• Journal of the Korean Wood Science and Technology
• /
• v.32 no.2
• /
• pp.26-32
• /
• 2004

Chemical compositions and chemical structure of lignin and alkali cooking condition and fiber length of red pepper were investigated and compared to those of woods. The chemical compositions of red pepper were higher component of extraction than that of wood. The contents of carbon and hydrogen of Klason lignin in red pepper were similar to that of pine and birch wood. On the other hand, the contents of oxygen and nitrogen of Klason lignin in the red pepper were higher than that of wood. The result of nitrobenzene oxidation shows that Klason lignin of red pepper was similar to lignin of softwood. The best alkali cooking condition of red pepper was 0.2%-anthraquinone, active alkali of 20% and liquor ratio of 1:7. The fiber length of red pepper was about 0.47 mm. Therefore, the red pepper fiber will be able to use special purpose of short fiber.

• Composites Research
• /
• v.35 no.4
• /
• pp.242-247
• /
• 2022

This study has a different direction from the existing technology of applying recycled carbon fiber obtained by recycling waste CFRP to CFRP again. A study was conducted to utilize recycled carbon fiber as a raw material for manufacturing a carbon/carbon (C/C) composite material comprising carbon as a matrix. First, it was attempted to recycle a commonly used epoxy resin composite material through a thermal decomposition process. By applying the newly proposed oxidation-inert atmosphere conversion technology to the pyrolysis process, the residual carbon rate of 1~2% was improved to 19%. Through this, the possibility of manufacturing C/C composite materials utilizing epoxy resin was confirmed. However, in the case of carbon obtained by the oxidation-inert atmosphere controlled pyrolysis process, the degree of oxygen bonding is high, so further improvement studies are needed. In addition, short-fiber C/C composite material specimens were prepared through the crushing and disintegrating processes after thermal decomposition of waste CFRP, and the optimum process conditions were derived through the evaluation of mechanical properties.

• Journal of the Korea Concrete Institute
• /
• v.22 no.6
• /
• pp.777-786
• /
• 2010

This paper examines the flexural behavior of full-scale prestressed concrete girders that were constructed of steel fiber reinforced ultra high performance concrete (UHPC). This study is designed to provide more information about the bending characteristics of UHPC girders in order to establish a reasonable prediction model for flexural resistance and deflection for future structural design codes. Short steel fibers have been introduced into prestressed concrete T-girders in order to study their effects under flexural loads. Round straight high strength steel fibers were used at volume fraction of 2%. The girders were cast using 150~190 MPa steel fiber reinforced UHPC and were designed to assess the ability of steel fiber reinforced UHPC to carry flexural loads in prestressed girders. The experimental results show that steel fiber reinforced UHPC enhances the cracking behavior and ductility of beams. Moreover, when ultimate failure did occur, the failure of girders composed of steel fiber reinforced UHPC was observed to be precipitated by the pullout of steel fibers that were bridging tension cracks in the concrete. Flexural failure of girders occurred when the UHPC at a particular cross section began to lose tensile capacity due to steel fiber pullout. In addition, it was determined that the level of prestressing force influenced the ultimate load capacity.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.19
• /
• pp.83-99
• /
• 1975

The earliness to flowering was completely dominant over the lateness, and the short plant height and stem length were partially dominant over the tall. The heavy stem weight, however, was recessive to the light. Heritability values for the flowering period, plant height, dry stem weight and fiber ratio were high, while those of days to initial flowering, stem length and fiber weight were low. Flowering period, plant height, stem weight, dry stem weight and fiber ratio were closely related to fiber weight or fiber yield. The selection index estimated jointly the plant height ($X_1$), dry stem weight($X_2$) and fiber weight($X_3$); that is 0.0020$X_1$-0.0047$X_2$-0.0181$X_3$, was the most efficient one for the selection practices. The plant height was the most reliable character for the increased genetic advances and the relative selection efficiences. Effects of locations and genotype-environment interactions were highly significant in most of the characters investigated.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.25 no.4
• /
• pp.261-283
• /
• 2023

This study aimed to review the performance stability of PET (Polyethylene terephthalate) fiber reinforcing materials among the synthetic fiber types for which the application of performance reinforcing materials to fiber-reinforced concrete is being reviewed by examining short-term and long-term performance changes. To this end, the residual performance was analyzed after exposing the PET fiber to an acid/alkali environment, and the flexural strength and equivalent flexural strength of the PET fiber-reinforced concrete mixture by age were analyzed, and the surface of the PET fiber collected from the concrete specimen was examined using a scanning microscope (SEM). The changes in were analyzed. As a result of the acid/alkali environment exposure test of PET fiber, the strength retention rate was 83.4~96.4% in acidic environment and 42.4~97.9% in alkaline environment. It was confirmed that the strength retention rate of the fiber itself significantly decreased when exposed to high-temperature strong alkali conditions, and the strength retention rate increased in the finished yarn coated with epoxy. In the test results of the flexural strength and equivalent flexural strength of the PET fiber-reinforced concrete mixture, no reduction in flexural strength was found, and the equivalent flexural strength result also did not show any degradation in performance as a fiber reinforcement. Even in the SEM analysis results, no surface damage or cross-sectional change of the PET reinforcing fibers was observed. These results mean that no damage or cross-section reduction of PET reinforcing fibers occurs in cement concrete environments even when fiber-reinforced concrete is exposed to high temperatures in the early stage or depending on age, and the strength of PET fibers decreases in cement concrete environments. The impact is judged to be of no concern. As the flexural strength and equivalent flexural strength according to age were also stably expressed, it could be seen that performance degradation due to hydrolysis, which is a concern due to the use of PET fiber reinforcing materials, did not occur, and it was confirmed that stable residual strength retention characteristics were exhibited.

