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41.
A. J. L. Fernandes 《Monthly notices of the Royal Astronomical Society》2000,315(4):657-668
Long-slit spectra of the molecular outflow Herbig–Haro (HH) 46/47 have been taken in the J and K near-infrared bands. The observed H2 line emission confirms the existence of a bright and extended redshifted counter-jet outflow south-west of HH 46. In contrast with the optical appearance of this object, we show that this outflow seems to be composed of two different emission regions characterized by distinct heliocentric velocities. This implies an acceleration of the counter-jet.
The observed [Fe ii ] emission suggests an average extinction of 7–9 visual magnitudes for the region associated with the counter-jet.
Through position–velocity diagrams, we show the existence of different morphologies for the H2 and [Fe ii ] emission regions in the northern part of the HH 46/47 outflow. We have detected for the first time high-velocity (−250 km s−1 ) [Fe ii ] emission in the region bridging HH 46 to HH 47A. The two strong peaks detected can be identified with the optical positions B8 and HH 47B.
The H2 excitation diagrams for the counter-jet shock suggest an excitation temperature for the gas of T ex ≈2600 K . The lack of emission from the higher energy H2 lines, such as the 4–3 S(3) transition, suggests a thermal excitation scenario for the origin of the observed emission. Comparison of the H2 line ratios with various shock models yielded useful constraints about the geometry and type of these shocks. Planar shocks can be ruled out whereas curved or bow shocks (both J- and C-type) can be parametrized to fit our data. 相似文献
The observed [Fe ii ] emission suggests an average extinction of 7–9 visual magnitudes for the region associated with the counter-jet.
Through position–velocity diagrams, we show the existence of different morphologies for the H
The H
42.
43.
M. Marques Fernandes T. Stumpf T. Rabung Th. Fanghänel 《Geochimica et cosmochimica acta》2008,72(2):464-474
In order to characterize and quantify the substitution of Ca(II) by Cm(III) (coordination, charge compensation), homogeneous Cm(III) coprecipitated calcite was synthesized in a mixed-flow-through experiment. Two sets of experiments were conducted at pH 8.1 and at pH 12.5.At pH 8.1 two calcites, a calcite with a low Cm3+ concentration (LCMpH8.1) and a calcite with a high M3+ (Gd3+ and Cm3+) concentration (HCMpH8.1) were grown and investigated by time resolved laser fluorescence spectroscopy. The Cm(III) emission spectra of LCMpH8.1 and HCMpH8.1 show the same Cm(III) fluorescence signals for two Cm(III) species; Cm(III) species (1) with a peak maximum at 606.2 nm and Cm(III) species (2) with a peak maximum at 620.3 nm. Cm(III) species (1) has a mean lifetime of τ = 386 ± 40 μs and Cm(III) species (2) has a mean lifetime of τ = 1874 ± 200 μs. A lifetime of 386 μs correlates with 1.3 water molecule in the first coordination sphere of the Cm ion whereas a lifetime of 1874 μs indicates the total loss of the Cm(III) hydration sphere. According to the fluorescence emission peak position and the fluorescence emission lifetime, Cm(III) species (1) is identified as a surface sorbed species whereas Cm(III) species (2) is identified as a Cm(III) incorporated into the calcite lattice.Cm(III) fluorescence emission spectra of Cm(III) doped calcite grown at pH 12.5 (LCMpH12.5) show the same peak maxima which are found for LCMpH8.1 and HCMpH8.1 grown at pH 8.1 but an additional emission band at 608.2 nm (3) is found, which can be assigned to a further Cm(III) species. Fluorescence emission lifetime measurements show that this Cm(III) species (3) has a lifetime of τ = 477 ± 25 μs, which correlates with 0.9 water molecules in the first coordination sphere. Cm(III) species (3) is suggested to be a CmOH2+ incorporated species. 相似文献
44.
Fast error analysis of continuous GPS observations 总被引:4,自引:1,他引:3
It has been generally accepted that the noise in continuous GPS observations can be well described by a power-law plus white
noise model. Using maximum likelihood estimation (MLE) the numerical values of the noise model can be estimated. Current methods
require calculating the data covariance matrix and inverting it, which is a significant computational burden. Analysing 10 years
of daily GPS solutions of a single station can take around 2 h on a regular computer such as a PC with an AMD AthlonTM 64 X2 dual core processor. When one analyses large networks with hundreds of stations or when one analyses hourly instead
of daily solutions, the long computation times becomes a problem. In case the signal only contains power-law noise, the MLE
computations can be simplified to a process where N is the number of observations. For the general case of power-law plus white noise, we present a modification of the MLE equations
that allows us to reduce the number of computations within the algorithm from a cubic to a quadratic function of the number
of observations when there are no data gaps. For time-series of three and eight years, this means in practise a reduction
factor of around 35 and 84 in computation time without loss of accuracy. In addition, this modification removes the implicit
assumption that there is no environment noise before the first observation. Finally, we present an analytical expression for
the uncertainty of the estimated trend if the data only contains power-law noise.
Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. 相似文献
45.
