• Journal of the Korean earth science society
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• v.40 no.4
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• pp.353-381
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• 2019

The general world model for homogeneous and isotropic universe has been proposed. For this purpose, we introduce a global and fiducial system of reference (world reference frame) constructed on a (4+1)-dimensional space-time, and assume that the universe is spatially a 3-dimensional hypersurface embedded in the 4-dimensional space. The simultaneity for the entire universe has been specified by the global time coordinate. We define the line element as the separation between two neighboring events on the expanding universe that are distinct in space and time, as viewed in the world reference frame. The information that determines the kinematics of the geometry of the universe such as size and expansion rate has been included in the new metric. The Einstein's field equations with the new metric imply that closed, flat, and open universes are filled with positive, zero, and negative energy, respectively. The curvature of the universe is determined by the sign of mean energy density. We have demonstrated that the flat universe is empty and stationary, equivalent to the Minkowski space-time, and that the universe with positive energy density is always spatially closed and finite. In the closed universe, the proper time of a comoving observer does not elapse uniformly as judged in the world reference frame, in which both cosmic expansion and time-varying light speeds cannot exceed the limiting speed of the special relativity. We have also reconstructed cosmic evolution histories of the closed world models that are consistent with recent astronomical observations, and derived useful formulas such as energy-momentum relation of particles, redshift, total energy in the universe, cosmic distance and time scales, and so forth. The notable feature of the spatially closed universe is that the universe started from a non-singular point in the sense that physical quantities have finite values at the initial time as judged in the world reference frame. It has also been shown that the inflation with positive acceleration at the earliest epoch is improbable.

• Advances in nano research
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• v.10 no.4
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• pp.359-371
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• 2021

A tumor immune interaction is a main topic of interest in the last couple of decades because majority of human population suffered by tumor, formed by the abnormal growth of cells and is continuously interacted with the immune system. Because of its wide range of applications, many researchers have modeled this tumor immune interaction in the form of ordinary, delay and fractional order differential equations as the majority of biological models have a long range temporal memory. So in the present work, tumor immune interaction in fractional form provides an excellent tool for the description of memory and hereditary properties of inter and intra cells. So the interaction between effector-cells, tumor cells and interleukin-2 (IL-2) are modeled by using the definition of Caputo fractional order derivative that provides the system with long-time memory and gives extra degree of freedom. Moreover, in order to achieve more efficient computational results of fractional-order system, a discretization process is performed to obtain its discrete counterpart. Furthermore, existence and local stability of fixed points are investigated for discrete model. Moreover, it is proved that two types of bifurcations such as Neimark-Sacker and flip bifurcations are studied. Finally, numerical examples are presented to support our analytical results.

• Journal of Korea Society of Industrial Information Systems
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• v.25 no.6
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• pp.143-158
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• 2020

This study examines the effect of VMD (Visual merchandising) of unmanned stores and the affordance of unmanned systems on a customer's value and intention of revisit. The proposed research model and developed hypotheses were tested using structural equations modeling based on data collected from 297 customers with experience in unmanned stores. The results of the study confirm the positive effects of the unmanned system's affordance and unmanned stores' VMD on customer value. In addition, there is a positive relationship between a customer's value and intention of revisit. The study provides valuable insights into the sustainability of unmanned stores after post-COVID 19 and the importance of developing unmanned stores' VMD and affordance.

• Steel and Composite Structures
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• v.39 no.5
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• pp.631-643
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• 2021

The aim of this work is to study the hygro-thermo-mechanical bending responses of simply supported FG plate resting on a Winkler-Pasternak elastic foundation. The effect transverse shear strains is taken into account in which the zero transverse shear stress condition on the top and bottom surfaces of the plate is ensured without using any shear correction factors. The developed model contains only four unknowns variable which is reduced compared to other HSDTs models. The material properties of FG-plate are supposed to vary across the thickness of the plate according to power-law mixture. The differential governing equations are derived based on the virtual working principle. Numerical outcomes of bending analysis of FG plates under hygro-thermo-mechanical loads are performed and compared with those available in the literature. The effects of the temperature, moisture concentration, elastic foundation parameters, shear deformation, geometrical parameters, and power-law-index on the dimensionless deflections, axial and transverse shear stresses of the FG-plate are presented and discussed.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.379-386
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• 2020

The present study examined the effect of bottom ash aggregate contents on the compressive strength gain and mechanical properties(modulus of elasticity and rupture and splitting tensile strength) of concrete. Main test parameters were water-to-cement ratio and bottom ash aggregate contents for replacement of natural sand. Test results showed that the 28-days compressive strength of concrete and mechanical properties normalized by the compressive strength tended to decrease with the increase in bottom ash fine aggregate content. When compared with fib 2010 model equations, bottom ash aggregate concrete exhibited the following performances: lower rates of compressive strength gain at early ages but greater rates at long-term ages; slightly higher measurements for modulus of elasticity and rupture; and lower measurements for splitting tensile strength.

