Academic literature on the topic 'Time-dependent point interactions'
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Journal articles on the topic "Time-dependent point interactions"
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Correggi, Michele, Gianfausto Dell’Antonio, Rodolfo Figari, and Andrea Mantile. "Ionization for Three Dimensional Time-Dependent Point Interactions." Communications in Mathematical Physics 257, no. 1 (February 18, 2005): 169–92. http://dx.doi.org/10.1007/s00220-005-1293-x.
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Carlone, Raffaele, Michele Correggi, Marco Falconi, and Marco Olivieri. "Emergence of Time-Dependent Point Interactions in Polaron Models." SIAM Journal on Mathematical Analysis 53, no. 4 (January 2021): 4657–91. http://dx.doi.org/10.1137/20m1381344.
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Dell'Antonio, G. F., R. Figari, and A. Teta. "A Limit Evolution Problem for Time-Dependent Point Interactions." Journal of Functional Analysis 142, no. 1 (November 1996): 249–75. http://dx.doi.org/10.1006/jfan.1996.0149.
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Kuhn, J., F. M. Zanetti, A. L. Azevedo, A. G. M. Schmidt, Bin Kang Cheng, and M. G. E. da Luz. "Time-dependent point interactions and infinite walls: some results for wavepacket scattering." Journal of Optics B: Quantum and Semiclassical Optics 7, no. 3 (March 1, 2005): S77—S85. http://dx.doi.org/10.1088/1464-4266/7/3/011.
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RENARD, V. T., T. OTA, N. KUMADA, and H. HIRAYAMA. "POSITIVE MAGNETO-RESISTANCE IN A POINT CONTACT: POSSIBLE MANIFESTATION OF INTERACTIONS." International Journal of High Speed Electronics and Systems 17, no. 03 (September 2007): 495–99. http://dx.doi.org/10.1142/s0129156407004680.
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We report a non-monotonic and strongly temperature dependent magneto-resistance observed in clean quantum point contacts. At the same time the conductance of the point contact varies linearly with temperature. This unexpected behavior may be related to electron-electron interactions.
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Rudra, P. "Symmetry group of point transformations for the time-dependent Schrödinger equation: Harmonic interactions among nucleons." Physical Review C 44, no. 4 (October 1, 1991): 1486–92. http://dx.doi.org/10.1103/physrevc.44.1486.
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Flick, Johannes, Michael Ruggenthaler, Heiko Appel, and Angel Rubio. "Kohn–Sham approach to quantum electrodynamical density-functional theory: Exact time-dependent effective potentials in real space." Proceedings of the National Academy of Sciences 112, no. 50 (December 1, 2015): 15285–90. http://dx.doi.org/10.1073/pnas.1518224112.
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The density-functional approach to quantum electrodynamics extends traditional density-functional theory and opens the possibility to describe electron–photon interactions in terms of effective Kohn–Sham potentials. In this work, we numerically construct the exact electron–photon Kohn–Sham potentials for a prototype system that consists of a trapped electron coupled to a quantized electromagnetic mode in an optical high-Q cavity. Although the effective current that acts on the photons is known explicitly, the exact effective potential that describes the forces exerted by the photons on the electrons is obtained from a fixed-point inversion scheme. This procedure allows us to uncover important beyond-mean-field features of the effective potential that mark the breakdown of classical light–matter interactions. We observe peak and step structures in the effective potentials, which can be attributed solely to the quantum nature of light; i.e., they are real-space signatures of the photons. Our findings show how the ubiquitous dipole interaction with a classical electromagnetic field has to be modified in real space to take the quantum nature of the electromagnetic field fully into account.
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Hofmeister, Anne M., and Everett M. Criss. "Constraints on Newtonian Interplanetary Point-Mass Interactions in Multicomponent Systems from the Symmetry of Their Cycles." Symmetry 13, no. 5 (May 11, 2021): 846. http://dx.doi.org/10.3390/sym13050846.
