bluuebunny/crossref_metadata_2025 huggingface dataset:
Long Term Consistency of Handwriting Grip Kinetics in Adults
Authors: Ghali Bassma , Mamun Khondaker A. , Chau Tom
Published: February 2014

While there is growing interest in clinical applications of handwriting grip kinetics, the consistency of these forces over time is not well-understood at present. In this study, we investigated the short- and long-term intra-participant consistency and inter-participant differences in grip kinetics associated with adult signature writing. Grip data were collected from 20 adult participants using a digitizing tablet and an instrumented pen. The first phase of data collection occurred over 10 separate days within a three week period. To ascertain long-term consistency, a second phase of data collection followed, one day per month over several months. In both phases, data were collected three times a day. After pre-processing and feature extraction, nonparametric statistical tests were used to compare the within-participant grip force variation between the two phases. Participant classification based on grip force features was used to determine the relative magnitude of inter-participant versus intra-participant differences. The misclassification rate for the longitudinal data were used as an indication of long term kinetic consistency. Intra-participant analysis revealed significant changes in grip kinetic features between the two phases for many participants. However, the misclassification rate, on average, remained stable, despite different demarcations of training, and testing data. This finding suggests that while signature writing grip forces may evolve over time, inter-participant kinetic differences consistently exceeds within-participant force changes in the long-term. These results bear implications on the collection, modeling and interpretation of grip kinetics in clinical applications.
Predicting Bone Remodeling in Response to Total Hip Arthroplasty: Computational Study Using Mechanobiochemical Model
Authors: Tavakkoli Avval Pouria , Klika Václav , Bougherara Habiba
Published: February 2014

Periprosthetic bone loss following total hip arthroplasty (THA) is a serious concern leading to the premature failure of prosthetic implant. Therefore, investigating bone remodeling in response to hip arthroplasty is of paramount for the purpose of designing long lasting prostheses. In this study, a thermodynamic-based theory, which considers the coupling between the mechanical loading and biochemical affinity as stimulus for bone formation and resorption, was used to simulate the femoral density change in response to THA. The results of the numerical simulations using 3D finite element analysis revealed that in Gruen zone 7, after remarkable postoperative bone loss, the bone density started recovering and got stabilized after 9% increase. The most significant periprosthetic bone loss was found in Gruen zone 7 (−17.93%) followed by zone 1 (−13.77%). Conversely, in zone 4, bone densification was observed (+4.63%). The results have also shown that the bone density loss in the posterior region of the proximal metaphysis was greater than that in the anterior side. This study provided a quantitative figure for monitoring the distribution variation of density throughout the femoral bone. The predicted bone density distribution before and after THA agree well with the bone morphology and previous results from the literature.
Bending of the Looping Heart: Differential Growth Revisited
Authors: Shi Yunfei , Yao Jiang , Xu Gang , Taber Larry A.
Published: February 2014

In the early embryo, the primitive heart tube (HT) undergoes the morphogenetic process of c-looping as it bends and twists into a c-shaped tube. Despite intensive study for nearly a century, the physical forces that drive looping remain poorly understood. This is especially true for the bending component, which is the focus of this paper. For decades, experimental measurements of mitotic rates had seemingly eliminated differential growth as the cause of HT bending, as it has commonly been thought that the heart grows almost exclusively via hyperplasia before birth and hypertrophy after birth. Recently published data, however, suggests that hypertrophic growth may play a role in looping. To test this idea, we developed finite-element models that include regionally measured changes in myocardial volume over the HT. First, models based on idealized cylindrical geometry were used to simulate the bending process in isolated hearts, which bend without the complicating effects of external loads. With the number of free parameters in the model reduced to the extent possible, stress and strain distributions were compared to those measured in embryonic chick hearts that were isolated and cultured for 24 h. The results show that differential growth alone yields results that agree reasonably well with the trends in our data, but adding active changes in myocardial cell shape provides closer quantitative agreement with stress measurements. Next, the estimated parameters were extrapolated to a model based on realistic 3D geometry reconstructed from images of an actual chick heart. This model yields similar results and captures quite well the basic morphology of the looped heart. Overall, our study suggests that differential hypertrophic growth in the myocardium (MY) is the primary cause of the bending component of c-looping, with other mechanisms possibly playing lesser roles.
Graph-Theoretic Sensitivity Analysis of Multibody Systems
Authors: Banerjee Joydeep M. , McPhee John J.
Published: February 2014

