Literatura académica sobre el tema "Rayleigh`s phase function"
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Artículos de revistas sobre el tema "Rayleigh`s phase function"
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Koroleva, Tat’iana. "Rayleigh wave velocity maps beneath the Caucasus from the Caucasus seismic network (CNET)". Russian Journal of Seismology 2, n.º 3 (30 de septiembre de 2020): 70–77. http://dx.doi.org/10.35540/2686-7907.2020.3.06.
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Ambient noise surface wave tomography is a widely used method for determining the velocity structure of the upper layers of the Earth. It is based on the fact that the cross-correlation function (CCF) of noise at two stations, averaged over a long time interval, determines the Green's function of the surface wave. This allows us to estimate the group and phase velocities of surface waves on the paths between stations. The method was applied to the records of the vertical components of 67 seismic stations of the Caucasian network CNET network, which were obtained during 2018. The cross-correlation functions for all interstation paths were calculated. The dispersion curves of group and phase Rayleigh velocities for periods from 5 to 30 s were obtained by means of frequency-time analysis. The lateral distribution of the velocities was received for periods from 7 to 22 s, which correlate with velocity structure at depths of 5-25 km. The group and phase velocity maps for Rayleigh wave for periods 7, 10, 12, 14, 17, 22 s are presented.
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Forbriger, Thomas, Lingli Gao, Peter Malischewsky, Matthias Ohrnberger y Yudi Pan. "A single Rayleigh mode may exist with multiple values of phase-velocity at one frequency". Geophysical Journal International 222, n.º 1 (17 de marzo de 2020): 582–94. http://dx.doi.org/10.1093/gji/ggaa123.
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SUMMARY Other than commonly assumed in seismology, the phase velocity of Rayleigh waves is not necessarily a single-valued function of frequency. In fact, a single Rayleigh mode can exist with three different values of phase velocity at one frequency. We demonstrate this for the first higher mode on a realistic shallow seismic structure of a homogeneous layer of unconsolidated sediments on top of a half-space of solid rock (LOH). In the case of LOH a significant contrast to the half-space is required to produce the phenomenon. In a simpler structure of a homogeneous layer with fixed (rigid) bottom (LFB) the phenomenon exists for values of Poisson’s ratio between 0.19 and 0.5 and is most pronounced for P-wave velocity being three times S-wave velocity (Poisson’s ratio of 0.4375). A pavement-like structure (PAV) of two layers on top of a half-space produces the multivaluedness for the fundamental mode. Programs for the computation of synthetic dispersion curves are prone to trouble in such cases. Many of them use mode-follower algorithms which loose track of the dispersion curve and miss the multivalued section. We show results for well established programs. Their inability to properly handle these cases might be one reason why the phenomenon of multivaluedness went unnoticed in seismological Rayleigh wave research for so long. For the very same reason methods of dispersion analysis must fail if they imply wave number kl(ω) for the lth Rayleigh mode to be a single-valued function of frequency ω. This applies in particular to deconvolution methods like phase-matched filters. We demonstrate that a slant-stack analysis fails in the multivalued section, while a Fourier–Bessel transformation captures the complete Rayleigh-wave signal. Waves of finite bandwidth in the multivalued section propagate with positive group-velocity and negative phase-velocity. Their eigenfunctions appear conventional and contain no conspicuous feature.
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Burns, P. y E. Meiburg. "Sediment-laden fresh water above salt water: nonlinear simulations". Journal of Fluid Mechanics 762 (27 de noviembre de 2014): 156–95. http://dx.doi.org/10.1017/jfm.2014.645.
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AbstractWhen a layer of particle-laden fresh water is placed above clear, saline water, both double-diffusive and Rayleigh–Taylor instabilities may arise. The present investigation extends the linear stability analysis of Burns & Meiburg (J. Fluid Mech., vol. 691, 2012, pp. 279–314) into the nonlinear regime, by means of two- and three-dimensional direct numerical simulations (DNS). The initial instability growth in the DNS is seen to be consistent with the dominant modes predicted by the linear stability analysis. The subsequent vigorous growth of individual fingers gives rise to a secondary instability, and eventually to the formation of intense plumes that become detached from the interfacial region. The simulations show that the presence of particles with a Stokes settling velocity modifies the traditional double-diffusive fingering by creating an unstable ‘nose region’ in the horizontally averaged profiles, located between the upward-moving salinity and the downward-moving sediment interface. The effective thickness $l_{s}$ ($l_{c}$) of the salinity (sediment) interface grows diffusively, as does the height $H$ of the nose region. The ratio $H/l_{s}$ initially grows and then plateaus, at a value that is determined by the balance between the flux of sediment into the rose region from above, the double-diffusive/Rayleigh–Taylor flux out of the nose region below, and the rate of sediment accumulation within the nose region. For small values of $H/l_{s}\leqslant O(0.1)$, double-diffusive fingering dominates, while for larger values $H/l_{s}\geqslant O(0.1)$ the sediment and salinity interfaces become increasingly separated in space and the dominant instability mode becomes Rayleigh–Taylor like. A scaling analysis based on the results of a parametric study indicates that $H/l_{s}$ is a linear function of a single dimensionless grouping that can be interpreted as the ratio of inflow and outflow of sediment into the nose region. The simulation results furthermore indicate that double-diffusive and Rayleigh–Taylor instability mechanisms cause the effective settling velocity of the sediment to scale with the overall buoyancy velocity of the system, which can be orders of magnitude larger than the Stokes settling velocity. While the power spectra of double-diffusive and Rayleigh–Taylor-dominated flows are qualitatively similar, the difference between flows dominated by fingering and leaking is clearly seen when analysing the spectral phase shift. For leaking-dominated flows a phase-locking mechanism is observed, which intensifies with time. Hence, the leaking mode can be interpreted as a fingering mode which has become phase-locked due to large-scale overturning events in the nose region, as a result of a Rayleigh–Taylor instability.
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Xia, Jianghai, Richard D. Miller y Choon B. Park. "Estimation of near‐surface shear‐wave velocity by inversion of Rayleigh waves". GEOPHYSICS 64, n.º 3 (mayo de 1999): 691–700. http://dx.doi.org/10.1190/1.1444578.
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The shear‐wave (S-wave) velocity of near‐surface materials (soil, rocks, pavement) and its effect on seismic‐wave propagation are of fundamental interest in many groundwater, engineering, and environmental studies. Rayleigh‐wave phase velocity of a layered‐earth model is a function of frequency and four groups of earth properties: P-wave velocity, S-wave velocity, density, and thickness of layers. Analysis of the Jacobian matrix provides a measure of dispersion‐curve sensitivity to earth properties. S-wave velocities are the dominant influence on a dispersion curve in a high‐frequency range (>5 Hz) followed by layer thickness. An iterative solution technique to the weighted equation proved very effective in the high‐frequency range when using the Levenberg‐Marquardt and singular‐value decomposition techniques. Convergence of the weighted solution is guaranteed through selection of the damping factor using the Levenberg‐Marquardt method. Synthetic examples demonstrated calculation efficiency and stability of inverse procedures. We verify our method using borehole S-wave velocity measurements.
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Zhang, Zhen-Dong y Tariq Alkhalifah. "Wave-equation Rayleigh-wave dispersion inversion using fundamental and higher modes". GEOPHYSICS 84, n.º 4 (1 de julio de 2019): EN57—EN65. http://dx.doi.org/10.1190/geo2018-0506.1.
