• Steel and Composite Structures
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• v.46 no.1
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• pp.1-13
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• 2023

Elastic bending of imperfect functionally graded sandwich plates (FGSPs) laying on the Winkler-Pasternak foundation and subjected to sinusoidal loads is analyzed. The analyses have been established using the quasi-3D sinusoidal shear deformation model. In this theory, the number of unknowns is condensed to only five unknowns using integral-undefined terms without requiring any correction shear factor. Moreover, the current constituent material properties of the middle layer is considered homogeneous and isotropic. But those of the top and bottom face sheets of the graded porous sandwich plate (FGSP) are supposed to vary regularly and continuously in the direction of thickness according to the trigonometric volume fraction's model. The corresponding equilibrium equations of FGSPs with simply supported edges are derived via the static version of the Hamilton's principle. The differential equations of the system are resolved via Navier's method for various schemes of FGSPs. The current study examine the impact of the material index, porosity, side-to-thickness ratio, aspect ratio, and the Winkler-Pasternak foundation on the displacements, axial and shear stresses of the sandwich structure.

• Geomechanics and Engineering
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• v.31 no.4
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• pp.365-373
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• 2022

In order to investigate the damage evolution law of rock specimens under cyclic loading, cyclic loading tests under constant loads with different amplitudes were carried out on limestone specimens with high strength and brittleness values using acoustic emission (AE) technology and the energy evolution and AE characteristics were evaluated. Based on dissipated energy density and AE counts, the damage variable of specimen was characterized and two damage evolution processes were analyzed and compared. The obtained results showed that the change of AE counts was closely related to radial deformation. Higher cyclic loading values result in more significant radial strain of limestone specimen and larger accumulative AE counts of cyclic loading segment, which indicated Felicity effect. Regarding dissipated energy density, the damage of limestone specimen was defined without considering the influence of radial deformation, which made the damage value of cyclic loading segment higher at lower amplitude loads. The damage of cyclic loading segment was increased with the magnitude of load. When dissipated energy density was applied to define damage, the damage value at unloading segment was smaller than that of AE counts. Under higher cyclic loading values, rocks show obvious damage during both loading and unloading processes. Therefore, during deep rock excavation, the damages caused by the deformation recovery of unloading rocks could not be ignored when considering the damage caused by abutment pressure.

• Korean Journal of Construction Engineering and Management
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• v.24 no.6
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• pp.36-44
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• 2023

The aim of this study is to predict the potential for bid-rigging among public construction bidders and develop preventive and responsive measures. By employing the Fraud Triangle Theory (FTT), which considers the factors of opportunity, pressure, and rationalization, we analyze and explore the bid-rigging potential among construction industry professionals. A survey is conducted among General and specialized construction firms to validate the FTT research model and predict individual bid-rigging tendencies. The results indicate that higher levels of pressure, greater opportunities, and stronger rationalization increase the likelihood of individual bid-rigging. Moreover, more opportunities and stronger rationalization also raise the potential for bid-rigging by others. Understanding these dynamics enhances our knowledge and contributes to the development of policies aimed at preventing bid-rigging.

• The Journal of the Convergence on Culture Technology
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• v.9 no.5
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• pp.105-110
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• 2023

This article attempts to analyze John Greenleaf Whittier's anti-slavery poems. As a Quaker, he criticizes and satirizes the rife slavery in the mid nineteenth century. His thoughts are based on his religious belief. "The Farewell of a Virginia Slave Mother" depicts the mother who lost daughter for she was sold to the South. The harsh state of the corrupt South is described. In "Massachusettes to Virginia," the speaker, deploring the moral corruption of Virginia, denounces any attempt to return slaves to slave states. With a moonrise as a socio-political symbol, "Arisen at Last" celebrates the passage of law to protect fugitive slaves. Written after the Civil War, "The Peace Autumn" celebrates the peaceful situation in which Emancipation was declared. His efforts contributed to the abolitionist literature.

• Journal of Korean Society of Rural Planning
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• v.29 no.4
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• pp.27-34
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• 2023

Recently, worldwide to respond to climate change and secure sustainability. Korea aimed to increase water use efficiency by implementing integrated management according to the water management unification policy. Therefore, the necessity of establishing and operating governance is expanding to ensure the sustainability of agricultural water. In this study aims to evaluate the importance of agricultural water governance components and provide essential data for the participation of stakeholders in the efficient use of agricultural water in Korea. For this study, a total of 19 respondents to the ANP survey for this study were composed of experts in agricultural water and governance in Korea. As a result, the ranking for the main components was in the order of law, policy, and systems(0.222), core subjects(0.191), information sharing and communication(0.180), budget support(0.178), mutual learning(0.124), and external experts(0.105). The most important components for the operation of agricultural water governance are laws, policies, and systems. Since Korea's agricultural water management is a public management system, national standards are considered the first priority. This study, which is the purpose of the agricultural water governance model, evaluated the importance of the constituent components for participating in demand management with a sense of responsibility. Moreover, if agricultural water governance is expanded nationwide by reflecting agricultural and water resource policies in the future, it is believed that positive effects can be achieved in increasing utilization efficiency and securing sustainability through agricultural water saving.

