• 디지털융복합연구
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• 제12권10호
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• pp.265-270
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• 2014

기존의 음성 인식 알고리즘은 어휘들 간의 순서가 정해져 있지 않으며, 음성 인식 환경 변화에 따른 잡음으로 인한 음성 검출이 정확하지 못한 단점을 가지며, 검색 시스템은 키워드의 의미가 다양하여 정확한 정보를 인지하지 못한다. 본 연구에서는 사건 기반 시맨틱 온톨로지 추론 모델을 제안하였으며, 제안된 시스템에서 음성 인식 특징을 추출하기 위해 ERB 필터를 이용하여 특징 추출하는 모델을 구축하였다. 제안된 모델은 성능 평가를 위해 지하철역, 지하철 잡음을 사용하였고 잡음 환경의 SNR -10dB, -5dB 신호에서 잡음 제거를 수행하여 왜곡도를 측정한 결과 2.17dB, 1.31dB의 성능이 향상됨을 확인하였다.

• 대한전기학회논문지:시스템및제어부문D
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• 제53권5호
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• pp.345-352
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• 2004

Currently, high data rate PLC(Power Line Communications), up to 100 Mbps, which use frequency bandwidth between 2 MHz and 30 MHz is investigated very hard, and commercial PLC modem for low voltage powerline network (indoor) is coming soon into communication market. For the purpose of developing a fit communication system which has little distortion of signal and attenuation, it is surely necessary to know about channel environments of powerline. Especially, the impedance measurement of the powerline and impedance matching are very important. As is known, since medium-voltage powerline (22.9 ㎸) is still working, it is not so simple to measure the powerline impedance. In our study, a portable impedance measurement equipment is developed. It consists of coupling capacitor, a drain coil and impedance matching transformer. The equipment is easily connected to medium voltage line and impedance of power line is measured using a network analyzer. Also, measurement results are used for impedance matching of PLC signal. In fact, matching transformer with several different impedances are used. The matching transformer is connected between coupling capacitor and signal port. In this paper, the developed portable impedance measurement equipment and impedance measurement results are presented. Also impedance matching technique using matching transformers will be explained. We showed the result of the improved performance by the impedance matching.

• 한국전자파학회논문지
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• 제10권7호
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• pp.1104-1110
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• 1999

일반적으로 거리 탐지용 레이더로 FM-CW 레이더 방식을 사용한다. 이 경우 FM-CW의 신호원으로 사용 되는 전압제어발진기의 제어전압과 출력주파수의 비선형성이 측정결과에 영향을 주게 된다. 최근 비선형성 보정에 대한 신호처리와 하드웨어적인 방법으로 많은 연구가 진행되고 있다. 본 논문에서는 기준 선호를 이 용하여 전압제어발진기의 비선형성으로 인해 측정결과에 발생하는 거리 단면의 왜곡을 보정하는 신호처리 기 법을 제안하였다. 이에 대한 성능을 검증하기 위해서 간단한 실험을 수행하였고, 결과를 제시하였다. 제안한 기법에 의해 거리 단면 왜곡의 영향 감소와 분해능이 향상됨을 확인할 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2132-2135
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• 2005

Cylindrical type air core pulse transformers capable of passing high voltage and energy pulse waveforms with high efficiency and low distortion require a much more delicate design balance of physical dimensions and electrical parameters than iron or ferrite core units. The structure of an air core high voltage pulse transformer is relatively simple, but considerable attention is needed to prevent breakdown between transformer windings. Since the thickness of the windings in spiral type is on the order of sub-millimeter, field enhancement at the edge of the windings is very high. It is, therefore, important to find proper electrical insulation Parameter to make the system compact. Several shapes of the winding are considered for air core pulse transformer development. In this paper, we are described design procedure, parameters measure and experiment results of air core type HV pulse transformer.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.212-215
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• 2003

This paper presents constitution of a moderate price thermography system for on-line measurement. All objects with some temperature above absolute zero radiate in the infrared. The intensities and spectra of the infrared radiated from some object depend on the conditions and temperature distributions on the surface of the objects, and the temperature distributions differ from each others with different undersurface structures. Consequently, infrared radiation is useful for diagnosis of the conditions on the surface and undersurface of electric power apparatus. But the present, because engineers directly measure the temperatures of apparatuses in off-line, the measured data do not always have the information of the past. The proposed system is able to analyze not only the information of the past but the trend of deterioration, and the system is able to compensate for the distortion of surface temperature as to weather conditions. The thermal image histogram is equalized to upgrade observability, and a pan-tilter is adopted to control of direction for any target point.

