• Advances in nano research
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• v.17 no.3
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• pp.197-211
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• 2024

This work investigates the thermo-mechanical vibration frequencies of an embedded composite nano-beam restrained with elastic springs at both ends. Composite nanobeam consists of a matrix and short fibers as reinforcement elements placed inside the matrix. An approach based on Fourier sine series and Stokes' transform is adopted to present a general solution that can examine the elastic boundary conditions of the short-fiber-reinforced nanobeam considered with the Halpin-Tsai model. In addition to the elastic medium effect considered by the Winkler model, the size effect is also considered on the basis of nonlocal strain gradient theory. After creating an eigenvalue problem that includes all the mentioned parameters, this problem is solved to examine the effects of fiber and matrix properties, size parameters, Winkler stiffness and temperature change. The numerical results obtained at the end of the study show that increasing the rigidity of the Winkler foundation, the ratio of fiber length to diameter and the ratio of fiber Young's modulus to matrix Young's modulus increase the frequencies. However, thermal loads acting in the positive direction and an increase in the ratio of fiber mass density to matrix mass density lead to a decrease in frequencies. In this study, it is clear from the eigenvalue solution calculating the frequencies of thermally loaded embbeded short-fiber-reinforced nanobeams that changing the stiffness of the deformable springs provides frequency control while keeping the other properties of the nanobeam constant.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.490-495
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• 2000

This paper presents the dynamic behavior of stay cable with Lead-Shear damper( LSD) near the support. This kind of research about the dynamic behavior of LSD is essential to design LSD in order to mitigate the ambient vibration of stay cable. The hysteresis curve of LSD was assumed to be perfect elasto-plastic behavior based on the real hysteretic behavior of such lead-based dampers. Mechanical model of LSD was equivalent Kelvin model and sag effect of stay cable was considered. Yielding force (also referred as size) of LSD was selected as a design parameter. Effects of tension of stay cable and installation point of LSD were studied. It was found that optimal size of LSD exists for each case of stay cable.

• Advances in nano research
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• v.6 no.2
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• pp.93-112
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• 2018

An analytical solution of the buckling governing equations of functionally graded piezoelectric (FGP) nanobeams obtained by using a developed third-order shear deformation theory is presented. Electro-mechanical properties of FGP nanobeam are supposed to change continuously in the thickness direction based on power-law model. To capture the small size effects, Eringen's nonlocal elasticity theory is adopted. Employing Hamilton's principle, the nonlocal governing equations of a FG nanobeams made of piezoelectric materials are obtained and they are solved using Navier-type analytical solution. Results are provided to show the effect of different external electric voltage, power-law index, nonlocal parameter and slenderness ratio on the buckling loads of the size-dependent FGP nanobeams. The accuracy of the present model is verified by comparing it with nonlocal Timoshenko FG beams. So, this study makes the first attempt for analyzing buckling behavior of higher order shear deformable FGP nanobeams.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.2
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• pp.191-197
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• 2016

RCAR low speed impact test estimates repair cost of the impacted vehicle. In this study, for a mid-size vehicle front body model, structural performance for RCAR low speed impact were analyzed with changing the bumper stay shape and size. First, for improving the impact load transfer mechanism to side member the stay rear section shape at connecting area with side member was modified and the stay outer was redesigned to be normal to the barrier. Next, the investigation on stay thickness effect was carried out and the performances of several models with different forming shape were compared. The final design showed 13mm decrease in the maximum barrier intrusion distance and greatly reduced side member deformation. Additional analyses explained the validity of the final design.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.12
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• pp.5759-5763
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• 2012

I conducted structural model analysis which is considered the influence of "government policy and micro-enterprise manager's characteristics" on management performance through effective analysis on governmental policy for micro-enterprise funding, training and consulting support. This study results showed characteristics of micro-enterprise manager and government policy significant to management performance. In the structural model, significant independent variables are customer's accessibility, promotion availability, goods mobility, customer attractive ability, effectiveness of funding, size of supported training, and effectiveness of training and satisfaction of supported consulting size.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.2 no.1
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• pp.70-75
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• 1992

A model for a microstructural residual stress in a ferroelectric material is proposed. Based on this model, two facts are estimated. One of them is that the residual stress on a grain boundary is larger than that on a domain boundary. Another one is that the microstructural residual stress decrease with increasing grain size. These facts are confirmed by the microcrack morphology and the dependence of dielectric constant hysteresis between heating and cooling on grain size in $PbZr_{0.4}Ti_{0.6}O_3$ ceramics.

• Journal of the Korean Institute of Telematics and Electronics
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• v.18 no.6
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• pp.30-37
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• 1981

Numerical calculations have beee made of the effect of grain size on the three-dimensional carrier density, the quantum efficiency, and the AMI efficiency of 30$\mu$m polycrystalliue silicon p-n junction solar cells. Quantum efficiencies calculated for the polycrystalline silicon solar cells are compared to the monocrystalline cases. An efficiency of 12% can theoretically be obtained with grain size 100$\mu$m, and 6% for 5$\mu$m grains.

• Structural Engineering and Mechanics
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• v.60 no.4
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• pp.707-727
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• 2016

In this paper, thermal vibration of a nonlocal functionally graded (FG) plates with arbitrary boundary conditions under linear and non-linear temperature fields is explored by developing a refined shear deformation plate theory with an inverse cotangential function in which shear deformation effect was involved without the need for shear correction factors. The material properties of FG nanoplate are considered to be temperature-dependent and graded in the thickness direction according to the Mori-Tanaka model. On the basis of non-classical higher order plate model and Eringen's nonlocal elasticity theory, the small size influence was captured. Numerical examples show the importance of non-uniform thermal loadings, boundary conditions, gradient index, nonlocal parameter and aspect and side-to-thickness ratio on vibrational responses of size-dependent FG nanoplates.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.161-166
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• 2008

In general structures, cleavage fracture may develop under the low constraint condition of larger scale yielding with a shallow surface crack. However, standard procedures for fracture toughness testing require very severe restrictions of specimen geometry. So the standard fracture toughness data makes the integrity assessment irrationally conservative. In this paper, cleavage fracture toughness tests have been made on side-grooved PCVN (precracked charpy V-notch) type specimens (10 by 10 by 55 mm) with varying crack depth, The constraint effects on the crack depth ratios are quantitatively evaluated by scaling model and Weibull stress method using 3-D finite clement method, After correction of constraint loss due to shallow crack depths, the statistical size effect are also corrected according to the standard ASTM E 1921 procedure, The results snowed a good agreement in the geometry correction regardless of the crack size, while some over-corrections were observed in the corrected values of $T_0$.

• Journal of the Korean Operations Research and Management Science Society
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• v.22 no.1
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• pp.159-182
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• 1997

This study is to establish the validity of EDI adoption model Korean Companies. The research model is hypothesized in the external factors of company directly affect on EDI adoaption and the internal factors of company moderately affect on the direct effect. The external factors of company consists of economic factors, organizational power factors, and technological factor. The internal factors of company consists of the size of the company, innovative tendency of the top management, and maturity of the information technology. In the result of data analysis-the data were collected from a total of 81 companies in 6 industries adopted variables are the existence of EDI standard, transaction frequency, inter-organizational bargaining power, and pressure from industry association. Also size of the company and innovative tendency of the top management in a company's internal factors were adopted as moderate variables.