• Strategy21
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• 통권31호
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• pp.220-250
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• 2013

South Korean national security strategy should be developed to effectively handle and counter increasing maritime threats and challenges. There are three major maritime threats South Korea faces today; maritime disputes on the EEZ boundary and Dokdo islet issues, North Korean threats, and international maritime security. Maritime disputes in the region are getting intensified and turned into a military confrontation after 2010. Now regional countries confront each other with military and police forces and use economic leverage to coerce the others. They are very eager to create advantageous de facto situations to legitimize their territorial claims. North Korean threat is also increasing in the sea as we witnessed in the Cheonan incident and Yeonpyoung shelling in 2010. North Korea resorts to local provocations and nuclear threats to coerce South Korea in which it may enjoy asymmetric advantages. The NLL area of the west sea would be a main hot spot that North Korea may continue to make a local provocation. Also, South Korean national economy is heavily dependent upon foreign trade and national strategic resources such as oil are all imported. Without an assurance on the safety of sea routes, these economic activities cannot be maintained and expanded. This paper argues that South Korea should make national maritime strategy and enhance the strength of naval forces. As a middle power, its national security strategy needs to consider all the threats and challenges not only from North Korea but also to maritime security. This is not a matter of choice but a mandate for national survival and prosperity. This paper discusses the importance of maritime security, changing characteristics of maritime threats and challenges, regional maritime disputes and its threat to South Korea's security, and South Korea's future security strategy and ways to enhance the role of naval forces. Our national maritime strategy needs to show middle and long term policy directions on how we will protect our maritime interests. Especially, it is important to build proper naval might to carry out all the roles and missions required to the military.

• 한국광학회지
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• 제17권4호
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• pp.312-316
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• 2006

본 연구에서는 유기 섬광체와 플라스틱 광섬유를 이용하여 치료용 전자선의 계측을 위한 광섬유 방사선 센서를 제작하였다. 또한, 선형가속기에서 발생되는 고 에너지 전자선에 의해 광섬유 방사선 센서를 이용한 전자선 계측에 있어 방해요소로 존재하는 체렌코프 빛을 감법 및 광학 필터링을 이용하여 제거하였고 두 가지방법들을 비교, 분석하였다.

• 대한치과교정학회지
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• 제19권1호
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• pp.21-44
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• 1989

Incipient changes of the periodontal tissue in the pressure zones of rat molar subjected to the experimental force were studied by the transmission electron microscope. Experimental animals were consisted in 3 control and 21 experimental rats, of which one maxillary first molar was moved buccally with a fixed appliance which were exerting the force of 15 gm. After experimental period of 1 hour, 3 hours, 6 hours, 24 hours, 2 days, 3 days and 7 days, the animal were sacrificed with cardiac perfusion of $2.5\%$ glutaraldehyde in the sodium cacodylate buffer and the experimental teeth with surrounding periodontal structures were processed for electron microscope. At the beginning of the tooth movement, periodontal ligaments of the pressure were compressed and collagenous fibers were arranged parallel to the root of the teeth and cell free zones in company with cell necrosis were followed. Cell free zones at the periodontal ligaments appeared in the 3 hour survival group, and getting severe with time lapse it became widespread in 2-3 day survival group and undermining bone resorption as a healing process was observed in 7 day survival group. Dilatation of mitochondria and swelling of the rER in the fibroblast and other connective tissue cells in the periodontal ligament were observed in the 3 hour survival group, which were characteristics of the incipient changes in the compressed periodontal ligament. Dilatation of nuclear membrane and pyknosis were followed by the destruction of the nucleus and cell membrane. There were no evidence in cell damage or necrosis of the alveolar bone adjacent to the hyalinized area of periodontal ligaments.

• 센서학회지
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• 제15권3호
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• pp.186-191
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• 2006

In general, Cerenkov light is produced by a charged particle that passes through a medium with a velocity greater than that of visible light. Although the wavelength of Cerenkov light is very broad, the peak is in the almost visible range from 400 to 480 nm. Therefore, it always causes a problem to detect a real light signal that is generated in the scintillator on the fiber-optic sensor tip for dose measurements of high-energy electron beam. The objectives of this study are to measure, characterize and remove Cerenkov light generated in a fiber-optic radiation sensor tip to detect a real light signal from the scintillator. In this study, the intensity of Cerenkov light is measured and characterized as a function of incident angle of electron beam from a LINAC, and as a function of the energy of electron beam. As a measuring device, a photodiode-amplifier system is used, and a subtraction method using a background optical fiber is investigated to remove Cerenkov light.

• 대한기계학회논문집A
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• 제34권12호
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• pp.1837-1842
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• 2010

화석에너지의 고갈로 인한 대체 에너지 연구는 최근 수십 년 동안 계속 행해지고 있다. 원자력 에너지와 비교해서 낮은 전기발생 효율에도 불구하고, 환경친화적이며 태양이라는 영구성으로 태양에너지는 주목 받고 있다. 본 논문에서는 태양전지의 효율에 가장 영향을 미치는 인자로 햇빛 입사각의 변화와 Top Connector 형상이라 가정하고 MATLAB 과 MathCAD 를 이용하여 모사하였다. 실험모사 결과 상용화 제품인 500um 선폭, 5um 높이 Top Connector 형상과 비교하여, 최고 10%의 태양전지 효율증가는 Top Connector 후막 두께가 25~50 um, 선폭 두께가 50~100um 영역에서 찾을 수 있었다. 10 만 cps 의 점도를 갖는 은페이스를 500um 의 MDDW (Micro-Dispensing Deposition Writing) 직접분사 노즐을 이용하여 성공적으로 25 um 후막을 형성하였다.

