• Journal of the Society of Disaster Information
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• v.15 no.4
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• pp.459-468
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• 2019

Purpose: The cavity exploration of the lower part of the road is carried out to prevent ground-sinking. However, the detected communities cannot be identified by the cavity location and history information, such as repackaging the pavement. Therefore, the field applicability of RFID systems was evaluated in this study to enable anyone to accurately identify information. Method: During temporary recovery, tag recognition distance and recognition rate were measured according to underground burial materials and telecommunication tubes using RFID systems with electronic tag chips attached to the bottom of the rubber cap. Result: The perceived distance and perceived rate of depth for each position of the electron tag did not significantly affect the depth up to 15cm, but it did have some effect if the depth was 20cm. In addition, water effects from nearby underground facilities and rainfall are relatively small, and the effects of wind will need to be considered during the weather conditions of the road. Conclusion: The RFID tags for field application of the pavement management system store various information such as location and size of cavity, identification date, cause of occurrence, and surrounding underground facilities to maximize cavity management effect with a system that can be computerized and mobile utilization.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.896-905
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• 2010

The sensor networks can be used attractively for various application areas. Time synchronization is important for any Ubiquitous Sensor Networks (USN) systems. USN makes extensive use of synchronized time in many contexts for data fusion. However existing time synchronization protocols are available only for homogeneous sensor nodes of USN. It needs to be extended or redesigned in order to apply to the USN with heterogeneous sensor nodes. Because heterogeneous sensor nodes have different clock sources with the SinkNode of USN, it is impossible to be synchronized global time. In addition, energy efficiency is one of the most significant factors to influence the design of sensor networks, as sensor nodes are limited in power, computational capacity, and memory. In this paper, we propose specific time synchronization based on master-slave topology for the global time synchronization of USN with heterogeneous sensor nodes. The time synchronization master nodes are always able to be synchronized with the SinkNode. Then time synchronization master nodes enable time synchronization slave nodes to be synchronized sleep periods. The proposed master-slave time synchronization for heterogeneous sensor nodes of USN is also helpful for power saving by maintaining maximum sleep time.

• The KIPS Transactions:PartA
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• v.9A no.4
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• pp.399-404
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• 2002

Along the evolution of information and communication technologies, manufacturing embedded systems such as PDA (personal digital assistant), HPC (hand -held PC), settop box. and information appliance became realistic. And RTOS (real-time operating system) and filesystem have been played essential re]os within the embedded systems as well. For the filesystem of embedded systems, flash memory has been used extensively instead of traditional hard disk drives because of embedded system's requirements like portability, fast access time, and low power consumption. Other than these requirements, nonvolatile storage characteristic of flash memory is another reason for wide adoption in industry. However, there are some technical challenges to cope with to use the flash memory as an indispensable component of the embedded systems. These would be relatively slow cleaning time and the limited number of times to write-and-clean. In this paper, a new cleaning policy is proposed to overcome the problems mentioned above and relevant performance comparison results will be provided. Ranking cleaning policy(RCP) decides when and where to clean within the flash memory considering the cost of cleaning and the number of times of cleaning. This method will maximize not only the lifetime of flash memory but also the performance of access time and manageability. As a result of performance comparison, RCP has showed about 10 ~ 50% of performance evolution compared to traditional policies, Greedy and Cost-benefit methods, by write throughputs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.304-304
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• 2006

One method of Electric Power Generation is to use piezoelectric materials, which form transducers that are able to interchange electrical energy and mechanical force or strain. This study describes the fabrication and properties of piezoelectric transducers for Power Generation application. The structure of the transducers was ceramic-metal-ceramic 3-layered parallel type The center metal layer of phosphorous bronze was bonded by two piezoelectric layers of which have sputtered Ag/Cu(or Ni/Cu) electrode layers on both sides.. The Energy generated by the vibration of piezoelectric transducers Can be achieved by adjusting a suitable piezoelectric constant and mechanical structures. The piezoelectric material used in this application showed the electrical properties of r=4400, $d_{33}\;=\;750\;(10^{-12}\;m/V)$, $d_{31}\;=\;-300\;(10^{-12}\;m/V)$, $k_{33}\;=\;71%$, $Qm\;=\;85$, $T_c\;=\;210^{\circ}C$.

