Mechanical Engineering Commons^™

A Biomechanical Comparison Of Polymethylmethacrylate-Reinforced And Expansive Pedicle Screws In Pedicle-Screw Revisions, Bora Bostan, Irfan Esenkaya, Taner Gunes, Mehmet Erdem, Murat Asci, Mehmet Halidun Kelestemur, Cengiz Sen

Faculty Publications - Mechanical Engineering

Objectives: Different techniques and choices exist for revision of pedicle screws, two of which are pedicle screw combined with cement augmentation and expansive pedicle screw fixation. This biomechanical study was designed to compare the pullout strengths of two different revision techniques. Methods: Fourteen lumbar vertebrae obtained from four calves (mean age 15 months) were divided into two groups equal in number. Monoaxial 6.0-mm pedicle screws were inserted into the right pedicles, and axial pullout testing was performed at a rate of 10 mm/min and failure strengths were recorded. Revision was performed with the same-sized pedicle screws reinforced with polymethyl-methacrylate in …

Gender Dimorphic Acl Strain In Response To Combined Dynamic 3d Knee Joint Loading: Implications For Acl Injury Risk, Kiyonori Mizuno, Jack T. Andrish, Antonie J. Van Den Bogert, Scott G. Mclean

Mechanical Engineering Faculty Publications

While gender-based differences in knee joint anatomies/laxities are well documented, the potential for them to precipitate gender-dimorphic ACL loading and resultant injury risk has not been considered. To this end, we generated gender-specific models of ACL strain as a function of any six degrees of freedom (6DOF) knee joint load state via a combined cadaveric and analytical approach. Continuously varying joint forces and torques were applied to five male and five female cadaveric specimens and recorded along with synchronous knee flexion and ACL strain data. All data (~10,000 samples) were submitted to specimen-specific regression analyses, affording ACL strain predictions as …

An Elaborate Data Set Characterizing The Mechanical Response Of The Foot, Ahmet Erdemir, Pavana A. Sirimamilla, Jason P. Halloran, Antonie J. Van Den Bogert

Mechanical Engineering Faculty Publications

Mechanical properties of the foot are responsible for its normal function and play a role in various clinical problems. Specifically, we are interested in quantification of foot mechanical properties to assist the development of computational models for movement analysis and detailed simulations of tissue deformation. Current available data are specific to a foot region and the loading scenarios are limited to a single direction. A data set that incorporates regional response, to quantify individual function of foot components, as well as the overall response, to illustrate their combined operation, does not exist. Furthermore, the combined three-dimensional loading scenarios while measuring …

Comment On "A Stochastic Biomechanical Model For Risk And Risk Factors Of Non-Contact Anterior Cruciate Ligament Injuries", Antonie J. Van Den Bogert, Scott G. Mclean

Mechanical Engineering Faculty Publications

No abstract provided.

Assessing Vaginal Surgical Skills Using Video Motion Analysis, Gouri B. Diwadkar, Antonie J. Van Den Bogert, Matthew D. Barber, J. Eric Jelovsek

Mechanical Engineering Faculty Publications

OBJECTIVE: To demonstrate the feasibility of using video motion analysis to quantitate a key step of vaginal hysterectomy and define measurable differences between novice and experienced surgical trainees during vaginal hysterectomy.

METHODS: Analyses focused on clamping, transecting, and suturing the left uterosacral ligament. Using a cutoff of 25, trainees were grouped as experienced (n=14) and novice (n=9) based on the total number of vaginal hysterectomies performed by each trainee. Contrasting-groups analysis was used to determine cutoff values that separated novices from experts.

