bluuebunny/crossref_metadata_2025 huggingface dataset:
Free Asymmetric Vibrations of Composite Full Circular Cylindrical Shells Stiffened by a Bonded Central Shell Segment
Authors: Yuceoglu U. , O¨zerciyes V.
Published: April 2008

This study is concerned with the “Free Asymmetric Vibrations of Composite Full Circular Cylindrical Shells Stiffened by a Bonded Central Shell Segment.” The base shell is made of an orthotropic “full” circular cylindrical shell reinforced and/or stiffened by an adhesively bonded dissimilar, orthotropic “full” circular cylindrical shell segment. The stiffening shell segment is located at the mid-center of the composite system. The theoretical analysis is based on the “Timoshenko-Mindlin-(and Reissner) Shell Theory” which is a “First Order Shear Deformation Shell Theory (FSDST).” Thus, in both “base (or lower) shell” and in the “upper shell” segment, the transverse shear deformations and the extensional, translational and the rotary moments of inertia are taken into account in the formulation. In the very thin and linearly elastic adhesive layer, the transverse normal and shear stresses are accounted for. The sets of the dynamic equations, stress-resultant-displacement equations for both shells and the in-between adhesive layer are combined and manipulated and are finally reduced into a ”Governing System of the First Order Ordinary Differential Equations” in the “state-vector” form. This system is integrated by the “Modified Transfer Matrix Method (with Chebyshev Polynomials).” Some asymmetric mode shapes and the corresponding natural frequencies showing the effect of the “hard” and the “soft” adhesive cases are presented. Also, the parametric study of the “overlap length” (or the bonded joint length) on the natural frequencies in several modes is considered and plotted.
A Micro-Focusing Stage Applied to Optical Pick-Up Head
Authors: Lee Chia-Wen , Lai Chung-Feng , Fang Weileun
Published: April 2008

Presently, various micromachined actuators have been employed to tune the tracking and focusing of the light beam of optical pick-up head [1–2]. This work demonstrates a novel micro-focusing stage for optical pick-up head application. As in Fig. 1a, the presented micro-focusing stage for optical pick-up head is consisted of four parts: out-of-plane actuator, connecting joint, through hole, and focusing lens plate. The stress-induced beams acted as the self-assembly mechanism to lift up focusing lens plate. In addition, the stress-induced beams also acted as the out-of-plane electrostatic actuator after deposited with an electrode layer. Unlike the design in [3], a through hole underneath the lens plate is allowed in this case for the incident light beam. After properly driving the stress-induced beams, the position of the focusing plate was controlled, as shown in Fig. 1b. The stage had piston motion to adjust the focal point of the lens. Moreover, the stage had tilt motion, so as to ensure that the lens paralleled the disk surface. Thus, the incident laser beam was always orthogonal with the disk surface.
Dynamic Simulation of a Full Vehicle With Magneto-Rheological Damper
Authors: Hou Baolin , Goncalves F. D. , Sandu C. , Ahmadian M.
Published: April 2008

The numerical dynamic simulation of a full vehicle incorporating a magneto-rheological (MR) damper in the primary suspension is studied using the automatic dynamic analysis package ADAMS and the control software SIMULINK. The full vehicle model is built under ADAMS. The interaction between the tire and the road profile is simulated using the ADAMS/TIRE capabilities. The UA tire model is used to model the dynamic characteristics of the tires. A 3-D road profile model is built based on the spatial power spectrum density of a random road profile. This road profile satisfies not only some random distribution law, but also adapts to the numerical simulation requirement of the tire model. In order to model the dynamic characteristics of the primary suspension MR damper, a non-parametric model of an MR damper is proposed which can conveniently be incorporated into the vehicle dynamic model. Two kinds of control policies, a common skyhook and the so-called ‘non-jerk’ skyhook, are adopted to control the current applied to the MR damper. The simulation results imply that either one of the two skyhook control policies can obtain a good compromise between so-called “soft damping” and “hard damping,” and non-jerk skyhook control policy can curb some higher frequency components which are observed in the acceleration response of the chassis. This study also shows that virtual prototype technology is an effective approach for investigating the dynamic behavior of MR dampers for complex systems.
Free Flexural Vibrations of Bonded and Centrally Doubly Stiffened Composite Orthotropic Base Plates or Panels
Authors: Yuceoglu U. , O¨zerciyes V. , C¸il K.
Published: April 2008

