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1
Cox, Simon John. "Pressure impulses caused by wave impact." Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266731.
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Wu, Cheng Y. (Cheng Yi) 1938. "Wave-wave interactions and the infrasonic pressure field in the ocean." Thesis, University of Auckland, 1988. http://hdl.handle.net/2292/2469.
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Building on Kibblewhite's long term investigations of the nonlinear wave-wave interactions and the infrasonic ocean noise and the microseisms these induce, this thesis further explores the physical nature of these processes. The classical description of this interaction, which takes into account only the homogeneous component of the induced field, has been extended to include the inhomogeneous component. A complete expression for the wave induced noise spectrum is established following a geometrical analysis of the dispersion relations among interacting waves. The relative importance of these two components and their directivity properties are also calculated and discussed. It is shown that while at observation points deeper than 500 meters the effects of the inhomogeneous component can be regarded as negligible, it can cause an increase of noise level of up to 40 dB in the region near the surface of the sea. Furthermore, in contrast to the nearly omni-directional distribution of the homogeneous component of the induced acoustic field, there is a tendency for the energy associated with the inhomogeneous component to focus in the wind direction. Based upon a multilayer analysis of a visco-elastic geoacoustic model, Green's functions and the spectral transfer functions relating the surface source pressure field to the underwater noise and microseism fields are derived for both near and far field cases. A 3-dimensional presentation defined on the dispersion plane (frequency and horizontal wave number) is introduced to describe the sea bottom reflection-loss and, Green's functions, and is extended to include the inhomogeneous region for the first time. The characteristics of this 3-D presentation are explained in terms of the geoacoustic parameters. The influence of the interaction of multiple seas (and swell) on the induced acoustic field are also discussed in this thesis. All these effects are considered in the calculation of the synthetic spectra of both the noise and microseism field. When compared with measured data excellent agreement is found between the theoretical and experimental results, which provides further confirmation that the nonlinear interaction is the most important source of the infrasonic ocean noise, as well as confirming the basic validity of the procedure introduced by Kibblewhite and Ewans to derive the ocean noise spectra from microseism records.
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Wood, Deborah Jane. "Pressure-impulse impact problems and plunging wave jet impact." Thesis, University of Bristol, 1997. http://hdl.handle.net/1983/c3dbd4c5-5082-4c71-a16e-3daa969e22ee.
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Sorvoja, H. (Hannu). "Noninvasive blood pressure pulse detection and blood pressure determination." Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:9514282728.
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This thesis describes the development of pressure sensor arrays and a range of methods suitable for the long-term measurement of heart rate and blood pressure determination using a cuff and a pressure sensor array on the radial artery. This study also reviews the historical background of noninvasive blood pressure measurement methods, summarizes the accuracies achieved and explains the requirements for common national and international standards of accuracy.
Two prototype series of pressure transducer arrays based on electro-mechanical film (EMFi) were designed and tested. By offering high (∼TΩ) resistance, EMFi is an excellent material for low-current long-term measurement applications. About 50 transducer arrays were built using different configurations and electrode materials to sense low-frequency pressure pulsations on the radial artery in the wrist. In addition to uniform quality, essential requirements included an adequate linear response in the desired temperature range. Transducer sensitivity was tested as a function of temperature in the range of 25–45 °C at varying static and alternating pressures. The average sensitivity of the EMFi used in the transducers proved adequate (∼2.2 mV/mmHg and ∼7 mV/mmHg for normal and high sensitive films) for the intended purpose.
The thesis also evaluates blood pressure measurements by the electronic palpation method (EP) and compares the achieved accuracy to that of the oscillometric method (OSC) using average intra-arterial (IA) blood pressure as a reference. All of these three measurements were made simultaneously for each person. In one test group, measurements were conducted on healthy volunteers in sitting and supine position during increasing and decreasing cuff pressure. Another group, comprising elderly cardiac patients, was measured only in the supine position during cuff inflation. The results showed that the EP method was approximately as accurate as the OSC method with the healthy subjects and slightly more accurate with the cardiac patient group. The advantage of the EP method is that also the wave shape and velocity of arterial pressure pulses is available for further analysis, including the assessment of arterial stiffness.
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Sabkha, Aimen. "Implantable Wireless Surface Acoustic Wave Sensors for Blood Pressure Measurement." Thesis, Oxford Brookes University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491086.
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Brasek, Thomas Peyton. "Response of dual-layered structures subjected to shock pressure wave." Thesis, Monterey, California. Naval Postgraduate School, 1994. http://hdl.handle.net/10945/30529.
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The response of coated, metallic structures subjected to shock pressure waves is studied. The coating is either an elastic material or nearly incompressible rubber of variable stiffness separating the structure from an air or water medium. The stress, nodal velocity, and internal energy of the coated structure are compared to a system without a coating (homogeneous system) to examine the effect of various coating types and configurations on the response of the structure to shock conditions. The results show that a mismatch of impedance, pc sub o, between the coating and structure governs the degree of energy exchange between the coating and structure at the interface. The impedance mismatch between the structure and a rubber coating at the threshold value is termed the critical difference. If the impedance mismatch exceeds the critical difference, the dynamic response will be more adverse. A softer coating generally has a smaller impedance and tends to concentrate stress wave energy in the underlying structure.
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Eriksson, Lars. "Design and dimensioning of pressure vessel for a marine substation." Thesis, Uppsala University, Electricity, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-114426.
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This thesis presents the mechanical design and dimensioning of a pressure vessel, which is to be used as housing for a marine substation in a wave power park. A concept for generation of electricity from ocean waves is being developed at the Division of electricity at Uppsala University. The concept is based on the use of a permanent magnet linear generator, placed on the seabed, connected via a line to a buoy at the surface. The generated electricity from a group of generators is transmitted in sea cables to a marine substation where conversion and transformation takes place before the electricity is transmitted to shore. To reduce the risk of water leakage, the gas pressure inside the marine substation is larger than the surrounding water pressure. The substation can be pressurized before submersion, which requires the housing to be designed as a pressure vessel. The pressure vessel has been dimensioned with formula based methods according to EN 13445, the European standard for unfired pressure vessels. The construction has been based on modifying a standard pressure tank. The housing has been designed for installation and sealing of a large number of electrical connectors. The connectors have been placed in a way that allows for future cable coupling with remotely operated vehicles and simplifies maintenance of the substation. Another design consideration has been to facilitate submersion by reducing the buoyancy of the substation.
