• 광산업정보
• /
• 통권1호
• /
• pp.74-83
• /
• 2000

지난 8월 10일 한국광산업진흥회 초대회장으로 취임한 김종수(LG이노텍 대표)회장이 산업자원부를 방문해 신국환 장관과 광산업계 발전을 위해 만났다. 이번 만남에서는 지난 4월 출범한 한국광산업진흥회의 초대회장을 받은 김종수 회장은 신임회장으로서의 소감과 광산업진흥회 발전방안 등을 이야기하며 산업자원부의 협조를 부탁했다. 이에 대해 신국환 장관은 광산업은 21세기 지식 기반시대를 대비하기 위한 국가전략산업으로 발전시키기 위해 함께 노력하자고 강조했다.

• Design & Manufacturing
• /
• 제17권4호
• /
• pp.24-32
• /
• 2023

In this study, we introduce research aimed at minimizing machining errors without compromising productivity by compensating for the machining errors caused by tool deformation. Our approach experimentally establishes the direct correlation between cutting depth and machining error, and creates predictive models using mathematical functions. This method allows for the prediction of compensated cutting depths to obtain the desired cutting profiles, thereby maximizing the compensation of machining errors in the cutting process.

• Design & Manufacturing
• /
• 제17권4호
• /
• pp.57-62
• /
• 2023

As a representative method for mass production, a multi-cavity type mold capable of simultaneously molding products of the same shape can be applied. It has the advantage of improving the productivity from several times to several tens of times, but it may cause disadvantages which is the quality deviation with each cavity. This study, therefore, has tried to increase the cavity filling balance by using a melt flipper and a flow distance control part in the runner part of the mold. Along with this, the design and manufacturing of air vents during injection molding have been verified through experimental methods to achieve a higher level of multi-cavity filling balance and dimensional accuracy.

• 마이크로전자및패키징학회지
• /
• 제28권4호
• /
• pp.85-89
• /
• 2021

AlGaN 기반 UV-C 발광다이오드(LEDs)에 전기화학적 전위차 활성화(EPA)에 의한 p-형 활성화를 진행하였다. 높은 저항과 낮은 전도도를 유발하는 중성 Mg-H의 복합체의 수소원자를 EPA를 이용하여 제거하여 p-형 활성화 효율을 높였다. 중성 Mg-H 복합체는 주요 매개 변수인 용액, 전압, 시간에 의해 Mg^-과 H⁺로 분해되며, 2차 이온질량 분광법(SIMS) 분석을 통하여 개선된 정공 캐리어의 농도를 확인할 수 있었다. 이 메커니즘은 결국 내부 양자효율(IQE)의 증가, 광 추출 효율 향상, 역 전류 영역의 누설전류 값 개선, 접합 온도 개선 등을 이루어 결과적으로 UV-C LED의 수명을 향상시켰다. 체계적인 분석을 위해 SIMS, Etamax IQE 시스템, 적분구, 전류-전압(I-V) 측정 등을 사용하였으며, 그 결과를 기존의 N₂-열 처리 방법과 비교 평가하였다.

• Tribology and Lubricants
• /
• 제39권2호
• /
• pp.76-80
• /
• 2023

This paper describes an experimental investigation of the effect of cooling flow rate on gas foil thrust bearing (GFTB) performance. In a newly developed GFTB test rig, a non-contact type pneumatic cylinder provides static loads to the test GFTB and a high-speed motor rotates a thrust runner up to the maximum speed of 80 krpm. Force sensor, torque arm connected to another force sensor, and thermocouples measures the applied static load, drag torque, and bearing temperature, respectively, for cooling flow rates of 0, 25, and 50 LPM at static loads of 50, 100, and 150 N. The test GFTB with the outer radius of 31.5 mm has six top foils supported on bump foil structures. During the series of tests, the transient responses of the bearing drag torque and bearing temperature are recorded until the bearing temperature converges with time for each cooling flow rate and static load. The test data show that the converged temperature decreases with increasing cooling flow rate and increases with increasing static load. The drag torque and friction coefficient decrease with increasing cooling flow rate, which may be attributed to the decrease in viscosity and lubricant (air) temperature. These test results suggest that an increase in cooling flow rate improves GFTB performance.

• Tribology and Lubricants
• /
• 제39권2호
• /
• pp.81-85
• /
• 2023

This study presents an experimental investigation of the effects of surface roughness on gas foil thrust bearing (GFTB) performance. A high-speed motor with the maximum speed of 80 krpm rotates a thrust runner and a pneumatic cylinder applies static loads to the test GFTB. When the motor speed increases and reaches a specific speed at which a hydrodynamic film pressure generated within the gap between the thrust runner and test GFTB is enough to support the applied static load, the thrust runner lifts off from the test GFTB and the friction mechanism changes from the boundary lubrication to the hydrodynamic lubrication. The experiment shows a series of lift-off test and load-carrying capacity test for two thrust runners with different surface roughnesses. For a constant static load of 15 N, thrust runner A with its lower surface roughness exhibits a higher start-up torque but lower lift-off torque than thrust runner B with a higher surface roughness. The load capacity test at a rotor speed of 60 krpm reveals that runner A results in a higher maximum load capacity than runner B. Runner A also shows a lower drag torque, friction coefficient, and bearing temperature than runner B at constant static loads. The results imply that maintaining a consistent surface roughness for a thrust runner may improve its static GFTB performance.

• Tribology and Lubricants
• /
• 제39권5호
• /
• pp.203-211
• /
• 2023

This study experimentally investigates the effects of angular acceleration on the friction and wear performances of a gas foil thrust bearing (GFTB) using a typical GFTB with six pads. The outer radius of the bearing is 31.5 mm, the total bearing area is 2,041 mm² , and the bump foil and incline (ramp) height are both 500 ㎛. The newly developed GFTB test rig for measuring the friction torque and coefficient measures the axial load, drag torque, lift-off speed, and touch-down speed. The experiment is conducted for angular accelerations of 78.5, 314.2, and 328.3 rad/s² at axial loads of 5, 10, and 15 N, respectively. The test shows that the start-up friction coefficient increases with increasing axial load at the same angular acceleration, and the friction coefficient decreases with increasing angular acceleration under the same axial load. As the angular acceleration increases, the lift-off speed at the motor start-up increases, and the touch-down speed at the motor stop decreases. The wear distance of the GFTB for a single on/off cycle increases with increasing axial load at the same angular acceleration and decreases nonlinearly with increasing angular acceleration under the same axial load. The test results suggest that adjusting the rotational angular acceleration helps reduce bearing friction and wear.