bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibration Confinement in a Flexible Truss-Structure
Authors: Choura Slim A.
Published: July 2023

In this paper, the vibration of a flexible truss-structure, described as a finite element model, is confined and suppressed simultaneously using feedback. The structure is assumed to possess regions that are sensitive to vibrations. The control objective is concerned with the isolation of the sensitive regions from vibrational amplitudes. This necessitates the employment of point force actuators for altering the eigenvalues and mode shapes of the structure. The modified eigenstructure of the system allows the confinement of vibration away from the sensitive regions. In order to avoid build-up of vibrational amplitudes during the confinement process, the proposed feedback contains a mechanism for vibration suppression. In addition, the proposed control strategy demonstrates that the vibrational amplitudes associated with the sensitive regions are brought faster to rest as opposed to those associated with the remaining regions of the structure. We show that the confinement-suppression of structural vibration is possible with a reduced amount of actuators whose number is less or equal to the dimension of the structure model.
ℋ∞ Controller Design for Wing/Store Flutter Suppression
Authors: Gade Prasad V. N. , Inman Daniel J.
Published: July 2023

In this paper an ℋ∞ control algorithm is applied to design a feedback system for active wing/store flutter suppression. A two degree-of-freedom model of a typical section of an airfoil with an external store in incompressible flow is used for analysis. A state space representation is obtained by using a second order rational approximation of the complex Theodorsen function. The active suppression concept is based on the classical decoupler pylon technique that involves the use of passive soft spring-damper elements to decouple the wing torsion mode from the store pitch inertia effects. The current approach proposes to use a piezo wafer strut as an active device to desensitize the wing from store pitch effects and to eventually aid in increasing the flutter speed. Due to some modeling simplifications made in the analysis, a controller design is attempted that yields a closed-loop system that is robust in the face of unstructured uncertainties without sacrificing the nominal performance. A mixed-sensitivity problem in ℋ∞ control theory is solved where the issues of robust stability and performance measures are explicitly handled.
Boundary Control of a Flexible Link Electrically Driven Gantry Robot
Authors: Baicu Catalin F. , Rahn Christopher D. , Dawson Darren M.
Published: July 2023

Gantry robots are used for precision manufacturing and material handling in the electronics, nuclear, and automotive industries. Light flexible links require less power but may vibrate excessively. In this paper, an implementable boundary controller is developed to damp out undesirable vibrations in a flexible link gantry robot driven by a brushed DC motor. Hamilton’s principle produces the governing equations of motion and boundary conditions for the flexible link. The electrical subsystem dynamics for a permanent magnet brushed DC motor couple with the link dynamics to form a hybrid ODE-PDE system. Through an embedded desired current control law, an integrator backstepping controller generates the desired control force on the mechanical subsystem. A velocity observer estimates the gantry velocity eliminating one feedback sensor. Numerical simulations using a Galerkin discretized model demonstrate the improved vibration damping characteristics provided by the backstepping boundary control law. Experimental results confirm the theoretical predictions, showing twenty times faster transient decay than PD control with backstepping boundary control.
Vibration Analysis of Slow Speed Machines
Authors: Hussain Mirza S.
Published: July 2023

This paper describes the hardware and data analysis techniques required to diagnose problems in slow speed machines, down to 1.8 RPM. Transducer selection, data collection and the physics of the applied technology are also discussed. Technology to facilitate defect identification, location, size and severity are included. Actual case histories from on-line operating machines are used as examples of each problem. The combination of the frequency spectra and time signal are used for defect identification, and the economics of accurate diagnosis are discussed.
The Application of Optimal Pole Placement Technique in Structural Control
Authors: Chang Chih-Chen , Yu Lung-On
Published: July 2023

An optimal pole placement technique is proposed for the vibration control of a structure modeled as a single-degree-of-freedom (SDOF) system subjected to a white noise ground excitation. The objective of the proposed technique is to shift the closed-loop poles into a prescribed region in the complex plane using the smallest amount of control force variance. The Kuhn-Tucker necessary conditions and second order necessity and sufficiency theorem are used to solve for the control gain and the corresponding optimal pole locations in the prescribed region. With the use of independent modal space control (IMSC) theory, this algorithm is further applied to a single-degree-of-freedom system equipped with an active mass driver (AMD). Numerical results show that the algorithm is efficient and can be used to design the AMD for seismic vibration control of tall building.
Generating Command Inputs to Eliminate Residual Vibration via Direct Optimization and Quadratic Programming Techniques
Authors: Pai M. C. , Sinha A.
Published: July 2023

This paper deals with the construction of optimal command inputs to eliminate residual vibration in a flexible structure with single and multiple modes as well. First, the time-optimal command inputs are generated by direct parametric optimization with Lagrangian multipliers. Next, the command input is generated in the form of a sequence of step commands via the method of quadratic programming in which the sum of squares of step commands is minimized. The results from numerical simulations are presented.
Analytical and Experimental Analysis of a Neural-Based Hybrid Vibration Control for Cable-Stayed Bridges
Authors: Shoureshi Rahmat A. , Bell Mark
Published: July 2023

