• 한국통신학회논문지
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• 제37권6B호
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• pp.474-482
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• 2012

이동형 게이트웨이(MG: Mobile Gateway)는 버스와 같은 차량에 탑승한 사용자들에게 인터넷 서비스를 제공하기 위한 무선랜 장치이다. 논문에서 다루는 MG는 인터넷 연결을 위해 도로변에 설치된 무선랜 기반 소형기지국(RSU AP : Road Side Unit AP)에 접속한다. 차량 이동 중에도 안정적인 통신 서비스를 제공하려면 MG의 접속 RSU가 바뀌는 핸드오프 과정이 빠르고 안정적으로 처리되어야 한다. 그런데 무선랜 기술 특성 상 핸드오프 과정의 통신 단절을 줄이는 데는 물리적 한계가 있다. 본 논문에서는 RSU 접속을 위한 무선랜 인터페이스를 복수 개로 사용하여 끊김 없는 핸드오프를 실현하는 다중 인터페이스 MG (MIMG : Multi-Interface MG)를 제안한다. 안정적인 핸드오프를 위한 구체적 방법으로 MIMG로부터 RSU로의 패킷 전송 단절을 제거하기 위한 Link Sharing 기법, RSU로부터 MIMG로의 패킷 전송 단절을 제거하기 위한 Path Sharing 기법을 제안한다. 우리는 임베디드 보드를 이용하여 제안한 핸드오프 기법을 실현한 MIMG를 구현하였고 이를 이용하여 성능 평가실험을 수행하였다. 실험 결과 단일 인터페이스를 가진 MG와 달리 MIMG는 핸드오프 시의 통신 단절을 제거할 수 있었고 대역폭도 50% 이상 향상됨을 확인하였다.

• 한국화재조사학회지
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• 제7권1호
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• pp.55-68
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• 2005

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 2006년도 춘계공동학술대회 논문집
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• pp.1034-1035
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• 2006

본 논문에서는 기존의 노드 단절 문제와 관련이 있는 k-서버 단절 문제를 정의하고, 계산 복잡도 및 근사해성에 대해 규명하였다. k-서버 단절 문제는 비근사성(inapproximaton)을 갖으며, 우리는 k가 고정됐을 때 0.5-근사해법을 갖는다는 것을 보였다.

• 전자공학회논문지CI
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• 제40권6호
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• pp.22-31
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• 2003

데이터베이스 시스템에서 기존의 동시성 제어전략은 통신 중단이 빈번히 발생하는 모바익 컴퓨팅 환경 하에서는 부적절하다. 모바일 컴퓨팅에서는 거래들을 처리하기 위한 시간이 극히 제한적이다. 이러한 시간을 가장 효율적으로 활용하기 위해서는 단기거래위주의 처리가 바람직하다 통신 중단으로 인한 Service Handoff는 특히 단기거래인 경우 모바일 거래들의 성능을 저하시킬 수 있다. 이타적 잠금 기법은 lock/unlock연산 이외에 donate 연산을 사용하기 때문에 단기거래 들에 대해 효율적이다. 모바일 컴퓨팅에서 이타적 잠금 기법을 사용했을 경우 단기거래의 성능은 향상될 수 있다.

• 한국보육지원학회지
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• 제13권1호
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• pp.107-124
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• 2017

Objectives: The purpose of this study was to investigate the effects of children's pride and shame on their interactive peer play, mediated by their daily stress. Methods: The participants of this study were 172 five-year-old children (80 boys and 92 girls) attending kindergartens or child-care centers in Chungbuk, Korea. The data were analyzed by descriptive and correlational analyses, and structural equation modeling using SPSS 19.0 and AMOS 21.0. Results: Children's shame had a significant indirect effect on their interactive peer play, including play-disruption, play-disconnection and play-interactions, mediated by daily stress; children's shame had a significant direct effect on play interaction. However, children's pride did not have a direct effect on daily stress and an indirect effect on their interactive peer play. In other words, high levels of shame among children led to high perceived daily stress. In turn, perceived daily stress increased play-disconnection and play-disruption, while it decreased play-interactions. Meanwhile children's shame led to a low level of play-interaction among young children. Conclusion/Implications: The results imply that children's perceived shame would influence their behaviors in social contexts as well as their psychological wellbeing such as the level of daily stress.

