• Structural Engineering and Mechanics
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• v.89 no.4
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• pp.349-362
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• 2024

High-performance fiber-reinforced cement composites (HPFRCC) are new materials created and used to repair, strengthen, and improve the performance of different structural parts. When exposed to tensile tension, these materials show acceptable strain-hardening. All of the countries of the globe currently seem to have a need for these building materials. This study aims to create a low-carbon HPFRCC (high ductility) that is made from materials that are readily available locally which has the right mechanical qualities, especially an increase in tensile strain capacity and environmental compatibility. In order to do this, the effects of fiber volume percent (0%, 0.5%, 1%, and 2%), and determining the appropriate level, filler type (limestone powder and silica sand), cement type (ordinary Portland cement, and limestone calcined clay cement or LC3), matrix hardness, and fiber type (ordinary and oxygen plasma treated polypropylene fiber) were explored. Fibers were subjected to oxygen plasma treatment at several powers and periods (50 W and 200 W, 30, 120, and 300 seconds). The influence of the above listed factors on the samples' three-point bending and direct tensile strength test results has been examined. The results showed that replacing ordinary Portland cement (OPC) with limestone calcined clay cement (LC3) in mixtures reduces the compressive strength, and increases the tensile strain capacity of the samples. Furthermore, using oxygen plasma treatment method (power 200 W and time 300 seconds) enhances the bonding of fibers with the matrix surface; thus, the tensile strain capacity of samples increased on average up to 70%.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.5-8
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• 2005

The purpose of this study is to investigate the mechanical characteristics of plain and steel fiber high strength concrete under uniaxial and biaxial loading condition. A number of plain and steel fiber high strength concrete cubes having 28 days compressive strength of 82.7Mpa (12,000psi) were made and tested. Four principal compression stress ratios, and four fiber concentrations were selected as major test variables. From test results, it is shown that confinement stress in minor stress direction has pronounced effect on the strength and deformational behavior. Both of the stiffness and ultimate strength of the plain and fiber high strength concrete increased. The maximum increase of ultimate strength occurred at biaxial stress ratio of 0.5 in the plain high strength concrete and the value were recorded 30 percent over than the strength under uniaxial condition. The failure modes of plain high strength concrete under uniaxial compression were shown as splitting type of failure but steel fiber concrete specimens under biaxial condition showed shear type failure.

• Journal of Sensor Science and Technology
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• v.14 no.3
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• pp.169-179
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• 2005

A multiplexed bend loss type single-mode fiber-optic sensor system was prepared to measure the displacement of several cm of the civil engineering structures such as many bridges, tunnels and various buildings. This bend loss type fiber-optic sensor used the signal difference between two reflection signals due to various bend losses generating at a pair of optical connectors by using OTDR (optical time domain reflectometer) for measuring displacements. And the experiments were conducted for showing the measurement feasibility on the range of 10 cm, and the multiplexing experiments were also performed to measure the displacements of 5 measuring positions of an object by setting these 5 fiber-optic sensors on a single mode fiber simultaneously.

• Structural Engineering and Mechanics
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• v.73 no.4
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• pp.437-445
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• 2020

The microstructure and mechanical properties of concrete will degrade significantly at high temperatures, thus affecting the bond strength between reinforcing steel and surrounding concrete in reinforced concrete members. In this study, the effect of individual and hybrid fiber on the local bond-slip behavior of lightweight aggregate concrete (LWAC) after exposure to elevated temperatures was experimentally investigated. Tests were conducted on local pullout specimens (150 mm cubes) with a reinforcing bar embedded in the center section. The embedment lengths of the pullout specimens were 4.2 times the bar diameter. The parameters investigated included concrete type (control group: ordinary LWAC; experimental group: fiber reinforced LWAC), concrete strength, fiber type, and targeted temperature. The test results showed that for medium-strength LWACs exposed to high temperatures, the use of only steel fibers did not significantly increase the residual bond strength. Moreover, the addition of individual and hybrid fiber had little effect on the residual bond strength of the high-strength LWAC after exposure to a temperature of 800℃.

• Journal of Oral Medicine and Pain
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• v.13 no.1
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• pp.61-69
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• 1988

The study of the muscle fiver composition and the muscle fiver type conversion during unilateral edentulous condition was undertaken in the rostral superficial masseter muscle of the whiter rat. 16 4-week-old male white rats weighting approximately 130gm that crowns of left upper and lower molare were cut intentionally, were divided into 4 groups (one control group and 3 experimental groups). After experimental groups were sacrificed by etherization in 6 days($E_1$), 18 days($E_2$) and 36 days($E_3$) separately, samples of the rostral superficial masseter muscle were obtained bilaterally and the proportion of type I, type IIA, type IIB, and type IIC fibers was determined and counted according to their histochemical activity of myosin ATPase (at pH 9.4, pH 4.6, and pH 4.2)and PAD staining. The obtained results were as follows : 1. The rostral superficial masseter muscle of the white rat contained approximately 47.5% type I fiber and 52.5% type II fiber. 2. Type I/ Type II ratio of molar-present side was increased significantly in the group E2 (18 days group) 3. Type IIA fiber was increased at molar-present side and decreased at molar-absent side in experimental groups.

