bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Centrifugal Blower Noise
Authors: Banks Christopher L. , Wu Sean F.
Published: December 2021

This paper presents the results of an ongoing investigation of noise radiation from centrifugal blowers used in passenger vehicles. The semi-empirical formulation previously derived by the authors (1998) for predicting noise spectra of centrifugal blowers running in a free field is extended to centrifugal blowers installed in a HVAC scroll housing. Because of the presence of the scroll and cutoff, the flow fields are different from those in a free field. Accordingly, the noise generation mechanisms become much more difficult to analyze and model. The previous model assumed a monopole type sound radiation pattern, and predicted the broadband component of the noise spectra well. This model is extended to include the contributions of both monopole and directional dipole sound radiation. It is this complex radiation that is characteristic of a centrifugal blower situated inside a scroll housing with a cutoff. Comparisons of the calculated and measured noise spectra were demonstrated, and good agreements were obtained in all cases.
Design Considerations for Flow Noise in Automotive Air Handling Systems
Authors: Warner David W. , Humbad Niranjan G. , Alzahabi Basem , Porada Robert A.
Published: December 2021

Noise from automotive air handling systems is an important issue for driver and passenger comfort. This study was undertaken to quantify the flow noise from the blower and remaining system, and to develop an analytical predictive model for airflow noise. Tests were conducted on four different vehicle Air Handling Systems (AHS) comprised of blower, heat exchangers, ducts and panel registers. Flow and noise data were measured. Test results suggest that overall noise is dominated by blower noise. A predictive model for airflow noise was developed. This model suggests system pressure drop (Δp) and system airflow (q) being dominant parameters in the noise predictions. The noise variation scales as flow velocity to the power 5.75. The developed model for flow noise can be very useful in the design process to estimate noise levels for new systems from CFD/CAE analyses.
Experimental Measurement of Compressional Damping in an Elastic-Viscoelastic-Elastic Sandwich Beam
Authors: Sisemore Carl L. , Smaili Ahmad A. , Darvennes Corinne M.
Published: December 2021

This article presents the results of an experimental investigation into the compressional vibration in an elastic-viscoelastic-elastic three-layer sandwich beam. The fundamental assumption of most of the current mathematical models is that shear deformation results in the largest energy losses for damping while compressional damping is negligible. In this experiment the relative displacements of the base beam and the constraining layer were measured directly to determine the amount of compression in the viscoelastic core. The experiment showed a maximum difference of 25% between the base beam and constraining layer motions. This suggests that neglecting compressional damping in the mathematical model is an erroneous assumption under most circumstances.
Confinement Efficiency of FRP Wrapping on Concrete
Authors: Wu Hwai-Chung
Published: December 2021

A high fiber modulus is often believed to be the key element of a successful Fiber Reinforced Plastics (FRP) wrap for strengthening concrete structures. This demand for high fiber modulus, together with durability concern, lead to the choice of carbon, as used in many retrofitting applications. In this paper, such concept will be examined from a micromechanical consideration by taking account of mechanical interaction between FRP sheet and concrete. Concrete failure is initiated by wing crack propagation under compressive loads. An explicit relationship of the amount of confining pressure and FRP configuration (fiber type, architecture, and orientation), taking the interaction into account, is of critical importance for FRP performance optimization. The mechanical interaction dominates the composite behavior from the first bent-over point to the peak load in a load/displacement curve. The detailed interaction under compression is described, and unique insights obtained from the model are discussed in this paper.
Vibration Characteristics of the Automotive Rearview Mirror
Authors: Song Fuyin , Ayorinde Emmanuel O.
Published: December 2021

Vibration performance is a critical factor in the design of automotive rearview mirrors. Because of the complexities involved in the structure of the rearview mirror, its mounting location on the vehicle and its operational conditions, design optimization from finite element analysis is a necessary procedure in order to obtain good vibration response and reduce costs. This paper summarizes the results for design optimization and material selection from finite element analysis (FEA) conclusions. The finite element analysis results indicated that design optimization is very important in the final performance of part vibration and deformation. For design innovations that reduce parts count, decrease costs, and preserve or improve product quality, it may be a critical factor to utilize higher performance composites in place of more traditional materials. Several materials are studied with regard to their properties and dynamic performances. The results could help to achieve cost reduction in part design and to obtain design optimization for current and future programs.
Vibration Response of Golf Clubs With Steel and Composite Shafts
Authors: Barpanda Dev , Nori Chandrasekhar , Mantena P. Raju
Published: December 2021

