bluuebunny/crossref_metadata_2025 huggingface dataset:
The Physics of the Secondary Flows of Viscoelastic Fluids in Straight Tubes
Authors: Siginer Dennis A.
Published: November 2021

A survey of secondary flows of viscoelastic liquids in straight tubes is given including recent work pointing at striking analogies with transversal deformations associated with the simple shearing of solid materials. The importance and implications of secondary flows of viscoelastic fluids in heat transfer enhancement are explored together with the difficulties in detecting weak secondary flows (dilute, weakly viscoelastic solutions) in a laboratory setting. Recent new work by the author and colleagues which explores for the first time the structure of the secondary flow field in the pulsating flow of a constitutively nonlinear simple fluid, whose structure is defined by a series of nested integrals over semi-infinite time domains, in straight tubes of arbitrary cross-sections is summarized. The transversal field arises at the second order of the perturbation of the nonlinear constitutive structure, and is driven by first order terms which define the linearly viscoelastic longitudinal flow in the hierarchy of superposed linear flows stemming from the perturbation of the constitutive structure. Arbitrary conduit contours are obtained through a novel approach to the concept of domain perturbation. Time averaged, mean secondary flow streamline contours are presented for the first time for triangular, square and hexagonal pipes.
Laminar Flow Through a Circular Pipe With Side Inlets
Authors: Umina John A.
Published: November 2021

This study focuses on steady axisymmetric flows of a Newtonian incompressible fluid through circular pipes with side inlets. Circular tubes with a set of holes along their sidewalls are used in a number of medical procedures as straight catheters to transfer fluid into or out of the human body. We argue that all previous work on the analogous problem of flow through porous ducts is inapplicable to the problem of fluid flow through side holes of a straight pipe, due to unrealistic side inlet conditions. In this paper, we present a linear, quasi one-dimensional analysis to predict the flux of fluid that each inlet transfers based on hydraulic resistivities of both the inlets and the duct. We also perform numerical simulations to predict this inlet flux for a more complicated three-dimensional case. Finally, we show that a nonlinear analysis is necessary to determine the resistivities for this complicated flow.
Effect of Tube Diameter on Wall Shear Stress Measurements Using Preston Tubes
Authors: Sutardi  , Ching C. Y.
Published: November 2021

The effect of tube diameter (d) on wall shear stress (τw) measurements using Preston tubes has been investigated in a zero pressure gradient turbulent boundary layer. Five different outside diameter tubes of 1.46, 1.82, 3.23, 4.76 and 5.54 mm, corresponding to (d/δ) of 0.022, 0.027, 0.048, 0.071 and 0.082 were used to measure τw at Reynolds numbers based on momentum thickness (Rθ) of 2800 to 4100. The calibration curves of Patel (1965) and Bechert (1995) are both dependent on the tube diameter. The maximum difference in the τw measurements from the different tubes using Patel’s calibration is about 8%, while Bechert’s calibration gives a maximum difference of approximately 18%. Based on the present measurements, a new Preston tube calibration equation that is less sensitive to the tube diameter is proposed.
Flow Visualization of a Chemically Reacting Boundary Layer
Authors: Crepeau John C. , McIlroy Hugh M.
Published: November 2021

This paper gives results of an experimental study to determine the effect that a surface reaction has on a boundary layer flow. An innovative technique has been developed to visualize the effect a surface reaction has on a flat plate boundary layer flow. A mixture of mineral oil and hexanoic acid flowed at low Reynolds number over a metal plate embedded with a small piece of sodium. The reaction between the hexanoic acid and the sodium metal produced hydrogen bubbles, which rose to the surface. Upstream of the reaction, dye was injected into the laminar flow, and the interaction between the bubbles and the dye was recorded. Results show that bubble entrainment stretch and bend the dye filaments, convect fluid away from the reaction, and create vortices downstream and to the sides of the reaction. These results show that a surface reaction can introduce velocity fluctuations into an otherwise laminar flow. Farther downstream the flow relaminarizes.
A 3D Unsteady Flow Analysis in a Doubly Constricted Tube
Authors: Rathish Kumar B. V. , Yamaguchi T. , Liu H. , Himeno R.
Published: November 2021

Unsteady flow dynamics in a doubly constricted vessel is analyzed by using a time accurate Finite Volume solution of three dimensional incompressible Navier-Stokes equations. Computational experiments are carried out for various values of Reynolds number in order to assess the criticality of multiple mild constrictions in series and also to bring out the subtle 3D features like vortex formation. Studies reveal that pressure drop across a series of mild constrictions can get physiologically critical. Further this pressure drop is found to be sensitive to the spacing between the constrictions and also to the oscillatory nature of the inflow profile.
Peristaltic Pumping
Authors: Tadjfar M. , Yamaguchi T. , Himeno R.
Published: November 2021