A graph-theoretic formulation to perform sensitivity analysis on multibody systems is presented in this article. In this formulation, linear graphs are used to capture the system topologies from which a graph-theoretic formulation simultaneously generates the system equations and the sensitivity equations. This ensures the automated, accurate, and efficient generation of sensitivity equations. The basic formulation steps are outlined to illustrate the process of the generation of sensitivity equations. The salient aspects of multibody systems are presented along with a brief description of the software platform that has been used to implement the algorithm. A 3D pendulum and a double-wishbone suspension system are analyzed to demonstrate the application of the algorithm. The results are validated by using a finite difference formulation. Finally, the efficiency of the software implementation is assessed by comparing the computational costs associated with the proposed method and that of existing methods.
Identifying Key Parameters for Design Improvement in High-Dimensional Systems With Uncertainty
Authors: Fender Johannes , Graff L. , Harbrecht H. , Zimmermann Markus
Published: February 2014

Key parameters may be used to turn a bad design into a good design with comparatively little effort. The proposed method identifies key parameters in high-dimensional nonlinear systems that are subject to uncertainty. A numerical optimization algorithm seeks a solution space on which all designs are good, that is, they satisfy a specified design criterion. The solution space is box-shaped and provides target intervals for each parameter. A bad design may be turned into a good design by moving its key parameters into their target intervals. The solution space is computed so as to minimize the effort for design work: its shape is controlled by particular constraints such that it can be reached by changing only a small number of key parameters. Wide target intervals provide tolerance against uncertainty, which is naturally present in a design process, when design parameters are unknown or cannot be controlled exactly. In a simple two-dimensional example problem, the accuracy of the algorithm is demonstrated. In a high-dimensional vehicle crash design problem, an underperforming vehicle front structure is improved by identifying and appropriately changing a relevant key parameter.
A Constrained Extended Kalman Filter for State-of-Charge Estimation of a Vanadium Redox Flow Battery With Crossover Effects
Authors: Yu Victor , Headley Alex , Chen Dongmei
Published: February 2014

One of the main issues with vanadium redox flow batteries (VRFBs) is that vanadium ions travel across the membrane during operation which leads to a concentration imbalance and capacity loss after long-term cycling. Precise state-of-charge (SOC) monitoring allows the operator to effectively schedule electrolyte rebalancing and devise a control strategy to keep the battery running under optimal conditions. However, current SOC monitoring methods are too expensive and impractical to implement on commercial VRFB systems. Furthermore, physical models alone are neither reliable nor accurate enough to predict long-term capacity loss due to crossover. In this paper, we present an application of using an extended Kalman filter (EKF) to estimate the total vanadium concentration in each half-cell by combining three voltage measurements and a state prediction model without crossover effects. Simulation results show that the EKF can accurately predict capacity loss for different crossover patterns over a few hundred cycles.
Predicting the Physical and Chemical Ignition Delays in a Military Diesel Engine Running n-Hexadecane Fuel
Authors: Hamilton Len , Luning Prak Dianne , Cowart Jim
Published: February 2014

There are currently numerous efforts to create renewable fuels that have similar properties to conventional diesel fuels. One major future challenge is evaluating how these new fuels will function in older legacy diesel engines. It is desired to have physically based modeling tools that will predict new fuel performance without extensive full scale engine testing. This study evaluates two modeling tools that are used together to predict ignition delay in a military diesel engine running n-hexadecane as a fuel across the engine's speed-load range. AVL-FIRE® is used to predict the physical delay of the fuel from the start of injection until the formation of a combustible mixture. Then a detailed Lawrence Livermore National Laboratory (LLNL) chemical kinetic mechanism is used to predict the chemical ignition delay. This total model predicted ignition delay is then compared to the experimental engine data. The combined model predicted results show good agreement to that of the experimental data across the engine operating range with the chemical delay being a larger fraction of the total ignition delay. This study shows that predictive tools have the potential to evaluate new fuel combustion performance.
Evolution of Multi-Agent Systems as Continua
Authors: Rastgoftar Hossein , Jayasuriya Suhada
Published: February 2014

In this paper, a new framework for evolution of multi-agent systems (MAS) based on principles of continuum mechanics is developed. Agents are treated as mass particles of a continuum whose evolution (both translation and deformation) is modeled as a homeomorphism from a reference to the current configuration. Such a mapping assures that no two mass particles of the continuum occupy the same location at any given time, thus guaranteeing that inter-agent collision is avoided during motion. We show that a special class of mappings whose Jacobian is only time varying and not spatially varying has some desirable properties that are advantageous in studying swarms. Two specific scenarios are studied where the evolution of a swarm from one configuration to another occurs with no inter-agent collisions while avoiding obstacles, under (i) zero inter-agent communication and (ii) local inter-agent communication. In the first case, a desired map is computed by each agent all knowing the positions of a few leader agents in a reference and the desired configurations. In the second case, paths of n + 1 leader agents evolving in an n-D space are known only to the leaders, while positions of follower agents evolve through updates that are based on positions of n + 1 adjacent agent through local communication with them. The latter is based on a set of weights of communication of follower agents that are predicated on certain distance ratios assigned on the basis of the initial formation of the MAS. Properties of homogeneous maps are exploited to characterize the necessary communication protocol.
A Note on the Normalized Approach to Simulating Moisture Diffusion in a Multimaterial System Under Transient Thermal Conditions Using ansys 14 and 14.5
Authors: Liu Dapeng , Park Seungbae
Published: February 2014

