WorldWideScience

Sample records for exact time-reversal focusing

  1. Exactly soluble local bosonic cocycle models, statistical transmutation, and simplest time-reversal symmetric topological orders in 3+1 dimensions

    Science.gov (United States)

    Wen, Xiao-Gang

    2017-05-01

    We propose a generic construction of exactly soluble local bosonic models that realize various topological orders with gappable boundaries. In particular, we construct an exactly soluble bosonic model that realizes a (3+1)-dimensional [(3+1)D] Z2-gauge theory with emergent fermionic Kramers doublet. We show that the emergence of such a fermion will cause the nucleation of certain topological excitations in space-time without pin+ structure. The exactly soluble model also leads to a statistical transmutation in (3+1)D. In addition, we construct exactly soluble bosonic models that realize 2 types of time-reversal symmetry-enriched Z2 topological orders in 2+1 dimensions, and 20 types of simplest time-reversal symmetry-enriched topological (SET) orders which have only one nontrivial pointlike and stringlike topological excitation. Many physical properties of those topological states are calculated using the exactly soluble models. We find that some time-reversal SET orders have pointlike excitations that carry Kramers doublet, a fractionalized time-reversal symmetry. We also find that some Z2 SET orders have stringlike excitations that carry anomalous (nononsite) Z2 symmetry, which can be viewed as a fractionalization of Z2 symmetry on strings. Our construction is based on cochains and cocycles in algebraic topology, which is very versatile. In principle, it can also realize emergent topological field theory beyond the twisted gauge theory.

  2. Time reversal focusing of elastic waves in plates for an educational demonstration.

    Science.gov (United States)

    Heaton, Christopher; Anderson, Brian E; Young, Sarah M

    2017-02-01

    The purpose of this research is to develop a visual demonstration of time reversal focusing of vibrations in a thin plate. Various plate materials are tested to provide optimal conditions for time reversal focusing. Specifically, the reverberation time in each plate and the vibration coupling efficiency from a shaker to the plate are quantified to illustrate why a given plate provides the best spatially confined focus as well as the highest focal amplitude possible. A single vibration speaker and a scanning laser Doppler vibrometer (SLDV) are used to provide the time reversal focusing. Table salt is sprinkled onto the plate surface to allow visualization of the high amplitude, spatially localized time reversal focus; the salt is thrown upward only at the focal position. Spatial mapping of the vibration focusing on the plate using the SLDV is correlated to the visual salt jumping demonstration. The time reversal focusing is also used to knock over an object when the object is placed at the focal position; some discussion of optimal objects to use for this demonstration are given.

  3. Exact Synthesis of Reversible Circuits Using A* Algorithm

    Science.gov (United States)

    Datta, K.; Rathi, G. K.; Sengupta, I.; Rahaman, H.

    2015-06-01

    With the growing emphasis on low-power design methodologies, and the result that theoretical zero power dissipation is possible only if computations are information lossless, design and synthesis of reversible logic circuits have become very important in recent years. Reversible logic circuits are also important in the context of quantum computing, where the basic operations are reversible in nature. Several synthesis methodologies for reversible circuits have been reported. Some of these methods are termed as exact, where the motivation is to get the minimum-gate realization for a given reversible function. These methods are computationally very intensive, and are able to synthesize only very small functions. There are other methods based on function transformations or higher-level representation of functions like binary decision diagrams or exclusive-or sum-of-products, that are able to handle much larger circuits without any guarantee of optimality or near-optimality. Design of exact synthesis algorithms is interesting in this context, because they set some kind of benchmarks against which other methods can be compared. This paper proposes an exact synthesis approach based on an iterative deepening version of the A* algorithm using the multiple-control Toffoli gate library. Experimental results are presented with comparisons with other exact and some heuristic based synthesis approaches.

  4. Focusing over Optical Fiber Using Time Reversal

    DEFF Research Database (Denmark)

    Piels, Molly; Porto da Silva, Edson; Estaran Tolosa, Jose Manuel

    2015-01-01

    A time-reversal array in multimode fiber is proposed for lossless remotely controlled switching using passive optical splitters. The signal to be transmitted is digitally pre-distorted so that it is routed through the physical layer in order to arrive at only one receiver in an array. System...... performance in the presence of additive white gaussian noise, modal group delay, and timing error is investigated numerically for single-mode and 10-mode fiber. Focusing using a two-transmitter array and 44 km of single- mode fiber is demonstrated experimentally for 3 GBd QPSK signals with a bit error rate...

  5. Time-Reversal Generation of Rogue Waves

    Science.gov (United States)

    Chabchoub, Amin; Fink, Mathias

    2014-03-01

    The formation of extreme localizations in nonlinear dispersive media can be explained and described within the framework of nonlinear evolution equations, such as the nonlinear Schrödinger equation (NLS). Within the class of exact NLS breather solutions on a finite background, which describe the modulational instability of monochromatic wave trains, the hierarchy of rational solutions localized in both time and space is considered to provide appropriate prototypes to model rogue wave dynamics. Here, we use the time-reversal invariance of the NLS to propose and experimentally demonstrate a new approach to constructing strongly nonlinear localized waves focused in both time and space. The potential applications of this time-reversal approach include remote sensing and motivated analogous experimental analysis in other nonlinear dispersive media, such as optics, Bose-Einstein condensates, and plasma, where the wave motion dynamics is governed by the NLS.

  6. Time-reversal focusing of an expanding soliton gas in disordered replicas

    KAUST Repository

    Fratalocchi, Andrea; Armaroli, A.; Trillo, S.

    2011-01-01

    We investigate the properties of time reversibility of a soliton gas, originating from a dispersive regularization of a shock wave, as it propagates in a strongly disordered environment. An original approach combining information measures and spin glass theory shows that time-reversal focusing occurs for different replicas of the disorder in forward and backward propagation, provided the disorder varies on a length scale much shorter than the width of the soliton constituents. The analysis is performed by starting from a new class of reflectionless potentials, which describe the most general form of an expanding soliton gas of the defocusing nonlinear Schrödinger equation.

  7. Time-reversal focusing of an expanding soliton gas in disordered replicas

    KAUST Repository

    Fratalocchi, Andrea

    2011-05-31

    We investigate the properties of time reversibility of a soliton gas, originating from a dispersive regularization of a shock wave, as it propagates in a strongly disordered environment. An original approach combining information measures and spin glass theory shows that time-reversal focusing occurs for different replicas of the disorder in forward and backward propagation, provided the disorder varies on a length scale much shorter than the width of the soliton constituents. The analysis is performed by starting from a new class of reflectionless potentials, which describe the most general form of an expanding soliton gas of the defocusing nonlinear Schrödinger equation.

  8. On the focusing conditions in time-reversed acoustics, seismic interferometry, and Marchenko imaging

    NARCIS (Netherlands)

    Wapenaar, C.P.A.; Van der Neut, J.R.; Thorbecke, J.W.; Vasconcelos, I.; Van Manen, D.J.; Ravasi, M.

    2014-01-01

    Despite the close links between the fields of time-reversed acoustics, seismic interferometry and Marchenko imaging, a number of subtle differences exist. This paper reviews the various focusing conditions of these methods, the causality/acausality aspects of the corresponding focusing wavefields,

  9. Speckle-scale focusing in the diffusive regime with time reversal of variance-encoded light (TROVE)

    Science.gov (United States)

    Judkewitz, Benjamin; Wang, Ying Min; Horstmeyer, Roarke; Mathy, Alexandre; Yang, Changhuei

    2013-04-01

    Focusing of light in the diffusive regime inside scattering media has long been considered impossible. Recently, this limitation has been overcome with time reversal of ultrasound-encoded light (TRUE), but the resolution of this approach is fundamentally limited by the large number of optical modes within the ultrasound focus. Here, we introduce a new approach, time reversal of variance-encoded light (TROVE), which demixes these spatial modes by variance encoding to break the resolution barrier imposed by the ultrasound. By encoding individual spatial modes inside the scattering sample with unique variances, we effectively uncouple the system resolution from the size of the ultrasound focus. This enables us to demonstrate optical focusing and imaging with diffuse light at an unprecedented, speckle-scale lateral resolution of ~5 µm.

  10. Speckle-scale focusing in the diffusive regime with time-reversal of variance-encoded light (TROVE).

    Science.gov (United States)

    Judkewitz, Benjamin; Wang, Ying Min; Horstmeyer, Roarke; Mathy, Alexandre; Yang, Changhuei

    2013-04-01

    Focusing of light in the diffusive regime inside scattering media has long been considered impossible. Recently, this limitation has been overcome with time reversal of ultrasound-encoded light (TRUE), but the resolution of this approach is fundamentally limited by the large number of optical modes within the ultrasound focus. Here, we introduce a new approach, time reversal of variance-encoded light (TROVE), which demixes these spatial modes by variance-encoding to break the resolution barrier imposed by the ultrasound. By encoding individual spatial modes inside the scattering sample with unique variances, we effectively uncouple the system resolution from the size of the ultrasound focus. This enables us to demonstrate optical focusing and imaging with diffuse light at unprecedented, speckle-scale lateral resolution of ~ 5 μm.

  11. DSP-Based Focusing over Optical Fiber Using Time Reversal

    DEFF Research Database (Denmark)

    Piels, Molly; Porto da Silva, Edson; Estaran Tolosa, Jose Manuel

    2014-01-01

    A time-reversal array in multimode fiber is proposed for lossless switching using passive optical splitters. Numerical investigations are performed, and a two-transmitter array that routes a 3GBd QPSK signal through the physical layer is demonstrated experimentally.......A time-reversal array in multimode fiber is proposed for lossless switching using passive optical splitters. Numerical investigations are performed, and a two-transmitter array that routes a 3GBd QPSK signal through the physical layer is demonstrated experimentally....

  12. Time-reversed ultrasonically encoded (TRUE) focusing for deep-tissue optogenetic modulation

    Science.gov (United States)

    Brake, Joshua; Ruan, Haowen; Robinson, J. Elliott; Liu, Yan; Gradinaru, Viviana; Yang, Changhuei

    2018-02-01

    The problem of optical scattering was long thought to fundamentally limit the depth at which light could be focused through turbid media such as fog or biological tissue. However, recent work in the field of wavefront shaping has demonstrated that by properly shaping the input light field, light can be noninvasively focused to desired locations deep inside scattering media. This has led to the development of several new techniques which have the potential to enhance the capabilities of existing optical tools in biomedicine. Unfortunately, extending these methods to living tissue has a number of challenges related to the requirements for noninvasive guidestar operation, speed, and focusing fidelity. Of existing wavefront shaping methods, time-reversed ultrasonically encoded (TRUE) focusing is well suited for applications in living tissue since it uses ultrasound as a guidestar which enables noninvasive operation and provides compatibility with optical phase conjugation for high-speed operation. In this paper, we will discuss the results of our recent work to apply TRUE focusing for optogenetic modulation, which enables enhanced optogenetic stimulation deep in tissue with a 4-fold spatial resolution improvement in 800-micron thick acute brain slices compared to conventional focusing, and summarize future directions to further extend the impact of wavefront shaping technologies in biomedicine.

  13. Time reversal in photoacoustic tomography and levitation in a cavity

    International Nuclear Information System (INIS)

    Palamodov, V P

    2014-01-01

    A class of photoacoustic acquisition geometries in R n is considered such that the spherical mean transform admits an exact filtered back projection reconstruction formula. The reconstruction is interpreted as a time reversion mirror that reproduces exactly an arbitrary source distribution in the cavity. A series of examples of non-uniqueness of the inverse potential problem is constructed based on the same geometrical technique. (paper)

  14. Time-reversal invariance in multiple collisions between coupled masses

    International Nuclear Information System (INIS)

    Crawford, F.S.

    1989-01-01

    The time evolution of two mechanical oscillators coupled by a spring can (but need not) exhibit an instant t = 2t' when the initial conditions at t = 0 have been exactly restored. When that is the case, then at t = t' energy and momentum have been exchanged exactly as in an elastic collision between two free particles, and the evolution of the system from t = t' to 2t' is related to that from 0 to t' by time-reversal invariance. A similar ''simulation of elastic scattering'' at t = t' can occur for two free particles coupled via collisions with an intermediary mass that bounces back and forth between the two particles provided the intermediary is left at rest at t = t'. Examined here is the time evolution of the exchange of momentum and energy for these two examples, determining the values of the coupling spring constant (or mass value) of the intermediating spring (or mass) needed to simulate single elastic scattering between free particles, and looking at the manifestation of time-reversal invariance

  15. Crossover driven by time-reversal symmetry breaking in quantum chaos

    International Nuclear Information System (INIS)

    Taniguchi, N.; Hashimoto, A.; Simons, B.D.; Altshuler, B.L.

    1994-01-01

    Parametric correlations of the energy spectra of quantum chaotic systems are presented in the presence of time-reversal symmetry-breaking perturbations. The spectra disperse as a function of two external perturbations, one of which preserves time-reversal symmetry, while the other violates it. Exact analytical expressions for the parametric two-point autocorrelation function of the density of states are derived in the crossover region by means of the supermatrix method. For the orthogonal-unitary crossover, the velocity distribution is determined and shown to deviate from Gaussian. (orig.)

  16. Time reversibility in the quantum frame

    Energy Technology Data Exchange (ETDEWEB)

    Masot-Conde, Fátima [Escuela Superior Ingenieros, Dpt. Física Aplicada III, Universidad de Sevilla Isla Mágica, 41092- Sevilla (Spain)

    2014-12-04

    Classic Mechanics and Electromagnetism, conventionally taken as time-reversible, share the same concept of motion (either of mass or charge) as the basis of the time reversibility in their own fields. This paper focuses on the relationship between mobile geometry and motion reversibility. The goal is to extrapolate the conclusions to the quantum frame, where matter and radiation behave just as elementary mobiles. The possibility that the asymmetry of Time (Time’s arrow) is an effect of a fundamental quantum asymmetry of elementary particles, turns out to be a consequence of the discussion.

  17. Elastic least-squares reverse time migration

    KAUST Repository

    Feng, Zongcai; Schuster, Gerard T.

    2016-01-01

    Elastic least-squares reverse time migration (LSRTM) is used to invert synthetic particle-velocity data and crosswell pressure field data. The migration images consist of both the P- and Svelocity perturbation images. Numerical tests on synthetic and field data illustrate the advantages of elastic LSRTM over elastic reverse time migration (RTM). In addition, elastic LSRTM images are better focused and have better reflector continuity than do the acoustic LSRTM images.

  18. Elastic least-squares reverse time migration

    KAUST Repository

    Feng, Zongcai

    2016-09-06

    Elastic least-squares reverse time migration (LSRTM) is used to invert synthetic particle-velocity data and crosswell pressure field data. The migration images consist of both the P- and Svelocity perturbation images. Numerical tests on synthetic and field data illustrate the advantages of elastic LSRTM over elastic reverse time migration (RTM). In addition, elastic LSRTM images are better focused and have better reflector continuity than do the acoustic LSRTM images.

  19. Time-reversed ultrasonically encoded optical focusing through highly scattering ex vivo human cataractous lenses

    Science.gov (United States)

    Liu, Yan; Shen, Yuecheng; Ruan, Haowen; Brodie, Frank L.; Wong, Terence T. W.; Yang, Changhuei; Wang, Lihong V.

    2018-01-01

    Normal development of the visual system in infants relies on clear images being projected onto the retina, which can be disrupted by lens opacity caused by congenital cataract. This disruption, if uncorrected in early life, results in amblyopia (permanently decreased vision even after removal of the cataract). Doctors are able to prevent amblyopia by removing the cataract during the first several weeks of life, but this surgery risks a host of complications, which can be equally visually disabling. Here, we investigated the feasibility of focusing light noninvasively through highly scattering cataractous lenses to stimulate the retina, thereby preventing amblyopia. This approach would allow the cataractous lens removal surgery to be delayed and hence greatly reduce the risk of complications from early surgery. Employing a wavefront shaping technique named time-reversed ultrasonically encoded optical focusing in reflection mode, we focused 532-nm light through a highly scattering ex vivo adult human cataractous lens. This work demonstrates a potential clinical application of wavefront shaping techniques.

  20. Non invasive transcostal focusing based on the decomposition of the time reversal operator: in vitro validation

    Science.gov (United States)

    Cochard, Étienne; Prada, Claire; Aubry, Jean-François; Fink, Mathias

    2010-03-01

    Thermal ablation induced by high intensity focused ultrasound has produced promising clinical results to treat hepatocarcinoma and other liver tumors. However skin burns have been reported due to the high absorption of ultrasonic energy by the ribs. This study proposes a method to produce an acoustic field focusing on a chosen target while sparing the ribs, using the decomposition of the time-reversal operator (DORT method). The idea is to apply an excitation weight vector to the transducers array which is orthogonal to the subspace of emissions focusing on the ribs. The ratio of the energies absorbed at the focal point and on the ribs has been enhanced up to 100-fold as demonstrated by the measured specific absorption rates.

  1. Single-molecule stochastic times in a reversible bimolecular reaction

    Science.gov (United States)

    Keller, Peter; Valleriani, Angelo

    2012-08-01

    In this work, we consider the reversible reaction between reactants of species A and B to form the product C. We consider this reaction as a prototype of many pseudobiomolecular reactions in biology, such as for instance molecular motors. We derive the exact probability density for the stochastic waiting time that a molecule of species A needs until the reaction with a molecule of species B takes place. We perform this computation taking fully into account the stochastic fluctuations in the number of molecules of species B. We show that at low numbers of participating molecules, the exact probability density differs from the exponential density derived by assuming the law of mass action. Finally, we discuss the condition of detailed balance in the exact stochastic and in the approximate treatment.

  2. Time reversal invariance for a nonlinear scatterer exhibiting contact acoustic nonlinearity

    Science.gov (United States)

    Blanloeuil, Philippe; Rose, L. R. Francis; Veidt, Martin; Wang, Chun H.

    2018-03-01

    The time reversal invariance of an ultrasonic plane wave interacting with a contact interface characterized by a unilateral contact law is investigated analytically and numerically. It is shown analytically that despite the contact nonlinearity, the re-emission of a time reversed version of the reflected and transmitted waves can perfectly recover the original pulse shape, thereby demonstrating time reversal invariance for this type of contact acoustic nonlinearity. With the aid of finite element modelling, the time-reversal analysis is extended to finite-size nonlinear scatterers such as closed cracks. The results show that time reversal invariance holds provided that all the additional frequencies generated during the forward propagation, such as higher harmonics, sub-harmonics and zero-frequency component, are fully included in the retro-propagation. If the scattered waves are frequency filtered during receiving or transmitting, such as through the use of narrowband transducers, the recombination of the time-reversed waves will not exactly recover the original incident wave. This discrepancy due to incomplete time invariance can be exploited as a new method for characterizing damage by defining damage indices that quantify the departure from time reversal invariance. The sensitivity of these damage indices for various crack lengths and contact stress levels is investigated computationally, indicating some advantages of this narrowband approach relative to the more conventional measurement of higher harmonic amplitude, which requires broadband transducers.

  3. Focused fluorescence excitation with time-reversed ultrasonically encoded light and imaging in thick scattering media

    International Nuclear Information System (INIS)

    Lai, Puxiang; Suzuki, Yuta; Xu, Xiao; Wang, Lihong V

    2013-01-01

    Scattering dominates light propagation in biological tissue, and therefore restricts both resolution and penetration depth in optical imaging within thick tissue. As photons travel into the diffusive regime, typically 1 mm beneath human skin, their trajectories transition from ballistic to diffusive due to the increased number of scattering events, which makes it impossible to focus, much less track, photon paths. Consequently, imaging methods that rely on controlled light illumination are ineffective in deep tissue. This problem has recently been addressed by a novel method capable of dynamically focusing light in thick scattering media via time reversal of ultrasonically encoded (TRUE) diffused light. Here, using photorefractive materials as phase conjugate mirrors, we show a direct visualization and dynamic control of optical focusing with this light delivery method, and demonstrate its application for focused fluorescence excitation and imaging in thick turbid media. These abilities are increasingly critical for understanding the dynamic interactions of light with biological matter and processes at different system levels, as well as their applications for biomedical diagnosis and therapy. (letter)

  4. Remote Whispering Applying Time Reversal

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Brian Eric [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-07-16

    The purpose of this project was to explore the use of time reversal technologies as a means for communication to a targeted individual or location. The idea is to have the privacy of whispering in one’s ear, but to do this remotely from loudspeakers not located near the target. Applications of this work include communicating with hostages and survivors in rescue operations, communicating imaging and operational conditions in deep drilling operations, monitoring storage of spent nuclear fuel in storage casks without wires, or clandestine activities requiring signaling between specific points. This technology provides a solution in any application where wires and radio communications are not possible or not desired. It also may be configured to self calibrate on a regular basis to adjust for changing conditions. These communications allow two people to converse with one another in real time, converse in an inaudible frequency range or medium (i.e. using ultrasonic frequencies and/or sending vibrations through a structure), or send information for a system to interpret (even allowing remote control of a system using sound). The time reversal process allows one to focus energy to a specific location in space and to send a clean transmission of a selected signal only to that location. In order for the time reversal process to work, a calibration signal must be obtained. This signal may be obtained experimentally using an impulsive sound, a known chirp signal, or other known signals. It may also be determined from a numerical model of a known environment in which the focusing is desired or from passive listening over time to ambient noise.

  5. A time reversal damage imaging method for structure health monitoring using Lamb waves

    International Nuclear Information System (INIS)

    Zhang Hai-Yan; Cao Ya-Ping; Sun Xiu-Li; Chen Xian-Hua; Yu Jian-Bo

    2010-01-01

    This paper investigates the Lamb wave imaging method combining time reversal for health monitoring of a metallic plate structure. The temporal focusing effect of the time reversal Lamb waves is investigated theoretically. It demonstrates that the focusing effect is related to the frequency dependency of the time reversal operation. Numerical simulations are conducted to study the time reversal behaviour of Lamb wave modes under broadband and narrowband excitations. The results show that the reconstructed time reversed wave exhibits close similarity to the reversed narrowband tone burst signal validating the theoretical model. To enhance the similarity, the cycle number of the excited signal should be increased. Experiments combining finite element model are then conducted to study the imaging method in the presence of damage like hole in the plate structure. In this work, the time reversal technique is used for the recompression of Lamb wave signals. Damage imaging results with time reversal using broadband and narrowband excitations are compared to those without time reversal. It suggests that the narrowband excitation combined time reversal can locate and determine the size of structural damage more precisely, but the cycle number of the excited signal should be chosen reasonably

  6. Underwater Time Service and Synchronization Based on Time Reversal Technique

    Science.gov (United States)

    Lu, Hao; Wang, Hai-bin; Aissa-El-Bey, Abdeldjalil; Pyndiah, Ramesh

    2010-09-01

    Real time service and synchronization are very important to many underwater systems. But the time service and synchronization in existence cannot work well due to the multi-path propagation and random phase fluctuation of signals in the ocean channel. The time reversal mirror technique can realize energy concentration through self-matching of the ocean channel and has very good spatial and temporal focusing properties. Based on the TRM technique, we present the Time Reversal Mirror Real Time service and synchronization (TRMRT) method which can bypass the processing of multi-path on the server side and reduce multi-path contamination on the client side. So TRMRT can improve the accuracy of time service. Furthermore, as an efficient and precise method of time service, TRMRT could be widely used in underwater exploration activities and underwater navigation and positioning systems.

  7. Measurement of the speed of sound in trabecular bone by using a time reversal acoustics focusing system

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kang Il [Kangwon National University, Chuncheon (Korea, Republic of); Choi, Bok-Kyoung [Maritime Security Research Center, KIOST, Ansan (Korea, Republic of)

    2014-10-15

    A new method for measuring the speed of sound (SOS) in trabecular bone by using a time reversal acoustics (TRA) focusing system was proposed and validated with measurements obtained by using the conventional pulse-transmission technique. The SOS measured in 14 bovine femoral trabecular bone samples by using the two methods was highly correlated each other, although the SOS measured by using the TRA focusing system was slightly lower by an average of 2.2 m/s. The SOS measured by using the two methods showed high correlation coefficients of r = 0.92 with the apparent bone density, consistent with the behavior in human trabecular bone in vitro. These results prove the efficacy of the new method based on the principle of TRA to measure the SOS in trabecular bone.

  8. Time-dependent Networks as Models to Achieve Fast Exact Time-table Queries

    DEFF Research Database (Denmark)

    Brodal, Gerth Stølting; Jacob, Rico

    2001-01-01

    We consider efficient algorithms for exact time-table queries, i.e. algorithms that find optimal itineraries. We propose to use time-dependent networks as a model and show advantages of this approach over space-time networks as models.......We consider efficient algorithms for exact time-table queries, i.e. algorithms that find optimal itineraries. We propose to use time-dependent networks as a model and show advantages of this approach over space-time networks as models....

  9. Time-reversal acoustics and ultrasound-assisted convection-enhanced drug delivery to the brain.

    Science.gov (United States)

    Olbricht, William; Sistla, Manjari; Ghandi, Gaurav; Lewis, George; Sarvazyan, Armen

    2013-08-01

    Time-reversal acoustics is an effective way of focusing ultrasound deep inside heterogeneous media such as biological tissues. Convection-enhanced delivery is a method of delivering drugs into the brain by infusing them directly into the brain interstitium. These two technologies are combined in a focusing system that uses a "smart needle" to simultaneously infuse fluid into the brain and provide the necessary feedback for focusing ultrasound using time-reversal acoustics. The effects of time-reversal acoustics-focused ultrasound on the spatial distribution of infused low- and high-molecular weight tracer molecules are examined in live, anesthetized rats. Results show that exposing the rat brain to focused ultrasound significantly increases the penetration of infused compounds into the brain. The addition of stabilized microbubbles enhances the effect of ultrasound exposure.

  10. Time reversibility, computer simulation, algorithms, chaos

    CERN Document Server

    Hoover, William Graham

    2012-01-01

    A small army of physicists, chemists, mathematicians, and engineers has joined forces to attack a classic problem, the "reversibility paradox", with modern tools. This book describes their work from the perspective of computer simulation, emphasizing the author's approach to the problem of understanding the compatibility, and even inevitability, of the irreversible second law of thermodynamics with an underlying time-reversible mechanics. Computer simulation has made it possible to probe reversibility from a variety of directions and "chaos theory" or "nonlinear dynamics" has supplied a useful vocabulary and a set of concepts, which allow a fuller explanation of irreversibility than that available to Boltzmann or to Green, Kubo and Onsager. Clear illustration of concepts is emphasized throughout, and reinforced with a glossary of technical terms from the specialized fields which have been combined here to focus on a common theme. The book begins with a discussion, contrasting the idealized reversibility of ba...

  11. Time measurement - technical importance of most exact clocks

    International Nuclear Information System (INIS)

    Goebel, E.O.; Riehle, F.

    2004-01-01

    The exactness of the best atomic clocks currently shows a temporal variation of 1 second in 30 million years. This means that we have reached the point of the most exact frequency and time measurement ever. In the past, there was a trend towards increasing the exactness in an increasingly fast sequence. Will this trend continue? And who will profit from it? This article is meant to give answers to these questions. This is done by presenting first the level reached currently with the best atomic clocks and describing the research activities running worldwide with the aim of achieving even more exact clocks. In the second part, we present examples of various areas of technical subjects and research in which the most exact clocks are being applied presently and even more exact ones will be needed in the future [de

  12. Time-Dependent Networks as Models to Achieve Fast Exact Time-Table Queries

    DEFF Research Database (Denmark)

    Brodal, Gert Stølting; Jacob, Rico

    2003-01-01

    We consider efficient algorithms for exact time-table queries, i.e. algorithms that find optimal itineraries for travelers using a train system. We propose to use time-dependent networks as a model and show advantages of this approach over space-time networks as models.......We consider efficient algorithms for exact time-table queries, i.e. algorithms that find optimal itineraries for travelers using a train system. We propose to use time-dependent networks as a model and show advantages of this approach over space-time networks as models....

  13. Time reversal technique for gas leakage detection.

    Science.gov (United States)

    Maksimov, A O; Polovinka, Yu A

    2015-04-01

    The acoustic remote sensing of subsea gas leakage traditionally uses sonars as active acoustic sensors and hydrophones picking up the sound generated by a leak as passive sensors. When gas leaks occur underwater, bubbles are produced and emit sound at frequencies intimately related to their sizes. The experimental implementation of an acoustic time-reversal mirror (TRM) is now well established in underwater acoustics. In the basic TRM experiment, a probe source emits a pulse that is received on an array of sensors, time reversed, and re-emitted. After time reversal, the resulting field focuses back at the probe position. In this study, a method for enhancing operation of the passive receiving system has been proposed by using it in the regime of TRM. Two factors, the local character of the acoustic emission signal caused by the leakage and a resonant nature of the bubble radiation at their birth, make particularly effective scattering with the conjugate wave (CW). Analytical calculations are performed for the scattering of CW wave on a single bubble when CW is formed by bubble birthing wail received on an array, time reversed, and re-emitted. The quality of leakage detection depends on the spatio-temporal distribution of ambient noise.

  14. High-resolution and super stacking of time-reversal mirrors in locating seismic sources

    KAUST Repository

    Cao, Weiping

    2011-07-08

    Time reversal mirrors can be used to backpropagate and refocus incident wavefields to their actual source location, with the subsequent benefits of imaging with high-resolution and super-stacking properties. These benefits of time reversal mirrors have been previously verified with computer simulations and laboratory experiments but not with exploration-scale seismic data. We now demonstrate the high-resolution and the super-stacking properties in locating seismic sources with field seismic data that include multiple scattering. Tests on both synthetic data and field data show that a time reversal mirror has the potential to exceed the Rayleigh resolution limit by factors of 4 or more. Results also show that a time reversal mirror has a significant resilience to strong Gaussian noise and that accurate imaging of source locations from passive seismic data can be accomplished with traces having signal-to-noise ratios as low as 0.001. Synthetic tests also demonstrate that time reversal mirrors can sometimes enhance the signal by a factor proportional to the square root of the product of the number of traces, denoted as N and the number of events in the traces. This enhancement property is denoted as super-stacking and greatly exceeds the classical signal-to-noise enhancement factor of. High-resolution and super-stacking are properties also enjoyed by seismic interferometry and reverse-time migration with the exact velocity model. © 2011 European Association of Geoscientists & Engineers.

  15. Harmonic oscillator in heat bath: Exact simulation of time-lapse-recorded data and exact analytical benchmark statistics

    DEFF Research Database (Denmark)

    Nørrelykke, Simon F; Flyvbjerg, Henrik

    2011-01-01

    The stochastic dynamics of the damped harmonic oscillator in a heat bath is simulated with an algorithm that is exact for time steps of arbitrary size. Exact analytical results are given for correlation functions and power spectra in the form they acquire when computed from experimental time...

  16. Nonlinear Time-Reversal in a Wave Chaotic System

    Science.gov (United States)

    Frazier, Matthew; Taddese, Biniyam; Ott, Edward; Antonsen, Thomas; Anlage, Steven

    2012-02-01

    Time reversal mirrors are particularly simple to implement in wave chaotic systems and form the basis for a new class of sensors [1-3]. These sensors work by applying the quantum mechanical concepts of Loschmidt echo and fidelity decay to classical waves. The sensors make explicit use of time-reversal invariance and spatial reciprocity in a wave chaotic system to remotely measure the presence of small perturbations to the system. The underlying ray chaos increases the sensitivity to small perturbations throughout the volume explored by the waves. We extend our time-reversal mirror to include a discrete element with a nonlinear dynamical response. The initially injected pulse interacts with the nonlinear element, generating new frequency components originating at the element. By selectively filtering for and applying the time-reversal mirror to the new frequency components, we focus a pulse only onto the element, without knowledge of its location. Furthermore, we demonstrate transmission of arbitrary patterns of pulses to the element, creating a targeted communication channel to the exclusion of 'eavesdroppers' at other locations in the system. [1] Appl. Phys. Lett. 95, 114103 (2009) [2] J. Appl. Phys. 108, 1 (2010) [3] Acta Physica Polonica A 112, 569 (2007)

  17. A semi-analytical model of a time reversal cavity for high-amplitude focused ultrasound applications

    Science.gov (United States)

    Robin, J.; Tanter, M.; Pernot, M.

    2017-09-01

    Time reversal cavities (TRC) have been proposed as an efficient approach for 3D ultrasound therapy. They allow the precise spatio-temporal focusing of high-power ultrasound pulses within a large region of interest with a low number of transducers. Leaky TRCs are usually built by placing a multiple scattering medium, such as a random rod forest, in a reverberating cavity, and the final peak pressure gain of the device only depends on the temporal length of its impulse response. Such multiple scattering in a reverberating cavity is a complex phenomenon, and optimisation of the device’s gain is usually a cumbersome process, mostly empirical, and requiring numerical simulations with extremely long computation times. In this paper, we present a semi-analytical model for the fast optimisation of a TRC. This model decouples ultrasound propagation in an empty cavity and multiple scattering in a multiple scattering medium. It was validated numerically and experimentally using a 2D-TRC and numerically using a 3D-TRC. Finally, the model was used to determine rapidly the optimal parameters of the 3D-TRC which had been confirmed by numerical simulations.

  18. Exact solutions of sl-boson system in U(2l + 1) reversible O(2l + 2) transitional region

    CERN Document Server

    Zhang Xin

    2002-01-01

    Exact eigen-energies and the corresponding wavefunctions of the interacting sl-boson system in U(2l + 1) reversible O(2l +2) transitional region are obtained by using an algebraic Bethe Ansatz with the infinite dimensional Lie algebraic technique. Numerical algorithm for solving the Bethe Ansatz equations by using mathematical package is also outlined

  19. Elastic least-squares reverse time migration

    KAUST Repository

    Feng, Zongcai

    2017-03-08

    We use elastic least-squares reverse time migration (LSRTM) to invert for the reflectivity images of P- and S-wave impedances. Elastic LSRTMsolves the linearized elastic-wave equations for forward modeling and the adjoint equations for backpropagating the residual wavefield at each iteration. Numerical tests on synthetic data and field data reveal the advantages of elastic LSRTM over elastic reverse time migration (RTM) and acoustic LSRTM. For our examples, the elastic LSRTM images have better resolution and amplitude balancing, fewer artifacts, and less crosstalk compared with the elastic RTM images. The images are also better focused and have better reflector continuity for steeply dipping events compared to the acoustic LSRTM images. Similar to conventional leastsquares migration, elastic LSRTM also requires an accurate estimation of the P- and S-wave migration velocity models. However, the problem remains that, when there are moderate errors in the velocity model and strong multiples, LSRTMwill produce migration noise stronger than that seen in the RTM images.

  20. Elastic least-squares reverse time migration

    KAUST Repository

    Feng, Zongcai; Schuster, Gerard T.

    2017-01-01

    We use elastic least-squares reverse time migration (LSRTM) to invert for the reflectivity images of P- and S-wave impedances. Elastic LSRTMsolves the linearized elastic-wave equations for forward modeling and the adjoint equations for backpropagating the residual wavefield at each iteration. Numerical tests on synthetic data and field data reveal the advantages of elastic LSRTM over elastic reverse time migration (RTM) and acoustic LSRTM. For our examples, the elastic LSRTM images have better resolution and amplitude balancing, fewer artifacts, and less crosstalk compared with the elastic RTM images. The images are also better focused and have better reflector continuity for steeply dipping events compared to the acoustic LSRTM images. Similar to conventional leastsquares migration, elastic LSRTM also requires an accurate estimation of the P- and S-wave migration velocity models. However, the problem remains that, when there are moderate errors in the velocity model and strong multiples, LSRTMwill produce migration noise stronger than that seen in the RTM images.

  1. Acoustic wave focusing in complex media using Nonlinear Time Reversal coded signal processing

    Czech Academy of Sciences Publication Activity Database

    Dos Santos, S.; Dvořáková, Zuzana; Lints, M.; Kůs, V.; Salupere, A.; Převorovský, Zdeněk

    2014-01-01

    Roč. 19, č. 12 (2014) ISSN 1435-4934. [European Conference on Non-Destructive Testing (ECNDT 2014) /11./. Praha, 06.10.2014-10.10.2014] Institutional support: RVO:61388998 Keywords : ultrasonic testing (UT) * signal processing * TR- NEWS * nonlinear time reversal * NDT * nonlinear acoustics Subject RIV: BI - Acoustics http://www.ndt.net/events/ECNDT2014/app/content/Slides/590_DosSantos_Rev1.pdf

  2. Introduction to time reversal theory

    International Nuclear Information System (INIS)

    Henley, E.M.

    1987-01-01

    Theory and reaction mechanisms relevant to time reversal invariance are reviewed. Consequences of time reversal invariance are presented under the headings of CP tests, electromagnetic moments, weak emissions or absorptions, and scattering reactions. 8 refs., 4 figs

  3. Status of time reversal invariance

    International Nuclear Information System (INIS)

    Henley, E.M.

    1989-01-01

    Time Reversal Invariance is introduced, and theories for its violation are reviewed. The present experimental and theoretical status of Time Reversal Invariance and tests thereof will be presented. Possible future tests will be discussed. 30 refs., 2 figs., 1 tab

  4. Issues in measure-preserving three dimensional flow integrators: Self-adjointness, reversibility, and non-uniform time stepping

    International Nuclear Information System (INIS)

    Finn, John M.

    2015-01-01

    Properties of integration schemes for solenoidal fields in three dimensions are studied, with a focus on integrating magnetic field lines in a plasma using adaptive time stepping. It is shown that implicit midpoint (IM) and a scheme we call three-dimensional leapfrog (LF) can do a good job (in the sense of preserving KAM tori) of integrating fields that are reversible, or (for LF) have a “special divergence-free” (SDF) property. We review the notion of a self-adjoint scheme, showing that such schemes are at least second order accurate and can always be formed by composing an arbitrary scheme with its adjoint. We also review the concept of reversibility, showing that a reversible but not exactly volume-preserving scheme can lead to a fractal invariant measure in a chaotic region, although this property may not often be observable. We also show numerical results indicating that the IM and LF schemes can fail to preserve KAM tori when the reversibility property (and the SDF property for LF) of the field is broken. We discuss extensions to measure preserving flows, the integration of magnetic field lines in a plasma and the integration of rays for several plasma waves. The main new result of this paper relates to non-uniform time stepping for volume-preserving flows. We investigate two potential schemes, both based on the general method of Feng and Shang [Numer. Math. 71, 451 (1995)], in which the flow is integrated in split time steps, each Hamiltonian in two dimensions. The first scheme is an extension of the method of extended phase space, a well-proven method of symplectic integration with non-uniform time steps. This method is found not to work, and an explanation is given. The second method investigated is a method based on transformation to canonical variables for the two split-step Hamiltonian systems. This method, which is related to the method of non-canonical generating functions of Richardson and Finn [Plasma Phys. Controlled Fusion 54, 014004 (2012

  5. Exact time-dependent exchange-correlation potentials for strong-field electron dynamics

    International Nuclear Information System (INIS)

    Lein, Manfred; Kuemmel, Stephan

    2005-01-01

    By solving the time-dependent Schroedinger equation and inverting the time-dependent Kohn-Sham scheme we obtain the exact time-dependent exchange-correlation potential of density-functional theory for the strong-field dynamics of a correlated system. We demonstrate that essential features of the exact exchange-correlation potential can be related to derivative discontinuities in stationary density-functional theory. Incorporating the discontinuity in a time-dependent density-functional calculation greatly improves the description of the ionization process

  6. Exact norm-conserving stochastic time-dependent Hartree-Fock

    International Nuclear Information System (INIS)

    Tessieri, Luca; Wilkie, Joshua; Cetinbas, Murat

    2005-01-01

    We derive an exact single-body decomposition of the time-dependent Schroedinger equation for N pairwise interacting fermions. Each fermion obeys a stochastic time-dependent norm-preserving wave equation. As a first test of the method, we calculate the low energy spectrum of helium. An extension of the method to bosons is outlined

  7. Exact wavefunctions for a time-dependent Coulomb potential

    International Nuclear Information System (INIS)

    Menouar, S; Maamache, M; Saadi, Y; Choi, J R

    2008-01-01

    The one-dimensional Schroedinger equation associated with a time-dependent Coulomb potential is studied. The invariant operator method (Lewis and Riesenfeld) and unitary transformation approach are employed to derive quantum solutions of the system. We obtain an ordinary second-order differential equation whose analytical exact solution has been unknown. It is confirmed that the form of this equation is similar to the radial Schroedinger equation for the hydrogen atom in a (arbitrary) strong magnetic field. The qualitative properties for the eigenstates spectrum are described separately for the different values of the parameter ω 0 appearing in the x 2 term, x being the position, i.e., ω 0 > 0, ω 0 0 = 0. For the ω 0 = 0 case, the eigenvalue equation of invariant operator reduces to a solvable form and, consequently, we have provided exact eigenstates of the time-dependent Hamiltonian system

  8. Exact axially symmetric galactic dynamos

    Science.gov (United States)

    Henriksen, R. N.; Woodfinden, A.; Irwin, J. A.

    2018-05-01

    We give a selection of exact dynamos in axial symmetry on a galactic scale. These include some steady examples, at least one of which is wholly analytic in terms of simple functions and has been discussed elsewhere. Most solutions are found in terms of special functions, such as associated Lagrange or hypergeometric functions. They may be considered exact in the sense that they are known to any desired accuracy in principle. The new aspect developed here is to present scale-invariant solutions with zero resistivity that are self-similar in time. The time dependence is either a power law or an exponential factor, but since the geometry of the solution is self-similar in time we do not need to fix a time to study it. Several examples are discussed. Our results demonstrate (without the need to invoke any other mechanisms) X-shaped magnetic fields and (axially symmetric) magnetic spiral arms (both of which are well observed and documented) and predict reversing rotation measures in galaxy haloes (now observed in the CHANG-ES sample) as well as the fact that planar magnetic spirals are lifted into the galactic halo.

  9. Cesarean section and the manipulation of exact delivery time.

    Science.gov (United States)

    Fabbri, Daniele; Monfardini, Chiara; Castaldini, Ilaria; Protonotari, Adalgisa

    2016-07-01

    Physicians are often alleged responsible for the manipulation of delivery timing. We investigate this issue in a setting that negates the influence of financial incentives on physician's behavior. Working on a sample of women admitted at the onset of labor in a big public hospital in Italy we estimate a model for the exact time of delivery as driven by individual Indication to Cesarean Section (ICS) and covariates. We find that ICS does not affect the day of delivery but leads to a circadian rhythm in the likelihood of delivery. The pattern is consistent with the postponement of high ICS deliveries in the late night\\early morning shift. Our evidence hardly supports the manipulation of timing of births as driven by medical staff's "demand for leisure". Physicians seem to manipulate the exact timing of delivery to reduce exposure to risk factors extant during off-peak periods. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  10. Reversible perspective and splitting in time.

    Science.gov (United States)

    Hart, Helen Schoenhals

    2012-01-01

    The element of time--the experience of it and the defensive use of it--is explored in conjunction with the use of reversible perspective as a psychotic defense. Clinical material from a long analysis illustrates how a psychotic patient used the reversible perspective, with its static splitting, to abolish the experience of time. When he improved and the reversible perspective became less effective for him, he replaced it with a more dynamic splitting mechanism using time gaps. With further improvement, the patient began to experience the passage of time, and along with it the excruciating pain of separation, envy, and loss.

  11. Time reversal for ultrasonic transcranial surgery and echographic imaging

    Science.gov (United States)

    Tanter, Mickael; Aubry, Jean-Francois; Vignon, Francois; Fink, Mathias

    2005-09-01

    High-intensity focused ultrasound (HIFU) is able to induce non-invasively controlled and selective destruction of tissues by focusing ultrasonic beams within organs, analogous to a magnifying glass that concentrates enough sunlight to burn a hole in paper. The brain is an attractive organ in which to perform ultrasonic tissue ablation, but such an application has been hampered by the strong defocusing effect of the skull bone. Our group has been involved in this topic for several years, providing proofs of concept and proposing technological solutions to this problem. Thanks to a high-power time-reversal mirror, presented here are in vivo thermal lesions induced through the skull of 12 sheep. Thermal lesions were confirmed by T2-weighted magnetic resonance post-treatment images and histological examination. These results provide striking evidence that noninvasive ultrasound brain surgery is feasible. A recent approach for high-resolution brain ultrasonic imaging will also be discussed with a skull aberration correction technique based on twin arrays technology. The correction of transcranial ultrasonic images is implemented on a new generation of time-reversal mirrors relying on a fully programmable transmit and receive beamformer.

  12. New quasi-exactly solvable Hermitian as well as non-Hermitian PT ...

    Indian Academy of Sciences (India)

    Abstract. We start with quasi-exactly solvable (QES) Hermitian (and hence real) as ... the time reversal transformation t → −t and further, one replaces i → −i. One can ..... F M Fernandez, R Guardiola, J Ros and M Znojil, J. Phys. A32, 3105 ...

  13. Precise Time-of-Flight Calculation For 3-D Synthetic Aperture Focusing

    DEFF Research Database (Denmark)

    Andresen, Henrik; Nikolov, Svetoslav; Jensen, Jørgen Arendt

    2009-01-01

    in elevation can be achieved by applying synthetic aperture (SA) focusing to the beamformed in-plane RF-data. The proposed method uses a virtual source (VS) placed at the elevation focus for postbeamforming. This has previously been done in two steps, in plane focusing followed by SA post-focusing in elevation......, because of a lack of a simple expression for the exact time of flight (ToF). This paper presents a new method for calculating the ToF for a 3D case in a single step using a linear array. This method is more flexible than the previously proposed method and is able to beamform a fewer number of points much...

  14. Classical reconstruction of interference patterns of position-wave-vector-entangled photon pairs by the time-reversal method

    Science.gov (United States)

    Ogawa, Kazuhisa; Kobayashi, Hirokazu; Tomita, Akihisa

    2018-02-01

    The quantum interference of entangled photons forms a key phenomenon underlying various quantum-optical technologies. It is known that the quantum interference patterns of entangled photon pairs can be reconstructed classically by the time-reversal method; however, the time-reversal method has been applied only to time-frequency-entangled two-photon systems in previous experiments. Here, we apply the time-reversal method to the position-wave-vector-entangled two-photon systems: the two-photon Young interferometer and the two-photon beam focusing system. We experimentally demonstrate that the time-reversed systems classically reconstruct the same interference patterns as the position-wave-vector-entangled two-photon systems.

  15. Reversibility and irreversibility from an initial value formulation

    International Nuclear Information System (INIS)

    Muriel, A.

    2013-01-01

    From a time evolution equation for the single particle distribution function derived from the N-particle distribution function (A. Muriel, M. Dresden, Physica D 101 (1997) 297), an exact solution for the 3D Navier–Stokes equation – an old problem – has been found (A. Muriel, Results Phys. 1 (2011) 2). In this Letter, a second exact conclusion from the above-mentioned work is presented. We analyze the time symmetry properties of a formal, exact solution for the single-particle distribution function contracted from the many-body Liouville equation. This analysis must be done because group theoretic results on time reversal symmetry of the full Liouville equation (E.C.G. Sudarshan, N. Mukunda, Classical Mechanics: A Modern Perspective, Wiley, 1974). no longer applies automatically to the single particle distribution function contracted from the formal solution of the N-body Liouville equation. We find the following result: if the initial momentum distribution is even in the momentum, the single particle distribution is reversible. If there is any asymmetry in the initial momentum distribution, no matter how small, the system is irreversible.

  16. Time-reversal symmetry breaking in quantum billiards

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, Florian

    2009-01-26

    The present doctoral thesis describes experimentally measured properties of the resonance spectra of flat microwave billiards with partially broken timereversal invariance induced by an embedded magnetized ferrite. A vector network analyzer determines the complex scattering matrix elements. The data is interpreted in terms of the scattering formalism developed in nuclear physics. At low excitation frequencies the scattering matrix displays isolated resonances. At these the effect of the ferrite on isolated resonances (singlets) and pairs of nearly degenerate resonances (doublets) is investigated. The hallmark of time-reversal symmetry breaking is the violation of reciprocity, i.e. of the symmetry of the scattering matrix. One finds that reciprocity holds in singlets; it is violated in doublets. This is modeled by an effective Hamiltonian of the resonator. A comparison of the model to the data yields time-reversal symmetry breaking matrix elements in the order of the level spacing. Their dependence on the magnetization of the ferrite is understood in terms of its magnetic properties. At higher excitation frequencies the resonances overlap and the scattering matrix elements fluctuate irregularly (Ericson fluctuations). They are analyzed in terms of correlation functions. The data are compared to three models based on random matrix theory. The model by Verbaarschot, Weidenmueller and Zirnbauer describes time-reversal invariant scattering processes. The one by Fyodorov, Savin and Sommers achieves the same for systems with complete time-reversal symmetry breaking. An extended model has been developed that accounts for partial breaking of time-reversal invariance. This extended model is in general agreement with the data, while the applicability of the other two models is limited. The cross-correlation function between forward and backward reactions determines the time-reversal symmetry breaking matrix elements of the Hamiltonian to up to 0.3 mean level spacings. Finally

  17. Time-reversal symmetry breaking in quantum billiards

    International Nuclear Information System (INIS)

    Schaefer, Florian

    2009-01-01

    The present doctoral thesis describes experimentally measured properties of the resonance spectra of flat microwave billiards with partially broken timereversal invariance induced by an embedded magnetized ferrite. A vector network analyzer determines the complex scattering matrix elements. The data is interpreted in terms of the scattering formalism developed in nuclear physics. At low excitation frequencies the scattering matrix displays isolated resonances. At these the effect of the ferrite on isolated resonances (singlets) and pairs of nearly degenerate resonances (doublets) is investigated. The hallmark of time-reversal symmetry breaking is the violation of reciprocity, i.e. of the symmetry of the scattering matrix. One finds that reciprocity holds in singlets; it is violated in doublets. This is modeled by an effective Hamiltonian of the resonator. A comparison of the model to the data yields time-reversal symmetry breaking matrix elements in the order of the level spacing. Their dependence on the magnetization of the ferrite is understood in terms of its magnetic properties. At higher excitation frequencies the resonances overlap and the scattering matrix elements fluctuate irregularly (Ericson fluctuations). They are analyzed in terms of correlation functions. The data are compared to three models based on random matrix theory. The model by Verbaarschot, Weidenmueller and Zirnbauer describes time-reversal invariant scattering processes. The one by Fyodorov, Savin and Sommers achieves the same for systems with complete time-reversal symmetry breaking. An extended model has been developed that accounts for partial breaking of time-reversal invariance. This extended model is in general agreement with the data, while the applicability of the other two models is limited. The cross-correlation function between forward and backward reactions determines the time-reversal symmetry breaking matrix elements of the Hamiltonian to up to 0.3 mean level spacings. Finally

  18. Exact solution of a quantum forced time-dependent harmonic oscillator

    Science.gov (United States)

    Yeon, Kyu Hwang; George, Thomas F.; Um, Chung IN

    1992-01-01

    The Schrodinger equation is used to exactly evaluate the propagator, wave function, energy expectation values, uncertainty values, and coherent state for a harmonic oscillator with a time dependent frequency and an external driving time dependent force. These quantities represent the solution of the classical equation of motion for the time dependent harmonic oscillator.

  19. Exact solutions to the time-fractional differential equations via local fractional derivatives

    Science.gov (United States)

    Guner, Ozkan; Bekir, Ahmet

    2018-01-01

    This article utilizes the local fractional derivative and the exp-function method to construct the exact solutions of nonlinear time-fractional differential equations (FDEs). For illustrating the validity of the method, it is applied to the time-fractional Camassa-Holm equation and the time-fractional-generalized fifth-order KdV equation. Moreover, the exact solutions are obtained for the equations which are formed by different parameter values related to the time-fractional-generalized fifth-order KdV equation. This method is an reliable and efficient mathematical tool for solving FDEs and it can be applied to other non-linear FDEs.

  20. High-frequency Total Focusing Method (TFM) imaging in strongly attenuating materials with the decomposition of the time reversal operator associated with orthogonal coded excitations

    Science.gov (United States)

    Villaverde, Eduardo Lopez; Robert, Sébastien; Prada, Claire

    2017-02-01

    In the present work, the Total Focusing Method (TFM) is used to image defects in a High Density Polyethylene (HDPE) pipe. The viscoelastic attenuation of this material corrupts the images with a high electronic noise. In order to improve the image quality, the Decomposition of the Time Reversal Operator (DORT) filtering is combined with spatial Walsh-Hadamard coded transmissions before calculating the images. Experiments on a complex HDPE joint demonstrate that this method improves the signal-to-noise ratio by more than 40 dB in comparison with the conventional TFM.

  1. Formulations and exact algorithms for the vehicle routing problem with time windows

    DEFF Research Database (Denmark)

    Kallehauge, Brian

    2008-01-01

    In this paper we review the exact algorithms proposed in the last three decades for the solution of the vehicle routing problem with time windows (VRPTW). The exact algorithms for the VRPTW are in many aspects inherited from work on the traveling salesman problem (TSP). In recognition of this fact...

  2. Time in Science: Reversibility vs. Irreversibility

    Science.gov (United States)

    Pomeau, Yves

    To discuss properly the question of irreversibility one needs to make a careful distinction between reversibility of the equations of motion and the choice of the initial conditions. This is also relevant for the rather confuse philosophy of the wave packet reduction in quantum mechanics. The explanation of this reduction requires also to make precise assumptions on what initial data are accessible in our world. Finally I discuss how a given (and long) time record can be shown in an objective way to record an irreversible or reversible process. Or: can a direction of time be derived from its analysis? This leads quite naturally to examine if there is a possible spontaneous breaking of the time reversal symmetry in many body systems, a symmetry breaking that would be put in evidence objectively by looking at certain specific time correlations.

  3. Archimedean-type force in a cosmic dark fluid. I. Exact solutions for the late-time accelerated expansion

    International Nuclear Information System (INIS)

    Balakin, Alexander B.; Bochkarev, Vladimir V.

    2011-01-01

    We establish a new self-consistent model in order to explain from a unified viewpoint two key features of the cosmological evolution: the inflation in the early Universe and the late-time accelerated expansion. The key element of this new model is the Archimedean-type coupling of the dark matter with dark energy, which form the so-called cosmic dark fluid. We suppose that dark matter particles immersed into the dark energy reservoir are affected by the force proportional to the four-gradient of the dark energy pressure. The Archimedean-type coupling is shown to play a role of effective energy-momentum redistributor between the dark matter and the dark energy components of the dark fluid, thus providing the Universe evolution to be a quasiperiodic and/or multistage process. In the first part of the work we discuss a theoretical base and new exact solutions of the model master equations. Special attention is focused on the exact solutions, for which the scale factor is presented by the anti-Gaussian function: these solutions describe the late-time acceleration and are characterized by a nonsingular behavior in the early Universe. The second part contains qualitative and numerical analysis of the master equations; we focus there on the solutions describing a multi-inflationary Universe.

  4. Exact Time-Dependent Wave Functions of a Confined Time-Dependent Harmonic Oscillator with Two Moving Boundaries

    International Nuclear Information System (INIS)

    Lo, C.F.

    2009-01-01

    By applying the standard analytical techniques of solving partial differential equations, we have obtained the exact solution in terms of the Fourier sine series to the time-dependent Schroedinger equation describing a quantum one-dimensional harmonic oscillator of time-dependent frequency confined in an infinite square well with the two walls moving along some parametric trajectories. Based upon the orthonormal basis of quasi-stationary wave functions, the exact propagator of the system has also been analytically derived. Special cases like (i) a confined free particle, (ii) a confined time-independent harmonic oscillator, and (iii) an aging oscillator are examined, and the corresponding time-dependent wave functions are explicitly determined. Besides, the approach has been extended to solve the case of a confined generalized time-dependent harmonic oscillator for some parametric moving boundaries as well. (general)

  5. Optical Time Reversal from Time-Dependent Epsilon-Near-Zero Media

    Science.gov (United States)

    Vezzoli, Stefano; Bruno, Vincenzo; DeVault, Clayton; Roger, Thomas; Shalaev, Vladimir M.; Boltasseva, Alexandra; Ferrera, Marcello; Clerici, Matteo; Dubietis, Audrius; Faccio, Daniele

    2018-01-01

    Materials with a spatially uniform but temporally varying optical response have applications ranging from magnetic field-free optical isolators to fundamental studies of quantum field theories. However, these effects typically become relevant only for time variations oscillating at optical frequencies, thus presenting a significant hurdle that severely limits the realization of such conditions. Here we present a thin-film material with a permittivity that pulsates (uniformly in space) at optical frequencies and realizes a time-reversing medium of the form originally proposed by Pendry [Science 322, 71 (2008), 10.1126/science.1162087]. We use an optically pumped, 500 nm thick film of epsilon-near-zero (ENZ) material based on Al-doped zinc oxide. An incident probe beam is both negatively refracted and time reversed through a reflected phase-conjugated beam. As a result of the high nonlinearity and the refractive index that is close to zero, the ENZ film leads to time reversed beams (simultaneous negative refraction and phase conjugation) with near-unit efficiency and greater-than-unit internal conversion efficiency. The ENZ platform therefore presents the time-reversal features required, e.g., for efficient subwavelength imaging, all-optical isolators and fundamental quantum field theory studies.