Peristaltic pumping in a cylindrical tube is simulated. The unsteady, three-dimensional, incompressible Navier-Stokes equations are solved numerically. A flow solver written for parallel architecture and capable of dealing with moving boundaries and moving grids is used. The solver uses a second-order in time and third-order upwind finite volume method for solving time-accurate incompressible flows utilizing pseudo-compressibility technique. In this study, the flow of an axisymmetric “Wine-glass” shaped, single, peristaltic wave is analyzed. The wall wave, quickly, establishes a pressure wave in the flow which pumps fluid in the tube as it moves down the tube. The pressure wave, established by the contracting geometric wall wave, grows and diffuses into the upstream and downstream direction in time due to the action of viscosity.
Complex Fluid-Structure Interaction in Ink Jet Printer Mechanisms
Authors: Reich Alton J. , Dionne Paul J.
Published: November 2021

Recent advances in the ability to couple fluid and structural analyses have made it possible to simulate the behavior of increasingly complex physical systems. This paper focuses on the simulation of the fluid-structure interaction within a typical ink jet printer. The simulations demonstrate several different methods that may be used to eject a droplet of ink from a reservoir. In each case a membrane at the bottom of the ink reservoir is deformed. The movement of the membrane imparts the momentum necessary for droplet ejection to the fluid. The simulations were performed with a commercial CFD code (CFD-ACE+) that uses a modular simulation approach. This approach allows the tight coupling of the different physical phenomena that contribute to the droplet ejection process.
The Use of the 3D-Viscous Codes in the Analysis of High Speed High Pressure Ratio Centrifugal Impellers
Authors: Mekhail Tarek , Hui Du Zhao , Ping Chen Han , Janson Willem
Published: November 2021

The flow inside a centrifugal impeller has various complex three dimensional phenomena (flow separation, jet-wake structure, shock wave, etc.). In this study, the internal flow field calculation of Samsung, high pressure ratio, high speed, centrifugal impeller with splitter blades is obtained by commercially available CFX-Tascflow code with CFX-Turbogrid for grid generation. The results are compared to that obtained previously by Denton and Dawes codes. The impeller is used in the first stage centrifugal compressor of an industrial gas turbine. The CFX-Tascflow results showed some differences Mach number contours. Also, the calculations are performed for Krain’s backswept impeller and the results are compared to the experimental measurements. Simulation of tip clearance has been done and the results were in a good agreement with the previous experiments.
Enabling the Transition to ECP Braking
Authors: Dougherty Bryan A.
Published: November 2021

This paper addresses the limitations of conventional freight train air brake systems, the stalled adoption of Electronically Controlled Pneumatic (ECP) brakes and a cost-effective industry transition to ECP technology.

There are two types of ECP train braking systems (cable and radio) and three types of electronically controlled freight car brake control valves. This paper describes the different types ECP braking systems and their limitations and provides a clear path to enable a fleet wide railcar transition to ECP braking technology.
Effects of Coupler Height Mismatch on Tank Car Stub Sills
Authors: Prabhakaran Anand , Sharma Vinaya , Peña Jose S.
Published: November 2021

Revenue service tests of tank cars conducted by the Association of American Railroads (AAR) as part of the ‘Freight Equipment Environmental Sampling Tests’ (FEEST) program have measured high coupler vertical loads. It is believed that such high vertical loads can cause significant damage to the structural integrity of tank car stubsills, thereby seriously affecting operational safety. Also, it is suspected that coupler height mismatches are a major source of these vertical forces, and thereby contribute to stubsill failures. The focus of this paper is the study of the effect of coupler height mismatches on stub sill integrity. As part of this study a tank car loaded to 266,200 lb. was instrumented and tested, in static conditions and during impact. The static tests consisted of a series of longitudinal load (squeeze) tests conducted at three different coupler heights, and vertical load tests with forces being applied at the coupler shank. The impact tests consisted of a series of impacts at speeds ranging from 2 mph to 8.5 mph for the following coupler mismatch levels: a) Struck and striking car at the same level, b) Struck car 2″ higher, and c) Struck car 2″ lower. In addition to the testing, finite element models were developed to help in studying additional operating conditions. These models were validated using the test results. The results from the testing indicate that coupler height mismatches have a significant effect on the vertical force levels and the stress levels seen at critical car locations. The stresses in critical areas are generally higher when the struck car is lower. Differences over 50% (compared to when the cars are level) were noted at the head brace, when the struck car was 2″ lower than the hammer car. The tests also established the criticality of vertical forces on the structural integrity of the stubsill. On average, a 50,000 lb. vertical force can generate as much stress as a 680,000 lb. longitudinal force. This work is being funded by the Office of Research & Development of the Federal Railroad Administration (FRA).
Damage Modeling and Detection in Smart Composites
Authors: Chattopadhyay Aditi , Dragomir-Daescu Dan
Published: November 2021