In a previous paper (Barpanda and Mantena, 1998), the dynamic response of three commercially available hockey sticks with wooden, aluminum and graphite shafts was characterized using a combined modal analysis and vibration response approach. The extension of this technique to golf clubs with steel and graphite shafts is reported here. Using an instrumented impact hammer, a complete modal survey is initially conducted on the golf clubs to study their dynamic behavior. A comparative study of the modal parameters (natural frequency, damping and mode shapes) of the golf clubs provides valuable information for design optimization. The contour and associated vector plots of the mode shapes are very useful for generating node (zero displacement) lines on the club-head surface. A two-accelerometer technique was then used to perform vibration response tests on the impact surface. Linear and angular vibration level maps were plotted for identifying ‘sweet spot regions’ on the impact surface. These tests yield quasi-quantitative information regarding the level of vibrations felt by a player due to simultaneous linear and angular motion of the shaft and club-head. The mapping also serves as an effective tool for determining the relative merits of steel and graphite shafted club heads based on their vibration performance. Results of modal analysis and vibration response tests indicate that the golf club with a graphite shaft had a larger sweet spot zone enclosing the area of maximum node line density compared to the club with a steel shaft. The combined strategy of using both modal analysis and vibration response measurements provides a better understanding of the dynamic response of golf clubs made with different materials.
Self-Repairing Approaches for Resin Infused Composites Subjected to Low Velocity Impact
Authors: Motuku Molefi , Janowski Gregg M. , Vaidya Uday K.
Published: December 2021

Low velocity impact response (LVIR) of glass reinforced polymer composites (GRPCs), which have the potential to self repair both micro- and macro-damage, has been investigated. This class of materials falls under the category of passive smart polymer composites. The self-repairing mechanism is achieved through the incorporation of hollow fibers in addition to the normal solid reinforcing fibers. The hollow fibers store the damage-repairing solution or chemicals that are released into the matrix or damaged zone upon fiber failure. Plain-weave S-2 glass fabric reinforcement, DERAKANE vinyl ester 411-C50 and EPON-862 epoxy resin systems were considered for this study. Different tubing materials were investigated for potential use for storing the repairing chemicals instead of the actual hollow repair-fibers and included borosilicate glass micro-capillary pipets, flint glass Pasteur pipets, copper tubing and aluminum tubing. Composite panels were fabricated by using vacuum assisted resin transfer molding (VARTM) process. The present investigation addressed fabrication of self-repairing composite panels, the processing quality, selection of storage material for the repairing solution and, release and transportation of repairing solution.
Simulation of Assembly and Operation of Pre-Stressed, Heat-Shrinkable Structural Composite Connectors
Authors: Gibson Ronald F. , Baxi Jvalit K. , Stoll Frederick , Bettinger David , Johnson Vincent
Published: December 2021

This paper describes the finite element numerical simulation of the mechanical behavior of a pre-stressed, heat-shrinkable, fiber reinforced polymer composite connector during assembly and operation. A multi-step finite element analysis has been developed to simulate the stresses and deformations developed due to prestressing and heat-shrinking during assembly. Then the viscoelastic creep during storage of the connector was modeled and compared with measured creep in order to estimate the practical storage life of the connector. Finally, the mechanical behavior of the joint during operation was simulated by the use of four point bending tests, and again the predictions from the multi-step finite element analysis were compared with measurements.
Using Stop Band Formation for Characterizing Interphase Properties of Composite Models Having Square Fiber Arrangements
Authors: Cai Liang-Wu
Published: December 2021

The formation of stop bands over which waves cannot propagate through composites having square fiber arrangements has been observed in previous full-scale deterministic simulations. In this paper, characteristics of the cut-off frequency of the stop band are investigated via systematic full-scale simulations and related to the physical properties of the interphase in a three-phase composite model.
Integral Equations for Acoustic Scattering in a Viscous Fluid
Authors: Newmark Marc S. , Nagem Raymond J.
Published: December 2021

A set of integral equations is derived for acoustic scattering from arbitrarily shaped two-dimensional bodies in a viscous fluid medium. The integral equations are discretized for numerical computation, and computational results are given for scattering from a finite planar strip. Our results show that viscosity may produce significant effects near a sharp edge of a rigid scatterer, even in cases where viscosity has only a small influence on the remainder of the acoustic field.
A New Transverse Electromagnetic Microactuator Using the Radial Magnetic Field Guided by Symmetric Twin Magnets
Authors: Ryu Ji-Chul , Kang Tae Goo , Cho Young-Ho
Published: December 2021

This paper presents an electromagnetic microactuator using the copper coil, electroplated on a p+-silicon diaphragm. The microactuator generates a vertical motion of the diaphragm using the radial components of the magnetic field on the coil plane. In order to guide and concentrate the magnetic field in the radial direction, we propose a new microactuator structure with twin magnets. The microactuator shows values of resonant frequency and quality factor in the ranges of 10.51±0.22kHz and 46.6±3.3, respectively. The twin magnet microactuator generates the maximum peak-to-peak amplitude of 4.4μm for the AC rms current of 26.8mA. showing 2.4 times larger amplitude than the single magnet microactuator.
Composition Dependent Magnetostrictive Properties of NiFe Thin Films
Authors: Rissing Lutz H. , Gatzen Hans H.
Published: December 2021

