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1
Gopalakrishnamurthy, Sharath H. "Structural integrity inspection using dynamic responses /." free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p1418023.
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姜瑞娟 and Ruijuan Jiang. "Identification of dynamic load and vehicle parameters based on bridge dynamic responses." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31244270.
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Wu, Xiaoxiao M. Eng Massachusetts Institute of Technology. "Wind-induced dynamic responses of structures with outrigger systems." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99621.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (page 55).
A multi-degree of freedom lumped mass model with rotational springs was built to investigate the influence of outrigger system on the natural periods and mode shapes of a structure. The presence of outrigger system was found to significantly stiffen the structure, reducing the natural periods and distorting the mode shapes. The influences of outrigger system on the modal properties of a structure vary with the change of its number, locations and rotational stiffness. Wind-induced along-wind and across-wind responses of structures with and without outrigger system were analyzed, compared and discussed. It was found that the outrigger system can effectively decrease the along-wind responses (peak displacements and accelerations) and its influence is the most significant when it's located at the middle of the structural height. For across-wind responses, the outrigger system(s) could help with the prevention of vortex-induced resonance, if its location(s) is(are) appropriately chosen, by shifting the natural periods of the original structure without outrigger away from the frequency of vortex shedding. Two methodologies were proposed for the design of outrigger systems in two different scenarios, one with the number and locations of outrigger(s) preset and the other not. For the first scenario, the corresponding methodology is a checking process and for the second, it is a designing process. Both methodologies are aimed at preventing vortex-induced resonance and minimizing along-wind peak displacements and accelerations, satisfying related human comfort criteria for motions and lateral drifts requirements.
by Xiaoxiao Wu.
M. Eng.
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Yang, Xiusheng. "Greenhouse microclimate : transport processes, plant responses and dynamic modeling." The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1145370914.
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Pang, Wyming Lee. "Quantitative analysis of genetic expression responses to dynamic microenvironmental perturbation." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3245319.
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Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed March 2, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 320-337).
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Yu, Da. "Dynamic responses of PCB under product level free drop impact." Diss., Online access via UMI:, 2008.
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Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Mechanical Engineering, 2008.Includes bibliographical references.
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Schmidt, Daniel, Castro Germano Andresa Mara De, and Thomas Lothar Milani. "Aspects of Dynamic Balance Responses: Inter- and Intra-Day Reliability." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-188620.
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The Posturomed device is used as a scientific tool to quantify human dynamic balance ability due to unexpected perturbations, and as a training device. Consequently, the question arises whether such measurements are compromised by learning effects. Therefore, this study aimed to analyze inter- and intra-day reliability of dynamic balance responses using the Posturomed. Thirty healthy young subjects participated (24.3±3.2 years). The Posturomed was equipped with a triggering mechanism to enable unexpected, horizontal platform perturbations. A force platform was used to quantify Center of Pressure (COP) excursions for two time intervals: interval 1 (0–70 ms post perturbation) and interval 2 (71–260 ms post perturbation). Dynamic balance tests were performed in single leg stances in medio-lateral and anterior-posterior perturbation directions. Inter- and intra-day reliability were assessed descriptively using Bland-Altman plots and inferentially using tests for systematic error and intra-class-correlations. With regard to the mean COP excursions for every subject and all intervals, some cases revealed significant differences between measurement sessions, however, none were considered relevant. Furthermore, intra class correlation coefficients reflected high magnitudes, which leads to the assumption of good relative reliability. However, analyzing inter- and intra-day reliability using Bland-Altman plots revealed one exception: intra-day comparisons for the anterior-posterior direction in interval 2, which points towards possible learning effects. In summary, results reflected good overall reliability with the exception of certain intra-day comparisons in the anterior-posterior perturbation direction, which could indicate learning effects in those particular conditions.
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Wu, Liwen. "Dynamic hyporheic responses to transient discharge, temperature and groundwater table." Doctoral thesis, Humboldt-Universität zu Berlin, 2020. http://dx.doi.org/10.18452/22236.
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Obwohl der Bedeutung von hyporheischen Zonen als Übergangsbereiche zwischen Flüssen und angrenzenden alluvialen Aquiferen eine wachsende Anerkennung zuteilwird, sind dynamische hyporheische Reaktionen auf instationäre hydrologische Bedingungen weiterhin signifikant untererforscht. Um diese Lücke zu schließen, liegt der Fokus dieser Doktorarbeit insbesondere auf den Effekten transienter Abflussverhalten und Temperaturschwankungen in Flüssen auf die raumzeitliche Variabilität von hyporheischen Austauschprozessen. Unter Beachtung dieser Ziele wird ein neues physikalisch basiertes numerisches Modell vorgeschlagen und schließlich angewandt, um systematisch die hyporheischen, durch Sedimentoberflächenstrukturen ausgelösten Reaktionen auf eine Reihe von künstlichen und natürlichen Abflussregimen abzuschätzen. Parameter wie das räumliche Ausmaß der hyporheischen Zone, hyporheische Austauschrate, mittlere Aufenthaltszeit, Temperatur des hyporheischen Flusses sowie das Denitrifikationspotenzial werden definiert, um den Einfluss der Antriebskräfte und Regulatoren auf dynamische hyporheische Reaktionen zu quantifizieren. Die Ergebnisse zeigen, dass mit zunehmendem Abfluss generell das räumliche Ausmaß der hyporheischen Zone vergrößert wird; jedoch bestimmen geomorphologische Bedingungen und Grundwasserflüsse erheblich das Ausdehnen und Zusammenziehen hyporheischer Zonen zusammen mit Strömungen, Wärme- und Stoffaustausch zwischen Fluss und Grundwasser. Temperaturvariabilität, ein wichtiger Faktor, welcher oft in hydrodynamischen Studien vernachlässigt wird, zeigt direkte kontrollierende Effekte beim Bestimmen hyporheischer Austauschraten und mittlerer Aufenthaltszeiten. Weiterhin spielt die Dynamik von Grundwasserständen eine entscheidende Rolle bei hyporheischen Austauschprozessen. Das Optimieren der Terminierung von Grundwasserförderung ist ausschlaggebend für die Regulierung von Wasserqualität, Nährstoffkreisläufen und der Entstehung thermischer hyporheischer Refugien.Although there is a growing recognition of the importance of hyporheic zones as transitional areas connecting rivers and adjacent alluvial aquifers, the dynamic hyporheic responses to unsteady hydrological conditions are still significantly understudied. To bridge this gap, the present PhD thesis primarily focuses on the effects of transient river discharge and temperature fluctuations on the spatiotemporal variability of hyporheic exchange processes. With these objectives in mind, a novel physically based numerical model is proposed and then applied to systematically evaluate bedform-induced hyporheic responses to a series of synthetic and natural hydrological regimes. Metrics including spatial hyporheic extent, hyporheic exchange rate, mean residence time, temperature of hyporheic flux, and denitrification potential are defined to quantify the impact of drivers and modulators of dynamic hyporheic responses. Results indicate that increasing river discharge generally enlarges the spatial hyporheic extent; however, geomorphological settings and groundwater fluxes substantially modulate the expansion and contraction of hyporheic zones along with flow, heat and solute exchange between river and groundwater. Temperature variability, an important factor which is often neglected in hydrodynamic studies, displays direct controlling effects in determining hyporheic exchange rates and mean residence times. Groundwater table dynamics also play a critical role in hyporheic exchange processes. Optimizing the timing of aquifer pumping is crucial for regulation of water quality, nutrient cycling, and the formation of thermal hyporheic refugia. The findings largely advanced our mechanistic understandings of dynamic hyporheic responses to varying transient flow and temperature conditions, and therefore shed lights on improving river management and restoration strategies.
