• International Journal of Internet, Broadcasting and Communication
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• v.13 no.2
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• pp.82-92
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• 2021

Purpose: It has been reported that the diversity and abundance of microbes in the vagina decrease due to the use of antimicrobial agents, and the high recurrence rate of female vaginitis due to this suggests that a new treatment is needed. Methods: In the experiment, we detected that 10% potassium sorbate solution, 1% eucalyptus oil solution, 1% tea tree oil solution, 400 µL/10 mL grapefruit seed extract solution, 100% lactic acid, 10% acetic acid solution, and 10% lactic acid solution were prepared and used. After adjusting the pH to 4, 5, and 6 with lactic acid and acetic acid in the mixed culture medium, each bacterium was inoculated into the medium and incubated for 72 h at 35℃. Incubate and 0 h each. 24 h. 48 h. The number of bacteria was measured after 72 h. Results: In the mixed culture test between lactic acid bacteria and pathogenic microorganisms, lactic acid bacteria showed good results at pH 5-5.5. Potassium sorbate, which has varying antibacterial activity based on the pH, killed pathogenic bacteria and allowed lactic acid bacteria to survive at pH 5.5. Conclusion: The formulation ratio obtained through this study could be used for the development of a feminine cleanser that can be used as a substitute for antibacterial agents. Further, the findings of this study may be able to solve the problem of antimicrobial resistance in the future.

• Steel and Composite Structures
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• v.43 no.5
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• pp.603-623
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• 2022

This article is dedicated to predict the natural frequencies of joined conical shell structures made of Functionally Graded Material (FGM). The structure includes two conical segments. The equivalent material properties are found by using the rule of mixture based on Voigt model. In addition, three well-known patterns are employed for distribution of material properties throughout the thickness of the structure. The main objective of the present research is to propose a novel exponential pattern and obtain the related equivalent material properties. Furthermore, the Donnell type shell theory is used to obtain the governing equations of motion. Note that these equations are obtained by employing First-order Shear Deformation Theory (FSDT). In order to discretize the governing system of differential equations, well-known and efficient semi-analytical scheme, namely Generalized Differential Quadrature Method (GDQM), is utilized. Different boundary conditions are considered for various types of single and joined conical shell structures. Moreover, an applicable modification is considered for the continuity conditions at intersection position. In the first step, the proposed formulation is verified by solving some well-known benchmark problems. Besides, some new numerical examples are analyzed to show the accuracy and high capability of the suggested technique. Additionally, several geometric and material parameters are studied numerically.

• Advances in Computational Design
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• v.7 no.1
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• pp.1-17
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• 2022

In this study, a new strategy is presented to transmit the fundamental elastic beam problem into the modern optimization platform and solve it by using artificial intelligence (AI) tools. As a practical example, deflection of Euler-Bernoulli beam is mathematically formulated by 2nd-order ordinary differential equations (ODEs) in accordance to the classical beam theory. This fundamental engineer problem is then transmitted from classic formulation to its artificial-intelligence presentation where the behavior of the beam is simulated by using neural networks (NNs). The supervised training strategy is employed in the developed NNs implemented in the heuristic optimization algorithms as the fitness function. Different evolutionary optimization tools such as genetic algorithm (GA) and particle swarm optimization (PSO) are used to solve this non-linear optimization problem. The step-by-step procedure of the proposed method is presented in the form of a practical flowchart. The results indicate that the proposed method of using AI toolsin solving beam ODEs can efficiently lead to accurate solutions with low computational costs, and should prove useful to solve more complex practical applications.

• Journal of the Korean Society of Safety
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• v.37 no.4
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• pp.80-91
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• 2022

The purpose of this study is to contribute to strengthening the response of local governments to the emergence of new infectious diseases by identifying the urban characteristics affecting their spread. To this end, the urban characteristics influencing the spread of infectious diseases were identified from previous studies. Moreover, the variations in the impact of urban characteristics that affected the number of confirmed COVID-19 patients was spatially analyzed using geographically weighted regression (GWR). The analysis indicated that the explanatory power of the GWR was approximately 12.4% higher than that of the ordinary least squares method. Moreover, the explanatory power of the model in the northern regions, such as Seoul, Gyeonggi, and Gangwon, was particularly high, indicating that the urban characteristics affecting the spread of COVID-19 vary by region. The results of this study can be used as a basis for suggesting the formulation of customized policies reflecting the characteristics of each local government rather than a uniform spread reduction policy.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.17 no.1
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• pp.28-35
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• 2021

The flow accelerated corrosion (FAC) is one of significant aging and degradation mechanism and can affect structural integrity of CANDU feeder pipes. Pipe burst can occur under normal operation pressure (min. 10 MPa) if wall-thinning of the feeder pipe due to FAC is accumulated. Previous studies considered simple shapes of feeder pipe with local wall-thinning in order to conservatively assess structural integrity of wall-thinned feeder pipe. In this paper, a new FE model is developed, having an actual shape of the feeder pipe (double bent) as well as the actual wall-thinning shape and location based on the in-service inspection result. Then, the burst pressure assessment of the wall-thinned feeder pipe is performed using lower bound limit load analysis considering elastic-perfectly plastic material. In addition, an improved formulation to predict the burst pressure of the wall-thinned feeder pipe is presented and the safety margin is compared with an existing assessment method.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.29 no.2
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• pp.73-78
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• 2023

