• Composites Research
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• v.36 no.6
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• pp.402-407
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• 2023

Activated carbon fibers (ACFs) are fibrous form of activated carbon (AC) with higher mechanical strength and flexibility, which make them suitable for building modules for applications including directional gas flow such as air and gas purification. Similarly, ACFs are anticipated to excel in the efficient capture of CO₂. However, due to the difficulties in fabricating monofilament carbon fibers at a laboratory scale, most of the studies regarding ACFs for CO₂ capture have relied on electrospun carbon fibers. In this study, we fabricated monofilament carbon fibers from PAN-based monofilament precursors by stabilization and carbonization. Then, ACFs were successfully prepared by chemical activation using KOH. Different weight ratios ranging from 1:1 to 1:4 were employed in the fabrication of ACFs, and the samples were designated as ACF-1 to ACF-4, respectively. As a function of KOH ratio, increase in surface area could be observed. However, the CO₂ adsorption trend did not follow the surface area trend, and the ACF-3 with second largest surface area exhibited the highest CO₂ adsorption capacity. To understand the phenomena, nitrogen content and ultramicropore distribution, which are important factors determining CO₂ adsorption capacity, were considered. As a result, while nitrogen content could not explain the phenomena, ultramicropore distribution could provide a reasoning that the excessive etching led ACF-4 to develop micropore structure with a broader distribution, resulting in high surface area yet deteriorated CO₂ adsorption.

• Composites Research
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• v.36 no.2
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• pp.126-131
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• 2023

Growing environmental concerns regarding pollution caused by conventional plastics have increased interest in biodegradable polymers as alternative materials. The purpose of this study is to develop a 100% biodegradable nanocomposite material by introducing organic nucleating agents into the biodegradable and thermoplastic resin, poly(lactic acid), to improve its properties. Accordingly, cellulose nanofibers, an eco-friendly material, were adopted as a substitute for inorganic nucleating agents. To achieve a uniform dispersion of cellulose nanofibers (CNFs) within PLA, the aqueous solution of nanofibers was lyophilized to maintain their fibrous shape. Then, they were subjected to primary mixing using a twin-screw extruder. Test specimens with double mixing were then produced by injection molding. Differential scanning calorimetry was employed to confirm the reinforced physical properties, and it was found that the addition of 1 wt% CNFs acted as a reinforcing material and nucleating agent, reducing the cold crystallization temperature by approximately 14℃ and increasing the degree of crystallization. This study provides an environmentally friendly alternative for developing plastic materials with enhanced properties, which can contribute to a sustainable future without consuming inorganic nucleating agents. It serves as a basis for developing 100% biodegradable green nanocomposites.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.21 no.2
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• pp.225-234
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• 1991

This study was designed to investigate the effects of the posterior slope of the articular eminence and the condylar angulation to the posterior slope of the articular eminence on internal derangement of TMJ. The materials consisted of 78 transcranial oblique lateral projections of 31 normal subjects and 47 internal derangement patients. The results were as follows: 1. The posterior slope of the articular eminences in normal group were larger than that in abnormal group, but there were not significant differences between each group about the condylar angulation to the posterior slope of the articular eminences. 2. The differences between in the right and left sides in patients who were affected unilaterally and bilaterally were larger than that in normal groups. 3, In patients affected unilaterally, there were not significant differences between affected joints and unaffected joints about the posterior slope of the articular eminence and the condylar angulation to the posterior slope of the articular eminence. 4. In abnormal group, there were significant differences between each group about condylar angulation to the post, slope of the articular eminence (ant. disk displacement without reduction > fibrous adhesion > ant. disk displacement with reduction), but not about the post, slope of the articular eminence.

• Fire Science and Engineering
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• v.22 no.3
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• pp.208-215
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• 2008

Existent wood wool cement boards are low-quality cement boards made out of wood chip wastes. Recently, however, they are produced by making wood chips into fibrous forms to have good looks and excellent performances in sound absorption and thermal insulation. Though they have been broadly used in the advanced countries, they were rather expensive products with limited use in Korea having no domestic manufacturers of them. Since 2005, however, it has been possible for the boards to be used in various fields due to their lowered prices and stable supplies by the arrival of domestic manufacturers. For the purpose of encouraging broad use of the boards, this research aims to explore their practical applications by way of assessing the flame retardant and fire resistant performances when they are applied to dry-wall system.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.159.2-159.2
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• 2010

Asbestos is the collective name for a group of naturally occurring minerals in their fibrous form and hydrous silicates of magnesium and a mineral fiber that has been used commonly in a variety of building construction materials for insulation and as a fire-retardant. Asbestos has been used for a wide range of manufactured goods, because of its fiber strength and heat resistant properties. Nevertheless harmful of asbestos is quite serious. Exposure to airborne friable asbestos may result in a potential health risk because persons breathing the air may breathe in asbestos fibers. Continued exposure can increase the amount of fibers that remain in the lung. Fibers embedded in lung tissue over time may cause serious lung diseases including asbestosis, lung cancer. In this paper, we carried out as fundamental study for dispose of asbestos cement slate safely and perfectly. Melting Temperature of asbestos need to more than $1,520^{\circ}C$ and specially asbestos cement slate need more energy than that of pure asbestos. We need to decrease melting temperature of asbestos cement slate for economical efficiency. To the purpose, glass and bottom ash were chosen as additives for basicity control. we analyzed about properties of asbestos cements slate, melting characteristics on the additives ratio and temperature. We confirmed about harmlessness of melting slag through analysis of scanning electron microscope(SEM) and x-ray diffractometer(XRD).

