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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.
21

Anwendung des stratifizierten Krigings auf ERS-1 und ERS-2 Radaraltimeterdaten zur Untersuchung von Eishöhenänderungen im Lambert Gletscher/Amery Eisschelf-System, Ostantarktis = Application of stratified kriging to ERS-1 and ERS-2 radar altimeter data to investigate ice elevation changes in the Lambert Glacier/Amery Ice Shelf system, East Antarctica /

Stosius, Ralf. January 2007 (has links)
Thesis (doctoral)--Universität Trier, 2005. / Includes bibliographical references (p. 118-129).
22

Některé otázky předcertifikačních testů EMC / Some Aspects of EMC Pre-Compliance Testing

Vídenka, Rostislav January 2010 (has links)
This doctoral thesis deals with EMC pre-compliance testing of radiated disturbance. The thesis summarizes present pieces of knowledge about restricting of disturbing ambient signals and focuses on restricting of test site imperfection influence on the measurement results. Pre-compliance test site “calibration” uses comparison signal sources. There were added up the recommendations for “calibration” steps, too. The semi-anechoic vs. fully-anechoic chambers measurements results were compared. Some methods for dealing with ambient disturbing signals were discussed and high attention was applied to the test site choice and the minimal dimension geometry was recommended. There are presented recommendations for pre-compliance radiated disturbance measurements in the conclusion with the stress on available test equipment.
23

Hodnocení vlivu interpolace při koregistraci radarových snímků / Evaluation of influence of interpolation methods on coregistration of radar images

Slačíková, Jana January 2010 (has links)
Evaluation of influence of interpolation methods on coregistration of radar images Abstract SAR interferogram processing requires subpixel coregistration of SAR image pair for accurate phase differencing. Errors in alignment introduce phase noise in SAR interferogram. Last step in coregistration is resampling one of SAR images. Also this step introduces errors in SAR interferogram. The resampling algorithms Nearest Neighbor, Bilinear interpolation, Cubic Convolution and advanced methods such as Raised Cosine kernel, Knab interpolation kernel and Truncated Sinc were tested on ERS tandem data and compared. The results were compared with the theory and simulations of earlier investigations (Hanssen, Bamler, 1999), (Migliaccio, Bruno, 2003) and (Cho ... [et al.], 2005). The main experiment in this work was to examine and compare resampling methods on real data to evaluate their effect on the interferometric phase quality and DEM generation. The coregistration performance was evaluated by the coherence (Touzi ... [et al.], 1999) and the sum of phase differences (Li ... [et al.], 2004). No evidence showed that computationally intensive algorithms produced better quality of interferogram than Cubic Convolution. The possibilities of evaluating by means of the accuracy of the final InSAR DEM (Li, Bethel, 2008) were...
24

An electrified road future. : A feasibility study of electric road systems (ERS) for the logistic sector in Sweden.

Lykogianni, Georgia Maria, Österlind, Malin January 2014 (has links)
Electrification of transportation could be one pathway into sustainability since the electricity production can originate from renewable and low carbon energy sources. Electrifying the road could also reduce the battery dependence and further increase the vehicle efficiency in sense of energy consumption and load capacity when thinking of storage of electric energy in vehicle batteries. Not only is the Electric Road System (ERS) a rather new concept, it also raises concerns about consequences on health, safety, environment and public acceptance. The aim of this master thesis, within the logistics domain, is to interdisciplinary investigate the concept of electrified roads and to define potential blockers and in various extents investigate their feasibility. The potential blockers are assessed at a system level meaning that the depth of analysis of each aspect depends on the amount of data available and the relative importance according to the experts. Given the limits of research time, points that require more investigation have been indicated. This study will have a focus on freight vehicles since that is the vehicle considered to lack alternative solution towards decarbonization. The areas chosen for a closer analysis are health, safety and environment. The information available regarding the ERS impact on those areas is very limited even though they seem to constitute crucial factors for gaining the public acceptance. By investigating energy usage and CO 2 emissions in different phases of the ERS, the feasibility of the environment is assessed. Investigating the Electromagnetic Fields (EMF) produced by the inductive on-road charging technology, part of the ERS, approaches the possible health effects of ERS. Health effects of particles and pollutants are also touched upon. Accidents involving Electric Vehicles (EVs) and the transportation of dangerous goods through ERS will also be analyzed in the safety chapter. Ongoing projects and available technologies are used and taken into consideration throughout the study. Feedback from the industry and people involved with the ERS concept contribute in defining the fields facing significant uncertainties. In the last part, two scenarios are being analyzed in the sense of testing the feasibility of the inductive on-road charging in city logistics and for the big city triangle. This study has its base in literature reviews and interviews with experts within the industry. The different ERS technologies are still under development why many specific parameters are confidential. This poses some unintentional limits to this study in the sense of difficulty drawing specific conclusions. Therefore factors such as commercialization of the vehicle, health, safety and development time remain uncertain. Others such as environmental impact seem to benefit from the ERS, while others motivates the introduction of ERS such as the battery manufacturing.
25

