bluuebunny/crossref_metadata_2025 huggingface dataset:
Wavelet PSO-Based LQR Algorithm for Optimal Structural Control Using Active Tuned Mass Dampers
Authors: Abdollahirad Mahdi , Yanik Arcan , Aldemir Unal
Published: July 2018

This study presents a new method to find the optimal control forces for active tuned mass damper. The method uses three algorithms: discrete wavelet transform (DWT), particle swarm optimization (PSO), and linear quadratic regulator (LQR). DWT is used to obtain the local energy distribution of the motivation over the frequency bands. PSO is used to determine the gain matrices through the online update of the weighting matrices used in the LQR controller while eliminating the trial and error. The method is tested on a 10-story structure subject to several historical pulse-like near-fault ground motions. The results indicate that the proposed method is more effective at reducing the displacement response of the structure in real time than conventional LQR controllers.
Nonlinear Free Vibration of Piezoelectric Functionally Graded Beams in Thermal Environment
Authors: Fallah Ali , Ahmadian Mohammad Taghi , Barari Ahmad
Published: July 2018

Nonlinear free vibration analysis of piezoelectric functionally graded (PFG) beams in thermal environment with any boundary conditions are investigated. The nonlinear governing Equation of motion is derived based on the Euler-Bernoulli beam theory and Von Karman’s strain-displacement relation. Simple analytical expression is presented for the nonlinear natural frequency using energy balanced method (EBM). Results are validated and compared with available results in the literature. Effects of different parameters such as vibration amplitude, boundary conditions, material inhomogenity, electrical and thermal loading on the nonlinear behavior of PFG beams are presented.
A Tilting Pad Journal Bearing Model for Coupled Fluid Dynamical-Rotor Dynamical Analyses
Authors: Conti R. , Frilli A. , Galardi E. , Meli E. , Nocciolini D. , Pugi L. , Rindi A. , Rossin Stefano
Published: July 2018

Turbomachines are continuously developing in order to reach higher levels of speed, power and efficiency and the classical Fixed Geometry Journal Bearings have been replaced by Tilting Pad Journal Bearings to avoid instability phenomena. In this paper, the authors propose an innovative quasi-3D TPJB modelling approach that allows the simultaneous and coupled analysis of the typical phenomena involved in TPJB operations. The authors focused on the accurate analysis of the interactions between the rotor and the lubricant supply plant and on the fluid dynamical effects due to the bearing that cause those couplings, aiming at reaching a good compromise between the accuracy and the numerical efficiency of the model (mandatory to analyze systems with many bearings).

The TPJB model has been developed and experimentally validated in collaboration with Nuovo Pignone General Electric S.p.a. which provided the technical data of the system and the results of experimental tests.
On the Comparison Between Displacement Modal Testing and Strain Modal Testing
Authors: Mucchi Emiliano , Dalpiaz Giorgio
Published: July 2018

The conventional modal testing, hereafter referred as Displacement Modal Testing (DMT) is based on measurement of displacement, velocity or acceleration as well as excitation force. An enormous literature regards the DMT, on the contrary, a few papers address modal testing based on strain gauges or strain sensor, hereafter referred as Strain Modal Testing (SMT). The main reason of this scenario is due to practical problems in the use of strain gauges as calibration procedure, ground loop, sensitivity not adequate at high frequency, bonding quality. In this work, a novel piezoelectric strain sensor is used for SMT. It is demonstrated in the present work that this sensor overcomes the practical drawbacks related to the use of strain gauges. Thus, SMT based on piezoelectric strain sensors can be a valid alternative to DMT, usually based on accelerometers. Comparisons between the modal testing results concerning brackets with different constraint conditions using both accelerometers and strain sensors are given in terms of modal parameters, highlighting their pros and cons.
A New Approach for Piezoelectric Switched Shunt Damping on Inductance
Authors: Kamiya Keisuke
Published: July 2018

A technique to suppress vibration using piezoelectric elements connected to a shunt circuit is called piezoelectric shunt damping. Many studies on this subject have been reported. Among them a technique called switched shunt damping exists. In switched shunt damping developed so far, a switch is placed in the shunt circuit in series to the piezoelectric element, and is used to switch the shunt circuit from an open circuit to a closed circuit. Depending on the elements used in the shunt circuit, various types of switched shunt damping exist. This paper presents a new approach for switched shunt damping on inductance. The presented shunt circuit is composed of a resistance, an inductance and a switch connected in parallel with the inductance. Thus, when the switch is open the shunt circuit becomes an LR circuit, and when the switch is closed it becomes a resistive circuit. Furthermore, switching is operated based on the charge on the piezoelectric element, so that no sensors to conduct the switching are needed. To check the performance of vibration suppression by the proposed method, numerical simulations and experiments are conducted. The results show that the presented switched shunt damping have high performance of vibration suppression.
Identification of Anisotropic Material Parameters in Elastic Tissue Using Magnetic Resonance Imaging of Shear Waves
Authors: Tweten Dennis J. , Okamoto Ruth J. , Schmidt John L. , Garbow Joel R. , Bayly Philip V.
Published: July 2018

