• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.114-118
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• 2009

이 논문에서는 울돌목 시험조류발전소에 구축 중인 구조건전성 감시시스템의 계획, 설치 및 활용에 대하여 소개하였다. 현재 시험조류발전소에 설치된 센서로는 전기저항식 변형률계, 광섬유 FBG(Fiber Bragg Grating) 센서, 압전형 MFC(Macro Fiber Composite) 센서, 2축 경사계, 서보형 가속도계 등과 같은 지지구조물의 구조거동을 감시하기 위한 센서와 토크 센서, RPM 센서 등 발전 계통에 대한 감시를 위한 센서, 그리고 H-ADCP(Horizontal Acoustic Doppler Current Profiler)와 같은 외력조건에 대한 계측 장비 등이 있다. 센서 설치 후 현재까지 부분적으로 계측된 자료를 소개하고, 향후 건전성 감시시스템 개선 계획을 소개하였다.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.134-136
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• 2005

Homogenization method is adopted to predict the permeability tenor for glass fiber plain woven fabrics. Calculating the permeability tensor numerically is an encouraging task because the permeability tensor is a key parameter in resin transfer molding (RTM). Based on multi-scale approach of the homogenization method, the permeability for the micro-unit cell within fiber tow is computed and compared with that obtained from flow analysis for the same micro-unit cell. It is found that they are in good agreement. In order to calculate the permeability tensor of macro-unit cell for the plain woven fabrics, the Stokes and Brinkman equations which describe inter-tow and intra-tow flow respectively are employed as governing equations. The effective permeabilities homogenized by considering intra-tow flow are compared with those obtained experimentally. Control volume finite element method (CVFEM) is used as a numerical method. It is shown that the asymptotic expansion homogenization method is an attractive method to predict the effective permeability for heterogeneous media.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.635-638
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• 2007

In this paper, we described the fundamental concepts of proposed structural health monitoring system for Uldolmok Tidal Current Power Plant focusing on the use of smart sensors including fiber bragg grating sensors and macro fiber composite sensors. The structural health monitoring system can play an important role to maintain the structural safety for offshore structures like as bridges and high-rise buildings. In the case of tidal current power plant, the monitoring system is much more important since the structures are usually constructed at the site with severer environmental loadings such as high current speed.

• International Journal of Industrial Entomology and Biomaterials
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• v.16 no.2
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• pp.61-66
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• 2008

In this paper, the regenerated silk fibroin (SF)/nylon 6 blend filaments were fabricated using wet spinning technique and the effect of coagulant on the post drawing and morphology of blend filaments was investigated. In the result of wet spinnability, methanol, acetone, DMF, and THF showed relatively good coagulation strength and fiber formation for the regenerated SF. On the contrary, they did not exhibit strong enough to produce a uniform nylon 6 filament due to the lack of coagulation strength. In the examination of post drawing performance, methanol showed the highest maximum draw ratio of the blend filament over all blend ratios. The maximum draw ratio of SF/nylon 6 blend filaments decreased with the reduction of SF content regardless of type of coagulant. SEM observation showed the consistent result with that of post-drawing performance. As SF content decreased, the uniform and regular structure was changed to irregular one. In particular, the severe macro-phase separation between SF and nylon 6 could be detected in the 50/50 SF/nylon 6 blend filaments coagulated in methanol and THF.

• Smart Structures and Systems
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• v.22 no.4
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• pp.369-382
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• 2018

Novel design of interdigitated electrodes capable of increasing the performance of piezoelectric transducers are proposed. The new electrodes' geometry improve the electromechanical coupling by offering an enhanced adaptation of the electric field to the interdigitated electrode configuration. The proposed analysis is based on finite element modeling and takes into account local polarization effect. It is shown that the proposed electrodes considerably increase the strain generation compared to flat electrode arrangement used for Macro Fiber Composite (MFC) and Active Fiber Composite (AFC) actuators. Also, electric field singularities are reduced allowing better reliability of the transducer against electric failure.

• Smart Structures and Systems
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• v.18 no.3
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• pp.389-403
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• 2016

Structural deflection can be identified from measured strains from long gague sensors, but the sensor layout scheme greatly influences on the accuracy of identified resutls. To determine the optimal sensor layout scheme for accurate deflection identification of the tied arch bridge, the method of optimal layout of long-gauge fiber optic sensors is studied, in which the characteristic curve is first developed by using the bending macro-strain curve under multiple target load conditions, then optimal sensor layout scheme with different number of sensors are determined. A tied arch bridge is studied as an example to verify the effectiveness and robustness of the proposed method for static and dynamic deflection identification.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.4
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• pp.274-286
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• 2005

