• Journal of the Microelectronics and Packaging Society
• /
• v.29 no.2
• /
• pp.11-18
• /
• 2022

Recently, as flexible electronic device-related technologies have received worldwide attention, the development of wiring and bonding technologies using liquid metals is required in order to improve problems such as formability in the manufacturing process of flexible devices and performance and durability in the bending state. In response to these needs, various studies are being conducted to use gallium and gallium-based alloys (eutectic Ga-In and eutectic Ga-In-Sn, etc.) liquid metals, with low viscosity and excellent electrical conductivity without toxicity, as low-temperature bonding materials. In this paper, the latest research trends of low-temperature bonding technology using gallium and gallium-based alloys are summarized and introduced. These technologies are expected to become important base technologies for practical use in the fields of manufacturing flexible electronic devices and low-temperature bonding in microelectronic packages in the future.

• Clean Technology
• /
• v.29 no.2
• /
• pp.135-144
• /
• 2023

Pseudomonas aeruginosa and Staphylococcus aureus are the two most frequently encountered pathogens responsible for chronic wound infections, often coexisting in such cases. These infections exhibit heightened virulence compared to single infections, leading to unfavorable patient outcomes. The interaction among microorganisms within polymicrobial infections has been shown to exacerbate disease progression. Polymicrobial infections, prevalent in various contexts such as the respiratory tract, wounds, and diabetic foot, typically involve diverse microorganisms, with Pseudomonas aeruginosa and Staphylococcus aureus being the most commonly identified pathogens. This study aimed to compare the growth patterns of bacteria under a concentration gradient of toxic chemicals, focusing on a Gram-negative strain of Pseudomonas aeruginosa and a Gram-positive strain of Staphylococcus aureus. The minimum inhibitory concentration (MIC), which signifies the concentration at which bacterial growth is inhibited, was determined by performing broth microdilution and assessing the bacteria's growth curves. The growth curves of both Pseudomonas aeruginosa and Staphylococcus aureus were confirmed, and the exponential growth phases were applied to calculate the doubling times of bacteria. The MIC value for each toxic chemical was determined through broth microdilution. These results allowed for the identification of disparities in growth rates between Gram-positive and Gram-negative bacteria, as well as differences in resistance to individual toxic substances. We expect that this approach has a strong potential for further development towards the innovative treatment of bacteria-associated infections.

• Journal of Ocean Engineering and Technology
• /
• v.32 no.4
• /
• pp.272-278
• /
• 2018

Recently, the use of hazardous chemicals has been continuously increasing. Therefore, the international trade volume is growing and chemical accidents have increased. Nowadays, the safety awareness of the public has increased. As a result, the management and supervision of hazardous chemicals have been strengthened. However, the port policy of Korea has focused on increasing the volume of cargo through facility development. Thus, the port management of hazardous chemicals has been relatively neglected. For national economic growth and society, the port management of hazardous chemicals should be considered to efficiently ensure safety and economic growth. Therefore, this study assumed scenarios where hazardous materials were moved in a dangerous container, not only on appropriate wharfs but also in ports that were close to a big city. The BTX substances were selected among the toxic chemicals with large import and export volumes, and the risk distance and damage effects were predicted using various risk assessment programs. It is expected that this could be used to improve a port safety management system and could be utilized to determine the safety distance in case of an accident.

• Journal of the Korean Institute of Gas
• /
• v.17 no.4
• /
• pp.9-17
• /
• 2013

Butanethiol is known as a typical odorant with hydrogen sulfide, methyl mercaptan, methyl sulfide, but on the physical and chemical properties and biological hazard assessment, including inhalation toxicity data are very scarce. Butanethiol as a colorless transparent liquid, and has physic-chemical characteristics with flash point as $-23^{\circ}C$ and strong fire risk, boiling point $84-85^{\circ}C$, vapor pressure 80.71 mmHg ($25^{\circ}C$), freezing point $-140.14^{\circ}C$. From whole body exposure with SD rats, the $LC_{50}$ is above 2,500 ppm (9.22mg/L), and then it is classified as the acute toxic chemical (inhalation) category 4 according to the governmental notification No. 2012-14.

• Journal of Aerospace System Engineering
• /
• v.17 no.1
• /
• pp.51-58
• /
• 2023

Hypergolic propellants, which can ignite themselves without an ignition source, are difficult to handle due to their corrosiveness and toxicity. Therefore, it is necessary to develop green hypergolic propellants with little or no toxicity. In this study, basic research on green hypergolic ignition propellants was conducted. With 95% hydrogen peroxide as an oxidizer and CNU_HGFv1 as a fuel, ignition and combustion characteristics of propellants were evaluated through a drop test, an ignition test, and a combustion test. As a result of the drop test, the ignition delay time was 9.7 ms. It was 27 ms in the ignition test, which was fast enough to be used as a propellant. As a result of the combustion test, a combustion efficiency of 95.4~98.1% was achieved at about 11.7 bar. It was confirmed that fast and stable combustion was possible without hard start or combustion instability.