Intelligent civil engineering structures which posses the capability to resist catastrophic seismic activities and high load degradation are of great interest to the scientific community and to the population at large. This research focuses on vibration reduction in large civil engineering structures using intelligent control techniques and multiple low power actuation devices. Electromagnetic shakers and hydromechanical adaptive filters are utilized as actuation devices. A complex, nonlinear civil engineering structure is considered, mathematically modeled, analyzed, and retrofitted with these actuators for experimental purposes.. A 1/150 scale model of the existing cable-stayed bridge was constructed from aluminum, steel, high tensile strength piano wire, and guitar machine heads (to facilitate cable tensioning) and is mounted on a rectangular steel base. The prototype has a standard cable-stayed bridge design with dual A-frame towers and a fan-type cable arrangement. It has an overall length of 10.5 feet and a tower height of approximately 1.5 feet. It is the goal of this paper to present intelligent control schemes that utilize a fixed controller design for disturbance rejection and uses intelligent adaptive controller to handle small plant perturbations. An adaptive control strategy that encompasses vibration reduction, system identification, hybrid actuation (i.e. the use of active, semi-active, and passive actuators in a single control system), and combined feedforward / feedback control is sought. Intelligent methods of system identification and disturbance prediction are also incorporated. Experimental results obtained from the experimental prototype are presented.
Design Optimisation of a Controllable Vibration Damper for Vehicle Suspension Applications
Authors: Peel D. J. , Stanway R. , Bullough W. A.
Published: July 2023

In this paper the authors consider the problem of optimising the design of a magneto-rheological (MR) damper for controlling the lateral vibrations of a modern rail vehicle. It is shown how, using generalised test data, the primary control variable (i.e. the applied magnetic field) can be related to the desired force-velocity envelope of the MR damper. Optimisation of the damper design is then considered, taking account of the damper dimensions and available space envelope, the dynamics (due to compressibility and inertia) of the MR fluid and the configuration of the magnetic circuit.

Using data from a commercially available MR fluid, it is shown how a controllable damper can be designed to improve upon the specification for a conventional lateral railcar damper. With zero applied magnetic field the MR damper is shown to be capable of providing a fail-safe minimum value of damping. Increasing the magnetic field provides a maximum equivalent damping level in excess of that available from a conventional hydraulic damper. Over the frequency range from 1 to 10 Hz it is suggested that dynamic effects would not cause significant degradation of performance. Furthermore, for the MR fluid considered, the electrical power consumption would be unlikely to exceed 100 watts.
A Linear Theory of Three-Layer Damped Sandwich Shell Vibrations
Authors: Hu Yuh-Chung , Huang Shyh-Chin
Published: July 2023

Generic differential equations of motion for a three-layer sandwich shell with viscoelastic core are derived. The Hamilton’s principle and Donnell-Mushtari-Vlasov simplification are employed in the derivation. The differential equations, unlike the existing models with five displacements, contain only three displacements, that are one transverse displacement and two in-plane displacements of the host structure. The proposed theory is generic and can be specialized to account for many other commonly occurring geometry, such as spheres, cylinders, plates, cones, ..., etc. The theory can be directly applied to the studies of shells / plates with constrained damping (CLD) layer. The theory can also be degenerated into one single layer or two-layer structures. Specialization of the generic theory to cylindrical shell is focused and an example is demonstrated in this paper. The results of one single layer shell agreed well with the classical shell theory. Two-layer shell models proved to be accurate and can be used for the studies of active vibration control and smart material developments.
Design Impact of Piezoelectric Actuator Nonlinearities
Authors: Main John A. , Garcia Ephrahim
Published: July 2023

This paper presents data supporting the need for including the nonlinear effects inherent in voltage control of piezoelectric stack actuators in order to generate accurate system models. The describing function approach was used in this investigation as an example. While the use of the describing functions does improve overall accuracy of the system model, it is demonstrated that the extreme sensitivity of the describing functions to amplitude at low actuator displacements still compromises the accuracy of models of systems that include voltage-controlled piezoelectric actuators.

It is also demonstrated that using charge-feedback control with the piezoelectric actuators makes the need for nonlinear model elements less pressing since the charge control describing functions are much nearer unity than their voltage control counterparts. The charge control describing functions are also less amplitude dependent, so estimates of system performance can be made with greater confidence.
Spatially Distributed Opto-Mechanical Shell Actuators: Opto-Thermoelectromechanics and Control
Authors: Tzou H. S. , Liu B.
Published: July 2023

