• Review of KIISC
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• v.30 no.5
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• pp.25-33
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• 2020

산업 제어 시스템 대상 원격 관제 기술은 관리자의 즉각적 대응을 통해 산업 재해 발생 확률 저하를 위한 핵심기술로 주목받고 있다. 그러나 산업 제어 시스템 원격 관제 기술은 원격의 관리자와 통신하기 위해 외부 네트워크 연결이 필수적이며, 따라서 공격자들에게 기존 산업 제어 시스템에 존재하지 않던 새로운 네트워크 취약점을 노출하게 된다. 산업 제어시스템은 네트워크 취약점을 해결하기 위해 터널링 프로토콜 또는 패킷 암호화 솔루션을 사용하고 있지만, 이러한 솔루션은 패킷 메타데이터를 분석하는 네트워크 트래픽 분석 공격을 방어하지 못한다. 공격자는 네트워크 트래픽 분석을 통해 패킷의 송수신 대상, 통신 빈도, 활성화 상태 등을 알 수 있으며 획득한 정보를 다음 공격을 위한 초석으로 사용할 수 있다. 따라서 기존의 솔루션들이 해결하지 못하는 산업 제어 시스템 네트워크 환경에서 발생하는 잠재적인 문제들을 해결하기 위해 네트워크 트래픽 분석 난이도를 향상시켜 분석을 방어하는 솔루션이 필요하다. 본 논문에서는 패킷 메타데이터를 분석하는 네트워크 트래픽 분석 공격을 어렵게 하고자 패킷 분할 및 병합 기반 네트워크 트래픽 난분석화 기법을 제안한다. 본 논문에서 제안하는 기법의 참여자인 관리자와 산업 기기는 각각 일정한 크기의 그룹으로 묶인다. 그리고 원격 관제를 위해 관리자와 산업 기기 간 송수신되는 모든 패킷을 대상으로 분할 노드를 경유하도록 한다. 분할노드는 패킷의 난분석화를 위한 핵심 요소로써, 관리자와 산업 기기 사이에 송수신되는 모든 패킷을 상호 목적 대상 그룹의 개수로 분할한다. 그리고 분할한 패킷 조각에 패킷 식별자와 번호를 부여하여 패킷 조각을 모두 수신한 목적대상이 올바르게 패킷을 병합할 수 있도록 하였다. 그리고 분할노드는 목적 대상이 속한 그룹의 모든 참여자에게 서로 다른 패킷 조각들을 전달함으로써 공격자가 패킷의 흐름을 알 수 없도록 하여 산업 제어 시스템 정보를 수집하는 것을 방어한다. 본 논문에서 제안하는 패킷 분할 및 병합 기반 트래픽 난분석화 기법을 통해 산업 제어 시스템을 대상으로 한 트래픽 분석 공격을 방어함으로써 네트워크 공격의 피해를 줄이고 추가적인 네트워크 공격을 차단할 수 있을 것으로 기대된다.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 2006.06a
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• pp.288-293
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• 2006

최근 반도체 개발 및 제조부문에서는 급속도로 성장한 Mobile 시장과 Digital Consumer Trend 에 주도적으로 대응하고자 빠른 속도의 기술적 변화를 추진하여 왔으며, 이에 따라 현장에서 발생하는 기술적 문제의 유형 또한 점점 복잡 다양해지고 있다. 기존 Commodity 제품의 경우, 세대 전환이 느리게 진행되어, 이에 수반되는 기술적 문제의 난이도와 그 발생 종류가 현재 대비 상대적으로 단순하였다. 그러나 최근 다품종 주문형 제품비중 확대로, 발생되는 문제점들이 Field Application 과 tight 한 연관성을 지니고 있어, 문제의 발생 경로, 원인 파악과 해결 대책 수립에 상당한 초기대응 시간을 필요하며, 관련 부서와의 실시간 협업 및 Cross-Checking을 통하지 않고서는 문제에 대한 최적 Solution 을 결정하기 힘든 현실이 되었다. 이러한 기술 이슈 해결 과정에 기 발생했던 유사 이슈 처리 과정 및 결과 자료가 문제 해결에 크게 기여할 수 있으나, 종래의 지식관리 시스템 체계로는 이러한 실무 형 지식을 획득하기 어려운 부분이 한계점으로 지적되고 있다. 본 논문에서는 이러한 문제점 개선이 가능한 실무형 지식 관리 (AKM: Actual Knowledge Management) 기반의 기술적 이슈 추적 관리 시스템(TITS: Technical Issue Tracking System) 구축 사례를 제시하고자 한다. TITS 는 1) 기술 이슈의 발의 및 전파 기능과 2) 이슈 해결을 위한 Action Item 부여 및 의견 교환 기능 3) 해결된 이슈의 처리 결과 등록 기능 4) 유사 이슈 사례 검색 기능 등의 크게 4 개 모듈오 구성 되어있다. 이 시스템을 통해 반도체 엔지니어들은 기술적 이슈의 발생 시점부터, 원안분석, 대책 협의 ; Action Item 수립 등 문제 해결 과정과 결과 등록 시점까지 Real time Tracking이 가능해 졌으며, 본 시스템을 통해 처리된 모든 기술적 이슈 정보는 Issue Case Database 에 분류 저장되어, 향후 유사 이슈 발생 시, 이를 활용함으로써, 빠른 초기 대응 및 문제 해결에 직접적인 도움을 받을 수 있게 되었다.

