Moving inhomogeneous envelopes of stars
Oskinova, Lidia M; Hamann, Wolf-Rainer
2016-01-01
Massive stars are extremely luminous and drive strong winds, blowing a large part of their matter into the galactic environment before they finally explode as a supernova. Quantitative knowledge of massive star feedback is required to understand our Universe as we see it. Traditionally, massive stars have been studied under the assumption that their winds are homogeneous and stationary, largely relying on the Sobolev approximation. However, observations with the newest instruments, together with progress in model calculations, ultimately dictate a cardinal change of this paradigm: stellar winds are highly inhomogeneous. Hence, we are now advancing to a new stage in our understanding of stellar winds. Using the foundations laid by V.V. Sobolev and his school, we now update and further develop the stellar spectral analysis techniques. New sophisticated 3-D models of radiation transfer in inhomogeneous expanding media elucidate the physics of stellar winds and improve classical empiric mass-loss rate diagnostics...
Moving impurity in an inhomogenous Bose-Einstein condensate
Mathew, Ranchu; Tiesinga, Eite
2016-05-01
We study the dynamics of a non-uniform Bose-Einstein condensate (BEC) under the influence of a moving weak point-like impurity. When the condensate density varies slowly compared to its healing length the critical velocity of the impurity, beyond which the condensate becomes unstable, can be calculated using the Local Density Approximation (LDA). This critical velocity corresponds to the smallest local sound speed. The LDA breaks down when the length scale of density variations is of the order of the healing length. We have calculated corrections to the critical velocity in this regime as an asymptotic expansion in the size of the BEC. We also discuss the experimental implications of our calculations by studying the stability of the atomic analogue of a Superconducting Quantum Interference Device (SQUID). The atom-SQUID consists of a BEC in a ring trap with rotating barrier. The impurity corresponds to imperfections in the ring trap.
Rapidly Moving Divertor Plates In A Tokamak
Energy Technology Data Exchange (ETDEWEB)
S. Zweben
2011-05-16
It may be possible to replace conventional actively cooled tokamak divertor plates with a set of rapidly moving, passively cooled divertor plates on rails. These plates would absorb the plasma heat flux with their thermal inertia for ~10-30 sec, and would then be removed from the vessel for processing. When outside the tokamak, these plates could be cooled, cleaned, recoated, inspected, and then returned to the vessel in an automated loop. This scheme could provide nearoptimal divertor surfaces at all times, and avoid the need to stop machine operation for repair of damaged or eroded plates. We describe various possible divertor plate designs and access geometries, and discuss an initial design for a movable and removable divertor module for NSTX-U.
Pierce, Allan D.
1989-01-01
Transient sound propagation in an inhomogeneous moving medium is considered. For circumstances in which the medium is slowly varying over distances of a wavelength but possibly varying substantially over the propagation distance, a derivation is given of a new wave equation, which implicitly allows for diffraction and scattering and which also is consistent with earlier geometrical acoustics formulations. This wave equation is used as a starting point to derive a version of the Helmholtz-Kirchhoff integral relation that applies to inhomogeneous moving medium. It is suggested that a good approximation to the Green's function that appears in this relation is that derived from geometrical acoustics, the approximation becoming progressively better the shorter the distance between surfaces in the computation. It should also be at least as good as conventional ray acoustics, but can account for diffraction effects, such as at caustics.
Indian Academy of Sciences (India)
D Mandal; P C Pal; S Kumar
2014-04-01
The disturbance and propagation of SH-type waves in an anisotropic soil layer overlying an inhomogeneous elastic half-space by a moving stress discontinuity is considered. Stress discontinuity moves with non-uniform velocity and is impulsive in nature. The displacements are obtained in exact form by themethod due to Cagniard modified by de Hoop. The numerical result is calculated for special cases and the natures are depicted graphically.
Inspecting rapidly moving surfaces for small defects using CNN cameras
Blug, Andreas; Carl, Daniel; Höfler, Heinrich
2013-04-01
A continuous increase in production speed and manufacturing precision raises a demand for the automated detection of small image features on rapidly moving surfaces. An example are wire drawing processes where kilometers of cylindrical metal surfaces moving with 10 m/s have to be inspected for defects such as scratches, dents, grooves, or chatter marks with a lateral size of 100 μm in real time. Up to now, complex eddy current systems are used for quality control instead of line cameras, because the ratio between lateral feature size and surface speed is limited by the data transport between camera and computer. This bottleneck is avoided by "cellular neural network" (CNN) cameras which enable image processing directly on the camera chip. This article reports results achieved with a demonstrator based on this novel analogue camera - computer system. The results show that computational speed and accuracy of the analogue computer system are sufficient to detect and discriminate the different types of defects. Area images with 176 x 144 pixels are acquired and evaluated in real time with frame rates of 4 to 10 kHz - depending on the number of defects to be detected. These frame rates correspond to equivalent line rates on line cameras between 360 and 880 kHz, a number far beyond the available features. Using the relation between lateral feature size and surface speed as a figure of merit, the CNN based system outperforms conventional image processing systems by an order of magnitude.
Thermal waves induced by a rapidly moving line source
Rostami, A. A.; Shamsai, M.
For the cases involving a fast moving heat source or extremely short pulses emitted by lasers or short time after the start of transients, the classical theory of heat conduction breaks down since the wave nature of heat transport dominates. In this study, the temperature field due to a fast moving line source was determined analytically using the wave concept. The results are given for different values of thermal Mach number (M=V/C). For M>1 the heat affected zone is confined in a wedge shape region behind the source. The wedge half angle is equal to sin-1 (1/M). It was confirmed that the difference between the results of diffusion and wave models depends on the corresponding time scale and the relaxation time. Zusammenfassung Im Falle schnell bewegter Wärmequellen oder extrem kurzer Laserpulse sowie unmittelbar nach Beginn transienter Vorgänge versagt die klassische Theorie der Wärmeleitung, da die Wellennatur des Wärmetransportes dominiert. In der vorliegenden Studie wurde das durch eine raschbewegte Linienquelle ausgelöste Temperaturfeld auf der Basis des Wellenkonzepts analytisch bestimmt, und zwar für verschiedene Werte der thermischen Mach-Zahl (M=V/C). Für M>1 bleibt der von der Wärmeausbreitung erfaßte Bereich auf eine keilförmige Zone hinter der Quelle beschränkt, wobei der halbe Keilwinkel gleich sin-1 (1/M) ist. Es konnte gezeigt werden, daß der Unterschied zwischen den Ergebnissen des Diffusions- und des Wellenmodells von der entsprechenden Zeitskala und von der Relaxationszeit abhängt.
Rumyantseva, O. D.; Shurup, A. S.
2017-01-01
The paper considers the derivation of the wave equation and Helmholtz equation for solving the tomographic problem of reconstruction combined scalar-vector inhomogeneities describing perturbations of the sound velocity and absorption, the vector field of flows, and perturbations of the density of the medium. Restrictive conditions under which the obtained equations are meaningful are analyzed. Results of numerical simulation of the two-dimensional functional-analytical Novikov-Agaltsov algorithm for reconstructing the flow velocity using the the obtained Helmholtz equation are presented.
Directory of Open Access Journals (Sweden)
D. Yu. Klimushkin
2008-06-01
Full Text Available The generation of a high-m Alfvén wave by substorm injected energetic particles in the magnetosphere is studied. The wave is supposed to be emitted by an alternating current created by the drifting particle cloud or ring current inhomogeneity. It is shown that the wave appears in some azimuthal location simultaneously with the particle cloud arrival at the same spot. The value of the azimuthal wave number is determined as m~ω/ωd, where ω is the eigenfrequency of the standing Alfvén wave and ωd is the particle drift frequency. The wave propagates westward, in the direction of the proton drift. Under the reasonable assumption about the density of the energetic particles, the amplitude of the generated wave is close to the observed amplitudes of poloidal ULF pulsations.
Chaudhuri, Abhishek; Sreeram, P A; Sengupta, Surajit
2002-10-21
We study the steady state structure and dynamics of an interface in a pure Ising system on a square lattice placed in an inhomogeneous external field with a profile designed to stabilize a flat interface and translated with velocity v(e). For small v(e), the interface is stuck to the profile, is macroscopically smooth, and is rippled with a periodicity in general incommensurate with the lattice parameter. For arbitrary orientations of the profile, the local slope of the interface locks in to one of infinitely many rational values (devil's staircase) which most closely approximates the profile. These "lock-in" structures and ripples disappear as v(e) increases. For still larger v(e) the profile detaches from the interface.
Disorder trapping by rapidly moving phase interface in an undercooled liquid
Galenko, Peter; Danilov, Denis; Nizovtseva, Irina; Reuther, Klemens; Rettenmayr, Markus
2017-08-01
Non-equilibrium phenomena such as the disappearance of solute drag, the origin of solute trapping and evolution of disorder trapping occur during fast transformations with originating metastable phases [D.M. Herlach, P.K. Galenko, D. Holland-Moritz, Metastable solids from undrercooled melts (Elsevier, Amsterdam, 2007)]. In the present work, a theoretical investigation of disorder trapping by a rapidly moving phase interface is presented. Using a model of fast phase transformations, a system of governing equations for the diffusion of atoms, and the evolution of both long-range order parameter and phase field variable is formulated. First numerical solutions are carried out for a congruently melting binary alloy system.
Transient Flow in Rapidly Filling Air-Entrapped Pipelines with Moving Boundaries
Institute of Scientific and Technical Information of China (English)
ZHANG Yongliang; K. Vairavamoorthy
2006-01-01
A mathematical model is presented for transient flow in a rapidly filling pipeline with an entrapped air pocket. The influence of transient shear stress between the pipe wall and the flowing fluid is taken into account. A coordinate transformation technique is employed to generate adaptive moving meshes for the multiphase flow system as images of the time-independent computational meshes in auxiliary domains. The method of characteristics is used to reduce the coupled nonlinear hyperbolic partial differential equations governing the motion of the filling fluid, entrapped air, and blocking fluid to ordinary differential equations.Numerical solution of resulting equations shows that the transient shear stresses have only a small damping effect on the pressure fluctuations. The peak pressure in the entrapped air pocket decreases significantly with increasing initial entrapped air volume, but decreases slightly with increasing initial entrapped air pressure.
A new rapid kindling variant for induction of cortical epileptogenesis in freely moving rats
Directory of Open Access Journals (Sweden)
Juan Carlos Morales
2014-07-01
Full Text Available Kindling, one of the most used models of experimental epilepsy is based on daily electrical stimulation in several brain structures. Unlike the classic or slow kindling protocols (SK, the rapid kindling types (RK described until now require continuous stimulation at suprathreshold intensities applied directly to the same brain structure used for subsequent electrophysiological and inmunohistochemical studies, usually the hippocampus. However, the cellular changes observed in these rapid protocols, such as astrogliosis and neuronal loss, could be due to experimental manipulation more than to epileptogenesis-related alterations. Here, we developed a new RK protocol in order to generate an improved model of temporal lobe epilepsy (TLE which allows gradual progression of the epilepsy as well as obtaining an epileptic hippocampus, thus avoiding direct surgical manipulation and electric stimulation over this structure. This new protocol consists of basolateral amygdala (BLA stimulation with 10 trains of biphasic pulses (10s;50Hz per day with 20 minutes-intervals, during 3 consecutive days, using a subconvulsive and subthreshold intensity, which guarantees tissue integrity. The progression of epileptic activity was evaluated in freely moving rats through EEG recordings from cortex and amygdala, accompanied with synchronized video recordings. Moreover, we assessed the effectiveness of RK protocol and the establishment of epilepsy by evaluating cellular alterations of hippocampal slices from kindled rats. RK protocol induced convulsive states similar to SK protocols but in 3 days, with persistently lowered threshold to seizure induction and epileptogenic-dependent cellular changes in amygdala projection areas. We concluded that this novel RK protocol introduces a new variant of the chronic epileptogenesis models in freely moving rats, which is faster, highly reproducible and causes minimum cell damage with respect to that observed in other experimental
A new rapid kindling variant for induction of cortical epileptogenesis in freely moving rats
Morales, Juan Carlos; Álvarez-Ferradas, Carla; Roncagliolo, Manuel; Fuenzalida, Marco; Wellmann, Mario; Nualart, Francisco Javier; Bonansco, Christian
2014-01-01
Kindling, one of the most used models of experimental epilepsy is based on daily electrical stimulation in several brain structures. Unlike the classic or slow kindling protocols (SK), the rapid kindling types (RK) described until now require continuous stimulation at suprathreshold intensities applied directly to the same brain structure used for subsequent electrophysiological and immunohistochemical studies, usually the hippocampus. However, the cellular changes observed in these rapid protocols, such as astrogliosis and neuronal loss, could be due to experimental manipulation more than to epileptogenesis-related alterations. Here, we developed a new RK protocol in order to generate an improved model of temporal lobe epilepsy (TLE) which allows gradual progression of the epilepsy as well as obtaining an epileptic hippocampus, thus avoiding direct surgical manipulation and electric stimulation over this structure. This new protocol consists of basolateral amygdala (BLA) stimulation with 10 trains of biphasic pulses (10 s; 50 Hz) per day with 20 min-intervals, during 3 consecutive days, using a subconvulsive and subthreshold intensity, which guarantees tissue integrity. The progression of epileptic activity was evaluated in freely moving rats through electroencephalographic (EEG) recordings from cortex and amygdala, accompanied with synchronized video recordings. Moreover, we assessed the effectiveness of RK protocol and the establishment of epilepsy by evaluating cellular alterations of hippocampal slices from kindled rats. RK protocol induced convulsive states similar to SK protocols but in 3 days, with persistently lowered threshold to seizure induction and epileptogenic-dependent cellular changes in amygdala projection areas. We concluded that this novel RK protocol introduces a new variant of the chronic epileptogenesis models in freely moving rats, which is faster, highly reproducible and causes minimum cell damage with respect to that observed in other
Energy Technology Data Exchange (ETDEWEB)
Munson, Matthew S.; Karp, Eric M.; Nimlos, Claire T.; Salit, Marc; Beckham, Gregg T.
2016-12-05
Biomass conversion processes such as pretreatment, liquefaction, and pyrolysis often produce complex mixtures of intermediates that are a substantial challenge to analyze rapidly and reliably. To characterize these streams more comprehensively and efficiently, new techniques are needed to track species through biomass deconstruction and conversion processes. Here, we present the application of an emerging analytical method, gradient elution moving boundary electrophoresis (GEMBE), to quantify a suite of acids in a complex, biomass-derived streams from alkaline pretreatment of corn stover. GEMBE offers distinct advantages over common chromatography-spectrometry analytical approaches in terms of analysis time, sample preparation requirements, and cost of equipment. As demonstrated here, GEMBE is able to track 17 distinct compounds (oxalate, formate, succinate, malate, acetate, glycolate, protocatechuate, 3-hydroxypropanoate, lactate, glycerate, 2-hydroxybutanoate, 4-hydroxybenzoate, vanillate, p-coumarate, ferulate, sinapate, and acetovanillone). The lower limit of detection was compound dependent and ranged between 0.9 and 3.5 umol/L. Results from GEMBE were similar to recent results from an orthogonal method based on GCxGC-TOF/MS. Overall, GEMBE offers a rapid, robust approach to analyze complex biomass-derived samples, and given the ease and convenience of deployment, may offer an analytical solution for online tracking of multiple types of biomass streams.
Capdeville, Y.; Cupillard, P.; Marigo, J. J.
2012-04-01
The modeling of seismic elastic wave full waveform in a limited frequency band is now well established with a set of efficient numerical methods like the spectral element, the discontinuous Galerking or the finite difference methods. The constant increase of computing power with time has now allowed the use of seismic elastic wave full waveforms in a limited frequency band to image the elastic properties of the earth. Nevertheless, inhomogeneities of scale much smaller the minimum wavelength of the wavefield associated to the maximum frequency of the limited frequency band, are still a challenge for both forward and inverse problems. In this work, we tackle the problem of elastic properties and topography varying much faster than the minimum wavelength. Using a non periodic homogenization theory and a matching asymptotic technique, we show how to compute effective elastic properties, how to compute local correctors and how remove the fast variations of the topography and replace it by a smooth Dirichlet to Nemann operator at the surface. After showing some 2D and 3D forward modeling numerical examples, we will discuss the implications of such a development for both forward and inverse problems.
Disk Inhomogeneities and the Origins of Planetary System Architectures and Observational Properties
Hasegawa, Yasuhiro
2013-01-01
Recent high-resolution observations show that protoplanetary disks have various kinds of structural properties or inhomogeneities. These are the consequence of a mixture of a number of physical and chemical processes taking place in the disks. Here, we discuss the results of our comprehensive investigations on how disk inhomogeneities affect planetary migration. We demonstrate that disk inhomogeneities give rise to planet traps - specific sites in protoplanetary disks at which rapid type I migration is halted. We show that up to three types of traps (heat transitions, ice lines and dead zones) can exist in a single disk, and that they move differently as the disk accretion rate decreases with time. We also demonstrate that the position of planet traps strongly depends on stellar masses and disk accretion rates. This indicates that host stars establish preferred (initial) scales of their planetary systems. Finally, we discuss the possible observational signatures of disk inhomogeneities.
Chasing a complete understanding of a rapid moving rock slide: the La Saxe landslide
Crosta, G. B.; Cancelli, P.; Tamburini, A.; Alberto, W.; Broccolato, M.; Castellanza, R.; Frattini, P.; Agliardi, F.; Rivolta, C.; Leva, D.
