• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.275-282
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• 2021

High-molecular-weight maleic anhydride-grafted polylactic acids (HMMA-g-PLA) compatibilizers were prepared by melt grafting in a twin screw extruder using di(tert-butyl-perxoyisopropyl)benzene (PK-14; as initiator), maleic anhydride (MA), and divinylbenzene (DVB). To determine the properties of the prepared HMMA-g-PLA compatibilizers, Fourier transform infrared (FTIR), Melt index (MI), and back-titration analyses were performed. On increasing DVB concentration, grafting yield of HMMA-g-PLA increased but MI decreased because 𝛽-scission of PLA was restrained by the DVB, and thus, the molecular weight of HMMA-g-PLA increased. PLA-based wood-plastic composites (WPCs) were prepared using HMMA-g-PLA by melt blending through a single screw extruder. The flexural and impact strengths of WPCs compatibilized with HMMA-g-PLA were greater than those of WPCs produced without HMMA-g-PLA. Scanning electron microscope (SEM) studies indicated that increased mechanical properties were caused by excellent interfacial adhesion between PLA and wood fibers due to the addition of HMMA-g-PLA. However, rather high contents of HMMA-g-PLA reduced the mechanical properties of WPCs. We believe that lower molecular-weight of HMMA-g-PLA added as an compatibilizer, compared with PLA polymer, caused the reduction of mechanical properties.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.194-199
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• 2008

In this study, the effective method to esterify the free fatty acids in jatropha oil was examined. Compared to other plant oils, the acid value of jatropha oil was remarkably high, 11.5 mgKOH/g. So direct transesterification by a base catalyst was not suitable for the oil. After the free fatty acids were esterified with methanol, jatropha oil was transesterified. The activities of four solid acid catalysts were tested and Amberlyst-15 showed the best activity for the esterification. After constructing the experiment matrix based on RSM and analyzing the statistical data, the optimal esterification conditions were determined to be 6.79% of methanol and 17.14% of Amberlyst-15. After the pretreatment, jatropha biodiesel was produced by the transesterification using KOH in a pressurized batch reactor. Jatropha biodiesel produced could meet the major specifications of Korean biodiesel standards; 97.35% of FAME, 8.17 h of oxidation stability, 0.125% of total glycerol and $0^{\circ}C$ of CFPP.

• Journal of Korean Society of Forest Science
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• v.84 no.2
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• pp.178-185
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• 1995

Air pollution effects on soil chemical properties, denitrifying and sulfur-reducing bacteria and lichens were examined around the Yeochun industrial estate. Soil samples were collected from mountain and/or mountain edges around the Namhae Chemical Corp., which is located at the southern edge of the estate, and sampled plots which were selected at 2km, 4km, 6km, 8km, and 10km apart from the industrial estate. The forest soils around the industrial estate could be classified into the Reddish yellow forest soil group, but soil pH was quite lower than the soils of the group. Because of the extremely low soil pH, microbial activity related to mineralization of organic matter was expected to be very low even though C/N ratio ranged from 15 to 20. As a result, soil organic matter and total nitrogen in soil were relatively high compared to the soils of the group. In general, soil chemical properties around the industrial estate up to 4km apart from the estate were significantly different from the rest(more than 6km apart from the estate) possibly due to air pollution. However, denitrifying bacteria and sulfur-reducing bacteria did not show significant differences in colony forming units by the distances from the industrial estate. By the way, lichens showed distinct differences in frequencies and coverages by the distances from the industrial estate possibly due to air pollution. The corticolous lichens showed more sensitive response to the air pollution compared to the saxicolous lichens.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.3
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• pp.447-463
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• 2001

Dendroaspis natriuretic peptide (DNP), a fourth member of the natriuretic peptide isolated from the venom of the Dendroaspis angusticeps snake, has been reported to be present in human plasma and atrial myocardium and caused vasorelaxation and diuresis in experimental animals. However, it is uncertain whether they are present in peripheral organs other than the heart and its further physiological roles also remains to be clarified. To assess the possible physiological role of DNP in the salivary glands, I investigated the localization of DNP peptide in the rat salivary glands by immunohistochemistry and the binding sites for radiolabelled DNP in the rat salivary glands and oral mucosa using in vitro autoradiography. DNP immunoreactivity was widely distributed in the submandibular, sublingual and parotid glands, particularly in the ducts such as the intercalated and striated ducts, where atrial natriuretic peptide (ANP) was colocalized in consecutive sections, but not in acini. High density $^{125}I-DNP$ binding sites were localized in the epithelia of the tongue and hard palate, while low density binding sites for $^{125}I-DNP$ were also distributed in the submandibular, sublingual, and parotid glands. In the hard palate and tongue, the precise location of this binding was revealed on the basal and parabasal cells of the epithelia by emulsion microautoradiography. These results suggest that DNP may not only have a role in the salivary glands but also play a role in the regulation of growth in the oral epithelium, particularly in the hard palate and tongue.

