• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7B
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• pp.1220-1228
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• 1999

In this paper, we deal with an important network design problem in providing multimedia telecommunication services. The problem is to find an optimal gateway location and fiber routing, while minimizing the total cost. The cost elements are the installation cost of add-drop multiplexer and fiber cables. We have developed effective heuristic procedures for the problem. The performance of the developed heuristic shows promising computational results.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.209-209
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• 2006

Ultra-fine fibers are spun by expensive fiber spinning technology using special spinnerets. Ultra-fine fibrous materials have attracted considerable attentions because of their potential applications as high performance wiping cloths, water absorbent sound proofing materials and moisture transfer sporting good. However, production expense of ultra-fine fibers is 5 to 7 times higher than general textile materials. The objective of this research is to develop cost-effective recycling process to produce multi-functional ultra-fine fibrous material in terms of the development of garnetting and carding machines for ultra-fine fibrous material waste and scrap. The efficiency of sound absorption for the recycled polyester nonwoven increased with decreasing length and thickness of component fibers, which was attributed to the reduction of air permeability. It is expected that high value and cost-effective textile products are developed using ultra-fine fibrous wastes and that sound proofing material and oil absorbent f

• The Journal of Natural Sciences
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• v.9 no.1
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• pp.169-175
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• 1997

In this study, it was investigated about dyeability, light-fastness, wash-fastness and tensile strength in PET fiber using the effective carrier solvent such as benzyl alcohol, benzaldehyde and acetophenone. As a results, dyeability in mixed solvent was better than that of single solvent. And dyeability in mixed solvents of benzyl aldehyde and acetophenone was of them. But effective carrier action was resulted in decrease of properties such as light-fastness and tensile strength of PET fiber after dyeing.

• Current Optics and Photonics
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• v.1 no.6
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• pp.567-572
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• 2017

A novel slotted-core hexagonal photonic crystal fiber (PCF) for terahertz (THz) wave guiding is proposed in this paper. A trade-off managed between effective material loss (EML) and birefringence for efficient guidance of THz waves is illustrated in this article. The rectangular slot shaped air-holes break the symmetry of the porous-core which offers ultra-high birefringence of $8.8{\times}10^{-2}$. The proposed structure offers low bending loss of $1.07{\times}10^{-34}cm^{-1}$ and extremely low effective material loss (EML) of $0.035cm^{-1}$ at an operating frequency of 1.0 THz. In addition other guiding properties such as power fraction, dispersion and confinement loss are also discussed. The proposed THz waveguide can be effectively used for convenient transmission of THz waves.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.4
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• pp.515-523
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• 2003

Shape memory is physical phenomenon which a platically metal is restored to its original shape by a solid state phase change by heating. TiNi alloy the most effective material in the shape memory alloy(SMA). To study(measure) recovery stress of intelligent composite. Ti50-Ni50 shape memory matrix with prestrain SMA fiber. When SMA fiber of the intelligent composite is heated over austenite starting temperature(As) by electric heating. a recovery stress are generated. The recovery stress of the intelligent composite was measured by strain gage or photoelastic experiment. Measuring method of recovery stress by photoelastic experiment was developed in this research. It was certified that photoelastic experiment was more effective and more precise than strain gage method in the measurement of recovery stress.

• Advanced Composite Materials
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• v.16 no.2
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• pp.135-149
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• 2007

In the automobile industry, structural health monitoring of fiber reinforced polymer composite parts is a widespread need for maintenance before breakdown of the functional elements or a complete vehicle. High performance sensors are generally used in many of the structural health monitoring operations. Within this study, a carbon fiber sewing thread has been used as a low cost laminate failure sensing element. The experimentation plan was set up according to the electrical conductance and flexibility of carbon fiber threads, advantages of preforming operations, and sewing mechanisms. The influence of the single thread damages by changing the electrical resistance and monitoring the impact location by using carbon thread sensors has been performed. Innovative utilization of relatively cost-effective carbon threads for monitoring the delamination of metallic inserts from the basic composite laminate structure is a highlighting feature of this study.

