• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.352-355
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• 1998

Dense $ Pb(Zr, Ti)O_3(PZT)/Al_2O_3$ nanocomposites were prepared by the 28 GHz microwave heating method and conventional electric furnace sintering. Electrical and mechanical properties of the composites were investigated. The fracture strength of the PZT composites with 0.1vol% $Al_2O_3$ was significantly improved in both sintering methods. Smaller grain size and effective reinforcement of the PZT matrix by the second phase were considered to be responsible for the excellent fracture strength. Planar electromechanical coupling factor Kp of the composites sintered by 28GHz microwave heating was higher than that of the materical prepared by the conventional route. It seemed that the control of the reaction between PZT and $Al_2O_3$ by the microwave rapid sintering resulted in the high piezoelectric properties.

• YAKHAK HOEJI
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• v.43 no.3
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• pp.316-319
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• 1999

Chrysin 7-Ο-crotonate was synthesized by condensing crotonic acid with chrysin in organic solvent, tetrahydrofuran (THF) using dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP). Its structure was indentified by NMR, MS, UV, IR etc. We also investigated the physico-chemical properties and set up the quantitative anytical method of this compound. The correlation coefficient of calibration curve measured at the isobestic point (340 nm) on this compound was approximately 0.9994 by absorption spetrophtometry. Detection limit was 1.6ng at S/N=3 by using a RP column by HPLC. The hair growth effect fo chrysin 7-Ο-crotonate on the hair of black mouse (C57BL/6), was carried out using paste method. When its ethanol solution was administered to this black mouse by route of skin, this compound promoted the growth of hair.

• Korean Journal of Materials Research
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• v.17 no.2
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• pp.86-90
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• 2007

The organic-capped Ba-Ti-O nanolayers were coated uniformly on spherical Ni particles for multilayer ceramic capacitor (MLCC) applications via the formation of Ti-hydroxide nano-coating layers and their subsequent reaction with Ba-stearate at $180^{\circ}C$. The capping of organic shell on oxide coating layer changed the hydrophilic surface structure into hydrophobic one, which significantly improved the dispersion behavior in hydrophobic solvents such as terpineol and butanol. In addition, the uniform coating of Ba-Ti-O layer was advantageous to prevent Ni oxidation. This method provides a useful chemical route to fabricate organic-soluble Ba-Ti-O coated Ni particles for a highly integrated passive component.

• Proceedings of the KSR Conference
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• 2001.05a
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• pp.58-65
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• 2001

Many changes in the railway environment has directly affected to the railway company. To cope immediately with the influence of environment and to promote productivity, the railway company has to introduce an efficient train operation system and related core technologies. The railway system is composed or large-scale infrastructures ann high-cost trains. Simulation method is one or core technologies and also is efficient tool for planning and analyzing this kind of complex system. The purpose of this research is to develop multi-train traffic simulator considering high-speed train for GyongBu-Line. To achieve this objective, the elements of railway system was analyzed, and as a result, a data structure modeling for the railway system such as rail-Tine infrastructure, rain, timetable and operational route is presented. The developed simulator is composed of three major part : input-module, main-module, and output module. The concept and brief explanation of each module will be treated.

• Journal of the Korean Ceramic Society
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• v.54 no.6
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• pp.499-505
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• 2017

Flexible silicon carbide fibrous mats were fabricated by a combination of electrospinning and a polymer-derived ceramics route. Polycarbosilane was used as a solute with various solvent mixtures, such as toluene and dimethylformamide. The electrospun PCS fibrous mats were cured under a halogen vapor atmosphere and heat treated at $1300^{\circ}C$. The structure, fiber morphology, thermal behavior, and crystallization of the fabricated SiC fibrous mats were analyzed via scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermal imaging. The prepared SiC fibrous mats were composed of randomly distributed fibers approximately $3{\mu}m$ in diameter. The heat radiation of the SiC fiber mats reached $1600^{\circ}C$ under microwave radiation at a frequency of 2.45 GHz.