Simulation of Chinese Sorghum Imports from a New Perspective: U.S. and Global Impacts

Zhang, Wei 15 June 2017 (has links)
This thesis aims to analyze the impacts on U.S. and global sorghum trade, and whether China will continue importing sorghum from the global sorghum market for feed use, if the Chinese government cancels its corn price support policy and corn temporary reserve program nationwide. This study uses the USDA-ERS China Model and the Country-Commodity Linked System (CCLS) to simulate the impacts on U.S. sorghum exports and the reduction of sorghum's global price, global production, and global trade volumes. The simulations are based on three scenarios: if China's sorghum import volume decreased by 50% from USDA-ERS's baseline projection, if China's sorghum import volume decreased by 35% each year from the previous year, and if China's sorghum import volume decreased by 70% from USDA-ERS's baseline projection in year one and by 90% from USDA-ERS's baseline projection in subsequent years. The modeling system is a large scale multi-country and multi-commodity partial equilibrium dynamic simulation model which solves for global prices and trade using individual country models. Policy instruments are applied to the China model and solved globally. The USDA-ERS China Model and the CCLS, used to project Chinese and global sorghum trends, includes the following policy instruments: tariffs, quotas, tariff rate quotas, export tax, direct payments, input subsidies, and procurement policies. This model simulates projections using price and income elasticities and assumed values for exogenous variables such as income and population growth. This model also incorporates behavior of state trading enterprises and WTO commitments into imported and exported equations for sorghum. / Master of Science / This research uses the USDA-ERS China model to analyze the impacts on U.S. and global sorghum trade, and whether China will continue importing sorghum for feed use, if the Chinese government cancels its corn price support policy nationwide. Results show that the decrease of China’s sorghum imports resulted in less sorghum demand and lower sorghum price in the global market. Sorghum exports for U.S. and other major sorghum exporters decreased significantly. The results show the necessity to seek new sorghum export opportunities worldwide for U.S. sorghum exporters. Meanwhile, U.S. sorghum exporters may change their cropping patterns to continue making profits by switching out of sorghum.
26

Unsupervised Change Detection Using Multi-Temporal SAR Data : A Case Study of Arctic Sea Ice / Oövervakad förändringsdetektion med multitemporell SAR data : En fallstudie över arktisk havsis

