• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.1016-1022
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• 2010

An Experimental study of cleaning solution has been performed on a high capacity steam boiler burning heavy fuel oil to on-line cleaning of deposit. The deposit is mixture of soot, slag, ash, metal oxide and clinker. The traditional technology of deposit cleaning was carried hand-crafted. The conventional technology of boiler cleaning method is mechanical removal by the worker while the boiler shut down operation. In this experiment, the deposit of mixture of soot, slag, ash, metal oxide and clinker has been removed by the cleaning agents without shut down of boiler burning. This study found out the optimum cleaning solution composition. The best results have been obtained when the mixture of ammonium nitrate and $MgNO_3$ were used in cleaning solution. The various transition metal effect was investigated for optimum mixing condition. In this research, the metal compound additive of the clean solution compoition was obtained. The combustion efficiency was improved by on-line cleaning with derived clean solution compoition. On-line cleaning method prevents the fouling and corrosion in the boiler and heat exchanger.

• Korean Chemical Engineering Research
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• v.60 no.1
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• pp.12-19
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• 2022

Cathode open-type PEMFC (Proton Exchange Membrane Fuel Cells) stacks, which are widely used in small transport-type PEMFC, have a problem with poor durability. Through the accelerated durability test of the 13-cell PEMFC stack, we tried to find the cause of the degradation of the stack and to contribute to the improvement of the durability of the cathode open stack. A hydrogen/air boundary is formed during start-up/shut-down (SU/SD) due to the structural problem of the cathode open stack in which the cathode is open to the atmosphere and it is difficult to maintain airtightness, thereby deteriorating the cathode. In this study, it was possible to evaluate the durability in a relatively short time by reducing the 54% of the initial performance by repeating SU/SD 1,800 times on the cathode open stack. After dismantling the stack, each cell was divided into two and the performance was analyzed. Overall, the anode outlet MEA, which facilitates air inflow, showed more severe electrode deterioration than the inlet MEA, confirming that the hydrogen/air boundary formation during SU/SD is the main cause of degradation.

• Journal of Radiation Protection and Research
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• v.36 no.4
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• pp.174-182
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• 2011

With the reactor operation conditions - 4.3 wt% $^{235}U$ initial enrichment, burn-up 55,000 MWd/MTU, average power 34 MW/MTU for three periods burned time for 539.2 days per period and cooling time for 100 hours after shut down, to set up the condition to determine the minimum height (depth) of spent fuel storage pool to shut off the radiation out of the spent fuel storage pool and to store spent fuels safely, the dose rate on the specific position directed to the surface of spent fuel storage pool induced by the neutron and gamma-ray from spent fuels are evaluated. The length of spent fuel is 381 cm, and as the result of evaluation on each position from the top of spent fuel to the surface of spent fuel storage pool, it is difficult for neutrons from spent fuels to pass through the water layer of maximum 219 cm (600 cm from the floor of spent fuel storage pool) and 419 cm (800 cm from the floor of spent fuel storage pool) for gamma-ray. Therefore, neutron and gamma-ray from spent fuels can pass through below 419 cm (800 cm from the floor) water layer directed to the surface of spent fuel storage pool.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.12
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• pp.519-528
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• 2021

The COVID-19 pandemic struck several countries in 2020. After the government officially announced that individuals will be working from home, shut public service agencies, and compelled people to wear masks and maintain social distance, several hundred business actors were forced to shut down their firms. The purpose of this study is to help companies determine the steps for a new marketing strategy for healthy food products in Indonesia. The number of samples was 500 respondents. The variance-based Structural Equation Modeling (SEM) method was used to conduct this investigation, which was similar to a marketing study. The findings show that in Indonesia, lifestyle and price perceptions influence healthy food product purchasing decisions. Meanwhile, brand awareness and customer attitudes had no bearing on healthy food products purchase decisions. The novelty of this study stems from the discovery of new opportunities for business players to market healthy food products during the current COVID-19 period. This opportunity arises as a result of changes in customer lifestyles and price perceptions, both of which must be taken into account by organizations to offer nutritious food items at reasonable rates in Indonesia.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.1
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• pp.35-44
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• 2011

Mathematical modelling for liquid rocket engine(LRE) main components were conducted to predict the dynamic characteristics when the LRE operates at the transient condition, which include engine start up, shut down, or thrust control. Propellant feeding system is composed of fuel and oxidizer feeding components except for regenerative cooling channel for the fuel circuit. Components modeling of pump, pipe, orifice, control valve, regenerative cooling channel and injector was serially made. Hydraulic tests of scale down component were made in order to validate modelling components. The mathematical models of engine components were integrated into LRE transient simulation program in concomitant with experimental validation.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.4
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• pp.481-496
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• 2020

