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1.
Hasan Avdan Senay Kayaci Avdan Aysun Akyuz Solen Balman 《Astrophysics and Space Science》2014,352(1):123-128
We report our findings on a new quasi-periodic oscillation (QPO) and a long period from the ultraluminous X-ray source (ULX) X-2 in nearby galaxy NGC 4736 based on the Chandra and XMM-Newton archival data. To examine the timing properties, power density spectra of the source have been obtained using Fast Fourier Transform. Also the spectral parameters of the source have been calculated by obtaining and fitting the energy spectra. Power density spectrum of this source reveals a QPO peak at \(0.73_{-0.14}^{+0.16}~\mathrm{mHz}\) with an fractional rms variability of 16 % using the Chandra data (in the year 2000-lower state of the source). The XMM-Newton data analysis indicates a peak at \(0.53_{-0.35}^{+0.09}~\mathrm{mHz}\) with a fractional rms variation of 5 % (in the year 2006-higher state of the source). These recovered QPOs overlap within errors and may be the same oscillation. In addition, we detect a long periodicity or a QPO in the Chandra data of about (5.2±2.0)×10?5 Hz (～5.4 h) over 3 σ confidence level. If this is a QPO, it is the lowest QPO detected from a ULX. The mass of the compact object in ULX X-2 is estimated using the Eddington luminosity and a disk blackbody model in the range (10–80) M ⊙. 相似文献
2.
Nuran Cikcikoglu Yildirim Deniz Demirbilek Gokhan Onder Erguven Rahime Kayar Senay Basaran Dilan Tulpar 《Environmental Earth Sciences》2018,77(17):622
Leachate was a major cause of high risk classification. This landfill was set as one with highest possible risk classification due to high vulnerability of private water wells to contamination from leachate flows. The aim of this study is to determine the present and possible environmental risks of the leachate spreading from solid waste dumping site in Tunceli and offer solutions for those determined environmental risks. For this purpose, the characteristics of the leachate were monitored at two station points detected in the solid waste dumping site for 7 months. The characteristics of the leachate were found for pH between 7.9 and 8.7. Oxidation reduction potential (ORP) occurred between ??143 and ??48 mV while conductivity was between 2.8 and 2.6 mS. Total solid matter (TSM) and suspended solid matter (SSM) were between 1000 and 7000 mg/l, 0.2–22.5 mg/l, respectively, while total volatile solids (TVS) occurred between 300 and 1800 mg/l for the two stations. Alkalinity was approximately between 290 and 5210 mg/l, while biological oxygen demand (BOD5) and chemical oxygen demand (COD) results were 15–606 mg/l and 60–1160 mg/l, respectively, for two stations in all sampling time. In both stations, orthophosphate, ammonium nitrogen, nitrate, sulfate, and chloride analyses stayed between 3.04 and 921.1 mg/l; 0.29–619.36 mg/l; 8.94–135.04 mg/l; 125.9–1360.9 mg/l and 99.9–1249.9 mg/l, respectively, in 6 months. As a result of the characterization studies obtained from the leachate, it was found that the amounts of water entering into the waste mass and the retention period of the water in the mass were very effective in the temporal character change of the leachate. According to the Discharge Standards for Solid Waste Assessment and Disposal Facilities and Discharge to Waste Water Infrastructure Facilities of waste management regulation, the results were found to be risky. Consequently, the site in question needs to be urgently rehabilitated when considering the environmental risks of the leachate spreading from the site. 相似文献
3.
Reliable information on water use and availability at basin and field scales are important to ensure the optimized constructive uses of available water resources. This study was conducted with the specific objective to estimate Landsat-based actual evapotranspiration (ETa) using the Operational Simplified Surface Energy Balance (SSEBop) model across the state of South Dakota (SD), USA for the 1986–2018 (33-year) period. Validated ETa estimations (r2 = 0.91, PBIAS = −4%, and %RMSE = 11.8%) were further used to understand the crop water-use characteristics and existing historic mono-directional (increasing/decreasing) trends over the eastern (ESD) and western (WSD) regions of SD. The crop water-use characteristics indicated that the annual cropland water uses across the ESD and WSD were more or less met by the precipitation amounts in the area. The ample water supply and distribution have led to high rainfed and low percentage of irrigated cropland (~2.5%) in the state. The WSD faced greater crop-water use reductions than the ESD during drought periods. The landscape ETa responses across the state were found to be more sensitive than precipitation for the drought impact assessments. The Mann Kendall trend analysis revealed the absence of a significant trend (p > 0.05) in annual ETa at a regional scale due to the varying weather conditions in the state. However, about 12% and 9% cropland areas in the ESD and WSD, respectively, revealed a significant mono-directional trend at pixel scale ETa. Most of the pixels under significant trend showed an increasing trend that can be explained by the shift in agricultural practices, increased irrigated cropland area, higher productions, moisture regime shifts, and decreased risk of farming in the dry areas. The decreasing trend pixels were clustered in mid-eastern SD and could be the result of dynamic conversion of wetlands to croplands and decreased irrigation practices in the region. This study also demonstrates the tremendous potential and robustness of the SSEBop model, Landsat imagery, and remote sensing-based ETa modelling approaches in estimating consistent spatially distributed evapotranspiration. 相似文献
4.
