Academic literature on the topic 'Exit wave function'
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Journal articles on the topic "Exit wave function"
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Chevalier, J. P., and M. J. Hytch. "Simulating the exit wave function for uniformly disordered systems." Ultramicroscopy 52, no. 3-4 (December 1993): 253–59. http://dx.doi.org/10.1016/0304-3991(93)90033-t.
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Van Dyck, D., and J. H. Chen. "Towards an exit wave in closed analytical form." Acta Crystallographica Section A Foundations of Crystallography 55, no. 2 (March 1, 1999): 212–15. http://dx.doi.org/10.1107/s0108767398011337.
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A simple but sufficiently accurate expression is obtained for the exit wave of a crystal in zone-axis orientation. The exit wave at each atom column can be parametrized with only one parameter, which is a function of the projected `weight' of the column.
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Volkov, V., J. Wall, and Y. Zhu. "Exit Wave Function Retrieval from Diffraction Patterns with Variable SAED Aperture." Microscopy and Microanalysis 12, S02 (July 31, 2006): 1670–71. http://dx.doi.org/10.1017/s1431927606067122.
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Hohenstein, M. "Reconstruction of the exit surface wave function from experimental HRTEM micrographs." Ultramicroscopy 35, no. 2 (February 1991): 119–29. http://dx.doi.org/10.1016/0304-3991(91)90096-o.
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Bierwolf, R., and M. Hohenstein. "Premise-free reconstruction of the exit-surface wave function in HRTEM." Ultramicroscopy 56, no. 1-3 (November 1994): 32–45. http://dx.doi.org/10.1016/0304-3991(94)90144-9.
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Broeckx, J., M. Op de Beeck, and D. Van Dyck. "A useful approximation of the exit wave function in coherent STEM." Ultramicroscopy 60, no. 1 (August 1995): 71–80. http://dx.doi.org/10.1016/0304-3991(95)00053-4.
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Lee, Jongyeong, Yeongdong Lee, Jaemin Kim, and Zonghoon Lee. "Contrast Transfer Function-Based Exit-Wave Reconstruction and Denoising of Atomic-Resolution Transmission Electron Microscopy Images of Graphene and Cu Single Atom Substitutions by Deep Learning Framework." Nanomaterials 10, no. 10 (October 6, 2020): 1977. http://dx.doi.org/10.3390/nano10101977.
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The exit wave is the state of a uniform plane incident electron wave exiting immediately after passing through a specimen and before the atomic-resolution transmission electron microscopy (ARTEM) image is modified by the aberration of the optical system and the incoherence effect of the electron. Although exit-wave reconstruction has been developed to prevent the misinterpretation of ARTEM images, there have been limitations in the use of conventional exit-wave reconstruction in ARTEM studies of the structure and dynamics of two-dimensional materials. In this study, we propose a framework that consists of the convolutional dual-decoder autoencoder to reconstruct the exit wave and denoise ARTEM images. We calculated the contrast transfer function (CTF) for real ARTEM and assigned the output of each decoder to the CTF as the amplitude and phase of the exit wave. We present exit-wave reconstruction experiments with ARTEM images of monolayer graphene and compare the findings with those of a simulated exit wave. Cu single atom substitution in monolayer graphene was, for the first time, directly identified through exit-wave reconstruction experiments. Our exit-wave reconstruction experiments show that the performance of the denoising task is improved when compared to the Wiener filter in terms of the signal-to-noise ratio, peak signal-to-noise ratio, and structural similarity index map metrics.
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de Ruijter, W. J., M. R. McCartney, David J. Smith, and J. K. Weiss. "Exit-surface wave reconstruction using a focal series." Proceedings, annual meeting, Electron Microscopy Society of America 50, no. 2 (August 1992): 988–89. http://dx.doi.org/10.1017/s0424820100129577.
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Further advances in resolution enhancement of transmission electron microscopes can be expected from digital processing of image data recorded with slow-scan CCD cameras. Image recording with these new cameras is essential because of their high sensitivity, extreme linearity and negligible geometric distortion. Furthermore, digital image acquisition allows for on-line processing which yields virtually immediate reconstruction results. At present, the most promising techniques for exit-surface wave reconstruction are electron holography and the recently proposed focal variation method. The latter method is based on image processing applied to a series of images recorded at equally spaced defocus.Exit-surface wave reconstruction using the focal variation method as proposed by Van Dyck and Op de Beeck proceeds in two stages. First, the complex image wave is retrieved by data extraction from a parabola situated in three-dimensional Fourier space. Then the objective lens spherical aberration, astigmatism and defocus are corrected by simply dividing the image wave by the wave aberration function calculated with the appropriate objective lens aberration coefficients which yields the exit-surface wave.
