• 한국방사선학회논문지
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• 제17권4호
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• pp.497-506
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• 2023

의료기관의 방사선 업무 종사자의 경우 환자 보호와 정확한 시술을 위해 방사선 노출이 이루어져 저선량 피폭의 문제점을 안고 있다. 저선량 방사선 피폭은 주로 Apron 영역 이외에 신체 부분에서 발생되며, 가장 많은 곳이 손 등 피부이다. 특히, 의료인의 손은 시술 중 감각과 미세한 동작을 필요로 하기에 방사선 노출영역에서는 무방비 상태로 피폭의 위험성을 안고 있다. 납장갑 등 차폐체로 문제를 해결할 수 있지만, 이는 시술 중 손의 활동성을 제안하여 사용상의 어려움이 있다. 이러한 문제점을 해결하고자 기능성 방사선 보호효과를 얻을 수 있는 차폐크림을 개발하여 납당량 0.1 mmPb와 차폐성능을 비교하였다. 차폐크림 제조과정에서 크림의 밀도를 높이기 위해 기공을 줄이는 탈포과정을 추가하여 차폐성능을 개선하였다. 따라서 황산바륨을 주 재료로 사용한 차폐크림은 납 plate보다 차폐율이 낮은 실효에너지 영역에서는 59%, 높은 실효에너지에서는 37% 정도의 차이는 보여 기능성 방사선 방어효과가 있는 것으로 나타났다. 따라서 피부에 직접 사용할 수 있는 장점으로 상시 방어효과와 수술용 장갑 착용전에 사용이 가능한 것으로 사료된다.

• Journal of Radiation Protection and Research
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• 제27권2호
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• pp.121-126
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• 2002

본 연구는 지하수로부터 방출되어 가옥의 실내에 존재하는 라돈에 의한 체내축적량을 현실적으로 평가하는 방법을 보여준다. 먼저 지하수로부터 실내공기로 전달되는 과정을 모의하기 위해 2_구역모델을 개발하였다. 이 모델은 실내에서 발생하는 생활활동, 즉, 목욕, 세수, 세탁, 변기에서의 물사용에 의해 실내로 휘발, 이동하는 시간에 따를 라돈농도분포를 계산한다. 다음, 이 모델의 불확실성이 존재하는 입력인자들에 대해 불확실성분석을 수행하여 최종 실내라돈 농도분포를 결정하였다. 그리고 이러한 실내 라돈을 호흡하여 체내에 축적되는 양을 보다 정량적으로 모의하기 위해 PBPK 모델을 개발하였다. 불확실성이 포함된 라돈농도분포와 정량적인 체내축적모의를 위한 PBPK 모델의 결합으로 보다 현실적인 라돈의 체내축적량을 분석할 수 있다. 이러한 연구의 결과는 지하수로부터 발생하는 라돈에 의한 인체위해평가시 도움을 주리라고 판단된다.

• Corrosion Science and Technology
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• 제10권2호
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• pp.52-59
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• 2011

Corrosion of metallic materials occurs by the reaction with corrosive environment such as atmosphere, marine, soil, urban, high temperature etc. In general, reduction of thickness and cracking and degradation are resulted from corrosion. Corrosion in all industrial facilities and infrastructure causes large economic losses as well as a large number of accidents. Economic loss by corrosion has been reported to be nearly 1-6% of GNP or GDP. In order to reduce corrosion damage of industrial facilities, corrosion map as well as a systematic investigation of the loss of corrosion in each industrial sector is needed. The Corrosion Science Society of Korea in collaboration with 15 universities and institutes has started to survey on the cost of corrosion and corrosion map of Korea since 2005. This work presents the results of the survey on cost of corrosion by Uhlig, Hoar, and input-output methods, and the evaluation of atmospheric corrosion rate of carbon steel, weathering steel, galvanized steel, copper, and aluminum in Korea. The total corrosion cost was estimated in terms of the percentage of the GDP of industry sectors and the total GDP of Korea. According to the result of Input/output method, corrosion cost of Korea was calculated as 2.9% to GDP (2005). Time of wetness was shown to be categories 3 to 4 in all exposure areas. A definite seasonal difference was observed in Korea. In summer and fall, time of wetness was higher than in other seasons. Because of short exposure period (12 months), significant corrosion trends depending upon materials and exposure corrosion environments were not revealed even though increased mass loss and decreased corrosion rate by exposure time.