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Interplanetary interactions are the largest forces in our Solar System that disturb the planets from their elliptical orbits around the Sun, yet are weak (<10−3 Solar). Currently, these perturbations are computed in pairs using Hill’s model for steady-state, central forces between one circular and one elliptical ring of mass. However, forces between rings are not central. To represent interplanetary interactions, which are transient, time-dependent, and cyclical, we build upon Newton’s model of interacting point-mass pairs, focusing on circular orbits of the eight largest bodies. To probe general and evolutionary behavior, we present analytical and numerical models of the interplanetary forces and torques generated during the planetary interaction cycles. From symmetry, over a planetary interaction cycle, radial forces dominate while tangential forces average to zero. Our calculations show that orbital perturbations require millennia to quantify, but observations are only over ~165 years. Furthermore, these observations are compromised because they are predominantly made from Earth, whose geocenter occupies a complex, non-Keplerian orbit. Eccentricity and inclination data are reliable and suggest that interplanetary interactions have drawn orbital planes together while elongating the orbits of the two smallest planets. This finding is consistent with conservation principles governing the eight planets, which formed as a system and evolve as a system.
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Declémy, A., C. Rulliére, and Ph Kottis. "Solvation Dynamics Studied by Picosecond Fluorescence: Microscopic Reorientation and Longitudinal Relaxation of the Solvent." Laser Chemistry 10, no. 5-6 (January 1, 1990): 413–29. http://dx.doi.org/10.1155/1990/86536.
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The dynamics of the Time-Dependent Fluorescence Shift (TDFS) of a rigid polar excited probe dissolved in alcohol solvents at different temperatures have been studied by picosecond time-resolved spectroscopy. The results are compared to previously published results on well characterized polar systems. These results show that solvation dynamics in such systems are strongly scaled by the microscopic (singleparticle) reorientation time τM of the solvent molecules and/or by the (macroscopic) longitudinal relaxation time τL of the solvent. The key point governing this scaling is the relative interaction between the solvent molecules and the probe compared to the interaction between the solvent molecules. It is also shown that specific interactions, such as hydrogen bonded-complex formation, may play an important role.
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Burkitt, Anthony N., Hamish Meffin, and David B. Grayden. "Spike-Timing-Dependent Plasticity: The Relationship to Rate-Based Learning for Models with Weight Dynamics Determined by a Stable Fixed Point." Neural Computation 16, no. 5 (May 1, 2004): 885–940. http://dx.doi.org/10.1162/089976604773135041.
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Experimental evidence indicates that synaptic modification depends on the timing relationship between the presynaptic inputs and the output spikes that they generate. In this letter, results are presented for models of spike-timing-dependent plasticity (STDP) whose weight dynamics is determined by a stable fixed point. Four classes of STDP are identified on the basis of the time extent of their input-output interactions. The effect on the potentiation of synapses with different rates of input is investigated to elucidate the relationship of STDP with classical studies of long-term potentiation and depression and rate-based Hebbian learning. The selective potentiation of higher-rate synaptic inputs is found only for models where the time extent of the input-output interactions is input restricted (i.e., restricted to time domains delimited by adjacent synaptic inputs) and that have a time-asymmetric learning window with a longer time constant for depression than for potentiation. The analysis provides an account of learning dynamics determined by an input-selective stable fixed point. The effect of suppressive interspike interactions on STDP is also analyzed and shown to modify the synaptic dynamics.
Books on the topic "Time-dependent point interactions"
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Morawetz, Klaus. Interacting Systems far from Equilibrium. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198797241.001.0001.
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In quantum statistics based on many-body Green’s functions, the effective medium is represented by the selfenergy. This book aims to discuss the selfenergy from this point of view. The knowledge of the exact selfenergy is equivalent to the knowledge of the exact correlation function from which one can evaluate any single-particle observable. Complete interpretations of the selfenergy are as rich as the properties of the many-body systems. It will be shown that classical features are helpful to understand the selfenergy, but in many cases we have to include additional aspects describing the internal dynamics of the interaction. The inductive presentation introduces the concept of Ludwig Boltzmann to describe correlations by the scattering of many particles from elementary principles up to refined approximations of many-body quantum systems. The ultimate goal is to contribute to the understanding of the time-dependent formation of correlations. Within this book an up-to-date most simple formalism of nonequilibrium Green’s functions is presented to cover different applications ranging from solid state physics (impurity scattering, semiconductor, superconductivity, Bose–Einstein condensation, spin-orbit coupled systems), plasma physics (screening, transport in magnetic fields), cold atoms in optical lattices up to nuclear reactions (heavy-ion collisions). Both possibilities are provided, to learn the quantum kinetic theory in terms of Green’s functions from the basics using experiences with phenomena, and experienced researchers can find a framework to develop and to apply the quantum many-body theory straight to versatile phenomena.
