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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.
71

The Demographic and Economic Impacts by Tornado Touchdowns at the County Level, 1990 to 1998

Amendola, Jennifer L. 18 April 2008 (has links)
No description available.
72

Characterizing African Elephant (<i>Loxodonta Africana</i>) Population Dynamics and Distribution in Botswana

Barungwi, Amo Obusitswe 29 July 2021 (has links)
The African elephant (Loxodonta africana) is an iconic species that is globally threatened. Of the total continental population, 37% is found in Botswana, the highest number and density of elephants in Africa. Elephant management in this country remains challenging and complex as the population estimates and trends calculated by government and independent researchers (from aerial survey data) differ and continue to be highly debated, both locally and internationally. To add more clarity and potentially resolve this ongoing debate, this study evaluates aerial survey data collected by the Botswana government from 1990 to 2012 and compares it with population demographic field data collected in 2019-2020 to assess Botswana's elephant population trend in a multimodal fashion. I used two different methods to evaluate aerial survey count data, the log-linear regression model and the Exponential Growth Space State (EGSS) model. In addition, I used the population demographic field data to estimate the growth rate. From the results, the average annual growth rate from the linear regression and the EGSS were both 6.17%. The growth rate estimated from the population demographics field data was estimated to be 5.17%. The age structure was comprised of the six age classes with a general increase from one age structure to the next as expected with a non significant decline in age class 3 (5-10 years) likely associated with the difficulty in differentiating this age class from the bounding age classes. There were no significant differences in the sex ratio (0.49Males:0.51Females). The age structure remained the same from 2019 to 2020, suggesting no evidence that overharvesting impacted the elephant population age structure in northern Botswana. Range expansion has also been identified with the movement of the elephant population into the southern part of the country by 2012. Analysis of count and demographic data as well as the identification of range expansion suggest that the elephant population is growing at rate close to the maximum growth rate previously identified for this species. Data do not support assertions that the population is negatively impacted through illegal offtake. Independent studies that identify Botswana's elephant population as declining have relied on comparisons that are made between data sets obtained from divergent aerial survey methodology and survey area, elements that confound such conclusions. Estimating population trends and the growth rate of an open population is complex, never-the-less, with population growth potientially derived from both birth and/or external immigation. However, demographic data collected in during this study indicate that the fucundity rate is substantial and likely a dominating driver of the positive population growth trend. Multiple measures of population growth (aerial survey and demographic assessments) also provide the opportunity for cross-validation of derived population trends. Therefore, this study recommends that the Botswana government incorporate population demographic data (i.e., age classes) into their existing monitoring protocols. Longitudinal data collection provides a critical mechanism for understanding population trends over changing environmental dynamics and should be continued. Efforts to modify or change these approaches must employ mechanisms that will account for and standardize for differences in methodology. / Master of Science / Botswana, a semi-arid country with limited surface water sources, has the highest number of African elephants (Loxodonta africana) on the African continent. This iconic species is globally threatened, and its conservation status is highly debated, making its management complex for Botswana. The population trends for the Botswana population, from the aerial surveys, are highly debated locally and internationally. Therefore, this study re-evaluated the aerial survey data from the Botswana government (1990-2012) and estimated the population growth rate, then compared the growth rate from the aerial survey trends analysis to the growth rate from the elephant population demographics data (collected in 2019 and 2020). The results from the aerial survey data from 2012 estimated a total population of 207,545 (CI = 185,774 - 229,316) with an annual average population growth rate of 6.17%, similar to the growth rate 5% estimated from population demographic field data. Range expansion of the elephant population has also been detected since 2009, with elephants now found in previously unoccupied regions of the Central Kalahari Game Reserve and associated regions in Southern Botswana. These results suggest the elephant population in Botswana is growing at a rate close to the maximum growth rate identified for this species. There is no evidence for a declining or stable population trend or indicators suggesting harvesting pressures (poaching) are suppressing elephant numbers. The study shows the utility of incorporating various population sampling methodologies into species management in Botswana.
73