  6. Time reversal communication system

    Science.gov (United States)

    Candy, James V.; Meyer, Alan W.

    2008-12-02

    A system of transmitting a signal through a channel medium comprises digitizing the signal, time-reversing the digitized signal, and transmitting the signal through the channel medium. The channel medium may be air, earth, water, tissue, metal, and/or non-metal.

  7. A simple and efficient universal reversible Turing machine

    DEFF Research Database (Denmark)

    Axelsen, Holger Bock; Glück, Robert

    2011-01-01

    We construct a universal reversible Turing machine (URTM) from first principles. We take a strict approach to the semantics of reversible Turing machines (RTMs), under which they can compute exactly all injective, computable functions, but not non-injective ones. The natural notion of universalit...... factor slowdown, with no other complexity-wise cost wrt time and space. The URTM is also able to function as an inverse interpreter for RTMs at no asymptotic cost, simply by reversing the string representing the interpreted machine....

  8. Quasi-exact evaluation of time domain MFIE MOT matrix elements

    KAUST Repository

    Shi, Yifei; Bagci, Hakan; Shanker, Balasubramaniam; Lu, Mingyu; Michielssen, Eric

    2013-01-01

    A previously proposed quasi-exact scheme for evaluating matrix elements resulting from the marching-on-in-time (MOT) discretization of the time domain electric field integral equation (EFIE) is extended to matrix entries resulting from the discretization of its magnetic field integral equation (MFIE) counterpart. Numerical results demonstrate the accuracy of the scheme as well as the late-time stability of the resulting MOT-MFIE solver. © 2013 IEEE.

  9. Quasi-exact evaluation of time domain MFIE MOT matrix elements

    KAUST Repository

    Shi, Yifei

    2013-07-01

    A previously proposed quasi-exact scheme for evaluating matrix elements resulting from the marching-on-in-time (MOT) discretization of the time domain electric field integral equation (EFIE) is extended to matrix entries resulting from the discretization of its magnetic field integral equation (MFIE) counterpart. Numerical results demonstrate the accuracy of the scheme as well as the late-time stability of the resulting MOT-MFIE solver. © 2013 IEEE.

  10. Time reversibility of quantum diffusion in small-world networks

    Science.gov (United States)

    Han, Sung-Guk; Kim, Beom Jun

    2012-02-01

    We study the time-reversal dynamics of a tight-binding electron in the Watts-Strogatz (WS) small-world networks. The localized initial wave packet at time t = 0 diffuses as time proceeds until the time-reversal operation, together with the momentum perturbation of the strength η, is made at the reversal time T. The time irreversibility is measured by I = |Π( t = 2 T) - Π( t = 0)|, where Π is the participation ratio gauging the extendedness of the wavefunction and for convenience, t is measured forward even after the time reversal. When η = 0, the time evolution after T makes the wavefunction at t = 2 T identical to the one at t = 0, and we find I = 0, implying a null irreversibility or a complete reversibility. On the other hand, as η is increased from zero, the reversibility becomes weaker, and we observe enhancement of the irreversibility. We find that I linearly increases with increasing η in the weakly-perturbed region, and that the irreversibility is much stronger in the WS network than in the local regular network.

  11. An Exact Solution of the Gamma Ray Burst Arrival Time Analysis ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    An Exact Solution of the Gamma Ray Burst Arrival Time Analysis. Problem. S. Sinha ISRO Satellite Center, Bangalore 560 017, India. Abstract. An analytical solution of the GRB arrival time analysis is presented. The errors in the position of the GRB resulting from timing and position errors of different satellites are calculated.

  12. Reverse time migration by Krylov subspace reduced order modeling

    Science.gov (United States)

    Basir, Hadi Mahdavi; Javaherian, Abdolrahim; Shomali, Zaher Hossein; Firouz-Abadi, Roohollah Dehghani; Gholamy, Shaban Ali

    2018-04-01

    Imaging is a key step in seismic data processing. To date, a myriad of advanced pre-stack depth migration approaches have been developed; however, reverse time migration (RTM) is still considered as the high-end imaging algorithm. The main limitations associated with the performance cost of reverse time migration are the intensive computation of the forward and backward simulations, time consumption, and memory allocation related to imaging condition. Based on the reduced order modeling, we proposed an algorithm, which can be adapted to all the aforementioned factors. Our proposed method benefit from Krylov subspaces method to compute certain mode shapes of the velocity model computed by as an orthogonal base of reduced order modeling. Reverse time migration by reduced order modeling is helpful concerning the highly parallel computation and strongly reduces the memory requirement of reverse time migration. The synthetic model results showed that suggested method can decrease the computational costs of reverse time migration by several orders of magnitudes, compared with reverse time migration by finite element method.

  13. Exact results on diffusion in a piecewise linear potential with a time-dependent sink

    Energy Technology Data Exchange (ETDEWEB)

    Diwaker, E-mail: diwakerphysics@gmail.com [Central University of Himachal Pradesh, School of Physical and Astronomical Sciences (India); Chakraborty, Aniruddha [Indian Institute of Technology Mandi (India)

    2016-02-15

    The Smoluchowski equation with a time-dependent sink term is solved exactly. In this method, knowing the probability distribution P(0, s) at the origin, allows deriving the probability distribution P(x, s) at all positions. Exact solutions of the Smoluchowski equation are also provided in different cases where the sink term has linear, constant, inverse, and exponential variation in time.

  14. Exact analysis of Packet Reversed Packet Combining Scheme and Modified Packet Combining Scheme; and a combined scheme

    International Nuclear Information System (INIS)

    Bhunia, C.T.

    2007-07-01

    Packet combining scheme is a well defined simple error correction scheme for the detection and correction of errors at the receiver. Although it permits a higher throughput when compared to other basic ARQ protocols, packet combining (PC) scheme fails to correct errors when errors occur in the same bit locations of copies. In a previous work, a scheme known as Packet Reversed Packet Combining (PRPC) Scheme that will correct errors which occur at the same bit location of erroneous copies, was studied however PRPC does not handle a situation where a packet has more than 1 error bit. The Modified Packet Combining (MPC) Scheme that can correct double or higher bit errors was studied elsewhere. Both PRPC and MPC schemes are believed to offer higher throughput in previous studies, however neither adequate investigation nor exact analysis was done to substantiate this claim of higher throughput. In this work, an exact analysis of both PRPC and MPC is carried out and the results reported. A combined protocol (PRPC and MPC) is proposed and the analysis shows that it is capable of offering even higher throughput and better error correction capability at high bit error rate (BER) and larger packet size. (author)

  15. Exactly solvable string models of curved space-time backgrounds

    CERN Document Server

    Russo, J.G.; Russo, J G; Tseytlin, A A

    1995-01-01

    We consider a new 3-parameter class of exact 4-dimensional solutions in closed string theory and solve the corresponding string model, determining the physical spectrum and the partition function. The background fields (4-metric, antisymmetric tensor, two Kaluza-Klein vector fields, dilaton and modulus) generically describe axially symmetric stationary rotating (electro)magnetic flux-tube type universes. Backgrounds of this class include both the dilatonic Melvin solution and the uniform magnetic field solution discussed earlier as well as some singular space-times. Solvability of the string sigma model is related to its connection via duality to a much simpler looking model which is a "twisted" product of a flat 2-space and a space dual to 2-plane. We discuss some physical properties of this model as well as a number of generalizations leading to larger classes of exact 4-dimensional string solutions.

  16. New analytical exact solutions of time fractional KdV-KZK equation by Kudryashov methods

    Science.gov (United States)

    S Saha, Ray

    2016-04-01

    In this paper, new exact solutions of the time fractional KdV-Khokhlov-Zabolotskaya-Kuznetsov (KdV-KZK) equation are obtained by the classical Kudryashov method and modified Kudryashov method respectively. For this purpose, the modified Riemann-Liouville derivative is used to convert the nonlinear time fractional KdV-KZK equation into the nonlinear ordinary differential equation. In the present analysis, the classical Kudryashov method and modified Kudryashov method are both used successively to compute the analytical solutions of the time fractional KdV-KZK equation. As a result, new exact solutions involving the symmetrical Fibonacci function, hyperbolic function and exponential function are obtained for the first time. The methods under consideration are reliable and efficient, and can be used as an alternative to establish new exact solutions of different types of fractional differential equations arising from mathematical physics. The obtained results are exhibited graphically in order to demonstrate the efficiencies and applicabilities of these proposed methods of solving the nonlinear time fractional KdV-KZK equation.

  17. Time reversal imaging, Inverse problems and Adjoint Tomography}

    Science.gov (United States)

    Montagner, J.; Larmat, C. S.; Capdeville, Y.; Kawakatsu, H.; Fink, M.

    2010-12-01

    With the increasing power of computers and numerical techniques (such as spectral element methods), it is possible to address a new class of seismological problems. The propagation of seismic waves in heterogeneous media is simulated more and more accurately and new applications developed, in particular time reversal methods and adjoint tomography in the three-dimensional Earth. Since the pioneering work of J. Claerbout, theorized by A. Tarantola, many similarities were found between time-reversal methods, cross-correlations techniques, inverse problems and adjoint tomography. By using normal mode theory, we generalize the scalar approach of Draeger and Fink (1999) and Lobkis and Weaver (2001) to the 3D- elastic Earth, for theoretically understanding time-reversal method on global scale. It is shown how to relate time-reversal methods on one hand, with auto-correlations of seismograms for source imaging and on the other hand, with cross-correlations between receivers for structural imaging and retrieving Green function. Time-reversal methods were successfully applied in the past to acoustic waves in many fields such as medical imaging, underwater acoustics, non destructive testing and to seismic waves in seismology for earthquake imaging. In the case of source imaging, time reversal techniques make it possible an automatic location in time and space as well as the retrieval of focal mechanism of earthquakes or unknown environmental sources . We present here some applications at the global scale of these techniques on synthetic tests and on real data, such as Sumatra-Andaman (Dec. 2004), Haiti (Jan. 2010), as well as glacial earthquakes and seismic hum.

  18. Efficient exact-exchange time-dependent density-functional theory methods and their relation to time-dependent Hartree-Fock.

    Science.gov (United States)

    Hesselmann, Andreas; Görling, Andreas

    2011-01-21

    A recently introduced time-dependent exact-exchange (TDEXX) method, i.e., a response method based on time-dependent density-functional theory that treats the frequency-dependent exchange kernel exactly, is reformulated. In the reformulated version of the TDEXX method electronic excitation energies can be calculated by solving a linear generalized eigenvalue problem while in the original version of the TDEXX method a laborious frequency iteration is required in the calculation of each excitation energy. The lowest eigenvalues of the new TDEXX eigenvalue equation corresponding to the lowest excitation energies can be efficiently obtained by, e.g., a version of the Davidson algorithm appropriate for generalized eigenvalue problems. Alternatively, with the help of a series expansion of the new TDEXX eigenvalue equation, standard eigensolvers for large regular eigenvalue problems, e.g., the standard Davidson algorithm, can be used to efficiently calculate the lowest excitation energies. With the help of the series expansion as well, the relation between the TDEXX method and time-dependent Hartree-Fock is analyzed. Several ways to take into account correlation in addition to the exact treatment of exchange in the TDEXX method are discussed, e.g., a scaling of the Kohn-Sham eigenvalues, the inclusion of (semi)local approximate correlation potentials, or hybrids of the exact-exchange kernel with kernels within the adiabatic local density approximation. The lowest lying excitations of the molecules ethylene, acetaldehyde, and pyridine are considered as examples.

  19. Optimal One Bit Time Reversal For UWB Impulse Radio In Multi-User Wireless Communications

    DEFF Research Database (Denmark)

    Nguyen, Hung Tuan

    2008-01-01

    In this paper, with the purpose of further reducing the complexity of the system, while keeping its temporal and spatial focusing performance, we investigate the possibility of using optimal one bit time reversal (TR) system for impulse radio ultra wideband multi-user wireless communications...

  20. Exact-exchange time-dependent density-functional theory for static and dynamic polarizabilities

    International Nuclear Information System (INIS)

    Hirata, So; Ivanov, Stanislav; Bartlett, Rodney J.; Grabowski, Ireneusz

    2005-01-01

    Time-dependent density-functional theory (TDDFT) employing the exact-exchange functional has been formulated on the basis of the optimized-effective-potential (OEP) method of Talman and Shadwick for second-order molecular properties and implemented into a Gaussian-basis-set, trial-vector algorithm. The only approximation involved, apart from the lack of correlation effects and the use of Gaussian-type basis functions, was the consistent use of the adiabatic approximation in the exchange kernel and in the linear response function. The static and dynamic polarizabilities and their anisotropy predicted by the TDDFT with exact exchange (TDOEP) agree accurately with the corresponding values from time-dependent Hartree-Fock theory, the exact-exchange counterpart in the wave function theory. The TDOEP is free from the nonphysical asymptotic decay of the exchange potential of most conventional density functionals or from any other manifestations of the incomplete cancellation of the self-interaction energy. The systematic overestimation of the absolute values and dispersion of polarizabilities that plagues most conventional TDDFT cannot be seen in the TDOEP

  1. Exact solutions to the supply chain equations for arbitrary, time-dependent demands

    DEFF Research Database (Denmark)

    Warburton, Roger D.H.; Hodgson, J.P.E.; Nielsen, Erland Hejn

    2014-01-01

    , so users can determine the inventory behavior to any desired precision. To illustrate, we solve the equations for a non-linear, quadratic time-dependence in the demand. For practical use, only a few terms in the series are required, a proposition illustrated by the For All Practical Purposes (FAPP......We study the impact on inventory of an unexpected, non-linear, time-dependent demand and present the exact solutions over time to the supply chain equations without requiring any approximations. We begin by imposing a boundary condition of stability at infinity, from which we derive expressions...... for the estimated demand and the target work in progress when the demand is time-dependent. The resulting inventory equation is solved in terms of the Lambert modes with all of the demand non-linearities confined to the pre-shape function. The series solution is exact, and all terms are reasonably easy to calculate...

  2. New analytical exact solutions of time fractional KdV–KZK equation by Kudryashov methods

    International Nuclear Information System (INIS)

    Saha Ray, S

    2016-01-01

    In this paper, new exact solutions of the time fractional KdV–Khokhlov–Zabolotskaya–Kuznetsov (KdV–KZK) equation are obtained by the classical Kudryashov method and modified Kudryashov method respectively. For this purpose, the modified Riemann–Liouville derivative is used to convert the nonlinear time fractional KdV–KZK equation into the nonlinear ordinary differential equation. In the present analysis, the classical Kudryashov method and modified Kudryashov method are both used successively to compute the analytical solutions of the time fractional KdV–KZK equation. As a result, new exact solutions involving the symmetrical Fibonacci function, hyperbolic function and exponential function are obtained for the first time. The methods under consideration are reliable and efficient, and can be used as an alternative to establish new exact solutions of different types of fractional differential equations arising from mathematical physics. The obtained results are exhibited graphically in order to demonstrate the efficiencies and applicabilities of these proposed methods of solving the nonlinear time fractional KdV–KZK equation. (paper)

  3. Relation of exact Gaussian basis methods to the dephasing representation: Theory and application to time-resolved electronic spectra

    Science.gov (United States)

    Sulc, Miroslav; Hernandez, Henar; Martinez, Todd J.; Vanicek, Jiri

    2014-03-01

    We recently showed that the Dephasing Representation (DR) provides an efficient tool for computing ultrafast electronic spectra and that cellularization yields further acceleration [M. Šulc and J. Vaníček, Mol. Phys. 110, 945 (2012)]. Here we focus on increasing its accuracy by first implementing an exact Gaussian basis method (GBM) combining the accuracy of quantum dynamics and efficiency of classical dynamics. The DR is then derived together with ten other methods for computing time-resolved spectra with intermediate accuracy and efficiency. These include the Gaussian DR (GDR), an exact generalization of the DR, in which trajectories are replaced by communicating frozen Gaussians evolving classically with an average Hamiltonian. The methods are tested numerically on time correlation functions and time-resolved stimulated emission spectra in the harmonic potential, pyrazine S0 /S1 model, and quartic oscillator. Both the GBM and the GDR are shown to increase the accuracy of the DR. Surprisingly, in chaotic systems the GDR can outperform the presumably more accurate GBM, in which the two bases evolve separately. This research was supported by the Swiss NSF Grant No. 200021_124936/1 and NCCR Molecular Ultrafast Science & Technology (MUST), and by the EPFL.

  4. Modeling of the attenuation of stress waves in concrete based on the Rayleigh damping model using time-reversal and PZT transducers

    Science.gov (United States)

    Tian, Zhen; Huo, Linsheng; Gao, Weihang; Li, Hongnan; Song, Gangbing

    2017-10-01

    Wave-based concrete structural health monitoring has attracted much attention. A stress wave experiences significant attenuation in concrete, however there is a lack of a unified method for predicting the attenuation coefficient of the stress wave. In this paper, a simple and effective absorption attenuation model of stress waves in concrete is developed based on the Rayleigh damping model, which indicates that the absorption attenuation coefficient of stress waves in concrete is directly proportional to the square of the stress wave frequency when the damping ratio is small. In order to verify the theoretical model, related experiments were carried out. During the experiments, a concrete beam was designed in which the d33-model piezoelectric smart aggregates were embedded to detect the propagation of stress waves. It is difficult to distinguish direct stress waves due to the complex propagation paths and the reflection and scattering of stress waves in concrete. Hence, as another innovation of this paper, a new method for computing the absorption attenuation coefficient based on the time-reversal method is developed. Due to the self-adaptive focusing properties of the time-reversal method, the time-reversed stress wave focuses and generates a peak value. The time-reversal method eliminates the adverse effects of multipaths, reflection, and scattering. The absorption attenuation coefficient is computed by analyzing the peak value changes of the time-reversal focused signal. Finally, the experimental results are found to be in good agreement with the theoretical model.

  5. The exact LPT-bound for maximizing the minimum completion time

    NARCIS (Netherlands)

    Csirik, J.; Kellerer, H.; Woeginger, G.J.

    1992-01-01

    We consider the problem of assigning a set of jobs to a system of m identical processors in order to maximize the earliest processor completion time. It was known that the LPT-heuristic gives an approximation of worst case ratio at most 3/4. In this note we show that the exact worst case ratio of

  6. Multiples least-squares reverse time migration

    KAUST Repository

    Zhang, Dongliang; Zhan, Ge; Dai, Wei; Schuster, Gerard T.

    2013-01-01

    To enhance the image quality, we propose multiples least-squares reverse time migration (MLSRTM) that transforms each hydrophone into a virtual point source with a time history equal to that of the recorded data. Since each recorded trace is treated

  7. Exact solutions of time-dependent Dirac equations and the quantum-classical correspondence

    International Nuclear Information System (INIS)

    Zhang Zhiguo

    2006-01-01

    Exact solutions to the Dirac equations with a time-dependent mass and a static magnetic field or a time-dependent linear potential are given. Matrix elements of the coordinate, momentum and velocity operator are calculated. In the large quantum number limit, these matrix elements give the classical solution

  8. Kinetic Line Voronoi Operations and Their Reversibility

    DEFF Research Database (Denmark)

    Mioc, Darka; Anton, François; Gold, Christopher

    2010-01-01

    In Geographic Information Systems the reversibility of map update operations has not been explored yet. In this paper we are using the Voronoi based Quad-edge data structure to define reversible map update operations. The reversibility of the map operations has been formalised at the lowest level...... mechanisms and dynamic map visualisations. In order to use the reversibility within the kinetic Voronoi diagram of points and open oriented line segments, we need to assure that reversing the map commands will produce exactly the changes in the map equivalent to the previous map states. To prove...... that reversing the map update operations produces the exact reverse changes, we show an isomorphism between the set of complex operations on the kinetic Voronoi diagram of points and open oriented line segments and the sets of numbers of new / deleted Voronoi regions induced by these operations, and its...

  9. Tests of time reversal in neutron-nucleus scattering

    International Nuclear Information System (INIS)

    Bowman, J.D.

    1988-01-01

    Experiments to test time-reversal invariance are discussed. The experiments are based on observables constructed from the momentum and spin vectors of epithermal neutrons and from the spin of an aligned or polarized target. It is shown that the proposed tests are detailed balance tests of time-reversal invariance. The status of the experiments is briefly reviewed. 14 refs., 5 figs

  10. Least squares reverse time migration of controlled order multiples

    Science.gov (United States)

    Liu, Y.

    2016-12-01

    Imaging using the reverse time migration of multiples generates inherent crosstalk artifacts due to the interference among different order multiples. Traditionally, least-square fitting has been used to address this issue by seeking the best objective function to measure the amplitude differences between the predicted and observed data. We have developed an alternative objective function by decomposing multiples into different orders to minimize the difference between Born modeling predicted multiples and specific-order multiples from observational data in order to attenuate the crosstalk. This method is denoted as the least-squares reverse time migration of controlled order multiples (LSRTM-CM). Our numerical examples demonstrated that the LSRTM-CM can significantly improve image quality compared with reverse time migration of multiples and least-square reverse time migration of multiples. Acknowledgments This research was funded by the National Nature Science Foundation of China (Grant Nos. 41430321 and 41374138).

  11. Exact solution of the time-dependent harmonic plus an inverse harmonic potential with a time-dependent electromagnetic field

    International Nuclear Information System (INIS)

    Yuece, Cem

    2003-01-01

    In this paper, the problem of the charged harmonic plus an inverse harmonic oscillator with time-dependent mass and frequency in a time-dependent electromagnetic field is investigated. It is reduced to the problem of the inverse harmonic oscillator with time-independent parameters and the exact wave function is obtained

  12. The Geomagnetic Field During a Reversal

    Science.gov (United States)

    Heirtzler, James R.

    2003-01-01

    By modifying the IGRF it is possible to learn what may happen to the geomagnetic field during a geomagnetic reversal. If the entire IGRF reverses then the declination and inclination only reverse when the field strength is zero. If only the dipole component of the IGRF reverses a large geomagnetic field remains when the dipole component is zero and he direction of the field at the end of the reversal is not exactly reversed from the directions at the beginning of the reversal.

  13. Newmark-Beta-FDTD method for super-resolution analysis of time reversal waves

    Science.gov (United States)

    Shi, Sheng-Bing; Shao, Wei; Ma, Jing; Jin, Congjun; Wang, Xiao-Hua

    2017-09-01

    In this work, a new unconditionally stable finite-difference time-domain (FDTD) method with the split-field perfectly matched layer (PML) is proposed for the analysis of time reversal (TR) waves. The proposed method is very suitable for multiscale problems involving microstructures. The spatial and temporal derivatives in this method are discretized by the central difference technique and Newmark-Beta algorithm, respectively, and the derivation results in the calculation of a banded-sparse matrix equation. Since the coefficient matrix keeps unchanged during the whole simulation process, the lower-upper (LU) decomposition of the matrix needs to be performed only once at the beginning of the calculation. Moreover, the reverse Cuthill-Mckee (RCM) technique, an effective preprocessing technique in bandwidth compression of sparse matrices, is used to improve computational efficiency. The super-resolution focusing of TR wave propagation in two- and three-dimensional spaces is included to validate the accuracy and efficiency of the proposed method.

  14. Time reversal and parity tests

    International Nuclear Information System (INIS)

    Terwilliger, K.

    1975-01-01

    A recent review by Henley discusses the present status of Time Reversal and Parity symmetry violations, and comments on the implications for high energy hadron scattering. This note will briefly summarize the situation with particular attention to the sizes of possible effects, relating them to experimental accuracy available or reasonably possible at the ZGS

  15. Time-reversal and Bayesian inversion

    Science.gov (United States)

    Debski, Wojciech

    2017-04-01

    Probabilistic inversion technique is superior to the classical optimization-based approach in all but one aspects. It requires quite exhaustive computations which prohibit its use in huge size inverse problems like global seismic tomography or waveform inversion to name a few. The advantages of the approach are, however, so appealing that there is an ongoing continuous afford to make the large inverse task as mentioned above manageable with the probabilistic inverse approach. One of the perspective possibility to achieve this goal relays on exploring the internal symmetry of the seismological modeling problems in hand - a time reversal and reciprocity invariance. This two basic properties of the elastic wave equation when incorporating into the probabilistic inversion schemata open a new horizons for Bayesian inversion. In this presentation we discuss the time reversal symmetry property, its mathematical aspects and propose how to combine it with the probabilistic inverse theory into a compact, fast inversion algorithm. We illustrate the proposed idea with the newly developed location algorithm TRMLOC and discuss its efficiency when applied to mining induced seismic data.

  16. Exact solution of the generalized time-dependent Jaynes-Cummings Hamiltonian

    International Nuclear Information System (INIS)

    Gruver, J.L.; Aliaga, J.; Cerdeira, H.A.; Proto, A.N.

    1993-04-01

    A time-dependent generalization of the Jaynes-Cummings Hamiltonian is studied using the maximum entropy formalism. The approach, related to a semi-Lie algebra, allows to find three different sets of physical relevant operators which describe the dynamics of the system for any temporal dependence. It is shown how the initial conditions of the operators are determined via the maximum entropy principle density operator, where the inclusion of the temperature turns the description of the problem into a thermodynamical one. The generalized time-independent Jaynes-Cummings Hamiltonian is exactly solved as a particular example. (author). 14 refs

  17. A Perspective for Time-Varying Channel Compensation with Model-Based Adaptive Passive Time-Reversal

    Directory of Open Access Journals (Sweden)

    Lussac P. MAIA

    2015-06-01

    Full Text Available Underwater communications mainly rely on acoustic propagation which is strongly affected by frequency-dependent attenuation, shallow water multipath propagation and significant Doppler spread/shift induced by source-receiver-surface motion. Time-reversal based techniques offer a low complexity solution to decrease interferences caused by multipath, but a complete equalization cannot be reached (it saturates when maximize signal to noise ratio and these techniques in conventional form are quite sensible to channel variations along the transmission. Acoustic propagation modeling in high frequency regime can yield physical-based information that is potentially useful to channel compensation methods as the passive time-reversal (pTR, which is often employed in Digital Acoustic Underwater Communications (DAUC systems because of its low computational cost. Aiming to overcome the difficulties of pTR to solve time-variations in underwater channels, it is intended to insert physical knowledge from acoustic propagation modeling in the pTR filtering. Investigation is being done by the authors about the influence of channel physical parameters on propagation of coherent acoustic signals transmitted through shallow water waveguides and received in a vertical line array of sensors. Time-variant approach is used, as required to model high frequency acoustic propagation on realistic scenarios, and applied to a DAUC simulator containing an adaptive passive time-reversal receiver (ApTR. The understanding about the effects of changes in physical features of the channel over the propagation can lead to design ApTR filters which could help to improve the communications system performance. This work presents a short extension and review of the paper 12, which tested Doppler distortion induced by source-surface motion and ApTR compensation for a DAUC system on a simulated time-variant channel, in the scope of model-based equalization. Environmental focusing approach

  18. ExactPack Documentation

    Energy Technology Data Exchange (ETDEWEB)

    Singleton, Robert Jr. [Los Alamos National Laboratory; Israel, Daniel M. [Los Alamos National Laboratory; Doebling, Scott William [Los Alamos National Laboratory; Woods, Charles Nathan [Los Alamos National Laboratory; Kaul, Ann [Los Alamos National Laboratory; Walter, John William Jr [Los Alamos National Laboratory; Rogers, Michael Lloyd [Los Alamos National Laboratory

    2016-05-09

    For code verification, one compares the code output against known exact solutions. There are many standard test problems used in this capacity, such as the Noh and Sedov problems. ExactPack is a utility that integrates many of these exact solution codes into a common API (application program interface), and can be used as a stand-alone code or as a python package. ExactPack consists of python driver scripts that access a library of exact solutions written in Fortran or Python. The spatial profiles of the relevant physical quantities, such as the density, fluid velocity, sound speed, or internal energy, are returned at a time specified by the user. The solution profiles can be viewed and examined by a command line interface or a graphical user interface, and a number of analysis tools and unit tests are also provided. We have documented the physics of each problem in the solution library, and provided complete documentation on how to extend the library to include additional exact solutions. ExactPack’s code architecture makes it easy to extend the solution-code library to include additional exact solutions in a robust, reliable, and maintainable manner.

  19. The Two-Time Interpretation and Macroscopic Time-Reversibility

    Directory of Open Access Journals (Sweden)

    Yakir Aharonov

    2017-03-01

    Full Text Available The two-state vector formalism motivates a time-symmetric interpretation of quantum mechanics that entails a resolution of the measurement problem. We revisit a post-selection-assisted collapse model previously suggested by us, claiming that unlike the thermodynamic arrow of time, it can lead to reversible dynamics at the macroscopic level. In addition, the proposed scheme enables us to characterize the classical-quantum boundary. We discuss the limitations of this approach and its broad implications for other areas of physics.

  20. A Numerical Investigation of the Time Reversal Mirror Technique for Trans-skull Brain Cancer Ultrasound Surgery

    Directory of Open Access Journals (Sweden)

    H. Zahedmanesh

    2007-06-01

    Full Text Available Introduction: The medical applications of ultrasound on human brain are highly limited by the phase and amplitude aberrations induced by the heterogeneities of the skull. However, it has been shown that time reversing coupled with amplitude compensation can overcome these aberrations. In this work, a model for 2D simulation of the time reversal mirror technique is proposed to study the possibility of targeting any point within the brain without the need for craniotomy and to calculate the acoustic pressure field and the resulting temperature distribution within the skull and brain during a High Intensity Focused Ultrasound (HIFU transcranial therapy. Materials and Methods: To overcome the sensitivity of the wave pattern to the heterogeneous geometry of the skull, a real MRI derived 2D model is constructed. The model should include the real geometry of brain and skull. The model should also include the couplant medium which has the responsibility of coupling the transducer to the skull for the penetration of ultrasound. The clinical substance used as the couplant is water. The acoustic and thermal parameters are derived from the references. Next, the wave propagation through the skull is computed based on the Helmholtz equation, with a 2D finite element analysis. The acoustic simulation is combined with a 2D thermal diffusion analysis based on Pennes Bioheat equation and the temperature elevation inside the skull and brain is computed. The numerical simulations were performed using the FEMLAB 3.2 software on a PC having 8 GB RAM and a 2.4 MHz dual CPU. Results: It is seen that the ultrasonic waves are exactly focalized at the location where the hydrophone has been previously implanted. There is no penetration into the sinuses and the waves are reflected from their surface because of the high discrepancy between the speed of sound in bone and air.  Under the focal pressure of 2.5 MPa and after 4 seconds of sonication the temperature at the focus

  1. Exact solutions of time-fractional heat conduction equation by the fractional complex transform

    Directory of Open Access Journals (Sweden)

    Li Zheng-Biao

    2012-01-01

    Full Text Available The Fractional Complex Transform is extended to solve exactly time-fractional differential equations with the modified Riemann-Liouville derivative. How to incorporate suitable boundary/initial conditions is also discussed.

  2. Occupation times and exact asymptotics of small deviations of Bessel processes for Lp-norms with p>0

    International Nuclear Information System (INIS)

    Fatalov, V R

    2007-01-01

    We prove theorems on exact asymptotics of the distributions of integral functionals of the occupation time of Bessel processes. Using these results, we obtain exact asymptotics of small deviations for Bessel processes in the L p -norm. We use Laplace's method for the occupation times of Markov processes with continuous time. Computations are carried out for p=2 and p=1. We also solve extremal problems for the action functional

  3. Interplay of Coulomb interactions and disorder in three-dimensional quadratic band crossings without time-reversal symmetry and with unequal masses for conduction and valence bands

    Science.gov (United States)

    Mandal, Ipsita; Nandkishore, Rahul M.

    2018-03-01

    Coulomb interactions famously drive three-dimensional quadratic band crossing semimetals into a non-Fermi liquid phase of matter. In a previous work [Nandkishore and Parameswaran, Phys. Rev. B 95, 205106 (2017), 10.1103/PhysRevB.95.205106], the effect of disorder on this non-Fermi liquid phase was investigated, assuming that the band structure was isotropic, assuming that the conduction and valence bands had the same band mass, and assuming that the disorder preserved exact time-reversal symmetry and statistical isotropy. It was shown that the non-Fermi liquid fixed point is unstable to disorder and that a runaway flow to strong disorder occurs. In this paper, we extend that analysis by relaxing the assumption of time-reversal symmetry and allowing the electron and hole masses to differ (but continuing to assume isotropy of the low energy band structure). We first incorporate time-reversal symmetry breaking disorder and demonstrate that there do not appear any new fixed points. Moreover, while the system continues to flow to strong disorder, time-reversal-symmetry-breaking disorder grows asymptotically more slowly than time-reversal-symmetry-preserving disorder, which we therefore expect should dominate the strong-coupling phase. We then allow for unequal electron and hole masses. We show that whereas asymmetry in the two masses is irrelevant in the clean system, it is relevant in the presence of disorder, such that the `effective masses' of the conduction and valence bands should become sharply distinct in the low-energy limit. We calculate the RG flow equations for the disordered interacting system with unequal band masses and demonstrate that the problem exhibits a runaway flow to strong disorder. Along the runaway flow, time-reversal-symmetry-preserving disorder grows asymptotically more rapidly than both time-reversal-symmetry-breaking disorder and the Coulomb interaction.

  4. Least-squares reverse time migration of multiples

    KAUST Repository

    Zhang, Dongliang; Schuster, Gerard T.

    2013-01-01

    The theory of least-squares reverse time migration of multiples (RTMM) is presented. In this method, least squares migration (LSM) is used to image free-surface multiples where the recorded traces are used as the time histories of the virtual

  5. Energy drift in reversible time integration

    International Nuclear Information System (INIS)

    McLachlan, R I; Perlmutter, M

    2004-01-01

    Energy drift is commonly observed in reversible integrations of systems of molecular dynamics. We show that this drift can be modelled as a diffusion and that the typical energy error after time T is O(√T). (letter to the editor)

  6. Exact Solution of Space-Time Fractional Coupled EW and Coupled MEW Equations Using Modified Kudryashov Method

    International Nuclear Information System (INIS)

    Raslan, K. R.; Ali, Khalid K.; EL-Danaf, Talaat S.

    2017-01-01

    In the present paper, we established a traveling wave solution by using modified Kudryashov method for the space-time fractional nonlinear partial differential equations. The method is used to obtain the exact solutions for different types of the space-time fractional nonlinear partial differential equations such as, the space-time fractional coupled equal width wave equation (CEWE) and the space-time fractional coupled modified equal width wave equation (CMEW), which are the important soliton equations. Both equations are reduced to ordinary differential equations by the use of fractional complex transform and properties of modified Riemann–Liouville derivative. We plot the exact solutions for these equations at different time levels. (paper)

  7. Photoelectric effect in the relativistic domain revealed by the time-reversed process for highly charged uranium ions

    International Nuclear Information System (INIS)

    Stoehlker, T.; Mokler, P.H.; Kozhuharov, C.; Warczak, A.

    1996-10-01

    The photoelectric effect in the near relativistic energy regime of 80 to 350 keV is studied by the time-reversed process in ion-atom collisions, i.e. by the radiative capture of a quasi-free target electron. We review shell and subshell differential photon-angular distribution studies of radiative capture into highly-charged uranium ions. The experimental data are compared with exact relativistic calculations and give detailed insight into both the atomic structure of high-Z few-electron ions and into the fundamental electron-photon interaction process involved. In particular it is shown that the angular-differential measurements provide a unique method to study the magnetic interaction in relativistic electron-photon encoun- (orig.)

  8. Exact Time-Dependent Exchange-Correlation Potential in Electron Scattering Processes

    Science.gov (United States)

    Suzuki, Yasumitsu; Lacombe, Lionel; Watanabe, Kazuyuki; Maitra, Neepa T.

    2017-12-01

    We identify peak and valley structures in the exact exchange-correlation potential of time-dependent density functional theory that are crucial for time-resolved electron scattering in a model one-dimensional system. These structures are completely missed by adiabatic approximations that, consequently, significantly underestimate the scattering probability. A recently proposed nonadiabatic approximation is shown to correctly capture the approach of the electron to the target when the initial Kohn-Sham state is chosen judiciously, and it is more accurate than standard adiabatic functionals but ultimately fails to accurately capture reflection. These results may explain the underestimation of scattering probabilities in some recent studies on molecules and surfaces.

  9. Theta, time reversal and temperature

    Energy Technology Data Exchange (ETDEWEB)

    Gaiotto, Davide [Perimeter Institute for Theoretical Physics,Waterloo, Ontario, N2L 2Y5 (Canada); Kapustin, Anton [Walter Burke Institute for Theoretical Physics, California Institute of Technology,Pasadena, CA 91125 (United States); Komargodski, Zohar [Department of Particle Physics and Astrophysics, Weizmann Institute of Science,Rehovot 76100 (Israel); Seiberg, Nathan [School of Natural Sciences, Institute for Advanced Study,Princeton, NJ 08540 (United States)

    2017-05-17

    SU(N) gauge theory is time reversal invariant at θ=0 and θ=π. We show that at θ=π there is a discrete ’t Hooft anomaly involving time reversal and the center symmetry. This anomaly leads to constraints on the vacua of the theory. It follows that at θ=π the vacuum cannot be a trivial non-degenerate gapped state. (By contrast, the vacuum at θ=0 is gapped, non-degenerate, and trivial.) Due to the anomaly, the theory admits nontrivial domain walls supporting lower-dimensional theories. Depending on the nature of the vacuum at θ=π, several phase diagrams are possible. Assuming area law for space-like loops, one arrives at an inequality involving the temperatures at which CP and the center symmetry are restored. We also analyze alternative scenarios for SU(2) gauge theory. The underlying symmetry at θ=π is the dihedral group of 8 elements. If deconfined loops are allowed, one can have two O(2)-symmetric fixed points. It may also be that the four-dimensional theory around θ=π is gapless, e.g. a Coulomb phase could match the underlying anomalies.

  10. Theta, time reversal and temperature

    International Nuclear Information System (INIS)

    Gaiotto, Davide; Kapustin, Anton; Komargodski, Zohar; Seiberg, Nathan

    2017-01-01

    SU(N) gauge theory is time reversal invariant at θ=0 and θ=π. We show that at θ=π there is a discrete ’t Hooft anomaly involving time reversal and the center symmetry. This anomaly leads to constraints on the vacua of the theory. It follows that at θ=π the vacuum cannot be a trivial non-degenerate gapped state. (By contrast, the vacuum at θ=0 is gapped, non-degenerate, and trivial.) Due to the anomaly, the theory admits nontrivial domain walls supporting lower-dimensional theories. Depending on the nature of the vacuum at θ=π, several phase diagrams are possible. Assuming area law for space-like loops, one arrives at an inequality involving the temperatures at which CP and the center symmetry are restored. We also analyze alternative scenarios for SU(2) gauge theory. The underlying symmetry at θ=π is the dihedral group of 8 elements. If deconfined loops are allowed, one can have two O(2)-symmetric fixed points. It may also be that the four-dimensional theory around θ=π is gapless, e.g. a Coulomb phase could match the underlying anomalies.

  11. Parity- and time-reversal-violating moments of light nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Vries, Jordy de, E-mail: devries@kvi.nl [KVI, theory group (Netherlands)

    2013-03-15

    I present the calculation of parity- and time-reversal-violating moments of the nucleon and light nuclei, originating from the QCD {theta}-bar term and effective dimension-six operators. By applying chiral effective field theory these calculations are performed in a unified framework. I argue that measurements of a few light-nuclear electric dipole moments would shed light on the mechanism of parity and time-reversal violation.

  12. Bounding spectral gaps of Markov chains: a novel exact multi-decomposition technique

    International Nuclear Information System (INIS)

    Destainville, N

    2003-01-01

    We propose an exact technique to calculate lower bounds of spectral gaps of discrete time reversible Markov chains on finite state sets. Spectral gaps are a common tool for evaluating convergence rates of Markov chains. As an illustration, we successfully use this technique to evaluate the 'absorption time' of the 'Backgammon model', a paradigmatic model for glassy dynamics. We also discuss the application of this technique to the 'contingency table problem', a notoriously difficult problem from probability theory. The interest of this technique is that it connects spectral gaps, which are quantities related to dynamics, with static quantities, calculated at equilibrium

  13. How decision reversibility affects motivation.

    Science.gov (United States)

    Bullens, Lottie; van Harreveld, Frenk; Förster, Jens; Higgins, Tory E

    2014-04-01

    The present research examined how decision reversibility can affect motivation. On the basis of extant findings, it was suggested that 1 way it could affect motivation would be to strengthen different regulatory foci, with reversible decision making, compared to irreversible decision making, strengthening prevention-related motivation relatively more than promotion-related motivation. If so, then decision reversibility should have effects associated with the relative differences between prevention and promotion motivation. In 5 studies, we manipulated the reversibility of a decision and used different indicators of regulatory focus motivation to test these predictions. Specifically, Study 1 tested for differences in participants' preference for approach versus avoidance strategies toward a desired end state. In Study 2, we used speed and accuracy performance as indicators of participants' regulatory motivation, and in Study 3, we measured global versus local reaction time performance. In Study 4, we approached the research question in a different way, making use of the value-from-fit hypothesis (Higgins, 2000, 2002). We tested whether a fit between chronic regulatory focus and focus induced by the reversibility of the decision increased participants' subjective positive feelings about the decision outcome. Finally, in Study 5, we tested whether regulatory motivation, induced by decision reversibility, also influenced participants' preference in specific product features. The results generally support our hypothesis showing that, compared to irreversible decisions, reversible decisions strengthen a prevention focus more than a promotion focus. Implications for research on decision making are discussed.

  14. Current fluctuations and statistics during a large deviation event in an exactly solvable transport model

    International Nuclear Information System (INIS)

    Hurtado, Pablo I; Garrido, Pedro L

    2009-01-01

    We study the distribution of the time-integrated current in an exactly solvable toy model of heat conduction, both analytically and numerically. The simplicity of the model allows us to derive the full current large deviation function and the system statistics during a large deviation event. In this way we unveil a relation between system statistics at the end of a large deviation event and for intermediate times. The mid-time statistics is independent of the sign of the current, a reflection of the time-reversal symmetry of microscopic dynamics, while the end-time statistics does depend on the current sign, and also on its microscopic definition. We compare our exact results with simulations based on the direct evaluation of large deviation functions, analyzing the finite-size corrections of this simulation method and deriving detailed bounds for its applicability. We also show how the Gallavotti–Cohen fluctuation theorem can be used to determine the range of validity of simulation results

  15. A time-focusing Fourier chopper time-of-flight diffractometer for large scattering angles

    International Nuclear Information System (INIS)

    Heinonen, R.; Hiismaeki, P.; Piirto, A.; Poeyry, H.; Tiitta, A.

    1975-01-01

    A high-resolution time-of-flight diffractometer utilizing time focusing principles in conjunction with a Fourier chopper is under construction at Otaniemi. The design is an improved version of a test facility which has been used for single-crystal and powder diffraction studies with promising results. A polychromatic neutron beam from a radial beam tube of the FiR 1 reactor, collimated to dia. 70 mm, is modulated by a Fourier chopper (dia. 400 mm) which is placed inside a massive boron-loaded particle board shielding of 900 mm wall thickness. A thin flat sample (5 mm x dia. 80 mm typically) is mounted on a turntable at a distance of 4 m from the chopper, and the diffracted neutrons are counted by a scintillation detector at 4 m distance from the sample. The scattering angle 2theta can be chosen between 90deg and 160deg to cover Bragg angles from 45deg up to 80deg. The angle between the chopper disc and the incident beam direction as well as the angle of the detector surface relative to the diffracted beam can be adjusted between 45deg and 90deg in order to accomplish time-focusing. In our set-up, with equal flight paths from chopper to sample and from sample to detector, the time-focusing conditions are fulfilled when the chopper and the detector are parallel to the sample-plane. The time-of-flight spectrum of the scattered neutrons is measured by the reverse time-of-flight method in which, instead of neutrons, one essentially records the modulation function of the chopper during constant periods preceding each detected neutron. With a Fourier chopper whose speed is varied in a suitable way, the method is equivalent to the conventional Fourier method but the spectrum is obtained directly without any off-line calculations. The new diffractometer is operated automatically by a Super Nova computer which not only accumulates the synthetized diffraction pattern but also controls the chopper speed according to the modulation frequency sweep chosen by the user to obtain a

  16. Concerning tests of time-reversal invariance via the polarization-analyzing power equality

    International Nuclear Information System (INIS)

    Conzett, H.E.

    1982-01-01

    Previous tests of time-reversal invariance via comparisons of polarizations and analyzing powers in nuclear scattering have been examined. It is found that all of these comparisons fail as adequate tests of time-reversal invariance either because of a lack of experimental precision or the lack of sensitivity to any time-reversal symmetry violation

  17. Time reversal in polarized neutron decay: the emiT experiment

    CERN Document Server

    Jones, G L; Anaya, J M; Bowles, T J; Chupp, T E; Coulter, K P; Dewey, M S; Freedman, S J; Fujikawa, B K; García, A; Greene, G L; Hwang, S R; Lising, L J; Mumm, H P; Nico, J S; Robertson, R G H; Steiger, T D; Teasdale, W A; Thompson, A K; Wasserman, E G; Wietfeldt, F E; Wilkerson, J F

    2000-01-01

    The standard electro-weak model predicts negligible violation of time-reversal invariance in light quark processes. We report on an experimental test of time-reversal invariance in the beta decay of polarized neutrons as a search for physics beyond the standard model. The emiT collaboration has measured the time-reversal-violating triple-correlation in neutron beta decay between the neutron spin, electron momentum, and neutrino momentum often referred to as the D coefficient. The first run of the experiment produced 14 million events which are currently being analyzed. However, a second run with improved detectors should provide greater statistical precision and reduced systematic uncertainties.

  18. Reversal of Hartmann's procedure following acute diverticulitis: is timing everything?

    LENUS (Irish Health Repository)

    Fleming, Fergal J

    2012-02-01

    BACKGROUND: Patients who undergo a Hartmann\\'s procedure may not be offered a reversal due to concerns over the morbidity of the second procedure. The aims of this study were to examine the morbidity post reversal of Hartmann\\'s procedure. METHODS: Patients who underwent a Hartmann\\'s procedure for acute diverticulitis (Hinchey 3 or 4) between 1995 and 2006 were studied. Clinical factors including patient comorbidities were analysed to elucidate what preoperative factors were associated with complications following reversal of Hartmann\\'s procedure. RESULTS: One hundred and ten patients were included. Median age was 70 years and 56% of the cohort were male (n = 61). The mortality and morbidity rate for the acute presentation was 7.3% (n = 8) and 34% (n = 37) respectively. Seventy six patients (69%) underwent a reversal at a median of 7 months (range 3-22 months) post-Hartmann\\'s procedure. The complication rate in the reversal group was 25% (n = 18). A history of current smoking (p = 0.004), increasing time to reversal (p = 0.04) and low preoperative albumin (p = 0.003) were all associated with complications following reversal. CONCLUSIONS: Reversal of Hartmann\\'s procedure can be offered to appropriately selected patients though with a significant (25%) morbidity rate. The identification of potential modifiable factors such as current smoking, prolonged time to reversal and low preoperative albumin may allow optimisation of such patients preoperatively.

  19. Constraints on a parity-even/time-reversal-odd interaction

    International Nuclear Information System (INIS)

    Oers, Willem T.H. van

    2000-01-01

    Time-Reversal-Invariance non-conservation has for the first time been unequivocally demonstrated in a direct measurement, one of the results of the CPLEAR experiment. What is the situation then with regard to time-reversal-invariance non-conservation in systems other than the neutral kaon system? Two classes of tests of time-reversal-invariance need to be distinguished: the first one deals with parity violating (P-odd)/time-reversal-invariance non-conserving (T-odd) interactions, while the second one deals with P-even/T-odd interactions (assuming CPT conservation this implies C-conjugation non-conservation). Limits on a P-odd/T-odd interaction follow from measurements of the electric dipole moment of the neutron. This in turn provides a limit on a P-odd/T-odd pion-nucleon coupling constant which is 10 -4 times the weak interaction strength. Limits on a P-even/T-odd interaction are much less stringent. The better constraint stems also from the measurement of the electric dipole moment of the neutron. Of all the other tests, measurements of charge-symmetry breaking in neutron-proton elastic scattering provide the next better constraint. The latter experiments were performed at TRIUMF (at 477 and 347 MeV) and at IUCF (at 183 MeV). Weak decay experiments (the transverse polarization of the muon in K + →π 0 μ + ν μ and the transverse polarization of the positrons in polarized muon decay) have the potential to provide comparable or possibly better constraints

  20. Time-reversed lasing in the terahertz range and its preliminary study in sensor applications

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Yun, E-mail: shenyunoptics@gmail.com [Department of Physics, Nanchang University, Nanchang 330031 (China); Liu, Huaqing [Department of Physics, Nanchang University, Nanchang 330031 (China); Deng, Xiaohua [Institute of Space Science and Technology, Nanchang University, Nanchang 330031 (China); Wang, Guoping [Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072 (China)

    2017-02-05

    Time-reversed lasing in a uniform slab and a grating structure are investigated in the terahertz range. The results show that both the uniform slab and grating can support terahertz time-reversed lasing. Nevertheless, due to the tunable effective refractive index, the grating structure can not only exhibit time-reversed lasing more effectively and flexibly than a uniform slab, but also can realize significant absorption in a broader operating frequency range. Furthermore, applications of terahertz time-reversed lasing for novel concentration/thickness sensors are preliminarily studied in a single-channel coherent perfect absorber system. - Highlights: • Time-reversed lasing are investigated in the terahertz range. • The grating structure exhibit time-reversed lasing more effectively and flexibly than a uniform slab. • THz time-reversed lasing for novel concentration/thickness sensors are studied.

  1. A reverse time of flight analyzer facility at the ETRR-1 reactor

    Energy Technology Data Exchange (ETDEWEB)

    Maayouf, R M.A.; El-Shafey, A S; Khalil, M I [Reactor and Neutron Physics Dept., NRC, Atomic Energy Authority, Cairo (Egypt)

    1997-12-31

    The present work deals both with the theory and performance of a reverse-time-of-flight (RTOF) analyzer designed to analyze pulses emitted from a fourier chopper recently put into operation at the ETRR-1 reactor. The RTOF analyze was found to be adequate for use with pick up pulses from the fourier chopper which operates following a frequency window suitable for rotation rates from 0-9000 rpm; synchronically with neutron pulses from a {sup 6} Li glass detector set at time focusing geometry for scattering angle 20=90 degree. It was possible, with the present RTOF analyzer to obtain diffraction patterns at neutron wavelength range between 1 - 4 A within a resolution = 0.5%. 8 FIGS.

  2. Construction of exact invariants of time-dependent linear nonholonomic dynamical systems

    International Nuclear Information System (INIS)

    Fu Jingli; Jimenez, Salvador; Tang Yifa; Vazquez, Luis

    2008-01-01

    In this work, we build exact dynamical invariants for time-dependent, linear, nonholonomic Hamiltonian systems in two dimensions. Our aim is to obtain an additional insight into the theoretical understanding of generalized Hamilton canonical equations. In particular, we investigate systems represented by a quadratic Hamiltonian subject to linear nonholonomic constraints. We use a Lie algebraic method on the systems to build the invariants. The role and scope of these invariants is pointed out

  3. Construction of exact invariants of time-dependent linear nonholonomic dynamical systems

    Energy Technology Data Exchange (ETDEWEB)

    Fu Jingli [Institute of Mathematical Physics, Zhejiang Sci-Tech University, Hangzhou 310018 (China)], E-mail: sqfujingli@163.com; Jimenez, Salvador [Departamento de Matematica Aplicada TTII, E.T.S.I. Telecomunicacion, Universidad Politecnica de Madrid, 28040 Madrid (Spain); Tang Yifa [State Key Laboratory of Scientific and Engineering Computing, ICMSEC, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, PO Box 2719, Beijing 100080 (China); Vazquez, Luis [Departamento de Matematica Aplicada Facultad de Informatica, Universidad Complutense de Madrid, 28040 Madrid (Spain); Centro de Astrobiologia (CSIC-INTA), Torrejon de Ardoz, 28850 Madrid (Spain)

    2008-03-03

    In this work, we build exact dynamical invariants for time-dependent, linear, nonholonomic Hamiltonian systems in two dimensions. Our aim is to obtain an additional insight into the theoretical understanding of generalized Hamilton canonical equations. In particular, we investigate systems represented by a quadratic Hamiltonian subject to linear nonholonomic constraints. We use a Lie algebraic method on the systems to build the invariants. The role and scope of these invariants is pointed out.

  4. Reversibility: An Engineer's Point of View

    Energy Technology Data Exchange (ETDEWEB)

    Berest, Pierre [LMS, ecole Polytechnique (France)

    2012-07-01

    Reversibility is the most consistent option in a democratic country. However reversibility may also have several drawbacks which must be identified and mitigated. Reversibility of a geological repository is a relatively new idea in France. The 1991 law dedicated to nuclear waste management considered reversibility as a possible option. Fifteen years later, the 2006 law mandated that a deep repository must be reversible and that the exact content of this notion should be defined by a new law to be discussed by the Parliament in 2015. Reversibility was not a concern put forward by engineers. It clearly originated from a societal demand sponsored and formulated by the Parliament. Since 1991, the exact meaning of this mandate progressively became more precise. In the early days, reversibility meant the technical and financial capability to retrieve the wastes from the repository, at least for some period of time after being emplaced. Progressively, a broader definition, suggested by Andra, was accepted: reversibility also means that a disposal facility should be operated in such a way that a stepwise decision-making process is possible. At each step, society must be able to decide to proceed to the next step, to pause or to reverse a step. Several benefits can be expected from a reversible repository. Some technical safety concerns may be only recognised after waste emplacement. Radioactive wastes may become a resource whose recoverability is desirable. Regulations may change, alternative waste treatment or better disposal techniques may be developed, or the need to modify a component of the facility may arise. Looking back at how chemical or domestic wastes were managed some 50 years ago easily underscores that it is not unreasonable to hope for significant advances in the future. For scientists and engineers, reversibility proves to have several other merits. To design and build a good repository, time is needed. The operator of a mine or of an oil field knows that

  5. Estimate of Passive Time Reversal Communication Performance in Shallow Water

    Directory of Open Access Journals (Sweden)

    Sunhyo Kim

    2017-12-01

    Full Text Available Time reversal processes have been used to improve communication performance in the severe underwater communication environment characterized by significant multipath channels by reducing inter-symbol interference and increasing signal-to-noise ratio. In general, the performance of the time reversal is strongly related to the behavior of the q -function, which is estimated by a sum of the autocorrelation of the channel impulse response for each channel in the receiver array. The q -function depends on the complexity of the communication channel, the number of channel elements and their spacing. A q -function with a high side-lobe level and a main-lobe width wider than the symbol duration creates a residual ISI (inter-symbol interference, which makes communication difficult even after time reversal is applied. In this paper, we propose a new parameter, E q , to describe the performance of time reversal communication. E q is an estimate of how much of the q -function lies within one symbol duration. The values of E q were estimated using communication data acquired at two different sites: one in which the sound speed ratio of sediment to water was less than unity and one where the ratio was higher than unity. Finally, the parameter E q was compared to the bit error rate and the output signal-to-noise ratio obtained after the time reversal operation. The results show that these parameters are strongly correlated to the parameter E q .

  6. Analytical reverse time migration: An innovation in imaging of infrastructures using ultrasonic shear waves.

    Science.gov (United States)

    Asadollahi, Aziz; Khazanovich, Lev

    2018-04-11

    The emergence of ultrasonic dry point contact (DPC) transducers that emit horizontal shear waves has enabled efficient collection of high-quality data in the context of a nondestructive evaluation of concrete structures. This offers an opportunity to improve the quality of evaluation by adapting advanced imaging techniques. Reverse time migration (RTM) is a simulation-based reconstruction technique that offers advantages over conventional methods, such as the synthetic aperture focusing technique. RTM is capable of imaging boundaries and interfaces with steep slopes and the bottom boundaries of inclusions and defects. However, this imaging technique requires a massive amount of memory and its computation cost is high. In this study, both bottlenecks of the RTM are resolved when shear transducers are used for data acquisition. An analytical approach was developed to obtain the source and receiver wavefields needed for imaging using reverse time migration. It is shown that the proposed analytical approach not only eliminates the high memory demand, but also drastically reduces the computation time from days to minutes. Copyright © 2018 Elsevier B.V. All rights reserved.

