• Membrane Journal
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• v.29 no.1
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• pp.30-36
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• 2019

In this study, we reported a solid-state supercapacitor consisting of titanium nitride (TiN) nanofiber and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT-PSS) conducting polymer electrode and poly(vinyl alcohol) (PVA)-based polymer electrolyte membrane. The TiN nanofiber was selected as electrode materials due to high electron conductivity and 2-dimensional structure which is beneficial for scaffold effect. PEDOT-PSS is suitable for organic/inorganic composites due to good redox reaction with hydrogen ions in electrolyte and good dispersion in solution. By synergetic effect of TiN nanofiber and PEDOT-PSS, the PEDOT-PSS/TiN electrode showed higher surface area than the flat Ti foil substrate. The PVA-based polymer electrolyte membrane could prevent leakage and explosion problem of conventional liquid electrolyte and possess high specific capacitance due to the fast ion diffusion of small $H^+$ ions. The specific capacitance of PEDOT-PSS/TiN supercapacitor reached 75 F/g, which was much higher than that of conventional carbon-based supercapacitors.

• Journal of Periodontal and Implant Science
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• v.49 no.5
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• pp.330-343
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• 2019

Purpose: The aim of this study was to evaluate the use of dehydrated human amnion/chorion membrane (dHACM) to repair perforated sinus membranes in rabbits. Methods: Bilateral surgical windows (7.5-mm diameter) were prepared on the nasal bones of 14 rabbits. Standardized circular perforations (5-mm diameter) were made in the sinus membrane by manipulating implant twist drills. The perforated sinus membranes were repaired using dHACM or a resorbable collagen membrane (CM). The negative control (NC) group did not undergo perforated sinus membrane repair, while the positive control (PC) group underwent sinus augmentation without perforations. The same amount of deproteinized porcine bone mineral was grafted in all 4 groups. After 6 weeks, micro-computed tomography (micro-CT) and histomorphometric evaluations were conducted. Results: The micro-CT analysis revealed that the total augmented volume was not significantly different among the groups. In the dHACM group, newly formed bone filled the augmented area with remaining biomaterials; however, non-ciliated flat epithelium and inflammatory cells were observed on the healed sinus membrane. Histometric analysis showed that the percentage of newly formed bone area in the dHACM group did not differ significantly from that in the CM group. The dHACM group showed a significantly higher percentage of newly formed bone area than the NC group, but there was no significant difference between the dHACM and PC groups. Conclusions: dHACM could be a feasible solution for repairing sinus membrane perforations that occur during sinus floor augmentation.

• Membrane and Water Treatment
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• v.14 no.2
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• pp.85-93
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• 2023

Membrane separation is widely used for several applications such as water treatment, membrane reactors and climate change. Cross-linked organic-inorganic hybrid polyvinylidene fluoride (PVDF) / Tetraethyl orthosilicate (TEOS) was adopted for the preparation of optimized hollow membrane (HFM) for membrane distillation or other low pressure separators for mechanical properties and permeability under varying pretreatment schemes. HFMs were prepared on semi-pilot membrane fabrication system. Novel adopted post-treatment schemes involved soaking in glycerol, magnesium sulphate (MgSO₄), sodium hypochlorite (NaOCl), and isopropanol for different durations. All fibers were characterized for morphology using a scanning electron microscope (SEM), surface roughness using atomic force microscope (AFM), elemental composition by examining Energy Dispersive Spectroscopy (EDS), water contact angle (CA°) and porosity. The performance of the fibers was evaluated for pure water permeation flux (PWF). Post-treatment with MgSO₄ gave the highest both tensile modulus and flux. Assessment of properties and performance revealed comparable results with other organic-inorganic separators, HF or flat. In spite of few reported data on post treatment using MgSO₄ in presence of TEOS, this proves the potential of low cost treatment without negative impact on other membrane properties. The flux is also comparable with hypochlorite which manifests substantial precaution requirements in actual industrial use.The relatively high values of flux/bar for sample treated with TEOS, post treated with MgSO₄ and hypochlorite are 88 and 82 LMH/bar respectively.

• Membrane Journal
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• v.32 no.1
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• pp.66-73
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• 2022

In this study, a method for stabilizing treated water was conducted while maintaining high flux using a metal flat membrane module made of stainless steel. This module had a pore size of 13 ㎛, so it was possible to operate at a high flux from 60 LMH to 100 LMH. However, although SS leaked about 30~50 ppm during initial operation, aggregation was possible because SS acted as aggregation nucleus. While polymer membrane permeate does not have aggregation nucleus, so coagulation is possible but not flocculation. Typically clay or bentonite, which is used as aggregation nucleus, is additionally administered. In this study, the total phosphorus treatment and the quality of the treated water were to promote stability because flocculation was achieved only with SS leakage without the need for such a aggregation nucleus. Finally, the feasibility of operating a metal membrane filter capable of high flux in stable treated water to be applied to the MBR system.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.5
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• pp.800-809
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• 1987

For precise stress analysis of pressure vessel nozzle junction area, it should be modelized as a cylindrical shell with a cylindrical outlet attached on it, but because of its geometrical complexity, exact analysis and solution is very difficult to obtain. So, when the nozzle diameter is small compared to that of vessel, it is general to simplify the model as a flat plate with a cylinder. As the current nozzle shape is manufactured as "Through Type" to reduce the stress concentration around the nozzle junction part of pressure vessel, a theoretical analysis on the cylinder with finite length should be performed to accomodate this fact. In this paper, the general solutions which were obtained by applying Fulgge's theory to the finite length cylinder, membrane and bending theory to the flat plate were superposed to analyze the model. Each theoretical optimal values were obtained through the analysis of stress concentration caused by the variation of cylinder length and thickness, and these results were estimated by performing model experimentation.mentation.

