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

• Journal of Photoscience
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• v.9 no.2
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• pp.258-260
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• 2002

We investigated the interaction of serotonin and galanin (GA) by a double immunostaining method in the Japanese quail. Serotonin-immunoreactive (IR) cells were located in the paraventricular organ (PVO) and infundibular nucleus (IF). The number of the cells under short-day photoperiod (SD) was less in the dark phase than in the light phase. GA-IR cells were found in the PVO, IF and median eminence. The number of GA-IR cells in SD was significantly greater than that in long-day photoperiod (LD). Numerous GA- IR varicose fibers ran along serotonin- IR cell bodies and nerve fibers in the PVO and IF of the same sections. Very few serotonin-IR fibers ran along GA-IR cell bodies and GA-IR nerve fibers in the ventral part of the IF. The present results suggest that the possibility of functional interaction takes place between serotonin- and GA- IR neurons in the PVO and IF.

• The Korean Journal of Vision Science
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• v.20 no.4
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• pp.561-568
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• 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 Environmental Health Sciences
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• v.22 no.2
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• pp.43-57
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• 1996

To characterize worker's exposure to glass fibers, to find the correlation between airborne total dust concentrations and fiber concentrations and to recommend an appropriate evaluation method for worker's exposure to fibrous dusts in glass wool industry, we carried out this study. Average respirable fiber levels at five factories were 0.013-0.056 f/cc, and fairly below the OSHA PEL, 1 f/cc. A factory showed the lowest airborne fiber level, 0.013 f/cc, which was different significantly from those of other factories of which average fiber concentration was 0.046 f/cc. The cutting and grinding operations of insulation products resulted in higher airborne fiber cocentrations than any other processes(p<0.05). To characterize airborne fiber dimension, fiber length and diamter were determined using phase contrast microscope. The geometric means of airborne fiber lengths were $42-105 \mu m$. One factory had airborne fibers whose length distribution(GM = $105 \mu m$) was different from those of other factories(GM = $42-50 \mu m$). The percentages of respirable fibers less thinner than 3 gm were 38.9-90.9% at four factories, and two factories of them had the higher percentages than others. The findings explain for variation of airborne fiber diameters between factories. On the other hand, between the processes were the difference of fiber-length distributions observed. The cutting and grinding operations showed shorter fiber-length distributions than the fiber forming one. However, fiber-diameter distributions or respirable fiber contents were similar in all processes. The airborne fiber concentrations and the dust concentrations had relatively weak correlation(r=0.25), thus number of fibers couldn't be expected reliably from dust amount. Fiber count is appropriate for assessing accurate exposures and health effects caused by fibrous dusts including glass fibers. Ministry of Labor have established occupational exposure limit to glass fibers as nuisiance dust, but should establish it on the basis of respirable fiber concentration to provide adequate protection for worker's health

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.1
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• pp.20-26
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• 2015

Objectives: To evaluate the biodurability of Korean Chrysotile(KC), the changes in fibers numbers and changes in the element composition of fibers from the lung of Sprague-Dawley rats instilled KC(average size $4.74{\mu}m$, $59,043{\times}10^6$ fibers/mg) was estimated. Methods: Rats were administered 1 mg KC(low group) or 2 mg KC(high group) by a single intratracheal instillation. At each time point(5 days, 5 weeks, 10 weeks), the numbers of KC fibers and the changes of element composition(atomic %) of KC fibers from the lung of the rats were analyzed with transmission electron microscope equipped with energy dispersive X-ray spectrometer. Results: Over time, the number of fibers within the lungs of animals were reduced. The average length of the low and high group is significantly reduced from 5 days after administration. Over time, the fiber ratio of at least $5{\mu}m$ remaining in the lung tissue of the low concentration group was up but the high group was reduced. From day 5 after administration, the composition ratio(Mg) was significantly decreased in all groups. Conclusions: Size and composition of Korean Chrysotile in the lung tissue of rats was changed from 5 days.

• Steel and Composite Structures
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• v.18 no.6
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• pp.1465-1478
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• 2015

The effect of cutting off fibers on transient load in a polymeric matrix composite lamina was studied in this paper. The behavior of fibers was considered to be linear elastic and the matrix behavior was considered to be linear viscoelastic. To model the viscoelastic behavior of matrix, a three parameter solid model was employed. To conduct this research, finite difference method was used. The governing equations were obtained using Shear-lag theory and were solved using boundary and initial conditions before and after the development of break. Using finite difference method, the governing integro-differential equations were developed and normal stress in the fibers is obtained. Particular attention is paid the dynamic overshoot resulting when the fibers are suddenly broken. Results show that considering viscoelastic properties of matrix causes a decrease in dynamic load concentration factor and an increase in static load concentration factor. Also with increases the number of broken fibers, trend of increasing load concentration factor decreases gradually. Furthermore, the overshoot of load in fibers adjacent to the break in a polymeric matrix with high transient time is lower than a matrix with lower transient time, but the load concentration factor in the matrix with high transient time is lower.

