• Proceedings of the Korean Society of Computer Information Conference
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• 2010.07a
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• pp.525-526
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• 2010

2000년 대규모 DDoS 공격이래, 2009년 7월 7일 국가주요정부기관 및 인터넷 포털, 금융권 등의 웹사이트 대상으로 1차, 2차, 3차로 나누어 대규모 사이버 공격이 발생하였다. 지속적으로 발전되는 행태를 보이고 DDoS 공격에 대해 본 논문에서는 계층적인 침입탐지시스템을 설계하였다. 네트워크 패킷을 분석하기 위해 e-Watch, NetworkMiner등의 패킷, 프로토콜 분석도구를 이용하여 TCP/IP의 Layer별 공격을 분석한 후 패킷의 유입량, 로그정보, 접속정보, Port, Address 정보를 분석하고 계층침입에 대한 방어를 수행하도록 설계하였다. 본 논문은 DDoS(Distributed Denial of Service)에 대한 패킷 전송에 대해 계층적인 방어를 통해 보다 안정적인 패킷수신이 이루어진다.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.4
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• pp.654-659
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• 2003

Intrusive luxation that takes approximately three percent of permanent teeth commonly occures at anterior teeth. This intrusion frequently leads to pulp necrosis, root resorption, marginal bone loss and these complications are influenced by depth of intrusion and stage of root development. Various treatment approaches have been suggested to manage of intrusive luxation. Techniques aiming to reposition the intruded tooth include an observation for spontaneous re-eruption, surgical or orthodontic repositioning. We report two cases with clinically satisfactory results for traumatically intruded maxillary central incisor. In one case which has a large open apex and mild intrusion depth, we observed for spontaneous eruption and then repositioning by forced eruption method. In other case, which has been completely intruded, was repositioned by surgical extrusion and followed by apexification.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.6
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• pp.1706-1727
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• 2023

Under Water Sensor Networks (UWSN) has gained attraction among various communities for its potential applications like acoustic monitoring, 3D mapping, tsunami detection, oil spill monitoring, and target tracking. Unlike terrestrial sensor networks, it performs an acoustic mode of communication to carry out collaborative tasks. Typically, surface sink nodes are deployed for aggregating acoustic phenomena collected from the underwater sensors through the multi-hop path. In this context, UWSN is constrained by factors such as lower bandwidth, high propagation delay, and limited battery power. Also, the vulnerabilities to compromise the aquatic environment are in growing numbers. The paper proposes an Energy-Efficient standalone Intrusion Detection System (EEIDS) to entail the acoustic environment against malicious attacks and improve the network lifetime. In EEIDS, attributes such as node ID, residual energy, and depth value are verified for forwarding the data packets in a secured path and stabilizing the nodes' energy levels. Initially, for each node, three agents are modeled to perform the assigned responsibilities. For instance, ID agent verifies the node's authentication of the node, EN agent checks for the residual energy of the node, and D agent substantiates the depth value of each node. Next, the classification of normal and malevolent nodes is performed by determining the score for each node. Furthermore, the proposed system utilizes the sheep-flock heredity algorithm to validate the input attributes using the optimized probability values stored in the training dataset. This assists in finding out the best-fit motes in the UWSN. Significantly, the proposed system detects and isolates the malicious nodes with tampered credentials and nodes with lower residual energy in minimal time. The parameters such as the time taken for malicious node detection, network lifetime, energy consumption, and delivery ratio are investigated using simulation tools. Comparison results show that the proposed EEIDS outperforms the existing acoustic security systems.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.254-256
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• 2009

The performances of proton exchange membrane (PEM) water electrolysis depend on many factors such as materials, geometries, fabrication methods, operating conditions, and so forth. The fabrication method is concerned, membrane electrode assemblies (MEA) are a most important part to show different performances by different fabrication methods. The performance change of PEM water electrolysis was experimentally measured according to the fabrication differences of the anode electrodes. One point of view is the catalyst intrusion rate to the anode gas diffusion layer (GDL), and the other point of view is the catalyst loading distribution in depth of the anode GDL. Results show that the performances of MEA with deep intrusion of the catalysts are better in the range of low current densities but worse at higher current densities. The catalyst loading distribution does not affect significantly to the performance of PEM water electrolyser.

• New & Renewable Energy
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• v.5 no.4
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• pp.75-78
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• 2009

The performances of proton exchange membrane (PEM) water electrolysis depend on many factors such as materials, geometries, fabrication methods, operating conditions, and so forth. The fabrication method is concerned, membrane electrode assemblies (MEA) are a most important part to show different performances by different fabrication methods. The performance change of PEM water electrolysis was experimentally measured according to the fabrication differences of the anode electrodes. One point of view is the catalyst intrusion rate to the anode gas diffusion layer (GDL), and the other point of view is the catalyst loading distribution in depth of the anode GDL. Results show that the performances of MEA with deep intrusion of the catalysts are better in the range of low current densities but worse at higher current densities. The catalyst loading distribution does not affect significantly to the performance of PEM water electrolyser.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.14 no.1
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• pp.79-90
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• 2016

The second-stage near surface disposal facility for low and very low level radioactive waste's permanent disposal is to be built. During the institutional control period, the inadvertent intrusion of the general public is limited. But after the institutional control period, the access to the general public is not restricted. Therefore human who has purpose of residence and resource exploration can intrude the disposal facility. In this case, radioactive effects to the intruder should be limited within regulatory dose limits. This study conducted the safety assessment of human intrusion on the second-stage surface disposal facility through drilling and post drilling scenario. Results of drilling and post drilling scenario were satisfied with regulatory dose limits. The result showed that post-drilling scenario was more significant than drilling scenario. According to the human intrusion time and behavior after the closure of the facility, dominant radionuclide contributing to the intruder was different. Sensitivity analyses on the parameters about the human behavior were also satisfied with regulatory dose limits. Especially, manual redistribution factor was the most sensitive parameter on exposure dose. A loading plan of spent filter waste and dry active waste was more effective than a loading plan of spent filter waste and other wastes for the radiological point of view. These results can be expected to provide both robustness and defense in depth for the development of safety case further.

