Geochemical records seasonal climate variability from varved lake sediments     

Daryin  Andrey V.  Saarinen  Timo J. 《中国地球化学学报》2006,25(1):6-6

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K2O prograde zoning pattern in clinopyroxene from the Kokchetav diamond-grade metamorphic rocks: Missing part of metamorphic history and location of second critical end point for calc-silicate system     

Anastasiya O. Mikhno  Andrey V. Korsakov 《Gondwana Research》2013,23(3):920-930

Despite extensive studies of calc-silicate rocks of the Kokchetav massif, there is no satisfactory explanation of the origin of potassium-bearing clinopyroxene in alkali poor metamorphic rocks. In this paper we report the finding of potassium-bearing clinopyroxene with prograde zonation (K₂O increases from core to rim) from diamond-grade, but diamond-free UHP calc-silicate rocks of the Kokchetav massif. We believe that the crystallization of potassium-bearing clinopyroxene started on the prograde stage and slightly prior to the peak of UHP metamorphism. Thus, prograde metamorphic history is only traceable in diamond-free UHP calc-silicate rocks, while in diamond-bearing UHPM rocks it is completely reset. Fluid and polyphase solid inclusions, originally representing melt inclusions, occur in the core of potassium-bearing clinopyroxene and imply that melt and fluid may coexist in calc-silicate rocks even at 1000–1100 °C and 6–7 GPa.  相似文献   

Disproportion among Cladocera (Crustacea) skeletal components in lake sediment taphocoenoses and significance with respect to two methods of sub-fossil enumeration     

Zharov  Anton A.  Tchabovsky  Andrey V.  Kotov  Alexey A. 《Journal of Paleolimnology》2022,67(2):101-113

Journal of Paleolimnology - Analysis of Cladocera (Crustacea: Branchiopoda) subfossil remains in lake sediments features prominently in paleolimnological studies. It is well known, however, that...  相似文献   

Information and complexity measures applied to observed and simulated soil moisture time series     

Feng Pan  Yakov A. Pachepsky  Andrey K. Guber  Robert L. Hill 《水文科学杂志》2013,58(6):1027-1039

Abstract

Time series of soil moisture-related parameters provide important insights into the functioning of soil water systems. Analysis of patterns within such time series has been used in several studies. The objective of this work was to compare patterns in observed and simulated soil moisture contents to understand whether modelling leads to a substantial loss of information or complexity. The time series were observed at four plots in sandy soils within the USDA-ARS OPE3 experimental watershed, for a year; precipitation and evapotranspiration (ET) were measured and estimated, respectively, and used for soil water flow simulation with the HYDRUS-1D software. The information content measures are the metric entropy and the mean information gain, and complexity measures are the fluctuation complexity and the effective measure complexity. These measures were computed based on the binary encoding of soil moisture time series, and used probabilities of patterns, i.e. probabilities of joint or sequential appearance of symbol sequences. The information content of daily soil moisture time series was much smaller than that of rainfall data, and had higher complexity, indicating that soil worked essentially as an information filter. Information content and complexity decreased and increased with depth, respectively, demonstrating the increase in the information filtering action of soil. The information measures of simulated soil moisture content were close to those of the measurements, indicating the successful simulation of patterns in the data. The spatial variability of the information measures for simulated soil moisture content at all depths was less pronounced than the one of measured time series. Compared with precipitation and estimated ET, soil moisture time series had more structure and less randomness in this work. The information measures can provide useful complementary knowledge about model performance and patterns in observation and modelling results.

Citation Pan, F., Pachepsky, Y. A., Guber, A. K., & Hill, R. L. (2011) Information and complexity measures applied to observed and simulated soil moisture time series. Hydrol. Sci. J. 56(6), 1027–1039.  相似文献   

Surface phase transformations,surface complexation and solubilities of hydroxyapatite in the absence/presence of Cd(II) and EDTA     

Karin Viipsi  Staffan Sjöberg  Andrey Shchukarev  Kaia Tõnsuaadu 《Applied Geochemistry》2012

