• Journal of KIISE:Databases
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• v.37 no.1
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• pp.1-11
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• 2010

Recently, there has been a growing interest in the processing of continuous queries over multiple data streams. When the arrival rates of tuples exceed the memory capacity of the system, a load shedding technique is used to avoid the system becoming overloaded by dropping some subset of input tuples. In this paper, we propose an effective load shedding algorithm for multi-way windowed joins over multiple data streams. Most previous load shedding algorithms estimate the productivity of each tuple, i.e., the number of join output tuples produced by the tuple, based on its "join attribute value" and drop tuples with the lowest productivity. However, the productivity of a tuple cannot be accurately estimated from its join attribute value when the join attribute values are unique and do not repeat, or the distribution of the join attribute values changes over time. For these cases, we estimate the productivity of a tuple based on its "arrival order" on data streams, rather than its join attribute value. The proposed method can effectively estimate the productivity of a tuple even when the productivity of a tuple cannot be accurately estimated from its join attribute value. Through extensive experiments and analysis, we show that our proposed method outperforms the previous methods in terms of effectiveness and efficiency.

• Proceedings of the KIEE Conference
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• 1997.07c
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• pp.1115-1117
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• 1997

This paper proposes the automatic load shedding program using estimated power outage amount. Power outage amount estimation is implemented by the inverse problem analysis.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.83-91
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• 2015

This paper presents preventive and emergency control measures for on line transient stability (security) enhancement. For insecure operating state, generation rescheduling based on a real power generation shift factor (RPGSF) is proposed as a preventive control measure to bring the system back to secure operating state. For emergency operating state, two emergency control strategies namely generator shedding and load shedding have been developed. The proposed emergency control strategies are based on voltage magnitudes and rotor trajectories data available through Phasor Measurement Units (PMUs) installed in the systems. The effectiveness of the proposed approach has been investigated on IEEE-39 bus test system under different contingency and fault conditions and application results are presented.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.7
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• pp.971-977
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• 2015

The electric propulsion system requires more reliability and safety than the conventional propulsion system because any sudden changes of electric system would bring tremendous effects on the ship's safety and propulsion. So it is very important to consider the potential transient effects. This paper discusses one of the worst electric accident. That is, one or two of generators are out of service in normal seagoing condition. And the appropriate measures are simulated in order to prevent the frequency decline that can bring the other generator's tripping. In addition, the relation between the transient effects and the major factors(inertia of generator/motors, governor's drooping characteristic and response speed) are also identified using the ETAP software.

• International Journal of Computer Science & Network Security
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• v.22 no.3
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• pp.220-228
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• 2022

The directed tests produce an expectation model to assist the organization's heads and professionals with settling on the right and speedy choice. A directed deep learning strategy has been embraced and applied for SCADA information. In this paper, for the load shedding expectation overall power organization of Libya, a convolutional neural network with multi neurons is utilized. For contributions of the neural organization, eight convolutional layers are utilized. These boundaries are power age, temperature, stickiness and wind speed. The gathered information from the SCADA data set were pre-handled to be ready in a reasonable arrangement to be taken care of to the deep learning. A bunch of analyses has been directed on this information to get a forecast model. The created model was assessed as far as precision and decrease of misfortune. It tends to be presumed that the acquired outcomes are promising and empowering. For assessment of the outcomes four boundary, MSE, RMSE, MAPE and R2 are determined. The best R2 esteem is gotten for 1-overlap and it was 0.98.34 for train information and for test information is acquired 0.96. Additionally for train information the RMSE esteem in 1-overlap is superior to different Folds and this worth was 0.018.

• Journal of Korea Multimedia Society
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• v.12 no.9
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• pp.1242-1251
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• 2009

A DSMS(Data Stream Management System) in ubiquitous environment processes huge data that input from a number of sensor. The existed system is used with a load shedding method that is eliminated with a part of huge data stream when it doesn't process the huge data stream. The Load shedding method has to filter a part of input data. This is because, data completeness or reliability is decreased. In this paper, we proposed the overload prediction load balancing to maintain data completeness when the system has an overload. The proposed method predicts the overload time. and than it is decreased with data loss when achieves the prediction overload time. The performance evaluation shows that the proposed method performs better than the existed method.

• Wind and Structures
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• v.4 no.1
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• pp.19-30
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• 2001

This paper concerns computational response predictions when a tuned mass damper is intended to be used for the suppression of vortex shedding induced vibrations of e.g., a bridge deck. A general frequency domain theory is presented and its application is exemplified on a suspension bridge (where vortex shedding vibrations have been observed and where such an installation is a possible solution). Relevant load data are taken from previous wind tunnel tests. In particular, the displacement response statistics of the tuned mass damper as well as the bridge deck are obtained from time domain simulations, showing that after the installation of a TMD peak factors between three and four should be expected.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.6
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• pp.1034-1043
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• 2015

This is the continuation of a numerical study on vortex shedding from a blunt trailing-edge of a hydrofoil. In our previous work (Lee et al., 2015), numerical schemes for efficient computations were successfully implemented; i.e. multiple domains, the approximation of domain boundary conditions using cubic spline functions, and particle-based domain decomposition for better load balancing. In this study, numerical results through a hybrid particle-mesh method which adopts the Vortex-In-Cell (VIC) method and the Brinkman penalization model are further rigorously validated through comparison to experimental data at the Reynolds number of $2{\times}10^6$. The effects of changes in numerical parameters are also explored herein. We find that the present numerical method enables us to reasonably simulate vortex shedding phenomenon, as well as turbulent wakes of a hydrofoil.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.391-392
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• 2016

A phase shedding control algorithm to increase efficiency of 3-Phase interleaved boost converter is proposed. Conventional interleaved converter has low efficiency under the light load condition. In this paper, the number of phase is controlled in accordance with the load condition to increase the light load efficiency. The validity of proposed phase control algorithm is verified by simulation results based on measured efficiency.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.10
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• pp.472-479
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• 2001

In order to prevent voltage collapse. this paper introduces the idea of the intelligent system and operating polices for a power system, then presents the results of voltage stability studies for that power system. The intelligent system includes a dedicated computer doing calculation and evaluation jobs and several intelligent relays serving as last guards to carry out the pre-set remedies. In the intelligent system, P-V curves are used to determine the operating margin from the current operating point to the maximum operating point, or the nose point. This paper suggests an operating guide for voltage stability of a power system. The effectiveness of location ad amount of load shedding for the different power load models are studied.