• Geomechanics and Engineering
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• v.32 no.2
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• pp.125-135
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• 2023

Nonlinear vibration analysis of composite beam reinforced by carbon nanotubes resting on the nonlinear viscoelastic foundation is investigated in this study. The material properties of the composite beam is considered as a polymeric matrix by reinforced carbon nanotubes according to different distributions. With using Hamilton's principle, the governing nonlinear partial differential equations are derived based on the Euler-Bernoulli beam theory. In the nonlinear kinematic assumption, the Von Kármán nonlinearity is used. The Galerkin's decomposition technique is utilized to discretize the governing nonlinear partial differential equation to nonlinear ordinary differential equation and then is solved by using of multiple time scale method. The nonlinear natural frequency and the nonlinear free response of the system is obtained. In addition, the effects of different patterns of reinforcement, linear and nonlinear damping coefficients of the viscoelastic foundation on the nonlinear vibration responses and phase trajectory of the carbon nanotube reinforced composite beam are investigated.

• Structural Engineering and Mechanics
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• v.73 no.3
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• pp.225-238
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• 2020

This work treats the axisymmetric buckling of functionally graded (FG) porous annular/circular nanoplates based on modified couple stress theory (MCST). The nanoplate is located at the elastic medium which is simulated by Kerr foundation with two spring and one shear layer. The material properties of the porous FG nanostructure are assumed to vary through the nanoplate thickness based on power-law rule. Based on two variables refined plate theory, the governing equations are derived by utilizing Hamilton's principle. Applying generalized differential quadrature method (GDQM), the buckling load of the annular/circular nanoplates is obtained for different boundary conditions. The influences of different involved parameters such as boundary conditions, Kerr medium, material length scale parameter, geometrical parameters of the nanoplate, FG power index and porosity are demonstrated on the nonlinear buckling load of the annular/circular nanoplates. The results indicate that with increasing the porosity of the nanoplate, the nonlinear buckling load is decreased. In addition, with increasing the material length scale parameter to thickness ratio, the effect of spring constant of Kerr foundation on the buckling load becomes more prominent. The present results are compared with those available in the literature to validate the accuracy and reliability. A good agreement is observed between the two sets of the results.

• Structural Engineering and Mechanics
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• v.61 no.2
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• pp.209-220
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• 2017

The purpose of this paper is to study the geometrically nonlinear free vibration of functionally graded nano/micro beams (FGNBs) based on the modified couple stress theory. For practical applications, some analytical expressions of nonlinear frequencies for FGNBs on a nonlinear Pasternak foundation are developed. Hamilton's principle is employed to obtain nonlinear governing differential equations in the context of both Euler-Bernoulli and Timoshenko beam theories for a comprehensive investigation. The modified continuum theory contains one material length scale parameter to capture the size effect. The variation of two-constituent material along the thickness is modeled using Reddy's power-law. Also, the Mori-Tanaka method as an accurate homogenization technique is implemented to estimate the effective material properties of the FGNBs. The results are presented for both hinged-hinged and clamped-clamped boundary conditions. The nonlinear partial differential equations are reduced to ordinary differential equations using Galerkin method and then the powerful method of homotopy analysis is utilized to obtain the semi-analytical solutions. Eventually, the presented analytical expressions are used to examine the influences of the length scale parameter, material gradient index, and elastic foundation on the nonlinear free vibration of FGNBs.

• Journal of the Korean Society of Safety
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• v.35 no.4
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• pp.15-22
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• 2020

Scaffolding works are demolished after this structure is completed, and safety accidents often occur because they are installed differently from legal standards or frequently change during work. Therefore, in order to strengthen the safety of scaffolding, the Ministry of Land, Infrastructure and Transport required a need for design standards for temporary facilities that can systematically prevent and solve large-scale safety accidents that are repeatedly increasing during temporary construction. It has been enacted, and some contents have been revised for the past three years. However, construction site personnel do not know or know the revised matters, but often install scaffolding by the installer's experience rather than complying with relevant laws and regulations. It is the situation that the ground strength test of the foundation ground for the load applied to the floor of the column is omitted in most sites. Therefore, this study grasped the actual situation on the degree of recognition of the revised laws and regulations of the construction site and the foundation-based treatment of the floor working load of the scaffolding column, and derived problems. In addition, we intend to provide reference materials for the endurance test according to the ground conditions to small-scale small sites where it is difficult to conduct the test by carrying out the endurance test of the scaffolding ground according to the revised standards.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1046-1050
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• 2010

During construction of a sea-crossing bridge grouting was used to fill densely the space between the bottom of caisson and the ground. This grout mixture was mixed with an anti-washout admixture after locating accurately the pre-cast caisson on three concrete landing pads. This method differs significantly from the costly conventional method, for bridge foundations offshore, where concrete is placed in situ after excavating inside of a temporary concrete coffering wall. To verify the grouting method in advance, the full-scale field tests were performed twice on land. After identifying the fluidity of the grout material to be filled, finding some possible problems with the main construction and revising the original design, the main construction has been continuing successfully with 20 caissons completed to date. The purpose of this paper is to introduce for the first time in Korea the grouting method including the automatic and the manual monitoring system based on the main construction of the caisson foundation.