2012-04-01
Large deep seated slope deformations affect entire valley flanks and are characterized by slow to extremely slow present day displacement rates. Because of their extreme size, they are frequently characterized at their interior by secondary instabilities which can be classified as rockslides, that can originate large rock avalanches or can move at much faster rates with respect to the main mass. As a consequence local instabilities and reactivation of sectors of deep seated deformations should be carefully monitored and studied especially because they can affect strongly deformed and weakened rock masses. Because of these natural conditions and their preferential location in coincidence of slope steepening, these rockslides can undergo rapid evolution and activation putting the upmost urgency for monitoring, hazard and risk assessment. We present the case study of the La Saxe rockslide (Courmayeur, Aosta valley, Italy), located within a deep seated deformation affecting most of the 10 km long left hand flank of the Ferret valley (between 1340 m and 2300 m a.s.l.) and which underwent a major phase of acceleration in the last decade. The rockslide affects the extreme south western tip of the deep seated deformation at the outlet of Ferret valley, with an estimated volume of about 8 x 106 m3 of clay schists and thinly bedded black carbonates, intensely folded and faulted. An intense investigation activity has been performed in the last 2 years to reach a more complete understanding of the phenomenon. Boreholes have been drilled, logged, and instrumented to constrain the landslide volume, the rate of displacement at depth, and the water pressure. Displacement monitoring has been undertaken at successive steps by setting up sequentially: a distance measurement network (6 optical targets), a GPS network for periodic measurements (12 stations), a ground-based interferometer (GB-InSAR, LisaLab, by Ellegi, with 10 min acquisition intervals), a geodetic network based on a
Bouman, H.J.; Wimersma Greidanus, T.B. van
1979-01-01
A cannulation technique for frequent sampling of cerebrospinal fluid (CSF) in unanaesthetized freely moving rats is described. A permanent stainless steel cannula, constructed in such a way that no loss of CSF occurs, is placed into the rat's cisterna magna and fixed to the skull by anchoring screws
Alali, Sanaz; Gribble, Adam; Vitkin, I Alex
2016-03-01
A new polarimetry method is demonstrated to image the entire Mueller matrix of a turbid sample using four photoelastic modulators (PEMs) and a charge coupled device (CCD) camera, with no moving parts. Accurate wide-field imaging is enabled with a field-programmable gate array (FPGA) optical gating technique and an evolutionary algorithm (EA) that optimizes imaging times. This technique accurately and rapidly measured the Mueller matrices of air, polarization elements, and turbid phantoms. The system should prove advantageous for Mueller matrix analysis of turbid samples (e.g., biological tissues) over large fields of view, in less than a second.
Rapid Evidence Assessments of Research to Inform Social Policy: Taking Stock and Moving Forward
Thomas, James; Newman, Mark; Oliver, Sandy
2013-01-01
There is a tension between conducting comprehensive systematic reviews and completing them in time to meet policy-making deadlines. The "rapid evidence assessment" has been proposed as a solution to this; offering rigorous reviews in a condensed timescale. While used frequently in healthcare, this mode of reviewing presents considerable…
Moving Toward Quantifying Reliability - The Next Step in a Rapidly Maturing PV Industry: Preprint
Energy Technology Data Exchange (ETDEWEB)
Kurtz, Sarah; Sample, Tony; Wohlgemuth, John; Zhou, Wei; Bosco, Nick; Althaus, Joerg; Phillips, Nancy; Deceglie, Michael; Flueckiger, Chris; Hacke, Peter; Miller, David; Kempe, Michael; Yamamichi, Masaaki; Kondo, Michio
2015-12-07
Some may say that PV modules are moving toward being a simple commodity, but most major PV customers ask: 'How can I minimize chances of a module recall?' Or, 'How can I quantify the added value of a 'premium' module?' Or, 'How can I assess the value of an old PV system that I'm thinking of purchasing?' These are all questions that PVQAT (the International PV Quality Assurance Task Force) and partner organizations are working to answer. Defining standard methods for ensuring minimal acceptable quality of PV modules, differentiating modules that provide added value in the toughest of environments, and creating a process (e.g. through IECRE [1]) that can follow a PV system from design through installation and operation are tough tasks, but having standard approaches for these will increase confidence, reduce costs, and be a critical foundation of a mature PV industry. This paper summarizes current needs for new tests, some challenges for defining those tests, and some of the key efforts toward development of international standards, emphasizing that meaningful quantification of reliability (as in defining a service life prediction) must be done in the context of a specific product with design parameters defined through a quality management system.
Discovery of Rapidly Moving Partial X-ray Absorbers within gamma Cassiopeiae
Hamaguchi, K; Russell, C M P; Petre, R; Enoto, T; Morihana, K; Ishida, M
2016-01-01
Gamma Cassiopeiae is an enigmatic Be star with unusually strong hard X-ray emission. The Suzaku observatory detected six rapid X-ray spectral hardening events called "softness dips" in a ~100 ksec duration observation in 2011. All the softness dip events show symmetric softness ratio variations, and some of them have flat bottoms apparently due to saturation. The softness dip spectra are best described by either ~40% or ~70% partial covering absorption to kT ~12 keV plasma emission by matter with a neutral hydrogen column density of ~2-8e21 cm-2, while the spectrum outside of these dips is almost free of absorption. This result suggests the presence of two distinct X-ray emitting spots in the gamma Cas system, perhaps on a white dwarf companion with dipole mass accretion. The partial covering absorbers may be blobs in the Be stellar wind, the Be disk, or rotating around the white dwarf companion. Weak correlations of the softness ratios to the hard X-ray flux suggest the presence of stable plasmas at kT ~0.9 ...
Discovery of Rapidly Moving Partial X-ray Absorbers within Gamma Cassiopeiae
Hamaguchi, K.; Oskinova, L.; Russell, C. M. P.; Petre, R.; Enoto, T.; Morihana, K.; Ishida, M.
2016-12-01
Gamma Cassiopeiae is an enigmatic Be star with unusually strong hard X-ray emission. The Suzaku observatory detected six rapid X-ray spectral hardening events called “softness dips” in a ˜100 ks observation in 2011. All the softness dip events show symmetric softness-ratio variations, and some of them have flat bottoms apparently due to saturation. The softness dip spectra are best described by either ˜40% or ˜70% partial covering absorption to kT ˜ 12 keV plasma emission by matter with a neutral hydrogen column density of ˜(2-8) × 1021 cm-2, while the spectrum outside these dips is almost free of absorption. This result suggests the presence of two distinct X-ray-emitting spots in the γ Cas system, perhaps on a white dwarf (WD) companion with dipole mass accretion. The partial covering absorbers may be blobs in the Be stellar wind, the Be disk, or rotating around the WD companion. Weak correlations of the softness ratios to the hard X-ray flux suggest the presence of stable plasmas at kT ˜ 0.9 and 5 keV, which may originate from the Be or WD winds. The formation of a Be star and WD binary system requires mass transfer between two stars; γ Cas may have experienced such activity in the past.
Rapid multichannel impact-echo scanning of concrete bridge decks from a continuously moving platform
Mazzeo, Brian A.; Larsen, Jacob; McElderry, Joseph; Guthrie, W. Spencer
2017-02-01
Impact-echo testing is a non-destructive evaluation technique for determining the presence of defects in reinforced concrete bridge decks based on the acoustic response of the bridge deck when struck by an impactor. In this work, we build on our prior research with a single-channel impactor to demonstrate a seven-channel impact-echo scanning system with independent control of the impactors. This system is towed by a vehicle and integrated with distance measurement for registering the locations of the impacts along a bridge deck. The entire impact and recording system is computer-controlled. Because of a winch system and hinged frame construction of the apparatus, setup, measurement, and take-down of the apparatus can be achieved in a matter of minutes. Signal processing of the impact responses is performed on site and can produce a map of delaminations immediately after data acquisition. This map can then be used to guide other testing and/or can be referenced with the results of other testing techniques to facilitate comprehensive condition assessments of concrete bridge decks. This work demonstrates how impact-echo testing can be performed in a manner that makes complete bridge deck scanning for delaminations rapid and practical.
Inhomogeneous Big Bang Cosmology
Wagh, S M
2002-01-01
In this letter, we outline an inhomogeneous model of the Big Bang cosmology. For the inhomogeneous spacetime used here, the universe originates in the infinite past as the one dominated by vacuum energy and ends in the infinite future as the one consisting of "hot and relativistic" matter. The spatial distribution of matter in the considered inhomogeneous spacetime is {\\em arbitrary}. Hence, observed structures can arise in this cosmology from suitable "initial" density contrast. Different problems of the standard model of Big Bang cosmology are also resolved in the present inhomogeneous model. This inhomogeneous model of the Big Bang Cosmology predicts "hot death" for the universe.
Wang, Houyu; Shi, Yongting; Yan, Jian; Dong, Jingyu; Li, Si; Xiao, Hua; Xie, Haiyang; Fan, Liu-Yin; Cao, Cheng-Xi
2014-03-18
A novel concept and theory of moving reaction boundary (MRB) retardation signal (RMRB) was advanced for determination of total protein content via MRB electrophoretic titration (MRBET). The theoretical results revealed that the retardation extent of boundary displacment, viz., the RMRB value, was as a function of protein content. Thus, the RMRB value of a sample could be used to determine its total protein content according to the relevant calibration curve. To demonstrate the concept and theoretical results, a novel microdevice was designed for the relevant experiments of MRBET. The microdevice has 30 identical work cells, each of which is composed of five ultrashort single microchannels (5 mm). In the microdevice, fluorescein isothiocyanate (FITC) was used to denote MRB motion and RMRB value for the first time, the polyacrylamide gel (PAG) containing protein sample was photopolymerized in microchannels, and the MRB was created with acid or alkali and target protein sample. As compared to the classic Kjeldahl method and conventional MRBET performed in glass tube, the developed titration chip has the following merits: good sensitivity (0.3-0.4 μg/mL vs 150-200 μg/mL of protein concentration, 0.6-0.8 ng vs 30-2000 μg of absolute protein content), rapid analysis (20-60 s vs 15-200 min), and portable low-power (15 V vs 200 V).
Morin, Timothy R; Ghassem-Zadeh, Sean A; Lee, Juliet
2014-08-15
Retraction is a major rate-limiting step in cell motility, particularly in slow moving cell types that form large stable adhesions. Myosin II dependent contractile forces are thought to facilitate detachment by physically pulling up the rear edge. However, retraction can occur in the absence of myosin II activity in cell types that form small labile adhesions. To investigate the role of contractile force generation in retraction, we performed traction force microscopy during the movement of fish epithelial keratocytes. By correlating changes in local traction stress at the rear with the area retracted, we identified four distinct modes of retraction. "Recoil" retractions are preceded by a rise in local traction stress, while rear edge is temporarily stuck, followed by a sharp drop in traction stress upon detachment. This retraction type was most common in cells generating high average traction stress. In "pull" type retractions local traction stress and area retracted increase concomitantly. This was the predominant type of retraction in keratocytes and was observed mostly in cells generating low average traction stress. "Continuous" type retractions occur without any detectable change in traction stress, and are seen in cells generating low average traction stress. In contrast, to many other cell types, "release" type retractions occur in keratocytes following a decrease in local traction stress. Our identification of distinct modes of retraction suggests that contractile forces may play different roles in detachment that are related to rear adhesion strength. To determine how the regulation of contractility via MLCK or Rho kinase contributes to the mechanics of detachment, inhibitors were used to block or augment these pathways. Modulation of MLCK activity led to the most rapid change in local traction stress suggesting its importance in regulating attachment strength. Surprisingly, Rho kinase was not required for detachment, but was essential for localizing
Reionization of an Inhomogeneous Universe
Umemura, M; Susa, H
2001-01-01
Full radiative transfer in 3D space has been solved to pursue the reionization history in an inhomogeneous universe. It has been shown that the reionization of an inhomogeneous universe is not a prompt event, but a fairly slow process. Also, QSO absorption line systems are simulated with using the results of radiative transfer calculations. Ly$\\alpha$ continuum depression implies that the metagalactic UV intensity decreases rapidly with $z$ at $z>5$, and the reionization must have taken place between $z=6$ and 10. Finally, it is stressed that H$\\alpha$ forest is a more powerful tool to probe the reionization history and the density fluctuations in the universe at $z>5$.
Gerritsen, S.
2007-01-01
In this thesis we study wave propagation in inhomogeneous media. Examples of the classical (massless) waves we consider are acoustic waves (sound) and electromagnetic waves (light, for example). Interaction with inhomogeneities embedded in a reference medium alter the propagation direction, velocity
Gerritsen, S.
2007-01-01
In this thesis we study wave propagation in inhomogeneous media. Examples of the classical (massless) waves we consider are acoustic waves (sound) and electromagnetic waves (light, for example). Interaction with inhomogeneities embedded in a reference medium alter the propagation direction, velocity
Inhomogeneous electromagnetic gravitational collapse
Energy Technology Data Exchange (ETDEWEB)
Stein-Schabes, J.A.
1985-04-15
The collapse of an inhomogeneous dust cloud in the presence of an electromagnetic field is investigated in detail. The possibility of a naked singularity arising is studied using some known solutions for a spherical charged inhomogeneous dust cloud. It is found that locally naked singularities may develop when the arbitrary functions in the solution are chosen in a special way, but that a global naked singularity will not form. Also the role of the electromagnetic pressure is discussed.
Inhomogeneous Polyakov loop induced by inhomogeneous chiral condensates
Directory of Open Access Journals (Sweden)
Tomoya Hayata
2015-05-01
Full Text Available We study the spatial inhomogeneity of the Polyakov loop induced by inhomogeneous chiral condensates. We formulate an effective model of gluons on the background fields of chiral condensates, and perform its lattice simulation. On the background of inhomogeneous chiral condensates, the Polyakov loop exhibits an in-phase spatial oscillation with the chiral condensates. We also analyze the heavy quark potential and show that the inhomogeneous Polyakov loop indicates the inhomogeneous confinement of heavy quarks.
Inhomogeneous Polyakov loop induced by inhomogeneous chiral condensates
Energy Technology Data Exchange (ETDEWEB)
Hayata, Tomoya, E-mail: hayata@riken.jp [Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Theoretical Research Division, Nishina Center, RIKEN, Wako, Saitama 351-0198 (Japan); Yamamoto, Arata [Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Theoretical Research Division, Nishina Center, RIKEN, Wako, Saitama 351-0198 (Japan)
2015-05-11
We study the spatial inhomogeneity of the Polyakov loop induced by inhomogeneous chiral condensates. We formulate an effective model of gluons on the background fields of chiral condensates, and perform its lattice simulation. On the background of inhomogeneous chiral condensates, the Polyakov loop exhibits an in-phase spatial oscillation with the chiral condensates. We also analyze the heavy quark potential and show that the inhomogeneous Polyakov loop indicates the inhomogeneous confinement of heavy quarks.
Collapse of Langmuir solitons in inhomogeneous plasmas
Chen, Y A; Nishida, Y; Cheng, C Z
2016-01-01
Propagation of Langmuir solitons in inhomogeneous plasmas is investigated numerically. Through numerical simulation solving Zakharov equations, the solitons are accelerated toward the low density side. As a consequence, isolated cavities moving at ion sound velocities are emitted. When the acceleration is further increased, solitons collapse and the cavities separate into two lumps released at ion sound velocities. The threshold is estimated by an analogy between the soliton and a particle overcoming the self-generated potential well.
Wakes in inhomogeneous plasmas
Kompaneets, Roman; Nosenko, Vladimir; Morfill, Gregor E
2014-01-01
The Debye shielding of a charge immersed in a flowing plasma is an old classic problem in plasma physics. It has been given renewed attention in the last two decades in view of experiments with complex plasmas, where charged dust particles are often levitated in a region with strong ion flow. Efforts to describe the shielding of the dust particles in such conditions have been focused on the homogeneous plasma approximation, which ignores the substantial inhomogeneity of the levitation region. We address the role of the plasma inhomogeneity by rigorously calculating the point charge potential in the collisionless Bohm sheath. We demonstrate that the inhomogeneity can dramatically modify the wake, making it non-oscillatory and weaker.
The Rural Households in the Process of Rapid Urbanization:Unwilling to Move,Floating and Migratory
Institute of Scientific and Technical Information of China (English)
2012-01-01
I divide the rural households into three types:the rural households unwilling to move;the floating rural households;the migratory rural households.Through questionnaire survey of the married housewives in Anhui Province and Zhejiang Province,I conduct comparative analysis of income and expenditure,change in the status of family members,the couple’s housework time,the wives’ will to settle in the city and attitude towards life,related to these three types of rural households.Results show that promoting wives’ educational level and monthly family income will significantly make the wives in households unwilling to move,have stronger desire to make their children settle in the city;the housework time of the wives in the floating households is 3.4 times that of their husbands,the monthly income of the husbands in the floating households is significantly lower than that of the husbands in the migratory households,with heavy family burden assessed by themselves;the age of the wives in the migratory households is the smallest,and the educational level and income of them are the highest,but the monthly expenditure has not yet significantly expanded,and at the same time,the migratory households have the weakest desire to settle in the city.The recommendations concerning these three types of rural households are put forward as follows:promoting the skills of the members in the households unwilling to move,in agricultural cultivation,development of agricultural products and circulation of agricultural products;paying close attention to the floating rural households;promoting the government,enterprise,households to work together to stabilize the migratory households.
Antennas in inhomogeneous media
Galejs, Janis; Fock, V A; Wait, J R
2013-01-01
Antennas in Inhomogeneous Media details the methods of analyzing antennas in such inhomogeneous media. The title covers the complex geometrical configurations along with its variational formulations. The coverage of the text includes various conditions the antennas are subjected to, such as antennas in the interface between two media; antennas in compressible isotropic plasma; and linear antennas in a magnetoionic medium. The selection also covers insulated loops in lossy media; slot antennas with a stratified dielectric or isotropic plasma layers; and cavity-backed slot antennas. The book wil
Crisp, D J; W Moran; Pollington, A. D.
2012-01-01
We show that the inhomogenous approximation spectrum, associated to an irrational number \\alpha\\ always has a Hall's Ray; that is, there is an \\epsilon>0 such that [0,\\epsilon) is a subset of the spectrum. In the case when \\alpha\\ has unbounded partial quotients we show that the spectrum is just a ray.
Chemical inhomogeneities and pulsation
Turcotte, S
2001-01-01
Major improvements in models of chemically peculiar stars have been achieved in the past few years. With these new models it has been possible to test quantitatively some of the processes involved in the formation of abundance anomalies and their effect on stellar structure. The models of metallic A (Am) stars have shown that a much deeper mixing has to be present to account for observed abundance anomalies. This has implications on their variability, which these models also reproduce qualitatively. These models also have implications for other chemically inhomogeneous stars such as HgMn B stars which are not known to be variable and lambda Bootis stars which can be. The study of the variability of chemically inhomogeneous stars can provide unique information on the dynamic processes occurring in many types of stars in addition to modeling of the evolution of their surface composition.
