• Journal of Radiation Protection and Research
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• 제46권4호
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• pp.160-169
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• 2021

Background: Dual-energy X-ray images (DEI) can distinguish or improve materials of interest in a two-dimensional radiographic image, by combining two images obtained from separate low and high energies. The concepts of DEI performance describing the performance of double-exposure DEI systems in the Fourier domain been previously introduced, however, the performance of double-exposure DEI itself in terms of various parameters, has not been reported. Materials and Methods: To investigate the DEI performance, signal-difference-to-noise ratio, modulation transfer function, noise power spectrum, and noise equivalent quanta were used. Low- and high-energy were 60 and 130 kVp with 0.01-0.09 mGy, respectively. The energy-separation filter material and its thicknesses were tin (Sn) and 0.0-1.0 mm, respectively. Noise-reduction (NR) filtering used the Gaussian-filter NR, median-filter NR, and anti-correlated NR. Results and Discussion: DEI performance was affected by Sn-filter thickness, weighting factor, and dose allocation. All NR filtering successfully reduced noise, when compared with the dual-energy (DE) images without any NR filtering. Conclusion: The results indicated the significance of investigating, and evaluating suitable DEI performance, for DE images in chest radiography applications. Additionally, all the NR filtering methods were effective at reducing noise in the resultant DE images.

• 한국방사선학회논문지
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• 제15권7호
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• pp.957-964
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• 2021

PET/CT 검사 시 사용되는 F-18은 양전자를 방출하는 방사성동위원소이며, 높은 에너지의 소멸감마선과 베타선은 방사선작업종사자의 피폭을 초래하는 원인이 된다. 본 연구에서는 핵의학과에서 근무하는 방사선작업종사자의 피폭선량 저감방안의 일환으로, F-18에 대한 Apron의 낮은 차폐 효율의 원인을 규명하고, 아크릴로 이중 차폐한 Apron의 실효성을 평가하였다. L-Block, Apron+아크릴, Apron, 아크릴+Apron, 아크릴 다섯 개의 차폐체를 이용하여 선량을 측정하고, 몬테카를로 시뮬레이션을 수행하여 경향성을 비교하였다. 그 결과, 아크릴로 이중 차폐한 Apron의 차폐율이 Apron 단독 차폐한 경우보다 약 4~8% 높은 차폐효과가 있는 것으로 나타났다. 사용자의 활동성에 크게 영향이 가지 않는 범위 안에서 적절한 두께의 아크릴로 이중 차폐한 개인방호복은 방사선 작업종사자의 피폭저감화에 도움을 줄 수 있을 것이다.

• 한국콘텐츠학회논문지
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• 제17권7호
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• pp.12-21
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• 2017

이 연구는 주목 행동을 노출과 관여의 두 차원으로 구분하여 모바일 콘텐츠에 대한 주목 행동의 특징을 살펴보고, 주목 행동들 간에 어떤 관계를 갖는지 피키캐스트의 콘텐츠 데이터를 이용하여 탐구하였다. 우선, 이 연구는 이중위험효과(double-jeopardy)가 모바일 콘텐츠에서도 나타나는지 알아보기 위해 노출과 관여의 상관관계를 검증했다. 또한 플랫폼별, 주제 속성별(연성 및 경성)로 주목 행동이 어떻게 다른 양상을 띠는지 살펴보았다. 그 결과, 모바일 플랫폼에서도 노출과 관여 간에 긍정적인 상관관계가 존재하는 것을 확인하였다. 또한 플랫폼별로 주목 행동, 특히 공유 행동이 다른 양상을 띠는 것을 발견할 수 있었다. 주제 속성별로는, 연성 콘텐츠에 대해서는 즉각적인 반응인 댓글 수, 공유 등의 주목 지표들이 연관되어 있는 반면, 인지적인 노력이 필요한 경성 콘텐츠에 대해서는 소비시간과 완독률 같은 주목 지표들이 연관되어 있었다. 본 연구는 이용자 중심의 관점에 치중했던 기존 연구에서 벗어나 콘텐츠 중심의 관점으로 모바일 환경에서의 주목 행동의 본질을 새롭게 이해했다는 데 의의가 있다.

• 대한기계학회논문집A
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• 제20권10호
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• pp.3211-3223
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• 1996

In this paper, the propagation of elastic wave generated by loading impact to plates made of isotropic of anisotropic material was studied. And the influence of boundary conditions (free or clamped edge) upon the reflection of elastic wave was anlyzed. Also, double exposure holographic interferometer using ruby pulse laser was formed in order to investigate transient waves. Before the elasitc wave was reflected from the edges, the elastic wave of isotropic plate such as aluminum plate showed circular interferometric fringe pattern, whereas that of anisotropic plate such as epoxy composite laminates showed elliptical one. And the transverse displacement curves obtained from experiment and theory for both plates agreed well. Also, the waves reflected from the boundary edges showed much differences according to the boundary condition of edges.