The removal of Cd from aqueous solutions by hydroxyapatite (HAP) was investigated with and without EDTA being present. Batch experiments were carried out using synthetic hydroxyapatite with Ca/P 1.57 and a specific surface area of 37.5 m²/g in the pH range 4–9 (25 °C; 0.1 M KNO₃). The surface composition of the solid phases were analysed by X-ray Photoelectron Spectroscopy (XPS). The surface layer of HAP was found to undergo a phase transformation with a (Ca + Cd)/P atomic ratio of 1.4 and the involvement of an ion exchange process (Ca²⁺ ↔ Cd²⁺). The amount of Cd removed from the solution increased with increasing pH, reaching ≈100% at pH 9. In the presence of EDTA Cd removal was reduced due to the formation of [CdEDTA]²⁻ in solution. The solubility of HAP increases in the presence of EDTA at pH values above 5, mainly due to the formation of [CaEDTA]²⁻. In contrast to this, the solubility was found to decrease in the presence of Cd²⁺ and CdEDTA²⁻. Using XPS the formation of a Cd-enriched HAP surface was found, which was interpreted as the formation of a solid solution of the general composition: Ca_8.4-xCd_x(HPO_4)1.6(PO_4)4.4(OH_)0.4${\text{Ca}}_{8.4-x}{\text{Cd}}_x({\text{HPO}}_4{)}_{1.6}({\text{PO}}_4{)}_{4.4}(\text{OH}{)}_{0.4}$.  相似文献   

Sampling error distribution for the ensemble Kalman filter update step     

Andrey Kovalenko  Trond Mannseth  Geir N?vdal 《Computational Geosciences》2012,16(2):455-466

In recent years, data assimilation techniques have been applied to an increasingly wider specter of problems. Monte Carlo variants of the Kalman filter, in particular, the ensemble Kalman filter (EnKF), have gained significant popularity. EnKF is used for a wide variety of applications, among them for updating reservoir simulation models. EnKF is a Monte Carlo method, and its reliability depends on the actual size of the sample. In applications, a moderately sized sample (40–100 members) is used for computational convenience. Problems due to the resulting Monte Carlo effects require a more thorough analysis of the EnKF. Earlier we presented a method for the assessment of the error emerging at the EnKF update step (Kovalenko et al., SIAM J Matrix Anal Appl, in press). A particular energy norm of the EnKF error after a single update step was studied. The energy norm used to assess the error is hard to interpret. In this paper, we derive the distribution of the Euclidean norm of the sampling error under the same assumptions as before, namely normality of the forecast distribution and negligibility of the observation error. The distribution depends on the ensemble size, the number and spatial arrangement of the observations, and the prior covariance. The distribution is used to study the error propagation in a single update step on several synthetic examples. The examples illustrate the changes in reliability of the EnKF, when the parameters governing the error distribution vary.  相似文献   

The data zoo in Astro-WISE     

Gijs A. Verdoes Kleijn  Andrey N. Belikov  John P. McFarland 《Experimental Astronomy》2013,35(1-2):187-201

In this paper we describe the way the Astro-WISE information system (or simply Astro-WISE) supports the data from a wide range of instruments and combines multiple surveys and their catalogues. Astro-WISE allows ingesting of data from any optical instrument, survey or catalogue, processing of this data to create new catalogues and bringing in data from different surveys into a single catalogue, keeping all dependencies back to the original data. Full data lineage is kept on each step of compiling a new catalogue with an ability to add a new data source recursively. With these features, Astro-WISE allows not only combining and retrieving data from multiple surveys, but performing scientific data reduction and data mining down to the rawest data in the data processing chain within a single environment.  相似文献   

Astro-WISE interfaces     

Andrey N. Belikov  Willem-Jan Vriend  Gert Sikkema 《Experimental Astronomy》2013,35(1-2):301-318

From a simple text interface to a graphical user interfaces—Astro-WISE provides the user with a wide range of possibilities to interact with the information system according to the user’s tasks and use cases. We describe a general approach to the interfacing of a scientific information system. We use this approach to create a number of services, which allows the user to browse the data stored in the system, to process the data and to exchange the newly created images and catalogs with the users within the system and wider astronomical community. Reusability of interfaces and services is another important feature of our approach. It reduces the time and resources spent to interface other information systems created from Astro-WISE.  相似文献   

GNSS Software Receivers     

Sergey S. Pospelov  Andrey L. Botchkovski  Peter A. Krauss  Stefan Berberich 《GPS Solutions》2000,4(1):48-55

Software Global Navigation Satellite Systems (GNSS) receivers are those that implement signal correlation processing not in hardware, but in their software. The main problem for the development of real-time software (SW) multichannel GNSS receivers is the tremendous amount of calculations to perform signal correlation. The article reviews recent developments of SW GNSS receivers. The emphasis is made on the computationally effective correlation processing algorithms and the optimization of processing allocation to the receiver's hardware (HW) and SW. An architecture is suggested that implements the PRN signals despreading in a special HW preprocessor while all the other correlation processing functions are still kept in SW. The combination of the most time-consuming processing in HW, and all signal structure-dependent processing in SW, enables unique flexibility of sophisticated GNSS receiver design based on inexpensive digital signal processors. ? 2000 John Wiley & Sons, Inc.  相似文献   

On the supernova heating of the intergalactic medium     

Andrey V. Kravtsov †  Gustavo Yepes 《Monthly notices of the Royal Astronomical Society》2000,318(1):227-238

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