bluuebunny/crossref_metadata_2025 huggingface dataset:
The Dynamics of Particle Formation During SiH4:O2 Chemical Vapor Deposition: Implications for Materials Processing
Authors: Whitby Evan , Hoshino Masakazu , Ikegawa Masato
Published: July 2023

Particle size distributions were measured at a height 2 cm above a heated wafer in a chemical vapor deposition reactor, in the pressure range, P, of 650 < P < 3250 Pa, and compared with size distributions calculated with a two-dimensional numerical model that simulates fluid flow, heat transfer, chemical reactions, and particle formation, transport, and deposition. Both the measurements and the numerical simulations show that the particle number concentration at a height of 2 cm is proportional to P9 in the pressure range of 650 < P < 1950 Pa. A key result from this work is that at low pressures, cluster sticking coefficients strongly control the rate of cluster formation, and therefore the rate of particle formation.
A Numerical and Experimental Investigation of Morphology Development in Straight and Folded Molten Fibers During Melt Processing
Authors: Zhang D. F. , Liu Y. H. , Zumbrunnen D. A.
Published: July 2023

The morphological evolution of straight and folded molten fibers in shear flows was investigated systematically. Folded fibers were of interest since folding may occur during melt processing and since folded fibers resemble portions of more complex extended structures in melts subjected to chaotic mixing conditions. Shear flows represent local flow conditions within actual mixing cavities, continuous mixers, and extruders. A general three-dimensional numerical model of the time-dependent fluid flows within the minor phase (i.e., fiber) and major phase (i.e., the matrix) was developed. Interactions between the minor and major phase fluids via fully dynamical, three-dimensional interfaces were considered. The relation of morphological changes to the fibers, including break up, were disclosed. Numerical results were supplemented with micrographs of solidified polymeric fibers and sheets produced within a recently developed mixing cavity where mixing occurred due to chaotic advection.
Finite Element Analysis of the Advanced Photo System Bubble Spring Head/Film Interface
Authors: Haugh Donald J. , Brewen Alan T.
Published: July 2023

This paper describes the finite element model used to predict the spacing and contact pressure in an Advanced Photo System head/film interface. The particular interface analyzed was developed for use in photofinishing applications and is commonly referred to as a bubble spring interface, named after the flexure-like thin metal strip used to push the film against the magnetic head. The model results are validated by comparing predictions to measurements of the spring load-deflection profile and interferometrically measured head-to-film spacing contours. In addition, the model’s capability is demonstrated by using it to assess performance sensitivity to variations in spring load, head/film penetration, and film curl.
Experimental Characterization of Air Entrainment During High Speed Web Winding
Authors: Keshavan M. B. , Wickert J. A.
Published: July 2023

As a web is wound at speed onto a spool or roll, a thin layer of air becomes entrapped between the incoming web stream and the roll. The spiral-shaped air bearing which results separates adjacent web layers and can extend many wraps into the roll. The air entrained during the winding process increases the propensity for interlayer slippage, stack shifting, damage to the edges of the web, and non-uniform internal stresses. A new technique is discussed for measuring the film thickness of the entrained air layers during the winding process, and parameter studies quantify the effects of such winding variables as tension, transport speed, and surface roughness. With a view towards evaluating different web transport designs and operating conditions, three measures of air entrainment are discussed: (i) the cumulative thickness of all air layers, (ii) the thickness of the outermost air layer at the nip, and (iii) the rate at which air bleeds from the wound roll once it is brought to rest.
Control System Design for High-Speed Low-Tension Tape Transport
Authors: Mathur Priyadarshee D. , Messner William C.
Published: July 2023

This paper describes the entire process of control system design for a prototype high-speed, low-tension tape transport system. The speed and tension of the tape are regulated by controlling the relative displacement of the supply and take-up reels. The system is slowly time varying from changing reel packs, and is difficult to model because the spring constant of the tape depends on the operating speed and tension due to air entrainment in the take-up reel. In this paper, an iterative multi-input multi-output controller design approach is presented where a low performance controller is first designed to enable system identification around the desired operating speed and tension of the transport. The frequency response data is then used to design a fast settling controller. An adaptive ripple cancellation scheme for better tension regulation is demonstrated. Failure detection mechanisms and recovery algorithms that reduce the probability of tape damage are described.
Shock Fragility of Spindle Motors in Hard Drives
Authors: Salehizadeh Hamid
Published: July 2023

The susceptibility of spindle motor ball bearings in disk drives to axial shock is considered in this paper. When a hard drive is subjected to an axial shock, the spindle disk pack is excited axially and the ensuing vibrations lead to dynamic forces. Should the maximum force endured by the bearings exceed their rated carrying capacity, permanent bearing damage will take place at the ball/race interface which manifests itself in higher vibration and acoustic levels.

