• Journal of Advanced Marine Engineering and Technology
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• 제40권2호
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• pp.107-111
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• 2016

This paper presents electrochemical corrosion behaviors of cement mortar specimens in the high salinity condition. Chloride ion is known as the most detrimental parameter to cause the corrosion in reinforced concrete. Increasing the concrete cover thickness is one of the corrosion protection methods against chloride ion; so, this study mainly focuses on the effects of mortar cover thickness on corrosion protection. In specimens, rebar, which was a height of 200 mm and a diameter of 10 mm, was installed at the center of the small size form. Later on, mortar was injected into the form, and 10, 20, 30, 40, and 50 mm of the different mortar cover thicknesses were selected. Potential measurements, linear polarization resistance tests, and cyclic potentiodynamic polarization tests were performed for specimens that were exposed to seawater. These results were compared with visual inspection results of rebar. The results show that an increase in the cover thickness contributes to corrosion protection. In addition, the result of electrochemical corrosion tests generally agreed with that of an autopsy visual inspection.

• Journal of the Korean Institute of Rural Architecture
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• 제21권2호
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• pp.35-42
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• 2019

There are 17,427 reservoirs in Korea, of which about 96% were built before the mid 1980s. Therefore, aging is severe and reinforcement are necessary. In addition, aged reservoirs, which are more than 50 years old, account for 70% of the total. Therefore, there is a problem such as the collapse of the reservoir and the decrease of the storage capacity due to progress of aging with time. The grouting method using cement is mainly used as maintenance and reinforcement method of old reservoir. However, the grouting method using cement has engineering and environmental problems. In order to solve the engineering and environmental problems of cement grouting method, an eco-friendly grouting material was developed that mixes circular resource grouting binder, high molar ratio sodium silicate and colloidal silica. The engineering and environmental properties of the developed injection materials were evaluated by conducting gel time, homo-gel strength, sea water resistance test and environmental stability evaluation. Also, examined the possibility of replacing OPC existing aged reservoir reinforcement methods. As a result, it was found out that it was better than the conventional cement method in terms of engineering and environment. However, since this study is the result of laboratory test, it is necessary of verify the application at field of aged reservoir.

• Corrosion Science and Technology
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• 제19권6호
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• pp.310-317
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• 2020

This study investigated the damage to the specimen due to liquid droplet impingement erosion corrosion, which improved the corrosion resistance and durability via hard anodization of 5083-H321 aluminum alloy, which is widely used for small ships and marine structures. The experiment combined liquid droplet impingement erosion and electrochemical equipment with the flow rates in natural seawater solution. Subsequently, Tafel extrapolation of polarization curves was performed to evaluate damage due to the liquid droplet impingement erosion corrosion. The damaged surface was observed using a 3D microscope and a scanning electron microscope. The degree of pitting damage was measured using the Image J program, and the surface hardness was measured using the micro-Vickers hardness tester. The corrosion current density, area, depth, and ratio of the damaged areas increased with the increase in flow rate. The grain size of the damaged area at a flow rate of 20 m s-1 showed fewer and minor differences in height, and a smooth curved shape. The hardness of the damaged surface tended to decrease with increase in flow rate.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• 제25권2호
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• pp.87-104
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• 1989

