• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3909-3918
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• 2022

In the event of a severe accident, the reactor core may melt due to insufficient cooling. the high-temperature core melt will have a strong interaction (FCI) with the coolant, which may lead to steam explosion. Steam explosion would pose a serious threat to the safety of the reactors. Therefore, the study of steam explosion is of great significance to the assessment of severe accidents in nuclear reactors. This research focuses on the development of a two-dimensional steam explosion integrated analysis code called SEINA. Based on the semi-implicit Euler scheme, the three-phase field was considered in this code. Besides, the influence of evaporation drag of melt and the influence of solidified shell during the process of melt droplet fragmentation were also considered. The code was simulated and validated by FARO L-14 and KROTOS KS-2 experiments. The calculation results of SEINA code are in good agreement with the experimental results, and the results show that if the effects of evaporation drag and melt solidification shell are considered, the FCI process can be described more accurately. Therefore, it is proved that SEINA has the potential to be a powerful and effective tool for the analysis of steam explosions in nuclear reactors.

• Nuclear Engineering and Technology
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• v.53 no.3
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• pp.763-775
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• 2021

The thermal hydraulic performances of Steam Generator (SG) under both steady and transient operation conditions are of great importance for the safety and economy in nuclear power plants. In this paper, based on our self-developed SG thermal hydraulic analysis code STAF (Steam-generator Thermalhydraulic Analysis code based on Fluent), an improved new version STAF-CT (fully Coupling and Transient) is developed and introduced. Compared with original STAF, the new version code STAF-CT has two main functional improvements including "Transient" and "Fully Three Dimensional Coupling" features. In STAF-CT, a three dimensional energy transferring module is established which can achieve energy exchange computing function at the corresponding position between two sides of SG. The STAF-CT is validated against the international benchmark experiment data and the results show great agreement. Then the U-shaped SG in AP1000 nuclear power plant is modeled and simulated using STAF-CT. The results show that three dimensional flow fields in the primary side make significant effect on the energy source distribution between two sides. The development of code STAF-CT in this paper can provide an effective method for further SG high fidelity research in the nuclear reactor system.

• IEIE Transactions on Smart Processing and Computing
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• v.3 no.5
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• pp.298-305
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• 2014

In this study, a novel Randomly Shifted Certification Authority Authentication protocol was used in ad hoc networks to provide authentication by considering the MAC layer characteristics. The nodes achieve authentication through the use of public key certificates issued by a CA, which assures the certificate's ownership. As a part of providing key management, the active CA node transfers the image of the stored public keys to other idle CA nodes. Finally the current active CA randomly selects the ID of the available idle CA and shifts the CA ownership by transferring it. Revoking is done if any counterfeit or duplicate non CA node ID is found. Authentication and integrity is provided by preventing MAC control packets, and Enhanced Hash Message Authentication Code (EHMAC) can be used. Here EHMAC with various outputs is introduced in all control packets. When a node transmits a packet to a node with EHMAC, verification is conducted and the node replies with the transmitter address and EHMAC in the acknowledgement.

• Asia pacific journal of information systems
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• v.6 no.2
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• pp.171-200
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• 1996

Information Systems(IS) departments face many challenges in today's rapidly changing environment. One approach to understanding the challenges by IS departments is to survey IS managers in order to elicit their key issues. The study compares and contrasts the major findings of key information systems management issues in Korea and United States. It examines the key concerns of IS managers on these areas focusing on identifying and explaining regional similarities and differences. IS managers in Korea and United States show a reasonable level of agreement on the most critical issues they face. In some of the issues the differences are found and possible reasons for these differences are discussed. The study concludes by suggesting an evolution model that can explain the changing nature of the IS issues across time and nations.

• Journal of electromagnetic engineering and science
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• v.10 no.3
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• pp.171-174
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• 2010

In the paper, a printed dual-dipole array antenna is presented. A 4-way planar SIW power divider is adopted for feeding the array antenna. The dual-dipole is adopted as radiation elements which greatly improves the impedance band. The measured bandwidth larger than 31 % for VSWR$\leq$1.5 operating near 14 GHz is achieved and in agreement with the simulated results. The radiation E-plane and H-plane radiation pattern is presented in the paper. The radiation gain is also presented in the paper.