• Environmental Engineering Research
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• v.24 no.2
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• pp.347-353
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• 2019

Although membrane distillation (MD) has great promise for desalination of saline water sources, it is crucial to improve its thermal efficiency to reduce the operating cost. Accordingly, this study intended to examine the thermal energy efficiency of MD modules in a pilot scale system. Two different modules of hollow fiber membranes were compared in direct contact MD mode. One of them was made of polypropylene with the effective membrane area of $2.6m^2$ and the other was made of polyvinylidene fluoride with the effective membrane area of $7.6m^2$. The influence of operation parameters, including the temperatures of feed and distillate, feed flow rate, and distillate flow rate on the flux, recovery, and performance ratio (PR), was investigated. Results showed that the two MD membranes showed different flux and PR values even under similar conditions. Moreover, both flow rate and temperature difference between feed and distillate significantly affect the PR values. These results suggest that the operating conditions for MD should be determined by considering the module properties.

• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.876-879
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• 2004

The buried fiber optic cable as a distributed intrusion sensor for detecting and locating intruders along the long perimeters is proposed. Phase changes resulting from either the pressure of the intruder on the ground immediately above the buried fiber or from seismic disturbances in the vicinity are sensed by a phase-sensitive optical time-domain reflectometer. Light pulses from a Er:fiber cw laser with a narrow, <3kHz-range, spectral width and a frequency drift of < 1 MHz/min are injected into one end of the fiber, and the backscattered light from the fiber is monitored with a photodetector. Results of preliminary studies, measurement of phase changes produced by pressure and seismic disturbances in buried fiber optic cables and simulation of ${\varphi}-OTDR$ response over long fiber paths, to establish the feasibility of the concept are described. The field experiments indicate adequate phase changes, more than 1t-rad, are produced by intruders on foot and vehicle for burial depths in the 0.2 m to 1 m range in sand, clay and fine gravel soils. The simulations predict a range of 10 km with 35 m range resolution and 30 km with 90 m range resolution. This technology could in a cost-effective manner provide enhanced perimeter security.

• Journal of the Korean Society of Food Science and Nutrition
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• v.27 no.6
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• pp.1211-1216
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• 1998

The study was conducted to investigate the effect of cholesterol and fiber on serum lipid metabolism in rats. Male Sprague Dawley rats were administrated 1% cholesterol and 0.25% sodium cholate to induce hypercholesterolemia and were fed on diet containing three concentrations(0%, 5%, 10%) of cellulose and pectin, respectively. The rats were sacrified after 5 weeks of feeding periods. Serum triglyceride concentration was significantly decreased in proportion to level of fiber. Phospholipid concentration was more decreased in 10% fiber groups than 5% fiber groups but did not show any difference by fiber types. Free cholesterol and cholesteryl ester concentrations in serum were significantly decreased by fiber supplement and pectin was more effective than cellulose in cholesterol lowering effect. Whereas HDL cholesterol concentration and HDL C/TC were increased in proportion to level of fiber and the effect of pectin was not more significant than that of cellulose. Serum chylomicron cholesterol concentration also showed significant decrease by pectin supplement and LDL , VLDL cholesterol concentrations were more significantly decreased in 10% fiber groups than those of 5% fiber groups. The results indicate that 10% pectin may have beneficial roles in hypercholesterolemia.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.43 no.5
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• pp.27-33
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• 2011

Hemp bast pulp cooked at temperature below $100^{\circ}C$ followed by defibration by the knife and the valley beater, respectively was mixed with softwood pulp varying the amount of hemp pulp in order to find the optimum condition for making hemp-wood paper. Both the knife and the valley beaters contributed to the dispersion of pulp fiber well. Lots of shives were found when the knife beater was applied exclusively, but the fibers were dispersed well when freeness dropped to 600 mL CSF and 500 mL CSF by the valley beater. Air resistance decreased drastically below 500 mL CSF where rapid disrupture of pulp fiber occurred. As the values for freeness and hemp fiber content increased, so did roughness and bulk. It was apparent that the tear strength of hemp-wood paper was on the rise drastically as hemp fiber content increased. Nevertheless the optimum hemp fiber content of hemp-wood paper would be 20% considering the decrease in both tensile and burst strengths as well as sheet formation.