• Geomechanics and Engineering
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• v.12 no.2
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• pp.313-326
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• 2017

Based on the reliability theory and limit analysis method, the roof stability of a shallow tunnel is investigated under the condition of surface settlement. Nonlinear Hoek-Brown failure criterion is adopted in the present analysis. With the consideration of surface settlement, the internal energy and external work are calculated. Equating the rate of energy dissipation to the external rate of work, the expression of support pressure is derived. With the help of variational approach, a performance function is proposed to reliability analysis. Improved response surface method is used to calculate the Hasofer-Lind reliability index and the failure probability. In order to assess the validity of the present results, Monte-Carlo simulation is performed to examine the correctness. Sensitivity analysis is used to estimate the influence of different variables on reliability index. Among random variables, the unit weight significantly affects the reliability index. It is found that the greater coefficient of variation of variables lead to the higher failure probability. On the basis of the discussions, the reliability-based design is achieved to calculate the required tunnel support pressure under different situations when the target reliability index is obtained.

• Steel and Composite Structures
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• v.14 no.1
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• pp.85-104
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• 2013

The present work deals with the thermomechanical bending response of functionally graded plates resting on Winkler-Pasternak elastic foundations. Theoretical formulations are based on a recently developed refined trigonometric shear deformation theory (RTSDT). The theory accounts for trigonometric distribution of transverse shear stress, and satisfies the free transverse shear stress conditions on the top and bottom surfaces of the plate without using shear correction factor. Unlike the conventional trigonometric shear deformation theory, the present refined trigonometric shear deformation theory contains only four unknowns as against five in case of other shear deformation theories. The material properties of the functionally graded plates are assumed to vary continuously through the thickness, according to a simple power law distribution of the volume fraction of the constituents. The elastic foundation is modelled as two-parameter Pasternak foundation. The results of the shear deformation theories are compared together. Numerical examples cover the effects of the gradient index, plate aspect ratio, side-to-thickness ratio and elastic foundation parameters on the thermomechanical behavior of functionally graded plates. It can be concluded that the proposed theory is accurate and efficient in predicting the thermomechanical bending response of functionally graded plates.

• Structural Engineering and Mechanics
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• v.60 no.3
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• pp.489-505
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• 2016

Sinusoidal shear deformation theory (SSDT) is developed here for dynamic buckling of functionally graded (FG) nano-plates. The material properties of plate are assumed to vary according to power law distribution of the volume fraction of the constituents. In order to present a realistic model, the structural damping of nano-structure is considered using Kelvin-Voigt model. The surrounding elastic medium is modeled with a novel foundation namely as orthotropic visco-Pasternak medium. Size effects are incorporated based on Eringen'n nonlocal theory. Equations of motion are derived from the Hamilton's principle. The differential quadrature method (DQM) in conjunction with Bolotin method is applied for obtaining the dynamic instability region (DIR). The detailed parametric study is conducted, focusing on the combined effects of the nonlocal parameter, orthotropic visco-Pasternak foundation, power index of FG plate, structural damping and boundary conditions on the dynamic instability of system. The results are compared with those of first order shear deformation theory and higher-order shear deformation theory. It can be concluded that the proposed theory is accurate and efficient in predicting the dynamic buckling responses of system.

• Structural Engineering and Mechanics
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• v.61 no.6
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• pp.721-736
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• 2017

In this paper, free vibration characteristics of functionally graded (FG) nanobeams embedded on elastic medium are investigated based on third order shear deformation (Reddy) beam theory by presenting a Navier type solution for the first time. The material properties of FG nanobeam are assumed to vary gradually along the thickness and are estimated through the power-law and Mori-Tanaka models. A two parameters elastic foundation including the linear Winkler springs along with the Pasternak shear layer is in contact with beam. The small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. The nonlocal equations of motion are derived based on third order shear deformation beam theory through Hamilton's principle and they are solved applying analytical solution. According to the numerical results, it is revealed that the proposed modeling can provide accurate frequency results of the FG nanobeams as compared to some cases in the literature. The obtained results are presented for the vibration analysis of the FG nanobeams such as the influences of foundation parameters, gradient index, nonlocal parameter and slenderness ratio in detail.

• Advances in nano research
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• v.16 no.3
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• pp.313-324
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• 2024

The main aims of this study are to develop a new nonlocal quasi-3D theory for the free vibration behaviors of the functionally graded sandwich nanobeams. The sandwich beams consist of a ceramic core and two functionally graded material layers resting on elastic foundations. The two layers, linear spring stiffness and shear layer, are used to model the effects of the elastic foundations. The size-effect is considered using nonlocal elasticity theory. The governing equations of the motion of the functionally graded sandwich nanobeams are obtained via Hamilton's principle in combination with nonlocal elasticity theory. Then the Navier's solution technique is used to solve the governing equations of the motion to achieve the nonlocal free vibration behaviors of the nanobeams. A deep parametric study is also provided to demonstrate the effects of some parameters, such as length-to-height ratio, power-law index, nonlocal parameter, and two parameters of the elastic foundation, on the free vibration behaviors of the functionally graded sandwich nanobeams.

