44 research outputs found
Improved qualification and algorithms for illinisat-2 attitude determination and control
No full textThe University of Illinois has developed the IlliniSat-2 CubeSat bus, a generic scalable and modular design, utilizing commercially available off the shelf (COTS) parts. The Attitude Determination and Control System (ADCS) of the bus is purely magnetic, relying on magnetometers for determination and magnetorquers for actuation. The pure magnetic ADCS is favorable because of its low power, volume and mass contributions to the satellite’ platform, but this comes at the cost of weak system controllability and observability, and no flight heritage. To improve system reliability for operation in space, CubeSim, a hardware in the loop (HIL) simulation suite has been developed. The basic CubeSim setup consists of a tri-axial square Helmholtz cage (HC3), a dynamic power supply (PS), and a software package simulating the satellite’s attitude dynamics.
This thesis is split into three parts, the first section discusses the different methods for calibrating the PS and the HC3 to generate desired magnetic fields, and HIL simulation results for traditional determination and control algorithms, using lab grade sensors. Next, using the calibrated basic CubeSim setup, calibration of flight sensors and HIL results are shown.
The second part of the thesis discusses the hardware and software augmentation to the basic CubeSim for higher fidelity ADCS simulations, and the calibration of inertial sensors, necessary for increasing the observability of the ADCS.
Finally, the third section discusses the trajectory generation for the underactuated pure magnetic ADCS, named as the “Navigation controller”, used to generate reference trajectories for the ADCS that is finite horizon optimal. The trajectory is obtained using two independent techniques, and the computational complexity and speed is compared for onboard usage.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2020-05-01The student, - Vedant, accepted the attached license on 2018-04-26 at 12:06.The student, - Vedant, submitted this Thesis for approval on 2018-04-26 at 14:08.This Thesis was approved for publication on 2018-04-27 at 12:15.DSpace SAF Submission Ingestion Package generated from Vireo submission #12523 on 2018-08-31 at 17:21:41Made available in DSpace on 2018-09-04T20:42:00Z (GMT). No. of bitstreams: 2
VEDANT-THESIS-2018.pdf: 13038429 bytes, checksum: 6cfbb9a8b6d31339294d06a9972637ae (MD5)
LICENSE.txt: 4205 bytes, checksum: 4116bbc34cad8b0850f1952685d1296f (MD5)
Previous issue date: 2018-04-27Embargo set by: Seth Robbins for item 107323
Lift date: 2020-09-04T20:42:08Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 107323 on 2020-09-05T09:15:26Z
A self corrective vortex fluxing method for viscous fluid structure interaction problems
No full textComputational Fluid Dynamic Solvers for flow structure interaction problems rely on a delicate treatment of fluid and grid properties close to the boundary. Although such an approach is accurate, it proves to be inflexible when applied to complex deforming geometries. Here we combine remeshed vortex methods with a panel method to design a new Vortex Fluxing scheme that uses no special treatment of flow properties at the boundary. It was found that the panel method is capable of correcting any spurious vorticity flux into the wall during the no slip boundary application. This enables highly accurate, robust Direct Numerical Simulations by relaxing the need for small timesteps and allowing the use of coarse regular computational grids. The methodology was validated for rigid, rotating and deforming bodies.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2020-08-01The student, Vedant Dubey, accepted the attached license on 2018-07-06 at 01:53.The student, Vedant Dubey, submitted this Thesis for approval on 2018-07-06 at 02:04.This Thesis was approved for publication on 2018-07-06 at 10:35.DSpace SAF Submission Ingestion Package generated from Vireo submission #12750 on 2018-09-27 at 11:16:39Made available in DSpace on 2018-09-27T16:30:19Z (GMT). No. of bitstreams: 2
DUBEY-THESIS-2018.pdf: 6418473 bytes, checksum: a347fe74ea9976e2b896c56d595fbeb4 (MD5)
LICENSE.txt: 4209 bytes, checksum: 820159346747effad92786f714e1f993 (MD5)
Previous issue date: 2018-07-06Embargo set by: Seth Robbins for item 107778
Lift date: 2020-09-27T16:30:34Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 107778
Lift date: 2020-09-27T16:31:43Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 107778
Lift date: 2020-09-27T16:34:29Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 107778 on 2020-09-28T09:15:30Z
