bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Biomechanics of Penetrating Trauma
Authors: Yoganandan Narayan , Pintar Frank A. , Kumaresan Srirangam , Hargarten Stephen , Sances Anthony
Published: July 2023

The objective of this study was to investigate the biomechanics of penetrating trauma secondary to high velocity projectiles. Tests were conducted using 10 percent ordnance gelatin as a human tissue simulant. Two different types of projectiles were discharged into the gelatin block which was prepared with centrally placed nylon strings. A digital high-speed camera capable of recording up to 40,500 frames per second documented the path and the associated secondary wave effects. The data were analyzed with respect to the entrance and exit velocities, the time-varying velocity in the gelatin, and the penetration profile characteristics including the residual wound involvement. Depending on the design and construction of the projectile, a stark contrast in the dynamic effects was found. Results from these studies have the potential to delineate the biomechanical effects of high velocity projectiles and develop standards to ameliorate trauma secondary to the discharge.
Validation of Experimental Methods for Determining Inertial Properties of Human Subjects
Authors: Marsh M. Virginia , Todd Beth A. , Rasmussen Roy R. , Baughn Donna Jo , Albery Chris
Published: July 2023

Due to an expansion in the pilot population allowed to fly fighter aircraft, there is a need to measure whole-body centers of gravity and moments of inertia of individuals to determine the safety of ejection seats for this broader population. An adjustable seating system has been developed by the Vulnerability Assessment Branch of Armstrong Laboratory (AL/CFBV) and Systems Research Laboratory (SRL) located at Wright-Patterson Air Force Base (WPAFB) which can be used to measure the center of gravity and moments of inertia of an individual about any of three orthogonal axes. The accuracy of the technique has been verified with the use of two 68 kg (150 lb) test specimens, and it has been approved for human use. Results for a 62.6 kg Caucasian male subject compare well with those found in the literature for a 5th percentile Caucasian male (65.2 kg/143.7 lb) (NASA, 1978).
Low Cost Pressure Gauges
Authors: Dann-Johnson Summer , Johnson Wayne , Luckham Mike , Marsh Kristen
Published: July 2023

A design of a pressure measurement device to be used in balloon esophageal dilatation which has a mass produced cost of less than $4.60 per unit was required. A project budget of $500.00 was allotted for prototype development and research expenses. Two designs, a mechanical device and an electronic device, were selected for prototype development. The prototypes were fabricated and tested for repeatability and accuracy.
A Computational Study of the Flow in Branching Channels and Tubes
Authors: Hassan Amgad A. , Evrensel Cahit A.
Published: July 2023

Turbulent flow through a 3-D bifurcating circular tube and 2-D rectangular channel are computed. In both cases, the bifurcating angle was 604dG and parent to daughter diameter (tube) and channel height ratios were 1.4. These values correspond to the physiological averages. The results showed flow separation in the daughter branch in both cases and relatively strong secondary flow for the bifurcating tube. Also, the average velocity at the exit of the daughter branch was relatively smaller than the main branch for the tube, while these values were comparable for the rectangular channel.
Computational Fluid Mechanical Simulation of the Spontaneous Deformation and Alignment of the Endothelial Cell Model Under Fluid Shear Stress
Authors: Yamamoto Yasuhito , Yamaguchi Takami
Published: July 2023

In our previous reports[1–3], using three dimensional computational fluid mechanical models of the endothelial cells under culture condition as well as under the flow condition on the arteriolar wall, we showed that there is strong dependence of the local wall shear stress (WSS) distribution on the cellular shape factors and the alignment. In the present study, a spontaneous random motion of the endothelial cells under culture condition was simulated, and it was shown that the modeled endothelial cells deformed and aligned to the direction to reduce the wall shear stress at the summit of the cells exerted by the flow.
Design of a Rate Controlled Indentor for In Vivo Analysis of Residual Limb Tissues
Authors: Pathak Arvind P. , Silver-Thorn M. Barbara
Published: July 2023

A tissue tester was designed to enable rate controlled indentation of the soft tissues of the residual limbs of below-knee (BK) amputees. Thus viscoelastic phenomena such as pre-conditioning, hysteresis and stress relaxation could be assessed. The tissue tester accommodates indentor excursions of 0–30 mm, performs indentations at rates from 0–5 mm/s, measures reaction forces up to 44 N, and accommodates multiple loading/unloading cycles. The tissue tester is controlled via a notebook personal computer which makes the entire test system portable and amenable for use in a clinical or research environment. The system output consists of force-displacement curves obtained during cyclic loading of the tissue at varying indentation rates at sites of clinical significance to BK prosthetic design. Indentation followed by force monitoring over a fixed time duration allows stress relaxation of the tissue to be assessed. The indentor positioning error (mean error less than 4.4%) is independent of indentor position and load, but dependent on indentation rate. Indentation rates are accurate to within 3% of the desired value and are independent of indentor position and load.
Poroelastic Model of Vertebral Trabecular Bone in the Uniaxial Stress Condition and Experimental Validation
Authors: Hong Jung Hwa , Lim Tae-Hong
Published: July 2023

