• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.5
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• pp.179-186
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• 2010

When a structure is damaged, its dynamic responses (natural frequency, acceleration, strain) are found to be changed. The ANN(Artificial Neural Network) damage-assesment method is that some measured dynamic signals from the structural changing dynamic responses are applied to ANN to assess the structural damage. Although there have been some studies on a certain typical cases so far, it is rare to find studies about the characteristics of the ANN damage-assesment method or about its applicability, its strength and weakness. So this study researches on the characteristics of ANN damage assesment method and on a problem in application of the various dynamic responses to ANN. What the ANN damage assessment method usually does in past researches is to teach an ANN by using some response signals obtained from damaged structures under one kind of excitations and to identify the locations and the extents of damage of same structures under the same excitations. However, the excitations inflicted on the structures are not always the same. Thus this study experiments whether a ANN which is trained using the same excitations is able to identify the damage when different excitations inflict. All response signals are obtained from experimental models.

• Journal of Ocean Engineering and Technology
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• v.30 no.6
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• pp.474-483
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• 2016

Accidental events such as collisions, groundings, and hydrocarbon explosions in marine structures can cause catastrophic damage. Thus, it is extremely important to predict the extent of such damage, which determines the total amount of oil spills and the residual hull girder strength. Punching fracture tests were conducted by Choung (2009b), where various sizes of indenters and circular unstiffened steel plates with different thicknesses were used to quasi-statically realize damage extents. A three-dimensional fracture strain surface was developed based on a reference (Choung et al., 2015b), where the average stress triaxiality and average normalized Lode angle were used as the parameters governing the fracture of ductile steels. In this study, new numerical analyses were performed using very fine axisymmetric elements in combination with an Abaqus user-subroutine to implement the three-dimensional fracture strain surface. Conventional numerical analyses were also conducted for the tests to identify the best fit fracture strain values by changing the fracture strains. Based on the phenomenon of the average normalized Lode angle starting out positive and then becoming slightly negative, it was inferred that the shear stress primarily dominates in determining the fractures locations, with a partial contribution from the compressive stress. It should be stated that the three-dimensional fracture surface effectively predicted at least the shear stress-dominant fracture behavior of a mild steel.

• Spatial Information Research
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• v.19 no.5
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• pp.1-11
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• 2011

This study mainly focused on the method of accurately extracting damage information in the im agery change detection process using the constructed high resolution aerial im agery. Bongwha-gun in Gyungsangbuk-do which had been severely damaged from a localized torrential downpour at the end of July, 2008 was selected as study area. This study utilized aerial im agery having photographing scale of 30cm gray image of pre-disaster and 40cm color image of post-disaster. In order to correct errors from the differences of the image resolution of pre-/post-disaster and time series, the prelim inary phase of image processing techniques such as normalizing, contrast enhancement and equalizing were applied to reduce errors. The extent of the damage was calculated using one to one comparison of the intensity of each pixel of pre-/post-disaster im aged. In this step, threshold values which facilitate to extract the extent that damage investigator wants were applied by setting difference values of the intensity of pixel of pre-/post-disaster. The accuracy of optimal image processing and the result of threshold values were verified using the error matrix. The results of the study enabled the early exaction of the extents of the damages using the aerial imagery with identical characteristics. It was also possible to apply to various damage items for imagery change detection in case of utilizing multi-band im agery. Furthermore, more quantitative estimation of the dam ages would be possible with the use of numerous GIS layers such as land cover and cadastral maps.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.195-195
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• 2016

Kon - Ha Thanh River basin is the largest and the most important river basin in Binh Dinh, a province in the South Central Coast of Vietnam. In the lower rivers, frequent flooding and inundation caused by heavy rains, upstream flood and or uncontrolled flood released from upstream reservoirs, are very serious, causing damage to agriculture, socio-economic activity, human livelihood, property and lives. The damage is expected to increase in the future as a result of climate change. An advanced flood warning system could provide achievable non-structural measures for reducing such damages. In this study, we applied a modelling system which intergrates a 1-D river flow model and a 2-D surface flow model for simulating hydrodynamic flows in the river system and floodplain inundation. In the model, exchange of flows between the river and surface floodplain is calculated through established links, which determine the overflow from river nodes to surface grids or vice versa. These occur due to overtopping or failure of the levee when water height surpasses levee height. A GIS based comprehensive raster database of different spatial data layers was prepared and used in the model that incorporated detailed information about urban terrain features like embankments, roads, bridges, culverts, etc. in the simulation. The model calibration and validation were made using observed data in some gauging stations and flood extents in the floodplain. This research serves as an example how advanced modelling combined with GIS data can be used to support the development of efficient strategies for flood emergency and evacuation but also for designing flood mitigation measures.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.3
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• pp.410-420
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• 2010

