• Tribology and Lubricants
• /
• v.31 no.4
• /
• pp.183-188
• /
• 2015

This paper presents the experimental effects of lubricant with nanodiamond particles in sliding friction. In order to improve the performance of lubricants many additives are used, such as MoS₂, cadmium chloride, indium, sulfides, and phosphides. These additives are harmful to human health and to the environment, so alternatives are necessary. One such alternative is nanodiamond powder, which has a large surface area. In order to investigate the effect of nanodiamonds in lubricants under sliding friction, they are dispersed in the lubricant at a variety of concentrations (0 wt%, 0.1 wt%, 0.3 wt%, 0.5 wt%, and 1 wt%) using the matrix synthesis method. Friction and wear tests are performed according to the ASTM G99 method using a pin-on-disc tester at room temperature. The specimens used in this experiment are AISI 52100 ball bearings and AISI 1020 steel discs. During the test, lubricant mixed with nanodiamond is supplied constantly to keep the two bodies separated by a lubricant film. To maintain boundary lubrication, the speed is set to 0.18 m/s and a load of 294 N is applied to the disc through the pin. Results are recorded by using workbench software over the test duration of 10 minutes. Experimental results show that when the concentration of nanodiamond increases, the coefficient of friction decreases. However, above a nanodiamond concentration of 0.5 wt%, both the coefficient of friction and wear volume increase. From this experiment, the optimum concentration of nanodiamond showing a minimum coefficient of friction of 0.09 and minimum wear volume of 0.82 nm² was 0.5 wt%.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.49 no.2
• /
• pp.116-125
• /
• 2013

Jigging and angling fishery is prevalent in the East Sea of Korea and this fishery needs many lamps to attract the fish. And the fishing boat uses 24~47 ballasts by the vessel's tonnage to turn on the fishing lamp. A 3.5kW magnetic-type ballast being currently used at many fishing boats can drive two 1.5kW metal-halide lamps. Meanwhile, this ballast has large weight (25kg) and volume. Therefore it is one of reason for the over-consumption of energy and the fire, resulted from overheat and electrical short, occurs occasionally because the ballast is installed at narrow and hot engine room. In addition, most of magnetic ballast has several problems such as periodic condenser replacement, low energy efficiency and making lamp short life, etc. So it is necessary to improve or develop newly the electronic ballast, which has to be smaller, lighter and more efficient. An electronic ballast was designed for the fishing boat by considering duration and electromagnetic interference in the study. Its weight and volume are respectably 40% and 66% compared to current ballast on the basis of PCB. The metal-halide lamp's spectrum of the designed ballast was nearly same to that of the current ballast in the test of lighting. In particular, the light stability was improved and there isn't any radio interference. As mentioned above, it is expected that the developed electronic ballast can replace current magnetic ballast because of many advantages related to energy-saving.

• The Journal of the Korea Contents Association
• /
• v.19 no.12
• /
• pp.270-278
• /
• 2019

This study was performed to compare the aerodynamic characteristics of young and elderly adult male patients with voice disorders during continuous speech. Aerodynamic measurements were obtained after 12 young male patients and 9 elderly male patients read a paragraph. The elderly group showed longer duration, lower airflow rate and air volume than the younger group, but the differences were not significant except phonation time. So, when interpreting the meaning of aerodynamic measures of elderly voice disorder patients in the aspects of airflow and air volume, it should take into account various conditions(e. g. reading materials, pulmonary functions) as well as age.

• Journal of Environmental Health Sciences
• /
• v.43 no.5
• /
• pp.349-359
• /
• 2017

The objective of this study is to review the safety and health information displayed on containers of humidifier disinfectants (HD). We summarized not only general characteristics related to the marketing and manufacturing of HD, such as the duration sold and the name of the company, but also the safety and health information, such as identification of disinfectants, recommended use volume, and precautions. All of this information was reviewed by HD brand. We collected safety and health information from 31 HD brands. We found that companies that sold and manufactured HD brands differ. Two companies were found to sell their HD without permission after 2011 when the health effects caused by HD were widely known. The name of the disinfectants were not identified on the container of HD. The recommended volumes were found not to be based on toxicological evidence and set without consideration of the level of susceptibility of users. Most companies displayed phrases such "this HD is safe for humans, even children" on the front of the container. No inhalation and skin toxicity precautions were provided. In conclusion, most HD did not properly display information related to safety and health to protect the health of HD users. There has been no official investigation to evaluate the risks posed by HD, such as the sales volume by HD, identification of chemical disinfectants, or their concentration, nor have there been actions to control the chemical quality of HD. In addition, government actions to punish the malicious practices of companies that manufactured and sold HD were found to inappropriate.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.23 no.1
• /
• pp.17-26
• /
• 2010

