共查询到20条相似文献，搜索用时 15 毫秒
1.
Orbital-period variations of the low-mass, semi-detached eclipsing binary RT Per are analyzed. In addition to the secular variation of the orbital period determined by the mass transfer between the components, cyclic variations are also present. Both the light-time effect and magnetic oscillations can describe the cyclic orbital-period variations of RT Per. The secular period increase can be explained by a uniform flow of matter from the lower-mass to the higher-mass component at a rate of 0.60 × 10−8M-/year, with the total angular momentum being conserved. The period variations can be represented equally accurately by either a superposition of two cyclic variations or a superposition of a secular period increase and two cyclic variations. Approximately the same parameters are derived for the lower-period (36.8 year) variations when the times of minima are fitted with a linear or a quadratic formula. For the longer-period variation, a period of 275 years and amplitude of 0.104 days are found using the linear formula, or 89 years and 0.045 days using the quadratic formula.
相似文献2.
利用青海玉树国家基本气象观测站1961-2010年的总辐射常规观测资料, 分析了玉树地区总辐射的长期变化趋势. 结果表明: 玉树地区总辐射在1961-2010年期间总体呈现减弱趋势, 其变化经历了增强变"亮"-减弱变"暗"-增强变"亮"-震荡回落4个阶段; 春、夏季的总辐射变化趋势对年际变化趋势有主导作用. 小波分析表明, 玉树地区近50 a的总辐射变化过程中, 存在多时间尺度周期的变化特征; 长期变化趋势和国内其他站点的变化趋势相比均表现出减弱的趋势, 但各站点减弱趋势倾向率不同. 最后, 对比分析了总辐射和同期气象要素、MODIS反演的气溶胶AOD之间的关系. 相似文献
3.
年纹层发育的湖泊沉积物可以提供独立的、绝对定年的时间标尺,为重建高分辨率的区域古地磁场长期变化主曲线提供了难得的条件;基于长而连续的湖泊沉积物年纹层时间标尺建立的区域磁偏角和磁倾角长期变化参考曲线大大增强了岩芯对比和古地磁定年结果的精确性。此外,满足特定条件的湖泊沉积物还可以提供古地磁场强度长期变化的记录并有助于反映宇宙成因核素(如^14C、^10Be等)产生速率的变化、太阳活动等信息;目前,湖泊沉积物纹层年代学时间标尺及古地磁研究程度较高的主要是瑞典、芬兰和北美一些地区,区域古地磁场长期变化主曲线的地理分布并不均匀,因此在全球范围内寻找长序列的、连续的年纹层发育的湖泊进行古地磁研究可以更好地理解仪器观测记录以前的地磁场行为。 相似文献
4.
Lin-Sen Li 《Astronomy Reports》2008,52(10):806-810
We examine the influence of mass-loss due to stellar wind using the celestial mechanics of variable mass, and derive first-and
second-order solutions, taking into account the decreasing mass due to the stellar wind. The theoretical results show that
the semi-major axis exhibits secular and periodic variations in the first-and second-order theory. The orbital eccentricity
exhibits periodic, but no secular variation or changes. The longitude of periastron exhibits only periodic variations in the
first-order solution, but also secular variations in the second-order solution. The theoretical results are applied to the
binary star HD 698, and variability of the orbital elements of this star due to stellar-wind mass loss calculated.
Published in Russian in Astronomicheskiĭ Zhurnal, 2008, Vol. 85, No. 10, pp. 896–900.
The article was translated by the authors. 相似文献
5.
B R Arora V H Badshah B P Singh M G Arur P S Bains Jeevan Lal 《Journal of Earth System Science》1983,92(1):15-30
The magnetic measurements of declination (D), horizontal (H) and vertical (Z) components of earth’s magnetic field, collected from ground surveys between 1962 and 1966, are used to develop an analytical model of geomagnetic field variations over Indian region for the epoch 1965. In order to reflect spatial features with wavelengths of approximately 1000 km, sixth degree polynomial as a function of differential latitude and longitude is calculated by the method of least squares. The root mean square fit of the model to the input data is better than that accounted by the International Geomagnetic Reference Field for 1965.0. Isomagnetic charts drawn forD, H, Z and total force (F) reflect more details than that shown on world magnetic charts. Further, the values of the field at common repeat stations recorded between 1962 and 1974, after eliminating the field values for the epoch 1965.0, are used to get the secular variation as well as its spatial dependence again by means of polynomial which now includes coefficients which are functions of time and of geographical locations. The accuracy of coefficients is tested against the behaviour of secular variation at permanent magnetic observatories. The merits and limitations of the model are discussed. 相似文献
6.
