• Structural Engineering and Mechanics
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• v.38 no.4
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• pp.429-441
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• 2011

In large-scale problem, a huge size of computational resources is needed for a reliable solution which represents the detailed description of dynamic behavior. Recently, eigenvalue reduction schemes have been considered as important technique to resolve computational resource problems. In addition, the efforts to advance an efficiency of reduction scheme leads to the development of the multi-level system condensation (MLSC) which is initially based on the two-level condensation scheme (TLCS). This scheme was proposed for approximating the lower eigenmodes which represent the global behavior of the structures through the element-level energy estimation. The MLSC combines the multi-level sub-structuring scheme with the previous TLCS for enhancement of efficiency which is related to computer memory and computing time. The present study focuses on the implementation of the MLSC on the direct time response analysis and the frequency response analysis of structural dynamic problems. For the transient time response analysis, the MLSC is combined with the Newmark's time integration scheme. Numerical examples demonstrate the efficiency of the proposed method.

• Geomechanics and Engineering
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• v.20 no.4
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• pp.345-358
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• 2020

Numerous studies have repeatedly demonstrated the efficiency of using skirts to increase the bearing capacity and to reduce settlement of shallow foundations subjected to static loads. However, no efforts have been made to study the efficiency of using these skirts to reduce settlement produced by machine vibration, although machines are very sensitive to settlement and the foundations of these machines should be designed properly to ensure that the settlement produced due to machine vibration is very small. This research has been conducted to investigate the efficiency of using skirts as a technique to reduce the settlement of a strip foundation subjected to machine vibration. A two-dimensional finite element model has been developed, validated, and employed to achieve the aim of the study. The results of the analyses showed that the use of skirts reduces the settlement produced due to machine vibration. However, the percentage decrease of the settlement is remarkably influenced by the density of the soil and the frequency of vibration, where it rises as the frequency of vibration increases and declines as the soil density rises. It was also found that increasing skirt length increases the percentage decrease of the settlement. Importantly, the results obtained from the analyses have been utilized to derive new dynamic impedance values that implicitly consider the presence of skirts. Finally, novel design equations of dynamic impedance that implicitly account to the effect of the skirts have been derived and validated utilizing a new intelligent data driven method. These new equations can be used in future designs of skirted strip foundations subjected to machine vibration.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.3
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• pp.205-212
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• 2007

This paper presents a direct instantaneous torque control (DITC) of Switched Reluctance Motor (SRM) with a novel 4-level converter to develop a uniform torque and to improve a dynamic performance. The DITC method can reduce a high torque ripple of SRM. Drive efficiency and dynamic performance with conventional drive are low due to a slow excitation current build-up. Since the 4-level converter can obtain an addition boosted voltage to have a fast excitation and demagnetization, it can Improve dynamic performance and efficiency easily. To apply the DITC technique to a 4-level converter, a novel control scheme is presented according to the operating modes. Additionally, selection of capacitances of boosted capacitor and efficiency improvement of 4-level converter are analyzed. At last, the validity of proposed method is verified by some computer simulations md comparative experiments.

• Nuclear Engineering and Technology
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• v.54 no.3
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• pp.1109-1114
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• 2022

The SMART (System-integrated Modular Advanced ReacTor) is an integral-type small modular reactor developed by KAERI (Korea Atomic Energy Research Institute). This paper discusses the feasibility and applicability of a 3D-based equivalent model using dynamic condensation method for seismic analysis of a SMART control rod drive mechanism. The equivalent model is utilized for complicated seismic analysis during the design of the SMART. While the 1D-based beam-mass equivalent model is widely used in the nuclear industry for its calculation efficiency, the 3D-based equivalent model is suggested for the seismic analysis of SMART to enhance the analysis accuracy of the 1D-based equivalent model while maintaining its analysis efficiency. To verify the suggested model, acceleration response spectra from seismic analysis based on the 3D-based equivalent model are compared to those from the 1D-based beam-mass equivalent model and experiments. The accuracy and efficiency of the dynamic condensation method are investigated by comparison to analysis results based on the conventional modeling methodology used for seismic analysis.

