• 한국항해학회지
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• 제25권4호
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• pp.371-379
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• 2001

We have reported the new measurement system which was substituted digital filter for the analog filter in order to develop the optimal system that could find the time delay between each sensors with high accuracy. And also we have confirmed through the experiments that the accuracy of measurements were differentiated by the methods what kind of digital filter had been adopted. This paper suggests two algorithms which approximate the sound source's bearing and distance. One is that sound source's relative bearing can be approximately regarded as the gradient of hyperbolic asymptote, the other is that the source's range can be approximated under the condition of a long range source relative to the sensor's interval. And a series of experiments were carried out with the source's distance 22.42meters and the random bearing interval within the limits of $-90^{\circ}$~$+90^{\circ}$. As a result, we have recognized that the approximation methods could measure the bearing and distance with higher accuracy than the method using trigonometric relation could do.

• 한국소음진동공학회논문집
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• 제13권10호
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• pp.743-750
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• 2003

The equivalent source method(ESM) is used for the calculation of the internal pressure field for an enclosure which can have arbitrary boundary conditions and nay include internal objects which scatter the sound field. The advantage of using ESM is that it requires relatively low computing cost and is easy to model the internal diffracting objects. Typical ESM modeling uses two groups of equivalent source positions. One group includes the first order images of the source inside the enclosure. The Positions of the other group are usually on a spherical surface some distance outside the enclosure. The normal velocity on the surfaces of the enclosure walls is evaluated at a larger number of positions than there are equivalent sources. The sum of the squared difference between this velocity and the expected is minimized by adjusting the strength of the equivalent sources. This study is on the optimal far field sources positions when using the equivalent source method. In general, the far field sources are evenly distributed on a surface of a virtual sphere which is centered at the enclosure with a sufficiently large radius. In this study. optimal far field source locations are searched using simulated annealing method for various radii of spheres where far field sources are located. Simulation results showed that optimally located sources with adequate distance away from the enclosure center gave better result than sources with even distribution even with a smaller number of far field sources.

• 대한디지털의료영상학회논문지
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• 제14권2호
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• pp.39-46
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• 2012

Purpose : The purpose of this study was to reduce Entrance Surface Dose and maintain image quality by changing Source to Image receptor Distance. And we'd like to compare ESD on this study to DRLs in other contries. Materials and Methods : We used indirect DR system(Definium 8000, General Electric, USA)and phantom(ART-200X, Flukebiomedical, USA),glass dosimeters(GD-352M, Asahi Techno Glass, Japan)for this study. The imagies were obtained throuh 80kVp fixed, and different tube currents using AEC mode in $16{\times}16$(inch) field size and changing Source to Image receptor Distance from 100 cm to 130 cm per 10 cm unit. The phantom with attaching 5 glass dosimeters on abdomonal skin was set at supine and erect position as a anterioposterial projection on detector For measuring Entrance Surface Dose. Image analysis was conducted by histograms of Image J(1.46r) which was given from National Institutes of Health(NIH). Results : Due to inverse square law of distance, the tube currents were increasing 42.6 % in supine position and 32.6 % in erect position according to the change of Source to Image receptor Distance. While Entrance Surface Doses were rapidly decreasing 14.2 % in supine position and 29.4 % in erect position according to the change of Source to Image receptor Distance. As the results of histogram using Image J, pixel mean values from 100 cm to 110 cm, 120 cm and 130 cm were decreasing each 1.4%, 2.5%, 2.7%, 4.5%, 2.2 %, 5.8 % in supine, erect position. While standard deviations from 100 cm to 110 cm, 120 cm and 130 cm were increasing each 1.4 %, 2.5 %, 2.5 %, 4.0 %, 2.0 %, 4.9 % Consequently, there are no significant differences in abdomen images taken. Conclusion: As the results described above, we strongly recommend using long Sourceto Image receptor Distance than 100cm that we have been using. So, we should deliver less Entrance Surface Dose to the patients while maintaining image quality in abdomen radiography.

• The Journal of the Acoustical Society of Korea
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• 제19권3E호
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• pp.33-39
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• 2000

This study investigated whether the adjacency principle. demonstrated in a perceived visual space, can be applied to auditory space. In order to demonstrate an auditory adjacency principle, multiple sound sources were varied in direction and distance in an acoustically absorbant space. Specifically, a NEAR sound source was located 10° to the left of the listener's midline at a distance of 2 meters; a FAR sound source was located 10° to the right at a distance of 5 meters. These sources served as perceptual reference points with respect to the localization of three test sounds, all at a distance of 3 meters. Two of three test sounds were directionally closer to the NEAR and FAR reference sounds, respectively. The other was between the reference sources directionally. The listener was asked to judge the perceived distances and the loudness of the three test sounds and the two reference sounds. The results indicated that the apparent distances of the test sounds were most determined by the disparity of distance between each test sound and the reference sound most directionally adjacent to it. Therefore, the findings offer evidence that the adjacency principle can be applied to the auditory space.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.118.2-118
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• 2001

This research describes a development of laser distance sensor with precise resolution even in the case that the object surface has some curvature. There are typical two methods in measuring the distance by using laser light source, so called time of flight and optic-triangular methods. Both methods have an advantage and a disadvantage each other. In general, the time of flight method produces wide range of the measurement, but low accuracy. The other method is vice versa. In this research, the optic-triangular methods with one-dimensional CCD cell are proposed to obtain the precise distance measure from the sensor the surface of the curved object ...

