• Smart Structures and Systems
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• v.30 no.4
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• pp.339-351
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• 2022

Evaluating the current condition of existing structures is of primary importance for economic and safety reasons. This can be addressed by Structural System Identification (SSI). A reliable static SSI depends on well-designed sensor configuration and loading cases, as well as efficient parameter estimation algorithms. Static SSI by the Measurement Error-Minimizing Observability Method (MEMOM) is a model-based deterministic static SSI method that could estimate structural parameters from static responses. In the current state of the art, this method is only applicable when structures are subjected to one loading case. This might lead to lack of information in some local regions of the structure (such as the null curvatures zones). To address this issue, the SSI by MEMOM using multiple loading cases is proposed in this work. Observability equations obtained from different loading cases are concatenated simultaneously and an optimization procedure is introduced to obtain the estimations by minimizing the discrepancy between the predicted response and the measured one. In addition, a Genetic-Algorithm (GA)-based Optimal Sensor Placement (OSP) method is proposed to tackle the OSP problem under multiple static loading cases for the very first time. In this approach, the Fisher Information Matrix (FIM)'s determinant is used as the metric of the goodness of sensor configurations. The numerical examples of a 3-span continuous bridge and a 13-story frame, are analyzed to validate the applicability of the extended SSI by MEMOM and the GA-based OSP method.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.97-103
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• 2014

Among various lead-free solders, the Sn-58Bi solders have been considered as a highly promising lead-free solders because of its low melting temperature and high tensile strength. However, Sn-58Bi solder has the poor ductility. To enhance the mechanical property of Sn-58Bi solder, epoxy-enhanced Sn-58Bi solders have been studied. This study compared the microstructures and the mechanical properties of Sn-58Bi solder and Sn-58Bi epoxy solder with aging treatment. The solders ball were formed on the printed circuit board (PCB) with organic solderability preservative (OSP) surface finish, and then the joints were aged at 85, 95, 105 and $115^{\circ}C$ for up to 100, 300, 500 and 1000 hours. The shear test was conducted to evaluate the mechanical property of the solder joints. $Cu_6Sn_5$ intermetallic compound (IMC) layer grew with increasing aging time and temperature. The IMC layer for the Sn-58Bi epoxy solder was thicker than that for the Sn-58Bi solder. According to result of shear test, the shear strength of Sn-58Bi epoxy solder was higher than that of Sn-58Bi solder and the shear strength decreased with increasing aging time.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.402-407
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• 2008

Recent popularity in mobile electronics requires higher standard on the mechanical strength of electronic packaging. Thus, the method of soldering between chip and substrate in electronic packaging process is changing from conventional method using intermetallic compound to a new method using organic solderability preservative (OSP) in order to improve the stability and the reliability of final product. Since current organic solder preservatives have several serious problems like thermo-stability during packaging process, however, it is necessary to develop new OSPs having thermo-stability. The main purpose of this study is to investigate the effect of MeOH/IPA (Isopropyl alcohol) ratio on the fluxing of a new OSP, developed in previous research, andto find out an optimum formulation of flux components for the application of the OSP in current packaging process. As a result of this study, it was revealed that higher MeOH/IPA ratio in flux showed better performance of fluxing a new OSP.

• Biomedical Science Letters
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• v.3 no.2
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• pp.95-105
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• 1997

Currently, the laboratory diagnosis for lyme disease have been performed with the detection of antibodies against Borrelia burgdorferi. However there might be some difficulties in the interpretation of obtained results due to the usage of foreign isolates as an antigen in the test. Therefore the optimization of serological tests with Korean isolates of B. burgdorferi as an antigen would be needed to establish the standardized diagnostic method for the detection of antibodies against B. burgdorferi infection. In this study, the optimization of ELISA was investigated with experimentally challenged rabbit sera and sonicated B. burgdorferi antigens of Korean isolates. Of 217 human patient's sera with unknown fever, the mean seropositivities in ELISA, done under the optimized conditions obtained in this study, were found to be about 8％ against B. burgdorferi sensu late, showing the highest seropositivity of 14.3％ against B. afzelii. In immunoblotting assay with ELISA-positive human sera, the major reactive bands were 41kDa (flagellin) which might be the indication of early infection, and 27kDa, 31kDa (OspA), 34kDa (OspB) which are the characteristics of late infection. Obtained results in this study might strongly indicate the possibility of B. burgdorferi infections in Korea.

