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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.
591

Lateral Position Detection Using a Vehicle-Mounted Camera

Ågren, Elisabeth January 2003 (has links)
A complete prototype system for measuring vehicle lateral position has been set up during the course of this master’s thesis project. In the development of the software, images acquired from a back-ward looking video camera mounted on the roof of the vehicle were used. The problem of using computer vision to measure lateral position can be divided into road marking detection and lateral position extraction. Since the strongest characteristic of a road marking image are the edges of the road markings, the road marking detection step is based on edge detection. For the detection of the straight edge lines a Hough based method was chosen. Due to peak spreading in Hough space, the difficulty of detecting the correct peak in Hough space was encountered. A flexible Hough peak detection algorithm was developed based on an adaptive window that takes peak spreading into account. The road marking candidate found by the system is verified before the lateral position data is generated. A good performance of the road marking tracking algorithm was obtained by exploiting temporal correlation to update a search region within the image. A camera calibration made the extraction of real-world lateral position information and yaw angle data possible. This vision-based method proved to be very accurate. The standard deviation of the error in the position detection is 0.012 m within an operating range of ±2 m from the image centre. During continuous road markings the rate of valid data is on average 96 %, whereas it drops to around 56 % for sections with intermittent road markings. The system performs well during lane change manoeuvres, which is an indication that the system tracks the correct road marking. This prototype system is a robust and automatic measurement system, which will benefit VTI in its many driving behaviour research programs.
592

Facing Peak Oil and Climate Change: A Pragmatic Approach to a Re-localized Food Production System in Uppsala, Sweden