  7. Naphthalocyanine-based time reversal mirror at 800 nm

    International Nuclear Information System (INIS)

    Galaup, Jean-Pierre; Fraigne, Sebastien; Le Goueet, Jean-Louis; Likforman, Jean-Pierre; Joffre, Manuel

    2004-01-01

    We performed pulse shaping and time reversal experiments using spectral holography based on persistent spectral hole burning in free-base naphthalocyanine-doped films. The application of a new pulse re-compression scheme based on a programmable hole burning material acting as a time reversal mirror is considered. In this work, we adapted the Fourier transform spectral interferometry technique for measuring the amplitude and phase of photon echo signals produced by diffraction of femtosecond pulses on a spectral hologram. We therefore demonstrated that we could control the pulses diffracted from the hologram by shaping and then characterizing these pulses in both amplitude and phase by spectral interferometry

  8. Time-reversed absorbing condition: application to inverse problems

    International Nuclear Information System (INIS)

    Assous, F; Kray, M; Nataf, F; Turkel, E

    2011-01-01

    The aim of this paper is to introduce time-reversed absorbing conditions in time-reversal methods. They enable one to 'recreate the past' without knowing the source which has emitted the signals that are back-propagated. We present two applications in inverse problems: the reduction of the size of the computational domain and the determination, from boundary measurements, of the location and volume of an unknown inclusion. The method does not rely on any a priori knowledge of the physical properties of the inclusion. Numerical tests with the wave and Helmholtz equations illustrate the efficiency of the method. This technique is fairly insensitive to noise in the data

  9. Test of time-reversal invariance at COSY (TRIC)

    Energy Technology Data Exchange (ETDEWEB)

    Eversheim, D., E-mail: evershei@hiskp.uni-bonn.de; Valdau, Yu. [University Bonn, Helmholtz Institut fuer Strahlen- und Kernphysik (Germany); Lorentz, B. [Forschungszentrum Juelich, Institut fuer Kernphysik (Germany)

    2013-03-15

    At the Cooler Synchrotron COSY a novel (P-even, T-odd) null test of time-reversal invariance to an accuracy of 10{sup - 6} is planned as an internal target transmission experiment. The parity conserving time-reversal violating observable is the total cross-section asymmetry A{sub y,xz}. This quantity is measured using a polarized proton beam with an energy of 135 MeV and an internal tensor polarized deuteron target from the PAX atomic beam source. The reaction rate will be measured by means of an integrating beam current transformer. Thus, in this experiment the cooler synchroton ring serves as ideal forward spectrometer, as a detector, and an accelerator.

  10. Bounding spectral gaps of Markov chains: a novel exact multi-decomposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Destainville, N [Laboratoire de Physique Theorique - IRSAMC, CNRS/Universite Paul Sabatier, 118, route de Narbonne, 31062 Toulouse Cedex 04 (France)

    2003-04-04

    We propose an exact technique to calculate lower bounds of spectral gaps of discrete time reversible Markov chains on finite state sets. Spectral gaps are a common tool for evaluating convergence rates of Markov chains. As an illustration, we successfully use this technique to evaluate the 'absorption time' of the 'Backgammon model', a paradigmatic model for glassy dynamics. We also discuss the application of this technique to the 'contingency table problem', a notoriously difficult problem from probability theory. The interest of this technique is that it connects spectral gaps, which are quantities related to dynamics, with static quantities, calculated at equilibrium.

  11. Lie symmetry analysis, exact solutions and conservation laws for the time fractional Caudrey-Dodd-Gibbon-Sawada-Kotera equation

    Science.gov (United States)

    Baleanu, Dumitru; Inc, Mustafa; Yusuf, Abdullahi; Aliyu, Aliyu Isa

    2018-06-01

    In this work, we investigate the Lie symmetry analysis, exact solutions and conservation laws (Cls) to the time fractional Caudrey-Dodd-Gibbon-Sawada-Kotera (CDGDK) equation with Riemann-Liouville (RL) derivative. The time fractional CDGDK is reduced to nonlinear ordinary differential equation (ODE) of fractional order. New exact traveling wave solutions for the time fractional CDGDK are obtained by fractional sub-equation method. In the reduced equation, the derivative is in Erdelyi-Kober (EK) sense. Ibragimov's nonlocal conservation method is applied to construct Cls for time fractional CDGDK.

  12. Trial function method and exact solutions to the generalized nonlinear Schrödinger equation with time-dependent coefficient

    International Nuclear Information System (INIS)

    Cao Rui; Zhang Jian

    2013-01-01

    In this paper, the trial function method is extended to study the generalized nonlinear Schrödinger equation with time-dependent coefficients. On the basis of a generalized traveling wave transformation and a trial function, we investigate the exact envelope traveling wave solutions of the generalized nonlinear Schrödinger equation with time-dependent coefficients. Taking advantage of solutions to trial function, we successfully obtain exact solutions for the generalized nonlinear Schrödinger equation with time-dependent coefficients under constraint conditions. (general)

  13. Exactly solvable string models of curved space-time backgrounds

    International Nuclear Information System (INIS)

    Russo, J.G.

    1995-01-01

    We consider a new 3-parameter class of exact 4-dimensional solutions in closed string theory and solve the corresponding string model, determining the physical spectrum and the partition function. The background fields (4-metric, antisymmetric tensor, two Kaluza-Klein vector fields, dilaton and modulus) generically describe axially symmetric stationary rotating (electro)magnetic flux-tube type universes. Backgrounds of this class include both the ''dilatonic'' (a=1) and ''Kaluza-Klein'' (a=√(3)) Melvin solutions and the uniform magnetic field solution, as well as some singular space-times. Solvability of the string σ-model is related to its connection via duality to a simpler model which is a ''twisted'' product of a flat 2-space and a space dual to 2-plane. We discuss some physical properties of this model (tachyonic instabilities in the spectrum, gyromagnetic ratio, issue of singularities, etc.). It provides one of the first examples of a consistent solvable conformal string model with explicit D=4 curved space-time interpretation. (orig.)

  14. Modelling and Comparative Performance Analysis of a Time-Reversed UWB System

    Directory of Open Access Journals (Sweden)

    Popovski K

    2007-01-01

    Full Text Available The effects of multipath propagation lead to a significant decrease in system performance in most of the proposed ultra-wideband communication systems. A time-reversed system utilises the multipath channel impulse response to decrease receiver complexity, through a prefiltering at the transmitter. This paper discusses the modelling and comparative performance of a UWB system utilising time-reversed communications. System equations are presented, together with a semianalytical formulation on the level of intersymbol interference and multiuser interference. The standardised IEEE 802.15.3a channel model is applied, and the estimated error performance is compared through simulation with the performance of both time-hopped time-reversed and RAKE-based UWB systems.

  15. A digital matched filter for reverse time chaos.

    Science.gov (United States)

    Bailey, J Phillip; Beal, Aubrey N; Dean, Robert N; Hamilton, Michael C

    2016-07-01

    The use of reverse time chaos allows the realization of hardware chaotic systems that can operate at speeds equivalent to existing state of the art while requiring significantly less complex circuitry. Matched filter decoding is possible for the reverse time system since it exhibits a closed form solution formed partially by a linear basis pulse. Coefficients have been calculated and are used to realize the matched filter digitally as a finite impulse response filter. Numerical simulations confirm that this correctly implements a matched filter that can be used for detection of the chaotic signal. In addition, the direct form of the filter has been implemented in hardware description language and demonstrates performance in agreement with numerical results.

  16. Analysis of Time Reversible Born-Oppenheimer Molecular Dynamics

    Directory of Open Access Journals (Sweden)

    Lin Lin

    2013-12-01

    Full Text Available We analyze the time reversible Born-Oppenheimer molecular dynamics (TRBOMD scheme, which preserves the time reversibility of the Born-Oppenheimer molecular dynamics even with non-convergent self-consistent field iteration. In the linear response regime, we derive the stability condition, as well as the accuracy of TRBOMD for computing physical properties, such as the phonon frequency obtained from the molecular dynamics simulation. We connect and compare TRBOMD with Car-Parrinello molecular dynamics in terms of accuracy and stability. We further discuss the accuracy of TRBOMD beyond the linear response regime for non-equilibrium dynamics of nuclei. Our results are demonstrated through numerical experiments using a simplified one-dimensional model for Kohn-Sham density functional theory.

  17. Conductance fluctuations in disordered superconductors with broken time-reversal symmetry near two dimensions

    International Nuclear Information System (INIS)

    Ryu, S.; Furusaki, A.; Ludwig, A.W.W.; Mudry, C.

    2007-01-01

    We extend the analysis of the conductance fluctuations in disordered metals by Altshuler, Kravtsov, and Lerner (AKL) to disordered superconductors with broken time-reversal symmetry in d=(2+ε) dimensions (symmetry classes C and D of Altland and Zirnbauer). Using a perturbative renormalization group analysis of the corresponding non-linear sigma model (NLσM) we compute the anomalous scaling dimensions of the dominant scalar operators with 2s gradients to one-loop order. We show that, in analogy with the result of AKL for ordinary, metallic systems (Wigner-Dyson classes), an infinite number of high-gradient operators would become relevant (in the renormalization group sense) near two dimensions if contributions beyond one-loop order are ignored. We explore the possibility to compare, in symmetry class D, the ε=(2-d) expansion in d<2 with exact results in one dimension. The method we use to perform the one-loop renormalization analysis is valid for general symmetric spaces of Kaehler type, and suggests that this is a generic property of the perturbative treatment of NLσMs defined on Riemannian symmetric target spaces

  18. Theoretical test of Jarzynski's equality for reversible volume-switching processes of an ideal gas system.

    Science.gov (United States)

    Sung, Jaeyoung

    2007-07-01

    We present an exact theoretical test of Jarzynski's equality (JE) for reversible volume-switching processes of an ideal gas system. The exact analysis shows that the prediction of JE for the free energy difference is the same as the work done on the gas system during the reversible process that is dependent on the shape of path of the reversible volume-switching process.

  19. Prepotential approach to exact and quasi-exact solvabilities

    International Nuclear Information System (INIS)

    Ho, C.-L.

    2008-01-01

    Exact and quasi-exact solvabilities of the one-dimensional Schroedinger equation are discussed from a unified viewpoint based on the prepotential together with Bethe ansatz equations. This is a constructive approach which gives the potential as well as the eigenfunctions and eigenvalues simultaneously. The novel feature of the present work is the realization that both exact and quasi-exact solvabilities can be solely classified by two integers, the degrees of two polynomials which determine the change of variable and the zeroth order prepotential. Most of the well-known exactly and quasi-exactly solvable models, and many new quasi-exactly solvable ones, can be generated by appropriately choosing the two polynomials. This approach can be easily extended to the constructions of exactly and quasi-exactly solvable Dirac, Pauli, and Fokker-Planck equations

  20. Time reversal symmetry violation in the YbF molecule

    Energy Technology Data Exchange (ETDEWEB)

    Sauer, B. E., E-mail: ben.sauer@imperial.ac.uk; Devlin, J. A.; Hudson, J. J.; Kara, D. M.; Smallman, I. J.; Tarbutt, M. R.; Hinds, E. A. [Blackett Laboratory Imperial College London, Centre for Cold Matter (United Kingdom)

    2013-03-15

    We present a summary of the techniques used to test time reversal symmetry by measuring the permanent electric dipole moment of the YbF molecule. The results of a recent measurement (Hudson et al., Nature 473:493, 2011) are reported. We review some systematic effects which might mimic time reversal violation and describe how they are overcome. We then discuss improvements to the sensitivity of the apparatus, including both short term technical enhancements as well as a longer term goal to use laser cooled YbF in the experiment.

  1. Time reversal tests in polarized neutron reactions

    International Nuclear Information System (INIS)

    Asahi, Koichiro; Bowman, J.D.; Crawford, B.

    1998-01-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). In recent years the nuclear weak interaction has been studied in the compound nucleus via parity violation. The observed parity-violating effects are strongly enhanced by nuclear structure. The predictions are that the interaction of polarized neutrons with polarized nuclear targets could be also used to perform sensitive tests of time-reversal-violation because of the nuclear enhancements. The author has designed experiments to search for time-reversal violation in neutron-nucleus interactions. He has also developed techniques to polarize neutrons with laser-polarized 3 He gas targets. Using the polarized 3 He neutron spin filter, he has performed two experiments at LANSCE: an absolute neutron beam polarization measurement with an accuracy of 0.2--0.3% and a neutron spin-rotation measurement on a 139 La sample

  2. Exact solutions, finite time singularities and non-singular universe models from a variety of Λ(t) cosmologies

    Science.gov (United States)

    Pan, Supriya

    2018-01-01

    Cosmological models with time-dependent Λ (read as Λ(t)) have been investigated widely in the literature. Models that solve background dynamics analytically are of special interest. Additionally, the allowance of past or future singularities at finite cosmic time in a specific model signals for a generic test on its viabilities with the current observations. Following these, in this work we consider a variety of Λ(t) models focusing on their evolutions and singular behavior. We found that a series of models in this class can be exactly solved when the background universe is described by a spatially flat Friedmann-Lemaître-Robertson-Walker (FLRW) line element. The solutions in terms of the scale factor of the FLRW universe offer different universe models, such as power-law expansion, oscillating, and the singularity free universe. However, we also noticed that a large number of the models in this series permit past or future cosmological singularities at finite cosmic time. At last we close the work with a note that the avoidance of future singularities is possible for certain models under some specific restrictions.

  3. Focusing of electromagnetic waves

    International Nuclear Information System (INIS)

    Dhayalan, V.

    1996-01-01

    The focusing of electromagnetic waves inside a slab has been examined together with two special cases in which the slab is reduced to a single interface or a single medium. To that end the exact solutions for the fields inside a layered medium have been used, given in terms of the outside current source in order to obtain the solutions for the focused electric field inside a slab. Both exact and asymptotic solutions of the problem have been considered, and the validity of the latter has been discussed. The author has developed a numerical algorithm for evaluation of the diffraction integral with special emphasis on reducing the computing time. The numerical techniques in the paper can be readily applied to evaluate similar diffraction integrals occurring e.g. in microstrip antennas. 46 refs

  4. Exact milestoning

    International Nuclear Information System (INIS)

    Bello-Rivas, Juan M.; Elber, Ron

    2015-01-01

    A new theory and an exact computer algorithm for calculating kinetics and thermodynamic properties of a particle system are described. The algorithm avoids trapping in metastable states, which are typical challenges for Molecular Dynamics (MD) simulations on rough energy landscapes. It is based on the division of the full space into Voronoi cells. Prior knowledge or coarse sampling of space points provides the centers of the Voronoi cells. Short time trajectories are computed between the boundaries of the cells that we call milestones and are used to determine fluxes at the milestones. The flux function, an essential component of the new theory, provides a complete description of the statistical mechanics of the system at the resolution of the milestones. We illustrate the accuracy and efficiency of the exact Milestoning approach by comparing numerical results obtained on a model system using exact Milestoning with the results of long trajectories and with a solution of the corresponding Fokker-Planck equation. The theory uses an equation that resembles the approximate Milestoning method that was introduced in 2004 [A. K. Faradjian and R. Elber, J. Chem. Phys. 120(23), 10880-10889 (2004)]. However, the current formulation is exact and is still significantly more efficient than straightforward MD simulations on the system studied

  5. Plane-wave Least-squares Reverse Time Migration

    KAUST Repository

    Dai, Wei

    2012-11-04

    Least-squares reverse time migration is formulated with a new parameterization, where the migration image of each shot is updated separately and a prestack image is produced with common image gathers. The advantage is that it can offer stable convergence for least-squares migration even when the migration velocity is not completely accurate. To significantly reduce computation cost, linear phase shift encoding is applied to hundreds of shot gathers to produce dozens of planes waves. A regularization term which penalizes the image difference between nearby angles are used to keep the prestack image consistent through all the angles. Numerical tests on a marine dataset is performed to illustrate the advantages of least-squares reverse time migration in the plane-wave domain. Through iterations of least-squares migration, the migration artifacts are reduced and the image resolution is improved. Empirical results suggest that the LSRTM in plane wave domain is an efficient method to improve the image quality and produce common image gathers.

  6. Exact goodness-of-fit tests for Markov chains.

    Science.gov (United States)

    Besag, J; Mondal, D

    2013-06-01

    Goodness-of-fit tests are useful in assessing whether a statistical model is consistent with available data. However, the usual χ² asymptotics often fail, either because of the paucity of the data or because a nonstandard test statistic is of interest. In this article, we describe exact goodness-of-fit tests for first- and higher order Markov chains, with particular attention given to time-reversible ones. The tests are obtained by conditioning on the sufficient statistics for the transition probabilities and are implemented by simple Monte Carlo sampling or by Markov chain Monte Carlo. They apply both to single and to multiple sequences and allow a free choice of test statistic. Three examples are given. The first concerns multiple sequences of dry and wet January days for the years 1948-1983 at Snoqualmie Falls, Washington State, and suggests that standard analysis may be misleading. The second one is for a four-state DNA sequence and lends support to the original conclusion that a second-order Markov chain provides an adequate fit to the data. The last one is six-state atomistic data arising in molecular conformational dynamics simulation of solvated alanine dipeptide and points to strong evidence against a first-order reversible Markov chain at 6 picosecond time steps. © 2013, The International Biometric Society.

  7. The criterion for time symmetry of probabilistic theories and the reversibility of quantum mechanics

    International Nuclear Information System (INIS)

    Holster, A T

    2003-01-01

    Physicists routinely claim that the fundamental laws of physics are 'time symmetric' or 'time reversal invariant' or 'reversible'. In particular, it is claimed that the theory of quantum mechanics is time symmetric. But it is shown in this paper that the orthodox analysis suffers from a fatal conceptual error, because the logical criterion for judging the time symmetry of probabilistic theories has been incorrectly formulated. The correct criterion requires symmetry between future-directed laws and past-directed laws. This criterion is formulated and proved in detail. The orthodox claim that quantum mechanics is reversible is re-evaluated. The property demonstrated in the orthodox analysis is shown to be quite distinct from time reversal invariance. The view of Satosi Watanabe that quantum mechanics is time asymmetric is verified, as well as his view that this feature does not merely show a de facto or 'contingent' asymmetry, as commonly supposed, but implies a genuine failure of time reversal invariance of the laws of quantum mechanics. The laws of quantum mechanics would be incompatible with a time-reversed version of our universe

  8. Exact Algorithm for the Capacitated Team Orienteering Problem with Time Windows

    Directory of Open Access Journals (Sweden)

    Junhyuk Park

    2017-01-01

    Full Text Available The capacitated team orienteering problem with time windows (CTOPTW is a problem to determine players’ paths that have the maximum rewards while satisfying the constraints. In this paper, we present the exact solution approach for the CTOPTW which has not been done in previous literature. We show that the branch-and-price (B&P scheme which was originally developed for the team orienteering problem can be applied to the CTOPTW. To solve pricing problems, we used implicit enumeration acceleration techniques, heuristic algorithms, and ng-route relaxations.

  9. Timed Fast Exact Euclidean Distance (tFEED) maps

    NARCIS (Netherlands)

    Kehtarnavaz, Nasser; Schouten, Theo E.; Laplante, Philip A.; Kuppens, Harco; van den Broek, Egon

    2005-01-01

    In image and video analysis, distance maps are frequently used. They provide the (Euclidean) distance (ED) of background pixels to the nearest object pixel. In a naive implementation, each object pixel feeds its (exact) ED to each background pixel; then the minimum of these values denotes the ED to

  10. Subtleties in the BABAR measurement of time-reversal violation

    International Nuclear Information System (INIS)

    Efrati, Aielet

    2015-01-01

    A first measurement of time-reversal (T) asymmetries that are not also CP asymmetries has been recently achieved by the B A B AR collaboration. In this talk, which follows the work done in Ref. [1], I discuss the subtleties of this measurement in the presence of direct CP violation, CPT violation, wrong strangeness decays and wrong sign semi-leptonic decays. In particular, I explain why, in order to identify the measured asymmetries with time-reversal violation, one needs to assume (i) the absence of wrong strangeness decays or of CPT violation in strangeness changing decays, and (ii) the absence of wrong sign decays. (paper)

  11. Time reversibility of intracranial human EEG recordings in mesial temporal lobe epilepsy

    Science.gov (United States)

    van der Heyden, M. J.; Diks, C.; Pijn, J. P. M.; Velis, D. N.

    1996-02-01

    Intracranial electroencephalograms from patients suffering from mesial temporal lobe epilepsy were tested for time reversibility. If the recorded time series is irreversible, the input of the recording system cannot be a realisation of a linear Gaussian random process. We confirmed experimentally that the measurement equipment did not introduce irreversibility in the recorded output when the input was a realisation of a linear Gaussian random process. In general, the non-seizure recordings are reversible, whereas the seizure recordings are irreversible. These results suggest that time reversibility is a useful property for the characterisation of human intracranial EEG recordings in mesial temporal lobe epilepsy.

  12. Long-term stable time integration scheme for dynamic analysis of planar geometrically exact Timoshenko beams

    Science.gov (United States)

    Nguyen, Tien Long; Sansour, Carlo; Hjiaj, Mohammed

    2017-05-01

    In this paper, an energy-momentum method for geometrically exact Timoshenko-type beam is proposed. The classical time integration schemes in dynamics are known to exhibit instability in the non-linear regime. The so-called Timoshenko-type beam with the use of rotational degree of freedom leads to simpler strain relations and simpler expressions of the inertial terms as compared to the well known Bernoulli-type model. The treatment of the Bernoulli-model has been recently addressed by the authors. In this present work, we extend our approach of using the strain rates to define the strain fields to in-plane geometrically exact Timoshenko-type beams. The large rotational degrees of freedom are exactly computed. The well-known enhanced strain method is used to avoid locking phenomena. Conservation of energy, momentum and angular momentum is proved formally and numerically. The excellent performance of the formulation will be demonstrated through a range of examples.

  13. A block Krylov subspace time-exact solution method for linear ordinary differential equation systems

    NARCIS (Netherlands)

    Bochev, Mikhail A.

    2013-01-01

    We propose a time-exact Krylov-subspace-based method for solving linear ordinary differential equation systems of the form $y'=-Ay+g(t)$ and $y"=-Ay+g(t)$, where $y(t)$ is the unknown function. The method consists of two stages. The first stage is an accurate piecewise polynomial approximation of

  14. Constraints of a parity-conserving/time-reversal-non-conserving interaction

    International Nuclear Information System (INIS)

    Oers, Willem T.H. van

    2002-01-01

    Time-Reversal-Invariance non-conservation has for the first time been unequivocally demonstrated in a direct measurement at CPLEAR. One then can ask the question: What about tests of time-reversal-invariance in systems other than the kaon system? Tests of time-reversal-invariance can be distinguished as belonging to two classes: the first one deals with time-reversal-invariance-non-conserving (T-odd)/parity violating (P-odd) interactions, while the second one deals with T-odd/P-even interactions (assuming CPT conservation this implies C-conjugation non-conservation). Limits on a T-odd/P-odd interaction follow from measurements of the electric dipole moment of the neutron ( -26 e.cm [95% C.L.]). It provides a limit on a T-odd/P-odd pion-nucleon coupling constant which is less than 10 -4 times the weak interaction strength. Experimental limits on a T-odd/P-even interaction are much less stringent. Following the standard approach of describing the nucleon-nucleon interaction in terms of meson exchanges, it can be shown that only charged ρ-meson exchange and A 1 -meson exchange can lead to a T-odd/P-even interaction. The better constraints stem from measurements of the electric dipole moment of the neutron and from measurements of charge-symmetry breaking in neutron-proton elastic scattering. The latter experiments were executed at TRIUMF (497 and 347 MeV) and at IUCF (183 MeV). All other experiments, like detailed balance experiments, polarization - analyzing power difference determinations, and five-fold correlation experiments with polarized incident nucleons and aligned nuclear targets, have been shown to be at least an order to magnitude less sensitive. Is there room for further experimentation?

  15. Plane-wave least-squares reverse-time migration

    KAUST Repository

    Dai, Wei

    2013-06-03

    A plane-wave least-squares reverse-time migration (LSRTM) is formulated with a new parameterization, where the migration image of each shot gather is updated separately and an ensemble of prestack images is produced along with common image gathers. The merits of plane-wave prestack LSRTM are the following: (1) plane-wave prestack LSRTM can sometimes offer stable convergence even when the migration velocity has bulk errors of up to 5%; (2) to significantly reduce computation cost, linear phase-shift encoding is applied to hundreds of shot gathers to produce dozens of plane waves. Unlike phase-shift encoding with random time shifts applied to each shot gather, plane-wave encoding can be effectively applied to data with a marine streamer geometry. (3) Plane-wave prestack LSRTM can provide higher-quality images than standard reverse-time migration. Numerical tests on the Marmousi2 model and a marine field data set are performed to illustrate the benefits of plane-wave LSRTM. Empirical results show that LSRTM in the plane-wave domain, compared to standard reversetime migration, produces images efficiently with fewer artifacts and better spatial resolution. Moreover, the prestack image ensemble accommodates more unknowns to makes it more robust than conventional least-squares migration in the presence of migration velocity errors. © 2013 Society of Exploration Geophysicists.

  16. Factors affecting timing of closure and non-reversal of temporary ileostomies.

    Science.gov (United States)

    Sier, M F; van Gelder, L; Ubbink, D T; Bemelman, W A; Oostenbroek, R J

    2015-09-01

    Although stoma closure is considered a simple surgical intervention, the interval between construction and reversal is often prolonged, and some ileostomies may never be reversed. We evaluated possible predictors for non-reversal and prolonged interval between construction and reversal. In a cohort study of ileostomy patients treated in a large teaching hospital, we collected data from the surgical complication and enterostomal therapists' registries between January 2001 and December 2011. Parameters responsible for morbidity, mortality, length of stay and time interval between construction and reversal were analysed. Of 485 intentionally temporary ileostomies, 359 were reversed after a median of 5.6 months (IQR 3.8-8.9 months), while 126 (26%) remained permanent. End ileostomy and intra-abdominal abscess independently delayed reversal. Age, end ileostomy, higher body mass index and preoperative radiotherapy were independent factors for non-reversal. Median duration of hospitalisation for reversal was 7.0 days (5-13 days). Morbidity and mortality were 31 and 0.9%, respectively. In 20 patients (5.5%), re-ileostomy was necessary. A substantial number of ileostomies that are intended to be temporary will never be reversed. If reversed, the interval between construction and reversal is longer than anticipated, while morbidity after reversal and duration of hospitalisation are considerable. Besides a temporary ileostomy, there are two other options: no diversion or a permanent colostomy. Shared decision-making is to be preferred in these situations.

  17. Echodentography based on nonlinear time reversal tomography: Ultrasonic nonlinear signature identification

    Science.gov (United States)

    Santos, Serge Dos; Farova, Zuzana; Kus, Vaclav; Prevorovsky, Zdenek

    2012-05-01

    This paper examines possibilities of using Nonlinear Elastic Wave Spectroscopy (NEWS) methods in dental investigations. Themain task consisted in imaging cracks or other degradation signatures located in dentin close to the Enamel-Dentine Junction (EDJ). NEWS approach was investigated experimentally with a new bi-modal acousto-optic set-up based on the chirp-coded nonlinear ultrasonic time reversal (TR) concepts. Complex internal structure of the tooth is analyzed by the TR-NEWS procedure adapted to tomography-like imaging of the tooth damages. Ultrasonic instrumentation with 10 MHz bandwidth has been set together including laser vibrometer used to detect responses of the tooth on its excitation carried out by a contact piezoelectric transducer. Bi-modal TR-NEWS images of the tooth were created before and after focusing, which resulted from the time compression. The polar B-scan of the tooth realized with TR-NEWS procedure is suggested to be applied as a new echodentography imaging.

  18. Propagation characteristics of a focused laser beam in a strontium barium niobate photorefractive crystal under reverse external electric field.

    Science.gov (United States)

    Guo, Q L; Liang, B L; Wang, Y; Deng, G Y; Jiang, Y H; Zhang, S H; Fu, G S; Simmonds, P J

    2014-10-01

    The propagation characteristics of a focused laser beam in a SBN:75 photorefractive crystal strongly depend on the signal-to-background intensity ratio (R=Is/Ib) under reverse external electric field. In the range 20>R>0.05, the laser beam shows enhanced self-defocusing behavior with increasing external electric field, while it shows self-focusing in the range 0.03>R>0.01. Spatial solitons are observed under a suitable reverse external electric field for R=0.025. A theoretical model is proposed to explain the experimental observations, which suggest a new type of soliton formation due to "enhancement" not "screening" of the external electrical field.

  19. Time Reversal Reconstruction Algorithm Based on PSO Optimized SVM Interpolation for Photoacoustic Imaging

    Directory of Open Access Journals (Sweden)

    Mingjian Sun

    2015-01-01

    Full Text Available Photoacoustic imaging is an innovative imaging technique to image biomedical tissues. The time reversal reconstruction algorithm in which a numerical model of the acoustic forward problem is run backwards in time is widely used. In the paper, a time reversal reconstruction algorithm based on particle swarm optimization (PSO optimized support vector machine (SVM interpolation method is proposed for photoacoustics imaging. Numerical results show that the reconstructed images of the proposed algorithm are more accurate than those of the nearest neighbor interpolation, linear interpolation, and cubic convolution interpolation based time reversal algorithm, which can provide higher imaging quality by using significantly fewer measurement positions or scanning times.

  20. High-resolution and super stacking of time-reversal mirrors in locating seismic sources

    KAUST Repository

    Cao, Weiping; Hanafy, Sherif M.; Schuster, Gerard T.; Zhan, Ge; Boonyasiriwat, Chaiwoot

    2011-01-01

    Time reversal mirrors can be used to backpropagate and refocus incident wavefields to their actual source location, with the subsequent benefits of imaging with high-resolution and super-stacking properties. These benefits of time reversal mirrors

  1. Exact analysis of discrete data

    CERN Document Server

    Hirji, Karim F

    2005-01-01

    Researchers in fields ranging from biology and medicine to the social sciences, law, and economics regularly encounter variables that are discrete or categorical in nature. While there is no dearth of books on the analysis and interpretation of such data, these generally focus on large sample methods. When sample sizes are not large or the data are otherwise sparse, exact methods--methods not based on asymptotic theory--are more accurate and therefore preferable.This book introduces the statistical theory, analysis methods, and computation techniques for exact analysis of discrete data. After reviewing the relevant discrete distributions, the author develops the exact methods from the ground up in a conceptually integrated manner. The topics covered range from univariate discrete data analysis, a single and several 2 x 2 tables, a single and several 2 x K tables, incidence density and inverse sampling designs, unmatched and matched case -control studies, paired binary and trinomial response models, and Markov...

  2. Reversing the irreversible: From limit cycles to emergent time symmetry

    Science.gov (United States)

    Cortês, Marina; Smolin, Lee

    2018-01-01

    In 1979 Penrose hypothesized that the arrows of time are explained by the hypothesis that the fundamental laws are time irreversible [R. Penrose, in General Relativity: An Einstein Centenary Survey (1979)]. That is, our reversible laws, such as the standard model and general relativity are effective, and emerge from an underlying fundamental theory which is time irreversible. In [M. Cortês and L. Smolin, Phys. Rev. D 90, 084007 (2014), 10.1103/PhysRevD.90.084007; 90, 044035 (2014), 10.1103/PhysRevD.90.044035; 93, 084039 (2016), 10.1103/PhysRevD.93.084039] we put forward a research program aiming at realizing just this. The aim is to find a fundamental description of physics above the Planck scale, based on irreversible laws, from which will emerge the apparently reversible dynamics we observe on intermediate scales. Here we continue that program and note that a class of discrete dynamical systems are known to exhibit this very property: they have an underlying discrete irreversible evolution, but in the long term exhibit the properties of a time reversible system, in the form of limit cycles. We connect this to our original model proposal in [M. Cortês and L. Smolin, Phys. Rev. D 90, 084007 (2014), 10.1103/PhysRevD.90.084007], and show that the behaviors obtained there can be explained in terms of the same phenomenon: the attraction of the system to a basin of limit cycles, where the dynamics appears to be time reversible. Further than that, we show that our original models exhibit the very same feature: the emergence of quasiparticle excitations obtained in the earlier work in the space-time description is an expression of the system's convergence to limit cycles when seen in the causal set description.

  3. Accurate characterization of 3D diffraction gratings using time domain discontinuous Galerkin method with exact absorbing boundary conditions

    KAUST Repository

    Sirenko, Kostyantyn

    2013-07-01

    Exact absorbing and periodic boundary conditions allow to truncate grating problems\\' infinite physical domains without introducing any errors. This work presents exact absorbing boundary conditions for 3D diffraction gratings and describes their discretization within a high-order time-domain discontinuous Galerkin finite element method (TD-DG-FEM). The error introduced by the boundary condition discretization matches that of the TD-DG-FEM; this results in an optimal solver in terms of accuracy and computation time. Numerical results demonstrate the superiority of this solver over TD-DG-FEM with perfectly matched layers (PML)-based domain truncation. © 2013 IEEE.

  4. Time reversed Lamb wave for damage detection in a stiffened aluminum plate

    International Nuclear Information System (INIS)

    Bijudas, C R; Mitra, M; Mujumdar, P M

    2013-01-01

    According to the concept of time reversibility of the Lamb wave, in the absence of damage, a Lamb wave signal can be reconstructed at the transmitter location if a time reversed signal is sent back from the receiver location. This property is used for baseline-free damage detection, where the presence of damage breaks down the time reversibility and the mismatch between the reconstructed and the input signal is inferred as the presence of damage. This paper presents an experimental and a simulation study of baseline-free damage detection in a stiffened aluminum plate by time reversed Lamb wave (TRLW). In this study, single Lamb wave mode (A 0 ) is generated and sensed using piezoelectric (PZT) transducers through specific transducer placement and amplitude tuning. Different stiffening configurations such as plane and T-stiffeners are considered. Damage cases of disbonding of stiffeners from the base plate, and vertical and embedded cracks in the stiffened plate, are studied. The results show that TRLW based schemes can efficiently identify the presence of damage in a stiffened plate. (paper)

  5. Least-squares reverse time migration of multiples

    KAUST Repository

    Zhang, Dongliang

    2013-12-06

    The theory of least-squares reverse time migration of multiples (RTMM) is presented. In this method, least squares migration (LSM) is used to image free-surface multiples where the recorded traces are used as the time histories of the virtual sources at the hydrophones and the surface-related multiples are the observed data. For a single source, the entire free-surface becomes an extended virtual source where the downgoing free-surface multiples more fully illuminate the subsurface compared to the primaries. Since each recorded trace is treated as the time history of a virtual source, knowledge of the source wavelet is not required and the ringy time series for each source is automatically deconvolved. If the multiples can be perfectly separated from the primaries, numerical tests on synthetic data for the Sigsbee2B and Marmousi2 models show that least-squares reverse time migration of multiples (LSRTMM) can significantly improve the image quality compared to RTMM or standard reverse time migration (RTM) of primaries. However, if there is imperfect separation and the multiples are strongly interfering with the primaries then LSRTMM images show no significant advantage over the primary migration images. In some cases, they can be of worse quality. Applying LSRTMM to Gulf of Mexico data shows higher signal-to-noise imaging of the salt bottom and top compared to standard RTM images. This is likely attributed to the fact that the target body is just below the sea bed so that the deep water multiples do not have strong interference with the primaries. Migrating a sparsely sampled version of the Marmousi2 ocean bottom seismic data shows that LSM of primaries and LSRTMM provides significantly better imaging than standard RTM. A potential liability of LSRTMM is that multiples require several round trips between the reflector and the free surface, so that high frequencies in the multiples suffer greater attenuation compared to the primary reflections. This can lead to lower

  6. Exact infinite-time statistics of the Loschmidt echo for a quantum quench.

    Science.gov (United States)

    Campos Venuti, Lorenzo; Jacobson, N Tobias; Santra, Siddhartha; Zanardi, Paolo

    2011-07-01

    The equilibration dynamics of a closed quantum system is encoded in the long-time distribution function of generic observables. In this Letter we consider the Loschmidt echo generalized to finite temperature, and show that we can obtain an exact expression for its long-time distribution for a closed system described by a quantum XY chain following a sudden quench. In the thermodynamic limit the logarithm of the Loschmidt echo becomes normally distributed, whereas for small quenches in the opposite, quasicritical regime, the distribution function acquires a universal double-peaked form indicating poor equilibration. These findings, obtained by a central limit theorem-type result, extend to completely general models in the small-quench regime.

  7. Frames for exact inversion of the rank order coder.

    Science.gov (United States)

    Masmoudi, Khaled; Antonini, Marc; Kornprobst, Pierre

    2012-02-01

    Our goal is to revisit rank order coding by proposing an original exact decoding procedure for it. Rank order coding was proposed by Thorpe et al. who stated that the order in which the retina cells are activated encodes for the visual stimulus. Based on this idea, the authors proposed in [1] a rank order coder/decoder associated to a retinal model. Though, it appeared that the decoding procedure employed yields reconstruction errors that limit the model bit-cost/quality performances when used as an image codec. The attempts made in the literature to overcome this issue are time consuming and alter the coding procedure, or are lacking mathematical support and feasibility for standard size images. Here we solve this problem in an original fashion by using the frames theory, where a frame of a vector space designates an extension for the notion of basis. Our contribution is twofold. First, we prove that the analyzing filter bank considered is a frame, and then we define the corresponding dual frame that is necessary for the exact image reconstruction. Second, to deal with the problem of memory overhead, we design a recursive out-of-core blockwise algorithm for the computation of this dual frame. Our work provides a mathematical formalism for the retinal model under study and defines a simple and exact reverse transform for it with over than 265 dB of increase in the peak signal-to-noise ratio quality compared to [1]. Furthermore, the framework presented here can be extended to several models of the visual cortical areas using redundant representations.

  8. The imaginary-time path integral and non-time-reversal-invariant saddle points of the Euclidean action

    International Nuclear Information System (INIS)

    Dasgupta, I.

    1998-01-01

    We discuss new bounce-like (but non-time-reversal-invariant) solutions to Euclidean equations of motion, which we dub boomerons. In the Euclidean path integral approach to quantum theories, boomerons make an imaginary contribution to the vacuum energy. The fake vacuum instability can be removed by cancelling boomeron contributions against contributions from time reversed boomerons (anti-boomerons). The cancellation rests on a sign choice whose significance is not completely understood in the path integral method. (orig.)

  9. IR-safe and UV-safe integrands in the EFTofLSS with exact time dependence

    Energy Technology Data Exchange (ETDEWEB)

    Lewandowski, Matthew [Institut de Physique Théorique, Université Paris Saclay, CEA, CNRS, 91191 Gif-sur-Yvette (France); Senatore, Leonardo, E-mail: matthew.lewandowski@ipht.fr, E-mail: senatore@stanford.edu [Stanford Institute for Theoretical Physics, Stanford University, Stanford, 94306 CA (United States)

    2017-08-01

    Because large-scale structure surveys may very well be the next leading sources of cosmological information, it is important to have a precise understanding of the cosmological observables; for this reason, the Effective Field Theory of Large-Scale Structure (EFTofLSS) was developed. So far, most results in the EFTofLSS have used the so-called Einstein-de Sitter approximation, an approximation of the time dependence which is known to be accurate to better than one percent. However, in order to reach even higher accuracy, the full time dependence must be used. The computation with exact time dependence is sensitive to both infrared (IR) and ultraviolet (UV) effects in the loop integrands, and while these effects must cancel because of diffeomorphism invariance, they make numerical computation much less efficient. We provide a formulation of the one-loop, equal-time exact-time-dependence power spectrum of density perturbations which is manifestly free of these spurious IR and UV divergences at the level of the integrand. We extend our results to the total matter mode with clustering quintessence, show that IR and UV divergences cancel, and provide the associated IR- and UV-safe integrand. This also establishes that the consistency conditions are satisfied in this system. We then use our one-loop result to do an improved precision comparison of the two-loop dark-matter power spectrum with the Dark Sky N -body simulation.

  10. The Organization of Behavior Over Time: Insights from Mid-Session Reversal

    OpenAIRE

    Rayburn-Reeves, Rebecca M.; Cook, Robert G.

    2016-01-01

    What are the mechanisms by which behavior is organized sequentially over time? The recently developed mid-session reversal (MSR) task offers new insights into this fundamental question. The typical MSR task is arranged to have a single reversed discrimination occurring in a consistent location within each session and across sessions. In this task, we examine the relevance of time, reinforcement, and other factors as the switching cue in the sequential modulation of control in MSR. New analyse...

  11. Exact solutions of Feinberg–Horodecki equation for time-dependent ...

    Indian Academy of Sciences (India)

    proposed to find the exact solutions of the Feinberg–Horodecki equation for the .... is a polynomial of degree n and satisfies the Rodrigues relation [24] ... The discriminant of expression (15) under the square root has to be zero, so that the.

  12. Multi-source least-squares reverse time migration

    KAUST Repository

    Dai, Wei

    2012-06-15

    Least-squares migration has been shown to improve image quality compared to the conventional migration method, but its computational cost is often too high to be practical. In this paper, we develop two numerical schemes to implement least-squares migration with the reverse time migration method and the blended source processing technique to increase computation efficiency. By iterative migration of supergathers, which consist in a sum of many phase-encoded shots, the image quality is enhanced and the crosstalk noise associated with the encoded shots is reduced. Numerical tests on 2D HESS VTI data show that the multisource least-squares reverse time migration (LSRTM) algorithm suppresses migration artefacts, balances the amplitudes, improves image resolution and reduces crosstalk noise associated with the blended shot gathers. For this example, the multisource LSRTM is about three times faster than the conventional RTM method. For the 3D example of the SEG/EAGE salt model, with a comparable computational cost, multisource LSRTM produces images with more accurate amplitudes, better spatial resolution and fewer migration artefacts compared to conventional RTM. The empirical results suggest that multisource LSRTM can produce more accurate reflectivity images than conventional RTM does with a similar or less computational cost. The caveat is that the LSRTM image is sensitive to large errors in the migration velocity model. © 2012 European Association of Geoscientists & Engineers.

  13. Multi-source least-squares reverse time migration

    KAUST Repository

    Dai, Wei; Fowler, Paul J.; Schuster, Gerard T.

    2012-01-01

    Least-squares migration has been shown to improve image quality compared to the conventional migration method, but its computational cost is often too high to be practical. In this paper, we develop two numerical schemes to implement least-squares migration with the reverse time migration method and the blended source processing technique to increase computation efficiency. By iterative migration of supergathers, which consist in a sum of many phase-encoded shots, the image quality is enhanced and the crosstalk noise associated with the encoded shots is reduced. Numerical tests on 2D HESS VTI data show that the multisource least-squares reverse time migration (LSRTM) algorithm suppresses migration artefacts, balances the amplitudes, improves image resolution and reduces crosstalk noise associated with the blended shot gathers. For this example, the multisource LSRTM is about three times faster than the conventional RTM method. For the 3D example of the SEG/EAGE salt model, with a comparable computational cost, multisource LSRTM produces images with more accurate amplitudes, better spatial resolution and fewer migration artefacts compared to conventional RTM. The empirical results suggest that multisource LSRTM can produce more accurate reflectivity images than conventional RTM does with a similar or less computational cost. The caveat is that the LSRTM image is sensitive to large errors in the migration velocity model. © 2012 European Association of Geoscientists & Engineers.

  14. Non-linear time reversal ultrasonic pseudo-tomography

    Czech Academy of Sciences Publication Activity Database

    Převorovský, Zdeněk; Vejvodová, Šárka; Krofta, Josef; Převorovský, David

    2011-01-01

    Roč. 6, 3/4 (2011), s. 206-213 ISSN 1741-8410. [NDT in Progress. Praha, 05.11.2007-07.11.2007] R&D Projects: GA MPO(CZ) FR-TI1/274 Institutional research plan: CEZ:AV0Z20760514 Keywords : NDT * nonlinear elastic wave spectroscopy * time reversal mirrors * ultrasonic pseudo-tomography Subject RIV: BI - Acoustics http://www.inderscience.com/offer.php?id=43216

  15. Application of reverse transcription-PCR and real-time PCR in nanotoxicity research.

    Science.gov (United States)

    Mo, Yiqun; Wan, Rong; Zhang, Qunwei

    2012-01-01

    Reverse transcription-polymerase chain reaction (RT-PCR) is a relatively simple and inexpensive technique to determine the expression level of target genes and is widely used in biomedical science research including nanotoxicology studies for semiquantitative analysis. Real-time PCR allows for the detection of PCR amplification in the exponential growth phase of the reaction and is much more quantitative than traditional RT-PCR. Although a number of kits and reagents for RT-PCR and real-time PCR are commercially available, the basic principles are the same. Here, we describe the procedures for total RNA isolation by using TRI Reagent, for reverse transcription (RT) by M-MLV reverse transcriptase, and for PCR by GoTaq(®) DNA Polymerase. And real-time PCR will be performed on an iQ5 multicolor real-time PCR detection system by using iQ™ SYBR Green Supermix.

  16. Reverse Logistics

    OpenAIRE

    Kulikova, Olga

    2016-01-01

    This thesis was focused on the analysis of the concept of reverse logistics and actual reverse processes which are implemented in mining industry and finding solutions for the optimization of reverse logistics in this sphere. The objective of this paper was the assessment of the development of reverse logistics in mining industry on the example of potash production. The theoretical part was based on reverse logistics and mining waste related literature and provided foundations for further...

  17. Quantum-Enhanced Sensing Based on Time Reversal of Nonlinear Dynamics.

    Science.gov (United States)

    Linnemann, D; Strobel, H; Muessel, W; Schulz, J; Lewis-Swan, R J; Kheruntsyan, K V; Oberthaler, M K

    2016-07-01

    We experimentally demonstrate a nonlinear detection scheme exploiting time-reversal dynamics that disentangles continuous variable entangled states for feasible readout. Spin-exchange dynamics of Bose-Einstein condensates is used as the nonlinear mechanism which not only generates entangled states but can also be time reversed by controlled phase imprinting. For demonstration of a quantum-enhanced measurement we construct an active atom SU(1,1) interferometer, where entangled state preparation and nonlinear readout both consist of parametric amplification. This scheme is capable of exhausting the quantum resource by detecting solely mean atom numbers. Controlled nonlinear transformations widen the spectrum of useful entangled states for applied quantum technologies.

  18. Time-Reversal MUSIC Imaging with Time-Domain Gating Technique

    Science.gov (United States)

    Choi, Heedong; Ogawa, Yasutaka; Nishimura, Toshihiko; Ohgane, Takeo

    A time-reversal (TR) approach with multiple signal classification (MUSIC) provides super-resolution for detection and localization using multistatic data collected from an array antenna system. The theory of TR-MUSIC assumes that the number of antenna elements is greater than that of scatterers (targets). Furthermore, it requires many sets of frequency-domain data (snapshots) in seriously noisy environments. Unfortunately, these conditions are not practical for real environments due to the restriction of a reasonable antenna structure as well as limited measurement time. We propose an approach that treats both noise reduction and relaxation of the transceiver restriction by using a time-domain gating technique accompanied with the Fourier transform before applying the TR-MUSIC imaging algorithm. Instead of utilizing the conventional multistatic data matrix (MDM), we employ a modified MDM obtained from the gating technique. The resulting imaging functions yield more reliable images with only a few snapshots regardless of the limitation of the antenna arrays.

  19. Anti-Aliasing filter for reverse-time migration

    KAUST Repository

    Zhan, Ge

    2012-01-01

    We develop an anti-aliasing filter for reverse-time migration (RTM). It is similar to the traditional anti-aliasing filter used for Kirchhoff migration in that it low-pass filters the migration operator so that the dominant wavelength in the operator is greater than two times the trace sampling interval, except it is applied to both primary and multiple reflection events. Instead of applying this filter to the data in the traditional RTM operation, we apply the anti-aliasing filter to the generalized diffraction-stack migration operator. This gives the same migration image as computed by anti-aliased RTM. Download

  20. Exact coherent structures in an asymptotically reduced description of parallel shear flows

    Science.gov (United States)

    Beaume, Cédric; Knobloch, Edgar; Chini, Gregory P.; Julien, Keith

    2015-02-01

    A reduced description of shear flows motivated by the Reynolds number scaling of lower-branch exact coherent states in plane Couette flow (Wang J, Gibson J and Waleffe F 2007 Phys. Rev. Lett. 98 204501) is constructed. Exact time-independent nonlinear solutions of the reduced equations corresponding to both lower and upper branch states are found for a sinusoidal, body-forced shear flow. The lower branch solution is characterized by fluctuations that vary slowly along the critical layer while the upper branch solutions display a bimodal structure and are more strongly focused on the critical layer. The reduced equations provide a rational framework for investigations of subcritical spatiotemporal patterns in parallel shear flows.

  1. Exact coherent structures in an asymptotically reduced description of parallel shear flows

    International Nuclear Information System (INIS)

    Beaume, Cédric; Knobloch, Edgar; Chini, Gregory P; Julien, Keith

    2015-01-01

    A reduced description of shear flows motivated by the Reynolds number scaling of lower-branch exact coherent states in plane Couette flow (Wang J, Gibson J and Waleffe F 2007 Phys. Rev. Lett. 98 204501) is constructed. Exact time-independent nonlinear solutions of the reduced equations corresponding to both lower and upper branch states are found for a sinusoidal, body-forced shear flow. The lower branch solution is characterized by fluctuations that vary slowly along the critical layer while the upper branch solutions display a bimodal structure and are more strongly focused on the critical layer. The reduced equations provide a rational framework for investigations of subcritical spatiotemporal patterns in parallel shear flows. (paper)

  2. Exact route-length formulas and a storage location assignment heuristic for picker-to-parts warehouses

    NARCIS (Netherlands)

    Dijkstra, Arjan; Roodbergen, Kees Jan

    2017-01-01

    Order picking is one of the most time-critical processes in warehouses. We focus on the combined effects of routing methods and storage location assignment on process performance. We present exact formulas for the average route length under any storage location assignment for four common routing

  3. Langevin synchronization in a time-dependent, harmonic basin: An exact solution in 1D

    Science.gov (United States)

    Cadilhe, A.; Voter, Arthur F.

    2018-02-01

    The trajectories of two particles undergoing Langevin dynamics while sharing a common noise sequence can merge into a single (master) trajectory. Here, we present an exact solution for a particle undergoing Langevin dynamics in a harmonic, time-dependent potential, thus extending the idea of synchronization to nonequilibrium systems. We calculate the synchronization level, i.e., the mismatch between two trajectories sharing a common noise sequence, in the underdamped, critically damped, and overdamped regimes. Finally, we provide asymptotic expansions in various limiting cases and compare to the time independent case.

  4. Euclidean shortest paths exact or approximate algorithms

    CERN Document Server

    Li, Fajie

    2014-01-01

    This book reviews algorithms for the exact or approximate solution of shortest-path problems, with a specific focus on a class of algorithms called rubberband algorithms. The coverage includes mathematical proofs for many of the given statements.

  5. Ultrasound shock wave generator with one-bit time reversal in a dispersive medium, application to lithotripsy

    Science.gov (United States)

    Montaldo, Gabriel; Roux, Philippe; Derode, Arnaud; Negreira, Carlos; Fink, Mathias

    2002-02-01

    The building of high-power ultrasonic sources from piezoelectric ceramics is limited by the maximum voltage that the ceramics can endure. We have conceived a device that uses a small number of piezoelectric transducers fastened to a cylindrical metallic waveguide. A one-bit time- reversal operation transforms the long-lasting low-level dispersed wave forms into a sharp pulse, thus taking advantage of dispersion to generate high-power ultrasound. The pressure amplitude that is generated at the focus is found to be 15 times greater than that achieved with comparable standard techniques. Applications to lithotripsy are discussed and the destructive efficiency of the system is demonstrated on pieces of chalk.

  6. Exactly and quasi-exactly solvable 'discrete' quantum mechanics.

    Science.gov (United States)

    Sasaki, Ryu

    2011-03-28

    A brief introduction to discrete quantum mechanics is given together with the main results on various exactly solvable systems. Namely, the intertwining relations, shape invariance, Heisenberg operator solutions, annihilation/creation operators and dynamical symmetry algebras, including the q-oscillator algebra and the Askey-Wilson algebra. A simple recipe to construct exactly and quasi-exactly solvable (QES) Hamiltonians in one-dimensional 'discrete' quantum mechanics is presented. It reproduces all the known Hamiltonians whose eigenfunctions consist of the Askey scheme of hypergeometric orthogonal polynomials of a continuous or a discrete variable. Several new exactly and QES Hamiltonians are constructed. The sinusoidal coordinate plays an essential role.

  7. Comparison of source moment tensor recovered by diffraction stacking migration and source time reversal imaging

    Science.gov (United States)

    Zhang, Q.; Zhang, W.

    2017-12-01

    Diffraction stacking migration is an automatic location methods and widely used in microseismic monitoring of the hydraulic fracturing. It utilizes the stacking of thousands waveform to enhance signal-to-noise ratio of weak events. For surface monitoring, the diffraction stacking method is suffered from polarity reverse among receivers due to radiation pattern of moment source. Joint determination of location and source mechanism has been proposed to overcome the polarity problem but needs significantly increased computational calculations. As an effective method to recover source moment tensor, time reversal imaging based on wave equation can locate microseismic event by using interferometry on the image to extract source position. However, the time reversal imaging is very time consuming compared to the diffraction stacking location because of wave-equation simulation.In this study, we compare the image from diffraction stacking and time reversal imaging to check if the diffraction stacking can obtain similar moment tensor as time reversal imaging. We found that image produced by taking the largest imaging value at each point along time axis does not exhibit the radiation pattern, while with the same level of calculation efficiency, the image produced for each trial origin time can generate radiation pattern similar to time reversal imaging procedure. Thus it is potential to locate the source position by the diffraction stacking method for general moment tensor sources.

  8. Construction of the exact Fisher information matrix of Gaussian time series models by means of matrix differential rules

    NARCIS (Netherlands)

    Klein, A.A.B.; Melard, G.; Zahaf, T.

    2000-01-01

    The Fisher information matrix is of fundamental importance for the analysis of parameter estimation of time series models. In this paper the exact information matrix of a multivariate Gaussian time series model expressed in state space form is derived. A computationally efficient procedure is used

  9. Reversal time of jump-noise magnetization dynamics in nanomagnets via Monte Carlo simulations

    Science.gov (United States)

    Parthasarathy, Arun; Rakheja, Shaloo

    2018-06-01

    The jump-noise is a nonhomogeneous Poisson process which models thermal effects in magnetization dynamics, with special applications in low temperature escape rate phenomena. In this work, we develop improved numerical methods for Monte Carlo simulation of the jump-noise dynamics and validate the method by comparing the stationary distribution obtained empirically against the Boltzmann distribution. In accordance with the Néel-Brown theory, the jump-noise dynamics display an exponential relaxation toward equilibrium with a characteristic reversal time, which we extract for nanomagnets with uniaxial and cubic anisotropy. We relate the jump-noise dynamics to the equivalent Landau-Lifshitz dynamics up to second order correction for a general energy landscape and obtain the analogous Néel-Brown theory's solution of the reversal time. We find that the reversal time of jump-noise dynamics is characterized by Néel-Brown theory's solution at the energy saddle point for small noise. For large noise, the magnetization reversal due to jump-noise dynamics phenomenologically represents macroscopic tunneling of magnetization.

  10. Correlation in the statistical analysis of a reverse Fourier neutron time-of-flight experiment. Pt. 2

    International Nuclear Information System (INIS)

    Tilli, K.J.

    1982-01-01

    The significance of the correlation in the statistical analysis of reverse Fourier neutron time-of-flight observations has been evaluated by applying different methods of estimation to diffraction patterns containing peaks with Gaussian line shapes. Effects of the correlation between adjacent channels of a spectrum arise both from the incorrect weighting of the experiment's independent variables and from the misinterpretation of the number of independent observations in the data. The incorrect weighting bears the greatest effects on the width parameter of a Gaussian profile, and it leads to an increase in the relative weights of the broadest peaks of the diffraction pattern. If the correlation is ignored in the analysis, the estimates obtained for the parameters of a model will not be exactly the same as those evaluated from the minimum variance estimation, in which the correlation is taken into account. However, the differences will not be statistically significant. Nevertheless, the standard deviations will then be underestimated typically by a factor of two, which will have serious consequences on every aspect of the statistical inference. (orig.)

  11. Time-reversal symmetry breaking by ac field: Effect of ...

    Indian Academy of Sciences (India)

    deviate from 2 thus signalling on the time-reversal breaking by the ac field. ... is also the parity effect: the enchancement is only present if either P or Q is even. ... analysis (see figure 1) is possible and the ergodic zero-dimensional approx-.

  12. Transducer frequency response variations investigated by time reversal calibration

    Czech Academy of Sciences Publication Activity Database

    Kober, Jan; Převorovský, Zdeněk

    2016-01-01

    Roč. 26, č. 2 (2016), A16-A16 ISSN 1213-3825. [Europen Conference on Acoustic Emission Testing /32./. 07.09.2016-09.09.2016, Praha] Institutional support: RVO:61388998 Keywords : calibration * time reversal * transducer * frequency response Subject RIV: BI - Acoustics

  13. Exact, almost and delayed fault detection

    DEFF Research Database (Denmark)

    Niemann, Hans Henrik; Saberi, Ali; Stoorvogel, Anton A.