Moisture can have significant effects on the performance and reliability of electronic components. Accurately simulating moisture diffusion is important for designers and manufacturers to obtain a realistic reliability evaluation. Beginning with version 14, ansys is capable of simulating diffusion and related behaviors, such as hygroscopic swelling, with newly developed elements. However, a normalized approach is still required to deal with the discontinuity of concentrations at the material boundaries, and normalization of the moisture concentration in transient thermal conditions is tricky. Case studies have shown that normalizing the moisture concentration with respect to a time- or temperature-dependent material property will lead to erroneous results. This paper re-addresses the issues of performing diffusion simulations under transient thermal conditions and more general anisothermal conditions (temporally and spatially), and suggests an easy-to-use approach to cope with the limitations of the current version for users in the electronic packaging industry.
Numerical Study of Slat Screen Pattern Effect on Design Parameters of Tuned Liquid Dampers
Authors: Marivani Morteza , Hamed M. S.
Published: February 2014

Tuned liquid dampers (TLDs) are considered economical and effective dynamic vibration absorbers. They are increasingly being used to mitigate the dynamic resonant response of tall buildings and it is often designed to reduce the structure's acceleration at a serviceability limit state. Slat screens can increase the inherent damping factor of TLDs. They have been used as a common flow damping device in TLDs because of the simplicity of using them and also the ability to control their effects on the performance of a TLD. Two slat screens with the same solidity ratio and different patterns could have different effects on the TLD's performance. Many former numerical researches used the potential and linear theory as a base to describe the fluid flow behavior inside the TLD. The applicability of the linearized flow models was for the condition of the low amplitude of excitations. Under large excitation events such as high return period wind storms or earthquakes, the assumptions of linear theory are no longer valid. Moreover, in the linearized model, screens were modeled as a hydraulic resistance point as a function of the screen solidity ratio without the ability to consider the effect of screen pattern. In the present study, a numerical algorithm has been developed which can handle both the small and large amplitude of excitations. In this algorithm, the fluid flow through the screen is fully resolved and it can take into account the effect of the screen pattern on the TLD's performance. The major focus of this paper is to use this developed algorithm and conduct a numerical investigation to study the effects of the slat screen pattern on the inherent damping and natural frequency of the TLD, as the design parameters of the TLD. In this numerical investigation a selected TLD outfitted by different slat screens and interacted with the structure is exposed by both harmonic and random external excitations. The numerical results have been validated against experimental work. The effect of slat screen pattern on the damping effect and natural frequency of a TLD has been presented. Also in this study, two new parameters termed as slat ratio (SR) and effective solidity ratio (Seff) are presented to imply the physical significance of screen pattern.
Reduced Order Model for a Power-Law Fluid
Authors: Ocana M. , Alonso D. , Velazquez A.
Published: February 2014

This article describes the development of a reduced order model (ROM) based on residual minimization for a generic power-law fluid. The objective of the work is to generate a methodology that allows for the fast and accurate computation of polymeric flow fields in a multiparameter space. It is shown that the ROM allows for the computation of the flow field in a few seconds, as compared with the use of computational fluid dynamics (CFD) methods in which the central processing unit (CPU) time is on the order of hours. The model fluid used in the study is a polymeric fluid characterized by both its power-law consistency index m and its power-law index n. Regarding the ROM development, the main difference between this case and the case of a Newtonian fluid is the order of the nonlinear terms in the viscous stress tensor: In the case of the polymeric fluid these terms are highly nonlinear while they are linear when a Newtonian fluid is considered. After the method is validated and its robustness studied with regard to several parameters, an application case is presented that could be representative of some industrial situations.
Effect of Dimple Offset on the Operational Shock Performance of Small Form Factor Disk Drives
Authors: Bhargava Puneet , Bogy David B.
Published: February 2014

This paper discusses the effect of varying the suspension load dimple location on the shock robustness of small form factor hard disk drives. We use the CML shock simulator, which simulates the structural as well as the air bearing dynamics of the disk drive simultaneously. The location of the dimple is varied and simulations are run for various load positions on the back of the slider, while adjusting the pitch static attitude (PSA) and the roll static attitude (RSA) of the slider such that the flying attitude of the slider remains the same. We simulate shocks of 0.5 ms pulse width for a commercially available slider and suspension designs for a 1 in. drive. We observe that shock resistance is optimal when the dimple is offset toward the leading edge of the slider. This behavior is explained on the basis of a linearized air bearing model. It is also observed that moving the dimple too much toward the leading edge causes the mechanism of shock failure to change resulting in lower shock tolerances.
A Disturbance Cancellation Perspective on Vibration Control Using a Bistable Snap-Through Attachment
Authors: Johnson David R. , Harne R. L. , Wang K. W.
Published: February 2014