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Recorded surface waves often provide reasonable estimates of the S-wave velocity in the near surface. However, existing algorithms are mainly based on the 1D layered-model assumption and require picking the dispersion curves either automatically or manually. We have developed a wave-equation-based inversion algorithm that inverts for S-wave velocities using fundamental and higher mode Rayleigh waves without picking an explicit dispersion curve. Our method aims to maximize the similarity of the phase velocity spectrum ([Formula: see text]) of the observed and predicted surface waves with all Rayleigh-wave modes (if they exist) included in the inversion. The [Formula: see text] spectrum is calculated using the linear Radon transform applied to a local similarity-based objective function; thus, we do not need to pick velocities in spectrum plots. As a result, the best match between the predicted and observed [Formula: see text] spectrum provides the optimal estimation of the S-wave velocity. We derive S-wave velocity updates using the adjoint-state method and solve the optimization problem using a limited-memory Broyden-Fletcher-Goldfarb-Shanno algorithm. Our method excels in cases in which the S-wave velocity has vertical reversals and lateral variations because we used all-modes dispersion, and it can suppress the local minimum problem often associated with full-waveform inversion applications. Synthetic and field examples are used to verify the effectiveness of our method.
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Hsu, Kai y Cengiz Esmersoy. "Parametric estimation of phase and group slownesses from sonic logging waveforms". GEOPHYSICS 57, n.º 8 (agosto de 1992): 978–85. http://dx.doi.org/10.1190/1.1443323.
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Sonic logging waveforms consist of a mixture of nondispersive waves, such as the P‐ and S‐headwaves, and dispersive waves, such as the Stoneley and pseudo‐Rayleigh waves in monopole logging and the flexural wave in dipole logging. Conventionally, slowness dispersion curves of various waves are estimated at each frequency, independent of data at other frequencies. This approach does not account for the fact that slowness dispersion functions in sonic logging are continuous and, in most cases, smooth functions of frequency. We describe a parametric slowness estimation method that uses this property by locally approximating the wavenumber of each wave as a linear function of frequency. This provides a parametric model for the phase and group slownesses of the waves propagating across the receiver array. The estimation of phase and group slownesses is then carried out by minimizing the squared difference between the predicted and observed waveforms. The minimization problem is nonlinear and is solved by an iterative algorithm. Examples using synthetic and field data are shown and the results are compared with those obtained by the conventional Prony method. Based on the comparison, we conclude that the parametric method is better than the conventional Prony method in providing robust and stable slowness estimates.
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Mokhtar, T. A., R. B. Herrmann y D. R. Russell. "Seismic velocity and Q model for the shallow structure of the Arabian shield from short‐period Rayleigh waves". GEOPHYSICS 53, n.º 11 (noviembre de 1988): 1379–87. http://dx.doi.org/10.1190/1.1442417.
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The shear velocity and [Formula: see text] structure for the upper 1 km in different tectonic regions of the Arabian shield have been investigated using high‐frequency vertical component records of Rayleigh waves (1–20 Hz), which were recorded at source‐to‐receiver separations 55–80 km during a deep seismic refraction survey. Group and phase velocities of the fundamental and first higher modes were inverted for the shear‐wave velocity structure; Rayleigh‐wave attenuation coefficients were determined from the decay of the amplitude spectrum of the fundamental mode and used to invert for the [Formula: see text] structure. Models derived from the data were tested by calculating synthetic seismograms for the fundamental and the first higher modes from surface‐wave theory with a center of compression used to represent the source; both band‐pass filtered step and Dirac delta source time functions were tested. Modeling indicates that the shear‐wave velocity of the shield increases from 2.6 km/s to 3.4 km/s in the upper 400 m of the crust. [Formula: see text] increases from 30 in the upper 50 m to 150 at 500 m depth. The underlying material has a [Formula: see text] of 400–500 for the out‐cropping igneous rocks such as granite and may reach values higher than 700 for the metamorphic green schist rock. A band‐pass filtered Dirac delta source time function produces the synthetic that is the best fit with observations.
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Hobiger, Manuel, Paolo Bergamo, Walter Imperatori, Francesco Panzera, Agostiny Marrios Lontsi, Vincent Perron, Clotaire Michel, Jan Burjánek y Donat Fäh. "Site Characterization of Swiss Strong-Motion Stations: The Benefit of Advanced Processing Algorithms". Bulletin of the Seismological Society of America 111, n.º 4 (8 de junio de 2021): 1713–39. http://dx.doi.org/10.1785/0120200316.
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ABSTRACT Since 2009, 91 new strong-motion stations were built for the renewal of the Swiss Strong Motion Network. Another nine stations will be installed until 2022. For each new station, an extensive site characterization study is performed to model the 1D seismic-velocity profile and, for some sites, the liquefaction potential. Geophysical (passive and active surface-wave methods) and geotechnical cone penetration test (CPT) with additional pore-pressure measurement (CPTu) and seismic CPT (SCPT) methods are used. Analyzing the passive and active recordings with a variety of established and advanced methods, the fundamental frequency of the site, the polarization of the wavefield, the Love- and Rayleigh-wave phase-velocity dispersion curves, and the Rayleigh-wave ellipticity function are retrieved. The liquefaction potential is assessed using CPTu. SCPT measurements are sometimes used to determine the shallow underground structure. The benefits of the combination of different appropriate methods are shown for two examples—the borehole station SBUS in Buochs and the upcoming borehole station SCME in Collombey-Muraz. At both the sites, the CPTu measurements show an elevated liquefaction potential. Combining the passive and active data, the dispersion curves for Love and Rayleigh waves and Rayleigh-wave ellipticity curves are retrieved over a wide-frequency range and inverted for the S-wave velocity profile, in which the shallow part is constrained by the active or SCPT data, the intermediate part by the dispersion curves of the passive methods, and the deepest part by the ellipticity information. For Buochs, the 1D SH-wave amplification functions modeled for the velocity profiles are compared with the empirical amplification for earthquake recordings. Finally, an overview of the site characterization results for 52 of the newly installed seismic stations is given.
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MIURA, Hiroyuki, Atsuko MATSUO, Tatsuo KANNO, Michiko SHIGEFUJI y Tetsuo ABIRU. "Estimation of S-Wave Velocity Structure Model by Joint Inversion of Site Amplification, Receiver Function and Phase Velocity of Rayleigh Wave". Journal of JAEE 17, n.º 5 (2017): 5_78–5_95. http://dx.doi.org/10.5610/jaee.17.5_78.
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Asten, Michael W., William J. Stephenson y Stephen Hartzell. "Spatially averaged coherencies (krSPAC) and Rayleigh effective-mode modeling of microtremor data from asymmetric arrays". GEOPHYSICS 84, n.º 3 (1 de mayo de 2019): EN47—EN56. http://dx.doi.org/10.1190/geo2018-0524.1.
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The spatial autocorrelation and spatially averaged coherency (SPAC) methods of processing Rayleigh-wave microtremor noise observations for estimation of S-wave velocity profiles traditionally require a circular or triangular array symmetry to allow spatial (azimuthal) averaging of interstation coherencies over a constant station separation. Common processing methods allow for station separations to vary by typically [Formula: see text] in the azimuthal averaging before degradation of the SPAC spectrum is excessive. Transformation of a set of frequency-coherency spectra to wavenumber-coherency spectra (kr spectra) allows spatial averaging of spectra from multiple pairs of sensors irrespective of differences in spatial separation of the pairs. The method is called krSPAC and is implemented by iterative direct fitting of observed and model kr spectra to determine an optimal layered-earth S-wave velocity model. The observed kr spectra are updated with each iteration of the velocity model because the wavenumber is a function of model phase velocity that varies with each iteration of the modeling process. The method proves applicable when modeling either with the assumption of fundamental mode Rayleigh-wave propagation or with a summation of fundamental and higher modes. The method proves robust when compared with alternative methodologies using symmetric and asymmetric arrays on a sample of synthetic data and on field data in which station spacings vary from 70 to 800 m side lengths.
