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71.
Seung-Woo Lee Jan Kouba Bob Schutz Do Hyeong Kim Young Jae Lee 《Journal of Geodesy》2013,87(10-12):923-934
This paper addresses real-time monitoring of the precipitable water vapor (PWV) from GNSS measurements and presents some results obtained from 6-month long GNSS PWV experiments using international and domestic GNSS networks. In the real-time GNSS PWV monitoring system a server/client structure is employed to facilitate formation of PWV networks and single-differenced GNSS measurements are utilized to mitigate errors in GNSS satellites’ orbits and clocks. An issue relating to baseline length between the server and clients is discussed in detail and as a result the PWV monitor is configured to perform in two modes depending on the baseline length. The server estimates sequentially the zenith wet delay of the individual stations, which is then converted into the PWV of the stations. We evaluate system performance by comparing the real-time PWV solution with reference solutions including meteorological measurements obtained with radiosondes and deferred-time precision GNSS PWV solutions. Results showed that the standard deviation of difference between the real-time PWV and the reference solutions ranged from 2.1 to 3.4 mm in PWV for a 6-month long comparison, which was improved to 1.4 to 2.9 mm by reducing comparison period to 20 days in winter. 相似文献
72.
Do Young Oh 《Urban geography》2013,34(7):1066-1068
In this study, we use a Geographic Information System-based index to measure spatial accessibility of public high schools. The index is applied to the Baton Rouge Metropolitan Statistical Area in 1990, 2000, and 2010. Overall, urban areas had consistently worse accessibility scores compared with suburban and rural areas. High schools with more African American students tended to have poorer accessibility levels. Schools with lower accessibility tended to be associated with poorer average student performance, and the effect strengthened between 2000 and 2010. In developing a better understanding of the accessibility of public high schools, this paper reaffirms the significance of space, place, and race, and challenges the notion of declining relevance of accessibility in Louisiana public education policymaking. 相似文献
73.
M. A. Do 《新西兰海洋与淡水研究杂志》2013,47(1):99-108
The basic acoustical methods for estimating the volume backscattering strength and the absolute biomass density are commonly known. However, the detailed techniques for minimising errors in fitting the calibrated parameters of an echo sounding system in these computations are still not adequately examined and discussed. This paper describes and discusses the following computing techniques involved in the absolute biomass estimation: (i) the fitting of the calibrated time varied gain (TVG) curve, the selection of its operating interval, and the correction of its response; (ii) the compensation for the limitation of the signal bandwidth; (iii) the computation of the equivalent beam width of a transducer using its calibrated beam patterns; and (iv) the accuracy in the conversion from the volume backscattering to the absolute fish density using individual fish target strength measurements. 相似文献
74.
A. Erdem E. Budding E. Soydugan F. Soydugan S.S. Doğru D. Doğru M. Tüysüz A. Dönmez H. Bakiş Y. Kaçar C. Çiçek Z. Eker O. Demircan 《New Astronomy》2009,14(2):109-120
We present a photometric study of three chromospherically active stars with long periods (V340 Gem, SAO 62042 and FI Cnc). The observations were made at the ÇOMU Observatory in 2006 and 2007. We have made initial photometric analyses of V340 Gem and SAO 62042, which are newly discovered RS CVn–type SB1 binaries, and established the photometric variations of FI Cnc, which is a single G8III active star. Photometric rotation periods of these stars were obtained by analyzing their light variations. The light variations, observed over three or more consecutive orbital cycles, were investigated by using spot models with the program SPOT. We also discussed the surface differential rotation coefficient for the primary component of the SB1 binary star SAO 62042 in this study, using our own photometric period together with an orbital period taken from the literature. 相似文献
75.
