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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

An investigation of the relationship between seabed type and benthic and bentho-pelagic biota using acoustic techniques

Siwabessy, Paulus Justiananda Wisatadjaja January 2001 (has links)
A growing recognition of the need for effective marine environmental management as a result of the increasing exploitation of marine biological resources has highlighted the need for high speed ecological seabed mapping. The practice of mapping making extensive use of satellite remote sensing and airborne platforms is well established for terrestrial management. Marine biological resource mapping however is not readily available except in part from that derived for surface waters from satellite based ocean colour mapping. Perhaps the most fundamental reason is that of sampling difficulty, which involves broad areas of seabed coverage, irregularities of seabed surface and depth. Conventional grab sample techniques are widely accepted as a standard seabed mapping methodology that has been in use long before the advent of acoustic techniques and continue to be employed. However. they are both slow and labour intensive, factors which severely limit the spatial coverage available from practical grab sampling programs. While acoustic techniques have been used for some time in pelagic biomass assessment, only recently have acoustic techniques been applied to marine biological resource mapping of benthic communities. Two commercial bottom classifiers available in the market that use normal incidence echosounders are the RoxAnn and QTC View systems. Users and practitioners should be cautious however when using black box implementations of the two commercial systems without a proper quality control over raw acoustic data since some researchers in their studies have indicated problems with these two bottom classifiers such as, among others, a depth dependence. In this thesis, an alternative approach was adopted to the use of echosounder returns for bottom classification. / The approach used in this study is similar to,~ used in the commercial RoxAnn system. In grouping bottom types however, Multivariate analysis (Principal Component Analysis and Cluster Analysis) was adopted instead of the allocation system normally used in the RoxAnn system, called RoxAnn squares. In addition, the adopted approach allowed for quality control over acoustic data before further analysis was undertaken. As a working hypothesis, it was assumed that on average 0 and aE2 = 0 where E1 and E2 are the roughness and hardness indices, respectively, and RO is the depth. For roughness index (E1), this was achieved by introducing a constant angular integration interval to the tail of the first OM returns whereas for hardness index (E2), this was achieved by introducing a constant depth integration interval. Since three different frequencies, i.e. 12, 38 and kHz, were operated, Principal Component Analysis was used here to reduce the dimensionality of roughness and hardness indices, formed from the three operated qu frequencies separately. The k-means technique was applied to the first principal component of roughness index and the first principal comp component of hardness index to produce separable seabed types. This produced four separable seabed types, namely soft-smooth, soft-rough, hard-smooth and hard-rough seabeds. / Principal Component Analysis was also used to reduce the dimensionality of the area backscattering coefficient sA, a relative measure of biomass of benthic mobile biota. The bottom classification results reported here appear to be robust in that, where independent ground truthing was available, acoustic classification was generally congruent with ground truth results. When investigating the relationship between derived bottom type and acoustically assessed total biomass of benthic mobile biota, no trend linking the two parameters, however, appears. Nevertheless, using the hierarchical agglomerative technique applied to a set of variables containing average first principal component of the area backscattering coefficient sA, the average first principal component of roughness and hardness indices, the centroids of first principal component of roughness and hardness indices associated with the four seabed types and species composition of fish group of the common species in trawl stations available, two main groups of quasi acoustic population are observed in the North West Shelf (NWS) study area and three groups are observed in the South East Fisheries (SEF) study area. The two main groups of quasi acoustic population in the NWS study area and the three main groups of quasi acoustic population in the study area are associated with the derived seabed types and fish groups of the common species.
702

三向資料的主成分分析 / 3-way data principal component analysis

趙湘琪, Chao, Hsiang Chi Unknown Date (has links)
傳統的主成分分析(principal component analysis)法,只能分析二式二向的資料(2-mode 2-way data),若是要處裡三向三式的資料(3-mode 3-way data)或是更多維的資料,則必須用其它的方法。例如將某一向資料取平均數,再做分析。此法雖然可行,但卻忽略三向資料間可能潛藏的相關性。且社會科學的研究日趨複雜,三向資料也就更常見到,而我們可能也對三向資料間彼此的關聯感到興趣。因此在1960、1970年代,學者開始研究將主成分分析的模型加以擴展成適合分析三向資料的模型。本文除了介紹三向資料主成分分析所使用的Tucker3模型及其參數估計法外,也以28家股票上市公司為實例,探討資本結構影響因素於五年間(1989~1993年)在不同公司群組間的變化情形。
703

世代和年代生育率、死亡率模型的比較 / Comparing fertility and mortality models in the view of cohort and period

