• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.594-600
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• 2017

HVDC transmission systems can be configured in many ways to take into account cost, flexibility and operational requirements. [1] For long-distance transmission, HVDC systems may be less expensive and suffer lower electrical losses. For underwater power cables, HVDC avoids the heavy currents required to charge and discharge the cable capacitance of each cycle. For shorter distances, the higher cost of DC conversion equipment compared to an AC system may still be warranted, due to other benefits of direct current links. HVDC allows power transmission between unsynchronized AC transmission systems. Since the power flow through an HVDC link can be controlled independently of the phase angle between the source and the load, it can stabilize a network against disturbances due to rapid changes in power. HVDC also allows the transfer of power between grid systems running at different frequencies, such as 50 Hz and 60 Hz. This improves the stability and economy of each grid, by allowing the exchange of power between incompatible networks. This paper proposed to establish Korean HVDC technology through a cooperative agreement between KEPCO and LSIS in 2010. During the first stage (2012), a design of the ${\pm}80kV$ 60MW HVDC bipole system was created by both KEPCO and LSIS. The HVDC system was constructed and an operation test was completed in December 2012. During the second stage, the pole#2 system was fully replaced with components that LSIS had recently developed. LSIS also successfully completed the operation test. (2014.3)

• Journal of architectural history
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• v.23 no.1
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• pp.7-19
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• 2014

This study considers the proper repair techniques by examining the most representative repair cases of the Korean arch bridges and proposes the constructional manual which can apply similar occasions. The cases are Seonamsa Seungseongyo and Songgwangsa Geukrockgyo where this researcher had taken part in the repair works. This Study proposes the maintenance construction manual about the performance degradation drew by performance degradation of the both Korean arch bridges in the maintenance process. First, arch bridge maintenance should be carried out in the dry season, when water is impermeable in the bottom surface of the bridge. Moreover, risk factors of the maintenance should be excluded to secure the water vally flow, the bypass and the temporary bridge. Second, prior to repair, it has to precede (1)3D shooting (2)formal examination (3)structure safety test (4)geological and lithic surveys (5)arch curvature establishment and makeshift frame settlement before transformation (6)relationship expert comments. Third, if the baduk and the foundation stones are inevitable to replace due to performance degradation on the foundation, it should use the high quality stones and secure greater stress by extending the standard range. The foundation on irregular rock needs to be flattened and underside on the replaced materials require Grengyijil to deliver the equal loads. Fourth, In the process of dismantling the stones of the arched bridge, it could make heavy weathering degree and not reuse the materials. Charge should converge the expert advices to choose the reuseable, the conservate and the alternative materials, and increase the reutilization of the raw materials by preservation and reinforcement treatments. Fifth, the side wall should be repaired by the rubble work technique which is not able to pile compost satiety, so it must use long depth of masonary stones for reinforcement. It is considered to reinforce the stone wall in shore as much as possible and protect the abutment and the side wall on the upstream for the arch bridge maintenance works.

• Journal of Korean Society of Disaster and Security
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• v.15 no.3
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• pp.31-40
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• 2022

Domestic disaster risk maps are mainly produced and studied as a single disaster map by grid unit and disaster type. In particular, it is necessary to present an evaluation method of the disaster risk map that is more suitable for the relevant facility (local road) in order to utilize the work of practitioners who are mainly in charge of facility maintenance. In this study, an evaluation method was presented to evaluate the risk with a focus on local roads by using the landslide risk map and debris flow risk map provided by the Korea Forest Service. In addition, the risk was evaluated and verified for the provinces located in Gangwon-do. As a result of the evaluation, it was possible to evaluate the risk of grades 1 to 5 for 1,513 evaluation sections in the evaluation section with a total length of 234.59 km.

• CELLMED
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• v.13 no.14
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• pp.19.1-19.16
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• 2023

Objectives: To compare the efficacy of polyherbal Unani formulations in heavy menstrual bleeding due to endometrial hyperplasia. Methodology: A prospective, randomized comparative trial was conducted at Govt. Nizamia Tibbi College. Group A (n=20) received Itrifal Aftimoon 5g orally BID from menstruation day 3 to day 21 plus suprapubic Marham Dakhilyun application and per vaginally Marham Dakhilyun (5g) and Roghan Gul (10ml) application from menstruation day 5 to day 14. Group B (n=20) received Gulnar Farsi (2g), Phitakri Biryan (0.25g), Dammul Aqwain (0.25g), and Geru (2g), 2.5g powder orally BID, menstruation day 3 for 20 days plus Douche Bargh Sambhalu then Ḥamūl of Safuf Mazu (2g), Kalijiri (2g) and Roghan Gul (10ml) from menstruation day 3 to day 12 for 3 consecutive cycles. The primary outcome was pelvic ultrasound findings of endometrial thickness. The secondary outcome measures were improvement in haemoglobin percentage, change in menstrual flow and menstrual pattern. The level of significance was 5%. Results and conclusion: The intragroup comparison showed that the mean endometrial thickness at baseline and after treatment in groups A and B was extremely significantly different (P<0.0001). The intragroup comparison showed the mean haemoglobin percent at baseline and after treatment in group, A was significantly different (P<0.0001). After treatment, 50% and 60% of participants had normal duration and menstrual blood loss after treatment from baseline in Groups A and B respectively. However, further, phase II and III randomized standard controlled trials in larger samples are recommended to assess the efficacy of these group medicines.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.1
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• pp.21-26
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• 2014

