Academic literature on the topic 'Virtual particle exchange'
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Journal articles on the topic "Virtual particle exchange"
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Conrad, Michael. "Transient excitations of the Dirac vacuum as a mechanism of virtual particle exchange." Physics Letters A 152, no. 5-6 (January 1991): 245–50. http://dx.doi.org/10.1016/0375-9601(91)90099-t.
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Hartin, Anthony. "Strong field QED in lepton colliders and electron/laser interactions." International Journal of Modern Physics A 33, no. 13 (May 9, 2018): 1830011. http://dx.doi.org/10.1142/s0217751x18300119.
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The studies of strong field particle physics processes in electron/laser interactions and lepton collider interaction points (IPs) are reviewed. These processes are defined by the high intensity of the electromagnetic fields involved and the need to take them into account as fully as possible. Thus, the main theoretical framework considered is the Furry interaction picture within intense field quantum field theory. In this framework, the influence of a background electromagnetic field in the Lagrangian is calculated nonperturbatively, involving exact solutions for quantized charged particles in the background field. These “dressed” particles go on to interact perturbatively with other particles, enabling the background field to play both macroscopic and microscopic roles. Macroscopically, the background field starts to polarize the vacuum, in effect rendering it a dispersive medium. Particles encountering this dispersive vacuum obtain a lifetime, either radiating or decaying into pair particles at a rate dependent on the intensity of the background field. In fact, the intensity of the background field enters into the coupling constant of the strong field quantum electrodynamic Lagrangian, influencing all particle processes. A number of new phenomena occur. Particles gain an intensity-dependent rest mass shift that accounts for their presence in the dispersive vacuum. Multi-photon events involving more than one external field photon occur at each vertex. Higher order processes which exchange a virtual strong field particle resonate via the lifetimes of the unstable strong field states. Two main arenas of strong field physics are reviewed; those occurring in relativistic electron interactions with intense laser beams, and those occurring in the beam–beam physics at the interaction point of colliders. This review outlines the theory, describes its significant novel phenomenology and details the experimental schema required to detect strong field effects and the simulation programs required to model them.
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Szmidt, Kazimierz. "On the SPH Approximations in Modeling Water Waves." Archives of Hydro-Engineering and Environmental Mechanics 60, no. 1-4 (October 1, 2014): 63–86. http://dx.doi.org/10.2478/heem-2013-0009.
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Abstract This paper presents an examination of approximation aspects of the Smoothed Particle Hydrodynamics (SPH) in modeling the water wave phenomenon. Close attention is paid on consistency of the SPH formulation and its relation with a correction technique applied to improve the method accuracy. The considerations are confined to flow fields within finite domains with a free surface and fixed solid boundaries with free slip boundary conditions. In spite of a wide application of the SPH method in fluid mechanics, the appropriate modeling of the boundaries is still not clear. For solid straight line boundaries, a natural way is to use additional (virtual, ghost) particles outside the boundary and take into account mirror reflection of associated field variables. Such a method leads to good results, except for a vicinity of solid horizontal bottoms where, because of the SPH approximations in the description of pressure, a stratification of the fluid material particles may occur. In order to illustrate the last phenomenon, some numerical tests have been made. These numerical experiments show that the solid fluid bottom attracts the material particles and thus, to prevent these particles from penetration into the bottom, a mutual exchange of positions of real and ghost particles has been used in a computation procedure.
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Salam, A. "The Unified Theory of Resonance Energy Transfer According to Molecular Quantum Electrodynamics." Atoms 6, no. 4 (October 11, 2018): 56. http://dx.doi.org/10.3390/atoms6040056.
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An overview is given of the molecular quantum electrodynamical (QED) theory of resonance energy transfer (RET). In this quantized radiation field description, RET arises from the exchange of a single virtual photon between excited donor and unexcited acceptor species. Diagrammatic time-dependent perturbation theory is employed to calculate the transfer matrix element, from which the migration rate is obtained via the Fermi golden rule. Rate formulae for oriented and isotropic systems hold for all pair separation distances, R, beyond wave function overlap. The two well-known mechanisms associated with migration of energy, namely the R−6 radiationless transfer rate due to Förster and the R−2 radiative exchange, correspond to near- and far-zone asymptotes of the general result. Discriminatory pair transfer rates are also presented. The influence of an environment is accounted for by invoking the polariton, which mediates exchange and by introducing a complex refractive index to describe local field and screening effects. This macroscopic treatment is compared and contrasted with a microscopic analysis in which the role of a neutral, polarizable and passive third-particle in mediating transfer of energy is considered. Three possible coupling mechanisms arise, each requiring summation over 24 time-ordered diagrams at fourth-order of perturbation theory with the total rate being a sum of two- and various three-body terms.
