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11.
12.
Bora flow characteristics in a complex valley environment
Marija Bervida, Samo Stanič, Griša Močnik, Longlong Wang, Klemen Bergant, Xiaoquan Song, 2021, izvirni znanstveni članek

Opis: This paper complements the existing studies of Bora flow properties in the Vipava valley with the study of Bora turbulence in a lower region of the troposphere. The turbulence characteristics of Bora flow were derived from high resolution Doppler wind lidar measurements during eight Bora wind episodes that occurred in November and December 2019. Based on the vertical profiles of wind velocity, from 80 to 180 m above the valley floor, the turbulence intensity related to all three spatial directions and the along-wind integral length scales related to three velocity components were evaluated and compared to the approximations given in international standards. The resulting turbulence characteristics of Bora flow in a deep mountain valley exhibited interesting behaviour, differing from the one expected and suggested by standards. The intensity of turbulence during Bora episodes was found to be quite strong, especially regarding the expected values for that particular category of terrain. The specific relationship between along-wind, lateral and vertical intensity was evaluated as well. The scales of turbulence in the along-wind direction were found to vary widely between different Bora episodes and were rather different from the approximations given by standards, with the most significant deviations observed for the along-wind length scale of the vertical velocity component. Finally, the periodicity of flow structures above the valley was assessed, yielding a wide range of possible periods between 1 and 10 min, thus confirming some of the previous observations from the studies of Bora in the Vipava valley.
Ključne besede: doppler wind lidar, Bora wind, turbulence intensity, complex terrain, turbulence integral length scale
Objavljeno v RUNG: 05.11.2021; Ogledov: 1936; Prenosov: 42
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Do children derive exact meanings pragmatically? Evidence from a dual morphology language
Franc Marušič, Rok Žaucer, Amanda Saksida, Jessica Sullivan, Dimitrios Skordos, Longlong Wang, David Barner, 2021, izvirni znanstveni članek

Opis: Number words allow us to describe exact quantities like sixty-three and (exactly) one. How do we derive exact interpretations? By some views, these words are lexically exact, and are therefore unlike other grammatical forms in language. Other theories, however, argue that numbers are not special and that their exact interpretation arises from pragmatic enrichment, rather than lexically. For example, the word one may gain its exact interpretation because the presence of the immediate successor two licenses the pragmatic inference that one implies “one, and not two”. To investigate the possible role of pragmatic enrichment in the development of exact representations, we looked outside the test case of number to grammatical morphological markers of quantity. In particular, we asked whether children can derive an exact interpretation of singular noun phrases (e.g., “a button”) when their language features an immediate “successor” that encodes sets of two. To do this, we used a series of tasks to compare English-speaking children who have only singular and plural morphology to Slovenian-speaking children who have singular and plural forms, but also dual morphology, that is used when describing sets of two. Replicating previous work, we found that English-speaking preschoolers failed to enrich their interpretation of the singular and did not treat it as exact. New to the present study, we found that 4- and 5-year-old Slovenian-speakers who comprehended the dual treated the singular form as exact, while younger Slovenian children who were still learning the dual did not, providing evidence that young children may derive exact meanings pragmatically.
Ključne besede: Acquisition of quantity expressions, Acquisition of exactness, Pragmatics of grammatical number, Inferences on quantity, Dual, Slovenian
Objavljeno v RUNG: 13.12.2020; Ogledov: 2342; Prenosov: 0
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16.
Electromagnetic emission of white dwarf binary mergers
Jorge Armando Rueda, Remo Ruffini, Yu Wang, Carlo Luciano Bianco, J.M. Blanco-Iglesias, Mile Karlica, P. Lorén-Aguilar, Rahim Moradi, Narek Sahakyan, 2019, izvirni znanstveni članek

Opis: It has been recently proposed that the ejected matter from white dwarf (WD) binary mergers can produce transient, optical and infrared emission similar to the "kilonovae" of neutron star (NS) binary mergers. To confirm this we calculate the electromagnetic emission from WD-WD mergers and compare with kilonova observations. We simulate WD-WD mergers leading to a massive, fast rotating, highly magnetized WD with an adapted version of the smoothed-particle-hydrodynamics (SPH) code Phantom. We thus obtain initial conditions for the ejecta such as escape velocity, mass and initial position and distribution. The subsequent thermal and dynamical evolution of the ejecta is obtained by integrating the energy-conservation equation accounting for expansion cooling and a heating source given by the fallback accretion onto the newly-formed WD and its magneto-dipole radiation. We show that magnetospheric processes in the merger can lead to a prompt, short gamma-ray emission of up to ≈ 1046 erg in a timescale of 0.1-1 s. The bulk of the ejecta initially expands non-relativistically with velocity 0.01 c and then it accelerates to 0.1 c due to the injection of fallback accretion energy. The ejecta become transparent at optical wavelengths around ~ 7 days post-merger with a luminosity 1041-1042 erg s-1. The X-ray emission from the fallback accretion becomes visible around ~ 150-200 day post-merger with a luminosity of 1039 erg s-1. We also predict the post-merger time at which the central WD should appear as a pulsar depending on the value of the magnetic field and rotation period.
Ključne besede: Astrophysics - High Energy Astrophysical Phenomena
Objavljeno v RUNG: 20.07.2020; Ogledov: 2546; Prenosov: 0
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17.
On the GeV Emission of the Type I BdHN GRB 130427A
Remo Ruffini, Rahim Moradi, Jorge Armando Rueda, Carlo Luciano Bianco, Christian Cherubini, Simonetta Filippi, Yen-Chen Chen, Mile Karlica, Narek Sahakyan, Yu Wang, She Sheng Xue, Laura Beccera, 2019, izvirni znanstveni članek

