• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.273-275
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• 1999

This paper presents a dynamic equivalencing method in large electric power system for stability analysis. This method of modeling simplified equivalents for parts of the network outside the study area is to evaluate the stability of a study area modeled in detail. Generators are closely coupled in an electrical sense tend to swing together in groups during disturbances, and this behavior can be exploited to reduce the size of the power system model. The characteristics of generators swing together are referred to as coherency Coherency groups whose generators state trajectory are similar to the other generators state trajectory in the same coherency group by a certain disturbance. In this paper, procedures for forming dynamic equivalents of control devices of coherency-based generating units are proposed and the aggregation of the control devices such as excitation system and governor-turbine system is accomplished by this method. This method can deal with the aggregation of the same type of control devices and combination of hydro and steam unit or the many types of excitation systems. etc. This method is shown to be efficient in reducing the number of control device of generating units with small error in the study group by result of case study presented latter part of this paper.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.10
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• pp.915-921
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• 2004

In this paper, a variable structure controller(VSC) is used to control the position of the hydraulic servo system subjected to unknown disturbances. The system consists of two cylinders, which connected in series. One cylinder executes position control, the other executes force control to generate disturbances. In order to control each cylinder, interaction must be considered between two cylinders because two cylinders are connected in series. Therefore, the controller is designed regarding interaction between two cylinders as disturbances. Performance of the proposed controller was verified through experiments and compared to PID controller. The experiments showed that the proposed controller had a good performance and robustness.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.190-192
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• 2003

When generators trip on the occurrence of disturbance, the power system frequency declines by the amount of difference between demand and supply due to the imbalance between power generation and load. Even though the power system is operated with the same grid structure, generating capacity, and load, the resulting frequency decline and its recovery slope show different aspects according to the inertia constants of generators, spinning reserves, and the speed adjusting rates at the governors. From this point of view, we analysed differences of frequency decline at the various conditions in domestic power system.

• The KSFM Journal of Fluid Machinery
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• v.13 no.4
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• pp.18-24
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• 2010

For testing large-capacity pumps, the accurate flow rate measurement is needed in the test loop. As a measuring method of flow rate, venturi tube is recommended due to its low pressure loss. However, upstream disturbance of loop component such as a valve has an effect upon the accuracy of flow rate measurement. For controlling flow rate in case of high flow rate and large-scale piping system, a butterfly-type valve is generally used due to its compactness. However, a butterfly valve disturbs downstream flow by generating turbulence, cavities, or abrupt pressure change. In this study, the effect of downstream disturbance of butterfly valve on the flow rate measurement using a venturi tube is investigated. Test loop consists of circulation pump, reservoir, butterfly valve, venturi tube, and reference flow meter. The test is conducted with regard to a different valve opening angle of butterfly valve. According to the valve opening angle, the uncertainty of flow rate measurement is investigated.

• International Journal of Computer Science & Network Security
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• v.23 no.9
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• pp.134-140
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• 2023

The distributed system is playing a vital role in storing and processing big data and data generation is speedily increasing from various sources every second. Hadoop has a scalable, and efficient distributed system supporting commodity hardware by combining different networks in the topographical locality. Node support in the Hadoop cluster is rapidly increasing in different versions which are facing difficulty to manage clusters. Hadoop does not provide Node management, adding and deletion node futures. Node identification in a cluster completely depends on DHCP servers which managing IP addresses, hostname based on the physical address (MAC) address of each Node. There is a scope to the hacker to theft the data using IP or Hostname and creating a disturbance in a distributed system by adding a malicious node, assigning duplicate IP. This paper proposing novel node management for the distributed system using DNA hiding and generating a unique key using a unique physical address (MAC) of each node and hostname. The proposed mechanism is providing better node management for the Hadoop cluster providing adding and deletion node mechanism by using limited computations and providing better node security from hackers. The main target of this paper is to propose an algorithm to implement Node information hiding in DNA sequences to increase and provide security to the node from hackers.

