• Journal of Welding and Joining
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• 제33권1호
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• pp.54-60
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• 2015

Laser-arc hybrid welding has been considered as an effective pipe girth welding process since early 2000's. Tolerance for fit-up offsets such as gap and edge misalignment is one of most important requirements in pipe girth laser-arc hybrid welding, and several approaches using parameter optimization, a laser beam scanning and an arc oscillation have been tried. However the required offset tolerance has not been fully accomplished up to now and laser-arc hybrid welding has not been widely applied in pipeline construction than expected, despite of its high welding speed and deep penetration. In this study, internal welding was adopted to ensure the offset tolerance and sound back bead. The effect of welding parameters on bead shape was investigated at the flat position. Also tolerances for gap and edge misalignment were verified as 0.5 mm and 2.0 mm, respectively. The position welding trials were conducted at several welding positions from the flat to the overhead position in a downward direction. With the fixed welding speed, arc current for gas metal arc welding current and laser output power, adequate welding voltages for gas metal arc welding were suggested for each position.

• 품질경영학회지
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• 제26권4호
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• pp.250-264
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• 1998

The purpose of the thesis is to develop simulation program for forecasting of optical connector. So we can achieve the time and the money saving for making the optical connector. Optical performance (insertion loss) of optical connector mainly relies on 3 misalignment factors-ferrule factor due to mis-manufacture from design, auto-centering effect that is fiber behavior phenomena between hole and fiber, fiber misalignment factor. Simulation use experimental data with auto-centering effect and fiber factor and use pseudo data with ferrule through random number generation because it is developing stage. In this study we a, pp.y kernel density estimation method with experimental data in order to know whether it belong to or not specific parametric distribution family. And we simulate to forecast insertion loss of optical multifiber connector under specific design model using nonparametric bootstrap resampling data and parametric pseudo samples from uniform distribution. We obtain the tolerance specifications of misalignment factors satisfying not exceed in maximum 1.0dB and choose optimal hole diameter.

• Journal of Astronomy and Space Sciences
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• 제23권4호
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• pp.327-336
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• 2006

In this paper, gain loss of KVN (Korean VLBI Network) 21-m shaped Cassegrain antenna due to misalignment of antenna optics is calculated using ray-tracing method. It enables us to estimate alignment tolerances of feed and sub-reflector positioning. According to numerical results, KVN 21-m shaped Cassegrain antenna's gain loss is more sensitive to positions of feed and sub-reflector than in case of the equivalent classical Cassegrain antenna. The result of calculation is believed to be utilized as a possible guideline when checking the performance of the antenna system.

• 대한전자공학회논문지SD
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• 제41권7호
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• pp.13-20
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• 2004

미세 광학 벤치의 설계를 위해서 두 가지 테스트 벤치에 대해 결합효율을 계산하였다. 광섬유로 들어오고 나가게 되는 빛을 볼 렌즈를 통과한 것과 그렇지 않은 것으로 설계하였다. 미세 광학 벤치의 실제 제작 과정에서 발생할 수 있는 광소자들의 위치 에러를 고려하여 시뮬레이션을 하였고, 그것들의 허용오차를 -3 ㏈ 조건으로 정하였다. 볼 렌즈가 없는 fiber-to-fiber에서는 lateral misalignment가 2.7 um 그리고 tilt 에러가 5.8o 이내로 나타났다. 각각의 광섬유 앞단에 광의 집속을 위해 볼 렌즈가 놓여지면 working distance는 60 um로 확장되어지나, 각각의 광소자들이 놓여진 위치 파라미터 사이에 보다 강한 교호작용이 존재하기 때문에 tolerance design을 위해 교호작용을 함께 고려해야 한다.

• Journal of Power Electronics
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• 제18권1호
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• pp.277-288
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• 2018

Wireless inductive power transfer (IPT) technology is used in many applications today. A compact and high-frequency primary side inverter is one of the most important parts of a WPT system. In this study, a modified class EF-type voltage-fed multi-resonant inverter has been proposed for WPT application at a frequency range of 85-100 kHz. Instead of an infinite input choke inductor, a resonant inductor is used to reduce loss and power density. The peak voltage stress across the MOSFET has been reduced to almost 60% from a class-E inverter using a passive clamping circuit. A simple yet effective design procedure has been presented to calculate the various component values of the proposed inverter. The overall system is simulated using MATLAB/SimPowerSystem to verify the theoretical concepts. A 500-W prototype was built and tested to validate the simulated results. The inverter exhibited 90% efficiency at nearly perfect alignment condition, and efficiency reduced gradually with the misalignment of WPT coils. The proposed inverter maintains zero-voltage switching (ZVS) during considerable load changes and possesses all the inherent advantages of class E-type inverters.

