bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adaptive Feedback Linearization for the Control of a Typical Wing Section With Structural Nonlinearity
Authors: Ko Jeonghwan , Kurdila Andrew J. , Strganac Thomas W. 
Published: March 2022

Abstract
Earlier results by the authors have derived constructions of Lie algebraic partial feedback linearizing control methods for pitch and plunge primary control utilizing a single trailing edge actuator. In addition, a globally stable nonlinear adaptive control method was derived for a structurally nonlinear wing section with both a leading and trailing edge actuator. However, the global stability result described in a previous paper by the authors, while highly desirable, relied on the fact that the leading and trailing edge actuators rendered the system exactly feedback linearizable via Lie algebraic methods. In this paper, the authors derive an adaptive, nonlinear feedback control methodology for a structurally nonlinear typical wing section. The technique is advantageous in that the adaptive control is derived utilizing an explicit parameterization of the structural nonlinearity, and defining a partial feedback linearizing control via Lie algebraic methods that is parametrically dependent. The closed loop stability of the system is guaranteed to be stable via application of LaSalle’s in variance principle.
Reduced Order Aerodynamic Modeling of How to Make CFD Useful to an Aeroelastician
Authors: Dowell Earl H. , Hall Kenneth C. , Romanowski Michael C. 
Published: March 2022

Abstract
In this article, we review the status of reduced order modeling of unsteady aerodynamic systems. Reduced order modeling is a conceptually novel and computationally efficient technique for computing unsteady flow about isolated airfoils, wings, and turbomachinery cascades. Starting with either a time domain or frequency domain computational fluid dynamics (CFD) analysis of unsteady aerodynamic or aeroacoustic flows, a large, sparse eigenvalue problem is solved using the Lanczos algorithm. Then, using just a few of the resulting eigenmodes, a Reduced Order Model of the unsteady flow is constructed. With this model, one can rapidly and accurately predict the unsteady aerodynamic response of the system over a wide range of reduced frequencies. Moreover, the eigenmode information provides important insights into the physics of unsteady flows. Finally, the method is particularly well suited for use in the active control of aeroelastic and aeroacoustic phenomena as well as in standard aeroelastic analysis for flutter or gust response. Numerical results presented include: 1) comparison of the reduced order model to classical unsteady incompressible aerodynamic theory, 2) reduced order calculations of compressible unsteady aerodynamics based on the full potential equation, 3) reduced order calculations of unsteady flow about an isolated airfoil based on the Euler equations, and 4) reduced order calculations of unsteady viscous flows associated with cascade stall flutter, 5) flutter analysis using the Reduced Order Model. The presentation will include our most recent results including the use of A-one Orthogonal Decomposition as an alternative or complement to eigenmodes.
Integrated Design of Controllable Tensegrity Structures
Authors: Sultan C. , Skelton R. E. 
Published: March 2022

Abstract
Tensegrity structures represent a special class of spatial structures, having a continuous network of members in tension and a discontinuous network of members in compression. These members can serve simultaneously as sensors, actuators, and load carrying elements. Hence, structure and control design must be carried out together. This paper illustrates the use of tensegrity structures as adaptive structures. The paper addresses static design problems, presents the mathematical structure of the linear dynamic models, deals with the actuator locations, and integrates structure and controller design for output variance control problems. Through integration of static design, actuator selection and controller design, better performances are achieved compared with the case in which these tasks are carried out separately.
Power Flow Analysis of an Electrostrictive Actuator Driven by a PWM Amplifier
Authors: Zvonar Gregory A. , Lindner Douglas K. 
Published: March 2022

