• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 2002년도 춘계공동학술대회
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• pp.418-425
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• 2002

Bluetooth is an emerging technology expected to provide users with short range, low cost, pico-cellular wireless connectivity. The access to the medium for Bluetooth is based on a Master driven Time Division Duplexing (TDD) scheme. A slave transmits packets in the reverse slot only after the master polls the slave (or transmits a packet to the slave) in a forward slot. The master transmits packets to a slave in even slots while the slave transmits packets to the master in an odd slot. The way in which the master schedules packets transmission to slaves or polls them determines system performance. In this paper. we propose a traffic adaptive MAC scheduling scheme for Bluetooth. The proposed scheme adopts the ISAR (Intelligent Segmentation and Reassembly) policy, which adjusts the packet size to the traffic patterns, to adapt the polling frequency to the traffic conditions. Also for achieving fairness among master-slave connections our scheme includes a priority policy assinging prioritised service tlimes to each connection. By considering a scenario where a Bluetooth master is used as wireless access point to the Internet, we show that our scheme improve the system throughput and average queue delay with regard to a naive Round Robin (RR) scheme.

• 전기학회논문지
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• 제60권2호
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• pp.257-265
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• 2011

As the competitive market system has been introduced to the electrical power trade, the priority concern would be that the price of electrical power should be reasonable. It is because, when this rule is solid, we can avoid the distortion of competition and assure the greater efficiency in management. LMP(Locational Marginal Price) means marginal price at each bus. This components consist of energy, loss and congestion cost. At this point, the LMP result that is calculated by traditional model is changeable by the location of the slack and can not be used in bilateral Transaction. This paper proposed algorithm is proved its rationality and credibility by comparing the result of the simulation of virtual 6_bus system that is calculated by traditional method, and showed that the LMP components are changed according to the Transaction Strategy. Furthermore, It shows the effect of additional congestion cost on the transmission line that has bottle neck frequently by simulation.

• 한국실내디자인학회논문집
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• 제18권1호
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• pp.19-26
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• 2009

Aalto designed his own modern architecture in comparison with other modern architects of his days. It is because Aalto went beyond the principle of dogmatic functionalism based on his attitude not to copy images of functionalism but to fulfill function of the building. He decided architectural form and space according to logical basis including the effective use of light and sound. Vuoksenniska church, as is called the most exceptional and notable church in his works, was designed based on the fulfillment of program. As he knew that the program needed the extension of the main church space into social areas, he put emphasis on individuality of space rather than the wholeness of space. Sound and light analysis of Vuoksenniska church shows that Aalto tried to have adequate environment of each space at the start and Integrate them later. The spatial configuration of Vuoksenniska church shows that the individuality of space has priority over the wholeness of spaces. Discordance between roof form and ceiling is the best example for this matter. Aalto designed various windows that have different sizes, figure and location to induce desirable light for each space of the church. He also adjusted the shape of the ceiling and the angle of wall for a effective sound transmission. This result indicates that he knew the activity of the church is normally confined to one weekly morning and the whole space Is hardly used as a religious purpose.

• 한국안전학회지
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• 제26권3호
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• pp.8-14
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• 2011

The live-line works are very dangerous because of direct contacts with the distribution line or neighboring contacts. So the purpose of this study is to identify the risk factor by accident occurrence form and accident case analysis, and to suggest the quantified risk index by risk occurrence frequency and risk strength analysis. And the risk index assessment is researched by accident cases analysis on work type. Accident cases of transmission distribution line are researched based on data of the Ministry of Employment and Labor in the last ten-year period (2000~2009). In results of this paper, high risk isn't always a priority of safety measures. Risk occurrence frequency and risk strength have to be considered according to detail work types, work methods and conditions of field work. And safety management measures must be planned according to risk occurrence frequency and risk strength.

• 한국산학기술학회논문지
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• 제5권5호
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• pp.429-432
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• 2004

본 논문은 단일형태의 버퍼 구조로 물리적인 단일 큐의 시퀀서 갖고 논리적으로 다중 큐의 형태로 구성된 ATM스위치를 제안한다. 제안된 스위치는 순환적 순위 알고리즘이 적용되도록 하드웨어로 구현된 ATM 셀의 출력 포트에 따라 ATM 셀이 정렬되도록 프로시져를 수행시킨다. 이 구조는 물리적으로 단일 버퍼를 갖지만 논리적으로는 순환적으로 순위를 결정하여 출력포트에서의 상충을 최대한 억제하도록 설계된 다중 큐의 기능을 하고 있다. 향후 이러한 형태의 구조는 다양한 구조의 라우팅을 위한 스위치로 응용되고, 시스템 구성의 확장성에 있어서도 큰 장점을 지니고 있어, 전송 효율적인 면에서도 훌륭한 구조로 평가된다.

• 한국전자통신학회논문지
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• 제14권5호
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• pp.837-844
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• 2019

본 논문에서는 VANET(: Vehicular Ad Hoc Networks)환경에서 비-안전 애플리케이션을 위한 낮은 지연을 제공하기 위해 AMBM(: Adaptive Multi-channel Backoff Machisum)-MAC 프로토콜을 제안한다. 제안된 프로토콜은 우선 순위가 다른 비-안전 패킷간의 처리량의 극대화를 위해 WSA(: WAVE Service Advertisement)의 CW(: C hannel window)를 동적으로 조정하여 비-안전 패킷의 서비스품질을 보장한다. 또한 SC(: Service Channel)를 위한 채널조정 및 타임슬롯예약을 하기 위해 많은시간을 할당하고 CW 및 최적 CCI(: CC Interval)를 동적으로 조정함으로서 IEEE 1609.9, C-MAC(: Coordinated multi-channel MAC), Q-VCI(QoS Variable CCH Interval) 프로토콜보다 노드가 증가할 때 전송지연이 감소됨을 보인다.

