• Proceedings of the KSRS Conference
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• v.2
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• pp.938-941
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• 2006

Satellite synthetic aperture radar (SAR) images from 1995 to 2001 and field measurements of sea surface wind, sea state, and vertical stratification are used for statistical analyses of internal wave (IW) occurrence and SAR imaging conditions in the northern South China Sea (NSCS). Latitudinal distribution of IW packets shows that 22% of IW packets distributed in the east of $118^{\circ}E$ and 78% of IW packets in the west of $118^{\circ}E$. The yearly distribution of IW occurrence frequencies reveals an interannual variability. The monthly SAR-observed IW occurrence frequencies show that the high frequencies are distributed from April to July and reach a peak in June. The low occurrence frequencies are distributed in winter from December to February of next year. These statistical features are explained by solitary wave dynamics.

• Journal of the Ergonomics Society of Korea
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• v.5 no.2
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• pp.27-31
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• 1986

There has been a growing interest in the application of biorhythm theory to programmes of accident prevention and performance prediction. In order for biorhythm to be applie to practice its validity and reliability should be established. This paper reported the results of three different set of data, and these data were tabulated and analysed in various ways. The basic method of analysis consisted of stat- istical comparision of actual frequences of occurrence from the collected data with those frequencies which would be expected if biorhythm had no effect. The results of the occurrence data indicated that no definite evidence in support of the influence of the fundamentals could be detected. Actual frequencies of occurrence from the collected data were not significantly different them those expected assuming random occurrence.

• Fire Science and Engineering
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• v.28 no.2
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• pp.82-90
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• 2014

According to recent government's 3.0 operating paradigm for the opening and sharing of public information, relationship between humidity, temperature and fire occurrence were analyzed using the data in National Weather Service and National Emergency Management Agency. In order to analyze the relationships between humidity, temperature and fire occurrence, hourly frequency of fire occurrence compared with humidity and temperature ranges was suggested as an analysis method. Tendencies of fire occurrence frequencies were examined through this and characteristics of detailed attributes could be statistically identified. Results about hourly frequencies of fire occurrence by classifying the humidity ranges in each region showed increasing frequencies in all areas where the humidity is lower. Hourly frequencies of fire occurrence according to temperature ranges were identified to be similar in each area as well. In addition, characteristics of objects' attributes were analyzed including types of fire, igniting source of fire, initial complex, reasons of fire occurrence, and distinctive directions were suggested. Suggested method in this paper could be practically used when suggesting the frequency in each category in fire occurrence statistics of National Fire Information System.

• Journal of Environmental Science International
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• v.23 no.10
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• pp.1673-1691
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• 2014

Although most natural disaster related studies conducted in Korea recently have been related to typhoons or severe rainstorms, the occurrence frequency of disasters due to windstorms or rainstorms is also high. To reduce the strong wind damage caused by strong windstorms due to climate change, basic studies of strong winds are necessary. Therefore, in this study, the types and representative cases of windstorms that were observed to have been higher than 14 m/s, which is the criterion for strong-wind warnings from the Korea Meteorological Administration, were selected from among those windstorm cases that occurred on the Korean Peninsula for 10 years to conduct a statistical analysis of them and determine their synoptic meteorological characteristics. The cases of windstorms occurring on the Korean Peninsula were divided into six weather patterns according to the locations of the anticyclones/cyclones. Among these types, the SH type, which occurs when Siberian Highs expand into the Korean Peninsula, showed the highest occurrence frequency, accounting for at least the majority of the entire occurrence frequency of windstorms together with that of the EC type, which occurs when cyclones develop on the East Sea, and there was no clear yearly trend of the occurrence frequencies of windstorms. The monthly occurrence frequencies of windstorms were formed mainly by typhoons in the summer and the Siberian Highs in the winter, and the months with the highest windstorm occurrence frequencies were December and January, in which mainly the SH and EC type windstorms occurred. March showed the next highest occurrence frequency with10 times, and SH windstorms occurred the most frequently in March, followed by the CC, SC, and EC types of windstorms, in order of precedence. Therefore, attention to these types of windstorms is required. Countermeasures against storm and flood damage in Korea targeting the summer should be re-reviewed together with pre-disaster prevention plans, because cases of storm and flood damage due to windstorms occur more frequently than those due to typhoons, and they occur throughout the year.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.4
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• pp.707-715
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• 2008

This paper proposes an algorithm for efficient compression gray-level images by entropy encoder. The issue of the proposed method is to replace original data of gray-level images with particular ranked data. For this, first, before encoding a stream of gray-level values in an image, the proposed method counts co-occurrence frequencies for neighboring pixel values. Then, it replaces each pay value with particularly ranked numbers based on the investigated co-occurrence frequencies. Finally, the ranked numbers are transmitted to an entropy encoder. The proposed method improves the performance of existing entropy coding by transforming original gray-level values into rank based images using statistical co-occurrence frequencies of gray-level images. The simulation results, using gray-level images with 8-bits, show that the proposed method can reduce bit rate by up to 37.85% compared to existing conventional entropy coders.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.32.6-32
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• 2002

The damage localization of the structural system using the natural frequency measurement only is proposed. The existing methods use the changes of mode shape, strain mode shape or curvature mode shape before and after the damage occurrence as these shapes carry the geometric information of the structure. Basically, the change of natural frequencies of the structure can be used as the indicator of the damage occurrence but not as the indicator of the damage location as the natural frequency changes does not carry the geometric information of the structure. In this research, the feedback scope method that measures the natural frequency changes of the structure with and without the feedback Ioo...