Non-contact light-activated distributed opto-mechanical actuators represent a new class of distributed actuator which can induce distributed actuation without hard-wire connections. Active distributed control of flexible shells using distributed opto-mechanical shell actuators are investigated in this paper. A generic shell actuation theory is proposed and the governing opto-thermoelectro-mechancial equations of circular cylindrical shells are derived. The systems equations reveal the couplings among elasticity, photodeformation, pyroelectricity, and thermoelasticity. Optimization procedures for sensor/actuator placements to ensure the maximal observability and controllability of selected natural modes are proposed. Application is demonstrated and detailed control effectiveness is investigated. Numerical simulations suggest that the distributed optical actuators are effective for controlling low-frequency modes. Sensor/actuator placements and actuator sizes also dominate the control effectiveness of selected natural modes. Time history analyses suggest the Lyapunov control is more effective than the proportional feedback control.
Control of Semicircular Shells With Thermal Shock and Mechanical Excitations
Authors: Ye R. , Tzou H. S. , Tani J.
Published: July 2023

Shell-type components and structures are very common in many mechanical and structural systems, e.g., nozzles, pressure vessels, storage tanks, rockets, antenna dishes, etc. Modeling and analysis of adaptive piezothermoelastic shell laminates represents a high level of sophistication and complexity. Accordingly, a numerical method is developed to investigate the complicated temperature, mechanical, and control interactions of piezothermoelastic shell composites in this study. Constitutive equations, governing equations, and boundary conditions of a generic piezothermoelastic continuum are defined first. Strain-displacement relations, electric field-potential relations, thermal gradient-temperature relations of laminated shell composites are then defined. A new piezothermoelastic composite triangular shell finite element is formulated and developed. Matrix equations of the piezothermoelastic shell laminate are derived, in which mechanical, temperature, and electric force vectors are also defined. The electric force vector is used in active control of the shell laminates. Finite element solutions of a piezoelectric laminated composite plate are compared with experimental data and numerical solutions first. Distributed control of a piezoelectric laminated semicircular shell subjected to mechanical and temperature (thermal shock) excitations is investigated and control effectiveness evaluated.
On the Relationship Between Active and Passive Mode Localization
Authors: Yigit Ahmet S. , Choura Slim A.
Published: July 2023

Recently, some researchers proposed what is termed as “active mode localization” where all or some of the mode shapes are altered by feedback in such a way that the modes are spatially localized. The resulting closed loop behavior is similar, at least qualitatively, to the phenomenon known as “Anderson localization” or normal mode localization which occurs due to irregularities (disorders) in periodic structures. This study is an attempt to find the relationships between active and passive mode localization. It is demonstrated that similar results can be obtained by either a passive design which exhibits normal mode localization or by an active controller which is obtained by employing some of the recently proposed design methods of active mode localization. It is anticipated that the ideas proposed in this study will be useful in developing systematic methods for integrated structure/control designs.
Computation of Aerodynamic Noise Emitted From a Door Mirror of a Passenger Car and its Synthesis
Authors: Himeno Ryutaro , Fukushima Tatsuya , Ono Kenji
Published: July 2023

The aerodynamic noise caused by an outside door mirror of a passenger car was calculated and synthesized. Flows around the car including the mirror were computed using a finite-difference method and an overlapping grid technique. Sound pressure of the aerodynamic noise in far field from the car was computed with Curie’s formula using unsteady pressure distribution on the mirror which is numerically solved from the incompressible Navier-Stokes equations. The sound is then synthesized for engineers to evaluate. We investigate the relation between noise sources and the flow field, and find that the strong noise sources are distributed along sepalation lines. This means it possible to reduce the noise if we can avoid separation or fix sepalation lines. Considering it, we modified the mirror shape and succeeded to reduce the aerodynamic noise.
CFD Applications of Automotive Heat Exchangers
Authors: Halt David W. , Allan Valerie J. , Fish Garry R.
Published: July 2023

Computational Fluid Dynamics (CFD) results are shown in comparison to test data for a variety of louvered and lanced offset fin configurations commonly used in automotive heat exchangers. An intercooler heat exchanger used with turbocharger systems is also presented. A grid sensitivity study is performed which shows that grid converged solutions for 2D fin calculations can be computed in 16 minutes of HP C110 CPU time with reasonable comparison to test data. Temperature contours and surface heat flux plots show details of the flowfield and indicate areas where heat transfer is inhibited. This CFD procedure can be used to investigate heat transfer issues in other fin designs.
A Primitive Variable Finite-Volume Method for Incompressible Viscous Magnetohydrodynamic Flows
Authors: Agarwal Ramesh K.
Published: July 2023

A recently developed numerical method is employed for computing the numerical solutions of the incompressible Navier-Stokes equations in the presence of a magnetic field. The method is based on the pressure correction approach, but employs a regular grid finite-volume variable arrangement instead of the usual staggered grid arrangement. The pressure equation is derived such that effects which promote the well-known checkerboard instability are not present. A relevant compatibility constraint on pressure is satisfied by Neumann boundary conditions obtained using a vector identity. The transport equations for the magnetic field with solenoidal condition are solved with a similar approach. The unified computational framework is thus developed for the solution of incompressible viscous magnetohydrodynamic flows. Implemented in a second-order-accurate finite-volume code, the algorithm is used to compute the magnetohydrodynamic flow in a pipe. Numerical solution is compared with existing analytical and computational results for various Hartmann numbers.
Elements of an Approach to the Assessment of Systematic Uncertainty in Transient Measurements
Authors: Maciejewski Paul K.
Published: July 2023

