Is sky distribution of gamma-ray bursts random?     

L. G. Balázs  R. Vavrek  A. Mészáros  I. Horváth  Z. Bagoly  P. Veres  G. Tusnády 《Astrophysical Bulletin》2010,65(3):277-285

We investigate the full randomness of the angular distribution of gamma-ray bursts (GRBs) detected by the BATSE (the Burst and Transient Source Experiment). We divided the BATSE sample into 5 subsamples (short1, short2, intermediate, long1, long2 based on their durations and peak fluxes and studied the angular distributions separately. We used three methods, the Voronoi tesselation, minimal spanning tree and multifractal spectra to search for non-randomness in the subsamples. To investigate the eventual non-randomness in the subsamples we defined 13 test-variables (9 from the Voronoi tesselation, 3 from the minimal spanning tree and one from the multifractal spectrum). We performed Monte Carlo simulations taking into account the BATSE sky-exposure function. We tested the randomness by introducing squared Euclidean distances in the parameter space of the test-variables. We concluded that the short1, short2 groups deviate significantly (99.90%, 99.98%) from the full randomness in the distribution of the squared Euclidean distances, however, it is not the case with the long subsamples. In the intermediate group, the squared Euclidean distances also yield a significant deviation (98.51%).  相似文献   

Relationship between density,compressive strength,tensile strength and aggregate properties of andesites from Hungary     

Ákos Török  Balázs Czinder 《Environmental Earth Sciences》2017,76(18):639

Aggregate properties and strength parameters of four andesites from two operating Hungarian quarries of Nógrádkövesd (one lithotype) and Gyöngyössolymos (three lithotypes) are presented in this paper. Air-dry, water-saturated and freeze–thaw subjected specimens were tested on core-drilled cylindrical specimens, and the aggregate properties were also determined from the remaining part of the drilled rock blocks. Tensile strength values rapidly decreased from air-dry to water-saturated and finally to freeze–thaw subjected specimens. Linear relationships between air-dry and water-saturated bulk densities and between UCS and modulus of elasticity were found. Micro-fabric influences strength and aggregate parameters of studied andesites; fine porphyritic andesite has the highest UCS and tensile strength and the best micro-Deval results, while coarser porphyritic andesite has lower strength and aggregate parameters. Test results were compared with previously published rock mechanical data of intermediate and basic igneous rocks. A good exponential correlation was found between micro-Deval and UCS values of this paper and previously published data sets, but there was no indication that micro-Deval values correlate well with Los Angeles values.  相似文献   

Fission track etching studies of different planes of epidote     

K. D. Bal  Nand Lal  K. K. Nagpaul 《Physics and Chemistry of Minerals》1982,8(4):158-160

Etching characteristics of different planes of epidote indicate that the bulk etching rate V _g for the plane (100) is a minimum and also that no angular track orientation anisotropy is observable on this or on the basal plane. The significance of these studies in the light of fission track dating of the mineral has also been discussed.  相似文献   

Fission track annealing characteristics and dating of vermiculite     

O. P. Sharma  K. D. Bal  H. S. Saini  K. K. Nagpaul 《Physics and Chemistry of Minerals》1979,5(2):133-139

Fission track annealing experiments for vermiculite mineral have been performed under optimised etching conditions and a correction curve translating track length reduction to track density reduction has been constructed. The blocking/closing temperature of the fission track system in the mineral has been calculated to be 125°±30° C. The corrected fission track age of vermiculite from Kasipatnam (Visakhapatnam), South India, has been calculated as 544±14 Ma. The activation energy and average uranium concentration of the mineral are 1.7 eV and 9.9×10^?8 gg^?1 respectively.  相似文献   

Biostratigraphy and floristic evolution of coal swamp floras of a part of Talcher Basin,India: a window on a Permian temperate ecosystem     

Shreerup Goswami  Kamaljyoti Das  Mrutyunjaya Sahoo  Soumyaranjan Bal  Sanghamitra Pradhan  Kamal Jeet Singh  Anju Saxena 《Arabian Journal of Geosciences》2018,11(17):524

