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1
Anderson, Walter. "Parametric Investigation Toward Achieving an Optimal Magnetorheological Mount." University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1271339488.
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2
Jamshidi, Far Mehdi. "Investigation of fibre optical parametric amplifiers in telecommunications." Thesis, Swansea University, 2010. https://cronfa.swan.ac.uk/Record/cronfa42681.
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Fibre optical parametric amplifiers have been attracting much attention since their first demonstrations. They are capable of providing a high amount of gain over large bandwidth ranges. Since what we call a fibre optical parametric amplifier is technically a combination of one or two pumps and a suitable highly-nonlinear fibre, their evolution is closely dependent on the improvements in the highly-nonlinear fibre technology and on that of the pumps. Recently, the advent of silica-based highly-nonlinear fibres with proper dispersion characteristics and the availability of high-power erbium-doped fibre amplifiers capable of delivering several Watts of continuous-wave power have led to great improvements in achieving better performances with fibre optical parametric amplifiers. The fibre length required is reduced and fibre optical parametric amplifiers can be operated in the continuous-wave regime, which is necessary for being useful in telecommunications. This work is a report of an investigation of different aspects of fibre optical parametric amplifiers. After reviewing the fundamentals of the operation of this kind of amplifiers, the difficulties facing them are discussed. Among these issues, the problem of nonlinear cross-talk is investigated in more details. 1 experimentally proved that by reducing fibre length, it is possible to keep the crosstalk in a tolerable range. The amplification of 26 communication channels modulated at about 40 Gb/s aggregating to the total capacity of more than 1 Tb/s, while obtaining performance results comparable to those of erbium-doped fibre amplifiers may tone down the chief criticism on the parametric amplifiers. Two amplifiers with a record gain (60 dB for a two-pump amplifier) and a record bandwidth (270 nm in a one-pump amplifier) were demonstrated and it has been shown that there might be possibilities for improving the adverse effect of the Raman gain on the flatness of the gain spectra of the parametric amplifiers at the expense of losing some gain. A sample of a newly-developed bismuth-oxide highly-nonlinear fibre is used to construct a novel scheme for wavelength demultiplexing, and the possibility of simultaneous time- and wavelength demultiplexing is discussed.
3
Bayley, Christopher J. "Parametric investigation on the coalescence of coplanar fatigue cracks." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ26986.pdf.
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4
Knost, Daniel G. "Parametric Investigation of the Combustor-Turbine Interface Leakage Geometry." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/29145.
Full textAbstract:
Engine development has been in the direction of increased turbine inlet
temperatures to improve efficiency and power output. Secondary flows develop
as a result of a near-wall pressure gradient in the stagnating flow approaching
the inlet nozzle guide vane as well as a strong cross-passage gradient within the
passage. These flow structures enhance heat transfer and convect hot core flow
gases onto component surfaces. In modern engines it has become critical to cool
component surfaces to extend part life.
Bypass leakage flow emerging from the slot between the combustor and
turbine endwalls can be utilized for cooling purposes if properly designed. This
study examines a three-dimensional slot geometry, scalloped to manipulated
leakage flow distribution. Statistical techniques are used to decouple the effects
of four geometric parameters and quantify the relative influence of each on
endwall cooling levels and near-wall total pressure losses. The slot geometry is
also optimized for robustness across a range of inlet conditions.
Average upstream distance to the slot is shown to dominate overall cooling
levels with nominal slot width gaining influence at higher leakage flow rates.
Scalloping amplitude is most influential to near-wall total pressure loss as formation
of the horseshoe vortex and cross flow within the passage are affected.
Scalloping phase alters local cooling levels as leakage injection is shifted laterally
across the endwall.Ph. D.
5
Zechar, Nathan E. "Experimental Investigation of a Parametric Excitation of Whistler Waves." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1495802386539665.
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6
Kountzeris, Athanasios. "Investigation of ship roll motion by parametric identification techniques." Thesis, University of Sussex, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328345.
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7
Bayley, Christopher J. (Christopher James) Carleton University Dissertation Engineering Mechanical and Aerospace. "Parametric investigation on the coalescence of coplanar fatigue cracks." Ottawa, 1997.
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8
Anderson, Matthew Francis. "Parametric investigation of strain gauges in structural damage detection." Thesis, University of Iowa, 2013. https://ir.uiowa.edu/etd/2436.
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Vibration-based damage detection (VBDD) methods are used to detect damage in structural members non-evasively. This investigation began with two objectives: to prove a VBDD method could detect damage using strain gauges both analytically and experimentally, and to then use that method to determine the distance from a damaged area that strain gauges could be effective. Work began simultaneously using finite element software and physical experiments. It was determined that a VBDD method could detect damage with strain gauges in both settings. A parametric study was then completed that used probabilistic methods to identify an effective range for strain gauges over the length of the structural member.
9
Ocer, Nuri Erkin. "Parametric Investigation Of Spray Characteristics Using Interferometric Particle Imaging Technique." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12611397/index.pdf.
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Spray is an efficient tool in the usage whose primary objectives are to obtain droplets with increased liquid surface area and more dispersed liquid over a larger volume. The determination of spray characteristics has been a topic of extensive research recently. In the present investigation, the flow structure of a spray issuing from an oil burner nozzle was determined in a parametrical manner. The main tool in the experimental research is the Interferometric Particle Imaging (IPI) configuration. This method exploits the interference between light reflected from and refracted through individual transparent spray droplets which are illuminated by a laser light sheet in a wide angle forward-scatter region. Based on a scattering theory, the droplet diameter of spray particles can be related to the light pattern scattered from that particle. In addition, using double-framed images also enables the calculation of velocities associated with these particles. In this way, as a representation of spray structure, the droplet size and velocity distributions were obtained prior to a change in the primary parameters of liquid flow e.g. surface tension, viscosity, density and the injection pressure. The evolution of spray characteristics in space were also examined by conducting
measurements in different radial and axial locations relative to spray centerline.
10
Austin, Charles B. M. Arch Massachusetts Institute of Technology. "Cellular building components : investigation into parametric modeling and production logics." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33602.
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Thesis (M. Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 2005.MIT Institute Archives copy: P. 85-86 bound in reverse order.
Includes bibliographical references (p. 86).
Recent advances in digital fabrication technologies have sparked a renewed interest in topology and biological form. The ability to design and prototype structural forms inspired by nature has challenged architects preconceived notions of space and form. With the assistance of parametric modeling and rapid prototyping we now not only have the ability to physically generate complex forms, but also the ability to create a seemingly infinite number of formal variations. As a result, this has caused architects to push toward new spatial concepts. Among these new spatial concepts are those that seek to create entire building systems out of a single material solution. Inspiration for such systems can be found by studying organic cellular structures. Unlike the component based design processes of most architects, in which multiple problems are solved through multiple material solutions, natural systems tend to create solutions that solve multiple problems through one material solution. This thesis is interested in answering the question, "Is it possible to create a building system (both structure and enclosure) out of a single adaptable building unit?" Furthermore, can the building unit also be capable of transforming from being either permeable to impermeable? If so, how might this challenge our existing notions of boundaries?
by Charles B. Austin.
