• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.22 no.6
• /
• pp.415-423
• /
• 1990

In a laboratory model the response of the boundary layer flow over topography is studied in a rotating sliced cylinder by employing the source-sink analogy with Ekman layer dynamics. The boundary layer flow is produced by two different fluid. In the first experiment homogeneous fluid is used both for the source and the working fluid of the container. In the second experiment a denser fluid is used for the source with the same working fluid. For the homogeneous western boundary layer flow both the northward and the southward flow were affected by the topography(ridge) to produce a cyclonic motion near the ridge. When woughward moving heavy boundary flow of slower speed and the northward moving faster flow were present at the same time, the splitting of southward flow and the separating of the northward flow were observed with a cyclonic motion at the ridge. The most important factor that influence production of the cyclonic motion has been turned out to be the presence of the topography in the western boundary layer. In particular the role of the southward moving heavy flow over the interior flow pattern was found to be very significant.

• Journal of Korean Society for Atmospheric Environment
• /
• v.10 no.2
• /
• pp.116-123
• /
• 1994

The E- $\varepsilon$ turbulence numerical model was applied to a flow around triangular ridge in neutral boundary layer. Scale of cavity region, mean velocity, Reynolds stress and eddy diffusivity were investigated. The height of cavity region was in satifactory agreement with the wind tunnel data while the length of cavity region was underestimated. The man wind velocities outside the cavity region were well Predicted by the model, however in cavity region the mean wind velocities of wind tunnel data were larger than the model results Reynolds stress of cavity region was overestimated by the model. The eddy diffusivity of wake region was strongly modified under the influence of triangular ridge. The local minimum of the eddy diffusivity was occured in the lee of the ridge top.

• The Journal of the Petrological Society of Korea
• /
• v.8 no.1
• /
• pp.1-13
• /
• 1999

The Latite Ridge Latite in the East Tintic volcanic field, Utah in USA occurs as a welded ash-flow tuff, has 63.7-66 wt% $SiO_2$ on an anhydrous basis, and shows calc-alkaline affinities. The rocks fall in the trachyte field of IUGS classification. It is characterized by unusally high $K_2O$ content (5.9-7.6 wt%), relatively high equilibration temperature (950-973$^{\circ}C$), and biotites with high $TiO_2$ content (7.4-8.2wt%). Various differentiation processes were tested using the XLFRAC program to infer the origin of the Latite Ridge Latite. The results suggests that crystal fractionation from shoshonite is one possible process to generate the Latite Ridge Latite. Shoshonite of the East Tintic volcanic field was possibly formed by crystal fractionation from a subduction-related K-, Mg-rich mafic magma.

• Journal of the korean society of oceanography
• /
• v.32 no.4
• /
• pp.181-190
• /
• 1997

A large subtidal sand ridge (Jungang Satoe) in Asan Bay, on the west coast of Korea, was studied in order to understand the morphology and sediment transport trend in a macrotidal setting, by means of analyzing sediment samples, current data, side-scan sonographs and seismic profiles. The ridge is about 15 km long and 2-5 km wide, with a relief of about 15 m. It is elongated in the flow direction of flood (SE) and ebb (NW) tidal currents, but asymmetrical in cross section. The western and southwestern side of the ridge is characterized by relatively gentle slopes averaging 0.4$^{\circ}$, whereas on the northeastern side, relatively steep slopes were mapped with 1.6$^{\circ}$ slope angles. Tidal currents associated with the ridge are very strong; maximum surface velo-cities range from neap values of 50 cm/s to spring values of 130 cm/s. The shear velocities during flood and ebb are strong enough to erode and transport sands on the ridge. Sand waves and megaripples (dunes) are the most common bedforms produced by the tidal currents, which show regional differences in shape and size on the ridge. The distribution pattern of these bedforms in-dicates that the flood tidal currents are dominant on the offshore (northwest) side of the ridge, whereas the onsho.e (southeast) side of the ridge is ebb-dominated. The sand transport path as inferred from bedform orientations is directed toward the ridge crest on the flanks, whereas on the crest, it is near-longitudinal to the ridge axis. The convergent, upslope movement of sands on the ridge flanks appears to be important in sand ridge building and maintenance. A significant ridge migration toward the northeast can be suspected on the basis of the ridge morphology, which may cause offshore hazards for navigation.

