Processing and Ductile-Brittle Transitions in PM Manganese Steels

YesBrittleness in manganese steels can be associated with processing in a "wet¿ [micro]climate resulting in the formation of continuous oxide networks. The formation of these networks can be prevented by sintering in an atmosphere, also ¿local¿ in a semiclosed container, adhering to the Ellingham-Richardson oxide reduction criteria. When this requirement is satisfied, however, further types of ductile ¿ brittle transitions are observed. Rapid cooling, typically above 40°C/min, produces enough martensite to render Fe-(3-4)Mn-(0·6-0·7)C material macroscopically brittle. Quenched and conventionally tempered structures remain brittle. It is tentatively suggested that segregation of minor alloying/tramp element(s), as in cast materials, is responsible for this temper embrittlement. To overcome it, heat treatment at a temperature no higher than 200°C, recovery/stress relief, is recommended

Electronic spectroscopy of transient species in plasma discharges

The work was focused on the spectroscopic study of carbon chain species as well as small boron clusters in the gas phase. The experimental apparatus was built before, however, in order to produce boron species. The source had to be modified as in this case a solid sample of precursor had to be used. Up to now the apparatus could be used to study the electronic transitions of variety of the species producing only by discharging a suitable gas precursor. The heating system built for this purpose worked flawlessly and the first gas-phase electronic spectrum of B3 could be obtained. This experiment showed that solid-state precursors can be also used for the production of the exotic species in the gas phase, which increases significantly the potential of the CRD experiment. The heated source can be promising for further studies of the bare carbon chains C6+, C7+ and C9+. Their spectra were already measured in the neon matrix and solid precursor (perchloronaphtalene) was used in this case. Since C10Cl8 worked very well in the matrix experiment, it seems reasonable to assume that in the CRD experiment this precursor could work as well. As mentioned before, cavity ringdown spectroscopy combined with a supersonic slit jet plasma have been applied to obtain gas-phase spectra of the variety of carbon chain species. They ranged from rather short ones like HC4H+, to relatively long such as HC10H+. Most of them are linear, however, spectra of the nonlinear carbon chains were also measured (C4H4+, C6H4+ and C8H4+). High sensitivity of the cavity ringdown method and low temperature attained in a jet, in many cases allowed to obtain and analyze rotationally resolved electronic spectra. One of the main results of the work was obtaining the electronic spectrum of the pentaacetylene cation. It turned out to be the largest polyacetylene cation measured in the gas phase so far. Astrophysical relevance of the HC10H+ was considered, however, the work showed that HC10H+ can not be a carrier of the DIBs. There was no match with the hitherto reported diffuse interstellar bands in the near infrared. Apart from carbon chain species, the spectrum of the cyclic B3 molecule was also measured. It was the first detection of this molecule in the gas phase. The analysis of the rotational structure of the spectrum allowed the geometry of the molecule to be inferred, which turned out to be the first structural information on cyclic boron trimer in the gas phase

Tensile properties of Fe-3Mn-0¿6/0¿7C steels sintered in semiclosed containers in dry hydrogen, nitrogen and mixtures thereof

Ye

What is print? A Characterization of the printing industry in the United States

Print touches our lives constantly in the form of product packaging, books, newspapers, magazines, mail, or any of the wide variety of printed items we use every day. We consume it without even thinking about it. To treat printing as a stand-alone product, service, or process is impossible. It is a manufacturing industry in the strictest sense, but it is also a service industry. There are a number of other industries and services intertwined with printing, such as paper manufacturing, ink manufacturing, equipment manufacturing, print finishing, graphic design, marketing, distribution, mailing, and fulfillment services. This report will briefly touch on these ancillary industries as needed, but is not an exhaustive discussion of the relationships (be they financial, historical, or physical) between all of these and the printing industry. Instead, this report is intended to be an introduction to printing and its many facets. References, an appendix on the history of the industry, and a suggested reading list have been provided for further study

The ambivalence of comradeship in the appointment of principals: A threat to the provision of quality education

In this article, we problematise the practice of appointing principals on the basis of comradeship instead of excellence, qualifications and competency. The appointment of principals in South Africa has, over the years, become politicised and unionised to the extent that it is contextualised within comradeship narratives, thereby negating the competency and qualifications that are required to champion quality education – education that is essential to empower people. To cement its arguments, the article is couched in decoloniality, a framework that evokes the need to challenge coloniality, which has displaced professionalism and competency as criteria for appointing principals. The data for the study were generated through questionnaires completed by, and interviews with, 19 participants in KwaZulu-Natal (KZN) province. The article reports that most schools with comrade principals face challenges related to competency, learner performance and indiscipline. The article recommends that the Department of Basic Education revisit its   appointment policy for principals to ensure that competent principals are appointed, regardless of whether they are comrades or not. Keywords: comradeship; politics of belonging and othering; principalship; unionis

Collaborative Learning: A Veritable Tool for Promoting Classroom Participation Among Pre-Service Teachers in Rural Universities in South Africa

