Guided wave travel time tomography for bends
Volker, A.W.F.; Bloom, J.G.P.
2010-01-01
The concept of predictive maintenance using permanent sensors that monitor the integrity of an installation is an interesting addition to the current method of periodic inspections. Guided wave tomography has been developed to map the wall thickness using the travel times of guided waves. The method
Guided Wave Travel Time Tomography for Bends
Volker, A.W.F.; Zon, A.T. van
2012-01-01
The concept of predictive maintenance using permanent sensors that monitor the integrity of an installation is an interesting addition to the current method of periodic inspections. Guided wave tomography has been developed to map the wall thickness using the travel times of guided waves. The method
Recent developments in guided wave travel time tomography
Zon, A.T. van; Volker, A.W.F.
2014-01-01
The concept of predictive maintenance using permanent sensors that monitor the integrity of an installation is an interesting addition to the current method of periodic inspections. Guided wave tomography had been developed to create a map of the wall thickness using the travel times of guided
On a `time' reparametrization in relativistic electrodynamics with travelling waves
Fiore, Gaetano
2018-01-01
We briefly report on our method [23] of simplifying the equations of motion of charged particles in an electromagnetic (EM) field that is the sum of a plane travelling wave and a static part; it is based on changes of the dependent variables and the independent one (light-like coordinate ξ instead of time t). We sketch its application to a few cases of extreme laser-induced accelerations, both in vacuum and in plane problems at the vacuum-plasma interface, where we are able to reduce the system of the (Lorentz-Maxwell and continuity) partial differential equations into a family of decoupled systems of Hamilton equations in 1 dimension. Since Fourier analysis plays no role, the method can be applied to all kind of travelling waves, ranging from almost monochromatic to socalled "impulses".
Parsimonious wave-equation travel-time inversion for refraction waves
Fu, Lei
2017-02-14
We present a parsimonious wave-equation travel-time inversion technique for refraction waves. A dense virtual refraction dataset can be generated from just two reciprocal shot gathers for the sources at the endpoints of the survey line, with N geophones evenly deployed along the line. These two reciprocal shots contain approximately 2N refraction travel times, which can be spawned into O(N2) refraction travel times by an interferometric transformation. Then, these virtual refraction travel times are used with a source wavelet to create N virtual refraction shot gathers, which are the input data for wave-equation travel-time inversion. Numerical results show that the parsimonious wave-equation travel-time tomogram has about the same accuracy as the tomogram computed by standard wave-equation travel-time inversion. The most significant benefit is that a reciprocal survey is far less time consuming than the standard refraction survey where a source is excited at each geophone location.
Recent developments in guided wave travel time tomography
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Zon, Tim van; Volker, Arno [TNO, Stieltjesweg 1, P.O. box 155 2600 AD Delft (Netherlands)
2014-02-18
The concept of predictive maintenance using permanent sensors that monitor the integrity of an installation is an interesting addition to the current method of periodic inspections. Guided wave tomography had been developed to create a map of the wall thickness using the travel times of guided waves. It can be used for both monitoring and for inspection of pipe-segments that are difficult to access, for instance at the location of pipe-supports. An important outcome of the tomography is the minimum remaining wall thickness, as this is critical in the scheduling of a replacement of the pipe-segment. In order to improve the sizing accuracy we have improved the tomography scheme. A number of major improvements have been realized allowing to extend the application envelope to pipes with a larger wall thickness and to larger distances between the transducer rings. Simulation results indicate that the sizing accuracy has improved and that is now possible to have a spacing of 8 meter between the source-ring and the receiver-ring. Additionally a reduction of the number of sensors required might be possible as well.
Huang, Rui; Jin, Chunhua; Mei, Ming; Yin, Jingxue
2018-01-01
This paper deals with the existence and stability of traveling wave solutions for a degenerate reaction-diffusion equation with time delay. The degeneracy of spatial diffusion together with the effect of time delay causes us the essential difficulty for the existence of the traveling waves and their stabilities. In order to treat this case, we first show the existence of smooth- and sharp-type traveling wave solutions in the case of c≥c^* for the degenerate reaction-diffusion equation without delay, where c^*>0 is the critical wave speed of smooth traveling waves. Then, as a small perturbation, we obtain the existence of the smooth non-critical traveling waves for the degenerate diffusion equation with small time delay τ >0 . Furthermore, we prove the global existence and uniqueness of C^{α ,β } -solution to the time-delayed degenerate reaction-diffusion equation via compactness analysis. Finally, by the weighted energy method, we prove that the smooth non-critical traveling wave is globally stable in the weighted L^1 -space. The exponential convergence rate is also derived.
Nutto, C.; Steiner, O.; Schaffenberger, W.; Roth, M.
2012-02-01
Context. Observations of waves at frequencies above the acoustic cut-off frequency have revealed vanishing wave travel-times in the vicinity of strong magnetic fields. This detection of apparently evanescent waves, instead of the expected propagating waves, has remained a riddle. Aims: We investigate the influence of a strong magnetic field on the propagation of magneto-acoustic waves in the atmosphere of the solar network. We test whether mode conversion effects can account for the shortening in wave travel-times between different heights in the solar atmosphere. Methods: We carry out numerical simulations of the complex magneto-atmosphere representing the solar magnetic network. In the simulation domain, we artificially excite high frequency waves whose wave travel-times between different height levels we then analyze. Results: The simulations demonstrate that the wave travel-time in the solar magneto-atmosphere is strongly influenced by mode conversion. In a layer enclosing the surface sheet defined by the set of points where the Alfvén speed and the sound speed are equal, called the equipartition level, energy is partially transferred from the fast acoustic mode to the fast magnetic mode. Above the equipartition level, the fast magnetic mode is refracted due to the large gradient of the Alfvén speed. The refractive wave path and the increasing phase speed of the fast mode inside the magnetic canopy significantly reduce the wave travel-time, provided that both observing levels are above the equipartition level. Conclusions: Mode conversion and the resulting excitation and propagation of fast magneto-acoustic waves is responsible for the observation of vanishing wave travel-times in the vicinity of strong magnetic fields. In particular, the wave propagation behavior of the fast mode above the equipartition level may mimic evanescent behavior. The present wave propagation experiments provide an explanation of vanishing wave travel-times as observed with multi
MINIMIZING COMPUTATIONAL ERRORS OF TSUNAMI WAVE-RAY AND TRAVEL TIME
Directory of Open Access Journals (Sweden)
Andrei G. Marchuk
2008-01-01
Full Text Available There are many methods for computing tsunami kinematics directly and inversely. The direct detection of waves in the deep ocean makes it possible to establish tsunami source characteristics and origin. Thus, accuracy of computational methods is very important in obtaining reliable results. In a non-homogeneous medium where tsunami wave propagation velocity varies, it is not very easy to determine a wave-ray that connects two given points along a path. The present study proposes modification in the methodology of determining tsunami travel-times and of wave-ray paths. An approximate ray trace path can be developed from a source origin point to any other point on a computational grid by solving directly the problem - and thus obtain the tsunami travel- times. The initial ray approximation can be optimized with the use of an algorithm that calculates all potential variations and applies corrections to travel-time values. Such an algorithm was tested in an area with model bathymetry and compared with a non-optimized method. The latter exceeded the optimized method by one minute of travel-time for every hour of tsunami propagation time.
Time-domain theory of gyrotron traveling wave amplifiers operating at grazing incidence
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Ginzburg, N. S., E-mail: ginzburg@appl.sci-nnov.ru [Institute of Applied Physics of the Russian Academy of Sciences, 46, Ul' yanov St., Nizhny Novgorod (Russian Federation); Nizhny Novgorod State University, Gagarin Ave., 23, 603950 Nizhny Novgorod (Russian Federation); Sergeev, A. S.; Zotova, I. V.; Zheleznov, I. V. [Institute of Applied Physics of the Russian Academy of Sciences, 46, Ul' yanov St., Nizhny Novgorod (Russian Federation)
2015-01-15
Time-domain theory of the gyrotron traveling wave tube (gyro-TWT) operating at grazing incidence has been developed. The theory is based on a description of wave propagation by a parabolic equation. The results of the simulations are compared with experimental results of the observation of subnanosecond pulse amplification in a gyro-TWT consisting of three gain sections separated by severs. The theory developed can also be used successfully for a description of amplification of monochromatic signals.
Travelling Waves of an n-Species Food Chain Model with Spatial Diffusion and Time Delays
Fei Hu; Yuyin Xu; Z. Wang; Wei Ding
2014-01-01
We investigate an n-species food chain model with spatial diffusion and time delays. By using Schauder’s fixed point theorem, we obtain the result about the existence of the travelling wave solutions of the food chain model with reaction term satisfying the partial quasimonotonicity conditions.
Travelling Waves of an n-Species Food Chain Model with Spatial Diffusion and Time Delays
Directory of Open Access Journals (Sweden)
Fei Hu
2014-01-01
Full Text Available We investigate an n-species food chain model with spatial diffusion and time delays. By using Schauder’s fixed point theorem, we obtain the result about the existence of the travelling wave solutions of the food chain model with reaction term satisfying the partial quasimonotonicity conditions.
Traveling Wave Solutions of Space-Time Fractional Generalized Fifth-Order KdV Equation
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Dianchen Lu
2017-01-01
Full Text Available The Korteweg-de Vries (KdV equation, especially the fractional higher order one, provides a relatively accurate description of motions of long waves in shallow water under gravity and wave propagation in one-dimensional nonlinear lattice. In this article, the generalized exp(-Φ(ξ-expansion method is proposed to construct exact solutions of space-time fractional generalized fifth-order KdV equation with Jumarie’s modified Riemann-Liouville derivatives. At the end, three types of exact traveling wave solutions are obtained which indicate that the method is very practical and suitable for solving nonlinear fractional partial differential equations.
Hietala, Vincent M.; Vawter, Gregory A.
1993-01-01
The traveling-wave photodetector of the present invention combines an absorptive optical waveguide and an electrical transmission line, in which optical absorption in the waveguide results in a photocurrent at the electrodes of the electrical transmission line. The optical waveguide and electrical transmission line of the electrically distributed traveling-wave photodetector are designed to achieve matched velocities between the light in the optical waveguide and electrical signal generated on the transmission line. This velocity synchronization provides the traveling-wave photodetector with a large electrical bandwidth and a high quantum efficiency, because of the effective extended volume for optical absorption. The traveling-wave photodetector also provides large power dissipation, because of its large physical size.
Body wave travel times and amplitudes for present-day seismic model of Mars
Raevskiy, Sergey; Gudkova, Tamara
At the moment Martian interior structure models are constrained by the satellite observational data (the mass, the moment of inertia factor, the Love number k _{2}) (Konopliv et al., 2011) and high pressure experimental data (Bertka and Fei, 1997). Seismological observations could provide unparalleled capability for studying Martian interiors. Future missions include seismic experiments on Mars (Lognonné et al., 2012). The main instrument for these seismic experiments is a broadband seismometer (Robert et al., 2012). When seismic measurements are not yet available, physically consistent interior models, characterized by properties of relevant minerals, make possible to study of the seismic response of the planet. \\To estimate travel times for direct P, S, core reflected PcP, ScS and core refracted PKP body waves as a function of epicentral distance and hypocentral depth, as well as their amplitudes at the surface for a given marsquake, software product was developed in MatLab, as it encompasses many plotting routines that plot resulting travel times and ray paths. The computational results have been compared with the program TTBox (Knapmeyer, 2004). The code computes seismic ray paths and travel times for a one-dimentional spherical interior model (density and seismic velocities are functions of a radius only). Calculations of travel times tables for direct P, S, core reflected PcP, ScS and core refracted PKP waves and their amplitudes are carried out for a trial seismic model of Mars M14_3 from (Zharkov et al., 2009): the core radius is 1800 km, the thickness of the crust is 50 km. Direct and core reflected P and S waves are recorded to a maximum epicentral distance equal to about 100(°) , and PKP arrivals can be detected for epicental distances larger than 150(°) . The shadow zone is getting wider in comparison with previous results (Knapmeyer, 2010), as the liquid core radius of the seismic model under consideration is larger. Based on the estimates of
Deser, Stanley; Jackiw, Roman
1992-01-01
To travel into the past, to observe it, perhaps to influence it and correct mistakes of one's youth, has been an abiding fantasy of mankind for as long as we have been aware of a past. Here are described some recent scientific investigations on this topic.
Real-Time Monitoring of Shear Wave Traveling in Liver Tissue In Vivo
Machida, Hideyuki; Yagi, Shin-ichi; Kondo, Yuji; Murata, Yutaka; Akimoto, Shin
2004-05-01
Real-time imaging of tissue dynamic response caused by internal or external stress forces acting across a living tissue is promising for improving diagnostic quality and accuracy of clinical palpation as an “ultrasonic visualized palpation”. Thus we have investigated a real-time imaging system of local tissue displacement along an ultrasonic beam scanned across the living tissue, which realized straightforward but tissue-oriented physiological and dynamic color imaging on a conventional B-mode screen. System performance is fairly supported by a flexible design of a digital signal processor for real-time local cross correlation between successive two-dimensional complex speckle echo frames. Propagation of shear waves raised by external stress in a tissue phantom was clearly observed, so that real-time observation of shear wave traveling across a physiological liver tissue locally stressed by heartbeats was studied. As a result, we could confirm the characteristic shear wave propagation pattern by internal stress synchronous with heartbeat.
Directory of Open Access Journals (Sweden)
Koichi Narahara
2012-01-01
Full Text Available Nonlinear transmission lines, which define transmission lines periodically loaded with nonlinear devices such as varactors, diodes, and transistors, are modeled in the framework of finite-difference time-domain (FDTD method. Originally, some root-finding routine is needed to evaluate the contributions of nonlinear device currents appropriately to the temporally advanced electrical fields. Arbitrary nonlinear transmission lines contain large amount of nonlinear devices; therefore, it costs too much time to complete calculations. To reduce the calculation time, we recently developed a simple model of diodes to eliminate root-finding routines in an FDTD solver. Approximating the diode current-voltage relation by a piecewise-linear function, an extended Ampere's law is solved in a closed form for the time-advanced electrical fields. In this paper, we newly develop an FDTD model of field-effect transistors (FETs, together with several numerical examples that demonstrate pulse-shortening phenomena in a traveling-wave FET.
Bennett, James E. M.; Bair, Wyeth
2015-01-01
Traveling waves in the developing brain are a prominent source of highly correlated spiking activity that may instruct the refinement of neural circuits. A candidate mechanism for mediating such refinement is spike-timing dependent plasticity (STDP), which translates correlated activity patterns into changes in synaptic strength. To assess the potential of these phenomena to build useful structure in developing neural circuits, we examined the interaction of wave activity with STDP rules in simple, biologically plausible models of spiking neurons. We derive an expression for the synaptic strength dynamics showing that, by mapping the time dependence of STDP into spatial interactions, traveling waves can build periodic synaptic connectivity patterns into feedforward circuits with a broad class of experimentally observed STDP rules. The spatial scale of the connectivity patterns increases with wave speed and STDP time constants. We verify these results with simulations and demonstrate their robustness to likely sources of noise. We show how this pattern formation ability, which is analogous to solutions of reaction-diffusion systems that have been widely applied to biological pattern formation, can be harnessed to instruct the refinement of postsynaptic receptive fields. Our results hold for rich, complex wave patterns in two dimensions and over several orders of magnitude in wave speeds and STDP time constants, and they provide predictions that can be tested under existing experimental paradigms. Our model generalizes across brain areas and STDP rules, allowing broad application to the ubiquitous occurrence of traveling waves and to wave-like activity patterns induced by moving stimuli. PMID:26308406
Non-cooperative Fisher–KPP systems: traveling waves and long-time behavior
Girardin, Léo
2018-01-01
This paper is concerned with non-cooperative parabolic reaction–diffusion systems which share structural similarities with the scalar Fisher–KPP equation. These similarities make it possible to prove, among other results, an extinction and persistence dichotomy and, when persistence occurs, the existence of a positive steady state, the existence of traveling waves with a half-line of possible speeds and a positive minimal speed and the equality between this minimal speed and the spreading speed for the Cauchy problem. Non-cooperative KPP systems can model various phenomena where the following three mechanisms occur: local diffusion in space, linear cooperation and superlinear competition.
Zheng, F.
2011-01-01
Urban travel times are intrinsically uncertain due to a lot of stochastic characteristics of traffic, especially at signalized intersections. A single travel time does not have much meaning and is not informative to drivers or traffic managers. The range of travel times is large such that certain
Use of acoustic wave travel-time measurements to probe the near-surface layers of the Sun
Jefferies, S. M.; Osaki, Y.; Shibahashi, H.; Duvall, T. L., Jr.; Harvey, J. W.; Pomerantz, M. A.
1994-01-01
The variation of solar p-mode travel times with cyclic frequency nu is shown to provide information on both the radial variation of the acoustic potential and the depth of the effective source of the oscillations. Observed travel-time data for waves with frequency lower than the acoustic cutoff frequency for the solar atmosphere (approximately equals 5.5 mHz) are inverted to yield the local acoustic cutoff frequency nu(sub c) as a function of depth in the outer convection zone and lower atmosphere of the Sun. The data for waves with nu greater than 5.5 mHz are used to show that the source of the p-mode oscillations lies approximately 100 km beneath the base of the photosphere. This depth is deeper than that determined using a standard mixing-length calculation.
Obayashi, Masayuki; Ishihara, Yasushi; Suetsugu, Daisuke
2017-03-01
We conducted synthetic experiments to evaluate the effects of shallow-layer reverberation in oceanic regions on P-wave travel times measured by waveform cross-correlation. Time shift due to waveform distortion by the reverberation was estimated as a function of period. Reverberations in the crystalline crust advance the P-waves by a frequency-independent time shift of about 0.3 s in oceans. Sediment does not affect the time shifts in the mid-ocean regions, but effects as large as -0.8 s or more occur where sediment thickness is greater than 600 m for periods longer than 15 s. The water layer causes time delays (+0.3 s) in the relatively shallow (seismic tomography. We propose a simple method to correct relative P-wave travel times at two sites for shallow-layer reverberation by the cross-convolution of the crustal responses at the two sites. [Figure not available: see fulltext. Caption: .
Energy Technology Data Exchange (ETDEWEB)
Ambrose, David M.; Wilkening, Jon
2008-12-11
We classify all bifurcations from traveling waves to non-trivial time-periodic solutions of the Benjamin-Ono equation that are predicted by linearization. We use a spectrally accurate numerical continuation method to study several paths of non-trivial solutions beyond the realm of linear theory. These paths are found to either re-connect with a different traveling wave or to blow up. In the latter case, as the bifurcation parameter approaches a critical value, the amplitude of the initial condition grows without bound and the period approaches zero. We propose a conjecture that gives the mapping from one bifurcation to its counterpart on the other side of the path of non-trivial solutions. By experimentation with data fitting, we identify the form of the exact solutions on the path connecting two traveling waves, which represents the Fourier coefficients of the solution as power sums of a finite number of particle positions whose elementary symmetric functions execute simple orbits in the complex plane (circles or epicycles). We then solve a system of algebraic equations to express the unknown constants in the new representation in terms of the mean, a spatial phase, a temporal phase, four integers (enumerating the bifurcation at each end of the path) and one additional bifurcation parameter. We also find examples of interior bifurcations from these paths of already non-trivial solutions, but we do not attempt to analyze their algebraic structure.
Sequentially pulsed traveling wave accelerator
Caporaso, George J [Livermore, CA; Nelson, Scott D [Patterson, CA; Poole, Brian R [Tracy, CA
2009-08-18
A sequentially pulsed traveling wave compact accelerator having two or more pulse forming lines each with a switch for producing a short acceleration pulse along a short length of a beam tube, and a trigger mechanism for sequentially triggering the switches so that a traveling axial electric field is produced along the beam tube in synchronism with an axially traversing pulsed beam of charged particles to serially impart energy to the particle beam.
Traveling-Wave Membrane Photomixers
Wyss, R. A.; Martin, S. C.; Nakamura, B. J.; Neto, A.; Pasqualini, D.; Siegel, P. H.; Kadow, C.; Gossard, A. C.
2001-01-01
Traveling-wave photomixers have superior performance when compared with lumped area photomixers in the 1 to 3 THz frequency range. Their large active area and distributed gain mechanism assure high thermal damage threshold and elimination of the capacitive frequency roll-off. However, the losses experienced by the radio frequency wave traveling along the coplanar strips waveguide (due to underlying semi-infinite GaAs substrate) were a serious drawback. In this paper we present device designs and an experimental setup that make possible the realization of photomixers on membranes which eliminate the losses.
Aleiner, Igor L.; Faoro, Lara; Ioffe, Lev B.
2016-12-01
We extend the Keldysh technique to enable the computation of out-of-time order correlators such as . We show that the behavior of these correlators is described by equations that display initially an exponential instability which is followed by a linear propagation of the decoherence between two initially identically copies of the quantum many body systems with interactions. At large times the decoherence propagation (quantum butterfly effect) is described by a diffusion equation with non-linear dissipation known in the theory of combustion waves. The solution of this equation is a propagating non-linear wave moving with constant velocity despite the diffusive character of the underlying dynamics. Our general conclusions are illustrated by the detailed computations for the specific models describing the electrons interacting with bosonic degrees of freedom (phonons, two-level-systems etc.) or with each other.
Barnoud, A.; Coutant, O.; Bouligand, C.
2016-12-01
We aim at jointly inverting surface wave dispersion curves, earthquake travel times and gravimetric data to image the 3D structure of the volcanic island of Basse-Terre in Guadeloupe (Lesser Antilles). Imaging the 3D structure of this island is challenging, in particular due to the rough topography, the difficult access associated with the dense vegetation and the high level of seismic noise associated with tropical climate. The joint inversion of different types of data allows to derive a model compatible with all datasets, improving the resolution of the resulting model, due to the intrinsic sensitivities of the methods and to the different data coverages. Surface wave dispersion curves were obtained from ambient noise cross-correlations and provide seismic velocities with a good resolution in the upper 4 to 6 km. Travel times from the Lesser Antilles earthquake catalogue (CDSA/IPGP, Massin et al. 2013, Massin et al. 2014) are also included to improve the resolution at depth. Five datasets of terrestrial gravimetric data covering the whole island are available (Coron et al. 1975, Barthes et al. 1984, Gunawan 2005, Matthieu et al. 2011, Barnoud et al. 2016), constraining mostly the shallow lateral density variations. However coupling such datasets is not straightforward as it requires defining a coupling, a discretization and an inversion scheme adapted to the three methods. Our problem is coupled via the surface wave data and a P-wave velocity/density relationship (Carlson & Raskin 1984). We regularize the inverse problem using a Bayesian formalism (Tarantola & Valette 1982) and we discuss the advantages and limitations of two approaches to model the velocities of the subsurface: 1) a grid of nodes regularly spaced and 2) a Lagrangian interpolation on Gauss-Chebychev colocation nodes, equivalent to the use of a base of Chebychev polynomials (Boyd 2001). This work leads to the first 3D seismic velocity model of the island of Basse-Terre and therefore constitute a
Traveling Theta Waves in the Human Hippocampus
Zhang, Honghui
2015-01-01
The hippocampal theta oscillation is strongly correlated with behaviors such as memory and spatial navigation, but we do not understand its specific functional role. One hint of theta's function came from the discovery in rodents that theta oscillations are traveling waves that allow parts of the hippocampus to simultaneously exhibit separate oscillatory phases. Because hippocampal theta oscillations in humans have different properties compared with rodents, we examined these signals directly using multielectrode recordings from neurosurgical patients. Our findings confirm that human hippocampal theta oscillations are traveling waves, but also show that these oscillations appear at a broader range of frequencies compared with rodents. Human traveling waves showed a distinctive pattern of spatial propagation such that there is a consistent phase spread across the hippocampus regardless of the oscillations' frequency. This suggests that traveling theta oscillations are important functionally in humans because they coordinate phase coding throughout the hippocampus in a consistent manner. SIGNIFICANCE STATEMENT We show for the first time in humans that hippocampal theta oscillations are traveling waves, moving along the length of the hippocampus in a posterior–anterior direction. The existence of these traveling theta waves is important for understanding hippocampal neural coding because they cause neurons at separate positions in the hippocampus to experience different theta phases simultaneously. The theta phase that a neuron measures is a key factor in how that cell represents behavioral information. Therefore, the existence of traveling theta waves indicates that, to fully understand how a hippocampal neuron represents information, it is vital to also account for that cell's location in addition to conventional measures of neural activity. PMID:26354915
Crustal velocity structure of the Apennines (Italy from P-wave travel time tomography
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A. Amato
1996-06-01
Full Text Available In this paper we provide P-wave velocity images of the crust underneath the Apennines (Italy, focusing on the lower crustal structure and the Moho topography. We inverted P-wave arrival times of earthquakes which occurred from 1986 to 1993 within the Apenninic area. To overcome inversion instabilities due to noisy data (we used bulletin data we decided to resolve a minimum number of velocity parameters, inverting for only two layers in the crust and one in the uppermost mantle underneath the Moho. A partial inversion of only 55% of the overall dataset yields velocity images similar to those obtained with the whole data set, indicating that the depicted tomograms are stable and fairly insensitive to the number of data used. We find a low-velocity anomaly in the lower crust extending underneath the whole Apenninic belt. This feature is segmented by a relative high-velocity zone in correspondence with the Ortona-Roccamonfina line, that separates the northern from the southern Apenninic arcs. The Moho has a variable depth in the study area, and is deeper (more than 37 km in the Adriatic side of the Northern Apennines with respect to the Tyrrhenian side, where it is found in the depth interval 22-34 km.
Akram, Ghazala; Batool, Fiza
2017-10-01
The (G'/G)-expansion method is utilized for a reliable treatment of space-time fractional biological population model. The method has been applied in the sense of the Jumarie's modified Riemann-Liouville derivative. Three classes of exact traveling wave solutions, hyperbolic, trigonometric and rational solutions of the associated equation are characterized with some free parameters. A generalized fractional complex transform is applied to convert the fractional equations to ordinary differential equations which subsequently resulted in number of exact solutions. It should be mentioned that the (G'/G)-expansion method is very effective and convenient for solving nonlinear partial differential equations of fractional order whose balancing number is a negative integer.
Travel time data collection handbook
1998-03-01
This Travel Time Data Collection Handbook provides guidance to transportation : professionals and practitioners for the collection, reduction, and presentation : of travel time data. The handbook should be a useful reference for designing : travel ti...
Time Travel: The Role of Temporality in Enabling Semantic Waves in Secondary School Teaching
Matruglio, Erika; Maton, Karl; Martin, J. R.
2013-01-01
Based on the theoretical understandings from Legitimation Code Theory (Maton, 2013) and Systemic Functional Linguistics (Martin, 2013) underpinning the research discussed in this special issue, this paper focuses on classroom pedagogy to illustrate an important strategy for making semantic waves in History teaching, namely "temporal shifting". We…
Travel time reliability modeling.
2011-07-01
This report includes three papers as follows: : 1. Guo F., Rakha H., and Park S. (2010), "A Multi-state Travel Time Reliability Model," : Transportation Research Record: Journal of the Transportation Research Board, n 2188, : pp. 46-54. : 2. Park S.,...
Pickover, Clifford A.
1999-09-01
"Bucky Fuller thought big," Wired magazine recently noted, "Arthur C. Clarke thinks big, but Cliff Pickover outdoes them both." In his newest book, Cliff Pickover outdoes even himself, probing a mystery that has baffled mystics, philosophers, and scientists throughout history--What is the nature of time?In Time: A Traveler's Guide , Pickover takes readers to the forefront of science as he illuminates the most mysterious phenomenon in the universe--time itself. Is time travel possible? Is time real? Does it flow in one direction only? Does it have a beginning and an end? What is eternity? Pickover's book offers a stimulating blend of Chopin, philosophy, Einstein, and modern physics, spiced with diverting side-trips to such topics as the history of clocks, the nature of free will, and the reason gold glitters. Numerous diagrams ensure readers will have no trouble following along.By the time we finish this book, we understand a wide variety of scientific concepts pertaining to time. And most important, we will understand that time travel is, indeed, possible.
Travel time and travel cost in European air travel
Dusek, Tamas
2012-01-01
The aim of the study is to examine two issues of consumer air travel accessibility in Europe, namely flight time and ticket costs. The first part of the paper discusses the various methodological problems of creating time matrix and cost matrix of air travel. Because of problems of conceptualizing of the air travel network and the modifiable areal unit problem the analysis is conducted on several spatial levels. The smallest network consists of 15 busiest airports and the largest network has ...
Parametric form of QCD travelling waves
Peschanski, R.
2005-01-01
We derive parametric travelling-wave solutions of non-linear QCD equations. They describe the evolution towards saturation in the geometric scaling region. The method, based on an expansion in the inverse of the wave velocity, leads to a solvable hierarchy of differential equations. A universal parametric form of travelling waves emerges from the first two orders of the expansion.
Major dust storms and westward traveling waves on Mars
Wang, Huiqun
2017-04-01
Westward traveling waves are observed during major dust storm periods in northern fall and winter. The close correlation in timing makes westward traveling wave one of the signature responses of the Martian atmosphere to major dust storms. Westward traveling waves are dominated by zonal wave number m = 1 in the middle atmosphere and are typically characterized by long wave period. They are associated with significant temperature perturbations near the edge of the north polar vortex. Their wind signals extend to the low latitudes and the southern hemisphere. Their eddy momentum and heat fluxes exhibit complex patterns on a global scale in the middle atmosphere.
Molnar, P.; Chen, W.-P.
1984-01-01
S-P wave travel time residuals were measured in earthquakes in Tibet and the Himalaya in order to study lateral inhomogeneities in the earth's mantle. Average S-P residuals, measured with respect to Jeffrey-Bullen (J-B) tables for 11 earthquakes in the Himalaya are less than +1 second. Average J-B S-P from 10 of 11 earthquakes in Tibet, however, are greater than +1 second even when corrected for local crustal thickness. The largest values, ranging between 2.5 and 4.9 seconds are for five events in central and northern Tibet, and they imply that the average velocities in the crust and upper mantle in this part of Tibet are 4 to 10 percent lower than those beneath the Himalaya. On the basis of the data, it is concluded that it is unlikely that a shield structure lies beneath north central Tibet unless the S-P residuals are due to structural variations occurring deeper than 250 km.
New theory on the reverberation of rooms. [considering sound wave travel time
Pujolle, J.
1974-01-01
The inadequacy of the various theories which have been proposed for finding the reverberation time of rooms can be explained by an attempt to examine what might occur at a listening point when image sources of determined acoustic power are added to the actual source. The number and locations of the image sources are stipulated. The intensity of sound at the listening point can be calculated by means of approximations whose conditions for validity are given. This leads to the proposal of a new expression for the reverberation time, yielding results which fall between those obtained through use of the Eyring and Millington formulae; these results are made to depend on the shape of the room by means of a new definition of the mean free path.
Gleick, James
2016-01-01
From the acclaimed author of The Information and Chaos, here is a mind-bending exploration of time travel: its subversive origins, its evolution in literature and science, and its influence on our understanding of time itself. The story begins at the turn of the previous century, with the young H. G. Wells writing and rewriting the fantastic tale that became his first book and an international sensation: The Time Machine. It was an era when a host of forces was converging to transmute the human understanding of time, some philosophical and some technological: the electric telegraph, the steam railroad, the discovery of buried civilizations, and the perfection of clocks. James Gleick tracks the evolution of time travel as an idea that becomes part of contemporary culture—from Marcel Proust to Doctor Who, from Jorge Luis Borges to Woody Allen. He investigates the inevitable looping paradoxes and examines the porous boundary between pulp fiction and modern physics. Finally, he delves into a temporal shift that...
2-D traveling-wave patterns in binary fluid convection
Energy Technology Data Exchange (ETDEWEB)
Surko, C.M.; Porta, A.L. [Univ. of California, La Jolla, CA (United States)
1996-12-31
An overview is presented of recent experiments designed to study two-dimensional traveling-wave convection in binary fluid convection in a large aspect ratio container. Disordered patterns are observed when convection is initiated. As time proceeds, they evolve to more ordered patterns, consisting of several domains of traveling-waves separated by well-defined domain boundaries. The detailed character of the patterns depends sensitively on the Rayleigh number. Numerical techniques are described which were developed to provide a quantitative characterization of the traveling-wave patterns. Applications of complex demodulation techniques are also described, which make a detailed study of the structure and dynamics of the domain boundaries possible.
New exact travelling wave solutions of bidirectional wave equations
Indian Academy of Sciences (India)
where , , and d are real constants. In general, the exact travelling wave solutions will be helpful in the theoretical and numerical study of the nonlinear evolution systems. In this paper, we obtain exact travelling wave solutions of system (1) using the modiﬁed tanh–coth function method with computerized symbolic ...
Eberhart-Phillips, Donna; Fry, Bill
2017-08-01
We have developed a joint inversion of surface wave group velocity (U) and local earthquake travel-time (LET) data and applied it to the North Island, New Zealand, to improve the existing New Zealand wide 3-D seismic velocity model. This approach takes full advantage of the differing sensitivities of surface and body waves. The data are complementary, particularly at shallow depths where LET tomography suffers from vertical smearing and surface wave tomography is susceptible to horizontal smearing. The employed U observations are 2-D models at discrete periods which were developed for Rayleigh wave dispersion curves measured from the 1744 interstation Green's Functions obtained by stacked cross-correlations of broadband ambient noise data. In the volume surrounding each U observation, we distribute numerous points for relating the U observation to the gridded 3-D tomography model, analogous to points along a raypath. The partial derivatives at the points are computed using the U sensitivity kernels for Vp and Vs, with Vs related to Vp and Vp/Vs perturbations. Thus, the U observations are included along with the travel-time observations in a joint inversion to best fit the data and the existing tomography model. The resulting model favors the U where there is little travel-time resolution. The combined inversion used 2949 U observations at 6-16 s period and LET from 1509 earthquakes that extend to 370 km depth, and improved the model fit by reducing the U residual data variance by 62% and the LET by 9%. The resulting model generally has better constrained depth of shallow anomalies, with decreased velocity in the upper 2 km in the western North Island, and slight focusing of crustal high velocity features at 8 km depth. Significantly, the increased resolution in the shallowest 5 km of the model improves the utility of the 3-D model for use in seismic hazard assessment, wave propagation studies, and studies comparing seismic velocities to geological mapping.
Periodic Traveling Waves in Diatomic Granular Chains
Betti, Matthew; Pelinovsky, Dmitry E.
2013-10-01
We study bifurcations of periodic traveling waves in diatomic granular chains from the anti-continuum limit, when the mass ratio between the light and heavy beads is zero. We show that every limiting periodic wave is uniquely continued with respect to the mass ratio parameter, and the periodic waves with a wavelength larger than a certain critical value are spectrally stable. Numerical computations are developed to study how this solution family is continued to the limit of equal mass ratio between the beads, where periodic traveling waves of homogeneous granular chains exist.
Travelling waves in hybrid chemotaxis models
Franz, Benjamin; Painter, Kevin J; Erban, Radek
2013-01-01
Hybrid models of chemotaxis combine agent-based models of cells with partial differential equation models of extracellular chemical signals. In this paper, travelling wave properties of hybrid models of bacterial chemotaxis are investigated. Bacteria are modelled using an agent-based (individual-based) approach with internal dynamics describing signal transduction. In addition to the chemotactic behaviour of the bacteria, the individual-based model also includes cell proliferation and death. Cells consume the extracellular nutrient field (chemoattractant) which is modelled using a partial differential equation. Mesoscopic and macroscopic equations representing the behaviour of the hybrid model are derived and the existence of travelling wave solutions for these models is established. It is shown that cell proliferation is necessary for the existence of non-transient (stationary) travelling waves in hybrid models. Additionally, a numerical comparison between the wave speeds of the continuum models and the hybr...
Travelling waves in the lattice epidemic model
Directory of Open Access Journals (Sweden)
Zhixian Yu
2010-07-01
Full Text Available In this article, we establish the existence and nonexistence of travelling waves for a lattice non-monotone integral equation which is an epidemic model. Moreover, the wave is either convergent to the positive equilibrium or oscillating on the positive equilibrium at positive infinity, and has the exponential asymptotic behavior at negative infinity. For the non-monotone case, the asymptotic speed of propagation also coincides with the minimal wave speed.
Millimeter-wave gyrotron traveling-wave tube amplifiers
Du, Chao-Hai
2014-01-01
A gyrotron traveling-wave amplifier (gyro-TWT) with the high-power and broad-band capabilities is considered as a turn-on key for next generation high-resolution radar. The book presents comprehensive theory, methods, and physics related to gyro-TWT. The most challenging problem of instability competition has been for the first time addressed in a focused and systematic way, and reported via concise states and vivid pictures. The book is likely to meet the interest of researchers and engineers in radar and microwave technology, who would like to study the gyro-TWTs and to promote its application in millimeter-wave radars. Chao-Hai Du is a research professor, and Pu-Kun Liu is a full professor, at Peking University, Beijing, P. R. China.
Human cortical traveling waves: dynamical properties and correlations with responses.
Directory of Open Access Journals (Sweden)
Timothy M Patten
Full Text Available The spatiotemporal behavior of human EEG oscillations is investigated. Traveling waves in the alpha and theta ranges are found to be common in both prestimulus and poststimulus EEG activity. The dynamical properties of these waves, including their speeds, directions, and durations, are systematically characterized for the first time, and the results show that there are significant changes of prestimulus spontaneous waves in the presence of an external stimulus. Furthermore, the functional relevance of these waves is examined by studying how they are correlated with reaction times on a single trial basis; prestimulus alpha waves traveling in the frontal-to-occipital direction are found to be most correlated to reaction speeds. These findings suggest that propagating waves of brain oscillations might be involved in mediating long-range interactions between widely distributed parts of human cortex.
Traveling wave tube and method of manufacture
Vancil, Bernard K. (Inventor)
2004-01-01
A traveling wave tube includes a glass or other insulating envelope having a plurality of substantially parallel glass rods supported therewithin which in turn support an electron gun, a collector and an intermediate slow wave structure. The slow wave structure itself provides electrostatic focussing of a central electron beam thereby eliminating the need for focussing magnetics and materially decreasing the cost of construction as well as enabling miniaturization. The slow wave structure advantageously includes cavities along the electron beam through which the r.f. energy is propagated, or a double, interleaved ring loop structure supported by dielectric fins within a ground plane cylinder disposed coaxially within the glass envelope.
Travel time estimation using Bluetooth.
2015-06-01
The objective of this study was to investigate the feasibility of using a Bluetooth Probe Detection System (BPDS) to : estimate travel time in an urban area. Specifically, the study investigated the possibility of measuring overall congestion, the : ...
Traveling waves in an optimal velocity model of freeway traffic
Berg, Peter; Woods, Andrew
2001-03-01
Car-following models provide both a tool to describe traffic flow and algorithms for autonomous cruise control systems. Recently developed optimal velocity models contain a relaxation term that assigns a desirable speed to each headway and a response time over which drivers adjust to optimal velocity conditions. These models predict traffic breakdown phenomena analogous to real traffic instabilities. In order to deepen our understanding of these models, in this paper, we examine the transition from a linear stable stream of cars of one headway into a linear stable stream of a second headway. Numerical results of the governing equations identify a range of transition phenomena, including monotonic and oscillating travelling waves and a time- dependent dispersive adjustment wave. However, for certain conditions, we find that the adjustment takes the form of a nonlinear traveling wave from the upstream headway to a third, intermediate headway, followed by either another traveling wave or a dispersive wave further downstream matching the downstream headway. This intermediate value of the headway is selected such that the nonlinear traveling wave is the fastest stable traveling wave which is observed to develop in the numerical calculations. The development of these nonlinear waves, connecting linear stable flows of two different headways, is somewhat reminiscent of stop-start waves in congested flow on freeways. The different types of adjustments are classified in a phase diagram depending on the upstream and downstream headway and the response time of the model. The results have profound consequences for autonomous cruise control systems. For an autocade of both identical and different vehicles, the control system itself may trigger formations of nonlinear, steep wave transitions. Further information is available [Y. Sugiyama, Traffic and Granular Flow (World Scientific, Singapore, 1995), p. 137].
Travel time variability and rational inattention
DEFF Research Database (Denmark)
Fosgerau, Mogens; Jiang, Gege
2017-01-01
This paper sets up a rational inattention model for the choice of departure time for a traveler facing random travel time. The traveler chooses how much information to acquire about the travel time out-come before choosing departure time. This reduces the cost of travel time variability compared...
Monitoring Travel Time Reliability on Freeways
Tu, Huizhao
2008-01-01
Travel time and travel time reliability are important attributes of a trip. The current measures of reliability have in common that in general they all relate to the variability of travel times. However, travel time reliability does not only rely on variability but also on the stability of travel
Travelling Waves in Hyperbolic Chemotaxis Equations
Xue, Chuan
2010-10-16
Mathematical models of bacterial populations are often written as systems of partial differential equations for the densities of bacteria and concentrations of extracellular (signal) chemicals. This approach has been employed since the seminal work of Keller and Segel in the 1970s (Keller and Segel, J. Theor. Biol. 30:235-248, 1971). The system has been shown to permit travelling wave solutions which correspond to travelling band formation in bacterial colonies, yet only under specific criteria, such as a singularity in the chemotactic sensitivity function as the signal approaches zero. Such a singularity generates infinite macroscopic velocities which are biologically unrealistic. In this paper, we formulate a model that takes into consideration relevant details of the intracellular processes while avoiding the singularity in the chemotactic sensitivity. We prove the global existence of solutions and then show the existence of travelling wave solutions both numerically and analytically. © 2010 Society for Mathematical Biology.
The value of travel time variance
Fosgerau, Mogens; Engelson, Leonid
2010-01-01
This paper considers the value of travel time variability under scheduling preferences that are de�fined in terms of linearly time-varying utility rates associated with being at the origin and at the destination. The main result is a simple expression for the value of travel time variability that does not depend on the shape of the travel time distribution. The related measure of travel time variability is the variance of travel time. These conclusions apply equally to travellers ...
Valuation of Travel Time and TravelIer Information
Rietveld, Piet
2003-01-01
The value of travel time plays an important role in cost benefit analysis of infrastructureprojects. However, the issue of uncertainty on travel times and the implications this has forestimations of travel time values has received much less attention in the literature. In thispaper we compare
Travelling Waves in Hybrid Chemotaxis Models
Franz, Benjamin
2013-12-18
Hybrid models of chemotaxis combine agent-based models of cells with partial differential equation models of extracellular chemical signals. In this paper, travelling wave properties of hybrid models of bacterial chemotaxis are investigated. Bacteria are modelled using an agent-based (individual-based) approach with internal dynamics describing signal transduction. In addition to the chemotactic behaviour of the bacteria, the individual-based model also includes cell proliferation and death. Cells consume the extracellular nutrient field (chemoattractant), which is modelled using a partial differential equation. Mesoscopic and macroscopic equations representing the behaviour of the hybrid model are derived and the existence of travelling wave solutions for these models is established. It is shown that cell proliferation is necessary for the existence of non-transient (stationary) travelling waves in hybrid models. Additionally, a numerical comparison between the wave speeds of the continuum models and the hybrid models shows good agreement in the case of weak chemotaxis and qualitative agreement for the strong chemotaxis case. In the case of slow cell adaptation, we detect oscillating behaviour of the wave, which cannot be explained by mean-field approximations. © 2013 Society for Mathematical Biology.
Geyer, Anna
2016-01-01
Following a general principle introduced by Ehrnstr\\"{o}m et.al. we prove that for an equation modeling the free surface evolution of moderate amplitude waves in shallow water, all symmetric waves are traveling waves.
DEFF Research Database (Denmark)
Le Masurier, P.; Polak, J.; Pawlak, Janet
2015-01-01
A team of specialist market researchers and Value of Time experts comprising members from SYSTRA, Imperial College London and the Technical University of Denmark has conducted a formal audit and peer review of research undertaken by Arup/ITS Leeds/Accent to derive Value of Travel Time Savings...... Preference (RP) models that were used to derive final Values of Travel Time (VTT). This report contains the findings of our audit and peer review of the procedures adopted by the research team during data collection of the three surveys (SP, RP and Employers Surveys); a peer review of the reported approach...
Chaotic Traveling Waves in a Coupled Map Lattice
Kaneko, K
1993-01-01
Abstract: Traveling waves triggered by a phase slip in coupled map lattices are studied. A local phase slip affects globally the system, which is in strong contrast with kink propagation. Attractors with different velocities coexist, and form quantized bands determined by the number of phase slips. The mechanism and statistical and dynamical characters are studied with the use of spatial asymmetry, basin volume ratio, Lyapunov spectra, and mutual information. If the system size is not far from an integer multiple of the selected wavelength, attractors are tori, while weak chaos remains otherwise, which induces chaotic modulation of waves or a chaotic itinerancy of traveling states. In the itinerancy, the residence time distribution obeys the power law distribution, implying the existence of a long-ranged correlation. Supertransients before the formation of traveling waves are noted in the high nonlinearity regime. In the weaker nonlinearity regime corresponding to the frozen random pattern, we have found fluc...
Brown, Donna W.
2005-01-01
A Time Travel project in the library gives enthusiasm to students to connect with the past and reinforces their research skills while instilling respect for the past years. The librarian should choose one specific decade to highlight in the library and create an extravaganza that would allow memorabilia from that time period to be located without…
Directory of Open Access Journals (Sweden)
Yun-Li Chen
2007-01-01
Full Text Available Utilizing Ground Penetrating Radar (GPR, emitted electromagnetic (EM standing waves can be generated in underground voids. This phenomenon can be employed for the detection of subterranean voids and fractures when one has a proper understanding of relation between the widest inner length in an underground vacant space and half an EM wavelength. In this study, indoor and outdoor small-scale experiments verified the generation of EM standing waves. These responses were then applied in an arched-top cave covered by a single layer of backfill at Gongzihliao, Taiwan. Further studies were carried out at two other sites, including a fracture located in a granite mountain without regolith on the surface at Kinmen, and a deteriorating fishing port in Nanfangao, northeast Taiwan. Applying a band-pass filter with bandwidth narrower than a typical two-octave bandwidth produced the required standing waves with recognizable positions of minimum amplitude. A hyperbolic travel-time (HTT curve revealing the minimum amplitude, known as standing-wave nodes, indicates the presence of an underground hollow diffractor with the widest inner length in the vacant space being larger than half an EM wavelength. However, a HTT curve without nodal points signifies a hollow object with the widest inner length smaller than half an EM wavelength or an underground solid diffractor. An underground arched-top cave was detected by nodal points in the arc-like curves. When emitting the radar waves toward a wall, the interval of the nodes was used for estimating the wavelength of receiving GPR signals. Identifying the occurrence of nodal points in HTT or HTTlike curves in radargrams may assist the GPR interpreting work for underground tunnels, drainages, cavities, fractures, or solid objects.