The presence of damage in structures made out of composite and/or piezoelectric materials can cause significant degradation in structural performance. In the present paper, damage indices based on two-dimensional gapped smoothing technique and model strains are developed in order to enhance the accuracy in predicting the location and extent of damage in composite structures. Structural analysis is performed based on a refined higher order theory, which can capture the transverse shear effects in anisotropic laminates. An approach using the developed damage indices and the laminate model of the higher order theory is employed to model and identify delaminations in composite laminates. It is also used in the delamination analysis of composite laminates with piezoelectric actuators. The proposed modal strain based damage indexes are used to perform delamination analysis. Comparison study is performed to illustrate that the reliability and robustness of the new proposed damage indices in locating delaminations in composite and smart composite structures. The effects on modal strain and damage indices due to the presence of surface bounded piezoelectric actuators are also presented and discussed.
Analysis of Fatigue Damage Mechanisms and Residual Properties of Polymer Matrix Composites
Authors: Soutis Costas , Kashtalyan Maria
Published: November 2021

Resin dominated damage modes such as matrix cracking in the off-axis plies and matrix crack-induced local and edge delaminations are common failure mechanisms in composite laminates under tensile or thermal fatigue. Accurate prediction of the laminate stiffness and strength must consider all the above-mentioned damage modes. In the present paper, an approach is developed for the analysis of cross-ply laminates damaged by transverse and longitudinal cracks and transverse and longitudinal delaminations that initiate and grow along these cracks. It is based on the Equivalent Constraint Model (ECM) of the damaged ply and employs an improved 2-D shear lag method to determine the stress field in the cracked and locally delaminated ply. The method is applied to predict residual stiffness properties of cross-ply graphite/epoxy laminates using experimentally observed damage patterns.
Role of Frozen Water on the Fracture Growth of Composite Materials
Authors: Dutta Piyush K.
Published: November 2021

Delamination of composites is a fairly common failure mechanism. Its sensitivity to the interference of environmental parameters e.g. temperature and moisture is generally well known. Accelerated delamination induced by moisture at high temperature, which lowers the Tg (the glass transition temperature of the matrix), has been studied for decades. Also, predictive tests for durability of composite materials suggest boiling of composites as a technique to develop the predictive index for lifecycle prediction (Dewimille and Burnsell, 1983). However, these approaches ignore the dramatic degradation process of composites at subzero temperatures, and are based probably on the misleading but general concept that low temperature improves performance of materials. Of course, at subzero temperatures, there is a drastic increase in strengths (shear and tension), and hygroelasticity, (Ip, Dutta and Hui, 1996), but a sequence of processes conducive to fracture growth are also set in, especially when there are frequent incursions between the sub-zero and above-zero temperatures in moist environment. First, the thermal expansivity mismatch of the constituents induce mechanical stresses as high as 50% of the matrix strength (Lord and Dutta 1988), leading eventually, or under accelerative action of thermal cycling, to thermal cracking (Figure 1) (Dutta and Hui, 1996), which, in turn facilitates moisture penetration into the structure. Second, the liquid phase transport of moisture by capillary flow or microcracks (and to a lesser degree by diffusion) involves both flow and storage of water in microvoids, which lead to further degradation by chemical (e.g. hydrolysis), and physical (e.g. swelling strains) processes in an auto-accelerated manner. And the third, which has been least studied in literature, is the dramatic effect of expanded frozen water on interlaminar or interfacial crack extension at the sub-zero temperature.
Free Vibration of Spinning Stepped Timoshenko Beams Using Finite Element Method
Authors: Wang Z. C. , Cleghorn W. L. , Yu S. D.
Published: November 2021

Free lateral vibration of stepped shafts is investigated in this paper using the Timoshenko beam theory and the finite element method. Beam finite elements having two nodes and 16 degrees of freedom were employed to model flexural vibration of a stepped shaft for a total four field variables — two lateral displacements and two bending angles. Within each uniform segment, the stepped shaft is modeled as a substructure for which a system of equations of motion may be easily formulated using the Galerkin method. The global equations of motion for the entire stepped shaft are subsequently formulated by enforcing the displacement continuity and force equilibrium conditions across the interfaces between two adjacent substructures. The second order governing differential equations for a non self-adjoint dynamic system are then reduced to the equivalent first order differential equations for which eigenvalue problem is formulated and solved using the Matlab® program. Values of natural frequencies are in excellent agreement with those available in the literature. Effects of rotational springs attached to the end of a stepped shaft, used to simulate the non-classical boundary constraints of chuck on a work piece in a typical turning process, are also investigated. The bi-orthogonal conditions for modal vectors, which are useful in chatter analysis during turning processes, are given in this paper.
Visualization of Finite Element Automobile Crash Simulation Using Virtual Reality Technology
Authors: Moraes Ricardo , Nicholson David , Divo Eduardo
Published: November 2021

A prototype system is described for visualization of automotive crash. The system is based on integrating two tools: (a) Finite Element Analysis (FEA) and (b) Virtual Reality Visualization (VRV).