This study presents a decision making process for installation of wind barrier which is used to reduce the wind acting on running vehicle on expressway. At the first stage of this study, the lateral deviations of running vehicles under side winds were computed from the commercial softwares, CarSim and TruckSim, and then the critical wind speeds for car accident were evaluated from predefined risk index. To determine whether it is needed to install wind barrier or not, cost and benefit from wind barrier are calculated during lifetime. In obtaining car accidental risk, probabilistic distribution of wind speed, daily traffic volume, mixture ratio in the volume, and duration time for wind speed range are considered. It is recommended to install wind barrier if benefit from the barrier installation exceed construction cost. In the numerical examples, case studies were shown for risk and benefit calculation and main risky regions on Korean highway were all evaluated to identify the number of installation sites.

• The Korean Journal of Pain
• /
• v.33 no.1
• /
• pp.81-89
• /
• 2020

Background: For children with cleft palates, surgeries at a young age are necessary to reduce feeding or phonation difficulties and reduce complications, especially respiratory tract infections and frequent sinusitis. We hypothesized that dexmedetomidine might prolong the postoperative analgesic duration when added to bupivacaine during nerve blocks. Methods: Eighty patients of 1-5 years old were arbitrarily assigned to two equal groups (forty patients each) to receive bilateral suprazygomatic maxillary nerve blocks. Group A received bilateral 0.2 mL/kg bupivacaine (0.125%; maximum volume 4 mL/side). Group B received bilateral 0.2 mL/kg bupivacaine (0.125%) + 0.5 ㎍/kg dexmedetomidine (maximum volume 4 mL/side). Results: The modified children's hospital of Eastern Ontario pain scale score was significantly lower in group B children after 8 hours of follow-up postoperatively (P < 0.001). Mean values of heart rate and blood pressure were significantly different between the groups, with lower mean values in group B (P < 0.001). Median time to the first analgesic demand in group A children was 10 hours (range 8-12 hr), and no patients needed analgesia in group B. The sedation score assessment was higher in children given dexmedetomidine (P = 0.03) during the first postoperative 30 minutes. Better parent satisfaction scores (5-point Likert scale) were recorded in group B and without serious adverse effects. Conclusions: Addition of dexmedetomidine 0.5 ㎍/kg to bupivacaine 0.125% has accentuated the analgesic efficacy of bilateral suprazygomatic maxillary nerve block in children undergoing primary cleft palate repair with less postoperative supplemental analgesia or untoward effects.

• Journal of Korean Society of Transportation
• /
• v.23 no.1
• /
• pp.33-44
• /
• 2005

Railroad crossing crashes are fewer than road crashes, but with regard to crash severity, they can be serious injury crashes. There should be, therefore, enormous efforts to increase the safety of railroad crossings. The objective of this paper is to identify and understand factors associated with railroad crossing crashes. Statistical models are used to examine the relationships between crossing accidents and geometric elements of crossings. The results show the Poisson model is the most appropriate method for the crossing accidents, because overdispersion was not observed. This study identifies seven significant factors associated with railroad crossing crashes through the main and variant models. With regard to explanatory factors on crossing safety, the total traffic volume, daily train volume, presence of commercial area around crossings, distance of train detector from crossings, time duration between the activation of warning signals and gates, crossing types, and speed hump were found to affect the safety of railroad crossings.