• Journal of KIISE:Information Networking
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• v.36 no.5
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• pp.413-424
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• 2009

Wireless sensor network is based on an event driven system. Sensor nodes collect the events in surrounding environment and the sensing data are relayed into a sink node. In particular, when events are detected, the data sensing periods are likely to be shorter to get the more correct information. However, this operation causes the traffic congestion on the sensor nodes located in a routing path. Since the traffic congestion generates the data queue overflows in sensor nodes, the important information about events could be missed. In addition, since the battery energy of sensor nodes exhausts quickly for treating the traffic congestion, the entire lifetime of wireless sensor networks would be abbreviated. In this paper, a new congestion control method is proposed on the basis of genetic algorithm. To apply genetic algorithm, the data traffic rate of each sensor node is utilized as a chromosome structure. The fitness function of genetic algorithm is designed from both the average and the standard deviation of the traffic rates of sensor nodes. Based on dominant gene sets, the proposed method selects the optimal data forwarding sensor nodes for relieving the traffic congestion. In experiments, when compared with other methods to handle the traffic congestion, the proposed method shows the efficient data transmissions due to much less queue overflows and supports the fair data transmission between all sensor nodes as possible. This result not only enhances the reliability of data transmission but also distributes the energy consumptions across the network. It contributes directly to the extension of total lifetime of wireless sensor networks.

• Journal of KIISE:Information Networking
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• v.36 no.4
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• pp.339-350
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• 2009

In wireless sensor networks, the limited battery resources of sensor nodes have a direct impact on network lifetime. To reduce unnecessary power consumption, it is often the case that only a minimum number of sensor nodes operate in active mode while the others are kept in sleep mode. In such a case, however, the network service can be easily unreliable if any active node is unable to perform its sensing or communication function because of an unexpected failure. Thus, for achieving reliable sensing, it is important to maintain the sensing level even when some sensor nodes fail. In this paper, we propose a new fault-tolerance scheme, called FCP(Fault-tolerant Coverage Preserving), that gives an efficient way to handle the degradation of the sensing level caused by sensor node failures. In the proposed FCP scheme, a set of backup nodes are pre-designated for each active node to be used to replace the active node in case of its failure. Experimental results show that the FCP scheme provides enhanced performance with reduced overhead in terms of sensing coverage preserving, the number of backup nodes and the amount of control messages. On the average, the percentage of coverage preserving is improved by 87.2% while the additional number of backup nodes and the additional amount of control messages are reduced by 57.6% and 99.5%, respectively, compared with previous fault-tolerance schemes.

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.5
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• pp.531-536
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• 2006

Recently, many of researchers have been studied in data processing oriented middleware for wireless sensor networks with the rapid advances on sensor and wireless communication technologies. In a wireless sensor network, a middleware should handle the data loss problem at an intermediate sensor node caused by instantaneous data burstness to support efficient processing and fast delivering of the sensing data. To handle this problem, a simple data discarding or data compressing policy for reducing the total amount of data to be transferred is typically used. But, data discarding policy decreases the correctness of a collected data, in other hand, data compressing policy requires additional processing overhead with the high complexity of the given algorithm. In this paper, it proposes a data-average method for enhancing the efficiency of data aggregation and correctness where the sensed data should be delivered only with the limited computing power and energy resource. With the proposed method, unnecessary data transfer of the overlapped data is eliminated and data correctness is enhanced by using the proposed averaging scheme when an instantaneous data burstness is occurred. Finally, with the TOSSTM simulation results on TinyBB, we show that the correctness of the transferred data is enhanced.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.398-398
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• 2018

