Relevant bibliographies by topics / Nonspherical modes

Academic literature on the topic 'Nonspherical modes'

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Published: 1 June 2024

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Contents

  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers
  6. Reports

Journal articles on the topic "Nonspherical modes":

1

Dash, Nehal, and Ganesh Tamadapu. "Nonspherical oscillations of an encapsulated microbubble with interface energy under the acoustic field." Journal of the Acoustical Society of America 155, no. 4 (April 1, 2024): 2445–59. http://dx.doi.org/10.1121/10.0025390.

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Spherical instability in acoustically driven encapsulated microbubbles (EBs) suspended in a fluid can trigger nonspherical oscillations within them. We apply the interface energy model [N. Dash and G. Tamadapu, J. Fluid Mech. 932, A26 (2022b)] to investigate nonspherical oscillations of smaller radius microbubbles encapsulated with a viscoelastic shell membrane under acoustic field. Using the Lagrangian energy formulation, coupled governing equations for spherical and nonspherical modes are derived, incorporating interface energy effects, shell elasticity, and viscosity. Numerical simulations of governing equations revealed that the parametrically forced even mode excites even modes, while the odd modes excite both even and odd modes. The model demonstrates that finite amplitude nonspherical oscillations are identifiable in smaller radius EBs only when the interface parameters are introduced into the model; otherwise, they are not. Realizing that nonlinear mode coupling is responsible for saturation of instability resulting in stable nonspherical oscillations, we perform a steady-state and stability analysis using the slow-time equations obtained from Krylov–Bogoliubov perturbation method. Analytical expressions for modal amplitudes and stability thresholds are derived in terms of interface and material parameters. The stability curves are invaluable in determining the precise range of excitation pressure and frequency values required for the EB to exhibit finite amplitude nonspherical oscillations.
2

Arifi, Fathia F., and Michael L. Calvisi. "Optimal control of the nonspherical oscillations of encapsulated microbubbles." Journal of the Acoustical Society of America 151, no. 4 (April 2022): A108. http://dx.doi.org/10.1121/10.0010804.

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Encapsulated microbubbles (EMBs) were originally developed as contrast agents for ultrasound imaging but are more recently emerging as vehicles for intravenous drug and gene delivery. Ultrasound can excite nonspherical oscillations, or shape modes, that can enhance the acoustic signature of an EMB and also incite rupture, which promotes drug and gene delivery at targeted sites. Therefore, the ability to control shape modes can improve the efficacy of both the diagnosis and treatment mediated by EMBs. This work uses optimal control theory to determine the ultrasound input that maximizes a desired nonspherical EMB response (e.g., to enhance scattering or rupture), while minimizing the total acoustic input in order to enhance patient safety and reduce unwanted side effects. The optimal control problem is applied to a model of an EMB that accounts for small amplitude shape deformations. This model is solved subject to a cost function that maximizes the incidence of rupture or acoustic echo while minimizing the acoustic energy input. The optimal control problem is solved numerically through pseudospectral collocation methods using commercial optimization software. Single frequency and broadband acoustic forcing schemes are explored and compared. The results show that broadband forcing significantly reduces the acoustic effort required to incite EMB rupture relative to single frequency schemes. Furthermore, the acoustic effort required depends strongly on the shape mode that is forced to become unstable.
3

Pikalov, A. M., and A. V. Dorofeenko. "Magnons and Edge Modes in Chains of Nonspherical Magnetic Particles." Moscow University Physics Bulletin 76, no. 1 (January 2021): 42–46. http://dx.doi.org/10.3103/s0027134921010094.

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Bier, K. D., H. J. Jodl, and H. Däufer. "Raman spectroscopy of matrix-isolated hydrogen: I. Influence of matrices on defects." Canadian Journal of Physics 66, no. 8 (August 1, 1988): 708–15. http://dx.doi.org/10.1139/p88-117.