Opis: We propose that the inner engine of a type I binary-driven hypernova (BdHN) is composed of Kerr black hole (BH) in a non-stationary state, embedded in a uniform magnetic field B_0 aligned with the BH rotation axis and surrounded by an ionized plasma of extremely low density of 10^−14 g cm−3. Using GRB 130427A as a prototype, we show that this inner engine acts in a sequence of elementary impulses. Electrons accelerate to ultrarelativistic energy near the BH horizon, propagating along the polar axis, θ = 0, where they can reach energies of ~10^18 eV, partially contributing to ultrahigh-energy cosmic rays. When propagating with $\theta \ne 0$ through the magnetic field B_0, they produce GeV and TeV radiation through synchroton emission. The mass of BH, M = 2.31M ⊙, its spin, α = 0.47, and the value of magnetic field B_0 = 3.48 × 10^10 G, are determined self consistently to fulfill the energetic and the transparency requirement. The repetition time of each elementary impulse of energy ${ \mathcal E }\sim {10}^{37}$ erg is ~10^−14 s at the beginning of the process, then slowly increases with time evolution. In principle, this "inner engine" can operate in a gamma-ray burst (GRB) for thousands of years. By scaling the BH mass and the magnetic field, the same inner engine can describe active galactic nuclei.
Ključne besede: black hole physics, binaries, gamma-ray burst, neutron stars, supernovae, Astrophysics - High Energy Astrophysical Phenomena
Objavljeno v RUNG: 20.07.2020; Ogledov: 2758; Prenosov: 0
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18.
Magnetic Fields and Afterglows of BdHNe: Inferences from GRB 130427A, GRB 160509A, GRB 160625B, GRB 180728A, and GRB 190114C
Jorge Armando Rueda, Remo Ruffini, Mile Karlica, Rahim Moradi, Yu Wang, 2020, izvirni znanstveni članek

Opis: GRB 190114C is the first binary-driven hypernova (BdHN) fully observed from initial supernova (SN) appearance to the final emergence of the optical SN signal. It offers an unprecedented testing ground for the BdHN theory, which is here determined and further extended to additional gamma-ray bursts (GRBs). BdHNe comprise two subclasses of long GRBs, with progenitors a binary system composed of a carbon–oxygen star (COcore) and a neutron star (NS) companion. The COcore explodes as an SN, leaving at its center a newborn NS (νNS). The SN ejecta hypercritically accretes on both the νNS and the NS companion. BdHNe I are very tight binaries, where the accretion leads the companion NS to gravitationally collapse into a black hole (BH). In BdHN II, the accretion rate onto the NS is lower, so there is no BH formation. We observe the same afterglow structure for GRB 190114C and other selected examples of BdHNe I (GRB 130427A, GRB 160509A, GRB 160625B) and for BdHN II (GRB 180728A). In all cases, the afterglows are explained via the synchrotron emission powered by the νNS, and their magnetic field structures and their spin are determined. For BdHNe I, we discuss the properties of the magnetic field embedding the newborn BH, which was inherited from the collapsed NS and amplified during the gravitational collapse process, and surrounded by the SN ejecta.
Ključne besede: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics, General Relativity and Quantum Cosmology
Objavljeno v RUNG: 20.07.2020; Ogledov: 2529; Prenosov: 0
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19.
Lidar Observations of Mountain Waves During Bora Episodes
Longlong Wang, Marija Bervida, Samo Stanič, Klemen Bergant, William Eichinger, Benedikt Strajnar, 2020, objavljeni znanstveni prispevek na konferenci

Opis: Airflows over mountain barriers in the Alpine region may give rise to strong, gusty downslope winds, called Bora. Oscillations, caused by the flow over an orographic barrier, lead to formation of mountain waves. These waves can only rarely be observed visually and can, in general, not be reliably reproduced by numerical models. Using aerosols as tracers for airmass motion, mountain waves were experimentally observed during Bora outbreak in the Vipava valley, Slovenia, on 24-25 January 2019 by two lidar systems: a vertical scanning lidar positioned just below the peak of the lee side of the mountain range and a fixed direction lidar at valley floor, which were set up to retrieve two-dimensional structure of the airflow over the orographic barrier into the valley. Based on the lidar data, we determined the thickness of airmass layer exhibiting downslope motion, observed hydraulic jump phenomena that gave rise to mountain waves and characterized their properties.
Ključne besede: Bora, mountain waves, lidar observations
Objavljeno v RUNG: 08.07.2020; Ogledov: 2672; Prenosov: 0
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20.
Polarization Raman Lidar for Atmospheric Monitoring in the Vipava Valley
Longlong Wang, Samo Stanič, William Eichinger, Xiaoquan Song, Marko Zavrtanik, 2020, objavljeni znanstveni prispevek na konferenci

Opis: We report on the design, construction and performance of a polarization Raman lidar, built for atmospheric monitoring in the Vipava valley in SW Slovenia, a regional air pollution hot-spot where aerosols are expected to originate from a number of different sources. Its key features are automatized remote operation capability and indoor deployment, which provide high duty cycle in all weather conditions. System optimization and performance studies include the calibration of the depolarization ratio, merging of near-range (analog) and far-range (photon-counting) data, determination of overlap functions and validation of the retrieved observables with radiosonde data.
Ključne besede: polarization Ramal lidar, Vipava valley, atmospheric monitoring
Objavljeno v RUNG: 08.07.2020; Ogledov: 2905; Prenosov: 0
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