• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.27-30
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• 1998

In this paper, the inverter air-conditioner with Power Factor Correction(PFC) circuit is Presented for obtaining the good system efficiency and cost merit compared with the conventional inverter air-conditioner. The detailed design procedures for getting the optimal passive components are implemented. Through the simulation and experimental results, it is shown that the system efficiency can be improved. Using the designed components, the prototype system is builted and tested to verify the additional good performances of the proposed circuit.

• Korean Journal of Human Ecology
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• v.12 no.2
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• pp.225-236
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• 2003

The purposes of this study were to promote the consumer's recognition on the internet purchase of fashion products and to provide useful information which would help web-site plan design, product composition, and service of internet shopping mall. The subjects were consisted of 693 students who had experiences of the accesses to internet fashion shopping mills or experiences of purchasing through internet in Cheongju and Daejeon region. Data were analyzed by factor analysis, frequency, percentage, mean, standard deviation, t-test, ANOVA, and LSD. The Results were as follows: 1. Merit factors of the internet shopping were found to be shopping convenience and pursuit of product information. Whereas, demerit factors of the internet shopping to be complexity of order, delivery, functional and economic riskiness, and services. 2. Gender was the only factor differentiating the level of recognition toward the internet fashion shopping mall. And the level of recognition also showed significant differences according to period, time, purpose of access, type of shopping mall, purchase experience, and average purchase price.

• Electronic Materials Letters
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• v.14 no.6
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• pp.725-732
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• 2018

The thermoelectric and transport properties of Ti-doped FeVSb half-Heusler alloys were studied in this study. $FeV_{1-x}Ti_xSb$ (0.1 < x < 0.5) half-Heusler alloys were synthesized by mechanical alloying process and subsequent vacuum hot pressing. After vacuum hot pressing, a near singe phase with a small fraction of second phase was obtained in this experiment. Investigation of microstructure revealed that both grain and particle sizes were decreased on doping which would influence on thermal conductivity. No foreign elements pick up from the vial was seen during milling process. Thermoelectric properties were investigated as a function of temperature and doping level. The absolute value of Seebeck coefficient showed transition from negative to positive with increasing doping concentrations ($x{\geq}0.3$). Electrical conductivity, Seebeck coefficient and power factor increased with the increasing amount of Ti contents. The lattice thermal conductivity decreased considerably, possibly due to the mass disorder and grain boundary scattering. All of these turned out to increase in power factor significantly. As a result, the thermoelectric figure of merit increased comprehensively with Ti doping for this experiment, resulting in maximum thermoelectric figure of merit for $FeV_{0.7}Ti_{0.3}Sb$ at 658 K.

• Journal of Positioning, Navigation, and Timing
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• v.8 no.4
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• pp.139-152
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• 2019

The design of new navigation signals is a key factor in building new satellite navigation systems and/or modernizing existing legacy systems. Navigation signal design involves selecting candidate groups and evaluating and analyzing their signal performances. This process can be easily performed through software simulation especially at the beginning of the development phase. The analytical signal performance analysis software introduced in this study is implemented based on equations between the signal design parameters of Radio Navigation Satellite Service (RNSS) and the navigation signal figures-of-merit (FoMs). Therefore, this study briefly summarizes the RNSS signal design parameters and FoMs before introducing the developed software. After that, we explain the operating sequence of the implemented software including the Graphical User Interface (GUI), and calculate the FoMs of an example scenario to verify the feasibility of the software operations.

• Applied Science and Convergence Technology
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• v.24 no.6
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• pp.215-218
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• 2015

A pyroelctric properties of Ni(x)-doped PMNT systems were analyzed. Modified PMNT samples were prepared using the columbite structure method. Pyroelectric current, polarization, dielectric constant and dissipation factor of Ni-doped PMNT samples were measured as a function of temperature. By adding a small amount of NiO, pyroelectricity of PMNT is increased. Unlike the normal $ABO_3$ ferroelectric, Ni-doped PMNT showed properties for relaxor ferroelectric of causing the successive phase transition over a wide temperature. The optimum conditions for obtaining compositions with improvement ferroelectric properties are a nominal addition of 0.02 mole% Ni. Also, Ni-doped PMNT ferroelectric showed excellent pyroelectric figures of merit in the vicinity of room temperature. The pyroelectric coefficient ($0.00524C/m^2K$ at $25^{\circ}C$) and figures of merit ($F_v{\sim}0.039m^2/C$ and $F_d{\sim}0.664{\times}10^{-4}Pa^{-1/2}$) of composition PMNT with 0.02 mole% Ni are comparable to the earlier reports on lead-type pyroelectrics.

