• Korean Journal of Soil Science and Fertilizer
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• v.4 no.2
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• pp.187-192
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• 1971

This paper deals mainly with the genesis and classification of the Jeonnam series. These soils have brown to dark brown silt loam and silty clay loam A horizon(strong brown or reddish brown where eroded). Argillic B horizons are dominantly red or yellowish red silty clay loam to silty clay with moderately developed subangular blocky structure and with thin clay cutans on the ped faces. The C horizons are strongly and very deeply weathered strong brown, yellowish brown, pale brown and reddish yellow silty clay loam and sandy loam granitic saprolite. Content of clay increases with depth to a maximum between 100cm. Percolating water seems to be responsible for transportation and oriented deposition of clay. Chemically, soil reaction is strongly acid to medium acid throughout the profile. The content of organic matter is 1 to 2 percent, and decreases regularly with depth. Base saturation is low, based on amount of extractable cations. Characterisltically the Jeonnam series are similar to Red-Yellow Podzolic soils of the United States and are similar to Red-Yellow soils of the Japan. In the writer's opinion the Jeonnam soils are classified as Red Yellow soils. According to USDA 7th approximation, this soil can be classified as Typic Hapludults and in the FAO/UNESCO World Soil Map as Helvic Acrisols.

• The Korean Journal of Mycology
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• v.26 no.4 s.87
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• pp.562-573
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• 1998

The symbiotic activities of arbuscular mycorrhizal fungi (AMF) by analyzing spore density, symbiosis intensity and vertical distribution of AMF spores, phytomasses of higher plants such as Calamagrostis epigeios, Imperata cylindrica, Artemisia scoparia, Aster tripolium and Sonchus brachyotus, and physico-chemical properties of soil were determined in the rhizospheres of higher plants in abandoned two coastal reclaimed lands, which were constructed in 12 and 30 years ago, respectively. Vertical distribution of the AMF spores in the rhizospheres of higher plants was restricted within 20 cm depth from soil surface, which would be closely related with vertical distribution of root system, water table and soil aeration. Of vertical distribution of soil properties, W.C., A-P and K concentrations were increased as soil depth was lowered. In the coastal reclaimed lands, symbiotic activities of the AMF such as spore density and symbiotic intensity, were conspicuously stimulated by the increase of soil pH value, organic matter and total nitrogen concentrations, but inhibited by the increase of moisture, available phosphorus and sodium concentrations in the rhizosphere soil. Phosphorus absorption by higher plants growing in the reclaimed lands increased by the rise of symbiotic activities of AMF. Since symbiotic activities of AMF were stimulated with decreasing soil phosphorus concentrations, higher plants associated with AMF absorbed a large amount of phosphorus from the soil is low phosphorus concentrations.

• Journal of Wetlands Research
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• v.24 no.4
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• pp.213-223
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• 2022

This study was conducted to establish a Habitat Suitability index (HSI) based on literature research and field surveys on ecology and habitat of 'Hynobius leechii'. And this study will be used as basic data for qualitative evaluation of habitat environment. The survey sites were divided into natural habitats close to the prototype habitat and artificial restoration areas where Hynobius leechii was monitored. So the types of habitats were diversified. Hynobius leechii is a vulnerable species to climate change because it is affected by the microhabitat and has low mobility. HSI variables of Hynobius leechii were extracted through domestic and overseas literature, and standards were extracted from literature research and field survey. The standards were presented as a value of the physical allowable category in consideration of realization. To verify the study, an in-depth consultation was conducted by amphibians experts. HSI variables of Hynobius leechii were included 9 variables such as Overstory canopy cover(%), Understory cover(%), Water-pH, Soil-pH, Soil relative humidity(%), Leaf litter depth(cm), Rock substrates (%), Type of Coarse woody, Distance from Street or Pollutant(m).

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.5
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• pp.395-409
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• 2022

To overcome the limitation of conventional rock excavation methods, the excavation with abrasive waterjet has been actively developed. The abrasive waterjet excavation method has the effect of reducing blasting vibration and enhancing the excavation efficiency by forming a continuous free surface on the rock. However, the waterjet cutting performance varies with rock fracturing characteristics. Thus, it is necessary to analyze the cutting performance for various rocks in order to effectively utilize the waterjet excavation. In this study, cutting experiments with the high pressure waterjet system were performed for basalt and granite specimens. Water pressure, standoff distance, and traverse speed were determined as effective parameters for the abrasive waterjet cutting. The cutting depth and width of basalt specimens were analyzed to compare with granite results. The averaged cutting depth of basalt was shown in 41% deeper than granite; in addition, the averaged cutting width of basalt was formed by 18.5% narrower than granite. The results of this study are expected to be useful basic data for applying rock excavation site with low strength and high porosity such as basalt.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.3
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• pp.328-341
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• 2010

The authors adopt the Unmanned Undersea Vehicle(UUV), which has taken the shape of manta(Sohn et al. 2006). They call here it Manta-type Unmanned Undersea Test Vehicle(MUUTV). MUUTV is designed with the similar concept of UUV called Manta Test Vehicle(MTV), which was originally built by the Naval Undersea Warfare Center, USA(Lisiewicz and French 2000, Sirmalis et al. 2001, U.S. Navy 2004). The present study deals with evaluation of extreme motion of MUUTV at large attack angles. Extreme motion contains, for example, rising and depth change due to operation of hovering thrusters attached to MUUTV, lateral motion due to ocean current applied to MUUTV at low advance velocity, and so on. Numerical simulation technique has been utilized. The previous mathematical model on manoeuvring motion of MUUTV(Bae et al. 2009a) is basically adopted. Based on the results of present model experiment on extreme motion, the mathematical model is revised and supplemented in order to describe extreme motion. The hydrodynamic derivatives related to extreme motion are obtained from present model experiment and the other derivatives are referred to previous work(Bae et al. 2009a).

