• Journal of the Korean Wood Science and Technology
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• v.24 no.2
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• pp.55-60
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• 1996

Tripitaka Koreana were made during Coryo Dynasty from 1236 to 1251 A.D. Buddhist scriptures were engraved on 81.340 wooden plates. Some plates were varnished with Rhus lacquer, but most of them were uncoated. Macroscopically, most of the plates appeared intact due to the storage in a well-ventilated wooden house. Because, they were irregularly used for printings with ink, it can be assumed that they were repeatedly exposed to ink-water and drying processes. The present were made to examine the changes of wood cell structures occurred during long-term aging deterioration processes in these dry archaeological wooden plates. Light, scanning and transmission electron microscopes were employed for this study. Wedge-shaped cracks and delamilations were found from the lumen side toward the compound middle lamellae and they progressed toward primary or secondary walls. A large amount of hypae in vessels and the degradation of vessel-ray pit walls by the fungal hyphae were observed. When compared to the recent wood, the birefringence of wood fibers was considerably lower or completly disappeared, suggesting the degradation of crystalline cellulose in these wood samples. The degradation of the cell wall could be also revealed the calculation of crystallinity with X-ray diffraction and the size of crystalline region was estimated.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.12
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• pp.850-856
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• 2007

In a supercooled or capsule type ice storage system, aqueous solution (or water) may have trouble with non-uniform dissolution though the system contributes to the simplicity of system and ecological improvement. The non-uniform dissolution increases the instability of the system because it may cause an ice blockage in pipe or cooling part. In order to observe the supercooled state, a cooling experiment was performed with pressurization to an ethylene glycol(EG) 3 mass% solution in stationary state. Also, the effect of the pressurization from 101 to 505 kPa to the dissolution of supercooled aqueous solution was measured with the dissolution time of the supercooled aqueous solution at a fixed cooling rate of brine. At results, the dissolution of supercooled point decreased as the pressure of the aqueous solution in the vessel increased. Moreover, the dissolution point increased as the heat flux for cooling increased.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.469-474
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• 1997

To provide tile information ell severe accident progression is very important for advanced or new type of nuclear power plant (NPP) design. A parametric study, therefore was performed to investigate the effect of thermal hydraulic design parameters ell severe accident progression of pressurized water reactors (PWRs), Nine parameters, which are considered important in NPP design or severe accident progression, were selected among the various thermal hydraulic design parameters. The backpropagation neural network (BPN) was used to determine parameters, which might more strongly affect the severe accident progression, among mile parameters. For training. different input patterns were generated by the latin hypercube sampling (LHS) technique and then different target patterns that contain core uncovery time and vessel failure time were obtained for Young Gwang Nuclear (YGN) Units 3&4 using modular accident analysis program (MAAP) 3.0B code. Three different severe accident scenarios, such as two loss of coolant accidents (LOCAs) and station blackout(SBO), were considered in this analysis. Results indicated that design parameters related to refueling water storage tank (RWST), accumulator and steam generator (S/G) have more dominant effects on the progression of severe accidents investigated, compared to tile other six parameters.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.37 no.4
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• pp.12-23
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• 2014

The O&M (Operation and Maintenance) phase of offshore plants with a long life cycle requires heavy charges and more efforts than the construction phase, and the occurrence of an accident of an offshore plant causes catastrophic damage. So previous studies have focused on the development of advanced maintenance system to avoid unexpected failures. Nowadays due to the emerging ICTs (Information Communication Technologies) and sensor technologies, it is possible to gather the status data of equipment and send health monitoring data to administrator of an offshore plant in a real time way, which leads to having much concern on the condition based maintenance policy. In this study, we have reviewed previous studies associated with CBM (Condition-Based Maintenance) of offshore plants, and introduced an algorithm predicting the next failure time of the compressor which is one of essential mechanical devices in LNG FPSO (Liquefied Natural Gas Floating Production Storage and Offloading vessel). To develop the algorithm, continuous time Markov model is applied based on gathered vibration data.

