• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.12A
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• pp.1380-1386
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• 2004

Future communication networks would consist of wired and wireless access networks where there would be various types of traffic services. To meet the QoS requirements of those various traffic services simultaneously, new QoS control schemes are required. Since they are simple to deploy, cheep to manage, and easy to support subscriber mobility, wireless access networks are considered here. In this paper, a wireless joint buffer management and scheduling (W-JoBS) scheme, which is a modified version of the original JoBS algorithm at error-prone wireless access networks, is proposed. W-JoBS scheme is for providing service fairness among traffic classes with service compensation and channel-state dependent packet scheduling schemes. With computer simulation, this proposed W-JoBS scheme is evaluated and the performance of W-JoBS is compared with that of the original JoBS.

• Journal of Biomedical Engineering Research
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• v.23 no.3
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• pp.243-251
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• 2002

Synthetic zinc wave employs Pulsed plane wave as transmit beam with linear time delay curve. The received echoes in different transmit directions at different transmit times are superposed at imaging Points with Proper time delay compensation using synthetic focusing scheme. This scheme. which uses full aperture in transmit, obtains a high SNR image, and also features high lateral resolution by using two way dynamic focusing at all imaging depths. In this Paper, we consider the Problems in realization of synthetic zinc wave. Also. we have applied the scheme to obtain phantom and in-vivo images using a linear array of 5 MHz. In phantom test. experimental images show high resolution over a more extended imaging depth than conventional fixed Point transmit and receive dynamic focusing schemes In-vivo images show that the resolution could not overcome conventional focusing systems because of motion blurring and(or) aberration of tissue. but the frame rate tan be increased by a factor of more than 5 compared to conventional focusing schemes. with competitive resolution at all imaging depths .

• Journal of KIISE:Information Networking
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• v.27 no.2
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• pp.109-122
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• 2000

As the full-motion videos in MPEG are widely available nowadays, an editor that could easily edit such kind of media data is required to develop various multimedia applications. In order to concatenate and apply a transition effect to two video streams encoded in MPEG, they should be decoded first since there are dependencies in the frames in MPEG-encoded video stream. Since this decode-edit-encode process requires a huge amount of computing/storage resources, a new editing scheme that could apply various transition effects to MPEG video streams directly while keeping the quality of video data is strongly required. This paper proposes a new editing scheme that could apply three transition effects (such as fade-in, fade-out, and dissolve) to MPEG video streams in a compressed domain. In the proposed scheme, an extension of previous method in which the frames are partially decompressed and transition effects are applied is adopted for I- and P-frames. In addition, a new processing scheme for B-frame that could apply the transition effects in DCT domain directly using an approximation of motion compensation based on the motion vector to reference frames. Since this processing scheme could apply the transition effects in a compressed domain directly, the editing process could be speed-up about $3{\sim}4$ times faster than previous decode-edit-encoding method while keeping the quality of video data as good as the source data. The proposed scheme could be used to build a software-only MPEG video editing system that helps to edit MPEG video data even on a low-cost desk-top computer.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.3
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• pp.277-282
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• 2005

This paper describes a step-down AC voltage regulator using an AC chopper and auxiliary transformer, which is a series connected to the main input. The detail design of the AC regulator, logic and PWM pattern of the AC chopper is described and the three-phase AC regulator using two single­phase AC choppers with a three transformer configuration is proposed for three-phase application. The proposed three-phase system has the advantages of lower system cost due to reduced switch number and gate driver circuit as well as advantages of decreased size and weight because it uses a series compensated scheme. The proposed AC regulator has many benefits such as fast voltage control, high efficiency and simple control logic. Experimental results indicate that it can be used as a step-down AC voltage regulator for power saving purposes very efficiently.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.4
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• pp.117-122
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• 2006

Maximum efficiency control scheme in a stator flux-oriented induction motor drive is proposed for minimizing input dc power. Flux level is decreased in steps for searching the minimum input dc power. In addition, Torque equation, slip angular frequency, and decoupling compensation current considering iron loss resistance is used. Simulation and experimental results verify the effectiveness of the proposed method.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.436-442
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• 2015

In this paper, we develop an indoor localization device which embeds localization information into indoor light-emitting-diodes (LED) lighting systems. The key idea of our device is the use of the newly proposed "bit stuffing method". Through the use of stuff bits, our device is able to measure signal strengths even in transient states, which prohibits interference between lighting signals. The stuff bits also scatter the parts of the signal where the LED is turned on, thus provides quality indoor lighting. Additionally, for the indoor localization system based on RSSI and TDM to be practical, we propose methods for the control of LED lamps and compensation of received signals. The effectiveness of the proposed scheme is validated through experiments with a low-cost implementation including an indoor navigation task.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.11
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• pp.1560-1565
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• 2013

This paper proposes the control method for compensating for unbalanced grid current and reducing a total harmonic distortion (THD) of the grid current at the three-phase grid-connected inverter systems under unbalancd and distorted grid voltage conditions. The THD of the grid current caused by grid voltage harmonics is derived by considering the phase delay and magnitude attenuation due to the hardware low-pass filter (LPF). The Cauchy-Schwarz inequality theory is used in order to search more easily for a minimum point of THD. Both the gain and angle of a compensation voltage at the minimum point of THD of the grid current are derived. The negative-sequence components in the three-phase unbalanced grid voltage are cancelled in order to achieve the balanced grid current. The simulation and experimental results show the validity of the proposed control methods.

• ETRI Journal
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• v.23 no.4
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• pp.190-198
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• 2001

The performance of Motion Compensated Discrete Cosine Transform (MC-DCT) video coding is improved by using the region adaptive subband image coding [18]. On the assumption that the video is acquired from the camera on a moving platform and the distance between the camera and the scene is large enough, both the motion of camera and the motion of moving objects in a frame are compensated. For the compensation of camera motion, a feature matching algorithm is employed. Several feature points extracted using a Sobel operator are used to compensate the camera motion of translation, rotation, and zoom. The illumination change between frames is also compensated. Motion compensated frame differences are divided into three regions called stationary background, moving objects, and newly emerging areas each of which is arbitrarily shaped. Different quantizers are used for different regions. Compared to the conventional MC-DCT video coding using block matching algorithm, our video coding scheme shows about 1.0-dB improvements on average for the experimental video samples.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.12
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• pp.1256-1263
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• 2004

Output feedback passivation problem is studied when the given system is not minimum-phase or does not have relative degree one. Using a parallel connection with an additional dynamics, the authors provide a dynamic output feedback control law which renders the composite system passive. Sufficient conditions are presented under which the composite system is output feedback passive. As an application of the dynamic passivation scheme, a point-to-point control law for a flexible joint robot is presented when only the position measurements are available. This provides an alternative way of replacing the role of the velocity measurements for the proportional-derivative (PD) feedback law. The performance of the proposed control law is illustrated in the simulation studies of a manipulator with three revolute elastic joints.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.540-543
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• 1997

In this paper, a precise trajectory tracking method for mobile robot using a vision system is presented. In solving the problem of precise trajectory tracking, a hierarchical control structure is used which is composed of the path planer, vision system, and dynamic controller. When designing the dynamic controller, non-ideal conditions such as parameter variation, frictional force, and external disturbance are considered. The proposed controller can learn bounded control input for repetitive or periodic dynamics compensation which provides robust and adaptive learning capability. Moreover, the usage of vision system makes mobile robot compensate the cumulative location error which exists when relative sensor like encoder is used to locate the position of mobile robot. The effectiveness of the proposed control scheme is shown through computer simulation.