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Feng, Jiling. "Wave propagation in flexible tubes." Thesis, Brunel University, 2008. http://bura.brunel.ac.uk/handle/2438/5367.
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Wave dissipation was previously investigated intensively in the frequency domain, in which the dissipation of waves is described as attenuation of pressure pulse decay with respect to the frequency or harmonics. In this thesis, wave dissipation, including decay of pressure pulse, peak of wave intensity and wave energy, is investigated in the time domain using wave intensity analysis (WIA). Wave intensity analysis benefits to this research in several aspects including: 1) WIA allows for wave dissipation investigated in the time domain; 2) WIA does not make any assumptions about the tube's wall non-linearity and the analysis takes into account the effects of the vessel's wall viscoelastic properties, convective, frictional effects and fluid viscosity; 3) WIA offers a technique (separation) to study wave dissipation in one direction whilst taking into account the effect of reflections from the opposite direction; 4) The physical meaning of wave intensity provides a convenient method to study the dissipation of energy carried by the waves along flexible tubes. In this research, it is found that the degree of dissipation in flexible tube were not only affected by the mechanical properties of the wall property and viscosity of liquid but also by the other factors including initial pressure and pumping speed of piston as well as direction of wave in relation to direction of flow. Also an new technique to separate waves into forward and backward directions only using diameter and velocity might potentially be used to separate the waves in both directions non-invasively based on the non-invasive measurement of diameter (wall movement) available.
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Materano, Blanco Gilberto Ignacio. "Numerical modelling of pressure rise combustion for reducing emissions of future civil aircraft." Thesis, Cranfield University, 2014. http://dspace.lib.cranfield.ac.uk/handle/1826/9259.
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This work assesses the feasibility of designing and implementing the wave rotor
(WR), the pulse detonation engine (PDE) and the internal combustion wave
rotor (ICWR) as part of novel Brayton cycles able to reduce emissions of future
aircraft. The design and evaluation processes are performed using the
simplified analytical solution of the devices as well as 1D-CFD models. A code
based on the finite volume method is built to predict the position and
dimensions of the slots for the WR and ICWR. The mass and momentum
equations are coupled through a modified SIMPLE algorithm to model
compressible flow. The code includes a novel tracking technique to ensure the
global mass balance. A code based on the method of characteristics is built to
predict the profiles of temperature, pressure and velocity at the discharge of the
PDE and the effect of the PDEs array when it operates as combustion chamber
of gas turbines. The detonation is modelled by using the NASA-CEA code as a
subroutine whilst the method of characteristics incorporates a model to capture
the throttling and non-throttling conditions obtained at the PDE's open end
during the transient process. A medium-sized engine for business jets is
selected to perform the evaluation that includes parameters such as specific
thrust, specific fuel consumption and efficiency of energy conversion. The ICWR
offers the best performance followed by the PDE; both options operate with a
low specific fuel consumption and higher specific thrust. The detonation in an
ICWR does not require an external source of energy, but the PDE array
designed is simple. The WR produced an increase in the turbine performance,
but not as high as the other two devices. These results enable the statement
that a pressure rise combustion process behaves better than pressure
exchangers for this size of gas turbine. Further attention must be given to the
NOx emission, since the detonation process is able to cause temperatures
above 2000 K while dilution air could be an important source of oxygen.
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Roy, Matthew S. "Acute effects of facial cooling on arterial stiffness and wave reflection." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 56 p, 2007. http://proquest.umi.com/pqdweb?did=1397914231&sid=1&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Antonangeli, Daniele. "Elasticity and sound wave anisotropy of hcp-metals at high-pressure." Paris 6, 2005. http://www.theses.fr/2005PA066001.
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Bassili, Niclas, and Douglas Eriksson. "An evaluation of deterministic prediction of ocean waves using pressure data to assist a Wave Energy Converter." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-279600.
