101 |
Axial pull-out strength of 3.5 cortical and 4.0 cancellous bone screws placed in canine proximal tibias using manual and power tappingDemko, Jennifer Lynn 03 May 2008 (has links)
Many orthopedic conditions in dogs require the placement of bone screws in the proximal tibial metaphysis. Currently, both cortical and cancellous screws are used clinically depending on the surgeon’s preference; however, the ideal screw for use in the proximal tibia has not been determined. Currently, both the manual and power tapping techniques are used during surgical procedures of the proximal tibia in dogs. However, it is unknown if the use of power tapping when placing screws in the canine proximal tibial metaphysis affects screw purchase. Measurement of axial pull-out strength is traditionally used to evaluate and compare the holding power of screws inserted in bone. This study compares the axial pull-out strengths of 3.5 mm cortical and 4.0 mm cancellous screws inserted using manual and power tapping techniques in the proximal tibial metaphysis
|
102 |
Effect of Axial Oscillation on Performance of Hydrodynamic Journal BearingsWirsing, Thomas 13 May 2008 (has links)
No description available.
|
103 |
Performance of FRP-encased Steel-Concrete Composite ColumnsKarimi, Kian 04 1900 (has links)
<p> The thesis summarizes the experimental and analytical results of studies on the behavior of two FRP-encased steel-concrete composite columns under axial loading. Composite columns have been conventionally constructed using steel and concrete. This study utilizes FRP in combination with steel and concrete to manufacture composite columns with enhanced behavior. The first type of column is a concrete-encased steel column wrapped with epoxy-saturated glass and carbon fiber reinforced polymer (GFRP and CFRP) sheets in the transverse direction. The second type of composite column utilizes a GFRP tube that surrounds a steel I section column, which is subsequently filled with concrete. </p> <p> To the best of the author's knowledge, columns comprising FRP, steel and concrete in the shape of the proposed composite systems has not been reported on in the literature. This study includes two major phases. In the first phase, behavior of stub columns is investigated where stability effects are ignored and failure is governed by the loss of cross-sectional strength. In the second phase, influence of stability on the behavior of the proposed composite columns is studied by testing specimens with various slenderness ratios. </p> <p> To investigate the cross-sectional strength, a total of nine short (500 mm in height) composite column specimens were constructed and tested under axial compression. Five specimens were wrapped with FRP sheets and the remaining four were constructed using a GFRP tube. Experimental results showed significant enhancement in the behavior of the composite columns which was achieved due to confinement and composite action between the constituent materials. The compressive strength of the confined concrete core in the composite specimens constructed using FRP sheets and GFRP tube increased by a factor of 2.4 and 1.8, respectively. An analytical model was developed to predict crosssectional behavior of the proposed composited column. </p> <p> With the primary objective of investigating the influence of slenderness on the behavior of the composite columns, ten additional column specimens, ranging between 1,000 mm and 3,000 mm in height, were tested. Five specimens were constructed using FRP sheets and five constructed using the GFRP tube technique. It was found that the compressive strength of the confined concrete core in the longest tubular composite specimen was reduced to approximately 60% of that of the corresponding short specimen. No confinement was achieved in the longest FRP wrapped composite column specimen. </p> <p> Three bare steel columns, ranging between 500 mm and 3,000 mm in height, were also tested to facilitate comparison with the composite columns in terms of increased axial capacity, as well as stiffness and energy dissipation characteristics of the columns. The compressive strength, elastic axial stiffness and ultimate axial strain of the bare steel columns increased by a factor of up to 10, 6 and 3, respectively, in the composite columns constructed utilizing the concrete-filled GFRP tube. These factors were reduced to 5 .2, 2.5 and 2.6, respectively, in the concrete-encased steel columns wrapped with FRP jackets. </p> <p> Finally, an analytical model was developed to establish the capacity curves for the proposed composite columns accounting for slenderness effects. A simple design equation to predict the compressive strength of the tubular composite columns was proposed based on the capacity curve generated from the analytical model. Compressive capacity of the composite columns predicted using the proposed design equation showed favorable agreement with the experimental results. </p> / Thesis / Doctor of Philosophy (PhD)
|
104 |
Experimental and Numerical Study of Axial-Feed Hot Gas Tube Forming of PolypropyleneGavrilidou, Galini 07 1900 (has links)
Polymeric materials have attracted a lot of attention for the past several decades. Different sectors of manufacturing industry, such as packaging, building and automotive industry have introduced polymeric materials in their applications. Common polymer manufacturing processes include thermoforming and blow molding. In this research, characteristics of a new polymer manufacturing process, referred to as axial-feed hot gas tube forming (HGTF) are studied. Experimental studies were conducted to form a simple axisymmetric component from extruded polypropylene (PP) tube by varying several key process parameters such as internal pressure, temperature and axial feed. Tube shape and deformation characteristics were studied as a function of the above process parameters. In addition, two consecutive material models have been utilized for finite element simulation of axial-feed HGTF of PP tube using a commercial FE code. One of them is conventional hyperelastic Ogden material model and another is more advanced viscoelastic-viscoplastic Augmented Hybrid material model (AHM), that has been recently developed. Simulation results from two models were analyzed and compared with the experimental results and good general agreement has been obtained. Results showed that application of more advanced AHM material model led to improved prediction of part shape and strain distribution over the part profile. / Thesis / Master of Applied Science (MASc)
