• Nuclear Engineering and Technology
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• v.56 no.4
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• pp.1296-1309
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• 2024

The aim of this work is to explore the effect of the double subdiffusion on the stability in BWRs. A BWR novel reduced order model with double subdiffusion effects: reduced order fractional model (DS-F-ROM) to describe the neutron and heat transfer processes was proposed for this study. The double subdiffusion was developed with a fractional-order two-equation model, and with different fractional-orders and relaxation times. The stability analysis was carried out using the root-locus method and change from the s to the W domain and were confirmed using the time-domain evolution of neutron flux for a unit step change in reactivity. The results obtained using the reduced fractional-order model are presented for different anomalous diffusion coefficient values. Results are compared with normal diffusion and P1 equations, which are obtained straightforwardly with DS-ROM when relaxation time tends to zero, and when the anomalous diffusion coefficient tends to one, respectively.

• Journal of the Korean Society of Costume
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• v.56 no.7 s.107
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• pp.46-57
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• 2006

The purpose of this study is to analyze whether perceived utilitarian value and service qualify have an effect on repurchase intention of fashion merchandise in internet shopping. A survey was conducted from June 20 to July 30 in 2003, among married women aged in their 20s and 30s, on their purchase experience of fashion merchandise from internet shopping malls. The survey was conducted over the internet with 306 subjects. The statistical analysis methods were frequency analysis, reliability analysis, factor analysis, and multiple regression analysis. The results of this study were as follows. 1. A married women aged in their 20s and 30s were shown to high-purchasing on nightgown, underwear, women's pants, casual wear through internet shopping. Their perceived utilitarian value had an effect on repurchase intention of fashion merchandise in internet shopping. 2. The service quality factors were determined to be site reliability, site reactivity, order assurance, order easy, site organization. Service quality factors of site reactivity, order assurance, order easy, site organization had an effect on repurchase intention of fashion merchandise in internet shopping.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.4
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• pp.127-133
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• 2008

As the application of the MEMS parts increases, the structural safety of MEMS appears importantly. A lot of MEMS parts are made by a multi-grain silicon wafer, which is an orthotropic material. Moreover directions of the materials on each grain are distributed randomly. The stress analysis for the multi-grain is important factor in order to apply the MEMS parts to industrial applications. The finite element method (FEM) is commonly used by a stress analysis method but the boundary element method (BEM) is known as the result of the BEM is more accurate than that of the FEM since the fundamental solution are used. In this study, we derived the boundary integration equation for the orthotropic material by applying fundamental solutions with complex variables. The multi-region analysis procedure for the BEM and the multi-grain generation procedure by a random process technique are developed in order to apply the analysis of the multi-grain orthotropic material. The discontinuous element is used in order to remove the comer problem in the BEM. The results of the present method are compared with those of the finite element method in order to verify the present procedure.

• Health Policy and Management
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• v.21 no.2
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• pp.263-278
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• 2011

As the competition among hospitals become intensified, hospital management is required to carry out more effective marketing and positioning of the hospital. Successful positioning of a hospital requires the knowledge about how the concrete attributes inherent in the medical service associated with the customer values that customers seek eventually in the medical service. Thus, it is required for hospital management to understand which hospital attributes should be emphasized in order to improve the customer values. The hierarchical structure of service attributes can provide valuable information about effective positioning and advertising. To obtain such knowledge, we employed the order analysis technique as an objective means-end chain method. Order analysis is useful for identifying the causal structure among attributes. Thus, we can examine the underlying causal relationship and eventually the vertical structure of hospital selection attributes. For this study, we conducted a survey to obtain 370 responses for the analysis. The result suggests that hospital management had better increase the scale of hospital, improve the services of health care providers, and modernize the hospital facilities and equipments so as to enhance customer values and eventually to lead them to recommend the hospital to others. Our findings would provide the valuable information for hospital management to develop the more effective hospital positioning and marketing strategies.

• Structural Engineering and Mechanics
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• v.55 no.4
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• pp.719-742
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• 2015

This paper dealt the free vibration analysis of thick truncated conical composite sandwich shells with transversely flexible cores and simply supported boundary conditions based on a new improved and enhanced higher order sandwich shell theory. Geometries were used in the present work for the consideration of different radii curvatures of the face sheets and the core was unique. The coupled governing partial differential equations were derived by the Hamilton's principle. The in-plane circumferential and axial stresses of the core were considered in the new enhanced model. The first order shear deformation theory was used for the inner and outer composite face sheets and for the core, a polynomial description of the displacement fields was assumed based on the second Frostig's model. The effects of types of boundary conditions, conical angles, length to radius ratio, core to shell thickness ratio and core radius to shell thickness ratio on the free vibration analysis of truncated conical composite sandwich shells were also studied. Numerical results are presented and compared with the latest results found in literature. Also, the results were validated with those derived by ABAQUS FE code.