大數據預測通貨膨脹率 / Forecasting Inflation with Big Data

廖珈燕, Liao, Jia Yan Unknown Date (has links)
本文主要是透過 Google trends 網站提供的關鍵字搜尋量資料, 探討網路資料是否能夠提供通貨膨脹率的即時資訊。 透過美國消費者物價指數的組成細項作為依據,蒐集美國2004年1月至2015年12月的 Google trends 關鍵字變數,並藉由最小絕對壓縮挑選機制(Least absolute shrinkage and selection operator)、 彈性網絡(Elastic Net)以及主成分分析法(Principal component analysis)等等變數挑選機制,有效地整合大量的關鍵字資料。實證結果發現,透過適當變數挑選後的 Google trends 關鍵字變數確實可改善美國通貨膨脹率的即時預測表現,並為美國通貨膨脹率提供額外有效的資訊。此外,我們透過台灣的關鍵字資料檢驗,也確認Google trends 關鍵字資料可以幫助台灣通貨膨脹率的即時預測。
74

Direction and directedness in language change : an evolutionary model of selection by trend-amplification

Stadler, Kevin January 2017 (has links)
Human languages are not static entities. Linguistic conventions, whose social and communicative meaning are understood by all members of a speech community, are gradually altered or replaced, whether by changing their forms, meanings, or by the loss of or introduction of altogether new distinctions. How do large speech communities go about re-negotiating arbitrary associations in the absence of centralised coordination? This thesis first provides an overview of the plethora of explanations that have been given for language change. Approaching language change in a quantitative and evolutionary framework, mathematical and computational modelling is put forward as a tool to investigate and compare these different accounts and their purported underlying mechanisms in a rigorous fashion. The central part of the thesis investigates a relatively recent addition to the pool of mechanisms that have been proposed to influence language change: I will compare previous accounts with a momentum-based selection account of language change, a replicator-neutral model where the popularity of a variant is modulated by its momentum, i.e. its change in frequency of use in the recent past. I will discuss results from a multi-agent model which show that the dynamics of a trend-amplifying mechanism like this are characteristic of language change, in particular by exhibiting spontaneously generated s-shaped transitions. I will also discuss several empirical predictions made by a momentum-based selection account which contrast with those that can be derived from other accounts of language change. Going beyond theoretical arguments for the role of trends in language change, I will go on to present fieldwork data of speakers’ awareness of ongoing syntactic changes in the Shetland dialect of Scots. Data collected using a novel questionnaire methodology show that individuals possess explicit knowledge about the direction as well as current progression of ongoing changes, even for grammatical structures which are very low in frequency. These results complement previous experimental evidence which showed that individuals both possess and make use of implicit knowledge about age-dependent usage differences during ongoing sound changes. Echoing the literature on evolutionary approaches to language change, the final part of the thesis stresses the importance of explicitly situating different pressures either in the domain of the innovation of new or else the selection of existing variants. Based on a modification of the Wright-Fisher model from population genetics, I will argue that trend-amplification selection mechanisms provide predictions that neatly match empirical facts, both in terms of the diachronic dynamics of language change, as well as in terms of the synchronic distribution of linguistic traits that we find in the world.
75

Privatizing medical care in Hong Kong: a policy analysis.

January 1996 (has links)
by Ip Pui Shum. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references. / Acknowledgments --- p.ii / Abstract --- p.iii / List of Figures --- p.v / Abbreviations --- p.v / Chapter / Chapter 1. --- Introduction --- p.1 / Chapter 2. --- The Evolutionary Stages of Medical Care in Hong Kong --- p.28 / Chapter 3. --- Forging The Policy --- p.71 / Chapter 4. --- Privatization Incomplete --- p.100 / Chapter 5. --- Explaining Incompleteness --- p.135 / Chapter 6. --- Conclusion --- p.149 / Appendices --- p.156 / Chronology --- p.160 / Bibliography --- p.164
76