Fröjse, Linda January 2014 (has links)
The extent of Arctic sea ice has decreased over the years and the importance of sea ice monitoring is expected to increase. Remote sensing change detection compares images acquired over the same geographic area at different times in order to identify changes that might have occurred in the area of interest. Change detection methods have been developed for cryospheric topics. The Kittler-Illingworth thresholding algorithm has proven to be an effective change detection tool, but has not been used for sea ice. Here it is applied to Arctic sea ice data. The objective is to investigate the unsupervised detection of changes in Arctic sea ice using multi-temporal SAR images. The well-known Kittler-Illingworth algorithm is tested using two density function models, i.e., the generalized Gaussian and the log-normal model. The difference image is obtained using the modified ratio operator. The histogram of the change image, which approximates its probability distribution, is considered to be a combination of two classes, i.e., the changed and unchanged classes. Histogram fitting techniques are used to estimate the unknown density functions and the prior probabilities. The optimum threshold is selected using a criterion function directly related to classification error. In this thesis three datasets were used covering parts of the Beaufort Sea from the years 1992, 2002, 2007 and 2009. The SAR and ASAR C-band data came from satellites ERS and ENVISAT respectively. All three were interpreted visually. For all three datasets, the generalized Gaussian detected a lot of change, whereas the log-normal detected less. Only one small subset of a dataset was validated against reference data. The log-normal distribution then obtained 0% false alarm rate through all trials. The generalized Gaussian obtained false alarm rates around 4% for most of the trials. The generalized Gaussian achieved detection accuracies around 95%, whereas the log-normal achieved detection accuracies around 70%. The overall accuracies for the generalized Gaussian were about 95% in most trials. The log-normal achieved overall accuracies at around 85%. The KHAT for the generalized Gaussian was in the range of 0.66-0.93. The KHAT for log-normal was in the range of 0.68-0.77. Using one additional speckle filter iteration increased the accuracy for the log-normal distribution. Generally, the detection of positive change has been accomplished with higher level of accuracy compared with negative change detection. A visual inspection shows that the generalized Gaussian distribution probably over-estimates the change. The log-normal distribution consistently detects less change than the generalized Gaussian. Lack of validation data made validation of the results difficult. The performed validation might not be reliable since the available validation data was only SAR imagery and differentiating change and no-change is difficult in the area. Further due to the lack of reference data it could not be decided, with certainty, which distribution performed the best. / Ytan av arktisk havsis har minskat genom åren och vikten av havsisövervakning förväntas öka. Förändrigsdetection jämför bilder från samma geografiska område från olika tidpunkter föra att identifiera förändringar som kan ha skett i intresseområdet. Förändringsdekteringsmetoder har utvecklats för kryosfäriska ämnen. Tröskelvärdesbestämning med Kittler-Illingworth algoritmen har visats sig vara ett effektivt verktyg för förändringsdetektion, men har inte änvänts på havsis. Här appliceras algoritmen på arktisk havsis. Målet är att undersökra oövervakad förändringsdetektion i arktisk havsis med multitemporella SAR bilder. Den välkända Kittler-Illingworth algoritmen testas med två täthetsfunktioner, nämligen generaliserad normaldistribution och log-normal distributionen. Differensbilden erhålls genom den modifierad ratio-operator. Histogrammet från förändringsbilden skattar dess täthetsfunktion, vilken anses vara en kombination av två klasser, förändring- och ickeförändringsklasser. Histogrampassningstekniker används för att uppskatta de okända täthetsfunktionerna och a priori sannolikheterna. Det optimala tröskelvärdet väljs genom en kriterionfunktion som är direkt relaterad till klassifikationsfel. I detta examensarbete användes tre dataset som täcker delar av Beaufort-havet från åren 1992, 2002, 2007 och 2009. SAR C-band data kom från satelliten ERS och ASAR C-band data kom från satelliten ENVISAT. Alla tre tolkades visuellt och för alla tre detekterade generaliserad normaldistribution mycket mer förändring än lognormal distributionen. Bara en mindre del av ett dataset validerades mot referensdata. Lognormal distributionen erhöll då 0% falska alarm i alla försök. Generalised normaldistributionen erhöll runt 4% falska alarm i de flesta försöken. Generaliserad normaldistributionen nådde detekteringsnoggrannhet runt 95% medan lognormal distributionen nådde runt 70%. Generell noggrannheten för generaliserad normaldistributionen var runt 95% i flesta försöken. För lognormal distributionen nåddes en generell noggrannhet runt 85%. KHAT koefficienten för generaliserad normaldistributionen var i intervallet 0.66-0.93. För lognormal distributionen var den i intervallet 0.68-0.77. Med en extra speckle-filtrering ökades nogranneheten för lognormal distributionen. Generellt sett, detekterades positiv förändring med högre nivå av noggrannhet än negativ förändring. Visuell inspektion visar att generaliserad normaldistribution troligen överskattar förändringen. Lognormal distributionen detekterar konsistent mindre förändring än generaliserad normaldistributionen. Bristen på referensdata gjorde valideringen av resultaten svårt. Den utförda valideringen är kanske inte så trovärdig, eftersom den tillgänliga referensdatan var bara SAR bilder och att särskilja förändring och ickeförändring är svårt i området. Vidare, på grund av bristen på referensdata, kunde det inte bestämmas med säkerhet vilken distribution som var bäst.
27

