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You searched for subject:( Visibility properties). Showing records 1 – 3 of 3 total matches.

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Université de Sherbrooke

1. Ahmari, Ali. Amélioration du ciment acrylique osseux utilisé lors de vertébroplasties .

Degree: 2010, Université de Sherbrooke

Vertebroplasty is a new technique in orthopedic surgery for stabilizing fractured vertebra. In this technique acrylic bone cement as a biocompatible material is injected through a cannula inside of vertebra. There are several concerns in this technique that the most serious one is cement leakage out of vertebra. The main reasons are improper viscosity and lack of visibility. Clinicians who practice vertebroplasty use commercial highly concentrated radiopaque acrylic bone cement (more than 25%BaSO[subscript 4] or ZrO[subscript 2]) or a cement with manually added radiopaque agents. High density materials with attenuation under X-ray are good alternatives compared to conventional radiopaque agents (BaSO[subscript 4] or ZrO[subscript 2]) in acrylic bone cement for application in vertebroplasty. In the first part of this study, thermal and rheological properties of modified acrylic bone cement with conventional radiopaque agent (Barium Sulfate, BaSO[subscript 4]) are studied. Additions of barium sulfate are in the form of substitute or excess. In substitute formulation, barium sulfate is replaced with the same weight of powder and liquid to powder ratio kept constant. In the excess formulation, barium sulfate added as excess and liquid to powder ratio decreased. In the second part of this study, high density radiopaque agents are used as alternative radiopacifier. Experimental design technique is used to study the effect of X-ray conditions, concentration, type, and size of radiopaque agents on the visibility of bone cement. The visibility of bone cement was quantified by the measurement of contrast index. In the first project, it was found that the setting time increased with the increase of concentration of radiopacifier in substitute formulation of barium sulfate bone cement. With increase of barium sulfate concentration, excess formulations showed higher residual monomer but for substitute cement, we had a decreasing trend. Acrylic bone cements with excess formulation had higher initial viscosity compared to reference or substitute but the variation of viscosity with time was lower for substitute formulation and cements had higher working time. In the second project, contrast index was the same for barium sulfate, tungsten, and zirconium in the lower voltage but in higher voltage of X-ray lamp, tungsten and zirconium gave higher contrast index. Variation of current in X-ray lamp changed the contrast index of cement slightly compared to the effect of voltage. Bone cement with nano tungsten had higher contrast index compared to the cement with micro size tungsten although micro size zirconium as radiopacifier gave higher contrast index than nano size zirconium. Advisors/Committee Members: Baroud, Gamal (advisor).

Subjects/Keywords: Nano tungsten; Visibility properties; Rheological properties; Thermal properties; Radiopaque agents; Acrylic bone cement

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APA (6th Edition):

Ahmari, A. (2010). Amélioration du ciment acrylique osseux utilisé lors de vertébroplasties . (Masters Thesis). Université de Sherbrooke. Retrieved from http://savoirs.usherbrooke.ca/handle/11143/1556

Chicago Manual of Style (16th Edition):

Ahmari, Ali. “Amélioration du ciment acrylique osseux utilisé lors de vertébroplasties .” 2010. Masters Thesis, Université de Sherbrooke. Accessed October 21, 2019. http://savoirs.usherbrooke.ca/handle/11143/1556.

MLA Handbook (7th Edition):

Ahmari, Ali. “Amélioration du ciment acrylique osseux utilisé lors de vertébroplasties .” 2010. Web. 21 Oct 2019.

Vancouver:

Ahmari A. Amélioration du ciment acrylique osseux utilisé lors de vertébroplasties . [Internet] [Masters thesis]. Université de Sherbrooke; 2010. [cited 2019 Oct 21]. Available from: http://savoirs.usherbrooke.ca/handle/11143/1556.