RESULTS: Novice trainees took longer (112 seconds compared with 84 seconds) and had greater cumulative translational motion (92 …

Biomechanical Evaluation Of Glenohumeral Joint Stabilizing Muscles During Provocative Tests Designed To Diagnose Superior Labrum Anterior-Posterior Lesions, Vanessa J. C. Wood

Boise State University Theses and Dissertations

Despite considerable advances in the understanding of glenohumeral (GH) biomechanics and glenoid labral pathologies, arthroscopy remains the only definitive means of Superior Labrum Anterior-Posterior (SLAP) lesion diagnosis. Unfortunately, natural GH anatomic variants limit the reliability of radiography. Accurate clinical diagnostic techniques would be advantageous due to the invasiveness, patient risk, and financial cost associated with arthroscopy. Twenty provocative tests designed to elicit labral symptoms as a diagnostic sign have shown promising accuracy by their respective original authors, but later studies generally fail to reproduce those findings. The purpose of this study was to compare the behavior of GH joint stabilizing …

Mechanical Simulation Of Articular Cartilage Based On Experimental Results, Kevin Matthew Stewart

Master's Theses

Recently, a constituent based cartilage growth finite element model (CGFEM) was developed in order to predict articular cartilage (AC) biomechanical properties before and after growth. Previous research has noted limitations in the CGFEM such as model convergence with growth periods greater than 12 days. The main aims of this work were to address these limitations through (1) implementation of an exact material Jacobian matrix definition using the Jaumann-Kirchhoff (J-K) method and (2) quantification of elastic material parameters based upon research findings of the Cal Poly Cartilage Biomechanics Group (CPGBG). The J-K method was successfully implemented into the CGFEM and exceeded …

12 - ارائة مدلي جديد به منظور ارزيابي احساس حرارتي افراد در هنگام خواب, Alireza Zolfaghari, Mehdi Maerefat

Dr Alireza Zolfaghari

No abstract provided.

11 - مدلسازي و تحليل ناپاياي پاسخ حرارتي بدن انسان در هنگام خواب, Alireza Zolfaghari, Mehdi Maerefat

Dr Alireza Zolfaghari

No abstract provided.

Simulating The Growth Of Articular Cartilage Explants In A Permeation Bioreactor To Aid In Experimental Protocol Design, Timothy P. Ficklin, Andrew Davol, Stephen M. Klisch

Mechanical Engineering

Recently a cartilage growth finite element model (CGFEM) was developed to solve nonhomogeneous and time-dependent growth boundary-value problems (Davol et al., 2008, “A Nonlinear Finite Element Model of Cartilage Growth,” Biomech. Model. Mechanobiol., 7, pp. 295–307). The CGFEM allows distinct stress constitutive equations and growth laws for the major components of the solid matrix, collagens and proteoglycans. The objective of the current work was to simulate in vitro growth of articular cartilage explants in a steady-state permeation bioreactor in order to obtain results that aid experimental design. The steady-state permeation protocol induces different types of mechanical stimuli. When the specimen …

5 - امکان سنجي استفاده از سيستمهاي سرمايش تابشي سقفي با توجه به تنوع شرايط آب و هوايي و اقليمي در ايران, Alireza Zolfaghari, Mehdi Maerefat, Amir Omidvar

Dr Alireza Zolfaghari

No abstract provided.

A Real-Time, 3-D Musculoskeletal Model For Dynamic Simulation Of Arm Movements, Edward K. Chadwick, Dimitra Blana, Antonie J. Van Den Bogert, Robert F. Kirsch

Mechanical Engineering Faculty Publications

Neuroprostheses can be used to restore movement of the upper limb in individuals with high-level spinal cord injury. Development and evaluation of command and control schemes for such devices typically require real-time, ldquopatient-in-the-looprdquo experimentation. A real-time, 3-D, musculoskeletal model of the upper limb has been developed for use in a simulation environment to allow such testing to be carried out noninvasively. The model provides real-time feedback of human arm dynamics that can be displayed to the user in a virtual reality environment. The model has a 3-DOF glenohumeral joint as well as elbow flexion/extension and pronation/supination and contains 22 muscles …

10 - استفاده از پوششهاي همسانه؛ راهکاري مناسب در جهت همگن سازي حرارتي محيط و کاهش مصرف انرژي در بخشهاي اداري و آموزشي, Alireza Zolfaghari, Mehdi Maerefat, Amir Omidvar

Dr Alireza Zolfaghari

No abstract provided.

