• 한국통신학회논문지
• /
• 제31권3A호
• /
• pp.311-320
• /
• 2006

본 논문에서는 감지 대상과 싱크의 이동이 빈번한 유비쿼터스 센서 네트워크(USN) 환경을 위한 데이터 전달 프로토콜인 DDTM을 제안한다. 기존의 USN을 위한 대부분의 네트워크 프로토콜들은 감지 대상과 싱크의 이동을 고려하고 있지 않다. 따라서 이들의 이동시마다 플러딩이나 경로의 재설정이 요구되며 이것은 에너지 보존이 우선되는 USN의 수명에 있어 치명적인 문제가 될 수 있다. DDTM은 TTDD를 기반으로 감지 대상의 이동성을 고려한 데이터 전달 프로토콜이다. TTDD는 그리드를 이용하여 효율적으로 싱크의 이동성을 제공하지만 감지 대상의 이동 시 마다 감지 정보의 전달을 위한 그리드를 재구성해야 하기 때문에 그에 따른 많은 에너지 자원을 소비한다. DDTM은 감지 대상이 일정한 영역 내에서 이동할 경우 기존의 TTDD에서 생성한 그리드를 재활용함으로써 그리드 재구성에 요구되는 에너지 소비를 줄인다. 수학적 분석 모델을 이용하여 감지 대상이 이동 시 소비되는 DDTM과 TTDD의 전체 비용을 비교 분석하였으며, 분석 결과는 제안된 프로토콜이 TTDD보다 감지 대상의 이동성을 효율적으로 제공함을 보여준다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제9권3호
• /
• pp.872-885
• /
• 2015

The rapid increase of smart mobile devices and mobile applications has led to explosive growth of data traffic in cellular network. Offloading data traffic becomes one of the most urgent technical problems. Recent work has proposed to exploit opportunistic communications to offload cellular traffic for mobile data dissemination services, especially for accepting large delayed data. The basic idea is to deliver the data to only part of subscribers (called target-nodes) via the cellular network, and allow target-nodes to disseminate the data through opportunistic communications. Human mobility shows temporal and spatial characteristics and predictability, which can be used as effective guidance efficient opportunistic communication. Therefore, based on the regularity of human mobility we propose NodeRank algorithm which uses the encounter characteristics between nodes to choose target nodes. Different from the existing work which only using encounter frequency, NodeRank algorithm combined the contact time and inter-contact time meanwhile to ensure integrity and availability of message delivery. The simulation results based on real-world mobility traces show the performance advantages of NodeRank in offloading efficiency and network redundant copies.

• 한국ITS학회 논문지
• /
• 제22권1호
• /
• pp.219-232
• /
• 2023

모빌리티 서비스는 구축 대상 지역의 특성과 여건에 따라 변화할 필요가 있다. 이를 위해서는 해당 지역의 통행행태를 기종점 자료에 반영하여 모빌리티 패턴 및 특성 분석이 요구된다. 그러나 종래의 경우 행정 구역 기반의 존 체계를 기반으로 집계된 기종점 자료를 이용함에 따라 공간적 동질성을 담보하기 어렵기 때문에 신규 모빌리티와 같은 특수 목적성을 보이는 수단에 대한 본연의 통행 특성 분석에 한계가 있다. 이에 본 연구는 기존 존 체계에서 벗어나 데이터 기반의 클러스터링 기법 적용을 통해 설정된 집계 방식을 도출하여 기종점 통행패턴에 대한 공간적 분석을 수행한다. 제안 방법은 대중교통버스 및 택시와 같은 종래의 교통수단 뿐만 아니라 도심형 수요응답형 버스와 같은 신규 모빌리티 서비스에 대한 기종점 데이터 본연의 특징 벡터들을 기반으로 클러스터링을 하여 유사 공간적 특성을 반영한 지역 모빌리티의 이용 특성 분석을 가능하게 한다.

• 반도체디스플레이기술학회지
• /
• 제13권3호
• /
• pp.35-38
• /
• 2014

Flat panel displays fabricated on glass substrate use amorphous Si for data processing circuit. Recent progress in display technology requires a new material to replace the amorphous Si, and ZnO is a good candidate. ZnO is a wide bandgap (3.3 eV) semiconductor with high mobility and good optical transparency. ZnO is usually grown by sputtering using ZnO ceramic target. However, ceramic target is more expensive than metal target, and making large area target is very difficult. In this work we studied characteristics of ZnO thin-film transistor grown by rf sputtering using Zn metal target and $CO_2$. ZnO film was grown at $450^{\circ}C$ substrate temperature, with -70 V substrate bias voltage applied. By using these methods, our ZnO TFT showed $5.2cm^2/Vsec$ mobility, $3{\times}10^6$ on-off ratio, and -7 V threshold voltage.

• Journal of Preventive Medicine and Public Health
• /
• 제46권sup1호
• /
• pp.50-54
• /
• 2013

Out-of-home mobility is necessary for accessing commodities, making use of neighborhood facilities, and participation in meaningful social, cultural, and physical activities. Mobility also promotes healthy aging as it relates to the basic human need of physical movement. Mobility is typically assessed either with standardized performance-based tests or with self-reports of perceived difficulty in carrying out specific mobility tasks. Mobility declines with increasing age, and the most complex and demanding tasks are affected first. Sometimes people cope with declining functional capacity by making changes in their way or frequency of doing these tasks, thus avoiding facing manifest difficulties. From the physiological point of view, walking is an integrated result of the functioning of the musculoskeletal, cardio-respiratory, sensory and neural systems. Studies have shown that interventions aiming to increase muscle strength will also improve mobility. Physical activity counseling, an educational intervention aiming to increase physical activity, may also prevent mobility decline among older people. Sensory deficits, such as poor vision and hearing may increase the risk of mobility decline. Consequently, rehabilitation of sensory functions may prevent falls and decline in mobility. To promote mobility, it is not enough to target only individuals because environmental barriers to mobility may also accelerate mobility decline among older people. Communities need to promote the accessibility of physical environments while also trying to minimize negative or stereotypic attitudes toward the physical activity of older people.