• Journal of Korean Library and Information Science Society
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• v.2
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• pp.23-59
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• 1975

Indexes has not devcloped as an independent branch in library science from the beginning, but it has gradually evolved in a clo~eas sociation with catalog and under the direct influence of the development of publishing pro cesses and of the rapid social changes. Historically, index in the West can be traced back to eariler concordance. On the other hand, index in the Bast does not show a continuous development. It started with book catnlog, but other types of indexing were later 'adopted from the West. Indexing in the West and in the East can be summarized as follows: 1) In the West, Taylor considers Gesner's Pandectae was the first index but the Concordance of the Bible in 1247 was the first true index. Indexing method was first established later in 1545 in Gesner's Partitiones which appeared in three volumes. Classified index appeared after Partitions, but alphabetically ordered index was not developed until th eseventeenth century. The pxiodical index of La France S~auante in 1683 proved -its value, and Poole's An Alphabetical Index in the nineteenth century became the turning point in the development of indexing. After Poole's Index appeared periodical index and book catalog gradually began to be treated separately, and subject index and cross reference were incorporated into indexing. Also dictionary arrangement of the indexed items was adopted in the second half of the nincteenth, century after Charles A. Cutter developed his theory of rules for dictionary catalog and systematic studies of indexing were carried out by many scholars. In the twentieth century, index was mainly developed in the United States of America, especially by Wilson publishing Company. The general trend is to move away from the gcncral index to subject index. Also the ncwspapcr indcx such as The Times I~zdcx is 21 landmark in the history cf indcxing. 2) In China, thcs arc somc cvidcnccs that $Bizgluh(&), $ was the first indcx, but unforlunatcly the book itsclf has not been found as yet.

• The KIPS Transactions:PartB
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• v.19B no.4
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• pp.231-236
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• 2012

According to consumer behavior theory, human propensity can be divided into two regulatory focus types: promotion and prevention. These two types have much influence on the consumer's decision in many diverse areas. In this research, we apply regulatory focus theory to personalized recommendation to minimize the cold start problem and to improve the performance of recommendation algorithms. To achieve this goal, we extract the consumer behavior variables and information exploration activity index from web shopping logs. We then use them for classifying regulatory focus of the consumer. This research has the contribution to show the possibility of systematization of consumer behavior theory as an interdisciplinary research tool of social science and information technology. Based on this attempt, we will extend the research to IT services adapting theories on other areas.

• Korea Real Estate Review
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• v.27 no.1
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• pp.7-16
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• 2017

In this study, we examine whether there are prospect theory investment patterns for individual investors in the real estate market. We use the maximum potential profit rate and the maximum potential loss rate of individual investors as a research method and additionally analyze it using the Jeong and Park(2015) model. As a result of the analysis, it was found that the investment pattern according to the prospect theory and disposition effect for individual investors. And we find the difference between zoning areas. This difference in investment behavior is believed to be due to the purpose of the real estate and the existence of rent fee, which creates a difference in investment behavior depending on the purpose. The limitations of this study are the analysis measurement of potential profit and potential loss using the land price index like the study of jeong and Park(2015). This implies that a new property price index needs to be developed or a benchmark for real estate assets is needed for deeper study of real estate investment sentiment.

• Journal of KSNVE
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• v.8 no.5
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• pp.821-831
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• 1998

The actual ground vibrations due to NATM and foundation blasting at Seoul(weathered rock), Pusan(weathered rock) and Youngkwang(quartz andesite) have been measured, and the data were analyzed using reliability index($\beta$) to determinate the vibration equations and the maximum charge weight for efficient blast. These were suggested with the division of ultimate limit state($\beta$=0), serviceability limit state($\beta$=1.28) and safety state($\beta$=3), respectively. The reliability index 0 mean 50% data line obtained by the least squares best-fit line. The reliability index 1.28 and 3 represent bounds below 90% and 99.9% of the data, respectively. In this study, reliability index $\beta$=1.28 with security and economy was suggested. The maximum charge weight equations for efficient blast were obtained in W=(Vc/384.90)1.5151.D3(Seoul), W=(Vc/579.82)1.4706.D3(Pusan). W=(Vc/1654.01)1.3456.D3(Youngkwang), and the blast vibration equatiions in V=385(SD)-1.98(Seoul), V=580(SD)-2.04(Pusan), V=1654(SD)-2.23(Youngkwang), respectively. From this study, inference and analysis methods of vibration equations using reliability theory were established.

• Journal of Korean Society on Water Environment
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• v.22 no.1
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• pp.140-144
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• 2006

This study was performed to investigate the effect of organic characteristics and feed water solution chemistry on membrane fouling index such as Silt Density Index (SDI) and Modified Fouling Index (MFI). Specifically, Aldrich humic acids (AHA) and Suwannee river humic acids (SHA) were used in SDI/MFI experiments. Higher SDI values were observed with increasing organic concentration. AHA with larger molecular weight (MW) and SUVA (${\approx}UV_{254}/TOC$) resulted in higher SDI values, compared to SHA. The feed solution chemistry (i.e, pH, ionic strength, and hardness) also affects SDI values to some degree. In particular, SDI increased with increasing hardness ($Ca^{2+}$) concentration for AHA. Unlike SDI, the MFI developed on the basis of particle cake filtration theory, was not accurately assessed due to internal fouling by organics such as pore adsorption and subsequent pore blocking.