• Fire Science and Engineering
• /
• v.24 no.2
• /
• pp.106-113
• /
• 2010

Fire characteristics can be analyzed more realistically by using more accurate material properties related to the fire dynamics and one way to acquire these fire properties is to use one of the inverse property analyses. In this study the genetic algorithm which is frequently applied for the inverse heat transfer problems is selected to demonstrate the procedure of obtaining fire properties of the solid charring material with relatively simple chemical structure. The thermal decomposition on the surface of the test plate is occurred by receiving the radiative energy from external heat sources, and in this process the heat transfer through the test plate can be simplified by an unsteady 1-D problem. The inverse property analysis based on the genetic algorithm is then applied for the estimation of the properties related to the reaction pyrolysis. The input parameters for the analysis are the surface temperature and mass loss rate of the char plate which are determined from the unsteady 1-D analysis with a givenset of 8 properties. The estimated properties using the inverse analysis based on the genetic algorithm show acceptable agreements with the input properties used to obtain the surface temperature and mass loss rate with errors between 1.8% for the specific heat of the virgin material and 151% for the specific heat of the charred material.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.14 no.3
• /
• pp.163-175
• /
• 2011

Though polycyclic aromatic hydrocarbon compounds (PAHs) in marine sediment has been produced by many colleges and institution in Korea, it is difficult to compare PAHs data in a study area with those in other areas due to the lack of confidence for the quality of data from the other organization. Therefore, we suggested the protocol for PAHs analysis in marine sediment through examining the method of PAHs analysis described in over twenty scientific papers and reports. When a known amount of 23 PAHs were spiked into a sediment and anlyzed following this new protocol, very good recoveries were obtained. In addition, for college and institution with their own method to analyze PAHs can keep producing PAHs data without exchanging to this new PAHs protocol, the method to get a full confidence through the QA/QC for the PAHs data produced by these organization is included to the protocol.

• Economic and Environmental Geology
• /
• v.37 no.6 s.169
• /
• pp.613-629
• /
• 2004

Contamination of groundwater by volatile organic compounds (VOCs) was investigated for 168 groundwater wells in Ulsan area to study the natural attenuation of organic compounds in the aquifers. As groundwater contamination by VOCs is closely related to land use, 168 groundwater samples were classified into 4 different groups; agricultural, forestry, industrial, and residential & business. From analysis 65 out of 168 groundwater samples contained more than one VOC. Analysis of samples were performed fir 36 halogenated aliphatic hydrocarbons and 25 petroleum hydrocarbons set up by NAWQA of US geological survey. Twelve petroleum hydrocarbons were detected in 26 groundwater wells, but their concentrations were less than 1.5 g/L except for MTBE. Twenty three chlorinated aliphatic hydrocarbons, composed of 11 methanes, 6 ethanes and 6 ethenes, were detected in 63 groundwater samples. The range of methanes concentration was $ND\~330\;/gL,\;ethanes\;ND\~84\;gL$, and PCE and their derivatives $ND\~62\;g/L$. As the study area was comprised of the aerobic/denitrification zones and $Fe^{+3}$ redox condition, most of petroleum hydrocarbons were degraded well, while halogenated hydrocarbons were slowly biodegradation.

• Korean Journal of Materials Research
• /
• v.11 no.6
• /
• pp.502-507
• /
• 2001

The effect of solidification rate on the microstructure of directionally solidified IN792+ Hf superalloy has been studied. Solidification sequence and precipitation behavior of the alloy have been analysed by microstructural observation. The script carbide transformed to faceted carbide with decreasing solidification rates. The incorporation of ${\gamma}$ phase into the faceted carbide was due to dendritic growth of carbides. Some elongated carbide bars formed along the grain boundaries at a solidification rate of 0.5$\mu\textrm{m}$/s. Two zones, ${\gamma}$' forming elements enriched zone and depleted zone, were found in the residual liquid area. Eutectic ${\gamma}$/${\gamma}$' nucleated in the f forming elements enriched zone. Formation of eutectic ${\gamma}$/${\gamma}$' increased the ratio of (Ti+Hf+Ta+W)/Al and induced η phase precipitation. The ratio of (Ti+Hf+Ta+W)/Al decreased at lower solidification rates due to sufficient back diffusion in the residual liquid area. Hence, the Precipitation of the η Phase efficiently suppressed at the lower solidification rate.

