• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.5 no.2
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• pp.40-44
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• 2009

In this study, Event Corrective Action Supporting System (ECAS) is developed for the accident evaluation in nuclear power plant. The ECAS system can be used in supporting regulator and/or operator under event situation in nuclear power plants. The ECAS system consists of 5 modules including failure location module, failure analysis module, failure integrity evaluation module, system vulnerability evaluation module, and reporting and operating experience feedback module. The ECAS system will be used as sub module of Knowledge-Based Event Evaluation Network (K-EvENT) which is developing for the against the accident in nuclear power plants.

• Journal of Aerospace System Engineering
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• v.14 no.5
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• pp.26-32
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• 2020

In this study, a facility was constructed to supply liquid nitrogen to simulate combustion instability in a liquid rocket combustor. The pressurization and supply performances were predicted and verified through different experiments. The liquid nitrogen supply system was composed of a pressurized supply system, and a dome regulator was used to adjust the pressure of the pressurant. A cavitation venturi was used to control the mass flow rate of liquid nitrogen. The condition of liquid nitrogen supply was a mass flow rate of 2.55 kg/s and the venturi inlet pressure was above 100 bar. Based on the initial experiment, it was observed that the predicted amount of the pressurant was not sufficiently supplied and the target pressure was not supplied due to a drop in tank pressure. Through the modification of the established facilities, the target mass flow rate was successfully supplied and the cryogenic liquid nitrogen supply facility was verified.

• Journal of the Korean Institute of Gas
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• v.27 no.2
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• pp.86-94
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• 2023

This study was conducted with the purpose of preparing an alternative to improving the safety of civil pressure regulators installed instead of gas governors to supply city gas to apartment houses. First, problems were derived and solutions were presented by investigating the safety standards and installation status of domestic pressure regulators. In addition, using the DNV Phast-Safeti program, a quantitative risk assessment solution, risks such as gas leakage contained in pressure regulators installed in apartment houses and surrounding gas facilities were evaluated in terms of individual risks and societal risks, and measures were derived to reduce the risks in the installation and management of the pressure regulators.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1317-1321
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• 2009

Natural gas liquefaction plant and LNG carrier needs large capital investment. Therefore a lot of small or middle scale natural gas fields aren't developed due to poor profitability. If natural gas is made to gas hydrate instead of liquefaction, developing small-scale natural gas field can be profitable because building cost of gas hydrate plant and carrier are economical. Because the process of making gas hydrate consumes much energy, the gas hydrate formation process has to be optimized for energy consumption. In this study, gas hydrate formation process was investigated experimentally. Experimental apparatus consists of reactor, pressure regulator, chiller, and magnetic stirrer. 99.95% methane was used to make gas hydrate. Tests were conducted at variable pressure and temperature condition.

• Journal of the Korea Safety Management & Science
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• v.17 no.2
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• pp.229-234
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• 2015

Depending on the living styles, the types of energy consumed by households have changed, and the consumption has increased rapidly. Consequently, those have led to environmental issues, such as exhaustion of energy and the climate changes. As one of solutions to such issues, energy efficiency can be approached. Therefore, in this study, the gas water heater(115S type Rheem products) that made in Germany and obtain hot water using gas as a heat source is selected. a $1.0m^3$ water tank with a 6kW electronic heater is installed and a water temperature and pressure is maintain constantly also thermometer is injected. Two of gas meter, one of pressure regulator and three of time measurement devices are installed in a combustion facility and fuelling facility with a magnet valve so it can observe and record combustion reactions. Quantity of hot water that heated by boiler is recorded using a quantity measurement tank, and have been heated by the boiler have been to record and measure the amount and utilized the data acquired through measurement of all factors that are applied to acquire hot water in order to calculate the use rate of final energy. In conclusion, this researcher drew the economic strong points of the hot water generated by gas.

• Nuclear Engineering and Technology
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• v.53 no.3
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• pp.901-910
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• 2021

KHNP recently has obtained the approval for the commercialization of the modified 37-element (or 37 M) fuel bundle and now is loading the 37 M fuel bundles in CANDU-6 reactors in KOREA. One of the main issues for approval was the burnup limit. Due to CANDU design and neutronic characteristics, there was no specific burnup restriction of a fuel bundle. The absence of a burnup limit does not mean that a fuel bundle can stay in the CANDU reactor without a time limit. However, the regulator requested traditional design values as well as the burnup limit reflecting the computer code uncertainty. The method for the PWR burnup limit was not applied to the CANDU fuel bundle. Since there was no approved methodology to build the burnup limit with uncertainties, KHNP introduced a Monte-Carlo method coupled with a 95/95 approach to determine the conservative burnup limit from the viewpoint of the centerline temperature, internal pressure, strain measurement deviation. Moreover, to consider the uncertainties of various computing models, a converted power uncertainty was introduced. This paper presents the methodology and puts forward the limits on burnup, evaluated for each of the existing and modified fuel bundles, in consideration of the pressure tube aging condition.

