• 말소리와 음성과학
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• 제6권2호
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• pp.21-28
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• 2014

We propose a novel scheme for digital audio authentication of given audio files which are edited by inserting small audio segments from different environmental sources. The purpose of this research is to detect inserted sections from given audio files. We expect that the proposed method will assist human investigators by notifying suspected audio section which considered to be recorded or transmitted on different environments. GMM-UBM and GSV-SVM are applied for modeling the dominant environment of a given audio file. Four kinds of likelihood ratio based scores and SVM score are used to measure the likelihood for a dominant environment model. We also use an ensemble score which is a combination of the aforementioned five kinds of scores. In the experimental results, the proposed method shows the lowest average equal error rate when we use the ensemble score. Even when dominant environments were unknown, the proposed method gives a similar accuracy.

• Journal of Power Electronics
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• 제13권3호
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• pp.390-399
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• 2013

As a result of the depletion of fossil fuels and environmental contamination, it has become important to use renewable energy. For the stable utilization of renewable energy sources, energy storage devices must be used. In addition, renewable and distributed power sources with energy storage devices must operate stably under grid-connected mode. This paper proposed dynamic response modeling for renewable power generation systems including a charger/discharger with an energy storage device in order to derive a method to guarantee stable operation while fully utilizing the energy from the energy storage device. In this paper, the principle operation and design guidelines of the proposed scheme are presented, along with a performance analysis and simulation results using MATLAB and PSIM. Finally, a hardware prototype of a 1kW power conditioning system with an energy storage device has been implemented for experimental verification of the proposed converter system.

• 한국태양에너지학회 논문집
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• 제28권5호
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• pp.85-95
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• 2008

Photovoltaic conditioning systems normally use a maximum power point tracking (MPPT) technique to deliver the highest possible power to the load continuously when variations occur in the insolation and temperature. A unique method of tracking the maximum power points (MPPs) and forcing the boost converter system to operate close to these points is presented through deriving small-signal model and transfer function of boost converter considering input capacitor. This paper aims at modeling boost converter including fairly large equivalent series resistance(ESR) of input reservoir capacitor by state-space-averaging method and PWM switch model. In the future, properly designed controller for compensation will be constructed in 3kw real system for maximum photovoltaic power tracking control.

• 한국컴퓨터정보학회논문지
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• 제23권12호
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• pp.43-48
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• 2018

In this paper, more efficient classification result could be obtained by applying the combination of the Hidden Markov Model and SVM Model to HMSV algorithm gene expression data which simulated the stochastic flow of gene data and clustering it. In this paper, we verified the HMSV algorithm that combines independently learned algorithms. To prove that this paper is superior to other papers, we tested the sensitivity and specificity of the most commonly used classification criteria. As a result, the K-means is 71% and the SOM is 68%. The proposed HMSV algorithm is 85%. These results are stable and high. It can be seen that this is better classified than using a general classification algorithm. The algorithm proposed in this paper is a stochastic modeling of the generation process of the characteristics included in the signal, and a good recognition rate can be obtained with a small amount of calculation, so it will be useful to study the relationship with diseases by showing fast and effective performance improvement with an algorithm that clusters nodes by simulating the stochastic flow of Gene Data through data mining of BigData.

• Current Optics and Photonics
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• 제6권2호
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• pp.171-182
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• 2022

A single-photon laser and mid-wave infrared (MWIR) common aperture optical system was designed and developed to detect and range a long-distance civil aviation aircraft. The secondary mirror of the Ritchey-Chretien (R-C) optical system was chosen as a dichroic lens to realize the design of a common aperture system for the laser and MWIR. Point spread function (PSF) ellipticity was introduced to evaluate the coupling efficiency of the laser receiving system. A small aperture stop and narrow filter were set in the secondary image plane and an afocal light path of the laser system, respectively, and the stray light suppression ability of the small aperture stop was verified by modeling and simulation. With high-precision manufacturing technology by single point diamond turning (SPDT) and a high-efficiency dichroic coating, the laser/MWIR common aperture optical system with a 𝜑300 mm aluminum alloy mirror obtained images of buildings at a distance of 5 km with great quality. A civil aviation aircraft detection experiment was conducted. The results show that the common aperture system could detect and track long-distance civil aviation aircraft effectively, and the coverage was more than 450 km (signal-to-noise ratio = 6.3). It satisfied the application requirements for earlier warning and ranging of long-range targets in the area of aviation, aerospace and ground detection systems.

• 조명전기설비학회논문지
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• 제22권5호
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• pp.21-30
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• 2008

전력 에너지 소비의 급격한 증가와 환경오염, 화석연료의 고갈, 그리고 고유가에 대한 에너지 자원의 대처방안으로 신재생 에너지원에 대한 연구가 진행되고 있다. 다양한 대체 에너지들 중에서 연료전지 발전은 지속적인 원료공급시 연속적으로 화학반응 에너지를 직접 전기에너지로 변환시키는 기술로서 연료비 부담이 없으며, 에너지 변환효율이 높고, 대기오염이나 폐기물 발생이 없다. 또한 소규모 구성과 복합 구성이 가능하고, 전형적인 발전시스템과 달리 기계적인 진동과 소음이 낮다. 이처럼 연료전지를 이용한 발전시스템 분야의 연구와 실용화가 진행되고 있는 실정이다. 본 논문에서는 PSCAB/EMTDC를 사용하여 삼상 380[V], 50[kW]급 연료전지 발전시스템의 모델링 및 구성된 연료전지 발전시스템의 전력신호를 웨이블릿 기법으로 분석하고, 분석된 결과를 전력품질의 관점으로 평가하여 해당 시스템의 모의 성능을 평가하고자 한다. 이를 통하여 보다 상세한 연료전지 발전 모델과 운전에 따른 문제점을 도출할 수 있으며, 특히 계통연계 시 발생하는 다양한 전력품질 및 신호 특성을 선행하여 연구할 수 있다.

