• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.2
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• pp.116-123
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• 2005

Chirp spread spectrum method using both time and frequency component is fit to time varying channel such as powerline channel. The used chirp symbol based on the CEBus standard is the unit symbol which sweeps from 100kHz to 380kHz over a 25㎲. To evaluate the performance of between Chirp-SS and DSSS, we measured the bit error rate under Gaussian channel. Simulation result is shown that Chirp-SS has a about 3[dB] gain of SNR than DSSS. To verify the performance of implemented modem, it is made up the powerline channel environment. After adding several noises to it, we examined the receiving status of modem. The implemented modem is able to receive the signal over the powerline channel with having several noises and capacitive loads.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.9
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• pp.1188-1197
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• 1995

This paper describes an algorithm that reduces computational requirement of the Kalman filter and estimates the signal efficiently. The reference signals are mapped onto the orthogonal wavelet transform domain so that the eigenvalue spread of its autocorrelation matrix could be smaller than that in the time domain. In the wavelet transform domain the autocorrelation matrix is nearly diagonal. Therefore, the transformed signal can be decomposed each orthogonal elements. The Kalman filter can be applied to each orthogonal elements and computational requirement is reduced. The possibility of applying the parallel Kalman filter was verified through the theory and simulation. The eigenvalue spread in the wavelet transform domain is smaller 8.35 times than that in the time domain and the computational requirement is reduced from 1.4 times to 2. 93 times than that of the conventional Kalman filter.

• Steel and Composite Structures
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• v.20 no.2
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• pp.399-412
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• 2016

This paper evaluates the seismic response of three dimensional steel space buildings using the spread plastic hinge approach. A numerical study was carried out in which a sample steel space building was selected for pushover analysis and incremental nonlinear dynamic time history analysis. For the nonlinear analysis, three earthquake acceleration records were selected to ensure compatibility with the design spectrum defined in the Turkish Earthquake Code. The interstorey drift, capacity curve, maximum responses and dynamic pushover curves of the building were obtained. The analysis results were compared and good correlation was obtained between the idealized dynamic analyses envelopes with and static pushover curves for the selected building. As a result to more accurately account response of steel buildings, dynamic pushover envelopes can be obtained and compared with static pushover curve of the building.

• Journal of Biomedical Engineering Research
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• v.15 no.3
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• pp.305-316
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• 1994

All physical data in the real world are nonstationary signals that have the time varying statistical characteristics. Although few algorithms suitable to process the nonstationary signals have ever been suggested, these are treated the nonstationary signals under the assumption that the nonstationary signal is a piece-wise stationary signal. Recently, statistical analysis algorithms for the nonstationary signal have concentrated so much interest. In this paper, nonstationary EMG signals are mapped onto the orthogonal wavelet transform domain so that the eigenvalue spread of its autocorrelation matrix could be more smaller than that in the time domain. Then the model in the wavelet transform domain and an algorithm to estimate the model parameters are suggested. Also, an test signal generated by a white gaussian noise and the EMG signal are identified, and the algorithm performance is considered in the sense of the mean square error and the evaluation parameters.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.5
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• pp.795-801
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• 1994

The BiPbSrCaCuO superconductor was fabricated by diffusion of The dual layer composed of SrS12TCaS11TCuS12TOS1xT in upper layer and BiS12TPbSI0.3TCuS12TOS1yT in lower layer, and varified growh-mechanism of BiPbSrCaCuO superconducting phase. And, we produced optimum conditions of spread volume and each stage of sintering time were upper layer:Lower layer=1:0.2, 1:0.4, 1:0.6 and 24hr., 120hr., 210hr. From the result, the optimum conditions are spread volume(Upper layer:Lower layer=1:0.6), sintering time(210hrs.) at 820$^{\circ}C$.The BiPbSrCaCuO superconductor, fabricated optimum condition, showed zero resistance at critical temperature of 70k.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.1
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• pp.37-44
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• 2002

