• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.509-514
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• 2001

The Fibre-optic Bragg grating (FBG) sensor is broadly accepted as a structural health monitoring device for Fibre reinforced plastic (FRP) materials by either embedding into or bonding onto the structures. The accuracy of the strain measured by using the FBG sensor is highly dependent on the bonding characteristics among the bare optical fibre, protective coating, adhesive layer and host material. In general, the signal extracted from the embedded FBG sensor should reflect the straining condition of the host structure. This paper presents a theoretical model to evaluate the differential strains between the bare fibre and host material with different adhesive thickness and modulus of the protective coating of the embedded FBG sensor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.301-305
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• 2002

Among many structural dynamics modification methods for plate and shell vibration problems, embedding an emboss to the surface is very efficient. But deciding an optimal position and shape using optimization algorithm needs defining geometry and remeshing the model for every iteration step to implement the method, which takes much numerical cost. An equivalent element produced here lessen the cost by representing the geometrical characteristics of an emboss using the element's material properties and thickness becoming a geometrically homogenous element of the base plate or shell. Some efficient factors which let the equivalent system have the same dynamical response as the original system embedded with emboss will be shown and the degree of equivalence will be tested in terms of natural frequency matching.

• Corrosion Science and Technology
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• v.4 no.1
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• pp.29-32
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• 2005

A various structural materials are used in construction projects such as a stone, concrete, steel materials. Between of them, concrete are used widely. The compressive strength of concrete is high, and its maintenance and management is comparatively easy. The R.C Building will be superannuated as time passes. This program is generated by propagation of cracks. In order to manage such cracks, time and efforts, expense, etc. are required. In this study, glass sensors were embedding in a model beam and column and leakage of fluorescence and adhesive material was investigated. Further, currents in glass pipe were observed to find the leakage of liquid in glass pipes. Progressive cracks generated by cause the fracture of glass pipes. Therefore, the liquid become to flow and electric current stops, and the cracked part of the member can be found easily. Moreover, the adhesive delays progressive cracking system that responds in air, and the life of a structure can be made to extend. The purpose of this research is to develop of low price sensors that can perform of self-diagnosis in addition to ability of concrete repair concrete to damage.

• Composites Research
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• v.18 no.4
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• pp.1-7
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• 2005

In-situ structural health monitoring of filament wound pressure tanks were conducted during water-pressurizing test using embedded fiber Bragg grating (FBG) sensors. We need to monitor inner strains during working in order to verify the health condition of pressure tanks more accurately because finite element analyses on filament wound pressure tanks usually show large differences between inner and outer strains. Fiber optic sensors, especially FBG sensors can be easily embedded into the composite structures contrary to conventional electric strain gages (ESGs). In addition, many FBG sensors can be multiplexed in single optical fiber using wavelength division multiplexing (WDM) techniques. We fabricated a standard testing and evaluation bottle (STEB) with embedded FBG sensors and performed a water-pressurizing test. In order to increase the survivability of embedded FBG sensors, we suggested a revised fabrication process for embedding FBG sensors into a filament wound pressure tank, which includes a new protecting technique of sensor heads, the grating parts. From the experimental results, it was demonstrated that FBG sensors can be successfully adapted to filament wound pressure tanks for their structural health monitoring by embedding.

• Korean Journal of Construction Engineering and Management
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• v.10 no.4
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• pp.151-164
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• 2009

Strategic alliances developed as formalized inter-organizational relationships are core vehicles to share information, resources and knowledge. The structural characteristics of strategic network constructed by strategic alliances have been important agenda in strategic management discipline. This paper has two folds in analysing the strategic network formulated by project level alliances in Korean construction industry. First, we investigate the strategic network using the tools and methods of social network analysis, such as centrality, cohesion, structural equivalence, and power law. Second, the performance of firms within networks are analysed longitudinally with panel data analysis. We have found that the strategic networks in this industry has scale-free characteristics, where the degree distribution fits the power law, and the vertically equivalent structure is clear. We also present that the performance of firms are continuously affected by the degree centrality of firms in this network for the last 10 years.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.5
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• pp.511-521
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• 2015

