• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.265-266
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• 2007

New coding tools require the increase of the encoder complexity in H.264. In this paper we propose a fast mode decision method to reduce the computational complexity of mode decision. The simulation results shows that the proposed methods could reduce the coding time of overall sequences by 30% on average without any noticeable degradation of the coding efficiency.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.205-206
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• 2007

In stereo vision applications, disparity estimation is often performed to corresponding pixels. Using window-based correlations is a fast and standard approach to the disparity estimation. In this paper, we analyse the behaviour of the correlation-based disparity estimation and improve its performance by combining it with a segmentation scheme. Simulation results demonstrate that the proposed algorithm provides faithful disparity maps.

• Investigative Magnetic Resonance Imaging
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• v.4 no.1
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• pp.42-51
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• 2000

Purpose: Projection-type Fast Spin Echo (PFSE) imaging is robust to patient motion or flow related artifact compared to conventional Fast Spin Echo (FSE) imaging, however, it has difficulty in controlling $T_2$ contrast. In this paper, Tz contrast in the PFSE method is analyzed and compared with those of the FSE method with various effective echo times by computer simulation. The contrasts in the FSE and PFSE methods are also compared by experiments with volunteers. From the analysis and simulation, it is shown that ${T_2}-weighted$ images can well be obtained by the PFSE method proposed. Materials and methods: Pulse sequence for the PFSE method is implemented at a 1.0 Tesla whole body MRI system and $T_2$ contrasts in the PFSE and FSE methods are analyzed by computer simulation and experiment with volunteers. For the simulation, a mathematical phantom composed of various $T_2$ values is devised and $T_2$ contrast in the reconstructed image by the PFSE is compared to those by the FSE method with various effective echo times. Multi-slice ${T_2}-weighted$ head images of the volunteers obtained by the PFSE method are also shown in comparison with those by the FSE method at a 1.0 Tesla whole body MRI system. Results: From the analysis, $T_2$ contrast by the PFSE method appears similar to those by the FSE method with the effective echo time in a range of SO-lOOms. Using a mathematical phantom, contrast in the PFSE image appears close to that by the FSE method with the effective echo time of 96ms. From experiment with volunteers, multi-slice $T_2-weighted$ images are obtained by the PFSE method having contrast similar to that of the FSE method with the effective echo time of 96ms. Reconstructed images by the PFSE method show less motion related artifact compared to those by the FSE method. Conclusion: The projection-type FSE imaging acquires multiple radial lines with different angles in polar coordinate in k space using multiple spin echoes. The PFSE method is robust to patient motion or flow, however, it has difficulty in controlling $T_2$ contrast compared to the FSE method. In this paper, it is shown that the PFSE method provides good $T_2$ contrast (${T_2}-weighted$ images) similar to the FSE method by both computer simulation and experiments with volunteers.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.6
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• pp.1194-1201
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• 2003

Measurements of network traffic have shown that self-similarity is a ubiquitous phenomenon spanning across diverse network environments. We have advance the framework of multiple time scale congestion control and show its effectiveness at enhancing performance for fast TCP prototype control. In this paper, we extend the fast TCP prototype control framework to window-based congestion control, in particular, TCP. This is performed by interfacing TCP with a large time scale control module which adjusts the aggressiveness of bandwidth consumption behavior exhibited by TCP as a function of "large time scale" network state. i.e., conformation that exceeds the horizon of the feedback loop as determined by RTT. Performance evaluation of fast TCP prototype is facilitated by a simulation bench-mark environment which is based on physical modeling of self-similar traffic. We explicate out methodology for discerning and evaluating the impact of changes in transport protocols in the protocol stack under self-similar traffic conditions. We discuss issues arising in comparative performance evaluation under heavy-tailed workload. workload.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.3
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• pp.33-43
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• 2000

The guarantee of the fast dynamics stability is essential for successful application of singular Perturbation technique to control systems design. Even though the fast dynamics of the control systems is rendered stable by an analog controller, the fast dynamics stability of the control systems resulted from an digital implementation of the analog controller can be impaired severely. In this paper, we first investigate the time sampling effects on singular perturbation based control systems by centering on a design example of recently developed singular perturbation based STT missile autopilot with high performance. The investigation shows that the stability margin the fast dynamics of the STT misile autopilot system decreases rapidly as the sampling interval of discretizing the analog autopilot increases. Under this analysis, we propose a composite digital controller with compensation for the decreasing stability margin of the fast dynamics due to time sampling to achieve better performance with respect to sampling time. The improved performance of the proposed composite digital controller is verified by simulation. This result shows that one needs to investigate time sampling effects in the digital implementation of singular perturbation based controllder, and then can have benefit from the investigation.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.4
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• pp.11-20
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• 1998

