• Journal of the Korean Society for Precision Engineering
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• v.25 no.6
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• pp.108-115
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• 2008

The wear on engine valve and seat insert is one of the most important factors affecting engine performance. The engine valve and seat insert must be able to withstand the severe environment that is created by: high temperature exhaust gases generated while the engine is running, rapid movement of the valve spring, high pressure generated in the explosive process. In order to study such problems, a simulator has been developed to generate and control high temperatures and various speeds during motion. The wear simulator is considered to be a valid simulation of the engine valve and seat insert wear process with various speeds during engine activity. This work focused on the test of various degrees of wear on four different exhaust valve materials such as HRV40, HRV40-FNV (face nitrided valve), STL #32, STL #6,. Throughout all tests performed in this study, the outer surface temperature of the seat insert was controlled at $350^{\circ}C$, the cycle number was $4.0{\times}10^6$, the test load was 6860 N, the fuel was LPG the test speed was 20 Hz (2400 RPM) and the seat insert material was HVS1-2. The mean (standard deviation) maximum roughness of the exhaust valve and seat insert was $25.44\;(3.16)\;{\mu}m$ and $27.53\;(3.60)\;{\mu}m$ at the HRV40, $21.58\;(2.38)\;{\mu}m$ and $25.94\;(3.07)\;{\mu}m$ at the HRV40-FNV, $36.73\;(8.98)\;{\mu}m$ and $61.38\;(7.84)\;{\mu}m$ at the STL #32, $73.64\;(23.80)\;{\mu}m$ and $60.80\;(13.49)\;{\mu}m$ at the STL #6, respectively. It was discovered that the maximum roughness of exhaust valve was lower as the high temperature hardness of the valve material was higher under the same test conditions such as temperature, test speed, cycle number, test load and seat insert material. The set of the HRV40-FNV exhaust valve and the HVS1-2 seat insert showed the best wear resistance.

• Journal of Platform Technology
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• v.6 no.4
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• pp.59-68
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• 2018

The objective of this study is to develop an embedded antenna structure with NFC and WPC composite functions. By selecting stable materials, the optimal component ratio of the polymer sheet was determined. The low cost embedded winding method compared to the existing FPCB was devised. During the winding process, characterization and process technology were developed. We also fabricated a ferrite mold to process the WPC grooves and developed the process technology for optimizing the WPC antenna. The following conclusions were obtained. (1) Optimum composition ratio was derived as Fe 87.5%, Si 7%, Al 5.5% and selected as the final material. (2) Optimal sheet conditions were derived from the experimental evaluation method and the experimental design method through the combination test of the optimized sheet and the conventional mass production FPCB. (3) According to coil diameter and inner diameter, Q value fluctuation, resistance value and efficiency fluctuation are obtained. Therefore, the most suitable coil condition is selected and Rx matching is performed. (4) The EMV load modulation test and the cognitive distance test of the polymer sheet and the ferrite sheet showed that the recognition distance of the polymer sheet at 1k and 4K was 32-33 mm and the recognition distance of the ferrite sheet at the same condition was 30-31 mm.

• The Journal of the Acoustical Society of Korea
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• v.41 no.5
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• pp.481-491
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• 2022

The active sonar transmission system consists of a transmitter that outputs an electrical signal and an underwater acoustic transducer that converts the amplified electrical signal into an acoustic signal. In general, the transmitter output characteristics are dependent on load impedance, and an underwater acoustic transducer, which is a transmitter load, has a characteristic that the electrical impedance varies largely according to frequency when driven. In such a variable impedance condition, the output of the active sonar transmission system may become unstable. Hence, this paper proposes a design and control technique of a sonar transmitter for transmitting a stable transmission signal even under variable impedance conditions of an underwater acoustic transducer in an active sonar transmission system. The electrical impedance characteristics of the underwater acoustic transducer are experimentally analyzed, and the sonar transmitter is composed of a single-phase full-bridge inverter, an LC filter, and a matching circuit. In this paper, the design and output control method of the sonar transmitter is proposed to protect the transmitter and transducer. It can secure stable output voltage characteristics even if it transmits the Linear Frequency Modulation (LFM) signal. The validity is verified through the simulation and the experiment.

