• Steel and Composite Structures
• /
• 제43권5호
• /
• pp.581-601
• /
• 2022

The main objective of this research work is to investigate the free vibration behavior of annular sandwich plates resting on the Kerr foundation at thermal conditions. This sandwich configuration is composed of two FGM face sheets as coating layer and a porous GPLRC (GPL reinforced composite) core. It is supposed that the GPL nanofillers and the porosity coefficient vary continuously along the core thickness direction. To model closed-cell FG porous material reinforced with GPLs, Halpin-Tsai micromechanical modeling in conjunction with Gaussian-Random field scheme is used, while the Poisson's ratio and density are computed by the rule of mixtures. Besides, the material properties of two FGM face sheets change continuously through the thickness according to the power-law distribution. To capture fundamental frequencies of the annular sandwich plate resting on the Kerr foundation in a thermal environment, the analysis procedure is with the aid of Reddy's shear-deformation plate theory based high-order shear deformation plate theory (HSDT) to derive and solve the equations of motion and boundary conditions. The governing equations together with related boundary conditions are discretized using the generalized differential quadrature (GDQ) method in the spatial domain. Numerical results are compared with those published in the literature to examine the accuracy and validity of the present approach. A parametric solution for temperature variation across the thickness of the sandwich plate is employed taking into account the thermal conductivity, the inhomogeneity parameter, and the sandwich schemes. The numerical results indicate the influence of volume fraction index, GPLs volume fraction, porosity coefficient, three independent coefficients of Kerr elastic foundation, and temperature difference on the free vibration behavior of annular sandwich plate. This study provides essential information to engineers seeking innovative ways to promote composite structures in a practical way.

• International Journal of Computer Science & Network Security
• /
• 제21권7호
• /
• pp.211-220
• /
• 2021

The aim of the study is to implement a factor analysis of the determinants of pricing in a state-regulated competitive market using economic and mathematical modelling methods and to develop ways to improve the pricing environment of the market under study. The purpose of the work defines the main objectives: (i) to investigate the features of the competitive model of the Ukrainian flour market; (ii) to analyse the current price conjuncture of the flour market and the dynamics of the main determinants of pricing; (iii)to develop ways of improving the price situation on the flour market on the basis of the factor analysis on the results of economic and mathematical modelling. In order to ensure the reliability and validity of the research results, the following methods were applied: the logical-dialectical method of scientific knowledge in the study of the main theoretical aspects of flour market functioning, the method of logical generalisation and synthesis, comparison, factor analysis, correlation and regression analysis, the graphical method, etc. It has been shown that pricing in a state-regulated competitive market has its own characteristics. For example, in the flour market the price of goods cannot be influenced by producers (sellers) by any methods, therefore determinants of pricing by indirect influence have been taken into account. The five-factor power model of wheat flour price has been constructed. It was substantiated that the price of wheat flour in Ukraine is mostly influenced by consumer price index (0.92 %). The received complex model of wheat flour price may be used also for medium-term forecasting and working out the ways of price formation optimization in the flour market.

• Smart Structures and Systems
• /
• 제30권1호
• /
• pp.75-88
• /
• 2022

Engineering structures in operation essentially belong to time-varying or nonlinear structures and the resultant response signals are usually non-stationary. For such time-varying structures, it is of great importance to extract time-dependent dynamic parameters from non-stationary response signals, which benefits structural health monitoring, safety assessment and vibration control. However, various traditional signal processing methods are unable to extract the embedded meaningful information. As a newly developed technique, variational mode decomposition (VMD) shows its superiority on signal decomposition, however, it still suffers two main problems. The foremost problem is that the number of modal components is required to be defined in advance. Another problem needs to be addressed is that VMD cannot effectively separate non-stationary signals composed of closely spaced or overlapped modes. As such, a new method named generalized adaptive variational modal decomposition (GAVMD) is proposed. In this new method, the number of component signals is adaptively estimated by an index of mean frequency, while the generalized demodulation algorithm is introduced to yield a generalized VMD that can decompose mode overlapped signals successfully. After that, synchrosqueezing wavelet transform (SWT) is applied to extract instantaneous frequencies (IFs) of the decomposed mono-component signals. To verify the validity and accuracy of the proposed method, three numerical examples and a steel cable with time-varying tension force are investigated. The results demonstrate that the proposed GAVMD method can decompose the multi-component signal with overlapped modes well and its combination with SWT enables a successful IF extraction of each individual component.