|
105 |
An Axial-Flux Switched Reluctance Motor for Light Electric VehiclesJack Gillies January 2020 (has links)
In an increasingly urgent climate crisis, the use of electric powertrains in smaller,
purpose-built vehicles can expedite the global adoption of electrification. This thesis discusses
the detailed design of an axial-flux switched reluctance motor for application in a light electric
vehicle, such as an E-motorcycle. A vehicle application is studied based on typical driving
conditions in an urban environment. The requirements of the propulsion motor are extracted,
and a baseline machine topology is analyzed for its performance and manufacturability,
towards the goal of a functional prototype. The prototype design includes a self-supporting
foil winding, designed to maximize the use of axial space and allow for good conductive heat
transfer to the machine casing. The rotor structure is found to be a limiting factor, where
maximum speed is limited by the mechanical stresses.
The performance of the motor is analyzed in detail, beginning with a numerical iron
loss model that is implemented to provide faster simulation time of the machine efficiency
than FEA. The efficiency is found to peak at 90%, comparable with other traction motors
of similar size on the market. The switching angles are studied, and the trade-offs between
torque quality and efficiency are quantified over the drive cycle. It was determined that
the vehicle could save 19.6 Wh/km by accepting poor torque quality and operating with
the most efficient control parameters. Thermal analysis is performed to determine the
realistic performance limitations. The machine was found to have power ratings of 7.12
kW instantaneous and 4.76 kW continuous. The final temperature of the winding during the
drive cycle was predicted not to exceed the temperature ratings of the insulation system.
Finally, the prototype is assembled, and a test plan is outlined for qualification of the motor. / Thesis / Master of Applied Science (MASc) / This thesis documents the design of a new type of electric motor that is intended to be used
in a small electric vehicle. The electric motor is different from the majority of motors used
in this application for two reasons: firstly, the motor is a switched reluctance motor, which
means that it does not contain any permanent magnets, offering cost savings and additional
robustness. Secondly, the machine takes the form of a disk, where the magnetic interface
between rotating and stationary components is on the face perpendicular to the axis of
rotation. Normally, electric motors have the magnetic interface on the cylindrical surface
which is parallel to the axis of rotation. The disk form factor presents multiple design
challenges, which when coupled with the switched reluctance motor type, are addressed.
A series of mathematical models are built to predict the performance of the motor in the
vehicular application. Finally, a prototype of the motor is constructed.
|
106 |
Axial loading of elliptical-section bonded rubber blocksTupholme, Geoffrey E., Horton, J.M. 13 July 2009 (has links)
No / Closed-form expressions for the small axial deflection and stress distribution of axially loaded rubber blocks of elliptical cross-section, whose ends are bonded to rigid plates, are derived using a superposition approach. The governing equations and conditions are satisfied exactly, based upon the classical theory of elasticity. Easily calculable expressions are derived for the corresponding apparent Young¿s modulus and the modified apparent Young¿s modulus in forms analogous to those previously given for blocks of circular cross-section.
|
107 |
Design and tests of a six-stage axial-flow compressor having a tip speed of 550 feet per second and a flat operating characteristic at constant speedMaynard, John W. Jr January 1958 (has links)
A six-stage axial-flow compressor with a 550 feet per second tip speed and a flat operating characteristic (constant stagnation-pressure ratio at constant speed over the operating range of the compressor) was designed and tested. The design theory and test results are presented in this thesis. It was designed for a constant power input per pound of flow regardless of mass flow. The design specific weight flow was 21.1 pounds per second per square foot of frontal area with an atmospheric discharge at an overall stagnation-pressure ratio of 3.25 and an inlet hub-tip radius ratio of 0.7. In order to reach design conditions the blade setting angles were reset and the machining notches at the root of the first three rotor blades were filled. In an attempt to increase the flat operating range of the compressor, the blade setting angles of the first two stages were increased and those of the last two stages were decreased. Also, the solidity of the first rotor was decreased. / Master of Science
|
108 |
Does transient increase in axial length elongation during accommodation attenuate with age?Laughton, D.S., Sheppard, A.L., Mallen, Edward A.H., Read, S.A., Davies, L.N. 12 March 2017 (has links)
Yes / Background: The aim was to profile transient accommodative axial length changes from
early adulthood to advanced presbyopia and to determine whether any differences exist
between the responses of myopic and emmetropic individuals.
