• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.4
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• pp.259-267
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• 2022

The existing method of deriving the fail-safe design requirements for the domestic developed rotary-wing aircraft system may miss the factors that cause critical system function failures, when being applied to the latest integrated avionics system. It is because the existing method analyzes the severity effect of the failures caused by a single item. To solve the issue, we present a systematic analysis procedure for deriving fail-safe design requirements of system architecture by utilizing functional hazard assessment and development assurance level analysis of SAE ARP4754A, international standard for complex system development. To demonstrate that our proposed procedure can be a solution for the aforementioned issue, we set up experimental environments that include common factors that can cause critical function failures of a system, and we conducted a cross-validation with the existing method. As a result, we showed that the proposed procedure can identify the potential critical common factors that the existing method have missed, and that the proposed procedure can derive fail-safe design requirements to control the common factors.

• Journal of the Korean Geotechnical Society
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• v.39 no.7
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• pp.17-30
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• 2023

This study investigates the impact of water immersion and high temperature on the shear strength of cemented sand through direct shear tests. Standard Jumunjin sand was used and cemented with binders, such as ultra-rapid hardening cement and an epoxy aqueous solution. The binder was mixed at concentrations of 4%, 8%, or 12%. Subsequently, cylindrical cemented specimens with a diameter of 64 mm and height of 25 mm were produced using compaction. The curing period was three days, and the specimens were cured under dry air, immersion, and heating conditions. The heating condition involved subjecting the immersed specimens to a microwave oven three times for three minutes to achieve an internal temperature of approximately 90℃. Regardless of the binder type, the cohesion of the cemented sand increased with higher binder content, whereas the internal friction angle exhibited a slight increase or decrease. Compared with ultra-rapid hardening cemented sand, epoxy-cemented sand displayed an average cohesion that was five times higher and an internal friction angle that was 10° higher. Overall, irrespective of binder type, the shear strength decreased during water immersion and increased during heating. Notably, the epoxy-cemented sand exhibited a three-fold increase in cohesion and a more than 20° increase in the internal friction angle during heating.

• Analytical Science and Technology
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• v.19 no.2
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• pp.149-154
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• 2006

A gas chromatography-mass spectrometric method was developed for the determination of formaldehyde in urine and saliva. In a 20 mL glass tube, 0.2 mL of urine or saliva was taken. Further, 1.8 mL of 0.1 M HCl, 0.1 mL of 2,000 mg/L 2,4-dinitrophenyl hydrazine and $20{\mu}l$ of 500 mg/L acetone-$d_6$ as internal standard were added in the tube and sealed tightly with cap. The solution was shaken for 20 min at room temperature and extracted using 4 mL of toluene. The extract was concentrated and redissolved with $100{\mu}l$ of acetonitrile, and then measured by gas chromatography-mass spectrometer (selected ion monitoring). The detection limit was 2.0 ng/mL and 0.5 ng/mL in saliva and urine, respectively. The calibration curves showed good linearity with r = 0.997 and 0.998 for saliva and urine, respectively. The method was used to analyze formaldehyde in rat urine after oral exposure. The developed method may be use ful to the monitoring for formaldehyde exposure in human.

• The Journal of the Acoustical Society of Korea
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• v.26 no.7
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• pp.361-365
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• 2007

Aero-pulsation noise, generally caused by geometric asymmetry of a rotating device, is one of considerable sources of annoyance in passenger cars using the turbocharged diesel engine. Main source of this noise is the compressor wheel in the turbocharger system, and can be reduced by after-treatment devices such as silencers, but which may increase the manufacturing cost. More effective solution is to improve the geometric symmetry over all, or to control the quality of components by sorting out inferior ones. The latter is more simple and reasonable than the former in view of manufacturing. Thus, an appropriate discrimination method should be needed to evaluate aero-pulsation noise level at the production line. In this paper, we introduce the accurate method which can measure the noise level of aero-pulsation and also present its evaluation criteria. Besides verifying the reliability of a measurement system - a rig test system-, we analyze the correlation between the results from rig tests and those from vehicle tests. The gage R&R method is carried out to check the repeatability of measurements over 25 samples. From the result, we propose the standard specification which can discriminate inferior products from superior ones on the basis of aero-pulsation noise level.

