확장 칼만 필터를 이용한 동적 전기 임피던스 단층촬영법

김봉석,김경연,김민찬,이윤준 濟州大學校 情報通信硏究所 2000 情報通信硏究所論文集 Vol.3 No.-

In electrical impedance tomography (EIT). the resistivity(impedance) distribution of the unknown object is estimated from boundary voltages induced by different current patterns with various reconstruction algorithms. In this paper. we propose a dynamic EIT reconstruction algorithm based on the extended Kalman filter(EKF). The reconstruction problem is formulated as dynamic equation which consists of the state equation and the observation equation and the unknown state is estimated recursively with the aid of the EKF. Computer simulations for the 16-channel synthetic data are provided to illustrate the reconstruction performance of the proposed algorithm.

Zr/Ti 비에 따른 PZT계 압전세라믹스의 온도안정성

임대관,현원석,이개명 濟州大學校 情報通信硏究所 1998 情報通信硏究所論文集 Vol.1 No.-

In this paper, temperature stabilities of Pb( Zr_xTi_(1-x))O₃ piezoelectric ceramic system according to Zr/Ti ratios were investigated. PZT ceramics with Zr/Ti =58/42, 56/44, 53/47, 50/50, 48/52 which are adjacent compositions to Mophotyophic phase were fabricated, and thermal aging effects on the specimen were measured. After thermal aging. the specimens with Zr/Ti=58/42, 56/44, 48/52 in them could have lower temperature coefficient for antiresonant frequency and the specimen with Zr/Ti = 58/42 which is a composition of Rhombohedral phase have had the lowest temperature coefficient for antiresonant frequency.

이동통신 기지국용 저잡음 광대역 증폭기 설계

이정란,양두영 濟州大學校 情報通信硏究所 1998 情報通信硏究所論文集 Vol.1 No.-

The balanced amplifier is a practical amplifier to implement a broadband amplifier that has flat gain and good input and output VSWR. Three-stage amplifier design procedure usually divided into three partition satisfying the following requirements : low noise figure. high gain and high power output. FHX35LG HEMT device is used in the design can be obtained low noise figure at the first-stage. MGA82563 MMIC device is used in the design can be maintained high gain at the second-stage. and AHI MMIC device is used in the design can be required high power output at the third-stage. The results show that power gain is 38.26 dB. noise figure is 0.96 dB. and flatness is 0.346 dB. These results appropriate for the specification of low noise amplifier for the mobile communications.

이동에이전트를 이용한 네트워크 패킷기반 침입탐지 시스템

방성민,송왕철 濟州大學校 情報通信硏究所 2000 情報通信硏究所論文集 Vol.3 No.-

The networked environment has the possibility of the illegal access to the private informations and the attacks via networks. Therefore. security management technologies to protect networks from intrusions and network attacks have been given much attention. Intrusion detection system is an important component of the security management system for large network. It is hard to adapt to the heterogeneous internet environment because of the conventional intrusion detection system depends on the specific system environments. The new intrusion detection architecture with mobile agent technology is proposed in the paper. The mobile agent is an itinerary software program that autonomously runs on behalf of its operator in a network environment. It helps the adaptability in the intrusion detection system and decrease the network traffic. For the purpose. we analyze the attack patterns and design the new intrusion detection architecture.

헤어핀 콤 공진기를 이용한 대역통과 필터 설계

오데레사,김흥수 濟州大學校 情報通信硏究所 2000 情報通信硏究所論文集 Vol.3 No.-

The design of bandpass filter using a hairpin resonator limits a characteristic impedance of a transmission line and the length of coupled lines. which shifts a resonance frequency. In accordance with the design of bandpass filter. a line width and gap is calculated from a loapass prototype filter. but an accurate length of lines are not calculated. The line length is decided in accordance with coupling between lines which is not neighborhood using electro-magnetic analysis tool. In this paper. considering of coupling between all of lines an accurate length of lines calculated from a method of a transmission line analysis. The result of simulation is in close agreement with those of design parameter.

