Search results

This paper aims to detail the reactive flow simulations of a LOX/CH4 multi-element rocket engine. The work has been conducted within the framework of the HYPROB-BREAD project whose main objective is the design, manufacture and testing of a LOX/LCH4 regeneratively cooled ground demonstrator.

Numerical simulations have been carried out with both commercial software and CIRA software developed in house. Two sets of boundary conditions, nominal and experimental, have been applied from which a code-to-code validation has been effected with the former and a code-to-experiment validation with the latter.

The results presented include both flow data and heat fluxes as well as parameters associated with engine performance, and indicate an excellent agreement with experimental data of a LOX/CH4 multi-element rocket engine.

The research is unique as the CIRA code Numerical Experimental Tool (NExT) has been validated with the commercial software FLUENT as well as with experimental values from the firing of the LOX/CH4 rocket engine demonstrator.

The purpose of this study is to provide the description of a computational methodology to model the combined propulsive systems of hydrogen propelled air-breathing scramjet vehicles and to evaluate the pollutant and climate-changing emissions.

Emissions indexes of nitrogen oxide (EINO) and water vapour released by the air turbo rocket (ATR) and dual mode ramjet (DMR) engines of the STRATOFLY air-breathing, hypersonic scramjet vehicle, propelled by hydrogen/air were evaluated. ATR engine operation was assessed for several cruise conditions in both subsonic and supersonic flight regimes in Ecosimpro software, which is an object-oriented thermodynamic design and simulation platform. ATR combustor inlet flow conditions play a key role in the computation of species mass fractions, and these conditions are highly dependent on turbomachinery performance and engine flight regime. A propulsive operational database was created by varying mass flow rates of fuel and flight conditions such as cruise speed and altitude to investigate possible engine operations. The all-inlet conditions in this map are provided to the Cantera-Python chemical/combustion chemistry solver implementing a specially designed and formulated 0D kinetic-thermodynamic methodology successfully used to model and simulate the electric spark ignition required to activate the combustion process of the reacting mixture in the ATR combustion chambers, whereas the coupled aero-thermodynamic/aero-propulsive 0D/1D code i.e. Scramjet PREliminary Aerothermodynamic Design (SPREAD), designed and developed by the Italian Aerospace Research Centre (CIRA) was used for DMR calculations. Results show low emissions of NO according to the optimized design of the ATR; on the other hand, a tuning of operational conditions is needed for DMR, with its complete re-design to be more conclusive. Analogously, the released amount of water vapour is in good agreement with the required combustion efficiency and the expected propulsive performance.

Results show low emissions of NO according to the optimized design of the ATRs; on the other hand, a tuning of operational conditions is needed for DMR, with its complete re-design to be more conclusive. Analogously, the released amount of water vapour is in good agreement with the required combustion efficiency and the expected propulsive performance.

Applications of innovative 0D/1D chemical kinetic methodology and in-house codes.

The purpose of this paper is to investigate the existence of sticky floor and glass ceiling effects in the gender wage gap (GWG) among Spanish managers. In addition, the paper determines if the pay gap at every quantile is a result of the gender characteristic differences, or the differences in returns to those characteristics.

The paper exploits a counterfactual decomposition analysis, using quantile regression, to decompose the GWG into one component that is based on differences in characteristics and one component that is based on differences in coefficients across the wage distribution.

A significant GWG over all the wage distribution is found. Such a gap exhibits a clear U-shaped pattern, thus pointing out both significant sticky floor and glass ceiling effects. Furthermore, the paper shows that such pattern is mainly determined by the coefficient effect, whose relative incidence is almost continuously increasing along the wage distribution.

While it is difficult to give a definitive explanation for the significant U-shaped pattern in the GWG and for the bigger incidence of the glass ceiling, the authors suggest two possible explanations that are consistent with these findings. The paper leaves the identification of these explanations to future research.

The pattern of rising coefficient effects at higher quantiles suggests that the glass ceiling is a more relevant question than the sticky floor. Indeed, at the highest wage quantiles, differences in characteristics make essentially no contribution to the overall wage gap. This suggests that upper-echelon female managers have the same characteristics as their male counterparts, which emphasizes the role of discrimination for these top-level jobs.

Despite the general GWG has been largely investigated, the analysis of a wage differential among managerial workers has certainly drawn much less attention. In particular just a few papers have investigated the existence of sticky floors and glass ceiling among managers. In addition, as to Spain, there is no empirical survey investigating and decomposing the gender pay gap among managers.