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The hydrogen molecule is treated as a model substance for matrix-isolation effects. Raman investigations are made concerning the influence of matrix material on the various modes of hydrogen. The opposite interaction, how the defect influences modes of the matrix, is the object of the following paper.For the doublet in the vibrational range of hydrogen in rare-gas solids, an assignment to Q1(0) and Q2(1) is made and well substantiated. In addition to matrix-shift considerations, temperature influences, ortho–para investigations, and aggregation effects, different sites are observable in the nonspherical matrices, N2 and O2, with a restriction of free rotation in nitrogen.
5

Kosolapova, L. A., and V. G. Malakhov. "A refined model of nonlinear nonspherical oscillations of a gas bubble in liquid." Proceedings of the Mavlyutov Institute of Mechanics 5 (2007): 241–47. http://dx.doi.org/10.21662/uim2007.1.029.

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A mathematical model of nonlinear oscillations of a gas bubble in a liquid is proposed, in which the change of the bubble surface shape is represented as a series of spherical harmonics, and the equations are accurate up to the third order with respect to the distortion amplitudes of the bubble spherical shape. It is shown that the application of the refined model can lead to modes of oscillation that differ from those obtained using the second-order model.
6

Canós Valero, Adrià, Hadi K. Shamkhi, Anton S. Kupriianov, Vladimir R. Tuz, Vjaceslavs Bobrovs, Yuri S. Kivshar, and Alexander S. Shalin. "Reaching the superscattering regime with BIC physics." Journal of Physics: Conference Series 2172, no. 1 (February 1, 2022): 012003. http://dx.doi.org/10.1088/1742-6596/2172/1/012003.

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Abstract We uncover a novel mechanism of superscattering from subwavelength resonators linked to the physics of bound states in the continuum (BICs). Enhanced scattering occurs due to constructive interference within the Friedrich-Wintgen mechanism of interfering resonances. Through this process, the scattering cross section of a single resonance can exceed the currently established limit. We develop a general non-Hermitian model to describe interfering resonances of quasi-normal modes, and study subwavelength dielectric nonspherical resonators exhibiting avoided crossing resonances and quasi-BIC states. Our results reveal novel physics of non-Hermitian systems suggesting important applications for metadevices.
7

Beyeh, N. Kodiah, Mario Cetina, and Kari Rissanen. "Binding Modes of Nonspherical Anions to N-Alkylammonium Resorcinarenes in the Solid State." Crystal Growth & Design 12, no. 10 (August 27, 2012): 4919–26. http://dx.doi.org/10.1021/cg3008409.

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Harkin, Anthony A., Tasso J. Kaper, and Ali Nadim. "Energy transfer between the shape and volume modes of a nonspherical gas bubble." Physics of Fluids 25, no. 6 (June 2013): 062101. http://dx.doi.org/10.1063/1.4807392.

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Guzik, Joyce A., T. H. Morgan, N. J. Nelson, C. Lovekin, K. Kosak, I. N. Kitiashvili, N. N. Mansour, and A. Kosovichev. "2-D and 3-D models of convective turbulence and oscillations in intermediate-mass main-sequence stars." Proceedings of the International Astronomical Union 11, A29B (August 2015): 540–43. http://dx.doi.org/10.1017/s1743921316006086.

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AbstractWe present multidimensional modeling of convection and oscillations in main-sequence stars somewhat more massive than the Sun, using three separate approaches: 1) Using the 3-D planar StellarBox radiation hydrodynamics code to model the envelope convection zone and part of the radiative zone. Our goals are to examine the interaction of stellar pulsations with turbulent convection in the envelope, excitation of acoustic modes, and the role of convective overshooting; 2) Applying the spherical 3-D MHD ASH (Anelastic Spherical Harmonics) code to simulate the core convection and radiative zone. Our goal is to determine whether core convection can excite low-frequency gravity modes, and thereby explain the presence of low frequencies for some hybrid γ Dor/δ Sct variables for which the envelope convection zone is too shallow for the convective blocking mechanism to drive gravity modes; 3) Applying the ROTORC 2-D stellar evolution and dynamics code to calculate evolution with a variety of initial rotation rates and extents of core convective overshooting. The nonradial adiabatic pulsation frequencies of these nonspherical models are calculated using the 2-D pulsation code NRO. We present new insights into pulsations of 1-2 M⊙ stars gained by multidimensional modeling.
10

Hartings, Justin M., Janice L. Cheung, and Richard K. Chang. "Temporal beating of nondegenerate azimuthal modes in nonspherical microdroplets: technique for determining the distortion amplitude." Applied Optics 37, no. 15 (May 20, 1998): 3306. http://dx.doi.org/10.1364/ao.37.003306.