• 한국산학기술학회논문지
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• 제12권2호
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• pp.829-834
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• 2011

고 집적 회로의 제작에 있어서 노광 공정은 가장 중요한 기술로 주로 마스크 방식의 노광 방법을 사용하지만 다품종 소량 생산 및 주기적인 제품 변화에 있어서 효율적이지 못하기 때문에 마스크리스 리소그래피 기술이 노광공정에서 각광받고 있다. 본 연구에서는 DMD를 이용한 마스크리스 리소그래피에 있어 다중 레이저 빔의 에너지와 중첩도와의 연관성을 시뮬레이션을 통해 분석하였다. 시뮬레이션을 통해 최적의 스캔 라인 간격을 제시하였고, LDI 시스템을 이용한 노광 실험을 통해 미세 페턴의 정밀도를 향상시킬 수 있었다.

• 한국방사선학회논문지
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• 제12권7호
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• pp.827-832
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• 2018

대규모 데이터에 기반한 실제 사용 조건의 장기유효선량 분석 연구는 부족하다. 본 연구에서는 국내 324개 의료기관에서 사용하는 흉부 X건 검사의 노출조건에 대해 전산모사를 이용한 장기선량을 계산하고 평가하였다. 실험결과, 저에너지 파라미터 대역에서 유효선량은 0.024 mSv이고 비장, 부신, 폐 순으로 높았다. 고에너지 노출파라미터 대역에서 유효선량은 0.123 mSv이고 신장, 비장, 부신 순으로 높게 나왔다. Park의 연구에서 제안한 화질과 피폭을 고려한 최적의 조건을 사용했을 때 유효선량은 0.017 mSv 로 나타났다. 사용 에너지가 높아질수록 장기 전체의 유효선량이 높아지고 그 중 신장이 가장 크게 증가하였다. 연구결과는 흉부X선 검사 시 참고자료가 되고 환자 피폭저감에 도움을 줄 것이다.

• 방사성폐기물학회지
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• 제2권2호
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• pp.113-124
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• 2004

본 연구에서는 인체 내에서 방사성핵종의 거동에 관하여 국제방사선방호위원회에서 권고한 최근 호흡기 모델, 소화기 모델 및 생체동역학 모델을 사용하여 생물학적분석 자료로부터 섭취량과 예탁유효선량을 평가하기 위한 BIDAS 프로그램을 개발하였다. 프로그램은 생물학적분석 자료를 관리하는 데이터베이스 모듈, 각 방사성 핵종에 대한 예측 생물학적분석 양을 내장하고 있는 모듈, 측정된 생물학적분석 양에 근거하여 급성 및 만성 피폭으로부터 섭취량과 선량을 평가하는 계산모듈 등으로 구성되어 있다. 본 논문은 프로그램의 특성과 검증결과에 대해 기술한다.

• Journal of the Optical Society of Korea
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• 제20권2호
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• pp.269-275
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• 2016

This study has investigated the feasibility of 980-nm low-energy pulsed near-infrared laser stimulation to evoke auditory responses, as well as the effects of radiant exposure and pulse duration on auditory responses. In the experiments, a hole was drilled in the basal turn of the cochlea in guinea pigs. An optical fiber with a 980-nm pulsed infrared laser was inserted into the hole, orientating the spiral ganglion cells in the cochlea. To model deafness, the tympanic membrane was mechanically damaged. Acoustically evoked compound action potentials (ACAPs) were recorded before and after deafness, and optically evoked compound action potentials (OCAPs) were recorded after deafness. Similar spatial selectivity between optical and acoustical stimulation was found. In addition, OCAP amplitudes increased with radiant exposure, indicating a photothermal mechanism induced by optical stimulation. Furthermore, at a fixed radiant exposure, OCAP amplitudes decreased as pulse duration increased, suggesting that optical stimulation might be governed by the time duration over which the energy is delivered. Thus, the current experiments have demonstrated that a 980-nm pulsed near-infrared laser with low energy can evoke auditory neural responses similar to those evoked by acoustical stimulation. This approach could be used to develop optical cochlear implants.