• Korea Trade Review
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• v.46 no.3
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• pp.185-201
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• 2021

This paper analyzes the penalty tax system under the Customs Act of Korea and examines whether the penalty tax provision violate the constitutional principle of proportionality when imposed on a person who does not made import declaration intentionally or travelers who has not been made an import declaration of their carry-on items. It examines the provisions that adopt a penalty tax as a means to secure the effectiveness of the customs law. In relation to penalty tax, the case studies of the Supreme Court and Constitutional Court of Korea are analyzed by major issues such as the legal nature of the penalty tax, whether the penalty tax is unconstitutional, and the reasons for exemption from the penalty tax. There is no reasonable basis for the high penalty tax imposed on travelers' carry-on items for which import declaration has not been made. It is necessary to unify the penalty tax imposed when an import declaration is not made and the penalty tax on traveler's carry-on items. It is necessary to establish a limit on penalty tax and to create new regulations to exempt or reduce penalty tax when punished by administrative punishment to avoid double jeopardy. It is necessary to effectively secure the effectiveness of the Customs Act by converting the penalty tax into civil penalty that does not presuppose the faithful and accurate performance of tax obligations by the taxpayer. The government revised the penalty tax system in the Customs Act in 2019, but there are still many types of penalty tax and there are elements that are unconstitutional. It seems that the Korean government should lower the burden on the people by improving the system for the penalty tax system.

• Computers and Concrete
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• v.33 no.1
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• pp.27-39
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• 2024

In this study, the authors investigate the free vibration behavior of three-phases functionally graded sandwich plates using a novel nth-order shear deformation theory. These plates are composed of a homogeneous core and two face-sheet layers made of different functionally graded materials. This is the novel type of the sandwich structures that can be applied in many fields of mechanical engineering and industrial. The proposed theory only requires four unknown displacement functions, and the transverse displacement does not need to be separated into bending and shear parts, simplifying the theory. One noteworthy feature of the proposed theory is its ability to capture the parabolic distribution of transverse shear strains and stresses throughout the plate's thickness while ensuring zero values on the two free surfaces. By eliminating the need for shear correction factors, the theory further enhances computational efficiency. Equations of motion are established using Hamilton's principle and solved via Navier's solution. The accuracy and efficiency of the proposed theory are verified by comparing results with available solutions. The authors then use the proposed theory to investigate the free vibration characteristics of three-phases functionally graded sandwich plates, considering the effects of parameters such as aspect ratio, side-to-thickness ratio, skin-core-skin thicknesses, and power-law indexes. Through careful analysis of the free vibration behavior of three-phases functionally graded sandwich plates, the work highlighted the significant roles played by individual material ingredients in influencing their frequencies.

• Korean Journal of Construction Engineering and Management
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• v.25 no.1
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• pp.23-31
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• 2024

This study highlights the importance of understanding the fair bidding behavior of bid practitioners in order to eliminate bid-rigging, which has a detrimental impact on the construction industry and the overall economy. The research collected survey data from bid practitioners in the Daegu and Gyeongbuk regions of South Korea and analyzed the causal relationships between attitudes towards bid-rigging, subjective norms, perceived behavioral control, and the intention to engage in fair bidding using PLS-SEM analysis. The analysis results confirm that attitudes towards bid-rigging and perceived behavioral control are significant variables predicting the intention to engage in fair bidding among bid practitioners. This indicates that bid practitioners' perceptions of bid-rigging and personal behavioral control influence their willingness and actions towards fair bidding. The insights gained from this research provide valuable insights into bid practitioners' behavioral changes and can aid in the development of policies and measures to promote fair bidding and prevent bid-rigging.

• Structural Engineering and Mechanics
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• v.90 no.1
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• pp.19-26
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• 2024

In recent years, an increasing number of experimental studies have shown that the practical application of mature active control systems requires consideration of robustness criteria in the design process, including the reduction of tracking errors, operational resistance to external disturbances, and measurement noise, as well as robustness and stability. Good uncertainty prediction is thus proposed to solve problems caused by poor parameter selection and to remove the effects of dynamic coupling between degrees of freedom (DOF) in nonlinear systems. To overcome the stability problem, this study develops an advanced adaptive predictive fuzzy controller, which not only solves the programming problem of determining system stability but also uses the law of linear matrix inequality (LMI) to modify the fuzzy problem. The following parameters are used to manipulate the fuzzy controller of the robotic system to improve its control performance. The simulations for system uncertainty in the controller design emphasized the use of acceleration feedback for practical reasons. The simulation results also show that the proposed H∞ controller has excellent performance and reliability, and the effectiveness of the LMI-based method is also recognized. Therefore, this dynamic control method is suitable for seismic protection of civil buildings. The objectives of this document are access to adequate, safe, and affordable housing and basic services, promotion of inclusive and sustainable urbanization, implementation of sustainable disaster-resilient construction, sustainable planning, and sustainable management of human settlements. Simulation results of linear and non-linear structures demonstrate the ability of this method to identify structures and their changes due to damage. Therefore, with the continuous development of artificial intelligence and fuzzy theory, it seems that this goal will be achieved in the near future.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.95-104
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• 2006

The presence of cavitations under pavements or behind tunnel linings of concrete is likely to result in collapse. One method of detecting such voids by non-destructive means is low frequency type radar(GPR). By the way, the size and thickness of small cavitation can't be detected by the present radar technology with low frequency and low resolution when it apply to civil structures like that. To overcome these problems and limitations, this study aims to develope and propose a new analysis method for estimating the depth, cross-sectional size and thickness of cavitations using low frequency radar. A new proposed method is based on the experiments that are carried out for analyzing the correlation between the measurement values(the amplitudes of radar return) of low frequency radar and various type of cavitations. In this process, the threshold value for radar image processing which aims to represent only cavitations to be fitted size can be obtained. As the results, it is clarified that a proposed method has a possibility of estimating cavitation depth, size and thickness with good accuracy in laboratory scale.