• Journal of the Korean Chemical Society
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• v.65 no.3
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• pp.203-208
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• 2021

As part of our attempt to discover novel active compounds against multi-drug resistant pathogens, we hereby report two new complexes of iron(III) with formulae: [Fe(L₁)₂(H₂O)₂]Cl₃ and [Fe(L₁)₂(L₂)(H₂O)]Cl₂ where L₁ = 1,10-phenanthroline (C₁₂H₈N₂) and L₂ = guanide (C₅H₄N₅O^-). The synthesized complexes were characterized using spectroscopic analysis (ESI-MS, ICP-OES, FT-IR, and UV-Vis), cyclic voltammetry, CHN analysis, gravimetric chloride determination, melting point determination, and conductance measurement. Octahedral geometries are assigned to both complexes. In vitro antibacterial activity was tested on two Gram-positive (Staphylococcus aureus, Streptococcus epidermidis) and two Gram-negative (Escherichia coli and Klebsiella pneumoniae) bacteria using the disc diffusion method. The complexes demonstrated appreciable activity against these pathogens. Interestingly, the [Fe(L₁)₂(L₂)(H₂O)]Cl₂ complex manifested a higher degree of inhibition against the drug-resistant Gram-negative bacteria than the commercially available drug, namely erythromycin.

• Wind and Structures
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• v.37 no.4
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• pp.275-287
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• 2023

Subgrade differential settlement of high-speed railways was a pivotal issue that could increase the risk of trains operation. The risk will be further increased when trains in the subsidence zone are affected by crosswinds. In this paper, the computational fluid dynamics (CFD) model and finite element (FE) model were established, and the data transmission interface of the two models was established by fluid-solid interaction (FSI) method to form a systematic crosswind-train-track-subgrade dynamic model. The risk of high-speed train encountering crosswind in settlement area was analyzed. The results showed that the aerodynamic force of the trains increased significantly with the increase in crosswind speed. The aerodynamic force of the trains could reach 125.14 kN, significantly increasing the risk of derailment and overturning. Considering the influence of crosswind, the risk of train operation could be greatly increased. The safety indices and the wheel-rail force both increased with the increase of the wind speed. For the high-speed train running at 350 km/h, the warning value of wind speed was 10.2 m /s under the condition of subgrade settlement with wavelength of 20 m and amplitude of 15 mm.

• Computers and Concrete
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• v.26 no.4
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• pp.351-365
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• 2020

This work presents numerical and experimental analyses of the behavior of reinforced-concrete deep beams with unconventional geometries. The main goal here is to experimentally and numerically study these geometries to find possible new behaviors due to the material nonlinearity of reinforced concrete with complex geometries. Usually, unconventional geometries result from innovative designs; in general, studies of reinforced concrete structures are performed only on conventional members such as beams, columns, and labs. To achieve the goal, four reinforced-concrete deep beams with geometries not addressed in the literature were tested. The models were numerically analyzed with the Adaptive Micro Truss Model (AMTM), which is the proposed method, to address new geometries. This work also studied the main parameters of the constitutive model of concrete based on a statistical analysis of the finite element (FE) results. To estimate the ultimate loads, FE simulations were performed using the Monte Carlo method. Based on the obtained ultimate loads, a probabilistic distribution was created, and the final ultimate loads were computed.

• Journal of Korean Association for Spatial Structures
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• v.16 no.3
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• pp.67-78
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• 2016

Determining of the shape in the process of design for natural draught cooling tower is very important, because the shape of hyperbolic shell is respond sensitively to dynamic behavior of the whole cooling tower against wind load. In engineering practice, the geometric parameters have been determining based on the natural frequency. This study analyses influence of the tower shell geometric parameters on the structural behavior. For three representative models were selected, they were analyzed based on evaluation of damage by means of nonlinear FE-method. As a result, a hyperbolic rotational shell with the small radius overall was the lowest damage index induced by sufficient capacity of the stress redistribution and thus a wind-insensitive structure.

• Computers and Concrete
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• v.18 no.6
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• pp.1097-1112
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• 2016

Fire loading causes a critical collapse of RC (Reinforced Concrete) Structures since the embedded steels inside are relative week against high elevated temperature. Several numerical frameworks for fire resistance have been proposed, however they have limitations such as unstable convergence and long calculation period. In the work, 2-D nonlinear FE technique is proposed using Galerkin method for RC structures under fire loading. Closed-form element stiffness with a triangular element is adopted and verified with fire test on three RC slabs with different fire loading conditions. Several simulations are also performed considering fire loading conditions, water contents, and cover depth. The proposed numerical technique can handle time-dependent fire loading, convection, radiation, and material properties. The proposed technique can be improved through early-aged concrete behavior like moisture transport which varies with external temperature.

• Journal of the Korean Society of Industry Convergence
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• v.2 no.2
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• pp.125-130
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• 1999

It is already known that hardness value of cold-forged product is in close conjunction with its effective strain. This paper presents the method to predict the relation between effective strains and hardness values by using FE-simulation of hardness test from the conception that hardness indicates resistance to plastic deformation. The results of FE-simulation for the material with pre-strain arc compared with those of experiments of the references to show the feasibility of the proposed method.

• Journal of Magnetics
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• v.5 no.3
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• pp.106-109
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• 2000

The single stroke hot deformation is a simple method fur the fabrication of anisotropic NdFeB magnets. In order to obtain the optimum conditions, Taguchi method of experimental design was applied in this work. The optimum conditions obtained on the basis of coercivity in Taguchi analysis was a little different from those of remanence and maximum energy Product. The contribution of each factor to magnetic Properties was calculated in detail.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.270-273
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• 2009

This work describes a method of determining material parameters included in recrystallization and grain growth models. Focus is on the recrystallization and grain growth models of Ni-Fe base superalloy, Alloy 718. High temperature compression tests at different strain, strain rate and temperature conditions were chosen to determine the material parameters of dynamic recrystallization model. The critical strain and dynamically recrystallized grain size and fraction at various process variables were quantitated with the microstructual analysis and strain-stress relationships of the compression tests. Besides, isothermal heat treatments were utilized to fit the material constants included in the grain growth model. Verification of the determined material parameters is carried out by comparing the measured data obtained from other compression tests.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2000.10a
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• pp.246-252
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• 2000

This paper presents an explanatory study of combining the finite element and boundary element methods to achieve an efficient and accurate analysis of frame structure containing shear wall. This model analyzes the frame by finite element method and the shear wall by boundary element method. The purpose of this study is the specific case that boundary element is surrounded by finite element. If material properties of shear wall are relatively the very smaller than it of frame structure, the displacement shape of each node is calculated exactly. And if the solution of displacement is the larger, the displacement shape is approximated more accurately.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.572-579
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• 2001

Recent industrial requirements for highly precise shape processing have brought the electric discharge machining (EDM) in great need. High precision in EDM is primarily achieved by high performance controllers. However there exists inherent precision loss due to structural deformation. On this background, we study structural deformation characteristics of wire cut EDM via finite element (FE) analysis and axiomatic design. Two different wire cut EDMs are selected as analysis models. 3D CAD package I-Deas is first used to construct FE models of wire cut EDMs, and then ABAQUS FE code is used for following structural analysis. Pertinency of FE mesh refinement is discussed in terms of ${\eta}-factor$. It is shown that performance accuracy of EDM depends strongly on the structural characteristics. Some design enhancements are suggested in an axiomatic design point of view. Finally we provide weight and temperature induced displacement discrepancies between wire end points as position functions of each subframe.