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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
991

Injection Locking Of Semiconductor Mode-locked Lasers For Long-term Stability Of Widely Tunable Frequency Combs

Williams, Charles 01 January 2013 (has links)
Harmonically mode-locked semiconductor lasers with external ring cavities offer high repetition rate pulse trains while maintaining low optical linewidth via long cavity storage times. Single frequency injection locking generates widely-spaced and tunable frequency combs from these harmonically mode-locked lasers, while stabilizing the optical frequencies. The output is stabilized long-term with the help of a feedback loop utilizing either a novel technique based on Pound-Drever-Hall stabilization or by polarization spectroscopy. Error signals of both techniques are simulated and compared to experimentally obtained signals. Frequency combs spaced by 2.5 GHz and ~10 GHz are generated, with demonstrated optical sidemode suppression of unwanted modes of 36 dB, as well as RF supermode noise suppression of 14 dB for longer than 1 hour. In addition to the injection locking of actively harmonically mode-locked lasers, the injection locking technique for regeneratively mode-locked lasers, or Coupled OptoElectronic Oscillators (COEOs), is also demonstrated and characterized extensively.
992

Mass spectrometry imaging using cytometry by time-of-flight strategies for brain tissues: a literature review

Akbari, Behnaz 01 November 2022 (has links)
Mass spectrometry (MS) as an analytical approach could provide comprehensive identification and quantitation of the biomolecules (proteins, peptides, nucleic acids, lipids) in a cell, tissue, or organism, from biomarker discovery to prediction of response to therapy or intervention. Inductively coupled plasma mass spectrometry (ICP-MS), can determine the elemental composition of materials and has been used for below ppt levels (ppq) and better in some cases (transuranics and non-metals) to detect metals and other elements in water, soil, and air or blood and urine samples. Mass cytometry is an implementation of ICP-MS to single-cell analysis; it is based on metal isotope-tagged antibodies to quantify these bioconjugates. Imaging mass cytometry (IMC), a commercially available immunohistochemistry laser ablation-inductively coupled plasma-time-of-flight-mass spectrometry (LA-ICP-TOF-MS) system, was designed for molecular biomarkers imaging in the tissue sections (e.g., brain) through metal-tagged antibodies (typically, lanthanides). This thesis highlights the contributions of ICP-TOF-MS-based approaches towards advanced developments of mass cytometry (CyTOF) and discusses its biomedical applications for investigating neurodegenerative diseases while comparing it to other imaging modalities such as PET, MRI, Allen brain, etc. In conclusion, CyTOF, as a high-dimensional imaging tool, provides information on many clinical applications, such as hematopoiesis, transplantation, cancer, and autoimmunity.
993

