bluuebunny/crossref_metadata_2025_split huggingface dataset:
Capability and Variability of Trunk Performance During Upright Isometric Pure and Combined Exertions
Authors: Sheikhzadeh Ali , Nordin Margareta , Parnianpour Mohamad 
Published: December 2021

Abstract
High physically demanding tasks during daily living activities and industrial tasks are best represented by a with combination of the sagittal and lateral or transverse torque. Based on the results of this study, the combination of sagittal and transverse torque present higher risk of spinal injury compared to pure exertions, all muscles presenting higher activity. The capability and controllability of the generated torques are significantly lowered during combined exertions. These results suggest that the trunk muscles will be taxed at a higher relative load while performing combined loading tasks, increasing the probability of muscle fatigue and low back injury.
On an Idealized Wrapping Loading of the Human Spine
Authors: Shirazi-Adl A. , Parnianpour M. 
Published: December 2021

Abstract
The kinetic redundancy of the complex human spinal system presents a rather insurmountable obstacle in estimating the activation patterns and passive-active load sharing. A plausible hypothesis is that the spinal posture, at a given task and load level, is so adjusted as to maintain equilibrium and a sufficient margin of safety against instability while minimizing the need for muscle exertion. Our recent in vivo and model studies support the importance of the pelvic tilt and lumbar curvature in mechanics of the human spine (Shirazi-Adl and Parnianpour, 1996, 1999). In view of very low compression load-carrying capacity (i.e., stability) of the passive ligamentous spine, attempts have been made to investigate optimal path of applied compression loading that could both stabilize the passive system and result in lower stresses and higher margin of safety against tissue failure (Aspeden, 1989; Gracovetsky et al., 1989). Recent in vitro experimental and model studies on the lumbar spine has demonstrated that the passive ligamentous lumbar spine with no musculature is stable under compression loads that remain perpendicular to disc mid-height planes (i.e., wrapping or continuous follower loads) (Patwardhan et al., 1998; Shirazi-Adl and Parnianpour, 1998). In this work, the response of the lumbar and thoracolumbar spine under wrapping compression loads is investigated in order to study the stabilizing effect of this idealized loading configuration as well as its effect on internal tissue-level stress/strain values.
Biomechanics of Human Cervical Spinal Column Under Physiologic Loads
Authors: Hollowell James P. , Kumaresan Srirangam , Yoganandan Narayan , Pintar Frank A. 
Published: December 2021

Abstract
The determination of the biomechanics of the human cervical spinal column under physiologic loads was a focus of the present study. The effects of pre-load on the load carrying capacity of spine were investigated. Structural morphology was divided into young, representing normal/non-degenerated, and old, representing abnormal/degenerated spines. Intact human cadaver cervical spinal columns were carefully isolated by maintaining the integrity of the ligamentous soft tissues. Fat and surrounding musculature were dissected. Radiographs of the specimens were obtained before the test. At each level of the cervical column, retroreflective targets were inserted into the bony articulations. Kinematic information was obtained from these targets. Principles of continuous motion analysis were used to determine the kinematics of the cervical column. A six-axis load cell was attached at the inferior end of the specimen. Flexion, extension, axial rotation, and lateral bending moments were applied. The specimens were tested with and without pre-load conditions. Results are presented with regard to variations in angular stiffness values as function of applied moment, pre-load, and spine condition. This study emphasizes the differing roles contributed by the load vector and specimen morphology on cervical spine biomechanics.
Equilibrium Point and Knee Joint Modeling
Authors: Li Li 
Published: December 2021

