1,721,080 research outputs found
Innovative design methodology with LTO noise prediction capabilities for future supersonic aircraft
Full text linkTo bring supersonic flight back to reality, it is crucial to demonstrate that future supersonic aircraft can reduce their environmental impact compared to the past. In line with this effort, the EU-funded MORE&LESS project is reviewing the environmental impact of supersonic aviation, by applying a multidisciplinary holistic framework to help check how enabling technologies of supersonic aircraft, trajectories, and operations comply with environmental requirements. The present study is part of this project and focuses on updating the traditional conceptual design process with methods for estimating the noise generated at airport level by supersonic aircraft. To achieve this, it is necessary to include some basic capability in the design flow, such as modelling for aircraft noise prediction and simulation of take-off and landing procedures. The approach used to consider these two elements is described in this paper. Preliminary results from Concorde-like case study are presented
Performance assessment of low-by-pass turbofan engines for low-boom civil supersonic aircraft
No full textThis paper presents an approach to evaluate the performance of low-bypass turbofan
engines without afterburner for a low-boom supersonic aircraft operating at Mach 1.5. The
proposed method focuses on optimizing the propulsive performance by minimizing fuel
consumption while meeting mission profile requirements. The study contributes to the
MORE&LESS project, providing methods for rapidly designing novel supersonic propulsion
concepts with improved environmental performance. The research conducts a thermodynamic
analysis for on-design engine conditions based on the Modified Specific Heat (MSH) gas model.
Specific non-installed thrust and fuel consumption are estimated for cruise phase. Then, the engine
cycle analysis is also performed to study off-design performance, including simplified models to
account for engine drag and calculate installed thrust and fuel consumption. MATLAB simulations
are employed to determine thrust and consumption based on the specific mission profile of the
Mach 1.5 case-study, allowing for comparison of different engine types. Ongoing work involves
the optimization of engine parameters such as compression ratio, bypass ratio, and turbine inlet
temperature, targeting further fuel consumption reduction and pollutant emission estimations
Multiple Tests for Dynamic Identification of a Reinforced Concrete Multi-Span Arch Bridge
Full text linkThis paper presents the results of an experimental dynamic campaign carried out on a reinforced concrete multi-span arch bridge. Five expeditious ambient vibration tests were conducted separately on five spans (one test in each span) of the bridge using only six piezoelectric uniaxial accelerometers. Modal parameters were identified through the well-known Enhanced Frequency Domain Decomposition (EFDD) procedure developed using Matlab R2021b software. At the same time, a finite element model was accurately implemented through a commercial software (Midas Civil) to evaluate the main modal features. A manual model update was successively pursued varying the elastic modulus of the reinforced concrete to make the identified and numerical modes as close as possible. A complete and suitable instrumentation to perform global experimental dynamic tests is not always available. Recursive/Multiple tests have different advantages: handy, easily executable, and could provide a more robust identification thanks to a statical characterization. The paper aims to highlight the peculiarities of recursive/multiple dynamic tests on multi-span arch bridges. The procedure also provides useful suggestions for designing a permanent and continuous vibration-based monitoring system
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Guidelines for the LTO Noise Assessment of Future Civil Supersonic Aircraft in Conceptual Design
Full text linkOne of the most critical regulatory issues related to supersonic flight arises from limitations imposed by community noise acceptability. The most efficient way to ensure that future supersonic aircraft will meet low-noise requirements is the verification of noise emissions from the early stages of the design process. Therefore, this paper suggests guidelines for the Landing and Take-Off (LTO) noise assessment of future civil supersonic aircraft in conceptual design. The supersonic aircraft noise model is based on the semi-empirical equations employed in the early versions of the Aircraft NOise Prediction Program (ANOPP) developed by NASA, whereas sound attenuation due to atmospheric absorption has been considered in accordance with SAE ARP 866 B. The simulation of the trajectory leads to the prediction of the aircraft noise level on ground in terms of several acoustic metrics (LAmax, SEL, PNLTM and EPNL). Therefore, a dedicated validation has been performed, selecting the only available supersonic aircraft of the Aircraft Noise and Performance database (ANP), that is, the Concorde, through the matching with Noise Power Distance (NPD) curves for LAmax and SEL, obtaining a maximum prediction error of +/- 2.19%. At least, an application to departure and approach procedures is reported to verify the first noise estimations with current noise requirements defined by ICAO at the three certification measurement points (sideline, flyover, approach) and to draw preliminary considerations for future low-noise supersonic aircraft design
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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