• 대한방사선기술학회지:방사선기술과학
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• 제37권2호
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• pp.101-107
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• 2014

이 연구는 디지털 유방확대촬영술에서 방사선 피폭을 감소시키며 영상의 질을 유지하기 위한 최적의 촬영조건을 알아보았다. 자동노출방식의 평균유선선량이 수동노출방식에 비해 높은 것으로 나타났다. 자동노출방식은 그리드(grid) 사용 여부에 따라 평균유선선량과 화질평가에 차이가 많았으나, 수동노출방식은 팬텀영상평가 점수에서만 차이가 있었다. 그러나 air gap technique을 사용할 경우 모든 노출방식에서 신호대잡음비의 증가가 뚜렷하게 나타났다. 따라서 유방확대촬영 시 air gap technique을 사용한다면 환자의 평균유선선량을 감소시키고 신호대잡음비를 높여 양질의 화질을 유지할 수 있을 것이다.

• 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.

• 한국방사선학회논문지
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• 제16권3호
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• pp.217-223
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• 2022

본 연구는 엑스선 흉부촬영에서 격자를 이용하여 촬영법과 Air Gap Technique을 이용한 촬영법에서 얻은 영상을 평가하기 위하여 대학병원 영상의학과에서 10년 이상 근무한 방사선사 선생님 5인에게 주관적 평가 ROC와 객관적 평가 SNR를 시행하였다. 분석한 결과는 Cronbach Alpha 값이 0.714로 유의하게 높았다. Air Gap Technique 촬영법에서 팬톰과 상수용체 간격을 20 cm 띄우고 관전압 100 kVp, 관전류와 촬영시간 8 mAs로 설정하고 촬영한 영상을 ROC 평가에서 18점, SNR 평가에서 6.149로 가장 높은 점수를 얻었다. 또한 격자를 이용하여 촬영법에서는 팬톰과 상수용체 간격을 15 cm 띄우고 관전압 110 kVp, 관전류와 촬영시간을 8 mAs에서 촬영 시 ROC 평가점수가 19점과 객관적평가인 신호대잡음비(SNR)가 6,622으로 가장 높은 점수를 받았다. 이에 격자를 이용하여 나타나는 격자의 cut-off 현상으로 인하여 재촬영뿐만 아니라 판독지연, 환자의 피폭선량 증가, 기계적 수명단축 등의 단점을 벗어나는 Air Gap Technique 촬영법을 활용한다면, 중환자실 및 응급환자를 위한 이동형 엑스선 촬영장비를 사용할 경우를 포함하여 흉부 촬영 시에 많은 도움이 되리라 사료된다.

• 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.

• 한국자동차공학회논문집
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• 제10권1호
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• pp.115-124
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• 2002

The optimum design of auto-catalyst needs a good compromise between the pressure drop and flow distribution in the monolith. One of the effective methods to achieve this goal is to use the concept of radially variable cell density. However, there has been no study of evaluating the usefulness of this method on light-off catalyst. We have computationally investigated the effectiveness of variable cell density technique applied to the light-off catalyst using a three-dimensional integrated CFD model. in which transient chemical reacting calculations are involved. Computed results show that variable cell density technique can reduce the accumulated emissions of CO and HC during the early 100sec of FTP cycle by 86.78 and 80.87%, respectively, The effect of air-gap between the monoliths has been also examined. It is found that air-gap has a beneficial effect on reducing pressure drop and cold-start emissions.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.195-198
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• 1999

A technique is investigated for achieving broadband properties by controlling the operation frequency of microstrip antennas. The control is achieved by applying DC bias to the microstrip antenna. Air gap antenna with PZT post is fabricated. by using in C-band. In the case of Air gap antenna, the variation of center frequency was about 16Mhz and the bandwidth was increased up to 123.3% at 15dB, 160.7% at 20dB than before applying DC bias respectively. The change property of frequency in air gap antenna is nearly the same the C-V property in PZT.

• 한국광학회지
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• 제20권4호
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• pp.207-210
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• 2009

공초점 방식을 이용하여 두 기판사이의 얇은 공기갭의 두께를 측정하는 방법을 제안하였다. 공기갭이 약 200 nm 이내 일때는 두 기판면이 초점의 레일리 영역 안에 있으므로 완전한 간섭신호를 측정할 수 있었다. 또 초점영역 근처에서의 간섭무늬만 측정되므로 다층 박막중에 존재하는 공기갭이라도 측정할 수 있는 장점이 있다. 간섭무늬 변화가 작은 영역을 제외하면 1 nm 이내의 안정도를 가진다.

• 전기의세계
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• 제29권10호
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• pp.660-666
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• 1980

The finite leement method is a effetive analysis technique for obtaining approximate solutions of continuum problems with boundary conditions. This paper deals with the programming for the application of this method and the preciser analysis of the magnetic field in the air gap of the linear stepper motor by the method. The finite element analysis based on the variational principle is adopted and the computer program for reducing input data and a large number of the memory words required by the system matrix is presented. The 2-dimensional analysis of the air gap is made and several cases according to varying the position are considered.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
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• pp.1414-1415
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• 2006

Air-gap type film bulk acoustic wave resonator device using ZnO for piezoelectric layer and sacrifice layer, deposited by RF magnetron sputter with various conditions, fabricated in this study. Also, membrane$(SiO_2)$ and top and bottom electrode(both Al) of piezoelectric layer deposited by RF magnetron sputter. Using micro electro mechanical systems(MEMS) technique, sacrifice layer removed and then air-gap formed. The results of each process checked by XRD, AFM, SEM to obtain good quality device.

• 조명전기설비학회논문지
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• 제27권10호
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• pp.86-92
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• 2013

In studies on an alternative insulating gas of $SF_6$ gas, the section of the alternative gas and an insulation technique to improve its low dielectric strength have been reported, but very few attempts have been made at the dependence of a gas pressure and a gap as well as the medium effect in the alternative gas. The purpose of this paper is to analyze the dependence of the gas pressure and the gap at surface flashover voltage in dry air. The dependence is analyzed based on the medium effect. The medium effect by the gas pressure and the gap can be explained by surface roughness of a solid dielectric and an electrode as well as an electric field which decreases due to the correlation between the collision ionization coefficient and the gap, respectively. In addition, an insulation technique which can fabricate a compact eco-friendly gas insulated switchgear is proposed by the results of this paper.