• 대한방사선치료학회지
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• 제22권1호
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• pp.47-51
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• 2010

목 적: 고 에너지 양성자치료에 있어서 Air gap (환자와 Beam 사출구 사이의 거리)의 변화는 Lateral Penumbra의 증가로 불필요한 조사야를 형성할 수 있고, 치료부위에서 최대선량 증가와 최소선량 감소로 선량분포의 균질성을 저하시킬 수 있다. 이에 Air gap 변화에 따른 선량분포에 대해 비교, 연구해 보고자 한다. 대상 및 방법: 본원에서 양성자치료를 받은 Lung, Liver 환자 6명을 선정하여 크기가 다른 조사야 A와 조사야 B에서 Air gap을 2, 4, 6, 8, 10 cm로 설정하여 Proton external beam planning system을 통해 치료계획을 세웠다. Air gap에 따른 Lateral Penumbra 영역 및 DVH (Dose Volume Histogram)를 비교하고 PCTV영역의 최대선량 및 최소선량 값을 비교하였다. 또한 PCTV내에 선량의 균질성을 알기 위하여 Homogeneity index값을 비교, 분석하였다. 결 과: 각각의 조사야에서 Air gap의 변화(2, 4, 6, 8, 10 cm)에 따른 Lateral Penumbra영역을 분석한 결과 조사야 A에서 Air gap 2~10 cm변화에 따라 평균 1.36~1.75 cm까지 약 28.7%가 지속적으로 증가하였고 조사야 B에서 평균 1.36~1.79 cm까지 약 31.6%가 지속적으로 증가하였다. DVH를 분석한 결과 최대선량의 상대선량 백분율은 Air gap 2~10 cm일 때 평균 108.1%에서 평균 110.3%까지 약 2.03%가 지속적으로 증가하였고 최소선량의 상대선량 백분율은 평균 93.9%에서 평균 90.8%까지 약 3.31%가 지속적으로 감소하였다. Homogeneity index값은 평균 Air gap 2~10 cm까지 1.09~2.6으로 2배 이상 증가하였다. 결 론: 양성자 치료에 있어서 Air gap이 증가함에 따라 Lateral Penumbra 영역이 증가함을 알 수 있었고, 치료부위에서 최대선량 값의 증가와 최소선량 값의 감소로 인하여 Homogeneity index값이 증가함으로써 PCTV내에 Beam의 균질성이 떨어지는 것을 알 수 있었다. 이에 추후 양성자치료시 Air gap을 줄이기 위한 노력이 필요할 것으로 사료된다.

• Computers and Concrete
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• 제26권2호
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• pp.161-173
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• 2020

Shear keys in precast concrete segmental bridges (PCSBs) are usually match-casting which is very labour intensive. In this research, an innovative match-casting-free construction was proposed by leaving small gap between the convex and the concave castellated shear keys in the joints of PCSBs. Specimen experiment, shear strength analysis and numerical simulation were conducted, investigating the loading performance of this new type of dry joints, the gap dry joints. Compared with match-casting joint specimens, it has been found from experiment that shear capacity of gap joint specimens significantly decreased ranging from 17.75% to 42.43% due to only partially constrained and contacted in case of gap dry joints. Through numerical simulation, the effects of bottom contacting location, the heights of the gap and the shear key base were analyzed to investigate strength reduction and methods to enhance shear capacity of gap joint specimens. Numerical results proved that shear capacity of gap dry joints under full contact condition was higher than that under partial contact. In addition, left contact destroyed the integrity of shear keys, resulting in significant strength reduction. Larger shear key base remarkably increased shear capacity of the gap joint. Experimental tests indicated that AASHTO provision underestimated shear capacity of the match-casting dry joint specimens, while the numerical results for the gap dry joint showed that AASHTO provision underestimated shear capacity of full contact specimens, but overestimated that of left contact specimens.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.133.2-133.2
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• 2014

A gap surface plasmon resonator have received considerable attention because it can dramatically enhance the absorption of the electromagnetic field. However, whereas most of studies were just focused on the absorption within a narrow range of wavelength, few studies have been performed for the broadband absorption in the visible range. Therefore, in this study, we discuss methods that can induce broadband light absorption using gap plasmon resonance in visible regime. The gap plasmon resonator will offer great potential for appplications to solar cells and bioimaging.

