• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 44
  • 10
  • 8
  • 8
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 99
  • 24
  • 15
  • 14
  • 14
  • 11
  • 11
  • 11
  • 10
  • 10
  • 9
  • 9
  • 9
  • 8
  • 8
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Contribution à l’étude de techniques de codage analogique pour l’imagerie microonde active et passive / Contribution to the study of analog encoding for active and passive microwave imaging

Kpre, Ettien lazare 26 October 2017 (has links)
Les systèmes d’imagerie microonde suscitent un grand intérêt actuellement dans le domaine de la recherche, notamment pour des applications de sécurité (scanners corporels, vision à travers les murs, etc). Plusieurs techniques d’acquisition déjà existantes permettent d’optimiser l’ouverture rayonnante afin de garantir une bonne résolution sur l’image finale. Cependant, le verrou actuel des systèmes d’imagerie est de pouvoir atteindre un temps de rafraîchissement temps réel et d’adresser un grand nombre d’antennes. La majorité des systèmes actuels peinent à concilier la rapidité et la résolution, tout en garantissant une bonne sensibilité. Les travaux réalisés dans ce manuscrit visent à proposer une alternative aux systèmes existants en se basant sur des techniques de codage analogique des signaux d’antennes. Globalement, l’objectif est de minimiser le nombre de récepteurs sans affecter les performances. Les architectures proposées sont essentiellement basées sur le concept du Radar MIMO (pour les systèmes actifs) et du radiomètre à synthèse d’ouverture interférométrique ou SAIR (pour les systèmes passifs). Ces deux systèmes permettent de réduire considérablement le nombre d’antennes sans affecter la résolution de l’image, ce qui permet une première levée de contraintes. En sus, des composants compressifs entièrement passifs sont utilisés pour réduire le nombre de récepteurs des systèmes Radar MIMO et SAIR. Ces composants à diversité spatiale et fréquentielle présentent des fonctions de transfert orthogonales. Utilisés en émission, ils permettent un adressage simultané et indépendant des antennes du réseau. En réception, ils permettent de coder les signaux reçus par les antennes vers un nombre de voies RF considérablement réduit. En appliquant des techniques de décodage appropriées, les signaux reçus par chacune des antennes peuvent être estimées afin d’appliquer les algorithmes dédiés à la reconstruction de l’image. Ces composants offrent l’avantage de réduire fortement le nombre de voies RF tout en conservant la même ouverture rayonnante et en autorisant une acquisition simultanée des signaux. Des démonstrateurs laboratoires ont été réalisés en bande S afin de montrer une preuve de faisabilité des alternatives proposées. Enfin, les résultats obtenus ont fait l'objet d'une demande de brevet et un prototype d'imageur radiométrique à ondes millimétriques est en cours de prototypage dans le cadre du projet ANR-PIXEL. / Microwave imaging systems are currently attracting great attention in the field of research, especially for security applications (body scanners, vision through walls, etc.). Several acquisition techniques already exist to optimize the antenna aperture in order to guarantee a good resolution on the final image. However, the current lock of imaging systems is to be able to achieve a real-time acquisition and address numerous antennas. Most of the current systems struggle to reconcile fast imaging and resolution while ensuring good sensitivity. The work carried out in this manuscript aims at proposing an alternative to the existing systems based on analog coding techniques of the antenna signals. Overall, the goal is to minimize the number of receivers without affecting performances. The proposed architectures are based essentially on the concept of the MIMO radar (for active systems) and the Synthetic Aperture Interferometric Radiometer or SAIR (for passive systems). These two systems allow a significant reduction of the number of antennas without affecting the resolution of the image, thus enabling a first lifting of constraints. In addition, passive compressive components are used to reduce the number of receivers in the MIMO Radar and the SAIR systems. These components with spatial and frequency diversity exhibit orthogonal transfer functions. Used in transmission, they allow simultaneous and independent addressing of each element of the antenna array. In reception, they allow the signals received by the antennas to be coded into a considerably reduced number of aggregate waveforms. By applying suitable decoding techniques, the signals received by each antenna can be estimated in order to apply imaging algorithms. These components offer the advantage of greatly reducing the number of RF channels while keeping the same number of antennas and allowing simultaneous acquisition of the signals. Laboratory demonstrators were carried out in S-band to demonstrate the feasibility of the proposed alternatives. Finally, the results obtained were the subject of a patent application and a prototype of a millimeter-wave radiometric imager is being developed in the framework of the ANR-PIXEL project.
82

