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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
481

Boundary Profile Representation for Objects and Their Surroundings in Outdoor Videos

Candamo, Joshua 17 August 2009 (has links)
A novel approach to represent the profile of objects using Gaussian models is presented. The profile is a representation of the object and its surrounding regions. The object profile can be viewed as a comprehensive feature of that object and its surrounding regions. Different algorithms to estimate the profile are described. Geometric descriptors of the model are also proposed. The profile model is empirically shown to be effective and easily applicable to certain object recognition and segmentation tasks. Application experiments include modeling thin and thick objects as straight-lines, curves, and blobs using different primitives such as gray-level intensities, RGB, and HSV color. The datasets used for empirical validation are quite challenging. Datasets include images and videos corresponding to outdoor video, most of them with moving cameras. Some of the typical problems faced with the used datasets are: digital scaling, compression artifacts, camera jitter, weather effects, and cluttered backgrounds. We demonstrate the potential of leveraging the context of objects of interest as a part of an online detection process. Sample applications including detection of wires, sea horizon, street, and vehicles in outdoor videos are considered.
482

Thermohydraulische Modellierung der Kondensation von Dampf in einer unterkühlten Flüssigkeitsströmung

Gregor, Sabine, Beyer, Matthias, Prasser, Horst-Michael January 2006 (has links)
Nach einer kurzen technischen Beschreibung der Mehrzweck-Thermohydraulikversuchsanlage TOPFLOW und der verwendeten Messtechnik werden die theoretischen Grundlagen zur Modellierung der Kondensation von Dampf in einer Wasserströmung erläutert. Dabei gehen die Autoren besonders auf die Auswahl geeigneter Modelle zur Beschreibung des Wärmeübergangs und der Zwischenphasengrenzfläche im Druckbereich zwischen 10 und 65 bar detailliert ein. Außerdem werden verschiedene Drift-Flux-Modelle auf ihre Tauglichkeit anhand von experimentellen Daten geprüft. Da Veränderungen thermodynamischer und strömungstechnischer Parameter hauptsächlich in axialer Richtung stattfinden, wurden diese Modelle in einen eindimensionalen Code eingebettet, mit dem der Strömungsverlauf entlang einer vertikalen Rohrleitung mit einer Länge von 8 m und einem Nenndurchmesser von 200 mm berechnet werden kann. Anschließend werden Aufbau und Funktion dieses Programms vorgestellt. Nachfolgend vergleichen die Autoren experimentelle und berechnete Strömungsverläufe bei der Kondensation von Dampf sowohl in einer unterkühlten Wasserströmung als auch nahe der Siedetemperatur. Dabei wird der Einfluss wichtiger Randbedingungen, wie z.B. Druck oder Primärblasengröße, auf die Kondensationsintensität analysiert. Eine Einschätzung der Fehlerbanden für die experimentellen Daten, die verwendeten Gittersensoren und die numerische Simulation schließen den Bericht ab.
483

Testing and Evaluation of a Novel Virtual Reality Integrated Adaptive Driving System