• Steel and Composite Structures
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• v.37 no.6
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• pp.711-731
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• 2020

This paper deals with free vibration of FG sandwich annular sector plates on Pasternak elastic foundation with different boundary conditions, based on the three-dimensional theory of elasticity. The plates with simply supported radial edges and arbitrary boundary conditions on their circular edges are considered. The influence of carbon nanotubes (CNTs) waviness, aspect ratio, internal pores and graphene platelets (GPLs) on the vibrational behavior of functionally graded nanocomposite sandwich plates is investigated in this research work. The distributions of CNTs are considered functionally graded (FG) or uniform along the thickness of upper and bottom layers of the sandwich sectorial plates and their mechanical properties are estimated by an extended rule of mixture. In this study, the classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. The core of structure is porous and the internal pores and graphene platelets (GPLs) are distributed in the matrix of core either uniformly or non-uniformly according to three different patterns. The elastic properties of the nanocomposite are obtained by employing Halpin-Tsai micromechanics model. A semi-analytic approach composed of 2D-Generalized Differential Quadrature Method (2D-GDQM) and series solution is adopted to solve the equations of motion. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. Some new results for the natural frequencies of the plate are prepared, which include the effects of elastic coefficients of foundation, boundary conditions, material and geometrical parameters. The new results can be used as benchmark solutions for future researches.

• Journal of Korea Water Resources Association
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• v.54 no.8
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• pp.607-616
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• 2021

The purpose of this study is to simulate the transport of nonuniform sediment considering the hiding-exposure effect numerically. In order to calculate the transport of multi-disperse suspended sediment mixtures, the set of advection-diffusion equations for each particle class is solved. The applicability of the numerical model is examined by comparing the simulation results with experimental data. In this study, we calculate the vertical distribution of total concentration of sediment particles using two approaches: (1) by considering the mixture as represented by a single size; and (2) by combining the concentration of the sediment corresponding to several particle size classes; From the simulation results, it is shown that both approaches calculate reasonable results due to the narrow range of size distribution. Under the condition of nonuniform sediment, the critical shear stress of the sediment particle is influenced by the size-selective entrainment, i.e., hiding-exposure effect. It is shown in this study that the effect of hiding-exposure effect on the erosion rates of fine sand is negligibly small.

• Journal of Korea Society of Industrial Information Systems
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• v.27 no.5
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• pp.99-117
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• 2022

This study examines the effect of customer experience management capability of a bank and job satisfaction and customer orientation of the frontline employee in bank. The proposed research model and developed hypotheses were tested using structural equations modeling based on data collected from 321 employees working in banks. The results of the study confirm the positive effects of employee training, employee empowerment, employee evaluation, cross functional work of customer experience management capability is job satisfaction and customer orientation. But channel integration is not supported job satisfaction and customer orientation. Performance management influenced customer orientation through job satisfaction. The study provides On a theoretical level valuable insights into the customer experience management competency at the organizational unit and but there is also a limitation that firms the is limited.

• Journal of Korea Society of Industrial Information Systems
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• v.27 no.2
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• pp.143-161
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• 2022

This study examines the effect of used trading app's consumption value and protection motivation and the perceived usefulness and continuous use intention. The proposed research model and developed hypotheses were tested using structural equations modeling based on data collected from 293 customers with experience in used transaction app's. The results of the study confirm the positive effects of the used trading app's consumption value and protection motive theory is perceived usefulness of customer. In addition, there is a positive relationship between a customer's perceived usefulness and continuous use intention of used trading app's. The study provides On a theoretical level valuable insights into the sustainability of transaction app's after post-COVID 19 and the importance of developing used trading app's consumption value and protection motivation, but there is also a limitation that the region is limited.

• The Journal of Asian Finance, Economics and Business
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• v.9 no.2
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• pp.61-69
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• 2022

The study intends to investigate a short-run and a long-run causality among money, income, and prices in the Keynesian and Monetarists framework. This study emphasizes the importance of unrecorded money, which exists alongside legal monetary assets and plays a dual function in determining economic prosperity. The underground economy, which is a hidden component of aggregate economic activity, is determined using Tanzi's monetary approach (Tanzi, 1980). This research uses a time series of annual data from 1990 to 2019 for this purpose. The data is extracted from the World Bank database for the monetary and development indicators. The study keeping in view the trending nature in data follows a unit root testing followed by the Autoregressive Distributive Lag Model (ARDL) to assess the long and short-run dynamics of causality among the variables. In both the pricing and income equations, the study finds a significant level link among the variables; however, there is no evidence of the presence of a level association in the money equation. The short-run causal relationship provides evidence of bi-directional causation between the supply of money and national income. The outcome of this study advise that though the view point of both the Monetarist and Keynesian school holds in both short and long run, however, in Pakistan only the Monetarists' role of money supply and income holds in Pakistan. This evidence would be of precise interest to the policy-makers.