This thesis investigates strengthening slender steel columns with carbon fibre reinforced polymer (CFRP) plates of various moduli. Three different types of CFRP were used in the study: Ultra-high modulus (430GPa), High modulus (212GPa) and Normal modulus (168GPa). In this study, specimens were grouped according to measured initial out-of-straightness values. The first section examines the effect of adding CFRP plates to the column flanges when buckling about the weak axis. Twelve columns, with a slenderness ratio of 197, were tested, of which nine were strengthened with CFRP. The main parameters tested were the level of initial out-of-straightness (length (L)/8387 to L/1020), CFRP modulus (168 to 430 GPa), CFRP reinforcement ratio (13% to 34%) and the length of CFRP plate (33% to 95% of L). The gain in axial strength due to CFRP retrofitting ranged from 11% to 29%, depending on the various parameters. The gain generally increased as CFRP modulus, initial out-of-straightness, or CFRP reinforcement ratio increased. Global buckling consistently governed the maximum load. In the case of the 430 GPa CFRP, buckling was followed by CFRP crushing in compression, then rupture in tension. The second section of the thesis examines the effect of CFRP plates added to the flanges and tested for buckling in the strong axis. Eight columns, with a slenderness ratio of 83, were tested of which five were strengthened with CFRP. The main parameters examined were the level of initial out-of-straightness (L/28889 to L/1635), CFRP modulus (168 to 430 GPa), CFRP reinforcement ratio (13% to 34%) and the axis of bending. The gain in axial strength due to CFRP retrofitting ranged from 0% to 25%, depending on the various parameters. The gain generally increased as initial out-of-straightness, or CFRP reinforcement ratio increased. The higher modulus did not perform as expected, showing no gain in strength, because the compressive strains were too large and the CFRP crushed before the specimen experienced any gain. Specimens compared with the weak axis, strengthened with normal modulus CFRP, had similar percentage gains in strength. / Thesis (Master, Civil Engineering) -- Queen's University, 2014-06-27 15:19:03.397

No description available.

The medial axis skeleton is a thin line graph that preserves the topology of a region. The skeleton has often been cited as a useful representation for shape description, region interpretation, and object recognition. Unfortunately, the computation of the skeleton is extremely sensitive to variations in the bounding contour. In this paper, we describe a robust method for computing the medial axis skeleton across a variety of scales. The resulting scale-space is parametric with the complexity of the skeleton, where the complexity is defined as the number of branches in the skeleton.

This thesis presents the use of Computer Numerically Controlled (CNC) machining as a method to manufacture anatomically-shaped synthetic grafts made from Calcium Polyphosphate (CPP) ceramic. Tissue-engineered cartilage is grown on the surface of these implants in vitro followed by in vivo implantation in the host’s body for osteochondral focal defect repair. While most current implants are manufactured from simple geometries and are not specific to one patient’s need, it is believed that custom manufactured implants (from computer tomography data) representing the exact shape of the original bone will be beneficial. This is because custom implants permit an even stress distribution on the cartilage, resulting in increased cartilage survival rates. The present study has successfully manufactured and delivered a custom designed implant with sufficient surface porosity and minimal chipping. This was accomplished by effectively modeling the machinability characteristics and finding the optimal cutting conditions for CPP. CPP’s machinability characteristics were investigated and a cutting force prediction model was developed. This model was verified by a comparison of experimental and predicted forces for a number of ball and flat endmilling tests. The optimal cutting conditions that would result in maximum surface porosity and minimal chipping were established through qualitative investigation of results from varied conditions using Scanning Electron Microscope (SEM) images. Using the established optimal cutting conditions from machinability studies, the multi-axis machining process for producing the designed custom implant was developed and all stages were simulated for accuracy and integrity of the final implant. The designed toolpaths were tested on prototyping wax and verified against the actual Computer Aided Design (CAD) model using an optical microscope. The same toolpaths were executed on a block of CPP and the final implant was again investigated for surface porosity and chipping. After final comparison against the CAD model using an optical microscope, the implant was delivered to surgeons for implantation.

