Monitoring precipitable water vapor in real-time using global navigation satellite systems     

Seung-Woo Lee  Jan Kouba  Bob Schutz  Do Hyeong Kim  Young Jae Lee 《Journal of Geodesy》2013,87(10-12):923-934

This paper addresses real-time monitoring of the precipitable water vapor (PWV) from GNSS measurements and presents some results obtained from 6-month long GNSS PWV experiments using international and domestic GNSS networks. In the real-time GNSS PWV monitoring system a server/client structure is employed to facilitate formation of PWV networks and single-differenced GNSS measurements are utilized to mitigate errors in GNSS satellites’ orbits and clocks. An issue relating to baseline length between the server and clients is discussed in detail and as a result the PWV monitor is configured to perform in two modes depending on the baseline length. The server estimates sequentially the zenith wet delay of the individual stations, which is then converted into the PWV of the stations. We evaluate system performance by comparing the real-time PWV solution with reference solutions including meteorological measurements obtained with radiosondes and deferred-time precision GNSS PWV solutions. Results showed that the standard deviation of difference between the real-time PWV and the reference solutions ranged from 2.1 to 3.4 mm in PWV for a 6-month long comparison, which was improved to 1.4 to 2.9 mm by reducing comparison period to 20 days in winter.  相似文献   

Effects of Lime‐Based Waste Materials on Immobilization and Phytoavailability of Cadmium and Lead in Contaminated Soil     

Jung Eun Lim  Mahtab Ahmad  Sang Soo Lee  Christopher L. Shope  Yohey Hashimoto  Kwon‐Rae Kim  Adel R. A. Usman  Jae E. Yang  Yong Sik Ok 《洁净——土壤、空气、水》2013,41(12):1235-1241

Low cost lime‐based waste materials have recently been used to immobilize metals in contaminated soils. This study was conducted to evaluate the effects of oyster shells and eggshells as lime‐based waste materials on immobilization of cadmium (Cd) and lead (Pb) in contaminated soil, as well as their effects on metal availability to maize plants (Zea mays L.). Oyster shells and eggshells were applied to soils at 1 and 5% w/w, after which they were subject to 420 days of incubation. The toxicity characteristic leaching procedure (TCLP) test was employed to determine the mobility of Cd and Pb in soils. The results showed that the addition of waste materials effectively reduced the metal mobility as indicated by the decrease in the concentration of TCLP‐extractable Cd and Pb, and this was mainly due to significant increases in soil pH (from 6.74 in untreated soil to 7.85–8.13 in treated soil). A sequential extraction indicated that the addition of such alkaline wastes induced a significant decline in the concentration of Cd in the exchangeable fraction (from 23.64% in untreated soil to 1.90–3.81% in treated soil), but it increased the concentration of Cd in the carbonate fraction (from 19.59% in untreated soil to 36.66–46.36% in treated soil). In the case of Pb, the exchangeable fraction was also reduced (from 0.67% in untreated soil to 0.00–0.01% in treated soil), and the fraction of Pb bound to carbonate was slightly increased (from 16.61% in untreated soil to 16.41–18.25% in treated soil). Phytoavailability tests indicated that the metal concentrations in the shoots of maize plant were reduced by 63.39–77.29% for Cd and by 47.34–75.95% for Pb in the amended soils, with no significant differences being observed for the amendment types and the application rates. Overall, these results indicate that oyster shells and eggshells can be used as low cost lime‐based amendments for immobilizing Cd and Pb in contaminated soils.  相似文献   

Convection in a rotating cylinder with its sidewall having a finite thermal conductance     

