• Steel and Composite Structures
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• v.46 no.6
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• pp.839-856
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• 2023

This work presents a simple four-unknown refined integral plate theory for mechanical and thermal buckling behaviors of functionally graded (FG) plates resting on Visco-Pasternak foundations. The proposed refined high order shear deformation theory has a new displacement field which includes indeterminate integral variables and contains only four unknowns in which any shear correction factor not used, with even less than the conventional theory of first shear strain (FSDT). Governing equations are deduced from the principle of minimum total potential energy and a Navier type analytical solution is adopted for simply supported FG plates. The Visco-Pasternak foundations is considered by adding the impact of damping to the usual foundation model which characterized by the linear Winkler's modulus and Pasternak's foundation modulus. The accuracy of the present model is demonstrated by comparing the computed results with those available in the literature. Some numerical results are presented to show the impact of material index, elastic foundation type, and damping coefficient of the foundation, on the mechanical and thermal buckling behaviors of FG plates.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2D
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• pp.191-198
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• 2010

The displacement of slope is a key factor in predicting the risk of a landslide. Therefore, the slope displacement should be continuously observed with high accuracy. Recently, high-tech equipment such as optical fiber sensor, GPS, total station and measuring instrument have been used. However, such equipment is poorly used in fields due to economics, environment, convenience and management. Because of this, development of substantial observational techniques for varied slope observation and field applications is needed. This study analyzed the possibility of terrestrial LiDAR for slope monitoring and suggested it as information-obtaining technique for slope investigation and management. For that, this study evaluated the monitoring accuracy of terrestrial LiDAR and performed GRID analysis to read the displacement area with the naked eye. In addition, it suggested a methodology for slope monitoring.

• Geomechanics and Engineering
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• v.34 no.2
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• pp.115-124
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• 2023

By conducting three-dimensional simulation with consideration of small-strain characteristics of soil stiffness, the effects of excavation geometry and tunnel cover to diameter ratio on deformation mechanisms of an existing tunnel located either at a side of basement or directly underneath the basement were systematically studied. Field measurements were used to verify the numerical model and model parameters. For basement excavated at a side of an existing tunnel, the maximum settlement and horizontal displacement of the tunnel are always observed at the tunnel springline closer to basement and tunnel crown, respectively, regardless of basement geometry. By increasing basement length and width by five times, the maximum movements of tunnel located at the side of basement and directly underneath the basement increase by 450% and 186%, respectively. Obviously, tunnel movements are more sensitive to basement length rather than basement width. For basement excavated at a side of an existing tunnel, tunnel movements at basement centerline become stable when basement length reaches 10 H_e (i.e., final excavation depth). Moreover, tunnel heaves due to overlying basement excavation become stable when the normalized basement length (L/H_e) is larger than 8.0. As tunnel cover to diameter ratio varies from 2.5 to 3.0, the maximum heave and tensile strain of tunnel due to overlying basement excavation decrease by up to 41.0% and 44.5%, respectively. If basement length is less than 8 H_e, the assumption of plane strain condition of basement-tunnel interaction grossly overestimates tunnel movements, and ignores tensile strain of tunnel along its longitudinal direction. Thus, three-dimensional numerical analyses are required to obtain a reasonable estimation of tunnel responses due to adjacent and overlying basement excavations in clay.

• Steel and Composite Structures
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• v.44 no.5
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• pp.721-740
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• 2022

In this paper, an accurate kinematic model has been developed to study the mechanical response of functionally graded (FG) sandwich beams, mainly covering the bending, buckling and free vibration problems. The studied structure with homogeneous hardcore and softcore is considered to be simply supported in the edges. The present model uses a new refined shear deformation beam theory (RSDBT) in which the displacement field is improved over the other existing high-order shear deformation beam theories (HSDBTs). The present model provides good accuracy and considers a nonlinear transverse shear deformation shape function, since it is constructed with only two unknown variables as the Euler-Bernoulli beam theory but complies with the shear stress-free boundary conditions on the upper and lower surfaces of the beam without employing shear correction factors. The sandwich beams are composed of two FG skins and a homogeneous core wherein the material properties of the skins are assumed to vary gradually and continuously in the thickness direction according to the power-law distribution of volume fraction of the constituents. The governing equations are drawn by implementing Hamilton's principle and solved by means of the Navier's technique. Numerical computations in the non-dimensional terms of transverse displacement, stresses, critical buckling load and natural frequencies obtained by using the proposed model are compared with those predicted by other beam theories to confirm the performance of the proposed theory and to verify the accuracy of the kinematic model.

