3,237 research outputs found

    Direct measurement of coating thermal noise in the AEI 10m prototype

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    A thermal noise interferometer for the characterization of thermal noise in high reflectivity mirrors has been commissioned and first direct measurements of coating thermal noise have been performed. This serves as an important step in the improvement of current and future gravitational wave detectors

    Characterisation and State Estimation of Magnetic Soft Continuum Robots

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    Minimally invasive surgery has become more popular as it leads to less bleeding, scarring, pain, and shorter recovery time. However, this has come with counter-intuitive devices and steep surgeon learning curves. Magnetically actuated Soft Continuum Robots (SCR) have the potential to replace these devices, providing high dexterity together with the ability to conform to complex environments and safe human interactions without the cognitive burden for the clinician. Despite considerable progress in the past decade in their development, several challenges still plague SCR hindering their full realisation. This thesis aims at improving magnetically actuated SCR by addressing some of these challenges, such as material characterisation and modelling, and sensing feedback and localisation. Material characterisation for SCR is essential for understanding their behaviour and designing effective modelling and simulation strategies. In this work, the material properties of commonly employed materials in magnetically actuated SCR, such as elastic modulus, hyper-elastic model parameters, and magnetic moment were determined. Additionally, the effect these parameters have on modelling and simulating these devices was investigated. Due to the nature of magnetic actuation, localisation is of utmost importance to ensure accurate control and delivery of functionality. As such, two localisation strategies for magnetically actuated SCR were developed, one capable of estimating the full 6 degrees of freedom (DOFs) pose without any prior pose information, and another capable of accurately tracking the full 6-DOFs in real-time with positional errors lower than 4~mm. These will contribute to the development of autonomous navigation and closed-loop control of magnetically actuated SCR

    A review of dynamics design methods for high-speed and high-precision CNC machine tool feed systems

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    With the development of CNC machine tools toward high speed and high precision, the traditional static design methods can hardly meet the demand. Hence, in this paper, the dynamics matching design methods of existing CNC machine tool feed systems were investigated and analyzed. Further, sub-system coupling mechanisms and optimization design studies were carried out for each sub-system. First, the required kinematic indexes must be achieved when designing the feed system dynamics of high-speed, high-precision CNC machine tools. Second, the CNC machine tool feed systems generally have four sub-systems: motion process, control system, motor, and mechanical structure. The coupling effect between the sub-systems should also be considered in the design. Based on the dynamics design, each sub-system should be optimized to maximize the system dynamic performance with minimum resource allocation. Finally, based on the review, future research directions within the field were detected

    Limited Information Shared Control and its Applications to Large Vehicle Manipulators

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    Diese Dissertation beschäftigt sich mit der kooperativen Regelung einer mobilen Arbeitsmaschine, welche aus einem Nutzfahrzeug und einem oder mehreren hydraulischen Manipulatoren besteht. Solche Maschinen werden für Aufgaben in der Straßenunterhaltungsaufgaben eingesetzt. Die Arbeitsumgebung des Manipulators ist unstrukturiert, was die Bestimmung einer Referenztrajektorie erschwert oder unmöglich macht. Deshalb wird in dieser Arbeit ein Ansatz vorgeschlagen, welcher nur das Fahrzeug automatisiert, während der menschliche Bediener ein Teil des Systems bleibt und den Manipulator steuert. Eine solche Teilautomatisierung des Gesamtsystems führt zu einer speziellen Klasse von Mensch-Maschine-Interaktionen, welche in der Literatur noch nicht untersucht wurde: Eine kooperative Regelung zwischen zwei Teilsystemen, bei der die Automatisierung keine Informationen von dem vom Menschen gesteuerten Teilsystem hat. Deswegen wird in dieser Arbeit ein systematischer Ansatz der kooperativen Regelung mit begrenzter Information vorgestellt, der den menschlichen Bediener unterstützen kann, ohne die Referenzen oder die Systemzustände des Manipulators zu messen. Außerdem wird ein systematisches Entwurfskonzept für die kooperative Regelung mit begrenzter Information vorgestellt. Für diese Entwurfsmethode werden zwei neue Unterklassen der sogenannten Potenzialspiele eingeführt, die eine systematische Berechnung der Parameter der entwickelten kooperativen Regelung ohne manuelle Abstimmung ermöglichen. Schließlich wird das entwickelte Konzept der kooperativen Regelung am Beispiel einer großen mobilen Arbeitsmaschine angewandt, um seine Vorteile zu ermitteln und zu bewerten. Nach der Analyse in Simulationen wird die praktische Anwendbarkeit der Methode in drei Experimenten mit menschlichen Probanden an einem Simulator untersucht. Die Ergebnisse zeigen die Überlegenheit des entwickelten kooperativen Regelungskonzepts gegenüber der manuellen Steuerung und der nicht-kooperativen Steuerung hinsichtlich sowohl der objektiven Performanz als auch der subjektiven Bewertung der Probanden. Somit zeigt diese Dissertation, dass die kooperative Regelung mobiler Arbeitsmaschinen mit den entwickelten theoretischen Konzepten sowohl hilfreich als auch praktisch anwendbar ist