Tesis sobre el tema "Rayleigh`s phase function"
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Can, Geylani. "S-phase checkpoint activity and function throughout the cell cycle". Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/268506.
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DNA damage or replication stress during S-phase can activate the S-phase checkpoint which executes a variety of responses, such as the inhibition of origin firing and replication fork stabilisation. Deregulation of the S-phase checkpoint leads to genomic instability, which has been implicated in diseases such as cancer. In this thesis, I aimed to address whether the S-phase checkpoint is regulated outside of S-phase, and how the S-phase checkpoint targets its substrates in budding yeast. Although this checkpoint has thus far been associated exclusively with S-phase, it remains unknown whether its responses such as inhibition of origin firing can also occur in other phases of the cell cycle. To investigate this, the targets of the S-phase checkpoint for the inhibition of origin firing were analysed outside of S-phase upon DNA damage. Interestingly, I showed that the S-phase checkpoint effector kinase Rad53 phosphorylates its targets to inhibit origin firing outside of S-phase upon DNA damage when there is no replication. I then set out to test whether inhibition of origin firing by Rad53 outside of S-phase might be important for faithful DNA replication. Having shown that the checkpoint response is not specific for any cell cycle phases, I then tested how the specificity of Rad53 for its substrates might be determined. After demonstrating that the essential replication protein Cdc45 is required for Rad53 to phosphorylate the initiation factor Sld3, the key residues of Cdc45 necessary for Rad53 interaction were identified. A Cdc45 allele was produced by mutating the identified residues. This allele of Cdc45 is a separation-of-function mutant which prevents Sld3 phosphorylation upon DNA damage, but retains its function in DNA replication. Because Cdc45 travels with the replication fork, it is possible that Cdc45 also targets Rad53 to the replication fork to stabilise it upon replication stress. Overall, this thesis provides evidence that the S-phase checkpoint can function throughout the cell cycle and that Cdc45 targets Rad53 to some of its substrates, and possibly plays a role in replication fork stabilisation.
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Balkew, Teshome Mogessie. "The SIR Model When S(t) is a Multi-Exponential Function". Digital Commons @ East Tennessee State University, 2010. https://dc.etsu.edu/etd/1747.
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The SIR can be expressed either as a system of nonlinear ordinary differential equations or as a nonlinear Volterra integral equation. In general, neither of these can be solved in closed form. In this thesis, it is shown that if we assume S(t) is a finite multi-exponential, i.e. function of the form S(t) = a+ ∑nk=1 rke-σkt or a logistic function which is an infinite-multi-exponential, i.e. function of the form S(t) = c + a/b+ewt, then we can have closed form solution. Also we will formulate a method to determine R0 the basic reproductive rate of an infection.
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Petojević, Tatjana [Verfasser]. "Activation of the Mcm2-7 helicase function by ancillary replication factors GINS and Cdc45 : The switch to S phase / Tatjana Petojevic". Berlin : Freie Universität Berlin, 2013. http://d-nb.info/1038211506/34.
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Lotfalizadeh, Behnood. "Modeling and Simulation of a Three-phase AC-DC Converter where the Impedances of the Feeding Lines are considered". Thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-32328.
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This thesis comprises modeling and simulation of an AC-DC converter (Battery charger). An AC-DC converter may cause a high frequency distortion in the electrical power network or augment the existing distortion caused by other devices connected to the network. The goal is to design a controller for suppressing this noise at a reasonable level. We hope the thesis can be considered as a step forward to solve the original problem. One needs an accurate model of the AC-DC converter, to design such a controller. This study tries to clarify the effects of theline inductance on the performance of the converter by modeling and simulating the converter during the commutation time. The idea is to model and simulate the converter for two different conditions; first in the Normal condition by neglecting the effect of line impedance, second in the Commutation condition by considering the effect of the line impedance on commutation of the diodes. One can perform a complete simulation of the converter with combining these two models. The thesis deals with AC-DC converters, Hamiltonian-port modeling, simulation and MATLAB programming using the functionality of the S-function and SIMULINK.
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Borsali, Redouane. "Etude theorique du comportement dynamique des melanges ternaires de polymere en solution : etude experimentale par spectroscopie rayleigh quasi-elastique". Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13138.
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L'etude d'un melange ternaire de polymeres en solution semidiluee presente deux modes de relaxation. Mise en evidence par diffusion de lumiere quasi-elastique de deux processus de diffusion: le premier, lent, correspond au mouvement relatif des deux polymeres; le second, rapide, correspond au mouvement cooperatif du reseau physique forme par les deux polymeres
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Šalda, Zbyněk. "Ukázky regulací s prediktivním řízením". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232182.
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This thesis deals with model predictive control principally Based Predictive Control (MPC). The first part describes the principle of predictive control, cost function, the choice of a constraints in regulation and the choice of weights. In the next section is an analysis system: a system with non-minimal phase (control water turbine), oscillating systems (trolley frame control) and system with a time-delay . In all of these systems is performed classical feedback control using PID control and concurrently regulation with the MPC. MPC is selected as the solution fy Mathworks Model Predictive Control Toolbox and Simulink. The results are then analyzed using the criteria of quality control.
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Štaffa, Jiří. "Ztráty jednofázového asynchronního motoru s trvale připojeným kondenzátorem". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-221263.
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This project deals with increasing efficiency of one phase induction motor with permanent split capacitor. We can whole thesis divide into two parts, the first one is basic and the second is interested in analysis and measurement. First part handles with construction of single phase induction motor, explanation of function principle, start and run of motor. Calculating of efficiency including type of losses, which reduce efficiency. Second part concerns analysis losses including moment load characteristic, motor measurement while rotor is locked, with no load operation, measuring mechanical and additional losses. Further there will be measured useful values for creation model for simulation (reactance of windings etc.). Than will be the model created in ANSYS Maxwell with module RMxprt. After analytic calculation in RMxprt and using Finite Element Method (FEM) load characteristics will be compared together. This comparison gives us information about accuracy of model for simulation. Simulation and measurement will be carried out on another engine with high quality ferromagnetic material used for magnetic circuit of motor. Further will be done simulation of motor with modifications shown in previous chapter for high efficiency.
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KELNER, SYLVIE. "Etude de la propagation des ondes sismiques dans les milieux fissurés : atténuation, anisotropie et migration de fluide induite par un séisme". Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10284.
