• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.22 no.6
• /
• pp.587-596
• /
• 2009

The fiber bridging model is the crucial factor to predict or analyze the tensile behavior of fiber reinforced cementitious composites. This paper presents the fiber bridging constitutive law considering the distribution of fiber inclined angle and the number of fibers in engineered cementitious composites. The distribution of fiber inclined angle and the number of fibers are measured and analyzed by the image processing technique. The fiber distribution are considerably different from those obtained by assuming two- or three-dimensional random distributions for the fiber inclined angle. The simulation of the uniaxial tension behavior was performed considering the distribution of fiber inclined angle and number of fibers measured by the sectional image analysis. The simulation results exhibit multiple cracking and strain hardening behavior that correspond well with test results.

• Proceedings of the Korean Fiber Society Conference
• /
• 1987.06a
• /
• pp.18-18
• /
• 1987

• Journal of the Korea Concrete Institute
• /
• v.26 no.3
• /
• pp.307-313
• /
• 2014

In order to predict the post-cracking tensile behavior of fiber reinforced concrete, it is necessary to evaluate the fiber orientation factor which indicates the number of fibers bridging a crack. For investigation of fiber orientation factor on a circular cross-section, in this paper, cylindrical steel fiber reinforced concrete specimens were casted with the variables of concrete compressive strength, circular cross-section size, fiber type, and fiber volumetric ratio. The specimens were cut perpendicularly to the casting direction so that the fiber orientation factor could be evaluated through counting the number of fibers on the circular cross-section. From the test results, it was investigated that the fiber orientation factor on a circular cross-section was lower than 0.5 generally adopted, as fibers tended to be perpendicular to the casting direction. In addition, it was observed that the fiber orientation factor decreased with an increase of the number of fibers per unit cross-section area. For rational prediction of the fiber orientation factor on a circular section, a rigorous model and a simplified equation were derived through taking account of a possible fiber inclination angle considering the circular boundary surface. From the comparison of the measured data and the predicted values, it was found that the fiber orientation factor was well predicted by the proposed model. The test results and the proposed model can be useful for researches on structural behavior of steel fiber reinforced columns with a circular cross-section.

• Magazine of the Korea Concrete Institute
• /
• v.2 no.3
• /
• pp.65-72
• /
• 1990

Theoretical expressions were dcrived for the numher of fibers per unit cross-sectional area in fiber reinforced concrete, with due consideration given to the effects of the surrounding boundaries. The number of fibers per unit cross-sectional area in steel fiber reinforced concrete was also measured experimentally for the specimens incorporating various volume fractions of fibers of different types. Statistical evaluation of the measured value was then performed in order to assess the differences in fiber concentration at different location on tbe cross section. Degree of reorientation of steel fibers in concrete occuring during vibration was examined by com¬paring the differences in the computed and measur'ed values of the number of fibers per unit cross-sectional area.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.921-924
• /
• 2008

Several techniques, including transmission X-ray photography and AC-impedance spectroscopy, are available for evaluating the fiber dispersion in a fiber reinforced concrete Evaluating the fiber dispersion in fiber reinfored concrete needs since the fibers bridge crackseffectively. However, these equipment is very expensive. Therefore this paper presents the quantitative evaluation method based on the image analysis of sectional image taken using an ordinary digital camera. After detecting the fiber accurately, the fiber dispersion characteristics are represented by the coefficient such as the fiber dispersion coefficient, the number of fibers in unit area, and the distribution of the fiber orientation. Test were performed to evaluate the effectiveness of proposed method and the dispersion characteristics of fibers according placing method and flow direction. Additionally, the effect of fiber dispersion characteristics on mechanical properties was investigated. Test results shows that fiber aligned along the flow direction and more fibers placed and dispersion was better on the section parallel to the flow direction. And about 50% difference in the flexural tensile strength according to the placing method occured.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2009.05a
• /
• pp.491-492
• /
• 2009

This paper presents evaluation results of fiber dispersion, number of fibers in a unit area, fiber orientation according to the mix-proportion of ECC and bridging stress calculated on the basis of fiber distribution characteristics.

