Degree Of Freedom Model Research Articles

Thermally favourable gauge mediation

We discuss the thermal evolution of the spurion and messenger fields of ordinary gauge mediation models taking into account the Standard Model degrees of freedom. It is shown that for thermalized messengers the metastable susy breaking vacuum becomes thermally selected provided that the susy breaking sector is sufficiently weakly coupled to messengers or to any other observable field.

Three-dimensional wave packet dynamics of H 2 + D 2 reaction

Initial state selected time-dependent wave packet calculations were carried out for the H 2( v 1 = high) + D 2( v 2 = low) reaction within a three degrees of freedom model. The probabilities for different competitive processes were studied on two realistic global potential energy surfaces (PESs) – BMKP and ASP. The orientation of the cold diatom did not greatly affect the reaction processes, while the orientation of the hot diatom had a significant effect. The BMKP surface generally gave lower energy thresholds than the ASP surface, except for the collision induced dissociation (CID) within the T II geometry where the hot diatom comes in head-on perpendicular to the cold diatom. Isotopic substitution effects were studied on the recent BMKP PES. The H 2 + D 2 reaction was more effective for CID and showed more structured probability curves for single exchange reaction (SE) and three-body complex formation (3BC) than the H 2 + H 2 reaction.

An Improvement of Broaching Prediction with a Nonlinear 6 Degrees of Freedom Model

This paper reports on the improvements of a simulation model for ship motions in following and quartering waves. The authors use a wave-piercing tumblehome vessel as a subject ship. The existing 4-DoF (degrees of freedom) model shows some limitation in its capability for predicting broaching of this vessel. In a free-running model experiment for the vessel, we observed rudder and propeller emersion from the water leading to broaching. This rudder and propeller emersions can significantly reduce steering performance. To express these rudder and propeller emersions, we should take account of not only roll but also pitch and heave.Therefore the authors develop a 6-DoF model. With the heave and pitch motion, we can calculate the local draft variation for calculating wave exiting forces and moments. Roll restoring variations are one of the important factors to estimate roll motions.Therefore we theoretically estimate restoring variations in wave then we found the tendency of variation dramatically changes due to the roll angle. Submergence of superstructure can be important for that variation. We also consider the variation of maneuvering coefficients and rudder forces in waves which are relevant to broaching. To estimate these variations, we conduct PMM tests, straight-line tests and rudder angle tests in waves using a scale model of subject ship. With some of these improvements, we obtain better agreements with experimental results than existing 4-DoF model.

動的陽解法FEMを基にした大規模構造のための溶接過渡変形・応力解析手法の提案

In the analysis of welding mechanics, it is difficult to analyze large-scale structures because of welding-specific moving local nonlinearity. In this research, the authors proposed a new numerical method for welding mechanics based on the Dynamic Explicit FEM. In the proposed method, the temperature step is divided into hundreds of time steps as implicit FEM and the displacements are computed for each time step based on dynamic explicit FEM until the whole system reaches the static equilibrium state. And, to achieve the static equilibrium state faster, modified mass and damping matrix are introduced. The modified mass and damping matrix are based on the Courant condition and the vibration theory, respectively. The proposed method and static implicit FEM are compared at the final path of multilayer welding of thick bead-on-plate to verify validity and accuracy. The transient and residual deformation and stress distribution of the proposed method show good agreement with those of static implicit FEM. In addition, the computing time and memory consumption of the proposed method are 1/12 and 1/40 times shorter than those of static implicit FEM, respectively, in 243,243 degree of freedom model. It is found that the proposed method has an advantage in large-scale analysis whose nodal points are more than tens of thousands.

OS0402 理想化陽解法を用いた多層溶接時における残留応力解析(OS4-1 シミュレーション技術,OS-4 溶接変形・残留応力の計測技術,シミュレーション技術)

In this research, the authors proposed a new numerical method for welding mechanics based on the dynamic explicit FEM, named Idealized Explicit FEM. The proposed method and static implicit FEM are compared at the final path of multilayer welding of thick bead-on-plat. It is verified that the transient and residual deformation and stress distribution of the proposed method show good agreement with those of static implicit FEM. In addition, the computing time and memory consumption of the proposed method are 1/12 and 1/40 times shorter than those of static implicit FEM, respectively, in 243,243 degree of freedom model. In addition, parallelization using Graphic Processing Unit (GPU) are applied to idealized explicit FEM to achieve faster computation. The developed method is applied to large scale welding problem that has more than 1 million degree of freedom. As a result, it is found that the developed method is very useful to analyze the large scale welding mechanics problem that has almost the same simulation scale as the practical structures.