Lönnerud, Anne January 2012 (has links)
Globalization and industrial agriculture have enabled consumers in Sweden and other countries in the Western world to enjoy foodstuffs from many parts of the world at very affordable monetary prices, but at the same time involving a lot of external costs in the form of environmental degradation, and a high dependency on foreign agricultural ecosystems as well as on oil and other non-renewable inputs, thus degrading sustainability and resilience in the food system. Accelerated climate change and the upcoming peak oil crisis call for a reorientation and a transition to a more locally-based system. The prospects for a re-localized food system have been investigated in a case study of Uppsala Municipality, Sweden. The results consist of a study of the current primary food production in Uppsala, also including an allotment garden survey, a study of how much additional food may be produced on idle land, and an analysis of opportunities and challenges for a re-localized food system in Uppsala. The allotment garden survey revealed that c. ten percent of the total area of plots containing cottage houses was used for food production, while the figure for plots without cottages was several times higher, c. 65 percent. The total estimated yield for allotment gardens in Uppsala Municipality was about 90 tons of vegetables and 48 tons of fruits and berries. Quantitative calculations on the yield produced by local farmers, horticulturists and leisure gardeners were made for the five categories grain, dairy products, eggs, meat, and vegetables, fruits and berries, together constituting about 85 percent of the total Swedish food consumption. The estimated balance of supply and demand differed a lot between food categories, ranging from 400 percent for grain to 20 percent for meat as well as for vegetables, fruits and berries. Due to empirical uncertainty, the latter figure should be interpreted with caution. For eggs and dairy products the balance of supply and demand was 67 percent and 50 percent respectively. A quantitative estimation for idle land showed that the greatest potential for an increased food production is within leisure gardening, which could be increased by 3.5 to 6 times. A transition to full self-sufficiency would, however, require drastically altered consumer habits towards seasonal vegetables and fruits and less beef in favor of vegetarian proteins. The qualitative analysis of possibilities and obstacles concluded that the greatest assets for a re-localized food production were the large production capacity within rural agriculture, the abundance of mostly unutilized private garden land, the increased interest for urban agriculture among the population, positive attitudes among consumers towards local food, and a relatively high general awareness of climate change and the need for a more sustainable society. Among the challenges were found lacking economic viability and access to suitable farmland, the centralized food industry, an imbalanced agricultural output, unsustainable consumer habits, the tendency among Swedish municipal planners to support exploitation of fertile soil, and a low awareness among both the population and decision makers regarding peak oil and social resilience generally. / Globaliseringen och det industriella jordbruket har möjliggjort för konsumenter i Sverige och andra västländer att få tillgång till matvaror till låga priser och från många olika delar av världen. Samtidigt har detta medfört ett högt pris i form av miljöförsämringar och ett stort beroende av utländsk jordbruksproduktion, samt av olja och andra råvaror som inte är förnybara. Resultatet har blivit ett livsmedelssystem med urholkad hållbarhet och ökad sårbarhet. Accelererande klimatförändringar och den kommande krisen i samband med oljetoppen manar till nyorientering och en övergång till ett mer lokalbaserat system. Denna fallstudie av Uppsala kommun har undersökt utsikterna att återknyta matproduktionen till lokala system. Resultaten omfattar både en studie av den nuvarande matproduktionen i Uppsala, vilken även inkluderade en enkätundersökning av kolonilotter, en studie av potentialen att öka matproduktionen på mark som idag inte används aktivt för det ändamålet, samt en analys av möjligheter och utmaningar för en lokal matproduktion i Uppsala. Enkätundersökningen visade att på kolonilotter med stugor användes ca tio procent av den totala ytan för matproduktion, medan motsvarande siffra för kolonilotter utan stugor var flera gånger högre, ca 65 procent. Den totala skörden för alla kommunala kolonilotter i Uppsala uppskattades till 90 ton grönsaker och 48 ton frukt och bär. För den totala matproduktionen från jordbruket, trädgårdsnäringen och fritidsodlingen gjordes beräkningar för fem olika kategorier: Spannmål, mejeriprodukter, ägg, kött samt grönsaker, frukt och bär, som tillsammans utgör ca 85 procent av den totala svenska matkonsumtionen. Den uppskattade försörjningsbalansen varierade starkt mellan olika kategorier, från 400 procent för spannmål till 20 procent för kött samt för grönsaker, frukt och bär. Osäkerheten kring det vetenskapliga underlaget gällande fritidsodlingen är dock stort, vilket gör att siffrorna för grönsaker, frukt och bär bör tolkas försiktigt. För ägg och mejeriprodukter var försörjningsbalansen 67 procent respektive 50 procent. Studien av obrukad mark visade att den största potentialen för en ökad matproduktion finns inom fritidsodlingen, som beräknades skulle kunna öka med 3.5 till 6 gånger. En övergång till full självförsörjning skulle dock kräva drastiska förändringar i konsumtionsvanorna mot säsongsbetonade grönsaker och frukt samt mindre nötkött till förmån för mer vegetabiliskt protein. Analysen av möjligheter och utmaningar för en återgång till en mer lokal matproduktion pekade på att de största fördelarna är den stora produktionskapaciteten inom jordbruket, den stora sammanlagda arealen privat trädgårdsmark som till stor del är outnyttjad för matproduktion, det ökande intresset för stadsodling bland befolkningen, positiva attityder till lokal mat bland konsumenter, och en relativt hög medvetenhet kring klimatförändringar och behovet av ett mer hållbart samhälle. Bland de viktigaste utmaningarna fanns den bristande ekonomiska lönsamheten inom yrkesodlingen, den centraliserade livsmedelsindustrin, obalansen inom jordbruksproduktionen, med överskott på spannmål och underskott på andra livsmedelsråvaror, ohållbara konsumtionsvanor, tendenser hos svenska kommunala tjänstemän att stödja exploatering av bördig mark, samt den låga graden av medvetenhet hos både befolkningen och beslutsfattarna kring oljetoppen och samhällets sårbarhet generellt.
593

MODELS OF EFFICIENT CONSUMER PRICING SCHEMES IN ELECTRICITY MARKETS

Celebi, Emre January 2005 (has links)
Suppliers in competitive electricity markets regularly respond to prices that change hour by hour or even more frequently, but most consumers respond to price changes on a very different time scale, i. e. they observe and respond to changes in price as reflected on their monthly bills. This thesis examines mixed complementarity programming models of equilibrium that can bridge the speed of response gap between suppliers and consumers, yet adhere to the principle of marginal cost pricing of electricity. It develops a computable equilibrium model to estimate the time-of-use (TOU) prices that can be used in retail electricity markets. An optimization model for the supply side of the electricity market, combined with a price-responsive geometric distributed lagged demand function, computes the TOU prices that satisfy the equilibrium conditions. Monthly load duration curves are approximated and discretized in the context of the supplier's optimization model. The models are formulated and solved by the mixed complementarity problem approach. It is intended that the models will be useful (a) in the regular exercise of setting consumer prices (i. e. , TOU prices that reflect the marginal cost of electricity) by a regulatory body (e. g. , Ontario Energy Board) for jurisdictions (e. g. , Ontario) where consumers' prices are regulated, but suppliers offer into a competitive market, (b) for forecasting in markets without price regulation, but where consumers pay a weighted average of wholesale price, (c) in evaluation of the policies regarding time-of-use pricing compared to the single pricing, and (d) in assessment of the welfare changes due to the implementation of TOU prices.
594

