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Journal Articles (Mechanical Engineering)

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  1. 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
  2. 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
  3. 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
  4. 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
  5. 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
  6. 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
  7. 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
  8. Gravity currents propagating up a slope in a two-layer fluid

    Title: Gravity currents propagating up a slope in a two-layer fluid
    Creator: Marleau, L. J.
    Description: Gravity currents produced by partial-depth lock-release and travelling along the base of a two-layer stratified ambient are investigated as they propagate along a rising slope. The initial gravity current front speed is found to be consistent with a theory adapted from Shin et al. [“Gravity currents produced by lock exchange,” J. Fluid Mech. 521, 1-34 (2004)] to the case of partial-depth currents in two-layer ambients. The subsequent evolution depends on the gravity current speed relative to the speed of the interfacial disturbance it creates. The deceleration of supercritical gravity currents, which travel faster than the interfacial disturbance, is gradual and agrees well with the relationship developed by Marleau et al. [“Gravity currents propagating up a slope,” Phys. Fluids 26, 046605 (2014)] for upslope gravity currents in uniform density ambients. In several subcritical cases, the gravity current suddenly came to rest as a consequence of interactions with the interfacial disturbance. The disturbance amplitude, speed, and width are found to be nearly constant during its evolution. In cases for which the ambient interface intersected the bottom slope, the amplitude, speed, and width were nearly constant up to the point where the lower layer shallowed and the disturbance transformed into an upslope-propagating gravity current.
    Subjects: Interfacial properties, Supercritical fluids, Electrical properties, Electric measurements, Height measurements
  9. Self-sustained nonlinear waves in traffic flow. [Download]

    Title: Self-sustained nonlinear waves in traffic flow.
    Creator: Flynn, M.R.
    Description: In analogy to gas-dynamical detonation waves, which consist of a shock with an attached exothermic reaction zone, we consider herein nonlinear traveling wave solutions to the hyperbolic (“inviscid”) continuum traffic equations. Generic existence criteria are examined in the context of the Lax entropy conditions. Our analysis naturally precludes traveling wave solutions for which the shocks travel downstream more rapidly than individual vehicles. Consistent with recent experimental observations from a periodic roadway [Y. Sugiyama et al., N. J. Phys. 10, 033001 (2008)], our numerical calculations show that nonlinear traveling waves are attracting solutions, with the time evolution of the system converging toward a wave-dominated configuration. Theoretical principles are elucidated by considering examples of traffic flow on open and closed roadways.
    Subjects:
    Date Created: 2009
  10. Constructing set-valued fundamental diagrams from jamiton solutions in second order traffic models.

    Title: Constructing set-valued fundamental diagrams from jamiton solutions in second order traffic models.
    Creator: Seibold, B.
    Description: Fundamental diagrams of vehicular traffic flow are generally multi-valued in the congested flow regime. We show that such set-valued fundamental diagrams can be constructed systematically from simple second order macroscopic traffic models, such as the classical Payne-Whitham model or the inhomogeneous Aw-Rascle-Zhang model. These second order models possess nonlinear traveling wave solutions, called jamitons, and the multi-valued parts in the fundamental diagram correspond precisely to jamiton-dominated solutions. This study shows that transitions from function-valued to set-valued parts in a fundamental diagram arise naturally in well-known second order models. As a particular consequence, these models intrinsically reproduce traffic phases.
    Subjects: fundamental diagram, Payne-Whitham, effective flow rate, traveling wave, Aw-Rascle-Zhang, Second order, sensor data, traffic model, jamiton
    Date Created: 2013