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La diffraction des ondes sismiques par des milieux fissures en deux dimensions (2d) est etudiee par une methode d'equations integrales aux frontieres ou les fonctions de green sont calculees par la methode des nombres d'ondes discrets (dwbiem : discrete wavenumber boundary integral equations method). Cette methode semi-analytique est particulierement bien adaptee aux problemes de la propagation des ondes sismiques dans un milieu homogene contenant des fissures vides ou remplies de fluide. Toutes les conversions d'ondes sont modelisees en appliquant la dwbiem. En premier lieu, nous avons etudie, par simulations numeriques, comment des milieux fissures pouvaient etre caracterises sismiquement. Nous avons ainsi pu observer des phenomenes d'attenuation et d'anisotropie, selon que la longueur d'onde du champ d'ondes incident est du meme ordre de grandeur ou qu'elle est plus grande que la longueur des fissures. Nous avons retrouve un resultat deja connu qui concerne l'attenuation des ondes elastiques lorsqu'elles traversent un milieu fissure : l'attenuation est maximale lorsque la longueur d'onde incidente est proche de la longueur des fissures. Par ailleurs, nous avons modelise la couche de granite fissuree du site de garner valley, en californie, en nous basant sur la theorie des milieux homogenes equivalents. Plusieurs modeles de milieux fissures restituent bien le taux d'anisotropie observe a garner valley. Une etude comparative de l'attenuation d'ondes s enregistrees la-bas et d'ondes s synthetiques permet de conclure que l'anisotropie s'explique par la presence de fissures verticales (et non horizontales) mais ne permet pas de privilegier un modele plus qu'un autre. Enfin, nous avons simule numeriquement la reponse hydro-mecanique d'un massif fracture a un seisme. Les deformations des fissures et les variations de pression dues au champ d'ondes rayonne par une faille en glissement permettent de connaitre les zones d'expulsion de fluide.
Libros sobre el tema "Rayleigh`s phase function"
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Fung, Amy D. A novel function of the S phase regulator Dfp1. Ottawa: National Library of Canada, 2002.
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Chance, Kelly y Randall V. Martin. Atmospheric Scattering. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780199662104.003.0007.
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This chapter describes elastic scattering events, where the wavelength of the scattered light is unchanged from that of the incident light and conservative scattering, scattering without absorption, sometimes closely approximated in clouds. The scattering regime, scattering versus wavelengths and scatterer size are introduced. Polarization in scattering is described by the Stokes vector and the polarization ellipse. Molecular (Rayleigh) scattering is presented and its atmospherically-important inelastic component, Raman scattering (the Ring effect) quantified. Mie scattering for spherical particles is described as is the commonly-used Henyey-Greenstein Mie phase function approximation. Non-spherical scatterers are introduced. The Ångstrom exponent and the expansion of phase functions in Legendre polynomials are described.
Capítulos de libros sobre el tema "Rayleigh`s phase function"
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Adler, Stephen L. "Stationary State Methods and Phase Methods". En Ouaternionic Quantum Mechanics and Ouanturn Fields, 124–58. Oxford University PressNew York, NY, 1995. http://dx.doi.org/10.1093/oso/9780195066432.003.0005.
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Abstract In this chapter we discuss a number of methods for handling stationary state problems in quaternionic quantum mechanics and then consider more generally methods in which the phase of the wave function plays a primary role. We first describe exact methods for reducing the anti Hermitian quaternionic Hamiltonian H to a complex Hermitian Hamiltonian H for an equivalent complex quantum mechanics problem. We then develop stationary state perturbation theory, and as an application compute the leading approximation to the Hamiltonian phase operator I H. We also give a quaternionic analog of the Rayleigh-Ritz variational principle. We proceed next to an extended discussion of the geometric phase in quaternionic quantum mechanics, in both the adiabatic and the nonadiabatic cases. Finally, we give the quaternionic generalization of the eikonal or WKB approximation.
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Negi, Seema, S. B. Singh y Kamlesh Bisht. "Fuzzy Reliability of Weighted-((f / (r, s)), k)/ (m, n) G System". En Advances in Systems Analysis, Software Engineering, and High Performance Computing, 20–42. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-7564-2.ch002.
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In this chapter, the authors study a weighted-((f / (r, s)), k)/ (m, n): G system. The system consists of mn components arranged in a matrix form and the system works if all the sub matrices of order (r, s), the total weight of the working components is greater than f and the total weight of the working components in the system is at least k. This chapter deals with the evaluation of fuzzy reliability and fuzzy mean time to failure of the considered system with the application of fuzzy universal generating function and fuzzy Rayleigh distribution. In this study, the authors formed some prepositions to understand the behaviour of the considered system with respect to different varying parameters and also present an illustrative example to understand them.
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Reed, Steven I. "Start and the Gl-S phase transition in budding yeast". En Cell Cycle Control, 40–62. Oxford University PressOxford, 1995. http://dx.doi.org/10.1093/oso/9780199634118.003.0003.
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Abstract Mechanisms to ensure that division occurs in a coordinated and regulated fashion are prerequisite for fitness and ultimately for viability of all cells. This means that the division process must be responsive to a host of internal and external signals that mediate, among other things, integration of division with the extracellular milieu, coordination of division with cellular growth and the occurrence of cell cycle events in the proper order. In the budding yeast, Saccharomyces cerevisiae,both the regulation of division by external signals and the coordination of growth and division occur in the Gl interval of the cell cycle (1). Operationally, there are two types of signal that severely restrain division in Gl in this organism: nutritional limitations (2–13) and the action of mating hormones (4, 14-22). Although the regulatory intents of these signals are quite disparate, each causes a cell cycle arrest characterized by completion of the ongoing cell cycle and arrest in the subsequent Gl interval (1). Additionally, changes in the cellular growth rate are coordinated with the division process to ensure a relatively constant cell size by altering specifically the length of the Gl interval: slow growth is accommodated by extending the length of Gl while rapid growth shortens Gl (5, 23–38). These observations led to the hypothesis of a universal Gl control mechanism in yeast (1). In its simplest formulation, this hypothesis states that all signals governing passage through Gl and entry in S phase do so by regulating the completion of an essential Gl function or event designated START; completion of START commits a cell to S phase and division; delay of completion of START delays entry into S phase; failure to complete START prevents initiation of S phase and imposes alternative fates upon cells.
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Berber, Stevan. "Transforms of Deterministic Continuous-Time Signals". En Discrete Communication Systems, 599–673. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198860792.003.0012.
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Chapter 12 presents a detailed analysis of continuous-time signals and systems in the frequency domain, including the theory of Fourier series and Fourier transforms, and key examples relevant for the analysis and synthesis of signals processed in the digital transceiver blocks of a communication system. The amplitude, magnitude, phase, and power spectra are defined and calculated for typical signals. In particular, the Fourier transform of periodic signals is presented, due to its importance in communication systems theory and practice. Using a unique notation that distinguishes energy and power signals, the correlation, power, and energy spectral density functions are inter-related by proving the Wiener–Khintchine theorem. A comprehensive analysis of a linear-time-invariant system, using the concepts of impulse response, system correlation function, and power spectral density, both for power signals and energy signals, is presented. In addition, Parseval’s theorem and the Rayleigh theorem are proven.
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P. Dzyuba, Vladimir y Roman Romashko. "Green’s Function Method for Electromagnetic and Acoustic Fields in Arbitrarily Inhomogeneous Media". En Perturbation Theory [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.94852.
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An analytical method based on the Green\'s function for describing the electromagnetic field, scalar-vector and phase characteristics of the acoustic field in a stationary isotropic and arbitrarily inhomogeneous medium is proposed. The method uses, in the case of an electromagnetic field, the wave equation proposed by the author for the electric vector of the electromagnetic field, which is valid for dielectric and magnetic inhomogeneous media with conductivity. In the case of an acoustic field, the author uses the wave equation proposed by the author for the particle velocity vector and the well-known equation for acoustic pressure in an inhomogeneous stationary medium. The approach used allows one to reduce the problem of solving differential wave equations in an arbitrarily inhomogeneous medium to the problem of taking an integral.