This thesis presents the use of Computer Numerically Controlled (CNC) machining as a method to manufacture anatomically-shaped synthetic grafts made from Calcium Polyphosphate (CPP) ceramic. Tissue-engineered cartilage is grown on the surface of these implants in vitro followed by in vivo implantation in the host’s body for osteochondral focal defect repair. While most current implants are manufactured from simple geometries and are not specific to one patient’s need, it is believed that custom manufactured implants (from computer tomography data) representing the exact shape of the original bone will be beneficial. This is because custom implants permit an even stress distribution on the cartilage, resulting in increased cartilage survival rates. The present study has successfully manufactured and delivered a custom designed implant with sufficient surface porosity and minimal chipping. This was accomplished by effectively modeling the machinability characteristics and finding the optimal cutting conditions for CPP. CPP’s machinability characteristics were investigated and a cutting force prediction model was developed. This model was verified by a comparison of experimental and predicted forces for a number of ball and flat endmilling tests. The optimal cutting conditions that would result in maximum surface porosity and minimal chipping were established through qualitative investigation of results from varied conditions using Scanning Electron Microscope (SEM) images. Using the established optimal cutting conditions from machinability studies, the multi-axis machining process for producing the designed custom implant was developed and all stages were simulated for accuracy and integrity of the final implant. The designed toolpaths were tested on prototyping wax and verified against the actual Computer Aided Design (CAD) model using an optical microscope. The same toolpaths were executed on a block of CPP and the final implant was again investigated for surface porosity and chipping. After final comparison against the CAD model using an optical microscope, the implant was delivered to surgeons for implantation.

No description available.

Many of the undesirable side effects that occur during orthodontic treatment can be attributed directly to a lack of understanding of the physics involved in a given adjustment of an orthodontic appliance. A large number of variables in orthodontic treatment are not within our control, such as growth and tissue response to appliances. However, the force placed on the tooth should be a controllable variable (1), and careful study of the physics underlying our clinical application, can help in reducing those undesirable side effects. If researchers and clinicians can quantify the force systems applied to the teeth, they can better understand clinical and histologic responses. Orthodontic force systems used in everyday orthodontic mechanics are considered indeterminate force systems, in other words, there are too many unknowns to determine the different components of these force systems. Until recently, much of the literature was restricted to experimental two-dimensional analyses of the biomechanical aspects of orthodontic force systems, and computer modeling of three-dimensional analyses. Very little evidence exists in the literature regarding three dimensional experimental measurement and analysis of orthodontic force systems (2). Force system measurements were made on one or two tooth models, however in order for us to understand the orthodontic force systems we need to simultaneously, measure in 3D, the forces being applied on every tooth in the dental arch. With the very recent technological advances in force/torque sensors technology, data acquisition and data representation, it became possible to measure those forces and reveal the force systems we are applying to the dentition. The purpose of this PhD research study is the design and construction of an experimental device that is capable of revealing the details of the force systems used in modern day orthodontic mechano-therapy of continuous arch technique. / Orthodontics

No description available.

This work finds curious the relationships of figures bound by and revolving around a central axis. As this series of figures are elaborated by mathematical operations, the complex nature of their combination removes apparent identity and synthesizes a simultaneous presence which is difficult to name. The drawings serve as a form of notation, similar to sheet music. As notation they aim to find their voice in the physical world. The drawings search for relationships which are then made tangible so they can be studied in light and act as a model to continue working. / Master of Architecture

At the crossing of a strong architectural edge and an axis line, it is necessary to articulate the intersection and acknowledge the moment. But what if, at the point of this intersection, other contextual factors work against the articulation? What if there is an opportunity to not only mark the intersection, but in doing so strengthen the edge condition, elevate the importance of the axis line and provide a celebrated threshold experience? This project looks at this very condition as it exists within the context of the Virginia Tech campus in Blacksburg, Virginia. At the intersection of the axis of symmetry for the campus and the building edge along Perry Street, there is no acknowledgment of this crossing. In fact, in its present condition, the intersection is beset by a breakdown in the edge condition and only a trace of the powerful axis line. In addressing the challenges that plague this existing condition, this project will seek to achieve four things with respect to the Virginia Tech campus, at large: 1. Articulate the termination point of the axis of symmetry for the campus by strengthening the pedestrian path that runs along the axis providing a clearly defined route to the Drill Field. 2. A redefinition of the edge along Perry Street, repairing the breech in the building wall and connecting the components that make up the edge. 3. Strengthen intersection of the edge and the axis/path line by developing a new pedestrian portal into the heart of campus thereby providing a formal entry point along an edge that currently does not articulate the entry points into campus. 4. Develop the architectural context within the site, bridging the divide between the architectural traditions of the campus core with the modernist vernacular of the Perry Street Edge. / Master of Architecture