• Korean Journal of Mathematics
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• v.10 no.1
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• pp.53-58
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• 2002

In this paper we consider the Cauchy problem $$dx(t)/dt=x(t)^n,\;x(0)=x_0$$. The domain of existence is lower semicontinuous for perturbations of the data. We present a simple formula for the time of existence which is exact when there exists no perturbations.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.7
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• pp.844-850
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• 2016

This study pertains to the extraction of the road noise component of signals from a vehicle's interior noise via the traditional frequency domain and time domain system identification methods. For road noise extraction based on the frequency domain system identification method, the appropriate matrix inversion strategy is investigated and causal and non-causal impulse response filters are compared. Furthermore, appropriate data lengths for the frequency domain system identification method are investigated. In addition to the traditional road noise extraction methods based on frequency domain system identification, a new approach to extract road noise via the time domain system identification method based on a parametric input-output model is proposed and investigated in the present study. In this approach, instead of constructing a higher order model for the full-band road noise, input and output signals are processed in the subband domain and lower order parametric models optimal to each subband are determined. These parametric models are used to extract road noises in each subband; the full band road noise is then reconstructed from the subband road noises. This study shows that both the methods in the frequency domain and the time domain successfully extract the road noise from the vehicle's interior noise.

• Journal of Information Technology Applications and Management
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• v.12 no.1
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• pp.111-123
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• 2005

Many indexing methods were proposed so that process moving object efficiently. Among them, indexing methods like the 3D R-tree treat temporal and spatial domain as the same. Actually, however. both domain had better process separately because of difference in character and unit. Especially in this paper we deal with limited region such as indoor environment since spatial domain is limited but temporal domain is grown. In this paper we present a novel indexing structure, namely STS-tree(Separation of Time and Space tree). based on limited region. STS-tree is a hybrid tree structure which consists of R-tree and one-dimensional TB-tree. The R-tree component indexes static object and spatial information such as topography of the space. The TB-tree component indexes moving object and temporal information.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.9
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• pp.1244-1249
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• 1995

Wavelet transform technique is applied to two important electromagnetic problems:1) to analyze the frequency-domain radar echo from finite-size targets and 2) to the integral solution of two- dimensional electromagnetic scattering problems. Since the frequency- domain radar echo consists of both small-scale natural resonances and large-scale scattering center information, the multiresolution property of the wavelet transform is well suited for analyzing such ulti-scale signals. Wavelet analysis examples of backscattered data from an open- ended waveguide cavity are presented. The different scattering mechanisms are clearly resolved in the wavelet-domain representation. In the wavelet transform domain, the moment method impedance matrix becomes sparse and sparse matrix algorithms can be utilized to solve the resulting matrix equationl. Using the fast wavelet transform in conjunction with the conjugate gradient method, we present the time performance for the solution of a dihedral corner reflector. The total computational time is found to be reduced.

• 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.

• Journal of the Korean Society for Railway
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• v.4 no.4
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• pp.155-161
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• 2001

In this paper, the method is suggested to prevent data collision or damage on RFID(Radio Frequency Identification) system, in case a reader reading multi-tag simultaneously, using binary-search algorithm and Time-domain anti-collision procedure at reader and tag, respectively. The RFID system is designed that Reader enable to communicate with Tag on 13.56MHz bandwidth which is ISM(Industrial Science Medical) bandwidth, antennas of Tag part are designed using MCRF335 Chip. When RF communication is achieved between reader and tag, in case that data is transmitted to reader pass through multiple tags simultaneously, a study on the anti-collision method for the situation that the data collision occurs is performed.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.53.2-53.2
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• 2016

We present our experiences with open-source spatio-temporal database systems for managing and analyzing big astronomical data acquired by wide-field time-domain sky surveys. Considering performance, cost, difficulty, and scalability of the database systems, we conduct comparison studies of open-source spatio-temporal databases such as GeoMesa and PostGIS that are already being used for handling big geographical data. Our experiments include ingesting, indexing, and querying millions or billions of astronomical spatio-temporal data. We choose the public VVV (VISTA Variables in the Via Lactea) catalogs of billions measurements for hundreds of millions objects as the test data. We discuss issues of how these spatio-temporal database systems can be adopted in the astronomy community.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.152-156
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• 1996

Identification of incipient faults and various events on the distribution feeders is very important to develop the prediction method of fault symptom. In this paper, the configuration of data acquisition system to get the real field data is introduced. And the Quantification of incipient faults is also discussed. Based on the acquired field data, how the time domain parameters of voltage and current signals are applied to this research is partly introduced.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• v.6 no.1
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• pp.44-50
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• 2003

If the accelerometers are used in measuring the response, the absolute values of the velocity and displacement are not usually obtainable because their initial values are not accounted for in the integration of the acceleration response. A new dynamic response conversion algorithm of both the time domain and the frequency domain is proposed for the problem in estimating the displacement data by defining the transformed responses. In this algorithm, the displacement response can be obtained from the measured acceleration records by integration without requiring the knowledge of the initial velocity and displacement information. The applicability of the technique is tested by an example problem using the real bridge's superstructure under several cases of moving load. In the response conversion procedure of the frequency domain, the identified response according to the frequency can be estimated by changing over the limits of integration. If the reliability of the identified responses is ensured, it is expected that the proposed method for estimating the impact factor can be useful in the bridge's dynamic test. This method can be useful in those practical cases when the direct measurement of the displacement is difficult as in the dynamic studies of huge structure.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.220-223
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• 2012

Generally, SAW device, which uses Time Domain Sampling, requires high speed AD converter because SAW device (TDS) needs high sampling speed as much as its high data speed. However, the high price of AD converter discourages makers from using it. On the other hand, SAW device, which uses Frequency Domain Sampling, does not required high speed AD converter because SAW device (FDS) does not need high sampling speed. It is very efficient in price comparison to its performance because high processing speed of SAW device (FDS) can be implemented using low price Embedded Systems. The purpose of the thesis is to solve the issues above by designing and realizing SAW device (FDS) using SAW sensor for TDS.