• Ocean Systems Engineering
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• v.9 no.3
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• pp.219-240
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• 2019

This paper presents the comparison between SFT response with linear and nonlinear cables. The dynamic response analysis of submerged floating tunnel (SFT) is presented computationally with linear and nonlinear tension legs cables. The analysis is performed computationally for two wave directions one at 90 degrees (perpendicular) to tunnel and other at 45 degrees to the tunnel. The tension legs or cables are assumed as linear and non- linear and the analysis is also performed by assuming one tension leg or cable is failed. The Response Amplitude Operators (RAO's) are computed for first order waves, second order waves for both failure and non-failure case of cables. For first order waves- the SFT response is higher for sway and heave degree of freedom with nonlinear cables as compared with linear cables. For second order waves the SFT response in sway degree of freedom is bit higher response with linear cables as compared with nonlinear cables and the SFT in heave degree of freedom has higher response at low time periods with nonlinear cables as compared with linear cables. For irregular waves the power spectral densities (PSD's) has been computed for sway and heave degrees of freedom, at $45^0$ wave direction PSD's are higher with linear cables as compared with nonlinear cables and at $90^0$ wave direction the PSD's are higher with non-linear cables. The mooring force responses are also computed in y and z directions for linear and nonlinear cables.

• International Journal of Computer Science & Network Security
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• v.22 no.4
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• pp.1-12
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• 2022

In order to overcome the power fluctuation issues in photovoltaic (PV) smart grid-connected systems and the inverter nonlinearity model problem, an adaptive backstepping command-filter and a double second order generalized Integrators (DSOGI) controller are designed in order to tune the AC current and the DC-link voltage from the DC side. Firstly, we propose to present the filter mathematical model throughout the PV system, at that juncture the backstepping control law is applied in order to control it, Moreover the command filter is bounded to the controller aiming to exclude the backstepping controller differential increase. Additionally, The adaptive law uses Lyapunov stability criterion. Its task is to estimate the uncertain parameters in the smart grid-connected inverter. A DSOGI is added to stabilize the grid currents and eliminate undesirable harmonics meanwhile feeding maximum power generated from PV to the point of common coupling (PCC). Then, guaranteeing a dynamic effective response even under very unbalanced loads and/or intermittent climate changes. Finally, the simulation results will be established using MATLAB/SIMULINK proving that the presented approach can control surely the smart grid-connected system.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• v.5 no.2
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• pp.43-49
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• 2024

Ecological monitoring provides indispensable data for biodiversity conservation and sustainable resource management. However, the complexity and variability inherent in ecological monitoring data necessitate robust verification processes to ensure data integrity. This study employed Benford's Law, a statistical principle traditionally used in fields such as finance and health sciences, to evaluate the authenticity of ecological monitoring data related to the abundance of migratory bird species across various locations in South Korea. Benford's Law anticipates a specific logarithmic distribution of leading digits in naturally occurring numerical datasets. Our investigation involved two stages of analysis: a first-order analysis considering the leading digit and a second-order analysis examining the first two digits of bird population counts. While the first-order analysis displayed moderate conformity to Benford's Law that suggested overall data integrity, the second-order analysis revealed more pronounced deviations, indicating potential inconsistencies or inaccuracies in certain subsets of the data. Although our data did not perfectly align with Benford's Law, these deviations underscore the complex nature of ecological research, which is influenced by a multitude of environmental, methodological, and human factors.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.1 s.256
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• pp.121-128
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• 2007

Enhanced lower order shear deformation theory is developed in this study. Generally, lower order theories are not adequate to predict accurate deformation and stress distribution through the thickness of laminated plate. For the accurate prediction of detailed stress and deformation distributions through the thickness, higher order zigzag theories have been proposed. However, in most cases, simplified zigzag higher order theory requires $C_1$, shape functions in finite element implementation. In commercial FE softwares, $C_1$, shape functions are not so common in plate and shell analysis. Thus zigzag theories are useful for the highly accurate prediction of thick composite behaviors but they are not practical in the sense that they cannot be used conveniently in the commercial package. In practice, iso-parametric $C_0$ plate model is the standard model for the analysis and design of composite laminated plates and shells. Thus in the present study, an enhanced lower order shear deformation theory is developed. The proposed theory requires only $C_0$ shape function in FE implementation. The least-squared energy error between the lower order theory and higher order theory is minimized. An enhanced lower order shear deformation theory(ELSDT) in this paper is proposed for smart structure under complex loadings. The ELSDT is constructed by the strain energy transformation and fully coupled mechanical, electric loading cases are studied. In order to obtain accurate prediction, zigzag in-plane displacement and transverse normal deformation are considered in the deformation Held. In the electric behavior, open-circuit condition as well as closed-circuit condition is considered. Through the numerous examples, the accuracy and robustness of present theory are demonstrated.

• Journal of Korean Society of Steel Construction
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• v.9 no.1 s.30
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• pp.3-11
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• 1997

Laminated composite shells exhibit properties comsiderably different from those of the single-layer shell. Thus, to obtain the more accurate solutions to laminated composite shells ptoblems, effects of shear strain should be condidered in analysis of them. A higher-order shear deformation theory requires no shear correction coefficients. This theory is used to determine the buckling loads of elastic shells. The theory accounts for parabolic distribution of the transverse shear through the thickness of the shell and rotary inertia. Exact solutions of simply-supported shells are obtained and the results are compared with the exact solutions of the first-order shear deformation theory, and the classical theory. The present theory predicts the buckling loads more accurately when compared to the first -order and classical theory.