• Journal of the Korean institute of surface engineering
• /
• v.16 no.3
• /
• pp.108-123
• /
• 1983

순수 Mo와 Mo-Nb, Mo-Ta($\leq$10 at% Nb. Ta)합금을 1,500-2,06$0^{\circ}C$ 범위에서 탄소의 고용도를 연구하였다. 특수한 침탄방법으로 C2H2를 시편에 침탄한후 열처리하여 부분적으로 석출하거나 완전석출에 관계없는 화학적 분석방법으로 행하였다. 순수 Mo에서 최대탄소 고용도는 logCCmax = 7.02-9,490/T이다. Nb, Ta를 미량첨가하여 탄소의 최대 고용도는 Arrhenius 식을 적용할 수 없다. Nb-, Ta- 농도와 온도에 따라 Mo2C와 Nb-,Ta-를 함유한 여러 가지 탄화물상을 만들거나 $\alpha$고용체와 Mo가 포함된 NbC, TaC와 평형상태를 나타나기 때문이다. 실험온도 범위에서 Nb, Ta를 첨가량을 증가하면 탄화물 내부에 NbC, TaC로 석출된다. 고온에 용해된 a-고용체는 150-200 oK/Min으로 냉각하면 석출물은 결정입계나 결정내부에 나타난다. 순수 Mo에 Nb, Ta를 첨가하여도 경도, 파괴실험에서와 같이 인장강도는 크게 증가하지 않는다.

• Proceedings of KOSOMES biannual meeting
• /
• 2006.05a
• /
• pp.85-92
• /
• 2006

Crude oil is complex mixture if thousands of different organic compound formed from a variety of organic materials that are chemically converted under differing geological conditions over long periods of time. Also oil composition varies according to crude source, refining, processing, handling and storage. The oil fingerprint method is application if specific knowledge of petrochemicals and use if sophisticated analytical equipment and techniques to identify the source(s) if oil pollution. KCG currently utilizes four primary analytical techniques: Gas Chromatography (GC), Fluorescence Spectroscopy(FL), Infrared Spectroscopy(IR) and Gas Chromatography mass spectrometer(GC/MS). Of all these techniques, GC technique are most widely used Gas Chromatography is used as a primary analytical method because high reliableness, high separating efficiency and repeatability.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.27 no.6
• /
• pp.313-318
• /
• 2017

The microstructure of a cobalt-base superalloy (ECY768) obtained by an investment casting process was studied. This work focuses on the resulting microstructures arising from different melt and mold temperatures in normal industrial environmental conditions. The characterization of the samples was carried out using optical microscopy, field emission scanning electron microscopy and energy-dispersive spectroscopy. In this study, the as-cast microstructure is an ${\alpha}-Co$ (face-centered cubic) dendritic matrix with the presence of a secondary phase, such as $M_{23}C_6-type$ carbides precipitated at grain boundaries. These precipitates are the main strengthening mechanism in this type of alloy. Other minority phases, such as the MC-type phase, was also detected and their presence could be linked to the manufacturing process and environment.

• Journal of Energy Engineering
• /
• v.23 no.3
• /
• pp.235-240
• /
• 2014

In this study, the torrefaction of food waste was conducted to characterize its product, to find out effect of the operating temperature and to assess the feasibility of being used as fuel. The operating temperature was varid from $180^{\circ}C{\sim}270^{\circ}C$ and heat was provided by using nitrogen gas or waste oil heat carrier. The solid yield and moisture content were reduced were reduced as temperature increased. The moisture content reduction and thermochemical conversion were observed at higher than $240^{\circ}C$. At low operating temperature, heat transfer efficiency was higher with wast oil heat carrier. As temperature increases, there was not difference in heat transfer efficiency of two different heating methods. The lower heating value product was increased from 660 to 6,400 Kcal/kg with nitrogen gas and 6,890 Kcal/kg with waste oil heat carrier. The elemental analysis indicates that, as temperature increases, the carbon content of product increases and oxygen content decreases. From the analysis of O/C and H/C, the torrefaction product was close to low grade coal. The characteristics of fuel converted from the food subsequent thermochemical treatment.

• Fire Science and Engineering
• /
• v.33 no.5
• /
• pp.7-12
• /
• 2019

To investigate the influence of the char layer formed during the combustion process on the pyrolysis of wood combustibles, ISO 5660-1 cone calorimetry experiments and Fire dynamics simulator (FDS) simulations were performed, and the results from these two methods were compared. The wood combustible selected as the fuel for this study, Douglas fir, has been widely used for the production of building materials, furniture, etc. The heat release rate (HRR) measured from the cone calorimetry experiment was in good agreement with the result predicted by the FDS simulation. However, the FDS simulation failed to predict the heat released by the smoldering combustion process, due to the absence of the char surface reaction in the model. The FDS simulation results clearly indicate that the char layer formed on the surface of combustibles produces a thermal barrier which prevents heat transfer to the interior, thickening the thermal depth and thus reducing the pyrolysis rate of combustibles.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.28 no.6
• /
• pp.250-255
• /
• 2018

The CoCrMo as-built alloys prepared by 3D-printing process are studied on tensile strength, wear resistance, crystal structure and microstructure after complex heat-treatment including HIP. In this study, HIP treatment for removing micropores, ambient heat-treatment for formation of metal carbides, and solution heat-treatment for homogenization of the created metal carbides were tried and characterized for applying to artificial joint. The complex heat-treatment effects of the CoCrMo as-built alloys prepared by 3D-printing process were owing to the densification during HIP, formation of metal carbides and homogenization of the created metal carbides. The effects of the complex heat-treatment were confirmed by XRD, FE-SEM and EDS.