• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.33 no.4
• /
• pp.385-394
• /
• 2023

Objectives: Firefighters could be exposed to a range of toxic chemicals during firefighting. When tyre burns, various toxic chemicals including volatile organic compounds(VOCs) could be emitted. In this study, the researchers assessed the VOC exposure of firefighters during tyre fire suppression through biomonitoring. Methods: There was a big tyre fire on 12 March 2023. Of the responding firefighters, we recruited 14 participants to collect their urine after firefighting. One week later, researchers collected firefighters' urine again right after their off-duty period. We analyzed each metabolite of benzene, toluene, xylene, and styrene in urine and compared their exposure level based on sampling time. Results: The detection rate for metabolite of benzene, toluene, styrene, and xylene in urine sampled at each time was 43%-64%, 100%, 86%-100%, and 100%, respectively. Except for the benzene, metabolite levels measured in urine after firefighting were similar to that from off-duty period. However, the median concentration of benzene metabolite in urine sampled after firefighting was three times higher compared to that from off-duty period(34.2 ㎍/g crea. and 10.9 ㎍/g crea., respectively.) The estimated airborne concentration of benzene calculated from metabolite level in urine was 0.16 ppm, which exceeded the recommended exposure level set by the National Institute for Occupational Safety and Health. Conclusions: This study shows that firefighters could be exposed to the high level of VOCs including benzene during their firefighting especially at tyre fire. These results could be used as a valuable data to prove firefighters' exposure to hazardous chemicals during their duty.

• Journal of Korean Society for Atmospheric Environment
• /
• v.20 no.2
• /
• pp.225-236
• /
• 2004

Diesel engines which emit a lot of PM and NOx have been known as a main air polluter. Especially, diesel particulate matters (OPM) including black smoke are hazardous air pollutants to human health and environment. The nations retaining advanced engine technologies have reinforced emission regulations. To meet these regulations diesel engine manufacturers have developed low-emission diesel engines, aftertreatment equipments, alternative fuel technologies and so on. In this study, particle number concentrations characteristics according to particle size and engine driving conditions were analyzed when these low-emission technologies were applied. There was a tendency of increasing particle number concentrations from heavy-duty diesel engines with increasing engine rpm and load rate. In the cases of COPF (Catalytic Diesel Particulate Filter), CNG (Compressed Natural Gas) engine and ULSD (Ultra Low Sulfur Diesel) more than 99% of particle number concentration were removed.

• 한국정보통신설비학회:학술대회논문집
• /
• 2009.08a
• /
• pp.242-247
• /
• 2009

In this paper, we investigate interference between short-range radiocommunication devices (SRDs) with frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS) methods when they are in the same frequency bands. In order to analyze interference from unwanted emission of SRD with DSSS to that of FHSS, Monte-Carlo (MC) simulation method is employed and interference probabilities are calculated. We simulate interference scenarios in accordance with several duty cycles and bandwidths. It is also assumed that the propagation model is free space The effect of distance between interfering transmitter and victim receiver is analyzed and bit error rate (BER) is simulated. From the interference analysis results, it is shown that duty cycle affects compatibility more than bandwidth does. Also, we can make sure of the separation distance which satisfies BER criterion when there are only one interfering transmitter and multiple interfering transmitters.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1996.10a
• /
• pp.52-57
• /
• 1996

Conductive Ceramic Matrix Composite(CMC) of TIC/Al2O3 and Metal Matrix Composite (MMC) of SiC/Al were experienced by the die sinking Electrical Discharge Machining(EDM) for different current and duty factor according to negative polarity. Inthis experimental study Material Removal Rate(MRR) maximum surface roughness four point bending stress distribution and Scanning Electron Microscopy(SEM) Photographs were analysed. the higher MRR was obtained for CMC than MMC but slowly decreased around duty factor of 0.67 for MMC and better surface morphology was found CMC than MMC. The SEM photographs of discharge traces for CMC showe uniform shape about 100 to 200${\mu}{\textrm}{m}$ in diameter but MMC showed irregular shape.

