A refined model for the influence of ocean tides on UT1 and polar motion     

U. Seiler  J. Wünsch 《Astronomische Nachrichten》1995,316(6):419-423

Periodic changes in Universal Time and polar motion have been derived from a numerical ocean model for a number of small partial tides. Combined with the results reported earlier our model now includes the 34 most important constituents of degree 2 (measured by the amplitude of the tidal potential). The results show that the terms neglected in all existing models amount to 80 μs in UT1 and to 0.3 mas in polar motion.  相似文献   

New mass formula for spherically symmetric stellar configurations     

U. Bleyer  L. Sh. Grigorian  R. M. Avakian  E. V. Chubarian 《Astronomische Nachrichten》1995,316(1):1-7

A new formula is derived for the mass of spherically symmetric stellar configurations. An expression will be given where the mass square is connected to an integral over the pressure of gravitating matter. This formula turns out to hold for Newtonian gravity, for Einstein's GRT, for projective and bimetric scalar-tensor and further theories of gravitation.  相似文献   

Estimation of daily space–time precipitation series for macroscale hydrological modelling     

U. Haberlandt  G. W. Kite 《水文研究》1998,12(9):1419-1432

An important problem in modelling macroscale basins, especially for sparsely observed regions, is the lack of precipitation information. Alternatives to using straightforward interpolated surface observations include the utilization of more advanced interpolation techniques and the use of additional precipitation information from atmospheric models. Conventional and geostatistical methods are applied for optimal interpolation and assimilation of observed and model precipitation. Various time-series of daily areal precipitation distributions are produced and compared using not only an internal precipitation validation, but also an objective verification based on stream flow simulations. The Mackenzie River Basin in north-western Canada is used as the study area and hydrological simulations are carried out with the model SLURP. It was found that better interpolation techniques and the use of combined precipitation data can improve the hydrological simulations and that the enhancements are related to the relative size of the simulation units used. © 1998 John Wiley & Sons, Ltd.  相似文献   

The Herbig Be Star IL Cep A as a Long-Periodic Spectroscopic Binary     

N. Z. Ismailov  M. A. Pogodin  U. Z. Bashirova  G. R. Bahaddinova 《Astronomy Reports》2020,64(1):23-33

The results of long-term spectral monitoring of the Herbig Be star IL Cep A are presented. A smooth variation in the parameters of the Нα and Нβ line emission component has been discovered. The helium absorption lines He I λ4922 and 5876 Å show seasonal changes, however, these changes do not correlate with changes in hydrogen emission. The radial velocities of the narrow lines D Na I and DIB λ5780, 5796 Å correspond to that of the interstellar medium. The hydrogen emission lines are apparently formed in a triple system, including a close pair of B stars and a remote low-mass K–A component. The orbital elements of this system were calculated using an approximate spectral binary model, where a close pair of massive B stars was considered as one massive component. The rationale for this approach for determining the elements of the orbit is given. The orbital period P = 3550 ± 28 days is determined and some other parameters of the orbit are estimated.  相似文献   

Field Tests of the Procedure for a Photogrammetric Estimation of Snow-Glacial Surface Albedo     

Zhuravskiy  D. M.  Prokhorova  U. V.  Ivanov  B. V.  Yanjura  A. S.  Kuprikov  N. M.  Kurapov  M. V. 《Izvestiya Atmospheric and Oceanic Physics》2020,56(9):927-935

Izvestiya, Atmospheric and Oceanic Physics - The results of using an original procedure for estimating albedo from the photogrammetric data and exposure parameters by an unmanned aerial vehicle...  相似文献   

Effects of heavy metals (Pb2+ and Cd2+) on the ultrastructure, growth and pigment contents of the unicellular cyanobacterium Synechocystis sp. PCC 6803     

