Highlights of the LINEAR survey

Lincoln Near-Earth Asteroid Research asteroid survey (LINEAR) observed approximately 10,000 deg$^2$ of the northern sky in the period roughly from 1998 to 2013. Long baseline of observations combined with good cadence and depth ($14.5 < r_{SDSS}< 17.5$) provides excellent basis for investigation of variable and transient objects in this relatively faint and underexplored part of the sky. Details covering the repurposing of this survey for use in time domain astronomy, creation of a highly reliable catalogue of approximately 7,200 periodically variable stars (RR Lyrae, eclipsing binaries, SX Phe stars and LPVs) as well as search for optical signatures of exotic transient events (such as tidal disruption event candidates), are presented.Comment: To be published in the proceedings of the GREAT-ITN conference "The Milky Way Unravelled by Gaia: GREAT Science from the Gaia Data Releases", 1-5 December 2014, University of Barcelona, Spain, EAS Publications Serie

Revealing the Nature of Extreme Coronal-line Emitter SDSS J095209.56+214313.3

Extreme coronal-line emitter (ECLE) SDSSJ095209.56+214313.3, known by its strong, fading, high ionization lines, has been a long standing candidate for a tidal disruption event, however a supernova origin has not yet been ruled out. Here we add several new pieces of information to the puzzle of the nature of the transient that powered its variable coronal lines: 1) an optical light curve from the Lincoln Near Earth Asteroid Research (LINEAR) survey that serendipitously catches the optical flare, and 2) late-time observations of the host galaxy with the Swift Ultraviolet and Optical Telescope (UVOT) and X-ray telescope (XRT) and the ground-based Mercator telescope. The well-sampled, $\sim10$-year long, unfiltered LINEAR light curve constrains the onset of the flare to a precision of $\pm5$ days and enables us to place a lower limit on the peak optical magnitude. Difference imaging allows us to estimate the location of the flare in proximity of the host galaxy core. Comparison of the \textsl{GALEX} data (early 2006) with the recently acquired Swift UVOT (June 2015) and Mercator observations (April 2015) demonstrate a decrease in the UV flux over a $\sim 10$ year period, confirming that the flare was UV-bright. The long-lived UV-bright emission, detected 1.8 rest-frame years after the start of the flare, strongly disfavors a SN origin. These new data allow us to conclude that the flare was indeed powered by the tidal disruption of a star by a supermassive black hole and that TDEs are in fact capable of powering the enigmatic class of ECLEs.Comment: Submitted to Ap

Current State of Development of Ship Structural Design and Optimization Methods

This paper presents state-of-the-art methodologies and methods used in the rationally-based structural design of ships and offshore structures, namely design support system, structural optimization, surrogate modelling and sensitivity analysis. It demonstrates their application in structural design of a platform support vessel. It ends with a list of benefits that a structural designer may expect when the presented methods/methodologies are used. It also shows the obstacles to their full implementation in the engineering practice

Current State of Development of Ship Structural Design and Optimization Methods

This paper presents state-of-the-art methodologies and methods used in the rationally-based structural design of ships and offshore structures, namely design support system, structural optimization, surrogate modelling and sensitivity analysis. It demonstrates their application in structural design of a platform support vessel. It ends with a list of benefits that a structural designer may expect when the presented methods/methodologies are used. It also shows the obstacles to their full implementation in the engineering practice

Improvement of beam finite element for ship structural analysis

U radu su opisane formulacije grednog konačnog elementa: hibridna, obična ekscentrična i modificirana ekscentrična koje se najčešće upotrebljavaju u analizi odziva brodskih konstrukcija. Ispitana je njihova točnost kod proračuna čvornih pomaka i normalnog aksijalnog naprezanja u odnosu na model s finom mrežom te je dana i njihova međusobna usporedba. Uočeni su problemi kod proračuna unutrašnje aksijalne sile i s njom povezanih naprezanja kod običnog ekscentričnog grednog elementa te je predložena korekcija. Izveden je i gredni konačni element sa sedam stupnjeva slobode te su pokazani njegovi nedostaci. Na kraju rada je opisan još i ljuskasti element koji je, uz modificirani ekscentrični gredni konačni element, ugrađen u program PLO2X te je prikazan detaljni proračun čvornih pomaka, unutrašnjih sila i naprezanja za promatranu konstrukciju.Hybrid, native eccentric and modified eccentric beam finite element formulations, most commonly employed in the analysis of the strength of ship structures, are described and discussed in this work. Their accuracy in terms of the nodal displacements and normal axial stresses is tested against a fine mesh model and they are also compared to each other. Existence of error in calculation of internal axial force and related stresses when native eccentric beam element is used was demonstrated and certain correction is proposed. A seven-degrees-of-freedom element is presented as well as the negative aspects of its use. At the end shell element implemented in PLO2X software together with modified eccentric beam element is described as well as detailed calculation of nodal degrees of freedom, internal forces and stresses for structure considered in this work