To estimate the dynamic bearing force and the shock fragility of a given drive, it is imperative to solve for the vibration of the drive when subjected to shock. This was achieved in the present work by simplifying the dynamics of a hard drive to that of a two degree of freedom mass-spring system. The equivalent mass and stiffness values were obtained by matching the modal frequencies of the 2 DOF model to those of the disk pack. The response of the model to axial shock was next obtained by numerical integration using the Runge-Kutta method. The non-linear bearing stiffness was incorporated using the Hertzian equations in the model. To validate the model, the response of a hard drive to axial shock was measured using an accelerometer mounted on the motor hub. Excellent agreement was obtained between calculated response and experimentally measured motor hub vibration. Having verified the model, the calculated maximum bearing force was used to estimate the drive’s shock threshold. It was found that base casting stiffness and damping play an important role in the dynamic amplification of the bearing force.
A System for Image Guided Computer Assisted Hip Surgery
Authors: Langlotz Frank , Stucki Manfred , Nolte Lutz P. , Gong Jianxing
Published: July 2023

The term periacetabular osteotomy (PAO) refers to a surgical intervention that attempts to correct dysplasia of the hip joint, particularly malposition of the acetabular roof which causes insufficient coverage of the femoral head. The procedure, as performed in Bern, consists of several osteotomies of the pubis, ischium, and ilium and a re-orientation of the acetabular fragment with subsequent fixation. Various solutions exist for a preoperative determination of the optimal re-orientation of the acetabular cup (Barrance et al., 1995, Klaue et al., 1988, Murphy et al., 1990). However, it has not been possible to apply the planning parameters accurately during the operation. In addition, some of the osteotomies have to be performed without direct visual access to the surgical object due to limitations in the anatomy and exposure. Consequently, there is potential to endanger the hip joint and surrounding structures. It is hypothesized that a combination of accurate 3D-motion tracking together with image interactive navigation may establish a link between surgical planning and execution. To our knowledge, this study introduces for the first time an operation-system for PAO that bridges surgical planning, secure intraoperative navigation during the osteotomies, and exact guidance during the re-orientation in accordance with a preoperative planning.
Transient Cavitation and Associated Shock Wave Generation Near a Stone Surface During Electrohydraulic Lithotripsy
Authors: Tong H. L. , Zhong P. , Cocks F. H. , Preminger G. M.
Published: July 2023

Electrohydraulic lithotripsy (EHL), utilizing spark-induced shock waves for stone comminution, is a common treatment modality for kidney and ureteral stones1–2. During EHL, a spark discharge at the tip of a small probe introduced endoscopically produces a vapor plasma and subsequently a cavitation bubble near the stone surface. Although it is believed that shock waves are generated by the expansion of the vapor plasma and the collapse of the cavitation bubble, the dynamics of this physical process has not been well understood3. In this study, hiqh-speed photography and acoustic measurement were used to characterize the transient cavitation bubble oscillation and associated shock wave generation during EHL.
Effects of Tissue Mimicking Material on Transient Cavitation Produced During Extracorporeal Shock Wave Lithotripsy
Authors: Cioanta I. , Zhong P. , Cocks F. H. , Preminger G. M.
Published: July 2023

Extracorporeal shock wave lithotripsy (ESWL) is a widely used treatment modality for kidney and ureteral stones1. Recent studies have shown that transient cavitation induced by the tensile components of the lithotripsy shock waves is a primary mechanism for both stone fragmentation and tissue injury2. Thus, the ability to detect and monitor the cavitation activity during ESWL is important to ensure the effectiveness and the safety of the treatment. In this study, we have used acoustic emission measurement and high-speed photography to assess the transient cavitation generated during ESWL. The effects of tissue mimicking material on ESWL-induced cavitation activity was examined.
Validation and Accuracy Assessment of the Micropipet Piconewton Force Transducer
Authors: Chesla Scott E. , Zhu Cheng
Published: July 2023

In processes that involve interactions of the cell with its environment, adhesion is often the initiating event for a particular cellular function. Adhesion assays are thus among the first to be used to characterize the essential molecular complexes involved. Recently, increasing attention has been focused on single molecular binding between a particular cellular receptor class and its ligand. Elucidation of the forces involved in single bonds can lead to better understanding of how cells deal with their environment via controlling the specificity and strength of their adhesions.
Finite Element Analysis of Pulsatile Flow in the Abdominal Aorta Under Resting and Exercise Conditions
Authors: Taylor Charles A. , Hughes Thomas J. R. , Zarins Christopher K.
Published: July 2023

It is hypothesized that the beneficial effect of exercise in retarding the progression of cardiovascular disease is due, at least in part, to the elimination of adverse hemodynamic conditions including high particle residence time and low wall shear stress [1]. In-vitro and in-vivo investigations have provided limited qualitative information on flow patterns in the abdominal aorta and the effect of exercise on eliminating adverse hemodynamic conditions [2]. A computer model of a normal human abdominal aorta was created to simulate aortic blood flow under rest and graded exercise, pulsatile, flow conditions. Flow patterns, wall shear stress and particle residence time were computed in the lesion-prone infrarenal aorta and the effect of exercise determined.
A Mathematical Model of Nonlinear Viscoelastic Materials
Authors: Song Gong , Todd Beth A.
Published: July 2023

A mathematical model has been developed for nonlinear viscoelastic material under constant one dimensional stress. The mathematical proof is given that the creep and recovery function of nonlinear viscoelastic material can be expressed as the infinite sum of the creep and recovery functions from the Burgers model. Based on the result, the relationship between strain and stress under constant stress is given.
Kinematics of the Knee Joint in Deep Flexion: An X-Ray Study
Authors: Kelly Brian P. , Hefzy Mohamed Samir , Cooke Derek T. D. V. , Harrison Laurie A.
Published: July 2023

