• Journal of Advanced Navigation Technology
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• v.24 no.2
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• pp.121-127
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• 2020

In this paper, we propose a dynamic spectrum hole grouping method that changes the grouping range of spectrum hole according to the resources amount required by secondary users in wideband spectrum cognitive wireless networks, and then the proposed method is applied to channel allocation for the secondary user service. The proposed method can improve waste of resources in the existing static spectrum hole grouping in virtue of grouping dynamically as much the predicted spectrum holes resources as secondary users require. Simulation results show that channel allocation method with the proposed dynamic grouping outperforms that with the static grouping method in resources utilization under acceptable secondary user service performance.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.2 s.72
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• pp.213-219
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• 2006

Topology optimization problem requires numerous repeated evaluations of objective function and design sensitivity for elements within design domain with various density distributions. The recently proposed two-level condensation scheme(TLCS) is very promising for the construction of reduced system and for an accurate and efficient analysis concerned about eigenvalue and dynamic problems. We used the two-level dynamic condensation scheme for the analysis and sensitivity computation part in the structural topology optimization problem. The results of the topology optimization for the reduced system show the TLCS provides high accuracy and computation efficiency compared to the full scale system within engineering accuracy.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.12
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• pp.995-1006
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• 1989

If robots have the ability to track the parts on a moving conveyor belt, the efficiency of the manipulation tasks will be increased. This paper presents a motion planning algorithm for conveyor tracking. Tracking trajectory of a robot manipulator is determined by belt speed, initial part position, and initial robot position. Torque limit, maximum velocity, maximum acceleration and maximum jerk are also taken into account. To obtain the tracking solution, the problem is converted to the linear quadratic tracking problem. We describe the manipulator dynamics as second order state equation using parametric functions. Constraints on torques and smoothness are converted to those on input and state variables. The solution of the state equation which minimizes the performance index is obtained by dynamic programming method. Numerical examples are then presented to demonstrate the utility of the motion planning method developed.

• Journal of Korea Multimedia Society
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• v.11 no.9
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• pp.1277-1285
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• 2008

In this paper, we first design the block diagram of the components for multi-mode SDR terminal based on SCA technology. It support both WIMAX mode and HSDPA mode. Then from the result of the analysis with a real SDR terminal implementation, we analyze which components of it have to be more lightweight. In addition we derive the general formula for the measure of dynamic reconfiguration time on the reconfiguration of the components. Finally we present a dynamic component-level reconfiguration algorithm with 22 stages based on the result of our analysis without violating the interface and procedure of SCA specification.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.39-42
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• 2010

최근 보행자가 교량의 진동에 의한 불안감을 느끼는 경우가 발생되면서 설계 단계에서 진동에 대한 고려하고 있다. 그러나 설계자는 범용유한요소프로그램에 이동하중을 적용하여 동적응답해석을 하는 것에 어려움을 느끼고 있으며 그 결과 Meister감각곡선에 의한 진동사용성 평가도 정확히 수행되지 않고 있다. 본 연구에서는 설계자들이 수행하는 교량의 진동사용성 평가방법의 간편한 적용을 위하여 이동하중모델 생성툴을 연구하였으며, 범용유한요소프로그램으로 모델링 된 교량의 매개변수를 변화해가며 진동사용성 평가를 수행하였고 연구 결과 중 매개변수의 하나인 보요소의 길이에 따른 진동사용성 평가결과만을 작성하였다. 평가결과 보요소의 길이에 따라 교량에 발생되는 진동과 가속도의 응답치가 다르게 나타났으며, 발생되는 주요주파수 범위도 다르게 해석되었다. 이러한 동적응답의 결과가 다르게 해석되면서 Meister 감각곡선에 의한 평가등급이 차이도 발생되었다. 따라서 정확한 진동사용성 평가를 위해서는 동적응답해석 시 다양한 매개변수에 의한 동적응답의 결과에 대한 연구는 물론 다양한 교량 형식과 그에 맞는 모델링에 대한 많은 연구가 필요할 것으로 사료된다.

• Journal of Broadcast Engineering
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• v.16 no.6
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• pp.1047-1057
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• 2011

In this paper, we propose a novel tone mapping method that implements histogram modification framework on two local regions that are classified using K-means clustering algorithm. In addition, we propose automatic parameter tuning method for histogram modification. The proposed method enhances local details better than the global histogram method. Moreover, the proposed method is fully automatic in the sense that it does not require intervention from human to tune parameters that are involved for computing tone mapping functions. In simulations and experimental studies, the proposed method showed better performance than existing histogram modification method.

• The Journal of the Acoustical Society of Korea
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• v.15 no.2
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• pp.49-54
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• 1996

In this paper, a photorefractive crystal is utilized as an output device, specifically as a time integrating detector for an acousto-optic correlator. In a standard time integrating acousto-optic architecture which uses CCDs, the output correlation signal is presented which includes bias. This results in a limitation on the effective dynamic range of the correlator. In a photorefractive crystal, light without spatial variation does not produce a cumulative bias signal and hence when the photorefractive crystal is used as the integrating detector, the correlation signal can be recorded and read out without bias. Important characteristics such as linearity dynamic range and integration time are also presented in this paper.

• Journal of the Institute of Convergence Signal Processing
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• v.11 no.2
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• pp.104-111
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• 2010

This paper presents an adaptive image enhancement method using the spatial frequency property in the DCT(discrete cosine transform) compressed domain. The dc coefficients, the illumination components of image, are adjusted to compress the dynamic range of image, and the ac coefficients are modified to enhance the contrast by using the human visual system(HVS) and the spatial frequency property. The ac coefficients are separated into vertical direction, horizontal direction, and mixed spatial frequency components, and adaptively modified to minimize the block artifacts that possibly occur in the image enhancement. The proposed method using dynamic range compression and adaptive contrast enhancement shows the advanced performance without the block artifact compared with existing method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.4
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• pp.322-331
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• 1988

In this thesis, an active RC filter using high order inverse chebyshev function is designed and the design method for cascading blocks with low sensitivity and maximum dynamic range is discussed. To have maximum dynamic range, we have proposed the simple algorithm with a pole-zero pairing, the cascading sequence by flatness matrix and optimum gain distribution for a given transfer function. And 2nd order Block is designed with negative feedback to improve the sensitivity problem which had a defect at active RC circuits. Using the suggested method, we have designed the active RC low pass filter of the normalized 7th order inverse chebyshev function, as a results, we have shown that this accord with the given specification.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.11
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• pp.1607-1617
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• 1993

The performance of Manchester-coded ASK optical wavelength division multiplexing(WDM) systems is evaluated laking into account the shot noise and the four wave mixing(FWM) caused by fiber nonlinearities. The result is compared to conventional non-return-to-zero(NRZ) systems for ASK modulation formats. Further, the dynamic range, defined as the ratio of the maximum input power(limited by the FWM), to the minimum input power(limited by receiver sensitivity), is evaluated. For 1.55 rm 16 channel WDM systems, the dynamic range of ASK Manchester coded systems shows a 2.0 dB improvement with respect to the NRZ. This result holds true for both dispersion-shifted fiber and conventional fiber it has been obtained for 10 GHz channel spacing, 1 Gbps/channel bit rate.