• Fire Science and Engineering
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• v.31 no.2
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• pp.17-23
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• 2017

The test methods using convection (flame) and radiation heat sources were compared to evaluate the thermal protective performance of the firefighter's protective clothing. In particular, the influence of the outer shell, mid-layer, and lining constituting the firefighter's protective clothing on the thermal protective performance was compared for convection and radiation heat sources. Tests for the thermal protective performance were carried out according to KS K ISO 9151 (convection), KS K ISO 6942 (radiation), and KS K ISO 17492 (convection and radiation). When tested under the same incident heat flux conditions ($80kW/m^2$), the heat transfer index ($t_{12}$ and $t_{24}$) for the radiation heat source was higher than that for the convection heat source. This means that radiation has a lesser effect than convection. For the convection heat source, the lining had the greatest effect on the thermal protective performance, followed by the mid-layer and the outer shell. On the other hand, for the radiation heat source, the effect on the thermal protective performance was great in the order of lining, outer shell, and mid-layer. Convection and radiation have fundamentally different mechanisms of heat transfer, and different heat sources can lead to different thermal protective performance results depending on the material composition. Therefore, to evaluate the thermal protective performance of the firefighter's protective clothing, it is important to test not only the convection heat source, but also the radiation heat source.

• Journal of Positioning, Navigation, and Timing
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• v.9 no.3
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• pp.207-214
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• 2020

In this paper, we implement linear-quadratic-Gaussian based vector tracking loop (LQG-VTL) instead of conventional extended Kalman filter based vector tracking loop (EKF-VTL). The LQG-VTL can improve the performance compared to the EKF-VTL by generating optimal control input at a specific performance index. Performance analysis is conducted through two factors, frequency thermal noise and frequency dynamic stress error, which determine total frequency tracking error. We derive the thermal noise and the dynamic stress error formula in the LQG-VTL. From frequency tracking error analysis, we can determine control gain matrix in the LQG controller and show that the frequency tracking error of the LQG-VTL is lower than that of the EKF-VTL in all C/N0 ranges. The simulation results show that the LQG-VTL improves performance by 30% in Doppler tracking, so the LQG-VTL can extend pre-integration time longer and track weaker signals than the EKF-VTL. Therefore, the LQG-VTL algorithm is more robust than the EKF-VTL in weak signal environments.

• 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.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.108.1-108.1
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• 2005

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.6
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• pp.826-833
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• 2010

Electric-thermal-structural actuated compliant mechanisms are mechanisms onto which electric voltage drop is applied as input instead of force. This mechanism is based on thermal expansion of material while being heated. Compliant mechanisms are designed subjected to electric charge input using BESO(bi-directional evolutionary structural optimization) method. Reliability-based topology optimization (RBTO) is applied to the topology design of actuators. performance measure approach (PMA), which has probabilistic constraints that are formulated in terms of the reliability index, is adopted to evaluate the probabilistic constraints. In this study, BESO method is used to obtain optimal topology of compliant mechanisms from initial design domain. PMA approach is used to evaluate reliability index. The procedure has been tested in numerical applications and compared with the results obtained by other methods to validate these approaches.

• Tribology and Lubricants
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• v.20 no.1
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• pp.33-40
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• 2004

This study represents the newly advanced formulation of hydraulic fluids for extended drain interval and introduces the performance results of used oil samples from various excavators. The used oil samples, in this paper, show that there is a sharp change in viscosity drop and moderate additive depletion when viscosity index of hydraulic oil is very high. For the extension of hydraulic fluid life, it is necessary to improve the stability of viscosity and oxidation. New target properties from the used oil analysis were proposed for extended life. Performance of newly developed hydraulic oil based on used oil analysis is compared with previously used one. The properties of new formulation are the viscosity index of 140 and improved thermal stability consists of VHVI base oil. Field test results showed the possibility of extension of fluid life. Additionally, for development of high performance product, new required propertied and performances were discussed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.10
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• pp.870-878
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• 2003

