• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.12
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• pp.595-601
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• 2000

This paper describes the improvement method of distance relaying algorithm for the underground transmission cables. Distance relaying algorithms have been mainly developing to protect the overhead transmission lines than the underground cables. If the cable systems are directly protected using distance relaying algorithm developed for overhead line without any improvement, there will be really occurred many misoperation in cable systems, because the cable systems consist of the conductor, the sheath, several grounding method, cable cover protection units(CCPUs), and grounding wire. Accordingly, the complicated phenomena are occurred, if there is a fault in cable systems. Therefore, to develope a correct distance relaying algorithm, such cable characteristics should be taken into account. This paper presents the process to improve distance relaying algorithm which is now used. REal cable system was selected to establish modeling in EMTP and ATP Draw. It was discovered through the detailed simulation during the fault that the large error existed between impedance measured at the relay point and real impedance is due to the resistance of grounding wire in each grounding method. And also compensation factor obtained by the simulation is proposed in this paper. It is proved that the factor proposed can fairly improve the accuracy of impedance at the relay point. It is evaluated that the protective ability will be really much improved, if the algorithm proposed in this paper is applied for cable systems of utility.

• Journal of the Korea Safety Management & Science
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• v.7 no.1
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• pp.127-135
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• 2005

In general one can find an enormous number of studies about the productivity of land, labor and capital, very little has been done so far to communicate about the productivity of corporate information creating and information-consuming resources in ways that are useful to business executives. In view of the enormous share of corporate spending on information resources it would be useful in planning, budgeting, as well as in performance evaluation to measure how information resources are used in creating EVA(economic value-added). The effectiveness in deploying information resources has potentially a greater effect on corporate financial performance than any other economic influence. That in because corporate executives have greater discretion in directing what their information management staffs will do than in setting the terms for materials purchases, employee compensation, taxes or interest rates. The expenses for information are mostly in the form of overhead costs. Because expenses for information are mostly overhead costs and not for costs of goods, the prudent decision-maker should have a wide array of discretionary options available for allocating this resource. This study is intended for analysis the factors that having effects on the enterprise information productivity and is to description the factor using a foreign enterprise case study.

• Journal of Electrical Engineering and Technology
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• v.1 no.3
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• pp.279-286
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• 2006

A method for estimating the instantaneous phasor of a fault current signal is proposed for high-speed distance protection that is immune to a DC-offset. The method uses a modified notch filter in order to eliminate the power frequency component from the fault current signal. Since the output of the modified notch filter is the delayed DC-offset, delay compensation results in the same waveform as the original DC-offset. Subtracting the obtained DC-offset from the fault current signal yields a sinusoidal waveform, which becomes the real part of the instantaneous phasor. The imaginary part of the instantaneous phasor is based on the first difference of the fault current signal. Since a DC-offset also appears in the first difference, the DC-offset is removed trom the first difference using the results of the delay compensation. The performance of the proposed method was evaluated for a-phase to ground faults on a 345kV 100km overhead transmission line. The Electromagnetic Transient Program was utilized to generate fault current signals for different fault locations and fault inception angles. The performance evaluation showed that the proposed method can estimate the instantaneous phasor of a fault current signal with high speed and high accuracy.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.383-386
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• 2001

Distance relay is tripped by the line impedance calculated at the relay point. Accordingly the accurate operation depends on the precise calculation of line impedance. Impedance can be accurately calculated in case of overhead line. However, in case of power cables or combined transmission lines, impedance can not be accurately calculated because cable systems have the sheath, grounding wires, and cable cover protection units (CCPUs). There are also several grounding systems in cable systems. Therefore, if there is a fault in cable system, these terms will severely be caused much error to calculation of impedance. Accordingly the proper compensation should be developed for the correct operation of the distance relay. This paper presents the distance calculating algorithm in combined transmission line with power cable using wavelet transform. In order to achieve such purpose, judgement method to discriminate the fault section in both sections was proposed using db1 coefficient summation. And also, error compensation factor was proposed for correct calculation of impedance in power cable.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.8
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• pp.29-39
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• 2015

This paper describes a design and implementation of fuzzy-based algorithm for hand-shake state detection and error compensation in the mobile optical image stabilization(OIS) motion detector. Since the gyro sensor output of the OIS motion detector includes inherent error signals, accurate error correction is required for prompt hand-shake error compensation and stable hand-shake state detection. In this research with a little computation overhead of fuzzy-based algorithm, the hand-shake error compensation could be improved by quickly reducing the angle and phase error for the hand-shake frequencies. Further, stability of the OIS system could be enhanced by the hand-shake states of {Halt, Little vibrate, Big vibrate, Pan/Tilt}, classified by subdividing the hand-shake angle. The performance and stability of the proposed algorithm in OIS motion detector is quantitatively and qualitatively evaluated with the emulated hand-shaking of ${\pm}0.5^{\circ}$, ${\pm}0.8^{\circ}$ vibration and 2~12Hz frequency. In experiments, the average error compensation gain of 3.71dB is achieved with respect to the conventional BACF/DCF algorithm; and the four hand-shake states are detected in a stable manner.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.319-322
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• 2002

