• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권10호
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• pp.2338-2356
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• 2013

In cognitive radio networks, acquiring the position information of the primary user is critical to the communication of the secondary user. Localization of primary users can help improve the efficiency with which the spectrum is reused, because the information can be used to avoid harmful interference to the network while simultaneity is exploited to improve the spectrum utilization. Despite its inherent inaccuracy, received signal strength based on range has been used as the standard tool for distance measurements in the location detection process. Most previous works have employed the path-loss propagation model with a fixed value of the path loss exponent. However, in actual environments, the path loss exponent for each channel is different. Moreover, due to the complexity of the radio channel, when the number of channel increases, a larger number of RSS measurements are needed, and this results in additional energy consumption. In this paper, to overcome this problem, we propose using the Bayesian compressive sensing method with a calibrated path loss exponent to improve the performance of the PU localization method.

• 한국식품영양학회지
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• 제22권4호
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• pp.612-617
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• 2009

This study was conducted to assess the information of food safety by college students according to mass-media reports. To accomplish this, a survey was conducted to investigate the preference and reliability, of primary mass-media sources of BSE information, and BSE-related knowledge of college students. The most common sources of media by male and female students were terrestrial television(60%), the internet(21%) and newspapers(11%) and terrestrial television(60%), newspapers (18%) and the internet(17%), respectively. The reliability of media of male students were terrestrial television(53%) and the internet(40%), while for female students these values were terrestrial television(55%) and internet(37%), respectively. In the case of male students, the primary sources of information regarding BSE were terrestrial television(54%) and the internet(38%), but for female students the primary sources were terrestrial television(57%) and the internet(37%). Both male and female students were found to have less knowledge regarding prions, SRM, and MM type genes associated with BSE when compared to the other factors associated with this disease. In addition, the important determining factors for the food purchase of male and female students both were the orders of taste, hygiene, price. The preferences for meats and the beef-alternative meats of male and female students were the orders of pork, chicken. Based on these results, greater efforts should be made to provide meaningful information regarding the safe production and distribution of meats.

• 한국문헌정보학회지
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• 제49권3호
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• pp.273-289
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• 2015

This study examined changes in citation index scores and rankings of thirty-five chemistry faculty members at Seoul National University using different co-authorship credit allocation models. Using 1,436 Web of Science papers published between 2007 and 2013, we applied the inflated, fractional, harmonic, network-based allocation, and harmonic+ models to calculate faculty's h-, R-, and normalization of h- and R- index scores and rankings. The harmonic+ model, which is based on our belief that contribution of primary authors should be the same regardless of collaboration, is designed to minimize the penalty for research collaboration imposed by harmonic and NBA models by boosting the contribution of collaborating primary authors to be on the equal footing with single authors. Although citation rankings by different models are correlated with each other within the same type of citation indicator, rankings of many faculty members changed across models, suggesting the importance of an accurate and relevant authorship credit allocation model in the citation assessment of researchers. The study also found that authorship patterns in conjunction with citation counts are important factors for robust authorship models such as harmonic and NBA, and harmonic+ model may be beneficial for collaborating primary authors. Future research that reexamines the models with updated empirical data would provide further insights into the robustness of the models.

• Bulletin of the Korean Chemical Society
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• 제27권10호
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• pp.1577-1580
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• 2006

The article reports the synthesis and enantiomeric recognition of a new chiral azophenolic pyridino-18-crown-6 ether, (S,S)-6, possessing diphenyl groups as chiral barriers. The association constants for the enantiomeric recognition of chiral primary amines (7-12) using chiral azophenolic pyridino-18-crown-6 ether, (S,S)-6, were determined by UV-visible titration method in acetonitrile at $25{^{\circ}C}$.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2003년도 가을 학술발표논문집 Vol.30 No.2 (3)
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• pp.400-402
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• 2003

Ad­hoc Network는 Mobile Node들 간에 Multi­hop 무선 링크로 구성되는 Network을 일컫는 말이며, 동시에 Network를 통제하는 Infrastructure없이 Node들 간의 상호 통신에 의해서 Network이 구성되기도 하고, Node들이 이동하거나 환경적인 장애에 의해서 일시적으로 Network이 구성되지 않기도 한다. 이 논문에서는 대표적인 On­demand Routing Algorithm인 DSR를 이용하여, 두 개의 경로를 유지하여 Primary Path에 문제가 발생하는 경우, Secondary Path가 Primary Path로 전환되어 Data를 전송하고, 이 전 Primary Path에 대하여 지역적으로 복구(Repair)를 수행하고, 설정된 Secondary Path에 대해서도 특정한 조건에서 복구작업을 수행함으로써 Ad­hoc Network에서 경로를 찾고 설정하는데 필요한 Routing Overhead를 줄이고 Ad­hoc Network의 특성상 반드시 보완하여야 하는 전송 Route에 대한 Robustness를 강화하는 방법이다.

