• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.4
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• pp.47-52
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• 2006

Using the equivalent ARMA model representation of the mixed random errors, we propose Klaman filter design methods for aided INS(Inertial Navigation System) which contains the gyroscope mixed random errors. At first step, considering the characteristic of indirect feedback Kalman filter used in the aided INS, we perform the time difference of equivalent ARMA model. Next, according to the order of the time differenced ARMA model, we achieve the state space conversion of that by two methods. If the order of AR part is greater than MA part, we use controllable or observable canonical form. Otherwise, we establish the state apace equation via the method that several step ahead predicts are included in the state variable, where we can derive high and low order models depending on the variable which is compensated from gyroscope output. At final step, we include the state space equation of gyroscope mixed random errors into aided INS Kalman filter model. Through the simulation, we show that both the high and low order filter models proposed give less navigation errors compared to the conventional filter which assume the mixed random errors as white noise.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.2C
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• pp.110-120
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• 2003

In this paper, we propose a Multiresolution Motion Estimation(MRME) adapted to Low-Band-Shift(LBS) method in wavelet domain. To overcome shift-variant property on wavelet coefficients, the LBS was previously proposed. This method which is applied to reference frame in video coding technique, has superior performance in terms of rate-distortion characteristic. However, this method needs more memory and computational complexity. In this paper, The computational complexity of the proposed method(LBS-MRME) is about 15.6% of that of existing method at 3-level wavelet transform. And although it has about 7 times as much as existing method's motion vector since each subband has different motion vector, it decreases motion compensated prediction error by detailed motion estimation, and then has better efficient coding performance. The experimental results with the proposed method showed about 0.3∼11.6% improvement of MAD performance in case of lossless coding, and 0.3∼3.0㏈ improvement of PSNR performance at the same bit rate in case of lossy coding.

• Journal of Broadcast Engineering
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• v.19 no.1
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• pp.64-74
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• 2014

The primary and ambient signal decomposition of a stereo sound is a key step to the stereo upmix. The principal component analysis (PCA) is one of the most widely used methods of primary-ambient signal decomposition. However, previous PCA-based decomposition algorithms assume that stereo sound sources are only amplitude-panned without any consideration of phase difference. So it occurs some performance degradation in case of live recorded stereo sound. In this paper, we propose a new PCA-based stereo decomposition algorithm that can consider the phase difference between the channel signals. The proposed algorithm overcomes limitation of conventional signal model using PCA with phase alignment. The phase alignment is realized by using inter-channel phase difference (IPD) which is widely used in parametric stereo coding. Moreover, Enhanced Modified PCA(EMPCA) is combined to solve the problem of conventional PCA caused by Primary to Ambient energy Ratio(PAR) and panning angle dependency. The simulation results are presented to show the improvements of the proposed algorithm.

• Journal of the Institute of Convergence Signal Processing
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• v.8 no.2
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• pp.113-118
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• 2007

In this paper, a novel approach to using Subcircuit of Pspice in designing feedback for DC-DC converter systems is proposed. Proposed new approach, the feedback design procedures which are based on small signal modeling are programmed as a subcircuit in Pspice. For this purpose, Analog Behavioral Modeling (ABM) is used. By using the subcircuit, the component values of the error compensation amplifier can be easily obtained by means of Pspice DC analysis. The methodology of development is presented in detail and application examples demonstrated the effectiveness of the proposed approach in designing feedbacks for DC-DC converters. The converter with PWM method used continuous current mode and calculated buck converter control signal with average and linear current technique. To decide pole and zero K-method was adapted and this kind of design procedure took stable function.