• Journal of Bio-Environment Control
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• v.11 no.4
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• pp.151-156
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• 2002

Root zone cooling, such as soil or nutrient solution cooling, is less expensive than air cooling in the whole greenhouse and is effective in promoting root activity, improving water absorption rate, decreasing plant temperature, and reducing high temperature stress. The heat transfer of a soil cooling system in a plastic greenhouse was analyzed to estimate cooling loads. The thermal conductivity of soil, calculated by measured heat fluxes in the soil, showed the positive correlation with the soil water content. It ranged from 0.83 to 0.96 W.m$^{[-10]}$ .$^{\circ}C$$^{[-10]}$ at 19 to 36％ of soil water contents. As the indoor solar radiation increased, the temperature difference between soil surface and indoor air linearly increased. At 300 to 800 W.m$^{-2}$ of indoor solar radiations, the soil surface temperature rose from 3.5 to 7.$0^{\circ}C$ in bare ground and 1.0 to 2.5$^{\circ}C$ under the canopy. Cooling loads in the root zone soil were estimated with solar radiation, soil water content, and temperature difference between air and soil. At 300 to 600 W.m$^{-2}$ of indoor solar radiations and 20 to 40％ of soil water contents,46 to 59 W.m$^{-2}$ of soil cooling loads are required to maintain the temperature difference of 1$0^{\circ}C$ between indoor air and root zone soil.

• Asia Marketing Journal
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• v.15 no.4
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• pp.103-129
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• 2014

Differentiated positioning becomes increasingly difficult when brand salience weakens. Also, the daily increase in new media use and information load has led to a social climate that regards advertising stimuli as spamming. For these reasons, the focus of advertisement-related communication is shifting from persuading consumers through the direct delivery of information to an emphasis on appealing to their emotions using matching stimuli to enhance persuasion effects. Recently, both academia and industry have increasingly shown an interest in storytelling methods that can generate positive emotional responses and attitude changes by arousing consumers' narrative processing. The purpose of storytelling is to elicit consumers' emotional experience to meet the objectives of advertisement producers. Therefore, the most important requirement for storytelling in advertising is that it evokes consumers' sympathy for the main character in the advertisement. This does not involve advertisements directly persuading consumers, but rather, consumers themselves finding an answer through the advertisement's story. Thus, consumers have an indirect experience regarding the product features and usage through empathy with the advertisement's main character. In this study, we took the results of a precedent study as the starting point, according to which consumers' emotional response can be altered depending on the storytelling methods adopted for storytelling ads. Previous studies have reported that drama-type and vignette-type storytelling methods have a considerably different impact on the emotional responses of advertising audiences, due to their different structural characteristics. Thus, this study aims to verify that emotional response aroused by different types of advertisement storytelling (drama ads vs. vignette ads) can be controlled by the socio-psychological gender difference of advertising audiences and that the interaction effects between the socio-psychological gender differences of the audience and the gender stereotype of emotions to which advertisements appeal can exert an influence on emotional responses to types of storytelling in advertising. To achieve this, an experiment was conducted employing a between-group design consisting of 2 (storytelling type: drama ads vs. vignette ads) × 2 (socio-psychological gender of the audience: masculinity vs. femininity) × 2 (advertising appeal emotion type: male stereotype emotion vs. female stereotype emotion). The experiment revealed that the femininity group displayed a strong and consistent empathy for drama ads regardless of whether the ads appealed to masculine or feminine emotions, whereas the masculinity group displayed a stronger empathy for drama ads appealing to the emotional types matching its own gender as well as for vignette ads. The theoretical contribution of this study is significant in that it sheds light on the controllability of the audiences' emotional responses to advertisement storytelling depending on their socio-psychological gender and gender stereotype of emotions appealed to through advertising. Specifically, its considerable practical contribution consists in easing unnecessary creative constraints by comprehensively analyzing essential advertising strategic factors such as the target consumers' gender and the objective of the advertisement, in contrast to the oversimplified view of previous studies that considered emotional responses to storytelling ads were determined by the different types of production techniques used. This study revealed that emotional response to advertisement storytelling varies depending on the target gender of and emotion type appealed to by the advertisement. This suggests that an understanding of the targeted gender is necessary prior to producing an advertisement and that in deciding on an advertisement storytelling type, strategic attention should be directed to the advertisement's appeal concept or emotion type. Thus, it is safe to use drama-type storytelling that expresses masculine emotions (ex. fun, happy, encouraged) when the advertisement target, like Bacchus, includes both men and women. For brands and advertisements targeting only women (ex. female clothes), it is more effective to use a drama-type storytelling method that expresses feminine emotions (lovely, romantic, sad). The drama method can be still more effective than the vignette when women are the main target and a masculine concept-based creative is to be produced. However, when male consumers are targeted and the brand concept or advertisement concept is focused on feminine emotions (ex. romantic), vignette ads can more effectively induce empathy than drama ads.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.3
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• pp.1-11
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• 1999

