The Spectrum and Dips of RE 0751+14: A Joint Evaluation of ROSAT and ASCA Archival Data     

Ümit Kiziloğlu  Altan Baykal  Murat Alev  Ersin Göğüş 《Astrophysics and Space Science》1998,259(2):191-203

Using archival ASCA and ROSAT observations of RE 0751+14, X- ray energy spectra, pulse profiles and the results of pulse timing analysis are presented. The energy spectra are well-fitted by a blackbody model at low energy and a Raymond-Smith model at high energy, together with a partial covering absorber. A fluorescence emission line at 6.4 keV with an equivalent width ∼ 220 eV was resolved for the first time. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Quality control and homogeneity of Turkish precipitation data     

Ozan Mert Göktürk  Deniz Bozkurt  Ömer Lütfi Şen  Mehmet Karaca 《水文研究》2008,22(16):3210-3218

Outlier trimming and homogeneity checking/correction were performed on the monthly precipitation time series of various lengths from 267 stations in Turkey. Outlier values are usually found during dry summer months, and are concentrated mostly over the southern parts of the country, where the dry period is most pronounced, implying natural extremes rather than wrong measurements. Homogeneity analysis was done using the Standard Normal Homogeneity Test, on an individual monthly basis, which led to many non‐testable series due to lack of reference stations, especially during summer months. Yet, remaining testable months were usually helpful for the assessment of homogenity, revealing a well distributed set of stations that proved to be homogeneous. There were still a number of stations which either could not be tested efficiently, or were classified as inhomogeneous. Lack of metadata is argued to be largely responsible for inefficient homogeneity testing. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

汛期强降水过程与月内低频降水的联系及其可能机制   总被引：3，自引：0，他引：3  

魏晓雯  梁萍  何金海  穆海振 《高原气象》2015,(3):722-731

利用1981 2010年中国753站逐日降水观测资料、NCEP/NCAR第二套逐日再分析资料及实况天气图等,选取长江中下游32次大范围持续性强降水过程,分析了该类强降水过程与月内(10~30天)低频降水的联系,并重点讨论了形成该类强降水过程的可能机制。结果表明:(1)长江中下游夏季降水具有显著的月内低频振荡周期。大范围持续性强降水过程基本位于降水低频振荡的峰值阶段。(2)梅汛期(6 7月)月内低频降水峰值位相前期,西太平洋副热带高压(下称西太副高)西伸北进,高低空急流发展加强。在强降水过程发生期,高中低层配置出现垂直方向上的最佳耦合;而台汛期(89月)低频降水峰值位相前期,西太副高东退南撤,低空急流逐渐南落至长江中下游东南部,与高空急流相配合,为强降水过程的发生提供了有利条件。(3)梅汛期东北亚低频位势高度低值区南下,与中纬太平洋西传的低频波列在长江中下游汇合。同时西太副高发展加强,造成了长江中下游降水峰值位相南高北低的低频位势高度分布,有利于强降水过程的发生;台汛期伴随从热带西太平洋到日本海低频波列的西北向移动,菲律宾东北部的低频气旋及其北侧低频反气旋的降水峰值位相分别移至长江中下游和东北亚地区,导致暖湿、干冷气流在长江流域交汇,进而造成强降水过程。(4)菲律宾以东洋面低频强对流可作为梅汛期和台汛期强降水过程发生的前期热带信号,提前低频降水峰值位相10天左右。  相似文献   

CCD BV and 2MASS photometric study of the open cluster NGC 1513     

S. Bilir  T. Güver  I. Khamitov  T. Ak  S. Ak  K. B. Coşkunoğlu  E. Paunzen  E. Yaz 《Astrophysics and Space Science》2010,326(1):139-150

