419 research outputs found
Multiple coverings with closed polygons
A planar set is said to be cover-decomposable if there is a constant
such that every -fold covering of the plane with translates of
can be decomposed into two coverings. It is known that open convex polygons are
cover-decomposable. Here we show that closed, centrally symmetric convex
polygons are also cover-decomposable. We also show that an infinite-fold
covering of the plane with translates of can be decomposed into two
infinite-fold coverings. Both results hold for coverings of any subset of the
plane.Comment: arXiv admin note: text overlap with arXiv:1009.4641 by other author
NagymennyisĂ©gű változĂłcsillagászati Ă©szlelĂ©sek feldolgozása Ă©s analĂzise = Reduction and analysis of large-scale variable star data sets
A következĹ‘ három fĹ‘ tĂ©makört vizsgáltuk: (a) periodikus tranzit detektálás Ă©s extraszolaris bolygĂłk vizsgálata a HATNet es a WHAT automata távcsövek Ă©szlelĂ©sei alapján; (b) a MACHO adatbázis RR Lyrae csillagainak periĂłdus analĂzise; (c) pulzálĂł változĂłcsillagok elmĂ©leti Ă©s empirikus vizsgálata. A következĹ‘ eredmĂ©nyeket kaptuk. TĂ©ma (a): kis apertĂşrájĂş, teljesen automatizált távcsövek alkalmasak nĂ©hány millimagnitĂşdĂł pontosságĂş Ă©szlelĂ©sekre Ă©s forrĂł Jupiterek (HJ-k) detektálására; a BLS algoritmusunk hatásos eszköz periodikus tranzitok keresĂ©sĂ©ben; az adatfeldolgozás miatt fellĂ©pĹ‘ szisztematikák kiszűrĂ©sĂ©nek hatĂ©kony eszköze a TFA algoritmusunk; a HD 189733 HJ rendszer valĂłjában egy hármas rendszer, K fĹ‘- es M másod-komponensekkel, valamint a fĹ‘komponens körĂĽl keringĹ‘ bolygĂłval. TĂ©ma (b): az LMC-ben találhatĂł alapmĂłdusĂş RR Lyrae csillagok 12%-a mutat Blashko jelensĂ©get. Ez az Ă©rtĂ©k szignifikánsan magasabb, mint az Ăşjabb analizisĂĽnk alapján az elsĹ‘ felhangĂş csillagokra kapott gyakoriság, amely a rendelkezĂ©sre állĂł adatok felhasználásával 7.5%-nak adĂłdott. TĂ©ma (c): nincs ellentmondás az RR Lyrae Ă©s a Cepheida változĂłk alapján a Baade-Wesselink mĂłdszer segĂtsĂ©gĂ©vel számĂtott távolságok között. Az LMC távolságára konzisztens Ă©rtĂ©keket kaptunk; több irreguláris változĂł fĂ©nygörbĂ©jĂ©nek analizálása alapján további megerĹ‘sĂtĂ©st kaptunk ezen csillagok kaotikus pulzáciĂłjára. | We have investigated the following three major topics: (a) periodic transit detection and extrasolar planetary studies based on large-scale photometric databases of the HATNet and WHAT automated telescopes; (b) frequency analysis of RR Lyrae stars in the MACHO database; (c) theoretical and empirical stellar pulsation studies. We obtained the following results. Topic (a): small aperture fully automated telescopes are able to gather few millimag precision photometric data and detect transits caused by hot Jupiters; our BLS algorithm is very efficient in searching for periodic transits; the effects of systematics due to errors in the data acquisition can be successfully filtered by our TFA algorithm; the hot Jupiter system HD 189733 is a triple system with a K primary and M secondary and the planet orbiting the primary. Topic (b): the incidence rate of the Blazhko stars pulsating in the fundamental mode is 12% in the LMC. This is significantly higher than that of the first overtone Blazhko stars (which is 7.5%, according to our new analysis of all available data. Topic (c): there is no contradiction between the distances derived by Baade-Wesselink analyses of RR Lyrae and Cepheid variables and they both yield consistent distances for the LMC; by analyzing the archival data of several irregular variables, we got further support for the presence of chaotic pulsations in these stars
Extraszoláris bolygó és változócsillag kutatás nagylátómezejű fotometriával = Extrasolar planet and variable star research by wide-field photometry