• Journal of Ship and Ocean Technology
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• v.9 no.2
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• pp.21-28
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• 2005

Recently moored offshore vessels like as FPSO(Floating Production Storage Offloading) are frequently deployed in seas for a long time. For successful operation, the motion behavior of such a vessel in waves must be clarified in advance either theoretically or experimentally. It is of particular interest to examine the behavior, when swells are superposed to seas with different incident angle. Such a situation is actually reported in some offshore oilfield. In this paper, the motion of a FPSO in irregular waves including swells is studied in time domain. Hydrodynamic coefficients and wave forces are calculated in frequency domain using three-dimensional singularity distribution method. Time memory function and added mass at infinite frequency are derived by Fourier transform utilizing hydrodynamic damping coefficients. In the process, the numerical accuracy of added mass at infinite frequency is carefully examined in association with free decay simulations. It is found from numerical simulations that swells significantly affect the vertical motion of FPSO mainly because of their longer period compared to the ordinary sea waves. In particular, the roll motion is largely amplified because the dominant period of swell is closer to the roll natural period than that of seas.

• Journal of Korean Port Research
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• v.2 no.1
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• pp.75-106
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• 1988

As port transport system consists of subsystems such as navigation system, cargo handling system, storage system, inland transport system, and Management and Information system, the productivity of this system is determined by the minimum level of subsystem. From the viewpoint of elaborating the efficiency of integrated system, it is valuable to determine the optimal level of harbour tug boat which is the most important factor of navigation system. This paper treats the optimal amount of harbour tug boat by simulation, and applied to Pusan port. In the course of simulation, an emperical formula is introduced for determining the Horse Power (HP) of tug boat by the ship's gross tonnage (G/T) refering to the cases of various ports of other countries, that is ; $Y=9.96X^{0.6}+569$. X : The gross tonnage of vessel (G/T). Y : The Horse Power (HP) of tug boat. The results of the simulation are summarized as follows ; 1) In 1987, three or four low-powered harbour tug boats, five mid-powered harbour tug boats and four high-powered harbour tug boats are necessary in the mean level. But, five or seven low-powered harbour tug boats, ten mid-powered harbour tug boats and eight high-powered harbour tug boats are necessary lest delay should occur at all. 2) In 1992, 1lee or four low-powered harbour tug boats, six mid-powered harbour tug boats and seven high-powered harbour tug boats are estimated and be necessary in the mean level.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.908-914
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• 2019

Fusion power shutdown system (FPSS) is a safety system to stop plasma in case of accidents or incidents. The gas injection system for the FPSS presented in this work is designed to research the flow development in a closed system. As the efficiency of the system is a crucial property, plenty of experiments are executed to get optimum parameters. In this system, the flow is driven by the pressure difference between a gas storage tank and a vacuum vessel with a source pressure. The idea is based on a constant volume system without extra source gases to guarantee rapid response and high throughput. Among them, valves and gas species are studied because their properties could influence the velocity of the fluid field. Then source pressures and volumes are emphasized to investigate the volume flow rate of the injection. The source pressure has a considerable effect on the injected volume. From the data, proper parameters are extracted to achieve the best performance of the FPSS. Finally, experimental results are used as a quantitative benchmark for simulations which can add our understanding of the inner gas flow in the pipeline. In generally, there is a good consistency and the obtained correlations will be applied in further study and design for the FPSS.

• Progress in Superconductivity and Cryogenics
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• v.25 no.3
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• pp.43-48
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• 2023

Polymer composites, especially glass fiber reinforced polymer (GFRP) are finding ever-increasing applications in areas such as superconductivity, space technology, cryogenic rocket engines, and cryogenic storage vessels. Various components made of polymer composites are much lighter than their metallic counterparts but have equivalent strength for ultra-low temperature applications. In this paper, we have investigated the tensile properties of an indigenously prepared unidirectional cylindrical hollow composite tube for its use as a neck of the cryogenic vessel. XRD and SEM of the tube are completed before cryogenic conditioning to ascertain the fiber and resin distribution in the matrix. The result shows that for composites, after 15, 30, 45, and 60 minutes of cryogenic conditioning at 77K in a liquid nitrogen bath, the strength and modulus increase significantly with the increase of strain rate and reach the optimum value for 45 minutes of conditioning. The results are encouraging as they will be helpful in assessing the suitability of GFRP in the structural design of epoxy-based components for cryogenic applications.

