COUPLED DYNAMICS OF CABLE-HARNESSED STRUCTURES: ANALYTICAL MODELING AND EXPERIMENTAL VALIDATION

This thesis presents analytical models to study the vibration characteristics of cable-harnessed beam structures motivated by space structure applications. The distributed parameter models proposed in this work considers into account the effect of coupling between various coordinates of vibration such as the bending in the out of plane, in-plane direction, axial and the torsion coordinates. The mathematical models are presented for structures with straight cable wrapping pattern at an offset distance, periodic and non-periodic wrapping pattern. Numerous theoretical simulations are performed to highlight the importance of having a coupled vibration model and the analytical models are validated with experiments. Chapter 2.1 presents a distributed parameter model to study the vibrations of beam with straight cable pattern at an offset distance. The structure is modelled using Euler-Bernoulli and Timoshenko beam theories. The presented model studies the effects of coupling between various coordinates of vibrations. Strain and kinetic energy expressions are developed using linear displacement field assumptions and Green-Lagrange strain tensor. The governing coupled partial differential equations for the cable-harnessed beam that includes the effects of the cable pre-tension are found using Hamilton’s principle. The effects of the offset position of the cable, pre-tension and radius are studied on the natural frequencies of the system. The natural frequencies from the coupled Euler Bernoulli, Timoshenko and decoupled analytical models are found and compared to the results of the Finite Element Analysis. In Chapter 2.2, a mathematical model to study the coupled vibrations in cable-harnessed beam with periodic wrapping pattern is presented. The structure is modeled using Euler-Bernoulli and Timoshenko beam theories. The fundamental element of the wrapping pattern consists of diagonal cable section along with lumped mass section at the end of each element. An equivalent fully coupled continuum model is presented with goal of obtaining constant coefficient partial differential equations. Sensitivity analysis by the varying the cable radius, number of fundamental elements on the natural frequencies is also performed. The concept of transition frequency in Timoshenko beam theory is also studied for cable-harnessed structures. The effect of cable radius on the transition frequency is presented. Natural frequencies and mode shapes for both the spectra are presented for simply supported boundary condition and the results are compared to the bare beam to show the effect of cabling on the behavior of the structure for both the spectra of Timoshenko beam theory. Chapter 2.3, presents an analytical model to study the coupled vibrations of cable-harnessed structures with non-periodic wrapping pattern. The exact coupled partial differential equations of the structure are developed using Euler-Bernoulli (EB) theory. The analytical model assumes each fundamental element of the structure has different displacement, which means the structure is discretized at the interface of two different fundamental elements by applying the continuity conditions along with the cantilever boundary condition and the model is solved for natural frequencies, mode shapes and frequency response functions. In non-periodic wrapping, the wrapping angle changes for each fundamental element. The coupled exact model developed in Chapter 2.3 is an improvement of the model presented for the periodic wrapping patterns and is compared to the decoupled model for non-periodic wrapping patterns. In Chapter 3.1, the experimental study and model validations for the coupled dynamics of a cable-harnessed beam structure are presented. The system under consideration for the experiment consists of multiple pre-tensioned cables attached along the length of the host beam structure positioned at an offset distance from the beam centerline. Analytical model presented by the coupled partial differential equations (PDEs) for various coordinates of vibrations are found and the frequency response functions (FRFs) obtained for both Euler-Bernoulli and Timoshenko-based models are compared to those from the experiments for validation. In Chapters 3.2 and 3.3, experiments are performed on the cabled beam structures with periodic and non-periodic wrapping patterns and the frequency response functions obtained from coupled and decoupled models are compared to the experimental frequency response functions. The experimental mode shape animation plots of the torsion dominant and in-plane dominant modes are also presented to identify the type of modes associated with the sharp peaks observed in the out-of-plane bending frequency response functions

Analytical Study of Coupling Effects for Vibrations of Cable-Harnessed Beam Structures

This paper presents a distributed parameter model to study the effects of the harnessing cables on the dynamics of a host structure motivated by space structures applications. The structure is modeled using both Euler-Bernoulli and Timoshenko beam theories. The presented model studies the effects of coupling between various coordinates of vibrations due to the addition of the cable. The effects of the cable’s offset position, pre-tension and radius are studied on the natural frequencies of the system. Strain and kinetic energy expressions using linear displacement field assumptions and Green-Lagrange strain tensor are developed. The governing coupled partial differential equations for the cable-harnessed beam that includes the effects of the cable pre-tension are found using Hamilton’s principle. The natural frequencies from the coupled Euler Bernoulli, Timoshenko and decoupled analytical models are found and compared to the results of the Finite Element Analysis.Natural Sciences and Engineering Research Council, Discovery Gran

Coupled Dynamics of Cable-Harnessed Structures: Experimental Validation

The experimental study and model validations for the coupled dynamics of a cable-harnessed beam structure are presented. The system under consideration consists of multiple pretensioned cables attached along the length of the host beam structure positioned at an offset distance from the beam centerline. Analytical model presented by the coupled partial differential equations (PDEs) for various coordinates of vibrations is found, and the displacement frequency response functions (FRFs) obtained for both Euler–Bernoulli and Timoshenko-based models are compared to those from the experiments for validation. The results are shown to be in very good agreement with the experiments.Natural Sciences and Engineering Research Council of Canada, Grant RGPIN-2016-0485

