• International journal of advanced smart convergence
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• 제7권3호
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• pp.23-36
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• 2018

In wireless communication, efficient spectrum usage is an issue that has been an attractive research area for many technologies. Recently new technologies innovations allow compact radios to transmit with power efficient communication over very long distances. For example, Low-Power Wide Area Networks (LPWANs) are an attractive emerging platform to connect the Internet-of-Things (IoT). Especially, LoRa is one of LPWAN technologies and considered as an infrastructure solution for IoT. End-devices use LoRa protocol across a single wireless hop to communicate to gateway(s) connected to the internet which acts as a bridge and relays message between these LoRa end-devices to a central network server. The use of the (ISM) spectrum sharing for such long-range networking motivates us to implement spectrum sensing testbed for cognitive radio network based on LoRa and GNU radio. In cognitive radio (CR), secondary users (SUs) are able to sense and use this information to opportunistically access the licensed spectrum band in absence of the primary users (PUs). In general, PUs have not been very receptive of the idea of opportunistic spectrum sharing. That is, CR will harmfully interfere with operations of PUs. Subsequently, there is a need for experimenting with different techniques in a real system. In this paper, we implemented spectrum sensing for cognitive radio networks based on LoRa and GNU Radio, and further analyzed corresponding performances of the implemented systems. The implementation is done using Microchip LoRa evolution kits, USRPs, and GNU radio.

• 정보관리연구
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• 제40권3호
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• pp.1-21
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• 2009

본 연구에서는 기존의 전거제어 방식의 단점을 보완할 수 있는 표목의 구조화 방안을 제시하고자 하였다. 먼저 표목의 연결 구조를 전거형식과 그 이형을 참조로 연결하는 구조에서 동등한 접근점 간의 연결 구조로 개선하였으며, 전거형식 대신 전거제어번호를 식별기호로 도입하는 방안을 고려하였다. 그리고 동명이인이나 동명이단체의 식별을 위해 관련 저작정보를 제시하는 등 추가 식별정보를 제시하였으며, 전거데이터 표기체계를 기술하여 전거데이터의 교환과 공유를 촉진시키는 데 활용하도록 하였다. 또한 이 연구에서 제시한 표목의 구조화 방식을 적용하여 전거레코드를 작성하기 위한 전거시스템을 구축하였다. 그 결과, 대표형식을 선정하는 데 있어서의 어려움이 있었던 기존의 방식과 달리 전거형식을 폐지해도 전거레코드의 작성 및 유지에 어려움이 없으며, 전거레코드의 식별과 교환 측면이 강화되었음을 확인하였다.

• 한국과학교육학회지
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• 제39권6호
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• pp.739-753
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• 2019

본 연구는 과학 논변 활동을 생산적으로 프레이밍하는 초임 과학교사의 반응적 교수 실행의 특징과 한계에 대해 프레이밍 관점에서 분석했다. 논변 수업을 해본 적이 없는 초임 교사와 2개 학급 총 52명의 중학생이 연구에 참여하였고, 자극과 반응 단원에서 논변 활동을 도입하였다. 학생들은 귀의 구조와 기능을 학습한 뒤, 고막이 찢어지면 들을 수 없을까에 대한 개인의 논변을 구성하고 논의를 통해 소집단 논변을 구성하는 활동에 참여하였다. 교사의 반응적 교수 실행이 활발한 집단 중에서 소집단 구성원의 특징이 유사하였으나 논변 활동의 양상이 달랐던 두 소집단을 초점 집단으로 선정하였다. 학생들의 소집단 논의 과정과 교사 면담, 학생 면담, 학생 추가 면담은 녹화·녹음 되었다. 이를 전사하여 인식론적 프레이밍과 위치 짓기 프레이밍의 관점에서 반응적 교수 실행의 특징과 한계에 대하여 분석하였다. 연구 결과, 교사는 논변 활동에서 촉진자로서 학생들의 아이디어를 공유시킨 후, 서로 다른 의견을 합의해야 한다고 프레이밍하고 있었다. 이는 반응적 교수 실행에서 일치하게 나타났다. 교사는 소집단 과학 논변 활동에서 촉진자로서 학생 사고를 이끌어내고 탐색함으로써 학생 의견을 더욱 명료하게 제시하도록 논의를 아이디어 공유 논의로 프레이밍한 후, 서로 다른 의견의 불일치를 부각시키며 논의를 논쟁적 논의로 전환시키고자 노력하였다. 하지만 교사의 생산적인 프레이밍이 학생들의 생산적인 실행을 보장하지는 않았다. 초임교사는 학습자에 대한 이해가 부족하여 학생들의 추론을 정교화시킬 때 개념을 활성화시켜주는 데에 한계를 보였으며, 학생들의 인식론적 프레이밍에 주목하지 못했다는 한계를 보였다. 본 연구는 과학 수업에서 학생에게 반응적인 교수를 실행하는 문화를 정착시키는 데에 기여할 것이다.