Although there has been an increasing interest in experimental research investigating time-dependent fluid phenomena, accepted methods for assessing and reporting measurement uncertainty, i.e., those contained in ANSI/ASME PTC 19.1 (1985), are restricted to time-independent measured variables. Complementing the work of Maciejewski (1996), which presents a method for assessing the random component of uncertainty in transient measurements, this paper presents a method for assessing the systematic component of uncertainty in transient measurements.
Inflectional Profile Boundary Layer Interaction With a Surface Mounted Circular Cylinder
Authors: Colton Mark B. , Decker William , Klewicki Joseph
Published: July 2023

The interaction between an inflectional boundary layer and a surface-mounted circular cylinder was investigated. A cylinder of height H and diameter d was placed downstream from a splitter plate placed at a height h above the floor of the wind tunnel test section, where h/H was 0.25. Velocity profiles were obtained for cases both with and without the plate. These profiles were examined for momentum content. Surface streaking and smoke injection visualizations were performed, indicating the presence of a horseshoe vortex around the base of the cylinder. Additionally, a second vortex of opposite sign vorticity was found upstream of and above the principal vortex. The results suggest that vortex roll-up in front of a bluff-body may have greater dependence on the inflow vorticity distribution than boundary layer separation phenomena.
A Two-Dimensional Demonstration Smoke Tunnel
Authors: Vaughn David N.
Published: July 2023

This project was the design and construction of a two-dimensional smoke tunnel, for use in the teaching of fluid mechanics courses as well as use in laboratory experimentation. Also part of the project was construction of the smoke generation system, inserting smoke into the flow such that flow characteristics could be observed. Finally, models for use with the tunnel were constructed.
Populating Product Data for Engineering Analysis With Applications to Printed Wiring Assemblies
Authors: Tamburini Diego R. , Peak Russell S. , Fulton Robert E.
Published: July 2023

The engineering data for products such as Printed Wiring Assemblies (PWAs) is a complex aggregation of heterogeneous information generated by a variety of design tools. At certain stages of the product development cycle this information is used to perform engineering analyses in order to validate the design against several criteria.

This paper addresses the problem of populating product data from several heterogeneous sources in order to support the informational needs of given engineering analyses. This is usually a tedious and error-prone process, which involves accessing the data — often manually — from different repositories. stored in different formats and in different locations. After the data is retrieved, it must be integrated in a way that is meaningful to the analysis models employed. This integration is unique in that much of the data representing the design of the complete product is not used at all in the analysis, while the data that is used has to undergo significant transformation and/or idealization before being fed into the analysis models.

This work proposes an object-oriented architecture to automate the data retrieval and population process. It generates a semantically meaningful set of data from which the analysis applications can extract the information they need more easily. The emerging Standard for the Exchange of Product Model Data (STEP) provides the neutral mechanisms needed by this architecture for describing and exchanging product data. The design and analysis of Printed Wiring Assemblies was chosen to test the concepts developed in this work. In this example, the goal is to assemble PWA product data created by several E/MCAD tools into a single integrated schema that supports the informational needs of specific thermomechanical analyses.
Novel Epoxy Compositions for Microelectronic Packaging Applications
Authors: Sambasivam Mahesh , Ghoshal Ram , Mukerji Proshanto
Published: July 2023

Using proprietary epoxies, new formulations have been developed for use in microelectronic packaging applications. The key features of these formulations are short cure cycle, long term stability at 25° C, very low cure volatile, low moisture absorption, low coefficient of thermal expansion (CTE), excellent adhesion to various substrates. The CTE does not change appreciably with temperature between 0–200°C. This unique behavior is attributed to the interpenetrating network-like (IPN) structure of the base resins in the cured state. Further evidence of the IPN structure is the broad loss modulus and tan 6, observed between −150°C and −150°C, in dynamic mechanical tests. The extensive curing reaction in these catalyst-cured systems results in a highly crosslinked polymer network with good moisture resistance (< 0.2°o after 14 days in 85°C/85% RH) and thermal stability (< 0.3 wt % at 300°C of the cured material). Under 85/85 conditions, no appreciable changes in modulus was observed. Extent of cure studies in a dynamic scanning calorimeter (DSC) show a complete cure with no postcure requirements. Cure cycles for these formulations range from 1 hour at 140°C to about 1 minute @170°C. Currently, cure stresses, fracture toughness (bulk and interfacial), and various reliability tests are being performed to characterize the underfill, glob top encapsulants, and die-attach adhesives.
A Study of Countermeasures for Upper Interior Head Impact
Authors: Deb Anindya , Calso Stephen M. , Saha Nripen K.
Published: July 2023

