Henryk Sanecki and Andrzej Piotr Zieliński
To provide more convenient tools for the investigation of real objects with different forms and positions of cracks, which requires fracture analysis of engineering structures.
Abstract
Purpose
To provide more convenient tools for the investigation of real objects with different forms and positions of cracks, which requires fracture analysis of engineering structures.
Design/methodology/approach
A method which uses the Trefftz‐type finite elements (T‐elements) was applied as an efficient tool to deal with various problems of fracture mechanics.
Findings
Numerical examples compare the results of the T‐element procedures with the commercial systems ALGOR® and ANSYS®, showing the advantages of using the former codes. Their effectiveness is especially visible in the solution of a crack propagation problem.
Research limitations/implications
Limitation to linear fracture mechanics.
Practical implications
A proposal of effective codes for engineering analysis of structures with cracks.
Originality/value
This paper presents the feasibility of the application of the T‐element method to a wider field of fracture analysis – crack propagation in engineering structures.
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A. Zielinski, J. Smulko, A. Krakowiak and K. Darowicki
The results of the electrochemical noise observations in 0H18N9 steel are presented. Current noise was obtained by potentiostatic measurements in aqueous solution of 0.1M H2SO4…
Abstract
The results of the electrochemical noise observations in 0H18N9 steel are presented. Current noise was obtained by potentiostatic measurements in aqueous solution of 0.1M H2SO4 and 0.06M Cl−. The recorded noise had an evident trend and peaks that are typically observed during pitting corrosion. The trend was removed by means of the third order polynomial approximation. The statistical hypothesis, i.e. the difference between the approximation and the observed noise, was tested. The results confirmed that current noise caused by pitting corrosion has nonstationary or weakly stationary character. The recorded noise was analysed using the Joint Time‐Frequency Analysis method, which is appropriate for nonstationary signals. The derived results confirmed the presence of pitting corrosion. It was usual for a few pits to form on the surface of the electrodes in distinct phases, and these were observed as peaks in current fluctuations.
P. Krawczyk, F. Frey and A.P. Zieliński
This paper aims to present development of a layer‐wise (LW) beam model for geometric nonlinear finite element analysis of laminated beams with partial layer interaction.
Abstract
Purpose
This paper aims to present development of a layer‐wise (LW) beam model for geometric nonlinear finite element analysis of laminated beams with partial layer interaction.
Design/methodology/approach
The model is built assuming first order shear deformation theory (FSDT) at layer level and moderate interlayer slips. LW kinematic, strain and stress fields are established in view of co‐rotational finite element formulation. Laminated beam equilibrium relations are developed in strong, weak and matrix form. A notion of interface shear stress is used to define layer interactions.
Findings
Through suitable choice of kinematic model the co‐rotational approach is shown to provide means of obtaining robust finite element formulation for geometric nonlinear analysis of laminated structures with interlayer slips.
Research limitations/implications
The proposed model is dedicated to geometric nonlinear finite element analysis of laminated beams undergoing large planar displacements, subject to small strains and moderate interlayer slips.
Originality/value
Novelty of the proposed approach is based on encompassing shear deformations in geometric nonlinear analysis of laminated beams with interlayer slips. Arbitrary number of layers is considered.
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Amy E. Ruhaak and Bryan G. Cook
Disruptive student behavior contributes to poor student outcomes, loss of classroom instructional time, and teacher burnout. Physical movement is an intervention that has been…
Abstract
Disruptive student behavior contributes to poor student outcomes, loss of classroom instructional time, and teacher burnout. Physical movement is an intervention that has been used to target and ameliorate disruptive student behavior for students with learning and behavioral disabilities. A review of two movement-based interventions – Brain Gym® and antecedent bouts of exercise – reveals different levels of research support. Brain Gym®, a commercial movement-based curriculum, is not supported by extant empirical research. Alternatively, a growing body of research empirically supports antecedent bouts of exercise as an effective behavioral intervention. This chapter provides a description and review of research for each intervention. Implications for instructional practice and recommendations are provided.
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Zhuo‐Jia Fu, Qing‐Hua Qin and Wen Chen
The purpose of this paper is to develop a hybrid‐Trefftz (HT) finite element model (FEM) for simulating heat conduction in nonlinear functionally graded materials (FGMs) which can…
Abstract
Purpose
The purpose of this paper is to develop a hybrid‐Trefftz (HT) finite element model (FEM) for simulating heat conduction in nonlinear functionally graded materials (FGMs) which can effectively handle continuously varying properties within an element.