• 한국통신학회논문지
• /
• 제32권7A호
• /
• pp.778-784
• /
• 2007

본 논문은 셀룰러 망에서 GSP와 같이 실시간 이동성을 파악할 수 있는 하드웨어를 탑재한 단말이 자신의 이동정보를 효율적으로 기지국에 전달하기 위하여 자신의 이동성 패턴을 인지하고 적절한 보고등록 알고리즘을 수행함으로써 핸드오프시 단말이 이동할 것으로 예상되는 목적 셀을 정확히 예측할 수 있는 방법을 제안한다. 특히 이동단말의 속도와 방향성에 따라서 이동성 패턴을 분류하고 이에 따른 적절한 보고등록 방법에 대하여 기술한다. 해당 알고리즘을 적용한 네트워크에서 단말은 이동정보 보고횟수와 핸드오프 호의 단절을 최소화하면서 동시에 무선자원의 사용 효율성을 증가시킬 수 있다. 우리는 시뮬레이션을 통해 제안된 방식이 기존의 방식보다 뛰어난 성능을 가져옴을 증명하였다.

• 한국항행학회논문지
• /
• 제2권1호
• /
• pp.43-52
• /
• 1998

본 논문에서는 다중 센서를 사용하는 센서 융합 환경에서 지형 정보의 사용이 다중 지상 표적 추적 성능에 어떠한 영향을 미치는가를 조사하였다. 지형 정보의 사용을 연계시와 표적의 발생을 제한하는 두 가지 경우에 대해 적용하였다. 전자의 경우는 거의 영향이 없었으나 후자의 경우는 오궤적의 수가 줄어드는 긍정적인 결과를 가져왔다. 결론적으로 지형 정보의 사용은 부가적인 센서의 운영으로 간주할 수 있기 때문에 좀 더 조심스러운 지형 정보의 사용이 요구된다.

• Journal of Astronomy and Space Sciences
• /
• 제29권4호
• /
• pp.413-422
• /
• 2012

In recent years, a number of missions have been planned and conducted worldwide on the planets such as Mars, which involves the unmanned robotic exploration with the use of rover. The rover is an important system for unmanned planetary exploration, performing the locomotion and sample collection and analysis at the exploration target of the planetary surface designated by the operator. This study investigates the development of mobility system for the rover ground model necessary to the planetary surface exploration for the benefit of future planetary exploration mission in Korea. First, the requirements for the rover mobility system are summarized and a new mechanism is proposed for a stable performance on rough terrain which consists of the passive suspension system with 8 wheeled double 4-bar linkage (DFBL), followed by the performance evaluation for the mechanism of the mobility system based on the shape design and simulation. The proposed mobility system DFBL was compared with the Rocker-Bogie suspension system of US space agency National Aeronautics and Space Administration and 8 wheeled mobility system CRAB8 developed in Switzerland, using the simulation to demonstrate the superiority with respect to the stability of locomotion. On the basis of the simulation results, a general system configuration was proposed and designed for the rover manufacture.

• 한국항공운항학회지
• /
• 제30권3호
• /
• pp.19-27
• /
• 2022

Urban Air Mobility is expected to resolve some problems in urban transportation such as traffic congestion and air pollution. Various studies for a large-scale commercialization of UAM are being actively conducted. To that end, the UAM Traffic Management system aims at securing a safety and an efficiency of UAM operations. In this study, a risk assessment model is proposed to evaluate the risk of collision between a vehicle and surrounding obstacles. The proposed model is conceived from the past studies for determining a proper separation distance between parallel runways for their independent operations. The model calculates the risk that the surveillance system fails to meet a target level of safety for a given buffer zone size between a designed route and surrounding obstacles. The model is applied to one of the routes proposed in K-UAM roadmap to evaluate its performances.

• 산업경영시스템학회지
• /
• 제38권4호
• /
• pp.11-21
• /
• 2015

In order to achieve success in ground operations, searching for moving targets is one of critical factors. Usually, the system of searching for adversary ground moving targets has complex properties which includes target's moving characteristics, camouflage level, terrain, weather, available search time window, distance between target and searcher, moving speed, target's tactics, etc. The purpose of this paper is to present a practical quantitative method for effectively searching for infiltrated moving targets considering aforementioned complex properties. Based upon search theories, this paper consists of two parts. One is infiltration route analysis, through terrain and mobility analysis. The other is building dynamic probability maps through Monte Carlo simulation to determine the prioritized searching area for moving targets. This study primarily considers ground moving targets' moving pattern. These move by foot and because terrain has a great effect on the target's movement, they generally travel along a constrained path. With the ideas based on the terrain's effect, this study deliberately performed terrain and mobility analysis and built a constrained path. In addition, dynamic probability maps taking terrain condition and a target's moving speed into consideration is proposed. This analysis is considerably distinct from other existing studies using supposed transition probability for searching moving targets. A case study is performed to validate the effectiveness and usefulness of our methodology. Also, this study suggests that the proposed approach can be used for searching for infiltrated ground moving target within critical time window. The proposed method could be used not only to assist a searcher's mission planning, but also to support the tactical commander's timely decision making ability and ensure the operations' success.