The problem of the “Free Flexural Vibrations of Bonded and Centrally Doubly Stiffened Composite Orthotropic Base Plates or Panels” is formulated and investigated. The composite plate or panel system is made up of an orthtropic base plate reinforced or doubly stiffened by the upper and lower stiffening orthotropic plate strips. The stiffening plate strips are at the mid-center and are adhesively bonded to the base plate. The base plate and the stiffening plate strips are considered as dissimilar orthotropic Mindlin plates. Thus, the analysis is based on a “First Order Shear Deformation Plate Theory (FSDPT)” of Mindlin type. In the very thin, linearly elastic adhesive layers, the transverse normal and shear stresses are included. The sets of the dynamic equations and other equations of plates and adhesive layers are finally reduced to a “Governing System of the First Order Ordinary Differential Equations.” Then, this system is integrated by means of the “Modified Transfer Matrix Method (with Interpolation Polynomials and/or Chebyshev Polynomials).” The mode shapes and the associated natural frequencies are calculated and some parametric studies are presented. Also, the influences of the “hard” and the “soft” adhesive layers on the natural frequencies and the mode shapes are shown.
Investigative Study of Local Sherwood Numbers Using Phase Measurement Interferometry
Authors: McGuire David , Dalton Tara M. , Davies Mark R.
Published: April 2008

This paper investigates the relationship between mass and momentum transport. This study of mass transfer is an important design consideration when looking at engineering processes such as evaporation, chemical reactions, corrosion and mixing. Little is know about the relationship. Using the non-intrusive optical technique of Electronic Speckle Pattern Interferometry (ESPI), concentration profile measurements were carried out. A phase-shifting algorithm was also employed to give whole field measurements. Momentum transport in the velocity boundary layer was examined using Particle Image Velocimetry (PIV), which is also a non-intrusive optical technique. The two measurements were taken independently so as to reduce the effect that seed particles may have on the interferometric measurements. A concentration profile was developed above a surface by passing airflow across a flat plate containing a well of ethanol. The rate of mass transfer is obtained from the concentration profile produced as the ethanol vapour diffuses into the airflow. The experiment is set up to measure diffusion from a flat plate and to compare it with the integral solution of the mass transfer equation. Data is presented to show the dependence of the Sherwood number on the Reynolds number.
Poisson Conduction Shape Factors for “Mixed Case” Counter-Current Heat Transfer Applications
Authors: Shrivastava Devashish , Roemer Robert B.
Published: April 2008

The effects of a source term and geometry on vessel-vessel and vessel-tissue Poisson conduction shape factors (VVPCSFs and VTPCSFs) are studied for uniformly heated, finite, non-insulated tissues for the ‘mixed case’ i.e., when the tissue boundary temperature lies in between the two vessel wall temperatures. In addition, two alternative formulations for the VTPCSFs are compared; while both formulations use the vessel wall temperature, one uses the tissue boundary temperature, and the other the area averaged tissue temperature. Results show that the VVPCSFs are only geometry dependent and do not depend on the applied power or the two vessel wall and tissue boundary temperatures. Conversely, the VTPCSFs are strong functions of these variables.
Evaluation of Tissue Convective Energy Balance Equation in Unheated Tissue With a Realistic Vessel Network
Authors: Shirvastava Devashish , Roemer Robert B.
Published: April 2008

This work presents the first numerical validation/sensitivity study of a new bio-heat equation, the tissue convective energy balance equation (TCEBE) in an unheated tissue with a simple but physiologically realistic 3D arterial blood vessel network. The validation of the TCEBE is performed by comparing its predictions of the tissue temperature field with the predictions of a test case in which the 3D conduction energy equation is solved in the tissue and the 1D convective energy equation is solved in the embedded blood vessel network. To perform the sensitivity analysis of the TCEBE, the effects of size of the vessels, and the inlet temperature of arterial blood on the tissue temperature distribution are presented. The relationship between the Pennes’ perfusion related term and the true tissue perfusion has also been investigated. Results show that 1) the TCEBE has a potential to replace the Pennes’ equation as a new, more accurate bio-heat equation, and 2) the Pennes’ perfusion related term is dominated by the heat transfer from larger vessels through their overall heat transfer coefficients, i.e. their ‘UA’ values, and the effect of true tissue perfusion on Pennes’ perfusion related term is negligible.
Repeatability of Establishing Anatomical Coordinate Systems and the Initial Configuration of the Knee
Authors: Bechtold Stephanie J. , Darcy Shon P. , Woo Savio L.-Y. , Debski Richard E.
Published: April 2008

Knee joint kinematics are a useful tool for diagnosing joint injury, assessing the effect of surgical procedures, and prescribing the correct rehabilitation protocols. Joint kinematics are measured using coordinate systems defined by anatomical landmarks. A change in location or orientation of these anatomical coordinate systems has been shown to affect the initial knee configuration and knee kinematics in all six degrees-of-freedom (DOF)[1–4]. Several methods have been utilized by researchers, but no universal methodology for determining the location and orientation of the anatomical coordinate systems has been established. The specific aim of this study was to compare the inter-observer repeatability of two methodologies for establishing anatomical coordinate systems and the initial configuration of the knee. The intra-observer repeatability of both methods was also determined to evaluate the effect of training level on establishing the anatomical coordinate systems.
Flow Formation in Micro-Size Fluid Flow Circuit
Authors: Koizumi Yasuo , Ohtake Hiroyasu , Tabuchi Naoya
Published: April 2008

