• Journal of the Korea Society for Simulation
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• v.29 no.4
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• pp.73-84
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• 2020

As the Internet began to become popular, there have been hacking and attacks on networks including systems, and as the techniques evolved day by day, it put risks and burdens on companies and society. In order to alleviate that risk and burden, it is necessary to detect hacking and attacks early and respond appropriately. Prior to that, it is necessary to increase the reliability in detecting network intrusion. This study was conducted on applying weight initialization and weight optimization to the KDD'99 dataset to improve the accuracy of detecting network intrusion. As for the weight initialization, it was found through experiments that the initialization method related to the weight learning structure, like Xavier and He method, affects the accuracy. In addition, the weight optimization was confirmed through the experiment of the network intrusion detection dataset that the Adam algorithm, which combines the advantages of the Momentum reflecting the previous change and RMSProp, which allows the current weight to be reflected in the learning rate, stands out in terms of accuracy.

• Journal of Sensor Science and Technology
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• v.10 no.4
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• pp.250-258
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• 2001

In this study, a lightning warning system (LWS) which can predict a lightning return stroke is developed, and the LWS is based on the measurement of electric field intensity at the ground level. The LWS consist of a rotation-type field mill as an electric field sensor, an impedance changer, a two-stage amplifier, and a microprocessor unit. From the calibration experiment, the frequency bandwidth and the maximum resolution of the LWS are $DC{\sim}200\;[Hz]$ and 73 [V/m], respectively. Also, the LWS can measure the electric field strength caused by a thunderstorm up to 18.7 [kV/m] at the ground. To ensure the sensing ability of the developed LWS in an actual situation, computer simulation using thundercloud models was carried out, and the result showed that the LWS can monitor the movement of thunderclouds within 6 [km] from the observation site.

• Journal of The Korean Association of Information Education
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• v.15 no.3
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• pp.345-353
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• 2011

Information and communication brings us some degree of convenient but also serious side effects. Especially, information and communication ethics is an important issue for elementary school children who are early stage in moral value. This paper proposes a triple-connected teaching and learning model. which can be applied to the elementary school children. in order to improve the educational level. The model is formed by selecting three discretionary teaching models, and applying independently them into the different classes with linking the contents for each class. A teacher can choose the teaching models based on what he wants to teach. Caring model, Home-Connected model and Simulation model were linked in our experiment. Experiments were conducted in the same condition but different learning models, Then, an educational effect was compared and analyzed in the educational level improvement point of view, between the Triple-connected teaching and learning model and the single teaching and learning model.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.4
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• pp.247-255
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• 2018

This paper proposes a transformer design of a direct cell-to-cell active cell balancing circuit with a multi-winding transformer for battery management system (BMS) applications. The coupling coefficient of the multi-winding transformer and the output capacitance of MOSFETs significantly affect the balancing current transfer efficiency of the cell balancing operation. During the operation, the multi-winding transformer stores the energy charged in a specific source cell and subsequently transfers this energy to the target cell. However, the leakage inductance of the multi-winding transformer and the output capacitance of the MOSFET induce an abnormal energy transfer to the non-target cells, thereby degrading the transfer efficiency of the balancing current in each cell balancing operation. The impacts of the balancing current transfer efficiency deterioration are analyzed and a transformer design methodology that considers the coupling coefficient is proposed to enhance the transfer efficiency of the balancing current. The efficiency improvements resulting from the selection of an appropriate coupling coefficient are verified by conducting a simulation and experiment with a 1 W prototype cell balancing circuit.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.4
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• pp.27-33
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• 2008

The clustering of gene expression data is used to analyze the results of microarray studies. This clustering is one of the frequently used methods in understanding degrees of biological change and gene expression. In biological research, MCL algorithm is an algorithm that clusters nodes within a graph, and is quick and efficient. We have modified the existing MCL algorithm and applied it to microarray data. In applying the MCL algorithm we put forth a simulation that adjusts two factors, namely inflation and diagonal tent and converted them by making use of Markov matrix. Furthermore, in order to distinguish class more clearly in the modified MCL algorithm we took the average of each row and used it as a threshold. Therefore, the improved algorithm can increase accuracy better than the existing ones. In other words, in the actual experiment, it showed an average of 70% accuracy when compared with an existing class. We also compared the MCL algorithm with the self-organizing map(SOM) clustering, K-means clustering and hierarchical clustering (HC) algorithms. And the result showed that it showed better results than ones derived from hierarchical clustering and K-means method.

