• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.6
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• pp.425-434
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• 2019

It is important to ensure the seismic safety of pile-bent bridges constructed in areas with thick soft ground consisting of various soil layers against seismic motion in these layers. In this study, several synthetic seismic waves that are compatible with the seismic design spectrum for rock sites were generated, and the ground acceleration history of each soil layer was obtained based on ground analyses. Using these acceleration histories, each soil layer was modeled using equivalent linear springs, and multi-support excitation analyses were performed using the input motion obtained at each soil layer. Due to the nonlinear behavior of the soft soil layers, the intensity of the input ground motion was not amplified, which resulted in the elastic behavior of the bridge. In addition, inputting the acceleration history obtained from a particular layer simultaneously into all the ground springs reduced the response. Therefore, the seismic performance of this type of bridge might be overestimated if multi-excitation analysis is not performed.

• Journal of the Korea Society of Computer and Information
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• v.13 no.2
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• pp.79-85
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• 2008

The middleware that provides RFID-based ubiquitous application service should process the data inputted constantly in real time, and acquire and deliver the answers of the questions in the application service. Studies for developing a Data Stream Management System(DSMS) has been performed in order to process a large amount of data stream inputted constantly in this way. Previous algorithms on data stream were mostly focused on reducing the average error between the answers of the successive questions and abandon the data according to the priority of them when a load occurs. This article is composed of presenting the necessity of the studies on the DSMS and speedy data processing, suggesting an algorithm to make Possible the speedy data processing using buffers and prompt questions and answers, and testing the performance of the data processing rate and whether a buffer is generated correspondingly to the algorithm suggested, in either a single or a multiple buffer, through simulations.

• The KIPS Transactions:PartD
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• v.13D no.3 s.106
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• pp.317-324
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• 2006

In this paper, we propose a new indexing technique to solve various queries which have a strong good point not only database indexing schema take advantage of converting from semi-structured data to structured data but also performance is more faster than before. We represent structure information of XML document between nodes of tree that additional numbering information which can be bit-stream without modified structure of XML tree. And, We add in indexing schema searching incidental structure information in the process. In Querying schema, we recover ancestor nodes through give information of node using indexing schema in complete path query expression as well as relative path query expression. Therefore, it takes advantage of making derivative query expression with given query. In this process, we recognize that indexing and querying schema can get searched result set faster and more accurate. Because response time is become shorter by bit operating, when query occur and it just needs information of record set earch node in database.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.2 s.21
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• pp.25-35
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• 2006

Recently seismic fragility analysis method has been widely used for the seismic probabilistic risk assessment of infrastructures such as nuclear power plants, buildings and bridges because of its probabilistic characteristics. Furthermore, this technique has been applied to large-scale social systems consisted of each infrastructures by combing GIS. In this paper, the applicability of this technique to domestic infrastructural systems was studied. The transportation network was selected as one of these domestic infrastructural systems. Example studies were peformed about Changwon city. Nonlinear time history analysis, with a maximal likelihood approach were conducted to establish the fragility curves of each infrastrucures (bridges). GIS analysis was also applied to the analysis of whole infrastructural systems. The results show that it is very useful to predict seismic probabilistic risk assessment of this domestic transportation network. However, it also shows that further studies such as more suitable damage criterion to domestic structure and precise nonlinear analysis techniques should be developed to predict more precise results.

• The KIPS Transactions:PartC
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• v.15C no.1
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• pp.69-78
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• 2008

In this paper, we propose the effective exchange-method of a user profile for adapted contents services in the contents adaptation system. The profiles continuously exchange among the devices of contents adaption system for providing the adapted contents to a user. The profile should be also exchanged according to periodic, aperiodic, event, request and response. Consequently, a lot of network traffic occur and computing power require. Solving theses problem, the profile exchange research needs. we analyze creation information, exchange information, and exchange form of the profile information in contents adaptation system for effective profile exchange and define exchange procedure of the profile using the analyzed profile information. we also propose providing method of the profile configured information for decreasing profile processing time and user setting method for decreasing the number of profile transmission. As a result of performance evaluation, providing method of the profile configured information reduce 7% processing time and user setting method decrease the number of profile transmission are effective to exchange the profile.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.463-463
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• 2010

