• Journal of the Korean Society for Heat Treatment
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• v.34 no.6
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• pp.272-280
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• 2021

The influence of acetylene flow rates on the carburizing behavior of an AISI 4115 steel in 1 ton-class mass production-type vacuum carburizing furnace has been studied through microstructure, carbon concentration, hardness analyses. The AISI 4115 steels were carburized with various flow rates (20, 32.7, 60 l/min) and locations in the furnace (top, center, bottom) at 950℃. The acetylene flow rate played an important role in controlling the carburizing properties of carburized samples, such as effective case depth and uniformity carburizing according to location in the furnace. At an acetylene flow rate of 20 l/min, the carburized samples had a shallow average hardened layer (0.645 mm) compared to the target hardening depth (1 mm) due to low carbon flux and spatial uniformity of carburization (17.8%) in the furnace. At a flow rate of 60 l/min, the carburized samples showed an average hardened layer (1.449 mm) deeper than the target hardening depth and had the spatial uniformity of carburization (98.8%). In particular, at a flow rate of 32.7 l/min, the carburized samples had an average hardened layer (1.13 mm) close to the target hardening depth and had the highest carburizing uniformity (99.1%). As a result, an appropriate flow rate of 32.7 l/min was derived to satisfy the target hardening depth and to have spatial uniform hardened layer in the furnace.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.6
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• pp.671-683
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• 1995

This study was aimed to provide understanding on the eco-physiological response of barley tillers as affected by sowing depth. Yield and yield contribution rate of tillers were investigated with the data of field experiments in the former Wheat and Barley Research Institute of Suwon, Korea from October 1983 to July 1984. When barley was sowed in various depth of 1, 3, 5, 7 and 9cm below the ground surface, 13 mainstem leaves appeared by 3 and 5cm treatments, and 11 leaves by 1, 7 and 9cm treatments. The effective tillers were observed from 8/0 in lcm depth, while 10/0 in 3-5cm depth and 9/0 in 7cm depth. There was no coleoptile tiller in 7cm depth sowing. Deep and shallow sowings produced fewer leaves and tillers, as early growth was hindered by deep sowing whereas cold damage was apparent in shallow sowing. Accordingly, more effective tillers per plant and higher grain weight per ear were observed in 3∼5cm depth sowing. Yield contribution by the tillers with various sowing depth was as follows: mainstem, 1, 2, 11, 3, 21, 4 and 12. The contribution of 1P, 13, 2P, 23 and 31 varied with the treatments.

• The Journal of Engineering Geology
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• v.25 no.4
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• pp.533-545
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• 2015

Spatial and seasonal variations in hydrogeochemical characteristics and the factors affecting the deterioration in quality of shallow portable groundwater in an agricultural area are examined. The aquifer consists of (from the surface to depth) agricultural soil, weathered soil, weathered rock, and bedrock. The geochemical signatures of the shallow groundwater are mostly affected by the NO₃⁻ and Cl⁻ contaminants that show a gradual downward increase in concentration from the upper area, due to the irregular distribution of contamination sources. The concentrations of the major cations do not varied with the elapsed time and the NO₃⁻ and Cl⁻ ions, when compared with concentrations in background groundwater, increase gradually with the distance from the upper area. This result suggests that the water quality in shallow groundwater deteriorates due to contaminant sources at the surface. The contaminations of the major contaminants in groundwater show a positive linear relationship with electrical conductivity, indicating the deterioration in water quality is related to the effects of the contaminants. The relationships between contaminant concentrations, as inferred from the ternary plots, show the contaminant concentrations in organic fertilizer are positively related to concentrations of NO₃⁻, Cl⁻, and SO₄²⁻ ions in the shallow portable groundwaters, which means the fertilizer is the main contaminant source. The results also show that the deterioration in shallow groundwater quality is caused mainly by NO₃⁻ and Cl⁻ derived from organic fertilizer with additional SO₄²⁻ contaminant from livestock wastes. Even though the concentrations of the contaminants within the shallow groundwaters and the contaminant sources are largely variable, it is useful to consider the ratio of contaminant concentrations and the relationship between contaminants in groundwater samples and in the contaminant source when analyzing deterioration in water quality.

