• Structural Engineering and Mechanics
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• v.4 no.6
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• pp.679-702
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• 1996

The finite element method is employed in conjunction with micromechanical modelling in order to assess the performance of ceramic thermal barrier coatings applied to structural components. The study comprises the conditions of the deposition of the coating by plasma spraying as well as the thermal cycling of the coated component, and it addresses particularly turbine blades. They are exposed to high temperature changes strongly influencing the behaviour of the core material and inducing damage in the ceramic material by intense straining. A concept of failure analysis is discussed starting from distributed microcracking in the ceramic material, progressing to the formation of macroscopic crack patterns and examining their potential for propagation across the coating. The theory is in good agreement with experimental observations, and may therefore be utilized in proposing improvements for a delayed initiation of failure, thus increasing the lifetime of components with ceramic thermal barrier coatings.

• Smart Structures and Systems
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• v.14 no.2
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• pp.129-144
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• 2014

In this paper, a fuzzy inference system and an analytical hierarchy process-based online evaluation technique is developed to monitor the condition of the 32-km Donghai Bridge in Shanghai. The system has 478 sensors distributed along eight segments selected from the whole bridge. An online evaluation subsystem is realized, which uses raw data and extracted features or indices to give a set of hierarchically organized condition evaluations. The thresholds of each index were set to an initial value obtained from a structure damage and performance evolution analysis of the bridge. After one year of baseline monitoring, the initial threshold system was updated from the collected data. The results show that the techniques described are valid and reliable. The online method fulfills long-term infrastructure health monitoring requirements for the Donghai Bridge.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.5
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• pp.563-570
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• 2004

Two-dimensional mesoscopic analysis (meso-analysis) is applied to solids including microdefects such as microcracks or holes. For the problem of effective moduli of microdefrcted solids, various approximate schemes are introduced by using microcrack density and hole density for macro level parameter. Also, microcracks distributed in the parallel direction and random direction are considered. Several numerical studies using meso-analysis are carried out and the results are compared with several approximate schemes in order to show the validity of proposed meso-analysis.

• Proceedings of the KACD Conference
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• 2003.11a
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• pp.558-559
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• 2003

Heme oxygenase(HO) is a microsomal enzyme, widely distributed in mammalian tissues, which has a major role in heme metabolism. The role of HO in different tissues has not, as yet, been fully characterized, but it is becoming evident that it is involved in a variety of cellular regulatory and protective mechanism. Therefore, in this report, we confirmed the idea of whether the presence of HO in human pulpal cell, and HO can be a principal mechanism of nitric oxide(NO) mediated pulpal cell damage, by adding a deprivation of NO and to gain clinical relationship. We also accessed the effects of HO in pulpal cells treated with hydrogen.(omitted)

• Computers and Concrete
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• v.7 no.2
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• pp.169-190
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• 2010

The focus of this research effort was characterization of the flexural and tensile properties of a specific ultra-high-strength, fiber-reinforced concrete material. The material exhibited a mean unconfined compressive strength of approximately 140 MPa and was reinforced with short, randomly distributed alkali resistant glass fibers. As a part of the study, coupled experimental, analytical and numerical investigations were performed. Flexural and direct tension tests were first conducted to experimentally characterize material behavior. Following experimentation, a micromechanically-based analytical model was utilized to calculate the material's tensile failure response, which was compared to the experimental results. Lastly, to investigate the relationship between the tensile failure and flexural response, a numerical analysis of the flexural experiments was performed utilizing the experimentally developed tensile failure function. Results of the experimental, analytical and numerical investigations are presented herein.

• Annual Conference of KIPS
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• 2013.11a
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• pp.906-909
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• 2013

The Semantic Web is leading us to a world of information sharing by enabling distributed knowledge aggregation and creation. RDF is the foundations of the Semantic Web. For secure Semantic web we need to secure RDF as well. Unauthorized access to an RDF document can change or damage its semantics or manipulate the relations between resources. This article includes the study of RDF security issues and analysis of the existing solutions. After finding limitations of existing solution, a hybrid approach has been proposed.

