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Articoli di riviste sul tema "Radiation from complex-shaped plates"
1
Atalla, Noureddine, e Alain Berry. "Acoustic Radiation from a Coupled Planar Semi-Complex Structure in Heavy Fluid". Journal of Ship Research 38, n. 03 (1 settembre 1994): 213–24. http://dx.doi.org/10.5957/jsr.1994.38.3.213.
Testo completoAbstract (sommario):
A mathematical model is derived to address the vibrations and sound radiation into a dense fluid, of a coupled system consisting of two semi-complex plates (i.e., supporting added mass, stiffeners, and having arbitrary elastic boundary conditions) linked in four points through multistage suspensions elements. The supporting plate is subjected to point, line or surface harmonic excitation, while the radiating plate is excited through the suspensions. Both plates are assumed to be baffled, and the radiating plate is fluid loaded. The model is based on a variational approach for the plates, and a matrix transfer approach is used to handle the coupling between the two-plates. The solution is found using a Rayleigh-Ritz expansion in terms of polynomial trial functions which are shown to allow for the arbitrary elastic boundary conditions and to facilitate the calculation of the radiation impedance matrix. The vibrations and noise design of the system is discussed. The main design indicators are the force transmissibilities between the different excitation and attachment points, the mean square velocity, the radiated power and the radiation efficiency of the radiating plate. Numerical examples are presented to show the effects of fluid loading and different design parameters (plates thickness, boundary conditions, added mass, stiffeners, etc.) on the radiated sound.
2
Taratorin, Andrey, e Vladimir Tupov. "PETAL-SHAPED SILENCERS USAGE FOR NOISE REDUCTION IN CYLINDRICAL CHANNELS". VOLUME 39, VOLUME 39 (2021): 99. http://dx.doi.org/10.36336/akustika20213999.
Testo completoAbstract (sommario):
The article presents data on the results of petal-shaped silencer mathematical modeling. Dissipative silencers of complex shapes are the most promising technology. This design allows for achieving the required noise reduction. At the same time, geometric shape optimization allows reducing the aerodynamic drag to the smallest values. The article compares the variants of the silencer with the rotation angles of the plates 45 and 70 degrees. The use of such plates allows you to increase the acoustic efficiency of the silencer by eliminating the radiation effect. In the article, there are the results of noise calculation from a dry cooling tower. The use of a petal-shaped silencer will significantly increase acoustic efficiency. The extra aerodynamic drag will be minimal. For comparison presented the results of modeling a cylindrical silencer. The cylindrical silencer has an equal through-section and long. Justified the approach to choosing the most preferred option. The initial velocity field of the gas or air flow in the channel determines the choice of silencer design.
3
Wen, Hua Bing, Lin Bo Liu, Zi Long Peng e Qi Dong Zhong. "Research on the Effects of Blocking Mass on Vibration Resistance Performance of L-Shaped Plates". Applied Mechanics and Materials 482 (dicembre 2013): 131–35. http://dx.doi.org/10.4028/www.scientific.net/amm.482.131.
Testo completoAbstract (sommario):
The theory of vibration resistance of blocking mass at the corner interface of L-shaped plates is put forward from the perspective of wave approach. The equation of transmission and reflection coefficients of flexure wave is deduced by the presented theory. Based on FE/SEA method, the vibration resistance performance of the hollow blocking mass at the corner interface of L-shaped plates was studied through numerical simulation. The results show that the hollow blocking mass can impede the propagation of the high frequency vibration waves, reduce the vibration and sound radiation of the latter plate, and increase the influence of the reflection waves on the former plate. However, the overall radiant energy is basically identical to the L-shaped plates without the hollow blocking mass.
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Tenenbaum, Roberto A., e Marcelo Bruno S. Magalhães. "A New Technique to Identify Arbitrarily Shaped Noise Sources". Shock and Vibration 13, n. 4-5 (2006): 219–32. http://dx.doi.org/10.1155/2006/231625.
Testo completoAbstract (sommario):
Acoustic intensity is one of the available tools for evaluating sound radiation from vibrating bodies. Active intensity may, in some situations, not give a faithful insight about how much energy is in fact carried into the far field. It was then proposed a new parameter, the supersonic acoustic intensity, which takes into account only the intensity generated by components having a smaller wavenumber than the acoustic one. However, the method is only efective for simple sources, such as plane plates, cylinders and spheres. This work presents a new technique, based on the Boundary Elements Method and the Singular Value Decomposition, to compute the supersonic acoustic intensity for arbitrarily shaped sources. The technique is based in the Kirchoff-Helmholtz equation in a discretized approach, leading to a radiation operator that relates the normal velocity on the source's surface mesh with the pressure at grid points located in the field. Then, the singular value decomposition technique is set to the radiation operator and a cutoff criterion is applied to remove non propagating components. Some numerical examples are presented.
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García A., Carlos, Nicolas Dauchez e Gautier Lefebvre. "Radiation of thin complex plates estimated with the landscape of localisation theory". Journal of the Acoustical Society of America 151, n. 4 (aprile 2022): A167. http://dx.doi.org/10.1121/10.0010996.
