bluuebunny/crossref_metadata_2025 huggingface dataset:
Buoyant and Rotational Flows During ACRT Vertical Bridgman Crystal Growth
Authors: Derby Jeffrey J. , Yeckel Andrew
Published: November 2021

Axisymmetric, time-dependent simulations of the high-pressure vertical Bridgman growth of large-diameter cadmium zinc telluride are performed to study the effect of accelerated crucible rotation (ACRT) on crystal growth dynamics. The model includes details of heat transfer, melt convection, solid-liquid interface shape, and dilute zinc segregation. Application of ACRT greatly improves mixing in the melt, but causes an overall increased deflection of the solid-liquid interface. The flow exhibits a Taylor-Görtler instability at the crucible sidewall, which further enhances melt mixing.
Correction of Hot-Wire Measurements in the Near Non-Conducting Wall Region
Authors: Wenzhong Li , Khoo B. C. , Diao Xu
Published: November 2021

The present paper is to determine the correction of hot-wire measurements when it is used to measure the shear flows region very close to the non-conducting wall. By numerical simulation of the Navier-Stokes and energy equations using the control volume method, we found that reasonably deployed grid distribution could largely reduce the computational domain size (for a typical Reynolds number for hot-wire near-wall measurements 4.0×10−3∼1.2, the domain boundary placing 650 diameters from the cylinder in front, rear and top is fair enough for accurate simulation, other than the domain boundary which places the 2000 diameters from the cylinder in front and top, and 3000 diameters from the cylinder in rear), and obtain the similar accuracy results for the correction of hot-wire measurements in the near-wall region. Numerical simulation results also show that, only taking the εf,εw (the maximum difference between the respective values of stream function and vorticity on successive iterations) as the criterion for convergence without judge to convergence of the temperature field seems not enough to obtain a convergent simulation result. This may be the possible reason which caused the discrepancy between the simulation results for hot-wire correction when using hot wire to measure the shear flows very close to the non-conducting wall.
Concurrent and Complementary Experimental and Computational Investigations for Hydrodynamic Design System of a Surface Ship
Authors: Rhee S. H. , Hino T. , Hirata N. , Kodama Y. , Kume K. , Takeshi H. , Ukon Y.
Published: November 2021

Results are reported of concurrent and complementary experimental and computational investigations on surface ship hydrodynamics at Ship Research Institute of Japan. The main goal of the investigations is to conceive an integrated hydrodynamic design system that can be utilized in shipbuilding industry. Model scale experimental data, which include global force and local flow measurements, are obtained by towing tank experiments. The experimental data provide validation benchmark for computational fluid dynamics simulations and are complemented by the results of computational investigations in terms of high-resolution data and turbulence quantities. The computational results also provide the global force and local flow data and are complemented by experimental data in various aspects such as breaking waves and sinkage and trim of the hull. The uncertainty assessment for experiments and the verification and validation for computational results provide the level of uncertainties and errors. Through the overall procedure that includes experimental and computational investigations with careful uncertainty analysis, an extensive set of information that can be provided to aid field designers is obtained. The future work includes further application to wave breaking and maneuvering ships in ambient waves using an unstructured grid method computer code and building a simulation-based-design system that comprises the information obtained throughout these investigations.
Flow Structures of Cavity-Channel Flows
Authors: Sun Xiaohua
Published: November 2021

Laminar, incompressible flows in a two-dimensional, T-shaped geometry are numerically investigated using a commercial CFD package. The geometry studied here is a square cavity attached to one side of a long, narrow channel. Fluid enters from one end of the channel, discharges into the cavity, and finds its way into the second part of the channel and eventually flows out of the domain. While the flat, top plate of the geometry remains stationary, the bottom part of the channel and the cavity move at a constant speed, in the same direction as the inlet velocity. As the ratio of the inlet velocity over the velocity of the moving bottom, r = Vin/U, changes, the vortex structures inside the square cavity experience a series of interesting changes.
Modeling of Laminated Composite Shells Featuring Damaged Interfaces
Authors: Librescu Liviu , Schmidt Rüdiger
Published: November 2021

This paper is devoted to the presentation of a general linear theory of laminated composite anisotropic shells of arbitrary shape and curvature, in which the effect of the interfacial damage induced by the imperfect bonding between the constituent laminae is incorporated. In this context, the imperfect interface conditions are described in terms of linear relations between the interface tractions in the normal and tangential directions, and the respective displacement jumps. In addition to the effects of imperfectly bonded interfaces, the theory incorporates the effects of transverse shear and transverse normal strain, the dynamic effects, as well as the anisotropy of constituent material layers. Due to its general character, this theory can contribute to a more reliable prediction, in the linear range, of the load carrying capacitiy and failure of laminated composite shell structures featuring imperfectly bonded interfaces.
Optimization of Smart Composite Plates With Segmented Active Constrained Layer Damping
Authors: Beri Rajan , Chattopadhyay Aditi
Published: November 2021

A rigorous multi-objective optimization procedure is developed to address the integrated structures/controls design of composite plates with surface bonded segmented active constrained layer (ACL) damping treatments. The Kresselmeier-Steinhauser function approach is used to formulate this multidisciplinary problem. The goal is to control vibration without incorporating a weight penalty. Objective functions and constraints include damping ratios, structural weight and natural frequencies. Design variables include the ply stacking sequence, dimensions and placement of segmented ACLs. The control systems design is performed using two separate optimal control systems based on linear quadratic regulator (LQR) theory and linear quadratic gaussian (LQG) theory.