Bo Y. Yi Gwang H. Lee Senay Horozal Dong G. Yoo Byong J. Ryu Nyeon K. Kang Sung R. Lee Han J. Kim 《Marine and Petroleum Geology》2011,28(10):1953-1966
The presence of gas hydrate in the Ulleung Basin, East Sea (Japan Sea), inferred by various seismic indicators, including the widespread bottom-simulating reflector (BSR), has been confirmed by coring and drilling. We applied the standard AVO technique to the BSRs in turbidite/hemipelagic sediments crosscutting the dipping beds and those in debris-flow deposits to qualitatively assess the gas hydrate and gas concentrations. These BSRs are not likely to be affected by thin-bed tuning which can significantly alter the AVO response of the BSR. The BSRs crosscutting the dipping beds in turbidite/hemipelagic sediments are of low-seismic amplitude and characterized by a small positive gradient, indicating a decrease in Poisson’s ratio in the gas-hydrate stability zone (GHSZ), which, in turn, suggests the presence of gas hydrate. The BSRs in debris-flow deposits are characterized by a negative gradient, indicating decreased Poisson’s ratio below the GHSZ, which is likely due to a few percent or greater gas saturations. The increase in the steepness of the AVO gradient and the magnitude of the intercept of the BSRs in debris-flow deposits with increasing seismic amplitude of the BSRs is probably due to an increase in gas saturations, as predicted by AVO model studies based on rock physics. The reflection strength of the BSRs in debris-flow deposits, therefore, can be a qualitative measure of gas saturations below the GHSZ. 相似文献
5.
Schloerb F. P. Devries C. H. Lovell A. J. Irvine W. M. Senay M. Wootten H. A. 《Earth, Moon, and Planets》1997,78(1-3):45-51
Observations of comets in the 18-cm OH transitions offer a means to probe gas production, kinematics, and OH excitation in
comets. We present initial results of OH observations of comet Hale-Bopp obtained with the NRAO 43 m antenna located in Greenbank,
WV. Maps of the emission provide strong constraints on the amount of quenching of the inversion of the OH ground state Λ-doublet
in the coma. Analysis of the total radio OH flux and maps of its radial brightness distribution indicate a quenched region
on the order of ∼500,000 km during March and April 1997. This large value is generally consistent with previous observations
of radio OH quenching in lower production rate comets when the high production rate of comet Hale-Bopp is considered.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Parameter Estimation for Groundwater Models under Uncertain Irrigation Data 总被引：1，自引：0，他引：1 
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下载免费PDF全文 Yonas Demissie Albert Valocchi Ximing Cai Nicholas Brozovic Gabriel Senay Mekonnen Gebremichael 《Ground water》2015,53(4):614-625
The success of modeling groundwater is strongly influenced by the accuracy of the model parameters that are used to characterize the subsurface system. However, the presence of uncertainty and possibly bias in groundwater model source/sink terms may lead to biased estimates of model parameters and model predictions when the standard regression‐based inverse modeling techniques are used. This study first quantifies the levels of bias in groundwater model parameters and predictions due to the presence of errors in irrigation data. Then, a new inverse modeling technique called input uncertainty weighted least‐squares (IUWLS) is presented for unbiased estimation of the parameters when pumping and other source/sink data are uncertain. The approach uses the concept of generalized least‐squares method with the weight of the objective function depending on the level of pumping uncertainty and iteratively adjusted during the parameter optimization process. We have conducted both analytical and numerical experiments, using irrigation pumping data from the Republican River Basin in Nebraska, to evaluate the performance of ordinary least‐squares (OLS) and IUWLS calibration methods under different levels of uncertainty of irrigation data and calibration conditions. The result from the OLS method shows the presence of statistically significant (p < 0.05) bias in estimated parameters and model predictions that persist despite calibrating the models to different calibration data and sample sizes. However, by directly accounting for the irrigation pumping uncertainties during the calibration procedures, the proposed IUWLS is able to minimize the bias effectively without adding significant computational burden to the calibration processes. 相似文献
7.