Testo completoAbstract (sommario):
The landscape of localisation is a practical tool that enables the prediction of the geographical localisation of localized modes and helps us to understand the transition between localized and delocalised states. Moreover, approximations based on the Rayleigh quotient and on a variant of Weyl’s law are employed to predict the eigenfrequencies for the Schro ¨ dinger operator in quantum mechanics, but they are also valid for the Laplace and biharmonic operators, which characterize the behaviour of most dynamical systems in acoustics and vibrations. When studying the acoustic radiation from a vibrating structure, three global parameters are key indicators: the mean squared velocity, the acoustic radiated power, and the radiation efficiency. The literature on this subject is very vast for the plate case, where for simple geometries, it is still possible to derive analytical solutions or, at least, very useful approximations. For more complex structures, numerical simulations seem to be appropriate for lack of a simpler solution. In this context, this work aims to give some light to create a direct relationship between these global parameters and the landscape of localisation function, based on the multipolar radiation behaviour presented by localized modes and estimated by geometrical means.
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Oji, Tatsuo, Stephen Q. Dornbos, Keigo Yada, Hitoshi Hasegawa, Sersmaa Gonchigdorj, Takafumi Mochizuki, Hideko Takayanagi e Yasufumi Iryu. "Penetrative trace fossils from the late Ediacaran of Mongolia: early onset of the agronomic revolution". Royal Society Open Science 5, n. 2 (febbraio 2018): 172250. http://dx.doi.org/10.1098/rsos.172250.
Testo completoAbstract (sommario):
The Cambrian radiation of complex animals includes a dramatic increase in the depth and intensity of bioturbation in seafloor sediment known as the ‘agronomic revolution’. This bioturbation transition was coupled with a shift in dominant trace fossil style from horizontal surficial traces in the late Precambrian to vertically penetrative trace fossils in the Cambrian. Here we show the existence of the first vertically penetrative trace fossils from the latest Ediacaran: dense occurrences of the U-shaped trace fossil Arenicolites from late Precambrian marine carbonates of Western Mongolia. Their Ediacaran age is established through stable carbon isotope chemostratigraphy and their occurrence stratigraphically below the first appearance of the trace fossil Treptichnus pedum . These Arenicolites are large in diameter, penetrate down to at least 4 cm into the sediment, and were presumably formed by the activity of bilaterian animals. They are preserved commonly as paired circular openings on bedding planes with maximum diameters ranging up to almost 1 cm, and as U- and J-shaped tubes in vertical sections of beds. Discovery of these complex penetrative trace fossils demonstrates that the agronomic revolution started earlier than previously considered.
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Atalla, N., e J. Nicolas. "A Formulation for Mean Flow Effects on Sound Radiation from Rectangular Baffled Plates with Arbitrary Boundary Conditions". Journal of Vibration and Acoustics 117, n. 1 (1 gennaio 1995): 22–29. http://dx.doi.org/10.1115/1.2873863.
Testo completoAbstract (sommario):
A general formulation of the sound radiation from fluid-loaded rectangular baffled plates with arbitrary boundary conditions has been developed by Berry et al. (JASA, Vol. 90, No. 4, Pt. 2, 1991). In this paper, an extension of this formulation to inviscid, uniform subsonic flow is considered. The analysis is based on a variational formulation for the transverse vibrations of the plate and the use of the extended, to uniformly moving media, form of the Helmholtz integral equation. The formulation shows explicitly the effect of the flow in terms of added mass, and radiation resistance. Furthermore, it avoids the difficult problem of integration in the complex domain, typical of the wavenumber transform approaches to fluid-loading problems. Comparison of the acoustic radiation impedance with existing studies supports the validity of the approach. The details of the formulation and its numerical implementation is exposed and a discussion of the flow effects on the radiation impedance of a rectangular piston is presented. It is shown that subsonic mean flow increases the modal radiation resistance at low frequencies and affects added mass more strongly than it affects radiation resistance.
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Putra, Azma, Nurain Shyafina, Noryani Muhammad, Hairul Bakri e Noor Fariza Saari. "Development of Hybrid Semi-Analytical and Finite Element Analysis to Calculate Sound Radiation from Vibrating Structure". Advanced Materials Research 845 (dicembre 2013): 71–75. http://dx.doi.org/10.4028/www.scientific.net/amr.845.71.
Testo completoAbstract (sommario):
Simple analytical model of plate dynamics usually applies for rectangular plate with simply supported edges. Analytical model of sound radiation from rectangular plate is also convenient, but not for other geometries and other boundary conditions. This paper presents a hybrid mathematical model which combines a semi-analytical model with the Finite Element Analysis (FEA) method to determine sound radiation from a vibrating structure. The latter is employed to calculate the vibration velocity of a structure with a rather complex geometry. The results are then used as the input in the semi-analytical model to calculate the radiated sound pressure through the Rayleigh integral. Results from the proposed model are presented here for the radiation efficiency of rectangular plates with different boundary conditions.
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Sedlmayr, Erwin. "From Molecules to Grains". International Astronomical Union Colloquium 146 (1994): 163–85. http://dx.doi.org/10.1017/s025292110002131x.
Testo completoAbstract (sommario):
Cosmic dust is an ubiquiteous component of the interstellar medium, the presence of which has severe bearings both upon the observations and upon the physical description and realistic modelling of astronomical objects. In most dusty objects, the grain component is intimately interwoven with the gas component and the radiation field, and, hence strongly affects the thermodynamical, the hydrodynamical and the chemical structure of the object. Therefore any consistent description of the astrophysical dust complex has to rely upon a treatment where these aspects are properly taken into account. In general this complex comprises the following problems:–Formation of small stable molecular clusters out of the gaseous phase–Growth of these clusters to macroscopic specimens (primary condensates: grains, plates, etc.)–Destruction of grains (e.g. thermal evaporation, sputtering, shattering), and–Physical and chemical processing of already existing grains (e.g. coagulation, chemical and thermal transformation, etc....).
