• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.30 no.2
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• pp.13-23
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• 1998

Two major cellulase components purified with sephadex G-75 and DEAE sepharose were applied to bleached kraft pulp to inverstigate the change of fiber properties. Cellulose viscosity was very sensitive to $C_x$ component treatment (more than 15% drop was observed) while being little influenced by $C_1$, component (only 2% drop). Fiber fraction longer than 2mm was reduced by $C_x$ treatment while short fiber fraction was increased greatly by more than 15%. There was little change in fiber length distribution by combined treatment of $C_1$ 1 and $C_x$ at equal. In this case, fine contents increased by more than 2.5% at equivalent refining time. WRV and Density were increased as the amount of $C_1$ or $C_x$ treatment was increased. $C_{x}$ was main cause for increasing them. But the effect fell as enzyme dosage.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.30-31
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• 2016

As the treatments of many kinds of explosive objects increase recently, it is in the trend that explosion accidents increase. Thus, many studies on HPFRCC (High-performance Fiber-reinforced Cement Composites) whose ductility is enhanced are being conducted actively in order to minimize the damages from explosion accidents. However, HPFRCC, the self-shrinkage of HPFRCC is on the rise as a problem since it becomes ultra-high strengthened by using low W/B. Thus, in this study, it is intended to evaluate the capacity for reducing the self-shrinkage of HPFRCC depending on some changes of ERCO(Emulsified Refined Cooking Oil) replacement ratio and the fiber replacement ratio between some short steel fibers (SS) and some long organic fibers (OL). As a result, it was found that some excellent effects are exerted since the self-shrinkage was reduced a lot as the ERCO replacement ratio increases and the fiber replacement ratio of SS rather than OL increases.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.8 no.4
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• pp.164-171
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• 1983

In this paper, angular division multiplexing of the optical multiplexing technique for transmitting several channels using a relatively short step-index fiber is described. Mode coupling and the output power distributionin the fiber for the plane wave excitations is calculated and the crosstalk level determination of the system is proposed. In the presence of the mode coupling, the pulse width in terms of the fiber's length and input condition is calculated in the slab waveguide and the fiber. For the input angles (

• Journal of the Optical Society of Korea
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• v.12 no.3
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• pp.126-130
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• 2008

We propose and experimentally demonstrate an effective method to reduce near-field speckle noise at the output of a 50 ${\mu}m$ graded index multimode fiber using a short cylindrical piezoelectric transducer(PZT) vibrating in the radial direction. The fiber was coiled as tightly as possible around the mandrel of the PZT and a periodic stretching effect was caused by the radial oscillations of the actuator. The output of the optical fiber using the He-Ne laser source was intensively observed by a CCD camera. By counting all the pixels corresponding to relative intensity graded into 256 levels in the selected area and by calculating standard deviation and mean value of the intensity, we could measure the speckle contrast and vibration effect quantitatively with reduction ratio of pixels and line profile of the illuminated region. It was clearly observed that the characteristics of the speckle pattern in the vibration-on state were significantly improved over that of the vibration-off state due to time-averaged smoothing.

• Korean Journal of Materials Research
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• v.31 no.11
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• pp.626-634
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• 2021

Cu matrix composites reinforced with chopped carbon fiber (CF), which is cost effective and can be well dispersed, are fabricated using electroless plating and hot pressing, and the effects of content and alignment of CF on the thermal properties of CF/Cu composites are studied. Thermal conductivity of CF/Cu composite increases with CF content in the in-plane direction, but it decreases above 10% CF; this is due to reduction of thermal diffusivity related with phonon scattering by agglomeration of CF. The coefficient of thermal expansion decreases in the in-plane direction and increases in the through-plane direction as the CF content increases. This is because the coefficient of thermal expansion of the long axis of CF is smaller than that of the Cu matrix, and the coefficient of thermal expansion of its short axis is larger than that of the Cu matrix. The thermal conductivity is greatly influenced by the agglomeration of CF in the CF/Cu composite, whereas the coefficient of thermal expansion is more influenced by the alignment of CF than the aggregation of CF.

