• Journal of Embryo Transfer
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• v.27 no.1
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• pp.37-43
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• 2012

This study evaluated a method of sorting X and Y chromosomes based on size using the forward angle light scatter related refractive index (FSC) of a flow cytometer. Hanwoo bulls sperm were separated to X and Y chromosomes by the parameters of FSC or Hoechst 33342 intensity. As a result, using monitor program linked flow cytometry during sorting processing, the purities were $97{\pm}0.57$ or $96{\pm}0.67%$ for the X-fraction and $96{\pm}0.33$ or $97{\pm}1.33%$ for the Y-fraction in the two sperm sorting methods. There were no differences in the X and Y ratios (X and Y %) between the sperm sorting methods based on FSC or DNA content. The proportions of female and male embryos used for in vitro fertilization and development were $66.03{\pm}3.31$ or $69.37{\pm}1.41%$, and $70.56{\pm}2.42$ or $56.11{\pm}3.09%$ when sperm were processed using the sex sorting method by FSC or Hoechst 33342. In conclusion, further study is needed to determine the optimum procedure and improve the nozzle to enhancing sorting accuracy or efficiency. Also, the findings of this study do not negate the possibility that the difference method of sperm sorting cannot use a UV laser beam.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.9
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• pp.1400-1409
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• 2001

This paper describes a fiber optic sensor suitable for non-contact detection of ultrasonic waves. This sensor is based on a fiber optic Sagnac interferometer. Quadrature phase bias between two interfering laser beams in Sagnac loop is introduced by a polarization controller. A stable quadrature phase bias can be confirmed by observing the interferometer output versus phase bias. This method eliminates a digital signal processing for detection of ultrasonic waves using Sagnac interferometer. Interference intensity is affected by the frequency of ultrasonic waves and the time delay of Sagnac loop. Collimator is attached to the end of the probing fiber to focus the light beam onto the specimen surface and to collect the reflected light back into the fiber probe. Ultrasonic waves produced by conventional ultrasonic transducers are detected. This fiber optic sensor based on Sagnac interferometer is very effective for detection of small displacement with high frequency such as ultrasonic waves used in conventional non-destructive testing.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.187-187
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• 2013

양자점(Quuantum dot, QD)은 0차원 특성을 가지는 구조로 양자 구속 효과로 인하여 bulk와 는 다른 구조적, 광학적, 전기적 특성을 가지고 있다. InAs QD는 size와 barrier의 bandgap 조절을 이용하여 쉽게 bandgap을 바꿀 수 있는 장점이 있어 solar cell, semiconductor laser diode, infrared photodetector 등으로 많은 연구가 이루어지고 있다. 일반적으로 Stranski-Krastanov (SK) mode로 성장한 InAs QD는 보통 GaAs epilayer와의 lattice mismatch (7%)를 이용하여 성장을 하고 이로 인하여 strain을 가지고 있고 QD의 density와 stack이 높을수록 strain이 커진다. 하지만 sub-monolayer (SML) QD 같은 경우 wetting layer가 생기는 지점인 1.7 ML이하에서 성장되는 성장 방식으로 SK-QD보다는 작은 strain을 가지게 된다. 또 QD의 size가 작아 SK-QD보다 큰 bandgap을 가지고 있다. 본 연구에서는 분자선 에피택시(molecular beam epitaxy, MBE)를 이용하여 semi-insulating GaAs substrate 위에 InAs QD를 0.5/1/1.5/1.7/2/2.5 monolayer로 성장을 하였다. GaAs과 InAs의 성장온도와 성장속도는 각각 $590^{\circ}C$, 0.8 ML/s와 $480^{\circ}C$, 0.2 ML/s로 성장을 하였으며 적층사이의 interruption 시간은 10초로 고정하였고 10주기를 성장하였다. Photoluminescence (PL)측정 결과 SML-QD는 size에 따라서 energy가 1.328에서 1.314 eV로 약간 red shift를 하였고 SK-QD의 경우 1.2 eV의 energy정도로 0.1 eV이상 red shift 하였다. 이는 QD size에 의하여 energy shift가 있다고 사료된다. 또 wetting layer의 경우 1.41 eV의 energy를 가지는 것으로 확인 하였다. SML-QD는 SK-QD 보다 반치폭(full width at half maximum, FWHM)이 작은 것은 확인을 하였고 strain field의 감소로 해석된다. 하지만 SML-QD의 경우 SK-QD보다 상대적으로 작은 PL intensity를 가지고 있었다. 이를 개선하기 위해서는 보다 높은 QD density를 요구하게 되는데 growth temperature, V/III ratio, growth rate 등을 변화주어서 연구할 계획이다.