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Li, Qiang, Qiang Yi, Rongxin Tang, Xin Qian, Kai Yuan, and Shiyun Liu. "A Hybrid Optimization from Two Virtual Physical Force Algorithms for Dynamic Node Deployment in WSN Applications." Sensors 19, no. 23 (November 22, 2019): 5108. http://dx.doi.org/10.3390/s19235108.
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With the rapid development of unmanned aerial vehicle in space exploration and national defense, large-scale wireless sensor network (WSN) became an important and effective technology. It may require highly accurate locating for the nodes in some real applications. The dynamic node topology control of a large-scale WSN in an unmanned region becomes a hot research topic recently, which helps improve the system connectivity and coverage. In this paper, a hybrid optimization based on two different virtual force algorithms inspired by the interactions among physical sensor nodes is proposed to address the self-consistent node deployment in a large-scale WSN. At the early stage, the deployment algorithm was to deploy the sensor nodes by leveraging the particle motions in dusty plasma to achieve the hexagonal topology of the so-called “Yukawa crystal”. After that, another virtual exchange force model was combined to present a hybrid optimization, which could yield perfect hexagonal topology, better network uniformity, higher coverage rate, and faster convergence speed. The influence of node position, velocity, and acceleration during the node deployment stage on the final network topology are carefully discussed for this scheme. It can aid engineers to control the network topology for a large number of wireless sensors with affordable system cost by choosing suitable parameters based on physical environments or application scenarios in the near future.
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Thompson, Andrew F., and Jean-Baptiste Sallée. "Jets and Topography: Jet Transitions and the Impact on Transport in the Antarctic Circumpolar Current." Journal of Physical Oceanography 42, no. 6 (June 1, 2012): 956–72. http://dx.doi.org/10.1175/jpo-d-11-0135.1.
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Abstract The Southern Ocean’s Antarctic Circumpolar Current (ACC) naturally lends itself to interpretations using a zonally averaged framework. Yet, navigation around steep and complicated bathymetric obstacles suggests that local dynamics may be far removed from those described by zonally symmetric models. In this study, both observational and numerical results indicate that zonal asymmetries, in the form of topography, impact global flow structure and transport properties. The conclusions are based on a suite of more than 1.5 million virtual drifter trajectories advected using a satellite altimetry–derived surface velocity field spanning 17 years. The focus is on sites of “cross front” transport as defined by movement across selected sea surface height contours that correspond to jets along most of the ACC. Cross-front exchange is localized in the lee of bathymetric features with more than 75% of crossing events occurring in regions corresponding to only 20% of the ACC’s zonal extent. These observations motivate a series of numerical experiments using a two-layer quasigeostrophic model with simple, zonally asymmetric topography, which often produces transitions in the front structure along the channel. Significantly, regimes occur where the equilibrated number of coherent jets is a function of longitude and transport barriers are not periodic. Jet reorganization is carried out by eddy flux divergences acting to both accelerate and decelerate the mean flow of the jets. Eddy kinetic energy is amplified downstream of topography due to increased baroclinicity related to topographic steering. The combination of high eddy kinetic energy and recirculation features enhances particle exchange. These results stress the complications in developing consistent circumpolar definitions of the ACC fronts.
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Zhou, Yuan, and Shoken M. Miyama. "The Energy Exchange between Different Masses in an Expanding Gravitating System." Symposium - International Astronomical Union 174 (1996): 387–88. http://dx.doi.org/10.1017/s0074180900001959.