Floods in Germany : analyses of trends, seasonality and circulation patterns

Petrow, Theresia January 2009 (has links)
Flood hazard estimations are conducted with a variety of methods. These include flood frequency analysis (FFA), hydrologic and hydraulic modelling, probable maximum discharges as well as climate scenarios. However, most of these methods assume stationarity of the used time series, i.e., the series must not exhibit trends. Against the background of climate change and proven significant trends in atmospheric circulation patterns, it is questionable whether these changes are also reflected in the discharge data. The aim of this PhD thesis is therefore to clarify, in a spatially-explicit manner, whether the available discharge data derived from selected German catchments exhibit trends. Concerning the flood hazard, the suitability of the currently used stationary FFA approaches is evaluated for the discharge data. Moreover, dynamics in atmospheric circulation patterns are studied and the link between trends in these patterns and discharges is investigated. To tackle this research topic, a number of different analyses are conducted. The first part of the PhD thesis comprises the study and trend test of 145 discharge series from catchments, which cover most of Germany for the period 1951–2002. The seasonality and trend pattern of eight flood indicators, such as maximum series and peak-over-threshold series, are analyzed in a spatially-explicit manner. Analyses are performed on different spatial scales: at the local scale, through gauge-specific analyses, and on the catchment-wide and basin scales. Besides the analysis of discharge series, data on atmospheric circulation patterns (CP) are an important source of information, upon which conclusions about the flood hazard can be drawn. The analyses of these circulation patterns (after Hess und Brezowsky) and the study of the link to peak discharges form the second part of the thesis. For this, daily data on the dominant CP across Europe are studied; these are represented by different indicators, which are tested for trend. Moreover, analyses are performed to extract flood triggering circulation patterns and to estimate the flood potential of CPs. Correlations between discharge series and CP indicators are calculated to assess a possible link between them. For this research topic, data from 122 meso-scale catchments in the period 1951–2002 are used. In a third part, the Mulde catchment, a mesoscale sub-catchment of the Elbe basin, is studied in more detail. Fifteen discharge series of different lengths in the period 1910–2002 are available for the seasonally differentiated analysis of the flood potential of CPs and flood influencing landscape parameters. For trend tests of discharge and CP data, different methods are used. The Mann-Kendall test is applied with a significance level of 10%, ensuring statistically sound results. Besides the test of the entire series for trend, multiple time-varying trend tests are performed with the help of a resampling approach in order to better differentiate short-term fluctuations from long-lasting trends. Calculations of the field significance complement the flood hazard assessment for the studied regions. The present thesis shows that the flood hazard is indeed significantly increasing for selected regions in Germany during the winter season. Especially affected are the middle mountain ranges in Central Germany. This increase of the flood hazard is attributed to a longer persistence of selected CPs during winter. Increasing trends in summer floods are found in the Rhine and Danube catchments, decreasing trends in the Elbe and Weser catchments. Finally, a significant trend towards a reduced diversity of CPs is found causing fewer patterns with longer persistence to dominate the weather over Europe. The detailed study of the Mulde catchment reveals a flood regime with frequent low winter floods and fewer summer floods, which bear, however, the potential of becoming extreme. Based on the results, the use of instationary approaches for flood hazard estimation is recommended in order to account for the detected trends in many of the series. Through this methodology it is possible to directly consider temporal changes in flood series, which in turn reduces the possibility of large under- or overestimations of the extreme discharges, respectively. / Hochwasserabschätzungen werden mit Hilfe einer Vielzahl von Methoden ermittelt. Zu diesen zählen Hochwasserhäufigkeitsanalysen, die hydrologische und hydraulische Modellierung, Abschätzungen zu maximal möglichen Abflüssen wie auch Langzeitstudien und Klimaszenarien. Den meisten Methoden ist jedoch gemein, dass sie stationäre Bedingungen der beobachteten Abflussdaten annehmen. Das heißt, in