• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.406-409
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• 1997

An economical 4-axis CNC controller employing step motors is designed and implemented in this paper. By using the inherent ability of holding position of the motor, the CNC controller uses open-loop control for removing trajectory error and for a simple hardware. Each drive of axis has an 8-bit microprocessor 89C52 and a PC controls the axes and pendant by means of RS232C serial communication. Backlash is also compensated at the axis controller. While compensating the backlash, the feed rate becomes zero in order to minimize trajectory error. The trajectories of 16ms interval are computed on PC and are sent to motor drives. In the drives, the trajectories are linearly interpolated for 2ms interval. The developed CNC does not require add-on specific motion card on PC. From the experimental results, the validity of the CNC controller based on step motor is proved.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2471-2473
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• 2005

We present a receding horizon control [RHC] algorithm for compensation of backlash at the input of a stable linear system under control rate constraints. The problem is posed as a receding horizon optimal control [RHOptC] problem for a piecewise affine [PWA] system by modelling the backlash nonlinearity as a PWA system with a state space partition consisting of three regions. The RHC problem involves solving, at each step, $3^N$ quadratic programmes[QP], where N is the optimization horizon. This strategy leads, at the cost of some performance degradation, to much smaller computational load since a feasible rather than optimal solution has to be obtained at each step.

• Journal of information and communication convergence engineering
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• v.3 no.1
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• pp.56-61
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• 2005

In this paper, we present a video rate control scheme for storage and delivery in which the time-varying viewing interests are controlled by human gaze. To track the gaze, the pupil's movement is detected using the three-step process : detecting face region, eye region, and pupil point. To control bit rates, the quantization parameter (QP) is changed by considering the static parameters, the video object priority derived from the pupil tracking, the target PSNR, and the weighted distortion value of the coder. As results, we achieved human interfaced visual model and corresponding region-of-interest rate control system.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.327-330
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• 2005

In this paper, we proposed that technique for reducing trailing artifact in MPEG-4 video. low bit-rate video is occured trailng artifact which remain part of moving object. Because MEMC doesn't work well in the degraded video. The proposed trailing artifact reduction approach has at its core three main steps. First step is to detect trailing artifact. Second step is applied intra block coding to remove trailing artifact. Finally, bit-rate control algorithm is used. Experimental result using an MPEG-4 based encoder indicate that the proposed method has overhead(bits) of about 2 percent and proposed method effective reduce or eliminate trailing artifact

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8C
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• pp.756-763
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• 2009

The Least Mean Square (LMS) algorithm is often used to restore signal corrupted by additive noise. A major defect of this algorithm is that the excess Mean Square Error (EMSE) increases linearly according to speech signal power. This result reduces the efficiency of performance significantly due to the large EMSE around the optimum value. Choosing a small step size solves this defect but causes a slow rate of convergence. The step size must be optimized to satisfy a fast rate of convergence and minimize EMSE. In this paper, the Instantaneous Gain Control (IGC) algorithm is proposed to deal with the situation as it exists in speech signals. Simulations were carried out using a real speech signal combined with Gaussian white noise. Results demonstrate the superiority of the proposed IGC algorithm over the LMS algorithm in rate of convergence, noise reduction and EMSE.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.10
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• pp.1814-1829
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• 2011

In this paper, we present a model-based video bit rate estimation scheme for reducing the bit rate while maintaining a given target quality in many video streaming services limited by network bandwidth, such as IPTV services. Each item of video content can be stored on a video streaming server and delivered with the estimated bit rate using the proposed scheme, which consists of the following two steps: 1) In the first step, the complexity of each intra-frame in a given item of video content is computed as a frame feature to extract a group of candidate frames with a lot of bits. 2) In the second step, the bit rate of the video content is determined by applying statistical analysis and hypothesis testing to that group. The experimental results show that our scheme can reduce the bit rate by up to 78% with negligible degradation of subjective quality, especially with the low-complexity videos commonly used in IPTV services.

