• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.229-230
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• 2021

This study is conducted to identify the setting time of mortar mixed with super retarding agent as a series of studies to predict setting time based on the equivalent age method. The experimental results showed that mixing super-retarding agents did not adversely affect the quality of mortar, and the equivalent age calculation showed similar results regardless of curing temperature.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.199-203
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• 2005

One of the most important hydrological response characteristics is the lag time. It is well known as being under the influence of the morphometric properties of the basin, which could be expressed by catchment shape descriptors. In this paper, the geometric characteristics of an equivalent ellipse proposed by Moussa(2003) is applied for the lag time analysis. The lag time is obtained from the rainfall-runoff observed data by the method of moments suggested by Nash(1960) and the relationships between the basin morphometric properties and the lag time are discussed as applied to 3 catchments in Korea. Additionally, the shapes of equivalent ellipse are examined how they are transformed from upstream area to downstream one. As a result, the relationship between descriptors based on a equivalent ellipse a+b and $a+b+{\epsilon}OM$, and the lag time is shown to be close and the shape of ellipse is presented to approach a circle along the river downwards. Also, the notion of compactness which is used to express the shape of an irregular plan-form is tried to apply.

• Structural Engineering and Mechanics
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• v.66 no.1
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• pp.139-149
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• 2018

Many practical engineering problems are associated with nonlinear systems subjected to nonstationary random excitations. Equivalent linearization methods are commonly used to seek for approximate solutions to this kind of problems. Compared to various approaches developed in the frequency and mixed time-frequency domains, though directly solving the system equation of motion in the time domain would improve computation efficiency, only limited studies are available. Considering the fact that the orthogonal functions have been widely used to effectively improve the accuracy of the approximated responses and reduce the computational cost in various engineering applications, an orthogonal-function-based equivalent linearization method in the time domain has been proposed in the current paper for nonlinear systems subjected to nonstationary random excitations. In the numerical examples, the proposed approach is applied to a SDOF system with a set-up spring and a SDOF Duffing oscillator subjected to stationary and nonstationary excitations. In addition, its applicability to nonlinear MDOF systems is examined by a 3DOF Duffing system subjected to nonstationary excitation. Results show that the proposed method can accurately predict the nonlinear system response and the formulation of the proposed approach allows it to be capable of handling any general type of nonstationary random excitations, such as the seismic load.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.5
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• pp.477-482
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• 2009

This study analyzes the result with dynamic simulation about deformation according to time when a car impacts bollard. These results are shown as followings. The maximum deformation is shown at the lower part of front grass in case of the impact of front or passenger seat but this deformation is shown at the lower part of rear bumper in case of double impact. The maximum equivalent stress is shown at the upper part by the side grass of driver seat at the elapsed time of 0.00075 second after impact in case of the impact of front or passenger seat but this deformation is shown at the front bonnet at the elapsed time of 0.004 second after the additional impact in case of double impact. The maximum total deformation or equivalent stress is shown nearly same in case of the impact of front or passenger seat. But the value of this deformation or equivalent stress in case of the impact of front or passenger seat is shown with 2 times or more than 17% respectively as this value in case of double impact.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.11
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• pp.3560-3572
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• 1996

This paper presents a new discrete-time fuzzy-sliding mode controller for robust vibration control of a smart structure featuring a piezofilm actuator. A governong equation of motion for the smart beam structure is derived and discrete-time codel with mismatched uncertainties such as parameter variations is constructed ina state space. A discrete-time sliding mode control system consisting of an equivalent controller and a discontinuous controller is formulated. In the design of the equivalent part, so called an equivalent controller separation method is adopted to achieve vzster convergence to a sliding surface without extension of a sliding region, in which the system robustness maynot be guaranteed. On the other hand, the discontinuous part is constructed on the basis of both the sliding and the convergence conditions using a time-varying feedback gain. The sliding moide controller is then incorporated with a fuzzy technique to appropriately determine principal control parameters such as a discountinuous feedback gain. Experimental implementation on the forced and random vibraiton controls is undertaken in order to demonstrate superior control performance of the proposed controller.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.1
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• pp.114-122
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• 2014

