• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.478-483
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• 2001

We experimentally attempted to understand the vibration characteristics of a flexible pipe excited by vortex shedding. This has been extensively studied in the past decades (For example, see ［2-9］). However, there are still areas that need more study. One of them is to study the relation between spatial characteristics of a flow induced vibrating pipe, such as its length, the distribution of wave number, and frequency responses. A non-linear mechanism between the responses of in-line and cross-flow directions is also an area of interests, if the pipe is relatively long so that structural modal density is reasonably high. In order to investigate such areas, two kinds of instrumented pipe were designed. The instrumented pipes, of which the lengths are equally 6m, are wound with rubber and silicon tape in different ways, having different vortex shedding conditions. One has uniform cross-section of diameter of 26. 7mm, and the other has equally spaced by 4 sub-sections, which are composed of different diameters of 75.9, 61.1, 45.6 and 26.7mm. Both pipes are towed in a water tank (200m ${\times}$ 16m ${\times}$ 7m) so that they experienced different vortex shedding excitations. The towing pipe experiments exhibit several valuable features. One of them is that the natural frequencies and their corresponding strain mode shapes dominate the strain response of the uniform pipe. However, for those of non-uniform pipe, the responses are more likely local and many modes participate in it.

• Archives of Plastic Surgery
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• v.35 no.6
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• pp.755-758
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• 2008

Purpose: In order to determine the amount of wound healing, objective sequential assessments of changes in wound size and depth are essential. Although a variety of measurements for wound healing have been proposed, a gold standard for quantifying day-to-day changes in healing has not been established. We present here a simple and non-invasive wound measurement method that quantitatively and accurately documents changes of the size of a raw surface and the volume of a soft tissue defect using a stereoimage optical topometer(SOT) system. Methods: Using a 5mm diameter biopsy punch, four circular wounds were created on abdominal area of a diabetic mouse. Photographs were taken using SOT system at baseline, 5th day and 10th postoperative day. The wound margin was traced on a digitalized photo and evaluated the area and the volume of the wound by SOT system. Results: The SOT system calculated a mean wound surface of $15.93{\pm}0.29mm^2$ and volume of $827.50{\pm}88.86$ intensity/pixel${\times}$area(I/PA) immediately after wounding. On the 5th day after the operation wound surface declined by $10.73mm^2$ and on the 10th day declined by $5.95mm^2$. The wound volume also declined from 827.50 I/PA to 161.75 I/PA and 30.50 I/PA on 0, 5th and 10th day, respectively. Conclusion: The SOT system described in this study represents a reliable, simple, practical, and non-invasive technique to accurately monitor and evaluate wound healing.

• Journal of Korean Society of Steel Construction
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• v.21 no.6
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• pp.563-574
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• 2009

This paper briefly describes the fundamental strategies--path-tracing, pin-pointing, and path-switching--in the computational elastic bifurcation theory of geometrically non-linear single-load-parameter conservative elastic spatial structures. The stability points in the non-linear elasticity may be classified into limit points and bifurcation points. For the limit points, the path tracing scheme that successively computes the regular equilibrium points on the equilibrium path, and the pinpointing scheme that precisely locates the singular equilibrium points were sufficient for the computational stability analysis. For the bifurcation points, however, a specific procedure for path-switching was also necessary to detect the branching paths to be traced in the post-buckling region. After the introduction, a general theory of elastic stability based on the energy concept was given. Then path tracing, an indirect method of detecting multiple bifurcation points, and path switching strategies were described. Next, some numerical examples of bifurcation analysis were carried out for a trussed stardome, and a pin-supported plane circular arch was described. Finally, concluding remarks were given.