This paper describes the application of a material parameter identification method based on elastic shear wave propagation to simulated and experimental data from magnetic resonance elastography (MRE). In MRE, the displacements of traveling transverse and longitudinal waves in elastic, biological tissue are captured as complex 3D images. Typically, the magnitude of these waves is small, and the equations of waves in linear elastic media can be used to estimate the material properties of tissue, such as internal organs, muscle, and the brain. Of particular interest are fibrous tissues which have anisotropic properties. In this paper, an anisotropic material model with three material parameters (shear modulus, shear anisotropy, and tensile anisotropy) is the basis for parameter identification. This model relates shear wave speed, propagation direction, and polarization to the material properties. A directional filtering approach is applied to isolate the speed and polarization of shear waves propagating in multiple directions. The material properties are then estimated from the material model and isolated shear waves using weighted least squares.
High-Dimensional Chaos Control Algorithms for Improved Piezoelectric Energy Harvesting Using a Bistable Structure
Authors: Geiyer Daniel , Kauffman Jeffrey L.
Published: July 2018

Linear cantilevered piezoelectric energy harvesters typically rely on excitation around a resonance frequency for peak operation. Compounding the problem, typical ambient environments either vary dynamically in time or possess energy distributed across a wide spectrum of frequencies. Nonlinear broadband techniques have been implemented with success, but rely on chance that steady-state high energy orbits result as opposed to the low energy or chaotic trajectories that coexist in the basin of attraction. This work aims to implement two high dimensional chaotic controllers for large period orbits located within the chaotic attractor. The first control law is defined using traditional OGY, while the second uses the principles of invariant manifolds and is therefore independent of the system Jacobian. Comparison of the two control methods aims to show that invariant principles are less computationally intensive and result in equivalent stabilized orbits. Furthermore, the only necessary measurement for control design is a single time series representing a state of the system. This article compares two methods of chaos control and their ability to stabilize a large period orbit within the chaotic attractor for improved broadband piezoelectric energy harvesting.
Sensitivity Analysis and Improvement of a Pseudo-Modal Approach for Damage Localization
Authors: Lofrano Egidio , Romeo Francesco , Paolone Achille
Published: July 2018

Localization of damages becomes rather challenging when the associated stiffness reduction is small in presence of structural uncertainties. This work presents a sensitivity analysis and an improvement of a novel pseudo-modal approach, recently proposed by the authors. Starting from free vibrations of the undamaged and damaged states, the method aims to maximize the damage signature embedded in the data exploiting the peculiar features of the Orthogonal Empirical Mode Decomposition technique. The role of the length of the signals and the boundary effects are here investigated; a cut-off rule useful for reducing the latter issue is also proposed.
Parametric Analysis of the Nonlinear Behavior of Rotating Structures
Authors: Xie Lihan , Baguet Sébastien , Prabel Benoit , Dufour Régis
Published: July 2018

In nonlinear rotordynamics, techniques can take advantage of the periodic steady state behavior to predict quickly and accurately the mass unbalance response to a series of parameters, especially with the presence of certain nonlinearities which leads to nonlinear dynamics and complicated responses. The method proposed here calculates the response curve by combining Harmonic Balance Method, Alternating Frequency-Time method and continuation. The singular points where a stability change often arises are detected with the sign change of the Jacobian determinant and then located through a penalty method that increases the solving equation system by a completing constraint. Tracking these points, which provides an efficient way to analyze parametrically the nonlinear behavior of a system, can be fulfilled, once again, by the continuation technique.
Computed Torque Control of Articulated Multibody Systems in the Generalized Divide and Conquer Algorithm Framework
Authors: Kingsley Cameron , Poursina Mohammad
Published: July 2018

An extension to the Generalized-Divide-and-Conquer Algorithm (GDCA) is presented in this paper in conjunction with the Computed-Torque-Control-Law (CTCL) to model and control fully actuated multibody systems. CTCL uses the inverse dynamics to provide control inputs to the system while, the dynamics of the system must be formed and solved in each iteration. Herein, the GDCA is extended to form and solve the inverse dynamics to find control torques. Further, this method is also extended to efficiently solve the equations of motion of the controlled system. This significantly reduces the complexity of modeling, simulating, and controlling the fully actuated multibody systems to O(n) or O(logn) operations in each iteration in the serial and parallel implementations, respectively.
Nonlinear Forced Vibration Analysis of a Non-Local Carbon Nanotube Carrying Intermediate Mass
Authors: Saadatnia Zia , Esmailzadeh Ebrahim
Published: July 2018