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Currently, existing devices for extracting electrical power from ocean waves all suffer from problems with low efficiency due to a lack of information about the incoming waves in advance. The complex dynamic nonlinear characteristics of the ocean make the prediction of these incoming waves a great challenge. This paper aims to investigate a deterministic short-term wave-by-wave prediction system, that can accurately predict the wave height and timing of the incoming waves, based on measurements from a submerged pressure sensor. The complete prediction process contains three steps, namely reconstruction, assimilation, and prediction. A nonlinear Weakly Dispersive Reconstruction method (WDM) is firstly employed to accurately calculate the surface elevation from the measured pressures. Afterwards, a variational assimilation method is used to convert the time series surface elevation to a spatial wavefield, to obtain initial conditions for the prediction. Lastly, a High Order Spectral Method (HOSM) deterministically predicts the evolution of the 2D irregular wavefield based on the acquired initial conditions. To verify the performance of this proposed prediction system, tests were conducted with data from irregular sea states with varying wave parameters, generated by simulations as well as model experiments in the controlled environment of a wave tank. The results show that the surface elevation can be predicted within 5% from the reference, for a future period of about 10 seconds for wavefields commonly experienced by a wave energy converter. Based on the results, a prediction is possible, but the accuracy heavily depends on the current sea state and the chosen prediction distance.The results have been compared against similar tests made using radar data and proven to be a viable alternative for certain sea states. In conclusion, pressure measurements, as a mean to sample an ocean wavefield, is shown to be a good option when combined with nonlinear reconstruction and prediction methods to assist the power harvesting capabilities of a wave energy converter.Nuvarande enheter för att extrahera elektrisk energi från havsvågor lider av stora problem med låg effektivitet på grund av brist på information om de inkommande vågorna. Det komplexa ickelinjära dynamiska beteendet hos havsvågor gör förutsägelsen av dem till en stor utmaning. Det här arbetet syftar till att undersöka ett deterministiskt kortsiktigt system för att förutspå våg för våg, som noggrant kan förutspå våghöjd och tidpunkt för de inkommande vågorna, baserat på mätdata från en dränkbar trycksensor. Den kompletta förutsägelseprocessen innehåller tre steg, rekonstruktion, assimilering och förutsägelse. En ickelinjär weakly dispersive reconstruction method används först för att med hög noggrannhet beräkna ythöjningen från det uppmätta trycket. Därefter, används en variational assimilation method för att konvertera en tidsserie av ythöjningen till ett rumsligt vågfält, för att erhålla initialvillkor för förutsägelsen. Slutligen används en High Order Spectral Method för att deterministiskt förutspå utvecklingen av det tvådimensionella oregelbundna vågfältet baserat på de förvärvade initialvillkoren. För att verifiera prestandan av det föreslagna förutsägelsesystemet, så genomfördes tester med data från olika oregelbundna havstillstånd med varierande parametrar, genererade av simuleringar, såväl som modellexperiment utförda i en kontrollerad miljö i form av en vågtank. Resultaten från testerna visar att ythöjningen förutspås inom 5% från referensen, för en period på 10 sekunder framåt i tiden, för vågor som ett vågkraftverk vanligtvis utsätts för. Baserat på resultatet, så är det möjligt att förutspå inkommande vågor, men noggrannheten beror kraftigt på det aktuella havstillståndet och det valda avståndet för förutsägelsen. Resultaten har jämförts mot liknande tester gjorda med radardata och visat sig vara ett genomförbart alternativ för vissa havstillstånd. Sammanfattningsvis visas det att tryckmätningar, som ett medel för att mäta ett havsvågfält, är ett bra alternativ när de kombineras med ickelinjära rekonstruktions- och förutsägelsemetoder för att hjälpa till att öka ett vågkraftverks energigenerering.
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Hope, Sarah A. "Arterial pressure waves : waveform characteristics, their associations and factors influencing their propagation." Monash University, Faculty of Medicine, Nursing and Health Sciences, 2003. http://arrow.monash.edu.au/hdl/1959.1/5566.
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Bell, James Andrew, and andrew bell@anu edu au. "The Underwater Piano: A Resonance Theory of Cochlear Mechanics." The Australian National University. Research School of Biological Sciences, 2006. http://thesis.anu.edu.au./public/adt-ANU20080706.141018.
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This thesis takes a fresh approach to cochlear mechanics. Over the last
quarter of a century, we have learnt that the cochlea is active and highly tuned,
observations suggesting that something may be resonating. Rather than accepting the standard traveling wave interpretation, here I investigate whether a resonance theory of some kind can be applied to this remarkable behaviour.¶
A historical survey of resonance theories is first conducted, and advantages
and drawbacks examined. A corresponding look at the traveling wave theory
includes a listing of its short-comings.¶
A new model of the cochlea is put forward that exhibits inherently high
tuning. The surface acoustic wave (SAW) model suggests that the three rows of outer hair cells (OHCs) interact in a similar way to the interdigital transducers of an
electronic SAW device. Analytic equations are developed to describe the conjectured interactions between rows of active OHCs in which each cell is treated as a point source of expanding wavefronts. Motion of a cell launches a wave that is sensed by the stereocilia of neighbouring cells, producing positive feedback. Numerical calculations confirm that this arrangement provides sharp tuning when the feedback gain is set just below oscillation threshold.¶
A major requirement of the SAW model is that the waves carrying the feedback have slow speed (5-200 mm/s) and high dispersion. A wave type with the
required properties is identified - a symmetric Lloyd-Redwood wave (or squirting wave) - and the physical properties of the organ of Corti are shown to well match those required by theory.¶
The squirting wave mechanism may provide a second filter for a primary
traveling wave stimulus, or stand-alone tuning in a pure resonance model. In both, cyclic activity of squirting waves leads to standing waves, and this provides a physical rendering of the cochlear amplifier.
In keeping with pure resonance, this thesis proposes that OHCs react to the
fast pressure wave rather than to bending of stereocilia induced by a traveling wave. Investigation of literature on OHC ultrastructure reveals anatomical features consistent with them being pressure detectors: they possess a cuticular pore (a small compliant spot in an otherwise rigid cell body) and a spherical body within (Hensens
body) that could be compressible. I conclude that OHCs are dual detectors, sensing displacement at high intensities and pressure at low. Thus, the conventional traveling wave could operate at high levels and resonance at levels dominated by the cochlear
amplifier. ¶
The latter picture accords with the description due to Gold (1987) that the cochlea is an underwater piano - a bank of strings that are highly tuned despite immersion in liquid.¶
An autocorrelation analysis of the distinctive outer hair cell geometry shows
trends that support the SAW model. In particular, it explains why maximum
distortion occurs at a ratio of the two primaries of about 1.2. This ratio also produces near-integer ratios in certain hair-cell alignments, suggesting that music may have a cochlear basis.¶
The thesis concludes with an evaluation and proposals to experimentally test
its validity.
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Green, Anna Catriona. "When light gets pushy : radiation pressure effects in interferometric gravitational wave detectors." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8512/.
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Advanced LIGO made the first direct observation of a gravitational wave in 2015. This signal, the largest measured so far, had a peak strain amplitude of 1 x 10-21 and frequency range 35-250 Hz. LIGO's sensitivity was achieved after decades of development. Suspended optics made from low-loss materials are employed in an optical configuration with multiple coupled cavities to increase the circulating power and shape the frequency response of the detector. This design results in radiation pressure that substantially alters the detector's behaviour. One challenging consequence is parametric instabilities, an unstable coupling between the optical field and mechanical resonances in the mirrors. My detailed investigations of parametric instabilities in both LIGO and ET, a planned next-generation detector, show that the severity of the instabilities depends on the complete optical configuration. With this model, an optimal operating point for LIGO can be determined and ET design choices can be weighed against potential instabilities. An 'optomechanical filter' has been proposed that uses radiation pressure to enhance the detector bandwidth. I test the analytical models against numerical simulations and outline an experimental research programme that will implement a trial filter.