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Haigh, S. J., H. Sawada, and Angus I. Kirkland. "Optimal tilt magnitude determination for aberration-corrected super resolution exit wave function reconstruction." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 367, no. 1903 (September 28, 2009): 3755–71. http://dx.doi.org/10.1098/rsta.2009.0124.
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Transmission electron microscope (TEM) images recorded under tilted illumination conditions transfer higher spatial frequencies than axial images. This super resolution information transfer is highly directional in a single image, but can be extended in all directions through the use of complementary beam tilts during exit wave function reconstruction. We have determined the optimal experimental tilt magnitude for aperture synthesis in an aberration-corrected TEM. It is shown that electron-optical aberration correction allows the use of larger tilt angles and reduces the constraints that are imposed on experimental data acquisition in an uncorrected microscope. We demonstrate that, in many cases, the resolution improvement achievable is now limited by the sample and not by instrumental parameters. An exit wave function is presented that has been successfully reconstructed from a dataset of aberration-corrected images, including images acquired at a beam tilt of 18 mrad, which clearly demonstrates a resolution improvement from 0.11 nm to better than 0.08 nm at 200 kV.
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Sayagués, Maria, Katherine Titmuss, Rudiger Meyer, Angus Kirkland, Jeremy Sloan, John Hutchison, and Richard Tilley. "Structural characterization of the n = 5 layered perovskite neodymium titanate using high-resolution transmission electron microscopy and image reconstruction." Acta Crystallographica Section B Structural Science 59, no. 4 (July 25, 2003): 449–55. http://dx.doi.org/10.1107/s0108768103010346.
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The structure of Nd5Ti5O17 has been refined from a reconstruction of the specimen exit-plane wave restored from a series of incrementally defocused high-resolution transmission electron microscope (HRTEM) images. The phase of the exit-plane wave shows contrast attributable to the oxygen anion sublattice and coupled with simulations provides confirmation of the composition of the cation sites as a function of sample thickness. The enhanced resolution in the exit-plane wave additionally allows a direct measurement of the `skewing' of the perovskite slabs.
Dissertations / Theses on the topic "Exit wave function"
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Colson, Tobias A., and tobiascolson@gmail com. "Large Angle Plasmon Scattering in Metals and Ceramics." RMIT University. Applied Sciences, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20090212.143048.
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This investigation is primarily concerned with the low loss, or plasmon region of an electron energy loss spectrum. Specifically, why these spectra have the shape and form that they do; what the significance of the material is in determining the shape and form of these spectra; what can be done with plasmon excited electrons; and how all of this fits in with the current theory of plasmon excitation. In particular, the concept of plasmon scattering being an energy transfer process of a coupled wave in the material is explored. This gives rise to slightly different explanations of the plasmon scattering process to the status quo. Multiple scattering is typically pictured as a combination of separate and independent, elastic and inelastic scattering events interactively contributing to a final exit wave function. However, this investigation explores the idea of the elastic and inelastic components being a coupled event, and what the consequences of this idea are from a conceptual point of view. The energy transfer process itself, does not deviate from a virtual particle exchange description that is consistent with the standard model. However, the two significant points made throughout the chapters are one: that the elastic and inelastic scattering events are coupled rather than separate, and two: that each succussive higher order scattering event in multiple scattering scenarios, are dependant and connecte d rather than independent.
Book chapters on the topic "Exit wave function"
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Metral, E., G. Rumolo, and W. Herr. "Impedance and Collective Effects." In Particle Physics Reference Library, 105–81. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-34245-6_4.
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AbstractAs the beam intensity increases, the beam can no longer be considered as a collection of non-interacting single particles: in addition to the “single-particle phenomena”, “collective effects” become significant. At low intensity a beam of charged particles moves around an accelerator under the Lorentz force produced by the “external” electromagnetic fields (from the guiding and focusing magnets, RF cavities, etc.). However, the charged particles also interact with themselves (leading to space charge effects) and with their environment, inducing charges and currents in the surrounding structures, which create electromagnetic fields called wake fields. In the ultra-relativistic limit, causality dictates that there can be no electromagnetic field in front of the beam, which explains the term “wake”. It is often useful to examine the frequency content of the wake field (a time domain quantity) by performing a Fourier transformation on it. This leads to the concept of impedance (a frequency domain quantity), which is a complex function of frequency. The charged particles can also interact with other charged particles present in the accelerator (leading to two-stream effects, and in particular to electron cloud effects in positron/hadron machines) and with the counter-rotating beam in a collider (leading to beam–beam effects). As the beam intensity increases, all these “perturbations” should be properly quantified and the motion of the charged particles will eventually still be governed by the Lorentz force but using the total electromagnetic fields, which are the sum of the external and perturbation fields. Note that in some cases a perturbative treatment is not sufficient and the problem has to be solved self consistently. These perturbations can lead to both incoherent (i.e. of a single particle) and coherent (i.e. of the centre of mass) effects, in the longitudinal and in one or both transverse directions, leading to beam quality degradation or even partial or total beam losses. Fortunately, stabilising mechanisms exist, such as Landau damping, electronic feedback systems and linear coupling between the transverse planes (as in the case of a transverse coherent instability, one plane is usually more critical than the other).