• 한국수학사학회지
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• 제32권6호
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• pp.281-299
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• 2019

Mathematical problem solving has become a major concern in school mathematics, and methods to enhance children's mathematical problem solving abilities have been the main topics in many mathematics education researches. In addition to previous researches about problem solving, the development of a mathematical problem solving method that enables children to establish mathematical concepts through problem solving, to discover formalized principles associated with concepts, and to apply them to real world situations needs. For this purpose, I examined the necessity of problem solving education and reviewed mathematical problem solving researches and problem solving models for giving the theoretical backgrounds. This study suggested the problem solving approach based on the intuitive and the formal inquiry which are the basis of mathematical discovery and inquiry process. And it is developed to keep the balance and complement of the conceptual understanding and the procedural understanding respectively. In addition, it consisted of problem posing to apply the mathematical principles in the application stage.

• Nuclear Engineering and Technology
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• 제41권8호
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• pp.1005-1014
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• 2009

The Dual Unit Optimizer 2000 MWe (DUO2000) is put forward as a new design concept for large power nuclear plants to cope with economic and safety challenges facing the $21^{st}$ century green and sustainable energy industry. DUO2000 is home to two nuclear steam supply systems (NSSSs) of the Optimized Power Reactor 1000 MWe (OPR1000)-like pressurized water reactor (PWR) in single containment so as to double the capacity of the plant. The idea behind DUO may as well be extended to combining any number of NSSSs of PWRs or pressurized heavy water reactors (PHWRs), or even boiling water reactors (BWRs). Once proven in water reactors, the technology may even be expanded to gas cooled, liquid metal cooled, and molten salt cooled reactors. With its in-vessel retention external reactor vessel cooling (IVR-ERVC) as severe accident management strategy, DUO can not only put the single most querulous PWR safety issue to an end, but also pave the way to very promising large power capacity while dispensing with the huge redesigning cost for Generation III+ nuclear systems. Five prototypes are presented for the DUO2000, and their respective advantages and drawbacks are considered. The strengths include, but are not necessarily limited to, reducing the cost of construction by decreasing the number of containment buildings from two to one, minimizing the cost of NSSS and control systems by sharing between the dual units, and lessening the maintenance cost by uniting the NSSS, just to name the few. The latent threats are discussed as well.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권7호
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• pp.3041-3063
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• 2018

Community search aims at finding a meaningful community that contains the query node and also maximizes (minimizes) a goodness metric. This problem has recently drawn intense research interest. However, most metric-based algorithms tend to include irrelevant subgraphs in the identified community. Apart from the user-defined metric algorithm, how can we search the natural community that the query node belongs to? In this paper, we propose a novel community search algorithm based on the concept of the k-hop and local distance dynamics model, which can naturally capture a community that contains the query node. The basic idea is to envision the nodes that k-hop away from the query node as an adaptive local dynamical system, where each node only interacts with its local topological structure. Relying on a proposed local distance dynamics model, the distances among nodes change over time, where the nodes sharing the same community with the query node tend to gradually move together, while other nodes stay far away from each other. Such interplay eventually leads to a steady distribution of distances, and a meaningful community is naturally found. Extensive experiments show that our community search algorithm has good performance relative to several state-of-the-art algorithms.