The maintenance of thermal equilibrium between the human body and its environment is one of the primary requirements for health, wellbeing and comfort. For the effective control of indoor thermal environment, thermostat or humidistat is used. But, it is not sufficient to control the indoor thermal environment using only one or two parameters as human response for the indoor comfortable environment. So an environmental thermal index is required for the control of indoor thermal environment effectively. In this study, a PMV sensor has been developed which has integrated from various kinds of individual sensors for temperature, humidity, air velocity, radiant temperature. After applying the PMV and PPD equation, it is possible to monitor the indoor thermal environment with the sensor system, which is adopted to the circuit for optimization according to the human response with the metabolic rate and activities. The measurement was carried out to verify the performance of the integrated sensor system in comparison with existing measurement system, the PMV meter. As a result, the possibility of applying the PMV sensor to control the indoor thermal environment simultaneously was examined.

• Journal of Korean Living Environment System
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• v.21 no.6
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• pp.959-964
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• 2014

Energy performance of building envelope components, including external walls, floors, roofs, windows and doors, is crutial for determining how much energy is required for heating and cooling in a building. Among various building technologies, a green roof system can be a good option for reducing heat gain and loss in new buildings as well as existing buildings for green remodeling. This paper evaluates the performance of green roof systems according to soil depth and Leaf Area Index (LAI) for existing buildings. It also attempts to quantify the energy saving effects on new and existing buildings with different insulation levels. Thermal performance of green roofs is mainly dependent on soil thickness and LAI. Installation of green roofs in deteriorated existing buildings can lead to improvements in roof insulation, due to the soil layer. An increase in soil depth leads to a decrease in heating load, regardless of conditions of vegetation on the green roof. Larger LAI values may reduce cooling loads in the cooling season. Installation of green roof in deteriorated existing buildings showed bigger energy saving effect in comparison to a case in new buildings. A simulation study showed that the installation of green roof systems in deteriorated existing buildings with low insulation levels, due to low thermal performance requirements when constructed, could improve the energy performance of the buildings similar or better to the peformance on new buildings with the most updated insulation standard. Thus, when remodeling a deteriorated building, green roofs could be a good option to meet the most recent energy requirements.

• Proceedings of the ESK Conference
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• 1998.04a
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• pp.188-193
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• 1998

The purpose of the study is to develop a numerical model based on experimental data to estimate the thermal comfort in the driving room of a motorcar. For the ecperiments, three air temperature level of 21, 23, 25 .deg. C are set to measure variable such as average skin temperature, R-R interval, the comfort sensation, and the performance level. By performing statistical analysis with the results obtainted, it is observed that two physiological factors-average skin temperature and R-R interval have significant relation with the thermal comfort in the driving room. Thus, those two factors are included as parameters in the proposed model to estimate the thermal comfort.

• Journal of the Korean Solar Energy Society
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• v.30 no.5
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• pp.107-114
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• 2010

Understanding of reflectance of solar concentrators is important for assessing concentration performance. However inaccurate data about refractive indices of constituent materials and dust accumulation on the surface often prevent figuring out reflectance variations. The current study proposes an approach calculating concentrator reflectance based on the refractive index of glass obtained from reflectance and transmittance measurements. This approach improved accuracy of solar-averaged reflectance from 2.9% to 0.4% compared to the use of existing reference data. Reflectance variations with incidence angles are negligible up to $60^{\circ}C$ at various glass thicknesses. When concentrators are contaminated with dust during 2 months specular reflectance loss of vertically exposed concentrators is less than 7%. However for horizontally exposed concentrators the loss significantly increases up to 40% while dependence of reflectance on incidence angles becomes strong. Measurements of hemispherical reflectance indicate that 80 percentage of the loss comes from scattering rather than absorption by dust. Data of refractive index and reflectance provided in the current study will help estimate or model the concentrated solar flux.