M.Arch.
11
Kim, Y.-H. "Parametric investigation of synthetic jet and its boundary layer control." Thesis, Cranfield University, 2005. http://dspace.lib.cranfield.ac.uk/handle/1826/11007.
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The
potential for active control of low Reynolds number boundary layers using synthetic jet
generators (SJG) has been established. The results from a four stage experimental study are
presented in which the operational and geometric parameters of a rectangular slot choice SJG are
optimised. A time-dependent, analysis of the SJG velocity profile is carried out in quiescent
conditions
prior to application of the SJG in (i) a nominally zero pressure gradient at plate
boundary layer (l.54>
12
Dedekarginoglu, Riza Can. "A Parametric Investigation Of Tip Injection For Active Tip Vortex Control." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612703/index.pdf.
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ABSTRACT
A PARAMETRIC INVESTIGATION OF TIP INJECTION FOR ACTIVE TIP VORTEX
CONTROL
Dedekarginoglu, Riza Can
M.Sc., Department of Aerospace Engineering
Supervisor :Asst. Prof. Dr. Oguz Uzol
December 2010, 79 pages
Wing tip vortex is a challenging phenomenon that reduces the lift generation at the tip region
of the wing. For aerial vehicles, several methodologies were presented for the sake of
controlling vortices and alleviating effects of tip loss.
In this study, the effect of wing tip injection on wing tip vortex structure was investigated
computationally. A NACA0015 profile rectangular wing was employed with an aspect ratio
of 3, at a free stream Reynolds number of 67000. 10 identical ejection holes along the wing
were prepared chordwise to provide cross sectional air flow in order to determine the net
effect of ejection over wing tip vortices and wake flow field.
Study setup consists of a wind tunnel that is 1.6m long, 0.6m wide and 0.6m high, which the
wing is attached to one side of it as a cantilever beam. Chord length of the wing is 0.1m and
span is 0.3m. A constant free stream air flow is maintained with 10 m/s of velocity.
Computer aided drawing (CAD) and grid generation were carried out using commercial
tools. Whole setup was drawn using Rhinoceros. Surface mesh was created using ANSYS
Gambit, ANSYS T-Grid software was used for generating the viscous mesh over the wing
and finally for volume mesh ANSYS Gambit was utilized once more. FLUENT was chosen
to be the flow solution tool with k-&omegaSST turbulence model. For 3 different angles of attack cases, respectively, 4°
, 8°
and 12°
, several injection scenarios were defined. There are 3 steady injection cases for each angle of attack case namely, no injection case, uniform injection case, triangular waveform injection case where there is no injection at the leading edge tip whereas there is injection which is equal to the uniform injection velocity at the trailing edge tip. Moreover there are 5 additional scenarios for 8°
angle of attack case that are, sinusoidal waveform injection case which consists of a chordwise velocity distribution shape that is a quarter sinus wave where maximum injection velocity is the same as the uniform velocity, reverse triangular waveform injection case where injection velocities were reversed with respect to triangular waveform case, two cases consisting of angled injections having both +15°
and -15°
with respect to the flapping axis of the wing. The effect of tube walls on the jet injection was neglected for all cases, therefore for the last case, in order to simulate pipe flow, a case is provided with uniform injection velocity. In that way, regardless of the solution method, a parametric study was performed. Considering each case, non-dimensional 3-axis velocity components, turbulent kinetic energy, vorticity magnitude, pressure, lift and drag values were computed and having the exactly same cases as an experimental study for 8°
angle of attack, a comparison of aerodynamic data series was presented. As results, it&rsquo
s observed that, vortex core locations were shifted upwards and away from the tip region. Increasing the turbulence level of the tip flow by tip injection, inherently the pressure difference became larger, however as the vortices ascend, tip loss decreases. In that way, a significant increase in the lift was observed while drag values are slightly increased, as well.
13
McCarthy, Matthew John. "Investigation of an all solid state synchronously pumped optical parametric oscillator." Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386664.
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14
Kim, Young-Hwan. "A parametric investigation of synthetic jet and its boundary layer control." Thesis, Cranfield University, 2005. http://dspace.lib.cranfield.ac.uk/handle/1826/11007.
Full textAbstract:
The potential for active control of low Reynolds number boundary layers using synthetic jet generators (SJG) has been established. The results from a four stage experimental study are presented in which the operational and geometric parameters of a rectangular slot choice SJG are optimised. A time-dependent, analysis of the SJG velocity profile is carried out in quiescent conditions prior to application of the SJG in (i) a nominally zero pressure gradient at plate boundary layer (l.54 > < l05 < ReX < 2.86 >
15
Naz, Naveed A. "Investigation into mid-infrared pulse shaping using an optical parametric oscillator." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/54050/.
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This thesis reports experimental indirect spectral transfer of shaped pulses from the near to mid-infrared via the use of an optical parametric oscillator. It was shown that good spectral fidelity of transfer can be achieved by making suitable adjustments to the OPO. The issues affecting the transfer process are discussed and experimental results are compared with existing theory. The shaping of the nearinfrared pulses was performed using a zero dispersion pulse shaper and a computer controlled spatial light modulator. A suitable search algorithm was written and, with the use of appropriate computer hardware, allowed a closed-feedback loop to be implemented. The computer controlled hardware was demonstrated to be able to autonomously optimise simple experiments in the mid-infrared and optimise the threshold of an optical parametric oscillator.
16
Hatna, Abdelmadjid. "Investigation of pre-processing approaches for NC machining of sculptured surfaces." Thesis, Brunel University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324767.
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17
Motley, Sarah E. "A Parametric Investigation of Pattern Separation Processes in the Medial Temporal Lobe." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3199.
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The hippocampus is thought to be involved in memory formation and consolidation, with computational models proposing the process of pattern separation as a means for encoding overlapping memories. Previous research has used semantically related targets and lures to investigate hippocampal responses to mnemonic interference. Here, we attempted to define the response function of the hippocampus and its inputs during pattern separation by parametrically varying target-lure similarity in a continuous recognition task. We also investigated the effect of task demands (intentional versus incidental encoding) on pattern separation processes. We collected functional magnetic resonance imaging (fMRI) data while participants were shown a series of objects. In the intentional paradigm, participants identified objects as "new" (novel stimuli), "old" (exact repetitions), or "rotated" (previously seen objects that were subsequently rotated by varied degrees). In the incidental paradigm, participants were shown the same stimuli but identified objects as "toy" or "not toy". Activation in the hippocampus was best fit with a power function, consistent with predictions made by computational models of pattern separation processes in the hippocampus. The degree of pattern separation was driven by the information most relevant to the task—pattern separation was seen in the left hippocampus when semantic information was more important to the task and seen in the right hippocampus when spatial information was more important. We also present data illustrating that top-down processes modulate activity in the ventral visual processing stream.
18
Wittkugel, Andrew E. "From static to dynamic: an investigation of flexible architecture." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1337286972.
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19
Kelly, Peter Joseph. "An empirical investigation of some parametric techniques for the reductive coding of speech." Thesis, Queen's University Belfast, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356900.