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Lee, Christine U. y James F. Glockner. "Case 3.26". En Mayo Clinic Body MRI Case Review, editado por Christine U. Lee y James F. Glockner, 184–85. Oxford University Press, 2014. http://dx.doi.org/10.1093/med/9780199915705.003.0096.
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52-year-old woman with abdominal discomfort and abnormal results on liver function tests Axial fat-suppressed FSE T2-weighted image (Figure 3.26.1) and diffusion-weighted image (b=600 s/mm2) (Figure 3.26.2) reveal a large mass with increased signal intensity partially surrounding the right hepatic vein and inferior vena cava. Axial arterial, portal venous, and equilibrium phase postgadolinium 3D SPGR images (...
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Jacobs, Jonathan B. y Louis F. Dell’osso. "Extension of the eXpanded Nystagmus Acuity Function to Vertical and Multiplanar Data". En Advances in Understanding Mechanisms and Treatment of Infantile Forms of Nystagmus, 143–46. Oxford University PressNew York, NY, 2008. http://dx.doi.org/10.1093/oso/9780195342185.003.0018.
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Abstract The original eXpanded Nystagmus Acuity Function (NAFX),which was based on the Nystagmus Acuity Function (NAF), is a mathematically derived relationship that relates visual acuity to the attempts at foveation that occur within nystagmus waveforms, based on the duration and cycle-to-cycle stability of these foveation periods. In the original function, the foveation window was defined as the times at which the target was within ±0.5° of the fovea and not moving faster than ±4.0 deg/s with respect to it. However, there are many patients who could not meet these criteria, so their nystagmus could not be analyzed by the NAF, prompting the development of the NAFX, which allows for larger foveation windows (up to ±6° by ±10 deg/s) by varying i, the foveation duration constant. The collection of , for all combinations of position and velocity limits is called the “tau surface,” and is shown in Figure 18.1A. While the shape does, in general, appear to be regular, there are obvious irregularities in the surface, most notably along the lower position values (left side of Fig. 18.1A). This was a consequence of some of the data that were used to generate the original surface: the “pseudopendular with foveating saccades” (PPfs) waveform has two saccades per cycle, and as the position limit was increased, the slow phase following the braking saccade was included in the calculation, inadvertently increasing the measured foveation time.
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Foiani, Marco, Giordano Liberi, Simonetta Piatti y Paolo Plevani. "Saccharomyces cerevisiae as a model system to study DNA replication". En Eukaryotic DNA Replication, 185–200. Oxford University PressOxford, 1999. http://dx.doi.org/10.1093/oso/9780199636815.003.0008.
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Abstract The budding yeast Saccharomyces cerevisiae represents a powerful tool to study DNA replication and the cell cycle regulatory pathways controlling entry into, and progression through S phase. In fact, the availability of the complete sequence of the S. cerevisiae genome, the identification of several DNA replication genes, together with the possibility of combining molecular genetic tools with classical techniques of genetics, biochemistry, and cell biology, make this system particularly useful to improve our knowledge of the DNA replication process at the molecular level. Moreover, by considering that the structure and function of most of the replication proteins and the regulatory circuits connecting DNA replication to other cell cycle events have been highly conserved during evolution, the information obtained using the S. cerevisiae or the S. pombe systems can be generally extended to other eukaryotic cells.
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Goody, R. M. y Y. L. Yung. "Radiative Transfer in a Scattering Atmosphere". En Atmospheric Radiation. Oxford University Press, 1989. http://dx.doi.org/10.1093/oso/9780195051346.003.0010.
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The source function for scattering, (2.32), is more complicated than a thermal source function on two accounts: it is not a function of local conditions alone, but involves conditions throughout the atmosphere, through the local radiation field, and the phase function, Pij(s, d), may be an extremely complex function of the directions, s and d, and the states of polarization, i and j. The general solution, (2.87), is still valid, but it is now an integral equation, involving the intensity both on the left-hand side and under the integral on the right-hand side. Successive approximations, starting with the first-order scattering term [third term on the right-hand side of (2.116)], are an obvious approach, and would lead to a solution, but there are more efficient and more accurate ways to solve the problem. Many methods are available because their fundamental theory has proved to be mathematically interesting and because there are important applications in neutron diffusion theory and astrophysics. These motivations are extraneous to atmospheric science, but the availability of the methodology has led to its adoption and extension to atmospheric problems. Many methods are available because their fundamental theory has proved to be mathematically interesting and because there are important applications in neutron diffusion theory and astrophysics. These motivations are extraneous to atmospheric science, but the availability of the methodology has led to its adoption and extension to atmospheric problems. Solutions to scattering problems can be elaborate and mathematically elegant; they can also be numerically onerous but, with access to modern computers, “exact” solutions are feasible, given the input parameters τv, av (=sv/ev), and Pi j. For monochromatic calculations with simple phase functions, numerical solutions present few difficulties. Nevertheless, the combination of unfamiliar formalism with inaccessible and undocumented algorithms can be daunting for those with only a peripheral interest in radiation calculations. It is, therefore, relevant to note that available data are imprecise and virtually never require the accuracy available from exact methods. Easily visualized two-stream approximations, combined with similarity relations to handle complex phase functions (see §§8.4.4 and 8.5.6), are often more than adequate, and some angular information can be added, if required, from the use of Eddington’s second approximation (§ 2.4.5).
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Rauch, Helmut y Samuel A. Werner. "Solid state physics applications". En Neutron Interferometry, 278–93. Oxford University PressOxford, 2000. http://dx.doi.org/10.1093/oso/9780198500278.003.0009.
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Abstract Most neutron interferometric experiments carried out until now have dealt with fundamental physics applications, but it was known from the beginning that the interferometric method could also open new horizons for solid state physics research. Samples with density or magnetic fluctuations or decomposition effects cause inhomogeneous phase shifts, which cause a measurable loss of contrast of the interference pattern. Such experiments give complementary information to small-angle, critical, and depolarization experiments (Rauch and Seidl 1987). Phase tomography with neutrons can be realized, which permits inspection of materials without absorbing or scattering neutrons at the object. By measuring the neutron coherence function (Section 4.2), one gets direct access to the correlation functions G(r, t) of condensed matter instead of measuring its Fourier transform S(Q,w) by spectroscopic methods. Various examples of related investigations will be discussed together with their future perspectives. The essentials of future neutron Fourier spectroscopy are formulated.
Actas de conferencias sobre el tema "Rayleigh`s phase function"
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Basak, Souvik y Nabanita Datta. "Monopile Depth Sizing of Fixed Offshore Wind Turbines on Indian Territorial Waters: Dynamic Analysis of Towers Under Wind and Ocean Loads". En ASME 2023 42nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/omae2023-104337.