• Structural Engineering and Mechanics
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• v.84 no.4
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• pp.437-452
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• 2022

For the first time, the higher-order shear and normal deformable plate theory (HOSNDPT) is used for the vibration and flutter analyses of the multilayer functionally graded graphene platelets reinforced composite (FG-GPLRC) plates under supersonic airflow. For modeling the supersonic airflow, the linear piston theory is adopted. In HOSNDPT, Legendre polynomials are used to approximate the components of the displacement field in the thickness direction. So, all stress and strain components are encountered. Either uniform or three kinds of non-uniform distribution of graphene platelets (GPLs) into polymer matrix are considered. The Young modulus of the FG-GPLRC plate is estimated by the modified Halpin-Tsai model, while the Poisson ratio and mass density are determined by the rule of mixtures. The Hamilton's principle is used to obtain the governing equations of motion and the associated boundary conditions of the plate. For solving the plate's equations of motion, the Galerkin approach is applied. A comparison for the natural frequencies obtained based on the present investigation and those of three-dimensional elasticity theory shows a very good agreement. The flutter boundaries for FG-GPLRC plates based on HOSNDPT are described and the effects of GPL distribution patterns, the geometrical parameters and the weight fraction of GPLs on the flutter frequencies and flutter aerodynamic pressure of the plate are studied in detail. The obtained results show that by increasing 0.5% of GPLs into polymer matrix, the flutter aerodynamic pressure increases approximately 117%, 145%, 166% and 196% for FG-O, FG-A, UD and FG-X distribution patterns, respectively.

• Journal of The Geomorphological Association of Korea
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• v.27 no.2
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• pp.29-46
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• 2020

In this study, changes in the fluvial landforms of the Yeoju section of the Han River, which was made up of the Han River Restoration Project, were examined through existing previous research data, government's environmental impact assessment data, satellite images, and field observations. For example, In the vicinity of Dori Island, the most upstream part of the study section, the location of the confluence of the Han River and Cheongmi Stream was changed, and it was found that a significant portion of the sand sedimentary layer disappeared. In the Bawuinupgubi area, the wetland, which is the first class in the ecological nature, was greatly modified, and the elevation of the ground rose as Gangcheon island and it was completely separated from the river by dredging The confluence of Geumdangcheon and the point bar of Yeonyang-ri in the south were also dredged, turned into an artificial waterfront park, and a chute channel remained in the form of a wetland was also developed as a recreational park. The deposional forms around Baekseok-ri islands also disappeared as dredging was carried out. Among the areas adjacent to the confluence of Bokcheon and Yangchon-ri Island, some sedimentay forms remains, but the abandonned channel between Yangchon-ri and the northern river bank has been changed into a riverside reservoir through dredging and embankment construction, and the waterway of the tributary river(Yazoo) has been greatly changed.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.33 no.3
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• pp.298-307
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• 2023

Objectives: The purpose of this study is to analyze the recent trends in patients with work-related musculoskeletal disorders in South Korea and to check the major results by reviewing the literature on the risk factors and prevalence of musculoskeletal diseases related to work. Methods: Industrial disaster data from the Ministry of Employment and Labor from 2012 to 2021 were used, and the literature was reviewed regarding risk factors for musculoskeletal diseases related to work using PubMed and RISS. Results: The trend of patients with work-related musculoskeletal disorders has increased overall since 2017 after declining until 2016, with a particularly notable increase in the average annual number of patients with physical burden work. The average annual rate per ten thousand people for patients with body burden work, non-accidental lower back pain, and carpal tunnel syndrome among work-related diseases was high in the mining industry. The average annual rate per ten thousand people for patients with accidental lower back pain was the highest in the fishing industry. Within the manufacturing field, it was the highest in the shipbuilding and ship repair industry. As a result of the literature review, the search rate for work-related musculoskeletal disease papers in unstructured work was high. In addition, physical stress factors were high among risk factors, and pain areas showed a high rate for the waist. Conclusion: Even after the institutional implementation of a hazard investigation system related to musculoskeletal diseases is implemented, the number of patients with occupational musculoskeletal disorders continues to increase. Therefore, it is necessary to conduct regular surveys and implement effective improvement activities for vulnerable industries or occupations.

