• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.3
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• pp.85-90
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• 2010

In this study, we have examined the monthly combustion characteristics of Quercus variabilis, a representing Quercus Spp. in Korea, using its living leaves over the period of from June to October. As a result, we were able to identify that their moisture content was about 114%~155%. The leaves of Quercus variabilis collected in October showed the lowest moisture content and nonflaming ignition temperature. The leaves of July showed the fastest flaming ignition time of 27s while those from September showed the longest persistence of flame with 105s, and also showed the highest total heat release amount. There was a noticeable difference in each month of the above period regarding total heat release amount and total smoke release amount with a gradual increase from June to October. The maximum smoke density was a bit higher in October leaves but there was no significant monthly difference. In addition, July leaves were shown to reach the maximum value in the shortest time of 795s.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2013.04a
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• pp.77-77
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• 2013

최근의 산업활동에서는 신규 원료 개발과 생산 효율성을 높이기 위하여 분체 공정이 증가하고 있는데, 미세 분진의 취급으로 분진운의 형성과 착화가 용이해지므로 분진폭발이나 화재 위험성이 증가하고 있다. 분진을 안전하게 사용하고 저장, 취급하기 위해서는 착화 전의 위험성 지표로서 최저발화온도(MIT ; Minimum Ignition Temperature)를 사전에 파악해 두는 것이 중요하다. 분진농도의 발화온도는 장치 내의 발화위험성이나 분진 취급 공정의 사고예방대책 관리를 위한 실용적 관점에서 중요하게 활용되는 폭발특성값이다. 또한 분진의 발화온도는 분진농도에 의존하며 농도변화에 따른 가장 낮은 온도를 MIT라고 한다. 본 연구에서는 화재폭발사고 빈도가 줄지 않고 있는 Mg 및 Mg-Al합금(60:40 wt%, 50:50 wt%, 40:60 wt%)을 대상으로 조성비율에 따른 최저발화온도를 실험적으로 조사하였다. Mg 및 Mg-Al(60:40 wt%), Mg-Al(50:50 wt%), Mg-Al(40:60 wt%) 시료의 평균입경은 142, 160, 151, $152{\mu}m$이다. MIT실험장치는 IEC 61241-2-1(Methods for Determining the Minimum Ignition Temperatures of Dust, 1994)에 준거하여 제작하여 사용하였다. 실험장치는 가열로, 분진운 시료홀더, 온도조절장치, 압축공기 제어장치 등으로 구성되어 있다. 구체적인 실험방법은 시험분진를 분진홀더에 장착하고 0.5 bar의 압축공기를 0.3 sec 동안 사용하여 일정 온도로 가열된 로의 내부로 분진운을 부유시킬 때에 분진운이 발화하여 가열로 하단부의 개방구에까지 화염이 전파하는지를 디지털비데오카메라로 기록, 평가하여 발화 유무를 판정하였다. Mg합금에 대한 MIT를 측정한 결과 $740^{\circ}C$가 얻어졌으며, Mg-Al(60:40 wt%)의 MIT는 $820^{\circ}C$로 조사되었다. 그러나 Mg-Al(50:50 wt%) 및 Mg-Al(40:60 wt%)에 대해서는 최대 가열로의 설정온도를 $890^{\circ}C$까지로 하여 농도를 변화시키면서 조사하였으나 발화가 일어나지 않았다. 문헌에 따르면 Mg입자 표면의 산화피막은 다공성으로 일정 온도에서 산화반응이 시간에 따라 직선적으로 증가하는데 반하여, Al의 산화피막은 보호 작용을 하여 일정 온도에서 산화반응속도가 표면과 내부의 농도 기울기에 의한 확산속도에 의존한다고 보고하고 있다. 본 연구결과를 토대로 Mg-Al합금의 발화특성을 고찰해 보면, Mg-Al합금에서 자기 전파성이 작은 Al성분의 증가는 착화지연이 증가하여 연소성이 감소하여 최저발화온도의 증가로 이어지는 것으로 추정되었다. 또한 발화온도는 주어진 조건의 온도장에서 분진이 존재하는 시간 길이에 따라 변화하므로, 발화온도를 실험적으로 측정하는 경우에는 측정장치나 방법에 따라 달라지므로 사업장의 현장에 발화온도를 적용하는 경우에는 장치 내의 분진의 존재시간을 고려할 필요가 있다.

• Journal of Radiation Protection and Research
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• v.15 no.2
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• pp.41-49
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• 1990

$^{88}SrCl_2$ was injected to the tail vein of Wistar rats and investigated its distribution and clearance in the tissues and blood. We also measured the changes in Sr binding to the blood plasma protein by administrating chelating agents and organic acids. For the blood, 60% of the Sr occurred in the plasma and 40% on the cell membrane. Fifty percent of Sr in the blood plasma was bound to plasma protein. Sr on the cell membrane seemed to be bound loosely. The binding in the lymphocyte was higher than in the erythrocyte .and granulocyte. Within one hour Sr was quickly disappeared from the blood stream, to be accumulated in the bone. Twenty four hours after the injection, Sr decreased rapidly in the organs of soft tissue, but slowly in the bone. The binding of Sr to plasma protien decreased from 57% of the control to 27-33% in the group treated with chelating agents, EDTA, EGTA and DTPA and to 19% and 40% in the groups treated with organic acids, citrate and oxalate, respectively.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.367-375
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• 1986

On the hypothesis that the unstable intermediates yield by the pre-reaction of auxiliary fuel become an initiator or an explosive center which promotes the chain reaction of main fuel, various organic compounds below $C_{10}$ are injected as an auxiliary fuel prior to main injection. In the previous papers, the effects of the auxiliary fuel additions on the ignition delay period, the stability of flame, the NO concentrations in their exhaust gases have been investigated. In the present paper, to confirm where the most suitable location of lean pre-mixture for the combustion of main fuel is, and how the lean pre-mixture is contacted with main fuel, the effects of the injection timing of auxiliary fuel and the turbulence on combustion processes are investigated. Moreover, from the schlieren and color photographs of flame in the combution field, it could be found that the ignition nuclei are formed in a wider region of main spray, and that these ignition nuclei promote the development of flame, which results in the reduction of flaming duration.