The aim of this study is to model and investigate the nonlinear transversal vibration of a carbon nanotube carrying an intermediate mass along the structure considering the nonlocal and non-classical theories. Due to the application of the proposed system in sensors, actuators, mass detection units among others, the analysis of forced vibration of such systems is of an important task being considered here. The governing equation of motion is developed by combining the Euler-Bernoulli beam theory and the Eringen non-local theory. The Galerkin approach is employed to obtain the governing differential equation of the system and the transient beam response for the clamped-hinged boundary condition. A strong perturbation method is utilized to solve the equation obtained and the system responses subjected to a harmonic excitation is examined. The steady-state motion is studied and the frequency response in an analytical form is obtained. Finally, results are evaluated for some numerical parameter values and their effect on the frequency responses are presented and fully discussed.
Nonlinear Vibration of Carbon Nanotube Resonators Considering Higher Modes
Authors: Askari Hassan , Esmailzadeh Ebrahim
Published: July 2018

Nonlinear forced vibration of the carbon nanotubes based on the Euler-Bernoulli beam theory is studied. The Euler-Bernoulli beam theory is implemented to find the governing equation of the vibrations of the carbon nanotube. The Pasternak and Nonlinear Winkler foundation is assumed for the objective system. It is supposed that the system is supported by hinged-hinged boundary conditions. The Galerkin procedure is employed in order to find the nonlinear ordinary differential equation of the vibration of the objective system considering two modes of vibrations. The primary and secondary resonant cases are developed for the objective system employing the multiple scales method. Influence of different factors such as length, thickness, position of applied force, Pasternak and Winkler foundation are fully shown on the primary and secondary resonance of the system.
Robust Pole Assignment for Friction Induced Vibration Based on Receptance Method
Authors: Liang Yao , Ouyang Huajiang , Yamaura Hiroshi
Published: July 2018

Friction induced vibration (FIV) attracts extensive attention of researchers due to its ubiquitousness and intriguing complexity. Disc brake squeal is deemed one of the typical FIV problems with eigenvalues of the brake system locating on the right-hand side half of the complex plane. In this research, an active state feedback control strategy is proposed for shifting the unstable eigenvalues of the brake system to the stable region. The presented control method is constructed based on the receptance method in which the knowledge of mass, damping and stiffness matrices is not required. Moreover, the robustness of the control method is explored against uncertainty in friction coefficient. The numerical simulation results demonstrate that the proposed method successfully places the required poles of the system and thus stabilises an unstable system in the presence of an uncertain parameter.
On the Nonlinear Dynamic Stability of Prestressable Structures
Authors: Sultan Cornel
Published: July 2018

Recent multidisciplinary advances enable actively controlled bar-tendon structures. A major control related challenge is the dynamic stability of these systems. Their low internal damping may result in less stable systems than desired, requiring special attention. This paper investigates the nonlinear dynamic stability of such assemblies, focusing on the situation when linearization fails to provide an answer. Conditions for simple and asymptotic nonlinear stability of prestressable configurations of these systems are derived using Lyapunov-LaSalle theory. Examples are included to illustrate theoretical results, emphasize connections between stability, mechanisms, and natural modes, and explain why only nonlinear asymptotic stability, instead of exponential stability, is achieved even when tendons are linearly damped.
Energy Dissipation Characteristics of a Mechanical Metastable Module Excited Near Resonance
Authors: Kidambi Narayanan , Harne R. L. , Wang K. W.
Published: July 2018

Recent studies have demonstrated that the energetic vibrations of strategically designed negative stiffness inclusions may lead to large and adaptable damping in structural/material systems. Many researchers examine these features using models of bistable elements. From the viewpoint of system integration, bistable, negative stiffness elements often interface with positive stiffness elastic members. Under such conditions, the structural/material system may exhibit coexisting metastable states. In other words, the macroscopic displacement/strain remains fixed while the reaction force statically and/or dynamically varies due to internal change similar to a phase transition. This coexistence of metastable states is not manifested in an individual (stand-alone) bistable element. Although the static and low frequency dynamics of structural/material systems possessing coexisting metastable states have been explored, much remains to be understood regarding the dynamics and energy dissipation characteristics of such systems when excited near resonance, where nonlinear dynamics may be more easily activated and damping design is of great importance. Thus, to effectively elucidate the enhanced versatility of damping properties afforded by exploiting negative stiffness inclusions in structural/material systems, this research investigates a mechanical module which leverages a coexistence of metastable states: an archetypal building block for system assembly. The studies employ analytical, numerical, and experimental findings to probe how near-resonant excitation can trigger multiple dynamic states, each resulting in distinct energy dissipation features. It is shown that, for lightly damped metastable mechanical modules, the effective energy dissipation may be varied across orders of magnitude via tailoring design and excitation parameters. Potential applications and prototype systems are discussed to bridge the discoveries to future practice.
Parameter Identification of Complex Structures Using Finite Element Model Updating Techniques
Authors: Giagopoulos Dimitrios , Arailopoulos Alexandros
Published: July 2018