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Ibragimov, Renat F., Yakov A. Kokorev, Anastasia P. Denisenko, Elena V. Ryabeva, Valery T. Samosadny e Hamza Hasnaoui. "Experimental determination of the induced activity in activation detectors of a complex geometric shape". Nuclear Energy and Technology 6, n. 3 (11 settembre 2020): 149–54. http://dx.doi.org/10.3897/nucet.6.57738.
Testo completoAbstract (sommario):
The paper presents the results of experimental determination of the induced activity in copper-/aluminum-based activation detectors when irradiated with neutrons with energies of about 14 MeV. The activation detectors were square-shaped metal plates with a thickness from 1.0 to 1.5 mm and a side size about 5.0 cm. These dimensions significantly exceed those of the detectors that are used in the research of high-intensity neutron fluxes. The detectors described in this work can be used for studying low-intensity neutron fluxes (with a flux density of up to 106 n/cm2∙s). It is shown that, when working with such detectors, it is possible to apply the usual methods for calculating the induced activity in thin activation detectors, with corrections that take into account the emerging features of the ‘neutron source - activation detector’ and ‘activation detector - secondary radiation detector’ geometries. The effects of absorption of primary and secondary radiation by the detector substance are also revealed. The Geant4 tools were used for calculating the geometric factors and theoretical induced activity. The study confirms the applicability of such activation detectors for solving the problem of determining the yield of neutrons with energies of about 14 MeV from a neutron generator target. The results of the experiments coincide, within the margin of error, with the results of simulations performed using the Geant4 tools.
Libri sul tema "Radiation from complex-shaped plates"
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West-Eberhard, Mary Jane. Developmental Plasticity and Evolution. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195122343.001.0001.
Testo completoAbstract (sommario):
The first comprehensive synthesis on development and evolution: it applies to all aspects of development, at all levels of organization and in all organisms, taking advantage of modern findings on behavior, genetics, endocrinology, molecular biology, evolutionary theory and phylogenetics to show the connections between developmental mechanisms and evolutionary change. This book solves key problems that have impeded a definitive synthesis in the past. It uses new concepts and specific examples to show how to relate environmentally sensitive development to the genetic theory of adaptive evolution and to explain major patterns of change. In this book development includes not only embryology and the ontogeny of morphology, sometimes portrayed inadequately as governed by "regulatory genes," but also behavioral development and physiological adaptation, where plasticity is mediated by genetically complex mechanisms like hormones and learning. The book shows how the universal qualities of phenotypes--modular organization and plasticity--facilitate both integration and change. Here you will learn why it is wrong to describe organisms as genetically programmed; why environmental induction is likely to be more important in evolution than random mutation; and why it is crucial to consider both selection and developmental mechanism in explanations of adaptive evolution. This book satisfies the need for a truly general book on development, plasticity and evolution that applies to living organisms in all of their life stages and environments. Using an immense compendium of examples on many kinds of organisms, from viruses and bacteria to higher plants and animals, it shows how the phenotype is reorganized during evolution to produce novelties, and how alternative phenotypes occupy a pivotal role as a phase of evolution that fosters diversification and speeds change. The arguments of this book call for a new view of the major themes of evolutionary biology, as shown in chapters on gradualism, homology, environmental induction, speciation, radiation, macroevolution, punctuation, and the maintenance of sex. No other treatment of development and evolution since Darwin's offers such a comprehensive and critical discussion of the relevant issues. Developmental Plasticity and Evolution is designed for biologists interested in the development and evolution of behavior, life-history patterns, ecology, physiology, morphology and speciation. It will also appeal to evolutionary paleontologists, anthropologists, psychologists, and teachers of general biology.
Capitoli di libri sul tema "Radiation from complex-shaped plates"
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Yung, Yuk L., e William B. DeMore. "Introduction". In Photochemistry of Planetary Atmospheres. Oxford University Press, 1999. http://dx.doi.org/10.1093/oso/9780195105018.003.0004.
Testo completoAbstract (sommario):
It is usual in the study of planets to consider the Earth first, and then the other planets, so that we can better understand how and why the rest of the solar system is different from us. In this book the order of study will be reversed: we shall first try to understand the solar system, and then we will ask why Earth is unique. We adopt this unconventional approach for two reasons. First, Earth's atmosphere today is the end-point of an evolution that started about 4.6 billion years ago. The pristine materials have all been drastically altered. However, by examining other parts of the solar system that have evolved to a lesser degree, we may deduce what the early Earth might have been like. Second, Earth's atmosphere today is largely determined by the complex biosphere, whose evolution has been intimately coupled to that of the atmosphere. In other words, ours is the only atmosphere in the solar system that supports life, and it is in turn modified by life. Therefore, to appreciate the beauty and the intricacy of our planet, we must start with simpler objects without life. Chemical composition is intimately connected to evolution, which in turn is driven by chemical change. In this book we attempt to provide a coherent basis for understanding the planetary atmospheres, to identify the principal chemical cycles that control their present composition and past history. Figure 1.1 gives an illustration of the intellectual framework in which our field of study is embedded. The unifying theme that connects the planets in the solar system is "origin"; that is, all planets share a common origin about 4.6 billion years ago. The subsequent divergence in the solar system may be partly attributed to evolution, driven primarily by solar radiation. The bulk of solar radiation consists of photons in the visible spectrum with a mean blackbody radiation temperature of 5800 K. The part that is responsible for direct atmospheric chemistry is a tiny portion (less than 1% of the total flux) in the ultraviolet. In addition, the sun emits a steady stream of corpuscular particles, known as the solar wind. While the sun provides the principal source of energy for change, the time rate of change is crucial, and that is where chemical kinetics and chemical cycles play pivotal roles.
