop a spider-type multiple-rotor system which can be used for attitude control of spacecraft. The multirotor system contains a large number of rotor-equipped rays, so it was called a 'Spider-type System', also it can be called 'Rotary Hedgehog'. These systems allow using spinups and captures of conjugate rotors to perform compound attitude motion of spacecraft. The paper describes a new method of spacecraft attitude reorientation and new mathematical model of motion in Hamilton form. Hamiltonian dynamics of the system is investigated with the help of Andoyer-Deprit canonical variables. These variables allow obtaining exact solution for hetero- and homoclinic orbits in phase space of the system motion, which are very important for qualitative analysis.
Rigid hoist articulated grapple system development for enhanced remote maintenance
International Nuclear Information System (INIS)
Witham, C.; White, P.; Garin, J.
1979-01-01
Remote maintenance and repair within nuclear environments have become more demanding of remote manipulation equipment in the last few years. A deficiency exists in the array of tools available for dexterous operations of loads in the 180-kg range. The development of a manipulation system with enhanced operator controls is discussed. This system is a six-degree-of-freedom manipulator with bilateral servo control. It is to be attached to a mobile support boom in order to operate throughout the nuclear cell. The manipulator is intended to work in conjunction with light duty servomanipulators, overhead crane systems, and through-the-wall mechanical master slaves
Comparative multibody dynamics analysis of falls from playground climbing frames.
Forero Rueda, M A; Gilchrist, M D
2009-10-30
This paper shows the utility of multibody dynamics in evaluating changes in injury related parameters of the head and lower limbs of children following falls from playground climbing frames. A particular fall case was used as a starting point to analyze the influence of surface properties, posture of the body at impact, and intermediate collisions against the climbing frame before impacting the ground. Simulations were made using the 6-year-old pedestrian MADYMO rigid body model and scaled head contact characteristics. Energy absorbing surfaces were shown to reduce injury severity parameters by up to 30-80% of those of rigid surfaces, depending on impact posture and surface. Collisions against components of a climbing frame during a fall can increase injury severity of the final impact of the head with the ground by more than 90%. Negligible changes are associated with lower limb injury risks when different surfacing materials are used. Computer reconstructions of actual falls that are intended to quantify the severity of physical injuries rely on accurate knowledge of initial conditions prior to falling, intermediate kinematics of the fall and the orientation of the body when it impacts against the ground. Multibody modelling proved to be a valuable tool to analyze the quality of eyewitness information and analyze the relative injury risk associated with changes in components influencing fall injuries from playground climbing frames. Such simulations can also support forensic investigations by evaluating alternative hypotheses for the sequence of kinematic motion of falls which result in known injuries.
Baker, Stephen B; Reid, Russell R; Burkey, Brooke; Bartlett, Scott P
2007-09-01
To shorten head frame wear time associated with external halo distraction (HD), we have adapted a protocol for maxillary distraction with the halo system that integrates plate fixation. All patients had a history of cleft lip and/or palate and maxillary retrusion > or = 8 mm. Five patients treated with this protocol and followed for at least 1 year were included in this study. The protocol included a 3-day latency period, variable maxillary distraction, and removal of the halo device with simultaneous rigid internal fixation. Two patients had a variable period of maxillomandibular fixation (MMF), which maintained the maxillary advancement and idealized intercuspal position while permitting further callus maturation. Cephalographs were obtained preoperatively, immediately following distractor removal, and 1 year after rigid internal fixation. The mean age at time of surgery was 18.7 years. The maxillary deficiency ranged from 8 to 15 mm (mean = 10.6 mm). All five patients demonstrated excellent occlusion. Cephalometric analysis 1-year post rigid internal fixation revealed minimal (maxillary distraction followed by MMF to maintain maxillary advancement may reduce halo device wear to 1 to 2 weeks. MMF optimizes occlusion by forcing the maxillary teeth into maximal intercuspal position. Rigid fixation is not only associated with less long-term relapse compared to nonrigid forms of fixation, but also minimizes the incidence of nonunion. This treatment protocol provides the advancement possible with distraction osteogenesis and the accuracy of orthognathic surgery, thereby minimizing external head frame wear.
International Nuclear Information System (INIS)
Amengonu, Yawo H; Kakad, Yogendra P
2014-01-01
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
Modeling of a light elastic beam by a system of rigid bodies
Directory of Open Access Journals (Sweden)
Šalinić Slaviša
2004-01-01
Full Text Available This paper has shown that a light elastic beam, in the case of small elastic deformations, can be modeled by a kinematic chain without branching composed of rigid bodies which are connected by passive revolute or prismatic joints with corresponding springs in them. Elastic properties of the beam are modeled by the springs introduced. The potential energy of the elastic beam is expressed as a function of components of the vector of elastic displacement and the vector of elastic rotation calculated for the elastic centre of the beam, which results in the diagonal stiffness matrix of the beam. As the potential energy of the introduced system of bodies with springs is expressed in the function of relative joint displacements, the diagonal stiffness matrix is obtained. In addition, these two stiffness matrices are equal. The modeling process has been demonstrated on the example of an elastic beam rotating about a fixed vertical axis, with a rigid body whose mass is considerably larger than the beam mass fixed to its free end. Differential equations of motion have been formed for this mechanical system. The modeling technique described here aims at expanding of usage of well developed methods of dynamics of systems of rigid bodies to the analysis of systems with elastic bodies. .
Analytic analysis of auxetic metamaterials through analogy with rigid link systems
Rayneau-Kirkhope, Daniel; Zhang, Chengzhao; Theran, Louis; Dias, Marcelo A.
2017-01-01
Recent progress in advanced additive manufacturing techniques has stimulated the growth of the field of mechanical metamaterials. One area particular interest in this subject is the creation of auxetic material properties through elastic instability. This paper focuses on a novel methodology in the analysis of auxetic metamaterials through analogy with rigid link lattice systems. Our analytic methodology gives extremely good agreement with finite element simulations for both the onset of elas...
Analytic analysis of auxetic metamaterials through analogy with rigid link systems
Rayneau-Kirkhope, Daniel; Zhang, Chengzhao; Theran, Louis; Dias, Marcelo A.
2018-02-01
In recent years, many structural motifs have been designed with the aim of creating auxetic metamaterials. One area of particular interest in this subject is the creation of auxetic material properties through elastic instability. Such metamaterials switch from conventional behaviour to an auxetic response for loads greater than some threshold value. This paper develops a novel methodology in the analysis of auxetic metamaterials which exhibit elastic instability through analogy with rigid link lattice systems. The results of our analytic approach are confirmed by finite-element simulations for both the onset of elastic instability and post-buckling behaviour including Poisson's ratio. The method gives insight into the relationships between mechanisms within lattices and their mechanical behaviour; as such, it has the potential to allow existing knowledge of rigid link lattices with auxetic paths to be used in the design of future buckling-induced auxetic metamaterials.
Validation of flexible multibody dynamics beam formulations using benchmark problems
Energy Technology Data Exchange (ETDEWEB)
Bauchau, Olivier A., E-mail: obauchau@umd.edu [University of Maryland (United States); Betsch, Peter [Karlsruhe Institute of Technology (Germany); Cardona, Alberto [CIMEC (UNL/Conicet) (Argentina); Gerstmayr, Johannes [Leopold-Franzens Universität Innsbruck (Austria); Jonker, Ben [University of Twente (Netherlands); Masarati, Pierangelo [Politecnico di Milano (Italy); Sonneville, Valentin [Université de Liège (Belgium)
2016-05-15
As the need to model flexibility arose in multibody dynamics, the floating frame of reference formulation was developed, but this approach can yield inaccurate results when elastic displacements becomes large. While the use of three-dimensional finite element formulations overcomes this problem, the associated computational cost is overwhelming. Consequently, beam models, which are one-dimensional approximations of three-dimensional elasticity, have become the workhorse of many flexible multibody dynamics codes. Numerous beam formulations have been proposed, such as the geometrically exact beam formulation or the absolute nodal coordinate formulation, to name just two. New solution strategies have been investigated as well, including the intrinsic beam formulation or the DAE approach. This paper provides a systematic comparison of these various approaches, which will be assessed by comparing their predictions for four benchmark problems. The first problem is the Princeton beam experiment, a study of the static large displacement and rotation behavior of a simple cantilevered beam under a gravity tip load. The second problem, the four-bar mechanism, focuses on a flexible mechanism involving beams and revolute joints. The third problem investigates the behavior of a beam bent in its plane of greatest flexural rigidity, resulting in lateral buckling when a critical value of the transverse load is reached. The last problem investigates the dynamic stability of a rotating shaft. The predictions of eight independent codes are compared for these four benchmark problems and are found to be in close agreement with each other and with experimental measurements, when available.
Rigid finite element method in analysis of dynamics of offshore structures
Energy Technology Data Exchange (ETDEWEB)
Wittbrodt, Edmund [Gdansk Univ. of Technology (Poland); Szczotka, Marek; Maczynski, Andrzej; Wojciech, Stanislaw [Bielsko-Biala Univ. (Poland)
2013-07-01
This book describes new methods developed for modelling dynamics of machines commonly used in the offshore industry. These methods are based both on the rigid finite element method, used for the description of link deformations, and on homogeneous transformations and joint coordinates, which is applied to the modelling of multibody system dynamics. In this monograph, the bases of the rigid finite element method and homogeneous transformations are introduced. Selected models for modelling dynamics of offshore devices are then verified both by using commercial software, based on the finite element method, as well as by using additional methods. Examples of mathematical models of offshore machines, such as a gantry crane for Blowout-Preventer (BOP) valve block transportation, a pedestal crane with shock absorber, and pipe laying machinery are presented. Selected problems of control in offshore machinery as well as dynamic optimization in device control are also discussed. Additionally, numerical simulations of pipe-laying operations taking active reel drive into account are shown.
Rigid Finite Element Method in Analysis of Dynamics of Offshore Structures
Wittbrodt, Edmund; Maczyński, Andrzej; Wojciech, Stanisław
2013-01-01
This book describes new methods developed for modelling dynamics of machines commonly used in the offshore industry. These methods are based both on the rigid finite element method, used for the description of link deformations, and on homogeneous transformations and joint coordinates, which is applied to the modelling of multibody system dynamics. In this monograph, the bases of the rigid finite element method and homogeneous transformations are introduced. Selected models for modelling dynamics of offshore devices are then verified both by using commercial software, based on the finite element method, as well as by using additional methods. Examples of mathematical models of offshore machines, such as a gantry crane for Blowout-Preventer (BOP) valve block transportation, a pedestal crane with shock absorber, and pipe laying machinery are presented. Selected problems of control in offshore machinery as well as dynamic optimization in device control are also discussed. Additionally, numerical simulations of...
Cross-Linked Liquid Crystalline Systems From Rigid Polymer Networks to Elastomers
Broer, Dirk
2011-01-01
With rapidly expanding interest in liquid crystalline polymers and elastomers among the liquid crystal community, researchers are currently exploring the wide range of possible application areas for these unique materials, including optical elements on displays, tunable lasers, strain gauges, micro-structures, and artificial muscles. Written by respected scientists from academia and industry around the world, who are not only active in the field but also well-known in more traditional areas of research, "Cross-Linked Liquid Crystalline Systems: From Rigid Polymer Networks to Elastomers&qu
Energy Technology Data Exchange (ETDEWEB)
Han, Jong-Boo; Song, Hajun; Kim, Sung-Soo [Chungnam Nat’l Univ., Daejeon (Korea, Republic of)
2017-06-15
Flexible multibody simulations are widely used in the industry to design mechanical systems. In flexible multibody dynamics, deformation coordinates are described either relatively in the body reference frame that is floating in the space or in the inertial reference frame. Moreover, these deformation coordinates are generated based on the discretization of the body according to the finite element approach. Therefore, the formulation of the flexible multibody system always deals with a huge number of degrees of freedom and the numerical solution methods require a substantial amount of computational time. Parallel computational methods are a solution for efficient computation. However, most of the parallel computational methods are focused on the efficient solution of large-sized linear equations. For multibody analysis, we need to develop an efficient formulation that could be suitable for parallel computation. In this paper, we developed a subsystem synthesis method for a flexible multibody system and proposed efficient parallel computational schemes based on the OpenMP API in order to achieve efficient computation. Simulations of a rotating blade system, which consists of three identical blades, were carried out with two different parallel computational schemes. Actual CPU times were measured to investigate the efficiency of the proposed parallel schemes.
Rigid-flexible coupling dynamics of three-dimensional hub-beams system
International Nuclear Information System (INIS)
Liu Jinyang; Lu Hao
2007-01-01
In the previous research of the coupling dynamics of a hub-beam system, coupling between the rotational motion of hub and the torsion deformation of beam is not taken into account since the system undergoes planar motion. Due to the small longitudinal deformation, coupling between the rotational motion of hub and the longitudinal deformation of beam is also neglected. In this paper, rigid-flexible coupling dynamics is extended to a hub-beams system with three-dimensional large overall motion. Not only coupling between the large overall motion and the bending deformation, but also coupling between the large overall motion and the torsional deformation are taken into account. In case of temperature increase, the longitudinal deformation caused by the thermal expansion is significant, such that coupling between the large overall motion and the longitudinal deformation is also investigated. Combining the characteristics of the hybrid coordinate formulation and the absolute nodal coordinate formulation, the system generalized coordinates include the relative nodal displacement and the slope of each beam element with respect to the body-fixed frame of the hub, and the variables related to the spatial large overall motion of the hub and beams. Based on precise strain-displacement relation, the geometric stiffening effect is taken into account, and the rigid-flexible coupling dynamic equations are derived using velocity variational principle. Finite element method is employed for discretization. Simulation of a hub-beams system is used to show the coupling effect between the large overall motion and the torsional deformation as well as the longitudinal deformation. Furthermore, conservation of energy in case of free motion is shown to verify the formulation
A Linear Active Disturbance Rejection Control for a Ball and Rigid Triangle System
Directory of Open Access Journals (Sweden)
Carlos Aguilar-Ibanez
2016-01-01
Full Text Available This paper proposes an application of linear flatness control along with active disturbance rejection control (ADRC for the local stabilization and trajectory tracking problems in the underactuated ball and rigid triangle system. To this end, an observer-based linear controller of the ADRC type is designed based on the flat tangent linearization of the system around its corresponding unstable equilibrium rest position. It was accomplished through two decoupled linear extended observers and a single linear output feedback controller, with disturbance cancelation features. The controller guarantees locally exponentially asymptotic stability for the stabilization problem and practical local stability in the solution of the tracking error. An advantage of combining the flatness and the ADRC methods is that it possible to perform online estimates and cancels the undesirable effects of the higher-order nonlinearities discarded by the linearization approximation. Simulation indicates that the proposed controller behaves remarkably well, having an acceptable domain of attraction.
Flexible joints in structural and multibody dynamics
Directory of Open Access Journals (Sweden)
O. A. Bauchau
2013-02-01
Full Text Available 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 deformations, identification of its stiffness characteristics is not so simple, specially if the joint is itself a complex system. When finite deformations occur, the definition of deformation measures becomes a critical issue. This paper proposes a family of tensorial deformation measures suitable for elastic bodies of finite dimension. These families are generated by two parameters that can be used to modify the constitutive behavior of the joint, while maintaining the tensorial nature of the deformation measures. Numerical results demonstrate the objectivity of the deformations measures, a feature that is not shared by the deformations measures presently used in the literature. The impact of the choice of the two parameters on the constitutive behavior of the flexible joint is also investigated.
Generalized Predictive Control of Dynamic Systems with Rigid-Body Modes
Kvaternik, Raymond G.
2013-01-01
Numerical simulations to assess the effectiveness of Generalized Predictive Control (GPC) for active control of dynamic systems having rigid-body modes are presented. GPC is a linear, time-invariant, multi-input/multi-output predictive control method that uses an ARX model to characterize the system and to design the controller. Although the method can accommodate both embedded (implicit) and explicit feedforward paths for incorporation of disturbance effects, only the case of embedded feedforward in which the disturbances are assumed to be unknown is considered here. Results from numerical simulations using mathematical models of both a free-free three-degree-of-freedom mass-spring-dashpot system and the XV-15 tiltrotor research aircraft are presented. In regulation mode operation, which calls for zero system response in the presence of disturbances, the simulations showed reductions of nearly 100%. In tracking mode operations, where the system is commanded to follow a specified path, the GPC controllers produced the desired responses, even in the presence of disturbances.
Directory of Open Access Journals (Sweden)
Sol Ha
2016-01-01
Full Text Available This paper suggests an event-based scenario manager capable of creating and editing a scenario for shipbuilding process simulation based on multibody dynamics. To configure various situation in shipyards and easily connect with multibody dynamics, the proposed method has two main concepts: an Actor and an Action List. The Actor represents the anatomic unit of action in the multibody dynamics and can be connected to a specific component of the dynamics kernel such as the body and joint. The user can make a scenario up by combining the actors. The Action List contains information for arranging and executing the actors. Since the shipbuilding process is a kind of event-based sequence, all simulation models were configured using Discrete EVent System Specification (DEVS formalism. The proposed method was applied to simulations of various operations in shipyards such as lifting and erection of a block and heavy load lifting operation using multiple cranes.
Alkhouri, Shadi; Waite, Peter D; Davis, Matthew B; Lamani, Ejvis; Kau, Chung How
2017-01-01
Distraction osteogenesis (DO) is a treatment option for patients with maxillary hypoplasia secondary to cleft lip and palate (CLP). The aim of this study is to present a technique for maxillary DO using Le Fort I osteotomy with rigid external distraction (RED) system. The patient presented in this paper was an Asian female with CLP aged 13 years and 6 months. She presented with severe midfacial deficiency with a Class III dental malocclusion with a negative overjet and concave facial profile. Cone-beam computed tomography images were recorded preoperatively and the operation performed involved a high Le Fort I osteotomy. The appliance fabricated was banded to upper first molars used for anchorage of the RED system. Distraction of the maxilla was initiated after 7-day latency period. Postoperative cephalometric analysis showed maxillary advancement anteriorly and superiorly, the total distraction treatment period was 10 days. The maxillary advancement was 10.5 mm and the SNA angle increased from 67.5° to 77.9°. Furthermore, the ANB angle changed from -9.8° to 1.6° and the occlusion changed from Class III to Class I. The profile of the face changed from concave to convex and a much better esthetic result was achieved. The study suggests RED system to be a reliable alternative procedure for the treatment of midfacial hypoplasia with or without cleft. Furthermore, it minimizes the risk of the surgical procedure and shortens the operating time.
Fiber Optic Systems for Light Curing Rigidization of Inflatable Structures, Phase I
National Aeronautics and Space Administration — Light (UV and visible) curing composite matrix resins are being explored as an attractive means for rigidizing inflatable spacecraft for large space-deployed...
Nurjaman, Hari; Faizal, Lutfi; Suaryana, Nyoman; Hariandja, Binsar; Gambiro, Purnomo, Wicaksono, Siswo
2017-11-01
The performance of highways in Indonesia until today is yet to be optimum. Flexible or rigid pavement construction generally do not reach designed service lives, either due to the fact that the construction do not meet specifications or unavoidable excessive load. Precast and prestressed concrete system has been applied since 2007, but unfortunately the application has not been optimum due to the fact that the construction method is not integrally carried out. This paper deals with a construction concept that developed in 2015-2017. The concept applies green construction based on integrated manufacture industry, starting from design, construction, function, maintenance and demolition. The concept is applied on the three highway sub-layers, i.e., sub grade, sub base, and surface, and drainage system. Sub grade improvement may use soil dislocation, chemical improvement or concrete matress. Sub base material uses foam mortar, which is material easy in quality control compared to conventional materials. Pavement material uses precast and prestressed concrete components with controlled quality, quickly function as flexible pavement, and moreover, may anticipate excessive loadings. Cost estimation is carried out integrated by life cycle cost: initial investment, obstruction while construction, and maintenance cost during operation. This innovation has passed tests in technical construction method aspects as well as construction work in 2015-2017, so it is available to support infrastructure construction acceleration which achieves quality demanded to date.
Estimating the magnitude of steric effects in rigid systems by NMR
International Nuclear Information System (INIS)
Yoneda, Julliane Diniz; Seidl, Peter Rudolf; Leal, Katia Zaccur
2008-01-01
The rapid advance of supramolecular chemistry has led to a better understanding of the forces and interactions that are responsible for many different phenomena. Among these, steric effects play an important role in determining the constraints to association between the species involved. Although the role of steric effects has been recognized for a long time, quantitative information has been mainly related to the comparison of these effects on a chemical reaction or conformational equilibrium rather than the properties of the group of atoms that is responsible for their manifestation. This situation has been changing with the increase in power of computational methods and the accumulation of data on model compounds that can be used for the purpose of comparison. Here we present a short review of our recent work on NMR of rigid carbocyclic systems and apply this type of approach to di- and triamantane systems. Our results show how NMR can be used to locate the segment of a molecule that is subjected to steric effects and evaluate the degree to which these effects will distort its geometry. (author)
Estimating the magnitude of steric effects in rigid systems by NMR
Energy Technology Data Exchange (ETDEWEB)
Yoneda, Julliane Diniz [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Programa Pos-Graduacao em Quimica Organica; Seidl, Peter Rudolf [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Escola de Quimica; Leal, Katia Zaccur, E-mail: pseidl@eq.ufrj.br [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Dept. de Fisico-Quimica. Programa de Pos-Graduacao em Quimica Organica
2008-07-01
The rapid advance of supramolecular chemistry has led to a better understanding of the forces and interactions that are responsible for many different phenomena. Among these, steric effects play an important role in determining the constraints to association between the species involved. Although the role of steric effects has been recognized for a long time, quantitative information has been mainly related to the comparison of these effects on a chemical reaction or conformational equilibrium rather than the properties of the group of atoms that is responsible for their manifestation. This situation has been changing with the increase in power of computational methods and the accumulation of data on model compounds that can be used for the purpose of comparison. Here we present a short review of our recent work on NMR of rigid carbocyclic systems and apply this type of approach to di- and triamantane systems. Our results show how NMR can be used to locate the segment of a molecule that is subjected to steric effects and evaluate the degree to which these effects will distort its geometry. (author)
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.
Attitude and Configuration Control of Flexible Multi-Body Spacecraft
Cho, Sung-Ki; Cochran, John E., Jr.
2002-06-01
Multi-body spacecraft attitude and configuration control formulations based on the use of collaborative control theory are considered. The control formulations are based on two-player, nonzero-sum, differential game theory applied using a Nash strategy. It is desired that the control laws allow different components of the multi-body system to perform different tasks. For example, it may be desired that one body points toward a fixed star while another body in the system slews to track another satellite. Although similar to the linear quadratic regulator formulation, the collaborative control formulation contains a number of additional design parameters because the problem is formulated as two control problems coupled together. The use of the freedom of the partitioning of the total problem into two coupled control problems and the selection of the elements of the cross-coupling matrices are specific problems addressed in this paper. Examples are used to show that significant improvement in performance, as measured by realistic criteria, of collaborative control over conventional linear quadratic regulator control can be achieved by using proposed design guidelines.
Attitude and Configuration Control of Flexible Multi-Body Spacecraft
Directory of Open Access Journals (Sweden)
Sungki Cho
2002-06-01
Full Text Available Multi-body spacecraft attitude and configuration control formulations based on the use of collaborative control theory are considered. The control formulations are based on two-player, nonzero-sum, differential game theory applied using a Nash strategy. It is desired that the control laws allow different components of the multi-body system to perform different tasks. For example, it may be desired that one body points toward a fixed star while another body in the system slews to track another satellite. Although similar to the linear quadratic regulator formulation, the collaborative control formulation contains a number of additional design parameters because the problem is formulated as two control problems coupled together. The use of the freedom of the partitioning of the total problem into two coupled control problems and the selection of the elements of the cross-coupling matrices are specific problems addressed in this paper. Examples are used to show that significant improvement in performance, as measured by realistic criteria, of collaborative control over conventional linear quadratic regulator control can be achieved by using proposed design guidelines.
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.
Mid-Lift-to-Drag Ratio Rigid Vehicle Control System Design and Simulation for Human Mars Entry
Johnson, Breanna J.; Cerimele, Christopher J.; Stachowiak, Susan J.; Sostaric, Ronald R.; Matz, Daniel A.; Lu, Ping
2018-01-01
The Mid-Lift-to-Drag Ratio Rigid Vehicle (MRV) is a proposed candidate in the NASA Evolvable Mars Campaign's (EMC) Pathfinder Entry, Descent, and Landing (EDL) architecture study. The purpose of the study is to design a mission and vehicle capable of transporting a 20mt payload to the surface of Mars. The MRV is unique in its rigid, asymmetrical lifting-body shape which enables a higher lift-to-drag ratio (L/D) than the typical robotic Mars entry capsule vehicles that carry much less mass. This paper presents the formulation and six-degree-of-freedom (6DOF) performance of the MRV's control system, which uses both aerosurfaces and a propulsive reaction control system (RCS) to affect longitudinal and lateral directional behavior.
Grenade, Charlotte; Moniotte, Nicolas; Rompen, Eric; Vanheusden, Alain; Mainjot, Amélie; De Pauw-Gillet, Marie-Claire
2016-01-01
In vitro studies about biomaterials biological properties are essential screening tests. Yet cell cultures encounter difficulties related to cell retention on material surface or to the observation of both faces of permeable materials. The objective of the present study was to develop a reliable in vitro method to study cell behavior on rigid and flexible/permeable biomaterials elaborating two specific insert-based systems (IBS-R and IBS-F respectively). IBS-R was designed as a specific cylin...
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.
A Non-smooth Newton Method for Multibody Dynamics
International Nuclear Information System (INIS)
Erleben, K.; Ortiz, R.
2008-01-01
In this paper we deal with the simulation of rigid bodies. Rigid body dynamics have become very important for simulating rigid body motion in interactive applications, such as computer games or virtual reality. We present a novel way of computing contact forces using a Newton method. The contact problem is reformulated as a system of non-linear and non-smooth equations, and we solve this system using a non-smooth version of Newton's method. One of the main contribution of this paper is the reformulation of the complementarity problems, used to model impacts, as a system of equations that can be solved using traditional methods.
Rigid body formulation in a finite element context with contact interaction
Refachinho de Campos, Paulo R.; Gay Neto, Alfredo
2018-03-01
The present work proposes a formulation to employ rigid bodies together with flexible bodies in the context of a nonlinear finite element solver, with contact interactions. Inertial contributions due to distribution of mass of a rigid body are fully developed, considering a general pole position associated with a single node, representing a rigid body element. Additionally, a mechanical constraint is proposed to connect a rigid region composed by several nodes, which is useful for linking rigid/flexible bodies in a finite element environment. Rodrigues rotation parameters are used to describe finite rotations, by an updated Lagrangian description. In addition, the contact formulation entitled master-surface to master-surface is employed in conjunction with the rigid body element and flexible bodies, aiming to consider their interaction in a rigid-flexible multibody environment. New surface parameterizations are presented to establish contact pairs, permitting pointwise interaction in a frictional scenario. Numerical examples are provided to show robustness and applicability of the methods.
Daneshjou, Kamran; Alibakhshi, Reza
2018-01-01
In the current manuscript, the process of spacecraft docking, as one of the main risky operations in an on-orbit servicing mission, is modeled based on unconstrained multibody dynamics. The spring-damper buffering device is utilized here in the docking probe-cone system for micro-satellites. Owing to the impact occurs inevitably during docking process and the motion characteristics of multibody systems are remarkably affected by this phenomenon, a continuous contact force model needs to be considered. Spring-damper buffering device, keeping the spacecraft stable in an orbit when impact occurs, connects a base (cylinder) inserted in the chaser satellite and the end of docking probe. Furthermore, by considering a revolute joint equipped with torsional shock absorber, between base and chaser satellite, the docking probe can experience both translational and rotational motions simultaneously. Although spacecraft docking process accompanied by the buffering mechanisms may be modeled by constrained multibody dynamics, this paper deals with a simple and efficient formulation to eliminate the surplus generalized coordinates and solve the impact docking problem based on unconstrained Lagrangian mechanics. By an example problem, first, model verification is accomplished by comparing the computed results with those recently reported in the literature. Second, according to a new alternative validation approach, which is based on constrained multibody problem, the accuracy of presented model can be also evaluated. This proposed verification approach can be applied to indirectly solve the constrained multibody problems by minimum required effort. The time history of impact force, the influence of system flexibility and physical interaction between shock absorber and penetration depth caused by impact are the issues followed in this paper. Third, the MATLAB/SIMULINK multibody dynamic analysis software will be applied to build impact docking model to validate computed results and
Charles, Alexandre; Ballard, Patrick
2016-08-01
The dynamics of mechanical systems with a finite number of degrees of freedom (discrete mechanical systems) is governed by the Lagrange equation which is a second-order differential equation on a Riemannian manifold (the configuration manifold). The handling of perfect (frictionless) unilateral constraints in this framework (that of Lagrange's analytical dynamics) was undertaken by Schatzman and Moreau at the beginning of the 1980s. A mathematically sound and consistent evolution problem was obtained, paving the road for many subsequent theoretical investigations. In this general evolution problem, the only reaction force which is involved is a generalized reaction force, consistently with the virtual power philosophy of Lagrange. Surprisingly, such a general formulation was never derived in the case of frictional unilateral multibody dynamics. Instead, the paradigm of the Coulomb law applying to reaction forces in the real world is generally invoked. So far, this paradigm has only enabled to obtain a consistent evolution problem in only some very few specific examples and to suggest numerical algorithms to produce computational examples (numerical modeling). In particular, it is not clear what is the evolution problem underlying the computational examples. Moreover, some of the few specific cases in which this paradigm enables to write down a precise evolution problem are known to show paradoxes: the Painlevé paradox (indeterminacy) and the Kane paradox (increase in kinetic energy due to friction). In this paper, we follow Lagrange's philosophy and formulate the frictional unilateral multibody dynamics in terms of the generalized reaction force and not in terms of the real-world reaction force. A general evolution problem that governs the dynamics is obtained for the first time. We prove that all the solutions are dissipative; that is, this new formulation is free of Kane paradox. We also prove that some indeterminacy of the Painlevé paradox is fixed in this
Simbody: multibody dynamics for biomedical research.
Sherman, Michael A; Seth, Ajay; Delp, Scott L
Multibody software designed for mechanical engineering has been successfully employed in biomedical research for many years. For real time operation some biomedical researchers have also adapted game physics engines. However, these tools were built for other purposes and do not fully address the needs of biomedical researchers using them to analyze the dynamics of biological structures and make clinically meaningful recommendations. We are addressing this problem through the development of an open source, extensible, high performance toolkit including a multibody mechanics library aimed at the needs of biomedical researchers. The resulting code, Simbody, supports research in a variety of fields including neuromuscular, prosthetic, and biomolecular simulation, and related research such as biologically-inspired design and control of humanoid robots and avatars. Simbody is the dynamics engine behind OpenSim, a widely used biomechanics simulation application. This article reviews issues that arise uniquely in biomedical research, and reports on the architecture, theory, and computational methods Simbody uses to address them. By addressing these needs explicitly Simbody provides a better match to the needs of researchers than can be obtained by adaptation of mechanical engineering or gaming codes. Simbody is a community resource, free for any purpose. We encourage wide adoption and invite contributions to the code base at https://simtk.org/home/simbody.
Energy Technology Data Exchange (ETDEWEB)
Mutter, F; Benjamin, P
1974-08-01
Because of a number of instances of stress corrosion cracking or crazing occurring in PVC pipes used in Dutch gas distribution systems, VEG-GASINSTITUUT began an intensive investigation of rigid PVC pipes and high-impact pipes in distribution use under various conditions and with varying service lives. The work led to an investigation of laboratory testing techniques in which the stress-cracking phenomenon found in practice could be duplicated under controllable conditions. Pipes of various materials were examined for their resistance to stress cracking, then this resistance was compared with other long- and short-term physical properties of the material.
New classes of tough composite materials-Lessons from natural rigid biological systems
Energy Technology Data Exchange (ETDEWEB)
Mayer, G. [Department of Materials Science and Engineering, Box 352120, University of Washington, Seattle, WA 98195-2120 (United States)]. E-mail: gmayer@u.washington.edu
2006-09-15
The structures and properties of a new class of composite materials, containing a predominantly high volume fraction ceramic or glass phase, combined with minor organic (adhesive) phases, have been studied. These composites have unusual combinations of mechanical properties, such as stiffness, strength, and toughness. They are based on the architecture of a rigid natural material, the nacre structure, such as those found in the shells of the abalone Haliotis rufescens, and those of other mollusk shells. The mechanisms underlying these properties have also been studied. Analogs (utilizing high-performance engineering materials), that mimic many of the mechanisms underlying those superior combinations of properties, have been built. The results of the foregoing investigations are discussed. It was found that the toughness of segmented composite beams which have high volume fractions of ceramic (89 v / o) exceeded those of continuous layered beams, as well as the monolithic ceramic (alumina) on which they are based.
New classes of tough composite materials-Lessons from natural rigid biological systems
International Nuclear Information System (INIS)
Mayer, G.
2006-01-01
The structures and properties of a new class of composite materials, containing a predominantly high volume fraction ceramic or glass phase, combined with minor organic (adhesive) phases, have been studied. These composites have unusual combinations of mechanical properties, such as stiffness, strength, and toughness. They are based on the architecture of a rigid natural material, the nacre structure, such as those found in the shells of the abalone Haliotis rufescens, and those of other mollusk shells. The mechanisms underlying these properties have also been studied. Analogs (utilizing high-performance engineering materials), that mimic many of the mechanisms underlying those superior combinations of properties, have been built. The results of the foregoing investigations are discussed. It was found that the toughness of segmented composite beams which have high volume fractions of ceramic (89 v / o) exceeded those of continuous layered beams, as well as the monolithic ceramic (alumina) on which they are based
How to combine binary collision approximation and multi-body potential for molecular dynamics
International Nuclear Information System (INIS)
Saito, Seiki; Nakamura, Hiroaki; Takayama, Arimichi; Ito, Atsushi M.; Kenmotsu, Takahiro
2010-01-01
Our group has been developing a hybrid simulation of the molecular dynamics (MD) and the binary collision approximation (BCA) simulation. One of the main problems of this hybridization model is that the multi-body potential suddenly appears at the moment when the simulation method switches from the BCA to the MD. This instantaneously emerged multi-body potential causes the acceleration or deceleration of atoms of the system. To solve this problem, the kinetic energy of atoms should be corrected to conserve the total energy in the system. This paper gives the solution. The hybrid simulation for hydrogen atom injection into a graphite material is executed in order to demonstrate the solution. (author)
National Research Council Canada - National Science Library
Schiehlen, W. O
2002-01-01
.... The virtual prototyping and dynamic modeling of such systems are, from an economical point of view, perspective fields of scientific investigations having in mind the huge expenses for their design...
Cortese, Antonio; Savastano, Mauro; Cantone, Antonio; Claudio, Pier Paolo
2013-07-01
A new palatal distractor device for bodily movement of the maxillary bones after complete segmented Le Fort I osteotomy for 1-stage transversal distraction and tridimensional repositioning on 1 patient is presented. The new distractor has an intrinsic tridimensional rigidity also in the fixation system by self-locking miniplates and screws for better control of the 2 maxillary fragments during distraction. Le Fort I distraction and repositioning procedure in association with a bilateral sagittal split osteotomy were performed on 1 patient with complete solution of the cross-bite and class III malocclusion. Results of dental and cephalometric analysis performed before surgery (T1), after surgery and distraction time (T2), and 18 months after surgery and orthodontic appliance removal (T3) are reported. No complications were encountered using the new distractor device. Advantages of this device and technique are presented including improved rigidity of both distraction (jackscrew) and fixation (4 self-locking miniplates and screws) systems resulting in complete control of the position of the 2 maxillary fragments during distraction and surgery. In addition, this new device allows resuming palatal distraction in the event of cross-bite relapse without causing dental-related problems or the risks of screw slackening.
Virlez, Geoffrey; Bruls, Olivier; Tromme, Emmanuel; Duysinx, Pierre
2012-01-01
Defects in kinematic joints can sometimes highly influence the simulation response of the whole multibody system within which these joints are included. For instance, the clearance, the friction, the lubrication and the flexibility affect the transient behaviour, reduce the component life and produce noise and vibration for classical joints such as prismatic, cylindric or universal joint. In this work, a new 3D cylindrical joint model which accounts for the clearance, the misalignment and the...
Directory of Open Access Journals (Sweden)
Alexander G. Tyapin
2018-03-01
Full Text Available Development of linear equations of motion for seismic analysis is discussed in the paper. The paper continues the discussion: the author does not agree with colleagues putting damping matrix into the right-hand part of the equation of motion describing dynamic loads. This disagreement refers to the most popular case of “rigid” motion of multiple supports. In this paper the author follows the logic of general “non-rigid” support motion and points out a step in the equation development when the transition to “rigid” support motion (as a particular case of “non-rigid” motion is spoiled by the opponents. In the author’s opinion, the mistake is in the implementation of the Rayleigh damping model for the right-hand part of the equation. This is in the contradiction with physical logic, as damping in the Rayleigh model is not really “internal”: due to the participation of mass matrix it works on rigid displacements, which is impossible for internal damping.
2016-03-01
around a libration point in the Earth -Moon system are used as unpredictable transfer pathways when traveling from one Earth orbit to another...spacecraft traveling from one Earth orbit to another in a multi- body environment, as well as characterizing the potential motions in the vicinity of...an inspiring account of how using the gravity of the Moon assisted in placing the satellite in a favorable Earth orbit after a rocket malfunction left
Michael-Tsabari, Nava; Lavee, Yoav
2012-06-01
Despite growing research interest in family businesses, little is known about the characteristics of the families engaging in them. The present paper uses Olson's (Journal of Psychotherapy & the Family, 1988, 4(12), 7-49; Journal of Family Therapy, 2000, 22, 144-167) Circumplex Model of Marital and Family Systems to look at first-generation family firms. We describe existing typologies of family businesses and discuss similarities between the characteristics of first-generation family firms and the rigidly enmeshed family type described in the Circumplex Model. The Steinberg family business (Gibbon & Hadekel (1990) Steinberg: The breakup of a family empire. ON, Canada: MacMillan) serves to illustrate the difficulties of rigidly enmeshed first-generation family firms. Implications for understanding troubled family businesses are discussed together with guidelines for the assessment of a family business in crisis and for intervention: enhancing open communication; allowing for more flexible leadership style, roles, and rules; and maintaining a balance between togetherness and separateness. © 2012 American Association for Marriage and Family Therapy.