Jae Min Hyun 《地球物理与天体物理流体动力学》2013,107(1-4):83-98

Abstract

An investigation is made of steady thermal convection of a Boussinesq fluid confined in a vertically-mounted rotating cylinder. The top and bottom endwall disks are thermal conductors at temperatures T_t and T_b with δT = T_t ? T_b >0. The vertical sidewall has a finite thermal conductance. A Newtonian heat flux condition is adopted at the sidewall. The Rayleigh number of the fluid system is large to render a boundary layer-type flow. Finite-difference numerical solutions to the full Navier-Stokes equations are obtained. The vertical motions within the buoyancy layer along the sidewall induce weak meridional flows in the interior. Because of the Coriolis acceleration, the meridional flows give rise to azimuthal flows relative to the rotating container. Strong vertical gradients of azimuthal flows exist in the regions near the endwalls. As the stratification effect increases, concentration of flow gradients in thin endwall boundary layers becomes more pronounced. The azimuthal flow field exhibits considerable horizontal gradients. The temperature field develops horizontal variations superposed on the dominant vertical distribution. As either the sidewall thermal conductance or the stratification effect decreases, the temperature distribution tends to the profile varying linearly with height. Comparisons of the sizes of the dynamic effects demonstrate that, in the bulk of flow field, the vertical shear of azimuthal velocity is supported by the horizontal temperature gradient, resulting in a thermal-wind relation.  相似文献   

Ulva and Enteromorpha (Ulvaceae, Chlorophyta) from two sides of the Yellow Sea: analysis of nuclear rDNA ITS and plastid rbcL sequence data     

王金锋  李楠  姜鹏  崔玉琳  林瀚智  赵瑾  刘正一  秦松 《中国海洋湖沼学报》2010,28(4):762-768

Ulvacean green seaweeds are common worldwide; they formed massive green tides in the Yellow Sea in recent years, which caused marine ecological problems as well as a social issue. We investigated two major genera of the Ulvaceae, Ulva and Enteromorpha, and collected the plastid rbcL and nuclear ITS sequences of specimens of the genera in two sides of the Yellow Sea and analyzed them. Phylogenetic trees of rbcL data show the occurrence of five species of Enteromorpha (E. compressa, E. flexuosa, E. intestinalis, E. linza and E. prolifera) and three species of Ulva (U. pertusa, U. rigida and U. ohnoi). However, we found U. ohnoi, which is known as a subtropical to tropical species, at two sites on Jeju Island, Korea. Four ribotypes in partial sequences of 5.8S rDNA and ITS2 from E. compressa were also found. Ribotype network analysis revealed that the common ribotype, occurring in China, Korea and Europe, is connected with ribotypes from Europe and China/Japan. Although samples of the same species were collected from both sides of the Yellow Sea, intraspecific genetic polymorphism of each species was low among samples collected worldwide.  相似文献   

Effects of Antimicrobial Air Filters on the Viability and Culturability of Airborne Bacteria          下载免费PDF全文

Gi Byoung Hwang  Bo Mi Kwon  Seung Jae Lee  Byung Uk Lee  Kyoung Mi Sim  Gwi‐Nam Bae  Jae Hee Jung 《洁净——土壤、空气、水》2016,44(10):1268-1277

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Geochemical characteristics of surface efflorescence on the seventh century stone pagoda in Republic of Korea   总被引：1，自引：0，他引：1  

Dong Sik Lee  Chan Hee Lee  Jiyoung Kim  Hee Jae Yang 《Environmental Geology》2009,58(1):197-204

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Estimation of net ecosystem metabolism of seagrass meadows in the coastal waters of the East Sea and Black Sea using the noninvasive eddy covariance technique     

Jae Seong Lee  Dong-Jin Kang  Elitsa Hineva  Violeta Slabakova  Valentina Todorova  Jiyoung Park  Jin-Hyung Cho 《Ocean Science Journal》2017,52(2):243-256

