• Elastomers and Composites
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• v.42 no.1
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• pp.47-54
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• 2007

Reaction kinetics of polyurethane elastomers (PU) were studied using dynamic DSC and TGA for three PU samples of general purpose (Sample A), high temperature cross-likable CASE purpose with MOCA (Sample B), and RT cross-likable CASE purpose grade (Sample C). From DSC results, sample with MOCA(Sample B) showed lower shift of peak temperature, while showing broader thermograms than those of general purpose grade (Sample A). On the other hand, RT cross-linkable PU grade (Sample C) showed an interesting double mode reaction patterns, i.e., a lower temperature reaction at about $70\;^{\circ}C$, and a higher temperature reaction in the range of $140{\sim}170\;^{\circ}C$, indicating that it requires 2-step reaction process in order to complete the reaction. Once the cross-linking reaction completed, however, TGA results showed that all the samples would be considered to have similar chemical structures, showing similar decomposition processes. Sample C, especially, had showed decomposition properties of both Sample A and Sample B. Formation activation energies calculated from Kissinger method showed 10.39, 65.85, 36.52(Low $T_p$) and 18.21(High $T_p$) kcal/mol, while decomposition activation energies were 31.94, 30.84, 24.16 kcal/mol, respectively.

• Ecology and Resilient Infrastructure
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• v.2 no.3
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• pp.198-205
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• 2015

Impacts of climate change on aquatic ecosystems range from changes in physiological processes of aquatic organisms to species distribution. In this study, MaxEnt that has high prediction power without nonoccurrence data was used to simulate fish distribution changes in the Geum river watershed according to climate change. The fish distribution in 2050 and 2100 was predicted with RCP 8.5 climate change scenario using fish occurrence data (a total of 47 species, including 17 endemic species) from 2007 to 2009 at 134 survey points and 9 environmental variables (monthly lowest, highest and average air temperature, monthly precipitation, monthly lowest, highest and average water temperature, altitude and slope). The fitness of MaxEnt modeling was successful with the area under the relative operating characteristic curve (AUC) of 0.798, and environmental variables that showed a high level of prediction were as follows: altitude, monthly average precipitation and monthly lowest water temperature. As climate change proceeds until 2100, the probability of occurrence for Odontobutis interrupta and Acheilognathus yamatsuatea (endemic species) decreases whereas the probability of occurrence for Microphysogobio yaluensis and Lepomis macrochirus (exotic species) increases. In particular, five fish species (Gnathopogon strigatus, Misgurnus mizolepis, Erythroculter erythropterus, A. yamatsuatea and A. koreensis) were expected to become extinct in the Geum river watershed in 2100. In addition, the species rich area was expected to move to the northern part of the Geum river watershed. These findings suggest that water temperature increase caused by climate change may disturb the aquatic ecosystem of Geum river watershed significantly.

• Korean journal of food and cookery science
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• v.13 no.3
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• pp.364-368
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• 1997

The vitamin C contents in Mulkimchi (watery kimchi prepared with Yulmoo, leaf radish) were analyzed during its fermentation and storage at 30$^{\circ}C$, 15$^{\circ}C$ and 4$^{\circ}C$, respectively. The total amount of vit. C in Mulkimchi fermented for 1 day at 30$^{\circ}C$ was rapidly increased to the highest level of 20 mg％. At this time, Mulkimchi showed pH 4.5 and 0.2% of total acidity expressed in lactic acid. The total microbes of the kimchi amounted to 10$\^$8/ cfu/$m\ell$ which are mostly found to be lactic acid bacteria. However, the amount of vitamin C in Mulkimchi was decreased gradually during the storage at 30$^{\circ}C$, 15$^{\circ}C$ and 4$^{\circ}C$ for 9 days. In the Mulkimchi fermentated at 15$^{\circ}C$, the maximum amount of vitamin C was 15 mg％ at 4 to 5 day-fermentation. The pH of this kimchi was 4.0 and its acidity was 0.15% as lactic acid. When the storage temperature was dropped to 4$^{\circ}C$ after 1 day-fermentation at 15$^{\circ}C$, its vitamin C didn't reach the above level after 9 day storage. As the fermentation temperature was kept at 4$^{\circ}C$, the content of vitamin C in Mulkimchi remained at 10 mg％ of its initial storage and didn't change through the 9 days storage.