There are design limitations of about 140 degrees of knee flexion on existing knee prostheses (Scuderi, et al., 1989). This represents a functional deficit, especially in the Middle East and other populations that have social and cultural requirements for squatting and kneeling. In order to develop new artificial joints that will allow for a larger range of motion, more needs to be understood about how normal knees work. The data available in the literature that describe knee mechanics is limited in that information for flexion past 140° is not available (O’Connor and Zavatsky, 1990). The purpose of this study is to evaluate normal knees, past 140° of flexion, using radiographs.
A New Structural Model for Vertebral Trabecular Bone and Preliminary Applications to the Study of Osteoporosis
Authors: Overaker David W. , Cuitiño Alberto M. , Langrana Noshir A. , Zimmerman Mark C.
Published: July 2023

The symmetry of trabecular bone architecture depends on the loading environment. The vertebrae of the spine are loaded primarily in one direction (axial), so that the trabecular bone often develops into a symmetric arrangement of vertical columns with reinforcing horizontal struts[1, 2, 3]. A considerable amount of research has been done to quantify the effects of ageing and osteoporosis on the trabecular architecture[2, 4]. All have observed the same trend: trabecular thickness and density decrease with age. The horizontal trabecular thickness and density values decrease more rapidly than those of the vertical trabeculae. Also, vertical trabeculae are always thicker and more dense than horizontal trabeculae.
The Compressive Creep Behavior of the Porcine Intervertebral Disc Is Affected by Frozen Storage
Authors: Bass Elisa C. , Duncan Neil A. , Hariharan Jayaram S. , Lotz Jeffrey C.
Published: July 2023

The mechanical properties of the intact intervertebral disc may change if the specimen has been frozen prior to testing. Previous studies of various tissues and of the time-independent behavior of the intact disc have yielded conflicting results. The effect of frozen storage on the time-dependent behavior of the intact disc has not been investigated. We measured the displacement vs. time response of fresh and fresh-frozen intact IVDs subjected to repeated cycles of compressive creep and relaxation, and analyzed the results using a 3-parameter fluid transport model. Frozen storage dramatically affected the time-dependent behavior of the disc in compression, and permanent damage to the disc is indicated.
Non-Contact Evaluation of In-Situ Surface Strain Distribution of the Anterior Cruciate Ligament
Authors: Runco Thomas J. , Sakane Masataka , Woo Savio L.-Y.
Published: July 2023

Quantitative data on the strain and strain distribution in the anterior cruciate ligament (ACL) during knee motion can help to characterize the complex role of this ligament and lend insight into injury mechanisms of the ACL [2]. In-vitro studies have examined the elongations of different fiber bundles within the ligament [1, 4, 5, 7]. Using a Hall effect transducer attached to the anteromedial (AM) aspect of the ACL, in-vivo data on the strain behavior in the ACL during passive and active knee flexion as well as during various exercises have been obtained [3]. The objective of this study was to develop a non-contact approach to quantify the in-situ surface strains along the ACL. This approach was then used to test the hypothesis that the strain distribution along the ACL is uneven.
Transition to Turbulence in a Bifurcating Airway Model
Authors: Ueda Yoshiro , Okaniwa Takashi , Oka Kotaro , Tanishita Kazuo
Published: July 2023

Transition to turbulence in oscillatory How has been studied in a bifurcating airway model. Velocities were measured with a two-colour laser-doppler velocimeter. In the parent tube the large velocity gradient of “V” shaped velocity profile produces turbulence near the tube center in the expiratory phase of the flow cycle. On the other hand in the the inspiratory phase of the flow cycle, turbulence occurs in the tube center in the daughter tube.
Windkessel Modeling of Cardiac Afterload in the Stage 21 and 24 Chick Embryo
Authors: Kalegaonkar Shrikant , Kempski Mark H.
Published: July 2023

Cardiac function and vascular hemodynamics in the adult are primarily regulated through neural control mechanisms. However, functional hemodynamic control during primary cardiac development occurs prior to central nervous system development [Pappano 77]. Studies in our laboratory have shown that peak volumetric blood flow rate is amplitude modulated in the preinnervated embryo [Kempski 93]. This peak amplitude variability suggests an early mechanism for hemodynamic regulation which supplements beat-to-beat regulation via Frank-Starling mechanisms. We speculate that changes in vascular flow impedance may be the mechanism of hemodynamic regulation prior to the advent of neural control [Kempski 93]. We hypothesize that these changes can be modeled using three-element Windkessel analogs of cardiac afterload (Fig. 1).
Reduced-Order Modeling for Hyperthermia: An Extended Balanced-Realization-Based Approach
Authors: Mattingly M. , Bailey E. A. , Dutton A. W. , Roemer R. B. , Devasia S.
Published: July 2023

The problem: Hyperthermia when used as an adjuvant to normal radiation therapy significantly increases treatment response rates in cancerous tumors. The goal of a hyperthermia treatment is to elevate the tumor tissue temperature to therapeutic levels, while maintaining the surrounding normal tissue at safe temperature levels.