The influence of Cenozoic tectonics on the groundwater-production capacity of fractured zones: a case study in Sao Paulo, Brazil 总被引:1,自引:0,他引:1
A new procedure is developed to correlate structural lineaments recognised through air-photo interpretation with subsurface
fracture features that are associated with zones of high groundwater production in fractured-rock environments. The analysis
approach is referred to as the homogeneous tectonic domain (HTD) method and involves correlating the lineament features of
a given area with the orientation of the primary stress fields and fracture structures associated with the recent tectonic
history that affected the region of study. The main premise of the method is that the most recent tectonic events in a given
area have had the most significant influence on the nature of the existing fracture network and subsequently on the regional
groundwater flow characteristics.
A study site was selected within the state of S?o Paulo, Brazil, where a complex tectonic history dating back to Precambrian
time has generated significant fracture porosity in the bedrock environment. The bedrock is heavily used in this area as a
domestic and industrial aquifer. The most recent tectonic activity is associated with five distinct Cenozoic events that generated
fracture features through both shear and extension stress fields. Due to the mode of formation, fracture zones generated by
extension tend to have the largest effective apertures and are the most conductive to groundwater. By applying the HTD method
in a series of test areas where specific Cenozoic events were dominant, fracture trends generated by shear and extension mechanisms
could be identified. Water-well production capacity was correlated with proximity to extension-type structures in most cases.
Other factors, such as the type of rock the well was completed in, had a much weaker influence on well capacity.
Through this application, the HTD approach is shown to provide a methodology for delineating fractured areas within rock environments
that have high potential for groundwater-resource development by combining classical lineament analysis with a clear understanding
of the tectonic history of a given area.
Electronic Publication 相似文献
46.
We present evidence for Ly pumping of the Lyman band system of molecular hydrogen in Herbig-Haro 7 and the bipolar outflow DR 21. For this study we have measured several vibrational-rotational emission lines of H2 whose energy levels are widely spaced and ranging from 6000 (v = 1) to 25000 Kelvin (v = 4). We show that the near-infrared H2 emission from the shocked gas in HH 7 can be well described by a bow C-type shock. The enhanced emission observed from the higher energy levels (v > 3) can be well modelled by employing the Ly pumping mechanism.In the DR 21 outflow the multi-line study showed that different physical conditions exist in the eastern and western emission lobes. The higher H2 line ratios measured in the eastern lobe suggests a higher Ly pump rate which may be locally produced in the fast bowshocks. The FUV radiation field emanating from the central HII regions may in addition be exciting the Lyman and Werner bands of H2 in the molecular lobes.We show that the observed H2 emission can be interpreted in terms of a simple model consisting of a C-type bowshock, which produces the low excitation H2 emission, and a FUV radiation field with enough Ly line radiation to produce the high excitation H2 emission through fluorescence. 相似文献
47.
Sandro da Silva Fernandes 《Celestial Mechanics and Dynamical Astronomy》1995,63(3-4):375-408
Expansions of the functions (r/a)cos
jv and (r/a)m
sin
jv of the elliptic motion are extended to highly eccentric orbits, 0.6627 ... <e<1. The new expansions are developed in powers of (e–e*), wheree* is a fixed value of the eccentricity. The coefficients of these expansions are expressed in terms of the derivatives of Hansen's coefficients with respect to the eccentricity. The new expansions are convergent for values of the eccentricity such that |e–e*|<(e*), where the radius of convergence (e*) is the same of the extended solution of Kepler's equation. The new expansions are intrinsically related to Lagrange's series. 相似文献
48.
A.O. Alothman R. M. Fernandes M.S. Bos S. Schillak B. Elsaka 《Arabian Journal of Geosciences》2016,9(8):529
We compute the secular tectonic motion of the Arabian plate, based on two different sets of Global Navigation Satellite System (GNSS) observations. The first set is formed by continuous GNSS (cGNSS) observations from 10 stations that are being operated since 2000 and have a data time span of at least 3.5 years. The cGNSS is supplemented with a second set of GNSS observations from 11 episodic stations (eGNSS) acquired between 2003 and 2009 (having at least six reoccupations). In order to evaluate the robustness of the solutions, we have estimated three different solutions using different parameterizations concerning the error models as follows: (a) estimating the velocities based only on the cGNSS sites; (b) combining the cGNSS and eGNSS, where the errors for the eGNSS solutions were rescaled to be consistent with those estimated for the cGNSS solutions; and (c) giving the same weight to all cGNSS and eGNSS solutions. Our conclusions show that case (b) is the preferred solution when the uncertainties of the eGNSS solutions are multiplied by a scale factor (4.1× in this particular case), since the inclusion of the eGNSS solutions allows to have a larger number of points with a better spatial distribution. Finally, we compare our angular velocity model with other models, in particular the most recent global models: GEODVEL (geodetic) and MORVEL (geophysical). We find that GEODVEL provides inaccurate predictions for the Arabian tectonic plate, whereas the MORVEL model shows a slightly better agreement with our solution. Our proposed model shows a significant improvement to model the present-day kinematics of Arabian plate. Thus, it is suggested to be used instead of the global models. As corollary, we also advocate that global models for present-day tectonic motions should be carefully verified for each modeled plate, so that dedicated regional models can provide better results. 相似文献
49.
Maclennan David N.; Fernandes Paul G.; Dalen John 《ICES Journal of Marine Science》2002,59(2):365-369
50.