Impact-resistant trim covers on vehicle pillars can aid in reducing HIC(d) (Head Injury Criterion, dummy) during upper interior headform impact. Reductions in HIC(d) also can be aided by an air-gap (i.e. packaging space) between trim and a typical pillar inner panel usually made of steel. For a given packaging space, further lowering of HIC(d) is possible using additional countermeasures such as crushable foam and integrally molded trim ribs which are discussed in this paper. The potential effectiveness of foams of different strengths and integrated ribs for trim is assessed via nonlinear finite element modeling and transient dynamic analysis using a commercial package (RADIOSS). Some comparisons between analysis and test results are also presented.
Laser-Induced Desorption and Ablation From Calcite by Visible and Mid-Infrared Lasers
Authors: Park Hee K. , Haglund Richard F.
Published: July 2023

We have compared desorption and ablation of calcite (CaCO3) when irradiated by the second harmonic of a Nd:YAG laser — which can excite optically active defects — and by a tunable infrared free-electron laser (FEL) (wavelength range λ = 2.5 – 8 μm) which can excite vibrational modes of the calcite without exciting defects by electronic transitions. Scanning electron microscopy (SEM) was applied to study the topography of the laser irradiated spot and plume emission spectroscopy was used to characterize plasma plumes. The dynamics of plume formation was investigated by probe beam transmission measurements. Ablation by visible laser light causes cracks a few mm long due to the excitation of defects inside the material and the accompanying mechanical stress on the crystal. On the other hand, the FEL-irradiated spots exhibited well-defined holes with carbonized walls and scattered droplets in the ablation crater, clear evidence of melting.
Influence of Joule Heating on EDM Processes of High-Electric-Resistivity Materials
Authors: Saeki Takefumi , Kunieda Masanori , Ueki Masanori , Satoh Yutaka
Published: July 2023

We investigate the removal mechanism of high-electric-resistivity materials in electrical discharge machining (EDM) processes by calculation of the workpiece temperature taking the Joule heating in the workpiece into account. The distribution of Joule heating inside the workpiece is calculated from the calculated electric potential distribution. Then considering both the heat flux from the arc column and the Joule heating, the time-dependent workpiece temperature is computed using the finite-difference method. From the computed temperature distribution it is found that the Joule heating causes a much greater temperature rise around the discharge spot in the machining of high-electric-resistivity materials than in the machining of metallic materials. This indicates that the removal of high-electric-resistivity materials in a single discharge is greater than that of metallic materials. However, it is found that a longer pulse interval is necessary to deionize the arc plasma and recover the insulation of the gap after each discharge, which results in a lower material removal rate in a series of pulse discharges.
Nucleation in Thin Film Processing
Authors: Hijikata Kunio , Miyazaki Koji , Inoue Takayoshi , Nakabeppu Osamu
Published: July 2023

In this study, the stability of a very thin film at the initial stage of deposition was investigated using perturbation theory. It is assumed that the critical wave length of perturbation on a continuous thin film corresponds to the nuclei diameter and we also propose that the surface tension of a thin film changes with the film thickness. With these assumptions, it can be shown that the nucleus diameter grows linearly with deposition time. It is interesting to note that the resulting equation is similar to the well-known contact angle equation. To confirm the result of the analysis, a vacuum deposition experiment was conducted. Copper nuclei on the substrate were observed using a transmission electron microscope (TEM) and diameters of island nuclei were measured. The results clearly show that the effective nuclei diameter grows linearly with deposition time. The good agreement between analysis and the experiment suggests the validity of this analysis.
A Metal-Droplet Deformation and Solidification Model With Substrate Remelting
Authors: Rangel R. H. , Bian X.
Published: July 2023

Metal droplet deposition is an important process with several applications in manufacturing. Some of these applications are encountered in spray and plasma-spray deposition and in micro-casting and net-shape manufacturing. The present work describes a model of droplet deformation and solidification which includes a solution of the mechanical energy equation containing kinetic and potential energy as well as viscous dissipation. In addition, the transient, convective-diffusive energy equation including viscous dissipation is solved in the deforming liquid phase by means of finite differences after appropriate coordinate transformations. The solid-phase transient energy equation is also solved in a transformed domain and the liquid and solid solutions are coupled to predict the actual growth of the solidification front. Because the solid energy equation is solved in the complete domain, which includes the substrate, it is possible to predict the behavior when remelting of the substrate occurs. Parametric studies are presented for a variety of relevant processing parameters.
Analysis of Friction-Induced Self-Excited Vibration of Contact Recording Head Slider
Authors: Ono Kyosuke , Suzuki Atsushi
Published: July 2023

This paper presents a theoretical analysis of the friction-induced self-excited vibration of a contact head slider that is one of the head design candidates for future high density recording disk storage. In order to understand the fundamental destabilizing mechanism of the contact slider, the slider-suspension system is modeled as a two-degree-of-freedom (DOF) system. The instability of this system is caused by the asymmetry of the stiffness matrix due to the friction force. The unstable region of this system is examined in terms of the normal and angular natural frequencies, frictional coefficient, slider mass center position and the contact and suspension stiffnesses. The destabilizing mechanism of friction force is made clear by illustrating the mode shape of the complex number. From this model, it is found that the system always becomes stable if the center of mass of the slider is located ahead of the torsional center of slider suspension.
On the Whirl Dynamics of Hydrodynamic Bearing Spindle in Information Storage Systems
Authors: Zang Yan , Hatch Michael R.
Published: July 2023