The theory of poroelasticity that includes the fluid-solid coupled mechanical interactions has been used to study the effect of intraosseous fluid flow on mechanical behavior of trabecular bone. The unique time-dependent behavior and strain rate effect of trabecular bone have been modeled by using the poroelastic theory.1,2 Thus, its general mechanical behavior including the time-dependent and elastic behavior can be predicted using the poroelastic theory. In this study, a 2-D poroelastic model was developed to investigate the effect of strain rate input on mechanical behavior of trabecular bone from the poroelastic constitutive equations under the uniaxial stress condition at various strain rate inputs. Compression tests in the uniaxial stress condition at various strain rates were also performed using bovine vertebral trabecular bone specimens to validate the poroelastic model.
Genetic Strategies for Tissue Engineering
Authors: Morgan Jeffrey R.
Published: July 2023

Recent advances in molecular genetics have resulted in the development of new technologies for the introduction and expression of genes in human somatic cells. These gene transfer technologies have given rise to a potentially new field of medical treatment known as gene therapy. Gene therapy is broadly defined as the transfer of genetic material to cells or tissues in order to achieve a therapeutic effect for inherited as well as acquired diseases. We are exploring the potential application of gene transfer technologies to the field of tissue engineering and are interested in determining if genetic modification can be used to enhance the function and/or performance of cells used as or part of biological substitutes for the restoration, maintenance or improvement of tissue function. We believe that gene transfer technologies will be an important addition to the field of tissue engineering.
Evaluation of 3D Biphasic Finite Element Analysis of Diarthrodial Joint Contact Using Proximity Data
Authors: Dunbar William L. , Spilker Robert L.
Published: July 2023

The mechanical response of cartilage layers in diarthrodial joints to the loads that arise during joint articulation is a problem of contact mechanics. We model cartilage as a biphasic material [1], and use finite element methods to solve the governing differential equations and boundary conditions, including those for contact [2]. Two-dimensional (2D) finite element formulations for biphasic contact have been developed [3], but the complex three-dimensional (3D) contact problem has not yet been solved. We are investigating approximations to the 3D biphasic contact analysis which are computationally feasible and provide insights into the response of physiological tissue layers. The purpose of this study is to evaluate one such method in which the equal-and-opposite applied load distribution on contacting deformable tissue layers is based on the calculated overlap (penetration) between the tissue volumes when they are allowed to rigidly interpenetrate. Our intention is to apply this method to the analysis of diarthrodial joints, where the biphasic tissue layer geometry is obtained using stereophotogrammetry (SPG) [4]. Here we present our approach and evaluate the method using a canonical axisymmetric problem for which an independent biphasic contact solution can be obtained for comparison.
The Effects of Rotator Cuff Tears and the Long Head of the Biceps on Glenohumeral Kinematics
Authors: Wang Vincent M. , Mow Van C. , Raimondo Rick A. , Flatow Evan L.
Published: July 2023

The active restraints of the shoulder, namely the shoulder girdle muscles and tendons, provide the dynamic stability necessary for coordinated and purposeful movement of the upper extremity. Rotator cuff (RC) disease can result in pain, weakness and impaired shoulder function. In studying the pathomechanics of RC tears, an understanding of the biomechanical role of the tendon of the long head of the biceps (LHB) is important, since rupture of the LHB often accompanies RC tears.
A Finite Element Solution of Viscous Flow in Stenotic Elastic Tubes Under an External Pressure and Longitudinal Tension
Authors: Liu Biyue , Tang Dalin
Published: July 2023

Blood flow in collapsible tubes with stenosis has been studied by many authors (Shapiro, 1977; Ku et al, 1990). Tang (1995) introduced an axisymmetric model for viscous flow in stenotic elastic tubes subject to a prescribed traveling external pressure wave and found that the traveling pressure wave has considerable effect on the tube contractions and expansions which are directly related to tube collapsing and re-opening. In this paper, a finite element method is developed to solve a nonlinear mathematical model with free moving boundary to study the viscous flow in stenotic elastic tubes. The model improves Tang’s model (1995) by including the longitudinal tension in the tube law (Pedley, 1992) and revising the boundary conditions to include axial motion of the tube wall.
A Computational Approach for the Evaluation of Left Ventricular Inotropy Based on the Inertial Characterization of the Early Ejection Phase: Comparison With DP/DT
Authors: Redaelli Alberto , Montevecchi Franco Maria
Published: July 2023

This paper presents a computational study, based on a fluid-structure interaction approach. The aim is to investigate the efficacy of the intraventricular pressure drop (dp/dx) and of the first derivative of aortic flow rate (df/dt) as indexes of the left ventricular function by comparison with dp/dt.
Mathematical Modeling and Optimization of the Immobilized Metal Affinity Chromatography
Authors: Patwardhan Anshuman V. , Ataai Mohammad M. , Zenouzi Mansour
Published: July 2023

Immobilized copper affinity chromatography experiments with E. coli cell extract have demonstrated that the cellular proteins of this most commonly used host organism elute from the column in a discontinuous fashion characterized by two major peaks. This result has interesting implications towards the mathematical modeling and subsequent optimization of IMAC. Namely, the elution behavior of the E. coli cell extract can be approximately simulated by simply two representative proteins that have a similar elution behavior as that of the peaks.