• Journal of the Korea Society of Computer and Information
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• v.16 no.2
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• pp.207-215
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• 2011

Due to the increasing availability and popularity of digital television (DTV), the numbers of TV channels and programs that can be selected by consumers are also increasing rapidly. Therefore, searching for interesting channels and program via remote controls or channel guide maps can be frustrating and slow. In this paper, in order to better satisfy consumers, we propose a dynamic channel surfing scheme that reduces the channel seek distance in DTV. The proposed scheme dynamically rearranges the channel sequences according to the channel currently being watched to reduce the channel seek distance. The results of a simulation experiment demonstrate that the proposed dynamic channel surfing scheme reduces the channel seek distance for DTV channel navigation when up-down channel selection interfaces are used.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.517-527
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• 1997

Magnetic Resonance Spectroscopic Imaging is a methodology combining the imaging and spectroscopy. It can provide the spectrum of each areas of image so that one can easily compare the spectrum of one position to another position of the image. In this study, we developed pulse sequence or the spectroscopic imaging method, RF wave forms or the saturation of water signal, computer simulations to validate our method, and confirmed the methodology with phantom experiment. Then we applied the spectroscopic method to human subject and identified a few important metabolites in in vivo. To develope a water saturating RF waveform, we used Shinnar-Le-Roux algorithm and obtained maximum phase RF waveform. With this RF pulse, it could suppress the water signal to 1:1000. The magnet is shimmed to under 1.0ppm with auto-shimming technique. The saturation bandwidth is 80Hz(2ppm). The water and fat seperation is 3.3ppm(about 140Hz at 1 Tesla magnet), the bandwidth is enough to resolve the difference. But we are more concerned about the narrow window in between the two peaks, in which the small quantity of metabolites reside. We performed the computer simulation and phantom experiments in 8*8 matrix form and showed good agreement in the image and spectrum. Finally we applied spectroscopic imaging to the brain of human subject. Only the lipid signal was shown in the periphery region which agrees with the at distribution in human head surface area. The spectrum inside the brain shows the important metabolites such as NAA, Cr/PCr, Choline. We here have shown the spectroscopic imaging which is normally done above 1.5 Tesla machine can be performed in the 1 Tesla Magnetic Resonance Imaging Unit.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.12
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• pp.2364-2375
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• 1994

For the efficient recognition of printed Korean characters, a multiplexed minimum average correlation energy(MMACE) filter is proposed. Proposed method solved the disadvantages of the tree structure algorithm which recognition system is very huge and recognition method is sophisticated. Using only one consonant MMACE filter and one vowel one, we recognized the full Korean character. Each MMACE filter is multiplexed by 4 K-tuple MACE filters which are synthesized by 24 consonants and vowels. Hence the proposed MMACE filter and the correlation distribution plane are divided by 4 subregion. We obtained the binary codes for the Korean character recognition from each correlation distribution subplane. And the obtained codes are compared with the truth table for consonants and vowels in computer. We can recognize the full Korean characters when substitute the corresponded consonant or vowel font of the consistent code to the correlation peak place in the output correlation plane. The computer simulation and optical experiment results show that the proposed compact Korean character recognition system using the MMACE filters has high discrimination capability.

• Journal of the Korea Society of Computer and Information
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• v.12 no.5
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• pp.49-56
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• 2007

This paper deals with grid job allocation and grid resource scheduling to provide a stable and quicker job processing service to grid users. In this paper, we proposed a fuzzy logic-based grid job scheduling model for an effective job scheduling in computational grid environment. The fuzzy logic-based grid job scheduling model measures resource efficiency of all grid resources by a fuzzy logic system based on diverse input parameters like CPU speed and network latency and divides resources into several groups by resource efficiency. And, the model allocates jobs to resources of a group with the highest resource efficiency. For performance evaluation, we implemented the fuzzy logic-based grid job scheduling model on the DEVS modeling and simulation environment and measured reduction rates of turnaround time, job loss, and communication messages in comparison with existing job scheduling models such as the random scheduling model and the MCT(Minimum Completion time) model. Experiment results that the proposed model is useful to improve the QoS of the grid job processing service.

• Journal of the Korean Institute of Navigation
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• v.5 no.2
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• pp.1-39
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• 1981

A doppler log is the typical device which can measure the ship's speed over the ground directly, by means of doppler effect of the underwater ultrasonic wave, which involves the error due to the sea bottom inclination, the trim and the incorrect transducer installation etc. The present doppler log adopts a single transducer, faced in the direction of themain beam, and therefore it is unable to correct the beam direction to eliminate the above mentioned error. Moreover, the frequencyis also limitted in a comparatively high range for getting a sharp beam with single transducer, and the speed over the ground can not be detectable at the deep sea, for an instance, over 200 meters. This paper describes a theoretical consideration for the doppler log error and an analysis by a computer on the observed speed data by a full size model ship. The result is verified that the most of doppler log error is caused by the ultrasonic beam angle of transducer. To eliminate the doppler log error due to the incorrect transducer installation and also to sharpen the beam for lower frequency range to expand measurable sea depth, this paper proposes a method of controlling the directivity adopting a linear transducer array and of controlling the directivity by the control of exciting current, and investigates by the computer simulation and make experiment with magnetostrictive ferrite transducer of 28, 50 and 75KHz. The experimental results are shown well coincide with the measured ones, and they are revealed that in case where the transducer interval is greater than 1 wavelength, the effective control of the beam direction is hardly performed with keeping adequate beam width and side lobe level. It is concluded that 6-elements array with inter element space of a half wavelength can make comparatively sharp beam and low side lobe level. The results obtained here will contribute very much to the improvement of the performance of doppler log.