• International Journal of Air-Conditioning and Refrigeration
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• v.15 no.3
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• pp.114-121
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• 2007

In this study, a modified reverse flow type, one of the triple effect absorption cycles, is studied for performance improvement. The cycle simulation is carried out by using EES(Engineering Equation Solver) program for the working fluid of $H_2O/LiBr$ solution. The split-ratios of solution flow rate, UA of each component, pumping mass flow rate of solution are considered as key parameters. The results show that the optimal SRH (split ratio of high side) and SRL (split ratio of low side) values are 0.596 and 0.521, respectively. Under these conditions, the COP is maximized to 2.1. The optimal pumping mass flow rate is selected as 3 kg/s and the corresponding UAEV A is 121 kW/K in the present system. The present simulation results are compared to the other literature results from Kaita's (2002) and Cho's (1998) triple effect absorption systems. The present system has a lower solution temperature and a higher COP than the Kaita's modified reverse flow, and it also gives a higher COP than the Cho's parallel flow by adjusting split ratios.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.6
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• pp.681-688
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• 2019

SM45C steel, which is widely used for mechanical structure, was carburized at 870℃ for 4 hours and tempered at 300℃ and 400℃ for 1, 3 and 6 hours. The tempered materials were evaluated for tensile test, hardness test and impact test. In particular, the hardness and the absorption energy were evaluate the reliability by the Weibull statistical analysis. 300℃-1h specimen is considered to be the best heat treatment condition in the tensile stress and the observation of fracture surface. 300℃-1h specimen showed larger shape and scale parameter than the other specimens, and Rockwell hardness variance was small and showed the best characteristics. 400℃-3h specimen showed larger shape and scale parameter than the other specimens, the dispersion of impact absorption energy is small, and showed excellent characteristics.

• Current Photovoltaic Research
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• v.4 no.3
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• pp.93-97
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• 2016

Light-emitting chromophores have been separated from silica spheres modified the surface with 3-(trimethoxysilyl)propylmethacrylate (TMSPM). The photoluminescence characteristics of the chromophores were investigated with various excitation wavelengths. The TMSPM was attached to the surface of silica spheres at $75^{\circ}C$. Large number of round shaped particles of the TMSPM was on the surface of silica spheres after 3 h reaction. The TMPSM was completely covered on the surface of the spheres after 6 h reaction. The surface modified silica spheres were soaked into acetone and stored for 20 days at ambient condition. The solution color slowly changed from light yellow to deep yellow with the increase of the storing time. The FTIR absorption peaks at 3348, 2869, 2927, 1715, 1453/1377, 1296, and $1120cm^{-1}$ represent C-OH, $R-CH_3$, $R_2-CH_2$, -C=O, C-H, C=C-H, and Si-O-Si absorption, respectively. The FTIR absorption peak at $1715cm^{-1}$ representing the ester -C=O stretching vibration for silica spheres stored for 20 days was increased compared with the spheres without aging. The UV-visible absorption peaks were at 4.51 eV (275 nm) and 3.91 eV (317 nm). There were two luminescence peaks at 2.51 eV (495 nm) and 2.25 eV (550 nm). The emission at 2.51 eV was dominant peak when the excitation energy was higher than 2.58 eV, and emission at 2.25 eV became dominant peak when the excitation energy was lower than 2.58 eV.

• Environmental Engineering Research
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• v.24 no.3
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• pp.389-396
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• 2019

The electrical energy consumption (EEC) in removal of NO by a $UV/H_2O_2$ oxidation process was introduced and related to removal efficiency of this gas. The absorption-reaction of NO was conducted in a bubble column reactor in the presence of $SO_2$. The variation in NO removal efficiency was investigated for various process parameters including NO and $SO_2$ inlet concentrations, initial concentration of $H_2O_2$ solution and gas flow rate. EEC values were obtained in these different conditions. The removal efficiency was increased from about 22% to 54.7% when $H_2O_2$ concentration increased from 0.1 to 1.5 M, while EEC decreased by about 70%. However, further increase in $H_2O_2$ concentration, from 1.5 to 2, had no significant effect on NO absorption and EEC. An increase in NO inlet concentration, from 200 to 500 ppm, decreased its removal efficiency by about 10%. However, EEC increased from $2.9{\times}10^{-2}$ to $3.9{\times}10^{-2}kWh/m^3$. Results also revealed that the presence of $SO_2$ had negative effect on NO removal percentage and EEC values. Some experiments were conducted to investigate the effect of $H_2O_2$ solution pH. The changing of pH of oxidation-absorption medium in the ranges between 3 to 10, had positive and negative effects on removal efficiency depending on pH value.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05c
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• pp.3-7
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• 2004

$HgGa_2S_4:CO^{2+}$ single crystal were grown by the chemical transport reaction(CTR) method. 1n the optical absorption spectrum of the $HgGa_2S_4:CO^{2+}$ single crystal measured at 298K, three groups of impurity optical absorption peaks consisting of three peaks, respectively, were observed at 673nm, 734nm, and 760nm, 1621nm, 1654nm, and 1734nm, and 2544nm, 2650nm, and 2678nm. At 10K, the three peaks(673nm, 734nm, and 760nm) of the first group were split to be twelve peaks. These impurity optical absorption peaks are assigned to be due to the electronic transitions between the split energy levels of $Co^{2+}$ sited in the $S_4$ symmetry point.