• Journal of Power System Engineering
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• v.10 no.3
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• pp.11-16
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• 2006

The pressure fluctuation in the intake and exhaust pipe of 4 stroke-cycle diesel engine is caused by reciprocating motion of piston for suction of fresh air and exhaust of burned gas. this gas dynamic effect can be utilized for increase the volumetric efficiency. Many empirical studies have been carried out to investigate the effects of intake pulsating flow on the volumetric efficiency. However, when the gas dynamic effects are utilized for the variable speed engine to increase its performance, The speed range in which the maximum volumetric efficiency is limited and there occurs some difficulties in lay-out of intake system because it become too long. During induction process, as waves travel both directions, they are reflected and interacted each other and pressure waves are transmitted through it. Hence, the flow becomes more complex and unsteady flow. These pressure waves act upon intake pulsating flow and affects on the volumetric efficiency. In this paper the effects of pulsating flow of intake and exhaust pipes on volumetric efficiency were examined and evaluated. It was found that volumetric efficiency was affected by pulsating flow of intake and exhaust pipes.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.8
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• pp.1529-1536
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• 2011

Recently, worldwide government policy is pursuing saving energy and preservation. add to this, the solar cells are getting the spotlight nonpolluting energy source, using a variety of products for solar cell. in this paper, we'll make solar tracking system for suitable of dynamic boat. we knew that general boats are using fixed solar cell, it's first time to use tracking system of solar cells for boats so it is hard to application. To solve this problem in this paper we use to a magnetic compass and GPS for suitable solar tracking system of dynamic movement and to analyze fixed and tracking solar system. frist. solar tracking device is designed two-axis control system. one-axis control system is taken a magnetic compass for making efficiency defence solar tracking sensor, two-axis control system apply GPS latitude and longitude data for SPA(Solar position algorithm) so we know the azimuth and altitude. it analyze data value of accuracy comparison from result. so the proposed algorithm confirm to have validity.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.638-642
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• 1994

The objectives of this work are to present the dynamic simulation strategy based on cluster-modular approach and to develop a prototype simulator. In addition, methods for the improvement of computational efficiency and applicability are studied. A process can be decomposed into several clusters which consist of strongly coupled units depending upon the process dynamics or topology. The combined approach of simultaneous and sequential simulation based on the cluster structure is implemented within the developed dynamic process simulator, MOSA(Multi Objective Simulation Architecture). Dynamic simulation for a utility plant is presented as a case study in order to prove the efficiency and flexibility of MOSA.

• 연구논문집
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• s.28
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• pp.49-58
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• 1998

In order to analyse the scavenging efficiency in a poppet valve type 2-stroke engine. visualization of scavenging flow and quantitative experiments for measuring scavenging efficiency were performed. The effect of shroud angle in RSSV which was developed by KIMM was evaluated under steady flow rig applying single-cycle method. Also dynamic simulator was used by using gas sampling with $CO_2$ and $O_2$gas. The $90^circ$ shroud RSSV was found to be the highest efficient system, and single-cycle and dynamic simulator test are very effective to save time and cost for the development of a 2-stroke engine.

• Journal of the Korean Society of Safety
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• v.35 no.5
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• pp.39-48
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• 2020

This study proposes a fast estimation method of dynamic reliability indices or failure probability for SDOF structure subjected to earthquake excitations. The proposed estimation method attempts to derive coefficient function for correcting dynamic effects from static reliability analysis in order to estimate the dynamic reliability analysis results. For this purpose, a total of 60 cases of structures with various characteristics of natural frequency and damping ratio under various allowable limits were taken into account, and various types of approximation coefficient functions were considered as potential candidate models for dynamic effect correction. Each reliability index was computed by directly performing static and dynamic reliability analyses for the given 60 cases, and nonlinear curve fittings for potential candidate models were performed from the computed reliability index data. Then, the optimal estimation model was determined by evaluating the accuracy of the dynamic reliability analysis results estimated from each candidate model. Additional static and dynamic reliability analyses were performed for new models with different characteristics of natural frequency, damping ratio and allowable limit. From these results, the accuracy and numerical efficiency of the optimal estimation model were compared with the dynamic reliability analysis results. As a result, it was confirmed that the proposed model can be a very efficient tool of the dynamic reliability estimation for seismically excited SDOF structure since it can provide very fast and accurate reliability analysis results.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.541_542
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• 2009

This paper reviews the definition and background of dynamic pricing which is the essential element of demand response system. Also, economic efficiency and related issues on dynamic pricing are studied. Several issues on design and operation of demand response system, which can implement the dynamic pricing, are described. Therefore the results will be helpful for developing the demand response system with dynamic pricing.