• Structural Engineering and Mechanics
• /
• v.89 no.3
• /
• pp.225-238
• /
• 2024

In this paper, a quasi-3D hyperbolic shear deformation theory for the bending responses of a functionally graded (FG) porous micro-beam is based on a modified couple stress theory requiring only one material length scale parameter that can capture the size influence. The model proposed accounts for both shear and normal deformation effects through an illustrative variation of all displacements across the thickness and satisfies the zero traction boundary conditions on the top and bottom surfaces of the micro-beam. The effective material properties of the functionally graded micro-beam are assumed to vary in the thickness direction and are estimated using the homogenization method of power law distribution, which is modified to approximate the porous material properties with even and uneven distributions of porosity phases. The equilibrium equations are obtained using the virtual work principle and solved using Navier's technique. The validity of the derived formulation is established by comparing it with the ones available in the literature. Numerical examples are presented to investigate the influences of the power law index, material length scale parameter, beam thickness, and shear and normal deformation effects on the mechanical characteristics of the FG micro-beam. The results demonstrate that the inclusion of the size effects increases the microbeams stiffness, which consequently leads to a reduction in deflections. In contrast, the shear and normal deformation effects are just the opposite.

• Structural Engineering and Mechanics
• /
• v.62 no.1
• /
• pp.113-123
• /
• 2017

The bi-material elastic system consisting of the circular hollow cylinder and the infinite elastic medium surrounding this cylinder is considered and it is assumed that on the inner free face of the cylinder a point-located axisymmetric time harmonic force, with respect to the cylinder's axis and which is uniformly distributed in the circumferential direction, acts. The shear-spring type imperfect contact conditions on the interface between the constituents are satisfied. The mathematical formulation of the problem is made within the scope of the exact equations of linear elastodynamics. The focus is on the frequency-response of the interface normal and shear stresses and the influence of the problem parameters, such as the ratio of modulus of elasticity, the ratio of the cylinder thickness to the cylinder radius, and the shear-spring type parameter which characterizes the degree of the contact imperfectness, on these responses. Corresponding numerical results are presented and discussed. In particular, it is established that the character of the influence of the contact imperfection on the frequency response of the interface stresses depends on the values of the vibration frequency of the external forces.

• The Journal of Engineering Geology
• /
• v.3 no.3
• /
• pp.267-278
• /
• 1993

Ground-water temperature is one of the parameters for observing diarges in the state of the ground-water regime in time and space, which relate to conditions for recharge as well as the influence of various natural and man-induced fadors on the regime. Because ground-water satura tes much of the rock materiats in the upper layer of the earth's csust the water temperature reflects in part the temperature of the water-bearing rocks. The mobffity and thennal capadty of groud-waters, however, serves to redistribute some of the heat within the stratosphere and to influence the developement of the geothermal regime within this sphere. The utilization of temperature data of the study area(25 points) in the solution of hydrogeologic problems requires an understanding of some of the fundamental aspects of subsurtice temperatures. These include the depth of penetration of heat waves generated of the surtace, the rate of propagation of the waves, and the geothermal gradient in the study area of Taegu.

• Structural Engineering and Mechanics
• /
• v.74 no.6
• /
• pp.809-819
• /
• 2020

For the first time, the influence of in-plane magnetic field on wave propagation of Graphene Nano-Platelets (GNPs) polymer composite nanoplates is investigated here. The impact of three- parameter Kerr foundation is also considered. There are two different reinforcement distribution patterns (i.e. uniformly and non-uniformly) while the material properties of the nanoplate are estimated through the Halpin-Tsai model and a rule of mixture. To consider the size-dependent behavior of the structure, Eringen Nonlocal Differential Model (ENDM) is utilized. The equations of wave motion derived based on a higher-order shear deformation refined theory through Hamilton's principle and an analytical technique depending on Taylor series utilized to find the wave frequency as well as phase velocity of the GNPs reinforced nanoplates. A parametric investigation is performed to determine the influence of essential phenomena, such as the nonlocality, GNPs conditions, Kerr foundation parameters, and wave number on the both longitudinal and flexural wave characteristics of GNPs reinforced nanoplates.

• Environmental Engineering Research
• /
• v.19 no.1
• /
• pp.31-36
• /
• 2014

In this study, the influence of the control and operational parameters within a sewage treatment plant were reviewed by performing multiple regression analysis on the effluent quality of the sewage treatment. The data used for this review are based on the actual data from a sewage treatment plant using the media process within the year 2012. The prediction models of chemical oxygen demand ($COD_{Mn}$) and total nitrogen (T-N) within the effluent of the 2nd settling tank based on the multiple regression analysis yielded the prediction accuracy measurements of 0.93 and 0.84, respectively; and it was concluded that the model was accurately predicting the variances of the actual observed values. If the data on the energy spent on each operating condition can be collected, then the operating parameter that conserves energy without violating the effluent quality standards of COD and T-N can be determined using the regression model and the standardized regression coefficients. These results can provide appropriate operation guidelines to conserve energy to the operators at sewage treatment plants that consume a lot of energy.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.23 no.4
• /
• pp.280-286
• /
• 2010