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van Boxel, Piet, Kirsten Macfarlane, and Joanna Weinberg, eds. The Mishnaic Moment. Oxford University Press, 2022. http://dx.doi.org/10.1093/oso/9780192898906.001.0001.
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This collection of essays treats a topic that has scarcely been approached in the literature on Hebrew and Hebraism in the early modern period. In the seventeenth century, Christians, especially Protestants, studied the Mishnah alongside a host of Jewish commentaries in order to reconstruct Jewish culture, history, and ritual, shedding new light on the world of the Old and New Testaments. Their work was also inextricably dependent upon the vigorous Mishnaic studies of early modern Jewish communities. Both traditions, in a sense, culminated in the monumental production in six volumes of an edition and Latin translation of the Mishnah published by Guilielmus Surenhusius in Amsterdam between 1698 and 1703. Surenhusius gathered up more than a century’s worth of Mishnaic studies by scholars from England, Germany, the Netherlands, and Sweden, as well as the commentaries of Maimonides and Obadiah of Bertinoro (c. 1455–c. 1515), but this edition was also born out of the unique milieu of Amsterdam at the end of the seventeenth century, a place which offered possibilities for cross-cultural interactions between Jews and Christians. With Surenhusius’s great volumes as an end-point, the essays presented here discuss for the first time the multiple ways in which the canonical text of Jewish law, the Mishnah (c. 200 CE), was studied by a variety of scholars, both Jewish and Christian, in early modern Europe. They tell the story of how the Mishnah generated an encounter between different cultures, faiths, and confessions that would prove to be enduringly influential for centuries to come.
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Wikle, Christopher K. Spatial Statistics. Oxford University Press, 2018. http://dx.doi.org/10.1093/acrefore/9780190228620.013.710.
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The climate system consists of interactions between physical, biological, chemical, and human processes across a wide range of spatial and temporal scales. Characterizing the behavior of components of this system is crucial for scientists and decision makers. There is substantial uncertainty associated with observations of this system as well as our understanding of various system components and their interaction. Thus, inference and prediction in climate science should accommodate uncertainty in order to facilitate the decision-making process. Statistical science is designed to provide the tools to perform inference and prediction in the presence of uncertainty. In particular, the field of spatial statistics considers inference and prediction for uncertain processes that exhibit dependence in space and/or time. Traditionally, this is done descriptively through the characterization of the first two moments of the process, one expressing the mean structure and one accounting for dependence through covariability.Historically, there are three primary areas of methodological development in spatial statistics: geostatistics, which considers processes that vary continuously over space; areal or lattice processes, which considers processes that are defined on a countable discrete domain (e.g., political units); and, spatial point patterns (or point processes), which consider the locations of events in space to be a random process. All of these methods have been used in the climate sciences, but the most prominent has been the geostatistical methodology. This methodology was simultaneously discovered in geology and in meteorology and provides a way to do optimal prediction (interpolation) in space and can facilitate parameter inference for spatial data. These methods rely strongly on Gaussian process theory, which is increasingly of interest in machine learning. These methods are common in the spatial statistics literature, but much development is still being done in the area to accommodate more complex processes and “big data” applications. Newer approaches are based on restricting models to neighbor-based representations or reformulating the random spatial process in terms of a basis expansion. There are many computational and flexibility advantages to these approaches, depending on the specific implementation. Complexity is also increasingly being accommodated through the use of the hierarchical modeling paradigm, which provides a probabilistically consistent way to decompose the data, process, and parameters corresponding to the spatial or spatio-temporal process.Perhaps the biggest challenge in modern applications of spatial and spatio-temporal statistics is to develop methods that are flexible yet can account for the complex dependencies between and across processes, account for uncertainty in all aspects of the problem, and still be computationally tractable. These are daunting challenges, yet it is a very active area of research, and new solutions are constantly being developed. New methods are also being rapidly developed in the machine learning community, and these methods are increasingly more applicable to dependent processes. The interaction and cross-fertilization between the machine learning and spatial statistics community is growing, which will likely lead to a new generation of spatial statistical methods that are applicable to climate science.