We present CCD BV and JHK _s 2MASS photometric data for the open cluster NGC 1513. We observed 609 stars in the direction of the cluster up to a limiting magnitude of V∼19 mag. The star-count method showed that the centre of the cluster lies at α ₂₀₀₀=04 ^h 09 ^m 36 ^s , δ ₂₀₀₀=49°28^′43^″ and its angular size is r=10 arcmin. The optical and near-infrared two-colour diagrams revealed the colour excesses in the direction of the cluster as E(B−V)=0.68±0.06, E(J−H)=0.21±0.02 and E(J−K _s )=0.33±0.04 mag. These results are consistent with normal interstellar extinction values. Optical and near-infrared Zero Age Main-Sequences (ZAMS) provided an average distance modulus of (m−M)₀=10.80±0.13 mag, which can be translated into a distance of 1440±80 pc. Finally, using Padova isochrones we determined the metallicity and age of the cluster as Z=0.015±0.004 ([M/H]=−0.10±0.10 dex) and log (t/yr)=8.40±0.04, respectively.  相似文献   

A combined hydrologic and hydraulic modeling approach for testing efficiency of structural flood control measures   总被引：3，自引：2，他引：1  

Gülay Onuşluel Gül  Nilgün Harmancıoğlu  Ali Gül 《Natural Hazards》2010,54(2):245-260

The necessity of estimating the degree and spatial extent of positive impacts with regard to protecting communities and properties through potential flood control projects can be considered one of the main reasons for performing flood modeling. This paper presents an overall systematic approach based on the simulation of some extreme event conditions, using a hydrological model to generate the resulting river flows and then using a hydraulic modeling exercise to decide upon floodplain evolution in the case-study area, Bostanli river basin, which has been under the threat of flooding for many years. The potential serviceability of the planned Bostanli Dam in the study area was examined by using the HEC-HMS and HEC-RAS modeling tools, both integrated with GIS functions for spatial operations. The results indicate that the dam construction as planned would have a somewhat positive impact as a potential flood control measure, since it seems to decrease the flood peaks of 68.9 and 158.7 m³/s (that would potentially be generated by 100- and 500-year storm events under current conditions) to 65.5 and 150.7 m³/s (when the dam is in operation), respectively. However, this seems to contribute little to the overall flood mitigation performance in the basin.  相似文献   

Application of an ice-ocean coupled model to Bohai Sea ice simulation     

Jia  Bin  Chen  Xue’en 《中国海洋湖沼学报》2021,39(1):1-13

The HAMSOM(Hamburg Shelf Ocean Model),a high-resolution regional ice-ocean coupled model,was applied to investigate the seasonal evolution of Bohai Sea ice for winter 2015/2016.HAM SOM was initialized with monthly climatological temperature and salinity data from WOA13 and driven by hourly meteorological data obtained from the NCEP above the sea surface and tides at the open boundary.The ice model used here is a modified Hibler-type dynamic-thermodynamic sea ice model based upon viscous-plastic rheology.The ice extent,concentration,area,thickness,length of ice season as well as the distance between the top of Liaodong Bay(North China) and the outer ice edge line were simulated and compared with the observed data.Three types of modeling experiments were carried out to investigate the effects of wind,tide,and both wind and tide on Bohai Sea ice.The re sults show that wind,as both a dynamic and a thermodynamic factor,has a significant impact on the ice thickness,ice area,and ice-freezing and ice breakup dates as well as the ice velocity,while tides are a dynamic factor that influences only the ice velocity.During the severe ice period,the wind speed intensity increased by 25%,the average ice thickness thickened by approximately 4.0 cm in Liaodong B ay,approximately 2.1 cm in Bohai B ay and approximately2.5 cm in Laizhou B ay,and the total ice coverage area and total ice actual area increased by about 2×10~4 km~2 and 1.4×10~4 km2,respectively.While the tidal amplitude intensity increased by 25%,the average ice velocity increased by approximately 0.1 m/s.  相似文献   

The effect of the geomagnetic activity to the hourly variations of ionospheric foF2 values at low latitudes     

Erdinç Timoçin  Ali Yeşil  İbrahim Ünal 《Arabian Journal of Geosciences》2014,7(10):4437-4442