When ships are sailing with large motions in rough waves, the slamming phenomenon occurs and the ships suffer from impulsive pressure loadings. Recently, ships are becoming lager and faster than before and it becomes more possible that the ships experience larger impacts on their bows and sterns. Many researchers have been performing the investigations on slamming experimentally and theoretically for a long time. Most of the research reported in the open literature focused on how to accurately estimate the amplitude of the peak pressure of slamming. According to the results of a recently published work, not only the amplitude of peak pressure but also the width of the peak may play an important role in predicting the extents of damage of impacted structures. The uncertainty of impulsive pressure loadings due to slamming has been indicated by many researchers. However, probabilistic treatments of the impulsive pressure loadings are few. In this study, drop tests were conducted on wedges having dead-rise angles of $0^{\circ}$ and $10^{\circ}$. Not only the amplitude of peak pressure but also the width of peak pressure were measured. Furthermore, the variations of those values are also provided for the probabilistic approach of the slamming problem.

• Journal of Chest Surgery
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• v.10 no.2
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• pp.281-294
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• 1977

Superior vena cava to pulmonary arterial shunting operation was made between the superior vena cava and the right pulmonary artery in the fashion of end-to-end anastomosis in 20 mongrel dogs. The experimental animals were divided into three group and blood flow in the superior vena cava was occluded for 20, 30 and 60 minutes respectively, and observations were made for the changes in caval pressure and cerebrospinal fluid pressure. And pathologic examinations were also performed. On occluding the caval blood flow, the superior vena caval pressure was sharply and immediately elevated from $103.5{\pm}19.8mmH_2O$ at thoracotomy to $556.4{\pm}86.lmmH_2O$ within 2 minutes to make its plateau thereafter, and the cerebrospinal fluid pressure followed closely the changes of the superior vena caval pressure in its level and pattern being elevated from $102.0{\pm}19.9mmH_2O$ to $490.5{\pm}79.9mmH_2O$. The drops of both the caval and cerebrospinal fluid pressures were definite and marked on opening the shunt flow through the anastomosis, but these postoperative pressures retained still higher ones above their levels measured at thoracotomy. The pathological examinations of the brain and the spinal cord were also performed in six animals. Characteristic changes uniformly seen in all area and in all animals were the findings of capillary congestion and perivascular edema. On the other hand, ischemic nerve cell changes were rather evident, revealing their degrees and extents being related to the prolongation of the time of caval occlusion which has followed by the sustained high pressures in both the superior vena and the cerebrospinal fluid. The experiment suggests the safety of this surgical procedure with minimal, if any, permanent damage as long as the occlusion of the caval blood flow is not prolonged beyond the expected.

• Journal of the Korean Society for Marine Environment & Energy
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• v.1 no.2
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• pp.82-95
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• 1998

In this paper, two series of numerical simulations are performed using LS/DYNA3D: The first series of numerical simulations are collision events between a 310,000 DWT double hull VLCC (struck ship) and two 35,000 and 105,000 DWT tankers (striking ships). Collisions are assumed to occur at the middle of the VLCC with the striking ships moving at right angle to the YLCC centerline. The second ones, grounding accidents of two 40,000 DWT Conventional and Advanced Double Hull lanker bottom structures, CONV/PD328 and ADH/PD328 models. The overall objective of this study is to understand the structural failure and energy absorbing mechanisms during collision and grounding events for double hull tanker side and bottom structures, which lead to the initiation of inner shell rupture and cause the kinetic energy dissipation to bring the ship to a stop. These numerical simulations will contribute to the estimation of damage extents of collision and grounding accidents and the future improvements in lanker safety at the design stage.

