• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.789-797
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• 2021

The worldwide sizes of container ships are rapidly increasing. The container ship size in 2005, which was about 9,200 TEU has increased to 24,000 TEU in recent times. In addition to the increase in the sizes of the container ships, the arrivals/departures of large container vessels to/from Korea have also increased. Hence, the necessity for reviewing safe passage of such vessels is emphasized. In the present study, a 24,000 TEU container vessel was used as a model ship to calculate the under-keel clearance (UKC) at Gadeok Channel through which vessels must pass to arrive at Busan New Port, in accordance with the Korean Port and Fishing Port Design Standards and Commentary. In addition, the maximum allowable speed that meets UKC standards was calculated using various squat formulas, whose results were then compared with the current speed limit standards. The analysis results show that Busan New Port requires 10% marginal water depth, and the squat that meets this requirement is 0.95 m. Gadeok Channel requires 15% marginal water depth, and the squat that meets this requirement is 1.78 m; in this case, the maximum allowable speed is calculated as 15 kts. Busan New Port has set the speed limit as 12 kts, which is higher than the calculated 11 kts. Thus, speed limit reconsideration is required in terms of safety. However, the set speed limit for Gadeok Channel is 12 kts, which is lower than the calculated 15 kts. Thus, additional considerations may be provided to increase the speed limits for smooth navigational passage of vessels. The present study, however, is constrained by the fact that it reflects only a limited number of elements in the UKC and allowable speed calculations; therefore, more accurate UKC and safe speed values can be suggested based on extended studies to this research.

• Food Engineering Progress
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• v.13 no.4
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• pp.235-242
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• 2009

The purpose of this study is to establish fundamental research data for quality characteristics of Jochung by analyzing traditional manufacturing process. Two different processed rices (non-glutinous rices cooked by steaming and using an electronic rice cooker) were compared in terms of water solubility index (WSI), water absorption index (WAI), paste viscosity, reducing suger content, solid content, and dextrose equivalent over soaking time. Reducing sugar content increased for the soaked non-glutinous rice, steamed sample and microwaved sample. After 4 hr, the WSI decreased as the soaking time increased. However, there was no significant difference between WAI of the raw non-glutinous rice and the soaked non-glutinous rice. As soaking time increased, paste and breakdown viscosity increased significantly. Rice was prepared by soaking in water for 12 hr followed by the saccharification time (4, 8, or 12 h) for manufacturing Jochung. The solid content and reducing sugar content of the Jochung increased as the soaking time increased. Reducing sugar content and dextrose equivalent of Jochung from steamed rice (cooked hard) were higher than those from microwaved ones. The amount of reducing sugar and dextrose equivalent was highest in Jochung from steamed rice cooked hard (saccarification for 12 hr), with 59.40${\pm}$0.11% and 76.99${\pm}$1.78, respectively. In conclusion, the highest quality characteristics were obtained in Jochung manufactured with non-glutinous rice soaked for 12 hr followed by sacharification for 12 hr.

• Korean Journal of Heritage: History & Science
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• v.38
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• pp.329-358
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• 2005

The Three storied Stone pagoda in Gameunsa Temple site, one of the early staged stone pagodas, has been known as a standard for Silla stone pagodas. A stone pagoda is not only a stone art work and but also a stone structure. Most studies and investigation of the stone pagoda has done mainly based on style and chronological research according to an art historical view. However, there is not an attempt to research the stone pagoda as a stone architecture. Most Korean experts at the stone pagoda has art history in their background. Engineers who can understand the structure of the stone pagoda are very limited. More architectural and engineering approach is need to research not only art historial understanding but also safety as a structure. We can find many technical know-how from our ancestors who made stone pagodas. 1. To reduce any deformation such as relaxation and sinking of BuJae which is caused by a heavy load, the BuJae (consist of a foundation stone and lower stereobates) should be enlarged. 2. A special construction method for connection between Myonsuk and Tangjoo was invented. This unique method is not used any longer after the Three storied Stone pagoda in Gameunsa Temple site. 3. The upper BuJae and the lower BuJae are missed each other by making a difference of Okgaesuk and Okgaebatchim in size. It is done for a distribution of perpendicular load and a prevention for relaxation of BuJae. 4. The center of gravity in the BuJae is located to the center of the stone pagoda by trimming the upper surface of the Okgaebatchim into a convex shape. The man who made stone pagodas had excellent knowledge on the engineering and techniques to understand the structure of the stone pagodas. We can confirm it as follows: the enlarged BuJae, dislocated connection between upper Bujae and lower BuJae, and moving the center of gravity close to the center of the stone pagoda.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.37 no.1
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• pp.1-11
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• 2019