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20
Malik, Rohit. "Experimental investigation of high-power continuous-wave fiber optical parametric amplifiers and oscillators." Thesis, Swansea University, 2010. https://cronfa.swan.ac.uk/Record/cronfa42491.
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Fiber optical parametric amplifiers (OPAs) are based on a highly-efficient four-wave mixing process. Their capability to give very high gain and large bandwidths have made them an attractive candidate for providing higher bandwidths for future telecommunication systems, such as wavelength-division multiplexed (WDM) photonics networks. In dynamic photonic networks a where number of channels are dropped and/or added all the time, the OPA gain for the other channels is affected. In this thesis we employed a well-known gain control technique, all-optical gain clamping (AOGC), and reduced the gain variation of fiber OPAs below 0.5 dB, under varying input conditions. We also showed an improvement in power penalties o at the bit-error rate of 10-8, from 2.5 dB to 0.5 dB for on/off keying modulation. We also investigated fiber optical parametric oscillators (OPOs). Using fiber OPAs as gain medium we realized two different continuous-wave (CW) OPOs, centred at 1561 nm and 1593 nm. One gave us watt-level output power from 1600 nm to 1670 nm, with overall tuning range of 211 nm. The output linewidth of signal and idler was measured to be 0.08 nm and 0.15 nm respectively. The OPO centred at 1593 nm gave us a record tuning range of 254 nm, and with 3 dB output coupling fraction, it gave us large output powers (20-27 dBm) from 1610 nm to 1720 nm. Using a large seed generated by a watt-level fiber OPO in the U-band, and using 3 W of CW pump source in the C-band for Raman amplification, we generated 3 W of CW output power. This gave us nearly 100% conversion efficiency. Launching a high-power CW pump with narrow linewidth into a fiber makes stimulated Brillouin scattering (SBS) a major problem. We investigated an SBS suppressor, based on a common technique of phase dithering of the pump to suppress the SBS. We compared a multitone modulation technique to modulation with a pseudo-random bit sequence (PRBS), and we showed that it can increase the SBS threshold by 4.18 dB, and is less expensive to implement.
21
Dumortier, Alexis Jean Louis. "Investigation of a medium with a large, negative parameter of nonlinearity and its application to the enhancement of a compact, omnidirectional, parametric source." Thesis, Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-07022004-160330/unrestricted/kottke%5Fpeter%5Fa%5F200407%5Fphd.pdf.
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Thesis (M.S.)--School of Mechanical Engineering, Georgia Institute of Technology, 2005. Directed by David Trivett.Trivett, David, Committee Chair ; Berthelot, Yves, Committee Member ; Rogers, Peter, Committee Member. Includes bibliographical references.
22
Navidpour, Nasir. "Non-linear finite element analysis and parametric investigation of low-rise reinforced concrete shear walls." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0021/MQ48172.pdf.
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23
Ikeh, L. "A parametric investigation on the influence and inhibition performance on CO2 corrosion of carbon steel." Thesis, University of Salford, 2017. http://usir.salford.ac.uk/44757/.
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The deposition of hydrate and corrosion in the pipeline remain a major challenge in the petroleum industry. Internal corrosion slows and decreases the production of oil and gas when associated with free water and reacts with organic acid. Experiments had shown that the corrosion products (ferrous and anhydrous ions) combine together to form a precipitate on iron surface that are porous and non-protective. To prevent these occurrence, Mono-Ethylene glycol (MEG) is been utilized in the pipeline as an antifreeze and anti-corrosion agent. It has been observed that the MEG need to be separated from acetic acid (HAc) and acid gases which enhances corrosion of mild steel in the oil field environment. Mono-Ethylene glycol and acetic acid also has an adverse effect of lowering the solubility of mineral salts and causing a higher risk of corrosion problem. The goal of this investigation is to determine the combined effect of acetic acid and mono-ethylene glycol on corrosion of carbon steel in CO2 saturated environment at three different temperatures of 25oC, 50oC and 80oC using a 3.5% wt. NaCl solution. (Weight loss) and (electrochemical) measurements using Linear polarization resistance (LPR), Electrochemical Impedance Spectroscope (EIS) and Potentiodynamic polarization(PDP) were employed in measuring the corrosion rate as a function of time on HAc and MEG concentrations. In addition, the efficiencies of three corrosion inhibitor based chemicals (the phosphate ester and the Oleic imidazoline salt) at different concentrations were also evaluated. Furthermore, the link between the nature of the film formed on the electrode material and the corrosion characteristics were investigated using the Scanning Electron Microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron scan (XPS). The weight loss results shows that the corrosion rate with HAc increases rapidly as the concentration of HAc was added to the solutions compared to the solution without HAC. The average corrosion rate with HAc at 25oC is about 0.72 mm/yr and increased to 1.05 mm/yr at 50oC. The highest corrosion rate was noted at 80oC with approximately 2.71 mm/yr. However, addition of 20% and 80% MEG reduced the corrosion rate at all temperatures studied. The electrochemical measurement results obtained show the corrosion rate in the presence of HAc increases as different concentrations of HAc were added to the system, and decrease with increased in exposure time as a result of protective film formed on the electrode surface. At 25oC, the average corrosion rate increases from 2.6 mm/y to 3.07 mm/yr. The applications of inhibitors lower the corrosion rate at all temperatures with average corrosion rate of 0.21 mm/yr, 0.44 mm/yr and 0.56 mm/yr at 25oC, 50oC and 80oC respectively. Similarly, the Nyquist and Bode plots of the EIS results indicate that the diameter of the depressed semi-circle decreases as different concentration of HAc and MEG were added to the solution, and the capacitive semi-circle sizes also decreases on addition of 20% and 80% MEG to the system. This decreased in corrosion rate can be attributed to the formation of iron carbonate film on the surface of the steel sample. The surface examination of the exposed samples reviews that a dense layer of iron carbonate and localized corrosion were observed in the absence of HAc at 80oC. On addition of HAc and MEG, the layers of the film became porous. High magnification of the scan results shows a small pits and localized corrosion on the electrode surface. The EDX and XPS analyses on the samples reviews that some of the elements are absence on addition of HAc to the solution.
24
Marsden, Philip Andrew. "Investigation of narrow-band semiconductor quantum well structures using a synchronously-pumped optical parametric oscillator." Thesis, University of Southampton, 2001. https://eprints.soton.ac.uk/30239/.
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Measurements of spin relaxation processes were made in the technologically interesting InGaAs/InP quantum well system. The first non-linear pump and probe measurements were performed in a single 80Å lattice-matched InGaAs/InP quantum well layer. To make these measurements a synchronously-pumped parametric oscillator was constructed, using periodically-poled lithium niobate as its non-linear element. Investigations of dominant carrier species and their associated spin relaxation were made as a function of temperature. A model was constructed for comparison to the experimental data showing the dominance of excitons at low temperature, with un-bound electron-hole effects dominating at temperatures above 100K.
25
Govender, Nishalin. "A parametric investigation into the membrane stresses of hydrostatically loaded circular and elliptic toroidal shells." Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/25284.