Fractals
No full textThis paper presents Fractals, an exploratory music project by the author, which aims to uniquely blend various genres across multiple sections. The distinctiveness of this project lies in the author’s experience as a versatile musician, with experience ranging from rock bands and big bands to chamber orchestras, coupled with proficiency as a producer/DJ. This background of musical experience allows the author to approach the blend of genres with a unique perspective. The collection of songs serves as a precursor for four separate EPs: The project is not just a musical amalgamation but also an academic inquiry into the evolution of these genres, including an analysis of influential works and a reflection on the potential for innovative soundscapes in electronic music. Through this project, the author endeavors to leave a personal stamp on the electronic music scene, showcasing a synthesis of diverse musical influences and creative experimentation. This endeavor aims to contribute a distinctive auditory experience to the electronic music landscape, underlined by the author\u27s unique musical journey. This paper was written with the assistance from generative artificial intelligence. Additional information in Appendix II.https://remix.berklee.edu/graduate-studies-production-technology/1375/thumbnail.jp
Ethical Considerations in Deploying AI Systems in Public Domains: Addressing the ethical challenges of using AI in areas like surveillance and healthcare
No full textThe general use of AI technology, especially in public sectors like security and even in the medical field, has been subject to a number of questions to do with ethics. This paper aims to understand the ethical dilemmas concerning the instantiation of Artificial Intelligence in these fields, specifically privacy, bias, responsibility, and openness concerns. In security, advanced technologies like facial recognition and predictive policing attract concerns pertaining to violation of privacy, importation of race bias, and lack of social control, among others. In health care, the AI systems employed in the diagnosis and treatment of patients call into question issues to do with patient choices, data privacy, and discrimination in medical treatment. Within the scope of the paper, the author considers contemporary ethical standards and legislation regulating AI creation and finds some deficiencies. In response to these issues, some of the potential work for the future highlighted in the paper includes enhancing the legal policies in the area of AI, insisting on the importance of ethical multi-disciplinary research, and creating awareness of the effects of AI in society. It underlines the requirement for responsible and explainable AI, the availability of efficient tools helping in monitoring and controlling AI, and increased people’s involvement in creating AI policies to state that the launched AI technologies will be compliant with the people’s benefit. With these suggestions, the paper sought to add knowledge to the ongoing discussion on AI ethics and ensure that decent utilization of AI systems is enhanced with reverence to human rights and ethical norms
KEY DETERMINANTS OF USING DERIVATIVE INSTRUMENTS IN THE USA
No full textThis piece of work attempts to distinguish among various theories of corporate hedging with the help of disclosure in 10-K or annual reports of 500 non-financial USA companies and collecting data manually about hedging activities. There is rather limited but growing use of derivative financial instrument for risk management currently. Modern financial theories predict some characteristics of firms that drive their decision to use derivative financial instrument or off-balance sheet transaction. In this work, empirical evidence on determinants of derivative instruments usage is provided with large sample of the USA’s non-financial firms. S&P 500 and 600 companies are chosen to be the initial sample size of this research. Centered on the evidence, author draws the followings conclusions. Both tax incentives and financial price exposure are directly related with the decision of whether firm’s use of derivatives instrument. Moreover, the probability of using derivatives is directly proportional with leverage & firm value on the one hand. On the other hand, the level of using derivatives is positively correlated with dividend payout. These findings in the studies are generally in line with previous theories except for market-to-book ratio which is used to represent growth opportunities is negatively associated rather positively associated with the usage of derivative financial instruments.
