• 한국연소학회:학술대회논문집
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• 2013.06a
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• pp.25-28
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• 2013

This study presents both experimental and numerical investigation of ignition characteristics of n-heptane and n-butanol mixture. The $O_2$ concentration was fixed to 9-10% to make high exhaust gas recirculation(EGR) rate condition. Experiments were performed using a rapid compression machine. In addition, a numerical study of the ignition delay time was performed using CHEMKIN codes to validate experimental results and predict chemical species after combustion process. The results showed that the ignition delay time increased with increasing n-butanol ratio and the reactivity decreased by low $O_2$ concentration.

• Journal of Bio-Environment Control
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• v.12 no.2
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• pp.95-100
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• 2003

To evaluate the effect of the fertilizer concentration after flowering on growth a31d fruit setting of ornamental pepper (Capsicum annuum L.), plants were fertilized with $100\;mg{\cdot}L^{-1} of N ($EC=0.8\;dS{\cdot}m^{-1}) until flowering, and then with 0 (no fertilizer), 100, 200 or $300\;mg{\cdot}L^{-1} of N (fertilizer solution EC of 0.15, 0.8, 1.45 or $2.10\;dS{\cdot}m^{-1}, respectively) until harvest. Maximum leaf area and shoot dry mass at the end of the growing period were obtained when plants were fertilized with $200\;mg{\cdot}L^{-1} of N. Total fruit number per plant at the end of the growing period was not different when plants were fertilized with 100,200 or 300 mg{\cdot}L^{-1}of N concentration. When plants were fertilized with $200\;mg{\cdot}L^{-1} of N, the number of fruits per plant was decreased significantly as compared to 100, 200 or $300\;mg{\cdot}L^{-1} of N, whereas the percentage of red fruits at the end of the growing period was maximized. Total fruit fresh weight per plant at the end of the growing period was highest with the concentration of $200\;mg{\cdot}L^{-1} of N. The EC of the growing medium remained within 0.8 to $1.2\;dS{\cdot}m^{-1}\;2.0\;to\;3.0dS{\cdot}m^{-1}, or 3.0 to 4.5 dS{\cdot}m^{-1}when fertilizer concentrations were 100, 200 or $300\;mg{\cdot}L^{-1} of N, respectively. Throughout most of the experiment, the pH of the growing medium remained within 5.4 to 6.2, but dropped to 4.9 near the end of the experiment when fertilizer concentration was 200 or 300\;mg{\cdot}L^{-1} of N. Content of most of the nutrients In the leaf was not affected by the different fertilizer concentration. Only aluminum was significantly affected and decreased linearly with increasing fertilizer concentration. The results from this study indicated that optimal fertilizer concentration after flowering for commercial production of ornamental pepper was 100 or $200\;mg{\cdot}L^{-1} of N. At these concentrations, the EC of the growing medium remained approximately within 0.8 to 1.2 and 2 to $3\;dS{\cdot}m^{-1}, respectively. This appears to be the optimal range for vegetative growth or fruit setting of ornamental pepper plants, and indicates that ornamental pepper can be grown with a fairly wide range of fertilizer concentrations.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.324-327
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• 1988

The photovoltaic performances of a-si : H$n^{+}-p-p^{+}$ solar cells have been investigated. The optimum substrate temperature for the deposition of a-Si : H $n^{+}-p-p^{+}$ cell decreases with increasing doping concentration of the p-layer, and is less than 200$^{\circ}C$ when the gas phase doping concentration is higher than 10 ppm. The results can be explained as the dependences of substrate temperature for the relaxation of silicon atoms and for the bonded hydrogen concentration in the p-layer.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.2
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• pp.145-148
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• 2008

Cationic surfactant can be used as cosmetics and chemical dispersants. The variation of critical micelle concentration (CMC) with temperature over the range $40^{\circ}C$ to $60^{\circ}C$ for N-octadecyl pyridinium bromide was measured by drop methods. Thermodynamic quantities such as free energy, enthalpy, entropy and heat capacity for micellization of N-octadecyl pyridinium bromide in water were calculated by fourth-degree polynominal equation In the result, free energy change was decreased generally by the increment of temperature.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.222-227
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• 2004