We have identified the mixture of Bovine Serum Albumin and Tuna Heart Cytochrome-C to be excellent representatives of the E. coli cell extract. The equilibrium and transport parameters of these proteins were determined experimentally and used in a detailed mathematical model incorporating multicomponent Langmuir isotherm, axial dispersion, film mass transfer and intraparticle diffusion. Target proteins of varying affinities were also included in the model.

Simulation results provided an excellent framework for identifying effective strategies for optimal column utilization as well as for attaining high resolution of the target protein.
Effect of Composition and Damage on Tensile Properties of Chondrocyte Culture Tissue
Authors: Fedewa M. M. , Leo P. , Oegema T. R. , Lewis J. L.
Published: July 2023

Cartilage cracks and fibrillates during the disease osteoarthritis, suggesting material failure as an essential feature of the degradation process. Assumedly, something occurs during the early disease process in the tissue microstructure that makes the material strength lower than normal. The details of this alteration and how the tissue components are organized to carry load is poorly known for cartilage. The purpose of this research was to determine how tissue material properties are related to tissue composition and microstructure and how disease may alter these. Tissue was grown in culture by chondrocytes from young rabbits using several growing media and treatments, and then analyzed for biochemistry and mechanical properties. A theoretical composites material model was used to fit the prefailure data(1).
Mechanical Properties of Chondrocytes and Chondrons
Authors: Guilak Farshid , Ting-Beall H. Ping , Jones Wendy R. , Lee Greta M. , Hochmuth Robert M.
Published: July 2023

The mechanical environment of articular cartilage has a strong modulatory influence on the anabolic and catabolic activities of the chondrocyte. The precise mechanisms by which mechanical loading is transduced to an intracellular signal are not well understood, but are likely to involve the conversion of mechanical factors to other physical phenomena (e.g., osmotic or fluid pressure, electrokinetic effects, etc.). Thus the pericellular matrix, which is the anatomic region immediately surrounding the chondrocyte, may play a dominant role in the mechanical interaction between the chondrocyte and the extracellular matrix [1,2]. Further, the local mechanical environment may also depend on characteristics of the chondrocyte itself, such as cell shape, mechanical properties, and orientation relative to other cells [2]. Previous studies suggest that chondrocytes behave as a viscoelastic solid material [3], although little is currently known regarding the mechanical properties of the pericellular matrix. Recently, techniques have been developed which permit the isolation of viable chondrocytes within their pericellular matrix following enzymatic digestion of the tissue [4]. This entity, composed of single or multiple chondrocytes within a pericellular matrix, has been termed the chondron [1]. The goals of this study were to utilize micropipette aspiration techniques to characterize the mechanical behavior and properties of chondrocytes and of the tissue comprising chondrons (i.e., the pericellular matrix).
Hepatic Tissue Engineering
Authors: Toner Mehmet
Published: July 2023

Each year, approximately 5000 individuals in the United States develop severe enough hepatic failure to require hepatic support. Of these patients, approximately 2000 will undergo orthotopic liver transplantation, currently the only available method for the clinical management of severe hepatic failure. For patients who are not selected for transplantation, there is no adequate treatment available. Those suffering from cirrhosis fight the seventh-leading cause of death in the United States and those suffering from acute liver failure face a mortality of greater than 80%. Although the replacement of liver function using nonbiological, biological, and semibiological or hybrid approaches his been attempted by many investigators, no means for reliable liver replacement, other than organ transplantation, currently exists. One of the most promising approaches for restoring liver function involves the use of cultured hepatocytes that would be part of an extracorporeal device. For a successful extracorporeal device containing stable and functioning hepatocytes, several critical technologies need further development including techniques for (1) long-term hepatocyte culture and methods for reconstructing “in-vivo-like” liver tissue in vitro (2) hepatocyte cryopreservation, and (3) effect of plasma perfusion or in-vivo like fluids on hepatocytes. In this presentation, we will review some of our most recent progress in these three areas. The following is a brief summary.
Towards the Development of a Bioartificial Pancreas: Long-Term In Vitro Functions of Immunoisolated Mouse Insulinoma Cells
Authors: Sambanis Thanassis , Papas Klearchos K. , Long Robert C. , Constantinidis Ioannis
Published: July 2023

A promising method for the long-term treatment of diabetes mellitus consists of the implantation of a functional bioartificial construct containing insulin-secreting cells. Cells are isolated from the immune system of the host by encapsulation in a synthetic semipermeable membrane which allows passage of cellular nutrients and metabolites, including insulin, but excludes antibodies and cytotoxic cells of the host. The effectiveness of such implants in restoring normoglycemia has been repeatedly demonstrated in both small and large diabetic animal models. A limitation to the large-scale application of such implants is cell availability. We are thus investigating the development of stable, functional bioartificial constructs based on transformed insulin-secreting cells that can be amplified in culture thus relaxing the cell availability constrain.
Response of the Spine to Sinusoidal Vertical Vibration
Authors: Kong Wayne Z. , Goel Vijay K. , Wilder David G. , Pope Malcolm H.
Published: July 2023