• Journal of the Korean Chemical Society
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• v.58 no.6
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• pp.580-589
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• 2014

The concepts used to explain specific phenomenon can be influenced by context or coherent regardless of context. The purpose of this study is to understand middle school students' concept of particles in particular context and to investigate the effects of context on concept of particles. A conceptual questionnaire was developed to find out how students represented particles in two contexts: solid and solution states of electrolytes, and ion precipitation reaction. The questionnaire was administered to $9^{th}$ grade students after classes of 'electrolyte and ions' unit. The responses of students were analyzed using framework developed for categorization of students' concepts. The results are as follows: First, it was found that students used various concepts on particles when they explained solid and solution state of electrolytes, respectively. Second, we identified students' concepts of particles used to explain ion precipitation reaction. In addition, we recognized that majority of students failed to write correct chemical symbols. Third, approximately 79% of students showed coherent responses for explanation of particles in solution state of both electrolytes and ion precipitation reaction. About 57% of students had scientific concepts. Some suggestions were made based on results for acquisition of scientific concepts on particles in different contexts.

• Journal of the Korean earth science society
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• v.28 no.1
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• pp.112-122
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• 2007

It is known that coal-derived fly ashes have the unique chemical composition and mineralogical characteristics. Since iron oxides in coal fly ash are enriched with heavy metals, the subsurface media including soils, underground water, and sea water are highly likely contaminated with heavy metals when the heavy metals are leached from fly ashes by water-fly ash interactions. The purpose of this study was to investigate how indigenous bacteria affect heavy metal leaching and mineralogy in fly ash slurry during the fly ash-seawater interactions in the ash pond located in Dangjin seashore, Korea. The average pH of ash pond seawater was 8.97 in nature. Geochemical data showed that microbial activity sharply increased after the 7th day of the 60-day course batch experiments. Compared with other samples including autoclaved and natural samples, ${SO_4}^{2-}$ was likely to decrease considerably in the fly ash slurry samples when glucose was added to stimulate the microbial activity. Geochemical data including Eh/pH, alkalinity, and major and trace elements showed that the bacteria not only immobilize metals from the ash pond by facilitating the chemical reaction with Mn, Fe, and Zn but may also be able to play an important role in sequestration of carbon dioxide by carbonate mineral precipitation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.595-601
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• 2020

During the safety inspection of nitrocellulose-made explosive containers stored for more than 10 years, cracks were found in the containers. Therefore, a failure cause analysis test was performed. First, the cause of failure through the failure tree analysis was conducted to select the factors that influenced failure. The changes in the properties of the container caused by the acceleration of the reaction were found to be the cause of the failure by confirming the influence on the environment and internal/external factors that may occur during storage. To confirm this, environmental tests, such as thermal shock test and vacuum thermal stability test, were performed using a naturally aged container to analyze the cause of failure, and an accelerated aging test was performed to reproduce the failure. Through this, the chemical reaction was accelerated by heat and charge, as in the result of the fault tree analysis, and it was confirmed that the physical properties of the container were changed. In addition, the service life of the container was estimated using the Arrhenius model for the storage life due to thermal aging.

• Journal of the Korean Chemical Society
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• v.27 no.5
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• pp.311-319
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• 1983

The dissociation constants of anilinium ion, o-toluidinium ion, phenol and o-chlorophenol were measured spectroscopically in aqueous solution over the temperature range of 10∼40$^{\circ}C$ and at the pressures up to 2,000 bars. The effects of temperature and pressure on the dissociation of the phenols are the same as those of the ordinary weak acids. Meanwhile the dissociation constants of anilinium ions are increased with temperature raising and decreased with pressure elevation. The effects of pressure on the constants can be explained by taking account of change of charge during dissociation reaction; there are increase in charge in the dissociation of phenols but anilinium ions are not. Several thermodynamic properties, ${\Delta}H^{circ}$,${\Delta}G^{circ}$, ${\Delta}S^{circ}$,${\Delta}V^{circ}$ and ${\beta}$ are calculated from those constants, and the dissociation reactions are discussed by them.

• Progress in Superconductivity and Cryogenics
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• v.25 no.4
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• pp.5-9
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• 2023

Lee, Kim, et al. reported in July 2023 that a modified lead apatite material, Pb_10-xCu_x(PO₄)₆O (0.9 < x < 1.1), exhibited superconductivity at room temperature and atmospheric pressure [1, 2]. However, their X-ray diffraction data clearly showed the presence of impurity phases, including Cu₂S, raising uncertainty about the sample quality. Subsequent studies have been conducted; however, different samples exhibited various physical properties. To verify the recipe for the sample growth process, we synthesized samples following the methodology outlined in the reference [1, 2]. An analysis of the structure and physical properties of the synthesized sample reaffirms the critical importance of high-quality sample growth.

• Fire Science and Engineering
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• v.13 no.3
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• pp.3-17
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• 1999

Smoldering is a non-flaming combustion mode, characterized by thermal degradation and c charring of the virgin material, evolution of smoke and emission of visible glow. A big fire may @ occur even in a confined environment having a limited amount of oxygen, due to smoldering c combustion through a porous solid material. This paper presents a theoretical analysis on the effect of smoldering combustion on fire occurrence based on a report about fire investigation of a real f fire accident. It is assumed that the propagation of the smolder wave is one-dimensional, d downward, opposing an upward forced flow and steady in a frame of reference moving with the s smolder wave. Smoldering combustion is modeled by a one-step reaction mechanism, without c considering pyrolysis. It is found that dominant parameters controlling smoldering combustion i include mass flux of oxidizer entering the reaction zone and void fraction of solid fuel. It is also found that the mechanism of transition to flaming is critically influenced by these two parameters.