• Asian Journal of Atmospheric Environment
• /
• v.2 no.1
• /
• pp.1-13
• /
• 2008

A numerical simulation method has been developed to predict atmospheric flow and stack gas diffusion using a calculation domain of several km around a stack under complex terrain conditions containing buildings. The turbulence closure technique using a modified k-$\varepsilon$-type model under a non hydrostatic assumption was used for the flow calculation, and some of the calculation grids near the ground were treated as buildings using a terrain-following coordinate system. Stack gas diffusion was predicted using the Lagrangian particle model, that is, the stack gas was represented by the trajectories of released particles. The numerical model was applied separately to the flow and stack gas diffusion around a cubical building and to a two-dimensional ridge in this study, before being applied to an actual terrain containing buildings in our next study. The calculated flow and stack gas diffusion results were compared with those obtained by wind tunnel experiments, and the features of flow and stack gas diffusion, such as the increase in turbulent kinetic energy and the plume spreads of the stack gas behind the building and ridge, were reproduced by both calculations and wind tunnel experiments. Furthermore, the calculated profiles of the mean velocity, turbulent kinetic energy and concentration of the stack gas around the cubical building and the ridge showed good agreement with those of wind tunnel experiments.

• Proceedings of the Korea Water Resources Association Conference
• /
• 1988.07a
• /
• pp.115-127
• /
• 1988

• Proceedings of the KIEE Conference
• /
• 1988.07a
• /
• pp.628-631
• /
• 1988

This paper describes a fingerprint classification on the basis of feature points(whorl, core) and feature vector and uses a syntactic approach to identify the shape of flow line around the core. Fingerprint image is divided into 8 by 8 subregions and fingerprint region is separated from background. For each subregion of fingerprint region, the dominant ridge direction is obtained to use the slit window quantized in 8 direction and relaxation is performed to correct ridge direction code. Feature points(whorl, core, delta) are found from the ridge direction code. First classification procedure divides the types of fingerprint into 4 class based on whorl and cores. The shape of flow line around the core is obtained by tracing for the fingerprint which has one core or two core and is represented as string. If the string is acceptable by LR(1) parser, feature vector is obtained from feature points(whorl, core, delta) and the shape of flow line around the core. Feature vector is used hierarchically and linearly to classify fingerprint again. The experiment resulted in 97.3 percentages of sucessful classification for 71 fingerprint impressions.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.49 no.1
• /
• pp.17-22
• /
• 2007

The heat flow characteristics of the Gudle (traditional Ondol) used a lot at farm houses have been performed with variations of Bunengki (Fireridge) by numerical analysis and field experiment. The Doedon-Gorae (Return-Firetunnel) Gudle is analyzed among the structure of Gudle. The distribution of heat flow in Gorse (Firetunnel) and the temperature distribution in floor of 3 Buneomgi (Fire ridge) was more uniform than that of 1 Buneomgi. The heat efficiency of 3 Buneomgi was higher than that of 1 Bunengki. That is, the 3 Bunengk is more efficient and more uniform temperature.

• Wind and Structures
• /
• v.34 no.4
• /
• pp.385-394
• /
• 2022

Global Warming has been driven majorly by the consumption of fossil fuels. Harnessing energy from wind is viable solution towards reducing carbon footprint created due to burning such fuels, However, wind turbines have their problems of flow separation and aerodynamic stall to tackle with. In an attempt to delay the stall angle and improve the aerodynamic characteristics of the NACA 0015 symmetrical aerofoil, lateral cylindrical ridges were attached to its suction surface, at chord positions ranging from 0.1c to 0.5c. The characteristics of the original and ridged aerofoils were obtained using simultaneous pressure readings taken in a wind tunnel, at a free stream Reynolds number of R_e = 2.81 × 10⁵ for a wide range of free stream angles of attack ranging from -45° to 45°. Depending on the ridge size, a delay in stall angle varying from 5° to 20° was achieved together with the maximum increase in lift in the post-stall phases. Additionally, efforts were made to identify the optimum position for each ridge.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.60 no.1
• /
• pp.111-120
• /
• 2018

The purpose of this study was to develop a ridge regression (RR) model to estimate BOD and TP load using runoff weighted value. The concept of runoff weighted value, based on distributed curve-number (CN), was introduced to reflect the impact of land covers on runoff. The estimated runoff depths by distributed CN were closer to the observed values than those by area weighted mean CN. The RR is a technique used when the data suffers from multicollinearity. The RR model was developed for five flow duration intervals with the independent variables of daily runoff discharge of seven land covers and dependent variables of daily pollutant load. The RR model was applied to Heuk river watershed, a subwatershed of the Han river watershed. The variance inflation factors of the RR model decreased to the value less than 10. The RR model showed a good performance with Nash-Sutcliffe efficiency (NSE) of 0.73 and 0.87, and Pearson correlation coefficient of 0.88 and 0.93 for BOD and TP, respectively. The results suggest that the methods used in the study can be applied to estimate pollutant load of different land cover watersheds using limited data.