Tectonomagnetic study in the seismoactive area of Narmada-Son lineament,central India: Preliminary results on repeat field observations 总被引：1，自引：0，他引：1
S. Y. Waghmare S. D. Pimprikar P. B. Gawali L. Carlo A. G. Patil 《Journal of Earth System Science》2009,118(3):261-272
Repeated measurements of the total geomagnetic field on the five profiles have revealed a picture of stress-induced tectonomagnetic
effect in the form of secular variation of the total geomagnetic field in the tectonically and seismically active area of
Jabalpur and adjoining areas of the Narmada-Son lineament (NSL), central India. For this experiment, a reference base station
was established within the study area at Jabalpur. Using proton precession magnetometers with a sensitivity of 0.1 nT, simultaneous
measurements of total geomagnetic field were made annually at the base and all field stations. Five cycles of repeated observations
have been performed between 2003 and 2007. For data analysis, a difference method has been applied and the residuals have
been calculated as secular variations of the total geomagnetic field with values ranging from ±0.1nT to about ±14.6nT/yr over
the different stations. The anomalies in secular variation of the total geomagnetic field may be related to anomalous accumulation
of tectonic stresses and tensions on the deep fault zones and crustal blocks due to recent geodynamic processes and active
geological inhomogeneities in the NSL. 相似文献
7.
显生宙海水成分、碳酸盐沉积和生物演化系统研究进展 总被引：6，自引：2，他引：6
简述了显生宙海水成分演化的特征、识别标志和成因解释模型以及存在的问题和今后研究的方向.不同时期海水的成分的差异,特别是海水的x(Mg)/x(Ca)值,导致了文石海、方解石海时期的碳酸盐沉积和早期成岩作用均存在差异,甚至影响了盆地深部成岩流体的特征.显生宙海生生物的演替和盛衰,特别是简单生物(如钙藻和海绵)和高产率生物(如造礁生物和碳酸盐沉积物主要生产者),明显体现了海水的x(Mg)/x(Ca)值周期性变化对海生生物的影响.这种影响也同样体现在古生代末期的生物大绝灭及随后的生物复苏样式上,在生物更替事件研究中应引起重视.因此,生物与环境的协同演化研究必须从地球系统科学的角度展开. 相似文献
8.
研究了1948-2001年南、北半球及欧亚大陆、非洲大陆、澳洲大陆、北美大陆、南美大陆、南极大陆和中国 7个大尺度区域 6～8月降水的长期趋势变化和年代际变化。结果表明，南、北半球 6～8月的降水都为负趋势，但南半球降水的负趋势在统计上不显著。在54年的时间段内，南半球 6～8月降水的递减速度为 0．12 mm／a，仅为北半球同期降水减幅（0．24 mm／a）的一半。南、北半球 6～8月降水量年代际尺度的振荡都非常明显，但是，南、北半球年代际变化的特征明显不同。目前北半球仍是在少雨时间段，而南半球处在降水量正常或多雨的时间段。分析还表明，非洲大陆 6～ 8月降水的年代际特征最明显，降水的负趋势也最为显著；欧亚大陆 6～8月降水也有着明显的年代际变化与明显的负趋势变化；澳洲大陆 6～8月降水的年际变化明显，年代际变化相对来说要小得多；北美大陆 6～8月降水的年际变化明显，但无明显的趋势变化。此外，分析了大尺度区域 6～ 8月降水之间的相关关系，发现部分区域大尺度降水量之间有明显的联系；分析了中国夏季降水的长期变化，发现中国夏季降水的年代际变化明显，但无明显的趋势变化。 相似文献
9.
D. D. Khandelwal Vineet Gahalaut Naresh Kumar Bhaskar Kundu Rajeev Kumar Yadav 《Natural Hazards》2014,74(3):1853-1861
We report GPS measurements of continuous observations from the multi-parametric geophysical observatory (MPGO) at Ghuttu, Garhwal Lesser Himalaya. Other than the evidence of secular motion depicting strain accumulation due to locking of the underneath seismically active detachment, measurements at Ghuttu show annual variation of ±4 mm on horizontal component. Such variations are more prominent in the north coordinate and do not directly correlate with the meteorological parameters such as variations in rainfall, water table, and atmospheric pressure measured at the MPGO observatory. These variations are also not the artefact of data processing and network. They correlate with the water load storage in the Ganga plains, with minimum in displacement coinciding with the maximum storage of water in Ganga plains immediately after the monsoon and vice versa. Such variations also appear to cause annual variation in the low-magnitude earthquake frequency in the Himalayan region, being relatively more in the winter period. 相似文献
10.