A 10 × 10 mm micro flow circuit of 1 × 1 mm cross-sectional flow area was manufactured. The circuit filled with water had two tanks with free surface and one dead-end branch with a closed tank. A single bubble was cyclically generated and condensed in the dead-end branch tank so as to create back-and-forth oscillatory flow in the branch pass. A flow state in the flow circuit was visualized by dissolving dye in fluid. The flow state was also recorded with a high speed video camera to derive a flow velocity by utilizing the PTV method. It was confirmed that uni-directional circulation flow was created in the flow circuit without any pumps and valves. Although the created flow was oscillatory, back ward flow was never observed. The time averaged velocity in the flow circuit was 1.5 × 10−2 m/s. This value was five times larger than the peak velocity of the oscillatory flow in the branch pass. The frequency of the oscillatory flow created in the flow circuit was one fifth of that in the branch pass.
Numerical Simulations of Biomass Co-Firing in a Fluidized Bed Combustor
Authors: Sreenivasa R. , Aung K.
Published: April 2008

Fluidized bed technology is an established technology for energy generation due to low operating temperatures, high system efficiency, fuel flexibility, and easier control of pollutants such as NOx and SO. Co-firing of biomass is an attractive option for power generation as it increases use of renewable and waste materials, thereby replacing the conventional coal. This paper investigated biomass co-firing in a fluidized bed using two models. The first model is based on the recent study on the high-volatile solid fuels in a fluidized bed. The first model considered the fluidized bed combustor as three distinct zones: bed zone, splashing zone, and freeboard zone, and took into account material balances in each zone. In addition, sub-models for estimating the pollutants such as NOx and SO were also included in the model. The second model was based on the coal combustion in a fluidized bed. The second model only considered bed and freeboard zones in a fluidized bed. The model for pollutant emissions was also included in the second model. The predictions of both models included char loading in the bed, combustion efficiency, and pollutant emissions. Predictions of both models were compared with the available experimental data to validate the models. The results of the study suggest that current coal models may be appropriate to apply for biomass co-firing in fluidized coal combustors as long as the biomass co-firing is limited to not more than 30% of the total fuel.
Development of a Robust Nonlinear Observer for a Single-Link Flexible Manipulator
Authors: Chalhoub Nabil G. , Kfoury Giscard A.
Published: April 2008

Accurate measurements of all the state variables of a given system are often not available due to the high cost of sensors, the lack of space to mount the transducers or the hostile environment in which the sensors must be located. The purpose of this study is to design a robust sliding mode observer that is capable of accurately estimating the state variables of the system in the presence of disturbances and model uncertainties. It should be emphasized that the proposed observer design can handle state equations expressed in the general form. The performance of the nonlinear observer is assessed herein by examining its capability of predicting the rigid and flexible motions of a compliant beam that is connected to a revolute joint. The simulation results demonstrate the ability of the observer in accurately estimating the state variables of the system in the presence of structured uncertainties and under different initial conditions between the observer and the plant. Moreover, they illustrate the deterioration in the performance of the observer when subjected to unstructured uncertainties of the system. Furthermore, the nonlinear observer was successfully implemented to provide on-line estimates of the state variables for two model-based controllers. The simulation results show minimal deterioration in the closed-loop response of the system stemming from the usage of estimated rather than exact state variables in the computation of the control signals.
Optimization Analysis of Maximum Energy Absorption Properties of Metallic Honeycomb and an Application in Designing Arresting Mechanism for Landing Gear Drop Testing
Authors: Aaron V. , Adibi-Sedeh A. H. , Bahr B.
Published: April 2008

Metallic honeycomb possess excellent kinetic energy absorption properties which can be used as an impact resistance members in structural applications. In order to design energy absorption systems in effective manner using honeycomb material, the various parameters affecting the energy absorption characteristics of the honeycomb should be evaluated. Parameters affecting the honeycomb will be evaluated using analytical methods and finite element analysis. Validated finite element models are used to study the parameters namely honeycomb width, mass of impact and dynamic load factor affecting the energy absorption characteristics of metallic honeycomb. Mathematical models are used to study the half wavelength of the buckling of the honeycomb cell and the factors affecting the dynamic crush strength. Sensitivity analysis is performed using response surface methods to determine the performance effect of the honeycomb cell parameters namely cell size, gauge thickness and inner-edge angle affecting the energy absorption properties. Regression equations are obtained to determine the optimized values of the honeycomb parameters. Guidelines will be provided for the designer to select appropriate honeycomb cell parameters for optimized energy absorption properties. As an application, these honeycombs models are used to design the arresting mechanism for landing gear drop tower for absorbing the impact energy and to protect the structural members and load cells in the event failure of the landing gear during the drop testing. On a whole this research will provide an insight of the energy absorption properties of metallic honeycomb affected by various parameters.
Geometric Design of Symmetric 3-RRS Constrained Parallel Platforms
Authors: Wolbrecht Eric , Su Hai-Jun , Perez Alba , McCarthy J. Michael
Published: April 2008

