• 한국산학기술학회논문지
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• 제6권5호
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• pp.432-438
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• 2005

본 논문에서는 반도체 제조를 위한 AC 서보 모터의 고정도 위치 제어에 관하여 연구하였다. 제어기는 150 MIPS의 고속 처리가 가능한 Tl사의 차세대 모터 제어용 DSP TMS320F2812를 이용하여 컨트롤러를 구성하였으며, 2,500 PPR 분해능의 광학식 증분형 엔코더가 장착 된 100W 용량의 PMSM을 위치 제어 하였다. 위치 제어기를 구성하기 위하여 속도 제어기와 전류 제어기를 하위 루프로 구성하였으며, 회전형 엔코더 4체배 된 신호를 이용하여 최대 10,000 PPR의 위치 제어를 수행 하였다. 이로부터 보다 많은 PPR을 지원하는 엔코더에서도 같은 방법으로 고정도 위치제어가 가능할 것이다.

• 한국자동차공학회논문집
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• 제13권4호
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• pp.58-65
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• 2005

A method measuring angular speed and estimating angular acceleration of an automotive wind shield wiper pivot with limited resources has been proposed. Limited resources refer to the fact that processes cannot be operated in real-time with a regular notebook running a Microsoft Windows. Also, they refer to the fact that data acquisition cards have only two general purpose counters as many generic cards do. An optical incremental encoder has been employed for measuring angular motion. To measure the angular speed of the pivot, periods for the encoder's output pulses have been measured as the speed is related to the reciprocal of the period. Since only information acquired from one counter channel is the magnitude of the angular speed, sign correction is necessary. Also the information for the exact time when a pivot passes left and right dead points is also missing and the situation is inherent to the hardware setup. To find out the zero-crossing time of the angular speed, a linear interpolation technique has been employed. Lastly, to overcome the imperfection of the mechanical encoders, the angular speed has been curve fitted to a spline. Angular acceleration can be obtained by a differentiation of the angular speed.

• 대한기계학회논문집A
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• 제26권4호
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• pp.745-753
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• 2002

It is required to evaluate nondestructively the crack depth of surface-breaking cracks for the assurance of safety of structure. Optical generation of ultrasound produces well defined pulses with a repeatable frequency content, that are free of any mechanical resonances; they are broad band and are ideal for the measurement of attenuation and scattering over a wide frequency range. Self-calibrating surface signal transmission measurement is very sensitive and practical tool for surface-breaking crack depth. In this paper, the self-calibrating technique by laser-based ultrasound is used to evaluate the depth of surface-breaking crack of material. It is suggested that the relationship between the signal transmission and crack depth can be used as a practical model for predicting the surface-breaking crack depths from the signal transmission measured in structure.

• 대한금속재료학회지
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• 제50권5호
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• pp.353-360
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• 2012

The corrosion product of archaeological iron objects is supposed to be removed because it causes re-corrosion. So far it is removed by scapel and sand blaster but they depend on the skill and experience of a conservator and the glass-dust of the sand blaster is harmful to humans. Therefore this study applies a laser cleaning system which is used in various industrial cleaning processes, to remove corrosion product from archaeological iron objects. In addition, this work studies the alternation of corrosion product after laser irradiation, which evaluates the reliability of the laser cleaning system. Optical microscopy, SEM-EDS, XRD, Raman have been used to observe and analyse the surface of the objects. The results show the capacity of laser cleaning some corrosion product, but blackening appears with increasing pulses and laser energy, and some corrosion products, goethite and hematite, are partially altered to magnetite. These problems, blackening and alternation of corrosion product, should be solved by further studies which find the optimal laser irradiation condition and use a wetting agent.

• 한국광학회지
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• 제3권1호
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• pp.50-54
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• 1992

마스크를 사용하지 않고 레이저 $(CW Ar^+$ laser, $\lambda=514.5nm)$ 광속을 이용하여 불산 용액이 첨가된 황산구리 전해질 용액내의 실리콘(Si, 100) 단결정 표면에 구리를 침착시켰으며, 이들 사이에서 일어나는 화학 반응식을 도금에서와 같이 양극 반응과 음극 반응으로 구분 하여 제안하였다. 또한 침착 되는 구리점의 직경을 전해질 용액에 첨가되는 불산용액의 양, 레이저 광속의 조사 시간과 관속의 세기에 따라 측정 분석하였다. p형 실리콘 단결정의 경우, 연속형 $Ar^+$ 레이저를 조사하였을때 구리 침착이 일어나고 펄스형 레이저 광속(Nd:YAG 레이저에 KDP결정을 사용하여 얻은 2차 고조파, $\lambda=530nm, $\tau=25nsce$)을 조사하였을 경우에는 침착이 일어나지 않았다. 그와는 반대로 n형 실리콘 단결정의 경우, 연속형 $Ar^+$ 레이저를 조사하였을 때는 구리 침착이 일어나지 않았으나, 펄스형 레이저 광속을 조사시켰을 경우에는 구리 침착이 일어남을 관찰하였다.

