• Proceedings of the Korean Information Science Society Conference
• /
• 2006.06d
• /
• pp.52-54
• /
• 2006

최근 데이타 중심 저장 방식의 센서 네트워크에서 다차원 범위 질의를 위한 인덱스들이 제시되고 있다. 기존에 제시된 다차원 범위 질의 인덱스는 일반적으로 다차원 속성 도메인과 센서 노드의 공간 도메인을 직접 매핑하여 데이타를 관리하는 구조로 되어있다. 그러나, 이러한 구조는 센서 노드의 공간 도메인을 정적으로 분할하기 때문에 센서 노드를 포함하지 않는 영역이 생성되어 데이타 저장 및 질의 처리에서 불필요한 통신이 발생하는 문제가 있다. 본 논문은 이러한 문제를 해결하기 위해 센서 노드의 공간 도메인이 센서 노드를 포함하도록 센서 네트워크 영역을 동적으로 분할하는 다차원 범위 질의 인덱스를 제안한다. 제안하는 인덱스는 센서 노드의 위치에 따라 센서 네트워크 영역을 동적으로 분할하여 데이타 저장 및 질의 처리시 목적 영역으로의 라우팅 경로를 최적화한다. 그리고, 분할된 영역은 모두 센서 노드를 포함함으로 센서 노드에서 발행하는 저장 부하를 분산시켜 전체 네트워크에서 발생하는 전체 통신비용을 줄인다. 실험 결과 제안한 인덱스는 DIM보다 전체 센서 네트워크와 hotspot의 통신비용에서 각각 최대 35%, 60%의 성능 향상을 보였다.

• Journal of Forest and Environmental Science
• /
• v.24 no.2
• /
• pp.79-88
• /
• 2008

Twenty-eight of 44 Indian Ceropegia species are endemic and their survival is threatened. As a step towards conservation, we implied in vitro methods for the sustainable propagule production in C. hirsuta, C. lawii, C. maccannii, C. oculata and C. sahyadrica. Effects of explant, growth regulators, sucrose and photoperiod were studied. High frequency microtuber production was achieved with the seedling-apical buds, grown on MS medium containing 4-6 mg $1^{-1}$ BAP, 3-8% (w/v) sucrose, under continuous illumination. Each microtuber, when subcultured proliferated to form a cluster of secondary microtubers. Every primary and secondary microtuber bore at least one shoot-bud and a root primordium. Each tuber (formed with any of the significantly effective treatments) weighed more than 500 mg, enough to plant directly in non-sterilized soils. Microtubers could be produced and proliferated round the year. Proliferation could be solely attributed to in vitro procedures as these plants bear solitary tubers in vivo. Microtubers could be sprouted in vitro to prepare ready to pot plantlets. As, this novel method succeeded for all five species, though they belong to different eco-physiological backgrounds, we recommend its implementation in the conservation programs for a broader range of Ceropegia species, supported by other integrated strategies.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.2 s.344
• /
• pp.1-6
• /
• 2006

This paper proposes association algorithm using load balancing for efficient AP selection under environment of wireless local area network(WLAN). Our scheme measures arrival time of association information when establishing the connection between access points and access terminal, analyzes the load condition of AP, and applies load balancing. AT selects and sets up low traffic AP by measuring traffic of connected access terminal, which can prevent over-franc of access points under hotspot environment that users access simultaneously. According to the above-described selection in a high speed wireless Internet service based on public WLAN technologies that are currently in operations. Further, it is possible to improve the efficiency of network management.

• Proceedings of the KSRS Conference
• /
• 2003.11a
• /
• pp.1149-1151
• /
• 2003

We performed a validation study of the MODIS active fire detection algorithm using high resolution SPOT image as the reference data set. Fire with visible smoke plumes are detected in the SPOT scenes, while the hotspots in MODIS data are detected using NASA's new version 4 fire detection algorithm. The detection performance is characterized by the commission error rate (false alarms) and the omission error rate (undetected fires). In the Sumatra and Kalimantan study area, the commission rate and the omission rate are 27% and 34% respectively. False alarms are probably due to recently burnt areas with warm surfaces. False negative detection occur where there are long smoke plumes and where fires occur in densely vegetated areas.

• Journal of Internet Computing and Services
• /
• v.9 no.5
• /
• pp.175-183
• /
• 2008

Wi-Fi defines the procedure to search an AP, authenticate both station and AP, and associate the new BSS or ESS which enables the link layer handoff. One of the problems for hotspot service of Wi-Fi is "passing-object", Wi-Fi describes the messages exchanges between two neighboring APs in BSS or ESS. If the station passes through the neighboring APs before completing link-layer handoff, the path where the tunneled packets should be sent is lost. In this paper, we propose to integrate the positioning entity in a service domain to keep track the high-speed movement.

