• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5194-5201
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• 2011

In this paper, an adaptive nonlinear friction compensation scheme for second-order nonlinear mechanical system with a partially known nonlinear dynamic friction is proposed to achieve asymptotic position and velocity tracking in the absence of disturbances and modeling errors. It is also shown that even with disturbances and modeling errors, in contrast to existing other adaptive control schemes, by proper adjustment of design parameters, reduced error bounds on position and velocity tracking can be achieved.

• Journal of Advanced Navigation Technology
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• v.7 no.1
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• pp.30-37
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• 2003

In this paper, we have analyzed the BER (Bit Error Rate) performance of MC-CDMA systems under indoor wireless environment with class A impulsive noise suggested by Middleton. For the performance evaluation, we considered from strong to weak impulsive noise characteristics. And we have evaluated the degree of performance improvement by using turbo code as a compensation technique to impulsive noise. From the result of analysis, it is found powerful performance improvement scheme must be adopted in the system under impulsive noise environment, and when turbo code scheme is adopted, system BER performance is improved by the $10^{-2}$. As the impulsive noise characteristics approaches AWGN characteristics, the degree of performance improvement by adopting turbo code become larger.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1500-1511
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• 2017

The purpose of this paper is to study a high-performance control scheme for neutral-point-clamping three-level (NPC-3L) inverter fed dual three-phase permanent magnet synchronous motor (PMSM) drives by considering some asymmetric factors such as the non-identical parameters in phase windings. To implement this, the system model is analyzed for dual three-phase PMSM drives with asymmetric factors based on the vector space decomposition (VSD) principle. Based on the equivalent circuits, PI controllers with feedforward compensation are used in the d-q subspace for regulating torque, where the cut-off frequency of the PI controllers are set at the twice the fundamental frequency for compensating both the additional DC component and the second order component caused by asymmetry. Meanwhile, proportional resonant (PR) controllers are proposed in the x-y subspace for suppressing the possible unbalanced currents in the phase windings. A dual three-phase space vector modulation (DT-SVM) is designed for the drive, and the balancing factor is designed based on the numerical fitting surface for balancing the DC link capacitor voltages. Experimental results are given to demonstrate the validity of the theoretical analysis and the proposed control scheme.

• Current Optics and Photonics
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• v.4 no.4
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• pp.310-316
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• 2020

We propose and experimentally demonstrate an all-optical radio frequency (RF) spectrum broadening system based on time compression. By utilizing the procedure of dispersion compensation values, the frequency domain is broadened by compressing the linear chirp optical pulse which has been multiplexed by the radio frequency. A detailed mathematical description elucidates that the time compression is a very preferred scheme for spectrum broadening. We also report experimental results to prove this method, magnification factor at 2.7, 8 and 11 have been tested with different dispersion values of fiber, the experimental results agree well with the theoretical results. The proposed system is flexible and the magnification factor is determined by the dispersion values, the proposed scheme is a linear system. In addition, the influence of key parameters, for instance optical bandwidth and the sideband suppression ratio (SSR), are discussed. Magnification factor 11 of the proposed system is demonstrated.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.6
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• pp.117-126
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• 2010

In the case of failure images with controlling lighting like backlighting and excessive frontlinghting, the compensation scheme for a specific area in an image is required. The interested region is first selected by user in our method to compensate the first frame. Then we define the matching function of brightness and energy function is proposed with weight of matching function and the relationship among the neighbors. Finally, the energy is minimized by the graph-cut algorithm to compensate the brightness of the first frame. Other frames are straightforwardly compensated using the results of the first frame. The brightness variations of the previous frame is transmitted to the next frame via motion vectors. The reliability of the brightness variation is calculated based on the motion vector reliability. Video compensation result is achieved by the process of the image case. Simulation show that the proposed algorithm provides more natural results than the conventional algorithms.