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Charonko, John James. "A Nondimensional Scaling Parameter for Predicting Pressure Wave Reflection in Stented Arteries." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/31906.
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Coronary stents have become a very popular treatment for cardiovascular disease, historically the leading cause of death in the United States. Stents, while successful in the short term, are subject to high failure rates (up to 24% in the first six months) due to wall regrowth and clotting, probably due to a combination of abnormal mechanical stresses and disruption of the arterial blood flow.
The goal of this research was to develop recommendations concerning ways in which stent design might be improved, focusing on the problem of pressure wave reflections. A one-dimensional finite-difference model was developed to predict these reflections, and effects of variations in stent and vessel properties were examined, including stent stiffness, length, and compliance transition region, as well as vessel radius and wall thickness. The model was solved using a combination of Weighted Essentially Non-Oscillatory (WENO) and Runge-Kutta methods. Over 100 cases were tested. Results showed that reasonable variations in these parameters could induce changes in reflection magnitude of up to ±50%. It was also discovered that the relationship between each of these properties and the resulting wave reflection could be described simply, and the effect of all of them together could in fact be encompassed by a single non-dimensional parameter. This parameter was titled â Stent Authority,â and several variations were proposed. It is believed this parameter is a novel way of relating the energy imposed upon the arterial wall by the stent, to the fraction of the incident pressure energy which is reflected from the stented region.Master of Science
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Schilling, Jennifer K. "High Pressure Hydrodynamic Shock Wave Effects on Tenderness of Early Deboned Broiler Breasts." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/31010.
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Breast muscles that are deboned prior to 4 to 6 h postmortem are highly variable and lacking in tenderness. The poultry industry currently provides costly storage space for intact broiler breasts during this 4 to 6 h period. This thesis evaluates tenderization techniques that if effective could eliminate the need for this additional 4 to 6 h storage time. The first objective of this study was to determine a relationship between Warner-Bratzler shear values (WBS) (1 cm by 1cm, variable length strips) and consumer tenderness acceptability of broiler breasts. The breasts were divided into five groups based on their WBS values. Consumers were presented with one sample (1 cm by 1 cm by 2 cm strips) at a time and asked to report the acceptability of the sample's tenderness on a 9-point hedonic scale. Of the 62 panelists, 93.5 % found chicken breasts with WBS values from 2.1 to 3.1 kg to be acceptable. Only 83.9 % of the panelists found the extremely tender chicken breast to be acceptable (1.1 to 1.9 kg). The percentage of consumers that found the samples acceptable decreased as the WBS values increased beyond 3.1 kg (P<0.05).
The second objective determined the effects of high pressure hydrodynamic shockwave (HSW) on tenderness (48 h postmortem) of early-deboned (52 min postmortem) breasts treated 25 minutes after deboning (70 min postmortem) or treated after storage (24 hr postmortem) and compared to the corresponding non-treated companion breasts. The effect of HSW treatment on early-deboned treated 25 min after deboned broiler breasts was determined by the following methods. Live broiler chickens were obtained from a commercial poultry company and slaughtered according to commercial processing standards. The effect of HSW on early deboned stored broiler breast was examined by deboning broiler breasts 45 min postmortem and storing (4 C) for 24 h. One breast from each bird was treated with hydrodynamic shockwave, while the companion breast was used as a control. Packaged breasts were placed in the center of a 20.23 cm diameter cylinder which was vertically positioned in the bottom of a water-filled HSW hemishell tank (30.4 cm diameter) and a shockwave was produced by and a shockwave was produced by detonating 40 grams of molecular explosive in the water. Early deboned (ED) breasts stored 24 h before treatment (2.5 kg, WBS) were 42% more tender than the companion ED control breasts (4.3 kg, WBS). The HSW treated breasts would be acceptable to approximately 94 % of consumers. The ED control breasts would be acceptable to only 67.7% of consumers. Early deboned and treated 25 min after deboning breasts (5.0 kg) were not different in WBS from their companion ED control breasts (4.6 kg). Early-deboned breasts treated immediately may require higher pressure shockwaves or delayed treatment. The HSW process can overcome the problem with tenderness associated with early deboning if the breasts are processed after storage thereby providing processors with the option to debone earlier.
A third objective was to examine the effects of electrically produced shockwaves on early deboned broiler breasts and normally processed turkey breast. Broiler breasts were treated with one Pulse Firing Network (PFN) or two PFN and 45 % Energy. Breasts treated with one PFN were not different than controls. Broiler breasts exposed to two PFN were 22 % more tender and different from the controls. Turkey breast portions exposed to two PFN and 72% Energy were different (12 % lower WBS values) from the control breast portion. Electrically produced shockwaves can tenderize stored, early deboned chicken breasts and aged turkey breasts.Master of Science
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Ronningen, Theodore J. "Low temperature helium pressure broadening of HCN." Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1118153531.
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Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xiv, 218 p.; also includes graphics (some col.) Includes bibliographical references (p. 208-218). Available online via OhioLINK's ETD Center
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Anderås, Emil. "Advanced MEMS Pressure Sensors Operating in Fluids." Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-173182.