• 디지털산업정보학회논문지
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• 제13권1호
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• pp.79-85
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• 2017

Vehicular ad-hoc networks (VANETs) cause link disconnection problems due to the rapid speed and the frequent moving direction change of vehicles. Link disconnection in vehicle-to-vehicle communication is an important issue that must be solved because it decreases the reliability of packet forwarding. From the characteristics of VANETs, greedy forwarding protocols using the position information based on the inter-vehicle distance have gained attention. However, greedy forwarding protocols do not perform well in the urban environment where the direction of the vehicle changes greatly. It is because greedy forwarding protocols select the neighbor vehicle that is closest to the destination vehicle as the next transmission vehicle. In this paper, we propose a greedy anycast forwarding (GAF) protocol to improve the reliability of the inter-vehicle communication. The proposed GAF protocol combines the greedy forwarding scheme and the anycast forwarding method. Simulation results show that the GAF protocol can provide a better packet delivery rate than existing greedy forwarding protocols.

• Journal of Korean Neurosurgical Society
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• 제44권2호
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• pp.101-104
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• 2008

Intracranial pial arteriovenous fistula (AVF) is a rare cerebrovascular lesion that has only recently been recognized as a distinct pathological entity. A 41-year-old woman (Patient 1) presented with the sudden development of an altered mental state. Brain CT showed an acute subdural hematoma. A red sylvian vein was found intraoperatively. A pial AVF was revealed on postoperative angiography, and surgical disconnection of the AVF was performed. A 10-year-old boy (Patient 2) presented with a 10-day history of paraparesis and urinary incontinence. Brain, spinal MRI and angiography revealed an intracranial pial AVF and a spinal perimedullary AVF. Endovascular embolization was performed for both lesions. The AVFs were completely obliterated in both patients. On follow-up, patient 1 reported having no difficulty in performing activities of daily living. Patient 2 is currently able to walk without assistance and voids into a diaper. Intracranial pial AVF is a rare disease entity that can be treated with surgical disconnection or endovascular embolization. It is important for the appropriate treatment strategy to be selected on the basis of patient-specific and lesion-specific factors in order to achieve good outcomes.

• Human Ecology Research
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• 제52권5호
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• pp.541-549
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• 2014

The purpose of this study was to analyze the effects of preschool children's behavioral and emotional regulation on their peer play behavior, focusing on gender differences. A total of 214 4- and 5-year-old children attending a child care center in South Korea participated in this study. The instruments used in this study were the Child Behavior Rating Scale, Emotion Regulation Checklist, and Penn Interactive Peer Play Scale. The collected data were analyzed using a Student's t -test, Pearson's partial correlation, and multiple regressions with the SPSS software ver. 16.0. The main results of this study are as follows: first, there was a significant gender difference in preschool children's behavioral regulation, emotional control, play interaction, and play disruption. However, there was no gender difference in preschool children's play disconnection. Second, preschool children's emotional control and behavioral regulation had positive effects on their play interaction irrespective of gender. Third, preschool children's emotional instability and emotional control had a positive influence on their play disruption irrespective of gender. Finally, the factors of behavioral regulation and emotional instability significantly predicted the boys' play disconnection, while for the girls, the significant predictor was emotional control. Further, implications for the use of early intervention targeting specific behavioral and emotional regulation problems have been discussed.

• 전자공학회논문지S
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• 제35S권8호
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• pp.120-129
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• 1998

본 논문은 PWM(Pulse width Modulation)전압형 인버어터를 사용하여 전원차단 경우나 전압변동 및 부하변동에 의한 출력전류 변화에도 일정한 출력전압을 유지하는 무정전 전원장치에 대해 논하였다. 본 시스템은 전압형 인버어터를 교류전원과 동기시켜 운전하고 정상상태에서는 전원으로부터 운전하고 정상상태에서는 전원으로부터 직류측에 연결된 축전지를 태양전지를 이용한 광기전력효과와 함께 일정전압을 충전하며, 전원의 차단, 전원의 전압변동 및 부하전류의 변화에도 일정한 전압을 유지하도록 하였다. 출력은 PWM방식에 의하여 양호한 파형이 되도록 하고 전원차단과 부하의 상태의 변화 및 전원 전압 변동에도 일정한 전압으로 출력됨을 실험을 통하여 확인할 수 있었다.

• 반도체디스플레이기술학회지
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• 제8권4호
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• pp.77-82
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• 2009

In robot operation, a motor with multi-degree of freedom motion control and an encoder for motor control are needed. To perform precise motion, location, and velocity control, the operation of motor and encoder with superior performance is important. In this paper, we studied performance evaluation system that can evaluate the performance of motor and encoder. The performance of motor and encoder can be evaluated in terms of disconnection check, signal variation count, and U, V, W signal check. Disconnection check verifies signal connection between a motor and an encoder, signal variation check verifies A, B signal by counting the number of signal A, B when a motor revolves, and U, V, W signal check verifies operating direction of a motor. The result is shown at graphic LCD integrated in system, and can be checked in PC with PC communication.