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Steel, Duncan G. "Free Particle, Wave Packet and Dynamics, Quantum Dots, Defects and Traps." In Introduction to Quantum Nanotechnology, 32–56. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780192895073.003.0003.
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This chapter continues with a study of the time independent Schrödinger equation and seeks to contrast the quantum behavior of a free particle with that of a particle localized in a potential quantum well. A free particle can exist over all space or can be localized in a wave package. The wave packet is a coherent superposition of the plane waves that make up the wave function that localizes the particle because of constructive and destructive interference. The wave packet spreads out in time because the waves leading to constructive interference get out of phase. In Chapter 2, the particle was localized by a quadratic potential energy. Here, the potentials are described as piecewise constant. The approach is based on assuming a one-dimensional space, x, which is relevant to many problems in the laboratory. The solution is easily generalized to higher dimensions (x-y or x-y-z), but the physics remains the same. The objective is to understand the shape of the eigenfunctions in space and to be able to relate this to the probability density of locating the particle, as well as understanding the relevance of these systems to today’s technology.
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Klainerman, Sergiu, and Jérémie Szeftel. "Decay Estimates for q (Theorem M1)." In Global Nonlinear Stability of Schwarzschild Spacetime under Polarized Perturbations, 213–63. Princeton University Press, 2020. http://dx.doi.org/10.23943/princeton/9780691212425.003.0005.
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This chapter examines the proof for Theorem M1, deriving decay estimates for the quantity q for k ≤ k small + 20 derivatives. To this end, it uses the wave equation satisfied by q. The spacetime M is decomposed as M = (int)M u (ext)M and that u is an outgoing optical function on (ext)M while u is an ingoing optical function. The chapter relies on the global frame defined in section 3.5, and r and m denote the corresponding scalar functions associated to it. It also proves two theorems on improved weighted estimates, as well as flux decay estimates for q.
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Bäckström, Anders. "Introduction." In Religion and Welfare in Europe. Policy Press, 2017. http://dx.doi.org/10.1332/policypress/9781447318972.003.0001.
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This introductory chapter provides an overview of the relationship between welfare and religion. The relationship between welfare and religion, as it developed during the 20th century, was shaped during the formative ‘golden years’ following 1945. Welfare became part of a modernity in which the relationship between religion and societal institutions—such as school, health, and social care—was weakening rapidly or in some cases had ceased to exist. Studies of different welfare regimes have revealed, however, that their roots lie in contrasting political, social and religious circumstances. These circumstances function as a historically based ‘glue’ that helps to explain the subtle values that connect religion and welfare within these different systems. The chapter then presents the project Welfare and Values in Europe: Transitions Related to Religion, Minorities and Gender (WaVE), which formed the background to the project featured in this volume.
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Keith Baker, Oliver. "Quantum Information Science in High Energy Physics." In Topics on Quantum Information Science [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.98577.
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We demonstrate that several anomalies seen in data from high energy physics experiments have their origin in quantum entanglement, and quantum information science more generally. A few examples are provided that help clarify this proposition. Our research clearly shows that there is a thermal behavior in particle kinematics from high energy collisions at both collider and fixed target experiments that can be attributed to quantum entanglement and entanglement entropy. And in those cases where no quantum entanglement is expected, the thermal component in the kinematics is absent, in agreement with our hypothesis. We show evidence that these phenomena are interaction independent, but process dependent, using results from proton-proton scattering at the Large Hadron Collider (LHC) and antineutrino-nucleus scattering at Fermilab. That is, this thermal behavior due to quantum entanglement is shown to exist in both the strong and electroweak interactions. However, the process itself must include quantum entanglement in the corresponding wave functions of interacting systems in order for there to be thermalization.
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Adenike, Adeniji Anthonia. "Tools and Techniques for Designing Effective Compensation Systems." In Encyclopedia of Human Resources Information Systems, 842–48. IGI Global, 2009. http://dx.doi.org/10.4018/978-1-59904-883-3.ch124.