• 정보처리학회논문지C
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• 제18C권6호
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• pp.441-444
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• 2011

본 논문은 망 상태 정보를 효율적으로 집단화하는 방법을 제시하였다. 이것은 비대칭 망에서 링크의 QoS(Quality of Service) 파라미터가 두개 이상일 때 기존 집단화 방법들이 갖는 정보의 부정확성을 줄이기 위한 방법이다. 제안 방법은 공간 복잡도를 줄이기 위해 다단계 토폴로지 변형 시 토폴로지를 구성하는 논리 링크들의 유사성을 측정, 유사한 링크들의 그룹화 후 통합 과정을 통해 논리 링크들의 정보 왜곡을 줄인다. 이 방법은 서비스경계라인을 논리 링크로 갖는 풀 메쉬 토폴로지를 스패닝 트리 토폴로지로 변형 시 적용한다. 또한 실험을 통하여 기존 방법 보다 집단화된 정보의 정확도와 질의 응답 정확도에서 나은 성능을 가짐을 증명하였다.

• 한국해양공학회지
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• 제31권2호
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• pp.177-182
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• 2017

This paper describes an unscented Kalman filter approach to estimate the bias in magnetic field measurements. A microelectromechanical systems attitude heading reference system (MEMS AHRS) was used to measure the magnetic field, together with the acceleration and angular rate. A magnetic field is usually used for yaw detection, while the acceleration serves to detect the roll and pitch. Magnetic field measurements are vulnerable to distortion due to hard-iron effect and soft-iron effect. The bias in the measurement accounts for the hard-iron effect, and this paper focuses on an approach to estimate this bias. The proposed method is compared with other methods through experiments that implement the navigation of an underwater robot using an AHRS and Doppler velocity log. The results verify that the compensation of the bias by the proposed method improves the navigation performance more than or comparable to the compensation by other methods.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권4호
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• pp.1866-1883
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• 2019

As the youngest branch of information hiding, network covert timing channels conceal the existence of secret messages by manipulating the timing information of the overt traffic. The popular model-based framework for constructing covert timing channels always utilizes cumulative distribution function (CDF) of the inter-packet delays (IPDs) to modulate secret messages, whereas discards high-order statistics of the IPDs completely. The consequence is the vulnerability to high-order statistical tests, e.g., entropy test. In this study, a rich security model of covert timing channels is established based on IPD chains, which can be used to measure the distortion of multi-order timing statistics of a covert timing channel. To achieve rich security, we propose two types of covert timing channels based on nested lattices. The CDF of the IPDs is used to construct dot-lattice and interval-lattice for quantization, which can ensure the cell density of the lattice consistent with the joint distribution of the IPDs. Furthermore, compensative quantization and guard band strategy are employed to eliminate the regularity and enhance the robustness, respectively. Experimental results on real traffic show that the proposed schemes are rich-secure, and robust to channel interference, whereas some state-of-the-art covert timing channels cannot evade detection under the rich security model.

• 대한조선학회논문집
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• 제58권6호
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• pp.382-390
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• 2021

The present study suggests the application of a depth camera for wave height field measurement, focusing on the calibration procedure and test setup. Azure Kinect system is used to measure the water surface elevation, with a field of view of 800 mm × 800 mm and repetition rate of 30 Hz. In the optimal optical setup, the spatial resolution of the field of view is 288 × 320 pixels. To detect the water surface by the depth camera, tracer particles that float on the water and reflects infrared is added. The calibration consists of wave height scaling and correction of the barrel distortion. A polynomial regression model of image correction is established using machine learning. The measurement results by the depth camera are compared with capacitance type wave height gauge measurement, to show good agreement.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.3918-3929
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• 2021

In this study, we experimentally investigate of a two-phase natural circulation loop that functions as a passive containment cooling system (PCCS). The experimental apparatus comprises two loops: a hot loop, for simulating containment under severe accidents, and a natural circulation loop, for simulating the PCCS. The experiment is conducted by controlling the pressure and inlet temperature of the hot loop in the range of 0.59-0.69 MPa (abs) and 119.6-158.8 ℃, respectively. The heat balance of the hot loop is established and compared with a natural circulation loop to assess the thermal reliability of the experimental apparatus, and an additional system is installed to measure the vapor mass flow rate. Furthermore, the thermal-hydraulic characteristics are considered in terms of a temperature, mass flow rate, heat transfer coefficient (HTC), etc. The flow rate of the natural circulation loop is induced primarily by flashing, and a distortion is observed in the local HTC because of the fully develop as well as subcooled boiling. As a result, we present the amount of heat capacity that the PCCS can passively remove according to the experimental conditions and compared the heat transfer performance using Chen's and Dittus-Boelter correlation.