• Journal of the Korea Society of Computer and Information
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• v.26 no.10
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• pp.101-108
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• 2021

In this paper, we analyze Shin's proposed dynamic ID-based user authentication scheme for TMIS(Telecare Medicine Information System), and Shin's authentication scheme is vulnerable to smart card loss attacks, allowing attackers to acquire user IDs, which enables user impersonation attack. In 2019, Shin's proposed authentication scheme attempted to generate a strong random number using ECC, claiming that it is safe to lose a smart card because it is impossible to calculate random number r'i due to the difficulty of the ECC algorithm without knowing random number ri. However, after analyzing Shin's authentication scheme in this paper, the use of transmission messages and smart cards makes it easy to calculate random numbers r'i, which also enables attackers to generate session keys. In addition, Shin's authentication scheme were analyzed to have significantly greater overhead than other authentication scheme, including vulnerabilities to safety analysis, the lack of a way to pass the server's ID to users, and the lack of biometric characteristics with slightly different templates.

• Korean Journal of Optics and Photonics
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• v.32 no.6
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• pp.314-322
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• 2021

A reflecting telescope consists of a concave primary mirror and a convex secondary mirror. The primary mirror is easy to measure, because it converges the beam from an interferometer, while the secondary mirror diverges the beam and so is not easy to measure, even though it is smaller than the primary mirror. In addition, the Korsch-type telescope uses the central area of the secondary mirror, so that the entire area of the secondary mirror needs to be measured, which the classical Hindle test cannot do. In this paper, we propose a double-stitching method that combines two separate area measurements: the annular area, measured using the Hindle stitching method, and the central area, measured using a spherical wave from the interferometer. We test the surface error of a convex asphere that is 202 mm in diameter, with 499 mm for its radius of curvature and -4.613 for its conic constant. The surface error is calculated to be 19.5±1.3 nm rms, which is only 0.7 nm rms different from the commercial stitching interferometer, ASI. Also, the two results show a similar 45° astigmatism aberration. Therefore, our proposed method is found to be valuable for testing the whole area of a convex asphere.

• Korean Journal of Culture and Social Issue
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• v.10 no.3
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• pp.19-36
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• 2004

An experimental research investigated the components of lottery games affecting lottery-purchasing behaviors and the psychological consequences of the behaviors. In the experiment, participants were given a chance to purchase a lottery tickets during a series of computer games and their decision of purchasing the lottery ticket was measured. Also, the size and probability of the lottery games were manipulated and the perceived difficulty, satisfaction of the mid-outcome, and perceived probability of success in the computer game were measured in order to examine their impacts on participants' lottery-purchasing decisions. In addition, the behavioral tendency, satisfaction of the final outcome, and perceived self-capability in the computer game were measured at the end of the computer games in order to examine the effects of lottery-purchasing experiences on the variables. Participants who perceived the games as easier and estimated the probability of their success highly were more likely to buy the lottery tickets. However, the winning prize and odd of lottery tickets, perceived satisfaction of their own performance, and the performance itself did not influence the purchasing decisions. The common beliefs on the negative effects of lottery-purchasing experiences on human motivation and behaviors were not supported. The implications of the present research findings and limitations of the experimental research on lottery were discussed.

• Investigative Magnetic Resonance Imaging
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• v.9 no.1
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• pp.9-15
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• 2005

Purpose : This study attempted to investigate the effects of supply of highly concentrated $(30\%)$ oxygen on human ability of visuospatial cognition using time course data analysis of functional Magnetic Resonance Imaging (fMRI). Materials and Methods : To select an item set in the visuospatial performance test, two questionnaires with similar difficulty were developed through group testing. A group test was administered to 263 college students. Two types of questionnaire containing 20 questions were developed to measure the ability of visuospatial cognition. Eight college students (right-handed male, average age of 23.5 yrs) were examined for fMRI study. The experiment consisted of two runs of the visuospatial cognition testing, one with $21\%$ level of oxygen and the other with $30\%$ oxygen level. Each run consisted of 4 blocks, each containing control and visuospatial items. Functional brain images were taken from 37 MRI using the single-shot EPI method. Using the subtraction procedure, activated areas in the brain during visuospatial tasks were color-coded by t-score. To investigate the time course data in each activated area from brain images, 4 typical regions (cerebellum, occipital lobe, parietal lobe, and frontal lobe) were selected. Results : The average accuracy was $50.63{\pm}8.63$ and $62.50{\pm}9.64$ for $21\%\;and\;30\%$ oxygen respectively, and a statistically significant difference was found in the accuracy between the two types of oxygen (p<0.05). There were more activation areas observed at the cerebellum, occipital lobe, parietal lobe and frontal lobe with $30\%$ oxygen administration. The rate of increase in the cerebellum, occipital lobe and parietal lobe was $17\%$ and that of the frontal lobe, $50\%$. Especially, there were increase of intensity of BOLD signal at the parietal lobe with $30\%$ oxygen administration. The increase rate of the left parietal lobe was $1.4\%$ and that of the right parietal lobe, $1.7\%$. Conclusion : It is concluded that while performing visuospatial tasks, high concentrations of oxygen administration make oxygen administration sufficient, thus making neural network activate more, and the ability to perform visuospatial tasks increase.