One approach to vibration control is to apply a force to a primary structure that opposes the excitation, effectively canceling the external disturbance. A familiar passive example of this approach is the linear-tuned mass absorber. In this spirit, the utility of a bistable attachment for attenuating vibrations, especially in terms of the high-orbit, snap-through dynamic, is investigated using the harmonic balance method and experiments. Analyses demonstrate the fundamental harmonic snap-through dynamic, having commensurate frequency with the single-frequency harmonic excitation, may generate adverse constructive forces that substantially reinforce the applied excitation, primarily at lower frequencies. However, both analyses and experiments indicate that such high-orbit dynamics may be largely destabilized by increased bistable attachment damping. Destructive forces, which substantially oppose the excitation, are unique in that they lead to a form of vibration attenuation analogous to strictly adding damping to the host structure, leaving its spectral characteristics largely unaltered. The experiments verify the analytical findings and also uncover nonlinear dynamics not predicted by the analysis, which render similar attenuation effects.
Optimal Control of a Wind Turbine With a Variable Ratio Gearbox for Maximum Energy Capture and Prolonged Gear Life
Authors: Shaltout Mohamed L. , Hall John F. , Chen Dongmei
Published: February 2014

An optimal control approach for a wind turbine drivetrain with a variable ratio gearbox is presented. The objective is to find the optimum shifting sequence of the variable ratio gearbox in order to maximize power generation and extend gear life. The employment of a variable ratio gearbox enhances the capabilities of the wind turbine to cope with wind speed variations. Based on the authors' preliminary study, the gear ratios of the variable ratio gearbox were carefully selected to maximize the wind energy capture. In this paper, a new control approach is proposed to achieve both extended gear service life and optimal energy harvesting. This new approach finds the gear shifting sequence that will minimize the tangential force on the gear tooth while maximizing the wind energy capture. The wind turbine drivetrain with a variable ratio gearbox is modeled and simulation results based on recorded wind data of different wind classes are presented and compared.
Frictional Indentation of Anisotropic Magneto-Electro-Elastic Materials by a Rigid Indenter
Authors: Zhou Yue-Ting , Zhong Zheng
Published: February 2014

An exact analysis on frictional contact between a rigid punch and anisotropic magneto-electro-elastic materials is performed, within the framework of the fully coupled theory. The indenter moves relative to magneto-electro-elastic materials, and Coulomb friction law is used. The mixed boundary value problem is reduced to singular integral equations of the second kind with analytical solution presented. For a triangular or semiparabolic indenter, explicit expression for surface physical in-plane stress, electrical displacement and magnetic induction are obtained. Influences of the friction coefficient and the volume fraction on contact behaviors are detailed under the prescribed contact loading conditions. Under either a triangular or semiparabolic indenter, the surface in-plane stress, electric displacement and magnetic induction are discontinuous and unbounded around the leading edge, and such a serious near-edge response can be relieved through adjusting the values of the friction coefficient or the volume fraction.
Influence of a Variable in Time Heat Transfer Coefficient on Stresses in Model of Power Plant Components
Authors: Okrajni Jerzy , Twardawa Mariusz
Published: February 2014

The paper discusses the issue of the modelling of strains and stresses resulting from heating and cooling processes of components in power plants. The main purpose of the work is to determine the mechanical behavior of power plant components operating under mechanical and thermal loading. The finite element method (FEM) has been used to evaluate the temperature and stresses changes in components as a function of time. Temperature fields in the components of power plants are dependent, among parameters, on variable heat-transfer conditions between components and the fluid medium, that may change its condition, flowing inside them. For this reason, an evaluation of the temperature field and the consequent stress fields requires the use of heat-transfer coefficients as time-dependent variables and techniques for determining appropriate values for these coefficients should be used. The methodology that combines computer modelling of the temperature fields with its measurements performed at selected points of the pipelines may be used in this case. The graphs of stress changes as a function of time have been determined for the chosen plant components. The influence of the heat transfer conditions on the temperature fields and mechanical behavior of components in question have been discussed.
Pre-emptive Rotor Blade Damage Identification by Blade Tip Timing Method
Authors: Guru Siddhartha S. , Shylaja S. , Kumar Sunil , Murthy Ramesh
Published: February 2014

