• 대한전자공학회논문지TC
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• 제49권5호
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• pp.72-76
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• 2012

이동성이 있는 센서 노드로 구성 된 센서 네트워크를 효율적으로 사용하기 위하여 고려해야 할 사항 중 중요한 것이 자원의 효율적인 사용과 신호를 빠르고 정확하게 보내는 것이다. 본 논문에서는 무선 센서 네트워크 내에서 SNR(Signal to Noise Ratio)과 릴레이 노드의 신호 증폭률 그리고 노드와 노드 간 직접적으로 통신하는 경우 경로의 이득의 변화에 따른 무선 센서 네트워크의 특성에 대하여 분석하고 다수의 협동 릴레이 노드가 존재할 때 선택기준을 제시하고 이에 따른 영향을 정량적으로 평가하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권2호
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• pp.611-627
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• 2017

For enhancing the coverage of wireless networks and increasing the spectrum efficiency, small cell networks (SCNs) are considered to be one of the most prospective schemes. Most of the existing literature on resource allocation among non-cooperative small cell base stations (SBSs) has widely drawn close attention and there are only a small number of the cooperative ideas in SCNs. Based on the motivation, we further investigate the cooperative approach, which is formulated as a coalition formation game with power control algorithm (CFG-PC). First, we formulate the downlink sub-channel resource allocation problem in an SCN as a coalition formation game. Pareto order and utilitarian order are applied to form coalitions respectively. Second, to achieve more availability and efficiency power assignment, we expand and solve the power control using particle swarm optimization (PSO). Finally, with our proposed algorithm, each SBS can cooperatively work and eventually converge to a stable SBS partition. As far as the transmit rate of per SBS and the system rate are concerned respectively, simulation results indicate that our proposed CFG-PC has a significant advantage, relative to a classical coalition formation algorithm and the non-cooperative case.

• Journal of Industrial and Engineering Chemistry
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• 제68권
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• pp.238-245
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• 2018

The skin experiences constant physical stimuli, such as stretching. Exposure to excessive physical stimuli stresses the skin and can accelerate aging. In this study, we applied a method that allowed human fibroblasts and keratinocytes to be perfused with media to form 3D skin equivalents that were then uniaxially 10%-stretched for 12 h per day (at either 0.01 or 0.05 Hz) for up to 7 days to form wrinkled skin-on-a-chip (WSOC). There was more wrinkling seen in skin equivalents under 0.01 Hz uniaxial stretching than there was for non-stretched skin equivalents. At 0.05 Hz, the stratum corneum almost disappeared from the skin equivalents, indicating that stretching was harmful for the epidermis. At both frequencies, the production of collagen and related proteins in the skin equivalents, such as fibronectin 10 and keratin, decreased more than those in the non-stretched equivalents, indicating that the dermis also suffered from the repeated tensile stress. These results suggest that WSOCs can be used to examine skin aging and as an in vitro tool to evaluate the efficacy of anti-wrinkle cosmetics and medicines.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권10호
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• pp.4231-4245
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• 2020

Non-orthogonal multiple access (NOMA) is widely studied in both academia and industry due to its high spectral efficiency over orthogonal multiple access (OMA). To effectively improve spectrum efficiency, an amplify-and-forward (AF) cooperative NOMA system is proposed as well as a novel detection scheme is proposed, in which we first perform successive interference cancellation (SIC) twice at U1 for the two signals received from two time slots to remove interference from symbol 2, then two new signals apply max ratio combining (MRC). In addition, a closed-form upper bound approximation for the ergodic capacity of our proposed system is derived. Monte-Carlo simulations and numerical analysis illustrate that our proposed system has better ergodic capacity performance than the conventional cooperative NOMA system with decode-forward (DF) relay, the conventional cooperative NOMA system with AF relay and the proposed AF cooperative NOMA system in [16]. In addition, we can see that ergodic capacity of all NOMA cooperative systems increase with the increase of transmit SNR. Finally, simulations display that power allocation coefficients have little effect on ergodic capacity of all NOMA cooperative systems. This is due to this fact that ergodic capacity of two symbols can be complementary with changing of power allocation coefficients.

