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1.
This paper describes an alternative approach for generating pointing models for telescopes equipped with serial kinematics, esp. equatorial or alt-az mounts. Our model construction does not exploit any assumption for the underlying physical constraints of the mount, however, one can assign various effects to the respective components of the equations. In order to recover the pointing model parameters, classical linear least squares fitting procedures can be applied. This parameterization also lacks any kind of parametric singularity. We demonstrate the efficiency of this type of model on real measurements with meter-class telescopes where the results provide a root mean square accuracy of 1.5?2 arcseconds. 相似文献
2.
Vida Safari Gilnaz Arzpeyma Fereshteh Rashchi Navid Mostoufi 《International Journal of Mineral Processing》2009,93(1):79-83
A new mathematical model was developed for leaching of zinc ores containing silicates such as hemimorphite which produce a gel during leaching with sulfuric acid. This model is based on the shrinking core model in which the particle size and the reacting core shrink simultaneously. It was shown that the actual dissolution time of the ore particles is longer than the time corresponding to the dissolution of chemical zinc oxide itself. It was suggested that because of the existence of silicates in the ore, a gelatinous layer was formed around the reacting core. Since the gel product is soft, it breaks apart when the particles collide and as a result, the particles shrink. However, a thin gelatinous layer always covers the reacting core which increases the mass transfer resistance and increases the leaching time. This model was applied to leaching of a zinc-rich tailing containing hemimorphite and the thickness of the gelatinous layer as well as the diffusion coefficient in this layer was determined. 相似文献
3.
Zs. K&#x;vri F. Vilardell I. Ribas K. Vida L. van Driel‐Gesztelyi C. Jordi K. Olh 《Astronomische Nachrichten》2007,328(9):904-908
We present B and V light curves of a large stellar flare obtained with the Wide Field Camera at the Isaac Newton 2.5‐m telescope (La Palma). The source object is a faint (mV = 21.38) foreground star in the field of the Andromeda galaxy, with its most probable spectral type being dM4. We provide an estimate of the total flare energy in the optical range and find it to be of the order of 1035 erg. The cooling phase of the large flare shows three additional weak flare‐like events, which we interpret as results of a triggering mechanism also observed on the Sun during large coronal mass ejections. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
4.
J. Vida I. Foyo-Moreno L. Alados-Arboledas 《Theoretical and Applied Climatology》1999,63(3-4):141-147
Summary Having in mind the high complexity of the sky radiance distribution, the Commission of the European Communities, in the frame
of the Solar Energy R&D in the European Community Programme, developed among other related fields of research a clear sky
radiance model. This model, the so-called EC-Model, was intended for the estimation of the diffuse irradiance falling on an
inclined surface by integration of the sky radiance field. It represents a progress development over its predecessor, the
Berlin model, and takes into account all the scientific knowledge about this topic, lying heavily on the principles of the
Liebelt formulation and the work of Steven and Unsworth on the observed relative radiance distribution. The European Solar
Radiation Atlas was in part prepared by the adoption of the EC-Model and could not take into account Valko’s new results about
sky radiance distributions, because of time coincidence and that only previous results were ready at the time it was published.
In this work, we focus on the EC-Model behaviour, against experimental sky radiance data from Toronto, Canada. The SKYSCAN’834
Data Set is a well-known database, which we have used in order to investigate the EC-Model behaviour both under its original
formulation (the one that has been used in the development of the Atlas) and under the modified version suggested by Valko’s
results. Even though we are considering data from outside Europe, the results of this test let us establish the model limitations
and the modifications that should be done to it.
Received August 4, 1998 相似文献
5.
F. J. Olmo J. Vida I. Foyo-Moreno J. Tovar L. Alados-Arboledas 《Theoretical and Applied Climatology》2001,69(3-4):253-263
Summary
Knowledge of the partition of global solar irradiance in its diffuse and direct beam components is required in different areas
of applied meteorology. In the absence of solar irradiance measurements parametric approaches have to be used instead. In
the present work, the parametric CPCR2 model has been analysed at Granada (37.18° N, 3.58° W, 660 m a.m.s.l), an inland location,
covering a period greater than three years. Only cloudless conditions are analysed. Angstr?m’s α and β coefficients have been
computed from measurements carried out with a sunphotometer. As the study reveals, the best performance of the parametric
model is conditioned to the availability of appropriate information on aerosols, especially when the interest is focused on
the direct and diffuse irradiance.
Received October 18, 1999/Revised December 18, 2000 相似文献
6.