Gästgifvars, Maria; Lauri, Hannu; Sarkanen, Annakaisa; Myrberg, Kai; Andrejev, Oleg; Ambjörn, Cecilia
2006-12-01
The Gulf of Finland is an elongated estuary located in the north-eastern extremity of the Baltic Sea. This semi-enclosed sea-area is subject to heavy sea traffic, and is one of the main risk areas for oil accidents in the Baltic. The continuous development and validation of operational particle drift and oil-spill forecasting systems is thus seen to be essential for this sea-area. Here, the results of a three-day drift experiment in May 2003 are discussed. The field studies were performed using GPS-positioned surface floating buoys. The aim of this paper is to evaluate how well models can reproduce the drift of these buoys. Model simulations, both in forecast and hindcast modes, were carried out by three different 3D hydrodynamic models, the results of which are evaluated by comparing the calculated drifts with observations. These models were forced by HIRLAM (High Resolution Limited Area Model) and ECMWF (European Centre for Medium-Range Weather Forecasts) meteorological forecast fields. The simulated drift of the buoys showed a good agreement with observations even when, during the study period, a rapidly-changing wind situation was observed to affect the investigation area; in this situation the winds turned about 100 degrees in half an hour. In such a case it is a very complicated task to forecast the drifters' routes: there is a need to regularly update the meteorological forcing fields and to use these regularly-updated fields throughout the simulations. It is furthermore recommended that forecasts should be made using several circulation models and several meteorological forecasts, in order to get an overview of the accuracy of the forecasted drifts and related differences in between the forecasts.
Energy Technology Data Exchange (ETDEWEB)
Miura, K.; Hayashi, J.; Sano, N. (Kyoto University, Kyoto (Japan). Research Laboratory of CArbonaceous Resources Conversion); Hashimoto, K. (Kyoto University, Kyoto (Japan). Faculty of Engineering); Iwakiri, H. (Kobe Steel, Ltd., Kobe (Japan))
1992-12-20
An experiment to manufacture coke with rapid temperature raising was carried out using an equipment simulating a vertical moving bed coke oven. Two kinds of trial manufacturing patterns were tested: Pattern A to raise coal temperature rapidly to about 450[degree]C, which is held for about 20 minutes, and then raised again to 800[degree]C at a rate of about 5[degree]C/min, and pattern B to raise the temperature from about 300[degree]C to 800[degree]C at a rate of about 5[degree]C/min. An experiment on test samples from heavy caking coal (PDH coal) and light caking coal (OP coal) revealed the following results: The PDH coal applied with the pattern A produced in about two hours a coke with quality equivalent to or better than practically used coke; the temperature raising pattern B resulted in no full lump formation even with the PDH coal; according to the temperature raising pattern A, manufacturing coke from the OP coal is impossible; however, if the PDH coal or pitch is mixed with the OP coal, coke may be manufactured. 6 refs., 11 figs., 2 tabs.
A formulation for dissolution in inhomogeneous temperature field
Fukagawa, Hiroki
2014-01-01
We propose equations governing the dissolution in inhomogeneous temperature field in terms of the variational principle. The derived equations clarify that the interface energy between solute and solvent has a significant effect on the process of the dissolution. The interface energy restrains the dissolution, and the moving interface involves the heat of dissolution.
Inhomogeneous anisotropic cosmology
Energy Technology Data Exchange (ETDEWEB)
Kleban, Matthew [Center for Cosmology and Particle Physics, New York University,4 Washington Place, New York, NY 10003 (United States); Senatore, Leonardo [Stanford Institute for Theoretical Physics and Department of Physics, Stanford University,382 Via Pueblo Mall, Stanford, CA 94306 (United States); Kavli Institute for Particle Astrophysics and Cosmology, Stanford University and SLAC,2575 Sand Hill Road, M/S 29, Menlo Park, CA 94025 (United States)
2016-10-12
In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with “flat” (including toroidal) and “open” (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are “flat” or “open”. Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with “flat” or “open” topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.
Inhomogeneous anisotropic cosmology
Kleban, Matthew; Senatore, Leonardo
2016-10-01
In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with ``flat'' (including toroidal) and ``open'' (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are ``flat'' or ``open''. Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with ``flat'' or ``open'' topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.
Moffat, J W
2016-01-01
An alternative to the postulate of dark energy required to explain the accelerated expansion of the universe is to adopt an inhomogeneous cosmological model to explain the supernovae data without dark energy. We adopt a void cosmology model, based on the inhomogeneous Lema\\^{i}tre-Tolman-Bondi solution of Einstein's field equations. The model can resolve observational anomalies in the $\\Lambda CDM$ model, such as the discrepancy between the locally measured value of the Hubble constant, $H_0=73.24\\pm 1.74\\,{\\rm km}\\,{\\rm s}^{-1}\\,{\\rm Mpc}^{-1}$, and the $H_0=66.93\\pm 0.62\\,{\\rm km}\\,{\\rm s}^{-1}\\,{\\rm Mpc}^{-1}$ determined by the Planck satellite data and the $\\Lambda CDM$ model, and the lithium $^{7}{\\rm Li}$ problem, which is a $5\\sigma$ mismatch between the theoretical prediction for the $^{7}{\\rm Li}$ from big bang nucleosynthesis and the value that we observe locally today at $z=0$. The void model can also resolve the tension between the number of massive clusters derived from the Sunyaev-Zel'dovich eff...
Inhomogeneous Thermal Quenches
Sohrabi, Kiyoumars A
2015-01-01
We describe holographic thermal quenches that are inhomogeneous in space. The main characteristic of the quench is to take the system far from its equilibrium configuration. Except special extreme cases, the problem has no analytic solution. Using the numerical holography methods, we study different observables that measure thermalization such as the time evolution of the horizon, two-point Wightman function and entanglement entropy (EE). Having an extra nontrivial spacial direction, allows us to study this peculiar generalization since we categorize the problem based on whether we do the measurements along this special direction or perpendicular to it. Exciting new features appear that are absent in the common computations in the literature, the appearance of negative EE valleys surrounding the positive EE hills and abrupt quenches that occupy the whole space at their universal limit are some of the results of this paper. We have tried to provide physical explanations wherever possible. The physical picture ...
Kasemsumran, Sumaporn; Suttiwijitpukdee, Nattaporn; Keeratinijakal, Vichein
2017-01-01
In this research, near-infrared (NIR) spectroscopy in combination with moving window partial least squares-discrimination analysis (MWPLS-DA) was utilized to discriminate the variety of turmeric based on DNA markers, which correlated to the quantity of curcuminoid. Curcuminoid was used as a marker compound in variety identification due to the most pharmacological properties of turmeric possessed from it. MWPLS-DA optimized informative NIR spectral regions for the fitting and prediction to {-1/1}-coded turmeric varieties, indicating variables in the development of latent variables in discrimination analysis. Consequently, MWPLS-DA benefited in the selection of combined informative NIR spectral regions of 1100 - 1260, 1300 - 1500 and 1880 - 2500 nm for classification modeling of turmeric variety with 148 calibration samples, and yielded the results better than that obtained from a partial least squares-discrimination analysis (PLS-DA) model built by using the whole NIR spectral region. An effective and rapid strategy of using NIR in combination with MWPLS-DA provided the best variety identification results of 100% in both specificity and total accuracy for 48 test samples.
Simple inhomogeneous cosmological (toy) models
I., Eddy G Chirinos; Zimdahl, Winfried
2016-01-01
Based on the Lema\\^itre-Tolman-Bondi (LTB) metric we consider two flat inhomogeneous big-bang models. We aim at clarifying, as far as possible analytically, basic features of the dynamics of the simplest inhomogeneous models and to point out the potential usefulness of exact inhomogeneous solutions as generalizations of the homogeneous configurations of the cosmological standard model. We discuss explicitly partial successes but also potential pitfalls of these simplest models. Although primarily seen as toy models, the relevant free parameters are fixed by best-fit values using the Joint Light-curve Analysis (JLA)-sample data. On the basis of a likelihood analysis we find that a local hump provides a better description of the observations than a local void. Future redshift-drift measurements are discussed as a promising tool to discriminate between inhomogeneous configurations and the $\\Lambda$CDM model.
Supramolecular polymers in inhomogeneous systems
Zweistra, H.J.A.
2007-01-01
This thesis describes theoretical results of supramolecular polymers in inhomogeneous systems. Supramolecular polymers are linear assemblies of which the monomers are joined by reversible bonds. Many types of supramolecular polymers have been synthesized in recent years. Moreover, there are numerous
Modelling Inhomogeneity in the Universe
Hellaby, Charles
2009-01-01
An overview of some recent developments in inhomogeneous models is presented. As the volume and precision of cosmological data improves, it will become more and more essential to understand the non-linear behaviour of the Einstein field equations. This requires the study of exact inhomogeneous solutions, including their density distributions, their evolution, their geometry, and their causal structure. Observations are strongly affected by the detailed geometry and evolution of a model, and therefore interpretation of observations depends on understanding them. It is generally assumed the universe is homogeneous if averaged over large enough scales, but to actually prove this is so, will require the assumption to be relaxed, and a rigorous inhomogeneous approach to be applied. Though the \\LT metric has long been used for models of spherical inhomogeneities, there have been a number of new results, including a variety of methods for creating models with specific properties, and their application to cosmic stru...
Inclusions and inhomogeneities under stress
CSIR Research Space (South Africa)
Nabarro, FRN
1996-02-01
Full Text Available Some general theorems, new and old, concerning the behaviour of elastic inclusions and inhomogeneities in bodies without or with external stress, are assembled. The principal new result is that arbitrary external tractions cannot influence the shape...
The Noncommutative Inhomogeneous Hopf Algebra
Lagraa, M
1997-01-01
From the bicovariant first order differential calculus over inhomogeneous Hopf algebra B we construct the set of right-invariant Maurer Cartan one-forms considered as a right-invariant basis of a bicovariant B-bimodule over which we develope the Woronowicz'general theory differential calculus on quantum groups. In this context, we derive the inhomogeneous commutation rules and investigate the properties of their different terms.
The Noncommutative Inhomogeneous Hopf Algebra
1997-01-01
From the bicovariant first order differential calculus on inhomogeneous Hopf algebra ${\\cal B}$ we construct the set of right-invariant Maurer-Cartan one-forms considered as a right-invariant basis of a bicovariant ${\\cal B}$-bimodule over which we develop the Woronowicz's general theory of differential calculus on quantum groups. In this formalism, we introduce suitable functionals on ${\\cal B}$ which control the inhomogeneous commutation rules. In particular we find that the homogeneous par...
Effective inhomogeneous inflation: curvature inhomogeneities of the Einstein vacuum
Energy Technology Data Exchange (ETDEWEB)
Buchert, Thomas [Universite Lyon 1, Centre de Recherche Astrophysique de Lyon, 9 Avenue Charles Andre, F-69230 Saint-Genis-Laval (France); Obadia, Nathaniel, E-mail: buchert@obs.univ-lyon1.fr, E-mail: nathaniel.obadia@ens-lyon.fr [Ecole Normale Superieure de Lyon, Centre de Recherche Astrophysique de Lyon, 46 Allee d' Italie, F-69364 Lyon Cedex 07 (France)
2011-08-21
We consider spatially averaged inhomogeneous universe models and argue that, already in the absence of sources, an effective scalar field arises through foliating and spatially averaging inhomogeneous geometrical curvature invariants of the Einstein vacuum. This scalar field (the 'morphon') acts as an inflaton, if we prescribe a potential of some generic form. We show that, for any initially negative average spatial curvature, the morphon is driven through an inflationary phase and leads-on average-to a spatially flat, homogeneous and isotropic universe model, providing initial conditions for pre-heating and, by the same mechanism, a possibly natural self-exit. (fast track communication)
Manifestations of Magnetic Field Inhomogeneities
Indian Academy of Sciences (India)
Lawrence Rudnick
2011-12-01
Both observations and simulations reveal large inhomogeneities in magnetic field distributions in diffuse plasmas. Incorporating these inhomogeneities into various calculations can significantly change the inferred physical conditions. In extragalactic sources, e.g., these can compromise analyses of spectral ageing, which I will illustrate with some current work on cluster relics. I also briefly re-examine the old issue of how inhomogeneous fields affect particle lifetimes; perhaps not surprisingly, the next generation of radio telescopes are unlikely to find many sources that can extend their lifetimes from putting relativistic electrons into a low-field ‘freezer’. Finally, I preview some new EVLA results on the complex relic in Abell 2256, with implications for the interspersing of its relativistic and thermal plasmas.
Comments on inhomogeneous anisotropic cosmology
Kaya, Ali
2016-01-01
Recently a new no-global-recollapse argument is given for some inhomogeneous and anisotropic cosmologies that utilizes surface deformation by the mean curvature flow. In this note we point out a few important issues about the proposed deformations and in particular indicate that in the presence of large spatial variations the mean curvature flow may deform an initially spacelike surface to a surface with null or timelike portions. The time evolution of the spatial scalar curvature that prevents recollapse is determined in normal coordinates, which shows the impact of inhomogeneities explicitly. Our analysis also indicates a possible caveat in numerical solutions that give rise to inflation.
Remarks on inhomogeneous anisotropic cosmology
Kaya, Ali
2016-08-01
Recently a new no-global-recollapse argument was given for some inhomogeneous and anisotropic cosmologies that utilizes surface deformation by the mean curvature flow. In this paper we discuss important properties of the mean curvature flow of spacelike surfaces in Lorentzian manifolds. We show that singularities may form during cosmic evolution, and the theorems forbidding the global recollapse lose their validity. The time evolution of the spatial scalar curvature that may kinematically prevent the recollapse is determined in normal coordinates, which shows the impact of inhomogeneities explicitly. Our analysis indicates a caveat in numerical solutions that give rise to inflation.
The Spontaneous Radiation of Electrons in a Plane Wiggler with Inhomogeneous Magnetic Field
Ayryan, E A; Izmailian, N Sh; Oganesyan, K B
2016-01-01
The spectral distribution of spontaneous emission of electrons moving in a plane wiggler with inhomogeneous magnetic field is calculated. We show that electrons do complicated motion consisting of slow(strophotron) and fast(undulator) parts. The equations of motion are averaged over fast undulator part and we obtain equations for connected motion. It is shown, that the account of inhomogenity of the magnetic field leads to appearance of additional peaks in the spectral distribution of spontaneous radiation.
Inhomogeneous microstructural growth by irradiation
DEFF Research Database (Denmark)
Krishan, K.; Singh, Bachu Narain; Leffers, Torben
1985-01-01
In the present paper we discuss the development of heterogeneous microstructure for uniform irradiation conditions. It is shown that microstructural inhomogeneities on a scale of 0.1 μm can develop purely from kinematic considerations because of the basic structure of the rate equations used to d...
Numerical micromagnetism of strong inhomogeneities
Energy Technology Data Exchange (ETDEWEB)
Andreas, Christian [Peter Grünberg Institut (PGI-6), Forschungszentrum Jülich GmbH, D-52428 Jülich (Germany); Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS UMR 7504, Strasbourg (France); Gliga, Sebastian [Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute, 5232 Villigen PSI (Switzerland); Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093 Zurich (Switzerland); Hertel, Riccardo, E-mail: hertel@ipcms.unistra.fr [Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS UMR 7504, Strasbourg (France)
2014-08-01
The size of micromagnetic structures, such as domain walls or vortices, is comparable to the exchange length of the ferromagnet. Both, the exchange length of the stray field l{sub s} and the magnetocrystalline exchange length l{sub k}, are material-dependent quantities that usually lie in the nanometer range. This emphasizes the theoretical challenges associated with the mesoscopic nature of micromagnetism: the magnetic structures are much larger than the atomic lattice constant, but at the same time much smaller than the sample size. In computer simulations, the smallest exchange length serves as an estimate for the largest cell size admissible to prevent appreciable discretization errors. This general rule is not valid in special situations where the magnetization becomes particularly inhomogeneous. When such strongly inhomogeneous structures develop, micromagnetic simulations inevitably contain systematic and numerical errors. It is suggested to combine micromagnetic theory with a Heisenberg model to resolve such problems. We analyze cases where strongly inhomogeneous structures pose limits to standard micromagnetic simulations, arising from fundamental aspects as well as from numerical drawbacks. - Highlights: • We discuss the impact of strong inhomogeneities on micromagnetic simulations. • Analysis of fundamental and numerical errors in micromagnetic point singularities. • Numerical and methodological errors in exchange energy terms are quantified. • Suggestion to combine atomistic Heisenberg models with micromagnetism in such cases.
Inhomogeneous Markov point processes by transformation
DEFF Research Database (Denmark)
Jensen, Eva B. Vedel; Nielsen, Linda Stougaard
2000-01-01
We construct parametrized models for point processes, allowing for both inhomogeneity and interaction. The inhomogeneity is obtained by applying parametrized transformations to homogeneous Markov point processes. An interesting model class, which can be constructed by this transformation approach......, is that of exponential inhomogeneous Markov point processes. Statistical inference For such processes is discussed in some detail....
CMB anisotropies from primordial inhomogeneous magnetic fields
Lewis, A
2004-01-01
Primordial inhomogeneous magnetic fields of the right strength can leave a signature on the CMB temperature anisotropy and polarization. Potentially observable contributions to polarization B-modes are generated by vorticity and gravitational waves sourced by the magnetic anisotropic stress. We compute the corresponding CMB transfer functions in detail including the effect of neutrinos. The shear rapidly causes the neutrino anisotropic stress to cancel the stress from the magnetic field, suppressing the production of gravitational waves and vorticity on super-horizon scales after neutrino decoupling. A significant large scale signal from tensor modes can only be produced before neutrino decoupling, and the actual amplitude is somewhat uncertain. Plausible values suggest primordial nearly scale invariant fields of ~ 10^(-10)G today may be observable from their large scale tensor anisotropy. They can be distinguished from primordial gravitational waves by their non-Gaussianity. Vector mode vorticity sources B-m...
Quasiadiabatic modes from viscous inhomogeneities
Giovannini, Massimo
2016-01-01
The viscous inhomogeneities of a relativistic plasma determine a further class of entropic modes whose amplitude must be sufficiently small since curvature perturbations are observed to be predominantly adiabatic and Gaussian over large scales. When the viscous coefficients only depend on the energy density of the fluid the corresponding curvature fluctuations are shown to be almost adiabatic. After addressing the problem in a gauge-invariant perturbative expansion, the same analysis is repeated at a non-perturbative level by investigating the nonlinear curvature inhomogeneities induced by the spatial variation of the viscous coefficients. It is demonstrated that the quasiadiabatic modes are suppressed in comparison with a bona fide adiabatic solution. Because of its anomalously large tensor to scalar ratio the quasiadiabatic mode cannot be a substitute for the conventional adiabatic paradigm so that, ultimately, the present findings seems to exclude the possibility of a successful accelerated dynamics solely...