Abstract
Human running behavior has been modeled as bouncing ball. In this regard, mass-spring model has been employed to study the mechanical characteristics of lower extremity during running. The mechanical adaptation of the lower extremity to the environment during running presents significant considerations in the understanding of the mechanism that governing the mass-spring system. A mass-spring model with a changing equilibrium point is developed in this study. The model predicts that the knee joint will experience three different stages during running stance phase. Each stage (phase) is associated with different joint stiffness, which is constant with in the each phase. The model further suggests that this unique stiffness could be estimated by using kinematics of knee joint only without kinetic measures. This model provides information that improves our understanding of knee joint mechanical behavior and neuromuscular control mechanism. It also has important clinical applications.
Nondestructive Evaluation of Fiberglass Reinforced Plastic Subjected to Combined Localized Heat Damage and Fatigue Damage Using Acoustic Emission
Authors: Nayeb-Hashemi H. , Kasomino P. , Saniei Nader 
Published: December 2021

Abstract
The effect of fatigue damage to unidirectional fiberglass composite specimens with prior contact heat damage was investigated. After damaging the specimens by contacting them to a hot tip at 360 °C, the specimens were subjected to fatigue loading at cyclic stress amplitude corresponding to 65% of the specimens’ ultimate tensile strength. The fatigue experiments was halted after 3000 cycles. The specimens were then subjected to tensile tests while monitoring their Acoustic Emission activity. In addition, acoustic emission activities of undamaged and contact heat damaged specimens were monitored during tensile tests for comparison with specimens with combined fatigue and heat damage. AE activities of all specimens can be categorized into three regions: an early rise in activity, a relatively dormant period in activity and a high exponential activity before failure. The early rise in activity did not appear on the specimens with combined contact heat and fatigue damage. For undamaged and contact heat damaged specimens, the period of the dormant activity was independent of the contact heat duration of less than 15 minutes. However, the period was a function of the contact heat duration for combined contact heat and fatigue damaged specimens. Analyzing event duration distribution identified micro-mechanisms of the damage growth upon tensile loading.
AE-stress delay concept was used to predict the state of the damage in the composite. A correlation between stress delay parameter and damage parameter was obtained for all of the specimens.
Fatigue life of contact heat damaged specimen was also studied. It was found that localized heat damage reduced the fatigue life significantly. Loss of matrix to transfer the load to the fibers uniformly was believed to be responsible for the reduction in the fatigue life.
Experimental Investigation of Compressive Overloads on Delamination Growth Behavior in Fatigued Composites
Authors: Pelegri Assimina A. , Valentine Charles 
Published: December 2021

Abstract
The behavior of laminated graphite/epoxy composites under variable amplitude compressive loading is studied. Laminate composites in aerospace applications undergo both compressive and tensile fatigue stresses as well as spectrum loading. These materials are particularly susceptible to compressive loads and overloads, which cause the growth of any small pre-existing delaminations. Such delamination growth, and the resulting sublaminate buckling, are major causes of fatigue failure. This experimental program investigates the effects of overloads on laminate composite specimens in which small delaminations are introduced during fabrication. The delamination growth is monitored in real time during fatigue tests. Different variable amplitude load spectra are applied, and the delamination position through the depth of the specimens is varied. Up to now, research has focused on constant amplitude fatigue testing or simple two block testing. Some variable amplitude studies have been done but attention has mostly been given to the reduction in residual strength or stiffness of the specimen. Much of the prior work is done in tension instead of compression. This investigation will provide data specifically on the growth behavior of pre-existing delaminations in composites under compressive overloads.
Durability and Damage Development in Woven Ceramic Matrix Composites Under Tensile and Fatigue Loading at Room and Elevated Temperatures
Authors: Haque Anwarul , Rahman Md. M. , Mohamed Hisham T. , Mahfuz Hassan , Vaidya Uday K. , Jeelani Shaik 
Published: December 2021

