• Journal of Korean Society of Water and Wastewater
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• v.30 no.5
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• pp.597-604
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• 2016

This study was begun with the object of actively reflection the rapid technological advancements of the electronical control and mechanical control industries to sewage disposal methods. Or focuses on applying a flow control method that utilizes inverters and automatic valves to sewage treatment process systems. This study proposes that sewage treatment process systems architects must acquire a certain degree of technical skills in the areas of electrical and mechanical controls in order to raise the standard of completeness of sewage treatment process systems. And further emphasizes that there is required continuous research on automatics valves that are used in sewage treatment.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.4
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• pp.101-107
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• 1996

This test was performed on the hydraulic automatic gauge control(AGC) system of adaptive mass flow method. Fundamental purpose of this study are performance evaluation of this AGC system under the actual rolling condition. It was concluded that the response of AGC system depends on the dynamic characteristics of a reel motor or roll position. The test results are as follows : 1) The control method of reel motor current is better than than of the roll position as AGC system. 2) The more steel strip thickness of delivery side is thick, the larger the gauge deviation is large, and the more it is thin, the larger the gauge deviation rate is large. 3) Because the gauge deviation is large at acceleration and deceleration speed than steady speed, so AGC system is better to adopt over 50m/min. By applying this AGC system, not only the accurary in strip thickness were improved but also productivity was improved dramatically.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.473-474
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• 2013

In this paper, a power flow control of PV hybrid module system with ESS is proposed. Photovoltaic(PV) hybrid module system is consist of individual converter, central inverter, and energy storage system(ESS). Because PV power can be changed in particular hours and environment condition, the power management control for ESS is required. In this paper, the power flow control method for PV hybrid module system with ESS is proposed. The validity of proposed control method is verified by simulations and theoretical analysis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.4
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• pp.355-363
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• 2005

A novel method for simultaneously measuring the fluid velocity and the large particle velocity in a particle-containing fluid flow is developed in this study. In this method, the fluid velocity and the large particle velocity are measured by PIV and PTV, respectively. The PIV and PTV images are obtained from the same flow images. Since a PIV result represents the average displacement of all particles in an interrogation area, it will include an error caused by the relative displacement between the large particles and the fluid. In order to reduce the false influence of large particles on the PIV calculation, the mean brightness of small PIV particle images is substituted to the locations of large particles in the PIV images. The simulation results showed that the new method significantly reduces the PIV error caused by the large particles even at the case where the large particles occupy area fraction as large as $20\%$ of the full image.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.8
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• pp.19-24
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• 2022

We developed a prototype from the design of a trim, which is the most important in the localization development of a 1500 Ib high-differential pressure-control valve used for boiler feedwater, and measured the flow coefficient, the most basic design data for valves. The following conclusions were drawn. The comparison of the design values of the flow coefficients for the existing X-trim and the multicore trim designed for localization development showed that they were almost identical, and the X-trim value was slightly lower. The comparison of the X-trim and multicore trim based on the valve flow coefficient test showed that they were generally similar, indicating no problem with the design. In the future, we plan to compare and analyze the flow paths for the X-trim and multicore trim via flow analysis.

• Nuclear Engineering and Technology
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• v.56 no.9
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• pp.3812-3825
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• 2024

The axial-flow-induced vibration of fuel rods in the nuclear power plant is closely related to nuclear safety. In this article, a numerical study is performed on vibration of two elastic cylinders arranged side-by-side in axial flow. Large eddy simulation is employed to predict the turbulent flow. The numerical method has been verified using the experimental root-mean-square vibration amplitude of a single cylinder. A wide range of inflow velocities u^*, incident turbulence intensity T_u and space ratio P/D have been examined, where D and P are the diameter and centre-to-centre distance of the cylinders, respectively. The results show that the vibration amplitudes increase with an increasing u^*, comparable to the case of a single cylinder in axial flow. However, the two cylinders could bend outwards during a relatively high u^* and low T_u. Although T_u significantly affects the amplitudes of the cylinders, it does not change the vibration frequency and the critical velocity at which buckling instability occurs. As the gap between the two cylinders is sufficiently small, the vibration amplitude enhances significantly due to the pronounced hydrodynamic interaction between the two elastic cylinders and surrounding fluid. The direction of buckling is no longer random but fixed.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.197-206
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• 2009

To improve the aerodynamic efficiency of Smart Unmanned Aerial Vehicle (SUAV), vortex generators and flow fence are applied on the surface and the tip of wing. The initially applied vortex generator increased maximum lift coefficient and delayed the stall angle while it produced excessive increase in drag coefficient. It turns out reduction of the airplane's the lift/drag ratio. The new vortex generators with L-shape and two different height, 3mm and 5mm, were used to TR-S4 configuration to maintain the desired level of maximum lift coefficient and drag coefficient. Flow fence was also applied at the end of both wing tip to reduce the interaction between nacelle and wing when nacelle tilting angles are large enough and produce flow separation. To examine the effect of flow fence, flow visualization and force and moment measurements were done. The variation of the aerodynamic characteristics of SUAV after applying flow control devices are summarized.

• Journal of the Korean Society of Earth Science Education
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• v.5 no.3
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• pp.225-234
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• 2012

The Purpose of this study is searching the effect of the flow level increasing by using flow learning on scientific achievement and attitude toward science in 4rd grade elementary school student's scientific learning factors, and the better way to approach scientific institude than now in used. Participants included 52 elementary school students. For this study, two classes were divided into experimental class and control class. The control class takes a regular instructions and the experimental class takes a flow learning instructions. Two chapter were selected, 'Plant's World' and 'Fossil and Rock', for this study. Students were treated for 18 hours. The results were as follows: First, flow learning related program about plant's world, fossil and rock is increasing 4rd grade elementary school students' flow level in science class. Second, students are not increasing their scientific achievement according to increasing their flow level. Third, students are not increasing their attitude toward science according to increasing their flow level. But in attitude toward scientific inquiry, adoption of attitude toward science and preference of job related science subordinated, students are increasing subordinate factors of attitude toward science.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.2
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• pp.165-174
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• 2007

Variable displacement type piston pump uses various controllers for controlling more than one state quantity like pressure, flow, power, and so on. These controllers need the mathematical model closely expressing dynamic behavior of pump for analyzing the stability of control systems which usually use various kinds of state variables. This paper derives the nonlinear mathematical model for variable displacement type piston pump. This model consists of two 1st oder differential equations by the continuity equations and one 2nd oder differential equation by the motion equation. To simplify the model we obtain the linear state variable model by differentiating the three nonlinear equations. And we verify this linearized model by comparison of simulation with experimentation and analyze the stability for the flow/pressure control. Finally this paper suggests the design compensation to ensure the stability of the systems.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.3
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• pp.190-198
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• 2018

This paper proposes a nonisolated, bidirectional, soft-switching DC - DC converter with PWM plus phase shift (PPS) control. The proposed converter has an input-parallel/output-series configuration and can achieve the interleaving effect and high voltage gains, resulting in decreased voltage ratings in all related devices. The proposed converter can operate under zero-voltage switching (ZVS) conditions for all switches in continuous conduction mode. The power flow of the proposed converter can be controlled by changing the phase shift angle, and the duty is controlled to balance the voltage of four high voltage side capacitors. The PPS control device of the proposed converter is simple in structure and presents symmetrical switching patterns under a bidirectional power flow. The PPS control also ensures ZVS during charging and discharging at all loads and equalizes the voltage ratings of the output capacitors and switches. To verify the validity of the proposed converter, an experimental investigation of a 2 kW prototype is performed in both charging and discharging modes under different load conditions and a bidirectional power flow.