• 방사성폐기물학회지
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• 제2권2호
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• pp.105-112
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• 2004

고준위 방사성폐기물 처분장에서 적용하고 있는 다중 방벽의 한 부분인 처분 용기는 벤토나이트 완충재의 팽윤과 지압으로부터 폐기물을 역학적으로 안정하게 보호함과 동시에 일정 기간 방사성폐기물의 유출을 억제하는 역할을 한다. 처분용기의 건전성은 엄격한 재질 선정과 품질 보증을 통해 확보된다. 그러나 용기 제작 과정이나 수송 중 예상치 못한 사건으로 인해 불량 용기가 발생할 가능성이 있다. 본 논문에서는 이와 같은 경우 방사성폐기물로 인해 생태계에 미치는 환경 영향을 연간 개인 선량으로 평가하였다. 연구결과 일부 불량 처분 용기가 발생하더라도 현 평가에 사용한 입력 데이터 범위에서는, 국내 고준위 방사성폐기물 처분 개념이 방사선적 안전성을 확보할 수 있는 것으로 판명되었다.

• 대한의용생체공학회:의공학회지
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• 제27권6호
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• pp.332-336
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• 2006

In this study, we have fabricated a fiber-optic radiation sensor using an organic scintillator for high energy electron beam therapy. The intensities of scintillating light from a fiber-optic radiation sensor are measured with different field size, electron beam energy and monitor unit of a clinical linear accelerator. To obtain percent depth dose(PDD), the amount of scintillating light is measured at different depth of polymethylmethacrylate(PMMA) phantom. Also the intensity of Cerenkov light is measured and characterized as a function of incident angle of electron beam and a subtraction method is investigated using a background optical fiber to remove a Cerenkov light.

• 한국인터넷방송통신학회논문지
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• 제14권6호
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• pp.41-46
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• 2014

여러 국가의 관련기관들은 지역 별로 방사능 정상범위를 제시해 주기적으로 검사하고 있으며 우리나라 역시 방사능 대책 인프라를 구축하여 항시 대비하고 있다. 특히 일본 후쿠시마 피폭사건과 같은 방사능오염이 빈번하게 발생함에 따라 방사능에 대한 사람들의 인식이 위험수준으로 변화하고 있다. 본 데이터는 방사능 정상수치와 관련해 미국정부에서 수집을 하여 각 속성정보들을 파악하고 초과한 수치를 비교분석하였다. 분석 방법으로는 군집화를 사용하고, 특히 EM 알고리즘과 SimpleKMeans 알고리즘을 토대로 실험하였다. 그 결과 정상범위 수치가 높을수록 초과할 확률이 높은 것으로 나타났으며 시간적비용이나 분석정도에 따라 사용할 알고리즘이 다를 수 있다는 것도 알 수 있다. 따라서 정상범위가 높은 지역일수록 해당 기관부처나 정부에서는 조사 빈도수를 높여 반영해야 한다.

• Journal of Radiation Protection and Research
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• 제9권2호
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• pp.55-60
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• 1984

Allyl diglycol carbonate(CR-39)에 조사(照射)된 60MeV의 질소이온을 검출하기 위한 최적부식 조건을 부식시간에 대한 비적밀도와 비적직경의 변화를 고려하여 $70^{\circ}C$, 20% NaOH 용액에 대해 부식시간 130분으로 정하였다. 이 조건에서 검출가능한 최대비적밀도는 $1.7{\times}10^7tr/cm^2$였으며 입사(入射)된 질소 이온의 총전하량의 증가에 따라 비적밀도가 선형적으로 증가하였다. 또한 $2{\mu}m$의 금박에 의한 질소 이온의 산란을 점선원(點線源)에 의한 Rutherford 산란으로 고려함으로써 측정된 상대산란확률이 이론치와 일치하여 선량측정이 가능하였으며 $12nC{\sim}100nC$의 입사(入射) 질소이온의 전하에 대해 $54{\sim}41%$의 검출 효율을 얻었다.

• Journal of Radiation Protection and Research
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• 제43권3호
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• pp.85-96
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• 2018

Background: A variety of inorganic scintillators have been developed and improved for use in radiation detection and measurement, and in situ gamma-ray spectrometry in the environment remains an important area in nuclear safety. In order to verify the feasibility of promising scintillators in an actual environment, a performance test is necessary to identify gamma-ray peaks and calculate the radioactivity from their net count rates in peaks. Materials and Methods: Among commercially available scintillators, $LaBr_3(Ce)$ scintillators have so far shown the highest energy resolution when detecting and identifying gamma-rays. However, the intrinsic background of this scintillator type affects efficient application to the environment with a relatively low count rate. An algorithm to subtract the intrinsic background was consequently developed, and the in situ calibration factor at 1 m above ground level was calculated from Monte Carlo simulation in order to determine the radioactivity from the measured net count rate. Results and Discussion: The radioactivity of six natural radionuclides in the environment was evaluated from in situ gamma-ray spectrometry using an $LaBr_3(Ce)$ detector. The results were then compared with those of a portable high purity Ge (HPGe) detector with in situ object counting system (ISOCS) software at the same sites. In addition, the radioactive cesium in the ground of Jeju Island, South Korea, was determined with the same assumption of the source distribution between measurements using two detectors. Conclusion: Good agreement between both detectors was achieved in the in situ gamma-ray spectrometry of natural as well as artificial radionuclides in the ground. This means that an $LaBr_3(Ce)$ detector can produce reliable and stable results of radioactivity in the ground from the measured energy spectrum of incident gamma-rays at 1 m above the ground.