• 한국레이저가공학회지
• /
• 제9권2호
• /
• pp.1-9
• /
• 2006

In this paper, we investigated the characteristics of fatigue fracture on TB(Tailored Blank) weldment by comparing the fatigue crack propagation characteristics of base metal with those of TB welded sheet used for vehicle body panels. We also investigated the influence of center crack on the fatigue characteristic of laser weld sheet of same thickness. We conducted an experiment on fatigue crack propagation on the base metal specimen of 1.2mm thickness of cold-rolled metal sheet(SPCSD) and 2.0mm thickness of hot-rolled metal sheet(SAPH440) and 1.2+2.0mm TB specimen. We also made an experiment on fatigue crack propagation on 2.0+2.0mm and 1.2+1.2mm thickness TB specimen which had center crack. The characteristics of fatigue crack growth on the base metal were different from those on 1.2+2.0mm thickness TB specimen. The fatigue crack growth rate of the TB welded specimens is slower in low stress intensity factor range $({\Delta}K)$ region and faster in high${\Delta}K$ region than that of the base metal specimens. The slant crack angle slightly influenced the crack propagation of the TB specimen of 2.0+2.0mm thinkness.

• 대한전자공학회논문지SD
• /
• 제44권7호통권361호
• /
• pp.24-30
• /
• 2007

본 연구에서는 광 논리 및 광 스위칭 시스템에 응용할 수 있는 수직 구조 레이저 - 완전 공핍 광 싸이리스터 (vertical cavity laser - depleted optical thyristor, VCL-DOT)를 제작하고, 본 연구실에서 제안한 차동 스위칭 방법을 이용하여 광 로직(AND, OR, NAND, NOR, INVERT) 함수를 구현하였고, 그 특성을 측정, 분석하였다. 제작한 VCL-DOT는 0.65 mA의 낮은 레이징 문턱 전류, 0.38 mW/mA의 높은 slope efficiency, 그리고 낮은 입력 광 파워에도 높은 민감도를 보인다. 차동 소자타입의 광 싸이리스터를 이용하면 복잡한 전기 회로를 이용하지 않고도, 집적화된 단일 소자에서 간단한 기준 광입력 시호의 파워를 제어함으로써 다양한 광 로직 게이트를 구현할 수 있다는 장점을 갖는다.

• Bulletin of the Korean Chemical Society
• /
• 제16권7호
• /
• pp.654-657
• /
• 1995

A series of excitation spectra (7Fo→5Do transition) of Eu(Ⅲ) ion in aqueous solution ([Eu(Ⅲ)]=1.12 × 10-2 mol L-1; pH 1.0 to 7.0) were obtained under CO2 free atmosphere using a pulsed tunable dye laser system. The broad and low intensity spectra (peak maximum: 578.89 nm) showed that the trivalent ion (Eu3+) underwent a low degree of hydrolysis at pH below 6.0. Eu(Ⅲ) hydroxo complex formation seemed more significant at pH above 6.0, shown by the occurrence of intense new peak at 578.63 nm. The spectra of those solutions prepared in N2 atmosphere showed no signs of the presence of interfering carbonate species. The Eu(Ⅲ) hydroxo complex formation was not observed when complexation studies between Eu(Ⅲ) ion and weak organic acids (e.g. glutarate and diglycolate) were conducted at pH 6.0 or below.

• Journal of Microbiology and Biotechnology
• /
• 제29권6호
• /
• pp.887-896
• /
• 2019

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)-based pathogen identification relies on the ribosomal protein spectra provided in the proprietary database. Although these mass spectra can discern various pathogens at species level, the spectra-based method still has limitations in identifying closely-related microbial species. In this study, to overcome the limits of the current MALDI-TOF MS identification method using ribosomal protein spectra, we applied MALDI-TOF MS of low-mass profiling to the identification of two genetically related Bacillus species, the food-borne pathogen Bacillus cereus, and the insect pathogen Bacillus thuringiensis. The mass spectra of small molecules from 17 type strains of two bacilli were compared to the morphological, biochemical, and genetic identification methods of pathogens. The specific mass peaks in the low-mass range (m/z 500-3,000) successfully identified various closely-related strains belonging to these two reference species. The intensity profiles of the MALDI-TOF mass spectra clearly revealed the differences between the two genetically-related species at strain level. We suggest that small molecules with low molecular weight, 714.2 and 906.5 m/z can be potential mass biomarkers used for reliable identification of B. cereus and B. thuringiensis.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
• /
• pp.306.1-306.1
• /
• 2016

