• 대한방사선기술학회지:방사선기술과학
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• 제42권6호
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• pp.429-434
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• 2019

The gonads are directly affected by radiation exposure during radiography of the pelvis, abdomen, and spine. Exposure of the gonads to radiation can cause genetic mutations and can result in the occurrence of malignant tumors. In this study, we created three types of shielding material shapes for shielding of the ovaries, which are the gonads of female during radiography of the pelvis, and comparative evaluations using shadow shielding methods. The source surface distance(SSD) was 100 cm and the field size was 42 cm × 43 cm. The three types of shielding material shapes(type 1, 2 and 3) were assessed and the entrance surface dose in the ovaries were measured. The thickness of the shielding material was expanded from 0.3 mm to 2.4 mm and after five repetitions, radiation values were measured and mean values were calculated. The mean dose were 3.09 mGy for type 1, 3.54 mGy for type 2, and 3.19 mGy for type 3, indicating that the measurements were the lowest for type 1. When an additional filter of 0.2 Cu + 1 Al was used, the dose were 3.72 mGy for type 1, 5.43 mGy for type 2, and 4.05 mGy for type 3, indicating that the measurements were the lowest for type 1. The results show that, even if the shielding material is not thick, in other words, even with a thickness of 2.94 mGy for the SN 3(0.9 mm) of type 1, shielding can be achieved, with a patient dose lower than the diagnostic reference level(3.42 mGy). Additionally, among the three types of shielding material, the type 1 appeared to be the most appropriate shielding material. It is thought that the use of shielding material could reduce the risk factors for stochastic effects or critical effects of ionizing radiation during pelvic or lumbar radiography.

• Nuclear Engineering and Technology
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• 제49권1호
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• pp.277-284
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• 2017

This paper presents the establishment and characterization of a neutron calibration field using a bare $^{252}Cf$ source of low neutron source strength in Vietnam. The characterization of the field in terms of neutron flux spectra and neutron ambient dose equivalent rates were performed by Monte Carlo simulations using the MCNP5 code. The anisotropy effect of the source was also investigated. The neutron ambient dose equivalent rates at three reference distances of 75, 125, and 150 cm from the source were calculated and compared with the measurements using the Aloka TPS-451C neutron survey meters. The discrepancy between the calculated and measured values is found to be about 10%. To separate the scattered and the direct components from the total neutron flux spectra, an in-house shadow cone of 10% borated polyethylene was used. The shielding efficiency of the shadow cone was estimated using the MCNP5 code. The results confirmed that the shielding efficiency of the shadow cone is acceptable.

• Journal of Welding and Joining
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• 제11권1호
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• pp.73-79
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• 1993

The phenomenon of metal transfer has been investigated for different transfer modes using a digital high speed motion analyzer and an arc shadow-graphing system based on a laser source and related optical system. It was observed that the pinch instability phenomenon did not occur for the globular transfer mode, since the liquid globule was then spherical rateher than a cylindrical liquid bar. On increasing the ratio of carbon dioxide to argon, the transition current from globular to spray transfer generally increased, but it is interesting that the transition was observed to occur at the lowest current in a 5% CO$_{2}$-95% argon gas mixture. For pure carbon dioxide and helium shielding gases, the drop frequency increased slowly with increasing current. At high currents or an argon based shielding gas, the length of liquid bar decreased as the carbon dioxide content increased. The acceleration of a droplet within the arc was determined using the gas drag force theory and was found to be greater than the experimental results.

• 한국농림기상학회지
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• 제23권4호
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• pp.306-315
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• 2021