In a thin film microtransformcr with a magnetostrictive core, the amount of coupling between the two transformer coils depends on the strain the core is exposed to. Therefore, such a device lends itself to be used as a highly efficient strain gauge. This paper investigates the usefulness of “permalloy”, a NiFe alloy, as a magnetostrictive thin film core material. NiFe 81/19, a composition with a magnetostrictive coefficient close to zero, is widely in use in magnetic data recording. To find a NiFe composition with maximal magnetostriction, the nickel content of NiFe films (which containalso a small amount of Ta) was varied between 35% and 81%. The films were deposited by co-sputtering. As a result, the composition of choice for a magnetostrictive core material was NiFe 43/57.
Distributed Resource Allocation for Smart Matter Using Decentralized Analog Computation and Communication
Authors: Ng Chee We , Jackson Warren B. , Schuylenbergh Koenraad Van , Biegelsen David K. , Hogg Tad , Berlin Andrew A.
Published: December 2021

The use of analog circuits implementing market allocation for potential control and coordination of large numbers of MEMS actuators, controllers, and/or sensors is investigated. While theoretical work has shown that markets can allocate actuation or control in a robust, flexible, and distributed fashion, this paper demonstrates that analog hardware implementation of the markets is promising for actuation allocation. Like human markets, the analog circuit implementations are robust against changes in actuator function or failures. The market wire offers rapid communication and coordination among large numbers of agents.
Assembly and Testing of Surface Micromachined, Piezoresistive Polysilicon Pressure Sensors
Authors: Miller Todd F. , Monk David J. , O’Brien Gary , Eaton William P. , Smith James H.
Published: December 2021

Surface micromachining is becoming increasingly popular for microelectromechanical systems (MEMS) and a new application for this process technology is pressure sensors. Uncompensated surface micromachined piezoresistive pressure sensors were fabricated by Sandia National Labs (SNL). Motorola packaged and tested the sensors over pressure, temperature and in a typical circuit application for noise characteristics. A brief overview of surface micromachining related to pressure sensors is described in the report along with the packaging and testing techniques used. The electrical data found is presented in a comparative manner between the surface micromachined SNL piezoresistive polysilicon pressure sensor and a bulk micromachined Motorola piezoresistive single crystal silicon pressure sensor.
On the Modeling of the Wheatstone-Bridge Piezoresistive Pressure Sensor: A Finite-Element-Based Approach
Authors: Ghaddar Chahid K. , Gilbert John R.
Published: December 2021

In this work we conduct a number of finite element simulations using the MEMCAD 5.0 system to evaluate the effect of various geometrical and process parameters on the Wheatstone bridge piezoresistive pressure sensor. In particular, results are presented for the following design parameters: the location of the resistors relative to the diaphragm edge; the angular orientation of the resistors; the planar dimensions of the resistors; and finally, the effects of dopant concentration profile and associated junction depth as computed by the limited-diffusion model.
Design, Analysis, Fabrication, and Testing of a MEMS Contact/Bending Sensor With Improved Dynamic Range
Authors: Truong Thieu Q. , Barnes Terrence G. , Lu Xiaoqing , Adams George G. , McGruer Nicol E.
Published: December 2021

Contact/bending sensors have been designed, analyzed, fabricated, and tested. These sensors are to be mounted on flexible antennae in order to provide a sense of touch for ambulatory underwater robotic lobsters. These biomimetic vehicles are designed to mimic some of the behavior patterns of real lobsters and are being built in order to search for and destroy mines in the littoral zone [1].

Two contact/bending sensors have been developed — a “standard” sensor and a “stopper” sensor. The standard sensor and stopper sensor are cantilever beam type microswitches fabricated on a thin flexible substrate. These sensors were fabricated using the Northeastern University Metal Micromachining (NUMEM) process [2]. The purpose of the stopper sensor design is to increase the dynamic range and alleviate the sensitivity limitations that are inherent in the standard sensor design.

Tests have shown the standard sensors close at a substrate radius of curvature that is 25% greater than the design values. Tests and SEM micrographs of the stopper sensors have shown that there are some processing issues which need to be addressed.
Measurement of Shear Stress and Temperature Using MEMS Fabricated Sensors
Authors: Breuer Kenneth S. , Bayt Robert L. , Nayaar Anju
Published: December 2021

The design, fabrication and testing of microfabricated thermal shear stress and temperature sensors are sensors is discussed. The devices are fabricated on a silicon substrate with a platinum sensor element 5 microns wide, 1000-Å thick and of varying length. The electrical leads are comprised of 5000-Å of gold deposited above the platinum sensor metal. The sensing area is isolated from the substrate by a thin membrane of silicon nitride covering a vacuum cavity. Test results are presented confirming the good thermal isolation of the sensor element from the substrate as well as the successful operation of the device.
Infrared Vision Using an Uncooled Thermo-Opto-Mechanical Camera: Design, Microfabrication, and Performance
Authors: Mao M. , Perazzo T. , Kwon O. , Zhao Y. , Majumdar A. , Varesi J. , Norton P.
Published: December 2021