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Bever, Thomas G. The Unity of Consciousness and the Consciousness of Unity. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190464783.003.0005.
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Every language-learning child eventually automatically segments the organization of word sequences into natural units. Within the natural units, processing of normal conversation reveals a disconnect between listener’s representation of the sound and meaning of utterances. A compressed or absent word at a point early in a sequence is unintelligible until later acoustic information, yet listeners think they perceived the earlier sounds and their interpretation as they were heard. This discovery has several implications: Our conscious unified experience of language as we hear and simultaneously interpret it is partly reconstructed in time-suspended “psychological moments”; the “poverty of the stimulus language learning problem” is far graver than usually supposed; the serial domain where such integration occurs may be the “phase,” which unifies the serial percept with structural assignment and meanings; every level of language processing overlaps with others in a “computational fractal”; each level analysis-by-synthesis interaction of associative-serial and structure dependent processes.
Book chapters on the topic "Time-dependent point interactions"
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Goss, W. M., Claire Hooker, and Ronald D. Ekers. "Brain Drain: Trip to US and Canada 1957–1959." In Historical & Cultural Astronomy, 427–36. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-07916-0_28.
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AbstractLetter from Pawsey to his mother, from Princeton end 1957:Pawsey’s 8½-month visit to the US in 1957–1958 occurred during a key period of the GRT deliberations (FFP design study completion at the end of 1957 and the site selection in early 1958). It also occurred in the context of shifts in relations within RPL and in the field of radio astronomy as it grew around the world. There was growing awareness in Australia about the increasing capacity, especially in the USA, to attract first-rate scientists overseas to lead the new research programs being established. Meanwhile, at RPL, Bowen’s frustrations with Pawsey were growing to such a degree that Pawsey was beginning to feel some disquiet about his position in CSIRO. An important outcome of Pawsey’s visit to the US was an unofficial “audition” for a leadership role in US radio astronomy. At this point Pawsey would realise that he would have more to offer a US community with its multiple new radio astronomy groups (similar to the multiple groups he had nurtured in the beginning of radio astronomy research in Australia), than the Australian groups which had become strong and less dependent on his leadership. Pawsey’s scientific interactions during this time were also important as he planned for the Paris Symposium of August 1958 in his role as chair of the IAU organising committee.
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FIGARI, RODOLFO. "TIME DEPENDENT AND NONLINEAR POINT INTERACTIONS." In Mathematical Physics and Stochastic Analysis, 184–97. WORLD SCIENTIFIC, 2000. http://dx.doi.org/10.1142/9789812792167_0015.
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"E. Time-dependent scattering theory for point interactions." In Solvable Models in Quantum Mechanics, 374–75. Providence, Rhode Island: American Mathematical Society, 2004. http://dx.doi.org/10.1090/chel/350/20.
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Levitan, Irwin B., and Leonard K. Kaczmarek. "Ion Channels, Membrane Ion Currents, and the Action Potential." In The Neuron, 103–26. Oxford University Press, 2015. http://dx.doi.org/10.1093/med/9780199773893.003.0006.
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The flow of ions down their electrochemical gradients, through populations of ion channels in the neuronal plasma membrane, gives rise to transmembrane ion currents. It is the sum of the various currents flowing at any point in time that determines the neuron’s membrane potential. Thus the normal firing pattern of a neuron, and its response to different kinds of stimulation, can be seen as a play of interactions among the currents flowing through the different kinds of ion channels in its membrane. The activities of the sodium and potassium channels responsible for axonal action potentials are themselves dependent on voltage. Voltage clamp studies, which allow the measurement of the current flowing through these channels at fixed voltage, have provided a detailed understanding of the sequence of changes in sodium and potassium channel activity that give rise to action potentials.
