• Clean Technology
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• v.25 no.3
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• pp.198-205
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• 2019

The adsorption equilibrium, kinetic, and thermodynamic parameters of brilliant green adsorbed by coconut based granular activated carbon were determined from various initial concentrations ($300{\sim}500mg\;L^{-1}$), contact time (1 ~ 12 h), and adsorption temperature (303 ~ 323 K) through batch experiments. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin, Harkins-Jura, and Elovich isotherm models. The estimated Langmuir dimensionless separation factor ($R_L=0.018{\sim}0.040$) and Freundlich constant ($n^{-1}=0.176{\sim}0.206$) show that adsorption of brilliant green by activated carbon is an effective treatment process. Adsorption heat constants ($B=12.43{\sim}17.15J\;mol^{-1}$) estimated by the Temkin equation corresponded to physical adsorption. The isothermal parameter ($A_{HJ}$) by the Harkins-Jura equation showed that the heterogeneous pore distribution increased with increasing temperature. The maximum adsorption capacity by the Elovich equation was found to be much smaller than the experimental value. The adsorption process was best described by the pseudo second order model, and intraparticle diffusion was a rate limiting step in the adsorption process. The intraparticle diffusion rate constant increased because the dye activity increased with increases in the initial concentration. Also, as the initial concentration increased, the influence of the boundary layer also increased. Negative Gibbs free energy ($-10.3{\sim}-11.4kJ\;mol^{-1}$), positive enthalpy change ($18.63kJ\;mol^{-1}$), and activation energy ($26.28kJ\;mol^{-1}$) indicate respectively that the adsorption process is spontaneous, endothermic, and physical adsorption.

• Korean Journal of Heritage: History & Science
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• v.52 no.3
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• pp.160-171
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• 2019

The sword with a ring pommel, which was excavated from the first stone chamber of the ancient tombs of Jeongchon Village in Naju, is a sword with a pentagon undecorated ring pommel consisting of a mother sword and two child swords. The sword with an undecorated ring pommel of Jeongchon comprises a ring pommel, a hilt, a knife, and a knife end decoration. This sword was coated with lacquer. The ring pommel is an iron frame covered with silver plate; however the silver tarnished into a light purple due to silver chloride corrosion, and iron corrosion originated from the inside is visible on the surface. Silver chloride corrosion is produced when silver objects are exposed to water, dissolved salts, and dissolved chloride ions when in a buried state. It changes objects into powder, making it difficult to preserve original shapes. The other silver artifacts found in the Jeongchon ancient tombs show similar signs of corrosion. The results of X-ray irradiation and a CT analysis showed that the sword had a ring at the end of the handle, a T-shaped hilt, and was probably connected to the handle end of a knife. If the shape of the mother sword can be inferred from the child swords, the mother sword had a ring pommel, decorations of the handle, covered with silver plate, and a gold ring and a silver line wound around the handle. It is assumed that the ring pommel was connected to the knife by welding because no holes were observed. The end decoration of the knife was made by using an iron plate formed into a shape, half covered by silk, and the other half decorated with silver plate and a gold ring. The sword with an undecorated ring pommel excavated from the ancient tombs of Jeongchon Village comprises the metals of gold, silver, and iron, and includes features of Baekje, Silla, and Gaya, which highlights the influence of surrounding historic sites and various cultures.

• Journal of Life Science
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• v.29 no.10
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• pp.1055-1061
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• 2019

Sarracenia purpurea as a carnivorous plant in the family Sarraceniaceae is known to require strong light for its growth and to absorb nutrients from the decomposed molecules of insects that are attracted by color, sweet juice, and the like. S. purpurea grew greenish in whole body under weak light conditions, while the whole of the insectivorous sac including leaves, is changed to dark red under strong light conditions. The phenomenon of reddish S. purpurea is thought to be related to the flavonoid pigment anthocyanin. Interestingly, the color change was not observed when S. purpurea was grown in a growth condition with abundant nitrogen fertilizer. The expression levels of anthocyanin contents and biosynthesis-related genes were strongly correlated with light intensity and nitrogen fertilizer. The anthocyanin content in the strong light condition ($240{\mu}mol\;m^{-2}s^{-1}$) was 6.15 times higher than that in the weak light ($40{\mu}mol\;m^{-2}s^{-1}$). In contrast, the anthocyanin contents were not significantly changed when 0.8% urea solution was supplied as nitrogen fertilizer. Consistently, CHALCONE SYNTHASE (CHS) gene was up-regulated by strong light and down-regulated by nitrogen fertilizer. These results suggest that the environmental changes of light and nitrogen in soil regulate the anthocyanin content in S. purpurea.