An uncooled infrared (IR) camera that is based on thermomechanical sensing and visible optical readout has been developed. The system contains a focal plane array (FPA) consisting of bimaterial cantilever beams made of silicon nitride (SiNx) and gold (Au) in each pixel. Absorption of incident IR radiation in the 8–14 μm wavelength range by SiNx in each cantilever beam raises its temperature, resulting in proportional deflection due to mismatch in thermal expansion of the two cantilever materials. To maximize the thermal performance, the conductance of each pixel was reduced to about five times of the radiation conductance. Based on thermomechanical analysis, the geometrical shape of the pixels were designed to maximize the cantilever sensitivity within the constraints of the pixel size and layout. Microfabrication of stress-balanced bimaterial cantilevers was achieved by varying the silicon concentration along the thickness of the SiNx films in order to balance the residual tensile stress in the Au film and the Cr adhesion layer between Au and SiNx. The optical design of each pixel was based on IR properties of the cantilever materials, IR absorption enhancement due to resonance cavity formation, as well as visible optics of deformable diffraction gratings. The latter formed the foundation for two different optical readout techniques that were both used for IR imaging. The results suggest that objects at temperatures as low as 30 °C can be imaged with the best noise-equivalent temperature difference (NETD) in the range of 2–5 K. It is estimated that further improvements that are currently being pursued can improve NETD to about 10 mK.
A New Driving Principle for Micromechanical Torsional Actuators
Authors: Schenk Harald , Dürr Peter , Kunze Detlef , Kück Heinz
Published: December 2021

An electrostatic driving principle for micromechanical torsional actuators is presented which allows to excite mechanical oscillations with large deflection angles at low driving voltages. This is achieved by a special electrode configuration which enables the usage of small electrode gaps. The functionality is demonstrated by various 1D-scanner chips which are fabricated in a CMOS-compatible process. When the excitation is synchronized with the oscillation a maximum deflection angle is obtained. For this case a theoretical description of the characteristic curve is given and compared to experimental results. Furthermore, FEM calculations on the deflection dependence of the capacitance are presented.
Simulation of Microfluidic Systems: A New Approach Considering Capillarity
Authors: Mellmann Jörg , Sesterhenn Michael , Löhr Markus , Stierle Bernhard , Strobelt Tilo , Zengerle Roland , Sandmaier Hermann
Published: December 2021

In this paper, a toolbox of lumped models for simulating (self-)priming and emptying of complex capillary networks is presented. Each model is a kind of an all-in-one-model, that considers inertia, friction, gravitation and capillarity and has been implemented on a conventional, commercially available, mixed-signal system-level simulator.

The toolbox contains fundamental microfluidic components which are lines with micromachined geometries, fittings, tees, dispensers and media transition elements.

With these all-in-one-models it is now possible for the first time to layout complex capillary networks by simulating not only the dynamic behavior of filled systems but even the priming and emptying.
Topspot: A New Method for the Fabrication of Biochips
Authors: Gruhler Holger , Hey Nicolaus , Müller Martin , Békési Stefan , Freygang Michael , Sandmaier Hermann , Zengerle Roland
Published: December 2021

We present a new method for generating microarrays of liquid droplets. This is of basic importance for the fabrication of so called biochips. To generate a microarray we use a print-module containing 24 nozzles. Each nozzle is connected to one of 24 different reservoirs on the same print-module. By applying a high acceleration to the print-module it can be achieved that all of the 24 nozzles eject a small droplet at the same time. This effect is due to the inertia of the liquid inside the print-module. This new method makes the production of low and medium density biochips much faster and significantly cheaper.
Numerical Modeling of Electroosmotically Driven Micro Flows
Authors: Dutta Prashanta , Beskok Ali , Warburton Timothy C.
Published: December 2021

Electroosmotically driven flows in micro-channels are analyzed analytically and numerically. Semi-analytical relations for the velocity and pressure distributions in micro channels are obtained for electric double layers that are much smaller than the channel height, by using the Helmholtz Smoluchowski velocity. Analytical relations for wall shear stress and pressure distribution are obtained. Amplification of the normal and shear stresses on the walls are observed and documented. A high-order (h/p type) spectral element method is developed, and verified for numerical simulation of electroosmotic micro fluidic flows. Finally, flow through a step channel geometry is analyzed to document the interaction of the electroosmotic forces with adverse pressure gradients. Significant changes within the separation patterns are observed.
Factors Influencing the Maintenance of Speed: A Driver Model Analysis
Authors: Thakur Kailash Prasad
Published: December 2021

This paper presents a driver model analysis of the maintenance of speed on highways by drivers of various capabilities. The results indicate that for an expert driver the speed is highly correlated with the free distance in front of the vehicle (or gap with the lead vehicle). Whereas, for a novice driver the speed is very poorly correlated with the gap. This correlation is always positive and varies between 0.05 for novice driver and 0.85 for expert driver. The correlation of speed with the risk-time (time to impact) showed a different trend. This correlation is negative and varies between 0.5 for an expert driver to 0.8 for novice ones. The results compare fairly well with the laboratory-based driver simulation studies carried out by Charlton. The effect of road roughness upon the maintenance of speed, gap and risk-time is also investigated.
Polyethylene Wear Characteristics in Retrieved Total Knee Replacements
Authors: Hall Emily A. , Bland Tracie M. , Lemons Jack E. , Cuckler John M. , Eberhardt Alan W.
Published: December 2021

Since the first observed failures of polyethylene in total knee replacements, researchers have documented wear patterns in an effort to understand the failure mechanisms associated with total knee replacements (TKR). This study documents five types of wear observed in polyethylene components from retrieved TKR, as well as gross deformation characteristics. Pertinent patient data and the type of polyethylene are also noted. Results show significant occurrence of pitting, delamination and abrasion in the majority of the components studied, consistent with previous reports.
Casing Design for an Oxygen Concentrator
Authors: Swindle Stephanie H. , Todd Beth A. , Cuttino James F.
Published: December 2021

Human bodies depend on a steady flow of oxygen for the heart and lungs. When a person has Chronic Obstructive Pulmonary Disorder (COPD), a device called an oxygen concentrator can be used to improve quality of life. An oxygen concentrator is an electrically powered device that takes in room air and converts it to an oxygen rich gas mixture suitable for breathing.