• 한국음향학회지
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• 제34권1호
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• pp.20-35
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• 2015

수중음향 전달채널의 임펄스 응답(Channel Impulse Response: CIR)은 음속구조(Sound Speed Profile: SSP)의 영향을 받으며, 채널 임펄스 응답의 변화는 수중음향통신 시스템의 성능에 중요한 영향을 미친다. 음속분포의 변화는 단기간 내에서도 나타날 수 있으며, 수중음향 모뎀 설계 시 반드시 고려되어야 한다. 이 논문은 2013년도에 제주도 동방해역에서 수행된 JACE13에서 취득된 데이터를 기반으로 음선전달 수치해석을 통해 단기간 동안 시간에 따라 변화하는 음속구조가 음향 신호 전달에 미치는 영향을 통계적으로 분석한 결과를 제시한다. 분석결과 송 수신기 수심별로 채널 임펄스 응답의 변화가 다양하게 나타나며, 송 수신기 수심이 깊을수록 음속구조의 변동에 따른 음향신호 전달 양상의 변화는 작아지고, 신호 준위가 높게 나타난다. 이 연구에서의 다양한 거리, 송, 수신기 수심에 따라 얻어진 채널 임펄스 응답 추정 결과는 수온약층에서의 하방굴절로 인한 연속된 해저면 반사와 작은 해저면 반사손실이 장거리 신호 전파에 중요한 요인이 될 수 있음을 보여주며, 시변동성을 갖는 해양환경에서의 수중 음향 통신은 시간에 따라서 성능이 충분히 달라질 수 있다는 것을 보여준다.

• 한국태양에너지학회 논문집
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• 제32권spc3호
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• pp.245-254
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• 2012

In photovoltaic system, the characteristics of photovoltaic module such as open circuit voltage and short circuit current will be changed because of cell temperature and solar radiation. Therefore, the boost converter of a PV system connects between the output of photovoltaic system and DC link capacitor of grid connected inverter as controlling duty ratio for maximum power point tracking(MPPT). This paper shows the dynamic characteristics of the boost converter by comparing single-loop and two-loop control algorithm using both analog and digital control. Both proposed compensation methods have been verified with computer simulation to demonstrate the validity of the proposed control schemes.

• Journal of electromagnetic engineering and science
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• 제18권3호
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• pp.188-198
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• 2018

In this study, we propose an approach for the design and satisfy the requirements of the fabrication of a small, lightweight, reliable, and stable ultra-wideband receiver for millimeter-wave bands and the contents of the approach. In this paper, we designed and fabricated a stable receiver with having low noise figure, flat gain characteristics, and low noise characteristics, suitable for millimeter-wave bands. The method uses the chip-and-wire process for the assembly and operation of a bare MMIC device. In order to compensate for the mismatch between the components used in the receiver, an amplifier, mixer, multiplier, and filter suitable for wideband frequency characteristics were designed and applied to the receiver. To improve the low frequency and narrow bandwidth of existing products, mathematical modeling of the wideband receiver was performed and based on this spurious signals generated from complex local oscillation signals were designed so as not to affect the RF path. In the ultra-wideband receiver, the gain was between 22.2 dB and 28.5 dB at Band A (input frequency, 18-26 GHz) with a flatness of approximately 6.3 dB, while the gain was between 21.9 dB and 26.0 dB at Band B (input frequency, 26-40 GHz) with a flatness of approximately 4.1 dB. The measured value of the noise figure at Band A was 7.92 dB and the maximum value of noise figure, measured at Band B was 8.58 dB. The leakage signal of the local oscillator (LO) was -97.3 dBm and -90 dBm at the 33 GHz and 44 GHz path, respectively. Measurement was made at the 15 GHz IF output of band A (LO, 33 GHz) and the suppression characteristic obtained through the measurement was approximately 30 dBc.

• 한국광학회지
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• 제18권4호
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• pp.235-240
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• 2007

본 논문에서는 10 Gbps급 데이터 전송을 위한 CPW(coplanar waveguide) 피드라인(feed-line)을 이용한 세라믹 스템(stem) 기반의 TO 패키지를 제안하였다. 기존의 금속 기반 TO 패키지에서 사용되는 실린더형 피드라인의 주파수 특성과 세라믹 패키지에서 사용되는 CPW 피드라인의 주파수 특성의 차이를 이론적으로 분석 비교하였다. 그리고 이들 패키지에 DFB 레이저다이오드(laser diode: LD)를 실장하여 측정된 3 dB 주파수 대역폭은 각각 3.5 GHz와 7.8 GHz로 사용된 패키지에 따라 큰 차이를 갖는 것을 밝혔다. 이러한 측정결과는 등가회로를 이용한 이론적인 계산결과와 잘 일치함도 확인하였다. 이상의 결과를 바탕으로 LD 광모듈의 주파수 특성을 개선하기 위한 방안으로 세라믹 재질의 비전도성 유전체를 스템으로 이용한 세라믹 스템 기반의 CPW 피드라인을 장착한 새로운 TO 패키지를 제안하였다. 제안된 패키지는 HFSS(high frequency structure simulator)를 이용하여 추출된 S 파라미터 값으로부터 기존의 금속 기반의 TO 패키지보다 월등히 넓은 주파수 특성을 얻을 수 있다는 것을 알 수 있었다.