• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.3 no.1 s.4
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• pp.75-83
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• 2004

This paper describes the design, fabrication, and measurement of a low side lobe antenna for RSE base station of the ETCS which is one of the ITS services. The antenna is installed on the gantry of road side and provides the wireless communication lint between vehicles and RSE. The required characteristics of ETCS base station antenna are low sidelobe and specific beam pattern by the road and install environment and installed place of OBU. To minimize the affects of multipath signal by reflection, Circular polarization is required. To get low sidelobe of antenna, array configuration and weighting factor by Taylor distribution in radiator elements are applied. The measured results of fabricated antenna are as follows; return loss of 130MHz by -10dB, an axial ratio of 2.6dB, and a gain of 17dBi. It is found that the measured beam patterns are similar to design results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.10
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• pp.887-894
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• 2016

The thermal control device using solid-liquid phase change material (PCM) is designed, manufactured, and experimented in thermal environment chamber. The n-Hexadecane is selected as a PCM and its melting point is placed within the component working temperature range. The PCM container is made of Al6061 and has the thermal spreading fins inside. To simulate the working condition for on-orbit satellite the heat pipes are used to connect the heater and radiator and the PCM thermal control device (PCMTD) is installed at the middle portion of heat pipes. The thermal buffer mass (TBM), which is same configuration and volume with PCMTD, is also manufactured to compare the thermal control performance. As a result, the PCMTD is not only more efficient than TBM in their temperature control features but both mass and power of compensation heater are reduced.

• International Journal of Fluid Machinery and Systems
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• v.4 no.3
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• pp.317-323
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• 2011

Mini centrifugal pumps having a diameter smaller than 100mm are employed in many fields; automobile radiator pump, ventricular assist pump, cooling pump for electric devices and so on. Further, the needs for mini centrifugal pumps would become larger with the increase of the application of it for electrical machines. It is desirable that the mini centrifugal pump design be as simple as possible as precise manufacturing is required. But the design method for the mini centrifugal pump is not established because the internal flow condition for these small-sized fluid machines is not clarified and conventional theory is not suitable for small-sized pumps. Therefore, we started research on the mini centrifugal pump for the purpose of development of high performance mini centrifugal pumps with simple structure. Three types of rotors with different outlet angles are prepared for an experiment. The performance tests are conducted with these rotors in order to investigate the effect of the outlet angle on performance and internal flow condition of mini centrifugal pumps. In addition to that, the blade thickness is changed because blockage effect in the mini centrifugal pump becomes relatively larger than that of conventional pumps. On the other hand, a three dimensional steady numerical flow analysis is conducted with the commercial code (ANSYS-Fluent) to investigate the internal flow condition. It is clarified from the experimental results that head of the mini centrifugal pump increases according to the increase of the blade outlet angle and the decrease of the blade thickness. In the present paper, the performance of the mini centrifugal pump is shown and the internal flow condition is clarified with the results of the experiment and the numerical flow analysis. Furthermore, the effects of the blade outlet angle and the blade thickness on the performance are investigated and the internal flow of each type of rotor is clarified by the numerical analysis results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.4 s.119
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• pp.358-363
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• 2007

The multi-band and wide-band antenna for a portable broadcasting terminal is proposed. The proposed antenna consists of two radiators with a parallel structure. The antenna has an enough wide impedance bandwidth for the DVB-H(Digital Video Broadcasting-Handheld) service band since two radiators have adjacent resonance frequencies and operates in the DAB(Digital Audio Broadcasting) service band using the third harmonic of the radiator 1. The fabricated antenna has VSWR characteristics of less than 2:1 in the frequency band $470{\sim}740\;MHz$ for DVB-H and $1,450{\sim}1,480\;MHz$ for DAB. The measured peak gain of the antenna is $1.97{\sim}4.10\;dBi$ in the DVB-H band and $1.98{\sim}2.04\;dBi$ in the DAB band.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.2
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• pp.161-166
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• 2009

In this paper, we propose the internal mobile antenna for TDMB and KPCS. The proposed antenna is made of different dielectric substrate and it has small size ($45{\times}8{\times}8\;mm$, about 2.8 cc) for mobile device. TDMB antenna is designed spiral structure that makes maximum current for each cell and KPCS antenna is PIFA that is usually used for internal antenna. In order to compensate length of resonance TDMB antenna has a large inductor above 100 nH. In this case, the inductor isolate KPCS signal at TDMB by cutting high frequency. Also the antenna has good isolation because TDMB radiator is parasitic element in KPCS band. We simulated the antenna by using CST microwave studio and measured performance of the antenna in anechoic chamber Proposed antenna has $-6{\sim}-14\;dBi$ gain for TDMB and $-3.5{\sim}-5\;dBi$ gain for KPCS.

• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.118-123
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• 1999

The recycle of the polycarbonate(PC)/acrylonitrile-butadiene-styrene(ABS) separated from the instrument panel (In-Panel) of the automotive was investigated. The small amount of polyurethane(PU) foam contained in the separated PC/ABS decreased the mechanical properties of the recycled PC/ABS. However, it is found that the PU foam formed the dispered phase of small particles at high temperature ($260^{\circ}C$) under high shear of the twin extruder, whereas it formed the big particles at low extrusion temperature ($220^{\circ}C$). The mechanical properties of the recycled PC/ABS extruded at high temperature was better than those at low temperature, which enabled the recycled PC/ABS seperated from In-Panel to be applied to the radiator grille without the addition of the compatibilizers or virgin PC/ABS. This was ascribed to the smaller particle sizes of the PU foam formed at high extrusion temperature under high shear.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.4
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• pp.25-32
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• 2012

Cold start driving cycles exhibit an increases in friction losses due to the low temperatures of metal components and media compared to the normal operating engine conditions. These friction losses are adversely affected to fuel economy. Therefore, in recent years, various techniques for the improvement of fuel economy at cold start driving cycles have been introduced. The main techniques are the upward control of coolant temperature and the fast warm-up techniques. In particular, the fast warm-up techniques are implemented with the coolant flow-controlled water pump and the WHRS (waste heat recovery system). This paper deals with an effect of fast ATF (automatic transmission fluid) warm-up on fuel economy using a recovery system of EGR gas waste heat in a diesel engine. On a conventional diesel engine, two ATF coolers have been connected in series, i.e., an air-cooled ATF cooler is placed in front of the condenser of air conditioning system and a water-cooled one is embedded into the radiator header. However, the new system consists of only a water-cooled heat exchanger that has been changed into the integrated structure with an EGR cooler to have the engine coolant directly from the EGR cooler. The ATF cooler becomes the ATF warmer and cooler, i.e., it plays a role of an ATF warmer if the temperature of ATF is lower than that of coolant, and plays a role of an ATF cooler otherwise. Chassis dynamometer experiments demonstrated the fuel economy improvement of over 2.5% with rapid increase in the ATF temperature.

• Journal of the Korea Society of Computer and Information
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• v.15 no.10
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• pp.99-104
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• 2010

In this paper, the internal antenna for mobile communication handset which is able to control both coupling coefficient and resonant frequency without any major modification of radiator and ground plane of PIFA(Planner Inverted F Antenna). The resonant frequency as well as amount of coupling between feeding point and shorting post can be adjusted by changing inductance. Because the inductor is connected on shorting post where the strength of electric field is weak, the performance reduction of the proposed antenna is very small enough to neglect. For the variation of the inductance value within 3.3nH, the resonant frequency of antenna can have operating range of 1650MHz ~ 1830MHz. And as be increased the inductance, the coupling coefficient of antenna is over coupled. This means that it can be electrically controlled the resonant frequency and input impedance of antenna by inductance and minimized the mismatch loss. Size reduction of 10% for PIFA is obtained without any major modifications of antenna elements. For the frequency range from 1650 to 1830MHz, reduction of the measured antenna gain is within 0.93dB as varying the value of inductance from 0 to 3.3nH.

• Journal of the Korean Institute of Telematics and Electronics
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• v.19 no.2
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• pp.14-22
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• 1982

The design and manufacfure technology of the large aperture cassegrain antenna was first studied in the country, and its performances in a trial manufactured product are measured and compared. In order to design this cassegrain antenna with reference to several literatures, the schemed order was decided. Especially, for the cassegrain antenna of 4.6m diameter which is becoming the television receiving antenna directly from satellite, in advanced countries, the 1/12 sized small section of its parabolic curved surface is made primarily with the precision of less difference than 1/16λ depth. Cares are taken also on the computer program so that the size and position of primary radiator may satisfy the minimum blocking with the given sub-reflector. The preformances of the designed antenna are shown as being 43dB in gain, 1.15 or less in VSWR, 1.1$^{\circ}$ of beam angle etc., and found to be not worse than those of foreign productions with similar type and size.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.1 s.92
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• pp.84-91
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• 2005

In this papers, we study the characteristics of dual band PIFA(Planar Inverted F antenna) for handy phones using H-type silt in the antenna radiators. Slit types on the antenna radiator vary resonance mechanism of the antenna and affect reactance component of impedance for the antenna. Therefore the antennas resonate at the dual band(cellular -band, Korea-PCS band), the bandwidth, input impedance and radiation patterns of the proposed antenna is affected by the silt length on the radiators. In order to demonstrate the validity of the proposed theory, it is implementation the antenna of the 4 types. From results for the experiment of the implementation antenna, -5 dB bandwidth of return loss is content with the allocated bandwidth of Cellular and Korea-PCS system the gains of the antenna is about -8$\~$ - 1 dB, the radiation patterns for x-polarized or y-polarized are omnidirectional pattern. From above the results of this papers, it is conclude mobile phones antenna for handy phones using this papers results.