Council of Science Editors:

Ahmari A. Amélioration du ciment acrylique osseux utilisé lors de vertébroplasties . [Masters Thesis]. Université de Sherbrooke; 2010. Available from: http://savoirs.usherbrooke.ca/handle/11143/1556


Texas A&M University

2. Hamdi, Marouen. Fundamental Understanding of Scratch and Mar Behavior of Polymers.

Degree: PhD, Mechanical Engineering, 2016, Texas A&M University

Scratch behavior on polymeric films was investigated. The effect of film orientation and architecture on scratch resistance was determined. Film orientation was obtained by uniaxial stretching and its architecture was modified by the addition of ethylene comonomers. Model polypropylene (PP) and polyamide (PA) systems were employed to study the effect of laminate structure on scratch resistance. Also, mar behavior on bulk polymeric materials was investigated. The impact of brightness, transparency, and color as well as surface friction and texture on mar visibility resistance was determined. These studies were conducted based on fundamental, experimental, numerical, psychophysical, and statistical approaches. Experimental tests were conducted with accordance to ASTM/ISO standard. They were complemented by numerical simulations performed using a sophisticated FEM model. The psychophysical approach is performed through human observation tests to validate the experimental findings. The obtained data was analyzed using multidimensional scaling (MDS) statistical approach. Scratch analysis demonstrates that scratch resistance is improved with higher film orientation and lower ethylene content. The FEM analysis shows that this improvement is associated with surface-to-interface shift of stress concentration. It is also found using the parametric analysis that scratch resistance is mainly improved due to higher film hardening coefficient and yield stress, but is insensitive to film modulus. It is also found that PP/PA has better scratch performance than PA/PP. This is mainly due to PP/PA low surface friction and graded structure, where upper PP layer absorbs scratch energy and lower PA layer protects the interface from high stress built-up. Mar analysis demonstrates that mar visibility resistance decreases with green, dark, smooth, and high-friction surfaces. Also, MDS results show that brightness, transparency, and color have respectively considerable, moderate, and insignificant effect on mar perception. Experimental findings indicate that mar visibility resistance can be quantified using the slope variation of mar contrast curve. FEM stress analysis shows that stress concentration is generated at the mar edge, then propagates towards inner mar area repetitively, reflecting stick-slip oscillations observed in experimental mar tests. The results found in these research studies serve as a practical tool to effectively design polymeric systems with appealing scratch and mar performance. Advisors/Committee Members: Sue, Hung-Jue (advisor), Hogan, Harry A. (committee member), Suh , Steve (committee member), Yuan, Joshua (committee member).

Subjects/Keywords: Scratch and mar; visibility resistance; FEM analysis; experimental and psychophysical tests; thin films; laminates; mechanical and perceptual properties

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APA (6th Edition):

Hamdi, M. (2016). Fundamental Understanding of Scratch and Mar Behavior of Polymers. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/159087

Chicago Manual of Style (16th Edition):

Hamdi, Marouen. “Fundamental Understanding of Scratch and Mar Behavior of Polymers.” 2016. Doctoral Dissertation, Texas A&M University. Accessed October 21, 2019. http://hdl.handle.net/1969.1/159087.

MLA Handbook (7th Edition):

Hamdi, Marouen. “Fundamental Understanding of Scratch and Mar Behavior of Polymers.” 2016. Web. 21 Oct 2019.

Vancouver:

Hamdi M. Fundamental Understanding of Scratch and Mar Behavior of Polymers. [Internet] [Doctoral dissertation]. Texas A&M University; 2016. [cited 2019 Oct 21]. Available from: http://hdl.handle.net/1969.1/159087.

Council of Science Editors:

Hamdi M. Fundamental Understanding of Scratch and Mar Behavior of Polymers. [Doctoral Dissertation]. Texas A&M University; 2016. Available from: http://hdl.handle.net/1969.1/159087

