• Fire Science and Engineering
• /
• v.16 no.1
• /
• pp.39-44
• /
• 2002

In this paper, we analysed the flame patterns and the electrical characteristics of the electric outlet which was fired at standby mode. The carbonized patterns indicated that the flame had spread about 50 cm to 70 cm. After the combustibles on wall started to burn, the temperature went up to about $300^{\circ}c$ in 150 sec. The flame formed ceiling jet and spread quickly. The tracking was generated at the shortest distance between two electrodes and the resistance was about 100$\Omega$ to 300$\Omega$ As the result of analysis using metallurgical microscope, the normal part of a blade holder showed amorphous structure, but the melted part of a blade holder damaged by tracking showed dendrite structure and void evenly. When the blade holder of damaged outlet was analyzed by SEM and EDX, we found that the structure and components of the normal part were different from those of melted part.

• Korean Journal of Remote Sensing
• /
• v.28 no.2
• /
• pp.181-189
• /
• 2012

Recently, interest in potential for estimating water quality using high resolution satellite images is increasing. However, low SNR(Signal to Noise Ratio) over inland water and radiometric errors such as non-linearity of brightness value of high resolution satellite images often lead to accuracy degradation in water quality estimation. Therefore radiometric correction should be carried out to estimate water quality for high resolution satellite images. For KOMPSAT-2 images parameters for brightness value-radiance conversion are not available and precise radiometric correction is difficult. To exploit KOMPSAT-2 images for water quality monitoring, it is necessary to investigate non-linearity of brightness value and noise over inland water. In this paper, we performed brightness value comparison between KOMPSAT-2 images and IKONOS/GeoEye-1, which are known to show the linearity. We used the images obtained over the same area and on the same date for comparison. As a result, we showed that although KOMPSAT-2 images are more noisy;the trend of brightness value and pattern of noise are almost similar to reference images. The results showed that appropriate target area to minimize the impact of noise was $5{\times}5$. Non-linearity of brightness value between KOMPSAT-2 and reference images was not observed. Therefore we could conclude that KOMPSAT-2 may be used for estimation of water quality parameters such as concentration of chlorophyll.

• Korean Journal of Remote Sensing
• /
• v.30 no.6
• /
• pp.817-827
• /
• 2014

In the satellite remote sensing, the operational environment of the satellite sensor causes image degradation during the image acquisition. The degradation results in noise and blurring which badly affect identification and extraction of useful information in image data. This study proposes a maximum a posteriori (MAP) estimation using Point-Jacobian iteration to restore a degraded image. The proposed method assumes a Gaussian additive noise and Markov random field of spatial continuity. The proposed method employs a neighbor window of spoke type which is composed of 8 line windows at the 8 directions, and a boundary adjacency measure of Mahalanobis square distance between center and neighbor pixels. For the evaluation of the proposed method, a pixel-wise classification was used for simulation data using various patterns similar to the structure exhibited in high resolution imagery and an unsupervised segmentation for the remotely-sensed image data of 1 mspatial resolution observed over the north area of Anyang in Korean peninsula. The experimental results imply that it can improve analytical accuracy in the application of remote sensing high resolution imagery.

• Korean Journal of Food Science and Technology
• /
• v.31 no.1
• /
• pp.164-170
• /
• 1999

Cracking of rice caused by moisture migration during storage under different relative humidity conditions was investigated for the establishment of safe storage condition of rice. Rice was cracked when a large difference in equilibrium relative humidity $({\Delta}ERH)$ between the rice and the environment was present. External and internal cracks were generated as the results of moisture desorption and adsorption, respectively. The external cracks by moisture desorption generated in all directions and shaped irregularly, while the internal cracks by moisture adsorption did in radial direction and showed a typical shape. The cracking trend could be analyzed by the Weibull function, and the cracking constant increased with ${\Delta}ERH$. The frequency of cracked rice increased linearly with In $({\Delta}ERH)$. The critical crack-inducing ${\Delta}ERH$ was $11.3{\sim}16.4%$ during desorption and $10.8{\sim}17.1%$ during adsorption. A diagram for the safe storage of rice was developed with respect to the initial moisture content and the water activity of rice.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.10 no.3
• /
• pp.220-224
• /
• 2017

In this paper, a method of feeding for the near field beam scanning array antenna with three dimensional focal point has been studied. The conventional array antenna theory is mostly about the far field points. The basic idea is to feed the transmitted signal so that it is in phase at the desired point. In this study, a method is proposed to compensate the phase to have the maximum received power at the point where the measurement point distance is near to the array antenna size. In the proposed method, 11 point source antennas are arrayed in three ways in free space. And the contour map is plotted by calculating the radiation patterns in the three dimensional space and the received signal intensities in the plane within the near space. As a result, it was confirmed that 3 dimensional beam scanning is possible also in the near field of the array antenna.