This study was conducted to analyze the conservation status by diagnostical methology for the front wall of Jungjeongdang area of Dodong-Seowon. The study was carried out as photogrammetry and mapping - investigation of materials and conservation status - analysis and evaluation of conservation status. The results are as follows. First, in the case of photogrammetry, each photograph was took in superposition, and the distortions of the photographs were corrected and synthesized. Based on this, actual survey drawings of the wall were prepared. Second, in case of material and conservation status, the wall is in the form of Wapyeondam and the material of the head part are tile, mud and lime, and the material of the body part are mud and tile. The mud was mixed with gravel, sand and straw. At the base part, amorphous natural stones and mud were used. The remarkable damage that appears on the wall is erosion of the base part, and some disintegration appears in the body part. There is a biological patina on the head and the base, and vegetation such as lichen is concentrated on the partial body. There was superficial deposit in the head part, and some tiles were broken or lost. Deep fissures are intensively located in some part of the eastern wall. Third, in the case of analysis and evaluation of the conservation status, it is considered that by the erosion of the foundation part and the disintegration of the body part, there is a possibility that physical damage will continue to be applied to the wall, so immediate action is necessary. The distribution of biological patina and vegetation does not appear to cause great problems in the wall, but it is necessary to reduce it in view of aesthetic problems. A cracked or missing tile would need to be replaced, and deep cracks in the eastern wall appear to have been caused by subsidence, and reinforcement of the underground is necessary to prevent further damage.

• Journal of the Korean Geotechnical Society
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• v.37 no.3
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• pp.19-30
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• 2021

The presence of the hydrate-bearing sediments in Ulleung Basin of South Korea has been confirmed from previous studies. Researches on gas production methods from the hydrate-bearing sediments have been conducted worldwide. As production mechanism is a complex phenomenon in which thermal, hydraulic, and mechanical phenomena occur simultaneously, it is difficult to accurately conduct the productivity and stability analysis of hydrate bearing sediments through lab-scale experiments. Thus, the importance of numerical analysis in evaluating gas productivity and stability of hydrate-bearing sediments has been emphasized. In this study, the numerical parametric analysis was conducted to investigate the effects of the bottom hole pressure and the depressurization rate on the gas productivity and stability of hydrate-bearing sediments during the depressurization method. The numerical analysis results confirmed that as the bottom hole pressure decreases, the productivity increases and the stability of sediments deteriorates. Meanwhile, it was shown that the depressurization rate did not largely affect the productivity and stability of the hydrate-bearing sediments. In addition, sensitivity analysis for gas productivity and stability of the sediments were conducted according to the depressurization rate in order to establish a production strategy that prevents sand production during gas production. As a result of the analysis, it was confirmed that controlling the depressurization rate from a low value to a high value is effective in securing the stability. Moreover, during gas production, the subsidence of sediments occurred near the production well, and ground heave occurred at the bottom of the production well due to the pressure gradient. From these results, it was concluded that both the productivity and stability analyses should be conducted in order to determine the bottom hole pressure when producing gas using the depressurization method. Additionally, the stress analysis of the production well, which is induced by the vertical displacements of sediments, should be evaluated.