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Davis, Juliet. "Shaping Caring Urban Atmospheres". In The Caring City, 88–111. Policy Press, 2022. http://dx.doi.org/10.1332/policypress/9781529201215.003.0006.
Testo completoAbstract (sommario):
In Chapter 4 I touched on the notion of atmosphere in the context of the design firm WES’s work, where it was framed as part of the liveability and accessibility of a street. I did not unpack the notion of urban atmosphere and its wider relevance to care practices and relations, however. I do this now in this chapter. As discussed in Chapter 2, the notion of atmosphere is complex, encompassing different meanings, areas of knowledge and modes of investigation. On the one hand, the atmosphere denotes the layers of gases, held in place by gravity, that surround a planet or other celestial body. The earth’s atmosphere is made up of five major layers together forming a continuous envelope about 480 kilometres thick around our planet. It plays a key role in supporting life on earth, constituting the air that organisms breathe, shielding the planet from ultraviolet (UV) radiation and keeping it warm through its insulating properties. The atmosphere, in these terms, including atmospheric conditions and weather patterns, is a focus of study within the physical and life sciences.
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Orme, Antony R. "The Tectonic Framework of South America". In The Physical Geography of South America. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195313413.003.0008.
Testo completoAbstract (sommario):
Tectonism is the science of Earth movements and the rocks and structures involved therein. These movements build the structural framework that supports the stage on which surface processes, plants, animals and, most recently, people pursue their various roles under an atmospheric canopy. An appreciation of this tectonic framework is thus a desirable starting point for understanding the physical geography of South America, from its roots in the distant past through the many and varied changes that have shaped the landscapes visible today. Tectonic science recognizes that Earth’s lithosphere comprises rocks of varying density that mobilize as relatively rigid plates, some continental in origin, some oceanic, and some, like the South American plate, amalgams of both continental and oceanic rocks. These plates shift in response to deep-seated forces, such as convection in the upper mantle, and crustal forces involving push and pull mechanics between plates. Crustal motions, augmented by magmatism, erosion, and deposition, in turn generate complex three-dimensional patterns. Although plate architecture has changed over geologic time, Earth’s lithosphere is presently organized into seven major plates, including the South American plate, and numerous smaller plates and slivers. The crustal mobility implicit in plate tectonics often focuses more attention on plate margins than on plate interiors. In this respect, it is usual to distinguish between passive margins, where plates are rifting and diverging, and active margins, where plates are either converging or shearing laterally alongside one another. At passive or divergent margins, such as the present eastern margin of the South American plate, severe crustal deformation is rare but crustal flexuring (epeirogeny), faulting, and volcanism occur as plates shift away from spreading centers, such as the Mid-Atlantic Ridge, where new crust is forming. Despite this lack of severe postrift deformation, however, passive margins commonly involve the separation of highly deformed rocks and structures that were involved in the earlier assembly of continental plates, as shown by similar structural legacies in the facing continental margins of eastern South America and western Africa. At active convergent margins, mountain building (orogeny) commonly results from subduction of oceanic plates, collision of continental plates, or accretion of displaced terranes.
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Graham, Alan. "Cause and Effect Factors Influencing the Composition and Distribution of North American Plant Formations through Late Cretaceous and Cenozoic Time". In Late Cretaceous and Cenozoic History of North American Vegetation (North of Mexico). Oxford University Press, 1999. http://dx.doi.org/10.1093/oso/9780195113426.003.0005.
Testo completoAbstract (sommario):
The arrangement of vegetation over the landscape is a product of interactions between the environment, the ecological characteristics of individual organisms, barriers, dispersal potential, epidemic disease, anthropogenic influences, and the partially serendipitous factor of propagule availability. Within the complex of environmental factors, several are of special importance in tracing the history of North American plant communities. They include climate; plate tectonics as a mechanism for orogeny, volcanism, land bridges, and terranes; and catastrophes. Each have numerous interacting subcomponents, feedbacks, and amplifiers, and although constraints of format make it necessary to discuss these separately and sequentially, they are interconnected and pertubation of one affects the entire system. Diagrams summarizing these factors are presented at the end of the following sections. The diagrams are not intended as models for, indeed, the single factor of climate could be expanded into a component so vastly complex that it would be counterproductive to a general summary. Similarly, the hydrological cycle, which involves the largest movement of any substance on Earth, cannot be fully treated because a “systems” view of its role in influencing climate is not available (Chahine, 1992) and the roles of water vapor (a greenhouse gas) and cloud cover are just now being quantified (Cess et al., 1995; Ramanathan et al., 1995). Rather, the diagrams illustrate some of the factors and relationships discussed in the text and serve as a reminder of the complex interactive nature of physical and biotic events. Plants are limited in their ecological amplitude. Several important corollaries follow from this observation; one of the most fundamental is that changes in climate cause extinctions promote evolution, and alter the range and habitats of organisms. Because climate plays a central role in the arrangement of modern communities (Gates, 1993; Kareiva et al., 1993; Woodward, 1987) and in the development and distribution of past assemblages (Brenchley, 1984; Crowley and North, 1991; Hecht, 1985a), reference to some elements of general climatology is necessary for understanding the diversification, radiation, and reshuffling of North American paleocommunities during the Late Cretaceous and Cenozoic.
