• Geophysics and Geophysical Exploration
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• v.4 no.4
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• pp.115-123
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• 2001

The bright spot is an indicator for natural gas on seismic stack sections, but it is also shown on layers where the acoustic impedance contrast is large. In order to distinguish sharply between gas and impedance contrast we need additional detailed data processing such as velocity analysis, AVO analysis and seismic complex analysis including measures of seismic amplitude, frequency, and phase. In this study, we performed detailed velocity analysis, complex analysis and DHI (Direct Hydrocarbon Indicator) analysis which is the result of amplitude variation according to the incident angles. The seismic complex analysis gives us the geological information which depends on geophysical properties at the interest layer. For the complex analysis, we computed several seismic attributes such as the instantaneous amplitude, the first and the second derivatives of the instantaneous amplitude, the instantaneous phase, the instantaneous frequency and weighted average instantaneous frequency. Then we applied these analysis techniques to a seismic data of Korea offshore which had been logged. From the result of this data analysis, it could be said that high possibility area for gas layer detection has amplitude anomalies in the instantaneous amplitude, the instantaneous frequency and the DHI section resulting from the AVO analysis. If there are not any other anomalies in detailed data processing, it will have low possibility for gas layer detection.

• Food Science of Animal Resources
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• v.31 no.6
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• pp.960-965
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• 2011

The content of benzo[a]pyrene from 69 smoked meat products commonly consumed in Korean food market was analysed with high performance liquid chromatography. Smoked meat products including smoked chicken, pork, turkey and duck were saponified, extracted and cleaned up to analyze the benzo[a]pyrene content. As a result of analysis from smoked meat products, the mean benzo[a]pyrene content was 0.42 ${\mu}g$/kg and the highest content of benzo[a]pyrene was 2.87 ${\mu}g$/kg detected in smoked chicken product. All somked meat products contained benzo[a]pyrene below the limit regulated by Korean Food and Drug Administration (KFDA). Exposure assessment of benzo[a]pyrene from smoked meat products ingestion was calculated by using National Health and Nutrition Survey (NHNS). The estimated lifetime average daily intake of benzo[a]pyrene was 0.187 ng/kg bw/d. Margin of exposure of benzo[a]pyrene was ranged from 1,657,754 to 3,957,219.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.8
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• pp.29-39
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• 2015

This paper describes a design and implementation of fuzzy-based algorithm for hand-shake state detection and error compensation in the mobile optical image stabilization(OIS) motion detector. Since the gyro sensor output of the OIS motion detector includes inherent error signals, accurate error correction is required for prompt hand-shake error compensation and stable hand-shake state detection. In this research with a little computation overhead of fuzzy-based algorithm, the hand-shake error compensation could be improved by quickly reducing the angle and phase error for the hand-shake frequencies. Further, stability of the OIS system could be enhanced by the hand-shake states of {Halt, Little vibrate, Big vibrate, Pan/Tilt}, classified by subdividing the hand-shake angle. The performance and stability of the proposed algorithm in OIS motion detector is quantitatively and qualitatively evaluated with the emulated hand-shaking of ${\pm}0.5^{\circ}$, ${\pm}0.8^{\circ}$ vibration and 2~12Hz frequency. In experiments, the average error compensation gain of 3.71dB is achieved with respect to the conventional BACF/DCF algorithm; and the four hand-shake states are detected in a stable manner.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.1
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• pp.1-8
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• 2016

The Korea Meteorological Administration has operated the Automatic Weather Stations, of the average 13 km horizontal resolution, to observe rainfall. However, an additional RADAR network also has been operated in all-weather conditions, because AWS network could not observed rainfall over the sea. In general, the rain rate is obtained by estimating the relationship between the radar reflectivity (Z) and the rainfall (R). But this empirical relationship needs to be optimized on the rainfall over the Korean peninsula. This study was carried out to optimize the Z-R relationship in the summer of 2014 using a parallel Micro Genetic Algorithm. The optimized Z-R relationship, $Z=120R^{1.56}$, using a micro genetic algorithm was different from the various Z-R relationships that have been previously used. However, the landscape of the fitness function found in this study looked like a flat plateau. So there was a limit to the fine estimation including the complex development and decay processes of precipitation between the ground and an altitude of 1.5km.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.6
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• pp.413-427
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• 1991

Variability of sea levels at Mukho and Ullungdo and sea level difference(SLD) associated with current is investigated. Time series of adjusted sea levels at both places have very similar pattern of change. Two components appear to contribute to the correlation between sea level and SLD. Low frequency thermosteric effect causes the sea level to rise and fall at the same time. Geostrophic effect of major currents is responsible for the sea level change in opposite ways at both sides. Two contributions have a cancelling effect for sea level change at Mukho while they are additive at Ullungdo. Characteristics of time series in frequency domain are divided into two parts with respect to 0.01 cycles per day(cpd). At Mukho, the cancelling effect yields small values of coherence for low-frequency bands whereas the dominant geostrophic influence may be responsible for the phase relations of about $\pm 180^{\circ}$ between sea level and SLD at higher frequency. Bimonthly dynamic height difference(DHD) between Mukho and Ullungdo is very significantly correlated with SLD. This result suggests that DHD thus the average velocity of current through the Mukho-Ullungdo section can successfully be diagnosed by the sea level records at both locations. For the annual variations, maximum SLD occurs at Mukho-Ullungdo section about 40 days later than the Korea Strait.

