• Journal of Environmental Science International
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• v.11 no.7
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• pp.663-667
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• 2002

The aerodynamic resistance($R_a$) to vertical transfer in the surface boundary layer can be formulated in terms of the friction velocity, height of observation, vertical heat flux and surface roughness. Unlike previous studies which focused on the role of $R_c$, present study perform additional tests using a variety of $R_a$ formulae. Several $R_a$ formulations available in the literature, suitable for unstable conditions, were tested for their influence on the dry deposition velocity. The canopy resistance($R_c$) determines the shape of the diurnal pattern, while a small amplitude diurnal cycle in $V_d$ was attributed to the aerodynamic resistance. The aerodynamic resistance is the major contributor to the formation of spikes in nighttime and $R_a$ is relatively important at night because the canopy resistance is smaller. All formulations show similar diurnal cycle and yield good agreement with the observations. Although present $V_d$ formulations are suitable for numerical air qualify models, the research must continue for further improvements in resistance parametrizations.

• Steel and Composite Structures
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• v.36 no.5
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• pp.569-586
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• 2020

The behavior of composite steel-concrete beams depends on the transmission of forces between two parts: the concrete slab and the steel I-beam. The shear connector is responsible for the interaction between these two parts. Recently, an alternative shear connector, called Truss Type connector, has been developed; it aligns efficient structural behavior, fast construction and implementation, and low cost when compared to conventional connectors applied in composite structures. However, there is still a lack of full understanding of the mechanical behavior of the Truss Type connector, due to its novelty. Thus, this study aims to analyze the influence of variation of geometric and physical parameters on the shear resistance of the Truss Type connector. In order to investigate those parameters, a non-linear finite element model, able to simulate push-out tests of Truss Type connectors, was specifically developed and validated with experimental results. A thorough parametric study, varying the height, the angle between rods, the diameter, and the concrete strength, was conducted to evaluate the shear resistance of the Truss Type connector. In addition, an equation to predict the resistance of the original Truss Type shear connector was proposed.

• Corrosion Science and Technology
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• v.16 no.1
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• pp.8-14
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• 2017

The corrosion behavior of a ferritic/martensitic steel T91 exposed to an aqueous solution containing chloride and sulfate ions is investigated depending on the stimulated all-volatile treatment (AVT) and under oxygenated treatment (OT) conditions. The corrosion of T91 steel under OT condition is severe, while the corrosion under AVT condition is not. The co-existence of chloride and sulfate ions has antagonistic effect on the corrosion of T91 steel in both AVT and OT conditions. Unlike to corrosion resistance in the aqueous solution, OT pretreatment provides T91 steel lower oxidation-resistance than VAT pretreatment. From scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) and X-ray diffraction (XRD) analysis, the lower corrosion resistance in the aqueous solution by VAT conditions possibly is due to the formation of pits. In addition, the lower oxidation resistance of T91 steel pretreated by OT conditions is explained as follows: the cracks formed during the immersion under OT conditions accelerated peeling-off rate of the oxide film.

• Journal of Environmental Health Sciences
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• v.21 no.2
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• pp.7-11
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• 1995

This study was carried out to investigate the change of average specific resistance according to filtration pressure, suspension concentration and filters for study phenomena occurring in cake filtration. As the results of this study, the following conclusions were obtained. It was estimated that the average specific resistance of filtration Was decreased in proportion to decreased of filtration pressure. But in very pressure, average specific resistance was increased. The average specific resistance value on filter medium by various pressure was showed as same trends under constant suspension concentration. This phenomenon was though that a carrain amount of fine particles in the cake was found to migrate throught the cake in the case of very thin at very low pressure. In relation to the change of suspension concentration, average specific resistance value become low according to decreased in supension concentration.

• Journal of Environmental Science International
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• v.17 no.11
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• pp.1203-1210
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• 2008

Flow resistance in a natural stream is caused by complex factors, such as the grains on the bed, vegetation, and bed-form, reach profile. Flow resistance in a generally stable gravel bed stream is due to protrudent grains from bed. Therefore, the flow resistance can be calculated by equivalent roughness in gravel bed stream, but estimation of equivalent roughness is difficult because nonuniform size and irregular arrangement of distributed grain on natural stream bed. In previous study, equivalent roughness is empirically estimated using characteristic grain size. However, application of empirical equation have uncertainty in stream that stream bed characteristic differs. In this study, we developed a model using an analytical method considering grain diameter distribution characteristics of grains on the bed and also taking into account flow resistance acting on each grain. Also, the model consider the protrusion height of grain.