The optimal designs show improved plate vibratory characteristics and reduced structural weight. In addition, the studies show that including a greater number of segmented ACL damping treatments of relatively smaller size provides optimum designs with better overall vibration suppression characteristics and lower structural weight, in comparison to using fewer ACL treatments of larger size. The choice of control system employed does not produce significant changes in the results of the optimization studies.

The impact of varying the properties and locations of the segmented ACLs, on the vibration suppression characteristics of the plate, is larger compared to the effect of varying ply stacking sequence alone. Composite tailoring, however, provides a viable means of improving vibration control of composite plates with segmented ACL damping, without altering the ACL configurations or incorporating a weight penalty. Results obtained indicate the importance of incorporating both structural and control objectives, simultaneously rather than sequentially, in the design problem to obtain meaningful design trends in such multidisciplinary problems.
Assessment of Solutions to Vibration Problems Involving Piecewise Constant Exertions
Authors: Dai L.
Published: November 2021

Direct analytical and numerical solutions are constructed for linear and nonlinear vibration problems involving piecewise constant exertions. Existence and uniqueness of the solutions and the truncation errors of the numerical calculations are also analysed. With the employment of a piecewise constant argument, vibration systems with piecewise constant exertions are connected with the corresponding systems with continuous exertions.
Radar Target Identification With JEM Effect
Authors: Yao Xiaodong , Jing Zhongliang
Published: November 2021

The jet engine modulation (JEM) effect is given. The backscattered characteristic of the electro-magnetic wave of airplane is analyzed. The spectral analysis technique based on cumulant is used to process the practical dynamic data by low-resolution radar, and the JEM spectral line is obtained. The implication for JEM target identification system is discussed based on the fuzzy neural network (FNN) and the short time Fourier transformation (STFT).
Differential Quadrature Element Method for the Analysis of Vibration of Frame Structures Having Nonprismatic Members Considering Warping Torsion
Authors: Chen Chang-New
Published: November 2021

The differential quadrature element method (DQEM) and the extended differential quadrature (EDQ) have been proposed by the author. The EDQ is used to the DQEM vibration analysis frame structures. The element can be a nonprismatic beam considering the warping due to torsion. The EDQ technique is used to discretize the element-based differential eigenvalue equations, the transition conditions at joints and the boundary conditions on domain boundaries. An overall discrete eigenvalue system can be obtained by assembling all of the discretized equations. A numerically rigorous solution can be obtained by solving the overall discrete eigenvalue system. Mathematical formulations for the EDQ-based DQEM vibration analysis of nonprismatic structures considering the effect of warping torsion are carried out. By using this DQEM model, accurate results of frame problems can efficiently be obtained.
Static Deflection and Free Vibration of Nonprismatic Beam Structures Solved by DQEM Using EDQ
Authors: Chen Chang-New
Published: November 2021

The development of (DQEM) analysis models of static deformation and free vibration problems of generic non-prismatic beam structures was carried out. The DQEM uses the extended differential quadrature (EDQ) to discretize the buckling equilibrium equation defined on each element, the transition conditions defined on the inter-element boundary of two adjacent elements and the boundary conditions of the beam. Numerical results solved by the developed numerical algorithm are presented. They prove that the DQEM efficient.
Measurement of the Optical Properties of Muscle Tissue In Vivo
Authors: Kopsombut P. L. , Willis D. , Schen A. E. , Xu L. X. , Xu X.
Published: November 2021

Along with rapid development of diagnostic and therapeutic applications of lasers in medicine, optical properties of various biological tissues have been extensively studied [1]. Most of the studies were performed in vitro owing to the complexity involved in in vivo measurement. To date, it is well understood that living tissue is an absorbing and scattering heterogeneous medium because of its complex structures including blood network. The transport theory cannot be readily used due to the heterogeneity and the absence of the optical properties of living tissues [2]. In this research, we have developed a procedure for measuring the total attenuation coefficient (μ1) of the exteriorized rat 2-D spinotrapezius muscle in the wavelength ranged from 480–560 nm using the collimated light from a Nitrogen-pumped dye laser and a high-sensitivity CCD camera.
Effect of Cell Density on Post-Thaw Viability in Cryopreserved Artificial Tissue
Authors: Ujihira Masanobu , Matsumura Yumi , Kuroda Chinatsu , Okaniwa Koji , Mabuchi Kiyoshi
Published: November 2021

