• Journal of Energy Engineering
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• v.11 no.2
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• pp.130-135
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• 2002

Bypass air conditioning systems are divided into three types; outdoor air bypass, mixed air bypass and return air bypass system. Among bypass air conditioning systems, a return air bypass system is more effective than other two systems because it doesn't induce unconditioned outdoor air into conditioned room. The numerical study on the bypass air conditioning system shows this system can maintain indoor RH(Relative Humidity) less than a conventional CAV (Constant Air Volume) air conditioning system by adjusting face and bypass dampers at part load. A simulator was built to compare results of a numerical experiment and those of a simulator experiment. The results of the simulator experiment was nearly same as those of the numerical experiment; when a design sensible load (the ratio of sensible load to total sensible load) was 70 percent (at this time, RSHF=0.7), indoor relative humidity (in case of both numerical experiments and simulator experiments) was maintained below 60% specified by ASHRAE STANDARD 62-1999. The bypass air conditioning system is expected to be applied to many buildings where the Percentage of latent loads or air change tate is high.

• Journal of Power System Engineering
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• v.20 no.6
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• pp.87-92
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• 2016

This research dealt with performance characteristics of OTEC system applying an ejector and additional pump. Each system using five kinds of working fluids was analyzed, and primary parameters with respect to entrainment ratio were examined: Turbine gross power, evaporation capacity, pump work, efficiency and volume flow ratio. The primary results were as following. The efficiency of ejector-pump OTEC system was dependent on entrainment of the ejector. The degree of efficiency change was different from applied working fluid, and amount of pump work was turned out to be primary factor affected system efficiency. Meanwhile, optimized entrainment ratio was different from applied working fluid since their different vapor density. System efficiency at optimized entrainmet ratio of each working fluid was around 5%, showing minor difference each other.

• Journal of Biomedical Engineering Research
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• v.41 no.1
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• pp.8-13
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• 2020

To develop cardiovascular simulator capable of implementing pulse waves similar to the human body, accurate information about reflection wave is required. However, the conclusion is still not clear and various discussions are underway. In this study, the pulse wave velocity of the tube used in the experiment was first determined by measuring the pressure waves at two points in a single tube system with the experimental device to implement the pulse wave transmission of blood vessels, and the superposition time and characteristics of the reflection wave were confirmed. After that, an air chamber was set at the reflection site, and the effect of the change of air volume on the reflection wave was investigated. Finally, the effect of the number of branches connected to a single tube on the reflection wave was investigated. The superposition time of the reflection wave can be controlled by the air volume of the air chamber, and the magnitude of the reflection wave is influenced by the number of reflection sites that generate the reflection wave. The results of this study may be of practical assistance to simulator researchers who want to implement pulse wave similar to clinical data. It is expected that the more results similar to clinical are provided, the greater the scope of the simulator's contribution to clinical cardiovascular research.

• Atmosphere
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• v.21 no.3
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• pp.243-256
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• 2011

This paper presents the development of new algorithm for identifying and tracking the convective cells in three dimensional reflectivity fields in Cartesian coordinates. First, the radar volume data in spherical coordinate system has been converted into Cartesian coordinate system by the bilinear interpolation. The three-dimensional convective cell has then been identified as a group of spatially consecutive grid points using reflectivity and volume thresholds. The tracking algorithm utilizes a fuzzy logic with four membership functions and their weights. The four fuzzy parameters of speed, area change ratio, reflectivity change ratio, and axis transformation ratio have been newly defined. In order to make their membership functions, the normalized frequency distributions are calculated using the pairs of manually matched cells in the consecutive radar reflectivity fields. The algorithms have been verified for two convective events in summer season. Results show that the algorithms have properly identified storm cells and tracked the same cells successively. The developed algorithms may provide useful short-term forecasting or nowcasting capability of convective storm cells and provide the statistical characteristics of severe weather.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.28 no.1
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• pp.7-13
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• 2020

A significant growth in local air traffic volume is leading to airway congestion and flight delays especially for Incheon-China and Incheon-Europe sectors. A key method to increase the airway capacity is to place a supplemental airway parallel to the existing one and in cooperation between the aviation authorities between China and Korea, a dual airway track was implemented on December 6, 2018. Here, we use airline A's flight data to analyze the congestion change effect of the new airway. Results show total delay time to Europe is reduced 51% (13.4 to 6.6 minutes) as the delay distribution for 16-30 minutes, 31 minutes and greater decreased from 23.2% to 8.2% and 8.7% to 1.0% respectively. The delay to China also decreased but the drop is not as significant as flights to Europe. This is caused by the difference in flight distance, traffic volume, and characteristics of flights landing and transiting China. Flights to Europe show a broad distribution in altitude allocation and reduction in aircraft separation demonstrating the effectiveness of a dual airway track.

