• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2471-2476
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• 2008

Turbulent flow and heat transfer to water at supercritical pressure flowing in vertical pipes is investigated using direct numerical simulation (DNS). A conservative space-time discretization scheme for variable-density flows at low Mach numbers is adopted in the present study to treat steep variations of fluid properties at supercritical pressure just above the thermodynamic critical point. The fluid properties at these conditions are obtained using PROPATH and used in the form of tables in the simulations. The buoyancy influence induced by strong variation of density across the pseudo-critical temperature proved to play an important role in turbulent flow and heat transfer at supercritical state. Depending on the degree of buoyancy influence, turbulent heat transfer may be enhanced or significantly deteriorated, resulting in local hot spots along the heated surface.

• International Commerce and Information Review
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• v.6 no.1
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• pp.191-210
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• 2004

There are increasing needs for an individual or enterprise to interchange documents electronically through communication network to enhance the efficiency of business, owing to rapid process of transactions. But e-commerce encounters the problems regarding the handling the electronic documents, that is to say, deposit and proof of the electronic documents. This paper deals with Authorized Electronic Data Depot as an integrated system for processing, relaying and proving documents that. Authorized Electronic Data Depot operates as e-enabler in exchanging documents in trust among administrative agencies and a comprehensive government directory, digital government seal certification system and DNS system. Authorized Electronic Data Depot leads public and private sectors to save the paper-related costs. But the regulations concerning an authorized electronic data depot is introduced in the course of revision of Electronic Transactions Act. The purpose of this paper is to suggest some guidelines in legalizing the authorized electronic data depot.

• Journal of the Korean Society of Safety
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• v.24 no.1
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• pp.14-20
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• 2009

Direct numerical simulations(DNS) were performed for the prediction of transient buoyant jet diffusion flames where the Froude numbers(Fr) are 5 and 160, respectively. The thermodynamic and transport properties were evaluated using CHEMKIN package to enhance the prediction performance of the DNS code. The simulated buoyant jet diffusion flame of Fr=5 and 160 showed the transient, dynamic motion well. It was identified that the buoyant jet flames were flickered periodically, and the simulated flickering frequency of the jet diffusion flame of Fr=5 was 12.5Hz, which was in good agreement with the experimental results. The flamelet structures of the buoyant jet diffusion flames could be well understood by comparing the scalar dissipation rates(SDR) and the heat release rates(HRR) of the flames. It was found that the SDR was strongly coupled with the HRR in the buoyant jet diffusion flames.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.04b
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• pp.959-962
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• 2002

DNSSEC은 IETF에서 논의중인 DNS 보안 표준으로서, DNS에 있어 가장 큰 잠재적 위협인 '도메인 네임에 대응되는 IP주소의 위변조 위협에 대응하기 위해 논의되고 있는 표준이다. 최근 네트워크 환경에서의 최상의 암호화 기법으로 자리잡은 공개키 암호화 기법을 이용하여, 도메인 Zone에 서명을 하여, 이러한 Zone 메시지를 받아보았을 때, 서명을 검증함으로서, DNS메시지가 중간에 위 변조없이 적정한 소스로부터 왔다는 것을 확인하는 것이다. 본 논문에서는 DNSSEC에서 가능한, 계층적 인증방식을 .KR 하위 도메인네임에서 활용할 수 있는 방안으로서, secure resolver를 이용한 도메인네임의 인증을 제시하였다.

• Bulletin of the Korean Chemical Society
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• v.10 no.6
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• pp.491-495
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• 1989

Resolution of enantiomers of DNS-amino acids has been achieved by a reversed phase liquid chromatography with an addition of a copper(Ⅱ) complex of N-benzyl-L-hydroxyproline to the mobile phase. N-Benzyl-L-hydroxyproline was prepared and used as a chiral ligand of copper(Ⅱ) chelate for the optical resolution. The pH and the concentration of copper(Ⅱ) chelate, organic solvent, and buffer agent in the mobile phase all affect the optical resolutions of dansyl amino acids. The elution orders between D and L-DNS-amino acids were different depending on the structure of the side chain of the amino acids. The retention mechanism for the chiral separation of the dansyl amino acids can be illustrated by the equilibrium of ligand exchange and by hydrophobic interaction with $C_{18}$ stationary phase. The chiral separation can be illustrated with cis and trans effect of the ligand exchange reaction.

• Bulletin of the Korean Chemical Society
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• v.9 no.6
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• pp.341-345
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• 1988

Separation of optical isomers of dansyl amino acids by a reversed phase liquid chromatography has been accomplished by adding a copper (II) chelate of N-benzyl-L-proline to the mobile phase. The pH, the eluent composition and the concentration of copper (II) chelate all affect the optical separations. The elution orders between D and L DNS-amino acids were consistant except dansyl phenylalanine showing that D forms of DNS-amino acids elute earlier than L forms. These behaviors are different from the results obtained by the use of copper (II) proline. The retention mechanism for the optical separation of the dansyl amino acids can be explained by the equilibrium of liqand exchange and by hydrophobic interaction.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.811-814
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• 2009

다양한 주소체계를 E.164번호로 통합하는 ENUM(tElephone NUmber Mapping) 기술은 휴대용 기기의 사용이 일반적인 현 시점에서 번호의 복잡성과 입력의 불편함과 같은 문제점을 가지고 있다. ENUM 번호를 키워드를 사용하여 매핑하는 Keyword DNS는 별도의 주소록을 사용하지 않고 ENUM 서비스를 사용할 수 있어 사용자의 편의성을 향상시킬 것이다. 본 논문은 ENUM과 Keyword ENUM을 설명하고 ENUM system과 Keyword ENUM system을 설계한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.07a
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• pp.58-61
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• 2020

본 논문은 UHD 모바일 환경에서 서비스 핸드오프를 위한 관련 파라미터를 DNS 프로토콜을 적용하여 통신망을 통해 제공하기 위한 서비스 핸드오프 제공 방법에 관한 것이다. 이를 위해 본 논문에서는 DNS 기반 서비스 핸드오프 프레임워크를 기술하고, 관련 기능을 검증하기 위한 서비스 핸드오프 송신 플랫폼과 RF 간 또는 RF 와 브로드밴드 간 핸드오프를 처리하기 위한 수신 플랫폼을 소개하고자 한다. 제안한 방법을 적용할 경우 지상파 UHD 모바일 수신기에 브로드밴드 모듈이 탑재될 경우, 사용자의 이동 동선에 최적으로 서비스 핸드오프 정보를 적응적으로 제공할 수 있어 핸드오프 성능을 향상시킬 수 있다.

• Advances in aircraft and spacecraft science
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• v.10 no.6
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• pp.521-543
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• 2023

Reynolds-averaged Navier-Stokes (RANS) models are extensively employed in industrial settings for the purpose of simulating intricate fluid flows. However, these models are subject to certain limitations. Notably, disparities persist in the Reynolds stresses when comparing the RANS model with high-fidelity data obtained from Direct Numerical Simulation (DNS) or experimental measurements. In this work we propose an approach to mitigate these discrepancies while retaining the favorable attributes of the Menter Shear Stress Transport (SST) model, such as its significantly lower computational expense compared to DNS simulations. This strategy entails incorporating an explicit algebraic model and employing a neural network to correct the turbulent characteristic time. The imposition of realizability constraints is investigated through the introduction of penalization terms. The assimilated Reynolds stress model demonstrates good predictive performance in both in-sample and out-of-sample flow configurations. This suggests that the model can effectively capture the turbulent characteristics of the flow and produce physically realistic predictions.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.373-374
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• 2005