• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.6 s.237
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• pp.662-670
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• 2005

The effect of heat loss on combustion performance and burning velocity of micro combustors in various conditions were exploited experimentally. Three different gases were used, and various geometric matrixes were considered to figure out the phenomena of combustion in a micro combustor. The micro combustors used in this study were constant volume combustors and had cylindrical shape. Geometric parameter of combustor was defined as combustor height and diameter. The effect of height was exploited parametrically as 1mm, 2mm and 3 mm and the effect of diameter was parameterized to be 7.5 mm and 15 mm. Three different combustibles which were Stoichiometric mixtures of methane and air, hydrogen and air, and mixture of hydrogen and air with fuel stoichiometry of two were used. By pressure measurement and visualization of flame propagation, characteristic of flame propagation was obtained. Flame propagations which were synchronized with pressure change within combustor were analyzed. From the analysis of images obtained during the flame propagations, burning velocity at each location of flame was obtained. About $7\%$ decrease in burning velocity of $CH_4/Air$ stoichiometric mixture compared with previous a empirical result was observed, and we can conclude that it is acceptable to use empirical equations for laminar premixed flame burning velocity to micro combustions. Results presented in this paper will give fine tool for analysis and prediction of combustion process within micro combustors.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.11
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• pp.1095-1103
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• 2014

WBAN has received great attention recently due to its versatile applicability. In this paper, antennas suitable for WBAN communication depending on the locations of mobile devices and the manufacturing of a human equivalent phantom are introduced. The effect of the body on the communication performance is largely dependent on the locations of devices. Specifically, the radiation and return loss characteristics of the antenna are greatly influenced by the characteristics of a medium existing in the near-field of an antenna. Thus, the proper WBAN antenna design is important in establishing a successful communication link between the transceivers. To consider the effect of the body on the antenna performance, the human equivalent phantom is also important factor in the WBAN antenna design and measurement. In introduction, categorization of the WBAN communication channel is introduced and antenna characteristics required for each communication channel are described. In the main subject section, several WBAN antenna design examples along with the implementation of the human equivalent phantom are discussed. In conclusion, the factors, which have to be considered in the design process, and future research are mentioned.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.10
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• pp.1166-1172
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• 2012

In this paper, by using a commercial EM simulator, we could obtain the array manifold which are phase responses of an array antenna for the incident plane wave and then verified the effectiveness of methodology after comparing with the measurement. The result shows that the array manifold can be calculated including not only the phase response of the ideal point sources but also the influences of the mutual coupling between antennas and the installed platform. Also it can exclude the interference of strong broadcasting signal and the disturbance of the multipath in the calibration process. Finally, to predict the performances of direction finding systems, a novel method using both the EM simulation-based receiving signal and the sparsely sampled array manifold with the parabolic estimation is proposed. This method can be utilized in the various fields of direction-finding since it shows the superior predictive performance even in low SNR conditions.

• Aerospace Engineering and Technology
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• v.12 no.2
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• pp.209-220
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• 2013

The process of designing and building a human-powered aircraft (HPA) and its performance analysis are introduced in this paper. Light Bros, the Chungnam National University HPA team, has developed Volante, a HPA, to compete in the 2012 exhibition of human-powered aircraft hosted by Korea Aerospace Research Institute. The power train system is composed of a two-blade propeller and Bevel-type gear and the ground test bed is built to simulate the operation. A study has been made to find a efficient propeller based upon the test result of thrust and power available from a pilot under various propeller conditions and running time. The load and structural analysis is conducted for the glider-shaped wing made of composite material which has very high aspect ratio. The spar is analyzed using finite element modeling followed by the comparison of its displacement and strain on structural test. As a result, the performance and safety is confirmed.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2006.11a
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• pp.674-679
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• 2006

The public research and development (R&D) funds for construction engineering is one of the key elements for the advancement of construction industry. Korean Ministry of Construction and Transportation is currently planning to produce approximately US$ 500 millions of research funds every year in Korea from year 2007. Along with the prospect for increasing R&D investment, there is of increasing pressures on the development of quantitative methodologies for assessing the performance of construction R&D results. Although there have been some general R&D project evaluation methods, they are not readily used for construction R&D research assessment due to the distinct characteristics of construction R&D. This paper presents a simple methodology that can make quantitative assessments of construction R&D performances. The proposed methodology is expected to assist government officials in objectively evaluating construction R&D performances and identifying the areas that require more R&D investment.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.6
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• pp.783-792
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• 2004

