• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.3
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• pp.127-130
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• 1987

The Cavitation inception in oil hydraulic pipeline was investigated experimentally and numerically. In the experiment, negative pressures below -1 MPa (absolute pressure) were measured, associated with the transient flows in oil hydraulic pipeline. These experimental results show that the common hydraulic oil in the experimental pipeline withstands large tensions. The growth of a spherical bubble in a infinite volume of viscous compressible fluid due to a stepwise pressure drop was investigated to obtain the critical bubble radius. The calculated value of the critical bubble radius corresponding to the negative pressure measured in the experiment is so small that the premised condition about the bubble shape in the analysis is unsatisfactory. The physical significance of this calculated result implies the fact that there hardly exist free bubbles which can act as cavitation nuclei in the experimental pipeline.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.287-290
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• 2011

그동안 사회는 유한한 에너지의 과도한 사용으로 인해 온난화가 발생하고, 기상이변과 사회적으로 여러 문제점이 나타나고 있다. 이러한 문제점을 해결하기 위해 정부는 그린 ICT를 국가전략으로 내세우고 있다. 늘어난 전력량의 큰 원인중 하나는 가전 제품들의 불필요한 재 작동에 있는데, 본 논문에서는 스마트 홈 시스템을 위한 가전기기 재가동 제어를 통해 점점 낭비되는 에너지를 절약 할 수 있는 방법을 제시한다.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.8 no.6
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• pp.493-503
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• 2018

The present study is a conceptual replication of O'Grady, Lee, and Choo's (2003) earlier study designed to investigate two hypotheses (linear distance hypothesis vs. structural distance hypothesis) in relation to L2 Korean learners' processing of Korean subject and object relative clauses (RCs) in a scholarly attempt to explicate Keenan and Comrie's (1977) Noun Phrase Accessibility Hierarchy (NPAH). In addition, the current study is intended to explore any potential role of working memory capacity (WMC) in the processing of Korean subject and/or object RCs. Chinese-speaking learners of Korean taking a language course offered at a local university in Korea participated in this experimental study. Among those recruited, only 23 learners completed the experimental tasks appropriately according to the specific instructions provided on each task, and thus, subsequent statistical analyses were conducted on their data. Fifteen Korean NSs were also recruited for the control group. Two experimental tasks were administerd to the participants: one picture selection task containing the same test items used in O'Grady et al.'s study to measure their processing of subject-object RCs and an operation span (OSPAN) task to measure their WMC. Somewhat differently from O'Grady et al.'s findings, the participating Chinese learners of Korean performed significantly better on object RCs than on subject RCs, seemingly lending support to the linear distance hypothesis. Further analyses, however, suggested that the results in favor of, or relative ease of processing, object relative clauses were due, most likely, to the learners' excessive use of the canonical sentence strategy, which also led to nonsignificant correlations between WMC and learner performance on the picture selection task.

• Nuclear Engineering and Technology
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• v.25 no.2
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• pp.276-284
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• 1993

The ABB-CE System-80 reactor power cutback system(RPCS) is designed to enable continuous operation of the reactor without trip in the events of the loss of one of the two main feedwater pumps and loss of load, and thus improves plant availability in a cost effective manner. In this study expansion of RPCS has been investigated for continuous reactor operation without trip in the event of an inward control element assembly(CEA) deviation including a single rod drop. Under the expanded function of RPCS the control system will provide a rapid core power reduction on demand by releasing CEAs to drop into the core and reduce the turbine power, if necessary, to follow the reactor power variation. This design feature which is included as the new design features to be incorporated in the ABB-CE System-80+ meets the EPRI advanced light water reactor(ALWR) requirements. For this study core analysis models of System-80+ have been developed to simulate the nuclear steam supply system(NSSS) response as well as the RPCS initiation of rapid CEA insertion. The results of this study demonstrate that the reactor trip can be avoided in the event of inward CEA deviation including a single rod drop by the RPCS initiation and thus the plant availability and capacity factor would be increased.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.6
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• pp.11-18
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• 2014