• Composites Research
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• v.26 no.4
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• pp.235-244
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• 2013

A volume integral equation method (VIEM) is introduced for the solution of elastostatic problems in an unbounded isotropic elastic solid containing multiple isotropic elliptical fibers of arbitrary orientation subject to uniform stress at infinity. The fibers are assumed to be long parallel elliptical cylinders composed of isotropic elastic material perfectly bonded to the isotropic matrix. The solid is assumed to be under plane strain on the plane normal to the cylinders. A detailed analysis of the stress field at the matrix-fiber interface for square and hexagonal packing of the fibers is carried out for different values of the number, orientation angles and concentration of the elliptical fibers. The accuracy and efficiency of the method are examined through comparison with results obtained from analytical and finite element methods.

• Food Science of Animal Resources
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• v.36 no.5
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• pp.583-593
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• 2016

The aim of this study was to investigate the effects of morphological characteristics of porcine muscle fibers on growth performance, muscle fiber characteristics, and pork quality taken from the longissimus dorsi muscle. A total of 239 crossbred pigs (164 castrated males and 75 females) were used in this study. Experimental pigs were categorized by the total number of muscle fiber (TNF: High and Low) and cross sectional area of muscle fiber (CSAF: Large, Middle, and Small). Their combinations were classified into six groups (High-Large, HL; High-Middle, HM; High-Small, HS; Low-Large, LL; Low-Middle, LM; Low-Small, LS). The TNF and CSAF were significantly (p<0.05) correlated with growth rate and carcass productivity, while the only of the type I number had no meaningful relationships excluding the correlation with loin area (p<0.001). The proportion of type I area was positively correlated with pH_{45 min} while the proportion of type IIB area was negatively correlated with pH_{45 min} and pH_{24 h} (p<0.05). Drip loss and protein denaturation had strong relationships with the proportion of type IIB number or area. The HL group exhibited the greatest growth performance. In addition, the HL group had significantly greater values in protein solubility than the other groups. In conclusion, this study suggest that high TNF combined to large CSAF improve the ultimate lean meat productivity and assure normal meat quality simultaneously with increased both proportion of number and area of type I, type IIA muscle fibers and lowered proportion of number and area of type IIB.

• Korean Journal of Veterinary Research
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• v.6 no.1
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• pp.82-91
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• 1966

Studies On the myelinated fibers of the recurrent laryneal nerves were made in five, species of domestic animals namely dog, pig, goat, horse and Korean ox. Throughout the studies, the following characteristics of the myelinated fibers were obtained. 1. The number, size and cross sectional area of the myelinated fibers seemed to be proportionally related to the animal body weights. 2. The highest peak of diameter size frequency distribution of the myelinated fibers, observed at the right cranial level, in dog, goat and horse were 4-6 micron group, while in the case of Korean ox, 10-12 micron group was the highest. 3. The highest peak of diameter size frequency distribution of the myelinated fibers, observed at the right caudal level of Korean ox was 6-8 micron group, and 4-6 micron group was the highest in the other animals. 4. The highest peak of diameter size frequency distribution of the myelinated fibers obsered at the left cranial level was same to that of right cranial level. 5. The highest peak of diameter size frequency distribution of the myelinated fibers, observed at the left caudal levels in dog, goat, horse and Korean ox was 4-6 micron group, while in case of pig, $14-16{\mu}$ group was the highest. 6. The largest cross sectional areas were found in the group of 10-16 micron in all species of animals. 7. The fiber diameter size frequency distribution of recurrent laryngeal nerves of dog, goat, pig and horse were bimodal and Korean ox seemed to be a unimodal.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.24 no.2
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• pp.130-136
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• 2014

Objectives: To evaluate the pulmonary toxicity of Korean Chrysotile(KC), the lung function and the number of fibers in the bronchoalveolar lavage fluid of Sprague-Dawley rats instilled with KC were estimated. Materials: Rats were administered 1 mg KC by a single intratracheal instillation. At each time point(5 days, 5 weeks, 10 weeks), the lung function of the rats was analyzed by pressure transducer and the amount of asbestos in the bronchoalveolar lavage fluid of the rats was calculated by transmission electron microscope equipped with energy dispersive X-ray spectrometer. Results: The lung function of the rats at 5 days after instillation of KC was confirmed to be degraded. However, after 5 weeks the test groups showed a tendency to recover lung function. Still, after 10 weeks the lung function of the test groups had not recovered completely. The number of fibers in the bronchoalveolar lavage fluid of the rats instilled with KC rapidly decreased. At 5 weeks the number of fibers had reduced to approximately 1/2 of that found at 5 days. Over time, at 10 weeks it had rapidly decreased to 1/100 that found at 5 days. Conclusions: Korean chrysotile fibers rapidly decreased in the lungs of rats, but the lung function of rats instilled KC does had not completely recovered by 10 weeks.