The prototype VRV system, recently developed by DUAL Incorporated of Lake Mary, FL in partnership with the University of Central Florida (UCF), consists of a PC-level graphics workstation, a head mounted display, motion trackers, a multi-degree of freedom mouse, drivers and a software toolkit, all of which have been established at DUAL and UCF.
Modeling and Prediction of Acoustic Resonance for Round Supersonic Jets
Authors: Cary A. W. , Bower W. W. , Cain A. B. , Kershen E. J.
Published: November 2021

A computationally rapid analysis tool has been developed to compute the acoustic resonance of off-design supersonic jets known as “screech”. For the case of round jets, the computational model is described which is based on coupling analytical representations of each of the four components of the resonance: 1) the shear layer instability; 2) the vortex/shock interaction; 3) the upstream-propagating acoustic radiation; and 4) the receptive coupling of scattered acoustic waves and instability waves at the nozzle lip. Comparisons among predicted and measured sound pressure levels and frequencies of the resonance are presented for a range of jet operating conditions.
The Effect of Temperature on the Viability of Deformed Cells
Authors: Takamatsu Hiroshi , Kumagae Norihiko , Rubinsky Boris
Published: November 2021

Recent studies show that during slow freezing of cells, in addition to chemical damage, the cells may be also injured by mechanical damage induced by ice crystal compression. A new experimental procedure is employed to develop a quantitative understanding of cell destruction by deformation with two parallel surfaces. The viability of deformed cells (prostatic carcinoma cells, 17.5 μm in mean diameter) is measured at 0 °C, 23 °C and 37 °C, and six different nominal gap sizes between 32 μm and 3.5 μm. The relation between measured viability and gap size at 0 °C and 23 °C are identical but the viability decreases at 37 °C. This may suggest that deformation damage is not related to the mechanical properties of the lipid membrane but the deformation of the cytoskeleton.
2-D Thermal Dose Optimization in High Intensity Focused Ultrasound Treatments Using the Adjoint Method
Authors: Loulou Tahar , Scott Elaine P.
Published: November 2021

A previously reported numerical technique, which uses adjoint method when optimizing 1D space variation of thermal dose in hyperthermia treatment is extended to the case of 2D problems [1]. Using a 2D transient computational model in the Penne’s bio-heat equation, optimization of thermal treatment during hyperthermia is shown to be effective and accurate. Numerical simulations are carried out with the 2D computational method to retrieve the prescribed thermal dose from the solution of an inverse thermal problem. The non-continuity of the temperature variation of thermal dose around the reference temperature is linearized over a small temperature interval. The adjoint method in conjunction with the conjugate gradient algorithm are employed to perform the optimization of the objective function. The results are obtained in terms of the computed thermal dose and the heat source to be applied. The numerical results, obtained for a simple treatment case show a good agreement between the estimated and desired thermal dose. However, the non-uniqueness of the obtained solution (the control function: heat source to be applied) is still under investigation and supports the need for further fundamental research.
Comparison of Drug Distribution Between Intravitreal Injection and a Controlled–Release Implant in a Rabbit Eye
Authors: Banerjee Rupak K. , Lutz Robert J. , Keyhani Keyvan , Dedrick Robert L. , King Brian , Robinson Michael
Published: November 2021

Due to physiological barriers within the eye, which limit penetration of many drugs from the systemic circulation into the vitreous, the most common method of treating retinal disease is direct intravitreal injection. However, this common procedure may be inappropriate for a wide range of drugs as it may lead to highly variable concentrations potentially causing higher toxicity for tissues inside the eye and limiting therapeutic effect.

A recent procedure is to use surgically implanted drug release device, called implant here, in the vitreous of the eye that allow controlled release of drug over a sustained period of time. For constant release of drug over 15 hours, a substantial reduction in peak drug concentration is predicted near the retina. When compared with the implant, a doubling of drug concentration would be expected for more than 3 hours near the retina for the intravitreal injection.
Experimentally Validated Vibration Fatigue Life Prediction Model for Ball Grid Array Solder Joint
Authors: Wong T. E. , Palmieri F. W. , Kachatorian L. A.
Published: November 2021

A newly developed methodology is used to support test validation of ball grid array (BGA) solder joint vibration fatigue life prediction model. This model is evolved from an empirical formula of universal slopes, which is derived from high-cycle fatigue test data using a curve fitting technique over 29 different materials of metals.

To develop the BGA solder joint vibration fatigue life prediction model, a test vehicles (TV), on which various sizes of BGA daisy-chained packages are soldered, is first designed, fabricated and subjected to random vibration tests with continuously monitoring the solder joint integrity. Based on the measurement results, a destructive physical analysis is then conducted to further verify the failure locations and crack paths of the solder joints. Next, a method to determine the stresses/strains of BGA solder joints resulting from exposure of the TV to random vibration environments is developed. In this method, a 3-D modeling technique is used to simulate the vibration responses of the BGA packages. Linear static and dynamic finite element analyses with MSC/NASTRAN™ computer code, combined with a volume-weighted average technique, are conducted to calculate the effective strains of the solder joints. In the calculation process, several in-house developed Fortran programs, in conjunction with the outputs obtained from MSC/NASTRAN™ static and frequency response analyses, are used to perform the required computations. Finally, a vibration fatigue life model is established with two unknown parameters, which can be determined by correlating the derived solder effective strains to the test data. This test-calibrated model is then recommended to serve as an effective tool to determine the integrity of the BGA solder joints during vibration. Selecting more study cases with various package sizes, solder ball configurations, vibration profiles to further calibrate this model is also recommended. An example of a 313-pin plastic and 304-pin ceramic BGAs is illustrated in the present study.
Thermal Aging Effect on the Ball Shear Strength of Pb-Free Solders on a Ceramic Substrate With Pd/Ag Surface Metallization
Authors: Huang Xing Jia , Lee Shi-Wei Ricky , Tse Wan Sze
Published: November 2021

