• Journal of Power Electronics
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• v.11 no.4
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• pp.576-582
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• 2011

This paper presents a novel control strategy for selective compensation of power quality (PQ) problems, depending upon the limited rating of voltage source inverters (VSIs), through a unified power quality conditioner (UPQC) in a three-phase four-wire distribution system. The UPQC is realized by the integration of series and shunt active power filters (APFs) sharing a common dc bus capacitor. The shunt APF is realized using a three-phase, four-leg voltage source inverter (VSI), while a three-leg VSI is employed for the series APF of the three-phase four-wire UPQC. The proposed control scheme for the shunt APF, decomposes the load current into harmonic components generated by consumer and distorted utility. In addition to this, the positive and negative sequence fundamental frequency active components, the reactive components and harmonic components of load currents are decomposed in synchronous reference frame (SRF). The control scheme of the shunt APF performs with priority based schemes, which respects the limited rating of the VSI. For voltage harmonic mitigation, a control scheme based on SRF theory is employed for the series APF of the UPQC. The performance of the proposed control scheme of the UPQC is validated through simulations using MATLAB software with its Simulink and Power System Block set toolboxes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.10
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• pp.5013-5034
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• 2019

In the Peer-to-Peer (P2P) streaming systems, peers randomly form a network overlay to share video resources with a data scheduling scheme. A data scheduling scheme can have a great impact on system performance, which should achieve two optimal objectives at the same time ideally. The two optimization objectives are to improve the perceived video quality and maximize the network throughput, respectively. Maximizing network throughput means improving the utilization of peer's upload bandwidth. However, maximizing network throughput will result in a reduction in the perceived video quality, and vice versa. Therefore, to achieve the above two objects simultaneously, we proposed a new data scheduling scheme based on multi-objective particle swarm optimization data scheduling scheme, called MOPSO-DS scheme. To design the MOPSO-DS scheme, we first formulated the data scheduling optimization problem as a multi-objective optimization problem. Then, a multi-objective particle swarm optimization algorithm is proposed by encoding the neighbors of peers as the position vector of the particles. Through extensive simulations, we demonstrated the MOPSO-DS scheme could improve the system performance effectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.12
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• pp.4588-4603
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• 2014

In this paper, we present a high-quality image authentication scheme based on absolute moment block truncation coding. In the proposed scheme, we use the parity of the bitmap (BM) to generate the authentication code for each compressed image block. Data hiding is used to authenticate whether the content has been altered or not. For image authentication, we embed the authentication code to quantization levels of each image block compressed by absolute moment block truncation coding (AMBTC) which will be altered when the host image is manipulated. The embedding position is generated by a pseudo-random number generator for security concerned. Besides, to improve the detection ability we use a hierarchical structure to ensure the accuracy of tamper localization. A watermarked image can be precisely inspected whether it has been tampered intentionally or incautiously by checking the extracted watermark. Experimental results demonstrated that the proposed scheme achieved high-quality embedded images and good detection accuracy, with stable performance and high expansibility. Performance comparisons with other block-based data hiding schemes are provided to demonstrate the superiority of the proposed scheme.

• Journal of Communications and Networks
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• v.11 no.1
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• pp.36-41
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• 2009

The IEEE 802.16 wireless metropolitan area network (WMAN) standard is designed to correct expensive communication costs in CDMA-based mobile communication systems and limited coverage problems in wireless LAN systems. Thus, the IEEE 802.16e standard can provide mobile high-speed packet access between mobile stations and the Internet service provider through the base station with cheap communication fees. To efficiently accommodate voice over IP (VoIP) services in IEEE 802.16 systems, an uplink quality of service packet-scheduling scheme is proposed, and its performance is evaluated with an NS-2 network simulator in this paper. Numerical results show that this proposed scheme can increase the system capacity by 100% more than in the unsolicited rand service (UGS) scheme and 30% more than the extended real-time polling service (ertPS) scheme, respectively.