Abstract
In this paper we analyze the power flow between stacked electrostrictor actuators and a pulse-width-modulated switching amplifier. An integrated model is developed with includes a dynamic structural model of the actuator, a dynamic model of the power electronics and a nonlinear electro-mechanical coupling mechanism. By analyzing the conversion of mechanical power to and from electrical power, a better understanding is gained of the interaction between the electrical amplifier and the actuators. Furthermore, this new insight provides for the design of more efficient closed loop controllers. This work focuses on the behavior of electrostrictive actuators with nonlinear actuator models. Also, with the inclusion of the dynamic model of the switching amplifier, the power flow can be traced directly back into the original power bus. The effect on the power flow of a nonlinear amplifier controller is also investigated. It is shown that the nonlinear controller, which reduced actuator velocity distortion, also reduces the maximum required power that the amplifier must process.
Simultaneous Optimization of Structural and Controller Parameters of Spring-Supported Beam for Vibration Control
Authors: Zhu Ye , Qiu Jinhao , Tani Junji , Urushiyama Yuta , Hontani Yasuhara 
Published: March 2022

Abstract
The modeling and formulation of simultaneous optimization problems with H2 and H∞ norm objective functions are discussed in the paper. They are applied to the simultaneous optimization of the cross-sectional parameters of a spring-supported beam and the parameters of the controller used to actively suppress the vibration of the beam. The H2 and H∞ norms of the transfer function from external disturbance to measured output are used as the objective functions. Simultaneous optimization is realized by iteratively executing structural optimization and controller optimization. Both serial and parallel approaches to combine structural optimization and controller optimization are investigated. The performance of both output and control input is improved significantly after simultaneous optimization. The simulation results show the great potential advantages of simultaneous optimization over traditional design methods.
A Method for Analysis of Vibration Systems With Integrated Active Elements
Authors: Hornung Thomas , Reimerdes Hans-G. , Günnewig Jochen 
Published: March 2022

Abstract
Designing smart structural systems with induced strain elements, like piezoelectric ceramic actuators, is a comprehensive issue, involving not only geometry and material data but also the behavior of the coupled host system as a main aspect. For an effective control of structural vibration due to external or environmental loads, an accurate description of the system is needed. An analytical based method for the characterization of the complete system under consideration of local increase of stiffness and mass by integrating sensor and actuator elements will be presented in this paper.
Two Dimensional Finite Element Analysis of Myocardial Infarction in the Human Left Ventricle
Authors: Sathyamoorthy Mohan 
Published: March 2022

Abstract
Diseases of the heart and blood vessels are the number one causes of patient mortality in the United States. Of these conditions, myocardial infarctions, more commonly known as heart attacks, are the most feared of cardiovascular pathologies. The American Heart Association has dedicated billions of dollars over the past four decades to basic science and clinical research to help prevent and treat heart attacks. Detailed assessment of three dimensional stress, strain, and deformation histories is important because it has been noted that reduced transmural strain and left ventricular torsion may be indicative of myocardial infarction resulting from ischemia [1]. Previous studies have been limited to clinical and experimental modalities of study. With the evolution of high speed computers and finite element softwares, detailed and effective biomechanical modeling of complex physiological systems such as the heart have been undertaken. The objective of this study is to utilize finite element analysis to assess local and global deformation and stress patterns in normal vs. imposed conditions of myocardial infarction. Such knowledge obtained a priori could be utilized by cardiothoracic surgeons and cardiologists to improve the efficacy of treatment and treatment options for patients suffering from heart disease.
Elastic Properties of 3D Cells for Trabecular Bone: Digital vs. Structural Finite Element Models
Authors: Ominsky Michael S. , Zysset Philippe K. , Goldstein Steven A. 
Published: March 2022

Abstract
Characterizing morphological and elastic properties of trabecular bone is a critical step towards understanding bone fragility. Idealized 3D cells for trabecular bone based on a tetrakaidecahedral geometry have been previously described to study morphology and its relationship to mechanical properties [1,2]. Two types of cells have been proposed: an open cell consisting of rectangular beams and a closed cell with hexagonal plates [Fig. 1]. The morphology of the cell is quantified by measures of structural density (SD) and mean intercept length (MIL). Structural density is mainly controlled by the aspect ratio t/l (thickness/length) of the beams or plates. Mean intercept length is controlled by the angle θ, which changes the cell’s anisotropy.
A Comprehensive Investigation of the Biomechanics of an Artificial Intervertebral Disc
Authors: Todd Dwight T. , Goel Vijay K. , Grosland Nicole M. , Gilbertson Lars G. , Wilder David G. , Pope Malcolm H. , Lankford James 
Published: March 2022