Inhomogeneous and interacting vacuum energy
De-Santiago, Josue; Wang, Yuting
2012-01-01
Vacuum energy is a simple model for dark energy driving an accelerated expansion of the universe. If the vacuum energy is inhomogeneous in spacetime then it must be interacting. We present the general equations for a spacetime-dependent vacuum energy in cosmology, including inhomogeneous perturbations. We show how any dark energy cosmology can be described by an interacting vacuum+matter. Different models for the interaction can lead to different behaviour (e.g., sound speed for dark energy perturbations) and hence could be distinguished by cosmological observations. As an example we present the cosmic microwave microwave background anisotropies and the matter power spectrum for two different versions of a generalised Chaplygin gas cosmology.
Inhomogeneous Cosmology with Numerical Relativity
Macpherson, Hayley J; Price, Daniel J
2016-01-01
We perform three-dimensional numerical relativity simulations of homogeneous and inhomogeneous expanding spacetimes, with a view towards quantifying non-linear effects from cosmological inhomogeneities. We demonstrate fourth-order convergence with errors less than one part in 10^6 in evolving a flat, dust Friedmann-Lemaitre-Roberston-Walker (FLRW) spacetime using the Einstein Toolkit within the Cactus framework. We also demonstrate agreement to within one part in 10^3 between the numerical relativity solution and the linear solution for density, velocity and metric perturbations in the Hubble flow over a factor of ~350 change in scale factor (redshift). We simulate the growth of linear perturbations into the non-linear regime, where effects such as gravitational slip and tensor perturbations appear. We therefore show that numerical relativity is a viable tool for investigating nonlinear effects in cosmology.
Inhomogeneous recombinations during cosmic reionization
Sobacchi, Emanuele; Mesinger, Andrei
2014-01-01
By depleting the ionizing photon budget available to expand cosmic HII regions, recombining systems (or Lyman limit systems) can have a large impact during (and following) cosmic reionization. Unfortunately, directly resolving such structures in large-scale reionization simulations is computationally impractical. Instead, here we implement a sub-grid prescription for tracking inhomogeneous recombinations in the intergalactic medium. Building on previous work parameterizing photo-heating feedb...
Quasiadiabatic modes from viscous inhomogeneities
Giovannini, Massimo
2016-01-01
The viscous inhomogeneities of a relativistic plasma determine a further class of entropic modes whose amplitude must be sufficiently small since curvature perturbations are observed to be predominantly adiabatic and Gaussian over large scales. When the viscous coefficients only depend on the energy density of the fluid the corresponding curvature fluctuations are shown to be almost adiabatic. After addressing the problem in a gauge-invariant perturbative expansion, the same analysis is repea...
Institute of Scientific and Technical Information of China (English)
Guo Yan
2007-01-01
@@ China has already become the world's largest manufacturer of cement,copper and steel.Chinese producers have moved onto the world stage and dominated the global consumer market from textiles to electronics with amazing speed and efficiency.
Inhomogeneous interface laser mirror coatings.
Ledger, A M
1979-09-01
Methods of improving the durability of thin-film laser mirror coatings for 10.6 microm using thorium fluoride, zinc selenide, and zinc sulfide materials have been investigated. The largest improvement in film durability was obtained by using inhomogeneous interface fabrication for all the dielectric-dielectric interfaces and by incorporating cerium fluoride protective overcoating material into the film design. Experimental results are given for enhanced reflectors, polarization-selective coatings, and buried-grating aperture-sharing coatings designed for high-power laser applications.
Directory of Open Access Journals (Sweden)
Federica Bardi
2017-02-01
Full Text Available This paper presents the main results of the GB-InSAR (ground based interferometric synthetic aperture radar monitoring of the Capriglio landslide (Northern Apennines, Emilia Romagna Region, Italy, activated on 6 April 2013. The landslide, triggered by prolonged rainfall, is constituted by two main adjacent enlarging bodies with a roto-translational kinematics. They activated in sequence and subsequently joined into a large earth flow, channelizing downstream of the Bardea Creek, for a total length of about 3600 m. The displacement rate of this combined mass was quite high, so that the landslide toe evolved with velocities of several tens of meters per day (with peaks of 70–80 m/day in the first month, and of several meters per day (with peaks of 13–14 m/day from early May to mid-July 2013. In the crown area, the landslide completely destroyed a 450 m sector of provincial roadway S.P. 101, and its retrogression tendency exposed the villages of Capriglio and Pianestolla, located in the upper watershed area of the Bardea Creek, to great danger. Furthermore, the advancing toe seriously threatened the Antria bridge, representing the “Massese” provincial roadway S.P. 665R transect over the Bardea Creek, the only strategic roadway left able to connect the above-mentioned villages. With the final aim of supporting local authorities in the hazard assessment and risk management during the emergency phase, on 4 May 2013 aerial optical surveys were conducted to accurately map the landslide extension and evolution. Moreover, a GB-InSAR monitoring campaign was started in order to assess displacements of the whole landslide area. The versatility and flexibility of the GB-InSAR sensors allowed acquiring data with two different configurations, designed and set up to continuously retrieve information on the landslide movement rates (both in its upper slow-moving sectors and in its fast-moving toe. The first acquisition mode revealed that the Capriglio and
Quasiadiabatic modes from viscous inhomogeneities
Giovannini, Massimo
2016-04-01
The viscous inhomogeneities of a relativistic plasma determine a further class of entropic modes whose amplitude must be sufficiently small since curvature perturbations are observed to be predominantly adiabatic and Gaussian over large scales. When the viscous coefficients only depend on the energy density of the fluid the corresponding curvature fluctuations are shown to be almost adiabatic. After addressing the problem in a gauge-invariant perturbative expansion, the same analysis is repeated at a nonperturbative level by investigating the nonlinear curvature inhomogeneities induced by the spatial variation of the viscous coefficients. It is demonstrated that the quasiadiabatic modes are suppressed in comparison with a bona fide adiabatic solution. Because of its anomalously large tensor to scalar ratio the quasiadiabatic mode cannot be a substitute for the conventional adiabatic paradigm so that, ultimately, the present findings seems to exclude the possibility of a successful accelerated dynamics solely based on relativistic viscous fluids. If the dominant adiabatic mode is not affected by the viscosity of the background a sufficiently small fraction of entropic fluctuations of viscous origin cannot be a priori ruled out.
3DHZETRN: Inhomogeneous Geometry Issues
Wilson, John W.; Slaba, Tony C.; Badavi, Francis F.
2017-01-01
Historical methods for assessing radiation exposure inside complicated geometries for space applications were limited by computational constraints and lack of knowledge associated with nuclear processes occurring over a broad range of particles and energies. Various methods were developed and utilized to simplify geometric representations and enable coupling with simplified but efficient particle transport codes. Recent transport code development efforts, leading to 3DHZETRN, now enable such approximate methods to be carefully assessed to determine if past exposure analyses and validation efforts based on those approximate methods need to be revisited. In this work, historical methods of representing inhomogeneous spacecraft geometry for radiation protection analysis are first reviewed. Two inhomogeneous geometry cases, previously studied with 3DHZETRN and Monte Carlo codes, are considered with various levels of geometric approximation. Fluence, dose, and dose equivalent values are computed in all cases and compared. It is found that although these historical geometry approximations can induce large errors in neutron fluences up to 100 MeV, errors on dose and dose equivalent are modest (<10%) for the cases studied here.
Influence of inhomogeneities on holographic mutual information and butterfly effect
Cai, Rong-Gen; Zeng, Xiao-Xiong; Zhang, Hai-Qing
2017-07-01
We study the effect of inhomogeneity, which is induced by the graviton mass in massive gravity, on the mutual information and the chaotic behavior of a 2+1-dimensional field theory from the gauge/gravity duality. When the system is near-homogeneous, the mutual information increases as the graviton mass grows. However, when the system is far from homogeneity, the mutual information decreases as the graviton mass increases. By adding the perturbations of energy into the system, we investigate the dynamical mutual information in the shock wave geometry. We find that the greater perturbations disrupt the mutual information more rapidly, which resembles the butterfly effect in chaos theory. Besides, the greater inhomogeneity reduces the dynamical mutual information more quickly just as in the static case.
Gandhi, Manoj; Evdokimova, Viktoria N; Cuenco, Karen T; Bakkenist, Christopher J; Nikiforov, Yuri E
2013-02-15
We recently reported that homologous chromosomes make contact at the sites of double-strand breaks (DSBs) induced by ionizing radiation (IR) and the restriction endonuclease I-PpoI in G₀/G₁-phase somatic human cells. The contact involves short segments of homologous chromosomes and is centered on a DSB that occurs in a gene; contact does not occur at a DSB in intergenic DNA. Contact between homologous chromosomes is abrogated by inhibition of transcription and requires the kinase activity of ATM, but not DNA-PK. Here, we report additional insights into the mechanism underlying this novel phenomenon. We identify four patterns of homologous chromosome contact, and show that contact between homologous arms, but not centrosomes, is induced by IR. Significantly, we demonstrate that contact is induced by IR in non-proliferating, G₀-phase human cells derived from tissue explants. Finally, we show that contact between homologous chromosomes is detectable as early as 5 min after IR. These results point to the existence of a mechanism that rapidly localizes homologous chromosome arms at sites of DSBs in genes in G₀-phase human cells.
Promyou, Surassawadee; Ketsa, Saichol; van Doorn, Wouter G
2014-11-15
The early visible effects of pollination in orchids are likely due to pollinia-borne chemicals. In Dendrobium we tested whether such compounds were water soluble and would diffuse in solid-aqueous phase, and determined both 1-aminocyclopropane-1-carboxylic acid (ACC) concentrations and auxin activity. Following pollination, the flower peduncle showed epinastic movement, followed by yellowing of the flower lip, flower senescence and ovary growth. Placing pollinia on agar blocks for 3, 6, 9 or 12h, prior to transferring them to the stigma, increased the time to these early postpollination effects or prevented them. Placing agar blocks that had been used for contact with the pollinia on the stigma also induced the early postpollination effects. The concentrations of ACC, the direct precursor of ethylene, in pollinia was lower the longer the pollinia had been in contact with the agar blocks, whilst the ACC content in the agar blocks increased with the period of contact. The auxin activity of the agar blocks also increased with the time of contact with pollinia. It is concluded that chemicals in the pollinia are responsible for the early visible postpollination effects, and that these (a) rapidly diffuse in aqueous media, and (b) comprise at least ACC and compounds with auxin activity. The idea is discussed that ACC plus auxin is adequate for the production of the early postpollination effects.
Magnetomigration of rare-earth ions in inhomogeneous magnetic fields.
Franczak, Agnieszka; Binnemans, Koen; Jan Fransaer
2016-10-05
The effects of external inhomogenous (gradient) magnetic fields on the movement of the rare-earth ions: Dy(3+), Gd(3+) and Y(3+), in initially homogeneous aqueous solutions have been investigated. Differences in the migration of rare-earth ions in gradient magnetic fields were observed, depending on the magnetic character of the ions: paramagnetic ions of Dy(3+) and Gd(3+) move towards regions of the sample where the magnetic field gradient is the strongest, while diamagnetic ions of Y(3+) move in the opposite direction. It has been showed that the low magnetic field gradients, such the ones generated by permanent magnets, are sufficient to observe the magnetomigration effects of the ions in solution. The present work clearly establishes the behavior of magnetically different ions in initially homogeneous aqueous solutions exposed to magnetic field gradients. To this avail, a methodology for measuring the local concentration differences of metal ions in liquid samples was developed.
MR image intensity inhomogeneity correction
(Vişan Pungǎ, Mirela; Moldovanu, Simona; Moraru, Luminita
2015-01-01
MR technology is one of the best and most reliable ways of studying the brain. Its main drawback is the so-called intensity inhomogeneity or bias field which impairs the visual inspection and the medical proceedings for diagnosis and strongly affects the quantitative image analysis. Noise is yet another artifact in medical images. In order to accurately and effectively restore the original signal, reference is hereof made to filtering, bias correction and quantitative analysis of correction. In this report, two denoising algorithms are used; (i) Basis rotation fields of experts (BRFoE) and (ii) Anisotropic Diffusion (when Gaussian noise, the Perona-Malik and Tukey's biweight functions and the standard deviation of the noise of the input image are considered).
Quantifying uncertainty from material inhomogeneity.
Energy Technology Data Exchange (ETDEWEB)
Battaile, Corbett Chandler; Emery, John M.; Brewer, Luke N.; Boyce, Brad Lee
2009-09-01
Most engineering materials are inherently inhomogeneous in their processing, internal structure, properties, and performance. Their properties are therefore statistical rather than deterministic. These inhomogeneities manifest across multiple length and time scales, leading to variabilities, i.e. statistical distributions, that are necessary to accurately describe each stage in the process-structure-properties hierarchy, and are ultimately the primary source of uncertainty in performance of the material and component. When localized events are responsible for component failure, or when component dimensions are on the order of microstructural features, this uncertainty is particularly important. For ultra-high reliability applications, the uncertainty is compounded by a lack of data describing the extremely rare events. Hands-on testing alone cannot supply sufficient data for this purpose. To date, there is no robust or coherent method to quantify this uncertainty so that it can be used in a predictive manner at the component length scale. The research presented in this report begins to address this lack of capability through a systematic study of the effects of microstructure on the strain concentration at a hole. To achieve the strain concentration, small circular holes (approximately 100 {micro}m in diameter) were machined into brass tensile specimens using a femto-second laser. The brass was annealed at 450 C, 600 C, and 800 C to produce three hole-to-grain size ratios of approximately 7, 1, and 1/7. Electron backscatter diffraction experiments were used to guide the construction of digital microstructures for finite element simulations of uniaxial tension. Digital image correlation experiments were used to qualitatively validate the numerical simulations. The simulations were performed iteratively to generate statistics describing the distribution of plastic strain at the hole in varying microstructural environments. In both the experiments and simulations, the
Inhomogenous loop quantum cosmology with matter
Blas, Daniel Martín-de; Marugán, Guillermo A Mena; 10.1088/1742-6596/360/1/012032
2013-01-01
The linearly polarized Gowdy $T^3$ model with a massless scalar field with the same symmetries as the metric is quantized by applying a hybrid approach. The homogeneous geometry degrees of freedom are loop quantized, fact which leads to the resolution of the cosmological singularity, while a Fock quantization is employed for both matter and gravitational inhomogeneities. Owing to the inclusion of the massless scalar field this system allows us to modelize flat Friedmann-Robertson-Walker cosmologies filled with inhomogeneities propagating in one direction. It provides a perfect scenario to study the quantum back-reaction between the inhomogeneities and the polymeric homogeneous and isotropic background.
Inflation in spherically symmetric inhomogeneous models
Energy Technology Data Exchange (ETDEWEB)
Stein-Schabes, J.A.
1986-11-01
Exact analytical solutions of Einstein's equations are found for a spherically symmetric inhomogeneous metric in the presence of a massless scalar field with a flat potential. The process of isotropization and homogenization is studied in detail. It is found that the time dependence of the metric becomes de Sitter for large times. Two cases are studied. The first deals with a homogeneous scalar field, while the second with a spherically symmetric inhomogeneous scalar field. In the former case the metric is of the Robertson-Walker form, while the latter is intrinsically inhomogeneous. 16 refs.
Holographic confinement in inhomogeneous backgrounds
Marolf, Donald; Wien, Jason
2016-08-01
As noted by Witten, compactifying a d-dimensional holographic CFT on an S 1 gives a class of ( d - 1)-dimensional confining theories with gravity duals. The proto-typical bulk solution dual to the ground state is a double Wick rotation of the AdS d+1 Schwarzschild black hole known as the AdS soliton. We generalize such examples by allowing slow variations in the size of the S 1, and thus in the confinement scale. Coefficients governing the second order response of the system are computed for 3 ≤ d ≤ 8 using a derivative expansion closely related to the fluid-gravity correspondence. The primary physical results are that i) gauge-theory flux tubes tend to align orthogonal to gradients and along the eigenvector of the Hessian with the lowest eigenvalue, ii) flux tubes aligned orthogonal to gradients are attracted to gradients for d ≤ 6 but repelled by gradients for d ≥ 7, iii) flux tubes are repelled by regions where the second derivative along the tube is large and positive but are attracted to regions where the eigenvalues of the Hessian are large and positive in directions orthogonal to the tube, and iv) for d > 3, inhomogeneities act to raise the total energy of the confining vacuum above its zeroth order value.
Inhomogeneous Universe Models with Varying Cosmological Term
Chimento, L P; Chimento, Luis P.; Pavon, Diego
1998-01-01
The evolution of a class of inhomogeneous spherically symmetric universe models possessing a varying cosmological term and a material fluid, with an adiabatic index either constant or not, is studied.
Inhomogenous quantum codes (Ⅰ):additive case
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
In this paper,the quantum error-correcting codes are generalized to the inhomogenous quantumstate space Cq1 Cq2 ··· Cqn,where qi(1 i n) are arbitrary positive integers.By attaching an abelian group Ai of order qi to the space Cqi(1 i n),we present the stabilizer construction of such inhomogenous quantum codes,called additive quantum codes,in term of the character theory of the abelian group A = A1⊕A2⊕···⊕An.As usual case,such construction opens a way to get inhomogenous quantum codes from the classical mixed linear codes.We also present Singleton bound for inhomogenous additive quantum codes and show several quantum codes to meet such bound by using classical mixed algebraic-geometric codes.
Pulsed Holography of Rapidly Moving Dust Particles
1981-05-31
orthodontal and dental work as a small "sand blatst" unit. Nitrogen gas at high pressure is passed through a regulator to reduce the pressure to the range 20...34projectile" is a 55 x 135 pmi particle emerging from the nozzle under 30 psi pressure, indicating a velocity of 20 to 60 rn/s. Resolution is
Exactly solvable one-dimensional inhomogeneous models
Energy Technology Data Exchange (ETDEWEB)
Derrida, B.; France, M.M.; Peyriere, J.
1986-11-01
The authors present a simple way of constructing one-dimensional inhomogeneous models (random or quasiperiodic) which can be solved exactly. They treat the example of an Ising chain in a varying magnetic field, but their procedure can easily be extended to other one-dimensional inhomogeneous models. For all the models they can construct, the free energy and its derivatives with respect to temperature can be computed exactly at one particular temperature.
