• Title/Summary/Keyword: time-varying coefficients

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Performance Improvement of Double Talk Detection before Convergence of the Echo Canceller by Using Linear Predictive Coding Filter Gain of the Primary Input Signal (주입력신호의 LPC 필터 이득을 이용한 반향제거기의 수렴전 동시통화검출 성능 개선)

  • Yoo, Jae-Ha
    • Journal of the Korean Institute of Intelligent Systems
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    • v.24 no.6
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    • pp.628-633
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    • 2014
  • This paper proposes a performance improvement method of the conventional double talk detection method which can operate before convergence of the echo canceller. The proposed method estimates the coefficients of the linear predictive coding(LPC) filter by using the primary input signal. The time-varying threshold for double talk detection is determined based on the LPC filter gain of the primary input signal level. The proposed method can reduce not only false detection rate which means wrong detection of single talk as double talk but also double talk detection delay. Computer simulation was performed using a long-term real speech signals. It is shown that the proposed method improves the conventional method in terms of lowering the false detection rate and shortening the detection delay.

Analysis of Hebei Spirit Collision Accident by Simulation (시뮬레이션에 의한 허베이스피리트호-삼성바지선 충돌사고 분석)

  • Kim, Sun-Young;Lee, Gyeong-Joong;Park, Se-Kil;Kim, Yeon-Gyu;Lee, Moon-Jin;Son, Nam-Sun;Gong, In-Young;Kim, Mi-Hyun
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2011.06a
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    • pp.85-86
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    • 2011
  • On 7 December 2007, the Hebei Spirit, a 260,000 dwt VLCC, anchored near Korea's Daesan Port, was collided with a passing crane-carrying barge Samsung1, which was under tow of two tugs Samsung T5 and Samho T3. In this study, the behaviour of Hebei Spirit at the time of the accident has been reproduced and analyzed by simulation. This study precedes the study for the investigation of any available countermeasures for Hebei Spirit to prevent the accident. The simulation has been done only for Hebei Spiri and the motion of Samsung barge is just given with recorded AIS data. Dynamic characteristics of Hebei Spirit have been modeled based on empirical data and her sea trial data. Effects of current, wave and wind are also estimateed using empirical formula. Considering uncertainty of environmental condition and control of Hebei Spirit, simulation has been done by varying engine control method and holding power coefficients of the anchor. Finally, based on simulations, the most plausible scenario on the state of anchor and engine control could cause real accidents.

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Responses and Stresses of Structural Vibration of a Camshaft (캠축의 구조 진동 응답 및 응력)

  • Choi, Myung-Jin
    • The Journal of the Acoustical Society of Korea
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    • v.32 no.3
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    • pp.208-213
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    • 2013
  • To get vibration responses, a camshaft is modelled as an unbalanced multiple rotor bearing system. Because of complex geometry and complicated load conditions, the finite element method is used. After the finite element equation of the system is constructed, Newmark's method is used to get the vibration responses. Whirl vibration responses of a V-8 engine camshaft are estimated and compared with measured responses. After the fluctuating stresses are obtained, fatigue analysis is performed based upon the modified Goodman's equation. Stress concentration effects are considered. In the whirl vibration of camshafts, the bending effect is dominant, and the bending deformation is dependent upon the span length between the adjacent bearing journals. For high speeds, the fluctuations of excitation forces are large, and it is known that nonlinear time varying bearing coefficients should be used for analysis.

Classification of Whale Sounds using LPC and Neural Networks (신경망과 LPC 계수를 이용한 고래 소리의 분류)

  • An, Woo-Jin;Lee, Eung-Jae;Kim, Nam-Gyu;Chong, Ui-Pil
    • Journal of the Institute of Convergence Signal Processing
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    • v.18 no.2
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    • pp.43-48
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    • 2017
  • The underwater transients signals contain the characteristics of complexity, time varying, nonlinear, and short duration. So it is very hard to model for these signals with reference patterns. In this paper we separate the whole length of signals into some short duration of constant length with overlapping frame by frame. The 20th LPC(Linear Predictive Coding) coefficients are extracted from the original signals using Durbin algorithm and applied to neural network. The 65% of whole signals were learned and 35% of the signals were tested in the neural network with two hidden layers. The types of the whales for sound classification are Blue whale, Dulsae whale, Gray whale, Humpback whale, Minke whale, and Northern Right whale. Finally, we could obtain more than 83% of classification rate from the test signals.