    1999-01-01

    Considers the problem of fault detection and isolation while using zero or almost zero threshold. A number of different fault detection and isolation problems using exact or almost exact disturbance decoupling are formulated. Solvability conditions are given for the formulated design problems....... The l-step delayed fault detection problem is also considered for discrete-time systems....

  14. Deep-Focusing Time-Distance Helioseismology

    Science.gov (United States)

    Duvall, T. L., Jr.; Jensen, J. M.; Kosovichev, A. G.; Birch, A. C.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    Much progress has been made by measuring the travel times of solar acoustic waves from a central surface location to points at equal arc distance away. Depth information is obtained from the range of arc distances examined, with the larger distances revealing the deeper layers. This method we will call surface-focusing, as the common point, or focus, is at the surface. To obtain a clearer picture of the subsurface region, it would, no doubt, be better to focus on points below the surface. Our first attempt to do this used the ray theory to pick surface location pairs that would focus on a particular subsurface point. This is not the ideal procedure, as Born approximation kernels suggest that this focus should have zero sensitivity to sound speed inhomogeneities. However, the sensitivity is concentrated below the surface in a much better way than the old surface-focusing method, and so we expect the deep-focusing method to be more sensitive. A large sunspot group was studied by both methods. Inversions based on both methods will be compared.

  15. Exact invariants in the form of momentum resonances for particle motion in one-dimensional, time-dependent potentials

    International Nuclear Information System (INIS)

    Goedert, J.; Lewis, H.R.

    1984-01-01

    A momentum-resonance ansatz of Lewis and Leach was used to study exact invariants for time-dependent, one-dimensional potentials. This ansatz provides a framework for finding invariants admitted by a larger class of time-dependent potentials that was known previously. For a potential that admits an exact invariant in this resonance form, we have shown how to construct the invariant as a functional of the potential in terms of the solution of a definite linear algebraic system of equations. We have found a necessary and sufficient condition on the potential for the existence of an invariant with a given number of resonances. There exist more potentials that admit invariants with two resonances than were previously known and we have found an example in parametric form of such a potential. We have also found examples of potentials that admit invariants with three resonances

  16. Lie symmetry analysis, conservation laws and exact solutions of the seventh-order time fractional Sawada–Kotera–Ito equation

    Directory of Open Access Journals (Sweden)

    Emrullah Yaşar

    Full Text Available In this paper Lie symmetry analysis of the seventh-order time fractional Sawada–Kotera–Ito (FSKI equation with Riemann–Liouville derivative is performed. Using the Lie point symmetries of FSKI equation, it is shown that it can be transformed into a nonlinear ordinary differential equation of fractional order with a new dependent variable. In the reduced equation the derivative is in Erdelyi–Kober sense. Furthermore, adapting the Ibragimov’s nonlocal conservation method to time fractional partial differential equations, we obtain conservation laws of the underlying equation. In addition, we construct some exact travelling wave solutions for the FSKI equation using the sub-equation method. Keywords: Fractional Sawada–Kotera–Ito equation, Lie symmetry, Riemann–Liouville fractional derivative, Conservation laws, Exact solutions

  17. Attenuation compensation in least-squares reverse time migration using the visco-acoustic wave equation

    KAUST Repository

    Dutta, Gaurav

    2013-08-20

    Attenuation leads to distortion of amplitude and phase of seismic waves propagating inside the earth. Conventional acoustic and least-squares reverse time migration do not account for this distortion which leads to defocusing of migration images in highly attenuative geological environments. To account for this distortion, we propose to use the visco-acoustic wave equation for least-squares reverse time migration. Numerical tests on synthetic data show that least-squares reverse time migration with the visco-acoustic wave equation corrects for this distortion and produces images with better balanced amplitudes compared to the conventional approach. © 2013 SEG.

  18. Exact and Heuristic Solutions to Minimize Total Waiting Time in the Blood Products Distribution Problem

    Directory of Open Access Journals (Sweden)

    Amir Salehipour

    2012-01-01

    Full Text Available This paper presents a novel application of operations research to support decision making in blood distribution management. The rapid and dynamic increasing demand, criticality of the product, storage, handling, and distribution requirements, and the different geographical locations of hospitals and medical centers have made blood distribution a complex and important problem. In this study, a real blood distribution problem containing 24 hospitals was tackled by the authors, and an exact approach was presented. The objective of the problem is to distribute blood and its products among hospitals and medical centers such that the total waiting time of those requiring the product is minimized. Following the exact solution, a hybrid heuristic algorithm is proposed. Computational experiments showed the optimal solutions could be obtained for medium size instances, while for larger instances the proposed hybrid heuristic is very competitive.

  19. Clean translation of an imperative reversible programming language

    DEFF Research Database (Denmark)

    Axelsen, Holger Bock

    2011-01-01

    We describe the translation techniques used for the code generation in a compiler from the high-level reversible imperative programming language Janus to the low-level reversible assembly language PISA. Our translation is both semantics preserving (correct), in that target programs compute exactly...... the same functions as their source programs (cleanly, with no extraneous garbage output), and efficient, in that target programs conserve the complexities of source programs. In particular, target programs only require a constant amount of temporary garbage space. The given translation methods are generic......, and should be applicable to any (imperative) reversible source language described with reversible flowcharts and reversible updates. To our knowledge, this is the first compiler between reversible languages where the source and target languages were independently developed; the first exhibiting both...

  20. Unitarity and time reversal in the Glauber model

    International Nuclear Information System (INIS)

    Lazard, C.; Lombard, R.J.

    1984-12-01

    It has been pointed out by Formanek (1976-1980) that for incident energies above the particle production threshold the usual Glauber formulation of particle-nucleus scattering violates unitarity and time reversal invariance. We propose a simple method for recovering T-invariance and we discuss unitarity in view of the proposed modification. Numerical estimates are given to check the importance of T-invariance effects

  1. A time-reversal invariant topological phase at the surface of a 3D topological insulator

    International Nuclear Information System (INIS)

    Bonderson, Parsa; Nayak, Chetan; Qi, Xiao-Liang

    2013-01-01

    A 3D fermionic topological insulator has a gapless Dirac surface state protected by time-reversal symmetry and charge conservation symmetry. The surface state can be gapped by introducing ferromagnetism to break time-reversal symmetry, introducing superconductivity to break charge conservation, or entering a topological phase. In this paper, we construct a minimal gapped topological phase that preserves both time-reversal and charge conservation symmetries and supports Ising-type non-Abelian anyons. This phase can be understood heuristically as emerging from a surface s-wave superconducting state via the condensation of eight-vortex composites. The topological phase inherits vortices supporting Majorana zero modes from the surface superconducting state. However, since it is time-reversal invariant, the surface topological phase is a distinct phase from the Ising topological phase, which can be viewed as a quantum-disordered spin-polarized p x + ip y superconductor. We discuss the anyon model of this topological phase and the manner in which time-reversal symmetry is realized in it. We also study the interfaces between the topological state and other surface gapped phases. (paper)

  2. The brief time-reversibility of the local Lyapunov exponents for a small chaotic Hamiltonian system

    International Nuclear Information System (INIS)

    Waldner, Franz; Hoover, William G.; Hoover, Carol G.

    2014-01-01

    Highlights: •We consider the local Lyapunov spectrum for a four-dimensional Hamilton system. •Its stable periodic motion can be reversed for long times. •In the chaotic motion, time reversal occurs only for a short time. •Perturbations will change this short unstable case into a different stable case. •These observations might relate chaos to the Second Law of Thermodynamics. - Abstract: We consider the local (instantaneous) Lyapunov spectrum for a four-dimensional Hamiltonian system. Its stable periodic motion can be reversed for long times. Its unstable chaotic motion, with two symmetric pairs of exponents, cannot. In the latter case reversal occurs for more than a thousand fourth-order Runge–Kutta time steps, followed by a transition to a new set of paired Lyapunov exponents, unrelated to those seen in the forward time direction. The relation of the observed chaotic dynamics to the Second Law of Thermodynamics is discussed

  3. Density-Dependent Conformable Space-time Fractional Diffusion-Reaction Equation and Its Exact Solutions

    Science.gov (United States)

    Hosseini, Kamyar; Mayeli, Peyman; Bekir, Ahmet; Guner, Ozkan

    2018-01-01

    In this article, a special type of fractional differential equations (FDEs) named the density-dependent conformable fractional diffusion-reaction (DDCFDR) equation is studied. Aforementioned equation has a significant role in the modelling of some phenomena arising in the applied science. The well-organized methods, including the \\exp (-φ (\\varepsilon )) -expansion and modified Kudryashov methods are exerted to generate the exact solutions of this equation such that some of the solutions are new and have been reported for the first time. Results illustrate that both methods have a great performance in handling the DDCFDR equation.

  4. Focusing procedures in time-of-flight mass spectrometry

    International Nuclear Information System (INIS)

    Ioanoviciu, D.

    2002-01-01

    Time-of-flight mass spectrometry is a fast growing field due to its ability to handle very fast processes and due to its theoretically unlimited mass range. The performances of the time-of-flight mass analysers are heavily dependent on the progress in ion optics, a periodically reviewed field. In this presentation the various focusing procedures in time-of-flight mass spectrometry are reviewed. For ions of the same charge and mass flight time differences result from different potentials at the location of formation and from the initial velocity spread. There is no simultaneous space and velocity focusing in time-of-flight mass spectrometry. Space focusing of first and second order can be reached in time-of-flight mass analysers having two homogeneous electric field ion sources followed by a field free space in front of the detector. Single and double stage homogeneous electric field mirrors can focus in time ions of different energies. These different energies result when ions leaving different initial sites and arriving simultaneously to an intermediate space focus. Convenient mass dispersion can be obtained by including a mirror. Initial velocity focusing is obtained by the delayed extraction procedure in drift space and mirror time-of-flight mass analysers. Post source pulse focusing aims at the same purpose. Ion source electrodes of hyperbolic shape, operated by high voltage pulses can bring major improvements of the resolution, especially at high masses. For each focusing procedure the geometric and/or electric conditions are given as well as the aberrations allowing the mass resolution determination. The various focusing procedures are compared and a prediction of their future performances was tempted. (author)

  5. Fast damage imaging using the time-reversal technique in the frequency–wavenumber domain

    International Nuclear Information System (INIS)

    Zhu, R; Huang, G L; Yuan, F G

    2013-01-01

    The time-reversal technique has been successfully used in structural health monitoring (SHM) for quantitative imaging of damage. However, the technique is very time-consuming when it is implemented in the time domain. In this paper, we study the technique in the frequency–wavenumber (f–k) domain for fast real-time imaging of multiple damage sites in plates using scattered flexural plate waves. Based on Mindlin plate theory, the time reversibility of dispersive flexural waves in an isotropic plate is theoretically investigated in the f–k domain. A fast damage imaging technique is developed by using the cross-correlation between the back-propagated scattered wavefield and the incident wavefield in the frequency domain. Numerical simulations demonstrate that the proposed technique cannot only localize multiple damage sites but also potentially identify their sizes. Moreover, the time-reversal technique in the f–k domain is about two orders of magnitude faster than the method in the time domain. Finally, experimental testing of an on-line SHM system with a sparse piezoelectric sensor array is conducted for fast multiple damage identification using the proposed technique. (paper)

  6. Quasi-exact solvability

    International Nuclear Information System (INIS)

    Ushveridze, A.G.

    1992-01-01

    This paper reports that quasi-exactly solvable (QES) models realize principally new type of exact solvability in quantum physics. These models are distinguished by the fact that the Schrodinger equations for them can be solved exactly only for certain limited parts of the spectrum, but not for the whole spectrum. They occupy an intermediate position between the exactly the authors solvable (ES) models and all the others. The number of energy levels for which the spectral problems can be solved exactly refer below to as the order of QES model. From the mathematical point of view the existence of QES models is not surprising. Indeed, if the term exact solvability expresses the possibility of total explicit diagonalization of infinite Hamiltonian matrix, then the term quasi-exact solvability implies the situation when the Hamiltonian matrix can be reduced explicitly to the block-diagonal form with one of the appearing blocks being finite

  7. Multiples least-squares reverse time migration

    KAUST Repository

    Zhang, Dongliang

    2013-01-01

    To enhance the image quality, we propose multiples least-squares reverse time migration (MLSRTM) that transforms each hydrophone into a virtual point source with a time history equal to that of the recorded data. Since each recorded trace is treated as a virtual source, knowledge of the source wavelet is not required. Numerical tests on synthetic data for the Sigsbee2B model and field data from Gulf of Mexico show that MLSRTM can improve the image quality by removing artifacts, balancing amplitudes, and suppressing crosstalk compared to standard migration of the free-surface multiples. The potential liability of this method is that multiples require several roundtrips between the reflector and the free surface, so that high frequencies in the multiples are attenuated compared to the primary reflections. This can lead to lower resolution in the migration image compared to that computed from primaries.

  8. General exact solution for homogeneous time-dependent self-gravitating perfect fluids

    International Nuclear Information System (INIS)

    Gaete, P.; Hojman, R.

    1988-01-01

    A procedure to obtain the general exact solution of Einstein equations for a self-gravitating spherically-symmetric static perfect fluid obeying an arbitrary equation of state, is applied to time-dependent Kantowsky-Sachs line elements (with spherical, planar and hyperbolic symmetry). As in the static case, the solution is generated by an arbitrary function of the independent variable and its first derivative. To illustrate the results, the whole family of (plane-symmetric) solutions with a ''gamma-law'' equation of state is explicity obtained in terms of simple known functions. It is also shown that, while in the static plane-symmtric line elements, every metric is in one to one correspondence with a ''partner-metric'' (both originated from the same generatrix function), in this case every generatrix function univocally determines one metric. (author) [pt

  9. Exact dynamics of a one dimensional Bose gas in a periodic time-dependent harmonic trap

    Science.gov (United States)

    Scopa, Stefano; Unterberger, Jéremie; Karevski, Dragi

    2018-05-01

    We study the unitary dynamics of a 1D gas of hard-core bosons trapped into a harmonic potential which varies periodically in time with frequency . Such periodic systems can be classified into orbits of different monodromies corresponding to two different physical situations, namely the case in which the bosonic cloud remains stable during the time-evolution and the case where it turns out to be unstable. In the present work we derive in the large particle number limit exact results for the stroboscopic evolution of the energy and particle densities in both physical situations.

  10. The double-slit experiment and the time-reversed fire alarm

    International Nuclear Information System (INIS)

    Halabi, T.

    2010-01-01

    When both slits of the double-slit experiment are open, closing one paradoxically increases the detection rate at some points on the detection screen. Feynman famously warned that temptation to understand such a puzzling feature only draws into blind alleys. Nevertheless, we gain insight into this feature by drawing an analogy between the double-slit experiment and a time-reversed fire alarm. Much as closing the slit increases probability of a future detection, ruling out fire drill scenarios, having heard the fire alarm, increases probability of a past fire (using Bayesian inference). Classically, Bayesian inference is associated with computing probabilities of past events. We therefore identify this feature of the double-slit experiment with a time-reversed thermodynamic arrow. We believe that much of the enigma of quantum mechanics is simply due to some variation of time's arrow. In further support of this, we employ a plausible formulation of the thermodynamic arrow to derive an uncertainty in classical mechanics that is reminiscent of quantum uncertainty.

  11. New Exact Solutions of Time Fractional Gardner Equation by Using New Version of F -Expansion Method

    International Nuclear Information System (INIS)

    Pandir, Yusuf; Duzgun, Hasan Huseyin

    2017-01-01

    In this article, we consider analytical solutions of the time fractional derivative Gardner equation by using the new version of F-expansion method. With this proposed method multiple Jacobi elliptic functions are situated in the solution function. As a result, various exact analytical solutions consisting of single and combined Jacobi elliptic functions solutions are obtained. (paper)

  12. On Lambda and Time Operators: the Inverse Intertwining Problem Revisited

    Science.gov (United States)

    Gómez-Cubillo, F.; Suchanecki, Z.; Villullas, S.

    2011-07-01

    An exact theory of irreversibility was proposed by Misra, Prigogine and Courbage, based on non-unitary similarity transformations Λ that intertwine reversible dynamics and irreversible ones. This would advocate the idea that irreversible behavior would originate at the microscopic level. Reversible evolution with an internal time operator have the intertwining property. Recently the inverse intertwining problem has been answered in the negative, that is, not every unitary evolution allowing such Λ-transformation has an internal time. This work contributes new results in this direction.

  13. Universality in exact quantum state population dynamics and control

    International Nuclear Information System (INIS)

    Wu, Lian-Ao; Segal, Dvira; Brumer, Paul; Egusquiza, Inigo L.

    2010-01-01

    We consider an exact population transition, defined as the probability of finding a state at a final time that is exactly equal to the probability of another state at the initial time. We prove that, given a Hamiltonian, there always exists a complete set of orthogonal states that can be employed as time-zero states for which this exact population transition occurs. The result is general: It holds for arbitrary systems, arbitrary pairs of initial and final states, and for any time interval. The proposition is illustrated with several analytic models. In particular, we demonstrate that in some cases, by tuning the control parameters, a complete transition might occur, where a target state, vacant at t=0, is fully populated at time τ.

  14. Time reversal signal processing in acoustic emission testing

    Czech Academy of Sciences Publication Activity Database

    Převorovský, Zdeněk; Krofta, Josef; Kober, Jan; Dvořáková, Zuzana; Chlada, Milan; Dos Santos, S.

    2014-01-01

    Roč. 19, č. 12 (2014) ISSN 1435-4934. [European Conference on Non-Destructive Testing (ECNDT 2014) /11./. Praha, 06.10.2014-10.10.2014] Institutional support: RVO:61388998 Keywords : acoustic emission (AE) * ultrasonic testing (UT) * signal processing * source location * time reversal acoustic s * acoustic emission * signal processing and transfer Subject RIV: BI - Acoustic s http://www.ndt.net/events/ECNDT2014/app/content/Slides/637_Prevorovsky.pdf

  15. Nonlinear Time Reversal Acoustic Method of Friction Stir Weld Assessment, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The goal of the project is demonstration of the feasibility of Friction Stir Weld (FSW) assessment by novel Nonlinear Time Reversal Acoustic (TRA) method. Time...

  16. Multisource Least-squares Reverse Time Migration

    KAUST Repository

    Dai, Wei

    2012-12-01

    Least-squares migration has been shown to be able to produce high quality migration images, but its computational cost is considered to be too high for practical imaging. In this dissertation, a multisource least-squares reverse time migration algorithm (LSRTM) is proposed to increase by up to 10 times the computational efficiency by utilizing the blended sources processing technique. There are three main chapters in this dissertation. In Chapter 2, the multisource LSRTM algorithm is implemented with random time-shift and random source polarity encoding functions. Numerical tests on the 2D HESS VTI data show that the multisource LSRTM algorithm suppresses migration artifacts, balances the amplitudes, improves image resolution, and reduces crosstalk noise associated with the blended shot gathers. For this example, multisource LSRTM is about three times faster than the conventional RTM method. For the 3D example of the SEG/EAGE salt model, with comparable computational cost, multisource LSRTM produces images with more accurate amplitudes, better spatial resolution, and fewer migration artifacts compared to conventional RTM. The empirical results suggest that the multisource LSRTM can produce more accurate reflectivity images than conventional RTM does with similar or less computational cost. The caveat is that LSRTM image is sensitive to large errors in the migration velocity model. In Chapter 3, the multisource LSRTM algorithm is implemented with frequency selection encoding strategy and applied to marine streamer data, for which traditional random encoding functions are not applicable. The frequency-selection encoding functions are delta functions in the frequency domain, so that all the encoded shots have unique non-overlapping frequency content. Therefore, the receivers can distinguish the wavefield from each shot according to the frequencies. With the frequency-selection encoding method, the computational efficiency of LSRTM is increased so that its cost is

  17. Tensor network method for reversible classical computation

    Science.gov (United States)

    Yang, Zhi-Cheng; Kourtis, Stefanos; Chamon, Claudio; Mucciolo, Eduardo R.; Ruckenstein, Andrei E.

    2018-03-01

    We develop a tensor network technique that can solve universal reversible classical computational problems, formulated as vertex models on a square lattice [Nat. Commun. 8, 15303 (2017), 10.1038/ncomms15303]. By encoding the truth table of each vertex constraint in a tensor, the total number of solutions compatible with partial inputs and outputs at the boundary can be represented as the full contraction of a tensor network. We introduce an iterative compression-decimation (ICD) scheme that performs this contraction efficiently. The ICD algorithm first propagates local constraints to longer ranges via repeated contraction-decomposition sweeps over all lattice bonds, thus achieving compression on a given length scale. It then decimates the lattice via coarse-graining tensor contractions. Repeated iterations of these two steps gradually collapse the tensor network and ultimately yield the exact tensor trace for large systems, without the need for manual control of tensor dimensions. Our protocol allows us to obtain the exact number of solutions for computations where a naive enumeration would take astronomically long times.

  18. Selective reversal of muscle relaxation in general anesthesia: focus on sugammadex

    Directory of Open Access Journals (Sweden)

    Sorin J Brull

    2009-04-01

    Full Text Available Sorin J Brull1, Mohamed Naguib21Department of Anesthesiology, Mayo Clinic College of Medicine, Mayo Clinic Hospital, Jacksonville, FL, USA; 2Department of Anesthesiology and Pain Medicine, The University of Texas M D Anderson Cancer Center,  Houston, TX, USAAbstract: Despite the significant improvements in the pharmacology of muscle relaxants in the past six decades, the search for the ideal muscle relaxant continues, mainly because of the incomplete efficacy and persistent side effects associated with their antagonism. Clinical concerns remain about the residual paralysis and hemodynamic side effects associated with the classic pharmacologic reversal agents, the acetylcholinesterase inhibitors. Although the development of the “ideal muscle relaxant” remains illusory, pharmacologic advancements hold promise for improved clinical care and patient safety. Recent clinical advances include the development of short-acting nondepolarizing muscle relaxant agents that have fast onset and a very rapid metabolism that allows reliable and complete recovery; and the development of selective, “designer” reversal agents that are specific for a single drug or class of drugs. This article reviews recent developments in the pharmacology of these selective reversal agents: plasma cholinesterases, cysteine, and sugammadex. Although each of the selective reversal agents is specific in its substrate, the clinical use of the combination of muscle relaxant with its specific reversal agent will allow much greater intraoperative titrating ability, decreased side effect profile, and may result in a decreased incidence of postoperative residual paralysis and improved patient safety.Keywords: selective reversal agents, cysteine, plasma cholinesterases, sugammadex

  19. Ultrasound breast imaging using frequency domain reverse time migration

    Science.gov (United States)

    Roy, O.; Zuberi, M. A. H.; Pratt, R. G.; Duric, N.

    2016-04-01

    Conventional ultrasonography reconstruction techniques, such as B-mode, are based on a simple wave propagation model derived from a high frequency approximation. Therefore, to minimize model mismatch, the central frequency of the input pulse is typically chosen between 3 and 15 megahertz. Despite the increase in theoretical resolution, operating at higher frequencies comes at the cost of lower signal-to-noise ratio. This ultimately degrades the image contrast and overall quality at higher imaging depths. To address this issue, we investigate a reflection imaging technique, known as reverse time migration, which uses a more accurate propagation model for reconstruction. We present preliminary simulation results as well as physical phantom image reconstructions obtained using data acquired with a breast imaging ultrasound tomography prototype. The original reconstructions are filtered to remove low-wavenumber artifacts that arise due to the inclusion of the direct arrivals. We demonstrate the advantage of using an accurate sound speed model in the reverse time migration process. We also explain how the increase in computational complexity can be mitigated using a frequency domain approach and a parallel computing platform.

  20. Estimating medication stopping fraction and real-time prevalence of drug use in pharmaco-epidemiologic databases. An application of the reverse waiting time distribution

    DEFF Research Database (Denmark)

    Støvring, Henrik; Pottegård, Anton; Hallas, Jesper

    2017-01-01

    Purpose: To introduce the reverse waiting time distribution (WTD) and show how it can be used to estimate stopping fractions and real-time prevalence of treatment in pharmacoepidemiological studies. Methods: The reverse WTD is the distribution of time from the last dispensed prescription of each......-hoc decision rules for automated implementations, and it yields estimates of real-time prevalence....... patient within a time window to the end of it. It is a mirrored version of the ordinary WTD, which considers the first dispensed prescription of patients within a time window. Based on renewal process theory, the reverse WTD can be analyzed as an ordinary WTD with maximum likelihood estimation. Based...

  1. Time-reversibility in seismic sequences: Application to the seismicity of Mexican subduction zone

    Science.gov (United States)

    Telesca, L.; Flores-Márquez, E. L.; Ramírez-Rojas, A.

    2018-02-01

    In this paper we investigate the time-reversibility of series associated with the seismicity of five seismic areas of the subduction zone beneath the Southwest Pacific Mexican coast, applying the horizontal visibility graph method to the series of earthquake magnitudes, interevent times, interdistances and magnitude increments. We applied the Kullback-Leibler divergence D that is a metric for quantifying the degree of time-irreversibility in time series. Our findings suggest that among the five seismic areas, Jalisco-Colima is characterized by time-reversibility in all the four seismic series. Our results are consistent with the peculiar seismo-tectonic characteristics of Jalisco-Colima, which is the closest to the Middle American Trench and belongs to the Mexican volcanic arc.

  2. Discover potential in a search for time-reversal invariance violation in nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Gudkov, Vladimir, E-mail: gudkov@sc.edu; Song, Young-Ho [University of South Carolina, Department of Physics and Astronomy (United States)

    2013-03-15

    Time reversal invariance violating (TRIV) effects in low energy physics could be very important in searching for new physics, being complementary to neutron and atomic electric dipole moment (EDM) measurements. In this relation, we discuss a sensitivity of some TRIV observables to different models of time-reversal (CP) violation and their dependencies on nuclear structure. As a measure of a sensitivity of TRIV effects to the value of TRIV nucleon coupling constant, we introduce a coefficient of a 'discovery potential', which shows a possible factor for improving the current limits of the EDM experiments by measuring nuclear TRIV effects.

  3. Analysis of Chemical Constituents of Melastoma dodecandrum Lour. by UPLC-ESI-Q-Exactive Focus-MS/MS

    Directory of Open Access Journals (Sweden)

    Jinfeng Wang

    2017-03-01

    Full Text Available The ethnic drug Melastoma dodecandrum Lour. (MDL is widely distributed throughout South China, and is the major component of Gong Yan Ping Tablets/Capsules and Zi Di Ning Xue San. Although the pharmacological effects of MDL have been well documented, its chemical profile has not been fully determined. In this study, we have developed a rapid and sensitive UPLC-ESI-Q-Exactive Focus-MS/MS method to characterize the chemical constituents of MDL in the positive and negative ionization modes. A comparison of the chromatographic and spectrometric data obtained using this method with data from databases, the literature and reference standards allowed us to identify or tentatively characterize 109 compounds, including 26 fatty acids, 26 organic acids, 33 flavonoids, six tannins, 10 triterpenoids, two steroids and six other compounds. Notably, 55 of the compounds characterized in this study have never been detected before in this plant. The information obtained in this study therefore enriches our understanding of the chemical composition of MDL and could be used in quality control, pharmacological research and the development of drugs based on MDL. In addition, this study represents the first reported comprehensive analysis of the chemical constituents of MDL.

  4. Non-Abelian parafermions in time-reversal-invariant interacting helical systems

    Science.gov (United States)

    Orth, Christoph P.; Tiwari, Rakesh P.; Meng, Tobias; Schmidt, Thomas L.

    2015-02-01

    The interplay between bulk spin-orbit coupling and electron-electron interactions produces umklapp scattering in the helical edge states of a two-dimensional topological insulator. If the chemical potential is at the Dirac point, umklapp scattering can open a gap in the edge state spectrum even if the system is time-reversal invariant. We determine the zero-energy bound states at the interfaces between a section of a helical liquid which is gapped out by the superconducting proximity effect and a section gapped out by umklapp scattering. We show that these interfaces pin charges which are multiples of e /2 , giving rise to a Josephson current with 8 π periodicity. Moreover, the bound states, which are protected by time-reversal symmetry, are fourfold degenerate and can be described as Z4 parafermions. We determine their braiding statistics and show how braiding can be implemented in topological insulator systems.

  5. Test of feasibility of a novel high precision test of time reversal invariance

    International Nuclear Information System (INIS)

    Samuel, Deepak

    2007-01-01

    The first results of a feasibility test of a novel high precision test of time reversal invariance are reported. The Time Reversal Invariance test at COSY (TRIC) was planned to measure the time reversal violating observable A y,xz with an accuracy of 10 -6 in proton-deuteron (p-d) scattering. A novel technique for measuring total cross sections is introduced and the achievable precision of this measuring technique is tested. The correlation coefficient A y,y in p-d scattering fakes a time-reversal violating effect. This work reports the feasibility test of the novel method in the measurement of A y,y in p-p scattering. The first step in the experimental design was the development of a hard real-time data acquisition system. To meet stringent latency requirements, the capabilities of Windows XP had to be augmented with a real-time subsystem. The remote control feature of the data acquisition enables users to operate it from any place via an internet connection. The data acquisition proved its reliability in several beam times without any failures. The analysis of the data showed the presence of 1/f noise which substantially limits the quality of our measurements. The origin of 1/f noise was traced and found to be the Barkhausen noise from the ferrite core of the beam current transformer (BCT). A global weighted fitting technique based on a modified Wiener-Khinchin method was developed and used to suppress the influence of 1/f noise, which increased the error bar of the results by a factor 3. This is the only deviation from our expectations. The results are presented and discussed. (orig.)

  6. Test of feasibility of a novel high precision test of time reversal invariance

    Energy Technology Data Exchange (ETDEWEB)

    Samuel, Deepak

    2007-07-01

    The first results of a feasibility test of a novel high precision test of time reversal invariance are reported. The Time Reversal Invariance test at COSY (TRIC) was planned to measure the time reversal violating observable A{sub y,xz} with an accuracy of 10{sup -6} in proton-deuteron (p-d) scattering. A novel technique for measuring total cross sections is introduced and the achievable precision of this measuring technique is tested. The correlation coefficient A{sub y,y} in p-d scattering fakes a time-reversal violating effect. This work reports the feasibility test of the novel method in the measurement of A{sub y,y} in p-p scattering. The first step in the experimental design was the development of a hard real-time data acquisition system. To meet stringent latency requirements, the capabilities of Windows XP had to be augmented with a real-time subsystem. The remote control feature of the data acquisition enables users to operate it from any place via an internet connection. The data acquisition proved its reliability in several beam times without any failures. The analysis of the data showed the presence of 1/f noise which substantially limits the quality of our measurements. The origin of 1/f noise was traced and found to be the Barkhausen noise from the ferrite core of the beam current transformer (BCT). A global weighted fitting technique based on a modified Wiener-Khinchin method was developed and used to suppress the influence of 1/f noise, which increased the error bar of the results by a factor 3. This is the only deviation from our expectations. The results are presented and discussed. (orig.)

  7. Simulation of Ultrasonic Beam Focusing on a Defect in Anisotropic, Inhomogeneous Media

    International Nuclear Information System (INIS)

    Jeong, Hyun Jo; Cho, Sung Jong; Erdenetuya, Sharaa; Jung, Duck Yong

    2011-01-01

    In ultrasonic testing of dissimilar metal welds, application of phased array technique in terms of incident beam focusing is not easy because of complicated material structures formed during the multi-pass welding process. Time reversal(TR) techniques can overcome some limitations of phased array since they are self-focusing that does not depend on the geometrical and physical properties of testing components. In this paper, we test the possibility of TR focusing on a defect within anisotropic, heterogeneous austenitic welds. A commercial simulation software is employed for TR focusing and imaging of a side-drilled hole. The performance of time reversed adaptive focal law is compared with those of calculated focal laws for both anisotropic and isotropic welds

  8. Dissociation between exact and approximate addition in developmental dyslexia.

    Science.gov (United States)

    Yang, Xiujie; Meng, Xiangzhi

    2016-09-01

    Previous research has suggested that number sense and language are involved in number representation and calculation, in which number sense supports approximate arithmetic, and language permits exact enumeration and calculation. Meanwhile, individuals with dyslexia have a core deficit in phonological processing. Based on these findings, we thus hypothesized that children with dyslexia may exhibit exact calculation impairment while doing mental arithmetic. The reaction time and accuracy while doing exact and approximate addition with symbolic Arabic digits and non-symbolic visual arrays of dots were compared between typically developing children and children with dyslexia. Reaction time analyses did not reveal any differences across two groups of children, the accuracies, interestingly, revealed a distinction of approximation and exact addition across two groups of children. Specifically, two groups of children had no differences in approximation. Children with dyslexia, however, had significantly lower accuracy in exact addition in both symbolic and non-symbolic tasks than that of typically developing children. Moreover, linguistic performances were selectively associated with exact calculation across individuals. These results suggested that children with dyslexia have a mental arithmetic deficit specifically in the realm of exact calculation, while their approximation ability is relatively intact. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Some factors affecting time reversal signal reconstruction

    Czech Academy of Sciences Publication Activity Database

    Převorovský, Zdeněk; Kober, Jan

    2015-01-01

    Roč. 70, September (2015), s. 604-608 ISSN 1875-3892. [ICU International Congress on Ultrasonics 2015. Metz, 10.05.2015-15.05.2015] Institutional support: RVO:61388998 Keywords : nondestructive testing * time reversal signal processing * ultrasonic source reconstruction * acoustic emission * coda wave interferometry Subject RIV: BI - Acoustic s http://ac.els-cdn.com/S1875389215007762/1-s2.0-S1875389215007762-main.pdf?_tid=1513a4a2-9e5b-11e5-9693-00000aab0f27&acdnat=1449655153_455a4e32a1135236d0796c3f973ff58e

  10. Experimental study of time-reversal invariance in neutron-nucleus interactions

    International Nuclear Information System (INIS)

    Shaparov, E.I.; Shimizu, H.M.

    1996-01-01

    Experimental approaches for the test of time-reversal invariance in neutron-nucleus interactions are reviewed. Possible transmission experiments with polarized neutron beams and polarized or aligned targets are discussed as well as neutron capture experiments with unpolarized resonance neutrons. 102 refs., 13 figs., 3 tabs

  11. Exact Optimum Design of Segmented Thermoelectric Generators

    Directory of Open Access Journals (Sweden)

    M. Zare

    2016-01-01

    Full Text Available A considerable difference between experimental and theoretical results has been observed in the studies of segmented thermoelectric generators (STEGs. Because of simplicity, the approximate methods are widely used for design and optimization of the STEGs. This study is focused on employment of exact method for design and optimization of STEGs and comparison of exact and approximate results. Thus, using new highly efficient thermoelectric materials, four STEGs are proposed to operate in the temperature range of 300 to 1300 kelvins. The proposed STEGs are optimally designed to achieve maximum efficiency. Design and performance characteristics of the optimized generators including maximum conversion efficiency and length of elements are calculated through both exact and approximate methods. The comparison indicates that the approximate method can cause a difference up to 20% in calculation of some design characteristics despite its appropriate results in efficiency calculation. The results also show that the maximum theoretical efficiency of 23.08% is achievable using the new proposed STEGs. Compatibility factor of the selected materials for the proposed STEGs is also calculated using both exact and approximate methods. The comparison indicates a negligible difference in calculation of compatibility factor, despite the considerable difference in calculation of reduced efficiency (temperature independence efficiency.

  12. Time Reversal Migration for Passive Sources Using a Maximum Variance Imaging Condition

    KAUST Repository

    Wang, H.; Alkhalifah, Tariq Ali

    2017-01-01

    The conventional time-reversal imaging approach for micro-seismic or passive source location is based on focusing the back-propagated wavefields from each recorded trace in a source image. It suffers from strong background noise and limited acquisition aperture, which may create unexpected artifacts and cause error in the source location. To overcome such a problem, we propose a new imaging condition for microseismic imaging, which is based on comparing the amplitude variance in certain windows, and use it to suppress the artifacts as well as find the right location for passive sources. Instead of simply searching for the maximum energy point in the back-propagated wavefield, we calculate the amplitude variances over a window moving in both space and time axis to create a highly resolved passive event image. The variance operation has negligible cost compared with the forward/backward modeling operations, which reveals that the maximum variance imaging condition is efficient and effective. We test our approach numerically on a simple three-layer model and on a piece of the Marmousi model as well, both of which have shown reasonably good results.

  13. Time Reversal Migration for Passive Sources Using a Maximum Variance Imaging Condition

    KAUST Repository

    Wang, H.

    2017-05-26

    The conventional time-reversal imaging approach for micro-seismic or passive source location is based on focusing the back-propagated wavefields from each recorded trace in a source image. It suffers from strong background noise and limited acquisition aperture, which may create unexpected artifacts and cause error in the source location. To overcome such a problem, we propose a new imaging condition for microseismic imaging, which is based on comparing the amplitude variance in certain windows, and use it to suppress the artifacts as well as find the right location for passive sources. Instead of simply searching for the maximum energy point in the back-propagated wavefield, we calculate the amplitude variances over a window moving in both space and time axis to create a highly resolved passive event image. The variance operation has negligible cost compared with the forward/backward modeling operations, which reveals that the maximum variance imaging condition is efficient and effective. We test our approach numerically on a simple three-layer model and on a piece of the Marmousi model as well, both of which have shown reasonably good results.

  14. Monitoring of Pre-Load on Rock Bolt Using Piezoceramic-Transducer Enabled Time Reversal Method.

    Science.gov (United States)

    Huo, Linsheng; Wang, Bo; Chen, Dongdong; Song, Gangbing

    2017-10-27

    Rock bolts ensure structural stability for tunnels and many other underground structures. The pre-load on a rock bolt plays an important role in the structural reinforcement and it is vital to monitor the pre-load status of rock bolts. In this paper, a rock bolt pre-load monitoring method based on the piezoceramic enabled time reversal method is proposed. A lead zirconate titanate (PZT) patch transducer, which works as an actuator to generate stress waves, is bonded onto the anchor plate of the rock bolt. A smart washer, which is fabricated by sandwiching a PZT patch between two metal rings, is installed between the hex nut and the anchor plate along the rock bolt. The smart washer functions as a sensor to detect the stress wave. With the increase of the pre-load values on the rock bolt, the effective contact surface area between the smart washer and the anchor plate, benefiting the stress wave propagation crossing the contact surface. With the help of time reversal technique, experimental results reveal that the magnitude of focused signal clearly increases with the increase of the pre-load on a rock bolt before the saturation which happens beyond a relatively high value of the pre-load. The proposed method provides an innovative and real time means to monitor the pre-load level of a rock bolt. By employing this method, the pre-load degradation process on a rock bolt can be clearly monitored. Please note that, currently, the proposed method applies to only new rock bolts, on which it is possible to install the PZT smart washer.

  15. The Organization of Behavior Over Time: Insights from Mid-Session Reversal.

    Science.gov (United States)

    Rayburn-Reeves, Rebecca M; Cook, Robert G

    2016-01-01

    What are the mechanisms by which behavior is organized sequentially over time? The recently developed mid-session reversal (MSR) task offers new insights into this fundamental question. The typical MSR task is arranged to have a single reversed discrimination occurring in a consistent location within each session and across sessions. In this task, we examine the relevance of time, reinforcement, and other factors as the switching cue in the sequential modulation of control in MSR. New analyses also highlight some of the potential mechanisms underlying this serially organized behavior. MSR provides new evidence and we offer some ideas about how cues interact to compete for the control of behavior within and across sessions. We suggest that MSR is an excellent preparation for studying the competition among psychological states and their resolution toward action.

  16. Testing the causality of Hawkes processes with time reversal

    Science.gov (United States)

    Cordi, Marcus; Challet, Damien; Muni Toke, Ioane

    2018-03-01

    We show that univariate and symmetric multivariate Hawkes processes are only weakly causal: the true log-likelihoods of real and reversed event time vectors are almost equal, thus parameter estimation via maximum likelihood only weakly depends on the direction of the arrow of time. In ideal (synthetic) conditions, tests of goodness of parametric fit unambiguously reject backward event times, which implies that inferring kernels from time-symmetric quantities, such as the autocovariance of the event rate, only rarely produce statistically significant fits. Finally, we find that fitting financial data with many-parameter kernels may yield significant fits for both arrows of time for the same event time vector, sometimes favouring the backward time direction. This goes to show that a significant fit of Hawkes processes to real data with flexible kernels does not imply a definite arrow of time unless one tests it.

  17. Time reversal invariance - a test in free neutron decay

    Energy Technology Data Exchange (ETDEWEB)

    Lising, Laura Jean [Univ. of California, Berkeley, CA (United States)

    1999-01-01

    Time reversal invariance violation plays only a small role in the Standard Model, and the existence of a T-violating effect above the predicted level would be an indication of new physics. A sensitive probe of this symmetry in the weak interaction is the measurement of the T-violating ''D''-correlation in the decay of free neutrons. The triple-correlation Dσn∙pe x pv involves three kinematic variables, the neutron spin, electron momentu, and neutrino (or proton) momentum, and changes sign under time reversal. This experiment detects the decay products of a polarized cold neutron beam with an octagonal array of scintillation and solid-state detectors. Data from first run at NIST's Cold Neutron Research Facility give a D-coefficient of -0.1 ± 1.3(stat.) ± 0.7(syst) x 10-3 This measurement has the greatest bearing on extensions to the Standard model that incorporate leptoquarks, although exotic fermion and lift-right symmetric models also allow a D as large as the present limit.

  18. Transmission mode acoustic time-reversal imaging for nondestructive evaluation

    Science.gov (United States)

    Lehman, Sean K.; Devaney, Anthony J.

    2002-11-01

    In previous ASA meetings and JASA papers, the extended and formalized theory of transmission mode time reversal in which the transceivers are noncoincident was presented. When combined with the subspace concepts of a generalized MUltiple SIgnal Classification (MUSIC) algorithm, this theory is used to form super-resolution images of scatterers buried in a medium. These techniques are now applied to ultrasonic nondestructive evaluation (NDE) of parts, and shallow subsurface seismic imaging. Results are presented of NDE experiments on metal and epoxy blocks using data collected from an adaptive ultrasonic array, that is, a ''time-reversal machine,'' at Lawrence Livermore National Laboratory. Also presented are the results of seismo-acoustic subsurface probing of buried hazardous waste pits at the Idaho National Engineering and Environmental Laboratory. [Work performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.] [Work supported in part by CenSSIS, the Center for Subsurface Sensing and Imaging Systems, under the Engineering Research Centers Program of the NSF (award number EEC-9986821) as well as from Air Force Contracts No. F41624-99-D6002 and No. F49620-99-C0013.

  19. A Baseline-Free Defect Imaging Technique in Plates Using Time Reversal of Lamb Waves

    International Nuclear Information System (INIS)

    Jeong, Hyunjo; Cho, Sungjong; Wei, Wei

    2011-01-01

    We present an analytical investigation for a baseline-free imaging of a defect in plate-like structures using the time-reversal of Lamb waves. We first consider the flexural wave (A 0 mode) propagation in a plate containing a defect, and reception and time reversal process of the output signal at the receiver. The received output signal is then composed of two parts: a directly propagated wave and a scattered wave from the defect. The time reversal of these waves recovers the original input signal, and produces two additional sidebands that contain the time-of-flight information on the defect location. One of the side-band signals is then extracted as a pure defect signal. A defect localization image is then constructed from a beamforming technique based on the time-frequency analysis of the side band signal for each transducer pair in a network of sensors. The simulation results show that the proposed scheme enables the accurate, baseline-free imaging of a defect. (fundamental areas of phenomenology(including applications))

  20. Sparse least-squares reverse time migration using seislets

    KAUST Repository

    Dutta, Gaurav

    2015-08-19

    We propose sparse least-squares reverse time migration (LSRTM) using seislets as a basis for the reflectivity distribution. This basis is used along with a dip-constrained preconditioner that emphasizes image updates only along prominent dips during the iterations. These dips can be estimated from the standard migration image or from the gradient using plane-wave destruction filters or structural tensors. Numerical tests on synthetic datasets demonstrate the benefits of this method for mitigation of aliasing artifacts and crosstalk noise in multisource least-squares migration.

  1. Comparison of Travel-Time and Amplitude Measurements for Deep-Focusing Time-Distance Helioseismology

    Science.gov (United States)

    Pourabdian, Majid; Fournier, Damien; Gizon, Laurent

    2018-04-01

    The purpose of deep-focusing time-distance helioseismology is to construct seismic measurements that have a high sensitivity to the physical conditions at a desired target point in the solar interior. With this technique, pairs of points on the solar surface are chosen such that acoustic ray paths intersect at this target (focus) point. Considering acoustic waves in a homogeneous medium, we compare travel-time and amplitude measurements extracted from the deep-focusing cross-covariance functions. Using a single-scattering approximation, we find that the spatial sensitivity of deep-focusing travel times to sound-speed perturbations is zero at the target location and maximum in a surrounding shell. This is unlike the deep-focusing amplitude measurements, which have maximum sensitivity at the target point. We compare the signal-to-noise ratio for travel-time and amplitude measurements for different types of sound-speed perturbations, under the assumption that noise is solely due to the random excitation of the waves. We find that, for highly localized perturbations in sound speed, the signal-to-noise ratio is higher for amplitude measurements than for travel-time measurements. We conclude that amplitude measurements are a useful complement to travel-time measurements in time-distance helioseismology.

  2. Reversible and non-reversible enlargement of cerebral spinal fluid spaces in anorexia nervosa

    International Nuclear Information System (INIS)

    Artmann, H.; Grau, H.; Adelmann, M.; Schleiffer, R.

    1985-01-01

    Brain CT studies of 35 patients with anoxia nervosa confirmed the observations of other authors: cerebral dystrophic changes correlate with weight loss and the reversibility of these changes also correlates with the normalization of body weight. Other corroborated facts are: the most numerous and most pronounced enlargements are of the cortical sulci and the interhemispheric fissure, moderate widening affects the ventricles and the rarest and most insignificant changes are those of the cerebellum. The reversibility of the changes showed a parallel to the extent of the changes themselves and to the duration of improvement of the body weight. The reversibility of the enlargement of the cortical sulci and of the distances between the frontal horns of the lateral ventricles was more often significant than that of the abnormal measurements of the cella media. This difference is based on minimal early acquired brain damage which occurs in 60% of our patients. This high incidence of early acquired minimal brain disease in patients with anorexia nervosa is here discussed as a nonspecific predisposing factor. Although there is no exact explanation of the etiology of the reversible enlargement of cerenral spinal fluid (CSF) spaces in anorexia nervosa, the changes resemble those in alcoholics. The mechanisms of brain changes in alcoholism, as shown experimentally, seem to us to throw light on the probable mechanism of reversible dystrophic brain changes in anorexia nervosa. (orig.)

  3. Reversible and non-reversible enlargement of cerebral spinal fluid spaces in anorexia nervosa

    Energy Technology Data Exchange (ETDEWEB)

    Artmann, H.; Grau, H.; Adelmann, M.; Schleiffer, R.

    1985-07-01

    Brain CT studies of 35 patients with anoxia nervosa confirmed the observations of other authors: cerebral dystrophic changes correlate with weight loss and the reversibility of these changes also correlates with the normalization of body weight. Other corroborated facts are: the most numerous and most pronounced enlargements are of the cortical sulci and the interhemispheric fissure, moderate widening affects the ventricles and the rarest and most insignificant changes are those of the cerebellum. The reversibility of the changes showed a parallel to the extent of the changes themselves and to the duration of improvement of the body weight. The reversibility of the enlargement of the cortical sulci and of the distances between the frontal horns of the lateral ventricles was more often significant than that of the abnormal measurements of the cella media. This difference is based on minimal early acquired brain damage which occurs in 60% of our patients. This high incidence of early acquired minimal brain disease in patients with anorexia nervosa is here discussed as a nonspecific predisposing factor. Although there is no exact explanation of the etiology of the reversible enlargement of cerenral spinal fluid (CSF) spaces in anorexia nervosa, the changes resemble those in alcoholics. The mechanisms of brain changes in alcoholism, as shown experimentally, seem to us to throw light on the probable mechanism of reversible dystrophic brain changes in anorexia nervosa.

  4. Exact folded-band chaotic oscillator.

    Science.gov (United States)

    Corron, Ned J; Blakely, Jonathan N

    2012-06-01

    An exactly solvable chaotic oscillator with folded-band dynamics is shown. The oscillator is a hybrid dynamical system containing a linear ordinary differential equation and a nonlinear switching condition. Bounded oscillations are provably chaotic, and successive waveform maxima yield a one-dimensional piecewise-linear return map with segments of both positive and negative slopes. Continuous-time dynamics exhibit a folded-band topology similar to Rössler's oscillator. An exact solution is written as a linear convolution of a fixed basis pulse and a discrete binary sequence, from which an equivalent symbolic dynamics is obtained. The folded-band topology is shown to be dependent on the symbol grammar.

  5. Robust and Reversible Audio Watermarking by Modifying Statistical Features in Time Domain

    Directory of Open Access Journals (Sweden)

    Shijun Xiang

    2017-01-01

    Full Text Available Robust and reversible watermarking is a potential technique in many sensitive applications, such as lossless audio or medical image systems. This paper presents a novel robust reversible audio watermarking method by modifying the statistic features in time domain in the way that the histogram of these statistical values is shifted for data hiding. Firstly, the original audio is divided into nonoverlapped equal-sized frames. In each frame, the use of three samples as a group generates a prediction error and a statistical feature value is calculated as the sum of all the prediction errors in the frame. The watermark bits are embedded into the frames by shifting the histogram of the statistical features. The watermark is reversible and robust to common signal processing operations. Experimental results have shown that the proposed method not only is reversible but also achieves satisfactory robustness to MP3 compression of 64 kbps and additive Gaussian noise of 35 dB.

  6. Reversibility of female sterilization.

    Science.gov (United States)

    Siegler, A M; Hulka, J; Peretz, A

    1985-04-01

    The discussion considers the current status of reversibility of sterilization in the US and describes clinical and experimental efforts for developing techniques designed for reversibility. It focuses on regret following sterilization, reversal potential of current sterilization techniques, patient selection, current reversal techniques, results of sterilization procedures, experimental approaches to reversal of current techniques of sterilization, and sterilization procedures devised for reversibility, in humans and in animals. Request is the 1st stage of reversal, but a request for sterilization reversal (SR) does not always mean regret for a decision made at the time. Frequently it is a wish to restore fertility because life circumstances have changed after a sterilization that was ppropriate at the time it was performed. Schwyhart and Kutner reviewed 22 studies published between 1949-69 in which they found that the percentage of patients regretting the procedure ranged from 1.3-15%. Requests for reversal remain low in most countries, but if sterilization becomes a more popular method of contraception, requests will also increase. The ideal operation considered as a reversaible method of sterilization should include an easy, reliable outpatient method of tubal occlusion with miniml risk or patient discomfort that subsequently could be reversed without the need for a major surgical intervention. Endoscopic methods have progressed toward the 1st objective. A recent search of the literature uncovered few series of SR of more than 50 cases. The 767 operations found were analyzed with regard to pregnancy outcome. The precent of live births varied from 74-78.8%, and the occurance of tubal pregnancies ranged from 1.7-6.5%. All of the confounding variables in patient selection and small numbers of reported procedures preclude any conclusion about the different techniques or the number of operations that give a surgeon a level of expertise. Few authors classify their

  7. A time reversal transmission approach for multi-user UWB communications

    DEFF Research Database (Denmark)

    Nguyen, Tuan Hung; Kovacs Z., Istvan; Eggers, Patrick

    2005-01-01

    In this paper we propose and evaluate the performance of the time reversal technique in impulse radio UWB communications. The evaluation was based on measured channel impulse responses in the UWB frequency band of 3 to 5 GHz of a 4x1 MISO system with both vertical and horizontal polarization at t...

  8. New results for time reversed symplectic dynamic systems and quadratic functionals

    Directory of Open Access Journals (Sweden)

    Roman Simon Hilscher

    2012-05-01

    Full Text Available In this paper, we examine time scale symplectic (or Hamiltonian systems and the associated quadratic functionals which contain a forward shift in the time variable. Such systems and functionals have a close connection to Jacobi systems for calculus of variations and optimal control problems on time scales. Our results, among which we consider the Reid roundabout theorem, generalize the corresponding classical theory for time reversed discrete symplectic systems, as well as they complete the recently developed theory of time scale symplectic systems.

  9. Two applications of time reversal mirrors: Seismic radio and seismic radar

    KAUST Repository

    Hanafy, Sherif M.; Schuster, Gerard T.

    2011-01-01

    Two seismic applications of time reversal mirrors (TRMs) are introduced and tested with field experiments. The first one is sending, receiving, and decoding coded messages similar to a radio except seismic waves are used. The second one is, similar

  10. Topological Field Theory of Time-Reversal Invariant Insulators

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Xiao-Liang; Hughes, Taylor; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-19

    We show that the fundamental time reversal invariant (TRI) insulator exists in 4 + 1 dimensions, where the effective field theory is described by the 4 + 1 dimensional Chern-Simons theory and the topological properties of the electronic structure is classified by the second Chern number. These topological properties are the natural generalizations of the time reversal breaking (TRB) quantum Hall insulator in 2 + 1 dimensions. The TRI quantum spin Hall insulator in 2 + 1 dimensions and the topological insulator in 3 + 1 dimension can be obtained as descendants from the fundamental TRI insulator in 4 + 1 dimensions through a dimensional reduction procedure. The effective topological field theory, and the Z{sub 2} topological classification for the TRI insulators in 2+1 and 3+1 dimensions are naturally obtained from this procedure. All physically measurable topological response functions of the TRI insulators are completely described by the effective topological field theory. Our effective topological field theory predicts a number of novel and measurable phenomena, the most striking of which is the topological magneto-electric effect, where an electric field generates a magnetic field in the same direction, with an universal constant of proportionality quantized in odd multiples of the fine structure constant {alpha} = e{sup 2}/hc. Finally, we present a general classification of all topological insulators in various dimensions, and describe them in terms of a unified topological Chern-Simons field theory in phase space.

  11. Reverse time migration of multiples for OBS data

    KAUST Repository

    Zhang, Dongliang

    2014-01-01

    Reverse time migration of multiples (RTMM) is applied to OBS data with sparse receiver spacing. RTMM for OBS data unlike a marine streamer acquisition is implemented in the common receiver gathers (CRG) and provides a wider and denser illumination for each CRG than the conventional RTM of primaries. Hence, while the the conventional RTM image contains strong aliasing artifacts due to a sparser receiver interval, the RTMM image suffers from this artifacts less. This benefit of RTMM is demonstrated with numerical test on the Marmousi model for sparsely sampled OBS data.

  12. Reverse time migration of multiples for OBS data

    KAUST Repository

    Zhang, Dongliang

    2014-08-05

    Reverse time migration of multiples (RTMM) is applied to OBS data with sparse receiver spacing. RTMM for OBS data unlike a marine streamer acquisition is implemented in the common receiver gathers (CRG) and provides a wider and denser illumination for each CRG than the conventional RTM of primaries. Hence, while the the conventional RTM image contains strong aliasing artifacts due to a sparser receiver interval, the RTMM image suffers from this artifacts less. This benefit of RTMM is demonstrated with numerical test on the Marmousi model for sparsely sampled OBS data.

  13. On the record process of time-reversible spectrally-negative Markov additive processes

    NARCIS (Netherlands)

    J. Ivanovs; M.R.H. Mandjes (Michel)

    2009-01-01

    htmlabstractWe study the record process of a spectrally-negative Markov additive process (MAP). Assuming time-reversibility, a number of key quantities can be given explicitly. It is shown how these key quantities can be used when analyzing the distribution of the all-time maximum attained by MAPs

  14. Time-resolved VUV spectroscopy in the EXTRAP-T2 reversed field pinch

    International Nuclear Information System (INIS)

    Hedqvist, A.; Rachlew-Kaellne, E.

    1998-01-01

    Time-resolved VUV spectroscopy has been used to investigate the effects of impurities in a reversed field pinch operating with a resistive shell. Results of electron temperature, impurity ion densities, particle confinement time and Z eff together with a description of the interpretation and the equipment are presented. (author)

  15. An exact and efficient first passage time algorithm for reaction–diffusion processes on a 2D-lattice

    International Nuclear Information System (INIS)

    Bezzola, Andri; Bales, Benjamin B.; Alkire, Richard C.; Petzold, Linda R.

