• 한국광학회:학술대회논문집
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• 한국광학회 2004년도 제15회 정기총회 및 동계학술발표회
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• pp.272-273
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• 2004

Optical connector is prone to take environment attack since it is exposed to various environmental conditions. As the data bit rate is increased in the modern optical communication system. the stability of optical connector becomes more important issue in complex network comprising of many connection by connectors. In this research, to estimate the influence of defects of connector, especially surface scratches, on the transmission, surface scratches were intentionally introduced on the cross sectional surface of optical connector and the insertion loss, return loss. and BER were measured as functions of geometry and density of scratches, Environmental conditioning was also performed onto these connectors and the variations of basic optical characteristics mentioned above were measured. Based on this measurement the lifetime of connectors was estimated by statistical prediction method.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1441-1447
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• 2008

This research studies the effects of community noise around railway, noise from the inside/outside noise of the High-Speed EMU. First study part of this year is research of the noise source. The modeling methodology for prediction of noise level including the frequency property, velocity dependence, sound pressure of noise source is investigate. Second part is research on the sound transmission loss. An exclusive program which could analyze the sound transmission loss of the floor, the sides(mirror), insulator in High-Speed EMU has to be developed. Third part is research on the train inside/outside and Prediction for community Noise. In order to predict the noise when the High-Speed EMU is traveling at the outside and along tunnels, the result of the research can be derived by evaluating the effect of the noise on the upper/middle parts of the carriage and on the railroad way round about with using the program.

• 한국전자통신학회논문지
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• 제19권1호
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• pp.1-10
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• 2024

실내 로비 환경에서 다중 경로에서 6, 10, 17 GHz 주파수 대역의 전파 특성을 분석하였다. 가시선(Line-of-sight, LOS) 및 비가시선(Non-line-of-sight, NLOS) 경로는 송신 안테나 위치에서 수신 안테나 위치까지 2-16 m (0.5 m 간격) 거리에서 측정되었다. 기본 전송 손실은 경로에 해당하는 FI(Floating intercept) 경로 손실 모델을 사용하여 세 가지 매개변수를 비교하였다. RMS(Root mean square) 지연 확산은 측정 결과를 누적 확률 10, 50, 90%로 비교하였다. 기둥의 존재와 특이한 로비 구조로 인해 측정된 모든 주파수에서 전파 손실과 전파 지연이 발생하였다. 이에 실내 로비 환경에 대한 측정 시나리오와 표준 측정 데이터 제공을 제안하였다. 이를 통해 다양한 구조의 실내 로비 환경에서 5G 및 밀리미터파 대역의 전파 특성에 대한 연구에 기여할 것이다.

• Journal of Advanced Marine Engineering and Technology
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• 제36권1호
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• pp.157-165
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• 2012

본 연구에서는 MMIC 상에서 온칩용 수동소자의 개발을 위해서, 주기적으로 배치된 용량성 소자를 이용한 단파장 전송선로를 연구하였다. PACD 구조의 전송선로는 기존의 마이크로스트립 전송선로에 비해, 단파장 특성과 낮은 특성 임피던스를 나타내었다. PACD 구조의 전송선로 구조는 기존의 마이크로스트립 전송선로 파장의 8%의 파장 단축효과를 나타낸다. MMIC 상에서의 온칩용 수동소자로서의 적합성을 판단하기 위하여 이론적으로 PACD 선로구조의 손실특성, 유효유전율, 전파상수, 대역폭 등의 기본 특성을 분석하였다. 위의 결과들을 통하여 PACD 구조의 전송선로는 MMIC 상에서 온칩용 수동소자로서의 특성에 효과적임을 알 수 있다.

• Journal of the Optical Society of Korea
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• 제19권4호
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• pp.376-381
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• 2015

Transmission characteristics of long-period fiber gratings (LPFGs) fabricated by periodically etching a conventional single-mode fiber (SMF) are investigated. After coating the SMF with photoresist, the cladding of the SMF is symmetrically and periodically removed by using a wet etching technique resulting in the formation of the LPFG. Tensile strain reinforces the coupling strength between the core and the cladding mode based on the photoelastic effect. The extinction ratio of the SMF-based LPFG at a wavelength of 1550.8 nm is measured to be -15.1 dB when the applied strain is $600{\mu}{\varepsilon}$. The ascent of ambient index shifts the resonant wavelength to shorter wavelength because of the increase of the effective refractive index of the cladding mode. The extinction ratio is diminished by increase in the ambient index because of the induction of the optical attenuation of the cladding mode. The transmission characteristics of the proposed LPFG with variations in torsion are also measured. The photoelastic effect based on torsion changes the extinction ratio and the resonant wavelength of the proposed SMF-based LPFG. The polarization-dependent loss of the LPFG is also increased by torsion because of the torsion-induced birefringence. The polarization-dependent loss of the LPFG at torsion of 8.5 rad/m is measured to be 3.9 dB.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.630-635
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• 1998