The effect of cell density on the post-thaw viability of cells in cryopreserved artificial tissue was studied. Human fibroblasts were three-dimensionally cultured for 2 days in a collagen sponge (ϕ20×1mm) as an extracellular matrix to imitate biological tissue (artificial tissue). Different cell densities for the artificial tissue were used, from 104 to 107 cells/cm3. Four artificial tissues were first stacked in a test chamber, then frozen at a slow or fast cooling rate (either 1 or 50°C/min) in a solution of Dulbecco’s Modified Eagle Medium, 20% Fetal Bovine Serum, and 10% dimethylsulfoxide, then kept frozen at −196°C for 2 hours, and finally thawed. The collagen matrix of the artificial tissue was dissolved using collagenase. Post-thaw viability of fibroblasts was evaluated by using a trypan blue exclusion assay. The experiments were prepared, and then the latent heat of artificial tissue (3.5×3.5×1mm) during the freezing process was measured by using a differential scanning calorimeter. Results show that with increasing cell density, the post-thaw viability decreased, whereas the latent heat was almost independent of cell density. With increasing cell density at the slow cooling rate, the degree of supercooling of the intracellular solution increased with decreasing temperature, possibly leading to intracellular freezing. Moreover, when the cell density was high, cell-to-cell contact or an obstruction to dehydration seemed to induce intracellular freezing. Therefore, the post-thaw viability seems to decrease as the number of cells exhibiting intracellular freezing increased.
Red Blood Cell Distribution Effect on Lung Diffusing Capacity: A Macroscopic Analysis
Authors: Kulish Vladimir V. , Lage José L. , Hsia Connie C. W. , Johnson Robert L.
Published: November 2021

A novel mathematical model derived from fundamental engineering principles for simulating the spatial and temporal gas diffusion process within the alveolar region of the lung was presented recently by Koulich et al. [1]. The model depends on a physical property of the alveolar region termed effective diffusivity, function of the diffusivity, solubility, and interface geometry of each alveolar constituent. Unfortunately, the direct determination of the effective diffusivity of the alveolar region is impractical because of the difficulty in describing the internal geometry of each alveolar constituent. However, the transient solution of the macroscopic model can be used in conjunction with the lung diffusing capacity (measured in laboratory via the single-breath technique) to determine the effective diffusivity of the alveolar region. With the effective diffusivity known, the three-dimensional effects of red blood cell distribution on the lung diffusing capacity can be predicted via numerical simulations. The results, obtained for normal (random), uniform, center-cluster, corner-cluster, and several chain-like distributions, unveil a strong relationship between the type of cell distribution and the lung diffusing capacity.
Thermal Therapy of Toe Nail Fungus
Authors: Chato John C.
Published: November 2021

A thermal treatment of toe nail fungus has been developed. The success of this procedure depends on the apparent thermal sensitivity of the fungus as well as on the transient thermal gradient developed in the toe nail, in the underlying fungus, and in the tissue underneath it while the outer surface of the toe nail is heated with a thin stream of 50 °C water. Each treatment, which is to be repeated several times in a predetermined fashion, lasts only a few seconds. The only danger is that if the treatment time is extended, the tissue under the toenail may suffer burn damage.
Development of a Novel In Vivo Assay for Assessment of Tissue Viability: A Cryosurgery Application
Authors: Elliott G. D. , Fron D. , McGrath J. J. , Seip C. , Crockett-Torabi E.
Published: November 2021

Our recent success with applying a novel Green Fluorescent Protein (GFP) viability assay to isolated cells after freezing has suggested possible utility for assessing viability of cells within tissues, both in situ, and intravitally. The current work seeks to establish that following freezing, changes in the fluorescent intensity of tumors grown from GFP-transfected cells will correlate with tissue damage as assessed by histological methods, thereby evaluating the use of a transfection-based assay for in vivo purposes. GFP-fluorescing R3230AC tumors were grown inside implanted dorsal skin flap chambers, and treated cryosurgically after 6-9 days of growth. Fluorescent images of the tumors were acquired at the center of the viewing area before, during, and for 6 hours following freezing. Following the observation period the animal was immediately euthanized and the tissue within the chamber was fixed in formalin and stained for histological analysis. The results of intravital microscopy in a centrally located test area revealed a large reduction in fluorescent intensity within the tumor tissue immediately following the final freeze-thaw cycle, with little subsequent change during the subsequent 6 hour observation period. In H&E section significant damage was observed in the central test areas. Taken together, this evidence suggests that the GFP assay is not limited to isolated cells, but can serve as the basis for intravital assessment of viability.
Stress Concentration in a Connectorized Optical Fiber
Authors: Malluck John F. , King Wilton W.
Published: November 2021

For the most part, analyses of fiber fractures in connectors have been in the form of postmortem fractography. Typically in these works, characteristics of prefracture stress states have been inferred from fracture surfaces, and plausible qualitative explanations have been advanced about the likely structural mechanics and circumstances leading to fractures. The authors and their colleagues have undertaken a number of investigations of relevant structural mechanics. These have served the useful purpose of elucidating gross mechanisms, but the influence of the fine details of stress distributions have been missing.