    2014-01-01

    We present an exact and efficient algorithm for reaction–diffusion–nucleation processes on a 2D-lattice. The algorithm makes use of first passage time (FPT) to replace the computationally intensive simulation of diffusion hops in KMC by larger jumps when particles are far away from step-edges or other particles. Our approach computes exact probability distributions of jump times and target locations in a closed-form formula, based on the eigenvectors and eigenvalues of the corresponding 1D transition matrix, maintaining atomic-scale resolution of resulting shapes of deposit islands. We have applied our method to three different test cases of electrodeposition: pure diffusional aggregation for large ranges of diffusivity rates and for simulation domain sizes of up to 4096×4096 sites, the effect of diffusivity on island shapes and sizes in combination with a KMC edge diffusion, and the calculation of an exclusion zone in front of a step-edge, confirming statistical equivalence to standard KMC simulations. The algorithm achieves significant speedup compared to standard KMC for cases where particles diffuse over long distances before nucleating with other particles or being captured by larger islands

  16. An exact and efficient first passage time algorithm for reaction–diffusion processes on a 2D-lattice

    Energy Technology Data Exchange (ETDEWEB)

    Bezzola, Andri, E-mail: andri.bezzola@gmail.com [Mechanical Engineering Department, University of California, Santa Barbara, CA 93106 (United States); Bales, Benjamin B., E-mail: bbbales2@gmail.com [Mechanical Engineering Department, University of California, Santa Barbara, CA 93106 (United States); Alkire, Richard C., E-mail: r-alkire@uiuc.edu [Department of Chemical Engineering, University of Illinois, Urbana, IL 61801 (United States); Petzold, Linda R., E-mail: petzold@engineering.ucsb.edu [Mechanical Engineering Department and Computer Science Department, University of California, Santa Barbara, CA 93106 (United States)

    2014-01-01

    We present an exact and efficient algorithm for reaction–diffusion–nucleation processes on a 2D-lattice. The algorithm makes use of first passage time (FPT) to replace the computationally intensive simulation of diffusion hops in KMC by larger jumps when particles are far away from step-edges or other particles. Our approach computes exact probability distributions of jump times and target locations in a closed-form formula, based on the eigenvectors and eigenvalues of the corresponding 1D transition matrix, maintaining atomic-scale resolution of resulting shapes of deposit islands. We have applied our method to three different test cases of electrodeposition: pure diffusional aggregation for large ranges of diffusivity rates and for simulation domain sizes of up to 4096×4096 sites, the effect of diffusivity on island shapes and sizes in combination with a KMC edge diffusion, and the calculation of an exclusion zone in front of a step-edge, confirming statistical equivalence to standard KMC simulations. The algorithm achieves significant speedup compared to standard KMC for cases where particles diffuse over long distances before nucleating with other particles or being captured by larger islands.

  17. Quantum quenches to the attractive one-dimensional Bose gas: exact results

    Directory of Open Access Journals (Sweden)

    Lorenzo Piroli, Pasquale Calabrese, Fabian H. L. Essler

    2016-09-01

    Full Text Available We study quantum quenches to the one-dimensional Bose gas with attractive interactions in the case when the initial state is an ideal one-dimensional Bose condensate. We focus on properties of the stationary state reached at late times after the quench. This displays a finite density of multi-particle bound states, whose rapidity distribution is determined exactly by means of the quench action method. We discuss the relevance of the multi-particle bound states for the physical properties of the system, computing in particular the stationary value of the local pair correlation function $g_2$.

  18. Anisotropy signature in extended images from reverse-time migration

    KAUST Repository

    Sava, Paul

    2012-11-04

    Reverse-time migration can accurately image complex geologic structures in anisotropic media. Extended images at selected locations in the earth, i.e. at common-image-point gathers (CIPs), carry enough information to characterize the angle-dependent illumination and to provide measurements for migration velocity analysis. Furthermore, inaccurate anisotropy leaves a distinctive signature in CIPs, which can be used to evaluate anisotropy through techniques similar to the ones used in conventional wavefield tomography.

  19. Anisotropy signature in extended images from reverse-time migration

    KAUST Repository

    Sava, Paul; Alkhalifah, Tariq Ali

    2012-01-01

    Reverse-time migration can accurately image complex geologic structures in anisotropic media. Extended images at selected locations in the earth, i.e. at common-image-point gathers (CIPs), carry enough information to characterize the angle-dependent illumination and to provide measurements for migration velocity analysis. Furthermore, inaccurate anisotropy leaves a distinctive signature in CIPs, which can be used to evaluate anisotropy through techniques similar to the ones used in conventional wavefield tomography.

  20. Alteration of a motor learning rule under mirror-reversal transformation does not depend on the amplitude of visual error.

    Science.gov (United States)

    Kasuga, Shoko; Kurata, Makiko; Liu, Meigen; Ushiba, Junichi

    2015-05-01

    Human's sophisticated motor learning system paradoxically interferes with motor performance when visual information is mirror-reversed (MR), because normal movement error correction further aggravates the error. This error-increasing mechanism makes performing even a simple reaching task difficult, but is overcome by alterations in the error correction rule during the trials. To isolate factors that trigger learners to change the error correction rule, we manipulated the gain of visual angular errors when participants made arm-reaching movements with mirror-reversed visual feedback, and compared the rule alteration timing between groups with normal or reduced gain. Trial-by-trial changes in the visual angular error was tracked to explain the timing of the change in the error correction rule. Under both gain conditions, visual angular errors increased under the MR transformation, and suddenly decreased after 3-5 trials with increase. The increase became degressive at different amplitude between the two groups, nearly proportional to the visual gain. The findings suggest that the alteration of the error-correction rule is not dependent on the amplitude of visual angular errors, and possibly determined by the number of trials over which the errors increased or statistical property of the environment. The current results encourage future intensive studies focusing on the exact rule-change mechanism. Copyright © 2014 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.

  1. Rattleback dynamics and its reversal time of rotation

    Science.gov (United States)

    Kondo, Yoichiro; Nakanishi, Hiizu

    2017-06-01

    A rattleback is a rigid, semielliptic toy which exhibits unintuitive behavior; when it is spun in one direction, it soon begins pitching and stops spinning, then it starts to spin in the opposite direction, but in the other direction, it seems to spin just steadily. This puzzling behavior results from the slight misalignment between the principal axes for the inertia and those for the curvature; the misalignment couples the spinning with the pitching and the rolling oscillations. It has been shown that under the no-slip condition and without dissipation the spin can reverse in both directions, and Garcia and Hubbard obtained the formula for the time required for the spin reversal tr [Proc. R. Soc. Lond. A 418, 165 (1988), 10.1098/rspa.1988.0078]. In this work, we reformulate the rattleback dynamics in a physically transparent way and reduce it to a three-variable dynamics for spinning, pitching, and rolling. We obtain an expression of the Garcia-Hubbard formula for tr by a simple product of four factors: (1) the misalignment angle, (2) the difference in the inverses of inertia moment for the two oscillations, (3) that in the radii for the two principal curvatures, and (4) the squared frequency of the oscillation. We perform extensive numerical simulations to examine validity and limitation of the formula, and find that (1) the Garcia-Hubbard formula is good for both spinning directions in the small spin and small oscillation regime, but (2) in the fast spin regime especially for the steady direction, the rattleback may not reverse and shows a rich variety of dynamics including steady spinning, spin wobbling, and chaotic behavior reminiscent of chaos in a dissipative system.

  2. Differential geometric invariants for time-reversal symmetric Bloch-bundles: The “Real” case

    International Nuclear Information System (INIS)

    De Nittis, Giuseppe; Gomi, Kiyonori

    2016-01-01

    Topological quantum systems subjected to an even (resp. odd) time-reversal symmetry can be classified by looking at the related “Real” (resp. “Quaternionic”) Bloch-bundles. If from one side the topological classification of these time-reversal vector bundle theories has been completely described in De Nittis and Gomi [J. Geom. Phys. 86, 303–338 (2014)] for the “Real” case and in De Nittis and Gomi [Commun. Math. Phys. 339, 1–55 (2015)] for the “Quaternionic” case, from the other side it seems that a classification in terms of differential geometric invariants is still missing in the literature. With this article and its companion [G. De Nittis and K. Gomi (unpublished)] we want to cover this gap. More precisely, we extend in an equivariant way the theory of connections on principal bundles and vector bundles endowed with a time-reversal symmetry. In the “Real” case we generalize the Chern-Weil theory and we show that the assignment of a “Real” connection, along with the related differential Chern class and its holonomy, suffices for the classification of “Real” vector bundles in low dimensions.

  3. Majorana bound states in two-channel time-reversal-symmetric nanowire systems

    DEFF Research Database (Denmark)

    Gaidamauskas, Erikas; Paaske, Jens; Flensberg, Karsten

    2014-01-01

    We consider time-reversal-symmetric two-channel semiconducting quantum wires proximity coupled to a conventional s-wave superconductor. We analyze the requirements for a non-trivial topological phase, and find that necessary conditions are 1) the determinant of the pairing matrix in channel space...

  4. Deformation effect and five-fold correlation time reversal test in neutron resonances using aligned 165Ho

    International Nuclear Information System (INIS)

    Huffman, P.R.; Roberson, N.R.; Gould, C.R.; Haase, D.G.

    1993-01-01

    In 1988, Bunakov proposed a test of parity (P) even time reversal (T) violation in the neighborhood of two interfering p-wave resonances of the same spin. A similar enhancement exists if a d-wave and s-wave resonance interfere. Until now, however, no suitable resonances have been located in nuclei which can be aligned, and the only tests of time reversal violation in neutron transmission have been carried out with MeV-energy neutrons. The authors estimate the deformation effect cross sections for neutron resonances in aligned 165 Ho, and estimate the sensitivity of a five-fold correlation time reversal test carried out on a resonance that exhibits a deformation effect

  5. Time reversal odd fragmentation functions in semi-inclusive deep inelastic lepton-hadron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Mulders, P.J. [National Inst. for Nuclear Physics and High Energy Physics, Amsterdam (Netherlands); Levelt, J. [Univ. of Erlangen-Nuernberg (Germany)

    1994-04-01

    In semi-inclusive scattering of polarized leptons from unpolarized hadrons, one can measure a time reversal odd structure function. It shows up as a sin({phi}) asymmetry of the produced hadrons. This asymmetry can be expressed as the product of a twist-three {open_quotes}hadron {r_arrow} quark{close_quotes} profile function and a time reversal odd twist-two {open_quotes}quark {r_arrow} hadron{close_quotes} fragmentation function. This fragmentation function can only be measured for nonzero transverse momenta of the produced hadron. Its appearance is a consequence of final state interactions between the produced hadron and the rest of the final state.

  6. Time-resolved VUV spectroscopy in the EXTRAP-T2 reversed field pinch

    Science.gov (United States)

    Hedqvist, Anders; Rachlew-Källne, Elisabeth

    1998-09-01

    Time-resolved VUV spectroscopy has been used to investigate the effects of impurities in a reversed field pinch operating with a resistive shell. Results of electron temperature, impurity ion densities, particle confinement time and 0741-3335/40/9/004/img1 together with a description of the interpretation and the equipment are presented.

  7. Benchmarking time-dependent renormalized natural orbital theory with exact solutions for a laser-driven model helium atom

    Energy Technology Data Exchange (ETDEWEB)

    Brics, Martins

    2016-12-09

    -called renormalized natural orbitals (RNOs), TDRNOT is benchmarked with the help of a numerically exactly solvable model helium atom in laser fields. In the special case of time-dependent two-electron systems the two-particle density matrix in terms of ONs and NOs is known exactly. Hence, in this case TDRNOT is exact, apart from the unavoidable truncation of the number of RNOs per particle taken into account in the simulation. It is shown that, unlike TDDFT, TDRNOT is able to describe doubly-excited states, Fano profiles in electron and absorption spectra, auto-ionization, Rabi oscillations, high harmonic generation, non-sequential ionization, and single-photon double ionization in excellent agreement with the corresponding TDSE results.

  8. Benchmarking time-dependent renormalized natural orbital theory with exact solutions for a laser-driven model helium atom

    International Nuclear Information System (INIS)

    Brics, Martins

    2016-01-01

    -called renormalized natural orbitals (RNOs), TDRNOT is benchmarked with the help of a numerically exactly solvable model helium atom in laser fields. In the special case of time-dependent two-electron systems the two-particle density matrix in terms of ONs and NOs is known exactly. Hence, in this case TDRNOT is exact, apart from the unavoidable truncation of the number of RNOs per particle taken into account in the simulation. It is shown that, unlike TDDFT, TDRNOT is able to describe doubly-excited states, Fano profiles in electron and absorption spectra, auto-ionization, Rabi oscillations, high harmonic generation, non-sequential ionization, and single-photon double ionization in excellent agreement with the corresponding TDSE results.

  9. Reverse Algols

    Science.gov (United States)

    Leung, K. C.

    1989-01-01

    Reverse Algols, binary systems with a semidetached configuration in which the more massive component is in contact with the critical equipotential surface, are examined. Observational evidence for reverse Algols is presented and the parameters of seven reverse Algols are listed. The evolution of Algols and reverse Algols is discussed. It is suggested that, because reverse Algols represent the premass-reversal semidetached phase of close binary evolution, the evolutionary time scale between regular and reverse Algols is the ratio of the number of confirmed systems of these two Algol types.

  10. Time reversal mirror and perfect inverse filter in a microscopic model for sound propagation

    International Nuclear Information System (INIS)

    Calvo, Hernan L.; Danieli, Ernesto P.; Pastawski, Horacio M.

    2007-01-01

    Time reversal of quantum dynamics can be achieved by a global change of the Hamiltonian sign (a hasty Loschmidt daemon), as in the Loschmidt Echo experiments in NMR, or by a local but persistent procedure (a stubborn daemon) as in the time reversal mirror (TRM) used in ultrasound acoustics. While the first is limited by chaos and disorder, the last procedure seems to benefit from it. As a first step to quantify such stability we develop a procedure, the perfect inverse filter (PIF), that accounts for memory effects, and we apply it to a system of coupled oscillators. In order to ensure a numerical many-body dynamics intrinsically reversible, we develop an algorithm, the pair partitioning, based on the Trotter strategy used for quantum dynamics. We analyze situations where the PIF gives substantial improvements over the TRM

  11. Precise discussion of time-reversal asymmetries in B-meson decays

    International Nuclear Information System (INIS)

    Morozumi, Takuya; Okane, Hideaki; Umeeda, Hiroyuki

    2015-01-01

    BaBar collaboration announced that they observed time reversal (T) asymmetry through B meson system. In the experiment, time dependencies of two distinctive processes, B_−→ (B"0)-bar and (B"0)-bar →B_− (− expresses CP value) are compared with each other. In our study, we examine event number difference of these two processes. In contrast to the BaBar asymmetry, the asymmetry of events number includes the overall normalization difference for rates. Time dependence of the asymmetry is more general and it includes terms absent in one used by BaBar collaboration. Both of the BaBar asymmetry and ours are naively thought to be T-odd since two processes compared are related with flipping time direction. We investigate the time reversal transformation property of our asymmetry. Using our notation, one can see that the asymmetry is not precisely a T-odd quantity, taking into account indirect CP and CPT violation of K meson systems. The effect of ϵ_K is extracted and gives rise to O(10"−"3) contribution. The introduced parameters are invariant under rephasing of quarks so that the coefficients of our asymmetry are expressed as phase convention independent quantities. Some combinations of the asymmetry enable us to extract parameters for wrong sign decays of B_d meson, CPT violation, etc. We also study the reason why the T-even terms are allowed to contribute to the asymmetry, and find that several conditions are needed for the asymmetry to be a T-odd quantity.

  12. Generation of an incident focused light pulse in FDTD.

    Science.gov (United States)

    Capoğlu, Ilker R; Taflove, Allen; Backman, Vadim

    2008-11-10

    A straightforward procedure is described for accurately creating an incident focused light pulse in the 3-D finite-difference time-domain (FDTD) electromagnetic simulation of the image space of an aplanatic converging lens. In this procedure, the focused light pulse is approximated by a finite sum of plane waves, and each plane wave is introduced into the FDTD simulation grid using the total-field/scattered-field (TF/SF) approach. The accuracy of our results is demonstrated by comparison with exact theoretical formulas.

  13. Exact Repetition as Input Enhancement in Second Language Acquisition.

    Science.gov (United States)

    Jensen, Eva Dam; Vinther, Thora

    2003-01-01

    Reports on two studies on input enhancement used to support learners' selection of focus of attention in Spanish second language listening material. Input consisted of video recordings of dialogues between native speakers. Exact repetition and speech rate reduction were examined for effect on comprehension, acquisition of decoding strategies, and…

  14. Least-squares reverse time migration of marine data with frequency-selection encoding

    KAUST Repository

    Dai, Wei; Huang, Yunsong; Schuster, Gerard T.

    2013-01-01

    The phase-encoding technique can sometimes increase the efficiency of the least-squares reverse time migration (LSRTM) by more than one order of magnitude. However, traditional random encoding functions require all the encoded shots to share

  15. Polar Kerr effect studies of time reversal symmetry breaking states in heavy fermion superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Schemm, E.R., E-mail: eschemm@alumni.stanford.edu [Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305 (United States); Levenson-Falk, E.M. [Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305 (United States); Department of Physics, Stanford University, Stanford, CA 94305 (United States); Kapitulnik, A. [Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305 (United States); Department of Physics, Stanford University, Stanford, CA 94305 (United States); Department of Applied Physics, Stanford University, Stanford, CA 94305 (United States); Stanford Institute of Energy and Materials Science, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States)

    2017-04-15

    Highlights: • Polar Kerr effect (PKE) probes broken time-reversal symmetry (TRS) in superconductors. • Absence of PKE below Tc in CeCoIn{sub 5} is consistent with dx2-y2 order parameter symmetry. • PKE in the B phase of the multiphase superconductor UPt3 agrees with an E2u model. • Data on URu2Si2 show broken TRS and additional structure in the superconducting state. - Abstract: The connection between chiral superconductivity and topological order has emerged as an active direction in research as more instances of both have been identified in condensed matter systems. With the notable exception of {sup 3}He-B, all of the known or suspected chiral – that is to say time-reversal symmetry-breaking (TRSB) – superfluids arise in heavy fermion superconductors, although the vast majority of heavy fermion superconductors preserve time-reversal symmetry. Here we review recent experimental efforts to identify TRSB states in heavy fermion systems via measurement of polar Kerr effect, which is a direct consequence of TRSB.

  16. Exact solution of nonsteady thermal boundary layer equation

    International Nuclear Information System (INIS)

    Dorfman, A.S.

    1995-01-01

    There are only a few exact solutions of the thermal boundary layer equation. Most of them are derived for a specific surface temperature distribution. The first exact solution of the steady-state boundary layer equation was given for a plate with constant surface temperature and free-stream velocity. The same problem for a plate with polynomial surface temperature distribution was solved by Chapmen and Rubesin. Levy gave the exact solution for the case of a power law distribution of both surface temperature and free-stream velocity. The exact solution of the steady-state boundary layer equation for an arbitrary surface temperature and a power law free-stream velocity distribution was given by the author in two forms: of series and of the integral with an influence function of unheated zone. A similar solution of the nonsteady thermal boundary layer equation for an arbitrary surface temperature and a power law free-stream velocity distribution is presented here. In this case, the coefficients of series depend on time, and in the limit t → ∞ they become the constant coefficients of a similar solution published before. This solution, unlike the one presented here, does not satisfy the initial conditions at t = 0, and, hence, can be used only in time after the beginning of the process. The solution in the form of a series becomes a closed-form exact solution for polynomial surface temperature and a power law free-stream velocity distribution. 7 refs., 2 figs

  17. A BEHAVIORAL-APPROACH TO LINEAR EXACT MODELING

    NARCIS (Netherlands)

    ANTOULAS, AC; WILLEMS, JC

    1993-01-01

    The behavioral approach to system theory provides a parameter-free framework for the study of the general problem of linear exact modeling and recursive modeling. The main contribution of this paper is the solution of the (continuous-time) polynomial-exponential time series modeling problem. Both

  18. Effective Lagrangians and parity-conserving time-reversal violation at low energies

    International Nuclear Information System (INIS)

    Engel, J.; Frampton, P.H.; Springer, R.P.

    1996-01-01

    Using effective Lagrangians, we argue that any time-reversal-violating but parity-conserving effects are too small to be observed in flavor-conserving nuclear processes without dramatic improvement in experimental accuracy. In the process we discuss other arguments that have appeared in the literature. copyright 1996 The American Physical Society

  19. The asymptotic and exact Fisher information matrices of a vector ARMA process

    NARCIS (Netherlands)

    Klein, A.; Melard, G.; Saidi, A.

    2008-01-01

    The exact Fisher information matrix of a Gaussian vector autoregressive-moving average (VARMA) process has been considered for a time series of length N in relation to the exact maximum likelihood estimation method. In this paper it is shown that the Gaussian exact Fisher information matrix

  20. Dissipative motion perturbation theory and exact solutions

    International Nuclear Information System (INIS)

    Lodder, J.J.

    1976-06-01

    Dissipative motion of classical and quantum systems is described. In particular, attention is paid to systems coupled to the radiation field. A dissipative equation of motion for a particle in an arbitrary potential coupled to the radiation field is derived by means of perturbation theory. The usual divrgencies associated with the radiation field are eliminated by the application of a theory of generalized functions. This theory is developed as a subject in its own right and is presented independently. The introduction of classical zero-point energy makes the classical equa tion of motion for the phase density formally the same as its quantum counterpart. In particular, it is shown that the classical zero-point energy prevents the collapse of a classical H-atom and gives rise to a classical ground state. For systems with a quadratic Hamiltoian, the equation of motion can be solved exactly, even in the continuum limit for the radiation field, by means of the new generalized functions. Classically, the Fokker-Planck equation is found without any approximations, and quantum mechanically, the only approximation is the neglect of the change in the ground state caused by the interaction. The derivation is valid even for strong damping and arbitrarily short times. There is no transient time. For harmonic oscillators complete equivalence is shown to exist between quantum mechanics and classical mechanics with zero-point energy. A discussion of the derivation of the Pauli equation is given and perturbation theory is compared with the exact derivation. The exactly solvable models are used to calculate the Langevin force of the radiation field. The result is that the classical Langevin force is exactly delta-correlated, while the quantum Langevin force is not delta-correlated at all. The fluctuation-dissipation theorem is shown to be an exact consequence of the solution to the equations of motion

  1. Incorporation of exact boundary conditions into a discontinuous galerkin finite element method for accurately solving 2d time-dependent maxwell equations

    KAUST Repository

    Sirenko, Kostyantyn; Liu, Meilin; Bagci, Hakan

    2013-01-01

    A scheme that discretizes exact absorbing boundary conditions (EACs) to incorporate them into a time-domain discontinuous Galerkin finite element method (TD-DG-FEM) is described. The proposed TD-DG-FEM with EACs is used for accurately characterizing

  2. Time reversal and the neutron

    International Nuclear Information System (INIS)

    Chupp, T. E.; Cooper, R. L.; Coulter, K. P.; Freedman, S. J.; Fujikawa, B. K.; Jones, G. L.; Garcia, A.; Mumm, H. P.; Nico, J. S.; Thompson, A. K.; Trull, C.; Wietfeldt, F. E.; Wilkerson, J. F.

    2013-01-01

    We have measured the triple correlation D n >/J n ·(β e x p-hat ν ) with a polarized cold-neutron beam (Mumm et al., Phys Rev Lett 107:102301, 2011; Chupp et al., Phys Rev C 86:035505, 2012). A non-zero value of D can arise due to parity-even-time-reversal-odd interactions that imply CP violation. Final-state effects also contribute to D at the level of 10  − 5 and can be calculated with precision of 1 % or better. The D coefficient is uniquely sensitive to the imaginary part of the ratio of axial-vector and vector beta-decay amplitudes as well as to scalar and tensor interactions that could arise due to beyond-Standard-Model physics. Over 300 million proton-electron coincidence events were used in a blind analysis with the result D = [ − 0.94±1.89 (stat)±0.97(sys)]×10  − 4 . Assuming only vector and axial vector interactions in beta decay, our result can be interpreted as a measure of the phase of the axial-vector coupling relative to the vector coupling, φ AV = 180.012 ° ± 0.028 °. This result also improves constrains on certain non-VA interactions.

  3. Time reversal and the neutron

    Energy Technology Data Exchange (ETDEWEB)

    Chupp, T. E., E-mail: chupp@umich.edu; Cooper, R. L.; Coulter, K. P. [Univeristy of Michigan (United States); Freedman, S. J.; Fujikawa, B. K. [University of California and Lawrence Berkeley Laboratory (United States); Jones, G. L. [Hamilton College (United States); Garcia, A. [University of Washington (United States); Mumm, H. P.; Nico, J. S.; Thompson, A. K. [National Institute of Standards and Technology (United States); Trull, C.; Wietfeldt, F. E. [Tulane University (United States); Wilkerson, J. F. [University of North Carolina (United States); Collaboration: emiT II Collaboration

    2013-03-15

    We have measured the triple correlation D/J{sub n}{center_dot}({beta}{sub e} x p-hat{sub {nu}}) with a polarized cold-neutron beam (Mumm et al., Phys Rev Lett 107:102301, 2011; Chupp et al., Phys Rev C 86:035505, 2012). A non-zero value of D can arise due to parity-even-time-reversal-odd interactions that imply CP violation. Final-state effects also contribute to D at the level of 10{sup - 5} and can be calculated with precision of 1 % or better. The D coefficient is uniquely sensitive to the imaginary part of the ratio of axial-vector and vector beta-decay amplitudes as well as to scalar and tensor interactions that could arise due to beyond-Standard-Model physics. Over 300 million proton-electron coincidence events were used in a blind analysis with the result D = [ - 0.94{+-}1.89 (stat){+-}0.97(sys)] Multiplication-Sign 10{sup - 4}. Assuming only vector and axial vector interactions in beta decay, our result can be interpreted as a measure of the phase of the axial-vector coupling relative to the vector coupling, {phi}{sub AV} = 180.012 Degree-Sign {+-} 0.028 Degree-Sign . This result also improves constrains on certain non-VA interactions.

  4. Time Reversal Acoustic Structural Health Monitoring Using Array of Embedded Sensors, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Time Reversal Acoustic (TRA) structural health monitoring with an embedded sensor array represents a new approach to in-situ nondestructive evaluation of air-space...

  5. Spatial filtering velocimetry revisited: exact short-time detecting schemes from arbitrarily small-size reticles

    International Nuclear Information System (INIS)

    Ando, S; Nara, T; Kurihara, T

    2014-01-01

    Spatial filtering velocimetry was proposed in 1963 by Ator as a velocity-sensing technique for aerial camera-control systems. The total intensity of a moving surface is observed through a set of parallel-slit reticles, resulting in a narrow-band temporal signal whose frequency is directly proportional to the image velocity. However, even despite its historical importance and inherent technical advantages, the mathematical formulation of this technique is only valid when infinite-length observation in both space and time is possible, which causes significant errors in most applications where a small receptive window and high resolution in both axes are desired. In this study, we apply a novel mathematical technique, the weighted integral method, to solve this problem, and obtain exact sensing schemes and algorithms for finite (arbitrarily small but non-zero) size reticles and short-time estimation. Practical considerations for utilizing these schemes are also explored both theoretically and experimentally. (paper)

  6. Exact boundary controllability of nodal profile for quasilinear hyperbolic systems

    CERN Document Server

    Li, Tatsien; Gu, Qilong

    2016-01-01

    This book provides a comprehensive overview of the exact boundary controllability of nodal profile, a new kind of exact boundary controllability stimulated by some practical applications. This kind of controllability is useful in practice as it does not require any precisely given final state to be attained at a suitable time t=T by means of boundary controls, instead it requires the state to exactly fit any given demand (profile) on one or more nodes after a suitable time t=T by means of boundary controls. In this book we present a general discussion of this kind of controllability for general 1-D first order quasilinear hyperbolic systems and for general 1-D quasilinear wave equations on an interval as well as on a tree-like network using a modular-structure construtive method, suggested in LI Tatsien's monograph "Controllability and Observability for Quasilinear Hyperbolic Systems"(2010), and we establish a complete theory on the local exact boundary controllability of nodal profile for 1-D quasilinear hyp...

  7. Reverse genetics with animal viruses. NSV reverse genetics

    International Nuclear Information System (INIS)

    Mebatsion, T.

    2005-01-01

    New strategies to genetically manipulate the genomes of several important animal pathogens have been established in recent years. This article focuses on the reverse genetics techniques, which enables genetic manipulation of the genomes of non-segmented negative-sense RNA viruses. Recovery of a negative-sense RNA virus entirely from cDNA was first achieved for rabies virus in 1994. Since then, reverse genetic systems have been established for several pathogens of medical and veterinary importance. Based on the reverse genetics technique, it is now possible to design safe and more effective live attenuated vaccines against important viral agents. In addition, genetically tagged recombinant viruses can be designed to facilitate serological differentiation of vaccinated animals from infected animals. The approach of delivering protective immunogens of different pathogens using a single vector was made possible with the introduction of the reverse genetics system, and these novel broad-spectrum vaccine vectors have potential applications in improving animal health in developing countries. (author)

  8. Exact Jacobians of Roe-type flux difference splitting of the equations of radiation hydrodynamics (and Euler equations) for use in time-implicit higher-order Godunov schemes

    International Nuclear Information System (INIS)

    Balsara, D.S.

    1999-01-01

    In this paper we analyze some of the numerical issues that are involved in making time-implicit higher-order Godunov schemes for the equations of radiation hydrodynamics (and the Euler or Navier-Stokes equations). This is done primarily with the intent of incorporating such methods in the author's RIEMANN code. After examining the issues it is shown that the construction of a time-implicit higher-order Godunov scheme for radiation hydrodynamics would be benefited by our ability to evaluate exact Jacobians of the numerical flux that is based on Roe-type flux difference splitting. In this paper we show that this can be done analytically in a form that is suitable for efficient computational implementation. It is also shown that when multiple fluid species are used or when multiple radiation frequencies are used the computational cost in the evaluation of the exact Jacobians scales linearly with the number of fluid species or the number of radiation frequencies. Connections are made to other types of numerical fluxes, especially those based on flux difference splittings. It is shown that the evaluation of the exact Jacobian for such numerical fluxes is also benefited by the present strategy and the results given here. It is, however, pointed out that time-implicit schemes that are based on the evaluation of the exact Jacobians for flux difference splittings using the methods developed here are both computationally more efficient and numerically more stable than corresponding time-implicit schemes that are based on the evaluation of the exact or approximate Jacobians for flux vector splittings. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  9. Spontaneous breaking of time-reversal symmetry in topological insulators

    Energy Technology Data Exchange (ETDEWEB)

    Karnaukhov, Igor N., E-mail: karnaui@yahoo.com

    2017-06-21

    Highlights: • Proposed a new approach for description of phase transitions in topological insulators. • Considered the mechanism of spontaneous breaking of time-reversal symmetry in topological insulators. • The Haldane model can be implemented in real compounds of the condensed matter physics. - Abstract: The system of spinless fermions on a hexagonal lattice is studied. We have considered tight-binding model with the hopping integrals between the nearest-neighbor and next-nearest-neighbor lattice sites, that depend on the direction of the link. The links are divided on three types depending on the direction, the hopping integrals are defined by different phases along the links. The energy of the system depends on the phase differences, the solutions for the phases, that correspond to the minimums of the energy, lead to a topological insulator state with the nontrivial Chern numbers. We have analyzed distinct topological states and phase transitions, the behavior of the chiral gapless edge modes, have defined the Chern numbers. The band structure of topological insulator (TI) is calculated, the ground-state phase diagram in the parameter space is obtained. We propose a novel mechanism of realization of TI, when the TI state is result of spontaneous breaking of time-reversal symmetry due to nontrivial stable solutions for the phases that determine the hopping integrals along the links and show that the Haldane model can be implemented in real compounds of the condensed matter physics.

  10. Splitting of the rate matrix as a definition of time reversal in master equation systems

    International Nuclear Information System (INIS)

    Liu Fei; Le, Hong

    2012-01-01

    Motivated by recent progress in nonequilibrium fluctuation relations, we present a generalized time reversal for stochastic master equation systems with discrete states, which is defined as a splitting of the rate matrix into irreversible and reversible parts. An immediate advantage of this definition is that a variety of fluctuation relations can be attributed to different matrix splittings. Additionally, we find that the accustomed total entropy production formula and conditions of the detailed balance must be modified appropriately to account for the reversible rate part, which was previously ignored. (paper)

  11. Measuring the spin Chern number in time-reversal-invariant Hofstadter optical lattices

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Dan-Wei, E-mail: zdanwei@126.com [Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, SPTE, South China Normal University, Guangzhou 510006 (China); Cao, Shuai, E-mail: shuaicao2004@163.com [Department of Applied Physics, College of Electronic Engineering, South China Agricultural University, Guangzhou 510642 China (China)

    2016-10-14

    We propose an experimental scheme to directly measure the spin Chern number of the time-reversal-invariant Hofstadter model in optical lattices. We first show that this model can be realized by using ultracold Fermi atoms with two pseudo-spin states encoded by the internal Zeeman states in a square optical lattice and the corresponding topological Bloch bands are characterized by the spin Chern number. We then propose and numerically demonstrate that this topological invariant can be extracted from the shift of the hybrid Wannier center in the optical lattice. By spin-resolved in situ detection of the atomic densities along the transverse direction combined with time-of-flight measurement along another spatial direction, the spin Chern number in this system is directly measured. - Highlights: • The cold-atom optical-lattice scheme for realizing the time-reversal-invariant Hofstadter model is proposed. • The intrinsic spin Chern number related to the hybrid Wannier center in the optical lattice is investigated. • Direct measurement of the spin Chern number in the proposed system is theoretically demonstrated.

  12. Exact Relativistic `Antigravity' Propulsion

    Science.gov (United States)

    Felber, Franklin S.

    2006-01-01

    The Schwarzschild solution is used to find the exact relativistic motion of a payload in the gravitational field of a mass moving with constant velocity. At radial approach or recession speeds faster than 3-1/2 times the speed of light, even a small mass gravitationally repels a payload. At relativistic speeds, a suitable mass can quickly propel a heavy payload from rest nearly to the speed of light with negligible stresses on the payload.

  13. Exact and Heuristic Algorithms for Runway Scheduling

    Science.gov (United States)

    Malik, Waqar A.; Jung, Yoon C.

    2016-01-01

    This paper explores the Single Runway Scheduling (SRS) problem with arrivals, departures, and crossing aircraft on the airport surface. Constraints for wake vortex separations, departure area navigation separations and departure time window restrictions are explicitly considered. The main objective of this research is to develop exact and heuristic based algorithms that can be used in real-time decision support tools for Air Traffic Control Tower (ATCT) controllers. The paper provides a multi-objective dynamic programming (DP) based algorithm that finds the exact solution to the SRS problem, but may prove unusable for application in real-time environment due to large computation times for moderate sized problems. We next propose a second algorithm that uses heuristics to restrict the search space for the DP based algorithm. A third algorithm based on a combination of insertion and local search (ILS) heuristics is then presented. Simulation conducted for the east side of Dallas/Fort Worth International Airport allows comparison of the three proposed algorithms and indicates that the ILS algorithm performs favorably in its ability to find efficient solutions and its computation times.

  14. Accelerating exact schedulability analysis for fixed-priority pre-emptive scheduling

    NARCIS (Netherlands)

    Hang, Y.; Jiale, Z.; Keskin, U.; Bril, R.J.

    2010-01-01

    The schedulability analysis for fixed-priority preemptive scheduling (FPPS) plays a significant role in the real-time systems domain. The so-called Hyperplanes Exact Test (HET) [1] is an example of an exact schedulability test for FPPS. In this paper, we aim at improving the efficiency of HET by

  15. Multiuser underwater acoustic communication using single-element virtual time reversal mirror

    Institute of Scientific and Technical Information of China (English)

    YIN JingWei; WANG YiLin; WANG Lei; HUI JunYing

    2009-01-01

    Pattern time delay shift coding (PDS) scheme is introduced and combined with spread spectrum tech-nique called SS-PDS for short which is power-saving and competent for long-range underwater acous-tic networks.Single-element virtual time reversal mirror (VTRM) is presented in this paper and validated by the lake trial results.Employing single-element VTRM in multiuser communication system based on SS-PDS can separate different users' information simultaneously at master node as indicated in the simulation results.

  16. New Limit on Time-Reversal Violation in Beta Decay

    International Nuclear Information System (INIS)

    Mumm, H. P.; Chupp, T. E.; Cooper, R. L.; Coulter, K. P.; Freedman, S. J.; Fujikawa, B. K.; Garcia, A.; Jones, G. L.; Nico, J. S.; Thompson, A. K.; Trull, C. A.; Wietfeldt, F. E.; Wilkerson, J. F.

    2011-01-01

    We report the results of an improved determination of the triple correlation DP·(p e xp v ) that can be used to limit possible time-reversal invariance in the beta decay of polarized neutrons and constrain extensions to the standard model. Our result is D=[-0.96±1.89(stat)±1.01(sys)]x10 -4 . The corresponding phase between g A and g V is φ AV =180.013 deg. ±0.028 deg. (68% confidence level). This result represents the most sensitive measurement of D in nuclear β decay.

  17. The nucleon electric dipole form factor from dimension-six time-reversal violation

    NARCIS (Netherlands)

    de Vries, J.; Mereghetti, E.; Timmermans, R. G. E.; van Kolck, U.

    2011-01-01

    We calculate the electric dipole form factor of the nucleon that arises as a low-energy manifestation of time-reversal violation in quark-gluon interactions of effective dimension 6: the quark electric and chromoelectric dipole moments, and the gluon chromoelectric dipole moment. We use the

  18. Time's arrow: A numerical experiment

    Science.gov (United States)

    Fowles, G. Richard

    1994-04-01

    The dependence of time's arrow on initial conditions is illustrated by a numerical example in which plane waves produced by an initial pressure pulse are followed as they are multiply reflected at internal interfaces of a layered medium. Wave interactions at interfaces are shown to be analogous to the retarded and advanced waves of point sources. The model is linear and the calculation is exact and demonstrably time reversible; nevertheless the results show most of the features expected of a macroscopically irreversible system, including the approach to the Maxwell-Boltzmann distribution, ergodicity, and concomitant entropy increase.

  19. Modeling L2,3-Edge X-ray Absorption Spectroscopy with Real-Time Exact Two-Component Relativistic Time-Dependent Density Functional Theory.

    Science.gov (United States)

    Kasper, Joseph M; Lestrange, Patrick J; Stetina, Torin F; Li, Xiaosong

    2018-04-10

    X-ray absorption spectroscopy is a powerful technique to probe local electronic and nuclear structure. There has been extensive theoretical work modeling K-edge spectra from first principles. However, modeling L-edge spectra directly with density functional theory poses a unique challenge requiring further study. Spin-orbit coupling must be included in the model, and a noncollinear density functional theory is required. Using the real-time exact two-component method, we are able to variationally include one-electron spin-orbit coupling terms when calculating the absorption spectrum. The abilities of different basis sets and density functionals to model spectra for both closed- and open-shell systems are investigated using SiCl 4 and three transition metal complexes, TiCl 4 , CrO 2 Cl 2 , and [FeCl 6 ] 3- . Although we are working in the real-time framework, individual molecular orbital transitions can still be recovered by projecting the density onto the ground state molecular orbital space and separating contributions to the time evolving dipole moment.

  20. Least-squares reverse time migration of marine data with frequency-selection encoding

    KAUST Repository

    Dai, Wei

    2013-08-20

    The phase-encoding technique can sometimes increase the efficiency of the least-squares reverse time migration (LSRTM) by more than one order of magnitude. However, traditional random encoding functions require all the encoded shots to share the same receiver locations, thus limiting the usage to seismic surveys with a fixed spread geometry. We implement a frequency-selection encoding strategy that accommodates data with a marine streamer geometry. The encoding functions are delta functions in the frequency domain, so that all the en- coded shots have unique non-overlapping frequency content, and the receivers can distinguish the wavefield from each shot with a unique frequency band. Since the encoding functions are orthogonal to each other, there will be no crosstalk between different shots during modeling and migration. With the frequency-selection encoding method, the computational efficiency of LSRTM is increased so that its cost is compara- ble to conventional RTM for both the Marmousi2 model and a marine data set recorded in the Gulf of Mexico. With more iterations, the LSRTM image quality is further improved. We conclude that LSRTM with frequency-selection is an efficient migration method that can sometimes produce more focused images than conventional RTM.

  1. Canonical transformations and exact invariants for dissipative systems

    International Nuclear Information System (INIS)

    Pedrosa, I.A.

    1986-01-01

    A simple treatment to the problem of finding exact invariants and related auxiliary equations for time-dependent oscillators with friction is presented. The treatment is based on the use of a time-dependent canonical transformation and an auxiliary transformation. (Author) [pt

  2. The time-reversal- and parity-violating nuclear potential in chiral effective theory

    NARCIS (Netherlands)

    Maekawa, C. M.; Mereghetti, E.; de Vries, J.; van Kolck, U.

    2011-01-01

    We derive the parity- and time-reversal-violating nuclear interactions stemming from the QCD (theta) over bar term and quark/gluon operators of effective dimension 6: quark electric dipole moments, quark and gluon chromo-electric dipole moments, and two four-quark operators. We work in the framework

  3. Statistics of resonances and time reversal reconstruction in aluminum acoustic chaotic cavities

    NARCIS (Netherlands)

    Antoniuk, O.; Sprik, R.

    2010-01-01

    The statistical properties of wave propagation in classical chaotic systems are of fundamental interest in physics and are the basis for diagnostic tools in materials science. The statistical properties depend in particular also on the presence of time reversal invariance in the system, which can be

  4. Comments on a direct approach to finding exact invariants for one-dimensional time-dependent classical hamiltonian

    International Nuclear Information System (INIS)

    Castro Moreira, I. de.

    1983-01-01

    A method introduced by Lewis and Leach for the obtention of exact invariants of the form I = Σ p sup(n) F sub(n) (q,t) for hamiltonian systems, is generalized and applied directly on the equations of motion. It gives us a general procedure to generates exact invariants also for non hamiltonian systems. (Author) [pt

  5. Exact analytical solution of time-independent neutron transport equation, and its applications to systems with a point source

    International Nuclear Information System (INIS)

    Mikata, Y.

    2014-01-01

    Highlights: • An exact solution for the one-speed neutron transport equation is obtained. • This solution as well as its derivation are believed to be new. • Neutron flux for a purely absorbing material with a point neutron source off the origin is obtained. • Spherically as well as cylindrically piecewise constant cross sections are studied. • Neutron flux expressions for a point neutron source off the origin are believed to be new. - Abstract: An exact analytical solution of the time-independent monoenergetic neutron transport equation is obtained in this paper. The solution is applied to systems with a point source. Systematic analysis of the solution of the time-independent neutron transport equation, and its applications represent the primary goal of this paper. To the best of the author’s knowledge, certain key results on the scalar neutron flux as well as their derivations are new. As an application of these results, a scalar neutron flux for a purely absorbing medium with a spherically piecewise constant cross section and an isotropic point neutron source off the origin as well as that for a cylindrically piecewise constant cross section with a point neutron source off the origin are obtained. Both of these results are believed to be new

  6. Role of echocardiography in reducing shock reversal time in pediatric septic shock: a randomized controlled trial

    Directory of Open Access Journals (Sweden)

    Ahmed A. EL-Nawawy

    Full Text Available Abstract Objective: To evaluate the role of echocardiography in reducing shock reversal time in pediatric septic shock. Methods: A prospective study conducted in the pediatric intensive care unit of a tertiary care teaching hospital from September 2013 to May 2016. Ninety septic shock patients were randomized in a 1:1 ratio for comparing the serial echocardiography-guided therapy in the study group with the standard therapy in the control group regarding clinical course, timely treatment, and outcomes. Results: Shock reversal was significantly higher in the study group (89% vs. 67%, with significantly reduced shock reversal time (3.3 vs. 4.5 days. Pediatric intensive care unit stay in the study group was significantly shorter (8 ± 3 vs. 14 ± 10 days. Mortality due to unresolved shock was significantly lower in the study group. Fluid overload was significantly lower in the study group (11% vs. 44%. In the study group, inotropes were used more frequently (89% vs. 67% and initiated earlier (12[0.5-24] vs. 24[6-72] h with lower maximum vasopressor inotrope score (120[30-325] vs. 170[80-395], revealing predominant use of milrinone (62% vs. 22%. Conclusion: Serial echocardiography provided crucial data for early recognition of septic myocardial dysfunction and hypovolemia that was not apparent on clinical assessment, allowing a timely management and resulting in shock reversal time reduction among children with septic shock.

  7. Stochastic epidemic-type model with enhanced connectivity: exact solution

    International Nuclear Information System (INIS)

    Williams, H T; Mazilu, I; Mazilu, D A

    2012-01-01

    We present an exact analytical solution to a one-dimensional model of the susceptible–infected–recovered (SIR) epidemic type, with infection rates dependent on nearest-neighbor occupations. We use a quantum mechanical approach, transforming the master equation via a quantum spin operator formulation. We calculate exactly the time-dependent density of infected, recovered and susceptible populations for random initial conditions. Our results compare well with those of previous work, validating the model as a useful tool for additional and extended studies in this important area. Our model also provides exact solutions for the n-point correlation functions, and can be extended to more complex epidemic-type models

  8. Exact scattering solutions in an energy sudden (ES) representation

    International Nuclear Information System (INIS)

    Chang, B.; Eno, L.; Rabitz, H.

    1983-01-01

    In this paper, we lay down the theoretical foundations for computing exact scattering wave functions in a reference frame which moves in unison with the system internal coordinates. In this frame the (internal) coordinates appear to be fixed and its adoption leads very naturally (in zeroth order) to the energy sudden (ES) approximation [and the related infinite order sudden (IOS) method]. For this reason we call the new representation for describing the exact dynamics of a many channel scattering problem, the ES representation. Exact scattering solutions are derived in both time dependent and time independent frameworks for the representation and many interesting results in these frames are established. It is shown, e.g., that in a time dependent frame the usual Schroedinger propagator factorizes into internal Hamiltonian, ES, and energy correcting propagators. We also show that in a time independent frame the full Green's functions can be similarly factorized. Another important feature of the new representation is that it forms a firm foundation for seeking corrections to the ES approximation. Thus, for example, the singularity which arises in conventional perturbative expansions of the full Green's functions (with the ES Green's function as the zeroth order solution) is avoided in the ES representation. Finally, a number of both time independent and time dependent ES correction schemes are suggested

  9. Exact PsTd invariant and PsTd symmetric breaking solutions, symmetry reductions and Bäcklund transformations for an AB-KdV system

    Science.gov (United States)

    Jia, Man; Lou, Sen Yue

    2018-05-01

    In natural and social science, many events happened at different space-times may be closely correlated. Two events, A (Alice) and B (Bob) are defined as correlated if one event is determined by another, say, B = f ˆ A for suitable f ˆ operators. A nonlocal AB-KdV system with shifted-parity (Ps, parity with a shift), delayed time reversal (Td, time reversal with a delay) symmetry where B =Ps ˆ Td ˆ A is constructed directly from the normal KdV equation to describe two-area physical event. The exact solutions of the AB-KdV system, including PsTd invariant and PsTd symmetric breaking solutions are shown by different methods. The PsTd invariant solution show that the event happened at A will happen also at B. These solutions, such as single soliton solutions, infinitely many singular soliton solutions, soliton-cnoidal wave interaction solutions, and symmetry reduction solutions etc., show the AB-KdV system possesses rich structures. Also, a special Bäcklund transformation related to residual symmetry is presented via the localization of the residual symmetry to find interaction solutions between the solitons and other types of the AB-KdV system.

  10. Factors affecting timing of closure and non-reversal of temporary ileostomies

    NARCIS (Netherlands)

    Sier, M. F.; van Gelder, L.; Ubbink, D. T.; Bemelman, W. A.; Oostenbroek, R. J.

    2015-01-01

    Although stoma closure is considered a simple surgical intervention, the interval between construction and reversal is often prolonged, and some ileostomies may never be reversed. We evaluated possible predictors for non-reversal and prolonged interval between construction and reversal. In a cohort

  11. Test of time reversal invariance in p-p elastic scattering at 198.5 MeV

    International Nuclear Information System (INIS)

    Davis, C.A.; Greeniaus, L.G.; Moss, G.A.

    1986-01-01

    A precise measurement of the polarization-analyzing power difference in p-p elastic scattering has been made at 198.5 MeV to improve the experimental limits on time reversal violation in proton-proton scattering in this energy region. The experiment was performed in a kinematic regime where sensitivities to time reversal violating amplitudes should be high. Experimental methods which eliminated the need to refer to absolute values of the beam polarization or to the analyzing power of a polarimeter were used. The result is (P-A) = 0.0047 with a statistical uncertainty of +- 0.0025 and a systematic uncertainty of +- 0.0015

  12. Breast cancer detection using time reversal

    Science.gov (United States)

    Sheikh Sajjadieh, Mohammad Hossein

    Breast cancer is the second leading cause of cancer death after lung cancer among women. Mammography and magnetic resonance imaging (MRI) have certain limitations in detecting breast cancer, especially during its early stage of development. A number of studies have shown that microwave breast cancer detection has potential to become a successful clinical complement to the conventional X-ray mammography. Microwave breast imaging is performed by illuminating the breast tissues with an electromagnetic waveform and recording its reflections (backscatters) emanating from variations in the normal breast tissues and tumour cells, if present, using an antenna array. These backscatters, referred to as the overall (tumour and clutter) response, are processed to estimate the tumour response, which is applied as input to array imaging algorithms used to estimate the location of the tumour. Due to changes in the breast profile over time, the commonly utilized background subtraction procedures used to estimate the target (tumour) response in array processing are impractical for breast cancer detection. The thesis proposes a new tumour estimation algorithm based on a combination of the data adaptive filter with the envelope detection filter (DAF/EDF), which collectively do not require a training step. After establishing the superiority of the DAF/EDF based approach, the thesis shows that the time reversal (TR) array imaging algorithms outperform their conventional conterparts in detecting and localizing tumour cells in breast tissues at SNRs ranging from 15 to 30dB.

  13. Lateral Casimir-Polder forces by breaking time-reversal symmetry

    Science.gov (United States)

    Oude Weernink, Ricardo R. Q. P. T.; Barcellona, Pablo; Buhmann, Stefan Yoshi

    2018-03-01

    We examine the lateral Casimir-Polder force acting on a circular rotating emitter near a dielectric plane surface. As the circular motion breaks time-reversal symmetry, the spontaneous emission in a direction parallel to the surface is in general anisotropic. We show that a lateral force arises which can be interpreted as a recoil force because of this asymmetric emission. The force is an oscillating function of the distance between the emitter and the surface, and the lossy character of the dielectric strongly influences the results in the near-field regime. The force exhibits also a population-induced dynamics, decaying exponentially with respect to time on time scales of the inverse of the spontaneous decay rate. We propose that this effect could be detected measuring the velocity acquired by the emitter, following different cycles of excitation and spontaneous decay. Our results are expressed in terms of the Green's tensor and can therefore easily be applied to more complex geometries.

  14. Reverse engineering of RFID devices

    NARCIS (Netherlands)

    Bokslag, W.

    2015-01-01

    This paper discusses the relevance and potential impact of both RFID and reverse engineering of RFID technology, followed by a discussion of common protocols and internals of RFID technology. The focus of the paper is on providing an overview of the different approaches to reverse engineering RFID

  15. Exact Solutions of the Space Time Fractional Symmetric Regularized Long Wave Equation Using Different Methods

    Directory of Open Access Journals (Sweden)

    Özkan Güner

    2014-01-01

    Full Text Available We apply the functional variable method, exp-function method, and (G′/G-expansion method to establish the exact solutions of the nonlinear fractional partial differential equation (NLFPDE in the sense of the modified Riemann-Liouville derivative. As a result, some new exact solutions for them are obtained. The results show that these methods are very effective and powerful mathematical tools for solving nonlinear fractional equations arising in mathematical physics. As a result, these methods can also be applied to other nonlinear fractional differential equations.

  16. Far-field detection of sub-wavelength Tetris without extra near-field metal parts based on phase prints of time-reversed fields with intensive background interference.

    Science.gov (United States)

    Chen, Yingming; Wang, Bing-Zhong

    2014-07-14

    Time-reversal (TR) phase prints are first used in far-field (FF) detection of sub-wavelength (SW) deformable scatterers without any extra metal structure positioned in the vicinity of the target. The 2D prints derive from discrete short-time Fourier transform of 1D TR electromagnetic (EM) signals. Because the time-invariant intensive background interference is effectively centralized by TR technique, the time-variant weak indication from FF SW scatterers can be highlighted. This method shows a different use of TR technique in which the focus peak of TR EM waves is unusually removed and the most useful information is conveyed by the other part.

  17. Numerical experimentation on focusing time and neutron yield in GN1 plasma focus machine

    International Nuclear Information System (INIS)

    Singh, Arwinder; Lee, Sing; Saw, S.H.

    2014-01-01

    In this paper, we have shown how we have fitted Lee's six phase model code to analyze the current waveform of the GN1 plasma focus machine working in deuterium gas. The Lee's 6-phase model codes was later configured to work between 0.5 to 6 Torr and the results of both focusing time and neutron yield was then compared with the published experimental results. The final results indicate that Lee's code, gives realistic plasma dynamics and focus properties together with a realistic neutron yield for GN1 plasma focus, without the need of any adjustable parameters, needing only to fit the computed current trace to a measured current trace. (author)

  18. Exact, almost and delayed fault detection: An observer based approach

    DEFF Research Database (Denmark)

    Niemann, Hans Henrik; Saberi, Ali; Stoorvogel, Anton A.

    1999-01-01

    This paper consider the problem of fault detection and isolation in continuous- and discrete-time systems while using zero or almost zero threshold. A number of different fault detections and isolation problems using exact or almost exact disturbance decoupling are formulated. Solvability...... conditions are given for the formulated design problems together with methods for appropriate design of observer based fault detectors. The l-step delayed fault detection problem is also considered for discrete-time systems . Moreover, certain indirect fault detection methods such as unknown input observers...

  19. Modified interferometric imaging condition for reverse-time migration

    Science.gov (United States)

    Guo, Xue-Bao; Liu, Hong; Shi, Ying

    2018-01-01

    For reverse-time migration, high-resolution imaging mainly depends on the accuracy of the velocity model and the imaging condition. In practice, however, the small-scale components of the velocity model cannot be estimated by tomographical methods; therefore, the wavefields are not accurately reconstructed from the background velocity, and the imaging process will generate artefacts. Some of the noise is due to cross-correlation of unrelated seismic events. Interferometric imaging condition suppresses imaging noise very effectively, especially the unknown random disturbance of the small-scale part. The conventional interferometric imaging condition is extended in this study to obtain a new imaging condition based on the pseudo-Wigner distribution function (WDF). Numerical examples show that the modified interferometric imaging condition improves imaging precision.

  20. Time-reversal-violating Schiff moment of 199Hg

    International Nuclear Information System (INIS)

    Jesus, J.H. de; Engel, J.

    2005-01-01

    We calculate the Schiff moment of the nucleus 199 Hg, created by πNN vertices that are odd under parity (P) and time-reversal (T). Our approach, formulated in diagrammatic perturbation theory with important core-polarization diagrams summed to all orders, gives a close approximation to the expectation value of the Schiff operator in the odd-A Hartree-Fock-Bogoliubov ground state generated by a Skyrme interaction and a weak P- and T-odd pion-exchange potential. To assess the uncertainty in the results, we carry out the calculation with several Skyrme interactions, the quality of which we test by checking predictions for the isoscalar-E1 strength distribution in 208 Pb, and estimate most of the important diagrams we omit

  1. The exact equation of motion of a simple pendulum of arbitrary amplitude: a hypergeometric approach

    International Nuclear Information System (INIS)

    Qureshi, M I; Rafat, M; Azad, S Ismail

    2010-01-01

    The motion of a simple pendulum of arbitrary amplitude is usually treated by approximate methods. By using generalized hypergeometric functions, it is however possible to solve the problem exactly. In this paper, we provide the exact equation of motion of a simple pendulum of arbitrary amplitude. A new and exact expression for the time of swinging of a simple pendulum from the vertical position to an arbitrary angular position θ is given by equation (3.10). The time period of such a pendulum is also exactly expressible in terms of hypergeometric functions. The exact expressions thus obtained are used to plot the graphs that compare the exact time period T(θ 0 ) with the time period T(0) (based on simple harmonic approximation). We also compare the relative difference between T(0) and T(θ 0 ) found from the exact equation of motion with the usual perturbation theory estimate. The treatment is intended for graduate students, who have acquired some familiarity with the hypergeometric functions. This approach may also be profitably used by specialists who encounter during their investigations nonlinear differential equations similar in form to the pendulum equation. Such nonlinear differential equations could arise in diverse fields, such as acoustic vibrations, oscillations in small molecules, turbulence and electronic filters, among others.