The cosmetics industry faces a significant challenge in addressing the decreased recycling rate of cosmetic containers due to the composite materials used to meet consumers' aesthetic satisfaction. To address thees issues, eco-friendly packaging solutions such as refill packaging and single-material use have been developed. However, the market for eco-friendly cosmetics packaging requires a product that meets consumers' demands for aesthetics, sensitivity, and eco-friendliness while also performing as well as existing products. This study presents a solution to the challenge of the decreased recycling rate of cosmetic containers by developing a new cosmetic packaging product for cream formulations. The product features an easily separable and dischargeable internal refill container, while maintaining the design aesthetics of the external container. Through various tests, the product was shown to be of equivalent quality and performance to existing cream cosmetic packaging, with no leakage or defects observed. Furthermore, the use of a single-material polypropylene refill container is expected to contribute to the improvement of the plastic recycling rate.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.1
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• pp.20-30
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• 2023

In this paper, the Energy Flow Finite Element Analysis (EFFEA) was performed to predict the acoustic and vibrational responses of complicated plate structures considering improved Fluid-Structure Interaction (FSI). For this, a new power transfer relationship was derived at the area junction where two different fluids are in contact on both sides of the plate. In order to increase the reliability of EFFEA of complicated plate structures immersed in a high-density fluid, the corrected flexural wavenumber and group velocity considering fluid-loading effect were derived. As the specific acoustic impedance of the fluid in contact with the plate increases, the flexural wavenumber of the plate increases. As a result, the flexural group velocity is reduced, and the spatial damping effect of the flexural energy density is increased. Additionally, for the EFFEA of arbitary-shaped built-up structures, the energy flow finite element formulation for the acoustic tetrahedral element was newly performed. Finally, for validation of the derived theory and developed software, numerical applications of complicated plate structures submerged in seawater or air were successfully performed.

• Structural Engineering and Mechanics
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• v.81 no.1
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• pp.39-50
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• 2022

Layer separation (delamination) is an essential threat to fiber-reinforced polymer (FRP) plates under dynamic, static, and fatigue loads. Under compressive load, the growth of delamination will lead to structural instability. The aim of this paper is to present a method using shape memory alloy (SMA) stitches to suppress the delamination growth in a FRP plate and to improve the buckling behavior of the plate with a rectangular hole. The present paper is divided into two parts. Firstly, a closed-form (CF) formulation for evaluating the buckling load of the FRP plate is presented. Secondly, the finite element method (FEM) will be employed to calculate the buckling loads of the plates which serves to validate the results obtained from the closed-form method. The novelty of this work is the development of the closed-form solution using the p-Ritz energy approach regarding the stress-dependent phase transformation of SMA to trace the equilibrium path. For the FEM, the Lagoudas constitutive model of the SMA material is implemented in FORTRAN programming language using a user material subroutines (VUMAT). The model is simulated in ABAQUS/Explicit solver due to the nature of the loading type. The cohesive zone model (CZM) is applied to simulate the delamination growth.

• Steel and Composite Structures
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• v.46 no.3
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• pp.293-318
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• 2023

This study aims to examine the elastic stiffness properties of Elliptic-Braced Moment Resisting Frame (EBMRF) subjected to lateral loads. Installing the elliptic brace in the middle span of the frames in the facade of a building, as a new lateral bracing system not only it can improve the structural behavior, but it provides sufficient space to consider opening it needed. In this regard, for the first time, an accurate theoretical formulation has been developed in order that the elastic stiffness is investigated in a two-dimensional single-story single-span EBMRF. The concept of strain energy and Castigliano's theorem were employed to perform the analysis. All influential factors were considered, including axial and shearing loads in addition to the bending moment in the elliptic brace. At the end of the analysis, the elastic lateral stiffness could be calculated using an improved relation through strain energy method based on geometric properties of the employed sections as well as specifications of the utilized materials. For the ease of finite element (FE) modeling and its use in linear design, an equivalent element was developed for the elliptic brace. The proposed relation was verified by different examples using OpenSees software. It was found that there is a negligible difference between elastic stiffness values derived by the developed equations and those of numerical analysis using FE method.

• Geomechanics and Engineering
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• v.34 no.2
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• pp.187-195
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• 2023

Intensive rainfall during the summer season in Korea has triggered numerous devastating landslides outside of downtown in mountainous areas. The 2D slope stability analysis that is generally used for cut slopes and embankments is inadequate to model slope failure in mountainous areas. This paper presents a new 3D slope stability formulation using the global sliding vector in the limit equilibrium method, and it uses an ellipsoidal slip surface for static and quasi-static analyses. The slip surface's flexibility of the ellipsoid shape gives a lower FS than the spherical failure shape in the Fellenius, Bishop, and Janbu's simplified methods. The increasing sub-columns of each column tend to increase the FS and converge to a steady value. The symmetrical geometric conditions of the convex turning corners do not indicate symmetrical failure of the surface in 3D analysis. Pseudo-static analysis shows that the horizontal seismic force decreases the FS and increases the mass volume at the critical failure state. The stability index takes the FS and corresponding sliding mass into consideration to assess the potential risk of slope failure in complex mountainous terrain. It is a valuable parameter for selecting a vulnerable area and evaluating the overall risk of slope failure.