Of the potential feedstocks for biofuels, microalgae is the most promising, and raceway ponds are the most cost-effective method for growing mircoalgal biomass. Nevertheless, biofuel production from algae must be more efficient to be competitive with traditional fuels. Previous studies using arrays of airfoils, triangles, and squares at high angles of attack show an increase in mixing in raceways and can improve productivity by up to a factor of 2.2. Some researchers say increasing mixing increases growth due to the flashing light effect while others claim it is the decrease in the fluid boundary layer of the cells that increases mass transfer. Whatever the reason, increasing growth by increasing mixing is a repeatable effect that is desirable to both reduce operation costs and increase production. An experimental raceway is constructed to test the effect of a delta wing (DW) on raceway hydraulics in the laboratory using fresh-water. The DW is an isosceles triangle made of plate material that is placed at a high angle of attack in the circulating raceway flow. Results from this investigation can be scaled to larger growth facilities use arrays of DWs. Two vortices are found downstream of the DW when used in this way and create significant vertical fluid circulation. Stereo particle image velocimetry (PIV) is used to quantify and optimize the use of delta wings as a means to increase fluid mixing. Stereo PIV gives three components of velocity in a measurement plane at an instant. Three studies are performed to determine the optimal paddle-wheel speed, angle of attack, and DW spacing in the raceway based on mixing. Two new mixing quantities are defined. The first is the Vertical Mixing Index (VMI) that is based on the vertical velocity magnitude, and the second is the Cycle Time required for an algal cell to complete a cycle from the bottom to the top and back again in the raceway. The power required to circulate the flow is considered in all results. The Paddle-wheel Speed Study shows that the VMI is not a function of streamwise velocity, which makes it very useful for comparison. The Cycle Time decreases quickly with streamwise velocity then levels out, revealing a practical speed for operation that is lower than typically used and consumes only half the power. The angle of 40° is optimal from the results of the Angle of Attack Study for both VMI and Cycle Time. The third study is the Vortex Dissipation Study and is used to measure the distance downstream before the vortices dissipate. This information is used to optimize the DW spacing for profit considering the additional costs of adding DWs.

With spatialized audio it lets developers create further experiences and provide accessibility options in video games and interactive media. The technology has evolved during the years, making it easier to use system such as Head-Related Transfer Functions in games. In this study the use of spatialized audio to navigate and locate smaller invisible objects in a larger area is explored, comparing spatialized audio panning with stereo panning. / <p>Det finns övrigt digitalt material (t.ex. film-, bild- eller ljudfiler) eller modeller/artefakter tillhörande examensarbetet som ska skickas till arkivet. / There are other digital material (eg film, image or audio files) or models/artifacts that belongs to the thesis and need to be archived. </p>

This research focuses on extracting road models from stereo video sequences taken from a moving vehicle. The proposed method combines color histogram based segmentation, active contours (snakes) and morphological processing to extract road boundary coordinates for conversion into Matlab or Multigen OpenFlight compatible polygonal representations. Color segmentation uses an initial truth frame to develop a color probability density function (PDF) of the road versus the terrain. Subsequent frames are segmented using a Maximum Apostiori Probability (MAP) criteria and the resulting templates are used to update the PDFs. Color segmentation worked well where there was minimal shadowing and occlusion by other cars. A snake algorithm was used to find the road edges which were converted to 3D coordinates using stereo disparity and vehicle position information. The resulting 3D road models were accurate to within 1 meter.

Polylactide (PLA) is a biodegradable and biocompatible polymer which is attracting much attention for environmental issues imposed by the petroleum-based polymers. PLA can be used as medical polymer in surgical sutures, implants tissue and many other areas. However, one of the main shortcomings of PLA is its brittleness in nature and relatively poor mechanical properties, which often limits its further application. It is generally accepted for polymeric materials that some mechanical properties of oriented structures can be improved as the molecular weight of PLA increases. The outcome of this thesis will provide the knowhow to achieve ultrahigh molecular weight of polylactides, and further to improve the mechanical properties and extend its range of applications. In this work, different catalytic systems for the synthesis of ultra-high molecular weight (UHMW) polylactide are considered. For the catalytic systems considered, the reaction conditions and initiators are investigated. The resulting molecular characteristics and mechanical properties of the synthesized polymers will be evaluated. On the contrary to the brittle nature of PLA, Poly(ε-carprolactone) (PCL) is elastic and flexible with a relatively low melting point (60 oC) and low glass transition temperature (-60 oC). Hence, ultra-high molecular weight PCL will be also synthesized by using the same catalytic systems employed for achieving UHMWPLAs. PCL is also used in different biomedical applications, such as in scaffolds for tissue engineering. It is well documented that the complementary physical properties of PLA and PCL have the potential to enhance toughness of PLA. To enhance the toughness and mechanical properties of the block copolymers attempt is made to synthesize ultra-high molar mass of the two polymers in the block copolymer. But their molar masses (and consequently their mechanical properties) are always on the low side. For this reason, the synthesis of high molecular mass PLA and PCL multiblocks will be attempted. Furthermore, it is interesting to study the synthesis of high molar masses PLLA and PDLA stereoblocks especially their ability to crystallize during the polymerization and test the possibility to prepare stereocomplex only during synthesis. The resulting molecular characteristics and mechanical properties of the synthesized multiblock-polymers will be also evaluated.