The Ecological Economics of Resilience: Designing a Safe-Fail Civilization

Stanley, Conrad B. J. January 2011 (has links)
There is mounting evidence that sustainable scale thresholds are now being exceeded worldwide and environmental resource shocks (e.g. climate change, water and oil shortages) may be inevitable in some regions of the world in the near future. These could result in severe economic breakdowns, welfare loss, and in the worst-case, the collapse of modern civilization. Therefore, a pre-eminent challenge of our times is to determine how to design a resilient (safe-fail) economy – one that can endure, adapt to and successfully recover from breakdowns when they occur. Surprisingly, while ecological economic theory relies heavily on natural science concepts such as thermodynamics, insufficient attention has been paid to the important ecological concept of resilience, particularly as it applies to economic design. The three major policy goals of current ecological economic theory (sustainable scale, just distribution and efficient allocation) focus instead on preventing environmental resource shocks and breakdowns, but given their unpredictability prevention may not always be possible. How resilience can inform the blossoming field of ecological economics is thus explored in this theoretical, transdisciplinary paper. Drawing on literature as diverse as archaeology and disaster planning, it develops six key principles of economic resilience and applies them to analyze the resilience of key societal systems including our money, electricity, water, transportation, information/communication and emergency response systems. Overall, economic resilience appears to be a unique concern that is not readily subsumed under any of the three existing ecological economic policy pillars. In fact, efforts to build in resilience have the potential to both complement and at times contradict the other three goals, especially efficiency. The need to further study these possible tradeoffs provides strong justification for adding a fourth distinct policy pillar, namely “Resilient Design”, to core ecological economic theory. Indeed, ecological economist’s longstanding criticism of economic growth meshes readily with the Resilience Alliance’s own figure-8 adaptive cycle theory critiquing the resilience costs of growth, providing significant opportunities for the future collaboration of these two fields in broadening global system theory.
595

CP-Free Space-Time Block Coded MIMO-OFDM System Design Under IQ-Imbalance in Multipath Channel

Huang, Hsu-Chun 26 August 2010 (has links)
Orthogonal frequency division multiplexing (OFDM) systems with cyclic prefix (CP) can be used to protect signal from the time-variant multipath channel induced distortions. However, the presence of CP could greatly decrease the effective data rate, thus many recent research works have been focused on the multiple-input multiple-output (MIMO) OFDM systems without CP (CP-free), equipped with the space-time block codes (ST-BC). The constraint of the conventional MIMO-OFDM (without using the ST-BC) system is that the number of receive-antenna has to be greater than the transmit-antenna. In this thesis, we first consider the ST-BC MIMO-OFDM system and show that the above-mentioned constraint can be removed, such that the condition become that the receive antenna should be greater than one, that is the basic requirement for MIMO system. It is particular useful and confirm to the recently specification, e.g., 3GPP LTE (Long Term Evolution) where the system deploy the 2¡Ñ2 or 4¡Ñ4 antennas systems. This thesis also considers the effects of peak-to-average power ratio (PAPR) in the transmitter and In-phase/ Quadrature-phase (IQ) imbalance in the receiver, and solves them by using the adaptive Volterra predistorter and blind adaptive filtering approach of the nonlinear parameters estimation and compensation, along with the power measurement, respectively. After the compensator of IQ imbalance in the receiver, an equalizer under the framework of generalized sidelobe canceller (GSC) is derived for interference suppression. To further reduce the complexity of receiver implementation, the partially adaptive (PA) scheme is applied by exploiting the structural information of the signal and interference signature matrices. As demonstrated from computer simulation results, the performance of the proposed CP-free ST-BC MIMO-OFDM receiver is very similar to that obtained by the conventional CP-based ST-BC MIMO-OFDM system under either the predistortion or compensation scenario.
596