• Journal of Nuclear Fuel Cycle and Waste Technology
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• v.1 no.1
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• pp.65-73
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• 2013

Temperature-dependent hydrolysis behaviors of aqueous U(VI) species were investigated with time-resolved laser fluorescence spectroscopy (TRLFS) in the temperature range from 15 to $75^{\circ}C$. The formation of four different U(VI) hydrolysis species was measured at pHs from 1 to 7. The predominant presence of $UO{_2}^{2+}$, $(UO_2)_2(OH){_2}^{2+}$, $(UO_2)_3(OH){_5}^+$, and $(UO_2)_3(OH){_7}^-$ species were identified based on the spectroscopic properties such as fluorescence wavelengths and fluorescence lifetimes. With an increasing temperature, a remarkable decrement in the fluorescence lifetime for all U(VI) hydrolysis species was observed, representing the dynamic quenching behavior. Furthermore, the increase in the fluorescence intensity of the further hydrolyzed U(VI) species was clearly observed at an elevated temperature, showing stronger hydrolysis reactions with increasing temperatures. The formation constants of the U(VI) hydrolysis species were calculated to be $log\;K{^0}_{2,2}=-4.0{\pm}0.6$ for $(UO_2)_2(OH){_2}^{2+}$, $log\;K{^0}_{3,5}=-15.0{\pm}0.3$ for $(UO_2)_3(OH){_5}^+$, and $log\;K{^0}_{3,7}=-27.7{\pm}0.7$ for $(UO_2)_3(OH){_7}^-$ at $25^{\circ}C$ and I = 0 M. The specific ion interaction theory (SIT) was applied for the extrapolation of the formation constants to infinitely diluted solution. The results of temperature-dependent hydrolysis behavior in terms of the U(VI) fluorescence were compared and validated with those obtained using computational methods (DQUANT and constant enthalpy equation). Both results matched well with each other. The reaction enthalpies and entropies that are vital for the computational methods were determined by a combination of the van't Hoff equation and the Gibbs free energy equation. The temperature-dependent hydrolysis reaction of the U(VI) species indicates the transition of a major U(VI) species by means of geothermal gradient and decay heat from the radioactive isotopes, representing the necessity of deeper consideration in the safety assessment of geologic repository.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.512-513
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• 2008

The study examined what effects 100kHz PWM LED light irradiation causes to bone marrow cells of SD-Rat when LED characterized cheap and safe is used onto the light therapy by replacing the low 1evel laser. We developed the equipment palpating cell proliferation using a high brightness LED. This equipment was fabricated using a micro-controller and a high brightness LED, and designed to enable us to control light irradiation time, intensity, frequency and so on. Especially, to control the light irradiation frequency, FPGA was used, and to control the change of output value, TLC5941 was used. Consequent1y, the current value could be controlled by the change of 1eve1 in Continue Wave(CW) and Pulse Width Modulation(PWM), and the output of a high brightness LED could be controlled stage by stage. 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 590nm transmittance of ELISA reader. As a result, the cell increase of Rat bone marrow cells was verified in 100kHz PWM LED light irradiation group as compared to non-irradiation group.

• Polymer(Korea)
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• v.37 no.1
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• pp.47-51
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• 2013

In this work, the effect of alumina nanofibers on thermal conductivity and fracture toughness of alumina nanofibers and powder filled epoxy (EP) composites were investigated with varying alumina nanofiber content from 20 to 100 phr. Thermal conductivity was tested using a laser flash analysis (LFA). The fracture toughness of the composites were studied through the critical stress intensity factor ($K_{IC}$) measurement. The mophologies were observed by scanning electron microscopy (SEM). From the results, it was found that the thermal conductivity was enhanced with increasing alumina nanofiber content, which played a key factor to determine the thermal conductivity. The $K_{IC}$ value was increased with increasing alumina nanofiber content, whereas the value decreased above 40 phr alumina nanofiber content. This was probably considered that the alumina nanofiber entangled each other in EP due to an excess of alumina nanofibers.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.179-179
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• 2010