A finite element model of the upper body was generated to predict the resonant frequency and response to sinusoidal vertical vibration. The model consisted of the lumbosacral spine modeled in detail, and the thorax and cervical spine simulated by beam-type elements. The head and internal organs of the thorax and abdominum were represented by mass elements. The resonant frequencies for vibration in the sagittal plane were extracted. The model was further used to study its response to the vertical vibration imposed at the sacrum and the effects of damping ratio. The first resonant frequency in the vertical direction was predicted as 7.91 Hz. The predicted transfer function was close to the measurements reported in the literature. Both magnitude and phase angle of transmissibility at the resonant frequency increased along the rastral direction. The vertical vibration imposed at the sacrum also caused significant A-P motion and rotation in the sagittal plane in the lumbar vertebrae. The attenuation of the spine to the imposed vibration increased with an increase in damping.
Insights Into the Formation and Characteristics of Leakage Flow Structures Through Bileaflet Mechanical Heart Valve Prostheses
Authors: Ellis Jeffrey T. , Healy Timothy M. , Fontaine Arnold A. , Saxena Rahul , Yoganathan Ajit P.
Published: July 2023

The design of bileaflet prosthetic heart valves deliberately includes some degree of retrograde flow upon valve closure. This reverse flow is intended to “wash out” the hinges of the valve and the areas between leaflet edges and the housing, in principle preventing areas of flow stasis and inhibiting thrombus formation. The speed, direction, and turbulent nature of retrograde flow structures are influenced by the geometry of the hinge which is unique to a given valve design. Typically, the retrograde flow can be classified into two primary events. One is the closure, or “squeeze” flow which occurs because of the onset of an adverse pressure gradient. As the leaflets close in response to this increasing adverse pressure gradient, blood continues to squeeze through the decreasing flow area between the leaflets and in the region between the leaflets and valve housing. Once the valve is closed, the second retrograde flow, the leakage jets, issue from small gaps between the leaflet edges and valve housing, and from the leaflet hinges. Due to the large pressure gradient initially present during valve closure, the leakage jets can be high velocity flows. The closing flow and leakage jets can cause damage to formed blood elements due to high levels of turbulent shear stress. The spatial structure and temporal behavior of these retrograde flow fields have not been previously characterized in great detail. Of particular concern is how these flows may be implicated in blood element damage and how their formation is affected by valve hinge geometry.
Oxygen Mass Transfer in a Stenosis: Effects of Blood-Wall Coupling
Authors: Moore J. A. , Ethier C. Ross , Kaazempur-Mofrad M.
Published: July 2023

Motivation: Arterial transport of blood-borne materials is essential for maintenance of normal arterial wall physiology. Disturbed transport of such materials, due for example to altered hemodynamic patterns caused by local geometric factors, may be linked to the pathogenesis of vascular diseases. A species which is of major interest is oxygen, since it is an important cellular metabolite. Abnormalities in arterial wall oxygen tension have been implicated in the formation of atherosclerotic lesions [5], and may also be linked to intimal hyperplasia [3]. Here we numerically model the transport of oxygen in blood and the arterial wall, taking into account oxygen consumption by cells in the artery wall, coupling of transport between blood and the wall, and the nonlinear oxygen binding properties of hemoglobin.
Analysis of the Stresses and Strains in UHMWPE Components for Total Joint Replacement After Chemical and Mechanical Degradation
Authors: Kurtz Steven M. , Bartel Donald L. , Rimnac Clare M.
Published: July 2023

The purpose of this study was to investigate the combined effects of chemical and mechanical degradation on the stresses in a conforming tibial component. A material model was developed to predict the large-deformation response of degraded UHMWPE as a function of density and cyclic stress. The finite element method was used to determine the stresses due to contact. Forty-five months of simulated degradation was found to increase the stresses associated with surface damage by 12–18%.
Contouring of Spine Implants: A Novel Approach Based on Surgical Navigation Techniques
Authors: Nolte Lutz P. , Liebschner Michael , Bourquin Yvan , Visarius Heiko
Published: July 2023

An often difficult and time-consuming factor inherent to various types of orthopaedic surgery is the contouring of longitudinal fixation devices, e.g. spinal implant rods or fracture fixation plates. These devices need to be bent during surgery to fit geometrical boundary conditions set by the individual anatomy/pathology as well as other components of the implant construct. This may be exemplified by spinal rods to be fit into the pattern set by the pedicle screws inserted as anchors. Inadequate contouring might lead to loosening or failure of associated implant components and/or question surgical outcome. Corrections after improper bending are difficult. Excessive rod bending might significantly alter the implant’s material properties and may cause fatigue failures.
Relation Between the Structural Asymmetry of Coronary Artery Branches and the Angle at Their Origin
Authors: Friedman Morton H. , Ding Zhaohua
Published: July 2023