• 환경생물
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• 제27권2호
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• pp.140-145
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• 2009

All organisms are being exposed to harmful factors present in the environmental. The combined action of various factors is a distinguishing feature of modern life. An interaction between two chemicals is considered as synergistic when the effect produced is greater than the sum of the two single responses. The biological effects due to the combined action of ionizing radiation with the other factor are hard to estimate and predict in advance. In the current study, we investigated the synergistic effects between ionizing and $HgCl_2$ using fish hepatoma cells (PLHC-1 cells). The results showed a dramatic decrease of cell viability after simultaneous treatment of PLHC-1 cells with ionizing radiation and $HgCl_2$. Neiither of the two had any cytotoxic effect when treated alone. The cytotoxicity of ionizing radiation was enhanced in the presence of $HgCl_2$. The synergistic effects were observed after exposure of the PLHC-1 cells to ionizing radiation combined with $HgCl_2$. The synergistic interaction was due to an increase of irreversibly damaged cells after the combined exposure. Analysis of the extent of synergistic interaction enables to make quantitative estimation of irreversibly damaged cells after the combined exposure. The present study suggests that PLHC-1 cells can serve as rapid screening tools for detecting the toxicity of harmful factors.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.398-398
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• 2007

The Liquid Crystal (LC) alignment uniformity is very important in LC devices. The alignment mechanism of LC molecules on a rubbed polyimide (PI) surface is very important for both LC fundamental research and application. So, Generally a rubbing method to align LC has been widely used to mass-produce LCD panels. But because rubbing method is contact method between rubbing fabric and indium-tin-oxide glass or flexible substrate, rubbing method has some defects, such as the electrode charges and the creation of contaminating particles. Thus we strongly recommend a non-contact alignment technique for getting rid of some defects of rubbing method. Most recently, the LC aligning capabilities achieved by ion-beam exposure on the organic and nonorganic thin film surface have been reported successfully. In this research, we studied the tilt angle generation and electro-optical performances for a NLC on homeotropic polyimide surfaces with ion-beam exposure. The LC aligning capabilities of a nematic liquid crystal (NLC) on a homeotropic PI surface using a new ion-beam method were studied. On the homeotropic PI surface, the tilt angle of the NLC by exposure ion-beam had a tendency to decrease as increased ion-beam energy density. And, on the homeotropic PI surface, the alignment character of the NLC with respect to ion-beam energy was good. And we achieved satisfactory result for EO character.

• Advances in concrete construction
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• 제5권5호
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• pp.513-537
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• 2017

In this study, the fracture toughness $K_{IC}$ of high performance concrete (HPC) was investigated by conducting three-point bending tests on a total of 240 notched beams of $500mm{\times}100mm{\times}100mm$ subjected to heating temperatures up to $450^{\circ}C$ with exposure times up to 16 hours and various heating and cooling rates. For a heating rate of $3^{\circ}C/min$, $K_{IC}$ for the hot concrete sustained a monotonic decrease trend with the increasing heating temperature and exposure time, from $1.389MN/m^{1.5}$ at room temperature to $0.942MN/m^{1.5}$ at $450^{\circ}C$ for 4-hour exposure time, $0.906MN/m^{1.5}$ for 8-hour exposure time and $0.866MN/m^{1.5}$ for 16-hour exposure time. For the cold concrete, $K_{IC}$ sustained a two-stage decrease trend, dropping slowly with the heating temperature up to $150^{\circ}C$ and then rapidly down to $0.869MN/m^{1.5}$ at $450^{\circ}C$ for 4-hour exposure time, $0.812MN/m^{1.5}$ for 8-hour exposure time and $0.771MN/m^{1.5}$ for 16-hour exposure time. In general, the $K_{IC}$ values for the hot concrete up to $200^{\circ}C$ were larger than those for the cold concrete, and an inverse trend was observed thereafter. The increase in heating rate slightly decreased $K_{IC}$, and at $450^{\circ}C$ $K_{IC}$ decreased from $0.893MN/m^{1.5}$ for $1^{\circ}C/min$ to $0.839MN/m^{1.5}$ for $10^{\circ}C/min$ for the hot concrete and from $0.792MN/m^{1.5}$ for $1^{\circ}C/min$ to $0.743MN/m^{1.5}$ for $10^{\circ}C/min$ for the cold concrete after an exposure time of 16 hours. The increase in cooling rate also slightly decreased $K_{IC}$, and at $450^{\circ}C$ $K_{IC}$ decreased from $0.771MN/m^{1.5}$ for slow cooling to $0.739MN/m^{1.5}$ for fast cooling after an exposure time of 16 hours. The fracture energy-based fracture toughness $K_{IC}$' was also assessed, and similar decrease trends with the heating temperature and exposure time existed for both hot and cold concretes. The relationships of two fracture toughness parameters with the weight loss and the modulus of rapture were also evaluated.