Although a few models are battery powered, oxygen concentrators are not easily portable because they are bulky and weigh between 25–50 lbs. In this study, components were identified for re design to reduce the overall weight of the device. For instance, the concentrator casing was identified as its heaviest component. Using finite element analysis, changes in wall thickness and dimensions can be investigated to reduce weight while maintaining structural integrity. By reducing the weight of the casing, the oxygen concentrator will be easier to transport.
Biomechanical Aspects of Odontoid Fracture Etiology: A Finite Element Investigation
Authors: Puttlitz Christian M. , Goel Vijay K. , Clark Charles R.
Published: December 2021

Fractures of the odontoid process of the second cervical vertebra comprise 7–13% of all cervical spine fractures. Anderson and D’Alzono [1974] have classified these fractures into three categories: Type I, Type II, and Type III. Type I fractures are oblique, usually avulsion, fractures of the superior-most aspect of the odontoid. Type II fractures, the most commonly-occurring, are produced at the juxtaposition of the process and the C2 body. Type III fractures involve propagation of the fracture through the C2 body.
Unsteady Flows Within a 2D Model of Multiple Lung Bifurcations
Authors: Ramuzat A. , Richard H. , Riethmuller M. L.
Published: December 2021

In our environment, chronic pulmonary illness due to pollution effects or asthmatic problems are increasing. To identify the contribution of pollution effect on the alterations in breath patterns, a better understanding of the human pulmonary system is needed. As a result, fields to be investigated are mostly flows in the lungs at high breathing frequency and aerosol deposition in lung bifurcations under unsteady conditions. The respiration pattern has to be better understood and investigated, to have the possibility to get the most appropriate palliative treatment. Most of the medical treatments are based on aerosol deposition in the bronchial tree.

The lung is a complex network of 23 successive generations of bifurcation (Weibel, 1963). The airways, from the trachea to the alveolar zone, divide by dichotomy and become shorter and narrower as they penetrate deeper into the lung. As a result, in vivo investigations of pulmonary flows are not possible, and in vitro experiments in models have to be performed.

Flows in the bifurcating airways of the lung are modeled to determine velocities and pressure fields. A complete description of steady flow in a single 3D bifurcation has been previously performed by experimental and numerical modeling. As a result of this study, it has been shown that the first bifurcation influences the flow in the second and in the third bifurcation when the length of the second bifurcation is not sufficiently long. To extend the investigations to a system of three generations, an experimental study of steady and unsteady flows has been carried out on a 2D multiple bifurcations model.
Application of a Robotic/UFS Testing System to the Measurement of Lumbar Spine Structural Properties
Authors: Doehring Todd C. , Gilbertson Lars G. , Moon Seong-Hwan , Kang James D. , Woo Savio L.-Y.
Published: December 2021

This study focuses on the application of new experimental techniques (robotic/UFS testing system), analytical tools (FEA), and physical models to the investigation of lumbar functional spinal unit structural properties.
Wall Shear Stress Distribution on the Surface of Realistic Endothelial Cell Model
Authors: Fukushima Shuichiro , Nagatsu Ai , Kaibara Makoto , Oka Kotaro , Tanishita Kazuo
Published: December 2021

Wall shear stress induced by blood flow affects morphology and physiology of endothelial cells. The specific mechanisms of mechano-biological interactions alternating shapes and functions have not been identified in the cells, because of the lack of a detailed description of microscopic flow near the cell surface. We therefore developed velocimetry using expanded cell model and demonstrated that the microscopic flow depended on three-dimensional cell shape (Fukushima et al., 1997, 1998). Furthermore, we determined wall shear stress distribution on cultured endothelial cells experimentally.
Evolutionary Biology of Airway Clearance
Authors: Krumpe Peter E.
Published: December 2021

The survival of air breathers depends upon maintaining clear airways. The primary defense of the airways under normal conditions is the mucociliary escalator. Only under conditions of airway inflammation does cough clearance mechanisms become predominant. In order to facilitate the expectoration of mucous and retained particulates, cells, and debris, coupling between the air stream and the mucous layer must occur. High linear velocity of the airstream and unstable flow regimes (vortices, eddies) facilitates development of waves in the mucous layer. Expectoration requires a catastrophic separation of mucous from underlying airway structures. The response of airways is initially to secrete a deeper mucous layer, and to remodel airway glands to produce a mucous blend having a higher elastic modulus. Mucous rheologic properties seem to be tailored by the presence of inflammation to become more easily cleared, even at lower air flow rates which are characteristic of lung disease. Airway oscillations (wheezes and rhonchi) which are physical findings associated with airway inflammation may further enhance mucous clearance by adding additional energy to the mucous layer, aiding catastrophic separation. Thus airway clearance is a highly evolved and coordinated example of evolutionary biology.
Impact of Washout Blades in a Multiple Disk Centrifugal Blood Pump
Authors: Holmes Michelle J. , Miller Gerald E.
Published: December 2021

