• 제목/요약/키워드: Air gap

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핵의학과 내 작업 환경에서 공기층 납치마의 피폭선량 감소 효과 평가 (Evaluation of Reductive Effect of Exposure Dose by Using Air Gap Apron in Nuclear Medicine Related Work Environment)

  • 이왕희;안성민
    • 한국콘텐츠학회논문지
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    • 제14권12호
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    • pp.845-853
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    • 2014
  • 본 연구는 핵의학과에서 가장 많이 사용되고 있는 $^{99m}Tc$에서 방출되는 140 keV 감마선을 기준으로, 세 가지 실험을 통해 기존에 사용되고 있는 납치마와 공기층 납치마를 이용해 Optically Stimulated Luminescence Dosimeter (OSLD) 선량계에 도달하는 선량을 측정하고, 공기층 납치마의 피폭선량 감소효과에 대해 연구했다. 그 결과 선량계와 납판 사이의 거리를 납치마의 공기층이라고 가정했을 때, 선량계와 0.2 mm 납판 사이의 거리가 없는 0 Cm일 때 측정된 10개의 선량계의 평균값은 0.515 mSv이고, 선량계와 납판 사이의 거리를 20 Cm로 떨어뜨린 경우 10개의 측정값의 평균이 0.138 mSv로 약 0.377 mSv의 선량 감소 효과를 보였다. 선량계와 0.5 mm 납판 사이의 거리가 없는 0 Cm일 때 10개의 선량계의 측정값의 평균은 0.296 mSv이고, 선량계와 납판 사이의 거리를 20 Cm로 떨어뜨린 경우 10개의 측정값의 평균이 0.075 mSv로 약 0.221 mSv의 선량 감소 효과를 보였다. 3일 간의 누적선량을 측정한 결과, 공기층이 없는 납치마의 경우 측정된 누적선량의 평균은 0.238 mSv, 공기층 납치마의 누적선량은 0.176 mSv로 0.062 mSv의 선량 감소 효과를 보였다. 한 달 간의 누적선량을 측정한 결과, 공기층이 없는 납치마의 누적선량의 평균은 0.59 mSv, 공기층 납치마의 누적선량은 0.54 mSv로 0.05 mSv의 선량 감소 효과를 보였다.

Analytical Calculation for Predicting the Air Gap Flux Density in Surface-Mounted Permanent Magnet Synchronous Machine

  • Feng, Yan-li;Zhang, Cheng-ning
    • Journal of Electrical Engineering and Technology
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    • 제12권2호
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    • pp.769-777
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    • 2017
  • The research of air gap flux density has a significant effect on predicting and optimizing the structure parameters of electrical machines. In the paper, the air gap coefficient, leakage flux factor and saturation coefficient are first analytically expressed in terms of motor properties and structure parameters. Subsequently, the analytical model of average air gap flux density for surface-mounted permanent magnet synchronous machines is proposed with considering slotting effect and saturation. In order to verify the accuracy of the proposed analytical model, the experiment and finite element analysis (FEA) are used. It shows that the analytical results keep consistency well with the experimental result and FEA results, and the errors between FEA results and analytical results are less than 5% for SPM with high power. Finally, the analytical model is applied to optimizing the motor structure parameters. The optimal results indicate that the analytical calculation model provides a great potential to the machine design and optimization.

선도체 대 평면전극 갭에서 평면전극에 연소화염 존재시 대기의 절연파괴 특성 (Breakdown Characteristics of Air in the Gap between Line Conductor and Plane Electrode in Case of Combustion Flame on the Plane Electrode)

  • 김인식
    • 조명전기설비학회논문지
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    • 제27권4호
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    • pp.73-80
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    • 2013
  • Breakdown characteristics of air in the vertical arrangement of line conductor and plane electrode in case of combustion flame on the plane electrode are examined by the application of AC. and DC voltages to the gap. In order to investigate the effect of paraffin flame on the breakdown characteristics of air, flashover voltages are measured according to the variation of the gap length and the horizontal distance between the flame and the line conductor. As the result of the experiment, flashover voltages are substantially lowered down to 29.8% in case of the AC voltage, and 16.1% in case of the negative DC voltage, when in the presence of the flame. from 100% when in the absence of flame. Flashover voltages of air in the range of smaller than 3㎝ at the horizontal distance are increased in the proportion of the gap length and the horizontal distance in case of both AC and negative DC voltages. But before the flashover occurs, the flame is extinguished by such corona wind that is produced from the line conductor when the gap length and the horizontal distance reach to a certain degree. The effect of relative air density and the phenomenon of thermal ionization are analysed as the reduction factors of flashover voltages, due to high temperature of the flame.

원자력 발전 원자로 용기의 열손실 설계인자에 관한 연구 (Parametric Study on the Heat Loss of the Reactor Vessel in the Nuclear Power Plant)

  • Jong-Ho Park;Seoug-Beom Kim
    • Journal of Advanced Marine Engineering and Technology
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    • 제28권5호
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    • pp.827-836
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    • 2004
  • The design parameter of the heat loss for the pressurized water reactor has been studied. The heat loss from the reactor vessel through the air gap. insulation are analysed by using the computational fluid dynamics code, FLUENT. Parametric study has been performed on the air gap width between the reactor vessel wall and the inner surface of the insulation, and on the insulation thickness. Also evaluated is the performance degradation due to the chimney effect due to gaps left between the panels during the installation of the insulation system. From the analysis results, the optimal with of air gap and insulation thickness and the value of heat loss are obtained The results show how the heat loss varies with the air gap width and insulation thickness. The temperature and the velocity distributions are also presented. From the results of the evaluation. the optimal air gap width and the optimal insulation thickness are obtained. As the difference between the predicted heat loss and measured heat loss from the reactor vessel is construed Primarily as losses due to chimney effect. the contribution of the chimney effect to the total heat loss is quantitatively indicated.

