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Search Results: 1 - 10 of 297536 matches for " ?afanda J "
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Modeling of stability of gas hydrates under permafrost in an environment of surface climatic change – terrestrial case, Beaufort-Mackenzie basin, Canada
J. Majorowicz,J. ?afanda,K. Osadetz
Climate of the Past Discussions , 2011, DOI: 10.5194/cpd-7-2863-2011
Abstract: Modeling of the onset of permafrost formation and succeeding gas hydrate formation in the changing surface temperature environment has been done for the Beaufort-Mackenzie Basin (BMB). Numerical 1-D modeling is constrained by deep heat flow from deep well bottom hole temperatures, deep conductivity, present permafrost thickness and thickness of Type I gas hydrates. Latent heat effects were applied to the model for the entire ice bearing permafrost and Type I hydrate intervals. Modeling for a set of surface temperature forcing during the glacial-interglacial history including the last 14 Myr was performed. Two scenarios of gas formation were considered; case 1: formation of gas hydrate from gas entrapped under deep geological seals and case 2: formation of gas hydrate from gas in a free pore space simultaneously with permafrost formation. In case 1, gas hydrates could have formed at a depth of about 0.9 km only some 1 Myr ago. In case 2, the first gas hydrate formed in the depth range of 290–300 m shortly after 6 Myr ago when the GST dropped from 4.5 °C to 5.5. °C. The gas hydrate layer started to expand both downward and upward subsequently. These models show that the gas hydrate zone, while thinning persists under the thick body of BMB permafrost through the current interglacial warming periods.
Repeated temperature logs from Czech, Slovenian and Portuguese borehole climate observatories
J. afanda, D. Rajver, A. Correia,P. D de ek
Climate of the Past (CP) & Discussions (CPD) , 2007,
Abstract: Two borehole climate observatories were established in Slovenia and Portugal within a joint Czech-Slovenian-Portuguese project in the years 2003-2005. Together with the older Czech observatory, which has been operating since the year 1994, they monitor air, soil and bedrock temperatures with the aim of studying air-ground coupling and the downward propagation of the surface temperature changes. We report here on repeated temperature logs carried out within 6 boreholes at the sites of the observatories and their surroundings within a time span of 8–20 years (1985–2005). The repeated logs revealed subsurface warming in all the boreholes amounting to 0.2–0.6°C below 20 m depth. The compatibility of the observed temporal changes of subsurface temperature with surface air temperature (SAT) series measured in Prague (since 1771), Ljubljana (since 1851) and Lisbon (since 1856) was checked by comparing repeated temperature logs with synthetic profiles that were calculated using SAT series as forcing functions. The depth of the Czech borehole (140 m) and the Portuguese borehole (180 m) was sufficient for a reconstruction of the ground surface temperature (GST) history of the last 150–200 years. Reconstructed GSTs were compared with the SAT series measured in Prague and Lisbon, respectively. The reconstructed histories reproduce reasonably well the amplitude of the recent warming inferred from the meteorological data, 1–1.5°C above the long-term mean. The depth (100 m) of the four repeatedly logged Slovenian boreholes was too shallow for inversion, but a climatic reconstruction was carried out for a deeper borehole, logged in 2006 and located within 5 km from the Slovenian observatory. The obtained GST history was compared with SAT series from Ljubljana.
