• 방사성폐기물학회지
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• 제18권1호
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• pp.51-62
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• 2020

본 연구는 감마스펙트럼 비율을 이용한 매립된 선원의 깊이 평가방법 개발 및 적용성 확인을 위해 진행되었다. 이를 위해 현장측정 HPGe 계측기 및 MCNP 전산모사를 이용하여 ¹³⁷Cs, ⁶⁰Co, ¹⁵²Eu 선원의 매질 내 깊이와 계측거리에 따른 Peak to Compton, Peak to Valley 비율(Q)의 변화를 평가하였다. 해당 결과를 이용해 계측거리 50 cm를 기준으로 PTV 및 PTC 비율(Q)과 매립 선원의 깊이 간의 상관 식을 도출하였다. 그리고 PTC 및 PTV 방법 이용 시 계측거리 변화에 따른 민감도를 평가한 결과, 50 cm 기준으로 계측거리가 20 cm로 감소할 경우 오차가 3 ~ 4 cm까지 증가하였다. 하지만 100 cm로 증가할 경우 계측거리에 의한 영향이 미미함을 확인하였다. 그리고 PTV 및 PTC 방법과 피크 영역의 계수율 변화를 통해 선원의 깊이를 평가하는 Two distance measurement 방법을 상호 비교하였다. 평가 결과 PTV 및 PTC 방법은 최대 1.87 cm의 오차, Two distance measurement 방법은 최대 2.69 cm의 오차를 나타내어 PTV, PTC 방법의 정확도가 비교적 높음을 확인하였다. 선원의 수평 방향 위치 변화 민감도 평가 결과 Two distance measurement 방법은 선원이 off-center 방향으로 30 cm 이동하였을 경우 최대 오차가 25.59 cm로 나타났다. 반면 PTV 및 PTC 방법은 최대 오차 8.04 cm로 현장 적용 시 높은 정확도를 나타낼 것으로 예상된다. 그리고 PTC 방법은 동일 시간 측정 시 다른 방법과 비교하여 낮은 표준편차를 나타내 신속한 평가가 가능할 것으로 기대된다.

• 대한의용생체공학회:의공학회지
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• 제28권2호
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• pp.265-270
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• 2007

Polarization imaging systems have been widely used to selectively characterize skin lesions. Nevertheless, current systems are used in single-mode due to the limitations of a fixed polarization mode and a single-working distance of light source, in which uniform light distribution is achieved on target area. To address such limitations, we developed a variable polarization imaging system based on multi-working distance of light source for various clinical diagnoses. In this study, we characterize the imaging system and present experiment results demonstrating its clinical usefulness. The imaging system consists of a CCD color camera, linear polarization filters, and a single-layered LED ring light source which provides uniform light distribution at multi-working distances. The first polarizer was placed on the light source and the second polarizer placed on objective lens provides continuous linear polarization angle from $0^{\circ}\;to\;90^{\circ}$. The clinical efficacy of the imaging system was investigated by acquiring and analyzing clinical images of skin wrinkle and dental plaque. With the experiments, we verified the potential usefulness of the imaging system for other clinical applications.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1997년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 1997
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• pp.126-131
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• 1997

Recently, the ground motion occurred by vehicles or trains has been recognized one of the major factors of damage of structures nearly the motion source. To isolate the environments from ground motions, it is necessary to understand the wave propagation in half spaces. Especially, Rayleigh wave is the primary concern because it transmits a major portion of the total source energy and decays the energy more slowly with response to distance than the other waves. In this study, the preliminary data(wave length and damping effect) to design the isolating system are obtained. For this, a field dynamic test is performed, using the exciter which can generate the 100kN vertical cyclic load in the range of 1-60 Hz is used. The fifteen accelerometers to measure the ground response are set up in 3 radial direction at intervals of 10 meters in each row. The wave lengths are calculated using the distance and the phase between the measuring points. The damping effects of the Rayleigh-wave are also observed from the experiments.

• 한국인터넷방송통신학회논문지
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• 제10권3호
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• pp.121-129
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• 2010

본 논문에서는 중계기의 위치에 따른 협력 통신의 성능을 분석한다. 이를 통해 최적의 중계기는 송신단과 수신단의 신호 전송의 성능을 높이거나 송신단의 신호를 수신단이 복호하지 못하였을 경우 재전송을 하는 일종의 송신단 역할을 한다. 본 논문에서는 최적의 중계기를 선택함으로써의 성능 향상을 보이며 관련 수식을 유도한다.

• International Journal of Internet, Broadcasting and Communication
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• 제12권3호
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• pp.46-55
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• 2020

Ad Hoc network is a special wireless network, mainly because the nodes are no control center, the topology is flexible, and the networking could be established quickly, which results the transmission stability is lower than other types of networks. In order to guarantee the transmission of data packets in the network effectively, an improved Queue Ad Hoc On-demand Distance Vector Routing protocol (Q-AODV) for node detection by using blockchain technology is proposed. In the route search process. Firstly, according to the node's daily communication record the cluster is formed by the source node using the smart contract and gradually extends to the path detection. Then the best optional path nodes are chained in the form of Merkle tree. Finally, the best path is chosen on the blockchain. Simulation experiments show that the stability of Q-AODV protocol is higher than the AODV protocol or the Dynamic Source Routing (DSR) protocol.