In this work, an integrated reverse engineering strategy is presented that takes into account the complete process, from the developing of CAD model and the experimental modal analysis procedures to computational effective model updating techniques. Modal identification and structural model updating methods are applied, leading to develop high fidelity finite element model of geometrically complex and lightweight bicycle frame, using acceleration measurements. First, exploiting a 3D Laser Scanner, the digital shape of the real bike frame was developed and the final parametric CAD model was created. Next the finite element model of the frame was created by using quadrilateral shell and hexahedral solid elements. Due to complex geometry of the structure, the developed model consists of about one million degrees of freedom. The identification of modal characteristics of the frame is based on acceleration time histories, which are obtained through an experimental investigation of its dynamic response in a support-free state by imposing impulsive loading. A high modal density modal model is obtained. The modal characteristics are then used to update the finite element model. Single and multiobjective structural identification methods with appropriate substructuring methods, are used for estimating the parameters (material properties and shell thickness properties) of the finite element model, based on minimizing the deviations between the experimental and analytical modal characteristics (modal frequencies and mode shapes). Direct comparison of the numerical and experimental data verified the reliability and accuracy of the methodology applied.
Fuzzy Uncertainty Analysis of a Tilting-Pad Journal Bearing
Authors: Cavalini Aldemir Ap , Lara-Molina Fabian Andres , Dourado Arinan , Steffen Valder
Published: July 2018

This paper is dedicated to the analysis of uncertainties affecting the load capability of a 4-pad tilting-pad journal bearing, in which the load is applied between two pads (load on pad configuration; LOP). A well-known stochastic method has been extensively used to model uncertain parameters, the so-called Monte Carlo simulation. However, in the present contribution, the inherent uncertainties of the bearings’ parameters (i.e. the pad radius, the oil viscosity, and the radial clearance) are modeled by using a fuzzy logic based analysis. This alternative methodology seems to be more appropriate when the stochastic process that characterizes the uncertainties is unknown. The analysis procedure is confined to the load capability of the bearing, being generated by the envelopes of the pressure fields developed on each pad. The hydrodynamic supporting forces are determined by considering a nonlinear model, which is obtained from the solution of the Reynolds’ equation. The most significant results are associated to the changes in the dynamic behavior of the bearing because of the reaction forces that are modified according the uncertainties introduced in the system. Finally, it is worth mentioning that the uncertainty analysis in this case provides relevant information both for design and maintenance of tilting-pad hydrodynamic bearings.
Efficient Uncertainty Quantification in Structural Dynamic Analysis Using Two-Level Gaussian Processes
Authors: Zhou Kai , Cao Pei , Tang Jiong
Published: July 2018

Uncertainty quantification is an important aspect in structural dynamic analysis. Since practical structures are complex and oftentimes need to be characterized by large-scale finite element models, component mode synthesis (CMS) method is widely adopted for order-reduced modeling. Even with the model order-reduction, the computational cost for uncertainty quantification can still be prohibitive. In this research, we utilize a two-level Gaussian process emulation to achieve rapid sampling and response prediction under uncertainty, in which the low- and high-fidelity data extracted from CMS and full-scale finite element model are incorporated in an integral manner. The possible bias of low-fidelity data is then corrected through high-fidelity data. For the purpose of reducing the emulation runs, we further employ Bayesian inference approach to calibrate the order-reduced model in a probabilistic manner conditioned on multiple predicted response distributions of concern. Case studies are carried out to validate the effectiveness of proposed methodology.
Shock and Vibration Isolation Using Internally Rotating Masses
Authors: Smith Eric , Ferri Al
Published: July 2018

This paper considers the use of a chain of springs and masses to reduce the transmission of shock and vibration through the system. The masses are equipped with internally rotating masses that absorb some of the axial vibration into internal kinetic energy of the masses. The internal masses have viscous damping, but no elastic or gravitational restraint. Previous research has shown that a single cart system attached to a vibrating structure can help mitigate shock through targeted energy transfer. This paper examines the potential for shock isolation provided by a chain of such systems. Through numerical simulations, tradeoffs are examined between displacement and transmitted force.
Shock Isolation Through Translational-to-Rotational Energy Transference
Authors: Smith Eric , Ferri Al
Published: July 2018

The design of isolation mounts is of critical importance in the protection of structures and sensitive equipment from damage or failure. Simultaneous protection from both shock and vibration is particularly challenging because of the broadband nature of the input signal and because of the deleterious effect of damping on high-frequency isolation. Prior work by the authors has shown that chains of translating mass/spring elements can act as a “mechanical filter” for input disturbances. However, in finite-length chains, wave reflections can result in secondary pulses that hit the structure and can diminish the effectiveness of the isolator. In this paper, a new type of isolator is developed that converts translational input forces into a combination of translational and rotational motion. If designed correctly, the rotational motion can be managed so that it does not result in additional forces transmitted to the structure. In effect, the isolator is able to trap some of the input energy into rotational vibration, preventing it from reaching the structure. Parametric simulation studies are conducted as various system parameters are varied.
Harmonic Balance Analysis and Experimental Validation of a Nonlinear Broadband Piezoelectric Energy Harvester for Low Ambient Vibrations
Authors: Leadenham Stephen , Erturk Alper
Published: July 2018