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Green-Pedersen, Christoffer. "The Issue Incentive Model of Party System Attention." In The Reshaping of West European Party Politics, 24–40. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198842897.003.0003.
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This chapter presents the ‘issue incentive model of party system attention’. This model uses the issue competition literature and policy agenda-setting theory as a platform for building a theoretical framework with individual issues as analytical points of departure, and at the same time, the model focuses on explaining the entire issue agenda and not just individual issues. The issue incentive model explains the issue content of party politics through the incentives that different issues offer to large, mainstream parties. The concept of the party system agenda is a key element in the framework as it is the dependent variable. The model is not focused on explaining party attention at a particular time such as during an election campaign, for instance; focus here is on attention in the medium term such as a decade. The concept of the party system agenda highlights the interaction among political parties and their shared perceptions of which issues are important. The incentives for large, mainstream parties with regard to a particular issue are argued to be decisive; partly because large, mainstream parties are much more flexible in terms of issue attention than niche parties are, and partly because the largest parties traditionally dominate government formation and thus politics. Furthermore, three types of incentives are argued to be particularly decisive for whether large, mainstream parties want to pay attention to an issue: issue characteristics, issue ownership, and coalition considerations.
Conference papers on the topic "Time-dependent point interactions"
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Hu, Zhen, and Sankaran Mahadevan. "Adaptive Surrogate Modeling for Multidisciplinary Reliability Analysis Under Time-Dependent Uncertainty." In ASME 2017 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/detc2017-67383.
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Multidisciplinary systems will remain in transient states when time-dependent interactions are present among the coupling variables. This brings significant challenges to time-dependent multidisciplinary system reliability analysis. This paper develops an adaptive surrogate modeling approach (ASMA) for multidisciplinary system reliability analysis under time-dependent uncertainty. The proposed framework consists of three modules, namely initialization, uncertainty propagation, and three-level global sensitivity analysis (GSA). The first two modules check the quality of the surrogate models and determine when and where we should refine the surrogate models. Approaches are then proposed to estimate the potential error of the failure probability estimate and determine the location of the new training point. In the third module (i.e. three-level GSA), a method is developed to decide which surrogate model to refine, through GSA at three different levels. These three modules are integrated together systematically and enable us to adaptively allocate the computational resources to refine different surrogate models in the system and thus achieve high accuracy and efficiency in time-dependent multidisciplinary system reliability analysis. Results of two numerical examples demonstrate the effectiveness of the proposed framework.
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Jahnke, Douglas, and Yiannis Andreopoulos. "Development of a Time-Resolved Catadioptric Stereo Digital Image Correlation Technique for the Study of Blast Loading of Composite Material Structures." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-64006.
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Impingement of blast or shock waves on structures is characterized by a substantial transient aerodynamic load that develops over the short time associated with the shock reflection time scale. This mutual interaction between the shock wave and the structure can cause significant deformation of the structure and high strain rates within the material resulting in damage. While accelerometers, strain gages and other single point measurement probes and their corresponding techniques can provide valuable information of the local displacement and strain during blast loading, better understanding of the complex phenomena involved in these interactions require time dependent information acquired simultaneously from multi points on the structure. Digital Image Correlation is a full-field noncontact optical technique which can provide time dependent information of the displacement of the structure and the resultant high strain rates generated during the loading. The present setup consists of a single high-frame-rate camera which can accommodate two simultaneous stereo images of the deforming structure on its CMOS chip. Four different planar mirrors, appropriately positioned, provide the stereo views of the specimen captured on the chip. The present layout offers several advantages over traditional systems with two different cameras. First, it provides identical system parameters for the two views which minimizes their differences and thus facilitating robust stereo matching. Second, it reduces calibration time since only one camera is used and third its cost is substantially lower than the cost of a system with two cameras. The technique is being developed and tested in a large scale shock tube facility during loading by shock/blast wave of various impulses. The specimens used are flat plates made of high-alloy steel, aluminum or composite materials. In the present paper the development of the technique will be described and preliminary results of qualification tests will be presented and discussed.
