• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.9 no.1
• /
• pp.25-30
• /
• 2013

The periodic inspection of piping and pressure vessels welds in nuclear power plant has to provide reliable result related to weld flaws, such as location, maximum amplitude response, ultrasonic length, height and finally the nature or flaw pattern. The founded flaw in ultrasonic inspection is accepted or rejected based on these data. Specially, the amplitude of flaw response is used as basic parameter for flaw sizing and it may cause some deviation in length sizing result. Currently the ultrasonic inspections in nuclear power plant components are performed by specific inspection procedure which describing inspection technique include inspection system, calibration methodology and flaw characterizing. To perform ultrasonic inspection during in-service inspection, reference gain should be established before starting ultrasonic inspection by the requirement of ASME code. This reference gain used as basic criteria to evaluate flaw sizing. Sometimes, a little difference in establishing reference gain between calibration and field condition can lead to deviation in flaw sizing. Due to this difference, the inspection result may cause flaw sizing error. Therefore, the objective of this study is to compare and evaluate the ultrasonic amplitude difference between air filled and water filled pipe in nuclear power plant. Additionally, the accuracy of flaw sizing is estimated by comparing both conditions.

• 한국태양에너지학회:학술대회논문집
• /
• 2008.11a
• /
• pp.81-84
• /
• 2008

This paper discussed the validity of wind force power generation in consideration of the topographical characteristics of Korea. In order to estimate the exact generation of wind power plants, we analyzed and compared wind resources in mountain areas and plain areas by introducing not only wind velocity, the most important variable, but also wind distribution and wind standard deviation that can reflect the influence of landform sufficiently. According to the results of this study, generation was higher at wind power plants installed in southwestern coastal areas where wind velocity was low than at those installed in mountain areas in Gangwondo where wind velocity was high. This suggests that the shape parameter of wind distribution is low due to the characteristics of mountain areas. and the standard deviation of wind velocity is large due to the effect of mountain winds, and therefore, actual generation is low in mountain areas although wind velocity is high.

• Tunnel and Underground Space
• /
• v.12 no.4
• /
• pp.268-276
• /
• 2002

In this study, a 3D coordinate measurement system equipped with a laser displacement meter for digitizing rock joint surface was established and the digitized data were used to calculate several roughness parameters. The parameters used in this study were micro avenge inclination $angle(i_{ave})$, average slope of joint $asperity(SL_{ ave})$, root mean square of $i-angle(i_{rms})$, standard deviation of height(SDH), standard deviation of $i-angle(SD_i)$, roughness profile $index(R_P)$, and fractal dimension(D). The relationships between the roughness parameters based on the digitzation of the surface profile were analyzed. Since the measured value varied according to the degree of reflection and the variation of colors at the measuring point, rock joint surface was painted in white to minimize the influence of the surface conditions. The comparison of the measured values and roughness parameters before and after painting revealed the better consequence from measurement on the painted surfaces. Also, effect of measuring interval was studied. As measured interval was increased, roughness parameters were exponentially decreased. The incremental sequence of degree of decrease was $SDH\; i_{ave},\; i_{rms},\; SD_i,\;and\; R_ p-1$. As a result of comparison of parameters from pin-type measurement system and laser type measurement system, all value of parameters were higher when laser-type measurement system was used, except SDH.

• International Journal of Concrete Structures and Materials
• /
• v.19 no.1E
• /
• pp.11-16
• /
• 2007

Recently, probabilistic neural network (PNN) has been proposed to predict the compressive strength of concrete for the known effect of improvement on PNN by the iteration method. However, an empirical method has been incorporated in the PNN technique to specify its smoothing parameter, which causes significant uncertainty in predicting the compressive strength of concrete. In this study, a modified probabilistic neural network (MPNN) approach is hence proposed. The global probability density function (PDF) of variables is reflected by summing the heterogeneous local PDFs which are automatically determined by the individual standard deviation of each variable. The proposed MPNN is applied to predict the compressive strength of concrete using actual test data from a concrete company. The estimated results of MPNN are compared with those of the conventional PNN. MPNN showed better results than the conventional PNN in predicting the compressive strength of concrete and provided promising results for the probabilistic approach to predict the concrete strength by using the individual standard deviation of a variable.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.19 no.5
• /
• pp.541-546
• /
• 2008

A novel, simple and broadband $90^{\circ}$ phase shifter was proposed and fabricated by the LTCC process. It is composed of a $180^{\circ}$ transmission line between two $90^{\circ}$ shorted transmission lines. Design equations for the proposed $90^{\circ}$ phase shifter are derived by the method of admittance parameter analysis. Based on design equations, $90^{\circ}$ phase shifter was designed and fabricated to operate in the C-band with ${\pm}2^{\circ}$ of phase deviation.