Plant-associated symbiotic Burkholderia species lack hallmark strategies required in mammalian pathogenesis

Burkholderia is a diverse and dynamic genus, containing pathogenic species as well as species that form complex interactions with plants. Pathogenic strains, such as B. pseudomallei and B. mallei, can cause serious disease in mammals, while other Burkholderia strains are opportunistic pathogens, infecting humans or animals with a compromised immune system. Although some of the opportunistic Burkholderia pathogens are known to promote plant growth and even fix nitrogen, the risk of infection to infants, the elderly, and people who are immunocompromised has not only resulted in a restriction on their use, but has also limited the application of non-pathogenic, symbiotic species, several of which nodulate legume roots or have positive effects on plant growth. However, recent phylogenetic analyses have demonstrated that Burkholderia species separate into distinct lineages, suggesting the possibility for safe use of certain symbiotic species in agricultural contexts. A number of environmental strains that promote plant growth or degrade xenobiotics are also included in the symbiotic lineage. Many of these species have the potential to enhance agriculture in areas where fertilizers are not readily available and may serve in the future as inocula for crops growing in soils impacted by climate change. Here we address the pathogenic potential of several of the symbiotic Burkholderia strains using bioinformatics and functional tests. A series of infection experiments using Caenorhabditis elegans and HeLa cells, as well as genomic characterization of pathogenic loci, show that the risk of opportunistic infection by symbiotic strains such as B. tuberum is extremely low

Time dimension in the relational model

Call number: LD2668 .T4 CMSC 1987 C52Master of ScienceComputing and Information Science

UCINet0: A Machine Learning based Receiver for 5G NR PUCCH Format 0

Accurate decoding of Uplink Control Information (UCI) on the Physical Uplink Control Channel (PUCCH) is essential for enabling 5G wireless links. This paper explores an AI/ML-based receiver design for PUCCH Format 0. Format 0 signaling encodes the UCI content within the phase of a known base waveform and even supports multiplexing of up to 12 users within the same time-frequency resources. Our first-of-a-kind neural network classifier, which we term UCINet0, is capable of predicting when no user is transmitting on the PUCCH, as well as decoding the UCI content of any number of multiplexed users, up to 12. Inference results with both simulated and hardware-captured field datasets show that the UCINet0 model outperforms conventional DFT-based decoders across all SNR ranges

Machine Learning Decoder for 5G NR PUCCH Format 0

5G cellular systems depend on the timely exchange of feedback control information between the user equipment and the base station. Proper decoding of this control information is necessary to set up and sustain high throughput radio links. This paper makes the first attempt at using Machine Learning techniques to improve the decoding performance of the Physical Uplink Control Channel Format 0. We use fully connected neural networks to classify the received samples based on the uplink control information content embedded within them. The trained neural network, tested on real-time wireless captures, shows significant improvement in accuracy over conventional DFT-based decoders, even at low SNR. The obtained accuracy results also demonstrate conformance with 3GPP requirements.Comment: Submitted to NCC conferenc

Enhancements for 5G NR PRACH Reception: An AI/ML Approach

Random Access is an important step in enabling the initial attachment of a User Equipment (UE) to a Base Station (gNB). The UE identifies itself by embedding a Preamble Index (RAPID) in the phase rotation of a known base sequence, which it transmits on the Physical Random Access Channel (PRACH). The signal on the PRACH also enables the estimation of propagation delay, often known as Timing Advance (TA), which is induced by virtue of the UE's position. Traditional receivers estimate the RAPID and TA using correlation-based techniques. This paper presents an alternative receiver approach that uses AI/ML models, wherein two neural networks are proposed, one for the RAPID and one for the TA. Different from other works, these two models can run in parallel as opposed to sequentially. Experiments with both simulated data and over-the-air hardware captures highlight the improved performance of the proposed AI/ML-based techniques compared to conventional correlation methods

Genomes of marine cyanopodoviruses reveal multiple origins of diversity

The marine cyanobacteria Prochlorococcus and Synechococcus are highly abundant in the global oceans, as are the cyanophage with which they co-evolve. While genomic analyses have been relatively extensive for cyanomyoviruses, only three cyanopodoviruses isolated on marine cyanobacteria have been sequenced. Here we present nine new cyanopodovirus genomes, and analyse them in the context of the broader group. The genomes range from 42.2 to 47.7 kb, with G+C contents consistent with those of their hosts. They share 12 core genes, and the pan-genome is not close to being fully sampled. The genomes contain three variable island regions, with the most hypervariable genes concentrated at one end of the genome. Concatenated core-gene phylogeny clusters all but one of the phage into three distinct groups (MPP-A and two discrete clades within MPP-B). The outlier, P-RSP2, has the smallest genome and lacks RNA polymerase, a hallmark of the Autographivirinae subfamily. The phage in group MPP-B contain photosynthesis and carbon metabolism associated genes, while group MPP-A and the outlier P-RSP2 do not, suggesting different constraints on their lytic cycles. Four of the phage encode integrases and three have a host integration signature. Metagenomic analyses reveal that cyanopodoviruses may be more abundant in the oceans than previously thought.National Science Foundation (U.S.). Center for Microbial Oceanography: Research and Education (Grant OCE-042560)National Science Foundation (U.S.). Center for Microbial Oceanography: Research and Education (Grant EF 0424599