Caractérisation spectrale locale à l'aide de la microscopie interférométrique : simulations et mesures / Local spectral characterization using coherence scanning interferometry : simulations and measurements

Claveau, Rémy 08 December 2017 (has links)
La microscopie interférométrique est une méthode de mesure qui repose sur l’acquisition et le traitement du signal issu de l’interaction de deux ondes, dites ondes « objet » et de « référence ». Ces ondes proviennent des réflexions de la lumière sur un miroir de référence et sur l’échantillon étudié. Bien qu’étant généralement utilisées pour les analyses topographiques ou tomographiques d’un échantillon, les données interférométriques peuvent être exploitées pour réaliser des caractérisations spectrales locales résolues dans les trois directions de l’espace. Dans ce projet, nous avons étudié les performances de cette technique ainsi que ses limitations lorsque l’échantillon se complexifie (dégradation du signal d’interférences). L’analyse a été appliquée à des matériaux réfléchissants pour des mesures en surface puis à des couches transparentes et diffusantes pour aller sonder le milieu en profondeur et extraire la réponse spectrale individuelle de structures localisées dans ce milieu. / White light interference microscopy is a measurement method based on the acquisition and processing of the signal coming from the interaction between two wave fronts, known as the “object” and “reference” wave-fronts. These waves come from the reflection of the light on a reference mirror and the sample studied. Usually used for topographic or tomographic analysis of a sample, the interferometric data can be exploited for spectroscopic purposes. The resulting spectral characterizations are spatially resolved in the three directions of space. In this project, we have studied the performance of this technique, as well as the associated limitations when the sample becomes more complex (degradation of the interferometric signal). The analysis has been first applied to reflective materials for surface measurements and subsequently to transparent and scattering layers for probing within the depth of the medium and then extracting the individual spectral response of the buried structures.
83

Radio astronomy techniques : the use of radio instruments from single dish radio telescopes to radio interferometers

De Witt, Aletha 03 1900 (has links)
New radio telescopes under development, will significantly enhance the capabilities of radio astronomy in the Southern Hemisphere. South Africa, in particular, is actively involved in the development of a new array (MeerKAT) as well as in the expansion of existing very long baseline interferometer arrays in the south. Participation in these new developments demands a thorough understanding of radio astronomy techniques, and data analysis, and this thesis focusses on two projects with the aim of gaining such experience. The Southern Hemisphere very long baselines array is not well served with calibrator sources and there are significant gaps in the present calibrator distribution on the sky. An adequately dense, well distributed, set of strong, compact calibrator or reference sources is needed. With this in mind, observations using the Southern Hemisphere long baseline array were conducted to investigate a sample of candidate calibrator sources. The compactness of the sources was investigated and new potential calibrators have been identified. Single antenna radio spectroscopy of OH masers has identified sources of 1720 MHz emission associated with supernova remnants at the shock interface between the expanding supernova remnant and a molecular cloud. Models indicate that these masers are shock excited and can only be produced under tight physical constraints. Out ows from newly-formed stars create nebulous regions known as Herbig-Haro objects when they interact with the surrounding medium, and these regions are potentially similar to those seen in supernova remnants. If conditions behind the shock fronts of Herbig-Haro objects are able to support 1720-MHz OH masers they could be a useful diagnostic tool for star formation. A survey toward Herbig-Haro objects using a single-dish radio telescope did detect 1720-MHz OH lines in emission, but neither their spectral signature nor follow-up observations with the Very Large Array showed evidence of maser emission. / Mathematical Sciences / Ph.D. (Astronomy)
84

Evaluation of the thermal stability of a low-coherence interferometer for precision surface profilometry