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Employees are the most essential resource of an organization. They are vital to a company’s success. Without them, it would seize to exist. Management will probably give employee compensation the first place in their priority list and rightly so. Because the importance that compensation holds for their lifestyle and self-esteem, individuals are very concerned that they be paid a fair and competitive wage. Organizations are concerned with pay not only because of its importance as a cost of doing business, but also because it motivates important decisions of employees about taking a job, leaving a job, and performance on the job. Hence, one of the most vital factors for attraction, motivation, and retention amongst the employees is the compensation system, policies, and review philosophies of any organization. Compensation as a function of human resource management that involves rewarding employees for performing organizational task is one of the most complex functions of the human resource manager. A lot of studies have shown the various components of compensation both for the executives and the employees, but no study has focused on the tools and techniques for designing and implementing effective compensation systems. Therefore, this article will look into these tools and techniques of effective compensation systems. To be able to do this effectively, we will look at the various definitions of compensation in the background to the study, the features of good compensation tools, the rationale for choosing effective compensation tools, and the various compensation tools we have—both intrinsic and extrinsic.
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Huq, Aziz Z. "How War Makes (and Unmakes) the Democratic State." In Cannons and Codes, 278–95. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780197509371.003.0016.
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Focusing on the figures of the terrorist and the migrant, Huq suggests that war in the twenty-first century, in partial contrast to its precursors, may prove costly to democracy. Whereas war once served to develop bureaucratic capacity, shrink wealth gaps, and expand the franchise, it is less likely to perform these functions in a period when war is increasingly cabined to distant zones of violence, mechanized, and privatized. Huq considers a pair of novels by Mohsin Hamid, The Reluctant Fundamentalist and Exit West. The former documents the transformation, and potential radicalization, of a young Pakistani professional in the wake of the September 11 attacks; the latter follows a couple from an unspecified city on the brink of civil war to the Greek island of Mykonos, then to London, and finally to Marin County, California, where their relationship dissolves. Whereas right-wing populists cast the terrorist and the migrant as racialized threats to civilization and national culture, Hamid’s protagonists instead embody a commitment to pluralism, inclusion, and democratic openness.
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"Physiological Basis of Electrogastrography." In Handbook of Electrogastrography, edited by Kenneth L. Koch and Robert M. Stern. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195147889.003.0007.
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In this chapter, the anatomical, functional, and in vivo myoelectrical characteristics of the normal stomach are reviewed. The anatomical regions of the stomach are shown in Figure 3.1. Major areas are the fundus, the body (corpus), antrum, and pyloroduodenal area. Extrinsic innervation of the stomach is provided by the vagus nerve and splanchnic nerves. The pacemaker region is shown on the greater curvature of the stomach between the fundus and the corpus. From the pacemaker region, spontaneous electrical depolarization and repolarization occurs and generates the myoelectrical waves that are termed the gastric pacesetter potentials, or slow waves. The prominent muscle layers of the stomach are the circular and the longitudinal muscle layers (see Fig. 3.1, middle). The oblique muscle layer is included in the muscularis. Between these smooth muscle layers lie the neurons of the myenteric plexus, the gastric components of the enteric nervous system. Afferent neurons, interneurons, and postganglionic parasympathetic neurons all have synaptic interactions in the myenteric plexus. Intrinsic neurons and extrinsic excitatory and inhibitory neurons from the vagus nerve and splanchnic nerves, intraluminal contents, and hormones modulate contraction and relaxation of the smooth muscle in the different regions of the stomach. Important anatomical and functional relationships exist among the circular smooth muscle layer, the myenteric neurons, and the interstitial cells of Cajal (ICCs) (see Fig. 3.1, bottom). The ICCs are the pacemaker cells, the cells that spontaneously depolarize and repolarize and set the myoelectrical rhythmicity of the stomach and other areas of the gastrointestinal tract. The interstitial cells are electrically coupled with the circular muscle cells. Low-amplitude rhythmic circular contractions occur at the pacemaker rhythm. Rhythmicity and contractility of the circular muscle layer are modulated by ongoing activity excitatory and inhibitory of myenteric neurons that synapse with the interstitial cells. The interstitial cells have a variety of other receptors. Electrocontractile activities of the gastric smooth muscle are modified by neuronal and hormonal inputs appropriate for fasting and specific postprandial conditions. Control of rhythmicity may be modulated by a variety of stimuli that affect the interstitial cells and is a focus of intense investigation.
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Caradonna, Jeremy L. "Eco-Nomics." In Sustainability. Oxford University Press, 2014. http://dx.doi.org/10.1093/oso/9780199372409.003.0008.