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Gostelow, J. P., and R. L. Thomas. "Interactions Between Propagating Wakes and Flow Instabilities in the Presence of a Laminar Separation Bubble." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-91193.
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Laminar separation was investigated experimentally on a flat plate under a strongly diffusing self-similar pressure distribution. This gave a long and thin laminar separation bubble. Boundary layer velocity traverses were performed at numerous longitudinal stations. Using a single hot wire a combination of individual traces, phase averaging and time averaging was used. To supplement this, an array of microphones was installed to give instantaneous contours of pressure perturbation and to investigate the time dependent flow features. Microphone data were consistent with the strong amplification, under the adverse pressure gradient, of instabilities predicted far upstream of the separation point. Driven at the Tollmien-Schlichting (T-S) frequency, these instabilities grew into turbulent spots developing in the shear layer of the separation bubble. Reattachment of the bubble was caused by transition of the separated shear layer. The waves were strongest in the later stages of transition. Once the coherence was lost, in a turbulent layer, the amplitude became diminished. Wake disturbances were injected into the flow and traced through the flow field. The wake interaction resulted in turbulent patches which penetrated to the wall. Following the patches was the calmed region, detectable as a region of reduced wave activity in the transition region following each turbulent strip. For a short time at the end of the calmed region the viscous instability waves continued to propagate for a considerable distance downstream, in concert with the calmed region, in an otherwise turbulent zone.
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Arora CharpeAnshuman Shastri, Namrata. "Psychophysical Analysis of Studying in Isolation: Learning in Pandemic Era." In Human Interaction and Emerging Technologies (IHIET-AI 2022) Artificial Intelligence and Future Applications. AHFE International, 2022. http://dx.doi.org/10.54941/ahfe100904.
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Working on visual display units (VDUs) for prolonged periods of time leads to peculiar effects on physical and cognitive functioning of the users. COVID-19 pandemic brought the world to a point where all the work activities and interactions became dependent on various types of VDUs. The teaching-learning process switched to virtual classrooms bringing about a shift in the knowledge exchange scenario across the globe. An optimisation of conditions for VDU usage needs to be done in order to minimise the long term effects and reduce discomforts while using any such technology based media. The study focuses on a real time comprehensive analysis of VDU usage related musculoskeletal disorders, particularly computer vision syndrome and postural problems. The exposure assessment in both physical and cognitive domains provides the basis for optimisation of conditions for VDU usage.
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Koch, Stephan W., Hartmut Haug, and Murray Sargent. "Semiconductor laser theory with many-body effects." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1988. http://dx.doi.org/10.1364/oam.1988.mj5.
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A theory of a semiconductor laser is developed that includes the many-body effects due to Coulomb interactions. The theory is valid for both 3-D bulk semiconductors as well as quasi-2-D quantum well structures. We emphasize plasma density-dependent band gap renormalization, broadening due to intraband scattering, and electron–hole Coulomb enhancement. The very short intraband scattering relaxation time allows us to eliminate the interband polarization adiabatically and to introduce a hydrodynamic description of the intraband kinetics. From this general formulation a diffusion equation for the carrier density is derived. The resulting diffusion coefficient decreases with carrier density and laser intensity due to the reduction of the electron drift. We use our theory in the problem of laser gain, index, and side mode instabilities. We show that near the laser operating point, our many-body theory can be approximated by a simple rate equation formalism. However, in contrast to the usual rate-equation theory, the semiconductor rate constants are functions of temperature, tuning, and carrier density.
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Zhang, Ziliang, Yuhang Wang, Cornelis Vuik, and Hadi Hajibeygi. "An Efficient Simulation Approach for Long-term Assessment of CO2 Storage in Complex Geological Formations." In SPE Reservoir Characterisation and Simulation Conference and Exhibition. SPE, 2023. http://dx.doi.org/10.2118/212635-ms.