    Prognostic and health management of critical aircraft systems and components: an overview

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    This article belongs to the Special Issue Feature Papers in Fault Diagnosis & Sensors 2023Prognostic and health management (PHM) plays a vital role in ensuring the safety and reliability of aircraft systems. The process entails the proactive surveillance and evaluation of the state and functional effectiveness of crucial subsystems. The principal aim of PHM is to predict the remaining useful life (RUL) of subsystems and proactively mitigate future breakdowns in order to minimize consequences. The achievement of this objective is helped by employing predictive modeling techniques and doing real-time data analysis. The incorporation of prognostic methodologies is of utmost importance in the execution of condition-based maintenance (CBM), a strategic approach that emphasizes the prioritization of repairing components that have experienced quantifiable damage. Multiple methodologies are employed to support the advancement of prognostics for aviation systems, encompassing physics-based modeling, data-driven techniques, and hybrid prognosis. These methodologies enable the prediction and mitigation of failures by identifying relevant health indicators. Despite the promising outcomes in the aviation sector pertaining to the implementation of PHM, there exists a deficiency in the research concerning the efficient integration of hybrid PHM applications. The primary aim of this paper is to provide a thorough analysis of the current state of research advancements in prognostics for aircraft systems, with a specific focus on prominent algorithms and their practical applications and challenges. The paper concludes by providing a detailed analysis of prospective directions for future research within the field.European Union funding: 95568

    Fictional Practices of Spirituality I: Interactive Media

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    "Fictional Practices of Spirituality" provides critical insight into the implementation of belief, mysticism, religion, and spirituality into worlds of fiction, be it interactive or non-interactive. This first volume focuses on interactive, virtual worlds - may that be the digital realms of video games and VR applications or the imaginary spaces of life action role-playing and soul-searching practices. It features analyses of spirituality as gameplay facilitator, sacred spaces and architecture in video game geography, religion in video games and spiritual acts and their dramaturgic function in video games, tabletop, or LARP, among other topics. The contributors offer a first-time ever comprehensive overview of play-rites as spiritual incentives and playful spirituality in various medial incarnations

    Magnetic Material Modelling of Electrical Machines

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    The need for electromechanical energy conversion that takes place in electric motors, generators, and actuators is an important aspect associated with current development. The efficiency and effectiveness of the conversion process depends on both the design of the devices and the materials used in those devices. In this context, this book addresses important aspects of electrical machines, namely their materials, design, and optimization. It is essential for the design process of electrical machines to be carried out through extensive numerical field computations. Thus, the reprint also focuses on the accuracy of these computations, as well as the quality of the material models that are adopted. Another aspect of interest is the modeling of properties such as hysteresis, alternating and rotating losses and demagnetization. In addition, the characterization of materials and their dependence on mechanical quantities such as stresses and temperature are also considered. The reprint also addresses another aspect that needs to be considered for the development of the optimal global system in some applications, which is the case of drives that are associated with electrical machines

    2023-2024 Undergraduate Catalog

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    2023-2024 undergraduate catalog for Morehead State University

    Experimental Assessment and Computational Modeling of Adhesive, Self Piercing Rivets (SPR), and Hybrid (Adhesive-SPR) Joints: Enhancing Joint Performance for Aluminum Sheet Material