Phase Behavior and Implications for Travel time Observables (PHASE 2)
2015-09-30
Phase behavior and implications for travel - time observables (PHASE-2) Emmanuel Skarsoulis Foundation for Research and Technology Hellas...perturbation behavior of travel time observables due to sound-speed perturbations. OBJECTIVES The objective is to study the behavior of the wave-theoretic...for this work came from the results of previous studies, supported by ONR, suggesting that the perturbation behavior of different travel - time
Catchment mixing processes and travel time distributions
National Research Council Canada - National Science Library
Botter, Gianluca
2012-01-01
...) of travel, residence and evapotranspiration times, which are comprehensive descriptors of the fate of rainfall water particles traveling through catchments, and provide key information on hydrologic...
Energy Technology Data Exchange (ETDEWEB)
Santos, Allan Xavier dos
2010-07-01
During the operation of a nuclear plant and other industrial plants, the operational time and the exposition to severe working conditions may cause the wear of its components, consequently, compromising the safety and the performance of the installation. The implementation of periodical inspections helps to ensure the safe operation and the best performance of the plant. In this way, the use of ultrasonic techniques for inspection and materials characterization becomes more and more attractive, since they offer quick, precise results and are technically ease to implement. The usual ultrasonic techniques, need to the measure the travelling time of the ultrasonic wave in the material examined in order to extract information useful to characterize it. Thus, the measurement of the travelling time of the ultrasonic wave is the overriding factor in most of the applications made with ultrasound. In this work a new technique was developed for measuring the travelling time of the ultrasonic wave using a Fourier's Fast Transformer (FFT). It will be shown mathematically and experimentally that it is possible to use the ultrasonic signal in the frequency domain to determine the travelling time of the ultrasonic wave. Five experiments were carried out for the experimental validation of this new technique. The materials used were 20 ceramic pastilles with different porosities and 3 aluminum plates of different thicknesses. The obtained results have shown that the new technique proposed in this work was able to determine the travelling time of the ultrasonic wave with the same precision as the conventional technique. It was shown, furthermore, that this new technique is able to measure the travelling time of the ultrasonic wave in situations where the conventional technique cannot be applied greatly expanding the range of application of ultrasonic testing and inspections. (author)
Geometrid outbreak waves travel across Europe.
Tenow, Olle; Nilssen, Arne C; Bylund, Helena; Pettersson, Rickard; Battisti, Andrea; Bohn, Udo; Caroulle, Fabien; Ciornei, Constantin; Csóka, György; Delb, Horst; De Prins, Willy; Glavendekić, Milka; Gninenko, Yuri I; Hrašovec, Boris; Matošević, Dinka; Meshkova, Valentyna; Moraal, Leen; Netoiu, Constantin; Pajares, Juan; Rubtsov, Vasily; Tomescu, Romica; Utkina, Irina
2013-01-01
We show that the population ecology of the 9- to 10-year cyclic, broadleaf-defoliating winter moth (Operophtera brumata) and other early-season geometrids cannot be fully understood on a local scale unless population behaviour is known on a European scale. Qualitative and quantitative data on O. brumata outbreaks were obtained from published sources and previously unpublished material provided by authors of this article. Data cover six decades from the 1950s to the first decade of twenty-first century and most European countries, giving new information fundamental for the understanding of the population ecology of O. brumata. Analyses on epicentral, regional and continental scales show that in each decade, a wave of O. brumata outbreaks travelled across Europe. On average, the waves moved unidirectionally ESE-WNW, that is, toward the Scandes and the Atlantic. When one wave reached the Atlantic coast after 9-10 years, the next one started in East Europe to travel the same c. 3000 km distance. The average wave speed and wavelength was 330 km year(-1) and 3135 km, respectively, the high speed being incongruous with sedentary geometrid populations. A mapping of the wave of the 1990s revealed that this wave travelled in a straight E-W direction. It therefore passed the Scandes diagonally first in the north on its way westward. Within the frame of the Scandes, this caused the illusion that the wave moved N-S. In analogy, outbreaks described previously as moving S-N or occurring contemporaneously along the Scandes were probably the result of continental-scale waves meeting the Scandes obliquely from the south or in parallel. In the steppe zone of eastern-most and south-east Europe, outbreaks of the winter moth did not participate in the waves. Here, broadleaved stands are small and widely separated. This makes the zone hostile to short-distance dispersal between O. brumata subpopulations and prevents synchronization within meta-populations. We hypothesize that hostile
Backus-Gilbert inversion of travel time data
Johnson, L. E.
1972-01-01
Application of the Backus-Gilbert theory for geophysical inverse problems to the seismic body wave travel-time problem is described. In particular, it is shown how to generate earth models that fit travel-time data to within one standard error and having generated such models how to describe their degree of uniqueness. An example is given to illustrate the process.
Traveling-Wave Maser for 32 GHz
Shell, James; Clauss, Robert
2009-01-01
The figure depicts a traveling-wave ruby maser that has been designed (though not yet implemented in hardware) to serve as a low-noise amplifier for reception of weak radio signals in the frequency band of 31.8 to 32.3 GHz. The design offers significant improvements over previous designs of 32-GHz traveling-wave masers. In addition, relative to prior designs of 32-GHz amplifiers based on high-electron-mobility transistors, this design affords higher immunity to radio-frequency interference and lower equivalent input noise temperature. In addition to the basic frequency-band and low-noise requirements, the initial design problem included a requirement for capability of operation in a closed-cycle helium refrigerator at a temperature .4 K and a requirement that the design be mechanically simplified, relative to prior designs, in order to minimize the cost of fabrication and assembly. Previous attempts to build 32- GHz traveling-wave masers involved the use of metallic slow-wave structures comprising coupled transverse electromagnetic (TEM)-mode resonators that were subject to very tight tolerances and, hence, were expensive to fabricate and assemble. Impedance matching for coupling signals into and out of these earlier masers was very difficult. A key feature of the design is a slow-wave structure, the metallic portions of which would be mechanically relatively simple in that, unlike in prior slow-wave structures, there would be no internal metal steps, irises, or posts. The metallic portions of the slow-wave structure would consist only of two rectangular metal waveguide arms. The arms would contain sections filled with the active material (ruby) alternating with evanescent-wave sections. This structure would be transparent in both the signal-frequency band (the aforementioned range of 31.8 to 32.3 GHz) and the pump-frequency band (65.75 to 66.75 GHz), and would impose large slowing factors in both frequency bands. Resonant ferrite isolators would be placed in the
Fellow travellers: Working memory and mental time travel in rodents.
Dere, Ekrem; Dere, Dorothea; de Souza Silva, Maria Angelica; Huston, Joseph P; Zlomuzica, Armin
2017-03-19
The impairment of mental time travel is a severe cognitive symptom in patients with brain lesions and a number of neuropsychiatric disorders. Whether animals are also able to mentally travel in time both forward and backward is still a matter of debate. In this regard, we have proposed a continuum of mental time travel abilities across different animal species, with humans being the species with the ability to perform most sophisticated forms of mental time travel. In this review and perspective article, we delineate a novel approach to understand the evolution, characteristics and function of human and animal mental time travel. Furthermore, we propose a novel approach to measure mental time travel in rodents in a comprehensive manner using a test battery composed of well-validated and easy applicable tests. Copyright © 2017. Published by Elsevier B.V.
Space-Qualified Traveling-Wave Tube
Wilson, Jeffrey D.; Krawczyk, Richard; Simons, Rainee N.; Williams, Wallace D.; Robbins, Neal R.; Dibb, Daniel R.; Menninger, William L.; Zhai, Xiaoling; Benton, Robert T.
2010-01-01
The L-3 Communications Electron Technologies, Inc. Model 999HA traveling-wave tube (TWT), was developed for use as a high-power microwave amplifier for high-rate transmission of data and video signals from deep space to Earth (see figure). The 999HA is a successor to the 999H a non-space qualified TWT described in High-Power, High-Efficiency Ka-Band Traveling-Wave Tube (LEW-17900-1), NASA Tech Briefs, Vol. 31, No. 2 (February 2007), page 32. Operating in the 31.8-to-32.3 GHz frequency band, the 999HA has been shown to generate 252 W of continuous- wave output power at 62 percent overall power efficiency a 75-percent increase in output power over the 999H. The mass of the 999HA is 35 percent less than that of the 999H. Moreover, taking account of the elimination of a Faraday cage that is necessary for operation of the 999H but is obviated by a redesign of high-voltage feed-throughs for the 999HA, the overall reduction in mass becomes 57 percent with an 82 percent reduction in volume. Through a series of rigorous tests, the 999HA has been qualified for operation aboard spacecraft with a lifetime exceeding seven years. Offspring of the 999HA will fly on the Kepler and Lunar Reconnaissance Orbiter missions.
Directory of Open Access Journals (Sweden)
Rashida Hussain
2017-04-01
Full Text Available In this paper, Novel (Gʹ/G-expansion method is used to find new generalized exact travelling wave solutions of fractional order coupled Burger’s equations in terms of trigonometric functions, rational functions and hyperbolic functions with arbitrary parameters. For the conversion of the partial differential equation to the ordinary differential equation, complex transformation method is used. Novel (Gʹ/G-expansion method is very effective and provides a powerful mathematical tool to solve nonlinear equations. Moreover, for the representation of these exact solutions we have plotted graphs for different values of parameters which were in travelling waveform.
Bifurcations and new exact travelling wave solutions for the ...
Indian Academy of Sciences (India)
2016-10-17
Oct 17, 2016 ... Abstract. By using the method of dynamical system, the bidirectional wave equations are considered. Based on this method, all kinds of phase portraits of the reduced travelling wave system in the parametric space are given. All possible bounded travelling wave solutions such as dark soliton solutions, ...
2010-01-01
... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Travel time. 630.207 Section 630.207... and General Provisions for Annual and Sick Leave § 630.207 Travel time. The travel time granted an employee under section 6303(d) of title 5, United States Code, is inclusive of the time necessarily...
Dynamic travel time estimation using regression trees.
2008-10-01
This report presents a methodology for travel time estimation by using regression trees. The dissemination of travel time information has become crucial for effective traffic management, especially under congested road conditions. In the absence of c...
Backward Wave Oscillation Thresholds in a Traveling-Wave Tube
Jassem, Abhijit; Wong, Patrick; Antoulinakis, Foivos; Lau, Y. Y.
2017-10-01
The threshold for the onset of backward wave oscillation (BWO) in a traveling-wave tube (TWT) was formulated by Johnson. In this paper, we extend Johnson's model to include random variations of circuit phase velocity along the tube axis. We find that Johnson's BWO threshold is minimally affected by these random variations. We next ignore these random variations, but include finite reflections at the two ends of a TWT and study their effects on Johnson's threshold. The latter theory is developed and being compared with results from an experimental helix test circuit. We will explore a 4-wave treatment for BWO, and its connection with the Briggs-Bers criterion for the existence of absolute instability. Work supported by DARPA, contract HR0011-16-C-0080 with Leidos, Inc., AFOSR Awards Nos. FA9550-15-1-0097, FA9550-14-1-0309, and L-3 Communications.
Coronal Mass Ejections travel time
Braga, Carlos Roberto; Souza de Mendonça, Rafael Rodrigues; Dal Lago, Alisson; Echer, Ezequiel
2017-10-01
Coronal mass ejections (CMEs) are the main source of intense geomagnetic storms when they are earthward directed. Studying their travel time is a key-point to understand when the disturbance will be observed at Earth. In this work, we study the CME that originated the interplanetary disturbance observed on 2013/10/02. According to the observations, the CME that caused the interplanetary disturbance was ejected on 2013/09/29. We obtained the CME speed and estimate of the time of arrival at the Lagrangian Point L1 using the concept of expansion speed. We found that observed and estimated times of arrival of the shock differ between 2 and 23 hours depending on method used to estimate the radial speed.
The Traveling Wave Reactor: Design and Development
Directory of Open Access Journals (Sweden)
John Gilleland
2016-03-01
Full Text Available The traveling wave reactor (TWR is a once-through reactor that uses in situ breeding to greatly reduce the need for enrichment and reprocessing. Breeding converts incoming subcritical reload fuel into new critical fuel, allowing a breed-burn wave to propagate. The concept works on the basis that breed-burn waves and the fuel move relative to one another. Thus either the fuel or the waves may move relative to the stationary observer. The most practical embodiments of the TWR involve moving the fuel while keeping the nuclear reactions in one place−sometimes referred to as the standing wave reactor (SWR. TWRs can operate with uranium reload fuels including totally depleted uranium, natural uranium, and low-enriched fuel (e.g., 5.5% 235U and below, which ordinarily would not be critical in a fast spectrum. Spent light water reactor (LWR fuel may also serve as TWR reload fuel. In each of these cases, very efficient fuel usage and significant reduction of waste volumes are achieved without the need for reprocessing. The ultimate advantages of the TWR are realized when the reload fuel is depleted uranium, where after the startup period, no enrichment facilities are needed to sustain the first reactor and a chain of successor reactors. TerraPower's conceptual and engineering design and associated technology development activities have been underway since late 2006, with over 50 institutions working in a highly coordinated effort to place the first unit in operation by 2026. This paper summarizes the TWR technology: its development program, its progress, and an analysis of its social and economic benefits.
Additive measures of travel time variability
DEFF Research Database (Denmark)
Engelson, Leonid; Fosgerau, Mogens
2011-01-01
This paper derives a measure of travel time variability for travellers equipped with scheduling preferences defined in terms of time-varying utility rates, and who choose departure time optimally. The corresponding value of travel time variability is a constant that depends only on preference...... parameters. The measure is unique in being additive with respect to independent parts of a trip. It has the variance of travel time as a special case. Extension is provided to the case of travellers who use a scheduled service with fixed headway....
The value of travel time variance
DEFF Research Database (Denmark)
Fosgerau, Mogens; Engelson, Leonid
2011-01-01
This paper considers the value of travel time variability under scheduling preferences that are defined in terms of linearly time varying utility rates associated with being at the origin and at the destination. The main result is a simple expression for the value of travel time variability that ...... on parameters, travellers may be risk averse or risk seeking and the value of travel time may increase or decrease in the mean travel time.......This paper considers the value of travel time variability under scheduling preferences that are defined in terms of linearly time varying utility rates associated with being at the origin and at the destination. The main result is a simple expression for the value of travel time variability...
Accurate estimation of indoor travel times
DEFF Research Database (Denmark)
Prentow, Thor Siiger; Blunck, Henrik; Stisen, Allan
2014-01-01
The ability to accurately estimate indoor travel times is crucial for enabling improvements within application areas such as indoor navigation, logistics for mobile workers, and facility management. In this paper, we study the challenges inherent in indoor travel time estimation, and we propose...... the InTraTime method for accurately estimating indoor travel times via mining of historical and real-time indoor position traces. The method learns during operation both travel routes, travel times and their respective likelihood---both for routes traveled as well as for sub-routes thereof. InTraTime...... allows to specify temporal and other query parameters, such as time-of-day, day-of-week or the identity of the traveling individual. As input the method is designed to take generic position traces and is thus interoperable with a variety of indoor positioning systems. The method's advantages include...
Network structure and travel time perception.
Parthasarathi, Pavithra; Levinson, David; Hochmair, Hartwig
2013-01-01
The purpose of this research is to test the systematic variation in the perception of travel time among travelers and relate the variation to the underlying street network structure. Travel survey data from the Twin Cities metropolitan area (which includes the cities of Minneapolis and St. Paul) is used for the analysis. Travelers are classified into two groups based on the ratio of perceived and estimated commute travel time. The measures of network structure are estimated using the street network along the identified commute route. T-test comparisons are conducted to identify statistically significant differences in estimated network measures between the two traveler groups. The combined effect of these estimated network measures on travel time is then analyzed using regression models. The results from the t-test and regression analyses confirm the influence of the underlying network structure on the perception of travel time.
Multimode Traveling-Wave Amplifier Tubes
Buck, E.
1981-02-01
The paper examines the recent developments which makes the Traveling Wave Tube (TWT) more powerful and efficient as a microwave amplifier than the solid state devices. Basic workings and efficiency, which can run, but usually do not, to 55%, are examined. The dependence of the performance of a given TWT upon the qualities of the beam and the manner of its focusing is described. Also described is the development of a multistage depressed collector (MDC) and its first application to a Communication Technology Satellite (CTS) tube, a 12 GHz, coupled-cavity, 200 watt TWT, which resulted in being operated in space for nearly four years and was both the most powerful and the most efficient (around 50%) communications TWT ever flown. It is predicted that the application of efficient refocusing and MDCs, made possible by computer simulations, will greatly increase tube efficiency, and thereby make practical, new multimode tubes which operate, as least partly, in a linear fashion.
BROADBAND TRAVELLING WAVE SEMICONDUCTOR OPTICAL AMPLIFIER
DEFF Research Database (Denmark)
2010-01-01
Broadband travelling wave semiconductor optical amplifier (100, 200, 300, 400, 800) for amplification of light, wherein the amplifier (100, 200, 300, 400, 800) comprises a waveguide region (101, 201, 301, 401, 801) for providing confinement of the light in transverse directions and adapted...... for propagation of the light in at least a first mode along a longitudinal axis (102, 202, 302) of the amplifier (100, 200, 300, 400, 800) in a propagation direction (103, 203, 303), and wherein the waveguide region (101, 201, 301, 401, 801) comprises a gain region (104, 204, 304, 404, 804) for amplifying......, 301, 401, 801) increases along the longitudinal axis (102, 202, 302), and wherein the ratio between the width (106, 206, 306) of the waveguide region (101, 201, 301, 401, 801) and the width (107, 207, 307) of the gain region (104, 204, 304, 404, 804) increases along the longitudinal axis (102, 202...
Static Trapping of Polar Molecules in a Traveling Wave Decelerator
Quintero-Perez, Marina; Jansen, Paul; Wall, Thomas E.; van den Berg, Joost E.; Hoekstra, Steven; Bethlem, Hendrick L.
2013-01-01
We present experiments on decelerating and trapping ammonia molecules using a combination of a Stark decelerator and a traveling wave decelerator. In the traveling wave decelerator, a moving potential is created by a series of ring-shaped electrodes to which oscillating high voltages (HV) are
Static trapping of polar molecules in a traveling wave decelerator
Quintero Perez, M.; Jansen, P.; Wall, T.E.; van den Berg, J.E.; Hoekstra, S.; Bethlem, H.L.
2013-01-01
We present experiments on decelerating and trapping ammonia molecules using a combination of a Stark decelerator and a traveling wave decelerator. In the traveling wave decelerator, a moving potential is created by a series of ring-shaped electrodes to which oscillating high voltages (HV) are
Bifurcation analysis and the travelling wave solutions of the Klein ...
Indian Academy of Sciences (India)
In this paper, we investigate the bifurcations and dynamic behaviour of travelling wave solutions of the Klein–Gordon–Zakharov equations given in Shang et al, Comput. Math. Appl. 56, 1441 (2008). Under different parameter conditions, we obtain some exact explicit parametric representations of travelling wave solutions by ...
expansion method and travelling wave solutions for the perturbed ...
Indian Academy of Sciences (India)
Abstract. In this paper, we construct the travelling wave solutions to the perturbed nonlinear. Schrödinger's equation (NLSE) with Kerr law non-linearity by the extended (G /G)-expansion method. Based on this method, we obtain abundant exact travelling wave solutions of NLSE with. Kerr law nonlinearity with arbitrary ...
The extended (G/G)-expansion method and travelling wave ...
Indian Academy of Sciences (India)
In this paper, we construct the travelling wave solutions to the perturbed nonlinear Schrödinger's equation (NLSE) with Kerr law non-linearity by the extended (′/)-expansion method. Based on this method, we obtain abundant exact travelling wave solutions of NLSE with Kerr law nonlinearity with arbitrary parameters.
Laboratory Test Results for the Travelling Wave Fault Location Scheme
Directory of Open Access Journals (Sweden)
Krzysztof Glik
2014-03-01
Full Text Available The article describes the travelling wave fault location algorithm for high voltage lines based on wavelet transform. The algorithm is implemented in a prototype and tested in the laboratory. The article presents the hardware and software part of a travelling wave fault locator, methodology and test results.
[Mental Space Navigation and Mental Time Travel].
Kawamura, Mitsuru
2017-11-01
We examined patients with mental space navigation or mental time travel disorder to identify regions in the brain that may play a critical role in mental time travel in terms of clinical neuropsychology. These regions included the precneus, posterior cingulate gyrus, retrosplenial cortex, and hippocampus, as well as the orbitofrontal cortex: the anterior and posterior medial areas were both shown to be important in this process. Further studies are required to define whether these form a network for mental time travel.
Traveling waves and compactons in phase oscillator lattices
Ahnert, Karsten; Pikovsky, Arkady
2008-09-01
We study waves in a chain of dispersively coupled phase oscillators. Two approaches—a quasicontinuous approximation and an iterative numerical solution of the lattice equation—allow us to characterize different types of traveling waves: compactons, kovatons, solitary waves with exponential tails as well as a novel type of semicompact waves that are compact from one side. Stability of these waves is studied using numerical simulations of the initial value problem.
Traveling-Wave Tube Efficiency Enhancement
Dayton, James A., Jr.
2011-01-01
Traveling-wave tubes (TWT's) are used to amplify microwave communication signals on virtually all NASA and commercial spacecraft. Because TWT's are a primary power user, increasing their power efficiency is important for reducing spacecraft weight and cost. NASA Glenn Research Center has played a major role in increasing TWT efficiency over the last thirty years. In particular, two types of efficiency optimization algorithms have been developed for coupled-cavity TWT's. The first is the phase-adjusted taper which was used to increase the RF power from 420 to 1000 watts and the RF efficiency from 9.6% to 22.6% for a Ka-band (29.5 GHz) TWT. This was a record efficiency at this frequency level. The second is an optimization algorithm based on simulated annealing. This improved algorithm is more general and can be used to optimize efficiency over a frequency bandwidth and to provide a robust design for very high frequency TWT's in which dimensional tolerance variations are significant.
Characteristic model of travelling wave ultrasonic motor.
Jingzhuo, Shi; Dongmei, You
2014-02-01
In general, the design and analysis of ultrasonic motor and motor's control strategy are based on mathematical model. The academic model is widely used in the analysis of traveling wave ultrasonic motor (TWUSM). But the dispersive characteristic of piezoelectric ceramics and other complicated process, such as the friction, make the model's precision not so accurate. On the other hand, identification modeling method, which is built based on the tested data, has obtained increasing application in the study of ultrasonic motor's control technology. Based on the identification model, many control strategies can be designed easily. But the identification model is an approximate model, so if a more accurate model of ultrasonic motor can be obtained, the analysis and design of motor control system will be more effective. Characteristic model is a kind of identification model which can accurately describe the characteristics of TWUSM. Based on the tested data, this paper proposes the modeling method of ultrasonic motor's characteristic model. The paper also makes a comparison of the effectiveness of different identification algorithms. Aiming at the speed control of ultrasonic motor, the influence of the parameter's initial values on the precision of model is discussed. The calculating results indicate the availability of this characteristic model. Copyright © 2013 Elsevier B.V. All rights reserved.
The cost of travel time variability
DEFF Research Database (Denmark)
Engelson, Leonid; Fosgerau, Mogens
2016-01-01
This paper explores the relationships between three types of measures of the cost of travel time variability: measures based on scheduling preferences and implicit departure time choice, Bernoulli type measures based on a univariate function of travel time, and mean-dispersion measures. We...
Traveling wave solutions of a highly nonlinear shallow water equation
Geyer, A.; Quirchmayr, Ronald
2018-01-01
Motivated by the question whether higher-order nonlinear model equations, which go beyond the Camassa-Holm regime of moderate amplitude waves, could point us to new types of waves profiles, we study the traveling wave solutions of a quasilinear evolution equation which models the propagation of
Traveling-wave ion mobility mass spectrometry of protein complexes
DEFF Research Database (Denmark)
Salbo, Rune; Bush, Matthew F; Naver, Helle
2012-01-01
The collision cross-section (Ω) of a protein or protein complex ion can be measured using traveling-wave (T-wave) ion mobility (IM) mass spectrometry (MS) via calibration with compounds of known Ω. The T-wave Ω-values depend strongly on instrument parameters and calibrant selection. Optimization...
Energy Technology Data Exchange (ETDEWEB)
Simmons, N. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Myers, S. C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Johannesson, G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Matzel, E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2012-10-06
[1] We develop a global-scale P wave velocity model (LLNL-G3Dv3) designed to accurately predict seismic travel times at regional and teleseismic distances simultaneously. The model provides a new image of Earth's interior, but the underlying practical purpose of the model is to provide enhanced seismic event location capabilities. The LLNL-G3Dv3 model is based on ∼2.8 millionP and Pnarrivals that are re-processed using our global multiple-event locator called Bayesloc. We construct LLNL-G3Dv3 within a spherical tessellation based framework, allowing for explicit representation of undulating and discontinuous layers including the crust and transition zone layers. Using a multiscale inversion technique, regional trends as well as fine details are captured where the data allow. LLNL-G3Dv3 exhibits large-scale structures including cratons and superplumes as well numerous complex details in the upper mantle including within the transition zone. Particularly, the model reveals new details of a vast network of subducted slabs trapped within the transition beneath much of Eurasia, including beneath the Tibetan Plateau. We demonstrate the impact of Bayesloc multiple-event location on the resulting tomographic images through comparison with images produced without the benefit of multiple-event constraints (single-event locations). We find that the multiple-event locations allow for better reconciliation of the large set of direct P phases recorded at 0–97° distance and yield a smoother and more continuous image relative to the single-event locations. Travel times predicted from a 3-D model are also found to be strongly influenced by the initial locations of the input data, even when an iterative inversion/relocation technique is employed.
Valuing travel time variability: Characteristics of the travel time distribution on an urban road
DEFF Research Database (Denmark)
Fosgerau, Mogens; Fukuda, Daisuke
2012-01-01
This paper provides a detailed empirical investigation of the distribution of travel times on an urban road for valuation of travel time variability. Our investigation is premised on the use of a theoretical model with a number of desirable properties. The definition of the value of travel time...... variability depends on certain properties of the distribution of random travel times that require empirical verification. Applying a range of nonparametric statistical techniques to data giving minute-by-minute travel times for a congested urban road over a period of five months, we show that the standardized...... travel time is roughly independent of the time of day as required by the theory. Except for the extreme right tail, a stable distribution seems to fit the data well. The travel time distributions on consecutive links seem to share a common stability parameter such that the travel time distribution...
Travel time variability and airport accessibility
Koster, P.R.; Kroes, E.P.; Verhoef, E.T.
2011-01-01
We analyze the cost of access travel time variability for air travelers. Reliable access to airports is important since the cost of missing a flight is likely to be high. First, the determinants of the preferred arrival times at airports are analyzed. Second, the willingness to pay (WTP) for
Potential applications of microstrip devices with traveling wave resonators
Directory of Open Access Journals (Sweden)
Glushechenko E. N.
2013-05-01
Full Text Available The shortcomings of the known microwave filters in microstrip lines are considered, the advantages of the use of directional traveling-wave filters in microstrip performance and examples of their potential applications are shown.
The classification of the single travelling wave solutions to the ...
Indian Academy of Sciences (India)
The discrimination system for the polynomial method is applied to variant Boussinesq equations to classify single travelling wave solutions. In particular, we construct corresponding solutions to the concrete parameters to show that each solution in the classification can be realized.
Thresholds and travelling waves for the geographical spread of infection.
Diekmann, O
1978-07-27
A nonlinear integral equation of mixed Volterra--Fredholm type describing the spatio-temporal development of an epidemic is derived and analysed. Particular attention is paid to the hair-trigger effect and to the travelling wave problem.
Microfabricated, 94 GHz, 25 W, Helical Traveling Wave Tube Project
National Aeronautics and Space Administration — Teraphysics Corporation proposes to design and develop a microfabricated, 94 GHz, 25 W traveling wave tube (TWT) with 53% efficiency for NASA applications. In Phase...
Hybrid Modelling of a Traveling Wave Piezoelectric Motor
DEFF Research Database (Denmark)
El, Ghouti N.
This thesis considers the modeling of the traveling wave piezoelectric motor (PEM). The rotary traveling wave ultrasonic motor "Shinsei type USR60" is the case study considered in this work. The traveling wave PEM has excellent performance and many useful features such as high holding torque, high...... of an ultrasonic traveling wave rotary piezoelectric motor. This approach is carried out on the basis of the experimental investigation combined with the electrical network method. Consequently, an insight in the analysis of the electromechanical coupling force factor, which is responsible for the electrical...... for control purposes. Consequently, a general state space model is derived on the basis of the special design of the motor of interest, which is a two phase symmetrical system. Furthermore, a simplified model is derived within the framework of various assumptions on the behavior of the stator, which makes...
Travelling waves in a singularly perturbed sine-Gordon equation
Derks, Gianne; Doelman, Arjen; van Gils, Stephanus A.; Visser, T.P.P.
2003-01-01
We determine the linearised stability of travelling front solutions of a perturbed sine-Gordon equation. This equation models the long Josephson junction using the RCSJ model for currents across the junction and includes surface resistance for currents along the junction. The travelling waves
Emergence of traveling waves in the spreading of dengue fever
Bianco, Simone; Faatz, Andrea; Cummings, Derek; Shaw, Leah
2010-03-01
Dengue fever is a multistrain mosquito-borne subtropical disease that exhibits complex oscillatory outbreaks. Epidemiological data from Thailand displays traveling waves of infection originating in Bangkok, the largest population center (Cummings et al., Nature 427: 344, 2004). We present a multistrain metapopulation model in which traveling wave like behavior results from migration coupling between heterogeneous regions. The region with the highest effective person-to-person contact rate leads the dynamics. A stochastic version of the model will also be presented.
The classification of the single travelling wave solutions to the ...
Indian Academy of Sciences (India)
Yang [18] studied the envelop solutions to DS equation; Fan [19] gave the classification of the single travelling wave solutions to ... Chree equation and give the classification of all its single travelling wave solutions with p = 1/2 and p = 3/2. ...... [4] W X Ma and B Fuchssteiner, J. Non-Linear Mech. 31, 329 (1996). [5] W X Ma ...
Exact traveling wave solutions of some nonlinear evolution equations
Kumar, Hitender; Chand, Fakir
2014-02-01
Using a traveling wave reduction technique, we have shown that Maccari equation, (2+1)-dimensional nonlinear Schrödinger equation, medium equal width equation, (3+1)-dimensional modified KdV-Zakharov-Kuznetsev equation, (2+1)-dimensional long wave-short wave resonance interaction equation, perturbed nonlinear Schrödinger equation can be reduced to the same family of auxiliary elliptic-like equations. Then using extended F-expansion and projective Riccati equation methods, many types of exact traveling wave solutions are obtained. With the aid of solutions of the elliptic-like equation, more explicit traveling wave solutions expressed by the hyperbolic functions, trigonometric functions and rational functions are found out. It is shown that these methods provide a powerful mathematical tool for solving nonlinear evolution equations in mathematical physics. A variety of structures of the exact solutions of the elliptic-like equation are illustrated.
Castro López, R.; Sun, Guo-Hua; Camacho-Nieto, O.; Yáñez-Márquez, C.; Dong, Shi-Hai
2017-09-01
We present analytical matter-wave solutions to a generalized Gross-Pitaevskii (GGP) equation with several new time and space varying nonlinearity coefficients and external fields. This is realized by taking a suitable similarity transformation to the GGP equation which makes the original partial differential equation into a stationary and ordinary differential equation. We report a few families of analytical solutions of the GGP equation with several new time and space varying nonlinearity interactions, in which some physically relevant soliton solutions are found. The profile features of the evolution wave functions depend on the different choices of the composite functions ξ.
Amplification of traveling magnetostatic waves by parametric pumping
Bashkovskiy, A. V.; Zubkov, V. I.; Krutsenko, I. V.; Melkov, G. A.
1984-07-01
An experiment was performed with traveling surface magnetostatic waves in a structure consisting of two parallel microstrip lines isolated from one another on a common Polycor base, both covered with a YIG (yttrium-iron garnet) film on a GGG (gallium-gadolinum garnet) substrate. An open dielectric pumping cavity resonator at the center of the 9.6 micron thick YIG film on its substrate side was operating in the parallel mode, with its magnetic field parallel to the constant external magnetic field, this mode of operation requiring less power than the transverse mode. The frequency of surface magneto-static waves on the YIG film (saturation magnetization 4 pi m sub o = 1750 Gs, width of resonance line 2 delta H= 0.5 Oe) was approx 4.7 GHz and the pumping frequency was approx. 9.4 GHz, with the intensity of the external magnetic field approx. 940 Oe. Heating of the film was avoided by pumping with pulses of 20 micro sec duration at a repetition rate of 50 Hz rather than with a continuous wave. This experiment for the first time revealed amplification of surface magnetostatic waves, the gain reaching 16 dB at a pumping powr of 2.2 W with 8 MHz bandwidth and 3 micro sec. delay time. Amplification occurred in a magnetic field of intensity H0 corresponding to maximum signal transmission from input to output microstrip line.
Ocean acoustic tomography - Travel time biases
Spiesberger, J. L.
1985-01-01
The travel times of acoustic rays traced through a climatological sound-speed profile are compared with travel times computed through the same profile containing an eddy field. The accuracy of linearizing the relations between the travel time difference and the sound-speed deviation at long ranges is assessed using calculations made for two different eddy fields measured in the eastern Atlantic. Significant nonlinearities are found in some cases, and the relationships of the values of these nonlinearities to the range between source and receiver, to the anomaly size associated with the eddies, and to the positions of the eddies are studied. An analytical model of the nonlinearities is discussed.
Drábek, Pavel; Takáč, Peter
2017-02-14
We consider a one-dimensional population genetics model for the advance of an advantageous gene. The model is described by the semilinear Fisher equation with unbalanced bistable non-Lipschitzian nonlinearity f(u). The "nonsmoothness" of f allows for the appearance of travelling waves with a new, more realistic profile. We study existence, uniqueness, and long-time asymptotic behavior of the solutions u(x, t), [Formula: see text]. We prove also the existence and uniqueness (up to a spatial shift) of a travelling wave U. Our main result is the uniform convergence (for [Formula: see text]) of every solution u(x, t) of the Cauchy problem to a single travelling wave [Formula: see text] as [Formula: see text]. The speed c and the travelling wave U are determined uniquely by f, whereas the shift [Formula: see text] is determined by the initial data.
Multimodal Network Equilibrium with Stochastic Travel Times
Directory of Open Access Journals (Sweden)
M. Meng
2014-01-01
Full Text Available The private car, unlike public traffic modes (e.g., subway, trolley running along dedicated track-ways, is invariably subject to various uncertainties resulting in travel time variation. A multimodal network equilibrium model is formulated that explicitly considers stochastic link capacity variability in the road network. The travel time of combined-mode trips is accumulated based on the concept of the mean excess travel time (METT which is a summation of estimated buffer time and tardy time. The problem is characterized by an equivalent VI (variational inequality formulation where the mode choice is expressed in a hierarchical logit structure. Specifically, the supernetwork theory and expansion technique are used herein to represent the multimodal transportation network, which completely represents the combined-mode trips as constituting multiple modes within a trip. The method of successive weighted average is adopted for problem solutions. The model and solution method are further applied to study the trip distribution and METT variations caused by the different levels of the road conditions. Results of numerical examples show that travelers prefer to choose the combined travel mode as road capacity decreases. Travelers with different attitudes towards risk are shown to exhibit significant differences when making travel choice decisions.
Periodic traveling interfacial hydroelastic waves with or without mass
Akers, Benjamin F.; Ambrose, David M.; Sulon, David W.
2017-12-01
We study the motion of an interface between two irrotational, incompressible fluids, with elastic bending forces present; this is the hydroelastic wave problem. We prove a global bifurcation theorem for the existence of families of spatially periodic traveling waves on infinite depth. Our traveling wave formulation uses a parameterized curve, in which the waves are able to have multivalued height. This formulation and the presence of the elastic bending terms allow for the application of an abstract global bifurcation theorem of "identity plus compact" type. We furthermore perform numerical computations of these families of traveling waves, finding that, depending on the choice of parameters, the curves of traveling waves can either be unbounded, reconnect to trivial solutions, or end with a wave which has a self-intersection. Our analytical and computational methods are able to treat in a unified way the cases of positive or zero mass density along the sheet, the cases of single-valued or multivalued height, and the cases of single-fluid or interfacial waves.
Bifurcation analysis and the travelling wave solutions of the Klein ...
Indian Academy of Sciences (India)
Math. Comput. 189, 271 (2007); Li et al, Appl. Math. Comput. 175, 61 (2006)). Keywords. Klein–Gordon–Zakharov equations; travelling wave solutions; bifurcation analysis. PACS Nos 05.45.Yv; 2.30.Jr; 04.20.Jb .... level h, it is shown that the exact periodic solutions evolute into solitary wave solution. In ref. [27], by using the ...
Highway travel time estimation with data fusion
Soriguera Martí, Francesc
2016-01-01
This monograph presents a simple, innovative approach for the measurement and short-term prediction of highway travel times based on the fusion of inductive loop detector and toll ticket data. The methodology is generic and not technologically captive, allowing it to be easily generalized for other equivalent types of data. The book shows how Bayesian analysis can be used to obtain fused estimates that are more reliable than the original inputs, overcoming some of the drawbacks of travel-time estimations based on unique data sources. The developed methodology adds value and obtains the maximum (in terms of travel time estimation) from the available data, without recurrent and costly requirements for additional data. The application of the algorithms to empirical testing in the AP-7 toll highway in Barcelona proves that it is possible to develop an accurate real-time, travel-time information system on closed-toll highways with the existing surveillance equipment, suggesting that highway operators might provide...
Establishing monitoring programs for travel time reliability.
2014-01-01
Within the second Strategic Highway Research Program (SHRP 2), Project L02 focused on creating a suite of methods by which transportation agencies could monitor and evaluate travel time reliability. Creation of the methods also produced an improved u...
Freeway travel-time estimation and forecasting.
2012-09-01
This project presents a microsimulation-based framework for generating short-term forecasts of travel time on freeway corridors. The microsimulation model that is developed (GTsim), replicates freeway capacity drop and relaxation phenomena critical f...
5 CFR 550.1404 - Creditable travel time.
2010-01-01
... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Creditable travel time. 550.1404 Section... ADMINISTRATION (GENERAL) Compensatory Time Off for Travel § 550.1404 Creditable travel time. (a) General. Subject... off for time in a travel status if— (1) The employee is required to travel away from the official duty...
Rietveld, P.; Zwart, B.; van Wee, B.; van Hoorn, T.
1999-01-01
This paper gives a detailed empirical analysis of the relationships between different indicators of costs of commuting trips by car: difference as the crow flies, shortest travel time according to route planner, corresponding travel distance, and reported travel time. Reported travel times are
Vector control method applied to a traveling wave in a finite beam.
Giraud, Frédéric; Giraud-Audine, Christophe; Amberg, Michel; Lemaire-Semail, Betty
2014-01-01
This paper presents the closed-loop control of exciters to produce a traveling wave in a finite beam. This control is based on a dynamical modeling of the system established in a rotating reference frame. This method allows dynamic and independent control of the phase and amplitude of two vibration modes. The condition to obtain the traveling wave is written in this rotating frame, and requires having two vibration modes with the same amplitude, and imposing a phase shift of 90° between them. The advantage of the method is that it allows easy implementation of a closed loop control that can handle parameter drift of the system, after a temperature rise, for example. The modeling is compared with measurement on an experimental test bench which also implements real-time control. We managed to experimentally obtain a settling time of 250 ms for the traveling wave, and a standing wave ratio (SWR) of 1.3.
Extremal inversion of lunar travel time data. [seismic velocity structure
Burkhard, N.; Jackson, D. D.
1975-01-01
The tau method, developed by Bessonova et al. (1974), of inversion of travel times is applied to lunar P-wave travel time data to find limits on the velocity structure of the moon. Tau is the singular solution to the Clairaut equation. Models with low-velocity zones, with low-velocity zones at differing depths, and without low-velocity zones, were found to be consistent with data and within the determined limits. Models with and without a discontinuity at about 25-km depth have been found which agree with all travel time data to within two standard deviations. In other words, the existence of the discontinuity and its size and location have not been uniquely resolved. Models with low-velocity channels are also possible.
Robustness of traveling waves in ongoing activity of visual cortex.
Nauhaus, Ian; Busse, Laura; Ringach, Dario L; Carandini, Matteo
2012-02-29
Numerous studies have revealed traveling waves of activity in sensory cortex, both following sensory stimulation and during ongoing activity. We contributed to this body of work by measuring the spike-triggered average of the local field potential (stLFP) at multiple concurrent locations (Nauhaus et al., 2009) in the visual cortex of anesthetized cats and macaques. We found the stLFP to be progressively delayed at increasing distances from the site of the triggering spikes, and interpreted this as a traveling wave of depolarization originating from that site. Our results were criticized, however, on two grounds. First, a study using the same recording techniques in the visual cortex of awake macaques reported an apparent lack of traveling waves, and proposed that traveling waves could arise artifactually from excessive filtering of the field potentials (Ray and Maunsell, 2011). Second, the interpretability of the stLFP was questioned (Kenneth Miller, personal communication), as the stLFP must reflect not only interactions between spike trains and field potentials, but also correlations within and across the spike trains. Here, we show that our data and interpretation are not imperiled by these criticisms. We reanalyzed our field potentials to remove any possible artifact due to filtering and to discount the effects of correlations within and across the triggering spike trains. In both cases, we found that the traveling waves were still present. In fact, closer inspection of Ray and Maunsell's (2011) data from awake cortex shows that they do agree with ours, as they contain clear evidence for traveling waves.
Up-date of traveling wave tube improvements
Buck, E.
1978-01-01
NASA research in the area of traveling wave tube technology is reviewed, with emphasis on the basic physics of guns and collectors and a computer model for the interaction between the electron beam and the RF circuit. The design of a multistage depressed collector, capable of multiplying tube efficiency by a factor of two or more, is presented; one such design has been adopted for commercial traveling wave tube production. A three-dimensional model of electron trajectories toward the collector also receives attention, as does the problem of RF circuit losses.
Dispersion-Engineered Traveling Wave Kinetic Inductance Parametric Amplifier
Zmuidzinas, Jonas (Inventor); Day, Peter K. (Inventor)
2014-01-01
A traveling wave kinetic inductance parametric amplifier comprises a superconducting transmission line and a dispersion control element. The transmission line can include periodic variations of its dimension along its length. The superconducting material can include a high normal state resistivity material. In some instances the high normal state resistivity material includes nitrogen and a metal selected from the group consisting of titanium, niobium and vanadium. The traveling wave kinetic inductance parametric amplifier is expected to exhibit a noise temperature below 100 mK/GHz.
Traveling-wave device with mass flux suppression
Swift, Gregory W.; Backhaus, Scott N.; Gardner, David L.
2000-01-01
A traveling-wave device is provided with the conventional moving pistons eliminated. Acoustic energy circulates in a direction through a fluid within a torus. A side branch may be connected to the torus for transferring acoustic energy into or out of the torus. A regenerator is located in the torus with a first heat exchanger located on a first side of the regenerator downstream of the regenerator relative to the direction of the circulating acoustic energy; and a second heat exchanger located on an upstream side of the regenerator. The improvement is a mass flux suppressor located in the torus to minimize time-averaged mass flux of the fluid. In one embodiment, the device further includes a thermal buffer column in the torus to thermally isolate the heat exchanger that is at the operating temperature of the device.
Evolutionary economics of mental time travel?
Boyer, Pascal
2008-06-01
What is the function of our capacity for 'mental time travel'? Evolutionary considerations suggest that vivid memory and imaginative foresight may be crucial cognitive devices for human decision making. Our emotional engagement with past or future events gives them great motivational force, which may counter a natural tendency towards time discounting and impulsive, opportunistic behavior. In this view, whereas simple episodic memory provides us with a store of relevant, case-based information to guide decisions, mental time travel nudges us towards more restrained choices, which in the long term are advantageous, especially so given human dependence on cooperation and coordination.
Photo-induced travelling waves in condensed Langmuir monolayers
Tabe, Y; Yokoyama, H
2003-01-01
We report the detailed properties of photo-induced travelling waves in liquid crystalline Langmuir monolayers composed of azobenzene derivatives. When the monolayer, in which the constituent rodlike molecules are coherently tilted from the layer normal, is weakly illuminated to undergo the trans-cis photo-isomerization, spatio-temporal periodic oscillations of the molecular azimuth begin over the entire excited area and propagate as a two-dimensional orientational wave. The wave formation takes place only when the film is formed at an asymmetric interface with broken up-down symmetry and when the chromophores are continuously excited near the long-wavelength edge of absorption to induce repeated photo-isomerizations between the trans and cis forms. Under proper illumination conditions, Langmuir monolayers composed of a wide variety of azobenzene derivatives have been confirmed to exhibit similar travelling waves with velocity proportional to the excitation power irrespective of the degree of amphiphilicity. T...
Traveling wave front solutions in lateral-excitatory neuronal networks
Directory of Open Access Journals (Sweden)
Sittipong Ruktamatakul
2008-05-01
Full Text Available In this paper, we discuss the shape of traveling wave front solutions to a neuronal model with the connection function to be of lateral excitation type. This means that close connecting cells have an inhibitory influence, while cells that aremore distant have an excitatory influence. We give results on the shape of the wave fronts solutions, which exhibit different shapes depend ing on the size of a threshold parameter.
On Irrotational Flows Beneath Periodic Traveling Equatorial Waves
Quirchmayr, Ronald
2017-06-01
We discuss some aspects of the velocity field and particle trajectories beneath periodic traveling equatorial surface waves over a flat bed in a flow with uniform underlying currents. The system under study consists of the governing equations for equatorial ocean waves within a non-inertial frame of reference, where Euler's equation of motion has to be suitably adjusted, in order to account for the influence of the earth's rotation.
