• Korean Security Journal
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• no.41
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• pp.241-261
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• 2014

The main objective of this research was to grasp using a structure equation analysis if an auxiliary police officer unit's measure of getting rid of assault gets to their adaptation to the unit through stress factor to reveal the cause of an auxiliary police officer unit's adaptation to unit. The data used for the research is survey data of all auxiliary police officer belonging to Ulsan Metropolitan Police Agency in 2011. The result of structure equation analysis showed that the mediated effect through stress was statistically meaningful in the level of p<.001. Also, the result of confirming the size of effect through standardized regression coefficients was that the effect of stress upon the adjustment to units was higher than the effect of unit's measure of getting rid of assault. Namely, unit's measure of getting rid of assault has a positive effect upon a conscripted policemen unit's adaptation to unit, but it showed that an auxiliary police officer unit's adaptation to unit had the bigger individual stress factor than that of unit's measure of getting rid of assault. From this, authorities should recognize that an auxiliary police officer's stress is a cause to determine their adaptation to units, and prepare its alternative.

• The Journal of the Korea institute of electronic communication sciences
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• v.4 no.1
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• pp.66-69
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• 2009

An adaptive echo canceller is necessary for an application such as a speakerphone, 3G image telephony and VoIP service system. These echo cancellers need to have many taps for filtering echo signals. Many taps cause computation data to increase and convergence speed to be low. To overcome these problems, An adaptive echo canceller with the advanced convergence speed is proposed in this paper. To improve the speed, we divide an echo band into subbands and place a subband filter to be adaptive for each subband. Each subband filter recognizes the echo signal as subband echo signals. So, dynamic range of subband is small, the convergence speed is fast. Moreover, as the number of Tap and weight update are estimated in each subband, the implementation complex of a adaptive filter is low.

• Journal of IKEEE
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• v.17 no.2
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• pp.111-118
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• 2013

In this paper, the subband nonlinear adaptive Volterra filters are introduced and its analysis are presented. From the eigenvalue analysis of the input correlation matrix, we show that the proposed subband adaptive Volterra filter has superior convergence performance as compared to the conventional one, which shows that the it can be useful for the recently proposed subband nonlinear adaptive echo canceller. Also, the optimum filter in each subband are introduced and verified from the computer simulations.

• The Journal of the Acoustical Society of Korea
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• v.21 no.1
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• pp.62-68
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• 2002

It is well known that the MDVR beamforming outperforms the conventional delay-sum beamformer in the sense of noise rejection and bearing resolution. However, the MDVR method requires long observation time to achieve high frequency resolution. The STMV method uses the steered covariance matrix of sensor data, so it has an ability to form an adaptive weight vector from a single time-series snapshot. But it uses the same weight vector across all frequencies. In this paper, we propose an SSMV method. The basic idea of the SSMV method is to decompose a full frequency band into several subbands to acquire a weight vector for each subband, individually. Also the wrap may be divided into several subarrays in order to reduce a computational load and the bandwidth of each subband. Simulations using real sea trial data show that the proposed SSMV method has good performance with short observation time.

• Journal of IKEEE
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• v.21 no.3
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• pp.202-210
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• 2017

Recently, some variable length adaptive filters which employ variable lengths taps for the input signal statistics are proposed [1-5]. In this paper, a new subband adaptive filter with variable filter tap length is proposed. The proposed subband variable length adaptive filters can optimize filter length for each subband which can result less computational complexities with respect to the conventional full band adaptive filters. When the signal in the full band has narrow spectrum, the conventional full band adaptive requires very long filter taps, whereas the proposed subband variable filter requires less taps with the spectrum split in subband. The computer simulation results reveals that in many case, in system identification with narrow band system estimation, the proposed adaptive filter has less computational complexities with faster convergence.