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St-Pierre, Luc. "The quasi-static and dynamic responses of metallic sandwich structures." Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/243443.
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Lattice materials are used as the core of sandwich panels to construct light and strong structures. This thesis focuses on metallic sandwich structures and has two main objectives: (i) explore how a surface treatment can improve the strength of a lattice material and (ii) investigate the collapse response of two competing prismatic sandwich cores employed in ship hulls. First, the finite element method is used to examine the effect of carburisation and strain hardening upon the compressive response of a pyramidal lattice made from hollow tubes or solid struts. The carburisation surface treatment increases the yield strength of the material, but its effects on pyramidal lattices are not known. Here, it is demonstrated that carburisation increases the plastic buckling strength of the lattice and reduces the slenderness ratio at which the transition from plastic to elastic buckling occurs. The predictions also showed that strain hardening increases the compressive strength of stocky lattices with a slenderness ratio inferior to ten, but without affecting the collapse mode of the lattice. Second, the quasi-static three-point bending responses of simply supported and clamped sandwich beams with a corrugated core or a Y-frame core are compared via experiments and finite element simulations. The role of the face-sheets is assessed by considering beams with (i) front-and-back faces present and (ii) front face present, but back face absent. These two beam designs are used to represent single hull and double hull ship structures, and they are compared on an equal mass basis by doubling the thickness of the front face when the back face is absent. Beams with a corrugated core are found to be slightly stronger than those with a Y-frame core, and two collapse mechanisms are identified depending upon beam span. Short beams collapse by indentation and for this collapse mechanism, beams without a back face outperform those with front-and back faces present. In contrast, longbeams fail by Brazier plastic buckling and for this collapse mechanism, the presence of a back face strengthens the beam. Third, drop weight tests with an impact velocity of 5 m/s are performed on simply supported and clamped sandwich beams with a corrugated core or a Y-frame core. These tests are conducted to mimic the response of a sandwich hull in a ship collision. The responses measured at 5 m/s are found to be slightly stronger than those measured quasi-statically. The measurements are in reasonable agreement with finite element predictions. In addition, the finite element method is used to investigate whether the collapse mechanism at 5 m/s is different from the one obtained quasi-statically. The predictions indicate that sandwich beams that collapse quasi-statically by indentation also fail by indentation at 5 m/s. In contrast, the simulations for beams that fail quasi-statically by Brazier plastic buckling show that they collapse by indentation at 5 m/s. Finally, the dynamic indentation response of sandwich panels with a corrugated core or a Y-frame core is simulated using the finite element method. The panels are indented at a constant velocity ranging from quasi-static loading to 100 m/s, and two indenters are considered: a flat-bottomed indenter and a cylindrical roller. For indentation velocities representative of a ship collision, i.e. below 10 m/s, the predictions indicate that the force applied to the front face of the panel is approximately equal to the force transmitted to the back face. Even at such low indentation velocities, inertia stabilisation effects increase the dynamic initial peak load above its quasi-static value. This strengthening effect is more important for the corrugated core than for the Y-frame core. For velocities greater than 10 m/s, the force applied to the front face exceeds the force transmitted to the back face due to wave propagation effects. The results are also found to be very sensitive to the size of the flat-bottomed indenter; increasing its width enhances both inertia stabilisation and wave propagation effects. In contrast, increasing the roller diameter has a smaller effect on the dynamic indentation response. Lastly, it is demonstrated that material strain-rate sensitivity has a small effect on the dynamic indentation response of both corrugated and Y-frame sandwich panels.
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Hao, Jinde. "Dynamic responses of soil anchorages using numerical and centrifuge modelling techniques." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2008. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=24846.
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Alexander, J. G. M. "Design excitations for dynamic stability assessment based on mapping weighted responses." Thesis, University of Strathclyde, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382277.
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Sun, Min. "Dissecting the genome-wide dynamic responses of the HIF transcriptional system." Thesis, University of Oxford, 2018. http://ora.ox.ac.uk/objects/uuid:0ccfa0d0-7f61-407e-adee-1631ea392a59.
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Hypoxia is an important stimulus for physiological processes such as development and adaptation to high altitude. It is also important in the pathology of many human diseases such as cancer, cardiovascular and diabetic disorders. The sequence-specific, heterodimeric transcription factor HIF (Hypoxia Inducible Factor) has been shown to play a key role in cellular adaptation to hypoxia. This work aimed to better understand the contribution of HIF to hypoxia-inducible gene expression through determining the range of HIF-target genes (both direct and indirect) by sequencing the whole transcriptome (RNA-seq) in HKC-8 wild type and a series of mutant cells (in which one or more components of the HIF-VHL pathway are inactivated). The work went on to examine the pan-genomic binding distribution of HIF polypeptides in response to different severity and duration of hypoxia and in cells bearing introduced mutations in the von Hippel- Lindau tumour suppressor (pVHL), the chromatin remodelling component BRG1-associated factor 180 (BAF180, encoded by PBRM1 gene), and the HIF asparaginyl hydroxylase, FIH (Factor Inhibiting HIF). This was performed using chromatin immunoprecipitation coupled to high-throughput sequencing (ChIP-seq), and was subjected to a range of quantitative and qualitative analyses. Analyses of hypoxic gene expression profiles demonstrated that the vast majority of hypoxia-dependent genes in HKC-8 cells were regulated by the canonical HIF pathway i.e. via dimerisation of either HIF-1α or HIF-2α with HIF-1β. There was little evidence for any HIFindependent contributions to gene expression in hypoxia under the conditions analysed. Analyses of hypoxia-dependent genes in HIF mutant cells revealed some persistent regulation by hypoxia that was less than in the wild type cells, and also a set of genes with a lipid metabolism signature that were more regulated by hypoxia in HIF-deficient cells. This observation might represent an adaptive response to enable cell survival in the absence of a functional HIF response. Having confirmed the critical role of the canonical HIF pathway in regulating hypoxic gene expression in the wild type cells, I then went on to study the canonical HIF DNA-binding profiles across the genome in response to various physiological and pathophysiological conditions as outlined above. It was hypothesised that these conditions might alter the profile of HIF binding as a result of changes in HIF protein abundance, or transcriptional function, as well as by the potential rearrangement of chromatin accessibility. Highly stringent canonical HIF binding sites were defined in each condition, and quantitative analyses of ChIP-seq signals were performed. Overall, the HIF binding signal at any one site was broadly proportional to the total binding for that HIF protein, with HIF-1α and HIF-2α behaving largely independently of each other and showing little evidence for redistribution of HIF DNA-binding profiles in response to different severity and duration of hypoxia, or in the mutant cells. In summary, this study demonstrates that the canonical HIF pathway is central to hypoxia-dependent gene regulation. HIF DNA-binding occurs over a quantitative continuum, which appears to be qualitatively unaltered under the conditions examined, with the applied interventions only altering the magnitude of HIF binding at the existing sites, rather than qualitatively generating new sites.
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Yang, Baozhong. "On the characteristics of fault-induced rotor-dynamic bifurcations and nonlinear responses." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/1135.