Considered here is a cylindrical-ferrule connector for which, typically, the ferrule is ceramic with an outside diameter of 2.5mm or 1.25mm. The fiber to be terminated is bonded into a small-bore axial hole (capillary) in the ferrule by an epoxy or similar adhesive. In addition, fiber insertion into the capillary is facilitated by ferrule designs that provide a conical entrance cavity leading to the capillary. A very high percentage of fiber failures, both in the laboratory and the field, occur at the transition region between the fiber and the capillary; so analysis is focused on that region.

The stress distribution within an optical fiber adhesively bonded to a ceramic ferrule is determined by the finite element method for uniform remote tension acting on the fiber. An axisymmetric model is constructed to represent the fiber, epoxy, and geometry of the ferrule under this particular loading condition. The resulting stress distribution is determined within the fiber and the epoxy layer using the ANSYS finite element code. Analysis of the stress distribution reveals the presence of two stress concentrations located at the surface of the fiber as the fiber enters the ferrule. One stress concentration occurs as the fiber encounters the epoxy within the conical cavity. The second stress concentration occurs as the fiber enters the capillary. These stress concentrations when combined with surface damage (flaws) may lead to fiber breakage. Further analysis reveals that a smooth fillet transition between entrance and capillary could significantly reduce the stress concentration at the capillary entrance. Finally, a simulation of epoxy debonding within the entrance cone reveals an increase of stress concentration at the capillary entrance.
Effect of Moisture on the Interfacial Adhesion of the Underfill/Solder Mask Interface
Authors: Ferguson Timothy P. , Qu Jianmin
Published: November 2021

A primary concern in microelectronic packaging is the role of moisture induced failure mechanisms. Moisture is a multidimensional concern in packaging, having an adverse effect on package reliability by introducing corrosion, development of hygro-stresses, and deterioration of polymer interfaces within the package. In this paper the effect of moisture on the interfacial adhesion of two no flow underfill materials with a commercially available soldermask coated FR-4 board is experimentally determined. Bilayer specimens with prefabricated interface cracks are used in a four point bending test to quantify the interfacial fracture toughness. Two groups of test specimens of varying underfill thickness were constructed. The first group was fully dried while the other was moisture preconditioned at 85°C/85%RH for 725 hours. The results of this study show that the interfacial toughness is significantly affected by the presence of moisture.
Bayesian Belief Network Modeling and Diagnosis of Xerographic Systems
Authors: Zhong Chunhui , Li Perry Y.
Published: November 2021

In this paper, a Bayesian Belief Network (BBN) approach to the modeling and diagnosis of xerographic printing systems is proposed. First, a continuous BBN model based on physics of the printing process and field data is developed. The model captures the causal relationships between the various physical variables in the system using conditional probability distributions. Next, the continuous BBN is discretized based on the principle of maximum entropy so that it can be implemented on commercially available software, Hugin. The resulting BBN can be used for the prediction of print quality behaviors, as well as for inference and fault diagnosis. Examples of network deduction and inference are presented to illustrate the usefulness of the BBN model.
Pulse Width Modulation Control of Robots With Structural Flexibility
Authors: Rathbun David B. , Berg Martin C.
Published: November 2021

The accuracy to which the end effector of a robotic manipulator can be positioned is often limited by structural flexibilities and nonlinear friction. This paper develops a control design methodology for such systems based on pulse width modulation. This methodology achieves comparatively very accurate point-to-point position control and does not require a high fidelity model of either the robot dynamics or the friction behavior. Conditions under which the controller must directly treat plant structural flexibility are presented. Conditions on parameters of the closed loop system that guarantee stability and a well defined level of performance are given. The methodology is demonstrated by application to a six axis industrial robot.
On the Discontinuity of the Costates for Optimal Control Problems With Coulomb Friction
Authors: Driessen Brian J. , Sadegh Nader
Published: November 2021

This work points out that the costates are actually discontinuous functions of time for optimal control problems with Coulomb friction. In particular these discontinuities occur at the time points where the velocity of the system changes sign. To our knowledge, this has not been noted before. This phenomenon is demonstrated on a minimum-time problem with Coulomb friction and the consistency of discontinuous costates and switching functions with respect to the input switches is shown.
Design of Adaptive Supervisors for Discrete Event Systems via Learning
Authors: Gordon Diana , Kiriakidis Kiriakos
Published: November 2021