Directory of Open Access Journals (Sweden)
Gerardo Peláez
2018-06-01
Full Text Available Input shaping is an Optimal Control feedforward strategy whose ability to define how and when a flexible dynamical system defined by Ordinary Differential Equations (ODEs and computer controlled would move into its operative space, without command induced unwanted dynamics, has been exhaustively demonstrated. This work examines the issue of Embedded Internet of Things (IoT Input Shaping with regard to real time control of multibody oscillatory systems whose dynamics are better described by differential algebraic equations (DAEs. An overhead crane hanging a double link multibody payload has been appointed as a benchmark case; it is a multibody, multimode system. This might be worst scenario to implement Input Shaping. The reasons can be found in the wide array of constraints that arise. Firstly, the reliability of the multibody model was tested on a Functional Mock-Up Interface (FMI with the two link payload suspended from the trolley by comparing the experimental video tapping signals in time domain faced with the signals extracted from the multibody model. The FFTs of the simulated and the experimental signal contain the same frequency harmonics only with somewhat different power due to the real world light damping in the joints. The application of this approach may be extended to other cases i.e., the usefulness of mobile hydraulic cranes is limited because the payload is supported by an overhead cable under tension that allows oscillation to occur during crane motion. If the payload size is not negligible small when compared with the cable length may introduce an additional oscillatory mode that creates a multibody double pendulum. To give the insight into the double pendulum dynamics by Lagrangian methods two slender rods as payloads are analyzed dealing with the overhead crane and a composite revolute-revolute joint is proposed to model the cable of the hydraulic crane, both assumptions facilitates an affordable analysis. This allows
Peláez, Gerardo; Vaugan, Joshua; Izquierdo, Pablo; Rubio, Higinio; García-Prada, Juan Carlos
2018-06-04
Input shaping is an Optimal Control feedforward strategy whose ability to define how and when a flexible dynamical system defined by Ordinary Differential Equations (ODEs) and computer controlled would move into its operative space, without command induced unwanted dynamics, has been exhaustively demonstrated. This work examines the issue of Embedded Internet of Things (IoT) Input Shaping with regard to real time control of multibody oscillatory systems whose dynamics are better described by differential algebraic equations (DAEs). An overhead crane hanging a double link multibody payload has been appointed as a benchmark case; it is a multibody, multimode system. This might be worst scenario to implement Input Shaping. The reasons can be found in the wide array of constraints that arise. Firstly, the reliability of the multibody model was tested on a Functional Mock-Up Interface (FMI) with the two link payload suspended from the trolley by comparing the experimental video tapping signals in time domain faced with the signals extracted from the multibody model. The FFTs of the simulated and the experimental signal contain the same frequency harmonics only with somewhat different power due to the real world light damping in the joints. The application of this approach may be extended to other cases i.e., the usefulness of mobile hydraulic cranes is limited because the payload is supported by an overhead cable under tension that allows oscillation to occur during crane motion. If the payload size is not negligible small when compared with the cable length may introduce an additional oscillatory mode that creates a multibody double pendulum. To give the insight into the double pendulum dynamics by Lagrangian methods two slender rods as payloads are analyzed dealing with the overhead crane and a composite revolute-revolute joint is proposed to model the cable of the hydraulic crane, both assumptions facilitates an affordable analysis. This allows developing a general
Model Reduction in Co-Rotated Multi-Body Dynamics Based on the Dual Craig-Bampton Method
Weerathunge Kadawathagedara, S.T.; Rixen, D.J.
2011-01-01
A new reduction method for dynamical analsis of multi-body systems is presented in this paper. It fundamentally differs from the ones previously published in the way kinematical constraints are handled. Our approach is based on component mode synthesis, but the specificity of articulated mechanism,
Masticatory biomechanics in the rabbit: a multi-body dynamics analysis.
Watson, Peter J; Gröning, Flora; Curtis, Neil; Fitton, Laura C; Herrel, Anthony; McCormack, Steven W; Fagan, Michael J
2014-10-06
Multi-body dynamics is a powerful engineering tool which is becoming increasingly popular for the simulation and analysis of skull biomechanics. This paper presents the first application of multi-body dynamics to analyse the biomechanics of the rabbit skull. A model has been constructed through the combination of manual dissection and three-dimensional imaging techniques (magnetic resonance imaging and micro-computed tomography). Individual muscles are represented with multiple layers, thus more accurately modelling muscle fibres with complex lines of action. Model validity was sought through comparing experimentally measured maximum incisor bite forces with those predicted by the model. Simulations of molar biting highlighted the ability of the masticatory system to alter recruitment of two muscle groups, in order to generate shearing or crushing movements. Molar shearing is capable of processing a food bolus in all three orthogonal directions, whereas molar crushing and incisor biting are predominately directed vertically. Simulations also show that the masticatory system is adapted to process foods through several cycles with low muscle activations, presumably in order to prevent rapidly fatiguing fast fibres during repeated chewing cycles. Our study demonstrates the usefulness of a validated multi-body dynamics model for investigating feeding biomechanics in the rabbit, and shows the potential for complementing and eventually reducing in vivo experiments.
Microstructural Dynamics and Rheology of Suspensions of Rigid Fibers
Butler, Jason E.; Snook, Braden
2018-01-01
The dynamics and rheology of suspensions of rigid, non-Brownian fibers in Newtonian fluids are reviewed. Experiments, theories, and computer simulations are considered, with an emphasis on suspensions at semidilute and concentrated conditions. In these suspensions, interactions between the particles strongly influence the microstructure and rheological properties of the suspension. The interactions can arise from hydrodynamic disturbances, giving multibody interactions at long ranges and pairwise lubrication forces over short distances. For concentrated suspensions, additional interactions due to excluded volume (contacts) and adhesive forces are addressed. The relative importance of the various interactions as a function of fiber concentration is assessed.
Rigidity of monodromies for Appell's hypergeometric functions
Directory of Open Access Journals (Sweden)
Yoshishige Haraoka
2015-01-01
Full Text Available For monodromy representations of holonomic systems, the rigidity can be defined. We examine the rigidity of the monodromy representations for Appell's hypergeometric functions, and get the representations explicitly. The results show how the topology of the singular locus and the spectral types of the local monodromies work for the study of the rigidity.
DEFF Research Database (Denmark)
Rijkhoff, Jan
2010-01-01
classes. Finally this article wants to claim that the distinction between rigid and flexible noun categories (a) adds a new dimension to current classifications of parts of speech systems, (b) correlates with certain grammatical phenomena (e.g. so-called number discord), and (c) helps to explain the parts......This article argues that in addition to the major flexible lexical categories in Hengeveld’s classification of parts of speech systems (Contentive, Non-Verb, Modifier), there are also flexible word classes within the rigid lexical category Noun (Set Noun, Sort Noun, General Noun). Members...... by the flexible item in the external world. I will then argue that flexible word classes constitute a proper category (i.e. they are not the result of a merger of some rigid word classes) in that members of flexible word categories display the same properties regarding category membership as members of rigid word...
Directory of Open Access Journals (Sweden)
Takayuki Kurashima
2015-09-01
Full Text Available Influential stakeholders have highlighted many constraints inherent in conventional scientific forest management plans for community forestry (CF and presented simpler alternatives. Nevertheless, some developing countries continue to use rigid, complex and high-cost plans and regulations. This article considers two issues: (1 why heavily-regulated or rigid CF systems were originally introduced and why they continue to be used in developing countries despite critiques and counterproposals; and (2 under what circumstances will such CF systems face an impasse, and what can be done to resolve the situation. Using Cambodia as a case study, we examine the development of a rigid CF system, review negative factors influencing the upland forested area, clarify the unfavorable situations arising from these factors and discuss likely problems associated with the CF management system. International organizations played a key role in the introduction and maintenance of rigid, complex and high-cost CF systems in Cambodia. Conflicts and crises arise when the administration prosecutes local farmers for illegal cultivation or deprives communities of CF management rights because of the expansion of commercial crop cultivation and the lack of adequate community management in response to unprecedented changes. A likely practical solution to the probable impasse is the development and funding of a functional network of CF management committees, rather than the adoption of an entirely new, alternative system.
Grenade, Charlotte; Moniotte, Nicolas; Rompen, Eric; Vanheusden, Alain; Mainjot, Amélie; De Pauw-Gillet, Marie-Claire
2016-12-01
In vitro studies about biomaterials biological properties are essential screening tests. Yet cell cultures encounter difficulties related to cell retention on material surface or to the observation of both faces of permeable materials. The objective of the present study was to develop a reliable in vitro method to study cell behavior on rigid and flexible/permeable biomaterials elaborating two specific insert-based systems (IBS-R and IBS-F respectively). IBS-R was designed as a specific cylindrical polytetrafluoroethylene (PTFE) system to evaluate attachment, proliferation and morphology of human gingival fibroblasts (HGFs) on grade V titanium and lithium disilicate glass-ceramic discs characteristics of dental prostheses. The number of cells, their covering on discs and their morphology were determined from MTS assays and microscopic fluorescent images after 24, 48 and 72 h. IBS-F was developed as a two components system to study HGFs behavior on guided bone regeneration polyester membranes. The viability and the membrane barrier effect were evaluated by metabolic MTS assays and by scanning electron microscopy. IBS-R and IBS-F were shown to promote (1) easy and rapid handling; (2) cell retention on biomaterial surface; (3) accurate evaluation of the cellular proliferation, spreading and viability; (4) use of non-toxic material. Moreover IBS-F allowed the study of the cell migration through degradable membranes, with an access to both faces of the biomaterial and to the bottom of culture wells for medium changing.
Low noise wing slat system with rigid cove-filled slat
Shmilovich, Arvin (Inventor); Yadlin, Yoram (Inventor)
2013-01-01
Concepts and technologies described herein provide for a low noise aircraft wing slat system. According to one aspect of the disclosure provided herein, a cove-filled wing slat is used in conjunction with a moveable panel rotatably attached to the wing slat to provide a high lift system. The moveable panel rotates upward against the rear surface of the slat during deployment of the slat, and rotates downward to bridge a gap width between the stowed slat and the lower wing surface, completing the continuous outer mold line shape of the wing, when the cove-filled slat is retracted to the stowed position.
Fluid-structure interaction in non-rigid pipeline systems - large scale validation experiments
International Nuclear Information System (INIS)
Heinsbroek, A.G.T.J.; Kruisbrink, A.C.H.
1993-01-01
The fluid-structure interaction computer code FLUSTRIN, developed by DELFT HYDRAULICS, enables the user to determine dynamic fluid pressures, structural stresses and displacements in a liquid-filled pipeline system under transient conditions. As such, the code is a useful tool to process and mechanical engineers in the safe design and operation of pipeline systems in nuclear power plants. To validate FLUSTRIN, experiments have been performed in a large scale 3D test facility. The test facility consists of a flexible pipeline system which is suspended by wires, bearings and anchors. Pressure surges, which excite the system, are generated by a fast acting shut-off valve. Dynamic pressures, structural displacements and strains (in total 70 signals) have been measured under well determined initial and boundary conditions. The experiments have been simulated with FLUSTRIN, which solves the acoustic equations using the method of characteristics (fluid) and the finite element method (structure). The agreement between experiments and simulations is shown to be good: frequencies, amplitudes and wave phenomena are well predicted by the numerical simulations. It is demonstrated that an uncoupled water hammer computation would render unreliable and useless results. (author)
Analysis of the Gyroscopic Stabilization of a System of Rigid Bodies
DEFF Research Database (Denmark)
Kliem, Wolfhard; Kliem, Wolfhard
1996-01-01
We study the gyroscopic of a three-body system. A new method offinding stability regions, based on mechanism and criteria for gyroscopicstabilization, is presented. Of particular interest in this connection isthe theory of interaction of eigenvalues. This leads to a complete 3-dimensionalanalysis......, which shows the regions of stability, divergence, and flutter ofa simple model of a rotating spaceship....
Lichtwarck-Aschoff, A.; Kunnen, E.S.; Geert, P.L.C. van
2009-01-01
The authors used a dynamic systems theoretical approach to examine intraindividual variability in emotional responses during the transitional period of adolescence. Longitudinal diary data were collected regarding conflicts between 17 teenage girls and their mothers over a period of a year. The
Approximate analysis of rigid plate loading on elastic multi-layered systems
CSIR Research Space (South Africa)
Maina, JW
2008-07-01
Full Text Available , this distribution was approximated using uniformly distributed multiple loads and analysis performed using Games. Results have shown good agreement with the theory for the case of a semi-infinite medium. Furthermore, extension of this method to multilayered system...
Analysis of the gyroscopic stabilization of a system of rigid bodies
DEFF Research Database (Denmark)
Kliem, Wolfhard; Seyranian, Alexander P.
1997-01-01
We study the gyroscopic stability of a three-body system. A new method of finding stability regions, based on mechanism and criteria for gyroscopic stabilization, is presented. Of particular interest in this connection is the theory of interaction of eigenvalues. This leads to a complete 3......-dimensional analysis, which shows the regions of stability, divergence, and flutter of a simple model of a rotating spaceship....
van Loon, JP; de Bont, LGM; Verkerke, GJ
The stability of a screw-fixed implantable device can be improved by eliminating the freedom of movement between the screws and the device. Two systems have been developed for rigidly connecting 2.0-mm bone screws to an implantable device, and the aim of this study was to test and compare the
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.
Finite Element Multibody Simulation of a Breathing Crack in a Rotor with a Cohesive Zone Model
Liong, Rugerri Toni; Proppe, Carsten
2013-01-01
The breathing mechanism of a transversely cracked shaft and its influence on a rotor system that appears due to shaft weight and inertia forces is studied. The presence of a crack reduces the stiffness of the rotor system and introduces a stiffness variation during the revolution of the shaft. Here, 3D finite element (FE) model and multibody simulation (MBS) are introduced to predict and to analyse the breathing mechanism on a transverse cracked shaft. It is based on a cohesive zone model (CZ...
A heterogeneous system based on GPU and multi-core CPU for real-time fluid and rigid body simulation
da Silva Junior, José Ricardo; Gonzalez Clua, Esteban W.; Montenegro, Anselmo; Lage, Marcos; Dreux, Marcelo de Andrade; Joselli, Mark; Pagliosa, Paulo A.; Kuryla, Christine Lucille
2012-03-01
Computational fluid dynamics in simulation has become an important field not only for physics and engineering areas but also for simulation, computer graphics, virtual reality and even video game development. Many efficient models have been developed over the years, but when many contact interactions must be processed, most models present difficulties or cannot achieve real-time results when executed. The advent of parallel computing has enabled the development of many strategies for accelerating the simulations. Our work proposes a new system which uses some successful algorithms already proposed, as well as a data structure organisation based on a heterogeneous architecture using CPUs and GPUs, in order to process the simulation of the interaction of fluids and rigid bodies. This successfully results in a two-way interaction between them and their surrounding objects. As far as we know, this is the first work that presents a computational collaborative environment which makes use of two different paradigms of hardware architecture for this specific kind of problem. Since our method achieves real-time results, it is suitable for virtual reality, simulation and video game fluid simulation problems.
International Nuclear Information System (INIS)
Kim, Hyun; Lee, Sung-Jae; Lim, Do-Hyung; Oh, Hyun-Ju; Lee, Kwon-Yong
2011-01-01
Recently, various types of semi-rigid pedicle screw fixation systems have been developed for the surgical treatment of the lumbar spine. They were introduced to address the adverse issues commonly found in traditional rigid spinal fusion--abnormally large motion at the adjacent level and subsequent degeneration. The semi-rigid system uses more compliant materials (nitinol or polymers) and/or changes in rod design (coiled or twisted rods) as compared to the conventional rigid straight rods made of Ti alloys (E = 114 GPa, υ = 0.32). However, biomechanical studies on the semi-rigid pedicle screw systems were usually limited to linear modeling of the implant and anatomic elements, which may not be capable of reflecting realistic post-operative motions of the spine. In this study, we evaluated the effects of nonlinearity in materials used for semi-rigid pedicle screw fixation systems to evaluate the changes in biomechanical behaviors using finite element analysis. Changes in range of motion (ROM) and center of rotation (COR) were assessed at the operated and adjacent levels. Actual load-displacement results of the semi-rigid rod from mechanical test were carried out to reflect the nonlinearity of the implant. In addition, nonlinear material properties of various spinal ligaments studies were used for the finite element modeling. The post-operative models were constructed by modifying the previously validated intact model of the L1-S1 spine. Eight different post-operative models were made to address the effects of nonlinearity-with a traditional stiffness modulus rod (with linear ligaments, case 1; with nonlinear ligaments, case 5), with a rigid rod (with linear ligaments, case 2; with nonlinear ligaments, case 6), with a soft rod (with linear ligaments, case 3; with nonlinear ligaments, case 7), and with a nonlinear rod (with linear ligaments, case 4; with nonlinear ligaments, case 8). To simulate the load on the lumbar spine in a neutral posture, follower load (400 N
Directory of Open Access Journals (Sweden)
Seungjae Lee
2017-03-01
Full Text Available Modular systems have been mostly researched in relatively low-rise structures but, lately, their applications to mid- to high-rise structures began to be reviewed, and research interest in new modularization subjects has increased. The application of modular systems to mid- to high-rise structures requires the structural stability of the frame and connections that consist of units, and the evaluation of the stiffness of structures that are combined in units. However, the combination of general units causes loss of the cross-section of columns or beams, resulting in low seismic performance and hindering installation works in the field. In addition, the evaluation of a frame considering such a cross-sectional loss is not easy. Therefore, it is necessary to develop a joint that is stable and easy to install. In the study, a rigidly connected modular system was proposed as a moment-resisting frame for a unit modular system, and their joints were developed and their performances were compared. The proposed system changed the ceiling beam into a bracket type to fasten bolts. It can be merged with other seismic force-resisting systems. To verify the seismic performance of the proposed system, a cyclic loading test was conducted, and the rigidly connected joint performance and integrated behavior at the joint of modular units were investigated. From the experimental results, the maximum resisting force of the proposed connection exceeded the theoretical parameters, indicating that a rigid joint structural performance could be secured.
Biomechanical Analysis and Evaluation Technology Using Human Multi-Body Dynamic Model
Energy Technology Data Exchange (ETDEWEB)
Kim, Yoon Hyuk; Shin, June Ho; Khurelbaatar, Tsolmonbaatar [Kyung Hee University, Yongin (Korea, Republic of)
2011-10-15
This paper presents the biomechanical analysis and evaluation technology of musculoskeletal system by multi-body human dynamic model and 3-D motion capture data. First, medical image based geometric model and material properties of tissue were used to develop the human dynamic model and 3-D motion capture data based motion analysis techniques were develop to quantify the in-vivo joint kinematics, joint moment, joint force, and muscle force. Walking and push-up motion was investigated using the developed model. The present model and technologies would be useful to apply the biomechanical analysis and evaluation of human activities.
Validation of flexible multibody dynamics beam formulations using benchmark problems
Bauchau, O.A.; Wu, Genyong; Betsch, P.; Cardona, A.; Gerstmayr, J.; Jonker, Jan B.; Masarati, P.; Sonneville, V.
2016-01-01
As the need to model flexibility arose in multibody dynamics, the floating frame of reference formulation was developed, but this approach can yield inaccurate results when elastic displacements becomes large. While the use of three-dimensional finite element formulations overcomes this problem, the
Evolution of Flexible Multibody Dynamics for Simulation Applications Supporting Human Spaceflight
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.
A topological classification of the Chaplygin systems in the dynamics of a rigid body in a fluid
International Nuclear Information System (INIS)
Nikolaenko, S S
2014-01-01
The paper is concerned with the topological analysis of the Chaplygin integrable case in the dynamics of a rigid body in a fluid. A full list of the topological types of Chaplygin systems in their dependence on the energy level is compiled on the basis of the Fomenko-Zieschang theory. An effective description of the topology of the Liouville foliation in terms of natural coordinate variables is also presented, which opens a direct way to calculating topological invariants. It turns out that on all nonsingular energy levels Chaplygin systems are Liouville equivalent to the well-known Euler case in the dynamics of a rigid body with fixed point. Bibliography: 23 titles
Directory of Open Access Journals (Sweden)
Patrick Piprek
2018-02-01
Full Text Available This paper presents an approach to model a ski jumper as a multi-body system for an optimal control application. The modeling is based on the constrained Newton-Euler-Equations. Within this paper the complete multi-body modeling methodology as well as the musculoskeletal modeling is considered. For the musculoskeletal modeling and its incorporation in the optimization model, we choose a nonlinear dynamic inversion control approach. This approach uses the muscle models as nonlinear reference models and links them to the ski jumper movement by a control law. This strategy yields a linearized input-output behavior, which makes the optimal control problem easier to solve. The resulting model of the ski jumper can then be used for trajectory optimization whose results are compared to literature jumps. Ultimately, this enables the jumper to get a very detailed feedback of the flight. To achieve the maximal jump length, exact positioning of his body with respect to the air can be displayed.
Quantum charged rigid membrane
Energy Technology Data Exchange (ETDEWEB)
Cordero, Ruben [Departamento de Fisica, Escuela Superior de Fisica y Matematicas del I.P.N., Unidad Adolfo Lopez Mateos, Edificio 9, 07738 Mexico, D.F. (Mexico); Molgado, Alberto [Unidad Academica de Fisica, Universidad Autonoma de Zacatecas, Zacatecas Zac. (Mexico); Rojas, Efrain, E-mail: cordero@esfm.ipn.mx, E-mail: amolgado@fisica.uaz.edu.mx, E-mail: efrojas@uv.mx [Departamento de Fisica, Facultad de Fisica e Inteligencia Artificial, Universidad Veracruzana, 91000 Xalapa, Veracruz (Mexico)
2011-03-21
The early Dirac proposal to model the electron as a charged membrane is reviewed. A rigidity term, instead of the natural membrane tension, involving linearly the extrinsic curvature of the worldvolume swept out by the membrane is considered in the action modeling the bubble in the presence of an electromagnetic field. We set up this model as a genuine second-order derivative theory by considering a non-trivial boundary term which plays a relevant part in our formulation. The Lagrangian in question is linear in the bubble acceleration and by means of the Ostrogradski-Hamiltonian approach, we observed that the theory comprises the management of both first- and second-class constraints. We thus show that our second-order approach is robust allowing for a proper quantization. We found an effective quantum potential which permits us to compute bounded states for the system. We comment on the possibility of describing brane world universes by invoking this kind of second-order correction terms.
Quantum charged rigid membrane
International Nuclear Information System (INIS)
Cordero, Ruben; Molgado, Alberto; Rojas, Efrain
2011-01-01
The early Dirac proposal to model the electron as a charged membrane is reviewed. A rigidity term, instead of the natural membrane tension, involving linearly the extrinsic curvature of the worldvolume swept out by the membrane is considered in the action modeling the bubble in the presence of an electromagnetic field. We set up this model as a genuine second-order derivative theory by considering a non-trivial boundary term which plays a relevant part in our formulation. The Lagrangian in question is linear in the bubble acceleration and by means of the Ostrogradski-Hamiltonian approach, we observed that the theory comprises the management of both first- and second-class constraints. We thus show that our second-order approach is robust allowing for a proper quantization. We found an effective quantum potential which permits us to compute bounded states for the system. We comment on the possibility of describing brane world universes by invoking this kind of second-order correction terms.
Rigid body dynamics of mechanisms
Hahn, Hubert
2003-01-01
The second volume of Rigid Body Dynamics of Mechanisms covers applications via a systematic method for deriving model equations of planar and spatial mechanisms. The necessary theoretical foundations have been laid in the first volume that introduces the theoretical mechanical aspects of mechatronic systems. Here the focus is on the application of the modeling methodology to various examples of rigid-body mechanisms, simple planar ones as well as more challenging spatial problems. A rich variety of joint models, active constraints, plus active and passive force elements is treated. The book is intended for self-study by working engineers and students concerned with the control of mechanical systems, i.e. robotics, mechatronics, vehicles, and machine tools. The examples included are a likely source from which to choose models for university lectures.
Nonlinear model order reduction for flexible multibody dynamics: a modal derivatives approach
Energy Technology Data Exchange (ETDEWEB)
Wu, Long, E-mail: L.Wu-1@tudelft.nl [Delft University of Technology, Faculty of Mechanical, Maritime and Materials Engineering (Netherlands); Tiso, Paolo, E-mail: ptiso@ethz.ch [ETH Zürich, Institute for Mechanical Systems (Switzerland)
2016-04-15
An effective reduction technique is presented for flexible multibody systems, for which the elastic deflection could not be considered small. We consider here the planar beam systems undergoing large elastic rotations, in the floating frame description. The proposed method enriches the classical linear reduction basis with modal derivatives stemming from the derivative of the eigenvalue problem. Furthermore, the Craig–Bampton method is applied to couple the different reduced components. Based on the linear projection, the configuration-dependent internal force can be expressed as cubic polynomials in the reduced coordinates. Coefficients of these polynomials can be precomputed for efficient runtime evaluation. The numerical results show that the modal derivatives are essential for the correct approximation of the nonlinear elastic deflection with respect to the body reference. The proposed reduction method constitutes a natural and effective extension of the classical linear modal reduction in the floating frame.
Weiss, Asia; Whiteley, Walter
2014-01-01
This book contains recent contributions to the fields of rigidity and symmetry with two primary focuses: to present the mathematically rigorous treatment of rigidity of structures, and to explore the interaction of geometry, algebra, and combinatorics. Overall, the book shows how researchers from diverse backgrounds explore connections among the various discrete structures with symmetry as the unifying theme. Contributions present recent trends and advances in discrete geometry, particularly in the theory of polytopes. The rapid development of abstract polytope theory has resulted in a rich theory featuring an attractive interplay of methods and tools from discrete geometry, group theory, classical geometry, hyperbolic geometry and topology. The volume will also be a valuable source as an introduction to the ideas of both combinatorial and geometric rigidity theory and its applications, incorporating the surprising impact of symmetry. It will appeal to students at both the advanced undergraduate and gradu...
Pukhlikov, Aleksandr
2013-01-01
Birational rigidity is a striking and mysterious phenomenon in higher-dimensional algebraic geometry. It turns out that certain natural families of algebraic varieties (for example, three-dimensional quartics) belong to the same classification type as the projective space but have radically different birational geometric properties. In particular, they admit no non-trivial birational self-maps and cannot be fibred into rational varieties by a rational map. The origins of the theory of birational rigidity are in the work of Max Noether and Fano; however, it was only in 1970 that Iskovskikh and Manin proved birational superrigidity of quartic three-folds. This book gives a systematic exposition of, and a comprehensive introduction to, the theory of birational rigidity, presenting in a uniform way, ideas, techniques, and results that so far could only be found in journal papers. The recent rapid progress in birational geometry and the widening interaction with the neighboring areas generate the growing interest ...
DEFF Research Database (Denmark)
Rijkhoff, Jan
2008-01-01
Studies in Language 32-3 (2008), 727-752. Special issue: Parts of Speech: Descriptive tools, theoretical constructs Jan Rijkhoff - On flexible and rigid nouns This article argues that in addition to the flexible lexical categories in Hengeveld’s classification of parts-of-speech systems (Contentive......, Non-Verb, Modifier), there are also flexible word classes within the rigid lexical category Noun (Set Noun, Sort Noun, General Noun). Members of flexible word classes are characterized by their vague semantics, which in the case of nouns means that values for the semantic features Shape...... and Homogeneity are either left undetermined or they are specified in such a way that they do not quite match the properties of the kind of entity denoted by the flexible item in the external world. I will then argue that flexible word classes constitute a proper category (i.e. they are not the result of a merger...
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 ...... engagement on the sprockets responsible for the polygonal effect is thoroughly analyzed and the induced impulsive forces developed during that action are treated by a strategy where kinematic constraints between sprockets and rollers are added and deleted....
Integration of car-body flexibility into train-track coupling system dynamics analysis
Ling, Liang; Zhang, Qing; Xiao, Xinbiao; Wen, Zefeng; Jin, Xuesong
2018-04-01
The resonance vibration of flexible car-bodies greatly affects the dynamics performances of high-speed trains. In this paper, we report a three-dimensional train-track model to capture the flexible vibration features of high-speed train carriages based on the flexible multi-body dynamics approach. The flexible car-body is modelled using both the finite element method (FEM) and the multi-body dynamics (MBD) approach, in which the rigid motions are obtained by using the MBD theory and the structure deformation is calculated by the FEM and the modal superposition method. The proposed model is applied to investigate the influence of the flexible vibration of car-bodies on the dynamics performances of train-track systems. The dynamics performances of a high-speed train running on a slab track, including the car-body vibration behaviour, the ride comfort, and the running safety, calculated by the numerical models with rigid and flexible car-bodies are compared in detail. The results show that the car-body flexibility not only significantly affects the vibration behaviour and ride comfort of rail carriages, but also can has an important influence on the running safety of trains. The rigid car-body model underestimates the vibration level and ride comfort of rail vehicles, and ignoring carriage torsional flexibility in the curving safety evaluation of trains is conservative.
2014-08-01
enhances flow incompressibility [20]. This correction takes into account the velocity of neighboring markers through a mean velocity evaluated within...interactions between individual markers; i.e., the right hand side of Eqs. (7) and (8), are accounted for, the total rigid body force and torque due to the...coordinate formulation. In: Proceedings of the ASME 2005 IDETC/ CIE . Orlando, Florida (2005). [35] Shabana A.: Flexible multibody dynamics: Review of
Analysis of Switched-Rigid Floating Oscillator
Directory of Open Access Journals (Sweden)
Prabhakar R. Marur
2009-01-01
Full Text Available In explicit finite element simulations, a technique called deformable-to-rigid (D2R switching is used routinely to reduce the computation time. Using the D2R option, the deformable parts in the model can be switched to rigid and reverted back to deformable when needed during the analysis. The time of activation of D2R however influences the overall dynamics of the system being analyzed. In this paper, a theoretical basis for the selection of time of rigid switching based on system energy is established. A floating oscillator problem is investigated for this purpose and closed-form analytical expressions are derived for different phases in rigid switching. The analytical expressions are validated by comparing the theoretical results with numerical computations.
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.
A multi-body vehicle for moving inside cluttered nuclear environment
International Nuclear Information System (INIS)
Littmann, F.; Chameaud, H.
1994-01-01
The paper presents the result of the TALOS (Technologies for Advanced locomotion Systems) programme. The general aim of the TALOS was to prove the feasibility of multi-body articulated vehicles for intervention missions in nuclear plant were high payload volume and mass are required, combined with great geometrical and obstacles constraints. This programme was based on one hand on the TLV (Train Like Vehicle) concept, developed by CEA ( Atomic Energy Commission) and on the other hand on the KfK experience on locomotion. The main difficulties of this programme were to find the mechanical linkage concept and the locomotion concept, and also to build an integrated mockup with linkage and locomotion concepts. (TEC). 4 refs., 5 figs
The systematics of the deexcitation of hot nuclei and the onset of multibody decay
International Nuclear Information System (INIS)
Bowman, D.R.; Peaslee, G.F.; Colonna, N.
1989-03-01
Results from the asymmetric reactions 80 and 100 MeV/uLa + C are presented and compared to earlier work with the same system at 18 and 50 MeV/u. Fragment-fragment correlations, cross sections, and distributions in velocity space indicate the continued dominance of a quasi-binary decay mechanism with increased emission of light charged particles. The distributions in velocity also indicate a progression toward a ''fireball'' type of reaction mechanism. However, the angular distributions of the emitted fragments are incompatible with statistical production mechanisms that have successfully explained the lower energy results, and indicate the dynamical nature of the emission process. Dalitz plots of triple complex fragment coincidences are presented in order to investigate the nature of the multibody decays. 18 refs., 9 figs
Error-transparent evolution: the ability of multi-body interactions to bypass decoherence
International Nuclear Information System (INIS)
Vy, Os; Jacobs, Kurt; Wang Xiaoting
2013-01-01
We observe that multi-body interactions, unlike two-body interactions, can implement any unitary operation on an encoded system in such a way that the evolution is uninterrupted by noise that the encoding is designed to protect against. Such ‘error-transparent’ evolution is distinct from that usually considered in quantum computing, as the latter is merely correctable. We prove that the minimum body-ness required to protect (i) a qubit from a single type of Pauli error, (ii) a target qubit from a controller with such errors and (iii) a single qubit from all errors is three-body, four-body and five-body, respectively. We also discuss applications to computing, coherent feedback control and quantum metrology. Finally, we evaluate the performance of error-transparent evolution for some examples using numerical simulations. (paper)
A multi-body vehicle for moving inside cluttered nuclear environment
Energy Technology Data Exchange (ETDEWEB)
Littmann, F.; Chameaud, H. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. des Procedes et Systemes Avances; Dorn, J. [Kernforschungszentrum Karlsruhe GmbH (Germany)
1994-12-31
The paper presents the result of the TALOS (Technologies for Advanced locomotion Systems) programme. The general aim of the TALOS was to prove the feasibility of multi-body articulated vehicles for intervention missions in nuclear plant were high payload volume and mass are required, combined with great geometrical and obstacles constraints. This programme was based on one hand on the TLV (Train Like Vehicle) concept, developed by CEA ( Atomic Energy Commission) and on the other hand on the KfK experience on locomotion. The main difficulties of this programme were to find the mechanical linkage concept and the locomotion concept, and also to build an integrated mockup with linkage and locomotion concepts. (TEC). 4 refs., 5 figs.
Soft soils reinforced by rigid vertical inclusions
Directory of Open Access Journals (Sweden)
Iulia-Victoria NEAGOE
2013-12-01
Full Text Available Reinforcement of soft soils by rigid vertical inclusions is an increasingly used technique over the last few years. The system consists of rigid or semi-rigid vertical inclusions and a granular platform for the loads transfer from the structure to the inclusions. This technique aims to reduce the differential settlements both at ground level as below the structure. Reinforcement by rigid inclusions is mainly used for foundation works for large commercial and industrial platforms, storage tanks, wastewater treatment plants, wind farms, bridges, roads, railway embankments. The subject is one of interest as it proves the recently concerns at international level in research and design; however, most studies deal more with the static behavior and less with the dynamic one.
Rigid supersymmetry with boundaries
Energy Technology Data Exchange (ETDEWEB)
Belyaev, D.V. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Van Nieuwenhuizen, P. [State Univ. of New York, Stony Brook, NY (United States). C.N. Yang Inst. for Theoretical Physics
2008-01-15
We construct rigidly supersymmetric bulk-plus-boundary actions, both in x-space and in superspace. For each standard supersymmetric bulk action a minimal supersymmetric bulk-plus-boundary action follows from an extended F- or D-term formula. Additional separately supersymmetric boundary actions can be systematically constructed using co-dimension one multiplets (boundary superfields). We also discuss the orbit of boundary conditions which follow from the Euler-Lagrange variational principle. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Unseren, M.A.
1994-04-01
A rigid body model for the entire system which accounts for the load distribution scheme proposed in Part 1 as well as for the dynamics of the manipulators and the kinematic constraints is derived in the joint space. A technique is presented for expressing the object dynamics in terms of the joint variables of both manipulators which leads to a positive definite and symmetric inertia matrix. The model is then transformed to obtain reduced order equations of motion and a separate set of equations which govern the behavior of the internal contact forces. The control architecture is applied to the model which results in the explicit decoupling of the position and internal contact force-controlled degrees of freedom (DOF).
Study regarding seat’s rigidity during rear end collisions using a MADYMO occupant model
Ionut Radu, Alexandru; Cofaru, Corneliu; Tolea, Bogan; Popescu, Mihaela
2017-10-01
The aim of this paper is to study the effects of different front occupant backseat’s rigidities in the case of a rear end collision using a multibody virtual model of an occupant. Simulation will be conducted in PC Crash, the most common accident reconstruction software using a MADYMO multibody occupant to simulate kinematics and dynamic of the passenger. Different backseat torques will be used to see how this will influence the acceleration in the head and torso of the occupant. Also, a real crash test is made to analyze the kinematics of the occupant. We believe that the softer seat’s rigidity will reduce not only the head’s acceleration but also reduces the effect of „whiplash” upon the neck due to the fact that the backseat will rotate backwards increasing its displacement and absorb some of the energy generated by the collision. Although a softer seat could reduce the head’s acceleration, a broken seat will increase it due to the fact that the impact of the backseat with the vehicle’s rear seats will generate a second collision. So, in order to achieve a lower acceleration, a controlled torque is recommended and a controlled angular displacement of the backseat is to be used.
Leuridan, Steven; Goossens, Quentin; Roosen, Jorg; Pastrav, Leonard; Denis, Kathleen; Mulier, Michiel; Desmet, Wim; Vander Sloten, Jos
2017-02-01
Accurate pre-clinical evaluation of the initial stability of new cementless hip stems using in vitro micromotion measurements is an important step in the design process to assess the new stem's potential. Several measuring systems, linear variable displacement transducer-based and other, require assuming bone or implant to be rigid to obtain micromotion values or to calculate derived quantities such as relative implant tilting. An alternative linear variable displacement transducer-based measuring system not requiring a rigid body assumption was developed in this study. The system combined advantages of local unidirectional and frame-and-bracket micromotion measuring concepts. The influence and possible errors that would be made by adopting a rigid body assumption were quantified. Furthermore, as the system allowed emulating local unidirectional and frame-and-bracket systems, the influence of adopting rigid body assumptions were also analyzed for both concepts. Synthetic and embalmed bone models were tested in combination with primary and revision implants. Single-legged stance phase loading was applied to the implant - bone constructs. Adopting a rigid body assumption resulted in an overestimation of mediolateral micromotion of up to 49.7μm at more distal measuring locations. Maximal average relative rotational motion was overestimated by 0.12° around the anteroposterior axis. Frontal and sagittal tilting calculations based on a unidirectional measuring concept underestimated the true tilting by an order of magnitude. Non-rigid behavior is a factor that should not be dismissed in micromotion stability evaluations of primary and revision femoral implants. Copyright © 2017 Elsevier Ltd. All rights reserved.
CP violation in multibody decays of beauty baryons
Energy Technology Data Exchange (ETDEWEB)
Durieux, Gauthier
2016-08-15
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{sub b}→Λφ→pπ K{sup +}K{sup -} decay are expected to vanish identically.
Aerodynamic and Mechanical System Modelling
DEFF Research Database (Denmark)
Jørgensen, Martin Felix
This thesis deals with mechanical multibody-systems applied to the drivetrain of a 500 kW wind turbine. Particular focus has been on gearbox modelling of wind turbines. The main part of the present project involved programming multibody systems to investigate the connection between forces, moments...
The two-body problem of a pseudo-rigid body and a rigid sphere
DEFF Research Database (Denmark)
Kristiansen, Kristian Uldall; Vereshchagin, M.; Gózdziewski, K.
2012-01-01
n this paper we consider the two-body problem of a spherical pseudo-rigid body and a rigid sphere. Due to the rotational and "re-labelling" symmetries, the system is shown to possess conservation of angular momentum and circulation. We follow a reduction procedure similar to that undertaken...... in the study of the two-body problem of a rigid body and a sphere so that the computed reduced non-canonical Hamiltonian takes a similar form. We then consider relative equilibria and show that the notions of locally central and planar equilibria coincide. Finally, we show that Riemann's theorem on pseudo......-rigid bodies has an extension to this system for planar relative equilibria....
