• Journal of the Korean Magnetics Society
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• v.17 no.1
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• pp.18-21
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• 2007

The hexagonal $HoMn_{1-x}-Fe_xO_3$(x=0.00, 0.05) thin films were prepared using pulsed laser deposition(PLD) method on $Pt/Ti/SiO_2/Si$ substrate. The microstructure and magnetic properties have been studied by x-ray diffraction(XRD), atomic force microscopy (AFH), scanning electron microscope(SEM:), x-ray photoelectron spectroscopy(XPS), and conversion electron $M\"{o}ssbauer$ spectroscopy(CEMS). From the analysis of the x-ray diffraction patterns, the crystal structure for all films was found to be a hexagonal($P6_3cm$), which was preferentially grown along(110) direction. The lattice constant $c_0$ of the film with x=0.05 was close to that of single crystal, whereas lattice constant $a_0$ with respect to single crystal shows a slight decrease. This difference of lattice parameters between film and single crystal was caused by the lattice mismatch between the film and $Pt/Ti/SiO_2/Si$ substrate. Conversion electron $M\"{o}ssbauer$ spectrum of $HoMn_{0.95}Fe_{0.05}O_3$ thin film shows an asymmetry doublet absorption ratio at room temperature, which is due to the oriented direction of crystallographic domains. This is corresponding with analysis of x-ray diffraction. The quadrupole splitting(${\Delta}E_Q$) at room temperature is found to be $1.62{\pm}0.01mm/s$. This large ${\Delta}E_Q$ was caused by asymmetry environment surrounding Fe ion.

• Journal of the Korean Chemical Society
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• v.45 no.3
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• pp.242-246
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• 2001

The quaternary thiophosphates, $A_2NiP_2S_6$ (A=Rb, Cs), have been synthesized with halide fluxes and structurally characterized by single-crystal X-ray diffraction technique. These compounds crystallize in the space group $C_{2h}^5-P2_1/n$ of the monoclinic system with two formula units in a cell of dimensions a=5.960(2), b=12.323(4), $c=7.491(3)\AA$, $\beta=97.05(3)^{\circ}$, and $V=546.0(3)\AA^3$ for Rb2NiP2S6 and a=5.957(4), b=12.696(7), $c=7.679(4)\AA$, $b=93.60(5)^{\circ}$, and $V=579.7(5)\AA^3$ for $Cs_2NiP_2S_6.$ These compounds are isostructural. The structure of $Cs_2NiP_2S_6$ is made up of one-dimensional $_\infty^1[NiP_2S_6^{2-}]$ chains along the a axis and these chains are isolated by $Cs^+$ ions. The Ni atom is octahedrally coordinated by six S atoms. These Ni$S_6$ octahedral units are linked by sharing three m-S atoms of the $[P_2S_6^{4-}]$ anions to form the infinite one-dimensional $_\infty^1[NiP_2S_6^{2-}]$ chain. For $Cs_2NiP_2S_6$, the magnetic susceptibility reveals an antiferromagnetic exchange interaction below 8K,which corresponds to the Neel temperature ($T_N$). Above $T_N$, this compound obeys Curie-Weiss law. The magnetic moment, C, and ${\theta}forCs_2NiP_2S_6$ are 2.77 B.M., 0.9593 K, and -19.02 K, respectively. The effective magnetic moment obtained from the magnetic data is agreed with the spin-only value of $Ni^{2+}d^8$(2.83 B.M.) system.

