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professors emeritus
Dahie Hong
Name
Jintaek Chung | Professor
Tel
+82-2 3290-3364
Fax
+82-2-928-9766
E-mail
jchung@korea.ac.kr
address
Room 310, Innovation Hall, School of Mechanical Engineering, Korea University, 5-Ga 1, Anam-dong, Sungbuk-Gu, Seoul, Korea, 136-713
Education
Feb. 1983 B.S. of Mechanical Engineering, Korea University, Korea
Feb. 1985 M.S. of Mechanical Engineering, Korea University, Korea
Aug. 1992 Ph.D. of Mechanical Engineering, University of Minnesota, U.S.A.
Lab.
Energy System & Turbomachinery Lab.
1. Investigation on the performance enhancement of embedded display package in hand held devices through temperature management
The objectives of this study are to investigate the thermal characteristics of embedded piezo-actuated display package (PADP) in hand held devices and to develop a temperature management system for the performance enhancements of the display package. The computational fluid dynamics (CFD) and an infrared camera were used for the investigation on the thermal characteristics of the PADP. This package which is integrated in micro beam projectors is used in portable devices such as cell phones, laptops, and personal digital assistants (PDAs), to name a few. Ambient temperature change is a critical factor affecting the performance of PADP. To reduce this effect of the ambient temperature change, a temperature control system using a micro heater and a temperature feedback circuit was developed. The numerical simulation was used for the design of the micro heater. Then, the micro heater was fabricated using photolithography. The feedback control for temperature maintenance was achieved by turning off the micro heater when overheated and turning it on when overcooled. A computational model of the transient thermal analysis for the feedback control system was also developed. The obtained theoretical results are in good agreement with the experimental measurements. Under this controlled system, the temperature of PADP was maintained at the target temperature within ± 0.5℃ temperature fluctuation.

2. Effect of printed circuit board structures on temperature-dependent gain characteristics of RF power amplifier chips
One of the most important problems in recent wireless component development is the problem of heat dissipation in small and dense radio frequency (RF) modules such as RF power amplifiers (PAs). In those modules, the thermal resistance of a semiconductor chip is a strong function of printed circuit boards (PCBs) as well as packages. In this work, hetero junction field effect transistor (HFET) RF PA test fixtures with various PCB structures have been made, and the junction temperatures of the HFETs mounted on those test fixtures have been obtained. In each test fixture, adjusting the ambient temperature changes, and thus the RF gain. However, the value of is uniquely determined by not by, irrespective of the type of the test fixture. The deviation from this universality is originated from the manufacturing dispersions of the PCBs and chips. The curve clearly verifies the interplay between thermal design of PCBs and RF properties of amplifiers.

3. Numerical Analysis of 5MW Gas Turbine System
On this study, the three-dimensional flow characteristics & performance evaluation of 5MW gas turbine system have been numerically investigated. The unsteadiness occurred at the passage and exit of each stage was observed using the unsteady state simulation of 3-stage turbine.