• 한국학교보건학회지
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• 제35권3호
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• pp.113-122
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• 2022

Purpose: The purpose of this study was to identify the effects of applying jigsaw cooperative learning to basic nursing practicums on self-directed learning ability, self-efficacy, and learning outcomes. Methods: This study was based on a non-equivalent control group design, and the subjects were nursing students. The study allocated 30 people in the experimental group and 30 people in the control group, and jigsaw cooperative learning was applied to the experimental group for 2 hours every week for a total of 8 weeks. The traditional educational method was applied to the control group. The collected data were analyzed using SPSS v26.0. Results: The experimental group to which jigsaw cooperative learning was applied showed statistically significant differences in self-directed learning ability (F=4.49, p=.038), self-efficacy (F=6.15, p=.016), and learning outcomes (F=19.48, p<.001) compared to the control group. Conclusion: By applying jigsaw cooperative learning to basic nursing practicums, this study confirmed its effect not only on the effective domain such as self-directed learning ability and self-efficacy, but also on learning outcomes in the practical domain. We propose future studies apply jigsaw cooperative learning to various practice classes to achieve learning outcomes that focus on cultivating students' practical capabilities.

• 방송공학회논문지
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• 제13권6호
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• pp.951-961
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• 2008

협력 통신은 각 노드가 데이터를 협력하여 전송하는 것으로, 자신의 노드 뿐 만 아니라 주변의 다른 노드들을 이용하여 데이터를 전송하는 통신 방식이다. 협력 통신을 하고 있는 모든 이동 노드로 부터 기지국으로 수신된 데이터를 결합하여 협력 다이버시티를 얻으므로 열악한 무선채널 환경에서 발생하는 극심한 페이딩을 억제시킴으로써 사용자의 QoS를 향상시킬 수 있다. 본 논문에서는 H.264/AVC에서 제공하는 에러에 대한 복원력을 높이기 위한 여러 가지 방식 중에서 유동적 매크로블록 순서화를 이용하고, 무선 채널에서는 협동 다이버시티를 이용하여 비디오 전송을 통해 화질을 향상 시킬 수 있는 기술을 제안한다. 사용자는 눈동자 추적기를 착용하고 있어서 소스 노드에게 현재 눈동자의 위치를 주기적으로 전송하고, 소스 노드는 그에 맞는 관심 영역 중심 코딩을 하게 된다. 관심영역과 비 관심영역으로 구분된 비디오를 서로 다른 채널을 통해서 전송함으로써 화질측면에서 더 높은 만족도를 얻게 됨을 확인하였다.

• Journal of Information Processing Systems
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• 제14권1호
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• pp.56-78
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• 2018

Security issue in mobile ad hoc network (MANET) is a promising research. In 2011, we had accomplished a survey of black hole attacks in MANETs. However network technology is changing with each passing day, a vast number of novel schemes and papers have been proposed and published in recent years. In this paper, we survey the literature on malicious attacks in MANETs published during past 5 years, especially the black hole attack. Black hole attacks are classified into non-cooperative and collaborative black hole attacks. Except black hole attacks, other attacks in MANET are also studied, e.g., wormhole and flooding attacks. In addition, we conceive the open issues and future trends of black hole detection and prevention in MANETs based on the survey results of this paper. We summarize these detection schemes with three systematic comparison tables of non-cooperative black hole, collaborative black hole and other attacks, respectively, for a comprehensive survey of attacks in MANETs.