Under cyclic loading, the fatigue failures of welded joints occur at weld toes which induce stress concentration by weld shape. So we need to obtain the peak stress and the S-N curve to assess the fatigue strength of welded joints. However the measurement of peak stress is of high uncertainty and low reproducibility, so we use nominal stress instead in fatigue tests of welded joints. In this study, fatigue tests to obtain S-N curves and FE analyses to obtain stress concentration factors were conducted for the two types of cruciform fillet welded joints, that is, load-carrying and non load-carrying types. Then we changed the obtained S-N curves to that based on peak stress using the hot-spot stress concept. From the analyses of the S-N curves obtained, we have concluded that there is a need to develop a new method to evaluate the fatigue life.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.4
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• pp.457-464
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• 2020

In this study, extraction of uranium(VI) from an aqueous nitric acid solution was investigated using tri-n-butyl phosphate (TBP) as an extractant in an ionic liquid, 1-alkyl-3-methylimidazolium bis (trifluoromethylsulfonyl)imide ([Cnmim][Tf2N]). The distribution ratio of U(VI) in 1.1 M TBP/[Cnmim][Tf2N] was significantly high when the concentration of nitric acid was low. The value of the distribution ratio decreased as the concentration of the nitric acid increased at lower acidities, and then increased with a nitric acid concentration of up to 8 M. This can be attributed to the different extraction mechanisms of U(VI) based on nitric acid concentrations. Thus, a cation exchange at low acidity levels and an ion-pair extraction at high acidity levels were suggested as the extraction mechanism of U(VI) in the TBP/[Cnmim][Tf2N] system.

• The Korean Journal of Ecology
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• v.15 no.2
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• pp.147-155
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• 1992

Litterfall, decomposition, and dynamics of n and p in decomposing litter were investigated for 2 years in red pine ( pinus densiflora) and chinese thuja( thuja orientalis)stands in the limestone area. Average litterfall in red pine and chinese thuja stands were 4, 535kgDM ha-1 yr-1 and 5, 010 kgDM ha-1 yr-1, respectively. Seasonal litterfall in red pine and chinese thuja stands showed peaks in November. concentrations of N and P in the needle litter were lowest in the winter when the greast litterfall occurred, and highest in the summer when the least litterfall occurred. However, those in chinese thuja scale leaf litter showed litter seasonal variation.amount of N and P returned to the forest floor through litterfall were 29.02kgN ha-1 yr-1 , 2.81 kg P ha-1 yr-1 for red pine stand, and 31.06 kg N ha-1 yr-1 , 2.86kgP ha-1 yr-1 for chinese thuja stand, respectively. After 21 mounts elapsed, needle and chinese thuja scale leaf litterbags lost 34.8% and 32.5% of the initial weight, respectively. N concentrations in the docomposing needle and chines thuja scale leaf litter decreased by 19% and 30%, respectively, after 1 month elapsed, and then gradually increased to exceed the initial concentration after 9 months elapsed and then gradually increased to exceed the initial concentration after 9 months elapsed in both of them, P in needle and chines thuja scale leaf litter decreased by 54% and 57% of the initial concentration, respectively, after 1 month elapsed. unlike N, P concentration in the decomposing litter did not exceed that of initial ones. Neyt immobilization period of N and P in decomposing litter did not occur over the study period.

