• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.9
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• pp.979-988
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• 2014

Recently, the interest in the thermal comfort is ever increasing as the time people stay in the automobile is gradually increasing. So far, however, the cooling performance of the HVAC(heating and ventilation air conditioning) system is evaluated by thermal environment criteria such as indoor air velocity and temperature, not by a thermal comfort index. Furthermore, the precise criteria has not been established yet when the thermal comfort for the automobile is evaluated using numerical analysis. In this study, the numerical analysis of automobile indoor thermal comfort according to various parameters such as HVAC operating mode, airflow, passenger boarding conditions is performed during the HVAC system's initial operating time(20 minutes). The solar ray tracing model and S2S radiation model are used and validated to simulate an external heat source. Based on this study, an evaluation model which can predict the thermal comfort index for the combination of the above parameters is presented.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.1
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• pp.57-64
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• 2009

This study intends to evaluate of the characteristics of pavement deformation and develop the model for prediction model in the asphalt layer using a regression analysis. In test, there are two different asphalt binders and 5 different aggregate types. The air voids of hot mix asphalt are 6% and 10% for target value. Repeated triaxial compression test with 3 different confining pressures was used for test at 3 different test temperatures. It is going to verify the main parameters for permanent deformation of HMA and to develop the distress model. This paper is to figure out the factor affecting the pavement deformation, and then to develop model the pavement deformation for asphalt mixture. Also, the reliability of prediction model has been studied. The permanent deformation prediction model for asphalt mixtures with temperature, loading time, and air voids has been developed and the proposed permanent deformation prediction model has been validated by using the multiple regression approach which is called Statistical Package for the Social Sciences(SPSS).

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.7
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• pp.627-631
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• 2012

Observable mathematical model of DDM (Direct Dirve Motor) was suggested. The motor that operates the object system directly is called DDM. DDM has many strong points, however, it has a significant disadvantage, that it is more sensitive to the external force than the motor with reduction gear. In other word, if the force is applied, air gap of the motor can be perturbed. This causes not only difficulty in motor control but also even more serious problem, such as the breakdown of motor. However, if the air gap variation can be estimated, it can help prevent these problems. DDM should be modeled to estimate the air gap variation. The type of researched DDM is PMSM (Permanent Magnet Synchronous Motor) and precedent model of PMSM includes only characteristics of electro-magnetic system and rotational motion. However, suggested model should also include characteristics of translational motion of rotor to estimate the air gap variation. Also, this model should satisfy observability condition, because state observer is designed based on this model.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.5
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• pp.743-749
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• 2010

The primary object of this study was to develop the control algorithm and program for automatic submersible buoy which is free to move vertically within the water column by adjusting weight and buoyancy forces by air control. The experiment was performed to validate the usefulness of the program in the indoor water tank. In the experiment, the automatic submerging and surfacing of the buoy were controlled by water-pressure gauge and air control system. The buoy is raised by injecting compressed air from a compressor and then is lowered by releasing the air. The submerging and surfacing characteristics of the buoy calculated with the numerical model were similar to measurements obtained with the experiment. It was concluded that the algorithm and program could be useful in analyzing various parameters and submerging mechanisms required to design new type of automatic submersible fish cage system.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.26 no.3
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• pp.9-22
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• 2018

Korea meteorological administration(KMA) has started to levy air meteorological service charge on both national and foreign carriers since 2005. The charge has grown on 2010 and 2014 twice. However, KMA has still kept asking airlines to agree with another increase in the charge due to the low cost of goods recovery ratio of 7%. The air meteorological charge has changed from 2,210 KRW at the beginning to 11,400 KRW as of June 2018. According to ARIMA intervention time series analysis, it was proven national carriers would make a payment of 831 million KRW 2018 and 1,024 million KRW 2019, showing 186.2% and 123.2% increase compared to last year respectively. The total amount of charge for both national LCC and foreign airlines was aggregated up to 1,952 million KRW 2019, 227% bigger than the charge paid at 2017. Considering the 50% increase of consumer price index last decade, the increased charge would impair the global competitiveness of national carriers. It could be suggested that current air meteorological charge scheme be improved to apply overseas trend and for national carriers to have a competitive advantage in global aviation market.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.6
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• pp.734-743
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• 2007

