• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 1998년도 가을 학술발표회논문집
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• pp.402-405
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• 1998

Among the production technologies of nonwoven fabrics, a needle punching technique has one of the long history aid holds still important place. At the present time, it is used not only for scrimming with woven or knitted fabrics and other nonwoven fabrics, but also for applying the special fibers blending nonwovens at the web forming process in ender to manufacture economical and high value added-Products such as home furnishing industrial and technical purpose. (omitted)

• 한국군사과학기술학회지
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• 제12권5호
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• pp.667-675
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• 2009

Faults can be generated at electric power systems by variety of both certain and uncertain reasons, which may cause harmful effects on electrical apparatuses under operation and stability of electric power system operations, and may also lead to great confusions and inconveniences to individual livings, public works, industrial activities, services, military affairs, etc.. In some cases, intentional inductions of faults are committed for specific purposes, and it is necessary to understand the procedures of fault by some foreign materials. In this paper, compositions and operations of electric power systems, summaries of electrical fault phenomena and fault protection, and restrictions to power system operation were outlined. And the analogies on the procedure of faults from former papers were introduced, and test results that revealed the validity of those analogies were also introduced.

• 한국주조공학회지
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• 제9권5호
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• pp.396-402
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• 1989

Metal fibers of Al and stainless steel were fabricated by the PDME method and the Taylor process. Tensile strength of metal fiber produced by both the PDME method and the Taylor process was much higher than that of conventionally solidified materials. Utilizing the PDME method, Al fiber with $100\;{\mu}m$ was fabricated under Ar gas atmosphere, and stainless steel fiber with $50\;{\mu}m$ was fabricated under 0.06 Torr vacuum. Continuous fiber of stainless steel was made by the Taylor process and the surface of this fiber was smother than that fabricated by the PDME method.

• Nuclear Engineering and Technology
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• 제55권3호
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• pp.1009-1014
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• 2023

Muon tomography is a useful method for monitoring special nuclear materials (SNMs) such as spent nuclear fuel inside dry cask storage. Multiple Coulomb scattering of muons can be used to provide information about the 3-dimensional structure and atomic number(Z) of the inner materials. Tomography using muons is less affected by the shielding material and less harmful to health than other measurement methods. We developed a muon detector for muon tomography, which consists of a plastic scintillator, 64 long wavelength-shifting (WLS) fibers attached to the top of the plastic scintillator, and silicon photomultipliers (SiPMs) connected to both ends of each WLS fiber. The muon detector can acquire X and Y positions simultaneously using a position determination algorithm. The design parameters of the muon detector were optimized using DETECT2000 and Geant4 simulations, and a muon detector prototype was built based on the results. Spatial resolution measurement was performed using simulations and experiments to evaluate the feasibility of the muon detector. The experimental results were in good agreement with the simulation results. The muon detector has been confirmed for use in a muon tomography system.

• Current Optics and Photonics
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• 제6권2호
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• pp.143-150
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• 2022

Anti-resonant hollow-core photonic crystal fiber (AR-HCF) has unique advantages, such as low nonlinearity and high damage threshold, which make it a promising candidate for high-power laser delivery at distances of tens of meters. However, due to the special structure, optical properties such as mode-field profile and bending loss of hollow-core fibers are different from those of solid-core fibers. These differences have limited the widespread use of AR-HCF in practice. In this paper we conduct numerical analysis of AR-HCFs with different structural parameters, to analyze their influences on an AR-HCF's optical properties. The simulation results show that with a 23-㎛ air-core diameter, the fundamental mode profile of an AR-HCF can well match that of the widely used Nufern's 20/400 fiber, for nearly-single-mode power delivery applications. Moreover, with the ratio of cladding capillary diameter to air-core diameter ranging from 0.6 to 0.7, the AR-HCF shows excellent optical characteristics, including low bending sensitivity while maintaining single-mode transmission at the same time. We believe these results lay the foundation for the application of AR-HCFs in the power delivery of high power fiber laser systems.