• Journal of Energy Engineering
• /
• v.28 no.4
• /
• pp.13-18
• /
• 2019

The high energy penalty in amine-based post-combustion CO₂ capture process is hampering its industrial scale application. An advanced process is designed by intensive heat integration within the conventional process to reduce the stripper duty. The study presents the technical feasibility for stripper duty reduction by intensive heat integration in CO₂ capture process. A rigorous rate-based model has been used in Aspen Plus® to simulate conventional and advanced process for a 300 MW coal-based power plant. Several design and operational parameters like split ratio, stripper inter-heater location and flowrate were studied to find the optimum values. The results show that advanced configuration with heat integration can reduces the stripper heat by 14%.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.13 no.2
• /
• pp.101-107
• /
• 2005

In this paper, optimized operating parameters were found using multi-dimensional engine simulation software (KIVA-3V) and micro-genetic algorithm for heavy duty diesel engine. The engine operating condition considered was at 1,737 rev/min and 57 % load. Engine simulation model was validated using an engine equipped with a high pressure electronic unit injector (HEUI) system. Three important parameters were used for the optimization - boost pressure, EGR rate and start of injection timing. Numerical optimization identified HCCI-like combustion characteristics showing significant improvements for the soot and $NO_X$ emissions. The optimized soot and $NO_X$ emissions were reduced to 0.005 g/kW-hr and 1.33 g/kW-hr, respectively. Moreover, the optimum results met EPA 2007 mandates at the operating point considered.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.10 no.6
• /
• pp.59-64
• /
• 2002

The effects of EGR on emissions were investigated by using a six-cylinder, 8 litre, turbo-charged, heavy-duty diesel engine with a low pressure route EGR system. The experiments were performed at various engine loads while the EGR rates were set from 0% to 30%. Hot and cooled EGR are achieved without cooling and with cooling respectively. To verify the possibility of EGR technology for the applications, test were performed with steady state test cycle. It was found that the exhaust emissions with the EGR system resulted in a very large reduction in oxides of nitrogen at the expense of higher smoke and PM emissions. Increasing the EGR rate leads to deteriorating specific fuel consumption and power at lower speed and higher load. Also, the reduction rates of NOx emissions for hot and cooled EGR are similar.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.12A
• /
• pp.1329-1338
• /
• 2007

Leading MAC protocols developed for duty-cycled WSNs such as B-MAC employ a long preamble and channel sampling. The long preamble introduces excess latency at each hop and suffers from excess energy consumption at non-target receivers. In this paper we propose AS-MAC (Asynchronous Sensor MAC), a low power MAC protocol for wireless sensor networks (WSNs). AS-MAC solves these problems by employing a series of preload approach that retains the advantages of low power listening and independent sleep schedule. Moreover AS-MAC offers an additional advantage such as flexible duty cycle as data rate varies. We demonstrate that AS-MAC is better performance than B-MAC through analysis and evaluation.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1999.05a
• /
• pp.245-250
• /
• 1999

The experimental study of die-sinking electrical discharge machining for alloy tool steel of STD-11 with circular electrode was conducted for various conditions of the peak current and duty factor with the change of internal size of electrode for distributing the amount of dielectric flow through the electrode. From this study, the material removal rate(MRR) was found to be increased with the peak current and duty factor. The more MRR was obtained for the case of electrode inside diameter of 10mm. The surface roughness and roundness values were analyzed regularity under various conditions, and these values were not affected by the inside diameter change of electrode.

• Proceedings of the KIEE Conference
• /
• 2003.07c
• /
• pp.1732-1734
• /
• 2003

An MgO thin film sputtering system for the PDP (Plasma Display Panel) applications has been developed. This system was manufactured with a vertical In-Line type of 42 inch, which has the length of 520 mm and the width of 900 mm. A reactive magnetron discharge for this sputtering was generated using an unipolar pulsed power supply which has functions of constant voltage (Max. 500 V) and current (Max. 15 A) control, frequency of $10{\sim}100$ kHz and duty ratio of $10{\sim}60$ %. The experiment was conducted under various conditions : $3{\sim}10$ mTorr of pressure, the ratio of $O_2$/Ar = $0.1{\sim}0.5$, 50 % of duty and power of $0.5{\sim}1.7$ kW. From the experiment, the deposition rate of a static state and a moving state were measured to be about 45 nm/min and 6 nm m/min at the distance of 50 mm between the target and the substrate, respectively.