Abstract
The biomechanics and wear characteristics of an experimental artificial disc prosthesis have been investigated through a three-part study. This study reports the results of in-vitro cadaveric testing, finite element modeling, and cyclic wear testing. Load-displacement data from the in-vitro testing and finite element model demonstrate that the artificial disc can provide comparable biomechanics to the intact case. The finite element model also predicts increased facet loads in extension. Results from the wear study show little gravimetric wear over two million cycles.
Altered Collateral Ligament Strain Following Total Knee Arthroplasty
Authors: Hairrell E. Nicki , Eberhardt Alan W. , Moeini Reza , Cuckler John 
Published: March 2022

Abstract
The geometric design of a total knee arthroplasty system can cause changes in the wear and fixation of the device, as well as the kinematics of the replaced joint (Nilsonn, et al., 1997). Troubles arise when trying to determine the strain behavior of the collateral ligaments of the knee, due to subject-to-subject variations (Crownshield et al., 1975). This study compared the strain in the collateral ligaments of the knee, before and after a total knee arthroplasty. It is hypothesized that this information can be used to indicate the effects of the TKA on these ligaments. If the strain after a TKA is greater than the normal physiological strain in these ligaments, this may be perceived as a source of discomfort or disfunction for the patient. Such a comparison of strain patterns may be used as a tool in the design of improved total knee arthroplasty system.
Interaction of Airflow With Mucus Simulant in a Channel
Authors: Evrensel Cahit A. , Hassan Amgad A. , Krumpe Peter E. 
Published: March 2022

Abstract
A common symptom of most obstructive airway diseases is the impaired muco-ciliary transport due to increased mucus viscosity and thickness. These persons must rely on the two-phase flow and cough as a lung clearance mechanism. The objective of this study is to understand the dynamics of the interface between the airflow and mucus layer better. This understanding is inherent to designing therapies to enhance the mucus clearance.
Strain Rate Affects Viscoelastic Measurements on Porcine Aortic Heart Valve Tissue Tested in Shear
Authors: Talman Eric , Boughner Derek 
Published: March 2022

Abstract
Mechanical testing of bioprosthetic heart valve tissue is an important aspect of engineering a successful artificial valve. The artificial tissue must be strong enough to withstand the tension associated with back-pressure during systole, yet pliable enough to undergo the complex deformations during valve opening and closing. Current prostheses have adequate strength but their pliability is reduced which may contribute to premature tissue failure.
Mixing Studies in Bioreactors
Authors: Menisher Tewodros , Metghalchi Mohamad , Gutoff Edgar B. 
Published: March 2022

