The Microstructure Formation of a Protective Oxide-Scale Layer on Small-Diameter FeCrAl Fibers

FeCrAl fibers, at high temperatures, form a protective oxide-scale layer dominated by aluminum oxide on the surface to prevent further oxidation of the base metal alloy. This study investigates the effects of heat treatment on the microstructure formation of the oxide-scale layer on small-diameter FeCrAl fibers, 12 and 17 µm, produced using a bundle drawing process. The morphology examination and chemical analyses of the small-diameter fibers exhibit the microstructure and chemical compositions of the surface and cross-section areas, revealing a distinctive interface layer with a high aluminum concentration between the base metal and the oxide-scale layer. Furthermore, thermogravimetric analysis results show that the 12 µm fibers have about a 60% higher oxidation rate than the 17 µm fibers—caused by the high outward diffusion of aluminum to the surface of the fibers due to their high surface-area-to-weight ratio. Consequently, the high growth rate of the nonuniform oxide-scale layer and the limited aluminum reservoir of the 12 and 17 µm diameter fibers lead to faster depletion of aluminum from the base metal alloy—limiting the lifetime and durability of the smaller-diameter fibers in high-temperature applications

Problems of Female Preservice Kuwaiti English Language Teachers During the Practicum Course

Knowledge of pre-service teachers' difficulties and the obstacles they face during their practicum is supremely important to designing and implementing a successful field experience. Based on this, the current study explored and discussed the most frequent problems that Kuwaiti English language pre-service teachers face during their practicum course. The purpose of this research is to learn more about the challenges and obstacles that female pre-service Kuwaiti English language teachers (n = 45) may experience throughout their practicum period. To achieve the intended outcomes, the study used a qualitative approach. Semi-structured interviews were conducted with female pre-service English language teachers at the college of Basic Education in Kuwait. The College of Basic Education plays a key role in providing qualified female teachers to the Ministry of Education through a training program that prepares potential English instructors to fulfil the career requirements of English instructors. According to the findings of the research, different issues have been aroused by the participants as they have complained about some aspects of the practicum course, including preparing lesson plans and workload, relationship with colleagues in the department, classroom management (especially dealing with students who have special cases), and academic supervisors. Interpretations of the results and recommendations are discussed in relation to the context of the study

Problems of Female Preservice Kuwaiti English Language Teachers During the Practicum Course

Knowledge of pre-service teachers' difficulties and the obstacles they face during their practicum is supremely important to designing and implementing a successful field experience. Based on this, the current study explored and discussed the most frequent problems that Kuwaiti English language pre-service teachers face during their practicum course. The purpose of this research is to learn more about the challenges and obstacles that female pre-service Kuwaiti English language teachers (n = 45) may experience throughout their practicum period. To achieve the intended outcomes, the study used a qualitative approach. Semi-structured interviews were conducted with female pre-service English language teachers at the college of Basic Education in Kuwait. The College of Basic Education plays a key role in providing qualified female teachers to the Ministry of Education through a training program that prepares potential English instructors to fulfil the career requirements of English instructors. According to the findings of the research, different issues have been aroused by the participants as they have complained about some aspects of the practicum course, including preparing lesson plans and workload, relationship with colleagues in the department, classroom management (especially dealing with students who have special cases), and academic supervisors. Interpretations of the results and recommendations are discussed in relation to the context of the study

Line and Subdivision Graphs Determined by T 4 -Gain Graphs

Let T 4 = { ± 1 , ± i } be the subgroup of fourth roots of unity inside T , the multiplicative group of complex units. For a T 4 -gain graph Φ = ( Γ , T 4 , φ ) , we introduce gain functions on its line graph L ( Γ ) and on its subdivision graph S ( Γ ) . The corresponding gain graphs L ( Φ ) and S ( Φ ) are defined up to switching equivalence and generalize the analogous constructions for signed graphs. We discuss some spectral properties of these graphs and in particular we establish the relationship between the Laplacian characteristic polynomial of a gain graph Φ , and the adjacency characteristic polynomials of L ( Φ ) and S ( Φ ) . A suitably defined incidence matrix for T 4 -gain graphs plays an important role in this context

Three Representation Types for Systems of Forms and Linear Maps

We consider systems of bilinear forms and linear maps as representations of a graph with undirected and directed edges. Its vertices represent vector spaces; its undirected and directed edges represent bilinear forms and linear maps, respectively. We prove that if the problem of classifying representations of a graph has not been solved, then it is equivalent to the problem of classifying representations of pairs of linear maps or pairs consisting of a bilinear form and a linear map. Thus, there are only two essentially different unsolved classification problems for systems of forms and linear maps

Surface Evaluation of a Multi-Pass Flexible Magnetic Burnishing Brush for Rough and Soft Ground 60/40 Brass

Burnishing is an advanced finishing process that produces higher-quality surfaces with better hardness and roughness than conventional finishing processes. Herein, a flexible magnetic burnishing brush comprising stainless steel pins under permanent magnet poles was used to investigate the influence of multiple passes and directions on the produced surface of soft and rough ground prepared brass. In total, five different samples were burnished on each of the two brass samples prepared. Four samples were processed in the same direction for up to four passes and the fifth sample was processed with two passes in the opposite direction. Results indicate that there was approximately a 30% increase in hardness and an 83% increase in microroughness for rougher-surface brass samples. For smoothly prepared surfaces, there was approximately a 14% increase in hardness and a 35% increase in microroughness. In the same direction of multi-pass burnishing, increasing the number of passes negatively affected surface roughness; for rougher surfaces, the surface hardness reduced and process uniformity increased owing to surface over-hardening and flaking mechanisms, and for smoother surfaces, the hardness, roughness, and process non-uniformity increased with the number of passes owing to repeated surface deformation at some locations and high flaking at other locations. Compared to single-pass burnishing, wherein the surface roughness and microhardness showed almost no change with high process uniformity, in burnishing with two opposite-direction passes, the produced surface exhibited better surface roughness, process uniformity, and microhardness improvements owing to a reverse strain mechanism. Hence, opposite burnishing passes are recommended