• Journal of Environmental Science International
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• v.31 no.4
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• pp.329-339
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• 2022

Better understanding the mechanism of black ice occurrence on the road in winter is necessary to reduce the socio-economic damage it causes. In this study, intensive observations of road weather elements and surface information under the influence of synoptic high-pressure patterns (22^nd December, 2020 and 29^th January, and 25^th February, 2021) were carried out using a mobile observation vehicle. We found that temperature and road surface temperature change is significantly influenced by observation time, altitude and structure of the road, surrounding terrain, and traffic volume, especially in tunnels and bridges. In addition, even if the spatial distribution of temperature and road surface temperature for the entire observation route is similar, there is a difference between air and road surface temperatures due to the influence of current weather conditions. The observed road temperature, air temperature and air pressure in Nongong Bridge were significantly different to other fixed road weather observation points.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1447-1448
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• 2011

The CSPE cables are used for three years in nuclear power plant. The accelerated thermal aging of chloro sulfonate polyethylene(CSPE) jacket of test cables were carried out for the period equal to 10, 20 and 30 years in air at 90 and $100^{\circ}C$, respectively. The electrical volume resistivity, density, XPS, FE-SEM, EDS and XRF of the accelerated thermal aging of CSPE were measured. The validation of condition monitering method of accelerated thermal aging CSPE was estimated by them. The best validation of condition monitoring method of accelerated aging CSPE is electrical volume resistivity because change thermal of the specimen showed distinction.

• Journal of the Korean Society of Combustion
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• v.5 no.2
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• pp.63-68
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• 2000

Combustion phenomenon in scale-downed combustor is investigated. As the combustor scale decreases surface to volume ratio increases and chamber size approaches quenching distance. As the combustor scales down surface to volume ratio increases resulting increased heat loss. And this heat loss can affect quenching and instability of the flame. To investigate this effect plastic mini combustor is made. Stoichiometricaly premixed Hydrogen / air gas is used as fuel. Initial chamber pressure and chamber size are varied and the effects are evaluated. Peak pressure decreased with the decrease in chamber height. As initial chamber pressure decreases peak pressure decreases and this change is more important than scale down effect till the chamber height of 1mm. With this result and further information following the experiments design parameter for micro engine can be established.

• The Journal of the Korea Contents Association
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• v.19 no.8
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• pp.284-292
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• 2019

To evaluate the usefulness of pediatric chest CT scans by comparing the dose, examination time, and image quality by applying Helical mode, High-pitch mode, and Volume Axial mode to minimize the radiation exposure and obtain high diagnostic value. Revolution (GE Healthcare, Wisconsin USA) was used to divide PBU-70 phantom into Helical mode, High-pitch mode, and Volume Axial mode. After acquiring images, ROI is set for each image, heart, bone, lung, and back-ground air, and the average value is obtained by measuring CT number (HU) and noise (SD). SNR and CNR were measured and compared with DLP values provided directly by the equipment. Determining statistical significance Statistical analysis was performed using ONE-WAY-ANAOVA using SPSS 21.0. In this experiment, it was possible to inspect at a short time without deterioration of image quality with the lowest dose when using volume axial mode. Although the detector coverage of 16 cm is limited to all pediatric chest CT scans, it is recommended to be actively used in pediatric patients, and further study is needed to apply other test sites in volume axial mode.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.3 no.1
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• pp.22-36
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• 1993

This study was conducted to evaluate the charcoal tube sampling method for carbon disulfide in the air. Breakthrough was investigated according to flow rate, sampling time and air volume. Also the storage stability by storage method and time was investigated. The results are summarized as follows. 1. The samples stored at room temperature($28.2^{\circ}C$), refrigerator($3.8^{\circ}C$) and freezer($-15.6^{\circ}C$) were analyzed every week to five weeks. At one week storage at room temperature, 3.5% of $CS_2$ in the front section of the charcoal tube migrated into the back section and 57.7% at five weeks. The amount of $CS_2$ in the back section of the charcoal increased continuously by storage time. Migration of $CS_2$ was slow at refrigerator, and stopped occur at freezer. Recovery rate $CS_2$ was 52-82% at room temperature and 92-101% at refrigerator, based on the amount at freezer as a reference value. Thus loss was observed at room temperature. 2. When 6-48 L of fresh air were passed through tubes with spiked amounts of 0.379 and 0.759mg sample, the amounts of $CS_2$ in the back section of charcoal were 5.7-132.4 and 0-92% of the amount in the front section, respectively. The total recovery rates of$CS_2$ from 0.379 and 0.759mg spiked sample were 35.7-101.0% and 9l.3-100.1%, respectively. $CS_2$ loss was observed in 0.379mg spiked sample, but not in 0.759mg spiked sample. In the spiked samples, the amount of $CS_2$ in the back section of charcoal was not affected by flow rate when the air volume was controlled. The amount of $CS_2$ in the back section of charcoal increased over sampling time. And the faster the flow rate, the more the migration amount when the sampling time was the same. 3. A known concentration, 10 ppm of $CS_2$, was produced in a 200 L Tedlar bag. When the air volume was 24, 36, 48 L, breakthrough was 5.8, 16.9, 47.4%, respectively. The sampling flow rate of 0.05, 0.1, 0.2 Lpm did not change the breakthrough rate. Breakthrough increased over sampling time. And the faster the flow rate, the more the breakthrough, when the sampling time was the same.