Large-area inventory of species composition using airborne laser scanning and hyperspectral data

5openInternationalInternational coauthor/editorTree species composition is an essential attribute in stand-level forest management inventories and remotely sensed data might be useful for its estimation. Previous studies on this topic have had several operational drawbacks, e.g., performance studied at a small scale and at a single tree-level with large fieldwork costs. The current study presents the results from a large-area inventory providing species composition following an operational area-based approach. The study utilizes a combination of airborne laser scanning and hyperspectral data and 97 field sample plots of 250 m2 collected over 350 km2 of productive forest in Norway. The results show that, with the availability of hyperspectral data, species-specific volume proportions can be provided in operational forest management inventories with acceptable results in 90% of the cases at the plot level. Dominant species were classified with an overall accuracy of 91% and a kappa-value of 0.73. Species-specific volumes were estimated with relative root mean square differences of 34%, 87%, and 102% for Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.), and deciduous species, respectively. A novel tree-based approach for selecting pixels improved the results compared to a traditional approach based on the normalized difference vegetation index.openØrka, Hans Ole; Hansen, Endre Hofstad; Dalponte, Michele; Gobakken, Terje; Næsset, ErikØrka, H.O.; Hansen, E.H.; Dalponte, M.; Gobakken, T.; Næsset, E

Effect of process parameters on flow length and flash formation in injection moulding of high aspect ratio polymeric micro features

This paper reports an investigation of the effects of process parameters on the quality characteristics of polymeric parts produced by micro injection moulding (μIM) with two different materials. Four injection moulding process parameters (injection velocity, holding pressure, melt temperature and mould temperature) were investigated using Polypropylene (PP) and Acrylonitrile Butadiene Styrene (ABS). Three key characteristics of the mouldings were evaluated with respect to process settings and the material employed: part mass, flow length and flash formation. The experimentation employs a test part with four micro fingers with different aspect ratios (from 21 up to 150) and was carried out according to the Design of Experiments (DOE) statistical technique. The results show that holding pressure and injection velocity are the most influential parameters on part mass with a direct effect for both materials. Both parameters have a similar effect on flow length for both PP and ABS at all aspect ratios and have higher effects as the feature thickness decreased below 300 μm. The study shows that for the investigated materials the injection speed and packing pressure were the most influential parameters for increasing the amount of flash formation, with relative effects consistent for both materials. Higher melt and mould temperatures settings were less influential parameters for increasing the flash amount when moulding with both materials. Of the two investigated materials, PP was the one exhibiting more flash formation as compared with ABS, when corresponding injection moulding parameters settings for both materials were considered

Measurement noise of a point autofocus surface topography instrument

Optical instruments for areal topography measurement can be especially sensitive to noise when scanning is required. Such noise has different sources, including those internally generated and external sources from the environment [1].For some instruments, it is not always possible to evaluate each single contributor. Nevertheless, it is possible to evaluate the noise added to the output during the normal use of the instrument. Such noise is defined in ISO 25178 part 605 [1] as “measurement noise”. In this work, the measurement noise is assessed for a commercial point autofocus instrument (Mitaka MLP-3SP), installed in the manufacturing metrology laboratory at The University of Nottingham. The investigation is carried out by areal acquisitions of 100µm×100µmwith a100×magnification objective and a sampling distance of 0.1µm along the x-axis and 1µm along the y-axis. The measurement noise is evaluated by applying established subtraction and averaging methods described elsewhere [2,3]. The results reveal a maximum calculated value of 20nm (subtraction method) and a minimum of 8nm (subtraction method). An oscillationis observed in the acquired surface topographies, which is due to a thermal drift induced by the air conditioning system. The disturbance can be reduced using the temperature correction tool in the software of the instrument. Experiments performed when the air conditioning system is inactive, showed drift of the instrument due to the temperature which is estimated, in the worst case, as 0.9µm/oC(calculated as Sz/ΔT), over one hour measuring time. The investigation was then repeated applying the temperature correction tool and the evaluation of the measurement noise results in a value of 2nm (both methods).The overall temperature variation, measured in the housing chamber of the instrument, is smaller than 0.1o C during each repeated measurement. In conclusion, the point autofocus instrument shows a clear dependence on the environmental noise. The measurement noise uncertainty contributor in the worst case is estimated to be unoise=20nmwhen the temperature correction tool Abstract submitted to the www.metprops2017.se conference is not applied [2].The use of the built-in temperature correction tool allows the measurement noise uncertainty contributor to be reduced tounoise=2nm