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.1
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• pp.36-43
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• 2017

The results of a numerical study on the performance of a propeller operating near a free surface are presented in this paper. The simulations are verified through comparison with experimental data, which was performed in a circulating water channel. The propeller performance as a function of the submerged depth was investigated. The effect of the propeller advance ratio on the wave patterns, flow structures around propeller, and thrust and torque of the propeller was also studied. Air ventilation was not observed for low advance coefficients. However, the simulations showed that wave pattern was strongly related to the tip vortex strength and inflow velocity. When air ventilation does not occur, the deduction of propeller thrust and torque increase for high advance coefficients.

• Ocean and Polar Research
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• v.33 no.spc3
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• pp.385-395
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• 2011

Time-series sediment traps were deployed at 1,000 m water depth of the northwestern subtropical Pacific from July 2009 to June 2010, with the aim of understanding temporal and spatial variations of sinking-particle fluxes. The opening and closing of the traps was synchronized at 18-day periods for 20 events. Total mass fluxes showed distinct seasonal variations with high values for the summer-fall seasons and relatively low values for winter-spring. This seasonal variation at two stations was characterized by a distinct difference in $CaCO_3$ fluxes between the two seasons. The enhanced $CaCO_3$ flux in the summer - fall seasons might be attributed to an increased planktonic foraminiferal flux. Total mass flux at FM10 station was nearly 50% higher than that at FM1 station. The difference in $CaCO_3$ fluxes between two stations contributed nearly 70% of the difference of total mass fluxes. The $CaCO_3$ flux was a major component controlling temporal and spatial variation of sinking - particle fluxes in the western subtropical Pacific Ocean.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.4
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• pp.251-257
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• 2014

This research is focused on coagulation and sand filtration process as a pretreatment of RO seawater desalination. RO systems require sufficient and reliable pretreatment process to produce superior quality of RO feedwater that can mitigate RO membrane fouling. This experiment was conducted to investigate the effectiveness of coagulation and filtration process under various experimental conditions including different coagulant dose, flocculation mixing intensity and time, turbidity, and filtration rate. The experimental results showed that the optimum pretreatment conditions resulting in lower SDI value suitable for RO feedwater were coagulation pH 6.5, raw water turbidity greater than 4 NTU, and media bed depth greater than 550 mm. However, flocculation mixing intensity, coagulant dose, and filtration rate relatively affected little on the filtration efficiency.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.7-13
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• 2017

A comfortable indoor environment is important considering that many hours are spent in residential or office space. A humidifier is used to control the indoor humidity. In particular, an element type humidifier has the advantage of a simple structure and low energy consumption. Two types of humidifiers - stationary or rotor - are commonly used for residential purposes. In this study, performance optimization was conducted for a rotor-type humidifying element used in a residential humidifier. The optimization included the rotation speed, water submersion depth, etc. The test range consisted of an open area to the air from 57 to 90%, rotation speed from 0.2 to 2.0 rpm, frontal air velocity from 0.5 to 2.5 m/s. The results showed that the optimal open area to air was 70%. On the other hand, the effects of the rotation speed on the moisture transfer rate was negligible. On the other hand, the pressure drop increased with increasing rotation speed. As the frontal air velocity increased, both the moisture transfer rate and pressure drop increased. The humidification capacity of the present element was 0.08 ~ 0.31 kg/hr. A comparison of the data with the theoretical results was made.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.2036-2041
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• 2005

The underwater multi-agent technology has many potential for the various activities related to ocean development/conservation in the near future. For example, in such fields as water pollution investigation, aquaculture control, or coral reef research, we feel a growing need for a system that realizes underwater continuous monitoring in the wide rang e. In this case, the target monitoring area will be sliced planar hierarchically toward the depth as monitoring layers, and many AUVs arranged on each layer track the given trajectory and gather various environmental information continuously, with communicating each other in the layer or with other layers. To realize those systems we need to develop AUV multi-agent technologies. So we are now building basic systems for basin experiment for the development of AUV multi-agent behavior. We must experience many situations and problems to be solved for the development of its elemental technologies by using real systems as well as our computer simulations. In this paper we introduce our concept of the experiment in the near future and the hardware/software design of our two types of handy AUVs and ultrasound ranging/communication system for that experiment. One AUV is designed using a 17inches-diameter glass sphere with DOS/V and RT-Linux based subsystems, which is intended to use not only in the basin but also in the calm real sea. The other AUV is designed for the basin experiment using a 7inches-diameter acrylic sphere with low-cost embedded system with SH-2 based subsystems. The basin experiment to verify the basic AUV facilities and ultrasound ranging for position detection was carried out.