• The Korean Journal of Physiology and Pharmacology
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• v.7 no.2
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• pp.65-71
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• 2003

Increasing evidences suggest that ischemia-induced vascular damage is an integral step in the cascade of the cellular and molecular events initiated by cerebral ischemia. In the present study, employing a mouse brain endothelioma-derived cell line, bEnd.3, and oxygen-glucose deprivation (OGD) as an in vitro stroke model, the role of nuclear factor kappa B (NF-${\kappa}B$) activation during ischemic injury was investigated. OGD was found to activate NF-${\kappa}B$ and to induce bEnd.3 cell death in a time-dependent manner. OGD phosphorylated neither 32 Ser nor 42 Tyr of $I{\kappa}B{\alpha}$. OGD did not change the amount of $I{\kappa}B{\alpha}$. The extents of OGD-induced cell death after 8 h, 10 h, 12 h and 14 h of OGD were 10%, 35%, 60% and 85%, respectively. Reperfusion following OGD did not cause additional cell death, indicating no reperfusion injury after ischemic insult in cerebral endothelial cells. Three known as NF-${\kappa}B$ inhibitors, including pyrrolidine dithiocarbamate (PDTC) plus zinc, aspirin and caffeic acid phenethyl ester (CAPE), inhibited OGD-induced NF-${\kappa}B$ activation and increased OGD-induced bEnd.3 cell death in a dose dependent manner. There were no changes in the protein levels of bcl-2, bax and p53 which are modulated by NF-${\kappa}B$ activity. These results suggest that NF-${\kappa}B$ activation might be a protective mechanism for OGD-induced cell death in bEnd.3.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.3
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• pp.282-286
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• 2016

This study was carried out to evaluate the effect of application of urea and combination of urea and pig manure compost (PMC) on the occurrence of and the recovery from ammonium ($NH_4{^+}$) toxicity in Chinese cabbage. To identify $NH_4{^+}$ toxicity of the crop four levels of urea at 0, 160, 320, and $480kg\;N\;ha^{-1}$ were applied, in addition, three levels of PMC at 10, 20, and $40M/T\;ha^{-1}$ was also applied with urea $320kg\;ha^{-1}$. For recovery $NH_4{^+}$ toxicity, six levels of sucrose were treated at the amount of 0, 600, 1,200, 1,800, 2,400, and $3,000kg\;C\;ha^{-1}$ at each level of combining treatments of urea and PMC. Our results showed that $NH_4{^+}$ toxicity was occurred at every urea application of $320kg\;N\;ha^{-1}$ regardless of PMC applied to the soils because $NH_4{^+}$ contents in the soils were more than $155mg\;kg^{-1}$ which was found to be the critical level to damage crop growth at 2 days after transplanting (DAT) in this experiment, the more sucrose was applied up to $1,800kg\;C\;ha^{-1}$ for the plants damaged by ammonium toxicity occurred at $320kg\;N\;ha^{-1}$, the greater extents recover the plants from the toxicity. PMC showed the similar effect with sucrose on recovering Chinese cabbage plants from $NH_4{^+}$ toxicity at 30 DAT.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.458-458
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• 2012

Climate extreme variability is a major cause of disaster such as flood and drought types occurred in Korea and its effects is also more severe damage in last decades which can be danger mature events in the future. The main aim of this study was to assess the effectives of climate change on drought for an agriculture as Nakdong basin in Korea using climate change data in the future from data of General Circulation Models (GCM) of ECHO-G, with the developing countries like Korea, the developed climate scenario of medium-high greenhouse gas emission was proposed of the SRES A2. The Standardized Precipitation Index (SPI) was applied for drought evaluation. The drought index (SPI) applied for sites in catchment and it is evaluated accordingly by current and future precipitation data, specific as determined for data from nine precipitation stations with data covering the period 1980-2009 for current and three periods 2010-2039, 2040-2069 and 2070-2099 for future; time scales of 3month were used for evaluating. The results determined drought duration, magnitude and spatial extent. The drought in catchment act intensively occurred in March, April, May and November and months of drought extreme often appeared annual in May and November; drought frequent is a non-uniform cyclic pattern in an irregular repetitive manner, but results showed drought intensity increasing in future periods. The results indicated also spatial point of view, the SPI analysis showed two of drought extents; local drought acting on one or more one of sites and entire drought as cover all of site in catchment. In addition, the meteorology drought simulation maps of spatial drought representation were carried out with GIS software to generate for some drought extreme years in study area. The method applied in this study are expected to be appropriately applicable to the evaluation of the effects of extreme hydrologic events, the results also provide useful for the drought warning and sustainable water resources management strategies and policy in agriculture basins.