• Journal of Korean Academy of Nursing
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• v.25 no.2
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• pp.193-209
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• 1995

The purpose of this study was to determine the effect of intermittent low - intensity, short duration exercise during hindlimb suspension on the mass, relative weight, myofibrillar protein content, cross-sectional area of Type I and Type II fibers and SDH activity in Type II(plantaris) muscle. To examine the effectiveness of intermittent low-intensity, short duration exercise on mass, myofibrillar protein content and fiber size, the hindlimbs of adult female Wistar rats were suspended(HS) and half of these rats walked on a treadmill for 45 min/day(9 min every 2h) at 5m /min and a 15$^{\circ}$grade (HS-EX). Plantaris wet weight was 19.67% significantly smaller(p<0.005) and relative plantaris weight was 6.25% smaller compared with those of control rats following seven days of hindlimb suspension. Plantaris wet weight and relative plantaris weight increased by 27.66%, 12.22% each through intermit-tent exercise during hindlimb suspension(p<0.005, p<0.05), moreover, plantaris wet weight and relative plantaris weight of the HS-EX rats were similar to those of control rats. Soleus wet weight and relative soleus weight decreased significantly by 31% and 22.0% in the HS rats(p<0.05). Soleus wet weight and relative soleus weight increased by 10.41%, 25.64% respectively through intermittent ex-ercise during hindlimb suspension, furthermore, soleus wet weight and relative weight of the HS-EX rats were closer to those of control rats. Myofibrillar protein content of plantaris and soleus decreased significantly by 51.49%, 59.65% each, following seven days of hindlimb suspension (p<0.005) Myofibrillar protein content of plantaris and soleus increased by 51.79%, 75.47% each with significance through intermittent exercise during hindlimb suspension(p<0.005). Myofibrillar protein content of plantaris and soleus in HS-EX rats was smaller than that of control rats. No change was observed in fiber type percentage following 1 week of hindlimb suspension or exercise during hindlimb suspension. The type I fiber cross-sectional area of both soleus and plantaris muscle was 18.72% and 41.07% lower in the HS than that of the controls (p<0.05, p<.001), that of both muscles was 6.60% and 29. 3％ greater in the HS-EX than that of the HS rats. HS plus intermittent low- intensity short duration exercise resulted in Type I fiber cross-sectional area closer to the controls. Type II fiber cross-sectional area of both plantaris and soleus muscle was 22.45% and 22.58% sl nailer in the HS than in the controls, that of both muschles in the HS-EX was 14.10%, 5.78% greater than HS. Intermittent exercise during hindlimb suspension resulted in Type I, II fiber cross-sectional area closer to the control value. There was no change in SDH activity following 1week of hindlimb suspension or exercise during hindlimb suspension in the plantaris muscle. The results suggest that intermittent low intensity short duration exercise can ameliorate Type II muscular atrophy Induced by hindlimb suspension.

• Journal of Korean Biological Nursing Science
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• v.13 no.1
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• pp.1-7
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• 2011

Purpose: The purpose of this study was to compare the hypertrophic effects of low-intensity exercise on weight, myofibrillar protein content and Type I, II fiber cross-sectional area of hindlimb muscles of rats between every other day exercise and every day exercise. Methods: Adult male Sprague-Dawley rats were assigned to 1 of 3 groups: control group (C, n=6), experimental group 1 (E1, n=7) and experimental group 2 (E2, n=7). Rats in E1 group had 7 sessions (every other day) and those in E2 group had 14 sessions (every day) of exercise in which they ran on a treadmill for 30 min/day at 10 m/min. Results: Muscle weight, cross-sectional area of type I fiber and myofibrillar protein content of soleus and myofibrillar protein content of plantaris in E1 group, and myofibrillar protein content of soleus and cross-sectional area of type I fiber of plantaris in E2 group were greater than those in C group. Cross-sectional area of type I fiber of soleus of E1 group was higher than E2 group while cross-sectional area of type I fiber of plantaris of E2 group was higher than E1 group. Conclusion: Hypertrophy of hindlimb muscles occurs from every other day exercise similar to every day exercise.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4
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• pp.95-106
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• 1992

This paper presents a comparative evaluation of five different types of steel fibers used as reinforcing material in concrete beams. Two types of plain and RC beams were prepared to compare the relative flexural behavior. The fibers used were dog bone (paddled), both ends hooked. コ-type straight. crimped and wavy type with aspect ratio of 43 to 75. Fiber volume fraction of 1 to 2% were used while shear span to depth ratio (aid) and steel ratio p were fixed. Fiber reinforcement effect index Ef and effective toughness index Te were adopted to evaluate fiber reinforcing effects. The effect of fiber reinforcement on flexural strength is higher in plain beams than in RC beams. Hooked and dog bone type fibers were found to be more effective than the other type ones in enhancing the flexural strength and post-peak energy absorption capacity of concrete beams.

• Journal of Electrical Engineering and Technology
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• v.4 no.3
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• pp.405-409
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• 2009

A polarization-independent multiwavelength-switchable fiber filter is proposed based on a polarization beam splitter and fiber coupler, which can function as a polarization-independent transmission or reflection-type interleaving filter. The proposed filter consists of a polarization beam splitter and a Sagnac birefringence loop composed of a 50:50 coupler, high birefringent fibers, and two quarter-wave plates. In the proposed filter, a transmission-type interleaver with a channel isolation > 18 dB or a reflection-type one with a channel isolation of ${\sim}3$ dB, whose channel spacing and switching displacement were 0.8 and 0.4 nm in common, respectively, could be obtained. A channel interleaving operation could be performed by the proper control of waveplates within the Sagnac birefringence loop.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.693-698
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• 2008

For designing intensity modulation type optical microphone, the irradiance distribution which can be applied to inclined-cut geometrical configuration is suggested. The model is important in analysis of response characteristics f3r intensity modulation type optical microphone. To overcome low sensitivity problem in intensity modulation type optical microphone, inclined-cut optical fiber is considered here. Based on optical geometry, the inclined-cut optical fiber sensor is designed and fabricated. The experiments are carried out to evaluate sensor performance.