• Survey Research
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• v.9 no.2
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• pp.51-83
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• 2008

While online surveys are considered to be the viable alternative to face-to-face and telephone surveys, many clients express a strong concern about the possibility of unreliable responses. Given this concern, survey experts hypothesize that amounts of time on responding can represent the extent to which respondents fill out the questions with sincerity. This study examines this hypothesis using data from an online survey sample of 1.052. Results strongly suggest that while "long time" informants are reliable, "short time" informants are not. Those in the short time group spend only 2.4 seconds per question and show very different patterns of responses to 49 Likert -typed questions. Logistic regression results imply that these unreliable respondents are interested in monetary gifts and maybe as a result, participate in surveys much more frequently. In conclusion, we provide some implications of these results to the quality of online surveys.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.6
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• pp.555-563
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• 2015

This paper presents signal processing algorithms of a frequency-modulated continuous-wave(FMCW) radar altimeter and provides a practical assessment technique. The radar altimeter is initially operated in search mode, when the radar altimeter detects a valid altitude, search mode is switched to track mode and a altitude being tracked is displayed. The sweep bandwidth in each mode is a function of altitude to narrow the beat frequency bandwidth. In addition, transmit power and receiver gain in each mode are controlled to compensate for the dynamic range of wide altitude range. To assess more realistic operation, the radar altimeter was tested using the crane setup. The crane test demonstrated that signal processing algorithms described in this paper resulted in a reduced measurement error rate.

• Journal of the Institute of Convergence Signal Processing
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• v.9 no.1
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• pp.89-97
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• 2008

Chaotic behavior in motor systems is undesired dynamics in real-time implementation since the speed is oscillated in a wide range and the torque is changed by a random manner. We present an adaptive control approach for time-varying permanent-magnet synchronous motors (PMSM) with chaotic phenomenon. We consider that its parameters are changed randomly within certain bounds. First, a nonlinear system model of a PMSM is transformed to derive a nominal linear control strategy. Then, an auxiliary control for compensating real-time control error occurred by system perturbation due to parameter change is designed by using Lyapunov stability theory. Numerical simulation is accomplished for evaluating its efficiency and reliability comparing with the traditional control method. Additionally, we test our control method in real-time motor experiment including a PSoC based drive system to demonstrate its practical applicability.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.49 no.2
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• pp.69-75
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• 2012

This paper presents a novel de-interlacing algorithm that can make up motion compensation errors by using maximum a posteriori (MAP) estimator. First, a proper registration is performed between a current field and its adjacent fields, and the progressive frame corresponding to the current field is found via MAP estimator based on the computed registration information. Here, in order to obtain a stable solution, well-known bilateral total variation (BTV)-based regularization is employed. Next, so-called feathering artifacts are detected on a block basis effectively. So, edge-directional interpolation is applied to the pixels where feathering artifact may happen, instead of the above-mentioned temporal de-interlacing. Experimental results show that the PSNR of the proposed algorithm is on average 4dB higher than that of previous studies and provides the better subjective quality than the previous works.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.4 s.316
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• pp.21-26
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• 2007

Output voltage waves of a DC/AC inverter system are likely to be distorted if variable loads e.g. motors or rectifiers exist in the output terminal. This paper designs a disturbance observer-based PI-controller for a single-phase inverter system that is robust against load changes. In this Paper, we regard the output voltage changes due to various loads as disturbances of the control system. Then we design a disturbance observer for estimation of the disturbances caused by the load current and any other error sources (such as parameter uncertainties and model mismatches etc.). In order to test the performance of the proposed control law, simulation studies are carried out for a single-phase inverter system using SimPowerSystem of Matlab Simuink. Compared to a simple PI-control, the disturbance observer-based controller shows enhanced performance in transient responses for step load changes.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.12
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• pp.1079-1085
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• 2010

A steady-state analytical model was presented for a loop heat pipe (LHP) with an evaporator that has a flat geometry. On the basis of a series of reviews of the relevant literature, a sequence of calculations was proposed to predict the temperatures and pressures at each important part of the LHP: the evaporator, liquid reservoir (compensation chamber), liquid line, vapor line, and condenser. The analysis of the evaporator, which is the only part in the LHP that has a capillary structure, was emphasized. Thin-film theory is applied to account for the pressure and temperature in the region adjacent to the liquid-vapor interface in the evaporator. The present study introduced a unique method to estimate the liquid temperature at the interface. Relative freedom was assumed in the configuration of a condenser with a simplified liquid-vapor interface. Our steady-state model was validated by experimental results available in the literature. The relative error was within 3% on the absolute temperature scale, and reasonable agreement was obtained.