• Environmental Engineering Research
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• v.25 no.3
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• pp.439-445
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• 2020

In the estimation of the aerosol single fiber efficiency using fibrous filters, there is a size range, where the particles penetrate most effectively through the fibrous collectors, and corresponding minimum single fiber efficiency. For small particles in which the diffusion mechanism is dominant, the Cunningham slip correction factor (C_c) affects the single fiber efficiency and the most penetrating particle size (MPPS). Therefore, for accurate estimation, C_c is essential to be considered. However, many previous studies have neglected this factor because of its complexity and the associated difficulty in deriving the appropriate parameterization particularly for the MPPS. In this study, the expression for the MPPS, and the corresponding expression for the minimum single fiber efficiency are analytically derived, and the effects of C_c are determined. In order to accommodate the slip factor for all particle-size ranges, C_c is simplified and modified. Overall, the obtained analytical expression for the MPPS is in a good agreement with the exact solution.

• Korean Journal of Materials Research
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• v.32 no.2
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• pp.107-113
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• 2022

Fibrous supercapacitors (FSs), owing to their high power density, good safety characteristic, and high flexibility, have recently been in the spotlight as energy storage devices for wearable electronics. However, despite these advantages, FCs face many challenges related to their active material of carbon fiber (CF). CF has low surface area and poor wettability between electrode and electrolyte, which result in low capacitance and poor long-term stability at high current densities. To overcome these limits, fibrous supercapacitors made using surface-activated CF (FS-SACF) are here suggested; these materials have improved specific surface area and better wettability, obtained by introducing porous structure and oxygen-containing functional groups on the CF surface, respectively, through surface engineering. The FS-SACF shows an improved ion diffusion coefficient and better electrochemical performance, including high specific capacity of 223.6 mF cm^-2 at current density of 10 ㎂ cm^-2, high-rate performance of 171.2 mF cm^-2 at current density of 50.0 ㎂ cm^-2, and remarkable, ultrafast cycling stability (96.2 % after 1,000 cycles at current density of 250.0 ㎂ cm^-2). The excellent electrochemical performance is definitely due to the effects of surface functionalization on CF, leading to improved specific surface area and superior ion diffusion capability.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.311-318
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• 1995

Increases in strength and ductilities of steel fiber reinforced concrete(SFRC) under direct tension and compression result in improvements of flexural behavior of reinforced steel fibrous concrete beam(RSFCB) Use of hooked steel fibers in stead of round steel fibers enhances futher the structural porperties of a beam due to their greater mechanical bond resistance compared to that of round steel fibers. Flexural strength, initial stiffness ductility and failure mechani는 of RSFCB are dependent upon material and structural parameters and among which are the volume fraction of fibers, reinforcement ratio, and casting depth of SFRC in a beam section. The flexural behavior of RSFCB's are examined experimentally in this study and some conclusions are made regarding those effects of main material and structural parameters on the overall behavior of RSFCB.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.397-401
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• 2008

The nanoparticle-agglomerates are synthesized by laser ablation, which have the morphology of dendrite structure. The filtration performance of a conventional micron-fibrous metal filter was improved by adhering nanoparticle-agglomerates onto the filter surface. The Sintered-Nanoparticle-Agglomerates-adhered Filter (SNAF) adhered with nanostructured material was made by heat treatment after deposition of nanoparticle-agglomerates sintered in aerosol phase onto the micron-fibrous metal filter. As the sintering temperature increases, the pressure drop of the filter increases a little but the filtration efficiency increases remarkably. This is due to increase of surface area of nanoparticle-agglomerates adhered onto the micron-fibrous metal filter.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.601-608
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• 2000

Steel fiber and Polymer are used widely for the reinforcement material of RC structures because of its excellence of durability, serviceability as well as mechanical properties. Polymer-Steel fibrous high strength concrete beam's input ratio are 1.0%. The shear span-to-depth ratio are 1.5, 2.8 and 3.6, compressive strength of specimens 320kg/㎠, 436kgf/㎠ and 520kgf/㎠ in 28 days. The static test was carried out to measure the ultimate load, the initial load of flexural crack and of diagonal crack, from which crack patte군 and fracture modes are earned. Also, stress-strain, load-strain and load-deflection are examined during the test cracks(shear crack, flexural crack, and diagonal tension crack), when the load values are sketched according to the growth of crack. Result are as follows; (1) The failure modes of the specimens increase in rigidity and durability in accordance with the increase of mixing steel fiber and polymer. (2) The load of initial crack was the same as the theory of shear-crack strength (3) Polymer-Steel fibrous high strength concrete beams have increased the deflection and strain at failure load, improving the brittleness of the high strength concrete. (4) In this result of study, an additional study need to make a need formular because the study is different from ACI formular and Zsutty formular.