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Journal articles

Dissertations / Theses on the topic "Nonspherical modes":

1

Fauconnier, Maxime. "Acoustofluidics of nonspherical microbubbles : physics and mechanical interaction with biological cells." Electronic Thesis or Diss., Lyon, 2021. http://www.theses.fr/2021LYSE1242.

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Sources d'effets acoustiques, mécaniques et thermiques importants, les microbulles de gaz sont largement utilisées à des fins industrielles et médicales. Entre autres, l'oscillation acoustique des microbulles permet d'internaliser des produits dans des cellules vivantes, ce qui ouvre la voie à de nombreuses applications thérapeutiques. Les régimes oscillatoires de grande amplitude nécessaires pour qu'il y ait une interaction significative avec les cellules peuvent être synonymes d'apparition d'instabilité de l'interface bulle et de modes dits non-sphériques d'oscillation de bulle, mais aussi d'implosion de bulle et de destruction cellulaire. Il semble donc nécessaire de contrôler leur dynamique afin de minimiser les effets néfastes et de maximiser l'action thérapeutique. Dans l’optique d’étudier l’action de la bulle oscillante à l’échelle cellulaire, ce manuscrit de thèse présente un travail expérimental en trois temps. Premièrement, la dynamique oscillatoire d'une bulle unique accrochée à une paroi est étudiée, notamment au travers des conditions d'apparition de ses modes non-sphériques. Dans un deuxième temps, les écoulements fluides, également appelés microstreaming, induits par une telle bulle non-sphérique sont analysés à partir d'une description quantitative de l'interface de bulle. Enfin, cette connaissance acquise sur une bulle oscillante est transposée à la configuration d'un couple bulle-cellule. Ces effets mécaniques induits s'appliquant sur une cellule à proximité sont analysés à la fois aux échelles de temps acoustique et fluidique
Sources of significant acoustic, mechanical and thermal effects, gas microbubbles are widely used for industrial and medical purposes. Among others, the acoustic oscillation of microbubbles make it possible to internalize products in living cells, which opens the way to numerous therapeutic applications. Large amplitude oscillatory regimes necessary for there to be a significant interaction with cells can be synonymous with the appearance of instability of the bubble interface and of the so-called nonspherical modes of bubble oscillation, but also to bubble collapse and cell destruction. It seems therefore necessary to control their dynamics in order to minimize the harmful effects and maximize the therapeutic action. With the view to study the action of the oscillating bubble at the cellular level, this thesis manuscript presents an experimental work in three stages. First, the oscillatory dynamics of a single bubble attached to a wall is studied, in particular through the conditions for the appearance of its nonspherical modes. Second, the appearance of fluid flows, also called microstreaming, induced by such a nonspherical bubble is analyzed on the basis of a quantitative description of its interface. Lastly, this knowledge acquired on an oscillating bubble is transposed to the configuration of a bubble-cell pair. The bubble-induced mechanical effects that apply on the cell are assessed at both the acoustic and the fluidic time scales
2

Cleve, Sarah. "Microstreaming induced in the vicinity of an acoustically excited, nonspherically oscillating microbubble." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEC028/document.

