• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.3
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• pp.247-255
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• 2010

Bonding strength of shotcrete is a significant influential factor which plays the role of collapse prevention of tunnel crown and of debonding prevention of shotcrete induced by the blasting vibration. Thus, the evaluation of the shotcrete bonding state is one of the core components for shotcrete quality control. In this study, the peak particle velocities induced by blasting were measured on the shotcrete in a tunnel construction site and its effect on the bonding state of shotcrete is investigated. Drilling and blasting technique was used for the excavation of intersection tunnel connecting the main tunnel with the service tunnel. Blast-induced vibrations were monitored at some points of the main tunnel and the service tunnel. The shotcrete bonding state was evaluated by using impact-echo test coupled with the time-frequency domain analysis which is called short-time Fourier transformation. Analysis results of blast-induced vibrations and the time-frequency domain impact-echo signals showed that the blasting condition applied to the excavation of intersection tunnel hardly affects on the tunnel shotcrete bonding state. The general blasting practice in Korea was evaluated to have a minor negative impact on shotcrete quality.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.05a
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• pp.506-510
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• 2004

A multi-phase interleaved buck converter is used to reduce current ripples and filter size of a power supply. This paper addresses the modelling and steady-state analysis of the multi-phase interleaved buck converter operated in discontinuous inductor current mode. The model is derived using an averaging technique in steady state. The do voltage ratio and the range of the discontinuous inductor current mode(DICM) and the continuous output current mode(COCM) are derived from the averaged state-space model. In addition, the efficiency is investigated according to the number of phase.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.1
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• pp.145-152
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• 2001

Thermal deformation of a machine tool structure can be evaluated from the analysis of the whole temperature field. However, it is extremely inefficient and impossible to know the whole temperature field by measuring temperatures at every point. So, the temperature estimator is required, which can predict the whole temperature field from the temperatures of just a few points. In this paper, a 1-dimensional heat transfer problem is modeled with modal analysis and state space equations. And then the state observer is designed to estimate the intensity of heat source and the whole temperature field in real time. The reliability of the estimator is verified by making comparison between solutions obtained from the proposed method and the exact solutions of examples. The proposed method is applied to the estimation of temperature distribution in a ball screw system.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1990.10a
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• pp.63-67
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• 1990

Many characteristics of space charge in insulating materials which is the cause of insulation break down was measured quantita-tively. It was confirmed that injection charge of the electrode was trapped to form mainly space charge. In the present paper, collecting potential was determined by TSSP and mean depths of space distribution was investigated by measuring variation quantity of space charge under the different bias time, voltage and temperature. Experimental resuts was in good agreement with model analysis on a stedy state.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.5
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• pp.230-237
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• 2003

Current mode control has been used for DC to DC converters for over twenty years. There are many different control schemes which use the inductor current signal in one way or another to control the DC to DC converter. In this paper, the state space averaging technique is applied for the analysis of flyback type current mode control circuit. We made real converter for the guarantee of stable output characteristic and proper design of feedback circuit. The validity of proposed method is verified from test result. The improvement of stability is confirmed by sinusoidal signal injection method with isolated transformer. It is known that phase margin is sufficient and gain crossover frequency fc is early 1/5 of switching frequency, fs, from the experimental result with frequency response analyzer.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.682-686
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• 1991

The purpose of a solar tracking system (STS) is to control the attitude of a space vehicle so that it will track the sun with high accuracy. In this paper, the literature of tracking of the sun in a plane is surveyed and a control modeling for the analysis of STS is presented by simultaneous transfer functions and state-space equations. Also a program for obtaining state variables by the single term Walsh series(STWS) approach is developed. The proposed approach is much simpler in analysis and easier in implementation than the Runge-Kutta numerical integration Method. The results of computer simulation are shown for the dynamic behaviors of vehicle axis, armature-controlled dc motor and controller of STS via a Runge-Kutta method and a single term Walsh series approach, respectively.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.4
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• pp.510-519
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• 2015

Concerning the issue of high-dimensions, hybrid uncertainties of randomness and intervals including implicit and highly nonlinear limit state function, reliability analysis based on the hybrid uncertainty reliability mode combining with back propagation neural network (HU-BP neural network) is proposed in this paper. Random variables and interval variables are as input layer of the neural network, after the training and approximation of the neural network, the response variables are obtained through the output layer. Reliability index is calculated by solving the optimization model of the most probable point (MPP) searching in the limit state band. Two numerical cases are used to demonstrate the method proposed in this paper, and finally the method is employed to solving an engineering problem of the aerospace friction plate. For this high nonlinear, small failure probability problem with interval variables, this method could achieve a good analysis result.

• Journal of Radiation Industry
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• v.4 no.1
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• pp.85-89
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• 2010

The radioactive experiments are carried out for diagnosis of a variety of industrial processes in terms of the operation condition and the efficiency by measuring the residence time distribution. However, it is not easy to interpret the residence time distribution using the conventional methods when the flow rate is not constant and a number of processes are coupled in a complicated manner. In these cases, they can be analyzed by describing the system with mathematical models that can be defined with the state-space equations. In this paper, the residence time distribution of sludge was measured with a radiotracer, $^{46}Sc-EDTA$, in the digester of which the flow rate varies with time. The digester was assumed as a linear time variant system since the flow rate changed during the experiment and the operation efficiency of the digester was calculated by applying the state-spae equations.

• The Korean Fashion and Textile Research Journal
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• v.9 no.1
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• pp.72-80
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• 2007

The purpose of this study is to identify the latest trend and type of retail space, and the features according to type of retail space of global prestige brand. To do this, literature analysis was executed by related books, articles, and theses. As a result, the latest trend of fashion retail space which has appeared after 2000 is as follows: 1) The differentiation of fashion brand through collaboration between fashion designers and architects, 2) retail space extension strategy, 3) retail space as a cultural space, 4) bold investment for retail space. The type of fashion retail space which has appeared after 2000 is as follows: 1) Spectacular flagship retail space of monumental scale, 2) global type retail space which exhibits common features through the whole world, 3) localization retail space which shows different features according to store location 4) innovative retail space out of traditional store form. The result of this study will be utilized when a domestic fashion brand establishes global marketing strategy of retail space.

• The Journal of Sustainable Design and Educational Environment Research
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• v.3 no.2
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• pp.21-37
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• 2003

This study has the purpose for analysis of each region's property in order to plan a elementary school's space according to community property. For this analysis. we used classification method through classification analysis. classification analysis is one of the useful statistical analysis methode for determining each region's policy through classifying regions which have a similar property. On this study, Seoul and Kyongkido is classified by 4 groups and each group has a different community property. Such a analysis is thought of helping establishing the objective. reasonable space-plan through comparative analysis between subjective claim and objective state indicator of each region.