Inhomogeneous Einstein-Rosen string cosmology
Clancy, Dominic; Feinstein, Alexander; Lidsey, James E.; Tavakol, Reza
1999-08-01
Families of anisotropic and inhomogeneous string cosmologies containing non-trivial dilaton and axion fields are derived by applying the global symmetries of the string effective action to a generalized Einstein-Rosen metric. The models exhibit a two-dimensional group of Abelian isometries. In particular, two classes of exact solutions are found that represent inhomogeneous generalizations of the Bianchi type VIh cosmology. The asymptotic behavior of the solutions is investigated and further applications are briefly discussed.
Inhomogeneous Fragmentation of the Rolling Tachyon
Felder, Gary N; Kofman, Lev
2004-01-01
Dirac-Born-Infeld type effective actions reproduce many aspects of string theory classical tachyon dynamics of unstable Dp-branes. The inhomogeneous tachyon field rolling from the top of its potential forms topological defects of lower codimensions. In between them, as we show, the tachyon energy density fragments into a p-dimensional web-like high density network evolving with time. We present an analytic asymptotic series solution of the non-linear equations for the inhomogeneous tachyon an...
2006-01-01
[figure removed for brevity, see original site] Context image for PIA03289 Moving Downhill This narrow canyon is part of Coprates Chasma. On the east side of the canyon a landslide is visible. The southern wall of the canyon is marked by bright and dark streaks where dust has slid down the cliff face. Image information: VIS instrument. Latitude -10.5N, Longitude 264.8E. 17 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.
General polarized ray-tracing method for inhomogeneous uniaxially anisotropic media
Sluijter, M.; De Boer, D.K.G.; Braat, J.J.M.
2008-01-01
Uniaxial optical anisotropy in the geometrical-optics approach is a classical problem, and most of the theory has been known for at least fifty years. Although the subject appears frequently in the literature, wave propagation through inhomogeneous anisotropic media is rarely addressed. The rapid ad
Effects of thermal inhomogeneity on 4m class mirror substrates
Jedamzik, Ralf; Kunisch, Clemens; Westerhoff, Thomas
2016-07-01
The new ground based telescope generation is moving to a next stage of performance and resolution. Mirror substrate material properties tolerance and homogeneity are getting into focus. The coefficient of thermal expansion (CTE) homogeneity is even more important than the absolute CTE. The error in shape of a mirror, even one of ZERODUR, is affected by changes in temperature, and by gradients in temperature. Front to back gradients will change the radius of curvature R that in turn will change the focus. Some systems rely on passive athermalization and do not have means to focus. Similarly changes in soak temperature will result in surface changes to the extent there is a non-zero coefficient of thermal expansion. When there are in-homogeneities in CTE, the mirror will react accordingly. Results of numerical experiments are presented discussing the impact of CTE in-homogeneities on the optical performance of 4 m class mirror substrates. Latest improvements in 4 m class ZERODUR CTE homogeneity and the thermal expansion metrology are presented as well.
Shear waves in inhomogeneous, compressible fluids in a gravity field.
Godin, Oleg A
2014-03-01
While elastic solids support compressional and shear waves, waves in ideal compressible fluids are usually thought of as compressional waves. Here, a class of acoustic-gravity waves is studied in which the dilatation is identically zero, and the pressure and density remain constant in each fluid particle. These shear waves are described by an exact analytic solution of linearized hydrodynamics equations in inhomogeneous, quiescent, inviscid, compressible fluids with piecewise continuous parameters in a uniform gravity field. It is demonstrated that the shear acoustic-gravity waves also can be supported by moving fluids as well as quiescent, viscous fluids with and without thermal conductivity. Excitation of a shear-wave normal mode by a point source and the normal mode distortion in realistic environmental models are considered. The shear acoustic-gravity waves are likely to play a significant role in coupling wave processes in the ocean and atmosphere.
Diamagnetic susceptibility of a confined donor in inhomogeneous quantum dots
Rahmani, K.; Zorkani, I.; Jorio, A.
2011-03-01
The binding energy and diamagnetic susceptibility χdia are estimated for a shallow donor confined to move in GaAs-GaAlAs inhomogeneous quantum dots. The calculation was performed within the effective mass approximation and using the variational method. The results show that the binding energy and the diamagnetic susceptibility χdia depend strongly on the core radius and the shell radius. We have demonstrated that there is a critical value of the ratio of the inner radius to the outer radius which may be important for nanofabrication techniques. The binding energy Eb shows a minimum for a critical value of this ratio depending on the value of the outer radius and shows a maximum when the donor is placed at the center of the spherical layer. The diamagnetic susceptibility is more sensitive to variations of the radius for a large spherical layer. The binding energy and diamagnetic susceptibility depend strongly on the donor position.
Ignatchenko, V. A.; Polukhin, D. S.; Tsikalov, D. S.
2017-10-01
A new self-consistent approximation proposed earlier, is compared with various existing approximations, as well as with a numerical simulation of solutions of the wave equation for a medium with one-dimensional inhomogeneities. The Green's function, found using the new approach, is the closest to the result obtained by the numerical simulation. The results of the work show that the new approach has undoubted advantages in the study of stochastic problems in media with longwave inhomogeneities. The new self-consistent approximation in some cases has advantages over a numerical method: a more rapid process of calculation and the possibility of consideration of three-dimensional problems.
Traveltime approximations for inhomogeneous HTI media
Alkhalifah, Tariq Ali
2011-01-01
Traveltimes information is convenient for parameter estimation especially if the medium is described by an anisotropic set of parameters. This is especially true if we could relate traveltimes analytically to these medium parameters, which is generally hard to do in inhomogeneous media. As a result, I develop traveltimes approximations for horizontaly transversely isotropic (HTI) media as simplified and even linear functions of the anisotropic parameters. This is accomplished by perturbing the solution of the HTI eikonal equation with respect to η and the azimuthal symmetry direction (usually used to describe the fracture direction) from a generally inhomogeneous elliptically anisotropic background medium. The resulting approximations can provide accurate analytical description of the traveltime in a homogenous background compared to other published moveout equations out there. These equations will allow us to readily extend the inhomogenous background elliptical anisotropic model to an HTI with a variable, but smoothly varying, η and horizontal symmetry direction values. © 2011 Society of Exploration Geophysicists.
Beginning inflation in an inhomogeneous universe
Energy Technology Data Exchange (ETDEWEB)
East, William E. [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Kleban, Matthew [Center for Cosmology and Particle Physics, New York University, New York, New York 10003 (United States); Linde, Andrei [SITP and Department of Physics, Stanford University,Stanford, California 94305 (United States); Senatore, Leonardo [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); SITP and Department of Physics, Stanford University,Stanford, California 94305 (United States)
2016-09-06
Using numerical solutions of the full Einstein field equations coupled to a scalar inflaton field in 3+1 dimensions, we study the conditions under which a universe that is initially expanding, highly inhomogeneous and dominated by gradient energy can transition to an inflationary period. If the initial scalar field variations are contained within a sufficiently flat region of the inflaton potential, and the universe is spatially flat or open on average, inflation will occur following the dilution of the gradient and kinetic energy due to expansion. This is the case even when the scale of the inhomogeneities is comparable to the initial Hubble length, and overdense regions collapse and form black holes, because underdense regions continue expanding, allowing inflation to eventually begin. This establishes that inflation can arise from highly inhomogeneous initial conditions and solve the horizon and flatness problems, at least as long as the variations in the scalar field do not include values that exceed the inflationary plateau.
An Improved Moving Mesh Algorithm
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
we consider an iterative algorithm of mesh optimization for finite element solution, and give an improved moving mesh strategy that reduces rapidly the complexity and cost of solving variational problems.A numerical result is presented for a 2-dimensional problem by the improved algorithm.
On electromagnetic field problems in inhomogeneous media
Mohsen, A.
1973-01-01
Analysis of electromagnetic fields in inhomogeneous media is of practical interest in general scattering and propagation problems and in the study of lenses. For certain types of inhomogeneities, the fields may be represented in terms of two scalars. In a general orthogonal coordinate system, these potentials satisfy second order differential equations. Exact solutions of these equations are known only for a few particular cases and in general, an approximate or numerical technique must be employed. The present work reviews and generalizes some of the main methods of attack of the problem. The results are presented in a form appropriate for numerical computation.
Cosmological perturbations from an inhomogeneous phase transition
Energy Technology Data Exchange (ETDEWEB)
Matsuda, Tomohiro, E-mail: matsuda@sit.ac.j [Laboratory of Physics, Saitama Institute of Technology, Fusaiji, Okabe-machi, Saitama 369-0293 (Japan)
2009-07-21
A mechanism for generating metric perturbations in inflationary models is considered. Long-wavelength inhomogeneities of light scalar fields in a decoupled sector may give rise to superhorizon fluctuations of couplings and masses in the low-energy effective action. Cosmological phase transitions may then occur that are not simultaneous in space, but occur with time lags in different Hubble patches that arise from the long-wavelength inhomogeneities. Here an interesting model in which cosmological perturbations may be created at the electroweak phase transition is considered. The results show that phase transitions may be a generic source of non-Gaussianity.
Soliton structure dynamics in inhomogeneous media
Guerrero, L E; González, J A
1998-01-01
We show that soliton interaction with finite-width inhomogeneities can activate a great number of soliton internal modes. We obtain the exact stationary soliton solution in the presence of inhomogeneities and solve exactly the stability problem. We present a Karhunen-Loeve analysis of the soliton structure dynamics as a time-dependent force pumps energy into the traslational mode of the kink. We show the importance of the internal modes of the soliton as they can generate shape chaos for the soliton as well as cases in which the first shape mode leads the dynamics.
Spectral Distortion in a Radially Inhomogeneous Cosmology
Caldwell, R R
2013-01-01
The spectral distortion of the cosmic microwave background blackbody spectrum in a radially inhomogeneous spacetime, designed to exactly reproduce a LambdaCDM expansion history along the past light cone, is shown to exceed the upper bound established by COBE-FIRAS by a factor of approximately 3000. This simple observational test helps uncover a slew of pathological features that lie hidden inside the past light cone, including a radially contracting phase at decoupling and, if followed to its logical extreme, a naked singularity at the radially inhomogeneous Big Bang.
Cosmic inhomogeneities and averaged cosmological dynamics.
Paranjape, Aseem; Singh, T P
2008-10-31
If general relativity (GR) describes the expansion of the Universe, the observed cosmic acceleration implies the existence of a "dark energy." However, while the Universe is on average homogeneous on large scales, it is inhomogeneous on smaller scales. While GR governs the dynamics of the inhomogeneous Universe, the averaged homogeneous Universe obeys modified Einstein equations. Can such modifications alone explain the acceleration? For a simple generic model with realistic initial conditions, we show the answer to be "no." Averaging effects negligibly influence the cosmological dynamics.
Spectral distortion in a radially inhomogeneous cosmology
Caldwell, R. R.; Maksimova, N. A.
2013-11-01
The spectral distortion of the cosmic microwave background blackbody spectrum in a radially inhomogeneous space-time, designed to exactly reproduce a ΛCDM expansion history along the past light cone, is shown to exceed the upper bound established by COBE-FIRAS by a factor of approximately 3700. This simple observational test helps uncover a slew of pathological features that lie hidden inside the past light cone, including a radially contracting phase at decoupling and, if followed to its logical extreme, a naked singularity at the radially inhomogeneous big bang.
Modeling inhomogeneous DNA replication kinetics.
Directory of Open Access Journals (Sweden)
Michel G Gauthier
Full Text Available In eukaryotic organisms, DNA replication is initiated at a series of chromosomal locations called origins, where replication forks are assembled proceeding bidirectionally to replicate the genome. The distribution and firing rate of these origins, in conjunction with the velocity at which forks progress, dictate the program of the replication process. Previous attempts at modeling DNA replication in eukaryotes have focused on cases where the firing rate and the velocity of replication forks are homogeneous, or uniform, across the genome. However, it is now known that there are large variations in origin activity along the genome and variations in fork velocities can also take place. Here, we generalize previous approaches to modeling replication, to allow for arbitrary spatial variation of initiation rates and fork velocities. We derive rate equations for left- and right-moving forks and for replication probability over time that can be solved numerically to obtain the mean-field replication program. This method accurately reproduces the results of DNA replication simulation. We also successfully adapted our approach to the inverse problem of fitting measurements of DNA replication performed on single DNA molecules. Since such measurements are performed on specified portion of the genome, the examined DNA molecules may be replicated by forks that originate either within the studied molecule or outside of it. This problem was solved by using an effective flux of incoming replication forks at the model boundaries to represent the origin activity outside the studied region. Using this approach, we show that reliable inferences can be made about the replication of specific portions of the genome even if the amount of data that can be obtained from single-molecule experiments is generally limited.
Effective permittivity of finite inhomogeneous objects
Raghunathan, S.B.; Budko, N.V.
2010-01-01
A generalization of the S-parameter retrieval method for finite three-dimensional inhomogeneous objects under arbitrary illumination and observation conditions is presented. The effective permittivity of such objects may be rigorously defined as a solution of a nonlinear inverse scattering problem.
On non-singular inhomogeneous cosmological models
Fernández-Jambrina, L
2009-01-01
In this talk we would like to review recent results on non-singular cosmological models. It has been recently shown that among stiff perfect fluid inhomogeneous spacetimes the absence of singularities is more common than it was expected in the literature. We would like to generalize these results and apply them to other matter sources.
Imaging of material inhomogeneities with flexural waves
Hörchens, L.
2010-01-01
The detection of inhomogeneities in plates or plate-like structures constitutes a major problem in the field of non-destructive testing. For a few decades, classical techniques based on X-ray radiography have - as far as possible - been complemented and replaced by the usage of vibrations or acousti
Multifractal Analysis of Inhomogeneous Bernoulli Products
Batakis, Athanasios; Testud, Benoît
2011-03-01
We are interested to the multifractal analysis of inhomogeneous Bernoulli products which are also known as coin tossing measures. We give conditions ensuring the validity of the multifractal formalism for such measures. On another hand, we show that these measures can have a dense set of phase transitions.
Waves and vibrations in inhomogeneous structures
DEFF Research Database (Denmark)
Jensen, Jakob Søndergaard
Denne afhandling omhandler bølger og vibrationer i inhomogene strukturer med speciel fokus på undersøgelse af båndgabsfænomenet og optimering af båndgabsstrukturer. Afhandlingen består af 21 artikler, hvoraf 17 er publiceret i internationale tidsskrifter og 4 er publiceret i konferenceproceedings...
Lie Algebra of Noncommutative Inhomogeneous Hopf Algebra
Lagraa, M
1997-01-01
We construct the vector space dual to the space of right-invariant differential forms construct from a first order differential calculus on inhomogeneous quantum group. We show that this vector space is equipped with a structure of a Hopf algebra which closes on a noncommutative Lie algebra satisfying a Jacobi identity.
Inhomogeneous generalization of some Bianchi models
Carmeli, M.; Charach, Ch.
1980-02-01
Vacuum Bianchi models which can be transformed to the Einstein-Rosen metric are considered. The models are used in order to construct new inhomogeneous universes, which are generalizations of Bianchi cosmologies of types III, V and VIh. Recent generalizations of these Bianchi models, considered by Wainwright et al., are also discussed.
Metric inhomogeneous Diophantine approximation in positive characteristic
DEFF Research Database (Denmark)
Kristensen, S.
We obtain asymptotic formulae for the number of solutions to systems of inhomogeneous linear Diophantine inequalities over the field of formal Laurent series with coefficients from a finite fields, which are valid for almost every such system. Here 'almost every' is with respect to Haar measure...
Field quantization in inhomogeneous absorptive dielectrics
Suttorp, L.G.; Wubs, Martijn
2004-01-01
The quantization of the electromagnetic field in a three-dimensional inhomogeneous dielectric medium with losses is carried out in the framework of a damped-polariton model with an arbitrary spatial dependence of its parameters. The equations of motion for the canonical variables are solved explicit
Magnetic properties in the inhomogeneous chiral phase
Yoshiike, Ryo; Tatsumi, Toshitaka
2016-01-01
We investigate the magnetic properties of quark matter in the inhomogeneous chiral phase, where both scalar and pseudoscalar condensates spatially modulate. The energy spectrum of the lowest Landau level becomes asymmetric about zero in the external magnetic field, and gives rise to the remarkably magnetic properties: quark matter has a spontaneous magnetization, while the magnetic susceptibility does not diverge on the critical point.
Wideband Flat Radomes Using Inhomogeneous Planar Layers
Directory of Open Access Journals (Sweden)
Mohammad Khalaj-Amirhosseini
2008-01-01
Full Text Available Inhomogeneous planar layers (IPLs are optimally designed as flat radomes in a desired frequency range. First, the electric permittivity function of the IPL is expanded in a truncated Fourier series. Then, the optimum values of the coefficients of the series are obtained through an optimization approach. The performance of the proposed structure is verified using some examples.
No hair theorem for inhomogeneous cosmologies
Energy Technology Data Exchange (ETDEWEB)
Jensen, L.G.; Stein-Schabes, J.A.
1986-03-01
We show that under very general conditions any inhomogeneous cosmological model with a positive cosmological constant, that can be described in a synchronous reference system will tend asymptotically in time towards the de Sitter solution. This is shown to be relevant in the context of inflationary models as it makes inflation very weakly dependent on initial conditions. 8 refs.
Wave propagation in axially moving periodic strings
Sorokin, Vladislav S.; Thomsen, Jon Juel
2017-04-01
The paper deals with analytically studying transverse waves propagation in an axially moving string with periodically modulated cross section. The structure effectively models various relevant technological systems, e.g. belts, thread lines, band saws, etc., and, in particular, roller chain drives for diesel engines by capturing both their spatial periodicity and axial motion. The Method of Varying Amplitudes is employed in the analysis. It is shown that the compound wave traveling in the axially moving periodic string comprises many components with different frequencies and wavenumbers. This is in contrast to non-moving periodic structures, for which all components of the corresponding compound wave feature the same frequency. Due to this "multi-frequency" character of the wave motion, the conventional notion of frequency band-gaps appears to be not applicable for the moving periodic strings. Thus, for such structures, by frequency band-gaps it is proposed to understand frequency ranges in which the primary component of the compound wave attenuates. Such frequency band-gaps can be present for a moving periodic string, but only if its axial velocity is lower than the transverse wave speed, and, the higher the axial velocity, the narrower the frequency band-gaps. The revealed effects could be of potential importance for applications, e.g. they indicate that due to spatial inhomogeneity, oscillations of axially moving periodic chains always involve a multitude of frequencies.