In many practical applications, modeling using event-driven dynamics leads to interconnected discrete event systems. Often, these tend to be large-scale event-varying structures, which need to possess certain event-invariant properties. Although supervisory control theory offers some methods for the synthesis of such discrete event systems, adaptive supervision is, by and large, an open problem. This paper proposes an approach to the design of adaptive supervisors based on a systematic revision of the desirable language, via a learning mechanism, so that the system’s properties are safe.
Yaw Dynamic Modeling for Improved High Speed Control of a Farm Tractor
Authors: Bevly David M. , Gerdes J. Christian , Parkinson Bradford W.
Published: November 2021

This paper presents the system identification of a farm tractor in order to improve automatic control at higher speeds and understand controller limitations from neglecting the yaw dynamics. Yaw dynamic models are developed for multiple speeds to show the effect of velocity on the model. The identified modeled yaw dynamics do not resemble any traditional analytical models. Additionally, the effect of velocity on the closed loop bandwidth of the controller for a given set of LQR controller weights is presented. Results are given that validate that as the closed loop bandwidth of LQR control weights approaches the regime of the unmodelled yaw dynamics, the controller can go unstable. Finally results show an improvement of the lateral tracking error (with a decrease in control effort) using the system identification model.
Nonlinear Air-to-Fuel Ratio and Engine Speed Control for Spark Ignition Engines
Authors: Wagner J. R. , Dawson D. M. , Liu Z.
Published: November 2021

The wide-range of operating conditions, inherent induction process nonlinearities, and gradual component degradations due to aging, have prompted research into model-based engine control algorithms. Consequentially, a variety of nonlinear and intelligent algorithms have been proposed and experimentally studied. Recent attention has focused on the simultaneous regulation of the air-to-fuel ratio and engine speed using a sliding mode control strategy. In this paper, a nonlinear model-based backstepping control strategy will be proposed for simultaneous air-to-fuel ratio control and speed tracking in passenger/light-duty automobile engines. For comparison purposes, a multi-surface sliding mode controller and an integrated speed-density air-to-fuel controller with attached engine speed regulation will be implemented. Representative numerical results will be presented and discussed.
An Analysis of Circular Bolted Flanged Joints on Solid Round Bars Subjected to External Bending Moments
Authors: Sawa Toshiyuki , Morohoshi Tsuneshi , Shimizu Akihiro
Published: November 2021

In designing bolted joints, it is important to know the contact stress distribution which governs the clamping effect or the sealing performance and to estimate the load factor (the ratio of an increment in axial bolt force to an external load) from bolt design standpoint. The clamping force by bolts and the external bending moment are axi-asymmetrical loads and not many investigations have seen reported which treat axi-asymmetrical. In this paper, the clamping effect, and the load factor for the case of solid round bars with circular flanges, subjected to external bending moments, are analyzed as an axi-asymmetrical problem using the three-dimensional theory of elasticity. Experiments were carried out concerning the contact stress distribution, and the load factor for the external bending moment (a relationship between an increment in axial bolt force, and external bending moment). The analytical results were in fairly good agreement with the experimental ones.
Analysis of the Tightening Process of Bolted Joint With a Tensioner: Effects of Interface Stiffness
Authors: Fukuoka Toshimichi
Published: November 2021

Hydraulic tensioners are widely used in tightening important structural members such as large-sized diesel engines and pressure vessels. The ratio of desired clamping force to initial tension, which is termed effective tensile coefficient, is the most important factor to be predicted in the actual operation for given joint configurations. In this paper, an elementary approach to estimate this coefficient, taking the effects of interface stiffness into account, is proposed using spring elements. The influences of interface stiffness at four contact surfaces on the coefficient are discussed, and it is shown that interface stiffness of pressure flank of threads and bearing surface of nut has dominant effects on the coefficient.
Preparation of Injectable Human Tissue Matrix
Authors: DeVore Dale P.
Published: November 2021

Autogenous tissue has always been the best material for implantation. When available and practical, autogenous tissue preparations are inherently safe with no potential for rejection, allergic or immunogenic reactions. However it is rare that such tissue is readily available. Thus, allograft tissues have been the next best choice for implantation to repair or replace damaged, diseased or inadequate tissues. A recent survey from the American Association of Tissue Banks (AATB) reported that more than 400,000 allograft tissues were transplanted in 1996. These tissues included bone, tendon, skin, fascia, and dura, pericardium and cardiovascular. Tissues are recovered from organ and tissue donors and donation is strictly regulated by the Food and Drug Administration (FDA) and AATB to ensure the safety of such transplants. In the last decade there have been no confirmed reports of AIDS transmission from allograft implants.
Dynamic Compression Stimulates the Development of Equilibrium Aggregate Modulus in Tissue Engineered Cartilage Constructs
Authors: Mauck Robert L. , Palmer Glyn D. , Wang Christopher C.-B. , Soltz Michael A. , Valhmu Wilmot B. , Ateshian Gerard A. , Hung Clark T.
Published: November 2021

