• Journal of Korean Society of Environmental Engineers
• /
• 제27권8호
• /
• pp.886-891
• /
• 2005

In this study, a novel bioreactor system using a submerged hollow fiber membrane module (so called hollow fiber membrane bioreactor, HFMB) was applied to investigate feasibility and biodegradation capacity of the system for the treatment of gaseous toluene. First an abiotic test was conducted to determine the mass transfer coefficient, showing the value was similar to that obtained from a diffuser system using fine bubbles. Second, in the presence of toluene-degrading microorganisms, the HFMB was operated at different inlet toluene loading rates of 50, 100, $500\;g/m^3/hr$, and overall removal efficiencies were maintained in the range of $70{\sim}80%$. In addition, elimination capacities(EC) were increased up to $800\;g/m^3/hr$, which was substantially higher than maximum ECs for toluene reported in the biofiltration literature. Consequently, the HFMB was considered as an alternative method over other conventional VOC-treating technologies.

• Korean Journal of Environmental Biology
• /
• 제32권4호
• /
• pp.311-318
• /
• 2014

PFOS (perfluorooctane sulfonate) is one of the perflourinated organic compound, which persist as a residual compound in the coastal environments. Intertidal mud crab Macrophthalmus japonicus mainly inhabits in coastal and bay ecosystems in Indo-Pacific region including Korea and reflects to environmental changes. In the present study, M. japonicus were exposed to different concentrations of PFOS and various ecotoxicological end-points such as survival rate, elimination of appendages, changes of the crust and internal organ color changes were investigated. Interestingly, the PFOS exposure showed concentration-dependent decrease of survival rate. High PFOS exposure ($30{\mu}gL^{-1}$) showed a low survival rate of 24% at 168 hours. Further, in comparison with the controls, the rate of elimination of appendages was also considerably increased in a time dependent manner upon PFOS exposure. Notably, with progression of time, an increased exposure to PFOS, test species showed whitening effect in a concentration-dependent manner, whereas the crab crust color was unchanged in the control. In addition, change in internal organs color and their visibility (clarity) observed in PFOS exposed crabs compared to control. Taken together, we suggest, eco-toxicology end-points of M. japonicus exposed to PFOS gave important biological information which could be useful to identify toxic contamination in the marine benthic environments.

• Korean Journal of Food Science and Technology
• /
• 제41권2호
• /
• pp.117-121
• /
• 2009

Soybean curd (SC) is prepared through the elimination of water-insoluble components and molding by pressing. However, whole soybean curd (WSC) is made without the elimination of water-insoluble components and pressing. Therefore, it was considered that the components contained in WSC might be different from those in SC and we compared their contents of various components, hardness, and morphological features for this study. Ash, dietary fiber, and niacin contents were significantly higher in WSC than in SC. In addition, the carbohydrate and vitamin $K_1$ contents of WSC tended to be higher than those in SC, whereas the hardness of WSC was lower than that of SC. Moreover, electron microscopic analysis showed that the morphological characteristic of WSC consisted of considerably more fine retiform tissues in comparison to SC. Based on their compared nutrition, functional, and quality characteristics, it was suggested that WSC might be superior to SC.

• KIPS Transactions on Software and Data Engineering
• /
• 제12권2호
• /
• pp.59-76
• /
• 2023

Since the COVID-19 era, the rise in apartment prices has been unconventional. In this uncertain real estate market, price prediction research is very important. In this paper, a model is created to predict the actual transaction price of future apartments after building a vast data set of 870,000 from 2015 to 2020 through data collection and crawling on various real estate sites and collecting as many variables as possible. This study first solved the multicollinearity problem by removing and combining variables. After that, a total of five variable selection algorithms were used to extract meaningful independent variables, such as Forward Selection, Backward Elimination, Stepwise Selection, L1 Regulation, and Principal Component Analysis(PCA). In addition, a total of four machine learning and deep learning algorithms were used for deep neural network(DNN), XGBoost, CatBoost, and Linear Regression to learn the model after hyperparameter optimization and compare predictive power between models. In the additional experiment, the experiment was conducted while changing the number of nodes and layers of the DNN to find the most appropriate number of nodes and layers. In conclusion, as a model with the best performance, the actual transaction price of apartments in 2021 was predicted and compared with the actual data in 2021. Through this, I am confident that machine learning and deep learning will help investors make the right decisions when purchasing homes in various economic situations.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• 제18권6호
• /
• pp.237-241
• /
• 2008