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Spectral Modeling of Haegeum Using Cepstral Analysis (캡스트럼 분석을 이용한 해금의 스펙트럼 모델링)

  • Hong, Yeon-Woo;Kang, Myeong-Su;Cho, Sang-Jin;Kim, Jong-Myon;Lee, Jung-Chul;Chong, Ui-Pil
    • The Journal of the Acoustical Society of Korea
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    • v.29 no.4
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    • pp.243-250
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    • 2010
  • This paper proposes a spectral modeling of Korean traditional instrument, Haegeum, using cepstral analysis to naturally describe Haegeum sounds varying with time. To get a precise result of cepstral analysis, we set the frame size to 3 periods of input signal and more cepstral coefficients are used to extract formants. The performance is enhanced by flexibly controlling the cutoff frequency of bandpass filter depending on the resonances in the synthesis process of sinusoidal components and the deleting peaks remained in the residual signal. To detect the change of pitch, we divide the input frames into silence, attack, and sustain region and determine which region the current frame is involved in. Then, the proposed method readjusts the frame size according to the fundamental frequency in the case of the current frame is in attack region and corrects the extraction errors of the fundamental frequency for the frames in sustain region. With these processes, the synthesized sounds are much more similar to the originals. The evaluation result through the listening test by a Haegeum player says that the synthesized sounds are almost similar to originals (96~100 % similar to the original sounds).

The effect of heaving motion of multiple wave energy converters installed on a floating platform on global performance

  • Dongeun Kim;Yeonbin Lee;Yoon Hyeok Bae
    • Ocean Systems Engineering
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    • v.13 no.4
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    • pp.349-365
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    • 2023
  • Targeting a floating wave and offshore wind hybrid power generation system (FWWHybrid) designed in the Republic of Korea, this study examines the impact of the interaction, with multiple wave energy converters (WECs) placed on the platform, on platform motion. To investigate how the motion of WECs affects the behavior of the FWWHybrid platform, it was numerically compared with a scenario involving a 'single-body' system, where multiple WECs are constrained to the platform. In the case of FWWHybrid, because the platform and multiple WECs move in response to waves simultaneously as a 'multi-body' system, hydrodynamic interactions between these entities come into play. Additionally, the power take-off (PTO) mechanism between the platform and individual WECs is introduced for power production. First, the hydrostatic/dynamic coefficients required for numerical analysis were calculated in the frequency domain and then used in the time domain analysis. These simulations are performed using the extended HARP/CHARM3D code developed from previous studies. By conducting regular wave simulations, the response amplitude operator (RAO) for the platform of both single-body and multi-body scenarios was derived and subsequently compared. Next, to ascertain the difference in response in the real sea environment, this study also includes an analysis of irregular waves. As the floating body maintains its position through connection to a catenary mooring line, the impact of the slowly varying wave drift load cannot be disregarded. To assess the influence of the 2nd-order wave exciting load, irregular wave simulations were conducted, dividing them into cases where it was not considered and cases where it was included. The analysis of multi-degree-of-freedom behavior confirmed that the action of multiple WECs had a substantial impact on the platform's response.

Driving Current Control for Time-Stable RGB LED Backlighting Using Time-Varying Transform Matrix (시변 변환 행렬을 이용한 시간에 안정된 RGB LED Backlighting 구동 전류 제어)

  • Park, Kee-Hyon;Ha, Yeong-Ho
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.46 no.4
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    • pp.42-49
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    • 2009
  • This paper proposes a driving current control method for a back light unit (BLU), consisting of red, green, and blue (RGB) light-emitting diodes (LEDs), whereby an RGB optical sensor is used to check the output color stimulus variation to enable a time-stable color stimulus for light emission by the RGB LED BLU. First, to obtain the present color stimulus information of the RGB LED BLU, an RGB to XYZ transform matrix is derived to enable CIEXYZ values to be calculated for the RGB LED BLU from the output values of an RGB optical sensor. The elements of the RGB to XYZ transform matrix are polynomial coefficients resulting from a polynomial regression. Next, to obtain the proper duty control values for the current supplied to the RGB LEDs, an XYZ to Duty transform matrix is derived to calculate the duty control values for the RGB LEDs from the target CIEXYZ values. The data used to derive the XYZ to Duty transform matrix are the CIEXYZ values for the RGB LED BLU estimated from the output values of the RGB optical sensor and corresponding duty control values applied to the RGB LEDs for the present, first preceding, and second preceding sequential check points. With every fixed-interval check of the color stimulus of the RGB LED BLU, the XYZ to Duty transform matrix changes adaptively according to the present lighting condition of the RGB LED BLU, thereby allowing the RGB LED BLU to emit the target color stimulus in a time-stable format regardless of changes in the lighting condition of the RGB LEDs.

