• 한국통신학회논문지
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• 제38B권10호
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• pp.832-842
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• 2013

Cognitive Radio has attracted intensive interests of the researchers, recently. The data rate always increases in the emerging technologies. The increased data rate poses mainly two challenges for spectrum sensing. One is that the state of primary user (PU) is fast and alternatively varying between "on/off" in a spectrum sensing window. The other is that the asynchronicity among the reports in a cooperative spectrum sensing setting becomes more apparent. Both of them would deteriorate the spectrum sensing performance. Thus, we propose an asynchronous cooperative spectrum sensing method to cope with these two challenges. A likelihood ratio test based spectrum sensing is developed for a single cooperator. The likelihood ratio is obtained in the setting of fast varying PU state. The likelihood ratio test is uniformly powerful according to the Neyman-pearson lemma. Furthermore, the asynchronicity among the cooperators are studied. Two sets of fusion weights are discussed for the asynchronous time among cooperators. One is designed based on the condition probability of the PU state variation and the other one is designed based on the queueing theory. The simulation results are provided with different fusion methods. The performance improvements are demonstrated.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2017년도 추계학술대회
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• pp.609-610
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• 2017

무선 통신 서비스의 증가에 따라 부족한 스펙트럼을 효율적으로 사용하고자하는 인지무선통신기법이 주목받고 있다. 인지무선통시에서는 주 사용자에 대한 간섭을 최소화하려는 노력이 중요한 기술적 요소가 된다. 본 논문에서 고려하고 있는 멀티채널을 갖는 에드혹 인지무선네트워크에서 멀티홉전송을 하기 위해서는 주 사용자와의 충돌뿐아니라 채널간의 간섭을 고려하여 경로 및 채널 선택이 이루어 져야한다. 멀티채널 환경에서 무선인지통신은 채널 간에 간섭과 주 사용자와의 충돌에 따라 서로 다른 용량를 갖게 된다. 본 논문에서는 멀티채널 환경에서 채널 간 간섭을 최소화하며 주 사용자와의 충돌을 줄임으로써 전송용량을 높일 수 있는 멀티홉 전송방식을 제안하고 성능을 비교 분석하였다.

• International Journal of Computer Science & Network Security
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• 제22권2호
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• pp.394-398
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• 2022

The article determines that the study of the development of scientific and didactic knowledge about the educational process in higher education should be built mainly on the basis of qualitative research methods that ensure the identification and understanding of the changes taking place in didactic knowledge, in the unity of their internal and external manifestations. On the basis of the epistemological model of the study of science, a generalized model of didactic knowledge about the educational process in higher education, including didactic relations as a theoretical core, subject of research, research methods and positions of researchers, ways of interaction between science and educational practice, and thematic structures of didactic knowledge; scientific and methodological problems of didactic knowledge about the educational process in higher education at the present stage of its developments due to the post-nonclassical transformation and orientation of research towards the humanitarian ideal of scientific character.

• 한국컴퓨터정보학회논문지
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• 제27권11호
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• pp.305-314
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• 2022

본 연구는 중국 안산시의 초중등학교 교사들의 "사회적 사고방식"을 연구하려는 시도가 이루어졌다. 연구를 진행하기 위해 안산시에 있는 298명 교사를 선정하여 설문조사를 실시하였다. 본 연구는 문헌조사와 설문조사를 결합한 방법을 채택하였다. 그 결과 안산시 초·중등학교 교사들의 전반적인 '사회심리학' 수준이 상대적으로 높은 것으로 나타났다. 교육 배경이 다른 교사의 직업 만족도에는 상당한 차이가 있습니다. 경로 모델은 변수 간의 상호 작용 메커니즘을 보여줍니다. 일반적인 자기 효능감과 업무 몰입도는 이 메커니즘에서 중요한 역할을 합니다.

• 복식문화연구
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• 제16권2호
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• pp.397-407
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• 2008

Recently, influence of color has been expanded in various fields including design field. Among human five senses, visual sense is best for information capturing, and 80% of information judgment by visual sense is from color. Color is emotion and image. Hanbok is marked by its beautiful color combinations. The guiding principle of such color chords was Obangsaek, or the traditional Korean five base colors. The method of this study is to consider concepts of Obangsaek derived from the principles of yin-yang and the five elements and is to investigate application of Obangsaek. And the purpose of this study is to understand traditional colors and is to provide judgment criteria on various color combinations based on Korean aesthetic sense for development of textile design. The degree of nation culture depends on the level of research, analysis and application on traditional colors. Obangsaek, Korean traditional color is splendid and primary color. Also, Obangsaek has symbolic and lucky meanings. These colors are still the primary source of coloring. Obangsaek has been reinterpreted by application on textile design, some into base colors and others into diverse shades. So this study will help in the aspect of development on Korean style design.