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Rotor-dynamic stability is a very important subject impacting the design, control, maintenance, and operating safety and reliability of rotary mechanical systems. As rotor-dynamic nonlinearities are significantly more prominent at higher rotary speeds, the demand for better and improved performance achievable through higher speeds has rendered the use of a linear approach for rotor-dynamic analysis both inadequate and ineffective. To establish the fundamental knowledge base necessary for addressing the need, it is essential that nonlinear rotor-dynamic responses indicative of the causes of nonlinearity, along with the bifurcated dynamic states of instability, be fully characterized. The objectives of the research are to study the various rotor-dynamic instabilities induced by crack breathing and bearing fluid film forces using a model rotor-bearing system and to investigate the applicability of the fundamental concept of instantaneous frequency for characterizing rotor-dynamic nonlinear responses. A comprehensive finite element model incorporating translational and rotational inertia, bending stiffness and gyroscopic moment is developed. The intrinsic modes extracted using the Empirical Mode Decomposition along with their instantaneous frequencies resolved using the Hilbert transform are applied to characterize the inception and progression of bifurcations suggestive of the changing rotor-dynamic state and impending instability. The dissertation presents and demonstrates an effective approach that integrates nonlinear rotor-dynamics, instantaneous time-frequency analysis, advanced notions of dynamic system diagnostics and numerical modeling applied to the detection and identification of sensitive variations indicative of a bifurcated dynamic state. All presented studies on rotor response subjected to various system configurations and ranges of parameters show good agreements with published results. Under the influence of crack opening, the rotor-bearing model system displays transitional behaviors typical of a nonlinear dynamic system, going from periodic to period-doubling, chaotic to eventual failure. When film forces are also considered, the model system demonstrates very different behaviors and failures from different settings and ranges of control parameters. As a result, a dynamic failure curve differentiating zones of stability and bifurcated instability from zones of dynamic failure is constructed and proposed as an alternative to the traditional stability chart. Observations and results such as these have important practical implications on the design and safe operation of high performance rotary machinery.
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Chicarella, Cristina. "Dynamic analyses of SDOF and MDOF systems and their responses to seismic actions." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
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Tan, Hock Chuan. "Load-induced damage evaluation in reinforced concrete structures using dynamic response signatures." Thesis, University of Aberdeen, 2000. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU602019.
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The purpose of this thesis is to assess and develop a non-destructive evaluation (NDE) procedure for evaluating the integrity of rectangular and square reinforced concrete (RC) slabs. This procedure employs both dynamic frequency and deformation response signatures to track changes in the slab following dynamic excitation. Such a procedure could provide a good basis for practising engineers to conduct nondestructive testing (NDT) and evaluation of general RC structures. The response of RC floor slabs to dynamic excitation have been experimentally studied at 1/3rd scale for two aspect ratios (square and rectangular), three concrete grades, and with and without cement replacement under clamped edge conditions. The model slabs were subjected to series of quasi-static loading and unloading sequences, to increasing load levels until failure was reached. At the unloaded part of each load cycle, the slabs were subjected to dynamic excitations, alternately using a hand-held, Bruel and Kjaer (B and K) impact hammer, and broad-band burst chirp shaker excitation. For the larger square slabs, at each unloaded part of the load cycle, a 265 gm steel ball bearing dropped from a fixed, standard height to provide more robust impulse excitation. All of the slabs were instrumented with optimally located accelerometers and strain gauges to capture the slab responses. The acceleration, deflection and strain readings resulting from the dynamic excitation were recorded at incremental load steps, from the initial unloaded state up to failure, and subsequently evaluated and analysed. The results show that the changes resulting from damage are readily observable, in the fundamental and higher modes of vibration and in the load-deflection and strain responses. These changes have been examined and analysed in both the time and frequency domains, and using other techniques, to establish the viability of this approach in evaluating the integrity of RC and other complex structures.
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Wu, Liwen [Verfasser]. "Dynamic hyporheic responses to transient discharge, temperature and groundwater table / Liwen Wu." Berlin : Humboldt-Universität zu Berlin, 2020. http://d-nb.info/1224233018/34.
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Walker, Louise. "Dynamic responses of the fungal cell wall to stress and antifungal treatment." Thesis, University of Aberdeen, 2010. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=136783.
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The main aim of this project was to determine the potential of increased chitin content as a mechanism of resistance to caspofungin in different fungal pathogens. C. albicans wild-type cells were pre-grown with a combination of CaCl2 and CFW prior to caspofungin treatment. This result sin a three-fold increase in cell wall chitin. Wild-type cells, which had elevated chitin content, were less susceptible to caspofungin. Priming cells to activated chitin synthesis was also able to compensate for the loss of the normally essential CaCHS1, through formation of three novel forms of salvage septa. In the absence of both CaChs1 and CaChs3, which are typically involved in septum formation, the class I chitin synthases, CaChs2 and CaChs8, could be stimulated to synthesise a proximally offset salvage septum. When CaChs3 was the only remaining chitin synthase, treatment with CaCl2 and CFW, led to the formation of thick chitin-rich salvage septa. CaChs2 and CaChs3 could be stimulated by treatment with CaCl2 and CFW to synthesise a thin salvage septum similar to the septum of wild-type cells. All three salvage septa were capable of restoring viability and cell division in C. albicans. The compensatory increase in chitin content in response to caspofungin treatment was not specific to C. albicans because clinical isolates of C. tropicalis, C. parapsilosis and C. guilliermondii and the filamentous fungus, A. fumigatus, also demonstrated an increase in chitin content after treatment with caspofungin. Isolates of C. glabrata and C. krusei showed no change in chitin content when exposed to caspofungin. The results of this thesis highlight the potential for using chitin synthase inhibitors in combination therapy with the echinocandins.
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Ricci, Nicola S. M. Massachusetts Institute of Technology. "Dynamic system perspective for design : ility-driving elements as responses to uncertainty." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90789.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2014.Thesis: S.M. in Technology and Policy, Massachusetts Institute of Technology, Engineering Systems Division, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 209-218).
This thesis is concerned with the design of complex artificial systems. For such systems, there is a growing need to deliver value to stakeholders beyond the initial functional requirements and to cope with rapidly changing outer environments. This thesis presents a conceptual framework and a structured approach for thinking about and designing systems that can exhibit the emergence of desirable lifecycle properties (i.e., ilities). To set the ground for the research contributions, a literature overview on (1) complex sociotechnical systems, (2) uncertainty in such systems, and (3) ways to cope with such uncertainty is given. Furthermore, the larger research effort concerning a method for architecting Systems of Systems with ilities is discussed to frame the remainder of the thesis. The dynamic system perspective for design is discussed, as well as a formal way of modeling the space of possibilities for designers of complex systems (i.e., what the system can be, as well as what its outer environment and expectations can be). In this perspective, uncertainty is modeled as perturbations, which are operators on these spaces of possibilities. Similarly, ility-driving elements (IDEs) are introduced and modeled as operators on such spaces as well. Two main types of ility-driving elements are discussed and formally defined: change options and resistance properties. The former, akin to real options in business, enable the system to change over time so as to cope with perturbations and sustain (or enhance) value delivery. The latter, on the other hand, impede undesired changes in system value delivery. Lastly, IDE Analysis - a structured approach for generating, evaluating and selecting ility-driving elements - is introduced, and demonstrated on a running case application to a Maritime Security System of Systems. This approach requires an initial baseline design concept, and considers a set of relevant perturbations as a starting point. The thesis ends with general discussions around applicability of research and possible areas for future research, as well as conclusions regarding key contributions.
by Nicola Ricci.
S.M.
S.M. in Technology and Policy
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Roy, Brian David. "The influence of alterations in plasma volume on physiological responses to dynamic exercise." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0026/NQ51225.pdf.
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Edenheim, Arvid. "Using Primary Dynamic Factor Analysis on repeated cross-sectional surveys with binary responses." Thesis, Linköpings universitet, Artificiell intelligens och integrerade datorsystem, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-165580.