• Journal of Environmental Science International
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• v.14 no.2
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• pp.157-165
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• 2005

This study was conducted to determine optimum design parameters in nitrification and denitrfication of chemical fertilizer wastewater using pilot plant, Jet Loop Reactor. The chemical fertilizer wastewater which contains low amounts of organic carbon and has a high nitrogen concentration requires a post-denitrfication system. Organic nitrogen is hydrolyzed above $86\%$, and the concentration of organic nitrogen was influent wastewater 126mg/L and of effluent wastewater 16.4mg/L, respectively. The nitrification above $90\%$ was acquired to TKN volumetric loading below $0.5\;kgTKN/m^3{\cdot}d$, TKN sludge loading below $0.1\;kgTKN/kgVSS{\cdot}d$ and SRT over 8days. The nitrification efficiency was $90\%$ or more and the maximum specific nitrification rate was $184.8\;mgTKN/L{\cdot}hr$. The denitrification rate was above $95\%$ and the concentration of $NO_3-N$ was below 20mg/L. This case was required to $3\;kgCH_3OH/kgNO_3-N$, and the effluent concentration of $NO_3^--N$ was below 20mg/L at $NO_3^--N$ volumetric loading below $0.7\;kgNO_3^--N/m^3{\cdot}d$ and v sludge loading below $0.12\;kgNO_3^-N/kgVSS{\cdot}d$. At this case, the maximum sludge production was $0.83\;kgTS/kgT-N_{re}$ and the specific denitrfication rate was $5.5\;mgNO_3-N/gVSS{\cdot}h$.

• Polymer(Korea)
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• v.32 no.6
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• pp.549-554
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• 2008

In order to synthesize polymer particle containing inorganic material, styrene and n-butylmethacrylate were copolymerized with alumina by dispersion polymerization. The weight ratio of styrene to n-butylmethacrylate was 3 : 1. A poly(N-vinyl pyrrolidon) was added as stabilizer. 2,2'-AzobisCisobutyronitrile) and 3-methacryloxypropyl trimethoxysilane were used as initiator and coupling agent, respectively. The weight ratio of 70 : 30 of isopropanol to distilled water was used as dispersion medium. According to the TEM measurement, we could confirm that alumina was dispersed into the polymer particle. The increase 'of concentration of alumina resulted in enhancement of particle size, but decreased its distribution. By the XRD method, it was found that the increase of alumina concentration showed the increase of intensity in peak and the increased 2$\theta$ value. From the TGA measurement, the increase of alumina concentration caused high heat resistance of the polymer. With respect to the type of initiator, the longer half life of initiator, the smaller particle size. We also found that the increase of particle stabilizer concentration made the decreased of particle size due to the accelerated generation of polymer particle in the early stage of reaction.

• Journal of Preventive Medicine and Public Health
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• v.39 no.2
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• pp.171-176
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• 2006

Objectives : The objective of this study is to assess the factors influencing biological monitoring of textile coating factory workers exposed to N,N-dimethylformamide(DMF). Methods : We studied 35 workers who were occupationally exposed to DMF from 9 textile coating factories. The study was carried out in two phases; summer and winter. While air concentration of DMF, temperature and humidity were assessed in order to monitor the atmospheric conditions, biological monitoring was done to determine the internal dose by analyzing the N-methylformamide(NMF) collected from urine at the beginning and end of the shift. Questionnaires and medical surveillance were also obtained during the two phases. Results : Median air concentrations of DMF in winter and summer were 1.85 ppm and 2.78 ppm respectively. Also the difference between the urinary NMF concentration at the beginning and end of the shift $({\Delta}NMF)$ was always significant in each season (P < 0.001). The correlations between log DMF in air, log end-of-shift urinary NMF (r=0.555, P < 0.001) and log ${\Delta}NMF$ (r = 0.444, P < 0.001) was statistically significant in summer. The temperature, humidity, a shift system and different styles of clothing worn were significantly different during the two phases. In a multivariate analysis, temperature and the concentration of DMF in the air were the main factors influencing biological monitoring of textile coating factory workers. Conclusions : Concerning more comprehensive prevention measures to reduce exposure for those workers occupationally exposed to DMF, dermal exposure conditions such as temperature and humidity together with the air concentration of DMF should be assessed and biological monitoring is necessary to reduce adverse health effects, especially during the summer.