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This study explores the membrane stresses of hydrostatically loaded elliptical and circular toroidal tanks. Equations are derived, using the membrane theory of shells, to obtain equations which can accurately describe the meridional and hoop stress behaviour at locations sufficiently far away from any bending disturbance occurring within the shell. The derived expressions are validated using the finite element software ADINA, indicating excellent agreement between the analytical and numerical solutions. A parametric study is undertaken, whereby the membrane profiles for prolate, oblate and circular toroidal shells is investigated. Parameters which are varied are the opening and aspect ratio of toroidal shells. Stress resultant profiles are shown for numerous cases in order to aid designers on suitable ratios to minimise membrane stresses for use when designing hydrostatically loaded toroidal shells. Lastly, numerical examples are investigated, keeping the volume constant and comparing the surface area due to a variation of opening and aspect ratios. It was found that when investigating toroidal shells, considerations are required when choosing the aspect ratio and opening ratios. Based on the results obtained, compromises between prolate and circular cross-sections with relatively small opening ratios are recommended in order to minimise the cost and maximise the structural efficiency, based on the membrane stresses occurring within the shell.
26
Jenkins, Gwenllian. "Investigation of schema modes in the eating disordered population." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/4038.
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Many eating disordered patients fail to respond to traditional cognitive behaviour therapy. As a result it has been suggested that further research needs to be completed to determine the cognitive processes and mechanisms that underpin these disorders. This research aims to empirically test Young’s Schema Mode concept (Young et al., 2003) within the eating disordered population and determine the relationship between schema modes and early maladaptive schemata, experience of invalidation of emotion during childhood and symptoms of anxiety and depression. In total 15 patients from an outpatient eating disorders service and 28 non patient controls completed the Schema Mode Inventory, The Young Schema Questionnaire, the Hospital Anxiety and Depression Scale, The Invalidating Childhood Environment Scale, and measures of eating disordered pathology. Non parametric analyses were completed to determine the differences between the two groups. The relationship between all measures was determined using correlation analyses. The eating disordered group were significantly more dysfunctional than the control group across all schema modes and early maladaptive schemata. Both groups did not display uniformity in their dysfunctional schema modes. The eating disordered group had raised scores in the detached self soother, the compliant surrender and the vulnerable child mode, whereas the control group had lower scores in the detached protector and the vulnerable child modes. The measure if eating pathology was not associated with the total score on any questionnaire measure. This research indicates that the schema mode concept may be a useful addition to the schema model of eating disorders.
27
Samant, Swinal R. "A parametric investigation of the influence of atrium facades on the daylight performance of atrium buildings." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/12303/.
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Atria have proliferated in a range of contemporary buildings and daylighting is perhaps their most valuable aspect. This thesis is an exploration of the effects of atrium facades on the daylight performance of an atrium and its adjoining spaces. It examines the effects of atrium wall surface reflectance distribution patterns, different surface types, and the location, size and proportion of fenestration and opaque areas in an atrium’s facade. The study seeks to provide knowledge that would be most useful at the early design stages of a project. The study uses Daylight Factor (DF) and Average Daylight Factor (ADF) to examine daylight levels in an atrium building. Chapters Two and Three develop an understanding of key daylighting concepts and consider specific daylight linked atrium parameters related to this study; atrium geometry and enclosing surfaces each of which is examined through an extensive literature review. Chapter Four demonstrates the effects of reflectance distributions and diffuse and specular surfaces on DFs across the atrium floor using physical scale models. Following this, in Chapter Five, the experiments are repeated using RADIANCE and results from the two methods are compared to establish their accuracies. ADF values, calculated using Littlefair’s (2002) algorithm, are also compared with those obtained from physical scale model and RADIANCE. Chapter Six establishes the range of atrium well indices in which surface reflectance distributions affect DFs. This then informs the experiments of Chapter Seven which ascertain the influence of different facade compositions (with variable and even fenestration from the atrium roof to its floor) on daylight availability in atrium buildings. To contextualise work undertaken in this thesis, the research findings are compared with data from real buildings. Finally, specific conclusions with regards to the effects of atrium facades on daylighting in atrium buildings are drawn before more wide-reaching inferences are made.
28
Adil, Arsalan. "Parametric investigation of the mechanical response of two-dimensional composite scarf joints via finite element modeling." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98587.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 263-265).
A parametric investigation was conducted in order to characterize the mechanical response of two-dimensional composite scarf joints subjected to extensional loading, to determine the associated response sensitivities to joint parameters, and to establish the fundamental operative joint mechanics. The geometric parameters of equal scarf angles, adhesive thickness, and unequal scarf angles, and the laminate parameter of similar laminate configurations of both adherends of [+/-[theta]₂/0₂]S, [[theta]/0=0]₂S, and homogenized [[theta]₂/0₂]S (equivalently homogeneously orthotropic) were explored for values of [theta] of 45° and 15°. The ply regions of the laminates were modeled as transversely isotropic T700/2510 carbon/epoxy composite material, and the adhesive region as isotropic FM 300-2K polymer film adhesive. Linear elastic plane strain analyses were performed via finite element modeling. The results indicate that the overall mechanical response of two-dimensional composite scarf joints in the joint region is influenced by the global/macroscopic joint features of 'effective' through-thickness stiffness properties of the configuration in the joint region, and equilibrium considerations along the bondline, and by the local joint features manifested at the tips of the adherends at the ends of the joint region and through ply-by-ply level mismatch in stiffness properties within the adherend. The global peaks in the magnitudes of strains occur in the adhesive, and the distributions of strains in the adhesive essentially reflect the distributions of strains along the bondline in the adherend. The distributions of strains in the adherend along the bondline reflect the distribution of stiffness properties of the adherend through the thickness, and are governed by the local effects of mismatch in stiffness properties between the [theta] and 0° plies along with the lengthscale of the effective ply thickness. Sharp changes in the magnitudes of strains occur near the acute and obtuse tips of the adherend, and these are related to the overall length-scales of the configuration and show similar aspects to those occurring in laminated structures with ply drop-offs. The magnitudes of strains show the greatest sensitivity to variations in the scarf angle of the configuration, increasing with increasing values of scarf angle and associated changes in bondline length, but show little sensitivity to variations in the adhesive thickness of the configuration. For the asymmetric configurations of unequal scarf angles, the response characteristics exhibit combined effects of variations in scarf angles and adhesive thickness, and exhibit signicant asymmetry in the cross-sectional distribution of far-field longitudinal strain. Recommendations for further work are presented.
by Arsalan Adil.
S.M.
29
Pessu, Frederick Oritseweneye. "Investigation of pitting corrosion of carbon steel in sweet and sour oilfield corrosion conditions : a parametric study." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/11227/.