Hydrodynamic bearing (HDB) spindles currently being developed for information storage systems such as hard disk drives (HDDs) typically consist of two journal bearings with herringbone grooves. In this work, translational and conical motions of lightly loaded herringbone groove journal bearings are analyzed. For translational motion, the full eigenvalue solution for a typical HDB in a small form factor HDD may be simplified using scaling analysis. Perturbation equations for the stiffness and damping coefficients are derived from the Reynolds equation and solved for the lightly loaded herringbone groove bearing. The resulting analysis shows that the translational motion consists of a forward whirl mode and a backward whirl mode. The whirl frequencies of the two modes have the same magnitude but opposite sign. In addition, a simplified analysis shows that for a no-load herringbone groove journal bearing the in-line stiffness is not trivial while the cross coupling damping vanishes. On the other hand, for the conical mode eigenvalues, the same scaling analysis only applies when the bearing span is large. For typical HDB in HDDs, the conical whirl frequencies depend strongly on bearing and rotor geometries. Numerical calculations were carried out to demonstrate the validity and limitation of the theoretical analysis.
Flow Past Large Obstructions Between Corotating Disks in Fixed Cylindrical Enclosures
Authors: Suzuki Hiroshi , Humphrey Joseph A. C.
Published: July 2023

Numerical calculations have been performed for isothermal, laminar, three-dimensional flow past one or two fixed obstructions radially aligned and symmetrically located between a pair of disks corotating in a fixed cylindrical enclosure. The single-obstruction cases respectively model the influence on the flow of (a) a magnetic head arm support and (b) an air lock. The dual-obstruction cases model the simultaneous presence of these two objects. The air lock produces an interdisk cross-stream plane blockage of 62% while the two head arm supports produce blockages of 31% and 62%, respectively. For the cases with the air lock and arm support simultaneously present, the circumferential angle between them is fixed to 40° or 80°. Velocity, pressure, shear stress and the disk torque coefficient are predicted mostly for a Reynolds number (Re = Ω R22/v) corresponding to 10,000, approximately, where R2, Ω, and v are the disk radius, the disk angular velocity in rad/s, and the kinematic viscosity of air at 300 K, respectively. The calculations show that a large blockage significantly alters the interdisk flow characteristics by markedly raising the pressure ahead of an obstruction and accelerating the flow through the empty space around it. This induces a detached reversed flow region ahead of the obstruction quite distinct from that in its wake. The disk surface pressure distributions point to a potential source of dynamical instability in rotating disk flows with obstructions. The variations of the disk torque coefficient with Re and geometry generally agree with the theoretical expression of Humphrey et al. (1992). It is shown that the bulk of the drag on an obstruction is form drag as opposed to friction drag.
Dynakey Ergonomics: Physical Use Envelope for Retail Environments
Authors: Lehman Katherine R. , Sutarno Chrisanto G.
Published: July 2023

Few ergonomic guidelines or standards for integrated key panel and display units exist. Ergonomic VDT standards all discuss use of keyboards and displays as separate entities (ISO 9241 (4 and 5), HFES 100-1988, and CSA-Z412-M89). NCR’s new DynaKey™ product incorporates the operator display and key panel in a side-by-side fashion to take advantage of its original human interface. A recommended envelope model (REM) was developed in order to provide positioning guidelines for the use of this product in retail environments requiring low-intensity keying. The theoretical basis for this envelope model, model validation experiment, and constrained environment test are discussed in this paper.
A New Approach Towards Robot-Assisted Orthopedic Surgery Based on Human Factor Analysis
Authors: Brandt Guido , Radermacher Klaus , Erbse Stephan , Rau Günter , Lavallée Stéphane , Staudte Hans-Walter
Published: July 2023

There is an increasing discrepancy between the accuracy of surgical planning based on modern diagnostics like bi-planar x-ray imaging, computertomography (CT) or Magnet Resonance Imaging (MRI) and the accuracy achieved by the surgeon performing a free-hand execution of the surgical plan.
Finite Element Analysis of Root Stresses Developed During Endodontic Procedures
Authors: Joyce Timothy P. , Silver-Thorn M. Barbara , Austin B. Peter , Witek Thomas J.
Published: July 2023

Nonlinear finite element (FE) analysis was used to investigate stresses in the tooth root dentin resulting from the endodontic processes of tooth restoration. The stresses developed during the filling of the root canal, positioning of a metallic post, placement of a ceramc crown, and application of masticatory and occlusal loadings were examined to investigate the causes of vertical root fractures. The areas of stress concentration in the dentin predicted by the models were found near the coronal canal opening and compared favorably with common clinical locations of vertical root failure. In addition, the obturation forces measured experimentally using simulated canals corresponded well (within 15%) with those estimated by the FE analyses.
A Model for Pulmonary Capillary Blood Flow
Authors: Dhadwal Amit , Wiggs Barry , Doerschuk Claire M. , Kamm Roger D.
Published: July 2023

