• International Journal of Naval Architecture and Ocean Engineering
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• 제11권2호
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• pp.782-795
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• 2019

Safety is always acritical focus of exploration of ocean resources, and it is well recognized that human factor is one of the major causes of accidents and breakdowns. Our research developed a dynamic human reliability assessment approach, Predicted Mean Vote-Cognitive Reliability and Error Analysis Method (PMV-CREAM), that is applicable to monitoring the cognitive reliability of oceanauts during deep-sea missions. Taking into account the difficult and variable operating environment of manned submersibles, this paper analyzed the cognitive actions of oceanauts during the various procedures required by deep-sea missions, and calculated the PMV index using human factors and dynamic environmental data. The Cognitive Failure Probabilities (CFP) were calculated using the extended CREAM approach. Finally, the CFP were corrected using the PMV index. This PMV-CREAM hybrid model can be utilized to avoid human error in deep-sea research, thereby preventing injury and loss of life during undersea work. This paper verified the method with "Jiaolong" manned submersible 7,000 m dive test. The"Jiaolong" oceanauts CR(Corrected CFP) is dynamic from 3.0615E-3 to 4.2948E-3, the CR caused by the environment is 1.2333E-3. The result shown the PMV-CREAM method could describe the dynamic human reliability of manned submersible caused by thermal environment.

• 약학회지
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• 제58권5호
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• pp.287-293
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• 2014

Alzheimer's disease (AD), most common form of dementia is characterized that memory deficit and loss of cognitive function. This study was evaluated cognitive enhancing effect of water and ethanol extracts of Codonopsis lanceolata and compared using Morris water maze and passive avoidance test. The water and 70% ethanol extracts (100, 300 and 500 mg/kg) were administered to mice. The neuroprotective effect on glutamate-induced cell death in HT22 cells was additionally investigated using MTT assay. Results showed 70% ethanol extract of Codonopsis lanceolata enhanced cognitive function than water extract, as shown by decrease in escape latency time in Morris water maze test. In passive avoidance test, 70% ethanol extract also increased the latency time compared to the water extract. Furthermore, 70% ethanol extract significantly protected neuronal cell against glutamate cytotoxicity and showed higher than neuroprotective effect of water extract. These results indicate that 70% ethanol extract more improve spatial cognitive ability and protected neuronal cells than water extract.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권3호
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• pp.1336-1356
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• 2017

The spectrum scarcity crisis has resulted in a shortage of resources for many emerging wireless services, and research on dynamic spectrum management has been used to solve this problem. Game theory can allocate resources to users in an economic way through market competition. In this paper, we propose a bidding game-based spectrum allocation mechanism in cognitive radio network. In our framework, primary networks provide heterogeneous wireless service and different numbers of channels, while secondary users have diverse bandwidth demands for transmission. Considering the features of traffic and QoS demands, we design a weighted interference graph-based grouping algorithm to divide users into several groups and construct the non-interference user-set in the first step. In the second step, we propose the dynamic bidding game-based spectrum allocation strategy; we analyze both buyer's and seller's revenue and determine the best allocation strategy. We also prove that our mechanism can achieve balanced pricing schema in competition. Theoretical and simulation results show that our strategy provides a feasible solution to improve spectrum utilization, can maximize overall utility and guarantee users' individual rationality.

• 한국ITS학회 논문지
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• 제9권1호
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• pp.27-33
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• 2010

주파수 부족 및 비효율적 활용을 완화시키기 위해 제안된 무선인지시스템은 기존의 1차 사용자에게 대한 간섭을 주지 않도록 하면서 유휴주파수를 사용하게 하는 기술로서 최근 주목받고 있는 차세대 이동통신 시스템이다. 최근 FCC는 실질적으로 TV대역에 무선인지 시스템을 적용하도록 하면서 관련된 규정을 개정하였고 TV대역의 유휴주파수에 대하여 고정기기 및 개인 휴대기기에 대한사용을 허가하도록 방침을 정하였으며 2009년 DTV로 전환 완료 이후 해당 기기들의 사용은 본격화 될 것이다 무선인지 시스템의 기본 방침안 면허 사용자에 대한 보호를 위하여 TV대역사용에서의 우선순위가 가장 높은 신호인 TV 및 무선마이크에 대한 보호가 이루어져야하는데 이를 위해 정확한 1차 사용자에 대한 검출，즉 TV대역의 1차 사용자인 DTV에 대한 정확한 스펙트럼 센싱이 이루어져야 한다. 본 논문에서는 스펙트럼 센싱 성능이 우수한 파일릿 센성을 이용하여 DTV신호를 검출하도록 하였고 DTV신호검출의 신뢰성 향상을 위하여 협력 센싱기반의 파일릿 센싱을 수행하여 DTV신호의 검출 확률의 정확성 및 신뢰성을 높이도록 하였다. 또한 각 단일 센싱 결과를 취합하여 판단하는 과정에서 효율적인 판단을 위해 다수의결법을 제안한다.