Taudt, Ch., Baselt, T., Nelsen, B., Assmann, H., Greiner, A., Koch, E., Hartmann, P. 09 August 2019 (has links)
Manufacturing of precise structures in MEMS, semiconductors, optics and other fields requires high standards in manufacturing and quality control. Appropriate surface topography measurement technologies should therefore deliver nm accuracy in the axial dimension under typical industrial conditions. This work shows the characterization of a dispersion-encoded low-coherence interferometer for the purpose of fast and robust surface topography measurements. The key component of the interferometer is an element with known dispersion. This dispersive element delivers a controlled phase variation in relation to the surface height variation which can be detected in the spectral domain. A laboratory setup equipped with a broadband light source (200 - 1100 nm) was established. Experiments have been carried out on a silicon-based standard with height steps of 100 nm under different thermal conditions such as 293.15 K and 303.15 K. Additionally, the stability of the setup was studied over periods of 5 hours (with constant temperature) and 15 hours (with linear increasing temperature). The analyzed data showed that a height measurement of 97.99 ± 4:9nm for 293.15 K and of 101.43 ± 3:3nm for 303.15 K was possible. The time-resolved measurements revealed that the developed setup is highly stable against small thermal uctuations and shows a linear behaviour under increasing thermal load. Calibration data for the mathmatical corrections under different thermal conditions was obtained.
85

Measurement of surface topographies in the nm-range for power chip technologies by a modified low-coherence interferometer

Taudt, Ch., Baselt, T., Nelsen, B., Aßmann, H., Greiner, A., Koch, E., Hartmann, P. 29 August 2019 (has links)
This work introduces a modified low-coherence interferometry approach for nanometer surface-profilometry. The key component of the interferometer is an element with known dispersion which defines the measurement range as well as the resolution. This dispersive element delivers a controlled phase variation which can be detected in the spectral domain and used to reconstruct height differences on a sample. In the chosen setup, both axial resolution and measurement range are tunable by the choice of the dispersive element. The basic working principle was demonstrated by a laboratory setup equipped with a supercontinuum light source (Δλ = 400 ̶ 1700 nm). Initial experiments were carried out to characterize steps of 101 nm on a silicon height standard. The results showed that the system delivers an accuracy of about 11.8 nm. These measurements also served as a calibration for the second set of measurements. The second experiment consisted of the measurement of the bevel of a silicon wafer. The modified low-coherence interferometer could be utilized to reproduce the slope on the edge within the previously estimated accuracy. The main advantage of the proposed measurement approach is the possibility to collect data without the need for mechanically moving parts.
86

Two-dimensional low-coherence interferometry for the characterization of nanometer wafer topographies

Taudt, Ch., Baselt, T., Nelsen, B., Aßmann, H., Greiner, A., Koch, E., Hartmann, P. 30 August 2019 (has links)
Within this work a scan-free, low-coherence interferometry approach for surface profilometry with nm-precision is presented. The basic setup consist of a Michelson-type interferometer which is powered by a supercontinuum light-source (Δλ = 400 - 1700 nm). The introduction of an element with known dispersion delivers a controlled phase variation which can be detected in the spectral domain and used to reconstruct height differences on a sample. In order to enable scan-free measurements, the interference signal is spectrally decomposed with a grating and imaged onto a two-dimensional detector. One dimension of this detector records spectral, and therefore height information, while the other dimension stores the spatial position of the corresponding height values. In experiments on a height standard, it could be shown that the setup is capable of recording multiple height steps of 101 nm over a range of 500 µm with an accuracy of about 11.5 nm. Further experiments on conductive paths of a micro-electro-mechanical systems (MEMS) pressure sensor demonstrated that the approach is also suitable to precisely characterize nanometer-sized structures on production-relevant components. The main advantage of the proposed measurement approach is the possibility to collect precise height information over a line on a surface without the need for scanning. This feature makes it interesting for a production-accompanying metrology.
87

Studies of the Interferometric Phase and Doppler Spectra of Sea Surface Backscattering Using Numerically Simulated Low Grazing Angle Backscatter Data

Chae, Chun Sik 19 June 2012 (has links)
No description available.
88

The taiji and infinity-loop microresonators: examples of non-hermitian photonic systems