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With the growing popularity of business analytics, companies experience an increasing need of reliable data. Although the availability of behavioural data showing what the consumers do has increased, the access to data showing consumer mentality, what the con- sumers actually think, remain heavily dependent on tracking surveys. This thesis inves- tigates the performance of a Dynamic Factor Model using respondent-level data gathered through repeated cross-sectional surveys. Through Monte Carlo simulations, the model was shown to improve the accuracy of brand tracking estimates by double digit percent- ages, or equivalently reducing the required amount of data by more than a factor 2, while maintaining the same level of accuracy. Furthermore, the study showed clear indications that even greater performance benefits are possible.
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Witcher, Kristina Grace. "Cortical microglia undergo dynamic structural and transcriptional responses to diffuse traumatic brain injury." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555501248603129.
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Pavic, Aleksandar. "Vibration serviceability of long-span cast in-situ concrete floors." Thesis, University of Sheffield, 1999. http://etheses.whiterose.ac.uk/3486/.
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This thesis describes an investigation into the vibration serviceability of long-span and slender in-situ concrete floors, which are typically post-tensioned. The motivation for the research is the present trend towards increased slenderness of post-tensioned floors supporting open-plan high- quality offices where vibration serviceability may easily become the governing design criterion. The vibration serviceability issue in post-tensioned floors is now also recognised by the UK Concrete Society which proposed, for the first time, guidelines for performing a vibration serviceability check when designing office floors. The guidelines were published in Concrete Society Technical Report 43 (CSTR43) in 1994 and its publication prompted the initialisation of this research project. There were two reasons for this. Firstly, problems were reported with the reliability and practical application of these guidelines, and, secondly, the guidelines were not experimentally verified which is unusual for any design provision related to vibration serviceability. In order to improve understanding of the dynamic performance of a rather specific group of office floors which are long-span and made of cast in-situ concrete, a combined experimental and analytical approach has been adopted. A state-of-the-art facility comprising hardware and software suitable for field modal testing and dynamic response measurements of prototype floor structures was commissioned as a part of this research. The facility is built up around the instrumented sledge hammer, which served as the main excitation source in modal testing, and multi-degree-of-freedom vibration parameter estimation procedures utilising measured floor frequency response functions. The main testing programme consisted of modal testing of four prototype floor structures of varying complexity weighing between 13 and 1000 tonnes. All four slab structures were slender and made of in-situ concrete. These tests were complemented by measurements of the floors' acceleration responses to a single person walking excitation tuned to create as large as realistically possible responses. The modal testing experimental data (measured natural frequencies, mode shapes and modal damping ratios) were used to validate numerical finite element (FE) models representing each floor structure. To do this, advanced FE model correlation and manual updating procedures were employed. Results of these exercises highlighted a number of important issues related to the dynamic behaviour of the concrete floors investigated. Firstly, the bending stiffness of in-situ concrete columns and walls contributed significantly to overall floor bending stiffness and must be considered. Secondly, higher modes of vibration which are close to the fundamental frequency appear in concrete floors, and should not be neglected as they can be easily excited by walking leading to dynamic responses greater than those associated with the fundamental mode. Thirdly, the width of band beams contributes significantly to the lateral stiffness of post-tensioned floors, which, in turn, may be very beneficial for their vibration serviceability. The validated numerical FE models were then used to check the performance of three representative walking excitation models available in the literature. It was shown that, in general, all three models overestimated the measured response to the third harmonic of the walking excitation, which is particularly important for low-frequency office floors. Only one of the models did so in a way which is not overly conservative. This model is recommended for use in vibration serviceability assessment of post-tensioned floors. Finally, gross oversimplification of these important issues is identified as the principal reason for the failure of the current CSTR43 vibration serviceability guidelines to predict reliably vibration response of a wide range of post-tensioned in-situ cast concrete floors.
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Tipper, Christine. "Attention in a meaningful world: brain responses to behavioral relevance." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/211.
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While it is known that primitive, low-level visual stimuli such as abrupt visual onsets or luminance changes can bias attentional orienting without willful intent on the part of the observer, comparatively little is known about how attention functions in rich, dynamic, meaningful contexts, such as those that comprise our everyday lives. The primary motivating hypothesis of this investigation is that, given our intrinsic needs as evolved social organisms, as well as our capability for behavioral flexibility, the attention system should be sensitive not only to low-level stimulus features, but also to complex stimuli that provide behaviorally relevant information. Three separate lines of research will be presented, each one providing a unique perspective on this issue. The first examined attentional orienting to socially relevant stimuli, finding that eye gaze serves as particularly potent cue for attentional orienting, driving the cortical orienting network more robustly than non-social stimuli, and resulting in a larger attention-related modulation of the early visual processing of stimuli appearing at attended locations. The second line of inquiry investigated patterns of eye movements while participants viewed naturalistic navigational scenes, revealing a dynamic interplay of orienting to the various behaviorally relevant aspects of the scene. The third set of studies specifically addressed whether, given the relevance of heading information for guiding navigational behavior, there is evidence that attention can be oriented automatically to the heading point in an optic flow field simulating the patterns of visual stimulation that accompany self-motion. Together, the results converge on the conclusion that attention can be oriented automatically in a dynamic, flexible, and continuous manner on the basis of complex visual stimuli that provide behaviorally relevant information.
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Dakin, Christopher James. "The development of stochastic vestibular stimulation and its application to dynamic vestibular evoked responses." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43284.
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The vestibular system provides sensory information regarding linear and angular motion of the head for tasks such as spatial navigation and postural stabilization. In these dynamic environments examination of vestibular signals is experimentally difficult given current techniques. Recently, continuous stochastic stimuli have shown promise in addressing some limitations in current vestibular probes and might provide a useful tool for investigating the dynamic behaviour of the vestibular system. The purpose of this thesis is a) to develop further the stochastic stimulus format by examining the customizability of the stimulus bandwidth and the stimulus’ effectiveness in extracting dynamic responses, and b) to use these advancements to explore dynamic vestibular function during locomotion and head rotation.
Exploration of the customizability of stimulus bandwidth revealed that a single broad bandwidth stimulus provides similar information to the sum of a series of sinusoidal stimuli or narrow bandwidth stimuli, but in much less time, and that stimulus bandwidth can be modified, by removing frequencies below 2 Hz, to attenuate the postural perturbation created by the stimulus. In a dynamic context the stochastic stimulus was also shown to be very effective in extracting the time varying modulation of vestibular-evoked responses during motion by identifying phase-dependent vestibular responses in the gastrocnemius during locomotion. The stochastic stimulus was then used to examine vestibular modulation and suppression during locomotion and vestibular spatial transformation during head turn. During locomotion, phase-dependent modulation of vestibular responses was observed in muscles of the leg and hip. In some muscles around the ankles these responses are attenuated with increasing cadence and walking speed. Lastly the transmission and spatial transformation of these vestibular-evoked responses are not hindered by motion and the spatial transformation occurs in nearly real time during head rotation.
In general, the stochastic stimulus can be customized to reduce postural sway and is effective in extracting the dynamic modulation of vestibular influence on muscle activation.
The identification of widespread phase-dependent vestibular coupling in the lower limbs and continuous spatial transformation of vestibular signals demonstrates that the stochastic waveform is an effective tool for the investigation of human vestibular physiology in dynamic contexts.
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Hickey, Matthew Sean. "Hormonal and metabolic responses to opioid antagonism during dynamic exercise : influence of exercise intensity." Virtual Press, 1993. http://liblink.bsu.edu/uhtbin/catkey/862279.