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We investigate whether or not the energy exchange occurs between two species groups of particles in an expanding two-component gravitating system, and we derive the relaxation time scale for energy exchange in such a phase. This is accomplished by solving the dynamic equation coupled with Poisson's equation. We derive a characteristic time determined by the various mass and velocity ratios. When the expansion time does not exceed the characteristic time, energy exchange between the two components is possible and depends on the mass ratio. Once the characteristic time is exceeded, there is virtually no relaxation at all in system. When m2 ≫ m1, the transfer of energy becomes inefficient. Therefore, energy exchange between two species of particle in an expanding two-component gravitating system depends not only on the mass ratio but also on the expansion time.
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Ding, B., and J. W. Darewych. "Variational formulation of relativistic four-body systems in quantum field theory: scalar quadronium." Canadian Journal of Physics 80, no. 5 (May 1, 2002): 605–12. http://dx.doi.org/10.1139/p02-061.
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We discuss a variational method for describing relativistic four-body systems within the Hamiltonian formalism of quantum field theory. The scalar Yukawa (or WickCutkosky) model, in which scalar particles and antiparticles interact via a massive or massless scalar field, is used to illustrate the method. A Fock-space variational trial state is used to describe the stationary states of scalar quadronium (two particles and two antiparticles) interacting via one-quantum exchange and virtual annihilation pairwise interactions. Numerical results for the ground-state mass and approximate wave functions of quadronium are presented for various strengths of the coupling, for the massive and massless quantum exchange cases. PACS Nos.: 11.10Ef, 11.10St, 03.70+k, 03.65Pm
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Salam, A. "Bridge-Mediated RET between Two Chiral Molecules." Applied Sciences 11, no. 3 (January 23, 2021): 1012. http://dx.doi.org/10.3390/app11031012.
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Molecular quantum electrodynamics (QED) theory is employed to calculate the rate of resonance energy transfer (RET) between a donor, D, described by an electric dipole and quadrupole, and magnetic dipole coupling, and an identical acceptor molecule, A, that is mediated by a third body, T, which is otherwise inert. A single virtual photon propagates between D and T, and between T and A. Time-dependent perturbation theory is used to compute the matrix element, from which the transfer rate is evaluated using the Fermi golden rule. This extends previous studies that were limited to the electric dipole approximation only and admits the possibility of the exchange of excitation between a chiral emitter and absorber. Rate terms are computed for specific pure and mixed multipole-dependent contributions of D and A for both an oriented arrangement of the three particles and for the freely tumbling situation. Mixed multipole moment contributions, such as those involving electric–magnetic dipole or electric dipole–quadrupole coupling at one center, do not survive random orientational averaging. Interestingly, the mixed electric–magnetic dipole D and A rate term is non-vanishing and discriminatory, exhibiting a dependence on the chirality of the emitter and absorber, and is entirely retarded. It vanishes, however, if D and A are oriented perpendicularly to one another. Near- and far-zone asymptotes of isotropic contributions to the rate are also evaluated, demonstrating radiationless short-range transfer and inverse-square radiative exchange at very large separations.
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Schickinger, Matthias, Martin Zacharias, and Hendrik Dietz. "Tethered multifluorophore motion reveals equilibrium transition kinetics of single DNA double helices." Proceedings of the National Academy of Sciences 115, no. 32 (July 23, 2018): E7512—E7521. http://dx.doi.org/10.1073/pnas.1800585115.
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We describe a tethered multifluorophore motion assay based on DNA origami for revealing bimolecular reaction kinetics on the single-molecule level. Molecular binding partners may be placed at user-defined positions and in user-defined stoichiometry; and binding states are read out by tracking the motion of quickly diffusing fluorescent reporter units. Multiple dyes per reporter unit enable singe-particle observation for more than 1 hour. We applied the system to study in equilibrium reversible hybridization and dissociation of complementary DNA single strands as a function of tether length, cation concentration, and sequence. We observed up to hundreds of hybridization and dissociation events per single reactant pair and could produce cumulative statistics with tens of thousands of binding and unbinding events. Because the binding partners per particle do not exchange, we could also detect subtle heterogeneity from molecule to molecule, which enabled separating data reflecting the actual target strand pair binding kinetics from falsifying influences stemming from chemically truncated oligonucleotides. Our data reflected that mainly DNA strand hybridization, but not strand dissociation, is affected by cation concentration, in agreement with previous results from different assays. We studied 8-bp-long DNA duplexes with virtually identical thermodynamic stability, but different sequences, and observed strongly differing hybridization kinetics. Complementary full-atom molecular-dynamics simulations indicated two opposing sequence-dependent phenomena: helical templating in purine-rich single strands and secondary structures. These two effects can increase or decrease, respectively, the fraction of strand collisions leading to successful nucleation events for duplex formation.