Franchi, Riccardo 01 June 2023 (has links)
This thesis theoretically and experimentally studies the characteristics of integrated microresonators (MRs) built by passive (no gain) and non-magnetic materials and characterized by both Hermitian and non-Hermitian Hamiltonians. In particular, I have studied three different microresonators: a typical Microring Resonator (MR), a Taiji Microresonator (TJMR), which consists of a microresonator with an embedded S-shaped waveguide, and a new geometry called the Infinity-Loop Microresonator (ILMR), which is characterized by a microresonator shaped like the infinity symbol coupled at two points to the bus waveguide. To get an accurate picture of the three devices, they were modeled using both the transfer matrix method and the temporal coupled mode theory. Neglecting propagation losses, the MR is described by a Hermitian Hamiltonian, while the TJMR and the ILMR are described by a non-Hermitian one. An important difference between Hermitian and non-Hermitian systems concerns their degeneracies. Hermitian degeneracies are called Diabolic Points (DPs) and are characterized by coincident eigenvalues and mutually orthogonal eigenvectors. In contrast, non-Hermitian degeneracies are called Exceptional Points (EPs). At the EP, both the eigenvalues and the eigenvectors coalesce. The MR is at a DP instead, and the TJMR and the ILMR are at an EP. Since the TJMR and ILMR are at an EP, they have interesting features such as the possibility of being unidirectional reflectors. Here, it is shown experimentally how in the case of the TJMR this degeneracy can also be used to break Lorentz reciprocity in the nonlinear regime (high incident laser powers), discussing the effect of the Fabry-Perot of the bus waveguide facets. The effect of backscattering, mainly due to the waveguide surface-wall roughness, on the microresonators is also studied. This phenomenon induces simultaneous excitation of the clockwise and counterclockwise modes, leading to eigenvalue splitting. This splitting makes the use of typical quality factor estimation methods unfeasible. To overcome this problem and mitigate the negative effects of backscattering, a new experimental technique called interferometric excitation is introduced. This technique involves coherent excitation of the microresonator from both sides of the bus waveguide, allowing selective excitation of a single supermode. By adjusting the relative phase and amplitude between the excitation fields, the splitting in the transmission spectrum can be eliminated, resulting in improved quality factors and eigenvalue measurements. It is shown that this interferometric technique can be exploited under both stationary and dynamic conditions of time evolution. The thesis also investigates the sensing performance of the three microresonators as a function of a backscattering perturbation, which could be caused, for example, by the presence of a molecule or particle near the microresonator waveguide. It is shown that the ILMR has better performance in terms of responsivity and sensitivity than the other two microresonators. In fact, it has both the enhanced sensitivity due to the square root dependence of the splitting on the perturbation (characteristic of EPs) and the ability to completely eliminate the region of insensitivity as the backscattering perturbation approaches zero, which is present in both the other two microresonators. To validate the models used, they were compared with experimental measurements both in the linear regime and, for TJMR, also in the nonlinear regime, with excellent agreement.
89

Gravitational Waves From Inspiralling Compact Binaries : 3PN Polarisations, Angular Momentum Flux And Applications To Astrophysics And Cosmology

