• Journal of Environmental Science International
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• v.24 no.4
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• pp.383-391
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• 2015

As occurrence of gradually increasing extreme temperature events in Jeju Island, a hybrid downscaling technique that simultaneously applies by dynamical method and statistical method has implemented on design rainfall in order to reduce flood damages from severe storms and typhoons.As a result of computation, Case 1 shows a strong tendency to excessively compute rainfall, which is continuously increasing. While Case 2 showed similar trend as Case 1, low design rainfall has computed by rainfall in A1B scenario. Based on the design rainfall computation method mainly used in Preventive Disaster System through Pre-disaster Effect Examination System and Basic Plan for River of Jeju Island which are considering climatic change for selecting 50-year and 100-year frequencies. Case 3 selecting for Jeju rain gage station and Case 1 for Seogwipo rain gage station. The results were different for each rain gage station because of difference in rainfall characteristics according to recent climatic change, and the risk of currently known design rainfall can be increased in near future.

• Journal of the Korean housing association
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• v.18 no.4
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• pp.1-7
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• 2007

The principle of Korean Traditional Housing was to be harmonized with the nature with shapes according to regional climate and materials easily available from the region. These environmentally friendly characteristics protected indoor environment from climate changes. The characteristics of Korean traditional housing to control indoor environment would be very useful for contemporary housing in that current issues, improving housing amenity and wellbeing, had basic goals same with what Korean Traditional Housing had. Though it could be found characteristics of indoor thermal environment heated by Ondol Heating System, analyses of evaluation made by occupants of the rooms were insufficient because most of the studies had been focused on the measurement of indoor thermal factors. Thus, with an evaluation of occupants for the indoor thermal comfort and an estimation of discomfort derived from the result of vertical temperature distribution, it was studied whether the agreeable indoor range of rooms, of which was Jeonju Hanok Living Experience Center, heated by Ondol Heating System corresponded to the agreeable indoor range presented in references.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.365-370
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• 2004

Generally, component and FR-4 board are connected by solder joint. Because material properties of components and FR-4 board are different, component and FR-4 board show different coefficients of thermal expansion (CTE) and thus strains in component and board are different when they are heated. That is, the differences in CTE of component and FR-4 board cause the dissimilarity in shear strain and solder joint' failure. The first order Taylor series expansion of the limit state function incorporating with Tresca failure criterion is used in order to estimate the failure probability of solder joints under heated condition. Using shear stresses and shear strains appeared on the solder joint, we estimate the failure probability of solder joints with the Tresca failure criterion. The effects of random variables such as CTE, distance of the solder joint from the neutral point(DNP), temperature variation and height of solder on the failure probability of the solder joint are systematically studied by using the failure probability model with first order reliability method(FORM).

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2221-2226
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• 2008

The objective of this paper is to describe the experimental and numerical investigation of the analysis of the heat transfer in a solar chemical reactor. These are compared about methane steam reforming process in the solar chemical reactor which was a volumetric absorber consisting of honeycomb and a multilayered catalyst supports. With this high operating temperature, convective heat loss, thermal fracture are important features for designing SCR. In order to estimate the system performance and to design the actual solar reactor with various conditions, CFD analysis was used in this study. The nickel oxide porous metal is inserted inside the solar chemical reactor to increase the conversion rate of the reforming reaction. Simulation has been carried out based on the experimental data. According to the simulation results, the optimum methane-steam mole ratio and thickness and numbers of catalyst supports were obtained.