To achieve these treatment goals, researchers have investigated the use of model based controllers for hyperthermia. These model based controllers perform well; however, the complex and inhomogeneous nature of the tumor and surrounding tissue leads to large finite element, bio heat transfer models which make real time control computationally intractable. Hence, techniques are needed to reduce the model size, while retaining an acceptable degree of accuracy in the input-output map (the map from the applied power to the measured temperatures).
A General Mathematical Multibody Model for Diarthrodial Joints: Application and Validation Using the Patellofemoral Joint
Authors: Kwak S. D. , Ateshian G. A. , Blankevoort L. , Ahmad C. S. , Gardner T. R. , Grelsamer R. P. , Henry J. H. , Mow V. C.
Published: July 2023

An accurate mathematical model of a diarthrodial joint can be a powerful tool in investigating the mechanical behavior of a joint and the effects of pathologies and surgical procedures. Recognizing the potential of such a model, many investigators have previously developed mathematical models of a diarthrodial joint (e.g., Wismans et al., 1980; Blankevoort et al., 1991; Hirokawa, 1991; Hefzy and Yang, 1993; Heegaard et al., 1995). Most of these models, however, were limited to two body models specific to a particular joint; moreover, many of these models have not been thoroughly validated by comparing their results to experimental results obtained from the same individual specimen. Therefore, a more general mathematical 3-D multibody model capable of simulating different joints has been developed. It incorporates accurate joint geometry and wrapping of ligaments and tendons around bony or articular surfaces to predict the equilibrium pose, contact areas, contact forces, and ligament forces. Furthermore, to validate the model, the model has been applied to the patellofemoral joint, and its predictions were compared to actual experimental results.
Effects of Meniscectomy on the Tensile Properties of Articular Cartilage
Authors: Elliott Dawn M. , Setton Lori A. , Shah Maulin P. , Vail T. Parker , Guilak Farshid
Published: July 2023

Partial or complete removal of the meniscus has been found to produce progressive degeneration in the knee characteristic of osteoarthritis (OA) (4). Experimental models of meniscectomy have been successful in reproducing many changes in articular cartilage with OA, including fibrillation, compositional and metabolic changes (2,5,9,11). In both human OA and experimental models of joint instability, loss of tensile stiffness of the articular cartilage has been reported as an early sign of degeneration (1,6,8,10). Little is currently known of the mechanical properties of cartilage following meniscectomy and their relationship to progressive degeneration (7). The objective of this study was to quantify the tensile properties of articular cartilage in an experimental model of meniscectomy and to compare these findings with those of both human OA and experimental models of joint instability.
Effect of Disc Degeneration on Streaming Potential of Human Anulus Fibrosus
Authors: Gu W. Y. , Rabin J. , Lai W. M. , Rawlins B. A. , Mow V. C.
Published: July 2023

The streaming potential responses of anulus fibrosus (AF) from human intervertebral discs to steady and sinusoidal (ie, dynamic) applied pressures were measured and analyzed. It was found that the streaming potential response was linear for non-degenerate AF specimens, and there was no phase lag. For degenerate AF specimens, the response was nonlinear. The magnitudes of the streaming potential response were significantly different between non-degenerate and degenerate AF specimens: non-degenerate = 5.38 ± 0.88 mV/MPa; and degenerate = 4.41 ± 0.99 mV/MPa. This phenomenon offers a possible way for detecting AF degeneration in vivo.
Electrostatic Endothelial Cell Seeding Technique for Small Diameter (< 6 mm) Vascular Prostheses: In Vitro Evaluation
Authors: Bowlin Gary L. , Rittgers Stanley E.
Published: July 2023

The occurrence of vascular disease due to atherosclerosis interrupts the normal function (delivery of blood flow) and physiology of the blood vessels. One treatment for this condition is to by-pass the occluded section using a non-essential, autologous vessel (Saphenous vein) or a synthetic graft (Dacron or e-PTFE). Synthetic graft materials as by-pass grafts prove to be problematic when using the small diameter (< 6 mm) diameter grafts.
A Dynamic System Model of an Off-Road Cyclist
Authors: Wang Eric L. , Hull Maury L.
Published: July 2023

The increasing popularity of off-road cycling has lead to an increasing use of suspension systems. To understand the effectiveness of suspension systems, a two dimensional dynamic system model of a bicycle and rider would be useful. To achieve this however, an accurate dynamic description of the rider is necessary.
Lower Extremity Finite Element Model for Crash Simulation
Authors: Schauer Dale A. , Perfect Scott A.
Published: July 2023

A lower extremity model has been developed to study occupant injury mechanisms of the major bones and ligamentous soft tissues resulting from vehicle collisions. The model is based on anatomically correct digitized bone surfaces of the pelvis, femur, patella and the tibia. Many muscles, tendons and ligaments were incrementally added to the basic bone model. We have simulated two types of occupant loading that occur in a crash environment using a non-linear large deformation finite element code.
Convective Mass Transfer of ATP and Shear Stress in a 3-D Model of the Human Carotid Bifurcation
Authors: Lutostansky Elizabeth M. , Ku David N.
Published: July 2023