李心維, Lee, Sin Wei Unknown Date (has links)
臺灣婦女生育率下降快速,近年來屢創新低,堪稱全球生育率最低的國家,總生育率自民國89年1.68、降為民國98年1.03,民國99年甚至降至0.90以下,提升生育率成為政府施政的重要課題。因為資料限制,生育率大多以總生育率(Total Fertility Rate)表示,而非較能反映婦女一生生育總數的世代完成生育率(Completed Cohort Fertility Rate)。這兩者間存有不少差異,以生育率下降的臺灣為例,總生育率會因生育時機遞延而低估世代生育率,以總生育率詮釋生育率可能有瑕疵。有鑒於此,本文以比較「世代」及「年代」兩者的差異,以生育率及死亡率為研究對象,探討較適宜描述臺灣特性的模型。 由於世代生育率會有資料不足的問題,本文使用外推法(Extrapolation)補足年齡較高(如35歲以上)的婦女生育率,並以四種模型估計年代生育率與世代生育率,包括Gamma模型、Gompertz模型、主成份分析(Principle Component Analysis)與單一年齡組個別估計法,希望找出適合預測臺灣世代完成生育率的模型。除了台灣資料,也用日本、法國與美國的世代生育率資料,比較各國世代生育率模型的異同。另外,本文也以世代及年代兩種觀點,類似生育率的探討方式,比較常用死亡率模型的優劣。 不論是生育率或是死亡率資料,配適模型結果皆以世代資料可得到較好的估計結果,生育率以單一年齡組個別估計法為最佳的模型,死亡率則以Gamma模型、主成份分析、單一年齡組個別估計法為較佳的模型。 / Taiwan’s fertility rates have been declining radically in recent years, much faster than most countries in the world. For example, the total fertility rate (TFR) is 1.68 in 2000, 1.03 in 2009, and even reduces to 0.90 in 2010. Therefore, one of the top priorities for Taiwan government policies is to enhance the willingness of having children. Due to the data availability, the TFR is used more often, although the completed cohort fertility rate (CFR) is a more reasonable measurement. However, previous studies showed that the TFR is likely to be influenced by the deferring (i.e., tempo effect) of childbearing and produces misleading results. In order to measure the effect of deferring childbearing, this study focuses on exploring the difference of measures in the view of cohort and period (especially the CFR vs. TFR) and evaluates which fertility and mortality model is more appropriate for Taiwan. Because there are fewer complete cohort fertility data, we use extrapolation to make up the higher age-group fertility data (such as aged 35 and above). We consider four fertility models in this study, including Gamma model, Gompertz model, principal component analysis, and individual group estimation. We use the data from Taiwan, Japan, France and United State data to evaluate these fertility models. The results indicate that the parametric models (Gamma and Gompertz) have the worst performance, probably due to the rapid change of fertility behaviors. In addition, similar to evaluating the fertility models, we compare the performance of frequently used mortality models using the cohort and period mortality data. The result shows that using cohort data to estimate fertility and mortality is better than period data. Also individual group estimation is the best model to fit fertility; the better models to fit mortality are Gamma model, principle component analysis and individual group estimation.
704

ToF-SIMS Investigations on Dental Implant Materials and Adsorbed Protein Films

Bernsmann, Falk 13 July 2007 (has links) (PDF)
In this work the two experimental dental implant materials FAT and FAW, made of fluoroapatite particles embedded in polymer matrices, and films of the proteins lysozyme, amylase and bovine serum albumin (BSA), adsorbed to the two dental implant materials, were investigated with time-of-flight secondary ion mass spectrometry (ToF-SIMS) and the multivariate data analysis technique discriminant principal component analysis (DPCA).
705

An Optimization-Based Approach to the Funding of a Loan Portfolio

Brushammar, Tobias, Windelhed, Erik January 2004 (has links)
<p>This thesis grew out of a problem encountered by a subsidiary of a Swedish multinational industrial corporation. This subsidiary is responsible for the corporation’s customer financing activities. In the thesis, we refer to these entities as the Division and the Corporation. The Division needed to find a new approach to finance its customer loan portfolio. Risk control and return maximization were important aspects of this need. The objective of this thesis is to devise and implement a method that allows the Division to make optimal funding decisions, given a certain risk limit. </p><p>We propose a funding approach based on stochastic programming. Our approach allows the Division’s portfolio manager to minimize the funding costs while hedging against market risk. We employ principal component analysis and Monte Carlo simulation to develop a multicurrency scenario generation model for interest and exchange rates. Market rate scenarios are used as input to three different optimization models. Each of the optimization models presents the optimal funding decision as positions in a unique set of financial instruments. By choosing between the optimization models, the portfolio manager can decide which financial instruments he wants to use to fund the loan portfolio. </p><p>To validate our models, we perform empirical tests on historical market data. Our results show that our optimization models have the potential to deliver sound and profitable funding decisions. In particular, we conclude that the utilization of one of our optimization models would have resulted in an increase in the Division’s net income over the past 3.5 years.</p>
706

