• Journal of the Korea Organic Resources Recycling Association
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• v.3 no.2
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• pp.37-45
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• 1995

The performance and the operational problems of UASB(Upflow Anaerobic Sludge Blanket) reactor for treatment of dairy wastewaters were investigated. Synthetic milk wastewater was successfully treated up to the loading rate of 3.9kg $COD/m^3.day$, with a specific gas production rate of 1. 23 I/I. day and a COD removal efficiency of over 90%. However, the sludge rising was observed at the loading rate of 2.1kg $COD/m^3.day$, due probably to the formation of scum layer at the surface of settling compartment. The BMP(biochemical methane potential) of raw milk wastewater and ice cream wastewater, measured by using SBT(serum bottle test), were 0.135 and 0.66ml $CH_4/mg\;COD_{added}$, respectively. The sludge activity increased more than 8 times from 0.159g $COD-CH_4/g$ VSS. d during 90 days of operation.

• Journal of the Mineralogical Society of Korea
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• v.29 no.2
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• pp.35-45
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• 2016

Clays, which are abundant in nature and eco-friendly, have been utilized throughout human history due to their characteristic physicochemical properties. Recently, a variety of clays such as montmorillonite, kaolinite, sepiolite and layered double hydroxide with or without chemical modification have been extensively studied for potential application in industries. Clays that possess a large specific surface area, high aspect ratio, nanometer sized layer thickness and controllable surface charge could be utilized as polymer fillers after appropriate chemical modifications. These modified clays can improve mechanical and gas barrier properties of polymer materials but also provide sustained antibacterial activity to polymer films. Furthermore, engineered clays can be utilized as scavengers for chemical or biological pollutants in water or soil, because they have desirable adsorption properties and chemical specificity. In this review, we are going to introduce recent researches on engineered clays for potential applications in future industries such as food packaging and environmental remediation.

• Journal of the Korean Ceramic Society
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• v.52 no.6
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• pp.462-466
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• 2015

This paper reports the microstructure of hot-pressed $ZrB_2$-SiC ceramics with added $B_4C$ as characterized by transmission electron microscopy. $ZrB_2$ has a melting point of $3245^{\circ}C$, a relatively low density of $6.1g/cm^3$, and specific mechanical properties at an elevated temperature, making it a candidate for application to environments with ultra-high temperatures which exceed $2000^{\circ}C$. Due to the non-sinterability of $ZrB_2$-based ceramics, research on sintering aids such as $B_4C$ or $MoSi_2$ has become prominent recently. From TEM investigations, an amorphous layer with contaminant oxide is observed in the vicinity of $B_4C$ grains remaining in hot-pressed $ZrB_2$-SiC ceramics with $B_4C$ as an additive. The effect of a $B_4C$ addition on the microstructure of this system is also discussed.

• Journal of Electrochemical Science and Technology
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• v.6 no.4
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• pp.121-130
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• 2015

The micro emulsion method has been successfully used for preparing perovskite LaCoO₃ with uniform, fine-shaped nanoparticles showing high activity as electro catalysts in oxygen reduction reactions (ORRs). They are, therefore, promising candidates for the air-cathode in metal-air rechargeable batteries. Since the activity of a catalyst is highly dependent on its specific surface area, nanoparticles of the perovskite catalyst are desirable for catalyzing both oxygen reduction and evolution reactions. Herein, LaCoO₃ powder was also prepared by sol-gel method for comparison, with a broad particle distribution and high agglomeration. The electro catalytic properties of LaCoO₃ and LaCoO₃-carbon Super P mixture layers toward the ORR were studied comparatively using the rotating disk electrode technique in 0.1 M KOH electrolyte to elucidate the effect of carbon Super P. Koutecky-Levich theory was applied to acquire the overall electron transfer number (n) during the ORR, calculated to be ~3.74 for the LaCoO₃-Super P mixture, quite close to the theoretical value (4.0), and ~2.7 for carbon-free LaCoO₃. A synergistic effect toward the ORR is observed when carbon is present in the LaCoO₃ layer. Carbon is assumed to be more than an additive, enhancing the electronic conductivity of the oxide catalyst. It is suggested that ORRs, catalyzed by the LaCoO₃-Super P mixture, are dominated by a 2+2-electron transfer pathway to form the final, hydroxyl ion product.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.5
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• pp.147-153
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• 2018

Beacon enables one to measure distance indoors based on low-power Bluetooth low energy (BLE) technology, while GPS (Global Positioning System) only can be used outdoors. In measuring indoor distance using Beacon, RSSI (Received Signal Strength Indication) is considered as the one of the key factors, however, it is influenced by various environmental factors so that it causes the huge gap between the estimated distance and the real. In order to handle this issue, we propose the adaptive ANN (Artificial Neural Network) based approach to measuring the exact distance using Beacon. First, we has carried out the preprocessing of the RSSI signals by applying the extended Kalman filter and the signal stabilization filter into decreasing the noise. Then, we suggest the multi-layered ANNs, each of which layer is learned by specific training data sets. The results showed an average error of 0.67m, a precision of 0.78.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.2
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• pp.57-61
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• 2008