It has been shown by several research groups over the past few years that vibration energy harvesters with intentionally designed nonlinear stiffness components can be used for frequency bandwidth enhancement under harmonic excitation for sufficiently strong vibration amplitudes. In order to overcome the need for high excitation intensities that are required to exploit nonlinear dynamic phenomena, we have developed an M-shaped piezoelectric energy harvester configuration that can exhibit a nonlinear frequency response under low vibration levels. This configuration is made from a continuous bent spring steel with piezoelectric laminates and a proof mass, and no magnetic components. Careful design of this nonlinear architecture that minimizes piezoelectric softening further enables the possibility of achieving the jump phenomenon in hardening at base acceleration levels on the order of a few milli-g. In the present work, such a design is explored for both primary and secondary resonance excitations at different vibration levels and for different electrical loads. Following the primary resonance excitation case that offers more than 600 % increase in the half-power bandwidth as compared to the linear system at a root-mean-square excitation level as low as 0.04g, secondary resonance behavior is investigated with a focus on 1:2 and 1:3 superharmonic resonance neighborhoods. A multi-term harmonic balance formulation is employed for a computationally effective yet high-fidelity analysis of this high-quality-factor system with quadratic and cubic nonlinearities. In addition to primary resonance and secondary (superharmonic) resonance cases, multi-harmonic excitation is modeled and experimentally validated.
Experimental Assessment of Joint-Like Modal Models for Structures
Authors: Segalman Daniel J. , Allen Matthew S. , Eriten Melih , Hoppman Kurt
Published: July 2018

Several of the authors, and others, have explored the use of modal-like models for structures having nonlinearities associated with compressive joints (such as bolted connections.) In these models, the deformations are treated as consisting of modal expansions, but with the modal coordinates that evolving nonlinearly over time. There have been several theoretical treatments of this strategy and the authors report here on an early effort to confirm the approach through experiment.

For this purpose simple structures consisting of pairs of plates were assembled using four bolted connections. The structures were excited by modal hammer at various locations and the modes identified by scanning laser vibrometer. In each case, multiple modes were excited and the evolution of modal coordinates was achieved by band-pass filtering at the relevant frequencies.

Making some simple kinematic assumptions about relative deformations of the component plates and exploiting symmetries permits the mapping from ring-down of each mode to constitutive behavior of each joint. If the strategy of using joint-like modal models for bolted structures is valid, the joint constitutive models deduced from any mode should be adequate to predict the apparent, but nonlinear modal behavior at other resonances. Multiple test specimens were manufactured to assess this predictive capability in the context of part-to-part variability intrinsic to the dynamics of such structures.
Recurrence Analysis of Experimental Time Series of a Rotor Response With Bearing Outer Race Faults
Authors: Kwuimy C. A. Kitio , Samadani M. , Kankar P. K. , Nataraj C.
Published: July 2018

In this paper, the time series response of a rotor with bearing outer race faults is analyzed. The recurrence quantification analysis (RQA) parameters deduced from the recurrence plot (RP) of the system response are used to delve into characterization of the specific and overall behavior of the system. Attention is focused on the variation of the RQA parameters for healthy and defective states of the system. The results of this investigation are encouraging for further application of the method of RP in the diagnostics and analysis of bearing faults. In fact, it is shown that appropriate classification of the RQA can be effectively used to detect outer race faults and serve as a discriminant for fault severity.
Toward a Microfluidic Implementation of a Digital Potentiometer
Authors: Zavrel Erik A. , Shen Xiling
Published: July 2018

Herein, we report on the motivation for, design of, and progress toward a microfluidic implementation of a digital potentiometer for various physical and life science applications.
The Application of Series Elastic Actuators in the Hydraulic Ankle-Foot Orthosis
Authors: Kim Jeong Yong , Durfee William
Published: July 2018

Advances in ankle-foot orthosis (AFO) technology have been trending toward more powerful and lightweight devices. A hydraulic series elastic actuator (HSEA) was explored to design a lightweight powered AFO that meets the high peak power demand of ankle gait. With its excellent power density and its ability to separate the power supply from the actuator using a hose, hydraulic power was used, combined with an SEA that takes advantage of the high-peak and low-average power profile of ankle gait to store energy and release it during the push-off stage of gait. The parameters required for the SEA were determined and validated using simulation. A gait pattern that would require 235W of motor power was able to be tracked using a motor rated at 95W. The actuator weight of the hydraulic ankle-foot orthosis (HAFO) at the ankle was 0.35, which is 43% of an equivalent electromechanical system. A novel design of an HSEA with a clutch capability is proposed for future HAFO applications.
Fracture Toughness Characterization and Mixed-Mode Fracture Finite Element Modeling for Accurate Biopsy Needle Cutting Force Prediction
Authors: Si Yen Ng , Lan Guan-Jhong , Lin Chi-Lun
Published: July 2018