Fault simulatior has been used to compute exact fault coverages of test vectors for digial circuits. But it is time consuming because execution time is proportional to square of circuit size. Recently, several algorithms for testability analysis have been published to cope with these problems. COP is very fast and accurate but cannot be used for sequential circuits, while STAFAN can be used for sequential circuits but needs vast amount of execution time due to good circuit simulation. We proposed EXTASEC which gave fast and accurate fault coverage. But it shows noticeable errors for a few sequential circuits. In this paper, it is shown that the inaccuracy is due to uninitializble flipflops, and we propose ITEM to improve the EXTASEC algorithm. ITEM is an improved evaluation method of fault coverage by analysis of backward lines and uninitializable flipflops. It is expected to perform efficiently for very large circuits where execution time is critical.

• Proceedings of the KIEE Conference
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• 2005.05a
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• pp.236-238
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• 2005

In this paper, we propose a new discrete-time predictive current controller for a PMLSM(permanent magnet linear synchronous motor). The main objectives of the current controllers are that the measured stator current is tracked the command current value accurately and the transient interval is shorten as much as possible, in order to obtain high-performance of ac drive system. The conventional predictive current controller is hard to implement in full digital current controller since a finite calculation time causes a delay between the current sensing time and the time that take to apply the voltage to motor. A new control strategy is the schema that gets the fast adaptation of transient current change, the fast transient response tracking. Moreover, the simulation results will be verified the improvements of Predictive controller and accuracy of the current controller.

• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.4
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• pp.534-542
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• 2017

This paper presents a fast locking technique for a fractional-N PLL frequency synthesizer. The technique directly measures $K_{VCO}$ on a chip, computes the VCO's target tuning voltage for a given target frequency, and directly sets the loop filter voltage to the target voltage before the PLL begins the normal closed-loop locking process. The closed-loop lock time is significantly minimized because the initial frequency of the VCO are put very close to the desired final target value. The proposed technique is realized and designed for a 4.3-5.3 GHz fractional-N synthesizer in 65 nm CMOS and successfully verified through extensive simulations. The lock time is less than $12.8{\mu}s$ over the entire tuning range. Simulation verifications demonstrate that the proposed method is very effective in reducing the synthesizer lock time.

• IEMEK Journal of Embedded Systems and Applications
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• v.11 no.6
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• pp.353-359
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• 2016

In this paper, we propose a high performance L1 cache structure for the high clock CPU. The proposed cache memory consists of three parts, i.e., a direct-mapped cache to support fast access time, a two-way set associative buffer to reduce miss ratio, and a way-select table. The most recently accessed data is stored in the direct-mapped cache. If a data has a high probability of a repeated reference, when the data is replaced from the direct-mapped cache, the data is stored into the two-way set associative buffer. For the high performance and fast access time, we propose an one way among two ways set associative buffer is selectively accessed based on the way-select table (WST). According to simulation results, access time can be reduced by about 7% and 40% comparing with a direct cache and Intel i7-6700 with two times more space respectively.

• The Journal of the Acoustical Society of Korea
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• v.31 no.7
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• pp.427-434
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• 2012

The overlap-add technique based on waveform similarity (WSOLA) method is known to be an efficient high-quality algorithm for time scaling of speech signal. The computational load of WSOLA is concentrated on the repeated normalized cross-correlation (NCC) calculation to evaluate the similarity between two signal waveforms. To reduce the computational complexity of WSOLA, this paper proposes a fast NCC computation method, in which NCC is obtained through pre-calculated sum tables to eliminate redundancy of repeated NCC calculations in the adjacent regions. While the denominator part of NCC has much redundancy irrespective of the time-scale factor, the numerator part of NCC has less redundancy and the amount of redundancy is dependent on both the time-scale factor and optimal shift value, thereby requiring more sophisticated algorithm for fast computation. The simulation results show that the proposed method reduces about 40%, 47% and 52% of the WSOLA execution time for the time-scale compression, 2 and 3 times time-scale expansions, respectively, while maintaining exactly the same speech quality of the conventional WSOLA.