• Journal of Communications and Networks
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• 제14권1호
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• pp.51-62
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• 2012

The exponential growth in wireless services has resulted in an overly crowded spectrum. The current state of spectrum allocation indicates that most usable frequencies have already been occupied. This makes one pessimistic about the feasibility of integrating emerging wireless services such as large-scale sensor networks into the existing communication infrastructure. Cognitive radio is an emerging dynamic spectrum access technology that can be used for flexibly and efficiently achieving open spectrum sharing. Cognitive radio is an intelligent wireless communication system that is aware of its radio environment and that is capable of adapting its operation to statistical variations of the radio frequency. In ad hoc cognitive radio networks, a common control channel (CCC) is usually used for supporting transmission coordination and spectrum-related information exchange. Determining a CCC in distributed networks is a challenging research issue because the spectrum availability at each ad hoc node is quite different and dynamic due to the interference between and coexistence of primary users. In this paper, we propose a novel CCC selection protocol that is implemented in a distributed way according to the appearance patterns of primary systems and connectivity among nodes. The proposed protocol minimizes the possibility of CCC disruption by primary user activities and maximizes node connectivity when the control channel is set up. It also facilitates adaptive recovery of the control channel when the primary user is detected on that channel.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2005년도 한국컴퓨터종합학술대회 논문집 Vol.32 No.1 (B)
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• pp.22-24
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• 2005

이동 컴퓨팅 환경에서 통신 네트워크가 갖는 무선 채널 대역폭의 협소함과 이동 단말기의 에너지 제약으로 인해, 다수의 이동 클라이언트들에게 데이터를 전달할 때에는 다수의 클라이언트들의 동시 데이터 접근을 지원하는 브로드캐스트 방법을 사용함으로써 제약점들을 보완할 수 있다. 본 논문에서는 클라이언트의 에너지와 데이터에 대한 접근시간(access time)의 효율을 높이기 위해 데이터의 접근빈도(access frequency)를 고려한 브로드캐스트 방법과 브로드캐스트 인덱스를 추가하는 방법을 함께 반영한 OAF(Data Access Frequencies)브로드캐스팅 기법을 제안한다. DAF브로드캐스팅 기법은 데이터의 접근빈도를 고려한 인덱스를 교차하여 추가함으로써 접근빈도가 높은 데이터를 원하는 다수의 사용자에 대한 접근시간을 줄임으로써 모든 사용자의 평균 접근시간을 줄이는데 목적이 있다. 수학적 분석을 통해 DAF브로드캐스팅 기법을 평가하고 기존의 브로드캐스트 방법과 DAF브로드캐스팅 기법의 성능을 비교 분석한다.

• 한국항해항만학회지
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• 제31권2호
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• pp.141-149
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• 2007

The competitiveness of container terminals hinges on minimizing the time vessels spend in port and on schedule services. Many previous researches on container terminals have tried to optimize the equipment allocation plan and to improve the activity of resources. Nevertheless, there have been few researches conducted on yard tractors, which move containers between the quay and the yard. The aim of this study is to propose the use of Real Time Location Systems (RTLS) based Dynamic Planning for yard tractors. Only RFID (Radio Frequency Identification) tags, which are attached to yard tractors, are able to support RTLS implementation. The system can provide real time job ordering in terms of load balancing using the information on location, in regards to the movement of yard tractors. This study will present the practical feasibility of RTLS, which can ultimately reduce the congestion of Hot Queues in container terminals. As a result, container terminals can be more productive and competitive. In order to accomplish the purpose of this study, we examined previous studies on the competitiveness of container terminals and summarized the potential of RTLS using RFID. In addition, we identified the role of yard tractors and proposed the two rules of Dynamic Planning for the yard tractors. We then fulfilled computational experiments on how yard tractors carrying containers by RTLS ordering Finally, the benefits and the implications of this study are discussed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권1호
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• pp.203-228
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• 2012

It is expected that device-to-device (D2D) communication is allowed to underlay future cellular networks such as IMT-Advanced for spectrum efficiency. This article studies the mechanisms of D2D communication and interference avoidance when the D2D subsystem reuses uplink resources and downlink spectrums with a cellular system, respectively. We firstly propose an effective scheme to establish and maintain D2D communication. Moreover, a novel method to deal with the resource allocation and interference avoidance issues by utilizing the network peculiarity of a hybrid network to share the uplink resource is proposed. Most research focuses on reusing the uplink spectrums, but how to share the downlink frequency bands is seldom addressed. To share the downlink spectrums and avoid the interference to the primary cellular devices, a labeled time slots based mechanism is proposed. Implementation details are described in a real cellular system and simulation results prove that satisfying performance can be achieved by using the proposed mechanisms.

• Journal of Yeungnam Medical Science
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• 제7권1호
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• pp.133-144
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• 1990

귀중한 혈액을 적절량 수혈함으로써 불필요한 노력과 혈액의 소모를 방지하며, 필요한 수술에 맞추어 소요 혈액량을 파악함으로 해서 혈액공급의 원할을 기할 수 있다. 1987년 1월부터 1988년 12월까지 2년간 영남대학교 의과대학 부속병원에서 수술에 사용된 혈액량을 주요 수술의 방법별로 조사하여, 각 수술에서의 수혈 빈도, 평균수혈량 및 예상 적정수혈량 등을 산정하고, 수혈량과 수혈환자의 나이, 수술전 혈색소치, 체중, 성별, 혈액형과의 관계를 살펴보았으며, 이를 토대로 하여 수술전 의뢰혈액량의 지침이 되도록 하였다.