Unapređenje grednog konačnog elementa za analizu brodske konstrukcije

U radu su opisane formulacije grednog konačnog elementa: hibridna, obična ekscentrična i modificirana ekscentrična koje se najčešće upotrebljavaju u analizi odziva brodskih konstrukcija. Ispitana je njihova točnost kod proračuna čvornih pomaka i normalnog aksijalnog naprezanja u odnosu na model s finom mrežom te je dana i njihova međusobna usporedba. Uočeni su problemi kod proračuna unutrašnje aksijalne sile i s njom povezanih naprezanja kod običnog ekscentričnog grednog elementa te je predložena korekcija. Izveden je i gredni konačni element sa sedam stupnjeva slobode te su pokazani njegovi nedostaci. Na kraju rada je opisan još i ljuskasti element koji je, uz modificirani ekscentrični gredni konačni element, ugrađen u program PLO2X te je prikazan detaljni proračun čvornih pomaka, unutrašnjih sila i naprezanja za promatranu konstrukciju

Testni primjer za strukturnu optimizaciju

U ovom radu se razmatraju različite formulacije grednog konačnog elementa koji se upotrebljava u metodi konačnih elemenata. Na početku je dana kratka teorijska osnova svakog od tri razmatrana elementa: hibridnog grednog konačnog elementa te dva ekscentrična gredna konačna elementa (obični ekscentrični gredni konačni element i modificirani ili kompatibilni gredni konačni element). Potom je izrađen jednostavni teorijski model s tri skupine rubnih uvjeta, tri različita slučaja opterećenja te tri različite gustoće mreže konačnih elemenata. Za svaku kombinaciju slučaja opterećenja i rubnih uvjeta prikazani su rezultati proračuna naprezanja, vertikalnih pomaka i parametara podobnosti. Isti proračun je izvršen i na modelu stvarnog broda (Ro-Pax) s prikazanim rezultatima proračuna za jedan uzdužnjak i sponju odabrane palube tog broda. \Na kraju su sve tri formulacije međusobno uspoređene u smislu izračunatih naprezanja, vertikalnih pomaka i parametara podobnosti

Investigating Cepheid ℓ\ell Carinae's Cycle-to-cycle Variations via Contemporaneous Velocimetry and Interferometry

Baade-Wesselink-type (BW) techniques enable geometric distance measurements of Cepheid variable stars in the Galaxy and the Magellanic clouds. The leading uncertainties involved concern projection factors required to translate observed radial velocities (RVs) to pulsational velocities and recently discovered modulated variability. We carried out an unprecedented observational campaign involving long-baseline interferometry (VLTI/PIONIER) and spectroscopy (Euler/Coralie) to search for modulated variability in the long-period (P $\sim$ 35.5 d) Cepheid Carinae. We determine highly precise angular diameters from squared visibilities and investigate possible differences between two consecutive maximal diameters, $\Delta_{\rm{max}} \Theta$. We characterize the modulated variability along the line-of-sight using 360 high-precision RVs. Here we report tentative evidence for modulated angular variability and confirm cycle-to-cycle differences of $\ell$ Carinae's RV variability. Two successive maxima yield $\Delta_{\rm{max}} \Theta$ = 13.1 $\pm$ 0.7 (stat.) {\mu}as for uniform disk models and 22.5 $\pm$ 1.4 (stat.) {\mu}as (4% of the total angular variation) for limb-darkened models. By comparing new RVs with 2014 RVs we show modulation to vary in strength. Barring confirmation, our results suggest the optical continuum (traced by interferometry) to be differently affected by modulation than gas motions (traced by spectroscopy). This implies a previously unknown time-dependence of projection factors, which can vary by 5% between consecutive cycles of expansion and contraction. Additional interferometric data are required to confirm modulated angular diameter variations. By understanding the origin of modulated variability and monitoring its long-term behavior, we aim to improve the accuracy of BW distances and further the understanding of stellar pulsations.Comment: Accepted for publication in MNRAS. 19 pages, 13 figures, 10 table