Abstract
Fluid mixing is a very important factor that needs to be considered in the design of bioreactors. Growing cells in bioreactors require sufficient amounts of nutrients and oxygen for their growth. The transfer of these nutrients to the cells can be ensured by sufficient mixing, yet excessive shear can destroy the cells. This study compares two impellers used for mixing: the “Dumbo Ear” impeller and the high efficiency A310 impeller.
Mixing time is used as the criteria of the performance of the impellers. Mixing time is defined as the time taken for the disappearance of the pink color of Phenolphthalein indicator in a basic solution by the rapid addition of acid. A known amount and concentration of sodium hydroxide is added to a bioreactor containing distilled water with a known amount phenolphthalein, turning the solution pink. Using pressure driven dispensing system (Figure 1), excess hydrochloric acid is rapidly injected to neutralize the base. The time it takes for the solution to become colorless is recorded as the mixing time. The mixing time is measured as a function of rotational speed for different locations of the impeller. The results are reported in figures 2–6.
Figure 2 compares Dumbo Ear impeller with the A310 at a clearance-to-height ratio (C/H) of 0.44 for a vertically centered shaft. In all the cases studied, the Dumbo Ear impeller out-performed the A310. The effect of varying clearance of the impeller on the mixing time was also investigated. Unlike the A310, the Dumbo Ear impeller showed better mixing as the clearance is reduced (Figure 3). In studying the effect of shaft angle on mixing time, two ways of pivoting the impeller were utilized. In the first case the impeller was pivoted at the intersection of the tank centerline with the top surface of the liquid. The impeller was also pivoted so as to maintain the bottom of the impeller shaft at the centerline of the tank. Thus in one case the impeller shaft entered the liquid at the centerline of the tank, and in the other case it did not, but the base of the shaft remained at the centerline. The shear forces will be different in the two cases because the clearances will be different. Figure 4 shows the variation in mixing time for a 15° shaft angle. In most of the cases studied, pivoting at the surface of the liquid gives a shorter mixing than pivoting at bottom of the impeller shaft. Figures 5 & 6 compare the mixing times for vertical and pivoted impellers for the two types of pivoting. In both types, tilting impeller reduces the mixing time.
This mixing study showed that in most cases, at the same rotational speeds, the Dumbo Ear impeller gave shorter mixing times than the A310. Also, tilting the Dumbo Ear impeller and having a small bottom clearance gave the shortest blending times. However, in all cases, one has to consider the increased shear forces on cells when clearance between the blades to the walls is reduced.
Hydrodynamics in Cell Rolling and Adhesion
Authors: Zhao Yihua , Skalak Richard , Chien Shu 
Published: March 2022

Abstract
Formulas for the slow viscous motion of a sphere in the presence of a solid wall have been used in analyzing the phenomena of cell rolling and adhesion. The established theories, such as the ones by Brenner and his colleagues [1,2,3], address the ideal situation in which both the sphere and the wall are smooth. However, biological cells such as leukocytes have numerous surface protrusions (microvilli). Therefore, the applicability of the theories of smooth spheres to the problem of cell rolling and adhesion needs to be examined. Also, to facilitate the design and analysis of experiments, it is desirable to have a simple solution that can provides some physical insights into the process.
Computational Fluid Dynamics Analysis of Pulsatile Flow Over an Isolated Intravascular Stent Strut
Authors: Ainsworth Stephen D. , Ochterbeck Jay M. , Langan Eugene M. , LaBerge Martine 
Published: March 2022

Abstract
Knowledge of the distinct fluid dynamic factors created by an intravascular stent, placed in an atherosclerotic artery and subjected to pulsatile flow, is limited. A computational fluid dynamics modeling approach was used in this research to analyze and measure the effect of single stent struts on the flow separation and reattachment points, and re-circulation regions. With the overall goal to effectively model a comprehensive stented atherosclerotic artery, this preliminary study focused on two dimensional flow at various points in the cross-section of a stent subjected to steady and pulsatile flow. The reattachment point is an area of increased wall shear stress gradients, and thus a concern when considering intimal hyperplasia. The results show that the reattachment point is a function of the longitudinal cross sectional geometry of the stent. Pulsatile flow results show the motion of the reattachment point with increasing and decreasing flow, as well as the relationship of the geometrical design of the stent and the existence of reattachment points between struts.
Mechanics of Heterogeneous Atherosclerotic Human Aorta: Correlation With Positive Staining for MMP-1
Authors: Beattie Deborah , Vito Raymond , Bilusic Zrinka , Xu Chengpei , Glagov Seymour 
Published: March 2022

Abstract
We hypothesize that mechanical factors within heterogeneous atherosclerotic human arteries are important, either as primary determinants of plaque stability or as influences on relevant cell activity. We developed an experimental system to measure the finite deformation of diseased human arterial cross sections at physiologic pressures. Strains are calculated using interpolation functions. The distributions of lipid, calcified, healthy and fibrous tissue are measured using differential staining and light microscopy. The presence of matrix metalloproteinase 1 is also quantified. Histologic features and deformations are incorporated into a plane stress finite element model and tissue constituent material properties, stresses and strain energies are determined using an optimization procedure. Results show correlation of stress and strain distributions with histologic make up of the tissue and with staining for matrix metalloproteinase (MMP-1).
Analysis of Instability and Self-Excited Vibration for Collapsible Tube by Distributed Parameter Model
Authors: Hayashi Satoru , Hayase Toshiyuki , Miura Yuji 
Published: March 2022