The Amplification in FEL with Inhomogeneous Magnetic Field
Oganesyan, K B
2016-01-01
The gain in a plane wiggler with inhomogeneous magnetic field is calculated.. It is shown, that the account of inhomogenity of the magnetic field leads to appearance of additional peaks in the amplification
Parametrization of turbulent fluxes over inhomogeneous landscapes
Panin, G. N.; Bernhofer, Ch.
2008-12-01
Reasons for the nonclosure of the heat balance in the atmospheric boundary layers over natural land surfaces are analyzed. Results of measuring the heat-balance components over different land surfaces are used. The Cabauw (Netherlands) data (obtained throughout 1996 over a grass surface with intermittent shrubs and single trees) and the data from the Anchor station in Germany (measured over coniferous forest in 2000-2001) are analyzed. In all, the analysis involves about fifty thousand independent values of the heat-balance components measured in the experiments, which should be indicative of the reliability of the results obtained in the paper. The data have shown that the heat balance is not closed and the imbalance is 50-250 W/m2. The sum of the latent and sensible heat fluxes λ E + H = STF is found to be systematically smaller than the difference between the net radiation and the heat flux into the ground R n - G. It is shown that the main cause of a systematic heat imbalance in the atmospheric boundary layers over inhomogeneous land surfaces is that the methods of surface-flux measurement and estimation are based on the theory that requires the hypothesis of stationarity and horizontal homogeneity. Direct data analysis has shown that the heat imbalance increases with landscape inhomogeneity. In the paper, a parametrization of the heat imbalance is carried out and the coefficient k f ( z {0/ ef }/ L ef ) is introduced as a measure of inhomogeneity. For this, data from the experiments FIFE, KUREX, TARTEX, SADE, etc., are also used. Empirical formulas are presented to refine the results of direct measurements and calculations of surface fluxes over natural (inhomogeneous) land surfaces from profile and standard (using bulk parametrizations) data. These formulas can also be used to determine surface fluxes over inhomogeneous underlying land surfaces in order to take into account so-called subgrid-scale effects in constructing prediction models.
Vortex structure in a long Josephson junction with two inhomogeneities
Energy Technology Data Exchange (ETDEWEB)
Andreeva, O.Yu. [Tumen Thermal Networks OAO ' TRGK' , Tobolsk 626150 (Russian Federation); Boyadjiev, T.L. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Shukrinov, Yu.M. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation)], E-mail: shukrinv@theor.jinr.ru
2007-09-01
We study the vortex structure in the long Josephson junctions with one and two rectangular inhomogeneities in the barrier layer. In case of one inhomogeneity we demonstrate the existence of the asymmetric fluxon states. The disappearance of the mixed fluxon-antifluxon states is shown when the position of the inhomogeneity shifted to the end of the junction. In case of two inhomogeneities the change of the amplitude of Josephson current through the inhomogeneity in the end of the junction makes strong effect on the stability of the fluxon states and smoothes the maximums on the dependence 'critical current-magnetic field'.
Vortex structure in a long Josephson junction with two inhomogeneities
Andreeva, O. Yu.; Boyadjiev, T. L.; Shukrinov, Yu. M.
2007-09-01
We study the vortex structure in the long Josephson junctions with one and two rectangular inhomogeneities in the barrier layer. In case of one inhomogeneity we demonstrate the existence of the asymmetric fluxon states. The disappearance of the mixed fluxon-antifluxon states is shown when the position of the inhomogeneity shifted to the end of the junction. In case of two inhomogeneities the change of the amplitude of Josephson current through the inhomogeneity in the end of the junction makes strong effect on the stability of the fluxon states and smoothes the maximums on the dependence “critical current-magnetic field”.
How Forest Inhomogeneities Affect the Edge Flow
DEFF Research Database (Denmark)
Boudreault, Louis-Étienne; Dupont, Sylvain; Bechmann, Andreas
2016-01-01
is investigated using large-eddy simulation. The three-dimensional forest structure is prescribed in the model using high resolution helicopter-based lidar scans. After evaluating the simulation against wind measurements upwind and downwind of the forest leading edge, the flow dynamics are compared between......Most of our knowledge on forest-edge flows comes from numerical and wind-tunnel experiments where canopies are horizontally homogeneous. To investigate the impact of tree-scale heterogeneities (>1 m) on the edge-flow dynamics, the flow in an inhomogeneous forest edge on Falster island in Denmark...... the scanned forest and an equivalent homogeneous forest. The simulations reveal that forest inhomogeneities facilitate flow penetration into the canopy from the edge, inducing important dispersive fluxes in the edge region as a consequence of the flow spatial variability. Further downstream from the edge...
Localized standing waves in inhomogeneous Schrodinger equations
Marangell, R; Susanto, H
2010-01-01
A nonlinear Schrodinger equation arising from light propagation down an inhomogeneous medium is considered. The inhomogeneity is reflected through a non-uniform coefficient of the non-linear term in the equation. In particular, a combination of self-focusing and self-defocusing nonlinearity, with the self-defocusing region localized in a finite interval, is investigated. Using numerical computations, the extension of linear eigenmodes of the corresponding linearized system into nonlinear states is established, particularly nonlinear continuations of the fundamental state and the first excited state. The (in)stability of the states is also numerically calculated, from which it is obtained that symmetric nonlinear solutions become unstable beyond a critical threshold norm. Instability of the symmetric states is then investigated analytically through the application of a topological argument. Determination of instability of positive symmetric states is reduced to simple geometric properties of the composite phas...
Automatically generated code for relativistic inhomogeneous cosmologies
Bentivegna, Eloisa
2017-02-01
The applications of numerical relativity to cosmology are on the rise, contributing insight into such cosmological problems as structure formation, primordial phase transitions, gravitational-wave generation, and inflation. In this paper, I present the infrastructure for the computation of inhomogeneous dust cosmologies which was used recently to measure the effect of nonlinear inhomogeneity on the cosmic expansion rate. I illustrate the code's architecture, provide evidence for its correctness in a number of familiar cosmological settings, and evaluate its parallel performance for grids of up to several billion points. The code, which is available as free software, is based on the Einstein Toolkit infrastructure, and in particular leverages the automated code generation capabilities provided by its component Kranc.
Inhomogeneous Fragmentation of the Rolling Tachyon
Felder, G N; Felder, Gary N.; Kofman, Lev
2004-01-01
Dirac-Born-Infeld type effective actions reproduce many aspects of string theory classical tachyon dynamics of unstable Dp-branes. The inhomogeneous tachyon field rolling from the top of its potential forms topological defects of lower codimensions. In between them, as we show, the tachyon energy density fragments into a p-dimensional web-like high density network evolving with time. We present an analytic asymptotic series solution of the non-linear equations for the inhomogeneous tachyon and its stress energy. The generic solution for a tachyon field with a runaway potential in arbitrary dimensions is described by the free streaming of noninteracting massive particles whose initial velocities are defined by the gradients of the initial tachyon profile. Thus, relativistic particle mechanics is a dual picture of the tachyon field effective action. Implications of this picture for inflationary models with a decaying tachyon field are discussed.
Primordial inhomogeneities from massive defects during inflation
Firouzjahi, Hassan; Karami, Asieh; Rostami, Tahereh
2016-10-01
We consider the imprints of local massive defects, such as a black hole or a massive monopole, during inflation. The massive defect breaks the background homogeneity. We consider the limit that the physical Schwarzschild radius of the defect is much smaller than the inflationary Hubble radius so a perturbative analysis is allowed. The inhomogeneities induced in scalar and gravitational wave power spectrum are calculated. We obtain the amplitudes of dipole, quadrupole and octupole anisotropies in curvature perturbation power spectrum and identify the relative configuration of the defect to CMB sphere in which large observable dipole asymmetry can be generated. We observe a curious reflection symmetry in which the configuration where the defect is inside the CMB comoving sphere has the same inhomogeneous variance as its mirror configuration where the defect is outside the CMB sphere.
Primordial inhomogeneities from massive defects during inflation
Firouzjahi, Hassan; Rostami, Tahereh
2016-01-01
We consider the imprints of local massive defects, such as a black hole or a massive monopole, during inflation. The massive defect breaks the background homogeneity. We consider the limit that the physical Schwarzschild radius of the defect is much smaller than the inflationary Hubble radius so a perturbative analysis is allowed. The inhomogeneities induced in scalar and gravitational wave power spectrum are calculated. We obtain the amplitudes of dipole, quadrupole and octupole anisotropies in curvature perturbation power spectrum and identify the relative configuration of the defect to CMB sphere in which large observable dipole asymmetry can be generated. We observe a curious reflection symmetry in which the configuration where the defect is inside the CMB comoving sphere has the same inhomogeneous variance as its mirror configuration where the defect is outside the CMB sphere.
Strong Primordial Inhomogeneities and Galaxy Formation
Khlopov, M Ya; Sakharov, Alexander S
2002-01-01
The new element of theory of galaxy formation, strong primordial inhomogeneities, is shown to be a reflection of unstable large scale structures of topological defects, created in second order phase transitions in the inflationary Universe. In addition to {\\it archioles-like} large scale correlation of the primordial inhomogeneity of energy density of coherent scalar field oscillations, the same mechanism, based on the second order phase transitions on the inflational stage and the domain wall formation upon the end of inflation, leads to the formation of massive black hole clusters that can serve as nuclei for the future galaxies. The number of black holes with $M \\sim 100M_{\\odot}$ and above is comparable with the number of galaxies within the modern cosmological horizon. The primordial fractal structure of galaxies can find natural grounds in the framework of model we developed . The proposed approach offers the physical basis for new scenarios of galaxy formation in the Big Bang Universe.
Inhomogeneities from quantum collapse scheme without inflation
Directory of Open Access Journals (Sweden)
Gabriel R. Bengochea
2015-04-01
Full Text Available In this work, we consider the problem of the emergence of seeds of cosmic structure in the framework of the non-inflationary model proposed by Hollands and Wald. In particular, we consider a modification to that proposal designed to account for breaking the symmetries of the initial quantum state, leading to the generation of the primordial inhomogeneities. This new ingredient is described in terms of a spontaneous reduction of the wave function. We investigate under which conditions one can recover an essentially scale free spectrum of primordial inhomogeneities, and which are the dominant deviations that arise in the model as a consequence of the introduction of the collapse of the quantum state into that scenario.
Theory of Thomson scattering in inhomogeneous media
Kozlowski, P M; Gericke, D O; Regan, S P; Gregori, G
2016-01-01
Thomson scattering of laser light is one of the most fundamental diagnostics of plasma density, temperature and magnetic fields. It relies on the assumption that the properties in the probed volume are homogeneous and constant during the probing time. On the other hand, laboratory plasmas are seldom uniform and homogeneous on the temporal and spatial dimensions over which data is collected. This is partic- ularly true for laser-produced high-energy-density matter, which often exhibits steep gradients in temperature, density and pressure, on a scale determined by the laser focus. Here, we discuss the modification of the cross section for Thomson scattering in fully-ionized media exhibiting steep spatial inhomogeneities and/or fast temporal fluctuations. We show that the predicted Thomson scattering spectra are greatly altered compared to the uniform case, and may even lead to violations of detailed balance. Therefore, careful interpretation of the spectra is necessary for spatially or temporally inhomogeneous ...
Theory of Thomson scattering in inhomogeneous media
Kozlowski, P. M.; Crowley, B. J. B.; Gericke, D. O.; Regan, S. P.; Gregori, G.
2016-04-01
Thomson scattering of laser light is one of the most fundamental diagnostics of plasma density, temperature and magnetic fields. It relies on the assumption that the properties in the probed volume are homogeneous and constant during the probing time. On the other hand, laboratory plasmas are seldom uniform and homogeneous on the temporal and spatial dimensions over which data is collected. This is particularly true for laser-produced high-energy-density matter, which often exhibits steep gradients in temperature, density and pressure, on a scale determined by the laser focus. Here, we discuss the modification of the cross section for Thomson scattering in fully-ionized media exhibiting steep spatial inhomogeneities and/or fast temporal fluctuations. We show that the predicted Thomson scattering spectra are greatly altered compared to the uniform case, and may lead to violations of detailed balance. Therefore, careful interpretation of the spectra is necessary for spatially or temporally inhomogeneous systems.
Inhomogeneities from quantum collapse scheme without inflation
Energy Technology Data Exchange (ETDEWEB)
Bengochea, Gabriel R., E-mail: gabriel@iafe.uba.ar [Instituto de Astronomía y Física del Espacio (IAFE), UBA-CONICET, CC 67, Suc. 28, 1428 Buenos Aires (Argentina); Cañate, Pedro, E-mail: pedro.canate@nucleares.unam.mx [Instituto de Ciencias Nucleares, UNAM, México D.F. 04510, México (Mexico); Sudarsky, Daniel, E-mail: sudarsky@nucleares.unam.mx [Instituto de Ciencias Nucleares, UNAM, México D.F. 04510, México (Mexico)
2015-04-09
In this work, we consider the problem of the emergence of seeds of cosmic structure in the framework of the non-inflationary model proposed by Hollands and Wald. In particular, we consider a modification to that proposal designed to account for breaking the symmetries of the initial quantum state, leading to the generation of the primordial inhomogeneities. This new ingredient is described in terms of a spontaneous reduction of the wave function. We investigate under which conditions one can recover an essentially scale free spectrum of primordial inhomogeneities, and which are the dominant deviations that arise in the model as a consequence of the introduction of the collapse of the quantum state into that scenario.
Equilibrium figures of inhomogeneous synchronous binary asteroids
Descamps, P.
2010-06-01
The present paper deals with the application of the classical theory of equilibrium figures of two rotating liquid masses to the case where bodies exhibit a radially stratified internal density distribution so that they can be considered as inhomogeneous bodies. The derived ellipsoidal shape solutions are applied to five real systems of equal-sized synchronous asteroids. Furthermore, internal inhomogeneity puts strong constraints on the surface grain density. A satisfactory model fit is achieved with internal densities of asteroids steadily increasing outwards. In particular, from such an approach we derived grain densities of the considered systems in agreement with their mineralogical composition inferred from reflectance spectroscopy. According to this new approach, 4492 Debussy, presently of unknown spectral type, is predicted to appear as a C-type object with a grain density on the order of 2 g/cm 3.
Improving Thermoelectric Properties of Nanowires Through Inhomogeneity
González, J. Eduardo; Sánchez, Vicenta; Wang, Chumin
2017-05-01
Inhomogeneity in nanowires can be present in the cross-section and/or by breaking the translational symmetry along the nanowire. In particular, the quasiperiodicity introduces an unusual class of electronic and phononic transport with a singular continuous eigenvalue spectrum and critically localized wave functions. In this work, the thermoelectricity in periodic and quasiperiodically segmented nanobelts and nanowires is addressed within the Boltzmann formalism by using a real-space renormalization plus convolution method developed for the Kubo-Greenwood formula, in which tight-binding and Born models are, respectively, used for the calculation of electric and lattice thermal conductivities. For periodic nanowires, we observe a maximum of the thermoelectric figure-of-merit ( ZT) in the temperature space, as occurred in the carrier concentration space. This maximum ZT can be improved by introducing into nanowires periodically arranged segments and an inhomogeneous cross-section. Finally, the quasiperiodically segmented nanowires reveal an even larger ZT in comparison with the periodic ones.
Geometrical approach to light in inhomogeneous media
Piwnicki, P
2002-01-01
Electromagnetism in an inhomogeneous dielectric medium at rest is described using the methods of differential geometry. In contrast to a general relativistic approach the electromagnetic fields are discussed in three-dimensional space only. The introduction of an appropriately chosen three-dimensional metric leads to a significant simplification of the description of light propagation in an inhomogeneous medium: light rays become geodesics of the metric and the field vectors are parallel transported along the rays. The new metric is connected to the usual flat space metric diag[1,1,1] via a conformal transformation leading to new, effective values of the medium parameters leading to an effective constant value of the index of refraction n=1. The corresponding index of refraction is thus constant and so is the effective velocity of light. Space becomes effectively empty but curved. All deviations from straight line propagation are now due to curvature. The approach is finally used for a discussion of the Riema...
Observational Aspects of an Inhomogeneous Cosmology
Saulder, Christoph; Zeilinger, Werner W
2012-01-01
One of the biggest mysteries in cosmology is Dark Energy, which is required to explain the accelerated expansion of the universe within the standard model. But maybe one can explain the observations without introducing new physics, by simply taking one step back and re-examining one of the basic concepts of cosmology, homogeneity. In standard cosmology, it is assumed that the universe is homogeneous, but this is not true at small scales (<200 Mpc). Since general relativity, which is the basis of modern cosmology, is a non-linear theory, one can expect some backreactions in the case of an inhomogeneous matter distribution. Estimates of the magnitude of these backreactions (feedback) range from insignificant to being perfectly able to explain the accelerated expansion of the universe. In the end, the only way to be sure is to test predictions of inhomogeneous cosmological theories, such as timescape cosmology, against observational data. If these theories provide a valid description of the universe, one expe...
Inference of magnetic fields in inhomogeneous prominences
Milic, Ivan; Atanackovic, Olga
2016-01-01
Most of the quantitative information about the magnetic field vector in solar prominences comes from the analysis of the Hanle effect acting on lines formed by scattering. As these lines can be of non-negligible optical thickness, it is of interest to study the line formation process further. We investigate the multidimensional effects on the interpretation of spectropolarimetric observations, particularly on the inference of the magnetic field vector. We do this by analyzing the differences between multidimensional models, which involve fully self-consistent radiative transfer computations in the presence of spatial inhomogeneities and velocity fields, and those which rely on simple one-dimensional geometry. We study the formation of a prototype line in ad hoc inhomogeneous, isothermal 2D prominence models. We solve the NLTE polarized line formation problem in the presence of a large-scale oriented magnetic field. The resulting polarized line profiles are then interpreted (i.e. inverted) assuming a simple 1D...
Electromagnetic field representation in inhomogeneous anisotropic media
Mohsen, A.
