• Nuclear Engineering and Technology
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• v.52 no.12
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• pp.2860-2866
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• 2020

Oxide dispersion-strengthened materials W-1wt%Pr₂O₃ and W-1wt%La₂O₃ were synthesized by wet chemical method and spark plasma sintering. The field emission scanning electron microscopy (FE-SEM) analysis, XRD and Vickers microhardness measurements were conducted to characterize the samples. The irradiations were carried out with a 5 keV helium ion beam to fluences up to 5.0 × 10²¹ ions/m² under 600 ℃ using the low-energy ion irradiation system. Transmission electron microscopy (TEM) study was performed to investigate the microstructural evolution in W-1wt%Pr₂O₃ and W-1wt%La₂O₃. At 1.0 × 10²⁰ He⁺/m², the average loops size of the W-1wt%Pr₂O₃ was 4.3 nm, much lower than W-1wt% La₂O₃ of 8.5 nm. However, helium bubbles were not observed throughout in both doped W materials. The effects of pre-irradiation with 1.0 × 10²¹ He⁺/m² on trapping of injected deuterium in doped W was studied by thermal desorption spectrometry (TDS) technique using quadrupole mass spectrometer. Compared with the samples without He⁺ pre-irradiation, deuterium (D) retention of doped W materials increased after He⁺ irradiation, whose retention was unsaturated at the damage level of 1.0 × 10²²D₂⁺/m². The present results implied that irradiation effect of He⁺ ions must be taken into account to evaluate the deuterium retention in fusion material applications.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.23 no.3
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• pp.183-190
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• 2017

Carton clamp truck is widely perceived as the high-efficient handling equipment of factory premises and warehouse by its capability of palletless handling. Therefore, the significance of a lab-based handling simulation is becoming higher with the growth of clamp truck usage. In this study, preliminary FEA and design of handling test courses for the lab-based simulation of carton clamp truck handling were performed, and the PSD analyses were performed for the modified one for the test course proposed by Park et al. (2017) as well as ASTM D 6055 and ISTA 3B standards. For the vibration in all directions, the vibration energy intensity analyzed by ISTA 3B standard showed higher than that by the other two cases. A FEA was performed for the handling operation of the sudden stop of the clamps after lifting the target HCP (heavyweight refrigerator corrugated package, w=180 kgf) up to the specified height. The slip distance between the clamp arm and the target HCP was 0.85 mm. The simulation result of 0.85 mm was 3.7 times lower than the experimental result (3.2 mm) obtained by Park et al. (2017), and it was estimated that the deviation comes from both the experimental error by weight imbalance of target HCP, and excessive simplification during the FE modelling of target HCP.

• Smart Structures and Systems
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• v.26 no.3
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• pp.331-343
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• 2020

In this paper, based on the CPT, motion equations for a sandwich plate containing a core and two integrated face-sheets have derived. The structure rests on the Visco-Pasternak foundation, which includes normal and shear modules. The piezo-magnetic core is made of CoFe₂O₄ and also is subjected to 3D magnetic potential. Two face sheets at top and bottom of the core are under electrical fields. Also, in order to obtain more accuracy, the effect of flexoelectricity has took into account at face sheets' relations in this work. Flexoelectricity is a property of all insulators whereby they polarize when subject to an inhomogeneous deformation. This property plays a crucial role in small-scale rather than macro scale. Employing CPT, Hamilton's principle, flexoelectricity considerations, the governing equations are derived and then solved analytically. By present work a detailed numerical study is obtained based on Piezoelectricity, Flexoelectricity and modified couple stress theories to indicate the significant effect of length scale parameter, shear correction factor, aspect and thickness ratios and boundary conditions on natural frequency of sandwich plates. Also, the figures show that there is an excellent agreement between present study and previous researches. These finding can be used for automotive industries, aircrafts, marine vessels and building industries.

• Composites Research
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• v.24 no.2
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• pp.22-29
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• 2011

To increase the performance of thick-walled cylinders recently their length is continually enlarged. For that reason it is important to reduce weight of the thick-walled cylinders. In this paper the FE models to predict and estimate effects on the composite tapes were created with MSC.Nastran/Patran v.2005. First of all a autofrettage method was applied to the 2D model of the AISI4340 cylinder reduced the thick. And then the comparison of the numerical results with analysis results showed and verified by using T300/5208, IM7/PETI5, IM7/8552 tapes. Those are predicted to the effects of the angle of the composite tapes and elastic modulus according to the composite properties.

• Current Photovoltaic Research
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• v.8 no.1
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• pp.33-38
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• 2020

Single-phased SnS thin films have been prepared by RF magnetron sputtering at various deposition pressures. The effect of deposition pressure on the structural and optical properties of polycrystalline SnS thin films was studied using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible-near infrared (UV-Vis-NIR) spectrophotometer. The XRD analysis revealed the orthorhombic structure of the SnS thin films oriented along the (111) plane direction. As the deposition pressure was increased from 5 mTorr to 15 mTorr, the intensity of the peak on the (111) plane increased, and the intensity decreased under the condition of 20 mTorr. The binding energy difference at the Sn 3d_5/2 and S 2p_3/2 core levels was about 324.5 eV, indicating that the SnS thin film was prepared as a pure Sn-S phase. The optical properties of the SnS thin films indicate the presence of direct allowed transitions with corresponding energy band gap in the rang 1.47-1.57 eV.