• Corrosion Science and Technology
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• v.19 no.4
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• pp.174-188
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• 2020

Atmospheric corrosion is a natural surface degradation process of metal due to changes in environmental parameters in the surrounding atmosphere. It is very sensitive to environmental parameters such as temperature, relative humidity, sulphur dioxide, and chloride, making it a major global economic challenge. Existing forecasting empirical corrosion models including the ISO standard are based on statistical analysis of experimental studies without considering the behavior of atmospheric parameters. The present study proposes a reliable global empirical model for estimating short and long-term atmospheric corrosion rates based on environmental parameters and corrosion mechanisms obtained from a parametric study. Repercussion of atmospheric corrosion rate due to individual and combined influences of environmental parameters specifies their importance in the estimation. New global empirical coefficients obtained for environmental parameters are statistically established (R² =0.998) with 95% confidence limit. They are validated using experimental datasets of existing studies observed at 88 different continental locations. The current proposed model can predict atmospheric corrosion by means of corrosion formation mechanisms influenced by combined effects of environmental parameters, further abating applicability limitations of location and time.

• Aerospace Engineering and Technology
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• v.9 no.1
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• pp.125-132
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• 2010

Estimation of pressurant mass flowrate and its total mass required to maintain propellant tank pressure during propellant outflow is very important for design of pressurization control system and pressurant storage tank. Especially, more pressurant mass is required to maintain pressure in cryogenic propellant tank, because of reduced specific volume of pressurant due to heat transfer between pressurant and tank wall. So, basic model for propellant tank ullage calculation was proposed to estimate ullage and tank wall temperature distribution, required pressurant mass, and energy distribution of pressurant in ullage. Both test and theoretical analysis have been conducted, but only theoretical modeling method was addressed in this paper.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.120-127
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• 2017

High temperature oxygen and water vapor was generated from catalytic decomposition of rocket grade highly concentrated hydrogen peroxide, and monopropellant thruster system was developed and applied into space propulsion system. In this research, background research and conceptual design of underwater propulsion system using catalytic decomposition of hydrogen peroxide was progressed. Two types of system was designed with different steam injection methods. Propulsion system that has ring-type steam injector was manufactured and performance estimation of system was performed with different nozzle exit area. Performance evaluation with central steam injection type jet engine will be progressed in the future.

• Journal of the Semiconductor & Display Technology
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• v.7 no.2
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• pp.13-17
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• 2008

In this paper, in order to get the characteristics of the lithium secondary cell, such as charge and discharge characteristic, temperature characteristic, self-discharge characteristic and the capacity recovery rate etc, we build a thermal model that estimate the impedance of battery by experiment & simulation. In this one-dimensional model, Seven governing equations are made to solve seven variables c, $c_s,\;\Phi_1,\;\Phi_2,\;i_2$, j and T. The thermal model parameters used in this model have been adjusted according to the experimental data measured in the laboratory. The result(Voc, Impedance) of this research can be used in BMS(Battery Management System), so an efficient method of using battery is developed.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.2
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• pp.69-76
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• 2002

To obtain a high performance in a vector controlled induction motor, it is essential to know the instantaneous position of the rotor flux which depends on the rotor time constant. But the rotor time constant mainly varies due to the temperature rise in the motor winding, so real time compensating algorithm is necessary. This paper proposes that it uses short duration pulses added to the constant flux command current and then resultant torque command current produced by speed controller is utilized for the rotor resistance estimation. This method has advantage with a low computational requirement and does not require voltage sensors. The proposed method is proved by simulations and experimentals.

• Proceedings of the KIEE Conference
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• 2004.05b
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• pp.173-175
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• 2004

The degree of contamination on outdoor insulators is one of the most importance factor to determine the pollution level of outdoor insulation. Outdoor insulators in coastal are affected due to salty wind blowing from the seaside. The sea salt is known as the most dangerous pollutant. As known through the preceding study, the generation of salt pollutant and the pollution degree of outdoor insulators have a close relation in accordance with meteorological conditions, such as temperature, humidity, dewpoint, wind velocity and wind direction. Therefore, at first, we have analyzed relation between meteorological conditions and contaminants for development of prediction method. In this paper, we have investigated a statistical estimation technique based on actual data for equivalent salt deposit density(ESDD) of outdoor insulators which were installed in Kochang field test substation with multiple linear regression analysis.