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The purpose of this study is to develop a lower bainite structure consists of a dispersion of fine carbide inside plates of bainitic ferrite from chemical composition unmodified conventional pearlitic steel under bainitic transformation and to investigate its effect on tensile properties and wear resistance.

A commercial hypereutectoid pearlitic rail steel was subjected to three different bainitic transformation treatments followed by tempering to develop a desirable microstructure with a DIL805 BÄHR dilatometer. A comprehensive microstructural study was performed by scanning electron microscopy and energy dispersive x-ray spectroscopy. Finally, the mechanical properties and wear resistance were evaluated by tensile, microhardness, and pin-on-disc tests.

The results showed that the best combination of mechanical properties and sliding wear resistance was obtained in the sample subjected to bainitic transformation at 300°C for 600 s followed by tempering at 400°C for 300 s. This sample, which contained a bainitic ferrite structure, exhibited approximately 20% higher hardness and approximately 53% less mass loss than the as-received pearlitic sample due to the mechanically induced transformation in the contact surface.

Although pearlitic steel is widely used in the construction of railways, recent studies have revealed that bainitic transformation at the same rail steels exhibited higher wear resistance and fatigue strengths than conventional pearlitic rail at the same hardness values. Such a bainitic microstructure can improve the mechanical properties and wear resistance, which is a great interest in the railway industry.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2019-0282/

The purpose of this paper is to present the results of a metallurgical, mechanical and tribological characterization of the weld and heat-affected zone (HAZ) of aluminothermic welding of premium rails used in heavy haul, looking into the origins of the squat defects associated with rail wear.

A full factorial design of experiment was carried out for 24 welds of premium and super premium rails. The factors studied were chemical composition, welding gap and preheating time. The welds were inspected visually and by ultrasound to detect superficial and internal defects and characterized by macrographic analysis, hardness profile, tensile tests and microstructural characterization in scanning electronic microscopy. Pin-on-disk test were carried out to compare the tribological behavior of the different regions of the weld rail.

Squat formation was shown to be associated with spheroidized pearlite regions formed on the HAZ of the welds, presenting near half the hardness of the weld metal. Thermal analysis showed that spheroidized pearlite is a result of partial austenitization at these positions. Tribological tests showed that low hardness regions presented smaller wear resistance than both the weld metal and the parent rail. Tensile test of the whole region resulted in brittle fracture along the weld metal.

The results showed that it is essential to reduce the dimensions of the HAZ and the width of the hardness drop area to mitigate squat formation in the HAZ edges.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0020/

Identifying and prioritizing the risks are considered as critical issues in risk management; otherwise, non-considering the risks will lead to the problems such as delays in project implementation, increased costs, loss of reputation, loss of clients, reduced revenue and liquidity and even bankruptcy. The paper aims to discuss these issues.

In this paper, the factors influencing the organization risk tolerance level were identified. Then, the factors increasing and decreasing the risk tolerance level were determined by a decision-making model. Finally, a comprehensive model was considered for risk measuring and preparing a risk failure structure chart, in order to determine the factors influencing it as well as the measurement criteria and then they were ranked using the taxonomy method. In this study, the size of the statistical population was 130 (six small and medium manufacturer and service provider companies). Based on Cochran’s sample size formula, 97 questionnaires containing 30 questions were randomly distributed among the population. Validity and reliability of the questionnaire were confirmed. The data were analyzed by SPSS 22.

Given the hypotheses of this study, the first hypothesis was rejected and the other hypotheses were accepted. The final ranking was done using the taxonomy method; the personality of the project manager was ranked at first; income, credit and capital were ranked second and the number of personnel was ranked third. Moreover, the TOPSIS method was used for ranking to compare the results.

In this research, the identification and ranking of these factors have taken place in several small- and medium-sized organizations; in addition, the rankings are conducted using the taxonomy decision-making method.

The purpose of this paper is to analyze the effects of complex boundary conditions on natural convection of a yield stress fluid in a square enclosure heated from below (uniformly and non-uniformly) and symmetrically cooled from the sides.

The governing equations are solved numerically subject to continuous and discontinuous Dirichlet boundary conditions by Galerkin’s weighted residuals scheme of finite element method and using a non-uniform unstructured triangular grid.

