• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.4
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• pp.364-374
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• 2012

The purpose of this study is to perform the reliability-corrected development cost estimation of the launch vehicle at the conceptual design phase. In order to estimate the launch vehicle development cost, the estimation method based on the independent variable such as the rocket performance and dry mass has been mainly implemented up to now. This approach has made the approximate cost estimation possible, however, the cost variation according to the reliability requirement could not be reflected. In this paper, the cost estimation methodology that introduces the reliability factor in addition to the performance and mass in the TRANSCOST model is presented in order to improve the limitation of current cost estimation method. The development cost of KSLV(Korea Space Launch Vehicle)-II is estimated on the basis of this newly implemented concept with reliability as an added parameter.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.5
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• pp.241-248
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• 1999

Recently, many linear motion generators and motors are rapidly finding applications that ranges from short stroke linear motion vibrators, such as dynamic cone type loudspeakers to stirling engine driven linear reciprocating alternators, compressors, textile machines etc. The stroke-length may go up to 2m, and the maximum speed is in the range of 5 to 10m/s with oscillating frequency as high as 15 kHz. Therefore, the linear oscillating actuators(LOAs) may be considered as variable speed drivers of precise controller with stoke-length and reversal periods during the reciprocating motion. In this paper, the design, fabrication, experiments, and extraction of control parameters of a moving coil type LOA for driving of linear reciprocating motion control systems, are treated. The actuator consists of the NdFeB permanent magnets with high specific energy as the stator produced magnetic field, a coil-wrapped nonmagnetic hollow rectangular bobbin structure, and an iron core as a pathway for magnetic flux. Actually, the design is accomplished by using FEM analysis for the basic configuration of a magnetic circuit, and characteristic equations for coil design. In order to apply as the drivers of a linear motion reciprocating control system, the control parameters and circuit parameters, such as input voltage-stoke, exciting frequency-stoke, coil inductance and so on, are extracted from the analysis and experiments on concerning a fabricating LOA.

• Journal of Korean Society for Quality Management
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• v.48 no.1
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• pp.29-50
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• 2020

Purpose: Targeting the members of manufacturing and Service industry Quality Control team this study is going is to carry out research about whether the outcome of OCB(Organizational Citizenship Behaviors) and organization can be brought about by organizational culture that is suitable for them. this study tries to identify the direct･indirect causal relationship between these variables and OCB by selecting organizational culture as a leading variable and job satisfaction as a parameter. Methods: SPSS 22.0 was used for data analysis and AMOS 18.0 statistical program for structural equation model analysis. For the descriptive statistics this study verified reliability analysis, feasibility analysis, structural equation model analysis, research hypothesis, and mediating effects. Results: As a result of path analysis estimating the regression coefficients for the linear structure analysis of the correlations between variables for the hypothesis verification, the rational culture among the organizational culture types of the manufacturing Quality Control team showed a positive (+) effect on the job satisfaction, and hierarchical culture has negative(-) effect on job satisfaction. Conclusion: This study suggested that the composition and friendly behavior of desirable organizational culture has a very close relationship in connection between job satisfaction and OCB by examining the causal relationship between OCB for improvement activities for organizational culture by establishing the organizational culture and job satisfaction of the manufacturing Quality Control team.

• Nuclear Engineering and Technology
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• v.27 no.3
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• pp.336-343
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• 1995

The Self Tuning Regulator(STR) method which is an approach of adaptive control theory, is ap-plied to design the fully automatic power controller of the nonlinear reactor model. The adaptive control represent a proper approach to design the suboptimal controller for nonlinear, time-varying stochastic systems. The control system is based on a third­order linear model with unknown, time-varying parameters. The updating of the parameter estimates is achieved by the recursive extended least square method with a variable forgetting factor. Based on the estimated parameters, the output (average coolant temperature) is predicted one-step ahead. And then, a weighted one-step ahead controller is designed so that the difference between the output and the desired output is minimized and the variation of the control rod position is small. Also, an integral action is added in order to remove the steady­state error. A nonlinear M plant model was used to simulate the proposed controller of reactor power which covers a wide operating range. From the simulation result, the performances of this controller for ramp input (increase or decrease) are proved to be successful. However, for step input this controller leaves something to be desired.