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The environmental movement of the 1960s and 1970s overshadows a second, less heralded intellectual development that took place at the exact same time: the birth of “ecological economics.” A cluster of nonconforming economists in this period drew on the fledgling science of ecology to rethink many of the assumptions of neoclassical economics, with its “growthmania,” general indifference toward pollution and ecosystem destruction, and dogmatic belief that “tastes and preferences” are innate in humans rather than culturally shaped. What emerged was a new school of thought that integrated ecological concerns into an essentially capitalist economic framework. These iconoclasts brought together the dual nature of the Greek word “oikos” (literally: household), which is the etymological root of both “economics” and “ecology.” They asserted that the human “household” could not exist without a healthy and functional natural environment. This has become the essential insight of economic sustainability—the second “E” of sustainability: that the world needs economic systems that exist harmoniously with nature (and which promote social equality and justice). Those who practice the economics of sustainability in the present day— William E. Rees, Mathis Wackernagel, Peter Victor, Tim Jackson, Richard Heinberg, and many others—are the heirs of these early critics who challenged the hegemony of business-as-usual economics. First-wave ecological economics shares the readability of the classic environmental works discussed in the previous chapter. The main authors associated with ecological economics—E. J. Mishan, E. F. Schumacher, Kenneth Boulding, Howard T. Odum, Nicholas Georgescu-Roegen, Herman Daly, Amory Lovins, and the members of the shadowy-sounding Club of Rome—went out of their way to write nontechnical books that were meant to appeal to the average-educated reader. Collectively, these authors ask deep and penetrating philosophical questions: What is the point of endless economic growth? What are the environmental costs of a wasteful and fossil-fuel-addicted consumer society? What is the best way to measure the well-being of a society? What is the role of economics in ensuring that human society remains within its ecological limits and avoids overshoot and collapse? How can nature, society, and the economy be studied as a single system?
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Dyall, Kenneth G., and Knut Faegri. "Molecular Properties." In Introduction to Relativistic Quantum Chemistry. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195140866.003.0019.
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Strictly speaking, in quantum mechanics a measurable property is defined as an observable connected to a self-adjoint operator. However, in common usage the term molecular property is loosely taken to mean any physical attribute of a molecule, preferably amenable to experimental measurement. Common examples of properties of interest to chemists are molecular structure, thermodynamic quantities, spectroscopic transition energies and intensities, and various electric and magnetic moments. The amenability to experiment may exist only in principle—one of the strong points of modern computational chemistry is the possibility of studying phenomena occurring under conditions that lie beyond the present experimental capabilities. Sometimes, differential effects between different theoretical models are also regarded as properties: thus the correlation energy is generally considered to be the difference between the Hartree–Fock energy and the energy obtained from a complete many-electron treatment (e.g. full CI or MBPT to all orders). At best only the latter of these is accessible to experiment. Similarly, certain relativistic effects (e.g. bond contraction) only appear as the difference between results from a relativistic and a nonrelativistic calculation. The calculation of molecular properties in a relativistic framework follows the same principles as for the nonrelativistic case once a wave function or electron density of adequate quality is available. Our aim here is therefore not to provide explicit expressions and formulas for the calculation of a more or less complete catalog of properties. However, in relativistic calculations of molecular properties there are some aspects of the theory that warrant special care and consideration. In particular, we need to know how to handle features such as Lorentz invariance, gauge invariance, and negativeenergy states. Moreover, the electric and magnetic fields appear as natural parts of the relativistic Hamiltonian, and we therefore expect that properties involving these may require a different treatment from the nonrelativistic case where terms involving external fields are grafted onto the nonrelativistic Hamiltonian, often based on some reduction or approximation from the relativistic case.
Conference papers on the topic "Exit wave function"
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Orekhov, Viktor L., and Mahesh V. Panchagnula. "Non-Intrusive Technique for Measuring Instability Wave Amplitudes at Simplex Swirl Atomizer Exit." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-14865.
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An optical method for non-intrusive wave amplitude measurement is examined. An experimental setup was constructed to produce sprays of various fluids including Canola oil and glycerin-water mixtures, such that precise control of pressure up to 140 psi was possible. A spray was produced by a 20 Gallon per hour oil burner nozzle at varying pressures. Initially, a smooth laminar conical sheet was noticed which eventually was found to break up into droplets. A laser was passed through the laminar conical sheet and was projected onto a surface on the other side and resulted in a vertical linear projection. This projection is postulated to be formed due to the scanning motion of the laser beam as instability waves pass through the laser. The angle of this scan was found to be a function of pressure, cone angle, and distance of laser from nozzle. High resolution images were taken of the film profile as well as the projected image and image analysis software was used to calculate cone angles and angular scan of the laser. Tests were performed with Canola Oil as well as a mixture of glycerin and water in order to evaluate the effect of viscosity and surface tension on the measurements. The resulting data was used to illustrate a principle for determining the instability wave amplitude using this technique.