1973-01-01
Some of the basic developments in the theory of electromagnetic field representation in terms of Hertz vectors are reviewed. A solution for the field in an inhomogeneous anisotropic medium is given in terms of the two Hertz vectors. Conditions for presentation of the field in terms of uncoupled transverse electric and transverse magnetic modes, in a general orthogonal coordinate system, are derived when the permeability and permittivity tensors have only diagonal components. These conditions are compared with some known special cases.
Inhomogeneous Monte Carlo simulations of dermoscopic spectroscopy
Gareau, Daniel S.; Li, Ting; Jacques, Steven; Krueger, James
2012-03-01
Clinical skin-lesion diagnosis uses dermoscopy: 10X epiluminescence microscopy. Skin appearance ranges from black to white with shades of blue, red, gray and orange. Color is an important diagnostic criteria for diseases including melanoma. Melanin and blood content and distribution impact the diffuse spectral remittance (300-1000nm). Skin layers: immersion medium, stratum corneum, spinous epidermis, basal epidermis and dermis as well as laterally asymmetric features (eg. melanocytic invasion) were modeled in an inhomogeneous Monte Carlo model.
Spatially discontinuous ionization phenomenon in inhomogeneous soil
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
By using X-ray film imaging technology,a phenomenon of discontinuous ionization was observed in the inhomogeneous soil around the grounding electrode on which a surge voltage was applied.A simplified two-phase solid-gas model was built to study the electric field distribution in the soil to explain the discontinuous ionization phenomenon.Analysis showed the differences of the dielectric properties,the shapes and sizes of soil particles can cause discontinuous ionization in the soil.
Programming of inhomogeneous resonant guided wave networks.
Feigenbaum, Eyal; Burgos, Stanley P; Atwater, Harry A
2010-12-06
Photonic functions are programmed by designing the interference of local waves in inhomogeneous resonant guided wave networks composed of power-splitting elements arranged at the nodes of a nonuniform waveguide network. Using a compact, yet comprehensive, scattering matrix representation of the network, the desired photonic function is designed by fitting structural parameters according to an optimization procedure. This design scheme is demonstrated for plasmonic dichroic and trichroic routers in the infrared frequency range.
Production of heavy elements in inhomogeneous cosmologies
Rauscher, Thomas; Applegate, James H.; Cowan, John J.; Thielemann, Friedrich-Karl; Wiescher, Michael
1994-07-01
Baryon density inhomogeneities during big bang nucleosynthesis can result from a variety of possible causes (e.g., quantum chromodynamic and electroweak phase transitions; cosmic strings). We present here the consequences of such inhomogeneities with special emphasis on the production of heavy elements in a parameter study, varying the global baryon-to-photon ratio eta (which is related to the baryon density and the Hubble constant via eta10 = 64.94 Omegab(H0/50)2 and the length scale of the density inhomogeneities. The production of heavy elements beyond Fe can only occur in neutron-rich environments; thus, we limit our study to neutron-rich zones, originating from neutron diffusion into low-density regions. In this first calculation including elements heavier than Si, we prove an earlier hypothesis that under such conditions r-process elements can be produced, strongly enhanced by the process of fission cycling. Primordial r-process abundances are, however, very sensitive to the choice of eta. Significant amounts, comparable to or larger than the (permitted) floor of heavy-element abundances found in low-metallicity stars at the onset of galactic evolution, can only be obtained for values in excess of eta10 = 133 (i.e., Omegab(h50)2 = 2.0; e.g., Omegab = 1, H0 = 71, or Omegab = 0.5, H0 = 100) and large length scales of inhomogeneities, which minimize the back-diffusion of neutrons into proton-rich regions. Recent investigations analyzing the primordial abundances of light elements seem to set tighter limits, eta10 less than 26 to 39 (Omega b)(h50)2 less than 0.4 to 0.6, from He-4 and apparently considerably lower values based on Li, Be, and B. Under such conditions the predicted abundances of heavy elements are a factor of 105 or more below presently observable limits.
Inversion identities for inhomogeneous face models
Frahm, Holger; Karaiskos, Nikos
2014-10-01
We derive exact inversion identities satisfied by the transfer matrix of inhomogeneous interaction-round-a-face (IRF) models with arbitrary boundary conditions using the underlying integrable structure and crossing properties of the local Boltzmann weights. For the critical restricted solid-on-solid (RSOS) models these identities together with some information on the analytical properties of the transfer matrix determine the spectrum completely and allow to derive the Bethe equations for both periodic and general open boundary conditions.
Inversion identities for inhomogeneous face models
Directory of Open Access Journals (Sweden)
Holger Frahm
2014-10-01
Full Text Available We derive exact inversion identities satisfied by the transfer matrix of inhomogeneous interaction-round-a-face (IRF models with arbitrary boundary conditions using the underlying integrable structure and crossing properties of the local Boltzmann weights. For the critical restricted solid-on-solid (RSOS models these identities together with some information on the analytical properties of the transfer matrix determine the spectrum completely and allow to derive the Bethe equations for both periodic and general open boundary conditions.
Inversion identities for inhomogeneous face models
Energy Technology Data Exchange (ETDEWEB)
Frahm, Holger; Karaiskos, Nikos
2014-10-15
We derive exact inversion identities satisfied by the transfer matrix of inhomogeneous interaction-round-a-face (IRF) models with arbitrary boundary conditions using the underlying integrable structure and crossing properties of the local Boltzmann weights. For the critical restricted solid-on-solid (RSOS) models these identities together with some information on the analytical properties of the transfer matrix determine the spectrum completely and allow to derive the Bethe equations for both periodic and general open boundary conditions.
Metric inhomogeneous Diophantine approximation in positive characteristic
DEFF Research Database (Denmark)
Kristensen, S.
We obtain asymptotic formulae for the number of solutions to systems of inhomogeneous linear Diophantine inequalities over the field of formal Laurent series with coefficients from a finite fields, which are valid for almost every such system. Here 'almost every' is with respect to Haar measure o......-infinity laws for Hausdorff measure in the spirit of Jarník's Theorem. The latter result depends on extending a recently developed slicing technique of Beresnevich and Velani to the present setup....
Redshift-distance relation in inhomogeneous cosmology
Scharf, Günter
2015-01-01
We continue to study a cosmological model with large-scale inhomogeneity. Working in the cosmic rest frame we determine null geodesics, redshift and area and luminosity distance. Combining the result with Hubble's law enables us to calculate the distance of the local group of galaxies from the origin where the Big Bang gas taken place. We obtain a surprisingly small value of about 2 million light years.
Synchronized Firing in Coupled Inhomogeneous Excitable Neurons
Institute of Scientific and Technical Information of China (English)
ZHENG Zhi-Gang; WANG Fu-Zhong
2002-01-01
We study the firing synchronization behavior of the inhomogeneous excitable media. Phase synchronizationof neuron firings is observed with increasing the coupling, while the phases of neurons are different (out-of-phase synchronization). We found the synchronization of bursts can be greatly enhanced by applying an external forcing (in-phasesynchronization). The external forcing can be either a periodic or just homogeneous thermal noise. The mechanismresponsible for this enhancement is discussed.PACS numbers: 05.45.-a, 87.10.+e
Metric inhomogeneous Diophantine approximation in positive characteristic
DEFF Research Database (Denmark)
Kristensen, Simon
2011-01-01
We obtain asymptotic formulae for the number of solutions to systems of inhomogeneous linear Diophantine inequalities over the field of formal Laurent series with coefficients from a finite fields, which are valid for almost every such system. Here `almost every' is with respect to Haar measure o......-infinity laws for Hausdorff measure in the spirit of Jarník's Theorem. The latter result depends on extending a recently developed slicing technique of Beresnevich and Velani to the present setup....
Cosmic Inhomogeneities and the Average Cosmological Dynamics
Paranjape, Aseem; Singh, T. P.
2008-01-01
If general relativity (GR) describes the expansion of the Universe, the observed cosmic acceleration implies the existence of a `dark energy'. However, while the Universe is on average homogeneous on large scales, it is inhomogeneous on smaller scales. While GR governs the dynamics of the \\emph{in}homogeneous Universe, the averaged \\emph{homogeneous} Universe obeys modified Einstein equations. Can such modifications alone explain the acceleration? For a simple generic model with realistic ini...
On inhomogeneous straining in compressed sylvinite
Barannikova, S. A.; Nadezhkin, M. V.; Zuev, L. B.; Zhigalkin, V. M.
2010-06-01
Spatiotemporal distributions of local components of the distortion tensor of quasi-plastic materials—saliferous rocks (sylvinite)—have been studied under active compressive straining conditions using double-exposure speckle photography techniques. The strain localization patterns are presented and the features of macroscopic strain inhomogeneity are considered for inelastic behavior of the material. Results obtained for the slow wave processes in deformed saliferous rocks are compared to analogous data available for ionic crystals.
Temperature fluctuations in an inhomogeneous diffusive fluid
Haba, Z
2014-01-01
We discuss metric perturbations of the relativistic diffusion equation around the homogeneous Juttner equilibrium of massless particles in a homogeneous expanding universe. The metric perturbation describes matter distribution and the gravitational wave background in an inhomogeneous universe. We show that the lowest order perturbation can be treated as a variation of temperature. We derive a formula expressing temperature fluctuations in terms of the diffusion and tensor power spectrum. We discuss the multipole expansion of the fluctuations in the presence of diffusion.
Diamagnetic susceptibility of a magneto-donor in Inhomogeneous Quantum Dots
Mmadi, A.; Rahmani, K.; Zorkani, I.; Jorio, A.
2013-05-01
The binding energy and diamagnetic susceptibility χdia are investigated for a shallow donor confined to move in a spherical Inhomogeneous Quantum Dots "IQD" in the presence of a magnetic field. The calculation was performed with the use of a variational method in the effective mass approximation. We describe the effect of the quantum confinement by an infinite deep potential. The results for a spherical Inhomogeneous Quantum Dots made out of [Ga1-xAlxAs (Core)/GaAs (Well)/Ga1-xAlxAs (Shell)] show that the diamagnetic susceptibility and the binding energy increase with the magnetic field. There are more pronounced for large spherical layer. The binding energy and the diamagnetic susceptibility depend strongly on the donor position. We remark that the diamagnetic susceptibility presents a minimum corresponding to a critical value of the ratio of the inner radius to the outer radius , this critical value is important for nanofabrication techniques.
Loop quantum cosmology: Anisotropies and inhomogeneities
Wilson-Ewing, Edward
In this dissertation we extend the improved dynamics of loop quantum cosmology from the homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker space-times to cosmological models which allow anisotropies and inhomogeneities. Specifically, we consider the cases of the homogeneous but anisotropic Bianchi type I, II and IX models with a massless scalar field as well as the vacuum, inhomogeneous, linearly polarized Gowdy T3 model. For each case, we derive the Hamiltonian constraint operator and study its properties. In particular, we show how in all of these models the classical big bang and big crunch singularities are resolved due to quantum gravity effects. Since the Bianchi models play a key role in the Belinskii, Khalatnikov and Lifshitz conjecture regarding the nature of generic space-like singularities in general relativity, the quantum dynamics of the Bianchi cosmologies are likely to provide considerable intuition about the fate of such singularities in quantum gravity. In addition, the results obtained here provide an important step toward the full loop quantization of cosmological space-times that allow generic inhomogeneities; this would provide falsifiable predictions that could be compared to observations.
Viscosity of confined inhomogeneous nonequilibrium fluids.
Zhang, Junfang; Todd, B D; Travis, Karl P
2004-12-01
We use the nonlocal linear hydrodynamic constitutive model, proposed by Evans and Morriss [Statistical Mechanics of Nonequilibrium Liquids (Academic, London, 1990)], for computing an effective spatially dependent shear viscosity of inhomogeneous nonequilibrium fluids. The model is applied to a simple atomic fluid undergoing planar Poiseuille flow in a confined channel of several atomic diameters width. We compare the spatially dependent viscosity with a local generalization of Newton's law of viscosity and the Navier-Stokes viscosity, both of which are known to suffer extreme inaccuracies for highly inhomogeneous systems. The nonlocal constitutive model calculates effective position dependent viscosities that are free from the notorious singularities experienced by applying the commonly used local constitutive model. It is simple, general, and has widespread applicability in nanofluidics where experimental measurement of position dependent transport coefficients is currently inaccessible. In principle the method can be used to predict approximate flow profiles of any arbitrary inhomogeneous system. We demonstrate this by predicting the flow profile for a simple fluid undergoing planar Couette flow in a confined channel of several atomic diameters width.
A method for quantifying visual field inhomogeneities.
Anderson, Jennifer E; Leslie Cameron, E; Levine, Michael W
2014-12-01
It is well known that performance is not homogeneous across the visual field, even at isoeccentric locations. Several inhomogeneities in particular have been identified - a Horizontal-Vertical Anisotropy (HVA - better performance in the horizontal than in the vertical direction); a Vertical Asymmetry (VA - better performance in the lower than the upper visual field); and a Vertical Meridian Asymmetry (VMA - better performance below than above the point of fixation on the vertical meridian). Performance has also been reported to be particularly poor at the location directly above the point of fixation, i.e., the "North" (N) location and sometimes at the location directly below the point of fixation, i.e., the "South" (S) location. These phenomena are typically characterized by statistics that compare performance across the visual field to a homogeneous (circular) model. Here we propose an alternative method for assessing visual field inhomogeneities, which involves comparing performance to an elliptical model of the visual field. We maintain that this method provides a more robust analysis of visual field inhomogeneities because it does not overestimate the North and South effects.
Structural elucidation of inhomogeneous lignins from bamboo.
Wen, Jia-Long; Sun, Shao-Long; Xue, Bai-Liang; Sun, Run-Cang
2015-01-01
A better understanding of the inhomogeneous molecular structure of lignin from bamboo is a prerequisite for promoting the "biorefinery" technologies of the bamboo feedstock. A mild and successive method for fractionating native lignin from bamboo species was proposed in the present study. The molecular structure and structural inhomogeneity of the isolated lignin polymers were comprehensively investigated by elemental analysis, carbohydrate analysis, state-of-the-art NMR and analytical pyrolysis techniques (quantitative (13)C NMR, (13)C-DEPT 135 NMR, 2D-HSQC NMR, (31)P NMR, and pyrolysis-GC-MS). The results showed that the proposed method is effective for extracting lignin from bamboo. NMR results showed that syringyl (S) was the predominant unit in bamboo lignin over guaiacyl (G) and p-hydroxyphenyl (H) units. In addition, the lignin was associated with p-coumarates and ferulates via ester and ether bonds, respectively. Moreover, various substructures, such as β-O-4, β-β, β-5, β-1, and α,β-diaryl ether linkages, were identified and quantified by NMR techniques. Based on the results obtained, a proposed schematic diagram of structural heterogeneity of the lignin polymers extracted from the bamboo is presented. In short, well-defined inhomogeneous structures of native lignin from bamboo will facilitate further applications of bamboo in current biorefineries.
Rotational inhomogeneities from pre-big bang?
Giovannini, Massimo
2005-01-01
The evolution of the rotational inhomogeneities is investigated in the specific framework of four-dimensional pre-big bang models. While minimal (dilaton-driven) scenarios do not lead to rotational fluctuations, in the case of non-minimal (string-driven) models, fluid sources are present in the pre-big bang phase. The rotational modes of the geometry, coupled to the divergenceless part of the velocity field, can then be amplified depending upon the value of the barotropic index of the perfect fluids. In the light of a possible production of rotational inhomogeneities, solutions describing the coupled evolution of the dilaton field and of the fluid sources are scrutinized in both the string and Einstein frames. In semi-realistic scenarios, where the curvature divergences are regularized by means of a non-local dilaton potential, the rotational inhomogeneities are amplified during the pre-big bang phase but they decay later on. Similar analyses can also be performed when a contraction occurs directly in the str...
Inference of magnetic fields in inhomogeneous prominences
Milić, I.; Faurobert, M.; Atanacković, O.
2017-01-01
Context. Most of the quantitative information about the magnetic field vector in solar prominences comes from the analysis of the Hanle effect acting on lines formed by scattering. As these lines can be of non-negligible optical thickness, it is of interest to study the line formation process further. Aims: We investigate the multidimensional effects on the interpretation of spectropolarimetric observations, particularly on the inference of the magnetic field vector. We do this by analyzing the differences between multidimensional models, which involve fully self-consistent radiative transfer computations in the presence of spatial inhomogeneities and velocity fields, and those which rely on simple one-dimensional geometry. Methods: We study the formation of a prototype line in ad hoc inhomogeneous, isothermal 2D prominence models. We solve the NLTE polarized line formation problem in the presence of a large-scale oriented magnetic field. The resulting polarized line profiles are then interpreted (i.e. inverted) assuming a simple 1D slab model. Results: We find that differences between input and the inferred magnetic field vector are non-negligible. Namely, we almost universally find that the inferred field is weaker and more horizontal than the input field. Conclusions: Spatial inhomogeneities and radiative transfer have a strong effect on scattering line polarization in the optically thick lines. In real-life situations, ignoring these effects could lead to a serious misinterpretation of spectropolarimetric observations of chromospheric objects such as prominences.
Indian Academy of Sciences (India)
Johannes Breur; Sitabhra Sinha
2005-04-01
Formation of feedback loops of excitation waves (reentrant circuit) around non-conducting ventricular scar tissue is a common cause of cardiac arrhythmias, such as ventricular tachycardia, often leading to death. This is typically treated by rapid stimulation from an implantable device (ICD). However, the mechanisms of reentry termination success and, more importantly, failure, are poorly understood. To study such mechanisms, we simulated pacing termination of reentry in a model of cardiac tissue having significant restitution and dispersion properties. Our results show that rapid pacing dynamically generates conduction inhomogeneities in the reentrant circuit, leading to successful pacing termination of tachycardia. The study suggests that more effective pacing algorithms can be designed by taking into account the role of such dynamical inhomogeneities.
Effect of layerwise structural inhomogeneity on stress- corrosion cracking of steel tubes
Perlovich, Yu A.; Krymskaya, O. A.; Isaenkova, M. G.; Morozov, N. S.; Fesenko, V. A.; Ryakhovskikh, I. V.; Esiev, T. S.