• Journal of Preventive Medicine and Public Health
• /
• 제55권1호
• /
• pp.1-9
• /
• 2022

An index that evaluates the health level of a population group considering both death and loss of function due to disease is called a summary measure of population health (SMPH). SMPHs are broadly divided into life year indices and life expectancy indices, the latter of which comprise healthy life expectancy (HLE). HLE is included as a policy target in various national and regional level healthcare plans, and the term "HLE" is commonly used in academia and by the public. However, the overall level of understanding of HLE-such as the precise definition of HLE and methods of calculating HLE-still seems to be low. As discussed in this study, the types of HLE are classified into disability-free life expectancy, disease-free life expectancy, quality-adjusted life expectancy, self-rated HLE, and disability-adjusted life expectancy. Their characteristics are examined to facilitate a correct understanding and appropriate utilization of HLE. In addition, the Sullivan method, as a representative method for calculating HLE, is presented in detail, and major issues in the process of calculating HLE, such as selection of the population group and age group, estimation of death probability, calculation of life years, and incorporation of health weights, are reviewed. This study will help researchers to select an appropriate HLE type and evaluate the validity of HLE research results, and it is expected to contribute to the vitalization of HLE research.

• Steel and Composite Structures
• /
• 제43권1호
• /
• pp.79-90
• /
• 2022

In this study, the dynamic behavior of functionally graded layered deep beams with viscoelastic core is investigated including the porosity effect. The material properties of functionally graded layers are assumed to vary continuously through thickness direction according to the power-law function. To investigate porosity effect in functionally graded layers, three different distribution models are considered. The viscoelastically cored deep beam is exposed to harmonic sinusoidal load. The composite beam is modeled based on plane stress assumption. The dynamic equations of motion of the composite beam are derived based on the Hamilton principle. Within the framework of the finite element method (FEM), 2D twelve -node plane element is exploited to discretize the space domain. The discretized finite element model is solved using the Newmark average acceleration technique. The validity of the developed procedure is demonstrated by comparing the obtained results and good agreement is detected. Parametric studies are conducted to demonstrate the applicability of the developed methodology to study and analyze the dynamic response of viscoelastically cored porous functionally graded deep beams. Effects of viscoelastic parameter, porosity parameter, graduation index on the dynamic behavior of porous functionally graded deep beams with viscoelastic core are investigated and discussed. Material damping and porosity have a significant effect on the forced vibration response under harmonic excitation force. Increasing the material viscosity parameters results in decreasing the vibrational amplitudes and increasing the vibration time period due to increasing damping effect. Obtained results are supportive for the design and manufacturing of such type of composite beam structures.

• 대한후두음성언어의학회지
• /
• 제33권2호
• /
• pp.103-109
• /
• 2022

Background and Objectives The Voice Perceived Present Control scale (VPPC) has been developed to provide better insight into patients' perceived control over their thoughts or behaviors related to voice disorders. The objective of the present study was to validate the Korean VPPC (K-VPPC) by evaluating its internal consistency and reliability. Materials and Method All items of the English VPPC were translated into Korean. Content validity was analyzed through three Delphi survey rounds by an expert panel (n=44) with active clinical and research experience in treating dysphonic patients. Twenty-three patients with a heterogeneous diagnosis of dysphonia and twenty-three gender-matched vocally normal controls (total n=46) were asked to complete the K-VPPC and the Korean Voice Handicap Index-10 (KVHI-10). Psychometric properties including internal consistency and reliability were evaluated to examine the appropriateness of cross-cultural use of K-VPPC. Results Cronbach's alpha coefficient of K-VPPC was 0.89 for dysphonic patients, indicating good internal consistency in clinical samples. Furthermore, patients with dysphonia scored significantly lower on the total score of K-VPPC and higher on voice handicap than the vocally normal controls. Spearman's correlation coefficients indicated an inverse and moderate association between the K-VPPC and all domains of KVHI-10 (Spearman's r=-0.44- -0.68). Conclusion The findings of the current study indicated that the K-VPPC is a valid and reliable tool for the assessment of perceived control in Korean patients with dysphonia. Therefore, the K-VPPC could be a useful and complementary tool for the comprehensive evaluation of dysphonia, thereby improving care in Korean patients with voice disorders.