• Food Science and Preservation
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• v.20 no.3
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• pp.304-316
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• 2013

To determine the appropriate harvest maturity of mulberry to prolong the freshness during distribution, mulberries were classified into three groups (80%, 90%, and 100%) based on their degree of maturity and then compared for their firmness, color, anthocyanin, soluble solids content, pH, titratable acidity, viable cell, mold and sensory quality. They were then investigated for quality changes by maturity under different distribution temperature at $20^{\circ}C$, $10^{\circ}C$ and $0^{\circ}C$. Immediately after harvest, the 80% matured mulberries were shown to be the firmest and 1.74 and 2.64 times firmer than 90% and 100% matured mulberries respectively. The more mature the mulberries were the lower the "a" value was while anthocyanin content was higher. The soluble solids content and pH of mulberries increased as they matured. Less mature the mulberries were the higher titratable acidity was and lower microbial levels in mulberries were. In terms of sensory quality, color of the 100% matured mulberries was the highest but the 90% matured mulberries were most preferred based on other sensory indexes. In comparison to storability of mulberries by maturity, although the firmness of the 80% matured mulberry decreased rapidly, they were the firmest during distribution periods. The level of mold of the 100% matured mulberries was higher than others. Moreover, the more mature mulberries were the quicker they deteriorated. According to quality indexes, depending on maturity and sensory evaluation of mulberry distributed at different temperatures, the storability of the 80 and 90% matured mulberries were higher than that of the 100% matured mulberries. In conclusion, judging by their sensory quality, the 90% matured mulberries were more appropriate for harvesting than the 80% matured mulberries.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.7
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• pp.380-394
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• 2015

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2014. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of heat and mass transfer, cooling and heating, and air-conditioning, the flow inside building rooms, and smoke control on fire. Research issues dealing with duct and pipe were reduced, but flows inside building rooms, and smoke controls were newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for thermal contact resistance measurement of metal interface, a fan coil with an oval-type heat exchanger, fouling characteristics of plate heat exchangers, effect of rib pitch in a two wall divergent channel, semi-empirical analysis in vertical mesoscale tubes, an integrated drying machine, microscale surface wrinkles, brazed plate heat exchangers, numerical analysis in printed circuit heat exchanger. In the area of pool boiling and condensing, non-uniform air flow, PCM applied thermal storage wall system, a new wavy cylindrical shape capsule, and HFC32/HFC152a mixtures on enhanced tubes, were actively studied. In the area of industrial heat exchangers, researches on solar water storage tank, effective design on the inserting part of refrigerator door gasket, impact of different boundary conditions in generating g-function, various construction of SCW type ground heat exchanger and a heat pump for closed cooling water heat recovery were performed. (3) In the field of refrigeration, various studies were carried out in the categories of refrigeration cycle, alternative refrigeration and modelling and controls including energy recoveries from industrial boilers and vehicles, improvement of dehumidification systems, novel defrost systems, fault diagnosis and optimum controls for heat pump systems. It is particularly notable that a substantial number of studies were dedicated for the development of air-conditioning and power recovery systems for electric vehicles in this year. (4) In building mechanical system research fields, seventeen studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, and renewable energies, piping in the buildings. Proposed designs, performance performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the evaluation of work noise in tunnel construction and the simulation and development of a light-shelf system. The subjects of building energy were worked on the energy saving of office building applied with window blind and phase change material(PCM), a method of existing building energy simulation using energy audit data, the estimation of thermal consumption unit of apartment building and its case studies, dynamic window performance, a writing method of energy consumption report and energy estimation of apartment building using district heating system. The remained studies were related to the improvement of architectural engineering education system for plant engineering industry, estimating cooling and heating degree days for variable base temperature, a prediction method of underground temperature, the comfort control algorithm of car air conditioner, the smoke control performance evaluation of high-rise building, evaluation of thermal energy systems of bio safety laboratory and a development of measuring device of solar heat gain coefficient of fenestration system.

• Korean Journal of Food Science and Technology
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• v.35 no.4
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• pp.635-641
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• 2003

