• Geomechanics and Engineering
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• v.16 no.6
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• pp.577-588
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• 2018

A major concern in deep excavation project in soft clay deposits is the potential for adjacent buildings to be damaged as a result of the associated excessive ground movements. In order to accurately determine the wall deflections using a numerical procedure such as the finite element method, it is critical to use the correct soil parameters such as the stiffness/strength properties. This can be carried out by performing an inverse analysis using the measured wall deflections. This paper firstly presents the results of extensive plane strain finite element analyses of braced diaphragm walls to examine the influence of various parameters such as the excavation geometry, soil properties and wall stiffness on the wall deflections. Based on these results, a multivariate adaptive regression splines (MARS) model was developed for inverse parameter identification of the soil relative stiffness ratio. A second MARS model was also developed for inverse parameter estimation of the wall system stiffness, to enable designers to determine the appropriate wall size during the preliminary design phase. Soil relative stiffness ratios and system stiffness values derived via these two different MARS models were found to compare favourably with a number of field and published records.

• Journal of Soil and Groundwater Environment
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• v.24 no.1
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• pp.1-9
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• 2019

This study presents a technical perspective to the fate characteristics of phenol and m-cresol, which represent some of the most common organic chemicals found in chemical spill accidents, and likely to persist in soil and groundwater due to their highly stable physicochemical properties. Some cases of domestic and foreign chemical accidents linked to phenol and m-cresol contamination were compiled. Due to their low organic carbon-water partitioning coefficient (Koc), phenol and m-cresol tend to migrate into groundwater and remained as dissolved phase. On the other hands, phenol and m-cresol can be readily decomposed by microbes in soil and groundwater under appropriate conditions. Therefore, the fate characteristics of these chemicals are highly contingent on environmental conditions. Thus, if a great quantity of leakage is occurred by chemical accidents, the up-to-date and correct information about fate characteristics taking into account both the chemical and environmental conditions is greatly needed to minimized the potential hazards from these chemicals.

• Journal of Surface Science and Engineering
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• v.52 no.3
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• pp.156-162
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• 2019

Electroless Ni-P coatings are widely used in the chemical, mechanical, and electronic industries because of their excellent wear and abrasion resistance. In this study, The influence of pH values on properties of Ni-P-PTFE composite coatings was investigated. To improve mold lubrication, Ni-P-PTFE composite coatings at different pH value were studied. The morphology and phase structure of Ni-P-PTFE composite coatings were analyzed by scanning electron microscopy(SEM) and X-ray diffractometry(XRD). The result showed that Ni-P-PTFE composite coating is composed of Ni, P and PTFE. It exhibits an amorphous structure and good Corrosion Resistance to the substrate. Ni-P-PTFE composite coatings have higher open circuit potential than that of the substrate, which obtained at pH value of 5.0 optimal integrated properties.

• Korean Journal of Environmental Agriculture
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• v.38 no.2
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• pp.104-109
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• 2019

BACKGROUND: The invasive hornet Vespa velutina nigrithorax has becomes a public concern in rural and urban South Korea. The technologies are necessary to develop a way to counter V. velutina. In an effort to develop a way to counter V. velutina, we found that a bacillus strain, named Bacillus sp. BV-1, produces volatile compounds that attract V. velutina. METHODS AND RESULTS: Field trials of V. velutina attraction were performed using plates and traps containing BV-1 cultures grown on sugar medium. When the sugar medium and sugar-grown BV-1 cultures in the plates were placed close together, V. velutina visited preferably the plates with the BV-1 cultures. Significantly more V. velutina were caught in the traps containing BV-1 cultures than in those containing only sugar medium. Headspace solid-phase microextraction coupled with GC/MS analysis of BV-1 cultures detected 2-methyl-1-propanol, 3-methyl-1-butanol, 3-methylbutanoic acid, ethyl hexanoate, 2-pheylethanol, ethyl octanoate, and ethyl decanoate as the major volatiles. CONCLUSION: BV-1 cultures were suggested as potential agents for managing V. velutina as they produce volatile compounds that attract the hornet.

• Structural Engineering and Mechanics
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• v.70 no.5
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• pp.623-637
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• 2019

This paper analyzes the non-stationary vibration and super-harmonic resonances in nonlinear dynamic motion of viscoelastic nano-resonators. For this purpose, a new coupled size-dependent model is developed for a plate-shape nano-resonator made of nonlinear viscoelastic material based on modified coupled stress theory. The virtual work induced by viscous forces obtained in the framework of the Leaderman integral for the size-independent and size-dependent stress tensors. With incorporating the size-dependent potential energy, kinetic energy, and an external excitation force work based on Hamilton's principle, the viscous work equation is balanced. The resulting size-dependent viscoelastically coupled equations are solved using the expansion theory, Galerkin method and the fourth-order Runge-Kutta technique. The Hilbert-Huang transform is performed to examine the effects of the viscoelastic parameter and initial excitation values on the nanosystem free vibration. Furthermore, the secondary resonance due to the super-harmonic motions are examined in the form of frequency response, force response, Poincare map, phase portrait and fast Fourier transforms. The results show that the vibration of viscoelastic nanosystem is non-stationary at higher excitation values unlike the elastic ones. In addition, ignoring the small-size effects shifts the secondary resonance, significantly.