Dissertations / Theses on the topic "Virtual particle exchange"
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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.
Books on the topic "Virtual particle exchange"
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Morawetz, Klaus. Relativistic Transport. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198797241.003.0022.
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The quantum kinetic equations for relativistic baryon-meson systems are derived from Kadanoff and Baym equations. It is shown that the virtual exchange of mesons create an effective Yukawa potential between the nucleons. Binding properties of nuclear matter are discussed and the problem of Coester line is explored which means that only three-particle correlations or relativistic effective masses can describe the binding of nuclear matter correctly. The derived kinetic equations show in-medium processes of scattering and particle creation and destruction which are forbidden for free-scattering. The corresponding in-medium cross sections are presented.
Book chapters on the topic "Virtual particle exchange"
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Yamazaki, Toshimitsu. "PIONS IN NUCLEI: FROM VIRTUAL-PION EXCHANGE TO REAL-PION TRANSFER." In Perspectives on Particle Physics, 44–58. WORLD SCIENTIFIC, 1989. http://dx.doi.org/10.1142/9789814434133_0004.
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Nissen, Elke, Catherine Felce, and Catherine Muller. "Virtual exchange: from students’ expectations to perceived outcomes." In Virtual exchange: towards digital equity in internationalisation, 139–55. Research-publishing.net, 2021. http://dx.doi.org/10.14705/rpnet.2021.53.1296.
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What do students expect before starting a Virtual Exchange (VE) with peers? Are their initial expectations mirrored in the final outcomes they perceive after the VE experience? Or, else, do students acknowledge benefits and acquired skills which they did not expect at first? This study draws on qualitative and quantitative data collected across a variety of VE settings within the Erasmus+ EVOLVE project (16 VEs and 248 students in total). In a mixed-methods approach, it confronts students’ expectations and perceived outcomes in order to outline the learning potential of VE, beyond the specific learning objectives set in the different Higher Educational (HE) courses in which a VE was implemented. It brings to light that the overlap between students’ expectations and the benefits they see is only partial. The declared outcomes deviate more from the course learning objectives than the initial expectations do, and they are, unsurprisingly, more nuanced and manifold. Expectations of intercultural and language practice and skills development are more often aligned with outcomes voiced by students than is the case for digital and disciplinary skills. What stands out is a great occurrence of transferable skills in the outcomes, including collaborative, relational, and communicative skills that are not always promoted in the course objectives.
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Roulet, Geoffrey. "Supporting Online Collaborative Mathematical Exploration." In Adoption of Virtual Technologies for Business, Educational, and Governmental Advancements, 228–37. IGI Global, 2013. http://dx.doi.org/10.4018/978-1-4666-2053-7.ch019.
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Math-Towers is a collaborative mathematics environment for pupils in grades 7 to 9. Using a fantasy adventure game context, students are presented with a mathematical challenge, given online tools for working on the problem, and provided with a messaging system by which they may exchange ideas and partial solutions. This paper presents the philosophy behind the design of Math-Towers and, using a complexity science framework, explores the extent to which it has been successful in meeting goals. The technical and social problems encountered and revisions made to address these are also described.
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Vance, Colin. "The Semi-Market and Semi-Subsistence Household: The Evidence and Test of Smallholder Behavior." In Integrated Land-Change Science and Tropical Deforestation in the Southern Yucatan. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780199245307.003.0021.