본 연구는 유리온실 내에서 초분광 영상을 취득하였을 때 차광 커튼과 할로겐이 DN value스펙트럼에 미치는 영향에 관한 것이다. 국립식량과학원 남부작물부 유리온실에 설치된 자동영상취득시스템을 이용하였으며 30° 기울어진 보정용 Tarp (1.4×1.4 m, 12%)를 설치한 후 하우징과 거리별(0.7~2.1 m) 영상데이터를 4가지 조건으로 3반복 취득했다. 차광 커튼과 할로겐을 모두 사용하지 않고 영상을 취득하였을 경우, 직달광부분과 그림자부분은 550 nm를 기준으로 스펙트럼의 변동성이 커졌다. 직달광부분과 그림자부분의 평균 변동계수(Coefficient of variation, CV)값은 각각 1.8%, 4.2%이며 그림자 유무에 관계없이 CV값을 계산 할 경우 12.5%로 증가되었다. 차광 커튼을 사용하지 않고 할로겐만을 이용한 경우 직달광부분과 그림자 부분의 CV 값은 2.6%, 10.6%이고 그림자 유무에 관계없이 CV 값을 계산할 경우 11.2%로 나타났으며 하우징과 거리에 따른 할로겐 보광량 차이로 인해 스펙트럼 변화폭이 증가되었다. 차광커튼만을 사용한 경우 CV 값은 1.6%이며 직달광과 그림자부분의 구분이 사라졌다. 차광 커튼과 할로겐을 모두 사용한 경우 하우징과 거리에 따른 할로겐의 보광량 차이로 CV 값은 10.2%로 증가했다. 할로겐과 차광 커튼을 모두 사용한 영상의 높이 범위 별 CV 값을 계산하였을 때 0.1 m 범위는 1.4%, 0.2 m범위는 1.9%, 0.3 m 범위는 2.6%, 0.4 m 범위는 3.3%로 나타났다. 따라서 온실에서 표준화된 영상데이터를 취득하기 위해서는 차광 커튼을 이용해 광을 균일하게 해야하고 할로겐램프를 이용해 보광 할 경우 대상의 수직 높이가 0.2 m 미만이며 대상과 하우징의 거리가 일정하게 유지 되었을 때 유효하다고 판단된다.

• 한국소음진동공학회논문집
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• 제15권8호
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• pp.891-896
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• 2005

On the basis of theoretical studies on the effect of the cylinders attached to semi-infinite screens, the tangential sound power-transport parallel to the surface of the attached cylinder is minimized by means of a secondary sound field, which is generated from a part of the attached cylinder. The numerical study shows the possibility of deflecting the incident sound by minimizing the sound field of the upper sections. The acoustical shadow region was more pronounced in both near- and far-field compared to the passive case with rigid surface, i.e. without active control. For a relatively wide frequency range it was possible to enhance shielding effects only with few secondary sources and error microphones. In this paper effects of control parameters on the actively controlled sound field near the top edge of noise barriers are studied. Results of numerical study and model measurements are shown and discussed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.32-34
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• 2007

The X-ray projection system has long been used for steel-tube inspection and weld monitoring. The thickness of tubes and welded areas is based on the evaluation of radiographic shadow projections. The traditional tangential measurement estimates the distance of border lines of the projected wall shadows of a tube onto a radiographic image detector. The detected image in which although there is a variety of noise may be sectioned into several partitions according to its specific blocks. Imaging noise originates from most of elements of the system, such as shielding CCD camera, imaging screen, X-ray source, inspected object, electronic circuits and etc. The tangential projection incorrectness and noise influence on imaging quality. In this paper we first sectionalize the X-ray image on the basis of vertical contrast difference. And next functional and statistic analysis are carried on at each region. Geometrical distance and unsharpness of the edge caused by visual evaluation uncertainties are also discussed.

• Journal of Electrical Engineering and information Science
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• 제3권2호
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• pp.245-250
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• 1998

Novel fabrication process of vertical spring for micro mirror array is proposed. The proposed fabrication process adopts a shadow evaporation process using shielding screen structure on top of the sacrificial layer. The 50${\times}$50 micro mirror arrays are fabricated using the proposed process and ceramic packaged. The static and dynamic characteristics of mirror are measured. The mirror plate touches substrate at 16V and the response time of about 16.8 ${\mu}\textrm{s}$. The resonant frequency of mirror is 16kHz. The spring thickness is calculated from static characteristic to be 1075${\AA}$.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.482-485
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• 2004

On the basis of theoretical studies on the effect of the cylinders attached to semi-infinite screens, the tangential sound power-transport parallel to the surface of the attached cylinder is minimized by means of a secondary sound field, which is generated from a part of the attached cylinder. The numerical study shows the possibility of deflecting the incident sound by minimizing the acoustic surface impedance of the upper sections. The acoustical shadow region was more pronounced in both near- and far-field compared to the passive case with rigid surface, i.e. without active control. For a relatively wide frequency range it was possible to enhance shielding effects only with few secondary sources and error microphones. In this paper effects of some control parameters on the actively controlled sound field near the top edge of noise barriers are studied. Results of numerical study and model measurements are shown and discussed.

