• Advances in aircraft and spacecraft science
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• v.4 no.3
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• pp.219-235
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• 2017

The large container ships and fast patrol boats are complex marine structures. Therefore, their global mechanical behaviour has long been modeled mostly by refined beam theories. Important issues of cross section warping and bending-torsion coupling have been addressed by introducing special functions in these theories with inherent assumptions and thus compromising their robustness. The 3D solid Finite Element (FE) models, on the other hand, are accurate enough but pose high computational cost. In this work, different marine vessel structures have been analysed using the well-known Carrera Unified Formulation (CUF). According to CUF, the governing equations (and consequently the finite element arrays) are written in terms of fundamental nuclei that do not depend on the problem characteristics and the approximation order. Thus, refined models can be developed in an automatic manner. In the present work, a particular class of 1D CUF models that was initially devised for the analysis of aircraft structures has been employed for the analysis of marine structures. This class, which was called Component-Wise (CW), allows one to model complex 3D features, such as inclined hull walls, floors and girders in the form of components. Realistic ship geometries were used to demonstrate the efficacy of the CUF approach. With the same level of accuracy achieved, 1D CUF beam elements require far less number of Degrees of Freedom (DoFs) compared to a 3D solid FE solution.

• Structural Engineering and Mechanics
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• v.69 no.3
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• pp.269-281
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• 2019

This work addresses a three-dimensional nonlinear structural analysis of the constructive phases of a cable-stayed segmental concrete bridge using The Finite Element Method through ANSYS, version 14.5. New subroutines have been added to ANSYS via its UPF customization tool to implement viscoelastoplastic constitutive equations with cracking capability to model concrete's structural behavior. This numerical implementation allowed the use of three-dimensional twenty-node quadratic elements (SOLID186) with the Element-Embedded Rebar model option (REINF264), conducting to a fast and efficient solution. These advantages are of fundamental importance when large structures, such as bridges, are modeled, since an increasing number of finite elements is demanded. After validating the subroutines, the bridge located in Rio de Janeiro, Brazil, and known as "Ponte do Saber" (Bridge of Knowledge, in Portuguese), has been numerically modeled, simulating each of the constructive phases of the bridge. Additionally, the data obtained numerically is compared with the field data collected from monitoring conducted during the construction of the bridge, showing good agreement.

• Corrosion Science and Technology
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• v.18 no.3
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• pp.78-85
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• 2019

The International Maritime Organization (IMO) will administer a new 0.5% global sulfur cap on fuel content from 1 January 2020, lowering from the present 3.5% limit. Seawater $SO_x$ (sulfur oxide) scrubbing is especially spray scrubbing and a promising alternative to complying with the IMO regulation. However, the ionization of $SO_2$ (sulfur dioxide) and the $H_2SO_4$ (sulfuric acid) formed from $SO_3$ (sulfur trioxide) is proposed to accelerate corrosion of the internal seawater pipe. Apparently, the corrosion of the scrubber seawater piping system occurs in a severe and frequent manner. Hence, in this study, electrochemical measurement and weight loss of carbon steel (used as seawater pipe in most of the ships) in diluted sulfuric acid solution were investigated to determine corrosion rate, corrosion current density, corrosion potential, electrochemical behavior, and impressed-current density. Accordingly, the corrosion rate of carbon steel sheet in various diluted sulfuric acid solutions was observed to be greater than that in natural seawater, thus suggesting the fundamental data to deal with corrosion problems in scrubber seawater pipe.

• Membrane and Water Treatment
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• v.10 no.3
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• pp.201-206
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• 2019

In this study, we performed an electrowinning process for effective removal of metals (Cu and Ni) in solution and their recovery as solid forms. A complete removal of Cu and Ni (1,000 mg/L) was observed during four times recycling test, indicating that our electrowinning system can ensure the efficient metal removal with high stability and durability. In addition, we investigated effect of operation parameters (i.e., concentration of boric acid only for Ni, variation of pH, concentration of electrolyte ($H_2SO_4$), and cell voltage) on the efficiency of metal removal (Cu and Ni) during the electrowinning. The addition of boric acid significantly enhanced removal efficiency of Ni as the concentration of boric acid increased up to 10 g/L. Compared to negligible pH effect (pH 1, 2, and 4) on the Cu removal, we observed the increase in removal efficiency of Ni as the pH increased from 1 to 4. The electrolyte concentration did not significantly influence the removal of Cu and Ni in this study. We also obtained great removal rates of Cu and Ni at 2.5 V and 4.0 V, which were much faster than those at lower voltages. Finally, almost 99% of each Cu and Ni (1,000 mg/L) was selectively removed from the mixture of metals by adjusting pH and addition of boric acid after the completion of Cu removal. The findings in this study can provide a fundamental knowledge about effect of important parameters on the efficiency of metal recovery during the electrowinning.