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Guzel, Bulent, and Fatih C. Korkmaz. "Experimental Investigation of Water Exit Under Hydrophobic Effects." In ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/omae2016-54636.
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Prediction of hydrodynamic loads during water exit of a body is of a great importance in designing the marine vehicles that take off from the free water surface such as sea planes and wing-in-ground effect vehicles (WIG), and that pierce through the free surface like missiles and submarines. The results of an experimental investigation on water exit of two different geometries, sphere and flat plate, with hydrophobic surfaces are presented in this paper. With and without the hydrophobic effects present, different fluid dynamics phenomena like free surface evolution, deformation and break up of free surface, wave generation, splash, air entrapment and water detachment from the solid surfaces during a water exit event have been examined. The non-dimensional exit coefficient, Ce is a function of the total vertical hydrodynamic force which depends on the geometry of the object and the hydrodynamic conditions along with the water parameters. Our study is aimed at understanding and modeling the nonlinear free surface effects and the dynamics of water exit under an extended range of parameters including hydrophobic effects. In this study, due to lack of the experimental data on the water exit problem in literature, water exit tests have been set up, first for initially partially immersed spheres and flat plates, with their center above the free surface, to be towed vertically from the water surface at various speeds. Secondly, buoyancy driven water exit of a fully immersed sphere is investigated. It is observed that when the sphere rises up, it first starts deforming the free surface, and then pierces into it. The thin water layer attached to the surface of the sphere is drawn back to the test tank as the sphere moves further upward. This causes breaking of the free surface, air entrapment and wave generation in the water tank. From digital images captured using a high speed camera, free surface breakup and water detachment at different velocities are observed and the time evolution of the water detachment and the exit characteristics are measured during a water exit event. The position of the sphere and its velocity are plotted against time. A detailed measurement of the global loads on the test objects during exit is carried out by employing strain gauges. We also showed the effects of water detachment on the test bodies during exit and after fully exited via strain gauges. All this data is also collected under the hydrophobic effects, to show how the change in surface characteristics would have significant impacts on the water exit phenomenon. Analyzing the difference in occurrence of water flow separation, the change in kinetic energy of the fluid and the free surface deformation under the hydrophobic effects may help give a better explanation of the phenomena observed during water exit and improve the design characteristics of marine structures for a water exit event.
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Dean, Adam, Barton L. Smith, and Zachary E. Humes. "Steady Circulation Generated From Oscillating Flow Through a Hollow Cone at the Exit of a Pipe." In ASME 2005 Fluids Engineering Division Summer Meeting. ASMEDC, 2005. http://dx.doi.org/10.1115/fedsm2005-77454.
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A numerical approach to optimizing heat removal from a standing wave thermoacoustic engine by generating steady circulation at the outlet is described. The open-ended standing wave engine makes use of a hollow cone placed opening outwards and flush with the open end of the engine. Parallel paths within and without the cone create asymmetric minor losses. These are designed to induce circulation and heat removal. If successful, this will eliminate the need of a cold heat exchanger. The numerical models make use of the commercial RANS numerical solver FLUENT. Orders of magnitude increase in heat flux out of the engine’s open tube as compared to an engine without a cone are demonstrated. Three cones are evaluated at a range of flow parameters. Performance is found to be a strong function of the displacement amplitude compared to the engine diameter. In addition, these results are compared to an experiment that provides velocity data.
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Lear, William E., and Robert P. Kielb. "The Effect of Blade Angle Design Selection on Wave-Turbine Engine Performance." In ASME 1996 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-gt-259.
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Wave rotors have been investigated over several decades in part due to their potential for increasing the maximum cycle temperature in gas turbine engines via their self-cooling mechanism. Recent activities in this field have centered on the experiments and CFD design tools developed at NASA Lewis Research Center. Because of the fundamental objectives of that program, the work to date has concentrated on wave rotors rather than wave turbines. Wave turbines differ from wave rotors in that the flow passages are curved, similar to conventional turbines, so that the unit produces net shaft power. The purpose of this paper is to present an analysis technique which is used to quantify the substantial impact which blade curvature has on the maximum gas expansion ratio, and hence on the maximum cycle temperature. Limited optimization of the overall pressure ratio allows the maximum specific power and the corresponding efficiency to be found as a function of wave turbine inlet and exit blade angles and Mach number. A potential increase in specific power of 69% and a 6.8 percentage point increase in thermal efficiency over a conventional gas-turbine engine can be achieved through the use of a wave turbine.