A major challenge facing the tissue engineering of articular cartilage is the ability to grow tissue constructs that have the proper mechanical and biochemical properties that permit cartilage to serve its load-bearing function. This study tested the hypothesis that physiologic deformational loading enhances the formation of functional material properties in cell-seeded agarose constructs (versus free-swelling constructs).
Effects of Distortion of the Aorta on the Blood Flow and Its Significance on the Localization of High Wall Shear Stress Region
Authors: Mori Daisuke , Liu Hao , Yamaguchi Takami
Published: November 2021

The aorta is the largest artery in the body. It consists of the ascending aorta that leaves the left ventricle, the aortic arch where it curves about 180°, and the descending aorta. Three prominent branches to the head and upper limbs leave the aortic arch. In addition to this complex configuration, it was recently pointed out that the centerline of the aortic arch does not lie in a plane, and has a three dimensional (3D) distortion. This distortion induces very strong deviation of the 3D structure of the blood flow from that usually assumed to occur in flows in simple curved pipes (Caro et al. 1996). This 3D flow structure is thought to be responsible for some serious aortic diseases, including aortic aneurysms. It has been reported that the flow in a real human aorta is not the well-known twin vortex-type symmetrical secondary flow that is well established theoretically and experimentally for a simple curved pipe. Kilner et al. (1993) observed a single helical and retrograde secondary flow pattern by Magnetic Resonance Imaging (MRI).
The Effects of Implantation Techniques on Platelet Activation in a Mechanical Heart Valve: A Numerical Study
Authors: Li Yanmei , Bluestein Danny
Published: November 2021

A numerical simulation of pulsatile turbulent flow was conducted past a St. Jude Medical MHV in the aortic position, to study the effects of valve implantation technique on the thromboembolic potential of the valve. The effects of valve orientation and the suturing technique employed were examined in terms of the thromboembolic potential of the valve. It was demonstrated that the combination of a valve that is not aligned with the axis of the blood flow and subannularly sutured pledgets, produced accelerating jet flow through the valve orifices and a wider wake of periodic shed vortices in the valve’s leaflets wake. Platelets paths that exposed the platelets to the highest shear levels led them to entrapment within the shed vortices, indicating an increased risk of cardioembolism via the potential free emboli formation in the wake.
Bioengineered Muscle Implants
Authors: Bowlin G. L. , Wise Barbara , Terracio L. , Simpson D. G.
Published: November 2021

Fundamental research has defined many of the mechanistic events that mediate congenital malformations and the pathological disease processes that alter cardiac structure and function. Despite these efforts, there are a limited number of clinical treatment options available for many of these conditions. In many cases, even for disease processes that cause focal defects in the ventricular wall, the only viable treatment is the complete replacement of the damaged organ by transplant. Unfortunately, the supply of cardiac tissue that is available for transplant therapy remains chronically, and critically, short of demand. The reconstruction of a specific domain of dysfunctional ventricular tissue with a cell-based therapy is a potential avenue of treatment. One of the most direct strategies in this type of treatment regime is the injection of a suspension of fetal or neonatal cardiac myocytes into the injured domain. In small animal models, two limitations have become apparent with this strategy. First, differentiated myocytes do not undergo migration when they are injected into scar tissue and as a result they tend to remain concentrated in the vicinity of the injection site. Second, the myocytes that survive in the injection site are not well integrated into the healthy tissue and contract at rates that are independent of the surrounding myocardium. The long-term objective of this project is to circumvent the limitations of injection therapy by fabricating a cardiac muscle prosthesis that mimics the three dimensional architecture of the intact heart.
Biomechanical Problems With Contact Pressure Distribution in the Knee Joint After Total Knee Arthroplasty
Authors: Giachetti R. S. , Amirouche F. M. , Aram L. A. , Gonzalez M.
Published: November 2021

The most critical aspect to the life of Total Knee Arthroplasty is the surgical fit. This project’s goal is to use a 3-D Finite Element Model of the TKA modified knee and create dynamic pressure profiles across the condylar surfaces. Then validate the results through experimental data so that it can be used to fit TKAs.

The ANSYS™ model currently contains 10,000 elements and represents the whole tibial piece including the femoral component surface. Loading of the model is restricted to the condylar surface and the bottom of the piece is constrained to zero displacement. The experimental aspect of the project consists of a cadaver leg fitted with the prosthesis and is able to record real time pressure across the condyles as a function of time and joint angle.