Fowler, Matthew R 07 April 2010 (has links)
Virtual simulators have proven to be extremely effective tools for training individuals for tasks that might otherwise be cost-prohibitive, dangerous, or impractical. One advantage of using a virtual simulator is that it provides a safe environment for emergency scenarios. For many years the United States military and NASA have used simulators, including those affixed with drive-by-wire (DBW) controls, effectively and efficiently to train subjects in a variety of ways. A DBW system utilizes electrical circuits to actuate servo motors from a given input signal to achieve a desired output. In DBW systems the output is not directly mechanically connected to a control surface (steering, acceleration, deceleration, etc.); usually, the input controller is linked by electrical wires to a localized servo motor where direct control can be given. This project is aimed at developing a novel simulator for a future training program using DBW systems that caters specifically to individuals who currently use or will be using for the first time vehicle modifications in order to drive and maintain their independence. Many of these individuals use one or a combination of powered steering, acceleration, braking, or secondary DBW controls to drive. The simulator integrates a virtual training environment and advanced electronic vehicle interface technology (AEVIT) DBW controls (4-way joystick, gas-brake lever/small zero-effort steering wheel). In a 30 participant study of three groups (able-bodied individuals, elderly individuals, and individuals with disability), it was found that training with a DBW joystick steering system will require more instruction and simulator practice time than a gas-brake lever/small steering wheel combination (GB/S) to obtain a similar level of competency. Drivers using the joystick completed predetermined driving courses in longer times, at slower speeds, with more errors than the other DBW system. On average, the reaction time to a stopping signal was fastest with the gas-brake lever at 0.54 seconds. Reaction times for the standard vehicle controls and the joystick were 0.741 and 0.677 seconds respectively. It was noted that reaction times using DBW controls were shorter overall. When driving in traffic, drivers committed 4.9, 5.1, and 8.3 driving infractions per minute using standard vehicle controls (No Drive by Wire, (NDBW)), the gas/brake and steering system, and joystick system respectively. Most drivers felt that the GB/S system was easier to learn, easier to operate, safer, and more reliable than the joystick system.
484

The anthelmintic effect of copper oxide wire particle (COWP) boluses against Haemonchus contortus in indigenous goats in South Africa

Spickett, Andrea 02 March 2010 (has links)
A field trial was conducted to test the anthelmintic effect of a single dose of 4g of copper oxide wire particles (COWP) in bolus form in indigenous goats belonging to small scale communal farmers in three areas in the Bergville district of Kwa-Zulu Natal Province, South Africa namely Dukuza, Ogade and Hoffenthal. Faecal egg counts (FECs) determined by both the McMaster and Pitchford–Visser methods, FAMACHA / Dissertation (MSc (Veterinary Tropical Diseases))--University of Pretoria, 2009. / Veterinary Tropical Diseases / unrestricted
485

Wakes behind wind turbines - Studies on tip vortex evolution and stability

Odemark, Ylva January 2012 (has links)
The increased fatigue loads and decreased power output of a wind turbine placed in the wake of another turbine is a well-known problem when building new wind power farms. In order to better estimate the total power output of a wind power farm, knowledge about the development and stability of wind turbine wakes is crucial. In the present thesis, the wake behind a small-scale model turbine was investigated experimentally in a wind tunnel. The velocity in the wake was measured with hot-wire anemometry, for different free stream velocities and tip speed ratios. To characterize the behaviour of the model turbine, the power output, thrust force and rotational frequency of the model were also measured. These results were then compared to calculations using the Blade Element Momentum (BEM) method. New turbine blades for the model was constructed using the same method, in order to get an estimate of the distribution of the lift and drag forces along the blades. This information is needed for comparisons with certain numerical simulations, which however remains to be performed.By placing the turbine at different heights in a turbulent boundary layer, the effects of forest turbulence on wind turbine outputs (power and thrust) could also be investigated.The evolution of the tip vortices shed from the turbine blades was studied by performing velocity measurements around the location of the tip vortex breakdown. The vortices' receptivity to disturbances was then studied by introducing a disturbance in the form of two pulsed jets, located in the rear part of the nacelle. In order to introduce a well-defined disturbance and perform phase-locked measurements, a new experimental setup was constructed and successfully tested for two different disturbance frequencies. The mean streamwise velocity and the streamwise turbulence intensity was found to scale well with the free stream velocity and the spreading of the wake was found to be proportional to the square root of the downstream distance.  The comparison for power and thrust between measurements and BEM calculations showed good agreement in some cases but worse agreement when the pitch angle of the blades was small.The velocity measurements showed that the tip vortices can be susceptible to disturbances and an earlier breakdown could be detected. However, more measurements need to be made to fully investigate the dependance on disturbance frequency and amplitude. / QC 20120504
486

Dynamic Body Armor Shape Sensing Using Fiber Bragg Gratings and Photoassisted Silicon Wire-EDM Machining

