• Fire Science and Engineering
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• v.25 no.6
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• pp.64-72
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• 2011

The concrete void slab structure with the existing mushroom slab, is the structure that maximizes the advantages, while minimizing the weakness with removing useless body force of the concrete part, located on the center of the slab cross-section, which does not need to support the structural weight. In this research, a fire test is performed to analyze how the blaze behave according to the thickness of slab cover, with the practical span length of concrete void slab for the slab length 7.5 m. With this heating test, we assumed the uniform-load-model considering fixed loads and live loads, and chose the standard fire test condition. We measured the temperature changes and the deflection character according to the depth from the heat exposure side, and assessed the resisting capability according to the standard KS F 2257-1. The result comes out with the EPS model can secure about 2 hour fire-resisting-capability with 50 mm of cover depth.

• Journal of the Korean Society of Safety
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• v.28 no.6
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• pp.29-35
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• 2013

The purpose of this study is to investigate the steel bar corrosion and degree of reinforced concrete bridge, and analyze the cause of corrosion occurrence. Therefore they could ensure the durability and stability as to suggest the corrosion prevention of reinforced concrete structure. To study the corrosion state reinforced concrete structure, We investigate the cover of concrete, the compressive strength by schmidt hammer, the neutralization test of site, the compressive strength of core and the measurement of neutralized depth. As the results of test, the corrosion-grade of reinforced concrete structure which the degree of corrosion is 3, 4 degree get to 18% in the used time of 40 years and the time elapsed of 25 years. Therefore the corrosion of steel bar give rise to public discussion. The degree of corrosion is serious, and the neutralization come to the cover of concrete.

• Journal of Ecology and Environment
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• v.46 no.1
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• pp.8-17
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• 2022

Background: Parthenium hysterophorus L. (Asteraceae; hereafter Parthenium) is an invasive alien species of global significance because of its' negative ecological and socioeconomic impacts. This species is spreading rapidly from lowland Tarai to Middle Mountain regions in Nepal. In the present study, we analyzed the impacts of Parthenium on plant community composition including their soil seedbank in subtropical grasslands located in central Nepal. Data was collected in a 10 m long transects passing through areas of high (> 90% cover), medium (40%-60%) and low (< 10%) levels of Parthenium cover using a plot of 1 m². Altogether, we sampled 90 plots in 30 transects. Seedling emergence method was used to estimate soil seedbank density in the soil samples (0-10 cm depth) collected from the plots with high Parthenium cover. Results: There was no significant difference in the plant species richness at different levels of Parthenium invasion whereas there was a significant change in the species composition of above ground flora due to Parthenium invasion. There was also a significant difference in species composition between soil seedbank and aboveground flora in the highly invaded plots. Parthenium was the most dominant in soil seedbank, contributing 65% to the total soil seedbank. Conclusions: Our study suggests that Parthenium has considerable negative impact on the native grassland flora, and the dominance of Parthenium in the soil seedbank means there is a challenge for its management. It also suggests the need of monitoring the soil seedbank dynamics while managing Parthenium weed.

• ALGAE
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• v.23 no.1
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• pp.83-90
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• 2008

Eelgrass beds are very productive and provide nursery functions for a variety of fish and shellfish species. Management for the conservation of eelgrass beds along the Korean coasts is critical, and requires comprehensive strategies such as vegetation mapping. We suggest a mapping method to spatial distribution and quantify of eelgrass beds using a digital echosounder. Echosounding data were collected from the northeast part of Kwangyang Bay, on the south of Korea, in March, 2007. A transducer was attached to a boat equipped with a DGPS. The boat completed a transect survey scanning whole eelgrass beds of 11.7 km2 with a speed of 1.5-2 m s-1 (3-4 knot). The acoustic reflectivity of eelgrass allowed for detection and explicit measurements of canopy cover and height. The results showed that eelgrass bed was distributed in depth from 1.19 to 3.6 m (below MSL) and total dry weight biomass of 4.1 ton with a vegetation area of 4.05 km2. This technique was found to be an effective way to undertake the patch size and biomass of eelgrass over large areas as nondestructive sampling.