• Current Optics and Photonics
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• 제7권3호
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• pp.297-303
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• 2023

In this paper, we demonstrated a high-energy (285 mJ) mid-infrared flashlamp-pumped electro-optically 𝚀-switched Er:YAG master oscillator power amplifier (MOPA) system and comprehensively investigated its temporal, spectral, and spatial characteristics. To increase the output energy, we optimized the delay between the timings at which the flashlamps of the master oscillator and power amplifier were triggered. In addition, the output energy was improved while minimizing thermal effects by cooling the MOPA system to a temperature slightly above the dew point. Consequently, the MOPA structure boosted the output energy without damaging the lithium niobate Pockels cell, which is a crucial element in 𝚀-switching. This design realized pulses with energies up to 0.285 J and pulse durations of approximately 140 ns at a wavelength of 2,936.7 nm. This high-energy mid-IR Er:YAG MOPA system can be used for various scientific, engineering, and military underwater applications.

• 생명과학회지
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• 제25권8호
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• pp.953-959
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• 2015

광유전학은 생체 조직 및 세포에서 유전공학적으로 발현된 광민감성 단백질을 이용하여 목표로 하는 분자/세포 활동을 조절하기 위한 광학 및 분자적 전략들의 조합이다. 광유전학은 빛을 이용하여 신경세포의 발화 여부를 결정하는 세포막 채널을 빨리 열고 닫는 방법을 포함한다. 이 기술은 녹조류의 광민감성 단백질들을 특정 뇌세포에 넣는데서 시작되었다. 이렇게 하면 세포들은 파랑이나 노락색의 펄스로 켜지거나 꺼질 수 있다. 빨리 개폐되는 광민감성 양이온 채널인 자연계에 존재하는 조류 단백질인 channelrhodopsin-2 (ChR2)를 이용하여 활동전위의 숫자와 빈번도를 조절할 수 있다. ChR2는 다른 세포들은 영향을 주지 않으면서 한 유형의 신경세포만 조작할 수 있는 길을 제시하는데, 이는 전례가 없는 특이성이다. 이 기술은 빛을 이용하여 단일 발화와 시냅스 사건 수준에서 신경신호전달을 변경시킬 수 있도록 하여 신경과학자와 의생명공학자들에게 널리 적용될 수 있는 도구를 제공한다. 녹조류와 레이저, 유전자 치료, 광섬유의 희한한 조합은 이전에 결코 불가능했던 정밀도로 뇌 속 깊은 곳의 신경 회로 지도를 그릴 수 있도록 해주었다. 이것은 우울증, 불안, 정신분열, 중독, 수면병, 그리고 자폐증 같은 질환의 원인을 밝히는데 도움을 줄 것이다. 광유전학은 파킨슨병, 강박장애, 그리고 전기 펄스가 있는 다른 질환들을 치료하는데 사용되는 기존 이식 도구들을 개선시킬 수 있다. 광유전학 장치는 상기 장치들이 할 수 있는 것보다 더 많이 뇌세포의 특정 세포들을 대상으로 할 수 있다. 신경세포 이외의 일반 세포들에도 광유전학 도구들을 적용하는 연구들이 증가하고 있다.

• Journal of Acupuncture Research
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• 제20권5호
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• pp.118-132
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• 2003

