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Yoon Y.,Yeungnam University | Yoon Y.,Eco Friendly Auto Parts Technology Institute | Park B.-H.,Yeungnam University | Park B.-H.,Daegu University | And 4 more authors.
Applied Thermal Engineering | Year: 2017

External gear pumps are typically used as positive displacement machines that are capable of developing high pressures while operating at low suction pressures in hydraulic systems. Considerable attention has paid recently been given to investigating the flow characteristics and enhancing pump efficiency using theoretical, numerical, and experimental approaches. In this study, three-dimensional (3D) numerical simulations of an external gear pump were conducted to study the effects of 3D geometrical design parameters on pump performance characteristics such as the flow rate. The characteristics of internal flow are also presented with respect to the internal pressure peak, local cavitation, and delivery pressure ripple. The immersed solid method (ISM) was used to simulate the operation of a gear pump under extreme conditions of high rotational speed. We found that the maximum flow rate of the gear pump is a strong function of the gear tip clearance and lateral clearance. Using the 3D model, the effect of the lateral clearance on flow rate is highlighted. © 2017 Elsevier Ltd

Kim K.-H.,Hyundai Heavy Industries | Kim D.-Y.,Hyundai Heavy Industries | Park Y.-Y.,Hyundai Heavy Industries | Kim Y.-D.,Defense Agency for Technology and Quality DTaQ
Journal of Protective Coatings and Linings | Year: 2011

A study was conducted to investigate the characteristics of rapid cure polyurea or urethane hybrid coating systems with higher fracture elongation for the highly stressed, exposed deck areas of marine vessels. Two types of polyurea or urethane hybrid coating mixtures with different levels of urea content were formulated, including aluminum oxide as non slip aggregate. Free films and coated specimens were prepared for the assessment of fracture elongation and adhesion strength. Some of these specifications were applied over power tool-cleaned steel and others were applied over abrasive blast-cleaned steel. Coated specimens with dimensions of L300mm × W30mm × steel plate thickness 5mm/coated layer thickness 2mm were also prepared for tensile strength testing. The results of the assessment of fatigue on film using the test samples revealed that the fatigue of the steel plate was about 190 MPa when it was subject to 2 million cycles of impact having 200 MPa.

Park K.-H.,Defense Agency for Technology and Quality DtaQ | Yi K.-H.,Daegu University
Journal of Power Electronics | Year: 2013

Commercial home appliances using remotely controlled systems consume electric power while in standby mode to prepare for receiving a remote turn-on signal. The proposed power system can significantly reduce standby power consumption without increasing cost. Furthermore, since a Electronic Double Layer Capacitor (EDLC) is used as an auxiliary power storage element, the life cycle is longer and system reliability can be better than with existing approaches. When the energy of the EDLC is not sufficient for turning on the appliance, the power system charges the EDLC without affecting the main system. The proposed power system is verified with a commercial LCD TV and a 3.93mW standby consumption is obtained. This standby consumption can be regarded as zero standby equipment according to the IEC-62031 standard.

Park K.-H.,Defense Agency for Technology and Quality DTaQ | Yi K.-H.,Daegu University
Journal of Power Electronics | Year: 2013

A highly efficient sustaining driver is proposed for plasma display panels (PDPs). When the PDP is charged and discharged, the proposed sustaining driver employs an address voltage source used in an addressing period. A voltage source is used for fully charging the panel to the sustaining voltage, and an initial inductor current helps the panel discharge to 0 V. The resonance between the panel and an inductor is made by shifting the voltage and current bias level when charging and discharging the panel. As a result, the proposed circuit can reduce power consumption, switching loss, heat dissipation, and production cost. Experimental results of a 42-inch PDP are provided to verify the operation and features of the proposed circuit.

Kwon W.-B.,Gwangju Institute of Science and Technology | Choi Y.-K.,Defense Agency for Technology and Quality DTaQ | Park C.-S.,Gwangju Institute of Science and Technology
Microwave and Optical Technology Letters | Year: 2015

We propose and experimentally demonstrate an eight-tap transversal filter using a multiwavelength optical source and a dispersive fiber. The multiple wavelengths corresponding to taps are generated by combining broadband optical sources with the arrayed waveguide gratings providing equal wavelength spacing. This method has the advantage of providing a constant time delay between taps together with a dispersive medium (i.e., fiber). The free spectral range (FSR) of the filter is changed by controlling the fiber length. The experimental results showed an FSR of 7.03 GHz and a main to secondary sidelobe ratio of 12.1 dB with 0.8-nm wavelength spacing, and 3.46 GHz and 13.4 dB with 1.6-nm wavelength spacing, respectively. © 2015 Wiley Periodicals, Inc.

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