• Journal of the Korean Electrochemical Society
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• v.6 no.1
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• pp.36-40
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• 2003

Freezing of water in a polymer electrolyte membrane fuel cell (PEMFC) may cause severe problems in driving a fuel cell vehicle during the winter time. Characteristics of PEMFC which suffered low temperatures below zero degree was examined with the thermal cycles from 80 to $-10^{\circ}C$. With the thermal cycles, the cell performance was degraded due to the phase transformation and volume changes of water. Effects of freezing of water in PEMFC on the electrode structure and polarization resistance were examined by BET analysis, cyclic voltammetry, and AC impedance spectroscopy.

• Korean Business Review
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• v.14
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• pp.169-187
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• 2001

In the recent efficiency study became accomplished generally a listed company, the efficiency study of small manufacturing industry is deficient. The purpose of this study analysis efficiency of small manufacturing industry by using the DEA model. DEA model is non-financial approach method to measure relative efficiency by input factors and output. The panel data from 1996 to 1999 are used for the analysis. The relative mean-efficiency can be summarized as follows. The wholesale trade and commission trade manufacturing industry 68.99%, communication equipment manufacturing industry 60.58%, food products and beverages manufacturing industry 91.05%, motor vehicles, trailers and semitrailers manufacturing industry 85.80%, basic metals manufacturing industry 88.96%, pulp, paper and paper products manufacturing industry 96.53%, chemical and chemical products manufacturing industry appeared with 78.67%. The results is expected to provide the empirical evidence useful to enhancing the competitiveness of manufacturing industry in korea.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2761-2770
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• 2010

In this study, we have developed QSAR models for a series of 38 piperidine-4-carboxamide CCR5 antagonists using CoMFA, CoMSIA and HQSAR methods. Developed models showed good statistics in terms of $q^2$ and $r^2$ values. Best predictions obtained with standard CoMFA model ($r^2$ = 0.888, $q^2$ = 0.651) and combined CoMSIA model ($r^2$ = 0.892, $q^2$ = 0.665) with electrostatics and H-bond acceptor parameter. The validity of developed models was assessed by test set of 9 compounds, which showed good predictive correlation coefficient for CoMFA (0.804) and CoMSIA (0.844). Bootstrapped analysis showed statistically significant and robust CoMFA (0.968) and CoMSIA (0.936) models. Best HQSAR model was obtained with a $q^2$ of 0.662 and $r^2$ of 0.936 using atom, connection, hydrogen, donor and acceptor as parameters and fragment size (7-10) with optimum number of 6 components. Predictive power of developed HQSAR model was proved by test set and it was found to be 0.728.

• Journal of the Korean Chemical Society
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• v.57 no.3
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• pp.398-404
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• 2013

In this study, the analogies in the chemistry domain of middle school science textbooks developed under the 2007 revised National Curriculum were analyzed. A total of 235 analogies were found in 27 middle school science textbooks analysed, which means that one analogy per 10 pages was used on average. The number of analogies found in each textbook considerably varied depending on both publishing company and chemistry domain. Functional analogies, verbal and pictorial analogies, analogies with abstract target and concrete analog, enriched analogies, everyday contexts analogies, student-centered analogies, and analogies with low systematicity were frequently used. On presenting the analogies in the textbooks, the term analogy and description about the limitations of the analogies were rarely mentioned. In comparison with the analogies in the science textbooks developed under the 7th National Curriculum, the frequency of analogies per page was increased. There were positive changes in the aspects of representation, extent of mapping and artificiality. No differences, however, were found in the patterns of the other aspects.

• KSBB Journal
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• v.30 no.1
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• pp.11-20
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• 2015

Radiation causes various pathophysiological alterations in living animals, and it causes death at high doses by multiple mechanisms, including direct DNA damage and indirect oxidative stress. The search for useful radioprotectors has been an important issue in the field of radiation biology. Ideal radioprotectors should have low toxicity and an extended window of protection. As many synthetic compounds have toxic side effects, the natural products have attracted scientific attention as radioprotectors. Natural products that have been recently shown to be effective with various biological activities were found to have radioprotective effect. The aim of this review is to summary the recent research of the radioprotective effects of natural foods, especially focused on the glycobiological properties of mushrooms.

• Safety and Health at Work
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• v.7 no.1
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• pp.6-11
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• 2016

Background: A permit to work (PTW) is a formal written system to control certain types of work which are identified as potentially hazardous. However, human error in PTW processes can lead to an accident. Methods: This cross-sectional, descriptive study was conducted to estimate the probability of human errors in PTWprocesses in a chemical plant in Iran. In the first stage, through interviewing the personnel and studying the procedure in the plant, the PTW process was analyzed using the hierarchical task analysis technique. In doing so, PTWwas considered as a goal and detailed tasks to achieve the goal were analyzed. In the next step, the standardized plant analysis risk-human (SPAR-H) reliability analysis method was applied for estimation of human error probability. Results: The mean probability of human error in the PTW system was estimated to be 0.11. The highest probability of human error in the PTW process was related to flammable gas testing (50.7%). Conclusion: The SPAR-H method applied in this study could analyze and quantify the potential human errors and extract the required measures for reducing the error probabilities in PTW system. Some suggestions to reduce the likelihood of errors, especially in the field of modifying the performance shaping factors and dependencies among tasks are provided.