• Journal of Korea Multimedia Society
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• v.17 no.4
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• pp.466-477
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• 2014

Many image hiding schemes based on least significant bit (LSB) transformation have been proposed. One of the LSB-based image hiding schemes that employs diamond encoding was proposed in 2008. In this scheme, the binary secret data is converted into base n representation, and the converted secret data is concealed in the cover image. Here, we show that this scheme has two vulnerabilities: noticeable spots in the stego-image, i.e., a non-smooth embedding result, and inefficiency caused by rough re-adjustment of falling-off-boundary value and impractical base translation. Moreover, we propose a new scheme that is efficient and produces a smooth and high quality embedding result by restricting n to power of 2 and using a sophisticated re-adjustment procedure. Our experimental results show that our scheme yields high quality stego-images and is secure against RS detection attack.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.7
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• pp.546-551
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• 2014

This paper proposes an opportunistic subchannel allocation (OSA) scheme for relay-based marine communication networks to improve a sum-rate capacity. In most previous works for relay-based networks, each RS delivers the data received from the BS immediately to the corresponding ships in each frame. The achievable data-rate of the two-hop transmission (BS-RS and RS-ship links) is thus limited by the channel quality between BS-RS and RS-ship links. Hence, the radio resources can be wasted according to the difference in the channel quality between the BS-RS link and the RS-ship link. The proposed OSA scheme reduces the waste of radio resources by efficiently and independently allocating the radio resources at the BS-RS link and at the RS-ship link according to the channel quality of each link. The proposed OSA scheme, however, increases the computational complexity, because the BS finds the optimal OFDMA resource by checking the channel quality of all BS-RS links and RS-ship links. The simulation results show that the sum-rate capacity of the proposed OSA scheme improves maximum 14.0% compared with the conventional scheme.

• Journal of KIISE:Information Networking
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• v.30 no.6
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• pp.787-798
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• 2003

The flow label field in IPv6 has been proposed to provide the QoS. Since the existing flow label specification scheme like random-number format utilizes the label only as the identifier of flow, it is not appropriate for providing differentiated services according to the characteristics of various types of real-time traffic. This paper proposes a hybrid scheme that makes use of the flow label fields as components of flow and QoS parameters as well. To be specific, this paper investigates a scheme that both guarantees the end-to-end service quality and utilizes efficiently backbone resources by allowing users to specify QoS parameters using flow labels. Assuming an MLPS-TE network as the backbone, we compare the performance of our proposed scheme with that of random-number scheme through simulation. The simulation result shows that our scheme is more efficient than the existing one in terms of the transmission rate as well as the resource utilization of the backbone.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.9
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• pp.1305-1311
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• 2022

With the recent rapid development of mobile terminals and personal computers and the advent of neural network technology, real-time face swapping using images has become possible. In particular, the cycle generative adversarial network made it possible to replace faces using uncorrelated image data. In this paper, we propose an input data processing scheme that can improve the quality of face swapping with less training data and time. The proposed scheme can improve the image quality while preserving facial structure and expression information by combining facial landmarks extracted through a pre-trained neural network with major information that affects the structure and expression of the face. Using the blind/referenceless image spatial quality evaluator (BRISQUE) score, which is one of the AI-based non-reference quality metrics, we quantitatively analyze the performance of the proposed scheme and compare it to the conventional schemes. According to the numerical results, the proposed scheme obtained BRISQUE scores improved by about 4.6% to 14.6%, compared to the conventional schemes.

• Water for future
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• v.21 no.4
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• pp.407-414
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• 1988

The purpose of this paper is to study the following ; (1) how the stability and sensitivity of a given stream water quality model can be analyzed theoretically by means of the stability theory and the sensitivity theory, and (2) point out that the results of this study prove that numerical analysis for the given stream water quality model is reliable, and the model is sensitive for the variations of parameters. A stability theory which is described by the infinite Fourier series is used to analyze the numerical scheme of the model. The numerical shheme is used a backward implicit scheme. a sensitivity theory which is described by the first order linear vector equation is used to analyze theoretically the effect of variations of water quality parameters such as BOD loads, flow rate, temperature. The results of sensitivity theory are of general applicability and are presented in a analytical form. The results of this study seems to be satisfactory for the reliability of stream water quality model with respect to the numerical scheme and the variations of the water quality parameters.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.220-221
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• 2020

Strarting with Buyeong Apartment in Dongtan-2 disrict in 2017, collective complaints of residents are frequently occurring due to low quality problem such as improper construction and defects of apartment houses. Because of this, the Ministry of Land and Transport is preparing a comprehensive improvement scheme to improve the quality of Apartment Housing(AH), taking into account the continuing complaints from the residents of AH and the problem raised by the National Assembly. The basic profile of the improvement scheme is induce the tenants and experts to discover and point out defects that are repaired until the date of use inspection or due date. For this purpose, we suggested this defects management system linkaged by the preliminary inspection and quality inspection system for prospective occupants. In this context, this paper aims to suggest an effective likage method between the preliminary inspection of prospective residents and the quality inspection system implemented by local governments as an ordinance.