The cycle of external indebtedness of dependent countries has become a huge constraint on any strategy for radical social change.

Argentina has recently entered a new process of debt overhang and renegotiation with the International Monetary Fund and private global creditors. The dominant debate around the country's foreign debt revolves around the conditions that can guarantee the sustainability of repayment. The underlying objective is to remain in the debt system that produces and reproduces dependency.

This chapter will seek to analyze the question of debt sustainability from another point of view: Is it possible to guarantee the (financial) sustainability of the debt at the same time as guaranteeing the sustainability of life? Our argument is that by remaining in the global debt system, Argentina creates conditions that violate the requirements for the sustainability of human and nonhuman life. Drawing on a discussion from Marxist dependency theory and the traditions of Marxist feminism and environmentalism, we will discuss how the debt sustainability argument presupposes the impossibility of reproducing life. In particular, we will show how the conditions required to guarantee debt sustainability in Argentina entail the deepening of the superexploitation of the “productive” and “reproductive” labor force, and the exacerbation of extractivism, putting social reproduction in crisis.

The purpose of this paper is to review the contributions of what has been established as Latin American thought, as science, technology, and innovation (STI) in Latin America have been strongly related to development.

The analysis method is based on the review of a group of Latin American and Latinoamericanista (Latin Americanist) authors who were selected on the basis of their contributions to the explanation and proposals of public policy related to STI. The following are some of the questions that guide the analysis. How much has STI in Latin American thought contributed to the development theory? Given the fact that there are other dominant mainstreams, can we say that Latin American thought is still relevant?

The main conclusion of this work is that Latin American thought is still applied to current Latin American development discussions. This can be proven by the creation of particular concepts and analytical frameworks such as structural heterogeneity, development styles, authentic and spurious competitiveness, Sabato’s Triangle, the centre-periphery model, and STI policy practices.

This paper gathered contributions and categorised them into three dimensions: state participation (intensity, composition), industrialisation as the impulse for development, and instruments and public policy actions that can be implemented or have already been implemented.

El propósito de este trabajo es el de reflexionar sobre algunas aportaciones provenientes de lo que hemos denominado pensamiento latinoamericano en relación con la innovación, la ciencia, la tecnología y su relación con el desarrollo.

El método de análisis se basa en la revisión de un conjunto de autores latinoamericanos y latinoamericanistas que hemos seleccionado con base en sus aportaciones para la explicación y sus propuestas de política pública en relación con la CTI. Algunas preguntas que guían nuestro análisis son las siguientes: ¿en qué medida el pensamiento latinoamericano en CTI ha contribuido a la teoría del desarrollo? y ¿dada la existencia de otros enfoques que predominan como pensamiento único, podemos hablar de una vigencia del pensamiento latinoamericano?

La principal conclusión de nuestro trabajo es que hay un pensamiento latinoamericano vigente que ha sido y aún es un referente actual para la discusión del desarrollo en la región latinoamericana, como lo muestran la creación de conceptos y esquemas analíticos como los de heterogeneidad estructural, estilos de desarrollo, la competitividad auténtica y espuria, el Triángulo de Sábato, centro-periferia, así como estrategias de política en CTI.

Como parte del marco analítico hemos agrupado al conjunto de aportaciones en tres direcciones: a) la participación del Estado (intensidad, composición); b) la industrialización como impulso al desarrollo y c) los instrumentos y medidas de política pública a implementar o que han sido implementados.

The purpose of this study is to identify the main perspectives and trends in educational data mining (EDM) in the e-learning environment from a managerial perspective.

This paper proposes a systematic literature review to identify the main perspectives and trends in EDM in the e-learning environment from a managerial perspective. The study domain of this review is restricted by the educational concepts of e-learning and management. The search for bibliographic material considered articles published in journals and papers published in conferences from 1994 to 2023, totaling 30 years of research in EDM.

From this review, it was observed that managers have been concerned about the effectiveness of the platform used by students as it contains the entire learning process and all the interactions performed, which enable the generation of information. From the data collected on these platforms, there are improvements and inferences that can be made about the actions of educators and human tutors (or automatic tutoring systems), curricular optimization or changes related to course content, proposal of evaluation criteria and also increase the understanding of different learning styles.

This review was conducted from the perspective of the manager, who is responsible for the direction of an institution of higher education, to assist the administration in creating strategies for the use of data mining to improve the learning process. To the best of the authors’ knowledge, this review is original because other contributions do not focus on the manager.