• Bulletin of the Korean Chemical Society
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• v.30 no.1
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• pp.53-56
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• 2009

At room-temperature, a facile, seedless, and environmentally benign green route for the synthesis of star like PbS nanoclusters at 7 min in aqueous solution of 1-ethyl-3-methylimidazolium ethyl sulfate, [EMIM] [$EtSO_{4}$], room-temperature ionic liquid (RTIL), via ultrasonic irradiation is proposed. The X-ray diffraction studies display that the products are excellently crystallized in the form of cubic structure. An energy dispersive X-ray spectroscopy (EDX) investigation reveals the products are extremely pure. The absorption spectra of the product exhibit band gap energy of about 4.27 eV which shows an enormous blue shift of 3.86 eV that can be attributed to very small size of PbS nanoparticles produced and quantum confinement effect. A possible formation mechanism of the PbS nanoparticles using ultrasonic irradiation in aqueous solution of the RTIL is presented.

• Korean Journal of Materials Research
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• v.18 no.3
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• pp.123-127
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• 2008

The production of tin oxide ($SnO_2$) microrods on iridium (Ir)-coated substrates was achieved through the thermal evaporation of Sn powders in which a sufficiently high $O_2$ partial pressure was employed. Scanning electron microscopy revealed that the product consisted of microrods with diameters that ranged from 0.9 to $40\;{\mu}m$. X-ray diffraction, high-resolution transmission electron microscopy, and selected area electron diffraction indicated that the microrods were $SnO_2$ with a rutile structure. As the microrod tips were free of metal particles, it was determined that the growth of $SnO_2$ microrods via the present route was dominated by a vapor-solid mechanism. The thickening of rod-like structures was related to the utilization of sufficiently high $O_2$ partial pressure during the synthesis process, whereas low $O_2$ partial pressure facilitated the production of thin rods.

• Korean Journal of Geomatics
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• v.4 no.2
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• pp.53-57
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• 2004

Due to the traffic congestion and public-oriented transportation policies of Seoul, public transportation is receiving attention and being used increasingly. However, current transport routes configuration is showing unbalanced accessibility throughout the city area creating differences in time, expenses and metal burden of users who travel the same distances. One of the reasons is that transport route planning has been partially empirical and non-quantitative tasks due to lack of relevant methods for assessing the complexity of the transport routes. This paper presents a method to compute the connectivity of public transport system based on the topological structure of the network of transport routes. The main methodological issue starts from the fact that the more transfers take place, the deeper the connectivity becomes making that area evaluated as less advantageous as for public transport accessibility. By computing the connectivity of each bus or subway station with all others in a city, we can quantify the differences in the serviceability of city areas based on the public transportation. This paper is based on the topological interpretation of the routes network and suggests an algorithm that can automate the computation process. The process is illustrated using a simple artificial network data built in a GIS.

• Convergence Security Journal
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• v.5 no.1
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• pp.53-62
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• 2005

Virus protection infrastructure managementis network infrastructure management, traffic route management, virus protection zone expansion, and virus protection management for gateway area. This research paper provides a diagnosis of characteristics and weaknesses of the structure of existing virus protection infrastructure, and recommends an improved multi-level virus protection infrastructure as a measure for correcting these weaknesses. Improved virus protection infrastructure filters unnecessary mail at the gateway stage to reduce the load on server. As a result, numberof transmission accumulation decreases due to the reduction in the CPU load on the Virus wall and increase in virus treatment rate.

• Journal of Korean Society of Rural Planning
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• v.15 no.3
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• pp.33-45
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• 2009

This study tried to establish a tentative renewal guideline on spatial structure of the Hub-myun's center villages which would be positioned as sub-centers in the rural settlement hierarchy in Korea. Space Syntax Method was used to analyze the locational characteristics of community facilities in the center villages of 8 pilot project areas which were selected in the nationwide scale. The base-maps for spatial analysis works were prepared firstly from satellite pictures and adjusted through field check. Generally, connectivity and global integration values of center villages were calculated as higher than hinterland villages, which would mean better accessible spatial characteristics in the center villages. And a tentative renewal guideline was proposed for road route improvement and relocation of community facilities in the Hub-myun's center villages.