• Journal of Environmental Health Sciences
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• v.50 no.3
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• pp.221-228
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• 2024

Background: Social interest is increasing due to frequent accidents caused by chemicals in the electronics industry. Objectives: The purpose of this study is to present a management plan by evaluating the exposure characteristics of dichloromethane (DCM), trichloromethane (TCM), and tetramethyl ammonium hydroxide (TMAH), which are high-risk substances to which people may be exposed in the electronics industry in South Korea. Methods: To investigate the handling companies and status of the hazardous chemicals DCM, TCM, and TMAH, the handling status of the three substances was classified based on electronics industry-related codes from the 2019 Work Environment Survey (Chemical Handling and Manufacturing) data with work environment measurement results for five years. Results: DCM, TCM, and TMAH are commonly used as cleaning agents in the electronics industry. For DCM, it was found that all work environment measurement results from 2018 to 2021 but not 2022 exceeded the exposure standard. Conclusions: Identifying the distribution channels of hazardous chemicals is an intervention point that can reduce exposure to hazardous chemicals. It requires management through tracking systems such as unique verification numbers at the import and manufacturing stages, and proper cultivation of and related support for handling chemicals by business managers.

• The Journal of the Convergence on Culture Technology
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• v.10 no.3
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• pp.53-59
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• 2024

The novel "The Grapes of Wrath" shows the painful reality of Americans during the Great Depression through the migration journey of the Tom Jod's family, who had no choice but to move from Oklahoma to California and their hardships in California. This presents empathy for their wrath and offers hope for a brotherly solution. This article presents institutional solutions against each novel situation from the perspective of the Constitution, labor law, and competition law. From a constitutional perspective, the poverty of Oklahoma's smallholders is not a result of choice, but is caused by the natural environment and capital concentration, so it is suggested that the government have to intervene to guarantee a minimum standard of living to realize equal rights. From a labor law perspective, worker supply projects are unconstitutional because they constitute intermediate exploitation of labor, and immigrants like the Joad family have the right to form labor unions. From a competition law perspective, it was shown that the large landowners' setting of fruit prices constitutes predatory pricing, and the farmers' attempts to pay similarly low wages constitute collusion. Through this, the attempt was made to recognize that the law is a means to resolve the public wrath that may currently exist, and to show that the story in the novel can bring empathy and understanding to minorities. It is hoped that reading novels can be a way to help interpret the law and sympathize with others as an indicator of a just society.

• Land and Housing Review
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• v.15 no.3
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• pp.165-175
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• 2024

As living standards improve, the demand for quiet and comfortable environments is increases. However, noise sources are rising due to population growth, urbanization, and industrialization. One solution to this problem is low-noise asphalt pavement, which has fewer installation regulations and can reduce noise at the source. Despite its advantages, there are few evaluation cases and no domestic guidelines for low-noise asphalt pavement. This study aims to evaluate the overall performance of low-noise asphalt pavement on roads in Seoul, focusing on average noise levels, skid resistance, and permeability. Noise measurements were conducted using a digital noise analyzer according to the Ministry of Environment's standards. Results indicated that noise reduction was maintained for 1 to 2 years but decreased over time. Skid resistance, assessed with the British Pendulum Tester, showed excellent performance with values above the standard of 57 in the initial stages after paving. Permeability, evaluated using the KS F 2394 method, was initially effective across all sections but declined over time.

• Korean Journal of Soil Science and Fertilizer
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• v.42 no.6
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• pp.513-521
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• 2009

The primary goal of this research was to develop an optimized analytical procedure for soil analysis based on ion-selective microelectrodes for agricultural purposes, which can perform on-site measurement of various ions in soil easily and rapidly. For the simple and rapid on-site diagnosis, an analysis of soil chemicals was performed employing a multicomponent-in-situ-extractant and an evaluation of ionselective microelectrodes were conducted through the regressive correlation method with a standard analytical approach widely employed in this area. Examination of sensor responses between various soil nutrient extractants revealed that 0.01M HCl and 1M LiCl provided the most ideal Nernstian response. However, 1M LiCl deteriorated the selective response for analytes due to high concentration (1M) of lithium cation. Thus, employing either 0.1M HCl as an extractant followed by 10 times dilution, or 0.01M HCl as an extractant without further dilution was chosen as the optimal extractant composition. A study of regressive correlation between results from ion-selective microelectrodes and those from the standard analytical procedure showed that analyses of $K^+$, $Na^+$, $Ca^{2+}$, and $NO_3{^-}$ showed the excellent consistency between two methods. However, the response for $NH_4{^+}$ suffered the severe interference from $K^+$. In addition, the selectivity for $Mg^{2+}$ over $Ca^{2+}$ was not sufficient enough since available ionophores developed so far do not provide such a high selectivity for $Mg^{2+}$. Therefore, as an agricultural on-site diagnostic instrument, the device in development requires further research on $NH_4{^+}$ analysis in the soil sample, development of $Mg^{2+}$-selective ionophore, and more detailed study focused on potassium, one of the most important plant nutrients.

