• Journal of Korean Association for Spatial Structures
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• v.17 no.1
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• pp.49-58
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• 2017

The result of the previous work leads to the idea that the inner area of the hyperbolic shell generator should be minimized for the cooling tower with higher first natural frequency. In this study the inner area of the hyperbolic shell generator was graphically established under varying height of the throat and angle of the base lintel. From the graph, several shell geometries were selected and analysed in the aspect of the natural frequency. Three representative towers reinforced differently due to different first natural frequencies were analysed non-linearly and evaluated using a damage indicator based on the change of natural frequencies. The results demonstrated that the damage behaviour of the tower reinforced higher due to a lower first natural frequency was not necessarily advantageous than the others.

• Journal of KIISE:Databases
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• v.28 no.3
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• pp.373-383
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• 2001

The distance join is a spatial join which finds data pairs in the order of distance when associating two spatial data sets. This paper proposes several methods to optimize the adaptive multi-stage distance join, presented in [1]. First, we optimize the sweeping index formula which is used for selecting sweeping axis during plane sweeping. Second, to improve the performance of a priority queue used for maintaining node pairs, we propose to use the maximum distance of a node pair as the second priority of the queue. Moreover, we compare trade-offs in estimating the cut-off distance between under uniformity assumption of data distribution and non-uniformity assumption. The experiments show that the proposed methods greatly improve the performance of the algorithm in CPU cost as well as in I/O cost.

• Korean Journal of Agricultural and Forest Meteorology
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• v.19 no.3
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• pp.120-129
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• 2017

Agrometeorological advisories for farms and orchards are issued when daily weather exceeds a predefined range of the local reference climate, which is a long-term average of daily weather for the location. The reference climate at local scales is prepared by various simplification methods, resulting in uncertainty in the agrometeorological advisories. We restored daily weather data for the 1981-2010 period and analyzed the differences in prediction results of weather risk by comparing with the temporal and spatial simplified normal climate values. For this purpose, we selected the agricultural drought index (ADI) among various disaster related indices because ADI requires many kinds of weather data to calculate it. Ten rural counties within the Seomjin River Basin were selected for this study. The normal value of 'temporal simplification' was calculated by using the daily average value for 30 years (1981-2010). The normal value of 'spatial simplification' is the zonal average of the temporally simplified normal values falling within a standard watershed. For residual moisture index, temporal simplification normal values were overestimated, whereas spatial simplification normal values were underestimated in comparison with non-simplified normal values. The ADI's calculated from January to July 2017 showed a significant deviation in terms of the extent of drought depending on the normal values used. Through this study, we confirmed that the result of weather risk calculation using normal climatic values from 'simplified' methods can affect reliability of the agrometeorological advisories.

• Journal of Wetlands Research
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• v.23 no.3
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• pp.201-212
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• 2021

In wetland protection areas, a phytosociological research was conducted on willow forests, which plays an important ecological and environmental role and is the main material for ecological restoration. A total of 61 relevés were collected according to the Z-M(Zürich-Montpellier) school's method and the characteristics of plant communities and the composition of the species were identified. A total of 9 plant communities including 237 taxa were differentiated. Willow species showing the high r-NCD(relative net contribution degree) value in study areas were Salix koriyanagi, Salix chaenomeloides, Salix triandra subsp. nipponica, Salix gracilistyla and Salix pierotii. Poaceae was the most diverse in species, followed by Asteraceae, Apiaceae, Polygonaceae and Fabaceae. Life form type of willow forests in wetland protection areas was determined to be Th(therophytes)-R₅(non-clonal form)-D₄(clitochores)-e(erect form) type. The naturalized plants and invasive alien species were identified as 24 taxa and 4 taxa, respectively. Naturalized and disturbance indices were 10.1% and 41.4%, respectively. The results of the site-species ordination by Non-Metric Multidimensional Scaling(NMDS), wetland types and altitude gradient were the main ecological factors determining the spatial distribution of plant communities. Diversity index and evenness index were high in mountainous palustrine wetlands with relatively high altitude, and the disturbance index, naturalized index and appearance rate of annual plant were high in riverine and lacustrine wetlands with low altitude.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.217-224
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• 2002

It is very important to measure and visualize the changes in the physical properties of fluid flow because this is the foundation of measurement techniques used in aerodynamics, heat transfer, plasma diagnostics, and stress analysis of transparent models. The optical methods are advantageous over probe-based techniques in the optical methods are of high speed, non-contact and are capable of providing full-field results with high spatial resolution. Therefore we propose the electronic speckle pattern interferometry(ESPI) that gives us a solution to overcome those limitations. In this paper the experimental results show qualitative and quantitative visualization of changes in the physical properties of the candle and alcohol lamp with 3D plotting. And we obtained the refractive index, mass density and temperature distribution of fluids. The results clearly show the process of flow phenomena and give the feasibility of quantitative interpretation of gasdynamics.