Modeling of Underwater Bomb Trajectory for Mine Clearance

The falling of a Joint Direct Attack Munition (JDAM) through a water column was modeled using a six degrees of freedom model (called STRIKE35), which contains three components: hydrodynamics, semi-empirical determination of the drag/ lift/torque coefficients (depending on the Reynolds number and the angle of attack), and water surface characteristics.To validate and verify this model, three underwater bomb trajectory tests were conducted in the Naval Air Warfare Center, Weapons Division (NAWC/WD) in the middle of Indian Wells Valley, California. During the test, several JDAMs were dropped from an airplane into two frustum ponds with the same bottom diameter of approximately 30.5 m, different surface diameters (61 m, 79 m), and different depths (7.6 m, 12.1 m). High-speed digital cameras with light/pressure sensors, and a global positioning system were used to record the location and orientation of JDAMs. Model—data inter comparison shows the capability of STRIKE35, which may lead to a new approach (breaching technology) of sea mine clearance in very shallow water (water depth less than 12.2 m, i.e. 40 ft).

Mechanism Analysis of Automobile Brake Groan Based on Seven Degrees of Freedom Model

Based on the review of researches on the vibration and noise related to automobile brake, a seven degrees of freedom nonlinear dynamics model is established, including powertrain system, brake subsystem and tire system. the numerical method is used for this study, calculation and analysis results show that the mechanism of brake groan is the stick-slip phenomenon between brake disk and friction pads. Brake groan can intensify corresponding to the increase of pressure in normal direction.

Two DOF model with friction to simulate rope climbing accident

AbstractA two degree of freedom model is considered consisting of an elastic rope with a point mass on each end. The rope is hanging over a fixed drum and the contact is modeled frictional. The Eytelwein formula for rope friction can not directly be solved for the rope forces, because of the elasticity of the rope. An extended way to calculate the rope forces will be shown and used to solve the equations of motion for the system. Some numerical results show the motion of the two masses. The considered mechanical system was used to simulate a lead climbing accident. In the case of lead climbing one end of the rope is tied rigidly to the climber then goes through a carabiner that is fixed in the wall and runs down to a second person called the belayer. The elasticity of the rope makes sure that the forces acting on the climber stay low and avoid a sudden stop. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Crack kinking in brittle materials

Although they are rooted in the mechanics of solids and in its history, most crack propagation criteria reveal incorrect safe equilibrium domains. With the obvious exception of the maximum energy release rate, all of them show unacceptable energy dissipation in mixed mode crack growth. They convey important physical information and allow a degree of freedom in material modeling, in the same spirit as the elastic limit surfaces in the mechanics of materials. Maintaining such a degree of freedom in modeling brittle material behavior while preserving the mandatory requirements in terms of energy and of safe equilibrium domain is investigated in this paper, in the light of a recently proposed incremental description of (linear elastic) fracture mechanics.