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Des bulles micrométriques sont utilisées dans divers domaines, notamment dans des applications médicales basées sur les ultrasons. Il est possible d’exploiter différents effets des bulles, comme par exemple leur résonance acoustique ou leur effet destructeur en cavitation inertielle. Un autre mécanisme exploitable est la génération de micro-écoulements, appelé microstreaming, induits autour d’une bulle. Ces écoulements sont relativement lents par rapport aux oscillations rapides de la bulle. Le microstreaming et les contraintes de cisaillement associées jouent un rôle important dans la perméabilisation d’une membrane cellulaire, mais il manque encore une compréhension détaillée de l’écoulement induit. Afin d’améliorer la compréhension des phénomènes physiques, ce travail se concentre sur les écoulements induits autour d’une bulle d’air dans piégée et excitée acoustiquement dans de l’eau et oscillante en modes de surface. La partie expérimentale se décompose de deux étapes. Dans un premier temps, il est nécessaire de contrôler la dynamique de la bulle, en particulier ses modes de surface et son orientation. Ceci est réalisé par coalescence entre deux bulles. Dans un second temps, le microstreaming est généré et enregistré simultanément à la dynamique de bulle. De cette manière il est possible de corréler les motifs d'écoulement aux oscillations de la bulle. Le grand nombre de motifs obtenus peut être classé selon le mode dominant et la taille de la bulle. Une étude plus détaillée de la dynamique de bulle permet de déduire les paramètres importants qui mènent à une telle variété de motifs de microstreaming. Afin de confirmer les résultats expérimentaux, un modèle analytique a été développé. Il est basé sur les équations de la mécanique des fluides de deuxième ordre et moyennées en temps, la dynamique d'interface de la bulle obtenue expérimentalement sert de donnée d’entrée au modèle. Ce manuscrit contient en supplément une section sur la génération de microjets par l'implosion d'agents de contraste. Ces jets peuvent apparaître en cas d’excitation acoustique suffisamment élevée. L’impact de ces jets sur parois présente un autre mécanisme responsable de la perméabilisation de membranes cellulaires
Microbubbles find use in several domains, one of them being medical ultrasound applications. Different characteristics of those bubbles such as their acoustic resonance or their destructive effect during inertial cavitation can be exploited. Another phenomenon induced around acoustically excited bubbles is microstreaming, that means a relatively slow mean flow with respect to the fast bubble oscillations. Microstreaming and its associated shear stresses are commonly agreed to play a role in the permeabilization of cell membranes, a detailed understanding of the induced flows is however missing. To acquire basic physical knowledge, this work focuses on the characterization of streaming induced around an air bubble in water, more precisely around a single acoustically trapped and excited, nonspherically oscillating bubble. The experimental part consists of two steps. First, the bubble dynamics, in particular the triggered shape mode and the orientation of the bubble have to be controlled. For this, the use of bubble coalescence proves to be an adequate method. In a second step, the microstreaming is recorded in parallel to bubble dynamics. This allows to correlate the obtained streaming patterns to the respective shape oscillations. The large number of obtained pattern types can be classified, in particular with respect to the mode number and bubble size. A close investigation of the bubble dynamics allows furthermore deducing the important physical mechanisms which lead to such a variety of streaming patterns. In order to confirm the experimental findings, an analytical model has been developed. It is based upon time-averaged second-order fluid mechanics equations and the experimentally obtained bubble dynamics serves as input parameters. Supplementary to the microstreaming work, this manuscript contains a short section on directed jetting of contrast agent microbubbles, which might appear at high acoustic driving. The impact of those microjets on cell membranes presents another mechanism made responsible for the permeabilization of cell membranes
3

Duan, Qingwei. "Diffusion de la lumière en trois dimensions par des grosses particules non-sphériques par le modèle de Tracé de Rayons Vectoriels Complexes." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMR018.

