• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.4
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• pp.725-734
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• 2021

To prevent tire accidents, we developed an application that can check tire safety using the app-inventor and the bluetooth communication. The temperature sensor measures ambient temperature, the pressure sensor measures tire pressure, the laser sensor has a distance of more than 50mm, and an angle of 45° to measure for the optimal tire. We have developed an application that determines tire condition based on measured wear and tear levels, works through the Bluetooth module via App Inventor, and identifies tire condition and expected replacement condition on the user's mobile phone.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.1
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• pp.18-24
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• 2015

In this study, a $CO_2$ air-conditioning system was investigated with different types of electrically driven compressors, parallel flow type gas cooler, four-pass type evaporator, internal heat exchanger integrated with accumulator, and electric expansion valve. The experimental study was conducted under various operating conditions (ie., different rotational compressor speeds, air inlet temperatures and air velocity coming into heat exchangers). The experimental results showed the cooling capacity was 3.5kW at $35^{\circ}C$ ambient temperature when the vehicle was idle (ie., the worst condition for cooling off the gas cooler). In terms of performance effect of the compressor, the e-RP model had a slightly better cooling capacity and coefficient of performance than the e-GR model under the same test conditions. An experimental equation for optimum cooling-performance control was also suggested based on the results. A high-pressure control algorithm for the super critical cycle was determined to achieve both maximum cooling performance and efficient energy consumption. The results from the experimental equation coincided with those of previous experimental studies.

• Journal of ILASS-Korea
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• v.9 no.3
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• pp.8-14
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• 2004

Characteristics of droplet vaporization at high ambient pressures and temperatures which are supercritical conditions is studied numerically by formulating one dimensional vaporization model in liquid dodecane and air. Modified Soave-Redlich-Kwong state equation is used to condider real gas effect. Non-ideal behavior of properties at near critical and supercritical conditions is considered in the high pressure condition. Characteristic spatial distribution of properties with various conditions of pressure and temperature is evaluated in order to understand vaporizing evolution.

• Journal of Korean Society for Atmospheric Environment
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• v.11 no.1
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• pp.85-93
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• 1995

Measurements of ground level ozone concentrations were made in a rural area of Chongwon (Choongbook Province) from June 1993 to July 1994. High values frequently exceeding 100 ppb (ambient air qualyty standard of Korea) were recorded. High ozone concentrations in the boundary layer were primarily correlated with the several meteorological parameters in warm seasons: pressure, radiation, temperature, precipitation and wind velocity. The annual average concentration of ozone at Chongwon was 17ppb, and this value was relatively higher than those for other cities in Korea. O$\_$3/ concentrations were observed to increase when the ridge of a surface anticyclone was passing over the region, and maximum values(.geq.100 ppb) were observed on the rear sides of high pressure centers and in the warm sectors of cyclones(well head of cold fronts). The ozone concentrations had a negative correlation with the concentration of primary pollutants(e.g., total hydrocarbons).

• Clinical and Experimental Pediatrics
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• v.63 no.1
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• pp.3-7
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• 2020

High-flow nasal cannula (HFNC) is a relatively safe and effective noninvasive ventilation method that was recently accepted as a treatment option for acute respiratory support before endotracheal intubation or invasive ventilation. The action mechanism of HFNC includes a decrease in nasopharyngeal resistance, washout of dead space, reduction in inflow of ambient air, and an increase in airway pressure. In preterm infants, HFNC can be used to prevent reintubation and initial noninvasive respiratory support after birth. In children, flow level adjustments are crucial considering their maximal efficacy and complications. Randomized controlled studies suggest that HFNC can be used in cases of moderate to severe bronchiolitis upon initial low-flow oxygen failure. HFNC can also reduce intubation and mechanical ventilation in children with respiratory failure. Several observational studies have shown that HFNC can be beneficial in acute asthma and other respiratory distress. Multicenter randomized studies are warranted to determine the feasibility and adherence of HFNC and continuous positive airway pressure in pediatric intensive care units. The development of clinical guidelines for HFNC, including flow settings, indications, and contraindications, device management, efficacy identification, and safety issues are needed, particularly in children.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.7
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• pp.1780-1786
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• 1995