This study validates previous work and also generates new pressure data indicative of normal flexion-extension motion in the TKA modified joint. This enables the exact alignment of the joint, thus creating a perfect fit and eliminating premature failure of TKAs.
Role of Hard Tissue Inelastic Properties in the Damage Behavior of Trabecular Bone
Authors: Yeh Oscar C. , Keaveny Tony M.
Published: November 2021

Relatively little is known about the inelastic properties of trabecular hard tissue. In cortical tissue, age-related changes in mechanical properties were primarily observed in the postyield regime [1, 2]. Most notably, the ultimate strain was found to decrease by 9% per decade [1]. If similar changes in inelastic properties exist in trabecular tissue, there could be implications for the damage behavior of trabecular bone at the whole specimen “apparent” level. Understanding the role of these inelastic properties may help researchers identify which properties of trabecular tissue are vital to characterize and may improve understanding of age-related increases in skeletal fragility.
Finite Element Modeling of Penetrating Traumatic Brain Injuries
Authors: Pintar Frank A. , Kumaresan Srirangam , Stemper Brian , Yoganandan Narayan , Gennarelli Thomas A.
Published: November 2021

Recent advances in the treatment of penetrating gunshot wounds to the head have saved lives. These advances are largely reported using retrospective analysis of patients with recommendations for treatment. Biomechanical quantification of intracranial deformation/stress distribution associated with the type of weapon (e.g., projectile geometry) will advance clinical understanding of the mechanics of penetrating wounds. The present study was designed to delineate the biomechanical behavior of the human head under penetrating impact of two different projectile geometries using a nonlinear, three-dimensional finite element model. The human head model included the skull and brain. The qualitative comparison of the model output with each type of projectile during various time steps indicates that the deformation/stress progresses as the projectile penetrates the tissue. There is also a distinct difference in the patterns of displacement for each type of projectile. The present study is a first step in the study of the biomechanics of penetrating traumatic brain injuries.
Comparative Testing of Commercial, Modified and Non-Automotive Seat Backs
Authors: Muzzy William H. , Khadilkar Anil V. , Yeager Robin , Laviano Claude W.
Published: November 2021

A series of comparison tests was conducted on several automotive seats to find the range of forces required to fail them when a load was applied to the seat back at the upper cross member. A simple calculation for each seat was performed to compare the moment (or amount of rotating force at the seat back pivot point) that was required for the seat back to fail. In addition, two of the seat designs were reinforced to increase the seat back moment. This was done to assess the requirements necessary to strengthen the seat back’s resistance to failure when an occupant loaded it in a rear line of force crash.
Effect of Cortical and Cancellous Bone Anisotropy on Peri-Implant Stresses and Strains in the Posterior Mandible
Authors: O’Mahony Aisling M. , Williams John L.
Published: November 2021

We computed the bone-implant interface stresses for a bullet-shaped dental implant in the human mandible under combined vertical and horizontal loading. We also calculated the principal strains in the bone surrounding the implant. Two cases were compared: One in which the bone was considered to have isotropic elastic constants and the other in which transverse isotropy was assumed. Anisotropy increased the peak stresses and strains around both the implant-cancellous and implant-cortical bone interfaces.
Modulus of Toughness Measurements of Urinary Calculi
Authors: Wang Shyh-Jen
Published: November 2021

Objective: To improve the efficacy of ESWL treatment, it is desirable to identify the physical properties of urinary calculi that could offer direct correlation with their fragilities during ESWL and thus could be used to guide treatment procedures for more effective stone fragmentation.

Method: The 30 stone specimens removed surgically were compressed by an axial testing system to measure the compressive strength and trace the stress-strain curve. Image analysis software SigmaScan (Jandel Co.) was used to calculate the area under the stress-strain curve, the modulus of toughness, for each stone.

Result: The values of compressive strength measured were similar to those reported by other researchers. The modulus of toughness of urinary calculi correlates with the stone fragility during ESWL clinically.

Conclusion: The modulus of toughness could be an index to evaluate the physical property of urinary calculi that could be used to guide treatment procedures for more effective stone fragmentation.
Modeling of Composite With Meso-Localized Damage Accounting for Local Stress Distribution
Authors: Wu Yadong , Nakagaki Michihiko
Published: November 2021

The existing constitutive models of composite were usually built on the relation between the phase-average stress and strain, as treated in monolithic materials. In the present work, however, it was found that the averaged characteristic of the phase material, in which the plastic damage occurs, is quite different from that of the monolithic material. And the morphology of the non-uniform local properties remarkably gives effects on the global property of the composite. In order to model the local phenomenon in composite, a statistical distribution function was proposed to describe the local stress and the local plasticity. Furthermore by applying Localized Rigidity Method (LRM), which was proposed by the authors, a mixture law to estimate the percentage of the local plastic damage regions is developed. A numerical calculation was performed to investigate the nonlinear phenomena of the composite with the meso-localized plasticity, and the high performance of the present model was verified.
Probabilistic Modeling of Fatigue Crack Growth in Ti-6Al-4V
Authors: Soboyejo W. O. , Soboyejo A. B. O. , Shen W.
Published: November 2021

This paper presents the results of a combined experimental and analytical study of the probabilistic nature of fatigue crack growth in Ti-6Al-4V. A simple experimental fracture mechanics is presented for obtaining statistical fatigue crack growth parameters from one or two fatigue tests. The experimental studies of long fatigue crack growth show that the variabilities in the long fatigue crack growth rate and the Paris coefficient are well described by the log-normal distribution. The variabilities in the Paris exponent are also shown to be well characterized by a Weibull distribution. The measured statistical distributions are incorporated into a probabilistic fracture mechanics framework for the estimation of material reliability. The implications of the results are also discussed for the probabilistic analysis of fatigue crack growth in engineering components and structures.
Damage Tolerance in Biomedical Implants: Cardiac Valves and Endovascular Stents
Authors: Ritchie R. O.
Published: November 2021