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In an attempt to investigate the role of the endogenous opioid peptides in substrate utilization and hormonal responses to exercise, eight trained cyclists completed two exercise trials at each of two distinct intensity/duration combinations. Briefly, cyclists completed two trials at 70% VO2max for 90 minutes and two trials at 90% VO2max until exhaustion. Trials were conducted following the administration of the opiate antagonist naloxone (NAL) (0.1 mg-kg-1 bolus + 0.1 mg-kg-1-·hr-1) or volume matched saline (SAL). Serum glucose was maintained at significantly higher levels at 60 and 90 minutes of exercise in 70% NAL vs 70% SAL. Serum glucose was significantly higher at all points during exercise and at 30 and 60 minutes of recovery in 90% NAL vs 90% SAL. Serum insulin was not altered by naloxone administration at either 70% or 90% trials. Serum Cpeptide was significantly higher at 60 and 90 minutes in 70%-NAL vs 70% SAL, and was significantly lower during exercise in 90%-NAL vs 90% SAL. Plasma glucagon was not different during exercise in the 70% trials, but was significantly higher during exercise in 90%-NAL vs 90%-SAL. The glucagon:insulin molar ration was not significantly altered by naloxone administration in any trial. Rating of peceived exertion was significantly higher during exercise in 70%-NAL, but was not different during exercise in the 90% trials. However, time to exhaustion was significantly (18%) reduced in 90%-NAL vs 90%-SAL. No systematic differences were observed in the cardiorespiratory responses to exercise at either intensity, although pulmonary ventilation was modestly (7%) elevated in 90%-NAL. Thus, opiate antagonism prevents the decline in serum glucose seen in prolonged exercise without altering substrate oxidation, and with minimal influence on the pancreatic hormone response. In contrast, opiate antagonism potentiates the hyperglycemic response to high intensity exercise at least in part by altering pancreatic hormone responses which may contribute to the hyperglycemia.School of Physical Education
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Hayward, Peter J. "On the computation of periodic responses for nonlinear dynamic systems with multi-harmonic forcing." Thesis, University of Sussex, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429733.
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Gaughan, John Beckley. "Respiration rate and rectal temperature responses of feedlot cattle in dynamic, thermally challenging environments /." St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16104.pdf.
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Horton, Jonathan F. "Dynamic responses of a 20-ton capacity feed buoy in an open ocean environment." Restricted access (UM), 2008. http://libraries.maine.edu/gateway/oroauth.asp?file=orono/etheses/37803141.pdf.
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These (M.S.)--University of New Hampshire, 2008.Title from PDF title page. Available through UMI ProQuest Digital Dissertations. Includes bibliographical references (leaves 58-59). Also issued in print.
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Kendall, Peter K. "Numerical study of effects of fluid-structure interaction on dynamic responses of composite plates." Thesis, Monterey, California : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Sep/09Sep%5FKendall.pdf.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, September 2009.Thesis Advisor(s): Kwon, Young W. "September 2009." Description based on title screen as viewed on 6 November 2009. Author(s) subject terms: Fluid-structure interaction, composite, carbon fiber composite, dynamic response, finite element. Includes bibliographical references (p. 95-96). Also available in print.
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Mohamed, Omar R. Ibrahim. "Study of energy efficient supercritical coal-fired power plant dynamic responses and control strategies." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3662/.
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The world is facing the challenge of global warming and environment protection. On the other hand, the demand of electricity is growing fast due to economic growth and increase in population. Since the growth in demand is also a heavy factor in energy equations, then the renewable energy alone is not able to generate enough electricity to fill the gap within a short time of period. Therefore, fossil fuel such as coal fired power plants cannot be ruled out immediately due to their generation capacity and flexibility in load following. However, any new coal fired stations should be cleaner compared with traditional power plants. Supercritical power plants are one of the most suitable choices for environmental enhancement and higher efficiency. However, there has been an issue of whether or not to adopt this technology in the UK because it is not clear whether the performance for SC plants can satisfy the British Gird Code requirement. This thesis reports a study of dynamic responses of SC power plants through mathematical modeling, and simulation for Gird Code compliance. It also presents a new control strategy based on an alternative configuration of generalized predictive control for power plant control.
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Parker-Price, Susan. "Young infants' attention and emotional responses to dynamic and static bimodal displays of affect." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/38546.
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Daniel, Jean-Baptiste. "Dynamic prediction of milk yield and composition responses to dietary changes in dairy cows." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLA009/document.
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Afin de répondre à la diversification des objectifs de la filière laitière (ex. efficacité alimentaire, santé et longévité des animaux, etc.), et ceci dans un contexte de forte volatilité des prix du lait et des intrants, la quantification des réponses multiples aux changements de régimes alimentaires représente un intérêt afin d’aider les producteurs laitiers à optimiser la ration des animaux. Le principal objectif de ce travail a consisté à développer et évaluer un modèle de prédiction des réponses de l’ingestion, de la quantité et composition du lait aux changements de régimes alimentaires chez la vache laitière. Une méta-analyse a ainsi été appliquée sur une grande base de données de la littérature afin de quantifier la réponse de l’ingestion aux régimes, et les réponses laitières (quantité totale, sécrétion des composants du lait et composition du lait) aux changements d’énergie nette (UFL) et protéines métabolisables (PDI) de la ration. Un élément clé dans le développement de ces équations de réponses était qu’elles soient applicables à travers différent potentiel laitier. Ceci a pu être atteint en exprimant les apports PDI et UFL par rapport à une situation nutritionnel pivot, qui correspond à une efficacité d’utilisation des PDI de 67% et une efficacité d’utilisation des UFL par lait de 100% (équivalente à un bilan énergétique nul). Construite à partir des efficacités PDI et UFL, une approche a été proposée pour estimer les apports PDI et UFL à la situation pivot, à partir desquels les équations de réponses peuvent s’appliquer. Evalué sur deux jeux de données indépendants, cette approche a permis de prédire les réponses de production laitière, productions de matières grasses, lactose et protéines du lait aux changements d’apports PDI et UFL avec une bonne précision pour des rations considérablement différentes, et à travers différents stades de lactation. Dans un autre modèle, les effets du stade physiologique (stade de lactation, stade de gestation, croissance) sur les performances animal, i.e. production laitière, productions de matières grasses, lactose et protéines du lait, changement de composition corporelle et ingestion, ont été quantifiés à travers des animaux de potentiel laitier différent. Il a été constaté que la structure du modèle était adéquate pour simuler les performances de différentes races laitières (Holstein, Rouge Danoise et Jersiaise). Afin de prédire les conséquences d’un changement alimentaire sur le long terme, les équations de réponses, centrées sur la situation nutritionnel pivot, ont été intégrées au sein du modèle dynamique. Cette intégration a pu se faire en appliquant le concept du pivot au modèle dynamique afin d’obtenir des courbes pivot, à partir desquelles les lois de réponses s’appliquent. Le modèle construit est le premier à intégrer les deux grands types de régulation biologique (homéostase et l’homéorhèse) chez la vaches laitière permettant de prédire les performances animales à partir d’une définition précise du potentiel laitierIn order to better cope with the increasing diversity of objective in dairy production (e.g. feed efficiency, animal health, animal longevity, etc.) in a context of high volatility of feed and milk prices, quantification of animal’s multiple responses to dietary changes is of particular interest to help dairy farmers in optimizing the diet. The main aim of the present study was to develop and evaluate a model to predict the responses in dry-matter intake, milk yield, milk component yields and contents to changes in dietary composition in dairy cows. A meta-analysis of the literature was conducted to quantify dry-matter intake response to changes in diet composition, and milk responses (yield, milk component yields and milk composition) to changes in dietary net energy (NEL) and metabolizable protein (MP) in dairy cows. A key point in the development of these response equations was that they could be apply on animals of varying production potential. This was achieved by expressing MP and NEL supply relative to a pivot nutritional status, defined as the supply of MP and NEL resulting to MP efficiency of 0.67 and NEL efficiency of 1. Based on MP and NEL efficiency, an approach was proposed to estimate the pivot MP and NEL supplies, around which the response equations can be applied. Evaluated with two independent datasets, this approach predicted milk yield and milk component yields responses to change in MP and NEL supply with a good accuracy for diets that are substantially different, and across all stages of lactation. In another model, the effect of physiological status (lactation stage, gestation, growth) on animal performance, i.e. milk yield, milk component yields, body composition change and dry-matter intake, were quantified across a range of animal potential. It was found that the model structure was adequate to simulate performance of different dairy breeds (Holstein, Danish Red and Jersey). To predict the long-term consequences of a dietary change, response equations, centred on the pivot nutritional status, were integrated into the dynamic model. This integration has been possible by applying the pivot concept into the dynamic model. This way, lactation pivot curves were calculated, from which response equations are applied. The model built is the first to integrate the two major biological regulations (homeostasis and homeorhesis) in dairy cows that predicts animal performance using a precise definition of milk potential
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Parrish, Ginger S. "The Cardiovascular Responses to Static and Dynamic Muscular Contractions in Adults with Cerebral Palsy." Thesis, University of North Texas, 1988. https://digital.library.unt.edu/ark:/67531/metadc331040/.