• Journal of the Korean Magnetics Society
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• v.9 no.3
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• pp.136-142
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• 1999

$Ni_{0.65}Zn_{0.35}Cu_{0.3}Fe_{1.7}O_4$ has been studied with x-ray diffraction, Mossbauer spectroscopy, and vibrating sample magnetometer. The crystal structure is found to be a cubic spinel with the lattice constant $a_0=8.403{\AA}$. Mossbauer spectra of have been taken at various temperatures ranging from 12 K to 665 K. as the temperature increases toward $T_N$ a systematic line broadening effect in the Mossbauer spectrum is observed and interpreted to originate from different temperature dependencies of the magenetic hyperfine fields at various iron sites. Also, by using binomial distribution equation we obtained the hyperfine fields of tetrahedral[A] and octahedral sites[B], $H_{hf}(A)=470\;kOe,\; H_{hf}(B0)=495 \;kOe,\; H_{hf}(B1)=485\;kOe, \;H_{hf}(B2)=453\;kOe,\; H_{hf}(B3)=424\;kOe,\; H_{hf}(B4)=390\;kOe,\; H_{hf}(Bavr)=451\;kOe$ respectively at room temperature. The isomer shift indicates that the iron ions are ferric at tetrahedral[A] and octahedral sites[B], respectively. The Neel temperature is determined to be $T_N=665\;K$. The results of the VSM data gave the magnetic moment and coercivity values of $M_S=66\; emu/g\;and\;H_C=36\;Oe$.

• Applied Chemistry for Engineering
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• v.30 no.3
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• pp.297-302
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• 2019

In order to investigate structural changes of the pyrolysis fuel oil (PFO), the volatile matters and heavy oil fractions were separated from PFO by heat treatment temperature. As a result of $^1H-NMR$ analysis of volatile matters, 1~2 ring aromatic compounds contained in the petroleum residue were mostly removed at a temperature before $340^{\circ}C$. Moreover, new peaks corresponding to aliphatic hydrocarbons were detected at the chemical shift of 2.0~2.4 ppm. It is attributed that the aliphatic hydrocarbon sidechain was cracked from the aromatic compound by the cracking reaction occurred at $320^{\circ}C$. The C/H mole ratio and aromaticity increased with increasing the heat treatment temperature. Therefore, from the structural analysis results of heavy oil fractions and volatile matters from PFO, the decomposition of the aliphatic sidechain by cracking reaction and the separation of volatile matters by boiling point of components were mostly affected structure changes of the PFO.

• The Korean Journal of Quaternary Research
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• v.17 no.2
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• pp.165-165
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• 2003

A borehole core ECSDP-102 (about 68.5 m long) has been investigated to get information on paleoenvironmental changes in response to the sea-level fluctuations during the period of late Quaternary. Several AMS $\^$14/C ages show that the core ECSDP-102 recorded the depositional environments of the northern East China Sea for approximately 60 ka. The Yangtze River discharged huge amounts of sediment into the northern East China Sea during the marine isotope stage (MIS) 3. In particular, $\delta$$\^$13/Corg values reveal that the sedimentary environments of the northern East China Sea, which is similar to the Holocene conditions, have taken place three times during the MIS 3. It is supported by the relatively enriched $\delta$$\^$13/Corg values of -23 to -21$\textperthousand$ during the marine settings of MIS 3 that are characterized by the predominance of marine organic matter akin to the Holocene. Furthermore, we investigated the three Holocene sediment cores, ECSDP-101, ECSDP-101 and YMGR-102, taken from the northern East China Sea off the mouth of the Yangtze River and from the southern Yellow Sea, respectively. Our study was focused primarily on the onset of the post-glacial marine transgression and the reconstructing of paleoenvironmental changes in the East China Sea and the Yellow Sea during the Holocene. AMS $\^$14/C ages indicate that the northern East China Sea and the southern Yellow Sea began to have been flooded at about 13.2 ka BP which is in agreement with the initial marine transgression of the central Yellow Sea (core CC-02). $\delta$$\^$18/O and $\delta$$\^$13/C records of benthic foraminifera Ammonia ketienziensis and $\delta$$\^$13/Corg values provide information on paleoenvironmental changes from brackish (estuarine) to modem marine conditions caused by globally rapid sea-level rise since the last deglaciation. Termination 1 (T1) ended at about 9.0-8.7 ka BP in the southern and central Yellow Sea, whereas T1 lasted until about 6.8 ka BP in the northern East China Sea. This time lag between the two seas indicates that the timing of the post-glacial marine transgression seems to have been primarily influenced by the bathymetry. The present marine regimes in the northern East China Sea and the whole Yellow Sea have been contemporaneously established at about 6.0 ka BP. This is strongly supported by remarkably changes in occurrence of benthic foraminiferal assemblages, $\delta$$\^$18/O and $\delta$$\^$13/C compositions of A. ketienziensis, TOC content and $\delta$$\^$13/Corg values. The $\delta$$\^$18/O values of A. ketienziensis show a distinct shift to heavier values of about 1$\textperthousand$ from the northern East China Sea through the southern to central Yellow Sea. The northward shift of $\^$18/O enrichment may reflect gradually decrease of the bottom water temperature in the northern East China Sea and the Yellow Sea.