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Cette thèse est dédiée à une étude de diffusion de la lumière dans l’espace (3D) d’une onde plane ou d’un faisceau laser, dans le cadre du modèle tracée de rayons vectoriels complexes (VCRM Vectorial Complex Ray Model en anglais), par une grosse particule de surface lisse. Les principaux travaux réalisés se résument comme suit : Dans un premier temps, une méthode de calcul pour la diffusion 2D de l’onde plane par un cylindre infini de section quelconque est proposée. Cette méthode est ensuite appliquée à la simulation de l’intensité diffusée de l’onde plane par un cylindre elliptique composé (CEC), dont la section est formée par deux demi-ellipses de paramètres différents. Les effets de la déformation, de l’indice de réfraction et de la direction de l’onde incidente sur les champs diffusés, en particulier les positions des arcs-en-ciel ainsi que leurs dispositions de l’intensité, sont analysées quantitativement. Puis, les travaux se sont étendus à la diffusion dans l’espace (3D) d’une onde plane par une particule de forme quelconque en tenant en compte les déphasages dus aux lignes focales et au chemin optique, la divergence et la convergence du front d’onde, et la polarisation croisée. Un algorithme d’interpolation basé sur la triangulation est développé qui permet de prendre en compte l’inférence des rayons diffusés dans l’espace. La méthode proposée pour la diffusion 3D est appliquée à la simulation de l’intensité diffusée d’une onde plane par un jet de liquide réel. Ceci a permis d’interpréter le mécanisme de diffusion dans l’espace: l’analyse de mode de diffusion, la séparation ou l’interférence de différents ordres. Une expérience est menée pour vérifier la méthode de calcul et pour examiner les résultats simulés. Afin de prendre en compte la forme du faisceau incident, une méthode de description d’un faisceau gaussien elliptique incident par rayons est proposée, qui permet de calculer l’intensité diffusée en 3D d’un faisceau gaussien circulaire ou elliptique par une grosse particule. Le calcul de l’intensité diffusée en champ lointain d’un faisceau gaussien elliptique par un jet de liquide réel est réalisé avec succès. Les champs de diffusion aux alentours des arcs-en-ciel du premier et du second ordre pour les faisceaux incidents de différents angles et divergences sont étudiés
In the framework of vectorial complex ray model (VCRM), this thesis aims to solve the three-dimensional (3D) scattered intensity of plane wave or shaped beam by a large particle of any smooth surface. The main work and achievements are summarized as follows: As the first step, the calculation method based on VCRM for the 2D scattered intensity of plane wave by a cylinder of any smooth cross section is proposed. And the proposed method is applied to solving the scattered intensity of plane wave by a composite elliptical cylinder (CEC), whose cross section can take various shapes ranging from circular, elliptical to highly-deformed. The effects of shape deformation, refractive index and incident direction on the scattering fields, especially on the rainbows, are quantitatively analyzed. Based on VCRM, the ray tracing, the phase shifts due to focal lines and optical path, the divergence and convergence of wavefront, and the cross polarization in 3D scattering are addressed. An interpolation algorithm based on triangulation has been developed which permits to take into account the interference of 3D scattered rays, thus breaking through the bottle-neck problem for VCRM in the extension to 3D scattering. The proposed method, which is based on VCRM while allows to calculate 3D scattering field, is applied to simulating the 3D scattered intensity of plane wave by a real liquid jet. Furthermore, taking advantage of the ability of VCRM for interpreting the scattering mechanism, a systematic analysis is made for the scattered light of different orders, in regard to their separation or interference in 3D space. An experiment is carried out to verify the proposed method for 3D scattering and to examine the simulated results. In the framework of VCRM, a ray description method for incident elliptical Gaussian beam is proposed, thus providing one feasible way to calculate the 3D scattered intensity of elliptical or circular Gaussian beam by a large particle of any smooth surface. The calculation for the 3D far-field scattered intensity of elliptical Gaussian beam by a real liquid jet is successfully achieved. The scattering fields near the first- and second-order rainbows for incident beams of different divergence angles are investigated in 3D space. These results as well as the proposed method open a promising way to characterize finely the structure of a real liquid jet and particles of other complex surfaces

Books on the topic "Nonspherical modes":

1

Borghese, Ferdinando, Paolo Denti, and Rosalba Saija. Scattering from Model Nonspherical Particles. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-662-05330-0.

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Borghese, F. Scattering from model nonspherical particles: Theory and applications to environmental physics. 2nd ed. Berlin: Springer, 2007.

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Borghese, Ferdinando. Scattering from Model Nonspherical Particles: Theory and Applications to Environmental Physics. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003.

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Rother, Tom. Electromagnetic wave scattering on nonspherical particles: Basic methodology and simulations. Berlin: Springer, 2009.

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Scattering from Model Nonspherical Particles. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-37414-5.

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Denti, Paolo, Rosalba Saija, and Ferdinando Borghese. Scattering from Model Nonspherical Particles: Theory and Applications to Environmental Physics. Springer London, Limited, 2007.

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Borghese, F., P. Denti, and R. Saija. Scattering from Model Nonspherical Particles (Physics of Earth and Space Environments). 2nd ed. Springer, 2006.

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Denti, Paolo, Rosalba Saija, and Ferdinando Borghese. Scattering from Model Nonspherical Particles: Theory and Applications to Environmental Physics. Springer Berlin / Heidelberg, 2010.