A kis-teleszkĂłpos/nagy-látĂłszögű fotometriai feltĂ©rkĂ©pezĹ‘ programjaink (HATNet es WHAT) segĂtsĂ©gĂ©vel 13 fedĂ©si extraszoláris bolygĂłt (TEP-et) fedeztĂĽnk fel. TömegĂĽk a NeptunĂ©tĂłl egĂ©szen a barna törpe csillagok határához közeli Ă©rtĂ©kekig terjednek (a Jupiter tömegĂ©nek 8%-nak megfelelĹ‘ tömegű HAT-P-11b-tĹ‘l a HAT-P-2b-ig, melynek tömege a JupiterĂ©nek 9-szerese). Több, a Jupiter tömegĂ©nĂ©l alacsonyobb tömegű bolygĂłk között az alacsony tartományban kiemelekedik a HAT-P-12b, amelynek tömege a SzaturnuszĂ©nak 2/3-a. A keringĂ©si periĂłdusok a 2 Ă©s 5.6 nap közötti tartományban szĂłrĂłdnak, melyek közĂĽl a leghosszabb az összes (szám szerint 69) TEP hosszĂş-periĂłdus tartományának vĂ©gĂ©n (annak 10%-ban) találhatĂł. Más paramĂ©terek, mint pĂ©ldául a sűrűsĂ©g vagy a pálya excentricitás, szintĂ©n szĂ©les tartományt fednek le. Fontos megemlĂteni a HAT-P-13b,c-t, amely az elsĹ‘ olyan többszörös bolygĂłrendszer, amelynek az egyik (a rövidebb periĂłdusĂş) tagja egyben fedĂ©si bolygĂł is. A pulzálĂł csillagok terĂĽletĂ©n megmutattuk, hogy pulzáciĂłs Ă©s fejlĹ‘dĂ©si modellek felhasználásával csupán a periĂłdusok ismeretĂ©ben lehetsĂ©ges a kĂ©tmĂłdusĂş RR Lyrae csillagok paramĂ©tereinek meghatározása. Ezek a paramĂ©terek jĂł egyezĂ©st mutatnak a fĂĽggetlen mĂłdon meghatározott mennyisĂ©gekkel, mint pĂ©ldaul a fĂ©messĂ©ggel, hĹ‘mĂ©rsĂ©klettel Ă©s távolsággal. | Within the small telescope/wide field of view photometric survey projects HATNet and WHAT, we have discovered 13 transiting extrasolar planets (TEPs) spanning from the mass of Neptune (HAT-P-11b with mass 8% that of the Jupiter) to near the brown dwarf limit (HAT-P-2b, with 9 Jupiter masses). We also have a planet (HAT-P-12b) with a mass two-third that of the Saturn and several others in the sub-Jupiter mass range. Orbital periods range from 2 days to 5.6 days, the latter value is in the upper 10% at the long period tail of the 69 TEPs discovered so far. Other parameters, such as eccentricity and density also span wide ranges. We highlight HAT-P-13b,c, the first multiple system, in which the short-periodic component is transiting. In the field of pulsating variables we have shown that the physical parameters for double-mode RR Lyrae stars derived solely from their periods by using evolutionary and pulsation models are in good agreement with other, independently computed quantities, such as metallicity, temperature and distance
The hard life of air bubbles crossing a fluid/fluid interface
We investigate the dynamics of isolated air bubbles crossing the horizontal interface separating two Newtonian immiscible liquids initially at rest by means of experiments and DNS. High-speed video imaging is used to obtain a detailed evolution of the various interfaces involved in the system. The size of the bubbles and the viscosity contrast between the two liquids are varied by more than one and four orders of magnitude, respectively, making it possible to obtain bubble shapes ranging from spherical to toroidal. A variety of flow regimes is observed, including that of small bubbles remaining trapped at the fluid–fluid interface in a film-drainage configuration. In most cases, the bubble succeeds in crossing the interface without being stopped near its undisturbed position and, during a certain period of time, tows a significant column of lower fluid which sometimes exhibits a complex dynamics as it lengthens in the upper fluid. Direct numerical simulations of several selected experimental situations are performed with a code employing a volume-of-fluid type formulation of the incompressible Navier–Stokes equations. Comparisons between experimental and numerical results confirm the reliability of the computational approach in most situations but also points out the need for improvements to capture some subtle but important physical processes, most notably those related to film drainage. Influence of the physical parameters highlighted by experiments and computations, especially that of the density and viscosity contrasts between the two fluids and of the various interfacial tensions, is discussed and analysed in the light of simple models
More planetary candidates from K2 Campaign 5 using TRAN_K2
Context. The exquisite precision of space-based photometric surveys and the unavoidable presence of instrumental systematics and intrinsic stellar variability call for the development of sophisticated methods that distinguish these signal components from those caused by planetary transits. Aims: Here, we introduce the standalone Fortran code TRAN_K2 to search for planetary transits under the colored noise of stellar variability and instrumental effects. We use this code to perform a survey to uncover new candidates. Methods: Stellar variability is represented by a Fourier series and, when necessary, by an autoregressive model aimed at avoiding excessive Gibbs overshoots at the edges. For the treatment of systematics, a cotrending and an external parameter decorrelation were employed by using cotrending stars with low stellar variability as well