Hot-press sintering of AlN ceramics were carried out with $Y_2O_3$ as sintering additive at a sintering temperature $1,750{\sim}1,850^{\circ}C$. The effect of $Y_2O_3$ addition and sintering time on sintering behavior and thermal conductivity of AlN ceramics was investigated. $Y_2O_3$ added AlN showed noticeably higher denazification rate than pure AlN. The thermal conductivity of AlN specimens was promoted by the addition of $Y_2O_3$ in spite of the formation of YAG secondary phase in AlN grain boundaries and grain boundary triple junction because $Y_2O_3$ addition could reduced the oxygen contents in AlN lattice which is primary factor of thermal conductivity. Typically, the thermal conductivity of 5 wt% $Y_2O_3$ added specimen was dramatically improved by the increase of sintering time because the elimination of YAG secondary phases from the grain boundary due to the evaporation, as well as the grain-growth of AlN grains.

• Korean Journal of Food Science and Technology
• /
• 제41권5호
• /
• pp.528-535
• /
• 2009

Three domestic varieties of red grapes were utilized for the fermentation of wines, including Campbell, Muscat Bailey A (MBA), and Sheridan. The grapes were treated by four different methods before fermentation, which included conventional fermentation for red wine, fermentation with skin-removed grapes, fermentation with grapes and addition of removed skins, and fermentation with grape juice. Three different grape varieties with four different treatments did not show any differences in terms of $^{\circ}Bx$ and alcohol changes during fermentation. However, the L value of the MBA wine was lower and darker than the L values of wines prepared from Campbell and Sheridan grapes. The wines prepared from grapes with the addition of removed skins were darker and had 30% higher polyphenol concentrations than those of wines made from grapes by the conventional method, regardless of the grape varieties. Sensory evaluations of dry-type wines demonstrated that quality was higher for those made from Campbell and MBA grapes with the addition of removed skins than for wines made by the conventional method. Whereas for sweet-type wines, the wine that was made from the skin-removed grapes (Sheridan) was more favorable than that made by the conventional method.

• Korean Journal of Microbiology
• /
• 제39권1호
• /
• pp.8-15
• /
• 2003

To evaluate the effects of slow release fertilizer and chemical dispersant on oil biodegradation, mesocosm studies were conducted on sand seashore. The rapid removal rates (85%) of aliphatic hydrocarbons and the simultaneous decreases of n-$C_{17}$/pristane (69%) and $n-C_{18}/phytane$ (61%) ratios by the addition of slow-release fertilizer (SRF) within 37 days of experiment indicated that SRF could enhance the oil degrading activity of indigenous microorganisms in sand mesocosm. Although the growth of heterotrophic bacteria and petroleumdegrading bacteria in the mesocosm treated with $Corexit 9527^{R}$ was stimulated, the biological oil removal based on the ratios of $Corexit 9527^{R}$ and $n-C_{18}/phytane$ was inhibited. Removal rates of aliphatic hydrocarbons (56%), and n-$C_{17}$/pristane (27%) and $n-C_{18}/phytane$ (17%) ratios by the addition of chemical dispersant $Corexit 9527^{R}$ were similar or lower than those values of control (50, 60, 46%), respectively. The biodegradation activity, however, when simultaneously treated with SRF and $Corexit 9527^{R}$, was not highly inhibited and even recovered after the elimination of chemical dispersant. From these results it could be concluded that the addition of SRF enhanced the oil removal rate in oligotrophic sand seashore and chemical dispersant possibly inhibit the oil biodegradation. Hence, in order to prevent the unrestrained usage of chemical dispersant in natural environments contaminated with oil, the National Contingency Plan of Oil Spill Response should be carefully revised in consideration of the application for bioremedaition techniques.