Sinha, Siddhartha January 2008 (has links)
Binary systems comprising of compact objects like neutron stars (NS) and/or black holes (BH) lose their energy and angular momentum via gravitational waves (GW). Radiation reaction due to the emission of GW results in a gradual shrinking of the binary orbit and an accompanying gradual increase in the orbital frequency. The preliminary phase of the binary evolution when the radiation-reaction time-scale is much larger than the orbital time-scale is called the inspiral phase. GW emitted during the final stages of the inspiral phase constitute one of the most important sources for the ground-based laser interferometric GW detectors like LIGO, VIRGO and the proposed space-based detector LISA. For the ground-based detectors, NS and/or stellar mass BH binaries are primary sources, while for LISA super-massive BH (SMBH) binaries are potential targets. Inspiralling compact binaries (ICB) are among the prime targets for interferometric detectors because using approximation schemes in general relativity (GR) like the post-Minkowskian (PM) and the post-Newtonian (PN) approximations one can compute the GW emitted by them with sufficient accuracy both for their detection and parameter estimation leading to GW astronomy. The extreme weakness of gravitational interactions implies that if a GW signal from an ICB is incident on a detector, it will be buried in the noisy detector output. Therefore, sophisticated data analysis techniques are required for detecting the signal in presence of the dominant noise and also estimating the parameters of the signal. From the pre-calculated theoretical waveforms called templates, one already knows the structure of the waveform from an ICB. The technique for detecting signals which are of known form in a noisy detector is matched filtering. This technique consists of cross-correlating the output of a noisy detector assumed to contain the signal of known form with a set of templates. It then finds an ‘optimal’ template that would produce, on average, the highest signal-to-noise ratio (SNR). The efficient performance of matched filtering as a data-analysis strategy for GW signals from ICB presupposes very accurate theoretical templates. Slight mismatches between the signal and the template will result in a loss of signal to noise ratio. Computing very accurate theoretical templates and including effects such as eccentricity are challenging tasks for the theoreticians. This thesis addresses some of the issues related to the waveform modelling of the ICB and their implications for GW data analysis. It is known theoretically that compact binaries reduce their eccentricity through the emission of GW. When GW signals from prototype ICB reach the GW detector bandwidth, their orbits are almost circular. Hence one usually models the binary orbit to be circular for computation of the search templates. The waveform from an ICB in a circular orbit is, at any given PN order of approximation, a linear combination of a finite number of harmonics of the orbital frequency. At the lowest order of approximation, called the Newtonian order, the waveform comprises a single harmonic at twice the orbital frequency. Inclusion of higher order PN corrections lead to the appearance of higher harmonics of the orbital frequency. Since the amplitudes of the higher harmonics contain higher powers of the PN expansion parameter, relative to the Newtonian order, they are referred to as amplitude corrections. The phase of each harmonic, determined by the orbital phase, is known upto 3.5PN order (nPN is the order of approximation equivalent to terms ~(v/c)2n beyond the Newtonian order, where v denotes the binary’s orbital velocity and c is the speed of light). Matched filtering is more sensitive to the phase of the signal rather than its amplitude, since the correlation builds up as long as the signal and the template remain in phase. Motivated by this fact, search templates so far have been a waveform model involving only the dominant harmonic (at twice the orbital frequency), although the phase evolution itself is included upto the maximum available PN order. Such waveforms, in which all amplitude corrections are neglected, but the phase is treated to the maximum available order, are called restricted waveforms (RWF) and these are generally used in the data-analysis of ground-based detectors and also simulated searches for the planned LISA. However, recent studies, in the case of ground-based interferometers, showed that going beyond the RWF approximation could improve the efficiency of detection as well as parameter estimation of the inspiral signal. After a brief overview of the properties of GW and their detection strategies in chapter 1, in chapters 2 and 3, we investigate the implications of going beyond the RWF, in the context of the planned space-based Laser Interferometric Space Antenna (LISA). The sensitivity of ground-based detectors is limited by seismic noise below 20Hz. On the other hand, the space-based LISA will be designed to be sensitive to GWs of frequency (10−4 _1)Hz. The most important source in this frequency band are supermassive BH (SMBH) binaries. There is strong observational evidence for the existence of SMBH with masses in the range of in most galactic nuclei. Mergers of such galaxies result in SMBH binaries whose evolution is governed by the emission of GW. Observation of the GW from SMBH binaries at high redshifts is one of the major science goals of LISA. These observations will allow us to probe the evolution of SMBHs and structure formation and provide an unique opportunity to test General Relativity (and its alternatives) in the strong field regime of the theory. Observing SMBH coalescences with high (100-1000) SNR is crucial for performing all the aforementioned tests. The LISA bandwidth (10−4_ 1)Hz determines the range of masses accessible to LISA because the inspiral signal would end when the system’s