• Korean Journal of Optics and Photonics
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• v.22 no.2
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• pp.96-101
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• 2011

Operational and thermal characteristics of a thin disk Yb:YAG crystal with a thickness of 0.8 mm were studied using as a pumping source a fiber-coupled 930 nm laser diode. The heat generated in the crystal was dissipated by placing both surfaces in contact with copper plates with central hole, and the dependence of the temperature change in the illuminated spot on hole size was investigated by measuring the spectral change of the lasing peaks. The slope efficiency and optical-to-optical efficiency with respect to the LD pump power were as high as 42.2% and 34.8%, respectively. The temperature at the illuminated spot increased with diode current and with increasing hole size of the copper plate. When the hole size considerably exceeded the crystal thickness, the temperature rise deviated from the linear increase at high pump power.

• 전자공학회논문지 IE
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• v.48 no.2
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• pp.32-39
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• 2011

The output image of the uncooled thermal infrared camera is difficult the identification of target because of the limited dynamic range and the various noises. Retinex algorithm based on the theory of the human visual perception is known to be effective contrast enhancement technique. However, the image quality is insufficient when it is adopted to the narrow dynamic range image as the infrared image. In this paper, we propose the revised retinex algorithm to enhance the contrast of the infrared image. To improve the contrast enhancement performance, we designed the new dynamic range compression function instead of log function. To reduce the noise and compensate the loss of edge, we added the contrast compensation procedure in the MSR image generation process. According to the output picture comparing and numerical analysis, the proposed algorithm shows the better contrast enhancement performance and the more suitable method for the infrared image enhancement.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.5
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• pp.262-266
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• 2013

A new concept of periapical radiography, intra oral x-ray tube and detector system is introduced. It is new system that a miniature x-ray tube is inserted into mouse and it acquired digital image using external detector. In this study, we have investigated temperature and dose distribution of insertional x-ray tube for periapical radiography. To analyze temperature characteristic of x-ray tube, we attached the thermocouple to surface of x-ray tube and we measured the temperature according to distance. Also, we measured the dose distribution of a miniature x-ray tube according to distance. As a result, temperature was constant to $27^{\circ}C$ over 2mm without cooling system, dose distribution of x-ray tube was 3.14 and 1.84mGy in 3 and 5cm, respectively. Therefore, the proposed x-ray system works in lower dose than conventional dental x-ray system. Thus, it is considered that new concept of system will have a significant effect on medical imaging technology.

• Journal of the Korean Chemical Society
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• v.21 no.6
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• pp.427-433
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• 1977

A neutron activation method has been developed for the simultaneous determination of chromium, iron, lanthanum, scandium and zinc in river-water samples. The sample is sealed in the silica ampoule without pretreatment and irradiated for a week at a thermal neutron flux of $1{\times}10^{13}n{\cdot}cm^{-2}{\cdot}sec^{-1}$. After cooling for about two days, the elements in the sample are sequentially extracted at different pH by 0.1M oxine-chloroform solution. The organic layers are checked by Gamma-ray spectrometry with $″3\;{\times}\;3″$ NaI (T1) detector connected to a 800-channel pulse hight analyzer. The ppb concentration of the elements in most of river-water samples could be determined by this method. The tracer study for the quantitative separation of the elements was also carried out.

• Resources Recycling
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• v.6 no.1
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• pp.29-34
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• 1997

The feasibility of using the industrial inorganic waste materials such as l~mestone sludge. Soundly sand. coal fly 'ash, and chemical glasses as a raw material for cement clinker by melting treatmeut was iovestigated. The slag wh~ch is obtained from thc melts of the mixtnres of waste materials is composed of P-C,S(ZCaO - SIOJ and C,AS(ZCaO . AI,O, . SiO,) phases. The effect of melting tempcrabre, coaling condition and CIS ratio on the fo~mation of P-C,S phasc was examed. In order to obtain thc P-CiS phase which is useful in thc utilhtion as a clinkcr malcrid, it B found that sudl considerations as low melting temperature as possible of the wastc mixhire, quenching the melts and law CIS ratio of the mlxhlre are necessary.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.11
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• pp.7-13
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• 2002

