• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.1059-1065
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• 2010

An analysis was conducted to predict the hydraulic performance of a reactor coolant pump (RCP) of SMART at the off-design as well as design points. In order to reduce the analysis time efficiently, a single passage containing an impeller and a diffuser was considered as the computational domain. A stage scheme was used to perform a circumferential averaging of the flux on the impeller-diffuser interface. The pressure difference between the inlet and outlet of the pump was determined and was used to compute the head, efficiency, and break horse power (BHP) of a scaled-down model under conditions of steady-state incompressible flow. The predicted curves of the hydraulic performance of an RCP were similar to the typical characteristic curves of a conventional mixed-flow pump. The complex internal fluid flow of a pump, including the internal recirculation loss due to reverse flow, was observed at a low flow rate.

• Nuclear Engineering and Technology
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• v.44 no.7
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• pp.727-734
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• 2012

A new advanced safety feature of DVI+ (Direct Vessel Injection Plus) for the APR+ (Advanced Power Reactor Plus), to mitigate the ECC (Emergency Core Cooling) bypass fraction and to prevent switching an ECC outlet to a break flow inlet during a DVI line break, is presented for an advanced DVI system. In the current DVI system, the ECC water injected into the downcomer is easily shifted to the broken cold leg by a high steam cross flow which comes from the intact cold legs during the late reflood phase of a LBLOCA (Large Break Loss Of Coolant Accident)For the new DVI+ system, an ECBD (Emergency Core Barrel Duct) is installed on the outside of a core barrel cylinder. The ECBD has a gap (From the core barrel wall to the ECBD inner wall to the radial direction) of 3/25~7/25 of the downcomer annulus gap. The DVI nozzle and the ECBD are only connected by the ECC water jet, which is called a hydrodynamic water bridge, during the ECC injection period. Otherwise these two components are disconnected from each other without any pipes inside the downcomer. The ECBD is an ECC downward isolation flow sub-channel which protects the ECC water from the high speed steam crossflow in the downcomer annulus during a LOCA event. The injected ECC water flows downward into the lower downcomer through the ECBD without a strong entrainment to a steam cross flow. The outer downcomer annulus of the ECBD is the major steam flow zone coming from the intact cold leg during a LBLOCA. During a DVI line break, the separated DVI nozzle and ECBD have the effect of preventing the level of the cooling water from being lowered in the downcomer due to an inlet-outlet reverse phenomenon at the lowest position of the outlet of the ECBD.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.1
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• pp.42-47
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• 2016

This paper presents the development of a floating outboard type of compact water jet propulsion system. The planning case of the water jet system is developed by performing precision processing after manufacturing FRP (Fiber Reinforced Plastics) from plug mold casting. This system is composed of an intake, impeller, diffuser, reverse bucket, and main shaft. In addition, a rebuilt engine was applied through marine engineering. The water jet propulsion system performance was verified to discharge a maximum $0.29m^3/s$ of flow rate and 37 m/s of flow velocity in a test pool on land. A field test was performed by installing the water jet propulsion device on board a ship that was tested off the coast of Korea. The weight of the hull, engine, and other equipment was approximately 1.2 tons, and the sailing speed was a maximum 22 knots at 3,600 rpm.

• Food Science and Biotechnology
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• v.18 no.1
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• pp.207-212
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• 2009

Celandine (Chelidonium majus, family Papaveraceae) is an herb used extensively in traditional Korean medicine. To investigate its antioxidant and antiproliferative activities, the methanolic extract of celandine was introduced. The antioxidant properties of the extract were tested using various in vitro systems, including hydroxyl radical scavenging assay, DNA damage protection assay, 1,1-diphenyll-2-2-pricylhydrazyl (DPPH) free radical scavenging activity, metal chelating activity, and reducing power assay. The extract exhibited stronger antioxidant activity ($IC_{50}=7.92{\mu}g/mL$) against hydroxyl radicals in the Fenton system than butylated hydroxyanisole ($IC_{50}=51.46{\mu}g/mL$) and $\alpha$-tocopherol ($IC_{50}=67.48{\mu}g/mL$). Likewise, damage to the plasmid pBR 322 induced by hydroxyl radicals was found to be protected by the extract at a concentration of $400{\mu}g/mL$. Cellular proliferation and the induction of apoptosis were also examined by a cellular proliferation assay, flow cytometry, and mRNA expression analysis. Taken together, the extract significantly inhibited the growth of HT-29 cells in a concentration- and time-dependent manner, and gradually increased both the proportion of apoptotic cells and the expression of caspase-3. Overall, our research suggests that celandine possesses antioxidant and antiproliferative properties.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.6
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• pp.117-123
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• 2015