ZnO semiconductor material has been widely utilized in various applications in semiconductor device technology owing to its unique electrical and optical features. It is a promising as solar cell material, because of its low cost, n-type conductivity and wide direct band gap. In this work ZnO/Si heterojunctions were fabricated by using pulsed laser deposition. Vacuum chamber was evacuated to a base pressure of approximately $2{\times}10^{-6}Torr$. ZnO thin films were grown on p-Si (100) substrate at oxygen partial pressure from 5mTorr to 40mTorr. Growth temperature of ZnO thin films was set to 773K. A pulsed (10 Hz) Nd:YAG laser operating at a wavelength of 266 nm was used to produce a plasma plume from an ablated a ZnO target, whose density of laser energy was $10J/cm^2$. Thickness of all the thin films of ZnO was about 300nm. The optical property was characterized by photoluminescence and crystallinity of ZnO was analyzed by X-ray diffraction. For fabrication ZnO/Si heterojunction diodes, indium metal and Al grid patterns were deposited on back and front side of the solar cells by using thermal evaporator, respectively. Finally, current-voltage characteristics of the ZnO/Si structure were studied by using Keithly 2600. Under Air Mass 1.5 Global solar simulator with an irradiation intensity of $100mW/cm^2$, the electrical properties of ZnO/Si heterojunction photovoltaic devices were analyzed.

• 한국전기전자재료학회논문지
• /
• 제21권8호
• /
• pp.760-765
• /
• 2008

Low power laser therapy is internationally certified and is known to be effective in stimulating DNA in living organisms, increasing protein synthesis and activating cell division, smoothing blood circulation, promoting cell activation, cell regeneration and function. It also has anti-inflammatory, anti-edemic, anti-fibrous dysplastic and neuralogic hyperfunctional effects. This study was intended to verify the effect of LED irradiation therapy on wound healing in cell and animal tests by applying LED irradiator using a laser and laser diode, which was independently designed and developed to emit beams of similar wavelength to that of a laser. This equipment was fabricated using a micro-controller and a high brightness LED, and designed to enable us to control light irradiation time, intensity and reservation. In case of cell proliferation experiment, each experiment was performed to irradiation group and non-irradiation group for tissue cells. MTT assay method was chosen to verify the cell increase of two groups and the effect of irradiation on cell proliferation was examined by measuring 590 nm transmittance of micro-plate reader. In the wound healing experiment, 1$cm^2$ wounds on the skin wound of SD-Rat(Sprague-Dawley Rat) were made. Light irradiation group and none light irradiation group divided, each group was irradiated one hour a day for 9 days. As a result, the cell increase of tissue cells was verified in irradiation group as compared to non-irradiation group. And, compared with none light irradiation group, the lower incidence of inflammation and faster recovery was shown in light irradiation group.

• 한국광학회지
• /
• 제10권2호
• /
• pp.107-113
• /
• 1999

수차가 적은 홀로그래픽 스캐너는 기존의 렌즈나 거울과 같은 광학 소자의 사용 매수를 줄임으로써 제작 가격을 낮출 수 있다는 잠재적인 장점을 갖고 있다. 본 연구에서는 홀로그래픽 스캐너 설계에 광선 추적버블 적용하여 스캔 기능과 초점을 맺는 기능을 동시에 할 수 있는 홀로그래픽 광학 소자를 설계하였으며, 수차가 없는 직선의 스캔 라인을 얻기 위한 기록 및 재생 구조와 hologon 구조에 대해 조사하였다. Prototype으로 제작된 홀로그래픽 스캐너에서 bow는 전체 스캔 폭 300 mm에서 $\pm$133$\mu\textrm{m}$이었으며, spot의 크기는 100 $\mu\textrm{m}$ 이하로 얻을 수 있었다. 실험 결과 광선 추적을 이용한 설계 데이터의 유용성을 검증하였고 레이저 프린터나 디스플레이 분야 등으로의 응용 가능성을 제시하였다.

