• The Transactions of the Korean Institute of Electrical Engineers
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• v.31 no.8
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• pp.33-38
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• 1982

This paper deals with the simplification of the transfer function in a frequency domain, viz. the integral of the squared errors between the original and the simplified model is minimized and the latter is estimated by the Walsh function. It tries to minimize the errors between the frequency responses of the two functions. This method is compared with the existing method by means of a numercal example. The frequency response of this simplified model approximates closely to that of the original model. The proposed method is simpler in analysis and easier in implementation than the existing methods. Though the Walsh function can be easily generated with the discrete values, it has errors because its zero crossings are not continuous. This method aims at the reduction of the errors in the real parts and the imaginary parts of the two functions by dividing into the more sub-intervals, and selecting the reduced-order model according to the response of the model. As a result, it can be applied for the simplification of higher order functions into lower order functions and for the design of control systems.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.298-302
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• 2002

Equivalent volume estimation of the coupler and two coupled microphones has a key role in standard microphone pressure calibration. The equivalent volume of the microphone is determined by the dynamic characteristics of the diaphragm system and front cavity. Therefore the modal parameters of diaphragm system - natural frequency and damping fatter - should be measured explicitly for the estimation of the equivalent volume. The diaphragm system is composed of the vibrating diaphragm, back slit behind diaphragm, pressure equalization vent, and front cavity which are acoustically coupled. In the measurement, the electrostatic actuator was used to excite the system with the swept sine, and the frequency response was obtained. The close actuator in front of the diaphragm must influence the radiation impedance of the system, and then the modal parameters. From the measured frequency response, the natural frequency and the damping factor could be estimated with the Complex exponential method based on the Prony model and the zero crossing real and imaginary plot.

• Journal of Korean Society for Quality Management
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• v.20 no.1
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• pp.158-167
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• 1992

This paper represents the new techniques for optimal sampling plans of reliability applying the mathematical complex number(real and imaginary number) in the complex system of reliability. The research formulation represent a mathematical model Which preserves all essential aspects of the main and auxiliary factors of the research objectives. It is important to formule the problem in good agreement with the objective of the research considering the main and auxilary factors which affect the system performance. This model was repeatedly tested to determine the required statistical chatacteristics which in themselves determine the actual and standard distributions. The evaluation programs and techniques are developed for establishing criteria for sampling plans of reliability effectiveness, and the evaluation of system performance was based on the complex stochastic process(derived by the Runge-Kutta method. by kolmogorv's criterion and the transform of a solution to a Sturon-Liouville equation.) The special structure of this mathematical model is exploited to develop the optimal sampling plans of reliability in the complex system.

• Journal of Technologic Dentistry
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• v.6 no.1
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• pp.27-30
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• 1984

This investigation was performed to study the relationship of the dental midline(an imaginary line between the centeal incisors) to the philtrum. 2,400 subjects with natural dentitions were examined. The group of the subjects was composed of 1,560 men and 840 women who had all of the upper and lower six anteriors and 0 to 4 missing teeth. Ages of the subjects ranged from 18 to 27 years. The obtained results were as follow: 1. The rates of the subjects whose philtrum and maxillary dental midline coincided was 64.92% and that of the subjects whose upper and lower dental midlines coincided was 29.17%and these rates are statistically significant, when compared respectively with those of the subjects whose philtrum and maxillary dental midline, and whose upper and lower dental midline's didn't coincide. 2. The difference between rates for the two sexes is not statistically significant. 3. Tooth missing significantly decreases the rates of the coincidence of the upper and lower dental midlines but its influence on the rates of coincidence of the dental midline to the philtrum is not significant.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1365-1370
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• 2004

It has been reported that if eight small nozzles are arranged along the circle of 40 $^{\sim}$ 72 times the diameter of single nozzle, the propane non-premixed flames are not extinguished even in 200m/s, In this research, experiments were extended to the methane flame. Nine nozzles were used- eight was evenly located along the perimeter of the imaginary circle and one at the geometric center. The space between nozzles, s, the exit velocity and the role of the jet from the center nozzle were considered. On the contrary to the propane non-premixed case, the maximum blowout velocity for the methane diffusion flame was achieved when small amount of fuel is supplied through the center nozzle and s/d equals around 21. In the laminar region, the flame attached at the center nozzle anchored the outer lifted flames.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1347-1352
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• 2001