• Computers and Concrete
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• v.25 no.4
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• pp.355-367
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• 2020

This paper proposed a numerical investigation based on finite elements analysis (FEA) in order to study the punching shear behavior of reinforced concrete (RC) flat slabs using ABAQUS and SAP2000 programs. Firstly, the concrete and the steel reinforcements were modeled by hexahedral 3D solid and linear elements respectively, and the nonlinearity of the used materials was considered. In order to validate this model, experimental results considered in literature were compared with the proposed FE model. After validation, a parametric study was performed. The parameters include the slab thickness, the flexure reinforcement ratios and the axial membrane loads. Then, to reduce the time of FEA, a simplified modelling using 3D layered shell element and shear hinge concept was also induced. The effect of the footings settlement was studied using the proposed simplified nonlinear model as a case study. Results of numerical models showed that increase of the slab thickness by 185.7% enhanced the ultimate load by 439.1%, accompanied with a brittle punching failure. The punching failure occurred in one of the tested specimens when the tensile reinforcement ratio increased more than 0.65% and the punching capacity improved with increasing the horizontal flexural reinforcement; it decreased by 30% with the settlement of the outer footings.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1994.10a
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• pp.1-8
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• 1994

A variable-node-flat shell element designated as CLS which has variable mid-side nodes with drilling freedom has been presented in this paper. The shell element to be applied in finite element analysis has been developed by combining a membrane element named as CLM with drilling rotation d.o.f. and plate bending element. The combined shell element possess six degrees of freedom per node. By introducing the variable-node elements which have physical midside nodes, some difficulties associated with imposing displacement constraints on irregular nodes to enforce interelement compatibility in common adaptive h-refinement on quadrilateral mesh are easily overcome. Detailed numerical studies show the excellent performance of the new shell elements developed in this study.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.8 s.179
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• pp.1968-1799
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• 2000

A warpage analysis program has been developed for fiber-reinforced injection molded parts. The warpage is predicted from the residual stress and anisotropic thermo-mechanical properties coupled with fiber orientation in the integrated injection molding simulation. A simple elastic model is used for the calculation of thermally and pressure-induced residual stresses which are employed as the initial conditions in the structural analysis. To improve the reliability of warpage analysis, a new triangular flat shell element superimposing well-known efficient plate bending and membrane element is presented. The numerical examples address the necessity to use anisotropic models for fiber-reinforced materials and show that predicted warpage is in good agreement with experimentally measured one.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.04a
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• pp.317-324
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• 1998

A nonlinear anile element formulation of flat shell elements with drilling d.o.f, is presented for the geometrical nonlinear analysis of thin-walled structures. The shell element to be applied in finite element analysis was developed by combining a membrane element named as CLM with drilling rotation d.o.f, and plate bending element. The combined shell element possesses six degrees of freedom per node. The element showed the excellent performance in the linear analysis of the folded plate structures, in which the normal rotational rigidity of folded plates is considered, therefore, using this element geometrical nonlinear analysis of those structures is fulfilled in this study. An incremental total Larangian approach is adopted through out in which displacements are referred to the original configuration. Comparing the results with those of other researches shows the performance of this element and a folded plate structure is analyzed as an example.

• Membrane Journal
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• v.27 no.1
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• pp.68-76
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• 2017

Flat membrane with $0.4{\mu}m$ pore size was prepared with PVdF (polyvinylidene fluoride) nanofiber, which has the advantages such as excellent strength, chemical resistance, non-toxicity, and incombustibility. The spiral wound module was manufactured with the flat membrane and a woven paper. Hybrid water treatment process was composed of the PVdF nanofibers spiral wound microfiltration and granular activated carbon (GAC) adsorption column. Effect of GAC packing mass was investigated by comparing the case of recycling or discharging the treated water using the synthetic solution of kaolin and humic acid. After each filtration experiment, water back-washing was performed, and recovery rate and filtration resistances were calculated. Also, effect of GAC adsorption was compared by measuring turbidity and $UV_{254}$ absorbance. As a result, there was no effect of GAC packing mass on turbidity treatment rate; however, the treatment rate of $UV_{254}$ absorbance was 0.7~3.6% for recycling the treated water, and increased to 3.2-5.7% for discharging the treated water. In the case of recycling the treated water, reversible filtration resistance ($R_r$) and irreversible filtration resistance ($R_{ir}$) trended to decrease as increasing GAC packing mass; however, total fitration resistance ($R_t$) was almost constant, and recovery rate of water back-washing trended to increase a little.