2,949 research outputs found
Design sequences for sensory studies: achieving balance for carry-over and position effects.
No full textIn sequences of human sensory assessments, the response toa stimulus may be influenced by previous stimuli. When investigating this phenomenon experimentally with several types or levels of stimulus, it is useful to have treatment sequences which are balanced for first-order carry-over effects. The requirement of balance for each experimental participant leads us to consider sequences of n symbols comprising an initial symbol followed by n ;blocks' each containing a permutation of the symbols. These sequences are designed to include all n (2) ordered pairs of symbols once each, and to have treatment and sequence position effects which are approximately or thogonal. Such sequences were suggested by Finney and Outhwaite (1956), who were able to find examples for particular values of n. We describe and illustrate acomputer algorithm for systematically enumerating the sequences for those values of n for which they exist. Criteria are proposed for choosing between the sequences according to the nearness to orthogonality of their treatment and position effects
Multiple Imputation and Random Forests (MIRF) for Unobservable, High-Dimensional Data
No full textUnderstanding the genetic underpinnings to complex diseases requires consideration of sophisticated analytical methods designed to uncover intricate associations across multiple predictor variables. At the same time, knowledge of whether single nucleotide polymorphisms within a gene are on the same (in cis) or on different (in trans) chromosomal copies, may provide crucial information about measures of disease progression. In association studies of unrelated individuals, allelic phase is generally unobservable, generating an additional analytical challenge. In this manuscript, we describe a novel approach that combines multiple imputation and random forests for this high-dimensional, unobservable data setting. An application to a cohort of HIV-1 infected individuals receiving anti-retroviral therapies is presented. A simulation study is also presented to characterize method performance
Multiplicative models for combining information from several sensory experiments : A Bayesian analysis
No full textConsider the situation in which several quantitative sensory experiments are carried out on the same type of product, and the assessors in these experiments are drawn from a common pool. The data from such a sequence of experiments contain information on the relative biases and variability of individual assessors, and on any temporal influences on the experiments. This information can be extracted by extending models for individual experiments to encompass variation between them. Because each assessor takes part in several experiments, adjustment can be made for the absence of individuals from some of them. By including future experiments in the extended models, it is also possible to use information on assessors' previous performance to reduce the average variance of product differences in future. Such a combination of information over experiments is illustrated using a sequence of 45 apple-tasting experiments conducted with the main aim of monitoring assessor performance over time. Models with multiplicative interaction terms have been used for modelling heterogeneous interaction between assessors and products in individual sensory experiments. Under the assumption that the data are normally distributed (or can be suitably transformed) we extend such models to analyse data from sequences of experiments. A Bayesian approach is used because of the complexity of the extended model and the need to incorporate future experiments
A variance components factor model for genetic association studies: a Bayesian analysis.
No full textStudies of gene-trait associations for complex diseases often involve multiple traits that may vary by genotype groups or patterns. Such traits are usually manifestations of lower-dimensional latent factors or disease syndromes. We illustrate the use of a variance components factor (VCF) model to model the association between multiple traits and genotype groups as well as any other existing patient-level covariates. This model characterizes the correlations between traits as underlying latent factors that can be used in clinical decision-making. We apply it within the Bayesian framework and provide a straightforward implementation using the WinBUGS software. The VCF model is illustrated with simulated data and an example that comprises changes in plasma lipid measurements of patients who were treated with statins to lower low-density lipoprotein cholesterol, and polymorphisms from the apolipoprotein-E gene. The simulation shows that this model clearly characterizes existing multiple trait manifestations across genotype groups where individuals' group assignments are fully observed or can be deduced from the observed data. It also allows one to investigate covariate by genotype group interactions that may explain the variability in the traits. The flexibility to characterize such multiple trait manifestations makes the VCF model more desirable than the univariate variance components model, which is applied to each trait separately. The Bayesian framework offers a flexible approach that allows one to incorporate prior information