Abstract
This paper investigates the damage development in SiC/SiNC woven composites under tensile and cyclic loading both at room and elevated temperatures. The ultimate strength, failure strain, proportional limit and modulus data at a temperature range of 23°C–1380°C are generated. The tensile strength and the modulus of SiC/SiNC woven composites have been observed to decrease insignificantly with increased temperatures beyond the linear portion of the stress/strain plot. The stress/strain plot shows a pseudo-yield point at 25% of the failure strain (εf) which indicates damage initiation in the form of matrix cracking. The evolution of damage beyond 0.25 εf both at room and elevated temperature comprises of multiple matrix cracking, interfacial debonding and fiber pullout. Although the nature of the stress/strain plot shows damage-tolerant behavior under static loading both at room and elevated temperature, the life expectancy of SiC/SiNC composites degrades significantly under cyclic loading at elevated temperature. This is mostly due to the interactions of fatigue damage caused by the mechanically induced plastic strain and the damage developed by the creep strain. The in situ damage evolutions are monitored by acoustic event parameters, ultrasonic C-scan and stiffness degradation.
Energy Analysis of Piezoelectric-Actuated Structures Driven by Linear Amplifiers
Authors: Leo Donald J. 
Published: December 2021

Abstract
Energy expressions for a piezoelectric actuator coupled to a resonant mechanical load are analyzed for the purpose of determining the energy requirements of controlled structures. The analysis illustrates that the energy dissipated within the linear amplifier is a function of four parameters: the driving frequency, the piezoelectric coupling coefficient, the relative stiffness of the actuator and load, and the amplifier supply voltage. The piezoelectric actuator and the mechanical load are assumed to be lossless to highlight the relationship between energy dissipated within the amplifier and the energy stored in the actuator. For a specific frequency, the minimum energy dissipation within the amplifier is equal to twice the stored electrical energy in the piezoelectric when the amplifier voltage is equal to the driving voltage of the actuator. Additional energy is dissipated within the amplifier when the supply voltage is greater than the driving voltage. In the case when the actuator displacement is constant as a function of frequency, the energy dissipation in the amplifier decreases near the resonance of the coupled electromechanical system and reaches a minimum when the piezoelectric charge due to the applied voltage is equal and opposite to the charge induced by the load. The steady-state amplitude of the charge, and hence the actuator current, is equal to zero at this frequency. The results illustrate that energy dissipation is minimized when the actuator is operated at near the resonance or antiresonance of the coupled electromechanical system.
A General Method for a Piezothermoelastic Plate of Crystal Class 6mm Subjected to Axisymmetric Loading
Authors: Wang Xiangqing , Agrawal Om Prakash 
Published: December 2021

Abstract
Applications of piezoelectric materials for the development of “intelligent” structural and mechanical systems through sensing, actuation, and control have received considerable recent interest. In this document, we present a general solution method for piezothermoelasticity for hexagonal piezoelectric solids of class 6 mm. In the formulation presented, potential functions are introduced to represent the coupled thermal, elastic, and mechanical fields, which satisfy the thermal, mechanical, and electrical equilibrium and prescribed boundary conditions. The formulation is similar to those presented by Ashida, Tauchert, and Noda (1993, 1994), however, it is simpler and direct, and it eliminates the need to discuss special cases. To demonstrate applications of the technique, a piezothermoelasticity problem subjected to axisymmetric thermal, electrical and mechanical loads on a plate is considered. Numerical calculations for the stresses and the electrical potential are carried out for a cadmium selenide body exhibiting class 6mm symmetry. Results of these calculations are presented graphically.
Mechanics of Electrostrictive Materials With Periodic Microstructure
Authors: Somphone T. , Yu N. 
Published: December 2021

Abstract
The effective properties as well as local elastic and electric fields in smart electrostrictive composite materials with periodic microstructure are estimated by using the Fourier series technique (Nemat-Nasser et al., 1993) and the equivalent inclusion method (Eshelby, 1957). The developed model involves many microstructural parameters and can provide guidelines for the design of flexible, nonlinear electrostrictive transducers.
Mechanical Characterization of Shape Memory Alloy Composites for Designing Smart Structures
Authors: Bruck Hugh A. , Moore Charles L. 
Published: December 2021