den genutzten Zeitreihen dürfen keine Trends vorliegen. Vor dem Hintergrund des Klimawandels und nachgewiesener Trends in atmosphärischen Zirkulationsmustern, stellt sich jedoch die Frage, ob sich diese Veränderungen nicht auch in den Abflussdaten widerspiegeln. Ziel der Dissertation ist daher die Überprüfung der Annahme von Trendfreiheit in Abflüssen und Großwetterlagen, um zu klären, ob die aktuell genutzten stationären Verfahren zur Hochwasserbemessung für die vorhandenen Daten in Deutschland geeignet sind. Zu prüfen ist des Weiteren, inwiefern regional und saisonal eine Verschärfung bzw. Abschwächung der Hochwassergefahr beobachtet werden kann und ob eindeutige Korrelationen zwischen Abflüssen und Großwetterlagen bestehen. Den ersten Schwerpunkt der vorliegenden Dissertation bildet die deutschlandweite Analyse von 145 Abflusszeitreihen für den Zeitraum 1951–2002. Acht Hochwasserindikatoren, die verschiedene Aspekte der Hochwasser-Charakteristik beleuchten, werden analysiert und bezüglich möglicher Trends getestet. Um saisonalen Unterschieden in der Hochwassercharakteristik der einzelnen Regionen gerecht zu werden, werden neben jährlichen auch saisonale Reihen untersucht. Die Analyse von Maximalreihen wird durch Schwellenwertanalysen ergänzt, die die Hochwasserdynamik bzgl. Frequenz und Magnitude detaillierter erfassen. Die Daten werden auf verschiedenen Skalen untersucht: sowohl für jeden einzelnen Pegel wie auch für ganze Regionen und Einzugsgebiete. Nicht nur die Analyse der Abflussdaten bietet die Möglichkeit, Bewertungen für die zukünftige Hochwasserabschätzung abzuleiten. Auch Großwetterlagen bilden eine bedeutende Informationsquelle über die Hochwassergefahr, da in der Regel nur ausgewählte Zirkulationsmuster die Entstehung von Hochwasser begünstigen. Die saisonal differenzierte Untersuchung der Großwetterlagen und die Prüfung einer Korrelation zu den Abflüssen an 122 mesoskaligen Einzugsgebieten bilden deshalb den zweiten Schwerpunkt der Arbeit. Hierzu werden tägliche Daten der über Europa dominierenden Großwetterlage (nach Hess und Brezowsky) mit Hilfe verschiedener Indikatoren untersucht. Analysen zum Hochwasserpotential der einzelnen Wetterlagen und weiterer Einflussfaktoren werden für das mesoskalige Einzugsgebiet der Mulde in einer separaten Studie durchgeführt. Für diese Detail-Studie stehen 15 Abflusszeitreihen verschiedener Länge im Zeitraum 1909–2002 zur Verfügung. Um die Daten von Abflüssen und Großwetterlagen bezüglich vorhandener Trends zu testen, werden verschiedene Methoden genutzt. Der Mann-Kendall Test wird mit einem Signifikanzniveau von 10% (zweiseitiger Test) angewendet, was statistisch sichere Bewertungen ermöglicht. Neben der Prüfung der gesamten Datenreihe werden multiple zeitlich-variable Trendanalysen mit Hilfe eines Resampling-Ansatzes durchgeführt. Darüber hinaus werden räumlich differenzierte Analysen durchgeführt, um die saisonale Hochwassercharakteristik einzelner Regionen besser zu verstehen. Diese werden durch Tests zur Feldsignifikanz der Trends ergänzt. Mit der vorliegenden Arbeit kann gezeigt werden, dass die Hochwassergefahr für einzelne Regionen im Winterhalbjahr signifikant steigt. Davon sind insbesondere Gebiete in Mitteldeutschland betroffen. Die Verschärfung der Hochwassergefahr durch eine längere Persistenz ausgewählter Großwetterlagen konnte ebenfalls für das Winterhalbjahr nachgewiesen werden. Sommerhochwasser zeigen zwar ebenfalls steigende, aber auch fallende Trends, die räumlich geclustert sind. Im Elbe- und Weser-Einzugsgebiet sinken die Abflüsse signifikant, im Donau- und Rheineinzugsgebiet steigen sie nachweisbar. Darüber hinaus ist eine signifikante Abnahme der Anzahl verschiedener Großwetterlagen sowohl im Sommer als auch im Winter zu verzeichnen. Bzgl. der Studie zum Mulde-Einzugsgebiet konnte ein zweigeteiltes Hochwasserregime nachgewiesen werden. In den Wintermonaten treten häufig kleine Hochwasser auf, die auch die Mehrheit der jährlichen Maximalwerte bilden. Sommerhochwasser sind seltener, können aber extreme Ausmaße annehmen. Ein Vergleich der geschätzten Jährlichkeiten mit verschiedenen Zeitreihen zeigt die Notwendigkeit der Berücksichtigung saisonaler Aspekte für die Bemessung von Hochwassern. Aufgrund der Ergebnisse müssen die bisher genutzten stationären Verfahren als nicht mehr geeignet bewertet werden. Es wird daher die Nutzung instationärer Verfahren zur Abschätzung von Extremhochwasser und der damit verbundenen Bemessung von Schutzmaßnahmen empfohlen, um den teilweise vorliegenden Trends in den Daten Rechnung zu tragen. Durch diesen Ansatz ist es möglich, zeitlich dynamische Veränderungen im Hochwassergeschehen stärker zu berücksichtigen. Darüber hinaus sollten saisonale Aspekte des Einzugsgebietes Eingang in die Gefahrenabschätzung finden.
77