• Journal of the Korean GEO-environmental Society
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• v.22 no.6
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• pp.17-26
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• 2021

Ground investigation and result analysis generally used to examine all sorts of structures' subsidence or stability can be classified into sandy soil and cohesive soil, and analysis on the liquid limit of soil is utilized to evaluate the physical properties of ground and types or technical behavior of soil. The most widely used method to analyze liquid limit is Casagrande with which liquid limit can be calculated relatively easily; however, it is fairly difficult to apply it to soil equipped with intermediate properties. Therefore, concerning the properties of soil having the intermediate properties of sedimentary ground, this researcher mixed the clay from Yangsan, Gwangyang, and Busan with sandy soil to make intermediate soil and then carried out the test of consistency limit and also evaluated applicability by using the suggested formula of consistency revision. The sample of intermediate soil was the mixture of clay and sandy soil, and to produce intermediate soil, the content (F_c) of fine soil was applied as 50%, 75%, or 100%. Regarding the physical properties of intermediate soil, to maintain the properties of clay in the natural state, bentonite was added at a fixed rate for controlling the properties of clay, and then, consistency was analyzed. By adopting the formula of consistency revision suggested in advanced research, this author analyzed consistency based on the experiment and consistency based on the suggested formula of revision. Also, about intermediate soil collected at the site, consistency based on the experiment and consistency based on the suggested formula of revision were analyzed comparatively, and about intermediate soil collected, this researcher analyzed particle size and calculated the content (F_c) of fine soil to analyze intermediate soil in diverse conditions. Moreover, about intermediate soil collected at the site, the suggested formula of consistency revision was applied to calculate the compression index, and the compression index based on the experiment and the compression index based on the suggested formula were analyzed comparatively to evaluate the applicability of the suggested formula.

• Journal of the Korean Geosynthetics Society
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• v.20 no.4
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• pp.85-93
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• 2021

The seventy percentage of Korean Peninsular is covered by the mountainous area, and the depth of west sea and south sea is relatively shallow. Therefore, a large scale land reclamation from the sea has been implemented for the construction of industrial complex, residental area, and port and airport facilities. The common problem of reclaimed land is consisted of soft ground, and hence it has low load bearing capacity as well as excessive settlement upon loading on the ground surface. The hollow concrete block has been used to reinforce the loose and soft foundation soil where the medium-high apartment or one-story industrial building is being planned to be built. Recently the earthquakes with the magnitude of 4.0~5.0 have been occurred in the west coastal and southeast coastal areas. Lee (2019) reported the advantages of hollow concrete block reinforced shallow foundation through the static laboratory bearing capacity tests. In this study, the dynamic behavior of hollow concrete block reinforced sandy ground with filling the crushed stone in the hollow space has been investigated by the means of shaking table test with the size of shaking table 1000 mm × 1000 mm. Three types of seismic wave, that is, Ofunato, Hachinohe, Artificial, and two different accelerations (0.154 g, 0.22 g) were applied in the shaking table tests. The horizontal displacement of structure which is situated right above the hollow concrete block reinforced ground was measured by using the LVDT. The relative density of soil ground are varied with 45%, 65%, and 85%, respectively, to investigate the effectiveness of reinforcement by hollow block and measured the magnitude of lateral movement, and compared with the limit value of 0.015h (Building Earthquake Code, 2019). Based on the results of shaking table test for hollow concrete block reinforced sandy ground, honeycell type hollow block gives a large interlocking force due to the filling of crushed stone in the hollow space as well as a great interface friction force by the confining pressure and punching resistance along the inside and outside of hollow concrete block. All these factors are contributed to reduce the great amount of horizontal displacement during the shaking table test. Finally, hollow concrete block reinforced sandy ground for shallow foundation is provided an outstanding reinforced method for medium-high building irrespective of seismic wave and moderate accelerations.