Directional constraint of endpoint force emerges from hindlimb anatomy

Postural control requires the coordination of force production at the limb endpoints to apply an appropriate force to the body. Subjected to horizontal plane perturbations, quadruped limbs stereotypically produce force constrained along a line that passes near the center of mass. This phenomenon, referred to as the force constraint strategy, may reflect mechanical constraints on the limb or body, a specific neural control strategy or an interaction among neural controls and mechanical constraints. We used a neuromuscular model of the cat hindlimb to test the hypothesis that the anatomical constraints restrict the mechanical action of individual muscles during stance and constrain the response to perturbations to a line independent of perturbation direction. In a linearized neuromuscular model of the cat hindlimb, muscle lengthening directions were highly conserved across 10,000 different muscle activation patterns, each of which produced an identical, stance-like endpoint force. These lengthening directions were closely aligned with the sagittal plane and reveal an anatomical structure for directionally constrained force responses. Each of the 10,000 activation patterns was predicted to produce stable stance based on Lyapunov stability analysis. In forward simulations of the nonlinear, seven degree of freedom model under the action of 200 random muscle activation patterns, displacement of the endpoint from its equilibrium position produced restoring forces, which were also biased toward the sagittal plane. The single exception was an activation pattern based on minimum muscle stress optimization, which produced destabilizing force responses in some perturbation directions. The sagittal force constraint increased during simulations as the system shifted from an inertial response during the acceleration phase to a viscoelastic response as peak velocity was obtained. These results qualitatively match similar experimental observations and suggest that the force constraint phenomenon may result from the anatomical arrangement of the limb.

Structural Vibration Reduction by Switch Shunting of Piezoelectric Elements: Modeling and Optimization

This work deals with the reduction of structural vibrations by means of synchronized switch damping techniques on piezoelectric elements. Piezoelectric patches are attached to the vibrating structure and connected to an electrical circuit that includes a switch. The latter allows to continuously switch the piezoelectric elements from an open-circuit state to a specific electric impedance, synchronously with the mechanical oscillations. The present study focuses on two goals: (i) the quantification of the added damping, (ii) the optimization of the electric circuit parameters, carried out on a one degree of freedom model. The free and forced responses of one mode of the mechanical structure are studied in detail. The precise time response of the system is obtained with semi-analytical models for the two cases where the electrical impedance is a simple resistance (synchronized switch damping on short circuit) or a resistance in series with an inductance (synchronized switch damping on inductor). The damping added by the device is estimated. In all cases, the main result of the study is that the piezoelectric coupling factor is the only parameter to optimize and has to be maximized in order to maximize the added damping. An optimal value of the electric circuit quality factor is obtained when using an inductance, for free and forced response.

A Multi Objective Optimization Approach to Optimize Vehicle Ride and Handling Characteristics

Vehicle suspension design must fulfill some conflicting criteria. Among those is ride comfort which is attained by minimizing the acceleration transmitted to the sprung mass, via suspension spring and damper. Also good handling of a vehicle is a desirable property which requires stiff suspension and therefore is in contrast with a vehicle with good ride. Among the other desirable features of a suspension is the minimization of the maximum travel of suspension. This travel which is called suspension working space in vehicle dynamics literature is also a design constraint and it favors good ride. In this research a full car 8 degrees of freedom model has been developed and the three above mentioned criteria, namely: ride, handling and working space has been adopted as objective functions. The Multi Objective Programming (MOP) discipline has been used to find the Pareto Front and some reasoning used to chose a design point between these non dominated points of Pareto Front. Keywords—Vehicle, Ride, Handling, Suspension, Working Space, Multi Objective Programming.

Semiclassical Description of Electronic Excitation Population Transfer in a Model Photosynthetic System

Recently, Fleming’s group observed direct evidence that the electronic excitation energy (and population) transfers coherently rather than through incoherent hopping motions in the Fenna−Mathews−Olson pigment−protein complex. Ishizaki and Fleming further developed a hierarchy equation approach to describe this excitation population transfer dynamics in a model photosynthetic system. Here, we treat this same model system via the linearized approximation to the semiclassical (SC) initial value representation (IVR) for time correlation functions, in combination with the Meyer−Miller−Stock−Thoss model for the electronic degrees of freedom. Our approach is able to describe the long-lived quantum coherent dynamics, in excellent agreement with Ishizaki−Fleming’s results. Moreover, the advantage of the linearlized SC-IVR approach is that it can be applied to any molecular model for which classical MD simulations are feasible, all the way up to a full all-atom MD simulation, while at the same time treating the electronic and nuclear dynamics in a consistent fashion.

1113 タイヤ自由度を考慮した二輪車の動特性に関する研究(OS2-3 路面とタイヤ,OS2 交通・物流システムのダイナミクス,オーガナイズド・セッション(OS))

In the theoretical research maneuverability and stability of the two-wheeled vehicle, the most famous one is called four degree of freedom model that sharp announced. The dynamic characteristic of the tire is considered in this model, cornering stiffness and camber stiffness are generated by the delay for the sideslip and camber angle by the first. However, when such tire characteristics are used, the vibration phenomenons wobble and weave is not theoretically expressible. So this paper, it focuses attention on the side rigidity and twist rigidity of the tire and analyzed the tire model consider the rigidity value into the four degree of freedom model.