• Journal of the Korean Ceramic Society
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• v.41 no.1
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• pp.76-80
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• 2004

Nano-sized ZnO colloids were prepared by use of spray combustion method. for combustion reaction, $Zn(NO_3)_2{\cdot}6H_2O$ and $CH_6N_4O$ were employed as an oxidizer and a fuel. Exothermic peak was shown at $230^{\circ}C$ by DTA/TGA, and it was considered as a combustion reaction followed by ignition of the precursor mixture. In case of spray combustion method, because insufficient contents of molecules and radicals generated from precursor droplets may lead an incomplete igmition, the ignition temperature of combustion chamber was chosen at $500^{\circ}C$. For diminishing aerosol coagulation, the droplet number concentration was reduced by filter media. The fluid was laminar with 2.5 seconds of aerosol residence time. The synthesized colloids had spherical shape with 180 nanometer size, and the crystalline phase was ZnO with hexagonal structure.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.3
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• pp.81-87
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• 2009

In this study, we have investigated the combustibility of five shrubs growing in Youngdong area such as Lindera obtusiloba, Lespedeza maximowiczii, Zanthoxylum piperitum, Zanthoxylum schinifolium, and Corylus heterophylla var. thunbergii using the ignition temperature tester, the cone calorimeter and the smoke density chamber in order to estimate the danger of a forest fire. The results showed that Lespedeza maximowiczii has the lowest ignition temperature, the fastest ignition time and the highest average release concentrations of CO and $CO_2$. Zanthoxylum piperitum and Zanthoxylum schinifolium showed the highest level in heat release and smoke release, respectively. Therefore, we have concluded that Lespedeza maximowiczii has the highest ignitibility, Zanthoxylum piperitum the most intensive fire spread and fire intensity, and Zanthoxylum schinifolium and Lespedeza maximowiczii most difficult to escape from a forest fire.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.12
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• pp.1043-1050
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• 2010

Fuel stratification and thermal stratification occur in the HCCI combustion chamber on a microscopic scale. They affect the ignition and combustion processes. In this study, the effect of the inhomogeneity in the mixture gas on the HCCI combustion process was investigated. Two-dimensional chemiluminescence images were captured using a framing camera to evaluate the flame structure. DME was used as the test fuel. First, the effect of inhomogeneity in the fuel distribution in the premixture was investigated for the four-stroke optically accessible engine. Then, by comparing the combustion of the homogeneous mixture in the rapid compression machine, which does not contain any residual gas, with the combustion in the four-stroke engine, the effect of inhomogeneity in temperature due to the residual gas was analyzed. The results showed that a time lag appears spatially in combustion under inhomogeneous conditions in the four-stroke engine. The spatial variation in the combustion without the residual gas in the rapid compression machine is less than that in the combustion in the four-stroke engine.

• Journal of the Korean Chemical Society
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• v.37 no.9
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• pp.806-812
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• 1993

Complexes of $Cu(I)(hfac)PR_3$(P: phosphine and R: Me, Et and Bu) as Cu(I)(${\beta}$-diketonate) compounds have been synthesized and their electrochemical properties have been investigated using glassy carbon and carbon microelectrode in aprotic solvent. Reduction process of $Cu(I)(hfac)PR_3$ compounds carried out one electron pathway to Cu(0) by cyclic voltammetry in acetonitrile solution. Chronoamperometric curve using carbon microelectrode shows that these complexes are one electron process and diffusion coefficients are $4.5{\sim}6.7{\times}10^{-6}cm^2$/sec.

• Applied Chemistry for Engineering
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• v.18 no.2
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• pp.194-198
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• 2007

Veneer plate was painted by the treatment with ammonium salts such as ammonium chloride (AMCR), ammonium sulfate (AMSF), monoammonium phosphate (MAPP), and diammonium phosphate (DAPP) at room temperature. The physical property and flammability of painted veneer plate were investigated. In order to evaluate flammability of the treated veneer with ammonium salts, heat release rate (HRR) of the veneer was measured by a cone calorimeter according to ISO 5660-1 standard. The flammability painted veneener plate with ammonium salts was reduced compared to virgin veneer plate. The flashover possibility of veneer plates treated with these ammonium salts was examined by R. V. Petrella's classification using time to ignition and peak heat release rate. The specific gravities of veneer plates treated with only ammonium sulfate were higher than that of virgin veneer plate. Also, the veneer plates treated with ammonium salts showed lower equilibrium moisture contents over virgin veneer.

• Fire Science and Engineering
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• v.23 no.1
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• pp.33-39
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• 2009

In this study, the combustion properties, which are called the reaction-to-fire's performance, of sandwich panels were tested and analyzed according to both ISO 5660 (cone calorimeter method) and EN 13823 (SBI). Several variables including ignition time, mass loss, heat release rate, smoke production rate and $O_2$ density about four sandwich panels and four core materials (thermal insulation material) were evaluated. Combustion properties' similarity and difference of sandwich panels and core materials were compared by materials and test methods respectively. Finally test results were evaluated by Japanese standard building code, National Building code of Canada and EN 13501-1 as well.