BSCT 320${\times}$240 IRFPA detector module is implemented, which is a key component in uncooled thermal imaging systems. The detector module consists of two parts, infrared sensitive pixel array and read-out integrated circuit(ROIC). The BSCT 320${\times}$240 pixels are made by laser scribe process and 10-${\mu}m$ micro-bump to satisfy 50-${\mu}m$ pitch and 95-% fill-factor. The ROIC has been designed to electrically address the pixels sequentailly and to improve signal-to-noise ratio with single transistor amplifier, HPF, tunable LPF and clamp circuit. The fabricated hybrid chip of detector and ROIC has been mounted on the TEC built-in ceramic package for more stable operation and tested for lots of electrical and optical properties. The IRFA sample has shown successful properties and met with good results of fill-factor, detectivity and responsivity.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.7
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• pp.103-110
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• 2014

Recent TSV based 3D Integrated Circuit (IC) technology needs more powerful thermal management techniques. However, because cooling cost and form factor are restricted, thermal management are emphasis on software based techniques. But in case of throttling thermal management which one of the most candidate technique, increasing bus occupation induce total performance decrease. To solve communication bottleneck issue in TSV based 3D SoC, we proposed adaptive throttling technique Experimental results show that the proposed method can improve throughput by about 72% compare with minimal path routing.

• Korean Journal of Optics and Photonics
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• v.20 no.5
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• pp.276-280
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• 2009

A Cr:YAG crystal was used as a saturable absorber for passive Q-switching of a Nd:$YVO_4$ laser which was pumped by a 1-W continuous wave laser diode. The first surface of the Cr:YAG was high-reflection coated for the pump wavelength. The high-reflection coating improved the absorption efficiency of the pump beam in the Nd:$YVO_4$ through double pass absorption. It also prevented pump beam induced partial bleaching of the Cr:YAG. The peak-to-peak pulse fluctuation of passively Q-switched laser output was approximately 4 %. The minimum pulse-width was measured to be 7.11 ns. Also, the average pulse repetition rate was 9 kHz and the maximum output power was 16.27 mW.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.151.2-151.2
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• 2012

터보펌프 구동에 사용된 가스발생기 생성가스를 연소기로 공급하여 주추력 발생에 사용하는 다단연소 사이클 로켓엔진은 고추력을 요하는 우주 발사체에 널리 사용되고 있다. 다단연소 사이클 로켓엔진에 사용되는 가스발생기를 예연소기라 부르며 케로신과 액체산소를 추진제로 하는 다단연소 사이클 로켓엔진에는 산화제 과잉 예연소기가 사용된다. 예연소기는 터보펌프 구동을 목적으로 하기 때문에 예연소기 생성가스의 횡단면 온도분포는 터빈에 의해 제한되는 온도범위 내에서 균일하여야 하며 넓은 운전영역에서 안정적인 연소가 이루어져야 한다. 산화제 과잉 예연소기는 모든 추진제가 혼합헤드를 통해 분사되는 방식과 추진제를 혼합헤드와 연소실로 나누어 공급하는 방식이 있다. 기술검증을 위해 산화제 일부와 연료를 혼합헤드를 통해 연소실에 공급하여 1차 연소시키고 나머지 산화제를 연소실 냉각채널을 거쳐 연소실 중앙의 분사공을 통해 연소실로 주입하여 기화시키는 형태로 최종적으로 연소압 20MPa, 혼합비 60에서 작동하는 산화제 과잉 예연소기를 설계하여 연소시험을 수행하였다. 혼합헤드에는 별도의 점화용 분사기 없이 전체 연료 분사기를 통해 점화용 연료인 TEA/TEB 혼합물을 분사하여 점화하였다. 추진제를 2단으로 공급할 수 있도록 고안된 가압식 연소시험 설비에서 10회, 누적 60초 이상의 연소시험이 성공적으로 수행되었다. 연소시험결과 넓은 작동영역에서 안정적 연소특성과 생성가스 온도 분포의 균일성을 확인할 수 있었다. 고온 고압의 산화제 과잉 예연소기 기술 확보를 통해 케로신/액체산소 다단연소 사이클 로켓엔진 개발을 위한 기술적 기반을 마련하였다.

• Applied Biological Chemistry
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• v.40 no.5
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• pp.395-399
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• 1997

Lintnerization properties and yield of enzyme-resistant starch in maize starches with different amylose content were investigated. Hydrolytic patterns of starches showed two distinct stages. With decreasing the amylose content, hydrolysis extents of starch increased. X-ray diffraction patterns of Amloca, PFP and commercial maize starch were the A crystalline type, and those of Amaizo 5 and Amylomaize VII were the B crystalline type. As acid hydrolysis time increased, the relative crystallinity of starches increased. After heating-cooling treatment was repeated up to 4 times, the yield of RS increased with increasing the amylose content. The yields of RS in lintnerzed maize starches decreased with acid treatment.