• 대한조선학회논문집
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• 제56권3호
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• pp.217-230
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• 2019

In this study, a fatigue damage estimation for an ice-going vessel navigating through broken ice fields was carried out. A numerical model to simulate the interaction between ice and structure developed using the finite element method was introduced. Time series of stresses calculated by the proposed model and the corresponding fatigue analysis results are presented. The numerical model enables the long time analysis through an efficient interaction model, the application of the periodic media analysis and the convolution integral, and it allows the stress time history to be extracted directly using the finite element method. To describe the probability distribution of stress amplitudes, the 2-parameter Weibull model was applied to the calculated stress time history, and the fatigue damage was calculated using the Palmgren-Miner rule. Finally, the fatigue damage considering the ice conditions of the Baltic Sea was calculated using the proposed method and LR method, and the results were compared to each other.

• The Journal of Asian Finance, Economics and Business
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• 제8권4호
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• pp.69-81
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• 2021

The aim of this paper is to identify the key determinants in the Gulf Cooperation Council (GCC) countries for Foreign Direct Investment (FDI) inflows by using a balanced data panel for the period from 1995 to 2018. This study covers GCC countries in their entirety. The study uses ten explanatory variables, namely, trade ratio, gross domestic product, external balance, fuel exports, gross savings, international tourism, military expenditure, net foreign assets, services value added, and total natural resources. The authors have tried to find the best fit model from the differences methods considered such as OLS, GLS regression with the help of Hausman test, and country by country regressions as additional analysis. The study revealed a significantly positive association between inflation, trade ratio, gross domestic product, gross savings, and net foreign assets with FDI. On the contrary, international tourism was revealed to have a negative association with FDI. The sample of all GCC countries chosen for this study has not been considered widely by any earlier study. Moreover, this study covered many determinants of FDI that add to the previous literature. It is a significant contribution to the current research body and stresses the originality of this paper.

• The Journal of Asian Finance, Economics and Business
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• 제9권6호
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• pp.343-362
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• 2022

Amidst the Covid-19 pandemic, human resources play a vital role in the health industry because the staff all has to confront a lot of stresses in serving the country and the people to overcome the severe contagiousness and infection of the virus. It is also the case of Family General Hospital, Da Nang (Vietnam). Therefore, the Hospital identifies talented personnel as a core resource in its sustainable development strategy. Researching on how to retain talented staff to serve the sustainable and long-term development of a private hospital such as Family Hospital is extremely necessary, especially when there are fewer large and modern private health facilities for the healthcare system in Central Vietnam compared to the North and the South. With the analysis of survey data and in-depth interviews from both qualitative and quantitative perspectives (via SPSS 20.0), especially the ANOVA and EFA analyses, and linear multiple regression (Generation 1 methods), this study aims to clarify the aspects that affect the talent retention in the representative Family Hospital. The lessons learned have been a good reference for similar private healthcare models in the process of bringing health-related services to a new level in the competition.

• 한국가시화정보학회지
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• 제20권2호
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• pp.70-77
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• 2022

Skeletal muscle tissues feature cellular heterogeneity, including differentiated myofibers, myoblasts, and satellite cells. Thanks to the presence of undifferentiated myoblasts and satellite cells, skeletal muscle tissues can self-regenerate after injury. In skeletal muscle regeneration, the collective motions among these cell types must play a significant role, but little is known about the dynamic collective behavior during the regeneration. In this study, we constructed in vitro platform to visualize the migration behavior of skeletal muscle cells in specific conditions that mimic the biochemical environment of injured skeletal muscles. We then visualized the spatiotemporal distribution of stresses arising from the differential collectiveness in the cellular clusters under different conditions. From these analyses, we identified that the heterogeneous population of muscle cells exhibited distinct collective migration patterns in the injury-mimicking condition, suggesting selective activation of a specific cell type by the biochemical cues from the injured skeletal muscles.

• Steel and Composite Structures
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• 제44권3호
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• pp.407-421
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• 2022

Prefabricated hybrid wind turbine towers (WTTs) are promising due to height increase. This study proposes the use of ultra-high performance concrete (UHPC) to develop a new type of WTT without the need to use reinforcement. It is demonstrated that the UHPC WTT structure without reinforcing bars could achieve performance similar to that of reinforced concrete WTTs. To simplify the design of WTT, a design approach for the calculation of stresses at the horizontal joints of a WTT is proposed. The stress distribution near the region of the horizontal joint of the WTT structure under normal operating conditions and different load actions is studied using the proposed approach, which is validated by the finite element method. A further parametric study shows that the degree of prestressing and the bending moment both significantly affect the principal stress. The shear-to-torsion ratio also shows a significant influence on the principal tensile stress.

