Pléiades project: Assessment of georeferencing accuracy, image quality, pansharpening performence and DSM/DTM quality

Pléiades 1A and 1B are twin optical satellites of Optical and Radar Federated Earth Observation (ORFEO) program jointly running by France and Italy. They are the first satellites of Europe with sub-meter resolution. Airbus DS (formerly Astrium Geo) runs a MyGIC (formerly Pléiades Users Group) program to validate Pléiades images worldwide for various application purposes. The authors conduct three projects, one is within this program, the second is supported by BEU Scientific Research Project Program, and the third is supported by TÜBİTAK. Assessment of georeferencing accuracy, image quality, pansharpening performance and Digital Surface Model/Digital Terrain Model (DSM/DTM) quality subjects are investigated in these projects. For these purposes, triplet panchromatic (50 cm Ground Sampling Distance (GSD)) and VNIR (2 m GSD) Pléiades 1A images were investigated over Zonguldak test site (Turkey) which is urbanised, mountainous and covered by dense forest. The georeferencing accuracy was estimated with a standard deviation in X and Y (SX, SY) in the range of 0.45m by bias corrected Rational Polynomial Coefficient (RPC) orientation, using ~170 Ground Control Points (GCPs). 3D standard deviation of ±0.44m in X, ±0.51m in Y, and ±1.82m in Z directions have been reached in spite of the very narrow angle of convergence by bias corrected RPC orientation. The image quality was also investigated with respect to effective resolution, Signal to Noise Ratio (SNR) and blur coefficient. The effective resolution was estimated with factor slightly below 1.0, meaning that the image quality corresponds to the nominal resolution of 50cm. The blur coefficients were achieved between 0.39-0.46 for triplet panchromatic images, indicating a satisfying image quality. SNR is in the range of other comparable space borne images which may be caused by de-noising of Pléiades images. The pansharpened images were generated by various methods, and are validated by most common statistical metrics and also visual interpretation. The generated DSM and DTM were achieved with ±1.6m standard deviation in Z (SZ) in relation to a reference DTM.Airbus Defence and SpaceBEU/2014-47912266-01TÜBİTAK/114Y38

Biodiversity inventories in high gear: DNA barcoding facilitates a rapid biotic survey of a temperate nature reserve

Comprehensive biotic surveys, or ‘all taxon biodiversity inventories’ (ATBI), have traditionally been limited in scale or scope due to the complications surrounding specimen sorting and species identification. To circumvent these issues, several ATBI projects have successfully integrated DNA barcoding into their identification procedures and witnessed acceleration in their surveys and subsequent increase in project scope and scale. The Biodiversity Institute of Ontario partnered with the rare Charitable Research Reserve and delegates of the 6th International Barcode of Life Conference to complete its own rapid, barcode-assisted ATBI of an established land trust in Cambridge, Ontario, Canada

Studi Awal Desain Pebble Bed Reactor Berbasis Htr-pm dengan Skema Resirkulasi Bahan Bakar Once-through-then-out

STUDI AWAL DESAIN PEBBLE BED REACTOR BERBASIS HTR-PM DENGAN RESIRKULASI BAHAN BAKAR ONCE-THROUGH-THEN-OUT. Reaktor nuklir tipe pebble bed reactor (PBR) adalah salah satu reaktor canggih dengan fitur keselamatan pasif yang kuat. Pada desain tipe ini berpotensi untuk dilakukan kogenerasi yang bermanfaat untuk pengolahan berbagai mineral di berbagai pulau di Indonesia. Operasi PBR dapat lebih disederhanakan dengan menerapkan skema pengisian bahan bakar once-through-then-out (OTTO) dimana bahan bakar pebble hanya akan melewati teras reaktor sekali. Penelitian ini bertujuan untuk mengetahui dampak kuantitatif dari Perubahan skema resirkulasi bahan bakar terhadap performa teras PBR dan mendapatkan desain optimasi awal reaktor tipe PBR dengan skema resirkulasi OTTO. Perangkat lunak PEBBED digunakan untuk memperoleh teras setimbang PBR dengan berbagai skema resirkulasi bahan bakar. Hasil perhitungan memberikan data dampak penerapan skema resirkulasi bahan bakar berbeda, khususnya skema OTTO. Selanjutnya diperoleh desain optimasi awal desain PBR berbasis HTR-PM dengan skema siklus OTTO dimana daya harus diturunkan hingga 115 MWt untuk mempertahankan fitur keselamatan. Kesederhanaan operasi reaktor dan komponen yang lebih sedikit dengan skema OTTO tetap membuat desain optimasi awal ini menjadi alternatif desain yang menarik, meskipun daya yang diperoleh lebih kecil dari desain referens

Predicting the spread of covid-19 and the impact of government measures at the early stage of the pandemic: The Dutch case—Stricter but short-term measures are better

In this paper, we investigate the spread of COVID-19 and the impact of government measures at the early stage of the pandemic (before the introduction of the vaccines) in the Netherlands. We build a multiple linear regression model to predict the effective reproduction rate using key factors and measures and integrate it with a system dynamics model to predict the spread and the impact of measures against COVID-19. Data from February to November 2020 is used to train the model and data until December 2020 is used to validate the model. We use data about the key factors, e.g., disease specific such as basic reproduction rate and incubation period, weather related factors such as temperature, and controllable factors such as testing capacity. We consider particularly the following measures taken by the government: wearing facemasks, event allowance, school closure, catering services closure, and self-quarantine. Studying the strategy of the Dutch government, we control these measures by following four main policies: doing nothing, mitigation, curbing, elimination. We develop a systems dynamic model to simulate the effect of policies. Based on our numerical experiments, we develop the following main insights: It is more effective to implement strict, sharp measures earlier but for a shorter duration than to introduce measures gradually for a longer duration. This way, we can prevent a quick rise in the number of infected cases but also to reduce the number of days under measures. Combining the measures with a high testing capacity and with effective self-quarantine can significantly reduce the spread of COVID-19