The thermal bridge occurring in a building influences its thermal performance and durability. The domestic typical multi-unit residential buildings suffer thermal losses resulting from thermal bridges of the balcony slab. To minimize the thermal loss between inside and outside of the balcony slab, thermal bridge breaker(TBB) systems have been developed and applied in building construction. Although thermal bridge breaker systems for reinforced concrete(RC) wall-slab joints can improve the thermal performance of a building, it is necessary to verify the structural performance of TBB systems whether they provide proper resistance for cyclic loading. In order to investigate the structural characteristics of TBB systems embedded in RC slabs, cyclic tests of wall-slab joints were performed by applying two reversed cycles at each up to 30 cycles. The test results show that the RC slabs embedding TBBS systems can present excellent structural performance and the maximum moment capacity, energy dissipation capacity and ductility of TBBs systems are enhanced compared to those of the typical RC slabs.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.4
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• pp.372-379
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• 2023

International oil prices are expected to increase from $85 a barrel this year to up to $100 a barrel in the second half of the year; this is likely to increase orders for offshore plants in the global market. One main characteristic of offshore plants is that a large helideck is located on the top side, and aluminum alloys are used as the basic material of the structure for weight reduction and corrosion resistance. Shipowners are increasing the size of helicopters to quickly evacuate lives in the event of an emergency, and the safety use load of devices that can stably secure helicopters to the deck is also required to increase. Owing to the nature of the aluminum material, the structural strength caused by welding is greatly reduced; therefore, the fixing device must be designed by embedding it in the deck and fixing it with bolts. In this study, a model applying aluminum alloy 6082-T6 was developed to develop a helicopter fastening device that can be used for large helidecks (diameter = 28 m). The developed item was verified through nonlinear structural strength calculation to satisfy the load used for the actual fastening condition. The load condition with a 45° showed a lower ultimate strength than the 90° case owing to local plastic collapse. The nonlinear structural collapse behavior showed a result similar to that of the experimental test. The main contents derived from this study are considered to be reference materials when evaluating the structural strength of similar aluminum equipment.

• Journal of Information Technology Applications and Management
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• v.27 no.1
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• pp.147-171
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• 2020

In-app advertisement is a fast-growing trend in mobile advertising, where user acceptance of ads is facilitated by the fact that users have voluntarily downloaded the app through which the ad is served. However, research in this ad category is limited. This study applies an extended version of the theory of planned behavior. Analysis results from 412 young mobile users in Vietnam using structural equation modeling showed that while localization and perceived enjoyment affected user intention to watch in-app ads as expected, perceived behavioral control and trust did not. Such results may be due to embedding the ads to applications, confusing users' behavioral intentions. The results underline the need for more future research in the area. In practical terms, companies should improve localization and entertainment aspects of ads to create more relevant and engaging advertisements.

• ETRI Journal
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• v.36 no.3
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• pp.479-489
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• 2014

This paper presents a model-based image steganography method based on Watson's visual model. Model-based steganography assumes a model for cover image statistics. This approach, however, has some weaknesses, including perceptual detectability. We propose to use Watson's visual model to improve perceptual undetectability of model-based steganography. The proposed method prevents visually perceptible changes during embedding. First, the maximum acceptable change in each discrete cosine transform coefficient is extracted based on Watson's visual model. Then, a model is fitted to a low-precision histogram of such coefficients and the message bits are encoded to this model. Finally, the encoded message bits are embedded in those coefficients whose maximum possible changes are visually imperceptible. Experimental results show that changes resulting from the proposed method are perceptually undetectable, whereas model-based steganography retains perceptually detectable changes. This perceptual undetectability is achieved while the perceptual quality - based on the structural similarity measure - and the security - based on two steganalysis methods - do not show any significant changes.

• Smart Structures and Systems
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• v.25 no.4
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• pp.423-432
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• 2020

In this paper, a novel but practical approach named series/parallel multi-sensing technique was proposed to evaluate the bolt looseness in a bolt group. The smart washers (SWs), which were fabricated by embedding a Lead Zirconate Titanate (PZT) transducer into two flat metal rings, were installed to the bolts group. By series connection of SWs, the impedance signals of different bolts can be obtained through only one sweep. Therefore, once the loosening occurred, the shift of different peak frequencies can be used to locate which bolt has loosened. The proposed multi input single output (MISO) damage detection scheme is very suitable for the structural health monitoring (SHM) of joint with a large number of bolts connection. Another notable contribution of this paper is the proposal of 3-dB bandwidth root mean square deviation (3 dB-RMSD) which can quantitatively evaluate the severity of bolt looseness. Compared with the traditional naked-eye observation method, the equivalent circuit based 3-dB bandwidth can accurately define the calculation range of RMSD. An experiment with three bolted connection specimens that installed the SWs was carried out to validate our proposed approach. Experimental result shows that the proposed 3 dB-RMSD based multi-sensing technique can not only identify the loosened bolt but also monitor the severity of bolt looseness.