Czech Academy of Sciences Publication Activity Database
Nguyen, H.Q.; Čelikovský, Sergej
2012-01-01
Roč. 1, č. 3 (2012), s. 179-187 ISSN 2223-7038 R&D Projects: GA ČR(CZ) GAP103/12/1794 Institutional support: RVO:67985556 Keywords : Attitude control * adaptive fault estimation * LMI * PDF Subject RIV: BC - Control Systems Theory http://lib.physcon.ru/doc?id=02c925f7e4ab
Feskov, Serguei V.; Ivanov, Anatoly I.
2018-03-01
An approach to the construction of diabatic free energy surfaces (FESs) for ultrafast electron transfer (ET) in a supramolecule with an arbitrary number of electron localization centers (redox sites) is developed, supposing that the reorganization energies for the charge transfers and shifts between all these centers are known. Dimensionality of the coordinate space required for the description of multistage ET in this supramolecular system is shown to be equal to N - 1, where N is the number of the molecular centers involved in the reaction. The proposed algorithm of FES construction employs metric properties of the coordinate space, namely, relation between the solvent reorganization energy and the distance between the two FES minima. In this space, the ET reaction coordinate zn n' associated with electron transfer between the nth and n'th centers is calculated through the projection to the direction, connecting the FES minima. The energy-gap reaction coordinates zn n' corresponding to different ET processes are not in general orthogonal so that ET between two molecular centers can create nonequilibrium distribution, not only along its own reaction coordinate but along other reaction coordinates too. This results in the influence of the preceding ET steps on the kinetics of the ensuing ET. It is important for the ensuing reaction to be ultrafast to proceed in parallel with relaxation along the ET reaction coordinates. Efficient algorithms for numerical simulation of multistage ET within the stochastic point-transition model are developed. The algorithms are based on the Brownian simulation technique with the recrossing-event detection procedure. The main advantages of the numerical method are (i) its computational complexity is linear with respect to the number of electronic states involved and (ii) calculations can be naturally parallelized up to the level of individual trajectories. The efficiency of the proposed approach is demonstrated for a model
International Nuclear Information System (INIS)
Zhang Xuping; Mills, James K.; Cleghorn, William L.
2009-01-01
Modeling of multibody dynamics with flexible links is a challenging task, which not only involves the effect of rigid body motion on elastic deformations, but also includes the influence of elastic deformations on rigid body motion. This paper presents coupling characteristics of rigid body motions and elastic motions of a 3-PRR parallel manipulator with three flexible intermediate links. The intermediate links are modeled as Euler-Bernoulli beams with pinned-pinned boundary conditions based on the assumed mode method (AMM). Using Lagrange multipliers, the fully coupled equations of motions of the flexible parallel manipulator are developed by incorporating the rigid body motions with elastic motions. The mutual dependence of elastic deformations and rigid body motions are investigated from the analysis of the derived equations of motion. Open-loop simulation without joint motion controls and closed-loop simulation with joint motion controls are performed to illustrate the effect of elastic motion on rigid body motions and the coupling effect amongst flexible links. These analyses and results provide valuable insight to the design and control of the parallel manipulator with flexible intermediate links
Geometric integrators for stochastic rigid body dynamics
Tretyakov, Mikhail
2016-01-05
Geometric integrators play an important role in simulating dynamical systems on long time intervals with high accuracy. We will illustrate geometric integration ideas within the stochastic context, mostly on examples of stochastic thermostats for rigid body dynamics. The talk will be mainly based on joint recent work with Rusland Davidchak and Tom Ouldridge.
Geometric integrators for stochastic rigid body dynamics
Tretyakov, Mikhail
2016-01-01
Geometric integrators play an important role in simulating dynamical systems on long time intervals with high accuracy. We will illustrate geometric integration ideas within the stochastic context, mostly on examples of stochastic thermostats for rigid body dynamics. The talk will be mainly based on joint recent work with Rusland Davidchak and Tom Ouldridge.
Torsional Rigidity of Minimal Submanifolds
DEFF Research Database (Denmark)
Markvorsen, Steen; Palmer, Vicente
2006-01-01
We prove explicit upper bounds for the torsional rigidity of extrinsic domains of minimal submanifolds $P^m$ in ambient Riemannian manifolds $N^n$ with a pole $p$. The upper bounds are given in terms of the torsional rigidities of corresponding Schwarz symmetrizations of the domains in warped...
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
Finite-size effects on multibody neutrino exchange
Abada, A; Rodríguez-Quintero, J; Abada, As
1998-01-01
The effect of multibody massless neutrino exchanges between neutrons inside a finite-size neutron star is studied. We use an effective Lagrangian, which incorporates the effect of the neutrons on the neutrinos. Following Schwinger, it is shown that the total interaction energy density is computed by comparing the zero point energy of the neutrino sea with and without the star. It has already been shown that in an infinite-size star the total energy due to neutrino exchange vanishes exactly. The opposite claim that massless neutrino exchange would produce a huge energy is due to an improper summation of an infrared-divergent quantity. The same vanishing of the total energy has been proved exactly in the case of a finite star in a one-dimensional toy model. Here we study the three-dimensional case. We first consider the effect of a sharp star border, assumed to be a plane. We find that there is a non- vanishing of the zero point energy density difference between the inside and the outside due to the refraction ...
Integrating Multibody Simulation and CFD: toward Complex Multidisciplinary Design Optimization
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.
Gil, Yeongjoon; Wu, Wanqing; Lee, Jungtae
2012-01-01
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. PMID:23112605
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.
Algebraic Methods for Counting Euclidean Embeddings of Rigid Graphs
I.Z. Emiris; E.P. Tsigaridas; A. Varvitsiotis (Antonios); E.R. Gasner
2009-01-01
textabstract The study of (minimally) rigid graphs is motivated by numerous applications, mostly in robotics and bioinformatics. A major open problem concerns the number of embeddings of such graphs, up to rigid motions, in Euclidean space. We capture embeddability by polynomial systems
Multibody motion in implicitly constrained director format with links via explicit constraints
DEFF Research Database (Denmark)
Nielsen, Martin Bjerre; Krenk, Steen
2013-01-01
A conservative time integration algorithm is developed for constrained mechanical systems of kinematically linked rigid bodies based on convected base vectors. The base vectors are represented in terms of their absolute coordinates, hence the formulation makes use of three translation components...
Development of New Generation of Multibody System Computer Codes
2012-11-02
absolute nodal coordinate formulation (ANCF) that has many desirable features (Dufva et al, 2005; Garcia- Vallejo et al, 2008; Schwab and Meijaard, 2010...Beam Element Based on the Absolute Nodal Coordinate Formulation," Sound and Vibration, Vol. 280, pp. 719-738. 4. Garcia- Vallejo , D., Mayo, J., and
Van-Wierts, S.; Bernatchez, P.
2012-04-01
Coastal erosion is an important issue within the St-Lawrence estuary and gulf, especially in zones of unconsolidated material. Wide beaches are important coastal environments; they act as a buffer against breaking waves by absorbing and dissipating their energy, thus reducing the rate of coastal erosion. They also offer protection to humans and nearby ecosystems, providing habitat for plants, animals and lifeforms such as algae and microfauna. Conventional methods, such as aerial photograph analysis, fail to adequately quantify the morphosedimentary behavior of beaches at the scale of a hydrosedimentary cells. The lack of reliable and quantitative data leads to considerable errors of overestimation and underestimation of sediment budgets. To address these gaps and to minimize acquisition costs posed by airborne LiDAR survey, a mobile terrestrial LiDAR has been set up to acquire topographic data of the coastal zone. The acquisition system includes a LiDAR sensor, a high precision navigation system (GPS-INS) and a video camera. Comparison of LiDAR data with 1050 DGPS control points shows a vertical mean absolute error of 0.1 m in beach areas. The extracted data is used to calculate sediment volumes, widths, slopes, and a sediment budget index. A high accuracy coastal characterization is achieved through the integration of laser data and video. The main objective of this first project using this system is to quantify the impact of rigid coastal protective structures on sediment budget and beach morphology. Results show that the average sediment volume of beaches located before a rock armour barrier (12 m3/m) were three times narrower than for natural beaches (35,5 m3/m). Natural beaches were also found to have twice the width (25.4 m) of the beaches bordering inhabited areas (12.7 m). The development of sediment budget index for beach areas is an excellent proxy to quickly identify deficit areas and therefore the coastal segments most at risk of erosion. The obtained
Cracking of open traffic rigid pavement
Directory of Open Access Journals (Sweden)
Niken Chatarina
2017-01-01
Full Text Available The research is done by observing the growth of real structure cracking in Natar, Lampung, Indonesia compared to C. Niken’s et al research and literature study. The rigid pavement was done with open traffic system. There are two main crack types on Natar rigid pavement: cracks cross the road, and cracks spreads on rigid pavement surface. The observation of cracks was analyzed by analyzing material, casting, curing, loading and shrinkage mechanism. The relationship between these analysis and shrinkage mechanism was studied in concrete micro structure. Open traffic make hydration process occur under vibration; therefore, fresh concrete was compressed and tensioned alternately since beginning. High temperature together with compression, cement dissociation, the growth of Ca2+ at very early age leads abnormal swelling. No prevention from outside water movement leads hydration process occur with limited water which caused spreads fine cracks. Limited water improves shrinkage and plastic phase becomes shorter; therefore, rigid pavement can’t accommodate the abnormal swelling and shrinking alternately and creates the spread of cracks. Discontinuing casting the concrete makes both mix under different condition, the first is shrink and the second is swell and creates weak line on the border; so, the cracks appear as cracks across the road.
Topological orders in rigid states
International Nuclear Information System (INIS)
Wen, X.G.
1990-01-01
The authors study a new kind of ordering topological order in rigid states (the states with no local gapless excitations). This paper concentrates on characterization of the different topological orders. As an example the authors discuss in detail chiral spin states of 2+1 dimensional spin systems. Chiral spin states are described by the topological Chern-Simons theories in the continuum limit. The authors show that the topological orders can be characterized by a non-Abelian gauge structure over the moduli space which parametrizes a family of the model Hamiltonians supporting topologically ordered ground states. In 2 + 1 dimensions, the non-Abelian gauge structure determines possible fractional statistics of the quasi-particle excitations over the topologically ordered ground states. The dynamics of the low lying global excitations is shown to be independent of random spatial dependent perturbations. The ground state degeneracy and the non-Abelian gauge structures discussed in this paper are very robust, even against those perturbations that break translation symmetry. The authors also discuss the symmetry properties of the degenerate ground states of chiral spin states. The authors find that some degenerate ground states of chiral spin states on torus carry non-trivial quantum numbers of the 90 degrees rotation
Energy Technology Data Exchange (ETDEWEB)
Gross, Volker [ZF Friedrichshafen AG, Friedrichshafen (Germany)
2011-07-01
The legal regulations and the customers' requirements as regards vehicle comfort are growing more and more stringent. This also includes the transmission systems, as they are expected not so show any obvious acoustic or dynamic weaknesses. Modern simulation methods permit evaluation and optimization of structure-borne and airborne noise in the early stage of development. Especially the FE method is a well-established technique for the simulation of structure-borne sound. With regard to complex transmissions, multibody simulations (MBS) can provide valuable insights for a realistic evaluation of the dynamic behaviour of a transmission. This is demonstrated using a truck transmission as an example. (orig.)
Schilder, Jurnan Paul; Ellenbroek, Marcellinus Hermannus Maria; de Boer, A.
2017-01-01
In this work, the floating frame of reference formulation is used to create a flexible multibody model of slender offshore structures such as pipelines and risers. It is shown that due to the chain-like topology of the considered structures, the equation of motion can be expressed in terms of
Advances in Chimera Grid Tools for Multi-Body Dynamics Simulations and Script Creation
Chan, William M.
2004-01-01
This viewgraph presentation contains information about (1) Framework for multi-body dynamics - Geometry Manipulation Protocol (GMP), (2) Simulation procedure using Chimera Grid Tools (CGT) and OVERFLOW-2 (3) Further recent developments in Chimera Grid Tools OVERGRID, Grid modules, Script library and (4) Future work.
DEFF Research Database (Denmark)
Damkjær, Jesper; Erleben, Kenny
2009-01-01
and a simultaneous descend in the tandem traversal. The data structure design and traversal are highly specialized for exploiting the parallel threads in the NVIDIA GPUs. As proof-of-concept we demonstrate a GPU implementation for a multibody dynamics simulation, showing an approximate speedup factor of up to 8...
Search for Exclusive Multibody Non-DD Decays at the ψ(3770) Resonance
International Nuclear Information System (INIS)
Huang, G.S.; Miller, D.H.; Pavlunin, V.; Sanghi, B.; Shipsey, I.P.J.; Adams, G.S.; Cravey, M.; Cummings, J.P.; Danko, I.; Napolitano, J.; He, Q.; Muramatsu, H.; Park, C.S.; Thorndike, E.H.; Coan, T.E.; Gao, Y.S.; Liu, F.; Artuso, M.; Boulahouache, C.; Blusk, S.
2006-01-01
Using data collected at the ψ(3770) resonance with the CLEO-c detector at the Cornell e + e - storage ring, we present searches for 25 charmless decay modes of the ψ(3770), mostly multibody final states. No evidence for charmless decays is found
Constraint treatment techniques and parallel algorithms for multibody dynamic analysis. Ph.D. Thesis
Chiou, Jin-Chern
1990-01-01
Computational procedures for kinematic and dynamic analysis of three-dimensional multibody dynamic (MBD) systems are developed from the differential-algebraic equations (DAE's) viewpoint. Constraint violations during the time integration process are minimized and penalty constraint stabilization techniques and partitioning schemes are developed. The governing equations of motion, a two-stage staggered explicit-implicit numerical algorithm, are treated which takes advantage of a partitioned solution procedure. A robust and parallelizable integration algorithm is developed. This algorithm uses a two-stage staggered central difference algorithm to integrate the translational coordinates and the angular velocities. The angular orientations of bodies in MBD systems are then obtained by using an implicit algorithm via the kinematic relationship between Euler parameters and angular velocities. It is shown that the combination of the present solution procedures yields a computationally more accurate solution. To speed up the computational procedures, parallel implementation of the present constraint treatment techniques, the two-stage staggered explicit-implicit numerical algorithm was efficiently carried out. The DAE's and the constraint treatment techniques were transformed into arrowhead matrices to which Schur complement form was derived. By fully exploiting the sparse matrix structural analysis techniques, a parallel preconditioned conjugate gradient numerical algorithm is used to solve the systems equations written in Schur complement form. A software testbed was designed and implemented in both sequential and parallel computers. This testbed was used to demonstrate the robustness and efficiency of the constraint treatment techniques, the accuracy of the two-stage staggered explicit-implicit numerical algorithm, and the speed up of the Schur-complement-based parallel preconditioned conjugate gradient algorithm on a parallel computer.
Magnetism and magnetostriction in a degenerate rigid band
International Nuclear Information System (INIS)
Kulakowski, K.; Barbara, B.
1990-09-01
We investigate the influence of the spin-orbit coupling on the magnetic and magnetoelastic phenomena in ferromagnetic band systems. The description is within the Stoner model of a degenerate rigid band, for temperature T = O. (author). 14 refs
Rigidity of Glasses and Macromolecules
Thorpe, M. F.
1998-03-01
The simple yet powerful ideas of percolation theory have found their way into many different areas of research. In this talk we show how RIGIDITY PERCOLATION can be studied at a similar level of sophistication, using a powerful new program THE PEBBLE GAME (D. J. Jacobs and M. F. Thorpe, Phys. Rev. E) 53, 3682 (1996). that uses an integer algorithm. This program can analyse the rigidity of two and three dimensional networks containing more than one million bars and joints. We find the total number of floppy modes, and find the critical behavior as the network goes from floppy to rigid as more bars are added. We discuss the relevance of this work to network glasses, and how it relates to experiments that involve the mechanical properties like hardness and elasticity of covalent glassy networks like Ge_xAs_ySe_1-x-y and dicuss recent experiments that suggest that the rigidity transition may be first order (Xingwei Feng, W. J.Bresser and P. Boolchand, Phys. Rev. Lett 78), 4422 (1997).. This approach is also useful in macromolecules and proteins, where detailed information about the rigid domain structure can be obtained.
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.
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.
Rigidly foldable origami gadgets and tessellations
Evans, Thomas A.; Lang, Robert J.; Magleby, Spencer P.; Howell, Larry L.
2015-01-01
Rigidly foldable origami allows for motion where all deflection occurs at the crease lines and facilitates the application of origami in materials other than paper. In this paper, we use a recently discovered method for determining rigid foldability to identify existing flat-foldable rigidly foldable tessellations, which are also categorized. We introduce rigidly foldable origami gadgets which may be used to modify existing tessellations or to create new tessellations. Several modified and new rigidly foldable tessellations are presented. PMID:26473037
Energy Technology Data Exchange (ETDEWEB)
Bansal, Artee; Asthagiri, D.; Cox, Kenneth R.; Chapman, Walter G., E-mail: wgchap@rice.edu [Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77251 (United States)
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.
Stresses in Circular Plates with Rigid Elements
Velikanov, N. L.; Koryagin, S. I.; Sharkov, O. V.
2018-05-01
Calculations of residual stress fields are carried out by numerical and static methods, using the flat cross-section hypothesis. The failure of metal when exposed to residual stresses is, in most cases, brittle. The presence in the engineering structures of rigid elements often leads to the crack initiation and structure failure. This is due to the fact that rigid elements under the influence of external stresses are stress concentrators. In addition, if these elements are fixed by welding, the residual welding stresses can lead to an increase in stress concentration and, ultimately, to failure. The development of design schemes for such structures is a very urgent task for complex technical systems. To determine the stresses in a circular plate with a welded circular rigid insert under the influence of an external load, one can use the solution of the plane stress problem for annular plates in polar coordinates. The polar coordinates of the points are the polar radius and the polar angle, and the stress state is determined by normal radial stresses, tangential and shearing stresses. The use of the above mentioned design schemes, formulas, will allow more accurate determination of residual stresses in annular welded structures. This will help to establish the most likely directions of failure and take measures at the stages of designing, manufacturing and repairing engineering structures to prevent these failures. However, it must be taken into account that the external load, the presence of insulation can lead to a change in the residual stress field.
Rigidity-tuning conductive elastomer
Shan, Wanliang; Diller, Stuart; Tutcuoglu, Abbas; Majidi, Carmel
2015-06-01
We introduce a conductive propylene-based elastomer (cPBE) that rapidly and reversibly changes its mechanical rigidity when powered with electrical current. The elastomer is rigid in its natural state, with an elastic (Young’s) modulus of 175.5 MPa, and softens when electrically activated. By embedding the cPBE in an electrically insulating sheet of polydimethylsiloxane (PDMS), we create a cPBE-PDMS composite that can reversibly change its tensile modulus between 37 and 1.5 MPa. The rigidity change takes ˜6 s and is initiated when a 100 V voltage drop is applied across the two ends of the cPBE film. This magnitude of change in elastic rigidity is similar to that observed in natural skeletal muscle and catch connective tissue. We characterize the tunable load-bearing capability of the cPBE-PDMS composite with a motorized tensile test and deadweight experiment. Lastly, we demonstrate the ability to control the routing of internal forces by embedding several cPBE-PDMS ‘active tendons’ into a soft robotic pneumatic bending actuator. Selectively activating the artificial tendons controls the neutral axis and direction of bending during inflation.
Rigidity-tuning conductive elastomer
International Nuclear Information System (INIS)
Shan, Wanliang; Diller, Stuart; Tutcuoglu, Abbas; Majidi, Carmel
2015-01-01
We introduce a conductive propylene-based elastomer (cPBE) that rapidly and reversibly changes its mechanical rigidity when powered with electrical current. The elastomer is rigid in its natural state, with an elastic (Young’s) modulus of 175.5 MPa, and softens when electrically activated. By embedding the cPBE in an electrically insulating sheet of polydimethylsiloxane (PDMS), we create a cPBE–PDMS composite that can reversibly change its tensile modulus between 37 and 1.5 MPa. The rigidity change takes ∼6 s and is initiated when a 100 V voltage drop is applied across the two ends of the cPBE film. This magnitude of change in elastic rigidity is similar to that observed in natural skeletal muscle and catch connective tissue. We characterize the tunable load-bearing capability of the cPBE–PDMS composite with a motorized tensile test and deadweight experiment. Lastly, we demonstrate the ability to control the routing of internal forces by embedding several cPBE–PDMS ‘active tendons’ into a soft robotic pneumatic bending actuator. Selectively activating the artificial tendons controls the neutral axis and direction of bending during inflation. (paper)
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
Formica, Matteo; Cavagnaro, Luca; Basso, Marco; Zanirato, Andrea; Felli, Lamberto; Formica, Carlo
2015-11-01
To evaluate the results of a novel rigid-dynamic stabilization technique in lumbar degenerative segment diseases (DSD), expressly pointing out the preservation of postoperative lumbar lordosis (LL). Forty-one patients with one level lumbar DSD and initial disc degeneration at the adjacent level were treated. Circumferential lumbar arthrodesis and posterior hybrid instrumentation were performed to preserve an initial disc degeneration above the segment that has to be fused. Clinical and spino-pelvic parameters were evaluated pre- and postoperatively. At 2-year follow-up, a significant improvement of clinical outcomes was reported. No statistically significant difference was noted between postoperative and 2-year follow-up in LL and in disc/vertebral body height ratio at the upper adjacent fusion level. When properly selected, this technique leads to good results. A proper LL should be achieved after any hybrid stabilization to preserve the segment above the fusion.
International Nuclear Information System (INIS)
Fox, T.; Kotzian, M.; Roesch, N.
1992-01-01
The authors present an INDO/S Molecular-orbital investigation of organic molecules containing a barrelene moiety that provides a rigid link between an aromatic donor and a maleic ester acceptor group. Molecules of this type have recently been synthesized and characterized spectroscopically. The authors discuss the ground state and various excited states both in vacuo and in solution. Solvent effects are incorporated by use of an electrostatic cavity model which is not restricted to a spherical cavity, but allows for a cavity shape that is adapted to the solute molecule. The calculations indicate low-lying charge-transfer (CT) excitations in the region of the first aromatic transitions, even in the gas phase
Directory of Open Access Journals (Sweden)
Thierry Nalpas
2011-01-01
Full Text Available En este trabajo se presenta un estudio de modelamiento análogo sobre la naturaleza, geometría y cinemática de la deformación a lo largo de fallas de rumbo dada la presencia de un bloque rígido en su trayectoria de deformación. Los modelos análogos están apropiadamente escalados considerando las características reológicas de los materiales que se desean contrastar en la deformación. Dos grandes parámetros fueron probados: la configuración del bloque rígido, variando su forma y tamaño, y el monto del desplazamiento. Los resultados experimentales muestran el desarrollo de rotaciones, fallas y pliegues como producto de la presencia de un bloque rígido en la trayectoria de falla. Los diversos casos geométricos probados pueden ser empleados para su comparación con sistemas de fallas de rumbo en los cuales existen diferencias litológicas de comportamiento reológico diferencial, como por ejemplo el caso del 'Núcleo rígido de Limón Verde' al sur de Chuquicamata, ubicado en la trayectoria del sistema de fallas de Domeyko.This work addresses the kinematic effects of a rigid block in strike-slip systems by using analogue models. The experiments (size, behaviour of materials were scaled down in order to represent deformation of the tested rheologic contrast conditions in deformation. Two main parameters were tested: the configuration of the rigid block, changing its form and size, and the amount of displacement. The experiments evidenced the development of rotations, faults and folds along the fault trajectory, as resulting from the presence of the rigid block during the deformation. Testing of diverse geometric situations may be used for comparison to strike-slip fault systems in which different lithologies and rheologic behaviour exist, for example, presence of the 'Limón Verde rigid core' along the Domeyko fault system, just south of Chuquicamata.
Verification of the Rigidity of the Coulomb Field in Motion
Blinov, S. V.; Bulyzhenkov, I. É.
2018-06-01
Laplace, analyzing the stability of the Solar System, was the first to calculate that the velocity of the motion of force fields can significantly exceed the velocity of light waves. In electrodynamics, the Coulomb field should rigidly accompany its source for instantaneous force action in distant regions. Such rigid motion was recently inferred from experiments at the Frascati Beam Test Facility with short beams of relativistic electrons. The comments of the authors on their observations are at odds with the comments of theoreticians on retarded potentials, which motivates a detailed study of the positions of both sides. Predictions of measurements, based on the Lienard-Wiechert potentials, are used to propose an unambiguous scheme for testing the rigidity of the Coulomb field. Realization of the proposed experimental scheme could independently refute or support the assertions of the Italian physicists regarding the rigid motion of Coulomb fields and likewise the nondual field approach to macroscopic reality.
Multibody neutrino exchange in a neutron star neutrino sea and border effects
Abada, A; Rodríguez-Quintero, J; Abada, As
1998-01-01
The interaction due to the exchange of massless neutrinos between neutrons is a long-range force. Border effects on this multibody exchange inside a dense core are studied and computed analytically in 1 + 1 dimensions. We demonstrate in this work that a proper treatment of the star's border effect automatically incorporates the condensate contribution as a consequence of the appropriate boundary conditions for the neutrino Feynman propagator inside the star. The total multibody exchange contribution is infrared-safe and vanishes exactly in 1 + 1 dimensions. The general conclusion of this work is that the border effect does not modify the result that neutrino exchange is infrared-safe. This toy model prepares the ground and gives the tools for the study of the realistic 3 + 1 star.
Schilder, J.; Ellenbroek, M.; de Boer, A.
2017-12-01
In this work, the floating frame of reference formulation is used to create a flexible multibody model of slender offshore structures such as pipelines and risers. It is shown that due to the chain-like topology of the considered structures, the equation of motion can be expressed in terms of absolute interface coordinates. In the presented form, kinematic constraint equations are satisfied explicitly and the Lagrange multipliers are eliminated from the equations. Hence, the structures can be conveniently coupled to finite element or multibody models of for example seabed and vessel. The chain-like topology enables the efficient use of recursive solution procedures for both transient dynamic analysis and equilibrium analysis. For this, the transfer matrix method is used. In order to improve the convergence of the equilibrium analysis, the analytical solution of an ideal catenary is used as an initial configuration, reducing the number of required iterations.
State and force observers based on multibody models and the indirect Kalman filter
Sanjurjo, Emilio; Dopico, Daniel; Luaces, Alberto; Naya, Miguel Ángel
2018-06-01
The aim of this work is to present two new methods to provide state observers by combining multibody simulations with indirect extended Kalman filters. One of the methods presented provides also input force estimation. The observers have been applied to two mechanism with four different sensor configurations, and compared to other multibody-based observers found in the literature to evaluate their behavior, namely, the unscented Kalman filter (UKF), and the indirect extended Kalman filter with simplified Jacobians (errorEKF). The new methods have some more computational cost than the errorEKF, but still much less than the UKF. Regarding their accuracy, both are better than the errorEKF. The method with input force estimation outperforms also the UKF, while the method without force estimation achieves results almost identical to those of the UKF. All the methods have been implemented as a reusable MATLAB® toolkit which has been released as Open Source in https://github.com/MBDS/mbde-matlab.
Structure-preserving integrators in nonlinear structural dynamics and flexible multibody dynamics
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...
Physical essence of the multibody contact-sliding at atomic scale
Han, Xuesong
2014-01-01
Investigation the multibody contact-sliding occurred at atomic discrete contact spot will play an important role in determine the origin of tribology behavior and evaluates the micro-mechanical property of nanomaterials and thus optimizing the design of surface texture. This paper carries out large scale parallel molecular dynamics simulation on contact-sliding at atomic scale to uncover the special physical essence. The research shows that some kind of force field exists between nanodot pair and the interaction can be expressed by the linear combination of exponential function while the effective interaction distance limited in 1 angstrom for nanodot with several tens of nanometer diameter. The variation tendency about the interaction force between nanodot array is almost the same between nanodot pairs and thus the interaction between two nanodot array can be characterized by parallel mechanical spring. Multibody effect which dominates the interaction between atoms or molecules will gradually diminish with the increasing of length scales.
Directory of Open Access Journals (Sweden)
Polach P.
2008-11-01
Full Text Available Vertical dynamic properties of the ŠKODA 21 Tr low-floor trolleybus were investigated on an artificial test track when driving with a real vehicle and when simulating driving with a multibody model along a virtual test track. Driving along the artificial test track was aimed to determine vertical dynamic properties of the real trolleybus and on the basis of them to verify computer trolleybus models. Time histories and extreme values of the air springs relative deflections are the monitored quantities. Due to differences of the experiments and the computer simulations results the influences of the characteristics of the spring-damper structural elements of the axles suspension and the radial characteristics of the tires used in the trolleybus multibody model on the extreme values of the monitored quantities are evaluated.
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.
Elasticity of Relativistic Rigid Bodies?
Smarandache, Florentin
2013-10-01
In the classical Twin Paradox, according to the Special Theory of Relativity, when the traveling twin blasts off from the Earth to a relative velocity v =√{/3 } 2 c with respect to the Earth, his measuring stick and other physical objects in the direction of relative motion shrink to half their lengths. How is that possible in the real physical world to have let's say a rigid rocket shrinking to half and then later elongated back to normal as an elastic material when it stops? What is the explanation for the traveler's measuring stick and other physical objects, in effect, return to the same length to their original length in the Stay-At-Home, but there is no record of their having shrunk? If it's a rigid (not elastic) object, how can it shrink and then elongate back to normal? It might get broken in such situation.
Functionally rigid bistable [2]rotaxanes
DEFF Research Database (Denmark)
Nygaard, Sune; Leung, Ken C-F; Aprahamian, Ivan
2007-01-01
defines an unambiguous distance of 1.5 nm over which the ring moves between the MPTTF and NP units. The degenerate NP/NP [2]rotaxane was used to investigate the shuttling barrier by dynamic 1H NMR spectroscopy for the movement of the CBPQT4+ ring across the new rigid spacer. It is evident from...... better control over the position of the ring component in the ground state but also for control over the location of the CBPQT4+ ring during solution-state switching experiments, triggered either chemically (1H NMR) or electrochemically (cyclic voltammetry). In this instance, the use of the rigid spacer......Two-station [2]rotaxanes in the shape of a degenerate naphthalene (NP) shuttle and a nondegenerate monopyrrolotetrathiafulvalene (MPTTF)/NP redox-controllable switch have been synthesized and characterized in solution. Their dumbbell-shaped components are composed of polyether chains interrupted...
Associative memory through rigid origami
Murugan, Arvind; Brenner, Michael
2015-03-01
Mechanisms such as Miura Ori have proven useful in diverse contexts since they have only one degree of freedom that is easily controlled. We combine the theory of rigid origami and associative memory in frustrated neural networks to create structures that can ``learn'' multiple generic folding mechanisms and yet can be robustly controlled. We show that such rigid origami structures can ``recall'' a specific learned mechanism when induced by a physical impulse that only need resemble the desired mechanism (i.e. robust recall through association). Such associative memory in matter, seen before in self-assembly, arises due to a balance between local promiscuity (i.e., many local degrees of freedom) and global frustration which minimizes interference between different learned behaviors. Origami with associative memory can lead to a new class of deployable structures and kinetic architectures with multiple context-dependent behaviors.
Rigidity spectrum of Forbush decrease
International Nuclear Information System (INIS)
Sakakibara, S.; Munakata, K.; Nagashima, K.
1985-01-01
Using data from neutron monitors and muon telescopes at surface and underground stations, the average rigidity spectrum of Forbush decreases (Fds) during the period of 1978-1982 were obtained. Thirty eight Ed-events are classified into two groups, Hard Fd and Soft FD according to size of Fd at the Sakashita station. It is found that a spectral form of a fractional-power type (P to the-gamma sub 1 (P+P sub c) to the -gamma sub2) is more suitable than that of a power-exponential type or of a power type with an upper limiting rigidity. The best fitted spectrum of the fractional-power type is expressed by gamma sub1 = 0.37, gamma sub2 = 0.89 and P subc = 10 GV for Hard Fd and gamma sub1 = 0.77, gamma sub2 = 1.02 and P sub c - 14GV for Soft Fd
Signature of Thermal Rigidity Percolation
International Nuclear Information System (INIS)
Huerta, Adrián
2013-01-01
To explore the role that temperature and percolation of rigidity play in determining the macroscopic properties, we propose a model that adds translational degrees of freedom to the spins of the well known Ising hamiltonian. In particular, the Ising model illustrate the longstanding idea that the growth of correlations on approach to a critical point could be describable in terms of the percolation of some sort of p hysical cluster . For certain parameters of this model we observe two well defined peaks of C V , that suggest the existence of two kinds of p hysical percolation , namely connectivity and rigidity percolation. Thermal fluctuations give rise to two different kinds of elementary excitations, i.e. droplets and configuron, as suggested by Angell in the framework of a bond lattice model approach. The later is reflected in the fluctuations of redundant constraints that gives stability to the structure and correlate with the order parameter
Bansal, Artee; Valiya Parambathu, Arjun; Asthagiri, D.; Cox, Kenneth R.; Chapman, Walter G.
2017-04-01
We present a theory to predict the structure and thermodynamics of mixtures of colloids of different diameters, building on our earlier work [A. Bansal et al., J. Chem. Phys. 145, 074904 (2016)] that considered mixtures with all particles constrained to have the same size. The patchy, solvent particles have short-range directional interactions, while the solute particles have short-range isotropic interactions. The hard-sphere mixture without any association site forms the reference fluid. An important ingredient within the multi-body association theory is the description of clustering of the reference solvent around the reference solute. Here we account for the physical, multi-body clusters of the reference solvent around the reference solute in terms of occupancy statistics in a defined observation volume. These occupancy probabilities are obtained from enhanced sampling simulations, but we also present statistical mechanical models to estimate these probabilities with limited simulation data. Relative to an approach that describes only up to three-body correlations in the reference, incorporating the complete reference information better predicts the bonding state and thermodynamics of the physical solute for a wide range of system conditions. Importantly, analysis of the residual chemical potential of the infinitely dilute solute from molecular simulation and theory shows that whereas the chemical potential is somewhat insensitive to the description of the structure of the reference fluid, the energetic and entropic contributions are not, with the results from the complete reference approach being in better agreement with particle simulations.
Torsional rigidity, isospectrality and quantum graphs
International Nuclear Information System (INIS)
Colladay, Don; McDonald, Patrick; Kaganovskiy, Leon
2017-01-01
We study torsional rigidity for graph and quantum graph analogs of well-known pairs of isospectral non-isometric planar domains. We prove that such isospectral pairs are distinguished by torsional rigidity. (paper)
Creation of 3D Multi-Body Orthodontic Models by Using Independent Imaging Sensors
Directory of Open Access Journals (Sweden)
Armando Viviano Razionale
2013-02-01
Full Text Available In the field of dental health care, plaster models combined with 2D radiographs are widely used in clinical practice for orthodontic diagnoses. However, complex malocclusions can be better analyzed by exploiting 3D digital dental models, which allow virtual simulations and treatment planning processes. In this paper, dental data captured by independent imaging sensors are fused to create multi-body orthodontic models composed of teeth, oral soft tissues and alveolar bone structures. The methodology is based on integrating Cone-Beam Computed Tomography (CBCT and surface structured light scanning. The optical scanner is used to reconstruct tooth crowns and soft tissues (visible surfaces through the digitalization of both patients’ mouth impressions and plaster casts. These data are also used to guide the segmentation of internal dental tissues by processing CBCT data sets. The 3D individual dental tissues obtained by the optical scanner and the CBCT sensor are fused within multi-body orthodontic models without human supervisions to identify target anatomical structures. The final multi-body models represent valuable virtual platforms to clinical diagnostic and treatment planning.
Huang, Juyang
2002-08-01
Experimental evidences have indicated that cholesterol may adapt highly regular lateral distributions (i.e., superlattices) in a phospholipid bilayer. We investigated the formations of superlattices at cholesterol mole fraction of 0.154, 0.25, 0.40, and 0.5 using Monte Carlo simulation. We found that in general, conventional pairwise-additive interactions cannot produce superlattices. Instead, a multibody (nonpairwise) interaction is required. Cholesterol superlattice formation reveals that although the overall interaction between cholesterol and phospholipids is favorable, it contains two large opposing components: an interaction favoring cholesterol-phospholipid mixing and an unfavorable acyl chain multibody interaction that increases nonlinearly with the number of cholesterol contacts. The magnitudes of interactions are in the order of kT. The physical origins of these interactions can be explained by our umbrella model. They most likely come from the requirement for polar phospholipid headgroups to cover the nonpolar cholesterol to avoid the exposure of cholesterol to water and from the sharp decreasing of acyl chain conformation entropy due to cholesterol contact. This study together with our previous work demonstrate that the driving force of cholesterol-phospholipid mixing is a hydrophobic interaction, and multibody interactions dominate others over a wide range of cholesterol concentration.
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
Geometry, rigidity, and group actions
Farb, Benson; Zimmer, Robert J
2011-01-01
The study of group actions is more than a hundred years old but remains to this day a vibrant and widely studied topic in a variety of mathematic fields. A central development in the last fifty years is the phenomenon of rigidity, whereby one can classify actions of certain groups, such as lattices in semi-simple Lie groups. This provides a way to classify all possible symmetries of important spaces and all spaces admitting given symmetries. Paradigmatic results can be found in the seminal work of George Mostow, Gergory Margulis, and Robert J. Zimmer, among others.The p
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.
Wei, Y.; Barradas Berglind, J.J; van Rooij, M.; Prins, WA; Jayawardhana, B.; Vakis, A. I.
2017-01-01
In this work, a numerical model is developed in order to investigate the adaptability of the multi-pump multi-piston power take-off ((MPPTO)-P-2) system of a novel wave energy converter (WEC). This model is realized in the MATLAB/SIMULINK environment, using the multi-body dynamics solver Multibody
Rigid external maxillary distraction and rhinoplasty for pyknodysostosis.
Varol, Altan; Sabuncuoglu, Fidan Alakus; Sencimen, Metin; Akcam, Timur; Olmez, Hüseyin; Basa, Selçuk
2011-05-01
This article reports the treatment of an 33-year-old female patient with pyknodysostosis by rigid external distraction II midface distraction system. The patient with pyknodysostosis described in this report had severe midfacial hypoplasia. Correction of this by use of routine orthognathic surgery would require osteosynthesis and bone grafting. Risk of infection and/or nonunion after such a surgical procedure was considered too great, and therefore the possibility of treatment by distraction osteogenesis of the maxilla was evaluated. The rigid external distraction II midface distraction system was used to relocate the hypoplastic maxilla at anterior-inferior projection. Distraction osteogenesis should be considered as the primary reconstructive method for maxillofacial deformities in patients with sclerosing bone dysplasias, since this is the second reported case treated successfully with rigid external distraction.