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Rother, Tom, and Michael Kahnert. Electromagnetic Wave Scattering on Nonspherical Particles: Basic Methodology and Simulations. Springer, 2016.

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Rother, Tom, and Michael Kahnert. Electromagnetic Wave Scattering on Nonspherical Particles: Basic Methodology and Simulations. Springer, 2013.

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Book chapters on the topic "Nonspherical modes":

1

Araújo, Francisco X. "Nonspherical Radiation Driven Wind Models Applied to Be Stars." In Angular Momentum and Mass Loss for Hot Stars, 171–76. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-2105-4_16.

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Liou, K. N., and Y. Gu. "Radiative Transfer in Cirrus Clouds: Light Scatting and Spectral Information." In Cirrus. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195130720.003.0017.

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The importance of cirrus clouds in climate has been recognized in the light of a number of intensive composite field observations: the First ISCCP Regional Experiment (FIRE) I in October-November 1986; FIRE II in November-December 1991; the European experiment on cirrus (ICE/EUCREX) in 1989; Subsonic Aircraft: Contrail and Cloud Effect Special Study (SUCCESS) in April 1996. Based on observations from the ground-based lidar and radar, airborne instrumentation, and satellites, cirrus clouds are typically located in the upper troposphere and lower stratosphere (Liou 1986). The formation, maintenance, and dissipation of cirrus clouds are directly associated with synoptic and mesoscale disturbances as well as related to deep cumulus outflows. Increases of high cloud cover have been reported at a number of urban airports in the United States based on surface observations spanning 40 years (Liou et al. 1990; Frankel et al. 1997). These increases have been attributed to the contrails and water vapor produced by jet airplane traffic. Satellite observations from NOAA polar-orbiting High-Resolution Infrared Radiation Sounder (HIRS) using the CO2 slicing method (Wylie et al. 1994) also show that cirrus cloud cover substantially increased between 60° S and 60° N during a 4-year period from June 1989 to September 1993. Understanding the role of cirrus clouds in climate must begin with reliable modeling of their radiative properties for incorporation in climate models as well as determination of the global variability of their composition, structure, and optical properties. Development of the remote sensing methodologies for the detection and retrieval of the ubiquitous visible and subvisual cirrus clouds requires the basic scattering, absorption, and polarization data for ice crystals in conjunction with appropriate radiative transfer models. We present the fundamentals involving radiative transfer in cirrus clouds and review pertinent research. In section 13.1, an overview of the subject of light scattering by ice crystals is presented in which we discuss a unification of the geometric optics approach for large ice particles and the finite-difference time domain numerical solution for small ice particles, referred to as the unified theory. Section 13.2 presents radiative transfer in cirrus clouds involving two unique properties: orientation of nonspherical ice crystals and cloud inhomogeneity.

Conference papers on the topic "Nonspherical modes":

1

Mead, Robert D., Karl D. Brommer, Andrew M. Rappe, and J. D. Joannopoulos. "Donor and acceptor modes in photonic band-gap materials." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/oam.1991.mq1.

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A dielectric material with a 3-D periodicity may have a photonic gap in its frequency spectrum in which propagating electromagnetic modes are forbidden.1 Recently, a number of materials that have such a gap have been discovered.2,3 Electromagnetic modes with frequencies in this forbidden region must be localized in all three dimensions. We show that lattice imperfections can introduce such exponentially localized states in the photonic band gap. We focus on the frequency spectrum of dielectric structures containing defects in an FCC lattices of nonspherical atoms,3 and compare the results of our calculations with the experiments of Yablonovitch. We consider impurities of two types: air spheres in the dielectric region and dielectric spheres in the air region. In both cases, localized photon modes are found to be introduced into the gap. Variation of the size of the impurity sphere leads to complete tunability of the frequency of this localized mode. We also discuss the localization of light at the surface of a photonic band-gap material.
2

Minin, Igor, and Oleg Minin. "Photonics of mesoscale nonspherical and non axysimmetrical dielectric particles and application to cuboid-chain with air-gaps waveguide based on periodic terajet-induced modes." In 2015 17th International Conference on Transparent Optical Networks (ICTON). IEEE, 2015. http://dx.doi.org/10.1109/icton.2015.7193645.