For an efficient finite-difference time-domain(FDTD) analysis of coaxial-probe feeding structures in radio frequency(RF) and microwave bands, an interrelation between equivalent source modeling techniques is investigated. In existing literature, equivalent source models with delta-gap or magnetic-frill concepts have been developed by many researchers. It is well known that FDTD implementation and computational accuracy of these source models are slightly different. In this paper, the interrelation between FDTD equivalent source models for coaxial feeding structures under the quasi-static approximation(QSA) is presented. As a function of FDTD equivalent source models, time-domain and frequency-domain responses of a coaxial-probe fed conical monopole antenna are calculated numerically. And comparison results of computational accuracy and efficiency are provided.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.1
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• pp.30-38
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• 2003

UDP library of Verilog HDL has been used for simulation of digital systems. But it takes a lot of time and efforts to generate a gate-level library equivalent to the UDP library manually due to the characteristic of UDP that does not support synthesis. It is indispensable to generate equivalent gate-level model in testing the digital systems because fault coverage can be reduced without the equivalent gate-level models. So, it is needed to automate the process of generating the equivalent gate-level models. An algorithm to solve this problem has been proposed, but it is unnecessarily complex and time-consuming. This paper suggests a new improved algorithm to implement the conversion to gate-level models, which exploits the characteristic of UDP Experimental results are demonstrated to show the effectiveness of the new algorithm.

• Steel and Composite Structures
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• v.19 no.5
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• pp.1055-1075
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• 2015

In order to investigate the accuracy and applicability of steel equivalent constitutive model, the calculated results were compared with typical tests of steel frames under static and dynamic loading patterns firstly. Secondly, four widely used models for time history analysis of steel frames were compared to discuss the applicability and efficiency of different methods, including shell element model, multi-scale model, equivalent constitutive model (ECM) and traditional beam element model (especially bilinear model). Four-story steel frame models of above-mentioned finite element methods were established. The structural deformation, failure modes and the computational efficiency of different models were compared. Finally, the equivalent constitutive model was applied in seismic incremental dynamic analysis of a ten-floor steel frame and compared with the cyclic hardening model without considering damage and degradation. Meanwhile, the effects of damage and degradation on the seismic performance of steel frame were discussed in depth. The analysis results showed that: damages would lead to larger deformations. Therefore, when the calculated results of steel structures subjected to rare earthquake without considering damage were close to the collapse limit, the actual story drift of structure might already exceed the limit, leading to a certain security risk. ECM could simulate the damage and degradation behaviors of steel structures more accurately, and improve the calculation accuracy of traditional beam element model with acceptable computational efficiency.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.6
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• pp.81-86
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• 2006

Routing signal lines in PCB, line shapes would be straight or bent. time-domain and frequency-domain evaluation of the signal property and interference are archived by precise Modeling of differential signal line. Some of CAD tools can extract equivalent circuit model parameters. but it takes a long time and heavy loads. This paper introduces a basic RLC equivalent circuit model parameter extraction technique for bent differential structures using genetic algorithm by this technique, we can model equivalent circuit of bent differential structures more faster.

• Journal of the Korea Institute of Building Construction
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• v.8 no.3
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• pp.111-117
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• 2008

This study provides the setting time prediction method of super retarding concrete incorporating mineral admixtures at the same time including fly ash(FA), blast furnace slag(BS) based on maturity method. The setting time was retarded, as super retarding agent contents increase and curing temperature decreases. In addition, apparent activation energy by Arrhenius function was ranged from $24{\sim}35KJ/mol$ with slightly difference along with mixture proportion. This value is smaller than existing value $30{\sim}50KJ/mol$. It is Indicated that equivalent age using setting time can be a proper method to predict setting time and it also exhibited comparable relativity between prediction value and measurement value. Therefore, this study provided setting time prediction value with super retarding agent contents and mineral admixture combination. Setting time prediction equation provided herein is possibly valid for estimating precise setting time of the super retarding concrete at the job site.