• Journal of Korean Society of Coastal and Ocean Engineers
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• v.1 no.1
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• pp.44-49
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• 1989

Cohesive sedimentation mechanism is affected by various physico-chemical factors. Thus, the field observations and the laboratory experiments for cohesive sediment have been reported for decades. Erosion and deposition test was carried out with cohesive sediment material sampled in the Keum River Estuary in this study. The change of the suspended cohesive sediment concentration was measured for various flow conditions, which have the purpose to determine the critical shear stress and the coefficients for erosion and deposition . The critical shear stress and the coefficient for erosion were determined in the flume test. The equilibrium concentration was determined for each shear stress and the relationship between the normalized equilibrium cocentration with the initial cocentration (Ceq/co) and the equivalent shear stress was obtained. The experimental results were compared with the other results and showed fairly well agreements with them.

• Journal of Environmental Science International
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• v.30 no.12
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• pp.1015-1025
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• 2021

Our research work aimed to evaluate cover crop effects of winter rye on soil characteristics, soil conservation, and yield productivities on potato fields with 15% slope during a fallowed period. There were two controls of bared field without any cultivation and conventional potato cultivation without winter rye. Potato cultivation increased soil pH, organic matter, available phosphate, and exchangeable cation regardless of cover crop cultivation. Sub-soil, particularly, all components of soil chemical properties showed higher value in winter rye cultivation than conventional cultivation. Higher soil density was observed on cover crop cultivation than conventional cultivation resulting from root residues of the cover crop both topsoil and subsoil. Cover crop residues positively affected plant growth and reduced the amount of soil erosion by holding the soil. Although severe soil erosion was seen in conventional cultivation, winter rye cultivation declined soil erosion by 47% during the fallow period on potato slope fields. Distinct soil bacterial communities were detected among treatments and some OTU(Operational Taxonomic Unit)s showed significantly higher abundance in winter rye treatment. Total yield and commercial rate demonstrated no significant differences while higher tuber phosphate, K⁺, and Mg²⁺ contents were observed in winter rye cultivation.

• Corrosion Science and Technology
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• v.20 no.6
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• pp.466-474
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• 2021

A wet type scrubber for merchant vessel uses super austenitic stainless steels with pitting resistance equivalent number (PREN) of 40 or higher for operation in a harsh corrosive environment. However, it is expensive due to a high nickel content. Thus, electrochemical behavior and cavitation erosion characteristics of UNS S32750 as an alternative material were investigated. Microstructure analysis revealed fractions of ferritic and austenitic phases of 48% and 52%, respectively, confirming the existence of ferritic matrix and austenitic island. Potentiodynamic polarization test revealed damage at the interface of the two phases because of galvanic corrosion due to different chemical compositions of ferritic and austenitic phases. After a cavitation test, a compressive residual stress was formed on the material surface due to impact pressure of cavity. Surface hardness was improved by water cavitation peening effect. Hardness value was the highest at 30 ㎛ amplitude. Scanning electron microscopy revealed wave patterns due to plastic deformation caused by impact pressure of the cavity. The depth of surface damage increased with amplitude. Cavitation test revealed larger damage caused by erosion in the ferritic phase due to brittle fracture derived from different strain rate sensitivity index of FCC and BCC structures.

• Korean Journal of Environment and Ecology
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• v.34 no.5
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• pp.413-424
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• 2020

Environmental policies and industry practices have recently seen a gradual paradigm shift from reactive management to proactive prevention of environmental impacts. Accordingly, preventive conservation policies are carried out to address the increasing value of protecting soils and soil functions as resources are limited. To propose a direction for future soil erosion research, we analyzed domestic and international research trends of soil erosion, based on journal papers retrieved from the Web of Science databases over the last decade, using VOSviewer for keyword co-occurrence analysis. The results showed that the number of publications on soil erosion per land area in Korea ranked high worldwide. In particular, studies on the soil erosion control were found to account for a more significant proportion than other countries. The active ongoing studies on soil erosion in Korea indicate that the country has recognized the severity of soil erosion resulting from climate, topography, and land use. However, the number of keywords found in the studies on the soil erosion control in Korea was relatively smaller than those found at the international level, indicating the need to diversify and expand the study subjects. In particular, studies on the soil erosion process and the related physical and chemical soil properties are necessary to find the fundamental solutions to soil erosion problems.