Abstract
Actuators with large displacement ranges are being designed for smart structures by utilizing the unconventional mechanical behavior of Shape Memory Alloys (SMAs). This behavior is characterized by deformation recovery through thermally activated phase transformations. However, because of this deformation mechanism, conventional constitutive models cannot be employed to predict the mechanical behavior of SMAs. Appropriate constitutive models have been proposed, but their application can be computationally intensive. In this investigation, SMA wire-reinforced fiberglass composites are fabricated to determine the relationship between the mechanical response of the composite and the composition of SMA wire reinforcement. A modified linear Rule-of-Mixtures (ROM) formulation is proposed for predicting the mechanical behavior of the SMA composites. This simple, uniaxial constitutive model provides a reasonable prediction of SMA composite mechanical behavior, and is computationally efficient enough to use with Finite Element Analyses for designing smart structures that contain heterogeneous compositions.
Efficient Actuation Utilizing Fuel Cell Power Sources
Authors: Leo Donald J. 
Published: December 2021

Abstract
The performance of a fuel cell-powered piezoceramic actuator is investigated analytically and experimentally. Fuel cells are electrochemical engines that are comparable to batteries in specific energy density and can be instantly ‘recharged’ with the addition of fuel. This study focuses on the use of a methanol-powered alkaline fuel cell as a DC power source for a piezoceramic actuator exciting a thin beam. The fuel cell consists of a non precious metal cathode, a platinum anode, and a potassium hydroxide (KOH) electrolyte. The performance of the fuel cell is investigated by determining the voltage and power output as a function of the load current. A peak power of 30 mW is obtained with a 1M KOH electrolyte and 47 mW is obtained with a 4M concentration. A power analysis of constant-amplitude piezoceramic actuator demonstrates that low-power, efficient actuation is achieved by driving the actuator near an antiresonance of the coupled electromechanical systems. The antiresonance frequencies are determined from an admittance analysis of the coupled actuator and structure. Experimental results demonstrate that the power required for actuation in the kilohertz range is reduced from 4.5 to 1 mW by exciting the actuator at a known antiresonance, thus reducing the load on the fuel cell and increasing the effective lifetime of the actuator.
Passive and Active Control of Solar Array Vibrations Induced by the Change of Thermal Input
Authors: Tabacchi L. , Natori M. C. 
Published: December 2021

Abstract
The behaviour of large and flexible space structures, if compared with compact and rigid ones, is largely influenced by thermal loads in orbit. In this paper, the control of a spacecraft attitude disturbance, induced by cyclic temperature variations in the solar array substructures, is investigated. Both passive and active control techniques have been considered to reduce the vibration amplitude. A new version of tension mechansim powered by constant force springs is compared with a previous mechanism from the point of view of induced disturbances in the satellite attitude. A new algorithm for closed-loop pole placement of a symmetric, second order dynamical system is presented, and results of closed-loop numerical simulations are shown. Finally, experimental investigations are discussed and the relative results are presented.
Experiments in Robust Active Vibration Control Design for Slewing Flexible Structures
Authors: Wilson D. G. , Starr G. P. , Parker G. G. , Robinett R. D. 
Published: December 2021

Abstract
In this paper we present a hybrid Sliding Mode Control (SMC) and Constant Amplitude Feedback Control (CAFC) architecture for slewing flexible structures. The SMC controller is used to servo the flexible structure and the CAFC is used to suppress residual vibrations of the flexible structure. A single-axis encoder/DC motor/harmonic drive assembly is used for large angle slewing. A graphite/epoxy composite structure with embedded strain sensors/actuators is used for active vibration suppression. The results of this study include the analytical dynamic and control system development with experimental verification. The hybrid control algorithm uses the output sensor data from the encoder and strain sensor along with filters to derive velocity information to compute the control effort for the motor and strain actuators. Near-minimum time maneuvers based on an equivalent rigid structure are used to slew the flexible active structure. The tip mass was varied to evaluate control system robustness. Experimental slewing studies were performed to compare the benefits of using active rather than passive structures. For the active case the experimental results showed a reduction in residual vibration and settling time.
Effect of the SAR Distribution of a Radio Frequency (RF) Coil on the Temperature Field Within a Human Leg: Numerical Studies
Authors: Ling J. X. , Hand Jeffrey W. , Young Ian R. 
Published: December 2021