• 한국콘텐츠학회논문지
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• 제22권4호
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• pp.535-546
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• 2022

본 연구는 S 대학교의 온라인 협력학습 질의응답에 관한 설문조사 결과를 바탕으로 온라인 비대면 교육 학업성취도 향상을 위한 요소들을 탐색하고자 하였다. 코로나 상황으로 전면 비대면 온라인 수업 시행으로 인한 교수자와 학습자 모두 심리적 고립감을 느끼기 쉬우며 학습 무기력 상태에서 혼자 공부하여야 하고 문제를 해결해 가야 하는 어려운 시기에 온라인 교육의 장점은 살리고 단점은 최소화하는 방법의 하나로 온라인 협력 학습 방법론을 적용한 수업 사례를 공유함으로써 여러 교수자와 학습자에게 미래 교육의 방향성을 제시하고자 하였다. 비대면 온라인 학습과 온라인 협력학습, 학습 촉진 방법론에 관한 선행연구를 검토하였고 구체적인 학습 촉진 방법으로 온라인 질의응답 방법론을 채택하여 연구를 진행하였다. 묻고 답하기(Q&A) 과정에서 학습자는 자신의 학습 내용을 점검하고 지식을 나누고 소통할 기회를 가질 수 있었으며, 질문자와 답변자의 익명성 보장, 향상점수제, 절대평가와 같은 성과평가 관련 요소들이 질의응답을 활용한 온라인 협력학습의 성공 요소로 설문 분석 결과 밝혀졌다. 온라인 비대면 학습이 지속될 가능성이 큰 미래에 실제 적용 가능한 작은 변화이지만 유의미한 교수방법론 적용사례를 공유함으로써 교수자와 학습자 모두에게 능동적이고 적극적으로 학습 현장을 바꾸고 보완해 함께 실력을 향상해 나갈 방법 및 방향성을 제시할 수 있을 것으로 기대한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권3호
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• pp.999-1021
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• 2023

Differential spatial modulation uses the antenna index to transmit information, which improves the spectral efficiency, and completely bypasses any channel side information in the recommended setting. A generalized distributed multiple turbo coded-cooperative differential spatial modulation based on distributed multiple turbo code is put forward and its performances in Rayleigh fading channels is analyzed. The generalized distributed multiple turbo coded-cooperative differential spatial modulation scheme is a coded-cooperation communication scheme, in which we proposed a new joint parallel iterative decoding method. Moreover, the code matched interleaver is considered to be the best choice for the generalized multiple turbo coded-cooperative differential spatial modulation schemes, which is the key factor of turbo code. Monte Carlo simulated results show that the proposed cooperative differential spatial modulation scheme is better than the corresponding non-cooperative scheme over Rayleigh fading channels in multiple input and output communication system under the same conditions. In addition, the simulation results show that the code matched interleaver scheme gets a better diversity gain as compared to the random interleaver.

• Asian Pacific Journal of Cancer Prevention
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• 제15권5호
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• pp.2089-2094
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• 2014

Background: Although many prognostic factors have been identified for lung cancers, new ones are needed to determine the course of the disease. Recently, a high neutrophil to lymphocyte ratio (NLR) prior to surgery or treatment has been shown to be an indicator of prognosis for cancer. The aim of this study was to investigate the value of NLR as a prognostic factor and the correlation between NLR and other probable clinical prognostic factors in non small cell lung cancer patients prior to treatment. Materials and Methods: Data of patients who were diagnosed with non-small cell lung cancer in our institution were retrospectively reviewed. Demographic and clinicopathologic characteristics were recorded. NLR was calculated before the application of any treatment. Results: A total of 299 patients, 270 (90%) males and 29 (10%) females, were included in the study. Age (p<0.001) stage (p<0.001), Eastern Cooperative Oncology Group performance status (p<0.001), weight loss (p<0.001), anemia (p<0.001), histopatology (p<0.001), NLR ${\geq}3$ (p=0.048), NLR ${\geq}4$ (p=0.025) and NLR ${\geq}5$ (p=0.018) were found to be the prognostic factors. Age, anemia, Eastern Cooperative Oncology Group performance status, the stage, NLR (${\geq}5$) were an independent prognostic factors. There was a positive correlation between NLR and the Eastern Cooperative Oncology Group performance status (0.23, p=0.001), the C reactive protein levels (r=0.36, p<0.001). Conclusions: Prior to treatment high NLR was found as an independent poor prognosis factor. Besides, NLR correlated with Eastern Cooperative Oncology Group performance status and the C reactive protein levels.