9 - ارائه روشي جديد براي ارزيابي شرايط حرارتي بدن در شرايط پيچيدة محيطي, Alireza Zolfaghari, Mehdi Maerefat

Dr Alireza Zolfaghari

No abstract provided.

8 - روشي جديد براي مدلسازي پاسخ حرارتي بدن به شدت اغتشاشات جريان هواي وزشي و تخمين نارضايتي حرارتي ناشي از کوران, Amir Omidvar, Alireza Zolfaghari, Mehdi Maerefat

Dr Alireza Zolfaghari

No abstract provided.

An Inverse Method For Predicting Tissue-Level Mechanics From Cellular Mechanical Input, Wangdo Kim, Derek C. Tretheway, Sean S. Kohles

Mechanical and Materials Engineering Faculty Publications and Presentations

Extracellular matrix (ECM) provides a dynamic three-dimensional structure which translates mechanical stimuli to cells. This local mechanical stimulation may direct biological function including tissue development. Theories describing the role of mechanical regulators hypothesize the cellular response to variations in the external mechanical forces on the ECM. The exact ECM mechanical stimulation required to generate a specific pattern of localized cellular displacement is still unknown. The cell to tissue inverse problem offers an alternative approach to clarify this relationship. Developed for structural dynamics, the inverse dynamics problem translates measurements of local state variables (at the cell level) into an unknown or …

Application Of The Actor-Critic Architecture To Functional Electrical Stimulation Control Of A Human Arm, Philip Thomas, Michael Branicky, Antonie Van Den Bogert, Kathleen Jagodnik

Mechanical Engineering Faculty Publications

Clinical tests have shown that the dynamics of a human arm, controlled using Functional Electrical Stimulation (FES), can vary significantly between and during trials. In this paper, we study the application of the actor-critic architecture, with neural networks for the both the actor and the critic, as a controller that can adapt to these changing dynamics of a human arm. Development and tests were done in simulation using a planar arm model and Hill-based muscle dynamics. We begin by training it using a Proportional Derivative (PD) controller as a supervisor. We then make clinically relevant changes to the dynamics of …

Concurrent Simulation Of Neuromuscular Control And Tissue Deformation Is Possible By Adaptive Surrogate Modeling, Jason P. Halloran, Ahmet Erdemir, Antonie J. Van Den Bogert

Mechanical Engineering Faculty Publications

No abstract provided.

Adaptive Surrogate Modeling For Efficient Coupling Of Musculoskeletal Control And Tissue Deformation Models, Jason P. Halloran, Ahmet Erdemir, Antonie J. Van Den Bogert

Mechanical Engineering Faculty Publications

Background

Finite element (FE) modeling and multibody dynamics have traditionally been applied separately to the domains of tissue mechanics and musculoskeletal movements, respectively. Simultaneous simulation of both domains is needed when interactions between tissue and movement are of interest, but this has remained largely impractical due to high computational cost.

Method of Approach

Here we present a method for concurrent simulation of tissue and movement, in which state of the art methods are used in each domain, and communication occurs via a surrogate modeling system based on locally weighted regression. The surrogate model only performs FE simulations when regression from …

Design And Characterization Of A Shock And Vibration Mitigation Seat System, George Samaan Ladkany

UNLV Theses, Dissertations, Professional Papers, and Capstones

Extensive research has been conducted into the development of pneumatic seatbladder systems for shock and vibration mitigation for use in current U.S military vehicle envelopes. This research expands on the previous work through an elaborate experimental characterization of four prototype air bladder seat cushion systems. The experimental characterization conducted included shock testing, continuous vibration, and internal dynamic pressure measured during the shock event.

The shock testing was conducted both at the Army Research Lab as well at UNLV. The shock testing conducted at UNLV was performed on a drop tower designed and constructed during the time of this research. The …