• 한국환경복원기술학회지
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• 제22권2호
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• pp.1-12
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• 2019

Open space planners and designers should consider scientific and quantified functions of trees when they have to locate where to plant the tree. However, until now, most planners and designers could not consider them because of lack of tool for considering scientific and quantitative tree functions. This study introduces a tree location supporting tool which focuses on the multi-objective including scientific function using ACO (Ant colony optimization). We choose shading effect (scientific function), shielding, and openness as objectives for test application. The results show that when the user give a high weight to a particular objective, they can obtain the optimal results with high value of that objective. When we allocate higher weight for the shading effect, the tree plans provide larger shadow value. Even when compared with current tree plan, the study result has a larger shading effect plan. This result will reduce incident radiation to the ground and make thermal friendly open space in the summer. If planners and designers utilize this tool and control the objectives, they would get diverse optimal tree plans and it will allow them to make use of the many environmental benefits from trees.

• 대한교통학회지
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• 제23권3호
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• pp.21-34
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• 2005

항공의 전 분야에 있어 항공안전은 아무리 강조해도 지나치지 않으며 항공안전에 주의를 기울이지 못하여 발생되는 항공기사고(aircraft accidents)는 항공기의 전 비행단계중 약 70%가 비행장주위의 이 착륙단계에서 일어나는 CFIT(Controlled Flight into Terrain) 사고라는 것은 주지의 사실이다. 이러한 점을 고려 할 때에 비행장주위의 장애물(obstacle)을 관리(control)하는 것은 항공기사고를 방지하고 비행장의 장기적인 존속을 보장한다는 측면에서 항공안전차원의 안전운항에 지대한 역할을 한다고 할 수 있다. 그러나 안전운항이 보장되는 범위 내에서 비행장주위의 장애물에 대한 제한을 효율적으로 관리하고 비행장주위의 규제에 따른 사유재산권의 제한을 해소하며, 장애물을 관리하는데 소요되는 노력을 경감하기 위한 차폐이론(Shielding)의 적용 역시, 안전운항과 더불어 비행장주위 공역을 효율적으로 활용할 수 있다는 측면에서 중요하게 고려하여야 할 사항이다. 실제로 국제민간항공기구(ICAO)나 항공선진국들은 기존장애물의 영향이 미치는 음영면 이하의 장애물은 장애물로 간주하지 않는다는 차폐이론 적용하여 건축규제를 완화하거나 장애물 표시등의 의무를 면제하고 있다. 물론 이와 같은 차폐이론의 적용은 국제적으로 통일된 차폐기준에 따라 적용되는 것이 아니며 각 국가의 상황에 따라 또는 각 비행장의 환경에 따라 신규장애물의 차폐 여부를 확인하고 항공학적인 연구를 통하여 안전운항에 영향이 없다는 판단 하에 적용 관리하고 있다. 국내에서도 비행장주위에 장애물제한에 관하여 항공법에 규정하고 있고, 최근 개정안으로 제시되어진 동법 시행규칙에서는 국제민간항공기구의 차폐기준의 적용을 포함하는 신규 규정을 포함시켜 놓았다. 그러나 이러한 규정만으로는 비행장 주위의 항공장애물을 체계적으로 관리하기가 어려우며, 특히 국내 비행장 주위의 공역에서 차폐이론적용에 필요한 세부기준이 제시되어 있지 않다는 점에서 논란의 여지가 많다. 따라서 본 연구에서는 항공장애물과 관련된 국제민간항공기구(ICAO)의 규정 및 항공선진국들의 관련 규정을 검토 분석하고 국내의 현황과 비교 분석한 후 국제기준에 비추어 국내환경에서도 적용 가득한 비행장 공역에서의 항공장애물관리규정(안)의 방향을 제시하고자 한다. 특히 논란의 여지가 많은 차폐이론의 적용에 이어 명확한 기준방안을 제시하여 항공안전과 효율적인 공역운영을 위한 대안을 설정하는데 도움을 주고자 한다.