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Abstract A semi-analytical dynamic analysis of the monopile tower of an offshore wind turbine is presented. The linearly tapered, hollow, steel tower (with circular cross-section) is modeled as a Euler-Bernoulli cantilever beam with a tip mass, which is partially submerged in water, and partially embedded in the sea-bed as a monopile. The total tower length depends on the water depth at the location, the blade length, and the soil characteristics. The blade length, and hence, the swept area also influences the power captured (rated power) and hence, the nacelle (machinery) weight, which acts as a vertical compressive load on the tower. First, the tower is analyzed for its natural frequencies, which depends on several design parameters: tower geometry, tip mass, the depth of submergence, and depth of the monopile. A parametric study of free vibration is done for the tip mass, depth of submergence in water, and the depth of soil embedment. The tip mass adds to the kinetic inertia and the compressive load, decreasing the natural frequencies. The “added mass” or fluid inertia of the surrounding water (fluid radiation pressure in phase with the flexural acceleration) reduces the natural frequencies. The soil around the embedded monopile is modeled as a distribution of parallel translational springs, which restricts the horizontal motion and increases the natural frequencies. The variation of these frequencies, generated by the energy-based Rayleigh-Ritz method in MATLAB, are analyzed as a function of these parameters, to draw and optimize guidelines for structural design. The non-uniform beam mode-shapes are also generated by the weighted superposition of the admissible function (uniform cantilever beam mode shapes). This is followed by the quantification of the various loads: (i) Wind loads (constant load, turbulence, gust, and vortex-shedding), and (ii) ocean loads (current, waves, and vortex-shedding). First, the quasi-static responses (to the steady wind and ocean current loads) are analyzed to generate the quasi-static stresses. This is followed by the frequency domain analysis for the response to and random waves (Pierson-Moskowitz spectrum). Using the normal mode superposition principle, the dynamic stress amplitudes are generated to establish the safety factors. The depth of the monopile is optimized to withstand the maximum stresses, and also to avoid resonance with the dynamic loads. Since India has started looking into the expansion of the nascent offshore wind industry, a case study is done for a promising location on the Indian Territorial waters. The Gulf of Kutch (off the coast of Gujarat) has a strong wind potential. The location (22.5 N, 70 E), which is north of the industrial city of Jamnagar, is chosen for this study of the optimization of the monopile depth. The average wind speed here is about 6.5 m/s, which gives a design wind speed of about 9 m/s, at 50 m agl. For a 1 MW rated power of one offshore wind turbine, the blade radius is 40 m, requiring a dry tower height of about 80 m. The water depth in the Gulf of Kutch is about 30 m, and the sub-sea soil is rocky. The current speed in this region is a maximum of about 0.8 m/s in the SW monsoon season. Considering all of this, the monopile depth optimization process is detailed and design recommendations are given.
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Awasthi, Amit, Stephen Mckeown, C. Sahay y Bahgat Sammakia. "Selection of Method for Fatigue Life Prediction Under Random Loading". En ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/epp-24738.
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Abstract Solder fatigue continues to be one the primary reliability concerns in electronic packages. Three basic factors are necessary to cause fatigue failure. These are (i) a stress of sufficiently high value, (ii) varying amplitude stress, and (iii) a number of cycles of applied stress. Fatigue failure of a solder joint may also occur under cyclic thermal loading. The goal of this project is to compare the experimental results of fatigue testing with the various theoretical approaches (Rainflow counting method, Steinberg’s 3 band approach, and Rayleigh’s method) and come up with a formulation that would predict solder fatigue failure under random vibration loading. Experiments have been performed to collect data. Initially various components having frequency range from 20–2000Hz were combined at random phase to produce a random profile. Rainflow cycle counting was done on 125 random profiles using an algorithm developed by downing (1982). The basic assumption made in this algorithm is that the strain-time history starts with either the maximum peak or the minimum valley. Further each cycle was segregated into one of the three bands depending on the value of the range of the cycle. It was found that the results matched very closely with Gaussian distribution curve. The first phase of testing was to observe the behavior of aluminum and soldered copper (forming a lap joint) specimens under completely reversed sinusoidal loading in order to evaluate S-N curve. Three different stress levels were chosen and all experiments were carried out at a frequency of 20Hz. The second phase of testing consisted of observing the behavior of both the samples under semi-random loading. Random waveform was generated through a waveform function generator and was externally fed to the MTS machine. The present paper presents the result of experiments along with the applicability to the three approaches to prediction.
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Xu, Jing y Lian-Kuan Chen. "Optical Phase Remodulation for 10-Gb/s WDM-PON with Enhanced Tolerance to Rayleigh Noise". En Optical Fiber Communication Conference. Washington, D.C.: OSA, 2010. http://dx.doi.org/10.1364/ofc.2010.othg3.
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Guo, Zhiqing, Li-An Bian, Mingtuan Lin, Ranhao Chen, Yan Wang y Shu Xie. "A Metasurface with Phase and Magnitude Modulation Function". En 2022 IEEE MTT-S International Microwave Workshop Series on Advanced Materials and Processes for RF and THz Applications (IMWS-AMP). IEEE, 2022. http://dx.doi.org/10.1109/imws-amp54652.2022.10106951.
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Ushifusa, Hiroyuki, Konosuke Sugasawa y Kazuaki Inaba. "Rayleigh Scattering of Supercritical Carbon Dioxide in Dynamic Phase Transition". En ASME 2015 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/pvp2015-45741.
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A new experimental device was developed to observe and measure the dynamic generation of supercritical CO2 (scCO2) in a closed chamber. The temperature and pressure were measured locally using a thin thermocouple and a pressure transducer, respectively. The Rayleigh scattering in the chamber was visualized using a high-speed video camera. The liquid CO2 was heated by a ceramic heater located at the top or bottom of the chamber. Using this new experimental device, the color variation due to Rayleigh scattering was observed. The temperature profile was stable and scCO2 was generated slowly within a few seconds when heating occurred at the top. For heating at the bottom, scCO2 was created faster within 1 s. Additionally, natural convection, turbulence, and a phenomenon resembling boiling were observed. Numerical simulations of the scCO2 creation in a chamber were also performed using the COMSOL Multiphysics application along with the PROPATH package to obtain the thermophysical properties of CO2. The simulation results showed that scCO2 creation for heating at the top was stable due to the gas-like properties of the scCO2 near the heater. For heating at the bottom, the density distribution initially depended on the temperature distribution. However, as natural convection developed, the flow in the chamber was perturbed and the density distribution depended on both the temperature distribution and the density fluctuation caused by the convection vortices. The same tendency was observed in the experimental results. Using PROPATH, the density variation in the scCO2 generation was estimated from the measured temperature and pressure. The P-T diagram and density variation were compared in each experiment.
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Jing Xu, Lian-Kuan Chen y Chun-Kit Chan. "High extinction ratio phase re-modulation for 10-Gb/s WDM-PON with enhanced tolerance to rayleigh noise". En 2010 9th International Conference on the Optical Internet (COIN). IEEE, 2010. http://dx.doi.org/10.1109/coin.2010.5546411.
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Vashisth, D. y B. Shekar. "Inversion of Rayleigh-Wave Phase and Group Velocity Dispersion Curves for S-Wave Velocity by Grey Wolf Optimization". En 81st EAGE Conference and Exhibition 2019. European Association of Geoscientists & Engineers, 2019. http://dx.doi.org/10.3997/2214-4609.201901454.
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Chow, C. W., G. Talli y P. D. Townsend. "Reduction of Rayleigh Noise in 10Gb/s DWDM-PONs by Wavelength Detuning and Phase Modulation Induced Spectral Broadening". En 2006 32nd European Conference on Optical Communications - (ECOC 2006). IEEE, 2006. http://dx.doi.org/10.1109/ecoc.2006.4801426.
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Lyu, Yun-Peng, Lei Zhu y Chong-Hu Cheng. "Design of Ultra-Wideband, Multi-Wideband, and Multi-Function Phase Shifters Based on Multiple Resonant Technology : (Invited Talk)". En 2019 IEEE MTT-S International Wireless Symposium (IWS). IEEE, 2019. http://dx.doi.org/10.1109/ieee-iws.2019.8803894.
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Wilkinson, D., P. Vowden, L. Gilka, S. M. Rajah y R. C. Kester. "PLATELET FUNCTION IN VASOSPASTIC DISORDERS". En XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643476.