Count on the brain / using EEG oscillations and eye movements to disentangle intelligent problem-solving in math

Dix, Annika 11 January 2016 (has links)
Wir können Mathematikleistungen über fluide Intelligenz (FI) vorhersagen. Der Einfluss von FI auf kognitive Prozesse und neuronale Mechanismen, die mathematischen Fähigkeiten in verschiedenen Teildisziplinen zugrunde liegen, ist jedoch wenig verstanden. Vorliegende Arbeit spezifiziert FI-bezogene Unterschiede in diesen Prozessen und Mechanismen beim Lösen von Geometrie-, Arithmetik- und Algebra-Aufgaben. Mithilfe eines multimethodalen Ansatzes beleuchtet sie das Zusammenspiel zwischen FI, Leistung und Faktoren wie Aufgabenkomplexität, Lernen und Strategiewahl, die kognitive Prozesse und Anforderungen beim Problemlösen beeinflussen. Leistungsunterschiede wurden durch Messung von Reaktionszeiten und Fehlerraten, Strategien durch Augenbewegungsanalyse erfasst. Als Indikator kortikaler Aktivität diente die ereigniskorrelierte (De-)Synchronisation (ERD/ERS) im Alpha-Band. Um kognitive Prozesse zu unterscheiden, haben wir die ERD/ERS im Theta-Band und den Alpha-Unterbändern einbezogen. Beim Lösen unvertrauter geometrischer Analogien zeichnete sich hohe FI durch verstärkte Verarbeitung visuell-räumlicher Informationen zum Repräsentieren von Merkmalszusammenhängen aus. Schüler mit hoher FI passten ihre Strategiewahl den Anforderungen flexibler an. Erstmals konnten wir durch trialweise Identifikation von Strategien FI-bezogene Unterschiede in der neuronalen Effizienz der Strategieausführung feststellen. Beim Lösen vertrauter arithmetischer und algebraischer Terme zeigten sich bei Schülern mit hoher im Vergleich zu Schülern mit durchschnittlicher FI geringere Anforderungen zur Aktualisierung numerischer Repräsentationen und eine bessere Leistung in komplexen Aufgaben. Weitere Analysen legen nahe, dass Schüler mit hoher FI Zusammenhänge in der Aufgabenstruktur besser erkennen und passende Routinen abrufen können. Die Fähigkeit Zusammenhangsrepräsentationen zu bilden könnte demnach ein Schlüsselaspekt zur Erklärung FI-abhängiger Unterschiede in mathematischen Fähigkeiten sein. / Fluid intelligence (FI) is a strong predictor of mathematical performance. However, the impact of FI on cognitive processes and neural mechanisms underlying differences in mathematical abilities across different subdivisions is not well understood. The present work specifies FI-related differences in these processes and mechanisms for students solving geometric, arithmetic, and algebraic problems. We chose a multi-methodological approach to shed light on the interplay between FI, performance, and factors such as task complexity, learning, and strategy selection that influence cognitive processes and task demands in problem-solving. We measured response times and error rates to evaluate performance, eye movements to identify solution strategies, and the event-related (de-)synchronization (ERD/ERS) in the broad alpha band as indicator of general cortical activity. Further, we considered the ERD/ERS in the theta band and the alpha sub-bands to distinguish between associated cognitive processes. For unfamiliar geometric analogy tasks, students with high FI built relational representations based on a more intense processing of spatial information. Strategy analyses revealed a more adaptive strategy choice in response to increasing task demands compared to students with average FI. Further, we conducted the first study identifying strategies and related cortical activity trial-wise and thereby identified FI-related differences in the neural efficiency of strategy execution. For solving familiar arithmetic and algebraic problems, high compared to average FI was associated with lower demands on the updating of numbers leading to a better performance in complex tasks. Further analyses suggest that students with high FI had an advantage to identify the relational structure of the problems and to retrieve routines that match this structure. Thus, the ability to build relational representations might be one key aspect explaining FI-related difference in mathematical abilities.
28

