398 research outputs found
Electrostatic monitoring of wind turbine gearbox on oil-lubricated system
No full textThe electrostatic sensing technique has been verified to be a viable method for tribo-contact monitoring under laboratory conditions in previous investigations. This paper reports on the evolution of electrostatic monitoring on a real oil-lubricated wind turbine gearbox, using a modified oil-line sensor. In a nominal test and a ramp-up test, features were extracted and the presence of debris can be detected. The permutation entropy was further introduced in an accelerated life test. It can accurately reflect the wear condition of the gearboxes and detect early faults earlier than conventional techniques, which also has a better sensitivity and performance degradation trend than time-domain features
RF micro-systems for 5G front-end signal processing
No full textThe fifth-generation (5G) communication has sparked great research interest in developing the next generation radio frequency (RF) front ends for more stringent requirements on performance, power consumption, and spectral utilization efficiency. More parallel RF bands and paths are added in the same form factor, along with which come more components and tighter integration. Designing portable systems faces the new challenge of reducing component size while still operating at RF, where the path attenuation is low and fading is readily manageable. Satisfactory size reduction is particularly difficult for passive components that rely on the principle of waveguiding and thus scale with electromagnetic (EM) wavelength at RF (typical ~10s cm). Hence, radical size reduction by several orders of magnitude can only be attained by resorting to a physical domain other than EM, namely acoustic waves with wavelengths 4~5 orders of magnitude smaller. In fact, acoustic devices at RF, such as surface or bulk acoustic wave devices, have been widely used for mobile phone applications. Other acoustic elements, such as couplers, correlators, and impedance matching networks, have also shown promising potential to outperform the state-of-the-art EM counterparts. However, the past developments often battled the challenge of efficiently accessing the acoustics over a sufficiently wide bandwidth and subsequently producing application-worthy performance, because of the fundamental limitations from the lack of high electromechanical coupling (k2) and low damping piezoelectric platforms. Recently, thanks to the advances in materials, design, and fabrication, LiNbO3 thin-film has been proved as a promising low-loss, wideband, and frequency-diverse acoustic platform for novel functions toward high-performance 5G front-end signal processing.
Based on acoustic devices in LiNbO3 thin films, this thesis aims to design and demonstrate several classes of novel RF microsystems that can enable conventional signal processing functions with better performance or new tasks for emerging applications. First, the acoustic systems are used as passive signal processing elements for the Internet of Things (IoT) applications. The high figure of merit (FoM) LiNbO3 resonator array is used as the impedance matching element for interfacing with the high impedance CMOS rectifiers in the IoT-inspired wake-up radio. The high FoM, adequately large static capacitance and spurious free performance collectively contribute to a high voltage gain over 20. Another type of microsystem for IoT applications is 1-dB IL acoustic delay lines (ADLs) on the S0 mode in thin-film LiNbO3, showing record-breaking low IL over a larger bandwidth, opening new horizons for low-power RF acoustic signal processing. Second, the miniature nonreciprocal component based on switched high-performance delay elements is demonstrated for full duplex radio. The wideband and long delay featured by the high-performance LiNbO3 ADLs significantly benefit the performance, including the dynamic switching induced IL and intra-modulations, while relaxing the requirements for synthesizing and synchronizing the control signals. The demonstrated 4 port circulator shows a highly symmetric performance across the 4-ports with 18.8 dB nonreciprocal contrast between the IL (6.6 dB) and isolation (25.4 dB) over an FBW of 8.8% at a center frequency 155 MHz, all of which are accomplished with a record low switching frequency of 877.22 kHz. Upon further optimizations, such circulators can potentially outperform ferrite-based devices in loss, bandwidth, and isolation while offering more compact size and reconfigurable operation. Third, low-loss wideband GHz S0 mode ADLs are explored for self-interference cancellation in full-duplex radio. The fabricated miniature acoustic delay lines show a fractional bandwidth of 4% and a minimum IL of 3.2 dB at a center frequency of 0.96 GHz. Various delays ranging from 20 ns to 900 ns have been obtained for digitally addressable delay synthesis. Multiple acoustic delay lines with center frequencies from 0.9 to 2 GHz have been demonstrated. The demonstrated ADLs can potentially provide wide-range and high-resolution reconfigurable delays for future SIC applications. Finally, design and measurement of 5 GHz antisymmetric mode acoustic delay lines for 5G enhanced mobile broadband (eMBB) applications are presented; the demonstrated ADLs significantly surpass the state of the art with similar feature sizes in center frequency. The implemented ADLs at 5 GHz show a minimum insertion loss of 7.94 dB and a fractional bandwidth around 4%. In addition to the remarkable device performance, these designs also point out the opportunities to advance the operation frequencies of acoustic devices toward the wideband and high-frequency signal processing functions required for future 5G applications.