The relationship between the geometry of branch points on the left anterior descending coronary artery, and the morphometry of the proximal portions of the daughter vessels, was examined. The geometry at 23 branch points on 15 human hearts was derived from multiplane contrast angiograms, and the histology at 28 sites along the daughter vessels was obtained from transverse sections using computerized techniques. The angle of the branch at which the daughter originated was positively correlated with the maximum thicknesses of the intima and media, and with their circumferential asymmetry. The results suggest that large branch angles may favor eccentric intimal thickening, a morphological entity which is thought to be predisposed to lipid accumulation and atherosclerosis.
Biomechanical Analysis of the C1-C2 Transarticular Screw Fixation Technique
Authors: DiAngelo Denis J. , Jansen Thomas H. , Eckstein Eugene C. , Dull Scott T. , Foley Kevin T.
Published: July 2023

Transarticular screw fixation (TASF) is an accepted surgical treatment for pathologic C1-C2 instability due to trauma, ligamentous laxity or degenerative disorders. Previous biomechanical tests have found C1-C2 TASF with a posterior graft to have increased rotational and shear stiffness, as compared with posterior wiring techniques. A complete mechanical analysis of the C1-C2 TASF construct was performed to determine the primary mode of loading. The greatest stress placed on the fixated C1-C2 motion segment was a bending stress developed during flexion and extension.
Influence of Vasoactive Drugs on Wall Shear Stress Distribution in a Compliant Aortic Bifurcation Model
Authors: Lee C. S. , Tarbell John M.
Published: July 2023

The present study compares wall shear rate distributions in a compliant aortic bifurcation model under different hemodynamic states: normal condition, Angiotensin II infusion (vasoconstrictor), and Isoproterenol infusion (vasodilator). The abdominal aortic flow waveforms corresponding to each state were generated in an in vitro flow loop with proper control of wall motion and phase angle between pressure and flow waveforms. The photochromic technique was employed to measure wall shear rates on the moving wall. A low shear stress zone was observed on the outer wall from 5 mm to 15 mm distal to the curvature site. The distribution of wall shear rate was found to be different for the three hemodynamic states simulated in the present study indicating that vasoactive drugs can alter the near wall fluid dynamic environment in the bifurcation.
Stress-Growth Relationships in the Developing Rabbit Distal Femur
Authors: Lerner Amy L. , Kuhn Janet L. , Hollister Scott J.
Published: July 2023

Several pediatric orthopaedic conditions appear to be related to mechanical influences on bone growth. In this study we tested the hypothesis that there is a relationship between bone growth rates and mechanical stresses which are present in the growth plate during normal development. The model selected was the rabbit distal femur, which exhibits a dramatic growth plate curvature resulting from variations in bone growth rates.
A Model of the Artificial Knee for Computer Assisted Functional Planning in Total Knee Replacement
Authors: Martelli Sandra , Marcacci Maurilio , Ellis Randy , Zaffagnini Stefano
Published: July 2023

Long term results of Total Knee Replacement (TKR) are highly dependent on the balance and positioning of the implant. The preoperative planning for a correct TKR positioning is based on the ideal adaptation of shape and kinematics of the prosthesis to the individual features of the patient.
Computational Biomechanics of Artificial Ligament and Tendons: A Finite Element Analysis
Authors: Chu Tai-Ming , Sokol Mroslaw
Published: July 2023

Reconstruction of the Anterior Cruciate Ligament (ACL) has been a major focus in sports medicine over twenty years. Severe or un-repairable damage of the ACL due to sport injury is a major problem faced by orthopedic surgeons and engineers. In order to replace or reconstruct an injured ACL, the mechanical properties as well as the dimensional limitation of the material used must be similar to the biological ligaments. Although excessive literature describes experimental investigation on the mechanical property and clinical application of the ligament material, there are little analytical studies that describe strains, stresses, and endurance in the bone/ligament/bone complex. The Finite Element Analysis (FEA) is a method to study this problem. The objectives of the present investigation are (1) developing a finite element model (FEM) of an artificial ligament yarn, the emphasis is put on the development of the elastic FEM, and (2) analyzing stress distribution in the ligament yarn fibers due to various loading conditions and design parameters. Results obtained from the FEM of the ACL prosthesis yarn are confirmed by experimental measurements using tensile test.
Physical Properties of a New Orthopaedic Supporting Material for Posture Control in Chairs and Beds
Authors: Chang J. K. L. , Lao M. T. , Tao X. M.
Published: July 2023

The prevalence of back discomfort has prompted the search for better orthopaedic supporting material in chairs and beds. A new warp-knit fabric has been developed to provide orthopaedic sleeping support without using traditional box-spring or spring-in-mattress devices. Described in an US patent [1] by one of the authors, J.K.L. Chang, the fabric is warp knitted with a lock-knit stitch with a laid-in yarn, using three guide bars with nylon and elastic yarns. As shown in Figure 1, if a pressure is exerted on any single loop which is only 0.5 mm2 in area, the pressure will be passed to the 11 neighbouring yarns, then further propagated via other adjacent yarns to a much larger area.

This fabric has also been used in chairs. The fabric is stretched over the frame of a chair under different tensions along the length of the chair body so that it gives a contour fit to the person’s body, and put tension on the lumbar and raise the knee higher than the buttock to put the person in a good sitting posture.