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Abstract We present an efficient compositional framework for simulation of CO2 storage in saline aquifers with complex geological geometries during a lifelong injection and migration process. To improve the computation efficiency, the general framework considers the essential hydrodynamic physics, including hysteresis, dissolution and capillarity, by means of parameterized space. The parameterization method translates physical models into parameterized spaces during an offline stage before simulation starts. Among them, the hysteresis behavior of constitutive relations is captured by the surfaces created from bounding and scanning curves, on which relative permeability and capillarity pressure are determined directly with a pair of saturation and turning point values. The new development also allows for simulation of realistic reservoir models with complex geological features. The numerical framework is validated by comparing simulation results obtained from the Cartesian-box and the converted corner-point grids of the same geometry, and it is applied to a field-scale reservoir eventually. For the benchmark problem, the CO2 is injected into a layered formation. Key processes such as accumulation of CO2 under capillarity barriers, gas breakthrough and dissolution, are well captured and agree with the results reported in literature. The roles of various physical effects and their interactions in CO2 trapping are investigated in a realistic reservoir model using the corner-point grid. It is found that dissolution of CO2 in brine occurs when CO2 and brine are in contact. The effect of residual saturation and hysteresis behavior can be captured by the proposed scanning curve surface in a robust way. The existence of capillarity causes less sharp CO2-brine interfaces by enhancing the imbibition of the brine behind the CO2 plume, which also increases the residual trapping. Moreover, the time-dependent characteristics of the trapping amount reveals the different time scales on which various trapping mechanisms (dissolution and residual) operate and the interplay. The novelty of the development is that essential physics for CO2 trapping are considered by the means of parameterized space. As it is implemented on corner-point grid geometries, it casts a promising approach to predict the migration of CO2 plume, and to assess the amount of CO2 trapped by different trapping mechanisms in realistic field-scale reservoirs.
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Zhu, Zhifu, and Xiaoping Du. "Extreme Value Metamodeling for System Reliability With Time-Dependent Functions." In ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/detc2015-46162.
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The reliability of a system is usually measured by the probability that the system performs its intended function in a given period of time. Estimating such reliability is a challenging task when the probability of failure is rare and the responses are nonlinear and time variant. The evaluation of the system reliability defined in a period of time requires the extreme values of the responses in the predefined period of time during which the system is supposed to function. This work builds surrogate models for the extreme values of responses with the Kriging method. For the sake of computational efficiency, the method creates Kriging models with high accuracy only in the region that has high contributions to the system failure; training points of random variables and time are sampled simultaneously so that their interactions could be considered automatically. The example of a mechanism system shows the effectiveness of the proposed method.
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Hu, Zhen, and Xiaoping Du. "Efficient Global Optimization Reliability Analysis (EGORA) for Time-Dependent Limit-State Functions." In ASME 2014 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/detc2014-34281.
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If a limit-state function involves time, the associated reliability is defined within a period of time. The extreme value of the limit-state function is needed to calculate the time-dependent reliability, and the extreme value is usually highly nonlinear with respect to random input variables and may follow a multimodal distribution. For this reason, a surrogate model of the extreme response along with Monte Carlo simulation is usually employed. The objective of this work is to develop a new method, called the Efficient Global Optimization Reliability Analysis (EGORA), to efficiently build the surrogate model. EGORA is based on the Efficient Global Optimization (EGO) method. Different from the current method that generates training points for random variables and time independently, EGORA draws training points for the two types of input variables simultaneously and therefore accounts for their interaction effects. The other improvement is that EGORA only focuses on high accuracy at or near the limit state. With the two improvements, the new method can effectively reduce the number of training points. Once the surrogate model of the extreme response is available, Monte Carlo simulation is applied to calculate the time-dependent reliability. Good accuracy and efficiency of EGORA are demonstrated by three examples.
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Muniz, E. M., J. W. Martin, M. A. Shaver, and F. Richard. "New Laboratory Workflow to Evaluate Shale Time-Dependent Wellbore Instabilities." In International Geomechanics Symposium. ARMA, 2022. http://dx.doi.org/10.56952/igs-2022-076.