• Journal of Convergence for Information Technology
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• v.9 no.10
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• pp.81-86
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• 2019

Problems related to information overload and harmful information have already expanded to national social problems as well as personal problems. This study explores the causes of Internet addiction, exposure to harmful information, malicious comments, fake information/information manipulation, and new alternatives that have recently been felt as social problems. Assuming that existing technologies/policies were not applied effectively, psychological cause analysis was performed for the fundamental problem approach. As a result, internal problems such as obsession with knowledge/understanding of wrong information/black and white stereotypes and prejudice were analyzed as main causes. Each proposed solution aims to help improve national technology/policy regarding internet addiction and blocking harmful information.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.4
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• pp.901-911
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• 2012

The removal of security vulnerabilities during the developmental stage is found to be much more effective and much more efficient than performing the application during the operational phase. The underlying security vulnerabilities in software have become the major cause of cyber security incidents. Thus, secure coding is drawing much attention for one of its abilities includes minimizing security vulnerabilities at the source code level. Removal of security vulnerabilities at the software's developmental stage is not only effective but can also be regarded as a fundamental solution. This thesis is a research about the methods of Mobile-Secure Coding Self Assessment in order to evaluate the security levels in accordance to the application of mobile secure coding of every individual, groups, and organizations.

• Journal of the Korea Safety Management & Science
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• v.22 no.4
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• pp.17-26
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• 2020

In Korea, primary school (also junior high school) is compulsory and free since 2004. But it looks high school is also compulsory, as over 80% of adults has a high school diploma currently. For 20 years improving high school education is only education-oriented, rather than occupation-oriented. And, the mismatch between the occupational requirement and the lesson from school is getting larger. To resolve this issue, the Korean government builds and utilizes National Competency Standards(NCS) to realize a competence-oriented society. With NCS, the government enables to run of a work-study program and tries to suggest the fundamental solution to improve occupational ability and the unemployment of young people. However, the prejudice against the education level and occupation is still engrained, and it is hard to match the education-career-qualification based on NCS. Therefore, we study NCS from the definition to the utilization, suggest an improving method to flexibly utilized the standards in the fields, and continuously improve and develop the NCS.

• Structural Engineering and Mechanics
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• v.77 no.5
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• pp.571-586
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• 2021

The present paper studies the influence of the inhomogeneous initial stresses in the bi-layered hollow cylinder and it is assumed that these stresses are caused by the hydrostatic pressures acting on the interior and outer free surfaces of the cylinder. The study is made by utilizing the version of the three-dimensional linearized theory of elastic waves in bodies with initial stresses for which the initial stress-strain state in bodies is determined within the scope of the classical linear theory of elasticity. For the solution to the corresponding eigenvalue problem, the discrete-analytical method is employed. Numerical results are presented and analyzed for concrete selected pairs of materials. According to these results and their analyses, it is established that, unlike homogeneous initial stresses, the influence of the inhomogeneous initial stresses on the torsional wave dispersion has not only quantitative but also qualitative character. For instance, in particular, it is established that as a result of the initial stresses caused by the hydrostatic pressure acting in the interior free surface of the cylinder, the cut-off frequency appears for the fundamental dispersive mode and the values of this frequency increase with the intensity of this pressure.

• The Journal of Economics, Marketing and Management
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• v.11 no.4
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• pp.65-76
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• 2023

Purpose: It suggests that in order to compare economic development between large cities, this paper aims to exclude factors such as GDP, trade, manpower, R&D, then present newly an analysis of others (inflation, exports, middle-class, competitiveness, digital). Research design, data, and methodology: In the period of rapid digitalization of the world, we would like to deal with different analysis factors than before. This is because digitalization and prices have the greatest impact on the region in terms of national competitiveness. Random sampling was used as the sample size of this study to generate various values for the annual income of the middle class and the competitiveness index, and the analysis method was used. This is because the income of the middle class can lead the digitalization of the country and accelerate it to standardization. Results: Based on these analysis, it is necessary to reduce the inflation rate of digitalization, it is necessary to lower inflation rates. This can be more fundamental than interest rates. If the demand for digitalization is reduced, national competitiveness, national competitiveness will lower national competitiveness. By building a hub for middle class, you can reduce this inflation rate without China's oversupply. Conclusion: This is because it is difficult to maintain competitiveness through interest rate control, as prices rise, and inflation can become unstable. This study can seek digital acceptance by the middle class as a solution to problems like the regional economic confrontation of new globalization inflation environment.

• Journal of Korean Society of Forest Science
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• v.112 no.1
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• pp.1-10
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• 2023

Urbanization and industrialization associated with rapid economic development have resulted in air pollution in urban areas, which adversely affects human health and the environment around the world. Growing awareness of the health effects of airborne particulate matter (PM) has led to the emergence of urban greening as a promising eco-friendly, nature-based solution to reduce the concentration of PM (especially PM_2.5) to which individuals are exposed, thereby promoting public health. In this review, we highlight fundamental insights about PM and recent research on the ability of urban greening to capture PM. Reports from the scientific literature on PM published from 1992 to 2021 were retrieved from Google Scholar. Here, we explore some of the main complex relationships between leaf traits and the ability to retain PM for research or management to optimize greenspaces.