A clinic trial has been carried out involving three nursing homes, two institutions and eight individuals in USA. It has been observed that the fabric structure and this mechanism of “de-localising pressure” make people, sitting or sleeping on this supporting system, feel comfortable, with reduced pain and reduced chance of getting back sores.

Experiments are being conducted in order to study relevant physical properties of the fabric related to the results of the clinical trial. Results from these tests will be presented including static and dynamic tensile properties, bending, shear, lateral compression and surface properties, air-permeability, thermal properties and flammability of the fabric. Comparison will be made between the supporting system made from the fabric and that from artificial leather/foam system.

A prototype chair will be demonstrated during the conference.
Fatigue Failure Prediction in the Polyethylene Component of a Total Knee Replacement Based on Cyclic Rolling
Authors: Natarajan R. N. , Andriacchi T. P. , Beard B. J. , Amirouche F. M. L.
Published: July 2023

As the knee flexes, the contact moves from anterior to posterior position. This process involves the initiation and stopping of rolling. As a result, tractive forces are generated at the tibio-femoral articulation (1). While several studies have addressed the issue of a cyclically moving load (2,3), the effect of the tractive rolling force on stresses in polyethylene was not studied.
The Role of Proteoglycans in the Frictional Properties and Normal Stress Effect of Articular Cartilage
Authors: Wang L. H. , Ateshian G. A. , Saed-Nejad F. , Ratcliffe A.
Published: July 2023

Articular cartilage, comprising the sliding surfaces of diarthrodial joint, produces very low friction coefficients and has excellent wear properties. Understanding the lubrication of diarthrodial joints has been an important objective in the field of biomechanics since the early part of this century. But not until the 60s has the role of cartilage in joint lubrication been specifically investigated in parallel with the development of cartilage mechanics. The role of cartilage in joint lubrication includes the time, velocity, and load dependence of cartilage friction (McCutchen, 1962; Malcom 1967; Wright and Dowson, 1967); furthermore, in our own recent investigations, it has been observed that cartilage exhibits a very significant normal stress effect under steady frictional shear (Wang and Ateshian, 1995). Furthermore, it was observed that the normal stress effect persists even after removal of the surface zone (Wang and Ateshian, 1996), demonstrating that this effect is attributable to intrinsic properties of the cartilage rather than a boundary lubricant adsorbed to the surface. Following these studies, it was hypothesized that the normal stress effect is related to the proteoglycans present in the tissue, since Theological studies of proteoglycan solutions (Zhu et al., 1991) have been shown to exhibit a normal stress under steady shear; hence it is possible that proteoglycans in the tissue matrix impart to the interstitial fluid a non-Newtonian behavior which is responsible for the observed normal stresses. Therefore, the goal of this study was to determine the effect of specific removal of glycosaminoglycan chains on the normal stress.
Rolling Resistance of Articular Cartilage due to Interstitial Fluid Flow
Authors: Ateshian Gerard A. , Wang Huiqun
Published: July 2023

The typical frictional coefficients reported for articular cartilage are in the range of 0.002–0.15 or greater [1,2,3]. The excellent lubrication and wear characteristics of cartilage have been attributed to various mechanisms which consider the interfacial shear stress that arises at the surfaces of articulating cartilage layers to be the primary mechanism of friction in joints. A secondary mechanism which may contribute to the frictional coefficient of joints is the rolling resistance due to the hysteretic energy loss of viscoelastic cartilage, as has been shown for engineering bearings made of viscoelastic materials [4,5]. In cartilage, the primary viscoelastic response of the tissue is believed to be caused by the flow of interstitial fluid relative to the solid phase [6].
Effect of Component Placement on the Patellofemoral Joint After Total Knee Arthroplasty
Authors: Zhang Anna X. , Miller Mark C. , Berger Richard A. , Sherwood Christopher P. , Petrella Anthony J. , Rubash Harry E.
Published: July 2023

Seven human cadaveric specimens were tested on a knee simulator to study the effect of femoral component external rotation and patellar component medialization on the patellofemoral joint after total knee arthroplasty. The femoral component was externally rotated by 0°, 2.5°, and 5°, and the patellar component was positioned at the geometric center and 3.7mm medial to the geometric center. Only one of the specimens subluxed. Medialization of the patellar component was found to decrease the lateral force on the patella and increase the lateral tilt of the patella. The external rotation of the femoral component had a complicated interaction with the patella, and the overall effect was less obvious. Neither the femoral component rotation nor the patellar component medialization had a large effect on the normal patellofemoral forces.
Effects of Arterial Hemodynamics and Cyclic Strain on Platelet Deposition to Human Saphenous Vein Segments Perfused Ex-Vivo
Authors: Severyn Donald A. , Muluk Satish C. , Vorp David A.
Published: July 2023

