• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.582-585
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• 2004

Oyster fanning structures in tidal flats are well detected by SAR system. Each frame of these artificial structures is composed of two vertical and one horizontal wooden pole. We investigate characteristics of polarimetric features in the target structures. In this paper, the results of AIRSAR L-band POLSAR data and experiments in laboratory are discussed. The ratio of single bounce to double bounce scattering depends of vertical pole height, direction of horizontal pole to radar look direction, and incidence angle as well as sea surface condition. We have conducted laboratory experiments. According to target scale, Ku-band and targets downsized by scale of 10 are used. The results of the experiments are summarized as: i) total power of the backscattering is more affected by vertical poles than a horizontal pole; ii) and backscattering from a horizontal pole is sensitive to the relative radar look direction to target array. We conclude that water level can be effectively measured by using interferometric phase and backscattering intensity if vertical poles in the water are observed by L-band HH- or VV-polarization. Measurement of tide height can be further improved if double bounced components are separated from fully polarized SAR data.

• The Journal of the Acoustical Society of Korea
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• v.20 no.2E
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• pp.17-24
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• 2001

In this paper, we propose the bootstrap and aggregating (bagging) vector quantization (VQ) classifier to improve the performance of the text-independent speaker recognition system. This method generates multiple training data sets by resampling the original training data set, constructs the corresponding VQ classifiers, and then integrates the multiple VQ classifiers into a single classifier by voting. The bagging method has been proven to greatly improve the performance of unstable classifiers. Through two different experiments, this paper shows that the VQ classifier is unstable. In one of these experiments, the bias and variance of a VQ classifier are computed with a waveform database. The variance of the VQ classifier is compared with that of the classification and regression tree (CART) classifier[1]. The variance of the VQ classifier is shown to be as large as that of the CART classifier. The other experiment involves speaker recognition. The speaker recognition rates vary significantly by the minor changes in the training data set. The speaker recognition experiments involving a closed set, text-independent and speaker identification are performed with the TIMIT database to compare the performance of the bagging VQ classifier with that of the conventional VQ classifier. The bagging VQ classifier yields improved performance over the conventional VQ classifier. It also outperforms the conventional VQ classifier in small training data set problems.

• Journal of Korean Elementary Science Education
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• v.30 no.2
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• pp.152-161
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• 2011

The purpose of this study is to diagnose difficulties and problems that the preservice teachers experience when teaching inquiry-based classes in elementary science and to improve their professionalism through prescriptive instruction consulting utilizing PDRE (preparation, diagnosis, reflective implementation, evaluation) model. The result of this study was as follows. First, preservice teachers considered themselves to be lack of scientific knowledge, but this study confirmed that the application of instruction consulting improved their understandings in scientific concepts and principles and corrected their misconceptions. Second, preservice teachers experienced difficulties in variables that might influence the results of experiments, cautions for the experiments and unexpected results of experiments, and this consulting allowed them to gain instruction ability to cope with such circumstances and solve problems effectively. Third, preservice teachers experienced difficulties in applying instructional model into their classes and preparing lesson plans, but consulting actually made limited but positive changes in their abilities. However, from a longer-term perspective, quantitative increase in their teaching opportunities, the development and distribution of example manuals, and the utilization of various class materials provided by the assistant centers for teaching and learning should be achieved side by side.

• Journal of Microbiology and Biotechnology
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• v.23 no.2
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• pp.149-155
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• 2013

Heterologous expression of a putative $K^+/H^+$ antiporter of Streptomyces coelicolor A3(2) (designated as sha4) in E. coli and Streptomyces hygroscopicus JCM4427 showed enhanced tolerance to $K^+$ stress, acidic-pH shock, and/or geldanamycin production under $K^+$ stress. In a series of $K^+$ extrusion experiments with sha4-carrying E. coli deficient in the $K^+/H^+$ antiporter, a restoration of impaired $K^+$ extrusion activity was observed. Based on this, it was concluded that sha4 was a true $K^+/H^+$ antiporter. In different sets of experiments, the sha4-carrying E. coli showed significantly improved tolerances to $K^+$ stresses and acidic-pH shock, whereas sha4-carrying S. hygroscopicus showed an improvement in $K^+$ stress tolerance only. The sha4-carrying S. hygroscopicus showed much higher geldanamycin productivity than the control under $K^+$ stress condition. In another set of experiments with a production medium, the secretion of geldanamycin was also significantly enhanced by the expression of sha4.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.5 no.3
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• pp.187-197
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• 1993

In this study, the numerical analysis and experiments of the hot water storage using the thermal stratification techniques were carried out. The CPU time for a typical run of the the thermal stratification up to 900 seconds took one week for a $81{\times}31$ mesh size and 10 days for a $118{\times}31$ mesh size, respectively, for a cylindrical shape of the storage. In the initial stage, the numerical results were in favorable agreement with the experimental results, but it showed that the temperature gradients in the storage decreased gradually with time. It was also found that the increase of ${\delta}t$ decreased the convergent speed due to the intensive fluctuation of the velocity field in every iteration. The increase of numbers of grids is projected to forecast a more accurate result, but it made the computing time longer and woul slow down convergence. At the experiments of the flow visualization, it was confirmed that the thermal stratification was apparently built up due to the installation of diffuser at the lower part of the storage. Thus, the thermal performance of the storage could be improved by installing the diffusers at the inlet and outlet.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.514-514
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• 2017