Fracture toughness is an important mechanical property of materials that describes the failure of material by cracking. Yet, characterizing fracture toughness in soft tissue cutting is still a challenging task as the behavior of the soft tissue may vary under different tissue, cutting and pre-crack conditions [1]. Predicting cutting force has been important to needle biopsy design, surgical planning/training, and other surgical operations. However, in order to obtain accurate predictions, understanding the fracture toughness is crucial. In this study, we present an approach to characterize the fracture toughness directly from cutting experiments of hollow needle cutting soft tissue mimicking materials. Cutting tests are carried out to obtain the dynamic force response of gelatin samples when being cut by non-rotational and rotational hollow needles. The data is used to establish a mixed-mode fracture behavior which is then used to implement a cohesive surface based finite element model. Nearly 1% difference of the axial cutting force between the simulation and experimental results showed that the approach is capable of predicting accurate cutting force in rotational needle biopsy. The approach also has the potential to be used to predict the cutting force in various types of needle biopsy.
Finite Element Modeling and Analysis of Ventricular Septal Defect Occluders
Authors: Li Yiming , Sun Kun , Song Chengli
Published: July 2018

Transcatheter closure of ventricular septal defect (VSD) has become an alternative therapy to open-chest surgery because of simple procedure, less invasion, and high safety [1–2]. The most important occluder device of the therapy is double-disc structure which occludes the VSD, with the discs of the occluder clamp the margin of VSD while the waist of the occluder supports the VSD hole (Figure 1(a)). Commercially available occluders are woven by 72 nitinol wires (Figure1(b)) and then formed by heat treatment. However, the implantation of metal occluders in perimembranous part will result in a substantial risk of complete atrioventricular block (cAVB) averaging 3.5%, because of its close proximity to the conduction system, which passes at the posterior border of defects [3]. To improve the biocompatibility, Huang [4] developed biodegradable VSD occluders (Figure 1(c)) which woven by polydioxanone (PDO) wires and can be fully absorbed within 24 weeks after implantation.
Evaluation of a Novel Gait Training Device Using a Pressure Suit to Support Body Weight
Authors: Koehler-McNicholas Sara R. , Cataldo Alana , Koch Elizabeth , Rud Brittany , Gude Laura , Brenteson Charlotte , Johnson Doug , Wigness Bruce , Hauck John , Oddsson Lars , Hansen Andrew H.
Published: July 2018

Supporting body weight and balance control are foundations of our ability to move and function independently. However, neurological disease, injury, and aging often threaten these prerequisites of functional independence, leading to a decrease in quality of life. In the United States alone, 7.5 million individuals have survived stroke, traumatic brain injury (TBI), or spinal cord injury (SCI), and over a million new patients are diagnosed every year [1–2]. To improve gait function in these patient populations, partial body weight-supported gait training is a widely-used rehabilitation therapy. In general, the therapeutic quality of partial body weight-supported gait training is directly proportional to the amount of time patients are able to tolerate an upright posture (either standing or walking). To achieve an upright posture, therapists must first attach a support system (e.g., gait belt, harness lift system, exoskeleton), then several therapists must assist the patient into a standing position. Depending on the patient’s level of impairment, several therapists may also be needed to support and assist the patient while standing and walking, then again to remove the support system at the end of therapy. Accordingly, multiple therapists are often needed to provide a small quantity of upright physical therapy time with standard support systems. Furthermore, use of standard support systems can be uncomfortable and fatiguing for the patient, further reducing their actual therapeutic treatment time [3].
Vagus Nerve Stimulation for Blood Pressure and Heart Rate Regulation
Authors: O’Clock George D. , KenKnight Bruce H. , Tolkacheva Elena G.
Published: July 2018

For more than 27 years, implanted vagus nerve stimulation (VNS) devices, with electric current outputs in the 1 to 3.5 mA range, have been developed for many health care applications, including epilepsy and heart disease [1]. Mechanical compression approaches for VNS were administered under surgical conditions, using forceps, in the 1800’s [2]. Outcomes such as Electrocardiogram (ECG) data, blood pressure (BP), and heart rate (HR) were evaluated. Also, non-invasive (NI) mechanical compression of the vagus nerve for various nervous system disorders using hand, thumb, finger and belt pressure was popular in the 1800’s [3]. Cyberonics (now LivaNova) received the first FDA clearance for a surgically implanted electrical VNS device to treat refractory epilepsy in 1997.
Design of a Percutaneous Articular Fracture Reduction Simulator
Authors: Tatum Marcus , Thomas Geb W. , Anderson Donald D.
Published: July 2018

The American Board of Orthopaedic Surgery has mandated dedicated skills training for first-year orthopedic surgical residents.1 Most residency programs address this requirement with training exercises with cadavers and plastic foam bones. Some programs incorporate one or more simulators in their skills training, including several sophisticated virtual reality simulators and a variety of low-tech simulators. Simulators are helpful because they can provide repeatable educational experiences and quantitative performance assessment. Unfortunately, few simulators have been developed for orthopedic trauma skills training. Even fewer simulators have been developed and validated with more advanced students, such as residents in their 3rd or 4th year of training, and for more complex surgeries. In contrast to the completely virtual surgical simulation using haptic feedback devices and sophisticated renderings of soft tissue deformation, our group has chosen to use physical models, real surgical instruments and position tracking in conjunction with virtual reality.2–4 The physical models provide experience with the surgical tools, and enable more realistic hand movements and haptic cue feedback.
A Semi-Stented and Chorded Mitral Valve Prosthesis: Design and Method of Chordal Setting and In Vitro Testing
Authors: Kotzé R. , Deorsola L.
Published: July 2018

