• Transactions of Materials Processing
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• v.25 no.1
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• pp.5-11
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• 2016

The control of the roll velocities is essential in maintaining stability during ring rolling, but such control is difficult. The determination of the best roll velocities can be helped with the use of FE simulations and processing maps, which give the useful information such as power dissipation and flow instability for hot metal forming processes. In the current study, the workability of 7050 aluminum alloy is evaluated by using processing map. With the developed information, the stability of the ring rolling condition, called the Constant Growth Velocity Condition (CGVC), is evaluated.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.1
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• pp.145-153
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• 1997

This paper proposes a constant frequency controlled forward zero voltage switching multi resonant converter (ZVS-MRC) which operates with a fixed duty ratio. The proposed converter is obtained from a conventional forward ZVS-MRC by placing a saturable core in parallel with the secondary side of the transformer. Experimental results are presented for a proposed converter which operates at 1.5MHz switching frequency with an output power of 50W (5V/10A). The merits of the proposed converter include ; 1) reduced voltage stress to the main switch compared with the conventional counterpart, 2) ease on designing the magnetic components including EMI and output filter, and 3) simple control scheme.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.585-590
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• 1999

The conventional $CO_2$ inverter arc machine has constant voltage output characteristic and uses constant wire speed controller for welding current control. By adoption of PWM inverter to the welding machine, the spattering was reduced rather than the thyrister arc welding machine or AC arc welding machine. Moreover, by the high switching frequency, the output reactor size could be reduced evidently. Recently, the studies on optimal voltage and current waveform for the welding performance improvement have been studied. In this paper, a new instantaneous output current control scheme during the short circuit mode was proposed and showed the capability of arc stability improvement and the reduction of spatter generation.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.34 no.8
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• pp.331-337
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• 1985

An inverter-excited induction generator is discussed in this paper. A brief review of the capacitor-excited induction generator is given and the steady state characteristics of the induction generator excited by an inverter are evaluated. It is shown that the output voltage of the system can be controlled by adjusting the slip, for given operating conditions. The introduction of feedback control makes it possible to control the output voltage stably over the wide range of speed and load. Experimental results are given. The output of the induction generator is then converted into a CVCF(Constant Voltage-Constant Frequency) power source using a PWM inverter with simple control circuit.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.127.6-127
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• 2001

In this paper, we deal with two bias compensation algorithms of acceleration sensor for measuring the galloping on power transmission line. Firstly, the block diagram of galloping measurement system is given and a galloping model is presented. Secondly, two compensation algorithms, a simple compensation and a period compensation, are proposed. A simple compensation algorithm use the drafts of velocity and distance at fixed periods, so it is useful for constant bias case. Next, a period compensation algorithm can compensate a periodic bias. This algorithm use the previous measured data and compensated data for constant period, where the period is obtained by FFT method. Lastly, the effectiveness of proposed algorithms is verified by comparing between two algorithms in simulation, and its characteristics and the bias error bound are shown, respectively.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.3
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• pp.48-55
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• 2003

This study investigates the effect of temperature and electric field strength on the Bingham characteristics of Electro-Rheological(ER) fluids which change their Yield shear stress and viscosity by temperature and electric field strength. It is found that under constant temperature the Yield sheal stress and viscosity of ER fluids proportionally increase with the applied electric field strength, and under constant applied electric field strength the Yield shear stress and viscosity of ER fluids decrease with the increasing temperature. These results are considered to be applied to the fluid and pneumatic power industry.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.92-97
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• 2009

The performance of cooling fan is affected by many peripheral parts, such as radiator, condenser, engine block and etc. Higher power has been requested in more confined automobile engine room. Thus, cooling performance becomes very important to remove the heat generated from the automobile engine more efficiently. In this paper, the performance of cooling fan including effects of engine block is investigated by using a fan tester based on the ASHRAE and the AMCA standards. A flow rate - gap distance curves and a flow rate - engine block constant curves are obtained from this study.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.77-82
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• 2001

Thermal design for KOMPSAT-2 propulsion system has been performed. Overall design requirements and the constitution for propulsion system is described. To meet the thermal design requirements, both a primary and a redundant heater circuit, each with two thermostats placed in series, will protect each hydrazine-wetted components, even if one heater circuit fails to operate. Heater power is turned off if any one of these thermostats is opened at its higher setpoint. Thus, even if one thermostat is failed closed, the second thermostat will turn off the heater. All such components shall be insulated with MLI. Propulsion heater sizing based on the constant worst cold case condition is conducted through thermal analysis. All heaters selected for propulsion components operate to prevent propellant freezing satisfying the thermal requirements for the propulsion subsystem over the worst case average voltage, i.e. 25 volts.

• Journal of Industrial Technology
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• v.3
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• pp.95-101
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• 1983

This study aims at the determination of the coefficienties of runoff and infiltration affecting runoff. The rating curve is more available than the peak flood runoff to determine flood control plan of flood control reservoir and the volume of hydroelectric power plant, or to make multipurpose dam. In hydrologic analysis and design, it is necessary to develop relations between precipitation and runoff, possible using some of the factors affecting runoff as parameters. In order to calculate the runoff discharge, the runoff process constituting elements are divided to the surface runoff, the subsurface runoff and the groundwater runoff. By comparing the computed hydrograph with the measured hydrograph, determinned the watershed TANK Model constant Varying the tank model constant for approximating the computed hydrograph to the measured hydrograph.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.6
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• pp.518-525
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• 2006

The present experiments have been performed for obtaining the melting heat transfer characteristics of micro-encapsulated solid-liquid phase-change material and water mixture slurry flow in a circular tube heated with constant wall heat flux. The phase change material having a low melting point was selected for a domestic cooling system in the present study. The governing parameters were found to be latent heat material concentration, heat flux, and the slurry velocity. The experimental results revealed that the increase of tube wall temperature of latent microcapsule slurry was lower than that of water caused by the heat absorption of fusion.