A non-thermal pasteurization technology, high Pulsed Electric Field (PEF) has been thought to be a new alternative processing technology instead of heating. The objective of this study was to examine and compare the effect of PEF and High Temperature Short Time (HTST) treatments on the physicochemical, microbiological and sensory characteristics of citrus juices. Total sugar and titratable acidity values of fresh citrus juice and two treatments were not significantly different each other at p<0.05. The concentration of vitamin C in fresh citrus juice $(31.2{\pm}0.59\;mg%)$ was not significantly different with the value of PEF treatment $(29.4{\pm}0.75\;mg%)$ but was significantly higher than the value of HTST treatment $(27.4{\pm}0.75\;mg%)$. The color values (L, a, and b) in PEF treatment were significantly lower than the fresh citrus juice, but were higher than the values of HTST treatment. Both total bacterial cell counts $(6.65\;{\pm}\;0.08\;log_{10}(cfu/mL))$ and yeast counts $(7.79{\pm}0.07\;log_{10}(cfu/mL))$ in fresh citrus juice were significantly reduced by PEF $(1.39{\pm}0.14,\;2.42{\pm}0.1\;log_{10}(cfu/mL))$ as well as HTST treatment (0, 0). PE activity of fresh citrus juice $(1.3{\pm}0.12\;units/mL)$ was significantly reduced by PEF treatment $(0.11{\pm}0.01\;units/mL)$ and was totally inactivated by HTST treatment. Sensory evaluation scores in flavor, taste and overall acceptability between the fresh and PEF treated citrus juices $(7.2{\sim}7.5)$ were not significantly different but the values of HTST treatment $(5.1{\sim}5.8)$ were lower than others. Consequently, PEF treatment is thought to be a good alternative pasteurization method for fresh citrus juice to HTST treatment due to its strong pasteurization effect, reduced destruction of nutrients and good sensory characteristics.

• Journal of Animal Environmental Science
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• v.2 no.1
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• pp.41-52
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• 1996

This experiment was carried out to study the effect of sprinkler and fan cooling system on the physiological parameter, milk production and milk composition for Holstein cows in hot, humid climates. Thirty cows were assigned to one of two sections of open-sided loose barn. Water nozzles of sprinkler system were spaced in line at 1.2m intervals. Forced air was provided by 85cm diameter fans at rate of 3.4㎥/sec. The results obtained from these experiments are as follows: 1. There was no significant difference in meteorological data between control and fan + sprinkler cooling system(treatment group). 2. Skin temperature and rectal temperature of the treatment group were significantly lower than those of the control group (32.96 : 39.53$^{\circ}C$ vs 34.02 : 41.21$^{\circ}C$ respectively) (P<0.05). 3. Serum cortisol concentration of the treatment group(0.90$\mu\textrm{g}$/dL) was lower than that of control group(1.44$\mu\textrm{g}$/dL)(P<0.05). 4. Milk production of cows cooled with a sprinkler and fan cooling system was significantly higher than that of no cooling system (P<0.0l). 5. Lactose, protein and solid-not-fat content of milk were not changed by the treatments. Milk fat content of the control(3.23%) was low compared with the treatment group(3.38%). Somatic cell count was reduced by 26.63% in the treatment. The results indicate that a sprinkler and fan cooling systems can provide an effective means to relieve heat stress and enhance productivity of lactating Holstein cows during hot and humid summer season.

• Clean Technology
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• v.27 no.4
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• pp.332-340
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• 2021

With the recent reinforcement of emission standards, it is necessary to make efforts to reduce NOx from air pollutant-emitting workplaces. The NOx reduction method mainly used in industrial facilities is selective catalytic reduction (SCR), and the most commercial SCR catalyst is the ceramic honeycomb catalyst. This study was carried out to reduce the NOx emitted from steel plants by applying De-NOx catalyst coated on metallic monolith. The De-NOx catalyst was synthesized through the optimized coating technique, and the coated catalyst was uniformly and strongly adhered onto the surface of the metallic monolith according to the air jet erosion and bending test. Due to the good thermal conductivity of metallic monolith, the De-NOx catalyst coated on metallic monolith showed good De-NOx efficiency at low temperatures (200 ~ 250 ℃). In addition, the optimal amount of catalyst coating on the metallic monolith surface was confirmed for the design of an economical catalyst. Based on these results, the De-NOx catalyst of commercial grade size was tested in a semi-pilot De-NOx performance facility under a simulated gas similar to the exhaust gas emitted from a steel plant. Even at a low temperature (200 ℃), it showed excellent performance satisfying the emission standard (less than 60 ppm). Therefore, the De-NOx catalyst coated metallic monolith has good physical and chemical properties and showed a good De-NOx efficiency even with the minimum amount of catalyst. Additionally, it was possible to compact and downsize the SCR reactor through the application of a high-density cell. Therefore, we suggest that the proposed De-NOx catalyst coated metallic monolith may be a good alternative De-NOx catalyst for industrial uses such as steel plants, thermal power plants, incineration plants ships, and construction machinery.

• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.52-58
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• 2023

With the increasing awareness of the importance of carbon neutrality in response to global climate change, the utilization of hydrogen as a carbon-free fuel source is also growing. Hydrogen is commonly used in fuel cells (FC), but it can also be utilized in internal combustion engines (ICE) that are based on combustion. Particularly, ICEs that already have established infrastructure for production and supply can greatly contribute to the expansion of hydrogen energy utilization when it becomes difficult to rely solely on fuel cells or expand their infrastructure. However, a disadvantage of utilizing hydrogen through combustion is the potential generation of nitrogen oxides (NOx), which are harmful emissions formed when nitrogen in the air reacts with oxygen at high temperatures. In particular, for the EURO-7 exhaust regulation, which includes cold start operation, efforts to reduce exhaust emissions during the warm-up process are required. Therefore, in this study, the characteristics of nitrogen oxides and fuel consumption were investigated during the warm-up process of cooling water from room temperature to 88℃ using a 2-liter direct injection spark ignition (SI) engine fueled with hydrogen. One advantage of hydrogen, compared to conventional fuels like gasoline, natural gas, and liquefied petroleum gas (LPG), is its wide flammable range, which allows for sparser control of the excessive air ratio. In this study, the excessive air ratio was varied as 1.6/1.8/2.0 during the warm-up process, and the results were analyzed. The experimental results show that as the excessive air ratio becomes sparser during warm-up, the emission of nitrogen oxides per unit time decreases, and the thermal efficiency relatively increases. However, as the time required to reach the final temperature becomes longer, the cumulative emissions and fuel consumption may worsen.

• Korean Journal of Agricultural Science
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• v.13 no.1
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• pp.82-89
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• 1986

This experiment was carried out to determine the optimum freezing and thawing rates of the hamster embryos. The female hamsters were induced to superovulate by intraperitoneal injections of 30 i.u. PMSG and mated with males of the same strain of 4 days the PMSG injection. They were killed and embryos were flushed from the oviduct and uterine horn on 3 days after mating. Embryos were flushed with a modified Dulbecco's phosphate-buffered saline and equilibrated with 1.5 M-dimethylsulphoxide by a 3-step procedure. The freezing rates of the samples were $1^{\circ}C/min$ from room temperature to $-6^{\circ}C$ and the samples were seeded at $-6^{\circ}C$. After being held for 3 min at the seeding temperature, the rates were $0.3^{\circ}C/min$ from $-6^{\circ}C$ to $-35^{\circ}C$. From $-35^{\circ}C$ to $-70^{\circ}C$, the rates were divided into $0.1^{\circ}C/min$, $1^{\circ}C/min$ and $10^{\circ}C/min$, respectively. At $-70^{\circ}C$ the samples were plunged directly into liquid nitrogen. The samples were thawed at $4^{\circ}C/min$ and $12^{\circ}C/min$ from $-196^{\circ}C$ to $37^{\circ}C$, and for 2 min in $37^{\circ}C$ water bath, respectively. The average numbers of ovulation points and embryos recovered were 35.1 and 27.0 appearing 77.0% recovery rates. Eight cell embryos in the embryos recovered were 24.8. The survival rates of embryos according to the freezing rates were 55.5~67.7% at $0.1^{\circ}C/min$, 58.8~64.9% at $1^{\circ}C/min$ and 40.5~44.7% at $10^{\circ}C/min$, respectively. The survival rates at $10^{\circ}C/min$ were significantly low. The survival rates of embryos according to the thawing rates were 53.5% at $4^{\circ}C/min$, 53.7% at $12^{\circ}C/min$ and 59.1% in $37^{\circ}C$ water bath. The survival rates, in $37^{\circ}C$ water bath were slightly higher, but we did not find any differences among them. In conclusion, the best freezing rates of hamster embryos were $1^{\circ}C/min$ from the room temperature to $-6^{\circ}C/min$, $0.3^{\circ}C/min$ from $-6^{\circ}C/min$ to $-35^{\circ}C$ and $-0.1^{\circ}C/min$ or $1^{\circ}C/min$ from $-35^{\circ}C$ to $-70^{\circ}C$. The hamster embryos thawed for 2 min in $37^{\circ}C$ water bath showed the best survival rates.

