• Smart Structures and Systems
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• v.30 no.5
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• pp.433-446
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• 2022

Despite efforts to reduce unexpected accidents at confined construction sites, choking accidents continue to occur. Because of the poorly ventilated atmosphere, particularly in long, confined underground spaces, workers are subject to dangerous working conditions despite the use of artificial ventilation. Moreover, the traditional monitoring methods of using portable gas detectors place safety inspectors in direct contact with hazardous conditions. In this study, a long-range (LoRa)-based wireless safety monitoring system that features the network organization, fault-tolerant, power management, and a graphical user interface (GUI) was developed for underground construction sites. The LoRa wireless data communication system was adopted to detect hazardous gases and oxygen deficiency within a confined underground space with adjustable communication range and low power consumption. Fault tolerance based on the mapping information of the entire wireless sensor network was particularly implemented to ensure the reliable operation of the monitoring system. Moreover, a sleep mode was implemented for the efficient power management. The GUI was also developed to control the entire safety-monitoring system and to manage the measured data. The developed safety-monitoring system was validated in an indoor testing and at two full-scale water pipeline construction sites.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.5
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• pp.608-615
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• 2011

The objective of this study is to investigate the flow characteristics of polluted air behavior in rectangular tunnels using a PIV system and a commercial CFD program. The PIV experiments are simulated by using the olive oil as the tracer particles in scaled rectangular tunnels. Each model has one of four different outlet vents, each dimensionless L/H ratio of which is 0, 0.375, 0.75 and 1.125, respectively as the locations of each outlet are away from the vertical centerline through the inlet. A commercial CFD program, ANSYS CFX, was used to examine the velocity fields and the pressure distributions in numerical simulations. The kinematic viscosity of the air flow of $1.51{\times}10^{-5}m^2/s$ and the flow velocity of 0.3 m/s at the inlet are given under the same conditions in order to analyze the polluted air flow characteristics experimentally and computationally. This study is considered to examine the effect of the outlet locations in the naturally ventilated tunnel models.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.393-402
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• 1993

Two field test installations are discussed. In the first one a new ammonia sensor and an accurate ventilation rate sensor are combined. They are installed in the exhaust chimney in a ventilated pig house. The relative humidity and the room temperature are measured as well. In the second one, an in situ NH$_3$longrightarrowNO converter with subsequent NOx analyser is also being added for accurate ammonia measurement . In this way , the continuous measurement of the total NH$_3$emission can be obtained , the performance of the NH$_3$ sensor can be evaluated, and the ammonia reduction techniques can be tested. The outputs of measurement are fed into a data acquisition system then to a PC in the laboratory. There has been realised the first test installation with which research on the new ammonia sensor is carried out. The primary research results are presented.

• Tribology and Lubricants
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• v.13 no.4
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• pp.10-17
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• 1997

The present study describes an experimental investigation of temperature fluctuations associated with thermal instability. Surface temperatures of brake disk and pad were monitered at various locations in a caliper type brake system during drag braking conditions. It was found that the thermal instability appeared in pad more seriously than in disk. The temperatures at various circumferential positions fluctuate synchronously, whereas the center temperature fluctuates with 180$^{\circ}$ phase difference from the outer and inner radius temperatures. The temperature and amplitude of the temperature perturbations are increased due to the increase of contact area in the center location. It was also found that the thermal instability was dominantly determined by the increase of rotation speed and pressure. And the modification of ventilation path could retard the onset of thermal instability.

• Journal of the Korean Institute of Educational Facilities
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• v.11 no.2
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• pp.17-23
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• 2004

The purpose of this study concerns the improvement of air quality in school classrooms. Polluted indoor air is improved by efficient ventilation systems. So it is important to measure the amount of ventilation needed in classrooms. First, the amount of natural ventilation were measured through a tracer gas method. And we have established a heat recovery ventilation system from 4 cases of airflow in classrooms, and we have measured the change of $CO_2$ density. According to air quality measurements in the classrooms, the density of $CO_2$ is well above environmental standards which are acceptable. When the amount of ventilated airflow increases, indoor air quality is improved. It is surveyed that the most suitable amount of external inducted air is 770 CMH to satisfy $CO_2$ less than 1,000 ppm in classrooms. For improvement of air quality in classrooms, we must consider a suitable ventilation plan and installation of ventilation systems when constructing school buildings.