• Advances in nano research
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• 제12권2호
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• pp.117-137
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• 2022

Effect of thickness stretching on free vibration, bending and buckling behavior of carbon nanotubes reinforced composite (CNTRC) laminated nanoplates rested on new variable elastic foundation is investigated in this paper using a developed four-unknown quasi-3D higher-order shear deformation theory (HSDT). The key feature of this theoretical formulation is that, in addition to considering the thickness stretching effect, the number of unknowns of the displacement field is reduced to four, and which is more than five in the other models. Two new forms of CNTs reinforcement distribution are proposed and analyzed based on cosine functions. By considering the higher-order nonlocal strain gradient theory, microstructure and length scale influences are included. Variational method is developed to derive the governing equation and Galerkin method is employed to derive an analytical solution of governing equilibrium equations. Two-dimensional variable Winkler elastic foundation is suggested in this study for the first time. A parametric study is executed to determine the impact of the reinforcement patterns, nonlocal parameter, length scale parameter, side-t-thickness ratio and aspect ratio, elastic foundation and various boundary conditions on bending, buckling and free vibration responses of the CNTRC plate.

• Structural Engineering and Mechanics
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• 제84권6호
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• pp.707-722
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• 2022

In this study, a new refined hyperbolic shear deformation theory (RHSDT) is developed using an equivalent single-layer shell displacement model for the static bending and free vibration response of cross-ply laminated composite spherical shells. It is based on a new kinematic in which the transverse displacement is approximated as a sum of the bending and shear components, leading to a reduction of the number of unknown functions and governing equations. The proposed theory uses the hyperbolic shape function to account for an appropriate distribution of the transverse shear strains through the thickness and satisfies the boundary conditions on the shell surfaces without requiring any shear correction factors. The shell governing equations for this study are derived in terms of displacement from Hamilton's principle and solved via a Navier-type analytical procedure. The validity and high accuracy of the present theory are ascertained by comparing the obtained numerical results of displacements, stresses, and natural frequencies with their counterparts generated by some higher-order shear deformation theories. Further, a parametric study examines in detail the effect of both geometrical parameters (i.e., side-to-thickness ratio and curvature-radius-to-side ratio), on the bending and free vibration response of simply supported laminated spherical shells, which can be very useful for many modern engineering applications and their optimization design.

• Structural Engineering and Mechanics
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• 제84권6호
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• pp.783-798
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• 2022

This study attempts to investigate the impact of thickness stretching and nonlinear hygro-thermo-mechanical loading on the bending behavior of FG beams. Young's modulus, thermal expansion, and moisture concentration coefficients vary gradually and continuously according to a power-law distribution in terms of the volume fractions of the constituent materials. In addition, the interaction between the thermal, mechanical, and moisture loads is involved in the governing equilibrium equations. Using the present developed analytical model and Navier's solution technique, the numerical results of non-dimensional stresses and displacements are compared with those obtained by other 3D theories. Furthermore, the present analytical model is appropriate for investigating the static bending of FG beams exposed to intense hygro-thermo-mechanical loading used for special technical applications in aerospace, automobile, and civil engineering constructions.

• 소성∙가공
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• 제32권5호
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• pp.287-293
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• 2023

This study aims to develop a computational framework based on the finite element method for modeling the hydrogen embrittlement in martensitic steel. The hydrogen embrittlement is a well-known phenomenon, in which the hydrogen penetrates into the surface, flows through the microstructure and finally leads to pre-mature fracture under external or internal stresses. The current numerical model takes into account the effect of hydrogen on the plasticity and failure behavior of martensitic steel under various stress states. This allows for the construction of a failure criterion that accounts for conventional stress states and hydrogen concentration. The developed model is capable of simulating hydrogen diffusion through the lattice based on the distribution of hydrostatic stress. Additionally, it can calculate the hydrogen concentration in trapped sites, such as dislocations, using a local equilibrium assumption, often referred to as Oriani's equilibrium. The developed model parameters are identified through the tensile tests with and without hydrogen environment, and the performance of model can be validated by analyzing fractured automotive part in the hydrogen environment.

• 한국토양동물학회지
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• 제3권2호
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• pp.91-105
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• 1998

This study was conducted to analyze oribatid mites communities in deciduous forests in Namsan and Kwangreung on which different levels of environmental stresses might press, and to select potential condidate of biological indicator species. In overall, pH was lower in soil than in litter layer. Also soil pH, total nitrate content and soluble sulfate content were significantly higher in Namsan than in Kwangreung (p<0.05). The flora in Namsan and Kwangreung deciduous forests were dominated by Quercus mongolica, and Carpinus laxiflora respectively. It indicated that Namsan was in the lower stage of the floral succession. The number of species of oribatid mites was significantly higher in Kwangreung (39 families, 65 genera and 114 species) than in Namsan (32 families, 53 genera and 89 species) (p<0.05). Common species found in two regions were 77 species. Mean density of oribatid mites was 1.8 times higher in Kwangreung than in Namsan and this difference came mainly from litter layer. Among correlation analyses between environmental factors and oribatid mites density and species number, only density was negatively correlated with fresh litter depth in Namsan litter layer (r=-0.89, p<0.05). The pH which was considered to affect distribution of oribatid mites didn't show significant results.