Seismic Design of Composite Plate Shear Walls -- Concrete-Filled

Morgan Renee Broberg (14210369) 07 December 2022 (has links)
<p>Composite plate shear walls – concrete-filled (C-PSW/CF) are a new innovative lateral force resisting system intended for high-rise buildings. The walls consist of parallel steel faceplates connected with tie bars and filled with concrete. This dissertation introduces the C-PSW/CF </p> <p>system and coupled C-PSW/CFs consisting of C-PSW/CF walls and composite coupling beams. Three studies are presented herein covering seismic design parameters for C-PSW/CFs, non-linear modeling techniques for composite coupling beams, and the design philosophy for coupled C-PSW/CFs.</p> <p> </p> <p>The first study summarizes the results of a recent FEMA P695 study completed to verify seismic design parameters for uncoupled C-PSW/CFs with rectangular flange plate boundary elements. Seven archetype structures were: (i) designed, (ii) modeled using a benchmarked fiber-based finite element analysis approach, (iii) subjected to nonlinear pushover analysis, (iv) subjected to incremental nonlinear dynamic analysis to failure for 22-sets of scaled ground motions, and (v) the results were statistically analyzed to assess performance. These structures ranged from three (3) to twenty-two (22) stories and included both planar and C-shaped wall configurations. As part of this design process, recommendations for stiffness approximations for linear analysis of C-PSW/CFs</p> <p>were developed. Additionally, these nonlinear incremental dynamic analysis results were post-processed to determine the rotation and strain demands at the base of these structures at the design basis, maximum considered, and failure level earthquakes. These results showed that the rotation and strain demand at failure level earthquakes were comparable regardless of the ground motion. Ultimately, this FEMA P695 approach verified the R factor of 6.5, C<sub>d</sub> factor of 5.5, and Ω<sub>0</sub> of 2.5 for C-PSW/CFs with boundary elements. </p> <p><br></p> <p>The second study proposes modeling approaches for composite coupling beams used in combination with C-PSW/CFs. Capturing the behavior of these components is critical to understanding the system behavior of coupled C-PSW/CFs, as the coupling beam components undergo yielding, plastification, and fracture prior to collapse of coupled C-PSW/CF walls. Although steel-concrete composite walls have been a known structural system for decades, only recently have coupled C-PSW/CF systems been investigated and implemented as a seismic force resisting system. As the interest in coupled C-PSW/CF systems increases, the necessity of reliable nonlinear modeling techniques for pushover, cyclic, and seismic analysis has become apparent. This paper presents fiber-based options for modeling composite coupling beam components of coupled C-PSW/CF walls for use in nonlinear and seismic response analyses. Recommendations include effective steel and concrete stress-strain curves, modeling parameters for fiber-based </p> <p>materials, and concentrated plasticity options for additional computational efficiency. These recommendations are then implemented for a full-scale coupling beam section. </p> <p><br></p> <p>In the final study, a capacity design principle is used to establish a basis for the seismic design of coupled composite plate shear walls – concrete filled (CC-PSW/CF) systems. This design philosophy implements a strong wall-weak coupling beam approach, where flexural yielding in coupling beams occurs before flexural yielding at the base of walls. The coupling beams are sized </p> <p>to resist the calculated seismic lateral force level. The walls are sized to resist an amplified seismic lateral force corresponding to the overall plastic mechanism for the structure, while accounting for the capacity-limited forces from the coupling beams and the coupling action between the walls. Based on this philosophy, recommendations and requirements for appropriate sizing of coupling beams and C-PSW/CFs are presented. These recommendations are used to design four example (8-22 story) structures and evaluate their seismic behavior. The structures were modeled using 2D finite element models and fiber-based models subjected to monotonic and time history analysis. </p> <p>The nonlinear inelastic behavior and seismic responses of the example structures were in accordance with the capacity limited design philosophy (strong wall-weak beam), thus confirming the philosophy’s  efficacy. </p>
994

Evaluation of a computational method for natural fiber-reinforced plastics / Bedömning av en beräkningsmetod för naturfiberförstärkta plaster