The main goal of the present study is to establish the techniques and methodolgies of turbine performance test through evaluating the objective turbine test piece, and checking the reliability of the self-developed test facility by performing a series of turbine tests under ambient temperature condition. A high speed coupling, a lubrication system and a test bed of the test facility were modified through a series of preliminary test in order to reduce the vibration and oil leakage. The flowrate control of the test facility and data acquisition were accomplished by using a software called "Labview" The measurement of shaft horse power and control of rotational speed according to the conditions of turbine rotation were performed by a separate system. The preliminary evaluation of the measured data suggests that the developed test facility and the test technique can be used reliably for the performance test of turbines with the minor improvement.provement.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.6
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• pp.63-71
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• 1998

In a diesel engine the phenomenon of spray impaction on a combustion chamber wall has been taken as an undesirable matter because of the deposition of fuel on the surfaces, and the subsequent slow evaporation and mixing with air resulting in unburned hydrocarbons. Therefore many researches have concentrated on avoiding fuel impaction on surfaces. On the contrary done a number of studies using spray wall impactions in a positive way, which makes the droplets smaller, changes the direction into free spaces far from the wall and also improves mixing with air. In this paper the angle variations of the impaction land sufrace prepared for the injection spray is analysed as a simulative manner. The spray dispersions, vapor distributions and flow fields are compared with impacting angle variation. The results show more angle give more vapor distribution until $15^{\circ}$.

• Nuclear Engineering and Technology
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• v.54 no.2
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• pp.546-553
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• 2022

Narrow rectangular channels are employed in nuclear research reactors that use plate-type nuclear fuels, high heat-flux compact heat exchangers, and high-performance micro-electronics cooling systems. Two-phase flow in narrow rectangular channels is important, and it needs to be better understood because it is considerably different than that in round tubes. In this study, mechanistic models were developed for the flow regime transition criteria for various flow regimes in co-current air-water two-phase flow for vertical downward flow inside a narrow rectangular channel. The newly developed criteria were compared to a flow regime map of downward air-water two-phase flow inside a narrow rectangular channel with a 2.35-mm gap width under ambient temperature and pressure conditions. Overall, the proposed model showed good agreement with the experimental data.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.6
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• pp.643-647
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• 2014

Two types of fuel supply method ar used in CNG vehicles. One is premixed ignition and the other is gas-jet ignition. In premixed ignition, the fuel is introduced with intake air so that homogeneous air-fuel mixture may form. The ignitability of this method depends on the global equivalence ratio. In gas-jet ignition, CNG is introduced directly into the engine combustion chamber. The overall mixture is stratified by retarded fuel injection. In this study, a visualization technique was employed to obtain fundamental properties regarding overall mixture formation of direct injected CNG fuel inside a constant volume chamber. Jet angles, penetrations and projected jet area with respect to ambient pressure are investigated. The penetration decreases apparently and the time reaching the CVC wall was delayed as the chamber pressure increases. This is caused by the higher inertia of the fluid elements that the injected fluid must accelerate and push aside. It is same to liquid fuel such as diesel and gasoline, but this phenomenon is far more prominent for the gaseous fuel.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.3
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• pp.183-192
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• 2002

Concentrations of $\alpha$- and ${\gamma}$-hexachlorocyclohexane (HCH) were measured in ambient air samples at a two week intervals between July 1999 and February 2000 at Ansung, Kyonggi province. Their concentration levels averaged at 78 ($\alpha$-HCH) and 18 pg/m$^3$(${\gamma}$-HCH). Although the use of HCHs was ceased in South Korea since 1979, their residues are still present in air even after nearly 20 years. Given the composition of the two main HCH pesticide formulation (technical HCH antral lindane), the $\alpha$/${\gamma}$-HCH ratio in air is a useful indicator on the regional scale. The moderately low $\alpha$/${\gamma}$-HCH ration in this study indicates previous usage of both technical HCH and lindane. The relationship of temperature with gas-phase partial pressures was also examined using the Clausius-Clapeyron equation. Slopes generated by linear regression analysis between partial pressure (In P) and 1/T were considerably steep thor HCHs. It is thus suggested that their concentrations are controlled by re-volatilization processes from surfaces in the local surroundings of the sampling site.