• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.2
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• pp.129-134
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• 2009

In this paper, we proposed a miniaturized Balun-BPF structure using semi-lumped line The conventional Ring Balun-BPF relatively has a big size structure because they consist of two ring resonators, wide line width ring-resonators for low loss and $\lambda/4$transmission line inverters. The ring resonators are miniaturized to 1/4 size by semi-lumped line and we added triangle patches in the ring resonator for compact Balun-BPF structure. The fabricated Balun-BPF is miniaturized to 1/4 size and contains symmetrical output characteristics of balance ports.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.3
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• pp.170-176
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• 2017

In this paper, we proposed the miniaturized structure of the Log-Periodic Dipole Array(LPDA) antenna for PS-LTE(Pubic Safety-Long Term Evolution) service. The length of array dipole was shortened by adding a fractal tree element with iteration to the array dipole to miniaturize the LPDA antenna. As the result, the proposed LPDA antenna was reduced up to 25 %, compared a typical LPDA antenna. To validation of the proposed LPDA antenna specification, the proposed LPDA antenna is fabricated using aluminum with 1.5 mm thickness and performances are measured. Comparison between simulation result and experiment shows good agreement.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.109-118
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• 2003

The recent trend towards miniaturization causes an increased demand for parts with very small dimensions. Milli-structure components are classified as a component group whose size is between macro- and micro-scale. The manufacturing process of these components of thin sheet metal forming has a microscopic properties in addition to a typical phenomenon of bulk deformation because of the forming size. Also, the material properties and the deformation behavior change with miniaturization, which means that, a coarse grained materials show a higher resistance against deformation, when the grain size is in the range of the sheet thickness. In this study, a new numerical approach is proposed to simulate intergranular milli-structure in forming by the finite element method. The grain element and grain boundary element are introduced to simulate the milli-structure in the bending. The grain element is used to analyze the deformation of individual grain while the grain boundary element is for the investigation on the movement of the grain boundary. Also, the result of the finite element analysis is confirmed by a series of milli-sized forming experiments.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.10
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• pp.710-717
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• 2007

Electric and telecommunication industries are constantly striving towards miniaturization of electronic devices. Miniaturization of chips creates extra space on PCBs that can be populated with additional components, which decreases the heat transfer surface area and generates very high heat flux. Even though an air-cooling technology for telecommunication equipment has been developed in accordance with rapid growth in electrical industry, it is confronted with the limitation of cooling capacity due to the rapid increase of heat density. In this study, liquid-cooling heat exchangers with MPCM slurries were designed and tested by varying geometry and operating conditions. The liquid-cooling heat exchangers with 4-paths showed higher cooling performance than the others. The cooling performance of liquid cooling heat exchanger with MPCM slurries was more enhanced than that of the air cooling system. It's performance was also slightly superior to that of the water cooling system at the inlet temperature of $19^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.636-640
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• 2003

As industrial technology was developed, necessity for small size motor was increased on various fields such as medical treatment and robotics. The motor should be simple structure, and it has easy process of manufacture to overcome the limit of miniaturization. So, "the windmill type ultrasonic motor" is enough to satisfy these conditions. In this paper, windmill type ultrasonic motor which was proposed by B.Koc and K.Uchino, was analyzed and fabricated with modified endcap shape. Displacements of arms of the proposed endcap were compared with the previous endcap, using the finite element analysis program (ANSYS). Better rotational characteristics was expected in proposed model as result of FEA. Experimentally, rotary motors of 3.5 [cm] diameter were fabricated, and the speed and torque of the motor were measured. As a result, speed and torque were changed in proportion to the electrical input voltages. And low efficiency which was different from an expectation was obtained in this motor. So, various problems should be improved for practical use.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.2
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• pp.95-101
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• 2008

This paper presents a novel bandpass filter design method for suppressing spurious response in the GSM band and effectively reducing the overall size with the unbalanced-conditioned metamaterials. Compared to the conventional bandpass filters based on half-or quarter-wave resonators, the CRLH(composite right/left-handed) bandpass filter works excellently in harmonic-suppression by 40$\sim$50 dB and 80 %-miniaturization using the zero-order resonators bridged by Inductive-coupling Inverters suggested first time. The proposed technique, with the equivalent circuit and dispersion diagram, is validated by performance predictions and experiments.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.10
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• pp.414-419
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• 2016

Air flow measurement is a fundamental and important task for testing, adjusting, and balancing of HVAC system. However, it is difficult to carry out in the field due to the large size and weight of the flow meter. In this study, for the purpose of developing a small and portable flow meter, we proposed a different method of static pressure measurement and verified it experimentally. In the proposed method, static pressure difference was measured by inserting a tube inside the chamber before and after the nozzles. The results were compared with measurements according to the ANSI/ASHRAE standard. The results were in good agreement, indicating that the inserted tube method could be used for static pressure measurement of a portable flow meter. The proposed method eliminates the pressure tubes that are attached outside, which results in smaller size and easy handling.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.02a
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• pp.266-273
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• 2002

Milli-structure components are classified as a component group whose size is between macro and micro scales, that is, about less than 20mm and larger than 1mm. The bending of these components of thin sheets has a typical phenomenon of bulk deformation because of the forming size. The recent trend towards miniaturization causes an increased demand for parts with very small dimensions. The conceptual miniature bending process enables the production of such parts with high productivity and accuracy. The stress values of the flow curve decrease with miniaturization, which means that coarse grained materials show a higher resistance against deformation, when the grain size is in the range of the sheet thickness. In this paper, a new numerical approach is proposed to simulate intergranular milli-structure in forming by the finite element method. The grain element and grain boundary element are introduced to simulate the milli-structure of strip in the bending. The grain element is used to analyze the deformation of individual grain while the grain boundary element is for the investigation on the movement of the grain boundary. Also, the result of the finite element analysis is confirmed by a series of milli-sized forming experiments.

• Journal of Sensor Science and Technology
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• v.14 no.4
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• pp.250-257
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• 2005

Respiratory tubes with the length of 35 mm and the diameter of 10, 15, and 20 mm were made and both the static($P_{S}$) and dynamic($P_{D}$) pressures were measured for steady flow rates ranging 1-12 l/sec. Regression analysis resulted successful fitting of $P_{S}$ and $P_{D}$ data with quadratic equations with correlation coefficients higher than 0.99. The measurement standards of the American Thoracic Society (ATS) were applied to $P_{S}$ data, which demonstrated the smallest tube diameter of 15 mm to satisfy the ATS standards. The maximum $P_{D}$ value of the velocity type transducer with the diameter of 15 mm was estimated to be 75 cm$H_{2}O$, implying approximately 7 times larger sensitivity than the widely used pneumotachometer. These results showed that the velocity type respiratory air flow transducer is a unique device accomplishing miniaturization with the sensitivity increased, thus would be of great advantage to develop portable devices.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.12
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• pp.1233-1238
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• 2003

In this paper, radially corrugated circular-type microstrip patch antenna was devised and manufactured for GPS (center frequency: 1.575 GHz). Radially corrugated circular-type microstrip patch antenna having radiational corrugation-patch contributed to add size reduction ratio by lowering the resonant frequency because the edge current also has the extended and perpendicular path. As a result, radially corrugated circular-type microstrip patch antenna has 28 % area reduction than planer circular-type patch antenna for linear polarization and 27.7 % area reduction than planer circular-type patch antenna for circular polarization. Radially corrugated circular-type microstrip patch antenna is suitable for miniaturized receive antenna for GPS which has the characteristic of gain 2.1 dBd, axiai ratio 1.3 dB, 2 dB axial bandwidth 15 MHz(0.9 %).