• Journal of Environmental Science International
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• v.24 no.7
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• pp.851-864
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• 2015

This study analyzed the climate regime shift using statistical change-point analysis on the time-series tropical cyclone (TC) frequency that affected Japan in July to September. The result showed that there was a significant change in 1995 and since then, it showed a trend of rapidly decreasing frequency. To determine the reason for this, differences between 1995 to 2012 (9512) period and 1978 to 1994 (7894) period were analayzed. First, regarding TC genesis, TCs during the 9512 period showed a characteristic of genesis from the southeast quadrant of the tropical and subtropical western North Pacific and TCs during the 7894 period showed their genesis from the northwest quadrant. Regarding a TC track, TCs in the 7894 period had a strong trend of moving from the far east sea of the Philippines via the East China Sea to the mid-latitude region in East Asia while TCs in the 9512 period showed a trend of moving from the Philippines toward the southern part of China westward. Thus, TC intensity in the 7894 period, which can absorb sufficient energy from the sea as they moved a long distance over the sea, was stronger than that of 9512. Large-scale environments were analyzed to determine the cause of such difference in TC activity occurred between two periods. During the 9512 period, anomalous cold and dry anticyclones were developed strongly in the East Asia continent. As a result, Korea and Japan were affected by the anomalous northerlies thereby preventing TCs in this period from moving toward the mid-latitude region in East Asia. Instead, anomalous easterlies (anomalous trade wind) were developed in the tropical western Pacific so that a high passage frequency from the Philippine to the south China region along the anomalous steering flows was revealed. The characteristics of the anomalous cold and dry anticyclone developed in the East Asia continent were also confirmed by the analysis of air temperature, relative humidity and sensible heat net flux showing that most regions in East Asia had negative values.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.1
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• pp.16-24
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• 2011

The sound speed of seawater can be calculated by the empirical formula as a function of temperature, salinity and pressure. It is little affected by salinity because the average salinity is 34 psu and varies within a few psu seasonally and spatially in the ocean. Recently, low-salinity water of 24 psu flows into the western sea area of Jeju Island due to the flood of the Yangtze River in China during summer, affecting sound speed profile. In this paper, it was analyzed how environmental changes affected to the underwater communication - the sound speed of low-salinity water was calculated, and the communication channel was estimated by the simulated acoustic rays while the transmitting and receiving depth and the range were varied with and without the low-salinity layer. And The BER (Bit error rate) was calculated by BPSK(Binary phase shift key) modulation and the effects of the low-salinity water on the BER was investigated. The sound speed profile was changed to have positive slope by the low-salinity layer at the sub-surface up to 20 m of depth, forming acoustic wave propagation channel at the sub-surface resulting in the decrease of most of the BER Consequently, this paper suggests that it is important to consider changes of the ocean environment for correctly analyzing the underwater communication and the detection capability.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.6
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• pp.806-811
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• 2003

Effects of pH, temperature, light, sugars, organic acids, metal ions, ascorbic acid, thiamine nicotinic acid and pyridoxine on the stability of the color of the cranberry solution were investigated. The pH had marked influences on the color of the cranberry solution: i.e., the color of the cranberry solution was more intense at low pH. It showed characteristic bathochromic shift as the pH of the solution increased. The half-lives of olor value were 34 days at 37$^{\circ}C$, 91 mins at 9$0^{\circ}C$ and 29 mins at 12$0^{\circ}C$. Light gave an adverse effect to the stability of the color. The color degradation can be minimized by shielding the light from the cranberry solution. Among the sugars tested, fructose was the most deleterious followed by sucrose, galactose, maltose and glucose. Fumaric acid was found to be the most effective in stabilizing the color followed by citric acid, malic acid, acetic acid, while tartaric acid was found to be deleterious. Among the metal ions tested N $a^{+}$ and $Mg^{2+}$ were found to be effective in stabilizing the color, while M $n^{2+}$ was found to be the most deleterious followed by F $e^{2+}$, $K^{+}$ and $Ca^{2+}$. Ascorbic acid was found to be deleterious considerably followed by thiamine, while nicotinic acid and pyridoxine were found to be effective in stabilizing the color feebly.or feebly.

• Journal of the Korean Chemical Society
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• v.25 no.6
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• pp.351-360
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• 1981

Ultraviolet spectrophotometric investigations have been carried out on the system of durene with iodine, bromine, iodine monochloride and iodine monobromide in carbon tetrachloride. The results reveal the formation of the charge transfer complexes of the type, $C_6H_2(CH_3)_4{\cdot}X_2$ or $C_6H_2(CH_3)_4{\cdot}IX$(X denotes halogen atoms). The equilibrium constant were obtained in consideration of that absorption maxima due to the formation of the charge transfer complexes shift to blue with the increasing temperatures. The thermodynamic parameters, ${\Delta}H,\;{\Delta}G\;and\;{\Delta}S$ for the formation of the charge transfer complexes were calculated from these values. These results indicate that the relative stabilities of the durene complexes at each temperature decrease in the order, $ICl>IBr>I_2>Br_2$. This order may be a measure of their relative acidities toward durene, which is explained in terms of the relative polarizabilities of halogen molecules and the relative electronegativities of halogen atoms. These results combined with previous study of this series indicated that the relative stabilities of the polymethylbenzene complexes with iodine increase in the order; Benzene