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Kiefer, W. "Raman-Mie scattering from optically levitated single particles." In International Laser Science Conference. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/ils.1986.thf2.

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We report on a Raman microprobe technique where micron-sized solid particles or liquid droplets are trapped in stable optical potential wells using only the force of radiation pressure from a continuous gas laser. We demonstrate this technique with Raman spectra from spherical as well as nonspherical single particles of sizes ranging between ~5 and 40μm. The particles are stably supported by a vertically directed focused TEM00-modecwargon-ion laser of ~500 mW. From the optically levitated single microparticles we took the light-scattering spectra, which, in the case of spherical particles, show pronounced structural resonances. The observed resonances could be assigned by using the well-known Lorenz-Mie formalism, and a good correlation is found between experimental and theoretically predicted spectra. It was further found that, for particular liquid droplets, quite high-order numbers of the natural modes of oscillation of a sphere play a dominant role. We describe the intensities of the resonances in the Raman-Mie spectra particularly through the volume averaged internal field intensity. We also show that the internal angle-averaged electric field intensity is localized near, but not confined to, the sphere surface.
4

Neu, Sean S., John T. Brlansky, and Michael L. Calvisi. "Nonspherical Dynamics and Shape Mode Stability of Ultrasound Contrast Agent Microbubbles." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-66423.

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Ultrasound contrast agents (UCAs) are shell encapsulated, gas-filled microbubbles developed originally for ultrasound imaging enhancement. UCAs are approximately 1–10 micrometers in diameter with a shell typically comprised of lipid, protein, or polymer. When injected into the bloodstream, the high compressibility of these microbubbles, relative to the surrounding blood and tissue, and their highly nonlinear response to ultrasound, leads to strong enhancement of the blood-tissue contrast in the resulting ultrasound image. While UCAs have been commercially available since the early 1990’s [1] for ultrasound imaging, they are more recently being exploited for therapeutic applications, for example, as vehicles for drug delivery and gene therapy, and thermal and mechanical tissue ablation. The effectiveness of UCAs in therapeutic applications depends strongly on the nonspherical character of the bubble oscillation, which can effect the breakup and release of therapeutic agents from the UCA, as well as the formation of high-speed jets near the tissue interface. In this work, two different models for nonspherical oscillation of UCAs are presented: one for small shape oscillations of a lipid-coated bubble, and one for large nonspherical oscillations of a polymer-coated bubble. Nonspherical shape mode stability and dynamics are investigated with each model for ranges of ultrasonic frequency and amplitude relevant to medical applications.
5

Angle, Brandon R., Matthew J. Rau, and Margaret L. Byron. "Effect of Mass Distribution on Falling Cylindrical Particles at Intermediate Reynolds Numbers." In ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ajkfluids2019-5458.

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Abstract In natural sedimentation, many particles of interest are both large and nonspherical. Some common particle types (e.g. naturally occurring aggregates) do not have a uniform mass distribution. As a result, the centers of mass and buoyancy are not co-located, leading to more complex settling dynamics. Here we investigated the orientation and terminal velocity of freely falling cylinders, in which the mass distribution was either constant (uniform-density, UD) or bipartite, undergoing a step function halfway along the length (compound-density, CD). Cylinders had relatively low aspect ratios (1 < AR < 4), and fell at intermediate Reynolds numbers (of order 100). The cylinders, initially horizontal, were released at the top of a tall hexagonal still-water tank, and imaged by a high-speed camera. Two low-speed cameras simultaneously captured 1) full cylinder trajectory and 2) landing position. We recorded the terminal velocity, fall orientation, and landing site of each cylinder. Results showed significant differences in the settling characteristics of uniform- vs. compound-density cylinders. UD cylinders of AR = 1 fell broadside initially, whereas AR = 1 CD cylinders fell vertically. However, both cases showed oscillation in cylinder orientation upon descent. UD cylinders with AR = 2 and AR = 4 consistently fell broadside, with minimal cylinder axis oscillation. CD cylinders with AR = 2 fell with two different modes. In mode 1, cylinders rotated 90° from their initial orientation before beginning to oscillate about the vertical axis. In mode 2, cylinder orientation remained constant at a slight angle from the horizontal. This mode was also observed in the CD AR = 4 cylinders, which fell at a constant (tilted) orientation angle and moved horizontally as they fell. The landing sites for all CD cylinders were biased toward the side of the target where the denser end of the cylinder was initially oriented, whereas UD cylinders landed in a uniform distribution around the tank center. In general, cylinders with the smallest vertical projected area fell with the greatest terminal velocity; however, the mechanisms controlling orientation remain unclear. Our results have important implications for predicting the settling behavior of naturally-occurring particles, and lay the groundwork for further study of particles settling in complex flows such as turbulence. Given our results in still water, the interplay between the buoyant torques created by the offset between the center of mass and center of volume are likely to strongly impact particle motion in turbulence.
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Miller, Joshua E., Bruce A. Davis, Robert J. McCandless, Alberto Delgado, Donald J. Henderson, Arturo Pardo, Daniel Rodriguez, and Marcus S. Sandy. "Development of Analysis Techniques for Non-Spherical Hypervelocity Impacts." In 2022 16th Hypervelocity Impact Symposium. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/hvis2022-34.