• Journal of Environmental Science International
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• v.27 no.11
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• pp.967-974
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• 2018

In this study, we evaluated the photocatalytic oxidation efficiency of aromatic volatile hydrocarbons by using $WO_3$-doped $TiO_2$ nanotubes (WTNTs) under visible-light irradiation. One-dimensional WTNTs were synthesized by ultrasonic-assisted hydrothermal method and impregnation. XRD analysis revealed successful incorporation of $WO_3$ into $TiO_2$ nanotube (TNT) structures. UV-Vis spectra exhibited that the synthesized WTNT samples can be activated under visible light irradiation. FE-SEM and TEM images showed the one-dimensional structure of the prepared TNTs and WTNTs. The photocatalytic oxidation efficiencies of toluene, ethylbenzene, and o-xylene were higher using WTNT samples than undoped TNT. These results were explained based on the charge separation ability, adsorption capability, and light absorption of the sample photocatalysts. Among the different light sources, light-emitting-diodes (LEDs) are more highly energy-efficient than 8-W daylight used for the photocatalytic oxidation of toluene, ethylbenzene, and o-xylene, though the photocatalytic oxidation efficiency is higher for 8-W daylight.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.6
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• pp.499-512
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• 2016

The boundary reaction method(BRM) is a substructure time domain method, it removes global iterations between frequency and time domain analyses commonly required in the hybrid approaches, so that it operates as a two-step uncoupled method. The BRM offers a two-step method as follows: (1) the calculation of boundary reaction forces in the frequency domain on an interface of linear and nonlinear regions, (2) solving the wave radiation problem subjected to the boundary reaction forces in the time domain. In the time domain analysis, the near-field soil is modeled to simulate the wave radiation problem. This paper evaluates the performance of the BRM according to modeling extent of near-field soil for the nonlinear SSI analysis of base-isolated NPP structure. For this purpose, parametric studies are performed using equivalent linear SSI problems. The accuracy of the BRM solution is evaluated by comparing the BRM solution with that of conventional SSI seismic technique. The numerical results show that the soil condition affects the modeling range of near-field soil for the BRM analysis as well as the size of the basemat. Finally, the BRM is applied for the nonlinear SSI analysis of a base-isolated NPP structure to demonstrate the accuracy and effectiveness of the method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.9-16
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• 2020

A CFRP sheet has been applied as a structural reinforcement in the field, and various studies are conducted to evaluate the effect of CFRP sheets on reinforced concrete. Although many experiments were performed from previous studies, there are still limitations to analyze structural behaviors with various parameters in experiments directly. This study shows the FEA on structural behaviors of RC beams reinforced with CFRP sheets using ABAQUS software. To simulate debonding failure of CFRP sheets which is a major failure mode of RC beam with CFRP sheets, a cohesive element was applied between the bottom surface of RC beam and CFRP sheets. Both quasi-static method and 2-D symmetric FE model technique were performed to solve nonlinear problems. Results obtained from the FE models show good agreements with experimental results. It was found that reinforcement level of CFRP sheets is closely related to structural behavior of reinforced concrete including maximum strength, initial stiffness and deflection at failure. Also, as over-reinforcement of CFRP sheets could give rise to the brittle failure of RCstructure using CFRP sheets, an appropriate measure should be required when installing CFRP sheets in the structure.

• Korean Journal of Soil Science and Fertilizer
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• v.35 no.3
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• pp.145-152
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• 2002

The composition of primary minerals in the rocks and secondary minerals of clay fractions of the soil developed on the cinder cones in the foot of Halla Mt., Jeju Island was investigated. The effects of parent materials on the physico-chemical properties and mineralogical characteristics were evaluated by XRD, DTA with the chemical composition of $H^+$ saturated clays. The main rock-forming minerals of a residual cinder cones were plagioclase with subsidiary minerals of hematite, gibbsite and quartz in the red cinder cone and of augite, quartz, feldspars and olivine in black cinder cone. It is demonstrated that ignition loss and sesquioxides content were higher in the red cinder soil than black cinder, which was resulted in the intermittent eruption of volcanic activity. For the chemical analysis of whole soils, $SiO_2/Al_2O_3$ ratio was increased from 2 to 3, but Ignition loss is decreased and $K_2O$ content are very low with increasing the soil depth in regard to the composition and kinds of clay minerals. No clay formation from micas mineral were in volcanic ashes. Dominant clay minerals of the cinder cone soils as a black and red cinder cone soil were allophane with some quartz and feldspars, while vermiculite, illite, kaolin were coexisted as a subsidiary minerals. But the red cinder cones soils had more hematite and gibbsite of the clay fractions than the black soils with magnetite. The exothermic pick of DTA at about $660^{\circ}C$ for cinder cone soils might be corresponded the oxidation magnetite to hematite reation. With regarding to the compositions of mineral detected by X-ray diffractogram and the properties of minerals by D.T.A thermogram, the dominant clay mineral was allophane of the cinder cone soils with some ferrous compounds, red colour of the cinder cone soils which are originated in hematite.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.197-205
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• 2015

Offshore structures for the gas production are exposed to the risk of gas leaks, and gas explosions can result in fatal damages to the primary structures as well as secondary structures. To minimize the damage from the critical accidents, the study of the dynamic response of structural members subjected to blast loads must be conducted. Furthermore, structural dynamic analysis has to be performed considering relationships between the natural frequency of structural members and time duration of the explosion loading because the explosion pressure tends to increase and dissipate within an extremely short time. In this paper, the numerical model based on time history data were proposed considering the negative phase pressure in which considerable negative phase pressures were observed in CFD analyses of gas explosions. The undamped single degree of freedom(SDOF) model was used to characterize the dynamic response under the blast loading. A blast wall of FPSO topside was considered as an essential structure in which the wall prevents explosion pressures from the process area to utility and working areas. From linear/nonlinear transient analyses using LS-DYNA, it was observed that dynamic responses of structures were influenced by significantly the negative time duration.