The blade tip timing (BTT) method uses the differential arrival timings of the blades at case-mounted sensors to effectively characterize the vibrations of all blades in a rotor. This paper studies the use of the BTT method for pre-emptive prediction of rotor blade damage; through a careful monitoring of blade natural frequencies in conjunction with the blade tip position during an engine test. In the current study, the low pressure turbine stage of a developmental aero engine is instrumented with a combination of eddy current and optical sensors located circumferentially on the casing. This instrumentation effectively captures the engine order resonances of interest for the blade bending mode. During one of the normal engine tests, one of the blades in the LPT stage suddenly showed a drop in natural frequency beyond the allowable scatter and an abrupt change in the blade tip position. As the engine test was continued further, this drop in blade natural frequency and change in blade tip position progressively increased towards blade failure limits. Suspecting a propagating crack in the particular blade, the test was aborted and the engine was withdrawn for detailed inspection. Inspection of the rotor blades confirmed the presence of significant aerofoil crack in the suspect blade.
Influence of Large Wake Disturbances Shed From the Combustor Wall on the Leading Edge Film Cooling
Authors: Maria Mazzoni Cosimo , Klostermeier Christian , Rosic Budimir
Published: February 2014

The first vane leading edge film cooling is challenging because of the highest thermal load and the complex flow interaction between the hot mainstream gas and the coolant flow. This interaction varies significantly from the stagnation region to the regions of high curvature and acceleration further downstream. Additionally, in industrial gas turbines with multiple combustor chambers around the annulus the first vane leading edges may also be exposed to large wake disturbances shed from the upstream combustor walls. The influence of these vortical structures on the first vane leading edge film cooling is numerically analyzed in this paper. In order to assess the capabilities of the flow solver TBLOCK to simulate these complex interactions an experimental test case is modeled numerically. The test case is available in the open literature and consists of a cylindrical leading edge and two rows of film cooling holes representative of industrial practice. A LES turbulence modeling strategy with the WALE subgrid scale (SGS) model is applied and compared against experimental results. Based on this validation it is decided to analyze also the wake–leading edge interaction, dominated by large scale unsteady vortical structures, using the same WALE subgrid scale LES model. The initial flow domain with the cylindrical leading edge and cooling holes is extended to incorporate the effect of the combustor wall, which is modeled as a flat plate with a square trailing edge. The location and the size of the plate are scaled to be representative of industrial practice: the plate is located upstream from the leading edge at a distance twice the leading edge diameter, and the thickness of the plate is one half of the leading edge diameter. Two different clockwise positions of the vertical combustor wall model were investigated and compared with the datum configuration: the former where the axis of the plate and the leading edge are aligned (central wake location), the latter with the combustor wall circumferentially shifted up by a quarter of the leading edge diameter (circumferentially shifted wake location). Numerical predictions show that the shed vortices from the combustor wall trailing edge have a highly detrimental effect on the leading edge film cooling by periodically removing the coolant flow from the leading edge surface. This results in an increased unsteady thermal load. These negative effects are less significant in the case of circumferentially shifted wake, due to the combined action of both shed vortices.
A Comparative Computational Fluid Dynamics Study on Flamelet-Generated Manifold and Steady Laminar Flamelet Modeling for Turbulent Flames
Authors: Nakod Pravin , Yadav Rakesh , Rajeshirke Pravin , Orsino Stefano
Published: February 2014

The laminar flamelet model (LFM) (Peters, 1986, “Laminar Diffusion Flamelet Models in Non-Premixed Combustion,” Prog. Energy Combust. Sci., 10, pp. 319–339; Peters, “Laminar Flamelet Concepts in Turbulent Combustion,” Proc. Combust. Inst., 21, pp. 1231–1250) represents the turbulent flame brush using statistical averaging of laminar flamelets whose structure is not affected by turbulence. The chemical nonequilibrium effects considered in this model are due to local turbulent straining only. In contrast, the flamelet-generated manifold (FGM) (van Oijen and de Goey, 2000, “Modeling of Premixed Laminar Flames Using Flamelet-Generated Manifolds,” Combust. Sci. Technol., 161, pp. 113–137) model considers that the scalar evolution; the realized trajectories on the thermochemical manifold in a turbulent flame are approximated by the scalar evolution similar to that in a laminar flame. This model does not involve any assumption on flame structure. Therefore, it can be successfully used to model ignition, slow chemistry, and quenching effects far away from the equilibrium. In FGM, 1D premixed flamelets are solved in reaction-progress space rather than physical space. This helps better solution convergence for the flamelets over the entire mixture fraction range, especially with large kinetic mechanisms at the flammability limits (ANSYS FLUENT 14.5 Theory Guide Help Document, http://www.ansys.com). In the present work, a systematic comparative study of the FGM model with the LFM for four different turbulent diffusion/premixed flames is presented. The first flame considered in this work is methane-air flame with dilution air at the downstream. The second and third flames considered are jet flames in a coaxial flow of hot combustion products from a lean premixed flame called Cabra lifted H2 and CH4 flames (Cabra, et al., 2002, “Simultaneous Laser Raman-Rayleigh-LIF Measurements and Numerical Modeling Results of a Lifted Turbulent H2/N2 Jet Flame in a Vitiated Coflow,” Proc. Combust. Inst., 29(2), pp. 1881–1888; Lifted CH4/Air Jet Flame in a Vitiated Coflow, http://www.me.berkeley.edu/cal/vcb/data/VCMAData.html) where the reacting flow associated with the central jet exhibits similar chemical kinetics, heat transfer, and molecular transport as recirculation burners without the complex recirculating fluid mechanics. The fourth flame considered is a Sandia flame D (Barlow et al., 2005, “Piloted Methane/Air Jet Flames: Scalar Structure and Transport Effects,” Combust. Flame, 143, pp. 433–449), a piloted methane-air jet flame. It is observed that the simulation results predicted by the FGM model are more physical and accurate compared to the LFM in all the flames presented in this work. The autoignition-controlled flame lift-off is also captured well in the cases of lifted flames using the FGM model.
Risk Assessment of the Intake of Foods and Soil With the Radionuclides and the Air Radiation Dose After the Fukushima Nuclear Disaster
Authors: Fujinaga Aiichiro , Yoneda Minoru , Ikegami Maiko
Published: February 2014