The paper presents the kinematic synthesis of a symmetric parallel platform supported by three RRS serial chains. The dimensional synthesis of this three degree-of-freedom system is obtained using design equations for each of three RRS chains obtained by requiring that they reach a specified set of task positions. The result is 10 polynomial equations in 10 unknowns, which is solved using polynomial homotopy continuation. An example is provided in which the direction of the first revolute joint (2 parameters) and the z component of the base and platform are specified as well as the two task positions. The system of polynomials has a total degree of 4096 which means that in theory it can have as many solutions. Our example has 70 real solutions that define 70 different symmetric platforms that can reach the specified positions.
Constitutive Formulation of the Mechanical Properties of Synthetic Hydrogels
Authors: Rachev Alexander , ElShazly Tarek , Ku David N.
Published: April 2008

This study attempts to define a universal description of the constitutive formulation of mechanical properties of synthetic hydrogels that can be manufactured as load-bearing structures to replace diseased or damaged soft tissues. While the strain energy density function (SEF) describing the elastic properties of a soft tissue generally depends on two invariants, we propose a SEF that depends on only the first strain invariant. This allows quantifying the SEF from data of a uniaxial extension test. The single invariant SEF was used to predict the mechanical response of a thick-walled tube inflated by an internal pressure. The results show excellent concordance with recorded experimental data, indicating that the mechanical properties of elastic hydrogels can be accurately represented by a SEF that is an exponential function of the first strain invariant with two material constants.
A Modular Modeling Approach for the Design of Reconfigurable Machine Tools
Authors: Ersal Tulga , Stein Jeffrey L. , Louca Loucas S.
Published: April 2008

A new generation of machine tools called Reconfigurable Machine Tools (RMTs) is emerging as a means for industry to be more competitive in a market that experiences frequent changes in demand. New methodologies and tools are necessary for the efficient design of these machine tools. It is the purpose of this paper to present a modular approach for RMT servo axis modeling, which is part of a larger effort to develop an integrated RMT design and control environment. The components of the machine tool are modeled in a modular way, such that the model of any given configuration can be obtained by assembling the corresponding component models together based on the topology of the machine. The component models are built using the bond graph language that enables the straightforward development of the required modular library. These machine tool models can be used for the evaluation, design and control of the RMT servo axes. The approach is demonstrated through examples, and the benefits and drawbacks of this approach are discussed. The results show that the proposed approach is a promising step towards an automated and integrated RMT design environment, and the challenges in order to complete this goal are discussed.
Feedback Control of a Thermomechanical Inplane Microactuator Using Piezoresistive Displacement Sensing
Authors: Messenger Robert K. , McLain Timothy W. , Howell Larry L.
Published: April 2008

Feedback control has proven useful in improving reliability and performance for a variety of systems. However there has been limited success implementing feedback control on surface micromachined MEMS devices. The inherent difficulties in sensing microscale phenomena complicate the development of an economical transducer that can accurately monitor the states of a surface micromachined system. We have demonstrated a simple and effective sensing strategy that uses the piezoresistive property of the polysilicon thin film of which surface micromachined MEMS devices are fabricated. The states of the device are monitored by measuring the change in resistance of flexible members which deflect as the device moves. Measurement of the output displacement of an in-plane thermal actuator is presented as a candidate application. While there still is a noise issue to be dealt with, this approach provides adequate signal strength to implement feedback control using off-chip analog circuitry. Implementation of proportional/integral control on the system is successfully demonstrated.
Validation of Analytical Methods for Parallel Plate Fin Heat Sinks
Authors: Xu Guoping , Jung Henry
Published: April 2008

Several analytical models to predict heat transfer and pressure drop performance for parallel plate fin heat sinks are available in the literature. However, the experimental data to validate these models are very limited especially for high fin density heat sinks. In this paper, a new method is proposed to predict thermal performance in both laminar flow and turbulent flow. This method and other models selected from the literature have been compared to the test data. Experimental investigations were conducted with fully-duct flow for parallel plate fin heat sinks to measure overall thermal resistance and pressure drop. Three heat sinks with different fin materials and fin configurations are tested. We conclude by recommending some of the analytical methods for engineering applications by comparing the test data with predictions.
The Role and Limitations of Modeling and Simulation in Systems Design
Authors: Aughenbaugh Jason M. , Paredis Christiaan J. J.
Published: April 2008

To design today’s complex, multi-disciplinary systems, designers need a design method that allows them to systematically decompose a complex design problem into simpler sub-problems. Systems engineering provides such a framework. In an iterative, hierarchical fashion systems are decomposed into subsystems and requirements are allocated to these subsystems based on estimates of their attributes. In this paper, we investigate the role and limitations of modeling and simulation in this process of system decomposition and requirements flowdown. We first identify different levels of complexity in the estimation of system attributes, ranging from simple aggregation to complex emergent behavior. We also identify the main obstacles to the systems engineering decomposition approach: identifying coupling at the appropriate level of abstraction and characterizing and processing uncertainty. The main contributions of this paper are to identify these short-comings, present the role of modeling and simulation in overcoming these shortcomings, and discuss research directions for addressing these issues and expanding the role of modeling and simulation in the future.
A Parametric Sonic Crystal Modal Analysis Using Finite Element Modeling
Authors: Leung Alan C. , Matic Peter , Delsanto Pier Paolo , Hirsekorn Martin
Published: April 2008