An experimental study of model truss-type vertical gate consisting of a truss and a plate was presented in this paper to examine the structural dynamics of the gates. A 1:61 scale model was constructed for the 95 m prototype gate using an acrylic truss and an acrylonitrile butadiene styrene plate. The scaled model was tested in a 1.6 m wide concrete flume for two orientations to determine the effects of gate orientation on structural vibrations. Natural frequencies of the model gate was measured and calibrated with FEM predictions. Vertical vibrations were measured under various operational conditions, including a range of bottom opening heights and different upstream and downstream water levels. The gate model with reverse direction was preferred due to its low overall vibrational response and flow level combinations. The test results also provide a basic dataset for development of operations guidelines that minimize flow-induced vibrations of the gates.

• Journal of the Korean Society of Safety
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• v.37 no.4
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• pp.28-35
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• 2022

This study is aimed to develop a safety diagnosis system for fire pumps that detects normal and abnormal signals for the stable operation of the system. Hence, the following activities were carried out: first, a threshold value was identified for the normal operation and six abnormal operations (adherence of impeller, absence of water source, separation of pump and motor, run-stop operation, air inflow into the casing, and reverse-phase loss of the power line) reflecting changes in the current, flow and pressure of fire pumps; secondly, based on the identified signals, an algorithm capable of detecting three abnormal signals was developed and in terms of hardware, a current, pressure and flow sensor suitable for the analogue input values of NI-6009 was designed and installed. This combination of the hardware and software is applicable as a diagnosis system to ensure the stable operation of fire pumps.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.6
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• pp.803-812
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• 1998

In this study, testing equipment with which several kinds of valves can be tested was composed. Two kinds of tilting check valves and a swing check valve were tested to analyze their dynamic characteristics. The results of the experiment showed that the tilting check valves protected the pump but that the swing check valve could not protect the pump when the reverse flow rate was high. Also the dynamic equation of the tilting check valve was formulated and simulated using system characteristic constant t$_{c}$ and one method of predicting t$_{c}$ by comparing the results of the simulation with the results of the experiment was proposed.sed.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.77-78
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• 2011

태양광 에너지, 풍력 에너지 등의 분산전원은 수요지 근방에 설치되어 전력 손실이 적고, 신재생에너지로써 환경보존과 $CO_2$ 감소를 위하여 많이 사용되고 있다. 하지만 이러한 분산전원은 부하와 전원이 함께 연계되어 있어 전력품질 및 보호부분에서 문제를 일으킨다. 그 중 분산전원에 의한 역조류는 기존의 단방향 배전선로의 개폐기나 보호 협조기기에 문제를 발생할 수 있다. 본 논문에서는 분산전원으로 인한 역조류를 줄이기 위해 부하를 조절하는 시스템을 개발하였다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.12B no.1
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• pp.37-43
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• 2002

This paper proposes a new zero-current switching (ZCS) pulse-width modulation (PWM) switch cell that has no additional conduction loss of the main switch. In this cell, the main switch and the auxiliary switch turn on and turn off under zero current condition. The diodes commutate softly and the reverse recovery problems are alleviated. The conduction loss and the current stress of the main switch are minimized, since the resonating current for the soft switching does not flow through the main switch. Based on the proposed ZCS PWM switch cell, a new family of dc to dc PWM converters is derived. The new family of ZCS PWM converters is suitable for the high power applications employing IGBTs. Among the new family of dc to dc PWM converters, a boost converter was taken as an example and has been analyzed. Design guidelines with a design example are described and verified by experimental results from the 2.5㎾ prototype boost converter operating at 40KHz.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.3
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• pp.271-278
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• 2016

Recently, reverse osmosis (RO) is the most common process for seawater desalination. A common problem in both RO and thermal processes is the high energy requirements for seawater desalination. The one energy saving method when utilizing the osmotic power is utilizing pressure retarded osmosis (PRO) process. The PRO process can be used to operate hydro turbines for electrical power production or can be used directly to supplement the energy required for RO desalination system. This study was carried out to evaluate the performance of both single-stage PRO process and two-stage PRO process using RO concentrate for a draw solution and RO permeate for a feed solution. The major results, were found that increase of the draw and feed solution flowrate lead to increase of the production of power density and water permeate. Also, comparison between CDCF and CDDF configuration showed that the CDDF was better than CDCF for stable operation of PRO process. In addition, power density of two-stage PRO was lower than the one of single-stage. However, net power of two-stage PRO was higher than the one of single-stage PRO.