El Habachi, Aimad; Moissenet, Florent; Duprey, Sonia; Cheze, Laurence; Dumas, Raphaël
2015-07-01
Sensitivity analysis is a typical part of biomechanical models evaluation. For lower limb multi-body models, sensitivity analyses have been mainly performed on musculoskeletal parameters, more rarely on the parameters of the joint models. This study deals with a global sensitivity analysis achieved on a lower limb multi-body model that introduces anatomical constraints at the ankle, tibiofemoral, and patellofemoral joints. The aim of the study was to take into account the uncertainty of parameters (e.g. 2.5 cm on the positions of the skin markers embedded in the segments, 5° on the orientation of hinge axis, 2.5 mm on the origin and insertion of ligaments) using statistical distributions and propagate it through a multi-body optimisation method used for the computation of joint kinematics from skin markers during gait. This will allow us to identify the most influential parameters on the minimum of the objective function of the multi-body optimisation (i.e. the sum of the squared distances between measured and model-determined skin marker positions) and on the joint angles and displacements. To quantify this influence, a Fourier-based algorithm of global sensitivity analysis coupled with a Latin hypercube sampling is used. This sensitivity analysis shows that some parameters of the motor constraints, that is to say the distances between measured and model-determined skin marker positions, and the kinematic constraints are highly influencing the joint kinematics obtained from the lower limb multi-body model, for example, positions of the skin markers embedded in the shank and pelvis, parameters of the patellofemoral hinge axis, and parameters of the ankle and tibiofemoral ligaments. The resulting standard deviations on the joint angles and displacements reach 36° and 12 mm. Therefore, personalisation, customisation or identification of these most sensitive parameters of the lower limb multi-body models may be considered as essential.
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)....
Measuring $CP$ violation and mixing in charm with inclusive self-conjugate multibody decay modes
Malde, S.; Wilkinson, G.
2015-05-28
Time-dependent studies of inclusive charm decays to multibody self-conjugate final states can be used to determine the indirect $CP$-violating observable $A_\\Gamma$ and the mixing observable $y_{CP}$, provided that the fractional $CP$-even content of the final state, $F_+$, is known. This approach can yield significantly improved sensitivity compared with the conventional method that relies on decays to $CP$ eigenstates. In particular, $D \\to \\pi^+\\pi^-\\pi^0$ appears to be an especially powerful channel, given its relatively large branching fraction and the high value of $F_+$ that has recently been measured at charm threshold.
Rigid-plastic seismic design of reinforced concrete structures
DEFF Research Database (Denmark)
Costa, Joao Domingues; Bento, R.; Levtchitch, V.
2007-01-01
structural strength with respect to a pre-defined performance parameter using a rigid-plastic response spectrum, which is characteristic of the ground motion alone. The maximum strength demand at any point is solely dependent on the intensity of the ground motion, which facilitates the task of distributing......In this paper a new seismic design procedure for Reinforced Concrete (R/C) structures is proposed-the Rigid-Plastic Seismic Design (RPSD) method. This is a design procedure based on Non-Linear Time-History Analysis (NLTHA) for systems expected to perform in the non-linear range during a lifetime...... earthquake event. The theoretical background is the Theory of Plasticity (Rigid-Plastic Structures). Firstly, a collapse mechanism is chosen and the corresponding stress field is made safe outside the regions where plastic behaviour takes place. It is shown that this allows the determination of the required...
A concise introduction to mechanics of rigid bodies multidisciplinary engineering
Huang, L
2017-01-01
This updated second edition broadens the explanation of rotational kinematics and dynamics — the most important aspect of rigid body motion in three-dimensional space and a topic of much greater complexity than linear motion. It expands treatment of vector and matrix, and includes quaternion operations to describe and analyze rigid body motion which are found in robot control, trajectory planning, 3D vision system calibration, and hand-eye coordination of robots in assembly work, etc. It features updated treatments of concepts in all chapters and case studies. The textbook retains its comprehensiveness in coverage and compactness in size, which make it easily accessible to the readers from multidisciplinary areas who want to grasp the key concepts of rigid body mechanics which are usually scattered in multiple volumes of traditional textbooks. Theoretical concepts are explained through examples taken from across engineering disciplines and links to applications and more advanced courses (e.g. industrial rob...
Application of flexible multibody modelling for control synthesis in mechatronics
Aarts, Ronald G.K.M.; van Dijk, Johannes; Brouwer, Dannis Michel; Jonker, Jan B.; Samin, J.C.; Fisette, P.
2011-01-01
The models used in the conceptual phase of the mechatronic design should not be too complicated, yet they should capture the dominant system behaviour. This includes the computation of natural frequencies and mode shapes in a relevant frequency range. For the control system synthesis the low
Botulinum toxin in myotonia congenita: it does not help against rigidity and pain.
Dressler, Dirk; Adib Saberi, Fereshte
2014-05-01
Botulinum toxin (BT) is a potent local muscle relaxant with analgetic properties. Myotonia congenita (MC) is a genetic disorder producing muscle rigidity and pain. BT injected into the trapezius produced mild paresis, but no effect on rigidity and pain. There were no signs of systemic effects. Lack of BT efficacy on MC rigidity confirms its origin from muscle membrane dysfunction rather than from inappropriate neuromuscular activation. Lack of BT efficacy on pain could be caused by lack of anti-rigidity effect. It could also be due to separate non-muscular pain mechanisms unresponsive to BT.
Viscoelastic materials with anisotropic rigid particles: stress-deformation behavior
Sagis, L.M.C.; Linden, van der E.
2001-01-01
In this paper we have derived constitutive equations for the stress tensor of a viscoelastic material with anisotropic rigid particles. We have assumed that the material has fading memory. The expressions are valid for slow and small deformations from equilibrium, and for systems that are nearly
Prediction of railway induced ground vibration through multibody and finite element modelling
Directory of Open Access Journals (Sweden)
G. Kouroussis
2013-04-01
Full Text Available The multibody approach is now recognized as a reliable and mature computer aided engineering tool. Namely, it is commonly used in industry for the design of road or railway vehicles. The paper presents a framework developed for predicting the vibrations induced by railway transportation. Firstly, the vehicle/track subsystem is simulated, on the basis of the home-made C++ library EasyDyn, by mixing the multibody model of the vehicle and the finite element model of the track, coupled to each other through the wheel/rail contact forces. Only the motion in the vertical plane is considered, assuming a total symmetry between left and right rails. This first step produces the time history of the forces exerted by the ballast on the foundation, which are then applied to a full 3-D FEM model of the soil, defined under the commercial software ABAQUS. The paper points out the contribution of the pitch motion of the bogies and carbodies which were neglected in previous publications, as well as the interest of the so-called coupled-lumped mass model (CLM to represent the influence of the foundation in the track model. The potentialities of the model are illustrated on the example of the Thalys high-speed train, riding at 300 km h−1 on the Belgian site of Mévergnies.
International Nuclear Information System (INIS)
Wu, Jianing; Yan, Shaoze; Zuo, Ming J.
2016-01-01
Mechanism reliability is defined as the ability of a certain mechanism to maintain output accuracy under specified conditions. Mechanism reliability is generally assessed by the classical direct probability method (DPM) derived from the first order second moment (FOSM) method. The DPM relies strongly on the analytical form of the dynamic solution so it is not applicable to multi-body mechanisms that have only numerical solutions. In this paper, an indirect probability model (IPM) is proposed for mechanism reliability evaluation of multi-body mechanisms. IPM combines the dynamic equation, degradation function and Kaplan–Meier estimator to evaluate mechanism reliability comprehensively. Furthermore, to reduce the amount of computation in practical applications, the IPM is simplified into the indirect probability step model (IPSM). A case study of a crank–slider mechanism with clearance is investigated. Results show that relative errors between the theoretical and experimental results of mechanism reliability are less than 5%, demonstrating the effectiveness of the proposed method. - Highlights: • An indirect probability model (IPM) is proposed for mechanism reliability evaluation. • The dynamic equation, degradation function and Kaplan–Meier estimator are used. • Then the simplified form of indirect probability model is proposed. • The experimental results agree well with the predicted results.
Management of rigid post-traumatic kyphosis.
Wu, S S; Hwa, S Y; Lin, L C; Pai, W M; Chen, P Q; Au, M K
1996-10-01
Rigid post-traumatic kyphosis after fracture of the thoracolumbar and lumbar spine represents a failure of initial management of the injury. Kyphosis moves the center of gravity anterior. The kyphosis and instability may result in pain, deformity, and increased neurologic deficits. Management for symptomatic post-traumatic kyphosis always has presented a challenge to orthopedic surgeons. To evaluate the surgical results of one stage posterior correction for rigid symptomatic post-traumatic kyphosis of the thoracolumbar and lumbar spine. The management for post-traumatic kyphosis remains controversial. Anterior, posterior, or combined anterior and posterior procedures have been advocated by different authors and show various degrees of success. One vertebra immediately above and below the level of the deformity was instrumented posteriorly by a transpedicular system (internal fixator AO). Posterior decompression was performed by excision of the spinal process and bilateral laminectomy. With the deformed vertebra through the pedicle, the vertebral body carefully is removed around the pedicle level, approximating a wedge shape. The extent to which the deformed vertebral body should be removed is determined by the attempted correction. Correction of the deformity is achieved by manipulation of the operating table and compression of the adjacent Schanz screws above and below the lesion. Thirteen patients with post-traumatic kyphosis with symptoms of fatigue and pain caused by slow progression of kyphotic deformities received posterior decompression, correction, and stabilization as a definitive treatment. The precorrection kyphosis ranged from 30-60 degrees, with a mean of 40 degrees +/- 10.8 degrees. After correction, kyphosis was reduced to an average of 1.5 degrees +/- 3.8 degrees, with a range from -5 degrees to 5 degrees. The average angle of correction was 38.8 degrees +/- 10.4 degrees, with a range from 25 degrees to 60 degrees. Significant difference was found
Vincent, Jean-Baptiste
This Master's thesis is part of a multidisciplinary optimisation project initiated by the Consortium for Research and Innovation in Aerospace in Quebec (CRIAQ) ; this project is about designing and manufacturing a morphing wing demonstrator. The morphing design adopted in this project is based on airfoil thickness variation applied to the upper skin. This morphing generates a change in the laminar to turbulent boundary layer transition position on top of the wing. The position of this transition area leads to significant changes in the aerodynamic performance of the wing. The study presented here focuses on the design of the conventional aileron actuation system and on the characterization of the high sensitivity differential pressure sensors installed on the upper skin in order to determine the laminar to turbulent transition position. Furthermore, the study focuses on the data acquisition system for the morphing wing structural test validation. The aileron actuation system is based on a linear actuator actuated by a brushless motor. The component choice is presented as well as the command method. A static validation as well as wind tunnel validation is presented. The pressure sensor characterization is performed by installing three of those high sensitivity differential pressure sensors in a bi-dimensional known airfoil. This study goes through the process of determining the sensor position in order to observe the transition area by using a computational fluid dynamics (CFD) statistic approach. The validation of the laminar to turbulent transition position is carried out with a series of wind tunnel tests. A structural test has been executed in order to validate the wing structure. This Master's thesis shows the data acquisition system for the microstrain measurement installed inside the morphing wing. A hardware and software architecture description is developed and presented as well as the practical results.
Danquechin Dorval, Antoine; Meredieu, Céline; Danjon, Frédéric
2016-01-01
Background and Aims Storms can cause huge damage to European forests. Even pole-stage trees with 80-cm rooting depth can topple. Therefore, good anchorage is needed for trees to survive and grow up from an early age. We hypothesized that root architecture is a predominant factor determining anchorage failure caused by strong winds. Methods We sampled 48 seeded or planted Pinus pinaster trees of similar aerial size from four stands damaged by a major storm 3 years before. The trees were gathered into three classes: undamaged, leaning and heavily toppled. After uprooting and 3D digitizing of their full root architectures, we computed the mechanical characteristics of the main components of the root system from our morphological measurements. Key Results Variability in root architecture was quite large. A large main taproot, either short and thick or long and thin, and guyed by a large volume of deep roots, was the major component that prevented stem leaning. Greater shallow root flexural stiffness mainly at the end of the zone of rapid taper on the windward side also prevented leaning. Toppling in less than 90-cm-deep soil was avoided in trees with a stocky taproots or with a very big leeward shallow root. Toppled trees also had a lower relative root biomass – stump excluded – than straight trees. Conclusions It was mainly the flexural stiffness of the central part of the root system that secured anchorage, preventing a weak displacement of the stump. The distal part of the longest taproot and attached deep roots may be the only parts of the root system contributing to anchorage through their maximum tensile load. Several designs provided good anchorage, depending partly on available soil depth. Pole-stage trees are in-between the juvenile phase when they fail by toppling and the mature phase when they fail by uprooting. PMID:27456136
Clément, Julien; Dumas, Raphaël; Hagemeister, Nicola; de Guise, Jaques A
2015-11-05
Soft tissue artifact (STA) distort marker-based knee kinematics measures and make them difficult to use in clinical practice. None of the current methods designed to compensate for STA is suitable, but multi-body optimization (MBO) has demonstrated encouraging results and can be improved. The goal of this study was to develop and validate the performance of knee joint models, with anatomical and subject-specific kinematic constraints, used in MBO to reduce STA errors. Twenty subjects were recruited: 10 healthy and 10 osteoarthritis (OA) subjects. Subject-specific knee joint models were evaluated by comparing dynamic knee kinematics recorded by a motion capture system (KneeKG™) and optimized with MBO to quasi-static knee kinematics measured by a low-dose, upright, biplanar radiographic imaging system (EOS(®)). Errors due to STA ranged from 1.6° to 22.4° for knee rotations and from 0.8 mm to 14.9 mm for knee displacements in healthy and OA subjects. Subject-specific knee joint models were most effective in compensating for STA in terms of abduction-adduction, inter-external rotation and antero-posterior displacement. Root mean square errors with subject-specific knee joint models ranged from 2.2±1.2° to 6.0±3.9° for knee rotations and from 2.4±1.1 mm to 4.3±2.4 mm for knee displacements in healthy and OA subjects, respectively. Our study shows that MBO can be improved with subject-specific knee joint models, and that the quality of the motion capture calibration is critical. Future investigations should focus on more refined knee joint models to reproduce specific OA knee geometry and physiology. Copyright © 2015 Elsevier Ltd. All rights reserved.
Initial Development of an Electronic Testis Rigidity Tester
Directory of Open Access Journals (Sweden)
Petros Mirilas
2011-01-01
Full Text Available We aimed to develop our previously presented mechanical device, the Testis Rigidity Tester (TRT, into an electronic system (Electronic Testis Rigidity Tester, ETRT by applying tactile imaging, which has been used successfully with other solid organs. A measuring device, located at the front end of the ETRT incorporates a tactile sensor comprising an array of microsensors. By application of a predetermined deformation of 2 mm, increased pressure alters linearly the resistance of each microsensor, producing changes of voltage. These signals were amplified, filtered, and digitized, and then processed by an electronic collector system, which presented them as a color-filled contour plot of the area of the testis coming into contact with the sensor. Testis models of different rigidity served for initial evaluation of ETRT; their evacuated central spaces contained different, increasing glue masses. An independent method of rigidity measurement, using an electric weight scale and a micrometer, showed that the more the glue injected, the greater the force needed for a 2-mm deformation. In a preliminary test, a single sensor connected to a multimeter showed similar force measurement for the same deformation in these phantoms. For each of the testis models compressed in the same manner, the ETRT system offered a map of pressures, represented by a color scale within the contour plot of the contact area with the sensor. ETRT found certain differences in rigidity between models that had escaped detection by a blind observer. ETRT is easy to use and provides a color-coded “insight“ of the testis internal structure. After experimental testing, it could be valuable in intraoperative evaluation of testes, so that the surgeon can decide about orchectomy or orcheopexy.
DEFF Research Database (Denmark)
Jørgensen, Martin Felix; Pedersen, Niels Leergaard; Sørensen, Jens Nørkær
2014-01-01
multiple planetary gears are not taken into account. Finite Element Method (FEM) calculations show that when the wind turbine runs close to the maximum wind speed, the maximum gear tooth stress is in the range of 500–700 MPa, which is considered to be realistic using a “worst-case” method. The presented...... for not only transferring torque but also for calculating the gear tooth and internal body reaction forces. The method is appropriate for predicting gear tooth stresses without considering all the complexity of gear tooth geometries. This means that, e.g. gear tooth load-sharing and load-distribution among...
Strategic rigidity and foresight for technology adoption among electric utilities
International Nuclear Information System (INIS)
Shah, Arsalan Nisar; Palacios, Miguel; Ruiz, Felipe
2013-01-01
The variation in the adoption of a technology as a major source of competitive advantage has been attributed to the wide-ranging strategic foresight and the integrative capability of a firm. These possible areas of competitive advantage can exist in the periphery of the firm's strategic vision and can get easily blurred as a result of rigidness and can permeate in the decision-making process of the firm. This article explores how electric utility firms with a renewable energy portfolio can become strategically rigid in terms of adoption of newer technologies. The reluctance or delay in the adoption of new technology can be characterized as strategic rigidness, brought upon as a result of a firm's core competence or core capability in the other, more conventional technology arrangement. This paper explores the implications of such rigidness on the performance of a firm and consequently on the energy eco-system. The paper substantiates the results by emphasizing the case of Iberdrola S.A., an incumbent firm as a wind energy developer and its adoption decision behavior. We illustrate that the very routines that create competitive advantage for firms in the electric utility industry are vulnerable as they might also develop as sources of competitive disadvantage, when firms confront environmental change and uncertainty. - Highlights: • Present a firm-level perspective on technology adoption behavior among electric utilities. • Firms with mature technology can become rigid towards newer technologies. • Case study analysis of a major electric utility firm. • Implications of ‘technology rigidness’ on the energy eco-system
Rigid pricing and rationally inattentive consumer
Czech Academy of Sciences Publication Activity Database
Matějka, Filip
158 B, July (2015), s. 656-678 ISSN 0022-0531 Institutional support: PRVOUK-P23 Keywords : rational inattention * imperfect information * nominal rigidity Subject RIV: AH - Economics Impact factor: 1.097, year: 2015
Rigid pricing and rationally inattentive consumer
Czech Academy of Sciences Publication Activity Database
Matějka, Filip
158 B, July (2015), s. 656-678 ISSN 0022-0531 Institutional support: RVO:67985998 Keywords : rational inattention * imperfect information * nominal rigidity Subject RIV: AH - Economics Impact factor: 1.097, year: 2015
Crack identification for rigid pavements using unmanned aerial vehicles
Bahaddin Ersoz, Ahmet; Pekcan, Onur; Teke, Turker
2017-09-01
Pavement condition assessment is an essential piece of modern pavement management systems as rehabilitation strategies are planned based upon its outcomes. For proper evaluation of existing pavements, they must be continuously and effectively monitored using practical means. Conventionally, truck-based pavement monitoring systems have been in-use in assessing the remaining life of in-service pavements. Although such systems produce accurate results, their use can be expensive and data processing can be time consuming, which make them infeasible considering the demand for quick pavement evaluation. To overcome such problems, Unmanned Aerial Vehicles (UAVs) can be used as an alternative as they are relatively cheaper and easier-to-use. In this study, we propose a UAV based pavement crack identification system for monitoring rigid pavements’ existing conditions. The system consists of recently introduced image processing algorithms used together with conventional machine learning techniques, both of which are used to perform detection of cracks on rigid pavements’ surface and their classification. Through image processing, the distinct features of labelled crack bodies are first obtained from the UAV based images and then used for training of a Support Vector Machine (SVM) model. The performance of the developed SVM model was assessed with a field study performed along a rigid pavement exposed to low traffic and serious temperature changes. Available cracks were classified using the UAV based system and obtained results indicate it ensures a good alternative solution for pavement monitoring applications.
On the modeling of the intervertebral joint in multibody models for the spine
International Nuclear Information System (INIS)
Christophy, Miguel; Curtin, Maurice; Faruk Senan, Nur Adila; Lotz, Jeffrey C.; O’Reilly, Oliver M.
2013-01-01
The need to develop feasible computational musculoskeletal models of the spine has led to the development of several multibody models. Central features in these works are models for the ligaments, muscles, and intervertebral joint. The purpose of the present paper is to show how experimental measurements of joint stiffnesses can be properly incorporated using a bushing element. The required refinements to existing bushing force functions in musculoskeletal software platforms are discussed and further implemented using a SpineBushing element specific to the intervertebral joint. Four simple lumbar spine models are then used to illustrate the accompanying improvements. Electronic supplemental material for this article includes a complementary review of formulations of stiffness matrices for the intervertebral joint
Weak decays of doubly heavy baryons. Multi-body decay channels
Energy Technology Data Exchange (ETDEWEB)
Shi, Yu-Ji; Wang, Wei; Xing, Ye; Xu, Ji [Shanghai Jiao Tong University, INPAC, Shanghai Key Laboratory for Particle Physics and Cosmology, MOE Key Laboratory for Particle Physics, Astrophysics and Cosmology, School of Physics and Astronomy, Shanghai (China)
2018-01-15
The newly-discovered Ξ{sub cc}{sup ++} decays into the Λ{sub c}{sup +}K{sup -}π{sup +}π{sup +}, but the experimental data has indicated that this decay is not saturated by any two-body intermediate state. In this work, we analyze the multi-body weak decays of doubly heavy baryons Ξ{sub cc}, Ω{sub cc}, Ξ{sub bc}, Ω{sub bc}, Ξ{sub bb} and Ω{sub bb}, in particular the three-body nonleptonic decays and four-body semileptonic decays. We classify various decay modes according to the quark-level transitions and present an estimate of the typical branching fractions for a few golden decay channels. Decay amplitudes are then parametrized in terms of a few SU(3) irreducible amplitudes. With these amplitudes, we find a number of relations for decay widths, which can be examined in future. (orig.)
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...
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.
Flexible and rigid cystoscopy in women.
Gee, Jason R; Waterman, Bradley J; Jarrard, David F; Hedican, Sean P; Bruskewitz, Reginald C; Nakada, Stephen Y
2009-01-01
Previous studies have evaluated the tolerability of rigid versus flexible cystoscopy in men. Similar studies, however, have not been performed in women. We sought to determine whether office-based flexible cystoscopy was better tolerated than rigid cystoscopy in women. Following full IRB approval, women were prospectively randomized in a single-blind manner. Patients were randomized to flexible or rigid cystoscopy and draped in the lithotomy position to maintain blinding of the study. Questionnaires evaluated discomfort before, during, and after cystoscopy. Thirty-six women were randomized to flexible (18) or rigid (18) cystoscopy. Indications were surveillance (16), hematuria (15), recurrent UTIs (2), voiding dysfunction (1), and other (2). All questionnaires were returned by 31/36 women. Using a 10-point visual analog scale (VAS), median discomfort during the procedure for flexible and rigid cystoscopy were 1.4 and 1.8, respectively, in patients perceiving pain. Median recalled pain 1 week later was similar at 0.8 and 1.15, respectively. None of these differences were statistically significant. Flexible and rigid cystoscopy are well tolerated in women. Discomfort during and after the procedure is minimal in both groups. Urologists should perform either procedure in women based on their preference and skill level.
Determination of Weight Suspension Rigidity in the Transport-Erector Aggregates
Directory of Open Access Journals (Sweden)
V. A. Zverev
2016-01-01
Full Text Available The aim is to determine weight suspension rigidity in aggregates designed to perform technological transport-erector operations at the miscellaneous launch complexes.We consider the weight suspension comprising the following distinctive structural components: the executive weight-lowering mechanism, polyspast mechanism, rope, traverse, and rods. A created structural dynamic model of suspension allowed us to define weight suspension rigidity. Within the framework of design analysis of a dynamic model we determined the rigidity of its structural units, i.e. traverse, rope, and polyspast.Known analytical relationships were used to calculate the rope rigidity. To determine rigidity of polyspast and traverse have been created special models based on the finite element method. For each model deformation in the specific points under the test load have been defined. Data obtained were used to determine trigidity of traverses and polyspast, and also rigidity of suspension in total. The rigidity models of polispast mechanism and traverse have been developed and calculated using the software complex "Zenit-95".As the research results, the paper presents a dynamic model of the weight suspension of the transport-erector aggregate, the finite element models of the polispast mechanism and traverse, an algorithm for determining the weight suspension rigidity and relevant analytical relationships.Independent calculation of weight suspension rigidity enables us to simplify further dynamic calculation of the aggregate-weight system because it allows attaining a simpler model of the aggregate-weight system that uses the weight suspension model as an element of equivalent rigidity. Despite this simplification the model allows us to determine correctly weight movement parameters and overloads in the aggregate-weight system in the process of technical operations.
H infinity controller design to a rigid-flexible satellite with two vibration modes
International Nuclear Information System (INIS)
De Souza, A G; De Souza, L C G
2015-01-01
The satellite attitude control system (ACS) design becomes more complex when the satellite structure has components like, flexible solar panels, antennas and mechanical manipulators. These flexible structures can interact with the satellite rigid parts during translational and/or rotational manoeuvre damaging the ACS pointing accuracy. Although, a well-designed controller can suppress such disturbances quickly, the controller error pointing may be limited by the minimum time necessary to suppress such disturbances thus affecting the satellite attitude acquisition. This paper deals with the rigid-flexible satellite ACS design using the H infinity method. The rigid-flexible satellite is represented by a beam connected to a central rigid hub at one end and free at the other one. The equations of motions are obtained considering small flexible deformations and the Euler-Bernoulli hypothesis. The results of the simulations have shown that the H-infinity controller was able to control the rigid motion and suppress the vibrations. (paper)
Matrix rigidity regulates cancer cell growth and cellular phenotype.
Directory of Open Access Journals (Sweden)
Robert W Tilghman
2010-09-01
Full Text Available The mechanical properties of the extracellular matrix have an important role in cell growth and differentiation. However, it is unclear as to what extent cancer cells respond to changes in the mechanical properties (rigidity/stiffness of the microenvironment and how this response varies among cancer cell lines.In this study we used a recently developed 96-well plate system that arrays extracellular matrix-conjugated polyacrylamide gels that increase in stiffness by at least 50-fold across the plate. This plate was used to determine how changes in the rigidity of the extracellular matrix modulate the biological properties of tumor cells. The cell lines tested fall into one of two categories based on their proliferation on substrates of differing stiffness: "rigidity dependent" (those which show an increase in cell growth as extracellular rigidity is increased, and "rigidity independent" (those which grow equally on both soft and stiff substrates. Cells which grew poorly on soft gels also showed decreased spreading and migration under these conditions. More importantly, seeding the cell lines into the lungs of nude mice revealed that the ability of cells to grow on soft gels in vitro correlated with their ability to grow in a soft tissue environment in vivo. The lung carcinoma line A549 responded to culture on soft gels by expressing the differentiated epithelial marker E-cadherin and decreasing the expression of the mesenchymal transcription factor Slug.These observations suggest that the mechanical properties of the matrix environment play a significant role in regulating the proliferation and the morphological properties of cancer cells. Further, the multiwell format of the soft-plate assay is a useful and effective adjunct to established 3-dimensional cell culture models.
Matrix Rigidity Regulates Cancer Cell Growth and Cellular Phenotype
Tilghman, Robert W.; Cowan, Catharine R.; Mih, Justin D.; Koryakina, Yulia; Gioeli, Daniel; Slack-Davis, Jill K.; Blackman, Brett R.; Tschumperlin, Daniel J.; Parsons, J. Thomas
2010-01-01
Background The mechanical properties of the extracellular matrix have an important role in cell growth and differentiation. However, it is unclear as to what extent cancer cells respond to changes in the mechanical properties (rigidity/stiffness) of the microenvironment and how this response varies among cancer cell lines. Methodology/Principal Findings In this study we used a recently developed 96-well plate system that arrays extracellular matrix-conjugated polyacrylamide gels that increase in stiffness by at least 50-fold across the plate. This plate was used to determine how changes in the rigidity of the extracellular matrix modulate the biological properties of tumor cells. The cell lines tested fall into one of two categories based on their proliferation on substrates of differing stiffness: “rigidity dependent” (those which show an increase in cell growth as extracellular rigidity is increased), and “rigidity independent” (those which grow equally on both soft and stiff substrates). Cells which grew poorly on soft gels also showed decreased spreading and migration under these conditions. More importantly, seeding the cell lines into the lungs of nude mice revealed that the ability of cells to grow on soft gels in vitro correlated with their ability to grow in a soft tissue environment in vivo. The lung carcinoma line A549 responded to culture on soft gels by expressing the differentiated epithelial marker E-cadherin and decreasing the expression of the mesenchymal transcription factor Slug. Conclusions/Significance These observations suggest that the mechanical properties of the matrix environment play a significant role in regulating the proliferation and the morphological properties of cancer cells. Further, the multiwell format of the soft-plate assay is a useful and effective adjunct to established 3-dimensional cell culture models. PMID:20886123
Rigid Body Sampling and Individual Time Stepping for Rigid-Fluid Coupling of Fluid Simulation
Directory of Open Access Journals (Sweden)
Xiaokun Wang
2017-01-01
Full Text Available In this paper, we propose an efficient and simple rigid-fluid coupling scheme with scientific programming algorithms for particle-based fluid simulation and three-dimensional visualization. Our approach samples the surface of rigid bodies with boundary particles that interact with fluids. It contains two procedures, that is, surface sampling and sampling relaxation, which insures uniform distribution of particles with less iterations. Furthermore, we present a rigid-fluid coupling scheme integrating individual time stepping to rigid-fluid coupling, which gains an obvious speedup compared to previous method. The experimental results demonstrate the effectiveness of our approach.
Spontaneous droplet trampolining on rigid superhydrophobic surfaces
Schutzius, Thomas M.; Jung, Stefan; Maitra, Tanmoy; Graeber, Gustav; Köhme, Moritz; Poulikakos, Dimos
2015-11-01
Spontaneous removal of condensed matter from surfaces is exploited in nature and in a broad range of technologies to achieve self-cleaning, anti-icing and condensation control. But despite much progress, our understanding of the phenomena leading to such behaviour remains incomplete, which makes it challenging to rationally design surfaces that benefit from its manifestation. Here we show that water droplets resting on superhydrophobic textured surfaces in a low-pressure environment can self-remove through sudden spontaneous levitation and subsequent trampoline-like bouncing behaviour, in which sequential collisions with the surface accelerate the droplets. These collisions have restitution coefficients (ratios of relative speeds after and before collision) greater than unity despite complete rigidity of the surface, and thus seemingly violate the second law of thermodynamics. However, these restitution coefficients result from an overpressure beneath the droplet produced by fast droplet vaporization while substrate adhesion and surface texture restrict vapour flow. We also show that the high vaporization rates experienced by the droplets and the associated cooling can result in freezing from a supercooled state that triggers a sudden increase in vaporization, which in turn boosts the levitation process. This effect can spontaneously remove surface icing by lifting away icy drops the moment they freeze. Although these observations are relevant only to systems in a low-pressure environment, they show how surface texturing can produce droplet-surface interactions that prohibit liquid and freezing water-droplet retention on surfaces.
Nonlinear dynamics mathematical models for rigid bodies with a liquid
Lukovsky, Ivan A
2015-01-01
This book is devoted to analytically approximate methods in the nonlinear dynamics of a rigid body with cavities partly filled by liquid. It combines several methods and compares the results with experimental data. It is useful for experienced and early-stage readers interested in analytical approaches to fluid-structure interaction problems, the fundamental mathematical background and modeling the dynamics of such complex mechanical systems.
Polyester Polyols from Waste PET Bottles for Polyurethane Rigid Foams
Evtimova, Rozeta; Lozeva, Yordanka; Schmidt, Karl-Heinz; Wotzka, Michael; Wagner, Peter; Behrendt, Gerhard
2003-01-01
This paper describes a modified process to produce polyester polyols from PET wastes derived from the “bottle fraction residue” of the German Dual System (DSD) [11] employing a waste oligoester condensate of the polyesterification process with the addition of some glycols of longer chain and occasional modification with further dicarboxylic acids to produce polyester polyols of a broad range of properties which are further reacted to form polyurethane or polyisocyanurate rigid foams for insul...
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.
Market structure, price rigidity, and performance in the Indonesian food and beverages industry
Setiawan, M.
2012-01-01
Keywords: industrial concentration, price rigidity, technical efficiency, price-cost margin, Structure-Conduct-Performance (SCP), new empirical industrial organization (NEIO), Indonesian food and beverages industry, Data Envelopment Analysis (DEA), system of equations
National Research Council Canada - National Science Library
Hammons, Michael
1998-01-01
.... The objective of this research was to obtain data on the response of the ng'id pavement slab-joint-foundation system by conducting laboratory-scale experiments on jointed rigid pavement models...
Identifying Floppy and Rigid Regions in Proteins
Jacobs, D. J.; Thorpe, M. F.; Kuhn, L. A.
1998-03-01
In proteins it is possible to separate hard covalent forces involving bond lengths and bond angles from other weak forces. We model the microstructure of the protein as a generic bar-joint truss framework, where the hard covalent forces and strong hydrogen bonds are regarded as rigid bar constraints. We study the mechanical stability of proteins using FIRST (Floppy Inclusions and Rigid Substructure Topography) based on a recently developed combinatorial constraint counting algorithm (the 3D Pebble Game), which is a generalization of the 2D pebble game (D. J. Jacobs and M. F. Thorpe, ``Generic Rigidity: The Pebble Game'', Phys. Rev. Lett.) 75, 4051-4054 (1995) for the special class of bond-bending networks (D. J. Jacobs, "Generic Rigidity in Three Dimensional Bond-bending Networks", Preprint Aug (1997)). This approach is useful in identifying rigid motifs and flexible linkages in proteins, and thereby determines the essential degrees of freedom. We will show some preliminary results from the FIRST analysis on the myohemerythrin and lyozyme proteins.
Euler-Poincare Reduction of Externall Forced Rigid Body Motion
DEFF Research Database (Denmark)
Wisniewski, Rafal; Kulczycki, P.
2004-01-01
If a mechanical system experiences symmetry, the Lagrangian becomes invariant under a certain group action. This property leads to substantial simplification of the description of movement. The standpoint in this article is a mechanical system affected by an external force of a control action....... Assuming that the system possesses symmetry and the configuration manifold corresponds to a Lie group, the Euler-Poincaré reduction breaks up the motion into separate equations of dynamics and kinematics. This becomes of particular interest for modelling, estimation and control of mechanical systems......-known Euler-Poincaré reduction to a rigid body motion with forcing....
Euler-Poincare Reduction of a Rigid Body Motion
DEFF Research Database (Denmark)
Wisniewski, Rafal; Kulczycki, P.
2005-01-01
|If a mechanical system experiences symmetry, the Lagrangian becomes invariant under a certain group action. This property leads to substantial simplification of the description of movement. The standpoint in this article is a mechanical system afected by an external force of a control action....... Assuming that the system possesses symmetry and the configuration manifold corresponds to a Lie group, the Euler-Poincare reduction breaks up the motion into separate equations of dynamics and kinematics. This becomes of particular interest for modeling, estimation and control of mechanical systems......-known Euler-Poincare reduction to a rigid body motion with forcing....
Euler-Poincaré Reduction of a Rigid Body Motion
DEFF Research Database (Denmark)
Wisniewski, Rafal; Kulczycki, P.
2004-01-01
If a mechanical system experiences symmetry, the Lagrangian becomes invariant under a certain group action. This property leads to substantial simplification of the description of movement. The standpoint in this article is a mechanical system affected by an external force of a control action....... Assuming that the system possesses symmetry and the configuration manifold corresponds to a Lie group, the Euler-Poincaré reduction breaks up the motion into separate equations of dynamics and kinematics. This becomes of particular interest for modelling, estimation and control of mechanical systems......-known Euler-Poincaré reduction to a rigid body motion with forcing....
Sattar, M.; Wei, C.; Jalali, A.; Sattar, R.
2017-07-01
To address the impact of solar array (SA) anomalies and vibrations on performance of precision space-based operations, it is important to complete its accurate jitter analysis. This work provides mathematical modelling scheme to approximate kinematics and coupled micro disturbance dynamics of rigid load supported and operated by solar array drive assembly (SADA). SADA employed in analysis provides a step wave excitation torque to activate the system. Analytical investigations into kinematics is accomplished by using generalized linear and Euler angle coordinates, applying multi-body dynamics concepts and transformations principles. Theoretical model is extended, to develop equations of motion (EoM), through energy method (Lagrange equation). The main emphasis is to research coupled frequency response by determining energies dissipated and observing dynamic behaviour of internal vibratory systems of SADA. The disturbance model captures discrete active harmonics of SADA, natural modes and vibration amplifications caused by interactions between active harmonics and structural modes of mechanical assembly. The proposed methodology can help to predict true micro disturbance nature of SADA operating rigid load. Moreover, performance outputs may be compared against actual mission requirements to assess precise spacecraft controller design to meet next space generation stringent accuracy goals.
Chen, Shanzhen; Gersabeck, Marco
This thesis presents two searches for direct charge-parity ($CP$) violation in multi-body decays in the charm-sector at LHCb, the development of techniques for performing model-independent searches for direct $CP$ violation in multi-body decays, and the development of studies of radiation damage effects in the LHCb vertex detector. LHCb is a dedicated experiment to study New Physics in the decays of heavy hadrons at the Large Hadron Collider (LHC) at CERN. The detector includes a high precision vertex detector surrounding the $pp$ interaction region made with silicon strip sensors. Studies of the effects of radiation damage in LHC run-2 for the operation of this detector are presented and the determination of the operational bias voltages of the silicon strip sensors is discussed. An unbinned model independent technique for $CP$ violation searches in multi-body decays called the energy test is used for the first time. The selection and treatment of the coordinates used to describe the phase-space of the de...
Quantum mechanics of a generalised rigid body
International Nuclear Information System (INIS)
Gripaios, Ben; Sutherland, Dave
2016-01-01
We consider the quantum version of Arnold’s generalisation of a rigid body in classical mechanics. Thus, we quantise the motion on an arbitrary Lie group manifold of a particle whose classical trajectories correspond to the geodesics of any one-sided-invariant metric. We show how the derivation of the spectrum of energy eigenstates can be simplified by making use of automorphisms of the Lie algebra and (for groups of type I) by methods of harmonic analysis. We show how the method can be extended to cosets, generalising the linear rigid rotor. As examples, we consider all connected and simply connected Lie groups up to dimension 3. This includes the universal cover of the archetypical rigid body, along with a number of new exactly solvable models. We also discuss a possible application to the topical problem of quantising a perfect fluid. (paper)
Durable bistable auxetics made of rigid solids
Shang, Xiao; Liu, Lu; Rafsanjani, Ahmad; Pasini, Damiano
2018-02-01
Bistable Auxetic Metamaterials (BAMs) are a class of monolithic perforated periodic structures with negative Poisson's ratio. Under tension, a BAM can expand and reach a second state of equilibrium through a globally large shape transformation that is ensured by the flexibility of its elastomeric base material. However, if made from a rigid polymer, or metal, BAM ceases to function due to the inevitable rupture of its ligaments. The goal of this work is to extend the unique functionality of the original kirigami architecture of BAM to a rigid solid base material. We use experiments and numerical simulations to assess performance, bistability and durability of rigid BAMs at 10,000 cycles. Geometric maps are presented to elucidate the role of the main descriptors of BAM architecture. The proposed design enables the realization of BAM from a large palette of materials, including elastic-perfectly plastic materials and potentially brittle materials.