• The Korean Journal of Vision Science
• /
• v.20 no.4
• /
• pp.561-568
• /
• 2018

Purpose : The size and regular array of the collagen fibers in the corneal stroma have very close correlation with transparency. Simulation was carried out to investigate the change of light transmittance according to the array structure and collagen fiber layer thickness. Methods : The collagen fibers in corneal stroma were arranged in regular hexagonal, hexagonal, square and random shapes with OptiFDTD simulation software, and the light transmittance was analyzed. In square array, the light transmittance according to the density change was confirmed by when the number of collagen fibers in the simulation space was the same and the light transmittance was examined when the number and density of collagen fibers were changed. Results : When the number of collagen fibers is the same, the density becomes smaller and the thickness of the fibrous layer becomes thicker in order of arrangement of square, regular hexagonal, random and hexagonal. As a result of measuring the light transmittance by changing the array structure, the light transmittance measured at the detector at the same position was almost similar regardless of the array structure. In the detectors D0, D1, D2 and D3, the maximum transmittance is shown in square, hexagonal and square, regular hexagonal and regular hexagonal array structure, and the minimum transmittance is hexagonal, random, hexagonal and square, and square array structure. However, the difference between the maximum transmittance and the minimum transmittance was almost the same within 1%. When the number of collagen fibers was the same, the light transmittance of the rectangular array structure decreased with increasing fiber layer thickness. And as the thickness increased, the light transmittance decreased more when the number of collagen fibers decreased. Conclusion : Even though the collagen array structure changed, the light transmittance is almost similar regardless of the arrangement structure. However, as the array structure was changed, the thickness of the collagen fiber layer changed, and as the thickness increased, the light transmittance decreased. In other words, the transparency of the corneal stroma is more closely related to the thickness of the fibrous layer than the array of collagen fibers.

• Journal of Oral Medicine and Pain
• /
• v.33 no.4
• /
• pp.295-303
• /
• 2008

The lingual branch of the trigeminal nerve transmitts general sensation from anterior two thirds of the tongue, also bearing within sheath fibers of chordal tympani branch of the facial nerve. Chorda tympani nerve carries special taste sensations from the anterior two thirds of the tongue and sub-serves the existing trigeminal pathway. Chorda tympani nerve and the lingual nerve innervate to fungiform papilla and distribution of fungiform papilla on tongue dorsum is variable according to anatomical location. The purpose of this report is to assess that the relationship of the number of fungiform papilla and the ability of two-point discrimination of tongu dorsum. Twenty-six healthy students(male:female=13:13) whose mean age was $30{\pm}3$ participated in our study. Two-point discrimination thresholds were measured to evaluate the spatial acuity of touch sensation. The measurement was carried out at the tip and posterolateral region of dorsal tongue. After two-point discrimination test, we took the pictures of their dorsal tongue dyed with methylene blue with digital camera. There were no significant differences between the number of fungiform papilla and the two-point discrimination threshold. But, we found that there were the intraregional and intersubject variations of spatial acuity of the tongue. During the test on the posterolateral region of the dorsal tongue, students appealed the difficulty of discrimination of one point and two point.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.917-920
• /
• 2008

ECC is a special kind of high performance cementititous composite which exhibits typically more than 2% tensile strain capacity by bridging microcracks at a crack section. Therefore, micromechanics should be adopted to obtain multiple cracking and strain hardening behavior. This paper propose a linear elastic analysis method to simulate the multiple cracking and strain hardening behavior of ECC. In an analysis, the stress-crack opening relation modified considering the orientation of fibers and the number of effective fibers is adopted. Furthermore, to account for uncertainty of materials and interface between materials, the randomness is assigned to the tensile strength(${\sigma}_{fci}$), elastic modulus($E_{ci}$), peak bridging stress(${\sigma}_{Bi}$) and crack opening at peak bridging stress(${\delta}_{Bi}$), initial stress at a crack section due to chemical bonding, (${\sigma}_{0i}$), and crack spacing(${\alpha}_cX_d$). Test results shows the number of cracking and stiffness of cracked section are important parameters and strain hardening behavior and maximum strain capacity can be simulated using the proposed method.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2016.04a
• /
• pp.865-867
• /
• 2016

본 논문에서는 섬유근접센서를 이용하여 측정한 맥박을 평가하기 위해 Biopac MP150에서 획득한 Electrocardiography(ECG)와의 관계를 보았다. 섬유근접센서는 요골동맥에서의 맥박을 측정하기 위해 $5{\times}5$ 크기로 설계하였고, 전처리 과정과 필터링을 거쳐 획득한 데이터 값은 ECG 데이터와 Peak Point의 개수를 비교하여 올바른 맥박이 측정되었는지를 판단하였다. 그 결과 섬유근접센서와 MP150에서 측정한 두 데이터의 Peak Point가 모두 동일한 결과를 보였다.