Search results

A key challenge found in additive manufacturing is the difficulty to produce components with replicable microstructure and mechanical performance in distinct orientations. This study aims to investigate the influence of build orientation on the fracture toughness of additively manufactured AlSi10Mg specimens.

The AlSi10Mg specimens were manufactured using the selective laser melting (SLM) technology. The fracture toughness was experimentally determined (under ASTM E399-09) using C(T) specimens manufactured in different orientations. The microstructure of the specimens was examined using metallography to determine the effects of grain orientation on fracture toughness.

The fracture toughness magnitude of manufactured specimens ranged between 36 and 50 MPam, which closely matched conventional bulk material and literature values regarding AlSi10Mg components. The C(T) specimens printed in the T-L orientation yielded the highest fracture toughness. The grain orientation and fracture toughness values confirm the anisotropic nature of SLM parts where the T-L-oriented specimen obtained the highest K_IC value. A clear interaction between the melt pool boundaries and micro-slipping during the loading application was observed.

The novelty of this paper consists in elucidating the relationship between grain orientation and fracture toughness of additively manufactured AlSi10Mg specimens because of the anisotropy generated by the different melting pool boundaries and orientations in SLM. The findings show that melt pool boundaries can behave as easier pathways for cracks to propagate and subsequently reduce the fracture toughness of specimens with cracks perpendicular to the build direction.

An experimental and numerical study of thermal profiles of 316 L stainless steel during selective laser melting (SLM) was developed. This study aims to present a novel approach to determine the significance and contribution of thermal numerical modeling enhancement factors of SLM.

Surface and volumetric heat models were proposed to compare the laser interaction with the powder bed and substrate, considering the powder size, absorptance and propagation of the laser energy through the effective depth of the metal layer. The approach consists in evaluating the contribution of the thermal conductivity anisotropic enhancement factors to establish the factors that minimized the error of the predicted results vs the experimental data.

The level of confidence of the carried-out analysis is of 97.8% for the width of the melt pool and of 99.8% for the depth of the melt pool. The enhancement factors of the y and z spatial coordinates influence the most in the predicted melt pool geometry.

Nevertheless, the methodology presented in this study is not limited to 316 L stainless steel and can be applied to any metallic material used for SLM processes.

This study is focused on 316 L stainless steel, which is commonly used in SLM and is considered a durable material for high-temperature, high-corrosion and high-stress situations.

The additive manufacturing (AM) technology is a relatively new technology becoming global. The AM technology may have health benefits when compared to the conventional industrial processes, as the workers avoid extended periods of exposure present in conventional manufacturing.

This study presents a novel approach to determine the significance and contribution of thermal numerical modeling enhancement factors of SLM. It was found that the volumetric heat model and anisotropic enhancement thermal approaches used in the present research, had a good agreement with experimental results.

The purpose of this paper is to explore the relationship between clientelist relationships and economics in public relations practice in European Mediterranean countries and Latin America. It considers the cases of Greece, Italy, Portugal, Spain, Brazil, Chile, and Mexico.

This paper uses a critical-conceptual method through a re-conceptualization of themes from secondary qualitative analyses of existing qualitative data sets and reviews of published qualitative papers.

The public relations practice in these two regions is similar. The characteristics of the public relations landscape in these countries must be understood in relation to a broader history of clientelism and economics emphasizing government relationships at the expense of other publics, as well as the lack of scale economies. Persuasive models are prevalent, although a number of forces – including integration in supranational organizations, democratization, and globalization – have strengthened the use of symmetrical models.

This is not an empirical survey, there is a need of quantitative studies among practitioners and government officials that can measure empirically the nature of their relationships in a number of countries. This essay opens a door for future studies and cross-cultural comparisons about the role that clientelism plays in the PR practice of cultures and countries.

The paper offers useful background information, such as the primacy that media relations still have in the public relations practice, for foreign public relations executives, agency heads, and managers of public relations who are directly involved with or managing international public relations campaigns in these countries.

