• Journal of the Korean Ceramic Society
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• v.41 no.3
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• pp.202-209
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• 2004

Hydroxyapatite(HA)/TiO$_2$ composite powders were prepared by mixing of spherical TiO$_2$ (10-15 nm, 500 nm) and needle-shaped HA (50-70 nm, 120-250 nm) powders which had been synthesized through precipitation, sol-gel and hydrothermal methods. From the three types of starting composite powders (HA/TiO$_2$ wt% of 75/25, 50/50, and 25/75), dense $\beta$-TCP/TiO$_2$ composites were prepared by hot-pressing at 800-100$0^{\circ}C$ for 30 min under the pressure of 30 ㎫ in Af atmosphere. The $\beta$-TCP/TiO$_2$ composites showed different microstructures and sintering densities depending on their powder morphology, composition and sintering temperature. With increasing the sintering temperature and the content of TiO$_2$, sintered density was increased and microstructure became more homogeneous.

• Journal of Hydrogen and New Energy
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• v.24 no.2
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• pp.160-171
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• 2013

$LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ powder for cathode materials in lithium rechargeable batteries was treated by atmospheric plasma containing hydrogen to investigate the relationship between charge/discharge performance and physical/chemical changes of materials. Hydrogen plasma at atmosphere pressure was irradiated on the surface of active materials, and the change for their crystal structure, surface morphology, and chemical composition were observed by XRD, SEM-EDS and titration method, respectively. The crystal structure and surface morphology of $H_2$ plasma-treated powders were not changed but their chemical compositions were slightly varied. For charge/discharge test, $H_2$ plasma affected initial capacity and rate capability of active materials but continuous cycling was not subject to plasma treatment. Therefore, it was observed that $H_2$ plasma treatment affected the surface of materials and caused the change of chemical composition.

• Journal of Hydrogen and New Energy
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• v.28 no.3
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• pp.300-307
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• 2017

This study is to investigate particle size and velocity profile of gasoline port injector using Phase Doppler Particle Analyzer (PDPA). In this experiment, a GV 250 Delphi port injector used for motorcycles was used for liquid injection. The injector consists of four holes and has a static flow rate of 2.13 g/s. The fuel used in the injection was N-heptane, which is similar to gasoline, as an alternative fuel. The test fuel was injected at an atmospheric temperature of $20^{\circ}C$ and an open atmosphere of 1 atm. The injection time was 10 ms and the injection pressure was 3.5 bar in PDPA experiment. The experimental target position was fiexd at 30, 50 and 75 mm from the nozzle tip and data were collected for a total of 10,000 samples. The experimental results show that the length diameter (D10), the Sauter mean diameter ($D_{32}$), and the mean droplet velocity (MDV) are $45-54{\mu}m$, $99-115{\mu}m$ and 15-21 m/s, respectively.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1512-1515
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• 1996

Dense $SiC-ZrB_2$ electro-conductive ceramic composites were obtained by hot pressing for high temperature structural application. The influences of the $ZrB_2$ additions an the mechanical and electrical properties of $SiC-ZrB_2$ composites were investigated. Samples were prepared by adding 15, 30, 45 vol.% $ZrB_2$ particles as a second phase to a SiC matrix. Sintering of monolithic SiC and $SiC-ZrB_2$ composites were achieved by hot pressing under a $10^{-4}$ torr vacuum atmosphere from 1000 to $2000^{\circ}C$ with a pressure of 30 MPa and held for 60 minutes at $2000^{\circ}C$. SiC and $SiC-ZrB_2$ samples obtained by hot pressing were fully dense with the relative densities over 99%. Flexural strength and fracture toughness of the samples were improved with the $ZrB_2$ contents. In the case of SiC sample containing 30vol.% $ZrB_2$, the flexural strength and fracture toughness showed 45% and 60% increase, respectively compared to those of monolithic SiC sample. The electrical resistivities of $SiC-ZrB_2$ composites were measured utilizing the four-point probe method and they decreased significantly with Increasing $ZrB_2$ contents. The resistivity of SiC-30vol.% $ZrB_2$ showed $6.50{\times}10^{-4}{\Omega}{\cdot}cm$.