• Journal of Chest Surgery
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• v.36 no.4
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• pp.229-241
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• 2003

Background:Autogenous vein is the preferred vascular graft for patients who require coronary artery bypass surgery or peripheral arterial bypass surgery. When an autogenous vein is not available, an allograft saphenous vein can be used as an alternative conduit. Although arterial homograft has been under investigation since the beginning of this century, the viability of endothelial cells and the optimum mode of storage for the venous and arterial allografts is controversial. In addition, with the recently gained knowledge of vascular endothelial functions, such as the production of nitric oxide or thrombomodulin, the viability and antigenicity of endothelial cells are being studied again. The purpose of this study was to evaluate the viability of endothelial cells in the preserved human saphenous veins. Material and Method: The veins were stored in a $4^{\circ}C$ RPMI (Roswell Park Memorial Institute) 1640 solution including 10% fetal calf serum, for one, three, five, seven or fourteen days. After the completion of the storage period, the veins were divided into two groups: Group I: studied immediately at $4^{\circ}C$ (cold) storage (I-1, I-3, I-5, I-7, I-14), and Group II: studied after storage at $-196^{\circ}C$ liquid nitrogen tank (cryopreservation) in an RPMI 1640 solution containing 10% DMSO for two weeks (II-1, II-3, II-5, II-7, II-14). Light microscopy and scanning electron microscopy (SEM), frypan blue exclusion testing, and thrombomodulin immunohistochemistry were performed. Result: In a morphometric study using SEM, there was statistically significant increase in Gundry Score in Groups I-7, I-14, II-5, II-7, and II-14 and showed cellular destruction (p<0.05). In the thrombomodulin immunohistochemistry study, there was reactivity in Groups I-1, I-3, and I-5, but the cryopreserved group revealed decreased reactivity (p<0.05). The trypan blue exclusion testing also showed superior viability in cold storage Group I. Conclusion: Venous allografts preserved in a $4^{\circ}C$ RPMI 1640 solution showed well preserved endothelial cellular integrity and thrombomodulin expression at up to seven days of preservation. Although cryopreservation of venous allografts stored in 10% DMSO -RPMI 1640 solution maintained the endothelial cellular structure on SEM, immunohistochemistry from the thrombomodulin and trypan blue exclusion testing showed decreased viability, It remains to be seen whether the decreased thrombomodulin reactivity could be restored, and what the nature to the relationship is between thrombomodulin and long-term patency of allografts.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.595-603
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• 2012

International Thermonuclear Experimental Reactor (ITER) will be constructed in 2019 according to the JIA (Joint Implementation Agreement) of 7 countries. The ITER fusion fuel cycle consists of fusion vacuum vessel, tritium plant and fuelling system. The tritium plant provides the functions of storage, delivery, separation, removal and recovery of the deuterium and tritium used as fusion fuels for the ITER. The tritium plant systems supply deuterium and tritium from external sources and treat all tritiated fluids from ITER operation through Storage and Delivery System (SDS), Tokamak Exhaust Processing (TEP), Isotope Separation System (ISS), Water Detritiation System & Atmosphere Detritiation System (WDS & ADS) and Analysis System (ANS). In this paper, the functions and design requirements of the major systems in the tritium plant and the status of R&D are described. Korean party is developing the SDS for ITER tritium plant and partially attaining the WDS technology through the construction and operation experience of the Wolsong Tritium Removal Facility (WTRF). Now it is expected that researchers in other fields such as chemical engineering take part in the development of upcoming technologies for ISS and TEP.