Covering the Boundary of a Simple Polygon with Geodesic Unit Disks

We consider the problem of covering the boundary of a simple polygon on n vertices using the minimum number of geodesic unit disks. We present an O(n \log^2 n+k) time 2-approximation algorithm for finding the centers of the disks, with k denoting the number centers found by the algorithm

Apodization in high-contrast long-slit spectroscopy. Closer, deeper, fainter, cooler

The spectroscopy of faint planetary-mass companions to nearby stars is one of the main challenges that new-generation high-contrast spectro-imagers are going to face. In a previous work we presented a long slit coronagraph (LSC), for which the presence of a slit in the coronagraphic focal plane induces a complex distribution of energy in the Lyot pupil-plane that cannot be easily masked with a binary Lyot stop. To alleviate this concern, we propose to use a pupil apodization to suppress diffraction, creating an apodized long slit coronagraph (ALSC). After describing how the apodization is optimized, we demonstrate its advantages with respect to the CLC in the context of SPHERE/IRDIS long slit spectroscopy (LSS) mode at low-resolution with a 0.12" slit and 0.18" coronagraphic mask. We perform different sets of simulations with and without aberrations, and with and without a slit to demonstrate that the apodization is a more appropriate concept for LSS, at the expense of a significantly reduced throughput (37%) compared to the LSC. Then we perform detailed end-to-end simulations of the LSC and the ALSC that include realistic levels of aberrations to obtain datasets representing 1h of integration time on stars of spectral types A0 to M0 located at 10 pc. We insert spectra of planetary companions at different effective temperatures (Teff) and surface gravities (log g) into the data at angular separations of 0.3" to 1.5" and with contrast ratios from 6 to 18 mag. Using the SD method to subtract the speckles, we show that the ALSC brings a gain in sensitivity of up to 3 mag at 0.3" with respect to the LSC, which leads to a much better spectral extraction below 0.5". In terms of Teff, we demonstrate that at small angular separations the limit with the ALSC is always lower by at least 100K, inducing an increase of sensitivity of a factor up to 1.8 in objects' masses at young ages. [Abridged]Comment: 15 pages, 17 figures. Accepted for publication in A&

TERAFOR: DEXi-based multicriteria model for considering all multiple functions of tree formations in temperate agroforestry areas

info:eu-repo/semantics/publishedVersio

First light of the VLT planet finder SPHERE I. Detection and characterization of the substellar companion GJ 758B

GJ 758 B is a brown dwarf companion to a nearby (15.76%) solar-type, metal-rich (M / H = + 0.2 dex) main-sequence star (G9V) that was discovered with Subaru/HiCIAO in 2009. From previous studies, it has drawn attention as being the coldest (~600 K) companion ever directly imaged around a neighboring star. We present new high-contrast data obtained during the commissioning of the SPHERE instrument at the Very Large Telescope (VLT). The data was obtained in Y-, J-, H-, and K_s-bands with the dual-band imaging (DBI) mode of IRDIS, thus providing a broad coverage of the full near-infrared (near-IR) range at higher contrast and better spectral sampling than previously reported. In this new set of high-quality data, we report the re-detection of the companion, as well as the first detection of a new candidate closer-in to the star. We use the new eight photometric points for an extended comparison of GJ 758 B with empirical objects and four families of atmospheric models. From comparison to empirical object, we estimate a T8 spectral type, but none of the comparison objects can accurately represent the observed near-IR fluxes of GJ 758 B. From comparison to atmospheric models, we attribute a T_(eff) = 600 ± 100 K, but we find that no atmospheric model can adequately fit all the fluxes of GJ 758 B. The lack of exploration of metal enrichment in model grids appears as a major limitation that prevents an accurate estimation of the companion physical parameters. The photometry of the new candidate companion is broadly consistent with L-type objects, but a second epoch with improved photometry is necessary to clarify its status. The new astrometry of GJ 758 B shows a significant proper motion since the last epoch. We use this result to improve the determination of the orbital characteristics using two fitting approaches: Least-Squares Monte Carlo and Markov chain Monte Carlo. We confirm the high-eccentricity of the orbit (peak at 0.5), and find a most likely semi-major axis of 46.05 AU. We also use our imaging data, as well as archival radial velocity data, to reject the possibility that this is a false positive effect created by an unseen, closer-in, companion. Finally, we analyze the sensitivity of our data to additional closer-in companions and reject the possibility of other massive brown dwarf companions down to 4–5 AU

The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfs at wide orbits. IV. Gravitational instability rarely forms wide, giant planets