RF acoustic microsystems demonstrated in this thesis have shown promising prospects for 5G front-end signal processing applications. Thanks to the simultaneously low damping and wideband performance at RF, acoustic devices based on LiNbO3 thin films are auspicious candidates to provide the design flexibilities and high performance required for various 5G application scenarios. Further development in high-performance RF acoustic devices may put on the horizon an RF front-end synthesized either purely or predominantly from an RF acoustic component kit.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-12-01The student, Ruochen Lu, accepted the attached license on 2019-09-12 at 09:43.The student, Ruochen Lu, submitted this Dissertation for approval on 2019-09-12 at 10:03.This Dissertation was approved for publication on 2019-09-13 at 16:52.DSpace SAF Submission Ingestion Package generated from Vireo submission #14451 on 2020-02-28 at 17:35:17Made available in DSpace on 2020-03-02T22:38:37Z (GMT). No. of bitstreams: 4
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Previous issue date: 2019-09-13Embargo set by: Seth Robbins for item 113969
Lift date: 2022-03-02T22:39:04Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemLimited Restriction Lifted for Item 113969 on 2022-03-03T10:15:08Z
Methods and models for analyzing and controlling the safety in operations of autonomous marine systems
No full textAutonomous marine systems (AMS), such as autonomous underwater vehicles (AUVs), and unmanned surface vehicles (USVs) have evolved over the past decades. Maritime autonomous surface ships (MASS) are gradually being developed and commissioned. AMS are applied in different types of industries and research. Examples include the application of USVs or AUVs for ocean monitoring, and the development of MASS for future cargo and personnel transportation.
In these operations, AMS can help reduce the risk of personnel exposure to harsh environments, reduce the operational costs, and improve the efficiency and performance of the human operators. However, compared to conventional marine systems, new types of failure might be introduced to AMS operations due to unforeseen interdependencies in the system design, dynamic operating environments, maintenance challenges, insufficient situation awareness and decision-making from human operators, etc. Also, AMS functions are constantly being improved, and the operations of AMS are becoming more complex and advanced. The safety issues of these systems have become even more critical. Techniques for analyzing and controlling the safety of AMS operations are therefore required.
The overall aim of this PhD project is to develop methods and models for analyzing and controlling safety in operations of AMS. It is refined into the following three research objectives that are addressed in five research articles:
• Identify and analyze hazards and hazardous events in the operation of autonomous marine systems and evaluate the applicability of relevant methods as a basis for online risk modeling of autonomous marine systems.
• Analyze the dynamic changes in the operating environment and system status, and model their impacts on the safe operation.
• Propose a general method for developing online risk models for autonomous marine systems and operations, supporting risk-based control.
The work presented here reviews the existing methods and models and identifies the main research challenges and gaps with respect to the above research objectives. The research presented in the thesis addressed some of these issues. The main contributions of this thesis are summarized as follows:
• Investigation of the potential hazards/ hazardous events during the operation with multiple AMS and how these hazards/ hazardous events may affect the safe and reliable operations of AMS. The results highlight the importance of considering unsafe interactions in hazard identification or risk assessment in AMS operations.