• 산업경영시스템학회지
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• 제29권4호
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• pp.100-106
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• 2006

We analyze a voice/data integrated traffic model of the cellular mobile communication system with hybrid guard channels for voice and handoff calls. In a multi-service integrated wireless environment, quality of service guarantee is crucial for smooth transportation of real time information. Real time voice traffic requires a guaranteed upper bounded on both delay and packet error rate, whereas data traffic does not. Voice traffic has high transmission priority over data packets. Thus one of the important problems is the design of admission control schemes which can efficiently accommodate the differential quality of service requirements. In this paper, a hybrid guard channel scheme is considered in which arriving calls are assigned channels as long as the number of busy channels in the cell is below a predetermined first threshold. When the number of busy channels reaches the first threshold, new originating data calls are queued in the infinite data buffer. Then reaches second threshold, only handoff calls are assigned the remaining channels and new originating voice calls are blocked. We evaluate the system by a two-dimensional Markov chain approach and generating function method and obtain performance measures included blocking probability and forced termination probability.

• 보건행정학회지
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• 제32권1호
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• pp.45-52
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• 2022

Background: There are regional variations in the incidence of coronavirus disease 2019 (COVID-19), which means that some regions are more exposed to the risk of COVID-19 than others. Therefore, this study aims to investigate regional variations in the incidence of COVID-19 in Korea and identify risk factors associated with the incidence of COVID-19 using community-level data. Methods: This study was conducted at the districts (si·gun·gu) level in Korea. Data of COVID-19 incidence by districts were collected from the official website of each province. Data was also obtained from the Korean Statistical Information Service and the Community Health Survey; socio-demographic factor, transmission pathway, healthcare resource, and factor in response to COVID-19. Community risk factors that drive the incidence of COVID-19 were selected using a least absolute shrinkage and selection operator regression. Results: As of June 2021, the incidence of COVID-19 differed by more than 80 times between districts. Among the candidate factors, sex ratio, population aged 20-29, local financial independence, population density, diabetes prevalence, and failure to comply with the quarantine rules were significantly associated with COVID-19 incidence. Conclusion: This study suggests setting COVID-19 quarantine policy and allocating resources, considering the community risk factors. Protecting vulnerable groups should be a high priority for these policies.

• 한국콘텐츠학회논문지
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• 제13권1호
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• pp.30-39
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• 2013

초소형 CMOS 카메라 센서나 마이크로 폰과 같이 멀티미디어 데이터를 수집할 수 있는 모듈들이 개발되면서 기존의 무선 센서 네트워크 기술을 확장한 무선 멀티미디어 센서 네트워크 기술 및 응용에 대한 연구가 활발하게 수행되고 있다. 이러한 응용에서 멀티미디어 데이터 저장 및 처리 기술, 데이터 전송 기술 등과 같은 다양한 기반 기술들이 요구된다. 특히, 실제 환경에 적용하기 위해서는 멀티미디어 데이터에 대한 보안 기술은 필수적이다. 본 논문은 다양한 해킹 기술 중 하나인 스니핑 공격을 방어하기 위해, 데이터 전송 경로를 위험요소로부터 물리적으로 회피시키기 위한 다중 경로 라우팅 기법을 제안한다. 제안하는 기법은 위험요소의 움직임을 토대로 지리적으로 인근에 위치한 센서 노드에 준비태세 단계와 데이터의 중요도에 따른 우선순위를 설정한다. 이를 기반으로 준비태세 단계와 데이터우선 순위를 고려하여 안전한 경로를 통해 위험요소 우회 다중 경로 라우팅을 수행한다. 시뮬레이션 결과 기존 기법에 비해 약 5% 전송지연 시간을 갖지만 위험요소가 데이터를 공격 및 감청 할 수 있는 감청율은 약 18% 낮음을 확인함으로써 제안하는 기법의 우수성을 확인하였다.

• 한국통신학회논문지
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• 제31권4A호
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• pp.421-430
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• 2006

본 논문에서는 IEEE 802.11a 무선랜(WLAN) 환경에서 Cross Layer 기반의 채널 모니터링(Cross-Layered Monitoring: CLM)을 이용한 네트워크 적응형 고선명(high definition: HD) MPEG-2 TS 비디오 스트리밍 시스템을 제안한다. 무선 채널 모니터링을 위해 AE(access point)는 MAC(medium access control) 계층의 전송 상태를 주기적으로 측정하고 응용 계층의 스트리밍 서버로 전달한다. 이것은 비디오 스트리밍 응용 프로그램이 피드백 기반의 종단간 모니터링(End-to-End Monitoring: E2EM) 기법을 적용할 때보다 가변적인 무선 채널 상태에 좀 더 빠르고 효과적으로 적응할 수 있게 한다. 스트리밍 서버는 네트워크에 적응적인 전송을 위해 측정된 무선 채널 상태에 따라 우선순위 기반의 프레임 폐기(priority-based frame dropping)를 수행한다. 이를 위해 스트리밍 서버는 실시간 파싱(real-time parsing)과 프레임 기반의 패킷 우선순위화(frame-based prioritized packetization) 기능을 제공한다. 성능 평가를 위해 IEEE 802.11a 무선랜 환경에서의 다양한 스트리밍 실험을 수행한다. 실험 결과는 제안 시스템이 시간에 따라 가변하는 무선 채널 상태에서 기존 기법에 비해 종단간 비디오 스트리밍의 품질을 향상시킬 수 있음을 보여준다.