• Smart Structures and Systems
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• v.6 no.3
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• pp.197-209
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• 2010

The structural state of a bridge is currently examined by visual inspection or by wired sensor techniques, which are relatively expensive, vulnerable to inclement conditions, and time consuming to undertake. In contrast, wireless sensor networks are easy to deploy and flexible in application so that the network can adjust to the individual structure. Different sensing techniques have been used with such networks, but the acoustic emission technique has rarely been utilized. With the use of acoustic emission (AE) techniques it is possible to detect internal structural damage, from cracks propagating during the routine use of a structure, e.g. breakage of prestressing wires. To date, AE data analysis techniques are not appropriate for the requirements of a wireless network due to the very exact time synchronization needed between multiple sensors, and power consumption issues. To unleash the power of the acoustic emission technique on large, extended structures, recording and local analysis techniques need better algorithms to handle and reduce the immense amount of data generated. Preliminary results from utilizing a new concept called Acoustic Emission Array Processing to locally reduce data to information are presented. Results show that the azimuthal location of a seismic source can be successfully identified, using an array of six to eight poor-quality AE sensors arranged in a circular array approximately 200 mm in diameter. AE beamforming only requires very fine time synchronization of the sensors within a single array, relative timing between sensors of $1{\mu}s$ can easily be performed by a single Mote servicing the array. The method concentrates the essence of six to eight extended waveforms into a single value to be sent through the wireless network, resulting in power savings by avoiding extended radio transmission.

• Korean Journal of Ichthyology
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• v.28 no.4
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• pp.223-228
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• 2016

The anatomy and histology of the olfactory organ in Oryzias sinensis was researched using a stereo microscope and light microscope. In the gross structure, the paired olfactory organs on the dorsal part of the head consist of two nostrils (a circular anterior nostril and a slit posterior nostril in a distance), a single olfactory chamber and a single accessory nasal sac. In the histological study, the epithelium of the olfactory chamber is classified into both sensory and non-sensory regions. The sensory epithelium consists of olfactory receptor neurons, supporting cells, basal cells and vesicles, and is islet in distributional pattern. The non-sensory epithelium is composed of stratified epithelial cells and two types of mucous cells (acidic and neutral cells). The epithelium of the accessory nasal sac has swollen stratified epithelial cells, mucous cells with a rich glycoprotein. Such an olfactory anatomy and histology of O. sinensis may reflect its habitat surrounding stagnant and polluted water.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.2045-2049
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• 2018

An antenna arrays for a satellite navigation systems require more antenna elements to mitigate multiple jamming signals. In order to maintain the small array size while increasing the number of antenna elements, miniaturization technique is essential for antenna design. In this work, an electrically small circular microstrip patch antenna with a 3 dB hybrid coupler is designed as an element antenna, where the 3 dB hybrid coupler can yield the circularly polarized radiation characteristic. The miniaturized element antenna typically has too large capacitance in GPS L1 and GLONASS G1 bands, making it difficult to match with a single stand-alone non-Foster matching circuit (NFMC) in a stable state. Therefore, we propose a new matching technique, referred to as the hybrid matching method, which consists of a NFMC and a passive circuit. This passive tuning circuit manages reactance of antenna elements at an appropriate capacitance without a pole in the operating frequency range. The antenna array is fabricated, and the measured results show a reflection coefficient of less than -10 dB and an isolation of greater than 50 dB. In addition, peak gain of the proposed antenna is increased by 22.3 dB compared to the antenna without the hybrid matching network.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.6
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• pp.185-194
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• 1998

In this study, the rotary bending fatigue test was carried out with two kinds of material, S43C and S50C, using in the Front engine and Front drive wheels(F.F.) of vehicle. The one part of specimens was heated by high frequency induction method(about 1mm depth and $H_RC$ 56~60) and tested environment temperature were $-30^{\circ}C$, $+25^{\circ}C$ and $+80^{\circ}C$ in order to look over the influence of the heat treatment and the temperatures. In the experimented result at $+25^{\circ}C$ and $+80^{\circ}C$, the fatigue life of non-heated specimens were decreased about 35%, but that of heated specimens were decreased about only 5% at $+80^{\circ}C$ more than at $25^{\circ}C$. And in the experiment result at $-30^{\circ}C$ and $+25^{\circ}C$, the non-heated and heated specimens were about 110%, 120% higher fatigue life at $-30^{\circ}C$ than at the $+25^{\circ}C$ each other. On the other hand, the fatigue crack propagation rate of S50C was higher than that of S43C.