Results show that the overall heat transfer from the heated wall decreases in the case of non-uniform heating for both Newtonian and yield stress fluids. It is found that the effect of yield stress on heat transfer is almost similar in both uniform and non-uniform heating cases. The yield stress has a stabilizing effect, reducing the convection intensity in both cases. Above a certain value of yield number Y, heat transfer is only due to conduction. It is found that a transition of different modes of stability may occur as Rayleigh number changes; this fact gives rise to a discontinuity in the variation of critical yield number.

Besides the new numerical method based on the finite element and using a non-uniform unstructured grid for analyzing natural convection of viscoplastic materials with complex boundary conditions, the originality of the present work concerns the treatment of the yield stress fluids under the influence of complex boundary conditions.

The purpose of this paper is to analyze the natural convection of a yield stress fluid in a square enclosure with differentially heated side walls. In particular, the Casson model is considered which is a commonly used model.

The coupled conservation equations of mass, momentum and energy related to the two-dimensional steady-state natural convection within square enclosures are solved numerically by using the Galerkin's weighted residual finite element method with quadrilateral, eight nodes elements.

Results highlight a small degree of the shear-thinning in the Casson fluids. It is shown that the yield stress has a stabilizing effect since the convection can stop for yield stress fluids while this is not the case for Newtonian fluids. The heat transfer rate, velocity and Yc obtained with the Casson model have the smallest values compared to other viscoplastic models. Results highlight a weak dependence of Yc with the Rayleigh number: Yc∼Ra0.07. A supercritical bifurcation at the transition between the convective and the conductive regimes is found.

The originality of the present study concerns the comprehensive and detailed solutions of the natural convection of Casson fluids in square enclosures with differentially heated side walls. It is shown that there exists a major difference between the cases of Casson and Bingham models, and hence using the Bingham model for analyzing the viscoplastic behavior of the fluids which follow the Casson model (such as blood) may not be accurate. Finally, a correlation is proposed for the mean Nusselt number Nu¯.

The purpose of this paper is to determine and prioritize man-made threats that have the probability of occurring in civilian airports, as an important part of critical infrastructures in each country.

The paper is practical-developmental in terms of research type and its approach is descriptive. Desktop research methods and interviews (qualitative) have been used in identifying deliberate man-made threats that are faced by the civilian airports. Moreover, a questionnaire (quantitative) has been utilized to assess the civilian airports’ assets that are targets likely to be threatened and assess threats by determining and prioritizing.

The results of the paper show that the main threat faced by civilian airports is “Air and missile strikes.” An additional 15 threats endangering civilian airports that have been extracted and presented through integrating specialized literature were prioritized in the main components of civilian airports. This prioritization has been performed on the basis of the following five indicators: “Damage Severity,” “Threat Precedent,” “Target Attractiveness,” “Negative Consequences for the Enemy” and “Enemy Ability.”

This paper is extracted from master’s thesis that identifies and assesses the threats to civil airport, and prioritizes them, and the results were confirmed by the experts.

The purpose of this paper is to propose a new design strategy to enhance the bandwidth and efficiency of the power amplifier.

To realize the introduced design strategy, a power amplifier was designed using TSMC CMOS 0.18um technology for operating in the Ka-band, i.e. the frequency range of 26.5-40 GHz. To design the power amplifier, first, a power divider (PD) with a very wide bandwidth, i.e. 1-40 GHz, was designed to cover the whole Ka-band. The designed Doherty power amplifier consisted of two different amplification paths called main and auxiliary. To amplify the signal in each of the two pathways, a cascade distributed power amplifier was used. The main reason for combining the distributed structure and cascade structure was to increase the gain and linearity of the power amplifier.

Measurements results for designed power dividers are in good agreement with simulations results. The simulation results for the introduced structure of the power amplifier indicated that the gain of the proposed power amplifier at the frequency of 26-35 GHz was more than 30 dB. The diagram of return loss at the input and output of the power amplifier in the whole Ka-band was less than −8dB. The maximum power-added efficiency (PAE) of the designed power amplifier was 80%. The output P1dB of the introduced structure was 36 dB and the output power of the power amplifier was 36 dBm. Finally, the IP3 value of the power amplifier was about 17 dB.

The strategy presented in this paper is based on the usage of Doherty and distributed structures and a new wideband power divider to benefit from their advantages simultaneously.