• Advances in concrete construction
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• 제15권3호
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• pp.161-170
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• 2023

Ultra-high-performance concrete (UHPC) is produced using high amount of cementitious materials, very low water/cementitious materials ratio, fine-sized fillers, and steel fibers. Due to the dense microstructure of UHPC, it possesses very high strength, elasticity, and durability. Besides that, the UHPC exhibits high ductility and fracture toughness due to presence of fibers in its matrix. While the high ductility of UHPC allows it to undergo high strain/deflection before failure, the high fracture toughness of UHPC greatly enhances its capacity to absorb impact energy without allowing the formation of severe cracking or penetration by the impactor. These advantages with UHPC make it a suitable material for construction of the structural members subjected to special loading conditions. In this research work, the UHPC mixtures having three different dosages of steel fibers (2%, 4% and 6% by weight corresponding to 0.67%, 1.33% and 2% by volume) were characterized in terms of their mechanical properties including facture toughness, before using these concrete mixtures for casting the slab specimens, which were tested under high-energy impact loading with the help of a drop-weight impact test setup. The effect of fiber content on the impact energy absorption capacity and central deflection of the slab specimens were investigated and the equations correlating fiber content with the energy absorption capacity and central deflection were obtained with high degrees of fit. Finite element modeling (FEM) was performed to simulate the behavior of the slabs under impact loading. The FEM results were found to be in good agreement with their corresponding experimentally generated results.

• 한국산업보건학회지
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• 제33권3호
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• pp.273-279
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• 2023

Objectives: Objectives of this study were: 1) to introduce industrial situation and health hazards of synthetic fiber, 2) to review a case of chronic obstructive pulmonary disease in a worker exposed to synthetic fiber reported to the Korea Occupational Disease Surveillance Center, and 3) to suggest supplementary measures for the occupational health system for workers exposed to synthetic fibers. Methods: Respiratory exposure, health hazards, and exposure standards for synthetic fiber dust in Korea and other countries were reviewed. In addition, a case of chronic obstructive pulmonary disease due to exposure to nylon dust reported to the Korea Occupational Disease Surveillance Center was reviewed and summarized. Results: The worker was a 53-year-old non-smoking male who had been involved in the nylon weaving process for 26 years. He had shortness of breath from three years ago. He was diagnosed with chronic obstructive pulmonary disease. PM1.0, PM_2.5, and PM10 were measured at 26.6 ㎍/m³, 48.2 ㎍/m³, and 91.7 ㎍/m³, respectively. Fiber components estimated as nylon fiber were detected in the microscopic examination of a solid sample. Conclusions: For workers exposed to synthetic fiber dust, special health examinations of the respiratory system, regular work environment measurement, and work environment management through workplace health management should be performed. It is necessary to research on health effects of synthetic fibers.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.660-665
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• 1993

An elastic model is developed to predict the average thermal residual stresses in the matrix and fiber of a misoriented short fiber composite. The thermal residual stresses are induced by the mismatch in the coefficient of the thermal expansion of the matrix and fiber when the composite is subjected to a uniform temperature change. The model considers two special cases of fiber misorientation ; two-dimensional in-plane and three-dimensional axisymmetric. The analytical formulation of the model is based on Eshelby's equivalent inclusion method and is nuque in that it is able to account for interactions among fibers. The model is more general than past models and it is able to treat prior analyses of the simpler composite systems as extram cases. The present model is to investigate the effects of fiber volume fraction, distribution type, distribution cut-off angle, and aspect ratio on thermal residual stress for both in-plane and axisymmetric fiber misorientation. Fiber volum fraction, aspect ratio, and disturbution cut-off angle are shown to have more significant effects on the magnitude of the thermal residual stress than fiber distrubution type for both in-plane and axisymmetric misorientation.

• 대한의용생체공학회:의공학회지
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• 제10권3호
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• pp.229-236
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• 1989

This paper describes an idea of design and construction for a radial pulse wave detector, In acquiring arterial pulse signal noninvasively, a new combinational fiber-optic transducer was used which has a detecting part and a sensing part. The mechanism of detecting part is composed of special form of structure that can detect changing pulses in contact with skin, and transmits arterial wall movements to the sensing part. It consists of elastic reflector and optical fibers, which are arranged in a fiber pair. Then, the intensity of the reflected light will be proportional to the displacement changed by inclined reflector. Using this transducer, it expected to make a clinically useful tool for arterial pulse wave diagnosis, especially on the application of "MACK- CHIN" in the field of Korean traditional medicine, since : his transducer has a simple structure and has an easy and clear signal acquisition method.on method.

• Fibers and Polymers
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• 제4권1호
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• pp.32-37
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• 2003

The nonionic surfactant properties of ethoxylated azo dyes, such ai cloud point and surface tension have been investigated. The synthesized ethoxylated azo dyes could dye polyester fabric without any special pre-treatment. When the average number of ethylene oxide (EO) in the ethoxylated azo dye reached 6, its fixation could exceed $90^{\circ}C$ from the thermosol dyeing process. The average degree of condensation of ethylene glycol in the chain was interrelated with the dyeing results and did not affect on the maximum absorption wavelength (λmax) of the polyoxyethylene dye. When the average length of polyoxyethylene chain decreased, the molecular weight of dyes became smaller and the fixation of dyes was improved.