• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.9
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• pp.679-684
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• 2017

This paper presents an UHF(Ultra High Frequency) band small cavity structured RFID(Radio Frequency Identification) tag antenna with a long reading range, designed to apply on metal cart or pallet for auto-parts logistics. The size of tag antennas is $140{\times}60{\times}10mm^3$, attached on a exporting metal cart, and it can give the information of inventory and logistics of carts. By collecting the exported carts and increasing the recovery rate of missing carts or pallets, the paid import tax can be refunded when the carts are returned back to the manufacture. The tag antenna was equipped with a cover to prevent damage, and the dielectric constant of the cover is considered for the simulation. The reading range of the tag antenna is 12 m using LP(Linear Polarization), 10 m with CP(Circular Polarization) reader antennas. This 920 MHz UHF RFID cavity tag ensures the long reading distance of the antenna regardless of the material of the object where it is attached.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.11
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• pp.1285-1294
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• 2010

This study describes the design and verification of short range UWB(Ultra Wideband) imaging radar that is able to display high resolution radar image for front area of a UGV(Unmanned Ground Vehicle). This radar can help a UGV to navigate autonomously as it detects and avoids obstacles through foliage. We describe the relationship between bandwidth of transmitting signal and range resolution. A vivaldi antenna is designed and it's radiation pattern and reflection are measured. It is easy to make array antenna because of small size and thin shape. Aperture size of receiving array antenna is determined by azimuth resolution of radar image. The relation of interval of receiving antenna array, image resolution and aliasing of target on a radar image is analyzed. A vector network analyzer is used to obtain the reflected signal and corner reflectors as targets are positioned at grass field. Applicability of the proposed radar to UGV is proved by analysis of image resolution and penetrating capability for grass in the experiment.

• Journal of Astronomy and Space Sciences
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• v.20 no.4
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• pp.327-338
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• 2003

The aim of this paper is to describe the results of the study on the extreme-ultra-violet (EUV) solar telescope, which is designed to. a possible satellite mission. Since the EUV band can not be observed on the ground, the observation in EUV should be performed in space using a satellite or a rocket. Design of the Extreme-Ultra-Violet solar Telescope (BUVT) in this study is based on "Designing a small-sized engineering model of solar EUV telescope for a Korean satellite" (Han et al. 2001). Our EUVT design is satisfied with the requirements for a satellite in size and input voltage. The major goal of the study is to confirm if we can detect the specific wavelength (58.4nm to 62.9nm) with the EUVT. We describe re-designing of the EUVT to decrease a shelter ratio. Also we describe the technics in the optic system and the detector, which were used to manufacture the EUVT. We explain the detective program, which is to calculate the amount of the solar radiation, and the image data processing system.ng system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.8
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• pp.766-773
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• 2016

This paper proposes an aircraft-installed compact offset-parabolic-reflector antenna for the spinning direction-finding applications. The feeder of the reflector antenna is a LPDA antenna that has the ultra-wideband characteristics and the $45^{\circ}$ slant linear polarization. The reflector is designed to be slanted by $5^{\circ}$ in the elevation and to be small in size on the basis of the reference parabolic shape for the purpose of the high gain and mounting on the underside of aircraft fuselage. Over the ultra-wideband 20:1 bandwidth from S to Ka band, the measured average gain of the proposed antenna is 27.97 dBi, and the average half-power beam width is $4.55^{\circ}$ in the azimuth and $4.3^{\circ}$ in the elevation which is the pencil-beam radiation pattern. All the measured data are similar to the simulation results. The designed compact offset-parabolic-reflector antenna that is installed in the limited area has the ultra-wideband and high-gain characteristics. We expect that the newly designed antenna can be applied to the spinning direction-finding antenna system installed in an aircraft.

• Proceedings of the Korea Concrete Institute Conference
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• 1991.04a
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• pp.23-28
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• 1991

Silica-Fume, an industrial by product, has an extremely small average partical size of 0.1${\mu}{\textrm}{m}$ and when used as a concrete admixture fills the fine voids which exist in concrete. The purpose of this study is to investigate material properties of the high-strength concrete using Silica-Fume and Fly-Ash. The main variables studied are; a) water-cement ratio. b) Silica-Fume, Fly-Ash content. The maximum compressive strength of 1000Kg/$\textrm{cm}^2$ is achieved with a mix using 18% water-cement ratio, 20% Silica-Fume and 10% Fly-Ash ratio.

• Journal of the Korean Ceramic Society
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• v.30 no.3
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• pp.215-221
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• 1993

The Hydroxyapatite powders were prepared by Wet-direct and Hydrothermal synthesis using Ca(NO3)2.4H2O and (NH4)2.HPO4.Stoichiometric and good cristalline HAp powders were obtained 9$0^{\circ}C$ by wet-direct process. The aspect ratio of HAp powders prepared by hydrothermal synthesis was increased with increasing synthetic temperature. The HAp particles obtained at 20$0^{\circ}C$ for 10hr were needle shaped ultra fine crystals, about 100nm in size. Small amount of TCP was obtained above 80$0^{\circ}C$ after heat-treatment of hydrothermally synthesized HAp but good crystalline HAp phase was maintained up to 120$0^{\circ}C$ as the primary phase.

• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.92-94
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• 2003

Recently, the study on development of electrical and electronic device is done to get miniature, high degrees of integration and efficiency by using inorganic materials, the study of Langmuir-Boldgett(LB) method that uses organic materials because of the limitation for the ultra small size. In this paper, detected displacement current using PBLG and PBDG, deposition and observed the electrical characteristics to each 1, 3, 5, 7, 9 layers by LB method. Maximum value of change ratio of displacement current by the detected speed and temperature appeared almost lineally, could confirm that it are in comparison relation each other speed-temperature and displacement current. The structure of manufactured device is MIM. Also, we then examined of the MIM device by means of I-V. The I-V characteristic of the device is measured from 0 to +2[V]. The insulation property of a thin film is better as the distance between electrodes is larger.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.11
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• pp.685-689
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• 2016

Synthesis of the fluorescent Au nanoclusters is reported. The Au nanoclusters were synthesized via reduction of gold ions in reverse micelles with mild reducing agents. The Au nanoclusters show a bright red emission at 640 nm. The fluorescent Au nanoclusters attract great interest for sensor, electronic device and bio-imaging applications because of ultra-small size, high chemical stablity and bright emission. We believe that the fluorescent Au nanoclusters can have optoelectronic applications such as optical down conversion phosphors.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.641-645
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• 2001

Storage drives for mobile devices, such as laptop computers or PDAs, are changing now. The data density of storage drives is becoming higher and sizes of those are becoming smaller and thinner. Spindle motors for rotating disk are also becoming smaller and thinner. But, large torque is required to reduce seek time. In this research, inner rotor type spindle motor suitable for thin thickness has been developed. Rotor and stator are optimized structurally for large torque performance with small size. Especially, high vibration and shock performances, which are essential to mobile devices, are analyzed in detail.

• Transactions of the Society of Information Storage Systems
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• v.5 no.2
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• pp.53-57
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• 2009

This study is concerned with the design of a camera iris-shutter device for producing force. The camera iris-shutter with yoke should have a smaller size and a bigger magnetic force than the previous model. Since the induced magnetic force operates shutter movement, the magnetic force maximization for a given input current is an important issue. To achieve the goal, new system is designed by the topology optimization method. The design is refined through the design of experiments to find the detail camera iris shutter design satisfying design constraints.