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Search Results: 1 - 10 of 413402 matches for " U. Müller "
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Estimating linear functionals in nonlinear regression with responses missing at random
Ursula U. Müller
Statistics , 2009, DOI: 10.1214/08-AOS642
Abstract: We consider regression models with parametric (linear or nonlinear) regression function and allow responses to be ``missing at random.'' We assume that the errors have mean zero and are independent of the covariates. In order to estimate expectations of functions of covariate and response we use a fully imputed estimator, namely an empirical estimator based on estimators of conditional expectations given the covariate. We exploit the independence of covariates and errors by writing the conditional expectations as unconditional expectations, which can now be estimated by empirical plug-in estimators. The mean zero constraint on the error distribution is exploited by adding suitable residual-based weights. We prove that the estimator is efficient (in the sense of H\'{a}jek and Le Cam) if an efficient estimator of the parameter is used. Our results give rise to new efficient estimators of smooth transformations of expectations. Estimation of the mean response is discussed as a special (degenerate) case.
The Entlebuchers: people from the back of beyond?
U. Müller ,N. Backhaus
Social Geography (SG) & Discussions (SGD) , 2007, DOI: 10.5194/sg-2-11-2007
Abstract: Incorporated knowledge is structuring the way actors comport themselves and interact with their environment. Knowledge feeds on experiences, especially on recurrent or particularly intense ones. In our media-dominated societies, recurring visual representations of certain facts have a special formative power. Therefore, image analysis provide access to often un-reflected mental images that are to a certain degree the motivations for actions. With the research project "The power of images" we analysed how images influence sustainable regional development. As case study we analysed the self-determined re-definition of the Swiss Alpine region of Entlebuch as a biosphere reserve. Of the range of approaches open to us, a human geographical perspective was chosen: We were particularly interested in how visual representations suggest certain interactions with space. In order to get an overview of entire, image-laden publications, a quantitative approach was taken using categories of spatial appropriation. Results show that the outside view conceives the Entlebuch as a largely natural, idyllic region. In terms of the visualization of sustainable development, the biosphere Entlebuch appears to be a nature and landscape conservation project. The inside view (before the crucial poll, where people decided whether to obtain the status of a biosphere reserve or not) looked totally different: In the voter's information brochure the Entlebuch is presented as a (relatively modern) living and production space. Nearly no visual images depicting the Entlebuch as natural environment and idyllic cultural landscape respectively were published. Taking the historical and socio-economical context of the Entlebuch into consideration, the promoters of the biosphere reserve wanted to get rid of its backward image. However, two years after the poll the same promoters changed the way Entlebuch is presented in order to address the values of the target groups outside the region. Therefore, mere aesthetic images of nature and cultural landscapes were published. The study shows that image analysis can provide access to mental images that form part of practical knowledge (or even the unconscious) rather than of verbalised knowledge, for instance those which image producers might not be able to explain well during an interview. We can also detect the use of stereotypes, to which the image producers might not always want to admit. The developed method of image analysis is an attempt to process and analyse a great number of images without neglecting their context nor the reference to the research question.
Data of hydraulic properties of North East and North Central German soils
U. Schindler ,L. Müller
Earth System Science Data (ESSD) & Discussions (ESSDD) , 2010, DOI: 10.5194/essd-2-189-2010
Abstract: The paper presents a data base of soil physical and hydrological properties of North East and North Central German soils. Included are measured data of the soil water retention curve and the unsaturated hydraulic conductivity function. Information on geo-reference, soil type and horizon are given. Soil hydraulic functions were measured with the evaporation method. The applied measurement technique is described and information to actual innovations and advanced technology is given. Additional soil physical data like particle size distribution, dry bulk density, organic matter content and other variables are presented. The data base includes original measurement results of 278 organic and of 497 mineral soil samples from 103 sites. The mineral soils cover a wide range of texture classes and dry bulk densities. The organic soils and samples represent different states of decomposition and mineralization. Furthermore hydraulic functions are included of soils anthropogenically altered by deep plough sand covering measures.
The Entlebuchers: people from the back of beyond?