A multiple disk, centrifugal blood pump (MDCP) for use as a ventricular assist device or as a bridge to transplant device has previously been designed and its output characteristics have been analyzed (Miller et al. 1990, 1993). The propelling mechanism of this device consists of six multiple disks assembled in a parallel configuration. Upon rotation these disks create centrifugal and shearing forces, which work to propel the fluid. This pump operates at lower rotation rates than other rotary blood pumps. The lower rotation rates reduce the chance for hemolysis, but may promote thrombosis formation due to stagnant blood flow. Previous flow visualization studies conducted by Miller et al. (1995) analyzed the blood flow patterns within the device. Results of this study indicated a region of flow stagnation between the last solid disk and the housing. In this investigation, further studies were performed that verified this recirculation. To provide washout of this region, eight, small Lexan blades were attached to the back of the last disk. Reevaluation of the flow patterns, following the blade attachment, revealed that the addition of the blades was successful in producing washout, thus reducing the possibility of thrombosis formation.
Elevated Mean Translesional Pressure Gradients and Flow Limitation in Significant Human Coronary Stenoses Before Angioplasty
Authors: Banerjee Rupak K. , Back Lloyd H. , Back Martin R. , Cho Young I.
Published: December 2021

Blood flow was simulated in patients (Wilson et al. 1988) with physiologically significant coronary lesions (minimal lesion size dm = 0.95 mm; 68% mean diameter stenosis; measured coronary flow reserve (CFR) of 2.3) by using computational hemodynamics. Computed mean pressure gradients Δp˜ were about 9 mm Hg for basal flow, and flow limiting values about ∼ 35 mm Hg. Mean hyperemic flow rates were about 115 ml/min, and distal mean coronary pressures ∼ 55 mm Hg, a level known to cause ischemia in the subendocardium (Brown et al. 1984), and consistent with the occurrence of angina in the patients.
Development of Thin Metal Film Deposition Process for the Intravascular Catheter
Authors: Chung Seok , Chang Jun Keun , Han Dong Chul
Published: December 2021

To make some MF.MS devices such as sensors and actuators be useful in the medical application, it is required to integrate this devices with power or sensor lines and to keep the hole devices biocompatible. Integrating micro machined sensors and actuators with conventional copper lines is incompatible because the thin copper lines are not easy to handle in the mass production. To achieve the compatibility of wiring method between MEMS devices, we developed the thin metal film deposition process that coats micropattered thin copper films on the non silicon-wafer substrate. The process was developed with the custom-made three-dimensional thin film sputter/evaporation system. The system consists of process chamber, two branch chambers, substrate holder unit and linear/rotary motion feedthrough. Thin metal film was deposited on the biocompatible polymer, polyurethane (PellethaneR) and silicone, catheter that is 2 mm in diameter and 1,000 mm in length. We deposited Cr/Cu and Ti/Cu layer and made a comparative study of the deposition processes, sputtering and evaporation. The temperature of both the processes were maintained below 100°C, for the catheter not melting during the processes. To use the films as signal lines connect the signal source to the actuator on the catheter tip, we machined the films into desired patterns with the eximer laser. In this paper, we developed the thin metal film deposition system and processes for the biopolymeric substrate used in the medical MEMS devices.
Direct Flow Analysis on a Reconstructed 3D Image of a Physiologic Porcine Aortic Trifurcation
Authors: Banerjee Rupak K. , Huddleston Matthew , Sohan Shailendra Singh , Friedman Morton H.
Published: December 2021

The present study describes a detailed methodology, from 3D image reconstruction to flow analysis, for simulating the flow field in real arterial geometries. The procedure takes advantage of the latest state of the art technology in solid modeling, and is illustrated by application to a porcine aortic trifurcation. A Stereolithography (STL) format representation of the physical geometry is used in the Gambit™ (1998) preprocessor to create an identical, “virtual” geometry, which is subsequently meshed for flow analysis. With this simplified procedure, it is possible to take MRI or CAT scan images and perform computational flow analysis within physiologic-passageways, using commercially available solvers.
The Effects of Osmotic Pressure on the Viscoelastic and Physical Properties of Articular Chondrocytes
Authors: Guilak Farshid , Ting-Beall H. Ping
Published: December 2021

