• Journal of Advanced Marine Engineering and Technology
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• v.31 no.6
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• pp.761-767
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• 2007

We have developed novel optical-fiber sensors based on strain-induced long-period fiber gratings for monitoring the deformation of a hull. They have no external pressure for sustaining the mechanical formed gratings. The pressure, which provides a force to form the periodic grating along the single mode fiber, was realized by the bonding strength of a photopolymer. To reduce the polarization dependency of the sensors caused by the asymmetry structure of gratings, a Faraday Rotator Mirror (FRM) was utilized in this experiment. We have realized the polarization-insensitive function of the proposed sensors. The change of an external strain are measured by an optical spectrum analyzer. When the external stain increases. the attenuation at the resonant wavelength decreases and the loss peak was slightly shifted to the shorter wavelength.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.67-71
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• 2003

A hot press method was used to create the optimal fabrication condition for a Shape Memory Alloy(SMA) composite. The bonding strength between the matrix and the reinforcement within the SMA composite by the hot press method was more increased by cold rolling. In this study, the objective was to develop an on-line monitoring system in order to prevent the crack initiation and propagation by shape memory effect in SMA composite. Shape memory effect was used to prevent the SMA composite from crack propagation. For this system an optimal AE parameter should be determined according to the degree of damage and crack initiation. When the SMA composite was heated by the plate heater attached at the composite, the propagating cracks could be controlled by the compressive force of SMA.

• Korean Journal of Human Ecology
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• v.9 no.3
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• pp.63-68
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• 2006

Walnut colorants were extracted from walnut hull and their dyeing properties on cotton were investigated. Effect of dyeing conditions on dye uptake and effect of mordanting on dye uptake, color change and colorfastness were explored. Walnut colorants showed low affinity to cotton compared with wool and its isotherm adsorption curve was Freundlich type. It was considered that hydrogen bonding and van der Waal's force were involved in the adsorption of walnut colorants onto cotton. The dyed cotton showed YR color and there was no significant color change as pH changed. The dyed cotton showed generally high colorfastness except fastness to washing and light. Mordanting did not improve dye uptake and colorfastness, and not affect color of the dyed cotton significantly.

• Journal of the Korean Geophysical Society
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• v.9 no.1
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• pp.63-71
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• 2006

When surveying the cultural heritages especially in the case of stone structures, preserving their originalstate is of primary importance. For the effective assessment of survey results of stone structure, thedynamic characteristics of that system should be considered. Dynamic characteristics of stone masonry structures depend on several factors such as coefficients of friction, contact conditions, and number of layers of bonding stones. These factors can be estimated by using the dynamic analysis results. This paper describes a method for natural frequency determination of traditional stone arch bridge subjected to compressive force. For this purpose, multi-layered granite brick models of for arch bridge were made and fundamental frequencies corresponding increasing axial forces were measured.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.745-750
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• 2000

Steel plate bonding technique is most widely used in strengthening of existing concrete structures, but it has inherently a problem of the premature failure such as interface separation and rip off. So far, many studies have been arid out in the manner of laboratory tests for the reinforced concrete beams to find out he mechanism of the premature failure. However, in order to verify the characteristics of the premature failure, more reasonable local investigations are needed rather than such relatively global experimental works. In this study, therefore, the double lap test which simulate the pure shear loadings and the half beam tests which consider combined flexure-shear force have been done. There are, however, difficulties in getting the normal stress caused to premature failure, so that finite element analysis was performed, too. In numerical study, material nonlinearity was considered, and the interface element was applied to model the interface between steel plate and adhesive. From the results of experimental and numerical studies, a realistic failure criterion on the separation of steel plates has been derived.

• KCI Concrete Journal
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• v.12 no.2
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• pp.31-43
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• 2000

The extensive usage of pretensioned prestressed concrete component in modem construe- tion as structural members mandates precise understanding of its mechanism. Especially, an adequate transfer of prestressing force from steel tendons to concrete around the end regions of the member is a critical issue. Due to the importance of the topic, several investigators have formulated equations modeling the transfer bond length based on various bonding mechanism between steel and concrete. However, the existing models are still inadequate in predicting the bond development in pretensioned prestressed concrete members. Therefore, this study presents a model of transfer bond length based on rational theory that can simulate experimental results. The model is developed into solid mechanics based structural analysis computer program. The program is validated by comparing the analysis results with experimental results of bond stress distribution, concrete strain profiles, and transfer length in pretensioned prestressed concrete members. The proposed analytical procedure in this study can be utilized as a useful tool for realistic evaluation of transfer length in pretensioned prestressed concrete members.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.2
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• pp.149-157
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• 2003

The purpose of this paper is to quantitatively investigate aging state of epoxy coating on containment structure at nuclear power plant. In order to evaluate an physical bonding of the epoxy coating, adhesion test was performed on a degraded epoxy coating on concrete specimens fabricated by accelerated aging experiment. In addition, impedance data by ultrasonic test were measured to compare with adhesion data. From almost 50 % of the specimens, aging phenomena of epoxy coating such as pin hole, blistering was discovered. To improve reliability on quality degradation of epoxy, co-relation between two kinds of different data was analyzed. By tracing co-related these data, it was possible to figure out physical state of as-built epoxy coating. The possibility to develop new methodology of time - dependent aging state on epoxy coating was found and discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.284-284
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• 2010

We report a fabrication of 6, 13-bis(triisopropylsilylethynyl) (TIPS) pentacene nanowires that made on Si substrates by liquid bridge-nanotransfer molding (LB-nTM) with polyurethane acrylate (PUA) mold. LB-nTM is based on the direct transfer of various materials from a stamp to a substrate via a liquid bridge between them. In liquid bridge-transfer process, the liquid layer serves as an adhesion layer to provide good conformal contact and form covalent bonding between the TIPS-pentacene nanowire and the Si substrate. The patterned TIPS-Pentacene nanowires have been investigated by Atomic force microscopy (AFM), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and electrical properties.

• Journal of Welding and Joining
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• v.16 no.2
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• pp.48-56
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• 1998

This study was performed to find the best bonding conditions by comparing mechanical properties in thermoplastic resin of polyethylene (PE) and polyamide (PA) adhesion. Following results were obtained from the tests with varying welding time and welding pressure. Satisfactory adhesion was executed in ultrasonic welding for the same materials of PE and PA. The best welding conditions were found to be welding time of 1 second, welding pressure of 250kPa for PE-PE weding, 2 second and 350kPa for PA-PA welding. Welding time and welding pressure end to increase with the increase of materials strength. Dissimilar materials were adhered when adhesion and ultrasonc welding were performed simultaneously. The observation of the structure of ultrasonic welding area with microscope showed differenticated structures between well adhered region and badly adhered region.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.315-315
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• 2011

The ring formation and electronic properties of furan adsorbed on graphene layers grown on 6H-SiC(0001) has been investigated using atomic force microscopy (AFM), near edge X-ray absorption fine structure (NEXAFS) spectra for the C K-edge, and high resolution photoemission spectroscopy (HRPES). Moreover, we observed that furan molecules adsorbed on graphene could be used for chemical functionalization via the lone pair of electrons on the oxygen group, allowing chemical doping. We also found that furan spontaneously formed rings with one of three different bonding configurations and the electronic properties of the ring formed by furan on graphene can be described using by AFM, NEXAFS and HRPES, respectively.