• Journal of Communications and Networks
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• 제17권2호
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• pp.172-183
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• 2015

To provide an efficient link maintenance approach, we propose a cross layer medium access control (LM-MAC) protocol for multichannel cognitive radio ad hoc networks. Link establishment and reliable transmission are two key problems for a perfect link maintenance mechanism. Since the cognitive user (CU) pairs have to reestablish their links each frame, in the proposed MAC protocol, three different access modes are designed to guarantee transmission efficiency in continuous frames. To enhance the transmission reliability, each CU will create a father spectrum list (FSL) after joining in the network. FSL is divided into three groups of sub-channels with different functions to compensate the packet loss caused by the primary users' appearance and the deep fading. Meanwhile, since the transmitter and the receiver will share the same FSL, periodical cooperative sensing is adopted to further optimize the former problem. Finally, compared with the existing opportunistic multichannel (OMC)-MAC protocol, the proposed LM-MAC protocol achieves better system performance in terms of saturation throughput, continuity and access delay.

• 한국정보전자통신기술학회논문지
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• 제9권1호
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• pp.114-119
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• 2016

사물 인터넷과 멀티미디어 협동 작업 환경의 필요성을 기술하고, 그 기반 하에 CoAP 기반 스택에서의 오류 처리에 대해서 제안하였다. 본 논문은 CoAP 기반 게이트웨이 소프트웨어 스택에서의 오류 동기화에 대한 내용을 기술한다. 이 시스템은 CS_EDA, CS_ESA로 구성되어 있다. CS_EDA는 CoAP 기반 게이트웨이 소프트웨어 스택 환경에서 멀티미디어 원격 제어를 위하여 오류를 감지하는 에이전트이다. CS_ESA는 CoAP 기반 게이트웨이 소프트웨어 스택 환경에서 멀티미디어 원격 제어를 위하여 오류를 동기화하는 에이전트이다. CoAP 기반 게이트웨이 소프트웨어 스택에서의 멀티미디어 공동 작업 환경의 관점에서 오류 동기화는 협동 작업에 참가하는 참가자에게 상호작용적으로 오류를 동기화한다.

• 대한전기학회논문지:전력기술부문A
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• 제50권8호
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• pp.388-394
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• 2001

This paper presents how to determine the optimal operating points of Unified Power Flow controllers (UPFC) the line flow control of which can enhance system security level. In order to analyze the effect of these devices on the power system, the decoupled model has been employed as a mathematical model of UPFC for power flow analysis. The security index that indicates the level of congestion of transmission line has been proposed and minimized by iterative method. The sensitivity of objective function for control variables of and UPFC has been derived, and it represents the change in the security index for a given set of changes in real power outputs of UPFC. The proposed algorithm with sensitivity analysis gives the optimal set of operating points of multiple UPECs that reduces the index or increases the security margin and Marquart method has been adopted as an optimization method because of stable convergence. The algorithm is verified by the 10-unit 39-bus New England system that includes multiple FACTS devices. The simulation results show that the power flow congestion can be relieved in normal state and the security margin can be guaranteed even in a fault condition by the cooperative operation of multiple UPECs.

• 한국지능시스템학회논문지
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• 제16권6호
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• pp.710-715
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• 2006

최근 반도체 제조기술의 발달로 저가의 센서 노드의 개발이 가능해 짐에 따라 실제 시스템에 대한 모니터링 및 제어 시스템의 개발이 가능하게 되고 있다. 이에 본 연구에서는 센서 네트워크 어플리케이션 중 하나인 움직이는 물체의 추적을 위한 새로운 형태의 알고리즘을 제안하고자 한다. 제안된 알고리즘은 물체의 이동을 감지한 센서 노드들간의 협업을 통해 이동 물체의 움직임을 지속적으로 감지하는 것을 가능케 한다. 이로 인해 제안된 알고리즘은 타켓의 순간적인 놓침을 초래할 수 있는 예측 실패 등에 대해 강인한 특성을 갖는다. 또한 시뮬레이션 고찰을 통해 제안된 알고리즘이 랜덤한 움직임을 갖는 타켓에 대한 정확한 추적이 가능함을 확인하였다.

• Journal of Preventive Medicine and Public Health
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• 제54권1호
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• pp.1-7
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• 2021

The Korean government's strategy to combat coronavirus disease 2019 (COVID-19) has focused on non-pharmaceutical interventions, such as social distancing and wearing masks, along with testing, tracing, and treatment; overall, its performance has been relatively good compared to that of many other countries heavily affected by COVID-19. However, little attention has been paid to health equity in measures to control the COVID-19 pandemic. The study aimed to examine the unequal impacts of COVID-19 across socioeconomic groups and to suggest potential solutions to tackle these inequalities. The pathways linking social determinants and health could be entry points to tackle the unequal consequences of this public health emergency. It is crucial for infectious disease policy to consider social determinants of health including poor housing, precarious working conditions, disrupted healthcare services, and suspension of social services. Moreover, the high levels of uncertainty and complexity inherent in this public health emergency, as well as the health and socioeconomic inequalities caused by the pandemic, underscore the need for good governance other than top-down measures by the government. We emphasize that a people-centered perspective is a key approach during the pandemic era. Mutual trust between the state and civil society, strong accountability of the government, and civic participation are essential components of cooperative disaster governance.