Design/methodology/approach
In the proposed model, a T‐complete set of homogeneous solutions is first derived and used to represent the intra‐element temperature fields. As a result, the graded properties of the FGMs are naturally reflected by using the newly developed Trefftz functions (T‐complete functions in some literature) to model the intra‐element fields. The derivation of the Trefftz functions is carried out by means of the well‐known Kirchhoff transformation in conjunction with various variable transformations.
Findings
The study shows that, in contrast to the conventional FEM, the HT‐FEM is an accurate numerical scheme for FGMs in terms of the number of unknowns and is insensitive to mesh distortion. The method also performs very well in terms of numerical accuracy and can converge to the analytical solution when the number of elements is increased.
Originality/value
The value of this paper is twofold: a T‐complete set of homogeneous solutions for nonlinear FMGs has been derived and used to represent the intra‐element temperature; and the corresponding variational functional and the associated algorithm has been constructed.
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Krzysztof Grysa and Artur Maciag
The purpose of this paper is to derive the Trefftz functions (T-functions) for the Pennes’ equation and for the single-phase-lag (SPL) model (hyperbolic equation) with perfusion…
Abstract
Purpose
The purpose of this paper is to derive the Trefftz functions (T-functions) for the Pennes’ equation and for the single-phase-lag (SPL) model (hyperbolic equation) with perfusion and then comparing field of temperature in a flat slab made of skin in the case when perfusion is taken into account, with the situation when a Fourier model is considered. When considering the process of heat conduction in the skin, one needs to take into account the average values of its thermal properties. When in biological bodies relaxation time is of the order of 20 s, the thermal wave propagation appears. The initial-boundary problems for Pennes’ model and SPL with perfusion model are considered to investigate the effect of the finite velocity of heat in the skin, perfusion and thickness of the slab on the rate of the thermal wave attenuation. As a reference model, the solution of the classic Fourier heat transfer equation for the considered problems is calculated. A heat flux has direction perpendicular to the surface of skin, considered as a flat slab. Therefore, the equations depend only on time and one spatial variable.
Design/methodology/approach
First of all the T-functions for the Pennes’ equation and for the SPL model with perfusion are derived. Then, an approximate solutions of the problems are expressed in the form of a linear combination of the T-functions. The T-functions satisfy the equation modeling the problem under consideration. Therefore, approximating a solution of a problem with a linear combination of n T-functions one obtains a function that satisfies the equation. The unknown coefficients of the linear combination are obtained as a result of minimization of the functional that describes an inaccuracy of satisfying the initial and boundary conditions in a mean-square sense.
Findings
The sets of T-functions for the Pennes’ equation and for the SPL model with perfusion are derived. An infinite set of these functions is a complete set of functions and stands for a base functions layout for the space of solutions for the equation used to generate them. Then, an approximate solutions of the initial-boundary problem have been found and compared to find out the effect of finite velocity of heat in the skin, perfusion and thickness of the slab on the rate of the thermal wave attenuation.
Research limitations/implications
The methods used in the literature to find an approximate solution of any bioheat transfer problems are more complicated than the one used in the presented paper. However, it should be pointed out that there is some limitation concerning the T-function method, namely, the greater number of T-function is used, the greater condition number becomes. This limitation usually can be overcome using symbolic calculations or conducting calculations with a large number of significant digits.
Originality/value
The T-functions for the Pennes’ equation and for the SPL equation with perfusion have been reported in this paper for the first time. In the literature, the T-functions are known for other linear partial differential equations (e.g. harmonic functions for Laplace equation), but for the first time they have been derived for the two aforementioned equations. The results are discussed with respect to practical applications.
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Mariusz Deja and Dawid Zielinski
The purpose of this study is to evaluate the geometric quality of small diameter holes in parts printed by direct metal laser sintering (DMLS) technology. An in-process optical…
Abstract
Purpose
The purpose of this study is to evaluate the geometric quality of small diameter holes in parts printed by direct metal laser sintering (DMLS) technology. An in-process optical inspection method is proposed and assessed during a pilot study. The influence of the theoretical hole diameter assumed in a computer-aided design (CAD) system and the sample thickness (hole length) on the hole clearance was analyzed.
Design/methodology/approach
The samples are made of two different materials: EOS MaragingSteel MS1 and aluminium alloy EOS Aluminium consisted of straight through holes of different diameters and lengths. Dimensional and shape accuracy of the holes were determined with the use of the image processing software and the computer analysis of two-dimensional (2-D) images. The definition of the equivalent hole diameter was proposed to calculate the hole clearance. Feret’s diameters were determined for the evaluation of the shape accuracy.