We measured the community-scale metabolism of seagrass meadows in Bulgaria (Byala [BY]) and Korea (Hoopo Bay [HP]) to understand their ecosystem function in coastal waters. A noninvasive in situ eddy covariance technique was applied to estimate net O₂ flux in the seagrass meadows. From the high-quality and high-resolution time series O₂ data acquired over > 24 h, the O₂ flux driven by turbulence was extracted at 15-min intervals. The spectrum analysis of vertical flow velocity and O₂ concentration clearly showed well-developed turbulence characteristics in the inertial subrange region. The hourly averaged net O₂ fluxes per day ranged from -474 to 326 mmol O₂ m^-2 d^-1 (-19 ± 41 mmol O₂ m^-2 d^-1) at BY and from -74 to 482 mmol O₂ m^-2 d^-1 (31 ± 17 mmol O₂ m^-2 d^-1) at HP. The net O₂ production rapidly responded to photosynthetically available radiation (PAR) and showed a good relationship between production and irradiance (P-I curve). The hysteresis pattern of P-I relationships during daytime also suggested increasing heterotrophic respiration in the afternoon. With the flow velocity between 3.30 and 6.70 cm s^-1, the community metabolism during daytime and nighttime was significantly increased by 20 times and 5 times, respectively. The local hydrodynamic characteristics may be vital to determining the efficiency of community photosynthesis. The net ecosystem metabolism at BY was estimated to be -17 mmol O₂ m^-2 d^-1, which was assessed as heterotrophy. However, that at HP was 36 mmol O₂ m^-2 d^-1, which suggested an autotrophic state.  相似文献   

Quantification of Aquatic Nano Particles after Different Steps of Bodensee Water Purification with Laser‐induced Breakdown Detection (LIBD)     

Tobias Bundschuh  Roger Knopp  Rudi Winzenbacher  Jae Il Kim  Rainer Kster 《洁净——土壤、空气、水》2001,29(1):7-15

The laser‐induced breakdown detection (LIBD) is a very sensitive method for the direct detection of colloids based on the plasma generation on single particles by a focused, pulsed laser beam and the detection of the produced shock wave or plasma light emission. For the determination of colloid sizes the light emission of single plasmas is detected by a microscope CCD‐camera system. With known mean particle diameter and breakdown probability the particle concentration can be calculated. The application of the LIBD to monitor the change of colloid concentration and size during the purification steps of drinking water at the Bodensee (Lake Constance, Germany) water purification plant is shown. The breakdown probability, correlating to colloid number density, decreases with every purification step. By addition of FeCl₃ as a precipitating agent and with an additional filtration step, not only suspended matter, but also colloids are effectively removed. After this process a remaining particle concentration of 50 ng/L and a mean particle diameter of 27 nm are found.  相似文献   

Application of general circulation models to the study of stratospheric ozone     

London  Julius  Park  Jae 《Pure and Applied Geophysics》1973,106(1):1611-1617

Summary Observations of the ozone distribution indicate that modifications are required to the photochemical theory. These modifications involve ozone destruction by hydrogen and nitrogen products and ozone transport (both vertical and horizontal) due to atmospheric motions in the stratosphere. If the photochemical terms in the ozone continuity equation are omitted, changes due to atmospheric transport alone can be evaluated.Numerical computations were made of the three-dimensional wind structure as derived from the 12-layer (0–36 km) General Circulation Model developed by NCAR. The results showed that ozone is transported from the equatorial stratosphere poleward and downward in both hemispheres. The horizontal transport is primarily by the Hadley Cell in the tropics and by large-scale eddies in mid and high latitudes. The dominant mechanism for ozone transport are found to be similar to those derived for the horizontal heat and momentum transport found in other general circulation studies.  相似文献   

Dynamic analysis of structures using modified Lanczos co‐ordinates     

Byoung‐Wan Kim  Hyung‐Jo Jung  Woon‐Hak Kim  In‐Won Lee 《地震工程与结构动力学》2003,32(9):1469-1474

An efficient dynamic analysis method using the modified Lanczos co‐ordinates is presented. The proposed method is obtained by applying the modified Lanczos algorithm using Lanczos vectors that satisfy the stiffness‐orthonormality condition to the conventional Lanczos co‐ordinates method. The modified Lanczos co‐ordinates method is more efficient than the conventional method in the case of structures under multi‐input loads. The effectiveness of the modified Lanczos co‐ordinates method is verified by analysing a numerical example. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献