OECD 발표에 의하면 물산업 관련 인프라 투자 전망은 전세계 GDP 대비 2010~2020년 약 1.01%에서 2020~2030년 약 1.03%로 확대될 전망으로 다른 통신, 전력, 철도 인프라 투자수요보다 많을 것으로 전망하고 있다(파이넨셜 뉴스, 2013.3.21.). 우리나라는 2005년 베트남 홍강종합개발사업을 시작으로 2015년 기준으로 세계 35개국에 진출하고 있다. 그러나 대부분의 물 산업 진출 대상 국가는 미계측 유역이 많고 지상에서 계측된 수문 자료가 부족한 실정이다. Namgung and Lee(2014)에 의하면 네팔의 수력발전소 건설에 관측된 강우량 자료가 없어 발전소 하류 10km 지점의 유하량 자료를 이용하여 자료의 정확도 검증을 대신하여 적용한 바 있다. 이와 같이 계측자료가 없거나 부족한 지역에 대하여 기상 위성을 이용하여 추정된 강수량 자료가 해당 지역의 강수 특성을 파악하는데 중요한 자료로 이용될 수 있다. 글로벌 위성 기반의 강수량 관측에 대한 역사는 1979년에 IR방법에 의해 위성으로부터 강우자료를 유도하는 개념이 도입된 이후 1987년 다중 채널의 마이크로파(MW) 복사계를 이용한 방법, 이후 두 IR과 MW를 혼합한 방법에서, 1997년 TRMM위성의 PR(Precpipitation Radar)의 레이더를 이용하는 방법, 그리고 2014년 GPM 핵심 위성(GPM Core Observatory)에 탑재된 Dual PR에 의한 방법으로 위성강수의 정확도를 매우 높여가고 있다. 본 연구는 KOICA 사업으로 진행중인 필리핀 메트로 마닐라 홍수조기경보 및 모니터링 체계 구축사업 중 파시그-마라키나강(Pasig-Marakina) 유역의 2012년 8월의 홍수사상에 대한 위성강우 및 글로벌 지형자료를 이용하여 홍수 유출량을 추정하는 것으로 목적으로 하고 있다. 유역내 6개 관측소의 일일 강우량 자료와 GPM IMERG 일강우량 자료 상관분석 결과 약 0.623, Bias는 -0.147, RMSE는 15.7정도로 분석되었다. 홍수량 분석은 2012년 8월 홍수가 발생한 시기인 2012년 8월 1일 00(UTC)부터 2012년 8월 16일 00(UTC)까지의 1시간 간격의 위성강우자료와 글로벌 지형자료를 이용하였고, 한국건설기술연구원의 MapWindow 기반 GRM 모형(mwGRM)을 이용하였다. 분석 결과 첨부홍수가 발생한 시기는 8월 7일 18:00(UTC)였고, 첨두 홍수량은 $4,073.9m^3/sec$로 분석되었다. 향후 수위-유량 관계식에 의해 정확도평가를 수행할 계획이다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.483-494
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• 2022

Owing to the saturation of ground spaces in downtown areas, underground spaces are being developed increasingly. Underground spaces are utilized for transportation, water supply and sewerage, communication zones, electric power zones, and various cultural complexes. In Korea, for excavating underground spaces, blasting methods using gunpowder such as the New Austrian Tunneling Method (NATM) are mainly used. However, the blasting method causes vibration and noise during tunnel excavation, generating many complaints from residents in the vicinity of the excavation site. To address this problem, various methods have been developed, and recently, vibration and noise have been reduced using deep excavation. This study predicts blast vibration changes according to the depth, under the same blasting and tunnel conditions, using numerical analysis based on the blast vibration measurement data of the GTX-A route, the tunnel cross-section drawings, and ground investigation reports. Furthermore, the necessary separation distance from densely populated areas such as residential areas is suggested by analyzing the trend of decreasing blast vibration according to the distance from ground surface directly above the blasting location.

• Journal of the Society of Disaster Information
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• v.17 no.4
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• pp.684-693
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• 2021

Purpose: The purpose is to establish a safe facility environment from abnormal voltages such as lightning by developing a smart land resistance measuring device that can acquire real-time land resistance data using Arduino. Method: This paper studied design models and application cases by developing a land resistance acquisition and analysis system with Arduino and a power line communication (PLC) system. Some sites in the wind power generation complex in Gyeongsangnam-do were selected as test beds, and real-time land resistance data applied with new technologies were obtained. The electrode arrangement adopted a smart electrode arrangement using a combination of a Wenner four electrode arrangement and a Schlumberger electrode arrangement. Result: First, the characteristic of this technology is that the depth of smart multi-electrodes is organized differently to reduce the error range of the acquired data even in the stratigraphic structure with specificity between floors. Second, IT convergence technology was applied to enable real-time transmission and reception of information on land resistance data acquired from smart ground electrodes through the Internet of Things. Finally, it is possible to establish a regular management system and analyze big data accumulated in the server to check the trend of changes in various elements, and to model the optimal ground algorithm and ground system design for the IT convergence environment. Conclusion: This technology will reduce surge damage caused by lightning on urban infrastructure underlying the 4th industrial era and design an optimized ground system model to protect the safety and life of users. It is also expected to secure intellectual property rights of pure domestic technology to create jobs and revitalize our industry, which has been stagnant as a pandemic in the post-COVID-19 era.