• Journal of Broadcast Engineering
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• v.13 no.5
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• pp.622-635
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• 2008

Recently, high definition media services like HDTV and IPTV are growing. A fast reduced-size image extracting method is required to meet what those services require. Conventional DC image extracting methods, however, can't be applied to H.264/AVC streams since a spatial domain prediction scheme is adopted in H.264/AVC intra mode. To solve this problem, a thumbnail extraction method in H.264/AVC was proposed. However, the method has mismatch problem which was caused by round-off operation in intra prediction and mismatch between integer and floating point calculation. In this paper, we propose an error compensation method for extracting thumbnail directly in H.264/AVC bitstreams. The compensation method introduces the mismatch problem in thumbnail extraction and presents compensation values. Through the implementation and performance evaluation, proposed method compensated round-off error efficiently in D1 and HD sequences while the additional extraction time is negligible.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.5
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• pp.102-111
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• 2013

In this paper, we proposed a $4{\times}4$ block parallel architecture of interpolation for high-performance H.264/AVC Motion Compensation in 4K UHD($3840{\times}2160$) video real time processing. To improve throughput, we design $4{\times}4$ block parallel interpolation. For supplying the $9{\times}9$ reference data for interpolation, we design 2D cache buffer which consists of the $9{\times}9$ memory arrays. We minimize redundant storage of the reference pixel by applying the Search Area Stripe Reuse scheme(SASR), and implement high-speed plane interpolator with 3-stage pipeline(Horizontal Vertical 1/2 interpolation, Diagonal 1/2 interpolation, 1/4 interpolation). The proposed architecture was simulated in 0.13um standard cell library. The maximum operation frequency is 150MHz. The gate count is 161Kgates. The proposed H.264/AVC Motion Compensation can support 4K UHD at 72 frames per second by running at 150MHz.

• Journal of Korean Society of Forest Science
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• v.108 no.4
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• pp.618-627
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• 2019

An increase in damage to crops and facilities caused by wildlife such as wild boar causes serious social and economic problems to the rural economy in Korea. This study aims to estimate the economic losses incurred to rural households in mountain villages near protected areas in Korea due to the damage to agricultural and forestry production by wildlife. The case of mountain villages located in Toji-myeon, Gurye-gun near the Jirisan National Park was studied as an example. Data were collected by interviewing 84 households across six mountain villages in April and June 2016. The results indicate that the economic losses due to wildlife damage in 2015 were estimated to be 1.65 million KRW per household, which is a total of 138.63 million KRW for the 84 households. Among local products, the most damaged products were chestnut, fern-brake, wild pear, peach, and potato, whereas the most damaged products per production area were sweet potato, peach, corn, and potato. The potential economic losses caused by wildlife damage to agricultural and forestry production in whole Gurye-gun area was estimated to be around 4.0 billion KRW in 2015. However, the municipal government budget for the compensation of wildlife damage was only 0.9 percent of the potential rural economic losses caused by wildlife damage in 2015. The results of our study suggest that the compensation scheme for wildlife damage is inadequate in the respect of social justice. Considering the low financial capacity of the municipalities in mountain areas, the central government should take a progressive responsibility by allocating more financial resources for compensation of economic losses of rural households due to wildlife damage. The equitable and effective governance of wildlife conservation is required for sustainable development of rural communities near protected areas.

• 전자공학회논문지 IE
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• v.45 no.1
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• pp.44-49
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• 2008

In this paper, the performance for the non-linear satellite channel including the characteristics of group delay and gain ripple of transponder is analyzed with multi-level QAM-OFDM schemes. Comparing the BER performances between general OFDM and CI(Carrier Interferometry)-OFDM for various QAM schemes, the degree of performance improvement is presented in AWGN environments for specified nonlinear characteristics. The simulations are performed with the 36MHz bandwidth of transponder channel and 120Mbps transmission rate for QPSK, 8QAM, 16QAM, 32QAM, 64QAM schemes between normal and worst case condition. It is shown that the improvement measure by the CI-OFDM for the group delay of channel and nonlinear characteristic of HPA outperforms that for the gain ripple in the case of higher level QAM scheme in normal condition. And the simulation results show that the additional techniques like the channel coding and compensation scheme against the nonlinear characteristic are required for 32QAM and higher level QAM in worst case condition.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.9
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• pp.1551-1557
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• 2006

Since subscribers, who pay the same communication fees, have a strong desire to take similar services with the other users, it is an important issue to provide fairness among those subscribers wherever they are located. Therefore, in this paper we propose a QoS packet scheduler that can provide fairness among wireless LAN terminals and evaluate its performance using computer simulation. The key idea of this scheduler is to reduce the CW value of the wireless LAN terminal that has failed in sending its packets due to channel transmission error in order to offer the wireless MM terminal a higher transmission priority which is the idea of service compensation. We evaluate its performance using NS-2 network simulator, compare its numerical results to those of IEEE 802.11e without this scheme, and conclude that this scheme can reduce throughput difference between similar wireless LAN terminals.