Atherosclerosis is typically located near arterial bifurcations and in regions of flow separation, particularly in the sinus of the internal carotid artery. Hemodynamics has been implicated as a contributing factor to atherogenesis. Atherosclerotic lesion thickness and location has been statistically correlated with several hemodynamic factors including low and oscillatory wall shear stress.
Response of the Lumbar Spine in Large Compression Loads: Stability Demands in Neutral Postures
Authors: Shirazi-Adl A. , Parnianpour M.
Published: July 2023

In neutral standing and sitting postures, the human lumbar spine is known to be subjected to both compression force and flexion/lateral moments. For the whole trunk, the centre of mass has been reported to be about 2.0 cm anterior to the L1-L2 vertebral centroid [1]. Due to the asymmetry of the upper body about the sagittal plane, lateral moments likely exist as well. The magnitude of these moments is affected by the location of the line of gravity relative to the vertebrae, and therefore, by the spinal posture (ie, pelvic rotation and lumbar lordosis). Changes in the sagittal curvature of the human lumbar spine (ie, lordosis) has been recorded under external loads and in microgravity [2–4]. Smaller lordosis has been observed in standing radiographs of low-back pain population compared with those of normal volunteers [5]. The preservation of lordosis and its biomechanical consequences during daily activities and heavy lifting tasks remain still as a controversial issue.
Predicting Damage in Human Vertebral Cancellous Bone Using Large-Scale Linear Finite Element Models
Authors: Hou Fu J. , Fyhrie David P.
Published: July 2023

Tissue damage in human vertebral cancellous bone specimens was predicted at apparent ultimate stress using large-scale linear finite element (FE) models. Three-dimensional (3D) FE models were constructed from micro computed tomography (MCT) images of mechanically tested cancellous bone cylinders. The percentage of tissue damage was calculated and damage locations were examined and compared to observation from experiment. Two distinct damage groups were identified when damage was predicted by bone volume fraction (BV/TV). FE estimated average hard tissue stiffness was found to account for most of the separation between the two groups. This strongly suggests that tissue level bone material properties are important factors in determining cancellous bone tissue apparent strength. Damage locations predicted by FE corresponded with experiment.
The Effects of Prior Damage on the Rate-Dependent Torsional Strength of Human Cortical Bone
Authors: Jepsen Karl J. , Davy Dwight T.
Published: July 2023

The effects of damage accumulation on bone mechanical properties are not well understood. Previously, we identified a significant interaction between damage and the viscoelastic properties of human cortical bone loaded in torsion. In the current study, we further investigate this interaction by testing the hypothesis that damage accumulation significantly alters the rate-dependent nature of bone strength. The results indicated that increasing the twist rate of residual strength tests by only one order of magnitude was associated with a significant, 3-fold increase in strength and modulus degradation. The results suggest that damage accumulation may make cortical bone more susceptible to fracture at high loading rates, which has important implications for understanding the increased fracture frequency associated with falls in the elderly.
The Importance of Large Strain in Blood Vessel Mechanics
Authors: Ballyk Peter D. , Ojha Matadial , Walsh Colin
Published: July 2023

Although blood vessels undergo large strain, particularly near branches and graft artery junctions (Ballyk et al., 1995), small strain (large deformation) approximations of blood vessel mechanics are commonly used to determine intramural stress distributions. In this study, we examine the static inflation of blood vessels and demonstrate that, for physiological loads, small strain approximations lead to large errors, even if they include large deformations. To rectify these problems, we have developed a large strain finite element model of blood vessels.
Computations of the Wall Mechanical Response Under Unsteady Flows in Arterial Diseases
Authors: Yamaguchi Takami , Nakayama Tetsuya , Kobayashi Takuji
Published: July 2023

In our previous report[1], the fluid motion and the wall motion in models of the arterial stenosis and the abdominal aneurysm with thick deformable walls was computed. In the present study, further computation using the same model of the arterial stenosis and the abdominal aneurysm was carried out with a wider variety of fluid mechanical and physiological parameters. We also computed the wall/fluid interactions in a model with a unilateral stenosis simulating the early atherosclerotic plaque.
The Influence of Loading and Aspect Ratio on Bone Remodeling at the Bone-Implant Interface
Authors: He N. , Sadegh A. M.
Published: July 2023

The effect of loading and bead aspect ratio on bone remodeling at the bone-implant interface was investigated. Surface bone remodeling theory that utilizes strain rate, and boundary element method were employed. Seven cases of two dimensional models with a variety of bead aspect ratios were studied, and the final bone resorption and deposition were determined. Stresses were varied between 5 MPa and 30 MPa to determine the optimum loading for each aspect ratio.
Optimization of Material Properties of Passive Myocardium Using Epicardial Suction
Authors: Okamoto Ruth J. , Guccione Julius M. , Moulton Michael J. , Pasque Michael K.
Published: July 2023

Non-homogeneous changes in cardiac mechanical function occur in regional pathological disorders such as ischemic heart disease. Mathematical models provide a sound basis for the interpretation of these changes and their relation to local myocardial tissue properties. Existing models incorporate three-dimensional ventricular geometry, internal fibrous architecture of the ventricular walls and information about ventricular pressures. The ability of these models to predict mechanical function, however, depends on the incorporation of an accurate description of the intrinsic material properties of myocardial tissue. These material properties were estimated by Novak et al (1994) using biaxial test results from excised ventricular myocardium. Guccione et al (1991) used two-dimensional strains measured at one location with implanted beads to determine material properties in an intact heart. Taking advantage of recent developments in magnetic resonance imaging (MRI) for measuring cardiac deformation, we developed epicardial suction as a new test method for determining the material parameters in a three-dimensional constitutive relation describing ventricular myocardium (Okamoto et al, 1995).