• Geophysics and Geophysical Exploration
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• v.9 no.4
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• pp.279-290
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• 2006

The borehole radar methods used to tunnel detection are mainly classified into borehole radar reflection, directional antenna, crosshole scanning, and radar tomography methods. In this study, we have investigated the feasibility and limitation of each method to tunnel detection through case studies. In the borehole radar reflection data, there were much more clear diffraction signals of the upper wings than lower wings of the hyperbolas reflected from the tunnel, and their upper and lower wings were spreaded out to more than 10m higher and lower traces from the peaks of the hyperbolas. As the ratio of borehole diameter to antenna length increases, the ringing gets stronger on the data due to the increase in the impedance mismatching between antennas and water in the boreholes. It is also found that the reflection signals from the tunnel could be enhanced using the optimal offset distance between transmitter and receiver antennas. Nevertheless, the borehole radar reflection data could not provide directional information of the reflectors in the subsurface. Direction finding antenna system had a advantage to take a three dimensional location of a tunnel with only one borehole survey even though the cost is still very high and it required very high expertise. The data from crosshole scanning could be a good indicator for tunnel detection and it could give more reliable result when the borehole radar reflection survey is carried out together. The images of the subsurface also can be reconstructed using travel time tomography which could provide the physical property of the medium and would be effective for imaging the underground structure such as tunnels. Based on the results described above, we suggest a cost-effective field procedure for detection of a tunnel using borehole radar techniques; borehole radar reflection survey using dipole antenna can firstly be applied to pick up anomalous regions within the borehole, and crosshole scanning or reflection survey using directional antenna can then be applied only to the anomalous regions to detect the tunnel.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.4
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• pp.277-286
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• 2002

Most of the problems in dealing with the tunnel construction are the uncertainties and complexities of the stress conditions and rock strengths in ahead of the tunnel excavation. The limitations on the investigation technology, inaccessibility of borehole test in mountain area and public hatred also restrict our knowledge on the geologic conditions on the mountainous tunneling area. Nevertheless an extensive and superior geophysical exploration data is possibly acquired deep within the mountain area, with up to the tunnel locations in the case of alternative design or turn-key base projects. An appealing claim in the use of artificial neural networks (ANN) is that they give a more trustworthy results on our data based on identifying relevant input variables such as a little geotechnical information and biological learning principles. In this study, error back-propagation algorithm that is one of the teaching techniques of ANN is applied to presupposition on Rock Mass Ratings (RMR) for unknown tunnel area. In order to verify the applicability of this model, a 4km railway tunnel's field data are verified and used as input parameters for the prediction of RMR, with the learned pattern by error back propagation logics. ANN is one of basic methods in solving the geotechnical uncertainties and helpful in solving the problems with data consistency, but needs some modification on the technical problems and we hope our study to be developed in the future design work.

• Korean Journal of Environmental Biology
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• v.41 no.3
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• pp.229-246
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• 2023

The bitterling (Cyprinidae, Acheilongnathinae) is a temperate freshwater fish with a unique spawning symbiosis with host mussels. Female bitterlings use their extended ovipositors to lay eggs on the gills of mussels through the mussel's exhalant siphon. In the present study, in April of 2020, we investigated spawning frequencies and patterns of three bitterling fish species in host mussel species in the Nakdong River basin (Hoecheon). During field surveys, a total of four bitterling and three mussel species were found. We observed bitterling's spawning eggs/larvae in the three mussel species: Anodonta arcaeformis(proportion spawned: 45.5%), Corbicula fluminea(12.1%), and Nodularia douglasiae (45.2%). The number of bitterlings' eggs/larvae per mussel ranged from 1 to 58. Using our developed genetic markers, we identified the eggs/larvae of each bitterling species in each mussel species (except for A. macropterus): A. arcaeformis (spawned by Acheilognathus yamatsutae), C. fluminea (A. yamatsutae and Tanakia latimarginata), and N. douglasiae (A. yamatsutae, Rhodeus uyekii, and T. latimarginata). Approximately 57.6% of N. douglasiae mussel individuals had eggs/larvae of more than one bitterling species, suggesting that interspecific competition for occupying spawning grounds is intense. This is the first report on bitterling's spawning events in the Asian clam C. fluminea from Korea; however, it should be ascertained whether bitterling's embryo undergoes successful development inside the small mussel and leaves as a free-swimming juvenile. In addition, the importance of its conservation as a new host mussel species for bitterling fishes needs to be studied further.