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111.
Positions of sunspots between 1966 and 1976 as observed at Kandilli Observatory were used to determine the differential rotation of the Sun. A total of 202 sunspot groups which were E, F, G, H, and J-types were chosen, and a least-squares solution was calculated with their daily rotations. A gradient difference was found between the two hemispheres of the Sun. 相似文献
112.
Seasonal and spatial variability in scaling, correlation and wavelet variance parameter of daily streamflow data were investigated using 56 gauging stations from five basins located in two different climate zones. Multifractal temporal scaling properties were detected using a multiplicative cascade model. The wavelet variance parameter yielded persistence properties of the streamflow time series. Seasonal variations were found to be significant in that winter and spring seasons where large‐scale frontal events are dominant showed higher long‐term correlations and less multifractality than did summer and fall seasons. Coherent spatial variations were apparent. The Neches River basin located in a subtropic humid climate zone exhibited high persistence and long‐term correlation as well as less multifractality as compared with other basins. It is found that larger drainage areas tend to have smaller multifractality and higher persistence structure, and this tendency becomes apparent in regions that receive large amounts of precipitation and decreases towards arid regions. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
113.
Huib Jan Van Langevelde Ylva PihlstrÖm Anthony Beasley 《Astrophysics and Space Science》2005,295(1-2):249-255
Centaurus A, the nearest AGN shows molecular absorption in the millimeter and radio regime. By observing the absorption with VLBI, we try to constrain the distribution of the gas, in particular whether it resides in the circumnuclear region. Analysis of VLBA observations in four OH and two H2CO transitions is presented here, as well as molecular excitation models parameterized with distance from the AGN. We conclude that the gas is most likely associated with the tilted molecular ring structure observed before in molecular emission and IR continuum. The formaldehyde absorption shows small-scale absorption which requires a different distribution than the hydroxyl. 相似文献
114.
Özgür Kişi 《水文研究》2008,22(20):4142-4152
This paper proposes the application of a neuro‐wavelet technique for modelling monthly stream flows. The neuro‐wavelet model is improved by combining two methods, discrete wavelet transform and multi‐layer perceptron, for one‐month‐ahead stream flow forecasting and results are compared with those of the single multi‐layer perceptron (MLP), multi‐linear regression (MLR) and auto‐regressive (AR) models. Monthly flow data from two stations, Gerdelli Station on Canakdere River and Isakoy Station on Goksudere River, in the Eastern Black Sea region of Turkey are used in the study. The comparison results revealed that the suggested model could increase the forecast accuracy and perform better than the MLP, MLR and AR models. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
115.
The Characteristics of Polygonal Impact Craters on Venus 总被引:1,自引:0,他引:1
Marko Aittola Teemu Öhman Johannes J. Leitner Jouko Raitala 《Earth, Moon, and Planets》2007,101(1-2):41-53
Polygonal impact craters (PICs) are craters whose shape in plan view is more or less angular instead of being circular or ellipsoidal. This type of craters are present and often common on the Moon, Mercury, Mars and several asteroids and icy moons and after the careful analysis we found on Venus 131 impact craters, which show at least two straight rim segments. This survey proves that there are polygonal impact craters on Venus and they may provide a good tool to analyse the properties of the planet’s surface/crust/lithosphere as well as the impact process itself. This study also collaborates our previous results, that PICs are not an anomaly among craters, but an integral part of all impact craters regardless of their size or environment. We compared the polygonal impact craters to “normal”-shaped craters by using different characteristics (diameter, altitude, geologic setting, morphologic class, floor reflectance, degradation stage, and wall terracing). It turned out that the smaller crater sizes favor the formation of straight rim segments, but otherwise these craters show similar characteristics to other craters. Our study also shows that there are regions where the straight segments of the crater rims most clearly follow the orientations of the dominant tectonic features of the area. Thus, the orientations of crater walls reflect–at least in some places–the local tectonics and zones of weakness also on Venus and could thus tell us about the directions and distributions of fractures or other zones of weakness in the crust. 相似文献
116.
Abstract Event-based methods are used in flood estimation to obtain the entire flood hydrograph. Previously, such methods adopted in the UK have relied on pre-determined values of the input variables (e.g. rainfall and antecedent conditions) to a rainfall–runoff model, which is expected to result in an output flood of a particular return period. In contrast, this paper presents a method that allows all the input variables to take on values across the full range of their individual distributions. These values are then brought together in all possible combinations as input to an event-based rainfall–runoff model in a Monte Carlo simulation approach. Further, this simulation strategy produces a long string of events (on average 10 per year), where dependencies from one event to the next, as well as between different variables within a single event, are accounted for. Frequency analysis is then applied to the annual maximum peak flows and flow volumes. Citation Svensson, C., Kjeldsen, T.R., and Jones, D.A., 2013. Flood frequency estimation using a joint probability approach within a Monte Carlo framework. Hydrological Sciences Journal, 58 (1), 1–20. 相似文献
117.
Yılmaz Muhammet Alp Harun Tosunoğlu Fatih Aşıkoğlu Ömer Levend Eriş Ebru 《Natural Hazards》2022,110(2):1039-1060
Natural Hazards - Environmental changes have led to non-stationary flood risks in coastal cities. How to quantitatively characterize the future change trend and effectively adapt is a critical... 相似文献
118.
Natural Hazards - A moderate earthquake with a magnitude Mw of 6.8 occurred in the Sivrice district of Elaz?? Province in Eastern Turkey on January 24th, 2020. The mainshock and long-term... 相似文献
119.
Doğan Bülent Aşci Metin Karakaş Ahmet Pekşen Ertan Erener Arzu Çepni Murat Selim Yavuzyilmaz Selin Alahmad Mohammad Sertçelik Fadime Sertçelik İbrahim Kurtuluş Cengiz 《Natural Hazards》2021,109(2):1675-1716
Natural Hazards - The Northern Branch of the North Anatolian Fault System controls and deforms the Izmit Basin and the Sapanca Lake Basin in the study area. Unlike the Sapanca Lake Basin, the... 相似文献
120.
J. M. Mas-Hesse D. Kunth H. Atek G. Östlin C. Leitherer A. Petrosian D. Schaerer 《Astrophysics and Space Science》2009,320(1-3):35-38
The Lyα line is an important diagnostic of star formation and activity in galaxies. The analysis of Lyα is complicated due to the resonant nature of the line and radiative transfer effects. High spectral resolution studies of local starburst galaxies with the unprecedented UV capabilities of the HST have shown that this line is either seen in absorption or in emission and in the latter case with a P?Cygni profile indicative of a large scale outflow of neutral gas. Moreover, HST imaging obtained with HST-ACS of a sample of 6 star-forming galaxies has revealed that a substantial fraction of the Lyα photons are diffused far away from the emissive knots. Since the importance of Lyα for tracing large scale structure, correlation functions, and galaxy formation is recognized, Lyα will remain a very important probe of the distant universe for the foreseeable future, and it is therefore imperative to acquire a better understanding of what mechanisms regulate our ability to detect this line. 相似文献