as the chip position and the background flux level at the target. The filtering was done within the framework of the standard weighted least squares, where the weights are determined iteratively, to allow a robust fit and to separate the transit signal from stellar variability and systematics. Once the periods of the transit components are determined from the filtered data by the box-fitting least squares method, we reconstruct the full signal and determine the transit parameters with a higher accuracy. This step greatly reduces the excessive attenuation of the transit depths and minimizes shape deformation. Results: We tested the code on the field of Campaign 5 of the K2 mission. We detected 98% of the systems with all their candidate planets as previously reported by other authors. We then surveyed the whole field and discovered 15 new systems. An additional three planets were found in three multiplanetary systems, and two more planets were found in a previously known single-planet system. The source code TRAN_K2.F developed in this work is available at http://www.konkoly.hu/staff/kovacs/tran_k2.html, http://https://github.com
Elektrokémiai úton modulált planáris optikai hullámvezető szenzorok fejlesztése = Development of electrochemically assisted planar waveguide optical sensors
Munkánkban elektrokĂ©miai mĂłdszereket alkalmaztunk optikai szenzorok kĂ©szĂtĂ©sĂ©ben. ElektrokĂ©miai polimerizáciĂłval kĂĽlönbözĹ‘ monomereket felhasználva optikai szenzor rĂ©tegeket alakĂtottunk ki planáris indium-Ăłnoxid (ITO) felĂĽleten vĂzben oldott klĂłr mĂ©rĂ©sĂ©re. RĂ©szletesen vizsgáltuk poliluminol (PL) esetĂ©ban az leválasztási eljárások hatását a kemilumineszcenciás jelre, a kemilumineszcenciás meghatározások optimális körĂĽlmĂ©nyeit. A PL rĂ©teg alkalmas vĂzben oldott klĂłr mĂ©rĂ©sĂ©re közvetlenĂĽl is, de hidrogĂ©n-peroxid jelenlĂ©tĂ©ben a reakciĂł közel százszor Ă©rzĂ©kenyebb (kimut. hat: 0.1 mikroM). Immobilizált tormaperoxidáz enzimmel hidrogĂ©n peroxid mĂ©rĂ©sĂ©re alkalmas bioszenzort kĂ©szĂtettĂĽnk. ElektrokĂ©miai Ă©s kĂ©miai Ăşton regenerálhatĂł optikai szenzort kĂ©szĂtettĂĽnk rĂ©zion Ă©s klĂłr detektálására ITO felĂĽleten. A meghatározandĂł anyaggal törtĂ©nt szĂnreakciĂł után az ITO felĂĽletet megfelelĹ‘ potenciállal polarizáltuk, aminek következtĂ©ben a szenzor visszatĂ©rt eredeti állapotába Ă©s Ăşjabb mĂ©rĂ©sre vált alkalmassá. A polimerekben Ă©s gĂ©lekben Ă©rvĂ©nyes diffĂşziĂłs egyĂĽtthatĂłk meghatározására mikroelektrĂłdokkal mĂ©rĂ©seket Ă©s modellszámĂtásokat vĂ©geztĂĽnk. MegállapĂtottuk, hogy a szfĂ©rikus diffĂşziĂłt zavarĂł tárgyak a mĂ©rĂ©si eredmĂ©nyeket megváltoztatják. Planáris elrendezĂ©sű cellát javasoltunk a mĂ©rĂ©si hibák kikĂĽszöbölĂ©sĂ©re. AnĂłdos oxidáciĂłval porĂłzus mátrixot alakĂtottunk ki optikai ammĂłnia szenzorhoz Ă©s megvizsgáltuk az oxidáciĂł mĂłdjának a szenzorok analitikai tulajdonságaira gyakorolt hatását. | Electrochemical methods were used for the preparation of optical chemical sensors. Optical sensing layers were made of different monomers that were electropolymerized onto planar ITO for the determination of dissolved chlorine. The effect of the deposition method of polyluminol on the CL sign and the optimal conditions of the CL determinations were investigated in details. The PL layer was capable for direct measurement of dissolved chlorine, however a 100 fold increase was found in the presence of hydrogen peroxide (DL 0.1 microM). A biosensor for hydrogen peroxide was developed by using immobilized HRP enzyme. Planar optical sensors using electrochemical and chemical regeneration were prepared for Cu ion and for dissolved chlorine on ITO. After the color change - caused by the analyte ? was completed, the ITO was polarized with proper potential resulting in the reversing of the sensing membrane to its original state. Model calculations and experiments were performed by using microelectrodes for the determination of the diffusion coefficient in polymer and gel. It was found that an object in the space that disturbs the spheric distribution of the diffusing substance has influence on the measured data. A planar electrode array was suggested to avoid the error of determinations. Porous oxide layers were prepared by anodizing aluminum for a substrate for optical ammonia sensor. The effect of the oxidation conditions on the analytical parameters of the sensors were investigated
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