고휘도 고효율 백색 LED (lighting emitting diode)가 차세대 조명광원으로 급부상하고 있다. 백색 LED를 생산하기 위한 공정에서 MOCVD (유기금속화학증착)장비를 이용한 Epi wafer공정은 에피층과 기판의 격자상수 차이와 열팽창계수차이로 인하여 생성되는 에피결함의 제거를 위하여 기판과 GaN 박막층 사이에 완충작용을 해줄 수 있는 버퍼층 (Buffer layer)을 만들고 그 위에 InGaN/GaN MQW (Multi Quantum Well)공정을 하여 고휘도 고효율 백색 LED를 구현할 수 있다. 이 공정에서 기판의 온도가 불균일해지면 wafer 파장 균일도가 나빠지므로 백색 LED의 yield가 떨어진다. 균일한 기판 온도를 갖기 위한 조건으로 기판과 induction heater의 간격, 가스의 흐름, 기판의 회전, 유도가열코일의 디자인 등이 장비의 설계 요소이다. 코일에 교류전류를 흘려주면 이 코일 안 또는 근처에 있는 도전체에 와전류가 유도되어 가열되는 유도가열 방식은 가열 효율이 높아 경제적이고, 온도에 대한 신속한 응답성으로 인하여 열 손실을 줄일 수 있으며, 출력 온도 제어의 용이성 및 배출 가스 등의 오염 없다는 장점이 있다. 본 연구에서는 유도가열방식의 induction heater를 이용하여 회전에 의한 기판의 온도 균일도 측정을 하였다. 기초 실험으로 저항 가열 히터를 통하여 대류에 의한 온도 균일도를 평가하였다. 그 결과 gap이 3 mm일 때, 평균 온도 $166.5^{\circ}C$ 에서 불균일도 6.5 %를 얻었으며 이를 바탕으로 induction heater와 graphite susceptor의 간격이 3 mm일 때, 회전에 의한 온도 균일도를 측정을 하였다. 가열원은 induction heater (viewtong, VT-180C2)를 사용하였고, 가열된 graphite 표면의 온도를 2차원적으로 평가하기 위하여 적외선 열화상 카메라(Fluke, Ti-10)을 이용하여 온도를 측정하였다. 기판을 회전하면서 표면 온도의 평균과 표준 편차를 측정한 결과 2.5 RPM일 때 평균온도 $163^{\circ}C$ 에서 가장 좋은 5.5 %의 불균일도를 확인할 수 있었고, 이를 상용화 전산 유체 역학 코드인 CFD-ACE+의 모델링 결과와 비교 분석 하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2000.04a
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• pp.28-35
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• 2000

In order to acquire the precise and fast response for an analytical query, proper selection of the views to materialize in data warehouse is very crucial. In traditional algorithms, the whole relation is considered to be selected as materialized views. However, materializing the whole relation rather than a part of relation results in much worse performance in terms of time and space cost. Therefore, we present a new algorithm for selection of views to materialize using clustering method in order to improve the performance of data warehouse including this problem. In the presented algorithm, ASVMR(Algorithm for Selection of Views to Materialize using Reduced table), we first generate reduced tables in data warehouse using automatic clustering based on attribute-values density, then we consider the combination of reduced tables as materialized views instead of the combination of the original base relations. We also show the experimental results in which both time and space cost are approximately 1.8 times better than the conventional algorithms.

• Journal of Science and Technology Studies
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• v.19 no.3
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• pp.1-49
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• 2019

First proposed by Paul Crutzen and Eugene Stoermer in 2000, the concept of the Anthropocene has had staggering repercussions in a variety of disciplines. In response to the Anthropocene narrative as a problematization of the eco-ontological emergency that humanity is confronted with in the 21st-century, I will deal with the following theoretical themes in this article. Firstly, I will analyze the central agendas underlying the Anthropocene discourse: the expansion of human agency into the planetary level and the possibility of unprecedented catastrophes in the near future. Secondly, I will propose to address the Anthropocene discourse as problem-assemblage. Thirdly, I will examine Clive Himilton and Dipesh Chakrabarty's theses in order to understand the shock that was brought to bear on the humanities and social sciences by the Anthropocene narrative. Fourthly, I will reinterpret the allegory of the angel appearing in Benjamin's Theses on the Philosophy of History to explore new possibilities of transformative becoming of the subjectivity, focusing on the concept of patiency. Finally, I will present the concept of reflexive catastrophism.

• Convergence Security Journal
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• v.19 no.1
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• pp.3-10
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• 2019

The 5G network is a next-generation converged network that combines various ICT technologies to realize the need for high speed, hyper connection and ultra low delay, and various efforts have been made to address the security vulnerabilities of the previous generation mobile networks. However, the standards released so far still have potential security vulnerabilities, such as USIM deception and replication attack, message re-transmission attack, and race-condition attack. In order to solve these security problems, this paper proposes a new 5G-AKA protocol with PUF technology, which is a physical unclonable function. The proposed PUF-based 5G-AKA improves the security vulnerabilities identified so far using the device-specific response for a specific challenge and hash function. This approach enables a strong white-list policy through the addition of inexpensive PUF circuits when utilizing 5G networks in areas where security is critical. In addition, since additional cryptographic algorithms are not applied to existing protocols, there is relatively little burden on increasing computational costs or increasing authentication parameter storage.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.6
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• pp.359-366
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• 2020

In this study, a simulation-based damage estimation method for helidecks is proposed using an artificial neural network. The structural members that share a connecting node in the helideck are regarded as a damage group, and a total of 37,400 damage scenarios are numerically generated by applying randomly assigned damage to up to three damage groups. Modal analysis is then performed for all the damage scenarios, which are selectively used as either training or validation or verification sets based on the purpose of use. An artificial neural network with three hidden layers is constructed using a PyTorch program to recognize the patterns of the modal responses of the helideck model under both damaged and undamaged states, and the network is successively trained to minimize the loss function. Finally, the estimated damage rate from the proposed artificial neural network is compared to the actual assigned damage rate using 400 verification scenarios to show that the neural network is able to estimate the location and amount of structural damage precisely.