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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.
701

Effects of climate change on boreal wetland and riparian vegetation

Ström, Lotta January 2011 (has links)
Models of climate change predict that temperature will increase during the 21th century and the largest warming will take place at high northern latitudes. In addition to warming, predictions for northern Europe include increased annual precipitation and a higher proportion of the precipitation during winter falling as rain instead of snow. These changes will substantially alter the hydrology of rivers and streams and change the conditions for riverine communities. The warming is also expected to result in species adjusting their geographic ranges to stay within their climatic tolerances. Riparian zones and wetlands are areas where excess water determines the community composition. It is therefore likely that these systems will be highly responsive to alterations in precipitation and temperature patterns. In this thesis we have tested the predicted responses of riparian vegetation to climate-driven hydrologic change with a six year long transplant experiment (I). Turfs of vegetation were moved to a new elevation with shorter or longer flood durations. The results demonstrate that riparian species will respond to hydrologic changes, and that without rare events such as unusually large floods or droughts, full adjustment to the new hydrological regime may take at least 10 years. Moreover, we quantified potential effects of a changed hydrology on riparian plant species richness (II) and individual species responses (III) under different climate scenarios along the Vindel River in northern Sweden. Despite relatively small changes in hydrology, the results imply that many species will become less frequent than today, with stochastic extinctions along some reaches. Climate change may threaten riparian vegetation along some of the last pristine or near-natural river ecosystems in Europe. More extensive loss of species than predicted for the Vindel River is expected along rivers in the southern boreal zone, where snow-melt fed hydrographs are expected to be largely replaced by rain-fed ones. With a seed sowing experiment, we tested the differences in invasibility between open wetlands, forested wetlands and riparian zones (IV). All six species introduced were able to germinate and survive in all habitats and disturbance levels, indicating that the tested wetlands are generally invisible. Germination was highest in open wetlands and riparian zones. Increasing seed sowing density increased invasion success, but the disturbance treatments had little effect. The fact that seeds germinated and survived for 2 to 3 years in all wetland habitats indicates that wetland species with sufficiently high dispersal capacity and propagule pressure would be able to germinate and establish here in their respective wetland type. Our results clearly demonstrate that a changed climate will result in substantial changes to functioning, structure and diversity of boreal wetland and riparian ecosystems. To preserve species rich habitats still unaffected by dams and other human stressors, additional protection and management actions may have to be considered.
702

Phosphate Removal and Recovery from Wastewater by Natural Materials for Ecologically Engineered Wastewater Treatment Systems

Curran, Daniel Thomas 01 January 2015 (has links)
Eutrophication due to excess loading of phosphorus (P) is a leading cause of water quality degradation within the United States. The aim of this study was to investigate P removal and recovery with 12 materials (four calcite varieties, wollastonite, dolomite, hydroxylapatite, eggshells, coral sands, biochar, and activated carbon. This was accomplished through a series of batch experiments with synthetic wastewater solutions ranging from 10-100 mg PO₄-P/ L. The results of this study were used to establish large-scale, calcite-based column filter experiments located in the Rubenstein School of Environment and Natural Resources' Eco-Machine. Influent and effluent wastewater samples were routinely collected for 64 days. Measures of filter performance included changes in pH, percent reduction and mass adsorbed of P. After the columns reached saturation, filter media was analyzed for the mineralogical content by X-ray powder diffraction (XRD). In the batch experiments, P removal and recovery varied among the media and across treatments. The best performing minerals were calcite, wollastonite, and hydroxylapatite. Eggshells, activated carbon, and coral sands also reduced and adsorbed P. The remaining materials had the lowest reductions and adsorption of P. Results from batch experiments informed the design of large column filters within the Rubenstein School of the Environment and Natural Resources' Eco-Machine. Removal and adsorption rates of P by the three column filters were similar. The columns achieved an average P reduction of 12.53% (se = 0.98) and an average P adsorption of 0.649 mg PO₄-P/ kg media (se = 0.03) over a 4-h hydraulic retention time. Paired T-tests showed that P reductions were statistically significant (p-value < 0.05) on the majority of sampling dates until the columns reached saturation. Saturation was reached after 31 days for two of the columns and 36 days for the third column. The filter media consistently buffered the pH of the wastewater to approximately 6.0-7.0 with no indication of diminishing buffer capacity after saturation. XRD analysis was not able to detect any P species within the crystalline structure of the filter media. This research contributes to the understanding of how the selected media perform during P removal and recovery programs, while providing information on the performance of large column filters operating within advanced, ecologically engineered wastewater treatment systems.
703