• Journal of the Korean earth science society
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• v.21 no.1
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• pp.59-66
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• 2000

In Kyeongsang basin, there were very dynamic magmatic activities, resulting to form volcanic and plutonic rocks. A plutonic recycle appeared in this region. Presumption of the pressure for hornblende-bearing granitic rock among the plutonic rocks, can support important informations for the emplacement depth of Cretaceous Bulgugsa granites in Kyeongsang basin. $Al^T$(Al total) contents of hornblende is related to the pressure, oxygen fugacity, and compositions of other minerals having the solid solution. So we apply the $Al^T$ content of hornblende to several empirical and experimental geobarometer systems to presume the pressure and to determine the emplacement depth of Cretaceous Bulgugsa granites in Kyeongsang basin from the inferred pressure. With the result that we applied the $Al^T$ contents of hornblende to the various geobarometers, there was a positive relationship between the pressure and $Al^T$. The minimum pressure value ranges from 0.73 to 1.70kbar in Kyeongju and the maximum value from 2.02 to 3.16kbar in Kimhae. And then the tectonic setting in Kyeongsang basin has no relation to the emplacement depth of Cretaceous granites and means variations with the movement of vertical component in each area. As we suppose that the density of earth's crust is $2.8g/cm^3$, the average values of the emplacement depth ranges in each area range from 2.6 to 11.4km. These data confirm the previous idea about the emplacement depth of Cretaceous granites in Kyeongsang basin, and these geobarometers using the $Al^T$ contents of hornblende is available though they have much limits. Therefore Cretaceous Bulgugsa granites in Kyeongsang basin was the shallow depth intrusive rut and the exposed granites was the shallow depth crust.

• Journal of Korea Water Resources Association
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• v.56 no.3
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• pp.195-210
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• 2023

Additional deposition and erosion in large rivers in South Korea have continued to occur toward morphological stabilization after massive dredging through the four major river restoration project, subsequently requiring precise bathymetry monitoring. Hyperspectral bathymetry method has increasingly been highlighted as an alternative way to estimate bathymetry with high spatial resolution in shallow depth for replacing classical intrusive direct measurement techniques. This study introduced the conventional Optimal Band Ratio Analysis (OBRA) of hyperspectral bathymetry method, and evaluated the performance in a domestic large river in normal turbid and flow condition. Maximum measurable depth was estimated by applying correlation coefficient and root mean square error (RMSE) produced during OBRA with cascadedly applying cut-off depth, where the consequent hyperspectral bathymetry map excluded the region over the derived maximum measurable depth. Also non-linearity was considered in building relation between optimal band and depth. We applied the method to the Nakdong and Hwang River confluence as a large river case and obtained the following features. First, the hyperspectal method showed acceptable performance in morphological mapping for shallow regions, where the maximum measurable depth was 2.5 m and 1.25 m in the Nakdong and Hwang river, respectively. Second, RMSE was more feasible to derive the maximum measurable depth rather than the conventional correlation coefficient whereby considering various scenario of excluding range of in situ depths for OBRA. Third, highly turbid region in Hwang River did not allow hyperspectral bathymetry mapping compared with the case of adjacent Nakdong River, where maximum measurable depth was down to half in Hwang River.

• Journal of Korea Water Resources Association
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• v.53 no.11
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• pp.951-960
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• 2020

This study investigates the adjustment processes of the rivers after weir removal through laboratory experiments. Delta upstream eroded rapidly by flow at the initial stage of the experiments and the knickpoint migrates upward. Moreover, the knickpoint moves fast upward on the condition of alternate bars. The head cutting in the bed is developed fast at the initial stage. However, the erosion speed in the bed decreases with time. The well developed alternate bars migrates with keeping their shape downstream, and the bars affect the channel downstream to adjust new environments after weir removal. Maximum scouring depth downstream and the migration speed decrease over time after removing the weir. The scouring depth in the channel without alternate bars migrates with speed. However, the depth in the channel with alternate bars migrates slow downstream. The channel with alternate bars, in turn, is adjusted well to the new equilibrium states. The maximum scouring depth migrates downstream with time, and the scouring depth and its migration speed decreases with time. The dimensionless maximum scouring depth decreases with the migration speed of dimensionless maximum scouring depth because the deeply scoured places capture the sediments from upstream and the migration speed is slow as the places are filled with them. The dimensionless maximum scouring depth is shallow as the dimensionless backfilling speed is high. The dimensionless maximum scouring depth decreases rapidly less than 5 of dimensionless backfilling speed. However, the depth decreases slow more than 5 of it.