• Journal of Radiation Protection and Research
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• v.38 no.1
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• pp.1-9
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• 2013

Education and training is an important means of promoting safety culture and enhancing the level of competence of radiation worker in radiation protection. The existing international nuclear education and training of short duration has been carried out on the high-level officials and focussed on the classroom based training. The developing countries has been asking for support to cultivate their own technical experts to Korea which is a donor country exporting nuclear power plants. This paper summarizes the results of developing and operating the international education and training course to froster technical experts in radiation protection that emphasized practical training sessions and technical visits using the excellent domestic radiation facilities and infrastructure of education and training. It mentions the procedures of assessment and feedback as well. In an effort to maximize teaching-learning effects and to maintain consistency of the learning objectives, methods and assessment, SAT methodology has been applied on the processes of developing and operating the course. In the comparative and final assessment which were conducted at the beginning or at the end of training course, participants' average score increased around 2 points. The questionnaire of participants showed a high level of satisfaction of 4.0 points or above for the most of the questions. These imply teaching-learning methods applied to it might be effective. The teaching-learning methodologies may provide the opportunity to develop the customized training course for bringing up international technical experts and to shift educational paradigm from theory-oriented to on-site practice-based education.

• Geophysics and Geophysical Exploration
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• v.12 no.4
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• pp.316-327
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• 2009

A standard for national seismological observatory was proposed on 1999. Since then, Quanterra digitizer has been installed and is operating on almost all of seismic stations which belong to major seismic monitoring organizations. Quanterra digitizer produce and transmit real-time event packet and data packet. Characteristics of event packet and arrival time of each channel's data packet on data center were investigated. Packet selection criteria using signal to noise ratio (hereafter SNR) and signal period from real-time event packet based on 100 samples per second (hereafter sps) velocity data were developed. Estimation of epicenter using time information of the selected event packet were performed and tested. A series of experiment show that event packets were received approximately 3~4 second earlier than data packets and the number of event packet was only 0.3% compare to data packets. Just about 5% against all of event packets were selected as event packet were related P wave of real earthquake. Using the selected event packets we can estimate an epicenter with misfit less than 10 km within 20 sec for local earthquake over magnitude 2.5.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.10
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• pp.144-155
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• 1998

The array weights that will maximize the SNR for any type of noise environment are determined by the function of the antenna design configuration and the directions of receiving target and interference signals. The conventional SLCs(sidelobe cancellers) using the SNR maximization perform worst from the saturation of the receiving system of main channel when the main antenna has pattern with high gain at the arrival angle of strong interference. In this paper, the new SLC is accomplished by using two independent antenna architecture. Main antenna is implemented with adaptive nulling, which is used for rejecting high-power interference primarily. Auxiliary antenna is realized with adaptive array for receiving interference signal to be suppressed completely, which has a characteristics of sufficient gain for every direction. The new SLC is implemented with above both antennas. We show that the new SLC, which consists of the adaptive nulling main antenna and the adaptive array auxiliary antenna, is useful in reducing the effect of strong interference like jammer, because the adaptive nulling at main antenna prevents its receiver and signal processor for saturation by strong interference. The proposed SLC has improved SNR over the conventional SLCs. The improved SNR at sidelobe region is typically more than 7 dB for a given test signal. Moreover, it improves the SNR of about 20 dB under strong interference at mainlobe.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.9
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• pp.1-8
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• 2010

A digital phase wrapping modulation (DPM) open-loop polar transmitter can be efficiently applied to a wideband orthogonal frequency division multiplexing (OFDM) communication system by converting in-phase and quadrature signals to envelope and phase signals and then employing the signal mapping process. This mapping process is very similar to quantization in a general communication system, and when taking into account the error that appears during mapping process, one can replace the coordinates rotation digital computer (CORDIC) algorithm in the coordinate conversion part with the Taylor series approximation method. In this paper, we investigate the application of the Taylor series approximation to the cartesian to polar coordinate conversion part of a DPM polar transmitter for wideband OFDM systems. The conventional approach relies on the CORDIC algorithm. To achieve efficient application, we perform computer simulation to measure mean square error (MSE) of the both approaches and find the minimum approximation order for the Taylor series approximation compatible to allowable error of the CORDIC algorithm in terms of hardware design. Furthermore, comparing the processing speeds of the both approaches in the implementation with FPGA reveals that the Taylor series approximation with lower order improves the processing speed in the coordinate conversion part.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.2
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• pp.123-129
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• 2017

This paper proposes a new nonnegative matrix factorization (NMF) based direction-of-arrival (DOA) estimation method for multiple sound sources using a dual microphone array. First of all, sound signals coming from the dual microphone array are segmented into consecutive analysis frames, and a steered-response power phase transform (SRP-PHAT) beamformer is applied to each frame so that stereo signals of each frame are represented in a time-direction domain. The time-direction outputs of SRP-PHAT are stored for a pre-defined number of frames, which is referred to as a time-direction block. Next, In order to estimate DOAs robust to noise, each time-direction block is normalized along the time by using a block subtraction technique. After that, an unsupervised NMF method is applied to the normalized time-direction block in order to cluster the directions of each sound source in a multiple sound source environments. In particular, the activation and basis matrices are used to estimate the number of sound sources and their DOAs, respectively. The DOA estimation performance of the proposed method is evaluated by measuring a mean absolute error (MAE) and the standard deviation of errors between the oracle and estimated DOAs under a three source condition, where the sources are located in [$-35{\circ}$, 5m], [$12{\circ}$, 4m], and [$38{\circ}$, 4.m] from the dual microphone array. It is shown from the experiment that the proposed method could relatively reduce MAE by 56.83%, compared to a conventional SRP-PHAT based DOA estimation method.