• 지질공학
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• 제31권1호
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• pp.55-66
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• 2021

본 연구에서는 방사성폐기물 처분 시 천연방벽의 수리 특성 진화와 관련하여, 시추공 설치 및 확공이 결정질 암반 내 단열 및 수리 특성에 영향을 미칠 가능성을 평가하기 위해 수리-역학 연동 수치해석을 수행했다. 시추공 부근에서의 간극 열림과 투수성 변화 여부를 평가하기 위해 단열망을 기반으로 한 불연속체 해석 도메인을 이용했다. 단열암반에서의 현장수리시험 모사를 통해 주응력방향과 시추공 직경 변화의 영향을 평가하였다. 먼저 단열의 간극변화가 주응력방향에 의존함을 확인했다. 그리고 수직변위에 의한 간극크기 증가가 지배적이었다. 시추공 부근에 전단팽창이 집중되는 것도 단열의 수리지질학적 진화에 영향을 미칠 수 있음을 알 수 있었다. 수치해석 결과는 시추공 설치 및 확공에 따른 응력교란에 의해 단열 특성이 변화하여 단열 암반의 투수성이 증가할 수 있다는 것을 보여준다. 추후 본 연구모델을 기반으로 실제 크기의 처분공 주변에서의 정확한 수리적 변화를 분석하기 위해서는 3차원 해석모델로 보완되어야 할 것으로 판단되었다.

• 한국정보통신학회논문지
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• 제5권7호
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• pp.1257-1262
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• 2001

최근에 경제적인 대안으로 IP over WDM 네트워크가 주목을 받고 있다. IP over WDM은 광대역 수용 능력, 네트워크 확장성 외에 여러 장점을 가지고 있다. IP 기반에서, "lambda-labeling"은 IP over WDM에 직접적으로 적용할 수 있다. 본 논문에서는 현재 IETF측 중심으로 연구중인 MPLambdaS 개념을 기초로 하여 광 인터넷의 진화를 고려한 구조적인 접근 방법을 연구한다. MPLS 도메인과 MPLamdaS 도메인간에 연동을 고려하여 전자적인 다수의 LSP를 광 LSP로 모으는 레이블 스택 개념을 이용한 람다 LSP 터널링 기술을 적용하여 전자적인 MPLS 와 광 MPLamdaS 간의 연동 방안을 제안하고 이를 지원하는 Edge Optical LSR의 구조를 제안한다. 구조를 제안한다.

• Journal of Microbiology and Biotechnology
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• 제12권1호
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• pp.130-136
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• 2002

The internal transcribed spacer (ITS) region in the genus Tricholoma was analyzed, including for its primary nucleotide sequence and secondary structural characterization. The secondary structures of the ITS2 region in the genus Tricholoma were identified for use in bioinformatic processes to study molecular evolution and compare secondary structures. Ten newly sequenced ITS regions were added to the analysis and submitted to the GenBank database. The resulting structure from a minimum energy algorithm indicated the four-domain model, as previously suggested by others. The conserved secondary structure of the ITS2 sequences of the genus Tricholoma exhibited certain unique features, including pyrimidine tracts in the loops of domain A and a complete structure containing four domains, with motifs identified in other ITS2 secondary structures. A phylogenetic tree was derived from sequence alignment based on the secondary structures. From the resulting maximum parsimonious tree, it was found that the species in the genus Tricholoma had evolved monophyletically and were composed of four groups, as supported by the bootstrapping values and pileus color.

• 한국정보시스템학회지:정보시스템연구
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• 제18권3호
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• pp.47-70
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• 2009

Social network is one of the representative analytical method of the complexity theory and this research analyzed various and unique strategic alliance model of e-business domain using social network technique. A lot of small and medium firms of e-business field had developed many useful type of strategic alliances for the firms tried to maximize the effect of advertisement, marketing and to make up for their weak points and to compete with huge company with capital strength long before. But it is too rare to analyze the structure of the firm networks and to study the evolution and extension of business model considered the role of each company in the network. Social network analysis helps each firm's network easily visualized and completely modelized. Additionally, this paper cries to analyze the relationship between the role of hub and broke in the firm networks for strategic alliance, and financial performance. We demonstrate the firm with finer business model to the business environment can make higher financial performance. This implies that the firm that can create new finer business model, will lead the network of e-business firms and evolve the industry of e-business.

• 전기학회논문지
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• 제59권11호
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• pp.2108-2113
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• 2010

The Long Term Evolution (LTE) system is based on the Orthogonal Frequency Division Multiplexing (OFDM) and relies its channel estimation on the lattice-type pilot samples in the multipath fading channel environment. The estimation of the channel frequency response (CFR) makes use of the least squares estimate (LSE) for each pilot samples, followed by an interpolation both in time- and in frequency-domain to fill up the channel estimates for subcarriers corresponding to data samples. Any interpolation scheme could be adopted for this purpose. Depending on the requirements of the target system, we may choose a simple linear interpolation or a sophisticated one. For any choice of an interpolation scheme, these is a trade-off between estimation accuracy and numerical cost. For those wireless communication systems based on the OFDM and the preamble-type pilot structure, the DFT-based channel estimation and its variants have been successfully. Yet, it may not be suitable for the lattice-type pilot structure, since the pilot samples are not sufficient to provide an accurate estimate and it is known to be sensitive to the location as well as the length of the time-domain window. In this paper, we propose a simple interpolated based on the upsampling mechanism in the multirate signal processing. The proposed method provides an excellent alternative to the DFT-based methods in terms of numerical cost and accuracy. The performance of the proposed technique is verified on a multipath environment suggested on a 3GPP LTE specification.