• The Journal of the Korea Contents Association
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• v.12 no.11
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• pp.313-337
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• 2012

Recently, according to the being activated exhibition, it has been focused on the participants in order to enhance its interest and satisfaction. Consequently it is set up the model of research and the hypotheses based on the leading study of the physical environment of the exhibition and experience This study would like to analyze how the physical environments of the exhibition are effected on the factor of the experience and the participants' satisfaction. It also would like to check the factor of the experience to promote the participants' call and provide the useful information for the exhibitors to raise the participants' satisfaction. Being set the physical environment of the exhibition(layout accessibility, Facility aesthetics, facility cleanliness, convenience, comfort, human services) as a independent variable and fix the factor of experience (sense, feel, think, act and relate) as a parameter, the participants' satisfaction is identified. As a result of the research, the factor of experience is affected by the physical environment of the exhibition and the participants' satisfaction is affected by the factor of the experience. Therefore, the exhibitors have to consider the physical environments of the exhibition and the factor of experience for making the participants' satisfaction high when they hold the exhibitions.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.3
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• pp.50-57
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• 1996

A numerical method is presented to obtain the natural frequencies and mode shapes of the arbitrary tapered beams with static deflection due to arbitrary distributed dead loads. The differential equation governing free vibration of such beams is derived and solved numerically. The double integration method using the trapezoidal rule is used to solve the static behaviour of beams loaded arbitrary distributed dead load. Also, the Improved Euler method and the determinant search method are used to integrate the differential equation subjected to the boundary conditions and to determine the natural frequencies of the beams, respectively. In the numerical examples, the various geometries of the beams are considered : (1) linearly tapered beams as the arbitrary variable cross-section, (2) the triangular, sinusoidal and uniform loads as the arbitrary distributed dead loads and (3) the hinged-hinged, clamped-clamped and hinged-clamped ends as the end constraints. All numerical results are shown as the non-dimensional forms of the system parameters. The lowest three natural frequencies versus load parameter, slenderness ratio and section ratio are reported in figures. And for the comparison purpose, the typical mode shapes with and without the effects of static deflection are presented in the figure. According to the numerical results obtained in this analysis, the following conclusions may be drawn : (1) the natural frequencies increase when the effects of static deflections are included, (2) the effects are larger at the lower modes than the higher ones and (3) it should be betteF to include the effect of static deflection for calculating the frequencies when the beams are supported by both hinged ends or one hinged end.

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.1
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• pp.66-72
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• 2004

PID control has been well used for several decades. For PID algorithms, some tuning methods are used for selecting PID parameters and with these selected parameters, PID control system is designed. But in some cases various kinds of performance indices are used instead of well-known tuning rules, and so variable type of performance index must be tested so that the designed control system meets the some specifications. For 2 DOF PID controller design this paper presents a linear combinational type of performance indices constituting of index for robust performance, which is obtained by h infinity norm of a weighted complementary sensitivity function, including other time domain indices such as error, energy and changing rate of control input. By numerical methods, the optimal 2 DOF PID parameters are obtained. Therefore various types of 2 degree of freedom PID controllers such as I-PD controller are used so that this two degree of freedom PID controllers may give more desirable output characteristics. Simulations are done with MATLAB m file and mdl files.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.5 s.305
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• pp.115-122
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• 2005

There are some problems in directly applying the conventional MPEG bit-stream based watermarking schemes to the bit-stream of a new compression standard, H.264/AVC. In this paper we analyze the effects of the conventional DCT-based watermarking scheme to H.264/AVC, especially in terms of image distortions and bit-rate changes. It turns out that the intra-frame prediction md CAVLC of H.264/AVC with the watermarking worsen the image distortions and bit-rate changes. The experiment results show on average 28.17dB decrease in PSNR and 56.71% increase in bit-rate over all QPs.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.7
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• pp.32-38
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• 2012

In this paper, to eliminate intersymbol interference of the received signal due to multipath propagation, a parallel equalization algorithm using two error estimation functions is proposed. In the proposed algorithm, multilevel two-dimensional signals are considered as equivalent binary signals, then error signals are estimated using the sigmoid nonlinearity effective at the initial phase equalization and threshold nonlinearity with high steady-state performance. The two errors are scaled by a weight depending on the relative accuracy of the two error estimations, then two filters are updated differentially. As a result, the combined output of two filters was to be the optimum value, fast convergence at initial stage of equalization and low steady-state error level were achieved at the same time thanks to the combining effect of two operation modes smoothly. Usefulness of the proposed algorithm was verified and compared with the conventional method through computer simulations.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.4 s.316
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• pp.21-26
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• 2007

Output voltage waves of a DC/AC inverter system are likely to be distorted if variable loads e.g. motors or rectifiers exist in the output terminal. This paper designs a disturbance observer-based PI-controller for a single-phase inverter system that is robust against load changes. In this Paper, we regard the output voltage changes due to various loads as disturbances of the control system. Then we design a disturbance observer for estimation of the disturbances caused by the load current and any other error sources (such as parameter uncertainties and model mismatches etc.). In order to test the performance of the proposed control law, simulation studies are carried out for a single-phase inverter system using SimPowerSystem of Matlab Simuink. Compared to a simple PI-control, the disturbance observer-based controller shows enhanced performance in transient responses for step load changes.