• Current Optics and Photonics
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• 제6권4호
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• pp.381-391
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• 2022

Two-photon-polymerization additive-manufacturing systems feature high resolution and precision. However, there are few reports on specific methods and possible problems concerning the use of small lasers to independently build such platforms. In this paper, a femtosecond-laser two-photon-polymerization additive-manufacturing system containing an optical unit, control unit, monitoring unit, and testing unit is built using a miniature femtosecond laser, with a detailed building process and corresponding control software that is developed independently. This system has integrated functions of light-spot detection, interface searching, micro-/nanomanufacturing, and performance testing. In addition, possible problems in the processes of platform establishment, resin preparation, and actual polymerization for two-photon-polymerization additive manufacturing are explained specifically, and the causes of these problems analyzed. Moreover, the impacts of different power levels and scanning speeds on the degree of polymerization are compared, and the influence of the magnification of the object lens on the linewidth is analyzed in detail. A qualitative analysis model is established, and the concepts of the threshold broadening and focus narrowing effects are proposed, with their influences and cooperative relation discussed. Besides, a linear structure with micrometer accuracy is manufactured at the millimeter scale.

• 한국버섯학회지
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• 제9권4호
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• pp.190-193
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• 2011

Inonotus obliquus is a traditional medicine mushroom that was developed from traditional medicine originating in ancient. It has been applied for cancer or immunotherapy, but its effect on pulmonary tuberculosis is not reported. Therefore, we measured the pulmonary tuberculosis therapeutic effect of methyl alcohol extract from MGIT 960 system with fluorescent indicator. Inonotus obliquus extract showed 14 day more inhibitory activity than the positive control. In addition, the anti-pulmonary tuberculosis activity of Inonotus obliquus was $50{\mu}m$. These results suggest that Inonotus obliquus methyl alcohol extracts could contribute to inhibition of pulmonary tuberculosis.

• 수산해양교육연구
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• 제26권2호
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• pp.284-295
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• 2014

The purpose of the study was to validate the components of practical collaborative competencies by analyzing the perceptions of corporate personnel on practical collaborative competencies. The study reviewed the theories of collaborative intelligence, collective intelligence, cooperative learning, and learning communities. Based on the results of the literature review, the study derived seven categories of participative motivation for group activities, ability to share thinking and consciousness, motivation to share experiences, ability to control emotion, ability to promote interaction, creativity, and collaborative performance as the core competencies. To validate the elements, survey was conducted for 186 corporate personnels. The results showed that the personnels perceived the following elements as important collaborative competencies: participative motivation for group activities, motivation to form participatory atmosphere, ability to manage conflict effectively, ability to form relationships, ability to form positive team atmosphere.

• 디지털산업정보학회논문지
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• 제9권3호
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• pp.49-57
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• 2013

Power-saving PC software enables the inexpensive power control, but the installation of the power-saving software in all computers in the organization is not an easy task. Computer users in the organization are usually not cooperative as they do not think the power-saving cost is directly related to themselves. The PC power-saving system provides advantage to driving active participation in which users installs the power saving software by restricting IP address through the power management server. However, the problem with this approach is the security vulnerability to IP spoofing attacks, therefore we need to solve the problem that disrupt the entire network system rather than saving electric power. This paper proposes the security authentication system that can implement the efficiency saving power by providing high security for the members' computer system of the public institutions based on the PC power-saving system. Also, by analyzing it in comparison with other method, it is possible to check that the prospects of safety and efficiency are strengthened.

• ETRI Journal
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• 제40권2호
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• pp.227-236
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• 2018

Ultra-dense small cell networks (UD-SCNs) have been identified as a promising scheme for next-generation wireless networks capable of meeting the ever-increasing demand for higher transmission rates and better quality of service. However, UD-SCNs will inevitably suffer from severe interference among the small cell base stations, which will lower their spectral efficiency. In this paper, we propose a software-defined networking (SDN)-based hierarchical agglomerative clustering (SDN-HAC) framework, which leverages SDN to centrally control all sub-channels in the network, and decides on cluster merging using a similarity criterion based on a suitability function. We evaluate the proposed algorithm through simulation. The obtained results show that the proposed algorithm performs well and improves system payoff by 18.19% and 436.34% when compared with the traditional network architecture algorithms and non-cooperative scenarios, respectively.