U. Müller,N. Backhaus
Social Geography Discussions , 2006,
Abstract: Incorporated knowledge is structuring the way actors comport themselves and interact with their environment. Knowledge feeds on experiences, especially on recurrent or particularly intense ones. In our media-dominated societies, recurring visual representations of certain facts have a special formative power. Therefore, image analysis provide access to often un-reflected mental images that are to a certain degree the motivations for actions. With the research project "The power of images'' we analysed how images influence sustainable regional development. As case study we analysed the self-determined re-definition of the Swiss Alpine region of Entlebuch as a biosphere reserve. Of the range of approaches open to us, a human geographical perspective was chosen: We were particularly interested in how visual representations suggest certain interactions with space. In order to get an overview of entire, image-laden publications, a quantitative approach was taken using categories of spatial appropriation. Results show that the outside view conceives the Entlebuch as a largely natural, idyllic region. In terms of the visualization of sustainable development, the biosphere Entlebuch appears to be a nature and landscape conservation project. The inside view (before the crucial poll, where people decided whether to obtain the status of a biosphere reserve or not) looked totally different: In the voter's information brochure the Entlebuch is presented as a (relatively modern) living and production space. Nearly no visual images depicting the Entlebuch as natural environment and idyllic cultural landscape respectively were published. Taking the historical and socio-economical context of the Entlebuch into consideration, the promoters of the biosphere reserve wanted to get rid of its backward image. However, two years after the poll the same promoters changed the way Entlebuch is presented in order to address the values of the target groups outside the region. Therefore, mere aesthetic images of nature and cultural landscapes were published. The study shows that image analysis can provide access to mental images that form part of practical knowledge (or even the unconscious) rather than of verbalised knowledge, for instance those which image producers might not be able to explain well during an interview. We can also detect the use of stereotypes, to which the image producers might not always want to admit. The developed method of image analysis is an attempt to process and analyse a great number of images without neglecting their context nor the reference to the re
Recycling of radioactively contaminated scrap from the nuclear cycle and spin-off for other application
Quade, U.,Müller, W.
Revista de Metalurgia , 2005,
Abstract: In the 1980ies, Siempelkamp foundry in Krefeld, Germany, developed a process to melt medium and slightly radioactive metals from decommissioning and maintenance works in nuclear power plants. Since 1989, in the CARLA melting plant which is licensed according to the German radiation protection ordinance (StrlSchV), metals are being molten which, for the largest part, can be reused. Since 1998, in a second plant, the GERTA melting plant, metals with a content of mercury up to 1 weight %, natural radioactivity up to 500 Bq/g and other chemical contaminations are being molten and completely decontaminated, so that these metals can be reused in the steel cycle. The following text is describing the melting process, acceptance criteria for contaminated scrap and recycling paths for the produced ingots and slags. La fundición Siempelkamp en Krefeld, Alemania, desarrolló, en los a os 80, un proceso para fundir metales mediana y levemente radioactivos, procedentes de reparaciones o desmantelamiento de plantas nucleares. En la planta de fundición CARLA, que cumple los requisitos del decreto de protección contra radiaciones de la República Federal de Alemania, se funden metales desde 1989, de los cuales la mayor parte puede ser utilizada nuevamente. Desde 1998, en una segunda planta, fundición GERTA, se funden y descontaminan totalmente, metales de hasta un 1 % de peso de mercurio, con una radioactividad natural de hasta 500 Bq/g y con otros contaminantes químicos. De este modo los metales pueden ser nuevamente utilizados en el ciclo metálico. El texto adjunto describe el método para el fundido, los criterios para aceptar chatarra contaminada y las vías de utilización para los bloques de metal y escorias generadas en el proceso.
Data of hydraulic properties of North East and Central German soils
U. Schindler,L. Müller
Earth System Science Data Discussions , 2010, DOI: 10.5194/essdd-3-131-2010
Abstract: The paper presents a data base of soil hydrological properties of North East and Central German soils. Included are measured data of the soil water retention curve and the unsaturated hydraulic conductivity function. Information to geo reference, soil type and horizon are given. Additional soil physical data like particle size distribution, dry bulk density, organic matter content and other variables are presented and its measurement is methodically described. The data base includes original measurement results of 278 organic and of 497 mineral soil samples from 103 sites. The mineral soils cover a wide range of texture classes and dry bulk densities. The organic soils and samples vary in dependence on the degree of decomposition and mineralization, the dry bulk density and the total porosity.