Recently, with the tendency of more lightening, high-strength and high-speed in the marine industries such as marine structures, ships and chemical plants, the use of the aluminium Alloy is rapidly enlarge and there occurs much interest in the study of corrosion fatigue crack characteristics. In this paper, the initiation of surface crack and the propagation characteristics on the base metal and weld zone of 5086-H116 Aluminium Alloy Plate which is one of the Al-Mg serious alloy(A5000serious) used most when building the special vessels, were investigated by the plane bending corrosion fatigue under the environments of marine, air and applying cathodic protection. The effects of various specific resistances on the initiation, propagation behavior of corrosion fatigue crack and corrosion fatigue life in the base metal and heat affected zone were examined and its corrosion sensitivity was quantitatively obtained. The effects of corrosion on the crack depth in relation to the uniform surface crack length were also investigated. Also, the structural, mechanical and electro-chemical characteristics of the metal at the weld zone were inspected to verify the reasons of crack propagation behavior in the corrosion fatigue fracture. In addition, the effect of cathodic protection in the fracture surface of weld zone was examined fractographically by Scanning Electron Microscope(S.E.M.). The main results obtained are as follows; (1) The initial corrosion fatigue crack sensitibity under specific resistance of 25Ω.cm% show 2.22 in the base metal and 19.6 in the HEZ, and the sensitivity decreases as specific resistance increases (2) By removing reinforcement of weldment, the initiation and propagation of corrosion crack in the HAZ are delayed, and corrosion fatigue life increases. (3) As specific resistance decreases, the sensitivity difference of corrosion fatigue life in the base metal and HAZ is more susceptible than that of intial corrosion fatigue crack. (4) Experimental constant, m(Paris' rule) in the marine environment is in the range of about 3.69 to 4.26, and as specific resistance increases, thje magnitude of experimental constant, also increases and the effect by corrosion decreases. (5) Comparing surface crack length with crack depth, the crack depth toward the thickness of specimen in air is more deeply propagated than that in corrosion environment. (6) The propagation particulars of corrosion fatigue crack for HAZ under initial stress intensity factor range of $\Delta$k sub(li) =27.2kgf.mm super(-3/2) and stress ratio of R=0 shows the retardative phenomenon of crack propagation by the plastic deformation at crack tip. (7) Number of stress cycles to corrosion fatigue crack initiation of the base metal and the welding heat affected zone are delayed by the cathodic protection under the natural sea water. The cathodic protection effect for corrosion fatigue crack initiation is eminent when the protection potential is -1100 mV(SCE). (8) When the protection potential E=-1100 mV(SCE), the corrosion fatigue crack propagation of welding heat affected zone is more rapid than that of the case without protection, because of the microfissure caused by welding heat cycle.

• Journal of Navigation and Port Research
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• 제27권5호
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• pp.527-537
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• 2003

The characteristics of ship induced waves caused by navigation become widely different from both ship's speed and water depth condition. The ship induced waves specially generated in coastwise routes frequently give rise to call unforeseen danger for swimmers and small boats as well as shoreline erosion or sea wall destruction in coastal zones. The main concern of ship induced wave study until now is either how to reduce ship resistance or how to manoeuvre the ship safely under a constant water depth in the view point of shipbuilding engineers. Moreover, due to the trends for appearance of the high speed ships at the shallow coastal water, we are confronted with the danger of damages from those ship induced waves. Therefore, it is necessary to examine the development of ship induced waves and the influence of their deformation effects according to its propagation ray. In present study, in order to predict the development of the ship induced waves and their propagation under the conditions of complicate and variable shallow water depth with varying ship's speed, we constructed a computer model using Boussinesq equation with a fixed coordinate system and verified the model results by comparison with experimental results. Additionally, the model was applied under the variable water depth based on actual passage and we then confirmed the importance of the variable water depth consideration.

• Journal of the Korea Concrete Institute
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• 제21권5호
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• pp.639-647
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• 2009

In order to evaluate the durability of reinforced concrete structures under chloride attack from sea water and frost damage, it is important to analyze both the microstructural characteristics of concrete and its diffusion resistance of concrete against chloride ingress. In this study, a relation between micro-pore structures of concrete obtained by the Mercury Intrusion Porosimetry and accelerated chloride diffusivity as well as long term chloride diffusivity were studied for ground granulated blast furnace slag(GGBS) concrete. Different water-cement ratio of 40, 45, 50% and different unit cement concrete of 300, 350, 400 or 450 kg/$m^3$ of the GGBS concrete along with OPC concrete were used and freeze and thawing, and the change in diffusivity and microstructure were observed for both GGBS concrete and damaged GGBS concrete due to rapid freezing and thawing.

• Journal of the Korea Fashion and Costume Design Association
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• 제10권2호
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• pp.11-25
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• 2008

John William Waterhouse (1849-1917) is a painter renown for his romantic beautiful femme fatale images in the late 19th century in England. The purpose of this study is to examine the fashion in Waterhouse's femme fatale images. Waterhouse displays the devilism of femme fatale by the symbols of a wicked woman. He emphasized how wicked she is by means of water such as lake, river, and sea as well as symbols associated with demons such as forest, cave, naked woman, long hair, a monster-headed woman looking like an animal, water lily, and garden. On the other hand, he illustrates the woman's style as an image of a typical feminine beauty. Expressing naturally a fine-curved, immature girl's body with marvel-like white and clear skin in a kneeling down or crouching passive rose and depicting it as an innocent and fragile feminine image, he created a passive and lovely image of a young girl. With her eminent beauty and sex appeals, she lured men into danger. Words such as evil, women, and death had been used in describing her as femme fatale to emphasize her wickedness as well as to deliver the meaning across from the inside and to the outside. They also described her as a type of woman with body posture and fashion corresponding to the sexual ideology during the Victorian Age. His description of this fashion image was to show that femme fatale's fashion, which represents attraction and fatality, does not necessarily translate to an active fashion style that emphasizes sensuality. It also tends to minimize resistance and feelings of being threatened. Therefore, it allons us to acknowledge that even girlish body with innocent and frail-looking fashion can be a form of femme fatale, and that fashion styles is essential in forming the image of femininity.