• Wind and Structures
• /
• v.24 no.1
• /
• pp.79-93
• /
• 2017

Wind-induced fluctuating internal pressures in a building with a dominant opening can be described by a second-order non-linear differential equation. However, the accuracy and efficiency of the governing equation in predicting internal pressure fluctuations depend upon two ill-defined parameters: inertial coefficient $C_I$ and loss coefficient $C_L$, since $C_I$ determines the un-damped oscillation frequency of an air slug at the opening, while $C_L$ controls the decay ratio of the fluctuating internal pressure. This study particularly focused on the value of loss coefficient and its influence factors including: opening configuration and location, internal volumes, as well as wind speed and approaching flow turbulence. A simplified formula was presented to predict loss coefficient, therefore an approximate relationship between the standard deviation of internal and external pressures can be estimated using Vickery's approach. The study shows that the loss coefficient governs the peak response of the internal pressure spectrum which, in turn, will directly influence the standard deviation of the fluctuating internal pressure. The approaching flow characteristic and opening location have a remarkable effect on the parameter $C_L$.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.54 no.10
• /
• pp.480-486
• /
• 2005

This paper proposes a method to consider an aging failure probability and survival probability of power system components, though only aging failure probability has been considered in existing mean life calculation. The estimates of the mean and its standard deviation is calculated by using Weibull distribution, and each estimated parameters is obtained from Data Analytic Method (Type H Censoring). The parameter estimation using Data Analytic Method is simpler and faster than the traditional calculation method using gradient descent algorithm. This paper shows calculation procedure of the mean life and its standard deviation by the proposed method and illustrates that the estimated results are close enough to real historical data of combustion turbine generating units in Korean systems. Also, this paper shows the calculation procedures of a probabilistic failure prediction through a stochastic data analysis. Consequently, the proposed methods would be likely to permit that the new deregulated environment forces utilities to reduce overall costs while maintaining an are-related reliability index.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.48 no.2
• /
• pp.97-106
• /
• 1999

This paper proposes the structure and the algorithm of the Fuzzy-Neural Controller(FNNC) which is able to adapt itself to unknown plant and the change of circumstances at the Fuzzy Logic Controller(FLC) with the Neural Network. This Learning Fuzzy Logic Controller is made up of Fuzzy Logic controller in charge of a main role and Neural Network of an adaptation in variable circumstances. This construct optimal fuzzy controller applied to the 2-area load frequency control of power system, and then it would examine fitness about parameter variation of plant or variation of circumstances. And it proposes the optimal Scale factor method wsint three preformance functions( E, , U) of system dynamics of load frequency control with error back-propagation learning algorithm. Applying the controller to the model of load frequency control, it is shown that the FNNC method has better rapidity for load disturbance, reduces load frequency maximum deviation and tie line power flow deviation and minimizes reaching and settling time compared to the Optimal Fuzzy Logic Controller(OFLC) and the Optimal Control for optimzation of performance index in past control techniques.

• Proceedings of the KIEE Conference
• /
• 2001.07e
• /
• pp.80-85
• /
• 2001

Frequency is an important operating parameter of a power system. Frequency of a power system remains constant if sum of all the loads plus losses equals total generation in the system. However, the frequency starts to decrease if total generation is less than the sum of loads and tosses. On the other hand, the system frequency increases if total generation exceeds the sum of loads and losses. Electric power systems sustain transient frequency swings whenever the balance between generation and load does not no longer hold. To cope with this Constraints, it requires an accurate and high speedy frequency deviation estimation technique and suitable adjustment to obtain the power system energy balance. The fundamental frequency component of 3-phase signal is first extracted by using an algorithm based on FIR(finite duration impulse response) filter, a phase angle of a voltage. The rate change of the phase angle is used for estimation and speed in its process. Also, to confirm the validity of the proposed algorithm, the simulation results obtained by using EMTP(electro magnetic transients program) are shown.

• Proceedings of the SAREK Conference
• /
• 2008.06a
• /
• pp.895-900
• /
• 2008

It is the objective of the present study to conduct correlation analysis for deriving control parameters in vertical shafts using the results obtain by the design of experiments in the preceding research. The control parameters are categorized into objective parameters, derived parameters, condition parameters, operation parameters, and sensing parameters. The maximum pressure in the shaft should be sufficiently small in order to maintain exhaust hood performance. The pressure variations between floors should also be minimized in order to maintain uniform exhaust performance between floors and to save energy for excessive pressure drop in the shaft. The standard deviation based on -4Pa is proposed as an objective parameter to control pressure in shafts. The correlation equation has been obtained between the standard deviation and the sensing parameters of outdoor temperature and the pressure at the top of the shaft.