• Journal of Environmental Impact Assessment
• /
• v.22 no.6
• /
• pp.591-607
• /
• 2013

The objectives of the study were to evaluate the aquatic environment of an urban stream using various ecological parameters of biological biomarkers, physical habitat quality and chemical water quality and to develop a "Multimetric Eco-Model" ($M_m$-E Model) for the ecosystem evaluations. For the applications of the $M_m$-E model, three zones including the control zone ($C_Z$) of headwaters, transition zone ($T_Z$) of mid-stream and the impacted zone ($I_Z$) of downstream were designated and analyzed the seasonal variations of the model values. The biomarkers of DNA, based on the comet assay approach of single-cell gel electrophoresis (SCGE), were analyzed using the blood samples of Zacco platypus as a target species, and the parameters were used tail moment, tail DNA(%) and tail length (${\mu}m$) in the bioassay. The damages of DNA were evident in the impacted zone, but not in the control zone. The condition factor ($C_F$) as key indicators of the population evaluation indicator was analyzed along with the weight-length relation and individual abnormality. The four metrics of Qualitative Habitat Evaluation Index (QHEI) were added for the evaluations of physical habitat. In addition, the parameters of chemical water quality were used as eutrophic indicators of nitrogen (N) and phosphorus (P), chemical oxygen demand (COD) and conductivity. Overall, our results suggested that attributes of biomarkers and bioindicators in the impacted zone ($I_Z$) had sensitive response largely to the chemical stress (eutrophic indicators) and also partially to physical habitat quality, compared to the those in the control zone.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2004.11a
• /
• pp.153-158
• /
• 2004

The numerous investments have been introduced to design and assess mixing zone characteristics of wastewater discharges to the ocean. Specially It strive to meet water quality standard for persistent and bio-accumulative chemical contaminants at the point of discharge through continual improvement pollution prevention measures and other voluntary measures in the developed country. The goals that of this paper are to emphasize the regulatory mixing zone is defined as an allocated impact zone where the numeric water quality criteria may be exceeded as long as acutely toxic conditions are prevent. Furthermore, mixing zones be limited to an area or volume as small as practicable that with not interfere with the designated uses or the established community of aquatic life in the segment for which the uses are designated and the shape be a simple configuration that is easy to locate in the body of water and avoids impingement on biologically important areas and the shore hugging plumes should be avoided This results should be used with caution in evaluation the mixing zone characteristics of a discharge and only in conjunction with information from the effective marine outfall design as well as for the sound harbour design. Thus the numerical investigation using CORMIX has been performed to show the regulatory mixing zone in the near and far field of the marine outfall.

• Journal of Advanced Marine Engineering and Technology
• /
• v.33 no.1
• /
• pp.104-111
• /
• 2009

This paper shows the behaviors of macro- and micro-structures and mechanical properties for specimen's welding region welded by FSW. according to welding conditions with 5mm thickness aluminum 5083O alloy plate. It apparently results in defect-free weld zone in case traverse speed was changed to 32 mm/min under conditions of anti-clockwise direction and tool rotation speed such as 800 and 1250 rpm with tool's pin diameter of 5 ${\Phi}mm$ and shoulder diameter of 20 ${\Phi}mm$, pin length of 4.5 mm and tilting angle of $2^{\circ}$. The ultimate stress of ${\sigma}_T=331$ MPa and the yield point of 147 MPa are obtained at the condition of the travel speed of 32 mm/min with the tool rotation speed of 1250 rpm. There is neither voids nor cracks on bended surface of $180^{\circ}$ after bending test. The improvement of toughness after impact test was found. The lower rotating and traverse speed became, the higher were yield point, maximum stress and elongation(%) with the stresses and the elongation(%) versus the traverse speed diagram. Vickers hardness for cross section of welding zone were also presented. The typical macro-structures such as dynamically recrystallized zone, thermo-mechanically affected zone and heat affected zone and the micro-structures of the transverse cross-section were also showed. However, the author found out that the region of 6mm far away from shoulder circumference was affected by friction heat comprehensively, that is, hardness softened and that part of micro-structures were re-solid-solution or recrystallized, the author also knew that there is no mechanically deformation on heat affected zone but there are the flow of plastic deformation of $45^{\circ}$ direction on thermo-mechanically affected zone and the segregation of Al-Mg on nugget. The solid solution wt(%) of parent material as compared against of friction stir welded zone was comprehensively changed.

• Tunnel and Underground Space
• /
• v.24 no.3
• /
• pp.187-200
• /
• 2014

After excavation or blasting, rock properties within an excavation damaged zone can be perpetually weakened on account of stress redistribution or blasting impact. In the present study, the excavation damaged zone is applied to a rock slope. The objective of this research is to compare the mechanical stability of the rock slope depending on the presence of the damaged zone using 2-dimensional modeling and analyze factors affecting factor-of-safety. From the modeling, it was founded that the mechanical stability of the rock slope is significantly dependent on the presence of the damaged zone. In particular, factor-of-safety with a consideration of the damaged zone decreased by approximately 49.4% in comparison with no damaged zone. Factor analysis by fractional factorial design was carried out on factor-of-safety. It showed that the key parameters affecting factor-of-safety are angle of the slope, cohesion, internal friction angle and height.

