Spectral imaging has many applications, from methane detection using satellites to disease detection on crops. However, spectral cameras remain a costly solution ranging from 10 thousand to 100 thousand euros for the hardware alone. Here, we present a low-cost multispectral camera (LC-MSC) with 64 LEDs in eight different colors and a monochrome camera with a hardware cost of 340 euros. Our prototype reproduces spectra accurately when compared to a reference spectrometer to within the spectral width of the LEDs used and the ±1σ variation over the surface of ceramic reference tiles. The mean absolute difference in reflectance is an overestimate of 0.03 for the LC-MSC as compared to a spectrometer, due to the spectral shape of the tiles. In environmental light levels of 0.5 W m−2 (bright artificial indoor lighting) our approach shows an increase in noise, but still faithfully reproduces discrete reflectance spectra over 400 nm–1000 nm. Our approach is limited in its application by LED bandwidth and availability of specific LED wavelengths. However, unlike with conventional spectral cameras, the pixel pitch of the camera itself is not limited, providing higher image resolution than typical high-end multi- and hyperspectral cameras. For sample conditions where LED illumination bands provide suitable spectral information, our LC-MSC is an interesting low-cost alternative approach to spectral imaging.
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At this moment, no method is available to objectively estimate the temperature to which skeletal remains have been exposed during a fire. Estimating this temperature can provide crucial information in a legal investigation. Exposure of bone to heat results in observable and measurable changes, including a change in colour. To determine the exposure temperature of experimental bone samples, heat related changes in colour were systemically studied by means of image analysis. In total 1138 samples of fresh human long bone diaphysis and epiphysis, varying in size, were subjected to heat ranging from room temperature to 900 °C for various durations and in different media. The samples were scanned with a calibrated flatbed scanner and photographed with a Digital Single Lens Reflex camera. Red, Green, Blue values and Lightness, A-, and B-coordinates were collected for statistical analysis. Cluster analysis showed that discriminating thresholds for Lightness and B-coordinate could be defined and used to construct a model of decision rules. This model enables the user to differentiate between seven different temperature clusters with relatively high precision and accuracy. The proposed decision model provides an objective, robust and non-destructive method for estimating the exposure temperature of heated bone samples.
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Objective: The aim of this study was to obtain insight in specific elements influencing the use, non-use, satisfaction, and dissatisfaction of ankle foot orthoses (AFOs) and the presence of underexposed problems with respect to AFOs. Methods: A questionnaire was composed to obtain information from AFO users to investigate the variables associated with satisfaction and the relation between these variables. A specific feature of this study was the systematic analysis of the remarks made by the respondents about their AFO. Quantitative data analyses were used for analysing the satisfaction and qualitative analyses were used analysing the remarks of the respondents. A total of 211 users completed the questionnaire. Results: Our survey showed that 1 out of 15 AFOs were not used at all. About three quarters of the AFO users were satisfied and about one quarter was dissatisfied. Females and users living alone reported relatively high levels of dissatisfaction, especially in the field of dimensions, comfort, weight, safety and effectiveness. Dissatisfaction with respect to off-the-shelf AFOs for the item durability was higher than that for custom-made AFOs. In the delivery and maintenance process the items ‘maintenance’, ‘professionalism’ and ‘delivery follow-up’ were judged to be unsatisfactory. A large number of comments were made by the respondents to improve the device or process, mainly by the satisfied AFO users. These comments show that even satisfied users experience many problems and that a lot of problems of AFO users are ‘underexposed’. Conclusion: To improve user satisfaction, the user practice has to be identified as an important sub-process of the whole orthopaedic chain especially in the diagnosis and prescription, delivery tuning and maintenance, and evaluation phase.
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