Analytical approximation and numerical simulations for periodic travelling water waves
Kalimeris, Konstantinos
2017-12-01
We present recent analytical and numerical results for two-dimensional periodic travelling water waves with constant vorticity. The analytical approach is based on novel asymptotic expansions. We obtain numerical results in two different ways: the first is based on the solution of a constrained optimization problem, and the second is realized as a numerical continuation algorithm. Both methods are applied on some examples of non-constant vorticity. This article is part of the theme issue 'Nonlinear water waves'.
On the relationship between travel time and travel distance in the Netherlands
Rietveld, P.; Zwart, B.; van Wee, B.; van der Hoorn, A.I.J.M.
1999-01-01
This paper gives a detailed empirical analysis of the relationships between different indicators of costs of commuting trips by car: difference as the crow flies, shortest travel time according to route planner, corresponding travel distance, and reported travel time. Reported travel times are
The Traveling Wave Reactor： Design and Development
National Research Council Canada - National Science Library
John Gilleland Robert Petroski KevanWeaver
2016-01-01
... the nuclear reactions in one place-sometimes referred to as the standing wave reactor （SWR）. TWRs can operate with uranium reload fuels including totally depleted uranium, natural uranium, and low-enriched fuel （e.g., 5.5% 23sU and below...
Directory of Open Access Journals (Sweden)
Zhong-ye Tian
2014-01-01
Full Text Available The seismic responses of a long-span cable-stayed bridge under uniform excitation and traveling wave excitation in the longitudinal direction are, respectively, computed. The numerical results show that the bridge’s peak seismic responses vary significantly as the apparent wave velocity decreases. Therefore, the traveling wave effect must be considered in the seismic design of long-span bridges. The bridge’s peak seismic responses do not vary monotonously with the apparent wave velocity due to the traveling wave resonance. A new traveling wave excitation method that can simplify the multisupport excitation process into a two-support excitation process is developed.
A constant travel time budget? In search for explanations for an increase in average travel time
Rietveld, P.; Wee, van B.
2002-01-01
Recent research suggests that during the past decades the average travel time of the Dutch population has probably increased. However, different datasources show different levels of increase. Possible causes of the increase in average travel time are presented here. Increased incomes have
TRAVELING WAVE SOLUTIONS OF SOME FRACTIONAL DIFFERENTIAL EQUATIONS
Directory of Open Access Journals (Sweden)
SERIFE MUGE EGE
2016-07-01
Full Text Available The modified Kudryashov method is powerful, efficient and can be used as an alternative to establish new solutions of different type of fractional differential equations applied in mathematical physics. In this article, we’ve constructed new traveling wave solutions including symmetrical Fibonacci function solutions, hyperbolic function solutions and rational solutions of the space-time fractional Cahn Hillihard equation D_t^α u − γD_x^α u − 6u(D_x^α u^2 − (3u^2 − 1D_x^α (D_x^α u + D_x^α(D_x^α(D_x^α(D_x^α u = 0 and the space-time fractional symmetric regularized long wave (SRLW equation D_t^α(D_t^α u + D_x^α(D_x^α u + uD_t^α(D_x^α u + D_x^α u D_t^α u + D_t^α(D_t^α(D_x^α(D_x^α u = 0 via modified Kudryashov method. In addition, some of the solutions are described in the figures with the help of Mathematica.
Extending Regional Seismic Travel Time (RSTT) Tomography to New Regions
2011-09-01
layers overlay a mantle velocity profile that is simplified to two parameters: velocity at the Moho and a linear velocity gradient with depth. By... Moho depth of the starting model. (b) An example velocity/depth profile as defined at each node. The mantle portion of the profile is specified by...follows the contour of the Moho (e.g., Hearn, 1984). The head wave assumption results in poor travel time prediction at far-regional distance (>~700 km
Traveling wave solutions for reaction-diffusion systems
DEFF Research Database (Denmark)
Pedersen, Michael; Lin, Zhigui; Tian, Canrong
2010-01-01
This paper is concerned with traveling waves of reaction–diffusion systems. The definition of coupled quasi-upper and quasi-lower solutions is introduced for systems with mixed quasimonotone functions, and the definition of ordered quasi-upper and quasi-lower solutions is also given for systems...... with quasimonotone nondecreasing functions. By the monotone iteration method, it is shown that if the system has a pair of coupled quasi-upper and quasi-lower solutions, then there exists at least a traveling wave solution. Moreover, if the system has a pair of ordered quasi-upper and quasi-lower solutions......, then there exists at least a traveling wavefront. As an application we consider the delayed system of a mutualistic model....
The classification of the single travelling wave solutions to the ...
Indian Academy of Sciences (India)
2016-09-21
Sep 21, 2016 ... For example,. Fan used Liu's method [11,12] to invest the generalized equal width equation and Pochhammer–Chree equa- tion, and she obtained all the possible travelling wave solutions including elliptic functions and hyperelliptic functions. In this paper, we consider the variant Boussinesq equations [13].
New travelling wave solutions for nonlinear stochastic evolution ...
Indian Academy of Sciences (India)
The nonlinear stochastic evolution equations have a wide range of applications in physics, chemistry, biology, economics and finance from various points of view. In this paper, the (′/)-expansion method is implemented for obtaining new travelling wave solutions of the nonlinear (2 + 1)-dimensional stochastic ...
Traveling-wave deceleration of SrF molecules
van den Berg, J.E.; Chirayath Mathavan, Sreekanth; Meinema, C.; Nauta, Janko; Nijbroek, T. H.; Jungmann, K.; Bethlem, H. L.; Hoekstra, S.
We report on the production, deceleration and detection of a SrF molecular beam. The molecules are captured from a supersonic expansion and are decelerated in the X-2 Sigma(+) (v = 0, N = 1) state. We demonstrate the removal of up to 40% of the kinetic energy with a 2 m long modular traveling-wave
A generic travelling wave solution in dissipative laser cavity
Indian Academy of Sciences (India)
Using perturbation method, the stability region is identified. ... A split-step Fourier method and pseudospectral method have been used for direct numerical solution of the CGLE and travelling wave profiles identical to the analytical profiles ... School of Physics and Materials Science, Thapar University, Patiala 147 004, India ...
The classification of single travelling wave solutions to the Camassa ...
Indian Academy of Sciences (India)
Introduction. Classifications of single travelling wave solutions to some nonlinear differential equations have been obtained extensively by the complete discrimination system for polynomial method proposed by Liu [1–7]. Furthermore, Wang and Li [8] used Liu's method and factorization method proposed by Cornejo-Pérez ...
K-Band Traveling-Wave Tube Amplifier
Force, Dale A.; Simons, Rainee N.; Peterson, Todd T.; Spitsen, Paul C.
2010-01-01
A new space-qualified, high-power, high-efficiency, K-band traveling-wave tube amplifier (TWTA) will provide high-rate, high-capacity, direct-to-Earth communications for science data and video gathered by the Lunar Reconnaissance Orbiter (LRO) during its mission. Several technological advances were responsible for the successful demonstration of the K-band TWTA.
Exact travelling wave solutions for some important nonlinear ...
Indian Academy of Sciences (India)
The two-dimensional nonlinear physical models and coupled nonlinear systems such as Maccari equations, Higgs equations and Schrödinger–KdV equations have been widely applied in many branches of physics. So, finding exact travelling wave solutions of such equations are very helpful in the theories and numerical ...
Investigating The Travelling Wave Solution For an SIR Endemic ...
African Journals Online (AJOL)
This paper presents the travelling wave solution for an SIR endemic disease model with no disease related death when the spatial spread of the susceptible is not negligible. In this case the disease is driven by both the susceptible and the infective classes. The population is open since the disease is habitually prevalent in ...
Traveling wave solutions of the BBM-like equations
Energy Technology Data Exchange (ETDEWEB)
Kuru, S [Department of Physics, Faculty of Science, Ankara University 06100 Ankara (Turkey)], E-mail: kuru@science.ankara.edu.tr
2009-09-18
In this work, we apply the factorization technique to the Benjamin-Bona-Mahony-like equations, B(m, n), in order to get traveling wave solutions. We will focus on some special cases for which m {ne} n, and we will obtain these solutions in terms of the special forms of Weierstrass functions.
Thick barrier buckets using the SPS travelling wave structures
Bohl, T; Shaposhnikova, Elena; CERN. Geneva. SPS and LEP Division
2000-01-01
The barrier bucket technique has many interesting applications and has been tested in different laboratories around the world. In all these cases; specially designed, very broad band (Q = 1) cavities were installed in the ring. We used the existing travelling wave cavities in the SPS to create multi-period barrier buckets and hold the beam.
Numerical continuation of travelling waves and pulses in neural fields
Meijer, Hil Gaétan Ellart; Coombes, Stephen
2013-01-01
We study travelling waves and pulses in neural fields. Neural fields are a macroscopic description of the activity of brain tissue, which mathematically are formulated as integro-differential equations. While linear and weakly nonlinear analysis can describe instabilities and small amplitude
Symbolic computation and abundant travelling wave solutions to ...
Indian Academy of Sciences (India)
2016-12-09
Dec 9, 2016 ... 2Department of Mathematics, National University of Computer and Emerging Sciences, Lahore, Pakistan. 3Centre for Undergraduate Studies, ... in physical science and engineering. Many of these solutions are new and ... scientists to find exact travelling wave solutions of. NLEE, i.e. the inverse scattering ...
Travelling wave solutions for (N+ 1)-dimensional nonlinear evolution ...
Indian Academy of Sciences (India)
... Public Lectures · Lecture Workshops · Refresher Courses · Symposia. Home; Journals; Pramana – Journal of Physics; Volume 75; Issue 4. Travelling wave solutions for ( + 1)-dimensional nonlinear evolution equations. Jonu Lee Rathinasamy Sakthivel. Research Articles Volume 75 Issue 4 October 2010 pp 565-578 ...
Travelling wave solutions to nonlinear physical models by means of ...
Indian Academy of Sciences (India)
This paper presents the ﬁrst integral method to carry out the integration of nonlinear partial differential equations in terms of travelling wave solutions. For illustration, three important equations of mathematical physics are analytically investigated. Through the established ﬁrst integrals, exact solutions are successfully ...
2013-11-30
Travel time reliability information includes static data about traffic speeds or trip times that capture historic variations from day to day, and it can help individuals understand the level of variation in traffic. Unlike real-time travel time infor...
Dispersal, landscape and travelling waves in cyclic vole populations.
Berthier, Karine; Piry, Sylvain; Cosson, Jean-François; Giraudoux, Patrick; Foltête, Jean-Christophe; Defaut, Régis; Truchetet, Denis; Lambin, Xavier
2014-01-01
Travelling waves (TW) are among the most striking ecological phenomena emerging in oscillating populations. Despite much theory, understanding how real-world TW arise remains a challenge for ecology. Herein, we analyse 16-year time series of cyclic vole populations collected at 314 localities covering 2500 km² in France. We found evidence for a linear front TW spreading at a speed of 7.4 km year(-1) along a north-west/south-east direction and radiating away from a major landscape discontinuity as predicted by recent theory. The spatial signature of vole dispersal was assessed using genetic data collected at 14 localities. Both data sets were handled using similar autocorrelation approaches. Our results revealed a remarkable congruence of the spatial extent and direction of anisotropy of both demographic and genetic structures. Our results constitute the first empirical evidence that effective dispersal is limited in the direction of TW while most of the individual exchanges occur along the wave front. © 2013 John Wiley & Sons Ltd/CNRS.
Computing the center of mass for traveling alpha waves in the human brain.
Manjarrez, Elías; Vázquez, Montserrat; Flores, Amira
2007-05-11
The phenomenon of traveling waves of the brain is an intriguing area of research, and its mechanisms and neurobiological bases have been unknown since the 1950s. The present study offers a new method to compute traveling alpha waves using the center of mass algorithm. Electroencephalographic alpha waves are oscillations with a characteristic frequency range and reactivity to closed eyes. Several lines of evidence derived from qualitative observations suggest that the alpha waves represent a spreading wave process with specific trajectories in the human brain. We found that during a certain alpha wave peak recorded with 30 electrodes the trajectory starts and ends in distinct regions of the brain, mostly frontal-occipital, frontal-frontal, or occipital-frontal, but the position of the trajectory at the time in which the maximal positivity of the alpha wave occurs has a definite position near the central regions. Thus we observed that the trajectory always crossed around the central zones, traveling from one region to another region of the brain. A similar trajectory pattern was observed for different alpha wave peaks in one alpha burst, and in different subjects, with a mean velocity of 2.1+/-0.29 m/s. We found that all our results were clear and reproducible in all of the subjects. To our knowledge, the present method documents the first explicit description of a spreading wave process with a singular pattern in the human brain in terms of the center of mass algorithm.
Self-motion perception compresses time experienced in return travel.
Seno, Takeharu; Ito, Hiroyuki; Shoji, Sunaga
2011-01-01
It is often anecdotally reported that time experienced in return travel (back to the start point) seems shorter than time spent in outward travel (travel to a new destination). Here, we report the first experimental results showing that return travel time is experienced as shorter than the actual time. This discrepancy is induced by the existence of self-motion perception.
5 CFR 551.422 - Time spent traveling.
2010-01-01
... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Time spent traveling. 551.422 Section 551... Activities § 551.422 Time spent traveling. (a) Time spent traveling shall be considered hours of work if: (1... who is permitted to use an alternative mode of transportation, or an employee who travels at a time...
Static trapping of polar molecules in a traveling wave decelerator.
Quintero-Pérez, Marina; Jansen, Paul; Wall, Thomas E; van den Berg, Joost E; Hoekstra, Steven; Bethlem, Hendrick L
2013-03-29
We present experiments on decelerating and trapping ammonia molecules using a combination of a Stark decelerator and a traveling wave decelerator. In the traveling wave decelerator, a moving potential is created by a series of ring-shaped electrodes to which oscillating high voltages (HV) are applied. By lowering the frequency of the applied voltages, the molecules confined in the moving trap are decelerated and brought to a standstill. As the molecules are confined in a true 3D well, this kind of deceleration has practically no losses, resulting in a great improvement on the usual Stark deceleration techniques. The necessary voltages are generated by amplifying the output of an arbitrary wave generator using fast HV amplifiers, giving us great control over the trapped molecules. We illustrate this by experiments in which we adiabatically cool trapped NH3 and ND3 molecules and resonantly excite their motion.
Small energy traveling waves for the Euler-Korteweg system
Audiard, Corentin
2017-09-01
We investigate the existence and properties of traveling waves for the Euler-Korteweg system with general capillarity and pressure. Our main result is the existence in dimension two of waves with arbitrarily small energies. They are obtained as minimizers of a modified energy with fixed momentum. The proof builds upon various ideas developed for the Gross-Pitaevskii equation (and more generally nonlinear Schrödinger equations with non zero limit at infinity). Even in the Schrödinger case, the fact that we work with the hydrodynamical variables and a general pressure law both brings new difficulties and some simplifications. Independently, in dimension one we prove that the criterion for the linear instability of traveling waves from Benzoni-Gavage (2013 Differ. Integral Equ. 26 439-85) actually implies nonlinear instability.
Empirical Study of Travel Time Estimation and Reliability
Li, Ruimin; Chai, Huajun; Tang, Jin
2013-01-01
This paper explores the travel time distribution of different types of urban roads, the link and path average travel time, and variance estimation methods by analyzing the large-scale travel time dataset detected from automatic number plate readers installed throughout Beijing. The results show that the best-fitting travel time distribution for different road links in 15 min time intervals differs for different traffic congestion levels. The average travel time for all links on all days can b...
The origin of traveling waves in an emperor penguin huddle
Gerum, R. C.; Fabry, B.; Metzner, C.; Beaulieu, M.; Ancel, A.; Zitterbart, D. P.
2013-12-01
Emperor penguins breed during the Antarctic winter and have to endure temperatures as low as -50 °C and wind speeds of up to 200 km h-1. To conserve energy, they form densely packed huddles with a triangular lattice structure. Video recordings from previous studies revealed coordinated movements in regular wave-like patterns within these huddles. It is thought that these waves are triggered by individual penguins that locally disturb the huddle structure, and that the traveling wave serves to remove the lattice defects and restore order. The mechanisms that govern wave propagation are currently unknown, however. Moreover, it is unknown if the waves are always triggered by the same penguin in a huddle. Here, we present a model in which the observed wave patterns emerge from simple rules involving only the interactions between directly neighboring individuals, similar to the interaction rules found in other jammed systems, e.g. between cars in a traffic jam. Our model predicts that a traveling wave can be triggered by a forward step of any individual penguin located within a densely packed huddle. This prediction is confirmed by optical flow velocimetry of the video recordings of emperor penguins in their natural habitat.
Zhang, Dongsheng; Wang, Shiyu; Xiu, Jie
2017-11-01
Elastic wave quality determines the operating performance of traveling wave ultrasonic motor (TWUM). The time-variant circumferential force from the shrink of piezoelectric ceramic is one of the factors that distort the elastic wave. The distorted waveshape deviates from the ideal standard sinusoidal fashion and affects the contact mechanics and driving performance. An analytical dynamic model of ring ultrasonic motor is developed. Based on this model, the piezoelectric parametric effects on the wave distortion and contact mechanics are examined. Multi-scale method is employed to obtain unstable regions and distorted wave response. The unstable region is verified by Floquét theory. Since the waveshape affects the contact mechanism, a contact model involving the distorted waveshape and normal stiffness of the contact layer is established. The contact model is solved by numerical calculation. The results verify that the deformation of the contact layer deviates from sinusoidal waveshape and the pressure distribution is changed, which influences the output characteristics directly. The surface speed within the contact region is averaged such that the rotor speed decreases for lower torque and increases for larger torque. The effects from different parametric strengths, excitation frequencies and pre-pressures on pressure distribution and torque-speed relation are compared. Copyright © 2017 Elsevier B.V. All rights reserved.
Analysis of Modal Travel Time Variability Due to Mesoscale Ocean Structure
National Research Council Canada - National Science Library
Smith, Amy
1997-01-01
.... First, for an open ocean environment away from strong boundary currents, the effects of randomly phased linear baroclinic Rossby waves on acoustic travel time are shown to produce a variable overall...
Snakes mimic earthworms: propulsion using rectilinear travelling waves
Marvi, Hamidreza; Bridges, Jacob; Hu, David L.
2013-01-01
In rectilinear locomotion, snakes propel themselves using unidirectional travelling waves of muscular contraction, in a style similar to earthworms. In this combined experimental and theoretical study, we film rectilinear locomotion of three species of snakes, including red-tailed boa constrictors, Dumeril's boas and Gaboon vipers. The kinematics of a snake's extension–contraction travelling wave are characterized by wave frequency, amplitude and speed. We find wave frequency increases with increasing body size, an opposite trend than that for legged animals. We predict body speed with 73–97% accuracy using a mathematical model of a one-dimensional n-linked crawler that uses friction as the dominant propulsive force. We apply our model to show snakes have optimal wave frequencies: higher values increase Froude number causing the snake to slip; smaller values decrease thrust and so body speed. Other choices of kinematic variables, such as wave amplitude, are suboptimal and appear to be limited by anatomical constraints. Our model also shows that local body lifting increases a snake's speed by 31 per cent, demonstrating that rectilinear locomotion benefits from vertical motion similar to walking. PMID:23635494
Absolute Instability near Band Edges in a Traveling Wave Tube
Antoulinakis, Foivos; Lau, Y. Y.; Wong, Patrick; Jassem, Abhijit
2017-10-01
We re-examine the beam mode and its interaction with the circuit mode near the lower and upper band edges in a traveling wave tube. We find that an absolute instability may arise, according to the Briggs-Bers criterion, if the beam current is sufficiently high, even if the beam mode intersects with the circuit mode at a point in the (w, k) =(frequency, wavenumber) plane with a positive group velocity. This finding differs from the previous works for the lower band edge, and points to the vulnerability to absolute instabilities at both the upper and lower band edges of a TWT. When the threshold current is exceeded, the Green's function, at a fixed position, exponentiates in time as t**(1/3) initially, but as (wi*t) at later time, where wi is the imaginary part of w in the unstable pole-pinch root. Work supported by AFOSR Awards Nos. FA9550-14-1-0309, FA9550-15-1-0097, DARPA contract HR0011-16-C-0080 with Leidos, Inc., and L-3 Communications.
Exact traveling wave solutions for system of nonlinear evolution equations.
Khan, Kamruzzaman; Akbar, M Ali; Arnous, Ahmed H
2016-01-01
In this work, recently deduced generalized Kudryashov method is applied to the variant Boussinesq equations, and the (2 + 1)-dimensional breaking soliton equations. As a result a range of qualitative explicit exact traveling wave solutions are deduced for these equations, which motivates us to develop, in the near future, a new approach to obtain unsteady solutions of autonomous nonlinear evolution equations those arise in mathematical physics and engineering fields. It is uncomplicated to extend this method to higher-order nonlinear evolution equations in mathematical physics. And it should be possible to apply the same method to nonlinear evolution equations having more general forms of nonlinearities by utilizing the traveling wave hypothesis.
On the structure of spectra of travelling waves
Directory of Open Access Journals (Sweden)
Péter Simon
2003-10-01
Full Text Available The linear stability of the travelling wave solutions of a general reaction-diffusion system is investigated. The spectrum of the corresponding second order differential operator $L$ is studied. The problem is reduced to an asymptotically autonomous first order linear system. The relation between the spectrum of $L$ and the corresponding first order system is dealt with in detail. The first order system is investigated using exponential dichotomies. A self-contained short presentation is shown for the study of the spectrum, with elementary proofs. An algorithm is given for the determination of the exact position of the essential spectrum. The Evans function method for determining the isolated eigenvalues of $L$ is also presented. The theory is illustrated by three examples: a single travelling wave equation, a three variable combustion model and the generalized KdV equation.
Global Existence of Solutions to the Fowler Equation in a Neighbourhood of Travelling-Waves
Directory of Open Access Journals (Sweden)
Afaf Bouharguane
2011-01-01
Full Text Available We investigate a fractional diffusion/anti-diffusion equation proposed by Andrew C. Fowler to describe the dynamics of sand dunes sheared by a fluid flow. In this paper, we prove the global-in-time well-posedness in the neighbourhood of travelling-waves solutions of the Fowler equation.
Traveling wave deflector design for femtosecond streak camera
Pei, Chengquan; Wu, Shengli; Luo, Duan; Wen, Wenlong; Xu, Junkai; Tian, Jinshou; Zhang, Minrui; Chen, Pin; Chen, Jianzhong; Liu, Rong
2017-05-01
In this paper, a traveling wave deflection deflector (TWD) with a slow-wave property induced by a microstrip transmission line is proposed for femtosecond streak cameras. The pass width and dispersion properties were simulated. In addition, the dynamic temporal resolution of the femtosecond camera was simulated by CST software. The results showed that with the proposed TWD a femtosecond streak camera can achieve a dynamic temporal resolution of less than 600 fs. Experiments were done to test the femtosecond streak camera, and an 800 fs dynamic temporal resolution was obtained. Guidance is provided for optimizing a femtosecond streak camera to obtain higher temporal resolution.
Traveling wave deflector design for femtosecond streak camera
Energy Technology Data Exchange (ETDEWEB)
Pei, Chengquan; Wu, Shengli [Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xi' an Jiaotong University, Xi’an 710049 (China); Luo, Duan [Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Wen, Wenlong [Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China); Xu, Junkai [Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Tian, Jinshou, E-mail: tianjs@opt.ac.cn [Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China); Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006 (China); Zhang, Minrui; Chen, Pin [Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Chen, Jianzhong [Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xi' an Jiaotong University, Xi’an 710049 (China); Liu, Rong [Xi' an Technological University, Xi' an 710021 (China)
2017-05-21
In this paper, a traveling wave deflection deflector (TWD) with a slow-wave property induced by a microstrip transmission line is proposed for femtosecond streak cameras. The pass width and dispersion properties were simulated. In addition, the dynamic temporal resolution of the femtosecond camera was simulated by CST software. The results showed that with the proposed TWD a femtosecond streak camera can achieve a dynamic temporal resolution of less than 600 fs. Experiments were done to test the femtosecond streak camera, and an 800 fs dynamic temporal resolution was obtained. Guidance is provided for optimizing a femtosecond streak camera to obtain higher temporal resolution.
Analytical approximation and numerical simulations for periodic travelling water waves.
Kalimeris, Konstantinos
2018-01-28
We present recent analytical and numerical results for two-dimensional periodic travelling water waves with constant vorticity. The analytical approach is based on novel asymptotic expansions. We obtain numerical results in two different ways: the first is based on the solution of a constrained optimization problem, and the second is realized as a numerical continuation algorithm. Both methods are applied on some examples of non-constant vorticity.This article is part of the theme issue 'Nonlinear water waves'. © 2017 The Author(s).
Consciousness minus retrospective mental time travel.
Dias, Alvaro Machado; Britto, Luiz R G
2010-09-01
Abstract In this paper we apply the concept of mental time travel to introduce the basic features of full-blown conscious experiences (encapsulation in mental models and recollection). We discuss the perspective that Lamme's 'Level 3' experiences can be considered as part of the scope of phenomenological consciousness, in relation to which we emphasize the necessity to consider the different degrees of consciousness and how a particular situation compares to the conscious experiences present in resting states of wakefulness.
Development of a thermoacoustic travelling-wave refrigerator
Pierens, Matthieu; Thermeau, Jean-Pierre; Le Pollès, Thierry; Duthil, Patxi
2012-01-01
International audience; Thermoacoustic phenomenon deals with the interaction between heat and sound. This physical field is studied from the later seventies to develop heat machines for energy conversion. A thermoacoustic refrigerator uses a mechanical work, induced by an intense acoustic wave, to pump heat from a cold source and rejecting heat to an ambient source. In the framework of the European project called THATEA focusing on energy conversion efficiencies, a thermoacoustic travelling-w...
New exact travelling wave solutions of some complex nonlinear equations
Bekir, Ahmet
2009-04-01
In this paper, we establish exact solutions for complex nonlinear equations. The tanh-coth and the sine-cosine methods are used to construct exact periodic and soliton solutions of these equations. Many new families of exact travelling wave solutions of the coupled Higgs and Maccari equations are successfully obtained. These solutions may be important of significance for the explanation of some practical physical problems.
Back or to the future? Preferences of time travelers
National Research Council Canada - National Science Library
Florence Ettlin; Ralph Hertwig
2012-01-01
...., Gladiator, The Time Machine). Despite the ubiquity of time travel as a theme in cultural expression, the factors that underlie people's preferences concerning the direction of time travel have gone unexplored...
Polymers for Traveling Wave Ion Mobility Spectrometry Calibration
Duez, Quentin; Chirot, Fabien; Liénard, Romain; Josse, Thomas; Choi, ChangMin; Coulembier, Olivier; Dugourd, Philippe; Cornil, Jérôme; Gerbaux, Pascal; De Winter, Julien
2017-07-01
One of the main issues when using traveling wave ion mobility spectrometry (TWIMS) for the determination of collisional cross-section (CCS) concerns the need for a robust calibration procedure built from referent ions of known CCS. Here, we implement synthetic polymer ions as CCS calibrants in positive ion mode. Based on their intrinsic polydispersities, polymers offer in a single sample the opportunity to generate, upon electrospray ionization, numerous ions covering a broad mass range and a large CCS window for different charge states at a time. In addition, the key advantage of polymer ions as CCS calibrants lies in the robustness of their gas-phase structure with respect to the instrumental conditions, making them less prone to collisional-induced unfolding (CIU) than protein ions. In this paper, we present a CCS calibration procedure using sodium cationized polylactide and polyethylene glycol, PLA and PEG, as calibrants with reference CCS determined on a home-made drift tube. Our calibration procedure is further validated by testing the polymer calibration to determine CCS of numerous different ions for which CCS are reported in the literature. [Figure not available: see fulltext.
Travel Time to Hospital for Childbirth: Comparing Calculated Versus Reported Travel Times in France.
Pilkington, Hugo; Prunet, Caroline; Blondel, Béatrice; Charreire, Hélène; Combier, Evelyne; Le Vaillant, Marc; Amat-Roze, Jeanne-Marie; Zeitlin, Jennifer
2018-01-01
Objectives Timely access to health care is critical in obstetrics. Yet obtaining reliable estimates of travel times to hospital for childbirth poses methodological challenges. We compared two measures of travel time, self-reported and calculated, to assess concordance and to identify determinants of long travel time to hospital for childbirth. Methods Data came from the 2010 French National Perinatal Survey, a national representative sample of births (N = 14 681). We compared both travel time measures by maternal, maternity unit and geographic characteristics in rural, peri-urban and urban areas. Logistic regression models were used to study factors associated with reported and calculated times ≥30 min. Cohen's kappa coefficients were also calculated to estimate the agreement between reported and calculated times according to women's characteristics. Results In urban areas, the proportion of women with travel times ≥30 min was higher when reported rather than calculated times were used (11.0 vs. 3.6%). Longer reported times were associated with non-French nationality [adjusted odds ratio (aOR) 1.3 (95% CI 1.0-1.7)] and inadequate prenatal care [aOR 1.5 (95% CI 1.2-2.0)], but not for calculated times. Concordance between the two measures was higher in peri-urban and rural areas (52.4 vs. 52.3% for rural areas). Delivery in a specialised level 2 or 3 maternity unit was a principal determinant of long reported and measured times in peri-urban and rural areas. Conclusions for Practice The level of agreement between reported and calculated times varies according to geographic context. Poor measurement of travel time in urban areas may mask problems in accessibility.
Photo-induced travelling waves in condensed Langmuir monolayers
Energy Technology Data Exchange (ETDEWEB)
Tabe, Y [Yokoyama Nano-Structured Liquid Crystal Project, ERATO, Japan Science and Technology Corporation, 5-9-9 Tokodai, Tsukuba, Ibaraki 300-2635, Japan (Japan); Yamamoto, T [Yokoyama Nano-Structured Liquid Crystal Project, ERATO, Japan Science and Technology Corporation, 5-9-9 Tokodai, Tsukuba, Ibaraki 300-2635, Japan (Japan); Yokoyama, H [Yokoyama Nano-Structured Liquid Crystal Project, ERATO, Japan Science and Technology Corporation, 5-9-9 Tokodai, Tsukuba, Ibaraki 300-2635, Japan (Japan)
2003-06-01
We report the detailed properties of photo-induced travelling waves in liquid crystalline Langmuir monolayers composed of azobenzene derivatives. When the monolayer, in which the constituent rodlike molecules are coherently tilted from the layer normal, is weakly illuminated to undergo the trans-cis photo-isomerization, spatio-temporal periodic oscillations of the molecular azimuth begin over the entire excited area and propagate as a two-dimensional orientational wave. The wave formation takes place only when the film is formed at an asymmetric interface with broken up-down symmetry and when the chromophores are continuously excited near the long-wavelength edge of absorption to induce repeated photo-isomerizations between the trans and cis forms. Under proper illumination conditions, Langmuir monolayers composed of a wide variety of azobenzene derivatives have been confirmed to exhibit similar travelling waves with velocity proportional to the excitation power irrespective of the degree of amphiphilicity. The dynamics can be qualitatively explained by the modified reaction-diffusion model proposed by Reigada, Sagues and Mikhailov.
Contact frequency, travel time, and travel costs for patients with rheumatoid arthritis
DEFF Research Database (Denmark)
Sørensen, Jan; Linde, Louise; Hetland, Merete Lund
2014-01-01
Objectives. To investigate travel time, and travel cost related to contacts with health care providers for patients with rheumatoid arthritis (RA) during a three-month period. Methods. Patient-reported travel time and travel cost were obtained from 2847 patients with RA. Eleven outpatient clinics...... across Denmark recruited patients to the study. Data collected included frequency, travel time and travel costs for contacts at rheumatology outpatient clinics, other outpatient clinics, general practitioners, privately practicing medical specialists, inpatient hospitals and accident and emergency...... and 13 € on travelling per contact, corresponding to a total of 4.6 hours and 56 € during the 3-month period. There was great variation in patient travel time and costs, but no statistically significant associations were found with clinical and sociodemographic characteristics. Conclusion. The results...
Incorporating travel time reliability into the Highway Capacity Manual.
2014-01-01
This final report documents the activities performed during SHRP 2 Reliability Project L08: Incorporating Travel Time Reliability into the Highway Capacity Manual. It serves as a supplement to the proposed chapters for incorporating travel time relia...
Travel Time Data Collection Field Tests - Lessons Learned
1996-01-01
This report summarizes the process and lessons learned from the Standardized Travel Time Surveys and Field Test project. The field tests of travel time data collection were conducted in Boston, Seattle, and Lexington in 1993. The methodologies tested...
Analysis of travel time reliability on Indiana interstates.
2009-09-15
Travel-time reliability is a key performance measure in any transportation system. It is a : measure of quality of travel time experienced by transportation system users and reflects the efficiency : of the transportation system to serve citizens, bu...
Sensor distribution design of travel time tomography in explosion.
Guo, Yali; Han, Yan; Wang, Liming; Liu, Linmao
2014-07-15
Optimal sensor distribution in explosion testing is important in saving test costs and improving experiment efficiency. Aiming at travel time tomography in an explosion, an optimizing method in sensor distribution is proposed to improve the inversion stability. The influence factors of inversion stability are analyzed and the evaluating function on optimizing sensor distribution is proposed. This paper presents a sub-region and multi-scale cell partition method, according to the characteristics of a shock wave in an explosion. An adaptive escaping particle swarm optimization algorithm is employed to achieve the optimal sensor distribution. The experimental results demonstrate that optimal sensor distribution has improved both indexes and inversion stability.
Dynamics and bifurcations of travelling wave solutions of R(m, n ...
Indian Academy of Sciences (India)
Under different regions of para- metric spaces, various sufficient conditions to guarantee the existence of the above waves are given. Moreover, some explicit exact parametric representations of travelling wave solutions are listed. Keywords. R(m, n) equations; solitary wave; periodic wave; breaking wave; solitary cusp wave ...
Image Fusion for Travel Time Tomography Inversion
Directory of Open Access Journals (Sweden)
Liu Linan
2015-09-01
Full Text Available The travel time tomography technology had achieved wide application, the hinge of tomography was inversion algorithm, the ray path tracing technology had a great impact on the inversion results. In order to improve the SNR of inversion image, comprehensive utilization of inversion results with different ray tracing can be used. We presented an imaging fusion method based on improved Wilkinson iteration method. Firstly, the shortest path method and the linear travel time interpolation were used for forward calculation; then combined the improved Wilkinson iteration method with super relaxation precondition method to reduce the condition number of matrix and accelerate iterative speed, the precise integration method was used to solve the inverse matrix more precisely in tomography inversion process; finally, use wavelet transform for image fusion, obtain the final image. Therefore, the ill-conditioned linear equations were changed into iterative normal system through two times of treatment and using images with different forward algorithms for image fusion, it reduced the influence effect of measurement error on imaging. Simulation results showed that, this method can eliminate the artifacts in images effectively, it had extensive practical significance.
Travel-Time Maps: Linear Cartograms with Fixed Vertex Locations
Buchin, Kevin; Goethem, Arthur van; Hoffmann, Michael; van Kreveld, Marc; Speckmann, Bettina; Michael, P.
2014-01-01
Linear cartograms visualize travel times between locations, usually by deforming the underlying map such that Euclidean distance corresponds to travel time. We introduce an alternative model, where the map and the locations remain fixed, but edges are drawn as sinusoid curves. Now the travel time
Macroscopic travel time reliability diagrams for freeway networks
Tu, H.; Li, H.; Van Lint, J.W.C.; Knoop, V.L.; Sun, L.
2013-01-01
Travel time reliability is considered to be one of the key indicators of transport system performance. Knowledge of the mechanisms of travel time unreliability enables the derivation of explanatory models with which travel time reliability can be predicted and utilized in traffic management.
Urban travel time reliability at different traffic conditions
Zheng, Fangfang; Li, Jie; van Zuylen, H.J.; Liu, Xiaobo; Yang, Hongtai
2017-01-01
The decision making of travelers for route choice and departure time choice depends on the expected travel time and its reliability. A common understanding of reliability is that it is related to several statistical properties of the travel time distribution, especially to the standard deviation
Body-wave traveltime and amplitude shifts from asymptotic travelling wave coupling
Pollitz, F.
2006-01-01
We explore the sensitivity of finite-frequency body-wave traveltimes and amplitudes to perturbations in 3-D seismic velocity structure relative to a spherically symmetric model. Using the approach of coupled travelling wave theory, we consider the effect of a structural perturbation on an isolated portion of the seismogram. By convolving the spectrum of the differential seismogram with the spectrum of a narrow window taper, and using a Taylor's series expansion for wavenumber as a function of frequency on a mode dispersion branch, we derive semi-analytic expressions for the sensitivity kernels. Far-field effects of wave interactions with the free surface or internal discontinuities are implicitly included, as are wave conversions upon scattering. The kernels may be computed rapidly for the purpose of structural inversions. We give examples of traveltime sensitivity kernels for regional wave propagation at 1 Hz. For the direct SV wave in a simple crustal velocity model, they are generally complicated because of interfering waves generated by interactions with the free surface and the Mohorovic??ic?? discontinuity. A large part of the interference effects may be eliminated by restricting the travelling wave basis set to those waves within a certain range of horizontal phase velocity. ?? Journal compilation ?? 2006 RAS.
Experimental results using active control of traveling wave power flow
Miller, David W.; Hall, Steven R.
1991-01-01
Active structural control experiments conducted on a 24-ft pinned-free beam derived feedback compensators on the basis of a traveling-wave approach. A compensator is thus obtained which eliminates resonant behavior by absorbing all impinging power. A causal solution is derived for this noncausal compensator which mimics its behavior in a given frequency range, using the Wiener-Hopf. This optimal Wiener-Hopf compensator's structure-damping performance is found to exceed any obtainable by means of rate feedback. Performance limitations encompassed the discovery of frequencies above which the sensor and actuator were no longer dual and an inadvertent coupling of the control hardware to unmodeled structure torsion modes.
Chen, T.; Clayton, R. W.
2011-12-01
The 3D P- and S-wave attenuation and velocity structure of the Cocos subduction zone in Mexico is imaged using seismic events recorded by the MASE (100 seismometers running across central Mexico, 2005-2007) and VEOX (47 seismometers running across southern Mexico, 2007-2009) arrays, supplemented by stations from the National Seismic Network in Mexico (SSN). Using a spectral-decay method, we obtain a path attenuation operator t* for each seismogram in the frequency band 1 to 30 Hz, depending on the signal quality. These measurements are then inverted for 3D spatial variations in attenuation. Direct body-wave arrivals from local events are used for 3D velocity inversion. Deeper velocity structures along MASE and VEOX arrays are obtained by including teleseismic events. Inversion results show low attenuation associated with the Cocos slab, and show the slab dip angle increases from central to southern Mexico. High attenuation is imaged in the mantle wedge and the crust above. The highest attenuation is found in the crust near the active Los Tuxtlas volcanic field, probably related to the dehydration and melting process. Low velocity is observed in the mantle wedge and the crust above from velocity inversion. The Cocos slab is traced as high-velocity structure. The Cocos slab dips down to about 500 km in central Mexico along MASE array as shown by previous study (Perez-Campos, GRL, 2008). In southern Mexico along VEOX line, no clear continuous Cocos slab is observed deeper than about 150 km, which is also found by receiver function studies (Kim et al., in press; Perez-Campos et al., in press). There are some indications that the Cocos slab in southern Mexico near the Isthmus of Tehuantepec is truncated by some high-velocity structure dipping south from the Gulf of Mexico. This anomalous south-dipping structure is also seen in receiver function images, and may be related to the collision between the Yucatan Block and Mexico in the Miocene (Kim et al., in press).
New exact travelling wave solutions of bidirectional wave equations
Indian Academy of Sciences (India)
where a, b, c and d are real constants. Here x represents the distance along the channel, t is the elapsed time, the variable v(x, t) is the dimensionless deviation of the water surface from its undisturbed position and u(x, t) is the dimensionless horizontal velocity. This set of equations is used as a model equation for the ...
A hybrid travel time prediction framework for planned motorway roadworks
Calvert, S.C.; Lint, J.W.C. van; Hoogendoorn, S.P.
2010-01-01
In this paper we propose a hybrid motorway travel time prediction framework aimed at providing pre-trip travel information in case of roadworks. The framework utilises a first order macroscopic traffic flow model to predict the consequences in travel time of changes in both traffic demand and
Predicting travel time variability for cost-benefit analysis
Peer, S.; Koopmans, C.; Verhoef, E.T.
2010-01-01
Unreliable travel times cause substantial costs to travelers. Nevertheless, they are not taken into account in many cost-benefit-analyses (CBA), or only in very rough ways. This paper aims at providing simple rules on how variability can be predicted, based on travel time data from Dutch highways.
5 CFR 610.123 - Travel on official time.
2010-01-01
... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Travel on official time. 610.123 Section... DUTY Weekly and Daily Scheduling of Work Work Schedules § 610.123 Travel on official time. Insofar as practicable travel during nonduty hours shall not be required of an employee. When it is essential that this...
Establishing monitoring programs for travel time reliability. [supporting datasets
2014-01-01
The objective of this project was to develop system designs for programs to monitor travel time reliability and to prepare a guidebook that practitioners and others can use to design, build, operate, and maintain such systems. Generally, such travel ...
Travelling waves in models of neural tissue: from localised structures to periodic waves
Meijer, Hil Gaétan Ellart; Coombes, Stephen
2014-01-01
We consider travelling waves (fronts, pulses and periodics) in spatially extended one dimensional neural field models. We demonstrate for an excitatory field with linear adaptation that, in addition to an expected stable pulse solution, a stable anti-pulse can exist. Varying the adaptation strength
Lateralization of travelling wave response in the hearing organ of bushcrickets.
Palghat Udayashankar, Arun; Kössl, Manfred; Nowotny, Manuela
2014-01-01
Travelling waves are the physical basis of frequency discrimination in many vertebrate and invertebrate taxa, including mammals, birds, and some insects. In bushcrickets (Tettigoniidae), the crista acustica is the hearing organ that has been shown to use sound-induced travelling waves. Up to now, data on mechanical characteristics of sound-induced travelling waves were only available along the longitudinal (proximal-distal) direction. In this study, we use laser Doppler vibrometry to investigate in-vivo radial (anterior-posterior) features of travelling waves in the tropical bushcricket Mecopoda elongata. Our results demonstrate that the maximum of sound-induced travelling wave amplitude response is always shifted towards the anterior part of the crista acustica. This lateralization of the travelling wave response induces a tilt in the motion of the crista acustica, which presumably optimizes sensory transduction by exerting a shear motion on the sensory cilia in this hearing organ.
Lateralization of travelling wave response in the hearing organ of bushcrickets.
Directory of Open Access Journals (Sweden)
Arun Palghat Udayashankar
Full Text Available Travelling waves are the physical basis of frequency discrimination in many vertebrate and invertebrate taxa, including mammals, birds, and some insects. In bushcrickets (Tettigoniidae, the crista acustica is the hearing organ that has been shown to use sound-induced travelling waves. Up to now, data on mechanical characteristics of sound-induced travelling waves were only available along the longitudinal (proximal-distal direction. In this study, we use laser Doppler vibrometry to investigate in-vivo radial (anterior-posterior features of travelling waves in the tropical bushcricket Mecopoda elongata. Our results demonstrate that the maximum of sound-induced travelling wave amplitude response is always shifted towards the anterior part of the crista acustica. This lateralization of the travelling wave response induces a tilt in the motion of the crista acustica, which presumably optimizes sensory transduction by exerting a shear motion on the sensory cilia in this hearing organ.
Traveling waves in a spring-block chain sliding down a slope
Morales, J. E.; James, G.; Tonnelier, A.
2017-07-01
Traveling waves are studied in a spring slider-block model. We explicitly construct front waves (kinks) for a piecewise-linear spinodal friction force. Pulse waves are obtained as the matching of two traveling fronts with identical speeds. Explicit formulas are obtained for the wavespeed and the wave form in the anticontinuum limit. The link with localized waves in a Burridge-Knopoff model of an earthquake fault is briefly discussed.
Traveling wave resonant ring for electron cloud studies
Iriso, U; Laurent, J M; Mostacci, A
2004-01-01
Within the framework of the CERN program on electron cloud effects in accelerators, a coaxial multipacting test stand was built. In order to simulate bunched beam, the test stand is subjected to short rf pulses. The field strength in a traveling wave mode is sufficient to trigger multipacting in "as received" surfaces, but not in chambers treated to reduce the secondary emission yield. Thus a number of upgrades in the bench setup have been pursued, mainly in two directions. The first one is a general reduction in mismatching (i.e., electrical losses) amongst the different parts of the setup. Secondly, instead of dumping the pulsed power into a load, it is recirculated by means of a broadband working regime resonant ring. This ring required the design of a directional coupler with up to 1 kV dc isolation, very low transmission losses, and a four octave bandwidth. This paper reports on the steps required to build this traveling wave resonant ring (improvements on the chamber and implementation of the coupler) a...
A Traveling Wave Resonant Ring for Electron Cloud Studies
Iriso, U; Laurent, J M; Mostacci, A
2004-01-01
Within the framework of the CERN program on electron cloud effects in accelerators, a coaxial multipacting test stand was built. In order to simulate bunched beam, the test stand is subjected to short RF pulses. The field strength in a traveling wave mode is sufficient to trigger multipacting in “as received” surfaces, but not in chambers treated to reduce the secondary emission yield. Thus a number of upgrades in the bench set-up have been pursued, mainly in two directions. The first one is a general reduction in mismatching (i.e. electrical losses) amongst the different parts of the setup. Secondly, instead of dumping the pulsed power into a load, it is recirculated by means of a broadband working regime resonant ring. This ring required the design of a directional coupler with up to 1 kV DC isolation, very low transmission losses and a four octave bandwidth. This paper reports on the steps required to build this traveling wave resonant ring (improvements on the chamber and implementation of the coupler...
Electronic Power Conditioner for Ku-band Travelling Wave Tube
Kowstubha, Palle; Krishnaveni, K.; Ramesh Reddy, K.