• Korean Journal of Ichthyology
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• v.11 no.1
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• pp.52-61
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• 1999

Seasonal variation in species composition of fish with depth was determined by analysis of bimonthly samples collected by a beach seine at the shallow water (St. 1 < 1.5m) and by beam trawl at the two stations (St. 2, 5~7m and St. 3 > 15 m) from October 1997 to August 1998 off Ippa-do in Asan Bay. Of forty species identified, 13 species at St. 1,28 species at the St. 2 and 30 species at the St. 3 were collected. The fish density was also increased with depth. Favonigobius gymnauchen occupied 55.7% at St. 1 and 38.9% of the number of individuals at St. 2. Almost of fish collected at these two stations were juveniles, and they were principally collected in August and in November. At St. 3, relatively large fishes were collected. Among them Pholis fangi and Chaeturichthys stigmatias predominated in the number of individuals. Abundance was low, but a large number of species were collected in winter. Principal component analysis revealed that the species composition at the shallower stations was different from that at the deeper station. The number of species and abundance of fish in Asan Bay was lower than in the other western coastal waters of Korea. Species composition in the study area of sandy bottom was different from that in the inner Asan Bay of mud bottom.

• Economic and Environmental Geology
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• v.47 no.5
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• pp.533-540
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• 2014

The Wangdol-cho area, in the Hupo Bank, plays a very important role in main fishing grounds, leisure tourism and marine environmental researches of the East Sea. We analyzed the detailed bathymetry and classified the seabed characteristics of the Wangdol-cho area, based on seafloor backscattering images and sediment grain size. The Hupo Bank is developed in parallel with the eastern coastal line of Korean peninsula, and the shallowest area (Wangdol-cho) of the Hupo Bank is located along the eastern part of Hupo Port. The Wangdol-cho comprises three summits; north summit, middle summit, and south summit. The middle summit area among the three summits has the most shallow water depth with minimum about 6 m. The north summit shows about 8 m minimum depth and the south summit about 9 m. The bathymetry data around three summits represent undulating seabeds with many scattered underwater reefs and shallow water depth. The area between the underwater reefs, the flat seafloor in the northeastern part of the survey site, and the western steep slope area have relatively coarse sediments such as sandy gravel and gravelly sand. The bathymetry in the western side of the Wangdol-cho shows steep slope seabed, extending to the Hupo Basin. Fine sediments including mud and silty sand occur in the Hupo Basin area of the survey site. The submarine detailed topography and the analysis of the seafloor characteristics of the survey area are expected to contribute to management for marine environmental researches and sustainable use of ecosystems in the Wangdol-cho.

• Journal of Korea Water Resources Association
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• v.43 no.7
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• pp.657-666
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• 2010

The adjustment processes of mining pits in the disturbed channels by sand or gravel mining were investigated by laboratory experiments in this study. The pit migrated with speed when the river bed was steep. The pit migrated slow and steady when the pit was filling with sand, but the pit migrated with speed after the filling processes was finished. The submerged angle of repose in the pit was nearly constant during the pit was filling. The pit was filled with sand with speed as the channel slope was increased. It took time for the pit to be filled with sand as the pit dimension was increased. This meant that the disturbed channels by sand or gravel mining to adjust the new environment was dependent on the slope of the channels and the dimension of the pits. The dimensionless pit length was short and the dimensionless pit depth was shallow as the time was increased. The dimensionless pit depth was shallow, but the dimensionless pit migration speed was increased as the dimensionless shear velocity and the migration speed of the pit were increased. The dimensionless pit depth was increased with the dimensionless bar migration speed. The shape of the pit was deformed and migrated downstream in accordance with the location and shape of the biased bar front which was developed upstream.

• 한국해양학회지
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• v.29 no.3
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• pp.269-277
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• 1994

Process of resuspension and accumulation well explaines the characteristics of surface sediment size distribution and suspended material in Deukryang Bay. Most of the surface sediments of the bay show asymmetric unimodal size distribution, which is found also in sediments from western part of the inner shelf mud area between Keomundo and Yokchido islands. Investigation of the size curves indicates that surface sediment in Deukryang Bay is a deposit of suspended coastal sediment transported east along southern coast of Korea. The distribution pattern of coarse sit fraction content in the surface sediment is very similar to that of computed current velocity (Lee, 1994), suggesting that fine sediment on the bed may reassumed and accumulate repeatedly due to shallow depth and strong tidal current in Deukryang Bay. The process of repeated resuspension and accumulate repeatedly due to shallow depth and strong tidal current in Deukryang Bay. The process of repeated resuspension and accumulation seems to be responsible not only to the asymmetric size distribution of the surface sediment, but also to the amount of suspended material in the bay. The difference of suspended material concentration between surface and near bottom water in summer is two times as large as that the in winter. This seems to derive from the fact that stratification of water mass prevails in summer, while total water mass is vertically mixed in winter. It was found that the most important factors to decide distribution of suspended material in Deukryang Bay are the physical properties of water mass such as current velocity and stratification, and water depth, in part with the supply of suspended sediment by rivers.