• IEIE Transactions on Smart Processing and Computing
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• 제3권4호
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• pp.173-180
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• 2014

Random access protocols feature inherent sensing functionality and distributed coordination, making them suitable for cognitive radio communication environments, where secondary users must detect the white space of the primary spectrum and utilize the idle primary spectrum efficiently without centralized control. These characteristics have led to the adoption of carrier-sensing-multiple-access/collision-avoidance (CSMA/CA) in cognitive radio. This paper proposes a new analytical framework for evaluating the performance of a CSMA/CA protocol that considers the characteristics of idle periods based on the primary traffic behavior in cognitive radio systems. In particular, the CSMA/CA-based secondary network was analyzed in the terms of idle period utilization, which is the average effective data transmission time portion in an idle period. The use of the idle period was maximized by taking its statistical features into consideration.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1859-1862
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• 2002

The replication of data is used to increase its availability, improve the performance of a system, and advance the fault-tolerance of a system. In this paper, it is required for the information about the location of a primary site of the replicas of each data item. The replicas of each data item are hierarchically organized to a tree based on the fact that the root is the primary replica in partially replicated databases. It eliminates useless propagation since the propagation can be done to only sites having replicas following the hierarchy of data. And our algorithm schedules transactions so that the execution order of updates at each primary site is identical at all sites by using timestamp. Using our algorithm, the consistent data are supplied and the performance of read-only transactions can be improved by using tree structure of replicas of each data item.

• Journal of information and communication convergence engineering
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• 제11권4호
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• pp.223-228
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• 2013

Cognitive radio has been recently considered a promising technology to improve spectrum utilization by enabling secondary access to licensed bands that are not used by primary users temporarily or spatially. A prerequisite to this secondary access is the lack of interference to the primary system. This requirement makes spectrum sensing a key process for cognitive radio. In this study, we consider amplify and forward (AF)-based cooperative spectrum sensing for cognitive radio networks where multiple relay nodes are utilized to amplify and forward the primary user signal for better spectrum sensing, and maximum ratio combining is used for fusion detection by a cognitive coordinator. Further, the detection probability and the bit error rate of AF-based cooperative spectrum sensing are analyzed in fading multiple cognitive relay channels. The simulation results show that the AF-based cooperative spectrum sensing scheme outperforms the conventional scheme.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2011년도 추계학술대회
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• pp.597-598
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• 2011

인지 무선 네트워크에서 제어 및 데이터 정보 전송을 위한 최적의 채널 선택 방법으로 주사용자의 트래픽 정보를 이용하여 유휴 채널 구간을 예측하는 기법을 제안하다. 채널예측을 통해 채널을 선택함으로서 주 사용자에 대한 충돌을 최소화하고 전송효율을 증가시킬 수 있다. 시뮬레이션 결과 제안한 방법이 시스템 수율을 향상시킴과 동시에 주사용자에 대한 간섭 또한 적정한 임계치 이하로 줄이는 것을 확인할 수 있었다.

• 대한전자공학회논문지TC
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• 제49권8호
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• pp.39-45
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• 2012

본 논문에서는 주파수 공유 환경에서 일차 사용자가 양방향 중계기 (full duplex relay, FDR)를 사용하는 경우의 이차 사용자의 통신 용량에 대해서 분석한 논문이다. 주파수 공유 시스템에서, 이차 사용자가 일차 사용자의 주파수를 공유하기 위해서는 다양한 일차 사용자의 시스템에 맞는 주파수 공유 기법이 연구되어야 한다. 그러나 기존의 연구들은 오직 일대일 통신 기반의 일차 사용자 시스템만을 고려하였다. 일차 사용자가 FDR을 사용할 때는 일차 사용자의 중계기와 목적지가 이차 사용자로부터 동시에 간섭을 받게 된다. 따라서 기존의 일대일 통신 기반의 주파수 공유 기법 보다 좀 더 엄격한 간섭 제약이 적용되어야 한다. 따라서 본 논문에서는 일차 사용자가 FDR을 사용하는 주파수 공유 시스템에서 평균 및 순시 간섭 파워 제약 조건 하에서의 이차 사용자의 통신 용량을 분석한다. 또한 이러한 시스템에서 간섭 제약을 고려했을 때의 성능 열화를 분석한다. 모의 실험 결과를 통해서 평균 간섭 파워 제약 조건 하에서의 이차 사용자 통신 용량과 일차 사용자의 통신 용량이 순시 간섭 파워 제약 조건 하에서의 통신용량보다 성능이 좋음을 확인하였다.