Findings
The dependency between the equivalent hole diameter and the theoretical diameter was approximated by the linear function for a specific sample thickness. Additionally, a general empirical model for determining the hole clearance was developed, allowing for calculating the equivalent hole diameter as a function of a sample thickness and a theoretical hole diameter.
Practical implications
Developed functions can be used by designers for a proper assignment of a hole diameter to achieve the required patency. The relevant procedures and macros based on proposed empirical models can be embedded in CAD systems to support the designing process.
Originality/value
The analysis of the geometric quality of the holes in parts printed by DMLS was based on the computer analysis of 2-D images. The proposed method of assessing the shape accuracy of straight through holes is relatively cheap, is widely available and can be applied to the features of other shapes produced by three-dimensional printing.
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This paper aims to presents a new method of investigation of local properties of conformal coatings utilized in microelectronics.
Abstract
Purpose
This paper aims to presents a new method of investigation of local properties of conformal coatings utilized in microelectronics.
Design/methodology/approach
It is based on atomic force microscopy (AFM) technique supplemented with the ability of local electrical measurements, which apart from topography acquisition allows recording of local impedance spectra, impedance imaging and dc current mapping. Potentialities of the proposed AFM-assisted approach have been demonstrated on commercially available epoxy-coated electronic printed boards in as-received state and after six-year service.
Findings
The technique proved to be capable of identification, spatial localization and characterization of conformal coating defects.
Practical implications
The proposed approach can be utilized for assessment of protective film state in such demanding fields as electronics or electrotechnics where the classical techniques of anticorrosion coatings investigation cannot be employed due to small element dimensions and relatively low coating thickness.
Originality/value
The approach adopted by the author is novel in the field of organic coatings investigation.
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Austin Rong-Da Liang, Poh Theng Loo and Fu-Yung Kuan
In recent years, community-based tourism (CBT) in the global market has been combined with specific themes in order to establish various tourism activities. Relatively few studies…
Abstract
Purpose
In recent years, community-based tourism (CBT) in the global market has been combined with specific themes in order to establish various tourism activities. Relatively few studies have comprehensively investigated how this type of CBT should be developed. Therefore, this study takes CBT with festival themes combined with community characteristics as a case study, which explores what obstacles exist in CBT with a combination of community characteristics – the industrial history of sugar factories and external themes, such as, formal flower displays.
Design/methodology/approach
The thematic analysis is employed for data analysis of interviews. All interview participants were stakeholders.
Findings
This study identifies five types of obstacles: policy-related, environmental-related, innovation-related, industry-related and communication-related. Based on these findings, it is vital to consider both community and other characteristics of CBT. At the same time, after evaluating the rational perceptions of different stakeholders within the same type of obstacle, this study proposes a more specific and comprehensive development strategies for CBT.
Originality/value
To the best of the authors' knowledge, this is the first study of community agricultural tourism which collected the viewpoints of different stakeholders – tourists, residents, community associations, local businesses and the government. This study employs in-depth analysis of external policies and environmental and agricultural factors to discover and develop relevant coping strategies and implications.
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Tao Chen, Tanya Froehlich, Tingyu Li and Long Lu
Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder that is difficult to diagnose accurately due to its heterogeneous clinical manifestations. Comprehensive…
Abstract
Purpose
Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder that is difficult to diagnose accurately due to its heterogeneous clinical manifestations. Comprehensive models combining different big data approaches (e.g. neuroimaging, genetics, eye tracking, etc.) may offer the opportunity to characterize ASD from multiple distinct perspectives. This paper aims to provide an overview of a novel diagnostic approach for ASD classification and stratification based on these big data approaches.
Design/methodology/approach
Multiple types of data were collected and recorded for three consecutive years, including clinical assessment, neuroimaging, gene mutation and expression and response signal data. The authors propose to establish a classification model for predicting ASD clinical diagnostic status by integrating the various data types. Furthermore, the authors suggest a data-driven approach to stratify ASD into subtypes based on genetic and genomic data.
Findings
By utilizing complementary information from different types of ASD patient data, the proposed integration model has the potential to achieve better prediction performance than models focusing on only one data type. The use of unsupervised clustering for the gene-based data-driven stratification will enable identification of more homogeneous subtypes. The authors anticipate that such stratification will facilitate a more consistent and personalized ASD diagnostic tool.
Originality/value
This study aims to utilize a more comprehensive investigation of ASD-related data types than prior investigations, including proposing longitudinal data collection and a storage scheme covering diverse populations. Furthermore, this study offers two novel diagnostic models that focus on case-control status prediction and ASD subtype stratification, which have been under-explored in the prior literature.