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deBuys, William. "High Blue: The Great Downshift of Dryness". In A Great Aridness. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199778928.003.0006.
Testo completoAbstract (sommario):
Mapmakers typically depict the aridlands of the world in colors like buff and buckskin, in contrast to the greens of wetter regions. Their choice is true to reality, for dry places usually produce scant vegetation, and the bare ground, baked by unobstructed sun, tends to wear a washed-out shade of dun, or one of its cousins. In the North American Southwest, you might add a touch of rust to reflect the widespread iron-rich geology. In many areas, oxides of iron produce the pinkish flesh tones that make it easy to think the landscape is alive. If you also brush in some piney greens and spruce black for upland woods and forests, and dab smaller areas white to represent high-country snowcaps, you have a fair start toward capturing the palette of the region. But you would still be missing the most definitive color of the Southwest, which is found not beneath the feet, but overhead. You can look up, straight up, almost any day of the year, and there it is: an intense, infinite blue, miles deep and beyond reach. It is not merely bluish, not the watery blue of Scandinavian eyes, not the black-mixed blue of dark seas or bachelor buttons, not the hazy blue of glacier ice or distant mountains, but an Ur-blue, an über-blue, a defining quintessence. It is to other blues as brandy is to wine: a distillation, pure and heady. It can be a little deflating to reflect that the ethereal blue of southwestern skies results from mundane forces, that it is the product of solar radiation and atmospheric gases interacting in an environment shaped by climate. If the air held more water vapor, the sky would whiten overhead, as it does at the horizons, where the light that reaches our eyes has more atmosphere and diffusing vapor to travel through.
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Bunker, Bruce C., e William H. Casey. "The Ion Exchange Behavior of Oxides". In The Aqueous Chemistry of Oxides. Oxford University Press, 2016. http://dx.doi.org/10.1093/oso/9780199384259.003.0017.
Testo completoAbstract (sommario):
Oxides comprise the most common ion-exchange materials on our planet, with the clay minerals alone, formed by the weathering of rock, having a total mass of around 1025 g. This mass represents almost one-third of the total mass of Earth’s crust and is more than six times the mass of Earth’s oceans. These fine-grained ion exchange materials play a major role in mediating the concentrations of ionic species found in freshwater, groundwater, and our oceans (see Chapter 18). Oxide ion exchangers are also of critical importance in removing contaminants from the environment. Nowhere is this role more apparent than in the removal and sequestration of radioactive elements such as 137Cs, 90Sr, and 99Tc, which are serious hazards present in nuclear wastes. Oxide ion exchangers exhibit several properties that make them materials of choice for treating nuclear wastes, including high selectivity, enhanced stability to radiation damage relative to organic exchangers, and the potential as materials to be condensed further into solid waste after they are loaded with radioactive species. Oxide exchangers are extremely useful for extracting valuable cations from complex fluids, such as the lithium used in our highest energy density batteries. Ion exchange also represents a pathway for creating unique nanomaterials, with applications including battery separators, catalysts, optical materials, magnets, and materials for drug delivery. Oxides materials can exhibit exceptional properties as both cation and anion exchangers for a wide range of separation and water treatment technologies. Although the total ion-exchange capacity of an oxide is important for some applications, such as the deionization of water, separations require the use of oxides and hydroxides having the highest degree of ion-exchange selectivity. For selectivity, oxides must be designed with specific sites that exhibit a much higher affinity for one ion than any other, which requires much more sophistication than just generating a net charge. Here, we describe the key factors that control both the capacity and selectivity of inorganic ion exchangers, including (1) the role of acid–base reactions in controlling surface charge and ion-exchange capacity, (2) the role of local charge distributions in determining ion-exchange selectivity, and (3) the effect of shape and selective solvation on enhancing that selectivity.
Atti di convegni sul tema "Radiation from complex-shaped plates"
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Kim, Seong Hoon, Kyoungwoo Seo, Dae-young Chi e Juhyeon Yoon. "Generation of Pressure Distribution Inside a Decay Tank in a Research Reactor Using CFD". In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-63934.
Testo completoAbstract (sommario):
The Primary Cooling System (PCS) of a research reactor circulates coolant to remove the heat produced in the fuel or irradiation device. The core outlet coolant contains many kinds of radionuclides because it passes the reactor core [1]. As N-16 among them emits a very hard gamma ray, it not only causes radiation damage to some components but also requires very heavy shielding of the primary cooling loop. Since its half-life is 7.13s, its level can be effectively lowered by installing a decay tank including an internal structure to provide a transit time [2]. To ensure that the N-16 activity decreases enough before the coolant leaves the heavily shielded decay tank room, perforated plates are installed inside the decay tank. The perforated plates are designed to disturb and delay the PCS flow. Normally, when a flow from a relative narrow inlet nozzle goes out to an enlarged tank, it becomes a complex turbulent flow inside the tank. In addition, the PCS flow is frequently changed from zero to a normal flow rate owing to the research reactor characteristics. Thus, the integrity of the perforated plate shall be verified with the pump operation and shutdown condition.