Neutrophil concentration in the lung is approximately 60 times greater than in systemic blood (Hogg, 1987). This is a direct consequence of the delay experienced by a neutrophil when it encounters a vessel too small to pass through without first deforming. The process of deformation involves both the fluid dynamic forces and the resistance to deformation associated with neutrophil stiffness. This study develops a new model for flow in the pulmonary microcirculation to examine the distribution of pressure and how it is affected by local blockage by an entrapped neutrophil. The model, which accounts for anatomical and structural variability in the network, indicates that the pressure difference across a single capillary segment increases by ∼ 60% when obstructed. Changes in flow and pressure distribution are highly localized, however, due to the degree of interconnectedness exhibited by the network.
An Axisymmetric Model for Viscous Flow in Tapered Collapsible Stenotic Elastic Tubes
Authors: Tang Dalin
Published: July 2023

It has been known that arteries with stenosis may collapse under physiological conditions (Ku et al, 1990; Aoki & Ku, 1993). The mechanism of stenosis-induced collapsing is not yet well understood. Ku et al (1990, 1993) conducted a series of experimental investigations as well as numerical simulations using an inviscid one-dimensional model. Tang (1995) introduced an axisymmetric model for viscous flow in stenotic elastic tubes with a prescribed external pressure and found the tube contractions and expansions are much severe under pulsatile pressure conditions. However, the pressure conditions can neither be realized in the laboratories nor verified under in vivo conditions.
An Elastic Model of a Composite Cell Membrane: Interpretation and Design of Experiments
Authors: Spector Alexander A. , Brownell William E. , Popel Aleksander S.
Published: July 2023

Background. We study the elastic properties of the outer hair cell. The outer hair cell is a receptor cell located in the inner ear and recently considered as the major active component in the hearing process. The lateral wall of this cell is able to transmit the changes of the membrane potential into the changes of the length of the cell (Brownell et al., 1985). The outer hair cell is an elongated cylinder filled with a fluid and embedded into a surrounding structure of deformable elements. Through the electromechanical transduction, outer hair cells exert forces on the basilar membrane, the major vibrating element in the cochlea, and are believed to affect the tuning properties of the ear. Therefore, the elastic properties of the outer hair cell are crucial for the analysis of the role of the active element and for understanding the hearing process in general.
Analysis of the Effect on Normal Wrist Kinematics of Various Dynamic External Fixators
Authors: Patterson R. M. , Nicodemus C. L. , Viegas S. F.
Published: July 2023

Purpose: To better define normal carpal kinematics and evaluate the effect that dynamic fixators have on normal carpal kinematics.
Effects of Age on Joint Torques Used to Recover From a Forward Fall
Authors: Wojcik Laura A. , Thelen Darryl G. , Ashton-Miller James A. , Schultz Albert B. , Alexander Neil B.
Published: July 2023

Falls among members of the elderly population are associated with high rates of serious injury. Declines in the ability to recover balance in the early stages of a fall may contribute to this high rate of fall injury. An earlier study of the biomechanics of fall recovery in young subjects (Do et al., 1982) suggests that execution speed is a critical factor in the ability to take rapid steps to prevent a forward fall. It has also been shown that healthy elderly exhibit a significantly reduced capacity for the rapid generation of lower extremity joint torques (Thelen et al., 1995). Given this demonstrated reduction in torque capacity, it was hypothesized that healthy elderly would generate significantly smaller joint torques during attempted fall recoveries than would healthy young.
The Effects of Androgens and Estrogen on the Mechanical Properties of Bone in the Aged Ovariectomized Rat
Authors: Kasra Mehran , Vanin Carla , Casper Robert , Grynpas Marc
Published: July 2023

Sex steroids regulate normal bone metabolism. Deficiency of gonadal hormones in both males and females leads to osteopenia and osteoporosis (1,2). Estrogen is necessary for maintaining bone density in pre- and post-menopausal women, but the role of androgen is still unclear. The effects of testosterone and anabolic steroids on bone in women appear to be positive (3). There is also data supporting a positive effect of androgens on bone maintenance in ovariectomized rats. Testosterone can be converted to estrogen in vivo, unlike its metabolite 5 alpha dihydrotestosterone (DHT), which also binds to androgen receptors with high affinity. The objective of this study was to determine the effects of a non-aromatizable androgen (DHT) alone, or in combination with estrogen, on mechanical properties of cortical and trabeular bone in the aged ovariectomized female rat.
On a Theoretical Description of Hysteresis for Soft Tissues
Authors: Conway T. A. , Lam P. C. , Mazilu N.
Published: July 2023