Keywords: Derivatives, corporate hedging, risk management strategies, underinvestment cost and cost of financial distress
KEY DETERMINANTS OF USING DERIVATIVE INSTRUMENTS IN THE USA
No full textThis piece of work attempts to distinguish among various theories of corporate hedging with the help of disclosure in 10-K or annual reports of 500 non-financial USA companies and collecting data manually about hedging activities. There is rather limited but growing use of derivative financial instrument for risk management currently. Modern financial theories predict some characteristics of firms that drive their decision to use derivative financial instrument or off-balance sheet transaction. In this work, empirical evidence on determinants of derivative instruments usage is provided with large sample of the USA’s non-financial firms. S&P 500 and 600 companies are chosen to be the initial sample size of this research. Centered on the evidence, author draws the followings conclusions. Both tax incentives and financial price exposure are directly related with the decision of whether firm’s use of derivatives instrument. Moreover, the probability of using derivatives is directly proportional with leverage & firm value on the one hand. On the other hand, the level of using derivatives is positively correlated with dividend payout. These findings in the studies are generally in line with previous theories except for market-to-book ratio which is used to represent growth opportunities is negatively associated rather positively associated with the usage of derivative financial instruments.
Keywords: Derivatives, corporate hedging, risk management strategies, underinvestment cost and cost of financial distress
A simulation-based thermal process control method for multi-material laser-joining operations
No full textPublisher Copyright: © 2025 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.The use of multi-material assemblies is becoming increasingly common in sectors such as aeronautics. In this context, laser joining process offers the possibility to obtain strong and reliable metal-composite bonds without the need of mechanical fasteners or adhesives but temperature control during the process is a critical aspect to obtain good-quality joints. Controlling the temperature at the multi-material interface is the key to obtain high-quality joints. However, this is a variable that cannot be monitored during the process. In this paper, a method for thermal control in laser joining operations is presented which is based on creating temperature synthetic data, from ANSYS® simulation models, both for process planning optimization and for the creation of AI-based regression models to predict the interface temperature over time. A case study involving the laser joining of aluminium and PEEK (Polyether Ether Ketone) components is used. The results demonstrate that the experimentally validated temperature synthetic data, enhance process optimization, reducing the need for extensive physical experiments. Moreover, the creation and use of regression models has been demonstrated a viable approach for predicting the temperature at the interface. However, the accuracy on temperature prediction depends on the type of sensor used to monitor the temperature.Peer reviewe
Composite upcycling: An experimental study on mechanical behaviour of injection moulded parts prepared from recycled material extrusion printed parts, previously prepared using glass fibre polypropylene composite industry waste
No full textUpcycling pre-existing material extrusion (MEX) fabricated products is nascent as the industry's broader adaptation of MEX printers can be observed. This manuscript elucidates the post-process injection moulding manufacturing technique applied to MEX-printed thermoplastic composite waste materials composed of industrial glass fibre-reinforced polypropylene (GFRPP) composite. It evaluates the impact of glass fibre weight fractions (15 %, 30 %, and 40 %) on the injection moulded specimens' flexural and ultimate tensile strength. The mechanical performance of the injection moulded parts was compared with MEX additive manufactured parts derived from identical material. Homogeneous glass fibre distribution within the thermoplastic matrix was discerned in the injection moulded components utilising an optical light microscope. The mean ultimate tensile strength of the injection moulded parts was 29 MPa for the samples exhibiting a 40 % fibre weight fraction. It was demonstrated that the increase in glass fibre content from 15 % to 40 % improved the tensile strength, flexural strength, and elastic modulus of injection moulded specimens by 52 %, 135 %, and 52 %, respectively. Scanning electron microscopy (SEM) of the fracture surface of the injection moulded specimens revealed that the glass fibres predominantly displayed fibre pull-out rather than fibre breakage. Subsequent SEM imaging indicated that in contrast to the MEX printing manufacturing technique, the injection moulding fabrication process of GFRPP generally reduced porosity and minimised internal defects. The findings indicated that injection moulding post-process manufacturing possesses superior mechanical attributes compared to