Full textAbstract:
The challenges in managing localised corrosion failures in oilfields are large. In environments containing both CO2 and H2S gas, pitting corrosion of carbon steel is considered to be a common occurrence and particularly complex. The consequences of pitting corrosion failures are usually severe in terms of the health and safety or the environment as well as economic cost to the operators. The actual mechanisms and sequence of electrochemical activities for pitting corrosion in these environments is still not fully understood. The film formation characteristics and morphology in CO2 and H2S-containing systems are also known to influence the general and pitting corrosion behavior of carbon steel. However, questions still remain as to how different oilfield process parameters such as temperature, chloride ion concentration, in-situ pH of corrosion environment and the combined presence of CO2 and H2S gas could be influencing the corrosion kinetics and pitting corrosion process; pit initiation and pit propagation of carbon steel materials exposed to oilfield corrosion environments. A comprehensive and systematic investigation of the pitting corrosion behaviour of X65 carbon steel in sweet and sour corrosion environment has been carried out using a combination of electrochemical techniques and a robust set of post-experiment surface analysis techniques. The results confirms the notion that pitting corrosion process of carbon steel is very different from pitting corrosion in passive alloys and that the evolution of pitting corrosion of active materials in sweet and sour corrosion environments is governed by; the uniform corrosion contribution, the local environments; corrosion products and active ionic species and environmental parameters. In sour corrosion environments, pitting corrosion characterisation using the NPFLEX 3D interferometer and extensive analysis of corrosion product morphologies using the transmission electron microscope was able to show that FeS corrosion product formation occurs faster than FeCO3 in H2S-CO2-containing corrosion system leading to pit initiation and also that in scenarios where competitive precipitation of FeCO3 and FeS is likely, the risk of pitting corrosion is increased.
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Kou, Yan. "Load-settlement behaviour of geosynthetic-reinforced granular soil cover over the conduit." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2019. https://ro.ecu.edu.au/theses/2247.
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The buried conduits/pipes have been used for a comprehensive transport purpose, such as transporting water, gas, oil, sewage and other services. In recent years, many researchers have investigated the behaviour of the buried conduits under soil cover. Some researchers have attempted to use geosynthetic reinforcement within the soil cover to protect the buried conduit to extend their service life. Some studies have been conducted to investigate the behaviour of the reinforced-conduit covered with sandy soil, sandy gravel, silica or fly ash, etc. The researchers proposed some different methods, such as experimental, numerical and analytical methods which can improve the performance of the conduit. In recent years, the researchers have used different types of geosynthetics to protect the conduit, such as geotextile, geofoam or geogrid. However, an optimal design and the effectiveness of employing geosynthetic material for protecting the conduit require an extensive knowledge of the pressure distribution around conduit covered with reinforced soil cover as well as the deflection of conduit. In this research, an attempt has been made to investigate the behaviour of geotextile-reinforced sandy soil over the conduit to achieve the benefits of reinforcement. For this purpose, extensive laboratory measurements, numerical analysis and analytical investigation have been carried out.
In the laboratory experimental phase, the model footing tests were conducted in a rigid tank filled with sandy soil compacted at a relative density of 70% which is most common relative density in real life. The PVC pipe of 150 mm diameter was placed at a depth of 320 mm below the footing base. The geotextile reinforcement (single layer as well as two layers) of varying widths was installed at several depths, but always above the conduit. The experimental investigation aimed at: (i) observing the effect of the width of a single-layer of geosynthetic reinforcement on the footing settlement, and pressure around the conduit and its deflection, and (ii) studying the effect of the depth of geosynthetic reinforcement on footing settlement, and pressure around the conduit and its deflection. It was observed that the optimum width of geosynthetic for pressure reduction around the conduit, footing settlement reduction and deflection reduction around the conduit is equal to four times conduit diameter, and optimum depth is equal to 1.5 times conduit diameter below the surface. When the depth of geosynthetic layer is 1.5 times the conduit diameter depth, pressure reduction is 26.62% on the crown of the conduit, compared to unreinforced case when applied pressure is 200 kPa. It was also noted that the two layers of geosyntheitc reinforcement bring more benefits for pressure reduction. For example, when the depth of first layer of geotextile is 1.5 times the conduit diameter, the reduction in pressure on the crown of the conduit is about 34% for the applied pressure of 200 kPa.
A numerical model was developed and validated with the experimental findings to investigate the effect of depth of the geosynthetic reinforcement on footing settlement and conduit deflection. The numerical model also helped analyse the behaviour of reinforced soil cover over the large diameter conduit. The parametric study was carried out to investigate the effect of governing parameters (such as cohesion of the soil, friction angle of the soil and the interface reduction factor between the soil and geosynthetic layer) on the footing settlement and pressure on the crown of the conduit. In the large-scale conduit case, it is found that the optimum reduction takes place when the spacing between pipe and geosynthetic layer is equal to the conduit diameter. The pressure on the crown of the small diameter HDPE and PVC pipes reduced by 31% and 27%, respectively.
In the present work, analytical expression has also been developed for evaluating the pressure on the crown of the two-layer geosynthetic-reinforced sandy soil cover over the conduit. Using the analytical expression, a parametric study has been carried out. An illustrative example is also presented to explain how the analytical expression can be used.
This thesis has several graphical presentations, which can be quite useful for the practising engineers for designing the conduits covered with geosynthetic-reinforced soil cover without depending on expensive commercial software.
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Tey, Chun Yean. "Investigation of the thermo hydro mechanical behaviour of large scale experiments - including parametric studies on various critical factors." Thesis, Cardiff University, 2004. http://orca.cf.ac.uk/55971/.
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This thesis presents an investigation into the thermo/hydro/mechanical interactions occurring in two large scale experiments with different geometry setup designed for deep geological disposal of nuclear waste. The analysis of flow and deformation through unsaturated soils was performed using the proposed constitutive model. The following mechanisms are accommodated moisture flow in liquid and vapour forms, dry air flow including the movement of bulk air and the transport of dissolved air in the pore water, heat transfer by conduction, convection and latent heat of vapourisation, and the elasto-plastic deformation of unsaturated soils. The governing differential equations are solved spatially using a finite element technique and temporally using a finite difference technique. The numerical model was subsequently applied to two large scale experiments: AECL's Buffer/Container Experiment and AECL's Horizontal Canister In-room geometry. The analyses involved modelling the coupled thermo/hydro/mechanical interaction between the engineered buffer and the host rock, and the swelling phenomena at the buffer/rock interface. A comprehensive set of material parameters was determined for use in the numerical code. A theoretical formulation was developed to describe a time-dependent adsorption/desorption process associated with the micro/macro swelling phenomena occurring in bentonite-based buffer materials. This was implemented within the numerical model. The transient swelling behaviour of bentonite-based buffer materials was found to be influential in the simulation of an underground repository, in particular the resaturation behaviour in expansive clay. Sensitivity analyses on critical parameters identified for both geometry setups are presented and shown to affect the resaturation processes to varying degrees. This investigation has provided valuable insights into the repositories' behaviour.
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Kalaikadal, Deepak Saagar. "A Parametric Investigation of Gas Bubble Growth and Pinch-Off Dynamics from Capillary-Tube Orifices in Liquid Pools." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1342543385.
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Phillips, Erin Katherine. "Investigation of Required Tensile Strength Predicted by Current Reinforced Soil Design Methodologies." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/49246.
Full textAbstract:
Geosynthetic Reinforced Soil (GRS) is a promising technology that can be implemented
in walls, culverts, rock fall barriers, and bridge abutments. Its use in walls and abutments
is similar to Mechanically Stabilized Earth Walls (MSEW) reinforced with geosynthetics.