Sonic crystals are typically materials with millimeter scale arrays of acoustic resonators embedded in a matrix material. They provide sound attenuation in acoustic band gaps at frequencies approximately two orders of magnitude lower than those predicted by Bragg’s theory of reflection. There are many potential applications of sonic crystals as filters and frequency selective acoustic damping devices. Performance characteristics of single-cell and double cell based sonic crystal structures were computationally evaluated using finite element methods. In this work, the sonic crystal consisted of cylinder inclusions encased in a soft polymer coating and embedded in a block of epoxy matrix material. Parametric studies were performed to evaluate the effects of material properties of the inclusion, coating and matrix. Mode shapes were determined. A preliminary comparison with Local Interaction Simulation Approach (LISA) is presented. The influence of material property variation, without changing geometric features, on single-cell and double-cell sonic crystal performance is discussed.
Existence, Stability and Bifurcation of Periodic Motions in a Periodically Forced, Piecewise, Linear Oscillator With Impacts
Authors: Luo Albert C. J. , Chen Lidi
Published: April 2008

The nonlinear dynamics of a generalized, piecewise linear oscillator with perfectly plastic impacts is investigated. The generic mappings based on the discontinuous boundaries are constructed. Furthermore, the mapping structures are developed for the analytical prediction of periodic motions of such a system. The stability and bifurcation conditions for specified periodic motions are obtained. The periodic motions and grazing motion are demonstrated. This model is applicable to prediction of periodic motion in nonlinear dynamics of gear transmission systems.
On Uniqueness of Filippov’s Solutions for Non-Smooth Systems Having Multiple Discontinuity Surfaces With Applications to Control Engineering
Authors: Wu Qiong , Zeng Hairong , Sepehri Nariman
Published: April 2008

The analysis of the uniqueness of Filippov’s solutions to non-smooth control systems is important before the solutions can be sought. Such an analysis is extremely challenging when the discontinuity surface is the intersecting discontinuity surfaces. The key step is to study the intersections of the convex sets from Filippov’s inclusions and the sets containing vectors tangent to the discontinuity surfaces. Due to the fact that all the elements of these sets are functions of the states and time and their numerical values can not be obtained before the uniqueness of the solution is analyzed, the determination of such intersections, symbolically, is extremely difficult. In this paper, we propose to firstly transform the control system to a new state space where the discontinuity surfaces can be written in special forms. Secondly, we expand the sets associated with Filippov’s inclusion such that the determinations of the intersections become feasible. Two examples of practical non-smooth control systems are presented to demonstrate the efficacy of the method.
Robotic Microscope to Study the Kinematics of Morphogenetic Movements in Amphibian Embryos
Authors: Brodland G. Wayne , Veldhuis Jim H.
Published: April 2008

A robotic microscope system was developed to collect time-lapse images of live embryos from arbitrary viewing angles. Images were collected from 63 viewing angles and custom software was used to make a three-dimensional reconstruction of the surface of the embryo. The motion of surface points was tracked by image processing, deformation tensors F were calculated from the point correspondences, and decomposition techniques were utilized to extract principal strain magnitudes and directions from F. The highest observed strain rate was 28±5% per hour, along the midline of the neural plate during developmental stage 14, while the greatest contractile strain rate was −35±5% per hour, normal to the embryo midline during stage 15.
Water Movement in Tendon in Response to a Static Tensile Load Using One-Dimensional Magnetic Resonance Imaging
Authors: Helmer Karl G. , Nair Govind , Cannella Marco , Grigg Peter
Published: April 2008

Hydration is an important factor in determining the static and viscoelastic properties of soft tissues. Though the role water plays in determining the material properties of a soft tissue under compression is well known, there is little direct evidence of how water is mobilized in tensile-loaded soft tissues. Here, the redistribution of water in response to static tensile loading was investigated in rabbit Achilles tendons in vitro (N=7). The distribution of water was measured along a radially-oriented line, using a one-dimensional proton-density (M0) map created from fits to T2-weighted magnetic resonance imaging data. Experiments were performed on a 9.4 T/89 mm micro-imager. Proton density was measured before and during application of two cycles of a 7.5N tensile load. Cycle durations were 3 min preload, 42.67 min load on, 21.33 min off, 21.33 min on, and 21.33 min off. The load protocol resulted in a steady increase in proton density in the outside edge (rim) of the tendon during the load periods followed by a decrease during the unloaded periods. Proton-density values did not return to baseline following removal of load, signaling that the rehydration time constant is longer than that for extrusion. Proton-density values in the core or the tendon decreased during loading and were relatively constant during unloading.
Constitutive Modeling of Solute Diffusivity in Hydrated Soft Tissues
Authors: Gu Wei Yong , Yao Hai
Published: April 2008