The benefits of collaborative learning (CL) in teaching-learning have been well-documented. According to existing literature, it will help students and teachers learn from one another, develop good communication skills, foster a sense of community, trust and respect, and retain and apply the information in their future studies. Unfortunately, observation coupled with research shows that pre-service teachers’ participation in South Africa's rural universities is at its lowest ebb – a potential source of concern to education stakeholders given its futuristic implications in the light of CL benefits. Less pre-service teachers’ participation has been linked to cultural influence, environmental factors and students’ backgrounds and have negatively impacted students’ academic achievement. This paper seeks to typify CL as a panacea to pre-service teachers' apathy toward learning. In doing this, social constructivism theory (SCT) was adopted to underpin the study. Drawing from the principles of participatory action research, fifteen undergraduate students were randomly selected, and data was gathered with the instrumentation of semi-structured interviews and focus groups. The study revealed the think-peer-share strategy, group work strategy, micro-teaching strategy, positive feedback and encouragement, learner-centred method, and inquiry method as strategies for improving participation among pre-service teachers in rural universities. Recommendations were made in line with the findings of the study

Promoting student teachers’ adaptive capabilities through community engagement

The gap between student teachers and their ability to adapt to the school situation remains a challenge. The literature further indicates that there is an under-utilisation of students’ abilities in an ever-changing curriculum that should be responsive to the challenges with which communities are faced. This paper aims to report on the students’ adaptive capabilities through a school-initiated community engagement project. Approximately nine students were placed at schools on Saturdays while offering lessons to grade nine learners. A focus group interview was held with the students who offered natural sciences, mathematics and social sciences after the initiative. Findings of this study included raising the students’ awareness for the need and ability to improvise in order to attend to the needs of the school and their ability to go out and seek information from other schools, the university and experienced teachers. The students were also able to leave the handouts they had designed for the school. The study provides insights into the adaptability of students in schools and recommends further empowerment spaces for student teachers and the school community

Mentor-Mentee Experiences Amidst COVID-19: A Teaching Practice Case Study

Preparing student teachers for the world of work is seen globally as a challenge. This research aims to explore mentors and mentees experiences in teaching practice during the COVID-19 period. In order to explore the challenge in this study, the following research question guided the paper: What are the teaching practice experiences of mentors and mentees at a school during COVID-19? The research question is a result of limited research done on the experiences of two groups during COVID-19. Informed by the realist social theory, we generated data via telephonic interviews with mentors and mentees in one school. The data was generated through semi-structured Interviews and thematic analysis was a method employed in the analysis of the data. The results present challenges experienced by mentees which, amongst others, include a feeling of inadequacy or a lack of confidence in their abilities to bring about order to the classroom and a feeling of being excluded in meetings and extra-curricular activities. On the other hand, mentors receive mentees without any prior warning or without arrangements made to accommodate them and the absence of the university officials except for assessment. Based on the results, a collaborative approach should be employed to deal with some of the challenges experienced by mentors and mentees

Microstructure and mechanical properties of sintered (2-4)Mn-(0¿6.-0¿8)C steels

YesMechanical properties of 2¿4% manganese PM steels were determined in tension and in bending following laboratory sintering in dry, hydrogen rich atmospheres. Young's modulus determined by an extensometric technique was about 115 GPa; when measured by an ultrasonic method it was about 153 GPa, in accordance with the`law of mixtures¿. The microstructures, significantly devoid of oxide networks, were predominantly pearlitic, but frequently with variability for specimens similarly processed, resulting in appreciable variations in the stresses for macroscopic yielding and fracture. The majority of the experiments were conducted on 3 and 4Mn¿0·6C alloys and for these R0·1 was in the range 275¿500 MPa, tensile strength (TS) 300¿600 MPa, and (apparent) transverse rupture strength (TRS) 640¿1260 MPa. Statistical techniques were employed to analyse the data. When careful control of processing was maintained, the Weibull modulus was highest, at about 17, for TS of furnace cooled specimens, and lowest, about 6, for TRS of the rapidly cooled specimens. In order to interpret the significant differences between the TRS and the TS values, both apparently measuring the critical stress for cracking after strains of up to 7%, a two stage normalising technique for TRS was adopted. By taking account of the plastic strains preceding failure, the elastic`strength of materials¿ formula was modified to allow true fracture stresses to be calculated. It was also postulated that failure was initiated from a population of flaws of variable size and then the `normalised¿ bend strengths, smaller than TRSs, were shown to correspond well with TSs. It is suggested that this combined plasticity correction and Weibull analysis approach, which has a sound scientific basis, should be employed to interpret bend test data in preference to empirical correlations between TS and TRS

Managing the Culture of COVID-19 "New Normal" as a Motivation for University Students in South Africa

The advent of COVID-19 and its implication on university education has been the bone of contention in recent times. The COVID-19 emergency has led to a change in knowledge inputs, processes, and outputs. This trajectory has demotivated student approaches to their learning. In response to this revolution, this study provides motivational strategies through students' perspectives to respond to the underside of new normal among South African university students. Ubuntu underpins the study within the Transformative Paradigm lens and Participatory Research as a research design. Ten students of a particular module in a selected university in South Africa were chosen to participate in the study. They were selected using the snowballing sampling technique because the participants were under level 3 lockdown with little or no access to campus at the time of the study. Online interview via phone calls, email and WhatsApp, was conducted with the students, and the data were analysed using Thematic Analysis. The study revealed a lack of visualised physical engagement between students and their lecturers and unstable internet access and lack of the internet as the major challenges.  The study, therefore, recommends solutions that there should be adequate provision of effective online audio-visual sessions with enough space for student-lecturer’s interactions and low-tech online sessions and content deliveries