• Radiation Oncology Journal
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• v.19 no.2
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• pp.163-170
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• 2001

Purpose : The measurement of radiation survival using a clonogenic assay, the established standard, can be difficult and time consuming. In this study, We have used the MTT assay, based on the reduction of a tetrazolium salt to a purple formazan precipitate by living cells, as a substitution for clonogenic assay and have examined the optimal condition for performing this assay in determination of radiation sensitivity. Materials and Methods : Four human cancer cell lines - PCI-1, SNU-1066, NCI-H630 and RKO cells have been used. For each cell line, a clonogenic assay and a MTT assay using Premix WST-1 solution, which is one of the tetrazolium salts and does not require washing or solubilization of the precipitate were carried out after irradiation of 0, 2, 4, 6, 8, 10 Gy. For clonogenic assay, cells in $25\;cm^2$ flasks were irradiated after overnight incubation and the resultant colonies containing more than 50 cells were scored after culturing the cells for $10\~14$ days. For MTT assay, the relationship between absorbance and cell number, optimal seeding cell number, and optimal timing of assay was determined. Then, MTT assay was performed when the irradiated cells had regained exponential growth or when the non-irradiated cells had undergone four or more doubling times. Results : There was minimal variation in the values gained from these two methods with the standard deviation generally less than $5\%$, and there were no statistically significant differences between two methods according to t-test in low radiation dose (below 6 Gy). The regression analyses showed high linear correlation with the $R^2$ value of $0.975\~0.992$ between data from the two different methods. The optimal cell numbers for MTT assay were found to be dependent on plating efficiency of used cell line. Less than 300 cells/well were appropriate for cells with high plating efficiency (more than $30\%$). For cells with low plating efficiency (less than $30\%$), 500 cells/well or more were appropriate for assay. The optimal time for MTT assay was after 6 doubling times for the results compatible with those of clonogenic assay, at least after 4 doubling times was required for valid results. In consideration of practical limits of assay (12 days, in this study) cells with doubling time more than 3 days were inappropriate for application. Conclusion : In conclusion, it is found that MTT assay can successfully replace clonogenic assay of tested cancer cell lines after irradiation only if MTT assay was undertaken with optimal assay conditions that included plating efficiency of each cell line and doubling time at least.

• Journal of Food Hygiene and Safety
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• v.29 no.3
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• pp.234-240
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• 2014

Fluxapyroxad is classified as carboxamide fungicide that inhibits succinate dehydrogenase in complex II of mitochondrial respiratory chain, which results in inhibition of mycelial growth within the fungus target species. This study was carried out to assure the safety of fluxapyroxad residues in agricultural products by developing an official analytical method. A new, reliable analytical method was developed and validated using High Performance liquid Chromatograph-UV/visible detector (HPLC-UVD) for the determination of fluxapyroxad residues. The fluxapyroxad residues in samples were extracted with acetonitrile, partitioned with dichloromethane, and then purified with silica solid phase extraction (SPE) cartridge. Correlation coefficient($R^2$) of fluxapyroxad standard solution was 0.9999. The method was validated using apple, pear, peanut, pepper, hulled rice, potato, and soybean spiked with fluxapyroxad at 0.05 and 0.5 mg/kg. Average recoveries were 80.6~114.0% with relative standard deviation less than 10%, and limit of detection (LOD) and limit of quantification (LOQ) were 0.01 and 0.05 mg/kg, respectively. All validation parameters were followed with Codex guideline (CAC/GL 40). LC-MS (Liquid Chromatograph-Mass Spectrometer) was also applied to confirm the analytical method. Base on these results, this method was found to be appropriate fluxapyroxad residue determination and can be used as the official method of analysis.