A virtual model of the bench press exercise

The objective of this study was to design and validate a three degrees of freedom model in the sagittal plane for the bench press exercise. The mechanical model was based on rigid segments connected by revolute and prismatic pairs, which enabled a kinematic approach and global force estimation. The method requires only three simple measurements: (i) horizontal position of the hand ( x 0); (ii) vertical displacement of the barbell ( Z) and (iii) elbow angle ( θ). Eight adult male throwers performed maximal concentric bench press exercises against different masses. The kinematic results showed that the vertical displacement of each segment and the global centre of mass followed the vertical displacement of the lifted mass. Consequently, the vertical velocity and acceleration of the combined centre of mass and the lifted mass were identical. Finally, for each lifted mass, there were no practical differences between forces calculated from the bench press model and those simultaneously measured with a force platform. The error was lower than 2.5%. The validity of the mechanical method was also highlighted by a standard error of the estimate (SEE) ranging from 2.0 to 6.6 N in absolute terms, a coefficient of variation (CV) ⩽0.8%, and a correlation between the two scores ⩾0.99 for all the lifts ( p<0.001). The method described here, which is based on three simple parameters, allows accurate evaluation of the force developed by the upper limb muscles during bench press exercises in both field and laboratory conditions.

INVESTIGATION OF THE INFLUENCE OF THE ELBOW JOINT REACTION ON THE PREDICTED MUSCLE FORCES USING DIFFERENT OPTIMIZATION FUNCTIONS

Less attention is paid to joint reactions when optimization tasks are solved aiming to predict individual muscle forces driving a biomechanical model. The reactions are important, however, for joint stability and for prevention from injuries, especially for fast motions and submaximal loading. The purpose of the paper is to investigate the influence of the joint reaction as a criterion in an objective function and to study the possibilities for prediction of antagonistic co-contraction. Planar elbow flexions in the sagittal plane with duration from 0.4 to 2 s are simulated, and muscle forces and elbow joint reaction are calculated solving numerically optimization tasks formulated for models with one (elbow moment equation only) and two (elbow and shoulder moment equations) degrees of freedom (DOF). The objective function is a weighted sum of muscle forces and joint reaction raised to different powers. The following conclusions can be made: (1) if the joint reaction is included in the objective function, antagonistic co-contraction can be predicted even for 1 DOF model; in some situations the use of such objective function can destroy the synergistic muscles' action; (2) the prediction of antagonistic muscles' co-contraction for 2 DOF model depends on the way the biarticular muscles are modeled, and this is valid for both dynamic and quasistatic conditions; if there are no biarticular muscles, antagonistic co-contraction cannot be predicted in one joint using popular objective functions, like minimum of sum of muscle forces or muscle stresses raised to a power.

NONLINEAR PHENOMENA IN THE SINGLE-MODE DYNAMICS OF A CABLE-SUPPORTED BEAM

In this paper we discuss the practical usefulness of nonlinear dynamical analysis for the design of a planar cable-supported beam: we refer to a feasible case, assuming the value of the parameters corresponding to a realistic pedestrian footbridge. We consider a one degree of freedom model, obtained by the classical Galerkin reduction technique: the ensuing ordinary differential equation has both quadratic and cubic terms, due to geometric nonlinearities. Extensive numerical simulations are performed: they point out that this model, in spite of its apparent simplicity, is able to highlight the complex dynamics of the cable-supported beam, describing several common and uncommon nonlinear phenomena. Each of them is interpreted in terms of oscillations of the considered mechanical system; we explain the relevance of all the obtained results in the design of the examined structure under steady loads as wind and pedestrians, but also under transient phenomena as earthquake and gust; the ensuing issues, the most dangerous ranges and also the sensibility to perturbations are discussed in detail. In particular we deal with the importance, for an engineering design, of a careful interpretation of: isola bifurcation, transition to chaos both by period doubling cascade and reverse boundary crisis, multistability with coexistence of chaotic and periodic attractors, fractal basins boundaries, erosion of immediate basins, interrupted sequence of period doubling bifurcations. Also the effects of secondary attractors are analyzed, and it is shown that in general they cannot be neglected even if their range of existence is very small. We underline that all these investigations are performed choosing the excitation frequency far from resonances in order to alert the designer that the system dynamics may be complex independently of the activation mechanism due to resonance.