orbital frequency reaches the mass-dependent last stable orbit (LSO). In the test-mass approximation, the angular velocity ι at LSO is given by where M is the total mass of the binary. Search templates using the RWF, which contains only the dominant harmonic at twice the orbital frequency, cannot extract power in the signal beyond This further implies that the frequency range [0.1, 100] mHz corresponds to the range for the total mass of BH binaries that would be accessible to LISA. In chapter 2, we show that inclusion of higher harmonics will enhance the mass-range of LISA (for the same frequency range) and allow for the detection of SMBH binaries with total masses higher than The template employed in chapter 2 includes amplitude corrections upto 2.5PN order, while keeping the phase upto 3.5PN order. We call this template the full waveform (FWF). The FWF defined above contains higher harmonics of the orbital frequency, the highest of them being 7 times the orbital frequency. For a SMBH binary with total mass the dominant harmonic at LSO is less than the lower cut-off of the LISA bandwidth. Therefore, if one uses the RWF as a search template, this system is ‘invisible’ to LISA. However, the seventh harmonic can still enter the LISA bandwidth and produce a significant SNR and thus allow its detection. With the FWF, LISA can observe sources which are favoured by astronomical observations, but not observable with the RWF. More specifically, with the inclusion of all known harmonics LISA will be able to observe SMBH coalescences with total mass (and mass-ratio 0.1) for a low frequency cut-off of 10−4Hz (10−5Hz) with an SNR up to ~ 60 (~30) at a distance of 3 Gpc. The orbital motion of LISA around the Sun induces frequency, phase and amplitude modulations in the observed GW signal. These modulations carry information about both the source’s location and orientation. Determination of the angular coordinates of the source also allows determination of the luminosity distance of SMBH binaries. Therefore, SMBH binaries are often referred to as GW “standard sirens” (analogous to the electromagnetic “standard candles”). LISA would also be able to measure the “redshifted” masses of the component black holes with good accuracy for sources up to redshifts of a few. However, GW observations alone cannot provide any information about the redshift of the source. If the host galaxy or galaxy cluster is known one can disentangle the redshift from the masses by optical measurement of the redshift. This would not only allow one to extract the “physical” masses, but also provide an exciting possibility to study the luminosity distance-redshift relation providing a totally independent confirmation of the cosmological parameters. Further, this combined observation can be used to map the distribution of black hole masses as a function of redshift. Another outstanding issue in present day cosmology in which LISA can play a role is the dark energy and its physical origin. Probing the equation-of-state-ratio (w(z)) provides an important clue to the question of whether dark energy is truly a cosmological constant (i.e., w = -1). Assuming the Universe to be spatially flat, a combination of WMAP and Supernova Legacy Survey (SNLS) data yields significant constraints on Without including the spatial flatness as a prior, WMAP, large-scale structure and supernova data place a stringent constraint on the dark energy equation of state, For this to be possible, LISA should (a) measure the luminosity distance to the source with a good accuracy and (b) localize the coalescence event on the sky with good angular resolution so that the host galaxy/galaxy cluster can be uniquely identified. Based on analysis with the RWF, it is found that LISA’s angular resolution is not good enough to identify the source galaxy or galaxy cluster, and that other forms of identification would be needed. Secondly, weak lensing effects would corrupt the distance estimation to the same level as LISA’s systematic error. In chapter 3, we study the problem of parameter estimation in the context of LISA, but using the FWF. We investigate systematically the variation in parameter estimation with PN orders by critically examining the role of higher harmonics in the fast GW phasing and their interplay with the slow modulations induced due to LISA’s motion. More importantly, we explore the improvement in the estimation of the luminosity distance and the angular parameters due to the inclusion of higher harmonics in the waveform. We translate the error in the angular resolution to obtain the number of galaxies (or galaxy clusters) within the error box on the sky. We find that independent of the angular position of the source on the sky, higher harmonics improve LISA’s performance on both counts raised in earlier works based on the RWF. We show that the angular resolution enhances typically by a factor of ~2-500 (greater at higher masses) and the error on the estimation of the luminosity distance goes down by a factor of ~ 2-100 (again, larger at higher masses). For many possible sky positions and orientations of the source, the inaccuracy in our measurement of the dark energy would be at the level of a few percent, so that it would only be limited by weak lensing. We conclude that LISA could provide interesting constraints on cosmological parameters, especially the dark energy equation-of-state, and yet circumvent all the lower rungs of the cosmic distance ladder. Having emphasized the need to consider the FWF as a more powerful template, in chapter 4 we calculate a higher order term in the amplitude corrections of the waveform. In chapters 2 & 3, the FWF incorporated amplitude corrections upto 2.5PN order. In chapter 4 the waveform is calculated upto 3PN order. Recent progress in Numerical Relativity (NR) has resulted in computation of the late inspiral and subsequent merger and ringdown phases of the binary evolution (where PN theory