• Advances in nano research
• /
• v.15 no.4
• /
• pp.355-366
• /
• 2023

Biological corrosion, a crucial aspect of metal degradation, has received limited attention despite its significance. It involves the deterioration of metals due to corrosion processes influenced by living organisms, including bacteria. Soil represents a substantial threat to pipeline corrosion as it contains chemical and microbial factors that cause severe damage to water, oil, and gas transmission projects. To combat fouling and corrosion, corrosion inhibitors are commonly used; however, their production often involves expensive and hazardous chemicals. Consequently, researchers are exploring natural and eco-friendly alternatives, specifically nano-sized products, as potent corrosion inhibitors. This study aims to environmentally synthesize silver nanoparticles using an extract from Lagoecia cuminoides L and evaluate their effectiveness in preventing biological corrosion of buried pipes in soil. The optimal experimental conditions were determined as follows: a volume of 4 ml for the extract, a volume of 4 ml for silver nitrate (AgNO3), pH 9, a duration of 60 minutes, and a temperature of 60 degrees Celsius. Analysis using transmission electron microscopy confirmed the formation of nanoparticles with an average size of approximately 28 nm, while X-ray diffraction patterns exhibited suitable peak intensities. By employing the Scherer equation, the average particle size was estimated to be around 30 nm. Furthermore, antibacterial studies revealed the potent antibacterial activity of the synthesized silver nanoparticles against both aerobic and anaerobic bacteria. This property effectively mitigates the biological corrosion caused by bacteria in steel pipes buried in soil.

• Korean Journal of Radiology
• /
• v.21 no.6
• /
• pp.717-725
• /
• 2020

Objective: To assess left ventricular remodeling patterns using cardiac computed tomography (CT) in children with congenital heart disease and correlate these patterns with their clinical course. Materials and Methods: Left ventricular volume and myocardial mass were quantified in 17 children with congenital heart disease who underwent initial and follow-up end-systolic cardiac CT studies with a mean follow-up duration of 8.4 ± 9.7 months. Based on changes in the indexed left ventricular myocardial mass (LVMi) and left ventricular mass-volume ratio (LVMVR), left ventricular remodeling between the two serial cardiac CT examinations was categorized into one of four patterns: pattern 1, increased LVMi and increased LVMVR; pattern 2, decreased LVMi and decreased LVMVR; pattern 3, increased LVMi and decreased LVMVR; and pattern 4, decreased LVMi and increased LVMVR. Left ventricular remodeling patterns were correlated with unfavorable clinical courses. Results: Baseline LVMi and LVMVR were 65.1 ± 37.9 g/m² and 4.0 ± 3.2 g/mL, respectively. LVMi increased in 10 patients and decreased in seven patients. LVMVR increased in seven patients and decreased in 10 patients. Pattern 1 was observed in seven patients, pattern 2 in seven, and pattern 3 in three patients. Unfavorable events were observed in 29% (2/7) of patients with pattern 1 and 67% (2/3) of patients with pattern 3, but no such events occurred in pattern 2 during the follow-up period (4.4 ± 2.7 years). Conclusion: Left ventricular remodeling patterns can be characterized using cardiac CT in children with congenital heart disease and may be used to predict their clinical course.

• Tuberculosis and Respiratory Diseases
• /
• v.43 no.4
• /
• pp.491-499
• /
• 1996

Background : Pleural effusion is a common disease in clinical practice but its effect on pulmonary function and altered pulmonary mechanics after removal of effusion are not still largely understood. Previous studies have shown that there is little or a relatively small improvement in pulmonary function and arterial blood oxygenation after therapeutic thoracentesis. The present study was designed to assess the effect on pulmonary function of pleural effusion and to test whether there was a significant improvement in pulmonary function and arterial oxygenation after thoracentesis and to observe long tenn effect after thoracentesis. Method : We examined flow-volume curve, body box and arterial blood gas analysis according to severity of effusion, present symptom, and symptom duration. Then, we measured changes of pulmonary function after thoracentesis and observed longterm effect after thoracentesis. Result: 1) Pleural effusion cause restrictive pulmonary insufficiency. Not only functional impairment of small airway but also large airway is provoked. 2) MMFR, FEV1, Raw, POz are earlier improved than FVC and TLC after thoracentesis and patients without complication have mild restrictive pulmonary insufficiency after longterm observation. 3) FVC, FEV1, & TLC are similarly restricted as severity of pleural effusion and po, is relatively decreased. 4) Cases with symptom duration 1 week or less and cases with dyspnea have more severe pulmonary insufficiency than others. 5) The flow volume curves show a relatively greater improvement in flow rates at large lung volumes than small airway. 6) Significant relationship is shown between first thoracentesis amount and changes of FEV1, FVC, TLC. Conclusion: Pleural effusion cause restrictive pulmonary insufficiency and not only functional impairment of small airway impairment but also large airway is provoked. Then, Pulmonary function is progressively improved after thoracentesis and remained mild restrictive pulmonary insufficiency after recovery.