• Clinical Endoscopy
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• v.57 no.1
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• pp.11-17
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• 2024

Although magnifying endoscopy with narrow-band imaging is the standard diagnostic test for gastric cancer, diagnosing gastric cancer using this technology requires considerable skill. Artificial intelligence has superior image recognition, and its usefulness in endoscopic image diagnosis has been reported in many cases. The diagnostic performance (accuracy, sensitivity, and specificity) of artificial intelligence using magnifying endoscopy with narrow band still images and videos for gastric cancer was higher than that of expert endoscopists, suggesting the usefulness of artificial intelligence in diagnosing gastric cancer. Histological diagnosis of gastric cancer using artificial intelligence is also promising. However, previous studies on the use of artificial intelligence to diagnose gastric cancer were small-scale; thus, large-scale studies are necessary to examine whether a high diagnostic performance can be achieved. In addition, the diagnosis of gastric cancer using artificial intelligence has not yet become widespread in clinical practice, and further research is necessary. Therefore, in the future, artificial intelligence must be further developed as an instrument, and its diagnostic performance is expected to improve with the accumulation of numerous cases nationwide.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06a
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• pp.728-733
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• 1994

Scientific foundation for ultrasonic scale preventing devices construction was given in 40S-50S of this century but their production in former USSR was organized later in 70th. Several different principles of scale preventing is overviewed together with physical principles of ultrasonic method. Practical experience received in USSR in 80S is discussed. Technical decisions and inventions used for construction of the first device UZU-1 produced in Cheboksary plant are enumerated and principles of UZU-2 device are briefly sketched.

• Journal of the Korea Institute of Building Construction
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• v.4 no.3
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• pp.109-116
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• 2004

Normally easy task of plat in urban architecture is that using underground full of activities for increase building site efficiency. Especially for using underground space for the parking lot. Also utilize underground is more increase for fulfill requirement in modern society considered with environmental friendly architecture. The primary objective of this study is to apply analyzed formal foundation type for selecting the optimum type of parking lots considered with structural stability, economical efficiency, construction efficiency, construction duration. This study aim to on criteria decided through the questionaries for the selection considered with in the scale of second stories parking lots underground, parking volume is 80 and reinforced concrete structure. The bearing capacity is 6～8m and downward from surface, healthy ground bearing capacity is 40 t/m2. This study comparative analysis and discuss economical efficiency, construction efficiency, construction duration based constructivist stability which applied Single foundation, Mat foundation, Drop Mat foundation. The result of this study is as follows: First, the result of economical efficiency is that on the basis of single foundation, Drop Mat foundation is 1.88, Mat foundation 2.04 as a comparative analysis on the basis of total construction cost included material cost, labor coast and machinery cost. Second, the result of construction efficiency order is single foundation, Drop Mat foundation, Mat foundation as a comparative analysis on the based connected characteristics. Third, the result of construction duration is that on the basis of Mat Foundation, Drop Mat foundation is 1.33, single foundation is 1.87 as a comparative analysis Critical Path. Forth, Each foundational type characteristics order through the matrix method is that overall each formal type of foundation contraries at economical efficiency and construction efficiency, construction duration. Also expect contradiction between engineers and owners due to engineer pursuit construction duration and ewer to begin with economical efficiency. Fifth, The selection of suitable foundation formal type needs that based consider project characteristic and field condition as according to above result of a comparative analysis. As a result, a comparative analysis economical efficiency, construction efficiency, construction duration of Mat foundation, Drop Mat foundation, single foundation with 3Bay reinforced structure underground parking lots on the healthy ground.

• International Journal of Air-Conditioning and Refrigeration
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• v.16 no.4
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• pp.109-116
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• 2008

Ground temperature restoration characteristics are the crucial factors to evaluate whether a ground source heat pump system can keep long time steady operation. They are mainly dependent on soil thermal properties, layout of pile group, operation/shutoff ratio, cooling/heating load, thermal imbalance ratio and so on. On the one hand, several types of vertical pile foundation heat exchangers are intercompared to determine the most efficient one by performance test and numerical method. On the other hand, according to the layout of pile group of a practical engineering and running conditions of a GSHP system in Shanghai, the temperature distribution during a period of five years is numerically studied. The numerical results are analyzed and are used to provide some guidance for the design of large-scale GSHP system.

• KCID journal
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• v.10 no.2
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• pp.55-61
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• 2003

Bench scale experiments have been carried out to evaluate the adaptability of the anchor for improving the uplift capacity of foundation of pipe framed greenhouse which is typically adopted in conventional plastic film glazing greenhouses, such as 1-2W ty