Handedness in shearing auxetics creates rigid and compliant structures
Lipton, Jeffrey Ian; MacCurdy, Robert; Manchester, Zachary; Chin, Lillian; Cellucci, Daniel; Rus, Daniela
2018-05-01
In nature, repeated base units produce handed structures that selectively bond to make rigid or compliant materials. Auxetic tilings are scale-independent frameworks made from repeated unit cells that expand under tension. We discovered how to produce handedness in auxetic unit cells that shear as they expand by changing the symmetries and alignments of auxetic tilings. Using the symmetry and alignment rules that we developed, we made handed shearing auxetics that tile planes, cylinders, and spheres. By compositing the handed shearing auxetics in a manner inspired by keratin and collagen, we produce both compliant structures that expand while twisting and deployable structures that can rigidly lock. This work opens up new possibilities in designing chemical frameworks, medical devices like stents, robotic systems, and deployable engineering structures.
Effect of rigid inclusions on sintering
International Nuclear Information System (INIS)
Rahaman, M.N.; De Jonghe, L.C.
1988-01-01
The predictions of recent theoretical studies on the effect of inert, rigid inclusions on the sintering of ceramic powder matrices are examined and compared with experimental data. The densification of glass matrix composites with inclusion volume fractions of ≤0.15 can be adequately explained by Scherer's theory for viscous sintering with rigid inclusions. Inclusions cause a vast reduction in the densification rates of polycrystalline matrix composites even at low inclusion volume fractions. Models put forward to explain the sintering of polycrystalline matrix composites are discussed
Type number and rigidity of fibred surfaces
International Nuclear Information System (INIS)
Markov, P E
2001-01-01
Infinitesimal l-th order bendings, 1≤l≤∞, of higher-dimensional surfaces are considered in higher-dimensional flat spaces (for l=∞ an infinitesimal bending is assumed to be an analytic bending). In terms of the Allendoerfer type number, criteria are established for the (r,l)-rigidity (in the terminology of Sabitov) of such surfaces. In particular, an (r,l)-infinitesimal analogue is proved of the classical theorem of Allendoerfer on the unbendability of surfaces with type number ≥3 and the class of (r,l)-rigid fibred surfaces is distinguished
Rigid origami vertices: conditions and forcing sets
Directory of Open Access Journals (Sweden)
Zachary Abel
2016-04-01
Full Text Available We develop an intrinsic necessary and sufficient condition for single-vertex origami crease patterns to be able to fold rigidly. We classify such patterns in the case where the creases are pre-assigned to be mountains and valleys as well as in the unassigned case. We also illustrate the utility of this result by applying it to the new concept of minimal forcing sets for rigid origami models, which are the smallest collection of creases that, when folded, will force all the other creases to fold in a prescribed way.
Evaluating a method for automated rigid registration
DEFF Research Database (Denmark)
Darkner, Sune; Vester-Christensen, Martin; Larsen, Rasmus
2007-01-01
to point distance. T-test for common mean are used to determine the performance of the two methods (supported by a Wilcoxon signed rank test). The performance influence of sampling density, sampling quantity, and norms is analyzed using a similar method.......We evaluate a novel method for fully automated rigid registration of 2D manifolds in 3D space based on distance maps, the Gibbs sampler and Iterated Conditional Modes (ICM). The method is tested against the ICP considered as the gold standard for automated rigid registration. Furthermore...
A rigidity transition and glassy dynamics in a model for confluent 3D tissues
Merkel, Matthias; Manning, M. Lisa
The origin of rigidity in disordered materials is an outstanding open problem in statistical physics. Recently, a new type of rigidity transition was discovered in a family of models for 2D biological tissues, but the mechanisms responsible for rigidity remain unclear. This is not just a statistical physics problem, but also relevant for embryonic development, cancer growth, and wound healing. To gain insight into this rigidity transition and make new predictions about biological bulk tissues, we have developed a fully 3D self-propelled Voronoi (SPV) model. The model takes into account shape, elasticity, and self-propelled motion of the individual cells. We find that in the absence of self-propulsion, this model exhibits a rigidity transition that is controlled by a dimensionless model parameter describing the preferred cell shape, with an accompanying structural order parameter. In the presence of self-propulsion, the rigidity transition appears as a glass-like transition featuring caging and aging effects. Given the similarities between this transition and jamming in particulate solids, it is natural to ask if the two transitions are related. By comparing statistics of Voronoi geometries, we show the transitions are surprisingly close but demonstrably distinct. Furthermore, an index theorem used to identify topologically protected mechanical modes in jammed systems can be extended to these vertex-type models. In our model, residual stresses govern the transition and enter the index theorem in a different way compared to jammed particles, suggesting the origin of rigidity may be different between the two.
Combinatorial and Algorithmic Rigidity: Beyond Two Dimensions
2012-12-01
44]. Theorems of Maxwell- Laman type were ob- tained in [9, 15, 43]. 2 3. Counting and Enumeration. As anticipated in the project, we relied on methods...decompositions. Graphs and Combinatorics, 25:219–238, 2009. [43] I. Streinu and L. Theran. Slider-pinning rigidity: a Maxwell- Laman -type theorem. Discrete and
Birationally rigid varieties. I. Fano varieties
International Nuclear Information System (INIS)
Pukhlikov, A V
2007-01-01
The theory of birational rigidity of rationally connected varieties generalises the classical rationality problem. This paper gives a survey of the current state of this theory and traces its history from Noether's theorem and the Lueroth problem to the latest results on the birational superrigidity of higher-dimensional Fano varieties. The main components of the method of maximal singularities are considered.
Rigid polyurethane and kenaf core composite foams
Rigid polyurethane foams are valuable in many construction applications. Kenaf is a bast fiber plant where the surface stem skin provides bast fibers whose strength-to-weight ratio competes with glass fiber. The higher volume product of the kenaf core is an under-investigated area in composite appli...
Rigidity Sensing Explained by Active Matter Theory
Marcq, Philippe; Yoshinaga, Natsuhiko; Prost, Jacques
2011-01-01
The magnitude of traction forces exerted by living animal cells on their environment is a monotonically increasing and approximately sigmoidal function of the stiffness of the external medium. We rationalize this observation using active matter theory, and propose that adaptation to substrate rigidity results from an interplay between passive elasticity and active contractility.
About deformation and rigidity in relativity
International Nuclear Information System (INIS)
Coll, Bartolome
2007-01-01
The notion of deformation involves that of rigidity. In relativity, starting from Born's early definition of rigidity, some other ones have been proposed, offering more or less interesting aspects but also accompanied of undesired or even pathological properties. In order to clarify the origin of these difficulties presented by the notion of rigidity in relativity, we analyze with some detail significant aspects of the unambiguous classical, Newtonian, notion. In particular, the relative character of its kinetic definition is pointed out, allowing to predict and to understand the limitations imposed by Herglotz-Noether theorem. Also, its equivalent dynamic definition is obtained and, in contrast, its absolute character is shown. But in spite of this absolute character, the dynamic definition is shown to be not extensible to relativity. The metric deformation of Minkowski space by the presence of a gravitational field is interpreted as a universal deformation, and it is shown that, under natural conditions, only a simple deformation law is possible, relating locally, but in an one-to-one way, gravitational fields and gauge classes of two-forms. We argue that fields of unit vectors associated to the internal gauge class of two-forms of every space-time (and, in particular, of Minkowski space-time) are the relativistic analogues of the classical accelerated observers, i.e. of the classical rigid motions. Some other consequences of the universal law of gravitational deformation are commented
Rigid pricing and rationally inattentive consumer
Czech Academy of Sciences Publication Activity Database
Matějka, Filip
2010-01-01
Roč. 20, č. 2 (2010), s. 1-40 ISSN 1211-3298 R&D Projects: GA MŠk LC542 Institutional research plan: CEZ:AV0Z70850503 Keywords : rational inattention * nominal rigidity Subject RIV: AH - Economics http://www.cerge-ei.cz/pdf/wp/Wp409.pdf
Rigid Spine Syndrome among Children in Oman
Directory of Open Access Journals (Sweden)
Roshan Koul
2015-08-01
Full Text Available Objectives: Rigidity of the spine is common in adults but is rarely observed in children. The aim of this study was to report on rigid spine syndrome (RSS among children in Oman. Methods: Data on children diagnosed with RSS were collected consecutively at presentation between 1996 and 2014 at the Sultan Qaboos University Hospital (SQUH in Muscat, Oman. A diagnosis of RSS was based on the patient’s history, clinical examination, biochemical investigations, electrophysiological findings, neuro-imaging and muscle biopsy. Atrophy of the paraspinal muscles, particularly the erector spinae, was the diagnostic feature; this was noted using magnetic resonance imaging of the spine. Children with disease onset in the paraspinal muscles were labelled as having primary RSS or rigid spinal muscular dystrophy. Secondary RSS was classified as RSS due to the late involvement of other muscle diseases. Results: Over the 18-year period, 12 children were included in the study, with a maleto- female ratio of 9:3. A total of 10 children were found to have primary RSS or rigid spinal muscular dystrophy syndrome while two had secondary RSS. Onset of the disease ranged from birth to 18 months of age. A family history was noted, with two siblings from one family and three siblings from another (n = 5. On examination, children with primary RSS had typical features of severe spine rigidity at onset, with the rest of the neurological examination being normal. Conclusion: RSS is a rare disease with only 12 reported cases found at SQUH during the study period. Cases of primary RSS should be differentiated from the secondary type.
Yew, Alvin G.; Chai, Dean J.; Olney, David J.
2010-01-01
The goal of NASA's Magnetospheric MultiScale (MMS) mission is to understand magnetic reconnection with sensor measurements from four spinning satellites flown in a tight tetrahedron formation. Four of the six electric field sensors on each satellite are located at the end of 60- meter wire booms to increase measurement sensitivity in the spin plane and to minimize motion coupling from perturbations on the main body. A propulsion burn however, might induce boom oscillations that could impact science measurements if oscillations do not damp to values on the order of 0.1 degree in a timely fashion. Large damping time constants could also adversely affect flight dynamics and attitude control performance. In this paper, we will discuss the implementation of a high resolution method for calculating the boom's intrinsic damping, which was used in multi-body dynamics simulations. In summary, experimental data was obtained with a scaled-down boom, which was suspended as a pendulum in vacuum. Optical techniques were designed to accurately measure the natural decay of angular position and subsequently, data processing algorithms resulted in excellent spatial and temporal resolutions. This method was repeated in a parametric study for various lengths, root tensions and vacuum levels. For all data sets, regression models for damping were applied, including: nonlinear viscous, frequency-independent hysteretic, coulomb and some combination of them. Our data analysis and dynamics models have shown that the intrinsic damping for the baseline boom is insufficient, thereby forcing project management to explore mitigation strategies.
Vehicle response-based track geometry assessment using multi-body simulation
Kraft, Sönke; Causse, Julien; Coudert, Frédéric
2018-02-01
The assessment of the geometry of railway tracks is an indispensable requirement for safe rail traffic. Defects which represent a risk for the safety of the train have to be identified and the necessary measures taken. According to current standards, amplitude thresholds are applied to the track geometry parameters measured by recording cars. This geometry-based assessment has proved its value but suffers from the low correlation between the geometry parameters and the vehicle reactions. Experience shows that some defects leading to critical vehicle reactions are underestimated by this approach. The use of vehicle responses in the track geometry assessment process allows identifying critical defects and improving the maintenance operations. This work presents a vehicle response-based assessment method using multi-body simulation. The choice of the relevant operation conditions and the estimation of the simulation uncertainty are outlined. The defects are identified from exceedances of track geometry and vehicle response parameters. They are then classified using clustering methods and the correlation with vehicle response is analysed. The use of vehicle responses allows the detection of critical defects which are not identified from geometry parameters.
Directory of Open Access Journals (Sweden)
William I. Sellers
2017-07-01
Full Text Available The running ability of Tyrannosaurus rex has been intensively studied due to its relevance to interpretations of feeding behaviour and the biomechanics of scaling in giant predatory dinosaurs. Different studies using differing methodologies have produced a very wide range of top speed estimates and there is therefore a need to develop techniques that can improve these predictions. Here we present a new approach that combines two separate biomechanical techniques (multibody dynamic analysis and skeletal stress analysis to demonstrate that true running gaits would probably lead to unacceptably high skeletal loads in T. rex. Combining these two approaches reduces the high-level of uncertainty in previous predictions associated with unknown soft tissue parameters in dinosaurs, and demonstrates that the relatively long limb segments of T. rex—long argued to indicate competent running ability—would actually have mechanically limited this species to walking gaits. Being limited to walking speeds contradicts arguments of high-speed pursuit predation for the largest bipedal dinosaurs like T. rex, and demonstrates the power of multiphysics approaches for locomotor reconstructions of extinct animals.
Almost-global tracking for a rigid body with internal rotors
Nayak, Aradhana; Banavar, Ravi N.
2017-01-01
Almost-global orientation trajectory tracking for a rigid body with external actuation has been well studied in the literature, and in the geometric setting as well. The tracking control law relies on the fact that a rigid body is a simple mechanical system (SMS) on the $3-$dimensional group of special orthogonal matrices. However, the problem of designing feedback control laws for tracking using internal actuation mechanisms, like rotors or control moment gyros, has received lesser attention...
Marco Guerrazzi; Nicola Meccheri
2009-01-01
This paper offers a critical discussion of the concept of labour market rigidity relevant to explaining unemployment. Starting from Keynes’s own view, we discuss how the concept of labour market flexibility has changed over time, involving nominal or real wage flexibility, contract flexibility or labour market institution flexibility. We also provide a critical assessment of the factors that lead the search framework highlighting labour market rigidities (frictions) to challenge the more wide...
Multiscale multiphysics and multidomain models—Flexibility and rigidity
International Nuclear Information System (INIS)
Xia, Kelin; Opron, Kristopher; Wei, Guo-Wei
2013-01-01
The emerging complexity of large macromolecules has led to challenges in their full scale theoretical description and computer simulation. Multiscale multiphysics and multidomain models have been introduced to reduce the number of degrees of freedom while maintaining modeling accuracy and achieving computational efficiency. A total energy functional is constructed to put energies for polar and nonpolar solvation, chemical potential, fluid flow, molecular mechanics, and elastic dynamics on an equal footing. The variational principle is utilized to derive coupled governing equations for the above mentioned multiphysical descriptions. Among these governing equations is the Poisson-Boltzmann equation which describes continuum electrostatics with atomic charges. The present work introduces the theory of continuum elasticity with atomic rigidity (CEWAR). The essence of CEWAR is to formulate the shear modulus as a continuous function of atomic rigidity. As a result, the dynamics complexity of a macromolecular system is separated from its static complexity so that the more time-consuming dynamics is handled with continuum elasticity theory, while the less time-consuming static analysis is pursued with atomic approaches. We propose a simple method, flexibility-rigidity index (FRI), to analyze macromolecular flexibility and rigidity in atomic detail. The construction of FRI relies on the fundamental assumption that protein functions, such as flexibility, rigidity, and energy, are entirely determined by the structure of the protein and its environment, although the structure is in turn determined by all the interactions. As such, the FRI measures the topological connectivity of protein atoms or residues and characterizes the geometric compactness of the protein structure. As a consequence, the FRI does not resort to the interaction Hamiltonian and bypasses matrix diagonalization, which underpins most other flexibility analysis methods. FRI's computational complexity is of O
Bang-Bang Practical Stabilization of Rigid Bodies
Serpelloni, Edoardo
In this thesis, we study the problem of designing a practical stabilizer for a rigid body equipped with a set of actuators generating only constant thrust. Our motivation stems from the fact that modern space missions are required to accurately control the position and orientation of spacecraft actuated by constant-thrust jet-thrusters. To comply with the performance limitations of modern thrusters, we design a feedback controller that does not induce high-frequency switching of the actuators. The proposed controller is hybrid and it asymptotically stabilizes an arbitrarily small compact neighborhood of the target position and orientation of the rigid body. The controller is characterized by a hierarchical structure comprising of two control layers. At the low level of the hierarchy, an attitude controller stabilizes the target orientation of the rigid body. At the high level, after the attitude controller has steered the rigid body sufficiently close to its desired orientation, a position controller stabilizes the desired position. The size of the neighborhood being stabilized by the controller can be adjusted via a proper selection of the controller parameters. This allows us to stabilize the rigid body to virtually any degree of accuracy. It is shown that the controller, even in the presence of measurement noise, does not induce high-frequency switching of the actuators. The key component in the design of the controller is a hybrid stabilizer for the origin of double-integrators affected by bounded external perturbations. Specifically, both the position and the attitude stabilizers consist of multiple copies of such a double-integrator controller. The proposed controller is applied to two realistic spacecraft control problems. First, we apply the position controller to the problem of stabilizing the relative position between two spacecraft flying in formation in the vicinity of the L2 libration point of the Sun-Earth system as a part of a large space telescope
International Nuclear Information System (INIS)
Tanabe, M; Wakui, H; Sogabe, M; Matsumoto, N; Tanabe, Y
2010-01-01
A combined multibody and finite element approach is given to solve the dynamic interaction of a Shinkansen train (high-speed train in Japan) and the railway structure including post-derailment during an earthquake effectively. The motion of the train is expressed in multibody dynamics. Efficient mechanical models to express interactions between wheel and track structure including post-derailment are given. Rail and track elements expressed in multibody dynamics and FEM are given to solve contact problems between wheel and long railway components effectively. The motion of a railway structure is modeled with various finite elements and rail and track elements. The computer program has been developed for the dynamic interaction analysis of a Shinkansen train and railway structure including post derailment during an earthquake. Numerical examples are demonstrated.
Mangia, Anna Lisa; Cortesi, Matteo; Fantozzi, Silvia; Giovanardi, Andrea; Borra, Davide; Gatta, Giorgio
2017-04-22
The aims of the present study were the instrumental validation of inertial-magnetic measurements units (IMMUs) in water, and the description of their use in clinical and sports aquatic applications applying customized 3D multi-body models. Firstly, several tests were performed to map the magnetic field in the swimming pool and to identify the best volume for experimental test acquisition with a mean dynamic orientation error lower than 5°. Successively, the gait and the swimming analyses were explored in terms of spatiotemporal and joint kinematics variables. The extraction of only spatiotemporal parameters highlighted several critical issues and the joint kinematic information has shown to be an added value for both rehabilitative and sport training purposes. Furthermore, 3D joint kinematics applied using the IMMUs provided similar quantitative information than that of more expensive and bulky systems but with a simpler and faster setup preparation, a lower time consuming processing phase, as well as the possibility to record and analyze a higher number of strides/strokes without limitations imposed by the cameras.
Financial Constraints and Nominal Price Rigidities
DEFF Research Database (Denmark)
Menno, Dominik Francesco; Balleer, Almut; Hristov, Nikolay
This paper investigates how financial market imperfections and the frequency of price adjustment interact. Based on new firm-level evidence for Germany, we document that financially constrained firms adjust prices more often than their unconstrained counterparts, both upwards and downwards. We show...... that these empirical patterns are consistent with a partial equilibrium menu-cost model with a working capital constraint. We then use the model to show how the presence of financial frictions changes profits and the price distribution of firms compared to a model without financial frictions. Our results suggest...... that tighter financial constraints are associated with higher nominal rigidities, higher prices and lower output. Moreover, in response to aggregate shocks, aggregate price rigidity moves substantially, the response of inflation is dampened, while output reacts more in the presence of financial frictions...
Rigidity of the magic pentagram game
Kalev, Amir; Miller, Carl A.
2018-01-01
A game is rigid if a near-optimal score guarantees, under the sole assumption of the validity of quantum mechanics, that the players are using an approximately unique quantum strategy. Rigidity has a vital role in quantum cryptography as it permits a strictly classical user to trust behavior in the quantum realm. This property can be traced back as far as 1998 (Mayers and Yao) and has been proved for multiple classes of games. In this paper we prove ridigity for the magic pentagram game, a simple binary constraint satisfaction game involving two players, five clauses and ten variables. We show that all near-optimal strategies for the pentagram game are approximately equivalent to a unique strategy involving real Pauli measurements on three maximally-entangled qubit pairs.
Rigidity of the magic pentagram game.
Kalev, Amir; Miller, Carl A
2018-01-01
A game is rigid if a near-optimal score guarantees, under the sole assumption of the validity of quantum mechanics, that the players are using an approximately unique quantum strategy. Rigidity has a vital role in quantum cryptography as it permits a strictly classical user to trust behavior in the quantum realm. This property can be traced back as far as 1998 (Mayers and Yao) and has been proved for multiple classes of games. In this paper we prove ridigity for the magic pentagram game, a simple binary constraint satisfaction game involving two players, five clauses and ten variables. We show that all near-optimal strategies for the pentagram game are approximately equivalent to a unique strategy involving real Pauli measurements on three maximally-entangled qubit pairs.
Rigid cohomology over Laurent series fields
Lazda, Christopher
2016-01-01
In this monograph, the authors develop a new theory of p-adic cohomology for varieties over Laurent series fields in positive characteristic, based on Berthelot's theory of rigid cohomology. Many major fundamental properties of these cohomology groups are proven, such as finite dimensionality and cohomological descent, as well as interpretations in terms of Monsky-Washnitzer cohomology and Le Stum's overconvergent site. Applications of this new theory to arithmetic questions, such as l-independence and the weight monodromy conjecture, are also discussed. The construction of these cohomology groups, analogous to the Galois representations associated to varieties over local fields in mixed characteristic, fills a major gap in the study of arithmetic cohomology theories over function fields. By extending the scope of existing methods, the results presented here also serve as a first step towards a more general theory of p-adic cohomology over non-perfect ground fields. Rigid Cohomology over Laurent Series Fields...
Modeling the Flexural Rigidity of Rod Photoreceptors
Haeri, Mohammad; Knox, Barry E.; Ahmadi, Aphrodite
2013-01-01
In vertebrate eyes, the rod photoreceptor has a modified cilium with an extended cylindrical structure specialized for phototransduction called the outer segment (OS). The OS has numerous stacked membrane disks and can bend or break when subjected to mechanical forces. The OS exhibits axial structural variation, with extended bands composed of a few hundred membrane disks whose thickness is diurnally modulated. Using high-resolution confocal microscopy, we have observed OS flexing and disruption in live transgenic Xenopus rods. Based on the experimental observations, we introduce a coarse-grained model of OS mechanical rigidity using elasticity theory, representing the axial OS banding explicitly via a spring-bead model. We calculate a bending stiffness of ∼105 nN⋅μm2, which is seven orders-of-magnitude larger than that of typical cilia and flagella. This bending stiffness has a quadratic relation to OS radius, so that thinner OS have lower fragility. Furthermore, we find that increasing the spatial frequency of axial OS banding decreases OS rigidity, reducing its fragility. Moreover, the model predicts a tendency for OS to break in bands with higher spring number density, analogous to the experimental observation that transgenic rods tended to break preferentially in bands of high fluorescence. We discuss how pathological alterations of disk membrane properties by mutant proteins may lead to increased OS rigidity and thus increased breakage, ultimately contributing to retinal degeneration. PMID:23442852
Blast wave interaction with a rigid surface
International Nuclear Information System (INIS)
Josey, T.; Whitehouse, D.R.; Ripley, R.C.; Dionne, J.P.
2004-01-01
A simple model used to investigate blast wave interactions with a rigid surface is presented. The model uses a constant volume energy source analogue to predict pressure histories at gauges located directly above the charge. A series of two-dimensional axi-symmetric CFD calculations were performed, varying the height of the charge relative to the ground. Pressure histories, along with isopycnic plots are presented to evaluate the effects of placing a charge in close proximity to a rigid surface. When a charge is placed near a solid surface the pressure histories experienced at gauges above the charge indicate the presence of two distinct pressure peaks. The first peak is caused by the primary shock and the second peak is a result of the wave reflections from the rigid surface. As the distance from the charge to the wall is increased the magnitude of the second pressure peak is reduced, provided that the distance between the charge and the gauge is maintained constant. The simple model presented is able to capture significant, predictable flow features. (author)
Lateral rigidity of cracked concrete structures
International Nuclear Information System (INIS)
Castellani, A.; Chesi, C.
1979-01-01
Numerical results are discussed on the lateral rigidity of reinforced concrete structures with a given crack distribution. They have been favourably checked with experimental results for cylindrical shells under the effect of a thermal gradient producing vertical cracking or vertical plus horizontal cracking. The main effects characterizing the concrete behaviour are: (1) The shear transfer across a crack; (2) The shear transfer degradation after cyclic loading; (3) The tension stiffening provided by the concrete between crack and crack, in the normal stress transfer; (4) The temperature effect on the elastic moduli of concrete, when cracks are of thermal origin. Only the 1st effect is discussed on an experimental basis. Two broad cathegories of reinforced concrete structures have been investigated in this respect: shear walls of buildings and cylindrical containment structures. The main conclusions so far reached are: (1) Vertical cracks are unlikely to decrease the lateral rigidity to less than 80% of the original one, and to less than 90% when they do not involve the entire thickness of the wall; (2) The appearence of horizontal cracks can reduce the lateral rigidity by some 30% or more; (3) A noticeable but not yet evaluated influence is shown by cyclic loading. (orig.)
Directory of Open Access Journals (Sweden)
Daisuke Nishiura
2017-06-01
Full Text Available Simulation of a large number of deformable bodies is often difficult because complex high-level modeling is required to address both multi-body contact and viscoelastic deformation. This necessitates the combined use of a discrete element method (DEM and a finite element method (FEM. In this study, a quadruple discrete element method (QDEM was developed for dynamic analysis of viscoelastic materials using a simpler algorithm compared to the standard FEM. QDEM easily incorporates the contact algorithm used in DEM. As the first step toward multi-body simulation, the fundamental performance of QDEM was investigated for viscoelastic analysis. The amplitude and frequency of cantilever elastic vibration were nearly equal to those obtained by the standard FEM. A comparison of creep recovery tests with an analytical solution showed good agreement between them. In addition, good correlation between the attenuation degree and the real physical viscosity was confirmed for viscoelastic vibration analysis. Therefore, the high accuracy of QDEM in the fundamental analysis of infinitesimal viscoelastic deformations was verified. Finally, the impact response of a ballast and sleeper under cyclic loading on a railway track was analyzed using QDEM as an application of deformable multi-body dynamics. The results showed that the vibration of the ballasted track was qualitatively in good agreement with the actual measurements. Moreover, the ballast layer with high friction reduced the ballasted track deterioration. This study suggests that QDEM, as an alternative to DEM and FEM, can provide deeper insights into the contact dynamics of a large number of deformable bodies.
49 CFR 587.18 - Dimensions of fixed rigid barrier.
2010-10-01
... TRAFFIC SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) DEFORMABLE BARRIERS Offset Deformable Barrier § 587.18 Dimensions of fixed rigid barrier. (a) The fixed rigid barrier has a mass of not... 49 Transportation 7 2010-10-01 2010-10-01 false Dimensions of fixed rigid barrier. 587.18 Section...
Complex eigenvalue analysis of railway wheel/rail squeal
African Journals Online (AJOL)
DR OKE
Squeal noise from wheel/rail and brake disc/pad frictional contact is typical in railways. ... squeal noise by multibody simulation of a rail car running on rigid rails. ... system, traditional complex eigenvalue analysis by finite element was used.
International Nuclear Information System (INIS)
Stancanello, J.; Loeckx, D.; Francescon, P.; Calvedon, C.; Avanzo, M.; Cora, S.; Scalchi, P.; Cerveri, P.; Ferrigno, G.
2004-01-01
This work aims at comparing rigid, affine and Local Non Rigid (LNR) CT-3D Rotational Angiography (CT-3DRA) registrations based on mutual information. 10 cranial and 1 spinal cases have been registered by rigid and affine transformations; while LNR has been applied to the cases where residual deformation must be corrected. An example of CT-3DRA registration without regularization term and an example of LNR using the similarity criterion and the regularization term as well as 3D superposition of the 3DRA before and after the registration without the regularization term are presented. All the registrations performed by rigid transformation converged to an acceptable solution. The results about the robustness test in axial direction are reported. Conclusions: For cranial cases, affine transformation endowed with threshold-segmentation pre-processing can be considered the most favourable solution for almost all registrations; for some cases, LNR provides more accurate results. For the spinal case rigid transformation is the most suitable when immobilizing patient during examinations; in this case the increase of accuracy by using LNR registrations seems to be not significant
Iterative CT reconstruction with correction for known rigid motion
Energy Technology Data Exchange (ETDEWEB)
Nuyts, Johan [Katholieke Univ. Leuven (Belgium). Dept. of Nuclear Medicine; Kim, Jung-Ha; Fulton, Roger [Sydney Univ., NSW (Australia). School of Physics; Westmead Hospital, Sydney (Australia). Medical Physics
2011-07-01
In PET/CT brain imaging, correction for motion may be needed, in particular for children and psychiatric patients. Motion is more likely to occur in the lengthy PET measurement, but also during the short CT acquisition patient motion is possible. Rigid motion of the head can be measured independently from the PET/CT system with optical devices. In this paper, we propose a method and some preliminary simulation results for iterative CT reconstruction with correction for known rigid motion. We implemented an iterative algorithm for fully 3D reconstruction from helical CT scans. The motion of the head is incorporated in the system matrix as a view-dependent motion of the CT-system. The first simulation results indicate that some motion patterns may produce loss of essential data. This loss precludes exact reconstruction and results in artifacts in the reconstruction, even when motion is taken into account. However, by reducing the pitch during acquisition, the same motion pattern no longer caused artifacts in the motion corrected image. (orig.)
Influence of flock coating on bending rigidity of woven fabrics
Ozdemir, O.; Kesimci, M. O.
2017-10-01
This work presents the preliminary results of our efforts that focused on the effect of the flock coating on the bending rigidity of woven fabrics. For this objective, a laboratory scale flocking unit is designed and flocked samples of controlled flock density are produced. Bending rigidity of the samples with different flock densities are measured on both flocked and unflocked sides. It is shown that the bending rigidity depends on both flock density and whether the side to be measured is flocked or not. Adhesive layer thickness on the bending rigidity is shown to be dramatic. And at higher basis weights, flock density gets less effective on bending rigidity.
Understanding geological processes: Visualization of rigid and non-rigid transformations
Shipley, T. F.; Atit, K.; Manduca, C. A.; Ormand, C. J.; Resnick, I.; Tikoff, B.
2012-12-01
Visualizations are used in the geological sciences to support reasoning about structures and events. Research in cognitive sciences offers insights into the range of skills of different users, and ultimately how visualizations might support different users. To understand the range of skills needed to reason about earth processes we have developed a program of research that is grounded in the geosciences' careful description of the spatial and spatiotemporal patterns associated with earth processes. In particular, we are pursuing a research program that identifies specific spatial skills and investigates whether and how they are related to each other. For this study, we focus on a specific question: Is there an important distinction in the geosciences between rigid and non-rigid deformation? To study a general spatial thinking skill we employed displays with non-geological objects that had been altered by rigid change (rotation), and two types of non-rigid change ("brittle" (or discontinuous) and "ductile" (or continuous) deformation). Disciplinary scientists (geosciences and chemistry faculty), and novices (non-science faculty and undergraduate psychology students) answered questions that required them to visualize the appearance of the object before the change. In one study, geologists and chemists were found to be superior to non-science faculty in reasoning about rigid rotations (e.g., what an object would look like from a different perspective). Geologists were superior to chemists in reasoning about brittle deformations (e.g., what an object looked like before it was broken - here the object was a word cut into many fragments displaced in different directions). This finding is consistent with two hypotheses: 1) Experts are good at visualizing the types of changes required for their domain; and 2) Visualization of rigid and non-rigid changes are not the same skill. An additional important finding is that there was a broad range of skill in both rigid and non-rigid
Directory of Open Access Journals (Sweden)
Cristian Padilha Fontoura
2018-02-01
Full Text Available SAE Mini Baja competitions require efforts in developing a reliable vehicle project that enables their teams to manage time and resources wisely. Vehicle simulations are one the best ways to deal with these conditions and prevent failure during a test. This work outlines the methodology that was carried out for validating the multibody dynamics model of a Mini Baja vehicle through vertical acceleration data acquisition. The data was acquired with the vehicle in different sets of obstacles, based on those seen in previously held competitions. Simulation was done through ADAMS/Car, with the vehicle’s multibody model being simulated in different three-dimensional roads, counterpart to those where data acquisition took place. Simulation data, when compared to acquired acceleration signals for most of the obstacles, exhibited equivalence. Additional data computation revealed that the spectra in the frequency domain presented most severe loads concentrated between 0 and 20 Hz, incoming mostly from road unevenness. Gathering such data, by the presented approach can assist future analyses and guide the Baja Team in defining an improved project by predicting its dynamic behavior.
Awake craniotomy using electromagnetic navigation technology without rigid pin fixation.
Morsy, Ahmed A; Ng, Wai Hoe
2015-11-01
We report our institutional experience using an electromagnetic navigation system, without rigid head fixation, for awake craniotomy patients. The StealthStation® S7 AxiEM™ navigation system (Medtronic, Inc.) was used for this technique. Detailed preoperative clinical and neuropsychological evaluations, patient education and contrast-enhanced MRI (thickness 1.5mm) were performed for each patient. The AxiEM Mobile Emitter was typically placed in a holder, which was mounted to the operating room table, and a non-invasive patient tracker was used as the patient reference device. A monitored conscious sedation technique was used in all awake craniotomy patients, and the AxiEM Navigation Pointer was used for navigation during the procedure. This offers the same accuracy as optical navigation, but without head pin fixation or interference with intraoperative neurophysiological techniques and surgical instruments. The application of the electromagnetic neuronavigation technology without rigid head fixation during an awake craniotomy is accurate, and offers superior patient comfort. It is recommended as an effective adjunctive technique for the conduct of awake surgery. Copyright © 2015 Elsevier Ltd. All rights reserved.
A rigid porous filter and filtration method
Energy Technology Data Exchange (ETDEWEB)
Chiang, Ta-Kuan; Straub, Douglas, Straub L.; Dennis, Richard A.
1998-12-01
The present invention involves a porous rigid filter comprising a plurality of concentric filtration elements having internal flow passages and forming external flow passages there between. The present invention also involves a pressure vessel containing the filter for the removal of particulate from high pressure particulate containing gases, and further involves a method for using the filter to remove such particulate. The present filter has the advantage of requiring fewer filter elements due to the high surface area- to-volume ratio provided by the filter, requires a reduced pressure vessel size, and exhibits enhanced mechanical design properties, improved cleaning properties, configuration options, modularity and ease of fabrication.
Mechanical Characterization of Rigid Polyurethane Foams
Energy Technology Data Exchange (ETDEWEB)
Lu, Wei-Yang [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Mechanics of Materials
2014-12-01
Foam materials are used to protect sensitive components from impact loading. In order to predict and simulate the foam performance under various loading conditions, a validated foam model is needed and the mechanical properties of foams need to be characterized. Uniaxial compression and tension tests were conducted for different densities of foams under various temperatures and loading rates. Crush stress, tensile strength, and elastic modulus were obtained. A newly developed confined compression experiment provided data for investigating the foam flow direction. A biaxial tension experiment was also developed to explore the damage surface of a rigid polyurethane foam.
Rigidity of complete generic shrinking Ricci solitons
Chu, Yawei; Zhou, Jundong; Wang, Xue
2018-01-01
Let (Mn , g , X) be a complete generic shrinking Ricci soliton of dimension n ≥ 3. In this paper, by employing curvature inequalities, the formula of X-Laplacian for the norm square of the trace-free curvature tensor, the weak maximum principle and the estimate of the scalar curvature of (Mn , g) , we prove some rigidity results for (Mn , g , X) . In particular, it is showed that (Mn , g , X) is isometric to Rn or a finite quotient of Sn under a pointwise pinching condition. Moreover, we establish several optimal inequalities and classify those shrinking solitons for equalities.
Kalotka-Bratek, H; Drobinski, G; Klimczak, K; Busquet, P; Fraysse, J B; Bejean-Lebuisson, A; Grosgogeat, Y
1989-02-01
In 20 patients with pure aortic regurgitation we studied the relationship between the severity of regurgitation, as assessed haemodynamically by the percentage of leakage (%L), and the half-pressure (T 1/2 P) and half-velocity (T 1/2 V) times, as obtained from doppler aortic blood velocity curves, taking into account the rigidity of the systemic vascular circuit characterized by the pressure wave propagation velocity (PWPV). The systemic arterial circuit was supple in 14 patients (PWPV less than 7.5 m/sec) and rigid in 6 patients (PWPV greater than 7.5 m/sec). The regression slopes between %L and T 1/2 P and between %L and T 1/2 V were calculated with their confidence limits in the 14 patients with supple arteries. The 6 patients with rigid arteries fitted into this nomogram, thus demonstrating that systemic arterial rigidity makes no difference in the relationship between %L and doppler indices. The half-velocity and half-pressure times measured by doppler ultrasound were acquired from a velocity signal directly determined by the aortic regurgitation, without any detectable effect of vascular circuit rigidity. Being equivalent by nature to the signal decrease time constant, they are independent of the absolute protodiastolic value of diastolic pressure gradient or blood flow velocity. For this reason these two doppler parameters are reliable to evaluate the severity of aortic regurgitation.
Public policies targeting labour market rigidities
Directory of Open Access Journals (Sweden)
Andreea Claudia ŞERBAN
2013-02-01
Full Text Available Labour market rigidity becomes an issue of increasing importance under conditions of shocks associated with the economic crisis due to the need to increase the adaptability and responsiveness to them. Thus, labour market policies must be directed towards mitigating rigidities caused by institutional or demographic factors or certain mismatch between demand and supply of education qualifications. This paper highlights the major role of the active labour market policies targeting the increase of labour flexibility, stressing the importance and impact on the ability to adapt quickly and effectively to macroeconomic shocks. Located on a declining trend in the years preceding the crisis, spending on labour market policies increased in 2009 in all the Member States of the European Union. Spending differences are significant between countries, Romania being at the lowest end of the European Union. This requires special attention because the increased adaptability of workers through training, as active measure, is of major importance considering the increased speed of changes in the labour market.
Vertebral Column Resection for Rigid Spinal Deformity.
Saifi, Comron; Laratta, Joseph L; Petridis, Petros; Shillingford, Jamal N; Lehman, Ronald A; Lenke, Lawrence G
2017-05-01
Broad narrative review. To review the evolution, operative technique, outcomes, and complications associated with posterior vertebral column resection. A literature review of posterior vertebral column resection was performed. The authors' surgical technique is outlined in detail. The authors' experience and the literature regarding vertebral column resection are discussed at length. Treatment of severe, rigid coronal and/or sagittal malalignment with posterior vertebral column resection results in approximately 50-70% correction depending on the type of deformity. Surgical site infection rates range from 2.9% to 9.7%. Transient and permanent neurologic injury rates range from 0% to 13.8% and 0% to 6.3%, respectively. Although there are significant variations in EBL throughout the literature, it can be minimized by utilizing tranexamic acid intraoperatively. The ability to correct a rigid deformity in the spine relies on osteotomies. Each osteotomy is associated with a particular magnitude of correction at a single level. Posterior vertebral column resection is the most powerful posterior osteotomy method providing a successful correction of fixed complex deformities. Despite meticulous surgical technique and precision, this robust osteotomy technique can be associated with significant morbidity even in the most experienced hands.