Understanding the formation and evolution of giant planets (≥1 M_(Jup)) at wide orbital separation (≥5 AU) is one of the goals of direct imaging. Over the past 15 yr, many surveys have placed strong constraints on the occurrence rate of wide-orbit giants, mostly based on non-detections, but very few have tried to make a direct link with planet formation theories. In the present work, we combine the results of our previously published VLT/NaCo large program with the results of 12 past imaging surveys to constitute a statistical sample of 199 FGK stars within 100 pc, including three stars with sub-stellar companions. Using Monte Carlo simulations and assuming linear flat distributions for the mass and semi-major axis of planets, we estimate the sub-stellar companion frequency to be within 0.75–5.70% at the 68% confidence level (CL) within 20–300 AU and 0.5–75 M_(Jup), which is compatible with previously published results. We also compare our results with the predictions of state-of-the-art population synthesis models based on the gravitational instability (GI) formation scenario with and without scattering. We estimate that in both the scattered and non-scattered populations, we would be able to detect more than 30% of companions in the 1–75 M_(Jup) range (95% CL). With the threesub-stellar detections in our sample, we estimate the fraction of stars that host a planetary system formed by GI to be within 1.0–8.6% (95% CL). We also conclude that even though GI is not common, it predicts a mass distribution of wide-orbit massive companions that is much closer to what is observed than what the core accretion scenario predicts. Finally, we associate the present paper with the release of the Direct Imaging Virtual Archive (DIVA), a public database that aims at gathering the results of past, present, and future direct imaging surveys

Development of a Base Station for a Control Center

In this thesis, the objective was to design a base station for a startup company as a compliment to their main product, a control center device. The thesis resulted in a prototype that worked as intended and it fulfilled all desired criteria; charging ability, mountable on walls and placeable on flat horizontal surfaces. The prototype is divided into two parts: One unit, the station, and one unit that is designed as a shell for the control center. The latter allows the control center to receive charging, be placed easily on the station and allow it to stand on a flat horizontal surface. The company is very pleased with the results and looks forward for further development. Before generating any concepts, customer needs were identified through interviews from potential customers and lead users. The interviews got interpreted and evaluated which resulted in six complete product concepts. One of the concepts was chosen the best with highest score and also received the most positive feedback from the company. A prototype was built to represent the winning concept as close to a real product as possible. It included enough working parts to be able to prove the concept and give a better understanding of the product. Tests were made during the development process to make sure that everything worked properly. The thesis was completed successfully and satisfied both the development team and the company.In this thesis, the objective was to design a base station for a startup company as a compliment to their main product, a control center device. The thesis resulted in a prototype that worked as intended and it fulfilled all desired criteria; charging ability, mountable on walls and placeable on flat horizontal surfaces. The prototype is divided into two parts: One unit, the station, and one unit that is designed as a shell for the control center. The latter allows the control center to receive charging, be placed easily on the station and allow it to stand on a flat horizontal surface. The company is very pleased with the results and looks forward for further development. Before generating any concepts, customer needs were identified through interviews from potential customers and lead users. The interviews got interpreted and evaluated which resulted in six complete product concepts. One of the concepts was chosen the best with highest score and also received the most positive feedback from the company. A prototype was built to represent the winning concept as close to a real product as possible. It included enough working parts to be able to prove the concept and give a better understanding of the product. Tests were made during the development process to make sure that everything worked properly. The thesis was completed successfully and satisfied both the development team and the company

Kosovo-Serbia Negotiations

Negotiations are forms of conversation, communication and bilateral or multilateral dialogue to resolve any kind of problem. Negotiations between Kosovo and Serbia are regional and global, as evidenced by the involvement of the EU and the US in these negotiations. The only way to finally resolve the problem between Kosovo and Serbia is dialogue. The purpose of the research is to analyse and measure Kosovo’s opinion on resolving the problem with Serbia through dialogue and their opinion on Kosovo’s representation in the talks and the agreement reached in Washington. The research was conducted through a questionnaire with structured questions, while a total of 470 respondents from all over Kosovo participated. Statistical analyses were analysed through the SPSS program, while qualitative ones through the inductive method. Based on the results, we see that demographic factors such as gender, age, and qualification affect the citizens of Kosovo’s citizens to solve the problem with Serbia. Part of this research was also interviewing with experts on the Kosovo-Serbia dialogue. What we can recommend from this research is that dialogue should move from technical issues to political issues because the essence of this dialogue is political. The only way to its final solution is to reach an agreement that would include its resolution of all problems. The solution can be achieved through one of the possible scenarios in this paper in the theoretical and research part