• Journal of the Korean Society of Safety
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• v.29 no.2
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• pp.24-30
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• 2014

There have been controversies over whether explosion hazardous area(EHA) should be classified for facilities which use lighter-than-air gases such as city gas, hydrogen and ammonia. Two view points are confronting each other: an economic piont of view that these gases are lighter than air and disperse rapidly, hence do not form EHA upon release into the atmosphere, and a safety point of view that they are also inflammable gases, hence can form EHA although the extent is limited compared to heavy gases. But various standards such as KS, IEC, API, NFPA do not exclude light gases when classifying EHA and present examples of EHA for light gas facilities. This study calculates EHA using the hypothetical volume in the IEC code where the hole sizes required for the calculation were selected according to various nominal pipe sizes in such a way to conform to the EHA data in the API code and HSL. Then, 25 leakage scenarios were suggested for 5 different pipe sizes and 5 operating pressures that cover typical operating conditions of light gas facilities. The EHA for the minimum leakage scenario(25 mm pipe, 0.01MPa pressure) was found to correspond to a hypothetical volume larger than 0.1 $m^3$(medium-level ventilation). This confirms the validity of classifying EHA for facilities using lighter-than-air gases. Finally, a computer program called HACPL was developed for easy use by light gas facilities that classifies EHA according to operating pressures and pipe sizes.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.4
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• pp.455-461
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• 2001

The effect of exogenous gonadotrophins on superovulation in rabbits was examined. One hundred and sixteen sexually mature California, Chinchilla and New Zealand White rabbits were randomly allocated to control (100 IU hCG), PMSG-treated (100 IU HCG following 150 IU PMSG) and FSH-treated groups (0.3 mg/head /12 h for 3 days followed by 100 IU hCG). All does were mated after hCG injection and were sacrificed or laparotomized within 1 to 4 days postcoitus for counting the number of ovulation points. The number of ovulations was higher in FSH-treated animals than in the control and PMSG-treated groups (37.2 vs. 10.4 and 14.5, p<0.05). Follicle haemorrhagicum was observed in many cases in the PMSG-treated group. No significant difference in ovulation number was observed between left and right ovaries regardless of gonadotropin treatment. In another experiment, 2-cell stage embryos were collected at 26 h postmating and blastomeres were separated by mechanical pipetting or gentle pressure with a fine glass needle. Aggregated or chimeric embryos were produced from two single blastomeres from two breeds, New Zealand White and Chinchlla, with different coat colors. All the embryos were cultured in Ham's F-10 medium supplemented with 1.5% BSA (bovine serum albumin fraction V) and 10% PRS (pregnant rabbit serum), and incubated in a humidified atmosphere with 5% $CO_2$ at $38^{\circ}C$. After development to morula or early blastocyst, the embryos were transferred into the oviducts of recipient does. Results showed that 7 out of 10 does (70%) receiving intact embryos (control) became pregnant and 41 kits were delivered. However, no pregnancy was obtained from the recipient of either denuded demi- or aggregated embryos. It is suggested that embryos without zona pellucida could not develop to term in rabbits.