Both GRS and MSEW are reinforced soil technologies that use reinforcement to provide
tensile capacity within soil masses. However, the soil theories behind each method and
the design methodologies associated with GRS and MSEW technologies are quite
different.
Therefore, a study was undertaken to compare the required tensile strength predicted by
these various reinforced soil design methodologies. For the purposes of this study, the
required ultimate tensile strength was defined as the ultimate tensile strength needed in
the reinforcement after all applicable factors of safety, load factors, and reduction factors
were applied. The investigation explored both MSEW and GRS. GRS has been made an
FHWA "Every Day Counts" initiative. Due to the push to implement GRS technology, it
is critical to understand how GRS design methods differs from classic MSEW design
methods, specifically in the prediction of ultimate tensile strength required.
A parametric study was performed comparing five different reinforced soil analysis
methods. Two are current MSEW design methods and one was a proposed revision to an
existing MSEW design method. The final two were GRS design methods. These design
methods are among the most current and/or widely used design references in the United
States regarding reinforced soil technology. There are significant differences between the
methods in the governing soil theory particularly between GRS and MSEW design
methods. The goal of the study was to understand which design parameters had the most
influence on calculated values of the required ultimate tensile strength and nominal
"unfactored" tensile strength. A base case was established and a reasonable set of
parameter variations was determined. Two loading conditions were imposed, a roadway
loading scenario and a bridge loading scenario.
Based on parametric study findings, conclusions were drawn about which design
parameters had the most influence for different design methods. Additionally, the
difference in overall predicted required tensile strength was assessed between the various
methods. Finally, the underlying soil theory and assumptions employed by the different
methods and their influence on predicted required tensile strength values was interpreted.Master of Science
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Awrejcewicz, Jan, Lidiya Kurpa, and Olga Mazur. "Investigation of the parametric vibration of the orthotropic plates subjected to periodic in plane forces by multi-modal approximation and R-functions method." Thesis, NTU "KhPI", 2010. http://repository.kpi.kharkov.ua/handle/KhPI-Press/37138.
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The original method of studying parametric vibrations of orthotropic plate with complex shape is proposed. Suggested approach is based on combined application of variational methods and the R-functions theory. Using the proposed method and developed software the regular and chaotic regimes of T-shaped plate are analyzed.
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Chatterjee, Debanuj. "A theoretical investigation of fiber phase sensitive amplifiers for applications." Thesis, université Paris-Saclay, 2021. http://www.theses.fr/2021UPASP008.
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Les amplificateurs paramétriques à fibre optique (FOPA) sont prometteurs pour les systèmes de communication de demain. En particulier, les amplificateurs sensibles à la phase des fibres offrent des fonctionnalités intéressantes comme un faible bruit et un gain élevé, ce qui en fait des candidats potentiels pour des applications dans les liaisons photoniques micro-ondes. Cette thèse propose une étude théorique de tels amplificateurs sensibles à la phase destinés à certaines applications.La première partie de la thèse est consacrée au développement d'un modèle analytique pour la propagation de sept ondes continues à travers un FOPA. Le système est résolu lorsque les effets non linéaires de la fibre ne sont pas trop forts. Le modèle développé révèle le rôle important des ondes d'ordre supérieur dans la détermination des performances d'amplification du FOPA. Des stratégies sont formulées pour améliorer l'amplification. La possibilité d'une conversion de fréquence sensible à la phase avec seulement deux ondes de pompe est également prédite.Dans la deuxième partie de cette thèse, la possibilité d'introduire un amplificateur sensible à la phase dans une liaison photonique hyperfréquence pour la distribution de signaux analogiques est étudiée. Un modèle numérique est utilisé pour simuler comment les non-linéarités RF dans une liaison photonique hyperfréquence sont amplifiées par le FOPA. Les performances de la liaison lorsque le FOPA atteint la saturation du gain sont également étudiées. L'étude révèle la possibilité d'une atténuation de la non-linéarité RF en utilisant la non-linéarité de la fibre. La mise en œuvre de telles techniques pourrait conduire à la réalisation de liaisons photoniques hyperfréquences à longue portée et hautement linéaires pour les applications de déport d'antenneFiber optic parametric amplifiers (FOPA) are promising for tomorrow's communication systems. In particular, fiber phase sensitive amplifiers offer attractive functionalities like low noise and high gain which makes it a potential candidate for applications in microwave photonic links. This thesis provides a theoretical investigation of such fiber phase sensitive amplifiers aimed towards applications.The first part of the thesis is dedicated towards development of an analytical model for propagation of seven CW waves through a FOPA. The system was solved exactly when nonlinear effects of the fiber are not strong. The developed model unravelled the important role of the higher order waves in determining the amplification performance of the FOPA. Strategies were formulated to enhance the amplification and the possibility of a phase sensitive frequency conversion with just two pump waves was also predicted.In the second part of this thesis, the possibility of introducing a fiber phase sensitive amplifier in a microwave photonic link for analog signal distribution was investigated. A numerical model was utilized to simulate how the RF nonlinearities in a microwave photonic link are amplified by the FOPA. The performance of the link when the FOPA attains a gain saturation was also studied. The study revealed the possibility of RF nonlinearity mitigation using the fiber nonlinearity. Implementation of such techniques could lead to realization of long-range and highly linear microwave photonic links for antenna remoting applications
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Parackal, Bhavana. "An Investigation of Low Temperature Direct Propane Fuel Cells." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/35896.
Full textAbstract:
This research is directed toward the investigation of a low temperature direct propane fuel cell (DPFC). Modeling included a parametric study of a direct propane fuel cell using computational fluid dynamics (CFD), specifically FreeFem++ software. Polarization curves predicted by the CFD model were used to understand fuel cell performance. The predictions obtained from the computational fluid dynamics mathematical model for the fuel cell were compared with experimental results. The computational work identified some critical parameters (exchange current density, pressure, temperature) for improving the overall performance of the fuel cell. The model predictions clearly highlighted the role of catalysts in significantly enhancing the overall performance of a DPFC. Experiments were performed using commercial Nafion-Pt based membrane electrode assemblies (MEAs) to obtain a basis for comparison. It is the first report in the literature that a Pt-Ru (Platinum-Ruthenium) MEA was used in the investigation of a DPFC. Also, it was the first study that fed liquid water continuously to a DPFC by using interdigitated flow field (IDFF) at the anode to humidify the dry propane feed gas. During the experiments oscillations were observed at very low current densities i.e. in nA/cm2, which is a rare case and not reported in the literature to date. This observation has raised serious concerns about the existence of absolute open-circuit cell potential difference for a DPFC. The cycling behaviour observed with DPFC indicated the presence of a continuous degradation-regeneration process of the catalyst surface near open-circuit potential. The experimental work further evaluated the performance of fuel cell by measurement of polarization curves.
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Wang, Chunxin. "An investigation of bootstrap methods for estimating the standard error of equating under the common-item nonequivalent groups design." Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/1188.