Alan D. MacPherson James E. McConnell Anneliese Vance Vida Vanchan 《The Professional geographer》2006,58(3):266-277
This article examines the extant and potential impact of U.S. antiterrorism policies on Canada‐U.S. cross‐border commerce. Particular attention is focused on the cross‐border trade that takes place between southern Ontario (Canada) and western New York (United States). Evidence from a survey of Canadian and U.S. exporters suggests that U.S. antiterrorism measures have inflated the business costs of exporters on both sides of the border. These measures have also created shipment delays that ultimately imply lost revenues for producers, as well as higher prices for consumers. Security‐related initiatives motivated by a genuine concern for the well‐being of U.S. citizens may nevertheless act as nontariff barriers to bilateral trade. We argue that a potential long‐run consequence of these additional costs is trade diversion. The article concludes with a brief discussion of the implications of the empirical findings for the geography of Canada‐U.S. bilateral trade. 相似文献
7.
H. Korhonen K. Brogaard K. Holhjem S. Ramstedt J. Rantala C.C. Thne K. Vida 《Astronomische Nachrichten》2007,328(9):897-903
Magnetic activity in the photosphere and chromosphere of the M dwarf EY Dra is studied and possible correlations between the two are investigated using photometric observations in the V and R bands and optical and near infrared spectroscopy. The longitudinal spot configuration in the photosphere is obtained from the V band photometry, and the chromospheric structures are investigated using variations in the Hα line profile and observations of the Paschen β line. The shape of the V band light‐curve indicates two active regions on the stellar surface, about 0.4 in phase apart. The spectroscopic observations show enhanced Hα emission observed close to the phases of the photometrically detected starspots. This could indicate chromospheric plages associated with the photospheric starspots. Some indications of prominence structures are also seen. The chromospheric pressure is limited to log mTR < –4 based on the non‐detection of emission in the Paschen β wavelength region. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
8.
K. Vida Zs. Kőovári M. Švanda K. Oláh K.G. Strassmeier J. Bartus 《Astronomische Nachrichten》2007,328(10):1078-1080
We re-investigate UZ Libræ spectra obtained at KPNO in 1998 and 2000. From the 1998 data we compose 11 consecutive Doppler images using the Ca I-6439, Fe I-6393 and Fe I-6411 lines. Applying the method of average cross-correlation of contiguous Doppler images we find anti-solar differential rotation with a surface shear of α ≈ –0.03. The pilot application of the local correlation tracking technique for the same data qualitatively confirms this result and indicates complex flow pattern on the stellar surface. From the cross-correlation of the two available Doppler images in 2000 we also get anti-solar differential rotation but with a much weaker shear of α ≈ –0.004. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
9.
Damir Šegon Željko Andreić Peter S. Gural Korado Korlević Denis Vida Filip Novoselnik Ivica Skokić 《Earth, Moon, and Planets》2014,112(1-4):33-44
The predicted Draconid meteor shower outburst during October 2011 had been observed by a portion of the Croatian Meteor Network whose stations encountered clear weather. A total of 95 Draconid orbits have been calculated from 18 contributing stations, and in this paper we present results for 63 orbits obtained from the fully automatic observation and processing pipeline. Two methods of trajectory estimation were applied, showing better fit results using a linearly changing velocity model versus a constant velocity model. The estimated mean radiant position has been found to be at RA = 262.6°, Dec = +55.7°, with estimated geocentric velocity Vg = 20.7 km/s. 相似文献
10.
Irena Grgić Andreja Dovžan Gorazd Berčič Vida Hudnik 《Journal of Atmospheric Chemistry》1998,29(3):315-337
Laboratory experiments were conducted with real atmospheric aerosol particles as well as with synthetic solutions under dark conditions, to simulate some of the chemical features of aerosols. In solutions obtained by the leaching of aerosols (size range >D
ae: 0.4–1.6 m) that contained sufficient amounts of transition metal ions (e.g. Fe) and organic species (e.g. oxalate), S(IV) oxidation rates were significantly lower than those expected from the Fe-catalyzed S(IV) autoxidation in Milli-Q water. The results suggest that oxalate is responsible for much of the observed inhibition. Acetate and formate also inhibit the reaction, but to a much lesser extent. Oxalate has a strong inhibiting effect on the Fe-catalyzed S(IV) autoxidation at all investigated pH values (2.8, 3.7 and 4.5). It was established that Fe(III)-oxalato complexes affect the redox cycling of Fe(II)/Fe(III) and that the observed decrease of the reaction rate is caused by the reduced amount of catalytically active Fe(III) due to the complexation with oxalate. For the system Fe-S(IV)-O2-oxalate at initial pH 3.7 the reaction rate was calculated using exponential simplification to account for oxalate influence on the amount of free Fe(III) by the following equation:–rS(IV) = k · [S(IV)] · [Fe(III))] · e
-b·[Ox] 相似文献