• Earthquakes and Structures
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• v.14 no.2
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• pp.143-153
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• 2018

Correlation among different factors must be considered for selection of influencing factors in safety monitoring of high dam including positive correlation of variables. Therefore, a new factor selection method was constructed based on Copula entropy and mutual information theory, which was deduced and optimized. Considering the small sample size in high dam monitoring and distribution of daily monitoring samples, a computing method that avoids causality of structure as much as possible is needed. The two-dimensional normal information diffusion and fuzzy reasoning of pattern recognition field are based on the weight theory, which avoids complicated causes of the studying structure. Hence, it is used to dam safety monitoring field and simplified, which increases sample information appropriately. Next, a complete system integrating high dam monitoring and uncertainty prediction method was established by combining Copula entropy theory and information diffusion theory. Finally, the proposed method was applied in seepage monitoring of Nuozhadu clay core-wall rockfill dam. Its selection of influencing factors and processing of sample data were compared with different models. Results demonstrated that the proposed method increases the prediction accuracy to some extent.

• Journal of Magnetics
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• v.16 no.2
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• pp.150-156
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• 2011

Magnetoelectric (ME) transducers were originally intended for magnetic field sensors but have recently been used in vibration energy harvesting. In this paper, a new broadband vibration energy harvester has been designed and fabricated to be efficiently applicable over a range of source frequencies, which consists of two cantilever beams, two magnetoelectric (ME) transducers and a magnetic circuit. The effects of the structure parameters, such as the non-linear magnetic forces of the ME transducers and the magnetic field distribution of the magnetic circuit, are analyzed for achieving the optimal vibration energy harvesting performances. A prototype is fabricated and tested, and the experimental results on the performances show that the harvester has bandwidths of 5.6 Hz, and a maximum power of 0.25 mW under an acceleration of 0.2 g (with g = $9.8\;ms^2$).

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.2
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• pp.81-88
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• 2009

This paper proposed a session key exchange and authentication scheme on non-interactive key distribution algorithm using a community member's ID in ubiquitous networks. In ubiquitous network environment, User's context-awareness information is collected and used to provide a context-awareness service for someone who need it. However, in ubiquitous network environment, this kind of the Context-awareness information could be abused by a malicious nodes. The proposed scheme using the community member ID provides a session key exchange and mutual authentication between community members, and supports secure data communication. Also, when exchanging the session key and authenticating each other, this scheme reduces communication overhead and authentication delay compared to the AAA server scheme.

• Wind and Structures
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• v.30 no.4
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• pp.405-421
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• 2020

Quayside container cranes are important delivery machineries located in the most frontiers of container terminals, where strong wind attacks happen occasionally. Since the previous researches on quayside container cranes mainly focused on the mean wind load and static response characteristics, the fluctuating wind load and dynamic response characteristics require further investigations. In the present study, the aerodynamic wind loads on quayside container cranes were obtained from wind tunnel tests. The probabilistic and spectral models of the fluctuating aerodynamic loads were established. Then the joint probabilistic distributions of dynamic wind-induced responses were derived theoretically based on a series of Gaussian and independent assumption of resonant components. Finally, the results were validated by time domain analysis using wind tunnel data. It is concluded that the assumptions are acceptable. And the presented approach can estimate peak dynamic sliding force, overturning moments and leg uplifts of quayside container cranes effectively and efficiently.

• Journal of the Optical Society of Korea
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• v.20 no.5
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• pp.541-546
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• 2016

In this paper, by using the Rayleigh-Sommer field theory and the cross-spectral density function, the analytical expression for the intensity distribution of a double half-Gaussian hollow beam in a turbulent atmosphere is obtained. The influence of the initial spot size of this beam on its propagation properties in a turbulent atmosphere is simulated, and the intensity distributions for such beams with different spot sizes are obtained. The results show that the initial spot size has an important influence on the propagation properties in the near field, while this influence in the far field is very weak.

