• Composites Research
• /
• v.19 no.3
• /
• pp.1-6
• /
• 2006

As the structures of the high performance electronic equipments and devices recently become more complex, the electromagnetic interference (EMI) and compatibility (EMC) have been very essential for commercial and military purposes. Thus, sensitive electrical devices and densely packed systems need to be protected from electromagnetic wave. In this research, glass fabric/epoxy composites containing conductive multi-walled carbon nanotube (MWNT) and carbon fiber/epoxy composites as electrical shielding materials were fabricated and electrical properties of the composites were measured. The concerning frequency band is from 300 MHz to 1 GHz. The performances of composite shielding enclosures were predicted using electromagnetic wave 3-D simulation tool, CST Microwave Studio. The shielding enclosure made of carbon fiber/epoxy composites were fabricated and the shielding effectiveness (SE) was measured in the anechoic chamber.

• Proceedings of the Korea Contents Association Conference
• /
• 2015.05a
• /
• pp.175-176
• /
• 2015

몬테카를로 기법을 기반으로 한 모의실험을 통해 방사성 핵종별 주사기 차폐기구의 재질 및 두께에 대한 차폐분석 결과, 텅스텐, 납, 비스무스 경우 가장 높은 차폐효과를 보였다. 그러나 $^{18}F$ 선원의 경우, 차폐두께가 낮은 영역에서 저 원자번호 재질보다 더 높은 에너지를 나타냈으나, 이후 증가된 차폐두께에서는 더 낮은 에너지 분포를 나타냈다. 그 외 재질의 경우 구리, 철, 스테인리스 강, 황산바륨의 순서로 에너지가 낮은 분포를 나타냈고, 알루미늄, 플라스틱, 콘크리트, 물의 경우 핵종별로 각기 다른 양상을 나타냈으며, 상대적으로 감마선의 투과의 증가로 인해 전체적으로 차폐효과가 떨어지는 것으로 나타냈다.

• Radiation Oncology Journal
• /
• v.10 no.2
• /
• pp.155-161
• /
• 1992

The eye lens is known to be radiosensitive organ and catarat can be induced by relatively low dose of radiation. In the treatment of head and neck tumors, shielding blocks are frequently used to minimize dose on sensitive organs. The shielding block, which is made of high atomic number materials (cerrobend), produce significant dose perturbations in megavoltage photon beams. The effects of these perturbations of eye shielding blocks are measured with film and ion chambers for the treatment of head and neck malignancies. Optimum parameters for the treatment are suggested.

• The Journal of the Korea Contents Association
• /
• v.15 no.7
• /
• pp.282-288
• /
• 2015

A monte carlo simulation about shielding material and thickness of the syringe shield for radiation shield was performed. As a result of analysis, high atomic number materials such as tungsten, lead and bismuth have the highest shielding effect. However, $^{18}F$, $^{67}Ga$ and $^{111}In$ show high energy distribution in the region with thin shielding thickness. As the thickness of shielding materials increased, the energy distribution decreased due to reduction of ${\gamma}$-ray. In the case of low atomic number materials, they, showed energy distribution from highest to lowest, were barium sulfate, steel, stainless, iron and copper. Aluminum, plastic, concrete and water showed diverse aspect. they showed relatively high energy distribution because of increased ${\gamma}$-ray that penetrate the shield.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.15 no.2
• /
• pp.124-131
• /
• 2004

최근 국내에서 전자파 내성에 대한 규제실시로 전자파 차폐 기술에 대한 인식이 높아지고 있으며, 특히 시스템 레벨의 전자파 차폐효과에 대한 관심이 크게 고조되고 있다. 그러나 전자/통신기기에 대한 전자파 장해현상 문제를 제품 개발 기간 내에 완전하게 해결하기란 이론만큼 쉽지 않으며, 전자파 장해는 반복적인 설계 수정 및 디버깅 작업으로 밖에 해결할 수 없는 골치 아픈 문제로 생각되고 있다.(중략)

• Journal of Korean Society of Transportation
• /
• v.20 no.5
• /
• pp.55-66
• /
• 2002

In many countries the principle of shielding is employed to permit a more logical approach to restricting new construction and prescribing obstacle marking and lighting. It also reduces the number of cases of new construction requiring review by authorities. Shielding principles are employed when some object, an existing building or natural terrain, already penetrates above one of the obstacle limitation surfaces described in Annex 14. If it is considered that the nature of an object is such that its presence may be permanent, then additional objects within a specified area around it may be permitted to penetrate the surface without being considered as obstacle. The shielding effect of immovable obstacles laterally in final approach and missed approach areas is more uncertain. In certain circumstances, it nay be advantageous to preserve existing unobstructed cross section areas, particularly when the obstacle is close to the runway. This would guard against future changes in either approach or take-off climb area specifications or the adoption of a turned take-off procedure.

• Proceedings of the Korea Society for Industrial Systems Conference
• /
• 2002.06a
• /
• pp.62-68
• /
• 2002

In this paper, we have developed the Up-Convertor for CATV Head/End using 54∼750 MHz. We have individually designed and fabricated the main circuit of Up-converter such as Amplifier, frequency mixer, Voltage Controlled Oscillator(OSC), and we have realized the implementation for System Module in each circuit, so we have achieved a small size, light weight. and we have focused to have a shielding technique in high frequency bandwidth.

• Korean Chemical Engineering Research
• /
• v.45 no.6
• /
• pp.547-553
• /
• 2007

The catalytic cracking of n-octane over FER, MFI, MOR and BEA zeolites was studied by the protolytic cracking mechanism in order to understand the effect of pore structure of zeolites on their product composition and deactivation. The selectivities for $C_3$ and $C_3{^=}$ were high over the zeolites with medium pores due to additional cracking, while those for $C_4$ and $C_4{^=}$, the initial products, were high over the zeolites with large pores. MFI zeolite showed slow deactivation due to small carbon deposit, while FER zeolite with small pores deactivated rapidly with severe carbon deposit. The deactivation of BEA zeolite was slow even with a large amount of carbon deposit, but MOR zeolite showed a rapid deactivation even with a small amount of carbon deposit. The conversion measured along with the time on stream on these zeolite catalysts was simulated by a mechanism based on the simplified reaction path of n-octane cracking and the deactivation related to the pore blockage by carbon deposit.

• Progress in Medical Physics
• /
• v.12 no.1
• /
• pp.71-77
• /
• 2001

The region, near the edge of a radiation beam, where the dose changes rapidly according to the distance from the beam axis is known as the penumbra. There is a sharp dose gradient zone even in megavoltage photon beams due to source size, collimator, lead alloy block, other accessories, and internal scatter ray. We investigate dosimetric characteristics on penumbra regions of a standard collimator and compare to those of theoritical model for the optimal use of the system in radiotherapy. Peripheral dose distribution of 6 W Photon beams represents penumbral forming function as the depth. Also we have discussed that the peripheral dose distribution of clinical photon beams, differences between calculation dose use of emperical penumbral forming function and measurements in penumbral region. Predictions by emperical penumbral forming functions are compared with measurements in 3-dimensional water phantom and it is shown that the method is capable of reproduceing the measured peripheral dose values usually to within the statistical uncertainties of the data. The semiconductor detector and ion chamber were positioned at a dmax depth, 5cm depth, 10cm depth, and its specific ratio was determined using a scanning data. The effective penumbra, the distance from 80% to 20% isodose lines were analyzed as a function of the distance. The extent of penumbra will also expand with depth increase. Difference of measurement value and model functions value according to character of the detector show small error in dose distribution of the peripheral dose.