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Yoshida, Yasuhiro, Chungpyo Hong, Yutaka Asako, and Koichi Suzuki. "Experimental Investigation of Gaseous Flow in a Micro-Tube." In ASME 2009 7th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2009. http://dx.doi.org/10.1115/icnmm2009-82054.
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Experimental investigations on nitrogen gas flow characteristics were performed for a micro-tube. The micro-tube was fabricated in a stainless steel block by electrical discharge machining (EDM). The tube diameter was 326 μm and the ratio of length to diameter was 200. The stagnation pressure was chosen in such a way that the exit Mach number ranged from 0.1 to 1.4. The outlet pressure was fixed at atmospheric conditions. The pressure was locally measured at five locations along tube length to determine local values of Mach number and friction factor for a wide range of flow regime from laminar to turbulent flow. The result shows that f·Re is a function of Mach number and higher than incompressible value, 64 due to the compressibility effect. The values of f·Re were compared with f·Re correlation in literature. In additional experiments, Mach number at the micro-tube exit was measured by using a Shadowgraph system which visualizes the shock wave of the gas. The micro-tube with 400 μm in diameter was used for the experiment. The super sonic flow was observed since Mach number at the micro-tube exit was beyond unity. The experimental results for laminar flow were compared with the numerical results obtained by the arbitrary-Lagrangian-Eulerian method. The both results are in excellent agreement.
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Zhu, W. D., X. K. Song, and N. A. Zheng. "Dynamics Stability of a Translating String With a Sinusoidally Varying Velocity." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-38692.
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A new parametric instability phenomenon characterized by infinitely compressed, shock-like waves with a bounded displacement and an unbounded vibratory energy is discovered in a translating string with a constant length and tension and a sinusoidally varying velocity. A novel method based on the wave solutions and the fixed point theory is developed to analyze the instability phenomenon. The phase functions of the wave solutions corresponding to the phases of the sinusoidal part of the translation velocity, when an infinitesimal wave arrives at the left boundary, are established. The period number of a fixed point of a phase function is defined as the number of times that the corresponding infinitesimal wave propagates between the two boundaries before the phase repeats itself. The instability conditions are determined by identifying the regions in a parameter plane where attracting fixed points of the phase functions exist. The period-1 instability regions are analytically obtained, and the period-i (i > 1) instability regions are numerically calculated using bifurcation diagrams. The wave patterns corresponding to different instability regions are determined, and the strength of instability corresponding to different period numbers is analyzed.
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Sundaramurthy, Aravind, Raj K. Gupta, and Namas Chandra. "Design Considerations for Compression Gas Driven Shock Tube to Replicate Field Relevant Primary Blast Condition." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-63732.
Full textAbstract:
Detonation of a high explosive (HE) produces shock-blast wave, noise, shrapnel, and gaseous product; while direct exposure to blast is a concern near the epicenter; shock-blast can affect subjects even at farther distances. The latter is characterized as the primary blast with blast overpressure, time duration, and impulse as shock-blast wave parameters (SWPs). These parameters in turn are a function of the strength of the HE and the distance from the epicenter. It is extremely important to carefully design and operate the shock tube to produce a field relevant SWPs. In this work, we examine the relationship between shock tube adjustable parameters (SAPs) and SWPs to deduce relationship that can be used to control the blast profile and emulate the field conditions. In order to determine these relationships, 30 experiments by varying the membrane thickness, breech length (66.68 to 1209.68 mm) and measurement location was performed. Finally, ConWep was utilized for the comparison of TNT shock-blast profiles with the profiles obtained from shock tube. From these experiments, we observed the following: (a) burst pressure increases with increase in the number of membrane used (membrane thickness) and does not vary significantly with increase in the breech length; (b) within the test section, overpressure and Mach number increases linearly with increase in the burst pressure; however, positive time duration increases with increase in the breech length; (c) near the exit of the shock tube, there is a significant reduction in the positive time duration (PTD) regardless of the breech length.
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Yamanaka, Shingo, Takayuki Hirai, Yasunori Nihei, and Akira Sou. "Interaction Between Advanced Spar and Regular Waves." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-61788.
Full textAbstract:
Advanced spar type of the floating wind turbine with a short spar and a cylindrical column floater has been developed and tested recently. However, numerical methods to accurately simulate the interaction between the advanced spar and waves have not been established yet. In this study we simulated the free surface flow around an advanced spar in regular waves using open source computational fluid dynamics (CFD) software OpenFOAM to examine its applicability. We used olaFOAM which equipped with the functions to set the boundary conditions of wave generation at the inlet and wave absorption at the exit. An experiment of the advanced spar model fixed in space in the regular waves with various wave periods was also conducted to obtain an experimental database on the horizontal and vertical forces acting on the structure and pressure distribution on the floater surface. The results of the forces obtained by the numerical simulation, experiment, Morison’s equation were compared to examine the validity of the numerical model. Numerical and experimental results of the horizontal and vertical forces as well as pressure distribution on the floater surface were in good agreement, which confirmed the validity of the present numerical method. Then, we evaluated numerically the effects of the edge of the column by simulating a sharp-edged and a chamfered column floater. The result clarified that a chamfered edge decreased the wake which reduced the forces acting on the floater structure.