In this study, the relationship between the hourly changes of the ionospheric critic frequency values of F2 layers in low latitudes and geomagnetic activity is examined by using statistical methods. The ionospheric critical frequency data has been taken from the Manila (121.1° E, 14.7° N) ionosonde station. In order to investigate the effect of sun activity on ionospheric critical frequency, the data of 1981 when the sun was active and of 1985 when the sun was less active has been used. According to the Granger causality test results, on 5 % significance level, a causality relationship from disturbance storm time (Dst) index values to ionospheric critical frequency values direction has been observed. However, a causality relationship from ionospheric critical frequency values to Dst values has not been observed. From the results of cause-and-effect analysis, it is evaluated that the effect of a shockwave occurring in geomagnetic activity on ionospheric critical frequency continues along 72 h, that is, geomagnetic activity has a long-term effect on ionospheric critical frequency. The response of ionospheric critical frequency to geomagnetic activity substantially depends on seasons. This response is more observed especially in equinox period when the sun is active and in winter months. The increase in geomagnetic activity causes ionospheric critical frequency to decrease in night hours and increase in day hours. The same relationship has not been observed exactly, though observed very little in winter months, for 1985 when the sun was less active.  相似文献   

A New Rock Mass Quality Rating System: Rock Mass Quality Rating (RMQR) and Its Application to the Estimation of Geomechanical Characteristics of Rock Masses   总被引：1，自引：0，他引：1  

Ömer Aydan  Reşat Ulusay  Naohiko Tokashiki 《Rock Mechanics and Rock Engineering》2014,47(4):1255-1276

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Landslide susceptibility deterministic approach using geographic information systems: application to Breaza town, Romania     

Iuliana Armaş  Florin Vartolomei  Florica Stroia  Livioara Braşoveanu 《Natural Hazards》2014,70(2):995-1017

The study is a deterministic-based approach on landslide susceptibility. The purpose of the paper is to create quantitative susceptibility maps by joining the one-dimension infinite slope stability model with a raster-based GIS (ILWIS) and taking into account the spatial distribution of input parameters. A landslide-prone area, with relative homogeneous geology and geomorphology, located in the Subcarpathian sector of the Prahova River, Romania, was selected for the study. There are frequent problems caused by active landslides in the studied area, especially in years with heavy precipitation, often causing destruction of houses and roads situated on the slopes (1992, 1997, and 2005). Detailed surveys covering a 7-year period provided the necessary input data on slope parameters, hydrological components, and the geotechnical background. Two simulations were used: one on dry soil conditions and one on fully saturated soil conditions. A third test was based on the level of the groundwater table mapped in summer 2008. Detailed analyses were particularly focused on landslides to compare predicted results with actual results using field measurements. The model is very suitable for use in raster GIS because it can calculate slope instability on a pixel basis, each raster cell being considered individually. The drawback of the model is the highly detailed data of input parameters. Despite this disadvantage, in conclusion, the usefulness of slope stability models on a large-scale basis was emphasized under infinitely high failure plain conditions and lithological homogeneity.  相似文献   

Aquifer heterogeneity determination through the slope method     

Zekai Şen  Essam Wagdani 《水文研究》2008,22(12):1788-1795

In arid‐region wadis, groundwater storage lies within shallow Quaternary alluvium deposits, which are connected with the present‐day hydrological cycle and, therefore, are replenished due to occasional runoff and flash flood occurrences. The groundwater resources are precious in these environments; therefore, their potentiality must be assessed with care in the best manner. The aquifer potentiality is calculated after the storativity and transmissivity parameter estimations, which require rather long‐duration field tests with restrictive assumptions in the theoretical model developments, such as the homogeneity and isotropy. It is the main purpose of this paper to expose the fundamentals of the slope‐matching procedure (SMP) and its application for short‐duration field tests in arid‐region aquifers. In this manner, the subsurface hydrogeological behaviours of the bored land pieces at and around the well locations are prospected in a detailed and refined manner. It is shown that in many cases the classical techniques are appropriate, inconvenient and inapplicable with conclusive reliable results and conclusions. The application of the SMP is presented for some aquifer tests from the central western part of the Kingdom of Saudi Arabia. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献