Abstract
This paper presents a three dimensional Finite Element Model for studying the effect of the specific absorption rate (SAR) distribution of a RF coil on the temperature distribution within a human leg due to the energy deposit. The model consists of fat, muscle, and bone, and has 21,158 uniform elements. The 3-D leg model was derived from the tissue maps that are obtained from the 79 sequential MR images of a volunteer’s leg. The specific absorption rate (SAR) data are from the solution to the fundamental Maxwell’s electromagnetic equations of the leg with RF coil in place using finite difference time domain (FDTD) method. The blood perfusion term, which is a function of the local tissue temperature, along with the metabolic heat as well as the SAR term, are treated as one heat source term in the classical bio-heat transfer equation. A commercial FEA code, ANSYS, was used to solve the 3-D heat conduction equation with an additional iteration method to deal with the temperature dependent source term. The 3-D temperature fields without and with the SAR term were computed, as well as the changes in temperature. They predict that the maximum temperature change occurs in approximately the same location as the maximum local SAR. The map of the temperature change clearly shows how the presence of the RF coil affect the temperature distribution within the leg. With 2 watts absorbed in the leg, about 8.8 w/kg of peak SAR value, the maximum change in temperature of the leg is about 1.74° C.
Temperature Dependent Tissue Properties and Ultrasonic Lesion Formation
Authors: Kolios Michael C. , Sherar Michael D. , Hunt John W. 
Published: December 2021

Abstract
High intensity focused ultrasound has considerable potential for the noninvasive treatment of localised disease. A detailed understanding of the kinetics of tissue coagulation is required to optimise ultrasonic parameters. In this presentation a theoretical model was used to examine the effects of temperature dependent ultrasonic attenuation and absorption on the transient tissue temperature distributions and lesion dimensions. A finite difference algorithm was used to solve numerically the nonlinear form of the bioheat transfer equation in cylindrical coordinates. The lesion dimensions were calculated based on the time-temperature distributions in tissue by using a thermal dose threshold to define the lesion boundaries. The results were compared to published experimental data in which the the location of maximal energy deposition during short duration high intensity focused ultrasound irradiation of in vitro tissue was examined. It was found that the theoretical model did not predict the size and shape of the experimental lesions. To correctly predict lesion size and shape much higher values of attenuation and absorption were required than can be accounted for by thermal coagulation of the tissue alone. The values used suggest that for intensities greater than 3030 W/cm2 the effective local attenuation/absorption in the focal region increased by a factor of 10–20. It is finally shown that temperature dependent tissue changes should be incorporated in thermal models to avoid underestimation of the induced temperature distributions during high intensity focused ultrasound therapy.
Temperature Feedback Control for Hyperthermia of Chest Wall Volumes With Dual-Frequency Ultrasound
Authors: Moros Eduardo G. , Straube William L. , Myerson Robert J. 
Published: December 2021

Abstract
Therapeutic temperature distributions during hyperthermia treatments are very difficult to maintain (e.g., 41.5 to 43°C for 45 to 60 min.) due to many heat removal/loss mechanisms. Thermoregulatory responses of the human body are efficacious in preserving and re-establishing normothermic conditions, and are considered to be the main cause of temperature non-uniformities through effected changes in blood perfusion and blood flow in large vessels. From the very beginning of hyperthermia technology development temperature feedback control systems (temperature controllers) have been proposed as a way to counterbalance thermoregulation and improve thermal doses. Only a few controllers, however, have been thoroughly tested numerically, experimentally, and most importantly, clinically. In this paper the proportional-integral-derivative bang-bang (PIDBB) controller of Lin et al. (1990), originally designed for a scanned focused ultrasound system for deep localized hyperthermia, was applied numerically to a scanned dual-frequency planar ultrasound system for chest wall hyperthermia. It was found that PIDBB controller with the optimal parameter values as determined by Lin et al. (1990) performed satisfactorily in controlling temperatures in superficial chest wall volumes.