• Journal of Welding and Joining
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• 제29권6호
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• pp.77-81
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• 2011

In most industry, manual GTAW welding is preferred for formation of stable back bead in root weld of butt joint. However, manual GTAW welding has low productivity as compared with GMAW, also it has unstable bead quality which depend on skilled workers. So it is necessary to develop process of root pass welding by using automation GMAW that have stable back bead formation and high productivity. In this paper, the design of U-groove with 3mm root face was applied to extend the tolerance of misalignment in condition of standard root gap 1.5mm. Consequently, for the formation of stable back bead in root pass of butt welding, in case of the narrow root gap(0.5mm) the large arc force was applied by increasing the current and voltage. In case of the large root gap(2.5mm), the small arc force was applied by decreasing the current and voltage. Considering the various root gap, the required deposited metal was controlled by welding speed only.

• 한국광학회지
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• 제11권3호
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• pp.179-186
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• 2000

초고속정보통신망을 구성하는 교환기(ATM system)과 전송부문(B-NT(Broadband Network Termination) system, 10G 전송system 등)에 사용할 수 있는 155Mbps 수동 광정렬 방식의 광수신 모듈의 광결합 효율과 정렬오차 허용도를 게산하고 이를 적용한 엔지니어링 샘플로부터 이론치 비교와 flat-광섬유를 이용한 butt 커플링 패키지 방법으로 최대 -4.5dBm 광출력을 갖는 광송신기 제작 및 신뢰성 검사로 값싼 광송신기 제작에 대하여 알아보았다.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2008년도 한국우주과학회보 제17권2호
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• pp.34.4-35
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• 2008

The significant I&T process gain represented by reduction in overall budget expenditure can be obtained from the use of efficient alignment technique for large space optical systems. Such process gain tends to increase rapidly with an increase in aperture and/or in number of optical elements within the system. However, in practice, the alignment of multiple optical components tends to be rather difficult task because of the multiple coupling effects among the elements within the target system. In order to understand and hence identify the complex interplay of the wavefront coupling effects from the alignment process, the original differential wavefront sampling(DWS) method was presented elsewhere in recent years. DWS uses partial differential of the wavefront of optical component and perturbation value of the optical component against a particular alignment factor. The straightforward application of DWS for an off-axis optical system revealed that it tends to give incorrect estimation of the given misalignment state. In this study, we added off-axis correction terms to the original DWS algorithm and investigated its alignment performance. The performance simulation result for a Korsch type space optical system shows that the modified DWS is capable of bringing the misaligned system into the target alignment tolerance only after 3 iterations. It also shows that this new improved algorithm can be used to estimate the source misalignment as well. We are planning to apply this method for the alignment of a 800mm Korsch type telescope in the near future. We discuss the computational technique, simulation results and implications in details.

• 한국광학회지
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• 제24권1호
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• pp.29-38
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• 2013

본 논문에서는 점광원을 기준으로 설계된 자유 형상 렌즈(freeform lens)의 조명 성능과 LED 광원 크기와의 관계 및 공차 특성을 살펴보았다. 비교를 위해 발산 조명 모델(divergent illumination model)을 적용한 두 가지 렌즈와 중첩 조명 모델(overlapped illumination model)을 적용한 한가지 렌즈를 설계하였다. LED 광원이 커짐에 따라 평균 조도에 비해 조도 균일도가 상대적으로 크게 감소하였으며, 정렬 오차에 의한 성능 저하는 거의 발생하지 않았다. 하지만 LED 광원의 방출 특성 변화는 LED 광원 크기에 관계없이 조명 성능에 영향을 미치는 것으로 확인하였다. 발산 조명 모델로 설계된 렌즈가 전반적으로 우수한 성능을 보였지만, LED 방출 특성 변화에 대해서는 중첩 조명 모델로 설계된 렌즈의 성능이 상대적으로 적게 변화함을 알 수 있었다.

• 소음진동
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• 제11권1호
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• pp.125-131
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• 2001

There is a clearance between the parts of a machine due to design tolerance, manufacturing error, wear, looseness, or misalignment. If the clearance is large, the vibration and noise of the machine is generally large. Therefore, the analysis on the nitration and noise of a machine can tell the clearance of the machine, which reveals the condition of the machine, i.e., the existence of faults and the safety of the machine. The investigation of this kind of research should be on the basis of experimental results. A link mechanism with a clearance at a joint between the coupler and locker is made for the investigation of the condition monitoring of a machine due to clearance. The vibration and sound are measured from the link driving system during the operation. The signals are clarified using line enhancement technique. The noise removed signals are used to develop the dynamic model of the system for a model based fault diagnosis. Also this study showed that the clarified signals can be used for the calculation of the joint forces between the coupler and rocker and for the correlation between the vibration and sound levels and the clearance sizes.