• Journal of the Korea Organic Resources Recycling Association
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• v.8 no.4
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• pp.121-128
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• 2000

Landfill and lysimeter experiments were conducted to estimate the optimum air injection method for the degradation of waste in landfill and the pre-stabilization. Continuous injection with low pressure and quantity can be effective for pre-stabilization of old landfill due to the lower contents of volatile solids in landfill. Air injection and landfill gas (LFG)extraction showed that the SVE (Soil Vapor Extraction) effect by air ventilation was more significant than the biodegradation of organics. Theses results suggested that they could accelerate the biological stabilization of organic waste in landfills. It is also expected that they would reduce the problems including gas emission during the landfill mining, separation and/or transportation to such levels that might be discharged directly to the atmosphere or with minimal treatment, if required.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.18-19
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• 2005

EDDC(Evaporation using Drum in Dual Chamber) deposition system was manufactured for 100m long superconducting coated conductor. It is composed of reaction chamber, evaporation chamber and differential chamber. The drum is located across the differential and exposed to both of the evaporation chamber and the reaction chamber, and the tape is wound on the drum. The elements of superconducting material are co-evaporated from respective element boats in the evaporation chamber and deposited on the drum and reacted with oxygen in the reaction chamber. This process repeats by rotating the drum. When the total pressure of the reaction chamber was 5 mTorr, that of the evaporation chamber was $5{\sim}10^{-5}$Torr. This atmosphere can be achieved by means of differential pumping. There are four evaporator in the evaporation chamber. One is the radiation heating evaporator and the others are the high frequency induction evaporator. EDDC is one of promising methods for commercialization of superconducting coated conductor.

• Atmosphere
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• v.20 no.3
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• pp.287-306
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• 2010

An ensemble Kalman filter (EnKF) with Weather Research and Forecasting (WRF) Model is applied for Typhoon Wukong (200610) to investigate the performance of ensemble forecasts depending on experimental configurations of the EnKF. In addition, the ensemble sensitivity analysis is applied to the forecast and analysis ensembles generated in EnKF, to investigate the possibility of using the ensemble sensitivity analysis as the adaptive observation guidance. Various experimental configurations are tested by changing model error, ensemble size, assimilation time window, covariance relaxation, and covariance localization in EnKF. First of all, experiments using different physical parameterization scheme for each ensemble member show less root mean square error compared to those using single physics for all the forecast ensemble members, which implies that considering the model error is beneficial to get better forecasts. A larger number of ensembles are also beneficial than a smaller number of ensembles. For the assimilation time window, the experiment using less frequent window shows better results than that using more frequent window, which is associated with the availability of observational data in this study. Therefore, incorporating model error, larger ensemble size, and less frequent assimilation window into the EnKF is beneficial to get better prediction of Typhoon Wukong (200610). The covariance relaxation and localization are relatively less beneficial to the forecasts compared to those factors mentioned above. The ensemble sensitivity analysis shows that the sensitive regions for adaptive observations can be determined by the sensitivity of the forecast measure of interest to the initial ensembles. In addition, the sensitivities calculated by the ensemble sensitivity analysis can be explained by dynamical relationships established among wind, temperature, and pressure.

• Atmosphere
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• v.30 no.1
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• pp.17-30
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• 2020

KMA performed the special observation program to provide information about severe weather and to monitor typhoon PRAPIROON using the ship which called the Gisang 1 from 29 June 2018 to 4 July 2018 (UTC). For this period, upper-air was observed 21 times with 6 hour intervals using rawinsonde in the Gisang 1. We investigated the impact of upper-air observation data from the Gisang 1 on the performance of the operational convective scale model (we called LDAPS). We conducted two experiments that used all observation data including upper-air observation data from the Gisang 1 (OPER) and without it (EXPR). For a typhoon PRAPIROON case, track forecast error of OPER was lower than EXPR until forecast 24 hours. The intensity forecast error of OPER for minimum sea level pressure was lower than EXPR until forecast 12 hours. The intensity forecast error of OPER for maximum wind speed was mostly lower than EXPR until forecast 30 hours. OPER showed good performance for typhoon forecast compared with EXPR at the early lead time. Two precipitation cases occurred in the south of the Korean peninsula due to the impact of Changma on 1 July and typhoon on 3 July. The location of main precipitation band predicted from OPER was closer to observations. As assimilating upper-air data observed in the Gisang 1 to model, it showed positive results in typhoon and precipitation cases.