When iodine container for dental mouth treatment is opened, thread for treatment is cut by the blade in cap of container. Due to the problem of corrosion in a short period time after the reaction of metal blade to iodine solution, it gives impact on patient hygiene. In order to solve the problem, alternative products such as ceramic blade are developed and produced recently. In case of ceramic blade, it is produced by handwork and machine work. In this study, for the quantity production of ceramic blade with powder injection molding, we proposed a delivery system to have uniform charge of 20 cavity. Using Moldflow, simulation on 20 Cavity flow was performed. And then the mold was obtained through mold production and modification.(based on simulation) After injection molding, debinder, sintering process was achieved for ceramic blade, and the cap product was completed via insert injection on ceramic blade. In this study, we verified possibility of quantity production of ceramic blade which showed effective performance for cutting.

• The Transactions of the Korea Information Processing Society
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• v.3 no.1
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• pp.1-8
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• 1996

A conveyor system in corrugated manufacturing industry may be in charge of carriage/storage, and may control logistics flow and production activities of products in a manufacturing process which consists of corrugators, conveyors, and printer-slotter systems. It identifies problems that the conveyor system in this case study is overloaded and often operated manually. This research is to evaluate e the conveyor system though simulation model of technological evaluation beyond d eco-nomic and qualitative one. The rate of operation and the load of the conveyor system are used as parameters in the simulation. This paper suggests a direction to a new conveyor system implementation the basis of the results that are derived by new alternatives based on current model. The best alternative is supposed to be the number of conveyors and the operation times of the printer-slotter that may be increased at the same time.

• Korean Journal of Cognitive Science
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• v.12 no.1_2
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• pp.55-63
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• 2001

Speaking generally, agent-based technology is a kind of technology to handle the flood of information resulted from the popularization of the internet. Agent system is a multi-distributed system which consists of both homogeneous and heterogeneous agents. Generally there is a coordination agent in between which is in charge of control and m message flow among the application agents. The purpose of this thesis is to propose a coordination method among agents, some of which provide informations and some of which request them. In multi-agent system, the Information Providing Agent(IPA) registers its capabilities to Coordination Agent(CA) and the Information Requesting Agent(lRA) requests CA what it needs. To coordinate them with satisfactory results the coordination agent ought to have an ability to return a relatively proper data to the requester which is supposed to be similar even though it is not so exact as was intended. For this, this thesis proposes a scheme for an coordination agent to find an IPA which provides an information which correlates most closely with that of IRA.

• The KSFM Journal of Fluid Machinery
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• v.17 no.6
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• pp.29-37
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• 2014

Non-Newtonian fluid mechanics takes charge of an important role in the oil industries. Especially in the oil well drilling process, the drilling fluid such as mud keeps the drill bit cool and clean during drilling, with suspending drill cuttings and lubricating a drill bit. The purpose of this study is to examine the effect of fluid mud rheological properties to predict different characteristics of non-Newtonian fluid in the mud mixing tank on offshore drilling platforms. In this paper, ANSYS fluent package was used for the simulation to solve the hydrodynamic force and to evaluate mud mixing time. Prediction of the power consumption and the pumping effectiveness has been presented with different operating fluid models as Newtonian and non-Newtonian fluid. The comparison between Newtonain mud model and non-Newtonian mud model is confirmed by the CFD simulation method of drilling mud mixing tank. The results present useful information for the design of the drilling mud mixing tanks and provide some guidance on the use of CFD tool for such non-Newtonian fluid flow.

• Journal of Korean Society of Transportation
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• v.25 no.5
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• pp.183-193
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• 2007

Traditionally, a congestion charge based on first-best congestion pricing theory, namely, the theory of marginal cost pricing theory, is equal to the difference between marginal social cost and marginal private cost. It is charged on each link so as to derive a user equilibrium flow pattern to a system optimal one. Based on this theory this paper investigates on the characteristics of first-best congestion pricing of multiple user class on road with variable demand, and presents two methods for analysis of social and spatial equity. For these purposes, we study on the characteristics of first-best congestion pricing derived from system optimal in time and in monetary unit, and analyze equity from this congestion pricing with an example network.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.4
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• pp.412-419
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• 2012

Increasing demand for natural gas and higher natural gas prices in the recent decades have led many people to pursue unconventional methods of natural gas production. POSCO-Gwangyang synthetic natural gas (SNG) project was launched in 2010. As the market price of natural gas goes up, the increase of its price gets more sensitive due to the high cost of transportation and liquefaction. This project can make the SNG economically viable. In parallel with this project, KEPCO (Korea Electric Power Corporation) joined in launching the SNG Quality Standard Bureau along with KOGAS (Korea Gas Corporation), POSCO and so on. KEPCO Research Institute is in charge of SNG fueled gas turbine combustion test. In this research, several combustion tests were conducted to find out the effect of hydrogen contents in SNG on gas turbine combustion. The hydrogen in synthetic natural gas did not affect on gas turbine combustion characteristics which are turbine inlet temperature including pattern factor and emission performance. However, flame stable region in ${\Phi}$-Air flow rate map was shifted to the lean condition due to autocatalytic effect of hydrogen.