PETER TURNER 《Geology Today》1987,3(5):127-132
Magnetostratigraphy involves the study of changes in the Earth's magnetic field that are recorded in sediments and rocks. These include short-term fluctuations (secular variation), polarity transitions and magnetic reversal sequences. All have important applications in the Earth sciences. They can be used to calculate the rates of sea-floor spreading and sediment deposition rates, and for time-correlation of rock sequences, especially when no other means are available. 相似文献
11.
Lin-Sen Li 《Astronomy Reports》2016,60(4):420-424
The variation of the instantaneous rotational angular velocity of the rigid Earth in the lunar-solar gravitational field is studied. The formula is derived for variation of the instantaneous angular velocity of the rigid oblate Earth using the potential function from Euler’s dynamic equations. The theoretical results show that under the influence of the gravitational field of the Moon and the Sun the Earth instantaneous angular velocity varies with periodic terms, but without secular variations. Amplitudes of the periodic terms and their periods are calculated and discussed. 相似文献
12.
Paleomagnetic secular variation in a portion of the Bonneville Alloformation is compared with secular variation in lacustrine sediments in the Mono Basin, California, and with secular variation in Lake Lahontan sediments in the northwestern Great Basin. The comparison places an age of about 18,000 yr B.P., and a span of 1000 to 3000 yr, on part of a transgressive stage of Lake Bonneville near Delta, Utah, that is coeval with a wet period in the Lahontan Basin. 相似文献
13.
Extensive work on the palaeomagnetism of the Deccan traps by several workers has revealed only one reversal (normal-reverse-normal)
of the geomagnetic field during the period of eruption of these flows. The scatter in the natural remanent magnetic directions
of different flows in a sequence of these traps is rather large and it persists even after magnetic cleaning. Generally this
large scatter of directions is attributed to the geomagnetic secular variation during formation of the traps. Recent studies
of the magnetic properties of the trap samples indicate that the presence of multidomain magnetite in a lava sequence differs
from locality to locality in the Deccan trap province and so the stability of their natural remanent magnetization. While
these features can be clearly perceived, an understanding of the same seems to be quite difficult. However, it appears that
part of the scatter in directions could be due to the alteration of the magnetic minerals in the Deccan traps and hence it
would not be proper to relate the entire scatter to the secular variation. 相似文献
14.
Variations of the orbital periods of the eclipsing binaries RY Aur, GG Cas, RS Lep, and RV Tri are analyzed. The period variations in all of these systems can be represented as a superposition of a secular period decrease and cyclic variations that can be explained with the light-time effect due to the presence of a third body in the system. The secular period decrease could be due to magnetic braking.
相似文献15.
This paper presents relative secular variations of the total intensity of the geomagnetic field against a background of results of magnetic anomaly interpretation along seismic profile P4. Profile P4 crosses a Variscan folding zone in the Paleozoic Platform (PLZ), the Trans-European Suture Zone (TESZ), and the Polish part of the East European Craton (EEC). Secular geomagnetic field variations
measured in 1966–2000 along a line adjacent to seismic profile P4 were analysed. The study of secular variations, reduced to the base recordings at the Belsk Magnetic Observatory, showed that the growth of geomagnetic field at the East European Craton was slower than in the Trans-European Suture Zone and the Paleozoic Platform.A 2D crustal magnetic model was interpreted as a result of magnetic modelling, in which seismic, geological and geothermal data were also used. The modelling showed that there were significant differences in the magnetic model for geotectonic units, which had been earlier determined based on deep seismic survey data. It should be noted that a fundamental change of trend of the relative secular variations was observed at the slope of the Precambrian Platform. After analysing the geomagnetic field observed along profile P4, the hypothesis that the contact between Phanerozoic and Precambrian Europe lies in Poland's territory can be proven. 相似文献
16.