Non-nucleus Abalone half pearls were cultured by a new technique and their structural characteristics were analyzed using an electron microscopy. This technique was found to grow the pearls depending on the shape of the internal organ of an abalone because this technique induces the pearl layers without adding any nucleus on the specified damage region of a shell. The obtained pearls exhibit natural shapes with a specific luster. The SEM analysis shows that the pearl layers are about $0.34{\mu}m$ with an uniform thickness and the surface of the shell is characterized by the pyramid-shaped bulge with a regular arrangement, which is a typical feature of single-shell. These characteristics of the pearls are thought to develop in the highly-valued Korean gems.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1062-1065
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• 2004

The importance of display is becoming increasingly important due to the development of information and industry where it leads to diverse and abundant information in today's society. The demand and application range for FPD(Flat Panel Display), specifically represented by LCD(Liquid Crystal Display) and PDP(Plasma Display Panel), have been rapidly growing for its outstanding performance and convenience amongst many other forms of display. The current focus has been on OLED(Organic Light Emitting Diode) in the mobile form, which has just entered into mass production amid the different types of FPD. Many studies are being conducted in regards to device, vacuum evaporation, encapsulation, and drive circuits with the development of device as a matter of the utmost concern. This study develops a new type of light-emitting materials by synthesizing medical polymer organic chitosan and phosphor material CuS. Chitosan itself satisfies the Pool-Frenkel Effect, an I-V specific curve, with a thin film under $20{mu}m$, and demonstrates production possibility for a living body sensors solely with the thin film. Furthermore, it enables production possibility for EML of organic EL device(Emitting Layer) with liquid Green light emitting and Blue light emitting as a result of synthesis with phosphor material.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.36 no.1
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• pp.7-15
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• 2010

Complex human tissues harbor stem cells and precursor cells, which are responsible for tissue development or repair. Recently, dental tissues such as dental pulp, periodontal ligament (PDL), dental follicle have been identified as easily accessible sources of undifferentiated cells. These tissues contain mesenchymal stem cells that can be differentiate into bone, cartilage, fat or muscle by exposing them to specific growth conditions. In this study, the authors procured the stem cell from pulp, PDL, and dental follicle and differentiate them into osteoblast and examine the bone induction capacity. Dental pulp stem cell (DPSC), periodontal ligament stem cell (PDLSC), and dental follicle precursor cell (DFPC) were obtained from human 3rd molar and cultured. Each cell was analyzed for presence of stem cell by fluorescence activated cell sorter (FACs) against CD44, CD105 and CD34, CD45. Each stem cell was cultured, expanded and grown in an osteogenic culture medium to allow formation of a layer of extracellular bone matrix. Osteogenic pathway was checked by alizarin red staining, alkaline phosphatase (ALP) activity test and RT-PCR for ALP and osteocalcin (OCN) gene expression. According to results from FACs, mesenchymal stem cell existed in pulp, PDL, and dental follicle. As culturing with bone differentiation medium, stem cells were differentiated to osteoblast like cell. Compare with stem cell from pulp, PDL and dental follicle-originated stem cell has more osteogenic effect and it was assumed that the character of donor cell was able to affect on differential potency of stem cell. From this article, we are able to verify the pulp, PDL, and dental follicle from extracted tooth, and these can be a source of osteoblast and stem cell for tissue engineering.

• Composites Research
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• v.25 no.5
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• pp.141-146
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• 2012

The strength design for the lightweight bicycle wheel made of the Carbon/Epoxy composite laminates has been discussed in this paper. For bicycle wheel design, lightness of the wheel is important. Also, it has to satisfy the required strength under specific loading cases. Two testing methods for the bicycle wheel, i.e. vertical and complex loadings, are adopted in this study. Because the strengths of composite wheel is different in relation to the stacking sequence and the number of plies, it is important to decide an appropriate stacking sequence and number of layers for the composite wheel. From the finite element analysis results, the most stable sequence orientation and number of layers are determined. The stacking sequence $[0]_{8n}$, $[90]_{8n}$, $[0/90]_{2ns}$, $[{\pm}45]_{2ns}$, $[0/{\pm}45/90]_{ns}$ (n=1,2,3,4)are performed for finite element analysis. From results, $[0/{\pm}45/90]_{3s}$ lay-up is a good selection for the composite bicycle wheel. Also, the weakest point and layer are found in this study.

• Composites Research
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• v.29 no.4
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• pp.167-172
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• 2016

$Co_9S_8/reduced$ graphene (CSRG) has been prepared by a facile two step hydrothermal method and used as a supercapacitor electrode material. It is anticipated that the $Co_9S_8$ and reduced graphene oxide (RGO) would serve as a spacer material to each other to stop the agglomeration and simultaneous contribution of electrical double layer capacitance (RGO) and pseudocapacitance ($Co_9S_8$) would provide high electrochemical properties. The chemical analysis has been done by Fourier transform infrared spectroscopy and the morphology is characterised by field emission scanning electron microscopy. CSRG shows a high electrical conductivity of $98S\;m^{-1}$. The symmetric supercapacitor shows a specific capacitance of ${\sim}728F\;g^{-1}$ with a current density of $2A\;g^{-1}$. CSRG also showed an energy density of $25.2Wh\;kg^{-1}$ with a power density of $1000W\;kg^{-1}$.