• Journal of Broadcast Engineering
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• v.8 no.2
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• pp.204-208
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• 2003

In this paper, a new matrix vector formulation for a wavelet-based subband decomposition is introduced. This formulation provides a means to compute a regular multi-resolution analysis over many levels of decomposition. With this approach. any single channel linear space-invariant filtering problem can be cast into a multi-channel framework. This decomposition Is applied to the linear space-invariant image restoration problem and propose a frequency-adaptive constrained least squares(CLS) filter. In the proposed filter, we use different parameters adaptively according to subband characteristics. Experimental results are presented for the proposed frequency-adaptive CLS filter These experiments show that if accurate estimates of the subband characteristics are available, the proposed frequency adaptive CLS filter provides significant improvements over the traditional single channel filter.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06b
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• pp.63-65
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• 2012

최근 군사 모의 소프트웨어는 사용자의 다양한 요구 변화에 빠르게 적응하기 위해 컴포넌트를 조합하여 구성하는 방법으로 개발되고 있다. 이와 같은 소프트웨어에서 부대의 과업을 달성하기 위해 사용자의 관여 없이 부대구성원(부대원 또는 예하부대)의 전술적 행위(협업)를 모의하는 기술은 대규모의 군사 모의를 가능하게 하는 중요한 기술 중 하나이다. 부대 구성원의 협업을 모델링하고 구현하는 기술은 사용자(모의 부대장)로 하여금 부대구성원의 세부적인 제어를 요구하지 않고 자신이 제어하는 부대에 할당된 임무 달성에 집중시키는 등의 이점을 제공한다. 본 연구를 통해 우리는 군 도메인에서 사용하고 있는 OneSAF와 FLAMES, VR-Forces 등의 컴포넌트 기반의 모의 소프트웨어를 분석하고, 이들 소프트웨어에서 협업 모델의 위치를 설명한다. 다음으로 역할 개념을 기반으로 부대구성원들의 협업 모델을 제안한다. 본 연구에서는 프로토타입의 개발을 통해 제안 모델의 적용 가능성을 검증한다.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.37 no.6
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• pp.32-40
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• 2000

In this paper, we proposed a wavelet-based digital watermarking algorithm using human visual system and subband-adaptive threshold. After the original image is transformed by discrete wavelet transform, the perceptually significant coefficients of the each subband excluding the lowest level subbands are utilized to embed the watermark. To select perceptually significant coefficients for each subband, we use subband-adaptive threshold. For the selected coefficients in the high frequency subbands, the watermark is embedded using HVS. For those of the baseband, the watermark is embedded by conventional embedding method. We tested the performance of the proposed algorithm compared with conventional watermarking algorithm by computer simulation. The experimental results show that the proposed watermarking algorithm is less visible to human eyes and more robust to image compressions, image processings, and geometric transformations than the conventional algorithm.

• Journal of Korea Multimedia Society
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• v.6 no.7
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• pp.1149-1158
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• 2003

Content adaptive watermark embedding algorithm using a stochastic image model in the multiwavelet transform is proposed in this paper. A watermark is embedded into the perceptually significant coefficients (PSCs) of each subband using multiwavelet transform. The PSCs in high frequency subband are selected by SSQ, that is, by setting the thresholds as the one half of the largest coefficient in each subband. The perceptual model is applied with a stochastic approach based on noise visibility function (NVF) that has local image properties for watermark embedding. This model uses stationary Generalized Gaussian model characteristic because watermark has noise properties. The watermark estimation use shape parameter and variance of subband region. it is derive content adaptive criteria according to edge and texture, and flat region. The experiment results of the proposed watermark embedding method based on multiwavelet transform techniques were found to be excellent invisibility and robustness.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6C
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• pp.512-522
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• 2005

In this paper, an optimal determination method of the subband-frame size and mode-switching level is proposed for adaptive OFDM-TDD systems in frequency-selective time-varying channels. The optimization problem considering frequency selectivity. user's mobility, and the signaling overhead caused by the mode change information is formulated in the maximum spectral efficiency sense satisfying the target BER. Assuming that subband-frame size is given, the mode-switching level is first optimized so that the spectral efficiency can be maximized satisfying the target BER. The subband-frame size among candidates is then determined, which maximizes the spectral efficiency. Simulation results show that the proposed scheme outperforms conventional schemes, in terms of the spectral efficiency and the BER.