Summability of double sequences by weighted mean methods and Tauberian conditions for convergence in Pringsheim's sense
Ferenc Móricz,U. Stadtmüller
International Journal of Mathematics and Mathematical Sciences , 2004, DOI: 10.1155/s0161171204403329
Abstract: After a brief summary of Tauberian conditions for ordinary sequences of numbers, we consider summability of double sequences of real or complex numbers by weighted mean methods which are not necessarily products of related weighted mean methods in one variable. Our goal is to obtain Tauberian conditions under which convergence of a double sequence follows from its summability, where convergence is understood in Pringsheim's sense. In the case of double sequences of real numbers, we present necessary and sufficient Tauberian conditions, which are so-called one-sided conditions. Corollaries allow these Tauberian conditions to be replaced by Schmidt-type slow decrease conditions. For double sequences of complex numbers, we present necessary and sufficient so-called two-sided Tauberian conditions. In particular, these conditions are satisfied if the summable double sequence is slowly oscillating.
Assessment of urban vulnerability towards floods using an indicator-based approach – a case study for Santiago de Chile
A. Müller,J. Reiter,U. Weiland
Natural Hazards and Earth System Sciences (NHESS) & Discussions (NHESSD) , 2011, DOI: 10.5194/nhess-11-2107-2011
Abstract: Regularly occurring flood events do have a history in Santiago de Chile, the capital city of Chile and study area for this research. The analysis of flood events, the resulting damage and its causes are crucial prerequisites for the development of risk prevention measures. The goal of this research is to empirically investigate the vulnerability towards floods in Santiago de Chile as one component of flood risk. The analysis and assessment of vulnerability is based on the application of a multi-scale (individual, household, municipal level) set of indicators and the use of a broad range of data. The case-specific set of indicators developed in this study shows the relevant variables and their interrelations influencing the flood vulnerability in the study area. It provides a decision support tool for stakeholders and allows for monitoring and evaluating changes over time. The paper outlines how GIS, census, and remote sensing data as well as household surveys and expert interviews are used as an information base for the derivation of a vulnerability map for two municipalities located in the eastern part of Santiago de Chile. The generation of vulnerability maps representing the two different perspectives of local decision makers (experts) and affected households is exemplified and discussed using the developed methodology.
Problems with estimation and interpretation of oceanic heat transport – conceptual remarks for the case of Fram Strait in the Arctic Ocean
U. Schauer,A. Beszczynska-Mller
Ocean Science (OS) & Discussions (OSD) , 2009,
Abstract: While the concept of oceanic heat transport – or rather heat transport divergence – is well known, it is sometimes applied inaccurately. Often so-called "heat transports" are computed across a partial section which means that the volume flow through such a section is not zero. In this case the "heat transports" depend entirely on the choice of the temperature scale. The consequences of such arbitrariness are demonstrated with a simple calculation exercise for the passages to the Arctic Ocean. To circumvent the arising difficulties for the Fram Strait in the Arctic we propose a stream tube concept to define a net zero volume flow section which can, with coarse assumptions, be used to determine oceanic heat transport by the portion of Atlantic water flow that passes through Fram Strait. Weaknesses of this approach and consequences for observational strategies are discussed.
Problems with estimating oceanic heat transport – conceptual remarks for the case of Fram Strait in the Arctic Ocean
U. Schauer,A. Beszczynska-Mller
Ocean Science Discussions (OSD) , 2009,
Abstract: While the concept of oceanic heat transport – or rather heat transport divergence – is known since long, it is sometimes applied inaccurately. Often temperature transports are computed across sections with unbalanced volume flow which then depend entirely on the choice of the temperature scale. The consequences of such arbitrariness are demonstrated with a simple calculation exercise for the passages to the Arctic Ocean. To circumvent the arising difficulties for the Fram Strait as an example we propose a stream tube concept to define a net zero volume flow section which can, with coarse assumptions, be used to determine oceanic heat transport by the Atlantic water flow. Weaknesses of this approach and consequences for observational strategies are discussed.
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