• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.182-185
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• 2008

The thermal performance of air receiver with a change of flow direction for dish solar collector. This system is installed and operated in Incheon, Korea. The thermal capacity of the system is about 5 kW thermal. The aperture diameter of the cylindrical-shape receiver which is made of stainless steel is 100 mm, and the height is 210 mm. Experiments are being carried out to investigate the thermal performance variation of the receivers with several design parameters such as the shape of the receiver, the flow directions and the flow rate of air. First, air flows into the upper part of the receiver, which is the opposite side of the aperture. After the air flows through the inside receiver, that goes out of the receiver through 3 exits which are located near the aperture. Second, air flows into the backside of the receiver, Which is the forward side of the aperture. After the air flows through the inside receiver, that goes out of the receiver through 1 exit. The results show that the system efficiency and receiver efficiency increase as the volume flow rate increases as expected.

• Journal of the Korean Solar Energy Society
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• v.29 no.4
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• pp.22-27
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• 2009

This study focus on verification of the thermal efficiency of volumetric receiver with 5k Wth Dish-type solar thermal system. Spiral flow path shaped on receiver and working fluid(steam) flow along with this flow path. Porous material for radiation-thermal conversion used in former researches are substituted with the stainless steel wall installed along the spiral flow path. Numerical analysis for the flow path and temperature distributions are carried out. Numerical results are compared with experimental data. Using the numerical model, the heat transfer characteristics of spiral type receiver for dish-type solar thermal systems are known and the thermal performance of the receiver can be estimated.

• Progress in Medical Physics
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• v.1 no.1
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• pp.31-42
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• 1990

The finding of long lived free radicals produced by ionizing radiation in organic crystals and the quantification of this effect by electron spin resonance(ESR) spactroscopy has proven excellent dosimetric applicability. The tissue equivalent alanine dosimeter also appear appropriate for radiation therapy level dosimetry. The dose measurement was performed in a Rando phantom using high energy photons as produced by high energy medical linear accelerator and cobalt-60 teletherapy unit. The absorbed dose range of the ESR/alanine dosimetry system could be extended down to 0.1 Gy. The response of the alanine dosimeters was determined for photons at different therapeutic dose levels from less than 0.1 Gy to 100 Gy and the depth dose measurements were carried out for photon energies of 1.25MeV, 6 and 10 MV with alanine dosimeters in Rando phantom. Comparisons between ESR/alanine in a Rando phantom and ion chamber in a water phantom were made performing depth dose measurements to examine the agreement of both methods under field conditions.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.122-122
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• 2018

1. 배경 최근 IoT 기술이 발전함에 따라 각종 전자기기에 들어가는 센서들이 점점 늘어나고 있다. 특히 사용자 중심의 기기들은 기술이 발전함에 따라 집적화가 이루어지면서, 하나의 기기에서 온도, 습도, 조도 등의 다양한 정보를 처리하고 있다. 이에 따라 더 많은 기능을 사용하기 위해, 소모 전력 또한 점차 증가하고 있다. 그러나 부피는 한정되어 있어, 기존 배터리만으로는 증가하는 소모 전력을 모두 보완하기 어렵다. 또한 대표적인 사용자 중심 기기인 스마트폰에서는, 가장 많은 전력을 소모하는 부분이 점점 커지고 있다. 이에 대한 대책으로 버려지는 에너지를 수확하여 전기적인 에너지로 바꿔주는 에너지 하베스팅 기술이 각광을 받고 있다. 에너지 하베스팅 기술은 바람, 진동, 인체의 움직임 등의 기계적 에너지, 태양광, 실내등의 빛 에너지를 전기적인 에너지로 바꿔주는 기술을 말한다. 본 연구에서는 강유전체 고분자 내부에 양자점이 임베딩된 박막을 이용하여, 스마트폰에서 발생하는 빛 에너지와 손가락으로 디스플레이를 터치할 때 발생하는 기계적인 에너지를 모두 수확할 수 있는 새로운 소자를 제시하였다. 소자 내부에 있는 양자점은 빛 에너지를 산란 혹은 흡수하여 발광한 후, 고분자 내부의 전반사를 통해 양 옆에 있는 태양전지로 빛을 전달한다. 또한 컴포짓의 매트릭스를 이루고 있는 강유전체 폴리머인 P(VDF-TrFE)는 강유전 특성을 통해 마찰전기 에너지를 효율적으로 전기 에너지로 전환할 수 있다. 강유전체 특성에 의해 P(VDF-TrFE) 내부에 정렬된 Polarization은 퀀텀닷에 양자구속 스타크 효과(Quantum Confined Stark Effect)를 일으켜 더 긴 파장을 방출한다. 이렇게 바뀐 파장은 실리콘 태양전지에서 더 많이 흡수할 수 있는 영역으로 방출되어 태양전지 출력의 증가를 일으킨다. 마지막으로 실리콘 태양전지의 출력 증가를 보여줌으로써 이를 실험적으로 입증했다.

