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Journal Articles (Mechanical Engineering)

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  1. Finite plane deformations of elastic solids reinforced with fibers resistant to flexure: complete solution [Download]

    Title: Finite plane deformations of elastic solids reinforced with fibers resistant to flexure: complete solution
    Creator: Mahdi Zeidi
    Description: A model for the deformation of an elastic solid reinforced by embedded fibers is presented in which elastic resistance of the fibers to bending is incorporated. Within the framework of strain-gradient elasticity, we formulated the equilibrium equations and necessary boundary conditions which describe the finite plane deformations of fiber-reinforced composite materials. The resulting nonlinear partial differential equations are numerically solved by employing the finite element method. A complete analytical solutions is also obtained within the limitation of superposed incremental deformations.
    Subjects: Finite plane deformations, Fiber-reinforced material, Strain-gradient theory
    Date Created: 2018
  2. Notes on superposed incremental deformations in the mechanics of lipid membranes [Download]

    Title: Notes on superposed incremental deformations in the mechanics of lipid membranes
    Creator: Mahdi Zeidi
    Description: We present an analysis of the superposed incremental deformations of lipid membranes in contact with a circular substrate. A complete analytical solution describing the morphological transitions of lipid membranes is obtained via Monge parametric representation and admissible linearization. The corresponding solution demonstrates smooth and bounded behavior within the finite domain of interest (annular) and, more importantly, shows excellent stability as it approaches the boundary of the circular substrate with the radius of convergence compatible with a few nanometers. Under the prescription of the superposed incremental deformations, a complete analysis of the necessary boundary conditions, the anchoring condition of the lipid molecules on an edge, and other geometrical quantities of the membrane is illustrated for the case of the circular substrate–membrane system.
    Subjects: Lipid bilayers, substrate–membrane interaction, finite domain
    Date Created: 2017
  3. Mechanics of fiber composites with fibers resistant to extension and flexure [Download]

    Title: Mechanics of fiber composites with fibers resistant to extension and flexure
    Creator: Mahdi Zeidi
    Description: A model of elastic solids reinforced with fibers resistant to extension and bending is formulated in finite-plane elastostatics. The linear theory of the proposed model is also derived through which a complete analytical solution is obtained. The presented model can serve as an alternative two-dimensional Cosserat theory of non-linear elasticity.
    Subjects: finite elasticity, strain gradient theory, fiber-reinforced materials, extension and flexure, superposed incremental deformations
    Date Created: 2017
  4. Effect of object location on the density measurement and hounsfield conversion in a NewTom 3G cone-beam computed tomography unit [Download]

    Title: Effect of object location on the density measurement and hounsfield conversion in a NewTom 3G cone-beam computed tomography unit
    Creator: Lagravère, Manuel O.
    Description: Objectives: The purpose of this study was to determine the effect of an object's location in a cone beam CT imaging chamber (CBCT-NewTom 3G) on its apparent density and to develop a linear conversion coefficient for Hounsfield units (HU) to material density (g cm−3) for the NewTom 3G Scanner. Methods: Three cylindrical models of materials with different densities were constructed and scanned at five different locations in a NewTom 3G Volume Scanner. The average HU value for each model at each location was obtained using two different types of software. Next, five cylinders of different known densities were scanned at the exact centre of a NewTom 3G Scanner. The collected data were analysed using the same two types of software to determine a standard linear relationship between density and HU for each type of software. Results: There is no statistical significance of location of an object within the CBCT scanner on determination of its density. A linear relationship between the density of an object and the HU of a scan was ρ = 0.001(HU)+1.19 with an R2 value of 0.893 (where density, ρ, is measured in g cm−3). This equation is to be used on a range between 1.42 g cm−3 and 0.4456 g cm−3. Conclusions: A linear relationship can be used to determine the density of materials (in the density range of bone) from the HU values of a CBCT scan. This relationship is not affected by the object's location within the scanner itself.
    Subjects: Hounsfield Value, Computed Tomography, Bone Density
    Date Created: 2008
  5. Experimentally Determined Mechanical Properties of, and Models for, the Periodontal Ligament: Critical Review of Current Literature [Download]

    Title: Experimentally Determined Mechanical Properties of, and Models for, the Periodontal Ligament: Critical Review of Current Literature
    Creator: Fill, Ted S.
    Description: Introduction. This review is intended to highlight and discuss discrepancies in the literature of the periodontal ligament’s (PDL) mechanical properties and the various experimental approaches used to measure them. Methods. Searches were performed on biomechanical and orthodontic publications (in databases: Compendex, EMBASE, MEDLINE, PubMed, ScienceDirect, and Scopus). Results. The review revealed that significant variations exist, some on the order of six orders of magnitude, in the PDL’s elastic constants and mechanical properties. Possible explanations may be attributable to different experimental approaches and assumptions. Conclusions. The discrepancies highlight the need for further research into PDL properties under various clinical and experimental loading conditions. Better understanding of the PDL’s biomechanical behavior under physiologic and traumatic loading conditions might enhance the understanding of the PDL’s biologic reaction in health and disease. Providing a greater insight into the response of the PDL would be instrumental to orthodontists and engineers for designing more predictable, and therefore more efficacious, orthodontic appliances.
    Subjects: Mechanical properties, Periodontal Ligament
    Date Created: 2011
  6. Evaluation of diagnosis techniques used for spinal injury related back pain [Download]