• The Journal of the Acoustical Society of Korea
• /
• v.20 no.5
• /
• pp.83-91
• /
• 2001

This paper proposes the Focused beamforming to estimate the location of target residing near to the observation platform in the underwater environment. The Focused beamforming technique provides the location of target by the coherent summation of a series of incident spherical waveforms considering distinct propagation delay times at the sensor array. But due to the movement of the observation platform and the variation of the underwater environment, the shape of the sensor array is no longer to be linear but it becomes distorted as the platform moves. Thus the Focused beamforming should be peformed regarding to the geometric shape variation at each time. To estimate the target location, the artificial image plane comprised of cells is constructed, and the delays are calculated from each cell where the target could be proximity to sensors for the coherent summation. After the coherent combining, the beam pattern can be obtained through the Focused beamforming on the image plane. Futhermore to compensate the variation of the shape of the sensor array, the paper utilizes the Nth-order polynomial approximation to estimate the shape of the sensor array obeying the water pulley modeling. Simulation results show the performance of the Focused beamforming for different frequency bands of the radiated signal.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.8 no.1
• /
• pp.35-41
• /
• 1997

A series-fed microstrip array antenna of beamwidth $10^{\circ}$, squint angle $80^{\circ}$ and SLL -15 dB below is designed. Series-fed arrays are formed by interconnecting all the elements by high-impedance transmission lines and feeding the power at the first element and it is a traveling-wave antenna which is terminated with a matched load. Radiation patterns and impedance matching of the antenna are analyzed by Ensemble 4.0, which is a popular software package for designing printed antennas and arrays. The squint angle of beam can be controlled by the spacing between the elements. The major advantages of series-fed array antennas are that feed arangement is compact and the losses associated with the feeding network are less than those of a corporate feed type. The antennas are fabricated on the RT/Duroid Laminates of 62 mil thickness. The experimental results are very close to the specifications to be designed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.20 no.6
• /
• pp.55-62
• /
• 2006

For the fault diagnosis of three-phase induction motors, we construct a experimental unit and then develop a diagnosis algorithm based on pattern recognition. The experimental unit consists of machinery module for induction motor drive and data acquisition module to obtain the fault signal. As the first step for diagnosis procedure, preprocessing is performed to make the acquired current simplified and normalized. To simplify the data, three-phase current is transformed into the magnitude of Concordia vector. As the next step, feature extraction is performed by kernel principal component analysis(KPCA) and linear discriminant analysis(LDA). Finally, we used the classifier based on radial basis function(RBF) network. To show the effectiveness, the proposed diagnostic system has been intensively tested with the various data acquired under different electrical and mechanical faults with varying load.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.22 no.12
• /
• pp.1184-1187
• /
• 2011

In this letter, a planar monopole UWB antenna with dual band-notched characteristics is proposed. The band-stop characteristics is realized by embedding the 1st/3rd order Hilbert-curve slots on the patch. With the dimension adjustment of each Hilbert-curve slots, the band rejection from 3.3 to 3.7 GHz and from 5.3 to 6 GHz can be accomplished easily. The VSWR and radiation pattern of the fabricated antenna are measured, and the proposed antenna would be adequate to a UWB applications.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.3 no.2
• /
• pp.305-311
• /
• 1999

In this paper, it is designed a new type single layer patch antenna which is printed on a very thin film and separated from the ground-plane by foam with a low permitivity of 1.06 and a high thickness of around quarter wavelength. It allows the use of three-dimensional transition, from one level to another, so that its bandwidth can be enhanced by wideband impedance matching. The radiation pattern, return loss, and VSWR of the antenna are calculated using "IE3D" simulation package, and compared with the experimental results. Experimental results show that the bandwidth is about 65% of center frequency 6.8 GHz, return loss and VSWR are in a fairly good agreement with the calculations.culations.