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Today’s MEMS technology allows manufacturing of miniaturized, low power sensors that sometimes exceeds the performance of conventional sensors. The pressure sensor market today is dominated by MEMS pressure sensors. In this thesis two different pressure sensor techniques are studied. The first concerns ways to improve the sensitivity in the most commonly occurring pressure sensor, namely such based on the piezoresistive technique. Since the giant piezoresistive effect was observed in silicon nanowires, it was assumed that a similar effect could be expected in nano-thin silicon films. However, it turned out that the conductivity was extremely sensitive to substrate bias and could therefore be controlled by varying the backside potential. Another important parameter was the resistivity time drift. Long time measurements showed a drastic variation in the resistance. Not even after several hours of measurement was steady state reached. The drift is explained by hole injection into the buried oxide as well as existence of mobile charges. The piezoresistive effect was studied and shown to be of the same magnitude as in bulk silicon. Later research has shown the existence of such an effect where the film thickness has to be less than around 20 nm. The second area that has been studied is the pressure sensitivity of in acoustic resonators. Aluminium nitride thin film plate acoustic resonators (FPAR) operating at the lowest-order symmetric (S0), the first-order asymmetric (A1) as well as the first-order symmetric (S1) Lamb modes have been theoretically and experimentally studied in a comparative manner. The S0 Lamb mode is identified as the most pressure sensitive FPAR mode. The theoretical predictions were found to be in good agreement with the experiments. Additionally, the Lamb modes have been tested for their sensitivities to mass loading and their ability to operate in liquids, where the S0 mode showed good results. Finally, the pressure sensitivity in aluminium nitride thin film bulk wave resonators employing c- and tilted c-axis texture has been studied. The c-axis tilted FBAR demonstrates a substantially higher pressure sensitivity compared to its c-axis oriented counterpart.
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Ögün, Celal Mohan [Verfasser]. "Surface wave driven molecular low pressure plasmas for general lighting / Celal Mohan Ögün." Karlsruhe : KIT Scientific Publishing, 2016. http://www.ksp.kit.edu.
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Wolters, G. "Characteristics of wave impact induced pressure pulse propagation into cracks of coastal structures." Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419521.
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Patel, Darshan Shyam. "A Real-Time Technique for the Correction of Invasive Blood Pressure Measurements using Counter Pressure." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1205764260.
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Boneau, Trent Christopher. "A wavenumber investigation of the correlation between surface and far field acoustic pressure." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/19436.
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Gillespie, Donald G. (Donald Gardner). "Evaluating shear wave velocity and pore pressure data from the seismic cone penetration test." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/30573.
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Recent developments in cone penetration testing have resulted in the addition of both pore pressure measurements and seismometers. The seismometers allow shear wave velocity testing to be performed at designated intervals. Both of these additions were researched to improve their application and interpretation.
The significant factors effecting the pore pressure generated during cone penetration tests are discussed. The importance of various factors is especially dependent upon permeability, strength, and stiffness. For all sands tested, pore pressures lower than static were recorded behind the tip and higher than static were recorded on the face of the cone. It is believed that the large compressive stresses on the cone face result in positive pore pressures. As the cone tip passes a soil element unloading and continued shearing generate pore pressures lower than static in all sands. The sign of this pore pressure (higher or lower than static) was therefore considered primarily a function of the test equipment.
Pore pressure response and the rate of dissipation of excess pore pressures were found useful in distinguishing fine granular soils and explaining soil stratigraphy. In cohesive soils the details of pore pressure measurement were found to be important only in stiff soils. Pore pressures at all measurement locations were found to increase with soil strength in soft to firm clays but may be negative of static in very stiff clays. Pore pressures behind the cone tip were often negative of static in stiff clays.
Measurement techniques were refined to improve the accuracy of downhole shear wave velocity measurements. Comparisons of downhole and crosshole measurements were made at three well documented sites validating the technique. At several sites it was found useful to consider the Gmax values determined from shear wave velocity and density to distinguish soil type. Gmax to cone resistance ratios were shown to vary systematically with cone resistance values in sands. A wide range in Gmax to cone resistance was observed in clays. The dependence of both cone penetration resistance and Gmax to increased stress level or overburden stress is discussed.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Harvey, Craig W. "Shear wave velocities of sulphide-bearing assemblages as determined from high-pressure laboratory measurements." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq24851.pdf.
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Tasneem, Nazia. "Study of wave shaping techniques of split Hopkinson pressure bar using finite element analysis." Thesis, Wichita State University, 2005. http://hdl.handle.net/10057/2341.
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The split Hopkinson pressure bar (SHPB) continues to be one of the most common methods of testing materials at high rates of strain. Elevated rates of strain, such as those found in impact and explosive applications, have been shown to induce phenomena such as strain hardening and phase transitions that can significantly affect the strength of most materials. Due to its relative simplicity and robustness, the SHPB remains one of the preferred platforms for evaluating mechanical properties of materials at rates of strain approaching 10 4 in/in-s (s -1 ). At the National Institute for Aviation Research (NIAR), research has been conducted to study the wave shaping techniques of SHPB using finite element analysis. The SHPB consists of two long, slender cylindrical bars, denoted input and output bars that "sandwich" a cylindrical test specimen. Utilizing a high-pressure gas gun, a third cylindrical steel bar, known as the striker bar, is fired at the input bar, causing a compressive stress wave to travel through the input bar to the input bar - test specimen interface. At this interface, a portion of the stress wave propagates through the test specimen while the remainder of the pulse reflects back through the input bar as a tensile stress wave.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.
Includes bibliographic references (leaves 78-81).
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Sasoh, A., T. Ohtani, and K. Mori. "Pressure Effect in a Shock-Wave–Plasma Interaction Induced by a Focused Laser Pulse." American Physical Society, 2006. http://hdl.handle.net/2237/8852.
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Hirose, Eiichi. "A study of angular instability due to radiation pressure in LIGO gravitational wave detector." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2008. http://wwwlib.umi.com/cr/syr/main.
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Chen, Chih-yang, and 陳志洋. "Wave Pressure Formula of Deepwater Breakwaters with Wave Overtopping." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/36676617062968772581.
Full textAbstract:
碩士國立成功大學
水利及海洋工程學系碩博士班
96
This study proposed a modified Goda’s wave pressure formula to investigate the characters of pressure in deepwater breakwater with wave overtopping by using Shiu’s (2003) irregular wave pressure experimental data in deeper relative depth. Then, according to experimental results, the comparison and discussion between present modified formula and Goda’s formula on wave pressure statistics, total wave pressure force and accuracy. From the overtopping wave pressure profile, the result shows that the wave pressure in 1/7 water depth without evidence shrink. At the aspect of wave pressure statistics and wave pressure force, present modified formula are more conformable with experiment than Goda’s formula, and Goda’s formula will overestimate the actual wave pressure force when overtopping. Present formula, Goda’s formula and Haung&Lee’s (1996) formula are more accurate than Sainflou’s (1928) formula and Yeh’s (2001) formula when calculation with the sliding factor. Come to the conclusion, present modified wave pressure formula can be suitable for calculation wave pressure in deepwater breakwaters with wave overtopping.
