• Proceedings of the KSME Conference
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• 2003.11a
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• pp.956-961
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• 2003

Direct numerical simulations of flow over a circular cylinder are performed at two different Reynolds numbers (Re=220 and 300) that correspond to three-dimensional instabilities of mode A and mode B, respectively, to investigate the characteristics of drag and lift at these Reynolds numbers. The drag and lift coefficients are measured locally along the spanwise direction and their characteristics are studied in detail. The variation of total drag in time is large at Re=220, and the total drag becomes minimum when vortex dislocation occurs in the wake. The drag and lift variations in space are also closely associated with the evolution of vortex dislocation at this Reynolds number. At Re=300, vortex dislocation is not found in the wake and temporal variations of drag and lift are much smaller than those at Re=220, but their spatial variations are quite large due to the near-wake secondary vortices existing in the mode B instability.

• Atmosphere
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• v.18 no.4
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• pp.493-506
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• 2008

In order to examine the variational features of Asian dust outbreak in recent years, observed WMO synop data were employed for the period from 1996 to 2007. We first divided Asian dust source regions into four subregions; 1) Taklamakan, 2) Gobi, 3) Inner Mongolia-Manchuria and 4) Loess, and the meteorogical variables such as wind speed, precipitation and threshold wind speed observed during the Asian dust outbreak period were compared with those during non-Asian dust period. The results showed that temporal variation of occurrence frequency of dust outbreak had a strong positive correlation with the frequency of strong wind speed and low precipitation in each of the 4 source regions. Spatial distributions of frequency of dust occurrence after 2002 showed increasing trend in Gobi and Inner Mongolia-Manchuria but decreasing trend in Loess region. This is showing a shift in main source region toward Northwest, especially since 2003.

• Ocean and Polar Research
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• v.28 no.3
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• pp.331-337
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• 2006

Organophosphorus pesticides (OPs) were analyzed in surface water samples from the Saemangeum environment. IBP was the most abundant among 10 OPs analyzed, and accounted fur over 95% of total amount of OPs. Concentrations of IBP measured in Mangyeong River water and surface seawater ranged from 670 to 1100ng/l and from 45 to 1000 ng/l, respectively. In general, a decreasing trend of OP concentrations towards open sea was observed. The concentrations of IBP and salinity demonstrated a strong correlation $(r^2=0.96)$. This indicates that IBP showed conservative behavior in the study area, and seawater dilution is a major factor affecting distribution and variation of OPs in the Sammgem environment.

• Korean Journal of Hydrosciences
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• v.8
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• pp.41-56
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• 1997

A new routing computer model for the symmetric compound channel called the ASRMCS(Apparent Shear Force Muskingum-Cunge Method in Symmetry) has been developed. The Muskingum-Cunge routing method is adapted. The Apparent Shear Force (ASF) between the deep main channel and the shallow floodplan flow is introduced while the flow is routed. The nonlinear parameter method is applied. The temporal and spatial increments are varied according to the flow rate. The adaptation of above schemes is tested against the routed hydrographs using the DAMBRK model. The results of general routing practice of Muskingum-Cunge Method(GPMC) are also compared with those of above two models. The results of the new model match remarkably well with those of DAMBRK. The routed hydrographs show a smooth variation from the inflow boundary condition without any distortions caused by the difference of cross-section shape. However, the results of GPMC, showing early rise and fall of routed hydrograph, have considerable differences from those of the ASFMCS and DAMBRK.

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.1
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• pp.33-40
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• 1992

Up to now, monthly water balance analysis has been dominantly used for the water resources planning. But, it is more reasonable to explain the variation of spatial and temporal distribution of water by the daily water balance model with daily streamflow data. Since we are recently facing the problems of regional unbalance of water quantity, and of multiuse of irrigation water, and of deterioration of water quality, it is urgently needed to develop the daily water balance model to solve those problems and establish the rational plannings of agricultural water resources. In the circumstances, Daily water Balance(DAWABA) model for irrigation reservoirs was developed and the operation rule of irrigation resorvoir during drought season was established.