Multivariate non-invasive measurements of skin disorders

Nyström, Josefina January 2006 (has links)
<p>The present thesis proposes new methods for obtaining objective and accurate diagnoses in modern healthcare. Non-invasive techniques have been used to examine or diagnose three different medical conditions, namely neuropathy among diabetics, radiotherapy induced erythema (skin redness) among breast cancer patients and diagnoses of cutaneous malignant melanoma. The techniques used were Near-InfraRed spectroscopy (NIR), Multi Frequency Bio Impedance Analysis of whole body (MFBIA-body), Laser Doppler Imaging (LDI) and Digital Colour Photography (DCP).</p><p>The neuropathy for diabetics was studied in papers I and II. The first study was performed on diabetics and control subjects of both genders. A separation was seen between males and females and therefore the data had to be divided in order to obtain good models. NIR spectroscopy was shown to be a viable technique for measuring neuropathy once the division according to gender was made. The second study on diabetics, where MFBIA-body was added to the analysis, was performed on males exclusively. Principal component analysis showed that healthy reference subjects tend to separate from diabetics. Also, diabetics with severe neuropathy separate from persons less affected.</p><p>The preliminary study presented in paper III was performed on breast cancer patients in order to investigate if NIR, LDI and DCP were able to detect radiotherapy induced erythema. The promising results in the preliminary study motivated a new and larger study. This study, presented in papers IV and V, intended to investigate the measurement techniques further but also to examine the effect that two different skin lotions, Essex and Aloe vera have on the development of erythema. The Wilcoxon signed rank sum test showed that DCP and NIR could detect erythema, which is developed during one week of radiation treatment. LDI was able to detect erythema developed during two weeks of treatment. None of the techniques could detect any differences between the two lotions regarding the development of erythema.</p><p>The use of NIR to diagnose cutaneous malignant melanoma is presented as unpublished results in this thesis. This study gave promising but inconclusive results. NIR could be of interest for future development of instrumentation for diagnosis of skin cancer.</p>
707

Explorative Multivariate Data Analysis of the Klinthagen Limestone Quarry Data / Utforskande multivariat analys av Klinthagentäktens projekteringsdata

Bergfors, Linus January 2010 (has links)
<p> </p><p>The today quarry planning at Klinthagen is rough, which provides an opportunity to introduce new exciting methods to improve the quarry gain and efficiency. Nordkalk AB, active at Klinthagen, wishes to start a new quarry at a nearby location. To exploit future quarries in an efficient manner and ensure production quality, multivariate statistics may help gather important information.</p><p>In this thesis the possibilities of the multivariate statistical approaches of Principal Component Analysis (PCA) and Partial Least Squares (PLS) regression were evaluated on the Klinthagen bore data. PCA data were spatially interpolated by Kriging, which also was evaluated and compared to IDW interpolation.</p><p>Principal component analysis supplied an overview of the variables relations, but also visualised the problems involved when linking geophysical data to geochemical data and the inaccuracy introduced by lacking data quality.</p><p>The PLS regression further emphasised the geochemical-geophysical problems, but also showed good precision when applied to strictly geochemical data.</p><p>Spatial interpolation by Kriging did not result in significantly better approximations than the less complex control interpolation by IDW.</p><p>In order to improve the information content of the data when modelled by PCA, a more discrete sampling method would be advisable. The data quality may cause trouble, though with sample technique of today it was considered to be of less consequence.</p><p>Faced with a single geophysical component to be predicted from chemical variables further geophysical data need to complement existing data to achieve satisfying PLS models.</p><p>The stratified rock composure caused trouble when spatially interpolated. Further investigations should be performed to develop more suitable interpolation techniques.</p>
708

Ifrågasatta företagare : Konkursförvaltares syn på kvinnor och män som företagsgäldenärer under 1900-talet / Competent Business Owners? : How Receivers Viewed Women and Men in Business Bankruptcy during the 20th century

Axelsson, Maria January 2006 (has links)
<p>The principle purpose of this thesis has been to study and analyse the conception of men and women in business bankruptcy during the 20th century. The analysis is built on a theoretical gender perspective and, combining this view and business and bankruptcy research, the thesis has focused on five themes: business networks, bank contacts, business competence, business characteristics and finally bankruptcy causes. These themes have been in focus when analysing bankruptcies in Uppsala 1920-1939, 1988, 1992 and 1996. A questionnair- and interview study with receivers active in Sweden 2001 has also been carried out. From the bankruptcy cases that have been studied, no specific gender differences have really been discovered. There were some variations between men and women, but it is very hard to claim that these are related to the sex of the debtor more than to the branch or to the individuals. Changes from the inter-war period to the latter part of the 20th century are in these respects also small. The image that the receivers gave through the questionnaire and interview study indicates on the other hand that there existed a conception that men and women seemed different as business owners. It is obvious that there were many receivers who thought that women were different from men in a situation of business bankruptcy, even though several of them stated that they did not beleive in any gender differences.</p>
709