In this study, the acoustic properties of polyester sound absorbing materials with three different bulk densities were investigated by calculating and measuring the acoustic parameters in terms of characteristic impedance, propagation constant, and absorption coefficient. For the calculations, Delany and Bazley's empirical equation was used together with the experimentally obtained specific flow resistivities under steady flow conditions. For the experimental measurements, the well-known two-thickness method was accessed. The experimentally measured values of characteristic impedance and propagation constant were generally agreed well with the corresponding calculated values. Based on the comparisons between the calculations and measurements, it was found that the magnitude of the absorption coefficient was closely related to the characteristic impedance and the real part of the propagation constant. Especially, the maximum magnitude of the absorption coefficient was depended upon the imaginary part of the propagation constant indicating the phase change of the propagation constant.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.2953-2959
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• 2021

A new practical modeling of the Norton's power law creep is proposed and implemented to analyze the high temperature behaviors of Alloy 690 SG tube material. In the model, both the stress exponent n and the rate constant B are simply treated as the temperature dependent parameters. Based on the two-step optimization procedure, the temperature function of the rate constant B(T) was determined for the data set of each B value after fixing the stress exponent n value by using the prior optimized function at each temperature. This procedure could significantly reduce the numerical errors when using the power law creep equations. Based on the better description of the steady-state creep rates, the experimental rupture times could also be well predicted by using the Monkman-Grant relationship. Furthermore, the difference in tensile strengths at high temperatures could be very well estimated by assuming the imaginary creep stress related to the given strain rate after correcting the temperature effects on the elastic modulus.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.190-193
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• 2006

The definition of the Dual system is that the total seismic force resistance is to be provided by the combination of the moment frame and the shear walls or braced frames in proportion to their stiffness and the moment frame shall be capable of resisting at least 25% of the design force in Korean Building Code 2005 (KBC 2005). But, the definition of moment frame is ambiguous whether the moment frame include the imaginary columns in the shear wall (Case I) or include only the columns outside the shear wall (Case II). 60-story RC building was designed as dual system for Case I and Case II, and the required strength and reinforcement are compared. Moment and axial capacity of the shear wall of Case II decreased about 5% due to the absence of the column in the shear wall. The requirement of upper and bottom reinforcement of slab in Case II increased 13% and 40%, respectively, when compared to those of Case I. The required longitudinal reinforcement in columns for Case II is about 1.5 times larger than that of Case I.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1597-1609
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• 2015

This paper introduces the fundamentals of the conventional LC low-pass filter circuit in the fractional domain. First, we study the new fundamentals of fractional-order LC low-pass filter circuit including the pure real angular frequency, the pure imaginary angular frequency and the short circuit angular frequency. Moreover, sensitivity analysis of the impedance characteristics and phase characteristics of the LC low-pass filter circuit with respect to the system variables is studied in detail, which shows the greater flexibility of the fractional-order filter circuit in designs. Furthermore, from the filtering property perspective, we systematically investigate the effects of the system variables (LC, frequency f and fractional orders) on the amplitude-frequency characteristics and phase-frequency characteristics. In addition, the detailed analyses of the cut-off frequency and filter factor are presented. Numerical experimental results are presented to verify the theoretical results introduced in this paper.

• International Journal of Advanced Culture Technology
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• v.8 no.2
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• pp.176-183
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• 2020

This study inquired about the convergence learning program for childhood based on Erikson's play theory and design education for children's behavior development. I analyzed the convergence learning programs of Summer Camps in the Pacific Science Center, Galileo Learning. The contents of the programs show the most used imaginary and symbolic contents that represent the real-world problems which are related design thinking process. The curriculums and structure of the programs are based on the design thinking method and K-12 theory. The visual thinking method and the applications are used for expressing their creativity and approaching the technical skills easily. The play concept theory is an affirmative way to strengthen the children's psychological and social development. Therefore, the convergence learning program should integrate the design thinking process and apply the play concept theory for supporting and developing the children's behavior.