Full textAbstract:
The purpose of this study was to investigate the performance of the parametric bootstrap method and to compare the parametric and nonparametric bootstrap methods for estimating the standard error of equating (SEE) under the common-item nonequivalent groups (CINEG) design with the frequency estimation (FE) equipercentile method under a variety of simulated conditions.
When the performance of the parametric bootstrap method was investigated, bivariate polynomial log-linear models were employed to fit the data. With the consideration of the different polynomial degrees and two different numbers of cross-product moments, a total of eight parametric bootstrap models were examined. Two real datasets were used as the basis to define the population distributions and the "true" SEEs. A simulation study was conducted reflecting three levels for group proficiency differences, three levels of sample sizes, two test lengths and two ratios of the number of common items and the total number of items. Bias of the SEE, standard errors of the SEE, root mean square errors of the SEE, and their corresponding weighted indices were calculated and used to evaluate and compare the simulation results.
The main findings from this simulation study were as follows: (1) The parametric bootstrap models with larger polynomial degrees generally produced smaller bias but larger standard errors than those with lower polynomial degrees. (2) The parametric bootstrap models with a higher order cross product moment (CPM) of two generally yielded more accurate estimates of the SEE than the corresponding models with the CPM of one. (3) The nonparametric bootstrap method generally produced less accurate estimates of the SEE than the parametric bootstrap method. However, as the sample size increased, the differences between the two bootstrap methods became smaller. When the sample size was equal to or larger than 3,000, the differences between the nonparametric bootstrap method and the parametric bootstrap model that produced the smallest RMSE were very small. (4) Of all the models considered in this study, parametric bootstrap models with the polynomial degree of four performed better under most simulation conditions. (5) Aside from method effects, sample size and test length had the most impact on estimating the SEE. Group proficiency differences and the ratio of the number of common items to the total number of items had little effect on a short test, but had slight effect on a long test.
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Janssen, Michael T. "Investigations of parametric excitation in physical systems." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Jun%5FJanssen.pdf.
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Ha, Giap Xuan [Verfasser], Manfred W. [Akademischer Betreuer] Zehn, Manfred W. [Gutachter] Zehn, Christian [Gutachter] Hühne, and Monika [Gutachter] Bauer. "Numerical simulation and parametric investigation of the mechanical properties of fabric nap core sandwich / Giap Xuan Ha ; Gutachter: Manfred W. Zehn, Christian Hühne, Monika Bauer ; Betreuer: Manfred W. Zehn." Berlin : Technische Universität Berlin, 2019. http://d-nb.info/1184983623/34.
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Rentzelos, Theofanis. "Numerical Investigation of Rock Support Arches." Thesis, Luleå tekniska universitet, Geoteknologi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-76698.
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The Garpenberg mine, owned by the Boliden Mining group, has established a trial area at Dammsjön orebody in order to examine the possibility of increasing the productivity of the mine. The mine uses the rill mining method with a current rill height of 15 m. In order to increase the productivity, the mine is examining the possibility of increasing the height of the rill. The trial area is located at 882 m depth surrounded by dolomite on the hangingwall and quartzitic rock on the footwall side. Rock support arches have been installed, in addition to the regular support pattern, to test their effectiveness on stabilizing the ground around the drifts. The arches have been installed in every 6 m and every 3 m in different parts of the test area. Rock samples from the trial area were brought to the university laboratory for testing. The data gathered from the laboratory tests along with the data from the monitoring of the trial area were used to develop a calibrated numerical model. A three-dimensional (3-D) model was therefore created, by using the FLAC3D numerical code. After the calibration of the model a parametric study was conducted for different rill heights and different arch spacing to investigate the performance of the arches. Specifically, the case of no arch installation along with the cases of an installed arch every 6 m and 3 m were tested, for the rill heights of 15 m, 20 m, 25 m and 30 m. The study concluded that the arches assisted in reducing the ground convergence in the production drift. The results also showed that the total height of the rill bench yields regardless of its height. After the yielding, the rockmass can no longer support itself and caves under its own weight. The larger the rill height, the larger the volume of loose rock that has to be supported and thus, higher the convergence. Furthermore, it was also observed that, significant amount of convergence in the production drift occurred during the drifting of the top drive and less during the stoping of the rill bench. This indicates that, the timely installation of the arches is an important criterion for their performance.
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Elfergani, Issa T. "Investigation, design and implementation of frequency tuneable antennas for mobile handset and UWB applications : simulation and measurement of tunable antennas for handheld mobile handsets and UWB system, investigations of frequency tuneable range, antenna radiation performance and antenna design optimisation using parametric studies." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/13761.
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Jones, William P. "Investigations of nonlinear waves and parametric excitation." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Sep%5FJones%5FWilliam.pdf.
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Thesis (M.S. in Applied Physics)--Naval Postgraduate School, September 2005.Thesis Advisor(s):Bruce C. Denardo, Thomas Hofler. Includes bibliographical references (p. 63-64). Also available online.
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Milton, Martin John Terry. "Investigations of high-efficiency mixing and parametric amplification in nonlinear crystals." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303117.
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Perez, Tineo Cesar Augusto. "Theoretical and numerical investigations of the parametric resonance of the mechanical vibrissa." Master's thesis, Pontificia Universidad Católica del Perú, 2016. http://tesis.pucp.edu.pe/repositorio/handle/123456789/13549.
Full textAbstract:
In nature, vibrissae are tactile hairs of mammals used as sensor elements for the exploring the surrounding area. These hairs, also known as whiskers, can be found in different locations on an animals body. Mystacial vibrissae are distributed over a whiskerpad on a muzzle. Carpal vibrissae are located on the downside aspect of the forelimbs of mammals. The vibrissal hair has a conical shape and grows from a special heavily innervated hair follicle incorporating a capsule of blood. As the hair itself has no receptors along its length, the vibrissa may be considered as a system for transmitting forces and torques that arise from the contact between the hair and an object to sensory receptors inside the follicle.
The present thesis deals with the vibrational motion of vibrissae dur- ing natural exploratory behaviour from the mechanical point of view. The phenomenon of the parametric resonance of the vibrissa is investigated the- oretically and numerically. In the first part of this thesis, two mechanical models of an elastic beam are presented based on findings in the literature. The first model considers a straight beam with the linearly decreasing radius of the circular cross-section. The second model takes into account the circu- lar natural configuration of the cylindrical beam. Within these models, the small transverse vibration of the beam under a periodic following force at the tip are analysed using the Euler-Bernoulli beam theory and asymptotic methods of mechanics.
In the second part of the thesis, the numerical analysis of the problems is performed based on the finite element method using ANSYS 16.2 software. For each model, the dynamical response of the system on the parametric excitation is simulated for different frequency values.
It is shown theoretically and numerically that at specific ranges of the excitation frequency the phenomenon of the parametric resonance of the beam takes place. That means that the amplitude of vibrations of the beam increases exponentially with time, when it is stimulated within one of the frequency ranges of the parametric resonance. These ranges depend on the geometrical and material parameters of the beam model, as well as the am- plitude of the periodic excitation.Tesis
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Bömer, Christina [Verfasser]. "Energy resolved diffraction for investigating x-ray parametric down-conversion / Christina Bömer." Hamburg : Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky, 2020. http://d-nb.info/1235243966/34.