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Hsu, Yu-Hsiung, and 許裕雄. "Wave Pressure on Breakwater by Irregular Wave with Water Overtopping." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/43992632367639030660.
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碩士國立中興大學
土木工程學系
88
Estimating the quantity of wave overtopping is an essential part to seawall design. Most previous studies were only paid attention to the volume rate of wave overtopping. This paper investigated the effect of wave overtopping on the property of wave pressure on the composite breakwater by means of model experiments. This irregular wave type was Bretschneider-spectrum. Wave pressure was measured on the face of the breakwater at vertical and upright section. Through Kolmogorov-Smirnov goodness-of-fit to test experimental data, it reveals that Weibull function is a more suitable function to describe the probability distribution of wave pressure where still water level than log-normal and Rayleigh function. It was found from the experimental results that the wave pressure on the breakwater was reduced due to the wave overtopping, which was depended on the incident wave condition and the crest height of the breakwater above the still water level. Regression equation obtained in this study was useful for the water surface elevation and the crest height.
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Xu, Guo-Cheng, and 徐國城. "Effect of Wave Overtopping on Irregular Wave Pressure on Breakwaters." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/kuwx24.
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碩士國立成功大學
水利及海洋工程學系碩博士班
92
ABSTRACT The purpose of this study was to investigate effect of wave overtopping on irregular wave pressure on breakwaters. We carried out the overtopping experiments of breakwaters with different crown heights by using irregular waves. Then we compared the experimental results to discuss the relationship between the crown height and wave pressure. And we also compared the experimental results with Goda’s formula and Yeh’s (2001) formula with revise from Goda’s formula to discuss Yeh’s (2001) formula can be extends applied in irregular waves. The measurements reveal that the statistical values of total wave pressure due to effect of wave overtopping was reducible ranging 0％∼70％,comparing with the situation of non-overtopping wave upon breakwaters. The decreases in Hc/d、d/Ls and d’/d and increase in Ĥ/d will contribute to the decreases in the wave pressure force. The computation of Goda’s formula will overestimate the actual wave pressure force when wave overtopping. This overestimate wall more obvious when Ĥ/d was higher and d/Ls and Hc/d was lower, along with d’/d reduction, the ratio of overestimate regular meeting increases approximately 20%. Come to the conclusion, Yeh’s (2001) formula will comparatively conforms of the experiment results when wave overtopping. So, we can be extends applied the formula in irregular wave, and it is designing to be more economical and effectiveness.
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葉朝棋. "Effect of Wave Overtopping on Wave Pressure on Vertical Wall." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/51375509544393027060.
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碩士國立成功大學
水利及海洋工程學系
89
The purpose of this study is to investigate effect of wave overtopping on wave pressure on vertical wall. We carries out the overtopping expriments of vertical wall with different crown heights, by using regular waves. Then we compare the experimental results to discuss the relationship between the crown height and wave pressure. And we compare the experimental results with Sainflou’s and Goda’s formula to discuss whether the formulars can be applied in calculating the wave pressure on vertical wall, in the condition of wave overtopping. The results show, the wave pressure force due to the effect of wave overtopping was reducible ranging 0~45%, comparing with the situation of non-overtopping wave on vertical wall. The decreases in the ratio of the crown height to water depth, , and the ratio of the relative water depth, , will contribute to the decrease in the wave pressure force. The computations of Goda’s formula will overestimate the actual wave pressure force about 0 to 60%. A modified Goda’s wave presure formula has been proposed in this study to calculate wave pressure on vertical wall, in the condition of wave overtopping. And the modified Goda’s formula, which calculates the wave pressure force in wave overtopping, is better than Goda’s formula. Come to the conclusion, the modified Goda’s formula is more suitable for pratical design of vertical wall under the condition of wave overtopping.
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Lee, Wei-Ming, and 李偉銘. "Effect of Wave Overtopping on Wave Pressure on Composite Breakwaters." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/6tndfu.
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碩士國立成功大學
水利及海洋工程學系碩博士班
90
ABSTRACT The purpose of this study was to investigate effect of wave overtopping on wave pressure upon composite breakwaters. We carried out the overtopping expriments of composite breakwaters with different crown heights by using regular waves. Then we compared the experimental results to discuss the relationship between the crown height and wave pressure. And we also compared the experimental results with Sainflou’s and Goda’s formula to discuss whether the formulars can be applied in calculating the wave pressure upon composite breakwaters, in the condition of wave overtopping. In the end, we added the result of Yeh’s (2001) investigation on vertical walls to our conclusions. The measurements reveal that the total wave pressure due to effect of wave overtopping was reducible ranging 0~40%, comparing with the situation of non-overtopping wave upon composite breakwaters. The decreases in the ratio of the crown height to water depth, , and the ratio of the relative water depth, , will contribute to the decrease in the wave pressure force. The computations of Goda’s formula will overestimate the actual wave pressure force about 30% at the maximum for general design of breakwaters. A modified Goda’s wave presure formula can be used to calculate wave pressures reasonably on composite breakwaters for the condition of wave overtopping. And the modified Goda’s formula, which calculates the wave pressure force with wave overtopping, is better than Goda’s formula. Come to the conclusion, the modified Goda’s formula is suitable for practical design of composite breakwaters under the condition of wave overtopping.
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Hwang, Jia Shang, and 黃家祥. "Experimental Study on the Wave Pressure." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/90110742817656924156.
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Ho, Ming Shian, and 何明憲. "A Study of Transfer Function between Wave Height and Wave Pressure." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/25457062869467323490.