In the present study, solder balls of two Pb-free solder alloys, 95.5Sn-3.8Ag-0.7Cu and 91.8Sn-3.4Ag-4.8Bi, were reflowed on a ceramic substrate with the surface metallization of Pd/Ag. The specimens were subjected to thermal aging for 250 hours at the temperatures of 85°C, 125°C and 150°C, respectively. For comparison, specimens with 63Sn-37Pb solder were also fabricated and tested. Ball shear tests were performed to evaluate the effect of thermal aging on various solders. In general, the testing results indicated that the shear strength of solder balls decreased gradually with respect to the increase of thermal aging temperature. The shear strength of 95.5Sn-3.8Ag-0.7Cu solder balls was found to be least sensitive to the thermal aging. Besides, it was identified that the predominant failure mode in the ball shear tests was the fracture at the interface between the Pd/Ag metallization and the ceramic substrate.
Free Vibration Analysis for Thin Wire of Modern Wiresaw Between Sliced Wafers in Wafer Manufacturing Processes
Authors: Wei Songbin , Kao Imin
Published: November 2021

In wiresaw manufacturing process where thin wire moving at high speed is pushed onto ingot to produce slices of wafer, the wire is constrained by two wafer walls as it slices into the ingot. In this paper, we investigate the vibration of such wire under the constraints of wafer walls. To address this problem, the model for wire vibration with impact to wafer walls is developed. The equation of motion is discretized using the Galerkin’s method. The principle of impulse and momentum is utilized to solve the impact problem. The results of analysis and simulation indicate that the response under a pointwise sinusoidal excitation is neither periodical nor symmetric with respect to the horizontal axis, due to the excitation from the impact. The wire vibration behavior is affected dramatically by the wafer wall constraints.
Analysis of the Interaction Between Thin-Film Fluid Hydrodynamics and Wire Vibration in Wafer Manufacturing Using Wiresaw
Authors: Zhu Liqun , Bhagavat Milind , Kao Imin
Published: November 2021

In free abrasive wafer slicing process (FAM) using wiresaw, hydrodynamic pressure exerted by the thin slurry film is crucial to the process of cutting and material removal from substrate surface. It affects the process quality by introducing viscous damping effect to the transverse motion of the wire. The pressure distribution in the slurry film is subjected to the interaction of multi-physical phenomena induced in the wire-saw cutting process, including the axially moving wire transverse vibration under high tension (20N to 35N), as well as the hydrodynamic lubrication behavior of the thin slurry film. In this paper, the interaction between thin-film hydrodynamics and wire vibration is modeled using the coupling of basic Reynold’s equation for fluid lubrication and the dynamic equation describing the transverse vibration of the translating wire. The time-variant hydrodynamic pressure field is used to obtain the dynamic damping force exerted on the wire by the thin slurry film. A computational model is constructed and typical parametric studies are conducted based on the simulation results. Numerical scheme of semi-discretization is carried out to simulate the dynamic multi-disciplinary model. Galerkin method of weighted residual is used to carry out the spatial finite element discretization of the governing non-linear partial differential equations of the system with certain boundary conditions. In addition, Newmark method is applied to perform the time integration of the semi-discretized computational model from initial conditions. The direct numerical simulation dynamically yields the profile of the slurry hydrodynamic pressure distribution and the wire vibration response as functions of process parameters, such as the static film thickness of the slurry flow, wire translating speed and wire tension. From the simulation results, it is shown that the presence of the slurry film in the wiresaw process is important in eliminating the undesirable vibration modes and reducing the amplitude of wire vibration.
Stress Analysis of Wiresaw Slicing Piezoelectric Materials
Authors: Yang Fuqian
Published: November 2021

Using linear piezoelectricity theory, the stress and electric potential fields in a half infinite piezoelectric material under anti-plane mechanical loading in wiresaw slicing process has been studied by using appropriate boundary conditions and contact mechanics. Both electric field and electric displacement field are singular at the edges of the contact zone between wire and workpiece. The singularity of electric displacement arises from the electric loading and electro-mechanical interaction. Similar to the conventional contact mechanics, stress singularity occurs due to the contribution of both mechanical and electric loading. At a given mechanical loading, electric loading can either increase or decrease the stress applied to the piezoelectric half space in the slicing process, which depends on the relative direction of the electric field to that of mechanical loading.
Cooling of a PWB With Irregular Populated Chips
Authors: Ding Yiwu , Agonafer Dereje , Short Elliott
Published: November 2021

A simple analysis and series of 3-D CFD simulations are carried out to estimate the temperature for the 208-pin QFP chips on a PWB. The main feature of the problem is the low primary velocity (0.09∼0.36 m/s), which implies that 3D effects, buoyancy force, PWB thermal conductivity and radiation will have a big impact on the temperature profile. This is verified by using commercial CFD simulation codes. The results show CFD tools are ideally suited for these classes of problems.