2017-04-01
A highly sophisticated regulated power supply is known as electronic power conditioner (EPC) is required to energise travelling wave tubes (TWTs), which are used as RF signal amplifiers in satellite payloads. The assembly consisting of TWT and EPC together is known as travelling wave tube amplifier (TWTA). EPC is used to provide isolated and conditioned voltage rails with tight regulation to various electrodes of TWT and makes its RF performance independent of solar bus variations which are caused due to varying conditions of eclipse and sunlit. The payload mass and their power consumption is mainly due to the existence of TWTAs that represent about 35 % of total mass and about 70-90 % (based on the type of satellite application) of overall dc power consumption. This situation ensures a continuous improvement in the design of TWTAs and their associated EPCs to realize more efficient and light products. Critical technologies involved in EPCs are design and configuration, closed loop regulation, component and material selection, energy limiting of high voltage (HV) outputs and potting of HV card etc. This work addresses some of these critical technologies evolved in realizing and testing the state of art of EPC and it focuses on the design of HV supply with a HV and high power capability, up to 6 kV and 170 WRF, respectively required for a space TWTA. Finally, an experimental prototype of EPC with a dc power of 320 W provides different voltages required by Ku-band TWT in open loop configuration.
Validation of travel times to hospital estimated by GIS
Directory of Open Access Journals (Sweden)
Sauerzapf Violet
2006-09-01
Full Text Available Abstract Background An increasing number of studies use GIS estimates of car travel times to health services, without presenting any evidence that the estimates are representative of real travel times. This investigation compared GIS estimates of travel times with the actual times reported by a sample of 475 cancer patients who had travelled by car to attend clinics at eight hospitals in the North of England. Methods Car travel times were estimated by GIS using the shortest road route between home address and hospital and average speed assumptions. These estimates were compared with reported journey times and straight line distances using graphical, correlation and regression techniques. Results There was a moderately strong association between reported times and estimated travel times (r = 0.856. Reported travel times were similarly related to straight line distances. Altogether, 50% of travel time estimates were within five minutes of the time reported by respondents, 77% were within ten minutes and 90% were within fifteen minutes. The distribution of over- and under-estimates was symmetrical, but estimated times tended to be longer than reported times with increasing distance from hospital. Almost all respondents rounded their travel time to the nearest five or ten minutes. The reason for many cases of reported journey times exceeding the estimated times was confirmed by respondents' comments as traffic congestion. Conclusion GIS estimates of car travel times were moderately close approximations to reported times. GIS travel time estimates may be superior to reported travel times for modelling purposes because reported times contain errors and can reflect unusual circumstances. Comparison with reported times did not suggest that estimated times were a more sensitive measure than straight line distance.
Alexander, David M; Trengove, Chris; van Leeuwen, Cees
2015-11-01
An assumption nearly all researchers in cognitive neuroscience tacitly adhere to is that of space-time separability. Historically, it forms the basis of Donders' difference method, and to date, it underwrites all difference imaging and trial-averaging of cortical activity, including the customary techniques for analyzing fMRI and EEG/MEG data. We describe the assumption and how it licenses common methods in cognitive neuroscience; in particular, we show how it plays out in signal differencing and averaging, and how it misleads us into seeing the brain as a set of static activity sources. In fact, rather than being static, the domains of cortical activity change from moment to moment: Recent research has suggested the importance of traveling waves of activation in the cortex. Traveling waves have been described at a range of different spatial scales in the cortex; they explain a large proportion of the variance in phase measurements of EEG, MEG and ECoG, and are important for understanding cortical function. Critically, traveling waves are not space-time separable. Their prominence suggests that the correct frame of reference for analyzing cortical activity is the dynamical trajectory of the system, rather than the time and space coordinates of measurements. We illustrate what the failure of space-time separability implies for cortical activation, and what consequences this should have for cognitive neuroscience.
A rod type linear ultrasonic motor utilizing longitudinal traveling waves: proof of concept
Wang, Liang; Wielert, Tim; Twiefel, Jens; Jin, Jiamei; Wallaschek, Jörg
2017-08-01
This paper proposes a non-resonant linear ultrasonic motor utilizing longitudinal traveling waves. The longitudinal traveling waves in the rod type stator are generated by inducing longitudinal vibrations at one end of the waveguide and eliminating reflections at the opposite end by a passive damper. Considering the Poisson’s effect, the stator surface points move on elliptic trajectories and the slider is driven forward by friction. In contrast to many other flexural traveling wave linear ultrasonic motors, the driving direction of the proposed motor is identical to the wave propagation direction. The feasibility of the motor concept is demonstrated theoretically and experimentally. First, the design and operation principle of the motor are presented in detail. Then, the stator is modeled utilizing the transfer matrix method and verified by experimental studies. In addition, experimental parameter studies are carried out to identify the motor characteristics. Finally, the performance of the proposed motor is investigated. Overall, the results indicate very dynamic drive characteristics. The motor prototype achieves a maximum mean velocity of 115 mm s-1 and a maximum load of 0.25 N. Thereby, the start-up and shutdown times from the maximum speed are lower than 5 ms.
First-order variance of travel time in nonstationary formations
National Research Council Canada - National Science Library
Olaf A. Cirpka; Wolfgang Nowak
2004-01-01
... is the variance of travel time, i.e., the time it takes for a solute particle to be transported from the release point to an observation plane [ Shapiro and Cvetkovic , 1988 ; Dagan et al. , 1992 ]. The travel time is also given by the first temporal moment of a concentration breakthrough curve normalized by its zeroth moment [ Harvey and Gorelick , 1995 ]. Together with the variance of lateral displacement, the travel time variance has been used in solute‐flux approaches to macrod...
Kim, Hyomin; Clauer, C. Robert; Gerrard, Andrew J.; Engebretson, Mark J.; Hartinger, Michael D.; Lessard, Marc R.; Matzka, Jürgen; Sibeck, David G.; Singer, Howard J.; Stolle, Claudia; Weimer, Daniel R.; Xu, Zhonghua
2017-07-01
We report on simultaneous observations of electromagnetic ion cyclotron (EMIC) waves associated with traveling convection vortex (TCV) events caused by transient solar wind dynamic pressure (Pd) impulse events. The Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft located near the magnetopause observed radial fluctuations of the magnetopause, and the GOES spacecraft measured sudden compressions of the magnetosphere in response to sudden increases in Pd. During the transient events, EMIC waves were observed by interhemispheric conjugate ground-based magnetometer arrays as well as the GOES spacecraft. The spectral structures of the waves appear to be well correlated with the fluctuating motion of the magnetopause, showing compression-associated wave generation. In addition, the wave features are remarkably similar in conjugate hemispheres in terms of bandwidth, quasiperiodic wave power modulation, and polarization. Proton precipitation was also observed by the DMSP spacecraft during the wave events, from which the wave source region is estimated to be 72°-74° in magnetic latitude, consistent with the TCV center. The confluence of space-borne and ground instruments including the interhemispheric, high-latitude, fluxgate/induction coil magnetometer array allows us to constrain the EMIC source region while also confirming the relationship between EMIC waves and the TCV current system.
Sheehan, Anne F.; Solomon, Sean C.
1991-01-01
Measurements were carried out for SS-S differential travel time residuals for nearly 500 paths crossing the northern Mid-Atlantic Ridge, assuming that the residuals are dominated by contributions from the upper mantle near the surface bounce point of the reflected phase SS. Results indicate that the SS-S travel time residuals decrease linearly with square root of age, to an age of 80-100 Ma, in general agreement with the plate cooling model. A joint inversion was formulated of travel time residuals and geoid and bathymetric anomalies for lateral variation in the upper mantle temperature and composition. The preferred inversion solutions were found to have variations in upper mantle temperature along the Mid-Atlantic Ridge of about 100 K. It was calculated that, for a constant bulk composition, such a temperature variation would produce about a 7-km variation in crustal thickness, larger than is generally observed.
Accuracy of Travel Time Estimation using Bluetooth Technology
DEFF Research Database (Denmark)
Araghi, Bahar Namaki; Skoven Pedersen, Kristian; Tørholm Christensen, Lars
2012-01-01
Short-term travel time information plays a critical role in Advanced Traffic Information Systems (ATIS) and Advanced Traffic Management Systems (ATMS). In this context, the need for accurate and reliable travel time information sources is becoming increasingly important. Bluetooth Technology (BT......) has been used as a relatively new cost-effective source of travel time estimation. However, due to low sampling rate of BT compared to other sensor technologies, existence of outliers may significantly affect the accuracy and reliability of the travel time estimates obtained using BT. In this study......, the concept of outliers and corresponding impacts on travel time accuracy are discussed. Four different estimators named Min-BT, Max-BT, Med-BT and Avg-BT with different outlier detection logic are presented in this paper. These methods are used to estimate travel times using a BT derived dataset. In order...
Three-Dimensional Simulation of Traveling-Wave Tube Cold-Test Characteristics Using MAFIA
Kory, Carol L.; Wilson, Jeffrey D.
1995-01-01
The three-dimensional simulation code MAFIA was used to compute the cold-test parameters - frequency-phase dispersion, beam on-axis interaction impedance, and attenuation - for two types of traveling-wave tube (TWT) slow-wave circuits. The potential for this electromagnetic computer modeling code to reduce the time and cost of TWT development is demonstrated by the high degree of accuracy achieved in calculating these parameters. Generalized input files were developed for ferruled coupled-cavity and TunneLadder slow-wave circuits. These files make it easy to model circuits of arbitrary dimensions. The utility of these files was tested by applying each to a specific TWT slow-wave circuit and comparing the results with experimental data. Excellent agreement was obtained.
Travelling Wave Structure of an SPS RF Cavity
CERN PhotoLab
1974-01-01
The RF cavities for acceleration of particles in the SPS have a travelling-wave structure. They operate at a fixed frequency of 200 MHz (h = 4620). With a quality factor of Q = 100, the bandwidth covers the small frequency swing for the acceleration of protons from as low as 10 GeV to the top energy of 450 GeV. Later on, for the acceleration of ions, with a larger frequency swing, turn-to-turn phase jumps did the trick. Two cavities, each consisting of 5 tank sections, were installed in long straight section 3. Each cavity is driven by a power amplifier of 750 kW CW (1 MW pulsed). Another 2 cavities were added later on. See also 7411033 and 7802190.
Harmonic Generation in a Traveling-Wave Tube
Wong, Patrick; Zhang, Peng; Lau, Y. Y.; Greening, Geoffrey; Gilgenbach, Ronald; Chernin, David; Simon, David; Hoff, Brad
2016-10-01
Crowding of electron orbits in a traveling-wave tube (TWT) may lead to significant harmonic contents in the beam current, even in the linear regime. Here, we consider a wideband TWT that exhibits gain at the second harmonic. We analytically formulate equations governing the evolution of the generation of second harmonic, including axial variations of the Pierce parameters. The second harmonic output is phase-controlled by the input signal which consists only of a fundamental frequency. Several test cases are performed and compared with simulation using the CHRISTINE code. Reasonable agreement between theory and simulation is found. Work supported by AFOSR FA9550-15-1-0097, ONR N00014-16-1-2353, and L-3 Communications Electron Device Division.
Time Travel: Separating Science Fact from Science Fiction.
Al-Khalili, Jim
2003-01-01
Suggests that the subject of time travel is the best topic to introduce ideas behind some of the most beautiful and fundamental theories about the nature of space and time. Explains the distinction between the two directions of time travel and how relativity theory forced the abandonment of Newtonian notions about the nature of time. (Author/KHR)
Vehicle Travel Time Predication based on Multiple Kernel Regression
Wenjing Xu
2014-01-01
With the rapid development of transportation and logistics economy, the vehicle travel time prediction and planning become an important topic in logistics. Travel time prediction, which is indispensible for traffic guidance, has become a key issue for researchers in this field. At present, the prediction of travel time is mainly short term prediction, and the predication methods include artificial neural network, Kaman filter and support vector regression (SVR) method etc. However, these algo...
Macroscopic travel time reliability diagrams for freeway networks
Tu, H.; Li, H.; Van Lint, J.W.C.; Knoop, V.L.; Sun, L.
2013-01-01
Travel time reliability is considered to be one of the key indicators of transport system performance. Knowledge of the mechanisms of travel time unreliability enables the derivation of explanatory models with which travel time reliability can be predicted and utilized in traffic management. Inspired by the macroscopic fundamental diagram (MFD), describing the relationship between production (average flow completing the trips) and vehicle accumulation (average density) in a traffic network, t...
Quantifying travel time variability in transportation networks.
2010-03-01
Nonrecurring congestion creates significant delay on freeways in urban areas, lending importance : to the study of facility reliability. In locations where traffic detectors record and archive data, : approximate probability distributions for travel ...
Tonotopically arranged traveling waves in the miniature hearing organ of bushcrickets.
Directory of Open Access Journals (Sweden)
Arun Palghat Udayashankar
Full Text Available Place based frequency discrimination (tonotopy is a fundamental property of the coiled mammalian cochlea. Sound vibrations mechanically conducted to the hearing organ manifest themselves into slow moving waves that travel along the length of the organ, also referred to as traveling waves. These traveling waves form the basis of the tonotopic frequency representation in the inner ear of mammals. However, so far, due to the secure housing of the inner ear, these waves only could be measured partially over small accessible regions of the inner ear in a living animal. Here, we demonstrate the existence of tonotopically ordered traveling waves covering most of the length of a miniature hearing organ in the leg of bushcrickets in vivo using laser Doppler vibrometery. The organ is only 1 mm long and its geometry allowed us to investigate almost the entire length with a wide range of stimuli (6 to 60 kHz. The tonotopic location of the traveling wave peak was exponentially related to stimulus frequency. The traveling wave propagated along the hearing organ from the distal (high frequency to the proximal (low frequency part of the leg, which is opposite to the propagation direction of incoming sound waves. In addition, we observed a non-linear compression of the velocity response to varying sound pressure levels. The waves are based on the delicate micromechanics of cellular structures different to those of mammals. Hence place based frequency discrimination by traveling waves is a physical phenomenon that presumably evolved in mammals and bushcrickets independently.
Travelling wave solutions of the generalized Benjamin-Bona-Mahony equation
Energy Technology Data Exchange (ETDEWEB)
Estevez, P.G. [Departamento de Fisica Fundamental, Area de Fisica Teorica, Universidad de Salamanca, 37008 Salamanca (Spain); Kuru, S. [Departamento de Fisica Teorica, Atomica y Optica, Universidad de Valladolid, 47071 Valladolid (Spain); Department of Physics, Faculty of Science, Ankara University, 06100 Ankara (Turkey); Negro, J. [Departamento de Fisica Teorica, Atomica y Optica, Universidad de Valladolid, 47071 Valladolid (Spain)], E-mail: jnegro@fta.uva.es; Nieto, L.M. [Departamento de Fisica Teorica, Atomica y Optica, Universidad de Valladolid, 47071 Valladolid (Spain)
2009-05-30
A class of particular travelling wave solutions of the generalized Benjamin-Bona-Mahony equation is studied systematically using the factorization technique. Then, the general travelling wave solutions of Benjamin-Bona-Mahony equation, and of its modified version, are also recovered.
Dynamical behaviours and exact travelling wave solutions of ...
Indian Academy of Sciences (India)
2016-12-13
Dec 13, 2016 ... 2School of Mathematics and Statistics, Guizhou University of Finance and Economics, Guiyang,. Guizhou 550025, People's Republic of China. ∗. Corresponding author. ..... derivative of the wave function jumps down (or up) rapidly in a very short time interval. Lemma 2. [Existence of finite time interval of ...
Online Learning Solutions for Freeway Travel Time Prediction
Van Lint, J.W.C.
2008-01-01
Providing travel time information to travelers on available route alternatives in traffic networks is widely believed to yield positive effects on individual drive behavior and (route/departure time) choice behavior, as well as on collective traffic operations in terms of, for example, overall time
Variability of Travel Times on New Jersey Highways
2011-06-01
This report presents the results of a link and path travel time study conducted on selected New Jersey (NJ) highways to produce estimates of the corresponding variability of travel time (VTT) by departure time of the day and days of the week. The tra...
The cost of travel time variability: three measures with properties
DEFF Research Database (Denmark)
Engelson, Leonid; Fosgerau, Mogens
2016-01-01
This paper explores the relationships between three types of measures of the cost of travel time variability: measures based on scheduling preferences and implicit departure time choice, Bernoulli type measures based on a univariate function of travel time, and mean-dispersion measures. We...
2014-01-01
The second Strategic Highway Research Program (SHRP 2) Reliability program aims to improve trip time reliability by reducing the frequency and effects of events that cause travel times to fluctuate unpredictably. Congestion caused by unreliable, or n...
Analyses of the temperature field of traveling-wave rotary ultrasonic motors.
Lu, Xiaolong; Hu, Junhui; Zhao, Chunsheng
2011-12-01
In this paper, the transient and steady-state temperature field of a traveling-wave rotary ultrasonic motor is analyzed by the finite element method, based on a theoretical model of power loss of this motor in rated operation. Using this model, the temperature field of this motor is calculated and the effects of the heat conductivity of friction material, motor size, ambient temperature, and pressure on the temperature field are estimated. The calculated temperature distribution and transient temperature change agree with the experimental results. The variation of heat conductivity of the friction material has little effect on the minimum temperature in the motor but this variation seriously affects the maximum temperature in the motor when the heat conductivity of the friction material is lower than 0.5 W/(m°C). Two indices are defined to express the non-uniformity of temperature field and how quickly the temperature field reaches its steady state for traveling-wave ultrasonic motors of different sizes. It is found that traveling-wave ultrasonic motors with different sizes have different nonuniformity of temperature field and take different amounts of time to reach thermal steady state. The maximum temperature rise is lower when the ambient temperature is higher; the maximum temperature increases as the vacuum degree increases and it is not affected by the vacuum degree when the vacuum degree is too high (<10(-3) Pa).
Determination of Seismic Source Depths from Differential Travel Times
1975-06-30
MLm »Ei »• TT^C OF Btro*)* • »IMtOD COVCAfD £ Final Report N/A F08606-75-C-002S 13 •’•’JC»*«* fk tMfMT.faojCCT. T*m 1> HCFORT CAT...Identifica- tion of the depth phase is verified when the variations in the differential travel times are in agreement with the differential travel...when the variations in the differential travel times are in agreement with the differential travel time tables for the given source to station
Synchronization of chaotic modulated travelling waves in coupled rotating annuli
Castrejon-Pita, Alfonso A.; Read, Peter L.
2010-05-01
Synchronization is now well established as a phenomenon where coherent behaviour between two or more otherwise autonomous nonlinear systems subject to some degree of coupling is developed and maintained. Such behaviour has mostly been studied to date, however, in relatively low-dimensional discrete numerical systems or networks, and very simple laboratory experiments. But the possibility of similar kinds of behaviour in continuous or extended spatiotemporal systems has many potential practical implications, especially in geophysics. Recent investigations have found that some atmospheric teleconnections of oscillatory climate phenomena can be better understood and analysed via chaos synchronization theory. The use of well-controlled laboratory analogues may therefore have an important role to play in the study of natural systems that can only be observed and for which controlled and repeatable experiments are impossible. The laboratory experiment that we use in our research is the thermally driven, rotating baroclinic annulus. The combined effect of differential heating in the horizontal direction and uniform background rotation leads to the formation of a zonally-symmetric jet flow around the annulus that may become unstable to travelling baroclinic waves and exhibit a wide range of flow regimes including steady amplitude travelling waves, periodic amplitude modulated waves and a range of more complex spatiotemporal flows, culminating in forms of geostrophic turbulence. Motivated in part by studies of quasi-periodic and chaotic ‘index cycles' in previous laboratory experiments using the baroclinic annulus, we have investigated synchronization effects in a pair of baroclinically unstable flows in both periodic and chaotic regimes, thermally coupled via their (zonally symmetric) boundary conditions. When the coupling strength and the de-tuning were systematically varied, the experiment showed clear signs of phase synchronization. By increasing or decreasing the
The Role of Perspective in Mental Time Travel.
Ansuini, Caterina; Cavallo, Andrea; Pia, Lorenzo; Becchio, Cristina
2016-01-01
Recent years have seen accumulating evidence for the proposition that people process time by mapping it onto a linear spatial representation and automatically "project" themselves on an imagined mental time line. Here, we ask whether people can adopt the temporal perspective of another person when travelling through time. To elucidate similarities and differences between time travelling from one's own perspective or from the perspective of another person, we asked participants to mentally project themselves or someone else (i.e., a coexperimenter) to different time points. Three basic properties of mental time travel were manipulated: temporal location (i.e., where in time the travel originates: past, present, and future), motion direction (either backwards or forwards), and temporal duration (i.e., the distance to travel: one, three, or five years). We found that time travels originating in the present lasted longer in the self- than in the other-perspective. Moreover, for self-perspective, but not for other-perspective, time was differently scaled depending on where in time the travel originated. In contrast, when considering the direction and the duration of time travelling, no dissimilarities between the self- and the other-perspective emerged. These results suggest that self- and other-projection, despite some differences, share important similarities in structure.
Observation of the traveling component of an x-ray standing wave field
Energy Technology Data Exchange (ETDEWEB)
Lai, B.; Yun, W.B.; Chrzas, J.; Viccaro, P.J.
1994-03-01
We present the first systematic experimental study of the traveling component of a standing wave field, formed by interference of an incident beam with its specularly reflected part from a plane interface. The traveling component of the standing wave field propagates parallel to the interface and its existence manifests the dynamical aspect of the standing wave field. In our experiment, a multilayer structure was used to aid in the observation of the traveling wave component. The data measured are explained using a finite thickness diffraction grating model.
Traveling-wave tubes and backward-wave oscillators with weak external magnetic fields.
Abu-elfadl, T M; Nusinovich, G S; Shkvarunets, A G; Carmel, Y; Antonsen, T M; Goebel, D
2001-06-01
Recent development of plasma-assisted slow-wave oscillators [Goebel et al. IEEE Trans. Plasma Sci. 22, 547 (1994)], microwave sources that operate without guiding magnetic fields, has stimulated interest in the theoretical analysis of such tubes. In principle, in the absence of guiding magnetic fields, due to the space charge forces and the radial electric field of the wave, the electrons may propagate radially outward which increases electron coupling to the slow wave whose field is localized near the slow-wave structure (SWS). This increases the wave growth rate and efficiency, and hence allows one to shorten the interaction region. So the radial electron motion can be beneficial for operation if it does not lead to interception of electrons by the SWS. To avoid this interception a weak external magnetic field can be applied. The theory developed describes the effect of weak magnetic fields on the operation of traveling-wave tubes and backward-wave oscillators with electrons moving not only axially but also transversely. This theory allows one to estimate the magnetic field required for protecting the SWS from electron bombardment at different power levels. Theoretical predictions of the efficiency enhancement due to the weak magnetic field are confirmed in experiments.
Collection and analysis of 2013-2014 travel time data.
2017-07-04
This report documents the findings of Planning Study 27, Collection and Analysis of 2013-2014 Travel Time Data, which is a continuation of Planning Study 24, Analysis of Historical Travel Time Data. The main scope is to analyze newly acquired link-re...
The (′/-Expansion Method for Abundant Traveling Wave Solutions of Caudrey-Dodd-Gibbon Equation
Directory of Open Access Journals (Sweden)
Hasibun Naher
2011-01-01
Full Text Available We construct the traveling wave solutions of the fifth-order Caudrey-Dodd-Gibbon (CDG equation by the (/-expansion method. Abundant traveling wave solutions with arbitrary parameters are successfully obtained by this method and the wave solutions are expressed in terms of the hyperbolic, the trigonometric, and the rational functions. It is shown that the (/-expansion method is a powerful and concise mathematical tool for solving nonlinear partial differential equations.
Wandering Tales: Evolutionary origins of mental time travel and language
Directory of Open Access Journals (Sweden)
Michael Charles Corballis
2013-07-01
Full Text Available A central component of mind wandering is mental time travel, the calling to mind of remembered past events and of imagined future ones. Mental time travel may also be critical to the evolution of language, which enables us to communicate about the nonpresent, sharing memories, plans, and ideas. Mental time travel is indexed in humans by hippocampal activity, and studies also suggest that the hippocampus in rats is active when the animals replay or pre play activity in a spatial environment, such as a maze. Mental time travel may have ancient origins, contrary to the view that it is unique to humans. Since mental time travel is also thought to underlie language, these findings suggest that language evolved gradually from pre-existing cognitive capacities, contrary to the view of Chomsky and others that language and symbolic thought emerged abruptly, in a single step, within the past 100,000 years.
Wandering tales: evolutionary origins of mental time travel and language.
Corballis, Michael C
2013-01-01
A central component of mind wandering is mental time travel, the calling to mind of remembered past events and of imagined future ones. Mental time travel may also be critical to the evolution of language, which enables us to communicate about the non-present, sharing memories, plans, and ideas. Mental time travel is indexed in humans by hippocampal activity, and studies also suggest that the hippocampus in rats is active when the animals replay or pre play activity in a spatial environment, such as a maze. Mental time travel may have ancient origins, contrary to the view that it is unique to humans. Since mental time travel is also thought to underlie language, these findings suggest that language evolved gradually from pre-existing cognitive capacities, contrary to the view of Chomsky and others that language and symbolic thought emerged abruptly, in a single step, within the past 100,000 years.
Mode choice endogeneity in value of travel time estimation
DEFF Research Database (Denmark)
Mabit, Stefan Lindhard; Fosgerau, Mogens
The current way to estimate value of travel time is to use a mode-specific sample and hence to estimate mode-specific value of travel times. This approach raises certain questions concerning how to generalise the values to a population. A problem would be if there is an uncontrolled sample...... selection mechanism. This is the case if there is correlation between mode choice and the value of travel time that is not controlled for by explanatory variables. What could confuse the estimated values is the difficulty to separate mode effects from user effect. An example would be the effect of income...... of travel time we use a stated choice dataset. These data include binary choice within mode for car and bus. The first approach is to use a probit model to model mode choice using instruments and then use this in the estimation of the value of travel time. The second approach is based on the use of a very...
Travel time data collection for measurement of advanced traveler information systems accuracy
2003-06-01
The objective of this white paper is to recommend an approach to measuring ATIS travel time accuracy so that ITS planners might have the data they need to make cost effective decisions regarding deployment of surveillance technologies to support ATIS...
Travelling Wave Magnetic Resonance Imaging at 3 Tesla
Vazquez, F; Marrufo, O; Rodriguez, A O
2013-01-01
Waveguides have been successfully used to generate magnetic resonance images at 7 T with whole-body systems. The bore limits the magnetic resonance signal transmitted because its specific cut-off frequency is greater than the majority of resonant frequencies. This restriction can be overcome by using a parallel-plate waveguide whose cut-off frequency is zero for the transversal electric modes and it can propagate any frequency. To investigate the potential benefits for whole-body imaging at 3 T, we compare numerical simulations at 1.5 T, 3 T, 7 T, and 9 T via the propagation of the parallel-plate waveguide principal mode filled with a cylindrical phantom and two surface coils. B1 mapping was computed to investigate the feasibility of this approach at 3T. The point spread function method was used to measure the imager performance for the traveling-wave magnetic resonance imaging experiment. Human leg images were acquired to experimentally validate this approach. The principal mode shows very little field magni...
Catchment residence and travel time distributions: The master equation
National Research Council Canada - National Science Library
Gianluca Botter; Enrico Bertuzzo; Andrea Rinaldo
2011-01-01
Travel/residence time pdf's are related objects with different physical meaning A Master Equation for the residence time pdf is derived and solved analytically We develop a mathematical framework...
Modeling, implementation, and validation of arterial travel time reliability : [summary].
2013-11-01
Travel time reliability (TTR) has been proposed as : a better measure of a facilitys performance than : a statistical measure like peak hour demand. TTR : is based on more information about average traffic : flows and longer time periods, thus inc...
How travellers’ schedule their trips under uncertain travel times
DEFF Research Database (Denmark)
Hjorth, Katrine
Travel times play an important role when people decide where, when and how much to travel. But travel times are not always predictable from the traveller’s point of view: They may vary from day to day due to demand fluctuations, weather conditions, accidents and other unforeseen events that cause...... road capacity to decrease. We refer to this uncertainty as travel time variability (TTV). TTV is likely to affect how travellers schedule their trips, since it affects their probability of arriving late at their destination. We would like to account for TTV in traffic models and cost-benefit analyses......, but in practice there are limits to the kinds of behaviour that can be accommodated in such applications. For that reason, we are not solely interested in explaining travellers’ behaviour, but also in whether this behaviour can be approximated by behavioural models that are simple enough to be applied in traffic...
[Travel times of patients to ambulatory care physicians in Germany].
Schang, Laura; Kopetsch, Thomas; Sundmacher, Leonie
2017-12-01
The time needed by patients to get to a doctor's office represents an important indicator of realised access to care. In Germany, findings on travel times are only available from surveys or for some regions. For the first time, this study examines nationwide and physician group-specific travel times in the ambulatory care sector in Germany and describes demographic, supply-side and spatial determinants of variations. Using a full review of patient consultations in the statutory health insurance system from 2009/2010 for 14 physician groups (approximately 518 million cases), case-related travel times by car between patients' places of residence and physician's practices were estimated at the municipal level. Physicians were reached in less than 30 min in 90.8% of cases for primary care physicians and up to 63% of cases for radiologists. Patients between 18 and under 30 years of age travel longer to get to the doctor than other age groups. The average travel time at the county level systematically differs between urban and rural planning areas. In the case of gynecologists, dermatologists and ophthalmologists, the average journey time decreases with increasing physician density at the county level, but remains approximately constant from a recognisable point of inflection. There is no association between primary care physician density and travel time at the district level. Spatial analyses show physician group-specific patterns of regional concentrations with an increased proportion of cases with very long travel times. Patients' travel times are influenced by supply- and demand-side determinants. Interactions between influential determinants should be analysed in depth to examine the extent to which the time travelled is an expression of regional under- or over-supply rather than an expression of patient preferences.
A Dynamic Travel Time Estimation Model Based on Connected Vehicles
Directory of Open Access Journals (Sweden)
Daxin Tian
2015-01-01
Full Text Available With advances in connected vehicle technology, dynamic vehicle route guidance models gradually become indispensable equipment for drivers. Traditional route guidance models are designed to direct a vehicle along the shortest path from the origin to the destination without considering the dynamic traffic information. In this paper a dynamic travel time estimation model is presented which can collect and distribute traffic data based on the connected vehicles. To estimate the real-time travel time more accurately, a road link dynamic dividing algorithm is proposed. The efficiency of the model is confirmed by simulations, and the experiment results prove the effectiveness of the travel time estimation method.
Energy Technology Data Exchange (ETDEWEB)
Sun Tao; Morgan, Hywel; Green, Nicolas G [Nanoscale Systems Integration Group, School of Electronics and Computer Science, University of Southampton, SO17 1BJ (United Kingdom)], E-mail: ts04r@ecs.soton.ac.uk, E-mail: ng2@ecs.soton.ac.uk
2008-12-01
In AC electrokinetics, the application of an AC electric field to a suspension of particles results in the manipulation and separation of the particles also the movement of the fluid. One application is dielectrophoresis (DEP). The second effect is travelling wave dielectrophoresis (twDEP). This paper presents the analytical solutions of the dielectrophoretic and travelling wave forces for the interdigitated electrode arrays energised with either a two- or four-phase signal, respectively. The torque that rotates the particle in the four-phase travelling wave arrays is also analytically solved.
Theoretical Modeling and Implementation of Traveling Wave Sensor Based on PCB Coils
Directory of Open Access Journals (Sweden)
Zewen Li
2015-01-01
Full Text Available Based on analyzing characteristics of Rogowski coil, a new type of PCB traveling wave sensor with simple structure, high linearity, and anti-interference ability is proposed. The sensor has fine physical structure, which can effectively resist external electromagnetic interference by anti-interference measurement. In addition, it can greatly improve mutual inductance based on simple combinations. Simulations show that the new PCB traveling wave sensor can validly extract and deliver traveling wave signal and therefore realize fault location and protection accurately.
Travelling waves above the canopy of aquatic vegetation
Lyubimov, D.; Lyubimova, T.; Baidina, D.
2012-04-01
When fluid moves over a saturated porous medium with high permeability and porosity, the flow partially involves the fluid in porous medium, however, because of the great resistance force there arises sharp drop of tangential velocity. This leads to the development of instability similar to the Kelvin-Helmholtz instability on discontinuity surface of the tangential velocities of homogeneous fluids. Analogy becomes even more complete if we take into account the deformability of porous medium under the influence of pressure changes. Intensive vortices above the canopy of aquatic vegetation can lead to the coherent oscillations of vegetation, such traveling waves are called monami [1]. In the present paper we investigate stability of steady flow over a saturated porous medium. The importance of this problem is related to the applications to the dynamics of pollutants in the bottom layer of vegetation: the accumulation at low flow and salvo emissions with increasing velocity. We consider a two-layer system consisting of a layer of a viscous incompressible fluid and porous layer saturated with the same fluid located underneath. The lower boundary of the system is assumed to be rigid, the upper boundary - free and non-deformable. Weak slope of the river is taken into account. The problem is solved within the framework of single approach in which a two-layer system is described by a single system of equations for saturated porous medium and the presence of two layers is modeled by introducing variable permeability and porosity, depending on vertical coordinate. The flow in a saturated porous medium is described by the Brinkman model. Solution of the problem for steady flow shows that the velocity profile has two inflection points, which leads to the instability. The neutral curves are obtained for different values of the ratio d of porous layer thickness to full thickness. It is found that the dependence of critical Reynolds number on d is non-monotonic and the wave
A Data Model for Determining Weather's Impact on Travel Time
DEFF Research Database (Denmark)
Andersen, Ove; Torp, Kristian
2016-01-01
Accurate estimating travel times in road networks is a complex task because travel times depends on factors such as the weather. In this paper, we present a generic model for integrating weather data with GPS data to improve the accuracy of the estimated travel times. First, we present a data model...... for storing and map-matching GPS data, and integrating this data with detailed weather data. The model is generic in the sense that it can be used anywhere GPS data and weather data is available. Next, we analyze the correlation between travel time and the weather classes dry, fog, rain, and snow along...... with winds impact on travel time. Using a data set of 1.6 billion GPS records collected from 10,560 vehicles, over a 5 year period from all of Denmark, we show that snow can increase the travel time up to 27% and strong headwind can increase the travel time with up to 19% (compared to dry calm weather...
Wireless data collection system for real-time arterial travel time estimates.
2011-03-01
This project pursued several objectives conducive to the implementation and testing of a Bluetooth (BT) based system to collect travel time data, including the deployment of a BT-based travel time data collection system to perform comprehensive testi...
Influence of queue propagation and dissipation on route travel times
DEFF Research Database (Denmark)
Raovic, Nevena
into account (Bliemer, 2008). Yperman (2007) indicates that there is a significant difference in queue-propagation and queue-dissipation between the LTM and DQM. This results in different route travel times, and can further affect route choice. In this paper, different approaches to represent queue propagation...... and dissipation through the CTM, LTM and DQM are studied. A simple network allows to show how these approaches influence route travel time. Furthermore, the possibility of changing the existing DQM is considered in order to more realistically represent queue propagation and dissipation, which would lead to more...... accurate route travel times....
Valuation of travel time savings for intercity travel: The Madrid-Barcelona corridor
DEFF Research Database (Denmark)
Roman, Concepcion; Carlos Martin, Juan; Espino, Raquel
2014-01-01
(which started to operate in February 2008) competes directly with one of the densest airline domestic markets in the world, and its introduction produced substantial improvements in level of service, achieving reductions in travel time of more than 50% over the conventional train. A specifically...... encountered in WTP with respect to other travellers. Finally, the obtaining of the elasticity values for the choice probabilities provided us valuable information to understand competition in this market. (C) 2014 Elsevier Ltd. All rights reserved....
Investigation of a traveling wave thermoacoustic engine in a looped-tube
Directory of Open Access Journals (Sweden)
Novotný Petr
2014-03-01
Full Text Available In the present paper, four configurations of a traveling wave thermoacoustic engine in a looped tube were investigated by means of theoretical calculations and experiments. The effect of natural heat convection on their functionality was observed. Acoustic intensity was measured using a dual two microphone method. The stack was designed with few times higher dimension of channels than thermal penetration depth, due to the stack should not be called regenerator. Pressure distribution in the resonator was measured, and a good agreement with theoretical calculations from DELTAEC has been demonstrated.
An Exact Hot-Tube Solution For Thin Tape Helix Traveling-Wave Tube
Wong, Patrick; Lau, Y. Y.; Gilgenbach, Ronald; Chernin, David; Hoff, Brad
2017-10-01
The exact hot-tube dispersion relation for a thin tape helix traveling-wave tube (TWT) is derived for the first time, based on its exact cold-tube solution. This is an attempt to provide a reliable determination of the Pierce parameters, in particular the ``AC space-charge'' parameter QC, for a realistic TWT. The determination of QC remains an outstanding issue. The numerical results from the exact formulation will be compared with other approximate models of TWT that were commonly used in the literature for QC. This work was supported by AFOSR Grant No. FA9550-15-1-0097.
Collective transport for active matter run-and-tumble disk systems on a traveling-wave substrate
Sándor, Cs.; Libál, A.; Reichhardt, C.; Reichhardt, C. J. Olson
2017-01-01
We examine numerically the transport of an assembly of active run-and-tumble disks interacting with a traveling-wave substrate. We show that as a function of substrate strength, wave speed, disk activity, and disk density, a variety of dynamical phases arise that are correlated with the structure and net flux of disks. We find that there is a sharp transition into a state in which the disks are only partially coupled to the substrate and form a phase-separated cluster state. This transition is associated with a drop in the net disk flux, and it can occur as a function of the substrate speed, maximum substrate force, disk run time, and disk density. Since variation of the disk activity parameters produces different disk drift rates for a fixed traveling-wave speed on the substrate, the system we consider could be used as an efficient method for active matter species separation. Within the cluster phase, we find that in some regimes the motion of the cluster center of mass is in the opposite direction to that of the traveling wave, while when the maximum substrate force is increased, the cluster drifts in the direction of the traveling wave. This suggests that swarming or clustering motion can serve as a method by which an active system can collectively move against an external drift.
Assessing the Predictability of Scheduled-Vehicle Travel Times
DEFF Research Database (Denmark)
Tiesyte, Dalia; Jensen, Christian Søndergaard
2009-01-01
One of the most desired and challenging services in collective transport systems is the real-time prediction of the near-future travel times of scheduled vehicles, especially public buses, thus improving the experience of the transportation users, who may be able to better schedule their travel......, and also enabling system operators to perform real-time monitoring. While travel-time prediction has been researched extensively during the past decade, the accuracies of existing techniques fall short of what is desired, and proposed mathematical prediction models are often not transferable to other...... systems because the properties of the travel-time-related data of vehicles are highly context-dependent, making the models difficult to fit. We propose a framework for evaluating various predictability types of the data independently of the model, and we also compare predictability analysis results...
Dividing to unveil protein microheterogeneities: traveling wave ion mobility study.
Halgand, F; Habchi, Johnny; Cravello, Laetitia; Martinho, Marlène; Guigliarelli, Bruno; Longhi, Sonia
2011-10-01
Overexpression of a protein in a foreign host is often the only route toward an exhaustive characterization, especially when purification from the natural source(s) is hardly achievable. The key issue in these studies relies on quality control of the purified recombinant protein to precisely determining its identity as well as any undesirable microheterogeneities. While standard proteomics approaches preclude unbiased search for modifications, the optional technique of top-down tandem mass spectrometry (MSMS) requires the use of highly accurate and highly resolved experiments to reveal subtle sequence modifications. In the present study, the top-down MSMS approach combined with traveling wave ion mobility (TWIM) separation was evaluated for its ability to achieve high sequence coverage and to reveal subtle microheterogeneities that were hitherto only accessible with Fourier-transform ion cyclotron resonance-MS instruments. The power of this approach is herein illustrated in an in-depth analysis of both the wild type and K496C variant of the recombinant X domain (XD; aa's 459-507) of the measles virus phosphoprotein expressed in Escherichia coli . Using top-down MSMS combined with TWIM, we show that XD samples occasionally exhibit a microheterogeneity that could not be anticipated from the nucleotide sequence of the encoding constructs and that likely reflects a genetic drift, neutral or not, occurring during expression. In addition, a 1-oxyl-2,2,5,5-tetramethyl-δ3-pyrroline-3-methyl methanethiosulfonate nitroxide probe that was grafted onto the K496C XD variant was shown to undergo oxidation and/or protonation in the electrospray ionization source, leading to artifactual mass increases.
Limiting Behavior of Travelling Waves for the Modified Degasperis-Procesi Equation
Directory of Open Access Journals (Sweden)
Jiuli Yin
2014-01-01
Full Text Available Using an improved qualitative method which combines characteristics of several methods, we classify all travelling wave solutions of the modified Degasperis-Procesi equation in specified regions of the parametric space. Besides some popular exotic solutions including peaked waves, and looped and cusped waves, this equation also admits some very particular waves, such as fractal-like waves, double stumpons, double kinked waves, and butterfly-like waves. The last three types of solutions have not been reported in the literature. Furthermore, we give the limiting behavior of all periodic solutions as the parameters trend to some special values.
Travelling-wave solutions bifurcating from relative periodic orbits in plane Poiseuille flow
Rawat, Subhandu; Cossu, Carlo; Rincon, François
2016-06-01
Travelling-wave solutions are shown to bifurcate from relative periodic orbits in plane Poiseuille flow at Re = 2000 in a saddle-node infinite-period bifurcation. These solutions consist in self-sustaining sinuous quasi-streamwise streaks and quasi-streamwise vortices located in the bulk of the flow. The lower branch travelling-wave solutions evolve into spanwise localized states when the spanwise size Lz of the domain in which they are computed is increased. On the contrary, the upper branch of travelling-wave solutions develops multiple streaks when Lz is increased. Upper-branch travelling-wave solutions can be continued into coherent solutions to the filtered equations used in large-eddy simulations where they represent turbulent coherent large-scale motions.
Lunin, Andrei; Grudiev, Alexej
2011-01-01
Analytical solutions are derived for transient and steady state gradient distributions in the travelling wave accelerating structures with arbitrary variation of parameters over the structure length. The results of both the unloaded and beam loaded cases are presented.
Traveling Wave Solutions of ZK-BBM Equation Sine-Cosine Method
Directory of Open Access Journals (Sweden)
Sadaf Bibi
2014-03-01
Full Text Available Travelling wave solutions are obtained by using a relatively new technique which is called sine-cosine method for ZK-BBM equations. Solution procedure and obtained results re-confirm the efficiency of the proposed scheme.
Traveling Waves for Nonlinear Schrödinger Equations with Nonzero Conditions at Infinity
Chiron, David; Mariş, Mihai
2017-10-01
We prove the existence of nontrivial finite energy traveling waves for a large class of nonlinear Schrödinger equations with nonzero conditions at infinity (includindg the Gross-Pitaevskii and the so-called "cubic-quintic" equations) in space dimension { N ≥ 2}. We show that minimization of the energy at fixed momentum can be used whenever the associated nonlinear potential is nonnegative and it gives a set of orbitally stable traveling waves, while minimization of the action at constant kinetic energy can be used in all cases. We also explore the relationship between the families of traveling waves obtained by different methods and we prove a sharp nonexistence result for traveling waves with small energy.
Development of gyrotron traveling-wave tubes at IAP and GYCOM
Samsonov, S. V.; Denisov, G. G.; Gachev, I. G.; Bogdashov, A. A.; Mishakin, S. V.; Manuilov, V. N.; Belousov, V. I.; Sobolev, D. I.; Sokolov, E. V.; Soluyanova, E. A.; Tai, E. M.
2017-08-01
A brief review of research activity on gyrotron traveling-wave tube amplifiers (gyro-TWTs) with helically corrugated waveguides developing by the Institute of Applied Physics and GYCOM (Nizhny Novgorod, Russia) will be presented.
Yasuda, Shugo
2015-01-01
A Monte Carlo simulation for the chemotactic bacteria is developed on the basis of the kinetic modeling, i.e., the Boltzmann transport equation, and applied to the one-dimensional traveling population wave in a micro channel.In this method, the Monte Carlo method, which calculates the run-and-tumble motions of bacteria, is coupled with a finite volume method to solve the macroscopic transport of the chemical cues in the field. The simulation method can successfully reproduce the traveling population wave of bacteria which was observed experimentally. The microscopic dynamics of bacteria, e.g., the velocity autocorrelation function and velocity distribution function of bacteria, are also investigated. It is found that the bacteria which form the traveling population wave create quasi-periodic motions as well as a migratory movement along with the traveling population wave. Simulations are also performed with changing the sensitivity and modulation parameters in the response function of bacteria. It is found th...
Travel Time Information Service Utilising Mobile Phone Tracking
Directory of Open Access Journals (Sweden)
Caj Holm
2004-07-01
Full Text Available This paper discusses the suitability of mobile phone positioningdata for travel time information. The Finnish NationalRoad Administration Finnra has carried out a study on thesubject (1 and managed pilot installations on two road sections(6 in order to determine the feasibility of mobile phonetracking for traffic monitoring and management purposes. Accordingto the study and the pilots, the mobile phone positioningcan provide useful link monitoring data, i. e. the travel timeand speed. Mobile phone tracking was found to be a very promisingtool for implementing travel time information service todrivers.
Measurement and evaluation of transit travel time reliability
2011-01-01
Transportation system customers need consistency in their daily travel times to enable them to plan their daily : activities, whether that is a commuter on their way to work, a company setting up delivery schedules for justintime : manufacturin...
Modeling, implementation, and validation of arterial travel time reliability.
2013-11-01
Previous research funded by Florida Department of Transportation (FDOT) developed a method for estimating : travel time reliability for arterials. This method was not initially implemented or validated using field data. This : project evaluated and r...
Impact of data source on travel time reliability assessment.
2014-08-01
Travel time reliability measures are becoming an increasingly important input to the mobility and : congestion management studies. In the case of Maryland State Highway Administration, reliability : measures are key elements in the agencys Annual ...
Bluetooth-based travel time/speed measuring systems development.
2010-06-01
Agencies in the Houston region have traditionally used toll tag readers to provide travel times on : freeways and High Occupancy Vehicle (HOV) lanes, but these systems require large amounts of costly and : physically invasive infrastructure. Bluetoot...
Estimating spatial travel times using automatic vehicle identification data
2001-01-01
Prepared ca. 2001. The paper describes an algorithm that was developed for estimating reliable and accurate average roadway link travel times using Automatic Vehicle Identification (AVI) data. The algorithm presented is unique in two aspects. First, ...