Peak-to-Average Power Reduction Schemes in SFBC MIMO-OFDM Systems without Side Information

Ciou, Ying-Chi 30 July 2012 (has links)
Selected mapping (SLM) is a well-known technique used to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. Although SLM scheme can reduce PAPR efficiently, the side information (SI) must be transmitted to the receiver to indicate the candidate signal that generates the OFDM signal with the lowest PAPR. Robust channel coding schemes are typically adopted to prevent erroneous decoding of SI, leading to the lower bandwidth efficiency. To reduce PAPR efficiently and avoid the bandwidth efficiency loss caused by the transmission of SI, two novel PAPR reduction methods are proposed in SFBC MIMO-OFDM systems with two transmitter antennas that employs the Alamouti coding. The candidate signals are constructed in the frequency-domain and time-domain in the first proposed scheme and the second proposed scheme, respectively. In addition, the orthogonality of the space frequency block code is preserved resulting in the data recovery and the corresponding SI can be easily obtained from the conventional Alamouti detection method for both transmission methods. Simulation results show that the BER performance of a SFBC MIMO-OFDM system with the proposed SI detection algorithm is very close to that of perfect SI detection if the extension factor is larger than 1.3.
597

Design Of An Educational Purpose Multifunctional Dc/dc Converter Board

Baglan, Fuat Onur 01 August 2008 (has links) (PDF)
In this thesis a multifunctional DC/DC converter board will be developed for utilization as an educational experiment set in the switched-mode power conversion laboratory of power electronic courses. The board has a generic power-pole structure allowing for easy configuration of various power converter topologies and includes buck, boost, buck-boost, flyback, and forward converter topologies. All the converters can be operated in the open-loop control mode with a switching frequency range of 30-100 kHz and a maximum output power of 20 W. Also the buck converter can be operated in voltage mode control and the buck-boost converter can be operated in peak-current-mode control for the purpose of demonstrating the closed loop control performance of DC/DC converters. The designed board allows for experimentation on the DC/DC converters to observe the macroscopic (steadystate/ dynamic, PWM cycle and low frequency) and microscopic (switching dynamic) behavior of the converters. In the experiments both such characteristics can be clearly observed such that students at basic learning level (involving only the macroscopic behavior), and students at advanced learning level (additionally involving the parasitic effects) can benefit from the experiments. The thesis reviews the switch mode conversion principles, gives the board design and proceeds with the experiments illustrating the capabilities of the experimental system.
598

A PAPR Reduction Scheme for SFBC MIMO-OFDM Systems

Tsai, Kun-Han 11 August 2009 (has links)
In multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system which was used space frequency block coding (SFBC) method. It order to reduce the peak-to-average power ratio in several transmit antennas. We proposed two new architectures to simply the computational complexity on transmitter. According to the characteristics of SFBC structure which have M transmitter antennas. We can decomposed the interleaving subcarrier groups by used conversion vector to circular convolution with signal vector and shrink the inverse fast Fourier transform (IFFT) points. Therefore it can do the SFBC coding operation in time domain. By using combination of different cyclic shifts and phase rotations in U subcarrier groups can generate the P candidate signals. And it wouldn¡¦t increase the number of IFFT. The proposed transmitter architectures can improve the major drawback of high computational complexity in traditional selected mapping (SLM). The traditional SLM generate the P candidate signals needs MP IFFT units. Then in the condition of lose a little PAPR reduction performance, we can save the most of computational complexity.
599