Measuring coastal erosion along the coast of Ystad municipality using PSInSAR and SBAS / Mätning av stranderosionen längs Ystad kommuns kust med PSInSAR och SBAS

Halldén, Tom Halldén January 2017 (has links)
In this study the use of two radar interferometry methods, PSInSAR and SBAS, were tested as tools for measuring coastal erosion. If successful it would have allowed for measuring coastal erosion as a function of material lost. The study area used was Ystad municipality, in southern Sweden. Radar data for the study was provided by the ESA, the European space agency, from their ERS-2 and ENVISAT satellites, spanning the period 1998-2005. Unfortunately, even after many different configurations of settings were tested, the results indicated that both methods are very unsuited for use in rural areas such as Ystad, whether for measuring coastal erosion or otherwise. Both methods had severe problems achieving significant coverage after low coherence areas were masked out, and PSInSAR suffered from several anomalies. This is likely due to the highly vegetated nature of the landscape, which results in low coherence through temporal decorrelation. Of the two methods SBAS showed the most promise, but not nearly enough to be considereduseful. It is, based on the scientific literature, possible that simpler interferometry methods might have been more useful. This, and other possible ways to improve the results is something that this study discusses at length.
29

Auditory processing and motor systems: EEG analysis of cortical field potentials

January 2013 (has links)
Contemporary research has been examining potential links existing among sensory, motor and attentional systems. Previous studies using TMS have shown that the abrupt onset of sounds can both capture attention and modulate motor cortex excitability, which may reflect the potential need for a behavioral response to the attended event. TMS, however, only quantifies motor cortex excitability immediately following the deliverance of a TMS pulse. Therefore, the temporal development of how the motor cortex is modulated by sounds can’t be quantified using TMS. Thus, the purpose of the present study is to use time frequency analysis of EEG to identify the time course of cortical mechanisms underlying increased motor cortex excitability after sound onset. Subjects sat in a sound attenuated booth with their hands outstretched at 45-degree angles while frequency modulated sounds were intermittently presented from a speaker either in the left and right hemispace. Our results indicated a transient reduction in EEG power from 18-24 Hz (300-600 ms latency) and then a long lasting increase in EEG power that began at ~800 ms and continued until at least 1.7 sec. The latency of EEG power changes was shorter for sounds presented from the right speaker at both time periods. When sounds were presented from the right speaker the contralateral hemisphere over motor regions also showed greater power increases after 800 ms relative to the ipsilateral hemisphere. In addition, power increases were greater in the left-handed subjects (8-12 Hz). Results showed that sounds increased EEG power at the time of a previously observed increase in motor cortex excitability. Findings also suggest an increased attentional salience to the right hemispace in neurologically normal subjects and asymmetrical hemispheric activations in right and left-handers. / acase@tulane.edu
30