Alexandrine Marteel Vania Gaspari Claude F. Boutron Carlo Barbante Paolo Gabrielli Paolo Cescon Giulio Cozzi Christophe P. Ferrari Aurélien Dommergue Kevin Rosman Sungmin Hong Soon Do Hur 《Climatic change》2009,92(1-2):191-211
Cr, Fe, Rb, Ba and U were determined by inductively coupled plasma sector field mass spectrometry (ICP-SFMS) in various sections of the 3,270 m deep ice core recently drilled at Dome C on the high East Antarctic plateau as part of the EPICA program. The sections were dated from 263 kyr bp (depth of 2,368 m) to 672 kyr bp (depth of 3,062 m). When combined with the data previously obtained by Gabrielli and co-workers for the upper 2,193 m of the core, it gives a detailed record for these elements during a 672-kyr period from the Holocene back to Marine Isotopic Stage (MIS) 16.2. Concentrations and fallout fluxes of all elements are found to be highly variable with low values during the successive interglacial periods and much higher values during the coldest periods of the last eight climatic cycles. Crustal enrichment factors indicates that rock and soil dust is the dominant source for Fe, Rb, Ba and U whatever the period and for Cr during the glacial maxima. The relationship between Cr, Fe, Rb, Ba and U concentrations and the deuterium content of the ice appears to be similar before and after the Mid-Brunhes Event (MBE, around 430 kyr bp). Mean concentration values observed during the successive interglacials from the Holocene to MIS 15.5 appear to vary from one interglacial to another at least for part of the elements. Concentrations observed during the successive glacial maxima suggest a decreasing trend from the most recent glacial maxima (MIS 2.2 and 4.2) to the oldest glacial maxima such as MIS 14.2, 14.4 and 16.2, which could be linked with changes in the size distribution of dust particles transported from mid-latitude areas to the East Antarctic ice cap. 相似文献
76.
Zdzisław M. Migaszewski Agnieszka Gałuszka Stanisław Hałas Józef Dąbek Sabina Dołęgowska Irena Budzyk Ewa Starnawska Artur Michalik 《Environmental Geology》2009,57(1):29-40
In 2005 and 2006, hydrogeochemical study was carried out in the bipartite Wiśniówka Mała pit lake of the Holy Cross Mountains
(south-central Poland). This is the largest acidic water body in Poland. This report presents the element concentrations in
the water and sediment, stable sulfur and oxygen isotope ratios in the soluble sulfates, and stable oxygen isotope ratio in
the water. The scope of the investigation also encompassed mineralogical examinations (scanning electron microscope, X-ray
diffraction) of the sediment. The results of this study show that there is a spatial and temporal variability in concentrations
of most elements and sulfur isotope ratios in the examined pit lake. The water of the western pond displayed a lower pH with
a mean of 3.73 and higher conductivity (390 μS cm−1) as well as higher concentrations of sulfates (156 mg L−1) and most of the cations and anions. The concentrations of Fe2+ and Fe3+ averaged 0.8 and 0.4 mg·L−1. In contrast, the eastern pond water revealed a higher pH (mean of 4.36), lower conductivity (293 μS cm−1) and lower sulfate (90 mg L−1) and trace metal levels. Similar variations were recorded in the stable sulfur isotope ratios. The δ34SV-CDT(SO4
2−) values in the water of the western pit pond were in the range of −6.7 to −4.6‰ (mean of −5.6‰), whereas that in the eastern
pit pond ranged from −2.2 to −0.9‰ (−1.6‰). The alkalinity of the entire lake water was below 0.1 mg·L−1 CaCO3. No distinct difference in the δ18OV-SMOW(SO4
2−) was noted between the western and eastern pit ponds. Compared to the Purple Pond in the Sudetes (Poland) and similar sites
throughout the world, the examined pit lake is highlighted by distinctly low concentrations of sulfates, iron and other trace
metals. Based on this and other studies performed in the Holy Cross Mountains, a conclusion can be drawn that the SO4
2− in the Wiśniówka Mała pit lake water is a mixture of SO4
2− derived from the following sources: (1) pyrite oxidation (especially in the western pond water), (2) leaching of soluble
sulfates from soils and waste material, as well as (3) subordinate deposition of airborne sulfate precipitation. 相似文献
77.
