• Biomedical Engineering Letters
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• 제8권4호
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• pp.383-392
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• 2018

For prompt gamma ray imaging for biomedical applications and environmental radiation monitoring, we propose herein a multiple-scattering Compton camera (MSCC). MSCC consists of three or more semiconductor layers with good energy resolution, and has potential for simultaneous detection and differentiation of multiple radio-isotopes based on the measured energies, as well as three-dimensional (3D) imaging of the radio-isotope distribution. In this study, we developed an analytic simulator and a 3D image generator for a MSCC, including the physical models of the radiation source emission and detection processes that can be utilized for geometry and performance prediction prior to the construction of a real system. The analytic simulator for a MSCC records coincidence detections of successive interactions in multiple detector layers. In the successive interaction processes, the emission direction of the incident gamma ray, the scattering angle, and the changed traveling path after the Compton scattering interaction in each detector, were determined by a conical surface uniform random number generator (RNG), and by a Klein-Nishina RNG. The 3D image generator has two functions: the recovery of the initial source energy spectrum and the 3D spatial distribution of the source. We evaluated the analytic simulator and image generator with two different energetic point radiation sources (Cs-137 and Co-60) and with an MSCC comprising three detector layers. The recovered initial energies of the incident radiations were well differentiated from the generated MSCC events. Correspondingly, we could obtain a multi-tracer image that combined the two differentiated images. The developed analytic simulator in this study emulated the randomness of the detection process of a multiple-scattering Compton camera, including the inherent degradation factors of the detectors, such as the limited spatial and energy resolutions. The Doppler-broadening effect owing to the momentum distribution of electrons in Compton scattering was not considered in the detection process because most interested isotopes for biomedical and environmental applications have high energies that are less sensitive to Doppler broadening. The analytic simulator and image generator for MSCC can be utilized to determine the optimal geometrical parameters, such as the distances between detectors and detector size, thus affecting the imaging performance of the Compton camera prior to the development of a real system.

• 디지털융복합연구
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• 제17권11호
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• pp.315-325
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• 2019

본 연구는 중년직장인 대상으로 건강상태, 노후준비가 노화불안에 미치는 영향에 대한 구조모형을 검증하고자 시도되었다. 연구대상은 C시와 G시에 소재하는 기관 3개소에 근무하는 40~59세 중년 직장인 263명을 대상으로 설문지를 이용하여 자료를 수집하였다. 연구결과 첫째, 노화불안에 영향을 미치는 변수들의 직접효과는 노후준비가 가장 큰 요인으로 나타났으며, 그 다음 건강상태 순으로 나타났고 이들 변인들은 노화불안 정도를 52% 설명하였다. 둘째, 건강상태가 노후준비에 유의한 영향을 미쳤으며, 노후준비를 통한 노화불안에 유의한 간접효과가 있는 것으로 나타났다. 40~49세와 50~59세 직장인 집단을 조절변수로 하는 다중집단 조절효과에서 건강상태와 노화불안의 경로계수가 집단간 차이가 있어 부분조절효과가 있었다. 따라서 노화불안을 줄이기 위해서는 다양한 노후준비에 대한 방안모색이 중요하며, 신체적, 정신적 건강상태를 잘 유지할 수 있는 체계적인 관리 시스템이 필요하다고 사료된다.

• 한국의학물리학회지:의학물리
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• 제31권4호
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• pp.135-144
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• 2020

Purpose: Gafchromic films for proton dosimetry are dependent on linear energy transfers (LETs), resulting in dose underestimation for high LETs. Despite efforts to resolve this problem for single-energy beams, there remains a need to do so for multi-energy beams. Here, a bimolecular reaction model was applied to correct the under-response of spread-out Bragg peaks (SOBPs). Methods: For depth-dose measurements, a Gafchromic EBT3 film was positioned in water perpendicular to the ground. The gantry was rotated at 15° to avoid disturbances in the beam path. A set of films was exposed to a uniformly scanned 112-MeV pristine proton beam with six different dose intensities, ranging from 0.373 to 4.865 Gy, at a 2-cm depth. Another set of films was irradiated with SOBPs with maximum energies of 110, 150, and 190 MeV having modulation widths of 5.39, 4.27, and 5.34 cm, respectively. The correction function was obtained using 150.8-MeV SOBP data. The LET of the SOBP was then analytically calculated. Finally, the model was validated for a uniform cubic dose distribution and compared with multilayered ionization chamber data. Results: The dose error in the plateau region was within 4% when normalized with the maximum dose. The discrepancy of the range was <1 mm for all measured energies. The highest errors occurred at 70 MeV owing to the steep gradient with the narrowest Bragg peak. Conclusions: With bimolecular model-based correction, an EBT3 film can be used to accurately verify the depth dose of scanned proton beams and could potentially be used to evaluate the depth-dose distribution for patient plans.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권4호
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• pp.1317-1341
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• 2021