• 대한방사선기술학회지:방사선기술과학
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• 제5권1호
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• pp.63-70
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• 1982

In order to estimate characteristics and functions of multi hole focusing type collimator, the authors measured the sensitivity and resolution varing with the distance between the face of collimator and source by experimental study. The results obtained with this study are as follows. 1. In comparison with focal distance obtained fram sensitivity measurement of various multi hole focusing type collimator, collimator A, C, E was 10 cm and collimator B, D was 12 cm in focal distance. 2. In regard of resolution of collimators having 10 cm focal distance, collimator A showed the finest resolutions than any other collimator(C, E). 3. By comparison regarding sensitivity by focal dist ante, the shorter the distance than a give focal distance of collimator, the worse the sensitivity of collimator. 4. With regard to resolution by focal distance, the shorter the distance than a given focal distance of collimator, the worse the resolution of collimator.

• 천문학회보
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• 제40권1호
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• pp.69.1-69.1
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• 2015

Classical T Tauri star DG Tau is suggested as the driving source of parsec-scale jet which expands up to 650" (0.4 pc). To investigate the kinematics and physical properties of the jet, we have obtained the optical emission lines of $H{\alpha}$, [O I] ${\lambda}{\lambda}$6300, 6363, [N II] ${\lambda}{\lambda}$6548,6584, and [S II] ${\lambda}{\lambda}$6716, 6731 from HH 158 ad HH 702. The radial velocity of HH 158 is in the range of -50 to $-250km\;s^{-1}$. For HH 702, located at 650" from the source, it shows ~ $-80km\;s^{-1}$. In HH 158, the electron density ($n_e$) close to the star is ${\sim}10^4cm^{-3}$ and it decreases to ${\sim}10^2cm^{-3}$ at 14" away from the star. Electron temperature ($T_e$) is decreasing from >15,000 K to ~5,000 K with distance. Ionization fraction ($x_e$) is increasing from almost zero to > 0.4 along the distance. In HH 702, the values of $n_e$, $T_e$, and $x_e$ are similar to those estimated at 14" from source, where knot C of HH 158 is located. This may imply that the physical properties of the knot could persist through such a long distance in the space, and the gas could be re-excited by the shock during propagation of the jet. On the other hand, we cannot avoid the possibility that HH 702 is driven by another source rather than DG Tau because HH 158 and HH 702 show somewhat large difference in their inclination angles (${\Delta}i=21-35^{\circ}$).

• 한국소음진동공학회논문집
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• 제26권5호
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• pp.609-615
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• 2016

Measuring similarity between two signals is a key element of the location template matching (LTM) method which is one of impact source localization technique. As a measure of similarity, the correlation coefficient is most widely used, and the group delay based method is recently proposed to improve the accuracy of finding the impact source. In practice, the LTM method assumes that the similarity between two signals decreases as the distance between two corresponding impact points increases, where the distance between two neighboring impact points defines the grid spacing. In this paper, it is shown that this assumption is not always true but the correlation coefficients fluctuate forming a main robe and many side robes as the distance between two neighboring impact points increases. On the other hand, the standard deviation of group delay sharply increases with a small increase of the grid spacing. These are demonstrated by using a simple cantilever beam. Based on these findings, an optimal way of implementing the LTM method may be suggested by combining the correlation coefficient and the group delay based approaches.

• 전기학회논문지
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• 제61권3호
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• pp.373-379
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• 2012

This paper presents a fault location algorithm based on the adaptively estimated value of the local sequence source impedance for faults on a parallel transmission line. This algorithm uses only the local voltage and current signals of a faulted circuit. The remote current signals and the zero-sequence current of the healthy adjacent circuit are calculated by using the current distribution factors together with the local terminal currents of the faulted circuit. The current distribution factors consist of local equivalent source impedance and the others such as fault distance, line impedance and remote equivalent source impedance. It means that the values of the current distribution factors can change according to the operation condition of a power system. Consequently, the accuracy of the fault location algorithm is affected by the two values of equivalent source impedances, one is local source impedance and the other is remote source impedance. Nevertheless, only the local equivalent impedance can be estimated in this paper. A series of test results using EMTP simulation data show the effectiveness of the proposed algorithm. The proposed algorithm is valid for a double-circuit transmission line system where the equivalent source impedance changes continuously.

• 한국음향학회지
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• 제23권1호
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• pp.40-46
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• 2004

등가음원법은 일반적으로 실내에 위치한 음원에 의한 실내 음장을 모델링하기 위하여 원거리에 위치한 다수의 등가음원과 상대적으로 근방에 위치한 소수의 이미지음원들을 사용한다. 원거리음원은 일반적으로 실내 음장의 중심으로부터 적당히 먼 거리에 균일하게 위치시킨다. 이러한 원거리음원의 위치는 적절한 선택 여부에 따라, 계산 결과의 정확도와 이를 만족시키기 위해 필요한 음원의 수에 큰 영향을 미치게 된다. 본 연구에서는 등거리 상의 가상의 구형 표면에 위치시키는 기존의 방법 대신 모델링하는 실내 공간의 경계면과 닮은 꼴 형상으로 배치하여 그 영향을 조사하였다. 즉 가상의 직육면체 표면에 격자 형태로 균일하게 원거리음원들을 배치시키되, 음장의 중심으로부터의 거 리를 변화시켜가며 각 경우에 대하여 최적화 기법을 이용하여 최적의 원거리음원 위치들을 찾아내어 비교, 분석하였다.