The ultraluminous and hyperluminous infrared galaxies in the Sloan Digital Sky Survey, 2dF Galaxy Redshift Survey and 6dF Galaxy Survey     

Ho Seong Hwang  Stephen Serjeant  Myung Gyoon Lee  Kang Hwan Lee  Glenn J. White 《Monthly notices of the Royal Astronomical Society》2007,375(1):115-127

We present a result of cross-correlating the Infrared Astronomical Satellite Faint Source Catalogue with the spectroscopic catalogues of galaxies in the Fourth Data Release of the Sloan Digital Sky Survey, the Final Data Release of the 2dF Galaxy Redshift Survey (2dFGRS) and the Second Data Release of the 6dF Galaxy Survey. We have identified 324 ultraluminous infrared galaxies (ULIRGs) including 190 newly discovered ULIRGs, and two hyperluminous infrared galaxies. Adding these new ULIRGs, we increase the number of known ULIRGs by about 30 per cent. The reliability of the cross-correlation is estimated using the likelihood ratio method. The incompleteness of our sample introduced by the identification procedure in this study is estimated to be about 5 per cent. Our sample covers the redshift range of   z = 0.037–0.517  with a median redshift of     , which is larger than that     of the sample of previously known ULIRGs.  相似文献   

Application of a regionalized Clark IUH model with limited hydrologic data availability     

Kee‐Won Seong  James E. Ball  Yong‐Hak Lee 《水文研究》2008,22(18):3651-3660

To aid prediction of the flow hydrograph in a basin with limited data, a practical approach to determining a regionalized Clark instantaneous unit hydrograph (IUH) model is presented. The proposed model is described in terms of the synthetic time–area concentration curve, the concentration time, and a special regional similarity value that is valid in the whole basin. The latter was estimated from a Monte Carlo testing procedure based on the normal probability distribution of transformed regional similarity values composed of the time of concentration and the storage coefficient in gauged basins. The time–area concentration curve and the concentration time were calculated from a rational equation as in conventional methods. The method of transformation adopted was the Box–Cox power transformation, which is known to make non‐normal values resemble normal data. By introducing the regional similarity value into a Clark IUH, a statistically best estimate of IUH for given data conditions and its quantified degree of uncertainty were realized. The Wi River basin in Korea was used to test the applicability of the regionalized Clark IUH. The performance of the suggested methodology was evaluated by assuming an ungauged sub‐basin at the site. The results showed that the IUH model developed in this work was an effective tool, predicting a reliable hydrograph within the study area even though only limited data were available. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Potassium–Argon Ages of the Epithermal Gold–Silver Mineralization in the Haenam–Jindo Area,Southwestern Korea     

Chang Seong Kim  Seon‐Gyu Choi 《Resource Geology》2009,59(4):415-421

The Haenam–Jindo area, located on the southwestern margin of the Korean Peninsula, was the site of vigorous volcanic activity during the Late Cretaceous and Early Tertiary periods. Large parts of the area record strong hydrothermal alteration, and there exist many clay–alunite and gold–silver deposits. We undertook potassium–argon (K–Ar) age dating of five mineral samples (including adularia, sericite and alunite) from the Eunsan, Moisan and Gasado epithermal gold–silver deposits in this area. The purities of the samples were confirmed by X‐ray diffraction analysis. The K–Ar ages of adularia from the Eunsan deposit and adularia and sericite from the Moisan deposit (related to gold–silver mineralization) are 75.0 ± 1.6, 74.7 ± 1.6 and 75.1 ± 1.6 Ma, respectively. The similarity of these ages, combined with the close proximity and similar geochemical characteristics of the deposits, indicates that the mineralization occurred as part of a single hydrothermal system. The K–Ar ages of alunite at the surface and adularia at depth within the Gasado deposit are 82.2 ± 1.9 and 70.7 ± 1.9 Ma, respectively, revealing that the clay–alunite and gold–silver mineralization formed at different ages. K–Ar age data indicate that the gold–silver mineralization in this area occurred mainly at 75–70 Ma, resulting from hydrothermal activity in the Haenam–Jindo area (82–70 Ma). This is the first time that the mineralization of precious metals in Korea has been identified during this period.  相似文献   

Landforms and landscape evolution in the Skardu,Shigar and Braldu Valleys,Central Karakoram     