Improved mass accuracy in MALDI-TOF-MS analysis

Kempka, Martin January 2005 (has links)
<p>Mass spectrometry (MS) is an important tool in analytical chemistry today, particularly in the field of proteomics where identification of proteins is the central activity. The focus in this thesis has been to improve the mass accuracy of MS-analyses in order to improve the possibility for unambiguous identification of proteins.</p><p>In paper I a new peak picking algorithm has been developed for Matrix Assisted Laser Desorption/Ionization - Time of Flight - Mass Spectrometry (MALDI-TOF-MS). The new algorithm is based on the assumption that two sets of ions are formed during the ionisation, and that these two sets have different Gaussian-distributed velocity profiles. The algorithm then deconvolutes the spectral peak into two Gaussian distributions, were the narrower of the two distributions is utilized for peak picking. The two-Gaussian peak picking algorithm proved to be especially useful when dealing with weak, distorted peaks.</p><p>In paper II a novel chip-based target for MALDI analysis is described. The target features pairs of 50x50 μm anchors in close proximity. Each anchor within a pair could be individually addressed with different sample solutions. Each pair could then be irradiated with the MALDI laser, which allowed ionization to take place on separated anchors simultaneously. This made it possible for us to calibrate analytes with calibration standards that where physically separated from the analyte, but ionized simultaneously. The use of new chip-based MALDI target resulted in a 2-fold reduction of relative mass errors. We could also report a significant reduction of ion suppression. The small size of the anchors provided a good platform for efficient utilization of sample. This resulted in a detection limit of ca. 1.5 attomole of angiotensin I at a S/N of 22:1.</p>
600

High-Capacity Cool Thermal Energy Storage for Peak Shaving - a Solution for Energy Challenges in the 21st century

He, Bo January 2004 (has links)
<p>Due to climatic change, increasing thermal loads inbuildings and rising living standards, comfort cooling inbuildings is becoming increasingly important and the demand forcomfort cooling is expanding very quickly around the world. Theincreased cooling demand results in a peak in electrical powerdemand during the hottest summer hours. This peak presents newchallenges and uncertainties to electricity utilities and theircustomers.</p><p>Cool thermal storage systems have not only the potential tobecome one of the primary solutions to the electrical powerimbalance between production and demand, but also shift coolingenergy use to off-peak periods and avoid peak demand charges.It increases the possibilities of utilizing renewable energysources and waste heat for cooling generation. In addition, acool storage can actually increase the efficiency of combinedheat and power (CHP) generation provided that heat drivencooling is coupled to CHP. Then, the cool storage may avoidpeaks in the heat demand for cooling generation, and this meansthat the CHP can operate at design conditions in most oftime.</p><p>Phase Change Materials (PCMs) used for cool storage hasobtained considerable attention, since they can be designed tomelt and freeze at a selected temperature and have shown apromising ability to reduce the size of storage systemscompared with a sensible heat storage system because they usethe latent heat of the storage medium for thermal energystorage.</p><p>The goal of this thesis is to define suitable PCM candidatesfor comfort cooling storage. The thesis work combines differentmethods to determine the thermophysical properties oftetradecane, hexadecane and their binary mixtures, anddemonstrates the potential of using these materials as PCM forcomfort cooling storage. The phase equilibrium of the binarysystem has been studied theoretically as well asexperimentally, resulting in the derivation of the phasediagram. With knowledge of the liquid-solid phase equilibriumcharacteristics and the phase diagram, an improvedunderstanding is provided for the interrelationships involvedin the phase change of the studied materials. It has beenindicated that except for the minimum-melting point mixture,all mixtures melt and freeze within a temperature range and notat a constant temperature, which is so far often assumed in PCMstorage design. In addition, the enthalpy change during thephase transition (heat of fusion) corresponds to the phasechange temperature range; thus, the storage density obtaineddepends on how large a part of the phase change temperaturerange is valid for a given application.</p><p>Differential Scanning Calorimetery (DSC) is one frequentlyused method in the development of PCMs. In this thesis, it hasbeen found that varying results are obtained depending on theDSC settings throughout the measurements. When the DSC runs ata high heating/cooling rate it will lead to erroneousinformation. Also, the correct phase transition temperaturerange cannot be obtained simply from DSC measurement. Combiningphase equilibrium considerations with DSC measurements gives areliable design method that incorporates both the heat offusion and the phase change temperature range.</p><p>The potential of PCM storage for peak shaving in differentcooling systems has been demonstrated. A Computer model hasbeen developed for rapid phase equilibrium calculation. The useof phase equilibrium data in the design of a cool storagesystem is presented as a general methodology.</p><p><b>Keywords:</b>Comfort cooling, peak shaving, PCM, coolthermal storage system, DSC, phase change temperature range,the heat of fusion, phase equilibrium, phase diagram. Language:English</p>

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