Nowadays, the Internet of Things (IoT) is adopted to enable effective and smooth communication among different networks. In some specific application, the Wireless Sensor Networks (WSN) are used in IoT to gather peculiar data without the interaction of human. The WSNs are self-organizing in nature, so it mostly prefer multi-hop data forwarding. Thus to achieve better communication, a cross-layer routing strategy is preferred. In the cross-layer routing strategy, the routing processed through three layers such as transport, data link, and physical layer. Even though effective communication achieved via a cross-layer routing strategy, energy is another constraint in WSN assisted IoT. Cluster-based communication is one of the most used strategies for effectively preserving energy in WSN routing. This paper proposes a Bio-inspired cross-layer routing (BiHCLR) protocol to achieve effective and energy preserving routing in WSN assisted IoT. Initially, the deployed sensor nodes are arranged in the form of a grid as per the grid-based routing strategy. Then to enable energy preservation in BiHCLR, the fuzzy logic approach is executed to select the Cluster Head (CH) for every cell of the grid. Then a hybrid bio-inspired algorithm is used to select the routing path. The hybrid algorithm combines moth search and Salp Swarm optimization techniques. The performance of the proposed BiHCLR is evaluated based on the Quality of Service (QoS) analysis in terms of Packet loss, error bit rate, transmission delay, lifetime of network, buffer occupancy and throughput. Then these performances are validated based on comparison with conventional routing strategies like Fuzzy-rule-based Energy Efficient Clustering and Immune-Inspired Routing (FEEC-IIR), Neuro-Fuzzy- Emperor Penguin Optimization (NF-EPO), Fuzzy Reinforcement Learning-based Data Gathering (FRLDG) and Hierarchical Energy Efficient Data gathering (HEED). Ultimately the performance of the proposed BiHCLR outperforms all other conventional techniques.

• 한국정보통신학회논문지
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• 제24권6호
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• pp.768-777
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• 2020

본 논문에서는 이동 애드혹 네트워크에서 널리 사용되는 AODV 라우팅 프로토콜과 통신 노드의 이동성 때문에 발생하는 통신 경로 단절 등의 문제를 해결하기 위해 다중 경로설정을 지원하는 AODV 기법을 기반으로 개선된 다양한 연구 결과들을 분석한다. 그리고 AODV 기법이 사용하는 홉 기반 라우팅 기법의 문제점을 분석하고, 이를 개선하기 위해 홉 수를 주 메트릭으로 사용하면서 보조 메트릭으로 경로 지연시간의 합을 사용하는 새로운 C-AODV 라우팅 프로토콜을 설계하고, NS-3 네트워크 시뮬레이터에 구현하여 성능평가를 수행한다. 컴퓨터 시뮬레이션 성능평가 결과를 토대로 C-AODV 기법이 기존 AODV 기법과 비교하여 성능이 어느 정도 개선되는지 비교 분석하고 앞으로 개선할 사항 등을 제시한다.

• 한국정보전자통신기술학회논문지
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• 제13권6호
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• pp.545-555
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• 2020

본 논문에서는 부 대역 처리를 이용하는 수중 통신에서 은밀성과 성능 향상 관점에서 효율적인 송수신 구조를 제시하였다. 은밀성적인 측면에서는 암호화된 부호화 비트를 블록으로 나누어 각 비트의 정보를 이용하여 중심 주파수와 부 대역을 결정하므로 은밀성을 유지하는 측면에서 효과적이다. 수중 통신에서 성능적인 측면에서는 다중 경로 특성, 도플러 확산, 프레임 동기 등이 성능에 영향을 미치는 결정적인 요소이다. 따라서 본 논문에서는 이러한 요소들을 극복하기 위해, 비동기 에너지 검출 방식과 터보 등화 기법, 그리고 최적의 프레임 동기 방식을 제안하여 수신부에 적용하였다. 호수 실험에서 최적의 프레임 동기 방식을 수신부에 적용한 결과 다섯 개의 프레임 중에서 네 개의 프레임에서 오류를 모두 정정함을 확인하였다.