• Journal of Soil and Groundwater Environment
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• v.16 no.6
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• pp.122-132
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• 2011

Mercury accumulates in biota mainly as methylmercury. In nature, methylmercury shows high affinity to organic matter and $CH_3Hg^+$-organic matter complexation affects the mobility and bioavailabiity of methylmercury. In this study, we examined the methylmercury binding sites in an aquatic humic acid as affected by the pH condition using Hg $L_{III}$-edge extended X-ray absorption fine structure (EXAFS). We evaluated methylmercury binding humic ligands using methylmercury-thiol, methylmerury-carboxyl, and methylmercury-amine complexation models. When $CH_3Hg^+$-to-humic reduced sulfur ratio is 0.3, we found that most of $CH_3Hg^+$ binds to thiol ligands at pH 5 and 7. At pH 7, however, some carboxyl or amine ligand contribution is observed, unlike at pH 5 where $CH_3Hg^+$ almost exclusively binds to thiol ligands. The carboxyl or amine ligand contribution may indicate that some types of thiol ligands in the natural organic matter have relatively low complexation constants or acid dissociation constants compared to those of some carboxyl or amine ligands. Analysis results indicate that ~0.2 fraction of methylmercury binds to amine or carboxyl ligands and ~0.8 to thiol ligands at pH 7.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.10
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• pp.825-832
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• 2002

The present study investigated the enhancement of the absorption performance by the spring wrapped around the outer surface of the vertical falling film absorber tube. Heat and mass transfer enhancements were experimentally investigated, and flow visualization was performed to observe the wettability and flow pattern of the solution. The key experimental parameters were spring diameter (0.5, 1.0 mm) and spring pitch (1, 3, 10 mm), film Reynolds number (50~150), and concentration of LiBr-$H_2O$ solution (55, 60, 65 wt%). As the spring diameter was increased, the absorption mass flux, Sherwood number, Nusselt number, heat flux, and heat transfer coefficient were increased The Nusselt and Sherwood numbers showed the maximum at the spring pitch of 3mm, and the ratio of pitch to diameter of approximately 3 and 6 for the spring diamter of 0.5 mm, respectively.

• Atmosphere
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• v.21 no.3
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• pp.301-309
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• 2011

In this study, we compared light-absorption properties of aerosols observed in East and South Asia from black carbon (BC) mass concentration, aerosol scattering (${\sigma}_s$) and absorption (${\sigma}_a$) coefficients measurements at four sites: Korea Climate Observatory-Gosan (KCO-G), Korea Climate Observatory-Anmyeon (KCO-A), Maldives Climate Observatory-Hanimaadhoo (MCO-H) and Nepal Climate Observatory-Pyramid (NCO-P). No significant seasonal variations of BC mass concentration, ${\sigma}_s$ and ${\sigma}_a$, despite of wet removal of aerosols by precipitation in summer, were observed in East Asia, whereas dramatic changes of light-absorbing aerosol properties were observed in South Asia between dry and wet monsoon periods. Although BC mass concentration in East Asia is generally higher than that observed in South Asia, BC mass concentration at MCO-H during winter dry monsoon is similar to that of East Asia. The observed solar absorption efficiency (${\alpha}$) at 550 nm, where ${\alpha}={\sigma}_a/({\sigma}_s+{\sigma}_a)$, at KCO-G and KCO-A is higher than that in MCO-H due to large portions of BC emission from fossil fuel combustion. Interestingly, ${\alpha}$ at NCO-P is 0.14, which is two times great than that in MCO-H and is about 40% higher than that in East Asia, though BC mass concentration at NCO-P is the lowest among four sites. Consistently, the highest elemental carbon to sulphate ratio is found at NCO-P.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2382-2388
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• 2007

A series of dimethine cyanine dyes were synthesized in a fast, efficient and high yield by the condensation of quaternary salts with 1H-indole-3-carbaldehyde in the presence of piperidine under solvent-free microwave irradiation. The products were identified by 1H NMR, IR, UV-Vis spectra and elemental analysis. The absorption and fluorescence properties of these dyes were investigated both experimentally and theoretically. Calculations performed at a combination of time-dependent density functional theory (TD-DFT) and the polarizable continuum model (PCM) reproduced the π-π* type absorption bands of the dyes. Regression analysis was used for studying theoretical results of the absorption maxima in different solvents. Compared with experimental counterparts, estimated overall uncertainties in the absorption maxima were about ±2%.

• Journal of the Korean institute of surface engineering
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• v.32 no.3
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• pp.297-302
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• 1999

In situ measurement of infrared absorption spectra has been performed during low-temperature plasma-enhanced chemical vapor depositiion of silicon-oxide films using tetramethoxysilane as a silicon source. Several absorption bands due to the reactant molecules are clearly observed before deposition. In the plasma, these bands completely disappear at any oxygen mixing ratio. This result shows that most of the tetramethoxysilane molecules are dissociated in the rf plasma, even C-H bonds. Existence of Si-H bonds in vapor phase and/or on the film surface during deposition has been found by infrared diagnostics. We observed both a decrease in Si-OH absorption and an increase in Si-O-Si after plasma off, which means the dehydration condensation reaction continues after deposition. The rate of this reaction is much slower than the deposition ratio of the films.