specimens fabricated through MEX printing. The results have substantiated the successful transformation of waste industrial GFRPP material into standardised specimens through the injection moulding fabrication technique. This study shows the potential of upcycling printed engineering-grade components via injection moulding, thereby converting them into functional composites within a circular economy framework.This research was funded by the Department of Business, Enterprise and Innovation and administered by Enterprise Ireland under the Disruptive Technologies Innovation Fund, MI-DRONE Project (Contract Ref: DT 2020 0221). The authors would like to acknowledge the support provided by Taighde Éireann – Research Ireland, formerly Science Foundation Ireland under grant number 22/IRDIFB/10946, 16/RC/3872, 21/RC/10295-P2, and 12/RC/2302_2. This publication has also emanated in part from research conducted with the financial support of the Marie Skłodowska-Curie grant agreement no. 847402.peer-reviewe
APIS: Applications and Potentials of Intelligent Swarms for magnetospheric studies
No full textEarth's magnetosphere is vital for today's technologically dependent society. The energy transferred from the solar wind to the magnetosphere triggers electromagnetic storms on Earth, knocking out power grids and infrastructure - e.g., communication and navigation systems. Despite occurring on our astrophysical doorstep, numerous physical processes connecting the solar wind and our magnetosphere remain poorly understood. To date, over a dozen science missions have flown to study the magnetosphere, and many more design studies have been conducted. However, the majority of these solutions relied on large monolithic satellites, which limited the spatial resolution of these investigations, in addition to the technological limitations of the past. To counter these limitations, we propose the use of a satellite swarm, carrying numerous payloads for magnetospheric measurements. Our mission is named APIS - Applications and Potentials of Intelligent Swarms. The APIS mission aims to characterize fundamental plasma processes in the magnetosphere and measure the effect of the solar wind on our magnetosphere. We propose a swarm of 40 CubeSats in two highly-elliptical orbits around the Earth, which perform radio tomography in the magnetotail at 8-12 Earth Radii (R E) downstream, and the subsolar magnetosphere at 8-12 R E upstream. These maps will be made at both low-resolutions (at 0.5 R E, 5 seconds cadence) and high-resolutions (at 0.025 R E, 2 seconds cadence). In addition, in-situ measurements of the magnetic and electric fields, and plasma density will be performed by on-board instruments. In this publication, we present a design study of the APIS mission, which includes the mission design, navigation, communication, processing, power systems, propulsion and other critical satellite subsystems. The science requirements of the APIS mission levy stringent system requirements, which are addressed using Commercial Off-the-Shelf (COTS) technologies. We show the feasibility of the APIS mission using COTS technologies using preliminary link, power, and mass budgets. In addition to the technological study, we also investigated the legal considerations of the APIS mission. The APIS mission design study was part of the International Space University Space Studies Program in 2019 (ISU-SSP19) Next Generation Space Systems: Swarms Team Project. The authors of this publication are the participants of this 9-week project, in addition to the Chairs and Support staff. Electronic
An investigation of the influence of matrix properties and fibre–matrix interface behaviour on the mechanical performance of carbon fibre-reinforced PEKK and PEEK composites
No full textPoly-ether-ketone-ketone (PEKK) is an emerging alternative to poly-ether-ether-ketone (PEEK) as a matrix for high-performance carbon fibre (CF) reinforced composites. Herein, the results of an experimental investigation to examine the influence of matrix properties and fibre–matrix interface behaviour on the mechanical performances of CF/PEKK and CF/PEEK composites are presented. CF/PEKK presents superior strength under longitudinal tension, longitudinal and transverse compression, as well as in-plane shear. It also exhibits better interfacial shear strength (IFSS) than CF/PEEK, which contributes to its superior strength, as damage typically initiates at the fibre–matrix interface under in-plane loading. Predictions of different analytical models adopted from the literature, which assess the influence of fibre–matrix adhesion on the in-plane strength, compare favourably to the experiments. Under cyclic shear tests, CF/PEKK exhibited more gradual stiffness reductions and low shear plasticity until 5% shear strain, indicating a more damage tolerant matrix. Relative to CF/PEEK, CF/PEKK presents superior interlaminar shear strength (ILSS) and mode I fracture toughness (GIC), but similar mode II fracture toughness (GIIC). High GIC is due to a synergistic interaction between its inherently ductile matrix and high IFSS, while ILSS strongly correlates with IFSS. Overall, CF/PEKK offers a better combination of strength and toughness, exceeding CF/PEEK.</p