• Journal of the Korean Geosynthetics Society
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• v.11 no.2
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• pp.1-9
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• 2012

In order to review the utility of Lade's single hardening constitutive model, a series of isotropic compression-expansion tests and consolidated drained triaxial tests including as CTC, TC, RTC, and OSP were performed by Baekma river sand with various of stress path. Parameters required in model were determined using these tests. The accuracy of analysis was reviewed by back analysis of test results used to determine the 11 parameters of soil property through the test of each stress path. Also. for verifying the accuracy of prediction for the stress-strain behavior using failure criterion related 9 parameters with correlational equation and constant and yield criterion related parameters h, ${\alpha}$ and ${\eta}_1$, when stress path is different with each other, it has been obtained in the review result of stress path dependent characteristics of the constitutional model through the analyzing results of CTC, TC, RTC, OSP, and fine silica sand tests.

• Journal of Internet Computing and Services
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• v.22 no.3
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• pp.75-83
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• 2021

With the development of the IT industry and the increase of cultural activities, the demand for works increases, and they can be used easily and conveniently in an online environment. Accordingly, copyright infringement is seriously occurring due to the ease of copying and distribution of works. Some special types of Online Service Providers (OSP) use filtering-based technology to protect copyrights, but they can easily bypass them, and there are limits to blocking all illegal works, making it increasingly difficult to protect copyrights. Recently, most of the distributors of illegal works are a certain minority, and profits are obtained by distributing illegal works through many OSP and majority ID. In this paper, we propose a profiling technique for heavy uploader, which is a major analysis target based on illegal works. Creates a feature containing information on overall illegal works and identifies major heavy uploader. Among these, clustering technology is used to identify heavy uploader that are presumed to be the same person. In addition, heavy uploaders with high priority can be analyzed through illegal work Distributor tracking and behavior analysis. In the future, it is expected that copyright damage will be minimized by identifying and blocking heavy uploader that distribute a large amount of illegal works.

• Proceedings of the Materials Research Society of Korea Conference
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• 2006.05a
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• pp.26.2-26.2
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• 2006

• The Journal of Korea Robotics Society
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• v.3 no.4
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• pp.345-350
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• 2008

This study aims to propose the concept design of oil spill protection robot which can rapidly intervene to control the oil spillage situation at the sea. Taking into account the fact that a huge amount of oil is transported trans-continentally by oil tanker, none of industrialized countries are completely safe from the marine oil spill which results in social, economical and ecological damages to their communities. The employment of double hull-oil tanker, pipe line transporting can be most safe way. Yet complete prevention of oil spill is probably not realistic. Accordingly the alternative solution to control marine oil spill and minimize the damages caused by the incident using intelligent robot technology based on swarm control method is proposed. The main features of oil spill protection(OSP) robot is explained via following three perspectives. Firstly, from functional point of view, OSP robot system safely and efficiently replaces oil boom installation manually conducted by human workers with intelligent robot technology based on swarm control theory. For second, its modular architecture brings efficient storage of main components including oil boom and facilitates maintenance. For the last, its geometric form and shape enables whole system to be installed to helicopter, boat or oil tanker itself with ease and to rapidly deploy the units to the oil spill area.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.5 s.347
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• pp.45-50
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• 2006

As a settlement for the fiber access, the FTTH is an ideal mode for providing various high-bandwidth value added services including high definition IPTV to broadband users, and KT, the largest incumbent of Korea, started FTTH service from 2005. For FTTH deployment, it needs a cost-effective solution including reliability and maintenance costs. This paper analyzes the characteristics and technical issues for the main components of outside plant in general household area.

• Smart Structures and Systems
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• v.25 no.2
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• pp.169-181
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• 2020

Sensor placement is a crucial aspect of bridge health monitoring (BHM) dedicated to accurately estimate and locate structural damages. In addressing this goal, a sensor placement framework based on the deflection influence line (DIL) analysis is here proposed, for the optimal design of damage detection-oriented BHM system. In order to improve damage detection accuracy, we explore the change of global stiffness matrix, damage coefficient matrix and DIL vector caused by structural damage, and thus develop a novel sensor placement framework based on the Fisher information matrix. Our approach seeks to determine the contribution of each sensing node to damage detection, and adopts a distance correction coefficient to eliminate the information redundancy among sensors. The proposed damage detection-oriented optimal sensor placement (OSP) method is verified by two examples: (1) a numerically simulated three-span continuous beam, and (2) the Pinghu bridge which has existing real damage conditions. These two examples verify the performance of the distance corrected damage sensitivity of influence line (DSIL) method in significantly higher contribution to damage detection and lower information redundancy, and demonstrate the proposed OSP framework can be potentially employed in BHM practices.