• Comprehensive hazard identification works with a number of potential hazards/ hazardous events that may affect the safe operation of an under-ice AUV operation through various methods. The results contribute research and practical implications for improved engineering design and operational procedures to enhance the safety and robustness of future AMS operations in the Arctic.
• Identification of a list of evaluation criteria for online risk models for AMS and comprehensive evaluation of the applicability of several existing methods for online risk modeling of AMS. The evaluation results contribute to an appropriate first step towards a general framework for online risk modeling for AMS.
• Proposal for a dynamic risk analysis method to determine the dynamic changes in the operating environment and assess the environmental impact on the safe operation of AMS.
• Proposal for a novel dynamic maintenance planning method for AMS that addresses challenges in maintenance planning, including the high consequence of system shutdown, limited and irregular maintenance opportunities, and various dependencies among components.
• Proposal for a general framework for the online risk modeling of AMS to enhance the intelligence of the AMS, its situation awareness, and decision-making. The proposed framework addresses several challenges in developing online risk modeling, e.g., evidence uncertainty.
• Proposal for a two-level strategy to develop a supervisory risk control (SRC) system for AMS operations based on the developed online risk model. The SRC system can improve the intelligence of AMS by enabling its risk-based control.
In conclusion, the research and findings presented in the thesis provide researchers and practitioners in the field with a comprehensive overview of safety issues in AMS operations, and novel methods and models for analyzing and handling these. The proposed methods and models are expected to improve the safety of future AMS operations
Consumer co-creation in home 3D Printing: an investigation of the mediating psychological responses to self-printed products
No full textThis project contains all data related to a lab experiment on consumer co-creation in home 3D printing. The study investigates how model creation methods affect perceived ownership, uniqueness, and product evaluation. Data was collected through a lab-based experimental design and analyzed using Jamovi
Modeling of Uncontrolled Fluid Flow in Wellbore and its Prevention
No full textUncontrolled fluid flow in the wellbore is one of the most critical safety concerns for the oil and gas industry. The major focus of this dissertation is on blowout events given the most severe consequences associated with such incidents. The past tragedies reflect a strong need for not only understanding the mechanisms of blowout to accurately estimate the consequence, but also the approaches to managing and controlling the risks, uncertainties, and hazards associated with blowout events.
A fully integrated analytical model that couples the reservoir and wellbore has been proposed to investigate the fluid behaviors during the blowout events. This model could be used to simulate any potential blowout events for gas, oil, or oil/gas wells at onshore or offshore facilities. The reservoir, wellbore, and their interactions are coupled together to demonstrate a full picture of the potential well blowout incidents. The results reveal that understanding the importance of heat transfer and multi-phase flow behaviors is essential to accurately estimate the consequence of well blowouts. Well-established computational algorithms are developed to effectively estimate the blowout rate and total discharge amount during blowout incidents. The statistical analysis identifies the independent variables responsible for the maximum discharge; both reservoir permeability and the connected reservoir volume are the key variables.
The results of the blowout modeling could serve as the input for both consequence-based and risk-based approaches to assess the risk associated with the blowout events. The application of such approaches is demonstrated by the case study. The consequence-based approach is easier to be implemented and provide guidance to the operators based on the realistic worst-case scenario. It would be useful for drilling site location selection and preparation of emergency response plan. On the other hand, the risk-based approach enables the operators to have a comprehensive understanding of the particular well that they are working on, so that the risk associated with the blowout events can be effectively managed and controlled. The risk reduction plan based on the blowout risk assessment is also discussed in this dissertation
The Role of Concept Art in Science Fiction Films: A Study of the Process and Creation of Environment Concept Art
No full textSuccessful science fiction films have excellent concept art that integrates all the fantasy elements into a clear visual style, including characters, environments and various props. The aim of this thesis is to discuss concept art in science fiction films.