Process Models for CO2 Migration and Leakage : Gas Transport, Pore-Scale Displacement and Effects of Impurities

Basirat, Farzad January 2017 (has links)
Geological Carbon Storage (GCS) is considered as one of the key techniques to reduce the rate of atmospheric emissions of CO2 and thereby to contribute to controlling the global warming. A successful application of a GCS project requires the capability of the formation to trap CO2 for a long term. In this context, processes related to CO2 trapping and also possible leakage of CO2 to the near surface environment need to be understood. The overall aim of this thesis is to understand the flow and transport of CO2 through porous media in the context of geological storage of CO2. The entire range of scales, including the pore scale, the laboratory scale, the field experiment scale and the industrial scale of CO2 injection operation are addressed, and some of the key processes investigated by means of experiments and modeling.  First, a numerical model and laboratory experimental setup were developed to investigate the CO2 gas flow, mimicking the system in the near-surface conditions in case a leak from the storage formation should occur. The system specifically addressed the coupled flow and mass transport of gaseous CO2 both in the porous domain as well as the free flow domain above it. The comparison of experiments and modelling results showed a very good agreement indicating that the model developed can be applied to evaluate monitoring and surface detection of potential CO2 leakage. Second, the field scale CO2 injection test carried out in a shallow aquifer in Maguelone, France was analyzed and modeled. The results showed that Monte Carlo simulations accounting for the heterogeneity effects of the permeability field did capture the key observations of the monitoring data, while a homogeneous model could not represent them. Third, a numerical model based on phase-field method was developed and model simulations carried out addressing the effect of wettability on CO2-brine displacement at the pore-scale. The results show that strongly water-wet reservoirs provide a better potential for the dissolution trapping, due to the increase of interface between CO2 and brine with very low contact angles. The results further showed that strong water-wet conditions also imply a strong capillary effect, which is important for residual trapping of CO2. Finally, numerical model development and model simulations were carried out to address the large scale geological storage of CO2 in the presence of impurity gases in the CO2 rich phase. The results showed that impurity gases N2 and CH4 affected the spatial distribution of the gas (the supercritical CO2 rich phase), and a larger volume of reservoir is needed in comparison to the pure CO2 injection scenario. In addition, the solubility trapping significantly increased in the presence of N2 and CH4.
704

Digitalizovaný experiment - prostředek k osvojení vybraného učiva obecné chemie / Digitized experiments - The instrument for mastering of selected curriculum of general chemistry

Bartoš, Ivan January 2010 (has links)
By analyzing electronical tools, online applications and tutorials from Czech Republic and abroad I have come to the conclusion that it is necessary to create a flexible educational instrument which includes digitized chemical experiments for general chemistry. Following the analysis of present databases, CD ROMs and VHS containing pictured experiments I found out that a lot of spectacular experiments with pyrotechnical components have not been shooted at all or not in the range of "greater" chemicals quantity. The chosen programming language, in which FMDP was written, proved to be most efficient. This choice emerged from a discussion with programmers and was motivated in particular by larger possibilities of C# than HTML have. In addition to it the modification of the FMDP content is easy. The teachers with minimum of the PC-literacy can make any changes in FMDP, alternate any of its parts and adapt them for various internal and external conditions of education. With regard to the interview having found the needs of learners I filmed and digitized especially such experiments that present the chemical reactions accompanied by the rise of a smoke, light emission, explosion and a surprising turn of colours. On the basis of the statistical evaluation of statistical data containing marks achieved by...
705

Okolnosti vylučující protiprávnost a činnost lékaře / Circumstances of justification and medical practise

Strnad, Jan January 2013 (has links)
Responsibility of the doctor in criminal law and the circumstances under which it is possible to carry out medical procedures without the threat of legal punishment is a topic that has been, is and will be always up to date. It is a complex set of problems, which includes aspects of moral, medical and legal. In my thesis I focused on relationship between doctor's proffession and legal aspects of his work according to criminal law. Its goal is to describe the issue of the practice of medicine and circumstances of justification in terms of legislation in the Czech Republic. The thesis consists of three chapters. The first chapter provides an introduction to the problem and the reasons that led me to choose this topic work. The second chapter is devoted to criminal liability and is divided into two parts. The first contains the general conditions that are necessary for criminal liability of doctors. The second part contains the typical and most common possible crimes that may physician in the exercise of their profession commit. The third and most extensive chapter has focused on description of the circumstances of justification. The chapter is divided into four parts. Firstly it deals with self-defense and legitimate use of weapons that are not too common in the medical environment. Then I focus on...
706

Ochrana člověka za mimořádných událostí jako téma pro žáky středních odborných škol / Human Protection in Emergencies as a Theme for Vocational School Students