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.611-617
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• 2018

The application of health monitoring, including a fault detection technique, is needed to secure the structural safety of large structures. A 2-step crack identification method for detecting the crack location and size of the beam structure is presented. First, a crack occurrence region was estimated using the modified Laplacian operator for the strain mode shape obtained from the distributed local strain data. The crack location and size were then identified based on the natural frequencies obtained from the acceleration data and the neural network technique for the pre-estimated crack occurrence region. The natural frequencies of a cracked beam were calculated based on an equivalent bending stiffness induced by the energy method, and used to generate the training patterns of the neural network. An experimental study was carried out on an aluminum cantilever beam to verify the present method for crack identification. Cracks were produced on the beam, and free vibration tests were performed. A crack occurrence region was estimated using the modified Laplacian operator for the strain mode shape, and the crack location and size were assessed using the natural frequencies and neural network technique. The identified crack occurrence region agrees well with the exact one, and the accuracy of the estimation results for the crack location and size could be enhanced considerably for 3 damage cases. The presented method could be applied effectively to the structural health monitoring of large structures.

• Journal of the Korean association of regional geographers
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• v.11 no.4
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• pp.429-439
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• 2005

The propose of this study is to identify distributional characteristics of winter droughts through occurrence frequencies and to analyze synoptic characteristics on the sea level pressure fields and 500hPa levels in Korea. The regional distributions of winter droughts in occurrence frequency vary according to the monthly regional distributions of the variabilities of precipitation in Korea. In January and December, the eastern parts of Korea where the variabilities of precipitation show high, have high rate of drought frequencies, while the western parts have low rate of it. It means that the regional distribution of the drought frequencies in January and December shows the east-high and west-low pattern, In February the frequencies show the north-high and south-low pattern. In the distributions of the sea-level pressure and 500hPa level height anomalies, the positive anomalies appear around Korean Peninsula and Siberian high area, the negative anomalies on the Aleutian low area and the western parts of North Pacific Ocean during the drought period in January and February. The droughts appear when the inflow of warm and humid air from the south eastern parts blocked by the prevailing pressure patterns of the west-high and east-low. Therefore, the zonal wind of the Korean Peninsula is strong. The droughts of December reflect not only low frequencies of cyclone occurrence, also small inflow of warm and humid air from the southern parts stemming from positive anomalies over whole middle latitude of eastern parts of Asia including Korean Peninsula.

• Journal of Korean Home Economics Education Association
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• v.34 no.2
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• pp.1-19
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• 2022

The purpose of this study is to analyze the keywords of the middle school textbooks based on the 2015 revision of the technology and home economics curriculum to understand the core concepts and contents composition of the 'housing' unit. Using TEXTOM and UCINET programs, the frequencies and centralities of the keywords were analyzed, and CONCOR analysis was performed. The results are as follows. First, the content system of the 'housing' unit is divided into 'life culture' and 'safety' in the 'family life and safety' area. Second, in the 'safety' section, the frequencies of occurrence of the words were high in the order of indoor, occurrence, use, noise, and safety accidents, in the order of frequency of occurrence. It was confirmed that words related to daily life, safety accidents, and prevention were closely connected to each other. In the 'life culture' section, the frequencies of occurrence were high in the order of space, housing, family, and residential space, and the correlations between these keywords were also high. Third, the most influential core keywords were, indoor and occurrence in the 'safety' section, and space, family, and housing, in the 'life culture' section. Fourth, the 'safety' section were divided into two subunits, 'safe living environment' and 'comfortable living environment', and the 'life culture' section were divided into four subunits, 'living space composition', 'space utilization', 'housing value and lifestyle', and 'housing culture'.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.2485-2489
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• 2005

This paper introduces a new preprocessing scheme to replace original data of gray scale images with particular ordered data so that performance of lossless compression can be improved more efficiently. As a kind of preprocessing technique to maximize performance of entropy encoder, the proposed method converts the input image data into more compressible form. Before encoding a stream of the input image, the proposed preprocessor counts co-occurrence frequencies for neighboring pixel pairs. Then, it replaces each pair of adjacent gray values with particular ordered numbers based on the investigated co-occurrence frequencies. When compressing ordered image using entropy encoder, we can expect to raise compression rate more highly because of enhanced statistical feature of the input image. In this paper, we show that lossless compression rate increased by up to 37.85% when comparing results from compressing preprocessed and non-preprocessed image data using entropy encoder such as Huffman, Arithmetic encoder.