• 한국콘텐츠학회논문지
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• 제19권8호
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• pp.544-555
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• 2019

최근 급변하는 기업경영환경 속에서 인적자원관리에 대한 중요성은 커지고 있으며, 조직 내 업무효율성에 대한 관심도 증가하고 있다. 종업원은 조직에서 가장 중요하고 가치 있는 인적자원이라 할 수 있으며, 조직에서 목표 및 목적을 달성하는 데 가장 핵심적인 역할을 한다. 이에 본 연구에서는 직무만족을 인지적 만족도와 정서적 만족도로 구분하여 직무만족과 직무성과 간의 어떠한 관련성이 존재하는지 확인하다. 또한 리더십 유형이 만족도와 직무성과간에 어떤 조절효과가 있는지도 분석하였다. 인지적 만족도와 정서적 만족도가 직무성과에 영향을 주는지를 분석한 결과, 모두 영향을 주는 것으로 나타났다. 특히, 직무만족 중에서 정서적 만족도의 영향이 더 높게 나타났다. 다음으로, 리더십 유형의 영향력을 분석한 결과, 리더십이 직접적으로 조직성과에는 영향을 주지는 않는 것으로 나타났지만, 직무만족과 직무성과 사이에서 조절효과를 주는 것으로 나타났다. 즉, 거래적 리더십이 높을수록 정서적 만족도가 직무성과에 미치는 영향력이 더 높아지는 것으로 나타났다.

• 대한지구과학교육학회지
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• 제11권3호
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• pp.158-171
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• 2018

이 연구의 목적은 한국지질자원연구원 내 국제지질자 원인재개발센터의 지질과학 교육프로그램을 중심으로 중학생들의 인지적 발달수준에 따른 지질과학에 대한 태도와 교육만족도를 알아보고, 이들 사이에 어떠한 상관관계가 나타나는지 알아보는 데 있다. 연구대상은 2018년 국제지질자원인재개발센터에서 실시한 지질과학 교육프로그램에 참여한 중학생 282명 중 무선 표집 방법에 의한 139명이다. 따라서 연구결과는 다음과 같다. 첫째, 구체적 조작 단계는 44%, 과도기는 32%, 형식적 조작 단계는 24%로, 76%의 중학생들의 인지적 발달 수준은 형식적 수준에 도달하지 못하는 결과를 나타내었다. 또한 지질과학에 대한 태도는 통계적으로 유의미한 차이를 나타내었으며, 하위영역으로는 '지질 관련 과학수업 Geology-related science class', '교외 지질과학 Suburban geological science class', '지질과학과 기술에 대한인식 Recognition of geological science and technology'에서 통계적으로 유의미한 결과 값을 나타내었다. 둘째, 교육만족도는 인지적 발달수준에 따라 통계적으로 유의미한 차이는 없었다. 즉, 모든 인지적 수준의 연구 참여자들이 국제지질자원인재개발센터에서 진행하는 지질과학 교육프로그램에 대해서 높은 만족도를 나타내었다. 셋째, 교육만족도와 지질 과학에 대한 태도 사이의 상관관계는 통계적으로 의미 있는 정적 상관관계를 나타내었다. 따라서 학습 행동체계에 있어 국제지질자원인재개발센터의 교육 훈련에 참여한 연구 참여자들이 교육만족감을 높게 가질수록 지질 과학에 대한 태도도 긍정적으로 나타날 수 있다.