Metelková, Iva January 2014 (has links)
TITLE: Human Protection in Emergencies as a part of Health Education AUTHOR: Iva Metelková DEPARTMENT: Department of Education SUPERVISOR: PaedDr. Eva Marádová, CSc. ABSTRACT Human Protection in Emergency (HPE) is the subject of this theoretical research thesis. The theoretical part focuses on a set of human protection in emergency and military training in the broader historical context but also legislative context. Space is devoted to the unambiguous definition of related terms. Furthermore the course curriculum reform with emphasis on the level of secondary vocational education. The practical part is focused on the evaluation of the research that was conducted among the students of first and second years of nonscience oriented secondary vocational schools. Data for the research was obtained by questionnaire survey and analyzed the statistical method. The work also includes a draft concept for the implementation of the teaching of human protection in emergencies. The objective of this proposal is to ensure access to information concerning the HPE for students but also for teachers and that contribute to the formation of desirable patterns of behavior for participation in the incident. KEY WORDS: emergency event, protection of man, military training, vocational education, comparison, chemical experiment
707

Studium precese magnetizace v materiálech a strukturách pro spintroniku / Studium precese magnetizace v materiálech a strukturách pro spintroniku

Kašpar, Zdeněk January 2016 (has links)
In this thesis we studied precession mechanism in ferromagnetic thin film half-metal NiMnSb. We measured magnetization oscillations using optical pump and probe experiment at temperatures between 15 and 200 K and we evaluated the magnetic anisotropy fields, spin stiffness and Gilbert damping. New setup for ferromagnetic resonance measurement was built utilizing vector network analyser. With this setup we measured FMR at temperatures between 300 and 75 K. We evaluated the same parameters from FMR experiments as from the optical one. We found very good agreement in results obtained by the two methods. Powered by TCPDF (www.tcpdf.org)
708

Effect of the Flat Tax Reform on Labour Supply Elasticity at the Intensive and Extensive Margins: Evidence from the Czech Republic / Effect of the Flat Tax Reform on Labour Supply Elasticity at the Intensive and Extensive Margins: Evidence from the Czech Republic

Tomo, Ján January 2015 (has links)
The thesis deals with the estimation of labour supply responses to the personal income tax reform in the Czech Republic adopted in 2008 by applying quasi experimental design known as "difference-in-differences". By exploiting the different change in the effective tax rates for various population subgroups as a natural experiment and using microdata from European Labour Force Sur- vey we constructed the treatment and control groups according to the highest attained level of education serving as a proxy for an income range that assigns an individual to the particular tax bracket before and after policy change. Analysing one-person households we found significant negative effect on the labour force participation and significant positive effect on the hours work of the treated by comparing these outcomes for the treatment and control groups in the baseline and follow up periods before and after the reform. JEL Classification C21, D04, H24, H31, I38, J22 Keywords tax reform, labour supply, natural experiment, difference-in-differences Author's e-mail janxtomo@gmail.com Supervisor's e-mail gebicka@fsv.cuni.cz
709

Evoluce antisociálního trestání / The Antisocial Punishment Evolution

Schejbal, Martin January 2011 (has links)
This work statistically analyses hypotheses about the presence of antisocial punishment in study of economic experiments. Analysed data source is author's own ABM simulation of antisocial punishment environment. Tested hypotheses and ABM simulations are evolutionary oriented. This represents natural selection of evolving agents (and their groups) interacting with one another. Work is divided by two independent parts of presumptions. Crucial hypothesis of the first part is evolutional advantage from retaliatory punishment, the second part tests hypotheses of evolutional benefits resulting from group selection. Findings of the analysis allow us to accept these crucial hypothesis, and it may be concluded, that antisocial punishment can be regard as an evolutionary advantage, which directly advantages individuals, as well as whole groups.
710

Trigger and reconstruction farms in the HERA-B experiment and algorithms for a Third Level Trigger