• Journal of Information Processing Systems
• /
• v.2 no.2
• /
• pp.88-94
• /
• 2006

In wireless cellular networks, previous researches on admission control policies and resource allocation algorithm considered the QoS (Quality of Service) in terms of CDP (Call Dropping Probability) and CBP (Call Blocking Probability). However, since the QoS was considered only within a predetermined cell capacity, the results indicated a serious overload problem of systems not guaranteeing both CDP and CBP constraints, especially in the hotspot cell. That is why a close interrelationship between CDP, CBP and cell capacity exists. Thus, it is indispensable to consider optimal cell capacity guaranteeing multiple QoS (CDP and CBP) at the time of initial cell planning for networks deployment. In this paper, we will suggest a distributed determination scheme of optimal cell capacity guaranteeing both CDP and CBP from a long-term perspective for initial cell planning. The cell-provisioning scheme is performed by using both the two-dimensional continuous-time Markov chain and an iterative method called the Gauss-Seidel method. Finally, numerical and simulation results will demonstrate that our scheme successfully determines an optimal cell capacity guaranteeing both CDP and CBP constraints for initial cell planning.

• Proceedings of the Korean Information Science Society Conference
• /
• 2008.06b
• /
• pp.292-297
• /
• 2008

본 논문은 FPGA 기반 설계에서 주변보다 급격한 온도 변화를 보이는 hotspot들을 탐지하기 위한 열 감지 센서 수를 정하고, 센서의 놓여야 할 배치 장소를 결정하는 알고리즘을 제안한다. 열 감지 센서로는 동적으로 설계가 가능한 ring oscillator 센서 기술을 사용한다는 가정 하에, 센서의 사용 개수를 최소화함과 동시에 최적의 센서 배치 위치 찾는다. 기존의 연구의 단점은 센서가 감지하는 영역 범위를 적당한 크기의 정사각형으로 간주하였기에, 실제 원형의 관측 범위를 보이는 센서 감지 영역의 현실을 올바로 반영하지 못하였으며, 또한 잘 알려진 회로 분할(partition) 기법에 의존한 휴리스틱으로 최적의 결과를 보장하지는 못하였다. 이와는 달리 본 연구에서는 센서의 관측 범위를 원형으로 할 수도 있게 함과 동시에 최적의 해를 보장하는 센서 할당 및 배치 알고리즘을 제안한다. 구체적으로 본 제안 알고즘에서는 소위 “Candidate Coloring 기법”을 통해 센서가 놓여야 할 모든 후보 영역을 표시하며, “Candidate Filtering 기법”을 통해 불필요한 후보 영역들을 완전히 삭제하여 탐색 공간을 줄이게 되며 (해의 최적 해는 항상 유지 되도록 하면서), 마지막으로 Branch-and-Bound 알고리즘을 적용해 최적의 센서 할당 및 배치 결과를 찾아내었다.

• Proceedings of the KSRS Conference
• /
• v.1
• /
• pp.463-466
• /
• 2006

During Mid October of 2005 a mass mortality of the corals occurred surrounding Con Dao Islands (South Vietnam) where is the recognized as one of the most famous marine parks of Vietnam. Results from the field survey in October 2005 showed that the mass mortality of corals and benthos focused only on the North-West of the islands whereas there was almost no death recorded in the South - East parts. Based on field data it was assumed that an overlap between high water temperature ($>30^{\circ}C$) and low salinity (<25%o) during short term was the impact causing the situation. In this paper, we try to explain this phenomenon based on the hydrographical view together with analyzing ocean colour images. A coral bleaching warning system also is proposed for Condao site.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.32 no.3
• /
• pp.10-19
• /
• 2009

Wireless LAN systems have been widely implemented for supporting the wireless internet services especially in the hotspot areas such as hospitals, homes, conference rooms, and so on. Compared with wired LAN systems, wireless LAN systems have the advantages of the users' mobility support and low implementation and maintenance costs. IEEE 802.11 wireless LAN systems employ the backoff algorithm to avoid contentions among STAs when two or more STAs attempt to transmit their data frames simultaneously. The MAC efficiency can be improved if the CW values are adaptively changed according to the channel state of IEEE 802.11 wireless LANs. In this paper, a dynamic contention window control algorithm is proposed using the genetic algorithm to improve the MAC throughput of IEEE 802.11 wireless LANs.

• Strategy21
• /
• s.41
• /
• pp.85-107
• /
• 2017

The purpose of this article is to explore recent developments in piracy attacks at the global level. This article provides an overview of global trend of recent piracy attacks and presents global counter-piracy efforts at the international and governmental as well as industry level. The issue of piracy has been a grave concern of the globe, becoming the biggest threat to the safety and security navigation and seaborne trade. Overall, piracy attacks in recent years have greatly diminished owing to multi-faceted counter-piracy efforts. However, Southeast Asia and West Africa have reemerged as an hotspot of piracy. A worrisome trend in these regions is that many of piracy attacks are committed by militant groups for financing their activities. As a result, the level of violence and the sophistication of attacks have escalated. The problem of contemporary piracy is beyond a particular region or coastal state, but a common concern of the international community. In order to address the global piracy problem, international cooperation should be further strengthened at the global level as well as the regional level. As a way of counter-piracy measures in Southeast Asian waters, the creation of a joint regional coast guard to patrol the highly piracy concentration areas needs to be considered.