• Wind and Structures
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• v.31 no.5
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• pp.473-482
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• 2020

The first-order method for estimating the extreme wind pressure on building envelopes with consideration of the directionality of wind speed and wind pressure is improved to enhance its computational efficiency. In this improved method, the result is obtained directly from the empirical distribution of a random selection of annual maximum wind pressure samples generated by a Monte Carlo method, rather than from the previously utilized extreme wind pressure probability distribution. A discussion of the relationship between the first- and full-order methods indicates that when extreme wind pressures in a non-typhoon climate with a high return period are estimated with consideration of directionality, using the relatively simple first-order method instead of the computationally intensive full-order method is reasonable. The validation of this reasonableness is equivalent to validating two assumptions to improve its computational efficiency: 1) The result obtained by the full-order method is conservative when the extreme wind pressure events among different sectors are independent. 2) The result obtained by the first-order method for a high return period is not significantly affected when the extreme wind speeds among the different sectors are assumed to be independent. These two assumptions are validated by examples in different regions and theoretical derivation.

• Geomechanics and Engineering
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• v.20 no.5
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• pp.447-459
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• 2020

Based on the literature statistical method, the paper publication status of the isolated working face and the distribution of the rockburst coal mine were obtained. The numerical simulation method is used to study the stress distribution law of working face under different mining range. In addition, based on the similar material simulation test, the overlying strata failure modes and the deformation characteristics of coal pillars during the mining process of the isolated working face with thick-hard key strata are analyzed. The research shows that, under the influence of the key strata, the overlying strata formation above the isolated working face is a long arm T-type spatial structure. With the mining of the isolated working face, a series of damages occur in the coal pillars, causing the key strata to break and inducing the rockburst occurs. Combined with the mechanism of rockburst induced by the dynamic and static combined load, the source of dynamic and static load on the isolated working face is analyzed, and the rockburst monitoring methods and the prevention and control measures are proposed. Through the above research, the occurrence probability of rockburst can be effectively reduced, which is of great significance for the safe mining of deep coal mines.

• Interaction and multiscale mechanics
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• v.1 no.3
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• pp.369-379
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• 2008

A combined stochastic diffusion and mean-field model is developed for a systematic study of the grain growth in a pure single-phase polycrystalline material. A corresponding Fokker-Planck continuity equation is formulated, and the interplay/competition of stochastic and curvature-driven mechanisms is investigated. Finite difference results show that the stochastic diffusion coefficient has a strong effect on the growth of small grains in the early stage in both two-dimensional columnar and three-dimensional grain systems, and the corresponding growth exponents are ~0.33 and ~0.25, respectively. With the increase in grain size, the deterministic curvature-driven mechanism becomes dominant and the growth exponent is close to 0.5. The transition ranges between these two mechanisms are about 2-26 and 2-15 nm with boundary energy of 0.01-1 J $m^{-2}$ in two- and three-dimensional systems, respectively. The grain size distribution of a three-dimensional system changes dramatically with increasing time, while it changes a little in a two-dimensional system. The grain size distribution from the combined model is consistent with experimental data available.

• Journal of Satellite, Information and Communications
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• v.9 no.4
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• pp.7-12
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• 2014

Quantum cryptography is one of the most feasible fields using quantum mechanics. Therefore, quantum cryptography has consistently been researched, and a variety of cryptographic exchange method has been developed, such as BB84, etc. This paper explains a basic concept of quantum communications and quantum key distribution systems using quantum mechanics. Also, it introduces a reason of the development of quantum cryptography and attack scenarios which threaten the security of QKD. Finally, the experiment of this paper simulates quantum key attack by estimating qubit phases through a modeled quantum channel, and discusses needs of post-processing methods for overcoming eavesdropping.

• The Journal of Industrial Distribution & Business
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• v.13 no.3
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• pp.1-12
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• 2022

Purpose: The revenue sharing contract has been widely used in industries, and its ability to coordinate the supply chain system has been studied by numerous researchers. By reviewing the representative studies on the revenue sharing contract, this study intends to analyze the key features of this coordinating contract and identify its potential to be a more advanced coordination program than the original contract. Research design, data, and methodology: This study reviews past studies on the revenue sharing contract. The selected studies are investigated with a focus on how this contract is described to realize the supply chain coordination and the key issues that they address. Results: The literature review reveals that the revenue sharing contract requires standardized details about what and how to share. This study also finds additional issues that need to be addressed by researchers to improve this coordinating contract. Conclusions: Future researchers are advised to unify the detailed contents of the revenue sharing contract to confirm that it successfully coordinates the supply chain system. In addition, this study proposes key research issues that would enhance the role of revenue sharing contract as a supply chain coordination program.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.1010-1013
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• 2007