• Geophysics and Geophysical Exploration
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• v.3 no.3
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• pp.101-111
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• 2000

In order to assess the seawater intrusion, induction, temperature and conductivity of fluid, and natural gamma logs were obtained in nine wells at the three study areas having different hydrogeologic characteristics. Besides surface geophysical exploration, supplementary geophysical well logs were carried out to understand the hydrogeological characteristics related to the seawater intrusion in the study areas. The geophysical well logs have been proved to increase the accuracy of interpretation of the surface geophyscial exploration's data for assessment of seawater intrusion, and to get the optimum depth for a long monitoring of groundwater. They, also, revealed that the identification of hydrogeological units for strata's porosity was able to be achieved and were illustrated the applicability of geophysical well logs monitoring. Finally, geophysical well logs are expected to play to get the more quantitative information of seawater infusion, if it is fully collaborated with a better method that is strata's resistivity determination with not relatively much effected by seawater within the drilled borehole and that is the porosity measurement with built on small diameter PVC casing.

• Journal of IKEEE
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• v.26 no.4
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• pp.614-621
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• 2022

This paper proposes RIDS (Random Forest-Based Intrusion Detection), which is an intrusion detection system to detect hacking attack based on random forest. RIDS detects three typical attacks i.e. DoS (Denial of service) attack, fuzzing attack, and spoofing attack. It detects hacking attack based on four parameters, i.e. time interval between data frames, its deviation, Hamming distance between payloads, and its diviation. RIDS was designed in memory-centric architecture and node information is stored in memories. It was designed in scalable architecture where DoS attack, fuzzing attack, and spoofing attack can be all detected by adjusting number and depth of trees. Simulation results show that RIDS has 0.9835 accuracy and 0.9545 F1 score and it can detect three attack types effectively.

• Journal of Soil and Groundwater Environment
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• v.26 no.3
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• pp.1-13
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• 2021

Groundwater monitoring is commonly practiced with real-time sensors placed in several depth spots in aquifer. However, this method only provides monitoring data at the point where the sensors are installed. In this study, we developed a vertical line monitoring system (VLMS) that can provide continuous data of groundwater parameters along the vertical depth. The device was installed in a well located on the coast of the eastern part of Jeju island to monitor electrical conductivity, temperature, salinity, pH, dissolved oxygen, and oxidation-reduction potential over approximately 3 months from September 11 to December 3, 2020. The results indicated that the groundwater levels fluctuated with the tidal change of seawater level, and the upper and lower boundaries of the freshwater and saltwater zone in the groundwater were located at below 16 m and 36 m of mean sea level, respectively. There was a large variation in EC values during the high tide and temperature change was the greatest during flow tide. Although further investigation is needed for improvement of the device to obtain more accurate and reliable data, the device has a potential utility to provide fundamental data to understand the seawater intrusion and transport mechanisms in coastal aquifers.

• Journal of the Korean earth science society
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• v.43 no.4
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• pp.539-556
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• 2022

In the coastal areas of Jeju Island, composed of volcanic rocks, saltwater intrusion occurs due to excessive pumping and geological characteristics. Groundwater level and electrical conductivity (EC) in multi-depth monitoring wells in coastal areas were characterized from 2005 to 2019. During the period of the lowest monthly precipitation, from November 2017 until February 2018, groundwater level decreased by 0.32-0.91 m. During the period of the highest monthly precipitation, from September 2019 until October 2019, groundwater level increased by 0.46-2.95 m. Groundwater level fluctuation between the dry and wet seasons ranged from 0.79 to 3.73 m (average 1.82 m) in the eastern area, from 0.47 to 6.57 m (average 2.55 m) in the western area, from 0.77 to 8.59 m (average 3.53 m) in the southern area, and from 1.06 to 12.36 m (average 5.92 m) in the northern area. In 2013, when the area experienced decreased annual precipitation, at some monitoring wells in the western area, the groundwater level decreased due to excessive groundwater pumping and saltwater intrusion. Based on EC values of 10,000 ㎲/cm or more, saltwater intrusion from the coastline was 10.2 km in the eastern area, 4.1 km in the western area, 5.8 km in the southern area, and 5.7 km in the northern area. Autocorrelation analysis of groundwater level revealed that the arithmetic mean of delay time was 0.43 months in the eastern area, 0.87 months in the northern area, 10.93 months in the southern area, and 17.02 months in the western area. Although a few monitoring wells were strongly influenced by nearby pumping wells, the cross-correlation function of the groundwater level was the highest with precipitation in most wells. The seasonal autoregressive integrated moving average model indicated that the groundwater level will decrease in most wells in the western area and decrease or increase in different wells in the eastern area.