• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.1
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• pp.9-19
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• 1989

The impact stress and wave propagation of graphite/epoxy and glass/epoxy laminates subjected to the transverse low-velocity impact of steel balls are investigated theoretically. A plate finite element model based on Whitney and Pagano's theory for the analysis of heterogeneous and anisotropic plates taking into account of the transverse shear deformation is used for the theoretical investigation. This model is in conjuction with static contact laws. The basic element is a four-node quadrilateral with the five degrees-of-freedom per node. The reduced integration technique is used for shear locking associated with low-order function in application to thin plates. These two materials are composed of [0.deg./45.deg./0.deg./-45.deg./0.deg.]$_{2S}$ and [90.deg./45.deg./90.deg./-45.deg./90.deg.]$_{2S}$ stacking sequences and have clamped-clamped boundary conditions. Finally, the present results are compared with an existing solution and wave propagation theory and then impact stress and wave propagation phenomena are investigated.gated.

• Journal of the Korean Wood Science and Technology
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• v.29 no.3
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• pp.112-122
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• 2001

Laccase enzymes from Cerrena unicolor and Trametes versicolor were immobilized on the activated glass beads (CPG), silica gel (SG) and soil (SL). The heterogeneous matrices were activated by ${\gamma}$-aminopropyltriethoxysilane (APTES) and glutaraldehyde (GA), and their surfaces were coated by keratin (KER) on activated or non-activated CPG, SG and SL. The laccase activities were tested in the aqueous solution for the native and immobilized preparations using different pH and temperature conditions. By keratin coating on supports, in the cases of CPG-KER and SL-KER, the immobilization yield was increased from about 80% to 90%. Moreover, much less protein was immobilized in keratin coated matrices than in inorganic ones alone (e.g. on CPG-KER 57.6%, whereas on CPG alone 80.6%). Laccase immobilization on keratin coated inorganic matrices was generally more effective than that of non-coated matrices. Concerned to pH dependency, the optima pH for immobilized laccases generally shifted towards to higher values, 5.5-5.8 and even 5.9 in the case of keratin for C. unicolor and from 5.3 to 5.7 for T. versicolor, respectively, and decreased less gradually both in acidic and alkaline regions. The immobilized laccase was more stable against thermal denaturation. This seems particularly true at $75^{\circ}C$ in the case of C. unicolor, where the activity of immobilized enzyme is > 50% higher than that of the free enzyme. For T. versicolor the respective values were $65^{\circ}C$, and 50%.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.245-245
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• 2012

Syntheses of oxide supported metal catalysts by wet-chemical routes have been well known for their use in heterogeneous catalysis. However, uniform deposition of metal nanoparticles with controlled size and shape on the support with high reproducibility is still a challenge for catalyst preparation. Among various synthesis methods, arc plasma deposition (APD) of metal nanoparticles or thin films on oxide supports has received great interest recently, due to its high reproducibility and large-scale production, and used for their application in catalysis. In this work, Au and Pt nanoparticles with size of 1-2 nm have been deposited on titania powder by APD. The size of metal nanoparticles was controlled by number of shots of metal deposition and APD conditions. These catalytic materials were characterized by x-ray diffraction (XRD), inductively coupled plasma (ICP-AES), CO-chemisorption and transmission electron microscopy (TEM). Catalytic activity of the materials was measured by CO oxidation using oxygen, as a model reaction, in a micro-flow reactor at atmospheric pressure. We found that Au/$TiO_2$ is reactive, showing 100% conversion at $110^{\circ}C$, while Pt/$TiO_2$ shows 100% conversion at $200^{\circ}C$. High activity of metal nanoparticles suggests that APD can be used for large scale synthesis of active nanocatalysts. We will discuss the effect of the structure and metal-oxide interactions of the catalysts on catalytic activity.

• Journal of KIISE
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• v.42 no.2
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• pp.255-263
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• 2015

The sensor registry system has been developed for instant use and seamless interpretation of sensor data in a heterogeneous sensor network environment. However, the existing sensor registry system cannot provide information for interpretation of the sensor data in situations in which the network is unstable. This limitation causes several problems such as sensor data loss, inaccuracy of processed results, and low service quality. A method to resolve such problems in the aspect of software is presented herein. In other words, an extended sensor registry system is proposed to enable the stable use of sensor information, even under conditions of unstable network connection, by providing sensor information with a mobile device in advance through the user path prediction. The results of experiments and evaluation are also presented. The extended sensor registry system proposed in this paper enhances the stable usability of sensor information as well as improves the quality of sensor-based services.

• Korean Journal of Materials Research
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• v.8 no.12
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• pp.1176-1181
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• 1998

Characteristics of high frequency induction- hardened bearing steel have been investigated using 0.55wt.% C-1.68wt.% Mn specimens produced by vacuum induction melting (VIM). The K4 value in DIN 57602 of the specimens was assessed to be 6.41, high level of cleanliness. The specimens were high frequency induction-hardened to form heterogeneous submicron- lath martensite in the surface hardened layer with about 2.5mm in effective depth. Rolling contact fatigue tests were conducted in elasto-hydrodynamic lubricating conditions under a maximum Hertzian contact stress of$ 492kgmm^{-2}$ . It was found that microhardness in the subsurface, up to about $500\mu\textrm{m}$ in depth, below the raceway of rolling contact fatigued specimens was increased in comparison with that of induction-hardened layers. The depth of maximum microhardness- increased region was about $100\mu\textrm{m}$ from surface, showing white etching area. Crack initiation and propagation in the white etching area below the raceway of rolling contact fatigued specimens were observed.