1차원 나노구조를 갖는 ZnO를 성장하기 위해 Laser ablation, Chemical vapor deposition (CVD), Chemical transport method, Molecular beam epitaxy, Sputtering 등의 다양한 형성법들이 이용되어지고 있다. 특히 대량생산과 경제성 측면에서 많은 장점을 가지고 있는 CVD를 이용한 ZnO 성장 및 응용 연구가 활발하게 수행되고 있다. 본 연구에서는 Thermal CVD를 이용하여 반응물질과 기판 사이의 거리, 기판온도, $O_2$/Zn 비율 등의 성장변수를 변화시켜 ZnO 나노구조를 성장하고 구조 및 광학적 특성을 연구하였다. Scanning electron microscope를 통한 구조 특성평가 결과 반응물질과 기판 사이의 거리가 13 cm 이하의 조건에서 ZnO 나노구조들은 나노판(Nanosheet)과 나노선(Nanowire)이 혼재하여 성장된 것을 보였다. 그리고 반응물질과 기판사이의 거리가 15 cm 이상부터 나노판이 없어지고 수직한 ZnO 나노막대(Nanorod)가 형성되었다. 상온 Photoluminescence 스펙트럼에서 반응물질과 기판사이의 거리가 5에서 15 cm로 증가할수록 결함 (Defect)에 의해 발생된 515 nm 파장의 최대세기 (Maximum intensity)가 10배 이상 감소한 반면, ZnO 나노구조에 의한 378 nm 파장의 NBE발광 (Near band edge emission)은 8배 이상 증가하였다. 이러한 구조 및 광학적 결과로부터, 질서 없이 성장된 것보다 수직 성장된 ZnO 나노구조의 결정질(Crystal quality)이 좋은 것을 확인하였다. 이를 바탕으로 성장변수에 따른 ZnO 나노구조의 형성 메커니즘을 Zn와 O 원자의 성장거동을 기반으로 한 모델을 이용하여 해석하였다.

• Korean Journal of Remote Sensing
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• v.26 no.1
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• pp.9-20
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• 2010

The LIDAR data can be efficiently utilized for automatic reconstruction of 3D models of objects on the terrain and the terrain itself. In this paper, we attempted to generate simulated waveforms of FW (Full-Waveform) LIDAR (LIght Detection And Ranging). We performed the geometric modeling of the sensor and objects, and the radiometric modeling of the waveform intensity. First, we compute the origins and directions of the sub-beams by considering the divergence effects of a laser beam. We then searched for the locations at which the sub-beams intersected with the objects, such as ground, buildings and trees. Finally, we generate the individual waveforms of the reflected sub-beams and the waveform of the entire beam by summing the individual ones. With the experimental results, we confirmed the waveforms were reasonably generated, showing the characteristics of the surfaces the beam interacted with.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.2
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• pp.84-88
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• 2021

The change of the photoluminescence properties of La2O3-CaF2-Al2O3-SiO2 glass-ceramics doped with rare earth material, that is used as laser and optical sensors, was analyzed according to heat treatment temperature. The heat treatment conditions for fabricating glass-ceramics were obtained through non-isothermal thermal analysis, and X-ray diffraction analysis was performed to determine the degree of crystal growth and kinds of crystal phases generated according to the heat treatment temperature. Using Scherrer's equation, it was predicted that crystals with a size of 25~40 nm would be generated inside the glass-ceramics. Photoluminescence (PL) analysis showed that the specimens heat-treated at 660℃ to 670℃ for 1 hour had the highest PL intensity. Also, from the CIE color coordinate analysis, all glass-ceramics specimens emitted red-orange light regardless of the heat treatment condition.

• Journal of Radiation Protection and Research
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• v.43 no.4
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• pp.160-169
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• 2018

Background: This study aims to develop an integrated optical system that can simultaneously or selectively measure the signals obtained from radioluminescence (RL), thermoluminescence (TL), and optically stimulated luminescence (OSL), which are luminescence phenomena of materials stimulated by radioactivity, heat, and light, respectively. The luminescence mechanism of various materials could be investigated using the glow curves of the luminescence materials. Materials and Methods: RL/TL/OSL integrated measuring system was equipped with a X-ray tube (50 kV, $200{\mu}A$) as an ionizing radiation source to irradiate the sample. The sample substrate was used as a heating source and was also designed to optically stimulate the sample material using various light sources, such as high luminous blue light emitting diode (LED) or laser. The system measured the luminescence intensity versus the amount of irradiation/stimulation on the sample for the purpose of measuring RL, TL and OSL sequentially or by selectively combining them. Optical filters were combined to minimize the interference of the stimulation light in the OSL signal. A long-pass filter (420 nm) was used for 470 nm LED, an ultraviolet-pass filter (260-390 nm) was used for detecting the luminescence of the sample by PM tube. Results and Discussion: The reliability of the system was evaluated using the RL/OSL characteristics of $Al_2O_3:C$ and the RL/TL characteristics of LiF:Mg,Cu,Si, which were used as dosimetry materials. The RL/OSL characteristics of $Al_2O_3:C$ showed relatively linear dose-response characteristics. The glow curve of LiF:Mg,Cu,Si also showed typical RL/OSL characteristics. Conclusion: The reliability of the proposed system was verified by sequentially measuring the RL characteristics of radiation as well as the TL and OSL characteristics by concurrent thermal and optical stimulations. In this study, we developed an integrated measurement system that measures the glow curves of RL/TL/OSL using universal USB-DAQs and the control program.