The present megafloral assemblage recorded from the Barakar sediments of Dholpahar section along Singda rivulet near Gopal Prasad Village in Talcher Basin comprises of equisetaceous stems, Gangamopteris buriadica, Palaeovittaria kurzii and 19 species of the genus Glossopteris. Record of Gangamopteris, Palaeovittaria and many narrow mesh forms of Glosspteris viz., G. angustifolia, G. churiensis, G. communis, G. recurva, G. spatulata, G. stenoneura, G. tenuifolia, G. vulgaris and G. zeilleri from two older fossiliferous horizons demonstrates that these fossils were preserved during Lower Barakar sedimentation. The report of middle and broad mesh forms of Glossopteris viz., G. barakarensis, G. browniana, G. indica, G. intermittens, G. karharbariensis, G. nakkarea, G. oldhamii, G. taeniensis and G. retifera in the youngest fossiliferous horizons reveals that these fossils were preserved during the deposition of Upper Barakar sediments. The continuation of some of the Karharbari plant fossils in the early phase of Barakar Formation and their disappearance in the flora of Late Barakar suggests a shift in the climatic setup. Palaeoclimate and palaeovegetation of this area are also summarised in this study. Moreover, the fossil assemblages of different fossiliferous beds of Dholpahar section demonstrate the evolution of midrib and meshes in different reticulate leaves.  相似文献   

Automatic determination of 3D orientations of fossilized oyster shells from a densely packed Miocene shell bed     

Puttonen  Ana  Harzhauser  Mathias  Puttonen  Eetu  Mandic  Oleg  Székely  Balázs  Molnár  Gábor  Pfeifer  Norbert 《International Journal of Earth Sciences》2018,107(6):2125-2142

International Journal of Earth Sciences - Shell beds represent a useful source of information on various physical processes that cause the depositional condition. We present an automated method to...  相似文献   

Exploration of the high-redshift universe enabled by THESEUS     

Tanvir  N. R.  Le Floc’h  E.  Christensen  L.  Caruana  J.  Salvaterra  R.  Ghirlanda  G.  Ciardi  B.  Maio  U.  D’Odorico  V.  Piedipalumbo  E.  Campana  S.  Noterdaeme  P.  Graziani  L.  Amati  L.  Bagoly  Z.  Balázs  L. G.  Basa  S.  Behar  E.  De Cia  A.  Valle  M. Della  De Pasquale  M.  Frontera  F.  Gomboc  A.  Götz  D.  Horvath  I.  Hudec  R.  Mereghetti  S.  O’Brien  P. T.  Osborne  J. P.  Paltani  S.  Rosati  P.  Sergijenko  O.  Stanway  E. R.  Szécsi  D.  Tot́h  L. V.  Urata  Y.  Vergani  S.  Zane  S. 《Experimental Astronomy》2021,52(3):219-244

Experimental Astronomy - At peak, long-duration gamma-ray bursts are the most luminous sources of electromagnetic radiation known. Since their progenitors are massive stars, they provide a tracer...  相似文献   

Performance analysis of podded propulsors     

Şakir Bal  Mesut Güner 《Ocean Engineering》2009,36(8):556-563

In this study, the flow around the pod unit is analysed and the performance characteristics of the propeller on the pod are investigated. The main objective of the present work is to further improve the original numerical method developed before for the prediction of performance of podded propellers and to further validate the earlier developed numerical model with a specific emphasis on the hydrodynamic interaction amongst the propulsor components. While in the earlier numerical method, the axial induced velocities by pod and strut parts were included into the calculations on the propeller disc plane, in the present method the tangential induced velocities on the propeller disc plane are included in the calculations as well. The flow domain around the podded propeller is mainly divided into three parts; the axisymmetric pod part, the strut part and the propeller part. While the pod and strut parts are modelled by a low-order boundary element method (BEM), the propeller is represented by a vortex lattice method (VLM). Coupling of the BEM and the VLM is carried out in an iterative manner to incorporate the effect of the pod on the propeller, and vice versa. The present numerical method is applied to two different podded propellers with zero yaw angles in order to compare the results with those of experimental measurements. The present numerical method is also validated in the case of 15° of yaw angle for a podded propulsor. The effect of pod and strut on the propeller and vice versa are discussed.  相似文献   

Submerged macrophytes avoiding a negative feedback in reaction to hydrodynamic stress     