Fracture behaviors and acoustic emission (AE) characteristics of single-edge-notched monolithic aluminum plates and glass fiber/aluminum hybrid laminate plates have been investigated under tensile loads. AE signals from monolithic aluminum could be classified into two different types: signals with low frequency band and high frequency band. High frequency signals were detected in the post stage of loading beyond displacement of 0.45mm. For glass fiber/aluminum laminates, AE signals with high amplitude and long duration were additionally confirmed on FFT frequency analysis, which corresponded to macro-crack propagation and/or delamination between A1 and fiber layers. On the basis of the above AE analysis and fracture observation with optical microscopy and ultrasonic T scan, characteristic features of AE associated with fracture processes of single-edge-notched glass fiber/aluminum laminates were elucidated according to different fiber ply orientations.

• Computers and Concrete
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• v.22 no.5
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• pp.481-492
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• 2018

In this paper, a new hybrid fiber system (NHFS) is investigated for the application of slab. The steel fiber, polyvinyl alcohol (PVA) fiber and calcium carbonate ($CaCO_3$) whisker is added to form NHFS. The four-point bending test is carried out on the flexural properties of slab with plain, steel fiber, traditional hybrid fiber system (THFS) and NHFS reinforced cementitious composites. The flexural behavior is evaluated by ASTM C1018-97, JCI-SF4 and post-crack strength (PCS) technique. The evaluation parameters of flexural toughness such as toughness index (TI), equivalent flexural strength (EFS) and PCS are determined. The size of slab specimens is $15mm(thickness){\times}50mm(width){\times}200mm(length)$. The results show that adding $CaCO_3$ whisker to THFS can significantly improve the flexural strength, TI, EFS, PCS of the slab. The empirical relation between reinforcing index ($RI_v$) and flexural parameters show that flexural parameters of slabs increase first and then decrease; which indicates that optimum $RI_v$ values can be helpful in the considering the mix design of steel-PVA fibers-$CaCO_3$ whisker composites for achieving the desired flexural-related properties. The scanning electron microscopy is performed to observe the micro-morphological characteristics of the fracture surface, which proved the positive hybrid effect among the different fibers in cementitious composites. The NHFS can arrest the generation and propagation of the crack from micro to macro level.

• Food Science and Industry
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• v.52 no.1
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• pp.84-99
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• 2019

Dietary fiber is defined as soluble and insoluble polysaccharide consisted in the plant cell wall-associated fibers naturally occurring in fruits, vegetables, and cereal products, and of isolated fibers that are added to processed foods which are also artificially modified. There are so many difference types of dietary fibers as arabinoxylan, polydextrose chicory, oligosccharide. inulin, pectin, bran, cellulose, ${\beta}$-glucan, resistant starch and some seaweed polymers as alginate. Most of them provide many biological benefits in the intestine, as lower risk for developing coronary heart disease, stroke, hypertension, diabetes, obesity and some of the gastrointestinal disease like as colon cancer. And also lowering cholesterol levels, improves glycemic and insulin sensitivity to non-diabetic and diabetic persons including immune system. Beside of many benefits, average consumers in developed and under developing countries take far less amounts of dietary fiber that international organization recommended. Adequate intake of dietary fiber is 14g/1,000kcal base using the energy guide line of 2,000kcal/day for women and 26,000 kcal/day for men, dietary intake is 28g/day of adult women and 36g/day for adult men. The mechanisms behind the reported effects of dietary fiber on metabolic health are not fully well established. It is suggested that changes in intestinal viscosity resulting mucus increasing, macro-nutrients absorption, rate of passage of large intestinal, production of short chain fatty acids by fermentation. Production of gut hormones and changes of microbiota in intestine. It is necessary to do more research in this field in the future and combined interdisciplinary works together.

• Korean Journal of Optics and Photonics
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• v.8 no.2
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• pp.134-141
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• 1997

We design the single mode dispersion-compensating fibers (DCF) which may be necessary for upgrading the previously installed 1.31 ${\mu}{\textrm}{m}$ optical communication system to the 1.55 ${\mu}{\textrm}{m}$ system. To obtain the optimum index profile that allows large negative dispersion at 1.55 ${\mu}{\textrm}{m}$, parabolic-index, double-clad fibers are analyzed by applying the 1-D FEM to the scalar wave equation of optical fibers. In constideration of macro-bending loss, the fibers are designed so that the cutoff wavelength of the $LP_{01}$ mode is greateer than 1.80 ${\mu}{\textrm}{m}$. The computer simulations show that the lower bound of the dispersion at 1.55 ${\mu}{\textrm}{m}$ is limited to about -120 ps/nm . km for the fiber index profiles satisfying the $LP_{01}$'s cutoff condition.