    Title: Evaluation of diagnosis techniques used for spinal injury related back pain
    Creator: Janssen, Meaghan
    Description: Back pain is a prevalent condition affecting much of the population at one time or the other. Complications, including neurological ones, can result from missed or mismanaged spinal abnormalities. These complications often result in serious patient injury and require more medical treatment. Correct diagnosis enables more effective, often less costly treatment methods. Current diagnosis technologies focus on spinal alterations. Only approximately 10% of back pain is diagnosable, with current diagnostic technologies. The objective of this paper is to investigate and evaluate based on specific criteria current diagnosis technique. Nine diagnostic techniques were found in the literature, namely, discography, myelography, single photon emission computer tomography (SPECT), computer tomography (CT), combined CT & SPECT, magnetic resonance imaging (MRI), upright and kinematic MRI, plain radiography and cineradiography. Upon review of the techniques, it is suggested that improvements can be made to all the existing techniques for diagnosing back pain. This review will aid health service developers to focus on insufficient areas, which will help to improve existing technologies or even develop alternative ones.
    Subjects: Spinal injuries, Diagnosis techniques, Back pain
    Date Created: 2011
  7. Review of Maxillary expansion appliance activation methods: engineering and clinical perspectives [Download]

    Title: Review of Maxillary expansion appliance activation methods: engineering and clinical perspectives
    Creator: Romanyk, Dan L.
    Description: Objective. Review the reported activation methods of maxillary expansion devices for midpalatal suture separation from an engineering perspective and suggest areas of improvement. Materials and Methods. A literature search of Scopus and PubMed was used to determine current expansion methods. A U.S. and Canadian patent database search was also conducted using patent classification and keywords. Any paper presenting a new method of expansion was included. Results. Expansion methods in use, or patented, can be classified as either a screw- or spring-type, magnetic, or shape memory alloy expansion appliance. Conclusions. Each activation method presented unique advantages and disadvantages from both clinical and engineering perspectives. Areas for improvement still remain and are identified in the paper.
    Subjects: Maxillary expansion devices, Activation methods
    Date Created: 2010
  8. Clinical variability in arch wires: A preliminary study evaluating mechanical and surface characteristics of two different sized rectangular stainless steel wires [Download]

    Title: Clinical variability in arch wires: A preliminary study evaluating mechanical and surface characteristics of two different sized rectangular stainless steel wires
    Creator: Vena, Alessandro
    Description: Experimental characterization of arch wires has been performed in many previous studies; however with the advent of new arch wire materials being introduced, some new experimental methods and characterization are required. Since literature is available for comparison, this paper examines mechanical and physical characteristics of steel arch wires to quantify their variability in engineering terms. Furthermore, the effect of wire size on properties was evaluated using two of the most common wire sizes. Finally, manufacturing consistency was verified by testing samples from different lots.
    Subjects: Consistency, Mechanical Properties, Arch Wires, Geometry
    Date Created: 2007
  9. An Experimental Method for Stereolithic Mandible Fabrication and Image Preparation [Download]

    Title: An Experimental Method for Stereolithic Mandible Fabrication and Image Preparation
    Creator: Russett, Shawn
    Description: Reproduction of anatomical structures by rapid prototyping has proven to be a valid adjunct for craniofacial surgery, providing alternative methods to produce prostheses and development of surgical guides. The aim of this study was to introduce a methodology to fabricate asymmetric human mandibles by rapid prototyping to be used in future studies for evaluating mandibular symmetries. Stereolithic models of human mandibles were produced with varying amounts of asymmetry in the condylar neck, ramus and body of the mandible by means of rapid prototyping. A method for production of the synthetic mandibles was defined. Model preparation, landmark description and development of the experimental model were described. A series of synthetic mandibles ranging in asymmetry were accurately produced from a scanned human mandible. A method for creating the asymmetries, fabricating, coating and landmarking the synthetic mandibles was formulated. A description for designing a reproducible experimental model for image acquisition was also outlined. Production of synthetic mandibles by stereolithic modeling is a viable method for creating skeletal experimental models with known amounts of asymmetry.
    Subjects: Biomedical Engineering, Rapid Prototyping, Stereolithic Mandible Models, Image Processing
    Date Created: 2007
  10. A mathematical model to capture complex microstructure orientation on insect wings.

    Title: A mathematical model to capture complex microstructure orientation on insect wings.
    Creator: Polet, D. T.
    Description: Microstructures on insect wings can promote directional drop shedding, and the local orientation of these structures is expected to facilitate drop removal. However, microstructures may exhibit very different orientations at different locations on the wing. Using the march fly Penthetria heteroptera, we propose that local orientation of small hairs (microtrichia) reflects a balance of three nonexclusive strategies: (1) preventing water from becoming stuck in intervenous grooves (microtrichia point upslope), (2) shedding water off the wing as readily as possible (microtrichia point towards the nearest edge), and, (3) shedding water away from the body (microtrichia point distally). We present evidence for all three and show that local microtrichial orientation is seldom determined by any one factor. We develop a mathematical model that employs factor-specific weighting values determined via optimization. Our predictions are tested against the orientation of microtrichia randomly sampled from a P. heteroptera specimen. Using the best-fit weighting parameters, the model displays a median residual of 20°; no residual is greater than 46°. The model also reproduces qualitative aspects of microtrichial orientation, such as bifurcation midway between veins and convergence toward peaks. This strong correspondence between modelled and observed orientation supports the role of microtrichia as directional antiwetting devices and highlights the importance of considering both function and wing geometry to explain the organization of natural microstructure arrays.
    Subjects: Waxes, Molting, Insects, Aquatic Insects, Mathematical Models, Microstructure, Wings, Optimization
    Date Created: 2015