• Journal of Korea Multimedia Society
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• v.20 no.3
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• pp.500-510
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• 2017

Recently Lee et al. proposed an improved symmetric key-based remote user authentication scheme to eliminate the security weaknesses of Kumari et al.'s scheme. They hence claimed that their scheme is secure to various well-known attacks. However, we found that Lee et al.'s scheme is still insecure against outsider attack, smart card stolen and off-line password guessing attack. To overcome these security vulnerabilities, we propose an enhanced authentication scheme with key-agreement which is based on the fuzzy-extractor. Furthermore, we prove that the proposed scheme is more secure, and that it serves to gratify all of the required security properties. Finally, we compare the performance and functionality of the proposed scheme with those of previous schemes.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2006.06a
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• pp.171-175
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• 2006

Diffie-Hellman기반 키 합의 프로토콜들은 비교적 고비용의 연산인 지수연산으로 인해, 유선 네트워크 환경에 비해 저전력이고 컴퓨팅 자원이 제한되어 있는 무선 네트워크 환경에서는 비효율적이고 구현하기 어려운 문제가 있다. 이에 Yang등은 대리서버(Proxy Server)를 이용하여 Diffie-Hellman방식을 적용하면서도 단말 무선 네트워크 사용자의 지수연산부담을 감소시키는 효율적인 키 합의 프로토콜(이하 SEKAP)을 제안하였다. 그러나 SEKAP는 재전송공격(Replay Attack), 알려지지 않은 키 공유 공격(Unknown Key Share Attack), 그리고 키 노출로 인한 위장공격(Key Compromised Impersonation Attack) 등에 취약하며 전방향 안전성(Forward Secrecy)을 제공하지 못한다. 본 논문에서는 SEKAP가 위 공격들에 대해 취약함을 보이고, 세션키의 상호인증을 추가한 개선된 프로토콜을 제안한다.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.116-117
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• 2006

Increasing the solvent molecular size leads to shrinkage of the polymer chains and increase of the critical overlap concentrations. In addition, the dependency of $R_{g}$ on polymer concentration under normal solvent conditions and solvent molecular size is in good agreement with scaling laws. When the solvent molecular size approaches the ideal end-to-end distance of the polymer chain, an extra aggregation of polymer chains occurs, and the solvent becomes the so-called medium-sized solvent. When the size of solvent molecules is smaller than the medium size, the polymer chains are swollen or partially swollen. However, when the size of solvent molecules is larger than the medium size, the polymer coils shrink and segregate, enwrapped by the large solvent molecules.

• Korean Journal of Computational Design and Engineering
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• v.12 no.2
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• pp.95-100
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• 2007

Virtual Reality(VR) data in VR environments like Manufacturing industries are often created jointly by many creators. It is then necessary to provide protection of the joint-creatorship and the creatorship of each participating creator. This paper proposes Multiple Digital Watermarking Framework(MDWF) to solve the problem of joint-creatorship. The proposed framework, MDWF, makes use of 3D private watermarking technology and a novel key sharing protocol for joint-creatorship verification. MDWF embeds 3D private multiple watermarks for the creatorship of each participating creators in a non-overlapping manner during the creation process. After key agreement of all private keys, MDWF embeds an additional 3D private watermark for the joint-creatorship. Therefore MDWF successfully handles the creatorship dispute among creators. That is, each participation creator can prove his/her partial creatorship as well as joint-creatorship by MDWF. In addition, MDWF can solve the collusion problems because shared secret key(SSK) can be made by every users.

• ETRI Journal
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• v.31 no.4
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• pp.460-462
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• 2009

The emerging wireless networks require the design of new authentication protocols due to their dynamic nature and vulnerable-to-attack structure. Recently, Wu and others proposed a wireless authentication protocol which is claimed to be an improvement of the authentication protocol proposed by Lee and others which provides user anonymity. In this letter, we show that these protocols have a common flaw and that these protocols fail to provide user anonymity. We also propose a modification method to solve this problem.