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    The implementation of aluminum alloys in future vehicle construction (e.g., body-in-white) can reduce weight by 30-45%, improving the fuel economy of internal combustion vehicles and increasing the battery range of electric and hybrid variants. Critical to enabling the adoption of aluminum alloys and multi-material structures in the automotive industry are robust joining methods that play a crucial role in structural performance; crashworthiness; durability; and noise, vibration and harshness. Structural adhesives and self-piercing rivets (SPRs) have demonstrated aluminum and multi-material joining capability with promising mechanical performance, relative to traditional and emerging joining technologies. Hybrid joining, augmenting adhesives with SPRs, has been explored to address the limitations of individual joining methods and to enable further weight reduction opportunities. However, the limited mechanical response data on hybrid joints and lack of validated computational models often lead to expensive and time-consuming experimental testing and over-design of the joint. In the first phase of this research, experimental studies were undertaken to assess the mechanical response of adhesive, SPR and hybrid joints made with aluminum sheet material at specimen (coupon) and component (vehicle-scale structure) levels. First, seven aluminum surface preparation methods were investigated, and the method that achieved cohesive failure within the adhesive layer and maximized single-lap shear joint (SLJ) strength was adopted throughout the study. Next, the specimen-level experiments investigated the influence of loading mode, joint-level morphology, aluminum sheet thickness, and alloy type on joint strength, stiffness and energy absorption. Shear (SLJ) and tension (H-specimens) test specimens were created with adhesive, SPR, and hybrid joints using two aluminum alloys (AA6061-T6 and AA5052-H32) with three sheet metal thicknesses (1, 2 and 3 mm), commonly used in the automotive industry. All test specimens were fabricated in symmetrical configurations (the same alloy type and equal sheet thickness) for a total of 108 specimens (36 specimens per joining method), with three repeats for each test condition. The morphology of the adhesive, SPR and hybrid joints was quantified to ensure joint consistency and link the effect of joint attributes (e.g., bond line thickness and SPR mechanical interlock) to the mechanical response. Hybrid joining process variations were assessed to enhance joint strength and stiffness of hybrid joints made with thick sheet material, and the process with improved joint-level morphology was evaluated in subsequent specimen and component level tests. Lastly, vehicle-scale structural components were created from two hat sections made with 3 mm thick AA6061-T6 alloy and joined together to create a tube. The Caiman tubes were joined using adhesive, SPR, and hybrid joining, and then tested under Mode I loading with three repeats for each joining method. SLJ and H-specimens with adhesive joining exhibited higher strength (up to 360%) and stiffness (up to 422%) compared to SPR joints, while SPR joints demonstrated higher energy absorption (up to 352%) co-depending on the loading mode, aluminum sheet thickness, and alloy type. Hybrid joints with 1 and 2 mm thick sheets enhanced the performance of the individual joining methods, demonstrating strength and stiffness comparable to or higher than the individual joints, and energy absorption substantially higher (up to 336% higher than adhesive and up to 53.5% higher than SPR). Hybrid joints made with 3 mm sheets exhibited reduced strength and stiffness relative to adhesive joints; however, a statistically significant performance improvement was realized using the hybrid joining process variation proposed in this study for thick sheet material. Importantly, hybrid joining substantially increased the peak load and energy of the Caiman components relative to adhesive joining (244% and 1461%, respectively), highlighting the importance of hybrid joining relative to adhesive for bonded structures under Mode I loading. In the second phase of this research, finite element (FE) models of the specimen configurations (SLJ and H-specimen), and joining methods were created using a cohesive zone model (CZM) with material-level properties for adhesives, constraint and CZM models with parameters calibrated in this work for SPR rivets, and an integrated CZM-CZM and CZM-Constraint models for hybrid joints. The specimen-specific FE models were verified and validated using the experimental data for each sheet thickness (22 models in total). Next, FE models of the Caiman test were developed to validate the joining models at a component level (5 models in total), using the experimental load-displacement response and optical measurements of failure progression and joint separation. Lastly, FE investigations were conducted to assess the influence of key joint attributes, relevant to automotive, on the mechanical response of the joints. The FE models of the adhesive, SPR and hybrid joints were able to predict joint response for varying test specimen geometry, adherend thickness, and modes of loading. The hybrid CZM-CZM model demonstrated a high level of accuracy and excellent computational efficiency, predicting the Caiman test peak load within 9.5%, and with reduced simulation runtime compared to the CZM-Constraint model. The results of this research study highlighted important parameters in terms of automotive structure design trade-offs (e.g., joining method, joint morphology, sheet thickness and alloy type), while statistical analysis provided evidence that hybrid joining can enhance the strength, stiffness and energy absorption relative to adhesive or SPR joining. The demonstrated multi-scale approach to develop, verify and validate joining models allowed for predicting the mechanical response of the individual and hybrid joints under different modes of loading. The results of this research study provide an experimental and computational basis for research and design of structural-scale joining methods for lightweight vehicles
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