• Journal of information and communication convergence engineering
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• 제20권1호
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• pp.22-30
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• 2022

The reinforcement learning algorithm has proven its potential in solving sequential decision-making problems under uncertainties, such as finding paths to route data packets in wireless sensor networks. With reinforcement learning, the computation of the optimum path requires careful definition of the so-called reward function, which is defined as a linear function that aggregates multiple objective functions into a single objective to compute a numerical value (reward) to be maximized. In a typical defined linear reward function, the multiple objectives to be optimized are integrated in the form of a weighted sum with fixed weighting factors for all learning agents. This study proposes a reinforcement learning -based routing protocol for wireless sensor network, where different learning agents prioritize different objective goals by assigning weighting factors to the aggregated objectives of the reward function. We assign appropriate weighting factors to the objectives in the reward function of a sensor node according to its hop-count distance to the sink node. We expect this approach to enhance the effectiveness of multi-objective reinforcement learning for wireless sensor networks with a balanced trade-off among competing parameters. Furthermore, we propose SDN (Software Defined Networks) architecture with multiple controllers for constant network monitoring to allow learning agents to adapt according to the dynamics of the network conditions. Simulation results show that our proposed scheme enhances the performance of wireless sensor network under varied conditions, such as the node density and traffic intensity, with a good trade-off among competing performance metrics.

• 한국컴퓨터정보학회논문지
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• 제27권4호
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• pp.119-125
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• 2022

본 연구에서는 다문화청소년의 문화적응스트레스와 삶의 만족도 간의 경로에서 자아존중감과 학교생활적응의 매개효과를 살펴보고, 다문화청소년의 삶의 만족도 수준 향상 방안을 제안하고자 한다. 이를 위한 분석자료로 한국청소년 정책연구원의 다문화 청소년 4차, 5차, 6차 패널 데이터를 활용하였으며, 통계 프로그램 SPSS 23.0과 Amos 23.0 version을 이용한 다변량 잠재성장모형 분석을 실시하였다. 또한, 팬텀변수를 이용하여 자아존중감과 학교생활적응의 개별 매개효과를 검증하였다. 분석결과, 자아존중감과 학교생활 적응의 개별 매개효과를 확인할 수 있었으며, 이런 결과는 다문화 청소년의 삶의 만족도에 영향을 미치는 자아존중감과 학교생활 적응 수준 향상을 위해 다각적인 차원의 노력이 필요함을 시사한다. 이에 본 연구에서의 결과를 토대로 다문화청소년의 삶의 만족도 수준 향상을 위한 실천적인 방안을 구체적으로 제시하였다.

• 한국콘텐츠학회논문지
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• 제22권3호
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• pp.529-537
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• 2022

본 연구는 인구 고령화 및 1인가구의 증가 등의 사회문제를 고려하여 1인가구 중고령자의 사회참여활동, 인지기능, 우울의 관계를 분석하고 이 관계에 대하여 인지저하 및 치매의심 집단과 일반집단에 따른 집단비교 분석을 실시하는 데 목적을 두었다. 분석을 위해 경로분석 및 다집단분석을 실시하였고, 분석결과 1인가구 중 고령자의 사회참여활동은 인지기능 증가를 통해 우울을 감소시키는 것으로 나타났고, 사회참여활동의 긍정적 효과는 인지저하 및 치매의심 집단에서 더 강한 것으로 확인되었다. 이러한 결과를 토대로 사회참여활동과 사회참여활동을 촉진할 수 있는 방안, 인지기능이나 정신건강에 도움이 될 수 있는 프로그램 개발에 대한 시사점을 논의하였고, 특히 인지기능이 저하되어 있는 집단에서 사회참여활동의 효과가 더 긍정적이었다는 점을 감안하여, 요양시설 등에서 고립된 치료보다는 사회성 증진을 함께 도모할 수 있는 프로그램이나 치료방법의 필요성 등을 제언하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권9호
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• pp.3138-3151
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• 2022

Traffic safety and congestion are becoming more and more serious, especially the frequent occurrence of traffic accidents, which have caused great casualties and economic losses. Cellular Vehicle to Everything (C-V2X) can assist in safe driving and improve traffic efficiency through real-time information sharing and communication between vehicles. All vehicles communicate directly with Base Stations (BS), which will increase the base station load. And when the communicating vehicles are too far apart, too fast or there are obstacles in the communication path, the communication link can be unstable or even interrupted. Therefore, choosing an effective and reliable multi-hop relay-assisted Vehicle to Vehicle (V2V) communication can not only reduce the base station load and improve the system throughput but also expand the base station coverage and improve the communication quality of edge vehicles. Therefore, a communication area division scheme based on regular hexagon segmentation technology is proposed, a relay-assisted V2V communication mechanism is designed for the divided communication areas, and an efficient communication link is constructed by selecting the best relay node. Simulation results show that the scheme can improve the throughput of the system by nearly 55% and enhance the robustness of the V2V communication link.