• Journal of Korea Foundry Society
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• v.43 no.1
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• pp.3-10
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• 2023

This study was conducted to develop technology that can detect stomatal defects inside nonferrous metal products that may occur during die casting processes. Through this research, we intend to detect possible pores in the products in advance, block the distribution of defective products, and contribute to reducing possible losses due to damage to distributed products.

• Steel and Composite Structures
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• v.34 no.1
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• pp.1-15
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• 2020

This paper presents experimental and numerical studies on effects of local damages on the in-plane elastic-plastic buckling and strength of a fixed parabolic steel tubular arch under a vertical load distributed uniformly over its span, which have not been reported in the literature hitherto. The in-plane structural behaviour and strength of ten specimens with different local damages are investigated experimentally. A finite element (FE) model for damaged steel tubular arches is established and is validated by the test results. The FE model is then used to conduct parametric studies on effects of the damage location, depth and length on the strength of steel arches. The experimental results and FE parametric studies show that effects of damages at the arch end on the strength of the arch are more significant than those of damages at other locations of the arch, and that effects of the damage depth on the strength of arches are most significant among those of the damage length. It is also found that the failure modes of a damaged steel tubular arch are much related to its initial geometric imperfections. The experimental results and extensive FE results show that when the effective cross-section considering local damages is used in calculating the modified slenderness of arches, the column bucking curve b in GB50017 or Eurocode3 can be used for assessing the remaining in-plane strength of locally damaged parabolic steel tubular arches under uniform compression. Furthermore, a useful interaction equation for assessing the remaining in-plane strength of damaged steel tubular arches that are subjected to the combined bending and axial compression is also proposed based on the validated FE models. It is shown that the proposed interaction equation can provide lower bound assessments for the remaining strength of damaged arches under in-plane general loading.

• Journal of the Korea Society for Simulation
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• v.18 no.4
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• pp.39-47
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• 2009

Recently, the threat of DDoS attacks is increasing and many companies are planned to deploy the DDoS defense solutions in their networks. The DDoS attack usually transmits heavy traffic data to networks or servers and they cannot handle the normal service requests because of running out of resources. Since it is very hard to prevent the DDoS attack beforehand, the strategic plan is very important. In this work, we have conducted modeling and simulation of the DDoS attack by changing the number of servers and estimated the duration that services are available. In this work, the modeling and simulation is conducted using OPNET Modeler. The simulation result can be used as a parameter of trade-off analysis of DDoS defense cost and the service's value. In addition, we have presented a way of estimating the cost effectiveness in deployment of the DDoS defense system.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.23 no.2
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• pp.108-113
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• 2013

Objectives: Although several cases of lung diseases caused by indium have been reported in Japan, the United States and China, South Korea, which is estimated to have been the world's largest consumer of indium, has not yet established a criteria for the diagnosis of lung diseases caused by indium exposure. In this study, we tried to determine the applicability of the Krebs von den lungen-6, which has been widely recognized for its use with interstitial lung disease in Japan, as a biological exposure index for indium. Methods: Methods: The analysis of indium in serum was conducted by inductively coupled plasma mass spectrometry and the analysis of KL-6 in serum was carried out using enzyme-linked immunosorbent assay kit. Results: The indium levels in serum were distributed from below the detection limit to a peak of $125.78{\mu}g/L$, and the values of the KL-6 were distributed from 104.5 U/mL to 2162.2 U/mL. The serum indium and KL-6 showed good correlation ($R^2$=0.389,pfortrend=0.000) and smoking did not affect the KL-6. Conclusions: The usefulness of KL-6 as a specific biomarker for interstitial lung disease has been recognized. In addition, it is expected that effective prevention of health problems can be achieved by determining the lung-damage progress at an early stage according to individual susceptibility.