• 제어로봇시스템학회논문지
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• 제19권11호
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• pp.1022-1028
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• 2013

It is well knowns that based on the CSP (Common Spatial Pattern) algorithm, the linear projection of an EEG (Electroencephalography) signal can be made to spaces that optimize the discriminant between two patterns. Sharing disadvantages from linear time invariant systems, CSP suffers from the non-stationary nature of EEGs causing the performance of the classification in a BCI (Brain-Computer Interface) system to drop significantly when comparing the training data and test data. The author has suggested a simple idea based on the parallel model of CSP filters to improve the performance of BCI systems. The model was tested with a simple CSP algorithm (without any elaborate regularizing methods) and a perceptron learning algorithm as a classifier to determine the improvement of the system. The simulation showed that the parallel model could improve classification performance by over 10% compared to conventional CSP methods.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권5호
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• pp.1606-1623
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• 2015

Optical switching will be applied in datacenter networks because electronic switching is costly and power-consuming. In this paper, considering the ring-based interconnection using optical switching in the core of a datacenter, we study the home circuit (HC) construction for the labeled optical burst switching with home circuit (LOBS-HC), a new paradigm trying to share wavelengths among the HCs from the same source. In particular, aiming to construct HCs dynamically and properly, a scheme named optimal path matching and symmetric HC matching (OPM-SHM) is proposed. The main idea of OPM-SHM is to dynamically construct HCs by sharing wavelength(s) not only among the same-source HCs but also with symmetric HCs which have different sources other than the original LOBS-HC features. The simulation results demonstrate that OPM-SHM achieves better performance than some other methods in terms of burst loss rate and wavelength utilization of physical links. More specially, it maintains good load balancing for the datacenter network using an LOBS-HC ring. In addition, due to the symmetric feature of SHM, the proposed scheme can decrease the upper bound of the average hop count of the routing paths to half of the ring size.

• 디지털산업정보학회논문지
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• 제10권1호
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• pp.139-146
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• 2014

Through numerous mobile device technology advances, various multimedia contents is moving towards mobile devices from existing personal computer (PC). These paradigm has emerged taking into account these idea, the so-called N-Screen, N-Screen is user-centric service to provide running and sharing on everywhere via advanced smart system in C-P-N-T (Content, Platform, Network, Terminal). Therefore we must provide securing of various contents, openended platform, and user-centric service for efficient N-Screen service. For These characteristic of N-Screen, this paper propose design and implementation of user location-based N-Screen service system. The proposed system realize user location through user's smart phone and offer automatic streaming service to user. And also, we provide web service-based extended N-Screen service. Thus, user can access various device, such as laptop, tablet, and mobile device.

• 유통과학연구
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• 제14권9호
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• pp.25-29
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• 2016

Purpose - Finding top K persuaders in consumer network is an important problem in marketing. Recently, a new method of computing persuasion scores, interpreted as fixed point or stable distribution for given persuasion probabilities, was proposed. Top K persuaders are chosen according to the computed scores. This research proposed a new definition of persuasion scores relaxing some conditions on the matrix of probabilities, and a method to identify top K persuaders based on the defined scores. Research design, data, and methodology - A new method of computing top K persuaders is computed by singular value decomposition (SVD) of the matrix which represents persuasion probabilities between entities. Results - By testing a randomly generated instance, it turns out that the proposed method is essentially different from the previous study sharing a similar idea. Conclusions - The proposed method is shown to be valid with respect to both theoretical analysis and empirical test. However, this method is limited to the category of persuasion scores relying on the matrix-form of persuasion probabilities. In addition, the strength of the method should be evaluated via additional experiments, e.g., using real instances, different benchmark methods, efficient numerical methods for SVD, and other decomposition methods such as NMF.