E. N. Vinyaikin 《Astronomy Reports》2014,58(9):626-639
Many-year measurements of the radio flux of the young supernova remnant Cassiopeia A relative to the radio galaxy Cygnus A were continued at 290 and 151.5 MHz. The new data are used together with previously published observations carried out at decameter, meter, centimeter, and millimeter wavelengths to derive the frequency dependence of the secular variation of the radio flux density of Cas A: $d_\nu [\% year^{ - 1} ] = - (0.63 \pm 0.02) + (0.04 \pm 0.01)\ln \nu [GHz] + (1.51 \pm 0.16) \times 10^{ - 5} (\nu [GHz])^{ - 2.1} $ . The observed slowing of the secular variations with decreasing frequency at decameter wavelengths can be explained by a decrease in the optical depth of a remnant HII zone around Cas A with time due to recombination of hydrogen atoms. The new derived frequency dependence for the rate of the secular decrease, absolute and relative measurements of the radio flux density of Cas A carried out over the last 25 years, and the absolute spectrum of Cyg A are used to construct the spectrum of Cas A in the range 5–250 000 MHz predicted for epoch 2015.5. 相似文献
17.
N. Evelpidou P. Pirazzoli A. Vassilopoulos G. Spada G. Ruggieri A. Tomasin 《Geoarchaeology》2012,27(3):259-277
We present estimates for late Holocene relative sea level change along the Tyrrhenian coast of Italy based on morphological characteristics of eight submerged Roman fish tanks (piscinae) constructed between the 1st century B.C. and the 2nd century A.D. Underwater geomorphological features and archaeological remains related to past sea level have been measured and corrected using recorded tidal values. We conclude that local sea level during the Roman period did not exceed 58 ± 5 cm below the present sea level. These results broadly agree with previous observations in the region but contrast with recent analysis that suggests a significantly larger sea level rise during the last 2000 years. Using a glacial isostatic adjustment model, we explain how regional sea level change departs from the eustatic component. Our calculation of relative sea level during the Roman period provides a reference for isolating the long‐wavelength contribution to sea level change from secular sea level rise. Precise determination of sea level rise in the study area improves our understanding of secular, instrumentally observed, variations across the Mediterranean. © 2012 Wiley Periodicals, Inc. 相似文献
18.
We have discovered a 2–4 year periodicity in geomagnetic secular variation (SV) from data of 110 world magnetic observatories. The periodicity in the horizontal component (H) is most prominent and appears to be globally uniform in different regions, on all continents, and in both hemispheres. The quasi-periodic short-wavelength variations show up in the vertical component (Z) as well but locally superpose on long-wavelength regional anomalies. We presume that the short-period fluctuations may be produced by instability of the eccentric dipole (ED) axis proceeding from the analysis of the SV field and optimization modeling of the dipole field with varied ED parameters. 相似文献
19.
Metazoan fossils in the Gaojiashan Biota are famous for being well preserved and may provide new insights into the early evolution and skeletonization of Metazoans. We are studying the isotopic compositions of organic and carbonate carbon from a sequence of sedimentary rocks at the Gaojiashan section, northern Yangtze Platform, Shaanxi Province of China. Organic carbon isotope values display a range between –30.8‰ and –24.7‰ with clear stratigraphic variations. Carbonate carbon isotope data vary between 0.1‰ and +6‰. Positive δ13C values from sediments with Gaojiashan biota reflect temporal variations in carbon turnover, i.e. an increasing in photosynthetic carbon fixation followed by an increasing subsequent fractional organic carbon burial, and that related to bio-radiation such as increasing algae, bacteria, and original creatures productivity in biomass. These secular variations are interpreted to reflect perturbations of the regional carbon cycle, specifically changes in the fractional burial of organic carbon, and discuss the relationship between Gaojiashan biota and paleoenvrionmental variation. 相似文献
20.
A. M. Cherepashchuk V. F. Esipov A. V. Dodin V. V. Davydov A. A. Belinskii 《Astronomy Reports》2018,62(11):747-763
Spectroscopic monitoring of SS 433 was performed during the 11 years between 2007 and 2017. Shifts of the moving Hα emission lines are analyzed and corresponding radial velocity curves plotted. All published spectroscopic data on SS 433 are used to search for secular variations of the parameters of the kinematic model. Deviations of the model parameters from their mean values are observed during relatively short time intervals (several years), but no secular changes have been detected. The presence of a component varying periodically with the orbital period is confirmed for the velocity variations for the matter in the relativistic jets, possibly indicating that the orbit of SS 433 is slightly elliptical. The stability of the parameters of the kinematic model testifies that a model with a slaved accretion disk that follows the precession of the optical star’s rotation axis is very suitable for the supercritical accretion disk in the SS 433 system. 相似文献