• Proceedings of the KIEE Conference
• /
• 2001.05a
• /
• pp.34-37
• /
• 2001

This paper presents some results after comparing the characteristics of 3 algorithms, which are discrete Fourier transform based algorithm, least square method, and modified differential approximation algorithm, used at most distance relays all over the world. In case of the DFT based distance relaying algorithm, the length of the algorithm data window and the cut-off frequency of an anti-aliasing low-pass filter adopted are fixed. On the other hand, the data window lengths are changed according to the corresponding low-pass filters in the rest two algorithms. In series of tests, the apparent impedance estimated by the modified differential approximation algorithm shows faster and more stable characteristics of convergence than the two others.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.28 no.1
• /
• pp.63-69
• /
• 2015

In this paper, infrared reflector design targeting infrared stealth effect is presented using structural optimization based on the phase field method. The analysis model was determined to accomplish the design that an incident infrared wave was reflected to a desired direction. The design process was to maximize the objective value at the measuring domain located in a target region and the design objective was set to the Poynting vector value which represents the energy flux. Optimization results were obtained according to the variation of some parameter values related to the phase field method. The model with a maximum objective value was selected as the final optimal model. The optimal model was modified to eliminate the gray scale using the cut-off method and it confirmed improved performance. In addition, to check the desired effect in the middle wave infrared range(MWIR), the analysis was performed by changing the input wavelength. The finite element analysis and optimization process were performed by using the commercial package COMSOL combined with the Matlab programming.

• Journal of the Korean School Mathematics Society
• /
• v.16 no.3
• /
• pp.479-498
• /
• 2013

As education is one of key factors to improve national competitiveness, quality education becomes a top priority in all countries around the world. In South Korea, The Basic Skills Competency Test is administered annually to select below-basic third graders and provide intervention programs. The Basic Skills Competency Test was designed to diagnose the minimal competency of third graders according to a national-level standards. The purpose of this study was to analyze standard-setting procedures and set cut-off scores. This study offered the empirical evidence that standard-setting is generally applicable in schools by the modified Ebel method. More future researches addressing appropriate and efficient standard-setting methods in real school situations are needed to be taken in.

• Journal of the Korean Institute of Gas
• /
• v.9 no.2 s.27
• /
• pp.38-42
• /
• 2005

This study introduced concept of safety valve about development of valve for LP gas cylinders. LP gas cylinders are used more because of convenience of use, but a lot of accidents are occurred. Specially, it is used by purpose to injure glossary or others and is sometimes used to a demonstration tool. Korean government was making mandatory to use overuse cutoff valve to reduce accident, but it is real condition that product development is not following. In this study, introduce concept of safety valve that introduce more original safety concept than overuse cutoff valve. This was developed by method that insert module to present use valve and flowing of gas is controlled in state that hose or regulator un-connects to valve. Also, flowing of gas cut-off immediately if hose is cut or occurrence of overuse is produced even if is using normally.

• Wind and Structures
• /
• v.24 no.4
• /
• pp.351-365
• /
• 2017

The minimization method is widely used to predict the dynamic characteristics of a system. Generally, data recorded by experiment (for example displacement) tends to contain noise, and the error in the properties of the system is proportional to the noise level (NL). In addition, the accuracy of the results depends on various factors such as the signal character, filtering method or cut off frequency. In particular, coupled terms in multimode systems show larger differences compared to the true value when measured in an environment with a high NL. The iterative least square (ILS) method was proposed to reduce these errors that occur under a high NL, and has been verified in previous research. However, the ILS method might be sensitive to the signal processing, including the determination of cutoff frequency. This paper focused on improving the accuracy of the ILS method, and proposed the modified ILS (MILS) method, which differs from the ILS method by the addition of a new calculation process based on correlation coefficients for each degree of freedom. Comparing the results of these systems with those of a numerical simulation revealed that both ILS and the proposed MILS method provided good prediction of the dynamic properties of the system under investigation (in this case, the damping ratio and damped frequency). Moreover, the proposed MILS method provided even better prediction results for the coupling terms of stiffness and damping coefficient matrix.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2003.10a
• /
• pp.340-347
• /
• 2003

The aim of regularization of a structural configuration is to obtain a structure that consists of elements with identical or nearly identical length. And it is also possible to modify the configuration in a manner that the size of the elements vary in accordance with a specified pattern. For practical purpose, geodesic dome is cut off at a suitable place in order to make it fit on horizontal. Inevitably this pattern effects a change of element lengths. The purpose of this study is to verify a method for regularization of structural configuration by genetic algorithms and modify the element lengths of the dome. As a result of regularization of domes with various rise-span ratio, modified configurations have more regular element lengths and are more economical than initial configurations.