• 대한방사선기술학회지:방사선기술과학
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• 제45권6호
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• pp.483-489
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• 2022

This study proposes a new skull lateral examination, and provides an improved examination environment for patients and radiologists. The study was divided into three groups. One group was divided into the SID (source to image receptor distance) 110 ㎝ and 180 ㎝ in the skull lateral posture, the other group The other group was divided into an position in contact with the detector and an position without contact with the detector, and the other group was divided into male and female groups, considering that the difference in shoulder width between adult males and females would affect the dose and image quality. For dose evaluation, the ESD (entrance surface dose) was measured at the EAM (external auditory meatus), and the conditions were applied equally at 70 ㎸p, 200 ㎃, and 10 ㎃s. For image quality evaluation, SNR (signal to noise ratio) and CNR (contrast to noise ratio) were measured in frontal sinus, EAM, and sella turcica. As a result of ESD comparison, when sid 110 ㎝ to sid 180 ㎝ was changed among the three groups, ESD values decreased the most to 729.18±4.62 μ㏉ and 224.18±0.74 μ㏉ at 180 ㎝ (p<0.01). The values of SNR and CNR were statistically significant (p<0.01), but there was no qualitative difference. This shows that when the SID is 180 ㎝, it is possible to reduce the dose without lowering the image quality. So, It is suggested that the SID 180 ㎝ is used without contacting the detector when examining the skull lateral.

• Nuclear Engineering and Technology
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• 제54권8호
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• pp.3176-3180
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• 2022

A gamma irradiator is a well-developed installation for gamma radiation sterilization. A "shuffle-dwell" mode is preferable for high dose applications. A novel configuration of a shuffle-dwell gamma irradiator is proposed to increase energy utilization and throughput, which would result in higher profitability. While the minimum distance between any irradiation position and each source pencil, the minimum distance between the neighboring irradiation positions and the size of source pencils are kept the same as the current configuration, the irradiation positions and source pencils are rearranged based on the fact that radiation is emitted in an isotropic fashion. The computational results suggest that the proposed configuration requires an 8.7% smaller area and exposes the product to 11.8% more gamma radiation in a 10.7% shorter irradiation time. In other words, the proposed configuration needs a smaller area and shorter irradiation time to have a better performance compared to the current shuffle-dwell gamma irradiator. Note that the claim is based primarily on an analytical calculation. Experimental and manufacturing among other practical considerations will be taken into account in the future work to exhaustively evaluate the performance of the proposed configuration and to compare it with that of the traditional configuration.

• Radiation Oncology Journal
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• 제9권2호
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• pp.333-336
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• 1991

충남대학교병원 치료방사선과내 설치되어 있는 6MV선형가속기를 이용하여 음영을 측정하여 다음과 같은 결과를 얻었다. 1) 조사면 크기가 커질수록 음영폭은 중가하였으며 10x10 Cm 이상의 조사면에서는 계산한 음영폭보다 측정치가 대개 크게 나타났다. 조사면이 커질수록 이 차이는 더욱 증가하였다. 2) 깊이가 증가하면 음영폭도 증가하였다. 3) $90\%\~20\%$의 음영폭이 $80\%\~20\%$의 음영폭보다 컸으며 조사면이 커지고, 깊이가 증가할 수록 이 차이는 더 커졌다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.837-842
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• 2004

The positions of rotating sound sources have been localized by experiments with the Doppler effects removed. In order to do-Dopplerize the sound signals emitted from moving sources, two kinds of signal reconstruction methods were applied. One is the forward propagation method and the other is the backward propagation method. Forward propagation method analyze the source emission time based on the instantaneous distance between sensors and the assumed source position, then the signals are reconstructed with respect to the emission time. On the other hand, the backward method uses time delay to do-Dopplerize the acquired data for the received time of reference. In both techniques, the reconstructed signal data were processed using beamforming algorithm to produce power distributions at the frequency of interest. Experiments have been carried out for varying frequencies, rotating speeds and the object distances. Forward propagation method has shown better performance in locating source position than the backward propagation method.

• 한국산학기술학회논문지
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• 제10권6호
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• pp.1201-1206
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• 2009

음상의 거리정위에 있어서 중요한 물리적 요인으로는 알려진 음압레벨, 반사음, 양 귀간 차, 음원의 종류, 머리전달함수(HRTF) 등의 여러 요인들이 중요한 판단 자료로 이용되어진다고 알려져 있다. 본 논문에서는 거리판단에 사용되어지는 물리적 요인 중 음압레벨의 크기가 거리정위에 미치는 영향을 알아보기 위해 반사음이 존재하지 않은 무향실에서 음원의 출력 음압레벨을 일정한 경우와 귀 입력 음압레벨을 일정하게 한 경우에 대하여 청취실험을 통해 거리판단에 있어서 음압레벨의 영향에 대하여 고찰했다. 그 결과. 음원출력 음압레벨을 일정하게 한 경우와 귀 입력 음압레벨을 일정하게 한 청취실험에 있어서 제시한 음원거리보다 지각한 음상거리를 가깝게 정위하는 경향이 있다는 것이 관찰되었다. 또, 귀 입력 음압레벨이 일정한 경우에는 약 2m 정도까지의 거리에서는 실제 제시한 음원거리의 증가에 따라 지각한 음상의 거리가 음원거리에 대응하여 증가하지만, 그 이상의 거리에서는 음원거리의 증가에 따라 지각한 음상거리가 증가가 거의 없음을 알 수 있었다. 반면 음원출력 음압레벨이 일정한 경우에는 지각한 음상거리가 귀 입력 음압레벨이 일정한 경우보다 보다 더 먼 3m 정도의 거리까지 증가하고 있음을 알 수 있었다. 이와 같은 청취실험 결과로부터 반사음이 존재하지 않은 조건에서의 음상의 거리정위에는 음압레벨이 거리판단의 중요한 요소로 작용하고 있음이 확인되었다.