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Bang, Seunghoon. "Rarefaction wave interaction of pressure-gradient system." 2007. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-2162/index.html.
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楊嘉良. "The development of square pressure wave generator." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/64713661553425638282.
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碩士國立臺北科技大學
製造科技研究所
89
This thesis aims to design a technique for the manufacturing of the square pressure waves generator that can generate the square pressure signals to test the dynamic characteristics of the hydraulic system. The square pressure waves generator is composed of several components. The design and manufacture of the high-speed switch among them is the most important technique. The way of the continuous rotation of machine is used to be the principle of the on and off switch of the square pressure waves generator. The differential method is used to achieve the high frequency switch in order to replace the directional control valve that is composed of rotary and slide spools. During the real design and manufacture of the high-speed switch, we find that the function of the square pressure waves generator can be influenced by the important facts, such as surface roughness, clearance, the shape and dimensioning of the cannelure, pressure balance and lubrication. The square pressure waves generator is fabricated by the high-speed switch and other components. It is installed on the test platform and linked up with transmission equipment and driving motor. Thus, the whole square pressure waves generator has been completed with normal function. The test results in different frequency and pressure can achieve the anticipation, and can possess the good shape of the square pressure wave and the high frequency characteristics of 2000Hz. The main tasks of the study is to generate the square pressure wave signals up to the frequency of 2000 Hz in order to raise a direct, effective test equipment to find the dynamic characteristics of the hydraulic control system and can promote the system quality and increase the industrial competition.
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Gung, Shu-Sheng, and 龔書聖. "Numerical Analysis of Wave Pressure Transfer Function." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/m9246g.
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碩士國立成功大學
水利及海洋工程學系碩博士班
92
The purpose of this study is to co-operate with wave pressure data to analyze wave variety by Fourier approximation method, and derives pressure transfer function Kp; moreover, it probes relationships between transfer function Kp and each wave factor, and an empirical expression of the transfer function between wave height and wave pressure was obtained from these Kp data which is analyzed, then transform the experimental pressure spectrum into a transfer wave spectrum by the empirical expression, which is taken advantage of comparison with experimental wave spectrum to probe into the empirical expression how to apply to irregular wave. The study showed that the statement of the purpose of the study declares that wave height and Kp both must reach specific accuracy, and inaccuracy is getting smaller and smaller when depth of manometer diminishes. There both are obvious existing relationship between transfer function Kp and factors as wave height H、manometer depth z、water depth d and circle T , etc. The empirical expression of the study mentioned is that the parameter H/d、z/d、ω2|z|/g replaces chen (2002)ω2|H|/g、ω2|d|/g、ω2|z|/g, whose accuracy would heave effectively to put regular wave experiment data in use . And transfer wave spectrum coincide with experimental wave spectrum when it put irregular wave in use, and its irregular enlargement is more smaller when transfer wave spectrum is in high frequency , which showed that empirical expression of transfer function can agree with regular wave and irregular wave.
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曾健中. "Calculation For Wave Loads and Pressure Acting on a Ship in Waves." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/25764494013007082687.
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Chia-TzuChang and 張家嬨. "Transfer function between wave height and wave pressure or velocity of flow." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/53sa7b.
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碩士國立成功大學
水利及海洋工程學系
104
A series of ocean waves are generated by several regular waves of various sources. To understand the complex and irregular ocean phenomena, this research is based on regular waves. Modeling regular waves to laboratory experiments, and deal with experiment data onto four methods. These methods are transforming the wave pressure to wave height, transforming the wave pressure on velocity of flow, empirical correction formula and dimensional analysis. Base on the experiments with data, to investigate the relationships of wave pressure versus wave height and velocity of flow. The experimental results showed that the empirical correction coefficient N decreases to decreasing period, being greater than T=1(s) for gravity waves. Compare with Bergan, P.O. et al (1968) this research finds the period less than T=0.8(s) for short gravity waves, which it is not available used first-order linear theory to predict the wave pressure. The results showed that transforms function add velocity of flow item, the experimental wave height and theoretical wave height difference vary considerably. Even add velocity to the transform function, wave height still show inexact data onto the equation, and can’t predict surface water. This study directed applies to experiment with regular wave data, and used dimensional analysis to find the empirical correction formula. The results showed that the new empirical correction formula could apply to all regular wave experiments.
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Chiu, Yung-Fang, and 邱永芳. "Transfer function between wave height and wave pressure or water particle velocity." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/43263828926937874949.
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Liang, Cheng-Syu, and 梁呈旭. "The Double-crest Phenomenon of Wave Pressure In the Standing Wave Field." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/60582713579323972150.
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碩士國立中山大學
海洋環境及工程學系研究所
100
The real phenomena of sea surface are interacting by much kind of different waves.In these phenomena, the gravity standing wave is most important. The gravity standing wave is formed by two progressive waves that possessing same properties but opposite directions. Gravity standing wave can also form by the interaction of a progressive wave with it’s totally reflection wave. Because of the nonlinear interaction of two waves, there must result a double-crest phenomenon of wave pressure. It is dangerous for the navigation of ship when the double-crest appears, and it’s certainly to take the phenomenon into consideration when we are going to design a jetty. In this paper, it bases on the reference of Chen (1989, 1990) who obtained a third-order approximation of two-wave trains interactions in a uniform depth wave field. Further, in this paper, it checks the result that the double-crest phenomenon is formed by which one of these nonlinear terms. Furthermore, research the influences of wave steepness, wave periods, and water depths these factors will cause the crest diverges is also the purpose.
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Tseng, Chien-Kuei, and 曾建貴. "Wave-Induced Pore Pressure in Rubble Mound Breakwaters." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/59030392397870785120.
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Tang, Shih-Tse, and 唐世澤. "Water Surface Elevation Recovery from Wave Pressure Signals." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/32610434592276746584.