The human heat rate is roughly 40 million beats per year. To prosthetic implants such as mechanical heart valves and endovascular stents, this means that they must endure almost 109 fatigue cycles during the patient’s lifetime. To prevent premature mechanical failures of such devices, which inevitably lead to patient fatalities, considerations of damage-tolerant design and life-prediction methodologies represent a preferred approach. In this presentation, a damage-tolerant approach to life prediction and “quality control” for both metallic and ceramic heart valve prostheses is presented, based on the notion that the useful life of the device is governed by the time for incipient defects in the material to propagate, by stress corrosion or more critically fatigue, to failure. Based on these analyses, the relative benefits of metallic (Co-Cr, Ti-6Al-4V) vs. ceramic (pyrolytic carbon) valves are discussed. Finally, analogous considerations are presented for endovascular stents, particularly those processed by laser cutting of the superelastic Ni-Ti alloy Nitinol. Again, the relative benefits of Nitinol vs. more traditional metallic implant materials (stainless steel, Co-Cr, titanium, titanium alloys) are discussed.
The Effects of High Temperature Exposure on the Durability of Thermal Barrier Coatings
Authors: Yanar N. M. , Stiger M. J. , Pettit F. S. , Meier G. H.
Published: November 2021

Yttria-stabilized Zirconia (YSZ) coatings deposited by electron beam physical vapor deposition on platinum aluminide and NiCoCrAlY bond coats on single crystal superalloy substrates have been oxidized at temperatures between 1000 and 1200°C in air. The cyclic oxidation lives of the systems with platinum aluminide bond coats were substantially longer than those with NiCoCrAlY bond coats. The thermally grown oxide (TGO) that develops between the bond coat and the TBC during oxidation, as well as the bond coat and the TBC adjacent to the TGO, have been examined in detail using optical metallography, scanning electron microscopy (SEM), and cross-sectional transmission electron microscopy (XTEM). The YSZ is observed to undergo significant amounts of sintering. The TGO grows by the inward diffusion of oxygen and the outward diffusion of aluminum. In some cases, the outward growth component incorporates some of the TBC into the TGO. The depletion of aluminum results in phase changes in the bond coats. Failure of the TBCs occurs after fixed amounts of oxidation which result in increasing amounts of elastic energy being stored in the TGO and YSZ as well as degradation of the TGO-bond coat interface. The fracture path changed as a function of exposure time and temperature with larger amounts of separation occurring at the TGO/BC interface for higher temperatures and longer exposures in dry air. Failure can be accelerated in the presence of water vapor, particularly if spinel formation is induced. Fracture occurs primarily in the oxides, in this case. The fracture surface for systems with platinum aluminide bond coats often contains precipitates, which are rich in refractory metals. These features do not appear to be prevalent with NiCoCrAlY bond coats.
The mechanisms of harmonic sound generation during phonation: A multi-modal measurement-based approach
Authors: Lodermeyer Alexander , Bagheri Eman , Kniesburges Stefan , Näger Christoph , Probst Judith , Döllinger Michael , Becker Stefan
Published: November 2021

Sound generation during voiced speech remains an open research topic because the underlying process within the human larynx is hardly accessible for direct measurements. In the present study, harmonic sound generation during phonation was investigated with a model that replicates the fully coupled fluid-structure-acoustic interaction (FSAI). The FSAI was captured using a multi-modal approach by measuring the flow and acoustic source fields based on particle image velocimetry, as well as the surface velocity of the vocal folds based on laser vibrometry and high-speed imaging. Strong harmonic sources were localized near the glottis, as well as further downstream, during the presence of the supraglottal jet. The strongest harmonic content of the vocal fold surface motion was verified for the area near the glottis, which directly interacts with the glottal jet flow. Also, the acoustic back-coupling of the formant frequencies onto the harmonic oscillation of the vocal folds was verified. These findings verify that harmonic sound generation is the result of a strong interrelation between the vocal fold motion, modulated flow field, and vocal tract geometry.
Proximity-Labeling Reveals Novel Host and Parasite Proteins at the
Toxoplasma
Parasitophorous Vacuole Membrane
Authors: Cygan Alicja M. , Jean Beltran Pierre M. , Mendoza Alma G. , Branon Tess C. , Ting Alice Y. , Carr Steven A. , Boothroyd John C.
Published: November 2021

Toxoplasma
is an intracellular pathogen which resides and replicates inside a membrane-bound vacuole in infected cells. This vacuole is modified by both parasite and host proteins which participate in a variety of host-parasite interactions at this interface, including nutrient exchange, effector transport, and immune modulation.