In this study, a thick-film semiconductor odor gas sensor for the detection of $CH_3$SH was developed using SnO$_2$ as the main substrate and was investigated in terms of its sensitivity and reaction time. In the process of manufacturing the sensor, Taguchi's design of experiment (DOE) was applied to analyze the effects of a variety of parameters, including the substrate, the additives and the fabrication conditions, systematically and effectively. Eight trials of experiments could be possible using the 27 orthogonal array for the seven factors and two levels of condition, which originally demands 128 trials of experiments without DOE. The additives of Sb$_2$O$_{5}$ and PdCl$_2$ with the H$_2$PtCl$_{6}$ ㆍ6$H_2O$ catalyst were appeared to be important factors to improve the sensitivity, and CuO, TiO$_2$, V$_2$O$_{5}$ and PdO were less important. In addition, TiO$_2$, V$_2$O$_{5}$ and PdO would improve the reaction time of a sensor, and CuO, Sb$_2$O$_{5}$, PdCl$_2$ and H$_2$PtCl$_{6}$ㆍ6$H_2O$ were negligible. Being evaluated simultaneously in terms of both sensitivity and reaction time, the sensor showed the higher performance with the addition of TiO$_2$ and PdO, but the opposite results with the addition of CuO, V$_2$O$_{5}$, Sb$_2$O$_{5}$ and PdCl$_2$. The amount of additives were superior in the case of 1% than 4%. H$_2$PtCl$_{6}$ㆍ6$H_2O$ would play an important role for the increase of sensor performance as a catalyst.nce as a catalyst.

• Journal of the Korean Society of Visualization
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• v.7 no.2
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• pp.17-21
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• 2010

This paper presents the fabrication and performance measurement of a temperature sensor array on a flexible substrate attachable to a curved surface using MEMS technology. Specifically, the fabrication uses the well-developed printed circuit board fabrication technology for complex electrode definition. The temperature sensor array are lifted off with a $10{\times}10$ matrix in a $50\;mm{\times}50\;mm$ to visualize temperature distribution. Copper is used as temperature sensing material to measure the change in resistances with temperature increase. In a thermal oven with temperature control, the temperature sensor array is Characterized. The constant slope of resistance change is obtained and temperature distribution is measured from the relationship between resistance and temperature.

• Analytical Science and Technology
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• v.12 no.3
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• pp.218-223
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• 1999

A single use, screen-printed sensor for the measurement of liquid phase ethanol was developed and its electrochemical performance was investigated. Disposable type edthanol sensor was fabricated by serially screen printing the carbon paste, silverd pasted and insulator inlon a polyester substrate to pattern working and reference electrode sites and electrical contact. Alcohol dehydrogenase(ADH) or alcohol oxidase(AOD) together with appropriate electron transfer mediators was immobilized on the working electrode. To improve the sensitivity and reproducibility of carbon paste electrode, some pretreatment procedures were applied and their resultant electrochemical performance was examined. The disposable type electrochemical ethanol sensor developed in this study conveniently determines the ethanol in liquid samples such as blood and in fermentation process.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.4
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• pp.243-250
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• 2011

In order to investigate the effects of PAG oil concentration on heat transfer performance and pressure drop during gas cooling process of $CO_2$, the experiments on fin-tube heat exchanger of $CO_2$ heat pump were performed. The experimental apparatus consists of a gas cooler, a heater, a chiller, a mass flow meter, a pump and measurement system. Experiments were conducted in various experimental conditions, which were inlet temperature($110^{\circ}C$), mass flow rates (50, 55, 60, 65, 70 g/s) and PAG oil concentration(0 to 2.6 wt%). Heat transfer rate decreased with the increase of the oil concentration and the decrease of inlet pressure. And pressure drop increased with the increase of the oil concentration and mass flow rate of refrigerant. The COP reduction by deterioration of gas cooler performance with oil concentration was analyzed. When inlet pressure of gas cooler is 100 bar, the COP reduction was estimated by 6% under 1 wt% of oil concentration.

• Journal of the Korean Electrochemical Society
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• v.18 no.4
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• pp.137-142
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• 2015

$Mn_{1+X}Co_{2-X}O_4$ solid solutions with various Mn/Co ratios were synthesized by a combustion method, and used as cathode catalysts for lithium/air secondary battery. Their electrochemical and physicochemical properties were investigated. The morphology was examined by transmission electron microscopy (TEM), and the crystallinity was confirmed by X-ray diffraction (XRD) analyses. For the measurement of electrochemical properties, charge and discharge measurements were carried out at a constant current density of $0.2mA/cm^2$, monitoring the voltage change. Electrochemical impedance spectroscopy (EIS) analyses were also employed to examine the change in charge transfer resistance during charge-discharge process. $Mn_{1+X}Co_{2-X}O_4$ solid solutions showed enhanced cycleability as a cathode of Li/air secondary battery, and the performance was found to be strongly dependent on Mn/Co ratio. Among synthesized catalysts, $Mn_{1.5}Co_{1.5}O_4$ exhibited the best performance and cycleability, due to high charge transfer rate.