Developing a methodology to account for commercial motor vehicles using microscopic traffic simulation models

Schultz, Grant George 30 September 2004 (has links)
The collection and interpretation of data is a critical component of traffic and transportation engineering used to establish baseline performance measures and to forecast future conditions. One important source of traffic data is commercial motor vehicle (CMV) weight and classification data used as input to critical tasks in transportation design, operations, and planning. The evolution of Intelligent Transportation System (ITS) technologies has been providing transportation engineers and planners with an increased availability of CMV data. The primary sources of these data are automatic vehicle classification (AVC) and weigh-in-motion (WIM). Microscopic traffic simulation models have been used extensively to model the dynamic and stochastic nature of transportation systems including vehicle composition. One aspect of effective microscopic traffic simulation models that has received increased attention in recent years is the calibration of these models, which has traditionally been concerned with identifying the "best" parameter set from a range of acceptable values. Recent research has begun the process of automating the calibration process in an effort to accurately reflect the components of the transportation system being analyzed. The objective of this research is to develop a methodology in which the effects of CMVs can be included in the calibration of microscopic traffic simulation models. The research examines the ITS data available on weight and operating characteristics of CMVs and incorporates this data in the calibration of microscopic traffic simulation models. The research develops a methodology to model CMVs using microscopic traffic simulation models and then utilizes the output of these models to generate the data necessary to quantify the impacts of CMVs on infrastructure, travel time, and emissions. The research uses advanced statistical tools including principal component analysis (PCA) and recursive partitioning to identify relationships between data collection sites (i.e., WIM, AVC) such that the data collected at WIM sites can be utilized to estimate weight and length distributions at AVC sites. The research also examines methodologies to include the distribution or measures of central tendency and dispersion (i.e., mean, variance) into the calibration process. The approach is applied using the CORSIM model and calibrated utilizing an automated genetic algorithm methodology.
710

Removal processes in sewage treatment plants : Sludge quality and treatment efficiency of structurally diverse organic compounds

Olofsson, Ulrika January 2012 (has links)
Large and ever-increasing numbers of chemicals, including large quantities of a broad spectrum of organic compounds are used in modern society. More than 30 000 of the more than 100 000 chemical substances registered in the EU are estimated to be daily used, of which many will be discharged into the waste-streams handled by municipal sewage treatment plants (STPs). The main objective of the work underlying this thesis was to improve understanding of the relationships between the characteristics of sewage contaminants and their sewage treatment efficiency. Further objectives were to examine the relationships between socio-economic uses of chemicals and sludge quality, and the effects of regulatory actions on sludge quality. The quality of the sewage sludge and the levels and distribution patterns of the sludge contaminants, both within and between the STPs, seem to remain quite constant over time. The overall findings indicate that the levels of contaminants in sewage sludge seem to be largely independent of the location, size and treatment techniques applied at the STPs, and generally, of the types of human activity connected to them. The total and relative concentrations of the sludge contaminants were found to be fairly constant on a dry weight basis, with some exceptions, indicating that the pollutants originate from broad usage and diffuse dispersion rather than (industrial) point sources. The proportion of cyclic methylsiloxanes recovered in sludge seems to strongly depend on their vapour pressure, which decreases with the number of siloxane units. The higher water solubility and biodegradability of organophosphorus flame retardants and plasticizers than polybrominated diphenyl ethers (PBDEs) were also reflected in lower percentages (relative to their national use) found in sludge. Significant time-trends in levels of a-third of the sludge contaminants included in the annual national measurement program were detected over a period of seven years. The levels of compounds displaying significant time-trends generally decreased following declines in the quantities used nationally. However, a quarter of these compounds showed increasing trends, of which the linear methylsiloxanes followed the same trend as used quantities. The decaBDE was also found to be increasing in sludge, probably as a result of the phase-out of pentaBDE and octaBDE. The results indicate that the STP removal efficiency of anthropogenic substances, in Sweden, is generally good and that STPs, at least those in cold climates, do not efficiently remove certain polar contaminants. A non-targeted screening (by use of environmetrics and GCxGC-TOFMS) was performed and found to fulfil the objective to assess the STP removal efficiency, with emphasis to systematically analyse which compound classes that are not efficiently removed using the current STP technology. Many polar aromatic compounds were identified to be poorly removed. The acquired data on levels, profiles and variations in sludge contaminants (sludge quality) extend both the available information and understanding of the degree and nature of sludge contamination, which should help attempts to track changes in its contaminants and revisions, if necessary, of guideline values. This thesis also contributes to improve the knowledge base for the development of future STP technologies, and that archived sewage sludge can be used in retrospective analysis of new and emerging pollutants.

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