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Pilatis, Nick, Michael Whiteman, Paul Madden, Michael A. Macquisten, and A. John Moran. "Forced Combustion Experiments on Aero Combustors." In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45235.
Full textAbstract:
In the world of gas turbine combustion there is always the spectre of thermo-acoustic instability. Over the past few decades there has been significant effort afforded to researching the phenomenon of thermo-acoustics. The results of the research have produced numerous mathematical models and at system level these models have been used to predict and postdict where noise is likely to occur in a given system. The models also allow the combustion system to be numerically tested through the flight or operational envelope to identify areas where instability may occur before testing is carried out, thus reducing the risk of unexpected noise occurring. The weakness of many of these models is that they require, what is known as a flame transfer function. The flame transfer function is normally measured after the combustor has been fully designed and at a high TRL (Technology Readiness Level) so significant investment in time and money are already baked into the design. Remedial action if required can result in a significant loss of time and money in the development of the combustor. This paper describes the design and use of a test rig that allows combustion systems to be tested at much lower TRL. A ‘siren’ rig has been developed and used to identify what particular design changes in either combustor flow field or fuel delivery systems have effects on the thermo-acoustics. The exit boundary of the unit has a representative choked end point. This end point has the ability to be modulated in time, thus forcing the whole system. How the system reacts to the forcing is measured over a range of frequencies. The rig has been successfully used to influence design changes required to avoid combustion driven oscillations within the next generation of aero gas turbine combustors. The rig is not a representation of a complete 360 degree annular combustor system, but of a smaller sector. The objective is to isolate the Fuel Spray Nozzle (FSN) and corresponding combustor sector from acoustic resonances and derive functions expressing the relationship between unsteady heat release rate and unsteady aerodynamics for a range of operating conditions by controlling the modulation of air mass flow rate. Such functions can be used in conjunction with acoustic linear theory to predict wave modes and growth rates in combustor geometries.
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Mohammad, Bassam S., Preetham Balasubramanyam, Keith McManus, Jeffrey Ruszczyk, Ahmed M. Elkady, and Mark A. Mueller. "Combustion Dynamics Diagnostics and Mitigation on a Prototype Gas Turbine Combustor." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68570.
Full textAbstract:
Combustion dynamics have detrimental effects on hardware durability as well as combustor performance and emissions. This paper presents a detailed study on the impact of combustion dynamics on NOx and CO emissions generated from a prototype gas turbine combustor operating at a pressure of 180 psia (12.2 bars) with a pre-heat temperature of 720 F (655.3 K) (E-class machine operating conditions). Two unstable modes are discussed. The first is an intermittent mode, at 750 Hz, that emerges at flame temperatures near 2900°F (1866.5 K), resulting in high NOx and CO emissions. With increasing fuel flow, NOx and CO emissions continue to increase until the flame temperature reaches approximately 3250°F (2061 K), at which point the second acoustic mode begins to dominate. Flame images indicate that the intermittent mode is associated with flame motion which induces the high NOx and CO emissions. The second mode is also a 750 Hz, but of constant amplitude (no intermittency). Operation in this second 750 Hz mode results in significantly reduced NOx and CO emissions. At pressures higher than 180 psia (12.2 bars), the intermittent mode intensifies, leading to flashback at flame temperatures above 2850°F (1839 K). In order to mitigate the intermittent mode, a second configuration of the combustor included an exit area restriction. The exit area restriction eliminated the intermittent mode, resulting in stable operation and low emissions over a temperature range of 2700–3200°F (1755–2033 K). A comparison of the NOx emissions, as function of flame temperature, with previous published data for perfectly premixed indicates that, while the low amplitude 750 Hz oscillations have little effect, the intermittent mode significantly increases emissions. Mode shape analysis shows that the 750 Hz instability corresponds to the 1/4 wave axial mode. In the current research a ceramic liner is used while the previous published data was collected with a quartz liner. Typically, quartz is avoided due to reductions in effective flame temperature by radiation losses. Experiments showed that NOx emissions were not affected by the combustor liner type. This agreement between the quartz and ceramic liners data indicates limited effect from the radiation heat losses on NOx emissions.