• International Journal of Industrial Entomology and Biomaterials
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• v.40 no.1
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• pp.28-32
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• 2020

Recently, many studies have been undertaken on the wet spinning and electrospinning of silk because wet-spun fibers and electrospun webs of silk can be applied in the biomedical and cosmetic fields owing to the good biocompatibility of silk. The rheological properties of silk solution are important because they strongly affect the spinning performance of the silk solution and the structures of resultant fibrous materials. Therefore, as a preliminary study on the effect of solvent composition on the rheological properties of silk fibroin (SF) solution and structure of the resultant film, in the reported work, methanol was added to the SF formic acid solution. A small amount of methanol (i.e. 2%) added to the SF formic acid solution significantly altered the rheological properties of the solution: its shear viscosity increased by 10 folds at low shear and decreased on increasing the shear rate, demonstrating shear thinning behavior of the SF solution. Dynamic tests for the SF solution indicated that the addition of 2% methanol altered the viscous state of the SF formic acid solution to elastic. However, the molecular conformation (i.e. β-sheet conformation) of the regenerated SF film cast from formic acid remained unchanged on the addition of 2% methanol.

• Membrane and Water Treatment
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• v.11 no.3
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• pp.231-235
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• 2020

Industrialization and modern developments have led to an influx of toxic heavy metals into the aquatic environment, and the accumulation of heavy metals has serious adverse effects on humans. Among the various heavy metal treatment methods, adsorption is very useful and frequently used. Plastic materials, such as polypropylene and polyethylene, have been widely used as filter media due to their mechanical and chemical stability. However, the surface of plastic material is inert and therefore the adsorption capability of heavy metals is very limited. In this study, granular media and fiber media composed of polypropylene and polyethylene are used, and the surface modification was conducted in order to increase adsorption capability toward heavy metals. Oxygen plasma generated hydroxyl groups on the surface of the media to activate the surface, and then acrylic acid was synthesized on the surface. The grafted carboxyl group was confirmed by FT-IR and SEM. Heavy metal adsorption capability of pristine and surface modified adsorbents was also evaluated. Overall, heavy metal adsorption capability was increased by surface modification due to electrostatic interaction between the carboxyl groups and heavy metal ions. Fibrous PP/PE showed lower improvement compared to granular PP media because pore blockage occurred by the surface modification step, thereby inhibiting mass transfer.

• Applied Microscopy
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• v.19 no.1
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• pp.59-69
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• 1989

Ultrastructure of the secretory portion of the small ampullate gland in the orb web spider, Nephila clavata, has been investigated using the electron microscope. The secretory portion of this gland comprise two different regions which are a S-shaped storage sac and a long, convoluted tail. By the internal textures of the secretory granules, the sac is subdivided into two regions ; the proximal region near the tail and the distal region near the duct. Commonly single layered connectives cover the basal portion of the sac epithelium, and apical portion of the epithelial cells is occupied by the thick cuticles. Within the epithelial cells of both the proximal and distal region, several types of the secretory granules surrounded by a limiting membrane and had characteristic crystalloid are scattered throughout the cytoplasm. The granular size and its electron densities are not coincide with each other according to the maturation level of the granules. The wall of the tail is composed of single layer of columnar epithelial cells, and their nuclei are found at the basal portion of the cells. Dissimilar to the epithelial cells of the sac, apical cuticles are not found at this portion. In the cytoplasm of these cells, numerous secretory granules, synthesized from the rough endoplasmic reticula commonly and had fine fibrous materials, are found. At the cell surface bordering the lumen, microvilli are seen, arid along the cellular boundaries specialized septate junctions and desmosomes appeared.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.25 no.4
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• pp.350-355
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• 1999

Purpose : The purpose of this study was 1) to find nerve damage after inferior alveolar nerve transposition and 2) to examine whether the soft tissue or bone changes around the nerve produce the compression to the nerve in the healing period. Materials and Method : Inferior alveolar nerve was exposed through the bony window and the scratch was made in the bone to be thought as the inferior alveolar canal. Suture was made after the nerve was repositioned. The nerve and surrounding tissues were examined with the light microscope and the fluorescent microscope before surgery and at 1 month, 3 months, and 5 months after surgery. Results : After surgery, the epineurium was damaged and the nerve was divided to several fascicles covered with the perineurium The newly formed fibrous connective tissue and vessels were seen around fascicles. There was new bone formation. However the nerve was not compressed by the connective tissue or the new bone. Conclusion : The results of this study suggest that neurosensory disturbances after inferior alveolar nerve transposition are resulted by the direct trauma in surgery rather than the compression to the nerve by the scar or new bone formation in the healing period.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.48 no.3
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• pp.14-22
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• 2016

Pulping is a stage that can change fibrous raw materials into pumpable slurry. Recovered paper can be defibrated to individual fibers by shear stress generated by rotation of a rotor and water. Disintegration of recovered paper is more complicated than that of chemical pulp. When disintegration of recovered paper is poor, screening and cleaning efficiency will be worse and properties of paper will also be deteriorated. Therefore, pulping is an important treatment for improvement of availability of recovered paper and process runnability. In this study, degrees of disintegration of KOCC obtained from a linerboard mill was analyzed with a pilot-scale screen. Flake removal of KOCC slurry was performed by a pilot screen. Simple pumping action gave a positive effect on disintegration of KOCC. After pumping for 10 minutes, paper strength increased without the change of water retention value and fibrillation of KOCC slurry. This phenomena can be explained by modification of hornified surface of KOCC fibers by shear stress generated by pumping. Consequently, disintegration efficiency of KOCC can be enhanced by control of retention time at pulper or an agitation power at chests of papermaking process.