• Journal of KSNVE
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• v.6 no.6
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• pp.709-715
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• 1996

In recent years, the piping vibration in many Power Plants is being increased by the aged generating facilities due to a long time use. Generally, the pressure fluctuations associated with the flow-induced excitations in this case are broadband in nature. Mainly, the dominant sources of vibration are a vortex-shedding, plane waves and boundary layer turbulence. The peak level of the spectrum is proportional to the dynamic head. A severe disturbance in pipeline results in the generation of intense broadband internal sound waves which can propagate through the piping system. The characteristic frequencies of operating loads of 20%, 57%, 70%, 100% are 4 - 6 Hz and coincide with the results from impact hammering test and FEM analysis. We chose the wire energy absorbing rope restraint as a vibration reduction method after reviewing the various conditions such as site, installing space and economic cost etc. After installation, the vibration level was reduced about 54% in velocity.

• Current Industrial and Technological Trends in Aerospace
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• v.8 no.2
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• pp.54-64
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• 2010

A spacecraft contends with various vibration from the launch to the on-orbit operation, which is one of the major considerations in spacecraft design. The weight reduction has been indispensable to decrease the launch cost, however it produces worse disturbances for the spacecraft equipments. Besides, the load requirements at observation payload interfaces have became severe to secure their pointing stability as their images are required with high resolution. As a possible solution, a vibration isolation system is introduced and it reduces the vibration from the launch vehicle or isolates the spacecraft equipments from their generating/transmitted vibration. In this paper, it is examined the design consideration needed for the accommodation of the vibration isolation systems through the survey of recent applications of vibration mitigation technologies to spacecrafts.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.3
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• pp.278-285
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• 1999

This paper utilizes the method of Q-parameterization control to design a controller which solves the problem of imbalance in magnetic bearing systems. There are two methods to solve this problem using feedback controal. The first method is to compensate for the imbalance forces by generating opposing forces on the bearing surface (imbalance compensation). The second method is to make the rotor rotate around its axis of inertia (automatic balancing);in this case no imbalance forces will be generated. In this paper we deal with only imbalance compensation. The free parameter of the Q-parameterization controller is chosen such that these goals are achieved. After the introduction of a model of the magnetic bearing system, we explain the Q-parameterization controller design of the magnetic bearing system with emphasis on the rejection of sinusoidal disturbance for imbalance compensation design. The design objectives are formulated as a linear equations in the controller free paramete Q. Finally, simulation and experimental results are presented and showed the robustness and effectiveness of the proposed controllers.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.8
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• pp.1241-1246
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• 2013

Currently, The general transportation system arranges the armature on the full length of transportation lines. However, when this method is applied to the long distance transportation system, it causes an increase of material cost and manufacturing time. Thus, in order to resolve this problem, discontinuous arrangement method of the armature has been proposed. However, in the method of using stationary discontinuous armatures, mover can stop in the freewheeling section which is non-installations section when disturbance is generated and the mover can not be moved because armature control is impossible. Thus, the distance determination of armature is very important. Also, when the armature is arranged discontinuously the edge always exists due to the structure. Due to this edge, the cogging force is greatly generated during the entry and ejection of the mover to the armature. This cogging force causes thrust force ripple generating noise, vibration and decline of performance, it must be reduced. Therefore, in this paper, we examined the end edge cogging force generated by the stationary discontinuous armatures through 2-D numerical analysis using finite element method (FEM) and we figured out distance of armature for end edge cogging force minimization.

• Journal of Digital Contents Society
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• v.2 no.1
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• pp.51-61
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• 2001

The FLC(Fuzzy Logic Controller) is stronger to the disturbance and has the excellent characteristic to the overshoot of the initialized value than the classical controller, and also can carry out the proper control being out of all relation to the mathematical model and parameter value of the system. But it has the restriction which can't adopt the environment changes of the control system because of generating the fuzzy control rule through an expert's experience and the fixed value of the once determined control rule, and also can't converge correctly to the desired value because of haying the minute error of the controller output value. Now there are many suggested methods to eliminate the minute error, we also suggest the GA-FNNIC(Genetic Algorithm Fuzzy Neural Network Intelligence Controller) combined FLC with NN(Neural Network) and GA(Genetic Algorithm). In this paper, we compare the suggested GA-FNNIC with FLC and analyze the output characteristics, convergence speed, overshoot and rising time. Finally we show that the GA-FNNIC converge correctly to the desirable value without any error.