• Journal of Energy Engineering
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• v.17 no.4
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• pp.241-246
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• 2008

Increase of $CO_2$ by using fossil fuels makes mainly global warming and the international efforts to reduce the $CO_2$ emission is being promoted. Absorption process using aqueous alkanolamine solution to remove acid components in the mixed gases has been used commercially. This method was used to remove $CO_2$ in the flue gas in recent years. $CO_2$ Absorption characteristics of several aqueous alkanolamine solutions such as MEA, DEA and AMP was studied by measuring vapor-liquid-equilibrium(VLE) and absorption velocity in this study. VLE measuring equipment, shell and reactor type, was used to acquire VLE data, equilibrium $CO_2$ pressure(${P_{CO_2}}^*$) and time at each pulse gas input. We also acquired the $CO_2$ absorption velocity by measuring the time to arrive the VLE at $40{\sim}80^{\circ}C$ and first gas input. The $CO_2$ absorption capacity of MEA 10wt% solution was higher than two alkanolamine solutions at $40^{\circ}C$ and the equilibrium $CO_2$ loading was 0.5. Absorption capacity was excellent as follows; AMP>DEA>MEA. But absorption velocity was fast as follows; MEA>AMP>DEA. Though good absorbent was considered by many variables, absorption velocity and capacity was more important factor.

• Journal of Sensor Science and Technology
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• v.8 no.5
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• pp.359-367
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• 1999

CsI(Li) single crystals doped with 0.02, 0.1, 0.2 and 0.3 mole% lithium as an activator were grown by Czochralski method. The lattice structure of grown CsI(Li) single crystal was bcc, its lattice constant was $4.568\;{\AA}$. The absorption edge of CsI(Li) single crystal was 245 nm, and the spectral range of luminescence was $300{\sim}600\;nm$, its maximum luminescence intensity appeared at 425 nm. The energy resolutions of CsI(Li) single crystal doped with 0.2 mole% lithium were 14.5% for $^{137}Cs$(662 keV), 11.4% for $^{54}Mn$(835 keV) and 17.7% and 7.9% for $^{22}Na$(511 keV and 1275 keV), respectively. The relation formula of $\gamma$-ray energy versus energy resolution was ln (FWHM%) = -0.893lnE + 8.456 and energy calibration formula was ${\log}E_r=1.455\;{\log}(ch.)-1.277$. The phosphorescence decay time of CsI(Li) crystal doped with 0.2 mole% lithium was 0.51 s at room temperature, and its time resolution measured by CFT(constant-fraction timing method) was 9.0 ns.

• Journal of Radiation Protection and Research
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• v.37 no.1
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• pp.16-24
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• 2012

In the present study, a gamma-ray detector and associated signal processing circuit was developed for a side-absorber of a dual-mode Compton camera. The gamma-ray detector was made by optically coupling a CsI(Tl) scintillation crystal to a silicon photodiode. The developed signal processing circuit consists of two parts, i.e., the slow part for energy measurement and the fast part for timing measurement. In the fast part, there are three components: (1) fast shaper, (2) leading-edge discriminator, and (3) TTL-to-NIM logic converter. AC coupling configuration between the detector and front-end electronics (FEE) was used. Because the noise properties of FEE can significantly affect the overall performance of the detection system, some design criteria were presented. The performance of the developed system was evaluated in terms of energy and timing resolutions. The evaluated energy resolution was 12.0% and 15.6% FWHM for 662 and 511 keV peaks, respectively. The evaluated timing resolution was 59.0 ns. In the conclusion, the methods to improve the performance were discussed because the developed gamma-ray detection system showed the performance that could be applicable but not satisfactory in Compton camera application.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.349-356
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• 2004

자동차의 외관품질과 관련된 외판재용 고강도강으로는 내 dent성을 향상을 위해서 IF-HSS강과 BH강의 사용량이 크게 증가하였으며, 최근에는 490MPa급 DP강이 적용되기 시작하고 있다. 그리고 내판 판넬의 경우에는 고가공성 을 갖는 고강도강의 개발으로 고강도강의 사용량이 늘어나고 있다. 내판재 중 승객의 안전과 관련된 멤버, 필라와 같은 구조부재는 중간 정도의 강도를 갖는 고강도강을 주로 적용되어 왔으나, 최근 차체경량화 요구의 증가로 590MPa급 이상 고강도강이 적용되기 시작하였으며, 특히 고속변형에서 에너지 흡수능이 우수한 TRIP (Trans-formation Induced Plasticity)강 및 DP(Dual Phase)강에 대한 관심이 크게 증대되고 있다. 저속충돌에서 차체를 보호하는 범퍼보강재는 고강도화가 빠르게 진행되어, 현재는 석출경화강에 변태 조직 강화를 더한 780MPa급 이상의 초고강도강을 주로 사용하고 있으며, 1370MPa급 까지 적용하고 있다.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.162-167
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• 2004

The low velocity impact characteristics of composite laminate curved beams are investigated to increase damage tolerance and reduce the deflection. Drop weight impact tests of the composite curved beam were performed with respect to pre-load, then the damage after impact was measured by macrography. Also, finite element analyses were performed using ABAQUS to investigate the stress state of composite curved beam with respect to pre-load and impact. From the investigation, it was found that pre-load of the composite curved beams had much influence on impact damage of the curved beam, which showed good agreement with the experiment results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.10
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• pp.1155-1162
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• 2012

The purpose of this study is to investigate the effects of the bead shape on the crash performance of an aluminum crash box under a low-velocity impact condition. The initial peak load and impact energy absorption of a crash box with three types of bead shapes-edge concave, surface convex, and surface concave type-were studied through an FE analysis and an experiment. In addition, the effects of the bead shapes on the crash performance of the crash box were verified through a low-velocity-impact test with a front side member assembled with an aluminum crash box. The initial peak load of the surface-concave-type crash box was reduced by the bead, and therefore, deformation of the front side member at initial contact could be prevented. Furthermore, there was no deformation of the front side member after the impact test because the crash box with a surface-concave-type bead absorbed all the impact energy.