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In cerebral palsied adults, the cardiovascular responses to different types of exercise have not previously been ascertained. Therefore, the purpose of this study was to determine the blood pressure and heart rate responses of adults with cerebral palsy to static muscular contractions and to dynamic muscular contractions. Fifteen adults with cerebral palsy and 15 able-bodied adults (average age for each group = 30 years) performed a static exercise protocol and a dynamic resistance exercise protocol using each limb (or the limbs capable of meeting the requirements of the exercise protocol). Heart rate and blood pressure were assessed before, during, and after each exercise bout with each limb. During the static exercise protocol, each subject performed static contractions at 40% of maximal voluntary contraction to fatigue. The dynamic exercise protocol for each limb consisted of three 20-second bouts of hydraulic resistance exercise each of which was followed by 20 seconds of rest. No differences were found between the two groups of subjects in heart rate and blood pressure during static exercise. In dynamic exercise, however, the trend in heart rate from bout to bout differed between the groups. In addition, the cerebral palsied group's diastolic pressure was higher than that of the able-bodied group at the end of dynamic exercise. The findings of this study indicate that although the heart rate and blood pressure responses to dynamic resistance exercise in the cerebral palsied subjects differed from the responses of the able-bodied subjects, healthy adults with cerebral palsy may safely perform both static and dynamic resistance exercise. More research using this disabled population is needed so that guidelines for prescribing exercise for adults with cerebral palsy may be developed.
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Morris, Matthew. "Molecular mechanisms responsible for the dynamic modulation of macrophage responses to varying dosages of lipopolysaccharide." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/64253.
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The innate immune system depends for its effectiveness on the function of specialized pattern recognition receptors which enable it to target pathogens for destruction on the basis of conserved molecular patterns such as flagellin or lipopolysaccharide (LPS). Specifically, LPS is recognized by the Toll-like receptor 4 (TLR4), activating a signaling pathway which triggers the production of both pro- and anti-inflammatory mediators. Very low doses of LPS, however, preferentially induce pro-inflammatory cytokines, which can lead to persistent low-grade inflammation, a contributing factor in a host of chronic diseases. The mild pro-inflammatory skewing induced by super-low-dose LPS also potentiates the inflammatory response to later challenge with a higher dose of LPS in a phenomenon known as the "Shwartzman reaction" or "endotoxin priming". We investigated the mechanisms involved in pro-inflammatory skewing by super-low-dose LPS in THP-1 cells and found it to be governed by a regulatory circuit of competitive inhibition between glycogen synthase kinase 3 (GSK3) and Akt, which promote the activity of the transcription factors FoxO1 and CREB, respectively. Super-low-dose LPS mildly activated FoxO1 and pro-inflammatory gene transcription without inducing anti-inflammatory genes or activating CREB, and this pro-inflammatory skewing could be abolished by inhibition of GSK3 or direct activation of CREB. We then examined the dynamics of the LPS response at various different dosages in murine bone-marrow-derived macrophages (BMDM). The pro-inflammatory cytokine IL-12 was most strongly induced by intermediate LPS dosages, with very low or high doses inducing less robust IL-12 production. Knockout of the inhibitory TLR4 pathway molecules Lyn or IRAK-M resulted in sustained induction of IL-12 by high doses of LPS. By activating CREB, we were able to reduce inflammation in WT BMDM, and saw that this corresponded with increased phosphorylation of CREB. Overall, we are confident that this subnetwork is an important switch regulating the resolution of inflammation in response to TLR4 stimulation. Furthermore, we propose that endotoxin priming is an example of the generalized capacity of all signaling networks to recall prior states, and that an appreciation for the history and context of exposure to stimuli is critical for the understanding of signaling behavior.Ph. D.
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Draganescu, Mihai. "Study of supercritical coal-fired power plant dynamic responses and control for grid code compliance." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/73963/.
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The thesis is concerned with the study of the dynamic responses of a supercritical coal-fired power plant via mathematical modelling and simulation. Supercritical technology leads to much more efficient energy conversion compared with subcritical power generation technology so it is considered to be a viable option from the economic and environmental aspects for replacement of aged thermal power plants in the United Kingdom. However there are concerns for the adoption of this technology as it is unclear whether the dynamic responses of supercritical power plants can meet the Great Britain Grid Code requirement in frequency responses and frequency control. To provide answers to the above concerns, the PhD research project is conducted with the following objectives: to study the dynamic responses of the power plant under different control modes in order to assess its compliance in providing the frequency control services specified by the Great Britain Grid Code; to evaluate and improve the performance of the existing control loops of the power plant simulator and in this regard a controller based on the Dynamic Matrix Control algorithm was designed to regulate the coal flow rate and another controller based on the Generalized Predictive Control algorithm was implemented to regulate the temperature of the superheated steam; to conduct an investigation regarding frequency control at the power plant level followed by an analysis of the frequency control requirements extracted from the Grid Codes of several European and non-European countries. The structure and operation of the supercritical power plant was intensively studied and presented. All the simulation tests presented in this thesis were carried out by the mean of a complex 600 megawatts power plant simulator developed in collaboration with Tsinghua University from Beijing, China. The study of the conducted simulation tests indicate that it is difficult for this type of power plant to comply with the frequency control requirements of the Great Britain Grid Code in its current control method. Therefore, it is essential to investigate more effective control strategies aiming at improving its dynamic responses. In the thesis, new Model Predictive Control power plant control strategies are developed and the performance of the control loops and consequently of the power plant are greatly improved through implementation of Model Predictive Control based controllers.
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Williamson, Jon W. (Jon Whitney). "Cardiorespiratory Responses to Graded Levels of Lower-body Positive Pressure During Dynamic Exercise in Man." Thesis, University of North Texas, 1992. https://digital.library.unt.edu/ark:/67531/metadc278178/.
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Cardiorespiratory responses to incremental dynamic exercise were assessed across four different levels of lower-body positive pressure (LBPP) and, as a separate study, during constant load (i.e constant work rate) exercise below and above each subject's ventilatory threshold (VT), both with and without 45 torr of LBPP.
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Ranadive, Gauri Satishchandra. "Methodologies for Assessment of Impact Dynamic Responses." Thesis, 2014. http://etd.iisc.ernet.in/handle/2005/2794.