• Korean Journal of Animal Reproduction
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• v.27 no.3
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• pp.215-223
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• 2003

This study was to investigate the effects of fertilization time and culture medium of pig oocytes matured in-vitro by liquid boar sperm. The sperm rich fraction (30∼60 ml) was slowly cooled to room temperature (20∼23$^{\circ}C$) by 2 h after collection. Semen was transferred into 15 ml tubes, centrifuged at room temperature for 10 min 800 ${\times}$ g, and the supernatant solution was poured off. The concentrated sperm was resuspended with 5 ml of the LEN diluent to provide 1.0${\times}$10$^{9}$ sperm/ml at room temperature. The resuspended semen was cooled in a refrigerator to 4$^{\circ}C$. The medium used for oocyte maturation was TCM-199 supplemented with 26.19 mM sodium bicarbonate, 0.9 mM sodium pyruvate, 10 $\mu\textrm{g}$/ml insulin, 2 $\mu\textrm{g}$/ml vitamin B$_{12}$ , 25 mM HEPES, 10 $\mu\textrm{g}$/ml bovine apotransferrin, 150 $\mu$M cysteamine, 10 IU/ml PMSG, 10 IU/ml hCG, 10 ng/ml EGF, 0.4% BSA, 75 $\mu\textrm{g}$/ml sodium penicillin G, 50 $\mu\textrm{g}$/ml streptomycin sulfate and 10% pFF. After about 22 h of culture, oocytes were cultured without cysteamine and hormones for 22 h at 38.5$^{\circ}C$, 5% $CO_2$ in air. Oocytes were inseminated with liquid boar sperm stored at 4$^{\circ}C$ for 2 days after collection. Oocytes were coincubated for 1, 3, 6 and 9 h in 500 ${mu}ell$ mTBM fertilization media with 1.0${\times}$10$^{6}$ sperm/ml concentration, respectively. Thereafter, oocytes were transferred into 500 ${mu}ell$ NCSU-23, HEPES buffered NCSU-23, PZM-3 and PZM-4 culture media, respectively, for further culture of 6, 48 and 144 h. The rates of sperm penetration and male pronuclear formation were higher in the fertilization times for 6 and 9 h than in those for 1 and 3 h. The rates of cleaved oocytes were higher in the fertilization times for 6 and 9 h (85.0 and 84.6%) than in those for 1 and 3 h (61.1 and 76.8%). The percentage of blastocyst formation from the cleaved oocytes was highest in the fertilization time for 6 h (33.6%) than in that for 1, 3 and 9 h (11.4, 23.0 and 29.6%). Mean cell numbers per blastocyst were 32.9, 27.6, 26.3 and 24.4 in the fertilization times for 6, 9, 3 and 1 h, respectively. The rate of blastocyst from the cleaved oocytes and the number of cells per blastocyst were higher in HEPES buffered NCSU-23 culture medium than in NCSU-23, PZM-3 and PZM-4 culture media. In conclusion, we found out that liquid boar sperm stored at 4$^{\circ}C$ could be used for in-vitro fertilization of pig oocytes matured in-vitro. Also, we recommend the coincubation time of 6 h in 500 ${mu}ell$ TBM fertilization medium with 1${\times}$10$^{6}$ sperm/ml concentration and the HEPES buffered NCSU-23 culture medium for in-vitro fertilization of pig oocytes matured in-vitro.