• Resources Recycling
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• v.24 no.3
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• pp.66-75
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• 2015

The flexural performance of amorphous steel fibers having environmental and economy benefits due to relatively short manufacturing process were evaluated as well as that of hooked steel fibers by varing fiber length and volume fraction. Fiber lengths were 10 mm, 20 mm, 30 mm and fiber volume fractions were varied from 0.3% to 1.2%. Test results with flexural performance showed that mixing design needs to be careful because of relatively high volume of amorphous steel fiber compared to hooked steel fibers. High flexural strength was obtained from both longer fiber length and higher volume fraction. Residual strength and toughness of amorphous steel fiber were similar to that of hooked steel fiber, even though rapid dropping of applied load right after concrete matrix breaking. It can be judged that relatively high ability of energy dissipation around first cracking area relatively overcome rapid dropping of loading.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.04a
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• pp.471-478
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• 2004

The behavior of stocky concrete-filled glass fiber reinforced polymer(GFRP) tubes was studied experimentally and analytically The behavior is focused on the confining action of GRFP tube against concrete. In the experimental work, extensive tensile tests for GFRP tubes which have various fiber lay-out were conducted. And, also short length concrete filled GFRP tubes which have various tube thickness, diameter, and length were tested. In the analytical work, equations to describe the compressive stresses and strains at failure, as well as the entire stress-strain curve of the GFRP tubes were developed. A comparison between the experimental results and those of analytical results indicate that the proposed model provides satisfactory predictions for the compressive strengths, strains at failure, and stress-strain responses.

• The Journal of the Acoustical Society of Korea
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• v.21 no.1E
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• pp.25-30
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• 2002

We report on the development of a fiber optic hydrophone consists of a sensing Michelson interferometer and a compensating Mach-Zehnder interferometer for optical path length compensation. The double interferometer configuration has the following advantages: the hydrophone can be made more small; a laser source with a relatively short coherence length can be used; and the compensating interferometer can be located near the signal processing electronics, far away from the sensing interferometer and noise introduced by reference arm can be greatly reduced. The performance of the hydrophone is evaluated experimentally by immersing the sensing interferometer in a water tank to detect underwater acoustic signals generated by an acoustic wave projector. Experimental results show that over the frequency range of 1 to 4 kHz, the hydrophone has an almost flat response with an average normalized sensitivity of -302 dB re 1/ μ Pa.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.981-982
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• 1998

We fabricated sampled fiber grating by double-exposure method. First, a short-period grating was written into the hydrogen-loaded single mode fiber and then the refractive index was modulated over it by an amplitude mask. It was observed that several transmission dips appear due to the index modulation. The thermal and strain responses were measured over $40-180^{\circ}C$ and $0-1800\mu\varepsilon,$ respectively. The dips have the same and linear sensitivity to both physical quantities over the range of measurement.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.04a
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• pp.65-72
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• 1993

Steel fiber reinforced concrete(SFRC) which is made by short, randomly distributed steel fibers in concrete is superior in its tensile mechanical properties to plain concrete in enhancement of tensile strength and tensile ductility. These improvements are attributed to crack arresting mechanism and formation of longer crack paths due to fibers , which as a consequence lead to increase in energy absorption capacity of SFRC. In the post-peak region under tensile stresses, major macrocrack forms at critical section. The opening of this macrocrack is mainly resisted by both of the fiber pull-out bridging the cracked surfaces and the resistance by matrix softening. In this study, micromechaincal approach has been made in order to simulate tensile behavior of SFRC and based on which the theoretical model is presented. This model reflects the features of both the composite material concept and the spacing concept in predicting tensile strength of SFRC. The model also takes into account for the effects of matrix tensile softening and fiber bridging by pull-out on the resistance for the post-peak behavior of SFRC. It has been shown that the developed model satisfactory predicts the experimental results.