For the PWB under study, the worst case consists of an inlet air velocity of 0.09 m/s, no conduction in the board, and the board is laid horizontally, for which the buoyancy force is not well utilized). The resulting highest case temperature will be 110∼120C, which is close to the allowable case temperature 125C. Several heat spreader (heat sink) configurations are studied. One of them reduces the highest case temperature below 100C.

However, if the board conductivity is not too low (>0.5 W/mK), or if. the board is laid vertically and air is blown from bottom to top, there is no need for extra heat spreaders.
A Biomechanical Model of Lumbar Spine
Authors: Uppala Subramanya , Gao Robert X. , Cowan Scott , Lee K. Francis
Published: November 2021

The strength and stability of the lumbar spine are determined not only by the bone and muscles, but also by the visco-elastic structures and the interplay between the different components of the spine, such as ligaments, capsules, annulus fibrosis, and articular cartilage. In this paper we present a non-linear three-dimensional Finite Element model of the lumbar spine. Specifically, a three-dimensional FE model of the L4-5 one-motion segment/2 vertebrae was developed. The cortical shell and the cancellous bone of the vertebral body were modeled as 3D isoparametric eight-nodal elements. Finite element models of spinal injuries with fixation devices are also developed. The deformations across the different sections of the spine are observed under the application of axial compression, flexion/extension, and lateral bending. The developed FE models provided input to both the fixture design and experimental studies.
Finite Element Modeling and Mechanical Evaluation of Anteversion in Femur and Femoral Prosthesis
Authors: Arafati Nader , Lazennec Jean Yves , Ohayon Roger , Saillant Gérard
Published: November 2021

We studied the mechanical effects of anteversion of hip prosthesis, using a geometrical model of the femoral bone derived from computed tomography sections.

Linear elastic mechanical behavior was assumed for both cortical and trabecular bone. The results of finite element modeling were studied qualitatively. Stress distribution was evaluated during one-legged stance loading of models with various degrees of anteversion.

The undeniable impact of anteversion raises questions about the interpretation of bone remodeling. Anteversion modifies mechanical stresses, most notably those through the femoral shaft; they are rotated around the vertical axis in the same direction as the anteversion.

Changes in Von Mises stresses were larger than changes in longitudinal stresses, suggesting that anteversion may have a more significant impact on shear stresses, which may cause failure at the prosthesis-cement interface, particularly toward the middle of the femoral shaft.
Optimal Filtering to Improve Performance in Hard Disk Drives: Experimental Results
Authors: Magee David P.
Published: November 2021

Both minimum and nonminimum phase resonances can be found in the model of a hard disk drive actuator. The mechanism has been designed so that most of the resonant frequencies reside above the Nyquist rate of the sampled data control system. These resonances are often not excited until the demands for better system performance require a higher bandwidth controller. But once these resonances are excited, it is important to understand how these resonances alias in the discrete time control system so that effective compensation algorithms can be developed. The purpose of this paper is to demonstrate how nonminimum phase resonances alias in a sampled data control system and to design an optimal filtering algorithm that reduces their effect on the overall system performance. This paper will address these issues and demonstrate how resonances can be overcome which can eventually lead to improved hard disk drive performance.
Input Vector Identification and System Model Construction by Average Mutual Information
Authors: Deignan Paul B. , Meckl Peter H. , Franchek Matthew A. , Jaliwala Salim A. , Zhu George G.
Published: November 2021

A methodology for the intelligent, model-independent selection of an appropriate set of input signals for the system identification of an unknown process is demonstrated. In modeling this process, it is shown that the terms of a simple nonlinear polynomial model may also be determined through the analysis of the average mutual information between inputs and the output. Average mutual information can be thought of as a nonlinear correlation coefficient and can be calculated from input/output data alone. The methodology described here is especially applicable to the development of virtual sensors.
A New Optimization Strategy for Chemical Mechanical Polishing Process
Authors: Wang Gou-Jen , Chen Jau-Liang , Hwang Ju-Yi
Published: November 2021

In this paper, a systematic approach to achieve global optimum CMP process is carried out. In this new approach, orthogonal array technique adopted from the Taguchi method is used for efficient experiment design. The neural network (NN) technique is then applied to model the complex CMP process. Signal to Noise Ratio (S/N) Analysis (ANOVA) technique used in the conventional Taguchi method is also implemented to obtain the local optimum process parameters. Successively, the global optimum parameters are acquired in terms of the trained neural network. In order to increase the CMP throughput, a two-stage optimal strategy is also proposed. Experimental results demonstrate that the two-stage strategy can perform better then the original approach even though the polishing time is reduced by 1/6.
Fuzzy Sliding-Mode Control of a Variable Geometry Manipulator: Experimental Investigation
Authors: Choi J. , de Silva C. W. , Modi V. J. , Misra A. K.
Published: November 2021