Jesús Díaz-Curiel Sandra Rueda-Quintero Bárbara Biosca Georgina Doñate-Matilla 《Acta Geotechnica》2017,12(5):1119-1127
In this paper, we present a modification of the existing mathematical formulation used to obtain the allowable bearing pressure from dynamic penetration tests in order to extend its applicability to the design of shallow foundations. The conventional relationships adopted to obtain the allowable bearing pressure from penetrometer tests have a discontinuous gradient, and they are limited to a depth less than the footing width. The aim of this work was to find a relationship that permits the estimation of this pressure in cohesionless soils, from the results of dynamic probing super heavy tests, through a single non-piecewise and continuous relationship that remains valid up to depths several times the footing width. This equation was applied as part of the geomechanical characterization survey undertaken for the construction of an elevated helipad in the centre of the Iberian Peninsula. The survey results were considered satisfactory, and the construction was completed without structural problems. 相似文献
78.
在远距离遥测传输过程,被传输的讯号中断时,PTY—8遥测仪鉴频盘将输出幅度很大的脉冲干拢,严重地损害了记录图的质量,甚至有些已经记录到的地震波形被掩没在讯号中断后出现的高频脉冲干扰中。据此,我们设计了快速自动保护电路。使用此电路后,讯号中断和怀复在记录图上未出现任何脉冲,中断后记录呈一条直线。 相似文献
79.
J. P. Toutain F. Sortino B. Reynier B. Dupre M. Munoz A. Nonell M. Polve S. Chancha Do Vale 《Journal of Volcanology and Geothermal Research》2003,123(1-2):95
A new apparatus, Venturi Effect System (VES), designed for sampling volcanic plumes is described and tested at Vulcano (Italy). This device, together with purified basic NH4OH solutions, supplies optimal conditions to obtain reliable Stotal/Cl/F ratios and enrichment factors for metallic trace elements (MTE). Good concordance for acid gas ratios and metal enrichment factors in both the gas phase and the related plume allows the procedure to be validated. The VES appears in Vulcano conditions as a simple, robust and easily portable apparatus that allows reliable collection of both acid gases and MTE within a single sample and the analysis with current chemical methods (High Pressure Liquid Chromatography, Inductively Coupled Plasma–Mass Spectrometry). This apparatus may be suitable for more difficult volcanoes where only the plume can be sampled. 相似文献
80.
Mi Jung Lee Jong Ik Lee Soon Do Hur Yeadong Kim Jacques Moutte Elena Balaganskaya 《Lithos》2006,91(1-4):250-261
The Sr, Nd and Pb isotopic compositions for the Kovdor phoscorite–carbonatite complex (PCC), Kola Peninsula, NW Russia, have been determined to characterize the mantle sources involved and to evaluate the relative contributions of a plume and subcontinental lithospheric mantle in the formation of the complex. The Kovdor PCC is a part of the Kovdor ultramafic–alkaline–carbonatite massif, and consists of six intrusions. The initial isotopic ratios of the analyzed samples, calculated at 380 Ma, display limited variations: εNd, + 2.0 to + 4.7; 87Sr/86Sr, 0.70319 to 0.70361 (εSr, − 12.2 to − 6.2); 206Pb/204Pb, 18.38 to 18.74; 207Pb/204Pb, 15.45 to 15.50; 208Pb/204Pb, 37.98 to 39.28. The Nd and Sr isotope data of the Kovdor PCC generally fit the patterns of the other phoscorites and carbonatites from the Kola Alkaline Province (KAP), but some data are slightly shifted from the mixing line defined as the Kola Carbonatite Line, having more radiogenic 87Sr/86Sr ratios. However, the less radiogenic Nd isotopic compositions and negative Δ7/4 values of Pb isotopes of the analyzed samples exclude crustal contamination, but imply the involvement of a metasomatized lithospheric mantle source. Isotopic variations indicate mixing of at least three distinct mantle components: FOZO-like primitive plume component, EMI-like enriched component and DMM-like depleted component. The isotopic nature of the EMI- and DMM-like mantle component observed in the Kovdor samples is considered to be inherited from metasomatized subcontinental lithospheric mantle. This supports the previous models invoking plume–lithosphere interaction to explain the origin of the Devonian alkaline carbonatite magmatism in the KAP. 相似文献