• Proceedings of the Korean Fiber Society Conference
• /
• 2003.10a
• /
• pp.77-78
• /
• 2003

The surface evenness and texture of textile products are closely related with the irregularity of yarn thickness which has an important role to influence the quality and the process efficiency. For measuring yam thickness the capacitive method is known to dominate the market, delivering results that are in a close relation with the mechanical properties of yarn, while the optical method offers information that seems related rather with the apparent quality of yarn. If a thin light beam is applied for the optoelectrical measurement, it is very possible that this method can provide us with important information which is not obtainable from the capacitive type measurement. This paper reports the results of a study about the yarn thickness and its variation on the basis of a new measurement system using a laser slit beam. Analysis of the new system confirms that we can extract new information on the yarn irregularity ranging into much short wavelengths. Even the visual shade created by the yam doubling and twisting can be measured and represented well. Depending on the yam types, the thickness measurements show their own characteristics.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.6 no.4
• /
• pp.108-117
• /
• 1997

A continuum analysis has been performed for the application to the thermo-elasto-plastic behavior in a discontinuous metal matrix composite. an FEM (Finite Element Method) analysis was implemented to obtain the internal field quantities of composite as well as overall composite behavior and an experiment was demonstrated to compare with the numerical simulation . As the procedure, a reasonably optimized FE mesh generation, the appropriate imposition of boundary condition , and the relevant post processing such as elastoplastic thermomchanical analysis were taken into account. For the numerical illustration, an aligned axisymmetric single fiber model with temperature dependent material properties and precipitation hardening effect has been employed to assess field quantities. It was found that the residual stresses are induced substantially by the temperature drop during the thermal treatment and that the FEM results of the vertically and horizontally constrained model give a good agreement with experimental data.with non-woven carbon mat is about 24% higher than that of composite materials without non-woven carbon mat. Transverse tensile strength and torughness also increase by inserting non-woven carbon mat between layers.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
• /
• 2001.06a
• /
• pp.1123-1123
• /
• 2001

In recent years, a miniature spectrometer has been extensively developed due to the marriage of fiber optics and semiconductor detector array. This type of miniature spectrometer has advantages of low price and robustness due to the capability of mass production and no moving parts are required such as lenses, mirrors and scanning monochromator. These systems are ideal for use in teaching labs, process monitoring and field analyses. A portable near infrared (NIR) system has been developed for qualitative and quantitative analysis. This system includes a tungsten halogen lamp for light source, a fiber optics connected a light source, and a sample module to the microspectrometer, The size of spectrometer can be as small as 2.5 cm x 1.5 cm x 0.1 cm. Wavelength ranges can be chosen as 360-800 nm, 800-1100 nm and 1100-1900 nm depending on the type of detector. The software consists of various tools for multivariate analysis and pattern recognition techniques. To evaluate the system, long and short-term stability, wavelength accuracy, and stray light have been investigated and compared with conventional scanning type NIR spectrometer. This developed system can be sufficiently used for quantitative and qualitative analysis for various samples such as agricultural product, herbal medicine, food, petroleum, and pharmaceuticals, etc.

• International Journal of Concrete Structures and Materials
• /
• v.4 no.2
• /
• pp.113-118
• /
• 2010

This article aims to study the effects of adding steel fibers to concrete on the mechanical behavior of steel fiber concrete (SFC) slabs. After formulating the SFC, an experimental work was, first, conducted on $160\;{\times}\;320$ mm cylindrical specimens and $70\;{\times}\;70\;{\times}\;280$ mm prisms. Then, this study was carried out on 20 rectangular $1,100\;{\times}\;1,100\;{\times}\;60$ mm small slabs submitted to a distributed load. Two types of fibers with hooked ends were used: long fibers (LF) of a length of 50 mm and short fibers (SF) of a length of 35 mm. The studied parameters are compressive and tensile strengths and Young's modulus. Plain concrete (PC) small slabs were also prepared to be compared to the SFC specimens. The results showed that the compressive strength of SFC increased up to 25% while the splitting tests showed an improvement of the SFC reaching 45%. Tests on SFC small slabs also showed that a smaller deflection is obtained with respect to PC, which indicates an improvement in strength (up to 100%), in ductility and in resistance to cracking. The LF gives a better improvement in strength than the SF for a 70% $kg/m^3$ of steel proportioning.

• The Research Journal of the Costume Culture
• /
• v.21 no.1
• /
• pp.139-150
• /
• 2013

Fast fashion companies have generated enormous amounts of clothing and large quantities of unsold or short-lived clothing end up in the landfill. As if to counter fast fashion, sustainable fashion has arisen for environmentally friendly garments at different levels from the fiber stage to production stage. However it is still fraught with uncertainty of systems in the industry. Therefore, this study proposed a system to create re-valued clothing from recycled garments for retailers. The target companies are large-sized retailers like Levi's, Polo, Gap, or J-Crew which are consistently producing basic items such as Levi's 501 or Classic Polo shirts with middle-prices. At the material stage, this study recommended additional requirements of designing a garment with a long life cycle based on criteria of an ideal garment developed by Patagonia clothing company. Then, this study explored innovative ways that retailers might connect with consumers to allow direct interaction between them in terms of the process of collecting used clothes. Using recycled clothing as a source material, this study strove to offer a process of redesign where the concept of 'waste to fashion' is developed as reconstructions where old forms are transformed into new ones.