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If vasospastic disorders are associated with abnormal eicosanoid metabolism then disturbed platelet function may be observed. We have measured platelet aggregation (PAG) at 37°C to ADP (8 1:1 sequential dilutions from 10μM), collagen (2mg/l) and adrenaline (5μM) in 37 patients with Raynaud's syndrome (21 primary (RD), 9 secondary to scleroderma (RP) and 7 vibration white finger disease (VWF)) and 10 normal subjects (N). In addition we have determined the platelet aggregate ratio (PAR). PAG was expressed as the percentage fall in optical density after the addition of the aggregant. We also recorded the duration of the collagen lag phase and the concentration of ADP at which disaggregation occurred (DAC).Patients with RP showed enhanced PAG compared to normals. This reached significance for collagen lag phase (p<0.001), percentage PAG at 3 minutes to ADP 1.25μM (p<0.05) and the DAC (p<0.01). Similar differences were observed between patients with RP and VWF. Patients with RP also showed significantly enhanced PAG with regard to ADP 1.25μM (p<0.01) and the DAC, (p<0.05) compared to patients with RD. There was no significant difference in platelet function between normal subjects and patients with VWF or between normal subjects and patients with RD. Only with regard to DAC did patients with RD differ from patients with VWF (p<0.05). The differences observed in PAG were not reflected by the PAR. Patients with RP have significantly enhanced PAG when compared to all other groups. This may relate to eicosanoid metabolism and provides a rationale for treatment.
Informes sobre el tema "Rayleigh`s phase function"
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Meidan, Rina y Robert Milvae. Regulation of Bovine Corpus Luteum Function. United States Department of Agriculture, marzo de 1995. http://dx.doi.org/10.32747/1995.7604935.bard.
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The main goal of this research plan was to elucidate regulatory mechanisms controlling the development, function of the bovine corpus luteum (CL). The CL contains two different sterodigenic cell types and therefore it was necessary to obtain pure cell population. A system was developed in which granulosa and theca interna cells, isolated from a preovulatory follicle, acquired characteristics typical of large (LL) and small (SL) luteal cells, respectively, as judged by several biochemical and morphological criteria. Experiments were conducted to determine the effects of granulosa cells removal on subsequent CL function, the results obtained support the concept that granulosa cells make a substaintial contribution to the output of progesterone by the cyclic CL but may have a limited role in determining the functional lifespan of the CL. This experimental model was also used to better understand the contribution of follicular granulosa cells to subsequent luteal SCC mRNA expression. The mitochondrial cytochrome side-chain cleavage enzyme (SCC), which converts cholesterol to pregnenolone, is the first and rate-limiting enzyme of the steroidogenic pathway. Experiments were conducted to characterize the gene expression of P450scc in bovine CL. Levels of P450scc mRNA were higher during mid-luteal phase than in either the early or late luteal phases. PGF 2a injection decreased luteal P450scc mRNA in a time-dependent manner; levels were significantly reduced by 2h after treatment. CLs obtained from heifers on day 8 of the estrous cycle which had granulosa cells removed had a 45% reduction in the levels of mRNA for SCC enzymes as well as a 78% reduction in the numbers of LL cells. To characterize SCC expression in each steroidogenic cell type we utilized pure cell populations. Upon luteinization, LL expressed 2-3 fold higher amounts of both SCC enzymes mRNAs than SL. Moreover, eight days after stimulant removal, LL retained their P4 production capacity, expressed P450scc mRNA and contained this protein. In our attempts to establish the in vitro luteinization model, we had to select the prevulatory and pre-gonadotropin surge follicles. The ratio of estradiol:P4 which is often used was unreliable since P4 levels are high in atretic follicles and also in preovulatory post-gonadotropin follicles. We have therefore examined whether oxytocin (OT) levels in follicular fluids could enhance our ability to correctly and easily define follicular status. Based on E2 and OT concentrations in follicular fluids we could more accurately identify follicles that are preovulatory and post gonadotropin surge. Next we studied OT biosynthesis in granulosa cells, cells which were incubated with forskolin contained stores of the precursor indicating that forskolin (which mimics gonadotropin action) is an effective stimulator of OT biosynthesis and release. While studying in vitro luteinization, we noticed that IGF-I induced effects were not identical to those induced by insulin despite the fact that megadoses of insulin were used. This was the first indication that the cells may secrete IGF binding protein(s) which regonize IGFs and not insulin. In a detailed study involving several techniques, we characterized the species of IGF binding proteins secreted by luteal cells. The effects of exogenous polyunsaturated fatty acids and arachidonic acid on the production of P4 and prostanoids by dispersed bovine luteal cells was examined. The addition of eicosapentaenoic acid and arachidonic acid resulted in a dose-dependent reduction in basal and LH-stimulated biosynthesis of P4 and PGI2 and an increase in production of PGF 2a and 5-HETE production. Indomethacin, an inhibitor of arachidonic acid metabolism via the production of 5-HETE was unaffected. Results of these experiments suggest that the inhibitory effect of arachidonic acid on the biosynthesis of luteal P4 is due to either a direct action of arachidonic acid, or its conversion to 5-HETE via the lipoxgenase pathway of metabolism. The detailed and important information gained by the two labs elucidated the mode of action of factors crucially important to the function of the bovine CL. The data indicate that follicular granulosa cells make a major contribution to numbers of large luteal cells, OT and basal P4 production, as well as the content of cytochrome P450 scc. Granulosa-derived large luteal cells have distinct features: when luteinized, the cell no longer possesses LH receptors, its cAMP response is diminished yet P4 synthesis is sustained. This may imply that maintenance of P4 (even in the absence of a Luteotropic signal) during critical periods such as pregnancy recognition, is dependent on the proper luteinization and function of the large luteal cell.
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Hedrick, Jacob y Timothy Jacobs. PR-457-14201-R02 Variable NG Composition Effects in LB 2S Compressor Engines Phase I Engine Response. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), agosto de 2015. http://dx.doi.org/10.55274/r0010997.
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This is the final report summarizing work completed during the first phase of the PRCI study on large bore two stroke lean burn integral compressor engine response to variable natural gas compositions for the purposes of engine control development. Accomplished tasks include the completion of a detailed literature review covering the research topic, a parametric study of laminar flame speeds and ignition delays for binary methane and ethane mixtures up to 30%, and a GT-Power engine model of the Colorado State GMV-4 research engine with associated validation data from CSU�s variable ethane effects study. The chemistry of the combustion reaction is crucial to accurate modeling; laminar flame speeds and ignition delays as function of composition were determined from the solutions to published chemical kinetics mechanisms GRI-Mech3.0 and Saudi Aramco Mech1.3, respectively. The Wiebe coefficients correlated to variations in ethane composition and spark timing were regressed from the crank angle resolved heat release rates. The Wiebe coefficients are the most significant achievement of this phase of the project, since they quantify the heat release as a function of composition. At this time, the Wiebe parameters only reflect the relative changes in the model since certain aspect of the models geometry are pending resolution. Future phases of the project could use the developed GT-Power model and Wiebe coefficients for development of control schemes that maintain emissions, speed and torque limits, and maximize thermal efficiency during a variable fuel composition event.
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Phillips y Robinson. L51979 Gas Decompression Behavior Following the Rupture of High Pressure Pipelines-Phase 1. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), noviembre de 2002. http://dx.doi.org/10.55274/r0010194.