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Butterworth, Stuart David. "Investigations of a high power all-solid-state synchronously-pumped lithium triborate optical parametric oscillator." Thesis, University of Southampton, 1997. https://eprints.soton.ac.uk/394570/.
Full textAbstract:
The work presented in this thesis describes the operation of a high power all-solid-state synchronously pumped optical parametric oscillator based on a Brewster-angled lithium triborate crystal. The OPO is pumped by a resonant frequency doubled, amplified, diode-pumped mode-locked laser. Performance characteristics of the individual "modules" in the overall system are presented. The work describes the production of 2.0 psec pulses from a diode-pumped Nd:YLF laser using the passive mode-locking technique of additive-pulse-modelocking (APM). This method was the most convenient available at the time of this research, and provides the shortest pulses from the Nd:YLF laser and hence, the greatest peak power. Average power levels of 540mW were obtained in pulses having a peak power of 2.5kW. The pulses were subsequently amplified in a simple end-pumped Nd:YLF amplifier to average power levels of ~1W with peak powers of ~4kW. At these peak power levels, efficient single-pass harmonic generation was still not possible with the non-linear crystals available at the time, so the technique of resonant enhancement was employed. This produced 660mW of green light in an optimised resonator with a peak power of ~3.1kW at a conversion efficiency approaching 80%. These three individual stages when taken together, constitute the pump source for the LBO optical parametric oscillator. Continuous synchronous pumping was achieved using a temperature-tuned noncritically phase-matched lithium triborate crystal as the nonlinear gain medium. An extensive tuning range from 0.65 to 2.7µm was obtained with average output powers for the signal (idler) as high as 200mW (110mW). With the high intra-cavity powers of the resonated signal wave we observed significant chirping on the output pulses via self-phase modulation. By providing dispersion compensation via intra-cavity prisms the chirp was removed and produced transform-limited pulses of duration 1.6psec with peak powers of ~800W. As a result of this work it has been possible to provide a complete design strategy for achieving reliable operation of an all-solid-state picosecond source with broad tunability in the near infrared.
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Hirt, David M. "Parametric Study via Numerical Simulations of Natural Convection in Laterally Heated Cylindrical Enclosures: Investigating Characteristic Length." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron15227528176693.
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Demissie, Mathewos S. "Investigating center effects in a multi-center clinical trial study using a parametric proportional hazards meta-analysis model." College Park, Md.: University of Maryland, 2009. http://hdl.handle.net/1903/9588.
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Thesis (M.S.) -- University of Maryland, College Park, 2009.Thesis research directed by: Mathematical Statistics Program. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Voß, Daniel [Verfasser], Hartmut [Gutachter] Roskos, and John [Gutachter] Sheridan. "Investigations on terahertz imaging with pulsed optical parametric oscillator radiation and heterodyne Fourier techniques / Daniel Voß ; Gutachter: Hartmut Roskos, John Sheridan." Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2019. http://d-nb.info/1184986185/34.
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Becker, Eric. "Investigations experimentales et numeriques pour l’identification des parametres clefs du procede de thixoforgeage de l’acier sur le produit mis en forme." Paris, ENSAM, 2008. http://www.theses.fr/2008ENAM0038.
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L’industrie cherche en permanence à minimiser le temps et les coûts, à simplifier leur processus de fabrication tout en maximisant la qualité de leurs produits. Cette démarche s’applique pour l’industrie de la mise en forme des métaux. Dans ce contexte, un procédé innovant de mise en forme, le thixoforgeage, s’est développé, permettant d’obtenir des pièces de formes complexes aux qualités mécaniques élevées en minimisant le nombre de phases du processus de fabrication. Ce procédé utilise les propriétés de l’état semisolide des alliages métalliques, cet état étant obtenu par fusion partielle du solide. Dans le cadre de la mise en forme de l’acier à l’état semi-solide, les difficultés liées à la température de travail et la méconnaissance du comportement mécanique et thermomécanique du matériau rendent difficile le développement industriel du procédé. Cette thèse a l’ambition d’améliorer la compréhension du comportement de l’acier lors de sa mise en forme par thixoforgeage. L’objectif est également de développer l’exploitation du modèle original deux phases multiéchelle « micro-macro », et son implémentation dans les solveurs 2D et 3D de Forge 2007®. Pour atteindre cet objectif, des essais expérimentaux avec des dispositifs spécifiques et innovants ont été réalisés. Une étude paramétrique de l’opération de thixoforgeage a été mise en place. Les principaux paramètres de conduite du procédé ont été identifiés. Ces paramètres sont la vitesse de mise en forme, la température initiale de l’acier et la température initiale de l’outil. Pour chaque essai, l’évolution des efforts de mise en forme, la nature de l’écoulement et la qualité des pièces produites au travers de l’observation macrographiques et micrographiques de leur structure métallurgique et d’essais mécaniques, ont été étudiées. Des essais avec des outillages instrumentés ont également permis une caractérisation des échanges thermiques entre l’outil et la pièce lors de la mise en forme. Ce nombre important d’essais a permis de décrire l’influence et de montrer l’importance de ces paramètres dans la mise en forme par thixoforgeage. Ces essais ont également servi de base au recalage du modèle multiéchelle « micro-macro » et des coefficients d’échange thermique entre l’outil et la pièce. Les essais et les simulations ont été comparés afin de déterminer et améliorer la capacité prédictive du modèle implémenté dans le logiciel Forge2007®Industry is permanently looking for minimizing production time and cost, simplifying their manufacturing process while maximizing the quality of their products. This is applied by the metal forming industry. In this context, an innovative forming process, the thixoforging, is developed, making it possible to manufacture complex parts with elevated mechanical properties. Moreover the thixoforging permit to minimize the number of phases of the manufacturing process. This process uses the semi-solid state properties of metal alloys, this state being obtained by partial fusion of the solid. For steel thixoforging, the difficulties related to the work temperature and the lack of knowledge of the mechanical and thermomechanical behavior of the material. These make the industrial process development difficult. This thesis contributes to improve comprehension of the steel behaviour during thixoforging. The objective is also to develop the exploitation of the original multi-scale model “micro-macro”, and its implementation in the 2D and 3D Forge2007®. Software. To achieve this goal, experimental testing with a specific and innovative device was carried out. The main thixoforging parameters were identified and studied. These parameters are the forming speed, the initial steel temperature and the initial tool temperature. For each test, the evolution of the forming load, the nature of the plastic flow and the quality of the thixoforged parts characterised by the macrographic and micrographic observations of their metallurgical structure and mechanical tests, were studied. Tests with instrumented tools also allowed a characterization of heat exchange between the tool and the part during forming. This big number of tests made it possible to describe the influence and to show the importance of the forming speed, the initial temperature of the steel and the initial temperature of the tool during thixoforging of a part. These tests were also used as a basis for calibration of the “micro-macro” model multi-scale and the heat exchange coefficients between the tool and the part. The tests and simulations were compared in order to determine and improve the predictive model capacity implemented in Forge2007® software