Contact metamorphism of Silurian black shales by a basalt sill: geological evidence and thermal modeling in the Barrandian Basin
Suchy V,afanda J,Sykorová I,Stejskal M
Bulletin of Geosciences , 2004, DOI: 10.3140/bull.geosci.2004.03.133
Abstract: Organic-rich shales of the Liteň Formation (Silurian) were intruded by a series of several-meter thick doleritic basalt sills soon after their deposition. The effect of rapid thermal stress on organic and mineral diagenesis of shales around a representative 4mthick sill has been studied using optical microscopy, Fourier-Transform infrared (FT-IR) and micro-Raman spectroscopy of dispersed graptolite particles, gas chromatography-mass spectrometry (GC-MS) of organic extracts, and X-ray diffraction (XRD) of the clay fraction. Our data suggest that the sills have only had a local effect on the thermal maturity of the adjacent sediments. Graptolite reflectance values (3.0-3.6% Rmax) and bireflectance (up to 3.1%) higher than the regional diagenetic background (~1.8 Rmax) were found to be restricted to the narrow zone immediately adjacent to the igneous contacts, with detectable alteration starting to take effect at about 70 to 80% of sill thickness. Based on recent empirical correlations, these values may indicate contact-metamorphic temperatures between 320-420 °C. The optical properties of graptolite fragments within the contact aureole correlate closely with the chemical and structural transformation as expressed by FT-IR and Raman spectroscopy data. The graptolite periderm undergoes systematic depletion of aliphatic-containing groups toward the igneous contacts, and transforms into a condensed aromatic residuum of an increased crystalline ordering, similar to high-rank coal or kerogen. Extractable organic matter within the immediate contact zone is strongly depleted, but appreciably higher concentrations were obtained at a distance of 1.2mbelow the intrusion. This suggests that the organic matter along the contact was gasified during the igneous event, and the expelled volatiles condensed in 'micro-reservoirs' a certain distance from the sill. In contrast to the organic matter, clay minerals from the contact aureole reveal a lower degree of thermal metamorphism. The values of illite crystallinity (IC; up to 0.44° Δ2θ) and chlorite crystallinity (ChC; 0.30-0.34° Δ2θ) recorded in a narrow contact zone imply only minor elevation above the regional diagenetic background (IC ~ 0.60-0.70° Δ θ), and broadly evidence paleotemperatures in the range of 170-300 °C. The apparent discrepancy between the degree of thermal transformation of the organic matter and the clay minerals can be ascribed to the greater sensitivity of organic materials to geologically short metamorphic heating. The results from computer thermal modeling of the sill do not match the empirical ge
Repeated temperature logs from the sites of the Czech, Slovenian and Portuguese borehole climate stations
J. ?afanda,D. Rajver,A. Correia,P. Děde?ek
Climate of the Past Discussions , 2007,
Abstract: Two borehole climate stations were established in Slovenia and Portugal within a joint Czech-Slovenian-Portuguese project in the years 2003–2005. They completed the older Czech station, which has been operating since the year 1994. We report here on the repeated temperature logs carried out within 6 boreholes at the sites of the stations and their surroundings within a time span of 8–20 years (1985–2005). The repeated logs revealed subsurface warming in all the boreholes amounting to 0.2–0.6°C below the depth of the annual run at 20 m. The depth of the Czech borehole (140 m) and the Portuguese borehole (180 m) was sufficient enough for a reconstruction of the ground surface temperature (GST) history of the last 150–200 years and their comparison with the surface air temperature (SAT) series measured in Prague (since 1771) and Lisbon (1856), respectively. The reconstructed histories reproduce reasonably well the amplitude of the recent warming, 1–1.5°C above the long-term mean. The depth of all four Slovenian boreholes, 100 m, did not allow the inversion, but it was possible to apply it to a deep borehole 5 km apart from the Slovenian station. The obtained GST history was compared with SAT series from Ljubljana (since 1851). Alternatively, a compatibility of the observed temporal changes of subsurface temperature with surface air temperature series measured in Prague, Ljubljana and Lisbon was checked by comparing differences of the repeated logs with the synthetic ones. These were calculated by using the SAT series as a forcing function at a surface of transient geothermal models of the borehole sites. A degree of agreement varies from very well to rather poor, probably depending on unaccounted site specific factors, which are to be specified by a long-term temperature monitoring at the established stations.
Monitoring of air-ground temperature coupling and examples of shallow subsurface warming in Slovenia
Du?an Rajver,Jan ?afanda,Petr Dede?ek
Geologija , 2006,
Abstract: We have started with a long-term monitoring of the air-ground temperature coupling in three different climate provinces of Europe with the aim to explore the assumption on a long-term tracking of the mean annual surface air temperature and the ground surfacetemperature. Under the frame of a joint project the borehole climate stations have been established in three countries and the monitoring launched in Prague (Czech Republic) in 2002, near Kostanjevica (Slovenia) in November 2003, and near Evora (Portugal) inMay 2005. The monitoring is vital for the climatic interpretation of the ground surface temperature history that is obtained from present-day temperature-depth profiles that are measured in deep boreholes. With temperature measurements every 30 minutes in the air,in the soil and in the bedrock down to 40 m depth we are able to observe a propagation of surface soil temperature changes into depth. Gathered data on the differences between mean air and soil temperatures and its inter-annual variability from the Slovene stationare presented. The 2 year and 10 months long monitoring has given so far a rough estimation of the difference between mean annual soil and air temperatures to be around 1 °C. We present also examples of non-conductive features in the temperature time series both inthe soil and in bedrock. Another method of checking the air-ground temperature coupling is based upon repeated temperature measurements in the boreholes. The present rate of surface warming is large enough, and therefore, allows a reliable detection of the undergroundtemperature-time changes in the temperature-depth profiles that are acquired by repeated temperature logging with a time span of several years. We present the results of these repeated measurements in some chosen boreholes in Slovenia with the time span of measurements between 8 and 20 years.