K. K. I. U. Arunakumara  ZHANG Xuecheng 《中国海洋湖沼学报》2009,27(2)

The unicellular cyanobacterium Synechocystis sp. PCC 6803, a model organism known for its unique combination of highly desirable molecular genetic, physiological and morphological characteristics, was employed in the present study. The species was cultured in BG11 liquid medium contained various initial concentrations of Pb2+ and Cd2+ (0, 0.5, 1, 2, 4, 6 and 8 mg/L). The experiment was conducted for six days and the metal induced alterations in the ultrastructure, growth and pigment contents were assessed. Alterations in the ultrastructure of the Synechocystis sp. PCC 6803 ceils became evident with the increased (>4 mg/L Pb2+) metal concentration. The photosynthetic apparatus (thylakoid membranes) were found to be the worst affected. Deteriorated or completely destroyed thylakoid membranes have made large empty spaces in the cell interior. In addition, at the highest concentration (8 mg/L pb2+), the polyphosphate granules became more prominent both in size and number. Despite the initial slight stimulations (0.2, 3.8 and 6.5% respectively at 0.5, 1 and 2 mg/L Pb2+), both metals inhibited the growth in a dose-dependent manner as incubation progressed. Pigment contents (chlorophyll a, βcarotene and phycocyanin) were also decreased with increasing metal concentration. Cells exposed to 6 mg/L Pb2+, resulted in 36.56, 37.39 and 29.34% reductions of chlorophyll a, β carotene and phycocyanin respectively over the control. Corresponding reductions for the same Cd2+concentrations were 57.83, 48.94 and 56.90%. Lethal concentration (96 h LC50) values (3.47 mg/L Cd2+ and 12.11 mg/L Pb2+) indicated that Synechocystis sp. PCC 6803 is more vulnerable to Cd2+ than Pb2+.  相似文献   

The study of the long-term effects of a catastrophic black oil spill in the Kerch Strait     

G. A. Kolyuchkina  V. A. Spiridonov  U. V. Simakova  V. I. Peresypkin  N. A. Belyaev  P. V. Khlebopashev  A. V. Makarov  F. V. Sapozhnikov  V. V. Kozlovskii  E. S. Shapovalova 《Oceanology》2009,49(5):742-744

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Experimental studies on sloshing behavior due to horizontal movement of liquids in baffled tanks     

P.K. Panigrahy  U.K. Saha  D. Maity 《Ocean Engineering》2009,36(3-4):213-222

A series of experiments have been carried out in a developed liquid sloshing setup to estimate the pressure developed on the tank walls and the free surface displacement of water from the mean static level. The square tank attached to a shaking table can be moved to and fro by a cam arrangement driven by a DC motor. Pressure and displacement studies are done on the basis of changing excitation frequency of the shaking table and fill level in the tank. Experiments were carried out without and with baffles, and the consequent changes in the parameters are observed.  相似文献   

Application of a proportional-integral control for the estimation of static formation temperatures in oil wells     

G. Espinosa-Paredes  A. Morales-Díaz  U. Olea-González  J.J. Ambriz-Garcia 《Marine and Petroleum Geology》2009

A strategy based on proportional-integral (PI) feedback control was applied to solve an inverse heat transfer problem for estimating static formation temperatures (SFTs) from logged temperatures in oil wells. The PI control feedbacks the error between logged and simulated temperatures during the shut-in time process, existing SFT proposal. Thus, mathematically speaking an inverse heat transfer problem was solved in this way, since SFT represents the initial conditions (which are unknown) to solve the partial differential equations governing the heat transfer process in the wellbore-formation system. The mathematical model considers transient convective heat transfer due to circulation losses to the rock surrounding a well. The methodology was tested analyzing two oil wells (MB-3007 and MB-3009) from the Gulf of Mexico and results were compared against two classic methods. The method presented in this work needs only one temperature measurement for each fixed depth to estimate the SFT.  相似文献   

Impact of cropping pattern changes on the exploitation of water resources: A remote sensing and GIS approach     

Anil Sood  B. U. Choudhury  S. S. Ray  S. K. Jalota  P. K. Sharma  Shushma Panigrahy 《Journal of the Indian Society of Remote Sensing》2009,37(3):483-491

A remote sensing-based approach was applied to study the impact of changes in cropping system on the exploitation of water resources in two districts namely Ludhiana in central Punjab and Muktsar in South-Western Punjab. Rice-wheat remained dominant rotation in Ludhiana while cottonwheat rotation was replaced partially by rice-wheat in Muktsar within a span of over five years (1998–99 to 2003–04). The solo rice-wheat system in Ludhiana district has resulted in large-scale ground water exploitation as is evident from the faster decline in water table (up to 0.9m year⁻¹) and higher tube-wells density (440 per 1000 ha). As a result, nearly 60 per cent of the total area of Ludhiana district has the water table depth greater than 10m and in some blocks, it has reached to a depth of 22 m. In Muktsar district, corresponding rise in water table is 0.2m per year and tube well density is 114 per 1000 ha. Irrigation water associated with paddy cultivation in Ludhiana and adjoining areas moves laterally through the buried paleo-channels of Sutlaj in the deeper soil profile and gets accumulated in the basin lands of Muktsar and adjoining areas and causes an extra water flux and subsequent rise in water table, recorded at 3 to 7m depth. To minimize the hydrological imbalance of the state, it is suggested to diversify some of the area in the central districts from irrigation water intensive rice-wheat system to less water intensive cropping system.  相似文献