Visualization of spectral images

Spectral image sensors provide images with a large number of contiguous spectral channels per pixel. Visualization of these huge data sets is not a straightforward issue. There are three principal ways in which spectral data can be presented; as spectra, as image and in feature space. This paper describes several visualization methods and their suitability in the different steps in the research cycle. Combinations of the three presentation methods and dynamic interaction between them, adds significant to the usability. Examples of some software implementations are given. Also the application of volume visualization methods to display spectral images is shown to be valuabl

Chloride Ingress of Carbonated Blast Furnace Slag Cement Mortars

In the Netherlands civil engineering structures, such as overpasses, bridges and tunnels are generally built using blast furnace slag cement (BFSC, CEM III/B) concrete, because of its high resistance against chloride penetration. Although the Dutch experience regarding durability performance of BFSC concrete has been remarkably good, its resistance to carbonation is known to be sensitive, especially when the used slag percentage is high. In a field investigation on a highway overpass damage was found in sheltered elements such as abutments and intermediate supports, which was attributed to chloride induced corrosion enhanced by carbonation that occurred prior to the chloride exposure. Many structures built using BFSC could be prone to this mechanism, i.e. carbonation enhanced chloride induced corrosion, negatively affecting their durability. Focus of the research was given on the influence of carbonation on the chloride penetration resistance of BFSC mortars with varying slag content. In light of the characteristics from the overpass case, it was assumed that first there is a period of carbonation during sheltered exposure, and subsequently joint leakage causes exposure to chlorides. In order to identify the influence of slag content on carbonation, chloride penetration resistance and their coupled effect, mortars with twelve cement blends in a range of 0-70% slag were evaluated based on chloride migration coefficient, accelerated carbonation and electrical resistivity. This study shows that carbonation of BFSC mortars increases the porosity, consequently decreasing the chloride penetration resistance. Binders with 50% or more slag were found to have a significantly lower resistance after carbonation. Consequently, the chloride penetration resistance of a given concrete cover strongly depends on the duration of carbonation and the resulting carbonation depth, hence influencing its lifespan. The service life was estimated using a simplified model for the chloride penetration time of a combined carbonated and uncarbonated layer. It was found that mortar with a slag content between 35 and 50% that was carbonated before chloride exposure show the lowest influence of carbonation on the chloride penetration resistance. © Springer International Publishing AG 2018. Bam; Cement and Beton Centrum; et al.; Rijkswaterstaat - Ministry of Infrastructure and the Environment; Van Hattum en Blankevoort; VolkerInfr

Spectral image analysis for measuring ripeness of tomatoes

In this study, spectral images of five ripeness stages of tomatoes have been recorded and analyzed. The electromagnetic spectrum between 396 and 736 nm was recorded in 257 bands (every 1.3 nm). Results show that spectral images offer more discriminating power than standard RGB images for measuring ripeness stages of tomatoes. The classification error of individual pixels was reduced from 51% to 19%. Using a gray reference, the reflectance can be made invariant to the light source and even object geometry, which makes it possible to have comparable classification results over a large range of illumination conditions. Experimental results show that, although the error rate increases from 19% to 35% when using different light sources, it is still considerably below the 51% for RGB under a single light sourc

Detection of the tulip breaking virus (TBV) in tulips using optical sensors

The tulip breaking virus (TBV) causes severe economic losses for countries that export tulips such as the Netherlands. Infected plants have to be removed from the field as soon as possible. There is an urgent need for a rapid and objective method of screening. In this study, four proximal optical sensing techniques for the detection of TBV in tulip plants were evaluated and compared with a visual assessment by crop experts as well as with an ELISA (enzyme immunoassay) analysis of the same plants. The optical sensor techniques used were an RGB color camera, a spectrophotometer measuring from 350 to 2500 nm, a spectral imaging camera covering a spectral range from 400 to 900 nm and a chlorophyll fluorescence imaging system that measures the photosynthetic activity. Linear discriminant classification was used to compare the results of these optical techniques and the visual assessment with the ELISA score. The spectral imaging system was the best optical technique and its error was only slightly larger than the visual assessment error. The experimental results appear to be promising, and they have led to further research to develop an autonomous robot for the detection and removal of diseased tulip plants in the open field. The application of this robot system will reduce the amount of insecticides and the considerable pressure on labor for selecting diseased plants by the crop expert. © 2010 The Author(s

Geautomatiseerde (machinale) detectie van TBV in tulp: resultaten 2010 vervolg praktijkonderzoek ziekzoeken

Tulpenmozaïekvirus (TBV) veroorzaakt jaarlijks veel schade in tulpen. Vooral in de witte en gele cultivars is de afkeur groot. Om de virusdruk te verminderen worden in de praktijk door ziekzoekers viruszieke tulpen uit het veld verwijderd. Het is moeilijk ervaren ziekzoekers te vinden. Daarom is onderzoek gedaan naar een oplossing waarbij viruszieke tulpen op een geautomatiseerde wijze worden herkend en worden verwijderd. In 2009 is in nauwe samenwerking met een aantal ondernemers het project “praktijkproef ziekzoekkar” uitgevoerd, waarbij een rijdend platform met speciale camera‟s foto‟s maakte van geplante tulpen. Deze beelden werden met speciale software gescreend op de aanwezigheid van virussymptomen. Gebleken is dat deze ziekzoekkar in de cultivar Barcelona slechts 25 % van de zieke tulpen wist op te sporen tegen 39% door de ziekzoekers. Een serologische bladtoets op TBV fungeerde als referentie voor de bepaling of een tulp ziek was of niet. Dit vervolgproject beoogde in 2010 te onderzoeken of met een verbeterde versie van de ziekzoekkar virus geïnfecteerde tulpennauwkeuriger konden worden opgespoord

Healthcare expenditure prediction with neighbourhood variables:A random forest model

We investigated the additional predictive value of an individual’s neighbourhood (quality and location), and of changes therein on his/her healthcare costs. To this end, we combined several Dutch nationwide data sources from 2003 to 2014, and selected inhabitants who moved in 2010. We used random forest models to predict the area under the curve of the regular healthcare costs of individuals in the years 2011–2014. In our analyses, the quality of the neighbourhood before the move appeared to be quite important in predicting healthcare costs (i.e. importance rank 11 out of 126 socio-demographic and neighbourhood variables; rank 73 out of 261 in the full model with prior expenditure and medication). The predictive performance of the models was evaluated in terms of R2 (or proportion of explained variance) and MAE (mean absolute (prediction) error). The model containing only socio-demographic information improved marginally when neighbourhood was added (R2 +0.8%, MAE −€5). The full model remained the same for the study population (R2 = 48.8%, MAE of €1556) and for subpopulations. These results indicate that only in prediction models in which prior expenditure and utilization cannot or ought not to be used neighbourhood might be an interesting source of information to improve predictive performance

Microwave photovoltage and photoresistance effects in ferromagnetic microstrips

We investigate the dc electric response induced by ferromagnetic resonance in ferromagnetic Permalloy (Ni80Fe20) microstrips. The resulting magnetization precession alters the angle of the magnetization with respect to both dc and rf current. Consequently the time averaged anisotropic magnetoresistance (AMR) changes (photoresistance). At the same time the time-dependent AMR oscillation rectifies a part of the rf current and induces a dc voltage (photovoltage). A phenomenological approach to magnetoresistance is used to describe the distinct characteristics of the photoresistance and photovoltage with a consistent formalism, which is found in excellent agreement with experiments performed on in-plane magnetized ferromagnetic microstrips. Application of the microwave photovoltage effect for rf magnetic field sensing is discussed.Comment: 16 pages, 15 figure