• Journal of Powder Materials
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• v.26 no.5
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• pp.383-388
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• 2019

To improve the mechanical properties of aluminum, graphene has been used as a reinforcing material, yielding graphene-reinforced aluminum matrix composites (GRAMCs). Dispersion of graphene materials is an important factor that affects the properties of GRAMCs, which are mainly manufactured by mechanical mixing methods such as ball milling. However, the use of only mechanical mixing process is limited to achieve homogeneous dispersion of graphene. To overcome this problem, in this study, we have prepared composite materials by coating aluminum particles with graphene by a self-assembly reaction using poly vinylalcohol and ethylene diamine as coupling agents. The scanning electron microscopy and Fourier-transform infrared spectroscopy results confirm the coating of graphene on the Al surface. Bulk density of the sintered composites by spark plasma sintering achieved a relative density of over 99% up to 0.5 wt.% graphene oxide content.

• Applied Chemistry for Engineering
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• v.8 no.3
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• pp.410-415
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• 1997

Fibrious potassium hexatitanate whisker was produced from the calcination process using a mixture of the natural rutile ore and industrial $K_2CO_3$. Fibrous Potassium titanate was prepared by the following procedures the starting material consisting of $K_2O{\cdot}4.4TiO_2$ was calcined at $1050^{\circ}C$ for 3 hrs. The calcined products obtained under the above condition consisted mainly of potassium hexatitanate with a small admixture of potassium dititanate and potassium tetratitanate. Therefore the single phase of potassium hexatitanate was obtained by heat treatment of $850^{\circ}C$, 3 hrs.

• Korean Journal of Materials Research
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• v.27 no.3
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• pp.132-136
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• 2017

We synthesized potassium hexatitanate, ($K_2Ti_6O_{13}$, PT6), with a non-fibrous shape, by acid leaching and subsequent thermal treatment of potassium tetratitanate ($K_2Ti_4O_9$, PT4), with layered crystal structure. By controlling nucleation and growth of PT4 crystals, we obtained splinter-type crystals of PT6 with increased width and reduced thickness. The optimal holding temperature for the layered PT4 was found to be ${\sim}920^{\circ}C$. The length and width of the PT4 crystals were increased when the nucleation and growth time were increased. After a proton exchange reaction using aqueous 0.3 M HCl solution, and subsequent heat treatment at $850^{\circ}C$, the PT4 crystal transformed into splinter-type PT6 crystals. The frictional characteristics of the friction materials show that as the particle size of PT6 increases, the coefficient of friction (COF) and wear amounts of both the friction materials and counter disc increase.

• Journal of International Society for Simulation Surgery
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• v.3 no.1
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• pp.36-38
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• 2016

Fibrous dysplasia is a relatively rare disease but the management would be quite challenging. Because this is not a malignant tumor, the preservation of the facial contour and the various functions seems to be important in treatment planning. Until now the facial bone reconstruction with autogenous bone would be the standard. Although the autogenous bone would be the ideal one for facial bone reconstruction, donor site morbidity would be the inevitable problem in many cases. Meanwhile, various types of allogenic and alloplastic materials have been also used. However, facial bone reconstruction with many alloplastic material have produced no less complications including infection, exposure, and delayed wound healing. Because the 3D printing technique evolved so fast that 3D printed titanium implant were possible recently. The aim of this trial is to try to restore the original maxillary anatomy as possible using the 3D printing model, based on the mirrored three dimensional CT images based on the computer simulation. Preoperative computed tomography (CT) data were processed for the patient and a rapid prototyping (RP) model was produced. At the same time, the uninjured side was mirrored and superimposed onto the traumatized side, to create a mirror-image of the RP model. And we molded Titanium mesh to reconstruct three-dimensional maxillary structure during the operation. This prefabricated Titanium-mesh implant was then inserted onto the defected maxilla and fixed. Three dimensional printing technique of titanium material based on the computer simulation turned out to be successful in this patient. Individualized approach for each patient could be an ideal way to restore the facial bone.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.7
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• pp.562-568
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• 2014

This study aimed to identify changes in the physical properties of artificial mineral-fiber materials used as building insulation that had been installed in the outer walls of buildings for a long time. To achieve this goal, glass fiber and rock wool were collected from outer walls in actual buildings and their acoustic and thermal performances were measured. These were compared with measurements from similar products manufactured recently. The results showed that old, used samples had a lower sound absorption coefficient compared to recently manufactured materials. The old samples also displayed increased compressibility compared to new materials. For example, the compressibility difference for glass wool was 7.32 mm. Old samples had a dynamic stiffness $1.28MN/m^3$ higher than new material samples. The thermal conductivity of both old and new samples increased within creasing temperature. They showed similar results at temperatures between 0 and $20^{\circ}C$.