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Understanding household farming behavior among smallholders is an essential element of land-change studies inasmuch as a considerable portion of the world is dominated by land-users of this kind. Smallholders (peasants in some literature) are especially important within the tropical forests of Mexico, and the southern Yucatán peninsular region is no exception. This region, as elsewhere in the tropics, is characterized by underdeveloped markets and the consequent partial engagement of frontier farmers as market participants. Sparse exchange opportunities resulting from remoteness, low population density, and poorly developed infrastructure constrain these farmers to maintain a strong focus on consumption production, especially in terms of staple foods. Indeed, until the late 1960s, households in the region were totally subsistence-based and had virtually no experience with the agricultural market. Today, smallholder farmers retain consumption production, though a growing proportion also produce crops for sale. While this dual position in the market and in subsistence is an increasingly prevalent feature of smallholder farmers throughout the developing world, studies of deforestation commonly ascribe to them a wholly commercial orientation by employing profit-maximizing theoretical structures as a basis for econometrically modeling their land-use decisions (e.g. Chomitz and Gray 1996; Cropper, Griffiths, and Mani 1999; Cropper, Puri, and Griffiths 2001; Nelson, Harris, and Stone 2001; Nelson and Hellerstein 1997; Panayotou and Sungsuwan 1994; Pfaff 1999). In essence, the assertion of profit-maximization rests on the assumption that agents are fully engaged in markets, from which it follows that production, being strictly a function of farm technology and exogenously given input and output prices, is entirely independent of consumption and labor supply (Barnum and Squire 1979). This chapter explores the implications of relaxing the perfect-markets assumption for the modeling of semi-subsistence and commercial land-use decisions. By introducing variables measuring the consumption side of the colonist household, evidence is presented to suggest that, consistent with mixed or hybrid production themes (e.g. Singh, Squire, and Strauss 1986; Turner and Brush 1987), farmers operating in a context of thin product and/or labor markets do not exhibit behavior corresponding to that of a commercially oriented profit-maximizing farm.
Conference papers on the topic "Virtual particle exchange"
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Mobley, Michael J. "Diffraction described by virtual particle momentum exchange: the "diffraction force"." In SPIE Optical Engineering + Applications, edited by Chandrasekhar Roychoudhuri, Andrei Yu Khrennikov, and Al F. Kracklauer. SPIE, 2011. http://dx.doi.org/10.1117/12.906068.
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Mobley, Michael J. "The nature of light: a description of photon diffraction based upon virtual particle exchange." In Optics & Photonics 2005, edited by Chandrasekhar Roychoudhuri and Katherine Creath. SPIE, 2005. http://dx.doi.org/10.1117/12.637439.
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Mobley, Michael J. "Further investigation of an integrated picture of photon diffraction described by virtual particle momentum exchange." In SPIE Optical Engineering + Applications, edited by Chandrasekhar Roychoudhuri, Al F. Kracklauer, and Hans De Raedt. SPIE, 2013. http://dx.doi.org/10.1117/12.2023796.
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Jung, Thomas Josef, Malte Rast, Eric Guiffo Kaigom, and Juergen Rossmann. "Fast VR Application Development Based on Versatile Rigid Multi-Body Dynamics Simulation." In ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/detc2011-47621.
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More and more areas in research and development use Virtual Reality technologies. To quickly realize new applications at low costs, the reuse of existing functionality is of high importance. In the area of mobile robotics, physics based simulation components promise optimal reusability: The physical laws always stay the same and do not depend on the application. Hence, as long as the applications try to emulate reality, physics based simulation software will be reusable. Unfortunately, depending on the kind of application, different simulation models for different physical domains are needed: Particle models for fluids and soil, finite-elements for non-rigid bodies, multi-body systems and so on. However, for those applications developed at Institute for Man-Machine Interaction at the RWTH Aachen University, a multi-body dynamics component has taken a central role in the process of application development. It is fully integrated within a modern 3D-simulation and visualization tool. It is enhanced by generalized tools of contact graph analysis, which support the fast development of robust applications suitable for daily use. The paper discusses the benefit of this multi-body system as a platform for versatile application development, taking the following three applications as examples: The first example is the development of forest machine simulators for usage in education and training of machine operators. The existence of a purely kinematically realized, phenomenological implementation with widely equivalent range of functions allows a direct comparison of the programming efforts. The second example is the development of algorithms for space robot motion planning. The example demonstrates, how easy and effective innovative robotic simulation applications can be realized using a common, dynamics based simulation framework. The third example finally describes the development of a Virtual Testbed for legged lunar exploration robots. The Virtual Testbed example handles in detail the concept of “top-down-development” of simulation models. The refinement of the simulation of foot-soil-contact situations using a force exchange interface and the refinement of the actuator dynamics simulation using an energy exchange interface serve as examples.