  2. Exact Solutions of the Time Fractional BBM-Burger Equation by Novel (G′/G-Expansion Method

    Directory of Open Access Journals (Sweden)

    Muhammad Shakeel

    2014-01-01

    Full Text Available The fractional derivatives are used in the sense modified Riemann-Liouville to obtain exact solutions for BBM-Burger equation of fractional order. This equation can be converted into an ordinary differential equation by using a persistent fractional complex transform and, as a result, hyperbolic function solutions, trigonometric function solutions, and rational solutions are attained. The performance of the method is reliable, useful, and gives newer general exact solutions with more free parameters than the existing methods. Numerical results coupled with the graphical representation completely reveal the trustworthiness of the method.

  3. Bounds on Time Reversal Violation From Polarized Neutron Capture With Unpolarized Targets.

    Science.gov (United States)

    Davis, E D; Gould, C R; Mitchell, G E; Sharapov, E I

    2005-01-01

    We have analyzed constraints on parity-odd time-reversal noninvariant interactions derived from measurements of the energy dependence of parity-violating polarized neutron capture on unpolarized targets. As previous authors found, a perturbation in energy dependence due to a parity (P)-odd time (T)-odd interaction is present. However, the perturbation competes with T-even terms which can obscure the T-odd signature. We estimate the magnitudes of these competing terms and suggest strategies for a practicable experiment.

  4. Quantum decay model with exact explicit analytical solution

    Science.gov (United States)

    Marchewka, Avi; Granot, Er'El

    2009-01-01

    A simple decay model is introduced. The model comprises a point potential well, which experiences an abrupt change. Due to the temporal variation, the initial quantum state can either escape from the well or stay localized as a new bound state. The model allows for an exact analytical solution while having the necessary features of a decay process. The results show that the decay is never exponential, as classical dynamics predicts. Moreover, at short times the decay has a fractional power law, which differs from perturbation quantum method predictions. At long times the decay includes oscillations with an envelope that decays algebraically. This is a model where the final state can be either continuous or localized, and that has an exact analytical solution.

  5. Parity and time-reversal violation in nuclei and atoms

    International Nuclear Information System (INIS)

    Adelberger, E.G.

    1986-01-01

    Two topics are briefly reviewed: the parity (P)-violating NN interaction and the time-reversal (T) and P-violating electric moments (EDM's) of atoms. The ΔI = 1 P-violating NN amplitude dominated by weak π +- exchange is found to be appreciably smaller than bag-model predictions. This may be a dynamical symmetry of flavor-conserving hadronic weak processes reminiscent of the ΔI = 1/2 rule in flavor-changing decays. General principles of experimental searches for atomic EDM's are discussed. Atomic EDM's are sensitive to electronic or nuclear EDM's and to a P-and-T-violating electron-quark interaction. Even though the experimental precision is still ∼10 4 times worse than counting statistics, the recent results have reached a sensitivity to nuclear EDM's which rivals that of the neutron EDM data. Further significant improvements can be expected

  6. First passage times for multiple particles with reversible target-binding kinetics

    Science.gov (United States)

    Grebenkov, Denis S.

    2017-10-01

    We investigate the first passage problem for multiple particles that diffuse towards a target, partially adsorb there, and then desorb after a finite exponentially distributed residence time. We search for the first time when m particles undergoing such reversible target-binding kinetics are found simultaneously on the target that may trigger an irreversible chemical reaction or a biophysical event. Even if the particles are independent, the finite residence time on the target yields an intricate temporal coupling between particles. We compute analytically the mean first passage time (MFPT) for two independent particles by mapping the original problem to higher-dimensional surface-mediated diffusion and solving the coupled partial differential equations. The respective effects of the adsorption and desorption rates on the MFPT are revealed and discussed.

  7. Exact error estimation for solutions of nuclide chain equations

    International Nuclear Information System (INIS)

    Tachihara, Hidekazu; Sekimoto, Hiroshi

    1999-01-01

    The exact solution of nuclide chain equations within arbitrary figures is obtained for a linear chain by employing the Bateman method in the multiple-precision arithmetic. The exact error estimation of major calculation methods for a nuclide chain equation is done by using this exact solution as a standard. The Bateman, finite difference, Runge-Kutta and matrix exponential methods are investigated. The present study confirms the following. The original Bateman method has very low accuracy in some cases, because of large-scale cancellations. The revised Bateman method by Siewers reduces the occurrence of cancellations and thereby shows high accuracy. In the time difference method as the finite difference and Runge-Kutta methods, the solutions are mainly affected by the truncation errors in the early decay time, and afterward by the round-off errors. Even though the variable time mesh is employed to suppress the accumulation of round-off errors, it appears to be nonpractical. Judging from these estimations, the matrix exponential method is the best among all the methods except the Bateman method whose calculation process for a linear chain is not identical with that for a general one. (author)

  8. Exact results for integrable asymptotically-free field theories

    CERN Document Server

    Evans, J M; Evans, Jonathan M; Hollowood, Timothy J

    1995-01-01

    An account is given of a technique for testing the equivalence between an exact factorizable S-matrix and an asymptotically-free Lagrangian field theory in two space-time dimensions. The method provides a way of resolving CDD ambiguities in the S-matrix and it also allows for an exact determination of the physical mass in terms of the Lambda parameter of perturbation theory. The results for various specific examples are summarized. (To appear in the Proceedings of the Conference on Recent Developments in Quantum Field Theory and Statistical Mechanics, ICTP, Trieste, Easter 1995).

  9. THEORETICAL FRAMES FOR DESIGNING REVERSE LOGISTICS PROCESSES

    OpenAIRE

    Janusz K. Grabara; Sebastian Kot

    2009-01-01

    Logistics processes of return flow became more and more important in present business practice. Because of better customer satisfaction, environmental and financial aspects many enterprises deal with reverse logistics performance. The paper is a literature review focused on the design principles of reverse logistics processes Keywords: reverse logistics, designing.

  10. First direct observation of time-reversal violation

    International Nuclear Information System (INIS)

    Angelopoulos, A.; Apostolakis, A.; Aslanides, E.; Bertin, V.; Ealet, A.; Henry-Couannier, F.; Le Gac, R.; Montanet, F.; Touchard, F.; Backenstoss, G.; Benelli, A.; Kokkas, P.; Leimgruber, F.; Pavlopoulos, P.; Polivka, G.; Rickenbach, R.; Schietinger, T.; Tauscher, L.; Vlachos, S.; Bargassa, P.

    2000-01-01

    Using its unique capability of strangeness tagging at K 0 production in pp-bar→K ± π ± K 0 (K-bar) 0 ) and at decay with the lepton charge in semileptonic decays CPLEAR measured the semileptonic decay-rate asymmetry (R(K-bar) 0 →e + π - ν)-R(K 0 →e - π + ν-bar)/R(K-bar) 0 →e + π - ν)+R(K 0 →e - π + ν-bar). The asymmetry, fitted over the eigentime interval 1-20 τ S , yielded a non-zero result of (6.6±1.3 stat ±1.1 syst )x10 -3 . A thorough phenomenological analysis identifies T violation in K 0 mixing and/or CPT violation in semileptonic decays as possible interpretations. A confrontation with world data on neutral kaon decays, however, excludes the latter with sufficient precision to establish the result as the first direct observation of time reversal non-invariance

  11. Deterministic time-reversible thermostats: chaos, ergodicity, and the zeroth law of thermodynamics

    Science.gov (United States)

    Patra, Puneet Kumar; Sprott, Julien Clinton; Hoover, William Graham; Griswold Hoover, Carol

    2015-09-01

    The relative stability and ergodicity of deterministic time-reversible thermostats, both singly and in coupled pairs, are assessed through their Lyapunov spectra. Five types of thermostat are coupled to one another through a single Hooke's-law harmonic spring. The resulting dynamics shows that three specific thermostat types, Hoover-Holian, Ju-Bulgac, and Martyna-Klein-Tuckerman, have very similar Lyapunov spectra in their equilibrium four-dimensional phase spaces and when coupled in equilibrium or nonequilibrium pairs. All three of these oscillator-based thermostats are shown to be ergodic, with smooth analytic Gaussian distributions in their extended phase spaces (coordinate, momentum, and two control variables). Evidently these three ergodic and time-reversible thermostat types are particularly useful as statistical-mechanical thermometers and thermostats. Each of them generates Gibbs' universal canonical distribution internally as well as for systems to which they are coupled. Thus they obey the zeroth law of thermodynamics, as a good heat bath should. They also provide dissipative heat flow with relatively small nonlinearity when two or more such temperature baths interact and provide useful deterministic replacements for the stochastic Langevin equation.

  12. Contingent Commitments: Bringing Part-Time Faculty into Focus. Methodology Supplement

    Science.gov (United States)

    Center for Community College Student Engagement, 2014

    2014-01-01

    Center reporting prior to 2013 focused primarily on descriptive statistics (frequencies and means) of student and faculty behaviors. The goal of the analyses reported here and in "Contingent Commitments: Bringing Part-Time Faculty into Focus" is to understand the engagement of part-time or contingent faculty in various activities that…

  13. Electric Dipole States and Time Reversal Violation in Nuclei

    International Nuclear Information System (INIS)

    Auerbach, N.

    2016-01-01

    The nuclear Schiff moment is essential in the mechanism that induces a parity and time reversal violation in the atom. In this presentation we explore theoretically the properties and systematics of the isoscalar dipole in nuclei with the emphasis on the low-energy strength and the inverse energy weighted sum which determines the Schiff moment. We also study the influence of the isovector dipole strength distribution on the Schiff moment. The influence of a large neutron excess in nuclei is examined. The centroid energies of the isoscalar giant resonance (ISGDR) and the overtone of the isovector giant dipole resonance (OIVGDR) are given for a range of nuclei. (paper)

  14. Exact combinatorial approach to finite coagulating systems

    Science.gov (United States)

    Fronczak, Agata; Chmiel, Anna; Fronczak, Piotr

    2018-02-01

    This paper outlines an exact combinatorial approach to finite coagulating systems. In this approach, cluster sizes and time are discrete and the binary aggregation alone governs the time evolution of the systems. By considering the growth histories of all possible clusters, an exact expression is derived for the probability of a coagulating system with an arbitrary kernel being found in a given cluster configuration when monodisperse initial conditions are applied. Then this probability is used to calculate the time-dependent distribution for the number of clusters of a given size, the average number of such clusters, and that average's standard deviation. The correctness of our general expressions is proved based on the (analytical and numerical) results obtained for systems with the constant kernel. In addition, the results obtained are compared with the results arising from the solutions to the mean-field Smoluchowski coagulation equation, indicating its weak points. The paper closes with a brief discussion on the extensibility to other systems of the approach presented herein, emphasizing the issue of arbitrary initial conditions.

  15. Least-squares reverse time migration of marine data with frequency-selection encoding

    KAUST Repository

    Dai, Wei

    2013-06-24

    The phase-encoding technique can sometimes increase the efficiency of the least-squares reverse time migration (LSRTM) by more than one order of magnitude. However, traditional random encoding functions require all the encoded shots to share the same receiver locations, thus limiting the usage to seismic surveys with a fixed spread geometry. We implement a frequency-selection encoding strategy that accommodates data with a marine streamer geometry. The encoding functions are delta functions in the frequency domain, so that all the encoded shots have unique nonoverlapping frequency content, and the receivers can distinguish the wavefield from each shot with a unique frequency band. Because the encoding functions are orthogonal to each other, there will be no crosstalk between different shots during modeling and migration. With the frequency-selection encoding method, the computational efficiency of LSRTM is increased so that its cost is comparable to conventional RTM for the Marmousi2 model and a marine data set recorded in the Gulf of Mexico. With more iterations, the LSRTM image quality is further improved by suppressing migration artifacts, balancing reflector amplitudes, and enhancing the spatial resolution. We conclude that LSRTM with frequency-selection is an efficient migration method that can sometimes produce more focused images than conventional RTM. © 2013 Society of Exploration Geophysicists.

  16. Reverse hypothesis machine learning a practitioner's perspective

    CERN Document Server

    Kulkarni, Parag

    2017-01-01

    This book introduces a paradigm of reverse hypothesis machines (RHM), focusing on knowledge innovation and machine learning. Knowledge- acquisition -based learning is constrained by large volumes of data and is time consuming. Hence Knowledge innovation based learning is the need of time. Since under-learning results in cognitive inabilities and over-learning compromises freedom, there is need for optimal machine learning. All existing learning techniques rely on mapping input and output and establishing mathematical relationships between them. Though methods change the paradigm remains the same—the forward hypothesis machine paradigm, which tries to minimize uncertainty. The RHM, on the other hand, makes use of uncertainty for creative learning. The approach uses limited data to help identify new and surprising solutions. It focuses on improving learnability, unlike traditional approaches, which focus on accuracy. The book is useful as a reference book for machine learning researchers and professionals as ...

  17. Noncolocated Time-Reversal MUSIC: High-SNR Distribution of Null Spectrum

    Science.gov (United States)

    Ciuonzo, Domenico; Rossi, Pierluigi Salvo

    2017-04-01

    We derive the asymptotic distribution of the null spectrum of the well-known Multiple Signal Classification (MUSIC) in its computational Time-Reversal (TR) form. The result pertains to a single-frequency non-colocated multistatic scenario and several TR-MUSIC variants are here investigated. The analysis builds upon the 1st-order perturbation of the singular value decomposition and allows a simple characterization of null-spectrum moments (up to the 2nd order). This enables a comparison in terms of spectrums stability. Finally, a numerical analysis is provided to confirm the theoretical findings.

  18. Attenuation compensation in least-squares reverse time migration using the visco-acoustic wave equation

    KAUST Repository

    Dutta, Gaurav; Lu, Kai; Wang, Xin; Schuster, Gerard T.

    2013-01-01

    Attenuation leads to distortion of amplitude and phase of seismic waves propagating inside the earth. Conventional acoustic and least-squares reverse time migration do not account for this distortion which leads to defocusing of migration images

  19. Exactly soluble two-state quantum models with linear couplings

    International Nuclear Information System (INIS)

    Torosov, B T; Vitanov, N V

    2008-01-01

    A class of exact analytic solutions of the time-dependent Schroedinger equation is presented for a two-state quantum system coherently driven by a nonresonant external field. The coupling is a linear function of time with a finite duration and the detuning is constant. Four special models are considered in detail, namely the shark, double-shark, tent and zigzag models. The exact solution is derived by rotation of the Landau-Zener propagator at an angle of π/4 and is expressed in terms of Weber's parabolic cylinder function. Approximations for the transition probabilities are derived for all four models by using the asymptotics of the Weber function; these approximations demonstrate various effects of physical interest for each model

  20. Exact cosmological solutions for MOG

    International Nuclear Information System (INIS)

    Roshan, Mahmood

    2015-01-01

    We find some new exact cosmological solutions for the covariant scalar-tensor-vector gravity theory, the so-called modified gravity (MOG). The exact solution of the vacuum field equations has been derived. Also, for non-vacuum cases we have found some exact solutions with the aid of the Noether symmetry approach. More specifically, the symmetry vector and also the Noether conserved quantity associated to the point-like Lagrangian of the theory have been found. Also we find the exact form of the generic vector field potential of this theory by considering the behavior of the relevant point-like Lagrangian under the infinitesimal generator of the Noether symmetry. Finally, we discuss the cosmological implications of the solutions. (orig.)

  1. Exact performance analysis of decode-and-forward opportunistic relaying

    KAUST Repository

    Tourki, Kamel

    2010-06-01

    In this paper, we investigate a dual-hop decode-and-forward opportunistic relaying scheme where the source may or may not be able to communicate directly with the destination. In our study, we consider a regenerative relaying scheme in which the decision to cooperate takes into account the effect of the possible erroneously detected and transmitted data at the best relay. We derive an exact closed-form expression for the end-to-end bit-error rate (BER) of binary phase-shift keying (BPSK) modulation based on the exact statistics of each hop. Unlike existing works where the analysis focused on high signal-to-noise ratio (SNR) regime, such results are important to enable the designers to take decisions regarding practical systems that operate at low SNR regime. We show that performance simulation results coincide with our analytical results.

  2. Synthetic seismic monitoring using reverse-time migration and Kirchhoff migration for CO2 sequestration in Korea

    Science.gov (United States)

    Kim, W.; Kim, Y.; Min, D.; Oh, J.; Huh, C.; Kang, S.

    2012-12-01

    During last two decades, CO2 sequestration in the subsurface has been extensively studied and progressed as a direct tool to reduce CO2 emission. Commercial projects such as Sleipner, In Salah and Weyburn that inject more than one million tons of CO2 per year are operated actively as well as test projects such as Ketzin to study the behavior of CO2 and the monitoring techniques. Korea also began the CCS (CO2 capture and storage) project. One of the prospects for CO2 sequestration in Korea is the southwestern continental margin of Ulleung basin. To monitor the behavior of CO2 underground for the evaluation of stability and safety, several geophysical monitoring techniques should be applied. Among various geophysical monitoring techniques, seismic survey is considered as the most effective tool. To verify CO2 migration in the subsurface more effectively, seismic numerical simulation is an essential process. Furthermore, the efficiency of the seismic migration techniques should be investigated for various cases because numerical seismic simulation and migration test help us accurately interpret CO2 migration. In this study, we apply the reverse-time migration and Kirchhoff migration to synthetic seismic monitoring data generated for the simplified model based on the geological structures of Ulleung basin in Korea. Synthetic seismic monitoring data are generated for various cases of CO2 migration in the subsurface. From the seismic migration images, we can investigate CO2 diffusion patterns indirectly. From seismic monitoring simulation, it is noted that while the reverse-time migration generates clear subsurface images when subsurface structures are steeply dipping, Kirchhoff migration has an advantage in imaging horizontal-layered structures such as depositional sediments appearing in the continental shelf. The reverse-time migration and Kirchhoff migration present reliable subsurface images for the potential site characterized by stratigraphical traps. In case of

  3. TVT-Exact and midurethral sling (SLING-IUFT) operative procedures: a randomized study.

    Science.gov (United States)

    Aniuliene, Rosita; Aniulis, Povilas; Skaudickas, Darijus

    2015-01-01

    The aim of the study is to compare results, effectiveness and complications of TVT exact and midurethral sling (SLING-IUFT) operations in the treatment of female stress urinary incontinence (SUI). A single center nonblind, randomized study of women with SUI who were randomized to TVT-Exact and SLING-IUFT was performed by one surgeon from April 2009 to April 2011. SUI was diagnosed on coughing and Valsalva test and urodynamics (cystometry and uroflowmetry) were assessed before operation and 1 year after surgery. This was a prospective randomized study. The follow up period was 12 months. 76 patients were operated using the TVT-Exact operation and 78 patients - using the SLING-IUFT operation. There was no statistically significant differences between groups for BMI, parity, menopausal status and prolapsed stage (no patients had cystocele greater than stage II). Mean operative time was significantly shorter in the SLING-IUFT group (19 ± 5.6 min.) compared with the TVT-Exact group (27 ± 7.1 min.). There were statistically significant differences in the effectiveness of both procedures: TVT-Exact - at 94.5% and SLING-IUFT - at 61.2% after one year. Hospital stay was statistically significantly shorter in the SLING-IUFT group (1. 2 ± 0.5 days) compared with the TVT-Exact group (3.5 ± 1.5 days). Statistically significantly fewer complications occurred in the SLING-IUFT group. the TVT-Exact and SLING-IUFT operations are both effective for surgical treatment of female stress urinary incontinence. The SLING-IUFT involved a shorter operation time and lower complications rate., the TVT-Exact procedure had statistically significantly more complications than the SLING-IUFT operation, but a higher effectiveness.

  4. Time-Reversal Study of the Hemet (CA) Tremor Source

    Science.gov (United States)

    Larmat, C. S.; Johnson, P. A.; Guyer, R. A.

    2010-12-01

    Since its first observation by Nadeau & Dolenc (2005) and Gomberg et al. (2008), tremor along the San Andreas fault system is thought to be a probe into the frictional state of the deep part of the fault (e.g. Shelly et al., 2007). Tremor is associated with slow, otherwise deep, aseismic slip events that may be triggered by faint signals such as passing waves from remote earthquakes or solid Earth tides.Well resolved tremor source location is key to constrain frictional models of the fault. However, tremor source location is challenging because of the high-frequency and highly-scattered nature of tremor signal characterized by the lack of isolated phase arrivals. Time Reversal (TR) methods are emerging as a useful tool for location. The unique requirement is a good velocity model for the different time-reversed phases to arrive coherently onto the source point. We present results of location for a tremor source near the town of Hemet, CA, which was triggered by the 2002 M 7.9 Denali Fault earthquake (Gomberg et al., 2008) and by the 2009 M 6.9 Gulf of California earthquake. We performed TR in a volume model of 88 (N-S) x 70 (W-E) x 60 km (Z) using the full-wave 3D wave-propagation package SPECFEM3D (Komatitsch et al., 2002). The results for the 2009 episode indicate a deep source (at about 22km) which is about 4km SW the fault surface scarp. We perform STA/SLA and correlation analysis in order to have independent confirmation of the Hemet tremor source. We gratefully acknowledge the support of the U. S. Department of Energy through the LANL/LDRD Program for this work.

  5. Derivation of the Time-Reversal Anomaly for (2 +1 )-Dimensional Topological Phases

    Science.gov (United States)

    Tachikawa, Yuji; Yonekura, Kazuya

    2017-09-01

    We prove an explicit formula conjectured recently by Wang and Levin for the anomaly of time-reversal symmetry in (2 +1 )-dimensional fermionic topological quantum field theories. The crucial step is to determine the cross-cap state in terms of the modular S matrix and T2 eigenvalues, generalizing the recent analysis by Barkeshli et al. in the bosonic case.

  6. Quasi-exact solutions of nonlinear differential equations

    OpenAIRE

    Kudryashov, Nikolay A.; Kochanov, Mark B.

    2014-01-01

    The concept of quasi-exact solutions of nonlinear differential equations is introduced. Quasi-exact solution expands the idea of exact solution for additional values of parameters of differential equation. These solutions are approximate solutions of nonlinear differential equations but they are close to exact solutions. Quasi-exact solutions of the the Kuramoto--Sivashinsky, the Korteweg--de Vries--Burgers and the Kawahara equations are founded.

  7. Exact reconstruction in 2D dynamic CT: compensation of time-dependent affine deformations

    International Nuclear Information System (INIS)

    Roux, Sebastien; Desbat, Laurent; Koenig, Anne; Grangeat, Pierre

    2004-01-01

    This work is dedicated to the reduction of reconstruction artefacts due to motion occurring during the acquisition of computerized tomographic projections. This problem has to be solved when imaging moving organs such as the lungs or the heart. The proposed method belongs to the class of motion compensation algorithms, where the model of motion is included in the reconstruction formula. We address two fundamental questions. First what conditions on the deformation are required for the reconstruction of the object from projections acquired sequentially during the deformation, and second how do we reconstruct the object from those projections. Here we answer these questions in the particular case of 2D general time-dependent affine deformations, assuming the motion parameters are known. We treat the problem of admissibility conditions on the deformation in the parallel-beam and fan-beam cases. Then we propose exact reconstruction methods based on rebinning or sequential FBP formulae for each of these geometries and present reconstructed images obtained with the fan-beam algorithm on simulated data

  8. 3D Multi‐source Least‐squares Reverse Time Migration

    KAUST Repository

    Dai, Wei

    2010-10-17

    We present the theory and numerical results for least‐squares reverse time migration (LSRTM) of phase‐encoded supergathers, where each supergather is the superposition of phased‐encoded shots. Three type of encoding functions are used in this study: random time shift, random source polarity and random source location selected from a pre‐designed table. Numerical tests for the 3D SEG/EAGE Overthrust model show that multi‐source LSRTM can suppress migration artifacts in the migration image and remove most of the crosstalk noise from multi‐source data. Empirical results suggest that multi‐source LSRTM can provide a noticeable increase in computational efficiency compared to standard RTM, when the CSGs in a supergather are modeled and migrated together with a finite‐difference simulator. If the phase‐encoding functions are dynamically changed after each iteration of LSRTM, the best images are obtained. The potential drawback is that the final results are very sensitive to the accuracy of the starting model.

  9. Test of time-reversal invariance at COSY

    Energy Technology Data Exchange (ETDEWEB)

    Valdau, Yury [Helmholtz Institut fuer Strahlen- und Kernphysik, Bonn Univ. (Germany); National Research Center ' ' Kurchatov Institute' ' Petersburg Nuclear Physics Institute B.P. Konstantinov, Gatchina (Russian Federation); Eversheim, Dieter [Helmholtz Institut fuer Strahlen- und Kernphysik, Bonn Univ. (Germany); Lorentz, Bernd [Forschungszentrum Juelich, Institute fuer Kernphysik (Germany)

    2016-07-01

    The experiment to test the Time Reversal Invariance at Cosy (TRIC) is under the preparation by the PAX collaboration. It is planned to improve present limit on the T-odd P-even interaction by at least one order of magnitude using a unique genuine null observable available in double polarized proton-deuteron scattering. The TRIC experiment is planned as a transmission experiment using a tensor polarized deuterium target placed at the internal target place of the Cooler-Synchrotron COSY-Juelich. Total double polarized cross section will be measured observing a beam current change due to the interaction of a polarized proton beam with an internal tensor polarized deuterium target from the PAX atomic beam source. Hence, in this experiment COSY will be used as an accelerator, detector and ideal zero degree spectrometer. In addition to the high intensity polarized proton beam and high density polarized deuterium target, a new high precision beam current measurement system will be prepared for the TRIC experiment. In this report status of all the activities of PAX collaboration towards realization of the TRIC experiment will be presented.

  10. Imaging Method Based on Time Reversal Channel Compensation

    Directory of Open Access Journals (Sweden)

    Bing Li

    2015-01-01

    Full Text Available The conventional time reversal imaging (TRI method builds imaging function by using the maximal value of signal amplitude. In this circumstance, some remote targets are missed (near-far problem or low resolution is obtained in lossy and/or dispersive media, and too many transceivers are employed to locate targets, which increases the complexity and cost of system. To solve these problems, a novel TRI algorithm is presented in this paper. In order to achieve a high resolution, the signal amplitude corresponding to focal time observed at target position is used to reconstruct the target image. For disposing near-far problem and suppressing spurious images, combining with cross-correlation property and amplitude compensation, channel compensation function (CCF is introduced. Moreover, the complexity and cost of system are reduced by employing only five transceivers to detect four targets whose number is close to that of transceivers. For the sake of demonstrating the practicability of the proposed analytical framework, the numerical experiments are actualized in both nondispersive-lossless (NDL media and dispersive-conductive (DPC media. Results show that the performance of the proposed method is superior to that of conventional TRI algorithm even under few echo signals.

  11. Role of echocardiography in reducing shock reversal time in pediatric septic shock: a randomized controlled trial

    Directory of Open Access Journals (Sweden)

    Ahmed A. EL‐Nawawy

    2018-01-01

    Conclusion: Serial echocardiography provided crucial data for early recognition of septic myocardial dysfunction and hypovolemia that was not apparent on clinical assessment, allowing a timely management and resulting in shock reversal time reduction among children with septic shock.

  12. A Table Lookup Method for Exact Analytical Solutions of Nonlinear Fractional Partial Differential Equations

    Directory of Open Access Journals (Sweden)

    Ji Juan-Juan

    2017-01-01

    Full Text Available A table lookup method for solving nonlinear fractional partial differential equations (fPDEs is proposed in this paper. Looking up the corresponding tables, we can quickly obtain the exact analytical solutions of fPDEs by using this method. To illustrate the validity of the method, we apply it to construct the exact analytical solutions of four nonlinear fPDEs, namely, the time fractional simplified MCH equation, the space-time fractional combined KdV-mKdV equation, the (2+1-dimensional time fractional Zoomeron equation, and the space-time fractional ZKBBM equation. As a result, many new types of exact analytical solutions are obtained including triangular periodic solution, hyperbolic function solution, singular solution, multiple solitary wave solution, and Jacobi elliptic function solution.

  13. Reverse logistics system planning for recycling computers hardware: A case study

    Science.gov (United States)

    Januri, Siti Sarah; Zulkipli, Faridah; Zahari, Siti Meriam; Shamsuri, Siti Hajar

    2014-09-01

    This paper describes modeling and simulation of reverse logistics networks for collection of used computers in one of the company in Selangor. The study focuses on design of reverse logistics network for used computers recycling operation. Simulation modeling, presented in this work allows the user to analyze the future performance of the network and to understand the complex relationship between the parties involved. The findings from the simulation suggest that the model calculates processing time and resource utilization in a predictable manner. In this study, the simulation model was developed by using Arena simulation package.

  14. Time-reversal asymmetry: polarization and analyzing power in nuclear reactions

    International Nuclear Information System (INIS)

    Rioux, C.; Roy, R.; Slobodrian, R.J.; Conzett, H.E.

    1984-01-01

    Measurements of the proton polarization in the reactions 7 Li( 3 He, p vector) 9 Be and 9 Be( 3 He, p vector) 11 B and of the analyzing powers in the inverse reactions, initiated by polarized protons at the same center-of-mass energies, show significant differences. This implies the failure of the polarization-analyzing-power theorem and, prima facie, of time-reversal invariance in these reactions. The reaction 2 H( 3 He, p vector) 4 He and its inverse have also been investigated and show smaller differences. A discussion of instrumental asymmetries is presented

  15. Impact source identification in finite isotropic plates using a time-reversal method: theoretical study

    International Nuclear Information System (INIS)

    Chen, Chunlin; Yuan, Fuh-Gwo

    2010-01-01

    This paper aims to identify impact sources on plate-like structures based on the synthetic time-reversal (T-R) concept using an array of sensors. The impact source characteristics, namely, impact location and impact loading time history, are reconstructed using the invariance of time-reversal concept, reciprocal theory, and signal processing algorithms. Numerical verification for two finite isotropic plates under low and high velocity impacts is performed to demonstrate the versatility of the synthetic T-R method for impact source identification. The results show that the impact location and time history of the impact force with various shapes and frequency bands can be readily obtained with only four sensors distributed around the impact location. The effects of time duration and the inaccuracy in the estimated impact location on the accuracy of the time history of the impact force using the T-R method are investigated. Since the T-R technique retraces all the multi-paths of reflected waves from the geometrical boundaries back to the impact location, it is well suited for quantifying the impact characteristics for complex structures. In addition, this method is robust against noise and it is suggested that a small number of sensors is sufficient to quantify the impact source characteristics through simple computation; thus it holds promise for the development of passive structural health monitoring (SHM) systems for impact monitoring in near real-time

  16. In situ calibration of acoustic emission transducers by time reversal method

    Czech Academy of Sciences Publication Activity Database

    Kober, Jan; Převorovský, Zdeněk; Chlada, Milan

    2016-01-01

    Roč. 240, April (2016), s. 50-56 ISSN 0924-4247 Institutional support: RVO:61388998 Keywords : time reversed acoustic s * calibration * in situ * acoustic emission Subject RIV: BI - Acoustic s Impact factor: 2.499, year: 2016 http://ac.els-cdn.com/S0924424716300334/1-s2.0-S0924424716300334-main.pdf?_tid=0acf4736-ef6d-11e5-b826-00000aacb362&acdnat=1458568911_1c21eda9762b905a684ff939463ef3fe

  17. Reversible Communicating Processes

    Directory of Open Access Journals (Sweden)

    Geoffrey Brown

    2016-02-01

    Full Text Available Reversible distributed programs have the ability to abort unproductive computation paths and backtrack, while unwinding communication that occurred in the aborted paths. While it is natural to assume that reversibility implies full state recovery (as with traditional roll-back recovery protocols, an interesting alternative is to separate backtracking from local state recovery. For example, such a model could be used to create complex transactions out of nested compensable transactions where a programmer-supplied compensation defines the work required to "unwind" a transaction. Reversible distributed computing has received considerable theoretical attention, but little reduction to practice; the few published implementations of languages supporting reversibility depend upon a high degree of central control. The objective of this paper is to demonstrate that a practical reversible distributed language can be efficiently implemented in a fully distributed manner. We discuss such a language, supporting CSP-style synchronous communication, embedded in Scala. While this language provided the motivation for the work described in this paper, our focus is upon the distributed implementation. In particular, we demonstrate that a "high-level" semantic model can be implemented using a simple point-to-point protocol.

  18. Time resolved x-ray photography of a dense plasma focus

    International Nuclear Information System (INIS)

    Burnett, J.C.; Meyer, J.; Rankin, G.

    1977-01-01

    The temporal development of the hot plasma in a dense plasma focus is studied by x-ray streak photography of approximately 2 ns resolution time. It is shown that initially a uniform x-ray emitting pinch plasma is formed which subsequently cools down until x-ray emission stops after approximately 50 ns. At a time of around 100 ns after initial x-ray emission coinciding with the break-up time of the pinch a second burst of x-rays is observed coming from small localized regions. The observations are compared with results obtained from time-resolved shadow and schlieren photography of a similar dense focus discharge. (author)

  19. Exact solutions and symmetry analysis for the limiting probability distribution of quantum walks

    International Nuclear Information System (INIS)

    Xu, Xin-Ping; Ide, Yusuke

    2016-01-01

    In the literature, there are numerous studies of one-dimensional discrete-time quantum walks (DTQWs) using a moving shift operator. However, there is no exact solution for the limiting probability distributions of DTQWs on cycles using a general coin or swapping shift operator. In this paper, we derive exact solutions for the limiting probability distribution of quantum walks using a general coin and swapping shift operator on cycles for the first time. Based on the exact solutions, we show how to generate symmetric quantum walks and determine the condition under which a symmetric quantum walk appears. Our results suggest that choosing various coin and initial state parameters can achieve a symmetric quantum walk. By defining a quantity to measure the variation of symmetry, deviation and mixing time of symmetric quantum walks are also investigated.

  20. Exact solutions and symmetry analysis for the limiting probability distribution of quantum walks

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Xin-Ping, E-mail: xuxp@mail.ihep.ac.cn [School of Physical Science and Technology, Soochow University, Suzhou 215006 (China); Ide, Yusuke [Department of Information Systems Creation, Faculty of Engineering, Kanagawa University, Yokohama, Kanagawa, 221-8686 (Japan)

    2016-10-15

    In the literature, there are numerous studies of one-dimensional discrete-time quantum walks (DTQWs) using a moving shift operator. However, there is no exact solution for the limiting probability distributions of DTQWs on cycles using a general coin or swapping shift operator. In this paper, we derive exact solutions for the limiting probability distribution of quantum walks using a general coin and swapping shift operator on cycles for the first time. Based on the exact solutions, we show how to generate symmetric quantum walks and determine the condition under which a symmetric quantum walk appears. Our results suggest that choosing various coin and initial state parameters can achieve a symmetric quantum walk. By defining a quantity to measure the variation of symmetry, deviation and mixing time of symmetric quantum walks are also investigated.

  1. Simulation study of a chaotic cavity transducer based virtual phased array used for focusing in the bulk of a solid material.

    Science.gov (United States)

    Delrue, Steven; Van Den Abeele, Koen; Bou Matar, Olivier

    2016-04-01

    In acoustic and ultrasonic non-destructive testing techniques, it is sometimes beneficial to concentrate sound energy at a chosen location in space and at a specific instance in time, for example to improve the signal-to-noise ratio or activate the nonlinearity of damage features. Time Reversal (TR) techniques, taking advantage of the reversible character of the wave equation, are particularly suited to focus ultrasonic waves in time and space. The characteristics of the energy focusing in solid media using principles of time reversed acoustics are highly influenced by the nature and dimensions of the medium, the number of transducers and the length of the received signals. Usually, a large number of transducers enclosing the domain of interest is needed to improve the quality of the focusing. However, in the case of highly reverberant media, the number of transducers can be reduced to only one (single-channel TR). For focusing in a non-reverberant medium, which is impossible when using only one source, an adaptation of the single-channel reciprocal TR procedure has been recently suggested by means of a Chaotic Cavity Transducer (CCT), a single element transducer glued on a cavity of chaotic shape. In this paper, a CCT is used to focus elastic energy, at different times, in different points along a predefined line on the upper surface of a thick solid sample. Doing so, all focusing points can act as a virtual phased array transducer, allowing to focus in any point along the depth direction of the sample. This is impossible using conventional reciprocal TR, as you need to have access to all points in the bulk of the material for detecting signals to be used in the TR process. To asses and provide a better understanding of this concept, a numerical study has been developed, allowing to verify the basic concepts of the virtual phased array and to illustrate multi-component time reversal focusing in the bulk of a solid material. Copyright © 2016 Elsevier B.V. All

  2. Dynamical Response of Networks Under External Perturbations: Exact Results

    Science.gov (United States)

    Chinellato, David D.; Epstein, Irving R.; Braha, Dan; Bar-Yam, Yaneer; de Aguiar, Marcus A. M.

    2015-04-01

    We give exact statistical distributions for the dynamic response of influence networks subjected to external perturbations. We consider networks whose nodes have two internal states labeled 0 and 1. We let nodes be frozen in state 0, in state 1, and the remaining nodes change by adopting the state of a connected node with a fixed probability per time step. The frozen nodes can be interpreted as external perturbations to the subnetwork of free nodes. Analytically extending and to be smaller than 1 enables modeling the case of weak coupling. We solve the dynamical equations exactly for fully connected networks, obtaining the equilibrium distribution, transition probabilities between any two states and the characteristic time to equilibration. Our exact results are excellent approximations for other topologies, including random, regular lattice, scale-free and small world networks, when the numbers of fixed nodes are adjusted to take account of the effect of topology on coupling to the environment. This model can describe a variety of complex systems, from magnetic spins to social networks to population genetics, and was recently applied as a framework for early warning signals for real-world self-organized economic market crises.

  3. Zero field reversal probability in thermally assisted magnetization reversal

    Science.gov (United States)

    Prasetya, E. B.; Utari; Purnama, B.

    2017-11-01

    This paper discussed about zero field reversal probability in thermally assisted magnetization reversal (TAMR). Appearance of reversal probability in zero field investigated through micromagnetic simulation by solving stochastic Landau-Lifshitz-Gibert (LLG). The perpendicularly anisotropy magnetic dot of 50×50×20 nm3 is considered as single cell magnetic storage of magnetic random acces memory (MRAM). Thermally assisted magnetization reversal was performed by cooling writing process from near/almost Curie point to room temperature on 20 times runs for different randomly magnetized state. The results show that the probability reversal under zero magnetic field decreased with the increase of the energy barrier. The zero-field probability switching of 55% attained for energy barrier of 60 k B T and the reversal probability become zero noted at energy barrier of 2348 k B T. The higest zero-field switching probability of 55% attained for energy barrier of 60 k B T which corespond to magnetif field of 150 Oe for switching.

  4. Radioactive Reversal? The Fukushima Accident as a Focusing Event for Comparative Policy Change on Nuclear Energy

    Science.gov (United States)

    Sanchez, Victoria Justine

    This dissertation project examines the 2011 Fukushima nuclear accident as a focusing event for policy change on nuclear energy. For example, following the accident, Germany (and much of Europe) experienced a reversal of policy on nuclear energy. Conversely, many others such as China, Russia, and France, did not exhibit such a retraction against nuclear power, albeit with public debate about the risks and consequences of accidents. Why has there been dramatic policy change in some cases but not others? The political and literal fallout of Fukushima has provoked a wave of policy change towards nuclear energy at the national level. Through qualitative and quantitative measures, we can view Fukushima as an impetus for comparing the dynamics of nuclear policy change. Quantitatively, this project employs logistic regression to explore variables such as regime type, energy security, trade supply and demand, climate change concerns, and public acceptance are related to policy outcomes and change on nuclear energy in the post-Fukushima context of 49 different countries. Qualitatively, country cases (Russia, Germany, and Canada) are assessed into three categories based on the outcome of policy decisions on nuclear energy following Fukushima for a richer analysis. Beyond the Fukushima example, we can hope to better understand how political focusing events can gain influence in an international context.

  5. Increasing dwell time of mitomycin C in the upper tract with a reverse thermosensitive polymer.

    Science.gov (United States)

    Wang, Agnes J; Goldsmith, Zachariah G; Neisius, Andreas; Astroza, Gaston M; Oredein-McCoy, Olugbemisola; Iqbal, Muhammad W; Simmons, W Neal; Madden, John F; Preminger, Glenn M; Inman, Brant A; Lipkin, Michael E; Ferrandino, Michael N

    2013-03-01

    Abstract Background and Purpose: Topical chemotherapy for urothelial cancer is dependent on adequate contact time of the chemotherapeutic agent with the urothelium. To date, there has not been a reliable method of maintaining this contact for renal or ureteral urothelial carcinoma. We evaluated the safety and feasibility of using a reverse thermosensitive polymer to improve dwell times of mitomycin C (MMC) in the upper tract. Using a porcine model, four animals were treated ureteroscopically with both upper urinary tracts receiving MMC mixed with iodinated contrast. One additional animal received MMC percutaneously. The treatment side had ureteral outflow blocked with a reverse thermosensitive polymer plug. MMC dwell time was monitored fluoroscopically and intrarenal pressures measured. Two animals were euthanized immediately, and three animals were euthanized 5 days afterward. In control kidneys, drainage occurred at a mean of 5.3±0.58 minutes. Intrarenal pressures stayed fairly stable: 9.7±14.0 cm H20. In treatment kidneys, dwell time was extended to 60 minutes, when the polymer was washed out. Intrarenal pressures in the treatment kidneys peaked at 75.0±14.7 cm H20 and reached steady state at 60 cm H20. Pressures normalized after washout of the polymer with cool saline. Average washout time was 11.8±9.6 minutes. No histopathologic differences were seen between the control and treatment kidneys, or with immediate compared with delayed euthanasia. A reverse thermosensitive polymer can retain MMC in the upper urinary tract and appears to be safe from our examination of intrarenal pressures and histopathology. This technique may improve the efficacy of topical chemotherapy in the management of upper tract urothelial carcinoma.

  6. On thermodynamic and microscopic reversibility

    International Nuclear Information System (INIS)

    Crooks, Gavin E

    2011-01-01

    The word 'reversible' has two (apparently) distinct applications in statistical thermodynamics. A thermodynamically reversible process indicates an experimental protocol for which the entropy change is zero, whereas the principle of microscopic reversibility asserts that the probability of any trajectory of a system through phase space equals that of the time reversed trajectory. However, these two terms are actually synonymous: a thermodynamically reversible process is microscopically reversible, and vice versa

  7. PZT-Based Detection of Compactness of Concrete in Concrete Filled Steel Tube Using Time Reversal Method

    Directory of Open Access Journals (Sweden)

    Shi Yan

    2014-01-01

    Full Text Available A smart aggregate-based approach is proposed for the concrete compactness detection of concrete filled steel tube (CFST columns. The piezoceramic-based smart aggregates (SAs were embedded in the predetermined locations prior to the casting of concrete columns to establish a wave-based smart sensing system for the concrete compactness detection purpose. To evaluate the efficiency of the developed approach, six specimens of the CFST columns with the rectangular cross-section were produced by placing some artificial defects during casting of concrete for simulating various uncompacted voids such as cavities, cracks, and debond. During the test, the time reversal technology was applied to rebuild the received signals and launch the reversed signals again by SAs, to overcome the issue of the lack of the prototype. Based on the proposed nonprototype, two indices of time reversibility (TR and symmetry (SYM were applied to relatively evaluate the level of concrete compactness in the range of the two SAs. The experimental results show that the developed method can effectively detect the compactness of concrete in CFST columns.

  8. The invariance of classical electromagnetism under Charge-conjugation, Parity and Time-reversal (CPT) transformations

    Science.gov (United States)

    Norbury, John W.

    1989-01-01

    The invariance of classical electromagnetism under charge-conjugation, parity, and time-reversal (CPT) is studied by considering the motion of a charged particle in electric and magnetic fields. Upon applying CPT transformations to various physical quantities and noting that the motion still behaves physically demonstrates invariance.

  9. Computing exact bundle compliance control charts via probability generating functions.

    Science.gov (United States)

    Chen, Binchao; Matis, Timothy; Benneyan, James

    2016-06-01

    Compliance to evidenced-base practices, individually and in 'bundles', remains an important focus of healthcare quality improvement for many clinical conditions. The exact probability distribution of composite bundle compliance measures used to develop corresponding control charts and other statistical tests is based on a fairly large convolution whose direct calculation can be computationally prohibitive. Various series expansions and other approximation approaches have been proposed, each with computational and accuracy tradeoffs, especially in the tails. This same probability distribution also arises in other important healthcare applications, such as for risk-adjusted outcomes and bed demand prediction, with the same computational difficulties. As an alternative, we use probability generating functions to rapidly obtain exact results and illustrate the improved accuracy and detection over other methods. Numerical testing across a wide range of applications demonstrates the computational efficiency and accuracy of this approach.

  10. Anisotropy signature in reverse-time migration extended images

    KAUST Repository

    Sava, Paul C.; Alkhalifah, Tariq Ali

    2014-01-01

    Reverse-time migration can accurately image complex geologic structures in anisotropic media. Extended images at selected locations in the Earth, i.e., at common-image-point gathers, carry rich information to characterize the angle-dependent illumination and to provide measurements for migration velocity analysis. However, characterizing the anisotropy influence on such extended images is a challenge. Extended common-image-point gathers are cheap to evaluate since they sample the image at sparse locations indicated by the presence of strong reflectors. Such gathers are also sensitive to velocity error that manifests itself through moveout as a function of space and time lags. Furthermore, inaccurate anisotropy leaves a distinctive signature in common-image-point gathers, which can be used to evaluate anisotropy through techniques similar to the ones used in conventional wavefield tomography. It specifically admits a V-shaped residual moveout with the slope of the "V" flanks depending on the anisotropic parameter η regardless of the complexity of the velocity model. It reflects the fourth-order nature of the anisotropy influence on moveout as it manifests itself in this distinct signature in extended images after handling the velocity properly in the imaging process. Synthetic and real data observations support this assertion.

  11. Anisotropy signature in reverse-time migration extended images

    KAUST Repository

    Sava, Paul C.

    2014-11-04

    Reverse-time migration can accurately image complex geologic structures in anisotropic media. Extended images at selected locations in the Earth, i.e., at common-image-point gathers, carry rich information to characterize the angle-dependent illumination and to provide measurements for migration velocity analysis. However, characterizing the anisotropy influence on such extended images is a challenge. Extended common-image-point gathers are cheap to evaluate since they sample the image at sparse locations indicated by the presence of strong reflectors. Such gathers are also sensitive to velocity error that manifests itself through moveout as a function of space and time lags. Furthermore, inaccurate anisotropy leaves a distinctive signature in common-image-point gathers, which can be used to evaluate anisotropy through techniques similar to the ones used in conventional wavefield tomography. It specifically admits a V-shaped residual moveout with the slope of the "V" flanks depending on the anisotropic parameter η regardless of the complexity of the velocity model. It reflects the fourth-order nature of the anisotropy influence on moveout as it manifests itself in this distinct signature in extended images after handling the velocity properly in the imaging process. Synthetic and real data observations support this assertion.

  12. Exact piecewise flat gravitational waves

    NARCIS (Netherlands)

    van de Meent, M.

    2011-01-01

    We generalize our previous linear result (van de Meent 2011 Class. Quantum Grav 28 075005) in obtaining gravitational waves from our piecewise flat model for gravity in 3+1 dimensions to exact piecewise flat configurations describing exact planar gravitational waves. We show explicitly how to

  13. Least-squares reverse time migration with radon preconditioning

    KAUST Repository

    Dutta, Gaurav

    2016-09-06

    We present a least-squares reverse time migration (LSRTM) method using Radon preconditioning to regularize noisy or severely undersampled data. A high resolution local radon transform is used as a change of basis for the reflectivity and sparseness constraints are applied to the inverted reflectivity in the transform domain. This reflects the prior that for each location of the subsurface the number of geological dips is limited. The forward and the adjoint mapping of the reflectivity to the local Radon domain and back are done through 3D Fourier-based discrete Radon transform operators. The sparseness is enforced by applying weights to the Radon domain components which either vary with the amplitudes of the local dips or are thresholded at given quantiles. Numerical tests on synthetic and field data validate the effectiveness of the proposed approach in producing images with improved SNR and reduced aliasing artifacts when compared with standard RTM or LSRTM.

  14. Search for time reversal violation in neutron decay

    International Nuclear Information System (INIS)

    Gorel, P.

    2006-06-01

    The topic of this thesis is the implementation of an experimental setup designed to measure the R- and N-parameters in polarized neutron decay, together with the data analysis. Four observables are necessary for this measurement: the neutron polarization, the electron momentum and both transverse components of the electron polarization. These last two are measured using a Mott polarimeter. The other observables are determined using the same detectors. The precision to be reached on the R-parameter is 0.5%. A non zero value would sign a time reversal invariance violation and therefore would be a hint of physics beyond the Standard Model. This document presents the work done to prepare and optimize the experimental setup before the data acquisition run performed in 2004. Particular care was taken on the scintillator walls, used to trigger the acquisition and measure the electron energy. The second part concerns the implementation of methods to extract R and N from the data, and the study of the background recorded simultaneously. (author)

  15. Time-reversal-noninvariant, parity-conserving nuclear interactions

    International Nuclear Information System (INIS)

    Haxton, W.C.; Hoering, A.; Washington Univ., Seattle, WA; Melbourne Univ., Parkville, VIC

    1993-01-01

    In this paper the authors quantify the relationship between compound nucleus (CN) and electric dipole moment (edm) constraints on long-ranged time-reversal-noninvariant (TRNI), parity-conserving (PC) interactions. It begins by reviewing the work that has been done in compound nuclei. In the second section, it considers the general form of the TRNI PC interaction in meson exchange models. In the third section discusses one mechanism for generating an atomic edm, a TRNI PC nuclear interaction mediate by ρ exchange coupled with Z exchange between atomic electrons and the nucleus. While a variety of other mechanisms can similarly generate edms from TRNI PC interactions this example has some interesting experimental consequences. The limits extracted are then translated into a constraint on α, the ratio of typical TRNI and TRI N N matrix elements. It is concluded that such atomic edm limits on TRNI PC interactions are at least comparable to those obtained in the best CN studies. These limits from long-distance contributions to edms are then compared to the stringent bounds obtained recently by Conti and Khriplovich from studies of short-ranged mechanisms. 37 refs., 2 figs

  16. FOCUS: time-of-flight spectrometer for cold neutrons at SINQ

    Energy Technology Data Exchange (ETDEWEB)

    Janssen, S; Mesot, J [Lab. for Neutron Scattering ETH Zurich, Zurich (Switzerland) and Paul Scherrer Institute, Villigen (Switzerland); Hempelmann, R [Saarbruecken Univ., Physical Chemistry, Saarbruecken (Germany)

    1996-11-01

    The physical layout of the Time-Of-Flight spectrometer at the new spallation source SINQ is presented. The concept shows up a hybrid-TOF combining a Fermi-chopper with a crystal monochromator. The demand of a versatile and flexible instrument for several applications is taken into account by the option of switching from time-focusing to monochromatic focusing mode such that the spectrometer can be optimised for both quasielastic and inelastic scattering applications. (author) 5 figs., 2 tabs., 16 refs.

  17. Implementation on Electronic Circuits and RTR Pragmatical Adaptive Synchronization: Time-Reversed Uncertain Dynamical Systems' Analysis and Applications

    Directory of Open Access Journals (Sweden)

    Shih-Yu Li

    2013-01-01

    Full Text Available We expose the chaotic attractors of time-reversed nonlinear system, further implement its behavior on electronic circuit, and apply the pragmatical asymptotically stability theory to strictly prove that the adaptive synchronization of given master and slave systems with uncertain parameters can be achieved. In this paper, the variety chaotic motions of time-reversed Lorentz system are investigated through Lyapunov exponents, phase portraits, and bifurcation diagrams. For further applying the complex signal in secure communication and file encryption, we construct the circuit to show the similar chaotic signal of time-reversed Lorentz system. In addition, pragmatical asymptotically stability theorem and an assumption of equal probability for ergodic initial conditions (Ge et al., 1999, Ge and Yu, 2000, and Matsushima, 1972 are proposed to strictly prove that adaptive control can be accomplished successfully. The current scheme of adaptive control—by traditional Lyapunov stability theorem and Barbalat lemma, which are used to prove the error vector—approaches zero, as time approaches infinity. However, the core question—why the estimated or given parameters also approach to the uncertain parameters—remains without answer. By the new stability theory, those estimated parameters can be proved approaching the uncertain values strictly, and the simulation results are shown in this paper.

  18. Disease clusters, exact distributions of maxima, and P-values.

    Science.gov (United States)

    Grimson, R C

    1993-10-01

    This paper presents combinatorial (exact) methods that are useful in the analysis of disease cluster data obtained from small environments, such as buildings and neighbourhoods. Maxwell-Boltzmann and Fermi-Dirac occupancy models are compared in terms of appropriateness of representation of disease incidence patterns (space and/or time) in these environments. The methods are illustrated by a statistical analysis of the incidence pattern of bone fractures in a setting wherein fracture clustering was alleged to be occurring. One of the methodological results derived in this paper is the exact distribution of the maximum cell frequency in occupancy models.

  19. Exact solitary waves of the Fisher equation

    International Nuclear Information System (INIS)

    Kudryashov, Nikolai A.

    2005-01-01

    New method is presented to search exact solutions of nonlinear differential equations. This approach is used to look for exact solutions of the Fisher equation. New exact solitary waves of the Fisher equation are given

  20. Constraining the reversing and non-reversing modes of the geodynamo. New insights from magnetostratigraphy.

    Science.gov (United States)

    Gallet, Y.; Pavlov, V.; Shatsillo, A.; Hulot, G.

    2015-12-01

    Constraining the evolution in the geomagnetic reversal frequency over hundreds of million years is not a trivial matter. Beyond the fact that there are long periods without reversals, known as superchrons, and periods with many reversals, the way the reversal frequency changes through time during reversing periods is still debated. A smooth evolution or a succession of stationary segments have both been suggested to account for the geomagnetic polarity time scale since the Middle-Late Jurassic. Sudden changes from a reversing mode to a non-reversing mode of the geodynamo may also well have happened, the switch between the two modes having then possibly been controlled by the thermal conditions at the core-mantle boundary. There is, nevertheless, a growing set of magnetostratigraphic data, which could help decipher a proper interpretation of the reversal history, in particular in the early Paleozoic and even during the Precambrian. Although yielding a fragmentary record, these data reveal the occurrence of both additional superchrons and periods characterized by extremely high, not to say extraordinary, magnetic reversal frequencies. In this talk, we will present a synthesis of these data, mainly obtained from Siberia, and discuss their implication for the magnetic reversal behavior over the past billion years.

  1. Ergodic time-reversible chaos for Gibbs' canonical oscillator

    International Nuclear Information System (INIS)

    Hoover, William Graham; Sprott, Julien Clinton; Patra, Puneet Kumar

    2015-01-01

    Nosé's pioneering 1984 work inspired a variety of time-reversible deterministic thermostats. Though several groups have developed successful doubly-thermostated models, single-thermostat models have failed to generate Gibbs' canonical distribution for the one-dimensional harmonic oscillator. A 2001 doubly-thermostated model, claimed to be ergodic, has a singly-thermostated version. Though neither of these models is ergodic this work has suggested a successful route toward singly-thermostated ergodicity. We illustrate both ergodicity and its lack for these models using phase-space cross sections and Lyapunov instability as diagnostic tools. - Highlights: • We develop cross-section and Lyapunov methods for diagnosing ergodicity. • We apply these methods to several thermostatted-oscillator problems. • We demonstrate the nonergodicity of previous work. • We find a novel family of ergodic thermostatted-oscillator problems.

  2. Exact non-Markovian master equations for multiple qubit systems: Quantum-trajectory approach

    Science.gov (United States)

    Chen, Yusui; You, J. Q.; Yu, Ting

    2014-11-01

    A wide class of exact master equations for a multiple qubit system can be explicitly constructed by using the corresponding exact non-Markovian quantum-state diffusion equations. These exact master equations arise naturally from the quantum decoherence dynamics of qubit system as a quantum memory coupled to a collective colored noisy source. The exact master equations are also important in optimal quantum control, quantum dissipation, and quantum thermodynamics. In this paper, we show that the exact non-Markovian master equation for a dissipative N -qubit system can be derived explicitly from the statistical average of the corresponding non-Markovian quantum trajectories. We illustrated our general formulation by an explicit construction of a three-qubit system coupled to a non-Markovian bosonic environment. This multiple qubit master equation offers an accurate time evolution of quantum systems in various domains, and paves the way to investigate the memory effect of an open system in a non-Markovian regime without any approximation.

  3. Classical diffusion in a field-reversed mirror

    International Nuclear Information System (INIS)

    Auerbach, S.P.; Condit, W.C.