does not hold good) by a full-fledged numerical integration of the Einstein field equations. A new field has emerged recently consisting of high-accuracy comparisons between the PN predictions and the numerically-generated waveforms. Such comparisons and matching to the PN results have proved currently to be very successful. They clearly show the need to include high PN corrections not only for the evolution of the binary’s orbital phase but also for the modulation of the gravitational amplitude. This leads to one more motivation for the work in this chapter: providing the associated spin-weighted spherical harmonic decomposition to facilitate comparison and match of the high PN prediction for the inspiral waveform to the numerically-generated waveforms for the merger and ringdown. For the computation of waveforms from the inspiralling compact binaries one needs to solve the two-body problem in general relativity. The nonlinear structure of general relativity prevents one from obtaining a general solution to this problem. The two-body problem is tackled using the multipolar post-Minkowskian (MPM) wave generation formalism. The MPM formalism describes the radiation field of any isolated post-Newtonian source. The radiation field is first of all parametrized by means of two sets of radiative multipole moments. These moments are then related (by means of an algorithm for solving the non-linearities of the field equations) to the so-called canonical moments which constitute some useful intermediaries for describing the external field of the source. The canonical moments are then expressed in terms of the operational source moments obtained by matching to a PN source and are given by explicit integrals extending over the matter source and gravitational field. The extension of the waveform by half a PN order requires as inputs the relations between the radiative, canonical and source multipole moments for general sources at 3PN order. We also require the 3PN extension of the source multipole moments in the case of compact binaries. The waveform in the far-zone consists of two types of terms, instantaneous and hereditary. The instantaneous terms are determined by the dynamical state of the binary at the retarded time. The hereditary terms, on the other hand, depend on the entire past history of the source. These terms originate from the nonlinear interactions between the various multipole moments and also from backscattering off the curved spacetime generated by the waves themselves. In this chapter, we compute the contributions of all the instantaneous and hereditary terms (which include tails, tails-of-tails and memory integrals) up to 3PN order. The end results of this chapter are given in terms of both the 3PN plus and cross polarizations and the separate spin-weighted spherical harmonic modes. Though most of the sources will be in circular orbits by the time the GWs emitted by the system enter the sensitivity band of the laser interferometers, astrophysical scenarios such as Kozai mechanism could produce binaries which have nonzero eccentricity. Studies have shown that filtering the signal from an eccentric binary with circular orbit templates could significantly degrade the SNR. For constructing a phasing formula for eccentric binaries one has to compute the energy and angular momentum fluxes carried away by the GWs and then compute how the orbital elements evolve with time under gravitational radiation reaction. The far-zone energy and angular momentum fluxes, like the waveform, contain both instantaneous and hereditary contributions. The complete 3PN energy flux and instantaneous terms in the 3PN angular momentum flux are already known. In chapter 5, the hereditary terms in the 3PN angular momentum flux from an ICB moving in quasi-elliptical orbits are computed. A semi-analytic method in the frequency domain is used to compute the hereditary contributions. At 3PN order, the quasi-Keplerian representation of elliptical orbits at 1PN order is required. To calculate the tail contributions we exploit the doubly periodic nature of the motion to average the 3PN fluxes over the binary’s orbit. The hereditary part of the angular momentum flux provided here has to be supplemented with the instantaneous part to obtain the final input needed for the construction of templates for binaries moving in elliptical orbits, a class of sources for both the space based detectors and the ground based ones. Using the hereditary contributions in the 3PN energy flux, we also compute the 3PN accurate hereditary contributions to the secular evolution of the orbital elements of the quasi-Keplerian orbit description.
90

A microflow cytometer with simultaneous dielectrophoretic actuation for the optical assay and capacitive cytometry of individual fluid suspended bioparticles

Romanuik, Sean 14 September 2009 (has links)
Fluid suspended biological particles (bioparticles) flowing through a non-uniform electric field are actuated by the induced dielectrophoretic (DEP) force, known to be dependent upon the bioparticles’ dielectric phenotypes. In this work: a 10-1000 kHz DEP actuation potential applied to a co-planar microelectrode array (MEA) induces a DEP force, altering passing bioparticle trajectories as monitored using: (1) an optical assay, in which the lateral bioparticle velocities are estimated from digital video; and (2) a capacitive cytometer, in which a 1.478 GHz capacitance sensor measures the MEA capacitance perturbations induced by passing bioparticles, which is sensitive to the bioparticles’ elevations. The experimentally observed and simulated lateral velocity profiles of actuated polystyrene microspheres (PSS) and viable and heat shocked Saccharomyces cerevisiae cells verify that the bioparticles’ dielectric phenotypes can be inferred from the resultant trajectories due to the balance between the DEP force and the viscous fluid drag force.

Page generated in 0.0986 seconds