Polyurethane foam-disk passive air samplers (PAS) were deployed in a southern area of Korea for three months. The target compounds were 12 coplanar polychlorinated biphenyls (PCBs). The congener profiles measured in this study were the same as those in ambient air and emission gas from the incinerator. A gradient of the total PCBs in different regions (industrial>residential>rural) was observed, suggesting the industrial complex may be an important source of coplanar PCBs. In general, only gas-phase compounds are mainly sequestrated by PAS. In order to estimate the concentration of particle-phase PCBs, a gas/particle partition model was used. A combined result (gas+particle-phase PCBs) was compared with previous results, indicating that the level of coplanar PCBs in our study area is comparable to those in other urban sites in the world. The validation of this method for estimating the total concentration is required through additional backup studies.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.6
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• pp.640-652
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• 2007

The MM5, RAMS and WRF, meteorological models have provided the dynamical parameters as inputs to air quality model. A major content of this study is that significant characteristics of three models for high-ozone occurrence analyze for surface wind and air temperature fields and compare with observation data in Seoul metropolitan area. An analysis of air temperature field revealed that location of core in high temperature of MM5 and WRF differed from that of RAMS. MM5 and WRF indicated high temperature in Seoul but RAMS represented it on the outskirts of Seoul. MM5 and WRF were underestimated maximum temperature during daytime but RAMS simulated similar value with observation data. Surface wind field with three models, it was shown many differences at horizontal distribution of wind direction. RAMS indicated weak wind speed in land and strong sea breeze at coastal areas than MM5 and WRF. However wind speed simulated by three model were overestimated during both daytime and nighttime.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.10
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• pp.467-473
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• 2014

Since the operating conditions of HVAC systems are different from those for which they are designed, on-going commissioning is required to optimize the energy consumed and the environment in the building. This study presents a methodology to analyze operational data and its applications. A predicted operation model is to be produced through a statistical data analysis using multiple regressions in SPSS. In this model, the dependent variable is the pre-cooling time, and the independent variables include the power output of the supply air inverter during pre-cooling, the supply air set temperature during pre-cooling, the indoor temperature-indoor set temperature just before pre-cooling, supply heat capacity, and the lowest outdoor air temperature during non-cooling/non-heating hours. The correlation coefficient R2 of the multiple regression model between the pre-cooling hour and the internal/external factors is of 0.612, and this could be used to provide information related to energy conservation and operating guidance.

• Journal of the Korean Solar Energy Society
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• v.23 no.3
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• pp.7-14
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• 2003

Absorption potential of desiccant solution significantly decreases after absorbing moisture from humid air, and a regeneration process requires a great amount of energy to recover absorption potential of desiccant solution. In an effort to develop an energy efficient regenerator, this study examines a regeneration process using hot air heated by solar radiation to recover absorption potential by evaporating moisture in liquid desiccant. More specifically, this study is aimed at finding the optimum operating condition of the regenerator by utilizing a well-established statistical tool, so-called response surface methodology(RSM), which may provide a functional relationship between independent and dependent variables. It is demonstrated that an optimization model to find the optimum operating condition can be obtained using the functional relationship between regeneration rate and affecting factors which is approximated on the basis experimental results.

• Journal of Environmental Science International
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• v.7 no.6
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• pp.745-751
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• 1998

The well-mixed room model has been traditionally used to predict the concentrations of contaminants in indoor environments. However, this is inappropriate because the flow fields in many indoor environments distribute contaminants non-uniformly, due to imperfect air mixing. Thus, some means used to describe an imperfectly mixed room are needed. The simplest model that accounts for imperfect air mixing is a two-zone model. Therefore, this study on development of computer program far the two-zone model is carried out to propose techniques of estimating the concentration of contaminants in the room. To do this, an important consideration is to divide a room into two-zone, i.e. the lower and upper zone assuming that the air and contaminants are well mixed within each zone. And between the zones the air recirculation is characterized through the air exchange parameter. By this basic assumption, the equations for the conservation of mass are derived for each zone. These equations are solved by using the computational technique. The language used to develope the program is a VISUAL BASIC. The value of air exchange coefficient($f_12$) is the most difficult to forecast when the concentrations of contaminants in an imperfectly mixed room are estimated by the two-zone model. But, as the value of $f_12$ increases, the air exchange between each zone increases. When the value of $f_12$ is approximately 15, the concentrations in both zone approach each other, and the entire room may be approximately treated as a single well-mixed room. Therefore, this study is available for designing of the ventilation to improve the air quality of indoor environments. Also, the two-zone model produces the theoretical base which may be extended to the theory for the multi-zone model, that will be contributed to estimate the air pollution in large enclosures, such as shopping malls, atria buildings, atria terminals, and covered sports stadia.