In complex loading conditions, it is important to know, on one hand, the uniaxial behavior of materials and, on the other hand, how this uniaxial behavior changes with the state of material. Soft tissues offer one of the most attractive areas to exercise a mathematical model for the cyclic loading. Particular classes of soft tissues are interesting in that they exhibit a homographic relation between stress and strain, during uniaxial quasistatic experiments [1]. Our investigation of soft tissues behavior shows that this is a consequence of the fact that we can adequately approximate the experimental curve by a rational function and consider the measured strain as the eigenvalue of a matrix [2]. Now, assuming that the homography is valid, as the experimental data seems to indicate, we may use it to develop a description of the strain hysteresis phenomenon. For most materials, a knowledge of the hysteresis per cycle helps to define its fatigue life in low or high cycle loading. In the case of living tissues, the analytical modeling of the hysteretic response is necessary to understand the contribution of the fatigue and wear components in tissue failure mechanisms.
Can Vigorous Quadriceps Contraction Lead to ACL Failure?
Authors: Bach J. M. , Hull M. L.
Published: July 2023

It has been proposed that a vigorous quadriceps contraction can lead to ACL rupture. A set of experiments was performed to determine the relationship between increasing quadriceps force and ACL strain. The results indicate that the relationship between these two variables is almost perfectly linear for flexion angles of 0, 30, and 60 degrees indicating that it may be possible to rupture the ACL through isolated quadriceps contraction when the knee is near full extension.
Cryopreservation of Multicellular Tissue
Authors: Diller Kenneth R. , Freitas Robson Cintra de
Published: July 2023

The cryopreservation of living cells and tissues can provide a key source of materials for applications in tissue engineering as well as for direct transplantation to recipients. Successful recovery of living tissues from long term exposure to the deep subzero temperatures necessary to create a state of suspended animation requires careful and knowledgeable design of the processing protocol. This paper presents an analysis of the design issues which must be considered in the development of cryopreservation techniques for organized tissues and a brief summary of our work with a specific example, the pancreas islet of Langerhans.
The Effect of Acetabular Component Orientation on Load Transfer Through the Cadaver Pelvis
Authors: Klein Ross R. , Loebig Thomas G. , Anderson Donald D. , Mutschler Thomas A. , Ferguson Gary M.
Published: July 2023

The most common cause of failure in total hip arthroplasty (THA) is aseptic component loosening. The mechanical factors in femoral component loosening have been studied extensively, while the acetabular mechanics have received less attention (Oh and Harris, 1978; Huiskes et al., 1992).
Structural Damage of Porcine Bioprosthetic Heart Valves Subjected to Longterm Accelerated Testing
Authors: Sacks Michael S. , Smith David B.
Published: July 2023

Porcine bioprosthetic heart valves (PBHV) have poor long-term performance due to limited durability. PBHVs are commercially fixed at low trans-valvular pressures, which is thought to benefit mechanical durability by maintaining fiber crimp. However, there is no quantified data on PBHV structural changes under varying trans-valvular pressures. We have previously shown that small angle light scattering (SALS) is able to quantify changes in the collagen fiber architecture of PBHVs after 500 million cycles of in-vitro accelerated testing (1) To help clarify these issues, we investigated the changes in PBHV fiber architecture at different states of accelerated testing and trans-valvular pressures using SALS.
Strain Induced Pressure and Potential in Ligament and Tendon
Authors: Chen Chih-Tung , Vanderby Ray
Published: July 2023

Interstitial fluid can significantly affect the bio-environment and electromechanical properties of connective tissues (Grodzinsky, 1983]. Recently, several theories [Lai et al., 1989; Weinbaum et al., 1994] have been developed to describe the movement of ionic interstitial fluid in cartilage and wet bone. Ligaments and tendons, like other connective tissues, are abundant in interstitial fluid and display strong electrokinetic behavior [Chen and Vanderby, 1995]. The goal of this study is to develop a model for fluid pressure and electrokinetic behavior and to validate the model by measuring the strain generated potential (SGP) and fluid pressure in a rabbit patellar tendon (PT).
A Novel Method for Determination of Kinetic Rates of Surface Bound Receptor-Ligand Binding
Authors: Chesla Scott E. , Zhu Cheng
Published: July 2023

Cellular adhesion is important to many biological processes. These adhesive interactions are mediated by specific binding of cell surface receptors to their ligands. An important determinant of the receptor-ligand interaction is their kinetic rates. Existing bulk chemistry approaches for measuring rate constants require at least one of the reactants to be in solution. Therefore, at least one molecular species is able to move in three dimensions, and there is no force acting on the bond. This kind of rate constants is referred to as 3-D rates in the present paper. In contrast, in the case of cell adhesion, the motions of both molecular species are restricted to two-dimensional because both receptor and ligand are anchored to a surface (and the kinetic rates are thereby referred to as 2-D rates). In addition, dislodging forces usually exist which affect the dissociation. Because of these differences, the (3-D) rate constants measured via traditional approaches cannot be directly applied to the analysis of receptor-ligand binding kinetics in cell adhesion.