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Nanstad, Randy K., B. Richard Bass, Thomas M. Rosseel, John G. Merkle e Mikhail A. Sokolov. "Heavy-Section Steel Technology and Irradiation Programs: Retrospective and Prospective Views". In ASME 2007 Pressure Vessels and Piping Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/pvp2007-26677.
Testo completoAbstract (sommario):
In 1965, the Atomic Energy Commission (AEC), at the advice of the Advisory Committee on Reactor Safeguards (ACRS), initiated the process that resulted in the establishment of the Heavy Section Steel Technology (HSST) Program at Oak Ridge National Laboratory (ORNL). Dr. Spencer H. Bush of Battelle Northwest Laboratory, the man being honored by this symposium, representing the ACRS, was one of the Staff Advisors for the program and helped to guide its technical direction. In 1989, the Heavy-Section Steel Irradiation (HSSI) Program, formerly the HSST task on irradiation effects, was formed as a separate program, and this year the HSST/HSSI Programs, sponsored by the U.S. Nuclear Regulatory Commission (USNRC), celebrate 40 years of continuous research oriented toward the safety of light-water nuclear reactor pressure vessels. This paper presents a summary of results from those programs with a view to future activities. The HSST Program was established in 1967 and initially included extensive investigations of heavy-section low-alloy steel plates, forgings, and welds, including metallurgical studies, mechanical properties, fracture toughness (quasi-static and dynamic), fatigue crack-growth, and crack arrest toughness. Also included were irradiation effects studies, thermal shock analyses, testing of thick-section tensile and fracture specimens, and non-destructive testing. In the subsequent decades, the HSST Program conducted extensive large-scale experiments with intermediate-size vessels (with varying size flaws) pressurized to failure, similar experiments under conditions of thermal shock and even pressurized thermal shock (PTS), wide-plate crack arrest tests, and biaxial tests with cruciform-shaped specimens. Extensive analytical and numerical studies accompanied these experiments, including the development of computer codes such as the recent Fracture Analysis of Vessels Oak Ridge (FAVOR) code currently being used for PTS evaluations. In the absence of radiation damage to the RPV, fracture of the vessel is improbable. However, exposure to high energy neutrons can result in embrittlement of radiation-sensitive RPV materials. The HSSI Program has conducted a series of experiments to assess the effects of neutron irradiation on RPV material behavior, especially fracture toughness. These studies have included RPV plates and welds, varying chemical compositions, and fracture toughness specimens up to 4 in. thickness. The results of these investigations, in conjunction with results from commercial reactor surveillance programs, are used to develop a methodology for the prediction of radiation effects on RPV materials. Results from the HSST and HSSI Program are used by the USNRC in the evaluation of RPV integrity and regulation of overall nuclear plant safety.
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Kidner, Mike, Marty Johnson e Brad Batton. "Distributed Sensors for Active Structural Acoustic Control Using Large Hierarchical Control Systems". In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-42271.
Testo completoAbstract (sommario):
The active structural acoustic control of sound radiation in large structures, such as launch vehicle payload fairings, can require very complex control systems if the control architecture is centralized. For this reason hierarchical, decentralized, control architectures have been suggested as one method of simplifying the complexity of the system and improving the robustness of the system to failures. In a hierarchical configuration, individual actuators or groups of actuators act on local information and use this information to drive the system locally. Higher level, slower acting, master controllers can then be used to observe the global performance and adapt the behavior of the local control systems. The local control units can use feedforward, feedback or hybrid feedforward/feedback techniques. It has been previously shown that good performance can only be achieved if the non-radiating high order wavenumber components are removed from sensor signals. This paper develops both analytically and experimentally a two dimensional distributed structural sensor designed as a wavenumber filter. Filtering in the wavenumber domain is made more attractive since it does not cause the phase problems associated with filtering in the time domain. A numerical method for combining ring shaped sensors is presented. It is shown that low and band pass sensors can be created with relatively few ring elements. Experimental results using a two dimensional ring sensor (with eight rings) attached to a large plate structure is presented. Results show that by carefully combining the outputs from the sensor rings both low pass two dimensional wavenumber filters can be created.
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Collins, M., S. J. Harrison, P. H. Oosthuizen e D. Naylor. "Numerical Modeling of Radiative and Convective Heat Transfer From an Irradiated Complex Window Assembly". In ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-1413.
Testo completoAbstract (sommario):
Abstract The present numerical study examines the influence of heated, horizontal, and rotateable louvers on the convective and radiative heat transfer from a hot or cold vertical isothermal surface. The system models absorption of solar energy in a Venetian blind adjacent to the indoor surface of a window. Building on previous analyses, a steady, laminar, two-dimensional, conjugate conduction / convection / radiation model of this problem has been developed, and solutions have been obtained using the finite element method. Validation of the model against existing solutions has been undertaken. Results were obtained for two window temperatures (warm and cool compared to ambient), two louver to plate spacings, and three louver angles. The results clearly demonstrate the effect of the model variables on heat transfer from the plate surface. With few exceptions, steady periodicity along the plate was clearly demonstrated. More importantly, increased independence of the results from the louver angle as louver to plate distance increased was demonstrated.
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Oehlert, Karsten, Joerg R. Seume, Frank Siegel, Andreas Ostendorf, Bo Wang, Berend Denkena, Taras Vynnyk et al. "Exploratory Experiments on Machined Riblets for 2-D Compressor Blades". In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-43457.
