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.

No description available.

No description available.

No description available.

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)

Presently, aerial photography remains a popular method for surveillance of landscapes, and its uses continually grow as it is used to monitor trends in areas such as plant distribution and urban construction. The use of computer vision, or more specifically stereo vision, is one common method of gathering this information. By mounting a stereo vision system on the wings of an unmanned aircraft it becomes very useful tool. This technique however, becomes less accurate as stereo vision baselines become longer, aircraft wing spans are increased, and aircraft wings become increasingly flexible. Typically, ideal stereo vision systems involve stationary cameras with parallel fields of view. For an operational aircraft with a stereo vision system installed, stationary cameras can not be expected because the aircraft will experience random atmospheric turbulence in the form of gusts that will excite the dominate frequencies of the aircraft. A method of stereo image rectification has been developed for cases where cameras that will be allowed to deflect on the wings of an fixed wing aircraft that is subjected to random excitation. The process begins by developing a dynamic model the estimates the behavior of a flexible stereo vision system and corrects images collected at maximum deflection. Testing of this method was performed on a flexible stereo vision system subjected to resonance excitation where a reduction in stereo vision distance error is shown. Successful demonstration of this ability is then repeated on a flying wing aircraft by the using a modal survey to understand its behavior. Finally, the flying wing aircraft is subjected to random excitation and a least square fit of the random excitation signal is used to determine points of maximum deflection suitable for stereo image rectification. Using the same techniques for image rectification in resonance excitation, significant reductions in stereo distance errors are shown. / Master of Science