Methods: Ocular biometry was measured by the LenStar biometer (Haag-Streit, Switzerland)
in response to zero, 3.00 and 4.50 D accommodative stimuli in 35 emmetropes and 37 myopes,
aged 18 to 60 years. All results were corrected to reduce errors arising from the increase in crystalline
lens thickness with accommodation. Accommodative responses were measured sequentially
by the WAM 5500 Auto Ref/Keratometer (Grand Seiko, Hiroshima, Japan).
Results: Axial length increased significantly with accommodation (p < 0.001), with a mean corrected
increase in axial length of 2 18 μm and 8 16 μm observed at 3.00 and 4.50 D,
respectively. The magnitude of accommodative change in axial length was not dependent on
refractive error classification (p = 0.959); however, a significant reduction in the magnitude
and variance of axial length change was evident after 43 to 44 years of age (p < 0.002).
Conclusion: The negative association between transient increase in axial length and age,
in combination with reduced variance of data after age 43 to 44 years, is consistent with a
significant increase in posterior ocular rigidity, which may be influential in the development
of presbyopia. / DL received funds from the College of Optometrists, UK
|
109 |
A Compact Wideband Circularly Polarized Planar Monopole Antenna with Axial Ratio Bandwidth Entirely Encompassing the Antenna BandwidthAlnahwi, F.M., Al-Yasir, Yasir I.A., Ali, N.T., Gharbia, Ibrahim, See, C.H., Abd-Alhameed, Raed 05 August 2022 (has links)
Yes / The antenna presented in this study is a compact wideband monopole with wideband circular polarization that can be used across the whole antenna bandwidth. A rectangular C-shaped patch is partially covered by a ground plane in the proposed planar monopole antenna. Inserting a rectangular stub to the ground plane, etching a slit at the antenna patch, and adding a semicircular stub at the top of the antenna feed line increase the antenna impedance bandwidth (BW) and axial ratio bandwidth (ARBW). An FR4 substrate with overall dimensions of 25 mm×25 mm×1.6 mm is used to create the antenna. The antenna's observed impedance BW is 70% (4.55 GHz in the 4.3-8.85 GHz band), while the measured broadside ARBW is improved to a value of 82.2 percent (5.3 GHz along the range 3.8-9.1 GHz). The impedance BW is perfectly covered by the ARBW; hence the antenna can be considered circularly polarized throughout its operational spectrum. Within the antenna BW, the measured gain is greater than 1.5 dB.
|
110 |
A Comparison Study on a Set of Space Syntax based Methods : Applying metric, topological and angular analysis to natural streets, axial lines and axial segmentsXia, Xiaolin January 2013 (has links)
Recently, there has been an increasing interest in looking at urban environment as a complex system. More and more researchers are paying attention to the study of the configuration of urban space as well as human social activities within it. It has been found that correlation exists between the morphological properties of urban street network and observed human social movement patterns. This correlation implies that the influence of urban configurations on human social movements is no longer only revealed from the sense of metric distance, but also revealed from topological and geometrical perspectives. Metric distances, topological relationships and angular changes between streets should be considered when applying space syntax analysis to an urban street network. This thesis is mainly focused on the comparison among metric, topological and angular analyses based on three kinds of urban street representation models: natural streets, axial lines and axial segments. Four study areas (London, Paris, Manhattan and San Francisco) were picked up for empirical study. In the study, space syntax measures were calculated for different combinations of analytical methods and street models. These theoretical space syntax accessibility measures (connectivity, integration and choice) were correlated to the corresponding practical human movement to evaluate the correlations. Then the correlation results were compared in terms of analytical methods and street representation models respectively. In the end, the comparison of results show that (1) natural-street based model is the optimal street model for carrying out space syntax analysis followed by axial lines and axial segments; (2) angular analysis and topological analysis are more advanced than metric analysis; and (3) connectivity, integration and local integration (two-step) are more suitable for predicting human movements in space syntax. Furthermore, it can be hypothesized that topological analysis method with natural-street based model is the best combination for the prediction of human movements in space syntax, for the integration of topological and geometrical thinking.
|
Page generated in 0.0267 seconds