Velasco, Ivann Civi Lomas-E 01 June 2021 (has links)
In this thesis, a method to improve survivability is developed for fiber Bragg gratings under high velocity impact in dynamic body armor shape sensing applications by encasing the fiber in silicone. Utilizing the slipping of the fiber within the silicone channel, a proportionality relationship between the strain of the fiber to the acceleration of the impacting projectile is found and is used to obtain the rate of the back-face deformation. A hybrid model is developed to handle errors caused by the stick-slip of the fiber by fitting an inverse exponential to stuck sections found in a captured strain profile and double integrated to transform the stuck section to its equivalent slipping. Displacement errors below 10% was achieved using the hybrid model. A graphical user interface with a step-by-step walkthrough and a fiber Bragg grating interrogation system was designed for test engineers to utilize this technology. Test engineers from the Army Test Center in Aberdeen, MD were trained on this technology and successfully captured and processed shots using this technology. A method for cutting Silicon through wire-EDM machining is developed by utilizing the photoconductive properties of Silicon. Cut rates for unilluminated and illuminated Silicon was compared and a 3x faster cut was achieved on the illuminated cuts.
487

Optimization of experimental conditions of hot wire method in thermal conductivity measurements

Ma, Luyao January 2012 (has links)
This work studied the hot wire method in measuring thermal conductivity at room temperature. The purpose is to find the optimized experimental conditions to minimize natural convection in liquid for this method, which will be taken as reference for high temperature thermal conductivity measurement of slag. Combining room temperature experiments and simulation with COMSOL Multiphysics 4.2a, the study on different experimental parameters which may influence the accuracy of the measured thermal conductivity was conducted. The parameters studied were the diameter of crucible, the position of wire in the liquid, including z direction and x-y plane position, diameter of the hot wire, and current used in the measurement. In COMSOL simulations, the maximum natural convection velocity value was used to evaluate the natural convection in the liquid. The experiment results showed after 4~5 seconds of the measuring process, the natural convection already happened. Also when current was fixed, the thinner the hot wire, the larger convection it would cause. This is because thinner wire generates more heat per unit surface area. Using higher current in measuring, more heat generation improved accuracy of result but also had earlier and larger effect on convection. Both simulation and experiments showed that with the height of the liquid fixed, the smaller diameter of the crucible (not small to the level which is comparable with hot wire diameter), the higher the position in z direction (still covered by liquid), the less natural convection effect existed. But the difference was not significant. The radius-direction position change didn’t influence the result much as long as the wire was not too close to the wall.
488