• Asian Pacific Journal of Cancer Prevention
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• 제17권1호
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• pp.439-443
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• 2016

Background: To assess the effect of an information leaflet on the level of Chinese youth's knowledge about hepatitis B and hepatocellular carcinoma (HCC), the most common type of primary liver cancer (PLC). Materials and Methods: A total of 500 students, from two universities in the Chaoshan area of China, were randomly divided into an intervention group of 280 participants and a control group of 220. Baseline knowledge of HCC and hepatitis B was evaluated by questionnaire interview. Subsequently, only the intervention group was given an information leaflet of HCC and hepatitis B. Three months later, the two groups were contacted for a second interview. Changes in knowledge from baseline of HCC and hepatitis B were compared between the two groups. Results: There was no statistically significant difference in mean PRE-questionnaire scores between the intervention and control groups. However, the mean POST-questionnaire score was significantly higher in the intervention group after the intervention. The leaflet had the greatest effect on the participants' questionnaire score, and raised their level of knowledge about HCC and hepatitis B. Conclusions: The information leaflet intervention is significantly effective in improving the knowledge of HCC and hepatitis B among the youth.

• 대한원격탐사학회지
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• 제29권3호
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• pp.275-291
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• 2013

Monitoring the global Gross Primary Pproduction (GPP) is relevant to understanding the global carbon cycle and evaluating the effects of interannual climate variation on food and fiber production. GPP, the flux of carbon into ecosystems via photosynthetic assimilation, is an important variable in the global carbon cycle and a key process in land surface-atmosphere interactions. The Moderate-resolution Imaging Spectroradiometer (MODIS) is one of the primary global monitoring sensors. MODIS GPP has some of the problems that have been proven in several studies. Therefore this study was to solve the regional mismatch that occurs when using the MODIS GPP global product over Korea. To solve this problem, we estimated each of the GPP component variables separately to improve the GPP estimates. We compared our GPP estimates with validation GPP data to assess their accuracy. For all sites, the correlation was close with high significance ($R^2=0.8164$, $RMSE=0.6126g{\cdot}C{\cdot}m^{-2}{\cdot}d^{-1}$, $bias=-0.0271g{\cdot}C{\cdot}m^{-2}{\cdot}d^{-1}$). We also compared our results to those of other models. The component variables tended to be either over- or under-estimated when compared to those in other studies over the Korean peninsula, although the estimated GPP was better. The results of this study will likely improve carbon cycle modeling by capturing finer patterns with an integrated method of remote sensing.

• 한국통신학회논문지
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• 제33권11A호
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• pp.1013-1020
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• 2008

코그니티브 라디오(cognitive radio) 기술 중 같은 지역에서 코그니티브 사용자와 우선사용자가 주파수를 공유하여 사용하는 방법은 단위 지역 당 주파수 사용효율을 향상시킬 수 있는 중요한 기술로 인식되고 있다. 본 논문에서는 코그니티브 라디오 시스템이 우선사용자에게 간섭을 미치지 않으며 동일 지역에서 우선사용자와 주파수를 공유할 수 있는 직교 빔 형성 방법을 제안한다. 제안된 방법은 우선사용자의 채널상태정보(channel state information)로부터 얻어진 부공간에 직교하는 코그니티브 라디오 사용자를 위한 부공간을 형성함으로써 우선사용자에게 간섭을 주지 않으며 주파수를 공유할 수 있는 코그니티브 라디오 사용자를 위한 다중 빔을 생성한다. 그러고, 코그니티브 라디오 시스템의 합 용량을 증가시키기 위해 기회적 무선자원할당 기법을 적용하였다. 전산모의 실험을 통해 제안된 주파수 공유 방법이 우선사용자에게 간섭을 주지 않음을 보였고 코그니티브 라디오 기지국이 2개의 안테나를 사용할 경우 시스템 합용량이 일반 셀룰라 시스템의 빔 포밍을 적용한 결과와 유사하게 사용자 20명에서 최대 2.72bps/Hz를 얻을 수 있음을 확인하였다.

• 한국위성정보통신학회논문지
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• 제7권1호
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• pp.39-47
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• 2012

현재의 주파수 분배상황을 살펴보면 대부분의 주파수 대역이 고정 할당되어 있으며 특히 무선통신 환경에 가장 적합한 저주파 대역은 거의 사용할 여지가 없다. 이에 인지무선 기술은 무선통신환경에서 주파수 부족 문제를 해결하고 주파수 활용도를 높이기 위한 중요한 기술로 대두되고 있다. 본 논문에서는 SDR (Software Define Radio)플랫폼인 USRP (Universal Software Radio Peripheral) 보드와 SDR 개발 툴킷인 GNU Radio를 이용하여 실제 인지무선(Cognitive Radio : CR) 시스템에서 데이터를 송, 수신하였다. 구체적으로 스펙트럼 센싱 기술을 이용하여 면허 사용자의 주파수 사용 여부를 감지하여 이 정보를 데이터베이스로 넘겨준다. 정보를 넘겨받은 데이터베이스에서는 유전자 알고리즘을 이용하여 최적의 송신전력과 대역폭, 채널 정보를 인지무선 기기에 보내어 주어 인지무선 기기가 면허 사용자에게 아무런 간섭을 주지 않고 데이터 통신을 할 수 있도록 하였다.

• Journal of Communications and Networks
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• 제16권1호
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• pp.56-66
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• 2014

We propose a novel opportunistic access scheme for cognitive radios in an interweave cognitive system, that considers the channel gain as well as the predicted idle channel probability (primary user occupancy: Busy/idle). In contrast to previous work where a cognitive user vacates a channel only when that channel becomes busy, the proposed scheme requires the cognitive user to switch to the channel with the next highest idle probability if the current channel's gain is below a certain threshold. We derive the threshold values that maximize the long term throughput for various primary user transition probabilities and cognitive user's relative movement.