Schwanke, Ullrich 30 October 2000 (has links)
Das HERA-$B$-Experiment am Deutschen Elektronen-Synchrotron (DESY) in Hamburg dient der Untersuchung der Physik von Teilchen, die $b$-Quarks enthalten. Der Schwerpunkt des Ex\-pe\-ri\-mentes liegt auf der Messung der CP-Verletzung im System der neutralen $B$-Mesonen. Es wird erwartet, dass die pr\"azise Bestimmung der CP-Asymmetrie im Zerfallskanal $B^0(\bar{B}^0)\to J/\psi K_S^0$ gro{\ss}en Einfluss auf die Weiterentwicklung des Standardmodells der Elementarteilchenphysik und g\"angiger kosmologischer Theorien haben wird. Das HERA-$B$-Experiment nutzt den Protonenstrahl des HERA-Ringes, um in Kollisionen mit einem feststehenden Target paarweise $B$-Hadronen zu erzeugen. Die Wechselwirkungen werden in einem Vorw\"artsspektrometer mit etwa 600.000 Auslesekan\"alen nachgewiesen. Aufgrund der relativ niedrigen Schwerpunktsenergie von 41.6\,GeV sind Ereignisse mit $b$-Quarks im Vergleich zu Wechselwirkungen mit leichteren Quarks um etwa sechs Gr\"o{\ss}enordnungen unterdr\"uckt. Die Selektion von Signalereignissen stellt daher eine besondere Herausforderung dar. Sie wird von einem vierstufigen Datennahme- und Triggerystem \"ubernommen, das die Ereignisrate von 10\,MHz auf etwa 20\,Hz reduziert. Neben speziell entwickelter Elektronik werden im Triggersystem mehrere hundert handels\"ubliche PCs eingesetzt. Die Computer sind in zwei so genannten PC-Farmen mit jeweils mehr als 200 Prozessoren angeordnet, die die Rechenkapazit\"at f\"ur Triggerentscheidungen und die prompte Analyse der Ereignisdaten zur Verf\"ugung stellen. Auf der einen Farm laufen schnelle Triggerprogramme mit einer Rechenzeit von etwa 1--100\,ms pro Ereignis ab. Die andere Farm rekonstruiert die Ereignisse online, bevor die Daten auf Band dauerhaft archiviert werden. Die pro Ereignis aufgewandte Rechenzeit liegt dabei im Bereich einiger Sekunden. Die vorliegende Arbeit behandelt zwei Themenkreise. Einerseits wird die technische Umsetzung der Trigger- und der Rekonstruktionsfarm beschrieben. Besonderes Augenmerk liegt dabei auf den Software-Systemen, die den Farmen erforderliche Kalibrationsdaten verf\"ugbar machen und die zentrale \"Uberwachung der Ergebnisse der ablaufenden Programme gestatten. Der Hauptteil der Arbeit besch\"aftigt sich mit Algorithmen f\"ur eine dritte Triggerstufe, die zus\"atzlich zu existierenden Programmen auf der Triggerfarm zum Einsatz kommen sollen. Der Zerfall $B^0(\bar{B}^0)\to J/\psi X$ hat eine sehr klare Signatur, wenn das $J/\psi$ in ein $e^+e^-$- oder $\mu^+\mu^-$-Paar zerf\"allt. Im Triggersystem wird nach einem Paar entgegengesetzt geladener Leptonen des gleichen Typs gesucht, deren invariante Masse der des $J/\psi$ entspricht und deren Spuren von einem gemeinsamen Vertex in der N\"ahe des Targets ausgehen. Es wird davon ausgegangen, dass die Ausnutzung aller kinematischen Zwangsbedingungen ausreicht, um diesen Zerfallskanal klar von Untergrundereignissen zu trennen. Die dritte Triggerstufe soll dagegen auf Signalprozesse mit weniger kinematischen Beschr\"ankungen angewandt werden. Solche Ereignisse entstehen zum Beispiel dann, wenn zwei in der Proton-Target-Kollision erzeugte $B$-Mesonen semileptonisch zerfallen. Das Triggersystem selektiert lediglich die beiden Leptonen, die aber hier nicht von einem gemeinsamen Vertex kommen. Die dritte Triggerstufe soll f\"ur derartige Zerfallstopologien innerhalb von 100\,ms pro Ereignis weitere Kriterien zur Unterscheidung von Signal- und Untergrundprozessen aus den Daten extrahieren. In der Arbeit wird anhand von Monte-Carlo-Studien untersucht, inwieweit die Daten des Silizium-Vertexdetektors des Experimentes zur Entscheidungsfindung einer dritten Triggerstufe beitragen k\"onnen. Dabei wird die Rekonstruktion von Spuren aus der Zerfallskaskade der $B$-Hadronen zus\"atzlich zu den von der vorhergehenden Triggerstufe selektierten Lep\-ton\-en an\-ge\-strebt. Mithilfe einer schnellen Mustererkennung f\"ur den Vertexdetektor wird gezeigt, dass das Auffinden aller Spuren und die Anwendung von Triggeralgorithmen innerhalb des vorgegebenen Zeitfensters von 100\,ms m\"oglich sind. Die Bestimmung der Spurparameter nahe der Targetregion macht von der Methode des Kalman-Filters Gebrauch, um der Vielfachstreuung im Detektormaterial Rechnung zu tragen. Dabei tritt das Problem auf, dass weder der Impuls der gefundenen Spuren bekannt ist, noch die Materialverteilung im Vertexdetektor aus Zeitgr\"unden in aller Strenge ber\"ucksichtigt werden kann. Durch geeignete N\"aherungen gelingt es, eine ausreichende Genauigkeit f\"ur die Spurparameter zu erreichen. Die aufgefundenen Teilchen bilden den Ausgangspunkt f\"ur Triggeralgorithmen. Hierbei wird untersucht, welche Methoden am besten geeignet sind, um Signal- und Unter\-grund\-ereignisse voneinander