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Ito, Yuhei, Akira Hiwata, and Kotaro Sato. "Fundamental Study on Oil Mist Separation in Swirl Flow." In ASME 2013 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/fedsm2013-16254.
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Recently, the rotation rates used in fluid machines have been increasing as such machines continue to be downsized. However, these high rotation rates lead to the possibility of lubricant oil mist formed inside the compressor becoming mixed with the refrigerant gas, which can lead to a decrease in the heat exchange efficiency. The present study attempted to clarify the separation mechanism for refrigerant gas-lubricant oil mist two-phase flow during swirl flow in order to improve the oil mist separation efficiency. Both experiments and numerical simulations were carried out to investigate the relation between the oil mist separation efficiency and the flow characteristics in a test chamber containing a rotor. It was found that the flow characteristics were determined by the swirl number Sw, and the flow pattern was quite different for Sw = 1.0, 1.5 and 3.0. In addition, the oil mist separation efficiency increased with Sw and also showed a dependence on the chamber aspect ratio. The centrifugal force acting on a virtual particle in the chamber was also evaluated under various conditions.
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Mao, Xiaoan, Lei Shi, Artur J. Jaworski, and Wasan Kamsanam. "Heat Transfer on Parallel Plate Heat Exchangers in an Oscillatory Flow." In ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2010. http://dx.doi.org/10.1115/esda2010-24760.
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In thermoacoustic devices, an acoustic wave interacts with internal solid structures such as thermoacoustic stacks (regenerators), to either produce acoustic power due to an imposed temperature gradient, or to produce a heat pumping effect by an acoustic excitation. A cold and hot heat exchangers are usually placed on either side of these internal solid structures to enable heat communication between the thermoacoustic devices and their surroundings. Heat exchangers of various geometries have been extensively studied in steady flows and results are available from a collection of published articles and handbooks. However, there is still a lack of data for heat exchangers in an oscillatory flow, because the interaction of oscillatory flow with the solid boundary is governed by complicated fluid flow and heat transfer processes that are not fully understood. This work is a step towards a better understanding of the heat transfer mechanisms in the acoustically induced oscillatory flow within thermoacoustic systems, in particular obtaining the quantitative description of the heat transfer between heat exchangers and the stack. The assembly of a stack and heat exchangers is replaced by a simplified “stack-less” pair of heat exchangers, in order to focus on the generic heat transfer processes rather than the intricacies of practical thermoacoustic systems. The fins of the hot and cold heat exchangers are kept at constant temperatures by virtue of resistive heating and water cooling, respectively. Planar Laser Induced Fluorescence (PLIF) and Particle Image Velocimetry (PIV) are used to obtain the temperature and velocity fields around the fins. The heat flux between the heat exchanger fins and the fluid is analyzed phase-by-phase. The time dependent local heat transfer coefficient is obtained from the temperature gradient in the thermal boundary layer. The measurements are conducted at various levels of acoustic excitation in order to study the correlation between the non-dimensional heat transfer coefficient Nu and the Reynolds number. The effect of the flow behaviour at the end of the plates on the temperature field in the region is also studied. It is hoped that this work could lead to a better understanding of heat transfer on short plates in the acoustically induced oscillatory flows.
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Green, Leon. "Indirect Firing of Gas Turbines by Residual Coal-Water Fuel." In ASME 1985 International Gas Turbine Conference and Exhibit. American Society of Mechanical Engineers, 1985. http://dx.doi.org/10.1115/85-gt-168.
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Production of low-ash, low-sulfur coal-water fuel (CWF) will yield large quantities of high-ash but still low-sulfur “residual” CWF analogous to the residual fuel oil produced by petroleum refining. Relatively low in cost compared to the premium, low-ash CWF product, “resid” CWF will thus be available for in-plant industrial generation of conventional steam power or process heat. Due to its low sulfur content, however, a higher-value use of such a compliance fuel can be the indirect firing of gas turbines for the more efficient combination of power generation plus subsequent bottoming-cycle use or process heat applications (cogeneration). To limit NOx emissions, staged combustion will be required. Such operation can be accomplished starting with substoichiometric CWF reaction in “conventional” slurry burners followed by final combustion completed in the bottom region of a deep, intensely-mixed, fludized-bed heat exchanger. By virtue of the highly enhanced heat-transfer characteristics of the strongly-stirred bed of non-reactive particles, the normal limitation of rates of non-pressurized fire-side heat transfer is elevated. The fuel ash particles, milled fine by passage through the bed of refractory heat-transfer particles, are collected in a conventional baghouse. The conceptual design of such a combustion-driven, fluid-bed heat exchanger system fired by high-ash, residual coal-water fuel is outlined and its advantages over a conventional fluid-bed, solid-coal combustor for indirect firing of gas turbines are enumerated.
