Level of measurement

Résumé

Level of measurement or scale of measure is a classification that describes the nature of information within the values assigned to variables. Psychologist Stanley Smith Stevens developed the best-known classification with four levels, or scales, of measurement: nominal, ordinal, interval, and ratio. This framework of distinguishing levels of measurement originated in psychology and has since had a complex history, being adopted and extended in some disciplines and by some scholars, and criticized or rejected by others. Other classifications include those by Mosteller and Tukey, and by Chrisman. Stevens's typology Overview Stevens proposed his typology in a 1946 Science article titled "On the theory of scales of measurement". In that article, Stevens claimed that all measurement in science was conducted using four different types of scales that he called "nominal", "ordinal", "interval", and "ratio", unifying bo

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https://en.wikipedia.org/wiki/Level_of_measurement

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Use of compact Laser Doppler Velocimetry in reduced scale model testing of hydraulic machines

Loïc Andolfatto, François Avellan, Vincent Berruex, Andres Müller, Masashi Sakamoto

Laser based flow survey methods such as Laser Doppler Velocimetry (LDV) or Particle Image Velocimetry (PIV) have long been used for studying the flow in hydraulic machines. Even if the results have crucially improved our understanding of potentially destabilizing flow patterns in the draft tube at off-design conditions and the prediction of the stable operating range, these techniques are not systematically used for reduced scale model measurements in the frame of customer acceptance tests or development projects. In a not too distant past, the price, size and complexity of the necessary equipment and procedures exceeded the acceptable range for these projects. Recent developments however made them more accessible. Furthermore, the collaboration with experienced research institutes provides the necessary know-how as well as an added academic value by providing researchers with realistic test cases. This work reports a case study for which a compact LDV probe was used to measure the velocity field in the draft tube cone of a reduced scale physical model of a Francis turbine. The axial and tangential velocity profiles were established by performing measurements at several radial positions between the turbine centreline and the cone wall. The overall objective was the validation of numerical flow simulations across the entire operating range of the turbine, from partial to full load.

2018

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Genome-wide manipulations and measurements have made huge progress over the last decades. In Saccharomyces cerevisiae, a well-studied eukaryotic model organism, homologous recombination allows for systematic deletion or alteration of a majority of its genes. Important products of these manipulation techniques are two libraries of modified strains: A deletion library consisting of all viable knockout mutants, and a GFP library in which 4159 proteins are successfully tagged with GFP. In addition, the development of a method that allows for the systematic construction of double mutants led to a virtually infinite number of potential strains of interest. These advancements in combinatorial biology need to be matched by methods of data measurement and analysis. In order to simultaneously observe the spatio-temporal dynamics of thousands of strains from the GFP library, Dénervaud et al. developed a microfluidic platform that allows for parallel imaging of 1152 strains in a single experiment. On this platform, strains can be grown and monitored in a controllable environment for several days, which results in the imaging of several millions of cells during one experiment. To objectively and quantitatively analyze this immense amount of information, we implemented an image analysis pipeline, which can extract experiment-wide information on single-cell protein abundance and subcellular localization. The construction of a supervised classifier to quantify localization information on a single cell level is a new approach and was invaluable to detect dynamic localization changes within the proteome. Using five different stress conditions, we gained insight into temporal changes of abundance and localization of multiple proteins. For example, we found that while localization changes can often be fast and transient, long-term response of a cell is usually enabled by changes in abundance. This shows a well-orchestrated response of a cell to external stimuli. To extend knowledge about cellular mechanisms, we used our microfluidic platform for two separate screens, combining GFP-reporter with additional deletion mutants. The advantage of our platform in comparison to more common approaches lies in its simultaneous measurement of fluorescence and phenotypic information on cell size and growth. For each deletion, we can quantify not only its influence onto the respective GFP-reporter under changing conditions, but also its effect on cell growth and size. We showed that it is advantageous to combine this information, as it allows pointing out possible underlying mechanisms of gene network regulations. In a first screen we investigated the behavior of several gene networks upon UV irradiation damage. We were able to show that four gene deletions influenced the localization of ribonucleotide-diphosphate reductase (Rnr4p). A second screen was designed to find genes that influence the induction of the galactose network. This screen uses more than 500 deletions of genes mostly related to chromatin in combination with two different reporter strains. A main focus of this study was the inheritance of memory during galactose reinduction. We found several previously unknown genes that potentially influence either induction or reinduction and were picked as candidates for further inheritance studies. Our microfluidic platform allows for unprecedented studies of proteomes in flux. [...]

EPFL2015

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Measurement scale effects on the determination of sorption and degradation parameters for modelling chemical transport in the soil

Danrong Zhang

EPFL2003

Chargement

EPFL2015