Application of travel time information for traffic management.
2012-03-01
This report summarizes findings and implementations of probe vehicle data collection based on Bluetooth MAC address matching : technology. Probe vehicle travel time data are studied in the following field deployment case studies: analysis of traffic ...
Alvarez, Roberto; van Hecke, Martin; van Saarloos, Wim
1996-01-01
In many pattern forming systems that exhibit traveling waves, sources and sinks occur which separate patches of oppositely traveling waves. We show that simple qualitative features of their dynamics can be compared to predictions from coupled amplitude equations. In heated wire convection experiments, we find a discrepancy between the observed multiplicity of sources and theoretical predictions. The expression for the observed motion of sinks is incompatible with any amplitude equation descri...
Lienert, Matthias; Petrat, Sören; Tumulka, Roderich
2017-08-01
In non-relativistic quantum mechanics of N particles in three spatial dimensions, the wave function ψ( q 1, …, q N , t) is a function of 3N position coordinates and one time coordinate. It is an obvious idea that in a relativistic setting, such functions should be replaced by ϕ((t 1, q 1), …, (tN, q N )), a function of N space-time points called a multi-time wave function because it involves N time variables. Its evolution is determined by N Schrödinger equations, one for each time variable; to ensure that simultaneous solutions to these N equations exist, the N Hamiltonians need to satisfy a consistency condition. This condition is automatically satisfied for non-interacting particles, but it is not obvious how to set up consistent multi-time equations with interaction. For example, interaction potentials (such as the Coulomb potential) make the equations inconsistent, except in very special cases. However, there have been recent successes in setting up consistent multi-time equations involving interaction, in two ways: either involving zero-range (δ potential) interaction or involving particle creation and annihilation. The latter equations provide a multi-time formulation of a quantum field theory. The wave function in these equations is a multi-time Fock function, i.e., a family of functions consisting of, for every n = 0, 1, 2, …, an n-particle wave function with n time variables. These wave functions are related to the Tomonaga-Schwinger approach and to quantum field operators, but, as we point out, they have several advantages.
Speed ot travelling waves in reaction-diffusion equations
Energy Technology Data Exchange (ETDEWEB)
Benguria, R.D.; Depassier, M.C. [Facultad de Fisica, Pontificia Universidad Catolica de Chile, Avda. Vicuna Mackenna 4860, Santiago (Chile); Mendez, V. [Facultat de Ciencies de la Salut, Universidad Internacional de Catalunya, Gomera s/n 08190 Sant Cugat del Valles, Barcelona (Spain)
2002-07-01
Reaction diffusion equations arise in several problems of population dynamics, flame propagation and others. In one dimensional cases the systems may evolve into travelling fronts. Here we concentrate on a reaction diffusion equation which arises as a simple model for chemotaxis and present results for the speed of the travelling fronts. (Author)
[Memory of Past Events and Mental Time Travel in Apes].
Hirata, Satoshi
2017-11-01
Mental time travel refers to the ability to recall a past event and imagine the future. Some researchers claim that this ability is unique to humans, while others argue that nonhuman animals also possess this ability. A study on apes by using eye-tracking revealed that chimpanzees and bonobos can remember a single event for 24 hours, suggesting that they possess at least some elements of mental time travel.
2008-08-01
ODOTs policy for Dynamic Message Sign : utilization requires travel time(s) to be displayed as : a default message. The current method of : calculating travel time involves a workstation : operator estimating the travel time based upon : observati...
Travel at low energetic cost by swimming and wave-riding bottlenose dolphins.
Williams, T M; Friedl, W A; Fong, M L; Yamada, R M; Sedivy, P; Haun, J E
1992-02-27
Over the past 50 years there has been much speculation about the energetic cost of swimming and wave-riding by dolphins. When aligned properly in front of the bow of moving ships in the stern wake of small boats, on wind waves, and even in the wake of larger cetaceans, the animals appear to move effortlessly through the water without the benefit of propulsive strokes by the flukes. Theoretically, body streamlining as well as other anatomical and behavioural adaptations contribute to low transport costs in these animals. The economy of movement permitted by wave-riding has been perceived as an energetic advantage for the swimming dolphin, but has been hard to prove in the absence of physiological data for exercising cetaceans. Here we determine the aerobic and anaerobic costs of swimming and wave-riding in bottlenose dolphins and find that the minimum cost of transport for swimming dolphins is 1.29 +/- 0.05 J kg-1 m-1 at a cruising speed of 2.1 m s-1. Aerobic costs are nearly twice as high for swimming seals and sea lions, and 8-12 times higher for human swimmers. Wave-riding by dolphins provides additional benefits in terms of speed. The results indicate that behavioural, physiological and morphological factors make swimming an economical form of high-speed travel for dolphins.
Back or to the future? Preferences of time travelers
Directory of Open Access Journals (Sweden)
Ralph Hertwig
2012-07-01
Full Text Available Popular culture reflects whatever piques our imagination. Think of the myriad movies and books that take viewers and readers on an imaginary journey to the past or the future (e.g., Gladiator, The Time Machine. Despite the ubiquity of time travel as a theme in cultural expression, the factors that underlie people's preferences concerning the direction of time travel have gone unexplored. What determines whether a person would prefer to visit the (certain past or explore the (uncertain future? We identified three factors that markedly affect people's preference for (hypothetical travel to the past or the future, respectively. Those who think of themselves as courageous, those with a more conservative worldview, and---perhaps counterintuitively---those who are advanced in age prefer to travel into the future. We discuss implications of these initial results.
Behrens, Jan; Langelier, Sean; Rezk, Amgad R; Lindner, Gerhard; Yeo, Leslie Y; Friend, James R
2015-01-07
We present a versatile and very low-power traveling SAW microfluidic sorting device able to displace and separate particles of different diameter in aqueous suspension; the travelling wave propagates through the fluid bulk and diffuses via a Schröder diffuser, adapted from its typical use in concert hall acoustics to be the smallest such diffuser to be suitable for microfluidics. The effective operating power range is two to three orders of magnitude less than current SAW devices, uniquely eliminating the need for amplifiers, and by using traveling waves to impart forces directly upon suspended microparticles, they can be separated by size.
Pulse wave travel distance as a novel marker of ventricular-arterial coupling.
Obata, Yurie; Ruzankin, Pavel; Gottschalk, Allan; Nyhan, Daniel; Berkowitz, Dan E; Steppan, Jochen; Barodka, Viachaslau
2017-10-03
Each stroke volume ejected by the heart is distributed along the arterial system as a pressure waveform. How far the front of the pressure waveform travels within the arterial system depends both on the pulse wave velocity (PWV) and the ejection time (ET). We tested the hypothesis that ET and PWV are coupled together, in order to produce a pulse wave travel distance (PWTD = PWV × ET) which would match the distance from the heart to the most distant site in the arterial system. The study was conducted in 11 healthy volunteers. We recorded lead II of the ECG along with pulse plethysmography at ear, finger and toe. The ET at the ear and pulse arrival time to each peripheral site were extracted. We then calculated PWV followed by PWTD for each location. Taken into account the individual subject variability PWTDToe in the supine position was 153 cm (95% CI 146-160 cm). It was not different from arterial pathway distance from the heart to the toe (D Toe 153 cm). The PWTDFinger and PWTDEar were longer than the distance from the heart to the finger and ear irrespective of body position. ETEar and PWVToe appear to be coupled in healthy subjects to produce a PWTD that is roughly equivalent to the arterial pathway distance to the toe. We propose that PWTD should be evaluated further to test its potential as a noninvasive parameter of ventricular-arterial coupling in subjects with cardiovascular diseases.
Low-noise kinetic inductance traveling-wave amplifier using three-wave mixing
Vissers, M. R.; Erickson, R. P.; Ku, H.-S.; Vale, Leila; Wu, Xian; Hilton, G. C.; Pappas, D. P.
2016-01-01
We have fabricated a wide-bandwidth, high dynamic range, low-noise cryogenic amplifier based on a superconducting kinetic inductance traveling-wave device. The device was made from NbTiN and consisted of a long, coplanar waveguide on a silicon chip. By adding a DC current and an RF pump tone, we are able to generate parametric amplification using three-wave mixing (3WM). The devices exhibit gain of more than 15 dB across an instantaneous bandwidth from 4 to 8 GHz. The total usable gain bandwidth, including both sides of the signal-idler gain region, is more than 6 GHz. The noise referred to the input of the devices approaches the quantum limit, with less than 1 photon excess noise. We compare these results directly to the four-wave mixing amplification mode, i.e., without DC-biasing. We find that the 3WM mode allows operation with the pump at lower RF power and at frequencies far from the signal. We have used this knowledge to redesign the amplifiers to utilize primarily 3WM amplification, thereby allowing for direct integration into large scale qubit and detector applications.
Low-noise kinetic inductance traveling-wave amplifier using three-wave mixing.
Vissers, M R; Erickson, R P; Ku, H-S; Vale, Leila; Wu, Xian; Hilton, G; Pappas, D P
We have fabricated a wide-bandwidth, high dynamic range, low-noise cryogenic amplifier based on a superconducting kinetic inductance traveling-wave device. The device was made from NbTiN and consisted of a long, coplanar waveguide on a silicon chip. By adding a DC current and an RF pump tone we are able to generate parametric amplification using three-wave mixing. The devices exhibit gain of more than 15 dB across an instantaneous bandwidth from 4 to 8 GHz. The total usable gain bandwidth, including both sides of the signal-idler gain region, is more than 6 GHz. The noise referred to the input of the devices approaches the quantum limit, with less than 1 photon excess noise. Compared to similarly constructed four-wave mixing amplifiers, these devices operate with the RF pump at ~20 dB lower power and at frequencies far from the signal. This will permit easier integration into large scale qubit and detector applications.
TERRAPOWER, LLC TRAVELING WAVE REACTOR DEVELOPMENT PROGRAM OVERVIEW
Directory of Open Access Journals (Sweden)
PAVEL HEJZLAR
2013-11-01
Full Text Available Energy security is a topic of high importance to many countries throughout the world. Countries with access to vast energy supplies enjoy all of the economic and political benefits that come with controlling a highly sought after commodity. Given the desire to diversify away from fossil fuels due to rising environmental and economic concerns, there are limited technology options available for baseload electricity generation. Further complicating this issue is the desire for energy sources to be sustainable and globally scalable in addition to being economic and environmentally benign. Nuclear energy in its current form meets many but not all of these attributes. In order to address these limitations, TerraPower, LLC has developed the Traveling Wave Reactor (TWR which is a near-term deployable and truly sustainable energy solution that is globally scalable for the indefinite future. The fast neutron spectrum allows up to a ∼30-fold gain in fuel utilization efficiency when compared to conventional light water reactors utilizing enriched fuel. When compared to other fast reactors, TWRs represent the lowest cost alternative to enjoy the energy security benefits of an advanced nuclear fuel cycle without the associated proliferation concerns of chemical reprocessing. On a country level, this represents a significant savings in the energy generation infrastructure for several reasons 1 no reprocessing plants need to be built, 2 a reduced number of enrichment plants need to be built, 3 reduced waste production results in a lower repository capacity requirement and reduced waste transportation costs and 4 less uranium ore needs to be mined or purchased since natural or depleted uranium can be used directly as fuel. With advanced technological development and added cost, TWRs are also capable of reusing both their own used fuel and used fuel from LWRs, thereby eliminating the need for enrichment in the longer term and reducing the overall societal waste
Travel Time Information Service Utilising Mobile Phone Tracking
Caj Holm; Mario Anžek; Slobodan Kaštela
2004-01-01
This paper discusses the suitability of mobile phone positioningdata for travel time information. The Finnish NationalRoad Administration Finnra has carried out a study on thesubject (1) and managed pilot installations on two road sections(6) in order to determine the feasibility of mobile phonetracking for traffic monitoring and management purposes. Accordingto the study and the pilots, the mobile phone positioningcan provide useful link monitoring data, i. e. the travel timeand speed. Mobil...
2015-02-01
Although the freeway travel time data has been validated extensively in recent : years, the quality of arterial travel time data is not well known. This project : presents a comprehensive validation scheme for arterial travel time data based : on GPS...
Prestimulus amplitudes modulate P1 latencies and evoked traveling alpha waves
Directory of Open Access Journals (Sweden)
Nicole Alexandra Himmelstoss
2015-05-01
Full Text Available Traveling waves have been well documented in the ongoing, and more recently also in the evoked EEG. In the present study we investigate what kind of physiological process might be responsible for inducing an evoked traveling wave. We used a semantic judgment task which already proved useful to study evoked traveling alpha waves that coincide with the appearance of the P1 component. We found that the P1 latency of the leading electrode is significantly correlated with prestimulus amplitude size and that this event is associated with a transient change in alpha frequency. We assume that cortical background excitability, as reflected by an increase in prestimulus amplitude, is responsible for the observed change in alpha frequency and the initiation of an evoked traveling trajectory.
Modeling highway travel time distribution with conditional probability models
Energy Technology Data Exchange (ETDEWEB)
Oliveira Neto, Francisco Moraes [ORNL; Chin, Shih-Miao [ORNL; Hwang, Ho-Ling [ORNL; Han, Lee [University of Tennessee, Knoxville (UTK)
2014-01-01
ABSTRACT Under the sponsorship of the Federal Highway Administration's Office of Freight Management and Operations, the American Transportation Research Institute (ATRI) has developed performance measures through the Freight Performance Measures (FPM) initiative. Under this program, travel speed information is derived from data collected using wireless based global positioning systems. These telemetric data systems are subscribed and used by trucking industry as an operations management tool. More than one telemetric operator submits their data dumps to ATRI on a regular basis. Each data transmission contains truck location, its travel time, and a clock time/date stamp. Data from the FPM program provides a unique opportunity for studying the upstream-downstream speed distributions at different locations, as well as different time of the day and day of the week. This research is focused on the stochastic nature of successive link travel speed data on the continental United States Interstates network. Specifically, a method to estimate route probability distributions of travel time is proposed. This method uses the concepts of convolution of probability distributions and bivariate, link-to-link, conditional probability to estimate the expected distributions for the route travel time. Major contribution of this study is the consideration of speed correlation between upstream and downstream contiguous Interstate segments through conditional probability. The established conditional probability distributions, between successive segments, can be used to provide travel time reliability measures. This study also suggests an adaptive method for calculating and updating route travel time distribution as new data or information is added. This methodology can be useful to estimate performance measures as required by the recent Moving Ahead for Progress in the 21st Century Act (MAP 21).
Analytical travelling wave solutions and parameter analysis for the ...
Indian Academy of Sciences (India)
By using dynamical system method, this paper considers the (2+1)-dimensional Davey–Stewartson-type equations. The analytical parametric representations of solitary wave solutions, periodic wave solutions as well as unbounded wave solutions are obtained under different parameter conditions. A few diagrams ...
Reverse cochlear propagation in the intact cochlea of the gerbil: Evidence for slow traveling waves
S.W.F. Meenderink; M. van der Heijden (Marcel)
2010-01-01
textabstractThe inner ear can produce sounds, but how these otoacoustic emissions back-propagate through the cochlea is currently debated. Two opposing views exist: fast pressure waves in the cochlear fluids and slow traveling waves involving the basilar membrane. Resolving this issue requires
An Optimization Method of Time Window Based on Travel Time and Reliability
Directory of Open Access Journals (Sweden)
Fengjie Fu
2015-01-01
Full Text Available The dynamic change of urban road travel time was analyzed using video image detector data, and it showed cyclic variation, so the signal cycle length at the upstream intersection was conducted as the basic unit of time window; there was some evidence of bimodality in the actual travel time distributions; therefore, the fitting parameters of the travel time bimodal distribution were estimated using the EM algorithm. Then the weighted average value of the two means was indicated as the travel time estimation value, and the Modified Buffer Time Index (MBIT was expressed as travel time variability; based on the characteristics of travel time change and MBIT along with different time windows, the time window was optimized dynamically for minimum MBIT, requiring that the travel time change be lower than the threshold value and traffic incidents can be detected real time; finally, travel times on Shandong Road in Qingdao were estimated every 10 s, 120 s, optimal time windows, and 480 s and the comparisons demonstrated that travel time estimation in optimal time windows can exactly and steadily reflect the real-time traffic. It verifies the effectiveness of the optimization method.
Liu, T.; Zhang, H.
2016-12-01
Since introduced to seismic tomography about a decade ago, the technique of retrieving dispersion relations and travel times in noise cross-correlations has been one of the most rapidly developing method in seismology. Many seismologists have used this technique, and among them some have made significant discoveries. This method was originally introduced from acoustics into seismology. It was verified for acoustic waves that the noise cross-correlations resemble the Green's functions. However, since seismic waves are vector waves, and the noise sources are concentrated on the free surface, the conclusion in the acoustic case cannot be taken for granted in the seismological case. Thus, whether noise cross-correlations can replace seismograms in extracting the dispersion relations and the travel times should be studied thoroughly. In our study, we attempt to investigate the relation between the dispersion relations and travel times extracted in the noise cross-correlations and those extracted in the seismograms. We start with the general equation of noise cross-correlation, and write it in the form of normal-mode summation after assuming that the earth structure is spherically symmetric and the distribution of noise sources is laterally uniform. Then we use asymptotic analysis (traveling wave decomposition and mode-sum to ray-sum transformation) to write the surface-wave and body-wave representation of the noise cross-correlation, analyzing which we theoretically prove that as long as the earth model is spherically symmetric and the distribution of the noise sources is laterally uniform, the dispersion relations and the travel times extracted in noise cross-correlations are identical to those extracted in seismograms. In addition, numerical results are provided to verify our proof. This proposition establishes the feasibility theoretically, although only under very strict assumptions. Furthermore, we investigate the case in which the structure of the earth and the
Cloud-based design of high average power traveling wave linacs
Kutsaev, S. V.; Eidelman, Y.; Bruhwiler, D. L.; Moeller, P.; Nagler, R.; Barbe Welzel, J.
2017-12-01
The design of industrial high average power traveling wave linacs must accurately consider some specific effects. For example, acceleration of high current beam reduces power flow in the accelerating waveguide. Space charge may influence the stability of longitudinal or transverse beam dynamics. Accurate treatment of beam loading is central to the design of high-power TW accelerators, and it is especially difficult to model in the meter-scale region where the electrons are nonrelativistic. Currently, there are two types of available codes: tracking codes (e.g. PARMELA or ASTRA) that cannot solve self-consistent problems, and particle-in-cell codes (e.g. Magic 3D or CST Particle Studio) that can model the physics correctly but are very time-consuming and resource-demanding. Hellweg is a special tool for quick and accurate electron dynamics simulation in traveling wave accelerating structures. The underlying theory of this software is based on the differential equations of motion. The effects considered in this code include beam loading, space charge forces, and external magnetic fields. We present the current capabilities of the code, provide benchmarking results, and discuss future plans. We also describe the browser-based GUI for executing Hellweg in the cloud.
Slip-stick excitation and travelling waves excite silo honking
Directory of Open Access Journals (Sweden)
Warburton Katarzyna
2017-01-01
Full Text Available Silo honking is the harmonic sound generated by the discharge of a silo filled with a granular material. In industrial storage silos, the acoustic emission during discharge of PET-particles forms a nuisance for the environment and may ultimately result in structural failure. This work investigates the phenomenon experimentally using a laboratory-scale silo, and successfully correlates the frequency of the emitted sound with the periodicity of the mechanical motion of the grains. The key driver is the slip-stick interaction between the wall and the particles, characterized as a wave moving upwards through the silo. A quantitative correlation is established for the first time between the frequency of the sound, measured with an electret microphone, and the slip-frequency, measured with a high-speed camera. In the lower regions of the tube, both the slip-stick motion and the honking sound disappear.
Anelli, Filomena; Ciaramelli, Elisa; Arzy, Shahar; Frassinetti, Francesca
2016-11-01
Accumulating evidence suggests that humans process time and space in similar veins. Humans represent time along a spatial continuum, and perception of temporal durations can be altered through manipulations of spatial attention by prismatic adaptation (PA). Here, we investigated whether PA-induced manipulations of spatial attention can also influence more conceptual aspects of time, such as humans' ability to travel mentally back and forward in time (mental time travel, MTT). Before and after leftward- and rightward-PA, participants projected themselves in the past, present or future time (i.e., self-projection), and, for each condition, determined whether a series of events were located in the past or the future with respect to that specific self-location in time (i.e., self-reference). The results demonstrated that leftward and rightward shifts of spatial attention facilitated recognition of past and future events, respectively. These findings suggest that spatial attention affects the temporal processing of the human self. Copyright © 2016 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
Eric Dumonteil
2017-09-01
Full Text Available The Monte Carlo criticality simulation of decoupled systems, as for instance in large reactor cores, has been a challenging issue for a long time. In particular, due to limited computer time resources, the number of neutrons simulated per generation is still many order of magnitudes below realistic statistics, even during the start-up phases of reactors. This limited number of neutrons triggers a strong clustering effect of the neutron population that affects Monte Carlo tallies. Below a certain threshold, not only is the variance affected but also the estimation of the eigenvectors. In this paper we will build a time-dependent diffusion equation that takes into account both spatial correlations and population control (fixed number of neutrons along generations. We will show that its solution obeys a traveling wave dynamic, and we will discuss the mechanism that explains this biasing of local tallies whenever leakage boundary conditions are applied to the system.
Mitsotakis, Dimitrios; Assylbekuly, Aydar; Zhakebaev, Dauren
2016-01-01
In this Letter we consider long capillary-gravity waves described by a fully nonlinear weakly dispersive model. First, using the phase space analysis methods we describe all possible types of localized travelling waves. Then, we especially focus on the critical regime, where the surface tension is exactly balanced by the gravity force. We show that our long wave model with a critical Bond number admits stable travelling wave solutions with a singular crest. These solutions are usually referred to in the literature as peakons or peaked solitary waves. They satisfy the usual speed-amplitude relation, which coincides with Scott-Russel's empirical formula for solitary waves, while their decay rate is the same regardless their amplitude. Moreover, they can be of depression or elevation type independent of their speed. The dynamics of these solutions are studied as well.
Ultrasonic travel-time tomography in core plugs
Martins, Jorge L.; Soares, José A.; da Silva, Jadir C.
2007-06-01
This paper applies ultrasonic travel-time tomography in order to investigate the resolution (i.e. definition of dimension and shape) of velocity heterogeneities in tomograms from core plugs. Designing the tomographic algorithm involves two main steps, namely, modelling and inversion. In the modelling step, we use straight and curved ray-tracing schemes to calculate raypaths and travel times corresponding to the source-receiver configuration. The inversion step then submits a predefined norm of the residuals between calculated and measured travel times to a minimization process. The conjugate gradient method works to iteratively minimize the ell1 norm of travel-time residuals. Numerical experiments show that, in addition to the dominant frequency of the probing ultrasonic pulse, the resolution of tomograms from core plugs with high-contrast heterogeneities depends on the chosen ray-tracing scheme. In summary, if the rock sample exhibits low to moderate velocity contrasts, the tomographic algorithm using straight rays in the modelling step yields tomograms with good resolution. However, in the presence of high velocity contrasts, plausibly resolved tomograms can be obtained only by adopting a curved ray-tracing scheme. The application of ultrasonic tomography using travel-time data from real core plugs corroborates the results obtained with numerical data.
2010-07-01
... travel advance outstanding at the time I submit my travel claim? 301-52.14 Section 301-52.14 Public Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES... § 301-52.14 What must I do with any travel advance outstanding at the time I submit my travel claim? You...
Extended time-travelling objects in Misner space
Levanony, Dana
2011-01-01
Misner space is a two-dimensional (2D) locally-flat spacetime which elegantly demonstrates the emergence of closed timelike curves from causally well-behaved initial conditions. Here we explore the motion of rigid extended objects in this time-machine spacetime. This kind of 2D time-travel is found to be risky due to inevitable self-collisions (i.e. collisions of the object with itself). However, in a straightforward four-dimensional generalization of Misner space (a physically more relevant spacetime obviously), we find a wide range of "safe" time-travel orbits free of any self-collisions.
Issues in the valuation of travel time savings
DEFF Research Database (Denmark)
Gissel, Stine
1998-01-01
The subject of the paper is the valuation of travel time savings (emanating from investment in transport infrastructure). In the first part of the paper the question is approached within a microeconomic framework. It is discussed if and how the theory can give indications on the relative value...... of travel time elements and on the extrapolation of time values into the future. In the second part of the paper the same questions are investigated on the basis of the results of several empirical studies....
Skin friction drag reduction in turbulent flow using spanwise traveling surface waves
Musgrave, Patrick F.; Tarazaga, Pablo A.
2017-04-01
A major technological driver in current aircraft and other vehicles is the improvement of fuel efficiency. One way to increase the efficiency is to reduce the skin friction drag on these vehicles. This experimental study presents an active drag reduction technique which decreases the skin friction using spanwise traveling waves. A novel method is introduced for generating traveling waves which is low-profile, non-intrusive, and operates under various flow conditions. This wave generation method is discussed and the resulting traveling waves are presented. These waves are then tested in a low-speed wind tunnel to determine their drag reduction potential. To calculate the drag reduction, the momentum integral method is applied to turbulent boundary layer data collected using a pitot tube and traversing system. The skin friction coefficients are then calculated and the drag reduction determined. Preliminary results yielded a drag reduction of ≍ 5% for 244Hz traveling waves. Thus, this novel wave generation method possesses the potential to yield an easily implementable, non-invasive drag reduction technology.
Energy Technology Data Exchange (ETDEWEB)
Mitsotakis, Dimitrios, E-mail: dmitsot@gmail.com [Victoria University of Wellington, School of Mathematics, Statistics and Operations Research, PO Box 600, Wellington 6140 (New Zealand); Dutykh, Denys, E-mail: Denys.Dutykh@univ-savoie.fr [LAMA, UMR 5127 CNRS, Université Savoie Mont Blanc, Campus Scientifique, F-73376 Le Bourget-du-Lac Cedex (France); Assylbekuly, Aydar, E-mail: asylbekuly@mail.ru [Khoja Akhmet Yassawi International Kazakh–Turkish University, Faculty of Natural Science, Department of Mathematics, 161200 Turkestan (Kazakhstan); Zhakebayev, Dauren, E-mail: daurjaz@mail.ru [Al-Farabi Kazakh National University, Faculty of Mechanics and Mathematics, Department of Mathematical and Computer Modelling, 050000 Almaty (Kazakhstan)
2017-05-25
In this Letter we consider long capillary–gravity waves described by a fully nonlinear weakly dispersive model. First, using the phase space analysis methods we describe all possible types of localized travelling waves. Then, we especially focus on the critical regime, where the surface tension is exactly balanced by the gravity force. We show that our long wave model with a critical Bond number admits stable travelling wave solutions with a singular crest. These solutions are usually referred to in the literature as peakons or peaked solitary waves. They satisfy the usual speed-amplitude relation, which coincides with Scott–Russel's empirical formula for solitary waves, while their decay rate is the same regardless their amplitude. Moreover, they can be of depression or elevation type independent of their speed. The dynamics of these solutions are studied as well. - Highlights: • A model for long capillary–gravity weakly dispersive and fully nonlinear water waves is derived. • Shallow capillary–gravity waves are classified using phase plane analysis. • Peaked travelling waves are found in the critical regime. • The dynamics of peakons in Serre–Green–Naghdi equations is studied numerically.
Flow and travel time statistics in highly heterogeneous porous media
Gotovac, Hrvoje; Cvetkovic, Vladimir; Andricevic, Roko
2009-07-01
In this paper we present flow and travel time ensemble statistics based on a new simulation methodology, the adaptive Fup Monte Carlo method (AFMCM). As a benchmark case, we considered two-dimensional steady flow in a rectangular domain characterized by multi-Gaussian heterogeneity structure with an isotropic exponential correlation and lnK variance σY2 up to 8. Advective transport is investigated using the travel time framework where Lagrangian variables (e.g., velocity, transverse displacement, or travel time) depend on space rather than on time. We find that Eulerian and Lagrangian velocity distributions diverge for increasing lnK variance due to enhanced channeling. Transverse displacement is a nonnormal for all σY2 and control planes close to the injection area, but after xIY = 20 was found to be nearly normal even for high σY2. Travel time distribution deviates from the Fickian model for large lnK variance and exhibits increasing skewness and a power law tail for large lnK variance, the slope of which decreases for increasing distance from the source; no anomalous features are found. Second moment of advective transport is analyzed with respect to the covariance of two Lagrangian velocity variables: slowness and slope which are directly related to the travel time and transverse displacement variance, which are subsequently related to the longitudinal and transverse dispersion. We provide simple estimators for the Eulerian velocity variance, travel time variance, slowness, and longitudinal dispersivity as a practical contribution of this analysis. Both two-parameter models considered (the advection-dispersion equation and the lognormal model) provide relatively poor representations of the initial part of the travel time probability density function in highly heterogeneous porous media. We identify the need for further theoretical and experimental scrutiny of early arrival times, and the need for computing higher-order moments for a more accurate
Similarity-Based Prediction of Travel Times for Vehicles Traveling on Known Routes
DEFF Research Database (Denmark)
Tiesyte, Dalia; Jensen, Christian Søndergaard
2008-01-01
, historical data in combination with real-time data may be used to predict the future travel times of vehicles more accurately, thus improving the experience of the users who rely on such information. We propose a Nearest-Neighbor Trajectory (NNT) technique that identifies the historical trajectory......The use of centralized, real-time position tracking is proliferating in the areas of logistics and public transportation. Real-time positions can be used to provide up-to-date information to a variety of users, and they can also be accumulated for uses in subsequent data analyses. In particular...... of vehicles that travel along known routes. In empirical studies with real data from buses, we evaluate how well the proposed distance functions are capable of predicting future vehicle movements. Second, we propose a main-memory index structure that enables incremental similarity search and that is capable...
Propagating neocortical gamma bursts are coordinated by traveling alpha waves
Bahramisharif, A.; Gerven, M.A.J. van; Aarnoutse, E.J.; Mercier, M.R.; Schwartz, T.H.; Foxe, J.J.; Ramsey, N.F.; Jensen, O.
2013-01-01
Neocortical neuronal activity is characterized by complex spatiotemporal dynamics. Although slow oscillations have been shown to travel over space in terms of consistent phase advances, it is unknown how this phenomenon relates to neuronal activity in other frequency bands. We here present
DEFF Research Database (Denmark)
Mabit, Stefan Lindhard; Rich, Jeppe; Burge, Peter
2013-01-01
of travel time savings (VTTS). The final model, which was formulated as a nested logit model and included Box–Cox transformed travel time and cost attributes, revealed several interesting findings. Firstly, we found damping effects in both cost and time – most strongly in cost. Secondly, we found...... significant interactions among travel cost and time, and journey characteristics, such as distance and duration. This had direct impact on the VTTS, which was shown to decrease with distance and duration. Thirdly, we found that air travel implies a higher average VTTS, which is to be expected but rarely......The geographical scope of travel varies from short distances in urban areas to long distances across cities and countries. While urban travel has been widely analysed in the literature, travel over longer distances and particularly across countries, has received much less attention. While this may...
Evaluation of groundwater travel-time calculations for Yucca Mountain
Energy Technology Data Exchange (ETDEWEB)
Barnard, R.W.; Altman, S.J.; Arnold, B.W. [Sandia National Labs., Albuquerque, NM (United States)] [and others
1996-12-01
Groundwater flow through the unsaturated and saturated zones at Yucca Mountain has been modeled in support of the groundwater travel time regulations for the Department of Energy`s Yucca Mountain Site Characterization Project. Flow in the unsaturated zone was modeled using two conceptual models to test alternative methods of generating fast flow paths. Groundwater travel times from the potential repository location to the accessible environment range from less than 1,000 years to much more than 10,000 years, depending on the hydraulic properties of the rock units.
Classification of single travelling wave solutions to the generalized ...
Indian Academy of Sciences (India)
The investigation of exact solutions of nonlinear wave equations plays an important role in the study of nonlinear physical phenomena. Many authors started concentrating on researching the exact solutions of nonlinear wave equations [1,2]. For many nonlinear differential equations which can be directly reduced to the ...
Visualizations of Travel Time Performance Based on Vehicle Reidentification Data
Energy Technology Data Exchange (ETDEWEB)
Young, Stanley Ernest [National Renewable Energy Lab, 15013 Denver West Parkway, Golden, CO 80401; Sharifi, Elham [Center for Advanced Transportation Technology, University of Maryland, College Park, Technology Ventures Building, Suite 2200, 5000 College Avenue, College Park, MD 20742; Day, Christopher M. [Joint Transportation Research Program, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47906; Bullock, Darcy M. [Lyles School of Civil Engineering, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47906
2017-01-01
This paper provides a visual reference of the breadth of arterial performance phenomena based on travel time measures obtained from reidentification technology that has proliferated in the past 5 years. These graphical performance measures are revealed through overlay charts and statistical distribution as revealed through cumulative frequency diagrams (CFDs). With overlays of vehicle travel times from multiple days, dominant traffic patterns over a 24-h period are reinforced and reveal the traffic behavior induced primarily by the operation of traffic control at signalized intersections. A cumulative distribution function in the statistical literature provides a method for comparing traffic patterns from various time frames or locations in a compact visual format that provides intuitive feedback on arterial performance. The CFD may be accumulated hourly, by peak periods, or by time periods specific to signal timing plans that are in effect. Combined, overlay charts and CFDs provide visual tools with which to assess the quality and consistency of traffic movement for various periods throughout the day efficiently, without sacrificing detail, which is a typical byproduct of numeric-based performance measures. These methods are particularly effective for comparing before-and-after median travel times, as well as changes in interquartile range, to assess travel time reliability.
Breast cancer stage at diagnosis: is travel time important?
Henry, Kevin A; Boscoe, Francis P; Johnson, Christopher J; Goldberg, Daniel W; Sherman, Recinda; Cockburn, Myles
2011-12-01
Recent studies have produced inconsistent results in their examination of the potential association between proximity to healthcare or mammography facilities and breast cancer stage at diagnosis. Using a multistate dataset, we re-examine this issue by investigating whether travel time to a patient's diagnosing facility or nearest mammography facility impacts breast cancer stage at diagnosis. We studied 161,619 women 40 years and older diagnosed with invasive breast cancer from ten state population based cancer registries in the United States. For each woman, we calculated travel time to their diagnosing facility and nearest mammography facility. Logistic multilevel models of late versus early stage were fitted, and odds ratios were calculated for travel times, controlling for age, race/ethnicity, census tract poverty, rural/urban residence, health insurance, and state random effects. Seventy-six percent of women in the study lived less than 20 min from their diagnosing facility, and 93 percent lived less than 20 min from the nearest mammography facility. Late stage at diagnosis was not associated with increasing travel time to diagnosing facility or nearest mammography facility. Diagnosis age under 50, Hispanic and Non-Hispanic Black race/ethnicity, high census tract poverty, and no health insurance were all significantly associated with late stage at diagnosis. Travel time to diagnosing facility or nearest mammography facility was not a determinant of late stage of breast cancer at diagnosis, and better geographic proximity did not assure more favorable stage distributions. Other factors beyond geographic proximity that can affect access should be evaluated more closely, including facility capacity, insurance acceptance, public transportation, and travel costs.
How superluminal motion can lead to backward time travel
Nemiroff, Robert J
2015-01-01
It is commonly asserted that superluminal particle motion can enable backward time travel, but little has been written providing details. It is shown here that the simplest example of a "closed loop" event -- a twin paradox scenario where a single spaceship both traveling out and returning back superluminally -- does {\\it not} result in that ship straightforwardly returning to its starting point before it left. However, a more complicated scenario -- one where the superluminal ship first arrives at an intermediate destination moving subluminally -- can result in backwards time travel. This intermediate step might seem physically inconsequential but is shown to break Lorentz-invariance and be oddly tied to the sudden creation of a pair of spacecraft, one of which remains and one of which annihilates with the original spacecraft.
Reducing employee travelling time through smart commuting
Rahman, A. N. N. A.; Yusoff, Z. M.; Aziz, I. S.; Omar, D.
2014-02-01
Extremely congested roads will definitely delay the arrival time of each trip.This certainly impacted the journey of employees. Tardiness at the workplace has become a perturbing issue for companies where traffic jams are the most common worker excuses. A depressing consequence on daily life and productivity of the employee occurs. The issues of commuting distance between workplace and resident area become the core point of this research. This research will emphasize the use of Geographical Information System (GIS) technique to explore the distance parameter to the employment area and will focus on the accessibility pattern of low-cost housing. The research methodology consists of interview sessions and a questionnaire to residents of low-cost housing areas in Melaka Tengah District in Malaysia. The combination of these processes will show the criteria from the selected parameter for each respondent from their resident area to the employment area. This will further help in the recommendation of several options for a better commute or improvement to the existing routes and public transportations system. Thus enhancing quality of life for employees and helping to reduce stress, decrease lateness, absenteeism and improving productivity in workplace.
Some Further Results on Traveling Wave Solutions for the ZK-BBM( Equations
Directory of Open Access Journals (Sweden)
Shaoyong Li
2013-01-01
Full Text Available We investigate the traveling wave solutions for the ZK-BBM( equations by using bifurcation method of dynamical systems. Firstly, for ZK-BBM(2, 2 equation, we obtain peakon wave, periodic peakon wave, and smooth periodic wave solutions and point out that the peakon wave is the limit form of the periodic peakon wave. Secondly, for ZK-BBM(3, 2 equation, we obtain some elliptic function solutions which include periodic blow-up and periodic wave. Furthermore, from the limit forms of the elliptic function solutions, we obtain some trigonometric and hyperbolic function solutions which include periodic blow-up, blow-up, and smooth solitary wave. We also show that our work extends some previous results.
Simons, Rainee N.; Wintucky, Edwin G.
2014-01-01
This paper presents the design and test results of a CW millimeter-wave satellite beacon source, based on the second harmonic from a traveling-wave tube amplifier and utilizes a novel waveguide multimode directional coupler. A potential application of the beacon source is for investigating the atmospheric effects on Q-band (37-42 GHz) and V/W-band (71- 76 GHz) satellite-to-ground signals.
Development of Traveling Wave Actuators Using Waveguides of Different Geometrical Forms
Directory of Open Access Journals (Sweden)
Ramutis Bansevicius
2016-01-01
Full Text Available The paper covers the research and development of piezoelectric traveling wave actuators using different types of the waveguides. The introduced piezoelectric actuators can be characterized by specific areas of application, different resolution, and torque. All presented actuators are ultrasonic resonant devices and they were developed to increase amplitudes of the traveling wave oscillations of the contact surface. Three different waveguides are introduced, that is, symmetrical, asymmetrical, and cone type waveguide. A piezoelectric ring with the sectioned electrodes is used to excite traveling wave oscillations for all actuators. Operating principle, electrode pattern, and excitation regimes of piezoelectric actuators are described. A numerical modelling of the actuators was performed to validate the operating principle and to calculate trajectories of the contact points motion. Prototype actuators were made and experimental study was performed. The results of numerical and experimental analysis are discussed.
Memory, mental time travel and The Moustachio Quartet.
Clayton, Nicola; Wilkins, Clive
2017-06-06
Mental time travel allows us to revisit our memories and imagine future scenarios, and this is why memories are not only about the past, but they are also prospective. These episodic memories are not a fixed store of what happened, however, they are reassessed each time they are revisited and depend on the sequence in which events unfold. In this paper, we shall explore the complex relationships between memory and human experience, including through a series of novels 'The Moustachio Quartet' that can be read in any order. To do so, we shall integrate evidences from science and the arts to explore the subjective nature of memory and mental time travel, and argue that it has evolved primarily for prospection as opposed to retrospection. Furthermore, we shall question the notion that mental time travel is a uniquely human construct, and argue that some of the best evidence for the evolution of mental time travel comes from our distantly related cousins, the corvids, that cache food for the future and rely on long-lasting and highly accurate memories of what, where and when they stored their stashes of food.
A novel ultrasonic surface machining tool utilizing elastic traveling waves.
Ji, Ruinan; Jin, Jiamei; Wang, Liang; Zhang, Jianhui
2017-09-01
With the rapid development of modern industrial technology and high performance technology products, ultra-precision machining technology becomes increasingly important. However, joint clearance of kinematic pairs, lack of feeding accuracy and overlarge contact stress still limit the further improvement of ultra-precision machining technology. In this study, a novel surface machining method utilizing structural elastic waves was proposed, and a machining tool using the piezoelectric actuating principle was presented for verifying the proposed method. Two vibration modes with a phase shift of π/2 in both space and time domains are exited simultaneously in the elliptical motion of points on the structural surface. By means of adjusting driving signal parameters, such as frequency, voltage amplitude and phase shift, different machining performances could be achieved. The configuration and working vibration modes of the proposed machining tool were firstly calculated by the finite element method, and then the optimal working frequency of the machining tool prototype was determined by vibration characteristic experiments. At last, machining characteristic experiments were conducted to validate the proposed machining method. Experimental results showed that the minimum working contact force between the machining tool and workpiece was 1N, and the chipped depth of 1.93μm was achieved at the same contact force after machining for 5min. And at the conditions of the contact force of 6N, two driving voltages of 400V pp with a phase shift of π/2, and machining time of 5min, the prototype could achieve to machine the workpiece most efficiently and the roughness of the machined workpiece surface could be reached approximating 0.20μm. In conclusion, this proposed machining method could achieve a good quality machined surface with low residual stress and little damage by applying low contact force. Furthermore, it also had the advantage of no joint clearance error due to no
Spoor, Philip S.
2005-09-01
CFIC/QDrive has developed a food storage refrigerator for the Army based on thermoacoustic technology. This ``Phase II'' SBIR project is a continuation of a ``Phase I'' effort that explored using a standing-wave thermoacoustic cooler for the refrigerator. The standing-wave cooler was found to be too inefficient with too low a power density to be practical, so it was switched to an acoustic Stirling, or traveling-wave thermoacoustic (regenerator based) cooler for Phase II. The major challenges of this project were adapting the Stirling-style cooler to a food storage application, and not the fundamentals of the cooler itself (the one exception being the issue of acoustic streaming). The challenges include: Running at 60 Hz (without frequency-shifting electronics), heat exchange without circulating fluids, dynamic balance, guarantee of long life, efficiency, and compactness (power density). How these challenges were met and how they drove the design, in most cases away from what would be ideal for the cycle itself, will be discussed. Time permitting, how the additional pressure of low unit cost would affect this type of product development will also be discussed. [Research supported by the U. S. Army through a Small Business Innovation Research (SBIR) grant.
The A-priori Traveling Salesman Problem with Time Windows
DEFF Research Database (Denmark)
Larsen, Allan; Madsen, Oli B.G.; Solomon, Marius M.
2004-01-01
In this paper we examine the traveling saleman problem with time windows for various degrees of dynamism. In contrast to the static problem, where the dispatcher can plan ahead, in the dynamic version, part or all of the necessary information becomes available only during the day of operation. We...
An adaptive function of mental time travel: Motivating farsighted decisions.
Benoit, Roland G; Berkers, Ruud M W J; Paulus, Philipp C
2018-01-01
The episodic memory system allows us to experience the emotions of past, counterfactual, and prospective events. We outline how this phenomenological experience can convey motivational incentives for farsighted decisions. In this way, we challenge important arguments for Mahr & Csibra's (M&C's) conclusion that future-oriented mental time travel is unlikely to be a central function of episodic memory.
Modelling travel time reliability in public transport route choice behaviour
Swierstra, A.B.; van Nes, R.; Molin, E.J.E.
2017-01-01
The implementation of travel time reliability (TTR) in route choice behaviour is still not very common in transport models, especially not in a public transport context. The reasons probably are that it is difficult to measure and that there is no agreement how it best can be represented in
Flow calculations for Yucca Mountain groundwater travel time (GWTT-95)
Energy Technology Data Exchange (ETDEWEB)
Altman, S.J.; Arnold, B.W.; Barnard, R.W.; Barr, G.E.; Ho, C.K.; McKenna, S.A.; Eaton, R.R.
1996-09-01
In 1983, high-level radioactive waste repository performance requirements related to groundwater travel time were defined by NRC subsystem regulation 10 CFR 60.113. Although DOE is not presently attempting to demonstrate compliance with that regulation, understanding of the prevalence of fast paths in the groundwater flow system remains a critical element of any safety analyses for a potential repository system at Yucca Mountain, Nevada. Therefore, this analysis was performed to allow comparison of fast-path flow against the criteria set forth in the regulation. Models developed to describe the conditions for initiation, propagation, and sustainability of rapid groundwater movement in both the unsaturated and saturated zones will form part of the technical basis for total- system analyses to assess site viability and site licensability. One of the most significant findings is that the fastest travel times in both unsaturated and saturated zones are in the southern portion of the potential repository, so it is recommended that site characterization studies concentrate on this area. Results support the assumptions regarding the importance of an appropriate conceptual model of groundwater flow and the incorporation of heterogeneous material properties into the analyses. Groundwater travel times are sensitive to variation/uncertainty in hydrologic parameters and in infiltration flux at upper boundary of the problem domain. Simulated travel times are also sensitive to poorly constrained parameters of the interaction between flow in fractures and in the matrix.
The Electric Traveling Salesman Problem with Time Windows
DEFF Research Database (Denmark)
Roberti, Roberto; Wen, Min
2016-01-01
To minimize greenhouse gas emissions, the logistic field has seen an increasing usage of electric vehicles. The resulting distribution planning problems present new computational challenges.We address a problem, called Electric Traveling Salesman Problem with Time Windows. We propose a mixed...
A simple data fusion method for instantaneous travel time estimation
Do, Michael; Pueboobpaphan, R.; Miska, Marc; Kuwahara, Masao; van Arem, Bart; Viegas, J.M.; Macario, R.
2010-01-01
Travel time is one of the most understandable parameters to describe traffic condition and an important input to many intelligent transportation systems applications. Direct measurement from Electronic Toll Collection (ETC) system is promising but the data arrives too late, only after the vehicles
Exact Traveling-Wave Solution for Local Fractional Boussinesq Equation in Fractal Domain
Yang, Xiao-Jun; Machado, J. A. Tenreiro; Baleanu, Dumitru
The new Boussinesq-type model in a fractal domain is derived based on the formulation of the local fractional derivative. The novel traveling wave transform of the non-differentiable type is adopted to convert the local fractional Boussinesq equation into a nonlinear local fractional ODE. The exact traveling wave solution is also obtained with aid of the non-differentiable graph. The proposed method, involving the fractal special functions, is efficient for finding the exact solutions of the nonlinear PDEs in fractal domains.