The exposure routes by which the dispersion of radionuclides from the accident at the Fukushima atomic power plant were estimated, and the risk was evaluated based on the overall exposure routes, which include the ingestion of food, ingestion and inhalation of soil, and external air dose. This study shows that the air dose from this disaster should be less than 0.2 μSv/h to control the radiation dose with the consumption of food being less than 1 mSv/yr. However, to maintain the lifetime dose under 100 mSv, several mSv/yr is sufficient, considering radioactive decay and dilution by advection and diffusion.
Modeling Flexibility in Myosin V Using a Multiscale Articulated Multi-Rigid Body Approach
Authors: Haghshenas-Jaryani Mahdi , Bowling Alan
Published: February 2014

This paper presents a multiscale dynamic model for the simulation and analysis of flexibility in myosin V. A 3D finite segment model, a multirigid body model connected with torsional springs, is developed to mechanically model the biological structure of myosin V. The long simulation run time is one of the most important issues in the dynamic modeling of biomolecules and proteins due to the disproportionality between the physical parameters involved in their dynamics. In order to address this issue, the most-used models, based on the famous overdamped Langevin equation, omit the inertial terms in the equations of motion; that leads to a first order model that is inconsistent with Newton's second law. However, the proposed model uses the concept of the method of multiple scales (MMS) that brings all of the terms of the equations of motion into proportion with each other; that helps to retain the inertia terms. This keeps the consistency of the model with the physical laws and experimental observations. In addition, the numerical integration's step size can be increased from commonly used subfemtoseconds to submilliseconds. Therefore, the simulation run time is significantly reduced in comparison with other approaches. The simulation results obtained by the proposed multiscale model show a dynamic behavior of myosin V which is more consistent with experimental observations in comparison with other overdamped models.
Sensitivity Analysis of Smoothed Particle Hydrodynamics in PAM-CRASH for Modeling of Soft Soils
Authors: Dhillon Ranvir , El-Gindy Moustafa , Ali Rustam , Philipps David , Öijer Fredrik , Johansson Inge
Published: February 2014

The rapid progression of computational power and development of non-mesh particle modeling techniques provides solutions to problems which are not accurately modeled using traditional finite element analysis techniques. The field of soft soil modeling has been pressing on in recent years and the smoothed particle hydrodynamics (SPH) modeling method in PAM-CRASH provides opportunity for further advancement in accuracy.

This research focuses on the development of soft soil models using SPH with verification using pressure-sinkage and shear strength criterion. Soil model parameters such as geometry and contact model are varied to determine the effect of the parameters on the behaviour of the soft soil and relationships are developed. The developed virtual soil models are compared against existing soils to determine which soils are accurately modeled and further refinements are made to validate the models with existing empirical data.
A Design Oriented Reliability Methodology for Fatigue Life Under Stochastic Loadings
Authors: Hu Zhen , Du Xiaoping
Published: February 2014

Fatigue damage analysis is critical for systems under stochastic loadings. To estimate the fatigue reliability at the design level, a hybrid reliability analysis method is proposed in this work. The First Order Reliability Method (FORM), the inverse FORM, and the peak distribution analysis are integrated for the fatigue reliability analysis at the early design stage. Equations for the mean value, the zero upcrossing rate, and the extreme stress distributions are derived for problems where stationary stochastic processes are involved. Then the fatigue damage is analyzed with the peak counting method. The developed methodology is demonstrated by a simple mathematical example and is then applied to the fatigue reliability analysis of a shaft under stochastic loadings. The results indicate the effectiveness of the proposed method in predicting fatigue damage and reliability.
Coupled Bioaeroservoelastic Rotorcraft-Pilot Simulation
Authors: Masarati Pierangelo , Quaranta Giuseppe
Published: February 2014