zu trennen. Es erweist sich, dass das Auffinden von Spuren mit gro{\ss}em Impaktparameter aussichtsreichere Ans\"atze als eine Suche nach Sekund\"arvertices bietet. / The HERA-$B$ experiment at Deutsches Elektronen-Synchrotron (DESY) Hamburg aims at investigating the physics of particles containing $b$ quarks. The experiment focusses on measuring CP violation in the system of neutral $B$ mesons. It is expected that the precise determination of the CP asymmetry in the channel $B^0(\bar{B}^0)\to J/\psi K_S^0$ will have an impact on the further development of the Standard Model of Elementary Particle Physics and cosmological theories. The HERA-$B$ experiment uses the proton beam of the HERA storage ring in fixed-target mode. $B$ hadrons are produced in pairs when protons from the beam halo interact with target nuclei. The interactions are recorded by a forward-spectrometer with roughly 600.000 readout channels. At the HERA-$B$ centre-of-mass energy of 42.6\,GeV, the $b\bar{b}$ cross section is only a tiny fraction of the total inelastic cross section. Only one in about 10$^6$ events contains $b$ quarks, which turns the selection of signal events into a particular challenge. The selection is accomplished by a four-stage data acquisition and trigger system reducing the event rate from 10\,MHz to about 20\,Hz. Besides custom-made electronics, several hundreds of PCs are used in the trigger system. The computers are arranged in two so-called PC farms with more than 200 processors each. The PC farms provide the computing capacity for trigger decisions and the prompt analysis of event data. One farm executes fast trigger programs with a computing time of 1--100\,ms per event. The other farm performs online reconstruction of the events before data are archived on tape. The computing time per event is in the range of several seconds. This thesis covers two topics. In the beginning, the technical implementation of the trigger and the reconstruction farm are described. In doing so, emphasis is put on the software systems which make calibration data available to the farms and which provide a centralised view on the results of the executing processes. The principal part of this thesis deals with algorithms for a Third Level Trigger. This trigger is to come into operation on the trigger farm together with existing programs. Processes of the type $B^0(\bar{B}^0)\to J/\psi X$ have a very clean signature when the $J/\psi$ decays to a $e^+e^-$ or $\mu^+\mu^-$ pair. The trigger system attempts to identify two unlike-sign leptons of the same flavour whose invariant mass matches the $J/\psi$. In later steps, the tracks are required to originate from a common vertex close to the target. It is assumed that these kinematic constraints are sufficient to pick out events of this type among the copious background processes. In contrast, the Third Level Trigger is to be applied to signal processes with fewer kinematic constraints. Such events occur for example when two $B$ mesons, which were created in a proton-target collision, decay semileptonically. The trigger system selects merely the two leptons which do not originate from a common vertex in this case. The Third Level Trigger has 100\,ms at its disposal to extract further criteria from the data which can serve to distinguish between signal and background events. This thesis investigates with the aid of Monte-Carlo simulations how the data of the experiment's silicon vertex detector can contribute to the decisions of a Third Level Trigger. The trigger aims at reconstructing tracks from the decay cascade of $B$ mesons in addition to the leptons selected by the preceding trigger levels. A fast pattern recognition for the vertex detector demonstrates that the reconstruction of all tracks and the application of trigger algorithms are possible within the given time slot of 100\,ms. The determination of track parameters in the target region exploits the Kalman-filter method to account for the multiple scattering of particles in the detector material. The application of this method is, however, made difficult by two facts. First, the momentum of the reconstructed tracks is not known. And, second, the material distribution in the detector cannot be taken into consideration in detail due to timing limitations. Adequate approximations for the momentum and the material traversed by a particle help to accomplish a sufficient accuracy of the track parameters. The reconstructed tracks constitute the starting point of several trigger algorithms, whose suitability to select signal events is investigated. Our studies indicate that the reconstruction of tracks with large impact parameters is a more promising approach than a search for secondary vertices.

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