Clientelism is a cultural concept that translates to the work of organizations and consequently public relations as a form of organizational behavior.

This paper brings to the table the importance of the concept of clientelism in the PR practice as well as the existence of a similar PR culture between countries that are on different continents.

The objective of this chapter is to analyze diabetes onset in Mexico in terms of work relations and family. The authors examined the impacts of diabetes on inequalities, practices of violence among the Mexican population, analyzing gender relations in the context of having diabetes. Our research is based on mixed method approach. First, the authors conducted a survey among 110 diabetic persons in Chiapas and Nuevo León, two Mexican states from the North and the South. Results show that gender violence has impacts in both Mexican states despite of socioeconomical differences. Overall, diabetes is a complex social process that need to be analyzed on different social and socioeconomical levels. Gender violence is a particularly strong factor that has an impact on diabetes. The contribution of this research is based on understanding of diabetes onset as a social construction where gender violence, social cohesion and subjective wellbeing play a significant role in diabetes in the Mexican context. The outcomes of this research might have an impact on transformation of public health policy in Latin America and the Caribbean, from a medical approach to a sociocultural one in terms of diabetes as a chronic illness. Moreover, our results suggest that quality of life depends on the level of interacting within social groups, as diabetes is no longer a disease that affects an individual, but it is more a social phenomenon.

Although corporate structures in Japan and, to a lesser extent Korea, have been examined in the literature, in most cases the framework is not comparative. In other cases the framework is comparative, with keiretsu and chaebol compared to US conglomerates. A third foreign conglomerate, the Mexican grupo, has thus far escaped much serious attention by scholars. Attempts to compare the structure of keiretsu, chaebol, and grupo in terms of the other. Aims to identify what can be learned from comparing foreign corporate structures with other foreign corporate structures, rather than with corporate structures in the USA.

The thermal spraying technique of High-Velocity Oxygen Fuel (HVOF) coating was used to deposit coatings of an alloy composed of Ni-based substrates on stainless steel AISI 304. The aim of this study was to determine the mechanical properties such as hardness and bond strength that these coatings have when the spray distance is varied, as well as the microstructure and phases formed during the thermal spray process.

The coatings were applied by HVOF and characterized by scanning electron microscopy, image analysis, X-ray diffraction, microhardness and bond strength to analyze the mechanical properties.

The microstructure of the coatings showed low porosity, oxide content and interface contamination in the substrate–coating interface, without the presence of unmolten particles. The microhardness values reached 600 HV for the three spray distances used and the bond strength values reached over 55 MPa.

The use of coatings on aircraft components is growing dramatically owing to the high costs of advanced materials and the growing lifecycle requirements for high-performance systems, which are taken into account because of the variety of coatings and complexity of environmental factors.

The originality of this study lies in the development of new coating materials for the manufacture and protection of various turbine components. The value is based on the development of materials and processes to be used to manufacture them.

The purpose of this research was to develop new sustainability indicators consistent with the sand mould casting industry, through benchmarking of cleaner production (CP), in order to identify the levels of practice and performance of companies of the casting sector. In addition, a lean manufacturing checklist was specified in order to verify the presence of lean manufacturing techniques employed to eliminate waste towards CP. No previous work was found in the literature that attempts to assess practices and performance of companies performing sand mould casting (a significantly polluting manufacturing process) in the context of CP and lean manufacturing.

For the application of this benchmarking, nine companies from the sand mould casting sector were studied, where the profile of each company was analysed through eight variables and 47 indicators. Data was obtained through face-to-face visits and questionnaire application in the companies, and the data was analysed both quantitatively and qualitatively.

The results obtained were the diagnosis of companies' practices and performance resulting from their position in the benchmarking charts, as well as the identification of the areas in which companies should implement improvements aiming at achieving CP.

This research was developed specifically for sand mould casting companies, and each process has its own characteristics

14 companies were invited to participate in this survey, but nine companies agreed to participate. Unfortunately, there were companies that declined to participate in the survey.