This paper focuses a robust and knowledge-based control approach for multi-link robot manipulator systems. Based on the concepts of sliding-mode control and fuzzy logic control (FLC), a fuzzy sliding-mode controller has been developed in previous work. This controller possesses good robustness properties of sliding-mode control and the flexibility and ‘intelligent’ capabilities of knowledge-based control through the use of fuzzy logic. This paper presents experimental studies with fuzzy sliding-mode control as well as conventional sliding-mode control. The results show that the tracking error is guaranteed to converge to a specification in the presence of uncertainties. The performance of the fuzzy sliding-mode controller is found to be somewhat better than that of the conventional sliding-mode controller.
Hybrid Control for Thermoacoustic Instabilities
Authors: Haddad Wassim M. , Chellaboina VijaySekhar , Kablar Nataša A.
Published: November 2021

The complex interactions between acoustics and unsteady combustion is the driving energy mechanism for transmuting self-excited pressure and velocity oscillations in combustion systems. These oscillations, known as thermoacoustic instabilities, can have adverse effects on system performance. In this paper we propose an energy flow resetting control architecture as a means for achieving enhanced energy dissipation in combustion systems. The overall framework is based on a hybrid controller architecture wherein the closed-loop dynamical system is characterized by impulsive differential equations. The proposed framework is used to design high-performance hybrid controllers for suppressing thermoacoustic oscillations in combustion chambers by efficiently dissipating modal system energy.
Stabilization of Nonlinear Systems Using Quasi-Linear Models
Authors: Kiriakidis Kiriakos
Published: November 2021

Unconventional nonlinear models such as nonlinear ARMAX, Takagi-Sugeno fuzzy models, global linearizations, and linear hybrid systems are, at the highest level of abstraction, a sort of quasi-linear models, namely, Polytopic Linear Differential Inclusions (PLDIs). At present, quadratic stability has enabled, mainly via linear matrix inequalities, the analysis and design of a nonlinear system from the vertex matrices of its PLDI model. Proving stability by a globally quadratic Lyapunov function, however, entails conservatism. This paper proposes a less conservative framework by using piecewise-quadratic generalized Lyapunov functions. Further manipulation of the problem within such framework yields a set of bilinear rather than linear matrix inequalities.
A First Principle Engine Model for Up-Front Design
Authors: Ma Zheng-Dong , Perkins N. C. , Hwang Sheng-Jiaw
Published: November 2021

Computer-aided engineering is traditionally employed to evaluate existing engine designs or very mature designs for which detailed design information exists. The analyses are performed to validate and fine tune one design rather than exploring widely differing design concepts. Thus, these analyses are often performed only after a significant commitment has been made to a particular engine design. Computer-aided engineering, however, also has the potential for providing estimates of engine performance at the very onset of the engine design cycle. Such up-front estimates may then be used to lead the design process and to allow conceptually different engine designs to be quickly assessed. For instance, up-front estimates of engine vibration and forces transmitted through engine mounts would support target cascading of engine related noise and vibration requirements at the onset of the design cycle.

The objective of this paper is to review the formulation of a simulation tool to support up-front engine design for noise and vibration. This tool provides estimates of important engine noise and vibration measures based only upon a conceptual engine design. Major components of the engine model include a rigid engine block, a flexible crankshaft with hydrodynamic bearings, torsional and bending modes, and nonlinear (frequency/load dependent) engine mounts. The formulation of this model is detailed herein and sample results are reviewed for one engine design.
Direct Insertion Realization of Nonlinear Modular Models of Engineering Systems Using a Fixed Input-Output Structure
Authors: Byam Brooks P. , Radcliffe Clark J.
Published: November 2021

Computer modeling of engineering systems with a large number of interconnected multi degree of freedom (DOF) subsystems requires flexible modeling tools. Flexible modeling tools with arbitrary input-output structure formulate equations to fit the input-output structure of specific engineering systems at the cost of globally reformulating equations with every model change. Each equation formulation requires performance verification. This can be particularly cumbersome in large models. In previous work Byam and Radcliffe [1] designed modular modeling, a flexible modeling method that eliminates equation reformulation and enhances experimental model performance verification in large models. A fixed input-output structure for all multi DOF modular modeling elements eliminates equation reformulation. The cost is a connector to assemble elements adding complexity to the global model. Modular modeling analysis is a systematic realization of compatible standardized modular elements and connectors. Structural and automotive examples are given.
Alternative Causality Assignment Procedures in Bond Graph Language
Authors: Marquis-Favre Wilfrid , Scavarda Serge
Published: November 2021

This paper proposes to extend this set of causality assignment procedures. The proposed alternative procedures are mainly inspired by formulations developed in the mechanical domain. They enable Lagrange equations, Hamilton equations and Boltzmann-Hamel equations, as well as formulations with the Lagrange multipliers, to be obtained.