In this abstract, we describe a method for optimizing material properties that compares experimental measurements of in-plane displacements caused by epicardial suction with predicted displacement results from a finite element (FE) model simulating the experiment. A diagram of the method is shown in Fig. 1. We also discuss preliminary results from two experiments.
Computer Assisted Orthopaedic Surgery (CAOS): A Generalized Concept and Early Clinical Experience
Authors: Visarius Heiko , Langlotz Frank , Nolte Lutz P.
Published: July 2023

In most orthopaedic surgeries the relation between the image provided, the patient, and the surgical tool depends solely on the experience and ability of the surgeon. No direct connection between the surgical object (i.e. the patient) and the virtual object (i.e. the image) is present. However, use of information inherent to the image is a crucial contributor to surgical success.
The Hyper Hospital: Virtual Reality Mediated Network Based Medical Care
Authors: Yamaguchi Takami , Nakanishi Yuji , Yamazaki Kiyoyuki
Published: July 2023

The Hyper Hospital is a proposal of novel medical care system which is constructed on an electronic or computerized information network using virtual reality as the principal human interface [1]. The major purpose of the Hyper Hospital is to restore humane interactions between patients and various medical caretakers by making a much closer contact between them. This task will be accomplished by reforming the medical system rather patient-centered than provider-oriented current system by virtue of most advanced multi-media network information technology. The Hyper Hospital will be built as a distributed system on the real and the virtual world on the network, a node of which represents a variety of medical care facilities; for example, the out patient office, the nursing care center, the medical examination unit, the operating theater, etc (Fig.1). Above all, the Hyper Hospital space consists of the alternate reality space owned and exclusively controlled by the patient himself/herself. Most of the physical contact, such as the visit to the out patient office by the patient, is actualized by the electronic contact of the patient private space and the public space of the hospital system. Prescription of the drugs, special cares, even the administration to the ward will be integrated to the distributed electronic network.
Left Ventricular Flow Visualization by Magnetic Resonance Velocity Mapping
Authors: Milet Sylvain F. , Walker Peter G. , Houlind Kim , Kim W. Yong , Pedersen Erik M. , Yoganathan Ajit P.
Published: July 2023

Mitral flow measurement by Doppler ultrasound is a common diagnostic technique used in the evaluation of left ventricular function. With the more recent magnetic resonance (MR) velocity mapping technique, non-invasive three-dimensional cardiac flow velocity measurements can be performed during the entire cardiac cycle. MR requires different analysis methods than Doppler ultrasound does, New visualization and analysis tools need to be developed for the clinical use of MR velocity data.
Vein Graft Engineering
Authors: Liu Shu Q.
Published: July 2023

Vein grafts are commonly used to replace occluded arteries due to atherosclerosis. Unfortunately, vein graft occlusion occurs due to thrombosis and intimal hyperplasia [1], causing serious clinical problems such as repeated angioplasty and grafting surgeries and threatening the life of many patients. Thus vein graft occlusion has been one of the major problems in cardiovascular research.
Shear-Induced Intimal Thickening on the Bed of an End-to-Side Anastomosis Model
Authors: Ishibashi Hiroyuki , Park Hyoun , Ojha Matadial , Langdon Shari , Langille Lowell
Published: July 2023

The long-term failure of arterial bypass grafts and arteriovenous fistulae is often related to intimal hyperplasia that preferentially develops at the outflow or distal anastomosis. In studies using animal models, hyperplasia develops specifically around the suture line and on the bed across from the junction.
Axial Strain-Induced Stress Distributions at End-to-End and End-to-Side Graft-Artery Junctions: Clinical Implications
Authors: Ballyk Peter D. , Ojha Matadial , Walsh Colin
Published: July 2023

Suture-line intimal hyperplasia can lead to outflow stenosis of vascular bypass grafts. One prominent theory suggests that compliance mismatch between the graft and native vessel promotes suture-line hyperplasia, however, this theory has not yet been proven. Many studies have demonstrated that matching graft compliance to that of the artery leads to improved graft patency, but only a few have actually quantified the hyperplasia at compliant and non-compliant graft-artery junctions (Bassiouny et al., 1992; Trubel et al., 1994; Courtman, 1994).
Short-Timescale Thermometry and Reliability Studies of Metal Interconnects in VLSI Circuits
Authors: Ju Y. S. , Goodson K. E.
Published: July 2023