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Abstract Advanced steps have been made to develop techniques to manufacture, accelerate to orbital speeds, and diagnose the orientation for projectiles representative of the collected debris from the DebriSat experiment. This model validation work has enabled the development of numerical models of metallic, Whipple shields. Using these developed numerical models, work has begun on developing ballistic performance corrections to existing ballistic-limit equations for future use in threat assessments with an environment definition that includes nonspherical orbital debris. As described here, a slightly decreased performance is expected for a specific Whipple shield; however, much is left to do for additional projectile fineness ratios and shield characteristics.
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Arnott, W. Patrick, Y. Liu, Carl Schmitt, and John Hallett. "The Unreasonable Effectiveness of Mimicking Measured Infrared Extinction by Hexagonal Ice Crystals With Mie Ice Spheres." In Optical Remote Sensing of the Atmosphere. Washington, D.C.: Optica Publishing Group, 1997. http://dx.doi.org/10.1364/orsa.1997.othc.3.

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An armada of infrared1-2 and other remote sensing equipment have been developed and deployed to characterize clouds from the ground, from airplanes, and from satellites. Perhaps someday we will be able to trust this equipment to provide all the information we need about clouds - we no longer will have to fly through them and directly record particle statistics - but first, we must properly invert cloud radiative signatures to obtain particle information. To invert, obvious common thought has been that we must have proper numerical models for the single scattering properties of generally nonspherical cloud particles. We have been using a cloud box in the laboratory to measure radiative properties of spherical water3 and hexagonal ice particles4 in a controlled environment where clouds can be well characterized. Our first spectral extinction measurements (2-18 µm) were performed on ice clouds grown near water saturation at a variety of temperatures so that a wide range of particle morphologies from nearly equi-axed columns to sector plates were observed.4 Then we measured spectral extinction by water clouds so we could learn how to invert, using Lorenz-Mie theory, the extinction spectra to obtain particle size spectra, with the larger goal in mind of eventually retrieving ice particle size spectra using the discrete dipole approximation.3 We decided to first apply the inversion based on the Lorenz-Mie theory for ice spheres to the measured ice spectra (mostly so we could grin and giggle at the anticipated poor results), and found much to our surprise that the retrieved IR spectra matched the measurements even better than the water cloud results! Though the retrieved ice sphere size spectra are qualitatively in accord with the measured results, we have not yet found a proper principle to guide us in converting from the geometry of a hexagonal ice crystal to the geometry of a sphere. Ok, so the Mie model seems to work for mimicking the infrared spectral extinction by ice crystals, but are the inverted size spectra reasonable and useful? Come to the talk and find out.

Reports on the topic "Nonspherical modes":

1

Hwang, Soohwan, Andrew Tong, and Liang-Shih Fan. UNSUPERVISED LEARNING BASED INTERACTION FORCE MODEL FOR NONSPHERICAL PARTICLES IN INCOMPRESSIBLE FLOWS. Office of Scientific and Technical Information (OSTI), September 2023. http://dx.doi.org/10.2172/2007744.

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