• Korean Journal of Materials Research
• /
• 제21권7호
• /
• pp.357-363
• /
• 2011

In this paper, high temperature oxidation behavior of newly developed alloys, Ti-6Al-4Fe and Ti-6Al-1Fe, is examined. To understand the effect of Fe on the air oxidation behavior of the Ti-Al-Fe alloy system, thermal oxidation tests are carried out at $700^{\circ}C$ and $800^{\circ}C$ for 96 hours. Ti-6Al-4V alloy is also prepared and tested under the same conditions for comparison with the developed alloys. The oxidation resistance of the Ti-Al-Fe alloy system is superior to that of Ti-6Al-4V alloy. Ti-6Al-4V shows the worst oxidation resistance for all test conditions. This is not a result of the addition of Fe, but rather it is due to the elimination of V, which has deleterious effects on high temperature oxidation. The oxidation of the Ti-Al-Fe alloy system follows the parabolic rate law. At $700^{\circ}C$, Fe addition does not have a noticeable influence on the amount of weight gain of all specimens. However, at $800^{\circ}C$, Ti-6Al-4Fe alloy shows remarkable degradation compared to Ti-6Al-1Fe and Ti-6Al. It is discovered that the formation of $Al_2O_3$, a diffusion resistance layer, is remarkably hindered by a relative decrease of the ${\alpha}$ volume fraction. This is because Fe addition increases the volume fraction of ${\beta}$ phase within the Ti-6Al-xFe alloy system. Activities of Al, Ti, and Fe with respect to the formation of oxide layers are calculated and analyzed to explore the oxidation mechanism.

• 보존과학연구
• /
• 통권22호
• /
• pp.41-52
• /
• 2001

The wooden building is mainly damaged by the termite which have an effect of the structure by making emptied inner part of wood. One class, Japanese termite, inhabits throughout Korea and is often detected. So the deterioration by termite attacking the wooden building needs to be controlled. Termites are over 2,800 species in the world, usually they inhabit in the tropical or subtropical region and don’t over winter in dormant condition. So their activity and distribution are chiefly restricted by temperature and humidity. The termite inhabiting in Korea is Reticulitermes speratus kyushuensis Morimoto, which known to have an optimal temperature range at $12~30^{\circ}C$ and minimum temperature at $6^{\circ}C$ for activation. These temperatures correspond to the mean temperature($5.6^{\circ}C$~$25.8^{\circ}C$) from March to November and the activity time of termitein Seoul. In addition, as a result of environmental pollution by industrial development, the climate of Korea is getting warm. The increase of mean temperature in Korea has been $1.1^{\circ}C$ for the past seventy five years, so it is expected that the damage of wooden building by termite will increase gradually. Therefore, in order to protect wooden building from damages by termite, it needs not only development of new pest control methods, but also studies on the control of environmental factors having an effect on the activity and growth of termite. For the conservation of the large cultural properties such as the wooden building in the open air, it would be effective to use the methods of fumigation, insecticidal and antiseptic chemical treatment of wood materials, soil termiticideinjection treatment, and termite colony elimination system.

• International Journal of Industrial Entomology and Biomaterials
• /
• 제26권2호
• /
• pp.81-88
• /
• 2013

Wet-spun silk fibers have attracted the attention of many researchers because of 1) the unique properties of silk as a biomaterial, including good biocompatibility and cyto-compatability and 2) the various methods available to control the structure and properties of the fiber. Cellulose nanofibrils (CNFs) have typically been used as a reinforcing material for natural and synthetic polymers. In this study, CNF-embedded silk fibroin (SF) nanocomposite fibers were prepared for the first time. The effects of CNF content on the rheology of the dope solution and the characteristics of wet-spun CNF/SF composite fibers were also examined. A 5% SF formic acid solution that contained no CNFs showed nearly Newtonian fluid behavior, with slight shear thinning. However, after the addition of 1% CNFs, the viscosity of the dope solution increased significantly, and apparent shear thinning was observed. The maximum draw ratio of the CNF/SF composite fibers decreased as the CNF content increased. Interestingly, the crystallinity index for the silk in the CNF/SF fibers was sequentially reduced as the CNF content was increased. This phenomenon may be due to the fact that the CNFs prevent ${\beta}$-sheet crystallization of the SF by elimination of formic acid from the dope solution during the coagulation process. The CNF/SF composite fibers displayed a relatively smooth surface with stripes, at low magnification (${\times}500$). However, a rugged nanoscale surface was observed at high magnification (${\times}10,000$), and the surface roughness increased with the CNF content.