The failure of metal interconnects subjected to brief electrical-current pulses is a reliability concern in the integrated circuits industry, especially in connection with electrostatic discharge (ESD). The thermal design of interconnects and the study of their failure mechanisms require thermometry with high spatial and temporal resolution. This work uses scanning laser-reflectance thermometry to measure temperature distributions along metal interconnects subjected to electrical pulses of duration less than 1 μs and of peak current density over 1011 A/m2. The data reported here achieve temporal resolution better than 100 ns and spatial resolution near 1 μm. A calibration procedure for the temperature-dependent reflectance of interconnect structures is developed and the uncertainties associated with the prediction of this property are also discussed. Severe changes in the local interconnect surface topography are observed using atomic force microscopy when the local temperature rise exceeds 180 K for the passivated interconnects and 120 K for the unpassivated interconnects.
Temperature-Dependent Thermal Conductivity of Single-Crystal Silicon Layers in SOI Substrates
Authors: Asheghi M. , Touzelbaev M. N. , Goodson K. E. , Leung Y. K. , Wong S. S.
Published: July 2023

Self heating diminishes the reliability of SOI transistors, particularly those that must withstand electrostatic discharge (ESD) pulses. This problem is alleviated in part by lateral thermal conduction in the silicon device layer, whose thermal conductivity is not known. The present work develops a technique for measuring this property and provides data for layers in wafers fabricated using bond-and-etch-back (BESOI) technology. The room-temperature thermal conductivity data decrease with decreasing layer thickness, ds, to a value nearly 40 percent less than that of bulk silicon for ds = 0.42 μm. The agreement of the data with the predictions of phonon transport analysis between 20 and 300 K strongly indicates that phonon scattering on layer boundaries is responsible for a large part of the reduction. The reduction is also due in part to concentrations of imperfections larger than those in bulk samples, which results from the BESOI wafer fabrication process. The data show that the buried oxide in BESOI wafers has a thermal conductivity that is nearly equal to that of bulk fused quartz. The data provided here will lead to more accurate thermal simulations of SOI transistors and cantilever MEMS structures.
Application of Diffuse Mismatch Theory to the Prediction of Thermal Boundary Resistance in Thin-Film High-Tc Superconductors
Authors: Phelan Patrick E.
Published: July 2023

Thermal boundary resistance (Rb) plays an important role in the design and performance of thin-film high-temperature superconducting devices, such as infrared detectors and optical switches, which rely upon the temperature rise of the film as the basis for their operation. Although there is general agreement on the magnitude of Rb from experimental data, there is at present no generally accepted theory capable of predicting Rb for these films, particularly at the intermediate cryogenic temperatures where they are likely to be used. Here, the Diffuse Mismatch Model (DMM), which considers that all phonons reaching the interface between the film and substrate scatter diffusely, is applied to the calculation of Rb. The results indicate that although the DMM yields results slightly more in agreement with data than the Acoustic Mismatch Model (AMM), the experimental data lie far above the calculated values. Removing the assumptions involved in the derivation of the DMM in some cases improves the agreement with the experimental data, but additional features must be incorporated into the model to achieve quantitative agreement between theory and experiment.
Heat Transfer and Fluid Flow in Microchannels
Authors: Mala Gh. Mohiuddin , Li Dongqing , Dale J. D.
Published: July 2023

This paper investigates the effects of the electrical double layer at the solid-liquid interface on liquid flow and heat transfer through a microchannel between two parallel plates at constant and equal temperatures. A linear approximate solution of the Poisson-Boltzmann equation is used to describe the electrical double layer field near the solid-liquid interface. The electrical body force resulting from the double layer field is considered in the equation of motion. The equation of motion is solved for the steady state flow. Effects of the electrical double layer field and the channel size on the velocity distribution, streaming potential, apparent viscosity, temperature distribution and heat transfer coefficient are discussed in this paper.
New Methods of Measuring a Key Elastic-Piezoelectric Constant of Thin Films
Authors: von Preissig Fred J. , Zeng Hong , Kim Eun Sok
Published: July 2023

Microelectromechanical devices that contain piezoelectric thin films that serve as electrical-to-mechanical transducers (actuators) or mechanical-to-electrical transducers (sensors) are receiving increasing attention. The efficiency of transduction usually depends largely on the composite elastic-piezoelectric constant d31/(s11+s12)E of the piezoelectric film. Two new methods for measuring this constant, based on the same piezoelectric device, have been developed. The analytical theory behind these methods has been worked out in detail. One method involves the measurement of small mechanical displacements. Its application to a device containing polycrystalline ZnO yielded a value of 0.13 C/m2 for the constant. The other method requires only electrical and simple geometric measurements. Its experimental implementation has not yet been completed.
Micromechanical Structures for Fracture Testing of Brittle Thin Films
Authors: Jones Peter T. , Johnson George C. , Howe Roger T.
Published: July 2023

A new structure for determining the fracture characteristics of brittle thin films has been designed, fabricated and tested. The structure consists of a rigid central shuttle to which are attached a number of cantilever beams of varying lengths which will provide the desired fracture information. The central shuttle is tethered to the substrate by flexible beams which allow it to be moved controllably in one direction while the free ends of the cantilevers are prevented from movement by stops. By measuring the shuttle displacement at which the various beams fail, the failure strain of the beam material is determined. This structure design has been used to examine the fracture characteristics of a particular LPCVD polycrystalline silicon film, and the degradation in strength which occurs with exposure to hydrofluoric acid. The average strain at fracture measured for this heavily phosphorus doped polycrystalline silicon was 1.1% for a 10 minute exposure to hydrofluoric acid. This value drops to 0.84% after the material is exposed to hydrofluoric acid for 2 hours.
A Methodology to Study Wafer Level Response of Silicon Microstructures to Mechanical Shock
Authors: McIntyre David G. , Cunningham Shawn J. , Carper Judd S. , Jaramillo Paul D. , Tang William C.
Published: July 2023