• 소성∙가공
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• 제11권6호
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• pp.529-537
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• 2002

A series of load-relaxation tests and tensile tests were conducted to study the high temperature deformation mechanism of fine duplex gamma TiAl alloy at temperatures ranging from 800 to 105$0^{\circ}C$. Results of load relaxation test showed that deformation behavior at a small imposed strain ($\varepsilon$≒0.05) was dominated by dislocation glide and dislocation climb. To investigate the deformation behavior at a large amount of strain, the processing map was constructed using a dynamic materials model. Two domains were characterized in the processing map obtained at a strain level of 0.6. One domain was found at the region of 98$0^{\circ}C$ and $10^{-3}/sec$ with a peak efficiency of 48%, which was identified as a domain of dynamic recrystallization from the microstructural observation. The order was observed at the region of 125$0^{\circ}C$ and $10^{-4}/sec$ with a peak efficiency of 64%. The strain rate sensitivity measured indicates that the material was deformed by the superplasticity in the region.

• 융합정보논문지
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• 제9권9호
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• pp.52-57
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• 2019

DNS는 'Domain Name System'의 약자로, 네트워크 상에서 네트워크에 연결된 장지를 구분하기 위해 IP 주소를 사용하는데, IP는 일반 사용자가 쉽게 기억하기가 어려워 IP에 해당하는 별명같은 이름을 등록하여 관리하는 시스템을 말한다. 최근 들어 이러한 DNS를 악용하는 사례가 해외에서 늘고 있으며, 'DNS피오나지' 라고 불리는 배후 세력들이 새로운 룰과 악성코드를 개발하여 진화하고 있으며, 이런 공격은 해킹 성공률을 높이며, 가짜 사이트로 유도를 하는 등 데이터를 변경하거나 위조하고 있어 피해 사례가 증가되고 있는 상황이다. 글로벌 DNS 시스템 등 점점 통제를 할 수 없는 범위로 확대되고 있어, 이를 통제하기 위해 DNS피오나지 공격에 대한 분석과 대응책을 제시하여 안전한 DNS 시스템을 구축을 제안한다.

• Nuclear Engineering and Technology
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• 제56권2호
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• pp.688-706
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• 2024

Austenitic stainless steels (ASS) are extensively employed in various sectors such as nuclear, power, petrochemical, oil and gas because of their excellent structural strength and resistance to corrosion. SS304 and SS316 are the predominant choices for piping, pressure vessels, heat exchangers, nuclear reactor core components and support structures, but they are susceptible to stress corrosion cracking (SCC) in chloride-rich environments. Over the course of several decades, extensive research efforts have been directed towards evaluating SCC using diverse methodologies and models, albeit some uncertainties persist regarding the precise progression of cracks. This review paper focuses on the application of Acoustic Emission Technique (AET) for assessing SCC damage mechanism by monitoring the dynamic acoustic emissions or inelastic stress waves generated during the initiation and propagation of cracks. AET serves as a valuable non-destructive technique (NDT) for in-service evaluation of the structural integrity within operational conditions and early detection of critical flaws. By leveraging the time domain and time-frequency domain techniques, various Acoustic Emission (AE) parameters can be characterized and correlated with the multi-stage crack damage phenomena. Further theories of the SCC mechanisms are elucidated, with a focus on both the dissolution-based and cleavage-based damage models. Through the comprehensive insights provided here, this review stands to contribute to an enhanced understanding of SCC damage in stainless steels and the potential AET application in nuclear industry.

• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1296-1309
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• 2024

The aim of this work is to explore the effect of the double subdiffusion on the stability in BWRs. A BWR novel reduced order model with double subdiffusion effects: reduced order fractional model (DS-F-ROM) to describe the neutron and heat transfer processes was proposed for this study. The double subdiffusion was developed with a fractional-order two-equation model, and with different fractional-orders and relaxation times. The stability analysis was carried out using the root-locus method and change from the s to the W domain and were confirmed using the time-domain evolution of neutron flux for a unit step change in reactivity. The results obtained using the reduced fractional-order model are presented for different anomalous diffusion coefficient values. Results are compared with normal diffusion and P1 equations, which are obtained straightforwardly with DS-ROM when relaxation time tends to zero, and when the anomalous diffusion coefficient tends to one, respectively.

• 대한지리학회지
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• 제46권6호
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• pp.673-692
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• 2011

컴퓨터 기술의 발전으로 인해 근래 들어 수치지형발달모형을 개발하고 이를 이용하여 다양한 관점에서 지형발달과정의 역동성을 파악하기 위한 시도들이 활발하게 행해졌다. 하지만 국내에서는 수치지형발달모형을 활용하거나 개발하는 시도가 거의 없었다. 이에 본 연구에서는 2차원상에서 지질시간 규모의 지형발달을 모의하는 수치지형발달모형을 개발하고 이의 유용성을 확인해 보았다. 개발된 모형은 지표 구성물질을 기반암과 이동 가능한 토양으로 구분하고 토양층의 두께를 모의하기 위해 기반암 풍화를 포함한다. 이를 통해 사면에서는 운반제어환경뿐만이 아니라 풍화제어환경도 모의 가능하다. 또한 토양포행과 같은 사면에서의 점진적인 물질이동과는 별개로 활동(landslide) 역시 주요한 지형형성작용으로 포함한다. 그리고 하천 운반력이 하상물질의 양보다 큰 곳에서는 기반암 하상 침식이 발생하여 분리제어환경도 모의한다. 한편 무한 유향 알고리듬을 이용하여 흐름을 분배하기 때문에 최대하부 경사 유향 알고리듬을 이용할 때 나타나는 흐름 분배상의 문제점을 줄일 수 있다. 개발된 모형을 이용한 모의실험 결과, 본 모형은 지질시간 규모의 지형발달과정을 비교적 합리적으로 모의하였다.