Mechanical stress is an important factor in the regulation of chondrocyte metabolism and the maintenance of the cartilage extracellular matrix. Previous studies have shown that compression of cartilage explants alters cellular metabolism in a time- and spatially-varying manner which is correlated with the mechanical environment within the extracellular matrix [1]. Furthermore, cellular response has been shown to be influenced by mechanical, electrical, and physicochemical events which are coupled to deformation of the cells and the extracellular matrix. Therefore, detailed information on the stress-strain and physicochemical environments of individual cells in response to mechanical and osmotic stresses would improve our understanding of the sequence of events involved in mechanical signal transduction [2–4]. The goal of this study was to quantify the osmotic and viscoelastic properties of isolated chondrocytes and to test the hypothesis that the mechanical properties of the chondrocyte are influenced by their physicochemical (osmotic) environment.
Real-Time Observations of the Behavior of Cells Under Controlled Pressure and Shear Loads
Authors: Tsourkas Andrew , Bao Gang
Published: December 2021

The effect of mechanical loading on cells has aroused a great deal of interest in recent years. It is now widely accepted that mechanical loading is critical for both cell form and function. Although shearing of cells through fluid flow and tensile testing of cells have been widely practiced, there is still a lack of experiments focusing on the effects of controlled pressure and shear loads on cell behavior. The presence of compressive and shear deformations can be seen in a variety of cells ranging from chrondocytes during walking to cardiac myocytes during the cardiac cycle. The aim of our research is to relate the rate and magnitude of shear deformation in addition to applied pressure to issues such as restructuring of the cytoskeleton (i.e. microtubules), alterations in ion release and influx, and changes in cell function. The effects of changing the extra-cellular matrix (ECM) on the cellular response under pressure and shearing are also studied. By observing the effects of combined compression and shear on cells such as chondrocytes and cardiac myocytes, we hope to better understand the causes of diseases like osteoarthritis and congestive heart failure in connection to mechanical loads.
Chondrocyte Translocation and Orientation to Applied DC Electric Fields
Authors: Mauck Robert L. , Chao Pen-hsiu G. , Gilbert Beth , Valhmu Wilmot B. , Hung Clark T.
Published: December 2021

Chemical and mechanical stimuli are known to cause directed movement in a number of different cell types. Less prominently studied, direct current (DC) electric fields are known to induce a similar response. In this study, we report on DC electric field-induced chondrocyte migration and re-orientation. Galvanotaxis and galvanotropism, migration and shape change in response to applied DC electric fields, respectively, have been demonstrated in many cells. For instance, field strengths of 1–10 V/cm have been reported to induce migration in keratinocytes. corneal epithelial cells, bone cells, fibroblasts and neural cells [1,7,8,11]. Recently, we have demonstrated for the first time that chondrocytes exhibit a galvanotactic response, realigning and migrating in response to applied DC electric fields (6 V/cm) [6]. In cartilage, chondrocytes may see electric fields associated with streaming potentials estimated to be up to 15 V/cm with current densities of up to 0.1A/cm2 [2]. The aim of this study was to explore basic science aspects of directed cell migration under applied DC electric fields and to investigate the potential application of this phenomena for tissue engineering, healing and repair of cartilage. The ability to direct cell growth and function will have significant implications on the bioengineering of replacement tissues.
Development of an Experimental Procedure for Pre-Clinical Testing of Cemented Hip Replacements
Authors: Maher Suzanne A. , Prendergast Patrick J. , Waide D. Victor , Reid Alan J. , Lyons C. Garrett
Published: December 2021

Current standards for testing cemented femoral hip stems involve potting the distal third of the stem and applying a cyclic load, see ISO 7206-8. 1995(E). However, this procedure does not test implants for the most prevalent mode of failure — loosening of the prosthesis from the host bone (Malchau et al., 1993). To quantify the expected longevity of implants in a pre-clinical test, a protocol that establishes the rate of loosening of a prosthesis must be developed.

Using Radiostercophotogrammetry (RSA), Karrholm et al. (1994) have correlated migration of more than 1 mm within two years of implantation with early loosening of the implant. Therefore, by quantifying the migration of a prosthesis in a laboratory test for the equivalent of two years post implantation, its risk of loosening in vivo can be assessed. In the past, the motion of cemented implants in one direction has been quantified (Manley et al., 1987); whilst other researchers have performed a more complete analysis of the motion of prostheses, but for a limited number of loading cycles (e.g. Schneider et al., 1989). In most of these studies, prosthesis insertions were performed by surgeons. Not only does this introduce subjectivity into the pre-clinical test, but in the case of cemented replacements, variations in stem orientation and cementing pressures will occur. This paper presents the design and initial validation of procedures which may be used for pre-clinical testing of cemented hip stems.
Investigation of Performance of a Femoral Implant With a Plug Using Finite Element Analysis
Authors: Chu Taiming , Carstarphen Deanna Y.
Published: December 2021

