• Korean Journal of Metals and Materials
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• v.50 no.3
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• pp.224-232
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• 2012

In this study, the effect of hot-stamping heat treatment on the microstructure and hardness of TWB(Tailor Welded Blank) laser joints in Al-Si-coated boron steel and Zn-coated DP(Dual Phase)590 steel was investigated. In the TWB joints without heat treatment, hardness profiles showed local hardness deviation near the fusion zone. However, there was no hardness deviation in the heat treated specimen and its hardness was higher than that of the one without the heat treatment, due to a fully martensite microstructure. In the TWB joints of both the boron and DP steels, the maximum hardnesses were observed at the HAZ(Heat Affected Zone) near the base metal, and the hardness decreased gradually to the base metal. In the heat treated joints, the hardnesses of the HAZ and the base metal of the boron steel side were similar to the maximum hardness of the weld, while those of the HAZ and the base metal of the DP steel side were higher than the maximum hardness.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10b
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• pp.382-387
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• 1992

In order to obtain desired arc welding performance, we already developed an arc welding robot system that enabled coordinated motions of dual arm robots. In this system one robot arm holds a welding target as a positioning device, and the other robot moves the welding torch. Concerning to such a dual arm robot system, the positioning accuracy of robots is one important problem, since nowadays conventional industrial robots unfortunately don't have enough absolute accuracy in position. In order to cope with this problem, our robot system employed teaching playback method, where absolute error are compensated by the operator's visual feedback. Due to this system, an ideal arc welding considering the posture of the welding target and the directions of the gravity has become possible. Another problem still remains, while we developed an original teaching method of the dual arm robots with coordinated motions. The problem is that manual teaching tasks are still tedious since they need fine movements with intensive attentions. Therefore, we developed a 3-dimensional vision guided robot control method for our welding robot system with coordinated motions. In this paper we show our 3-dimensional vision sensor to guide our arc welding robot system with coordinated motions. A sensing device is compactly designed and is mounted on the tip of the arc welding robot. The sensor detects the 3-dimensional shape of groove on the target work which needs to be weld. And the welding robot is controlled to trace the grooves with accuracy. The principle of the 3-dimensional measurement is depend on the slit-ray projection method. In order to realize a slit-ray projection method, two laser slit-ray projectors and one CCD TV camera are compactly mounted. Tactful image processing enabled 3-dimensional data processing without suffering from disturbance lights. The 3-dimensional information of the target groove is combined with the rough teaching data they are given by the operator in advance. Therefore, the teaching tasks are simplified

• Korean Journal of Optics and Photonics
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• v.19 no.4
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• pp.334-340
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• 2008

We investigated the electromagnetically induced transparency (EIT) and the Hanle spectrum in a paraffin coated Rb vapor cell. The EIT spectrum was observed in the $F_g=2$, $3{\rightarrow}F_e=3$ transition of the $^{85}Rb$ $D_1$-line by using two independent external cavity diode lasers, and the Hanle spectrum was observed by using one external cavity diode laser in the $\Lambda$-type scheme between the Zeeman sublevels of the $F_g=2{\rightarrow}F_e=1$ transition of the $^{87}Rb$ $D_1$-line. In the Hanle spectrum, we could observe the dual-structured spectrum in the paraffin coated vapor cell. We investigated the dual-structured lineshape by applying an external magnetic field, and varying the direction of the magnetic field. The narrow linewidth of dual-structured EIT was measured to be approximately 200 Hz.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.323-324
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• 2011

현재 많은 blue LED소자의 제작 공정과 소자 표면에 texturing하는 과정이 보고되어 있다. 그 중n층이 위로 올라오는 수직형 LED 구조로 인해 표면 texturing 기술은 빛의 발광 효율을 증가 시킬 수 있는 중요한 기술 중 하나가 되었다. 1 이 연구에서, 우리는 InGaN을 바탕으로 한 LED 소자의 표면 roughening을 건식과 습식 공정을 모두 거치는 과정을 통하여 소자의 발광 효율을 높이는 시도를 하였다. 최근 전도성 물질 기판 위에 증착 되어 있는 수직형 LED 소자 2,3,4는 과거의 사파이어 기판 위에 증착 되어 있는 형태의 LED 소자에 비해 우수한 소자 특성을 보인다. 이는 과거 사파이어 기판을 사용함으로써 낮은 열적 특성과 더불어 전기 정도성에 몇 가지 제약을 초래하게 되었기 때문이다. 반면, 전도성 기판은 LED 구조의 back side ohmic contact을 가능하게 하였고, 더 나은 확산 특성을 보여 주었고 작동 전압 또한 감소 하였다. N층이 위에 있는 수직형 LED 소자는 KrF pulsed excimer laser로 인해 실현 되었다. 이 laser 빛이 투명한 사파이어 기판을 통해 얇은 GaN층에 입사되면, 기판과 GaN가 분리된다. 이 레이저 기술은 laser lift-off(LLO)로 성장된 기판으로부터 LED 구조를 분리하는데 성공하게 하였다. 우리는 건식 식각 공정을 이용하여 n 층이 위에 올라와 있는 구조인 수직형 LED 소자에 roughening을 주고 다시 이 표면에 습식 식각 공정을 적용하여 거친 부분의 거칠기를 또 한번 증가시켰다. 그리고 이 거칠어진 표면은 이 공정이 진행 되기 전의 소자에 비해 빛의 발광 효율이 증가 되었다. 이 두 공정을 포함한 식각 공정은 두 가지 장점이 생겼는데, 한가지는 GaN에서 외부로 방출할 수 있는 표면 지역이 증가되었고, 다른 한가지는 가파른 거칠기 특성으로 인해 critical angle을 증가시킨 것이다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.11
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• pp.921-933
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• 2018