• Computers and Concrete
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• v.23 no.1
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• pp.61-68
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• 2019

This paper presents a computational rational model to predict the ultimate and optimized load capacity of reinforced concrete (RC) beams strengthened by a combination of longitudinal and transverse fiber reinforced polymer (FRP) composite plates/sheets (flexure and shear strengthening system). Several experimental and analytical studies on the confinement effect and failure mechanisms of fiber reinforced polymer (FRP) wrapped columns have been conducted over recent years. Although typical axial members are large-scale square/rectangular reinforced concrete (RC) columns in practice, the majority of such studies have concentrated on the behavior of small-scale circular concrete specimens. A high performance concrete, known as polymer concrete, made up of natural aggregates and an orthophthalic polyester binder, reinforced with non-metallic bars (glass reinforced polymer) has been studied. The material is described at micro and macro level, presenting the key physical and mechanical properties using different experimental techniques. Furthermore, a full description of non-metallic bars is presented to evaluate its structural expectancies, embedded in the polymer concrete matrix. In this paper, the mechanism of mechanical interaction of smooth and lugged FRP rods with concrete is presented. A general modeling and application of various elements are demonstrated. The contact parameters are defined and the procedures of calculation and evaluation of contact parameters are introduced. The method of calibration of the calculated parameters is presented. Finally, the numerical results are obtained for different bond parameters which show a good agreement with experimental results reported in literature.

• Journal of Korea Trade
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• v.25 no.3
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• pp.1-20
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• 2021

Purpose - The purpose of this paper is to examine the welfare effects of standards harmonization between technologically asymmetric countries, and to determine optimal harmonization strategies for a country with mid-level technological advancement. Design/methodology - Following Salop's circular city model (Salop, 1979), this study constructs a simple, horizontally-differentiated oligopoly model in which three firms and three countries exist. Each country adopts different compatibility standards and each firm incurs conversion costs for foreign market access due to differences in standards. The conversion costs are related to technology; standards harmonization removes these costs between participating countries. The paper considers three cases: i) no harmonization; ii) harmonization with the more technologically-advanced country and iii) harmonization with the less technologically-advanced country. Findings - The paper first considers a scenario in which all three firms occupy some share of the market in each country. It shows that standards harmonization with both the technologically moreor less-advanced country always increases consumer surplus and social welfare. In addition, the producer surplus will increase if the harmonization partner has a higher technology level, whereas it may decrease if the partner has a lower technology level. It also shows that if most domestic export goods are in sectors with conversion costs above a certain level, harmonizing standards with a technologically more-advanced country should be prioritized. Such strategies, moreover, should be emphasized when there exists a large technology gap among countries. Lastly, the paper considers another scenario, in which harmonization leads to the foreclosure of the non-member firm from the member countries' markets. It shows that harmonization improves the social welfare of a mid-level technology country regardless of its partner's technology. It also shows that the country should prioritize harmonization with the technologically less-advanced country. Originality/value - Though some of the existing studies consider the welfare effects of harmonization, their main assumption is that firms have the same conversion technology. Since complying with standards often requires substantial technological advancement and technical expertise, harmonization of compatibility standards between countries with gaps in technological ability carries different implications. This paper investigates the welfare effects of this harmonization and determines an optimal harmonization strategy while considering technological asymmetry among countries in standards compliance.

• Journal of Korean Society on Water Environment
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• v.40 no.3
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• pp.131-139
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• 2024

This study investigated the chemical properties of Organic Soil Amendments (OSAs) made from organic waste. It also assessed the effectiveness of using these OSAs in the soil layer of Green Infrastructure (GI) to reduce stormwater runoff and non-point source pollutants. The goal was to improve the national environmental value through resource recycling and contribute to the circular economy transformation and carbon neutrality of urban GI. The OSAs used in this study consisted of spent coffee grounds and food waste compost. They were found to be nutrient-rich and stable as artificial soils, indicating their potential use in the soil layer of GI facilities. Applying OSAs to bio-retention cells and permeable pavement resulted in a reduction of approximately 11-17% in stormwater runoff and a decrease of about 16-18% in Total Phosphorus (TP) discharge in the target area. Increasing the proportion of food waste compost in the OSAs had a positive impact on reducing stormwater runoff and pollutant emissions. This study highlights the importance of utilizing recycled resources and can serve as a foundation for future research, such as establishing parameters for assessing the effectiveness of GI facilities through experiments. To enable more accurate analysis, it is recommended to conduct studies that consider both the chemical and biological aspects of substance transfer in OSAs.