• Korean Journal of Veterinary Research
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• v.55 no.1
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• pp.41-46
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• 2015

Increasing presence of wild boar around cities and suburban areas is a growing concern with respect to agronomy, environmental ecology, and public safety. In this study, antibiotic resistance profiles of Escherichia (E.) coli isolated from wild boar and domestic pig fecal samples were compared. Eighty E. coli samples were isolated from wild boars. Resistance of the bacteria to 14 common antimicrobial agents used in human and veterinary medicine was evaluated. Ninety-five E. coli isolates from domestic pig farms were used for comparison. Common and distinct antibiotic resistance patterns were observed when comparing wild boar and domestic pig isolates, indicating that wild boars may significantly influence environmental microbiology.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.730-739
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• 2010

Stress history increases in penetration resistance due to the increase in residual horizontal stress of granular soil. This study analyzes the effect of stress history on the results of CPT and DMT from calibration chamber specimen in OC as well as NC state. Test results show that the normalized cone resistance by mean effective stress correlates well with the relative density and the state parameter, whereas the normalized cone resistance with regard to vertical effective stress is a little affected by stress history. The horizontal stress index($K_D$) in DMT more reflects the influence of stress history on granular soil than the dilatometer modulus($E_D$) and cone resistance($q_c$). The $K_D/K_0$, in which the effect of stress history on $K_D$ is compensated by the at-rest coefficient of earth pressure, $K_0$, is related to relative density, state parameter and the normalized cone resistance by mean effective stress. It is also observed that the normalized dilatometer modulus by mean effective stress($E_D/{\sigma_m}'$) is unique correlated with the state parameter, regardless of stress history.

• Journal of the Korean Geotechnical Society
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• v.24 no.12
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• pp.53-63
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• 2008

In this study, the cone tip resistances of cemented sand are measured by performing a series of miniature cone penetration tests in large calibration chamber, and the relations with constrained modulus, unconfined compressive strength, and shear strength of cemented sand are suggested. Experimental results show that both the cone tip resistance and constrained modulus of sand increase with increasing cementation effect as well as relative density and confining stress. However, it is observed that the relative density and confining stress have more significant influence on cone tip resistance than constrained modulus of cemented sand. Since the cone penetration into the ground induces the damage of cementation, the cone tip resistance can't properly reflect the cementation effect of sand. An analysis based on the constrained modulus shows that the measured cone tip resistance underestimates the deformation modulus of cemented sand by about $70{\sim}85%$. In addition, this study establishes various relationships among the above soil properties from the regression analysis.

• International Journal of Highway Engineering
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• v.20 no.3
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• pp.1-9
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• 2018

PURPOSES : In order to evaluate a crack resistance at cold joint, sealing tape was adopted to apply at cold joint instead of typical tack coat material(RSC-4). The sealing tape was made by hot sealing material. The crack resistance as function of environmental and traffic loading was measured with visual observation. METHODS : In this study, the crack resistance was evaluated as function of environmental and traffic loading. The freeze-thaw method was adopted for environmental loading of asphalt pavement. condition. The damage of cold joint under freeze-thaw action is initiated by ice expansion load and accelerated by the interfacial damage between new and old asphalt pavement. The traffic loading was applied with wheel tracking machine on the cold joint area of the asphalt pavement for 3 hours at $25^{\circ}C$. The evaluation of crack resistance was measured with visual observation. The freeze-thaw results shows that the sealing tape was significantly increased the crack resistance based on. RESULTS : To estimate the crack resistance at cold joint area due to the environmental loading, the Freeze-thaw test was conducted by exposing the product to freezing temperature(approximately $-18^{\circ}C$) for 24 hours, and then allowing it to thaw at $60^{\circ}C$ for 24 hours. The tack coat material(RSC-4) was debonded after 21 cycles of the Freeze-thaw test. The first crack was observed after 14 freeze-thaw cycle with RSC-4 material. But, the sealing tape was not debonded after 24 cycle test. Also, the sealing tape shows the better performance of the crack resistance under the traffic loading with wheel track test. The crack was generated the under traffic loading with RSC-4(tack coating), however, the crack was not shown with sealing tape. It indicates that the sealing tape has a strong resistance of tensile stress due to traffic loading. CONCLUSIONS :Based on limited laboratory test result, a performance of crack resistance using the sealing tape is better than that of general tack coat material(RSC-4). It means that the sealing tape is possible to extend a pavement service life because the crack, one of the main pavement distresses, will be delayed.

• Journal of the Korean Geotechnical Society
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• v.29 no.10
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• pp.49-56
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• 2013

The use of geothermal energy has been increased for economic and environmental friendly utilization. Ground thermal conductivity and borehole thermal resistance are very important parameters in the design of geothermal heat pump system. This paper presents an experimental study of heat exchange rate of U and W type ground heat exchangers (GHEs) measured by thermal performance tests (TPTs). U and W type GHEs were installed in a partially saturated dredged soil deposit, and TPTs were conducted to evaluate heat exchange rates under 100-hr continuous operation condition. The heat exchange rates were also calculated by analytical models to estimate borehole thermal resistances and were compared with experimental results. It comes out that multi-pole and equivalent diameter (EQD) models resulted in more accurate agreement than shape factor (SF) model which is currently more often used.