Ethernet in Steer-by-wire Applications

Ibrahim, Muhammad January 2011 (has links)
A Controller Area Network (CAN) is a multi-master serial data communication bus designed primarily for the automotive industry. It is reliable and cost-effective and features error detection and fault confinement capabilities. CAN has been widely used in other applications, such as onboard trains, ships, construction vehicles, and aircraft. CAN has even been applied within the industrial automation segment in a range of devices such as programmable controllers, industrial robots, digital and analog I/O modules, sensors, etc. Despite its robustness and other positive features, the CAN bus has limitations in form of limited maximum data rate and maximum bus length. Also the CAN network topology is rigidly fixed which is a severe limiting factor in some of its application cases, therefore several industrial actors are evaluating alternatives to CAN. Ethernet is one of the potential candidates to replace CAN. It is a widespread and well knowntechnology, easily accessible, and many off-the-shelf solutions are available. It can support extended networks and offers wide possibilities in terms of network topology thanks to active switches. It features very high bandwidth, which has increased systematically from 10 Mbps to 100 Gbps year after year, always preserving backward compatibility to the maximum possible extent. The purpose of this thesis project is to investigate the possibility of replacing the CAN bus with Ethernet according to the following requirements: Standard off-the-shelf components and software stacks No modification of the network node application software, i.e. messages formatted accordingto CAN protocols must be transferred by means of Ethernet. A main issue is that CAN is time deterministic; it is always possible to predict the maximum latency in a message transfer. On the other hand Ethernet is still considered unreliable for time-critical applications, although the advent of Ethernet switches has minimized this non-deterministic behavior. A unique approach to this issue is offered as a result of the work done by Time Critical Networks, a newly started Swedish company. Their tool makes it possible to calculate the maximum forwarding time of a frame in an Ethernet network. This tool may make it possible to validate the use of Ethernet for time-critical applications. CPAC Systems, a company in the Volvo group which develops and manufactures steer-by-wire systems based on the CAN technology, wishes to verify whether Ethernet could now be considered as a solution to complement or replace CAN, thus overcoming CAN’s limitations. This verification is the goal of this master thesis project. The work was carried out through three different phase: First we performed a theoretical evaluation by modeling the Ethernet network using Time Critical Network’s tools. Next we verified the results by implementing the modeled CAN/Ethernet network that was previously modeled. Finally, we validated the solution by directly testing the modeled CAN/Ethernet in combination with CPAC System’s steer-by-wire technology. The results obtained show that Ethernet in combination with Time Critical Network’s modeling tool, when it comes to time-determinism, can be a complement and/or an alternative to the CAN bus. / En Controller Area Network (CAN) är en multi-master seriell datakommunikation buss utformad främst för fordonsindustrin. Den är pålitlig och kostnadseffektiv och har feldetektering och fel förmåga instängdhet. CAN har ofta används i andra tillämpningar, som ombord på tåg, fartyg, fordonkonstruktion, och flygplan. CAN har även använts inom industriautomation segmentet i en radapparater som programmerbara styrsystem, industrirobotar, digitala och analoga I/O-moduler, sensorer, etc. Trots sin robusthet och andra positiva egenskaper har CAN-bus begränsningar i form av begränsad maximal datahastighet och maximal buss längd. Även CAN nätverkstopologin är fast förankrade vilket är en svår begränsande faktor i några av dess tillämpning fall därför flera industriella aktörer utvärderar alternativ till CAN. Ethernet är en av de potentiella sökande för att ersätta CAN. Det är en utbredd och väl känd teknik, lättillgänglig, och många off-the-shelf lösningar finns tillgängliga. Det kan stödja utökade nätverk och erbjuder stora möjligheter när det gäller nätverkstopologin tack vare aktiv växlar. Den har mycket hög bandbredd, vilket har ökat systematiskt från 10 Mbps till 100 Gbps år efter år, alltid bevara bakåtkompatibilitet i största möjliga utsträckning. Syftet med detta examensarbete är att undersöka möjligheten att ersätta CAN-bussen med Ethernet i enlighet med följande krav: Standard off-the-shelf komponenter och stackar programvara Inga ändringar av nätverket nod programvara, formaterade dvs meddelanden enligt CAN protokollmåste överföras med hjälp av Ethernet. En viktig fråga är att CAN är dags deterministisk, det är alltid möjligt att förutse den maximala fördröjning i ett överfört meddelande. Å andra sidan Ethernet är fortfarande betraktas som otillförlitliga för tidskritiska applikationer, även om tillkomsten av Ethernet-switchar har minimeratdenna icke-deterministiska beteendeEn unik inställning till denna fråga är erbjuds som ett resultat av det arbete som tidskritiska Networks, ett nystartat svenskt företag. Deras verktyg gör det möjligt att beräkna den maximal avidarebefordran tid för en ram i ett Ethernet-nätverk. Detta verktyg kan göra det möjligt att valideraanvändningen av Ethernet för tidskritiska applikationer. CPAC Systems, ett bolag inom Volvokoncernen som utvecklar och tillverkar styr-by-wire-system baserade på CAN-tekniken, vill kontrollera om Ethernet nu kan betraktas som en lösning för att komplettera eller ersätta kan således övervinna CAN: s begränsningar. Denna kontroll är målet för detta examensarbete. Arbetet genomfördes genom tre olika fas: Först utförs en teoretisk utvärdering av modellering Ethernet-nätverk med hjälp av tidskritiska Networks verktyg. Nästa vi verifierat resultat genom att genomföra de modellerade CAN / Ethernet-nätverk som tidigare modellerats. Slutligen, validerade vi lösningen genom att direkt testa de modellerade CAN / Ethernet i kombination med CPAC Systems steer-by-wire-teknik. De resultat som erhållits visar att Ethernet i kombination med tidskritiska Networksmodelleringsverktyg, när det gäller tid-determinism, kan vara ett komplement och / eller ett alternativtill CAN-bussen.
489