It is important to diagnose casting companies regarding CP practices, performance and deployment potential. Thus, important negative issues in the company can be identified, and with this information, they can develop actions focussed on cases that need more attention. In addition, this work contributes to evaluate the relationship and efficiency of improvement actions developed by companies in the context of both lean manufacturing and CP, aiming to reduce or eliminate the environmental impact. The improvement of practices and performance of a company regarding CP is considered to be beneficial to supply chain management in the context of sustainability, as the other participating companies are likely to seek ways to reduce environmental impact, and the diagnostics provided by this work may also be used by those companies.

It is no coincidence that the universities were pioneers of the internet, for the medium lends itself uniquely well to academic debate and collaboration. We call this process of sharing ideas in cyberspace “virtual learning”, and the main goal of any such community is to create a shared understanding that will inspire research and development. This paper describes trends and issues in creating a Virtual Learning Community in systems engineering, drawing upon the results of an European ALFA‐funded project named COSME.

Reducing fuel consumption of unmanned aerial vehicles (UAVs) during transient operation is a cornerstone to achieve environment-friendly operations. The purpose of this paper is to develop a control scheme that improves the fuel economy of a turbojet in its full operating envelope.

A novel direct-thrust linear quadratic integral (LQI) approach, comprised by an optimal observer/controller satisfying specified performance parameters, is presented. The thrust estimator, based in a Wiener model, is validated with the experimental data of a micro-turbojet. Model uncertainty is characterized by analyzing variations between the identified model and measured data. The resulting uncertainty range is used to verify closed-loop stability with the circle criterion. The proposed controller provides stable responses with the specified performance in the whole operating range, even with after considering plant nonlinearities. Finally, the direct-thrust LQI is compared with a standard thrust controller to assess fuel economy and performance.

The direct-thrust LQI approach reduced the fuel consumption by 2.1090% in the most realistic scenario. The controllers were also evaluated using the environmental effect parameter (EEP) and transient-thrust-specific fuel consumption (T-TSFC). These novel metrics are proposed to evaluate the environmental impact during transient-thrust operations. The direct-thrust LQI approach has a more efficient fuel consumption according to these metrics. The results also show that isolating the thrust dynamics within the feedback loop has an important impact in fuel economy. Controllers were also evaluated using the EEP and T-TSFC. These novel metrics are proposed to evaluate the environmental impact during transient-thrust operations. The direct-thrust LQI approach has a more efficient fuel consumption according to these metrics. The results also show that isolating the thrust dynamics within the feedback loop has an important impact in fuel economy.

This study shows the design of an effective direct-thrust control approach that minimizes fuel consumption, ensures stable responses for the full operation range, allows isolating the thrust dynamics when designing the controller and is compatible with classical robustness and performance metrics. Finally, the study shows that a simple controller can reduce the fuel consumption of the turbojet during transient operation in scenarios that approximate realistic operating conditions.

This study aims to build on embedded approaches to stakeholder management and examines how organizational decision-makers consider social responsibility toward proximal stakeholders in crises that encompass an entire system of stakeholder relationships.

Within a criterion-based sample of eight Latin American private universities, this paper develops in-depth exploratory case studies to examine the prioritization of stakeholders in higher education institutions’ decision-making during the outbreak of the COVID-19 crisis.

Contrary to the notion that during crises organizations prioritize stakeholders that provide resources that are critical to survival, this study finds that in contextual crises stakeholder management is informed by social responsibility. In addition, the findings suggest that crises may be tipping points for changes toward mission-driven approaches to governance.

Acknowledging the roles of social responsibility and proximity in stakeholder management during contextual crises allows for more informed governance of organizations that face disruptions in their system of stakeholder relations.

This study contributes unique insights into the decision-maker’s prioritization of stakeholders during the COVID-19 crisis. The uncertainty associated with the emerging “new normal” allowed for an extreme test of socially embedded versus resource-oriented approaches to stakeholder management.