• Korean Journal of Remote Sensing
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• v.38 no.5_1
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• pp.447-460
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• 2022

It is well known that satellite synthetic aperture radar interferometry (InSAR) has been widely used for the observation of surface displacement owing to earthquakes, volcanoes, and subsidence very precisely. In wetlands where vegetation exists on the surface of the water, it is possible to create a water level change map with high spatial resolution over a wide area using the InSAR technique. Currently, a number of imaging radar satellites are in operation, and most of them support a ScanSAR mode observation to gather information over a large area at once. The Cienaga Grande de Santa Marta (CGSM) wetland, located in northern Colombia, is a vast wetland developed along the Caribbean coast. The CGSM wetlands face serious environmental threats from human activities such as reclamation for agricultural uses and residential purposes as well as natural causes such as sea level rise owing to climate change. Various restoration and protection plans have been conducted to conserve these invaluable environments in recognition of the ecological importance of the CGSM wetlands. Monitoring of water level changes in wetland is very important resources to understand the hydrologic characteristics and the in-situ water level gauge stations are usually utilized to measure the water level. Although it can provide very good temporal resolution of water level information, it is limited to fully understand flow pattern owing to its very coarse spatial resolution. In this study, we evaluate the L-band ALOS-2 PALSAR-2 ScanSAR mode to observe the water level change over the wide wetland area using the radar interferometric technique. In order to assess the quality of the interferometric product in the aspect of spatial resolution and coherence, we also utilized ALOS-2 PALSAR-2 stripmap high-resolution mode observations.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.606-612
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• 2022

Relatively high indoor CO₂ concentration (>1,000 ppm) has a negative impact on human health. In this work, indoor CO₂ adsorbent was developed by impregnating KOH or K₂CO₃ on commercial activated carbon, named as KOH/AC and K₂CO₃/AC. Commercial activated carbon (AC) showed relatively high BET surface area (929 m²/g) whereas KOH/AC and K₂CO₃/AC presented lower BET surface area of 13.6 m²/g and 289 m²/g. Two experimental methods of TGA (2,000 ppmCO₂, weight basis) and chamber test (initial concentration: 2,000 ppmCO₂, CO₂ IR analyzer) were used to investigate the adsorption capacity. KOH/AC and K₂CO₃/AC exhibited similar adsorption capacities (145~150 mg_CO2/g), higher than K₂CO₃/Al+Si supports adsorbent (84.1 mg_CO2/g_sample). Similarly, chamber test also showed similar trend. Both KOH/AC and K₂CO₃/AC represented higher adsorption capacities (KOH/AC: 93.5 mg_CO2/g K₂CO₃/AC: 94.5 mg_CO2/g_sample) K₂CO₃/Al+Si supports. This is due to the KOH or K₂CO₃ impregnation increased alkaline active sites (chemical adsorption), which is beneficial for CO₂ adsorption. In addition, the regeneration test results showed both K-based adsorbents pose a good regeneration and reusability. Finally, the current study suggested that both KOH/AC and K₂CO₃/AC have a great potential to be used as CO₂ adsorbent for indoor CO₂ adsorption.

• Journal of the Korean Geotechnical Society
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• v.22 no.6
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• pp.71-82
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• 2006

One of the most popular pre-reinforcement methods of tunnel heading in cohesionless soils would be the fore-polling of grouted pipes, known as RPUM (reinforced protective umbrella method) or UAM (umbrella arch method). This technique allows safe excavation even in poor ground conditions by creating longitudinal arch parallel to the tunnel axis as the tunnel advances. Some previous studies on the reinforcing effects have been performed using numerical methods and/or laboratory-based small scale model tests. The complexity of boundary conditions imposes difficulties in representing the tunnelling procedure in laboratory tests and theoretical approaches. Full-scale study to identify reinforcing effects of the tunnel heading has rarely been carried out so far. In this study, a large scale model testing for a tunnel in granular soils was performed. Reinforcing patterns considered are four cases, Non-Reinforced, Crown-Reinforced, Crown & Face-Reinforced, and Face-Reinforced. The behavior of ground and pipes as reinforcing member were fully measured as the surcharge pressure applied. The influences of reinforcing pattern, pipe length, and face reinforcement were investigated in terms of stress and displacement. It is revealed that only the Face-Reinforced has decreased sufficiently both vertical settlement in tunnel heading and horizontal displacement on the face. Vertical stresses along the tunnel axis were concentrated in tunnel heading from the test results, so the heading should be reinforced before tunnel advancing. Most of maximum axial forces and bending moments for Crown-reinforced were measured at 0.75D from the face. Also it should be recommended that the minimum length of the pipe is more than l.0D for crown reinforcement.