• Fashion & Textile Research Journal
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• v.25 no.6
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• pp.732-738
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• 2023

This study delves into the realm of upcycling beauty design by repurposing discarded CDs, magazines, and fabrics. The study outlines a meticulous process for transforming waste into beauty designs. We created three upcycling beauty design works as part of this investigation. The first creation, called Silver Leaf, uses the silver section of CDs to craft leaves and stems. Achromatic colors are used as makeup to achieve cyber-inspired imagery. After carrying out silver-gray eye makeup, the lips were completed by affixing a CD component. The second creation is a firebird crafted by cutting or folding fashion magazines to create essential items. The colorful firebird image was completed using vivid color makeup of shades such as red and yellow. After proceeding with red eye makeup, the lips were completed by cutting and pasting magazine cutouts. The third piece is a spring flower, which involved selectively cutting lace patterns to complete a beauty design extending from head to face. The colors are spring-themed and encompass pink, yellow, and blue. Pink, blue, and green eyeshadows were applied on the lace, attached from head to face, chest, and lips. This study advocates for the prospect of upcycling beauty design using sustainable materials by repurposing waste resources. It also introduces the possibilities of creative activities in this field through upcycling. The study aims to play a role in changing the perception of environmental conservation, a concern of our times, through the use of sustainable resources.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2021.04a
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• pp.18-18
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• 2021

Gomchwi using stuffed leaves is many cultivated for 'Gondalbi(Ligularia stenocephala)' among Gomchwi species. 'Gondalbi' species like to be cultivation on farm because of low the incense and the bitter taste, and high yield. But 'Gondalbi' caused to curtail yield that susceptibility of powdery mildew disease and shriveling and death of plant on summer season. To solve this problems, we crossed a Gomchwi and 'Handeari-gomchwi' to have resistance of powdery mildew disease and high yield. A new Gomchwi cultivar 'Jinmani' was bred by crossing between Gomchwi (Ligularia fischeri (Ledeb.) Turcz.) and Handaeri-gomchwi (Ligularia fischeri var. spiciformis Nakai). The selection and investigation of growth and yield characteristics were conducted from 2007 to 2020 in field and greenhouse of Highland Agriculture Research Institute, NICS, Rural Development Administration. The color of petiole ear was purple. trichome of petiole and leaf back non-existed, and luster of leaf back existed. Density of leaf vein was 4 degree among 1-5 degree in a newly developed cultivar 'Jinmani'. Plant height, leaf length, leaf width and petiole length were 55.7, 21.8, 22.2, and 33.9 cm, respectively in the 2nd year of growth characteristics. Plant size was similar with that of 'Gommany'. Bolting and flowering time were Aug. 5 and Sept. 5, respectively, and Bolting and flowering time of 'Gommany' showed similar to Aug. 8 and Sept. 1, respectively. 'Jinmani' showed higher number of leaves (202 ea.) per plant compared to 'Gommany' (159 ea.). Furthermore, yield was 67.9% higher in 'Jinmani' (2,569 g/plant) than in 'Gommany' (1,530 g/plant). 'Jinmani' showed lower leaf thickness (0.66mm) than 'Gommany' (0.69 mm), and consequently showed more hardness in leaf characteristics (25.1 kg/²) compared to 'Gommany' (24.3kg/cm²). 'Jinmani' showed similar strong resistance compared to 'Gommany' in the susceptibility of powdery mildew disease.

• Advances in aircraft and spacecraft science
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• v.10 no.4
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• pp.303-315
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• 2023

The primary goal of this research is to investigate flow separation phenomena using various turbulence models. Also investigated are the effects of free-stream turbulence intensity on the flow over a NACA 0018 airfoil. The flow field around a NACA 0018 airfoil has been numerically simulated using RANS at Reynolds numbers ranging from 100,000 to 200,000 and angles of attack (AoA) ranging from 0° to 18° with various inflow conditions. A parametric study is conducted over a range of chord Reynolds numbers for free-stream turbulence intensities from 0.1 % to 0.5 % to understand the effects of each parameter on the suction side laminar separation bubble. The results showed that increasing the free-stream turbulence intensity reduces the length of the separation bubble formed over the suction side of the airfoil, as well as the flow prediction accuracy of each model. These models were used to compare the modeling accuracy and processing time improvements. The K- SST performs well in this simulation for estimating lift coefficients, with only small deviations at larger angles of attack. However, a stall was not predicted by the transition k-kl-omega. When predicting the location of flow reattachment over the airfoil, the transition k-kl-omega model also made some over-predictions. The Cp plots showed that the model generated results more in line with the experimental findings.