Mitral subvalvular apparatus plays an important role in mitral and ventricular dynamics by preserving annuloventricular continuity, known to be fundamental for ventricular function. While some proposed mitral valve prostheses designs do attempt to account for this relationship by using papillary flaps, they are not adjustable and do not mimic the native saddle shaped mitral annulus. Unfortunately, these designs are not versatile as their papillary flap lengths cannot be altered and the prostheses are unsuitable for percutaneous implantation.

We address these issues through the design of a novel semistented and chorded mitral valve that better mimics the native mitral annulus, leaflets and chordae function and can be made from off-the-shelf biomaterials with the potential to be implanted percutaneously. We also propose a novel and reliable method to set the chordal lengths individually. Finally, we demonstrate the hydrodynamic performance of the valve, showing that it meets the minimum performance requirements stipulated by the international standard ISO 5840-3:2013.
Design and Simulation of Robotic Needle Guide for Transperineal Prostate Biopsy
Authors: Dehghani Hossein , Zhang Shihao , Kulkarni Pankaj , Biswas Pradipta , Simms Leslie , Song Sang-Eun
Published: July 2018

Prostate cancer is the third leading cause of cancer-related death for males in the United States [1]. Over three million Americans with prostate cancer were reported in 2016 [2] marking the prostate cancer as the most prevalent cancer among males in the US. In 2016, 180,890 new cases and 26,120 deaths were reported [1]. The prostate is a male reproductive gland located in the pelvis and surrounded by the rectum posteriorly and the bladder superiorly.
Thrombogenicity Testing for Blood-Contacting Medical Devices in an In Vitro Human Blood-Loop
Authors: Cunningham Matt , Howard Sarah , Beltrame Abby , Chen Yan , Smith Mark
Published: July 2018

Thrombogenicity testing continues to be a critical requirement for regulatory approval of blood-contacting medical devices and the ISO guidelines have recently been updates [1]. This new guideline ascribes value to both in vivo and in vitro testing including both the non-anticoagulated venous implant (NAVI) model, and the new methods for in vitro testing. One challenge with the animal-blood-based in vitro assays that have been validated and used for submissions is that they still may not accurately translate to clinical safety or predict the risk for thrombogenic potential in humans. We have previously described a model using minimally heparinized ovine blood and are continuing to improve the overall methodology [2,3]. In addition, we have transferred these methods to a human blood assay which therefore has enhanced potential for prediction of clinical risk. As with the ovine model, the key characteristics of a successful in vitro method include fresh blood, low levels of anticoagulation, flow conditions and minimization of air/blood interfaces. This human model integrates freshly harvested human blood containing minimal levels of heparin with variable flow from a unidirectional peristaltic pump and unlike many of the human blood assays, it can accommodate larger devices and higher flow rates than previously described [1,4]. Control materials which were optimized in the ovine model were also used to reproducibly elicit positive and negative thrombogenic responses. We feel that this model can be used for validation of the ovine model with cross comparisons of a number of legally marketed comparator devices. Alternatively, if the human blood methodology can be streamlined and performed cost effectively on a regular and basis, this assay could supplant the current ovine model and allow a highly predictive preclinical test for thrombogenicity of devices.
A Portable Ex Vivo Heart Perfusion Apparatus for Cardiac CT Imaging: Visible Heart® Mobile
Authors: Holm Mikayle A. , Mattson Alex , Mattison Lars , Gaasedelen Erik , Zhingre Sanchez Jorge , Iaizzo Paul A.
Published: July 2018

Medical device developers can often be limited in pre-clinical experimental testing of new products because of procedural complexities and safety concerns to the animal or patient. Though animal or human cadavers can be used for these types of studies thereby eliminating the need for safety precautions, the functional capabilities of the tissue can be lost. As a novel way to provide such functional device/tissue assessment, the Visible Heart® (VH®) Laboratory has developed reanimation methodologies1 that allow the four chambers of the heart to contract naturally ex vivo. Swine hearts are routinely reanimated using this methodology with a clear perfusate which allows for direct endoscopic visualization of functional cardiac anatomy and importantly the device/tissue interface. For the past two decades, these capabilities have been useful for testing early device prototypes and developing educational and procedural videos. More specifically, this approach provides the added convenience of manipulating catheters into the ex vivo prep and visually studying their behavior for validation experiments of new medical devices. Further, multimodal imaging comparative assessments using both 4D echocardiography and fluoroscopy have been routinely performed. Yet, as imaging modalities continue to develop and are utilized for device placements or post-procedure evaluations, we hope to expand VH® capabilities.
Development of Epicardial Circulatory Assist Devices: Material Considerations
Authors: Soohoo Elaine , Aranda-Michel Edgar , Kaissar Molly , Trumble Dennis R.
Published: July 2018