• Journal of Korean Academy of Nursing
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• v.41 no.2
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• pp.175-181
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• 2011

Purpose: This study was conducted to identify endotracheal colonization and the incidence of ventilator-associated pneumonia related to the type of endotracheal suction system. Methods: The participants in this study were ICU patients hospitalized between October 2009 to March 2010 who used ventilators for over 48 hr with closed (CSS, n=30) or open (OSS, n=32) suction systems. To standardize the pre-intervention suction system, a suctioning protocol was taught to the ICU nurses. Collected data were analyzed using ${\chi}^2$-test, Fisher's exact test, Wilcoxon rank sums test, Wilcoxon test, Log-rank test and Poisson regression. Results: Endotracheal colonization was higher in OSS than CSS from day 1 to day 8 while using a ventilator and there was a significant difference between the two groups. The CSS reached 50% of endotracheal colonization by the 4th day, whereas for the OSS, it was the 2nd day (p=.04). The incidence of ventilator-associated pneumonia showed no significant difference. Conclusion: For patients with a high risk of pneumonia, CSS must be used to lower endotracheal colonization.

• Journal of the Korean Home Economics Association
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• v.35 no.5
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• pp.239-248
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• 1997

to design nature-affinitive, reasonable and effcient thermal environment plannings and facilities, the holding patterns of heating-cooling facilities·accessory devices and residents' evaluation in Cheju Province were surveyed as well as residents' understanding for them. Major findings of this study are summarized as follows: 1) In the cooling system, the percentage of air-conditioner possessor was 19.4%, which was lower possessive rate than mainland's. The location of air-conditioner was mainly public area. That is, 55.3% of the location is livingroom, and the rest was Anbang. the general cooling accessory device was a fan. It was frequently used at the children's room and the dining room. The possessive patterns of air-conditioner depend on the characteristics of residents, such as the academic carrier and the average monthly income. Characteristics of house for air-conditioner possess depend on the location, house type, the size of floor space. 2) In the heating system, individual heating system reached to 57.3%. Heating accessory devices were oil stove and electric heating blanket. Only 32.2% of survey population were holders. 3) Residents preferred better ventilated room arrangement, which was characteristic of subtropical areas. 4) The preferred condition for heating-cooling facilities and accessory devices were strong solidity, less air pollution, and less noise.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.148-153
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• 2009

This paper considers the age of air in a ventilated space with multiple supply inlets. The local mean age of air at a point from one supply inlet is different from those from the other supply inlets. It is the purpose of the present paper to investigate theoretically the relations between the LMA's from each supply and overall combined LMA whether or not to trace the origins of supply air. Transient concentration distributions are calculated with a step-up injection of tracer gas at each supply inlet, and at both inlets simultaneously. The steady state concentration with a continuous tracer injection at a supply inlet works as a weighting factor for the corresponding LMA in calculating the average overall LMA from multiple inlets.

• Journal of the Korean Society of Safety
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• v.31 no.1
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• pp.25-32
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• 2016

A sensitivity analysis of FDS(Fire Dynamics Simulator) results for the input uncertainty of heat release rate (Q) which might be the most influencing parameter to fire behaviors was performed. The calculated results were compared with experimental data obtained by the OECD/NEA PRISME project. The sensitivity of FDS results with the change in Q was also compared with the empirical correlations suggested in previous literature. As a result, the change in the specified Q led to the different dependence of major quantities such as temperature and species concentrations for the over- and under-ventilated fire conditions, respectively. It was also found that the sensitivity of major quantities to uncertain value of Q showed the significant difference in results obtained using the previous empirical correlations.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.909-914
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• 2006

The purpose of this study is to analyze the thermal of DFS(double Facade System) and curtain wall in the heating period. The physical difference between curtain wall and double facade on thermal performance has been tested at the newly constructed laboratory, which can turn $360^{\circ}$ to confirm the characteristic of a facade with the various directions. This study divide on 'ventilated, airtight' and 'heated or unheated' conditions from the CASE 1, 2, 3, 4. The results showed thermal performance of double facade system which has been better than curtain wall. The heating energy of DFS reduced $8%{\sim}10%$ of energy consumption. comparable to SFS in experemted results. In view of the researching results so far achieved, the research came to a conclusion, that the curtain wall can save the energy in the heating period than a curtain wall.