• Transactions of The Korea Fluid Power Systems Society
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• v.4 no.1
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• pp.18-24
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• 2007

The continuously variable transmission (CVT) of which speed ratio can change continuously in a fixed range has the benefits of low fuel consumption and exhaust gas because it enables the engine of a vehicle to operate in a high efficiency range regardless of vehicle speed. The speed ratio of belt type CVT is controlled by adjusting line pressure. The one of the line pressure control methods, mechanical-hydraulic control is usually adopting VDT's control method, in which the secondary solenoid valve has two functions both a regulator and a line pressure controller. However, this control method could not show the high performance of CVT with optimal driving capability because of the limitation of simple control algorithm, and it could not gain market share sufficiently in spite of the advantage of CVT with low fuel consumption. On the other hand, the electro-hydraulic control method gives the enhancement of power performance and low fuel consumption by implementing various driving mode using the proportional control or PWM control. The key of CVT technique is to develop a control algorithm of the electro-hydraulic solenoid valve in order to implement the speed ratio efficiently. In this paper, the line pressure control algorithm is proposed and the hydraulic system is controlled using metal belt type CVT test rig and the embedded ECU platform.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.4
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• pp.291-298
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• 2013

In this paper a new hybrid-type control system is proposed which reduces the pump speed of an electro-hydraulic actuator consisting of a pressure-compensated variable displacement piston pump and a valve-controlled hydraulic cylinder, whenever the flow rate demand is low. In order to avoid interfering with the pressure regulator which also has an effect on swash plate angle, the pump speed is changed in proportion to the mean value of the speed component of position commands. Additionally a pressure switch is employed to prevent the system pressure from getting lower than a reference value. Based on computer simulation & experimental results, it is shown that the hybrid control can save the idling power up to 44% at a stand-by mode by reducing the pump speed from 1,800 rpm to 600 rpm without affecting the dynamic response of the electro-hydraulic actuator.

• Journal of Drive and Control
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• v.16 no.4
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• pp.1-8
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• 2019

The HPM (High-speed Power Matching) system is an electro-hydraulic control system. It directly controls the swash plate of the pump by selecting four-loop logic based on joystick signals, pump flow, and pressure signal to improve the efficiency and controllability of construction machines. In the NFC (Negative Flow Control) system, a typical pump control system using conventional open center type MCV, the loss is continuously generated by flow through the center bypass line even when the excavator is not in operation. Also, due to the slow response of the pump that indirectly controls the flow rate using the pressure regulator, peak pressure occurs at the start or stop of the operation. Conversely, the HPM system uses an MCV without center-by-pass flow path and the swash plate of a pump for the HPM is controlled by a high-speed proportional flow control valve. As a result, the HPM system minimizes energy loss in standby state of the excavator and enables peak pressure control through rapid electro-hydraulic control of a pump. In this paper, the concept of the HPM system algorithm is introduced and the hydraulic system efficiency is compared with the NFC system using the excavator SAT (System Analysis Tool).

• Smart Structures and Systems
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• v.20 no.3
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• pp.273-283
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• 2017

This paper presents and compares three feedback control strategies for active control of noise inside a 3-D vibro-acoustic cavity. These are a) control strategy based on direct output feedback (DOFB) b) control strategy based on linear quadratic regulator (LQR) to reduce structural vibrations and c) LQR control strategy with a weighting scheme based on structural-acoustic coupling coefficients. The first two strategies are indirect control strategies in which noise reduction is achieved through active vibration control (AVC), termed as AVC-DOFB and AVC-LQR respectively. The third direct strategy is based on active structural-acoustic control (ASAC). This strategy is an LQR based optimal control strategy in which the coupling between the various structural and the acoustic modes is used to design the controller. The strategy is termed as ASAC-LQR. A numerical model of a 3-D rectangular box cavity with a flexible plate (glued with piezoelectric patches) and with other five surfaces treated rigid is developed using finite element (FE) method. A single pair of collocated piezoelectric patches is used for sensing the vibrations and applying control forces on the structure. A comparison of frequency response function (FRF) of structural nodal acceleration, acoustic nodal pressure, and piezoelectric actuation voltage is carried out. It is found that the AVC-DOFB control strategy gives equal importance to all the modes. The AVC-LQR control strategy tries to consume the control effort to damp all the structural modes. It is seen that the ASAC-LQR control strategy utilizes the control effort more intelligently by adding higher damping to those structural modes that matter more for reducing the interior noise.