The purpose of this paper (systematic review and meta-analysis) is to synthesize and analyze studies that assessed Iranian hospital efficiency.

A systematic literature search was conducted using both international (the Institute for Scientific Information, Scopus and PubMed) and Iranian scientific (Magiran, IranMedex and Scientific Information Database) databases. The review included original studies that used the Pabon Lasso Model to examine Iranian hospital performance, published in Persian or English. A self-administered checklist was used to collect data. In total, 12 questions were used for quality assessment.

In total, 34 studies met our inclusion criteria. The fixed-effects meta-analysis indicated that 19.2 percent (95% confidence interval (CI): 15.6–23.2 percent) of hospitals were in Zone 1 (poor performance: low bed turnover rate (BTR) and bed occupancy rate (BOR) and high average hospital stay (ALoS)), 23.7 percent (95% CI: 20.1–27.8 percent) were in Zone 2, 31.7 percent (95% CI: 27.7–36 percent) in Zone 3 (good performance: high BTR and BOR and low ALoS) and 25.4 percent (95% CI: 21.7–29.5 percent) in Zone 4.

Results help Iranian health policymakers to understand hospital performance, which, in turn, may lead to promoting greater awareness and policy attention to improve Iranian hospital efficiency.

This study indicated that most Iranian hospitals had sub-optimal performance. Further studies are required to understand factors that explain the country’s hospital inefficiency.

The purpose of this study is to demonstrate that unsustainable revenues in municipalities are short term and may have an adverse effect on urban systems. Focusing on stable financial resources can reduce such adverse effects. According to the legal obligations of municipalities in the creation of sustainable revenue, developing tourism-based activities in municipalities can play a significant role in providing a sustainable income.

This study aims to assess the positive effects of economic opportunities related to tourism for the municipalities in Iran’s large-scale cities and to identify the hidden opportunities of tourism. Also, from interviews and analysis of themes based on the situation, task, action, result model, tourism opportunities have been extracted and classified.

As a result of this research, hidden income-generating opportunities of urban tourism have been identified for municipalities, including those depending on situation, tasks, actions and results. For each of these categories, strategies for the realization of tourism opportunities are presented. Tourism’s hidden opportunities include those relating to organizational aspects, tourism planning, tourism diplomacy, handicrafts, health tourism, event tourism and urban tourism marketing.

By taking advantage of these opportunities, income generation, employment and urban management will be improved in the municipalities.

The purpose of this paper is to analyze zero valent iron nanoparticles (NZVIs) by a novel green method, taken from Thymus vulgaris (TV) plant extract, were synthesized and applied to degrade reactive black 5 (RB5) azo dye.

The optimum conditions for the highest removal of RB5 dye were determined. Characterization of NZVIs was done by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The NZVIs were used for the removal of dye RB5, and the parameters affecting were discussed like pH, initial concentration, contact time and NZVIs dosage.

The characterization results of NZVIs by SEM, TEM, FTIR and XRD show that polyphenols, organic acids and proteins reduce not only the green synthesis of NZVIs but also the aggregation of nanoparticles. The maximum dye removal efficiency of 99.6 per cent occurred at pH 4, NZVIs dose of 600 mg/L, and contact time of 5 min. The adsorption of RB5 dye onto the NZVIs surface and scavenging of the azo bond (−N = N) by the strong reduction of NZVIs were the proposed mechanisms for dye removal. The application of NZVIs to treat wastewater containing reactive dye shows high degradation efficiency.

The findings may greatly benefit the application of the NZVIs taken from Thymus vulgaris (TV) in the fields of dye adsorption.

The present study is novel because it incorporated the morphological and structural properties of the synthesized NZVIs using a native plant of Iran and studied the capability of green-synthesized NZVIs to remove RB5 as a water contaminant.

The native plant presented here can be developed for reduced environmental pollution before discharge to accepted water.

The NZVIs is prepared via green-synthesized method, which is prepared with leaves of TV. There are two main innovations. One is that the novel NZVIs is prepared successfully by native plant via green-synthesized method. The other is that the optimized conditions were obtained for the removal of RB5 dye as a water contaminant. Furthermore, to the best of our knowledge, no study has ever investigated the removal of RB5 by NZVIs produced using a native plant in Iran.