Optimized imaging using non-rigid registration
International Nuclear Information System (INIS)
Berkels, Benjamin; Binev, Peter; Blom, Douglas A.; Dahmen, Wolfgang; Sharpley, Robert C.; Vogt, Thomas
2014-01-01
The extraordinary improvements of modern imaging devices offer access to data with unprecedented information content. However, widely used image processing methodologies fall far short of exploiting the full breadth of information offered by numerous types of scanning probe, optical, and electron microscopies. In many applications, it is necessary to keep measurement intensities below a desired threshold. We propose a methodology for extracting an increased level of information by processing a series of data sets suffering, in particular, from high degree of spatial uncertainty caused by complex multiscale motion during the acquisition process. An important role is played by a non-rigid pixel-wise registration method that can cope with low signal-to-noise ratios. This is accompanied by formulating objective quality measures which replace human intervention and visual inspection in the processing chain. Scanning transmission electron microscopy of siliceous zeolite material exhibits the above-mentioned obstructions and therefore serves as orientation and a test of our procedures. - Highlights: • Developed a new process for extracting more information from a series of STEM images. • An objective non-rigid registration process copes with distortions. • Images of zeolite Y show retrieval of all information available from the data set. • Quantitative measures of registration quality were implemented. • Applicable to any serially acquired data, e.g. STM, AFM, STXM, etc
Review of Soil Models and Their Implementation in Multibody System Algorithms
2012-02-01
to the Kayenta model (Brannon et. al., 2009). Soil is not always an isotropic material. Layering and fracture networks, as well as compaction and...in one plane, and there is a transversely anisotropic version of the Kayenta model. Anisotropy may also be addressed using fabric tensors (Wan and...Strains”, Computer Methods in Applied Mechanics and Engineering, 155, pp.73-95. 12. Brannon, R.M., Fossum, A.F., and Strack, O.E., 2009, “ KAYENTA : Theory
MAGNETOUR: Surfing Planetary Systems on Electromagnetic and Multi-Body Gravity Fields
National Aeronautics and Space Administration — MAGNETOUR enables a spacecraft to orbit and travel between multiple moons of an outer planet, using very little or even no propellant. To achieve this free-lunch...
Jet Ventilation during Rigid Bronchoscopy in Adults: A Focused Review
Directory of Open Access Journals (Sweden)
Laurie Putz
2016-01-01
Full Text Available The indications for rigid bronchoscopy for interventional pulmonology have increased and include stent placements and transbronchial cryobiopsy procedures. The shared airway between anesthesiologist and pulmonologist and the open airway system, requiring specific ventilation techniques such as jet ventilation, need a good understanding of the procedure to reduce potentially harmful complications. Appropriate adjustment of the ventilator settings including pause pressure and peak inspiratory pressure reduces the risk of barotrauma. High frequency jet ventilation allows adequate oxygenation and carbon dioxide removal even in cases of tracheal stenosis up to frequencies of around 150 min−1; however, in an in vivo animal model, high frequency jet ventilation along with normal frequency jet ventilation (superimposed high frequency jet ventilation has been shown to improve oxygenation by increasing lung volume and carbon dioxide removal by increasing tidal volume across a large spectrum of frequencies without increasing barotrauma. General anesthesia with a continuous, intravenous, short-acting agent is safe and effective during rigid bronchoscopy procedures.
Dynamics of parallel robots from rigid bodies to flexible elements
Briot, Sébastien
2015-01-01
This book starts with a short recapitulation on basic concepts, common to any types of robots (serial, tree structure, parallel, etc.), that are also necessary for computation of the dynamic models of parallel robots. Then, as dynamics requires the use of geometry and kinematics, the general equations of geometric and kinematic models of parallel robots are given. After, it is explained that parallel robot dynamic models can be obtained by decomposing the real robot into two virtual systems: a tree-structure robot (equivalent to the robot legs for which all joints would be actuated) plus a free body corresponding to the platform. Thus, the dynamics of rigid tree-structure robots is analyzed and algorithms to obtain their dynamic models in the most compact form are given. The dynamic model of the real rigid parallel robot is obtained by closing the loops through the use of the Lagrange multipliers. The problem of the dynamic model degeneracy near singularities is treated and optimal trajectory planning for cro...
A method for measuring the inertia properties of rigid bodies
Gobbi, M.; Mastinu, G.; Previati, G.
2011-01-01
A method for the measurement of the inertia properties of rigid bodies is presented. Given a rigid body and its mass, the method allows to measure (identify) the centre of gravity location and the inertia tensor during a single test. The proposed technique is based on the analysis of the free motion of a multi-cable pendulum to which the body under consideration is connected. The motion of the pendulum and the forces acting on the system are recorded and the inertia properties are identified by means of a proper mathematical procedure based on a least square estimation. After the body is positioned on the test rig, the full identification procedure takes less than 10 min. The natural frequencies of the pendulum and the accelerations involved are quite low, making this method suitable for many practical applications. In this paper, the proposed method is described and two test rigs are presented: the first is developed for bodies up to 3500 kg and the second for bodies up to 400 kg. A validation of the measurement method is performed with satisfactory results. The test rig holds a third part quality certificate according to an ISO 9001 standard and could be scaled up to measure the inertia properties of huge bodies, such as trucks, airplanes or even ships.
Thermostability in rubredoxin and its relationship to mechanical rigidity
Rader, A. J.
2010-03-01
The source of increased stability in proteins from organisms that thrive in extreme thermal environments is not well understood. Previous experimental and theoretical studies have suggested many different features possibly responsible for such thermostability. Many of these thermostabilizing mechanisms can be accounted for in terms of structural rigidity. Thus a plausible hypothesis accounting for this remarkable stability in thermophilic enzymes states that these enzymes have enhanced conformational rigidity at temperatures below their native, functioning temperature. Experimental evidence exists to both support and contradict this supposition. We computationally investigate the relationship between thermostability and rigidity using rubredoxin as a case study. The mechanical rigidity is calculated using atomic models of homologous rubredoxin structures from the hyperthermophile Pyrococcus furiosus and mesophile Clostridium pasteurianum using the FIRST software. A global increase in structural rigidity (equivalently a decrease in flexibility) corresponds to an increase in thermostability. Locally, rigidity differences (between mesophilic and thermophilic structures) agree with differences in protection factors.
Thermostability in rubredoxin and its relationship to mechanical rigidity
International Nuclear Information System (INIS)
Rader, A J
2010-01-01
The source of increased stability in proteins from organisms that thrive in extreme thermal environments is not well understood. Previous experimental and theoretical studies have suggested many different features possibly responsible for such thermostability. Many of these thermostabilizing mechanisms can be accounted for in terms of structural rigidity. Thus a plausible hypothesis accounting for this remarkable stability in thermophilic enzymes states that these enzymes have enhanced conformational rigidity at temperatures below their native, functioning temperature. Experimental evidence exists to both support and contradict this supposition. We computationally investigate the relationship between thermostability and rigidity using rubredoxin as a case study. The mechanical rigidity is calculated using atomic models of homologous rubredoxin structures from the hyperthermophile Pyrococcus furiosus and mesophile Clostridium pasteurianum using the FIRST software. A global increase in structural rigidity (equivalently a decrease in flexibility) corresponds to an increase in thermostability. Locally, rigidity differences (between mesophilic and thermophilic structures) agree with differences in protection factors
Coherent distributions for the rigid rotator
Energy Technology Data Exchange (ETDEWEB)
Grigorescu, Marius [CP 15-645, Bucharest 014700 (Romania)
2016-06-15
Coherent solutions of the classical Liouville equation for the rigid rotator are presented as positive phase-space distributions localized on the Lagrangian submanifolds of Hamilton-Jacobi theory. These solutions become Wigner-type quasiprobability distributions by a formal discretization of the left-invariant vector fields from their Fourier transform in angular momentum. The results are consistent with the usual quantization of the anisotropic rotator, but the expected value of the Hamiltonian contains a finite “zero point” energy term. It is shown that during the time when a quasiprobability distribution evolves according to the Liouville equation, the related quantum wave function should satisfy the time-dependent Schrödinger equation.
Static friction between rigid fractal surfaces.
Alonso-Marroquin, Fernando; Huang, Pengyu; Hanaor, Dorian A H; Flores-Johnson, E A; Proust, Gwénaëlle; Gan, Yixiang; Shen, Luming
2015-09-01
Using spheropolygon-based simulations and contact slope analysis, we investigate the effects of surface topography and atomic scale friction on the macroscopically observed friction between rigid blocks with fractal surface structures. From our mathematical derivation, the angle of macroscopic friction is the result of the sum of the angle of atomic friction and the slope angle between the contact surfaces. The latter is obtained from the determination of all possible contact slopes between the two surface profiles through an alternative signature function. Our theory is validated through numerical simulations of spheropolygons with fractal Koch surfaces and is applied to the description of frictional properties of Weierstrass-Mandelbrot surfaces. The agreement between simulations and theory suggests that for interpreting macroscopic frictional behavior, the descriptors of surface morphology should be defined from the signature function rather than from the slopes of the contacting surfaces.
Observational properties of rigidly rotating dust configurations
Energy Technology Data Exchange (ETDEWEB)
Ilyas, Batyr; Malafarina, Daniele [Nazarbayev University, Department of Physics, Astana (Kazakhstan); Yang, Jinye [Fudan University, Center for Field Theory and Particle Physics and Department of Physics, Shanghai (China); Bambi, Cosimo [Fudan University, Center for Field Theory and Particle Physics and Department of Physics, Shanghai (China); Eberhard-Karls Universitaet Tuebingen, Theoretical Astrophysics, Tuebingen (Germany)
2017-07-15
We study the observational properties of a class of exact solutions of Einstein's field equations describing stationary, axially symmetric, rigidly rotating dust (i.e. non-interacting particles). We ask the question whether such solutions can describe astrophysical rotating dark matter clouds near the center of galaxies and we probe the possibility that they may constitute an alternative to supermassive black holes at the center of galaxies. We show that light emission from accretion disks made of ordinary baryonic matter in this space-time has several differences with respect to the emission of light from similar accretion disks around black holes. The shape of the iron Kα line in the reflection spectrum of accretion disks can potentially distinguish this class of solutions from the Kerr metric, but this may not be possible with current X-ray missions. (orig.)
On real structures on rigid surfaces
International Nuclear Information System (INIS)
Kulikov, Vik S; Kharlamov, V M
2002-01-01
We construct examples of rigid surfaces (that is, surfaces whose deformation class consists of a unique surface) with a particular behaviour with respect to real structures. In one example the surface has no real structure. In another it has a unique real structure, which is not maximal with respect to the Smith-Thom inequality. These examples give negative answers to the following problems: the existence of real surfaces in each deformation class of complex surfaces, and the existence of maximal real surfaces in every complex deformation class that contains real surfaces. Moreover, we prove that there are no real surfaces among surfaces of general type with p g =q=0 and K 2 =9. These surfaces also provide new counterexamples to the 'Dif = Def' problem
On real structures on rigid surfaces
Energy Technology Data Exchange (ETDEWEB)
Kulikov, Vik S [Steklov Mathematical Institute, Russian Academy of Sciences (Russian Federation); Kharlamov, V M [Institut de Recherche Matematique Avanee Universite Louis Pasteur et CNRS 7 rue Rene Descartes (France)
2002-02-28
We construct examples of rigid surfaces (that is, surfaces whose deformation class consists of a unique surface) with a particular behaviour with respect to real structures. In one example the surface has no real structure. In another it has a unique real structure, which is not maximal with respect to the Smith-Thom inequality. These examples give negative answers to the following problems: the existence of real surfaces in each deformation class of complex surfaces, and the existence of maximal real surfaces in every complex deformation class that contains real surfaces. Moreover, we prove that there are no real surfaces among surfaces of general type with p{sub g}=q=0 and K{sup 2}=9. These surfaces also provide new counterexamples to the 'Dif = Def' problem.
Can deformation of a polymer film with a rigid coating model geophysical processes?
Volynskii, A. L.; Bazhenov, S. L.
2007-12-01
The structural and mechanical behavior of polymer films with a thin rigid coating is analyzed. The behavior of such systems under applied stress is accompanied by the formation of a regular wavy surface relief and by regular fragmentation of the coating. The above phenomena are shown to be universal. Both phenomena (stress-induced development of a regular wavy surface relief and regular fragmentation of the coating) are provided by the specific features of mechanical stress transfer from a compliant soft support to a rigid thin coating. The above phenomena are associated with a specific structure of the system, which is referred to as “a rigid coating on a soft substratum” system (RCSS). Surface microrelief in RCSS systems is similar to the ocean floor relief in the vicinity of mid-oceanic ridges. Thus, the complex system composed of a young oceanic crust and upper Earth's mantle may be considered as typically “a solid coating on a soft substratum” system. Specific features of the ocean floor relief are analyzed in terms of the approach advanced for the description of the structural mechanical behavior of polymer films with a rigid coating. This analysis allowed to estimate the strength of an ocean floor.
Dual Quaternion Variational Integrator for Rigid Body Dynamic Simulation
Xu, Jiafeng; Halse, Karl Henning
2016-01-01
In rigid body dynamic simulations, often the algorithm is required to deal with general situations where both reference point and inertia matrix are arbitrarily de- fined. We introduce a novel Lie group variational integrator using dual quaternion for simulating rigid body dynamics in all six degrees of freedom. Dual quaternion is used to represent rigid body kinematics and one-step Lie group method is used to derive dynamic equations. The combination of these two becomes the first Lie group ...
Computing the Free Energy along a Reaction Coordinate Using Rigid Body Dynamics.
Tao, Peng; Sodt, Alexander J; Shao, Yihan; König, Gerhard; Brooks, Bernard R
2014-10-14
The calculations of potential of mean force along complex chemical reactions or rare events pathways are of great interest because of their importance for many areas in chemistry, molecular biology, and material science. The major difficulty for free energy calculations comes from the great computational cost for adequate sampling of the system in high-energy regions, especially close to the reaction transition state. Here, we present a method, called FEG-RBD, in which the free energy gradients were obtained from rigid body dynamics simulations. Then the free energy gradients were integrated along a reference reaction pathway to calculate free energy profiles. In a given system, the reaction coordinates defining a subset of atoms (e.g., a solute, or the quantum mechanics (QM) region of a quantum mechanics/molecular mechanics simulation) are selected to form a rigid body during the simulation. The first-order derivatives (gradients) of the free energy with respect to the reaction coordinates are obtained through the integration of constraint forces within the rigid body. Each structure along the reference reaction path is separately subjected to such a rigid body simulation. The individual free energy gradients are integrated along the reference pathway to obtain the free energy profile. Test cases provided demonstrate both the strengths and weaknesses of the FEG-RBD method. The most significant benefit of this method comes from the fast convergence rate of the free energy gradient using rigid-body constraints instead of restraints. A correction to the free energy due to approximate relaxation of the rigid-body constraint is estimated and discussed. A comparison with umbrella sampling using a simple test case revealed the improved sampling efficiency of FEG-RBD by a factor of 4 on average. The enhanced efficiency makes this method effective for calculating the free energy of complex chemical reactions when the reaction coordinate can be unambiguously defined by a
Tile-based rigidization surface parametric design study
Giner Munoz, Laura; Luntz, Jonathan; Brei, Diann; Kim, Wonhee
2018-03-01
Inflatable technologies have proven useful in consumer goods as well as in more recent applications including civil structures, aerospace, medical, and robotics. However, inflatable technologies are typically lacking in their ability to provide rigid structural support. Particle jamming improves upon this by providing structures which are normally flexible and moldable but become rigid when air is removed. Because these are based on an airtight bladder filled with loose particles, they always occupy the full volume of its rigid state, even when not rigidized. More recent developments in layer jamming have created thin, compact rigidizing surfaces replacing the loose volume of particles with thinly layered surface materials. Work in this area has been applied to several specific applications with positive results but have not generally provided the broader understanding of the rigidization performance as a function of design parameters required for directly adapting layer rigidization technology to other applications. This paper presents a parametric design study of a new layer jamming vacuum rigidization architecture: tile-based vacuum rigidization. This form of rigidization is based on layers of tiles contained within a thin vacuum bladder which can be bent, rolled, or otherwise compactly stowed, but when deployed flat, can be vacuumed and form a large, flat, rigid plate capable of supporting large forces both localized and distributed over the surface. The general architecture and operation detailing rigidization and compliance mechanisms is introduced. To quantitatively characterize the rigidization behavior, prototypes rigidization surfaces are fabricated and an experimental technique is developed based on a 3-point bending test. Performance evaluation metrics are developed to describe the stiffness, load-bearing capacity, and internal slippage of tested prototypes. A set of experimental parametric studies are performed to better understand the impact of
Estimating the orientation of a rigid body moving in space using inertial sensors
Energy Technology Data Exchange (ETDEWEB)
He, Peng, E-mail: peng.he.1@ulaval.ca; Cardou, Philippe, E-mail: pcardou@gmc.ulaval.ca [Université Laval, Robotics Laboratory, Department of Mechanical Engineering (Canada); Desbiens, André, E-mail: andre.desbiens@gel.ulaval.ca [Université Laval, Department of Electrical and Computer Engineering (Canada); Gagnon, Eric, E-mail: Eric.Gagnon@drdc-rddc.gc.ca [RDDC Valcartier (Canada)
2015-09-15
This paper presents a novel method of estimating the orientation of a rigid body moving in space from inertial sensors, by discerning the gravitational and inertial components of the accelerations. In this method, both a rigid-body kinematics model and a stochastic model of the human-hand motion are formulated and combined in a nonlinear state-space system. The state equation represents the rigid body kinematics and stochastic model, and the output equation represents the inertial sensor measurements. It is necessary to mention that, since the output equation is a nonlinear function of the state, the extended Kalman filter (EKF) is applied. The absolute value of the error from the proposed method is shown to be less than 5 deg in simulation and in experiments. It is apparently stable, unlike the time-integration of gyroscope measurements, which is subjected to drift, and remains accurate under large accelerations, unlike the tilt-sensor method.
Estimating the orientation of a rigid body moving in space using inertial sensors
International Nuclear Information System (INIS)
He, Peng; Cardou, Philippe; Desbiens, André; Gagnon, Eric
2015-01-01
This paper presents a novel method of estimating the orientation of a rigid body moving in space from inertial sensors, by discerning the gravitational and inertial components of the accelerations. In this method, both a rigid-body kinematics model and a stochastic model of the human-hand motion are formulated and combined in a nonlinear state-space system. The state equation represents the rigid body kinematics and stochastic model, and the output equation represents the inertial sensor measurements. It is necessary to mention that, since the output equation is a nonlinear function of the state, the extended Kalman filter (EKF) is applied. The absolute value of the error from the proposed method is shown to be less than 5 deg in simulation and in experiments. It is apparently stable, unlike the time-integration of gyroscope measurements, which is subjected to drift, and remains accurate under large accelerations, unlike the tilt-sensor method
Maxwell rigidity and topological constraints in amorphous phase-change networks
International Nuclear Information System (INIS)
Micoulaut, M.; Otjacques, C.; Raty, J.-Y.; Bichara, C.
2011-01-01
By analyzing first-principles molecular-dynamics simulations of different telluride amorphous networks, we develop a method for the enumeration of radial and angular topological constraints, and show that the phase diagram of the most popular system Ge-Sb-Te can be split into two compositional elastic phases: a tellurium rich flexible phase and a stressed rigid phase that contains most of the materials used in phase-change applications. This sound atomic scale insight should open new avenues for the understanding of phase-change materials and other complex amorphous materials from the viewpoint of rigidity.
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.
Leonhard Euler and the mechanics of rigid bodies
Marquina, J. E.; Marquina, M. L.; Marquina, V.; Hernández-Gómez, J. J.
2017-01-01
In this work we present the original ideas and the construction of the rigid bodies theory realised by Leonhard Euler between 1738 and 1775. The number of treatises written by Euler on this subject is enormous, including the most notorious Scientia Navalis (1749), Decouverte d’un noveau principe de mecanique (1752), Du mouvement de rotation des corps solides autour d’un axe variable (1765), Theoria motus corporum solidorum seu rigidorum (1765) and Nova methodus motu corporum rigidorum determinandi (1776), in which he developed the ideas of the instantaneous rotation axis, the so-called Euler equations and angles, the components of what is now known as the inertia tensor, the principal axes of inertia, and, finally, the generalisation of the translation and rotation movement equations for any system. Euler, the man who ‘put most of mechanics into its modern form’ (Truesdell 1968 Essays in the History of Mechanics (Berlin: Springer) p 106).
Matrix methods applied to engineering rigid body mechanics
Crouch, T.
The purpose of this book is to present the solution of a range of rigorous body mechanics problems using a matrix formulation of vector algebra. Essential theory concerning kinematics and dynamics is formulated in terms of matrix algebra. The solution of kinematics and dynamics problems is discussed, taking into account the velocity and acceleration of a point moving in a circular path, the velocity and acceleration determination for a linkage, the angular velocity and angular acceleration of a roller in a taper-roller thrust race, Euler's theroem on the motion of rigid bodies, an automotive differential, a rotating epicyclic, the motion of a high speed rotor mounted in gimbals, and the vibration of a spinning projectile. Attention is given to the activity of a force, the work done by a conservative force, the work and potential in a conservative system, the equilibrium of a mechanism, bearing forces due to rotor misalignment, and the frequency of vibrations of a constrained rod.
A rigid motion correction method for helical computed tomography (CT)
International Nuclear Information System (INIS)
Kim, J-H; Kyme, A; Fulton, R; Nuyts, J; Kuncic, Z
2015-01-01
We propose a method to compensate for six degree-of-freedom rigid motion in helical CT of the head. The method is demonstrated in simulations and in helical scans performed on a 16-slice CT scanner. Scans of a Hoffman brain phantom were acquired while an optical motion tracking system recorded the motion of the bed and the phantom. Motion correction was performed by restoring projection consistency using data from the motion tracking system, and reconstructing with an iterative fully 3D algorithm. Motion correction accuracy was evaluated by comparing reconstructed images with a stationary reference scan. We also investigated the effects on accuracy of tracker sampling rate, measurement jitter, interpolation of tracker measurements, and the synchronization of motion data and CT projections. After optimization of these aspects, motion corrected images corresponded remarkably closely to images of the stationary phantom with correlation and similarity coefficients both above 0.9. We performed a simulation study using volunteer head motion and found similarly that our method is capable of compensating effectively for realistic human head movements. To the best of our knowledge, this is the first practical demonstration of generalized rigid motion correction in helical CT. Its clinical value, which we have yet to explore, may be significant. For example it could reduce the necessity for repeat scans and resource-intensive anesthetic and sedation procedures in patient groups prone to motion, such as young children. It is not only applicable to dedicated CT imaging, but also to hybrid PET/CT and SPECT/CT, where it could also ensure an accurate CT image for lesion localization and attenuation correction of the functional image data. (paper)
Convergent Synthesis of Rigid Macrocycles Containing One and Two Tetrathiafulvalene Units
DEFF Research Database (Denmark)
Simonsen, Klaus B.; Thorup, Niels; Becher, Jan
1997-01-01
The synthesis of rigid tetrathiafulvalenophanes containing one or two tetrathiafulvalene units is presented, together with a stepwise convergent synthesis of macrocyclic bis-tetrathiafulvalenes via several open dimeric tetrathiafulvalenes. These systems were investigated by cyclic voltammetry...... and by X-ray crystallography....
THE RIGIDITY OF THE EARTH'S INNER CORE
Directory of Open Access Journals (Sweden)
K. E. BULLEN
1953-06-01
Full Text Available The purpose of this paper is to examine and assess, in the
light of recent evidence, the theory lliat the Earth's inner core has
a significant rigidity.
The presenee of an inner core in the Earth is revealed from
observations of the seismie pliase PKP in the « sliadow zone » for
which the epicentral distance A lies in the range 105" < A < 143".
Miss I. Lehmann (r in 1936, followed by Gutenberg and Richter (2
in 1938, atlrihuted these observations to tlie presence of an inner
core; and Jeffreys (3 in 1939 applied Airy's theory of diffraetion
near a caustic to sliow that the alternative theory of diffraetion
round the outer boundary of the centrai core was not capable of
explaining tlie observations in the shadow zone. The existence of the
inner core has been fairly generallv accepted sinee tliis ealculation
of Jeffreys.
The theory of pseudo-rigid bodies
Cohen, Harley
1988-01-01
This monograph concerns the development, analysis, and application of the theory of pseudo-rigid bodies. It collects together our work on that subject over the last five years. While some results have appeared else where, much of the work is new. Our objective in writing this mono graph has been to present a new theory of the deformation of bodies, one that has not only a firm theoretical basis, but also the simplicity to serve as an effective tool in practical problems. Consequently, the main body of the treatise is a multifaceted development of the theory, from foundations to explicit solutions to linearizations to methods of approximation. The fact that this variety of aspects, each examined in considerable detail, can be collected together in a single, unified treat ment gives this theory an elegance that we feel sets it apart from many others. While our goal has always been to give a complete treatment of the theory as it now stands, the work here is not meant to be definitive. Theories are not ent...
Rigid multipodal platforms for metal surfaces
Directory of Open Access Journals (Sweden)
Michal Valášek
2016-03-01
Full Text Available In this review the recent progress in molecular platforms that form rigid and well-defined contact to a metal surface are discussed. Most of the presented examples have at least three anchoring units in order to control the spatial arrangement of the protruding molecular subunit. Another interesting feature is the lateral orientation of these foot structures which, depending on the particular application, is equally important as the spatial arrangement of the molecules. The numerous approaches towards assembling and organizing functional molecules into specific architectures on metal substrates are reviewed here. Particular attention is paid to variations of both, the core structures and the anchoring groups. Furthermore, the analytical methods enabling the investigation of individual molecules as well as monomolecular layers of ordered platform structures are summarized. The presented multipodal platforms bearing several anchoring groups form considerably more stable molecule–metal contacts than corresponding monopodal analogues and exhibit an enlarged separation of the functional molecules due to the increased footprint, as well as restrict tilting of the functional termini with respect to the metal surface. These platforms are thus ideally suited to tune important properties of the molecule–metal interface. On a single-molecule level, several of these platforms enable the control over the arrangement of the protruding rod-type molecular structures (e.g., molecular wires, switches, rotors, sensors with respect to the surface of the substrate.
Inflatable Tubular Structures Rigidized with Foams
Tinker, Michael L.; Schnell, Andrew R.
2010-01-01
Inflatable tubular structures that have annular cross sections rigidized with foams, and the means of erecting such structures in the field, are undergoing development. Although the development effort has focused on lightweight structural booms to be transported in compact form and deployed in outer space, the principles of design and fabrication are also potentially applicable to terrestrial structures, including components of ultralightweight aircraft, lightweight storage buildings and shelters, lightweight insulation, and sales displays. The use of foams to deploy and harden inflatable structures was first proposed as early as the 1960s, and has been investigated in recent years by NASA, the U.S. Air Force Research Laboratory, industry, and academia. In cases of deployable booms, most of the investigation in recent years has focused on solid cross sections, because they can be constructed relatively easily. However, solid-section foam-filled booms can be much too heavy for some applications. In contrast, booms with annular cross sections according to the present innovation can be tailored to obtain desired combinations of stiffness and weight through choice of diameters, wall thicknesses, and foam densities. By far the most compelling advantage afforded by this innovation is the possibility of drastically reducing weights while retaining or increasing the stiffnesses, relative to comparable booms that have solid foamfilled cross sections. A typical boom according to this innovation includes inner and outer polyimide film sleeves to contain foam that is injected between them during deployment.
Rigid Residue Scan Simulations Systematically Reveal Residue Entropic Roles in Protein Allostery.
Directory of Open Access Journals (Sweden)
Robert Kalescky
2016-04-01
Full Text Available Intra-protein information is transmitted over distances via allosteric processes. This ubiquitous protein process allows for protein function changes due to ligand binding events. Understanding protein allostery is essential to understanding protein functions. In this study, allostery in the second PDZ domain (PDZ2 in the human PTP1E protein is examined as model system to advance a recently developed rigid residue scan method combining with configurational entropy calculation and principal component analysis. The contributions from individual residues to whole-protein dynamics and allostery were systematically assessed via rigid body simulations of both unbound and ligand-bound states of the protein. The entropic contributions of individual residues to whole-protein dynamics were evaluated based on covariance-based correlation analysis of all simulations. The changes of overall protein entropy when individual residues being held rigid support that the rigidity/flexibility equilibrium in protein structure is governed by the La Châtelier's principle of chemical equilibrium. Key residues of PDZ2 allostery were identified with good agreement with NMR studies of the same protein bound to the same peptide. On the other hand, the change of entropic contribution from each residue upon perturbation revealed intrinsic differences among all the residues. The quasi-harmonic and principal component analyses of simulations without rigid residue perturbation showed a coherent allosteric mode from unbound and bound states, respectively. The projection of simulations with rigid residue perturbation onto coherent allosteric modes demonstrated the intrinsic shifting of ensemble distributions supporting the population-shift theory of protein allostery. Overall, the study presented here provides a robust and systematic approach to estimate the contribution of individual residue internal motion to overall protein dynamics and allostery.
Transferring the Cost of Wage Rigidity to Subcontracting Firms: The Case of Korea
Directory of Open Access Journals (Sweden)
Kwangho Woo
2016-08-01
Full Text Available We select a Korean case with ample subcontracting practices and a rigid wage system. Workplaces with subcontract transactions would have reason to impute the additional wage incremental costs associated with the seniority-based wage system (Hobong in Korea to subcontractors. Our empirical results identify the cost-transferring mechanism under which the cost of wage rigidity for contractors is transferred to subcontracting firms and aggravates the wage inequality among workers in contracting and subcontracting firms. We analyze the industrial difference in the intensity of this transferring mechanism and probe policy directions considering the improvement of both the subcontracting structure and pay system simultaneously. For the sustainability of firms, they need to reform a seniority-based wage system, an incentive-based wage system or a job-based wage system and the exploited subcontracting structure for creating share value.
BUTCHER, PR; KALVERBOER, A; MINDERAA, RB; VANDOORMAAL, EF; TENWOLDE, Y
1993-01-01
The associations between a mother's rigidity, her sensitivity in early (3 month) interaction and the quality of her premature infant's attachment at 13 months were investigated. Rigidity as a personality characteristic was not found to be significantly associated with sensitivity or quality of
Rocking Rotation of a Rigid Disk Embedded in a Transversely Isotropic Half-Space
Directory of Open Access Journals (Sweden)
Seyed Ahmadi
2014-06-01
Full Text Available The asymmetric problem of rocking rotation of a circular rigid disk embedded in a finite depth of a transversely isotropic half-space is analytically addressed. The rigid disk is assumed to be in frictionless contact with the elastic half-space. By virtue of appropriate Green's functions, the mixed boundary value problem is written as a dual integral equation. Employing further mathematical techniques, the integral equation is reduced to a well-known Fredholm integral equation of the second kind. The results related to the contact stress distribution across the disk region and the equivalent rocking stiffness of the system are expressed in terms of the solution of the obtained Fredholm integral equation. When the rigid disk is located on the surface or at the remote boundary, the exact closed-form solutions are presented. For verification purposes, the limiting case of an isotropic half-space is considered and the results are verified with those available in the literature. The jump behavior in the results at the edge of the rigid disk for the case of an infinitesimal embedment is highlighted analytically for the first time. Selected numerical results are depicted for the contact stress distribution across the disk region, rocking stiffness of the system, normal stress, and displacement components along the radial axis. Moreover, effects of anisotropy on the rocking stiffness factor are discussed in detail.
Patel, Jitendra Kumar; Natarajan, Ganesh
2018-05-01
We present an interpolation-free diffuse interface immersed boundary method for multiphase flows with moving bodies. A single fluid formalism using the volume-of-fluid approach is adopted to handle multiple immiscible fluids which are distinguished using the volume fractions, while the rigid bodies are tracked using an analogous volume-of-solid approach that solves for the solid fractions. The solution to the fluid flow equations are carried out using a finite volume-immersed boundary method, with the latter based on a diffuse interface philosophy. In the present work, we assume that the solids are filled with a "virtual" fluid with density and viscosity equal to the largest among all fluids in the domain. The solids are assumed to be rigid and their motion is solved using Newton's second law of motion. The immersed boundary methodology constructs a modified momentum equation that reduces to the Navier-Stokes equations in the fully fluid region and recovers the no-slip boundary condition inside the solids. An implicit incremental fractional-step methodology in conjunction with a novel hybrid staggered/non-staggered approach is employed, wherein a single equation for normal momentum at the cell faces is solved everywhere in the domain, independent of the number of spatial dimensions. The scalars are all solved for at the cell centres, with the transport equations for solid and fluid volume fractions solved using a high-resolution scheme. The pressure is determined everywhere in the domain (including inside the solids) using a variable coefficient Poisson equation. The solution to momentum, pressure, solid and fluid volume fraction equations everywhere in the domain circumvents the issue of pressure and velocity interpolation, which is a source of spurious oscillations in sharp interface immersed boundary methods. A well-balanced algorithm with consistent mass/momentum transport ensures robust simulations of high density ratio flows with strong body forces. The
Reversible Rigidity Control Using Low Melting Temperature Alloys
Shan, Wanliang; Lu, Tong; Majidi, Carmel
2013-03-01
Inspired by nature, materials able to achieve rapid rigidity changes have important applications for human body protection in military and many other areas. This talk presents the fabrication and design of soft-matter technologies that exhibit rapid reversible rigidity control. Fabricated with a masked deposition technique, the soft-matter composite contains liquid-phase and phase-changing metal alloys embedded in a soft and highly stretchable elastomer. The composite material can reversibly change its rigidity by three orders of magnitude and sustain large deformation.
The Almost Periodic Rigidity of Crystallographic Bar-Joint Frameworks
Directory of Open Access Journals (Sweden)
Ghada Badri
2014-04-01
Full Text Available A crystallographic bar-joint framework, C in Rd, is shown to be almost periodically infinitesimally rigid if and only if it is strictly periodically infinitesimally rigid and the rigid unit mode (RUM spectrum, Ω (C, is a singleton. Moreover, the almost periodic infinitesimal flexes of C are characterised in terms of a matrix-valued function, ΦC(z, on the d-torus, Td, determined by a full rank translation symmetry group and an associated motif of joints and bars.
APPLICATION OF RIGID LINKS IN STRUCTURAL DESIGN MODELS
Directory of Open Access Journals (Sweden)
Sergey Yu. Fialko
2017-09-01
Full Text Available A special finite element modelling rigid links is proposed for the linear static and buckling analysis. Unlike the classical approach based on the theorems of rigid body kinematics, the proposed approach preserves the similarity between the adjacency graph for a sparse matrix and the adjacency graph for nodes of the finite element model, which allows applying sparse direct solvers more effectively. Besides, the proposed approach allows significantly reducing the number of nonzero entries in the factored stiffness matrix in comparison with the classical one, which greatly reduces the duration of the solution. For buckling problems of structures containing rigid bodies, this approach gives correct results. Several examples demonstrate its efficiency.
New integrable problems in a rigid body dynamics with cubic integral in velocities
Elmandouh, A. A.
2018-03-01
We introduce a new family of the 2D integrable mechanical system possessing an additional integral of the third degree in velocities. This system contains 20 arbitrary parameters. We also clarify that the majority of the previous systems with a cubic integral can be reconstructed from it as a special version for certain values of those parameters. The applications of this system are extended to include the problem of motion of a particle and rigid body about its fixed point. We announce new integrable problems describing the motion of a particle in the plane, pseudosphere, and surfaces of variable curvature. We also present a new integrable problem in a rigid body dynamics and this problem generalizes some of the previous results for Sokolov-Tsiganov, Yehia, Stretensky, and Goriachev.
A study of semi-rigid support on ankle supination sprain kinematics.
Tang, Y M; Wu, Z H; Liao, W H; Chan, K M
2010-12-01
Ankle sprain injury is very common in sports and the use of ankle support is crucial. This research investigated the effect of an ankle brace in reducing the ankle angular displacement and angular velocity during sudden supination. In the experiment, 11 healthy males were tested. The bracing condition, semi-rigid ankle braces were investigated. The angular displacement and angular velocity of the ankle were computed. The motion-capture system was adopted to capture the three-dimensional coordinates of the reflective markers. The coordinates of the reflective markers were used to compute the ankle kinematics during simulated ankle supination. A mechanical supination platform was used to simulate the sprain motions. Experimental results showed that the semi-rigid brace tested significantly reduced the ankle angular displacement and angular velocity compared with control conditions during sudden supination. In conclusion, the semi-rigid-type brace can provide significant restriction to reduce the magnitudes of the angular displacement and angular velocity of the ankle during sudden supination sprain. The semi-rigid-type brace is suggested as the prophylactic bracing for the ankle. © 2009 John Wiley & Sons A/S.
Bucci, Lorenzo; Lavagna, Michèle; Guzzetti, Davide; Howell, Kathleen C.
2018-06-01
Interest on Large Space Structures (LSS), orbiting in strategic and possibly long-term stable locations, is nowadays increasing in the space community. LSS can serve as strategic outpost to support a variety of manned and unmanned mission, or may carry scientific payloads for astronomical observations. The paper focuses on analysing LSS in the Earth-Moon system, exploring dynamical structures that are available within a multi-body gravitational environment. Coupling between attitude and orbital dynamics is investigated, with particular interest on the gravity gradient torque exerted by the two massive attractors. First, natural periodic orbit-attitude solutions are obtained; a LSS that exploits such solutions would benefit of a naturally periodic body rotation synchronous with the orbital motion, easing the effort of the attitude control system to satisfy pointing requirements. Then, the solar radiation pressure is introduced into the fully coupled dynamical model and its effects investigated, discovering novel periodic attitude solutions. Benefits of periodic behaviours that incorporate solar radiation pressure are discussed, and analysed via the variation of some parameters (e.g reflection/absorption coefficients, position of the centre of pressure). As a final step to refine the current perturbed orbit-attitude model, a structure flexibility is also superimposed to a reference orbit-attitude rigid body motion via a simple, yet effective model. The coupling of structural vibrations and attitude motion is preliminarily explored, and allows identification of possible challenges, that may be faced to position a LSS in a periodic orbit within the Earth-Moon system.
1993-07-09
Calculate Oil and solve iteratively equation (18) for q and (l)-(S) forex . 4, Solve the velocity problemn through equation (19) to calculate q and (6)-(10) to...object.oriented models for the database to store the system information f1l. Using OOP on the formalism level is more difficult and a current field of...Multidimensional Physical Systems: Graph-theoretic Modeling, Systems and Cybernetics, vol 21 (1992), 5 .9-71 JV A RELATIONAL DATABASE FOR GENERAL
Oscillations of rigid bar in the special relativity
International Nuclear Information System (INIS)
Paiva, F.M.; Teixeira, A.F.F.