• Journal of IKEEE
• /
• v.22 no.3
• /
• pp.539-547
• /
• 2018

Grid-connected inverter is required to cut off the power supplied to the grid at the islanding condition, immediately. For this reason, an islanding detection is an indispensable function for grid-connected distributed generation system. Slip-Mode frequency Shift (SMS) islanding detection method is very popular method to determine the grid state. SMS method supplies the reactive power to the load according to the grid frequency. In the islanding condition of grid, this injected reactive power pulls out the grid frequency from the allowable range, then the inverter system can detect the islanding condition of the grid. The SMS method can detect the islanding state well and does not generate any harmonics of the grid current. However, the reactive power would be generated and the power quality is reduced even though the grid is not islanding condition, but normal condition. In this paper, a modified SMS method is proposed to remove the reactive power in the normal condition. The performance of the proposed method is evaluated by 600W single phase inverter experimental results.

• Korean Journal of Cognitive Science
• /
• v.35 no.1
• /
• pp.49-95
• /
• 2024

Polygraph examination, statement validity analysis and P300-based concealed information test are major three examination tools, which are use to determine a person's truthfulness and credibility in criminal procedure. Although polygraph examination is most common in criminal procedure, but it has little admissibility of evidence due to the weakness of scientific basis. In 1990s to support the weakness of scientific basis about polygraph, Farwell and Donchin proposed the P300-based concealed information test technique. The P300-based concealed information test has two strong points. First, the P300-based concealed information test is easy to conduct with polygraph. Second, the P300-based concealed information test has plentiful scientific basis. Nevertheless, the utilization of P300-based concealed information test is infrequent, because of the quantity of probe stimulus. The probe stimulus contains closed information that is relevant to the crime or other investigated situation. In tradition P300-based concealed information test protocol, three or more probe stimuli are necessarily needed. But it is hard to acquire three or more probe stimuli, because most of the crime relevant information is opened in investigative situation. In addition, P300-based concealed information test uses oddball paradigm, and oddball paradigm makes imbalance between the number of probe and irrelevant stimulus. Thus, there is a possibility that the unbalanced number of probe and irrelevant stimulus caused systematic underestimation of P300 amplitude of irrelevant stimuli. To overcome the these two limitation of P300-based concealed information test, one-probe P300-based concealed information test protocol is explored with various machine learning algorithms. According to this study, parameters of the modified one-probe protocol are as follows. In the condition of female and male face stimuli, the duration of stimuli are encouraged 400ms, the repetition of stimuli are encouraged 60 times, the analysis method of P300 amplitude is encouraged peak to peak method, the cut-off of guilty condition is encouraged 90% and the cut-off of innocent condition is encouraged 30%. In the condition of two-syllable word stimulus, the duration of stimulus is encouraged 300ms, the repetition of stimulus is encouraged 60 times, the analysis method of P300 amplitude is encouraged peak to peak method, the cut-off of guilty condition is encouraged 90% and the cut-off of innocent condition is encouraged 30%. It was also conformed that the logistic regression (LR), linear discriminant analysis (LDA), K Neighbors (KNN) algorithms were probable methods for analysis of P300 amplitude. The one-probe P300-based concealed information test with machine learning protocol is helpful to increase utilization of P300-based concealed information test, and supports to determine a person's truthfulness and credibility with the polygraph examination in criminal procedure.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.11 no.5
• /
• pp.340-348
• /
• 1986

The design of two-dimensional zero-phase FIR digital filters by transformations is a popular and well-developed technique, but is suffers from the disadvantage that in its current form the filters with only four quadrant symmetry can not be designed exactly circular symmetry at frequencies far from the origin. it is shown how symmetry requirement for the filters with any number of dimensions can be fulfilled with arbbitrary percision by adapting transformation with the appropriate series expansions. this transformation has been known generally as the McClellan transformation. In this paper, a simple method for ensuring exelent circular symmetry at frequencies far from the origin is presented. This method which employs the Modified Mcclellan trnsformation for the design of 2-D FIR filter form 1-D FIR filters is quite useful for the design of 2-D FIR filters with multiple cutoff boundaries such as band-pass filters.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.36D no.3
• /
• pp.66-74
• /
• 1999

InAlGaAs/InGaAs HBTs with the various emitter junction gradings(xf=0.0-1.0) and the modified collector structures (collector- I;n-p-n, collector-II;i-p-n) are simulated and analyzed by HMC (Hybrid Monte Carlo) method in order to find an optimum structure for the shortest transit time. A minimum base transit time($ au$b) of 0.21ps was obtainsed for HBT with the grading layer, which is parabolically graded from $x_f$=1.0 and xf=0.5 at the emitter-base interface. The minimum collector transit time($\tau$c) of 0.31ps was found when the collector was modified by inserting p-p-n layers, because p layer makes it possible to relax the electric field in the i-type collector layer, confining the electrons in the $\Gamma$-valley during transporting across the collector. Thus InAlGaAs/InGaAs HBT in combination with the emitter grading($x_f$=0.5) and the modified collector-III showed the transit times of 0.87 psec and the cut-off frequency (f$\tau$) of 183 GHz.