The existence of traveling wave solutions for a bistable three-component lattice dynamical system
Guo, Jong-Shenq; Wu, Chin-Chin
2016-01-01
We study the traveling wave solutions for a three-component lattice dynamical system. This problem arises in the modeling of three species competing two food resources in an environment with migration in which the habitat is one-dimensional and is divided into countable niches. We are concerned with the case when two species have different preferences of food and the third species has both preferences of food. To understand which species win the competition under the bistable condition, the existence of a traveling wave solution for this lattice dynamical system is proven.
Webb, Andrew G; Collins, Christopher M; Versluis, Maarten J; Kan, Hermien E; Smith, Nadine B
2010-02-01
Using a small resonant loop to produce a longitudinal traveling wave on a human 7-T system allows MR to be performed over the entire volume of the human leg. We have used this capability to perform localized proton MR spectroscopy of the lipid composition of muscle in volunteers with a coil placed approximately 30 cm away from the region of interest. Spectra with a reasonable signal-to-noise ratio can be acquired in a clinically relevant data acquisition time of less than 5 min using the loop in transmit/receive mode, maintaining the full flexibility to acquire spectra from any part of the calf and/or thigh. If a local receive coil is used in combination with the remote transmit coil, then the signal-to-noise improves significantly, as expected.
Orbital stability of periodic traveling-wave solutions for the log-KdV equation
Natali, Fábio; Pastor, Ademir; Cristófani, Fabrício
2017-09-01
In this paper we establish the orbital stability of periodic waves related to the logarithmic Korteweg-de Vries equation. Our motivation is inspired in the recent work [3], in which the authors established the well-posedness and the linear stability of Gaussian solitary waves. By using the approach put forward recently in [20] to construct a smooth branch of periodic waves as well as to get the spectral properties of the associated linearized operator, we apply the abstract theories in [13] and [25] to deduce the orbital stability of the periodic traveling waves in the energy space.
How to build a time machine: the real science of time travel
Clegg, Brian
2013-01-01
A pop science look at time travel technology, from Einstein to Ronald Mallett to present day experiments. Forget fiction: time travel is real.In How to Build a Time Machine, Brian Clegg provides an understanding of what time is and how it can be manipulated. He explores the fascinating world of physics and the remarkable possibilities of real time travel that emerge from quantum entanglement, superluminal speeds, neutron star cylinders and wormholes in space. With the fascinating paradoxes of time travel echoing in our minds will we realize that travel into the future might never be possible? Or will we realize there is no limit on what can be achieved, and take on this ultimate challenge? Only time will tell.
Directory of Open Access Journals (Sweden)
Md. Nur Alam
2014-03-01
Full Text Available The new approach of generalized (G′/G-expansion method is significant, powerful and straightforward mathematical tool for finding exact traveling wave solutions of nonlinear evolution equations (NLEEs arise in the field of engineering, applied mathematics and physics. Dispersive effects due to microstructure of materials combined with nonlinearities give rise to solitary waves. In this article, the new approach of generalized (G′/G-expansion method has been applied to construct general traveling wave solutions of the strain wave equation in microstructured solids. Abundant exact traveling wave solutions including solitons, kink, periodic and rational solutions have been found. These solutions might play important role in engineering fields.
Longitudinal spread of mechanical excitation through tectorial membrane traveling waves.
Sellon, Jonathan B; Farrahi, Shirin; Ghaffari, Roozbeh; Freeman, Dennis M
2015-10-20
The mammalian inner ear separates sounds by their frequency content, and this separation underlies important properties of human hearing, including our ability to understand speech in noisy environments. Studies of genetic disorders of hearing have demonstrated a link between frequency selectivity and wave properties of the tectorial membrane (TM). To understand these wave properties better, we developed chemical manipulations that systematically and reversibly alter TM stiffness and viscosity. Using microfabricated shear probes, we show that (i) reducing pH reduces TM stiffness with little change in TM viscosity and (ii) adding PEG increases TM viscosity with little change in TM stiffness. By applying these manipulations in measurements of TM waves, we show that TM wave speed is determined primarily by stiffness at low frequencies and by viscosity at high frequencies. Both TM viscosity and stiffness affect the longitudinal spread of mechanical excitation through the TM over a broad range of frequencies. Increasing TM viscosity or decreasing stiffness reduces longitudinal spread of mechanical excitation, thereby coupling a smaller range of best frequencies and sharpening tuning. In contrast, increasing viscous loss or decreasing stiffness would tend to broaden tuning in resonance-based TM models. Thus, TM wave and resonance mechanisms are fundamentally different in the way they control frequency selectivity.
Energy Technology Data Exchange (ETDEWEB)
Moradi, Hamed; Cally, Paul S., E-mail: hamed.moradi@monash.edu [Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Clayton, Victoria 3800 (Australia)
2014-02-20
The rapid exponential increase in the Alfvén wave speed with height above the solar surface presents a serious challenge to physical modeling of the effects of magnetic fields on solar oscillations, as it introduces a significant Courant-Friedrichs-Lewy time-step constraint for explicit numerical codes. A common approach adopted in computational helioseismology, where long simulations in excess of 10 hr (hundreds of wave periods) are often required, is to cap the Alfvén wave speed by artificially modifying the momentum equation when the ratio between the Lorentz and hydrodynamic forces becomes too large. However, recent studies have demonstrated that the Alfvén wave speed plays a critical role in the MHD mode conversion process, particularly in determining the reflection height of the upwardly propagating helioseismic fast wave. Using numerical simulations of helioseismic wave propagation in constant inclined (relative to the vertical) magnetic fields we demonstrate that the imposition of such artificial limiters significantly affects time-distance travel times unless the Alfvén wave-speed cap is chosen comfortably in excess of the horizontal phase speeds under investigation.
Method of calculating tsunami travel times in the Andaman Sea region.
Kietpawpan, Monte; Visuthismajarn, Parichart; Tanavud, Charlchai; Robson, Mark G
2008-07-01
A new model to calculate tsunami travel times in the Andaman Sea region has been developed. The model specifically provides more accurate travel time estimates for tsunamis propagating to Patong Beach on the west coast of Phuket, Thailand. More generally, the model provides better understanding of the influence of the accuracy and resolution of bathymetry data on the accuracy of travel time calculations. The dynamic model is based on solitary wave theory, and a lookup function is used to perform bilinear interpolation of bathymetry along the ray trajectory. The model was calibrated and verified using data from an echosounder record, tsunami photographs, satellite altimetry records, and eyewitness accounts of the tsunami on 26 December 2004. Time differences for 12 representative targets in the Andaman Sea and the Indian Ocean regions were calculated. The model demonstrated satisfactory time differences (<2 min/h), despite the use of low resolution bathymetry (ETOPO2v2). To improve accuracy, the dynamics of wave elevation and a velocity correction term must be considered, particularly for calculations in the nearshore region.
A traveling wave decelerator for neutral polar molecules.
Meek, Samuel A; Parsons, Maxwell F; Heyne, Georg; Platschkowski, Viktor; Haak, Henrik; Meijer, Gerard; Osterwalder, Andreas
2011-09-01
Recently, a decelerator for neutral polar molecules has been presented that operates on the basis of macroscopic, three-dimensional, traveling electrostatic traps [A. Osterwalder, S. A. Meek, G. Hammer, H. Haak, and G. Meijer, Phys. Rev. A 81, 051401 (2010)]. In the present paper, a complete description of this decelerator is given, with emphasis on the electronics and the mechanical design. Experimental results showing the transverse velocity distributions of guided molecules are shown and compared to trajectory simulations. An assessment of non-adiabatic losses is made by comparing the deceleration signals from (13)CO with those from (12)CO and with simulated signals. © 2011 American Institute of Physics
Acoustic tweezing of particles using decaying opposing travelling surface acoustic waves (DOTSAW).
Ng, Jia Wei; Devendran, Citsabehsan; Neild, Adrian
2017-10-11
Surface acoustic waves offer a versatile and biocompatible method of manipulating the location of suspended particles or cells within microfluidic systems. The most common approach uses the interference of identical frequency, counter propagating travelling waves to generate a standing surface acoustic wave, in which particles migrate a distance less than half the acoustic wavelength to their nearest pressure node. The result is the formation of a periodic pattern of particles. Subsequent displacement of this pattern, the prerequisite for tweezing, can be achieved by translation of the standing wave, and with it the pressure nodes; this requires changing either the frequency of the pair of waves, or their relative phase. Here, in contrast, we examine the use of two counterpropagating traveling waves of different frequency. The non-linearity of the acoustic forces used to manipulate particles, means that a small frequency difference between the two waves creates a substantially different force field, which offers significant advantages. Firstly, this approach creates a much longer range force field, in which migration takes place across multiple wavelengths, and causes particles to be gathered together in a single trapping site. Secondly, the location of this single trapping site can be controlled by the relative amplitude of the two waves, requiring simply an attenuation of one of the electrical drive signals. Using this approach, we show that by controlling the powers of the opposing incoherent waves, 5 μm particles can be migrated laterally across a fluid flow to defined locations with an accuracy of ±10 μm.
Kolstrup, M. L.; Maupin, V.
2015-10-01
We present a data-processing routine to compute relative finite-frequency travel time residuals using a combination of the Iterative Cross-Correlation and Stack (ICCS) algorithm and the Multi-Channel Cross-Correlation method (MCCC). The routine has been tailored for robust measurement of P- and S-wave travel times in several frequency bands and for avoiding cycle-skipping problems at the shortest periods. We also investigate the adequacy of ray theory to calculate crustal corrections for finite-frequency regional tomography in normal continental settings with non-thinned crust. We find that ray theory is valid for both P and S waves at all relevant frequencies as long as the crust does not contain low-velocity layers associated with sediments at the surface. Reverberations in the sediments perturb the arrival times of the S waves and the long-period P waves significantly, and need to be accounted for in crustal corrections. The data-processing routine and crustal corrections are illustrated using data from a~network in southwestern Scandinavia.
van Wee, B.; Rietveld, P.; Meurs, H.
2006-01-01
Recent research suggests that the average time spent travelling by the Dutch population has increased over the past decades. However, different data sources show different levels of increase. This paper explores possible causes for this increase. They include a rise in incomes, which has probably
Consequences of mixing assumptions for time-variable travel time distributions
Velde, van der Y.; Heidbüchel, I.; Lyon, S.W.; Nyberg, L.; Rodhe, A.; Bishop, K.; Troch, P.A.
2015-01-01
The current generation of catchment travel time distribution (TTD) research, integrating nearly three decades of work since publication of Water's Journey from Rain to Stream, seeks to represent the full distribution in catchment travel times and its temporal variability. Here, we compare
On exact traveling-wave solutions for local fractional Korteweg-de Vries equation
Yang, Xiao-Jun; Tenreiro Machado, J. A.; Baleanu, Dumitru; Cattani, Carlo
2016-08-01
This paper investigates the Korteweg-de Vries equation within the scope of the local fractional derivative formulation. The exact traveling wave solutions of non-differentiable type with the generalized functions defined on Cantor sets are analyzed. The results for the non-differentiable solutions when fractal dimension is 1 are also discussed. It is shown that the exact solutions for the local fractional Korteweg-de Vries equation characterize the fractal wave on shallow water surfaces.
Wintucky, Edwin G.; Simons, Rainee N.
2014-01-01
This paper presents the design, fabrication and test results for a novel waveguide multimode directional coupler (MDC). The coupler fabricated from two dissimilar waveguides is capable of isolating the power at the second harmonic frequency from the fundamental power at the output port of a traveling-wave tube (TWT). In addition to accurate power measurements at harmonic frequencies, a potential application of the MDC is in the design of a beacon source for atmospheric propagation studies at millimeter-wave frequencies.
On exact traveling-wave solutions for local fractional Korteweg-de Vries equation.
Yang, Xiao-Jun; Tenreiro Machado, J A; Baleanu, Dumitru; Cattani, Carlo
2016-08-01
This paper investigates the Korteweg-de Vries equation within the scope of the local fractional derivative formulation. The exact traveling wave solutions of non-differentiable type with the generalized functions defined on Cantor sets are analyzed. The results for the non-differentiable solutions when fractal dimension is 1 are also discussed. It is shown that the exact solutions for the local fractional Korteweg-de Vries equation characterize the fractal wave on shallow water surfaces.
Real-time travel time prediction framework for departure time and route advice
Calvert, S.C.; Snelder, M.; Bakri, T.; Heijligers, B.; Knoop, V.L.
2015-01-01
Heavily used urban networks remain a challenge for travel time prediction because traffic flow is rarely homogeneous and is also subject to a wide variety of disturbances. Various models, some of which use traffic flow theory and some of which are data driven, have been developed to predict traffic
Travelling wave solutions to nonlinear physical models by means of ...
Indian Academy of Sciences (India)
NPDEs is an important and attractive research area. Not all NPDEs are integrable. For ... Thus, based on the qualitative theory of ordinary differential equations. [22], if we can find a single first .... Equation (29) has appeared in the study of qualitative behaviours of wave-breaking [27,. 28]. A peaked solution of the form u(x, ...
Exact travelling wave solutions for some important nonlinear ...
Indian Academy of Sciences (India)
problems. More precisely, there is no unified method that can be used to handle all types of nonlinear problems. A powerful and effective method for finding exact ... Explicit solutions to nonlinear problems are of fundamental importance. ... fluid dynamics, fluid flow, quantum field theory, electromagnetic waves and so on [7].
A generic travelling wave solution in dissipative laser cavity
Indian Academy of Sciences (India)
2016-09-09
Sep 9, 2016 ... of solutions have been reported for the generalized. CGLE. In addition to stable stationary solutions, exact periodic and blow-up solutions have been derived using the homogeneous balance principle and Jacobi elliptic function. Peculiar results like periodic kink wave solu- tions, have been reported in ref.
National Research Council Canada - National Science Library
Osagie, Abel U; Nawawi, Mohd; Khalil, Amin Esmail; Abdullah, Khiruddin
We have investigated the average P-wave travel-time residuals for some stations around Southern Thailand, Peninsular Malaysia and Singapore at regional distances. Six years (January, 2010–December, 2015...
Travelling-wave amplitudes as solutions of the phase-field crystal equation
Nizovtseva, I. G.; Galenko, P. K.
2018-01-01
The dynamics of the diffuse interface between liquid and solid states is analysed. The diffuse interface is considered as an envelope of atomic density amplitudes as predicted by the phase-field crystal model (Elder et al. 2004 Phys. Rev. E 70, 051605 (doi:10.1103/PhysRevE.70.051605); Elder et al. 2007 Phys. Rev. B 75, 064107 (doi:10.1103/PhysRevB.75.064107)). The propagation of crystalline amplitudes into metastable liquid is described by the hyperbolic equation of an extended Allen-Cahn type (Galenko & Jou 2005 Phys. Rev. E 71, 046125 (doi:10.1103/PhysRevE.71.046125)) for which the complete set of analytical travelling-wave solutions is obtained by the http://www.w3.org/1999/xlink" xlink:href="RSTA20170202IM1"/> method (Malfliet & Hereman 1996 Phys. Scr. 15, 563-568 (doi:10.1088/0031-8949/54/6/003); Wazwaz 2004 Appl. Math. Comput. 154, 713-723 (doi:10.1016/S0096-3003(03)00745-8)). The general http://www.w3.org/1999/xlink" xlink:href="RSTA20170202IM2"/> solution of travelling waves is based on the function of hyperbolic tangent. Together with its set of particular solutions, the general http://www.w3.org/1999/xlink" xlink:href="RSTA20170202IM3"/> solution is analysed within an example of specific task about the crystal front invading metastable liquid (Galenko et al. 2015 Phys. D 308, 1-10 (doi:10.1016/j.physd.2015.06.002)). The influence of the driving force on the phase-field profile, amplitude velocity and correlation length is investigated for various relaxation times of the gradient flow. This article is part of the theme issue `From atomistic interfaces to dendritic patterns'.
Spreading Speed, Traveling Waves, and Minimal Domain Size in Impulsive Reaction–Diffusion Models
Lewis, Mark A.
2012-08-15
How growth, mortality, and dispersal in a species affect the species\\' spread and persistence constitutes a central problem in spatial ecology. We propose impulsive reaction-diffusion equation models for species with distinct reproductive and dispersal stages. These models can describe a seasonal birth pulse plus nonlinear mortality and dispersal throughout the year. Alternatively, they can describe seasonal harvesting, plus nonlinear birth and mortality as well as dispersal throughout the year. The population dynamics in the seasonal pulse is described by a discrete map that gives the density of the population at the end of a pulse as a possibly nonmonotone function of the density of the population at the beginning of the pulse. The dynamics in the dispersal stage is governed by a nonlinear reaction-diffusion equation in a bounded or unbounded domain. We develop a spatially explicit theoretical framework that links species vital rates (mortality or fecundity) and dispersal characteristics with species\\' spreading speeds, traveling wave speeds, as well as minimal domain size for species persistence. We provide an explicit formula for the spreading speed in terms of model parameters, and show that the spreading speed can be characterized as the slowest speed of a class of traveling wave solutions. We also give an explicit formula for the minimal domain size using model parameters. Our results show how the diffusion coefficient, and the combination of discrete- and continuous-time growth and mortality determine the spread and persistence dynamics of the population in a wide variety of ecological scenarios. Numerical simulations are presented to demonstrate the theoretical results. © 2012 Society for Mathematical Biology.
Estimation of Bimodal Urban Link Travel Time Distribution and Its Applications in Traffic Analysis
Directory of Open Access Journals (Sweden)
Yuxiong Ji
2015-01-01
Full Text Available Vehicles travelling on urban streets are heavily influenced by traffic signal controls, pedestrian crossings, and conflicting traffic from cross streets, which would result in bimodal travel time distributions, with one mode corresponding to travels without delays and the other travels with delays. A hierarchical Bayesian bimodal travel time model is proposed to capture the interrupted nature of urban traffic flows. The travel time distributions obtained from the proposed model are then considered to analyze traffic operations and estimate travel time distribution in real time. The advantage of the proposed bimodal model is demonstrated using empirical data, and the results are encouraging.
Köpp-Junk, Heidi
2013-01-01
Travel was a crucial element of ancient Egyptian culture. An extensive traffic system by land and by water already existed as early as the Old Kingdom, including various means of transport that did not fundamentally change right through to the New Kingdom. Traveling activity attested for various professions demonstrates that Egyptian society exercised a high degree of mobility. In the majority of cases, a journey was undertaken within the scope of the traveler’s work and on behalf of the phar...
Seismic model of Mars. 2. Free oscillations and travel times
Gudkova, Tamara; Lognonne, Philippe; Raevskiy, Sergey; Zharkov, Vladimir
When constructing an interior structure model of a planet, it is common used method to describe the model by a restricted set of parameters: the thickness of the crust, the location of phase transitions, the core radius. The variation of these parameters originates from the uncertainties in temperature profile, composition, elastic and anelastic properties of relevant minerals. Water content should also be considered as a compositional variable in the mantle. Olivine and its high pressure phases, wadsleyite and ringwoodite are particularly important as they constitute about 60 wt% of the Martian mantle and have probably large capacity for water in the Martian mantle (Zharkov and Gudkova, 2014). At present Mars’ internal density distribution is constrained by the recent estimates of the moment of inertia and the Love number k _{2} (Konoplive et al., 2011). Below we use the data from Earth studies and laboratory data (Mao et al., 2010, 2011, 2012,extrapolated for P-T conditions in Mars, and show how the admixture of water in the main Martian minerals influences velocity drops at phase transition boundaries in Martian interiors and study the effects of hydration on the periods of free oscillations and travel times for P, PcP, S, ScS waves , which could serve as additional constraints, if upcoming seismic experiments are successful, as they can potentially constrain mantle composition and make more precise the location of transition zones. It is of importance to determine the depth of the phase transitions in the mantle, as it will fix the temperature profile in Mars. Our analysis is based on a trial seismic model M14_3 from (Zharkov et al., 2009). The crust is 50 km thick (with density of 2.9 g/cm (3) ), the molar ratio Fe/(Fe+Mg) in the mantle is 0.20, the Fe-Ni core contains 70 mol % H in addition to 14 wt % S with radius of 1800 km. The bulk Fe/Si ratio is close to chondritic 1.7. The upper mantle extends down to 1590 km depth. Olivine-wadsleite transition zone
Investigating the distribution of the value of travel time savings
DEFF Research Database (Denmark)
Fosgerau, Mogens
2006-01-01
The distribution of the value of travel time savings (VTTS) is investigated employing various nonparametric techniques to a large dataset originating from a stated choice experiment. The data contain choices between a fast and more expensive alternative and a slow and less expensive alternative....... Increasing the implicit price of time leads to an increased share of respondents who decline to pay to save time. But a significant proportion of respondents, 13%, remain willing to pay to save time at the highest price of time in the design. This means that the right tail of the VTTS distribution...
On the income elasticity of the value of travel time
DEFF Research Database (Denmark)
Börjesson, Maria; Fosgerau, Mogens; Algers, Staffan
2012-01-01
Transport infrastructure is long-term and in appraisal it is necessary to value travel time savings for future years. This requires knowing how the value of time (VTT) will develop over time as incomes grow. This paper investigates if the cross-sectional income elasticity of the VTT is equal...... to inter-temporal income elasticity. The study is based on two identical stated choice experiments conducted with a 13 year interval. Results indicate that the relationship between income and the VTT in the cross-section has remained unchanged over time. As a consequence, the inter-temporal income...... be expected to increase further over time....
Baconneau, O.; van den Berg, G.J.B.; Brauner, C.-M.; Hulshof, J.
2004-01-01
We study travelling wave solutions of a one-dimensional two-phase Free Boundary Problem, which models premixed flames propagating in a gaseous mixture with dust. The model combines diffusion of mass and temperature with reaction at the flame front, the reaction rate being temperature dependent. The
The traveling-wave amplifier model of the cochlea adapted to dolphins
DEFF Research Database (Denmark)
Andersen, Lars Nonboe; Au, W.W.L.
1999-01-01
The traveling-wave amplifier (TWA) model of the cochlea [A. Hubbard, Science 259, 68–71 (1993)] has been shown to produce outputs that compare quite well with experimental data. A TWA model with parameters adjusted to fit the physiological properties of the dolphin cochlea was used as part...
Measurements on the SPS 200 MHz Travelling Wave Cavity towards an Impedance Model
Roggen, Toon; Caspers, Fritz; Vollinger, Christine; CERN. Geneva. ATS Department
2016-01-01
This note discusses the contribution of the SPS 200 MHz TWC (Travelling Wave Cavity) to the SPS longitudinal impedance model. The measurement method and setup is briefly explained and a comparison with simulations is discussed for both the fundamental pass band (FPB) as well as the Higher Order Modes (HOMs). In addition a number of improvements to the measurement setup are discussed.
Non-monotonic Travelling Wave Fronts in a System of Fractional Flow Equations from Porous Media
Zegeling, P.A.; Hönig, O.; Doster, F.; Hilfer, R.
2016-01-01
Motivated by observations of saturation overshoot, this article investigates generic classes of smooth travelling wave solutions of a system of two coupled nonlinear parabolic partial differential equations resulting from a flux function of high symmetry. All boundary resp. limit value problems of
A New Scheme for Experimental-Based Modeling of a Traveling Wave Ultrasonic Motor
DEFF Research Database (Denmark)
Mojallali, Hamed; Amini, R.; Izadi-Zamanabadi, Roozbeh
2005-01-01
In this paper, a new method for equivalent circuit modeling of a traveling wave ultrasonic motor is presented. The free stator of the motor is modeled by an equivalent circuit containing complex circuit elements. A systematic approach for identifying the elements of the equivalent circuit...
Electromagnetic Excitation of a Thin Wire: A traveling-Wave Approach
Bogerd, J.C.; Tijhuis, A.G.; Klaasen, J.J.A.
1998-01-01
An approximate representation for the current along a perfectly conducting straight thin wire is presented. The current is approximated in terms of pulsed waves that travel along the wire with the velocity of the exterior medium. At the ends of the wire, these pulses are partially reflected, with a
Periodic travelling waves in a non-integrable one-dimensional lattice
Valkering, T.P.
1982-01-01
The existence of a one-parameter family of periodic solutions representing longitudinal travelling waves is established for a one-dimensional lattice of identical particles with nearest-neighbour interaction. The potential is not given in closed form but is specified by only a few global properties.
The SPS acceleration system travelling wave drift-tube structure for the CERN SPS
Dôme, Georges
1976-01-01
The SPS accelerating structure is essentially a high energy proton linac, except for a small frequency swing during the acceleration cycle. It is operated almost CW with a travelling wave giving an energy gain around 0.1 MeV/m. The guide-lines for the design of such a structure are explained, and practical solutions are described. (3 refs).
Transverse kick in misaligned traveling wave structures driven at the fundamental mode
Energy Technology Data Exchange (ETDEWEB)
Whittum, D.H. [Stanford Univ., CA (US). Stanford Linear Accelerator Center; Henke, H. [Technical Univ. Berlin (Germany)
1998-04-01
Fabrication errors in traveling wave structures result in non-axisymmetric RF fields that couple to the rf drive at the fundamental mode frequency. The authors calculate the excitation of the dipole mode and the integrated effect on the beam, using the thin iris and small hole approximation.
Microwave heating offers a number of advantages over conventional heating methods, such as, rapid and volumetric heating, precise temperature control, energy efficiency and lower temperature gradient. In this article we demonstrate the use of 2450 MHz microwave traveling wave reactor to heat the cat...
Travelling waves for a Frenkel-Kontorova chain
Buffoni, Boris; Schwetlick, Hartmut; Zimmer, Johannes
2017-08-01
In this article, the Frenkel-Kontorova model for dislocation dynamics is considered, where the on-site potential consists of quadratic wells joined by small arcs, which can be spinodal (concave) as commonly assumed in physics. The existence of heteroclinic waves-making a transition from one well of the on-site potential to another-is proved by means of a Schauder fixed point argument. The setting developed here is general enough to treat such a Frenkel-Kontorova chain with smooth (C2) on-site potential. It is shown that the method can also establish the existence of two-transition waves for a piecewise quadratic on-site potential.
Renteria Marquez, I A; Bolborici, V
2017-05-01
This manuscript presents a method to model in detail the piezoelectric traveling wave rotary ultrasonic motor (PTRUSM) stator response under the action of DC and AC voltages. The stator is modeled with a discrete two dimensional system of equations using the finite volume method (FVM). In order to obtain accurate results, a model of the stator bridge is included into the stator model. The model of the stator under the action of DC voltage is presented first, and the results of the model are compared versus a similar model using the commercial finite element software COMSOL Multiphysics. One can observe that there is a difference of less than 5% between the displacements of the stator using the proposed model and the one with COMSOL Multiphysics. After that, the model of the stator under the action of AC voltages is presented. The time domain analysis shows the generation of the traveling wave in the stator surface. One can use this model to accurately calculate the stator surface velocities, elliptical motion of the stator surface and the amplitude and shape of the stator traveling wave. A system of equations discretized with the finite volume method can easily be transformed into electrical circuits, because of that, FVM may be a better choice to develop a model-based control strategy for the PTRUSM. Copyright © 2017 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
Dong Wang
2015-01-01
Full Text Available The traditional polarity comparison based travelling wave protection, using the initial wave information, is affected by initial fault angle, bus structure, and external fault. And the relationship between the magnitude and polarity of travelling wave is ignored. Because of the protection tripping and malfunction, the further application of this protection principle is affected. Therefore, this paper presents an ultra-high-speed travelling wave protection using integral based polarity comparison principle. After empirical mode decomposition of the original travelling wave, the first-order intrinsic mode function is used as protection object. Based on the relationship between the magnitude and polarity of travelling wave, this paper demonstrates the feasibility of using travelling wave magnitude which contains polar information as direction criterion. And the paper integrates the direction criterion in a period after fault to avoid wave head detection failure. Through PSCAD simulation with the typical 500 kV transmission system, the reliability and sensitivity of travelling wave protection were verified under different factors’ affection.
Time machine tales the science fiction adventures and philosophical puzzles of time travel
Nahin, Paul J
2017-01-01
This book contains a broad overview of time travel in science fiction, along with a detailed examination of the philosophical implications of time travel. The emphasis of this book is now on the philosophical and on science fiction, rather than on physics, as in the author's earlier books on the subject. In that spirit there are, for example, no Tech Notes filled with algebra, integrals, and differential equations, as there are in the first and second editions of TIME MACHINES. Writing about time travel is, today, a respectable business. It hasn’t always been so. After all, time travel, prima facie, appears to violate a fundamental law of nature; every effect has a cause, with the cause occurring before the effect. Time travel to the past, however, seems to allow, indeed to demand, backwards causation, with an effect (the time traveler emerging into the past as he exits from his time machine) occurring before its cause (the time traveler pushing the start button on his machine’s control panel to start his...
Test plan : Branson TRIP travel time/data accuracy
1998-06-01
The Branson Travel and Recreational Information Program (TRIP) in Branson, Missouri, and the I-40 Traveler and Tourist Information System (TTIS) in the I-40 corridor of Northern Arizona are two Field Operational Tests (FOTs) of Traveler Information S...
Traveling-wave-tube simulation: The IBC (Interactive Beam-Circuit) code
Energy Technology Data Exchange (ETDEWEB)
Morey, I.J.; Birdsall, C.K.
1989-09-26
Interactive Beam-Circuit (IBC) is a one-dimensional many particle simulation code which has been developed to run interactively on a PC or Workstation, and displaying most of the important physics of a traveling-wave-tube. The code is a substantial departure from previous efforts, since it follows all of the particles in the tube, rather than just those in one wavelength, as commonly done. This step allows for nonperiodic inputs in time, a nonuniform line and a large set of spatial diagnostics. The primary aim is to complement a microwave tube lecture course, although past experience has shown that such codes readily become research tools. Simple finite difference methods are used to model the fields of the coupled slow-wave transmission line. The coupling between the beam and the transmission line is based upon the finite difference equations of Brillouin. The space-charge effects are included, in a manner similar to that used by Hess; the original part is use of particle-in-cell techniques to model the space-charge fields. 11 refs., 11 figs.
Quantifying catchment-scale mixing and its effect on time-varying travel time distributions
Velde, van der Y.; Torfs, P.J.J.F.; Zee, van der S.E.A.T.M.; Uijlenhoet, R.
2012-01-01
Travel time distributions are often used to characterize catchment discharge behavior, catchment vulnerability to pollution and pollutant loads from catchments to downstream waters. However, these distributions vary with time because they are a function of rainfall and evapotranspiration. It is
Quantifying catchment-scale mixing and its effects on time varying travel time distributions
Velde, Y. van der; Torfs, P.J.J.F.; Zee, S.E.A.T.M. van der; Uijlenhoet, R.
2012-01-01
Travel time distributions are often used to characterize catchment discharge behavior, catchment vulnerability to pollution and pollutant loads from catchments to downstream waters. However, these distributions vary with time because they are a function of rainfall and evapotranspiration. It is
Congestion relief by travel time minimization in near real time : Detroit area I-75 corridor study.
2008-12-01
"This document summarizes the activities concerning the project: Congestion Relief by : Travel Time Minimization in Near Real Time -- Detroit Area I-75 Corridor Study since : the inception of the project (Nov. 22, 2006 through September 30, 2008). : ...
Tao, Zhi-Fu; Han, Zhong-Ling; Yao, Meng
2011-01-01
Using the difference of dielectric constant between malignant tumor tissue and normal breast tissue, breast tumor microwave sensor system (BRATUMASS) determines the detected target of imaging electromagnetic trait by analyzing the properties of target tissue back wave obtained after near-field microwave radicalization (conelrad). The key of obtained target properties relationship and reconstructed detected space is to analyze the characteristics of the whole process from microwave transmission to back wave reception. Using traveling wave method, we derive spatial transmission properties and the relationship of the relation detected points distances, and valuate the properties of each unit by statistical valuation theory. This chapter gives the experimental data analysis results.
A Regional Seismic Travel Time Model for North America
2010-09-01
ocean (thin crust) to approximately 200 km in regions of thick crust. Because the goal of this work is to produce a model for Pn travel-time...on Q crustal layers l = length of the ray path in a specified crustal layer (determined by layer thickness and ray parameter in Equations (2) and...far- regional distances when rays dive into the mantle and preferentially channel through the high-velocity ocean lithosphere . RSTT captures this
Change of Measure between Light Travel Time and Euclidean Distances
Directory of Open Access Journals (Sweden)
Heymann Y.
2013-04-01
Full Text Available The problem of cosmological distances is approached using a method based on the propagation of light in an expanding Universe. From the chan ge of measure between Light Travel Time and Euclidean Distances, a formula is deri ved to compute distances as a function of redshift. This formula is identical to Matti g’s formula (with q 0 = 1 / 2 which is based on Friedmann’s equations of general relativi ty.
Traveling wave solutions of the nonlinear Schrödinger equation
Akbari-Moghanjoughi, M.
2017-10-01
In this paper, we investigate the traveling soliton and the periodic wave solutions of the nonlinear Schrödinger equation (NLSE) with generalized nonlinear functionality. We also explore the underlying close connection between the well-known KdV equation and the NLSE. It is remarked that both one-dimensional KdV and NLSE models share the same pseudoenergy spectrum. We also derive the traveling wave solutions for two cases of weakly nonlinear mathematical models, namely, the Helmholtz and the Duffing oscillators' potentials. It is found that these models only allow gray-type NLSE solitary propagations. It is also found that the pseudofrequency ratio for the Helmholtz potential between the nonlinear periodic carrier and the modulated sinusoidal waves is always in the range 0.5 ≤ Ω/ω ≤ 0.537285 regardless of the potential parameter values. The values of Ω/ω = {0.5, 0.537285} correspond to the cnoidal waves modulus of m = {0, 1} for soliton and sinusoidal limits and m = 0.5, respectively. Moreover, the current NLSE model is extended to fully NLSE (FNLSE) situation for Sagdeev oscillator pseudopotential which can be derived using a closed set of hydrodynamic fluid equations with a fully integrable Hamiltonian system. The generalized quasi-three-dimensional traveling wave solution is also derived. The current simple hydrodynamic plasma model may also be generalized to two dimensions and other complex situations including different charged species and cases with magnetic or gravitational field effects.
Model Passengers’ Travel Time for Conventional Bus Stop
Directory of Open Access Journals (Sweden)
Guangzhao Xin
2014-01-01
Full Text Available Limited number of berths can result in a subsequent bus stopping at the upstream of a bus stop when all berths are occupied. When this traffic phenomenon occurs, passengers waiting on the platform usually prefer walking to the stopped bus, which leads to additional walking time before boarding the bus. Therefore, passengers’ travel time consumed at a bus stop is divided into waiting time, additional walking time, and boarding time. This paper proposed a mathematical model for analyzing passengers’ travel time at conventional bus stop based on theory of stochastic service system. Field-measured and simulated data were designated to demonstrate the effectiveness of the proposed model. By analyzing the results, conclusion was conducted that short headway can reduce passengers’ waiting time at bus stop. Meanwhile, the theoretical analysis explained the inefficiency of bus stops with more than three berths from the perspective of passengers’ additional walking time. Additional walking time will increase in a large scale when the number of berths at a bus stop exceedsthe threshold of three.
Duvall, Thomas L.; Liang, Zhi-Chao; Birch, Aaron; Gizon, Laurent; Schou, Jesper
2017-08-01
Time-distance helioseismology is one of the primary tools for studying the solar meridional circulation. However, travel-time measurements of the subsurface meridional flow suffer from a variety of systematic errors, such as a center-to-limb variation and an offset due to the P-angle uncertainty of solar images. Here we apply the time-distance technique to contemporaneous medium-degree Dopplergrams produced by SOHO/MDI and SDO/HMI to obtain the travel-time difference caused by meridional circulation throughout the solar convection zone. The P-angle offset in MDI images is measured by cross-correlating MDI and HMI images. The travel-time measurements in the south-north and east-west directions are averaged over the same observation period for the two data sets and then compared to examine the consistency of MDI and HMI travel times after correcting the systematic errors.The offsets in the south-north travel-time difference from MDI data induced by the P-angle error gradually diminish with increasing travel distance. However, these offsets become noisy for travel distances corresponding to waves that reach the base of the convection zone. This suggests that a careful treatment of the P-angle problem is required when studying a deep meridional flow. After correcting the P-angle and the removal of the center-to-limb effect, the travel-time measurements from MDI and HMI are consistent within the error bars for meridional circulation covering the entire convection zone. The fluctuations observed in both data sets are highly correlated and thus indicate their solar origin rather than an instrumental origin. Although our results demonstrate that the ad hoc correction is capable of reducing the wide discrepancy in the travel-time measurements from MDI and HMI, we cannot exclude the possibility that there exist other systematic effects acting on the two data sets in the same way.
Control of traveling-wave oscillations and bifurcation behavior in central pattern generators.
Landsman, Alexandra S; Slotine, Jean-Jacques
2012-10-01
Understanding synchronous and traveling-wave oscillations, particularly as they relate to transitions between different types of behavior, is a central problem in modeling biological systems. Here, we address this problem in the context of central pattern generators (CPGs). We use contraction theory to establish the global stability of a traveling-wave or synchronous oscillation, determined by the type of coupling. This opens the door to better design of coupling architectures to create the desired type of stable oscillations. We then use coupling that is both amplitude and phase dependent to create either globally stable synchronous or traveling-wave solutions. Using the CPG motor neuron network of a leech as an example, we show that while both traveling and synchronous oscillations can be achieved by several types of coupling, the transition between different types of behavior is dictated by a specific coupling architecture. In particular, it is only the "repulsive" but not the commonly used phase or rotational coupling that can explain the transition to high-frequency synchronous oscillations that have been observed in the heartbeat pattern generator of a leech. This shows that the overall dynamics of a CPG can be highly sensitive to the type of coupling used, even for coupling architectures that are widely believed to produce the same qualitative behavior.
Human seizures couple across spatial scales through travelling wave dynamics
Martinet, L.-E.; Fiddyment, G.; Madsen, J. R.; Eskandar, E. N.; Truccolo, W.; Eden, U. T.; Cash, S. S.; Kramer, M. A.
2017-04-01
Epilepsy--the propensity toward recurrent, unprovoked seizures--is a devastating disease affecting 65 million people worldwide. Understanding and treating this disease remains a challenge, as seizures manifest through mechanisms and features that span spatial and temporal scales. Here we address this challenge through the analysis and modelling of human brain voltage activity recorded simultaneously across microscopic and macroscopic spatial scales. We show that during seizure large-scale neural populations spanning centimetres of cortex coordinate with small neural groups spanning cortical columns, and provide evidence that rapidly propagating waves of activity underlie this increased inter-scale coupling. We develop a corresponding computational model to propose specific mechanisms--namely, the effects of an increased extracellular potassium concentration diffusing in space--that support the observed spatiotemporal dynamics. Understanding the multi-scale, spatiotemporal dynamics of human seizures--and connecting these dynamics to specific biological mechanisms--promises new insights to treat this devastating disease.
Travel time and concurrent-schedule choice: retrospective versus prospective control.
Davison, M; Elliffe, D
2000-01-01
Six pigeons were trained on concurrent variable-interval schedules in which two different travel times between alternatives, 4.5 and 0.5 s, were randomly arranged. In Part 1, the next travel time was signaled while the subjects were responding on each alternative. Generalized matching analyses of performance in the presence of the two travel-time signals showed significantly higher response and time sensitivity when the longer travel time was signaled compared to when the shorter time was sig...
Theory of fads: Traveling-wave solution of evolutionary dynamics in a one-dimensional trait space
Lee, Mi Jin; Yi, Su Do; Kim, Beom Jun; Baek, Seung Ki
2015-01-01
We consider an infinite-sized population where an infinite number of traits compete simultaneously. The replicator equation with a diffusive term describes time evolution of the probability distribution over the traits due to selection and mutation on a mean-field level. We argue that this dynamics can be expressed as a variant of the Fisher equation with high-order correction terms. The equation has a traveling-wave solution, and the phase-space method shows how the wave shape depends on the correction. We compare this solution with empirical time-series data of given names in Quebec, treating it as a descriptive model for the observed patterns. Our model explains the reason that many names exhibit a similar pattern of the rise and fall as time goes by. At the same time, we have found that their dissimilarities are also statistically significant.
Theory of fads: traveling-wave solution of evolutionary dynamics in a one-dimensional trait space.
Lee, Mi Jin; Yi, Su Do; Kim, Beom Jun; Baek, Seung Ki
2015-01-01
We consider an infinite-sized population where an infinite number of traits compete simultaneously. The replicator equation with a diffusive term describes time evolution of the probability distribution over the traits due to selection and mutation on a mean-field level. We argue that this dynamics can be expressed as a variant of the Fisher equation with high-order correction terms. The equation has a traveling-wave solution, and the phase-space method shows how the wave shape depends on the correction. We compare this solution with empirical time-series data of given names in Quebec, treating it as a descriptive model for the observed patterns. Our model explains the reason that many names exhibit a similar pattern of the rise and fall as time goes by. At the same time, we have found that their dissimilarities are also statistically significant.
Time series analysis of travel trends in Vermont
Varna M. Ramaswamy; Walter F. Kuentzel
1995-01-01
Vermont's travel and tourism industry is not keeping pace with the nation-wide growth in the travel industry. While travel indicators such as domestic travel expenditures, tourism generated employment, payroll and tax receipts have been steadily increasing across the United States, these indicators in Vermont peaked in 1978 and have declined ever since. The state...
Deng, Gao-Fu; Gao, Yi-Tian
2017-06-01
Under investigation in this paper is a generalized (3+1)-dimensional varible-coefficient nonlinear-wave equation, which has been presented for nonlinear waves in liquid with gas bubbles. The bilinear form, Bäcklund transformation, Lax pair and infinitely-many conservation laws are obtained via the binary Bell polynomials. One-, two- and three-soliton solutions are generated by virtue of the Hirota method. Travelling-wave solutions are derived with the aid of the polynomial expansion method. The one-periodic wave solutions are constructed by the Hirota-Riemann method. Discussions among the soliton, periodic- and travelling-wave solutions are presented: I) the soliton velocities are related to the variable coefficients, while the soliton amplitudes are unaffected; II) the interaction between the solitons is elastic; III) there are three cases of the travelling-wave solutions, i.e., the triangle-type periodical, bell-type and soliton-type travelling-wave solutions, while we notice that bell-type travelling-wave solutions can be converted into one-soliton solutions via taking suitable parameters; IV) the one-periodic waves approach to the solitary waves under some conditions and can be viewed as a superposition of overlapping solitary waves, placed one period apart.
Using prospect theory to investigate the low value of travel time for small time changes
DEFF Research Database (Denmark)
Hjorth, Katrine; Fosgerau, Mogens
A common finding in stated preference studies that measure the value of travel time (VTT), is that the measured per-minute VTT increases with the size of the time change considered, in conflict with standard neoclassical theory. The current paper tests prospect theory as a possible explanation...... time and money that pro- vide identification of the degrees of diminishing sensitivity for time and money gains and losses, thus enabling us to test and potentially falsify the prospect theory explanation. We apply a discrete choice model, in which choice depends on a reference-free value of travel......: More specifically, whether the phenomenon is generated by preferences being reference-dependent and exhibiting diminishing sensitivity for gains and losses, with a stronger degree of diminishing sensitivity for money than for travel time. We use stated preference data with trade-offs between travel...
Traveling Wave RF Systems for Helical Cooling Channels
Yonehara, K; Moretti, A; Popovic, M; Romanov, G; Neubauer, M; Johnson, R P; Thorndahl, L
2010-01-01
The great advantage of the helical ionization cooling channel (HCC) is its compact structure that enables the fast cooling of muon beam 6-dimensional phase space. This compact aspect requires a high average RF gradient, with few places that do not have cavities. Also, the muon beam is diffuse and requires an RF system with large transverse and longitudinal acceptance. A traveling wave system can address these requirements. First, the number of RF power coupling ports can be significantly reduced compared with our previous pillbox concept. Secondly, by adding a nose on the cell iris, the presence of thin metal foils traversed by the muons can possibly be avoided. We show simulations of the cooling performance of a traveling wave RF system in a HCC, including cavity geometries with inter-cell RF power couplers needed for power propagation.
MOHO ORIENTATION BENEATH CENTRAL CALIFORNIA FROM REGIONAL EARTHQUAKE TRAVEL TIMES.
Oppenheimer, David H.; Eaton, Jerry P.
1984-01-01
This paper examines relative Pn arrival times, recorded by the U. S. Geological Survey seismic network in central and northern California from an azimuthally distributed set of regional earthquakes. Improved estimates are presented of upper mantle velocities in the Coast Ranges, Great Valley, and Sierra Nevada foothills and estimates of the orientation of the Moho throughout this region. Finally, the azimuthal distribution of apparent velocities, corrected for dip and individual station travel time effects, is then studied for evidence of upper mantle velocity anisotropy and for indications of lower crustal structure in central California.