After a brief introduction of bond graphs and the causality concept, section 2 presents the three initial procedures (SCAP, LCAP, RCAP) with their modified versions (MSCAP, MLCAP, MRCAP). Section 3 goes through the alternative proposed procedures in detail. Section 4 deals with examples for the application of the alternative procedures proposed. Finally the conclusion shows the important features of such alternative causality assignment procedures on the use of bond graph language.
Using Exact Constraint to Design Flexure Mechanisms
Authors: Blanding Douglass L.
Published: November 2021

This paper presents a qualitative technique, known as “Exact Constraint Machine Design”, for synthesizing and analyzing the design of flexure mechanisms. This technique is presented more fully in the book: Exact Constraint: Machine Design using Kinematic Principles.
Compliant Transmissions: Design Methods and Applications
Authors: Kota Sridhar
Published: November 2021

The paper provides an overview of systematic design procedures and applications of compliant transmissions, which rely on elastic deformation to achieve, intended motion/force transmission function. The mechanisms described in this paper have compliance distributed throughout the structure without employing flexural hinges. Stroke-amplification mechanisms integrated with electrostatic linear actuators and thermal actuators in MEMS domain, and piezoceramic actuators ate illustrated as some of the applications of single-piece compliant transmissions. Additionally the concept of distributed compliance is illustrated with applications to shape-changing structures such as adaptive airfoils.
Dynamics of a Self-Propelling Wheel With Three Eccentric Masses
Authors: Das Tuhin K. , Mukherjee Ranjan
Published: November 2021

This paper investigates the dynamics of a rolling disk with three unbalance masses that can slide along radial spokes equispaced in angular orientation. The objective is to design trajectories for the masses that satisfy physical constraints and enable the disk to accelerate or move with constant velocity. The disk is designed to remain vertically upright and is constrained to move along a straight line. We design trajectories for constant acceleration through detailed analysis using a dynamic model. The analysis considers two separate cases; one where the potential energy of the system is conserved, and the other where it continually varies. Whereas trajectories conserving potential energy are limacons, the variable potential energy trajectories are the most general and allow greater acceleration. Following the strategy for constant acceleration maneuvers, we give a simple approach to tracking an acceleration profile and provide simulation results.
A Model-Based Control of Flexible-Joint Flexible-Link Robots Based on a V-Shape Lyapunov Function
Authors: Lee Ho-Hoon
Published: November 2021

This paper proposes a model-based control of flexible-joint flexible-link robots based on a V-shape Lyapunov function. The proposed control solves the control problems of the joint and link flexibility simultaneously and is not restricted by the degree of the flexibility. The proposed control guarantees the global asymptotic stability for the position and velocity control of the links and joints with all internal signals bounded. The effectiveness of the proposed control has been shown by computer simulation.
Motor Strategies and Perceptual Resolution
Authors: Jones Lynette A.
Published: November 2021

The focus of this research is on the motor strategies used by subjects to perceive force and viscosity and to determine the relation between these strategies and perceptual performance. In the present experiments the forces and movements made by subjects were recorded as they judged the viscosity of an electro-mechanical system by moving their forearm. Computer-controlled viscous forces were presented to subjects and differential thresholds were measured using an adaptive two-alternative forced-choice psychophysical technique. The threshold averaged 19% across subjects and ranged from 0.11 to 0.29. It was found that subjects were highly consistent in the movement and force profiles adopted to perceive viscosity and stiffness, using a limited range of motion in both experimental systems and perturbing the devices with rapidly changing movements and forces. Moreover, there were consistent differences between subjects in the variability of the forces and velocities produced that were associated with superior perceptual performance. These findings attest to the importance of having adequate bandwidth for presenting object properties realistically in a haptic display.
Implications of Haptic Interface Force Saturation on the Haptic Display of Detail
Authors: Kilchenman Marcia , Goldfarb Michael
Published: November 2021

The effects of force magnitude on human perception of size in a stylus-type haptic simulation are presented. Identification by size of ridges with both square and round cross-sections was studied while controlling the maximum level of force displayed by the haptic device. Test results indicate that performance, measured as a percent correct score in the identification experiments, improves as the maximum allowable level of force in the simulation increases. However, all test subjects reached a limit in their perception capabilities before reaching the maximum force output capabilities of the haptic interface hardware used in this research. This characteristic indicates that haptic interface hardware may be able to convey sufficient perceptual information to the user with relatively low levels of force feedback. The data is compiled to aid those who wish to design a haptic interface to meet certain requirements for physical detail within a haptic simulation.
Virtual Three Legged Race Using Networked Locomotion Interfaces
Authors: Noma Haruo , Nakaizumi Fumitaka , Yano Hiroaki , Miyasato Tsutomu , Iwata Hiroo
Published: November 2021

Our focus is on communications while walking together. When we walk together with another person, we sometimes find that our steps are synchronized. In addition, if we stop suddenly or quicken our pace while walking together, we change the subject with the motion as a trigger. In a group tour, moreover, although each member may intend to behave independently, the whole party moves together with no specific communications or rules among the members. In these cases, we suppose that people can perceive their partner’s motions and react to these motions unconsciously. Consciously, they do other complicated tasks such as talk, observe something and so on.