Bas-Relief Modeling from Normal Layers
No full textBas-relief is characterized by its unique presentation of intrinsic shape properties and/or detailed appearance using materials raised up in different degrees above a background. However, many bas-relief modeling methods could not manipulate scene details well. We propose a simple and effective solution for two kinds of bas-relief modeling (i.e., structure-preserving and detail-preserving), which is different from the prior tone mapping alike methods. Our idea originates from an observation on typical 3D models which are decomposed into a piecewise smooth base layer and a detail layer in normal field. Proper manipulation of the two layers contributes to both structure-preserving and detail-preserving bas-relief modeling. We solve the modeling problem in a discrete geometry processing setup that uses normal-based mesh processing as a theoretical foundation. Specifically, using the two-step mesh smoothing mechanism as a bridge, we transfer the bas-relief modeling problem into a discrete space, and solve it in a least-squares manner. Experiments and comparisons to other methods show that (i) geometry details are better preserved in the scenario with high compression ratios, and (ii) structures are clearly preserved without shape distortion and interference from details.Accepted author manuscriptMaterials and Manufacturin
FM Transceiver for Wireless Communication: Audio and Intermediate Frequency Amplifiers
No full textIn this bachelor thesis the design process of the audio and intermediate frequency amplifiers for a wireless FM tranceiver is documented and explained. The project was done using only descrete components for educational purposes.2019 Ivor Bas, Victor hoedemakerElectrical Engineerin
Inventory for a Reverse Journey. Photographic Image and Found Object - An investigation of travel and material transformation as a paradigm of artist's practice: Ed Ruscha, Douglas Huebler, Bas jan Ader, Jimmie Durham, Gustav Metzger, Kurt Schwitters & Cian Quayle.
No full textInventory for Reverse Journey is the title of a collection of photographic artefacts and found objects, which I have collected over the last twenty years. The title refers to one specific type of artist's journey, which is applicable to the `chronotope' of my archive, as a `metaphorical journey in space and time' (Bakhtin 1981, p. 81). The `city',`provincial town', `road', `threshold' and `interior' are recurrent motifs, which Bakhtin fused together to describe the historical evolution of the novel in relation to its different genres. Bakhtin's motifs are expanded as the basis of an evolutionary nomenclature of the artist's-journey, as a form of spatial mapping and identity formation. Alongside other sources from literature (Alain Robbe-Grillet), cinema (Michelangelo Antonioni), psychoanalysis (Kierkegaard) and critical theory (Walter Benjamin) I have developed a theoretical framework, which initially originated in an empirical process, that is reflected in the antecedents of this project. The research process, as a journey itself, has concretised this approach within a systems-based practice. This is mirrored in the work of the artists under investigation, as their differences and similarities are highlighted within a broad contextual analysis. Accordingly the tone of the writing shifts its register at different points in the thesis.
My journey is just one example of several paradigmatic formations of `travel' as a strategy, which investigates the work of six different artists, as a voluntary or involuntary form of exile. A deskilled use of the photographic image is examined in the work of Ed Ruscha, Douglas Huebler and Bas jan Ader in the spatial mapping of their chosen locations. The work of these artists manifests travel, as a strategy, in a benign form of regional and expatriate exile. The investigation shifts its focus from the New World to Europe, where the work of Jimmie Durham, Gustav Metzger and Kurt Schwitters is analysed in relation to their transformation of found objects and materials, and their relationship with a former 'home'. Their position registers different degrees of the `impossibility of return' to a point of origin, which exists in the mind rather than as a physical location. The transience of their work, and use of disparate materials, is counterbalanced by their physical presence in the work. Conversely Ader, Huebler and Ruscha