Temporal and spatial trends of organohalogens in guillemot (Uria aalge) from North Western Europe

Jörundsdóttir, Hrönn January 2009 (has links)
The Arctic and sub-Arctic region of the North Atlantic is a remote area, also in relations to environmental contaminants, such as POPs, BFRs and last but not least, PFCs. Both the BFRs and PFCs are considered emerging pollutants of significant environmental concern. The main objective of this thesis is to increase the knowledge and understanding of organohalogen compound distribution in the Nordic environment, their occurrence in biota and change over time. The temporal change of environmental contaminants in the Baltic Sea was monitored over the years 1971 to 2001, with emphasis on BCPS. Further, the pollution profile of the Nordic region was investigated by using common guillemot eggs. Further, to investigate a single remote site, Iceland, in more depth, eggs from seven marine bird species were collected and analysed. Both the organohalogen compounds mentioned above and their metabolites were investigated. The study focused also on an inter-species difference in the bird’s capability of metabolising xenobiotics. All environmental pollutants investigated in the Baltic Sea show decreasing levels over the time period investigated. BCPS showed a remarkably small change over time compared to other compounds. These results reinforce the previous findings, indicating the North Atlantic as remote where the concentrations of the organohalogens are lower compared to Europe in general. There are some exceptions however; the concentration of HCB is ubiquitously distributed across the study area. Further, the spatial trends of the PFCs are complicated and differ within the PFC group. When comparing bird species from Iceland, the concentration of organohalogens mainly depends on trophic level, while migration seems to contribute to a lesser extent. There are some similarities in the metabolism between the bird species investigated. However, the guillemot seems to distinguish itself from other marine birds, with a different composition of metabolites, indicating a different metabolic capacity. In conclusion, even human populations living in remote areas need to minimise the release of pollutants to the environment. Long term, well organised, and extensive governmental monitoring programs are highly recommended to follow the quality the environment and to detect any immediate and/or new threats of chemical pollutants.
78