Control and Automation of a Heat Shrink Tubing Process

Yousefi Darani, Shahrokh 08 1900 (has links)
Heat shrink tubing is used to insulate wire conductors, protect wires, and to create cable entry seals in wire harnessing industries. Performing this sensitive process manually is time consuming, the results are strongly dependent on the operator’s expertise, and the process presents safety concerns. Alternatively, automating the process minimizes the operators’ direct interaction, decreases the production cost over the long term, and improves quantitative and qualitative production indicators dramatically. This thesis introduces the automation of a heat shrink tubing prototype machine that benefits the wire harnessing industry. The prototype consists of an instrumented heat chamber on a linear positioning system, and is fitted with two heat guns. The chamber design allows for the directing of hot air from the heat guns onto the wire harness uniformly through radially-distributed channels. The linear positioning system is designed to move the heat chamber along the wire harness as the proper shrinkage temperature level is reached. Heat exposure time as a major factor in the heat shrink tubing process can be governed by controlling the linear speed of the heat chamber. A control unit manages the actuator position continuously by measuring the chamber’s speed and temperature. A model-based design approach is followed to design and test the controller, and MATLAB/Simulink is used as the simulation environment. A programmable logic controller is selected as the controller implementation platform. The control unit performance is examined and its responses follow the simulation results with adequate accuracy.
490

Improved Control Of cheese Manufacture Through continuous Vat Monitoring Of Coagulation Parameters Using The Hot Wire Method

LeFevre, Michael John 01 May 1995 (has links)
The hot wire method, with pH and temperature sensors, was evaluated to determine its usefulness and application for cheese production automation. Coagulation of milk substrate was measured with the hot wire instrument and by four other methods: Formagraph, Brookfield®, vixcometer, Omnispec™ bioactivity monitor, and Sommer and Matsen rolling bottle method. The hot wire, using the time at maximum slope, detected coagulation before methods that measure resistance to shear, and after methods that measure light reflectance. Coagulation time was not significantly different from the industry standard rolling bottle method used by Sommer and Matsen. the hot wire instrument was also used to distinguish samples that formed curd at different rates. This was accomplished by measuring the rate of temperature change of the hot wire probe during curd formation. Milk samples of varying protein, fat, and calcium concentrations were prepared to determine if the instrument could be used to predict a consistent curd cut-point. The pH level was also adjusted, and rennet additions were varied. Coagulation was monitored simultaneously with the hot wire system and a Formagraph. All five factors (pH, calcium, fat, protein, and rennet) had significant effects on cut time estimations (CT20) on the Formagraph. Linear correlations (R2) ranging from .74 to .94 were obtained using stepwise regressions when comparing hot wire and compositional data with the Formagraph. A Formagraph was used to measure effects of calcium, pH, and rennet changes on the coagulation properties of late lactation milk. Calcium, pH, and rennet treatments significantly affected the coagulation parameters measured by the Formagraph. However, response among the poor coagulating samples to treatments to improve coagulation was sample dependent. General composition and SDS-PAGE fractionation data could not be used as an indicator of poor or good coagulability of samples. The hot wire method worked well for monitoring coagulation time and curd firming rate, but did not measure maximum curd firmness well. Curd firming rates determined from the hot wire data are acceptable for estimation of a curd cut time. Added benefits of the hot wire method for monitoring cheese manufacture are that stirring, coagulation, and healing of curd can also be measured. Therefore, the rates of change of important parameters, such as pH, temperature, and coagulation during critical processing steps, can easily be determined by a computer and displayed, printed out, or saved for future evaluation.

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