are linked by a scale of decreasing visibility, as they are sublimated within their work in the formation of, what is now construed as, a unique photographic presence. The starting point for which is a return to the formative years of conceptualism in the 1960's, which set the scene for Durham and Metzger from the 1970's onwards. The spectre of Schwitters practice of forming (Formung) and unforming (Entformung) is significant for my analysis of the dematerialisation of the art-work and artist, by processes of series and repetition, distance and proximity, movement and stasis. Although `travel' is a ubiquitous term, I continue to use it as a portmanteau, which carries with it the themes and `salient' features of a typology of artist's journeys. In a moment of perceived obsolescence as digital information systems engender a culture of `selective-amnesia', these thoughts have informed my work, which runs parallel to the artist case-studies, and the material transformation of the photographic image and found object
Retour d\u92expériences après la tempête Xynthia en France, leçons pour les Pays Bas; les dégâts suite à l\u92inondation
No full textLe 28 février 2010, vers 2 heures du matin, la tempête Xynthia atteint la côte occidentale de la France. A plusieurs endroits, les digues, dunes et d\u92autres ouvrages cédèrent, donnant lieu à des inondations du littoral. Plus de 50.000 hectares de terres furent inondées. Au total, la France compta 47 morts suite à la tempête, la plupart d\u92entre eux suite à la crue. Essentiellement les régions de la Vendée et de la Charente-Maritime endurèrent de terribles privations. Les dégâts et les victimes ne sont pas uniquement la conséquence du phénomène naturel, mais également des interventions de l\u92homme ou le manque de celles-ci. Les Pays-Bas pourraient tirer des leçons de ces inondations côtières françaises. Les circonstances aux Pays-Bas et en France sont, dans une grande mesure, comparables. La France, elle aussi, connaît des zones côtières à basse altitude sensibles aux inondations. Certes, le niveau de protection aux Pays-Bas est plus élevé, mais une inondation aux Pays-Bas est aussi bien concevable. Tout comme en France, une inondation du littoral néerlandais est causée par une combinaison de la marée, d\u92une tempête et d\u92une surcote. Les législations et les réglementations présentent des concordances ; leurs bases datent de l\u92époque de Napoléon. Ce livre décrit l\u92inondation par la tempête Xynthia et ses conséquences. Nous en tirons des leçons et nous formulons des avis pour les Pays-Bas. Nous cherchons à nous associer à une protection contre l\u92inondation à trois volets: la prévention, l\u92aménagement du territoire et la maîtrise des catastrophes
Understanding the influence of beach morphology on the alongshore variance in wave run-up on an intermediate reflective beach, considering bars and cusps
No full textThe topic which is considered in this thesis is: understanding the influence of beach morphology on the alongshore variance in wave run-up on an intermediate reflective beach, considering bars and cusps. The focus of this thesis is laid inside the swash zone, in which the water motion is present of waves that run up and run down on a beach. Energy from wave run-up could deliver erosion to the beach. It is relevant to know what the magnitude is of run-up during extreme events, in order to protect the beach. Several studies are done to wave run-up. There are relations which specify run-up, however, the alongshore variability is not studied in detail and less knowledge is available about this topic. At Anmok beach in South-Korea an intermediate reflective beach is present containing beach cusps and crescentic sandbars. A rhythmic bar and beach state contains the most complex morphology, furthermore the morphology changes a lot within intermediate beaches (Wright and Short [1]). The characteristics of this beach are used to perform an analysis to the influence of cusp and bar morphology on alongshore variation in wave run-up. Run-up is composed of setup and swash. Setup is the super elevation of the mean water level, swash is ‘’a time-varying location of the intersection between the ocean and the beach’’ according to Stockdon, Holman [2]. Swash can be decomposed into two parts, incident band swash and infragravity band swash. Swash and setup depend on beach slope, deep-water wave height and the deep water period[2]. To analyse the alongshore variability multiple bathymetries have been generated on which 500 waves are modelled for 60 different wave condition. First of all a reference case is modelled with a uniform bathymetry. Secondly beach cusps are used as input with different length scales and at last a beach cusp with crescentic sandbar is used. The length scales of the cusps are 452, 300 and 100 metres. The bathymetries are idealized bathymetries with the characteristics of