Research Trends In Ceit Ms And Phd. Theses In Turkey: A Content Analysis

Ugur Erdogmus, Feray 01 February 2009 (has links) (PDF)
The main aim of this study is to look for trends in the instructional technology field in Turkey and to visualize general tendencies in the field in research topics, research types, and methodologies. Content analysis research design was used in this study. In this study, the unit of analysis was MS theses and PhD. theses published in instructional technology departments in Turkey, and the researcher aimed to analyze all of the population. Hence, 215 MS theses and 32 PhD. theses were analyzed in this study. The data were categorized according to characteristics of the MS theses and PhD. theses (author, university, advisor, and publication year), research topics, research methods, sample type, sample size, data collection methods and research settings. These categories were statistically analyzed. In these statistical analyses both frequencies of these categories and fluctuations of these categories in time were analyzed. The findings of the study indicated that most of the MS theses were published in the Middle East Technical University and most of the dissertations were published in Ankara University. In addition to this, most of the MS theses and PhD. theses used quantitative research methods, and experimental studies were the most popular type. Not surprisingly, the study results revealed that convenient sampling was the most preferred sampling method and most of the studies used 31 &ndash / 100 subjects in their samples. Moreover, questionnaires, aptitude tests and interview schedules were the most common data gathering instruments used, and higher education was the most preferred research environment for the studies analyzed. Finally, most of the MS theses and PhD. theses focused on delivery system media formats, comparison studies and learner variables.
79

What drives e-business trends? : With a focus on customer oriented trends and service digitization

Lindholm Johnsson, Anton January 2008 (has links)
<p>In this thesis I am going to investigate the trends within e-business, what it is that drive</p><p>these trends and why these drivers are of such importance. I chose this subject since I have</p><p>found it very interesting and useful in my career because of the importance it embraces in</p><p>today’s business world.</p><p>The aspect of e-commerce has changed a lot lately to in the beginning of the 1990s be</p><p>about being present on the Internet with a web site, to being about transactions, meaning</p><p>to buy or sell through digital media at the end of the 1990s, to today be about being used to</p><p>make profitability – an era that can be called e-business, because it is now that e-business</p><p>finally gets its big breakthrough and starts to be recognized as a necessity for companies to</p><p>survive. As long as e-business has existed so have trends in the same matter. What will be</p><p>the trends of e-business in the future? Impossible to say of course, but by taking today’s</p><p>major trends into consideration, and to look at what drives these trends might have, will</p><p>make it possible to get a glimpse of the future of this relatively new business phenomenon</p><p>called e-business.</p><p>To get the best result possible of my thesis I have made a wide literature study in the subject</p><p>by reading and examine accurate literature and articles as well as carried out interviews</p><p>with different IT-gurus and other persons that is thought to withhold a lot of information</p><p>about my chosen subject.</p><p>I have focused on two major trends being customer oriented trends and service digitization.</p><p>Customer oriented trends are trends which have their focus towards customers such</p><p>as customer service, offering more product choices and to have integrated solutions. Service</p><p>digitization is the transformation of paper-based transactions into the new integrated</p><p>multi-channel processes. The driver I have found of most significance and therefore focused</p><p>on is customers. Customers are important as drivers since they have adopted a new</p><p>role in the business process. Customers nowadays have found a way to let their voices to</p><p>be heard. With the help of blogs, social networks and wikis over the Internet they can express</p><p>their feelings and suggestions about products as well as companies and have so to say</p><p>gained a more active role as customers to also taking part of the development. This voice</p><p>of the customers is highly essential to listen to if you as a company want to survive in a</p><p>business world where customers get more and more power.</p><p>After finishing this study I came up with the importance of service, and especially customer</p><p>service as well of personalization and customization (to personalize the shopping experience</p><p>for the customer). Another important conclusion is the importance of customers,</p><p>both as trends to focus on, as well as drivers behind these trends.</p><p>ii</p><p>Acknowledgements</p>
80

Time trends hos gymnasieungdomar i Sverige- förändras självrapporterade psykiska besvär från 1970-talet till 2018? / Time trends in youths in Sweden- Does self-reported mental health change from 1973/74 to 2018?

Enlund Tuuvas, Jonas, Mörlin, Anders January 2018 (has links)
No description available.

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