• The Journal of the Korea Contents Association
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• v.10 no.1
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• pp.1-9
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• 2010

In this paper we present a shading technique for realistic rendering of the surfaces with irregular and complex textures using a single photograph. So far, most works have been using many photographs or special photographing equipment to render the surfaces with irregular and complex textures as well as dividing texture regions manually. We present an automatic selection method of the region segmentation techniques according to properties of materials. As our technique produces a reflectance model and the approximated Bidirectional Reflection Distribution Function(BRDF) parameters, it allows the recovery of the photometric properties of diffuse, specular, isotropic or anisotropic textured objects. Also it make it possible to present several synthetic images with novel lighting conditions and views.

• Journal of Digital Contents Society
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• v.8 no.4
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• pp.491-497
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• 2007

RPersonal area networking technology is becoming increasingly important in enabling useful wireless home applications. For example, Bluetooth and IEEE 802.11b standards are the most commonly deployed technologies for wireless home applications. However, because both standards share the same unlicensed ISM (Industrial, Scientific, Medical) radio spectrum, severe interference is inevitable and performance can be impaired significantly when heterogeneous devices using the two technologies come into close proximity. In this paper, we research Gaussian FSK Bluetooth system, which is an open specification technology for short-range wireless connectivity between electronic devices. In this paper, we analyzes the effects of co-channel interference on the performance of a Gaussian FSK Bluetooth system. Performance criteria used in the study are the signal to interference power ratio (SIR), interference index, and the bit error rate (BER) in the wireless channel. The effect of co-channel interference from various sources on the performance of a Gaussian FSK Bluetooth system is analyzed using an IGA(Impulsive Gaussian Approximation) method, and these quantities are plotted against Eb/No, $\rho$ and SIR for various channel conditions in figures.

• Korean Journal of Materials Research
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• v.26 no.3
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• pp.109-116
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• 2016

To achieve the fabrication of high-quality Ag-coated Cu particles through a wet chemical process, we reported herein pretreatment conditions using an ammonium-based mixed solvent for the removal of a $Cu_2O$ layer on Cu particles that were oxidized in air for 1 hr at $200^{\circ}C$ or for 3 days at room temperature. Furthermore, we discussed the results of post-Ag plating with respect to removal level of the oxide layer. X-ray diffraction results revealed that the removal rate of the oxide layer is directly proportional to the concentration of the pretreatment solvent. With the results of Auger electron spectroscopy using oxidized Cu plates, the concentrations required to completely remove 50-nm-thick and 2-nm-thick oxides within 5 min were determined to be X2.5 and X0.13. However, the optimal concentrations in an actual Ag plating process using Cu powder increased to X0.4 and X0.5, respectively, because the oxidation in powder may be accelerated and the complete removal of oxide should be tuned to the thickest oxide layer among all the particles. Back-scattered electron images showed the formation of pure fine Ag particles instead of a uniform and smooth Ag coating in the Ag plating performed after incomplete removal of the oxide layer, indicating that the remaining oxide layer obstructs heterogeneous nucleation and plating by reduced Ag atoms.

• Journal of Genetic Medicine
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• v.7 no.1
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• pp.9-15
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• 2010

Congenital hypothyroidism (CH) is detected at a rate of 1 in 3,000 to 4,000 live births, making it the most common congenital endocrine disorder worldwide. CH is most commonly caused by defects in thyroid development leading to thyroid dysgenesis or dyshormonogenesis. Congenital hypothyroidism is usually sporadic, but up to 2% of cases of thyroid dysgenesis are familial, and CH caused by organification defects is often inherited in a recessive manner. The candidate genes associated with this genetically heterogeneous disorder fall into two main groups: those causing thyroid gland dysgenesis and those causing dyshormonogenesis. Genes associated with thyroid gland dysgenesis include the TSHR gene in nonsyndromic CH, and Gsa and the thyroid transcription factor (TTF-1, TTF-2, and Pax-8) genes, which are associated with different complex syndromes that include CH. Among genes associated with dyshormonogenesis, the TPO and TG genes were initially described, and more recently PDS, NIS, and THOX2 gene defects. There is some evidence for a third group of CH conditions associated with iodothyronine transporter defects that are, in turn, associated with severe neurological sequelae.

• Development and Reproduction
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• v.24 no.3
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• pp.197-205
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• 2020

Diabetes mellitus is a common heterogeneous metabolic disorder, characterized by deposition of extracellular matrix, oxidative stress, and vascular dysfunction, thereby leading to gradual loss of function in multiple organs. However, little attention has been paid to gene expression changes in the lung under hyperglycemic conditions. In this study, we found that diabetes inuced histological changes in the lung of streptozotocin-induced diabetic mice. Global gene expression profiling revealed a set of genes that are up- and down-regulated in the lung of diabetic mice. Among these, expression of Amigo2, Adrb2, and Zbtb16 were confirmed at the transcript level to correlate significantly with hyperglycemia in the lung. We further evaluated the effect of human umbilical cord-derived perivascular stem cells (PVCs) on these gene expression in the lung of diabetic mice. Our results show that administration of PVC-conditioned medium significantly suppressed Amig2, Adrb2, and Zbtb16 upregulation in these mice, suggesting that these genes may be useful indicators of lung injury during hyperglycemia. Furthermore, PVCs offer a promising alternative cell therapy for treating diabetic complications via regulation of gene expression.