After nuclear power plants are permanently shut down and decommissioned, the remaining irradiated metal components such as stainless steel, carbon steel, and Inconel can be used as neutron absorber. This study investigates the possibility of reusing these metal components as neutron absorber materials, that is burnable poison. The absorption cross section of the irradiated metals did not lose their chemical properties and performance even if they were irradiated over 40-50 years in the NPPs. To examine the absorption capability of the waste metals, the lattice calculations of WH 17×17 fuel assembly were analyzed. From the results, Inconel-718 significantly hold-down fuel assembly excess reactivity compared to stainless steel 304 and carbon steel because Inconel-718 contains a small amount of boron nuclide. From the results, a 20wt% impurity of boron in irradiated Inconel-718 enhances the excess reactivity suppression. The application of irradiated Inconel-718 as a burnable absorber for SMR core was investigated. The irradiated Inconel-718 impurity with 20wt% of boron content can maintain and suppress the whole core reactivity. We emphasize that the irradiated metal components can be used as burnable absorber materials to control the reactivity of commercial reactor power and small modular reactors.

• Korea Journal of Hospital Management
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• v.6 no.1
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• pp.147-163
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• 2001

The purpose of this study was to find out the restructuring strategy for five provincial hospitals through the business analysis and survey of the service area. Through the survey of the service area of 5 hospitals. service area was classified into three groups, such as underserved area, adequate area, and overserved area. The strategy for the restructuring the clinical departments was set up based on the result of the business analysis and characteristics of the service area. The result of the study was as follows; 1) Whether or not a provincial hospital has specialized in specific area according to the circumstances and the needs of the community was the major factor influencing on the operating result of the hospital. 2) Provincial hospitals at the underserved area has to invest according to the changes of the occupancy rate and increasing pattern of the number of patients while maintaining the status as a general hospital. 3) Provincial hospitals at the adequate area has to lower the grade from the general hospital down to the hospital first and has to upgrade the competency through the restructuring the clinical departments and investment in specific area. 4) Provincial hospitals at the overserved area has to lower the grade from the general hospital down to the hospital first and has to seek ways to change the hospital fundamentally into geriatric hospital, pneumoconiosis hospital or psychiatric hospital etc. Provincial hospitals incapable to compete with private hospitals and clinics has to lower the grade from the general hospital down to the hospital first, to specialize in specific area and to restructure some clinical departments into rental base or self-operating basis. In case such methods are judged not so good solution, provincial hospitals has to find out ways such as shut-down of several departments or operating under the attending system.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.4
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• pp.112-122
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• 1999

In realistic control systems the nonlinear saturation attributes of the control actuator due to physical limitations should be taken into account This nonlinear saturation of actuators may cause not only deterioration of the control performance but also a large overshoot during start-up and shut-down. As the overshoot increases the system may become oscillatory unstable. in this paper the supervisor implementation which guarantees good performance for saturation operation and prevents reset wind up is presented, Moreover the sufficient conditions of the stability for saturated system using supervisory control with a dynamic controller are provided in the continuous-time and in the discrete-time domain Numerical example is illustrated to depict the efficiency of supervisory control for a typical satuaurated production-distribution system controlled by a discrete-time dynamic controller and to validate basic results by simulation.

• Journal of Power System Engineering
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• v.3 no.4
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• pp.28-35
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• 1999

An application of scroll compressor to the residential air conditioning and heat pump markets has generated many reliability problem, especially abnormal noise. Most of these noise problems is due to the check valve and compliance between FS(Fixed Scroll) and OS(Orbiting Scroll). FS and OS are the main parts of scroll compressor and are the main pumping part. But check valve has the role of protection of reverse rotation of OS when power is off. Check valve have several noise problems. Among them, shut down noise and valve movement noise is more than severe than any other problem. In this paper covers with these two noise problem.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.4
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• pp.583-588
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• 2016

The high-temperature steam pipes of thermal power plants are subjected to severe conditions such as creep and fatigue due to the power plant frequently being started up and shut down. To prevent critical pipes from serious damage and possible failure, inspection methods such as computational analysis and online piping displacement monitoring have been developed. However, these methods are limited in that they cannot determine the life consumption rate of a critical pipe precisely. Therefore, we set out to develop a life assessment system, based on a three-dimensional piping displacement monitoring system, which is capable of evaluating the life consumption rate of a critical pipe. This system was installed at the "M" thermal power plant in Malaysia, and was shown to operate well in practice. The results of this study are expected to contribute to the increase safety of piping systems by minimizing stress and extending the actual life of critical piping.