• Journal of Communications and Networks
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• 제11권2호
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• pp.122-133
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• 2009

As wireless spectrum resources become more scarce while some portions of frequency bands suffer from low utilization, the design of cognitive radio (CR) has recently been urged, which allows opportunistic usage of licensed bands for secondary users without interference with primary users. Spectrum sensing is fundamental for a secondary user to find a specific available spectrum hole. Cooperative spectrum sensing is more accurate and more widely used since it obtains helpful reports from nodes in different locations. However, if some nodes are compromised and report false sensing data to the fusion center on purpose, the accuracy of decisions made by the fusion center can be heavily impaired. Weighted sequential probability ratio test (WSPRT), based on a credit evaluation system to restrict damage caused by malicious nodes, was proposed to address such a spectrum sensing data falsification (SSDF) attack at the price of introducing four times more sampling numbers. In this paper, we propose two new schemes, named enhanced weighted sequential probability ratio test (EWSPRT) and enhanced weighted sequential zero/one test (EWSZOT), which are robust against SSDF attack. By incorporating a new weight module and a new test module, both schemes have much less sampling numbers than WSPRT. Simulation results show that when holding comparable error rates, the numbers of EWSPRT and EWSZOT are 40% and 75% lower than WSPRT, respectively. We also provide theoretical analysis models to support the performance improvement estimates of the new schemes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권1호
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• pp.149-168
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• 2015

In cognitive radio networks (CRNs), hybrid overlay and underlay sharing transmission mode is an effective technique for improving the efficiency of radio spectrum. Unlike existing works in the literature, where only one secondary user (SU) uses overlay and underlay modes, the different transmission modes should be allocated to different SUs, according to their different quality of services (QoS), to achieve the maximal efficiency of radio spectrum. However, hybrid sharing mode allocation for heterogeneous services is still a challenge in CRNs. In this paper, we propose a new resource allocation method for hybrid sharing transmission mode of overlay and underlay (HySOU), to achieve more potential resources for SUs to access the spectrum without interfering with the primary users. We formulate the HySOU resource allocation as a mixed-integer programming problem to optimize the total system throughput, satisfying heterogeneous QoS. To decrease the algorithm complexity, we divide the problem into two sub-problems: subchannel allocation and power allocation. Cutset is used to achieve the optimal subchannel allocation, and the optimal power allocation is obtained by Lagrangian dual function decomposition and subgradient algorithm. Simulation results show that the proposed algorithm further improves spectrum utilization with a simultaneous fairness guarantee, and the achieved HySOU diversity gain is a satisfactory improvement.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권7호
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• pp.2960-2976
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• 2018

The limited storage and computing capacity hinder the development of cognitive radio ad hoc networks (CRAHNs). To solve the problem, a new paradigm of cloud-based CRAHN has been proposed, in which a CRAHN will make use of the computation and storage resources of the cloud. This paper envisions an integrated CRAHN-cloud network architecture. In this architecture, some cognitive radio users (CUs) who satisfy the required metrics could perform as mobile gateway candidates to connect other ordinary CUs with the cloud. These mobile gateway candidates are dynamically clustered according to different related metrics. Cluster head and time-to-live value are determined in each cluster. In this paper, the gateway advertisement and discovery issues are first addressed to propose a hybrid gateway discovery mechanism. After that, a QoS-based gateway selection algorithm is proposed for each CU to select the optimal gateway. Simulations are carried out to evaluate the performance of the overall scheme, which incorporates the proposed clustering and gateway selection algorithms. The results show that the proposed scheme can achieve about 11% higher average throughput, 10% lower end-to-end delay, and 8% lower packet drop fractions compared with the existing scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권11호
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• pp.4367-4386
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• 2015

The concept of Internet of Things (IoT) has shed new light on WSN technologies. MAC protocol issues improving the network performance are important in WSNs because of the increase in demand for various applications to secure spectrum resources. Cognitive radio (CR) technology is regarded as a solution to the problems in this future wireless network. In recent years, energy efficiency has become an issue in CR networks. However, few relevant studies have been conducted. In this paper, an energy-efficient non-overlapping channel MAC (ENC-MAC) for CR-enabled sensor networks (CRSNs) is proposed. Applying the dedicated control channel approach, ENC-MAC allows the SUs to utilize channels in a non-overlapping manner, and thus spectrum efficiency is improved. Moreover, the cooperative spectrum sensing that allows an SU to use only two minislots in the sensing phase is addressed to en-hance energy efficiency. In addition, an analytical model for evaluating the performance, such as saturation throughput, average packet delay, and network lifetime, is developed. It is shown in our results that ENC-MAC remarkably outperforms existing MAC protocols.