A Finite Element Analysis was performed on the critical section of a titanium alloy femoral implant coupled with a cobalt-chromium Dall-Miles Cable Grip System (DMCGS). The critical section of the implant is defined at the hole where the wires of the DMCGS are threaded. Two models were generated for the analysis. The first model consisted of the critical section with a cobalt-chromium plug filled in at the hole. The second model consisted of the critical section without the plug in the hole. The models used in the study were based on a design developed by Howmedica Incorporated (called the “head-neck replacement”). One static simulation was performed on each model. This simulation represented the early stance phase of normal walking. The wires used in the simulations were pre-tensioned. The preliminary results of the analysis showed that the stresses in the model with the added plug were lower than those in the model without the plug. This indicated that a plug added to a femoral implant adjoined with the Dall-Miles Cable Grip System reduces the stress concentrations at the hole. Furthermore, the results of the study will provide insight into the modifications on design of femoral implants. This may well lead to an improvement in implant performance and better aid in the restoration of hip function for arthritic patients.
Measurement of Osteocyte Deformation Resulting From Fluid Flow Induced Shear Stress
Authors: Nicolella Daniel P. , Sprague Eugene , Bonewald Lynda
Published: December 2021

It has been shown that bone cells are more responsive to fluid flow induced shear stress as compared to applied substrate strain (Owan, et al., 1997, Smalt, et al., 1997). Using novel micromechanical analysis techniques, we have measured individual cell strains resulting from 10 minutes of continuous fluid flow at a flow rate that produces a shear stress of 15 dyne/cm2. Individual cell strains varied widely from less than 1.0% to over 25% strain within the same group of cells. The increased sensitivity of cells to fluid flow induced shear stress may be attributed to much greater cellular deformations resulting from fluid flow induced sheer stress.
Role of Vertebral Shell and Endplate Modulus on Whole Vertebral Body Stiffness
Authors: Liebschner Michael A. K. , Kopperdahl David L. , Keaveny Tony M.
Published: December 2021

The contribution of the cortical shell and endplate to the stiffness and strength of the vertebral body is not well understood. However, several studies have suggested that the cortical shell plays an important role in the fracture strength of the whole vertebral body as bone is progressively lost from the centrum due to aging and osteoporosis (Eastell 1991, Faulkner 1991, Kurowski 1986. Silva 1997). Silva et al. (1994) concluded that prediction of cortical bone geometry using computed tomography (CT) based measurements is subject to considerable uncertainly caused by image distortion and the low ratio of image resolution of 0.25 mm/pixel to cortical shell thickness (0.09–0.86 mm). Thus, in development of CT-based models of the vertebral body, particular attention should be paid to the details of shell modeling.
Transversely Isotropic Model of Osteonal Cortical Bone: Contribution of Haversian and Resorptive Porosity
Authors: Dong X. Neil , Huang Y. Young , Guo X. Edward
Published: December 2021

Age related changes in porosity of cortical bone have been previously reported. The cortical porosity increases with age in both men and women, from 4.6% in men and 4% in women at age 40 to 10% and more at age 80 (Laval-Jeantet et al., 1983). The porosity is defined as the percentage of cortical bone occupied by vascular and resorption cavities. There are a few quantitative data regarding the influences of Haversian canal and resorption space on porosity. Age related increases in Haversian canal size and Haversian canal number contribute to the increasing porosity of cortical bone for the elderly men and women (Thompson, 1980; Nyssen-behets et al., 1997). The number of osteoclastic resorption space is also greater in the old men than in the young men (Nyssen-Behets et al., 1997).
Effects of Stenosis Severity and Balloon Characteristics on Stresses in Balloon Angioplasty — A FEM Study
Authors: Gourisankaran Vijay
Published: December 2021

Studies of stresses in an artery under normal physiological pressure loads have been made to gain insight into the possible causes of plaque rupture and progression of atherosclerosis. This study addresses the effects of stenosis severity, and balloon stiffness on the peak stresses experienced in the system during angioplasty. It is proposed that the effectiveness and therefore success of an angioplasty procedure can be measured by the non-propensity for restenosis to occur, and the absence of high stresses in the diseased artery at peak balloon dilation pressures. The models used in this study use nonlinear material properties of the arterial wall and the balloon, large deformations during the angioplasty procedure and contact between the arterial wall and the balloon.
Virtual Position Control During Contact Tasks
Authors: English Chad E. , Russell Donald L.
Published: December 2021

It is well known that human limbs have spring-like behaviour that has been attributed to both compliance of the muscles and reflex action [Hogan, 1985; Mussa-Ivaldi et al., 1985]. These mechanics are the premise behind the Equilibrium Point (EP) Hypothesis for motor control [Bizzi et al., 1992; Shadmehr et al., 1993; Won & Hogan, 1995]. Essentially, EP theory suggests that muscles are activated such that they define a unique position of the limb in the workspace, called the virtual point, where there are no net joint moments [Bizzi et al., 1992]. (Some refer to this as the equilibrium point, but that notation can be confused with a contact equilibrium.)

If an amputee using a prosthetic limb uses the EP control technique naturally, it is necessary for the prosthesis to included mechanical properties sufficiently similar to those of a natural limb to produces similar results. The necessary mechanics, and limitations of not providing them, are the bulk of the authors’ current research. The current work examines the control of contact forces.

A variety of studies have examined virtual paths for unconstrained motions [Flash, 1987; Lan & Crago, 1994]. Others have implemented a predetermined virtual point path in an artificial manipulator during contact tasks [Hogan, 1987]. However, little information is available on the virtual point path required to produce desired contact properties. This study analytically and numerical investigates the virtual point path required to vary contact force without producing a motion of the limb along the surface.