First Part Of Results Research Articles

Overtopping device numerical study: Openfoam solution verification and evaluation of curved ramps performances

The Overtopping Device is a type of Ocean Waves Energy Converter (OWEC) which concept is storing water provided by incident waves above sea level to feed a set of low head turbines. Present study aims to perform 2D numerical analyses of near-shore overtopping devices platforms to investigate the influence of curvature of the platforms on water discharge by means of OpenFOAM code, which is an open source software. Current study performs comparisons between Fluent and OpenFOAM solutions as well (first part of results). Therefore, pointing out OpenFOAM as a potential tool for simulation of overtopping devices is also one of the objectives of this study. The software comparison is performed based on a case found in literature considering seven linear overtopping platforms configurations inside a wave tank. The discretization method is the Finite Volume method solving momentum, continuity, and a water volume fraction (Volume of Fluid method) equation used to capture waves air–water interface. Platforms curvatures investigation considers 12.5 m and 25 m length devices, with three different shapes: concave, linear and convex. All of those are 6 m height with 5 m immerse and 1 m above water level. The ramps are submitted to incident regular waves (1 m height, 65.4 m length and 7.5 s period) inside a 10 m depth wave channel. Results showed that OpenFOAM wave model complies with the expected characteristics determined with mathematical classical equations and also it is very coherent with Fluent results. About the ramps shapes, it was observed that ramps curvature may maximize the water mass that overtops into the tank. Moreover, this study agreed with literature that lower ramp height/length ratio leads to water discharge improvement for linear ramps for specified wave and constructions conditions. Other important observation is that curved platforms usage is a very good option to reduce devices sizes without losing energetic potential. This is pointed out because the convex 12.5 m length, which has length/ratio bigger than 25 m length devices, achieved the greatest water discharge among the analyzed geometries.

Materijali za floru Srbije iz herbarijumske kolekcije PZZP (1)

The Herbarium collection of the Institute for Nature Conservation of the Vojvodina province (PZZP) is one of the least known institutional collections in Serbia. In this article is presented the first part of results of the ongoing process of examination and revision of this collection. It covers data on interesting, new and noteworthy vascular plant taxa from 6 genera (Cytisus L., Lamium L., Lappula Moench, Lathyrus L., Leersia Sw. and Legousia Durande) included in 18 species, 5 subspecies, 3 varieties, 4 forms, as well as 4 taxa with undetermined status [stat. indet.] and one supposed nothospecies. One species and subspecies (Lappula heteracantha subsp. heterocarpa) and 5 taxa on the different infraspecific levels are new for a flora of Serbia.

A Driver-Based Approach to Airport Valuation

This paper presents the first part of results of extensive research on an alternative concept to airport valuation. It reviews raditional and alternative valuation measures, illustrated by a sample of eight publicly quoted European airports. The main objective is to derive a model taking account of the underlying key value drivers.A peer group analysis shows that only few sector multiples applied by the investors’ community are significantly correlated with key performance indicators based on business fundamentals. By contrast to the results of this alternative driver-based valuation approach, these market multiples are affected by stock market fluctuations and do not adequately reflect the financial position and true value, and hence supports this paper’s view that airports should be valued by recognising key success factors.

Plasma dynamics in PF-1000 device under full-scale energy storage: I. Pinch dynamics, shock-wave diffraction, and inertial electrode

This paper (paper I) presents the first part of results obtained with the PF-1000 facility for the first time at its upper energy limit (≈1 MJ). Special attention is paid here to plasma (‘pinch’) dynamics, which was investigated in relation to its electro-technical and radiation (especially neutron) characteristics with the help of a number of diagnostics, both time-integrated and with nanosecond temporal resolution. In these methods we utilized a Rogowski coil for the routine electro-technical measurements, visual multi-frame and streak cameras, soft x-ray pin-hole multi-frame cameras, PIN-diode assembly and PM tubes with scintillators for soft and hard x-rays as well as for neutron investigations together with a set of activation counters. In particular, the temporal cross correlation of different phenomena taking place during the discharge was investigated. The pinch's longevity appears to be 10–15 times larger than the ideal magnetohydrodynamic growth time (ratio of the pinch radius to the ion thermal velocity). It is demonstrated how the ‘target’ dynamics (pinch plasma of the dense plasma focus (DPF)) depends on and may be controlled by the electrode's size and the geometry of the chamber in this large-scale device. Diffraction of a shock wave together with a current sheath on an obstacle made at the DPF anode cap opens an opportunity for an inertial electrode to be used in future at larger DPF devices.

On regressing functions

Mathematical Logic QuarterlyVolume 4, Issue 7-11 p. 148-156 Article On regressing functions† George Kurepa, ZagrebSearch for more papers by this author George Kurepa, ZagrebSearch for more papers by this author First published: 1958 https://doi.org/10.1002/malq.19580040706Citations: 3 † First part of results presented 23. 12. 1953 in Beograd in Mathematics Institute of Serbian Academy of Science. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat Citing Literature Volume4, Issue7-111958Pages 148-156 RelatedInformation