Lim, Anna January 2023 (has links)
The importance of using natural fiber composites (NFCs) has been addressed as a substitution for synthetic fibers, such as glass and carbon fibers. This substitution contributes significantly to reducing greenhouse gas emissions, aligning with the environmental responsibilities of engineering industries. Wood fiber(WF) is one of the natural fibers (NFs) dominating the market in various businesses. As an excellent alternative to non-renewable sources, the demand for injection-molded applications using natural fiber-reinforced plastics has expanded across various sectors. Despite extensive prior research on the mechanical properties of WFs, there remains a need for a deeper understanding of the connection between fiber orientation and mechanical characteristics. This understanding is essential for developing computational methods aimed at ensuring structural integrity, cost-efficiency, and sustainability in real-world components. This study aims to evaluate coupled injection molding simulation to finite element method with mapping of fiber orientation tensor for a wood fiber composite (WFC). To achieve this, WFC’s mechanical properties and behavior under tensile loading conditions are investigated. The research methodology involves conducting uniaxial tensile testing on dog bone-shaped specimens at different fiber orientations (0 degrees, 45 degrees, and 90 degrees). Experimental data is collected, analyzed, and compared with the obtained results with numerical simulations to validate the accuracy of the models used. Additionally, the aspect ratio and volume fraction of the WFs are measured through both mathematical calculations and image analysis using MATLAB. The main contribution of this study can be summarized in two key observations. Firstly, the investigation of mechanical characteristics across different fiber orientations has revealed distinct patterns. Specimens aligned at 0 degrees exhibit noticeable differences in behavior compared to those at 45 and 90 degrees, highlighting the material's anisotropic nature. Secondly, the comparison between experimental data and computational simulations exhibits the effectiveness of the developed models. The close agreement between the two validates the accuracy of the predictive approach. Moreover, the consistent aspect ratio, volume fraction, and fiber orientation value obtained through both mathematical calculations and image analysis add credibility to the reliability of our measurements. Notably, the comparison with glass fibers (GFs) reveals that WFs exhibit considerably less breakage, highlighting their durability and potential suitability for various applications. / Betydelsen av att använda naturfiberkompositer har behandlats som en ersättning för syntetiska fibrer, såsom glas- och kolbaserade fibrer. Denna substitution bidrar betydligt till att minska utsläpp av växthusgaser och överensstämmer med ingenjörsbranschens miljöansvar. Träfiber är en av de naturfibrer som dominerar marknaden inom olika branscher. Som ett utmärkt alternativ till icke-förnybara källor har efterfrågan på formsprutade applikationer med naturfiberförstärkta plaster ökat inom olika sektorer. Trots omfattande tidigare forskning om träfibrers mekaniska egenskaper finns det fortfarande ett behov av en djupare förståelse för sambandet mellan fiberns orientering och dess mekaniska egenskaper. Denna förståelse är avgörande för att utveckla beräkningsmetoder som syftar till att säkerställa strukturell integritet, kostnadseffektivitet och hållbarhet i komponenter i den verkliga världen. Denna studie syftar till att utvärdera kopplad formsprutningssimulering med ändelementmetod och kartläggning av fibrernas orienteringstensor för en träfiberkomposit. För att uppnå detta undersöks träfiberkompositens mekaniska egenskaper och beteende under dragbelastningsförhållanden. Forskningsmetodiken innefattar genomförande av enaxlig dragprovning på hundbenformade provkroppar vid olika fibrers orientering (0 grader, 45 grader och 90 grader). Experimentella data samlas in, analyseras och jämförs med de erhållna resultaten från numeriska simuleringar för att validera modellernas noggrannhet. Dessutom mäts träfibrernas aspektratio och volymfraktion genom både matematiska beräkningar och bildanalys med hjälp av MATLAB. Huvudbidraget från denna studie kan sammanfattas i två centrala iakttagelser. För det första har undersökningen av mekaniska egenskaper vid olika fibrers orienteringar avslöjat tydliga mönster. Prover som är riktade i 0 grader uppvisar märkbara skillnader i beteende jämfört med de vid 45 och 90 grader, vilket understryker materialets anisotropa natur. För det andra visar jämförelsen mellan experimentella data och beräkningsmässiga simuleringar effektiviteten hos de utvecklade modellerna. Den nära överensstämmelsen mellan de båda validerar noggrannheten i den prediktiva metoden. Dessutom lägger de konsekventa värdena för aspektratio, volymfraktion och fibrernas orientering som erhållits genom både matematiska beräkningar och bildanalys trovärdighet till våra mätningar. Det bör noteras att jämförelsen med glasfiber visar att träfibrer uppvisar betydligt mindre brytning, vilket betonar deras hållbarhet och potentiella lämplighet för olika tillämpningar.
995

Targeting of peptide-binding receptors on cancer cells with peptide-drug conjugates

Worm, Dennis J., Els-Heindl, Sylvia, Beck-Sickinger, Annette G. 05 June 2023 (has links)
Specifically addressing cell surface molecules on cancer cells facilitates targeted cancer therapies that offer the potential to selectively destroy malignant cells, while sparing healthy tissue. Thus, undesired side-effects in tumor patients are highly reduced. Peptide-binding receptors are frequently overexpressed on cancer cells and therefore promising targets for selective tumor therapy. In this review, peptide-binding receptors for anti-cancer drug delivery are summarized with a focus on peptide ligands as delivery agents. In the first part, some of the most studied peptide-binding receptors are presented, and the ghrelin receptor and the Y1 receptor are introduced as more recent targets for cancer therapy. Furthermore, nonpeptidic small molecules for receptor targeting on cancer cells are outlined. In the second part, peptide conjugates for the delivery of therapeutic cargos in cancer therapy are described. The essential properties of receptor-targeting peptides are specified, and recent developments in the fields of classical peptide-drug conjugates with toxic agents, radiolabeled peptides for radionuclide therapy, and boronated peptides for boron neutron capture therapy are presented.
996