Optimum Air-Gap Flux Distribution with Third Harmonic Rotor Flux Orientation Adjustment for Five-Phase Induction Motor

  • Kang, Min;Yu, Wenjuan;Wang, Zhengyu;Kong, Wubin;Xiao, Ye
    • Journal of Electrical Engineering and Technology
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    • 제13권1호
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    • pp.315-325
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    • 2018
  • This paper investigates optimum air-gap flux distribution with third harmonic rotor flux orientation adjustment for five-phase induction motor. The technique of objective is to generate a nearly rectangular air-gap flux, and it improves iron utilization under variation loading conditions. The proportional relations between third harmonic and fundamental plane currents is usually adopted in the conventional method. However, misalignment between fundamental and third harmonic component occurs with variation loading. The iron of stator teeth is saturated due to this misalignment. This problem is solved by third harmonic rotor flux orientation adjustment simultaneously, and direction and amplitude are changed with mechanical load variation. The proposed method ensures that the air-gap flux density is near rectangular for a maximum value from no load to rated load. It is confirmed that the proposed method guarantees complete both planes decoupling with third harmonic flux orientation adjustment. The effectiveness of the proposed technique is validated experimentally.

흉부(胸部) 고관전압(高管電壓) 촬영(撮影)에 있어 Air Gap Technique를 이용한 산란선(散亂線) 경감(輕減)에 관(關)한 연구(硏究) (Reduction of Scattered Radiation by Air Gap Technique for High Kilovoltage Chest Roentgenography)

  • 허준;김창균;강홍석;윤철호;이상석;임한영;송재관
    • 대한방사선기술학회지:방사선기술과학
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    • 제3권1호
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    • pp.57-66
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    • 1980
  • X-ray grid is the most important means to reduce the scattered ray from patients, but alternative way is air gap technique that is another name of Groedel technique. This technique is mainly used in chest radiography. Authors performed an experimental study on the air gap technique for chest radiography and obtained the results as follows; 1. In using the high voltage air technique, scattered ray could be reduced effectively, while the percentage of scattered ray was slightly increased than conventional grid technique. 2. In film contrast, 30cm air gap technique was inferior to 12:1 grid technique and contrast improvement was increased when the object was thicker and higher voltage was used. 3. The patient exposure dose was reduced about $25{\sim}45%$ compared with conventional grid technique by air gap technique used.

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건축물 구획실간 틈새에서의 누설유동에 대한 수치모델 연구 (Study on Numerical Model of Leakage Flow at Gap between Compartments in a Building)

  • 김정엽;김지석
    • 설비공학논문집
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    • 제25권10호
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    • pp.562-567
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    • 2013
  • 1D-numerical analysis of the network algorithm with the orifice equation for the relationship between pressure difference and flowrate has been mostly used to analyse leakage flow at the gap. In this study, a 3D-numerical method applying momentum loss model to the gap region in the computational domain is represented to reflect effectively the effect of leakage flow by determining the proportion of pressure difference to air passage velocity. While the 3D-numerical method is verified through the computation of the two compartments model, the numerical analysis of the stack effect in a building stairway is performed. As the temperature of air outside drops, the pressure in the upper stairway and leakage flowrate through the gap in the door rise. The change of gap area does not have an effect on pressure in the stairway for the analysis conditions.

PZT틀 이용한 Air gap 안테나의 주파수 특성에 관한 연구 (Frequency properties of Air gap Antenna using PZT)

  • 김영훈;우형관;임승혁;송준태
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2000년도 춘계학술대회 논문집 전자세라믹스 센서 및 박막재료 반도체재료 일렉트렛트 및 응용기술
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    • pp.164-167
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    • 2000
  • This paper investigated that resonant frequencies of microstrip patch antenna were tunable when piezoelectric materals were used as the antenna substrates. The resonant frequencies of the air-gap antenna using the piezoelectric substrate were able to be controlled by applied AC voltage. The frequency variation of the antenn was great when PZT were applied voltage of the resonant frequency.

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셀룰로오스 섬유의 방사시 공기층 거리가 물성에 미치는 영향 (Effects of Air-Gap Distances on Properties of Cellulose Fiber Spun)

  • 홍영근;조성무;이화섭
    • 한국염색가공학회지
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    • 제5권2호
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    • pp.139-143
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    • 1993
  • The effects of air-gap distance on properties of cellulose fiber spun from the 6 wt% solution of cellulose in monohydrate N-methylmorpholine N-oxide (NMMO) were investigated. The diameter of fiber spun was drastically reduced in 10 cm of air-gap distance at fixed drawing speed, however, no great change was observed beyond 40 cm. As the distance lengthened, the Cellulose II structure was first appeared and followed by Cellulose II and IV mixed morphology. Also the degree of crystallinity and the size of crystals were tending to decrease.

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주파수 조정이 가능한 PZT Air-Gap Antenna (Frequency Agile Air-Gap Microstrip Antennas using PZT)

  • 우형관;하용만;오승재;송준태
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2001년도 하계학술대회 논문집
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    • pp.772-775
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    • 2001
  • This paper investigated that resonant frequencies of microstrip patch antenna were frequency aigle when PZT were used as the antenna substrates. The resonant frequencies of the antenna using the piezoelectric substrate were able to be controlled by applied voltage. The frequency variation of the air gap antenna was 16MHz when the voltage variation was 12[KV/cm].

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