This paper establishes in a new unified manner new mathematical models with core(iron) loss factor for two kinds of AC motors, induction and synchronous motors which are supposed to generate torque precisely or/and efficiently under vector controls. Our new models consist of three basic equations consistent with the others such as differential equation describing electromagnetic dynamics, torque equation describing torque generating mechanism, energy transmission equation describing how injected energy is wasted, saved or transmitted where all vector signals are defined in general frame of arbitrary instant angular velocity. It is clearly shown in our models that equivalent core-loss resistance can express appropriately and separately both eddy-current and hysteresis losses rather than mere vague loss. Proposed model of induction motor is the most compact in sense of the number of employed interior states and parameters. This compact model can also represent eddy-current and hysteresis losses of rotor as well as stator. For synchronous motor, saliency is taken into consideration. As well known model for cylindrical motor can be obtained directly from salient one as its special case.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.676-681
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• 2001

We usually divide the noise of exhaust system into pulsation noise and flow noise. Pulsation noise is the shock wave to occur when the burning gas of low pressure emits and include harmonic having basic frequency as the exhaust cycle of engine. Flow noise is the noise that is produced when gas flow emits into the atmosphere through the pipe and has the character of frequency like pink noise which has the high level of high frequency component. A muffler is divided into reflective type and absorptive type. We usually use the muffler compounding the property of them. In this study, it is the case of transfer matrix method that a muffler is compounded to analyze the elements of each section according to sound wave's proceed direction. But we use simple model. So, we use finite element method that takes short time to analyze. Acoustic analysis gives us transfer matrix to use FEA of SYSNOISE and we use STAR-CD for fluid analysis. We made database that is based on analytical results about the muffler of expansion type, extended type, offset type, reverse type, and perforated type and developed the muffler design system to perform work efficiently.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 심포지엄 논문집 정보 및 제어부문
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• pp.215-217
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• 2005

There are two types of packet loss probabilities used in both the network layer and the physical layer within the wireless transmitter such as a queueing discard probability and transmission loss probability. We analyze these loss performances in order to guarantee Quality of Service (QoS) which is the basic of the future network. The queuing loss probability is caused by a maximum allowable delay time and the transmission loss probability is caused by a wireless channel error. These two types of packet loss probabilities are not easily analyzed due to recursive feedback which, originates as a result at a queueing delay and a number of retransmission attempts. We consider a wireless transmitter to a M/D/1 queueing model. We configurate the model to have a finite-size FIFO buffer in order to analyze the real-time traffic streams. Then we present the approaches used for evaluating the loss probabilities of this M/D/1/K queueing model. To analyze the two types of probabilities which have mutual feedbacks with each other, we drive the solutions recursively. The validity and accuracy of the analysis are confirmed by the computer simulation. From the following solutions, we suggest a minimum of 'a Maximum Allowable Delay Time' for real-time traffic in order to initially guarantee the QoS. Finally, we analyze the required service rate for each type utilizing real-time traffic and we apply our valuable analysis to a N-user's wireless network in order to get the fundamental information (types of supportable real-type traffics, types of supportable QoS, supportable maximum number of users) for network design.

• 한국전자통신학회논문지
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• 제18권6호
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• pp.1031-1040
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• 2023

서로 다른 두 가지 실내 복도의 D2 건물과 E2 건물 2층에서 3, 6, 10, 17 GHz 주파수 대역에 대한 가시선(: Line of sight, LOS) 경로의 전파 특성을 측정 및 분석하였다. 송신 안테나를 고정한 상태에서 수신 안테나가 3 m에서 30 m까지 0.5 m 간격으로 측정한다. 두 실내 복도에 대한 분석은 기본 전송 손실, RMS(: Root mean square) 지연 확산 및 K-인자(: K-factor)를 적용하여 비교하였다. 기본 전송 손실은 FI(: Floating intercept) 경로 손실 모델의 손실 계수에서 D2 건물 보다 E2 건물의 실내 복도에서 더 높게 나타났다. 마찬가지로, 시간 영역에서 RMS 지연 확산이 E2 건물의 실내 복도에서 더 크다. 그러나 D2 건물의 실내 복도에서는 3, 6, 17 GHz 대역에서 더 높은 K-인자값을 나타냈고, 10 GHz 대역에서는 전파 전달도가 더 낮은 것으로 나타났다. 두 가지 실내 복도는 동일한 크기에도 불구하고 내부 구조와 재질이 다르기 때문에 전파 특성의 변화가 많다. 결과는 다양한 실내 환경에 대한 ITU-R 기고에 대한 측정 데이터를 제공한다.

• International Journal of Computer Science & Network Security
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• 제24권7호
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• pp.118-122
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• 2024

The dielectric material is a basic element which impacts considerably on a microstrip structure performances. This project demonstrates how filter performances such as gain, bandwidth, return loss and insertion loss change proportionally with substrate material variation. The RT/Duroid 5880 and the FR-4 are two dielectric materials proposed as substrates of a low pass microstrip filter. The design and simulation are done on ADS software. The transmission and reflection characteristics show that the RT/ Duroid 5880 as a dielectric substrate permits to obtain better performance as compared to the FR-4 substrate.