• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2003.07a
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• pp.21-25
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• 2003

Key exposure is the most devastating attacks in any crytographic scheme. In this paper, we investigate key exposure problem in blind signature. We then present a variant of Okamoto-Guillou-Quisquater (OGQ for short) blind signature scheme guaranteeing forward secrecy. Namely, even if current secret key is revealed, forging any signature valid in the past is impossible. Our proposed scheme exhibits an efficient key updating protocol and introduces no significant communication overhead.

• Structural Monitoring and Maintenance
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• v.1 no.3
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• pp.339-356
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• 2014

This study has been motivated to evaluate the practicality of numerical simulation of impedance monitoring for damage detection in steel column connection. In order to achieve the objective, the following approaches are implemented. Firstly, the theory of electro-mechanical (E/M) impedance responses and impedance-based damage monitoring method are outlined. Secondly, the feasibility of numerical simulation of impedance monitoring is verified for several pre-published experimental examples on steel beams, cracked aluminum beams, and aluminum round plates. Undamaged and damaged steel and aluminum beams are simulated to compare to experimental impedance responses. An aluminum round plate with PZT patch in center is simulated to investigate sensitive range of impedance responses. Finally, numerical simulation of the impedance-based damage monitoring is performed for a steel column connection in which connection bolts are damaged. From the numerical simulation test, the applicability of the impedance-based monitoring to the target steel column connection can be evaluated.

• Advances in concrete construction
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• v.9 no.4
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• pp.407-412
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• 2020

Due to the influence of nonlinearity and time-variation, it is difficult to establish an accurate model of concrete frame structures that adopt active controllers. Fuzzy theory is a relatively appropriate method but susceptible to human subjective experience to decrease the performance. To guarantee the stability of multi-time delays complex system with multi-interconnections, a delay-dependent criterion of evolved design is proposed in this paper. Based on this criterion, the sector nonlinearity which converts the nonlinear model to multiple rule base of the linear model and a new sufficient condition to guarantee the asymptotic stability via Lyapunov function is implemented in terms of linear matrix inequalities (LMI). A numerical simulation for a three-layer reinforced concrete frame structure subjected to earthquakes is demonstrated that the proposed criterion is feasible for practical applications.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1556-1557
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• 2008

"Biomimetics" is the study and simulation of biological systems with desired properties. In recent times, biomimetic surfaces have emerged as novel solutions for tribological applications in micro-electromechanical systems (MEMS). These biomimetic surfaces are attractive for MEMS application as they exhibit low adhesion/friction and wear properties at small-scales. In this paper, we present some of the examples of biomimetic surfaces that have potential application in small-scale devices.

• Geomechanics and Engineering
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• v.20 no.5
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• pp.385-397
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• 2020

This paper presents an application of artificial neural networks (ANNs) in settlement prediction of a foundation on sandy soil. In order to train the ANN model, a wide experimental database about settlement of foundations acquired from available literatures was collected. The data used in the ANNs model were arranged using the following five-input parameters that covered both geometrical foundation and sandy soil properties: breadth of foundation B, length to width L/B, embedment ratio D_f/B, foundation net applied pressure q_net, and average SPT blow count N. The backpropagation algorithm was implemented to develop an explicit predicting formulation. The settlement results are compared with the results of previous studies. The accuracy of the proposed formula proves that the ANNs method has a huge potential for predicting the settlement of foundations on sandy soils.

• Bulletin of the Korean Mathematical Society
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• v.57 no.3
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• pp.691-707
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• 2020

In this paper, we introduce and study the notions of weakly ⊕-supplemented modules, weakly D2 modules and weakly D2-covers. A right R-module M is called weakly ⊕-supplemented if every non-small submodule of M has a supplement that is not essential in M, and module M_R is called weakly D2 if it satisfies the condition: for every s ∈ S and s ≠ 0, if there exists n ∈ ℕ such that sⁿ ≠ 0 and Im(sⁿ) is a direct summand of M, then Ker(sⁿ) is a direct summand of M. The class of weakly ⊕-supplemented-modules and weakly D2 modules contains ⊕-supplemented modules and D2 modules, respectively, and they are equivalent in case M is uniform, and projective, respectively.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2012.06a
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• pp.129-129
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• 2012

Pumps are used widely in industry, the commercial sector and ships. A poorly selected pump or a pump that does not run at optimum design duty point is a classic symbol of wasted energy and money. It, therefore, becomes important to evaluate the efficiency of these pumps. This paper analyzes traditional technique and instrument to measure some parameters needed to calculate a pump efficiency. The pump efficiency measuring instrument (PEMI) was made and tested on real pump systems. It has been giver the accurate results compared with performance curve given by pump maker.

• Journal of Korean Foot and Ankle Society
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• v.20 no.1
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• pp.43-45
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• 2016

Development of a pseudoaneurysm around the ankle is an uncommon complication after surgery. We experienced a case of a pseudoaneurysm, which developed from the anterior tibial artery. A 44-year-old woman had sustained painful swelling of her right ankle after the removal of implants for a distal fibular fracture. The pseudoaneurysm was confirmed by ultrasonography and angiography. The patient was treated with an intervention using a coil and recovered without further complaints. This case report aims to increase the awareness of this complication with review of literature.

• KSTLE International Journal
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• v.9 no.1_2
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• pp.10-12
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• 2008

Silicon micro-patterns were fabricated on Si (100) wafers using photolithography and DRIE (Deep Reactive Ion Etching) fabrication techniques. The patterned shapes included micro-pillars and micro-channels. After the fabrication of the patterns, the patterned surfaces were chemically modified by coating Z-DOL (perfluoropolyether, PFPE) thin films. The surfaces were then evaluated for their micro-friction behavior in comparison with those of bare Si (100) flat, Z-DOL coated Si (100) flat and uncoated Si patterns. Experimental results showed that the chemically treated (Z-DOL coated) patterned surfaces exhibited the lowest values of coefficient of friction when compared to the rest of the test materials. The results indicate that a combination of both the topographical and chemical modification is very effective in reducing the friction property. Combined surface treatments such as these could be useful for tribological applications in miniaturized devices such as Micro/Nano-Electro-Mechanical-Systems (MEMS/NEMS).

• International Journal of Aeronautical and Space Sciences
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• v.11 no.4
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• pp.360-365
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• 2010

Three phase composite materials are widely used in the shipbuilding industry. When reinforced with fiber and particle, the physical and mechanical properties of polymer composite materials are improved. This paper presents the bending analysis of a three phase composite plate with an epoxy matrix, reinforced glass fiber and titanium oxide particles including creep effect when shear stress is taken into account. The obtained results indicate that creep strains lead to compression in the composite material. Introducing reinforced fibers and particles reduces the plate's deflection, when increasing the stretch coefficient allows the calculation of creep deflection during a long loading period.