This work presents the integration of a detailed biomechanical model of the arms of a helicopter pilot and an equivalently detailed aeroservoelastic model of a helicopter, resulting in what has been called a ‘bioaeroservoelastic’ analysis. The purpose is to investigate potential adverse interactions, called rotorcraft-pilot couplings, between the aeroservoelastic system and the controls involuntarily introduced by the pilot into the control system in response to rotorcraft vibrations transmitted to the pilot through the cockpit, the so-called biodynamic feedthrough. The force exerted by the pilot on the controls results from the activation of the muscles of the arms according to specific patterns. The reference muscular activation value as a function of the prescribed action on the controls is computed using an inverse kinetostatics/inverse dynamics approach. A first-order quasi-steady correction is adopted to mimic the reflexive contribution to muscle activation. Muscular activation is further augmented by activation patterns that produce elementary actions on the control inceptors. These muscular activation patterns, inferred using perturbation analysis, are applied to control the aircraft through the pilot’s limbs. The resulting biomechanical pilot model is applied to the aeroservoelastic analysis of a helicopter model expressly developed within the same multibody modeling environment to investigate adverse rotorcraft pilot couplings. The model consists of the detailed aeroelastic model of the main rotor, using nonlinear beams and blade element/momentum theory aerodynamics, a component mode synthesis model of the airframe structural dynamics, and servoactuator dynamics. Results in terms of stability analysis of the coupled system are presented in comparison with analogous results obtained using biodynamic feedthrough transfer functions identified from experimental data.
Fast Hybrid Genetic Clustering Algorithm for Design Structure Matrix
Authors: Borjesson Fredrik , Sellgren Ulf
Published: February 2014

Module formation is the step in which a product’s architecture is established in such a way that complex interactions are intra-modular and inter-modular interactions are more simple. If a matrix representation exists, such as a Design Structure Matrix, this involves clustering system entities into groups with strong intra-dependencies. For simple products, clustering may be done manually, but for complex products, computer tools are required. Existing clustering algorithms are either slow, or unable to guarantee a globally optimal solution. To enable iterative work and to make cluster analysis useful also in the detailing steps, efficient and effective computer algorithms are required. This paper presents an efficient and effective Genetic clustering algorithm, with the Minimum Description Length measure. To significantly reduce the time required for the algorithm to find a good clustering result, a knowledge aware heuristic element is included in the GA process. The efficiency and effectiveness of the algorithm is verified with four case studies.
Investigation of a Delayed Feedback Controller of MEMS Resonators
Authors: Masri Karim M. , Younis Mohammad I. , Shao Shuai
Published: February 2014

Controlling mechanical systems is an important branch of mechanical engineering. Several techniques have been used to control Microelectromechanical systems (MEMS) resonators. In this paper, we study the effect of a delayed feedback controller on stabilizing MEMS resonators. A delayed feedback velocity controller is implemented through modifying the parallel plate electrostatic force used to excite the resonator into motion. A nonlinear single degree of freedom model is used to simulate the resonator response. Long time integration is used first. Then, a finite deference technique to capture periodic motion combined with the Floquet theory is used to capture the stable and unstable periodic responses. We show that applying a suitable positive gain can stabilize the MEMS resonator near or inside the instability dynamic pull in band. We also study the stability of the resonator by tracking its basins of attraction while sweeping the controller gain and the frequency of excitations. For positive delayed gains, we notice significant enhancement in the safe area of the basins of attraction.
Estimating the Node-Level Behaviors in Complex Networks From Structural Datasets
Authors: Sha Zhenghui , Panchal Jitesh H.
Published: February 2014

There is an emerging class of networks that evolve endogenously based on the local characteristics and behaviors of nodes. Examples of such networks include social, economic, and peer-to-peer communication networks. The node-level behaviors determine the overall structure and performance of these networks. This is in contrast to exogenously designed networks whose structures are directly determined by network designers. To influence the performance of endogenous networks, it is crucial to understand a) what kinds of local behaviors result in the observed network structures and b) how these local behaviors influence the overall performance. The focus in this paper is on the first aspect, where information about the structure of networks is available at different points in time and the goal is to estimate the behavior of nodes that resulted in the observed structures. We use three different approaches to estimate the node-level behaviors. The first approach is based on the generalized preferential attachment model of network evolution. In the second approach, statistical regression-based models are used to estimate the node-level behaviors from consecutive snapshots of the network structure. In the third approach, the nodes are modeled as rational decision-making agents who make linking decisions based on the maximization of their payoffs. Within the decision-making framework, the multinomial logit choice model is adopted to estimate the preferences of decision-making nodes. The autonomous system (AS) level Internet is used as an illustrative example to illustrate and compare the three approaches.
Teaching Biomimicry With an Engineering-to-Biology Thesaurus
Authors: Nagel Jacquelyn K. S. , Nagel Robert L. , Eggermont Marjan
Published: February 2014

This paper presents research on the use of an engineering-to-biology thesaurus in an engineering classroom as an aid to teaching biomimicry. The leap from engineering to biological science has posed a challenge. Engineers often struggle with how to best use the vast amount of biological information available from the natural world around them. Often there is a knowledge gap, and terminology takes different meanings. Generally, the time required to learn and become fluent in biology poses too large a hurdle. The engineering-to-biology thesaurus was designed to allow engineers without advanced biological knowledge to leverage nature’s ingenuity during engineering design. The three key goals of this thesaurus are to (1) lessen the burden when working with knowledge from the biological domain by providing a link between engineering and biological terminology; (2) assist designers with establishing connections between the two domains; and (3) to facilitate biologically-inspired design.