Electric Road Systems for Trucks

Edfeldt, Erica, Andersson, Sanna January 2013 (has links)
An increased use of electricity in vehicles is considered an alternative to decrease the usage of fossil fuels. For private cars, plug-in electric vehicles using batteries are continuously being improved. However, the battery technology of today is not sufficient for trucks if they are to use only electricity. The battery technology is not sufficient to be able to supply the truck with enough propulsion energy to perform an entire drive. However, the hybrid drive technology enables a power recovery and charges the battery when the vehicle applies its brakes. The fuel usage can thereby be decreased through the energy recovery. This master thesis examines the potential of electric road systems, ERSs, which enables a continuous electricity supply to the vehicle when in motion. Similar technologies as an ERS has been used for a long time for trams, trolleybuses and trains, and historically there have also existed cases of electric truck systems. In this thesis the potential for ERSs is examined from the haulage contractor companies’ perspective, which would be users of this system. The potential is in regard to the energy usage per km, the CO2 emissions per km and the cost per km for an ERS vehicle (a hybrid vehicle using an ERS) compared to a hybrid vehicle and to a conventional vehicle. The cost per km includes energy cost, cost for using the ERS infrastructure and the additional vehicle cost. The method used in this study was first to create a broad picture of the concept of ERSs through reading articles, reports, web pages and through conducting interviews with stakeholders within the ERS market. The second part of the method was to create a technology model and an economic model. The models investigate the potential for ERSs through three different cases: a Distribution Case, a Long-Haulage Case and a Mining Case. For all three cases, the energy usage, the cost and the CO2 emissions per km for using a conventional vehicle, a hybrid vehicle and ERS vehicle were generated. Four alternative future scenarios were also tested, in which factors such as energy costs and infrastructure costs were varied. The results show the energy usage, the CO2 emissions and the profitability from the haulage contractor companies’ perspective. The results show that ERSs are not profitable for the Distribution Case in any of the tested scenarios. For the Long-Haulage Case, however, it is profitable in four out of the five tested scenarios. The Mining Case shows mixed profitability results, many times being just above or just below profitable. The energy usage decreased for all the cases and scenarios. Because of this, in combination with the relatively clean electricity production in Sweden, the decrease in CO2 emissions is very large. The 3 conclusions from this thesis are therefore that long-haulage routes show great potential for using ERSs, mining cases have some potential for using ERSs and if distribution routes are to use ERSs this would be only for lowered fossil fuel usage and environmental purposes. / För att minska användandet av fossila bränslen anses ökad användning av elektricitet i fordon vara ett potentiellt alternativ. För laddelbilar inom personbilssektorn förbättras batteritekniken ständigt. Dock ser inte batteriteknikens utveckling ut att vara tillräcklig för lastbilar om de ska kunna köra på enbart el. Även om batteritekniken inte är tillräcklig för att lastbilen ska kunna köra på enbart el så kan batterier användas i lastbilshybrider. Hybridsystemet möjliggör en energiåtervinning där batteriet kan laddas när fordonet bromsar. Bränsleanvändningen kan därmed minskas genom energiåtervinningen. Detta examensarbete utreder potentialen för elektriska vägsystem. Elektriska vägsystem möjliggör kontinuerlig överföring av elektricitet till lastbilar medan de kör. Liknande tekniker har länge använts för spårvagnar, trådbussar, tåg och även i viss utsträckning för trådlastbilar. I detta examensarbete utreds potentialen för elektriska vägsystem utifrån åkeriers perspektiv, eftersom dessa i så fall kommer att vara de som använder systemet. Potentialen bedöms genom att jämföra energianvändning per kilometer, CO2-utsläpp per kilometer och kilometerkostnad för en elvägslastbil jämfört med en konventionell lastbil och jämfört med en hybridlastbil. Kilometerkostnaden innefattar energikostnad, kostnad för att använda elvägsinfrastrukturen och den ytterligare fordonskostnaden. Metoden som användes i denna studie var först att skapa en bred bild av konceptet elektriska vägsystem genom att läsa artiklar, rapporter, hemsidor och att utföra intervjuer med aktörer inom elektriska vägsystem. Den andra delen av metoden var att skapa en ekonomisk och teknisk modell. Tre olika fall modellerades: ett distributionsfall, ett fjärrtrafikfall och ett gruvtransportfall. För dessa tre fall så genererades energianvändningen, CO2-utsläppen och kostnaden per km vid användning av en konventionell lastbil, en hybridlastbil och en hybrid som använder elektriska vägsystem. Fyra alternativa framtidsscenarion testades också, för vilka parametrar såsom energikostnader och infrastrukturkostnader varierades. Alla resultat visar energianvändningen, CO2-utsläppen och lönsamheten utifrån ett åkeriperspektiv. Resultaten visar att elektriska vägsystem inte är lönsamma för distributionsfallet i något av de testade scenarierna. För fjärrtrafik är det lönsamt i fyra av de fem testade scenarierna. Gruvtrafikfallet visar på blandade resultat, där det ofta är precis lönsamt eller nästan lönsamt med elektriska vägsystem. Energianvändningen minskar för alla fall och scenarier. Detta tillsammans med Sveriges relativt rena elektricitetsproduktion innebär att CO2-utsläppen minskar kraftigt. Slutsatserna från detta examensarbete är därför att fjärrtrafik påvisar stor potential för elektriska vägsystem, gruvtrafik har viss potential och distributionstrafik bör endast använda elektriska vägsystem av miljömässiga och fossilbränslereducerande skäl.

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