Distance relay is operated in calculating line impedance. It can be worked accurately in overhead line. However, power cables or combined transmission lines need compensation for calculated impedance because cable systems have sheaths, grounding wires and sheath voltage limiters(SVLs) Neuro-fuzzy can be viewed either as a fuzay system, a neural network or fuzzy neural network and it can estimate the location of the fault accurately. In this paper, fault section and fault location can be classified and estimated in neuro- fuzzy inference system and neural network.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.8
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• pp.3068-3078
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• 2015

Although the massive MIMO system supports a high throughput, it requires a lot of channel information for channel compensation. For the reduction of overhead, the massive MIMO system generally uses TDD as duplexing scheme. Therefore, the massive MIMO system is sensitive to rapidly changing fast fading in according to time. For the improvement of reduced SINR by fast fading, the adaptive power control is proposed. Unlike the conventional scheme, the proposed scheme considers mobility of device for adaptive power control. The simulation of the proposed scheme is performed with consideration for mobility of device. The result of the simulation shows that the proposed scheme improves SINR. Since SINR is decreased in according to the number of device in the network by unit of cell, each base station can accommodate more devices by the proposed scheme. Also, because the massive MIMO system with high SINR can use high order modulation scheme, it can support higher throughput.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.6C
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• pp.632-639
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• 2002

To reduce the area and power consumption in constant coefficient multiplications, the constant coefficient can be encoded using canonic signed digit(CSD) representation. When the partial product terms are added depending on the nonzero bit(1 or -1) positions in the CSD-encoded multiplier, all sign bits are properly extended before the addition takes place. In this paper, to reduce the overhead due to sign extension, a new method is proposed based on the fact that carry propagation in the sign extension part can be controlled such that a desired input bit can be propagated as a carry. Also, a fixed-width multiplier design method suitable for CSD multiplication is proposed. As an application, 43-tap filbert transformer for SSB/BPSK-DS/CDMA is implemented. It is shown that, about 16∼28% adders can be saved by the proposed method compared with the conventional methods.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.2
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• pp.311-326
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• 2018

This paper has experimented using News sample video with QCIF ($176{\times}144$) resolution in JM v10.2 code of H.264/AVC-MPEG. The region of interest (ROI) to be encrypted occurred the drift by unnecessarily referring to each frame continuously in accordance with the characteristics of the motion prediction and compensation of the H.264 standard. In order to mitigate the drift, the latest related research method of re-inserting encrypted I-picture into a certain period leads to an increase in the amount of additional computation that becomes the factor increasing the bit-rate overhead of the entire video. Therefore, the reference search range of the block and the frame in the ROI to be encrypted is restricted in the motion prediction and compensation for each frame, and the reference search range in the non-ROI not to be encrypted is not restricted to maintain the normal encoding efficiency. In this way, after encoding the video with restricted reference search range, this article proposes a method of RC4 bit-stream encryption for the ROI such as the face to be able to identify in order to protect personal information in the video. Also, it is compared and analyzed the experimental results after implementing the unencrypted original video, the latest related research method, and the proposed method in the condition of the same environment. In contrast to the latest related research method, the bit-rate overhead of the proposed method is 2.35% higher than that of the original video and 14.93% lower than that of the latest related method, while mitigating temporal drift through the proposed method. These improved results have verified by experiments of this study.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.6
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• pp.2811-2830
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• 2017

In this paper, we study the problem of mobile data offloading for a network that contains multiple mobile network operators (MNOs), multiple WiFi or femtocell access points (APs) and multiple mobile users (MUs). MNOs offload their subscribed MUs' data traffic by leasing the unused Internet connection bandwidth of third party APs. We propose a combinatorial auction-based two-stage matching mechanism comprised of MU-AP matching and AP-MNO matching. The MU-AP matching is designed to match the MUs to APs in order to maximize the total offloading data traffic and achieve better MU satisfaction. Conversely, for AP-MNO matching, MNOs compete for APs' service using the Nash bargaining solution (NBS) and the Vickrey auction theories and, in turn, APs will receive monetary compensation. We demonstrated that the proposed mechanism converges to a distributed stable matching result. Numerical results demonstrate that the proposed algorithm well capture the tradeoff among the total data traffic, social welfare and the QoS of MUs compared to other schemes. Moreover, the proposed mechanism can considerably offload the total data traffic and improve the network social welfare with less computation complexity and communication overhead.