• Journal of Korean Biological Nursing Science
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• v.4 no.1
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• pp.5-23
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• 2002

Purpose: To determine the effect of the Fall Prevention Program(EPP) on gait, balance and muscle strength in elderly women at a nursing home. Method: The subjects of this consisted of 38 elderly women between the ages of 70 to 89 years living at a nursing home located in Seoul. Each of the experimental group and control group was composed of 19 subjects. The subjects in experimental group have participated in FPP for the 8 weeks which consisted of exercise, education and foot care. They started to exercise for 40 minutes per session, 3 sessions a week during the 1st week at 40% of age adjusted maximum heart rate. From the 2nd week to the 4th week, they increased the duration of exercise to 50 minutes per session and the intensity to 60% of age-adjusted maximum heart rate. They participated in 50 minutes at 60% of age-adjusted maximum heart rate from the 5th week to the 8th week. Each exercise session consisted of 10 minutes of warming-up exercise, 30 minutes of conditioning exercise and 10 minutes of cooling-down exercise. They participated in education for 20 minutes per week from the 1st week to the 4th week. Then they participated in a 30-minute foot care program per week from the 5th week to the 8th week. Gait, balance and muscle strength for each subject were measured before and after FPP. Gait was evaluated by step length, step width, gait speed and walking distance. Balance was measured by the duration of standing on one leg with their eyes closed and open each, and a get-up and go test. Grip strength was measured by hand dynamometer. Hip extensor and flexor strength, knee extensor and flexor strength and ankle plantarflexor and dorsiflexor strength were measured by manual muscle tester. Data was analyzed using SPSS form Windows. t-test and Chi square test were utilized as a homogeneity test. Repeated measure ANOVA was used to test the effect of FPP. Result: 1) Step width significantly decreased, and step length, gait speed and walking distance significantly increased in the experimental group compared with the control group after FPP(p<0.005). 2) There was no significant change in standing time on one leg with their eyes closed after FPP. The standing time on leg with their eyes open and the time of "get-up and go" significantly decreased in the experimental group compared with the control group after FPP(p<0.005). 3) Muscle strength-grip strength, hip extensor and flexor strength-significantly increased in the experimental group compared with the control group after FPP(p<0.005). 4) There was no significant difference of frequency of fall between the experimental group and control group during the period of FPP. Conclusion: These results suggest that FPP can increase gait, balance and muscle strength of elderly women at a nursing home.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.6
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• pp.88-94
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• 2005

A swirl ratio of a charge in the cylinder could be calculated by measuring both the rotary speed of paddle and the intake air flow rate in the swirl measurement apparatus fur several positions of valve lift. The automation of the swirl ratio measurement for a cylinder head is achieved by controlling both the valve lift of cylinder head and a suction pressure of the surge tank, instead of controlling them manually. PID control of the surge tank pressure and positioning a valve lift of the cylinder head are also achieved by using two step motors, respectively. Rotating speed of a paddle are measured using an optical sensor and a counter. Flow rate are measured from ISA 1932 flow nozzle by reading a differential pressure gauge position using IEEE-1394 camera. Time to measure the swirl ratio for a port in the cylinder head is drastically reduced from an hour to 3 minutes by automation control of the apparatus.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.2
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• pp.15-20
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• 2012

This study is to propose and develop an integrated dynamics control system to improve and enhance the lateral stability and handling performance. To achieve this target, we integrate an AFS and a 4WS systems with a fuzzy logic controller. The IDCS determines active additional steering angle of front wheel and controls the steering angle of rear wheel. The results show that the IDCS improves the lateral stability and controllability on dry asphalt and snow paved road when double lane change and step steering inputs are applied. Yaw rate of the IDCS vehicle tracks reference yaw rate very well and body slip angle is reduced about by 50%. Response time of the IDCS vehicle is also decreased.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.454-458
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• 2004

A new algorithm for the rate control of videos considering the sensitivity of the human visual system is presented. The method adopts the three-step structure of MPEG2 TM5 rate control, and a new measure of macroblock activity based on spatio-temporal sensitivity is introduced for the adaptive quantization. Experimental results show that the spatio-temporal activity measure outperforms the spatial activity of TM5 in picture quality.