• Wind and Structures
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• 제30권4호
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• pp.367-378
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• 2020

Two-dimensional Delayed Detached Eddy Simulation (DDES) was carried out to investigate the uniform flow over a twin-box bridge deck (TBBD) with various gap ratios of L/C=5.1%, 12.8%, 25.6%, 38.5%, 73.3% and 108.2% (L: the gap-width between two girders, C: the chord length of a single girder) at Reynolds number, Re=4×104. The aerodynamic coefficients of the prototype deck with gap ratio of 73.3% obtained from the present simulation were compared with the previous experimental and numerical data for different attack angles to validate the present numerical method. Particular attention is devoted to the fluctuating pressure distribution and forces, shear layer reattachment position, wake velocity and flow pattern in order to understand the effects of gap ratio on dynamic flow interaction with the twin-box bridge deck. The flow structure is sensitive to the gap, thus a change in L/C thus leads to single-side shedding regime at L/C≤25.6%, and co-shedding regime at L/C≥35.8% distinguished by drastic changes in flow structure and vortex shedding. The gap-ratio-dependent Strouhal number gradually increases from 0.12 to 0.27, though the domain frequencies of vortices shedding from two girders are identical. The mean and fluctuating pressure distributions is significantly influenced by the flow pattern, and thus the fluctuating lift force on two girders increases or decreases with increasing of L/C in the single-side shedding and co-shedding regime, respectively. In addition, the flow mechanisms for the variation in aerodynamic performance with respect to gap ratios are discussed in detail.

• 대한기계학회논문집B
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• 제33권7호
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• pp.512-519
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• 2009

Flow pulsation in the gap connecting with two parallel channels is investigated by RANS and URANS approaches. The two parallel channels are connected by a small channel called for a gap. The parallel channels are designed to have different cross section area with its ratio of 0.5. Computations are conducted using a CFX 11.0 code. The bulk Reynolds number is 60,000. Predicted results are compared with the previous experimental data. Mean velocity profile at the center of gap region are compared with experiments for its validation. Spectral analysis on the lateral velocity in the center of the gap was performed. Auto correlation for the axial-flow velocity pattern was presented. The unsteady structure of the flow pulsation was visualized in the region of the gap in the parallel channel.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2810-2815
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• 2008

Flow pulsation in the gap connecting with two parallel channels is investigated by RANS and URANS approaches. The two parallel channels are connected by a small channel called for a gap. The parallel channels are designed to have different cross section area with its ratio of 0.5. Computations are conducted using a CFX 11.0 code. The bulk Reynolds number is 60,000. Predicted results are compared with the previous experimental result. Mean velocity profile at the center of gap region are compared with experiments for its validation. Spectral analysis on the lateral velocity in the center of the gap is presented. Auto and cross correlation for the axial-flow velocity pattern are presented. The unsteady structure of the flow pulsation was visualized in the region of the gap in the parallel channel.

• 비파괴검사학회지
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• 제26권6호
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• pp.403-410
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• 2006

Eddy current testing (ECT) signals produced by a differential bobbin coil probe vary according to probe design parameters such as the number of turns, geometry and coil gap size. In the present study, the characteristics of a differential bobbin coil probe signals are investigated by numerical simulation in order to determine the optimum coil gap. For verification of numerical simulation accuracy, a specially designed bobbin probe of which the coil gap can be adjusted is fabricated and a series of experiments to acquire signals from two kinds of standard tubes with the variation in coil gap is performed. Then, the experimental signals are compared to the simulation results. Based on this investigation, a decision on the optimum range of coil gap is made. The theoretically predicted signals agree very well to the experimental signals. In fact, this excellent agreement demonstrates a high potential of the simulation as a design optimization tool for ECT bobbin probes.