• Korean Journal of Ecology and Environment
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• 제55권1호
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• pp.19-34
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• 2022

This study was identified the distribution of vegetation in domestic estuaries and analysed the relationship with environmental fcators based on the health assessment data of the estuary ecosystem surveyed between 2016 and 2018. Of the 325 estuaries surveyed, 187 vegetation communites were investigated in 300 estuaries and 53 halophyte communites accounted for 28.3%. No vegetation distribution was found in the other 25 estuaries. Considering the circulation of estuary, 41 halophyte communites were investigated in open estuaries and 26 halophyte communites in closed estuaries. As a result of canonical correlation analysis (CCA) between the entire distributed vegetation community and environmental factors, salinity (conductivity), T-N, and T-P concentrations were strongly correlated. Among the riverbed material materials of the estuary, the composition ratio of silt, sand, and pebble was the most correlated. Therefor, it is estimated that the distribution location of the halophyte communites were differentiated by being influenced by the sea ares, estuary circulation type, resistance to salinity and riverbed material ratio.

• Tunnel and Underground Space
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• 제21권4호
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• pp.320-327
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• 2011

In this study, for stemming effect in blast of the mortar block body, the crushed granite sand as fine aggregate, which is waste rock obtained at the ○○ limestone mine, was investigated to compare with stemming materials such as sea sand, river sand, clayed soil and water can be acquired easily at the field. The mortar block body was manufactured with the dimensions of 50 cm width, 50 cm length and 70 cm height. The direct shear and sieve separator test were performed, and the properties of friction resistance were analyzed by the extrusion test for five stemming materials. Axial strain of steel bar and ejection velocity of stemming materials due to the explosive shock pressure in blasthole with the stemming length of 10 cm and 20 cm in the mortar blast test were measured by the dynamic data acquisition system. Among stemming materials, axial strain showed the largest value at the crushed granite sand as fine aggregate, and the ejection velocity was the smallest value at the stemming of water. The results has shown correlate with harden unit weight in blasthole, particle size distribution, shear resistance, and extrusion strength of stemming materials. The ejection velocity of stemming material at the mouth of blasthole and the axial strain of steel bar in the inside of blasthole tend to be inversely proportional to each other, represent exponentially.

• Journal of the Korean Society for Marine Environment & Energy
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• 제4권4호
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• pp.21-31
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• 2001

When an oil-spilling accident occurs at sea, it is of the primary importance to predict the amount of oil leakage for the swift response and decision-making. The simplest method of oil-leakage estimation is based on the hydrostatic pressure balance between oil inside the tank and seawater outside of leakage hole, that is the so-called Torricelli equilibrium relation. However, there exists discrepancy between the reality and the Torricelli relation, since the latter is obtained from the quasi-steady treatment of Bernoulli equation ignoring viscous friction. A preliminary experiment has been performed to find out the oil-leaking speed and shape. Soy-bean oil inside the inner tank was ejected into water of the outer tank through four different leakage holes to record the amount of oil leakage. Furthermore, a CFD (Computational Fluid Dynamics) method was utilized to simulate the experimental situation. The Wavier-Stokes equations were solved for two-density flow of oil and water. VOF method was employed to capture the shape of their interface. It is found that the oil-leaking speed varies due to the frictional resistance of the leakage hole passage dependent on its aspect ratio. The Torricelli factor relating the speed predicted by using the hydrostatic balance and the real leakage speed is assessed. For the present experimental setup, Torricelli factors were in the range of 35%~55% depending on the aspect ratio of leakage holes. On the other hand, CFD results predicted that Torricelli factor could be 52% regardless of the aspect ratio of the leakage holes, when the frictional resistance of leakage hole passage was neglected.