PADS를 이용한 전자 청진 시스템 설계

한철규,고성택,최민주 濟州大學校 情報通信硏究所 2000 情報通信硏究所論文集 Vol.3 No.-

Heart sound contains rich information regarding the dynamics of the heart and the auscultation has been a first choice of routine procedures for diagnosis of the heart. However. heart sounds captured using a conventional stethoscope are not often loud or clear enough for doctors to precisely classify their characteristics. especially. under the noisy environments of the hospital. A simple auscultation device that removed shortcomings of the conventional stethoscope was constructed in the study. The device employed a polymer based adherent differential output sensor(PADS) which was on contact with skin through a coupling medium and appropriated electronic circuits for signal amplification and conditioning. An ordinary headphone is taken to hear the captured heart sounds and the volume can be adjusted to hear well. It is also possible that the device sends the captured heart sound signals to a PC where the signals are further processed and visualized.

ATM 망에서 QOS 향상을 위한 적응 버퍼분할 공유기법에 관한 연구

정동성,이용학 濟州大學校 情報通信硏究所 1998 情報通信硏究所論文集 Vol.1 No.-

In this paper, we presented an ABPS scheme to improve the performance of previously announced BPS scheme. The block of high priority cell service had fixed efficiently to control that of low priority cell service, the first threshold had been controled by regulation low priority cell load and character function in the ABPS scheme proposed this paper. The performance of ABPS scheme had analytically used Markov chain. To compare ABPS scheme with the BPS scheme published before, we have analyzed cell loss rate according to traffic intensity. cell load of low priority, buffer size and character function. The ABPS scheme could be improve the quality of service and better efficiently utilize the resource of networks than those of the BPS scheme.

모드 정합법을 이용한 직교모드 변환기 해석 및 설계

문성익,양두영 濟州大學校 情報通信硏究所 2000 情報通信硏究所論文集 Vol.3 No.-

In this paper. the orthomode transducer of the antenna feed system is analyzed and designed. It consists of combining the common circular waveguide with the two sub-rectangular waveguide. The size of the circular and the rectangular waveguide are WC59. WR62 and the orthomode transducer considered the 13th high-order mode. From the boundary condition for the electromagnetic field. the scattering parameters are derived from the Hybrid electromagnetic mode theory. The computed results are compared with HFSS of 3D simulation tool for the microwave circuits. The results show a good characteristic that the S_(11) and S_(22) are below -15.5dB and S_(33) S_(44) are below -14dB in the range of 14.5~16.5GHz.

전송선로 해석법에 의한 감쇠극을 갖는 링 공진기의 대역통과 특성해석

오데레사,김흥수 濟州大學校 情報通信硏究所 1998 情報通信硏究所論文集 Vol.1 No.-

A microstrip ring resonator with attenuation pole is studied by using analysis method of transmission line. It is divided with two parts. the ring resonator itself and the gap between the ring resonator and the end of feedlines. to analyze the effect of attenuation poles. As the ripple become smaller, the phenomenon that the center frequency is disappeared and the series-parallel resonance frequencies are clearly appeared is observed by this method. At passband. a ring resonator has -8dB insertion loss, but the ring resonator with the poles -43dB insertion loss. The results are in close agreement with those of simulation by the Maxwell SI Eminence.

2차측에 정류회로를 이용한 유도전동기의 불평형 전압 운전해석

문경주,조용철,좌종근 濟州大學校 情報通信硏究所 1999 情報通信硏究所論文集 Vol.2 No.-

The Characteristics of unbalanced voltage operation for induction motor which has rectifier circuit in the secondary side are analyzed using a six elements ac circuit model referred to the primary side. The symmetrical component method is used to analyze motor performance and the positive and negative sequence circuit model are composed by taking account of the current overlap angle and the voltage drop of rectifier circuit. The characteristics of induction motor under unbalanced symmetrical voltage are computed and compared with the measured values to verify the proposed method