• Journal of Korean Society on Water Environment
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• v.27 no.1
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• pp.104-109
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• 2011

The removal efficiencies of 2-methylisoborneol (MIB) and geosmin were investigated to reveal removal characteristics of typical organic compounds causing disagreeable taste and odor at the conventional water treatment plant installed with pulsator clarifier patented by the French company $Degr{\acute{e}}mont$. The injection rate of Powdered Activated Carbon (PAC) into water was changed step wisely as we conducted jar tests in the laboratory and water treatment in the actual plant. 2-MIB concentration decreased linearly while geosmin did exponentially along with the injection rate of PAC at our jar tests. The removal efficiency of geosmin by PAC injection was considerably higher than that of 2-MIB. In the real pulsator clarifier, 2-MIB concentration started decreasing as the injection rate reached up to 10 mg/L of PAC. On the other hand, the concentration of geosmin in water decreased proportional to the injection rate of PAC. In the sand filtration, removal efficiencies of 2-MIB and geosmin on July were much higher than those on March. It was carefully suggested beforehand and found afterwards that general microorganisms notably existed in the sand filter with no chlorine in filter influent and backwash water and the sand filter biologically activated removed much more odor compounds. It was considered as the reason why the removal efficiency of 2-MIB and geosmin was increased. The microbial activity maybe increased in summer with water temperature rising and low filtration rate possibly increased contact time between odor compounds and general microorganisms.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.512-518
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• 2022

In this study, safety devices for ammonia tanks of a company in Ulsan petrochemical industrial complex were studied. The type of a tank is cylindrical and this tank was originally designed to store propylene in 1972. Due to the changes of the production schedule according to market environments, the usage of this tank has been changed to store ammonia. Despite of the changes of materials, there is no scientific information or reviews for guaranteeing the safety. Therefore, in this study, the current status of this tank is investigated to confirm that the operational conditions are complying with safety conditions. Moreover, the safety devices such as an ammonia absorbing system and water curtains are analyzed how they mitigate the impact of an accident. In addition, consequence analysis is performed to provide a proper emergency response plan. Throughout these analysis, it is confirmed that installed safety devices effectively mitigate the impact of accidents, and the necessary time for an emergency response plan is suggested when ammonia release.

• Safety and Health at Work
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• v.15 no.3
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• pp.284-291
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• 2024

Background: This study aimed to identify the prevalence of workplace hazards and organizational protection resources according to the size of the enterprise in the manufacturing industry of the Republic of Korea. Methods: We analyzed data of waged workers (weighted N = 5,879) from the Fifth Korean Working Conditions Survey (2017). Enterprise sizes were categorized as "micro enterprises" (less than five employees), "small enterprises" (5-49 employees) and "medium-large enterprises" (50 or more employees). Self-reported exposure to 18 physical, chemical, ergonomic, and psychological hazards were measured. The presence of organizational protection resources such as a labor union, a safety delegate working at the company, designated spaces to deal with safety, and the provision of health and safety information was evaluated. Results: Compared to workers in medium-large enterprises, those in micro enterprises showed a higher proportion of exposure to most of physical, chemical, ergonomic, and psychological hazards, except for exposure to solvents, prolonged sitting, and experiencing a state of emotional unrest. On the other hand, workers in micro enterprises had the lowest proportion of access to organizational protection resources. Conclusion: Our study demonstrates that manufacturing workers at the micro enterprise in the Republic of Korea are exposed to the most hazardous work environment and yet have access to the fewest organizational protection resources.

• Journal of the Korean Chemical Society
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• v.12 no.2
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• pp.65-80
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• 1968

The physico-chemical properties of nine selected thallium borosilicate glasses and other 21 supplementary compositions were investigated. Their composition-property curves are found to be in many respects analogous to those of other borosilicate glasses containing lithia, soda, and lead oxide. It is indicated that certain minima found in the composition-property curves of thallium borosilicate glasses might be caused by a change in boron coordination as has been observed to occur in the $Na_2O-B_2O_3-SiO_2$ glasses. Typical effects of thallium ions on the borosilicate glass are summarized as follows: 1) Addition of thallium ions increased density, refractive index, water solubility, linear coefficient of thermal expansion, and dielectric constant. 2) Increased concentration of thallium decreased the softening point of the glasses, caused fluorescence under ultraviolet radiation and smeared out the absorption edges up to $15{\mu}$ in the infrared region. An extensive liquid immiscibility was found by replication electron microscope technique in the $Tl_2O-B_2O_3-SiO_2$ system. The immiscibility covers a composition range roughly from 55 wt. % Tl2O to the binary system $B_2O_3-SiO_2.$ By acid treatment, it was found that the immiscible glass consists of separate silica-rich and boron-rich phases.