• ETRI Journal
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• 제40권6호
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• pp.745-758
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• 2018

A wide range of studies in various disciplines has focused on the Internet of Things (IoT) and cyber-physical systems (CPS). However, it is necessary to summarize the current status and to establish future directions because each study has its own individual goals independent of the completion of all IoT applications. The absence of a comprehensive understanding of IoT and CPS has disrupted an efficient resource allocation. To assess changes in the knowledge structure and emerging technologies, this study explores the dynamic research trends in IoT by analyzing bibliographic data. We retrieved 54,237 keywords in 12,600 IoT studies from the Scopus database, and conducted keyword frequency, co-occurrence, and growth-rate analyses. The analysis results reveal how IoT technologies have been developed and how they are connected to each other. We also show that such technologies have diverged and converged simultaneously, and that the emerging keywords of trust, smart home, cloud, authentication, context-aware, and big data have been extracted. We also unveil that the CPS is directly involved in network, security, management, cloud, big data, system, industry, architecture, and the Internet.

• The Journal of Korean Physical Therapy
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• 제34권5호
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• pp.224-233
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• 2022

Purpose: In Japan, the Long-Term Care Insurance Act has stipulated visiting rehabilitation since 2000. This study aimed to identify the actual conditions of visiting rehabilitation in Japan through a literature review of reports published by the Japanese government. Methods: This literature review was conducted on eight articles among various government reports on the topic of the actual conditions of visiting rehabilitation. These reports were published by the Ministry of Health, Labor and Welfare of Japan based on their own investigations or reports from an external agency entrusted with the task, and were issued between 2000 and 2021. Results: The characteristics of the visiting rehabilitation offices, their number, manpower allocation, the number of users, and their visits to each office were identified. Also, the characteristics of the users, number of users, age and required degree of long-term care, causative disease, and required medical care were identified. To evaluate the actual status of the visiting rehabilitation service, the service use time, frequency, period of use, intervention by doctors and the degree of such intervention, therapist's service content, visitors' address before the use of the service, reason, and timing of the service introduction, evaluation of the service effectiveness, combination of services and transfer destination after termination, and status after service termination were checked. Conclusion: Based on the Japanese experience where visiting rehabilitation was introduced and applied to long-term care insurance, it would be meaningful to review the factors that required benchmarking among the Japanese service models while designing a similar model in Korea.

• 동아시아경상학회지
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• 제11권1호
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• pp.53-71
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• 2023

Purpose - This study aims to find clues necessary for the direction of leadership development suitable for the current situation by exploring the direction in which leadership has been studied from the perspective of domestic researchers, along with the arrangement of leadership theories studied in various ways. Research design, data, and methodology - A total of 7,425 papers were obtained due to the search, and 5,810 papers with English abstracts were used for analysis. For analysis, word frequency analysis, word clouding, and co-occurrence were confirmed using Python 3.7. In addition, after classifying topics related to research trends through BERTopic and LDA, trends were identified through dynamic topic modeling and OLS regression analysis. Result - As a result of the BERTopic, 14 topics such as 'Leadership management and performance' and 'Sports leadership' were derived. As a result of conducting LDA on 1,976 outliers, five topics were derived. As a result of trend analysis on topics by year, it was confirmed that five topics, such as 'military police leadership' received relative attention. Conclusion - Through the results of this study, a study on the reinterpretation of past leadership studies, a study on LMX with an expanded perspective, and a study on integrated leadership sub-factors of modern leadership theory were proposed.

• 융합경영연구
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• 제11권1호
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• pp.21-30
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• 2023

Purpose: As one of the ongoing studies on the distribution industry, the purpose of this study is to identify the research trends on online shopping so far to propose not only the development of online shopping companies but also the possibility of coexistence between online and offline retailers and the development of the distribution industry. Research design, data and methodology: In this study, the English abstracts of 645 papers on online shopping registered in scienceON were obtained. For the analysis through BERTopic and LDA using Python 3.7 and identifying which topics were interesting to researchers. Results: As a result of word frequency analysis and co-occurrence analysis, it was found that studies related to online shopping were frequently conducted on factors such as products, services, and shopping malls. As a result of BERTopic, five topics such as 'service quality' and 'sales strategy' were derived, and as a result of LDA, three topics including 'purchase experience' were derived. It was confirmed that 'Customer Recommendation' and 'Fashion Mall' showed relatively high interest, and 'Sales Strategy' showed relatively low interest. Conclusions: It was suggested that more diverse studies related to the online shopping mall platform, sales content, and usage influencing factors are needed to develop the online shopping industry.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권12호
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• pp.4081-4098
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• 2022

With the aim of tackling the contradiction between computation intensive industrial applications and resource-weak Edge Devices (EDs) in Industrial Internet of Things (IIoT), a novel computation task offloading scheme in SDIN-enabled MEC based IIoT is proposed in this paper. With the aim of reducing the task accomplished latency and energy consumption of EDs, a joint optimization method is proposed for optimizing the local CPU-cycle frequency, offloading decision, and wireless and computation resources allocation jointly. Based on the optimization, the task offloading problem is formulated into a Mixed Integer Nonlinear Programming (MINLP) problem which is a large-scale NP-hard problem. In order to solve this problem in an accessible time complexity, a sub-optimal algorithm GPCOA, which is based on hybrid evolutionary computation, is proposed. Outcomes of emulation revel that the proposed method outperforms other baseline methods, and the optimization result shows that the latency-related weight is efficient for reducing the task execution delay and improving the energy efficiency.