Jonas Schoelynck  Dieter Meire  Kris Bal  Kerst Buis  Peter Troch  Tjeerd Bouma  Patrick Meire  Stijn Temmerman 《Limnologica》2013,43(5):371-380

In most aquatic ecosystems, hydrodynamic conditions are a key abiotic factor determining species distribution and aquatic plant abundance. Recently, local differences in hydrodynamic conditions have been shown to be an explanatory mechanism for the patchy pattern of Callitriche platycarpa Kütz. vegetation in lowland rivers. These local conditions consists of specific areas of increased shear zones, resulting in additional plant stress and erosion of the sediment on the one hand and local decreased shear zones resulting in zones favourable to plant growth and sedimentation of bed material on the other hand. In this study, the process of this spatial plant-flow-sedimentation interaction has been illustrated quantitatively by in situ flume measurements. By disturbing the incoming discharge on a single patch in such flume, we have quantified the behaviour and influence of a C. platycarpa patch under normal field conditions (base flow). Additionally, the behaviour of a C. platycarpa patch under different conditions of hydrodynamic stress has been examined in a laboratory flume. Indeed, flexible, submerged macrophytes are capable to adapt patch dimensions with changing stream velocities. At times of modest hydrodynamic stress, the species takes a position near the water surface and optimises its leaf stand, thereby maximising its photosynthetic capacity. At times of peak discharge, the patch will bend down towards the river bed and become more confined and streamlined, as such averting the stream velocity and diminishing the risk of breaking or being uprooted.In this paper, the processes of local hydrodynamic conditions on the patch and the patch’ intriguing life strategy of avoiding negative feedback was shown.  相似文献   

Origin and ascent history of unusually crystal-rich alkaline basaltic magmas from the western Pannonian Basin     

M. Éva Jankovics  Gábor Dobosi  Antal Embey-Isztin  Balázs Kiss  Tamás Sági  Szabolcs Harangi  Theodoros Ntaflos 《Bulletin of Volcanology》2013,75(9):1-23

The last eruptions of the monogenetic Bakony-Balaton Highland Volcanic Field (western Pannonian Basin, Hungary) produced unusually crystal- and xenolith-rich alkaline basalts which are unique among the alkaline basalts of the Carpathian–Pannonian Region. Similar alkaline basalts are only rarely known in other volcanic fields of the world. These special basaltic magmas fed the eruptions of two closely located volcanic centres: the Bondoró-hegy and the Füzes-tó scoria cone. Their uncommon enrichment in diverse crystals produced unique rock textures and modified original magma compositions (13.1–14.2 wt.% MgO, 459–657 ppm Cr, and 455–564 ppm Ni contents). Detailed mineral-scale textural and chemical analyses revealed that the Bondoró-hegy and Füzes-tó alkaline basaltic magmas have a complex ascent history, and that most of their minerals (～30 vol.% of the rocks) represent foreign crystals derived from different levels of the underlying lithosphere. The most abundant xenocrysts, olivine, orthopyroxene, clinopyroxene, and spinel, were incorporated from different regions and rock types of the subcontinental lithospheric mantle. Megacrysts of clinopyroxene and spinel could have originated from pegmatitic veins/sills which probably represent magmas crystallized near the crust–mantle boundary. Green clinopyroxene xenocrysts could have been derived from lower crustal mafic granulites. Minerals that crystallized in situ from the alkaline basaltic melts (olivine with Cr-spinel inclusions, clinopyroxene, plagioclase, and Fe–Ti oxides) are only represented by microphenocrysts and overgrowths on the foreign crystals. The vast amount of peridotitic (most common) and mafic granulitic materials indicates a highly effective interaction between the ascending magmas and wall rocks at lithospheric mantle and lower crustal levels. However, fragments from the middle and upper crust are absent from the studied basalts, suggesting a change in the style (and possibly rate) of magma ascent in the crust. These xenocryst- and xenolith-rich basalts yield divers tools for estimating magma ascent rate that is important for hazard forecasting in monogenetic volcanic fields. According to the estimated ascent rates, the Bondoró-hegy and Füzes-tó alkaline basaltic magmas could have reached the surface within hours to few days, similarly to the estimates for other eruptive centres in the Pannonian Basin which were fed by “normal” (crystal and xenoliths poor) alkaline basalts.  相似文献