The combustion flowfield at the near-injector region of a 50 N scale $N_2O/C_2H_5OH$ thruster was visualized using shadowgraph technique. The explosive ignition was occurred at the design spray condition, and the expanding combustion gas quenched the flame immediately. Approximately after 83 ms from the initial ignition, the propellant spray was re-ignited, and the flame was stabilized after 23 ms elapsed. In the increased oxidizer flow rate condition, the transient pressure at the moment of ignition was smoother than explosive ignition, and the blow down phenomenon was not appeared in the same operating sequence. In addition, the flame was stabilized within 17 ms, and it is caused by improved propellants mixing before ignition.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.6
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• pp.113-119
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• 2013

A main oxidizer shut-off valve (MOV) controls the supply of cryogenic liquid oxygen to the combustion chamber of liquid rocket engines by on/off operations. The main subjects to be introduced are not only the valve transient response during valve on/off procedures but also the characteristics of pneumatic and seat/poppet parts as core technologies in the development of the MOV, which is expected to be adopted for the Korea Space Launch Vehicle II. It is shown that the analytical prediction of the transient valve travel is in good agreement with experimental results. Friction and elastic forces on the valve moving part are quantitatively evaluated by structural analysis.

• Journal of IKEEE
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• v.26 no.2
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• pp.313-318
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• 2022

The feedback voltage detection structure is proposed to alleviate overshoot and undershoot caused by the removal of the existing external output capacitor. Conventional LDO regulators suffer from overshoot and undershoot caused by imbalances in the power supply voltage. Therefore, the proposed LDO is designed to have a more improved transient response to form a new control path while maintaining only the feedback path of the conventional LDO regulator. A new control path detects overshoot and undershoot events in the output stage. Accordingly, the operation speed of the pass element is improved by charging and discharging the current of the gate node of the pass element. LDO regulators with feedback voltage sensing architecture operate over an input voltage range of 3.3V to 4.5V and have a load current of up to 200mA at an output voltage of 3V. According to the simulation result, when the load current is 200mA, it is 73mV under the undershoot condition and 61mV under the overshoot condition.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.6
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• pp.505-511
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• 2015

Solid oxide fuel cell operate at high temperature ($800{\sim}1000^{\circ}C$). High temperature have an advantage of system efficiency, but a weak durability. In this study, linear state space controller is designed to handle the temperature of solid oxide fuel cell system for proper thermal management. System model is developed under simulink environment with Thermolib$^{(R)}$. Since the thermally optimal system integration improves efficiency, very complicated thermal integration approach is selected for system integration. It shows that temperature response of fuel cell stack and catalytic burner are operated at severe non-linearity. To control non-linear temperature response of SOFC system, gain scheduled linear quadratic regulator is designed. Results shows that the temperature response of stack and catalytic burner follows the command over whole ranges of operations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.160-166
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• 2018

This paper proposes an advanced suspension system and reports its performance in the framework of the preview control algorithm based on the RPS (road profile sensing) system and MSD system with the multi-stage damping characteristics. Typical disturbance inputs that cause excessive vibration and steering instability of an automobile are irregular obstacles that protrude or sink into the road surface to be driven. The control performance can be improved if information on the existence and shape function of its obstacle is known. Based on the results of the previous study, advanced research that uses the actuating system has been processed to be commercialized practically. For this purpose, a switching algorithm between the control logic and the multi-stage damping system was developed and its connectivity is presented. To verify the applicability of an actual vehicle, the proposed control system was implemented in full vehicle models and simulations were performed. The proposed system using the 3-DS actuator system, which is applied for structural simplicity, can improve the ride comfort and steering stability. In addition, the results indicate the feasibility of the intelligently controlled suspension system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.7
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• pp.105-111
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• 2006

The aircraft engine is to generate thrust for the maneuver of aircraft and to provide the power to the related hydraulic system and electrical system. Since the power provided to the systems is extracted from the high pressure compressor of aircraft engine, the extracted power is called horsepower extraction (HPX). If the HPX provided from the engine is smaller than the HPX required from the related systems, there could be abnormal engine behavior, like engine rollback or stall. Analysis on comparing the required HPX and the engine HPX capability had been performed during the T/A-50 FSD (Full Scale Development) period. The analysis results make the engine schedule changed, and T/A-50 flight test has been performed with the changed engine schedule. The analysis results and changing the engine control schedule were verified to be valid with the flight test results.