• Advances in environmental research
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• v.2 no.2
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• pp.99-118
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• 2013

Rainwater runoff has been identified as a significant source of contaminants having tremendous impact on the receiving aquatic environment. In the present study, trace element transport by the surface runoff in the predominantly urban catchment of Guwahati city, India was monitored with a view to determine the chemical denudation rates of the land surface. A number of trace metals, namely Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn were measured in the runoff after 70 major rain events within the city. Cadmium was found to be the least abundant metal and Iron was the most abundant metal in the runoff. The results are interpreted on the basis of temporal and spatial variations in their concentrations. These variations are quite large in some of the events and reflect changes in the local environmental setting, differences in water utilization, variations in runoff volume, gradient and quality.

• Journal of Environmental Impact Assessment
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• v.20 no.3
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• pp.349-356
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• 2011

This research is aim to analyze of changing landscape and according to phenological cycle from image information of coastal environment obtained by multi-media were analyzed by camera and satellite image. The digital camera and satellite image were used for tidal flat vegetation monitoring during the construction of Sihwa lake. The vegetation type and phenological cycle of Sihwa tidal flat have been changed with the Sihwa lake ecosystem. The environment changes of Sihwa tidal flat area and ecological change were analyzed by field work digital camera images and satellite images. The airborne, UAV and satellite images were classified with the changed elements of coastal ecological environment and tidal flat vegetation monitoring carried out the changed area and shape of vegetation distribution with time series images.

• ETRI Journal
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• v.44 no.4
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• pp.624-640
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• 2022

Taxi-demand forecasting and hotspot prediction can be critical in reducing response times and designing a cost effective online taxi-booking model. Taxi demand in a region can be predicted by considering the past demand accumulated in that region over a span of time. However, other covariates-like neighborhood influence, sociodemographic parameters, and point-of-interest data-may also influence the spatiotemporal variation of demand. To study the effects of these covariates, in this paper, we propose three models that consider different covariates in order to select a set of independent variables. These models predict taxi demand in spatial units for a given temporal resolution using linear and ensemble regression. We eventually combine the characteristics (covariates) of each of these models to propose a robust forecasting framework which we call the combined covariates model (CCM). Experimental results show that the CCM performs better than the other models proposed in this paper.

• Journal of the military operations research society of Korea
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• v.13 no.1
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• pp.1-18
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• 1987

This paper presents several adaptive linear predictive coding techniques based upon extension of recursive ladder filters. A 2-D recursive ladder filter is extended to a 3-D case which can adaptively track the variation of both spatial and temporal changes of moving images. Using the 2-D/3-D ladder filter and a previous farme predictor, two types of adaptive predictor-control schemes are proposed in which the prediction error at each pel can be obtained at or close to a minimum level. We also investigate several modifications of the basic encoding methods. Performance of the 2-D/3-D ladder filters, their adaptive control schemes, and variations in coding methods are evaluated by computer simulations on a real sequence and compared to the results of motion compensation and frame differential coders. As a validity test of the ladder filters developed, the error signals for the different predictors are compared and evaluated.

• Korean Journal of Remote Sensing
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• v.29 no.6
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• pp.611-619
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• 2013

Although the need of crop production has increased in Mongolia, crop cultivation is very limited because of the harsh climatic and topographic conditions. Crop lands are sparsely distributed with relatively small sizes and, therefore, it is difficult to survey the exact area of crop lands. The study aimed to find an easy and effective way of accurate classification to map crop lands in Mongolia using satellite images. To classify the crop lands over the study area in northern Mongolia, four classifications were carried out by using 1) Thematic Mapper (TM) image August 23, 2) TM image of July 6, 3) combined 12 bands of TM images of July and August, and 4) both TM images of July and August by layered classification. Wheat and potato are the major crop types and they show relatively high variation in crop conditions between July and August. On the other hands, other land cover types (forest, riparian vegetation, grassland, water and bare soil) do not show such difference between July and August. The results of four classifications clearly show that the use of multi-temporal images is essential to accurately classify the crop lands. The layered classification method, in which each class is separated by a subset of TM images, shows the highest classification accuracy (93.7%) of the crop lands. The classification accuracies are lower when we use only a single TM image of either July or August. Because of the different planting practice of potato and the growth condition of wheat, the spectral characteristics of potato and wheat cannot be fully separated from other cover types with TM image of either July or August. Further refinements on the spatial characteristics of existing crop lands may enhance the crop mapping method in Mongolia.