5,727 research outputs found

    Aerodynamic instabilities in high-speed air intakes and their role in propulsion system integration

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    High-speed air intakes often exhibit intricate flow patterns, with a specific type of flow instability known as ‘buzz’, characterized by unsteady shock oscillations at the inlet. This paper presents a comprehensive review of prior research, focused on unraveling the mechanisms that trigger buzz and its implications for engine stability and performance. The literature survey delves into studies concerning complex-shaped diffusers and isolators, offering a thorough examination of flow aerodynamics in unstable environments. Furthermore, this paper provides an overview of contemporary techniques for mitigating flow instability through both active and passive flow control methods. These techniques encompass boundary layer bleeding, the application of vortex generators, and strategies involving mass injection and energy deposition. The study concludes by discussing future prospects in the domain of engine-intake aerodynamic compatibility. This work serves as a valuable resource for researchers and engineers striving to address and understand the complexities of high-speed air induction systems.EU Erasmus+ Progra

    The effect of a nonlinear energy sink on the gust response of a wing

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    In this paper, the potential effectiveness of a nonlinear energy sink (NES) to absorb the energy from a wing that is vibrating as a result of flying in a gusty environment is investigated. The structural dynamics of the wing is simulated using a rigid airfoil mounted on two linear/nonlinear springs to represent the bending and torsional stiffness of the wing. The wing is subjected to a combination of gust and aerodynamic loads. The unsteady aerodynamic lift and moment are modelled using Wagner's theory. Furthermore, the gust loads are obtained by assuming two different gust profiles, e.g. sharp-edged and 1-cosine gust profiles. A nonlinear energy sink, which comprises of a concentrated mass, damper and a nonlinear spring, is attached to the wing, and its effectiveness to absorb the gust energy is investigated. The coupled nonlinear aeroelastic equations are integrated numerically to determine the response of the wing. To verify the developed aeroelastic model, the obtained results are compared with the available results in the literature and an excellent agreement is observed. The results highlight that adding the NES to the wing is capable of reducing the gust oscillation amplitude of the wing significantly when the NES parameters are chosen accordingly

    Intelligence Collection Priorities in an Age of Renewed Superpower Conflict: Toward a More Expansive Perspective

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    The new global setting of the post-Cold War allowed the United States and its intelligence agencies to broaden the nation’s mandate to include the environment, health, the global economy, and terrorism, among other considerations---although the military might of Russia and China had by no means disappeared and considerable resources would remain focused on military threat assessments.  This article explores the commitment of the United States to the ongoing mission of knowing about and thwarting military attacks, while at the same time taking into account a new host of once ignored worldwide threats to national security.   Received: 01-07-2024 Revised: 01-17-202

    Sociotechnical Imaginaries, the Future and the Third Offset Strategy

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    Composite Disturbance Filtering: A Novel State Estimation Scheme for Systems With Multi-Source, Heterogeneous, and Isomeric Disturbances

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    State estimation has long been a fundamental problem in signal processing and control areas. The main challenge is to design filters with ability to reject or attenuate various disturbances. With the arrival of big data era, the disturbances of complicated systems are physically multi-source, mathematically heterogenous, affecting the system dynamics via isomeric (additive, multiplicative and recessive) channels, and deeply coupled with each other. In traditional filtering schemes, the multi-source heterogenous disturbances are usually simplified as a lumped one so that the "single" disturbance can be either rejected or attenuated. Since the pioneering work in 2012, a novel state estimation methodology called {\it composite disturbance filtering} (CDF) has been proposed, which deals with the multi-source, heterogenous, and isomeric disturbances based on their specific characteristics. With the CDF, enhanced anti-disturbance capability can be achieved via refined quantification, effective separation, and simultaneous rejection and attenuation of the disturbances. In this paper, an overview of the CDF scheme is provided, which includes the basic principle, general design procedure, application scenarios (e.g. alignment, localization and navigation), and future research directions. In summary, it is expected that the CDF offers an effective tool for state estimation, especially in the presence of multi-source heterogeneous disturbances

    U.S. Senate and House Perspectives on Missile Defense Systems Opposed by Russia and China

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    The United States and its allies and partners have deployed three missile defense systems to protect against Iranian and North Korean missile threats: the European Phased Adaptive Approach, Terminal High Altitude Area Defense, and Ground-based Missile Defense. Russia and China oppose these systems because they view them as undermining their strategic interests. The purpose of the present study was to better understand the perspectives of Senate and House Armed Services Committee HASC members about the three missile defense systems in congressional hearings. The three models of the congressional behavior model, the preference, simple party, and asymmetric categories, and neorealism and neoliberalism schools of thought were applied with a qualitative content analysis case study approach. After comparing the perspectives of SASC and HASC leaders, some overarching themes for next steps were identified. Findings indicated there needed to be less focus in the United States Congress on alarmist rhetoric and more of a focus on why a specific country is a missile threat. This would go much further in educating and enhancing the awareness of the public and legislative branch. There needed to be more dialogue with nations that are deemed as missile threats to prevent misinterpretation and miscommunication. Lastly, financial resources and time are needed to refine and optimize missile defense systems which would lead to positive social change for the future

    Towards a General Complex Systems Model of Economic Sanctions with Some Results Outlining Consequences of Sanctions on the Russian Economy and the World

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    The main purpose of this paper is to present a complex nonlinear modelling approach to analyzing mixed capitalist economic systems. An application of a more elaborate version of this model is to explore the consequences of sanctions on the Russian economy and evaluate the model’s predictive successes or failures. Furthermore, the formal expanded nonlinear model presented in the appendix may be seen as an initial step to put the analysis of economic sanctions within a formal complex socio-economic systems framework. The results obtained from this structural complex multisectoral model so far seem fairly accurate in terms of agreement with measured values of observable economic variables. The political consequences are uncertain and are to be explored separately in a companion paper and ultimately in a book length treatment. Methodologically, the paper also presents the case for using Social Accounting Matrix (SAM)-based models for understanding problems of analyzing sanctions in an economywide context. Linear as well as Nonlinear models are presented in the appendix. The nonlinear modelling approach might prove to be especially relevant for studying the properties of multiple equilibria and complex dynamics

    Перекладацькі інновації

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    У матеріалах подані тези XІІІ Всеукраїнської студентської науково-практичної конференції «Перекладацькі інновації». До збірника ввійшли наукові дослідження, присвячені актуальним проблемам сучасного перекладу, мовознавства, лінгвістики, стилістики, методики та методології сучасних літературознавчих досліджень. Для мовознавців, перекладачів, викладачів і студентів філологічних та перекладацьких факультетів

    Repüléstudományi Közlemények 35.

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    Machine learning and mixed reality for smart aviation: applications and challenges

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    The aviation industry is a dynamic and ever-evolving sector. As technology advances and becomes more sophisticated, the aviation industry must keep up with the changing trends. While some airlines have made investments in machine learning and mixed reality technologies, the vast majority of regional airlines continue to rely on inefficient strategies and lack digital applications. This paper investigates the state-of-the-art applications that integrate machine learning and mixed reality into the aviation industry. Smart aerospace engineering design, manufacturing, testing, and services are being explored to increase operator productivity. Autonomous systems, self-service systems, and data visualization systems are being researched to enhance passenger experience. This paper investigate safety, environmental, technological, cost, security, capacity, and regulatory challenges of smart aviation, as well as potential solutions to ensure future quality, reliability, and efficiency
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