• 한국광학회지
• /
• 제1권1호
• /
• pp.1-6
• /
• 1990

Na 원자 증기에 대한 2광자 공명 3광자 이온화 실험을 실시하여 이온신호의 스펙트럼, 선폭, AC Stark 이동 및 이온화율의 레이저 강도 의존성 등을 측정하였으며, 이때 2광자 공명준위는 4D 준위[과정 I]와 5S 준위[과정 II] 였다. 과정 I과 II에서 이온신호 스펙트럼의 반치폭은 레이저의 강도(I)에 비례하였으며, 이온화율은 이론적으로 알려진 바와 같이 낮은 레이저 강도 영역에서 I3에 비례하여 증가하였다. 과정 I의 이온신호는 과정 II에 비해 20~25배 정도 컸으며, 3S$\longrightarrow$4D 전이의 Ac Stark 이동계수는 $174\pm60MHz/MW/textrm{cm}^2$로 측정되었다.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
• /
• pp.612-619
• /
• 2002

The dynamic behavior of Al-Mg alloys plasma was very unstable and this instability was closely related to the unstable motion of keyhole during laser irradiation. The keyhole fluctuated both in size and shape and its fluctuation period was about 440 ${\mu}{\textrm}{m}$. This instability has been estimated to be caused by the evaporation phenomena of metals with different boiling point and latent heats of vaporization. Therefore, the authors have conducted the spectroscopic diagnostics of plasma induced in the pulsed YAG laser welding of Al-Mg alloys in air and argon atmospheres. In the air environment, the identified spectra were atomic lines of Al, Mg, Cr, Mn, Cu, Fe and Zn, and singly ionized Mg line, as well as strong molecular spectrum of AlO, MgO and AIH. It was confirmed that the resonant lines of Al and Mg were strongly self-absorbed, in particular in the vicinity of pool surface. The self-absorption of atomic Mg line was more eminent in alloys containing higher Mg. These facts showed that the laser-induced plasma was relatively a low temperature and high density metallic vapor. The intensities of molecular spectra of AlO and MgO were different each other depending on the power density of laser beam. Under the low power density irradiation condition, the MgO band spectra were predominant in intensity, while the AlO spectra became much stronger in higher power density. In argon atmosphere the band spectra of MgO and AlO completely vanished, but AlH molecular spectra was detected clearly. The hydrogen source was presumably the hydrogen solved in the base Metal, absorbed water on the surface oxide layer or H$_2$ and $H_2O$ in the shielding gas. The temporal change in spectral line intensities was quite similar to the fluctuation of keyhole. The time average plasma temperature at 1 mm high above the surface of A5083 alloy was determined by the Boltzmann plot method of atomic Cr lines of different excitation energy. The obtained electron temperature was 3, 280$\pm$150 K which was about 500 K higher than the boiling point of pure aluminum. The electron number density was determined by measuring the relative intensities of the spectra1lines of atomic and singly ionized Magnesium, and the obtained value was 1.85 x 1019 1/㎥.

• 한국정보통신학회논문지
• /
• 제11권12호
• /
• pp.2335-2342
• /
• 2007

최근에 레이저를 임상치료에 응용하는 사례가 증가하고 있다. 그러나 전기적 관점에서 레이저 자극이 경락에서 어떠한 전기적 반응을 유도할 수 있는지에 대한 연구가 미흡하고, 명확한 치료효과에 대한 임상보고가 발표되지 않고 있다. 본 논문에서는 레이저자극과 수기자극이 경락전위 형성에 미치는 영향을 비교 관찰하여 전기적 관점에서 침술과정 및 침술효과에 대한 객관적 근거를 제시하고자 하였다. 수양명대장경상의 삼간혈(LI3)을 각각 자극했을 경우, 삼간혈(LI3)과 합곡혈(LI4)에서의 전위변화를 측정하였다. 그 결과, 레이저 자극 시, 평균 피크전위는 $7.53{\pm}3.44{\mu}V$로 매우 낮게 나타났고, 자극전후 전위패턴에 차이가 없어서 레이저 자극에 대한 유효한 전기반응으로 간주하기 어렵다. 접지조건에 대한 수기자극에서는 평균피크전위가 $2.65{\pm}1.53mV$로 매우 높게 측정되었고, 개인별, 접지조건에 따라 전위크기와 패턴이 다양하게 나타나고 전위패턴은 주로 캐패시터의 충방전 전위와 매우 비슷하게 나타났다. 또한, 절연자침의 경우에서는 접지조건에 관계없이 평균 피크 전위가 $0.25{\pm}0.16mV$로 수기자극 전위에 비하여 매우 낮게 나타났으며, 이는 침자극에 대한 유효한 전기 반응으로 간주하기 어렵다. 따라서, 전기적 관점에서 침술과정과 침술효과는 시술자와 피시술자간의 생체이온전하의 이동에 의한 에너지 교감현상임을 확인하고, 수기자극은 경락의 전기반응을 유도하는 반면, 레이저 자극은 경락의 전기적 반응을 유도하기 어렵다는 것을 확인하였다.