• Journal of Welding and Joining
• /
• v.34 no.5
• /
• pp.70-76
• /
• 2016

In this study, Microstructure and tensile properties in arc brazed joints of 1000MPa grade DP steel using Cu-Si insert metal were investigated. The fusion zone was composed of Cu phase which solidified a little Fe and Si. The former phase formed due to dilute the edge of base material by arc, although Fe was not solid solution in Cu at the room temperature. Cu3Si particles formed by crystallization at $1100^{\circ}C$ during faster cooling. After the tensile shear test, there are no differences between the brazed joint efficiencies. The maximum joint efficient was about 37% compared to strength of base metal. It is better than that of arc brazed joint of DP steel using Cu-Sn filler metal. Fracture position of all brazing conditions was in the fusion zone. Crack initiation occurred at three junction point which was a stress singularity point of upper sheet, lower sheet and the fusion zone. And then crack propagated across the fusion zone. The reason why the fracture occurred at fusion zone was that the hardness of fusion zone was lower than that of base material and heat affected zone. The correlation among maximum load and hardness of fusion zone and EST at fractured position was $R^2=0.9338$. Therefore, this means that hardness and EST can have great impact on maximum load.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.3 no.4
• /
• pp.915-922
• /
• 1999

The field dependent characteristics of electron transport with GaAs impact ionization have been analyzed, using GaAa full band E-k relationship. The E-k relationship is derived from empirical pseudopotential method, using Fermi's golden rule and local form factor, and Brillouin zone is divided into tetrahedrons for calculating impact ionization rate, and tetrahedron method, in which integrates each tetrahedrons, is used. Monte Carlo simulation is used for analyzing anisotropy of impact ionization. A result of transient analysis for impact ionization has presented that anisotropy of impact ionization only arises during transient state and impact ionization is isotropic under steady state. Anisotropic characteristics of impact ionization for GaAs, which is presented in this paper, can be used in carrying out a transient analysis for GaAs devices.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1994.04a
• /
• pp.191-198
• /
• 1994

The nonlinear dynamic behaviors of guardrail established on the local or high way have been investigated using BARRIER Ⅶ program with respect to four design variables such as section type of beams and posts, impact angle, impact velocity and vehicle weight. Computer simulation programs are sophisticated analytical models for analyzing dynamic vehicle/barrier interactions and provide a relatively inexpensive alternative to full scale crash testing. This study has been focused on the structural adequacy, occupant risk, and vehicle trajectory. For this purpose, the maximum deflection and impact force have been calculated to design the clear zone and to analyze effect of impact attenuation. Also, the acceleration of vehicle and exit angle after collision have been computed to estimate the occupant risk. From this study, it is suggested that we should strengthen the design criteria of guradrail to prevent from disastrous traffic accidents.

• Journal of Environmental Impact Assessment
• /
• v.3 no.1
• /
• pp.77-82
• /
• 1994

A Nationwide survey of ecosystem in the Republic of Korea was accomplished from 1986 to 1990 and in that survey, GIS and remote sensing were used partially. This was done by the Ministry of Environment(MOE), which introduced remote sensing and GIS for environment management in late 1980's. Especially the National Institute of Environmental Research (NIER) are under the research on systematization of environmental information with an ultimate goal of application of GIS and remote sensing to environmental impact assessment. Although the Korean peninsula is in a non-tropical zone, we introduce two case studies on remote sensing applications to ecosystem managements in the Republic of Korea. One is a study on change detection in urban vegetation of Seoul with Landsat data and the other is a study on detection of insect damaged pine tree area using Landsat TM data. The techniques involved and the conclusion from these studies were relevant to vegetation studies in tropical ecosystem.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.9 no.3
• /
• pp.76-82
• /
• 2000

It is well known that during the oxygen cutting process residual thermal stresses are produced in weldment. The local non-uniform heating and subsequent cooling which takes place during any welding process causes complex thermal strains and stresses to finally lead to residual stresses exceed to the yield stress. High tensile stresses combined with applied structural load in the region near the welded joint can given rise to distortion brittle fracture change of the fatigue strength and stress corrosion cracking. The appropriate treatment of the welded component which reduces the peak of he welding residual stresses is believed to lower risk of the fracture during the service of the structure. In this study the impact loading in oxygen cutting frame was applied to reduce the residual stress. After applying the impact loading redistribution of resid-ual stress was measured by cutting method and the effect of fatigue was tested.

• Journal of Welding and Joining
• /
• v.11 no.1
• /
• pp.42-51
• /
• 1993

In this study, investigations were conducted in calculating parameters of elastic-plastic fracture mechanics using single specimen. The validity of these testing methods was judged by the confirmation of multiple specimen method of stop block test. The results were as follows: In order to measure a fracture toughness using the instrumented impact test, two general requirement must be considered; One, setting up proper impact velocity considered the effect of loading and the other, the necessity of low blow test for obtaining true energy by the compliance correction. It was possible to detect a crack initiation point by calculating the compliance changing rate from a load-defection curve. Criterion of a stable crack growth, $T_{mat}$ could be estimated by using key-curve method for a base metal. and combining Kaiser's rebound compliance with Paris-Hutchison's $T_{appl}$ equation for the brittled zone of welding heat affected.at affected.d.