Kim, Hugh I.; Kim, Hyungjun; Pang, Eric S.; Ryu, Ernest K.; Beegle, Luther W.; Loo, Joseph A.; Goddard, William A.; Kanik, Isik
2009-01-01
A number of phosphatidylcholine (PC) cations spanning a mass range of 400 to 1000 Da are investigated using electrospray ionization mass spectrometry coupled with traveling wave ion mobility spectrometry (TWIMS). A high correlation between mass and mobility is demonstrated with saturated phosphatidylcholine cations in N2. A significant deviation from this mass-mobility correlation line is observed for the unsaturated PC cation. We found that the double bond in the acyl chain causes a 5% reduction in drift time. The drift time is reduced at a rate of ~1% for each additional double bond. Theoretical collision cross sections of PC cations exhibit good agreement with experimentally evaluated values. Collision cross sections are determined using the recently derived relationship between mobility and drift time in TWIMS stacked ring ion guide (SRIG) and compared to estimate collision cross-sections using empiric calibration method. Computational analysis was performed using the modified trajectory (TJ) method with nonspherical N2 molecules as the drift gas. The difference between estimated collision cross-sections and theoretical collision cross-sections of PC cations is related to the sensitivity of the PC cation collision cross-sections to the details of the ion-neutral interactions. The origin of the observed correlation and deviation between mass and mobility of PC cations is discussed in terms of the structural rigidity of these molecules using molecular dynamic simulations. PMID:19764704
Directory of Open Access Journals (Sweden)
Philippe Saltiel
2017-12-01
Full Text Available The central pattern generator (CPG architecture for rhythm generation remains partly elusive. We compare cat and frog locomotion results, where the component unrelated to pattern formation appears as a temporal grid, and traveling wave respectively. Frog spinal cord microstimulation with N-methyl-D-Aspartate (NMDA, a CPG activator, produced a limited set of force directions, sometimes tonic, but more often alternating between directions similar to the tonic forces. The tonic forces were topographically organized, and sites evoking rhythms with different force subsets were located close to the constituent tonic force regions. Thus CPGs consist of topographically organized modules. Modularity was also identified as a limited set of muscle synergies whose combinations reconstructed the EMGs. The cat CPG was investigated using proprioceptive inputs during fictive locomotion. Critical points identified both as abrupt transitions in the effect of phasic perturbations, and burst shape transitions, had biomechanical correlates in intact locomotion. During tonic proprioceptive perturbations, discrete shifts between these critical points explained the burst durations changes, and amplitude changes occurred at one of these points. Besides confirming CPG modularity, these results suggest a fixed temporal grid of anchoring points, to shift modules onsets and offsets. Frog locomotion, reconstructed with the NMDA synergies, showed a partially overlapping synergy activation sequence. Using the early synergy output evoked by NMDA at different spinal sites, revealed a rostrocaudal topographic organization, where each synergy is preferentially evoked from a few, albeit overlapping, cord regions. Comparing the locomotor synergy sequence with this topography suggests that a rostrocaudal traveling wave would activate the synergies in the proper sequence for locomotion. This output was reproduced in a two-layer model using this topography and a traveling wave
Existence of a directional Stokes drift in asymmetrical three-dimensional travelling gravity waves
Iooss, Gérard; Plotnikov, Pavel
2009-09-01
We consider periodic travelling gravity waves at the surface of an infinitely deep perfect fluid. The pattern is non-symmetric with respect to the propagation direction of the waves and we consider a general non-resonant situation. Defining a couple of amplitudes ɛ,ɛ along the basis of wave vectors which satisfy the dispersion relation, following Iooss and Plotnikov (2009), travelling waves exist with an asymptotic expansion in powers of ɛ,ɛ, for nearly all pair of angles made by the basic wave vectors with the critical propagation direction, and for values of the couple (ɛ12,ɛ22) in a subset of the plane, with asymptotic full measure at the origin. We prove the remarkable property that on the free surface, observed in the moving frame, the propagation direction of the waves differs from the asymptotic direction taken by fluid particles, by a small angle which is computed. To cite this article: G. Iooss, P. Plotnikov, C. R. Mecanique 337 (2009).
Directory of Open Access Journals (Sweden)
Yingxiang Liu
Full Text Available BACKGROUND: Ultrasonic motors (USM are based on the concept of driving the rotor by a mechanical vibration excited on the stator via piezoelectric effect. USM exhibit merits such as simple structure, quick response, quiet operation, self-locking when power off, nonelectromagnetic radiation and higher position accuracy. PRINCIPAL FINDINGS: A cylindrical type traveling wave ultrasonic motor using cantilever type composite transducer was proposed in this paper. There are two cantilevers on the outside surface of cylinder, four longitudinal PZT ceramics are set between the cantilevers, and four bending PZT ceramics are set on each outside surface of cantilevers. Two degenerate flexural vibration modes spatially and temporally orthogonal to each other in the cylinder are excited by the composite transducer. In this new design, a single transducer can excite a flexural traveling wave in the cylinder. Thus, elliptical motions are achieved on the teeth. The actuating mechanism of proposed motor was analyzed. The stator was designed with FEM. The two vibration modes of stator were degenerated. Transient analysis was developed to gain the vibration characteristic of stator, and results indicate the motion trajectories of nodes on the teeth are nearly ellipses. CONCLUSIONS: The study results verify the feasibility of the proposed design. The wave excited in the cylinder isn't an ideal traveling wave, and the vibration amplitudes are inconsistent. The distortion of traveling wave is generated by the deformation of bending vibration mode of cylinder, which is caused by the coupling effect between the cylinder and transducer. Analysis results also prove that the objective motions of nodes on the teeth are three-dimensional vibrations. But, the vibration in axial direction is minute compared with the vibrations in circumferential and radial direction. The results of this paper can guide the development of this new type of motor.
Bhattacharya, Jishnu; Hanasoge, Shravan M.; Birch, Aaron C.; Gizon, Laurent
2017-11-01
Aims: We develop a helioseismic inversion algorithm that can be used to recover subsurface vertical profiles of two-dimensional supergranular flows from surface measurements of synthetic wave travel times. Methods: We carried out seismic wave-propagation simulations with a two-dimensional section of a flow profile that resembles an average supergranule and a starting model that only has flows at the surface. We assumed that the wave measurements are entirely without realization noise for the purpose of our test. We expanded the vertical profile of the supergranule stream function on a basis of B-splines. We iteratively updated the B-spline coefficients of the supergranule model to reduce the travel-time differences observed between the two simulations. We performed the exercise for four different vertical profiles peaking at different depths below the solar surface. Results: We are able to accurately recover depth profiles of four supergranule models at depths up to 8-10 Mm below the solar surface using f-p4 modes under the assumption that there is no realization noise. We are able to obtain the peak depth and the depth of the return flow for each model. Conclusions: A basis-resolved inversion performs significantly better than an inversion in which the flow field is inverted at each point in the radial grid. This is an encouraging result and might act as a guide in developing more realistic inversion strategies that can be applied to supergranular flows in the Sun.
Roads, travel, and time ‘across Jordan' in Byzantine and early Islamic times
DEFF Research Database (Denmark)
Walmsley, Alan George
2009-01-01
Roads, means of travel and travel times required to journey from one place to another in antiquity are essential components in assessing the political, cultural and economic history of a region. This paper reviews archaeological and documentary material detailing the major routes that crossed...... Jordan, the manner in which they were transversed, and the time required to travel over them in the period ca. 300-800 CE. In this post-Roman period, roadways took on new meaning as the needs of empire gave way to wider, and more self-defining, social and economic requirements of late antiquity...
Innovative methods for calculation of freeway travel time using limited data : final report.
2008-01-01
Description: Travel time estimations created by processing of simulated freeway loop detector data using proposed method have been compared with travel times reported from VISSIM model. An improved methodology was proposed to estimate freeway corrido...
Freeway travel time estimation using existing fixed traffic sensors : phase 2.
2015-03-01
Travel time, one of the most important freeway performance metrics, can be easily estimated using the : data collected from fixed traffic sensors, avoiding the need to install additional travel time data collectors. : This project is aimed at fully u...
2015-08-31
Drivers desire real-time information when : traveling in order to make route choice : decisions. One type of information that can be : provided is current (dynamic) travel times on : two possible routes that serve a common : destination. In this way,...
Validation and augmentation of Inrix arterial travel time data using independent sources.
2015-02-01
Travel time data is a key input to Intelligent Transportation Systems (ITS) applications. Advancement in vehicle : tracking and identification technologies and proliferation of location-aware and connected devices has made network-wide travel time da...
Construction and installation of travel time signs on I-35 in Austin.
2016-08-01
Dynamic travel time signs (DTTS) provide current travel times to a specific destination via one or more : routes. These signs aid motorists in making route choice decisions en route. Through this project, three : DTTS were fabricated and installed on...
Comparison of methods for measuring travel time at Florida freeways and arterials.
2014-07-01
Travel time is an important performance measure used to assess the traffic operational quality of various types of highway : facilities. Previous research funded by the Florida Department of Transportation (FDOT) on travel time reliability developed,...
DOTD support for UTC project : travel time estimation using bluetooth, [research project capsule].
2013-10-01
Travel time estimates are useful tools for measuring congestion in an urban area. Current : practice involves using probe vehicles or video cameras to measure travel time, but this is a laborintensive and expensive means of obtaining the information....
Arterial link travel time estimation using loop detector data : phase 1
1997-11-01
The envisioned operational tests of Advanced Traveler Information Systems (ATIS) and Advanced Traffic Management Systems (ATMS) in the Minneapolis/St. Paul area call for the provision of timely and reliable travel times over an entire rod network. Un...
Assessing segment- and corridor-based travel-time reliability on urban freeways : final report.
2016-09-01
Travel time and its reliability are intuitive performance measures for freeway traffic operations. The objective of this project was to quantify segment-based and corridor-based travel time reliability measures on urban freeways. To achieve this obje...
Outer core density heterogeneity and the discrepancy between PKP and PcP travel time observations
G. Soldati; Boschi, L.; Piersanti, A.
2002-01-01
We derive 3-D maps of the Earth’s mantle, CMB and outer core by means of least squares tomographic inversions. The data set includes compressional wave travel time measurements associated with the phases P, PcP, PKPbc, PKPdf, all based on the bulletins of the International Seismological Centre (1964-1995), after source relocation by Antolik et al. [2001]. Maps of the CMB derived independently from only core-reflected (PcP) or only core-refracted (PKP) phases are not well cor...
Children’s Mental Time Travel during Mind Wandering
Directory of Open Access Journals (Sweden)
Qun eYe
2014-08-01
Full Text Available The prospective bias is a salient feature of mind wandering in healthy adults, yet little is known about the temporal focus of children’s mind wandering. In the present study, (I we developed the Temporal Focus of Mind Wandering Questionnaire for school-age children (TFMWQ-C, a 12-item scale with good test-retest reliability and construct validity. (II The criterion validity was tested by thought sampling in both Choice Reaction Time Task (CRT and Working Memory Task (WMT. A positive correlation was found between the temporal focus measured by the questionnaire and the one adopted during task-unrelated thoughts (TUTs by thought sampling probes, especially in the trait level of future-oriented mind wandering. At the same time, children who experienced more TUTs tended to show worse behavioral performance during tasks. (III The children in both tasks experienced more future-oriented TUTs than past-oriented ones, which was congruent with the results observed in adults; however, in contrast with previous research on adults, the prospective bias was not influenced by task demands. Together these results indicate that the prospective bias of mind wandering has emerged since the school age (9~13 years old, and that the relationship between mental time travel during mind wandering and the use of cognitive resources differs between children and adults. Our study provides new insights into how this interesting feature of mind wandering may adaptively contribute to the development of children’s mental time travel.
Age-Related Effects on Future Mental Time Travel
Directory of Open Access Journals (Sweden)
Filomena Anelli
2016-01-01
Full Text Available Mental time travel (MTT, the ability to travel mentally back and forward in time in order to reexperience past events and preexperience future events, is crucial in human cognition. As we move along life, MTT may be changed accordingly. However, the relation between re- and preexperiencing along the lifespan is still not clear. Here, young and older adults underwent a psychophysical paradigm assessing two different components of MTT: self-projection, which is the ability to project the self towards a past or a future location of the mental time line, and self-reference, which is the ability to determine whether events are located in the past or future in reference to that given self-location. Aged individuals performed worse in both self-projection to the future and self-reference to future events compared to young individuals. In addition, aging decreased older adults’ preference for personal compared to nonpersonal events. These results demonstrate the impact of MTT and self-processing on subjective time processing in healthy aging. Changes in memory functions in aged people may therefore be related not only to memory per se, but also to the relations of memory and self.
Age-Related Effects on Future Mental Time Travel.
Anelli, Filomena; Ciaramelli, Elisa; Arzy, Shahar; Frassinetti, Francesca
2016-01-01
Mental time travel (MTT), the ability to travel mentally back and forward in time in order to reexperience past events and preexperience future events, is crucial in human cognition. As we move along life, MTT may be changed accordingly. However, the relation between re- and preexperiencing along the lifespan is still not clear. Here, young and older adults underwent a psychophysical paradigm assessing two different components of MTT: self-projection, which is the ability to project the self towards a past or a future location of the mental time line, and self-reference, which is the ability to determine whether events are located in the past or future in reference to that given self-location. Aged individuals performed worse in both self-projection to the future and self-reference to future events compared to young individuals. In addition, aging decreased older adults' preference for personal compared to nonpersonal events. These results demonstrate the impact of MTT and self-processing on subjective time processing in healthy aging. Changes in memory functions in aged people may therefore be related not only to memory per se, but also to the relations of memory and self.
Feasibility of Traveling Wave Direct Energy Conversion of Fission Reaction Fragments
Tarditi, A. G.; George, J. A.; Miley, G. H.; Scott, J. H.
2013-01-01
Fission fragment direct energy conversion has been considered in the past for the purpose of increasing nuclear power plant efficiency and for advanced space propulsion. Since the fragments carry electric charge (typically in the order of 20 e) and have 100 MeV-range kinetic energy, techniques utilizing very high-voltage DC electrodes have been considered. This study is focused on a different approach: the kinetic energy of the charged fission fragments is converted into alternating current by means of a traveling wave coupling scheme (Traveling Wave Direct Energy Converter, TWDEC), thereby not requiring the utilization of high voltage technology. A preliminary feasibility analysis of the concept is introduced based on a conceptual level study and on a particle simulation model of the beam dynamics.
Traveling wave linear accelerator with RF power flow outside of accelerating cavities
Dolgashev, Valery A.
2016-06-28
A high power RF traveling wave accelerator structure includes a symmetric RF feed, an input matching cell coupled to the symmetric RF feed, a sequence of regular accelerating cavities coupled to the input matching cell at an input beam pipe end of the sequence, one or more waveguides parallel to and coupled to the sequence of regular accelerating cavities, an output matching cell coupled to the sequence of regular accelerating cavities at an output beam pipe end of the sequence, and output waveguide circuit or RF loads coupled to the output matching cell. Each of the regular accelerating cavities has a nose cone that cuts off field propagating into the beam pipe and therefore all power flows in a traveling wave along the structure in the waveguide.
A rotational traveling wave based levitation device - Modeling, design, and control
Gabai, Ran; Shaham, Ran; Cohen, Nadav; Bucher, Izhak
2016-01-01
Described is a device acting on an acoustically levitated object by manipulating the pressure and flow of a thin layer of air such that its rotation can be precisely controlled without mechanical contact. Virtual work analysis assists in simplifying the multi-actuator control problem into a problem governed by a controllable parameter. Actuation is done with a vibrating ring capable of producing ultrasonic standing and traveling waves, creating the acoustic excitation that affects the pressure in a thin, intermediate layer of gas. A distinctive vibration pattern is required to generate the temporal and spatial pressure field of the squeezed air layer that gives rise to both acoustic levitation force and rotational torque. Described are the physical and design development stages leading to an optimized structure, all followed by verifying and dynamics-calibration experiments. Moreover, by precisely controlling the ratio of standing and traveling waves in a closed-loop, one can affect the shear forces applied b...
2001-03-01
A real-time travel time prediction system (TIPS) was evaluated in a construction work : zone. TIPS includes changeable message signs (CMSs) displaying the travel time and : distance to the end of the work zone to motorists. The travel times displayed...
2001-03-01
A real-time travel time prediction system (TIPS) was evaluated in a construction work zone. TIPS includes changeable message signs (CMSs) displaying the travel time and distance to the end of the work zone to motorists. The travel times displayed by ...
A review of atmospheric gravity waves and travelling ionospheric disturbances: 1982-1995
Directory of Open Access Journals (Sweden)
K. Hocke
Full Text Available Recent investigations of atmospheric gravity waves (AGW and travelling ionospheric disturbances (TID in the Earth's thermosphere and ionosphere are reviewed. In the past decade, the generation of gravity waves at high latitudes and their subsequent propagation to low latitudes have been studied by several global model simulations and coordinated observation campaigns such as the Worldwide Atmospheric Gravity-wave Study (WAGS, the results are presented in the first part of the review. The second part describes the progress towards understanding the AGW/TID characteristics. It points to the AGW/TID relationship which has been recently revealed with the aid of model-data comparisons and by the application of new inversion techniques. We describe the morphology and climatology of gravity waves and their ionospheric manifestations, TIDs, from numerous new observations.
Investigating Dielectric and Metamaterial Effects in a Terahertz Traveling-Wave Tube Amplifier
Starinshak, David P.; Wilson, Jeffrey D.
2008-01-01
Adding material enhancements to a terahertz traveling-wave tube amplifier is investigated. Isotropic dielectrics, negative-index metamaterials, and anisotropic crystals are simulated, and plans to increase the efficiency of the device are discussed. Early results indicate that adding dielectric to the curved sections of the serpentine-shaped slow-wave circuit produce optimal changes in the cold-test characteristics of the device and a minimal drop in operating frequency. Additional results suggest that materials with simultaneously small relative permittivities and electrical conductivities are best suited for increasing the efficiency of the device. More research is required on the subject, and recommendations are given to determine the direction.
Collective Transport for Active Matter Run and Tumble Disk Systems on a Traveling Wave Substrate
Sándor, Cs.; Libál, A.; Reichhardt, C.; Reichhardt, C. J. Olson
2016-01-01
We numerically examine the transport of an assembly of active run-and-tumble disks interacting with a traveling wave substrate. We show that as a function of substrate strength, wave speed, disk activity, and disk density, a variety of dynamical phases arise that are correlated with the structure and net flux of disks. We find that there is a sharp transition into a state where the disks are only partially coupled to the substrate and form a phase separated cluster state. This transition is a...
Astronomy's New Messengers: A traveling exhibit on gravitational-wave physics
Cavaglià, Marco; Hendry, Martin; Márka, Szabolcs; Reitze, David H.; Riles, Keith
2010-01-01
The Laser Interferometer Gravitational-wave Observatory exhibit Astronomy's New Messengers: Listening to the Universe with Gravitational Waves is traveling to colleges, universities, museums and other public institutions throughout the United States. Astronomy's New Messengers primarily communicates with an adolescent and young adult audience, potentially inspiring them into the field of science. Acknowledging that this audience is traditionally a difficult one to attract, the exhibit publicly announces itself in a charismatic fashion to reach its principal goals of broadening the community of people interested in science and encouraging interest in science among young people.
Vehicle routing with stochastic time-dependent travel times
Lecluyse, C.; Woensel, van, T Tom; Peremans, H
2009-01-01
Abstract: Assigning and scheduling vehicle routes in a stochastic time-dependent environment is a crucial management problem. The assumption that in a real-life environment everything goes according to an a priori determined static schedule is unrealistic. Our methodology builds on earlier work in which the traffic congestion is captured based on queueing theory in an analytical way and applied to the VRP problem. In this paper, we in- troduce the variability in the traffic flows into the mod...
Exact Traveling Wave Solutions for Wick-Type Stochastic Schamel KdV Equation
Directory of Open Access Journals (Sweden)
Hossam A. Ghany
2014-01-01
Full Text Available F-expansion method is proposed to seek exact solutions of nonlinear partial differential equations. By means of Hermite transform, inverse Hermite transform, and white noise analysis, the variable coefficients and Wick-type stochastic Schamel KdV equations are completely described. Abundant exact traveling wave solutions for variable coefficients Schamel KdV equations are given. These solutions include exact stochastic Jacobi elliptic functions, trigonometric functions, and hyperbolic functions solutions.
Traveling-Wave Tube Cold-Test Circuit Optimization Using CST MICROWAVE STUDIO
Chevalier, Christine T.; Kory, Carol L.; Wilson, Jeffrey D.; Wintucky, Edwin G.; Dayton, James A., Jr.
2003-01-01
The internal optimizer of CST MICROWAVE STUDIO (MWS) was used along with an application-specific Visual Basic for Applications (VBA) script to develop a method to optimize traveling-wave tube (TWT) cold-test circuit performance. The optimization procedure allows simultaneous optimization of circuit specifications including on-axis interaction impedance, bandwidth or geometric limitations. The application of Microwave Studio to TWT cold-test circuit optimization is described.
Tarditi, A. G.; Chap, A.; Wolinsky, J.; Scott, J. H.
2015-01-01
A coordinated experimental and theory/simulation effort has been carried out to investigate the physics of the Traveling Wave Direct Energy Converter (TWDEC), a scheme that has been proposed in the past for the direct conversion into electricity of the kinetic energy of an ion beam generated from fusion reactions. This effort has been focused in particular on the TWDEC process in the high density beam regime, thus accounting for the ion beam expansion due to its space charge.
Conservation Laws and Traveling Wave Solutions of a Generalized Nonlinear ZK-BBM Equation
Directory of Open Access Journals (Sweden)
Khadijo Rashid Adem
2014-01-01
Full Text Available We study a generalized two-dimensional nonlinear Zakharov-Kuznetsov-Benjamin-Bona-Mahony (ZK-BBM equation, which is in fact Benjamin-Bona-Mahony equation formulated in the ZK sense. Conservation laws for this equation are constructed by using the new conservation theorem due to Ibragimov and the multiplier method. Furthermore, traveling wave solutions are obtained by employing the (G'/G-expansion method.
Traveling Wave Solutions of Reaction-Diffusion Equations Arising in Atherosclerosis Models
Directory of Open Access Journals (Sweden)
Narcisa Apreutesei
2014-05-01
Full Text Available In this short review article, two atherosclerosis models are presented, one as a scalar equation and the other one as a system of two equations. They are given in terms of reaction-diffusion equations in an infinite strip with nonlinear boundary conditions. The existence of traveling wave solutions is studied for these models. The monostable and bistable cases are introduced and analyzed.
2D Traveling Wave Array Employing a Trapezoidal Dielectric Wedge for Beam Steering
Host, Nicholas K.; Chen, Chi-Chih; Volakis, John L.; Miranada, Felix A.
2014-01-01
This presentation addresses the progress made so far in the development of an antenna array with reconfigurable transmission line feeds connecting each element in series. In particular, 2D traveling wave array employing trapezoidal Dielectric Wedge for Beam Steering will be discussed. The presentation includes current status of the effort and suggested future work. The work is being done as part of the NASA Office of the Chief Technologist's Space Technology Research Fellowship (NSTRF).
Artur Wymysłowski; Waldemar Wiejak; Piotr Słupski
2017-01-01
Travelling Wave Tube (TWT) is an electronic vacuum microwave device, which is used as a high power microwave amplifier, mainly in telecommunication purposes and radar systems. TWT's seem to be an alternative and a more reliable solution than semiconductor devices when building high power and high frequency applications. Thermal behaviour of TWT is one of the key aspects influencing its reliability and working parameters. In fact, the standard TWT is treated as a high power device and the supp...
A travelling wave model of ripple formation on ion bombarded surfaces
Energy Technology Data Exchange (ETDEWEB)
Numazawa, Satoshi, E-mail: s.numazawa@hzdr.de; Smith, Roger, E-mail: R.Smith@lboro.ac.uk
2013-05-15
We present a mathematical model describing surface modification resulting from atomic motion after ion bombardment. The model considers only the defect production and recovery process induced by the local atom rearrangement and is essentially independent of surface topography changes formed by both sputtering and surface diffusion. A stable analytic, travelling wave solution is presented for a specific incident angle, which agrees with experimental observation excellently.
Full Spectrum Conversion Using Traveling Pulse Wave Quantization
2017-03-01
achieving unprecedented state-of-the- art performance and Figures of Merit (FoM) for ultra high speed (>10 Gsps) converters. Keywords: Data conversion...Figure 1. Time Interleaved ADC. The current state of the art in ultra high speed interleaved ADCs leverages one of the oldest and simplest core ADC...simple, it relies on serial signal processing operations that determine its update rate. An 8-bit converter for instance typically requires a minimum of
2008-10-01
The FHWA has strongly encouraged transportation departments to display travel times on their Dynamic Message Signs (DMS). The Oregon : Department of Transportation (ODOT) currently displays travel time estimates on three DMSs in the Portland metropol...
Monitoring travel times in an urban network using video, GPS and Bluetooth
Jie, L.; Van Zuylen, H.J.; Chunhua, L.; Shoufeng, L.
2011-01-01
The travel time is an important measure for the quality of traffic. This paper discusses a few methods to measure or estimate the travel time in urban road networks. First of all, it is important to know that urban travel times display a large variation, so that the measurement of a single (average)
Wireless data collection system for travel time estimation and traffic performance evaluation.
2010-09-01
Having accurate and continually updated travel time and other performance data for the road and highway system has many benefits. From the perspective of the road users, having real-time updates on travel times will permit better travel and route pla...
A novel traveling wave piezoelectric actuated tracked mobile robot utilizing friction effect
Wang, Liang; Shu, Chengyou; Jin, Jiamei; Zhang, Jianhui
2017-03-01
A novel traveling wave piezoelectric-actuated tracked mobile robot with potential application to robotic rovers was proposed and investigated in this study. The proposed tracked mobile robot is composed of a parallelogram-frame-structure piezoelectric transducer with four rings and a metal track. Utilizing the converse piezoelectric and friction effects, traveling waves were propagated in the rings and then the metal track was actuated by the piezoelectric transducer. Compared with traditional tracked mechanisms, the proposed tracked mobile robot has a simpler and more compact structure without lubricant, which eliminates the problem of lubricant volatilization and deflation, thus, it could be operated in the vacuum environment. Dynamic characteristics were simulated and measured to reveal the mechanism of actuating track of the piezoelectric transducer. Experimental investigations of the traveling wave piezoelectric-actuated tracked mobile robot were then carried out, and the results indicated that the robot prototype with a pair of exciting voltages of 460 Vpp is able to achieve a maximum velocity of 57 mm s-1 moving on the foam plate and possesses the obstacle crossing capability with a maximum height of 27 mm. The proposed tracked mobile robot exhibits potential to be the driving system of robotic rovers.
Yang, Zhiyong; Heeger, David J.; Blake, Randolph
2014-01-01
Traveling waves of cortical activity, in which local stimulation triggers lateral spread of activity to distal locations, have been hypothesized to play an important role in cortical function. However, there is conflicting physiological evidence for the existence of spreading traveling waves of neural activity triggered locally. Dichoptic stimulation, in which the two eyes view dissimilar monocular patterns, can lead to dynamic wave-like fluctuations in visual perception and therefore, provides a promising means for identifying and studying cortical traveling waves. Here, we used voltage-sensitive dye imaging to test for the existence of traveling waves of activity in the primary visual cortex of awake, fixating monkeys viewing dichoptic stimuli. We find clear traveling waves that are initiated by brief, localized contrast increments in one of the monocular patterns and then, propagate at speeds of ∼30 mm/s. These results demonstrate that under an appropriate visual context, circuitry in visual cortex in alert animals is capable of supporting long-range traveling waves triggered by local stimulation. PMID:25343785
Valuation of travel time savings in viewpoint of WTA.
Shao, Chang-Qiao; Liu, Yang; Liu, Xiao-Ming
2014-01-01
In order to investigate the issues in measurement of value of travel time savings (VTTS), the willingness-to-accept (WTA) for the private car owner is studied by using surveyed data. It is convincing that trip purpose, trip length, time savings, cost savings, income, and allowance from employee have effects on the WTA. Moreover, influences of these variables are not the same for different trip purposes. For commuting trips, effects of income and allowance from employee are significant while time savings and cost savings are dominated for leisure and shopping trips. It is also found that WTA is much higher than expected which implies that there are a group of drivers who are not prone to switching to other trip modes other than passenger car.
Integrable, oblique travelling waves in quasi-charge-neutral two-fluid plasmas
Directory of Open Access Journals (Sweden)
G. M. Webb
2008-02-01
Full Text Available A Hamiltonian description of oblique travelling waves in a two-fluid, charge-neutral, electron-proton plasma reveals that the transverse momentum equations for the electron and proton fluids are exactly integrable in cases where the total transverse momentum flux integrals, P_{y}^{(d} and P_{z}^{(d}, are both zero in the de Hoffman Teller (dHT frame. In this frame, the transverse electric fields are zero, which simplifies the transverse momentum equations for the two fluids. The integrable travelling waves for the case P_{y}^{(d}=P_{z}^{(d}=0, are investigated based on the Hamiltonian trajectories in phase space, and also on the longitudinal structure equation for the common longitudinal fluid velocity component u_{x} of the electron and proton fluids. Numerical examples of a variety of travelling waves in a cold plasma, including oscillitons, are used to illustrate the physics. The transverse, electron and proton velocity components u_{jy} and u_{jz} (j=e, p of the waves exhibit complex, rosette type patterns over several periods for u_{x}. The role of separatrices in the phase space, the rotational integral and the longitudinal structure equation on the different wave forms are discussed.
National Research Council Canada - National Science Library
Zayed, E. M. E; Hoda Ibrahim, S. A; Abdelaziz, M. A. M
2012-01-01
The two variables ([superscript]G[variant prime][/superscript] /G,1/G) -expansion method is proposed in this paper to construct new exact traveling wave solutions with parameters of the nonlinear (3+1...
Jarosch, H. S.
1982-01-01
A method based on the use of constrained spline fits is used to overcome the difficulties arising when body-wave data in the form of T-delta are reduced to the tau-p form in the presence of cusps. In comparison with unconstrained spline fits, the method proposed here tends to produce much smoother models which lie approximately in the middle of the bounds produced by the extremal method. The method is noniterative and, therefore, computationally efficient. The method is applied to the lunar seismic data, where at least one triplication is presumed to occur in the P-wave travel-time curve. It is shown, however, that because of an insufficient number of data points for events close to the antipode of the center of the lunar network, the present analysis is not accurate enough to resolve the problem of a possible lunar core.
Travel times in the vadose zone: Variability in space and time
Sprenger, Matthias; Seeger, Stefan; Blume, Theresa; Weiler, Markus
2016-08-01
Water travel times reflect hydrological processes, yet we know little about how travel times in the unsaturated zone vary with time. Using the soil physical model HYDRUS-1D, we derived time variable travel time distributions for 35 study sites within the Attert catchment in Luxembourg. While all sites experience similar climatic forcing, they differ with regard to soil types (16 Cambisols, 12 Arenosols, and 7 Stagnosols) and the vegetation cover (29 forest and 6 grassland). We estimated site specific water flow and transport parameters by fitting the model simulations to observed soil moisture time series and depth profiles of pore water stable isotopes. With the calibrated model, we tracked the water parcels introduced with each rainfall event over a period of several years. Our results show that the median travel time of water from the soil surface to depths down to 200 cm is mainly driven by the subsequent rainfall amounts. The median time until precipitation is taken up by roots is governed by the seasonality of evapotranspiration rates. The ratio between the amount of water that leaves the soil profile by on the one hand and evaporation and transpiration on the other hand also shows an annual cycle. This time variable response due to climatic forcing is furthermore visible in the multimodal nature of the site specific master transit time distribution representing the flow-averaged probability density for rainwater to become recharge. The spatial variability of travel times is mainly driven by soil texture and structure, with significant longer travel times for the clayey Stagnosols than for the loamy to sandy Cambisols and Arenosols.
On the evaluation of Pierce parameters C and Q in a traveling wave tube
Simon, D. H.; Wong, P.; Chernin, D.; Lau, Y. Y.; Hoff, B.; Zhang, P.; Dong, C. F.; Gilgenbach, R. M.
2017-03-01
A study of an exactly solvable model of a traveling wave tube (TWT) shows that Pierce gain parameter C and space charge parameter Q generally depend on wavenumber k in addition to frequency ω. The choice of k at which C and Q are evaluated may strongly affect their values and, consequently, the values of the small signal gain obtained from 3- and 4-wave Pierce theory. In order to illustrate this effect, we calculate the spatial amplification rate, ki, from the exact dispersion relation for a dielectric TWT model which is exactly solvable. We compare this exact value of ki with approximate values obtained from Pierce's classical 3-wave and 4-wave dispersion relations, obtained by making various assumptions on k in the evaluation of C and Q. We find that the various ways to approximate C and Q will have a significant influence on the numerical values of ki. For our dielectric TWT example, Pierce's 4-wave TWT dispersion relation generally yields the most accurate values of ki if Q is evaluated for k = ω/v0, where v0 is the beam velocity, and if the complete frequency and wavelength dependence of C is retained. Pierce's 3-wave theory also yields accurate values of ki using a different form of Q from the 4-wave theory. The implications of this result for TWT design are explored.
Uni-directional waves over slowly varying bottom, part II: Deformation of travelling waves
Pudjaprasetya, S.R.; Pudjaprasetya, S.R.; van Groesen, Embrecht W.C.
1996-01-01
A new Korteweg-de Vries type of equation for uni-directional waves over slowly varying bottom has been derived in Part I. The equation retains the Hamiltonian structure of the underlying complete set of equations for surface waves. For flat bottom it reduces to the standard Korteweg-de Vries
1997-01-01
ADVANCE was an in-vehicle advanced traveler information system (ATIS) providing route guidance in real time that operated in the northwestern portion and northwest suburbs of Chicago, Illinois. It used probe vehicles to generate dynamically travel ti...
Simulation studies on the standing and traveling wave thermoacoustic prime movers
Skaria, Mathew; Rasheed, K. K. Abdul; Shafi, K. A.; Kasthurirengan, S.; Behera, Upendra
2014-01-01
Thermoacoustic systems have been a focus of recent research due to its structural simplicity, high reliability due to absence of moving parts, and can be driven by low grade energy such as fuel, gas, solar energy, waste heat etc. There has been extensive research on both standing wave and traveling wave systems. Towards the development of such systems, simulations can be carried out by several methods such as (a) solving the energy equation, (b) enthalpy flow model, (c) DeltaEC, a free software available from LANL, USA (d) Computational Fluid Dynamics (CFD) etc. We present here the simulation studies of standing wave and traveling wave thermoacoustic prime movers using CFD and DeltaEC. The CFD analysis is carried out using Fluent 6.3.26, incorporating the necessary boundary conditions with different working fluids at different operating pressures. The results obtained by CFD are compared with those obtained using DeltaEC. Also, the CFD simulation of the thermoacoustically driven refrigerator is presented.
Directory of Open Access Journals (Sweden)
Ronald C. Davidson
2015-09-01
Full Text Available This paper makes use of a one-dimensional kinetic model to investigate the nonlinear longitudinal dynamics of a long coasting beam propagating through a perfectly conducting circular pipe with radius r_{w}. The average axial electric field is expressed as ⟨E_{z}⟩=-(∂/∂z⟨ϕ⟩=-e_{b}g_{0}∂λ_{b}/∂z-e_{b}g_{2}r_{w}^{2}∂^{3}λ_{b}/∂z^{3}, where g_{0} and g_{2} are constant geometric factors, λ_{b}(z,t=∫dp_{z}F_{b}(z,p_{z},t is the line density of beam particles, and F_{b}(z,p_{z},t satisfies the 1D Vlasov equation. Detailed nonlinear properties of traveling-wave and traveling-pulse (soliton solutions with time-stationary waveform are examined for a wide range of system parameters extending from moderate-amplitudes to large-amplitude modulations of the beam charge density. Two classes of solutions for the beam distribution function are considered, corresponding to: (i the nonlinear waterbag distribution, where F_{b}=const in a bounded region of p_{z}-space; and (ii nonlinear Bernstein-Green-Kruskal (BGK-like solutions, allowing for both trapped and untrapped particle distributions to interact with the self-generated electric field ⟨E_{z}⟩.
Heterogeneous Data Fusion Method to Estimate Travel Time Distributions in Congested Road Networks.
Shi, Chaoyang; Chen, Bi Yu; Lam, William H K; Li, Qingquan
2017-12-06
Travel times in congested urban road networks are highly stochastic. Provision of travel time distribution information, including both mean and variance, can be very useful for travelers to make reliable path choice decisions to ensure higher probability of on-time arrival. To this end, a heterogeneous data fusion method is proposed to estimate travel time distributions by fusing heterogeneous data from point and interval detectors. In the proposed method, link travel time distributions are first estimated from point detector observations. The travel time distributions of links without point detectors are imputed based on their spatial correlations with links that have point detectors. The estimated link travel time distributions are then fused with path travel time distributions obtained from the interval detectors using Dempster-Shafer evidence theory. Based on fused path travel time distribution, an optimization technique is further introduced to update link travel time distributions and their spatial correlations. A case study was performed using real-world data from Hong Kong and showed that the proposed method obtained accurate and robust estimations of link and path travel time distributions in congested road networks.
Chen, Ruizhu; Zhao, Junwei
2018-02-01
Time–distance helioseismology measures acoustic travel times to infer the structure and flow field of the solar interior; however, both the mean travel times and the travel-time shifts suffer systematic center-to-limb variations, which complicate the interpretation and inversions of the time–distance measurements. In particular, the center-to-limb variation in travel-time shifts (CtoL effect) has a significant impact on the inference of the Sun’s meridional circulation, and needs to be removed from the helioseismic measurements, although the observational properties and the physical cause of the CtoL effect have yet to be investigated. In this study, we measure the CtoL effect in the frequency domain using Doppler-velocity data from the Solar Dynamics Observatory/Helioseismic and Magnetic Imager, and study its properties as a function of disk-centric distance, travel distance, and frequency of acoustic waves. It is found that the CtoL effect has a significant frequency dependence—it reverses sign at a frequency around 5.4 mHz and reaches maximum at around 4.0 mHz before the sign reversal. The tendency of frequency dependence varies with disk-centric distance in a way that both the sign-reversal frequency and the maximum-value frequency decrease closer to the limb. The variation tendency does not change with travel distance, but the variation magnitude is approximately proportional to travel distance. For comparison, the flow-induced travel-time shifts show little frequency dependence. These observational properties provide more clues on the nature of the CtoL effect, and also possibly lead to new ways of effect-removal for a more robust determination of the deep meridional flow.
Doubly Periodic Traveling Waves in a Cellular Neural Network with Linear Reaction
Directory of Open Access Journals (Sweden)
Lin JianJhong
2009-01-01
Full Text Available Szekeley observed that the dynamic pattern of the locomotion of salamanders can be explained by periodic vector sequences generated by logical neural networks. Such sequences can mathematically be described by "doubly periodic traveling waves" and therefore it is of interest to propose dynamic models that may produce such waves. One such dynamic network model is built here based on reaction-diffusion principles and a complete discussion is given for the existence of doubly periodic waves as outputs. Since there are 2 parameters in our model and 4 a priori unknown parameters involved in our search of solutions, our results are nontrivial. The reaction term in our model is a linear function and hence our results can also be interpreted as existence criteria for solutions of a nontrivial linear problem depending on 6 parameters.
Using travel times to simulate multi-dimensional bioreactive transport in time-periodic flows.
Sanz-Prat, Alicia; Lu, Chuanhe; Finkel, Michael; Cirpka, Olaf A
2016-04-01
In travel-time models, the spatially explicit description of reactive transport is replaced by associating reactive-species concentrations with the travel time or groundwater age at all locations. These models have been shown adequate for reactive transport in river-bank filtration under steady-state flow conditions. Dynamic hydrological conditions, however, can lead to fluctuations of infiltration velocities, putting the validity of travel-time models into question. In transient flow, the local travel-time distributions change with time. We show that a modified version of travel-time based reactive transport models is valid if only the magnitude of the velocity fluctuates, whereas its spatial orientation remains constant. We simulate nonlinear, one-dimensional, bioreactive transport involving oxygen, nitrate, dissolved organic carbon, aerobic and denitrifying bacteria, considering periodic fluctuations of velocity. These fluctuations make the bioreactive system pulsate: The aerobic zone decreases at times of low velocity and increases at those of high velocity. For the case of diurnal fluctuations, the biomass concentrations cannot follow the hydrological fluctuations and a transition zone containing both aerobic and obligatory denitrifying bacteria is established, whereas a clear separation of the two types of bacteria prevails in the case of seasonal velocity fluctuations. We map the 1-D results to a heterogeneous, two-dimensional domain by means of the mean groundwater age for steady-state flow in both domains. The mapped results are compared to simulation results of spatially explicit, two-dimensional, advective-dispersive-bioreactive transport subject to the same relative fluctuations of velocity as in the one-dimensional model. The agreement between the mapped 1-D and the explicit 2-D results is excellent. We conclude that travel-time models of nonlinear bioreactive transport are adequate in systems of time-periodic flow if the flow direction does not change
Metabolomics and lipidomics using traveling-wave ion mobility mass spectrometry.
Paglia, Giuseppe; Astarita, Giuseppe
2017-04-01
Metabolomics and lipidomics aim to profile the wide range of metabolites and lipids that are present in biological samples. Recently, ion mobility spectrometry (IMS) has been used to support metabolomics and lipidomics applications to facilitate the separation and the identification of complex mixtures of analytes. IMS is a gas-phase electrophoretic technique that enables the separation of ions in the gas phase according to their charge, shape and size. Occurring within milliseconds, IMS separation is compatible with modern mass spectrometry (MS) operating with microsecond scan speeds. Thus, the time required for acquiring IMS data does not affect the overall run time of traditional liquid chromatography (LC)-MS-based metabolomics and lipidomics experiments. The addition of IMS to conventional LC-MS-based metabolomics and lipidomics workflows has been shown to enhance peak capacity, spectral clarity and fragmentation specificity. Moreover, by enabling determination of a collision cross-section (CCS) value-a parameter related to the shape of ions-IMS can improve the accuracy of metabolite identification. In this protocol, we describe how to integrate traveling-wave ion mobility spectrometry (TWIMS) into traditional LC-MS-based metabolomic and lipidomic workflows. In particular, we describe procedures for the following: tuning and calibrating a SYNAPT High-Definition MS (HDMS) System (Waters) specifically for metabolomics and lipidomics applications; extracting polar metabolites and lipids from brain samples; setting up appropriate chromatographic conditions; acquiring simultaneously m/z, retention time and CCS values for each analyte; processing and analyzing data using dedicated software solutions, such as Progenesis QI (Nonlinear Dynamics); and, finally, performing metabolite and lipid identification using CCS databases and TWIMS-derived fragmentation information.
Cognitive mapping in mental time travel and mental space navigation.
Gauthier, Baptiste; van Wassenhove, Virginie
2016-09-01
The ability to imagine ourselves in the past, in the future or in different spatial locations suggests that the brain can generate cognitive maps that are independent of the experiential self in the here and now. Using three experiments, we asked to which extent Mental Time Travel (MTT; imagining the self in time) and Mental Space Navigation (MSN; imagining the self in space) shared similar cognitive operations. For this, participants judged the ordinality of real historical events in time and in space with respect to different mental perspectives: for instance, participants mentally projected themselves in Paris in nine years, and judged whether an event occurred before or after, or, east or west, of where they mentally stood. In all three experiments, symbolic distance effects in time and space dimensions were quantified using Reaction Times (RT) and Error Rates (ER). When self-projected, participants were slower and were less accurate (absolute distance effects); participants were also faster and more accurate when the spatial and temporal distances were further away from their mental viewpoint (relative distance effects). These effects show that MTT and MSN require egocentric mapping and that self-projection requires map transformations. Additionally, participants' performance was affected when self-projection was made in one dimension but judgements in another, revealing a competition between temporal and spatial mapping (Experiment 2 & 3). Altogether, our findings suggest that MTT and MSN are separately mapped although they require comparable allo- to ego-centric map conversion. Copyright © 2016 Elsevier B.V. All rights reserved.
Suburb-to-suburb intercity travel: Energy, time and dollar expenditures
Fels, M. F.
1976-01-01
The effect of adding suburb to terminal and terminal to suburb travel is examined. The energy consumed in entire trips was estimated. The total energy costs are compared with total travel times, and dollar costs to the traveler. Trips between origins in seven suburbs of Newark, New Jersey and destinations in two Washington, D. C. suburbs are analyzed.
IYL Blog: Astronomers travel in time and space with light
Mather, John C.
2015-01-01
As an astronomer, I use light to travel through the universe, and to look back in time to when the universe was young. So do you! All of us see things as they were when the light was emitted, not as they are now. The farthest thing you can easily see without a telescope is the Andromeda Nebula, which is a galaxy like the Milky Way, about 2.5 million light years away. You see it as it was 2.5 million years ago, and we really don't know what it looks like today; the disk will have rotated a bit, new stars will have been born, there could have been all kinds of exploding stars, and the black hole in the middle could be lighting up. People may be skeptical of the Big Bang theory, even though we have a TV show named for it, but we (I should say Penzias and Wilson) measured its heat radiation 51 years ago at Bell Telephone Labs in New Jersey. Their discovery marks the beginning of the era of cosmology as a measurement science rather than speculation. Penzias and Wilson received the Nobel Prize in 1978 for their finding, which had been predicted in 1948 by Alpher and Herman. By the way, heat radiation is just another form of light - we call it radiation because we can't see it, but it's exactly the same phenomenon of electromagnetic waves, and the only difference is the wavelength. In the old days of analog television, if you tuned your TV in between channels, about 1% of the snow that you could see came from the Big Bang. So when we look at the heat radiation of the early universe, we really are gazing right at what seems to us a cosmic fireball, which surrounds us completely. It's a bit of an illusion; if you can imagine what astronomers in other galaxies would see, they would also feel surrounded by the fireball, and they would also think they were in the middle. So from a mathematical version of imagination, we conclude that there is no observable center and no edge of our universe, and that the heat of the fireball fills the entire universe uniformly. Astronomers are
Space-time fractional Zener wave equation.
Atanackovic, T M; Janev, M; Oparnica, Lj; Pilipovic, S; Zorica, D
2015-02-08
The space-time fractional Zener wave equation, describing viscoelastic materials obeying the time-fractional Zener model and the space-fractional strain measure, is derived and analysed. This model includes waves with finite speed, as well as non-propagating disturbances. The existence and the uniqueness of the solution to the generalized Cauchy problem are proved. Special cases are investigated and numerical examples are presented.
Space–time fractional Zener wave equation
Atanackovic, T.M.; Janev, M.; Oparnica, Lj.; Pilipovic, S.; Zorica, D.
2015-01-01
The space–time fractional Zener wave equation, describing viscoelastic materials obeying the time-fractional Zener model and the space-fractional strain measure, is derived and analysed. This model includes waves with finite speed, as well as non-propagating disturbances. The existence and the uniqueness of the solution to the generalized Cauchy problem are proved. Special cases are investigated and numerical examples are presented. PMID:25663807
Dynamical Space-Time and Gravitational Waves
van Holten, J W
2016-01-01
According to General Relativity gravity is the result of the interaction between matter and space-time geometry. In this interaction space-time geometry itself is dynamical: it can store and transport energy and momentum in the form of gravitational waves. We give an introductory account of this phenomenon and discuss how the observation of gravitational waves may open up a fundamentally new window on the universe.
Modelling travel time perception in transport mode choices
Varotto, S.F.; Glerum, A.; Stathopoulos, A.; Bierlaire, M.; Longo, G.