Yeong Bae Seong  Michael P. Bishop  Andrew Bush  Penny Clendon  Luke Copland  Robert C. Finkel  Ulrich Kamp  Lewis A. Owen  John F. Shroder 《Geomorphology》2009,103(2):251-267

The Central Karakoram, which includes K2 in Pakistan, is one of the most rapidly rising areas on Earth and exhibits complex topography and extreme relief. Impressive valley fills and glacial landforms are present throughout the valleys. The dynamics of landscape evolution of the region are currently not well understood. Consequently, the landforms were mapped and assessed in the Skardu, Shigar, and Braldu valleys, to elucidate the spatio-temporal scale dependencies of surface processes active in the region. These valleys were examined using geomorphic field methods, remote sensing, geomorphometry, and terrestrial cosmogenic nuclides (TCNs) surface exposure dating. The glaciers in this region have oscillated considerably throughout the Late Quaternary, and four glacial stages have been recognized including at least six glacial advances. Surface processes readjusted after glacier retreat, and ubiquitous mass movements and catastrophic landsliding transported material from steep slopes to valley bottoms, while glaciofluvial meltwater and glacier outburst floods redistributed sediment down valley. Glacier geochronology and late Holocene ages of the outburst flood deposits indicate that landscape evolution has been dominated by glaciation and paraglaciation during the late Quaternary.  相似文献   

A Wind-tunnel Study of Atmospheric Boundary-Layer Flow over Vegetated Surfaces to Suppress PM10 Emission on Owens (dry) Lake     

Dae Seong Kim  Greg H. Cho  Bruce R. White 《Boundary-Layer Meteorology》2000,97(2):309-329

Dust storms on Owens (dry) Lake located 200 milesnortheast of Los Angeles, California, U.S.A., havecaused serious PM₁₀ emission problems. Alaboratory-based experimental study was conducted toinvestigate the efficiency of 'vegetation cover' onthe playa to suppress dust emission rates as part ofa mitigation plan.Erodible lakebed material and field vegetation (saltgrass) taken from Owens (dry) Lake were placed in awind tunnel to simulate near-surface wind flow in theatmospheric boundary layer. Vertical wind-speedprofiles and vertical PM₁₀-concentration profileswere measured over six different levels of surfacevegetation cover. In order to understand the mechanismof aeolian particle transport and dust injection intothe atmosphere, the roughness parameter, z₀, thefriction velocity, u_*, and the surface dragcoefficient, C_D, were carefully determined.An empirical equation was developed to predictPM₁₀ emission rates as a function of wind speedand level of vegetation coverage for Owens (dry) Lake.Although the current results apply only to theeffectiveness of vegetation cover to suppressPM₁₀ emissions at Owens playa, the procedure canbe employed for any arid area or region that mightutilize added vegetation as a mitigation measure.  相似文献   

Effective periods and seismic performance of steel moment resisting frames designed for risk categories I and IV according to IBC2009          下载免费PDF全文

Seong‐Hoon Jeong  Oh‐Sung Kwon  Kwang‐Ho Lee 《地震工程与结构动力学》2015,44(9):1427-1447

In current seismic design, structures that are essential for post‐disaster recovery, and hazardous facilities are classified as risk category IV and are designed with higher importance factors and stringent drift limits. These structures are expected to perform better in an earthquake event because a larger base shear and more stringent drift limit are used. Although this provision has been in the seismic design code over the last three decades, few studies have investigated the performance of essential structures. The aim of this study is to quantify the impact of higher importance factors and stringent drift limits on the seismic performance of steel moment resisting frames. A total of 16 steel structures are designed for Los Angeles and Seattle. Different risk categories are used for the design. The effects of the risk categories on the structural periods, and thus on the seismic force demand, are investigated. A suite of inelastic time history analyses are carried out to understand the probability of exceeding a specified limit state when the structures are subjected to different levels of earthquake events. The results show that the periods of the structures in risk category IV decrease by a factor of 0.5 to 0.8, and the strengths increase by a factor of 1.5 to 3.2. Seismic fragility analysis shows that the structures in risk category IV generally satisfy the probabilistic performance objectives. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

An efficient method for selecting and scaling ground motions matching target response spectrum mean and variance          下载免费PDF全文