There is a method to enhance the pure navigation performance of INS(Inertial Navigation System) through the rotation of inertial measurement unit to compensate error sources of inertial sensors each other and that INS using this principle of operation is called rotational INS. In this paper, the exact error analysis of rotational INS based on ring laser gyro considering the coupling effect with gravity and earth rate is performed to evaluate the navigation performance by inertial sensor error sources. And error analysis and performance evaluation result confirmed by modelling and simulation is also proposed in this paper.

• 한국연소학회:학술대회논문집
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• 2006.10a
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• pp.110-116
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• 2006

A new measurement technique based on a two-color pyrometry and modulated LII signals to measure local soot particle temperatures has been proposed and examined experimentally. The theoretical review suggests that modulated LII signals of soot particles is suitable for a two-color pyrometry as long as the temperature increase due to laser heating remains relatively small. The modulated LII signals from ethylene and propylene diffusion flames were simultaneously measured at 550 and 750 nm by a dual measurement system that consists of optical fibers, PMT and lock-in amps. The local soot particle temperatures of diffusion flames could be obtained using a two-color pyrometry and modulated LII signal based new technique.

• Current Optics and Photonics
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• v.4 no.1
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• pp.63-68
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• 2020

We built an optical parametric oscillator (OPO) generating orthogonally polarized signals at different wavelengths simultaneously, based on a periodically poled lithium niobate (PPLN) crystal. The OPO was pumped by ns-pulses at 1.064 ㎛ from a diode-pumped solid-state laser, where we found the type-0 and the type-1 quasi-phase matching conditions were satisfied simultaneously in the PPLN crystal. This enabled us to create a coherent light source which can emit dual signals which could be accessed easily by rotating a polarizer.

• Journal of Mechanical Science and Technology
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• v.17 no.1
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• pp.157-167
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• 2003

The exciplex fluorescence technique with the TMPD (tetamethyl-Ρ-phenylene-diamine) / naphthalene dopant system was applied in a combustion-type constant-volume spray chamber. A detailed set of calibration experiments has been performed in order to quantify the TMPD fluorescence signal. It has been demonstrated that the TMPD fluorescence intensity was directly proportional to concentration, was independent of the chamber pressure, and was not sensitive to quenching by either water vapor or carbon dioxide. Using a dual heated-jet experiment, the temperature dependence of TMPD fluorescence up to 1000 K was measured. The temperature field in the spray images was determined using a simple mixing model, and an iterative solution method was used to determine the concentration and temperature field including the additional effects of the laser sheet extinction. The integrated fuel vapor concentration compared favorably with the measured amount of injected fuel when all of the liquid fuel had evaporated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.441-441
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• 2012

Noise and vibration performance plays an important role in the development of rotating components, such as engines, drivelines, transmission systems, compressors and pumps. The presence of torsional vibrations and other specific phenomena require the dynamic behaviour of systems and components to be designed accurately in order to avoid comfort and durability related problems. This paper provides an overview of the instrumentation and challenges related to torsional vibration testing. The accuracy and performance of five measurement techniques (high-speed incremental encoder, dual beam laser interferometer, zebra tape, zebra disc, direct pulse measurements with magnetic probe) is investigated by measurements on a Fiat Punto 1.4 liter engine. The potential sources of error are discussed to explain the inaccuracies of each technique.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.11a
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• pp.599-602
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• 2005

본 논문에서는 기존 단극성 원 빔 레이저 방식의 단점을 개선하기 위하여 듀얼 빔을 응용한 차량용 레이저 레이더 시스템을 설계하엿다. 양극성 m-시퀀스를 두 개의 레이저 파장에 할당함으로써 2차원 OOC(orthogonal optical codes)와 유사한 특성을 갖도록 하고 수신부에서 두 개의 단극성 신호를 차동구조를 이용하여 양극성 신호로 합성하는 방법을 이용, SNR 개선 방안을 제시한다. 시뮬레이션 결과, 제안한 듀얼 빔 방식이 기존의 원 빔 단극성 신호방식의 레이져 레이더 시스템에 비해 3dB의 SNR 개선이 가능함을 확인하였다.