Based on the experimental results of electrical conductivity and hydraulic permeability, a new constitutive model for relative diffusivity (D/Do) of solutes in gels and tissues was developed. This model could predict the functional relationship between solute diffusivity and tissue deformation. This model could also quantitatively predict the effect of solute size on solute diffusivity in tissues. This study is important for the understanding of nutritional transport in cartilaginous tissues. It is also useful for the prediction of nutrition levels in tissue constructs during growth.
Parametric Identification of Chaotic Base-Excited Double Pendulum Experiment
Authors: Liang Yang , Feeny B. F.
Published: April 2008

An improved parametric identification of chaotic systems was investigated for a double pendulum. From recorded experimental response data, the unstable periodic orbits were extracted and later used in a harmonic balance identification process. By applying digital filtering, digital differentiation and linear regression techniques for optimization, the results were improved. Verification of the related simulation system and linearized system also corroborated the success of the identification algorithm.
Multiphasic Finite Element Analysis of Physical Signals and Solute Transport in the Human Intervertebral Disc
Authors: Yao Hai , Gu Wei Yong
Published: April 2008

A 3D finite element model for charged hydrated soft tissue containing charged/uncharged solutes was developed based on the multi-phasic mechano-electrochemical mixture theory [1–2]. This model was applied to analyze the mechanical, chemical and electrical signals within the human intervertebral disc under mechanical loading. The effects of tissue composition and material property on the physical signals and the transport of fluid, ions and nutrients were investigated. This study is important for understanding disc biomechanics, disc nutrition and disc mechanobiology.
Heat Transfer Enhancement in Nanofluid Suspensions
Authors: Vadasz Peter , Vadasz Johnathan J. , Govender Saneshan
Published: April 2008

The investigation into possible applications of the thermal wave conduction theory to explain the spectacular enhancement of heat flux by a factor of between 1.4 to 2.5 in nanofluid suspensions is presented. While other possible explanations have been proposed to settle this discrepancy they were not investigated into sufficient detail for providing a definite answer and they all apply at the nano-scale level rather than bridging between the nano-scale effects and the macro-system investigated. The possible mechanisms proposed so far are Brownian motion, liquid layering at the liquid/particle interface, ballistic phonon effects, nanoparticle clustering as well as convection and wave effects. Furthermore, most available methods for measuring thermal conductivity assume and make use explicitly of the Fourier mechanism of heat transfer. If somehow the nano-level heat transfer effects impact profoundly on the resulting heat flux at the macro-level, possibly via wave phenomena, the whole concept behind the measurement device might be flawed. The present paper presents a possible way by which the transitions from nano-scale via the micro-scales towards the macro-scale occur, hence bridging the gap from nano devices to macro systems performance.
Teaching Four and Five-Axis CNC Machining
Authors: Zamora David , Danielson Scott , Biekert Russel
Published: April 2008

Traditional metal-based manufacturing processes are being driven to multi-axis machining. Manufacturing time studies have proven that there are significant cycle time reductions using multi-axis CNC machining as compared to multi-fixture CNC machining. Four and five-axis machining requires the use of software to produce both required part geometry and the resulting tool paths. However, while the software and machine tool technology are present, engineers with the appropriate educational background are harder to find. The skills required to design, tool, program, and machine four and five-axis parts are part of few, if any, educational programs. The manufacturing engineering technology program at Arizona State University is actively addressing this shortfall. Educational materials have been developed, tested and employed in classes supporting simultaneous 4-axis machining utilizing a Haas VF2 and HRT210 4th axis rotary table. Similar materials for a Haas VF2 with TR160 5-axis trunnion, capable of simultaneous 5-axis machining, are being beta tested.
Distributed Control to Improve Performance of Thermoelectric Coolers
Authors: Harvey R. D. , Walker D. G. , Frampton K. D.
Published: April 2008

Thermoelectric coolers (TECs) have become potential solutions for chip cooling applications. However, the scope of TEC applicability is limited because of poor efficiency that is largely governed by material properties. This low efficiency causes increased heat production resulting in a very narrow band in which the TEC is effective. Since TECs are cooling units composed of numerous individual cooling elements, or thermocouples, the operating efficiency can be improved by implementing distributed control of the individual couples. Distributed control is a system for allowing each couple to be powered depending on the localized heat load. Distributed control would allow for increased cooling in hot spots while minimizing excess heat generated by the TEC in areas where it is not needed. The preliminary results suggest that this type of control may be feasible, and would result in a significant increase in the TEC effectiveness. The current model considers lateral heat conduction in the chip, as well as variable control of the individual thermocouples proportional to heat load. Results indicate that a 2-fold increase in COP is possible with independently controlled couples compared to a single cooler.
Benchmark Solutions for Computational Aeroacoustics (CAA) Code Validation
Authors: Scott James R.
Published: April 2008