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Evaluation of the performance of a product and its components under impact loading is one of the key considerations in design. In order to assess resistance to damage or ability to absorb energy through plastic deformation of a structural component, impact testing is often carried out to obtain the 'Force - Displacement' response of the deformed component. In this context, it may be noted that load cells and accelerometers are commonly used as sensors for capturing impact responses. A drop-weight impact testing set-up consisting of a moving impactor head with a lightweight piezoresistive accelerometer and a strain gage based compression load cell mounted on it is used to carry out the impact tests. The basic objective of the present study is to assess the accuracy of responses recorded by the said transducers, when these are mounted on a moving impactor head.
In the present work, a novel approach of theoretically evaluating the responses obtained from this drop-weight impact testing set-up for different axially loaded specimen has been executed with the formulation of an equivalent lumped parameter model (LPM) of the test set-up. For the most common configuration of a moving impactor head mounted load cell system in which dynamic load is transferred from the impactor head to the load cell, a quantitative assessment is made of the possible discrepancy that can result in load cell response. Initially, a 3-DOF (degrees-of-freedom) LPM is considered to represent a given impact testing set-up with the test specimen represented with a nonlinear spring. Both the load cell and the accelerometer are represented with linear springs, while the impacting unit comprising an impactor head (hammer) and a main body with the load cell in between are modelled as rigid masses. An experimentally obtained force-displacement response is assumed to be a nearly true behaviour of a specimen. By specifying an impact velocity to the rigid masses as an initial condition, numerical solution of the governing differential equations is obtained using Implicit (Newmark-beta) and Explicit (Central difference) time integration techniques. It can be seen that the model accurately reproduces the input load-displacement behaviour of the nonlinear spring corresponding to the tested component, ensuring the accuracy of these numerical methods.
The nonlinear spring representing the test specimen is approximated in a piecewise linear manner and the solution strategy adopted and implemented in the form of a MATLAB script is shown to yield excellent reproduction of the assumed load-displacement behaviour of the test specimen. This prediction also establishes the accuracy of the numerical approach employed in solving the LPM system. However, the spring representing the load cell yields a response that qualitatively matches the assumed input load-displacement response of the test specimen with a lower magnitude of peak load. The accelerometer, it appears, may be capable of predicting more closely the load experienced by a specimen provided an appropriate mass of the impactor system i.e. impacting unit, is chosen as the multiplier for the acceleration response. Error between input and computed (simulated) responses is quantified in terms of root mean square error (RMSE). The present study additionally throws light on the dependence of time step of integration on numerical results. For obtaining consistent results, estimation of critical time step (increment) is crucial in conditionally stable central difference method. The effect of the parameters of the impact testing set-up on the accuracy of the predicted responses has been studied for different combinations of main impactor mass and load cell stiffness. It has been found that the load cell response is oscillatory in nature which points out to the need for suitable filtering for obtaining the necessary smooth variation of axial impact load with respect to time as well as deformation. Accelerometer response also shows undulations which can similarly be observed in the experimental results as well. An appropriate standard SAE-J211 filter which is a low-pass Butterworth filter has been used to remove oscillations from the computed responses. A load cell is quite capable of predicting the nature of transient response of an impacted specimen when it is part of the impacting unit, but it may substantially under-predict the magnitudes of peak loads.
All the above mentioned analysis for a 3 DOF model have been performed for thin-walled tubular specimens made of mild steel (hat-section), an aluminium alloy (square cross-section) and a glass fibre-reinforced composite (circular cross-section), thus confirming the generality of the inferences drawn on the computed responses. Further, results obtained using explicit and implicit methodologies are compared for three specimens, to find the effect, if any, on numerical solution procedure on the conclusions drawn. The present study has been further used for investigating the effects of input parameters (i.e. stiffness and mass of the system components, and impact velocity) on the computed results of transducers. Such an investigation can be beneficial in designing an impact testing set-up as well as transducers for recording impact responses. Next, the previous 3 DOF model representing the impact testing set-up has been extended to a 5 DOF model to show that additional refinement of the original 3 DOF model does not substantially alter the inferences drawn based on it. In the end, oscillations observed in computed load cell responses are analysed by computing natural frequencies for the 3 DOF lumped parameter model. To conclude the present study, a 2 DOF LPM of the given impact testing set-up with no load cell has been investigated and the frequency of oscillations in the accelerometer response is seen to increase corresponding to the mounting resonance frequency of the accelerometer. In order to explore the merits of alternative impact testing set-ups, LPMs have been formulated to idealize test configurations in which the load cell is arranged to come into direct contact with the specimen under impact, although the accelerometer is still mounted on the moving impactor head. One such arrangement is to have the load cell mounted stationary on the base under the specimen and another is to mount the load cell on the moving impactor head such that the load cell directly impacts the specimen. It is once again observed that both these models accurately reproduce the input load-displacement behaviour of the nonlinear spring corresponding to the tested component confirming the validity of the model. In contrast to the previous set-up which included a moving load cell not coming into contact with the specimen, the spring representing the load cell in these present cases yields a response that more closely matches the assumed input load-displacement response of a test specimen suggesting that the load cell coming into direct contact with the specimen can result in a more reliable measurement of the actual dynamic response. However, in practice, direct contact of the load cell with the specimen under impact loading is likely to damage the transducer, and hence needs to be mounted on the moving head, resulting in a loss of accuracy, which can be theoretically estimated and corrected by the methodology investigated in this work.
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Chen, Hsin-Tung, and 陳信童. "Dynamic Responses of Secondary Systems in Base-Isolated Buildings by Response Spectrum Analysis." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/70227008237942622135.
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碩士國立臺灣大學
土木工程學研究所
94
This paper utilizes complex modal analysis technique to deal with a non-proportional damping composite system, which consists of a primary and a secondary systems. The outcome is presented by a response spectrum which is more convenient in the application of design. The interaction, tuning and non-classical damping between sub-systems must be taken into account in the structural analysis of a composite system. In addition, when the structures contain eccentricity, the torsional effect has to be evaluated in the analytical model. The present study obtains the modal characteristics of the composite system by simple modified method and general modified method. These methods offer a less numerical labor than the ordinary one. In regard to a base-isolated composite system, the study focuses on each individual sub-system and modifies the modal shapes by two phases. First, a system involving only the primary structure and its base isolation is analyzed. Then, it goes to the modification of the whole system which includes the secondary system. By using so, the analytical complexity is reduced substantially.
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Chen, Chien-Xiang, and 陳建翔. "Dynamic Responses of Secondary Systems inStructures Considering Soil-Structure Interactionby Response Spectrum Analysis." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/91387771922090294153.
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碩士國立臺灣大學
土木工程學研究所
97
This thesis utilizes complex modal analysis technique to deal with a non-classical damping composite system, which consist of primary and secondary systems. The outcome is presented by a response spectrum which is more convenient in the application of design. The interaction, tuning and non-classical damping between sub-systems must be taken into account in the structural analysis of composite system. The present study obtains the modal characteristics of the composite system by simple analysis method. The method offers a less numerical labor than the ordinary one. In regard to a composite system with added soil-structure interaction, the study focuses on each individual sub-system and modifies the modal shapes by two phases. By using so, the analytical complexity is reduced substantially.
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Yang, Bo-Siang, and 楊博翔. "Dynamic responses of hysteretic systemsunder two-frequency excitations." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/65323310085600589653.
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碩士國立臺灣科技大學
營建工程系
97
Dynamic responses of bi-linear hysteretic systems under two-frequency excitations characterized by a frequency ratio, n, are studied in this thesis. The analytical results show markedly different response characteristics as the excitation parameter n increases from unity. The classical beat phenomenon can be found for most cases with an n smaller than 1.1. On the other hand, a two-mode superposition in displacement is obvious when n is closer to an even number. To further explore its engineering implication, the indicated response features are compared based on a steady-state amplitude parameter referring to the Response Amplitude Factor, . An analytical expression of the parameter is first derived for the linear system and is then compared with numerical solutions evaluated for the nonlinear systems. The spectra demonstrate a two-peak response feature that conforms to the external excitation frequencies. The effects of stiffness softening are also clear as evidenced by a left-switch trend in the response peaks as the degree of nonlinearity increases. However, the variation in the peak magnitude is difficult to quantify
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Tzeng, Chi-Luen, and 曾啟倫. "Dynamic Responses of the Reid's Hysteretic Damping Model." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/07317517760398984259.