Naga Manohar Velpuri Gabriel B. Senay Matthew Schauer C. Amanda Garcia Ramesh K. Singh MacKenzie Friedrichs Stefanie Kagone Jonathan Haynes Terrence Conlon 《水文研究》2020,34(8):1697-1713
Upper Klamath Lake (UKL) is the source of the Klamath River that flows through southern Oregon and northern California. The UKL Basin provides water for 81,000+ ha (200,000+ acres) of irrigation on the U.S. Bureau of Reclamation Klamath Project located downstream of the UKL Basin. Irrigated agriculture also occurs along the tributaries to UKL. During 2013–2016, water rights calls resulted in various levels of curtailment of irrigation diversions from the tributaries to UKL. However, information on the extent of curtailment, how much irrigation water was saved, and its impact on the UKL is unknown. In this study, we combined Landsat-based actual evapotranspiration (ETa) data obtained from the Operational Simplified Surface Energy Balance model with gridded precipitation and U.S. Geological Survey station discharge data to evaluate the hydrologic impact of the curtailment program. Analysis was performed for 2004, 2006, 2008–2010 (base years), and 2013–2016 (target years) over irrigated areas above UKL. Our results indicate that the savings from the curtailment program over the June to September time period were highest during 2013 and declined in each of the following years. The total on-field water savings was approximately 60 hm3 in 2013 and 2014, 44 hm3 in 2015, and 32 hm3 in 2016 (1 hm3 = 10,000 m3 or 810.7 ac-ft). The instream water flow changes or extra water available were 92, 68, 45, and 26 hm3, respectively, for 2013, 2014, 2015, and 2016. Highest water savings came from pasture and wetlands. Alfalfa showed the most decline in water use among grain crops. The resulting extra water available from the curtailment contributed to a maximum of 19% of the lake inflows and 50% of the lake volume. The Landsat-based ETa and other remote sensing datasets used in this study can be used to monitor crop water use at the irrigation district scale and to quantify water savings as a result of land-water management changes. 相似文献
8.
We report the first detection of the nitrogen sulfide (NS) radical in a comet. The abundance relative to water is at least a few hundredths of a percent for Comet Hale-Bopp. 相似文献
9.
Deniz Cukur Senay Horozal Gwang H. Lee Dae C. Kim Hyun C. Han Moo H. Kang 《Marine Geophysical Researches》2011,32(3):363-381
The northern East China Sea Shelf Basin consists of three depressions (the Domi, Jeju, and Socotra Depressions), separated by basement highs or rises. Reconstruction of depth-converted seismic reflection profiles from these depressions reveals that the northern East China Sea Shelf Basin experienced two phases of rifting, followed by regional subsidence. Initial rifting in the Late Cretaceous was driven by the NW?CSE crustal stretching of the Eurasian plate, caused by the subduction of the Pacific plate beneath the plate margin. Major extension (~15 km) took place during the early phase of basin formation. The initial rifting was terminated by regional uplift in the Late Eocene-Early Oligocene, which was probably due to reorganization of plate boundaries. Rifting resumed in the Early Oligocene; the magnitude of extension was mild (<1 km) during this period. A second phase of uplift in the Early Miocene terminated the rifting, marking the transition to the postrift phase of regional subsidence. Up to 2,600 m of sediments and basement rock were removed by erosion during and after the second phase of uplift. An inversion in the Late Miocene interrupted the postrift subsidence, resulting in an extensive thrust-fold belt in the eastern part of the area. Subsequent erosion removed about 900 m of sediments. The regional subsidence has dominated the area since the Late Miocene. 相似文献
10.
Analysis of multi-channel seismic data from the northern East China Sea Shelf Basin (ECSSB) reveals three sub-basins (Socotra, Domi, and Jeju basins), separated by structural highs (Hupijiao Rise) and faulted basement blocks. These sub-basins show a typical rift-basin development: faulted basement and syn-rift and post-rift sedimentation separated by unconformities. Four regional unconformities, including the top of acoustic basement, have been identified and mapped from multi-channel seismic data. Faults in the acoustic basement are generally trending NE, parallel to the regional structural trend of the area. The depths of the acoustic basement range from less than 1000 m in the northwestern part of the Domi Basin to more than 4500 m in the Socotra Basin and 5500 m in the Jeju Basin. The total sediment thicknesses range from less than 500 m to about 1500 m in the northwest where the acoustic basement is shallow and reach about more than 5500 m in the south.Interpretation of seismic reflection data and reconstruction of three depth-converted seismic profiles reveal that the northern ECSSB experienced two phases of rifting, followed by regional subsidence. The initial rifting in the Late Cretaceous was driven by the NW-SE crustal stretching of the Eurasian Plate, caused by the subduction of the Pacific Plate beneath the Eurasian Plate. Extension was the greatest during the early phase of basin formation; estimated rates of extension during the initial rifting are 2%, 6.5%, and 3.5% in the Domi, Jeju, and Socotra basins, respectively. A regional uplift terminated the rifting in the Late Eocene-Early Oligocene. Rifting and extension, although mild, resumed in the Early Oligocene; while fluvio-lacustrine deposition continued to prevail. The estimated rates of extension during the second phase of rifting are 0.7%, 0.8%, and 0.5% in the Domi, Jeju, and Socotra basins, respectively. A second phase of uplift in the Early Miocene terminated the rifting, marking the transition to the post-rift phase of regional subsidence. Regional subsidence dominated the study area between the Early Miocene and the Late Miocene. An inversion in the Late Miocene interrupted the post-rift subsidence, resulting in an extensive thrust-fold belt in the eastern part of the area. Uplift and subsequent erosion were followed by regional subsidence. 相似文献