2015-01-01
Travel behaviour models typically rely on data afflicted by errors, in perception (e.g., over/under-estimation by traveller) and measurement (e.g., software or researcher imputation error). Such errors are shown to have a relevant impact on model outputs. So far a comprehensive framework to deal
Energy Technology Data Exchange (ETDEWEB)
Parchevsky, K. V.; Zhao, J.; Hartlep, T.; Kosovichev, A. G., E-mail: akosovichev@solar.stanford.edu [Stanford University, HEPL, Stanford, CA 94305 (United States)
2014-04-10
We performed three-dimensional numerical simulations of the solar surface acoustic wave field for the quiet Sun and for three models with different localized sound-speed perturbations in the interior with deep, shallow, and two-layer structures. We used the simulated data generated by two solar acoustics codes that employ the same standard solar model as a background model, but utilize different integration techniques and different models of stochastic wave excitation. Acoustic travel times were measured using a time-distance helioseismology technique, and compared with predictions from ray theory frequently used for helioseismic travel-time inversions. It is found that the measured travel-time shifts agree well with the helioseismic theory for sound-speed perturbations, and for the measurement procedure with and without phase-speed filtering of the oscillation signals. This testing verifies the whole measuring-filtering-inversion procedure for static sound-speed anomalies with small amplitude inside the Sun outside regions of strong magnetic field. It is shown that the phase-speed filtering, frequently used to extract specific wave packets and improve the signal-to-noise ratio, does not introduce significant systematic errors. Results of the sound-speed inversion procedure show good agreement with the perturbation models in all cases. Due to its smoothing nature, the inversion procedure may overestimate sound-speed variations in regions with sharp gradients of the sound-speed profile.
Simulation of TunneLadder Traveling-Wave Tube Input/Output Coupler Characteristics Using MAFIA
Kory, Carol L.; Qureshi, A. Haq
1996-01-01
RF input/output coupler characteristics for the TunneLadder traveling-wave tube have been calculated using the three-dimensional computer code, MAFIA and compared to experimental data with good agreement. Theory behind coupling of the TunneLadder interaction circuit to input and output waveguides is presented and VSWR data is calculated for variations on principal coupler dimensions to provide insight into manufacturing tolerances necessary for acceptable performance. Accuracy of results using MAFIA demonstrates how experimental hardware testing of three-dimensional coupler designs can be reduced.
An interleaved structure for a high-voltage planar transformer for a Travelling-wave Tube
DEFF Research Database (Denmark)
Zhao, Bin; Wang, Gang; Hurley, William G.
2016-01-01
is proposed to reduce leakage inductance and the insulation’s thickness is adjusted to optimize the electric isolation. In addition, the resistance and parasitic capacitance are investigated. With this method, a planar transformer used for a Travelling-Wave Tube Amplifier (TWTA) is designed. Calculations......Fully interleaved structure can significantly reduce leakage inductance in transformers, However， it is hard to apply them into high-voltage applications due to the electric insulation. In this paper, a partially interleaved structure that is suitable for high-voltage high frequency applications...
Asymptotics of QCD traveling waves with fluctuations and running coupling effects
Beuf, Guillaume
2008-09-01
Extending the Balitsky-Kovchegov (BK) equation independently to running coupling or to fluctuation effects due to pomeron loops is known to lead in both cases to qualitative changes of the traveling-wave asymptotic solutions. In this paper we study the extension of the forward BK equation, including both running coupling and fluctuations effects, extending the method developed for the fixed coupling case [E. Brunet, B. Derrida, A.H. Mueller, S. Munier, Phys. Rev. E 73 (2006) 056126, cond-mat/0512021]. We derive the exact asymptotic behavior in rapidity of the probabilistic distribution of the saturation scale.
Monthus, Cecile; Garel, Thomas
2008-01-01
For Anderson localization on the Cayley tree, we study the statistics of various observables as a function of the disorder strength $W$ and the number $N$ of generations. We first consider the Landauer transmission $T_N$. In the localized phase, its logarithm follows the traveling wave form $\\ln T_N \\simeq \\bar{\\ln T_N} + \\ln t^*$ where (i) the disorder-averaged value moves linearly $\\bar{\\ln (T_N)} \\simeq - \\frac{N}{\\xi_{loc}}$ and the localization length diverges as $\\xi_{loc} \\sim (W-W_c)^...
Exact Travelling Wave Solutions of two Important Nonlinear Partial Differential Equations
Kim, Hyunsoo; Bae, Jae-Hyeong; Sakthivel, Rathinasamy
2014-04-01
Coupled nonlinear partial differential equations describing the spatio-temporal dynamics of predator-prey systems and nonlinear telegraph equations have been widely applied in many real world problems. So, finding exact solutions of such equations is very helpful in the theories and numerical studies. In this paper, the Kudryashov method is implemented to obtain exact travelling wave solutions of such physical models. Further, graphic illustrations in two and three dimensional plots of some of the obtained solutions are also given to predict their behaviour. The results reveal that the Kudryashov method is very simple, reliable, and effective, and can be used for finding exact solution of many other nonlinear evolution equations.
Integrating a Traveling Wave Tube into an AECR-U ion source
Energy Technology Data Exchange (ETDEWEB)
Covo, Michel Kireeff; Benitez, Janilee Y.; Ratti, Alessandro; Vujic, Jasmina L.
2011-07-01
An RF system of 500W - 10.75 to 12.75 GHz was designed and integrated into the Advanced Electron Cyclotron Resonance - Upgrade (AECR-U) ion source of the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory. The AECR-U produces ion beams for the Cyclotron giving large flexibility of ion species and charge states. The broadband frequency of a Traveling Wave Tube (TWT) allows modifying the volume that couples and heats the plasma. The TWT system design and integration with the AECR-U ion source and results from commissioning are presented.
The existence of minimum speed of traveling wave solutions to a non-KPP isothermal diffusion system
Chen, Xinfu; Liu, Guirong; Qi, Yuanwei
2017-08-01
The reaction-diffusion system at =axx - abn ,bt = Dbxx + abn, where n ≥ 1 and D > 0, arises from many real-world chemical reactions. Whereas n = 1 is the KPP type nonlinearity, which is much studied and very important results obtained in literature not only in one dimensional spatial domains, but also multi-dimensional spaces, but n > 1 proves to be much harder. One of the interesting features of the system is the existence of traveling wave solutions. In particular, for the traveling wave solution a (x , t) = a (x - vt), b (x , t) = b (x - vt), where v > 0, if we fix lim x → - ∞ (a , b) = (0 , 1) it was proved by many authors with different bounds v* (n , D) > 0 such that a traveling wave solution exists for any v ≥v* when n > 1. For the latest progress, see [7]. That is, the traveling wave problem exhibits the mono-stable phenomenon for traveling wave of scalar equation ut =uxx + f (u) with f (0) = f (1) = 0, f (u) > 0 in (0 , 1) and, u = 0 is unstable and u = 1 is stable. A natural and significant question is whether, like the scalar case, there exists a minimum speed. That is, whether there exists a minimum speed vmin > 0 such that traveling wave solution of speed v exists iff v ≥vmin? This is an open question, in spite of many works on traveling wave of the system in last thirty years. This is duo to the reason, unlike the KPP case, the minimum speed cannot be obtained through linear analysis at equilibrium points (a , b) = (0 , 1) and (a , b) = (1 , 0). In this work, we give an affirmative answer to this question.
Time reversal in matter-wave optics
Hamamda, M.; Perales, F.; Dutier, G.; Mainos, C.; Baudon, J.; Boustimi, M.; Ducloy, M.
2011-01-01
The evolution of atomic wave packets experiencing so-called comoving potential pulses is examined theoretically, in the framework of the stationary-phase approximation. The negative refraction induced by this potential is a characteristic property of negative-index media, the atomic counterpart of negative-index materials of light optics. A novel process, specific of negative-index for matter waves, is evidenced, namely a narrowing of the wave packet transiently counterbalancing the natural spreading. This is the manifestation of a general property of negative-index media, i.e. a time reversal effect. It is shown that, for a statistical ensemble of wave packets leading to a moderate dispersion of the times of flight, this time reversal phenomenon should be observable.
Region-wide synchrony and traveling waves of dengue across eight countries in Southeast Asia.
van Panhuis, Willem G; Choisy, Marc; Xiong, Xin; Chok, Nian Shong; Akarasewi, Pasakorn; Iamsirithaworn, Sopon; Lam, Sai K; Chong, Chee K; Lam, Fook C; Phommasak, Bounlay; Vongphrachanh, Phengta; Bouaphanh, Khamphaphongphane; Rekol, Huy; Hien, Nguyen Tran; Thai, Pham Quang; Duong, Tran Nhu; Chuang, Jen-Hsiang; Liu, Yu-Lun; Ng, Lee-Ching; Shi, Yuan; Tayag, Enrique A; Roque, Vito G; Lee Suy, Lyndon L; Jarman, Richard G; Gibbons, Robert V; Velasco, John Mark S; Yoon, In-Kyu; Burke, Donald S; Cummings, Derek A T
2015-10-20
Dengue is a mosquito-transmitted virus infection that causes epidemics of febrile illness and hemorrhagic fever across the tropics and subtropics worldwide. Annual epidemics are commonly observed, but there is substantial spatiotemporal heterogeneity in intensity. A better understanding of this heterogeneity in dengue transmission could lead to improved epidemic prediction and disease control. Time series decomposition methods enable the isolation and study of temporal epidemic dynamics with a specific periodicity (e.g., annual cycles related to climatic drivers and multiannual cycles caused by dynamics in population immunity). We collected and analyzed up to 18 y of monthly dengue surveillance reports on a total of 3.5 million reported dengue cases from 273 provinces in eight countries in Southeast Asia, covering ∼ 10(7) km(2). We detected strong patterns of synchronous dengue transmission across the entire region, most markedly during a period of high incidence in 1997-1998, which was followed by a period of extremely low incidence in 2001-2002. This synchrony in dengue incidence coincided with elevated temperatures throughout the region in 1997-1998 and the strongest El Niño episode of the century. Multiannual dengue cycles (2-5 y) were highly coherent with the Oceanic Niño Index, and synchrony of these cycles increased with temperature. We also detected localized traveling waves of multiannual dengue epidemic cycles in Thailand, Laos, and the Philippines that were dependent on temperature. This study reveals forcing mechanisms that drive synchronization of dengue epidemics on a continental scale across Southeast Asia.
Couvidat, S.; Zhao, J.; Birch, A. C.; Kosovichev, A. G.; Duvall, T. L., Jr.; Parchevsky, K.; Scherrer, P. H.
2009-01-01
The Helioseismic and Magnetic Imager (HMI) instrument on board the Solar Dynamics Observatory (SDO) satellite is designed to produce high-resolution Doppler velocity maps of oscillations at the solar surface with high temporal cadence. To take advantage of these high-quality oscillation data, a time-distance helioseismology pipeline has been implemented at the Joint Science Operations Center (JSOC) at Stanford University. The aim of this pipeline is to generate maps of acoustic travel times from oscillations on the solar surface, and to infer subsurface 3D flow velocities and sound-speed perturbations. The wave travel times are measured from cross covariances of the observed solar oscillation signals. For implementation into the pipeline we have investigated three different travel-time definitions developed in time-distance helioseismology: a Gabor wavelet fitting (Kosovichev and Duvall, 1997), a minimization relative to a reference cross-covariance function (Gizon and Birch, 2002), and a linearized version of the minimization method (Gizon and Birch, 2004). Using Doppler velocity data from the Michelson Doppler Imager (MDI) instrument on board SOHO, we tested and compared these definitions for the mean and difference travel-time perturbations measured from reciprocal signals. Although all three procedures return similar travel times in a quiet Sun region, the method of Gizon and Birch (2004) gives travel times that are significantly different from the others in a magnetic (active) region. Thus, for the pipeline implementation we chose the procedures of Kosovichev and Duvall (1997) and Gizon and Birch (2002). We investigated the relationships among these three travel-time definitions, their sensitivities to fitting parameters, and estimated the random errors they produce
Climatic and landscape controls on travel time distributions across Europe
Kumar, Rohini; Rao, Suresh; Hesse, Falk; Borchardt, Dietrich; Fleckenstein, Jan; Jawitz, James; Musolff, Andreas; Rakovec, Oldrich; Samaniego, Luis; Yang, Soohyun; Zink, Matthias; Attinger, Sabine
2017-04-01
Travel time distributions (TTDs) are fundamental descriptors to characterize the functioning of storage, mixing and release of water and solutes in a river basin. Identifying the relative importance (and controls) of climate and landscape attributes on TDDs is fundamental to improve our understanding of the underlying mechanism controlling the spatial heterogeneity of TTDs, and their moments (e.g., mean TT). Studies aimed at elucidating such controls have focused on either theoretical developments to gain (physical) insights using mostly synthetic datasets or empirical relationships using limited datasets from experimental sites. A study painting a general picture of emerging controls at a continental scale is still lacking. In this study, we make use of spatially resolved hydrologic fluxes and states generated through an observationally driven, mesoscale Hydrologic Model (mHM; www.ufz.de/mhm) to comprehensively characterize the dominant controls of climate and landscape attributes on TDDs in the vadose zone across the entire European region. mHM uses a novel Multiscale Parameter Regionalization (MPR; Samaniego et al., 2010 and Kumar et al., 2013) scheme that encapsulates fine scale landscape attributes (e.g., topography, soil, and vegetation characteristics) to account for the sub-grid variability in model parameterization. The model was established at 25 km spatial resolution to simulate the daily gridded fluxes and states over Europe for the period 1955-2015. We utilized recent developments in TTDs theory (e.g., Botter et al., 2010, Harman et al., 2011) to characterize the stationary and non-stationary behavior of water particles transported through the vadose zone at every grid cell. Our results suggest a complex set of interactions between climate and landscape properties controlling the spatial heterogeneity of the mean travel time (TT). The spatial variability in the mean TT across the Pan-EU generally follows the climatic gradient with lower values in humid
Bani-Hani, M. A.; Karami, M. A.
2015-09-01
This paper presents vibration analysis and structural optimization of a swimming-morphing structure. The swimming of the structure is achieved by utilization of piezoelectric patches to generate traveling waves. The third mode shape of the structure in the longitudinal direction resembles the body waveform of a swimming eel. After swimming to its destination, the morphing structure changes shape from an open box to a cube using shape memory alloys (SMAs). The SMAs used for the configuration change of the box robot cannot be used for swimming since they fail to operate at high frequencies. Piezoelectric patches are actuated at the third natural frequency of the structure. We optimize the thickness of the panels and the stiffness of the springs at the joints to generate swimming waveforms that most closely resemble the body waveform of an eel. The traveling wave is generated using two piezoelectric sets of patches bonded to the first and last segments of the beams in the longitudinal direction. Excitation of the piezoelectric results in coupled system dynamics equations that can be translated into the generation of waves. Theoretical analysis based on the distributed parameter model is conducted in this paper. A scalar measure of the traveling to standing wave ratio is introduced using a 2-dimensional Fourier transform (2D-FFT) of the body deformation waveform. An optimization algorithm based on tuning the flexural transverse wave is established to obtain a higher traveling to standing wave ratio. The results are then compared to common methods in the literature for assessment of standing to traveling wave ratios. The analytical models are verified by the close agreement between the traveling waves predicted by the model and those measured in the experiments.
A near-quantum-limited Josephson traveling-wave parametric amplifier.
Macklin, C; O'Brien, K; Hover, D; Schwartz, M E; Bolkhovsky, V; Zhang, X; Oliver, W D; Siddiqi, I
2015-10-16
Detecting single-photon level signals—carriers of both classical and quantum information—is particularly challenging for low-energy microwave frequency excitations. Here we introduce a superconducting amplifier based on a Josephson junction transmission line. Unlike current standing-wave parametric amplifiers, this traveling wave architecture robustly achieves high gain over a bandwidth of several gigahertz with sufficient dynamic range to read out 20 superconducting qubits. To achieve this performance, we introduce a subwavelength resonant phase-matching technique that enables the creation of nonlinear microwave devices with unique dispersion relations. We benchmark the amplifier with weak measurements, obtaining a high quantum efficiency of 75% (70% including noise added by amplifiers following the Josephson amplifier). With a flexible design based on compact lumped elements, this Josephson amplifier has broad applicability to microwave metrology and quantum optics. Copyright © 2015, American Association for the Advancement of Science.
Theory of a Traveling Wave Feed for a Planar Slot Array Antenna
Rengarajan, Sembiam
2012-01-01
Planar arrays of waveguide-fed slots have been employed in many radar and remote sensing applications. Such arrays are designed in the standing wave configuration because of high efficiency. Traveling wave arrays can produce greater bandwidth at the expense of efficiency due to power loss in the load or loads. Traveling wave planar slot arrays may be designed with a long feed waveguide consisting of centered-inclined coupling slots. The feed waveguide is terminated in a matched load, and the element spacing in the feed waveguide is chosen to produce a beam squinted from the broadside. The traveling wave planar slot array consists of a long feed waveguide containing resonant-centered inclined coupling slots in the broad wall, coupling power into an array of stacked radiating waveguides orthogonal to it. The radiating waveguides consist of longitudinal offset radiating slots in a standing wave configuration. For the traveling wave feed of a planar slot array, one has to design the tilt angle and length of each coupling slot such that the amplitude and phase of excitation of each radiating waveguide are close to the desired values. The coupling slot spacing is chosen for an appropriate beam squint. Scattering matrix parameters of resonant coupling slots are used in the design process to produce appropriate excitations of radiating waveguides with constraints placed only on amplitudes. Since the radiating slots in each radiating waveguide are designed to produce a certain total admittance, the scattering (S) matrix of each coupling slot is reduced to a 2x2 matrix. Elements of each 2x2 S-matrix and the amount of coupling into the corresponding radiating waveguide are expressed in terms of the element S11. S matrices are converted into transmission (T) matrices, and the T matrices are multiplied to cascade the coupling slots and waveguide sections, starting from the load end and proceeding towards the source. While the use of non-resonant coupling slots may provide an
Standing and travelling waves in a spherical brain model: The Nunez model revisited
Visser, S.; Nicks, R.; Faugeras, O.; Coombes, S.
2017-06-01
The Nunez model for the generation of electroencephalogram (EEG) signals is naturally described as a neural field model on a sphere with space-dependent delays. For simplicity, dynamical realisations of this model either as a damped wave equation or an integro-differential equation, have typically been studied in idealised one dimensional or planar settings. Here we revisit the original Nunez model to specifically address the role of spherical topology on spatio-temporal pattern generation. We do this using a mixture of Turing instability analysis, symmetric bifurcation theory, centre manifold reduction and direct simulations with a bespoke numerical scheme. In particular we examine standing and travelling wave solutions using normal form computation of primary and secondary bifurcations from a steady state. Interestingly, we observe spatio-temporal patterns which have counterparts seen in the EEG patterns of both epileptic and schizophrenic brain conditions.
A computational role for bistability and traveling waves in motor cortex
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Stewart eHeitmann
2012-09-01
Full Text Available Adaptive changes in behavior require rapid changes in brain states yet the brain must also remain stable. We investigated two neural mechanisms for evoking rapid transitions between spatiotemporal synchronization patterns of beta oscillations (13--30Hz in motor cortex. Cortex was modeled as a sheet of neural oscillators that were spatially coupled using a center-surround connection topology. Manipulating the inhibitory surround was found to evoke reliable transitions between synchronous oscillation patterns and traveling waves. These transitions modulated the simulated local field potential in agreement with physiological observations in humans. Intermediate levels of surround inhibition were also found to produce bistable coupling topologies that supported both waves and synchrony. State-dependent perturbation between bistable states produced very rapid transitions but were less reliable. We surmise that motor cortex may thus employ state-dependent computation to achieve very rapid changes between bistable motor states when the demand for speed exceeds the demand for accuracy.
Kok, A.L.; Hans, Elias W.; Schutten, Johannes M.J.; Zijm, Willem H.M.
2010-01-01
For the intensively studied vehicle routing problem (VRP), two real-life restrictions have received only minor attention in the VRP-literature: traffic congestion and driving hours regulations. Traffic congestion causes late arrivals at customers and long travel times resulting in large transport
Chap, Andrew; Tarditi, Alfonso G.; Scott, John H.
2013-01-01
A Particle-in-cell simulation model has been developed to study the physics of the Traveling Wave Direct Energy Converter (TWDEC) applied to the conversion of charged fusion products into electricity. In this model the availability of a beam of collimated fusion products is assumed; the simulation is focused on the conversion of the beam kinetic energy into alternating current (AC) electric power. The model is electrostatic, as the electro-dynamics of the relatively slow ions can be treated in the quasistatic approximation. A two-dimensional, axisymmetric (radial-axial coordinates) geometry is considered. Ion beam particles are injected on one end and travel along the axis through ring-shaped electrodes with externally applied time-varying voltages, thus modulating the beam by forming a sinusoidal pattern in the beam density. Further downstream, the modulated beam passes through another set of ring electrodes, now electrically oating. The modulated beam induces a time alternating potential di erence between adjacent electrodes. Power can be drawn from the electrodes by connecting a resistive load. As energy is dissipated in the load, a corresponding drop in beam energy is measured. The simulation encapsulates the TWDEC process by reproducing the time-dependent transfer of energy and the particle deceleration due to the electric eld phase time variations.
Sassi, Fabrizio; Liu, Han-Li; Emmert, John T.
2016-02-01
The effects of breaking of traveling, planetary scale Rossby waves (TPWs) in the lower thermosphere are investigated with respect to the mixing of neutral constituents. We use numerical simulations of the Whole Atmosphere Community Climate Model, eXtended version, whose meteorology below 92 km is constrained by atmospheric specifications obtained from operational weather forecast/data assimilation system. The Fourier spectra show that the amplitude of TPWs with periods between 3 and 10 days are statistically significant in some years; the amplitude and phase of the band-pass filtered behavior is consistent with the behavior of the 5 day wave. A wavelet analysis using the S-transform shows that large variations with periods between 3 and 10 days can occur in relatively narrow temporal windows (20-30 days) during boreal winter. The momentum flux entering the lower thermosphere during the times of TPW amplification is shown to be large, and the amplifications of the TPWs in the thermosphere are not always associated with stratospheric sudden warming. The subtropical zonal accelerations are consistent with Rossby wave encountering a surf zone at low latitudes, resulting in wave breaking. The zonal acceleration is shown to be associated with a meridional diffusion, which is largest in the lower thermosphere where the wave activity and the wave breaking are also large. The ultimate effect on neutral density and composition is a meridional, down-gradient mixing; although this horizontal diffusion is largest below 110 km, the effects on the composition are amplified with increasing altitude, due to the diffusive separation of the thermosphere.
Electric Vehicle Routing Problem with Charging Time and Variable Travel Time
Sai Shao; Wei Guan; Bin Ran; Zhengbing He; Jun Bi
2017-01-01
An electric vehicle routing problem with charging time and variable travel time is developed to address some operational issues such as range limitation and charging demand. The model is solved by using genetic algorithm to obtain the routes, the vehicle departure time at the depot, and the charging plan. Meanwhile, a dynamic Dijkstra algorithm is applied to find the shortest path between any two adjacent nodes along the routes. To prevent the depletion of all battery power and ensure safe op...
Konerding, Uwe; Bowen, Tom; Elkhuizen, Sylvia G; Faubel, Raquel; Forte, Paul; Karampli, Eleftheria; Mahdavi, Mahdi; Malmström, Tomi; Pavi, Elpida; Torkki, Paulus
2017-04-01
The effects of travel distance and travel time to the primary diabetes care provider and waiting time in the practice on health-related quality of life (HRQoL) of patients with type 2 diabetes are investigated. Survey data of 1313 persons with type 2 diabetes from six regions in England (274), Finland (163), Germany (254), Greece (165), the Netherlands (354), and Spain (103) were analyzed. Various multiple linear regression analyses with four different EQ-5D-3L indices (English, German, Dutch and Spanish index) as target variables, with travel distance, travel time, and waiting time in the practice as focal predictors and with control for study region, patient's gender, patient's age, patient's education, time since diagnosis, thoroughness of provider-patient communication were computed. Interactions of regions with the remaining five control variables and the three focal predictors were also tested. There are no interactions of regions with control variables or focal predictors. The indices decrease with increasing travel time to the provider and increasing waiting time in the provider's practice. HRQoL of patients with type 2 diabetes might be improved by decreasing travel time to the provider and waiting time in the provider's practice. Copyright © 2017 Elsevier B.V. All rights reserved.
Application of travel time information for traffic management : technical summary.
2012-01-01
Using conventional methods, it is extremely costly to measure detailed traffic characteristics in high quality spatial or temporal resolution. For analyzing travel characteristics on roadways, the floating car method, developed in the 1920s, has hist...
Experimental Study of Linear Compressor Driven Traveling-wave Thermo Acoustic Refrigerator
Wu, Z.; Luo, E.; Dai, W.; Yu, G.
2006-04-01
The investigation on the performance of a traveling-wave thermoacoustic refrigerator driven by a self-made linear compressor is presented in this paper. The linear compressor is of moving-coil type, which has a moving coil, a piston with about 100 square centimeters cross section area, and a flexure bearing unit for piston support. The operating frequency can be adjusted to achieve a resonant status in order that the compressor can work with high electroacoustic efficiency. The thermoacoustic refrigerator operates on traveling-wave mode with acoustic power recovery. In the experiments, influence of different working frequencies on electroacoustic efficiency, lowest temperature, cooling power and COP is investigated. So far in the experiment with helium as working fluid, a lowest temperature of -29 °C is obtained, when the mean and oscillating pressures are 1.0MPa and 0.042MPa respectively and the temperature of room-temperature heat exchanger is kept around 15°C. And a maximum cooling power of about 28.5W@0°C is achieved under 1.5MPa mean pressure and 0.049MPa oscillating pressure. Besides, the performance of the linear compressor itself is also investigated, which is important for a reasonable evaluation of the refrigerator performance.
Johnson, Kennita A.; Vormohr, Hannah R.; Doinikov, Alexander A.; Bouakaz, Ayache; Shields, C. Wyatt; López, Gabriel P.; Dayton, Paul A.
2016-05-01
Acoustophoresis uses acoustic radiation force to remotely manipulate particles suspended in a host fluid for many scientific, technological, and medical applications, such as acoustic levitation, acoustic coagulation, contrast ultrasound imaging, ultrasound-assisted drug delivery, etc. To estimate the magnitude of acoustic radiation forces, equations derived for an inviscid host fluid are commonly used. However, there are theoretical predictions that, in the case of a traveling wave, viscous effects can dramatically change the magnitude of acoustic radiation forces, which make the equations obtained for an inviscid host fluid invalid for proper estimation of acoustic radiation forces. To date, experimental verification of these predictions has not been published. Experimental measurements of viscous effects on acoustic radiation forces in a traveling wave were conducted using a confocal optical and acoustic system and values were compared with available theories. Our results show that, even in a low-viscosity fluid such as water, the magnitude of acoustic radiation forces is increased manyfold by viscous effects in comparison with what follows from the equations derived for an inviscid fluid.
Study of rectangular beam folded waveguide traveling-wave tube for terahertz radiation
Lu, Fengying; Zhang, Changqing; Grieser, Manfred; Wang, Yong; Lü, Suye; Zhao, Guohui
2017-10-01
To gain higher power with a lower cathode current density and a simpler structure, a novel rectangular beam folded waveguide traveling-wave tube (RB-FW-TWT) operating at 220 GHz is proposed and analyzed in this paper and compared with the normal circular beam (CB) FW TWT. The dispersion characteristic was investigated based on an equivalent circuit model. The interaction impedance and the S-parameter of a RB-FW traveling-wave tube were analyzed by numerical simulations. A 3-D particle-in-cell code CST particle studio was introduced to analyze the performance of RB-FW TWT. The influence of the initial electron energy, frequency, input power, guiding magnetic field, and aspect ratio of the RB tunnel on the circuit performance was observed, and physical explanations were given. It reveals that the output power of RB-FW can reach 51.1 dBm, 8.4% dBm higher than a CB-FW, with a 3 dB bandwidth of 35 GHz when the beam voltage and current are set to 14.25 kV and 140 mA, respectively. An aspect ratio of 0.4 is recommended to optimize the high-frequency properties and circuit performance.
Pal, Debashis; Chakraborty, Suman
2012-07-01
We discover that thermoviscous expansion along a traveling wave in a microfluidic channel may be capable of generating a spatially uniform flow profile in a time-averaged sense. We further delineate that the resultant complex flow characteristics, realized by virtue of an intricate interplay between thermal compression-expansion waves and temperature-dependent viscosity variations and controlled by an external heating, may be remarkably characterized by a unique thermal penetration depth scale (analogous to Debye length in electro-osmosis) and a velocity scale (analogous to the Helmholtz Smulochowski velocity in electro-osmosis) that in turn depends on the considerations of “thin” and “thick” microchannel limits, as dictated by the thermal penetration depth as compared to the lateral extent of the microfluidic channel. We show that, when the thermal penetration depth is small as compared to the channel height, a uniform velocity profile is generated in the channel in a time-averaged sense. The velocity scale characterizing this uniform flow may be represented by a function of the thermal diffusivity, volumetric expansion coefficient and thermal viscosity coefficient of the fluid, characteristic amplitude and speed of the thermal wave, as well as the channel height. Results from the present study are expected to provide valuable insights towards arresting hydrodynamic dispersion in microchannels by nonelectrochemical means, following a pH-independent route.
A nonlinear analysis of the terahertz serpentine waveguide traveling-wave amplifier
Energy Technology Data Exchange (ETDEWEB)
Li, Ke, E-mail: like.3714@163.com; Cao, Miaomiao, E-mail: mona486@yeah.net [Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190 (China); Institute of Electronics, University of Chinese Academy of Sciences, Beijing 100190 (China); Liu, Wenxin, E-mail: lwenxin@mail.ie.ac.cn; Wang, Yong, E-mail: wangyong3845@sina.com [Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190 (China)
2015-04-15
A nonlinear model for the numerical simulation of terahertz serpentine waveguide traveling-wave tube (SW-TWT) is described. In this model, the electromagnetic wave transmission in the SW is represented as an infinite set of space harmonics to interact with an electron beam. Analytical expressions for axial electric fields in axisymmetric interaction gaps of SW-TWTs are derived and compared with the results from CST simulation. The continuous beam is treated as discrete macro-particles with different initial phases. The beam-tunnel field equations, space-charge field equations, and motion equations are combined to solve the beam-wave interaction. The influence of backward wave and relativistic effect is also considered in the series of equations. The nonlinear model is used to design a 340 GHz SW-TWT. Several favorable comparisons of model predictions with results from a 3-D Particle-in-cell simulation code CHIPIC are presented, in which the output power versus beam voltage and interaction periods are illustrated. The relative error of the predicted output power is less than 15% in the 3 dB bandwidth and the relative error of the saturated length is less than 8%.The results show that the 1-D nonlinear analysis model is appropriate to solve the terahertz SW-TWT operation characteristics.
Simulation analysis of rectangular dielectric-loaded traveling wave amplifiers for THz sources
Directory of Open Access Journals (Sweden)
Changbiao Wang
2007-12-01
Full Text Available Nonlinear simulation results for a 220-GHz rectangular dielectric-loaded traveling-wave amplifier are presented. Simulations are used to check a linear theory that is developed by phenomenological introduction of an effective dielectric parameter for electron beam channel, and it is found that the rf power gains from Pierce three-wave theory and particle simulations are in reasonable agreement. It is shown that the rf power gain during initial beam-wave interaction is positive; the falling on the initial rf power profile, which has been thought to be the rf power transferred to the beam for bunching buildup (negative gain effect, is probably resulting from numerical errors. Beam-wave interaction mechanism is analyzed by examining the evolution of beam bunching centers. Influences of various parameters on amplifier performance are examined, and transverse space-charge effect is analyzed. A symmetric excitation scheme for rf couplers is proposed, and rf field jumps on the common intersection line of vacuum, dielectric, and metal wall, which were found in rf simulations, are explained theoretically.
Liu, Kai; Cui, Meng-Ying; Cao, Peng; Wang, Jiang-Bo
2016-01-01
On urban arterials, travel time estimation is challenging especially from various data sources. Typically, fusing loop detector data and probe vehicle data to estimate travel time is a troublesome issue while considering the data issue of uncertain, imprecise and even conflicting. In this paper, we propose an improved data fusing methodology for link travel time estimation. Link travel times are simultaneously pre-estimated using loop detector data and probe vehicle data, based on which Bayesian fusion is then applied to fuse the estimated travel times. Next, Iterative Bayesian estimation is proposed to improve Bayesian fusion by incorporating two strategies: 1) substitution strategy which replaces the lower accurate travel time estimation from one sensor with the current fused travel time; and 2) specially-designed conditions for convergence which restrict the estimated travel time in a reasonable range. The estimation results show that, the proposed method outperforms probe vehicle data based method, loop detector based method and single Bayesian fusion, and the mean absolute percentage error is reduced to 4.8%. Additionally, iterative Bayesian estimation performs better for lighter traffic flows when the variability of travel time is practically higher than other periods.
Faraday waves under time-reversed excitation.
Pietschmann, Dirk; Stannarius, Ralf; Wagner, Christian; John, Thomas
2013-03-01
Do parametrically driven systems distinguish periodic excitations that are time mirrors of each other? Faraday waves in a Newtonian fluid are studied under excitation with superimposed harmonic wave forms. We demonstrate that the threshold parameters for the stability of the ground state are insensitive to a time inversion of the driving function. This is a peculiarity of some dynamic systems. The Faraday system shares this property with standard electroconvection in nematic liquid crystals [J. Heuer et al., Phys. Rev. E 78, 036218 (2008)]. In general, time inversion of the excitation affects the asymptotic stability of a parametrically driven system, even when it is described by linear ordinary differential equations. Obviously, the observed symmetry has to be attributed to the particular structure of the underlying differential equation system. The pattern selection of the Faraday waves above threshold, on the other hand, discriminates between time-mirrored excitation functions.
Using prospect theory to investigate the low marginal value of travel time for small time changes
DEFF Research Database (Denmark)
Hjorth, Katrine; Fosgerau, Mogens
2012-01-01
A common finding in stated preference studies that measure the value of travel time (VTT) is that the measured VTT increases with the size of the time change considered, in conflict with standard neoclassical economic theory. We present a new test of a possible explanation for the phenomenon...... that builds on the diminishing or constant sensitivity of the value functions in prospect theory.We use stated preference data with trade-offs between travel time and money that provide separate identification of the degrees of diminishing sensitivity for time and money gains and losses. This enables us...... to test and potentially falsify the prospect theory explanation. We conclude that prospect theory remains a potential explanation of the phenomenon....
Electric Vehicle Routing Problem with Charging Time and Variable Travel Time
Directory of Open Access Journals (Sweden)
Sai Shao
2017-01-01
Full Text Available An electric vehicle routing problem with charging time and variable travel time is developed to address some operational issues such as range limitation and charging demand. The model is solved by using genetic algorithm to obtain the routes, the vehicle departure time at the depot, and the charging plan. Meanwhile, a dynamic Dijkstra algorithm is applied to find the shortest path between any two adjacent nodes along the routes. To prevent the depletion of all battery power and ensure safe operation in transit, electric vehicles with insufficient battery power can be repeatedly recharged at charging stations. The fluctuations in travel time are implemented to reflect a dynamic traffic environment. In conclusion, a large and realistic case study with a road network in the Beijing urban area is conducted to evaluate the model performance and the solution technology and analyze the results.
Gravitational Waves and Time Domain Astronomy
Centrella, Joan; Nissanke, Samaya; Williams, Roy
2012-01-01
The gravitational wave window onto the universe will open in roughly five years, when Advanced LIGO and Virgo achieve the first detections of high frequency gravitational waves, most likely coming from compact binary mergers. Electromagnetic follow-up of these triggers, using radio, optical, and high energy telescopes, promises exciting opportunities in multi-messenger time domain astronomy. In the decade, space-based observations of low frequency gravitational waves from massive black hole mergers, and their electromagnetic counterparts, will open up further vistas for discovery. This two-part workshop featured brief presentations and stimulating discussions on the challenges and opportunities presented by gravitational wave astronomy. Highlights from the workshop, with the emphasis on strategies for electromagnetic follow-up, are presented in this report.
National Aeronautics and Space Administration — Space telecommunications require amplifiers that are efficient, high-power, wideband, small, lightweight, and highly reliable. Currently, helix traveling wave tube...
Watt-Meyer, O.; Kushner, P. J.
2015-12-01
The winter season over North America during 2013/14 was dominated by a persistent ridge-trough that brought warm and dry conditions to the southwestern U.S., and markedly cold temperatures to central and eastern North America [Wang et al., 2014; Hartmann, 2015]. In addition, several cold air outbreaks occurred during the winter season, the strongest of which was around 7 January 2014 and led to minimum daily temperature records being set at many weather stations including Atlanta, Austin, Chicago and New York [Screen et al., in press]. This study uses a novel decomposition of wave variability into standing and travelling components [Watt-Meyer and Kushner, 2015] to diagnose the anomalous circulation of the 2013/14 winter season. This spectral decomposition is an improvement on previous methods because it explicitly accounts for the covariance between standing and travelling waves, and because the real-space components of the signal can be easily reconstructed. An index representing the ridge-trough dipole is computed using mid-tropospheric heights and shown to be well correlated with surface temperatures over central and eastern North America. The contributions to this dipole index from standing waves, westward travelling waves, and eastward travelling waves are calculated. The analysis demonstrates that the cold air outbreak of 7 January 2014 was driven by a synoptic wave of record breaking amplitude intensifying a persistent background amplification of the typical ridge-trough structure seen during North American winter.
Towards Developing a Travel Time Forecasting Model for Location-Based Services: a Review
You, Jinsoo; Kim, Tschangho John
2003-01-01
Travel time forecasting models have been studied intensively as a subject of Intelligent Transportation Systems (ITS), particularly in the topics of advanced traffic management systems (ATMS), advanced traveler information systems (ATIS), and commercial vehicle operations (CVO). While the concept of travel time forecasting is relatively simple, it involves a notably complicated task of implementing even a simple model. Thus, existing forecasting models are diverse in their original formulatio...
Rural population travel time to health services, mapped on Geographic Information System (GIS
Directory of Open Access Journals (Sweden)
Ricardo Vicente Ferreira
2014-04-01
Full Text Available Distance and travel time are important parameters in the evaluation of access to health services, especially for the population living in the countryside. In the present work, a GIS-based methodology is developed for the mapping of rural road networks and the determination of travel impedances in order to optimize the travel time of the rural population to health care facilities. Data on rural roads classes, slope, sinuosity, visibility and land use are considered in the composition of the impedances synthesis and its application on car travel time. The methodology was applied to the region of Registro (SP, and the results indicate an unequal distribution of health services.
Bolborici, V; Dawson, F P; Pugh, M C
2014-03-01
Piezoelectric traveling wave rotary ultrasonic motors are motors that generate torque by using the friction force between a piezoelectric composite ring (or disk-shaped stator) and a metallic ring (or disk-shaped rotor) when a traveling wave is excited in the stator. The motor speed is proportional to the amplitude of the traveling wave and, in order to obtain large amplitudes, the stator is excited at frequencies close to its resonance frequency. This paper presents a non-empirical partial differential equations model for the stator, which is discretized using the finite volume method. The fundamental frequency of the discretized model is computed and compared to the experimentally-measured operating frequency of the stator of Shinsei USR60 piezoelectric motor. Copyright © 2013 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
Farhad Namdari
2016-06-01
Full Text Available Accurate fault classification and localization are the bases of protection for transmission systems. This paper presents a new method for classifying and showing location of faults by travelling waves and modal analysis. In the proposed method, characteristics of different faults are investigated using Clarke transformation and initial current traveling wave; then, appropriate indices are introduced to identify different types of faults. Continuous wavelet transform (CWT is employed to extract information of current and voltage travelling waves. Fault location and classification algorithm is being designed according to wavelet transform coefficients relating to current and voltage modal components. The performance of the proposed method is tested for different fault conditions (different fault distance, different fault resistances, and different fault inception angles by using PSCAD and MATLAB with satisfactory results
Experimental results of guided wave travel time tomography
Volker, A.W.F.; Bloom, J.G.P.
2010-01-01
Corrosion is one of the industries major issues regarding the integrity of assets. Currently inspections are conducted at regular intervals to ensure a sufficient integrity level of these assets. Cost reduction while maintaining a high level of reliability and safety of installations is a major
1.5 octave wideband traveling-wave tube with heavily-loaded helical slow-wave structure
Jung, S S; Han, S T; Jeon, S; Soukhov, A V; Park, G S
2001-01-01
Summary form only given. A 1.5 octave wideband traveling wave tube (TWT) with a helical structure loaded by the thick dielectric support rods has been designed and fabricated for the frequency range of 6-18 GHz. Helical slow-wave structure (SWS) was modeled using three- dimensional HFSS code. The nonresonant perturbation measurement using a thin copper wire with 20 mm diameter was performed to verify the phase velocity and interaction impedance of the helical structure. The performance of TWT was predicted using one-dimensional (1-D) nonlinear theory involving a macro particle beam model. The harmonic effect was considered in this calculation. The measured performance of TWT using a beam voltage 4 kV and a beam current of 120 mA was shown. These results were compared with a 1-D nonlinear theory. The comparison showed that the measured power and gain were less than the predicted one but had a similar trend over the operating frequency range. The 2nd harmonic levels at the low frequency range of 6-8 GHz were ne...
Couvidat, S.; Zhao, J.; Birch, A. C.; Kosovichev, A. G.; Duvall, Thomas L., Jr.; Parchevsky, K.; Scherrer, P. H.
2010-01-01
The Helioseismic and Magnetic Imager (HMI) instrument onboard the Solar Dynamics Observatory (SDO) satellite is designed to produce high-resolution Doppler-velocity maps of oscillations at the solar surface with high temporal cadence. To take advantage of these high-quality oscillation data, a time - distance helioseismology pipeline (Zhao et al., Solar Phys. submitted, 2010) has been implemented at the Joint Science Operations Center (JSOC) at Stanford University. The aim of this pipeline is to generate maps of acoustic travel times from oscillations on the solar surface, and to infer subsurface 3D flow velocities and sound-speed perturbations. The wave travel times are measured from cross-covariances of the observed solar oscillation signals. For implementation into the pipeline we have investigated three different travel-time definitions developed in time - distance helioseismology: a Gabor-wavelet fitting (Kosovichev and Duvall, SCORE'96: Solar Convection and Oscillations and Their Relationship, ASSL, Dordrecht, 241, 1997), a minimization relative to a reference cross-covariance function (Gizon and Birch, Astrophys. J. 571, 966, 2002), and a linearized version of the minimization method (Gizon and Birch, Astrophys. J. 614, 472, 2004). Using Doppler-velocity data from the Michelson Doppler Imager (MDI) instrument onboard SOHO, we tested and compared these definitions for the mean and difference traveltime perturbations measured from reciprocal signals. Although all three procedures return similar travel times in a quiet-Sun region, the method of Gizon and Birch (Astrophys. J. 614, 472, 2004) gives travel times that are significantly different from the others in a magnetic (active) region. Thus, for the pipeline implementation we chose the procedures of Kosovichev and Duvall (SCORE'96: Solar Convection and Oscillations and Their Relationship, ASSL, Dordrecht, 241, 1997) and Gizon and Birch (Astrophys. J. 571, 966, 2002). We investigated the relationships among
Extending shear-wave tomography for the lower mantle using S and SKS arrival-time data
Widiyantoro, S.; Kennett, B.L.N.; Hilst, R.D. van der
1998-01-01
Seismic tomography using S wave travel times faces the difficulty imposed by the interference between S and SKS phases near 83o epicentral distance, as the SKS phase overtakes the S waves in the mantle. If the cross-over is avoided completely by excluding S data beyond 82o then no resolution is
Time travel and warp drives a scientific guide to shortcuts through time and space
Everett, Allen
2012-01-01
Sci-fi makes it look so easy. Receive a distress call from Alpha Centauri? No problem: punch the warp drive and you're there in minutes. Facing a catastrophe that can't be averted? Just pop back in the timestream and stop it before it starts. But for those of us not lucky enough to live in a science-fictional universe, are these ideas merely flights of fancy—or could it really be possible to travel through time or take shortcuts between stars?Cutting-edge physics may not be able to answer those questions yet, but it does offer up some tantalizing possibilities. In Time Travel and W
A Simplified Network Model for Travel Time Reliability Analysis in a Road Network
Directory of Open Access Journals (Sweden)
Kenetsu Uchida
2017-01-01
Full Text Available This paper proposes a simplified network model which analyzes travel time reliability in a road network. A risk-averse driver is assumed in the simplified model. The risk-averse driver chooses a path by taking into account both a path travel time variance and a mean path travel time. The uncertainty addressed in this model is that of traffic flows (i.e., stochastic demand flows. In the simplified network model, the path travel time variance is not calculated by considering all travel time covariance between two links in the network. The path travel time variance is calculated by considering all travel time covariance between two adjacent links in the network. Numerical experiments are carried out to illustrate the applicability and validity of the proposed model. The experiments introduce the path choice behavior of a risk-neutral driver and several types of risk-averse drivers. It is shown that the mean link flows calculated by introducing the risk-neutral driver differ as a whole from those calculated by introducing several types of risk-averse drivers. It is also shown that the mean link flows calculated by the simplified network model are almost the same as the flows calculated by using the exact path travel time variance.
Epstude, K.; Peetz, J.
Humans have the unique capacity to mentally travel through time, that is, to reflect on the past, anticipate the future, and construct alternate realities in their minds. The ability to mentally travel through time affects a variety of social psychological topics. Representations of events can
Kovar K; Leijnse A; Uffink G; Pastoors MJH; Mulschlegel JHC; Zaadnoordijk WJ; LDL; IMD; TNO/NITG; Haskoning
2005-01-01
A modelling approach was developed, incorporated in the finite-element method based program LGMLUC, making it possible to determine the reliability of travel times of groundwater flowing to groundwater abstraction sites. The reliability is seen here as a band (zone) around the expected travel-time
Toward a formal foundation for time travel in stories and games
M. Helvensteijn (Michiel); F. Arbab (Farhad)
2016-01-01
textabstractTime-travel is a popular topic not only in science fiction, but in physics as well, especially when it concerns the notion of “changing the past”. It turns out that if time-travel exists, it will follow certain logical rules. In this paper we apply the tools of discrete mathematics to