Search results

Contra‐rotating turbines offer reduced size, weight, and cooling requirements, compared to conventional co‐rotating machinery. In spite of the associated mechanical complexity, their aero‐thermal performance is superior to conventional turbines, not only due to the elimination of stator blade rows, but also because lower turning airfoils can be implemented as a result. The purpose of this paper is to present a methodology to determine the optimum velocity triangles of the turbine, together with a two‐dimensional design and optimization tool to minimize the blade unsteady force using radial basis function network, coupled to a genetic algorithm. The proposed design methodology is illustrated with the aerodynamic design of a contra‐rotating two‐axis turbine, which is able to deliver the power necessary to drive the LOX and LH2 pumps of an improved expander rocket engine.

This paper presents a methodology to determine the optimum velocity triangles of the turbine, together with a two dimensional design and optimization tool to minimize the blade unsteady force using radial basis function network, coupled to a genetic algorithm. The proposed design methodology is illustrated with the aerodynamic design of a contra‐rotating two‐axis turbine, which is able to deliver the power necessary to drive the LOX and LH2 pumps of an expander rocket engine, namely the Japanese LE‐5B.

The airfoil optimizer allows reductions in the downstream pressure distortion of 40 per cent. Consequently, the unsteady forces in the downstream blade row are minimized.

This paper presents to turbomachinery designers in liquid propulsion a novel tool to enhance the aerodynamic performance while reducing the unsteady forces on the blades.

Peru’s recent macro-economic success has not translated into significant changes in the capabilities of the state to shape economic activities like Information and Communication Technologies (ICT) through specific policies, even though the country has drafted a national action plan, Agenda Digital del Perú, with stakeholders’ participation, as well as a National Broadband Plan. While there are some state programs that have been considered successes and are potentially examples for Peru and the region, the intent of having a full set of “information society” policies, as in the European Union, has failed.

The paper explores two sets of issues: the diffusion of internationally sourced policies and the capabilities of governments to impact the use of ICT. In the Peruvian case, the state has not been capable of both designing its own set of policies while still following the lead proposed at international fora. To understand the lack of success, it is necessary to differentiate between the shortcomings of local policy-making and the international agenda. Policy makers’ insistence on an “information society” approach is particularly prominent, as the term has been ever present as a policy objective while still lacking actual meaning.

This paper will explore the role of policy-making and the failures of digital policies. It will also consider the contradictory nature of a policy-making process that privileges policies stemming from international bodies over locally driven understandings of ICT policy needs.

The main goal of this paper is to evaluate the players' contribution and economic value in the soccer industry. Media visibility records provide us with comparable metrics to identify talent and make hiring decisions – these records can jointly capture sport (on-field) skills and other attractive (off-field) abilities.

This paper presents a valuation method that applies media visibility appraisals to estimate “theoretical values” of the transfer fees paid for hiring soccer players. The estimations are performed by analysing the evolution over time of the media exposure of about 5,000 individuals of more than 200 clubs.

The study’s empirical results reveal that, along with sport performance, the players' media status also affects their economic valuation, which explains why the clubs – in search of greater economic returns – fiercely compete for the most popular players. The paper also identifies the main factors determining the players' economic value. In predicting the players' transfer fees, some variables are statistically significant: individual media visibility, media visibility share of the player within his team, contract duration, status of the hiring team, years of experience, player's age at the end of the contract and the domestic league of the hiring team.

Professional sports provide reliable measures on individuals' performance that may help in the hiring process of workers. This paper identifies gifted soccer players while taking into account their skills as media leaders and the economic implications. Insofar as players' talents determine their teams' sport and economic achievements, the transfer fees paid for players must then be seen as a crucial factor. Measuring individual talent and being able to translate this talent into productivity levels entail serious methodological and empirical challenges.

Numerical and experimental results for different oncoming base-flow conditions indicate that nonuniform trailing edge blowing (NTEB) can expand the performance range of compressors and reduce the thrust on the rotor, while the efficiency of the compressor can be improved by more than 2 per cent.

Relevant aerodynamic parameters, such as total pressure, ratio of efficiency and axial thrust, are calculated and analyzed under conditions with and without NTEB. Measurements are performed downstream of two adjacent stator blades, at seven equidistantly spaced reference locations. The experimental measurement of the interstage flow field used a dynamic four-hole probe with phase lock technique.

An axial low-speed single-stage compressor was established with flow field measurement system and nonuniform blowing system. NTEB was studied by means of numerical simulations and experiments, and it is found that the efficiency of the tested compressor can be improved by more than 2 per cent.

Unlike most of the previous research studies which mainly focused on the rotor/stator interaction and trailing edge uniform blowing, the research results summarized in the current paper on the stator/rotor interaction used inlet guide vanes for steady and unsteady calculations. An active control of the interstage flow field in a low-speed compressor was used to widen the working range and improve the performance of the compressor.