• Structural Engineering and Mechanics
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• v.48 no.3
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• pp.291-308
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• 2013

Structural health monitoring is crucial to maintain the structural performance safely. Moreover, the Kullback-Leibler divergence (KLD) is applied usually to asset the similarity between different probability density functions in the pattern recognition. In this study, the KLD is employed to detect the damage. However the asymmetry of the KLD is a shortcoming for the damage detection, to overcoming this shortcoming, two other divergences and one statistic distribution are proposed. Then the damage identification by the KLD and its three descriptions from the symmetric point of view is investigated. In order to improve the reliability and accuracy of the four divergences, the gapped smoothing method (GSM) is adopted. On the basis of the damage index approach, the new damage index (DI) for detect damage more accurately based on the four divergences is developed. In the last, the grey relational coefficient and hypothesis test (GRCHT) is utilized to obtain the more precise damage identification results. Finally, a clear remarkable improvement can be observed. To demonstrate the feasibility and accuracy of the proposed method, examples of an isotropic beam with different damage scenarios are employed so as to check the present approaches numerically. The final results show that the developed approach successfully located the damaged region in all cases effect and accurately.

• The Transactions of the Korea Information Processing Society
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• v.4 no.10
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• pp.2493-2500
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• 1997

We propose a new key management scheme for multiuser group which is classified as hierarchical structure (sometimes it is called a multilevel security hierarchy) in the symmetric key cryptosystem. The proposed scheme is based on the trapdoor one-way permutations which are generated by the pseudo-random permutation algorithm, and it is avaliable for multilevel hierarchical structure composed of a totally ordered set and a partially ordered set, since it has advantage for time and storage from an implemental point of view. Moreover, we obtain a performance analysis by comparing with the other scheme, and show that the proposed scheme is very efficient for computing time of key generation and memory size of key storage.

• Journal of Power Electronics
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• v.19 no.2
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• pp.549-559
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• 2019

This paper proposes an adaptive sliding mode control (ASMC) strategy with an enhanced optimal reaching law (EORL) for the robust current tracking control of the boost converter based hybrid power source (HPS) in an electric vehicle (EV). A conventional ASMC strategy based on state observers and the hysteresis control method is used to realize the current tracking control for the boost converter based HPS. Then a novel enhanced exponential reaching law is proposed to improve the ASMC. Moreover, an enhanced exponential reaching law is optimized by particle swarm optimization. Finally, the adaptive control factor is redesigned based on the EORL. Simulations and experiments are established to validate the ASMC strategy with the EORL. Results show that the ASMC strategy with the EORL has an excellent current tracking control effect for the boost converter based HPS. When compared with the conventional ASMC strategy, the convergence time of the ASMC strategy with the EORL can be effectively improved. In EV applications, the ASMC strategy with the EORL can achieve robust current tracking control of the boost converter based HPS. It can guarantee the active and stable power distribution for boost converter based HPS.

• Journal of the Korea Society of Computer and Information
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• v.14 no.3
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• pp.103-111
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• 2009

IEEE 802.16e(Wibro) standard, providing robust mobile realtime data transmission technology, requires of faster and smooth execution of security mechanisms, such as key distribution and user authentications, during base station hopping. In particular, key management mechanisms such as redistribution and regeneration have an impact on digital contents transmission and realtime data transmission, not only in 802.16e environment, but also in typical transmission environment as well. This paper presents traffic management mechanisms designed to realtime digital contents (such as IPTV) transmission efficiency and increase the QoE by utilizing OKTEK methodology.

• Computers and Concrete
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• v.33 no.5
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• pp.509-518
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• 2024

In this study, we investigated the effect of shear-key placement on the performance of grouted connections in offshore wind-turbine structures. Considering the challenges of height control during installation, we designed and analyzed three grouted connection configurations. We compared the crack patterns and strain distribution in the shear keys under axial loading. The results indicate that the misalignment of shear keys significantly influences the ultimate load capacity of grouted connections. Notably, when the shear keys were positioned facing each other, the ultimate load decreased by approximately 15%, accompanied by the propagation of irregular cracks in the upper shear keys. Furthermore, the model with 50% misalignment in the shear-key placement exhibited the highest ultimate strength, indicating a more efficient load resistance than the reference model. This indicates that tensile-load-induced cracking and the formation of compressive struts in opposite directions significantly affect the structural integrity of grouted connections. These results demonstrate the importance of considering buckling effects in the design of grouted connections, particularly given the thin and slender nature of the inner sleeves. This study provides valuable insights into the design and analysis of offshore wind-turbine structures, highlighting the need for refined design formulas that account for shifts in shear-key placement and their structural implications.