Testo completoAbstract (sommario):
During the last decades, riblets have shown a potential for viscous drag reduction. Several investigations and measurements of skin-friction in the boundary layer over flat plates and on turbomachinery type blades with ideal riblet geometry have been reported in the literature. The purpose of the present study is to investigate whether laser machined and ground riblet-like structures could be successfully employed on conventional 2-D (NACA) compressor blades in order to assess the potential of industrial machining processes for the creation of the riblet effect. Perfectly trapezoid riblets were designed specifically for the flow parameters in the wind tunnel. Parameters describing the geometry and the deviation from ideal riblets are developed. Riblet machining by high precision material ablation has the potential of achieving micro-machining quality. In comparison to ns-laser processing using either Q-switched solid-state lasers or excimer lasers, the results for high precision material ablation show the enormous potential of ps-laser radiation and achieve the required quality, free of thermally induced defects and, consequently, with high reproducibility. For grinding riblets, geometrically defined microprofiles must firstly be generated via a profile dressing process and then ground onto the work piece surface. A precise adjustment of the grinding wheel system (grit, bonding) and the dressing/grinding conditions is necessary, in order to satisfy the opposing requirements at both dressing and grinding. The blade specimens were geometrically measured with a confocal microscope as well as secondary electron microscope using a specially developed riblet-oriented analysis. For verifying the measurement results, an Atomic Force Microscope was used. The specimens, i.e. flat plates and compressor blades, are aerodynamically tested in a cascade wind tunnel and properly scaled model surfaces were tested in an oil channel in order to quantify skin-friction reduction. Wake measurements of a cascade with NACA-profiles which have the resulting riblet-like structured surface show that the laser shaped as well as ground riblets reduce skin-friction almost as well as the ideal ones, which means a skin friction reduction of up to 7%.
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Hong, Jie, Jinhai Gao, Yanhong Ma e Meng Chen. "Local Thermal Buckling Analysis Method of Combustor Liner". In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59635.
Testo completoAbstract (sommario):
Aero-engine combustor liners are always plagued by local thermal buckling failure problems because of complex thermal and mechanical loading conditions caused by the continuously increasing thrust-to-weight ratio and turbine gas temperature. Traditional theoretical methods focus on simple plate and shell structures, and the numerical methods are not applicable in local thermal buckling analysis of complex structures and loading conditions. As a result, it is necessary to establish a local thermal buckling analysis method in which the failure mechanism must be taken into account. Firstly, the discriminant of thin-wall structure thermal buckling instability boundary is derived from governing equations of plates in which the stress function and deflection function are two variables, and the two buckling factors which are local temperature and compressive stress are included in the equations. Secondly, the three dimensional temperature distribution of a combustor liner is captured by the numerical simulation of an annular return-flow combustion chamber with ANSYS/CFX based on the thermal-fluid-solid coupling finite element (FE) method. The calculation includes the effect of heat source and heat radiation, the influence of variable flow field on heat transfer and variation of properties with temperature of the gas, kerosene, and the solid. In addition, the resultant imposed thermal load and design pressure load are used to capture the critical locations in the combustor liner through static analysis considering thermal buckling instability factors. The critical temperature and critical compressive stress which are the defining parameters of local thermal buckling discriminant are calculated with FE and the sub-model method. Then a judgment of local thermal buckling is performed through the discriminant. Analysis results for an example combustion chamber calculated by the method in this paper are compared with the experimental data. It is concluded that the local thermal buckling analysis method is accurate and valid.
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Collins, M., S. J. Harrison, D. Naylor e P. H. Oosthuizen. "An Interferometric Study of Convective Heat Transfer From an Irradiated Complex Window Assembly". In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/htd-24119.
Testo completoAbstract (sommario):
Abstract The present experimental study examines the influence of heated, horizontal, and rotateable louvers on the convective heat transfer from a heated or cooled vertical isothermal surface. The system represents an irradiated Venetian blind adjacent to the indoor surface of a window. Detailed temperature field and local surface flux data were obtained using a Mach-Zehnder Interferometer for two window temperatures (warm and cool compared to ambient) and irradiation levels, two louver to plate spacings, and three louver angles. The results have been used to validate a previous numerical study, in which a steady, laminar, two-dimensional, conjugate conduction / convection / radiation finite element model of this problem had been developed. The effect of the heated louvers on the heat transfer rate from the plate surface has been demonstrated and the results of the previous numerical study have been validated. With few exceptions, steady but periodic heat flux along the plate has been confirmed. More importantly, increased independence of the results from the louver angle as louver to plate distance increased was observed. Blind temperatures measured during the experiment also correlated well with those predicted numerically.
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Isaeva, Oksana, Marina Boronenko e Yura Boronenko. "Optical Diagnostics of the Dispersion Composition of Fuel-Air Flare". In 13th International Conference on Applied Human Factors and Ergonomics (AHFE 2022). AHFE International, 2022. http://dx.doi.org/10.54941/ahfe1001627.
