• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1995.10a
• /
• pp.769-772
• /
• 1995

Most turbo machines, which operate at high speeds, such as gas turbines, jet engines, pumps, and compressors are prone to perrturbing vibrations. The best vibration control method for rotors is to eliminate destabilizing factors. Careful balancing application of "more stable" oil-lubricated bearing, such as tilting pad bearings or use of anti-swirl devices in seals, are examplse of passive vibration control methods. the use of magnetic bearing is an active control method. An obvious advantage of active control is that it provides damping (or modifies system stiffness or other parameters) only when there is a need for that, i.e., in emergency states, while not affecting the rotor normal operational conditions. Moreover, active control methods provide exact position control through on-line control. In this study, a magnetic actuator, digital contrliier using DSP, and bipolar operational power supply/amplifiers were developed to show the effectiveness of reducing robot vibration. Also the curve fitting procedure to obtain the transfer function of frequency dependent component was developed. Results presented in this dissertation will provide a well-defined technical parameters in designing magnetic damper system.er system.

• Journal of Korean Vacuum Science & Technology
• /
• v.6 no.4
• /
• pp.149-152
• /
• 2002

We performed the modeling of the dielectric functions of C $d_{0.77}$M $g_{0.23}$Te by using parametric semiconductor model. Parametric model describes the analytic dielectric function as the summation of several energy-bounded Gaussian-broadened polynomials and provides a reasonably well parameterized function which can accurately reproduce the optical constants of semiconductor materials. We obtained the values of fitting parameters of the Mg composition 0.23 in the parametric model. From these parameters we could remove interference oscillations to obtain the dielectric function of C $d_{0.77}$M $g_{0.23}$Te alloy film for full 0.5-6.0 eV energy range.y range.

• Water for future
• /
• v.25 no.2
• /
• pp.67-78
• /
• 1992

Several field surveys were conducted to investigate changes of water quality with time in a tidal river. Results indicated that nitrification process were dependent on the change of salinity and suspended solids concenttration. Therefore laboratory batch experiments were conducted, using suspended solids and sediment taken from a tidal river, to study the effect of salinity on nitrification and to estimate kinetic parameters of it in the tidal river. suspended solids and sediment were sampled at a point in the middle stream. Sediments were collect from the aerobic layer of mud. The change of nitrogen concentration with time was clearly explained with Monod groth model and kinetic parameters were obtained by curve fitting method. Changes in NH4-N, NO2-N, and NO3-N concentrations in the river ROKKAU with time were simulated well using Lagrangian reference frame and parameter values obtained in the laboratory tests. T도 mechanism of nitrification by suspended solids and sediment in a tidal river is shown to depend on tidal effects.

• Journal of Korean Society for Quality Management
• /
• v.36 no.4
• /
• pp.87-92
• /
• 2008

It is common to use CUSUM charts for detecting small level shifts in processes control, in which reference value(k) and decision interval(h) are the design parameters to be determined. To control process with autocorrelation, CUSUM charts could be applied to residuals obtained from fitting ARIMA models. However, constant level shifts in processes lead to varying mean shifts in residual processes and thus standard CUSUM charts may need to be modified. In this paper, we study the performance of CUSUM charts with various design parameters applied to autocorrelated processes, especially focussing on ARMA(1,1) models, and propose how they can be determined to get better performance in terms of the average run length.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.06a
• /
• pp.571-575
• /
• 2000

The physical properties of the spatial model, mass, stiffness and damping matrix, can be defined by a specific natural frequency, damping ratio and mode shape. These modal parameters can be determined from a set of frequency response function(FRF) measured by exciting the structure and measuring the responses at various points around the structure. In this paper, The Transfer Matrix is obtained by experimental modal analysis for the 3-story scaled building model which TMD is installed on top and the physical properties of the spatial model is determined using the residue matrix and the location of poles from FRF measurement using polynomial curve fitting methods.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.15 no.2
• /
• pp.232-242
• /
• 2015

Analytical study of surface recombination at the $Si/SiO_2$ interface is carried out in order to set the optimum surface conditions that result in minimum dark base current and maximum open circuit voltage in silicon solar cells. Recombination centers are assumed to form a continuum rather than to be at a single energy level in the energy gap. It is shown that the presence of a hump in the dark I-V characteristics of high efficiency PERL cells is due to the dark current transition from a high surface recombination regime at low voltage to a low surface recombination regime at high voltage. Successful fitting of reported dark I-V characteristics of a typical PERL cell is obtained with several possible combinations of surface parameters including equal electron and hole capture cross sections.

• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.1882-1887
• /
• 2003

The response surface method (RSM) became one of famous meta modeling techniques, however its approximation errors give designers several restrictions. Classical RSM uses the least squares method (LSM) to find the best fitting approximation models from the all given data. This paper discusses how to construct RSM efficiently and accurately using moving least squares method (MLSM) with sensitivity information. In this method, several parameters should be determined during the construction of RSM. Parametric study and optimization for these parameters are performed. Several difficulties during approximation processes are described and numerical examples are demonstrated to verify the efficiency of this method.

• Korean Journal of Clinical Laboratory Science
• /
• v.40 no.1
• /
• pp.18-25
• /
• 2008

In classical titrimetric analyses, the major concern is the concentration of titrant, usually the aqueous solution of hydrochloric acid or sodium hydroxide, that could be changed as time goes by and it is accompanied with the inaccuracy of the resulting data. And the statistical approach, the nonlinear regression analysis, which is a well-known statistical method, was introduced to determine the accurate concentration of the titrant and the exact value of parameters, $K_a$, r, $C_a$, $C_b$, for 0.01 M aqueous solutions of analytes, sodium pyruvate, sodium acetate, sodium bicarbonate, ammonium hydroxide, ammonium chloride and acetic acid at $25^{\circ}C$. We used Gauss-Newton method for the linearlization of the nonlinear titration system and the two-parameter fitting showed appreciable convergent data for the parameters of the analytes set with the various range of $K_a$ value.

• The Korean Journal of Applied Statistics
• /
• v.7 no.2
• /
• pp.249-261
• /
• 1994

The purpose of this research is to obtain a Simple Logistic Curve for the curve fitting of Korean total Population. Based on the population census data from 1949 to 1990, the parameters are estimated by 3-group method. As the results, intercensal populations of Korea from 1950 to 190 are estimated, and Korean total populations from 1991 to 2010 A.D. are projected. And we also can suggest the upper asymptote 58, 616 thousands of Korean total population.

• Computational Structural Engineering : An International Journal
• /
• v.2 no.1
• /
• pp.1-10
• /
• 2002

Information on the distribution of the basic random variables is essential for the accurate evaluation of structural reliability. The usual method for determining the distribution is to fit a candidate distribution to the histogram of available statistical data of the variable and perform appropriate goodness-of-fit tests. Generally, such candidate distributions would have two parameters that may be evaluated from the mean value and standard deviation of the statistical data. In the present paper, a-parameter Gamma distribution, whose parameters can be directly defined in terms of the mean value, standard deviation and skewness of available data, is suggested. The flexibility and advantages of the distribution in fitting statistical data and its significance in structural reliability evaluation are identified and discussed. Numerical examples are presented to demonstrate these advantages.