We have investigated the influence of rapid thermal annealing (RTA) temperature on properties of Al-doped zinc oxide (AZO) thin films deposited on glass substrate by using radio-frequency magnetron sputtering. The RTA is performed in a nitrogen ambient in the temperature range from 300 to $600^{\circ}C$ for 1 minute in a rapid thermal annealer after growing the AZO thin films. The crystallographic structure and the surface morphology of AZO thin film are measured by using X-ray diffraction, and atomic force microscopy and scanning electron microscopy, respectively. The optical transmittance of the deposited thin films is examined in the wavelength range of 300-1100 nm, where the average transmittance is above the 90% in the visible and near-infrared regions. The optical bandgap is calculated from the Tauc's model, and it shows a significant dependence on the RTA temperature. As for the electrical properties of the thin films, the AZO thin film annealed at $400^{\circ}C$ shows the lowest electrical resistivity of $8.6{\times}10^{-3}{\Omega}cm$ and the Hall mobility of $11.3cm^2$/V-sec. These results suggest that the RTA temperature is an important parameter to influence on the structural, electrical, and optical properties of AZO thin films.

• Wind and Structures
• /
• v.24 no.1
• /
• pp.79-93
• /
• 2017

Wind-induced fluctuating internal pressures in a building with a dominant opening can be described by a second-order non-linear differential equation. However, the accuracy and efficiency of the governing equation in predicting internal pressure fluctuations depend upon two ill-defined parameters: inertial coefficient $C_I$ and loss coefficient $C_L$, since $C_I$ determines the un-damped oscillation frequency of an air slug at the opening, while $C_L$ controls the decay ratio of the fluctuating internal pressure. This study particularly focused on the value of loss coefficient and its influence factors including: opening configuration and location, internal volumes, as well as wind speed and approaching flow turbulence. A simplified formula was presented to predict loss coefficient, therefore an approximate relationship between the standard deviation of internal and external pressures can be estimated using Vickery's approach. The study shows that the loss coefficient governs the peak response of the internal pressure spectrum which, in turn, will directly influence the standard deviation of the fluctuating internal pressure. The approaching flow characteristic and opening location have a remarkable effect on the parameter $C_L$.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.23 no.1
• /
• pp.139-147
• /
• 2015

This paper is the second investigation on the evaluation methods of flow characteristics in a steady flow bench. In the previous work, several assumptions used in the steady flow bench were examined and it was concluded that the assumption of the solid rotation might cause serious problems. In this study, intake valve angle is selected as a main parameter for the assessment because the main flow direction to cylinder governed by this angle has the strongest influence on the in-cylinder flow pattern. For this purpose, four heads, which have the different angle, are prepared and the flow characteristics are estimated both by the conventional impulse swirl meter and a particle image velocimetry at 1.75 times bore position apart from the cylinder head, which is widely used plane in the steady flow measurement. The results show that both of the eccentricity and the velocity profile distort the flow characteristics when using the ISM at 1.75 plane, however, the effects of two factors act in the opposite direction. In addition, the profile's influence is much greater than that of the eccentricity.

• International Journal of Contents
• /
• v.14 no.2
• /
• pp.7-15
• /
• 2018

Online shopping is increasing worldwide. Providing customers actual feeling of the product is essential in online shopping. Various technological aids can be used to support visual feeling. When delivering visual tangibility, it is important to study which attributes are significant in product presentations that best portray the actual tactileness. In this perspective, we suggest 'visual tactility' (VT) as a parameter for delivering tangibility in visual presentation. By measuring visual tactility in different product types, latent factors of visual tactility were identified and their influence on purchase intention was determined in this study. We defined material properties of touch such as surface texture, hardness, temperature, and weight as Visual Tactility (VT), the influential factor of tactility. We investigated the influence of VT on product purchase intention and analyzed tactileness within four online product presentations: single static picture, multi static pictures, zoom, and video. Our purpose was to investigate underlying effects of visual tactile attributes on touch and determine their influences according to online product presentation formats. Our results showed that visual tactility positively affected purchase intention and that each attribute differed in importance according to product type. Moreover, this study revealed a strong relation between online product presentation and VT attributes. These results provide a guide when selecting which presentation is optimal for delivering a product's tactility in online shopping situation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07b
• /
• pp.985-988
• /
• 2004

The carrier lifetime of boron doped Cz silicon samples after light induced degradation could be improved by optimized rapid thermal processing (RTP). The important five different parameters varied in order to investigate which parameter is important for the stable lifetime after light induced degradation, $\tau_d$. The Plateau temperature and the Plateau time influenced on the lifetime after light induced degradation. Especially, the Plateau temperature showed a strong influence on the stable lifetime. The optimal plateau temperature is approximately $900^{\circ}C$ t for a plateau time of 120 s. The stable lifetime increased from $15\mu}s$ to $25.5{\mu}s$. The normalized defect concentration, $N_t^*$, decreased from $0.06{\mu}s^{-1}$ to $0.037{\mu}s^{-1}$ by RTP-process.