Seong Jin Ha  Sang Whan Han 《地震工程与结构动力学》2016,45(8):1381-1387

The purpose of this study is to propose an accurate and efficient method for selecting and scaling ground motions matching target response spectrum mean and variance, which does not require excessive computation and simulation. In the proposed method, a desired number of ground motions are sequentially scaled and selected from a ground motion library without iterations. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Hydraulic characteristics of a small Coastal Plain stream of the southeastern United States: effects of hydrology and season     

Hwa‐Seong Jin  G. Milton Ward 《水文研究》2005,19(20):4147-4160

Various physical and biological properties affect solute transport patterns in streams. We measured hydraulic characteristics of Payne Creek, a low‐gradient upper Coastal Plain stream, using tracer experiments and parameter estimation with OTIS‐P (one‐dimensional transport with inflow and storage with parameter optimization). The primary objective of this study was to estimate the effects of varying discharge, season, and litter accumulation on hydraulic parameters. Channel area A ranged from 0·081 to 0·371 m² and transient storage area A_s ranged from 0·027 to 0·111 m². Dispersion D ranged from 1·5 to 11·1 m² min⁻¹ and exchange coefficient α ranged from 0·009 to 0·038 min⁻¹. Channel area and dispersion were positively correlated to discharge Q, whereas storage area and exchange coefficient were not. Relative storage size A_s/A ranged from 0·17 to 0·59, and was higher during fall than other seasons under a similar Q. The fraction of median travel time due to transient storage ranged from 8·8 to 34·5% and was significantly correlated with Q through a negative power function. Both metrics indicated that transient storage was a significant component affecting solute transport in Payne Creek, especially during the fall. Comparison between the measured channel area A_c and A suggested that surface storage was dominant in Payne Creek. During fall, accumulation of leaf litter resulted in larger A and A_s and lower velocity and D than during other seasons with similar discharge. Seasonal changes in discharge and organic matter accumulation, and dynamic channel morphology affected the magnitude of transient storage and overall hydraulic characteristics of Payne Creek. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Provenance of recycled palynomorph assemblages recovered from surficial glaciomarine sediments in Bransfield Strait, offshore Antarctic Peninsula     

Sangheon Yi  David J. Batten  Seong Joo Lee 《Cretaceous Research》2005,26(6):906

Glaciomarine surficial sediments in cores taken from Bransfield Strait, adjacent to the Antarctic Peninsula, have yielded abundant recycled and contemporaneous (Pleistocene–Holocene) palynomorphs. The former are derived principally from Late Cretaceous–Palaeogene sediments and provide information on glaciomarine depositional conditions and sediment source areas. The composition of the assemblages suggests that they reflect vegetation that was endemic to the Weddellian Biogeographic Province, which includes what is now Seymour Island, James Ross Island and other parts of the Antarctic Peninsula region. The sediments concerned are considered to have accumulated as a result of ice-rafting and discharge of subglacial meltwater.  相似文献   

Adiabatic predictions and observations of cloud droplet spectral broadness     

Seong Soo Yum  James G. Hudson 《Atmospheric Research》2005,73(3-4):203-223

The evolution of cloud droplet size spectra is calculated using an adiabatic condensational growth model. Broadness (e.g., standard deviation of diameter) of cloud droplet spectra in adiabatic cloud parcels was determined to be critically dependent on cloud supersaturation. Although droplet spectra become narrower as growth continues, the rate of narrowing is slower when cloud supersaturation is lower. This actually leads to broader droplet spectra for more continental clouds or for weaker updrafts because both of these conditions are associated with lower cloud supersaturations. More continental type clouds, which have higher concentrations of smaller droplets, were indeed found to have larger dispersions (standard deviation of diameter/mean diameter of cloud droplets). Some of these results were consistent with observations, but the larger dispersions that were much more commonly observed for continental compared to maritime clouds were due almost exclusively to smaller droplets rather than broader droplet distributions. Contrary to the model calculations, typical observations show that cleaner clouds usually have broader droplet spectra. The gaps in magnitude between theory and observations of broadness are significant in all clouds. When cloud parcels that had ascended under different updraft conditions were compared at a constant cloud altitude, parcels with lower updrafts were predicted to have broader droplet spectra with larger mean diameters. This trend of apparent spectral broadening was consistent with observations for some near-adiabatic cloud parcels.  相似文献