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碩士國立交通大學
土木工程學系
84
In the present study an empirical transfer function between the wave pressure and wave height,which was established by Kuo and Chiu(1994) ,was applied to predict the history signals of the free water surface elevation from the wave pressure beneath the still water level.The Fast Fourier Transform(FFT) method is used to calculate the power spectral and history signals of wave height.The FFT method is compared with LCM method developed by Nielsen(1986) in this paper.It is found that both of FFT method and LCM method are accurately calculated when the pressure gages are locatted near the still water level.However, when the distance between the pressure gage and the still water level is longer,the FFT method with the empirical transfer function is more efficient and accurate than the LCM method. Furtherwore,the present study has decided on the cutoff frequency range,the weak point of the power spectral analisis which was resolved in this paper. Furthermore,the present study used the physical model test to investigate the transfer function between the wave pressure and the wave height in shallow water. By the analysis from the experimental data, we can find the transfer function is concern with the wave frequency and pressure gage locations. In addition ,the transfer functions of each older nonlinear components seem to be the same.
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YOU, YU-ZHENG, and 游于正. "Experimental study on shock pressure by Yandom wave." Thesis, 1990. http://ndltd.ncl.edu.tw/handle/10249088979026188314.
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Chen, Sung-Hui, and 陳松輝. "Transfer Function between Surface Wave and Subsurface Pressure." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/86889653229720064854.
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碩士國立成功大學
水利及海洋工程學系碩博士班
91
The purpose of this study is to investigate how to transform the wave pressure to surface wave. Based on the experimental data, a pressure transfer function was developed. A comparison with the wave spectrum calculated by present result, linear pressure response function and Chiu et al. transfer function （1993） was carried out to evaluated the application of each transfer functions. The result of the study shows that the transfer function is related to the dimensionless parameterw^2|z|/g,w^2d/g and w^2H/g. It is different with the result of Chiu et al.（1993）. The spectrum obtained by linear pressure response function and Chiu et al.（1993）is underestimated at the short significant wave period, deep water and large significant wave height. The estimation of wave spectrum using the pressure transfer function of this study is more accurate and is not influence by the depth of the gauge.
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Lin, Yen-Chih, and 林彥志. "Dynamic Characteristic of Reciprocating Pressure Square-wave Generator." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/vsg8xn.
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碩士國立臺北科技大學
機電整合研究所
97
The dynamic characteristics of the hydraulic system are the key factor for detailed control. This study aims to investigate the dynamic characteristics of square wave which produce from a reciprocating pressure square wave generator (RPSWG). RPSWG consists of 3-way 2-position valve and a spool which excited by a solenoid to generate pressure square wave. Experimental parameters are hydraulic input pressure, frequency, back pressure, spool velocity, and chamber volume. A piezoelectric pressure sensor was used for measuring the dynamic pressure of hydraulic system through the Fourier Fast Transform analyzer. system identification obtained with MATLAB analyzing software. As a result, the hydraulic pressure increases cause the system instable. The higher operating frequency makes The shorter time of steady state to promote the velocity of response. The back pressure increases cause the overshot reduction and the rising time increase. The speed of spool is quicker then the transition state will be shorter. The chamber volume of pressure is smaller can reduce the period of transition state and increase the reaction rate.
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BenjaminTsai and 蔡潔忞. "Wave-Induced Pore Pressure Changes in Sandy Seabed." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/tn787k.
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Sutar, Pawan. "Numerical Simulation of Pressure Wave Supercharger with Pockets Operating at Different Speeds." Thesis, 2020. http://hdl.handle.net/1805/25882.
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Indiana University-Purdue University Indianapolis (IUPUI)Pressure wave supercharger is an application of wave rotor technology that utilizes compression waves produced by high-pressure engine exhaust gas to compress the fresh intake air within the channels. The phenomena within the wave rotor channels are governed by compression and expansion waves initiated when the channel ends are periodically exposed to differing pressure ports. Two incoming fluids are brought into contact for a very short amount of time to facilitate efficient energy and momentum transfer, thereby exchanging pressure dynamically between the fluids by means of unsteady pressure waves. Since the energy transfer is based on unsteady pressure waves, correct matching of waves and ports is essential for optimum results. Mistiming of the waves in the channels is detrimental to the efficient exchange of pressure and low-pressure exhaust scavenging, which ensures minimum exhaust gas recirculation. Due to varying speed and load conditions of the unit to be supercharged, it is not always possible to maintain the rotor speed constant at the design point. To mitigate the effects of wave mistiming due to varying speed, a well-designed combination of wall-pockets was used in Comprex® pressure wave supercharger. The wall-pockets are the recesses provided in the endplates of pressure wave superchargers to create necessary pressure zones at desired locations. This thesis details an extensive qualitative and computational investigation of the performance of pressure wave superchargers with pockets. Numerical simulations of pressure wave superchargers have been performed using the wave rotor analysis codes employed at the Combustion and Propulsion Research Laboratory at IUPUI. This work also pays close attention to inspecting the numerical schemes and modeling of different physical phenomena used in each code. A comparative verification of the wave rotor analysis codes has been conducted to ensure that the same fundamental numerical scheme is correctly implemented in each code. The issue of low-pressure scavenging has been demonstrated by simulating the four-port (pocketless) pressure wave supercharger operating at lower speeds. The wall-pockets have been modeled using a simple lumped volume technique. The gas state in the lumped volume of pockets is estimated using the continuity and energy equations such that the net mass and energy fluxes between each pocket and the wave rotor channels are close to zero. The lumped volume models of pockets have been implemented in the four-port wave rotor configurations to simulate the pressure wave superchargers with pockets. The simulation results show that the pockets assist to maintain sufficient pressure in the desired zones to facilitate proper low-pressure scavenging during lower rotor speed operations. The Comprex simulation results have been observed to be in good agreement with experimental data and qualitative analysis. Specific observations on the performance of each code and comprehensive simulation results have been presented.
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Wadzuk, Bridget Marie Hodges Ben R. "Hydrostatic and non-hydrostatic internal wave models." 2004. http://repositories.lib.utexas.edu/bitstream/handle/2152/1428/wadzukb05259.pdf.
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