It is now common practice to utilize the quadrature RF coils to improve the signal-to-noise ratio (SNR) in the Magnetic Resonance Imaging (MRI) System. In addition, to make such an available SNR improvement, it is mandatory to use a well-designed quadrature coupler, which facilitates a perfect 3-dB coupling and quadrature-phase shift. However, the four ports matching condition has to be well considered during the RF excitation and the signal detection period. This work investigates the effects of such a mismatching condition (especially, due to patient) from the analysis, simulation, and real implementation and firstly proposes dynamic loading technique for a quadrature coupler and transmitting/receiving switch module to minimize a patient mismatching and enhance a system reliability. Also, we designed and implemented the quadrature coupler and transmitting/receiving switch module using microstrip. As a result, the SNR of our MRI system using the microstrip quadrature coupler and transmitting/receiving switch module with dynamic load increases 3 dB compared with the old one using USA quadrature switch. Also, the power capability of quadrature coupler and transmitting/receiving switch module is 5-kw peak power. Considering power loss and reduction of size, we used a RT/duroid 6010 substrate with high permittivity and for simulation we use Compact Software.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.2
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• pp.121-128
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• 2010

This paper presents a design of a 100 W high-efficiency power amplifier, whose operational frequency band expands from 30 to 512 MHz, using negative feedback network, push-pull structure, broadband RF choke, and transmission line transformer for balun configuration. The push-pull amplifier has been tuned for higher output power using a shunt capacitor as a matching component at its load especially for high-frequency region. The implemented power amplifier exhibited a very flat power gain of $18.34{\pm}0.9\;dB$ throughout the operating frequency band and very high power-added efficiency(PAE) of greater than 40% at an output power of 100 W. It also showed second- and third-harmonic distortion levels of below -34 dBc and -12 dBc, respectively, through the entire operating frequency band.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.6
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• pp.85-96
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• 2000

It is necessary that fully differential operational amplifier circuit should drive an external load in the VLSI design such as SCF(Switched Capacitor Filter), D/A Converter, A/D Converter, Telecommunication Circuit and etc. The conventional CMOS operational amplifier circuit has many problems according to CMOS technique. Firstly, Capacity of large loads are not able to operate well. The problem can be solve to use class AB stages. But large loads are operate a difficult, because an element of existing CMOS has a quadratic functional relation with input and output voltage versus output current. Secondly, Whole circuit of dynamic range decrease, because a range of input and output voltages go down according as increasing of intergration rate drop supply voltage. The problem can be improved by employing fully differential operational amplifier using differential output stage with wide output swing. In this paper, we proposed new current mirror has large output impedance and good current matching with input an output current and compared with characteristics for operational amplifier using cascoded current mirror. To obtain large output swing and low power consumption we suggest a fully differential operational amplifier. The circuit employs an output stage composed new current mirror and two amplifier stage. The proposed circuit is layout and circuit of capability is inspected through simulation program(SPICE3f).

• Journal of Energy Engineering
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• v.21 no.2
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• pp.152-157
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• 2012

Due to the global warming and energy exhaustion, energy efficiency improvement of construction is recognized the stream of times. To improve the efficiency of the building, in order to energy saving, passive elements should be applied. Then the first step be supposed that applying the new standards about the insulation boundary. The current insulation boundary standards are not reasonable as well as does not divide the purposes. As a result, energy is being wasted and many civil complaints are also occurred. To improve these problems, applying the insulation boundary need to divide the heating and non-heating and subdivide the purpose of construction. In this study, accurate real heating and air conditioning areas are presented that work on the new insulation boundary of purposes and applicable standards. This proposed, by the real heating and air conditioning areas, insulation boundary of purposes, matching the reasonable capacity and load of equipment, by working on standards by optimal maintenance can be energy saving, to present guidelines that environment improvement of actual residents as well as energy saving be expected.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.10
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• pp.892-899
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• 2016

In this paper, an X-band 50 W internally matched power amplifier is designed and fabricated using an $80{\times}150{\mu}m$ GaN HEMT that is developed by the $0.25{\mu}m$ GaN HEMT process of ETRI. The optimum source and load impedances are experimentally extracted from the loadpull measurement using impedance-transform-prematching circuits, and the transistor performance is predicted. The power performance of the internally matched power amplifier, whose matching circuits are fabricated on a substrate with ${\varepsilon}_r$ of 10.2, is measured under the pulsed mode of $100{\mu}s$ pulse period and 10 % duty cycle, and the best output power of 47.46 dBm(55.5 W) and the power-added efficiency of 46.6 % are obtained at 9.2 GHz. The output power of 47~47.46 dBm(50~55.7 W) is measured in 9.0~9.5 GHz, and the power-added efficiency is measured to be greater than 43 % in 9.0~9.3 GHz and above 36 % in 9.4~9.5 GHz.