The Microelectromechanical Systems literature is dominated by discussion of device and process innovation. Reliability issues have received little attention and yet they are a critical prerequisite to successful commercialization. The explosive growth of the field in the last decade, first in the academic arena and now in the commercial sensor industry, demands a well orchestrated effort to understand and quantify the reliability of silicon microstructures. A systematic method to characterize the response of silicon microstructures to mechanical shock has been developed and applied. This method can be used to characterize other stress types and process sequences as well.
Particle-Impact Experiment for Studying Dynamic Behavior of Brittle Materials
Authors: Andrews Erik W. , Kim Kyung-Suk
Published: July 2023

Results are presented from a particle-impact experiment to study the dynamic behavior of brittle materials. In the experiment a small, spherical particle of a brittle material impacts against a thick, hard anvil. The experimental configuration minimizes the damage to the target and allows one to focus on the damage to the particle. The impact process is observed using high-speed photography. Results are presented for tungsten carbide, alumina and silicon nitride particles striking a titanium diboride anvil. The radius of the particles ranged from 1.59 mm to 0.40 mm. It is observed that above a certain threshold velocity the particle undergoes fragmentation upon impact. This threshold velocity depends on the particle material properties, and decreases weakly with increasing particle radius. When plotted in a dimensionless form, the data for the different materials all fell within a narrow band. The non-dimensionalization was based on normalizing the threshold velocity by the longitudinal wave speed, and the particle radius by the intrinsic defect size in the material. In addition to reporting measurements of the threshold velocity, the observed patterns of particle fragmentation are described. This experiment provides a means of studying the threshold conditions for dynamic fragmentation and assessing the resistance to impact damage of brittle materials. In addition, this experiment should provide data valuable for the verification of models for the dynamic behavior of brittle materials.
Computational Modeling of Geometric and Material Nonlinearities With an Application to Impact Damage in Brittle Materials
Authors: Espinosa Horacio D. , Emore Gordon , Zavattieri Pablo
Published: July 2023

A model is presented for the dynamic finite element analysis of large-strain, high strain rate deformation behavior of materials. Both an isochoric plastic model for metals and a multiplane microcracking model for ceramics are introduced, and a temperature-dependent model is included. In addition, algorithms are presented for correcting finite element mesh distortion through mesh rezoning, optimization, and refinement. A surface-defined multibody contact algorithm designed to handle large relative displacements between bodies is included, with additions for friction and cohesive interfaces. A test example is examined, simulating a modified Taylor rod impact test in which an aluminum anvil strikes a ceramic specimen. Velocities are recorded at the free end of the ceramic and compared to experimental results. It is observed that the simulation produces the same overall features as the experimental data.
Cell Nucleation in Solid-State Polycarbonate-CO2 Foams: Evidence of a Triaxial Tensile Failure Mechanism
Authors: Holl Mark R. , Kumar Vipin , Garbini Joseph L. , Murray William R.
Published: July 2023

The mechanism for nucleation phenomenon in solid state microcellular foams is identified as a solid state failure process. This process originates at internal flaws within the gas-polymer matrix where it is induced by the presence of a state of hydrostatic tensile stress within the polymer matrix. The hydrostatic tensile stress is caused by the presence of the saturating gas within the polymer. The nucleation phenomenon is thermally activated at the effective glass transition temperature of the gas-polymer mixture. At this critical temperature, the hydrostatic tensile stress within the gas-polymer mixture is sufficient to cause the polymer matrix to fail, thereby creating a foam cell nucleus.

In general, the nucleation sites are observed to be flat, approximately circular, fracture sites. After the appearance of the initial fracture, gas diffuses from the gas-polymer matrix into the fracture. The fracture seam inflates during the growth process where growth begins with the appearance of a disk shaped fracture and concludes with an approximately spherical cell. The results and conclusions presented here are distinct from previous attempts to address the nucleation phenomena in solid state microcellular plastics, and suggest a new avenue to explain the cell nucleation phenomena observed in this process.
Comment on “Ultrastructure reveals ancestral vertebrate pharyngeal skeleton in yunnanozoans”
Authors: He Kaiyue , Liu Jianni , Han Jian , Ou Qiang , Chen Ailin , Zhang Zhifei , Fu Dongjing , Hua Hong , Zhang Xingliang , Shu Degan
Published: July 2023

Tian
et al
. (Research Articles, 8 July 2022, abm2708) hypothesized that yunnanozoans are stem-group vertebrates on the basis of “cellular cartilage”, “fibrillin microfibers”, and “subchordal rod” associated with the branchial arches of yunnanozoans. However, we reject the presence of cellular cartilage, fibrillin, and the phylogenetic proposal of vertebrate affinities based on ultrastructure and morphology of yunnanozoans from more than 8000 specimens.