• Journal of Ocean Engineering and Technology
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• v.23 no.5
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• pp.15-24
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• 2009

The results of a simulation study of variable liquid column oscillations in U-tanks with a novel control scheme are presented. The configuration under investigation is analogous to that of the tuned liquid-column damper used to suppress oscillatory motion in large structures like tall buildings and cargo ships. However, by virtue of an adequate controller, the response of amplitude of the U-tanks becomes larger in a desired frequency range. The motion of wave energy conversion system equipped with a variable liquid column oscillator is described by a series of nonlinear differential equations. The equations describe the motion of body under ocean wave excitation, and the motion of liquid with an air-spring effect caused by the compression and expansion of air in vertical liquid columns and air chambers. It is shown that the effect of the air-spring has a vital role to maintain the natural frequency of oscillation in the system to synchronize with the frequency of the ocean wave, thus the system provides the most effective mode for energy extraction from the ocean.

• Ocean and Polar Research
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• v.26 no.4
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• pp.635-646
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• 2004

Chronic outbreaks of green tide in the Nakdong estuary toll a heavy socioeconomic cost. The paper investigates the influence of sediments on the nitrogen eutrophication, being claimed as the primary cause of green tide. To measure the flux of nitrate at the sediments-water interface, sediment cores were taken in Jan., Mar., May and Sep., 2000 at Noksan located in the West-Nakdong river estuary. The dissolved oxygen was profiled and then the pore water was extracted in situ. Core samples were analyzed for their textural characteristics. Cores were incubated by a novel technique to measure the fluxes of nitrate $(NO_3^-)$ and ammonia $(NH_4^+)$ at the sediment-water interface. The dissolved oxygen was depleted usually within several millimeters in the top sediments. Nitrate started to decrease drastically at the layer where dissolved oxygen was nearly depleted. Nitrate was also exhausted within several centimeters, followed by ammonia build up rapidly. The flux at the sediments-water interface calculated from the pore water concentrations revealed that nitrate was removed from the water column into the sediments. The sediment incubation experiment confirmed the above result. On the other hand ammonia were released from the sediment to the water column. As the incubation went on, however, the nitrate concentration in the overlying water was dropped below that of a top sediment. Then the flux is reversed, i.e., nitrate was released from the sediments to the water column. The implication is that the sediment can supply nitrate to the water column if it falls below a certain level. Thus it is likely that sediments in the eutrophicated river buffers the nitrate concentration in the water column, which leads to a prolonged green tide.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.14-15
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• 2013

Green Frame is precast concrete column-beam structure. There are three types on column connection. The coupler type which is one of the three, need to be improved because of unstability caused by pre-installation of column before casting the slab, and quality deterioration caused by lack of workspace. Therefore, in this study, new coupler connection type with thread rebar is suggested. The result of this study shall be used for the efficiency analysis of the new coupler connection.

• KSBB Journal
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• v.23 no.1
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• pp.37-43
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• 2008

The use of antihemophilic factor IX complex has been associated with a variety of thrombotic complications, the major cause of which was the contamination of thrombogenic proteins such as vitamin K-dependent clotting factors II, VII, and X. In order to produce a commercial factor IX (GreenNine VF) free from thrombogenic potential, industrial-scale production process for high-purity factor IX from human plasma has been developed. The purification process contains cryo-precipitation, DEAE-sephadex A-50 anion-exchange chromatography, DEAE-toyopearl 650M anion-exchange column chromatography, heparin-sepharose 6FF affinity column chromatography, and CM-sepharose FF cation-exchange column chromatography. Also the process includes two viral inactivation and removal procedures, solvent/detergent treatment and nanofiltration using Viresolve NFP filter. The purification yield was 35.4%. The specific activity in the purified concentrate was 190.8 IU/mg which exceeded that in the factor IX complex (FacNine) by a factor of 48. The activities of factor II, VII, and X were not detected in GreenNine VF. SDS-PAGE analysis showed that GreenNine VF had the highest purity in comparison with commercially available high purity factor IX concentrates, Mononine, Octanyne, Berinin HS, and Immunine STIM plus 600. One batch size of the production was 2,400 vials of 250 IU product or 1,200 vials of 500 IU product from 1,600 L cryo-poor plasma.

• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.565-572
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• 2020

This study developed a software platform using machine learning of artificial intelligence to optimize the distillation column system. The distillation column is representative and core process in the petrochemical industry. Process stabilization is difficult due to various operating conditions and continuous process characteristics, and differences in process efficiency occur depending on operator skill. The process control based on the theoretical simulation was used to overcome this problem, but it has a limitation which it can't apply to complex processes and real-time systems. This study aims to develop an empirical simulation model based on machine learning and to suggest an optimal process operation method. The development of empirical simulations involves collecting big data from the actual process, feature extraction through data mining, and representative algorithm for the chemical process. Finally, the platform for the distillation column was developed with verification through a developed model and field tests. Through the developed platform, it is possible to predict the operating parameters and provided optimal operating conditions to achieve efficient process control. This study is the basic study applying the artificial intelligence machine learning technique for the chemical process. After application on a wide variety of processes and it can be utilized to the cornerstone of the smart factory of the industry 4.0.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.05a
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• pp.29-30
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• 2012

The precast concrete column-beam structure, Green Frame, allows the main structural members such as precast concrete column and beam to be produced on the site, resulting in a reduction of transportation cost and the margin of plant. However, existing plywood from for in-situ production of precast concrete members has problems like putting in inordinate human resource, falling-off in quality and workability. To solve those problems, form system for in-situ production of precast concrete members shall be developed. In this regard, this study aims to analyze the structural concept of from system for in-situ production. The result of this study will use for development of form system for in-situ production.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.171-172
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• 2011

Green column and green beam, key structural members of green frame, have the characteristics of post-lintel structure, thanks to the steel frame in the connection, enabling prompt and precise installation. The connection of green frame can be divided into 4 types, depending on its shape, and each type is associated with different characteristics and construction methods. Notably, as the connection between green columns have differing types and sequences of work, subject to the connection method in use, a connection method optimized for relevant site conditions need to be selected. Therefore, this study analyzed pros and cons of 4 different types of green frame connection methods. The results set forth herein will provide basic data for subsequent studies to comparatively analyze the performance and constructibility of different green frame connection methods.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.1
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• pp.47-52
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• 2010

The wave energy absorption efficiency and the first-order and the time-mean second-order wave loads of a three-dimensional bottom-mounted oscillating water column (OWC) chamber structure are studied. The potential problem is solved by making use of a hybrid Green integral equation associated with the finite-waterdepth free-surface Green function outside a twin chamber and the Rankine Green function inside taking account of the fluctuating air pressure inside the chamber. Numerical results of the primary wave energy converting efficiency and the oscillating and steady wave loads of a three-dimensional bottom-mounted OWC pilot plant have been presented.

• Korean Journal of Food Science and Technology
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• v.38 no.1
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• pp.5-9
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• 2006

Method for separation and quantification of methylxanthins, catechins, and theaflavins in Korean commercial teas (green, oolong, and black teas) was developed using reversed phase high-performance liquid chromatography (HPLC). After extraction with hot water, tea compounds were separated on Inertsil ODS-3v $(5\;{\mu}m)$ column, eluted with gradient of 7% acetonitrile and 93% of 20 mM phosphate buffer mixture for 7 min. Column effluent was monitored at 270 nm. This technique was effective for analyses of m methylxanthins, catechins, and theaflavins in teas and biological samples. In green and oolong teas, two kinds of methylxanthins and 7 of catechins were identified, whereas 4 theaflavins were only identified in black tea. Among seven catechins in green and oolong teas, EGCG showed highest amount, whereas ECG was highest in black tea. (theaflavins were found only in black teas) In all teas, theobromine content was lower than that of caffeine.

• Archives of Pharmacal Research
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• v.27 no.10
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• pp.1034-1036
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• 2004

Four compounds were isolated from Salicornia herbacea by repeated column chromatography. Their structures were identified as ${\beta}$-sitosterol (1), stigmasterol (2), uracil (3), and isorhamnetin-3-O-${\beta}$-D-glucopyranoside (4) by spectral analysis and comparison with the published data.