The Experimental Study on the Evaluation of Tidal Power Generation Output Using Water Tank (수조를 이용한 조력발전량산정에 관한 실험적 연구)

  • Jeong, Shin-Taek;Kim, Jeong-Dae;Ko, Dong-Hui;Choi, Woo-Jung;Oh, Nam-Sun
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.20 no.2
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    • pp.232-237
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    • 2008
  • A method to generate electric power from small scale water tank. For this purpose, manufacturing tank is investigated, measuring water level change at any time, and finally comparing experimental and theoretical value, are performed. Inner and outer tank are made to simulate flood and ebb generation. Two sets of pipe are connected between tanks, and experiments are performed under varying flowrate. Coefficients of flowrate are calculated comparing water level change data and theoretical value. Measured and theoretical water levels are highly correlated, and this ascertains that analytical equation simulates real water level changes well. Flowrate change depending on the existence of propeller and valve, on flood and ebb generation, shows the necessity of experiments in the process of manufacturing electric power system. Moreover, total energy calculated from experimental data agrees well with that of theoretical equation. In spite of small tidal power output, this generating system with optimum water tank can be applied to any place where high water level change occurs, and can make a contribution to producing new and renewable energy consequently.

Estimation of BDI Volatility: Leverage GARCH Models (BDI의 변동성 추정: 레버리지 GARCH 모형을 중심으로)

  • Mo, Soo-Won;Lee, Kwang-Bae
    • Journal of Korea Port Economic Association
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    • v.30 no.3
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    • pp.1-14
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    • 2014
  • This paper aims at measuring how new information is incorporated into volatility estimates. Various GARCH models are compared and estimated with daily BDI(Baltic Dry Index) data. While most researchers agree that volatility is predictable, they differ on how this volatility predictability should be modelled. This study, hence, introduces the asymmetric or leverage volatility models, in which good news and bad news have different predictability for future. We provide the systematic comparison of volatility models focusing on the asymmetric effect of news on volatility. Specifically, three diagnostic tests are provided: the sign bias test, the negative size bias test, and the positive size bias test. From the Ljung-Box test statistic for twelfth-order serial correlation for the level we do not find any significant serial correlation in the unpredictable BDI. The coefficients of skewness and kurtosis both indicate that the unpredictable BDI has a distribution which is skewed to the left and significantly flat tailed. Furthermore, the Ljung-Box test statistic for twelfth-order serial correlations in the squares strongly suggests the presence of time-varying volatility. The sign bias test, the negative size bias test, and the positive size bias test strongly indicate that large positive(negative) BDI shocks cause more volatility than small ones. This paper, also, shows that three leverage models have problems in capturing the correct impact of news on volatility and that negative shocks do not cause higher volatility than positive shocks. Specifically, the GARCH model successfully reveals the shape of the news impact curve and is a useful approach to modeling conditional heteroscedasticity of daily BDI.

Hardware Implementation of Real-Time Blind Watermarking by Substituting Bitplanes of Wavelet DC Coefficients (웨이블릿 DC 계수의 비트평면 치환방법에 의한 실시간 블라인드 워터마킹 및 하드웨어 구현)

  • 서영호;김동욱
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.3C
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    • pp.398-407
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    • 2004
  • In this paper, a blind watermarking method which is suitable to the video compression using 2-D discrete wavelet transform was proposed and implemented into the hardware using VHDL(VHSIC Hardware Description Language). The goal of the proposed watermarking algorithm is the authentication about the manipulation of the watermark embedded image and the detection of the error positions. Considering the compressed video image, the proposed watermarking scheme is unrelated to the quantization and is able to concurrently embed or extract the watermark. We experimentally verified that the lowest frequency subband(LL4) is not sensitive to the change in the spatial domain, so LL4 subband was selected for the mark space. And the combination of the bitplanes which has the properties of both the minimum degradation of the image and the robustness was chosen as the embedded Point in the mark space in LL4 subband. Since we know the watermark embedded positions and the watermark is embedded by not varying the value but changing the value, the watermark can be extracted without the original image. Also, for the security when exposing the watermark embedded position, we embed the encrypted watermark by the block cipher. The proposed watermark algorithm shows the robustness against the general image manipulation and is easily transplanted into the image or video compressor with the minimal changing in the structure. The designed hardware has 4037 LABs(24%) and 85 ESBs(3%) in APEX20KC EP20K400CF672C7 FPGA of Altera and stably operates in 82MHz clock frequency.