Anmok beach. The run-up and components are calculated and an analysis is done to the magnitude of run-up and the standard deviation along the beach. The magnitude of run-up is lower for a cusp system compared with the reference situation and even lower for the cusp bar system. Furthermore there are no large differences in magnitude of run-up between different cusp lengths. A larger alongshore variance is observed when a cusp (bar) system is present. A cusp system of 452 metres contains larger run-up at the horn compared with the embayment, this holds for large and small wave heights. The difference is 18% and 8.4% respectively. However, when a cusp bar system is present less alongshore variability is visible and an opposite behaviour is visible for small wave heights. In this case the same pattern can be seen for large wave heights. A difference of 3.68% is seen when the horn is compared with the embayment. However, for small wave heights the run-up is 10.5% smaller at a horn compared with an embayment. A cusp length of 100 metres shows different behaviour compared with a cusp length of 452 metres. Run-up is larger at an embayment compared to the horn. This holds for large wave heights. The alongshore variance is in this case larger compared to larger cusp lengths. A cusp of 452 metres and 300 metres leads to similar results, whereas a 100 metres cusp shows deviations. It could be edge waves which could have an influence on a cusp with a length of 100 metres.<br/
Intra-operative bacterial contamination : control and consequences
No full textEen combinatie van gedragsmaatregelen en een beter luchtinblaassysteem in de operatiekamer leidt tot een afname van het aantal bacteriën bij plaatsing van een knie- of heupprothese. Hierdoor neemt de kans af op infectie van de prothese en op problemen met wondgenezing na de operatie. Dit blijkt uit onderzoek van Bas Knobben, uitgevoerd bij de afdeling Orthopedie en de vakgroep Biomedical Engineering van het Universitair Medisch Centrum Groningen. Deze bevindingen kunnen ertoe bijdragen dat gewrichtsprothesen minder vaak infecteren en vervangen moeten worden. Hij promoveert op 26 april 2006 op zijn onderzoek aan de Rijksuniversiteit Groningen.
In elke operatiekamer kunnen ondanks strenge hygiënische maatregelen bacteriën voorkomen die een mogelijk risico vormen voor infectie van prothesen en problemen met wondgenezing na de operatie. Tot nu toe was de omvang hiervan onduidelijk. Uit het onderzoek van Knobben blijkt dat bij 36 procent van de plaatsingen van heupprothesen bacteriën aanwezig waren op het instrumentarium en op verwijderde botsnippers bij het inbrengen van de prothesen. Ook bleek er een verband te zijn tussen het vóórkomen van deze bacteriën en het optreden van verstoorde wondgenezing en infectie van de prothesen.
Gedragsmaatregelen
Knobben onderzocht of gedrags- en technische maatregelen, aanvullend op de gebruikelijke hygiënerichtlijnen, de kans op bacteriële besmetting tijdens de operatie verkleinen. Uit zijn onderzoek blijkt dat de combinatie van deze maatregelen in een operatiekamer de kans op aanwezigheid van bacteriën deed afnemen van 34 procent naar 8 procent. Tegelijk nam de kans op infectie van prothesen, verstoorde wondgenezing en wondinfectie beduidend af.
De gedragsmaatregelen die onder andere werden genomen, zijn het beperken van het spreken en het in- en uitlopen van de operatiekamer door het operatiekamerpersoneel, het gecontroleerd bewegen, het juiste gebruik van het neus-/mondkapje en een beter gebruik van het gebied onder de luchtstroom. Een van de technische maatregelen betrof het gebruik van een beter luchtinblaassysteem (laminaire airflow). Hierbij vindt een constante aanvoer van schone lucht plaats boven het operatiegebied en worden bacteriën via verticale luchtstromen afgevoerd.
Kosteneffectief
Met dit onderzoek toont Knobben aan dat gedragsmaatregelen en een beter luchtinblaassysteem in de operatiekamer infecties van prothesen en problemen met wondgenezing kunnen voorkomen. De maatregelen zijn bovendien kosteneffectief: de gemiddelde totale kosten per patiënt met een eerste (primaire) prothese zonder infectie zijn ongeveer € 15.000, zo’n 3,5 keer lager dan die van een patiënt met een geïnfecteerde prothese (ongeveer € 52.000). De resultaten van dit proefschrift hebben ertoe geleid dat het Universitair Medisch Centrum Groningen de aanvullende gedrags- en technische maatregelen toepast bij het plaatsen van prothesen.
Verdubbeling
In Nederland zijn in 2004 ongeveer 25.000 heup- en 20.000 knieprothesen geplaatst. De belangrijkste indicatie voor het plaatsen hiervan is gewrichtsslijtage. De verwachting is dat door vergrijzing het aantal mensen dat in aanmerking komt voor deze operaties de komende twintig jaar zal verdubbelen. Bij ongeveer één tot vier procent van de patiënten treedt na plaatsing een bacteriële infectie op.
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