A Probabilistic Formulation of the Diffusion Coefficient in Porous Media as Function of Porosity

We investigate the upscaling of diffusive transport parameters using a stochastic framework. At sub-REV (representative elementary volume) scale, the complexity of the pore space geometry leads to a significant scatter of the observed diffusive transport. We study a large set of volumes reconstructed from focused ion beam-scanning electron microscopy data. Each individual volume provides us sub-REV measurements on porosity and the so-called transport-ability, being a dimensionless parameter representing the ratio of diffusive flux through the porous volume to that through an empty volume. The detected scatter of the transport-ability is mathematically characterized through a probability distribution function (PDF) with a mean and variance as function of porosity, which includes implicitly the effect of pore structure differences among sub-REV volumes. We then investigate domain size effects and predict when REV scale is reached. While the scatter in porosity observations decreases linearly with increasing sample size as expected, the observed scatter in transport-ability does not converge to zero. Our results confirm that differences in pore structure impact transport parameters at all scales. Consequently, the use of PDFs to describe the relationship of effective transport coefficients to porosity is advantageous to deterministic semiempirical functions. We discuss the consequences and advocate the use of PDFs for effective parameters in both continuum equations and data interpretation of experimental or computational work. The presented statistics-based upscaling technique of sub-REV microscopy data provides a new tool in understanding, describing and predicting macroscopic transport behavior of microporous media.

Bond between Fibre-Reinforced Polymer Tubes and Sea Water Sea Sand Concrete: Mechanisms and Effective Parameters: Critical Overview and Discussion

Using fibre-reinforced polymers (FRP) in construction avoids corrosion issues associated with the use of traditional steel reinforcement, while seawater and sea sand concrete (SWSSC) reduces environmental issues and resource shortages caused by the production of traditional concrete. The paper gives an overview of the current research on the bond performance between FRP tube and concrete with particular focus on SWSSC. The review follows a thematic broad-to-narrow approach. It reflects on the current research around the significance and application of FRP and SWSSC and discusses important issues around the bond strength and cyclic behaviour of tubular composites. A review of recent studies of bond strength between FRP and concrete and steel and concrete under static or cyclic loading using pushout tests is presented. In addition, the influence of different parameters on the pushout test results are summarised. Finally, recommendations for future studies are proposed.

Application of Fuzzy Topsis and Taguchi Methods for Optimization Problems With Disruptive Risk

Ranking and choosing research projects and analyzing experiments are usually difficult and complex responsibilities for professional research councils at universities and research centers. Its complexity stems from having more than one variable in each project, and the participation of many decision-makers in the ranking process and selection of research projects based on many variables. The fuzzy set theory provides the required flexibility to show the uncertainty about the lack of knowledge, and also it can manage the uncertainty in the real world that the values of criteria are not defined properly. For this purpose, in the environment where the criteria of research projects are vaguely defined, the ranking methods such as Taguchi, which can reduce the number of experiments and making process more efficient, can be used for quality design in designing and processing product. In this work, first of all, the authors review fuzzy TOPSIS technique and the Taguchi method as well; then they approach research efficiency and optimization of the level of effective parameters in an experiment.

Studying the appointment scheduling window considering patient no-show behavior in one public and one private outpatient clinics

Purpose This study is carried out in one public and one private health-care centers based on different probabilities of patient’s no-show rate. The present study aims to determine the optimal queuing system capacity so that the expected total cost is minimized. Design/methodology/approach In this study an M/M/1/K queuing model is used for analytical properties of optimal queuing system capacity and appointment window so that total costs of these cases could be minimized. MATLAB software version R2014a is used to code the model. Findings In this paper, the optimal queuing system capacity is determined based on the changes in effective parameters, followed by a sensitivity analysis. Total cost in public center includes the costs of patient waiting time and rejection. However, the total cost in private center includes costs of physician idle time plus costs of public center. At the end, the results for public and private centers are compared to reach a final assessment. Originality/value Today, determining the optimal queuing system capacity is one of the most central concerns of outpatient clinics. The large capacity of the queuing system leads to an increase in the patient’s waiting-time cost, and on the other hand, a small queuing system will increase the cost of patient’s rejection. The approach suggested in this paper attempts to deal with this mentioned concern.

GENDER SPECIFICITY OF SUBJECTIVITY MANIFESTATIONS IN SITUATIONS OF AUTONOMY AND NON-AUTONOMY

The relevance of this article is due to the need to study the gender specifics of the relationship between the manifestations of subjectivity (mental states, procedural and effective parameters of the situation) with the basic psychological need for autonomy to apply the data obtained in the practice of psychological and pedagogical support of the educational process at the university. The goal of the empirical research was to determine the gender common and peculiar in the manifestations of subjectivity, depending on the degree of autonomy of the subject of activity. The main hypothesis was the assumption that there are differences in the manifestations of subjectivity in situations with different levels of autonomy among respondents of different genders. The sample consisted of 112 people (56 men and 56 women). The age of men was from 22 to 42 years (M=25, SD=3,5 years). The age of women was from 22 to 45 years (M=24, SD=2,8 years). The respondents - advanced students (n=112) in the form of a free essay described the situations of extrinsic and internal motivation when studying at the university and compared them with each other by any possible criteria. For data processing, the methods of content analysis, frequency analysis of text and the Fisher angular transformation criterion were used. Statistically significant differences in the emotional and intellectual-emotional manifestations of states in subjects of different sexes were revealed. In situations of autonomy, women more often experienced states of joy, interest and passion (p≤0,05), and men experienced pleasure (p≤0,01). The state of relief in situations of non-autonomy was more common for women than for men (p≤0,01). Differences in the frequency of mention of procedural and effective parameters of situations in respondents of different sexes were not found. The results of the study can be used in the development of programs for the adaptation of future specialists to changes in the labor market conditions.