와이브로 서비스는 고속 이동 인터넷 환경 속에서 고속으로 무선 인터넷 서비스를 제공하는 기술이다. 기존의 무선인터넷 서비스와 달리 이동성을 제공한다는 점에서 차별화를 제공한다. 이렇게 이동하는 단말에게 양질의 데이터를 안전하게 전송하기 위해서는 보안기술이 중요한 요소로 작용한다. 서비스를 제공하기 전에 단말(Mobile Station)과 RAS(Radio Access Stations)간의 인증을 바탕으로 상호 키(TEK:Traffic Encryption Key)를 분배하고 TEK를 바탕으로 데이터를 암호화해서 전송하게 된다. 기존의 인증 프로토콜에서는 RAS에서 단독으로 키를 생성하는 방식이지만, 본 논문에서는 기존의 프로토콜의 문제점으로 지적된 Replay Attack에 대해 DH(Diffie-Hellman) 키 분배(Key Distribution) 방식을 적용하는 프로토콜을 제안함으로써 취약점에 대비 하였다. 이를 통해 RAS에 집중되는 키 생성에 대한 오버헤드를 단말에 분산 시킬 수 있다. 이로써 제안된 프로토콜을 사용해서 기존의 프로토콜을 사용했을 때보다 보안강도를 높일 수 있다.

• Smart Structures and Systems
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• v.14 no.2
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• pp.209-224
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• 2014

With more and more built long-term structural health monitoring (SHM) systems, it has been considered to apply monitored data to learn the reliability of bridges. In this paper, based on a long-term SHM system, especially in which the sensors were embedded from the beginning of the construction of the bridge, a method to calculate the localized reliability around an embedded sensor is recommended and implemented. In the reliability analysis, the probability distribution of loading can be the statistics of stress transferred from the monitored strain which covered the effects of both the live and dead loads directly, and it means that the mean value and deviation of loads are fully derived from the monitored data. The probability distribution of resistance may be the statistics of strength of the material of the bridge accordingly. With five years' monitored strains, the localized reliabilities around the monitoring sensors of a bridge were computed by the method. Further, the monitored stresses are classified into two time segments in one year period to count the loading probability distribution according to the local climate conditions, which helps us to learn the reliability in different time segments and their evolvement trends. The results show that reliabilities and their evolvement trends in different parts of the bridge are different though they are all reliable yet. The method recommended in this paper is feasible to learn the localized reliabilities revealed from monitored data of a long-term SHM system of bridges, which would help bridge engineers and managers to decide a bridge inspection or maintenance strategy.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.1
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• pp.43-56
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• 2012

Wireless sensor networks consist of numerous small-sized nodes equipped with limited computing power and storage as well as energy-limited disposable batteries. In this networks, nodes are deployed in a large given area and communicate with each other in short distances via wireless links. For energy efficient networks, dynamic clustering protocol is an effective technique to achieve prolonged network lifetime, scalability, and load balancing which are known as important requirements. this technique has a characteristic that sensing data which gathered by many nodes are aggregated by cluster head node. In the case of cluster head node is exposed by attacker, there is no guarantee of safe and stable network. Therefore, for secure communications in such a sensor network, it is important to be able to encrypt the messages transmitted by sensor nodes. Especially, cluster based sensor networks that are designed for energy efficient, strongly recommended suitable key management and authentication methods to guarantee optimal stability. To achieve secured network, we propose a key management scheme which is appropriate for hierarchical sensor networks. Proposed scheme is based on polynomial key pool pre-distribution scheme, and sustain a stable network through key authentication process.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.6
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• pp.2567-2582
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• 2016

This paper investigates the impact of outdated channel state information (CSI) on the performance of the incremental amplify-and-forward (AF) opportunistic relaying (OR) over dual-hop Rayleigh fading channels. According to the definition of distribution function, we obtain the cumulative distribution function (CDF) of the actual combined signal-to-noise ratio (SNR) received at the destination. Based on this CDF, the closed-form expressions of the average spectral efficiency and outage probability are derived for the incremental AF OR under outdated CSI. Numerical results show that in the low region of the average SNR of the direct link, outdated CSI deteriorates the system performance, whereas in the high region, outdated CSI has almost no impact on the system performance.

• Mycobiology
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• v.38 no.1
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• pp.65-69
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• 2010

Based on a literature survey and assessment of the important features of lichen genus Buellia (spore shape and size, anatomy of the exciple as well as analysis of the lichen substances), the present paper describes four new records of B. maritima, B. polyspora, B. spuria and B. stellulata from South Korea. Among them, B. maritima and B. polyspora are firstly reported in East Asia including in China, the Korean Peninsula and Japan. Brief description of all the new records along with earlier described species placed under genus Amandinea and Hafellia are provided with their distribution and chemistry. A key to all the Buellia species reported so far from South Korea is also provided.