3. Toh, H.L. Suspended Sediment and Light Attenuation Characteristics in Singapore Waters:.

Degree: 2012, Delft University of Technology

Light is attenuated by materials present in the water column by scattering and absorption. The knowledge of light attenuation and its contributing factors influencing visibility/turbidity is unknown in Singapore waters. This MSc thesis consists of field measurement, laboratory experiment and numerical modelling in 3 parts; parameterisation of light attenuation coefficient〖 K〗_d, numerical modelling of underwater light field and visibility. The objectives of this thesis are; a) to determine the dynamics of optical properties in Singapore waters, b) to investigate factors contributing to light attenuation in Singapore waters and c) to model underwater light field and visibility using Hydrolight and Delft3D WAQ. This first part addresses the dynamics of light attenuation (in relation to low/high tide), the spectral nature of optically significant constituents (water, CDOM, phytoplankton and sediment) as well as the effects of particle size distribution (PSD) to light scattering. For PSD with a higher slope j in N(D) = 〖KD〗^(-j), the d50 ranges from 7.11 to 9.90 μm in Singapore Strait representing sediment dominated environment. Higher TSS during low tide is advection dominated while lower TSS during high tide is suspension dominated. Relative contributions of CDOM, chlorophyll and sediment to light attenuation coefficient〖 K〗_d is 1.4 – 6.5 % (average of 3.3 %), 1.3 – 62 % (average of 24 %) and 31.3 – 95.2 % (average of 70 %) respectively. Four (4) empirical equations to predict 〖 K〗_d was developed depending on its optical and physical characteristics. Underwater light field modelling shows that light attenuation depend mostly on the concentration of optically significant constituents and only weakly dependent on light structure, cloud cover and fluorescence. The modelled 〖 K〗_d from Hydrolight ranges from 1.2 to 2.3 m-1 with lower 〖 K〗_d in chlorophyll dominated waters while the empirical estimations underestimate K_(d(PAR)) compared to the modelled 〖 K〗_d from Hydrolight. The modelled Secchi depth, S_d ranges from 0.6 – 1.4m corresponding to euphotic depth z_eu of 2.0 – 3.8 m with deeper z_eu for chlorophyll dominated waters. The modelled visibility is generally lowest during Northeast (NE) followed by Southwest (SW) monsoon and Inter monsoon (IM) period with evidence of spatial homogeneity for all monsoons. The visibility model reproduces the recorded〖 S〗_d reasonably well except for Johor Strait and sheltered areas in WCP due to the fact that some processes are not unaccounted in the model. The 〖 K〗_d variation coincides with SSC variation with no phase difference; the visibility is lowest during spring low tide and highest during neap high tide. Convective interaction between the diurnal and semidiurnal components is important in offshore locations while the non-linearity of tidal propagation contributes in the shallow water of Johor estuary. The residual turbidity in Singapore waters is due to tides (semi diurnal and diurnal spring neap interactions) and non-tides (monsoonal effect) in approximately equal… Advisors/Committee Members: Winterwerp, J.C., Van Maren, D.S., Liew, S.C., Visser, P.J., Tkalich, P..

Subjects/Keywords: sediment dynamics; optical properties; water quality model; visibility; turbidity

…14 Figure 3-3: Hierarchy of optical properties and its interpretation (modified from… …Properties CDOM Chromophoric Dissolved Organic Matter DOM Dissolved Organic Matter ECP East… …Environmental Management Programs IM Inter monsoon IOP Inherent Optical Properties LCK Lim Chu… …increase in turbidity, which lead to the reduction in visibility. Turbidity increase causes… …increased turbidity corresponding to reduced visibility). However, processes responsible for… 

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Toh, H. L. (2012). Suspended Sediment and Light Attenuation Characteristics in Singapore Waters:. (Masters Thesis). Delft University of Technology. Retrieved from http://resolver.tudelft.nl/uuid:bec65307-9a87-416c-b0b2-1da55f316e97

Chicago Manual of Style (16th Edition):

Toh, H L. “Suspended Sediment and Light Attenuation Characteristics in Singapore Waters:.” 2012. Masters Thesis, Delft University of Technology. Accessed October 21, 2019. http://resolver.tudelft.nl/uuid:bec65307-9a87-416c-b0b2-1da55f316e97.

MLA Handbook (7th Edition):

Toh, H L. “Suspended Sediment and Light Attenuation Characteristics in Singapore Waters:.” 2012. Web. 21 Oct 2019.

Vancouver:

Toh HL. Suspended Sediment and Light Attenuation Characteristics in Singapore Waters:. [Internet] [Masters thesis]. Delft University of Technology; 2012. [cited 2019 Oct 21]. Available from: http://resolver.tudelft.nl/uuid:bec65307-9a87-416c-b0b2-1da55f316e97.

Council of Science Editors:

Toh HL. Suspended Sediment and Light Attenuation Characteristics in Singapore Waters:. [Masters Thesis]. Delft University of Technology; 2012. Available from: http://resolver.tudelft.nl/uuid:bec65307-9a87-416c-b0b2-1da55f316e97

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