• Journal of Korea Planning Association
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• v.53 no.7
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• pp.5-22
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• 2018

While the competitiveness of small and medium sized cities has become important for balanced development at the national scale, they have experienced continuous decline in population and employment, particularly those in non-capital regions. In addition, some of small and medium sized cities have been classified into shrinking cities that have declined due to their long-term structural reasons. To address these issues, a regional approach, by which a hub city and its surrounding small and medium sized cities can collaborate has been suggested. Given this background, the purpose of this study is to identify and delineate hub cities and their impact areas by using travel data as a functional network index. This study uses a centrality index to identify the hub cities of small and medium sized cities and Markov-chain model and cluster analysis to delineate regional boundaries. The mean first passage time (MFPT) generated from the Markov-chain model can be interpreted as functional distance of each region. The study suggests a methodological approach delineating the boundaries of regions incorporating functional relationships of hub cities and their impact areas, and provides 59 hub cities and their impact areas. The results also provide policy implications for regional spatial planning that addresses appropriate planning boundaries of regions for enhancing the economic competitiveness of small and medium sized cities and ensuring services for shrinking cities.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.2 s.308
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• pp.1-11
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• 2006

In this paper, we propose the novel video retrieval algorithm using non-parametric based motion classification in the shot-based video indexing structure. The proposed system firstly gets the key frame and motion information from each shot segmented by scene change detection method, and then extracts visual features and non-parametric based motion information from them. Finally, we construct real-time retrieval system supporting similarity comparison of these spatio-temporal features. After the normalized motion vector fields is created from MPEG compressed stream, the extraction of non-parametric based motion feature is effectively achieved by discretizing each normalized motion vectors into various angle bins, and considering a mean, a variance, and a direction of these bins. We use the edge-based spatial descriptor to extract the visual feature in key frames. Experimental evidence shows that our algorithm outperforms other video retrieval methods for image indexing and retrieval. To index the feature vectors, we use R*-tree structures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5B
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• pp.287-293
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• 2012

This study suggests the topographic index-based methodology which can be used to represent the saturation of soil and thereby change of variable runoff area at basin scale. ${\infty}$-flow direction method is applied to estimate topographic index because of its freedom from the restriction of 8-flow direction method as well as possibility of the minimum flow dispersion. From the comparison of topographic index distribution with the existing result the methodology is shown to be a workable one. It is judged that the representation of variable runoff area may be a systematic tool to investigate the dynamic and non-linear property of rainfall-runoff process because it can provide the explicit way to spatial distribution of basin saturation.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1005-1005
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• 2003

The purpose of this study is to evaluate the potential application of TERRA-ASTER data in Thailand. ASTER VNIR, SWIR and TIR data covering greater Bangkok and Chiangmai province were processed with various techniques in the spatial domain to study the applicability to various disciplines. ASTER data was also combined with other satellite data in order to utilize multi-sensor methods. It was found that VNIR data can clearly identify urban pattern including road network and vegetation index. While SWIR and TIR data can well separate between urban and non urban area and TIR data can differentiate among thermal surfaces. Furthermore, dense urban areas such as central business area could be highlighted. Land utilization, vegetable distribution and differences of temperature distribution were investigated.

• Korean Journal of Ecology and Environment
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• v.53 no.1
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• pp.22-30
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• 2020

In this study, we investigated the relationships between benthic macroinvertebrate assemblages and various environmental factors in Iancheon (NIA) and Bukcheon (NBC) streams, Korea. We collected benthic macroinvertebrates and 33 environmental factors in April 2017 at 9 sites (5 sites in NIA and 4 sites in NBC). We identified 93 species(5 phyla, 9 classes, 16 orders, and 53 families) and 69 species(5 phyla, 9 classes, 17 orders, and 47 families) in NIA and NBC streams, respectively. Considering benthic macroinvertebrate index (BMI), NIA (88.2) and NBC (80.2) streams were in "very good" status. Upstream areas showed the highest scores, 95.5 (NIA1) and 94.2 (NBC1), whereas BMI score was the lowest in downstream areas of both streams, especially in NBC4 (51.0 "bad" status). Cluster analysis and non-metric multidimensional scaling analysis represented the differences of benthic macroinvertebrate assemblages according to spatial and anthropogenic gradients. Our findings provide reference data and highlight the need for the continued monitoring to maintain the good status and manage macroinvertebrate diversity in these two streams, in Sangju-si, Korea.