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The ability to predict the behavior of a crack propagating in a steel natural gas transmission pipeline is of great importance. This is because a long-running fracture is costly, both in terms of the time taken for replacement, and associated lost revenue, and the cost of replacement of the pipe itself. The determination of ductile shear fracture arrest toughness levels requires an accurate knowledge of the gas decompression behavior following the rupture. In particular, there is a need to predict accurately the gas decompression wave velocity within the pipe as a function of initial pressure, temperature and gas composition. Although models developed in the 1970's have proved remarkably robust to date, even when stretched considerably beyond their range of validation, operational characteristics currently being considered range far beyond any that have been investigated on a realistic scale. There is, therefore, a need to produce a model that has been validated for conditions relevant to next generation pipeline projects. This report describes the work carried out in Phase 1 of a project to produce such a model. In Phase 1 a review of current knowledge was carried out and the work required in Phase 2 of the project was specified. This report describes Phase 1 of the gas decompression project. The aim of Phase 1 was to review the current state of knowledge on pipeline decompression. Carrying out this work has enabled the requirements for the model, the extent of validation that will be required and the proposed technical approach to be identified.
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Wagner, D. Ry, Eliezer Lifschitz y Steve A. Kay. Molecular Genetic Analysis of Flowering in Arabidopsis and Tomato. United States Department of Agriculture, mayo de 2002. http://dx.doi.org/10.32747/2002.7585198.bard.
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The primary objectives for the US lab included: the characterization of ELF3 transcription and translation; the creation and characterization of various transgenic lines that misexpress ELF3; defining genetic pathways related to ELF3 function regulating floral initiation in Arabidopsis; and the identification of genes that either interact with or are regulated by ELF3. Light quality, photoperiod, and temperature often act as important and, for some species, essential environmental cues for the initiation of flowering. However, there is relatively little information on the molecular mechanisms that directly regulate the developmental pathway from the reception of the inductive light signals to the onset of flowering and the initiation of floral meristems. The ELF3 gene was identified as possibly having a role in light-mediated floral regulation since elj3 mutants not only flower early, but exhibit light-dependent circadian defects. We began investigating ELF3's role in light signalling and flowering by cloning the ELF3 gene. ELF3 is a novel gene only present in plant species; however, there is an ELF3 homolog within Arabidopsis. The Arabidopsis elj3 mutation causes arrhythmic circadian output in continuous light; however, we show conclusively normal circadian function with no alteration of period length in elj3 mutants in dark conditions and that the light-dependent arrhythmia observed in elj3 mutants is pleiotropic on multiple outputs regardless of phase. Plants overexpressing ELF3 have an increased period length in constant light and flower late in long-days; furthermore, etiolated ELF3-overexpressing seedlings exhibit a decreased acute CAB2 response after a red light pulse, whereas the null mutant is hypersensitive to acute induction. This finding suggests that ELF3 negatively regulates light input to both the clock and its outputs. To determine whether ELF3's action is phase dependent, we examined clock resetting by light pulses and constructed phase response curves. Absence of ELF3 activity causes a significant alteration of the phase response curve during the subjective night, and overexpression of ELF3 results in decreased sensitivity to the resetting stimulus, suggesting that ELF3 antagonizes light input to the clock during the night. Indeed, the ELF3 protein interacts with the photoreceptor PHYB in the yeast two-hybrid assay and in vitro. The phase ofELF3 function correlates with its peak expression levels of transcript and protein in the subjective night. ELF3 action, therefore, represents a mechanism by which the oscillator modulates light resetting. Furthermore, flowering time is dependent upon proper expression ofELF3. Scientifically, we've made a big leap in the understanding of the circadian system and how it is coupled so tightly with light reception in terms of period length and clock resetting. Agriculturally, understanding more about the way in which the clock perceives and relays temporal information to pathways such as those involved in the floral transition can lead to increased crop yields by enabling plants to be grown in suboptimal conditions.
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Christopher, David A. y Avihai Danon. Plant Adaptation to Light Stress: Genetic Regulatory Mechanisms. United States Department of Agriculture, mayo de 2004. http://dx.doi.org/10.32747/2004.7586534.bard.
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Original Objectives: 1. Purify and biochemically characterize RB60 orthologs in higher plant chloroplasts; 2. Clone the gene(s) encoding plant RB60 orthologs and determine their structure and expression; 3. Manipulate the expression of RB60; 4. Assay the effects of altered RB60 expression on thylakoid biogenesis and photosynthetic function in plants exposed to different light conditions. In addition, we also examined the gene structure and expression of RB60 orthologs in the non-vascular plant, Physcomitrella patens and cloned the poly(A)-binding protein orthologue (43 kDa RB47-like protein). This protein is believed to a partner that interacts with RB60 to bind to the psbA5' UTR. Thus, to obtain a comprehensive view of RB60 function requires analysis of its biochemical partners such as RB43. Background & Achievements: High levels of sunlight reduce photosynthesis in plants by damaging the photo system II reaction center (PSII) subunits, such as D1 (encoded by the chloroplast tpsbAgene). When the rate of D1 synthesis is less than the rate of photo damage, photo inhibition occurs and plant growth is decreased. Plants use light-activated translation and enhanced psbAmRNA stability to maintain D1 synthesis and replace the photo damaged 01. Despite the importance to photosynthetic capacity, these mechanisms are poorly understood in plants. One intriguing model derived from the algal chloroplast system, Chlamydomonas, implicates the role of three proteins (RB60, RB47, RB38) that bind to the psbAmRNA 5' untranslated leader (5' UTR) in the light to activate translation or enhance mRNA stability. RB60 is the key enzyme, protein D1sulfide isomerase (Pill), that regulates the psbA-RN :Binding proteins (RB's) by way of light-mediated redox potentials generated by the photosystems. However, proteins with these functions have not been described from higher plants. We provided compelling evidence for the existence of RB60, RB47 and RB38 orthologs in the vascular plant, Arabidopsis. Using gel mobility shift, Rnase protection and UV-crosslinking assays, we have shown that a dithiol redox mechanism which resembles a Pill (RB60) activity regulates the interaction of 43- and 30-kDa proteins with a thermolabile stem-loop in the 5' UTR of the psbAmRNA from Arabidopsis. We discovered, in Arabidopsis, the PD1 gene family consists of II members that differ in polypeptide length from 361 to 566 amino acids, presence of signal peptides, KDEL motifs, and the number and positions of thioredoxin domains. PD1's catalyze the reversible formation an disomerization of disulfide bonds necessary for the proper folding, assembly, activity, and secretion of numerous enzymes and structural proteins. PD1's have also evolved novel cellular redox functions, as single enzymes and as subunits of protein complexes in organelles. We provide evidence that at least one Pill is localized to the chloroplast. We have used PDI-specific polyclonal and monoclonal antisera to characterize the PD1 (55 kDa) in the chloroplast that is unevenly distributed between the stroma and pellet (containing membranes, DNA, polysomes, starch), being three-fold more abundant in the pellet phase. PD1-55 levels increase with light intensity and it assembles into a high molecular weight complex of ~230 kDa as determined on native blue gels. In vitro translation of all 11 different Pill's followed by microsomal membrane processing reactions were used to differentiate among PD1's localized in the endoplasmic reticulum or other organelles. These results will provide.1e insights into redox regulatory mechanisms involved in adaptation of the photosynthetic apparatus to light stress. Elucidating the genetic mechanisms and factors regulating chloroplast photosynthetic genes is important for developing strategies to improve photosynthetic efficiency, crop productivity and adaptation to high light environments.