Floating breakwaters were treated as solid bodies without any perforation in previous studies. In this study, however, a floating breakwater is perforated to allow the partial absorption of the energy produced by incident waves and an air chamber is placed in the upper part to control the breakwater draft. A series of laboratory experiments for a floating breakwater installed with a mooring system are carried out. In general, a mooring system can be classified by the number of mooring points, the shape of the mooring lines, and the degree of line tension. In this study, a four-point mooring is employed since it is relatively easier to analyze the measured results. Furthermore, both the tension-leg and the catenary mooring systems have been adopted to compare the performance of the system. In laboratory experiments, the hydraulic characteristics of a floating breakwater were obtained and analyzed in detail. Also, a hydraulic model test was carried out on variable changes by changing the mooring angle and thickness of perforated wall. A hydraulic model was designed to produce wave energy by generating a vortex with the existing reflection method. Analysis on wave changes was conducted and the flow field around the floating breakwater and draft area, which have elastic behavior, was collected using the PIV system. From the test results the strong vortex was identified in the draft area of the perforated both-sides-type floating breakwater. Also, the wave control performance of the floating breakwater was improved due to the vortex produced as the tension in the mooring line decreased.

• Journal of Korean Society for Atmospheric Environment
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• v.32 no.4
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• pp.372-383
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• 2016

This study aimed at analyzing the sensitivity of ozone simulation in accordance with the meteorological nudging for a high nocturnal ozone episode. To demonstrate the effectiveness of nudging methods (e.g., nudging techniques and application domains), the following six experiments were designed: (1) control without nudging, (2) experiment with application of observation nudging to all domains (domain 1~4), and (3)~(6) experiments with application of grid nudging to domain 1, domain 1~2, domain 1~3 and all domains, respectively. As a result, the meteorological nudging had a direct (improvement of input data) and indirect (estimate natural emission) effect on ozone simulation. Nudging effects during the daytime were greater than those during the nighttime due to low accuracy of wind direction during the nighttime. On comparison of the nudging techniques, the experiments in which grid nudging was applied showed more improved results than the experiments in which observation nudging was applied. At this time point, the simulated concentrations were generally similar to the observed concentrations due to the increase in the nudging effect when grid nudging was applied up to the sub-domain. However, for high nocturnal ozone uptakes, the experiment in which grid nudging was applied do domain 1~3 showed better results than the other experiments. This is because, when grid nudging was applied to the high resolution domain (e.g., domain 4 with 1 km), the local characteristics were removed due to the smoothing effects of meteorological conditions.

• Journal of the Korean GEO-environmental Society
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• v.22 no.12
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• pp.59-63
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• 2021

This study presented the characteristics and additive effects of the grout with mixing ratio for developing of high-efficiency grouting technology under high depth conditions. The laboratory investigation were conducted with Portland cement (OPC) and micro cement (S8000-E) including viscosity experiments, particle size analysis experiments, Gel-Time experiments and uniaxial compressive strength experiments. As a result of the viscosity experiment, it was shown that OPC is advantageous in terms of viscosity, but S8000-E is suitable when considering the passage of rock joint intervals through particle size analysis. The Gel-Time experiment shows that it is not that difficult with injection as a grout material even when silica fume (SF) was applied. The strength of the cured material is improved as increase in the content of silica fium (SF). Within the range of the study, the optimal mixing ratio obtained through various experiments is S8000-E, w/c=70%, silica fium (SF)=6%, and 7 days.

• Journal of Ship and Ocean Technology
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• v.3 no.4
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• pp.1-14
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• 1999

The improved Green integral equation using the Kelvin-type Green function in known free of irregular frequencies where the integral over the inner free surface integral is removed from the integral equation, resulting in an overdetermined integral equation. The solution of the overdetermined Green integral equation is shown identical with the solution of the improved Green integral equation Using the B-spline higher order panel method, the overdetermined equation is discretized in two different ways; one of the resulting linear system is square and the other is redundant. Numerical experiments show that the solutions of both are identical. Using the present methods, the exact values and higher derivatives of the potential at any place over the wetted surface of the body can be found with much fewer panels than low order panel method.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06c
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• pp.358-363
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• 1994

This paper presents the improvement of the SCHMM using discrete VQ and One-Pass algorithm for keywords recognition in Korean continuous speech. The SCHMM using discrete VQ is a simple model that is composed of a variable mixture gaussian probability density function with dynamic mixture number. One-Pass algorithm is improved such that recognition rates are enhanced by fathoming any undesirable semisyllable with the low likelihood and the high duration penalty, and computation time is reduced by testing only the frame which is dissimilar to the previously testd frame. In recognition experiments for speaker-dependent case, the improved One-Pass algorithm has shown recognition rates as high as 99.7% and has reduced compution time by about 30% compared with the currently abailable one-pass algorithm.