The greater saphenous vein, extending from the ankle to the groin along the medial side of either leg, is commonly used as a bypass conduit to reroute blood around blockages in both the coronary and peripheral arterial systems. Unfortunately, saphenous vein grafts often fail requiring re-operation. For example, one review found failure in 8–30% of the coronary artery vein grafts 30 days following surgery (von Segesser, 1990). While intimal hyperplasia accounts for the majority of long-term failures, occlusion of the bypass grafts during the first month is primarily due to thrombosis (Cox et al., 1991).
A Transient Three-Dimensional Model of Micro Heat Pipes Used As an Integral Part of Semiconductor Devices
Authors: Huang X. Y. , Liu C. Y. , Toh K. C.
Published: July 2023

An analytical model is presented in this paper to simulate the transient temperature changes on a semiconductor device integrated with an array of micro heat pipes in response to the switch-on of a heat source inside the device. Effect of the embedded micro heat pipes is taken into account by assuming that the silicon wafer has a higher thermal conductivity in the direction of the heat pipe array than that in other two directions. Analytical solutions are obtained for various combinations of the heat sources and sinks, and a good agreement is shown by comparing the present solutions with the numerical results in the published paper.
Infrared Imaging Using Microcantilevers
Authors: Oden Patrick I. , Datskos Panos G. , Thundat Thomas G. , Wachter Eric A. , Warmack Robert J.
Published: July 2023

A micromechanical detector using microcantilever for infrared (IR) radiation is demonstrated. Because of their small size and low thermal mass, these microcantilever IR detectors are promising new family of IR sensors. This novel IR sensor is based on deflection due to IR adsorption induced thermal stress on a bimaterial cantilever which can be monitored with several methods such as optical deflection or piezoresistive. When laser-deflection-monitored Si4N4 microcantilevers coated with a 40nm thick coating of gold were irradiated by a low-power diode laser, the noise equivalent power and specific detectivity, NEP and D* were found to be 173pW/Hz and 7.18 × 108cmHz/W, respectively, when compensation for the laser reflectivity was made.
Computation of Supersonic Flow for Thin Film Deposition Using Expansion Through a Skimmer
Authors: Boyd Iain D. , Chen Gang
Published: July 2023

Deposition of silicon films through seeding of disilane molecules in a supersonic beam of molecular hydrogen is modeled using the direct simulation Monte Carlo technique. In this process, the beam is formed by rapid expansion of the heated gas through an orifice of diameter 250 μm and then through a skimmer. Application of the numerical method to model the gas dynamics of this process is discussed with reference to a number of simulation issues. Description is made of a parallelized implementation of the Monte Carlo method that enables computation of these geometrically complex, nonequilibrium flows. Results are presented for a representative system configuration. General features of the flow field are described. Detailed information is provided by the simulations on the properties of the disilane molecules as they impact at hyperthermal energies on the substrate surface. Comparison of the numerical results with available experimental data reveals good agreement offering the potential to optimize the deposition process using the Monte Carlo method as a design tool.
Flow Behavior Through Microfluidic Valves
Authors: Jiang X. N. , Zhou Z. Y. , Li Y. , Yang Y. , Ye X. Y.
Published: July 2023

Microvalves are the important components in the microfluid control systems. The flow behavior through two major types of silicon microvalves, with and without moving parts inside, were discussed in this paper. The silicon valves with different flexible flaps and the silicon nozzle/diffuser elements were designed and fabricated for the experimental research. The regression curve of the measurement results of the micro flap valve with the out port size of 200 × 200μm agree with the theoretical analytical model well. The flow coefficients through silicon nozzle/diffuser elements with the conical angle in width of 5°, 7.5° and 10° and the length of 3 mm as well as the relation between the flow resistance ratio of nozzle to diffuser and the geometric parameters were obtained.
The Impact of Design and Fabrication on the Dynamic Behavior of a Micro-Turbine
Authors: Wiegele Thomas G.
Published: July 2023

Four different micro-turbine designs were fabricated using the LIGA process in conjunction with a hermetic sealing operation. Each was characterized in terms of start-up velocity, operating velocity, peak velocity, efficiency and orientation by varying flowrates and pressures while measuring the angular velocity of the rotor. Measured data indicated that the distance between the rotor and the cover was the most significant determinant of performance. Design factors, such as turbine blade shape and stator design, were also significant.
Application of B.E.M. to Predict the Efficiency of Two Micro-Machines With Rigid Tails
Authors: Nasseri S. , Phan-Thien N.
Published: July 2023

This paper reports on the results of investigation of the swimming of two different micro-machines. Mechanically each of these micro-machines consists of a head (containing an electromechanical power source) and a tail which moves relative to the head as a rigid body. The problem is approached theoretically by considering the types of movement which can occur for these micro-machines immersed in a viscous medium. The first micro-machine has a tail which oscillates in vertical plane, therefore the trajectory of this machine is in that plane too. The tail of the second micro-machine rotates conically, so it produces a three dimensional helical path in space with its axis approximately along the direction of tail centreline.