• Advances in nano research
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• v.2 no.2
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• pp.121-133
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• 2014

Polymer nanocomposites are advanced nanomaterials which exhibit dramatic improvements in various mechanical, thermal and barrier properties as compared with the neat polymer. Polystyrene/ alumina nanocomposites were prepared by an ultrasound-assisted solution casting method at filler loadings ranging from 0.2 to 2% and also at different ultrasonic frequencies, viz. 58 kHz, 192/58 kHz, 430 kHz, 470 kHz and 1 MHz. The composites were subjected to mechanical property tests (tensile and impact tests) and cavitation erosion tests to study the enhancement in functional properties. Filler dispersion in the polymer matrix was observed by SEM analysis. The effect of frequency on filler dispersion in the matrix was studied by SEM analysis and functional property enhancement of the composite material. The composites prepared at dual (high/ low) frequency (192/58 kHz) were found to show better property enhancement at low filler loadings as compared with neat polymer and also with composites prepared without ultrasound, thus reinforcing the finding that ultrasound-assisted synthesis is a promising method for the synthesis of nanocomposites.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.1
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• pp.42-46
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• 2017

Dental erosion is defined as tooth structure loss by acidic chemical substance. It is caused by extrinsic factors such as acidic foods, drugs, and working environments, and also intrinsic factors such as gastric acid regurgitation in gastro-esophageal disorder or intensive vomiting in bulimia nervosa. These lesions can be treated with direct resin filling, laminate or full contour crown depending on the intensity of clinical problem. This is a case report about treatment of rare clinical case: labial erosion of anterior tooth caused by frequent intake of acidic fruit and palatal erosion of anterior tooth caused by intensive vomiting in bulimia nervosa.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.6
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• pp.739-745
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• 2013

In this study, we tried to define the erosion-corrosion behavior together with the resulting effects on a pipe that is a part of a feed water circulation system according to the pipe size and hot feed water environment. An erosioncorrosion analysis was performed through the Hayduk and Minhas model based on the chemical reaction between iron and oxygen, an essential corrosive factor. The erosion-corrosion rate against the pipe diameter and feed water temperature was then evaluated by means of finite element analysis using ABAQUS. As shown in the results, the feed water temperature was the main factor influencing the erosion-corrosion rate; in particular, it was expected that the thickness of 316 stainless steel would decrease by $2.59{\mu}m$ every year in a hot water environment at $290^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
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• 2005.02a
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• pp.76-76
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• 2005

• Journal of Adhesion and Interface
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• v.7 no.2
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• pp.19-25
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• 2006

Since the enzymatic degradation of microbial poly(hydroxylalkanoate)s (PHAs), such as poly[(R)-3-hydroxybutyrate] and poly[(R)-3-hydroxybutyrate-co-3-hydroxyvalerate] initially occurs by a surface erosion process, their degradation behaviors can be controlled by the change of surface property. In order to control the rate of enzymatic degradation, plasma modification technique was applied to change the surface property of microbial PHAs. The surface hydrophobic and hydrophilic properties of PHA films were introduced by $CF_3H$ and $O_2$ plasma exposures, respectively. The enzymatic degradation was carried out at $37^{\circ}C$ in 0.1 M potassium phosphate buffer (pH 7.4) in the presence of an extracellular PHB depolymerase purified from Alcaligenes facalis T1. The results showed that the significant retardation of initial enzymatic erosion of $CF_3H$ plasma-treated PHAs was observed due to the hydrophobicity and the enzyme inactivity of the fluorinated surface layers while the erosion rate of $O_2$ plasma-treated PHAs was not accelerated.

• Journal of Electrical Engineering and Technology
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• v.8 no.2
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• pp.345-353
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• 2013

This paper discusses the experimental results in an effort to understand the tracking and erosion resistance of the micro and nano size $Al_2O_3$ filled silicone rubber (SIR) material which has been studied under the AC voltages, with ammonium chloride as a contaminant, as per IEC 60587 test procedures. The characteristic changes in the tracking resistance of the micro and nano size filled specimens were analyzed through leakage current measurement and the eroded masses were used to evaluate the relative erosion and tracking resistance of the composites. The fundamental, third and fifth harmonic of the leakage current during the tracking study were analyzed using moving average current technique. It was observed that the harmonic components of leakage current show good correlation with the tracking and erosion resistance of the material. The thermogravimetry-derivative thermo gravimetric (TG-DTG) studies were performed to understand the thermal degradation of the composites. The physical and chemical studies were carried out by using scanning electron microscope (SEM), Energy Dispersive X-ray analysis (EDAX) and Fourier Transform Infra-red (FTIR) Spectroscopy. The obtained result indicated that the performance of nano filled SIR was better than the micro filled SIR material when the % wt. of filler increased.