• 대한방사선치료학회지
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• 제26권2호
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• pp.233-238
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• 2014

목 적 : 최근 사용이 급증하고 있는 미국 베리안사의 이클립스 치료계획 시스템은 치료기에 설치되어 있는 다엽콜리메이터의 충돌 보호를 위해 존재하는 하드웨어적 제한성을 립 갭이라는 설정을 통하여 소프트웨어적으로 극복함으로써 정확한 치료계획을 구현 할 수 있도록 한다. 본 연구에서는 이클립스 치료계획 시스템에 설정되어 있는 립 갭이 치료계획에 미치는 영향을 분석하고 정확한 임상적용에 이용할 수 있도록 하고자 한다. 대상 및 방법 : 연구에 사용되어진 이클립스 치료계획 시스템의 버전은 11.0이다. 시스템에 설정되어 있는 립 갭은 각 치료기와 광자 에너지별로 측정되었다. 일반적으로 0.05~0.30 mm의 값을 가지고 있고, 다엽콜리메이터의 교정상태에 따라 다르므로 일괄되게 적용하지 않고 측정를 통하여 적용한다. 본 연구에서는 세기변조와 용적변조 치료계획을 측정된 각각의 립 갭을 적용하고, 립 갭이 달라질 때마다 치료계획의 영향을 Dmax, CI 등을 이용하여 평가하였다. 결 과 : 동일한 치료계획을 각각의 치료기에서 립 갭을 변화하며 평가하였을 때, 립 갭이 0.05 mm ~ 0.50 mm로 증가할수록 Dmax, CI 의 값이 2~5% 이상 증가하였다. 세기변조방사선치료계획과 용적변조방사선치료계획 모두 동일한 경향을 나타내었고 각 치료계획 간의 유의성은 찾아 볼 수 없었다. 결 론 : 치료기의 다엽콜리메이터의 립 갭 설정은 일반적으로 고유한 측정값을 가지고 있다. 하지만, 다엽콜리메이터의 노후, 교정, 수리 및 점검 후에 립 갭은 변할 수 있고, 이러한 값은 결국 치료계획에 영향을 미치기 때문에 반드시 확인 후 치료에 적용해야 한다. 경우에 따라선 립 갭을 초기 설정값을 유지하는 할 수 있는데, 이는 치료계획에 미치는 영향을 무시할 수 있기 때문에 바람직하지 않다.

• 한국표면공학회지
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• 제53권3호
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• pp.124-129
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• 2020

This study is for the development of high temperature ALD SiO₂ film process, optimized for gap-fill process in manufacturing memory products, using a space-divided PE-ALD system equipped with an independent control dual plasma system and orbital moving unit. Space divided PE-ALD System has high productivity, and various applications can be applied according to Top Lid Design. But space divided ALD system has a limitation to realize concentric deposition map due to process influence due to disk rotation. In order to solve this problem, we developed an orbit rotation moving unit in which disk and wafer. Also we used Independent dual plasma system to enhance thin film properties. Improve productivity and film density for gap-fill process by having deposition and surface treatment in one cycle. Optimize deposition process for gap-fill patterns with different depths by utilizing our independently controlled dual plasma system to insert N₂and/or He plasma during surface treatment, Provide void-free gap-fill process for high aspect ratio gap-fill patterns (up to 50:1) with convex curvature by adjusting deposition and surface treatment recipe in a cycle.

• International Journal of Railway
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• 제4권4호
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• pp.93-96
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• 2011

The basic element of the EMS suspension is the electromagnet system, which suspends the vehicle without contact by attracting forces to the rails at the guideway. The suspension of a vehicle by attractive magnetic forces is inherently unstable and consequently it is continuously adjusted by the strength of the suspending electromagnet from rail irregularity and bending of the guideway. In order to improve reliable tracking, it needs to get feedback signals without measurement delay time. In this paper the concept of feedback control system with Kalman Filter in EMS is proposed. The input signals in the feedback control system are an air-gap and an acceleration signal. The air-gap signal with noise from the gap sensor is transformed to the filtered air-gap signal y without measurement delay time by using Kalman Filter. The filtered air-gap signal is transformed to a relative velocity and a relative acceleration signal. Then it multiplies these values by gain matrix in order to get the actuator's reference voltage value. The simulation results show that the dynamic responses of the suspension system can be improved by reducing the influence of measurement delay time of air-gap signals.