• 한국치위생학회지
• /
• 제23권4호
• /
• pp.277-286
• /
• 2023

Objectives: In this study, we aimed to develop a systematic tool that can evaluate the effects of interprofessional education (IPE) by applying four core competencies (values/ethics for interprofessional practice, roles/responsibilities, interprofessional communication, and teams and teamwork) and an educational evaluation model to evaluate the learning, behavior of learners, and results step by step. Methods: Previous studies on IPE evaluation tools were analyzed, and an evaluation tool (draft) was developed by modifying questions suitable for evaluation according to the Kirkpatrick model's stages and core competencies. The evaluation tool was completed by conducting a Delphi survey twice with 4-6 experts. To analyze the Delphi survey, the content validity index (CVI) was calculated, and the reliability coefficient (Cronbach's alpha coefficient) was used to measure reliability. Results: 29 questions on pre-education, consisting of learning and behavior stages, and 54 questions on post-education, consisting of reaction, learning, behavior, and results stages, were developed. The CVI and Cronbach's alpha coefficient values were >0.8 and >0.6, respectively. Conclusions: The IPE evaluation tool developed in this study is expected to contribute to the evaluation of the educational level of IPE and the identification of points for improvement when applied to various educational settings.

• Steel and Composite Structures
• /
• 제48권3호
• /
• pp.275-291
• /
• 2023

This paper has focused on presenting vibration analysis of trapezoidal sandwich plates with 3D-graphene foam reinforced polymer matrix composites (GrF-PMC) core and FG wavy CNT-reinforced face sheets. The porous graphene foam possessing 3D scaffold structures has been introduced into polymers for enhancing the overall stiffness of the composite structure. Also, 3D graphene foams can distribute uniformly or non-uniformly in the plate thickness direction. The effective Young's modulus, mass density and Poisson's ratio are predicted by the 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 First-order shear deformation theory of plate is utilized to establish governing partial differential equations and boundary conditions for trapezoidal plate. The governing equations together with related boundary conditions are discretized using a mapping-generalized differential quadrature (GDQ) method in spatial domain. Then natural frequencies of the trapezoidal sandwich plates are obtained using GDQ method. Validity of the current study is evaluated by comparing its numerical results with those available in the literature. It is explicated that 3D-GrF skeleton type and weight fraction, carbon nanotubes (CNTs) waviness and CNT aspect ratio can significantly affect the vibrational behavior of the sandwich structure. The plate's normalized natural frequency decreased and the straight carbon nanotube (w=0) reached the highest frequency by increasing the values of the waviness index (w).

• 한국산업보건학회지
• /
• 제33권1호
• /
• pp.78-90
• /
• 2023

Objectives: The purpose of this study is to standardize the process code of the work environment measurement database (WEMD) for the construction of a job-exposure matrix (JEM). Methods: The standard process code (SPC) was reclassified based on process similarity and drawing upon the code used in the existing K2B. It was supplemented through review by industrial hygiene experts. In addition, an index word database related to SPC was created and used for SPC search. A pilot evaluation project was conducted by experts to evaluate the validity of the newly reclassified standard process code. Results: A total of 70 final SPCs were developed, including 31 processes related to the construction industry. Using the Shiny program, we developed a standard code finder that can be used on the web (https://kscf.shinyapps.io/scf_app/). As a result of the pilot evaluation, it was determined that it was easier to search for standard codes than previous codes, so it was highly utilized. Conclusions: It is expected that JEM construction using industry-process information drawing on WEMD data will be possible using the 70 newly standardized process codes.

• Steel and Composite Structures
• /
• 제46권3호
• /
• pp.367-383
• /
• 2023

In this investigation, an improved integral trigonometric shear deformation theory is employed to examine the vibrational behavior of the functionally graded (FG) sandwich plates resting on visco-Pasternak foundations. The studied structure is modelled with only four unknowns' variables displacements functions. The simplicity of the developed model being in the reduced number of variables which was made with the help of the use of the indeterminate integral in the formulation. The current kinematic takes into consideration the shear deformation effect and does not require any shear correction factors as used in the first shear deformation theory. The equations of motion are determined from Hamilton's principle with including the effect of the reaction of the visco-Pasternak's foundation. A Galerkin technique is proposed to solve the differentials governing equations, which enables one to obtain the semi-analytical solutions of natural frequencies for various clamped and simply supported FG sandwich plates resting on visco-Pasternak foundations. The validity of proposed model is checked with others solutions found in the literature. Parametric studies are performed to illustrate the impact of various parameters as plate dimension, layer thickness ratio, inhomogeneity index, damping coefficient, vibrational mode and elastic foundation on the vibrational behavior of the FG sandwich plates.