2011-12-01
In the special relativity, a rigid bar slides on herself, with a extreme oscillating harmonically. We have discovered at the movement amplitude and in the bar length, indispensable for the elimination of non physical solutions
Rigid body motion in stereo 3D simulation
International Nuclear Information System (INIS)
Zabunov, Svetoslav
2010-01-01
This paper addresses the difficulties experienced by first-grade students studying rigid body motion at Sofia University. Most quantities describing the rigid body are in relations that the students find hard to visualize and understand. They also lose the notion of cause-result relations between vector quantities, such as the relation between torque and angular momentum. Consequently, the understanding of physical laws and conservation principles in free rigid body motion is hampered. This paper presents the capabilities of a 3D simulation, which aims to clarify these questions to the students, who are taught mechanics in the general physics course. The rigid body motion simulations may be observed at http://ialms.net/sim/, and are intended to complement traditional learning practices, not replace them, as the author shares the opinion that no simulation may fully resemble reality.
Resin Infusion Rigidized Inflatable Concept Development and Demonstration
National Aeronautics and Space Administration — A novel concept utilizing resin infusion to rigidize inflatable structures was developed at JSC ES. This ICA project intends to complete manufacturing of a prototype...
Genus Ranges of 4-Regular Rigid Vertex Graphs.
Buck, Dorothy; Dolzhenko, Egor; Jonoska, Nataša; Saito, Masahico; Valencia, Karin
2015-01-01
A rigid vertex of a graph is one that has a prescribed cyclic order of its incident edges. We study orientable genus ranges of 4-regular rigid vertex graphs. The (orientable) genus range is a set of genera values over all orientable surfaces into which a graph is embedded cellularly, and the embeddings of rigid vertex graphs are required to preserve the prescribed cyclic order of incident edges at every vertex. The genus ranges of 4-regular rigid vertex graphs are sets of consecutive integers, and we address two questions: which intervals of integers appear as genus ranges of such graphs, and what types of graphs realize a given genus range. For graphs with 2 n vertices ( n > 1), we prove that all intervals [ a, b ] for all a genus ranges. For graphs with 2 n - 1 vertices ( n ≥ 1), we prove that all intervals [ a, b ] for all a genus ranges. We also provide constructions of graphs that realize these ranges.
Re-analysis of exponential rigid-rotor astron equilibria
International Nuclear Information System (INIS)
Lovelace, R.V.; Larrabee, D.A.; Fleischmann, H.H.
1978-01-01
Previous studies of exponential rigid-rotor astron equilibria include particles which are not trapped in the self-field of the configuration. The modification of these studies required to exclude untrapped particles is derived
Rigidity theorem for Willmore surfaces in a sphere
Indian Academy of Sciences (India)
Home; Journals; Proceedings – Mathematical Sciences; Volume 126; Issue 2. Rigidity ... Center of Mathematical Sciences, Zhejiang University, Hangzhou 310027, People's Republic of China; College of Mathematics and Information Science, Jiangxi Normal University, Nanchang 330022, People's Republic of China ...
Role of Rigid Endoscopic Detorsion in the Management of Sigmoid ...
African Journals Online (AJOL)
had emergency surgery, with gangrenous bowel noted in 43 (72%) ... of any stable patient with clinical and radiological features ... peritonitis, underwent repeat rigid sigmoidoscopy. ... endoscopic detorsion was successful in all six cases.
Stabilization of Rigid Body Dynamics by Internal and External Torques
National Research Council Canada - National Science Library
Bloch, A. M; Krishnaprasad, P. S; Marsden, J. E; Sanchez de Alvarez, G
1990-01-01
...] with quadratic feedback torques for internal rotors. We show that with such torques, the equations for the rigid body with momentum wheels are Hamiltonian with respect to a Lie-Poisson bracket structure. Further...
Anti-synchronization of the rigid body exhibiting chaotic dynamics ...
African Journals Online (AJOL)
Based on a method derived from nonlinear control theory, we present a ... In this framework, the active control technique is modified and employed to design control ... state space of the two rigid bodies was verified by numerical simulations.
Thermally-Induced Structural Disturbances of Rigid Panel Solar Arrays
Johnston, John D.; Thornton, Earl A.
1997-01-01
The performance of a significant number of spacecraft has been impacted negatively by attitude disturbances resulting from thermally-induced motions of flexible structures. Recent examples of spacecraft affected by these disturbances include the Hubble Space Telescope (HST) and the Upper Atmosphere Research Satellite (UARS). Thermally-induced structural disturbances occur as the result of rapid changes in thermal loading typically initiated as a satellite exits or enters the Earth's shadow. Temperature differences in flexible appendages give rise to structural deformations, which in turn result in disturbance torques reacting back on the spacecraft. Structures which have proven susceptible to these disturbances include deployable booms and solar arrays. This paper investigates disturbances resulting from thermally-induced deformations of rigid panel solar arrays. An analytical model for the thermal-structural response of the solar array and the corresponding disturbance torque are presented. The effect of these disturbances on the attitude dynamics of a simple spacecraft is then investigated using a coupled system of governing equations which includes the effects of thermally-induced deformations. Numerical results demonstrate the effect of varying solar array geometry on the dynamic response of the system.
Topological classification of the Goryachev integrable case in rigid body dynamics
International Nuclear Information System (INIS)
Nikolaenko, S S
2016-01-01
A topological analysis of the Goryachev integrable case in rigid body dynamics is made on the basis of the Fomenko-Zieschang theory. The invariants (marked molecules) which are obtained give a complete description, from the standpoint of Liouville classification, of the systems of Goryachev type on various level sets of the energy. It turns out that on appropriate energy levels the Goryachev case is Liouville equivalent to many classical integrable systems and, in particular, the Joukowski, Clebsch, Sokolov and Kovalevskaya-Yehia cases in rigid body dynamics, as well as to some integrable billiards in plane domains bounded by confocal quadrics -- in other words, the foliations given by the closures of generic solutions of these systems have the same structure. Bibliography: 15 titles
Micoulaut, Matthieu
2010-07-21
A low temperature Monte Carlo dynamics of a Keating-like oscillator model is used to study the relationship between the nature of network glasses from the viewpoint of rigidity, the thermal reversibility during the glass transition and the strong-fragile behaviour of glass-forming liquids. The model shows that a Phillips optimal glass formation with minimal enthalpic changes is obtained under a cooling/annealing cycle when the system is optimally constrained by the harmonic interactions, i.e. when it is isostatically rigid. For these peculiar systems with a nearly reversible glass transition, the computed activation energy for relaxation time shows also a minimum, which demonstrates that isostatically rigid glasses are strong (Arrhenius-like) glass-forming liquids. Experiments on chalcogenide and oxide glass-forming liquids are discussed under this new perspective and confirm the theoretical prediction for chalcogenide network glasses whereas limitations of the approach appear for weakly interacting (non-covalent, ionic) systems.
1993-07-09
of rmultibod systems. Chapter 7. Centro de Estudios e Investigaciones Ticnicas de Guipuzcoa.. San Sebastian. Espafia. 18. Gantmacler F.R. (1959). The...Research Development, project P77; JNICT - Junta Nacional de Investigagio Cientifica e -i Tecnologica , Project STRD/CtIPRo569/92. Also the
Unifying Rigid and Soft Bodies Representation: The Sulfur Physics Engine
Directory of Open Access Journals (Sweden)
Dario Maggiorini
2014-01-01
Full Text Available Video games are (also real-time interactive graphic simulations: hence, providing a convincing physics simulation for each specific game environment is of paramount importance in the process of achieving a satisfying player experience. While the existing game engines appropriately address many aspects of physics simulation, some others are still in need of improvements. In particular, several specific physics properties of bodies not usually involved in the main game mechanics (e.g., properties useful to represent systems composed by soft bodies, are often poorly rendered by general-purpose engines. This issue may limit game designers when imagining innovative and compelling video games and game mechanics. For this reason, we dug into the problem of appropriately representing soft bodies. Subsequently, we have extended the approach developed for soft bodies to rigid ones, proposing and developing a unified approach in a game engine: Sulfur. To test the engine, we have also designed and developed “Escape from Quaoar,” a prototypal video game whose main game mechanic exploits an elastic rope, and a level editor for the game.
Obstacles to developing sustainable cities: the real estate rigidity trap
Directory of Open Access Journals (Sweden)
V. Kelly Turner
2017-06-01
Full Text Available Sprawl patterns of urbanization have large environmental consequences, and sustainable alternatives to conventional urban patterns of development have been promoted by a subset of planners, design professionals, and municipalities. These alternatives have not been widely adopted among real estate developers, actors with large influence over urban form and function. Existing explanations for this failure enumerate market and regulatory barriers but do not sufficiently describe the institutional structures that allow conventional approaches to prevail. A failure of real estate developers to adopt alternative forms of development can best be described in terms of a rigidity trap. Specifically, norms of practice within the real estate development industry combine with market and regulatory factors to favor existing practices and limit innovation. Moreover, these institutional factors also buffer the real estate development industry from feedback mechanisms and external signals that might otherwise trigger adaptation. Addressing the environmental consequences of urbanization not only requires novel approaches to urban design, but will also necessitate addressing systemic pathologies in the design implementation process.
Optical characterization and polarization calibration for rigid endoscopes
Garcia, Missael; Gruev, Viktor
2017-02-01
Polarization measurements give orthogonal information to spectral images making them a great tool in the characterization of environmental parameters in nature. Thus, polarization imagery has proven to be remarkably useful in a vast range of biomedical applications. One such application is the early diagnosis of flat cancerous lesions in murine colorectal tumor models, where polarization data complements NIR fluorescence analysis. Advances in nanotechnology have led to compact and precise bio-inspired imaging sensors capable of accurately co-registering multidimensional spectral and polarization information. As more applications emerge for these imagers, the optics used in these instruments get very complex and can potentially compromise the original polarization state of the incident light. Here we present a complete optical and polarization characterization of three rigid endoscopes of size 1.9mm x 10cm (Karl Storz, Germany), 5mm x 30cm, and 10mm x 33cm (Olympus, Germany), used in colonoscopy for the prevention of colitis-associated cancer. Characterization results show that the telescope optics act as retarders and effectively depolarize the linear component. These incorrect readings can cause false-positives or false-negatives leading to an improper diagnosis. In this paper, we offer a polarization calibration scheme for these endoscopes based on Mueller calculus. By modeling the optical properties from training data as real-valued Mueller matrices, we are able to successfully reconstruct the initial polarization state acquired by the imaging system.
International Nuclear Information System (INIS)
Caparrós, Alejandro; Péreau, Jean-Christophe; Tazdaït, Tarik
2013-01-01
Emission trading systems have been proposed in different regions to reduce polluting emissions and are in use in the European Union for carbon dioxide emissions. One of the objectives of these systems is to encourage firms to adopt advanced abatement technologies. However, permits also create an incentive to reduce output, which may be seen as negative by policy makers. We analyze the impact of a rigid labour market on these two outcomes, showing the conditions necessary to avoid reductions in production while keeping the incentives to improve abatement technologies. The analysis is done for oligopolistic firms engaged in international rivalry. - Highlights: ► Emission trading reduces production and improves abatement technologies. ► Policy makers see the first outcome as negative and the second as positive. ► This paper studies the impact of market rigidity on these two outcomes. ► It shows conditions to avoid the first outcome and maintain or enhance the second
Axisymmetric scattering of an acoustical Bessel beam by a rigid fixed spheroid
Mitri, F. G.
2015-01-01
Based on the partial-wave series expansion (PWSE) method in spherical coordinates, a formal analytical solution for the acoustic scattering of a zeroth-order Bessel acoustic beam centered on a rigid fixed (oblate or prolate) spheroid is provided. The unknown scattering coefficients of the spheroid are determined by solving a system of linear equations derived for the Neumann boundary condition. Numerical results for the modulus of the backscattered pressure (\\theta = \\pi) in the near-field an...
Active vibration reduction of rigid rotor by kinematic excitation of bushes of journal bearings
Directory of Open Access Journals (Sweden)
J. Ondrouch
2010-04-01
Full Text Available Possibilities of active lateral vibration reduction of a symmetric, rigid rotor supported by journal bearings are given. They were obtained by computational modelling. Efficiency of the feedback P and PD controllers in the stable revolution interval was examined. The linearized rotor system model was used. The results of the theoretical analysis are assigned for a testing stand where the bearing bush motions are deactivated by piezoelectric actuators connected to the controllers.
Soft-matter composites with electrically tunable elastic rigidity
International Nuclear Information System (INIS)
Shan, Wanliang; Lu, Tong; Majidi, Carmel
2013-01-01
We use a phase-changing metal alloy to reversibly tune the elastic rigidity of an elastomer composite. The elastomer is embedded with a sheet of low-melting-point Field’s metal and an electric Joule heater composed of a serpentine channel of liquid-phase gallium–indium–tin (Galinstan ® ) alloy. At room temperature, the embedded Field’s metal is solid and the composite remains elastically rigid. Joule heating causes the Field’s metal to melt and allows the surrounding elastomer to freely stretch and bend. Using a tensile testing machine, we measure that the effective elastic modulus of the composite reversibly changes by four orders of magnitude when powered on and off. This dramatic change in rigidity is accurately predicted with a model for an elastic composite. Reversible rigidity control is also accomplished by replacing the Field’s metal with shape memory polymer. In addition to demonstrating electrically tunable rigidity with an elastomer, we also introduce a new technique to rapidly produce soft-matter electronics and multifunctional materials in several minutes with laser-patterned adhesive film and masked deposition of liquid-phase metal alloy. (paper)
Soft-matter composites with electrically tunable elastic rigidity
Shan, Wanliang; Lu, Tong; Majidi, Carmel
2013-08-01
We use a phase-changing metal alloy to reversibly tune the elastic rigidity of an elastomer composite. The elastomer is embedded with a sheet of low-melting-point Field’s metal and an electric Joule heater composed of a serpentine channel of liquid-phase gallium-indium-tin (Galinstan®) alloy. At room temperature, the embedded Field’s metal is solid and the composite remains elastically rigid. Joule heating causes the Field’s metal to melt and allows the surrounding elastomer to freely stretch and bend. Using a tensile testing machine, we measure that the effective elastic modulus of the composite reversibly changes by four orders of magnitude when powered on and off. This dramatic change in rigidity is accurately predicted with a model for an elastic composite. Reversible rigidity control is also accomplished by replacing the Field’s metal with shape memory polymer. In addition to demonstrating electrically tunable rigidity with an elastomer, we also introduce a new technique to rapidly produce soft-matter electronics and multifunctional materials in several minutes with laser-patterned adhesive film and masked deposition of liquid-phase metal alloy.
Unified Creep Plasticity Damage (UCPD) Model for Rigid Polyurethane Foams.
Energy Technology Data Exchange (ETDEWEB)
Neilsen, Michael K. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lu, Wei-Yang [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Scherzinger, William M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hinnerichs, Terry D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lo, Chi S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2015-06-01
Numerous experiments were performed to characterize the mechanical response of several different rigid polyurethane foams (FR3712, PMDI10, PMDI20, and TufFoam35) to large deformation. In these experiments, the effects of load path, loading rate, and temperature were investigated. Results from these experiments indicated that rigid polyurethane foams exhibit significant volumetric and deviatoric plasticity when they are compressed. Rigid polyurethane foams were also found to be very strain-rate and temperature dependent. These foams are also rather brittle and crack when loaded to small strains in tension or to larger strains in compression. Thus, a new Unified Creep Plasticity Damage (UCPD) model was developed and implemented into SIERRA with the name Foam Damage to describe the mechanical response of these foams to large deformation at a variety of temperatures and strain rates. This report includes a description of recent experiments and experimental findings. Next, development of a UCPD model for rigid, polyurethane foams is described. Selection of material parameters for a variety of rigid polyurethane foams is then discussed and finite element simulations with the new UCPD model are compared with experimental results to show behavior that can be captured with this model.
Evaluation for rigidity of box construction of nuclear reactor building
International Nuclear Information System (INIS)
Yamakawa, Tetsuo
1979-01-01
A huge box-shaped structure (hereafter, called box construction) of reinforced concrete is presently utilized as the reactor building structure in nuclear power plants. Evaluation of the rigidity of the huge box construction is required for making a vibration analysis model of nuclear reactor buildings. It is necessary to handle the box construction as the plates to which the force in plane is applied. This paper describes that the bending theory in elementary beam theory is equivalent to a peculiar, orthogonally anisotropic plate, the shearing rigidity and film rigidity in y direction of which are put to infinity and the Poisson's ratio is put to zero, viewed from the two-dimensional theory of elasticity. The form factor of 1.2 for shearing deformation in rectangular cross section was calculated from the parabolic distribution of shearing stress intensity, and it is the maximum value. The factor is equal to 1.2 for slender beams, but smaller than 1.2 for short and thick beams, having tendency to converge to 1.0. The non-conformity of boundary conditions regarding the shearing force at the both ends of cantilevers does not affect very seriously the evaluation of shearing rigidity. From the above results, it was found that the application of the theory to the box construction was able to give the rigidity evaluation with sufficient engineering accuracy. The theory can also be applied to the evaluation of tube type ultrahigh buildings. (Wakatsuki, Y.)
Euler-Poincaré Reduction of Externally Forced Rigid Body Motion
DEFF Research Database (Denmark)
Wisniewski, Rafal; Kulczycki, P.
2004-01-01
If a mechanical system experiences symmetry, the Lagrangian becomes invariant under a certain group action. This property leads to substantial simplification of the description of movement. The standpoint in this article is a mechanical system affected by an external force of a control action....... Assuming that the system possesses symmetry and the configuration manifold corresponds to a Lie group, the Euler-Poincaré reduction breaks up the motion into separate equations of dynamics and kinematics. This becomes of particular interest for modelling, estimation and control of mechanical systems......-known Euler-Poincaré reduction to a rigid body motion with forcing....
Post-Newtonian conservation laws in rigid quasilocal frames
International Nuclear Information System (INIS)
McGrath, Paul L; Chanona, Melanie; Epp, Richard J; Mann, Robert B; Koop, Michael J
2014-01-01
In recent work we constructed completely general conservation laws for energy (McGrath et al 2012 Class. Quantum Grav. 29 215012) and linear and angular momentum (Epp et al 2013 Class. Quantum Grav. 30 195019) of extended systems in general relativity based on the notion of a rigid quasilocal frame (RQF). We argued at a fundamental level that these RQF conservation laws are superior to conservation laws based on the local stress–energy–momentum tensor of matter because (1) they do not rely on spacetime symmetries and (2) they properly account for both matter and gravitational effects. Moreover, they provide simple, exact, operational expressions for fluxes of gravitational energy and linear and angular momentum. In this paper we derive the form of these laws in a general first post-Newtonian (1PN) approximation, and then apply these approximate laws to the problem of gravitational tidal interactions. We obtain formulas for tidal heating and tidal torque that agree with the literature, but without resorting to the use of pseudotensors. We describe the physical mechanism of these tidal interactions not in the traditional terms of a Newtonian gravitational force, but in terms of a much simpler and universal mechanism that is an exact, quasilocal manifestation of the equivalence principle in general relativity. As concrete examples, we look at the tidal heating of Jupiter’s moon Io and angular momentum transfer in the Earth–Moon system that causes a gradual spin-down of the Earth and recession of the Moon. In both examples we find agreement with observation. (paper)
Rigidity of outermost MOTS: the initial data version
Galloway, Gregory J.
2018-03-01
In the paper Commun Anal Geom 16(1):217-229, 2008, a rigidity result was obtained for outermost marginally outer trapped surfaces (MOTSs) that do not admit metrics of positive scalar curvature. This allowed one to treat the "borderline case" in the author's work with R. Schoen concerning the topology of higher dimensional black holes (Commun Math Phys 266(2):571-576, 2006). The proof of this rigidity result involved bending the initial data manifold in the vicinity of the MOTS within the ambient spacetime. In this note we show how to circumvent this step, and thereby obtain a pure initial data version of this rigidity result and its consequence concerning the topology of black holes.
Authoritarianism, cognitive rigidity, and the processing of ambiguous visual information.
Duncan, Lauren E; Peterson, Bill E
2014-01-01
Intolerance of ambiguity and cognitive rigidity are unifying aspects of authoritarianism as defined by Adorno, Frenkel-Brunswik, Levinson, and Sanford (1982/1950), who hypothesized that authoritarians view the world in absolute terms (e.g., good or evil). Past studies have documented the relationship between authoritarianism and intolerance of ambiguity and rigidity. Frenkel-Brunswik (1949) hypothesized that this desire for absolutism was rooted in perceptual processes. We present a study with three samples that directly tests the relationship between right wing authoritarianism (RWA) and the processing of ideologically neutral but ambiguous visual stimuli. As hypothesized, in all three samples we found that RWA was related to the slower processing of visual information that required participants to recategorize objects. In a fourth sample, RWA was unrelated to speed of processing visual information that did not require recategorization. Overall, results suggest a relationship between RWA and rigidity in categorization.
Mitral stenosis due to pannus overgrowth after rigid ring annuloplasty.
Oda, Takeshi; Kato, Seiya; Tayama, Eiki; Fukunaga, Shuji; Akashi, Hidetoshi; Aoyagi, Shigeaki
2010-03-01
Although mitral stenosis (MS) due to pannus overgrowth after mitral valve repair for rheumatic mitral regurgitation (MR) is not uncommon, it is extremely rare in relation to non-rheumatic mitral regurgitation. Whilst it has been suggested that the rigid annuloplasty ring induces pannus overgrowth in the same manner as the flexible ring, to date only in cases using the flexible ring has pannus formation been confirmed by a pathological examination after redo surgery. The case is described of a woman who had undergone mitral valve repair using a 28 mm rigid ring three years previously because of non-rheumatic MR, and subsequently suffered from MS due to pannus formation over the annuloplasty ring. To the present authors' knowledge, this is the first report of MS due to pannus formation after mitral valve repair using a rigid annuloplasty ring to treat non-rheumatic MR documented at reoperation.
Encountered-Type Haptic Interface for Representation of Shape and Rigidity of 3D Virtual Objects.
Takizawa, Naoki; Yano, Hiroaki; Iwata, Hiroo; Oshiro, Yukio; Ohkohchi, Nobuhiro
2017-01-01
This paper describes the development of an encountered-type haptic interface that can generate the physical characteristics, such as shape and rigidity, of three-dimensional (3D) virtual objects using an array of newly developed non-expandable balloons. To alter the rigidity of each non-expandable balloon, the volume of air in it is controlled through a linear actuator and a pressure sensor based on Hooke's law. Furthermore, to change the volume of each balloon, its exposed surface area is controlled by using another linear actuator with a trumpet-shaped tube. A position control mechanism is constructed to display virtual objects using the balloons. The 3D position of each balloon is controlled using a flexible tube and a string. The performance of the system is tested and the results confirm the effectiveness of the proposed principle and interface.
Contact point generation for convex polytopes in interactive rigid body dynamics
DEFF Research Database (Denmark)
Silcowitz-Hansen, Morten; Abel, Sarah Maria Niebe; Erleben, Kenny
When computing contact forces in rigid body dynamics systems, most state-of-the-art solutions use iterative methods such as the projected Gauss–Seidel (PGS) method. Methods such as the PGS method are preferred for their robustness. However, the time-critical nature of interactive applications...... combined with the linear convergence rates of such methods, will often result in visual artifacts in the final simulation. With this paper, we address an issue which is of major impact on the animation quality, when using methods such as the PGS method. The issue is robust generation of contact points...... for convex polytopes. A novel contact point generation method is presented, which is based on growth distances and Gauss maps. We demonstrate improvements when using our method in the context of interactive rigid body simulation...
Begon, Mickaël; Andersen, Michael Skipper; Dumas, Raphaël
2018-03-01
Multibody kinematics optimization (MKO) aims to reduce soft tissue artefact (STA) and is a key step in musculoskeletal modeling. The objective of this review was to identify the numerical methods, their validation and performance for the estimation of the human joint kinematics using MKO. Seventy-four papers were extracted from a systematized search in five databases and cross-referencing. Model-derived kinematics were obtained using either constrained optimization or Kalman filtering to minimize the difference between measured (i.e., by skin markers, electromagnetic or inertial sensors) and model-derived positions and/or orientations. While hinge, universal, and spherical joints prevail, advanced models (e.g., parallel and four-bar mechanisms, elastic joint) have been introduced, mainly for the knee and shoulder joints. Models and methods were evaluated using: (i) simulated data based, however, on oversimplified STA and joint models; (ii) reconstruction residual errors, ranging from 4 mm to 40 mm; (iii) sensitivity analyses which highlighted the effect (up to 36 deg and 12 mm) of model geometrical parameters, joint models, and computational methods; (iv) comparison with other approaches (i.e., single body kinematics optimization and nonoptimized kinematics); (v) repeatability studies that showed low intra- and inter-observer variability; and (vi) validation against ground-truth bone kinematics (with errors between 1 deg and 22 deg for tibiofemoral rotations and between 3 deg and 10 deg for glenohumeral rotations). Moreover, MKO was applied to various movements (e.g., walking, running, arm elevation). Additional validations, especially for the upper limb, should be undertaken and we recommend a more systematic approach for the evaluation of MKO. In addition, further model development, scaling, and personalization methods are required to better estimate the secondary degrees-of-freedom (DoF).
Richard, Vincent; Cappozzo, Aurelio; Dumas, Raphaël
2017-09-06
Estimating joint kinematics from skin-marker trajectories recorded using stereophotogrammetry is complicated by soft tissue artefact (STA), an inexorable source of error. One solution is to use a bone pose estimator based on multi-body kinematics optimisation (MKO) embedding joint constraints to compensate for STA. However, there is some debate over the effectiveness of this method. The present study aimed to quantitatively assess the degree of agreement between reference (i.e., artefact-free) knee joint kinematics and the same kinematics estimated using MKO embedding six different knee joint models. The following motor tasks were assessed: level walking, hopping, cutting, running, sit-to-stand, and step-up. Reference knee kinematics was taken from pin-marker or biplane fluoroscopic data acquired concurrently with skin-marker data, made available by the respective authors. For each motor task, Bland-Altman analysis revealed that the performance of MKO varied according to the joint model used, with a wide discrepancy in results across degrees of freedom (DoFs), models and motor tasks (with a bias between -10.2° and 13.2° and between -10.2mm and 7.2mm, and with a confidence interval up to ±14.8° and ±11.1mm, for rotation and displacement, respectively). It can be concluded that, while MKO might occasionally improve kinematics estimation, as implemented to date it does not represent a reliable solution to the STA issue. Copyright © 2017 Elsevier Ltd. All rights reserved.
Vision-based stress estimation model for steel frame structures with rigid links
Park, Hyo Seon; Park, Jun Su; Oh, Byung Kwan
2017-07-01
This paper presents a stress estimation model for the safety evaluation of steel frame structures with rigid links using a vision-based monitoring system. In this model, the deformed shape of a structure under external loads is estimated via displacements measured by a motion capture system (MCS), which is a non-contact displacement measurement device. During the estimation of the deformed shape, the effective lengths of the rigid link ranges in the frame structure are identified. The radius of the curvature of the structural member to be monitored is calculated using the estimated deformed shape and is employed to estimate stress. Using MCS in the presented model, the safety of a structure can be assessed gauge-freely. In addition, because the stress is directly extracted from the radius of the curvature obtained from the measured deformed shape, information on the loadings and boundary conditions of the structure are not required. Furthermore, the model, which includes the identification of the effective lengths of the rigid links, can consider the influences of the stiffness of the connection and support on the deformation in the stress estimation. To verify the applicability of the presented model, static loading tests for a steel frame specimen were conducted. By comparing the stress estimated by the model with the measured stress, the validity of the model was confirmed.
Effects of Rigid and Soft Foot Orthoses on Dynamic Balance in Females With Flatfoot
Directory of Open Access Journals (Sweden)
Hassan Saeedi
2007-08-01
Full Text Available Background:Various types of foot orthoses are prescribed for people with flatfoot.It has been reported that orthoses not only improve the biomechanics of the lower limb, but also have good effects on some balance parameters in these subjects.It is hypothesized that the latter effect is dependent on the rigidity of the orthoses. The aim of this study was to evaluate and compare the effects of rigid and soft foot orthoses on dynamic balance in females with flatfoot. The Biodex Balance System was used in a clinical trial study. Methods: 20 healthy students with bilateral flatfoot were randomly assigned to two equal groups. Each participant was tested on two days with 2-week interval. On each day, dynamic stability test was performed while standing in single-leg stance on an unstable platform of the balance system in 3 conditions (barefoot, with shoe, shoe with orthosis. SPSS11.5 was used for statistical analysis. Results: A significant group-by-day-by-condition interaction was found. Both groups on day 2 testing had a decreased overall stability index while wearing orthoses. Overall stability index was significantly lower on day 2 testing. Conclusion: Foot orthoses, depending on the amount of rigidity, were associated with some improvements in dynamic balance in subjects with flatfoot.
Topology-Preserving Rigid Transformation of 2D Digital Images.
Ngo, Phuc; Passat, Nicolas; Kenmochi, Yukiko; Talbot, Hugues
2014-02-01
We provide conditions under which 2D digital images preserve their topological properties under rigid transformations. We consider the two most common digital topology models, namely dual adjacency and well-composedness. This paper leads to the proposal of optimal preprocessing strategies that ensure the topological invariance of images under arbitrary rigid transformations. These results and methods are proved to be valid for various kinds of images (binary, gray-level, label), thus providing generic and efficient tools, which can be used in particular in the context of image registration and warping.
Non-rigid image registration using bone growth model
DEFF Research Database (Denmark)
Bro-Nielsen, Morten; Gramkow, Claus; Kreiborg, Sven
1997-01-01
Non-rigid registration has traditionally used physical models like elasticity and fluids. These models are very seldom valid models of the difference between the registered images. This paper presents a non-rigid registration algorithm, which uses a model of bone growth as a model of the change...... between time sequence images of the human mandible. By being able to register the images, this paper at the same time contributes to the validation of the growth model, which is based on the currently available medical theories and knowledge...
Rigid particle revisited: Extrinsic curvature yields the Dirac equation
Energy Technology Data Exchange (ETDEWEB)
Deriglazov, Alexei, E-mail: alexei.deriglazov@ufjf.edu.br [Depto. de Matemática, ICE, Universidade Federal de Juiz de Fora, MG (Brazil); Laboratory of Mathematical Physics, Tomsk Polytechnic University, 634050 Tomsk, Lenin Ave. 30 (Russian Federation); Nersessian, Armen, E-mail: arnerses@ysu.am [Yerevan State University, 1 Alex Manoogian St., Yerevan 0025 (Armenia); Laboratory of Mathematical Physics, Tomsk Polytechnic University, 634050 Tomsk, Lenin Ave. 30 (Russian Federation)
2014-03-01
We reexamine the model of relativistic particle with higher-derivative linear term on the first extrinsic curvature (rigidity). The passage from classical to quantum theory requires a number of rather unexpected steps which we report here. We found that, contrary to common opinion, quantization of the model in terms of so(3.2)-algebra yields massive Dirac equation. -- Highlights: •New way of canonical quantization of relativistic rigid particle is proposed. •Quantization made in terms of so(3.2) angular momentum algebra. •Quantization yields massive Dirac equation.
Elastic properties of rigid fiber-reinforced composites
Chen, J.; Thorpe, M. F.; Davis, L. C.
1995-05-01
We study the elastic properties of rigid fiber-reinforced composites with perfect bonding between fibers and matrix, and also with sliding boundary conditions. In the dilute region, there exists an exact analytical solution. Around the rigidity threshold we find the elastic moduli and Poisson's ratio by decomposing the deformation into a compression mode and a rotation mode. For perfect bonding, both modes are important, whereas only the compression mode is operative for sliding boundary conditions. We employ the digital-image-based method and a finite element analysis to perform computer simulations which confirm our analytical predictions.
Extremal surfaces and the rigidity of null geodesic incompleteness
International Nuclear Information System (INIS)
Silva, I P Costa e; Flores, J L
2015-01-01
An important, if relatively less well known aspect of the singularity theorems in Lorentzian geometry, is to understand how their conclusions fare upon weakening or suppression of one or more of their hypotheses. Then, theorems with modified conclusion may arise, showing that those conclusions will fail only in special cases, at least some of which may be described. These are the so-called rigidity theorems, and have many important examples in the specialized literature. In this paper, we prove rigidity results for generalized plane waves and certain globally hyperbolic spacetimes in the presence of extremal compact surfaces. (paper)
Motion of a Rigid Body Supported at One Point by a Rotating Arm
Directory of Open Access Journals (Sweden)
Jeffrey D. Stoen
1993-01-01
Full Text Available This article details a scheme for evaluating the stability of motions of a system consisting of a rigid body connected at one point to a rotating arm. The nonlinear equations of motion for the system are formulated, and a method for finding exact solutions representing motions that resemble a state of rest is presented. The equations are then linearized and roots of the eigensystem are classified and used to construct stability diagrams that facilitate the assessment of effects of varying the body's mass properties and system geometry, changing the position of the attachment joint, and adding energy dissipation in the joint.
Take-off and Landing Using Ground Based Power - Landing Simulations Using Multibody Dynamics
Wu, P.; Voskuijl, M.; Van Tooren, M.J.L.
2014-01-01
A novel take-off and landing system using ground based power is proposed in the EUFP7 project GABRIEL. The proposed system has the potential benefit to reduce aircraft weight, emissions and noise. A preliminary investigation of the feasibility of the structural design of the connection mechanism
Rezaie-Dereshgi, Amir; Mohammad-Rafiee, Farshid
2018-04-01
The electrostatic interactions play a crucial role in biological systems. Here we consider an impermeable dielectric molecule in the solvent with a different dielectric constant. The electrostatic free energy in the problem is studied in the Debye-Hückel regime using the analytical Green function that is calculated in the paper. Using this electrostatic free energy, we study the electrostatic contribution to the twist rigidity of a double stranded helical molecule such as a DNA and an actin filament. The dependence of the electrostatic twist rigidity of the molecule to the dielectric inhomogeneity, structural parameters, and the salt concentration is studied. It is shown that, depending on the parameters, the electrostatic twist rigidity could be positive or negative.
Noise characteristics of barium ferrite particulate rigid disks
Kodama, Naoki; Inoue, Hitoshi; Spratt, Geoffrey; Uesaka, Yasutaro; Katsumoto, Masayuki
1991-04-01
This paper discusses the relationship between the noise characteristics and magnetic properties of longitudinal barium ferrite (Ba-F) rigid disks with different switching field distributions (SFD). The magnetomotive force dependencies of reverse dc-erase (RDC) noise are measured and compared with SFD values. Coated disks with acicular magnetic particles have dips and thin-film disks peaks in the RDC. In Ba-F disks, both cases are observed depending on the SFD values, though the depths or heights of the RDC noise are much smaller than those of coated disks with acicular particles or thin-film disks. Disks with small SFD values have peaks, and disks with large SFD values have dips. In order to find the relationship between noise properties and magnetic properties, interparticle interactions in Ba-F disks are investigated. Reverse dc remanence Id(H) and ac-demagnetized isothermal remanence Ir(H) are measured. Both are normalized by the saturation remanence. The deviation from the noninteracting system, ΔM = Id(H) - [1ΔM=Id(H)-[1- 2Ir(H)] and an interaction field factor (IFF) given by (H'r - Hr)/Hc, are derived from these remanent properties. Here, H'r is the field corresponding to 50% of the remanent magnetization, Hr is remanence coercivity. In Ba-F disks, ΔM shows positive interactions, and the peak heights of ΔM increase and IFF decrease with decreasing SFD values. Positive interactions between Ba-F particles seem to be caused by particle stacking. Therefore, particle stacking results in small SFD values and peak-type RDC noise.
Constrained Multi-Body Dynamics for Modular Underwater Robots — Theory and Experiments
DEFF Research Database (Denmark)
Nielsen, Mikkel Cornelius; Eidsvik, Ole Alexander; Blanke, Mogens
2018-01-01
This paper investigates the problem of modelling a system of interconnected underwater robots with highly coupled dynamics. The objective is to develop a mathematical description of the system that captures its most significant dynamics. The proposed modelling method is based on active constraint...... on a BlueROV vehicle to determine the model parameters. The applicability of the modelling approach is assessed by comparing experimental data to simulations of an equivalent model synthesised using the proposed theory....
Engineering model for low-velocity impacts of multi-material cylinder on a rigid boundary
Directory of Open Access Journals (Sweden)
Delvare F.
2012-08-01
Full Text Available Modern ballistic problems involve the impact of multi-material projectiles. In order to model the impact phenomenon, different levels of analysis can be developed: empirical, engineering and simulation models. Engineering models are important because they allow the understanding of the physical phenomenon of the impact materials. However, some simplifications can be assumed to reduce the number of variables. For example, some engineering models have been developed to approximate the behavior of single cylinders when impacts a rigid surface. However, the cylinder deformation depends of its instantaneous velocity. At this work, an analytical model is proposed for modeling the behavior of a unique cylinder composed of two different metals cylinders over a rigid surface. Material models are assumed as rigid-perfectly plastic. Differential equation systems are solved using a numerical Runge-Kutta method. Results are compared with computational simulations using AUTODYN 2D hydrocode. It was found a good agreement between engineering model and simulation results. Model is limited by the impact velocity which is transition at the interface point given by the hydro dynamical pressure proposed by Tate.
Rigidity of Nominal Wages of Non-Production Workers in Industrial Sector
Directory of Open Access Journals (Sweden)
Bambang Sulistiyono
2016-06-01
Full Text Available Excess supply of labor leads to low the levels of nominal wages received by workers. The amount of minimum wage rate exceeds the market wage rate. The determination of minimum wage is a factor manifested in the institutional and regulatory Provincial Minimum Wage or a District Minimum Wage. Unfortunately, it has made nominal wages difficult to drop below the minimum wage level. High or low level of nominal wages are associated with worker productivity. Further, nominal wages are rigid to go down. If they have increased, they can not be dropped in the future even though the company's performance is declined. Knowing that condition, in designing the remuneration system, an employer should pay attention to the rigidity of nominal wages, so that when company's performance declines, the company will not be interfered because of the wages burden. Furthermore, unions and government should consider the rigidity impact of nominal wages that go down. Thus, when macroeconomic conditions deteriorate and company's performance drops, the company will not go bankrupt due to high labor costs. If the company goes bankrupt, the workers will loose their jobs as a result of employment termination, while the government will face the unemployment problem.
Nonlinear mechanics of non-rigid origami: an efficient computational approach
Liu, K.; Paulino, G. H.