    1981-01-01

    Classical transport of particles and heat in field-reversed mirrors is discussed. The X-points (field nulls on axis) are shown to have no deleterious effect on transport; this conclusion is true for any transport model. For an elongated Hill's vortex equilibrium the classical diffusion coefficient is calculated analytically and used to construct an analytic solution to the transport equation for particles or energy; this yields exact results for particle and energy confinement times. These life-times are roughly 3 to 6 times shorter than previous heuristic estimates. Experimentally determined life-times are within a factor of 3 to 4 of our estimates. To assess the impact of these results on reactor designs, the authors construct an analytic reactor model in which neutral-beam input balances ion heat loss. Energy loss due to synchrotron radiation is calculated analytically and shown to be negligible, even with no wall reflection. Formulas are presented which give the reactor parameters in terms of plasma temperature, energy multiplication factor Q, and allowed neutron wall loading. The effect of anomalous resistivity is incorporated heuristically by assuming an anomalous resistivity which is enhanced by a factor A over classical resistivity. For large A the minimum power of a reactor scales as Asup(11/6). A=50 gives a reactor design which still seems reasonable, but A=200 leads to extremely large, high-power reactors. (author)

  4. CONDITIONS FOR EXACT CAVALIERI ESTIMATION

    Directory of Open Access Journals (Sweden)

    Mónica Tinajero-Bravo

    2014-03-01

    Full Text Available Exact Cavalieri estimation amounts to zero variance estimation of an integral with systematic observations along a sampling axis. A sufficient condition is given, both in the continuous and the discrete cases, for exact Cavalieri sampling. The conclusions suggest improvements on the current stereological application of fractionator-type sampling.

  5. Reversible and Embedded Watermarking of Medical Images for Telemedicine

    Directory of Open Access Journals (Sweden)

    Chung-Yen Su

    2015-08-01

    Full Text Available In this paper, we propose a new reversible watermarking of medical images for the applications in telemedicine. By using a bit-stream insertion scheme, the patient’s information can be treated as a watermark and can be embedded into the bit-stream of a cover image for remote transmission. The proposed method simplifies the design of traditional image coding after a reversible watermarking. Experimental results show that the compression ratio can be achieved up to 3.025. The watermarking capacity can be obtained over 0.75 bpp for some common images. In addition, the watermark can be extracted exactly and the cover image can be reconstructed either in a lossless way or a lossy way. The obtained results also show the improvement with respect to previous works.

  6. Attenuation compensation for least-squares reverse time migration using the viscoacoustic-wave equation

    KAUST Repository

    Dutta, Gaurav

    2014-10-01

    Strong subsurface attenuation leads to distortion of amplitudes and phases of seismic waves propagating inside the earth. Conventional acoustic reverse time migration (RTM) and least-squares reverse time migration (LSRTM) do not account for this distortion, which can lead to defocusing of migration images in highly attenuative geologic environments. To correct for this distortion, we used a linearized inversion method, denoted as Qp-LSRTM. During the leastsquares iterations, we used a linearized viscoacoustic modeling operator for forward modeling. The adjoint equations were derived using the adjoint-state method for back propagating the residual wavefields. The merit of this approach compared with conventional RTM and LSRTM was that Qp-LSRTM compensated for the amplitude loss due to attenuation and could produce images with better balanced amplitudes and more resolution below highly attenuative layers. Numerical tests on synthetic and field data illustrated the advantages of Qp-LSRTM over RTM and LSRTM when the recorded data had strong attenuation effects. Similar to standard LSRTM, the sensitivity tests for background velocity and Qp errors revealed that the liability of this method is the requirement for smooth and accurate migration velocity and attenuation models.

  7. Attenuation compensation for least-squares reverse time migration using the viscoacoustic-wave equation

    KAUST Repository

    Dutta, Gaurav; Schuster, Gerard T.

    2014-01-01

    Strong subsurface attenuation leads to distortion of amplitudes and phases of seismic waves propagating inside the earth. Conventional acoustic reverse time migration (RTM) and least-squares reverse time migration (LSRTM) do not account for this distortion, which can lead to defocusing of migration images in highly attenuative geologic environments. To correct for this distortion, we used a linearized inversion method, denoted as Qp-LSRTM. During the leastsquares iterations, we used a linearized viscoacoustic modeling operator for forward modeling. The adjoint equations were derived using the adjoint-state method for back propagating the residual wavefields. The merit of this approach compared with conventional RTM and LSRTM was that Qp-LSRTM compensated for the amplitude loss due to attenuation and could produce images with better balanced amplitudes and more resolution below highly attenuative layers. Numerical tests on synthetic and field data illustrated the advantages of Qp-LSRTM over RTM and LSRTM when the recorded data had strong attenuation effects. Similar to standard LSRTM, the sensitivity tests for background velocity and Qp errors revealed that the liability of this method is the requirement for smooth and accurate migration velocity and attenuation models.

  8. Time-dependent flow model of a generalized Burgers' fluid with fractional derivatives through a cylindrical domain: An exact and numerical approach

    Science.gov (United States)

    Safdar, Rabia; Imran, M.; Khalique, Chaudry Masood

    2018-06-01

    Exact solutions for velocity field and tangential stress for rotational flow of a generalized Burgers' fluid within an infinite circular pipe are derived by using the methods of Laplace and finite Hankel transformations. Firstly we take the position of fluid at rest and then the fluid flow due to the rotation of the pipe around the axis of flow having time dependant angular velocity. The exact solutions are presented in terms of the generalized Ga,b,c (., t) -functions. The corresponding results can be freely specified for the same results of Burgers', Oldroyd B, Maxwell, second grade and Newtonian fluids (performing the same motion) as particular cases of the results obtained earlier. The impact of the different parameters, individually and in comparison, are represented by graphical demonstrations. Secondly the numerical solutions for velocity and stress are also obtained with the help of Laplace transformation, Gaver Stehfest's algorithm and MATHCAD. Finally a comparison of both methods for the same problem is done and shows the consistency of results.

  9. Numerical Simulation of Ultrasonic Time Reversal Mirror in a Plate with Defect

    Czech Academy of Sciences Publication Activity Database

    Převorovský, Zdeněk; Krofta, Josef

    2008-01-01

    Roč. 13, č. 3 (2008), s. 1-5 ISSN 1435-4934. [NDT in Progress. Praha, 05.11.2007-07.11.2007] R&D Projects: GA ČR GA106/07/1393; GA ČR GA103/06/1711 Institutional research plan: CEZ:AV0Z20760514 Keywords : defect detection * nonlinear ultrasonic spectroscopy * time reversal mirror Subject RIV: BI - Acoustics http://www.ndt.net/ search /docs.php3?showForm=off&edit=1&MainSource=53&AuthorID=2812

  10. A Typology of Reverse Innovation

    DEFF Research Database (Denmark)

    von Zedtwitz, Max; Corsi, Simone; Søberg, Peder Veng

    2015-01-01

    secondary market introduction, this study expands the espoused definition of reverse innovation beyond its market-introduction focus with reversals in the flow of innovation in the ideation and product development phases. Recognizing that each phase can take place in different geographical locations...... taking place in an emerging country. This analytical framework allows recasting of current research at the intersection between innovation and international business. Of the 10 reverse innovation flows, six are new and have not been covered in the literature to date. The study addresses questions......’s portfolio of global innovation competence and capability. The implications for management are concerned with internal and external resistance to reverse innovation. Most significantly, while greater recognition and power of innovation in formerly subordinate organizational units is inconvenient to some...

  11. Exact solutions for rotating charged dust

    International Nuclear Information System (INIS)

    Islam, J.N.

    1984-01-01

    Earlier work by the author on rotating charged dust is summarized. An incomplete class of exact solutions for differentially rotating charged dust in Newton-Maxwell theory for the equal mass and charge case that was found earlier is completed. A new global exact solution for cylindrically symmetric differentially rotating charged dust in Newton-Maxwell theory is presented. Lastly, a new exact solution for cylindrically symmetric rigidly rotating charged dust in general relativity is given. (author)

  12. On valuing patches: estimating contributions to metapopulation growth with reverse-time capture-recapture modeling

    Science.gov (United States)

    Jamie S. Sanderlin; Peter M. Waser; James E. Hines; James D. Nichols

    2012-01-01

    Metapopulation ecology has historically been rich in theory, yet analytical approaches for inferring demographic relationships among local populations have been few. We show how reverse-time multi-state capture­recapture models can be used to estimate the importance of local recruitment and interpopulation dispersal to metapopulation growth. We use 'contribution...

  13. Detection of Tumor Cell-Specific mRNA in the Peripheral Blood of Patients with Breast Cancer — Evaluation of Several Markers with Real-Time Reverse Transcription-PCR

    Directory of Open Access Journals (Sweden)

    Ulrich Andergassen

    2013-01-01

    Full Text Available It is widely known that cells from epithelial tumors, e.g., breast cancer, detach from their primary tissue and enter blood circulation. We show that the presence of circulating tumor cells (CTCs in samples of patients with primary and metastatic breast cancer can be detected with an array of selected tumor-marker-genes by reverse transcription real-time PCR. The focus of the presented work is on detecting differences in gene expression between healthy individuals and adjuvant and metastatic breast cancer patients, not an accurate quantification of these differences. Therefore, total RNA was isolated from blood samples of healthy donors and patients with primary or metastatic breast cancer after enrichment of mononuclear cells by density gradient centrifugation. After reverse transcription real-time PCR was carried out with a set of marker genes (BCSP, CK8, Her2, MGL, CK18, CK19. B2M and GAPDH were used as reference genes. Blood samples from patients with metastatic disease revealed increased cytokine gene levels in comparison to normal blood samples. Detection of a single gene was not sufficient to detect CTCs by reverse transcription real-time PCR. Markers used here were selected based on a recent study detecting cancer cells on different protein levels. The combination of such a marker array leads to higher and more specific discovery rates, predominantly in metastatic patients. Identification of CTCs by PCR methods may lead to better diagnosis and prognosis and could help to choose an adequate therapy.

  14. Time Reversal Methods for Structural Health Monitoring of Metallic Structures Using Guided Waves

    Science.gov (United States)

    2011-09-01

    measure elastic properties of thin isotropic materials and laminated composite plates. Two types of waves propagate a symmetric wave and antisymmetric...compare it to the original signal. In this time reversal procedure wave propagation from point-A to point-B and can be modeled as a convolution ...where * is the convolution operator and transducer transmit and receive transfer function are neglected for simplification. In the frequency

  15. The functional variable method for finding exact solutions of some ...

    Indian Academy of Sciences (India)

    Abstract. In this paper, we implemented the functional variable method and the modified. Riemann–Liouville derivative for the exact solitary wave solutions and periodic wave solutions of the time-fractional Klein–Gordon equation, and the time-fractional Hirota–Satsuma coupled. KdV system. This method is extremely simple ...

  16. Reverse-symmetry waveguides: Theory and fabrication

    DEFF Research Database (Denmark)

    Horvath, R.; Lindvold, Lars René; Larsen, N.B.

    2002-01-01

    We present an extensive theoretical analysis of reverse-symmetry waveguides with special focus on their potential application as sensor components in aqueous media and demonstrate a novel method for fabrication of such waveguides. The principle of reverse symmetry is based on making the refractive...... index of the waveguide substrate less than the refractive index of the medium covering the waveguiding film (n(water) = 1.33). This is opposed to the conventional waveguide geometry, where the substrate is usually glass or polymers with refractive indices of approximate to1.5. The reverse configuration...... are combined with air-grooved polymer supports to form freestanding single-material polymer waveguides of reverse symmetry capable of guiding light....

  17. Position-dependent radiative transfer as a tool for studying Anderson localization: Delay time, time-reversal and coherent backscattering

    Science.gov (United States)

    van Tiggelen, B. A.; Skipetrov, S. E.; Page, J. H.

    2017-05-01

    Previous work has established that the localized regime of wave transport in open media is characterized by a position-dependent diffusion coefficient. In this work we study how the concept of position-dependent diffusion affects the delay time, the transverse confinement, the coherent backscattering, and the time reversal of waves. Definitions of energy transport velocity of localized waves are proposed. We start with a phenomenological model of radiative transfer and then present a novel perturbational approach based on the self-consistent theory of localization. The latter allows us to obtain results relevant for realistic experiments in disordered quasi-1D wave guides and 3D slabs.

  18. A fast exact sequential algorithm for the partial digest problem.

    Science.gov (United States)

    Abbas, Mostafa M; Bahig, Hazem M

    2016-12-22

    Restriction site analysis involves determining the locations of restriction sites after the process of digestion by reconstructing their positions based on the lengths of the cut DNA. Using different reaction times with a single enzyme to cut DNA is a technique known as a partial digestion. Determining the exact locations of restriction sites following a partial digestion is challenging due to the computational time required even with the best known practical algorithm. In this paper, we introduce an efficient algorithm to find the exact solution for the partial digest problem. The algorithm is able to find all possible solutions for the input and works by traversing the solution tree with a breadth-first search in two stages and deleting all repeated subproblems. Two types of simulated data, random and Zhang, are used to measure the efficiency of the algorithm. We also apply the algorithm to real data for the Luciferase gene and the E. coli K12 genome. Our algorithm is a fast tool to find the exact solution for the partial digest problem. The percentage of improvement is more than 75% over the best known practical algorithm for the worst case. For large numbers of inputs, our algorithm is able to solve the problem in a suitable time, while the best known practical algorithm is unable.

  19. Exact relativistic cylindrical solution of disordered radiation

    International Nuclear Information System (INIS)

    Fonseca Teixeira, A.F. da; Wolk, I.; Som, M.M.

    1976-05-01

    A source free disordered distribution of electromagnetic radiation is considered in Einstein' theory, and a time independent exact solution with cylindrical symmetry is obtained. The gravitation and pressure effects of the radiation alone are sufficient to give the distribution an equilibrium. A finite maximum concentration is found on the axis of symmetry, and decreases monotonically to zero outwards. Timelike and null geodesics are discussed

  20. Focusing and non-focusing modulation strategies for the improvement of on-line two-dimensional hydrophilic interaction chromatography × reversed phase profiling of complex food samples.

    Science.gov (United States)

    Montero, Lidia; Ibáñez, Elena; Russo, Mariateresa; Rastrelli, Luca; Cifuentes, Alejandro; Herrero, Miguel

    2017-09-08

    Comprehensive two-dimensional liquid chromatography (LC × LC) is ever gaining interest in food analysis, as often, food-related samples are too complex to be analyzed through one-dimensional approaches. The use of hydrophilic interaction chromatography (HILIC) combined with reversed phase (RP) separations has already been demonstrated as a very orthogonal combination, which allows attaining increased resolving power. However, this coupling encompasses different analytical challenges, mainly related to the important solvent strength mismatch between the two dimensions, besides those common to every LC × LC method. In the present contribution, different strategies are proposed and compared to further increase HILIC × RP method performance for the analysis of complex food samples, using licorice as a model sample. The influence of different parameters in non-focusing modulation methods based on sampling loops, as well as under focusing modulation, through the use of trapping columns in the interface and through active modulation procedures are studied in order to produce resolving power and sensitivity gains. Although the use of a dilution strategy using sampling loops as well as the highest possible first dimension sampling rate allowed significant improvements on resolution, focusing modulation produced significant gains also in peak capacity and sensitivity. Overall, the obtained results demonstrate the great applicability and potential that active modulation may have for the analysis of complex food samples, such as licorice, by HILIC × RP. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Entanglement, decoherence and thermal relaxation in exactly solvable models

    International Nuclear Information System (INIS)

    Lychkovskiy, Oleg

    2011-01-01

    Exactly solvable models provide an opportunity to study different aspects of reduced quantum dynamics in detail. We consider the reduced dynamics of a single spin in finite XX and XY spin 1/2 chains. First we introduce a general expression describing the evolution of the reduced density matrix. This expression proves to be tractable when the combined closed system (i.e. open system plus environment) is integrable. Then we focus on comparing decoherence and thermalization timescales in the XX chain. We find that for a single spin these timescales are comparable, in contrast to what should be expected for a macroscopic body. This indicates that the process of quantum relaxation of a system with few accessible states can not be separated in two distinct stages - decoherence and thermalization. Finally, we turn to finite-size effects in the time evolution of a single spin in the XY chain. We observe three consecutive stages of the evolution: regular evolution, partial revivals, irregular (apparently chaotic) evolution. The duration of the regular stage is proportional to the number of spins in the chain. We observe a 'quiet and cold period' in the end of the regular stage, which breaks up abruptly at some threshold time.

  2. Transition of unsteady velocity profiles with reverse flow

    OpenAIRE

    Das, Debopam; Arakeri, Jaywant H

    1998-01-01

    This paper deals with the stability and transition to turbulence of wall-bounded unsteady velocity profiles with reverse flow. Such flows occur, for example, during unsteady boundary layer separation and in oscillating pipe flow. The main focus is on results from experiments in time-developing flow in a long pipe, which is decelerated rapidly. The flow is generated by the controlled motion of a piston. We obtain analytical solutions for laminar flow in the pipe and in a two-dimensional channe...

  3. Reverse innovation in maternal health.

    Science.gov (United States)

    Firoz, Tabassum; Makanga, Prestige Tatenda; Nathan, Hannah L; Payne, Beth; Magee, Laura A

    2017-09-01

    Reverse innovation, defined as the flow of ideas from low- to high-income settings, is gaining traction in healthcare. With an increasing focus on value, investing in low-cost but effective and innovative solutions can be of mutual benefit to both high- and low-income countries. Reverse innovation has a role in addressing maternal health challenges in high-income countries by harnessing these innovative solutions for vulnerable populations especially in rural and remote regions. In this paper, we present three examples of 'reverse innovation' for maternal health: a low-cost, easy-to-use blood pressure device (CRADLE), a diagnostic algorithm (mini PIERS) and accompanying mobile app (PIERS on the Move), and a novel method for mapping maternal outcomes (MOM).

  4. The Causes of Preference Reversal.

    OpenAIRE

    Tversky, Amos; Slovic, Paul; Kahneman, Daniel

    1990-01-01

    Observed preference reversal cannot be adequately explained by violations of independence, the reduction axiom, or transitivity. The primary cause of preference reversal is the failure of procedure invariance, especially the overpricing of low-probability, high-payoff bets. This result violates regret theory and generalized (nonindependent) utility models. Preference reversal and a new reversal involving time preferences are explained by scale compatibility, which implies that payoffs are wei...

  5. Performance analysis of an acoustic time reversal system in dynamic and random oceanic environments

    Science.gov (United States)

    Khosla, Sunny Rajendra

    This dissertation provides a theoretical framework along with specific performance predictions for an acoustic time reversal system in shallow oceanic environments. Acoustic time-reversal is a robust means of retrofocusing acoustic energy, in both time and space, to the original sound-source location without any information about the acoustic environment in which it is deployed. The effect of three performance limiting oceanic complexities addressed, include (i)ambient noise field, (ii)reflection and volume scattering from a deterministic soliton internal wave traveling on the thermocline between two water masses, and (iii)volume scattering from a random superposition of linear internal waves convecting a gradient in the sound speed profile. The performance analysis establishes acoustic time reversal to be a promising technology for a two-way communication system in an oceanic medium. For an omni-directional noisy environment a general formulation for the probability of retrofocusing is developed that includes the effect of the medium, accounts for the system hardware and the acoustic parameters. Monte-Carlo simulations in both, a free-space environment and a shallow-ocean sound-channel environment compare well with theory. A 41 element TRA spanning a shallow water depth of 60 m is predicted to return a 70% focal probability at -15 dB SNR for a source to array range of 6 km. Preliminary research with broadband signals suggest that they should outperform narrowband response in both free space and sound channel environments. The impact of the nonlinear solitary waves is addressed using a two-path Green's function to treat the presence of a flat thermocline, and the single scattering Born approximation to address scattering from the soliton internal wave. It is predicted that a stationary soliton located along ray turning paths between the source and the TRA can lead to both enhanced and degraded focal performance. Based on extension of previous research in wave

  6. Antibiotic Resistance Determinant-Focused Acinetobacter baumannii Vaccine Designed Using Reverse Vaccinology.

    Science.gov (United States)

    Ni, Zhaohui; Chen, Yan; Ong, Edison; He, Yongqun

    2017-02-21

    As one of the most influential and troublesome human pathogens, Acinetobacter baumannii ( A. baumannii ) has emerged with many multidrug-resistant strains. After collecting 33 complete A. baumannii genomes and 84 representative antibiotic resistance determinants, we used the Vaxign reverse vaccinology approach to predict classical type vaccine candidates against A. baumannii infections and new type vaccine candidates against antibiotic resistance. Our genome analysis identified 35 outer membrane or extracellular adhesins that are conserved among all 33 genomes, have no human protein homology, and have less than 2 transmembrane helices. These 35 antigens include 11 TonB dependent receptors, 8 porins, 7 efflux pump proteins, and 2 fimbrial proteins (FilF and CAM87009.1). CAM86003.1 was predicted to be an adhesin outer membrane protein absent from 3 antibiotic-sensitive strains and conserved in 21 antibiotic-resistant strains. Feasible anti-resistance vaccine candidates also include one extracellular protein (QnrA), 3 RND type outer membrane efflux pump proteins, and 3 CTX-M type β-lactamases. Among 39 β-lactamases, A. baumannii CTX-M-2, -5, and -43 enzymes are predicted as adhesins and better vaccine candidates than other β-lactamases to induce preventive immunity and enhance antibiotic treatments. This report represents the first reverse vaccinology study to systematically predict vaccine antigen candidates against antibiotic resistance for a microbial pathogen.

  7. On exact solutions of scattering problems

    International Nuclear Information System (INIS)

    Nikishov, P.Yu.; Plekhanov, E.B.; Zakhariev, B.N.

    1982-01-01

    Examples illustrating the quality of the reconstruction of potentials from single-channel scattering data by using exactly solvable models are given. Simple exact solutions for multi-channel systems with non-degenerated resonance singularities of the scattering matrix are derived

  8. On the Green's function of the partially diffusion-controlled reversible ABCD reaction for radiation chemistry codes

    Energy Technology Data Exchange (ETDEWEB)

    Plante, Ianik, E-mail: ianik.plante-1@nasa.gov [Wyle Science, Technology & Engineering, 1290 Hercules, Houston, TX 77058 (United States); Devroye, Luc, E-mail: lucdevroye@gmail.com [School of Computer Science, McGill University, 3480 University Street, Montreal H3A 0E9 (Canada)

    2015-09-15

    Several computer codes simulating chemical reactions in particles systems are based on the Green's functions of the diffusion equation (GFDE). Indeed, many types of chemical systems have been simulated using the exact GFDE, which has also become the gold standard for validating other theoretical models. In this work, a simulation algorithm is presented to sample the interparticle distance for partially diffusion-controlled reversible ABCD reaction. This algorithm is considered exact for 2-particles systems, is faster than conventional look-up tables and uses only a few kilobytes of memory. The simulation results obtained with this method are compared with those obtained with the independent reaction times (IRT) method. This work is part of our effort in developing models to understand the role of chemical reactions in the radiation effects on cells and tissues and may eventually be included in event-based models of space radiation risks. However, as many reactions are of this type in biological systems, this algorithm might play a pivotal role in future simulation programs not only in radiation chemistry, but also in the simulation of biochemical networks in time and space as well.

  9. On the Green's function of the partially diffusion-controlled reversible ABCD reaction for radiation chemistry codes

    International Nuclear Information System (INIS)

    Plante, Ianik; Devroye, Luc

    2015-01-01

    Several computer codes simulating chemical reactions in particles systems are based on the Green's functions of the diffusion equation (GFDE). Indeed, many types of chemical systems have been simulated using the exact GFDE, which has also become the gold standard for validating other theoretical models. In this work, a simulation algorithm is presented to sample the interparticle distance for partially diffusion-controlled reversible ABCD reaction. This algorithm is considered exact for 2-particles systems, is faster than conventional look-up tables and uses only a few kilobytes of memory. The simulation results obtained with this method are compared with those obtained with the independent reaction times (IRT) method. This work is part of our effort in developing models to understand the role of chemical reactions in the radiation effects on cells and tissues and may eventually be included in event-based models of space radiation risks. However, as many reactions are of this type in biological systems, this algorithm might play a pivotal role in future simulation programs not only in radiation chemistry, but also in the simulation of biochemical networks in time and space as well

  10. Spontaneous breaking of time-reversal symmetry in strongly interacting two-dimensional electron layers in silicon and germanium.

    Science.gov (United States)

    Shamim, S; Mahapatra, S; Scappucci, G; Klesse, W M; Simmons, M Y; Ghosh, A

    2014-06-13

    We report experimental evidence of a remarkable spontaneous time-reversal symmetry breaking in two-dimensional electron systems formed by atomically confined doping of phosphorus (P) atoms inside bulk crystalline silicon (Si) and germanium (Ge). Weak localization corrections to the conductivity and the universal conductance fluctuations were both found to decrease rapidly with decreasing doping in the Si:P and Ge:P delta layers, suggesting an effect driven by Coulomb interactions. In-plane magnetotransport measurements indicate the presence of intrinsic local spin fluctuations at low doping, providing a microscopic mechanism for spontaneous lifting of the time-reversal symmetry. Our experiments suggest the emergence of a new many-body quantum state when two-dimensional electrons are confined to narrow half-filled impurity bands.

  11. Time-dependent beam focusing at the DARHT-II injector diode

    International Nuclear Information System (INIS)

    Eylon, S.; Henestroza, E.; Fawley, W.; Yu, S.

    1999-01-01

    The injector for the second axis of the Dual-Axis Radiographic Hydrotest Facility (DARHT) is being designed and constructed at LBNL. The injector consists of a single gap diode extracting 2(micro)s, 2kA, 3.2 MeV electron beam from a 6.5 inches diameter thermionic dispenser cathode. The injector is powered through a ceramic column by a Marx generator. We also investigated the possibility of extracting a beam current of 4 kA. The focusing system for the electron beam consists of a Pierce electrostatic focusing electrode at the cathode and three solenoidal focusing magnets positioned between the anode and induction accelerator input. The off-energy components (beam-head) during the 400 ns energy rise time are overfocused, leading to beam envelope mismatch and growth resulting in the possibility of beam hitting the accelerator tube walls. The anode focusing magnets can be tuned to avoid the beam spill in the 2kA case. To allow beam-head control for the 4kA case we are considering the introduction of time-varying magnetic focusing field along the accelerator axis generated by a single-loop solenoid magnet positioned in the anode beam tube. We will present the beam-head dynamics calculations as well as the solenoid design and preliminary feasibility test results

  12. Time-resolved measurements of the focused ion beams on PBFA II

    International Nuclear Information System (INIS)

    Mix, L.P.; Stygar, W.A.; Leeper, R.J.; Maenchen, J.E.; Wenger, D.F.

    1992-01-01

    A time-resolved camera has been developed to image the intense ion beam focus on PBFA II. Focused ions from a sector of the ion diode are Rutherford scattered from a thin gold foil on the diode axis and pinhole imaged onto an array of up to 49 PIN detectors to obtain the spatially and temporally resolved images. The signals from these detectors are combined to provide a movie of the beam focus with a time resolution of about 3 ns and a spatial resolution of 2 mm over a 12 mm field of view. Monte Carlo simulations of the camera response are used with the measured ion energy to account for the time-of-flight dispersion of the beam and to convert the recorded signals to an intensity. From measurements on an 81 degree sector of the diode, average intensities on a 6 mm sphere of about 5 TW/cm 2 and energies approaching 80 kJ/cm 2 are calculated for standard proton diodes. Corresponding numbers for a lithium diode are less than those measured with protons. The details of the analysis and image reconstruction will be presented along with scaled images from recent ion focusing experiments

  13. Reverse logistics policy – differences between conservative and innovative reverse logistics management

    Directory of Open Access Journals (Sweden)

    Alena Klapalová

    2013-01-01

    Full Text Available One of the of the key barriers that hampers effective and efficient management of reverse flows detected within a number of empirical surveys and case studies focused on reverse logistics and/or return management is business (organisational policy, specifically lack of policy, deficiency in existing policy or inferior policy. Despite this fact, there is a gap in literature which would show some evidence from practice that innovative reverse logistics policy both can pay off and is associated with certain aspects of reverse logistics management. Such proof can have several implications. It can support the call for better understanding and more research of the linkages of reverse logistics with other corporate functions, promote the acceptation of strategic character of reverse logistics and stress the role of RL policy within the rest of overall corporate management.The aim of this paper is to contribute and to enrich the existing body of knowledge concerning the above-mentioned gap through presentation of survey results that was realized in 2012 among managers of 244 Czech firms. The results demonstrate the statistically significant association between the innovativeness of RL policy and profitability of firms, quality of RL planning, perception of RL importance, level of RL knowledge and perception of product innovation importance for firms’ competitiveness and frequency of product innovation. They also reveal statistically significant differences between firms with conservative and innovative RL policy and the perceived existence of some barriers to manage RL.

  14. Digital Sequences and a Time Reversal-Based Impact Region Imaging and Localization Method

    Science.gov (United States)

    Qiu, Lei; Yuan, Shenfang; Mei, Hanfei; Qian, Weifeng

    2013-01-01

    To reduce time and cost of damage inspection, on-line impact monitoring of aircraft composite structures is needed. A digital monitor based on an array of piezoelectric transducers (PZTs) is developed to record the impact region of impacts on-line. It is small in size, lightweight and has low power consumption, but there are two problems with the impact alarm region localization method of the digital monitor at the current stage. The first one is that the accuracy rate of the impact alarm region localization is low, especially on complex composite structures. The second problem is that the area of impact alarm region is large when a large scale structure is monitored and the number of PZTs is limited which increases the time and cost of damage inspections. To solve the two problems, an impact alarm region imaging and localization method based on digital sequences and time reversal is proposed. In this method, the frequency band of impact response signals is estimated based on the digital sequences first. Then, characteristic signals of impact response signals are constructed by sinusoidal modulation signals. Finally, the phase synthesis time reversal impact imaging method is adopted to obtain the impact region image. Depending on the image, an error ellipse is generated to give out the final impact alarm region. A validation experiment is implemented on a complex composite wing box of a real aircraft. The validation results show that the accuracy rate of impact alarm region localization is approximately 100%. The area of impact alarm region can be reduced and the number of PZTs needed to cover the same impact monitoring region is reduced by more than a half. PMID:24084123

  15. Exact wave packet decoherence dynamics in a discrete spectrum environment

    International Nuclear Information System (INIS)

    Tu, Matisse W Y; Zhang Weimin

    2008-01-01

    We find an exact analytical solution of the reduced density matrix from the Feynman-Vernon influence functional theory for a wave packet in an environment containing a few discrete modes. We obtain two intrinsic energy scales relating to the time scales of the system and the environment. The different relationship between these two scales alters the overall form of the solution of the system. We also introduce a decoherence measure for a single wave packet which is defined as the ratio of Schroedinger uncertainty over the delocalization extension of the wave packet and characterizes the time-evolution behaviour of the off-diagonal reduced density matrix element. We utilize the exact solution and the decoherence measure to study the wave packet decoherence dynamics. We further demonstrate how the dynamical diffusion of the wave packet leads to non-Markovian decoherence in such a microscopic environment.

  16. Prospects for Searching for Time-Reversal Violation In Pa-229

    Science.gov (United States)

    Singh, Jaideep

    2017-09-01

    Certain pear-shaped nuclei are expected to have enhanced sensitivity to time-reversal and parity-violating interactions originating within the nuclear medium. In particular, Pa-229 is thought to be about 100,000 times more sensitive than Hg-199 which currently sets some of the most stringent limits for these types of interactions. Several challenges would first have to be addressed in order to take advantage of this discovery potential. First, there is not currently a significant source of Pa-229; however, there are plans to harvest Pa-229 from the FRIB beam dump. Second, the spin-5/2 nucleus of Pa-229 limits its coherence time while also making it sensitive to systematic effects related to local field gradients. On the other hand, this also gives Pa-229 an additional source of signal in the form of a magnetic quadrupole moment (MQM) which violates the same symmetries as an EDM but is not observable in spin-1/2 systems. Third, in order to compensate for the small atom numbers and short coherence times, the Pa-229 atoms would have to be probed with exceptionally large electric & magnetic fields that are only possible if Pa-229 is a part of a polar molecule or embedded inside of an optical crystal. I will present an our plans to test some of these concepts using stable Pr-141.

  17. Three dimensional time reversal optical tomography

    Science.gov (United States)

    Wu, Binlin; Cai, W.; Alrubaiee, M.; Xu, M.; Gayen, S. K.

    2011-03-01

    Time reversal optical tomography (TROT) approach is used to detect and locate absorptive targets embedded in a highly scattering turbid medium to assess its potential in breast cancer detection. TROT experimental arrangement uses multi-source probing and multi-detector signal acquisition and Multiple-Signal-Classification (MUSIC) algorithm for target location retrieval. Light transport from multiple sources through the intervening medium with embedded targets to the detectors is represented by a response matrix constructed using experimental data. A TR matrix is formed by multiplying the response matrix by its transpose. The eigenvectors with leading non-zero eigenvalues of the TR matrix correspond to embedded objects. The approach was used to: (a) obtain the location and spatial resolution of an absorptive target as a function of its axial position between the source and detector planes; and (b) study variation in spatial resolution of two targets at the same axial position but different lateral positions. The target(s) were glass sphere(s) of diameter ~9 mm filled with ink (absorber) embedded in a 60 mm-thick slab of Intralipid-20% suspension in water with an absorption coefficient μa ~ 0.003 mm-1 and a transport mean free path lt ~ 1 mm at 790 nm, which emulate the average values of those parameters for human breast tissue. The spatial resolution and accuracy of target location depended on axial position, and target contrast relative to the background. Both the targets could be resolved and located even when they were only 4-mm apart. The TROT approach is fast, accurate, and has the potential to be useful in breast cancer detection and localization.

  18. Conjugate gradient and cross-correlation based least-square reverse time migration and its application

    Science.gov (United States)

    Sun, Xiao-Dong; Ge, Zhong-Hui; Li, Zhen-Chun

    2017-09-01

    Although conventional reverse time migration can be perfectly applied to structural imaging it lacks the capability of enabling detailed delineation of a lithological reservoir due to irregular illumination. To obtain reliable reflectivity of the subsurface it is necessary to solve the imaging problem using inversion. The least-square reverse time migration (LSRTM) (also known as linearized reflectivity inversion) aims to obtain relatively high-resolution amplitude preserving imaging by including the inverse of the Hessian matrix. In practice, the conjugate gradient algorithm is proven to be an efficient iterative method for enabling use of LSRTM. The velocity gradient can be derived from a cross-correlation between observed data and simulated data, making LSRTM independent of wavelet signature and thus more robust in practice. Tests on synthetic and marine data show that LSRTM has good potential for use in reservoir description and four-dimensional (4D) seismic images compared to traditional RTM and Fourier finite difference (FFD) migration. This paper investigates the first order approximation of LSRTM, which is also known as the linear Born approximation. However, for more complex geological structures a higher order approximation should be considered to improve imaging quality.

  19. Magnetic reversals from planetary dynamo waves

    DEFF Research Database (Denmark)

    Sheyko, Andrey; Finlay, Chris; Jackson, Andrew

    2016-01-01

    A striking feature of many natural dynamos is their ability to undergo polarity reversals. The best documented example is Earth's magnetic field, which has reversed hundreds of times during its history. The origin of geomagnetic polarity reversals lies in a magnetohydrodynamic process that takes ...... to kinematic dynamo waves. Because our results are relevant in a regime of low viscosity and high magnetic diffusivity, and with geophysically appropriate boundary conditions, this form of dynamo wave may also be involved in geomagnetic reversals.......A striking feature of many natural dynamos is their ability to undergo polarity reversals. The best documented example is Earth's magnetic field, which has reversed hundreds of times during its history. The origin of geomagnetic polarity reversals lies in a magnetohydrodynamic process that takes...... place in Earth's core, but the precise mechanism is debated. The majority of numerical geodynamo simulations that exhibit reversals operate in a regime in which the viscosity of the fluid remains important, and in which the dynamo mechanism primarily involves stretching and twisting of field lines...

  20. Time-reversal of electromagnetic scattering for small scatterer classification

    International Nuclear Information System (INIS)

    Smith, J Torquil; Berryman, James G

    2012-01-01

    Time-reversal operators, or the alternatively labelled, but equivalent, multistatic response matrix methods, are used to show how to determine the number of scatterers present in an electromagnetic scattering scenario that might be typical of UneXploded Ordinance (UXO) detection, classification and removal applications. Because the nature of the target UXO application differs from that of many other common inversion problems, emphasis is placed here on classification and enumeration rather than on detailed imaging. The main technical issues necessarily revolve around showing that it is possible to find a sufficient number of constraints via multiple measurements (i.e. using several distinct views at the target site) to solve the enumeration problem. The main results show that five measurements with antenna pairs are generally adequate to solve the classification and enumeration problems. However, these results also demonstrate a need for decreasing noise levels in the multistatic matrix as the number n of scatterers increases for the intended practical applications of the method. (paper)

  1. Laser oriented 36K for time reversal symmetry measurements

    International Nuclear Information System (INIS)

    Young, A.R.; Anderson, W.S.; Calaprice, F.P.; Cates, G.D.; Jones, G.L.; Krieger, D.A.; Vogelaar, R.B.

    1995-01-01

    We have produced very large nuclear alignments in radioactive 36 K (half-life 0.34 sec) through laser optical pumping techniques. The 36 K was created through (p,n) reactions using a 50 nA, 22 MeV proton beam, and a 3.3 atmosphere 36 Ar target. Measurements were made with the target cell at room temperature, when direct optical pumping produces nuclear orientation in the 36 K, and at elevated temperatures 160 degree C and 180 degree C where the 36 K is oriented through a combination of direct optical pumping and spin exchange. The fraction of the maximal nuclear alignment for the 180 degree C data was determined to be 0.46±0.07 stat±0.05 syst through measurements of the γ-ray anisotropy following positron decay. Roughly 10 5 or more decays of oriented 36 K occurred each second. The application of the superallowed decay of 36 K to measurements of time-reversal symmetry in β decay is discussed

  2. Regarding on the exact solutions for the nonlinear fractional differential equations

    Directory of Open Access Journals (Sweden)

    Kaplan Melike

    2016-01-01

    Full Text Available In this work, we have considered the modified simple equation (MSE method for obtaining exact solutions of nonlinear fractional-order differential equations. The space-time fractional equal width (EW and the modified equal width (mEW equation are considered for illustrating the effectiveness of the algorithm. It has been observed that all exact solutions obtained in this paper verify the nonlinear ordinary differential equations which was obtained from nonlinear fractional-order differential equations under the terms of wave transformation relationship. The obtained results are shown graphically.

  3. Multisource least-squares reverse-time migration with structure-oriented filtering

    Science.gov (United States)

    Fan, Jing-Wen; Li, Zhen-Chun; Zhang, Kai; Zhang, Min; Liu, Xue-Tong

    2016-09-01

    The technology of simultaneous-source acquisition of seismic data excited by several sources can significantly improve the data collection efficiency. However, direct imaging of simultaneous-source data or blended data may introduce crosstalk noise and affect the imaging quality. To address this problem, we introduce a structure-oriented filtering operator as preconditioner into the multisource least-squares reverse-time migration (LSRTM). The structure-oriented filtering operator is a nonstationary filter along structural trends that suppresses crosstalk noise while maintaining structural information. The proposed method uses the conjugate-gradient method to minimize the mismatch between predicted and observed data, while effectively attenuating the interference noise caused by exciting several sources simultaneously. Numerical experiments using synthetic data suggest that the proposed method can suppress the crosstalk noise and produce highly accurate images.

  4. Magnetotelluric inversion via reverse time migration algorithm of seismic data

    International Nuclear Information System (INIS)

    Ha, Taeyoung; Shin, Changsoo

    2007-01-01

    We propose a new algorithm for two-dimensional magnetotelluric (MT) inversion. Our algorithm is an MT inversion based on the steepest descent method, borrowed from the backpropagation technique of seismic inversion or reverse time migration, introduced in the middle 1980s by Lailly and Tarantola. The steepest descent direction can be calculated efficiently by using the symmetry of numerical Green's function derived from a mixed finite element method proposed by Nedelec for Maxwell's equation, without calculating the Jacobian matrix explicitly. We construct three different objective functions by taking the logarithm of the complex apparent resistivity as introduced in the recent waveform inversion algorithm by Shin and Min. These objective functions can be naturally separated into amplitude inversion, phase inversion and simultaneous inversion. We demonstrate our algorithm by showing three inversion results for synthetic data

  5. Imperfect price-reversibility of US gasoline demand: Asymmetric responses to price increases and declines

    International Nuclear Information System (INIS)

    Gately, D.

    1992-01-01

    This paper describes a framework for analyzing the imperfect price-reversibility (hysteresis) of oil demand. The oil demand reductions following the oil price increases of the 1970s will not be completely reversed by the price cuts of the 1980s, nor is it necessarily true that these partial demand reversals themselves will be reversed exactly by future price increases. The author decomposes price into three monotonic series: price increases to maximum historic levels, price cuts, and price recoveries (increases below historic highs). He would expect that the response to price cuts would be no greater than to price recoveries, which in turn would be no greater than for increases in maximum historic price. For evidence of imperfect price-reversibility, he tests econometrically the following US data: vehicle miles per driver, the fuel efficiency of the automobile fleet, and gasoline demand per driver. In each case, the econometric results allow him to reject the hypothesis of perfect price-reversibility. The data show smaller response to price cuts than to price increases. This has dramatic implications for projections of gasoline and oil demand, especially under low-price assumptions. 26 refs., 13 figs., 3 tabs

  6. Exact, time-independent estimation of clone size distributions in normal and mutated cells.

    Science.gov (United States)

    Roshan, A; Jones, P H; Greenman, C D

    2014-10-06

    Biological tools such as genetic lineage tracing, three-dimensional confocal microscopy and next-generation DNA sequencing are providing new ways to quantify the distribution of clones of normal and mutated cells. Understanding population-wide clone size distributions in vivo is complicated by multiple cell types within observed tissues, and overlapping birth and death processes. This has led to the increased need for mathematically informed models to understand their biological significance. Standard approaches usually require knowledge of clonal age. We show that modelling on clone size independent of time is an alternative method that offers certain analytical advantages; it can help parametrize these models, and obtain distributions for counts of mutated or proliferating cells, for example. When applied to a general birth-death process common in epithelial progenitors, this takes the form of a gambler's ruin problem, the solution of which relates to counting Motzkin lattice paths. Applying this approach to mutational processes, alternative, exact, formulations of classic Luria-Delbrück-type problems emerge. This approach can be extended beyond neutral models of mutant clonal evolution. Applications of these approaches are twofold. First, we resolve the probability of progenitor cells generating proliferating or differentiating progeny in clonal lineage tracing experiments in vivo or cell culture assays where clone age is not known. Second, we model mutation frequency distributions that deep sequencing of subclonal samples produce.

  7. Numerical investigation on the effects of acceleration reversal times in Rayleigh-Taylor Instability with multiple reversals

    Science.gov (United States)

    Farley, Zachary; Aslangil, Denis; Banerjee, Arindam; Lawrie, Andrew G. W.

    2017-11-01

    An implicit large eddy simulation (ILES) code, MOBILE, is used to explore the growth rate of the mixing layer width of the acceleration-driven Rayleigh-Taylor instability (RTI) under variable acceleration histories. The sets of computations performed consist of a series of accel-decel-accel (ADA) cases in addition to baseline constant acceleration and accel-decel (AD) cases. The ADA cases are a series of varied times for the second acceleration reversal (t2) and show drastic differences in the growth rates. Upon the deceleration phase, the kinetic energy of the flow is shifted into internal wavelike patterns. These waves are evidenced by the examined differences in growth rate in the second acceleration phase for the set of ADA cases. Here, we investigate global parameters that include mixing width, growth rates and the anisotropy tensor for the kinetic energy to better understand the behavior of the growth during the re-acceleration period. Authors acknowledge financial support from DOE-SSAA (DE-NA0003195) and NSF CAREER (#1453056) awards.

  8. Reverse-mode PSLC multi-plane optical see-through display for AR applications.

    Science.gov (United States)

    Liu, Shuxin; Li, Yan; Zhou, Pengcheng; Chen, Quanming; Su, Yikai

    2018-02-05

    In this paper we propose an optical see-through multi-plane display with reverse-mode polymer-stabilized liquid crystal (PSLC). Our design solves the problem of accommodation-vergence conflict with correct focus cues. In the reverse mode PSLC system, power consumption could be reduced to ~1/(N-1) of that in a normal mode system if N planes are displayed. The PSLC films fabricated in our experiment exhibit a low saturation voltage ~20 V rms , a high transparent-state transmittance (92%), and a fast switching time within 2 ms and polarization insensitivity. A proof-of-concept two-plane color display prototype and a four-plane monocolor display prototype were implemented.

  9. New exact solutions of the mBBM equation

    International Nuclear Information System (INIS)

    Zhang Zhe; Li Desheng

    2013-01-01

    The enhanced modified simple equation method presented in this article is applied to construct the exact solutions of modified Benjamin-Bona-Mahoney equation. Some new exact solutions are derived by using this method. When some parameters are taken as special values, the solitary wave solutions can be got from the exact solutions. It is shown that the method introduced in this paper has general significance in searching for exact solutions to the nonlinear evolution equations. (authors)

  10. Multiple time-reversed guide-sources in shallow water

    Science.gov (United States)

    Gaumond, Charles F.; Fromm, David M.; Lingevitch, Joseph F.; Gauss, Roger C.; Menis, Richard

    2003-10-01

    Detection in a monostatic, broadband, active sonar system in shallow water is degraded by propagation-induced spreading. The detection improvement from multiple spatially separated guide sources (GSs) is presented as a method to mitigate this degradation. The improvement of detection by using information in a set of one-way transmissions from a variety of positions is shown using sea data. The experimental area is south of the Hudson Canyon off the coast of New Jersey. The data were taken using five elements of a time-reversing VLA. The five elements were contiguous and at midwater depth. The target and guide source was an echo repeater positioned at various ranges and at middepth. The transmitted signals were 3.0- to 3.5-kHz LFMs. The data are analyzed to show the amount of information present in the collection, a baseline probability of detection (PD) not using the collection of GS signals, the improvement in PD from the use of various sets of GS signals. The dependence of the improvement as a function of range is also shown. [The authors acknowledge support from Dr. Jeffrey Simmen, ONR321OS, and the chief scientist Dr. Charles Holland. Work supported by ONR.

  11. The optics of the Final Focus Test Beam

    International Nuclear Information System (INIS)

    Irwin, J.; Brown, K.; Bulos, F.; Burke, D.; Helm, R.; Roy, G.; Ruth, R.; Yamamoto, N.; Oide, K.

    1991-01-01

    The Final Focus Test Beam (FFTB), currently under construction at the end of the SLAC Linac, is being built by an international collaboration as a test bed for ideas and methods required in the design and construction of final focus systems for next generation e + e - linear colliders. The FFTB lattice shown is based on the previously developed principle of using sextupole pairs in a dispersive region to compensate chromaticity. The linear lattice was optimized for length, and implementation of diagnostic procedures. The transformations between sextupole pairs (CCX and CCY) are exactly -I, the matrix for the intermediate transformer (BX) is exactly diagonal, and the dispersion function has zero slope at the sextupoles and is thus zero at the minimum of the β x function in the intermediate transformer

  12. Exact discretization of Schrödinger equation

    Energy Technology Data Exchange (ETDEWEB)

    Tarasov, Vasily E., E-mail: tarasov@theory.sinp.msu.ru

    2016-01-08

    There are different approaches to discretization of the Schrödinger equation with some approximations. In this paper we derive a discrete equation that can be considered as exact discretization of the continuous Schrödinger equation. The proposed discrete equation is an equation with difference of integer order that is represented by infinite series. We suggest differences, which are characterized by power-law Fourier transforms. These differences can be considered as exact discrete analogs of derivatives of integer orders. Physically the suggested discrete equation describes a chain (or lattice) model with long-range interaction of power-law form. Mathematically it is a uniquely highlighted difference equation that exactly corresponds to the continuous Schrödinger equation. Using the Young's inequality for convolution, we prove that suggested differences are operators on the Hilbert space of square-summable sequences. We prove that the wave functions, which are exact discrete analogs of the free particle and harmonic oscillator solutions of the continuous Schrödinger equations, are solutions of the suggested discrete Schrödinger equations. - Highlights: • Exact discretization of the continuous Schrödinger equation is suggested. • New long-range interactions of power-law form are suggested. • Solutions of discrete Schrödinger equation are exact discrete analogs of continuous solutions.

  13. Exact discretization of Schrödinger equation

    International Nuclear Information System (INIS)

    Tarasov, Vasily E.

    2016-01-01

    There are different approaches to discretization of the Schrödinger equation with some approximations. In this paper we derive a discrete equation that can be considered as exact discretization of the continuous Schrödinger equation. The proposed discrete equation is an equation with difference of integer order that is represented by infinite series. We suggest differences, which are characterized by power-law Fourier transforms. These differences can be considered as exact discrete analogs of derivatives of integer orders. Physically the suggested discrete equation describes a chain (or lattice) model with long-range interaction of power-law form. Mathematically it is a uniquely highlighted difference equation that exactly corresponds to the continuous Schrödinger equation. Using the Young's inequality for convolution, we prove that suggested differences are operators on the Hilbert space of square-summable sequences. We prove that the wave functions, which are exact discrete analogs of the free particle and harmonic oscillator solutions of the continuous Schrödinger equations, are solutions of the suggested discrete Schrödinger equations. - Highlights: • Exact discretization of the continuous Schrödinger equation is suggested. • New long-range interactions of power-law form are suggested. • Solutions of discrete Schrödinger equation are exact discrete analogs of continuous solutions.

  14. Ageing without detailed balance in the bosonic contact and pair-contact processes: exact results

    International Nuclear Information System (INIS)

    Baumann, Florian; Henkel, Malte; Pleimling, Michel; Richert, Jean

    2005-01-01

    Ageing in systems without detailed balance is studied in the exactly solvable bosonic contact process and the critical bosonic pair-contact process. The two-time correlation function and the two-time response function are explicitly found. In the ageing regime, the dynamical scaling of these is analysed and exact results for the ageing exponents and the scaling functions are derived. For the critical bosonic pair-contact process, the autocorrelation and autoresponse exponents agree but the ageing exponents a and b are shown to be distinct

  15. Analysis of Current-mode Detectors For Resonance Detection In Neutron Optics Time Reversal Symmetry Experiment

    Science.gov (United States)

    Forbes, Grant; Noptrex Collaboration

    2017-09-01

    One of the most promising explanations for the observed matter-antimatter asymmetry in our universe is the search for new sources of time-reversal (T) symmetry violation. The current amount of violation seen in the kaon and B-meson systems is not sufficient to describe this asymmetry. The Neutron Optics Time Reversal Experiment Collaboration (NOPTREX) is a null test for T violation in polarized neutron transmission through a polarized 139La target. Due to the high neutron flux needed for this experiment, as well as the ability to effectively subtract background noise, a current-mode neutron detector that can resolve resonances at epithermal energies has been proposed. In order to ascertain if this detector design would meet the requirements for the eventual NOPTREX experiment, prototypical detectors were tested at the NOBORU beam at the Japan Proton Accelerator Research Complex (JPARC) facility. Resonances in In and Ta were measured and the collected data was analyzed. This presentation will describe the analysis process and the efficacy of the detectors will be discussed. Department of Energy under Contract DE-SC0008107, UGRAS Scholarship.

  16. Exact bidirectional X -wave solutions in fiber Bragg gratings

    Science.gov (United States)

    Efremidis, Nikolaos K.; Nye, Nicholas S.; Christodoulides, Demetrios N.

    2017-10-01

    We find exact solutions describing bidirectional pulses propagating in fiber Bragg gratings. They are derived by solving the coupled-mode theory equations and are expressed in terms of products of modified Bessel functions with algebraic functions. Depending on the values of the two free parameters, the general bidirectional X -wave solution can also take the form of a unidirectional pulse. We analyze the symmetries and the asymptotic properties of the solutions and also discuss additional waveforms that are obtained by interference of more than one solution. Depending on their parameters, such pulses can create a sharp focus with high contrast.

  17. Transition of unsteady velocity profiles with reverse flow

    Science.gov (United States)

    Das, Debopam; Arakeri, Jaywant H.

    1998-11-01

    This paper deals with the stability and transition to turbulence of wall-bounded unsteady velocity profiles with reverse flow. Such flows occur, for example, during unsteady boundary layer separation and in oscillating pipe flow. The main focus is on results from experiments in time-developing flow in a long pipe, which is decelerated rapidly. The flow is generated by the controlled motion of a piston. We obtain analytical solutions for laminar flow in the pipe and in a two-dimensional channel for arbitrary piston motions. By changing the piston speed and the length of piston travel we cover a range of values of Reynolds number and boundary layer thickness. The velocity profiles during the decay of the flow are unsteady with reverse flow near the wall, and are highly unstable due to their inflectional nature. In the pipe, we observe from flow visualization that the flow becomes unstable with the formation of what appears to be a helical vortex. The wavelength of the instability [simeq R: similar, equals]3[delta] where [delta] is the average boundary layer thickness, the average being taken over the time the flow is unstable. The time of formation of the vortices scales with the average convective time scale and is [simeq R: similar, equals]39/([Delta]u/[delta]), where [Delta]u=(umax[minus sign]umin) and umax, umin and [delta] are the maximum velocity, minimum velocity and boundary layer thickness respectively at each instant of time. The time to transition to turbulence is [simeq R: similar, equals]33/([Delta]u/[delta]). Quasi-steady linear stability analysis of the velocity profiles brings out two important results. First that the stability characteristics of velocity profiles with reverse flow near the wall collapse when scaled with the above variables. Second that the wavenumber corresponding to maximum growth does not change much during the instability even though the velocity profile does change substantially. Using the results from the experiments and the

  18. Performance analysis of passive time reversal communication technique for multipath interference in shallow sea acoustic channel

    Science.gov (United States)

    Kida, Yukihiro; Shimura, Takuya; Deguchi, Mitsuyasu; Watanabe, Yoshitaka; Ochi, Hiroshi; Meguro, Koji

    2017-07-01

    In this study, the performance of passive time reversal (PTR) communication techniques in multipath rich underwater acoustic environments is investigated. It is recognized empirically and qualitatively that a large number of multipath arrivals could generally raise the demodulation result of PTR. However, the relationship between multipath and the demodulation result is hardly evaluated quantitatively. In this study, the efficiency of the PTR acoustic communication techniques for multipath interference cancelation was investigated quantitatively by applying a PTR-DFE (decision feed-back filter) scheme to a synthetic dataset of a horizontal underwater acoustic channel. Mainly, in this study, we focused on the relationship between the signal-to-interference ratio (SIR) of datasets and the output signal-to-noise ratio (OSNR) of demodulation results by a parametric study approach. As a result, a proportional relation between SIR and OSNR is confirmed in low-SNR datasets. It was also found that PTR has a performance limitation, that is OSNR converges to a typical value depending on the number of receivers. In conclusion, results indicate that PTR could utilize the multipath efficiently and also withstand the negative effects of multipath interference at a given limitation.

  19. Novel Robust Optimization and Power Allocation of Time Reversal-MIMO-UWB Systems in an Imperfect CSI

    Directory of Open Access Journals (Sweden)

    Sajjad Alizadeh

    2013-03-01

    Full Text Available Time Reversal (TR technique is an attractive solution for a scenario where the transmission system employs low complexity receivers with multiple antennas at both transmitter and receiver sides. The TR technique can be combined with a high data rate MIMO-UWB system as TR-MIMO-UWB system. In spite of TR's good performance in MIMO-UWB systems, it suffers from performance degradation in an imperfect Channel State Information (CSI case. In this paper, at first a robust TR pre-filter is designed together with a MMSE equalizer in TR-MIMO-UWB system where is robust against channel imperfection conditions. We show that the robust pre-filter optimization technique, considerably improves the BER performance of TR-MIMO-UWB system in imperfect CSI, where temporal focusing of the TR technique is kept, especially for high SNR values. Then, in order to improve the system performance more than ever, a power loading scheme is developed by minimizing the average symbol error rate in an imperfect CSI. Numerical and simulation results are presented to confirm the performance advantage attained by the proposed robust optimization and power loading in an imperfect CSI scenario.