There currently exist many cardiac assist devices for the clinical treatment of congestive heart failure, which affects nearly 5 million Americans and costs the United States health care system nearly $32 billion annually [1]. The majority of these clinical devices help to improve cardiac perfusion by utilizing a blood pump — either pulsatile or continuous flow — cannulated to the circulatory system to create a parallel bypass for blood flow. These devices are typically very effective in the short term (days to months) but are typically limited by problems associated with chronic use [2]. Some of the most prevalent complications stem from the need for long-term system anticoagulation, invasive implant surgeries, catastrophic wear and tear of mechanical parts or drivelines, and infections at the percutaneous driveline site. Therefore, there is a great medical need to develop new or improve existing technologies to minimize and/or eliminate these adverse events.
An Electromagnetic Tracking Needle Clip: An Enabling Design for Low-Cost Image-Guided Therapy
Authors: Zhao Zhuo , Xu Sheng , Wood Bradford , Tse Zion Tsz Ho
Published: July 2018

Computer-assisted interventions (CAI) — which offer advantages such as increased accuracy, reduction of complications, and decreased intervention time — have increased in prevalence in recent years. A type of CAI called image-guided therapy (IGT) can be used to provide navigation for freehand procedures or guidance for localization of medical devices. Electromagnetic (EM) tracking technology can track instruments such as needle tips inside the patient body without the need for a line-of-sight, allowing for minimally invasive imaging-guided procedures [1–3].
Impedance of the Human Ankle During Standing for Posture Control
Authors: A. Ribeiro G. , Ficanha E. , Knop L. , Rastgaar M.
Published: July 2018

The stiffness and damping of anatomical joints can be modulated by muscle co-contraction, where antagonistic muscles contract simultaneously, increasing both the joint’s stiffness and damping. In a second order system, the mechanical impedance, or simply impedance, is a function of the system’s inertia, damping, and stiffness. The ankle impedance can be defined as the resultant force due to an external motion perturbation. The impedance modulation of the human ankle is required for stable walking. The estimation of the time-varying impedance modulation of the human ankle is the focus of research by different groups [1,2].
An Instrumented Urethral Catheter With Supercapacitor Based Force Sensor
Authors: Zhang Ye , Ahmadi Mahdi , Rajamani Rajesh
Published: July 2018

Urinary incontinence (UI), defined by the International Continence Society as “the complaint of any involuntary leakage of urine” [1], is believed to affect at least 13 million people in the United States. Around 80% of people affected are women [2,3]. The most common type of UI in women is stress urinary incontinence (SUI) [4]. Although not identified as life-threatening, UI may lead to withdrawal from social situations and reduced life quality.
Feasibility of Using a Printed Microstrip Antenna in Evaluation of Peripheral Microcirculation
Authors: Nelson David A. , Latif Saeed I. , Austin Chad , Chatham Jeremy
Published: July 2018

Peripheral Artery Disease (PAD) is a widespread and often undiagnosed condition associated with increased incidence of serious cardiovascular events. Current diagnostic tests for PAD may not be adequate for screening the large at-risk population. A new skin blood flow measurement technique using RF heating in the millimeter wave band, with simultaneous surface temperature measurement offers a potential method for screening individuals at risk for PAD quickly and easily. The feasibility of a transducer design incorporating a microstrip antenna and one or more infrared temperature sensors was evaluated in vitro, using a phantom skin material and a custom flow chamber. Results demonstrate the ability to heat the unperfused phantom by up to 7°C in less than 60 s, depending on antenna separation distance from the target surface. At a distance of 2 mm, preliminary results indicate the rate of temperature increase is sensitive to flowrate. These results suggest a possible method for noninvasive screening of individuals for PAD that is quick, easy and inexpensive.
A High Efficiency Tunable Resonance Pump for Biomedical Applications
Authors: Secord Thomas , Audi Milad
Published: July 2018

Medical devices utilize pumps in several different application domains including medicine dispensing systems, drug and fluid infusion systems, perfusion equipment, and left ventricular assist devices (LVADs). In this paper, we propose a novel pump design for applications where continuous flow at high efficiency is the functional goal, such as in an LVAD.
Wearable Tremor Reduction Device (TRD) for Human Hands and Arms
Authors: Rudraraju Sreekanth , Nguyen The
Published: July 2018

Parkinson’s disease (PD) and essential tremor (ET) are two common but unrelated diseases that cause movement disorders often involving with severe tremor. The two diseases affects tens of millions of people worldwide, but there is no known cure for them. The tremor not only pose difficulty in completing daily tasks but also impair patients’ social confidence. The objective of this project is to develop a wearable tremor reduction device for the upper limb. The device is obviously different from any previous devices because it is compact, lightweight, comfortable to wear and effective. It is expected to help patients manage the tremor symptoms and regain their normal life.