Closed-Loop Control of Functional Electrical Stimulation-Assisted Arm-Free Standing in Individuals With Spinal Cord Injury: A Feasibility Study

Objectives. The purpose of the present study was to show that the design of a neuroprosthesis for unsupported (arm-free) standing is feasible. We review findings suggesting that a closed-loop controlled functional electrical stimulation (FES) system should be able to facilitate arm-free quiet standing in individuals with spinal cord injury (SCI). Particularly, this manuscript identifies: 1) a control strategy that accurately mimics the strategy healthy individuals apply to regulate the ankle joint position during quiet standing and 2) the degrees of freedom (DOF) of the redundant, closed-chain dynamic system of bipedal stance that have to be regulated to facilitate stable standing. Methods and Results. First, we utilized a single DOF model of quiet standing (inverted pendulum) to analytically identify a proportional and derivative (PD) feedback controller that regulates the ankle torque in a physiologic manner despite a long sensory-motor time delay. Second, these theoretic results were experimentally validated by implementing the proposed PD controller to stabilize an individual with SCI during quiet standing. Third, a realistic, three-dimensional dynamic model of quiet standing with 12 DOF was used to determine the optimal combination of the minimum number of DOF that need to be regulated with the PD controller to ensure stability during quiet standing. Finally, perturbation simulations confirmed that the kinematics of this system are similar to those of healthy individuals during perturbed standing. Conclusions. The presented results suggest that stable standing can be achieved in individuals with SCI by controlling only six DOF in the lower limbs using FES, and that a PD controller actuating these DOF can stabilize the system despite a long sensory-motor time delay. Our finding that not all DOF in the lower limbs need to be regulated is particularly relevant for individuals with complete SCI, because some of their muscles may be denervated or difficult to access.

Tests on impact effect of partial fracture at steel frame connections

Impact effect of sudden fracture at steel frame connections under severe earthquake or other extreme loads is presented in this paper. The relation of impulse caused by structural fracture to the release of inner force at the cracked location, the magnitude of the response to impact on the basis of one degree of freedom model, and the ratio of the peak value of response to natural period of the system are investigated. Two types of fracture tests were designed and carried out both on uniaxial steel bar tensioned and moment resistant steel frame model. It is proven that the response during the fracture process can be measured quite well using high-frequency data processing system. It is also revealed that the instant fracture of structural connection is characterized by progressive and partial fracture. Numerical evaluation of the impact effect of connection fracture is carried out.

Huygens probe entry dynamic model and accelerometer data analysis

During the first phase of Huygens arrival into Titan's atmosphere the probe is subjected to gravitational and aerodynamic forces in aerodynamic hypersonic regime. Atmospheric drag exerts a strong deceleration on the capsule measured by Huygens atmospheric structure instrument (HASI) servo accelerometer. A 6 DOF (Degree of Freedom) model of the Huygens probe entry dynamics has been developed and used for data analysis. The accelerometer data are analysed and the model allows the retrieval of dynamics information of Huygens probe from 1545 km altitude down to end of the entry phase. Probe's initial conditions (velocity and position) were refined to match the measured deceleration profile resulting in a different altitude at interface epoch with respect to those of the Cassini Navigation Team. Velocity and position of probe at interface epoch are compatible with those used by Descent Trajectory Working Group (DTWG). Measurements acquired before atmosphere detection are used to estimate probe's angular rate, bound attitude and characterise the angle of attack profile which results to be lower than 4 ∘ during the whole entry. Probe's spin calculated (6.98 RPM) is slightly different with respect to DTWG of 7.28 RPM but considering a 2% error in the Inertia matrix these results are inside the 1 - σ error band.