In this paper, the results of a pilot study as well as a second study are presented. The pilot study was used to craft instructional materials involving the engineering-to-biology thesaurus. In the second study, sophomore engineering students enrolled in a design course were given a design task to complete using the thesaurus. The task focused on biomimetic concept development for their course project — designing a human-powered vehicle for a person with cerebral palsy. Results of the design task are presented.
Improving Stability Margins via Time Delay Control
Authors: Ulsoy A. Galip
Published: February 2014

While time delays typically lead to poor control performance, and even instability, previous research has shown that introduction of time delays in controlling a dynamic system can, in some cases, be beneficial. This paper presents a new benefit of time delay control for single-input single-output linear time invariant systems: it can be used to improve robustness, as measured by increased stability margins. The proposed method utilizes time delays to approximate state-derivative feedback, which can be used, together with state feedback, to reduce sensitivity and improve robustness. Additional sensors are not required since the state-derivatives are approximated using available measurements and time delays. The method is introduced using a scalar example, then applied to a single degree-of-freedom mechanical vibration control problem in simulations to demonstrate excellent performance with improved stability margins.
Interaction Forces Between the Rider and the 2-Wheeled Vehicle and Biomechanical Models
Authors: Bevilacqua Marco , Doria Alberto , Tognazzo Mauro
Published: February 2014

In two-wheeled vehicles the mass of the rider is a significant part of the total mass of the system and the rider influences the dynamic behavior both by means of the voluntary control actions and by means of the passive response of his body to the oscillations of the vehicle. The passive response of the rider’s body has a particular influence on roll motion, which is typical of two-wheeled vehicles. Roll oscillations generate inertia forces on the rider’s body, which moves with respect to the vehicle. Forces and torques generated by the rider on the handlebars, saddle and foot rests are different from the ones that would be generated if the body was rigidly fixed to the vehicle. Therefore, advanced simulation of two wheeled vehicles requires passive biomechanical models of the rider. This paper proposes a novel approach for the study of the passive response of the rider’s body that is based on measurements in the laboratory of the interaction forces between the rider and the vehicle. A special motorcycle mock-up is developed, it is driven by a hydraulic shaker that generates roll excitation with variable frequency. A system of load cells measures the lateral force and torque between the rider and the motorcycle mock-up. The study is carried out in the frequency domain, the passive response of rider’s body is represented by means of three frequency response functions (FRFs): lateral force FRF and torque FRF are the ratios between the lateral force/torque and the roll input; motion FRF is the ratio between the roll motion of the rider’s trunk and the roll input. The biomechanical models of the rider’s body that are developed in this work are able to simulate its response both in terms of interaction forces and motion. These models are composed by some rigid bodies with lumped stiffness and damping parameters in the articulations and in this way they represent a good compromise between accuracy and complexity. The biomechanical parameters of the models are identified by means of a genetic algorithm that aims to minimize a penalty function based on the difference between the three FRFs predicted by the model and the measured FRFs. Results show that a 5 degree of freedom model of the rider is able to represent the measured behavior both in terms of interaction forces and trunk motion.
Dynamic Model of Spherical Roller Bearing
Authors: Ghalamchi Behnam , Sopanen Jussi T. , Mikkola Aki M.
Published: February 2014

Rolling element bearings are essential machine elements in the rotating machinery. Extensive research has been conducted to study the dynamics of ball bearings, while studies related to spherical roller bearings are short-shrifted. On the other hand, the number of industrial applications that utilize spherical roller bearings has been increasing constantly. This is due to self-aligning nature and high-load capacity of spherical roller bearings. Typical applications are paper machines, steel rolling, marine equipment, geared transmissions and modern high power wind turbines. This study introduces a three-degree-of-freedom spherical roller bearing model that is computationally efficient, and it is designed to be used in the transient simulations of complete rotor-bearing systems. In the proposed model, the bearing forces are calculated as a function of contact deformation and bearing geometry parameters according to the non-linear Hertzian contact theory. In the numerical results, the important bearing design parameters such as diametral clearance, number of rollers and osculation are studied. Existence of varying compliance (VC) vibrations and the capability of the proposed model in the transient simulations of rotor-bearing systems are demonstrated. The bearing model is verified by using commercial bearing analysis software. Future improvements and model extension possibilities are also discussed.