• Journal of the Korean Society for Precision Engineering
• /
• v.32 no.11
• /
• pp.997-1005
• /
• 2015

In this study, modal analysis and equivalent static load analysis for valve supports of 26" gas piping in gas stations were conducted and the existing straight and inclined types of valve supports were compared using seismic performance testing. Also, a new valve support shape was suggested by optimizing position of fastener holes, width and thickness of the support, and size of bracket. Improvement in seismic performance by design optimization was verified through equivalent static load analysis. The seismic performance of the newly proposed valve support was greatly improved and the maximum displacement and maximum stress of the seismic load was about 20% lower than those of the existing valve support.

• Analytical Science and Technology
• /
• v.21 no.3
• /
• pp.237-243
• /
• 2008

Nano core shell structures of $TiO_2$ particles coated on surface of ZnO nanoparticles were prepared by the polymerized complex and sol-gel method. The average particle size of ZnO by the polymerized complex method showed 100 nm and the average particle size of $TiO_2$ by the sol-gel method showed below 10 nm. The average particle size of $ZnO@TiO_2$ nano core shell struture represented about 150 nm. The agglomeration between the ZnO particles using the polymerized complex method was highly controlled by the uniform absorption of $TiO_2$ colloid on the spherical ZnO surfaces. The driving force of heterogeneous bonding between ZnO and $TiO_2$ was induced by the Coulomb force. The ZnO and $TiO_2$ particles electrified with + and - charges, respectively, resulted in strong bonding by the difference of iso-electric point (IEP) when they laid neutrality pH area, depending on the heterogeneous surface electron electrified by the different zeta potential on the pH values.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.9 no.6
• /
• pp.601-605
• /
• 1999

$LiCoO_2$and $LiCo_{1-x}$$Ni_x$$O_2$ solid solutions were fabricated by the solid state reaction process. The structural cation mixing phenomena were investigated using XRD, SEM, particle size analysis and $^7$Li NMR,The synthesized LiCoO$_2$ and $LiCo_{1-x}Ni_XO_2$ microcrystallines showed the hexagonal layered structures. Mean particle sizes were increased with the increase of the amount of nickel in the solid solutions. The cation mixing effects were increased as increasing the fraction of nickel(x), x = 0.3, 0.5, 0.7. the peak frequency of $^7$Li NMR was shifted to the higher frequency and the line width increased as increasing the amount of nickel in the solid solutions.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.17 no.6
• /
• pp.238-244
• /
• 2007

Nano-sized ZnO crystals were successfully incorporated using ion exchange method in TMA-A zeolite synthesized by the hydrothermal method. The optimal composition for the synthesis of TMA-A zeolite was resulted in a solution of $Al(i-pro)_3$:2.2 TEOS:2.4 TMAOH:0.3 NaOH:200 $H_2O$. 0.3g of TMA-A zeolite and 5mol of $ZnCl_2$ solution were employed for the preparation of ZnO incorporated TMA-A zeolite. The ZnO incorporated TMA-A zeolite precursors, prepared from the process of mixing, stirring, centrifugal separation and drying, were calcined at temperatures from 400 to $600^{\circ}C$ for 3 h. The crystallization process of ZnO incorporated TMA-A zeolite was analyzed by X-ray diffraction (XRD). The Brunaur-Emett-Teller (BET) surface area of the ZnO incorporated TMA-A zeolite was measured. Subsequently, the morphology and the particle size depending on the temperature and time were observed using scanning electron microscopy(SEM), transmission electron microscopy(TEM) and particle size analyzer.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.20 no.1
• /
• pp.34-46
• /
• 2018

Climate change has become a major risk factor for the co-evolving ecological and societal systems that are interconnected through biogeochemical cycles. As the increasing emission of anthropogenic greenhouse gases (GHG) has been attributed to the principal cause of climate change, more attention has been given to the exchange between terrestrial sources/sinks of GHG and the atmosphere. In this review, we abridged a brief history of the background of GHG monitoring and the development of chamber method for the GHG measurement particularly from agriculture. Based on the reviews of prior domestic studies that analyzed the emission characteristics of GHG using chamber method, we discussed the concerns and the ways to improve chamber measurement to establish better scientific database for climate change adaptation.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.8 no.1
• /
• pp.83-90
• /
• 1998