Using the boundary element method for solving the traction equations on the surface of the tail, and a time dependent Euler kinematic scheme to plot the path, the translational velocity, angular velocity and the trajectory of each machine are calculated. Evaluation of the path and the direction of motion for each micro-machine using different dimensional parameters can give an idea of the efficiency for such machines with rigid tails.
Micromanipulation Using Distributed Electromagnetic Actuators
Authors: Inoue Tadanobu , Hamasaki Yukio , Shimoyama Isao , Miura Hirofumi
Published: July 2023

A method of micromanipulation using a microcoil array is proposed. Active coils drive permanent magnets on a work platform. The magnets can push mechanical parts to perform 2-dimensional assembly. Three-dimensional operation may be achieved from 2D magnet motion when the permanent magnets are parts of a closed loop spatial linkage. Manipulation on a 4 cm × 4 cm coil array was tested, and based on this large scale experiment, we fabricated a microcoil array using IC-based processes. A 4 × 4 microcoil array with 8 turns per coil was fabricated. The chip area, including bonding pads, is 3.6 mm × 3.6 mm. The minimum current necessary to attract a magnet and its speed were measured. A 0.6 mm × 0.6 mm × 0.3 mm magnet was found to move at 79 mm/s. The top speed for a magnet to follow a square trajectory was also measured. It was demonstrated that a 1.1 mg magnet could push a 13.4 mg object out of the microcoil array.
Membrane Micromotors Based on Piezoelectric Properties of PVDF Polymer Films
Authors: Jian Zhang , Shen De Xin , Wang Wei Yuan
Published: July 2023

A new type of micromotors, which employed piezoelectric polymer films, polyvinylidence fluoride (PVDF), had been fabricated. The polymer films with thickness 45μm, poling along thickness direction had been used with piezoelectric constant d33 = 19 to 22pcN−1. Aluminum had been evaporated on both faces of the films as electrode plates. The stators were formed by bonding PVDF films to brass diaphragms. The diaphragm thickness was 300μm. The upper-electrode pattern was formed by wet etching. The excitation principle of piezoelectric ultrasonic micromotors was discussed and the vibrational modes existing in stators were analysed in order to design the stators reasonably. A prototype micromotor was obtained by using small tin balls as rotors. Applied voltage 10V. the maximum value of rotation speed was about 14rpm. According to Hertz contact theory, the maximum pressure which the loads pressed on the vibrators had been calculated and compared with the experimental results. The difference of the rotation speed was contributed to the difference of the pressure. Additionally, a 100 hours continuous test showed that the characteristics of the micromotors had no obvious drop.
Measurement of Mechanical Properties of Electroplated Nickel-Iron Alloys
Authors: Chung Charles C. , Allen Mark G.
Published: July 2023

Electroplated materials often have mechanical properties that differ from their bulk counterparts. A microfabricated test device has been made to measure the Young’s and shear modulus of electroplated 80/20 nickel-iron (NiFe) in-situ for micro-electromechanical devices. The effective Young’s modulus was calculated to be E = 65GPa, which differs substantially from bulk NiFe with a E = 210GPa. The shear modulus was found to be G = 44GPa ± 15GPa which differs from the bulk shear modulus G = 80GPa.
A Viscoelastic Continuum Damage Model for Polymeric Composites
Authors: Abdel-Tawab Khaled I. , Weitsman Y. Jack
Published: July 2023

A comprehensive thermodynamic framework is proposed for modeling the behavior of polymeric composites exhibiting viscoelasticity, damage and permanent deformation. In the present formulation, the total strain is decomposed into viscoelastic and permanent components. The effect of damage on the constitutive behavior is introduced through direct coupling between damage and the internal state variables representing deformation of the undamaged (virgin) material. This approach accounts for time-dependent damage as well as damage-induced changes in material symmetry. The proposed constitutive model is applied to experimental data for swirl-mat polymeric composites.
Evaluation of Fracture Processes in Cement-Based Materials Under Compression Using Computer Vision
Authors: Choi Sokhwan , Shah Surendra P.
Published: July 2023

The heterogeneous nature of concrete requires a robust deformation measuring method to obtain a reliable information about the failure process of concrete. A non-destructive displacement evaluation system utilizing a image correlation scheme, often called computer vision, is developed to examined fracture process in cement-based materials. The technique is a full-field measuring method which gives an accuracy within the micron range. Displacement arrow diagrams or displacement contour maps reveal highly nonuniform deformations even at the early loading stages. The laboratory study shows that the technique has a potential for field application.
Stress-Strain Relationships of Open-Cell Foams
Authors: Todd Beth A. , Smith S. Leeann , Bunn Tera S.
Published: July 2023

Open-cell foams provide cushioning and precise positioning in medical applications. To design cushions and supporting surfaces with these types of foams, a thorough understanding of the foam material properties, such as the elastic tangent modulus, is needed. While these foam materials do not have the same type of stress-strain relationship as more traditional engineering materials, this relationship can be determined.

Four types of foam material were tested according to the ASTM D-3574-91, “Standard Methods of Testing Flexible Cellular Materials-Slab, Bonded and Molded Urethane Foams”. The variation in stiffness among the materials was approximately an order of magnitude.

The stress-strain relationships for all of the materials began with a linear region at small strains followed by a non-linear region at higher strains. The polyurethane materials also contained a linear transitional region which exhibited a reduced stiffness. The effect of applying a liquid proof coating to the foam was also investigated.