• Mycobiology
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• v.47 no.1
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• pp.126-133
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• 2019

Isaria javanica pf185 is an important entomopathogenic fungus with potential for use as an agricultural biocontrol agent. However, the effect of I. javanica pf185 on plant growth is unknown. Enhanced tobacco growth was observed when tobacco roots were exposed to spores, cultures, and fungal cell-free culture supernatants of this fungus. Tobacco seedlings were also exposed to the volatiles of I. javanica pf185 in vitro using I-plates in which the plant and fungus were growing in separate compartments connected only by air space. The length and weight of seedlings, content of leaf chlorophyll, and number of root branches were significantly increased by the fungal volatiles. Heptane, 3-hexanone, 2,4-dimethylhexane, and 2-nonanone were detected, by solid-phase micro-extraction and gas chromatography-mass spectrophotometry, as the key volatile compounds produced by I. javanica pf185. These findings illustrate that I. javanica pf185 can be used to promote plant growth, and also as a biocontrol agent of insect and plant diseases. Further studies are necessary to elucidate the mechanisms by which I. javanica pf185 promotes plant growth.

• Biomolecules & Therapeutics
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• v.27 no.2
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• pp.210-215
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• 2019

Colorectal cancer is one of the leading causes of cancer related death due to a poor prognosis. In this study, we investigated the effect of Gomisin G on colon cancer growth and examined the underlying mechanism of action. We found that Gomisin G significantly suppressed the viability and colony formation of LoVo cells. Gomisin G reduced the phosphorylation level of AKT implying that Gomisin G suppressed the PI3K-AKT signaling pathway. Gomisin G also induced apoptosis shown by Annexin V staining and an increased level of cleaved poly-ADP ribose polymerase (PARP) and Caspase-3 proteins. Furthermore, Gomisin G remarkably triggered the accumulation of cells at the sub-G1 phase which represents apoptotic cells. In addition, the level of cyclin D1 and phosphorylated retinoblastoma tumor suppressor protein (Rb) was also reduced by the treatment with Gomisin G thus curtailing cell cycle progression. These findings show the suppressive effect of Gomisin G by inhibiting proliferation and inducing apoptosis in LoVo cells. Taken together, these results suggest Gomisin G could be developed as a potential therapeutic compound against colon cancer.

• Corrosion Science and Technology
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• v.18 no.3
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• pp.110-116
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• 2019

Resistances to pitting corrosion of additive manufactured (AM) Ti-6Al-4V alloys in 0.6 M NaBr and 0.6 M NaCl aqueous solutions were compared using micro-droplet cell techniques. With respect to the pitting corrosion resistance, this study focused on two different types of halide anions in aqueous solutions, i.e. $Br^-$ and $Cl^-$. The differences between $Br^-$ and $Cl^-$ halide anions for breakdown on passive films of AM Ti-6Al-4V alloy were explained using Langmuir adsorption model with their equilibrium adsorption coefficients. The results of the analysis showed that the lower resistance to pitting potential of AM Ti-6Al-4V alloy in $Br^-$ aqueous solution was attributed to the higher equilibrium adsorption coefficient of Br-. In addition, micro-electrochemical test results showed that the pitting corrosion resistance of dark grains in additive manufactured Ti-6Al-4V alloy was lower as compared to that of bright grains due to the larger volume of ${\alpha}^{\prime}$ phase that caused the susceptibility to pit initiation.

• Applied Chemistry for Engineering
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• v.31 no.6
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• pp.697-700
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• 2020

We report the synthesis and characterization of quartz nanocrystals (NCs). Quartz NCs were synthesized from the dissolution of amorphous silica nanoparticle precursors under the mild hydrothermal condition of ~250 ℃ and autogenic pressure. It was confirmed that the average size of the nanostructure with a highly crystalline phase of α-quartz can be tuned in a relatively narrow range from 407.5 to 826.2 nm with respect to the reaction time. α-Quartz NCs have potential uses for technological applications in optoelectronics, sensing, and rechargeable battery devices.

• Korean Journal of Metals and Materials
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• v.49 no.3
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• pp.270-274
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• 2011

Plasma electrolytic oxidation (PEO) treatment was performed on squeeze cast AZ31 alloy and $Al_{18}B_4O_{33}w/AZ31$ composite. Scanning electron microscope (SEM) was employed to characterize the surface morphology and cross-section microstructure of the coating. The phase structures of the PEO coating were analyzed by X-ray diffraction (XRD). The corrosion resistance of the PEO coating was evaluated by electrochemical method. The results showed that the $Al_{18}B_4O_{33}$ whisker on the surface of the composite was decomposed and $MgAl_2O_4$ was formed in the PEO coating layer of $Al_{18}B_4O_{33}w/AZ31$ composite during PEO treatment. As a result, the electrochemical corrosion potential of the PEO coated $Al_{18}B_4O_{33}w/AZ31$ composite was increased compared with that of AZ31 alloy.