• 대한방사선기술학회지:방사선기술과학
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• 제24권1호
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• pp.17-22
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• 2001

Medical X-ray examination are increased double for the last $6{\sim}8$ years. Therefore a patient exposure dose should be decrease half every 7 years. We made an experiment on copper filter thickness to decrease a patient exposure dose up to half and compared to the Image quality by MTF. The results as follow 1. A thin region like extremities needs a thicker Cu filter as compared a thick region. 2. 1/2 reduction filter must be thicker when kVp Increase. 3. Exposure factor should be increas when using 1/2 reduction filter ; extremity is 4.0 times, chest 2.9 times, skull 1.62 times, and abdomen 1.58 times 4. The MTF of using 1/2 reduction filter is lower than without filter. But no difference of visual image. 5. 1/2 reduction filter compared with double speed screen showed almost same image quality.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.418-421
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• 1988

Holographic interferometry is applied in dental research to study the motion of teeth and the deformation of the associated facial structure. We consider double exposure holographic interferometry which has limiting factors such as the stability of fringes, the recording time, the amount of exposure, the localization of fringes and sensitivity. These factors are taken into account to make interferogram. The resulting interferogram gives fringe pattern which is analyzed qualitatively to determine the relative rotation and the deformation of the facial structure.

• 인지과학
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• 제6권1호
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• pp.47-71
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• 1995

글자의 이중상으로 인한 심리적 혼란감을 '글자멀미'라 정의하였고,눈운동 및 글자 인식 과정이 교란될 때 글자 멀미가 발생한다는 가설을 검증하기 위하여 자극의 노출시간과 글자의 친숙도가 글자 멀미에 미치는 효과를 측정하였다.글자 멀미는 자극 노출 시간이 50ms,100ms,3000ms로 길어짐에 따라,덜 친숙한 외국 문자보다는 친숙한 한글에서 유의미한 단어보다는 무의미한 단어에서 큰것으로 나타났다.이러한 실험발견은 이중상을 제거하려는 눈 운동이 실효를 거두지 못함에 따라 글자 멀미가 발생한다는 것,친숙한 글자일수록 글자 인식 과정의 개입을 더 강화하며 그결과 이중상에 의한 교란 효과가 증폭된다는것,글자 형태는 친숙하지만 의미추출이 어렵게 되면 이중상의 교란효과가 가중된다는 것을 암시한다.의미를 처리하는 경향이 클수록 이중상에 의한 글자 멀미가 심해진다는 가설을 좀 더 분명히 검증하기 위하여 여섯 개의 점으로 구성된 점자를 시각적으로 인식하도록 피험자들을 학습시킨 결과,학습율이 증가함에 따라 글자 멀미가 증가하는 것으로 나타나, 하나의 자극을 의미있는 상징으로 취급하여 해석하려 할때 글자멀미가 증가한다는 결론을 얻었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(2)
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• pp.213-216
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• 2002

A double-heterostructure AIGaAs/GaAs PHEMT (Pseudomorphic High Electron Mobility Transistor) using digital recess has been successfully realized. Futhermore, the differences of gm,nax, fT, fmax between two samples are as low as 0.62%, 1.58% and 2.56 % respectively. Experimental results are presented demonstrating the etch rate and Process invariability with respect to hydrogen peroxide and acid exposure times with uniformity among devices on a sample.

• Asian Journal for Public Opinion Research
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• 제12권2호
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• pp.122-141
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• 2024

Drawing on mere exposure effect, we proposed that more exposure to a city, as measured by the number of channels of exposure, would increase familiarity, city image, and intention to visit that city. We conducted a survey of university students in seven Asian countries, asking them about a total of 14 cities, at least one from each of the surveyed countries. Exposure was found to be a significant antecedent and was most powerful when mediated by familiarity. Some types of exposure were stronger than others. Personal exposure, in the form of having visited a city or knowing someone who has, was the strongest type of exposure, with more than double the effect of media exposure. Social media, which is difficult to classify as either personal or media, was assessed separately and had a much smaller effect. The mere exposure effect exists whether the intention to visit a city is related to pleasure (tourism) or business.

• Journal of Advanced Marine Engineering and Technology
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• 제20권1호
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• pp.56-66
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• 1996

In this study, the characteristics of generation and propagarion of transient wave induced in the assembly of four collecting plate upon the propagation of waves are analyzed. Also double exposure holographic inteferometry using ruby pulse laser is built in order to investigate the propagation of transient waves generated by impact load. When impact load was applied at edge of connecting band, the vibration of collecting plates was generated from the contact points between collecting plate and band which connects four collecting plates. Waves generated from the lower part and those reflected from the upper part were mixed as time went on and then formed very complex shapes. Also, when impact load was aplied at center of collecting plate, the waves propagating across the convexo-concave plane were reflected partly at curved section. Therefore the vibration amplitude was decreased as the transiet waves were propagated through the convexo-concave plane.