2017-10-01
Origami-inspired designs possess attractive applications to science and engineering (e.g. deployable, self-assembling, adaptable systems). The special geometric arrangement of panels and creases gives rise to unique mechanical properties of origami, such as reconfigurability, making origami designs well suited for tunable structures. Although often being ignored, origami structures exhibit additional soft modes beyond rigid folding due to the flexibility of thin sheets that further influence their behaviour. Actual behaviour of origami structures usually involves significant geometric nonlinearity, which amplifies the influence of additional soft modes. To investigate the nonlinear mechanics of origami structures with deformable panels, we present a structural engineering approach for simulating the nonlinear response of non-rigid origami structures. In this paper, we propose a fully nonlinear, displacement-based implicit formulation for performing static/quasi-static analyses of non-rigid origami structures based on `bar-and-hinge' models. The formulation itself leads to an efficient and robust numerical implementation. Agreement between real models and numerical simulations demonstrates the ability of the proposed approach to capture key features of origami behaviour.
Numerical algorithm for rigid body position estimation using the quaternion approach
Zigic, Miodrag; Grahovac, Nenad
2017-11-01
This paper deals with rigid body attitude estimation on the basis of the data obtained from an inertial measurement unit mounted on the body. The aim of this work is to present the numerical algorithm, which can be easily applied to the wide class of problems concerning rigid body positioning, arising in aerospace and marine engineering, or in increasingly popular robotic systems and unmanned aerial vehicles. Following the considerations of kinematics of rigid bodies, the relations between accelerations of different points of the body are given. A rotation matrix is formed using the quaternion approach to avoid singularities. We present numerical procedures for determination of the absolute accelerations of the center of mass and of an arbitrary point of the body expressed in the inertial reference frame, as well as its attitude. An application of the algorithm to the example of a heavy symmetrical gyroscope is presented, where input data for the numerical procedure are obtained from the solution of differential equations of motion, instead of using sensor measurements.
Rigidity and bradykinesia reduce interlimb coordination in Parkinsonian gait
Winogrodzka, Ania; Wagenaar, Robert C.; Booij, Jan; Wolters, Eric C.
2005-01-01
Objective: To assess the influence of rigidity and bradykinesia and the extent of dopaminergic degeneration on interlimb coordination during walking in early, drug-naive patients with Parkinson's disease (PD). Design: The interlimb coordination was examined during a systematic manipulation of
Calculating ensemble averaged descriptions of protein rigidity without sampling.
Directory of Open Access Journals (Sweden)
Luis C González
Full Text Available Previous works have demonstrated that protein rigidity is related to thermodynamic stability, especially under conditions that favor formation of native structure. Mechanical network rigidity properties of a single conformation are efficiently calculated using the integer body-bar Pebble Game (PG algorithm. However, thermodynamic properties require averaging over many samples from the ensemble of accessible conformations to accurately account for fluctuations in network topology. We have developed a mean field Virtual Pebble Game (VPG that represents the ensemble of networks by a single effective network. That is, all possible number of distance constraints (or bars that can form between a pair of rigid bodies is replaced by the average number. The resulting effective network is viewed as having weighted edges, where the weight of an edge quantifies its capacity to absorb degrees of freedom. The VPG is interpreted as a flow problem on this effective network, which eliminates the need to sample. Across a nonredundant dataset of 272 protein structures, we apply the VPG to proteins for the first time. Our results show numerically and visually that the rigidity characterizations of the VPG accurately reflect the ensemble averaged [Formula: see text] properties. This result positions the VPG as an efficient alternative to understand the mechanical role that chemical interactions play in maintaining protein stability.
Calculating ensemble averaged descriptions of protein rigidity without sampling.
González, Luis C; Wang, Hui; Livesay, Dennis R; Jacobs, Donald J
2012-01-01
Previous works have demonstrated that protein rigidity is related to thermodynamic stability, especially under conditions that favor formation of native structure. Mechanical network rigidity properties of a single conformation are efficiently calculated using the integer body-bar Pebble Game (PG) algorithm. However, thermodynamic properties require averaging over many samples from the ensemble of accessible conformations to accurately account for fluctuations in network topology. We have developed a mean field Virtual Pebble Game (VPG) that represents the ensemble of networks by a single effective network. That is, all possible number of distance constraints (or bars) that can form between a pair of rigid bodies is replaced by the average number. The resulting effective network is viewed as having weighted edges, where the weight of an edge quantifies its capacity to absorb degrees of freedom. The VPG is interpreted as a flow problem on this effective network, which eliminates the need to sample. Across a nonredundant dataset of 272 protein structures, we apply the VPG to proteins for the first time. Our results show numerically and visually that the rigidity characterizations of the VPG accurately reflect the ensemble averaged [Formula: see text] properties. This result positions the VPG as an efficient alternative to understand the mechanical role that chemical interactions play in maintaining protein stability.
Patient satisfaction related to rigid external distraction osteogenesis
van Eggermont, Bas; Jansma, J.; Bierman, M. W. J.; Stegenga, B.
2007-01-01
The aim of this study was to evaluate satisfaction with treatment among cleft lip and palate patients who underwent maxillary advancement using a rigid external distraction (RED) device. Nine patients (four boys, five girls), mean age 17.7 years (SD 4.0), were included in the study. Outcome measures
Short Communication: Statistical determination of the rigidity in ...
African Journals Online (AJOL)
From the graph of load against displacement, the rigidity in flexion at different moisture levels was determined from which the Young modulus was calculated. Linear regression models were fitted to the data and the results showed significant correlation coefficients between the Young modulus and moisture content for each ...
Connect-disconnect coupling for preadjusted rigid shafts
Bajkowski, F. W.; Holmberg, A.
1969-01-01
Coupling device enables a rigid shaft to be connected to or disconnected from a fixed base without disturbing the point of adjustment of the shaft in a socket or causing the shaft to rotate. The coupling consists of an externally threaded, internally slotted boss extending from the fixed base.
Rigidity percolation in dispersions with a structured viscoelastic matrix
Wilbrink, M.W.L.; Michels, M.A.J.; Vellinga, W.P.; Meijer, H.E.H.
2005-01-01
This paper deals with rigidity percolation in composite materials consisting of a dispersion of mineral particles in a microstructured viscoelastic matrix. The viscoelastic matrix in this specific case is a hydrocarbon refinery residue. In a set of model random composites the mean interparticle
Centrifuge modelling of rigid piles in soft clay
DEFF Research Database (Denmark)
Klinkvort, R.T.; Poder, M.; Truong, P.
2016-01-01
of this study is to employ centrifuge modelling in order to derive experimental p-y curves for rigid piles embedded in over-consolidated soft clay. A kaolin clay sample was prepared and pre-consolidated by applying a constant pressure at the soil surface, while different over-consolidation ratios were achieved...
Customizable rigid head fixation for infants: technical note.
Udayakumaran, Suhas; Onyia, Chiazor U
2016-01-01
The need and advantages of rigid fixation of the head in cranial surgeries are well documented (Berryhill et al., Otolaryngol Head Neck Surg 121:269-273, 1999). Head fixation for neurosurgical procedures in infants and in early years has been a challenge and is fraught with risk. Despite the fact that pediatric pins are designed, rigid head fixation involving direct application of pins to the head of infants and slightly older children is still generally not safe (Agrawal and Steinbok, Childs Nerv Syst 22:1473-1474, 2006). Yet, there are some surgeries in which some form of rigid fixation is required (Agrawal and Steinbok, Childs Nerv Syst 22:1473-1474, 2006). We describe a simple technique to achieve rigid fixation of the head in infants for neurosurgical procedures. This involves applying a head band made of Plaster of Paris (POP) around the head and then applying the fixation pins of the fixation frame directly on to the POP. We have used this technique of head fixation successfully for infants with no complications.
Study of rigidity of semiconducting vanadate glasses and its ...
Indian Academy of Sciences (India)
These parameters along with the coordination number of the glasses affect the glass transition temperature. The correlation between the elastic moduli and thermal properties of these samples showed that 0.25MoO3–0.25PbO–0.5V2O5 glass is the most rigid and has an applicable glass transition temperature for coating.
Rigidity theorem for Willmore surfaces in a sphere
Indian Academy of Sciences (India)
(Math. Sci.) Vol. 126, No. 2, May 2016, pp. 253–260. c Indian Academy of Sciences. Rigidity theorem for Willmore surfaces in a sphere. HONGWEI XU1 and DENGYUN YANG2,∗. 1Center of Mathematical Sciences, Zhejiang University, Hangzhou 310027,. People's Republic of China. 2College of Mathematics and ...
Accuracy limit of rigid 3-point water models
Izadi, Saeed; Onufriev, Alexey V.
2016-08-01
Classical 3-point rigid water models are most widely used due to their computational efficiency. Recently, we introduced a new approach to constructing classical rigid water models [S. Izadi et al., J. Phys. Chem. Lett. 5, 3863 (2014)], which permits a virtually exhaustive search for globally optimal model parameters in the sub-space that is most relevant to the electrostatic properties of the water molecule in liquid phase. Here we apply the approach to develop a 3-point Optimal Point Charge (OPC3) water model. OPC3 is significantly more accurate than the commonly used water models of same class (TIP3P and SPCE) in reproducing a comprehensive set of liquid bulk properties, over a wide range of temperatures. Beyond bulk properties, we show that OPC3 predicts the intrinsic charge hydration asymmetry (CHA) of water — a characteristic dependence of hydration free energy on the sign of the solute charge — in very close agreement with experiment. Two other recent 3-point rigid water models, TIP3PFB and H2ODC, each developed by its own, completely different optimization method, approach the global accuracy optimum represented by OPC3 in both the parameter space and accuracy of bulk properties. Thus, we argue that an accuracy limit of practical 3-point rigid non-polarizable models has effectively been reached; remaining accuracy issues are discussed.
Rigid rod spaced fullerene as building block for nanoclusters
Indian Academy of Sciences (India)
By using phenylacetylene based rigid-rod linkers (PhA), we have successfully synthesized two fullerene derivatives, C60-PhA and C60-PhA-C60. The absorption spectral features of C60, as well as that of the phenylacetylene moiety are retained in the monomeric forms of these fullerene derivatives, ruling out the possibility ...
Hydrodynamics of a flexible plate between pitching rigid plates
Kim, Junyoung; Kim, Daegyoum
2017-11-01
The dynamics of a flexible plate have been studied as a model problem in swimming and flying of animals and fluid-structure interaction of plants and flags. Motivated by fish schooling and an array of sea grasses, we investigate the dynamics of a flexible plate closely placed between two pitching rigid plates. In most studies on passive deformation of the flexible plate, the plate is immersed in a uniform flow or a wavy flow. However, in this study, the flexible plate experiences periodic deformation by the oscillatory flow generated by the prescribed pitching motion of the rigid plates. In our model, the pitching axes of the rigid plates and the clamping position of the flexible plate are aligned on the same line. The flexible plate shows various responses depending on length and pitching frequency of rigid plates, thickness of a flexible plate, and free-stream velocity. To find the effect of each variable on the response of the flexible plate, amplitude of a trailing edge and modal contribution of a flapping motion are compared, and flow structure around the flexible plate is examined.
Flexible (Polyactive®) versus rigid (hydroxyapatite) dental implants
Meijer, G.J.; Heethaar, J.; Cune, M.S.; de Putter, C.; van Blitterswijk, Clemens
1997-01-01
In a beagle dog study, the peri-implant bone changes around flexible (Polyactive®) and rigid hydroxyapatite (HA) implants were investigated radiographically by quantitative digital subtraction analysis and by assessment of marginal bone height, with the aid of a computerized method. A loss of
"Mind the trap": mindfulness practice reduces cognitive rigidity.
Directory of Open Access Journals (Sweden)
Jonathan Greenberg
Full Text Available Two experiments examined the relation between mindfulness practice and cognitive rigidity by using a variation of the Einstellung water jar task. Participants were required to use three hypothetical jars to obtain a specific amount of water. Initial problems were solvable by the same complex formula, but in later problems ("critical" or "trap" problems solving was possible by an additional much simpler formula. A rigidity score was compiled through perseverance of the complex formula. In Experiment 1, experienced mindfulness meditators received significantly lower rigidity scores than non-meditators who had registered for their first meditation retreat. Similar results were obtained in randomized controlled Experiment 2 comparing non-meditators who underwent an eight meeting mindfulness program with a waiting list group. The authors conclude that mindfulness meditation reduces cognitive rigidity via the tendency to be "blinded" by experience. Results are discussed in light of the benefits of mindfulness practice regarding a reduced tendency to overlook novel and adaptive ways of responding due to past experience, both in and out of the clinical setting.
A survey on stability and rigidity results for Lie algebras
Crainic, Marius; Schätz, Florian; Struchiner, Ivan
2014-01-01
We give simple and unified proofs of the known stability and rigidity results for Lie algebras, Lie subalgebras and Lie algebra homomorphisms. Moreover, we investigate when a Lie algebra homomorphism is stable under all automorphisms of the codomain (including outer automorphisms).
21 CFR 886.5916 - Rigid gas permeable contact lens.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Rigid gas permeable contact lens. 886.5916 Section 886.5916 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... against the cornea of the eye to correct vision conditions. The device is made of various materials, such...
Knowledge-In-Action: An Example with Rigid Body Motion
Da Costa, Sayonara Salvador Cabral; Moreira, Marco Antonio
2005-01-01
This paper reports the analysis of the resolution of a paper-and-pencil problem, by eight undergraduate students majoring in engineering (six) and physics (two) at the Pontifcia Universidade Catlica do Rio Grande do Sul, in Porto Alegre, Brazil. The problem concerns kinetics of a rigid body, and the analysis was done in the light of Johnson-Lairds…
Non-rigid registration by geometry-constrained diffusion
DEFF Research Database (Denmark)
Andresen, Per Rønsholt; Nielsen, Mads
1999-01-01
Assume that only partial knowledge about a non-rigid registration is given so that certain point, curves, or surfaces in one 3D image map to certain points, curves, or surfaces in another 3D image. We are facing the aperture problem because along the curves and surfaces, point correspondences...
Analysis of the Behaviour of Semi Rigid Steel End Plate Connections
Directory of Open Access Journals (Sweden)
Bahaz A.
2018-01-01
Full Text Available The analysis of steel-framed building structures with full strength beam to column joints is quite standard nowadays. Buildings utilizing such framing systems are widely used in design practice. However, there is a growing recognition of significant benefits in designing joints as partial strength/semi-rigid. The design of joints within this partial strength/semi-rigid approach is becoming more and more popular. This requires the knowledge of the full nonlinear moment-rotation behaviour of the joint, which is also a design parameter. The rotational behaviour of steel semi rigid connections can be studied using the finite element method for the following three reasons: i such models are inexpensive; ii they allow the understanding of local effects, which are difficult to measure accurately physically, and iii they can be used to generate extensive parametric studies. This paper presents a three-dimensional finite element model using ABAQUS software in order to identify the effect of different parameters on the behaviour of semi rigid steel beam to column end plate connections. Contact and sliding between different elements, bolt pretension and geometric and material non-linearity are included in this model. A parametric study is conducted using a model of two end-plate configurations: flush and extended end plates. The studied parameters were as follows: bolts type, end plate thickness and column web stiffener. Then, the model was calibrated and validated with experimental results taken from the literature and with the model proposed by Eurocode3. The procedure for determining the moment–rotation curve using finite element analysis is also given together with a brief explanation of how the design moment resistance and the initial rotational stiffness of the joint are obtained.
Energy Technology Data Exchange (ETDEWEB)
Quell, P. [aerodyn Energiesysteme GmbH, Rendsburg (Germany)
1996-12-31
Developments in the MW range are a further illustration of the well-known problem that a linear increase of the rotor surface area will result in an overproportional increase of mass. One classical approach for reducing weight is the installation of a two-blade rotor with a swivelling hub. In the course of the development activities for the 1.2 MW A1200 wind power system of Autoflug Energietechnik GmbH, it was investigated whether a pendulum hub is a technically and economically feasible concept for a plant of this size. For this purpose, two otherwise identical plants were projected and compared, one with a rigid hub and the other with a swivelling hub. Both systems were simulated using the dynamic program GAROS. With the loads thus determined, both concepts are detailed enough to permit a comprehensive cost comparison in consideration of the masses, the resulting cost, performance and reliability. [Deutsch] Der Entwicklungsprozess der Megawatt-Anlagen verdeutlicht den aus frueheren Untersuchungen bekannten Zusammenhang eines ueberproportionalen Massenzuwachses bei linear steigender Rotorflaeche. Ein klassischer Ansatz zur Reduzierung des Anlagengewichtes ist der Einsatz eines Zweiblatt-Rotors in Verbindung mit einer Pendelnabe. Im Rahmen der Entwicklungstaetigkeit fuer die 1,2 MW-Windkraftanlage A 1200 der Fa. Autoflug Energietechnik GmbH wurde untersucht, inwieweit der Einsatz einer Pendelnabe fuer eine Anlage dieser Groessenordnung ein technisch und wirtschaftlich sinnvolles Konzept darstellen kann. Dazu wurden zwei grundsaetzlich gleiche Anlagen mit Zweiblatt-Rotor unter Verwendung einer Pendelnabe und einer starren Nabe konzipiert und gegenuebergestellt. Zur Bewertung des Anlagenverhaltens sowie zur Ermittlung realitaetsnaher Belastungen werden sowohl die Anlagenversion mit Pendelnabe als auch die Version mit starrer Nabe mit dem Dynamikprogramm GAROS simuliert. Basierend auf den ermittelten Lasten werden beide Konzepte so detailliert, dass ein umfassender
Overveld, van C.W.A.M.
1991-01-01
A method is presented for approximating the motions of linked 3-dimensional rigid body systems that may be applied in the context of interactive motion specification for computer animation. The method is based on decoupling the ballistic (free) component of the motion of the points that constitute
Winogrodzka, A.; Wagenaar, R. C.; Bergmans, P.; Vellinga, A.; Booij, J.; van Royen, E. A.; van Emmerik, R. E.; Stoof, J. C.; Wolters, E. C.
2001-01-01
Tremor is one of the clinical hallmarks of Parkinson's disease (PD). Although it is accepted that other classic symptoms of PD such as rigidity and bradykinesia result from a degeneration of the nigrostriatal system and subsequent reduction in striatal dopamine, the pathophysiology of resting tremor
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...... 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...
DEFF Research Database (Denmark)
Estupinan, Edgar Alberto; Santos, Ilmar
2009-01-01
elements are supported by fluid film bearings, where the hydrodynamic interaction forces are described by the Reynolds equation. The system of nonlinear equations is numerically solved for three different restrictive conditions of the motion of the crank, where the third case takes into account lateral...... and tilting oscillations of the extremity of the crankshaft. The numerical results of the behaviour of the journal bearings for each case are presented giving some insights into design parameters such as, maximum oil film pressure, minimum oil film thickness, maximum vibration levels and dynamic reaction...
ANALYSIS OF A RIGID WALL IN AN ELASTIC WEIGHTY HALF-PLANE
Directory of Open Access Journals (Sweden)
K. V. Dmitrieva
2016-01-01
Full Text Available The analysis of stress-strain state of a rigid wall in an elastic weighty half-plane with a broken outline is carried out. To this end, the auxiliary problem of displacements definition in an elastic weighty quarter-plane was solved. Ritz method derived a formula to determine the displacements of elastic flat wedge boundaries in view of its own weight. On the basis of the received expressions the algorithm of displacements definition of a crack in an elastic weighty half-plane with a broken outline is developed. Analytical calculation of a rigid vertical wall located in an elastic weighty half-plane under the influence of a horizontal load, carried out by two methods: by Zhemochkin's method and finite difference method. In the problem statement an elastic half-plane is considered a model of the soil medium, therefore, only compressive normal stresses can arise on the connection of the wall with the elastic base. This assumption implies occurrence of discontinuities soil medium, and leads for the wall to an emergence of two dividing points of boundary conditions. The determination of the boundaries contact of the wall with the elastic half-plane, are not known in advance, is performed by iteratively way at each step set the position of dividing points of boundary conditions and the system of canonical equations of a corresponding method is written. If tensile stresses appear in wall-base contact and/or there is overlap of the crack edges occurs, then proceeds to the next iteration. Analysis of the results shows that the bending moment and shear forces in sections of the rigid wall in a broken weighty half-plane differ slightly from the same diagrams constructed for a rigid wall in an elastic weightless half-plane. The verification of the results of analytical calculation with the results received by using the LIRA 9.6 that implements the finite element method is obtained. The calculation results for the rigid wall in an elastic weighty half
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...... 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...
From time series analysis to a biomechanical multibody model of the human eye
International Nuclear Information System (INIS)
Pascolo, P.; Carniel, R.
2009-01-01
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.
Pediatric mandibular fractures treated by rigid internal fixation.
Wong, G B
1993-09-01
Mandibular fractures in the pediatric patient population are relatively uncommon. These patients present with their own unique treatment requirements. Most fractures have been treated conservatively by dental splints. Closed reduction techniques with maxillomandibular fixation (MMF) in very young children can pose several concerns, including cooperation, compliance and adequate nutritional intake. Rigid internal fixation of unstable mandibular fractures using miniplates and screws circumvents the need for MMF and allows immediate jaw mobilization. At major pediatric trauma institutions, there has been an increasing trend toward the use of this treatment when open reduction is necessary. This article presents a report of a five-year-old child who presented with bilateral mandibular fractures and was treated by rigid internal fixation and immediate mandibular mobilization.
Rigid inclusions-Comparison between analytical and numerical methods
International Nuclear Information System (INIS)
Gomez Perez, R.; Melentijevic, S.
2014-01-01
This paper compares different analytical methods for analysis of rigid inclusions with finite element modeling. First of all, the load transfer in the distribution layer is analyzed for its different thicknesses and different inclusion grids to define the range between results obtained by analytical and numerical methods. The interaction between the soft soil and the inclusion in the estimation of settlements is studied as well. Considering different stiffness of the soft soil, settlements obtained analytical and numerically are compared. The influence of the soft soil modulus of elasticity on the neutral point depth was also performed by finite elements. This depth has a great importance for the definition of the total length of rigid inclusion. (Author)
Rigidity of complete noncompact bach-flat n-manifolds
Chu, Yawei; Feng, Pinghua
2012-11-01
Let (Mn,g) be a complete noncompact Bach-flat n-manifold with the positive Yamabe constant and constant scalar curvature. Assume that the L2-norm of the trace-free Riemannian curvature tensor R∘m is finite. In this paper, we prove that (Mn,g) is a constant curvature space if the L-norm of R∘m is sufficiently small. Moreover, we get a gap theorem for (Mn,g) with positive scalar curvature. This can be viewed as a generalization of our earlier results of 4-dimensional Bach-flat manifolds with constant scalar curvature R≥0 [Y.W. Chu, A rigidity theorem for complete noncompact Bach-flat manifolds, J. Geom. Phys. 61 (2011) 516-521]. Furthermore, when n>9, we derive a rigidity result for R<0.
Rigid-beam model of a high-efficiency magnicon
International Nuclear Information System (INIS)
Rees, D.E.; Tallerico, P.J.; Humphries, S.J. Jr.
1993-01-01
The magnicon is a new type of high-efficiency deflection-modulated amplifier developed at the Institute of Nuclear Physics in Novosibirsk, Russia. The prototype pulsed magnicon achieved an output power of 2.4 MW and an efficiency of 73% at 915 MHz. This paper presents the results of a rigid-beam model for a 700-MHz, 2.5-MW 82%-efficient magnicon. The rigid-beam model allows for characterization of the beam dynamics by tracking only a single electron. The magnicon design presented consists of a drive cavity; passive cavities; a pi-mode, coupled-deflection cavity; and an output cavity. It represents an optimized design. The model is fully self-consistent, and this paper presents the details of the model and calculated performance of a 2.5-MW magnicon
MRS2016: Rigid Moon Rotation Series in the Relativistic Approximation
Pashkevich, V. V.
2017-03-01
The rigid Moon rotation problem is studied for the relativistic (kinematical) case, in which the geodetic perturbations in the Moon rotation are taken into account. As the result of this research the high-precision Moon Rotation Series MRS2016 in the relativistic approximation was constructed for the first time and the discrepancies between the high-precision numerical and the semi-analytical solutions of the rigid Moon rotation were investigated with respect to the fixed ecliptic of epoch J2000, by the numerical and analytical methods. The residuals between the numerical solution and MRS2016 in the perturbing terms of the physical librations do not exceed 80 mas and 10 arc seconds over 2000 and 6000 years, respectively.
Partial ring currents and cosmic ray magnetic cutoff rigidity variations
International Nuclear Information System (INIS)
Arens, M.
1978-01-01
A short introduction on cosmic ray modulation and a description of the magnetosphere, and of some physical processes occurring within its boundaries are presented. 20 geomagnetic storms are analysed together with the cosmic ray intensities during these storms as measured by Neutron Monitors. Using a semi-empirical method, the variations in the magnetic cutoff rigidity for the mountain stations Pic du Midi and Jungfraujoch are deduced. These stations are the most sensitive for measuring these variations. The analysis shows that all analyzed storms have an asymmetric development phase. Often the asymmetry even continues during part of the recovery phase. It is shown that variations in magnetic cutoff rigidity occur only during the asymmetric phase of the storm. The largest variations are found when the cosmic ray station is located in the late afternoon-midnight sector. (Auth.)
A rigid lamb syndrome in sheep in Rhodesia.
Rudert, C P; Lawrence, J A; Foggin, C; Barlow, R M
1978-04-29
A syndrome characterised by the birth of lambs with varying degrees of rigidity of the limbs and spine has been encountered on several occasions in Rhodesia. Outbreaks have occurred in autumn-born lambs from Dorper ewes grazing heavily fertilised Star grass cv No 2 (Cynodon aethiopicus) pastures. The condition appears to be exacerbated by the application of sulphur to the pasture and is partly prevented by the administration of selenium and vitamin E to the ewes before lambing. The aetiology is unknown.
Steady fall of a rigid body in viscous fluid
Czech Academy of Sciences Publication Activity Database
Nečasová, Šárka
2005-01-01
Roč. 63, Sp. Is. (2005), s. 2113-2119 ISSN 0362-546X. [Invited Talks from the Fourth World Congress of Nonlinear Analysts (WCNA 2004). Orlando , 30.7.2004-7.8.2004] R&D Projects: GA ČR(CZ) GA201/02/0684 Institutional research plan: CEZ:AV0Z1019905 Keywords : steady fall * rigid body * viscous fluid Subject RIV: BA - General Mathematics Impact factor: 0.519, year: 2005
NOLB: Nonlinear Rigid Block Normal Mode Analysis Method
Hoffmann , Alexandre; Grudinin , Sergei
2017-01-01
International audience; We present a new conceptually simple and computationally efficient method for nonlinear normal mode analysis called NOLB. It relies on the rotations-translations of blocks (RTB) theoretical basis developed by Y.-H. Sanejouand and colleagues. We demonstrate how to physically interpret the eigenvalues computed in the RTB basis in terms of angular and linear velocities applied to the rigid blocks and how to construct a nonlinear extrapolation of motion out of these veloci...
Oscillations of manometric tubular springs with rigid end
Cherentsov, D. A.; Pirogov, S. P.; Dorofeev, S. M.; Ryabova, Y. S.
2018-05-01
The paper presents a mathematical model of attenuating oscillations of manometric tubular springs (MTS) taking into account the rigid tip. The dynamic MTS model is presented in the form of a thin-walled curved rod oscillating in the plane of curvature of the central axis. Equations for MTS oscillations are obtained in accordance with the d’Alembert principle in projections onto the normal and tangential. The Bubnov-Galerkin method is used to solve the equations obtained.
On Polya's inequality for torsional rigidity and first Dirichlet eigenvalue
Berg, M. van den; Ferone, V.; Nitsch, C.; Trombetti, C.
2016-01-01
Let $\\Omega$ be an open set in Euclidean space with finite Lebesgue measure $|\\Omega|$. We obtain some properties of the set function $F:\\Omega\\mapsto \\R^+$ defined by $$ F(\\Omega)=\\frac{T(\\Omega)\\lambda_1(\\Omega)}{|\\Omega|} ,$$ where $T(\\Omega)$ and $\\lambda_1(\\Omega)$ are the torsional rigidity and the first eigenvalue of the Dirichlet Laplacian respectively. We improve the classical P\\'olya bound $F(\\Omega)\\le 1,$ and show that $$F(\\Omega)\\le 1- \
Vortex statistics for turbulence in a container with rigid boundaries
DEFF Research Database (Denmark)
Clercx, H.J.H.; Nielsen, A.H.
2000-01-01
The evolution of vortex statistics for decaying two-dimensional turbulence in a square container with rigid no-slip walls is compared with a few available experimental results and with the scaling theory of two-dimensional turbulent decay as proposed by Carnevale et al. Power-law exponents......, computed from an ensemble average of several numerical runs, coincide with some experimentally obtained values, but not with data obtained from numerical simulations of decaying two-dimensional turbulence with periodic boundary conditions....
Gas-induced friction and diffusion of rigid rotors
Martinetz, Lukas; Hornberger, Klaus; Stickler, Benjamin A.
2018-05-01
We derive the Boltzmann equation for the rotranslational dynamics of an arbitrary convex rigid body in a rarefied gas. It yields as a limiting case the Fokker-Planck equation accounting for friction, diffusion, and nonconservative drift forces and torques. We provide the rotranslational friction and diffusion tensors for specular and diffuse reflection off particles with spherical, cylindrical, and cuboidal shape, and show that the theory describes thermalization, photophoresis, and the inverse Magnus effect in the free molecular regime.
Modyfication of the Rigid Polyurethane-Polyisocyanurate Foams
Bogusław Czupryński; Joanna Liszkowska; Joanna Paciorek-Sadowska
2014-01-01
The effect of polyethylene glycol 1500 on physicomechanical properties of rigid polyurethane-polyisocyanurate (PUR-PIR) foams has been studied. It was found that application of polyethylene glycol 1500 for synthesis of foams in amount from 0% to 20% w/w had an effect on reduction of brittleness and softening point, while the greater the increase in compressive strength the higher its content in foam composition was. Wastes from production of these foams were ground and subjected to glycolysis...
LENUS (Irish Health Repository)
Ahmad, Nasir Zaheer
2012-06-01
Rigid sigmoidoscopy is sometimes performed at first presentation in colorectal clinics. We assessed the feasibility of flexible sigmoidoscopy in similar situations by comparing it with rigid sigmoidoscopy as a first investigative tool.
Towards Sub-Microarsecond Rigid Earth Nutation Series in the Hamiltonian Theory
National Research Council Canada - National Science Library
Souchay, Jean; Folgueira, M
2000-01-01
...) are based on the works of Kinoshita (1977) and Wahr (1979). In Kinoshita's work, the rigid Earth nutation series were calculated by the application of the Hamiltonian canonical equations to the rotation of the rigid and elliptical Earth...
Chiral Orientation of Skeletal Muscle Cells Requires Rigid Substrate
Directory of Open Access Journals (Sweden)
Ninghao Zhu
2017-06-01
Full Text Available Reconstitution of tissue morphology with inherent left–right (LR asymmetry is essential for tissue/organ functions. For skeletal muscle, the largest tissue in mammalian organisms, successful myogenesis requires the regulation of the LR asymmetry to form the appropriate muscle alignment. However, the key factor for reproducing the LR asymmetry of skeletal tissues in a controllable, engineering context remains largely unknown. Recent reports indicate that cell chirality may underlie the LR development in tissue morphogenesis. Here, we report that a rigid substrate is required for the chirality of skeletal muscle cells. By using alternating micropatterned cell-adherent and cell-repellent stripes on a rigid substrate, we found that C2C12 skeletal muscle myoblasts exhibited a unidirectional tilted orientation with respect to the stripe boundary. Importantly, such chiral orientation was reduced when soft substrates were used instead. In addition, we demonstrated the key role of actin stress fibers in the formation of the chiral orientation. This study reveals that a rigid substrate is required for the chiral pattern of myoblasts, paving the way for reconstructing damaged muscle tissue with inherent LR asymmetry in the future.
Experimental consequences of predicted charge rigidity of superconductors
Energy Technology Data Exchange (ETDEWEB)
Hirsch, J.E., E-mail: jhirsch@ucsd.edu [Department of Physics, University of California, San Diego, La Jolla, CA 92093-0319 (United States)
2012-08-15
The theory of hole superconductivity predicts that in superconductors the charged superfluid is about a million times more rigid than the normal electron fluid. We point out that this physics should give rise to large changes in the bulk and surface plasmon dispersion relations of metals entering the superconducting state, that have not yet been experimentally detected and would be in stark contradiction with the expected behavior within conventional BCS-London theory. We also propose that this explains the puzzling experimental observations of Avramenko et al. on electron sound propagation in superconductors and the puzzling experiments of de Heer et al. detecting large electric dipole moments in small metal clusters, as well as the Tao effect on aggregation of superconducting microparticles in an electric field. Associated with the enhanced charge rigidity is a large increase in the electric screening length of superconductors at low temperatures that has not yet been experimentally detected. The physical origin of the enhanced charge rigidity and its relation to other aspects of the theory of hole superconductivity is discussed.
Field dependent cosmic ray streaming at high rigidities
International Nuclear Information System (INIS)
Swinson, D.B.
1976-01-01
Data from underground μ meson telescopes at depths of 25, 40, and 80 mwe covering the period 1965--1973 have been analyzed as a function of interplanetary magnetic field direction. Cosmic ray streaming both in and perpendicular to the ecliptic plane, with directions dependent on the sense of the interplanetary magnetic field, is observed throughout the period at all depths. The field dependent streaming in the ecliptic plane exhibits some variability in amplitude and phase but contains a component in the direction perpendicular to the interplanetary magnetic field direction which is consistent with B x delN streaming due to a perpendicular cosmic ray density gradient pointing southward (higher density below the ecliptic plane than above it). In the case of the field dependent streaming perpendicular to the ecliptic plane the direction of the streaming has remained remarkably consistent over the 9-year period. One possible source of this streaming is B x delN streaming due to a radial heliocentric cosmic ray density gradient; this possibility is discussed along with other possible sources. There does not appear to be an obvious variation in the amplitude of the field dependent streaming either in or perpendicular to the ecliptic plane with increasing rigidity; both effects are still apparent at rigidities well above the 52-GV threshold rigidity of the Socorro 80-mwe telescope. The amplitudes of both anisotropies appear larger at solar maximum than at solar minimum
Rigid Body Energy Minimization on Manifolds for Molecular Docking.
Mirzaei, Hanieh; Beglov, Dmitri; Paschalidis, Ioannis Ch; Vajda, Sandor; Vakili, Pirooz; Kozakov, Dima
2012-11-13
Virtually all docking methods include some local continuous minimization of an energy/scoring function in order to remove steric clashes and obtain more reliable energy values. In this paper, we describe an efficient rigid-body optimization algorithm that, compared to the most widely used algorithms, converges approximately an order of magnitude faster to conformations with equal or slightly lower energy. The space of rigid body transformations is a nonlinear manifold, namely, a space which locally resembles a Euclidean space. We use a canonical parametrization of the manifold, called the exponential parametrization, to map the Euclidean tangent space of the manifold onto the manifold itself. Thus, we locally transform the rigid body optimization to an optimization over a Euclidean space where basic optimization algorithms are applicable. Compared to commonly used methods, this formulation substantially reduces the dimension of the search space. As a result, it requires far fewer costly function and gradient evaluations and leads to a more efficient algorithm. We have selected the LBFGS quasi-Newton method for local optimization since it uses only gradient information to obtain second order information about the energy function and avoids the far more costly direct Hessian evaluations. Two applications, one in protein-protein docking, and the other in protein-small molecular interactions, as part of macromolecular docking protocols are presented. The code is available to the community under open source license, and with minimal effort can be incorporated into any molecular modeling package.
Green waste cooking oil-based rigid polyurethane foam
Enderus, N. F.; Tahir, S. M.
2017-11-01
Polyurethane is a versatile polymer traditionally prepared using petroleum-based raw material. Petroleum, however, is a non-renewable material and polyurethane produced was found to be non-biodegradable. In quest for a more environmentally friendly alternative, wastecooking oil, a highly abundant domestic waste with easily derivatized structure, is a viable candidate to replace petroleum. In this study,an investigation to determine physical and chemical properties of rigid polyurethane (PU) foam from waste cooking oil (WCO) was carried out. WCO was first adsorbed by using coconut husk activated carbon adsorbent prior to be used for polyol synthesis. The purified WCO was then used to synthesize polyol via transesterification reaction to yield alcohol groups in the WCO chains structure. Finally, the WCO-based polyol was used to prepare rigid PU foam. The optimum formulation for PU formation was found to be 90 polyol: 60 glycerol: 54 water: 40 diethanolamine: 23 diisocyanate. The rigid PU foam has density of 208.4 kg/m3 with maximum compressive strength and capability to receive load at 0.03 MPa and 0.09 kN, respectively. WCO-based PU can potentially be used to replace petroleum-based PU as house construction materials such as insulation panels.
Performance of drift chambers in a magnetic rigidity spectrometer for measuring the cosmic radiation
International Nuclear Information System (INIS)
Hof, M.; Bremerich, M.; Menn, W.; Pfeifer, C.; Reimer, O.; Simon, M.; Mitchell, J.W.; Barbier, L.M.; Christian, E.R.; Ormes, J.F.; Streitmatter, R.E.; Golden, R.L.; Stochaj, S.J.
1994-01-01
A drift chamber tracking system was developed and flown as part of the IMAX balloon-borne magnetic spectrometer. The drift chamber uses a hexagonal drift-cell structure and is filled with pure CO 2 gas. It operated with high efficiency in the strong and inhomogenous field of a superconducting magnet, demonstrating a spatial resolution of better than 100 μm over most of the drift path for singly charged particles, as well as for helium and lithium nuclei. The drift chamber portion of the spectrometer achieved a maximum detectable rigidity of 175 and 250 GV/c for protons and helium respectively. ((orig.))
Matoz-Fernandez, D A; Linares, D H; Ramirez-Pastor, A J
2012-09-04
The statistical thermodynamics of straight rigid rods of length k on triangular lattices was developed on a generalization in the spirit of the lattice-gas model and the classical Guggenheim-DiMarzio approximation. In this scheme, the Helmholtz free energy and its derivatives were written in terms of the order parameter, δ, which characterizes the nematic phase occurring in the system at intermediate densities. Then, using the principle of minimum free energy with δ as a parameter, the main adsorption properties were calculated. Comparisons with Monte Carlo simulations and experimental data were performed in order to evaluate the outcome and limitations of the theoretical model.
Motion of a Rigid Rod Rocking Back and Forth Cubic-Quintic Duffing Oscillators
DEFF Research Database (Denmark)
Ganji, S. S.; Barari, Amin; Karimpour, S.
2012-01-01
In this work, we implemented the first-order approximation of the Iteration Perturbation Method (IPM) for approximating the behavior of a rigid rod rocking back and forth on a circular surface without slipping as well as Cubic-Quintic Duffing Oscillators. Comparing the results with the exact...... solution, has led us to significant consequences. The results reveal that the IPM is very effective, simple and convenient to systems of nonlinear equations. It is predicted that IPM can be utilized as a widely applicable approach in engineering....