NASA has conducted a series of Computational Aeroacoustics (CAA) Workshops on Benchmark Problems to develop a set of realistic CAA problems that can be used for code validation. In the Third (1999) and Fourth (2003) Workshops, the single airfoil gust response problem, with real geometry effects, was included as one of the benchmark problems. Respondents were asked to calculate the airfoil RMS pressure and far-field acoustic intensity for different airfoil geometries and a wide range of gust frequencies. This paper presents the validated solutions that have been obtained to the benchmark problem, and in addition, compares them with classical flat plate results. It is seen that airfoil geometry has a strong effect on the airfoil unsteady pressure, and a significant effect on the far-field acoustic intensity. Those parts of the benchmark problem that have not yet been adequately solved are identified and presented as a challenge to the CAA research community.
Investigation and Development of Proposed General Pressure Drop and Heat Transfer Correlations for Laminar Flow in a Toroidal Coiled Tube System
Authors: Bowman Anthony J. , Park Hyunjae
Published: April 2008

In this paper, the laminar flow pressure drop and heat transfer correlations published and applied to plain, coiled tube heat exchanger systems are extensively investigated. It was found that most correlations obtained for toroidal geometric systems have been applied to the analysis of helical and spiral tube systems. While toroidal (and helical) coils have a constant radius of curvature about the coil center-point (and center-line), spiral coils have a continuously varying radius of curvature, in which the flow does not reach a typical fully developed flow condition. The centrifugal forces, arising from the curved flow path, contribute to the enhancement of heat transfer (at the cost of additional pressure drop) over straight tube heat exchangers of the same length. In this paper, using published correlations and available experimental test data for pressure drop and heat transfer in toroidal tube systems, the proposed general correlations are developed by using a filtered-mean multiple regression method. The Coiling Influence Factors for the friction factor and heat transfer, CIFf and CIFh, respectively; defined and used in the authors’ previous works [1,2,3] it was found that the deviations between the proposed and published correlations are within about 3% for friction factor and 5–20% for heat transfer, depending on working fluid. In order to assess the validity of applying the generalized correlations developed in this work for toroidal tube systems, onto other curved tube systems, a numerical analysis of toroidal coil systems, using the commercially available CFD package (Fluent 6) has been explicitly performed. A comparison is made between the CFD result for average heat transfer (CIFh) with that predicted by the proposed general correlation for toroidal coils and available experimental data. As an extension of this work, a comparison of curved tube over straight tube heat exchanger effectiveness is made to highlight its use as a design optimization parameter and motivation for additional coiled tube heat exchanger research.
Finite Element Dynamic Response Analysis of the Human Knee Joint
Authors: Pfeiler T. Wayne , Kasra Mehran , Shirazi-Adl Aboulfazi , Cates Harold E.
Published: April 2008

Mechanical factors play an important role in the etiology of knee injuries and diseases such as osteoarthritis (OA). While performing daily, occupational, and sport activities, the joint is subjected to dynamic loads such as vibration and multiple impacts. According to an individual’s age, fitness, and weight, these activities may cause the joint load, stiffness, and damping to reach critical limits initiating or accelerating different knee disorders such as osteoarthritis [Wolfe et al., 1996]. Computational models of the knee have been developed over the past several decades. However, these models leave much to be desired, since they often over-simplify the geometry and material properties of the knee. Several two dimensional models have been created [Gill et al., 1996]. Three-dimensional analytical studies have become more common in recent years, and typically model the tibiofemoral joint [Abdel-Rahman et al., 1993; Blankevoort et al, 1991; Wisman et al., 1980]. These studies typically model only surfaces and neglect the effect of ligaments and menisci/cartilage.
A Two DOF Controller for a Multi-Finger Tactual Display Using a Loop-Shaping Technique
Authors: Israr Ali , Meckl Peter H. , Tan Hong Z.
Published: April 2008

The design and evaluation of a new controller for a multi-finger tactual (kinesthetic and cutaneous) display, the TACTUATOR, is discussed. A crucial performance requirement is that the relative amplitude of spectral components be preserved in terms of perceived intensity as judged by human users. In this article, we present a two degree-of-freedom controller consisting of a feedback controller and a pre-filter, and its digital implementation. The overall system was evaluated with frequency-response function measurements and with human psychophysical experiments. The measurement results confirm that the steady-state frequency response closely follows the design specifications. The psychophysical results indicate a deviation in the model of the human detection threshold curve at frequencies below 30 Hz. Future work will compensate for this deviation by reshaping the pre-filter. Our work demonstrates the validity of designing controllers that take into account not only the electromechanical properties of the hardware, but the sensory characteristics of the human user.
Contribution of Cell Mechanics to Acute Leukemia
Authors: Rosenbluth Michael J. , Lam Wilbur A. , Fletcher Daniel A.
Published: April 2008