  20. First direct observation of time-reversal non-invariance in the neutral-kaon system

    CERN Document Server

    Angelopoulos, Angelos; Aslanides, Elie; Backenstoss, Gerhard; Bargassa, P; Behnke, O; Benelli, A; Bertin, V; Blanc, F; Bloch, P; Carlson, P J; Carroll, M; Cawley, E; Chertok, M B; Danielsson, M; Dejardin, M; Derré, J; Ealet, A; Eleftheriadis, C; Faravel, L; Fetscher, W; Fidecaro, Maria; Filipcic, A; Francis, D; Fry, J; Gabathuler, Erwin; Gamet, R; Gerber, H J; Go, A; Haselden, A; Hayman, P J; Henry-Coüannier, F; Hollander, R W; Jon-And, K; Kettle, P R; Kokkas, P; Kreuger, R; Le Gac, R; Leimgruber, F; Mandic, I; Manthos, N; Marel, Gérard; Mikuz, M; Miller, J; Montanet, François; Müller, A; Nakada, Tatsuya; Pagels, B; Papadopoulos, I M; Pavlopoulos, P; Polivka, G; Rickenbach, R; Roberts, B L; Ruf, T; Santoni, C; Schäfer, M; Schaller, L A; Schietinger, T; Schopper, A; Tauscher, Ludwig; Thibault, C; Touchard, F; Touramanis, C; van Eijk, C W E; Vlachos, S; Weber, P; Wigger, O; Wolter, M; Zavrtanik, D; Zimmerman, D

    1998-01-01

    We report on the first observation of time-reversal symmetry violation through a comparison of the probabilities of $\\bar{K}^0$ transforming into $K^0$ and $K^0$ into $\\bar{K}^0$ as a function of the neutral-kaon eigentime $t$. The comparison is based on the analysis of the neutral-kaon semileptonic decays recorded in the CPLEAR experiment. There, the strangeness of the neutral kaon at time $t=0$ was tagged by the kaon charge in the reaction $p\\bar{p} \\rightarrow K^{\\pm} \\pi^{\\mp} K^0(\\bar{K}^0)$ at rest, whereas the strangeness of the kaon at the decay time $t=\\tau$ was tagged by the lepton charge in the final state. An average decay-rate asymmetry \\begin{equation*} \\langle^{R(\\bar{K}^0_{t=0} \\to e^+\\pi^-\

  1. High amplitude ultrasound pulse generation using time-reversal through a multiple scattering medium

    OpenAIRE

    ARNAL , Bastien; Pernot , Mathieu; Fink , Mathias; Tanter , Mickaël

    2012-01-01

    International audience; In histotripsy, soft tissues can be fragmented using very high pressure ultrasound pulses. Using time-reversal cavity is a way to generate high pressure pulses with a limited number of acoustic sources. The principle was already demonstrated by Montaldo et al. using a solid metal cavity, but low transmission coefficient was obtained due to the strong impedance mismatch at the metal/water interface. We propose here to use a waveguide filled with water containing a 2D mu...

  2. Synchrotron radiation focusing by a Bragg--Fresnel lens

    International Nuclear Information System (INIS)

    Aristov, V.V.; Basov, Y.A.; Snigirev, A.A.

    1989-01-01

    Since the discovery of x rays and until the present time the possibilities of their controlling and focusing have been widely discussed. In the hard spectrum region (λ∼1 A) the main focusing schemes are the following: geometrical focusing based on incoherent interaction of wave packets reflected by different regions of bending crystals and coherent (dynamic) focusing performed at the cost of the effect of refraction index angular dispersion near the exact Bragg angle value -θ B . A main disadvantage of geometrical focusing is low spatial resolution (∼0.1 mm) and temperature stability. In the case of coherent focusing a main disadvantage is a narrow angular aperture (∼10 sec. of arc) at spatial resolution (∼1--10 μm). Recently, advances in the development of diffraction physics and microstructuring technology open up possibilities for fabricating effective focusing x-ray optical elements---Bragg--Fresnel lenses (BFL)---with high spatial resolution (∼0.1 μm) at a wide angular aperture and high temperature stability. The present paper describes the main principles of Bragg--Fresnel optics (BFO). It presents the results on the synchrotron experiment and on observation of focusing. In this work the peculiarities of BFL diffraction contrast formation are investigated and image transmission using a BFL is performed. Possibilities of developing x-ray optical schemes of ultrahigh resolution on the basis of BFL elements are also discussed

  3. Personal attitudes toward time: The relationship between temporal focus, space-time mappings and real life experiences.

    Science.gov (United States)

    Li, Heng; Cao, Yu

    2017-06-01

    What influences how people implicitly associate "past" and "future" with "front" and "back?" Whereas previous research has shown that cultural attitudes toward time play a role in modulating space-time mappings in people's mental models (de la Fuente, Santiago, Román, Dumitrache & Casasanto, 2014), we investigated real life experiences as potential additional influences on these implicit associations. Participants within the same single culture, who are engaged in different intermediate-term educational experiences (Study 1), long-term living experiences (Study 2), and short-term visiting experiences (Study 3), showed their distinct differences in temporal focus, thereby influencing their implicit spatializations of time. Results across samples suggest that personal attitudes toward time related to real life experiences may influence people's space-time mappings. The findings we report on shed further light on the high flexibility of human conceptualization system. While culture may exert an important influence on temporal focus, a person's conceptualization of time may be attributed to a culmination of factors. © 2017 Scandinavian Psychological Associations and John Wiley & Sons Ltd.

  4. Exact solutions to some modified sine-Gordon equations

    International Nuclear Information System (INIS)

    Saermark, K.

    1983-01-01

    Exact, translational solutions to a number of modified sine-Gordon equations are presented. In deriving the equations and the solutions use is made of results from the theory of ordinary differential equations without moving critical points as given by Ince. It is found that kink-like solutions exist also in cases where the coefficients of the trigonometric terms are space- and time-dependent. (Auth.)

  5. A Robust Pre-Filter and Power Loading Design for Time Reversal UWB Systems over Time-Correlated MIMO Channels

    Directory of Open Access Journals (Sweden)

    Sajjad Alizadeh

    2014-04-01

    Full Text Available Conventional Time Reversal (TR technique suffers from performance degradation in time varying Multiple-Input Multiple-Output Ultra-Wideband (MIMO-UWB systems due to outdating Channel State Information (CSI over time progressions. That is, the outdated CSI degrades the TR performance significantly in time varying channels. The correlation property of time correlated channels can improve the TR performance against other traditional TR designs. Based on this property, at first, we propose a robust TR-MIMO-UWB system design for a time-varying channel in which the CSI is updated only at the beginning of each block of data where the CSI is assumed to be known. As the channel varies over time, pre-processor blindly pre-equalizes the channel during the next symbol time by using the correlation property. Then, a novel recursive power allocation strategy is derived over time-correlated time-varying TR-MIMO-UWB channels. We show that the proposed power loading technique, considerably improves the BER performance of TR-MIMO-UWB system in imperfect CSI with robust pre-filter. The proposed algorithms lead to a cost-efficient CSI updating procedure for the TR optimization. Simulation results are provided to confirm the new design performance against traditional method.

  6. Exact solutions of fractional mBBM equation and coupled system of fractional Boussinesq-Burgers

    Science.gov (United States)

    Javeed, Shumaila; Saif, Summaya; Waheed, Asif; Baleanu, Dumitru

    2018-06-01

    The new exact solutions of nonlinear fractional partial differential equations (FPDEs) are established by adopting first integral method (FIM). The Riemann-Liouville (R-L) derivative and the local conformable derivative definitions are used to deal with the fractional order derivatives. The proposed method is applied to get exact solutions for space-time fractional modified Benjamin-Bona-Mahony (mBBM) equation and coupled time-fractional Boussinesq-Burgers equation. The suggested technique is easily applicable and effectual which can be implemented successfully to obtain the solutions for different types of nonlinear FPDEs.

  7. Exactly energy conserving semi-implicit particle in cell formulation

    International Nuclear Information System (INIS)

    Lapenta, Giovanni

    2017-01-01

    We report a new particle in cell (PIC) method based on the semi-implicit approach. The novelty of the new method is that unlike any of its semi-implicit predecessors at the same time it retains the explicit computational cycle and conserves energy exactly. Recent research has presented fully implicit methods where energy conservation is obtained as part of a non-linear iteration procedure. The new method (referred to as Energy Conserving Semi-Implicit Method, ECSIM), instead, does not require any non-linear iteration and its computational cycle is similar to that of explicit PIC. The properties of the new method are: i) it conserves energy exactly to round-off for any time step or grid spacing; ii) it is unconditionally stable in time, freeing the user from the need to resolve the electron plasma frequency and allowing the user to select any desired time step; iii) it eliminates the constraint of the finite grid instability, allowing the user to select any desired resolution without being forced to resolve the Debye length; iv) the particle mover has a computational complexity identical to that of the explicit PIC, only the field solver has an increased computational cost. The new ECSIM is tested in a number of benchmarks where accuracy and computational performance are tested. - Highlights: • We present a new fully energy conserving semi-implicit particle in cell (PIC) method based on the implicit moment method (IMM). The new method is called Energy Conserving Implicit Moment Method (ECIMM). • The novelty of the new method is that unlike any of its predecessors at the same time it retains the explicit computational cycle and conserves energy exactly. • The new method is unconditionally stable in time, freeing the user from the need to resolve the electron plasma frequency. • The new method eliminates the constraint of the finite grid instability, allowing the user to select any desired resolution without being forced to resolve the Debye length. • These

  8. Exactly energy conserving semi-implicit particle in cell formulation

    Energy Technology Data Exchange (ETDEWEB)

    Lapenta, Giovanni, E-mail: giovanni.lapenta@kuleuven.be

    2017-04-01

    We report a new particle in cell (PIC) method based on the semi-implicit approach. The novelty of the new method is that unlike any of its semi-implicit predecessors at the same time it retains the explicit computational cycle and conserves energy exactly. Recent research has presented fully implicit methods where energy conservation is obtained as part of a non-linear iteration procedure. The new method (referred to as Energy Conserving Semi-Implicit Method, ECSIM), instead, does not require any non-linear iteration and its computational cycle is similar to that of explicit PIC. The properties of the new method are: i) it conserves energy exactly to round-off for any time step or grid spacing; ii) it is unconditionally stable in time, freeing the user from the need to resolve the electron plasma frequency and allowing the user to select any desired time step; iii) it eliminates the constraint of the finite grid instability, allowing the user to select any desired resolution without being forced to resolve the Debye length; iv) the particle mover has a computational complexity identical to that of the explicit PIC, only the field solver has an increased computational cost. The new ECSIM is tested in a number of benchmarks where accuracy and computational performance are tested. - Highlights: • We present a new fully energy conserving semi-implicit particle in cell (PIC) method based on the implicit moment method (IMM). The new method is called Energy Conserving Implicit Moment Method (ECIMM). • The novelty of the new method is that unlike any of its predecessors at the same time it retains the explicit computational cycle and conserves energy exactly. • The new method is unconditionally stable in time, freeing the user from the need to resolve the electron plasma frequency. • The new method eliminates the constraint of the finite grid instability, allowing the user to select any desired resolution without being forced to resolve the Debye length. • These

  9. Ultrasound-mediated Optical Imaging and Focusing in Scattering Media

    Science.gov (United States)

    Suzuki, Yuta

    Because of its non-ionizing and molecular sensing nature, light has been an attractive tool in biomedicine. Scanning an optical focus allows not only high-resolution imaging but also manipulation and therapy. However, due to multiple photon scattering events, conventional optical focusing using an ordinary lens is limited to shallow depths of one transport mean free path (lt'), which corresponds to approximately 1 mm in human tissue. To overcome this limitation, ultrasonic modulation (or encoding ) of diffuse light inside scattering media has enabled us to develop both deep-tissue optical imaging and focusing techniques, namely, ultrasound-modulated optical tomography (UOT) and time-reversed ultrasonically encoded (TRUE) optical focusing. While UOT measures the power of the encoded light to obtain an image, TRUE focusing generates a time-reversed (or phase-conjugated) copy of the encoded light, using a phase-conjugate mirror to focus light inside scattering media beyond 1 lt'. However, despite extensive progress in both UOT and TRUE focusing, the low signal-to-noise ratio in encoded-light detection remains a challenge to meeting both the speed and depth requirements for in vivo applications. This dissertation describes technological advancements of both UOT and TRUE focusing, in terms of their signal detection sensitivities, operational depths, and operational speeds. The first part of this dissertation describes sensitivity improvements of encoded-light detection in UOT, achieved by using a large area (˜5 cm x 5 cm) photorefractive polymer. The photorefractive polymer allowed us to improve the detection etendue by more than 10 times that of previous detection schemes. It has enabled us to resolve absorbing objects embedded inside diffused media thicker than 80 lt', using moderate light power and short ultrasound pulses. The second part of this dissertation describes energy enhancement and fluorescent excitation using TRUE focusing in turbid media, using

  10. Mean field approximation versus exact treatment of collisions in few-body systems

    International Nuclear Information System (INIS)

    Lemm, J.; Weiguny, A.; Giraud, B.G.

    1990-01-01

    A variational principle for calculating matrix elements of the full resolvent operator for a many-body system is studied. Its mean field approximation results in non-linear equations of Hartree (-Fock) type, with initial and final channel wave functions as driving terms. The mean field equations will in general have many solutions whereas the exact problem being linear, has a unique solution. In a schematic model with separable forces the mean field equations are analytically soluble, and for the exact problem the resulting integral equations are solved numerically. Comparing exact and mean field results over a wide range of system parameters, the mean field approach proves to be a very reliable approximation, which is not plagued by the notorious problem of defining asymptotic channels in the time-dependent mean field method. (orig.)

  11. Exact solutions, numerical relativity and gravitational radiation

    International Nuclear Information System (INIS)

    Winicour, J.

    1986-01-01

    In recent years, there has emerged a new use for exact solutions to Einstein's equation as checks on the accuracy of numerical relativity codes. Much has already been written about codes based upon the space-like Cauchy problem. In the case of two Killing vectors, a numerical characteristic initial value formulation based upon two intersecting families of null hypersurfaces has successfully evolved the Schwarzschild and the colliding plane wave vacuum solutions. Here the author discusses, in the context of exact solutions, numerical studies of gravitational radiation based upon the null cone initial value problem. Every stage of progress in the null cone approach has been associated with exact solutions in some sense. He begins by briefly recapping this history. Then he presents two new examples illustrating how exact solutions can be useful

  12. Strengthening the Role of Part-Time Faculty in Community Colleges. Focus Group Toolkit

    Science.gov (United States)

    Center for Community College Student Engagement, 2014

    2014-01-01

    The Center for Community College Student Engagement encourages colleges to hold focus groups with part-time and full-time faculty to learn about differences in the faculty and their experience at their college and to complement survey data. Survey responses tell the "what" about faculty's experiences; through conducting focus groups,…

  13. Perturbation of an exact strong gravity solution

    International Nuclear Information System (INIS)

    Baran, S.A.

    1982-10-01

    Perturbations of an exact strong gravity solution are investigated. It is shown, by using the new multipole expansions previously presented, that this exact and static spherically symmetric solution is stable under odd parity perturbations. (author)

  14. Homoclinic orbits around spinning black holes. I. Exact solution for the Kerr separatrix

    International Nuclear Information System (INIS)

    Levin, Janna; Perez-Giz, Gabe

    2009-01-01

    For equatorial Kerr orbits, we show that each separatrix between bound and plunging geodesics is a homoclinic orbit--an orbit that asymptotes to an energetically-bound, unstable circular orbit. We derive exact expressions for these trajectories in terms of elementary functions. We also clarify the formal connection between the separatrix and zoom-whirl orbits and show that, contrary to popular belief, zoom-whirl behavior is not intrinsically a near-separatrix phenomenon. This paper focuses on homoclinic behavior in physical space, while in a companion paper we paint the complementary phase space portrait. Although they refer to geodesic motion, the exact solutions for the Kerr separatrix could be useful for analytic or numerical studies of eccentric transitions from orbital to plunging motion under the dissipative effects of gravitational radiation.

  15. Matching NLO parton shower matrix element with exact phase space case of $W\\to l\

    CERN Document Server

    Nanava, G; Was, Z

    2010-01-01

    In practical applications PHOTOS Monte Carlo is often used for simulation of QED effects in decay of intermediate particles and resonances. Generated in such a way that samples of events cover the whole bremsstrahlung phase space. With the help of selection cuts, experimental acceptance can be then taken into account. The program is based on exact multiphoton phase space. To evaluate the program precision it is necessary to control its matrix element. Generally it is obtained using iteration of the universal multidimensional kernel. In some cases it is however obtained from the exact first order matrix element. Then, as a consequence, all terms necessary for non-leading logarithms are taken into account. In the present paper we will focus on the decays W -> l nu and gamma^* -> pi^+ pi^-. The Born level cross sections for both processes approach zero in some points of the phase space. Process dependent, compensating weight is constructed to implement exact matrix element, but it will be recommended for use onl...

  16. Decoupled equations for reverse time migration in tilted transversely isotropic media

    KAUST Repository

    Zhan, Ge; Pestana, Reynam C.; Stoffa, Paul L.

    2012-01-01

    Conventional modeling and migration for tilted transversely isotropic (TTI) media may suffer from numerical instabilities and shear wave artifacts due to the coupling of the P-wave and SV-wave modes in the TTI coupled equations. Starting with the separated P- and SV-phase velocity expressions for vertical transversely isotropic (VTI) media, we extend these decoupled equations for modeling and reverse time migration (RTM) in acoustic TTI media. Compared with the TTI coupled equations published in the geophysical literature, the new TTI decoupled equations provide a more stable solution due to the complete separation of the P-wave and SV-wave modes. The pseudospectral method is the most convenient method to implement these equations due to the form of wavenumber expressions and has the added benefit of being highly accurate and thus avoiding numerical dispersion. The rapid expansion method (REM) in time is employed to produce a broad band numerically stable time evolution of the wavefields. Synthetic results validate the proposed TTI decoupled equations and show that modeling and RTM in TTI media with the decoupled equations remain numerically stable even for models with strong anisotropy and sharp contrasts. © 2012 Society of Exploration Geophysicists.

  17. Decoupled equations for reverse time migration in tilted transversely isotropic media

    KAUST Repository

    Zhan, Ge

    2012-03-01

    Conventional modeling and migration for tilted transversely isotropic (TTI) media may suffer from numerical instabilities and shear wave artifacts due to the coupling of the P-wave and SV-wave modes in the TTI coupled equations. Starting with the separated P- and SV-phase velocity expressions for vertical transversely isotropic (VTI) media, we extend these decoupled equations for modeling and reverse time migration (RTM) in acoustic TTI media. Compared with the TTI coupled equations published in the geophysical literature, the new TTI decoupled equations provide a more stable solution due to the complete separation of the P-wave and SV-wave modes. The pseudospectral method is the most convenient method to implement these equations due to the form of wavenumber expressions and has the added benefit of being highly accurate and thus avoiding numerical dispersion. The rapid expansion method (REM) in time is employed to produce a broad band numerically stable time evolution of the wavefields. Synthetic results validate the proposed TTI decoupled equations and show that modeling and RTM in TTI media with the decoupled equations remain numerically stable even for models with strong anisotropy and sharp contrasts. © 2012 Society of Exploration Geophysicists.

  18. Interacting particle systems in time-dependent geometries

    Science.gov (United States)

    Ali, A.; Ball, R. C.; Grosskinsky, S.; Somfai, E.

    2013-09-01

    Many complex structures and stochastic patterns emerge from simple kinetic rules and local interactions, and are governed by scale invariance properties in combination with effects of the global geometry. We consider systems that can be described effectively by space-time trajectories of interacting particles, such as domain boundaries in two-dimensional growth or river networks. We study trajectories embedded in time-dependent geometries, and the main focus is on uniformly expanding or decreasing domains for which we obtain an exact mapping to simple fixed domain systems while preserving the local scale invariance properties. This approach was recently introduced in Ali et al (2013 Phys. Rev. E 87 020102(R)) and here we provide a detailed discussion on its applicability for self-affine Markovian models, and how it can be adapted to self-affine models with memory or explicit time dependence. The mapping corresponds to a nonlinear time transformation which converges to a finite value for a large class of trajectories, enabling an exact analysis of asymptotic properties in expanding domains. We further provide a detailed discussion of different particle interactions and generalized geometries. All our findings are based on exact computations and are illustrated numerically for various examples, including Lévy processes and fractional Brownian motion.

  19. Introduction to Focus Issue: Time-delay dynamics

    Science.gov (United States)

    Erneux, Thomas; Javaloyes, Julien; Wolfrum, Matthias; Yanchuk, Serhiy

    2017-11-01

    The field of dynamical systems with time delay is an active research area that connects practically all scientific disciplines including mathematics, physics, engineering, biology, neuroscience, physiology, economics, and many others. This Focus Issue brings together contributions from both experimental and theoretical groups and emphasizes a large variety of applications. In particular, lasers and optoelectronic oscillators subject to time-delayed feedbacks have been explored by several authors for their specific dynamical output, but also because they are ideal test-beds for experimental studies of delay induced phenomena. Topics include the control of cavity solitons, as light spots in spatially extended systems, new devices for chaos communication or random number generation, higher order locking phenomena between delay and laser oscillation period, and systematic bifurcation studies of mode-locked laser systems. Moreover, two original theoretical approaches are explored for the so-called Low Frequency Fluctuations, a particular chaotical regime in laser output which has attracted a lot of interest for more than 30 years. Current hot problems such as the synchronization properties of networks of delay-coupled units, novel stabilization techniques, and the large delay limit of a delay differential equation are also addressed in this special issue. In addition, analytical and numerical tools for bifurcation problems with or without noise and two reviews on concrete questions are proposed. The first review deals with the rich dynamics of simple delay climate models for El Nino Southern Oscillations, and the second review concentrates on neuromorphic photonic circuits where optical elements are used to emulate spiking neurons. Finally, two interesting biological problems are considered in this Focus Issue, namely, multi-strain epidemic models and the interaction of glucose and insulin for more effective treatment.

  20. Classes of exact Einstein Maxwell solutions

    Science.gov (United States)

    Komathiraj, K.; Maharaj, S. D.

    2007-12-01

    We find new classes of exact solutions to the Einstein Maxwell system of equations for a charged sphere with a particular choice of the electric field intensity and one of the gravitational potentials. The condition of pressure isotropy is reduced to a linear, second order differential equation which can be solved in general. Consequently we can find exact solutions to the Einstein Maxwell field equations corresponding to a static spherically symmetric gravitational potential in terms of hypergeometric functions. It is possible to find exact solutions which can be written explicitly in terms of elementary functions, namely polynomials and product of polynomials and algebraic functions. Uncharged solutions are regainable with our choice of electric field intensity; in particular we generate the Einstein universe for particular parameter values.

  1. On null tests of time-reversal invariance in scattering and reactions

    International Nuclear Information System (INIS)

    Conzett, H.E.

    1993-01-01

    There have been suggestions in the literature, both recently and in the more distant past, that, in the lowest-order Born approximation, time-reversal (T)-odd experimental observables in certain reactions are required by T-symmetry to vanish. These observables are the final-state spin-correlation coefficient C xy in the reaction e + e - → τ + τ - and the target analysing power A oy in the inclusive process ep → eX with a polarized proton target. These assertions are in direct conflict with a theorem that states that there can be no null-test of T-symmetry in such processes; that is, T-symmetry does not require any single observable to vanish. This talk addresses the resolution of that conflict

  2. Searching for serial refreshing in working memory: Using response times to track the content of the focus of attention over time.

    Science.gov (United States)

    Vergauwe, Evie; Hardman, Kyle O; Rouder, Jeffrey N; Roemer, Emily; McAllaster, Sara; Cowan, Nelson

    2016-12-01

    One popular idea is that, to support the maintenance of a set of elements over brief periods of time, the focus of attention rotates among the different elements, thereby serially refreshing the content of working memory (WM). In the research reported here, probe letters were presented between to-be-remembered letters, and response times to these probes were used to infer the status of the different items in WM. If the focus of attention cycles from one item to the next, its content should be different at different points in time, and this should be reflected in a change in the response time patterns over time. Across a set of four experiments, we demonstrated a striking pattern of invariance in the response time patterns over time, suggesting either that the content of the focus of attention did not change over time or that response times cannot be used to infer the content of the focus of attention. We discuss how this pattern constrains models of WM, attention, and human information processing.

  3. Exact optics - III. Schwarzschild's spectrograph camera revised

    Science.gov (United States)

    Willstrop, R. V.

    2004-03-01

    Karl Schwarzschild identified a system of two mirrors, each defined by conic sections, free of third-order spherical aberration, coma and astigmatism, and with a flat focal surface. He considered it impractical, because the field was too restricted. This system was rediscovered as a quadratic approximation to one of Lynden-Bell's `exact optics' designs which have wider fields. Thus the `exact optics' version has a moderate but useful field, with excellent definition, suitable for a spectrograph camera. The mirrors are strongly aspheric in both the Schwarzschild design and the exact optics version.

  4. Molecular Excitation Energies from Time-Dependent Density Functional Theory Employing Random-Phase Approximation Hessians with Exact Exchange.

    Science.gov (United States)

    Heßelmann, Andreas

    2015-04-14

    Molecular excitation energies have been calculated with time-dependent density-functional theory (TDDFT) using random-phase approximation Hessians augmented with exact exchange contributions in various orders. It has been observed that this approach yields fairly accurate local valence excitations if combined with accurate asymptotically corrected exchange-correlation potentials used in the ground-state Kohn-Sham calculations. The inclusion of long-range particle-particle with hole-hole interactions in the kernel leads to errors of 0.14 eV only for the lowest excitations of a selection of three alkene, three carbonyl, and five azabenzene molecules, thus surpassing the accuracy of a number of common TDDFT and even some wave function correlation methods. In the case of long-range charge-transfer excitations, the method typically underestimates accurate reference excitation energies by 8% on average, which is better than with standard hybrid-GGA functionals but worse compared to range-separated functional approximations.

  5. Top Management Support Partially Optimized Reverse Logistics in The Manufacturing Sector of Pakistan

    Directory of Open Access Journals (Sweden)

    Ms. Sitara Shafiq

    2013-07-01

    Full Text Available Supply chain management urges reverse logistics to be an effective tool for organizational competitive advantage. Reverse chains demand astute resource deployments and strategic focus by the top management. In Pakistan manufacturing industries employing reverse logistics for cost effectiveness reported heavy reliance on top management support. However, literature is yet not benefited by such empirical facts. This study hypothesized that top management support is key for cost effective reverse logistics. Collecting and analyzing reliable data for various elements of its variables of interests, the study confirmed considerable multi linear regression between top management support and cost effectiveness. Substantiating the hypothesis, it contributes that a significant impact of strategic focus and resource commitment by top management leads reverse logistics based manufacturers to success.

  6. CAPSULE REPORT: REVERSE OSMOSIS PROCESS

    Science.gov (United States)

    A failure analysis has been completed for the reverse osmosis (RO) process. The focus was on process failures that result in releases of liquids and vapors to the environment. The report includes the following: 1) A description of RO and coverage of the principles behind the proc...

  7. Comparison of extended mean-reversion and time series models for electricity spot price simulation considering negative prices

    International Nuclear Information System (INIS)

    Keles, Dogan; Genoese, Massimo; Möst, Dominik; Fichtner, Wolf

    2012-01-01

    This paper evaluates different financial price and time series models, such as mean reversion, autoregressive moving average (ARMA), integrated ARMA (ARIMA) and general autoregressive conditional heteroscedasticity (GARCH) process, usually applied for electricity price simulations. However, as these models are developed to describe the stochastic behaviour of electricity prices, they are extended by a separate data treatment for the deterministic components (trend, daily, weekly and annual cycles) of electricity spot prices. Furthermore price jumps are considered and implemented within a regime-switching model. Since 2008 market design allows for negative prices at the European Energy Exchange, which also occurred for several hours in the last years. Up to now, only a few financial and time series approaches exist, which are able to capture negative prices. This paper presents a new approach incorporating negative prices. The evaluation of the different approaches presented points out that the mean reversion and the ARMA models deliver the lowest mean root square error between simulated and historical electricity spot prices gained from the European Energy Exchange. These models posses also lower mean average errors than GARCH models. Hence, they are more suitable to simulate well-fitting price paths. Furthermore it is shown that the daily structure of historical price curves is better captured applying ARMA or ARIMA processes instead of mean-reversion or GARCH models. Another important outcome of the paper is that the regime-switching approach and the consideration of negative prices via the new proposed approach lead to a significant improvement of the electricity price simulation. - Highlights: ► Considering negative prices improves the results of time-series and financial models for electricity prices. ► Regime-switching approach captures the jumps and base prices quite well. ► Removing and separate modelling of deterministic annual, weekly and daily

  8. Fingering patterns in magnetic fluids: Perturbative solutions and the stability of exact stationary shapes

    Science.gov (United States)

    Anjos, Pedro H. A.; Lira, Sérgio A.; Miranda, José A.

    2018-04-01

    We examine the formation of interfacial patterns when a magnetic liquid droplet (ferrofluid, or a magnetorheological fluid), surrounded by a nonmagnetic fluid, is subjected to a radial magnetic field in a Hele-Shaw cell. By using a vortex-sheet formalism, we find exact stationary solutions for the fluid-fluid interface in the form of n -fold polygonal shapes. A weakly nonlinear, mode-coupling method is then utilized to find time-evolving perturbative solutions for the interfacial patterns. The stability of such nonzero surface tension exact solutions is checked and discussed, by trying to systematically approach the exact stationary shapes through perturbative solutions containing an increasingly larger number of participating Fourier modes. Our results indicate that the exact stationary solutions of the problem are stable, and that a good matching between exact and perturbative shape solutions is achieved just by using a few Fourier modes. The stability of such solutions is substantiated by a linearization process close to the stationary shape, where a system of mode-coupling equations is diagonalized, determining the eigenvalues which dictate the stability of a fixed point.

  9. Exact and approximate multiple diffraction calculations

    International Nuclear Information System (INIS)

    Alexander, Y.; Wallace, S.J.; Sparrow, D.A.

    1976-08-01

    A three-body potential scattering problem is solved in the fixed scatterer model exactly and approximately to test the validity of commonly used assumptions of multiple scattering calculations. The model problem involves two-body amplitudes that show diffraction-like differential scattering similar to high energy hadron-nucleon amplitudes. The exact fixed scatterer calculations are compared to Glauber approximation, eikonal-expansion results and a noneikonal approximation

  10. Dwell time adjustment for focused ion beam machining

    International Nuclear Information System (INIS)

    Taniguchi, Jun; Satake, Shin-ichi; Oosumi, Takaki; Fukushige, Akihisa; Kogo, Yasuo

    2013-01-01

    Focused ion beam (FIB) machining is potentially useful for micro/nano fabrication of hard brittle materials, because the removal method involves physical sputtering. Usually, micro/nano scale patterning of hard brittle materials is very difficult to achieve by mechanical polishing or dry etching. Furthermore, in most reported examples, FIB machining has been applied to silicon substrates in a limited range of shapes. Therefore, a versatile method for FIB machining is required. We previously established the dwell time adjustment for mechanical polishing. The dwell time adjustment is calculated by using a convolution model derived from Preston’s hypothesis. More specifically, the target removal shape is a convolution of the unit removal shape, and the dwell time is calculated by means of one of four algorithms. We investigate these algorithms for dwell time adjustment in FIB machining, and we found that a combination a fast Fourier transform calculation technique and a constraint-type calculation is suitable. By applying this algorithm, we succeeded in machining a spherical lens shape with a diameter of 2.93 μm and a depth of 203 nm in a glassy carbon substrate by means of FIB with dwell time adjustment

  11. On the exact conservation laws in thermal models and the analysis of AGS and SIS experimental results

    International Nuclear Information System (INIS)

    Keraenen, A.; Suhonen, E.; Cleymans, J.

    1999-01-01

    The production of hadrons in relativistic heavy ion collisions is studied using a statistical ensemble with thermal and chemical equilibrium. Special attention is given to exact conservation laws, i.e. certain charges are treated canonically instead of using the usual grand canonical approach. For small systems, the exact conservation of baryon number, strangeness and electric charge is to be taken into account. We have derived compact, analytical expressions for particle abundances in such ensemble. As an application, the change in K/π ratios in AGS experiments with different interaction system sizes is well reproduced. The canonical treatment of three charges becomes impractical very quickly with increasing system size. Thus, we focus our attention on exact conservation of strangeness, and treat baryon number and electric charge grand canonically. We present expressions for particle abundances in such ensemble as well, and apply them to reproduce the large variety of particle ratios in GSI SIS 2 A GeV Ni-Ni experiments. At the energies considered here, the exact strangeness conservation fully accounts for strange particle suppression, and no extra chemical factor is needed. (author)

  12. How the reverse supply chain contributes to a firm’s competitive strategy: a strategic alignment perspective

    DEFF Research Database (Denmark)

    Larsen, Samuel Brüning; Masi, Donato; Jacobsen, Peter

    2017-01-01

    The ongoing transition to a Circular Economy is changing the shape of Supply Chains. They are becoming more ‘Closed-Loop’, combining forward and reverse flows of products and materials. Reverse Supply Chains (RSCs), originally considered as a solution for handling waste or recovering residual value...... seven case studies, focusing on original equipment manufacturers (OEMs), show how the RSC can play a strategic, tactical, or operational role for the firm. The paper applies for the first time the concept of strategic alignment to the RSC and practitioners can use the proposed framework to analyse...

  13. Nonlinear elastic wave spectroscopy in symbiosis with time reversal for localization of defects: TR-NEWS

    Czech Academy of Sciences Publication Activity Database

    Dos Santos, S.; Vejvodová, Šárka; Převorovský, Zdeněk

    2009-01-01

    Roč. 19, č. 2 (2009), s. 14-14 ISSN 1213-3825. [NDT in PROGRESS. 12.11.2009-14.11.2009, Praha] R&D Projects: GA ČR GA106/07/1393; GA MPO(CZ) FR-TI1/274 Institutional research plan: CEZ:AV0Z20760514 Keywords : nonlinear elastic wave spectroscopy (NEWS) * ESAM * time reversal (TR) * TR-NEWS imaging * tomography * DORT Subject RIV: BI - Acoustics

  14. Exact scattering and diffraction of antiplane shear waves by a vertical edge crack

    Science.gov (United States)

    Tsaur, Deng-How

    2010-06-01

    Scattering and diffraction problems of a vertical edge crack connected to the surface of a half space are considered for antiplane shear wave incidence. The method of separation of variables is adopted to derive an exact series solution. The total displacement field is expressed as infinite series containing products of radial and angular Mathieu functions with unknown coefficients. An exact analytical determination of unknown coefficients is carried out by insuring the vanishing of normal stresses on crack faces. Frequency-domain results are given for extremely near, near, and far fields, whereas time-domain ones are for horizontal surface and subsurface motions. Comparisons with published data for the dynamic stress intensity factor show good agreement. The exact analytical nature of proposed solutions can be applied very conveniently and rapidly to high-frequency steady-state cases, enhancing the computation efficiency in transient cases when performing the fast Fourier transform. A sampled set of time slices for underground wave propagation benefits the interpretation of scattering and diffraction phenomena induced by a vertical edge crack.

  15. Imaging of first-order surface-related multiples by reverse-time migration

    Science.gov (United States)

    Liu, Xuejian; Liu, Yike; Hu, Hao; Li, Peng; Khan, Majid

    2017-02-01

    Surface-related multiples have been utilized in the reverse-time migration (RTM) procedures, and additional illumination for subsurface can be provided. Meanwhile, many cross-talks are generated from undesired interactions between forward- and backward-propagated seismic waves. In this paper, subsequent to analysing and categorizing these cross-talks, we propose RTM of first-order multiples to avoid most undesired interactions in RTM of all-order multiples, where only primaries are forward-propagated and crosscorrelated with the backward-propagated first-order multiples. With primaries and multiples separated during regular seismic data processing as the input data, first-order multiples can be obtained by a two-step scheme: (1) the dual-prediction of higher-order multiples; and (2) the adaptive subtraction of predicted higher-order multiples from all-order multiples within local offset-time windows. In numerical experiments, two synthetic and a marine field data sets are used, where different cross-talks generated by RTM of all-order multiples can be identified and the proposed RTM of first-order multiples can provide a very interpretable image with a few cross-talks.

  16. Ultrasonic brain therapy: First trans-skull in vivo experiments on sheep using adaptive focusing

    Science.gov (United States)

    Pernot, Mathieu; Aubry, Jean-Francois; Tanter, Michael; Fink, Mathias; Boch, Anne-Laure; Kujas, Michèle

    2004-05-01

    A high-power prototype dedicated to trans-skull therapy has been tested in vivo on 20 sheep. The array is made of 200 high-power transducers working at 1-MHz central and is able to reach 260 bars at focus in water. An echographic array connected to a Philips HDI 1000 system has been inserted in the therapeutic array in order to perform real-time monitoring of the treatment. A complete craniotomy has been performed on half of the treated animal models in order to get a reference model. On the other animals, a minimally invasive surgery has been performed thanks to a time-reversal experiment: a hydrophone was inserted at the target inside the brain thanks to a 1-mm2 craniotomy. A time-reversal experiment was then conducted through the skull bone with the therapeutic array to treat the targeted point. For all the animals a specified region around the target was treated thanks to electronic beam steering. Animals were finally divided into three groups and sacrificed, respectively, 0, 1, and 2 weeks after treatment. Finally, histological examination confirmed tissue damage. These in vivo experiments highlight the strong potential of high-power time-reversal technology.

  17. Introducing a checking technician allows pharmacists to spend more time on patient-focused activities.

    Science.gov (United States)

    Napier, Patti; Norris, Pauline; Braund, Rhiannon

    2018-04-01

    Internationally there is an increasing focus on the clinical and cognitive services that pharmacists can provide. Lack of time has been identified as a barrier to pharmacists increasing their clinical activities. Within the pharmacy workplace there are many tasks that can only be performed by a pharmacist. The final accuracy check of a dispensed prescription is currently the sole responsibility of pharmacists in New Zealand. This takes up a significant amount of time during a pharmacist's work day. The introduction of a checking technician role has been suggested to allow pharmacists more time to do more patient focused work. To investigate the amount of time pharmacy staff spend on specific activities and to establish whether the introduction of a checking technician into twelve pilot sites increased the amount of time that the pharmacists could spend on patient focused activities. This study utilised a self-reported work sampling technique in twelve pilot sites, selected from both the hospital and community settings. Work sampling using an electronic device was conducted at two time-points (before the implementation of a Pharmacy Accuracy Checking Technician (PACT) role and when the PACT was in place). Data was collected at 10 min intervals for the period of five days, a working week. Tasks were grouped into patient focused, dispensing and personal activities. The introduction of the PACT into the pilot sites saw a mean increase of 19% in pharmacists' patient focused activities and a mean 20% decrease in dispensing activities. The introduction of a checking technician role into New Zealand pharmacies demonstrated the potential to provide pharmacists with more time to spend on patient focused activities. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. CLINICAL-PHARMACOLOGY OF ROCURONIUM (ORG-9426) - STUDY OF THE TIME-COURSE OF ACTION, DOSE REQUIREMENT, REVERSIBILITY, AND PHARMACOKINETICS

    NARCIS (Netherlands)

    VANDENBROEK, L; WIERDA, JMKH; SMEULERS, NJ; VANSANTEN, GJ; LECLERCQ, MGL; HENNIS, PJ

    1994-01-01

    Study Objective: To evaluate the time course of action, dose requirement, reversibility, and pharmacokinetics of rocuronium (Org 9426) under 3 anesthetic techniques (nitrous oxide-fentanyl supplemented with propofol halothane, or isoflurane). Design: Prospective, randomized study. Setting: Operating

  19. Non-linear ultrasonic time-reversal mirrors in NDT

    Czech Academy of Sciences Publication Activity Database

    Převorovský, Zdeněk

    -, č. 4 (2012), s. 4-4 [World Conference on Nondestructive Testing /18./. 16.4.2012-20.4.2012, Durban] R&D Projects: GA MPO(CZ) FR-TI1/274; GA MPO(CZ) FR-T1/198; GA ČR(CZ) GAP104/10/1430 Institutional research plan: CEZ:AV0Z2076919 Keywords : non-linear ime reversal mirror * ultrasonic techniques * ESAM Subject RIV: BI - Acoustics http://www.academia-ndt.org/Downloads/AcademiaNews4.pdf

  20. Exact solutions in three-dimensional gravity

    CERN Document Server

    Garcia-Diaz, Alberto A

    2017-01-01

    A self-contained text, systematically presenting the determination and classification of exact solutions in three-dimensional Einstein gravity. This book explores the theoretical framework and general physical and geometrical characteristics of each class of solutions, and includes information on the researchers responsible for their discovery. Beginning with the physical character of the solutions, these are identified and ordered on the basis of their geometrical invariant properties, symmetries, and algebraic classifications, or from the standpoint of their physical nature, for example electrodynamic fields, fluid, scalar field, or dilaton. Consequently, this text serves as a thorough catalogue on 2+1 exact solutions to the Einstein equations coupled to matter and fields, and on vacuum solutions of topologically massive gravity with a cosmological constant. The solutions are also examined from different perspectives, enabling a conceptual bridge between exact solutions of three- and four-dimensional gravit...

  1. Exact gravitational quasinormal frequencies of topological black holes

    International Nuclear Information System (INIS)

    Birmingham, Danny; Mokhtari, Susan

    2006-01-01

    We compute the exact gravitational quasinormal frequencies for massless topological black holes in d-dimensional anti-de Sitter space. Using the gauge invariant formalism for gravitational perturbations derived by Kodama and Ishibashi, we show that in all cases the scalar, vector, and tensor modes can be reduced to a simple scalar field equation. This equation is exactly solvable in terms of hypergeometric functions, thus allowing an exact analytic determination of the gravitational quasinormal frequencies

  2. A general exact method for synthesizing parallel-beam projections from cone-beam projections via filtered backprojection

    International Nuclear Information System (INIS)

    Li Liang; Chen Zhiqiang; Xing Yuxiang; Zhang Li; Kang Kejun; Wang Ge

    2006-01-01

    In recent years, image reconstruction methods for cone-beam computed tomography (CT) have been extensively studied. However, few of these studies discussed computing parallel-beam projections from cone-beam projections. In this paper, we focus on the exact synthesis of complete or incomplete parallel-beam projections from cone-beam projections. First, an extended central slice theorem is described to establish a relationship between the Radon space and the Fourier space. Then, data sufficiency conditions are proposed for computing parallel-beam projection data from cone-beam data. Using these results, a general filtered backprojection algorithm is formulated that can exactly synthesize parallel-beam projection data from cone-beam projection data. As an example, we prove that parallel-beam projections can be exactly synthesized in an angular range in the case of circular cone-beam scanning. Interestingly, this angular range is larger than that derived in the Feldkamp reconstruction framework. Numerical experiments are performed in the circular scanning case to verify our method

  3. Finding optimal exact reducts

    KAUST Repository

    AbouEisha, Hassan M.

    2014-01-01

    The problem of attribute reduction is an important problem related to feature selection and knowledge discovery. The problem of finding reducts with minimum cardinality is NP-hard. This paper suggests a new algorithm for finding exact reducts

  4. Exact two-point resistance, and the simple random walk on the complete graph minus N edges

    International Nuclear Information System (INIS)

    Chair, Noureddine

    2012-01-01

    An analytical approach is developed to obtain the exact expressions for the two-point resistance and the total effective resistance of the complete graph minus N edges of the opposite vertices. These expressions are written in terms of certain numbers that we introduce, which we call the Bejaia and the Pisa numbers; these numbers are the natural generalizations of the bisected Fibonacci and Lucas numbers. The correspondence between random walks and the resistor networks is then used to obtain the exact expressions for the first passage and mean first passage times on this graph. - Highlights: ► We obtain exact formulas for the two-point resistance of the complete graph minus N edges. ► We obtain also the total effective resistance of this graph. ► We modified Schwatt’s formula on trigonometrical power sum to suit our computations. ► We introduced the generalized bisected Fibonacci and Lucas numbers: the Bejaia and the Pisa numbers. ► The first passage and mean first passage times of the random walks have exact expressions.

  5. Spectroscopic and impedance studies of reverse biased degraded dye solar cells

    CSIR Research Space (South Africa)

    Le Roux, Lukas J

    2011-03-01

    Full Text Available The work that is presented here is focused on the results that were obtained during studies of the performance of Dye Solar Cells under certain reverse bias conditions. This reverse voltage could permanently modify or damage a cell...

  6. Quaternionic formulation of the exact parity model

    Energy Technology Data Exchange (ETDEWEB)

    Brumby, S.P.; Foot, R.; Volkas, R.R.

    1996-02-28

    The exact parity model (EPM) is a simple extension of the standard model which reinstates parity invariance as an unbroken symmetry of nature. The mirror matter sector of the model can interact with ordinary matter through gauge boson mixing, Higgs boson mixing and, if neutrinos are massive, through neutrino mixing. The last effect has experimental support through the observed solar and atmospheric neutrino anomalies. In the paper it is shown that the exact parity model can be formulated in a quaternionic framework. This suggests that the idea of mirror matter and exact parity may have profound implications for the mathematical formulation of quantum theory. 13 refs.

  7. Quaternionic formulation of the exact parity model

    International Nuclear Information System (INIS)

    Brumby, S.P.; Foot, R.; Volkas, R.R.

    1996-01-01

    The exact parity model (EPM) is a simple extension of the standard model which reinstates parity invariance as an unbroken symmetry of nature. The mirror matter sector of the model can interact with ordinary matter through gauge boson mixing, Higgs boson mixing and, if neutrinos are massive, through neutrino mixing. The last effect has experimental support through the observed solar and atmospheric neutrino anomalies. In the paper it is shown that the exact parity model can be formulated in a quaternionic framework. This suggests that the idea of mirror matter and exact parity may have profound implications for the mathematical formulation of quantum theory. 13 refs

  8. Sample path analysis and distributions of boundary crossing times

    CERN Document Server

    Zacks, Shelemyahu

    2017-01-01

    This monograph is focused on the derivations of exact distributions of first boundary crossing times of Poisson processes, compound Poisson processes, and more general renewal processes.  The content is limited to the distributions of first boundary crossing times and their applications to various stochastic models. This book provides the theory and techniques for exact computations of distributions and moments of level crossing times. In addition, these techniques could replace simulations in many cases, thus providing more insight about the phenomenona studied. This book takes a general approach for studying telegraph processes and is based on nearly thirty published papers by the author and collaborators over the past twenty five years.  No prior knowledge of advanced probability is required, making the book widely available to students and researchers in applied probability, operations research, applied physics, and applied mathematics. .

  9. Real-time zymography and reverse zymography: a method for detecting activities of matrix metalloproteinases and their inhibitors using FITC-labeled collagen and casein as substrates.

    Science.gov (United States)

    Hattori, Shunji; Fujisaki, Hitomi; Kiriyama, Tomomi; Yokoyama, Tsukao; Irie, Shinkichi

    2002-02-01

    Zymography and reverse zymography are widely used techniques for identifying the proteolytic activity of enzymes and the presence of protease inhibitors in polyacrylamide gels. In the current studies, we utilized a fluorescein-isothiocyanate-labeled substrate to develop novel zymographic and reverse zymographic methods for detecting matrix metalloproteinases and tissue inhibitors of the metalloproteinases, respectively. Using a transilluminator, the results can be observed visually without stopping the enzymatic reaction. For this reason, we have named these methods real-time zymography and real-time reverse zymography. These methods have the following advantages compared with conventional protocols: (1) because the reaction can be repeatedly monitored on the polyacrylamide gels, optimization of the incubation time can be achieved without preliminary analyses; (2) higher sensitivity is achieved with a lower amount of substrate than with conventional methods; (3) a semi-quantitative analysis of matrix metalloproteinases is possible. An additional advantage of the real-time reverse zymography is that, because the fluorescence detection is specific for substrate digestion, the inhibitor bands can be easily distinguished from contaminating proteins.

  10. AN OVERVIEW ON RETAIL REVERSE LOGISTICS

    Directory of Open Access Journals (Sweden)

    Ioana Olariu

    2014-07-01

    Full Text Available This article is a theoretical approach on retail reverse logistics. Environmental concern and the current marketing strategy have spurred retailers to implement strategies to facilitate product returns from end customers. Reverse logistics, indicating the process of this return flow, encompasses such activities as the movement of returned products, facilities to accommodate returned items, and overall remedy process for returned items. The retail industry, under great competitive pressure, has used return policies as a competitive weapon. Grocery retailers were the first to begin to focus serious attention on the problem of returns and to develop reverse logistics innovations. Grocery retailers first developed innovations such as reclamation centers. Reclamation centers, in turn, led to the establishment of centralized return centers. Centralizing returns has led to significant benefits for most firms that have implemented them. Over the last several years, retailers have consolidated. Now, more than ever, reverse logistics is seen as being important. This reverse distribution activity can be crucial to the survival of companies, because the permanent goodwill of the company is at stake. Businesses succeed because they respond to both external and internal changes and adjust in an effective manner to remain competitive.

  11. Wide localized solutions of the parity-time-symmetric nonautonomous nonlinear Schrödinger equation

    Science.gov (United States)

    Meza, L. E. Arroyo; Dutra, A. de Souza; Hott, M. B.; Roy, P.

    2015-01-01

    By using canonical transformations we obtain localized (in space) exact solutions of the nonlinear Schrödinger equation (NLSE) with cubic and quintic space and time modulated nonlinearities and in the presence of time-dependent and inhomogeneous external potentials and amplification or absorption (source or drain) coefficients. We obtain a class of wide localized exact solutions of NLSE in the presence of a number of non-Hermitian parity-time (PT )-symmetric external potentials, which are constituted by a mixing of external potentials and source or drain terms. The exact solutions found here can be applied to theoretical studies of ultrashort pulse propagation in optical fibers with focusing and defocusing nonlinearities. We show that, even in the presence of gain or loss terms, stable solutions can be found and that the PT symmetry is an important feature to guarantee the conservation of the average energy of the system.

  12. New exact solutions of sixth-order thin-film equation

    Directory of Open Access Journals (Sweden)

    Wafaa M. Taha

    2014-01-01

    Full Text Available TheG′G-expansion method is used for the first time to find traveling-wave solutions for the sixth-order thin-film equation, where related balance numbers are not the usual positive integers. New types of exact traveling-wave solutions, such as – solitary wave solutions, are obtained the sixth-order thin-film equation, when parameters are taken at special values.

  13. Time reversal violation in radiative beta decay: experimental plans

    Science.gov (United States)

    Behr, J. A.; McNeil, J.; Anholm, M.; Gorelov, A.; Melconian, D.; Ashery, D.

    2017-01-01

    Some explanations for the excess of matter over antimatter in the universe involve sources of time reversal violation (TRV) in addition to the one known in the standard model of particle physics. We plan to search for TRV in a correlation between the momenta of the beta, neutrino, and the radiative gamma sometimes emitted in nuclear beta decay. Correlations involving three (out of four) momenta are sensitive at lowest order to different TRV physics than observables involving spin, such as electric dipole moments and spin-polarized beta decay correlations. Such experiments have been done in radiative kaon decay, but not in systems involving the lightest generation of quarks. An explicit low-energy physics model being tested produces TRV effects in the Fermi beta decay of the neutron, tritium, or some positron-decaying isotopes. We will present plans to measure the TRV asymmetry in radiative beta decay of laser-trapped 38mK at better than 0.01 sensitivity, including suppression of background from positron annihilation. Supported by NSERC, D.O.E., Israel Science Foundation. TRIUMF receives federal funding via a contribution agreement with the National Research Council of Canada.

  14. Exact boundary controllability for a series of membranes elastically connected

    Directory of Open Access Journals (Sweden)

    Waldemar D. Bastos

    2017-01-01

    Full Text Available In this article we study the exact controllability with Neumann boundary controls for a system of linear wave equations coupled in parallel by lower order terms on piecewise smooth domains of the plane. We obtain square integrable controls for initial state with finite energy and time of controllability near the optimal value.

  15. A Mini-Landscape of Exact MSSM Spectra in Heterotic Orbifolds

    CERN Document Server

    Lebedev, O; Raby, S; Ramos-Sánchez, S; Ratz, M; Vaudrevange, P K S; Wingerter, A; Lebedev, Oleg; Nilles, Hans Peter; Raby, Stuart; Ramos-Sanchez, Saul; Ratz, Michael; Vaudrevange, Patrick K.S.; Wingerter, Akin

    2007-01-01

    We explore a "fertile patch" of the heterotic landscape based on a Z_6-II orbifold with SO(10) and E_6 local GUT structures. We search for models allowing for the exact MSSM spectrum. Our result is that of order 100 out of a total 3\\times 10^4 inequivalent models satisfy this requirement.

  16. Laser heating of field-reversed configurations

    International Nuclear Information System (INIS)

    Carson, R.S.; Vlases, G.C.

    1983-01-01

    The experimental facility is a 21-cm-long solenoid with a 5.5-cm bore. The 4-cm ID quartz tube is filled with slowly flowing H 2 to 0.5-3.0 torr. Fields up to 6.5 T in 3.7 μsec are produced, with reverse-bias fields up -1.9 T. Preionization is by 40kA axial discharge 4.5 μsec before field-reversal is begun. The CO 2 laser used produces 300 to 400 J in 2 μsec, in an annular beam that can be defocused for preheating the outer edges of the plasma, or focused tightly for central-column heating and beam propagation during formation. The focusing system includes a return mirror for multiple passing of the laser energy. Diagnostics include compensated, diamagnetic flux loops, internal field probes, cross-tube and axial interferometers, fast photography, and spectroscopy

  17. The exact wavefunction factorization of a vibronic coupling system

    International Nuclear Information System (INIS)

    Chiang, Ying-Chih; Klaiman, Shachar; Otto, Frank; Cederbaum, Lorenz S.

    2014-01-01

    We investigate the exact wavefunction as a single product of electronic and nuclear wavefunction for a model conical intersection system. Exact factorized spiky potentials and nodeless nuclear wavefunctions are found. The exact factorized potential preserves the symmetry breaking effect when the coupling mode is present. Additionally nodeless wavefunctions are found to be closely related to the adiabatic nuclear eigenfunctions. This phenomenon holds even for the regime where the non-adiabatic coupling is relevant, and sheds light on the relation between the exact wavefunction factorization and the adiabatic approximation

  18. Expansion shock waves in the implosion process from a time-reversible molecular-dynamics simulation of a dual explosion process

    International Nuclear Information System (INIS)

    Komatsu, Nobuyoshi; Abe, Takashi

    2007-01-01

    Why does not an expansion shock wave exist in a gaseous medium in nature? The reason has been widely believed to be the irreversibility in nature, while an obvious demonstration for this belief has not been accomplished yet. In order to resolve the question from a microscopic viewpoint, an implosion process dual to an explosion process was investigated by means of the molecular-dynamics method (MD). To this aim, we employed a ''bit-reversible algorithm (Bit MD)'' that was completely time-reversible in a microscopic viewpoint and was free from any round-off error. Here we show that, through a dual implosion simulation (i.e., a time-reversible simulation of the explosion), a kind of expansion shock wave is successfully formed in the Bit MD simulation. Furthermore, we show that when the controlled noise is intentionally added to the Bit MD, the expansion shock wave disappears dramatically and turns into an isentropic expansion wave, even if the noise is extremely small. Since the controlled noise gives rise to the irreversibility in the Bit MD simulation, it can be concluded that the irreversibility in the system prohibits the expansion shock wave from appearing in the system

  19. Exact master equations for the non-Markovian decay of a qubit

    International Nuclear Information System (INIS)

    Vacchini, Bassano; Breuer, Heinz-Peter

    2010-01-01

    Exact master equations describing the decay of a two-state system into a structured reservoir are constructed. By employing the exact solution for the model, analytical expressions are determined for the memory kernel of the Nakajima-Zwanzig master equation and for the generator of the corresponding time-convolutionless master equation. This approach allows an explicit comparison of the convergence behavior of the corresponding perturbation expansions. Moreover, the structure of widely used phenomenological master equations with a memory kernel may be incompatible with a nonperturbative treatment of the underlying microscopic model. Several physical implications of the results on the microscopic analysis and the phenomenological modeling of non-Markovian quantum dynamics of open systems are discussed.

  20. Optimizing communication satellites payload configuration with exact approaches

    Science.gov (United States)

    Stathakis, Apostolos; Danoy, Grégoire; Bouvry, Pascal; Talbi, El-Ghazali; Morelli, Gianluigi

    2015-12-01

    The satellite communications market is competitive and rapidly evolving. The payload, which is in charge of applying frequency conversion and amplification to the signals received from Earth before their retransmission, is made of various components. These include reconfigurable switches that permit the re-routing of signals based on market demand or because of some hardware failure. In order to meet modern requirements, the size and the complexity of current communication payloads are increasing significantly. Consequently, the optimal payload configuration, which was previously done manually by the engineers with the use of computerized schematics, is now becoming a difficult and time consuming task. Efficient optimization techniques are therefore required to find the optimal set(s) of switch positions to optimize some operational objective(s). In order to tackle this challenging problem for the satellite industry, this work proposes two Integer Linear Programming (ILP) models. The first one is single-objective and focuses on the minimization of the length of the longest channel path, while the second one is bi-objective and additionally aims at minimizing the number of switch changes in the payload switch matrix. Experiments are conducted on a large set of instances of realistic payload sizes using the CPLEX® solver and two well-known exact multi-objective algorithms. Numerical results demonstrate the efficiency and limitations of the ILP approach on this real-world problem.