Objective: The aim of this study was to investigate the effects of Joksamni(ST36) combination on NAD PH-diaphorase, neuronal nitric oxide synthase(nNOS), neuropeptide Y(NPY) and vasoactive intestinal peptide (VIP) in the cerebral cortex of spontaneously hypertensive rat. Methods: The experimental groups were divided into four groups: Normal, Joksamni(ST36), Joksamni(ST36)+Eumneungcheon(SP9), and Joksamni(ST36)+Gokji(LI11). Needles were inserted into acupoints at the depth of 0.5cm with basic insertion method. Electroacupuncture was done under the condition of 2Hz electrical biphasic pulses with continuous rectangular wave lasting for 0.2ms until the muscles produced visible contractions. Such stimulation was applied continuously for 10 minutes, 1 time every 2 days for 10 sessions of treatments. Thereafter we evaluated changes in NADPH-d positive neurons histochemically and changes in nNOS, NPY and VIP positive neurons immunohistochemically. Results: The optical densities of NADPH-d positive neurons of the Joksamni(ST36)+Eumneungcheon(SP9) group in all areas of cerebral cortex and Joksamni(ST36)+Gokji(LI11) group in primary somatosensory cortex, visual cortex, auditory cortex, perirhinal cortex were significantly increased as compared to the Joksamni(ST36) group. The optical densities of NADPH-d positive neurons of the Joksamni(ST36)+Gokji(LI11) group were significantly decreased as compared to the Joksamni(ST36)+Eumneungcheon(SP9) group with the exception of primary somatosensory cortex. The optical densities of nNOS positive neurons of the Joksamni(ST36)+Eumneungcheon(SP9) group in all areas of cerebral cortex and Joksamni(ST36)+Gokji(LI11) group in auditory cortex, perirhinal cortex, insular cortex were significantly increased as compared to the Joksamni(ST36) group. The optical densities of nNOS positive neurons of the Joksamni(ST36)+Gokji(LI11) group were significantly decreased in all areas of cerebral cortex as compared to the Joksamni(ST36)+Eumneungcheon(SP9) group. The optical densities of NPY positive neurons of the Joksamni(ST36)+Gokji(LI11) group were significantly decreased in primary motor cortex, primary somatosensory cortex, cingulate cortex as compared to the Joksamni (ST36) and Joksamni(ST36)+Eumneungcheon(SP9) groups. The optical densities of VIP positive neurons of the Joksamni(ST36)+Eumneungcheon(SP9) group were significantly increased in all areas of cerebral cortex except for cingulate cortex as compared to the Joksamni(ST36) group. The optical densities of VIP positive neurons of the Joksamni(ST36)+Gokji(LI11) group were significantly decreased in auditory cortex, cingulate cortex, perirhinal cortex as compared to the Joksamni(ST36) group. The optical densities of VIP positive neurons of the Joksamni(ST36)+Gokji(LI11) group were significantly decreased in all areas of cerebral cortex as compared to the Joksamni(ST36)+Eumneungcheon(SP9) group. Conclusions: The result demonstrated that electroacupuncture on Joksamni(ST36) and its combination change the activities of the NO system and peptidergic system in the cerebral cortex of SHR and that acupoint combination is one of the important parameters for the effects.

• Current Optics and Photonics
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• 제4권1호
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• pp.69-80
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• 2020

A Rayleigh Lidar used for wind detection works by transmitting laser pulses to the atmosphere and receiving backscattering signals from molecules. Because of the weak backscattering signals, a lidar usually uses a high sensitivity photomultiplier as detector and photon counting technology for signal collection. The capturing of returned extremely weak backscattering signals requires the lidar to work on dark background with a long time accumulation to get high signal-to-noise ratio (SNR). Because of the strong solar background during the day, the SNR of lidar during daytime is much lower than that during nighttime, the altitude and accuracy of detection are also restricted greatly. Therefore this article describes an ultra-narrow bandwidth filter (UNBF) that has been developed on 354.7 nm wavelength of laser. The UNBF is used for suppressing the strong solar background that degrades the performance of Rayleigh wind lidar during daytime. The optical structure of UNBF consists of an interference filter (IF), a low resolution Fabry-Perot interferometer (FPI) and a high resolution FPI. The parameters of each optical component of the UNBF are presented in this article. The transmission curve of the aligned UNBF is measured with a tunable laser. Contrasting the result of with-UNBF and with-IF shows that the solar background received by a Licel transient recorder decreases by 50~100 times and that the SNR with-UNBF was improved by 3 times in the altitude range (35 km to 40 km) compared to with-IF at 10:26 to 10:38 on August 29, 2018. By the SNR comparison at four different times of one day, the ratio-values are larger than 1 over the altitude range (25~50 km) in general, the results illustrate that the SNR with-UNBF is better than that with-IF for Rayleigh Lidar during daytime and they demonstrate the effective improvements of solar background restriction of UNBF.

• 한국광학회지
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• 제15권5호
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• pp.455-460
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• 2004

1.064 $\mu\textrm{m}$ 파장의 연속발진 Nd:YAG 레이저를 펌핑 광원으로 하여 적외선 영역에서 광대역으로 파장 가변되는 연속발진 및 극초단펄스 C $r^{4+}$ :YAG 레이저를 자체 제작하였다. C $r^{4+}$ :YAG 레이저의 연속발진 및 펄스의 출력특성과 파장 가변 영역은 다음과 같다. 연속발진일 경우 1.436 $\mu\textrm{m}$에서 600 mW의 평균출력을 보였으나, 복굴절 필터를 삽입했을 경우는 1.492 $\mu\textrm{m}$근처에서 400 mW의 평균출력을 보였다. 펄스발진일 경우 1.436 $\mu\textrm{m}$에서 최초로 평균출력 320 mW의 모드록킹된 펄스가 발생하였지만 물 흡수대의 영향으로 불안정함을 피할 수 없었다. 따라서, 복굴절 필터를 사용하여 중심파장을 1.492 $\mu\textrm{m}$로 이동시켰으며 이 영역에서 안정한 상태의 모드록킹된 43 fs의 극초단 펄스를 생성하였다. 이 때의 평균출력은 280 mW이고, 반치폭(FWHM)은 45 nm이었다.