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This thesis describes an investigation into the experimental accuracy of a close-up stereo vision system. Surfaces are measured from any orientation through the synergy of a Coordinate Measurement Machine (CMM) and a custom made stereo vision head. Calibration of the stereo cameras is achieved using bundle adjustment non-linear optimization, commonly used in photogrammetry. Point set registration techniques are used to calibrate the stereo head with respect to the CMM coordinate system. The fully calibrated stereo vision system is used to provide experimental accuracy results under ideal imagining conditions. The system is then applied to the practical problem of sheet metal strain analysis. This problem involves many non-ideal imaging components that affect system accuracy. Experimental results for this non-deal situation are provided in the form of three-dimensional strain distribution plots. / Thesis / Master of Engineering (ME)

In this thesis a system which extracts 3D surfaces of arbitrary scenes under natural illumination is constructed using low-cost, off-the-shelf components. The system is implemented over a network of workstations using standardized distributed software technology. The architecture of the system is highly influenced by the performance requirements of multimedia applications which require 3D computer vision. Visible scene surfaces are extracted using a passive multi-baseline stereo technique. The implementation efficiently supports any number of cameras in arbitrary positions through an effective rectification strategy. The distributed software components interact through CORBA and work cooperatively in parallel. Experiments are performed to assess the effects of various parameters on the performance of the system and to demonstrate the feasibility of this approach. / Thesis / Master of Engineering (ME)

This dissertation proposes an approach for 3D micro-scale shape reconstruction using photometric stereo (PS) with surface normal integration (SNI). Based on the proposed approach, a portable cost-effective stationary system is developed to capture 3D shapes in the order of micrometer scale. The PS with SNI technique is adopted to reconstruct 3D microtopology since this technique is highlighted for its capability to reproduce fine surface details at pixel resolution. Furthermore, since the primary hardware components are merely a camera and several typical LEDs, the system based on PS with SNI can be made portable at low cost. The principal contributions are three folds. First, a PS method based on dichromatic reflectance model (DRM) using color input images is proposed to generalize PS applicable to a wider range of surfaces with non-Lambertian reflectances. The proposed method not only estimates surface orientations from diffuse reflection but also exploits information from specularities owing to the proposed diffuse-specular separation algorithm. Using the proposed PS method, material-dependent features can be simultaneously extracted in addition to surface orientations, which offers much richer information in understanding the 3D scene and poses more potential functionalities, such as specular removal, intrinsic image decomposition, digital relighting, material-based segmentation, material transfer and material classification. The second contribution is the development of an SNI method dealing with perspective distortion. The proposed SNI is performed on the image plane instead of on the target surface as did by orthographic SNI owing to the newly derived representation of surface normals. The motivation behind the representation is from the observation that spatially uniform image points are simpler for integration than the non-uniform distribution of surface points under perspective projection. The new representation is then manipulated to the so-called log gradient space in analogy to the gradient space in orthographic SNI. With this analogy, the proposed method can inherit most past algorithms developed for orthographic SNI. By applying the proposed SNI, perspective distortion can be efficiently tackled with for smooth surfaces. In addition, the method is PS-independent, which can keep the image irradiance equation in a simple form during PS. The third contribution is the design and calibration of a 3D micro-scale shape reconstruction system using the derived PS and SNI methods. This system is originally designed for on-site measurement of pavement microtexture, while its applicability can be generalized to a wider range of surfaces. Optimal illumination was investigated in theory and through numerical simulations. Five different calibrations regarding various aspects of the system were either newly proposed or modified from existing methods. The performances of these calibrations were individually evaluated. Efficacy of the developed system was finally demonstrated through comprehensive comparative studies with existing systems. Its capability for on-site measurement was also confirmed. / Ph. D.