Leukostasis is a life-threatening condition that occurs when leukemia cells accumulate in the vasculature of organs such as the brain and lungs. Recent evidence has shown that leukostasis is not simply due to the physical overcrowding of leukemia cells, as previously thought, but may result from specific mechanical properties of the cells and interactions between cells. Using atomic force microscopy (AFM), we obtained direct measurements of two mechanical properties that are likely involved in this condition: (1) stiffness of individual leukemia cells and (2) non-specific adhesion forces between leukemia cells. We found that myeloid leukemia cells were significantly stiffer than lymphoid leukemia cells. Cell-cell adhesion forces of the cell lines were not found to be statistically different. These results may help to explain the clinical observation that leukostasis occurs in myeloid leukemia at lower white blood cell counts than in lymphoid leukemia.
Simulation of the Residual Stresses Generated Due to Cement Polymerization in a THA
Authors: Vasquez Pablo , Nun˜o Natalia
Published: April 2008

A personalized 3D model of the proximal femur is reconstructed from medical CT-scan images. The mechanical properties of the cortical and spongious bones are extracted from the medical images. A finite element model of a personalized total hip arthroplasty is developed to investigate the effect of residual stresses due to cement curing in the load transfer during simplified heel strike.
Controlling Both Thermally Induced Loads in Back-to-Back Angular Contact Spindle Bearings
Authors: Harder John E. , Stein Jeffrey L.
Published: April 2008

Thermally induced bearing loads may cause serious problems for metal cutting spindles when used at high speeds. While proper spindle bearing setup can help minimize this problem, ultimately the plethora of factors that cause the loads to vary cannot be accounted for by the setup. Previous work has shown that bearing load control is possible, but that improved performance may be realized if the temperature environment of each bearing of a back-to-back pair is considered separately. The purpose of this paper is to provide the results of an experimental evaluation of a bearing load control strategy using two thermal actuators. A box spindle was modified and two electric heating tapes were placed around the front pair of back-to-back angular contact ball bearings, one around each bearing. Significant control over the bearing loads can be achieved for the conditions tested including some level of independent control. Unfortunately, there is cross-talk between the heat actuators and the bearing loads, and this interferes with the level of independent load control that can be achieved over the individual bearings. The significance of this issue is discussed and future research outlined. The authors conclude that it is possible to significantly reduce the transient load variation in both bearings with two rather than one actuator; additionally, the second control loop usually improves the steady-state behavior over that achievable with single heater placed over the rear bearing.
Formulation of a Gradient Enhanced Coupled Damage-Plasticity Model
Authors: Voyiadjis George Z. , Dorgan Robert J.
Published: April 2008

An overview of the formulation of a gradient enhanced continuum coupled damage-plasticity model as a constitutive framework to model the nonlocal response of materials is presented. The formulation uses a thermodynamically consistent framework to introduce material length scales through the gradients of the hardening variables. The development of evolution equations for plasticity and damage is treated in a similar mathematical approach and formulation since both address defects such as dislocations for the former and cracks/voids for the later. The gradient enhancements are investigated as powerful tools for modeling observations at the microscale that are not possible to interpret with classical deformation models. By the introduction of higher order gradients, this model is able to predict the size of localized zones based on material constants, as opposed to local models where the loss of ellipticity causes the localized zones to be mesh dependent. Justification for the gradient theory is given by approximating nonlocal theory through a truncated Taylor expansion.
Development and Validation of Online Models With Parameter Estimation for a Building Zone With VAV System
Authors: Wen Jin , Smith Theodore F.
Published: April 2008

The energy consumption by building heating, ventilating, and air conditioning (HVAC) systems has evoked more attention for energy efficient HVAC control and operation. Application of advanced control and operation strategies requires robust online system models. In this research, online models with parameter estimation for a building zone with variable air volume (VAV) system, which is one of the most common HVAC systems, are developed and validated using experimental data. Building zone temperature and VAV entering air flow are modeled based on physical rules and using only the measurements that are commonly available in a commercial building. Different series of validation tests were performed in a real-building test facility to examine the prediction accuracies for system outputs. Using the online system models with parameter estimation, the prediction errors for all the validation tests are less than 0.5°F for temperature outputs, and less than 50 ft3/min for air flow outputs. The online models can be further used for local and supervisory control, as well as fault detection applications.
Reduction of Thermographic Phosphors Data to Heat Rates
Authors: Crim P. R. , Walker D. G. , Allison S. W. , Goedeke S.
Published: April 2008

Thermographic phosphors have emerged as a new technique for measuring heat fluxes, which relies on the temperature dependent intensity decay of thermographic phosphors. However, instead of reducing the intensity data to temperatures, heating rate is estimated. It has been shown that the heating rate can provide significantly better heat flux estimates than temperature measurements. Because the technique is new, little is known about the quality of heating rate estimates. Further, the heating rate estimation depends on the introduction of additional free parameters, which increases the uncertainty of the estimates. The analysis presented here indicates that sample rates must be one to two orders of magnitude greater than the frequency at which the heat flux must be known. Also, the sensitivity of the intensity to higher-order derivatives is small suggesting that derivatives beyond the heating rate are not accessible with single-shot data.