• Journal of Food Hygiene and Safety
• /
• v.38 no.6
• /
• pp.430-441
• /
• 2023

Velvet antler is widely used as a traditional medicine, and numerous studies have demonstrated its tremendous nutritional and medicinal values including immunity-enhancing effects. This study aimed to investigate different deer velvet extracts (Sample 1: raw extract, Sample 2: dried extract, and Sample 3: freeze-dried extract) for proximate composition, uronic acid, sulfated glycosaminoglycan, sialic acid, collagen levels, and chemical components using ultra-performance liquid chromatography-quadrupole-time-of-light mass spectrometry. In addition, we evaluated the cytotoxic effect of the deer velvet extracts on BV2 microglia, HT22 hippocampal cells, HaCaT keratinocytes, and RAW264.7 macrophages using the cell viability MTT assay. Furthermore, we evaluated acute toxicity of the deer velvet extracts at different doses (0, 500, 1000, and 2000 mg/kg) administered orally to both male and female ICR mice for 14 d (five mice per group). After treatment, we evaluated general toxicity, survival rate, body weight changes, mortality, clinical signs, and necropsy findings in the experimental mice based on OECD guidelines. The results suggested that in vitro treatment with the evaluated extracts had no cytotoxic effect in HaCaT keratinocytes cells, whereas Sample-2 had a cytotoxic effect at 500 and 1000 ㎍/mL on HT22 hippocampal cells and RAW264.7 macrophages. Sample 3 was also cytotoxic at concentrations of 500 and 1000 ㎍/mL to RAW264.7 and BV2 microglial cells. However, the mice treated in vivo with the velvet extracts at doses of 500-2000 mg/kg BW showed no clinical signs, mortality, or necropsy findings, indicating that the LD50 is higher than this dosage. These findings indicate that there were no toxicological abnormalities connected with the deer velvet extract treatment in mice. However, further human and animal studies are needed before sufficient safety information is available to justify its use in humans.

• Journal of the Korean Chemical Society
• /
• v.60 no.2
• /
• pp.118-124
• /
• 2016

Parabens were commonly used for preventing the growth of microorganisms as preservatives in the pharmaceutical, cosmetic and food industry. Also, parabens are known endocrine disruptors because of their estrogenic effects on human. Parabens affect the endocrine system and show adverse effect such as, genital malformations, precocious puberty and testicular cancer in young children, infants and fetuses. In this study, we developed analytical method for four parabens (methyl paraben, ethyl paraben, propyl paraben, butyl paraben) in human breast milk which frequently consumed by newborn baby. The analytes were extracted using liquid-liquid extraction (LLE) after enzyme hydrolysis with protease and lipase, then quantitative analysis was performed by liquid chromatography tandem mass spectrometry (LC-MS/MS). The method validation results were as follows; the linearity of calibration curves were excellent with coefficient of determinations (r²) higher than 0.999, the limit of detections (LODs) were 0.019~0.044 ng/mL, the accuracies were 85.3~105.9% and the precisions were lower than 10%. The average concentration ± standard deviation of parabens in ten human breast milk sample were MP 0.660 ± 0.519 ng/mL, EP 1.631 ± 2.081 ng/mL and PP 0.326 ± 0.320 ng/mL, and BP was not detected.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.16 no.5
• /
• pp.431-443
• /
• 2014

In this paper case studies of artificial ground freezing, which have not been applied in Korea, have been investigated for the water cut-off in a subsea tunnel under high water pressure and the most commonly used cooling mediums of brine and liquid nitrogen are examined. Since sea water with pressure has the lower freezing point than pure water, the lower temperature cooling medium is required in the application of subsea tunnel. Also, the cooling medium must have refrigeration safety and is able to reduce executing time. Brine freezing system can reuse cooling medium and is safer than liquid nitrogen freezing. But it takes more time to freeze ground and needs complex circulation plants. On the other hand, liquid nitrogen freezing system can't recycle cooling medium and may cause breathing problems or asphyxiation through oxygen deficiency. But, freezing with liquid nitrogen is fast and requires simple refrigeration equipment. Principal elements of design for ground freezing in subsea tunnel have been extracted and these elements are needed further research.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2009.05a
• /
• pp.7-10
• /
• 2009

The development and evaluation of solid propellant were performed for the turbopump pyro starter, which start up the liquid propellant rocket engine for the Space Launch Vehicle (SLV). Requirements for the turbopump pyro starter propellant include the production of low flame temperature, low burning rate and nontoxic gas to protect the mechanical corrosion or air pollution. This study describes the development of the solid propellant composition which is based on PCP binder. DHG (Dihydroxy glyoxime), which has advantages of oxygen balance and ignition, was used as coolant. The mechanical properties and burning rate of the propellants were measured. Finally, static fired test was performed to prove the possibility of development.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.739-745
• /
• 2017

Research of ADN-based monopropellant thruster is progressed by developed countries in Europe to replace toxic hydrazine, and ADN-based monopropellant thruster system is the only system that was proved in space environment. In this research, ADN-based propellant and catalyst was fabricated to develop ADN-based monopropellant thruster, and catalytic combustion performance with fabricated propellant and catalyst were evaluated with DSC-TG analysis. Catalytic combustion of propellant and catalyst was determined with firing test using 5 N scale liquid monopropellant thruster.