• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2005.09a
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• pp.110-123
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• 2005

This paper proposes an intelligent method for the optimal load distribution of two cooperating robots(TCRs) using fuzzy logic. The proposed scheme requires the knowledge of the robots' dynamics, which in turn depend upon the characteristics of large flat panel displays(LFPDs) carried by the TCRs. However, the dynamic properties of the LFPD are not known exactly, so that the dynamics of the robots, and hence the required joint torque, must be calculated for nominal set of the LFPD characteristics. The force of the TCRs is an important factor in carrying the LFPD. It is divided into external force and internal force. In general , the effects of the internal force of the TCRs are not considered in performing the load distribution in terms of optimal time, but they are essential in optimal trajectory planning: if they are not taken into consideration, the optimal scheme is no longer fitting. To alleviate this deficiency, we present an algorithm for finding the internal-force factors for the TCRs in terms of optimal time. The effectiveness of the proposed system is demonstrated by computer simulations using two three-joint planner robot manipulators.

• 한국공간정보시스템학회:학술대회논문집
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• 2004.05a
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• pp.245-251
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• 2004

This paper discuss the conditionally sampled actual wind pressure distributions causing peak quasi-static wind loads in the large span roofs using the wind pressures at many locations on dome models measured simultaneously in a wind tunnel. The actual extreme pressure distributions are compared itk load-response-correlation (LRC) method and the quasi-steady pressure distributions. Based on the results, the reason for the discrepancy in the LRC pressure distribution and the actual extreme pressure distribution are discussed. Futhermore, a brief discussion is made of the equivalent static wind load estimation for the large span roofs.

• 전기의세계
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• v.23 no.3
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• pp.53-59
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• 1974

The purpose of this paper is to use hydraulic sources optimally on the hydro-thermal power coordination in power system of Korea by means of Multiple Dynamic Programming. Four principal hydraulic power plans of Korea; Whachon, Chunchon, Uiam and Chong-pyong which are located on Han river side are treated in this research. For the illustrative purpose, a case study was made on the year round monthy optimal water control under the given load distribution and constraints.

• Journal of KIISE:Software and Applications
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• v.27 no.4
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• pp.315-326
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• 2000

As Internet is being widely used as an infra of distributed applications, the most of today's softwares are changing into Internet-based distributed applications. The development methods using the middleware, like CORBA ORB, make the development of the web-based software easy. However, the performance verification method useful for an optimized software distribution is not provided at software development. Additionally, monitoring methods and metrics for dynamic load-balancing are not presented at run-time. This paper presents the method to monitor the message between objects, load metric, and metrics for load-balancing. To calculate a load of a node, we define events occurred between applications, time between the events, then extract the data related to a load. And we derive formula calculating the load from the extracted data. Then using the formula, we present the metrics for dynamic load-balancing. Moreover, we observe the utilization and efficiency of the monitoring algorithm, load metric, and load-balancing metrics.

• Wind and Structures
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• v.5 no.1
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• pp.49-60
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• 2002

This paper describes a simple method for evaluating the design wind loads for the structural frames of circular flat roofs with long spans. The dynamic response of several roof models were numerically analyzed in the time domain as well as in the frequency domain by using wind pressure data obtained from a wind tunnel experiment. The instantaneous displacement and bending moment of the roof were computed, and the maximum load effects were evaluated. The results indicate that the wind-induced oscillation of the roof is generally dominated by the first mode and the gust effect factor approach can be applied to the evaluation of the maximum load effects. That is, the design wind load can be represented by the time-averaged wind pressure multiplied by the gust effect factor for the first mode. Based on the experimental results for the first modal force, an empirical formula for the gust effect factor is provided as a function of the geometric and structural parameters of the roof and the turbulence intensity of the approach flow. The equivalent design pressure coefficients, which reproduce the maximum load effects, are also discussed. A simplified model of the pressure coefficient distribution is presented.