The first part of the thesis introduces myself at different periods in my creative development and the reason that I’m interested in film and choosing concept art for my professional direction. The primary purpose of this thesis concerns my creative processes and inspirations, in designing and illustrating environments for a science fiction story of my own creation. The thesis also investigates the utilization of environment concept art on Science Fiction films in three aspects: film color keynote, camera angle and visual effects. Through these three aspects the thesis studies three typical science fiction films.
In conclusion, the thesis shows how the background of films, games or animations, a like character’s personalities. The artwork component of this thesis is a series of background concept art, based on the studies of existing science fiction films and concept art. The final point of the thesis is to propose professional opportunities that would allow me to explore the interests outlined here
Thin-Film Lithium Niobate Acoustic Delay Line Oscillators
No full textIn this work, thin-film lithium niobate (LiNbO3) acoustic delay line (ADL) based oscillators are experimentally investigated for the first time for the application of single-mode oscillators and frequency comb generation. The design space for the ADL-based oscillator is first analyzed, illustrating that the key to low phase noise lies in high center frequency (fo), large delay (τ G), and low insertion loss (IL) of the delay. Therefore, two self-sustained oscillators employing low noise amplifiers (LNA) and a low IL, long delay (fo=157MHz, IL =2.9dB, τG= 200-440ns) SH0 mode ADLs are designed for a case study. The two SH0 ADL oscillators show measured phase noise of -109 dBc/Hz and -127 dBc/Hz at 10-kHz offset while consuming 16 mA and 48 mA supply currents, respectively. Although the carrier power of the proposed oscillator is lower than published state-of-the-art ADL oscillators, competitive phase noise performance is still attained thanks to the low IL. Finally, frequency comb generation is also demonstrated with the same delay line and a commercial RF feedback amplifier, showing a comb spacing of 3.4 MHz that matches the open-loop characterization.Accepted Author ManuscriptDynamics of Micro and Nano System
Low-loss and wideband acoustic delay lines
No full text This paper demonstrates low-loss acoustic delay lines (ADLs) based on shear-horizontal waves in thin-film LiNbO 3 for the first time. Due to its high electromechanical coupling, the shear-horizontal mode is suited for producing devices with large bandwidths. Here, we show that shear-horizontal waves in LiNbO 3 thin films are also excellent for implementing low-loss ADLs based on unidirectional transducers. The high acoustic reflections and large transducer unidirectionality induced by the mechanical loading of the electrodes on a LiNbO 3 thin film provide a great tradeoff between delay line insertion loss and bandwidth. The directionality for two different types of unidirectional transducers has been characterized. Delay lines with variations in the key design parameters have been designed, fabricated, and measured. One of our fabricated devices has shown a group delay of 75 ns with an IL below 2 dB over a 3-dB bandwidth of 16 MHz centered at 160 MHz (fractional bandwidth = 10%). The measured insertion loss for other devices with longer delays and different numbers of transducer cells are analyzed, and the loss contributing factors and their possible mitigation are discussed. Accepted Author ManuscriptDynamics of Micro and Nano System
A Multi-Task Learning Based Runoff Forecasting Model for Multi-Scale Chaotic Hydrological Time Series
No full textAccurately predicting runoff is crucial for managing water resources, preventing and mitigating floods, scheduling hydropower plant operations, and protecting the environment. The hydrological dynamic composite system that forms runoff is complex and random, and seemingly random behavior may be caused by nonlinear variables in a simple deterministic system, which poses a challenge to runoff prediction. In this paper, we construct parallel and multi-timescale reservoirs from a chaotic theory perspective to simulate the stochasticity of chaotic systems. We propose a multi-task-based "Decomposition-Integration-Prediction" (Multi-SDIPC) model for runoff prediction. To validate our research results, we use the Catchment Attributes and Meteorology for Large-Sample Studies (CAMELS) dataset and compare our proposed model with 10 baseline models. The results show that our model has an average NSE metric of 0.83 and exhibits higher accuracy, better generalization, and greater stability than the other models in multi-step forecasting. Based on our findings, we recommend wider application of the Multi-SDIPC model in different regions of the world for medium or long-term runoff prediction.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Transport Engineering and Logistic
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