• Journal of Positioning, Navigation, and Timing
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• v.11 no.4
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• pp.341-349
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• 2022

When designing a new RNSS signal, the performance analysis for the legacy signal providing the same service, is required to determine the performance requirements. However, there are few studies on the secured service (SS) signal performance analysis, and the waveform is the only published information on the signal design component of the SS signal. Therefore, in this paper, we introduce several figures-of-merit (FoMs) that can be used for performance analysis in terms of the waveform. And then, we calculate the FoMs, such as autocorrelation main peak to secondary peak ratio (AMSR), spectral efficiency, Gabor bandwidth, multipath error, and jamming resistance quality factor, for the existing SS signals and discuss the analysis results. Finally, we conclude that the superior waveform for each FoM is different, and that the consideration of the trade-off relationship between the FoMs is required for waveform design.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.2
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• pp.49-54
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• 2010

The n-type $Bi_2(Te,Se)_3$ powders were fabricated by melting/grinding method and were hot-pressed in order to compare thermoelectric properties of the hot-pressed specimens with those of the $Bi_2(Te,Se)_3$ ingot. Effects of mechanical milling treatment of the $Bi_2(Te,Se)_3$ powders on thermoelectric characteristics of a hot-pressed specimen were also examined. The hot-pressed $Bi_2(Te,Se)_3$ exhibited power factors of $27.3{\sim}32.3{\times}10^{-4}W/m-K^2$ which were superior to $24.2{\times}10^{-4}W/m-K^2$ of the ingot. The $Bi_2(Te,Se)_3$, hot-pressed after mechanical milling treatment of the powders, possessed a non-dimensional figure-of-merit of 1.02 at $100^{\circ}C$ and exhibited extrinsic-intrinsic transition at $130^{\circ}C$.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.03a
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• pp.298-303
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• 1998

Most of mechanical structures are combined of substructures such as beam and/or plates. There are few system with unibody structures but are not a few systems with united body structures. Generally the dynamic analysis of whole structures is perform ed under alternating load. However, the analysis of each joint area is more important than others for zero severity. This paper presents the results of analysis of concentration stress in bolt jointed structure with variable preload. At frist, a static vibration test was performed to find out a nominal stress of bolt joint ed plates from the relationship between natural frequency and nominal stress. Then a concentration stress was computed at contact point between bolt and plate in the structure. It is believed that the proposed method has promising implications for safer design with fatigue quality index of stress concentration factor and has merit for cost down and saving time at the beginning of vehicle development.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.246-249
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• 1995

This paper proposed a partial resonant swtiching three-phase high power factor converter using a lossless snubber. The proposed converter has a merit of simple controlled circuit because tile input current control discontinuously. And it is improve to input power factor that the snubber capacitor's energy regenerate to the AC source side. This topology is reduced a current/voltage stresses of resonant devices in addition to a partial resonant strategy. The result of simulations with the proposed topology included in this paper.

• Applied Science and Convergence Technology
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• v.25 no.5
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• pp.88-91
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• 2016

The $Pb[(Mg_{1/3}Ta_{2/3})_{0.7}Ti_{0.3}]O_3$+xwt%PbO systems at temperature of $1250^{\circ}C$ for 4 hours was successful synthesized. In this study, PbO-doped $Pb[(Mg_{1/3}Ta_{2/3})_{0.7}Ti_{0.3}]O_3$ systems with non-linear behaviors showed ordering-degree dependence at the low temperature range were prepared using the columbite precursor method. And the characteristic of remnant polarization vs. electric field were analyzed. The pyroelectric, dielectric and piezoelectric properties of partially disordered $Pb[(Mg_{1/3}Ta_{2/3})_{0.7}Ti_{0.3}]O_3$+xwt%PbO solid solutions were studied as a function of temperature, frequency, and electric field. It showed distinct features of temperature dependent of pyroelectric coefficient, spontaneous polarization and dielectric constant at about $50^{\circ}C$. The figure of merit was calculated as pyroelectric coefficient, dielectric constant and dissipation factor. It was found that the high voltage responsivity FV, high detectivity FD were $0.0373m^2/C$ and $0.6735{\times}10^{-4}Pa{-1/2}$, respectively, in the $Pb[(Mg_{1/3}Ta_{2/3})_{0.7}Ti_{0.3}]O_3$+3.0 wt%PbO system.