• Journal of the Korea Society of Computer and Information
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• v.11 no.1 s.39
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• pp.1-10
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• 2006

Load redistribution algorithm is a critical factor in computer system. In a receiver-initiated load redistribution algorithm, receiver(underloaded processor) continues to send unnecessary request messages for load transfer until a sender(overloaded processor) is found while the system load is light. Therefore, it yields many problems such as low CPU utilization and system throughput because of inefficient inter-processor communications until the receiver receives an accept message from the sender in this environment. This paper presents an approach based on genetic. algorithm(GA) for dynamic load redistribution in heterogeneous distributed systems. In this scheme the processors to which the requests are sent off are determined by the proposed GA to decrease unnecessary request messages.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.12
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• pp.575-583
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• 2001

Dynamic Voltage Restorer(DVR) which is installed between the supply and a critical load can restore voltage disturbances in distribution system. The restoration is based on injecting the same voltages as voltage sags. The ideal restoration is compensation to make the load voltages be unchanged. But voltage restoration involves real power or energy injection and the capability of energy storage is limited. So it must be considered how injection energy can be minimized and voltages can be made close to the voltages before fault. This paper describes conventional restoration techniques, which draw minimum energy from the DVR in order to correct a given voltage sag or swell. And this paper proposes a new concept of restoration technique to inject minimum energy. The proposed method is based on the definition of voltage tolerance in load side. Hence using the proposed method a particular disturbance can be corrected with less amount of storage energy compared to those of conventional methods.

• Journal of Power Electronics
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• v.16 no.1
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• pp.351-361
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• 2016

Power quality is a critical issue in distribution systems, where a dynamic voltage restorer (DVR) is commonly used to mitigate the voltage disturbances for loads. This paper deals with a nonlinear control for the three-phase four-wire (3P-4W) DVR under a grid voltage unbalance and nonlinear loads in the distribution system, where a novel control scheme based on the feedback linearization technique is proposed. Through feedback linearization, a nonlinear model of a DVR with a PWM voltage-source inverter (VSI) and LC filters is linearized. Then, the controller design of the linearized model is performed by applying the linear control theory, where the load voltages are kept constant by controlling the d-q-0 axis components of the DVR output voltages. To keep the load voltage unchanged, an in-phase compensation strategy is employed, where the load voltages are recovered to be the same as the previous voltage without a change in the magnitude. With this strategy, the performance of the DVR becomes faster and more stable even under unbalanced source voltages and nonlinear loads. The validity of the proposed control strategy has been verified by simulation and experimental results.

• Journal of Communications and Networks
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• v.11 no.1
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• pp.26-35
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• 2009

In this paper, we investigate how to do resource allocation to guarantee a minimum user data rate at low signaling overhead in multi-cell orthogonal frequency division multiple access (OFDMA) wireless systems. We devise dynamic resource allocation (DRA) algorithms that can minimize the QoS violation ratio (i.e., the ratio of the number of users who fail to get the requested data rate to the total number of users in the overall network). We assume an OFDMA system that allows dynamic control of frequency reuse factor (FRF) of each sub-carrier. The proposed DRA algorithms determine the FRFs of the sub-carriers and allocate them to the users adaptively based on inter-cell interference and load distribution. In order to reduce the signaling overhead, we adopt a hierarchical resource allocation architecture which divides the resource allocation decision into the inter-cell coordinator (ICC) and the base station (BS) levels. We limit the information available at the ICC only to the load of each cell, that is, the total number of sub-carriers required for supporting the data rate requirement of all the users. We then present the DRA with limited coordination (DRA-LC) algorithm where the ICC performs load-adaptive inter-cell resource allocation with the limited information while the BS performs intra-cell resource allocation with full information about its own cell. For performance comparison, we design a centralized algorithm called DRA with full coordination (DRA-FC). Simulation results reveal that the DRA-LC algorithm can perform close to the DRA-FC algorithm at very low signaling overhead. In addition, it turns out to improve the QoS performance of the cell-boundary users, and achieve a better fairness among neighboring cells under non-uniform load distribution.

• Journal of Electrical Engineering and Technology
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• v.11 no.3
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• pp.575-584
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• 2016

Considering the randomness and uncertainty of wind power, a reliability model of WTGs is established based on the combination of the Weibull distribution and the Markov chain. To analyze the failure mode quickly, we use the switch-section partitioning method. After defining the first-level load zone node, we can obtain the supply power sets of the first-level load zone nodes with each WTG. Based on the supply sets, we propose the dynamic division strategy of island operation. By adopting the fault analysis method with the attributes defined in the switch-section, we evaluate the reliability of the distribution network with WTGs using a sequential Monte Carlo simulation method. Finally, using the IEEE RBTS Bus6 test system, we demonstrate the efficacy of the proposed model and method by comparing different schemes to access the WTGs.