Abstract
The stability of a Starling resistor type collapsible tube circuit are studied on the basis of a distributed parameter model including no effect of flow separation at the collapsed part of the tube. The governing equations are spatially discretized into 200 sections and rearranged to 401 ordinary differential equations with respect to time. The stability of the circuit is examined by the characteristic equation of linearized governing equations. Transition of the stability according to variation of the flow rate is indicated as a root locus of the eigenvalues. The original nonlinear equations are numerically solved by Runge-Kutta scheme and the theoretical frequency and the amplitude of self-excited vibrations are compared with experimental results.
An Experimental System to Expose Perfused Vascular Segments to Cyclic Bending Ex-Vivo
Authors: Vorp David A. , Severyn Donald A. , Mears Jon R. 
Published: March 2022

Abstract
Portions of coronary and other blood vessels undergo cyclic bending due to attachment to the heart or crossing of joints [1,4,9]. Bending of a vascular segment alters the local transmural stresses and strains [5,13] as well as the shear stresses acting on the endothelial surface [8,11]. Fluctuations in both shear stress and in-plane stretch have been shown to influence endothelial cell and smooth muscle cell biology [12]. The purpose of the present work was to create a model to expose perfused, intact vascular segments to cyclic bending in-vitro. Such a system would enable the assessment of the biologic response of vascular tissue to combined alterations in transmural stress and shear stress produced by cyclic bending.
A Generalized Scheme for Surface-Fit of Dynamic Coronary Artery Tree Data
Authors: Pao Y. C. 
Published: March 2022

Abstract
The earliest geometric model used for computing stresses in the heart was a sphere. As computer tomography becomes increasingly utilized, the true geometry of the heart can be reconstructed three-dimensionally. However, for qualitative finite element analysis of the in vivo heart by applying the advanced theories of mechanics, idealized geometric shapes are still needed We have presented the spline-fitted spatial curve for study of the bending and twisting of the coronary artery tree of a beating heart [1]. The dynamic behavior of arterial branches near a bifurcation has been investigated based on the developed method. Anatomic landmarks such as the bifurcation points are necessary for study of the local behavior. Otherwise, implanted markers would be needed for identifying the investigated region. For global study of the whole heart or coronary artery tree [2], idealized geometry is more practical for approximated analyses.
An Overload Failure of a Dental Prosthesis: A 3D Finite Element Nonlinear Contact Analysis
Authors: Prabhu Ajit A. , Brunski John B. 
Published: March 2022

Abstract
Dental implants are extensively used to treat fully and partially edentulous patients. However, the success rates of clinical cases involving partially edentulous patients is lower than the fully edentulous cases.1 In one partially edentulous case that we have been examining, a prosthesis was supported by two screw-shaped, 3.75mm diameter Branemark implants as shown in Figure 1. The implants were separated by 7mm and were located in the molar region of the mandible. After the insertion of the implants and a healing period of 6 months, the prosthesis was put into function. After 3 months of loading, there was significant bone loss near the mesial implant which eventually lead to its mechanical failure. We have previously made a biomechanical analysis of this failed implant case using analytical2 and 3D finite element (FE) analysis.3 In the previous 3D FE study, the interface between the implant and the bone was assumed to be fully bonded. In this current investigation, the assumption of bonding vs no bonding is further investigated using 3D contact analysis. Surface to surface contact is a phenomenon that occurs between two contacting surfaces which are close to each other and might be in contact or separated depending on the interfacial stresses between the two surfaces. In this study the contact analysis is used to capture the bonding and non bonding between the bone and the implant interface.