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Amir, Noam, Oded Barzelay, Amir Yefet, and Tal Pechter. "Inspecting U-Tube Bundles Using Acoustic Pulse Reflectometry." In ASME 2009 Power Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/power2009-81018.
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Acoustic Pulse Reflectometry (APR) has recently been gaining acceptance for a variety of tube inspection applications, as a viable alternative to more entrenched technologies such as eddy current. In this paper we present a case study demonstrating how APR can be used successfully for inspecting U-tube bundles. This type of heat exchanger poses a great challenge to technologies which require traversal with a probe, due to the presence of tight bends in the tubes. These are usually not traversable by probes. APR, on the other hand, uses an acoustic pulse as a “virtual probe”, with the ability to navigate bends, elbows, fittings etc. with no difficulty. In this paper we show how the various typical faults are revealed in the acoustic measurements and demonstrate how the analysis software recognizes these faults and generates the report. In one case presented here we inspected 62 heat exchangers used to heat natural gas, containing 39 U-tubes each, totaling 2379 tubes. Each tube had an internal diameter of 11mm, wall thickness of 2.5mm, and a length of approximately 6 meters, though there was some variability in length due to different lengths of the U bends. An added difficulty in inspecting these tubes was that the tube sheet was about 80 centimeters in distance from the inspection port-hole. The average inspection time in the field was 25 seconds per tube. All measurements were logged to computer files, and automated fault detection software generated a full report showing the condition of the tubes, indicating degradations in wall thickness, full and partial blockages, and holes. In the second case study we examine the variability in u-tubes in a single bundle and discuss the effect this has on the results.
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Gobinath, N., and J. Cecil. "Investigation of a Framework for Collaborative Activities Across Heterogeneous Engineering Domains." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-82105.
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This paper describes the functions underlying the creation of a collaborative framework to support robust information exchange across heterogeneous engineering domains. The application context relates to nano manipulation of particles such as proteins; the initial findings relating to distributed accomplishment of target activities in this identified context will be elaborated in this paper. In the scenario being considered, the potential project partners who possess skills and resources related to nano tube design, synthesis, manipulation plan, and simulation are identified from a service directory to form a Virtual Enterprise, with which the final target physical manipulation is formulated. In the proposed framework, the user specifications are used by various planning activities and a detailed top level plan is generated, which is represented by <NTDS, NTSS, MPS, SS>, where NTDS (Nano Tube Design Specification) is a representation of the design attributes of a carbon nano tube, NTSS (Nano Tube Synthesis Specification) is a representation that describes the synthesis of nano tube depending upon the design specification, MPS (Manipulation Plan Specification) is a representation which allows to formulate a nano manipulation plan according to user specification, and SS (Simulation Specification) is a representation that allows to generate various test cases to evaluate the nanomanipulator and the associated manipulation plan. The proposed framework is composed of an enterprise level Planning Manager (which generates a detailed top level plan from the user specification), a Design Coordinator (that identifies and evaluates the candidate design companies to find a potential design that can be used for a target nano manipulation tasks), a Synthesis/Manufacturing Coordinator (which focuses on identifying candidate partners and resources capable of manufacturing a specified nano manipulator). In the modeled context, this manipulator is a Nano tube attached to the tip of Atomic Force Microscope (AFM) probe; a Manipulation Plan Coordinator focuses on identifying candidate manipulation plan generators, and a Simulation coordinator deals with identifying candidate simulation tool vendors who provide services to evaluate nano tube and nano manipulation plan. The framework is proposed with scalability in mind so that new modules can be support a ‘plug and play’ type of integration in depending on the customer requirements.