Testo completoAbstract (sommario):
One of the central problems of using heavy hydrocarbons as fuel for thermal burners and internal combustion engines is mixture formation. The purpose of this article is to present the results of optical diagnostics of the dispersion composition of a fuel-air torch according to the developed method. The technical means of the information acquisition and processing system can be a high-speed micropyrometric complex for measuring temperature and flame propagation velocity, the main elements of which are a personal computer and a VideoSprint high-speed video camera. The software includes the Origin data analysis package and ImageJ, a free image processing program. The peculiarity of the video camera is that it can detect low-intensity radiation due to amplification in microchannel plates, and the speed and multi-frame exposure is provided by an electronic shutter. To use video cameras as high-speed pyrometers, their preliminary calibration is necessary. During the calibration of the video camera, the non-linearity of the response of the measuring system depending on the exposure time was revealed. The study of the injection process in diesel mixture formation requires reliable information on the relationship between the speed characteristics of the fuel jet and the dynamics of the fuel supply cycle. Optical research methods do not destroy the structure of the fuel plume and allow obtaining information about the structure and dynamics of the flame development. The technique also makes it possible to obtain data on the root angles of fuel plumes and to estimate the distribution of aerosol particles along their length. For analysis, an experimental frame of the fuel atomization process was taken, made in the Videoscan VS-SST-285 system with an exposure of 39 µs, the delay time of the sync pulse from the pressure sensor was 300 µs. From the analysis of the fuel jet, it was found that the maximum fuel concentration is observed at the atomizer, in the initial zone of the jet and in the front (less than at the atomizer), and there is also a deviation of the torch core axis from the nozzle axis. As experiments show, a change in the angle of the spray cone by 10° and a deviation of the axis of the cone from the axis of the nozzle are permissible by 3-5°. Obtaining data for processing using a high-speed micropyrometric complex can greatly improve the quality of diagnostics. The result of experimental data processing according to the proposed method is consistent with the previously obtained results, which indicates great prospects for further development of this express diagnostic method to obtain numerical characteristics of fuel jet dispersity and improve the ecology of heavy hydrocarbon combustion processes.
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Swartzlander, C. A., D. R. Andersen e A. E. Kaplan. "Dark spatial solitons formed by complex gratings". In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oam.1990.thg3.
Testo completoAbstract (sommario):
We have previously observed bands, and even a grid, of dark solitons in the cross-section of a laser beam propagating through a self-defocusing material when a diffracting screen was placed at the entrance face of the nonlinear medium. The creation of spatial solitons is attributed to the coupling of diffracted radiation into a self-guiding nonlinear channel. Information encoded as spatial solitons may therefore be transferred in parallel over long distances without the need for large (or any) collection optics. A diffracting screen is a building block of spatial soliton devices. We have found the soliton eigenvalues (each corresponding to the normalized angle and depth of a soliton) for a generalized screen composed of units with two closely spaced opaque regions of width xA separated by a region of width xB and arbitrary phase ΦB. If the value of xB is large, fundamental dark solitons can form when ΦB = π. On the other hand, when xB is small, diffractive coupling of radiation from the opaque regions splits the degeneracy of the eigenvalues, much like level-splitting in coupled quantum wells. When a pure phase grating exists (xA = 0), a single pair of solitons is formed. Numerous applications of spatial dark solitons can be envisioned, including optical interconnecting, limiting, and computing operations.
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Bao, Weiguang, Fenfang Zhao e Takeshi Kinoshita. "Calculation of Wave Forces Acting on a Cylinder With a Porous Plate Fixed Inside". In ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79088.
Testo completoAbstract (sommario):
To evaluate wave forces and to estimate the motion of breakwater, a circular cylinder is investigated based on the linear wave theory in the present work. The cylinder possesses a porous sidewall, an impermeable bottom and a horizontal porous plate inside that is fixed in the cylinder to work as obstruct and make wave dissipation more effectively. To simplify the problem, the Darcy’s fine-pore model is applied to the boundary condition on the porous body surface. The boundary value problem is solved by means of the eigen-function expansion approach. The fluid domain is divided into three regions and different eigen-function series are used. The so-called dispersion relation for the region inside the cylinder is quite different from a conventional one due to the existence of the porous plate. It leads to eigen values of complex number. To obtain solutions for the radiation problems, particular solution should be constructed to take account of the normal velocity appearing on the porous boundary. The wave loads are evaluated by integrating the pressure difference on two sides of the wetted body surface. The theoretical works are in good consistence with the experimental results. The Haskind relations are examined for the porous body. It is found that the damping coefficient consists of two parts. In addition to the component of conventional wave-radiating damping, exists a second component caused by the porous effects.
Rapporti di organizzazioni sul tema "Radiation from complex-shaped plates"
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Corriveau, Elizabeth, Travis Thornell, Mine Ucak-Astarlioglu, Dane Wedgeworth, Hayden Hanna, Robert Jones, Alison Thurston e Robyn Barbato. Characterization of pigmented microbial isolates for use in material applications. Engineer Research and Development Center (U.S.), marzo 2023. http://dx.doi.org/10.21079/11681/46633.
Testo completoAbstract (sommario):
Organisms (i.e., plants and microorganisms) contain pigments that allow them to adapt and thrive under stressful conditions, such as elevated ultraviolet radiation. The pigments elicit characteristic spectral responses when measured by active and passive sensors. This research study focused on characterizing the spectral response of three organisms and how they compared to background spectral signatures of a complex environment. Specifically, spectra were collected from a fungus, a plant, and two pigmented bacteria, one of which is an extremophile bacterium. The samples were measured using Fourier transform infrared spectroscopy and dis-criminated using chemometric means. A top-down examination of the spectral data revealed that organisms could be discriminated from one an-other through principal component analysis (PCA). Furthermore, there was a strong distinction between the plant and the pigmented microorganisms. Spectral differences resulting in samples with the highest variance from the natural background were identified using PCA loading plots. The outcome of this work is a spectral library of pigmented biological candidates for coatings applications.