• Journal of the Korean Applied Science and Technology
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• v.36 no.3
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• pp.821-829
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• 2019

This study was conducted to evaluate the applicability of the extracts from nipa palm, molokhia, and finger root in functional cosmetics as a natural active ingredient. The extracts were obtained through the processes of heating under reflux with ethanol, filtration, concentration, and freeze-drying. UV absorption and blocking effects of the extracts were examined by using the UV-vis spectrophotometer equipped with an integrating sphere. Antioxidant activity and its stability between the extracts were compared using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. Also, total polyphenol content in the extracts was determined quantitatively using the Folin-Ciocalteu reagent, with gallic acid as the standard. Antibacterial activity of the extracts was investigated by the disc diffusion test against Staphylococcus aureus (gram-positive) and Escherichia coli (gram-negative). Finally, collagenase inhibitor assay was performed to examine the anti-wrinkle effect of the extracts. From the results of this study, the extract of nipa palm showed the potential for use in cosmetics as an antioxidant and anti-wrinkle agent, and the extract of finger root as a sunscreen and antibacterial agent.

• Anxiety and mood
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• v.15 no.2
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• pp.84-93
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• 2019

Objective : The aim of this study was to examine the relationship between occupational stress and depression, as it is seen to be corresponding with the work characteristics of local government officials. Methods : The data of 671 local government officials who participated in this study from July to December 2015 as a part of an occupational stress management program, were analyzed retrospectively in this study. Likewise, the participants completed questionnaires, including a short form of the Korean Occupational Stress Scale (KOSS), and the Beck Depression Inventory-II (BDI-II) the results of which were evaluated and reviewed. Results : The study noted that the subscales of occupational stress related to depression were varied, according to the work characteristics of the participants, after adjusting for age and job grade. It was found that the participant's variables of job insecurity, lack of reward, organizational system and occupational climate were significantly related to the development of a depressed mood in the participant in a general sense. Notably, the factor of interpersonal conflict was significantly related to depressed mood among the general administrative group; meanwhile, lack of reward in the welfare group and insufficient job control in the technical group were significantly associated with the likelihood of developing a depressed mood in participants reviewed. In the operation and maintenance of facilities group, job insecurity was significantly related with depressed mood, whereas job demand was related more with the incidence of depression in the field work group. Conclusion : This study revealed that the influence of occupational stress on depression varied according to the occupational characteristics experienced by the participants in the work environment. These findings may be used to enhance the occupational stress management program for local government officials according to their work characteristics, to bring awareness to this issue.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.14 no.3
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• pp.13-26
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• 2019

There is a growing interest in the entrepreneurial activity that has long been considered essential for sustainable economic development and value creating. Although it is strongly encouraged by focusing on the positive aspects of venturing, less has been paid attention to entrepreneurial failure, which is the biggest cause of hesitation in starting a business. The uncertain and risky nature of entrepreneurship implies a considerable possibility of failure. Even if it fails, the experience and knowledge of entrepreneurs acquired through entrepreneurship indeed offers valuable lessons for the re-venturing, which can serve as an important social asset that should not be lost. It has been argued that re-entering the same industry for the subsequent venture maximizes the learning effect through utilizing potential benefits from industry-specific knowledge. Although the re-startup after entrepreneurial failure is a very important topic in the studies on serial entrepreneurs, there is a paucity of systematic empirical investigation. This study responds to calls for more research on the re-startup after entrepreneurial failure, and specifically complements existing studies on serial entrepreneurs. Focusing on the entrepreneurs' attribution for the failure, we conducted an empirical analysis of how this affects the re-startup process. Moreover, we also examined the moderating effects of entrepreneurial self-efficacy and resilience. For the analyses, we surveyed the entrepreneurs who tried to re-start the subsequent business after the entrepreneurial failure through the "Revitalization Center for Strained Entrepreneur". The results found that failed entrepreneurs who blamed internal factors for their previous venture failures were likely to keep the same industry for their subsequent business. In addition, the positive effect of internal attribution on maintaining the same industry for the re-startup was found to be stronger when entrepreneurial self-efficacy and resilience were high.