An echo signal in the active sonar using a high frequency is mainly formed of a specular reflection from the surface of an object along with several equivalent scatter inside, which are characterized by the spatial distribution of the highlights on the object. This thesis proposed a model in which the synthesized echo signal can be expressed as a distributed simulated target. The proposed model is obtained after composing a signal based on the movement of highlights relative to the aspect angle from the discontinuous point of an external hull with a strong reflection from a spheroid underwater target. Because the proposed algorithm includes a synthesis of the signals related to the highlight spacial distribution, it can be applied to all kinds of systems used at a short range, and similar results were obtained to the actual measured results of all reflected signals in previous literature referring to the irregular factor application of an envelope.

• International Journal of Computer Science & Network Security
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• v.22 no.6
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• pp.163-171
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• 2022

Online services are widely spread, and their use increases day by day. As COVID-19 spread and people spent much time online, fraud scams have risen unexpectedly. Manipulation techniques have become more effective at swindling those lacking basic technological knowledge. Unfortunately, a user needs a quorum. The interest in preventing scammers from obtaining effective quality service has become the most significant obstacle, increasing the variety of daily Internet platforms. This paper is concerned with analyzing purchase data and extracting provided results. In addition, after examining relevant documents presenting research discussing them, the recommendation was made that future work avoids them; this would save a lot of effort, money, and time. This research highlights many problems a person may face in dealing with online institutions and possible solutions to the epidemic through theft operations on the Internet.

• Journal of the Society of Disaster Information
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• v.17 no.3
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• pp.617-626
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• 2021

Purpose: The purpose of this study is to evaluate the fire srpead risk of building exterior and roofing materials due to the firebrand of forest fire occurring in the urban areas. Method: In order to achieve this research purpose, by selecting building materials used for exterior and roofing materials of buildings, the time to ignition, total heat release, and heat release rate were investigated, and a forest fire firebrand system was established to the possibility of fire spread was confirmed. Result: As a result of the cone calorimeter test, the roofing material had a similar or faster ignition time due to radiant heat compared to the exterior material with the steel plate exposed to the outside, and showed a higher heat release rate and total heat release than the exterior material. Although it was affected by the flammable material, it was confirmed that it did not spread easily due to the limited amount of combustible material, and carbonization marks appeared inside. Conclusion: The cone calorimeter test method has been shown to be useful in understanding the combustion characteristics of building materials by radiant heat, but the fire spread due to a firebrand in a forest fire is directly affected by the flame due to the ignition of surrounding combustibles, so finding a direct correlation with the cone calorimeter method is difficult. It is judged that the roof material may be more vulnerable to the spread of fire due to the fire than the exterior material.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.8
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• pp.52-57
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• 2012

We propose a weighted time-reversal prefilter for indoor wireless communication systems. In the indoor wireless communication environments, the bit error rate (BER) performance is significantly degraded by the delay spread. The conventional schemes have complex receivers to recover deterioration of the BER. The proposed time-reversal prefilter simplifies the structure of receivers, minimizes the inter-symbol interference (ISI) and maintains the peak power level of the received signal. The simulation results show that the weighted time-reversal prefilter improves the BER performance in comparison with the conventional time-reversal prefilter.

• The Journal of the Acoustical Society of Korea
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• v.20 no.5
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• pp.92-99
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• 2001

To measure temporal variability of long- range transmission in northern part of the East Sea of Korea, low frequency acoustic sources were deployed on the continental shelf 0.4km south of Cape Shultz near the port of Vladivostok during October 1999. The transmissions of the phase modulated signals were recorded by VLA moored on the northern slope of Ulleung-do. The measured signals were processed for the acoustic arrivals and their variability in time. The temporal signal processing involves pulse compression of the phase-encoded signal, time spread and temporal coherence processing. Variability of the ocean sound speed field in time scales of short period seems to be dominated by random fluctuations caused by sound speed perturbation due to the vertical displacements associated with internal waves.