• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.5
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• pp.1023-1028
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• 2012

A MMIC (Monolithic Microwave Integrated Circuit) mixer chip using the Schottky diode of an GaAs p-HEMT process has been developed for the I/Q demodulator of non-contact near field microwave probing system. A single balanced mixer type is adopted to achieve simple structure of the I/Q demodulator. A quadrature hybrid coupler and a quarter wavelength transmission line for 180 degree hybrid are realized with lumped elements of MIM capacitor and spiral inductor to reduce the mixer chip size. According to the on-wafer measurement, this MMIC mixer covers RF and LO frequencies of 1650MHz to 2050MHz with flat conversion loss. The MMIC mixer with miniature size of $2.5mm{\times}1.7mm$ demonstrates conversion loss below 12dB for both variations of RF and LO frequencies, LO-to-IF isolation above 43dB and RF-to-IF isolation above 23dB, respectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.4
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• pp.331-341
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• 2013

In a solar domestic hot water (SDHW) system, solar energy is collected using collector panels, transferred to a circulating heat transfer fluid (brine), and eventually stored in a thermal storage tank (TST) as hot water. In this study, a computational fluid dynamics (CFD) model was developed to predict the solar thermal energy storage in a hybrid-type TST equipped with a helical jacket heater (mantle heat exchanger) and an immersed spiral coil heater. The helical jacket heater, which is the brine flow path attached to the side wall of a TST, has advantages including simple system design, low brine flow rate, and enhanced thermal stratification. In addition, the spiral coil heater further enhances the thermal performance and thermal stratification of the TST. The developed model was validated by the good agreement between the CFD results and the experimental results performed with the hybrid-type TST in SDHW settings.

• Journal of the Korean Geotechnical Society
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• v.30 no.4
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• pp.93-99
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• 2014

Use of geothermal energy has been increased for its economical application and environmentally friendly utilization. Particularly, for energy piles, a spiral coil type ground heat exchanger (GHE) is more preferred than line type GHEs such as U and W shaped GHEs. A PHC energy pile with spiral coil type GHE was installed in an area of partially saturated dredged soil deposit, and a thermal response test (TRT) was conducted for 240 hours under a continuous operation condition. Besides, remolded soil samples from different layers were collected in the field, and soil specimens were reconstructed according to the field ground condition. Non-steady state probe methods were conducted in the lab, and ground thermal conductivity and thermal diffusivity were measured for the different soil layers. An equivalent ground thermal conductivity was calculated from the lab test results and it was compared with the field TRT result. The difference was less than 5%, which advocates the use of an equivalent ground thermal conductivity for the multi-layered ground. Furthermore, this paper also represents an equivalent ground thermal diffusivity evaluation method which is another very important design parameter.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.2
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• pp.139-144
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• 2004

The flight control system designed for an unmanned airship, which is under development by KARI, is in reduced. First, the dynamic characteristics of the airship are addressed, which are fairly different from those of the nominal aircraft. In order to implement autonomous flight for the unmanned airship, flight control logic is designed including autopilot and guidance law. The autopilot is designed under consideration of the velocity region of the unmanned airship. The guidance laws are implemented in main operational modes such as point navigation, station keeping and spiral up/down for emergency return. Their simulation results are also presented in order to validate performances of the flight control system.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.873-876
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• 2005

A low noise amplifier(LNA) using electro-magnetic field simulator is designed in standard 0.25um CMOS process. Integrated spiral inductor is simulated using EM field solver. Then LNA is simulated with active device, capacitor and simulated inductor by EM field solver. A S11 and S21 of -15.45dB and 17.8dB at 2.3GHz as simulation results was achieved. A Noise Figure is 2.92dB. And Measurements show a S11 and S21 of -12.4dB and 17.8dB at 2.3GHz. A Noise Figure of 3.3dB was achieved.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1479-1480
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• 2011

In this paper, a novel design ultrasonic linear motor is proposed. The proposed motor consists of a ring type stator and a mover. They have spirals on their inner and outer surface, respectively. Along the spiral, a mover is travelled by a travelling extensional vibration mode of a ring type stator. Hence, a linear up-and-down motion is generated. Through the experimental data, we can verify the applicability regarding the autofocus lens drive.

• The Transactions of the Korea Information Processing Society
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• v.6 no.11S
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• pp.3299-3308
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• 1999

One of the most important prerequisites for a successful software process is the collaboration and software requirements negotiation of all stakeholders in the software development process. Remote users using computer networks can negotiate software requirements by computer supported system, and can share their informations. The goal of software requirements negotiation system is an integration of all win conditions and an agreement after resolution of conflicts. The existing systems need an exclusive system and must be dependent on specific platform and network. Users must have the knowledge of all stakeholder's status and use homogeneous collaborating applications. This paper presents the Web-based software requirements negotiation system for the purpose of resolution of the existing systems' problems. The Web-based software requirements negotiation system can be driven by WinWin Spiral model, and it is based on hybrid execution method. The proposed system is validated and tested on heterogeneous environments.

• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.217-219
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• 2009

본 논문에서는 NE6510179A 트랜지스터를 사용하고, 나선형 공진기를 이용하여 단일 고출력 발진기를 설계 측정하였다. 발진기의 출력과 주파수 선택을 공진기가 결정하므로, 공진기중에 Q값이 높은 나선형 공진기를 선택하였다. 이를 ADS Momentum을 이용하여 설계하여 제작 및 측정을 하였다. 이 때 측정된 단일 고출력 발진기의 성능은 22.61dBm @ 1.74GHz로 측정되었고, 위상잡음은 -146.76dBc/Hz @ 1MHz offset으로 측정 되었다.

• Design & Manufacturing
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• v.8 no.2
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• pp.50-55
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• 2014

Recently, semi-stack mold have been developed for satisfying the various elements required in the mold industry. The mold is possible using with general-purpose injection molding machine by weight reduction through the improvement of the mold structure. In order to do that, tension core, spiral cooling system and half runner system were applied. It is effective for increased productivity and decreased of loss to the materials. However, the mold is required the filling balance in order to improve the quality and efficiency. Thus this study performed that optimum design and analysis of semi-stack mold for filling balance.

• Journal of Electrical Engineering and Technology
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• v.3 no.1
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• pp.108-114
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• 2008

Polynomial networks have been known to have excellent properties as classifiers and universal approximators to the optimal Bayes classifier. In this paper, the use of polynomial neural networks is proposed for efficient implementation of the polynomial-based classifiers. The polynomial neural network is a trainable device consisting of some rules and three processes. The three processes are assumption, effect, and fuzzy inference. The assumption process is driven by fuzzy c-means and the effect processes deals with a polynomial function. A learning algorithm for the polynomial neural network is developed and its performance is compared with that of previous studies.