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碩士國立臺灣科技大學
營建工程系
97
Dynamic Response of the Reid's Hysteretic Damping Model Thesis Advisor : Ching-Tung Huang Graduate Student : Chi-Luen Tzeng ABSTRACT Response characteristics of single-degree-of-freedom dynamic systems with the classic Reid's Hysteretic Damping Model under simple harmonic loading are investigated in this thesis. The Reid's Hysteretic Damping is characterized by its frequency-independent loss modulus and the causality in its time-domain response. The investigation first focuses on an unstable vibration phenomenon of the indicated system and then is resolved with a two-phase switch mechanism in its controlling equation. The two-phase switch mainly involves a sequence of slide-stick motions whose triggering criteria are defined and the resulting response differences are also studied. The study results show that the stick phenomenon in the displacement response is more likely to occur as the restoring force increases or the external excitation frequency decreases. Likewise, the duration of stick state also increases under the above-mentioned conditions. The notion of equivalent linearization is employed to obtain an analytical approximation. A better response prediction is observed for systems with slight to mild nonlinearity, while the solution precision deteriorates as the degree of nonlinearity increases.
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LIN, SONG-CANG, and 林松蒼. "Dynamic responses of nearshore hinged breakwater to wave action." Thesis, 1990. http://ndltd.ncl.edu.tw/handle/14794329119060328967.
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Wang, Shii Chin, and 王璽欽. "Dynamic Responses of Unsteady Flow Through an Artifical structure." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/39754892361277443047.
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Smith, Mark Anthony. "Dynamic modelling to investigate transient responses in lime kilns." 2007. http://link.library.utoronto.ca/eir/EIRdetail.cfm?Resources__ID=788887&T=F.
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Lao, Yuan-syun, and 羅元壎. "Dynamic Responses of the High Speed Gear Cam Systems." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/s76738.
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碩士國立中山大學
機械與機電工程學系研究所
96
Abstract The gear-cam intermittent mechanism, mainly made up by cam, the sun gear, planet gear and planetary shelf , it has been used in automatically high speed die cutting and creasing machine. The main function of die cutting and creasing machine is cutting and creasing the cardboard, and through compounding the cam motion curves, it will can control the intermittent motion of a gear-cam intermittent mechanism and improve its dynamic characteristic. The effects of gear cam profile and driving speed on the dynamic responses of a box folding and die cutting machine are studied in this work. The input driving motor、gear、gear-cam and output chain mechanics are included in the dynamic system. The equation of motion of the whole system in derived by employing Lagrange’s equation the 4th order Runge-Kutta method is used to simulation the fine domain response of the nonlinear equation of motion. The effect of cam profile, and driving speed on the system dynamic response have been simulated and analysed in the work.
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Yang, Zong-Han, and 楊宗翰. "The Dynamic Responses of Pile with Different upper Structures." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/22746566829284229095.
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碩士國立中央大學
土木工程學系
104
There is limited plate land but too much population in Taiwan, so the area and price of land at city is very expensive. Therefore, skyscraper were often built in recent year. Taiwan locates at the west side of the Circum-Pacific seismic zone, earthquakes often occur in this area. In order to increase the stability of the structure, the moment response of pile foundation is getting more important. Three kinds of piles (L-Pile, M-Pile and S-Pile) arranged for four centrifuge modeling tests which were performed in an artificial acceleration field of 80 g. The response of pile foundation were simulated by physical modeling and the seismic loadings were applied by centrifuge shaking table. The prototype pile foundation was scaled to design the model pile, and it is reduced to 1/80 times in dimension to the centrifuge model. Three accelerometer arrays were installed in the soil layer to measure the acceleration histories during shaking. The response of bending moments along the pile would be obtained from the attached strain gauges. The rotation angle and deflection of pile along depth can be calculated. Especially, the S-Pile which without upper structure to investigate the contribution from pile head loading. Test results show that the frequencies of L-pile (with 10.8 m height of upper structure and mass of 1330 kN), M-pile (with 2.8 m height of upper structure and mass of 1330 kN) and S-pile (without upper structure) are 0.65 Hz, 1.99 Hz and 2.23 Hz, respectively. The soil resistance increases with the increasing depth for all models. The maximum bending moments of L-pile and M-pile occurred at 1.6 m (z/Dp=1.26, D is the diameter of pile) underground surface, and there is almost no significant bending moment along S-pile (z/Dp=3.8~11.3); the bending moments of L-Pile, M-Pile and S-Pile caused by Newton’s law, moment of inertia and soil displacement, respectively (L-Pile>M-Pile, 0.1×M-Pile≥S-Pile).
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CHEN, GUANG-MING, and 陳光銘. "Seismic Responses of Beam System by Dynamic-Stiffness Matrix." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/78022724152732425615.
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Hsieh, Huan-Sheng, and 謝煥昇. "Dynamic Responses of Secondary Systems in Structures with Added Viscoelastic Dampers by Response Spectrum Analysis." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/84155976855422006668.
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碩士國立臺灣大學
土木工程學研究所
95
This paper utilizes complex modal analysis technique to deal with a non-classical damping composite system, which consist of a primary and a secondary systems. The outcome is presented by a response spectrum which is more convenient in the application of design. The interaction, tuning and non-classical damping between sub-systems must be taken into account in the structural analysis of composite system. The present study obtains the modal characteristics of the composite system by simple analysis method. The method offers a less numerical labor than the ordinary one. In regard to a composite system with added viscoelastic dampers, the study focuses on each individual sub-system and modifies the modal shapes by two phases. By using so, the analytical complexity is reduced substantially.
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廖克弘. "The dimensionless parametric analyses for dynamic responses of circular foundation." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/49753102718451753670.
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Lin, Cheng-Hsun, and 林政勳. "Dynamic Responses of Slender Concrete Rods Due to Impact Hammers." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/18917495391136210993.
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碩士朝陽科技大學
營建工程系碩士班
91
In generally, when carrying out NDT field tests for piles, the influence of superstructures can not be effectively isolated, the signals obtained in the tests thus show certain complexity. Nevertheless, when boundary conditions or geometries are complicated, one would be able to recognize such spatial restraints on the test results, if one can induce the characteristics of the corresponding axial and lateral responses of piles and to summarize their generalizations. To obtain reliable test signals to correctly determine the boundary conditions or geometries of piles, one can usually use various kinds of hammer tips with different materials to produce different durations for the impact forces. Since the significant wavelengths of the stress waves are related to the durations of the impact forces, the selection of hammer tips would affect the assessment of the type and the size of defects. In this study, three slender concrete rods were erected and tested with seven different contacting tips of the impact hammer. To investigate the sensibility of impact durations to the detectibility of the defects, various numerical simulations and experiments were conducted. Four numerical models were used in this research; one-dimension line element, two-dimensional axialsymmetric element ,and ANSYS LS-DYNA SOLID 162 and ANSYS LS-DYNA SOLID 164 elements, to simulate the axial and lateral vibrations and wave propagations in an intact rod, a defective rod, and a rod with a weak layer. By comparing with results from numerical models and those of experiments, this study briefly generalizes the signal characteristics generated by various impact hammers on these three different rods.