• Geomechanics and Engineering
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• v.29 no.3
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• pp.339-348
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• 2022

The bored tunneling method is generally preferred for urban tunnel construction, However the cut & cover tunnel is still necessary for special conditions, such as metro station and access structures. In some case, deep excavation for cut & cover construction is planed of irregular and unusual shape, as a consequence, the convex and concave corner is often encountered during that excavation. In particular, discontinuity or imbalance of the support structure in the convex corner can lead to collapse, which may result in damages and casualties. In this study, the behavior of the convex corner of retaining structure were investigated using 3-dimensional numerical models established to be able to simulate the split-shaped behavior of convex corners. To improve the stability in the vicinity of the convex corner, several stabilizing measures were proposed and estimated numerically. It is found that linking two discretized wales at the convex corner can effectively perform the control of deformation. Furthermore, it was also confirmed that the stabilizing measures can be enhanced when the tie-material linking two discretized wales is installed at the depth of the maximum wall deflection.

• Journal of the Korean Society for Library and Information Science
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• v.48 no.3
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• pp.71-111
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• 2014

Metadata schemas are well recognized as one of the important technological components for archiving and preservation of digital resources. However, a single standard is not enough to cover the whole lifecycle for archiving and preserving digital resources. This means that we need to appropriately select metadata standards and combine them to develop metadata schemas to cover the whole lifecycle of resources (or records). Creating a unified framework to understand the features of metadata standards is necessary in order to improve metadata interoperability that covers the whole resource lifecycle. In this study, the author approached this issue from the task-centric view of metadata, proposing a Task model as a framework and analyzing the feature of archival metadata standards. The proposed model provides a new scheme to create metadata element mappings and to make metadata interoperable. From this study, the author found out that no single metadata standard can cover the whole lifecycle and also that an in-depth analysis of mappings between metadata standards in accordance with the lifecycle stages is required. The author also discovered that most metadata standards are primarily resource-centric and the different tasks in the resource lifecycle are not reflected in the design of metadata standard data models.

• International Journal of Concrete Structures and Materials
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• v.11 no.1
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• pp.151-159
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• 2017

The action of rainwater on reinforced concrete walls has led to an erosion phenomenon. The erosion is very apparent when the walls are inclined. This phenomenon is studied on a real site characterized by different architectural forms. The site dates back to the seventies; it was designed by the architect, modeler of concrete, Oscar Nie Meyer. On this site, the erosion has damaged the cover of the reinforcements and reduced its depth. In this research work, a method of quantification of the erosion is developed. Using this method, the amount of mass loss by erosion was measured on imprints taken from the site. The results are expressed by the rate of mass loss by erosion; they are associated to the height and the inclination of the walls. Moreover, laboratory analysis was carried out on samples taken from the site. From this study, it is recommended to consider the erosion, in any building code, to determine the cover thickness.

• Proceedings of the KSRS Conference
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• v.1
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• pp.110-113
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• 2006

This study is to grasp and analyse the temporal and spatial distribution of record-breaking heavy snowfall rarely occurred in the middle and southwest region of South Korea during March of 2004 and December of 2005 respectively. Snow cover area was extracted using the channels 1, 3 and 4 of NOAA AVHRR images and the snow depth distribution was spatially interpolated using snowfall data of meteorological stations. Using administration boundary and Digital Elevation Model from 1:5,000 NGIS digital map, the snowfall impact was assessed spatially and compared with the reports at that time.

• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.129-136
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• 1999

For the prediction of concrete-steel bond ability in reinforced concrete, many countries establish specifications for the pullout test. But these methods hardly to consider many parameters such as strength, shape, diameter and location of steel, concrete restrict condition by loading plate, strength of concrete and cover depth etc, and it is difficult to solve concentration and disturbance of stress. The purpose of this study is to propose a New Ring Test method which can be rational quantity evaluations of bond splitting mechanism. For this purpose, pullout test was carried out to assess the effect of several variables on bond splitting properties between reinforcing bar and concrete. Key variables are concrete compressive strength, concrete cover, bar diameter and rib spacing. Failure mode was examined and maximum bond stress-slip relationships were presented to show the effect of above variables. As the result, it appropriately expressed general characteristics of bond splitting mechanism, and it proved capability for standard test method.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.375-378
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• 1998

Scattering of TE waves by a periodic conducting surface with dielectric cover is considered. A method for the aalysis of scattering from periodic structures based on the numerical solution of the integral equations is further developed. Using periodicity (Floquet's theorem), the range of the integral equations is reduced to a single period where the kernels are the Green's functions for periodic arrays. The numerical solution of the intergral equations is obtained using the method of moments. From numerical results for the reflected power the effects of surface profile shape, period-to-depth ratio, and cover permittivity on the scattering behaviors are examined.