New components of the mercury’s perihelion precession  [PDF]
J. J. Smulsky
Natural Science (NS) , 2011, DOI: 10.4236/ns.2011.34034
Abstract: The velocity of perihelion rotation of Mercury's orbit relatively motionless space is computed. It is prove that it coincides with that calculated by the Newtonian interaction of the planets and of the compound model of the Sun’s rotation.
Simple General Purpose Ion Beam Deceleration System Using a Single Electrode Lens  [PDF]
J. Lopes, J. Rocha
World Journal of Engineering and Technology (WJET) , 2015, DOI: 10.4236/wjet.2015.33014
Abstract: Ion beam deceleration properties of a newly developed low-energy ion beam implantation system were studied. The objective of this system was to produce general purpose low-energy (5 to 15 keV) implantations with high current beam of hundreds of μA level, providing the most wide implantation area possible and allowing continuously magnetic scanning of the beam over the sample(s). This paper describes the developed system installed in the high-current ion implanter at the Laboratory of Accelerators and Radiation Technologies of the Nuclear and Technological Cam-pus, Sacavém, Portugal (CTN).
Constraints on velocity anisotropy of spherical systems with separable augmented densities
J. An
Physics , 2011, DOI: 10.1088/0004-637X/736/2/151
Abstract: If the augmented density of a spherical anisotropic system is assumed to be multiplicatively separable to functions of the potential and the radius, the radial function, which can be completely specified by the behavior of the anisotropy parameter alone, also fixes the anisotropic ratios of every higher-order velocity moment. It is inferred from this that the non-negativity of the distribution function necessarily limits the allowed behaviors of the radial function. This restriction is translated into the constraints on the behavior of the anisotropy parameter. We find that not all radial variations of the anisotropy parameter satisfy these constraints and thus that there exist anisotropy profiles that cannot be consistent with any separable augmented density.
On the augmented density of a spherical anisotropic dynamic system
J. An
Physics , 2010, DOI: 10.1111/j.1365-2966.2011.18324.x
Abstract: This paper presents a set of new conditions on the augmented density of a spherical anisotropic system that is necessary for the underlying two-integral phase-space distribution function to be non-negative. In particular, it is shown that the partial derivatives of the Abel transformations of the augmented density must be non-negative. Applied for the separable augmented densities, this recovers the result of van Hese et al. (2011).
Fractional calculus, completely monotonic functions, a generalized Mittag-Leffler function and phase-space consistency of separable augmented densities
J. An
Physics , 2012,
Abstract: Under the separability assumption on the augmented density, a distribution function can be always constructed for a spherical population with the specified density and anisotropy profile. Then, a question arises, under what conditions the distribution constructed as such is non-negative everywhere in the entire accessible subvolume of the phase-space. We rediscover necessary conditions on the augmented density expressed with fractional calculus. The condition on the radius part R(r^2) -- whose logarithmic derivative is the anisotropy parameter -- is equivalent to R(1/w)/w being a completely monotonic function whereas the condition on the potential part is stated as its derivative up to the order not greater than 3/2-b being non-negative (where b is the central limiting value for the anisotropy parameter). We also derive the set of sufficient conditions on the separable augmented density for the non-negativity of the distribution, which generalizes the condition derived for the generalized Cuddeford system by Ciotti & Morganti to arbitrary separable systems. This is applied for the case when the anisotropy is parameterized by a monotonic function of the radius of Baes & Van Hese. The resulting criteria are found based on the complete monotonicity of generalized Mittag-Leffler functions.
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