Stage transformation characteristics of Li, K and Na-graphite deintercalation compounds (GDICs) were studied under consideration of a deintercalation mechanism of the intercalants between carbon layers. Li-graphite intercalation compounds (GICs) synthesized by a controlling temperatures and pressures have been spontaneously decomposed in the atmosphere. By X-ray differaction analysis the $d_{001}$-values of stage 1 and 2 were identified to be 3.71 and 7.06 $\AA$, respectively. After 6 weeks, the deintercalation reaction of the Li-GICs ceased and only residual compounds could be observed. K-GICs were synthesized by the modified two-bulb method resulting in structural stabilities and stage transitions. By X-ray diffraction analysis the very stable K-graphite residue compounds were observed after 10 weeks. Na-GICs with stage 1 and 2 were synthesized using the high temperature and pressure technique. The temperature dependence of a deintercalation reaction and a thermal stability of Na-GICs were discussed. The structure changes of the Na-GDICs depending on heating rates were identified by X-ray diffraction. According to the deintercalation process, the stage transformations could be attributed to irregular deintercalations of the GDICs with disordered stage.

• Journal of the Korean Ceramic Society
• /
• v.39 no.3
• /
• pp.321-326
• /
• 2002

ZnWO$_4$ nano-powders were successfully prepared by polymerized complex method using zinc nitrate and tungstic acid as starting materials. In order to investigate the thermal decomposition and crystallization process, the polymeric precursors were heat-treated at temperatures from 300 to 600$^{\circ}$C for 3 h, and the heat-treated powders were characterized by XRD and FTIR. The surface morphology of the heat-treated powders were observed using SEM and TEM. The crystallite size was measured by X-ray analysis. Crystallization of the ZnWO$_4$ powders were detected at 400$^{\circ}$C and entirely completed at a temperature of 600$^{\circ}$C. The particles heat-treated 400 and 500$^{\circ}$C showed primarily co-mixed morphology with spherical and silkworm-like forms, while the particles heat-treated at 600$^{\circ}$C showed more homogeneous morphology. The average crystalline size were 19.9∼24.nm showing an ordinary tendency to increase with the temperatures from 400 to 600$^{\circ}$C.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.12 no.5
• /
• pp.229-233
• /
• 2002

Nano-sized ZnO particles were successfully synthesized at low temperatures by a polymerized complex method via an organochemical route. The polymeric precursors could be prepared using Zn nitrate hexahydrate and a mixed solution of citric acid and ethylene glycol as a chelating agent and a reaction medium. The polymeric precursors were calcined at temperatures from 300 to $700^{\circ}C$ for 3 h, and evaluated for degree of crystallization process, thermal decomposition, surface morphology and crystallite size. The thermal decomposition and crystallization process were analyzed by TG-DTA, FI-IR and XRD. The morphology and crystallite size of the calcined particles were evaluated by scanning electron microscopy (SEM), transmittance electron microscopy (TEM) and Scherrer's equation. Crystallization of the ZnO particles was detected at $300^{\circ}C$ and entirely completed above $400^{\circ}C$. Particles calcined between 400 and $700^{\circ}C$ showed a uniform size distribution with a round shape. The average particle sizes calcined at $400^{\circ}C$ for 3 hour were 30~40nm showing an ordinary tendency to increase with the temperatures.

• Journal of Mushroom
• /
• v.4 no.3
• /
• pp.106-110
• /
• 2006

A new commercial strain 'Jinhwang' of Pholiota adiposa was developed by hyphal anastomosis. It was developed with crossing between monokaryotic strains derived from ASI 24001 and ASI 24004. The optimum temperature of mycelial growth was $25^{\circ}C$ and that of fruiting body development was $15{\sim}18^{\circ}C$. The color of pileus was yellowish brown and many scales and gelatinous sheath were on cap. Average number of individuals a bottle was 26 and its stipe was thick. P. adiposa can be produced by box cultivation using cotton waste.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.12 no.3
• /
• pp.133-137
• /
• 2002

$ZnWO_4$ nano-powders were successfully synthesized at low temperature by polymerized complex method using zinc acetate and tungstic acid as starting materials. The polymeric precursors were heat-treated at temperatures from 300 to $600^{\circ}C$ for 3 h. The precursors and heat-treated powders were evaluated for crystallization process, thermal decomposition, surface morphology and crystallite size. Crystallization of the $ZnWO_4$ powders were detected at $400^{\circ}C$ and entirely completed at a temperature of $600^{\circ}C$. The particles heat-treated at $400^{\circ}C$ showed primarily co-mixed morphology with spherical and silk-worm-like forms, while the particles heat-treated at $500^{\circ}C$ showed more homogeneous morphology. The average crystalline sizes were 17.62~24.71 nm showing an ordinary tendency to increase with the temperatures from 400 to $600^{\circ}C$.