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Abstract Drilling through overburden shale often presents operational challenges, particularly when drilling high-angle wells. Chemical imbalance between the shale and the drilling fluid can lead to time-dependent wellbore instability resulting in stuck pipe; cavings; and, under extreme circumstances, loss of the well. This study provides a unique workflow combining a suite of laboratory measurements to evaluate rock-fluid interaction between shale and drilling fluids. The testing suite includes X-ray diffraction (XRD) for mineralogical composition; tight rock analysis (TRA) for fluid saturations and petrophysical properties; mercury injection capillary pressure (MICP) for pore throat radius analysis, pore water composition and water activity (aw) that is measured at ambient and elevated pressure using a new test system (patent pending); pressure penetration and membrane efficiency tests to evaluate pressure transmission through shale when exposed to drilling fluids; and modified thick-walled cylinder (mTWC) tests for screening potential adverse effects of drilling fluid on rock strength. Test results show how water activity measurements using synthetic brines can vary significantly from measurements made directly from the rock and under in-situ stress conditions. Water activity measurements made under stress correlate well with clay content and pore throat radius. From mTWC tests, the imbalance of aw can generate shale swelling and strength reduction. The pressure transmission tests show how the drilling fluids can plug the pores and reduce the pressure transmission rate to the formation. These data are instrumental in providing mitigating measures to avoid instability problems during drilling through overburden shales. Introduction Drilling high-angle development wells in shale can pose many operational risks requiring optimization of casing points, knowledge of safe mud weight profiles, and selection of the drilling fluid to counter rock-fluid interaction. Often the mud weight needs to be high enough to prevent shear collapse but low enough to not induce weak-bedding-plane failure (mechanical tensile failure) in the overburden. To determine the drilling window and optimum drilling mud weight for the well design, basic well logs and drilling reports are not enough to solve the problem alone; core measurements and advanced sonic are key ingredients to the wellbore stability model and subsequent predictions. Laboratory tests address both mechanical behavior through plane of weakness testing and modeling coupled with anisotropic characterization (Xi et al., 2020; Shaver et al., 2020) and evaluation of chemical shale interaction with drilling fluids to determine the effects of drilling time-dependent instability. This paper provides a novel laboratory testing approach to characterize shale time-dependent behavior to optimize drilling fluids used for shale formations.
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Chen, Kai, and Richard A. Foulds. "The Mechanics of Perturbed Upper Limb Movement Control." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-37201.
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The dependence of muscle force on muscle length gives rise to a “spring - like” behavior which has been shown to play an important role during movement. This study extended this concept and incorporated the influential factors of the mechanical behavior of the neural, muscular and skeletal system on the control of elbow movement. A significant question in motor control is determining how information about movement is used to modify control signals to achieve desired performance. One theory proposed and supported by Feldman et. is the equilibrium point hypothesis (EPH). In it the central nervous system (CNS) reacts to movement as a shift of the limb’s equilibrium posture. The EPH drastically simplified the requisite computations for multi-joint movements and mechanical interactions with complex dynamic objects in the context. Because the neuromuscular system is spring-like, the instantaneous difference between the arm’s actual position and the equilibrium position specified by the neural activity can generate the requisite torques, avoiding the complex “inverse dynamic” of computing the torques at the joints. Moreover, this instantaneous difference serves as a potential source of movement control related to limb dynamics and associated movement-dependent torques when perturbations are added. In this paper, we have used an EPH model to examine changes to control signals for arm movements in the context of adding perturbations in format of forces or torques. The mechanical properties and reflex actions of muscles crossing the elbow joint were examined during a planned 1 radian voluntary elbow flexion movement. Brief unexpected torque/force pulses of identical magnitude and time duration (4.5 N flexion switching to 50 N extension within 120ms) were introduced at various points of a movement in randomly selected trials. Single perturbation was implemented in different trials during early, mid, stages of the movement by pre-programmed 6DOF robotic arm (MOOG FCS HapticMaster). Changes in movement trajectory induced by a torque/ force perturbation determined over the first 120 ms by a position prediction formulation, and then a modified and optimization K-B-I (stiffness-damping-inertia) model was fit to the responses for predicting both non-perturbed and perturbed movement of elbow. The stiffness and damping coefficients estimate during voluntary movements were compared to values recorded of different subjects during trials. A least square nonlinear optimization model was designed to help determine the optimized impedance a subject could generate, and the identified of adapted of K-B-I in perturbed upper limb movements confirmed our assumption.