Response-calibration Techniques For Antenna-coupled Infrared Sensors

Krenz, Peter 01 January 2010 (has links)
Infrared antennas are employed in sensing applications requiring specific spectral, polarization, and directional properties. Because of their inherently small dimensions, there is significant interaction, both thermal and electromagnetic, between the antenna, the antenna-coupled sensor, and the low-frequency readout structures necessary for signal extraction at the baseband modulation frequency. Validation of design models against measurements requires separation of these effects so that the response of the antenna-coupled sensor alone can be measured in a calibrated manner. Such validations will allow confident extension of design techniques to more complex infrared-antenna configurations. Two general techniques are explored to accomplish this goal. The extraneous signal contributions can be measured separately with calibration structures closely co-located near the devices to be characterized. This approach is demonstrated in two specific embodiments, for removal of cross-polarization effects arising from lead lines in an antenna-coupled infrared dipole, and for removal of distributed thermal effects in an infrared phased-array antenna. The second calibration technique uses scanning near-field microscopy to experimentally determine the spatial dependence of the electric-field distributions on the signal-extraction structures, and to include these measured fields in the computational electromagnetic model of the overall device. This approach is demonstrated for infrared dipole antennas which are connected to coplanar strip lines. Specific situations with open-circuit and short-circuit impedances at the termination of the lines are investigated.
997

Electrochemical studies of external forcing of periodic oscillating systems and fabrication of coupled microelectrode array sensors

Clark, David 01 May 2020 (has links)
This dissertation describes the electrochemical behavior of nickel and iron that was studied in different acid solutions via linear sweep voltammetry, cyclic voltammetry, and potentiostatic measurements over a range of temperatures at specific potential ranges. The presented work displays novel experiments where a nickel electrode was heated locally with an inductive heating system, and a platinum (Pt) electrode was used to change the proton concentration at iron and nickel electrode surfaces to control the periodic oscillations (frequency and amplitude) produced and to gain a greater understanding of the systems (kinetics), oscillatory processes, and corrosion processes. Temperature pulse voltammetry, linear sweep voltammetry, and cyclic voltammetry were used for temperature calibration at different heating conditions. Several other metal systems (bismuth, lead, zinc, and silver) also produce periodic oscillations as corrosion occurs; however, creating these with pure metal electrodes is very expensive. In this work, metal systems were created via electrodeposition by using inexpensive, efficient, coupled microelectrode array sensors (CMASs) as a substrate. CMASs are integrated devices with multiple electrodes that are connected externally in a circuit in which all of the electrodes have the same amount of potential applied or current passing through them. CMASs have been used for many years to study different forms of corrosion (crevice corrosion, pitting corrosion, intergranular corrosion, and galvanic corrosion), and they are beneficial because they can simulate single electrodes of the same size. The presented work also demonstrates how to construct CMASs and shows that the unique phenomena of periodic oscillations that can be created and studied by using coated and bare copper CMASs. Furthermore, these systems can be controlled by implementing external forcing with a Pt electrode at the CMAS surface. The data from the single Ni electrode experiments and CMAS experiments were analyzed by using the Nonlinear Time-Series Analysis approach.
998

Fluid-Structure Interaction of a Variable Camber Compliant Wing

Miller, Samuel C. 27 May 2015 (has links)
No description available.
999

Coupled Modeling of Economic – Hydrological Systems: Examining Spatial Heterogeneity in Water Quality Benefits and Optimal Agricultural Land Use Management in Ohio

Liu, Hongxing 13 October 2017 (has links)
No description available.
1000

Combinatorial and probabilistic aspects of coupled oscillators

Yu, Han Baek 14 August 2018 (has links)
No description available.

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