• Journal of Life Science
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• v.29 no.2
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• pp.248-255
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• 2019

This research confirmed the diversity and characterization of gut microorganisms isolated from the intestinal organs of Muraenesox cinereus, collected on the Samcheonpo Coast and Seocheon Coast in South Korea. To isolate strains, Marine agar medium was basically used and cultivated at $37^{\circ}C$ and pH7 for several days aerobically. After single colony isolation, totally 49 pure single-colonies were isolated and phylogenetic analysis was carried out based on the result of 16S rRNA gene DNA sequencing, indicating that isolated strains were divided into 3 phyla, 13 families, 15 genera, 34 species and 49 strains. Proteobacteria phylum, the main phyletic group, comprised 83.7% with 8 families, 8 genera and 26 species of Aeromonadaceae, Pseudoalteromonadaceae, Shewanellaceae, Enterobacteriaceae, Morganellaceae, Moraxellaceae, Pseudomonadaceae, and Vibrionaceae. To confirm whether isolated strain can produce industrially useful enzyme or not, amylase, lipase, and protease enzyme assays were performed individually, showing that 39 strains possessed at least one enzyme activity. Especially the Aeromonas sp. strains showed all enzyme activity tested. This result indicated that isolated strains have shown the possibility of the industrial application. Therefore, this study has contributed for securing domestic genetic resources and the expansion of scientific knowledge of the gut microbial community in Muraenesox cinereus of South Korea.

• Journal of Life Science
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• v.29 no.2
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• pp.198-201
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• 2019

Recently, it has been reported that Bacillus mojavensis possesses antifungal properties and plant growth-promoting activities, which are similar to the characteristics of siderophore. In this study, the siderophore produced by B. mojavensis was assessed using a solid phase extraction (SPE) cartridge and liquid chromatography quadrupole time-of-flight tandem mass spectrometry (Q-TOF MS/MS). After B. mojavensis was incubated in phenol medium for 16 hr and lyophilized, the sample was dissolved in water and loaded to an SPE cartridge to remove interferences. The cartridge was washed with 5% methanol in water and eluted with 2% formic acid in methanol sequentially. The eluted solution was evaporated under a stream of nitrogen gas and reconstituted in methanol. The reconstituted sample was filtered, and $1{\mu}l$ of the sample was assessed using Q-TOF MS/MS. The mass spectrometer was operated using the positive electrospray ionization mode. Based on the mass spectrum and tandem mass spectrum, the siderophore produced by B. mojavensis was bacillibactin, one of the catechol types of siderophore with a molecular weight of 882.2556. This siderophore analysis could provide a justification for the study of B. mojavensis as a functional food and for pharmaceutical applications.

• Korean Chemical Engineering Research
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• v.59 no.2
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• pp.225-231
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• 2021

Sesame seed oil cakes are classified as the animal or plant origin among the flammable liquids, and the fire occurs due to the spontaneous ignition through the accumulation of heat during the storage of residues after the extraction of sesame oil. In order to elucidate the cause of the spontaneous ignition of sesame seed oil cakes, the thickness (3 cm, 5 cm, 7 cm and 14 cm) of the sample container was varied, and the spontaneous ignition temperature was measured depending on the storage volume. Thus, the spontaneous ignition temperature was measured to be 180 ℃ at the thickness of 3 cm, 160 ℃ at 5 cm, 145 ℃ at 7 cm and 130 ℃ at 14 cm. As the thickness of the sample container increased, the critical ignition temperature decreased, and the induction time to spontaneous ignition and the time to reach the maximum temperature became longer. Furthermore, the apparent activation energy by the critical ignition temperature, which is the average temperature of ignition and non-ignition, was 97.10 [kJ/mol]. With these data, ignition characteristics of sesame seed oil cakes were determined.

• Journal of Korea Foundry Society
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• v.41 no.2
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• pp.127-131
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• 2021

Based on its good compatibility with high-temperature environments, the Ti-48Al-2Cr-2Nb alloy is used for high-temperature materials of industrial equipment. In this study, a Ti-48Al-2Cr-2Nb alloy turbocharger turbine wheel was fabricated by a vacuum centrifugal casting method. The conditions that prevent misrun defects of the turbocharger turbine wheel blade from centrifugal casting using alumina molds were investigated. The microstructure of the alloy prepared by vacuum centrifugal casting was studied by means of optical microscopy (OM), with a micro-Vickers hardness analyzer (HV), by X-ray diffraction (XRD) and by SEM-EDS. The HV and SEM-EDS examinations of the as-cast Ti-48Al-2Cr-2Nb alloy showed that the thickness of the oxide layer (α-case) was typically less than 50 ㎛. At a high preheating temperature of 1,100℃, a moderate RPM of 260, and with an alumina mold with a large gate size, there were almost no misrun defects. Therefore, it was confirmed that a Ti-48Al-2Cr-2Nb alloy turbocharger turbine wheel with fewer misrun defects could be achieved through a high preheating temperature, a moderate RPM, a large gate size and an alumina mold to suppress the formation of alpha-case components.