2016-04-01
Based on X-ray texture and structure analysis data of the material of main gas pipelines it was shown that the layerwise inhomogeneity of tubes is formed during their manufacturing. The degree of this inhomogeneity affects on the tendency of tubes to stress- corrosion cracking under exploitation. Samples of tubes were cut out from gas pipelines located under various operating conditions. Herewith the study was conducted both for sections with detected stress-corrosion defects and without them. Distributions along tube wall thickness for lattice parameters and half-width of X-ray lines were constructed. Crystallographic texture analysis of external and internal tube layers was also carried out. Obtained data testifies about considerable layerwise inhomogeneity of all samples. Despite the different nature of the texture inhomogeneity of gas pipeline tubes, the more inhomogeneous distribution of texture or structure features causes the increasing of resistance to stress- corrosion. The observed effect can be explained by saturation with interstitial impurities of the surface layer of the hot-rolled sheet and obtained therefrom tube. This results in rising of lattice parameters in the external layer of tube as compared to those in underlying metal. Thus, internal layers have a compressive effect on external layers in the rolling plane that prevents cracks opening at the tube surface. Moreover, the high mutual misorientation of grains within external and internal layers of tube results in the necessity to change the moving crack plane, so that the crack growth can be inhibited when reaching the layer with a modified texture.
Osswald, P. J.; Erhard, S. V.; Rheinfeld, A.; Rieger, B.; Hoster, H. E.; Jossen, A.
2016-10-01
The influence of cell temperature on the current density distribution and accompanying inhomogeneities in state of charge (SOC) during cycling is analyzed in this work. To allow for a detailed insight in the electrochemical behavior of the cell, commercially available 26650 cells were modified to allow for measuring local potentials at four different, nearly equidistant positions along the electrodes. As a follow-up to our previous work investigating local potentials within a cell, we apply this method for studying SOC deviations and their sensitivity to cell temperature. The local potential distribution was studied during constant current discharge operations for various current rates and discharge pulses in order to evoke local inhomogeneities for temperatures ranging from 10 °C to 40 °C. Differences in local potentials were considered for estimating local SOC variations within the electrodes. It could be observed that even low currents such as 0.1C can lead to significant inhomogeneities, whereas a higher cell temperature generally results in more pronounced inhomogeneities. A rapid SOC equilibration can be observed if the variation in the SOC distribution corresponds to a considerable potential difference defined by the open circuit voltage of either the positive or negative electrode. With increasing temperature, accelerated equalization effects can be observed.
Degradation of the Bragg peak due to inhomogeneities.
Urie, M; Goitein, M; Holley, W R; Chen, G T
1986-01-01
The rapid fall-off of dose at the end of range of heavy charged particle beams has the potential in therapeutic applications of sparing critical structures just distal to the target volume. Here we explored the effects of highly inhomogeneous regions on this desirable depth-dose characteristic. The proton depth-dose distribution behind a lucite-air interface parallel to the beam was bimodal, indicating the presence of two groups of protons with different residual ranges, creating a step-like depth-dose distribution at the end of range. The residual ranges became more spread out as the interface was angled at 3 degrees, and still more at 6 degrees, to the direction of the beam. A second experiment showed little significant effect on the distal depth-dose of protons having passed through a mosaic of teflon and lucite. Anatomic studies demonstrated significant effects of complex fine inhomogeneities on the end of range characteristics. Monoenergetic protons passing through the petrous ridges and mastoid air cells in the base of skull showed a dramatic degradation of the distal Bragg peak. In beams with spread out Bragg peaks passing through regions of the base of skull, the distal fall-off from 90 to 20% dose was increased from its nominal 6 to well over 32 mm. Heavy ions showed a corresponding degradation in their ends of range. In the worst case in the base of skull region, a monoenergetic neon beam showed a broadening of the full width at half maximum of the Bragg peak to over 15 mm (compared with 4 mm in a homogeneous unit density medium). A similar effect was found with carbon ions in the abdomen, where the full width at half maximum of the Bragg peak (nominally 5.5 mm) was found to be greater than 25 mm behind gas-soft-tissue interfaces. We address the implications of these data for dose computation with heavy charged particles.
Shock-acceleration of a pair of gas inhomogeneities
Navarro Nunez, Jose Alonso; Reese, Daniel; Oakley, Jason; Rothamer, David; Bonazza, Riccardo
2014-11-01
A shock wave moving through the interstellar medium distorts density inhomogeneities through the deposition of baroclinic vorticity. This process is modeled experimentally in a shock tube for a two-bubble interaction. A planar shock wave in nitrogen traverses two soap-film bubbles filled with argon. The two bubbles share an axis that is orthogonal to the shock wave and are separated from one another by a distance of approximately one bubble diameter. Atomization of the soap-film by the shock wave results in dispersal of droplets that are imaged using Mie scattering with a laser sheet through the bubble axis. Initial condition images of the bubbles in free-fall (no holder) are taken using a high-speed camera and then two post-shock images are obtained with two laser pulses and two cameras. The first post-shock image is of the early time compression stage when the sphere has become ellipsoidal, and the second image shows the emergence of vortex rings which have evolved due to vorticity depostion by the shock wave. Bubble morphology is characterized with length scale measurements.
Diamagnetic susceptibility of a confined donor in inhomogeneous quantum dots
Energy Technology Data Exchange (ETDEWEB)
Rahmani, K; Zorkani, I; Jorio, A, E-mail: izorkani@hotmail.com [LPS, Faculte des sciences, Dhar Mehraz Fes, Fes, BP 1796 (Morocco)
2011-03-15
The binding energy and diamagnetic susceptibility {chi}{sub dia} are estimated for a shallow donor confined to move in GaAs-GaAlAs inhomogeneous quantum dots. The calculation was performed within the effective mass approximation and using the variational method. The results show that the binding energy and the diamagnetic susceptibility {chi}{sub dia} depend strongly on the core radius and the shell radius. We have demonstrated that there is a critical value of the ratio of the inner radius to the outer radius which may be important for nanofabrication techniques. The binding energy E{sub b} shows a minimum for a critical value of this ratio depending on the value of the outer radius and shows a maximum when the donor is placed at the center of the spherical layer. The diamagnetic susceptibility is more sensitive to variations of the radius for a large spherical layer. The binding energy and diamagnetic susceptibility depend strongly on the donor position.
Effects from inhomogeneities in the chiral transition
Taketani, B G; Taketani, Bruno G.; Fraga, Eduardo S.
2006-01-01
We consider an approximation procedure to evaluate the finite-temperature one-loop fermionic density in the presence of a chiral background field which systematically incorporates effects from inhomogeneities in the chiral field through a derivative expansion. We apply the method to the case of a simple low-energy effective chiral model which is commonly used in the study of the chiral phase transition, the linear sigma-model coupled to quarks. The modifications in the effective potential and their consequences for the bubble nucleation process are discussed.
Albedo and transmittance of inhomogeneous stratus clouds
Energy Technology Data Exchange (ETDEWEB)
Zuev, V.E.; Kasyanov, E.I.; Titov, G.A. [Institute of Atmospheric Optics, Tomsk (Russian Federation)] [and others
1996-04-01
A highly important topic is the study of the relationship between the statistical parameters of optical and radiative charactertistics of inhomogeneous stratus clouds. This is important because the radiation codes of general circulation models need improvement, and it is important for geophysical information. A cascade model has been developed at the Goddard Space Flight Center to treat stratocumulus clouds with the simplest geometry and horizontal fluctuations of the liquid water path (optical thickness). The model evaluates the strength with which the stochastic geometry of clouds influences the statistical characteristics of albedo and the trnasmittance of solar radiation.
Measurement of Density Inhomogeneity for Glass Pendulum
Institute of Scientific and Technical Information of China (English)
LIU Lin-Xia; LIU Qi; SHAO Cheng-Gang; ZHANG Ya-Ting; LUO Jun; Vadim Milyukov
2008-01-01
@@ The density inhomogeneity of a glass pendulum is determined by an optical interference method.The relative variations of the densities over a volume with sizes of 5 × 5 × 5mm3 are (0.64±0.97) × 10-5 and (0.99 ± 0.92) ×10-5 for the K9 glass and silica glass pendulum, respectively.These variations of densities contributing to the relative uncertainties of the Newtonian gravitational constant G are 0.20 ppm and 0.21 ppm in our experiment on measurement of G.
Heat transport in coupled inhomogeneous chains
Institute of Scientific and Technical Information of China (English)
Hu Tao; Bai Meng; Hu Ke; Tang Yi
2011-01-01
We first investigate the heat transport in a network model consisting of two coupled dimerized chains. Results indicate that the thermal resistance of each chain increases with the decrease of the mass ratio γ of the two types of atoms. Then, we find, when a light impurity or a heavy one is added in the two coupled homogeneous chains and coupled with a particle of another chain, the interface thermal resistances Rlint andRγint present different dependences on the mass ratio γ'. Finally, a persistent circulation of energy current is observed in coupled inhomogeneous chains with two pairs of interchain coupling.
CMB radiation in an inhomogeneous spherical space
Aurich, R; Lustig, S
2011-01-01
We analyse the CMB radiation in spherical 3-spaces with non-trivial topology. The focus is put on an inhomogeneous space which possesses observer dependent CMB properties. The suppression of the CMB anisotropies on large angular scales is analysed with respect to the position of the CMB observer. The equivalence of a lens space with a Platonic cubic space is shown and used for the harmonic analysis. We give the transformation of the CMB multipole radiation amplitude as a function of the position of the observer. General sum rules are obtained in terms of the squares of the expansion coefficients for invariant polynomials on the 3-sphere.
Cherenkov radiation threshold in random inhomogeneous media
Grichine, V M
2009-01-01
Cherenkov radiation in media with random inhomogeneities like aerogel or Earth atmosphere is discussed. The spectral-angular distribution of Cherenkov photons emitted by relativistic charged particle and averaged over the dielectric permittivity fluctuations shows angular broadening similarly to the case of media with the photon absorption. The broadening results in the smoothing of Cherenkov threshold, and therefore media with strong photon scattering have more extended dependence of Cherenkov light output on the particle speed. It can be potentially used for the particle identification
... Happens in the Operating Room? Are Your Bowels Moving? KidsHealth > For Kids > Are Your Bowels Moving? A A A What's in this article? What's ... to Know? en español ¿Se mueven tus intestinos? Moving your bowels means to poop. If you said " ...
Observable Deviations from Homogeneity in an Inhomogeneous Universe
Giblin, John T; Starkman, Glenn D
2016-01-01
How does inhomogeneity affect our interpretation of cosmological observations? It has long been wondered to what extent the observable properties of an inhomogeneous universe differ from those of a corresponding Friedman-Lemaitre-Robertson-Walker (FLRW) model, and how the inhomogeneities affect that correspondence. Here, we use numerical relativity to study the behavior of light beams traversing an inhomogeneous universe and construct the resulting Hubble diagrams. The universe that emerges exhibits an average FLRW behavior, but inhomogeneous structures contribute to deviations in observables across the observer's sky. We also investigate the relationship between angular diameter distance and the angular extent of a source, finding deviations that grow with source redshift. These departures from FLRW are important path-dependent effects with implications for using real observables in an inhomogeneous universe such as our own.
Full-wave solution of short impulses in inhomogeneous plasma
Indian Academy of Sciences (India)
Orsolya E Ferencz
2005-02-01
In this paper the problem of real impulse propagation in arbitrarily inhomogeneous media will be presented on a fundamentally new, general, theoretical way. The general problem of wave propagation of monochromatic signals in inhomogeneous media was enlightened in [1]. The earlier theoretical models for spatial inhomogeneities have some errors regarding the structure of the resultant signal originated from backward and forward propagating parts. The application of the method of inhomogeneous basic modes (MIBM) and the complete full-wave solution of arbitrarily shaped non-monochromatic plane waves in plasmas made it possible to obtain a better description of the problem, on a fully analytical way, directly from Maxwell's equations. The model investigated in this paper is inhomogeneous of arbitrary order (while the wave pattern can exist), anisotropic (magnetized), linear, cold plasma, in which the gradient of the one-dimensional spatial inhomogeneity is parallel to the direction of propagation.
Entanglement in Anisotropic Heisenberg XYZ Chain with Inhomogeneous Magnetic Field
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The thermal entanglement of a two-qubit anisotropic Heisenberg XYZ chain under an inhomogeneous magnetic field b is studied. It is shown that when inhomogeneity is increased to a certain value, the entanglement can exhibit a larger revival than that of less values of b. The property is both true for zero temperature and a finite temperature. The results also show that the entanglement and threshold temperature can be increased by increasing inhomogeneous external magnetic field.
Moody's Correlated Binomial Default Distributions for Inhomogeneous Portfolios
Mori, S.; Kitsukawa, K.; Hisakado, M.
2006-01-01
This paper generalizes Moody's correlated binomial default distribution for homogeneous (exchangeable) credit portfolio, which is introduced by Witt, to the case of inhomogeneous portfolios. As inhomogeneous portfolios, we consider two cases. In the first case, we treat a portfolio whose assets have uniform default correlation and non-uniform default probabilities. We obtain the default probability distribution and study the effect of the inhomogeneity on it. The second case corresponds to a ...
Determinantal formulae for the Casimir operators of inhomogeneous Lie algebras
Energy Technology Data Exchange (ETDEWEB)
Campoamor-Stursberg, Rutwig [Dpto. Geometria y Topologia, Fac CC Matematicas, Universidad Complutense de Madrid, Plaza de Ciencias, 3, E-28040 Madrid (Spain)
2006-03-10
Contractions of Lie algebras are combined with the classical matrix method of Gel'fand to obtain matrix formulae for the Casimir operators of inhomogeneous Lie algebras. The method is presented for the inhomogeneous pseudo-unitary Lie algebras Iu(p,q). This procedure is extended to contractions of Iu(p,q) isomorphic to an extension by a derivation of the inhomogeneous special pseudo-unitary Lie algebras Isu(p-1,q), providing an additional analytical method to obtain their invariants. Further, matrix formulae for the invariants of other inhomogeneous Lie algebras are presented.
Quantum electrodynamics of inhomogeneous anisotropic media
Energy Technology Data Exchange (ETDEWEB)
Lopez, Adrian E.R.; Lombardo, Fernando C. [Ciudad Universitaria, Departamento de Fisica Juan Jose Giambiagi, Buenos Aires (Argentina); IFIBA CONICET-UBA, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina)
2015-02-01
In this work we calculate the closed time path generating functional for the electromagnetic (EM) field interacting with inhomogeneous anisotropic matter. For this purpose, we first find a general expression for the electromagnetic field's influence action from the interaction of the field with a composite environment consisting in the quantum polarization degrees of freedom in each point of space, at arbitrary temperatures, connected to thermal baths. Then we evaluate the generating functional for the gauge field, in the temporal gauge, by implementing the Faddeev-Popov procedure. Finally, through the point-splitting technique, we calculate closed expressions for the energy, the Poynting vector, and the Maxwell tensor in terms of the Hadamard propagator. We show that all the quantities have contributions from the field's initial conditions and also from the matter degrees of freedom. Throughout the whole work we discuss how the gauge invariance must be treated in the formalism when the EM-field is interacting with inhomogeneous anisotropic matter. We study the electrodynamics in the temporal gauge, obtaining the EM-field's equation and a residual condition. Finally we analyze the case of the EM-field in bulk material and also discuss several general implications of our results in relation with the Casimir physics in a non-equilibrium scenario. (orig.)
Inhomogeneous Superconductivity in Condensed Matter and QCD
Casalbuoni, Roberto; Casalbuoni, Roberto; Nardulli, Giuseppe
2004-01-01
Inhomogeneous superconductivity arises when the species participating in the pairing phenomenon have different Fermi surfaces with a large enough separation. In these conditions it could be more favorable for each of the pairing fermions to stay close to its Fermi surface and, differently from the usual BCS state, for the Cooper pair to have a non zero total momentum. For this reason in this state the gap varies in space, the ground state is inhomogeneous and a crystalline structure might be formed. This situation was considered for the first time by Fulde, Ferrell, Larkin and Ovchinnikov, and the corresponding state is called LOFF. The spontaneous breaking of the space symmetries in the vacuum state is a characteristic feature of this phase and is associated to the presence of long wave-length excitations of zero mass. The situation described here is of interest both in solid state and in elementary particle physics, in particular in Quantum Chromo-Dynamics at high density and small temperature. In this revi...
Inhomogeneous chemical enrichment in the Galactic Halo
Kobayashi, Chiaki
2016-08-01
In a galaxy, chemical enrichment takes place in an inhomogeneous fashion, and the Galactic Halo is one of the places where the inhomogeneous effects are imprinted and can be constrained from observations. I show this using my chemodynamical simulations of Milky Way type galaxies. The scatter in the elemental abundances originate from radial migration, merging/accretion of satellite galaxies, local variation of star formation and chemical enrichment, and intrinsic variation of nucleosynthesis yields. In the simulated galaxies, there is no strong age-metallicity relation. This means that the most metal-poor stars are not always the oldest stars, and can be formed in chemically unevolved clouds at later times. The long-lifetime sources of chemical enrichment such as asymptotic giant branch stars or neutron star mergers can contribute at low metallicities. The intrinsic variation of yields are important in the early Universe or metal-poor systems such as in the Galactic halo. The carbon enhancement of extremely metal-poor (EMP) stars can be best explained by faint supernovae, the low [α/Fe] ratios in some EMP stars naturally arise from low-mass (~ 13 - 15M ⊙) supernovae, and finally, the [α/Fe] knee in dwarf spheroidal galaxies can be produced by subclasses of Type Ia supernovae such as SN 2002cx-like objects and sub-Chandrasekhar mass explosions.
Model of non-stationary, inhomogeneous turbulence
Bragg, Andrew D.; Kurien, Susan; Clark, Timothy T.
2017-02-01
We compare results from a spectral model for non-stationary, inhomogeneous turbulence (Besnard et al. in Theor Comp Fluid Dyn 8:1-35, 1996) with direct numerical simulation (DNS) data of a shear-free mixing layer (SFML) (Tordella et al. in Phys Rev E 77:016309, 2008). The SFML is used as a test case in which the efficacy of the model closure for the physical-space transport of the fluid velocity field can be tested in a flow with inhomogeneity, without the additional complexity of mean-flow coupling. The model is able to capture certain features of the SFML quite well for intermediate to long times, including the evolution of the mixing-layer width and turbulent kinetic energy. At short-times, and for more sensitive statistics such as the generation of the velocity field anisotropy, the model is less accurate. We propose two possible causes for the discrepancies. The first is the local approximation to the pressure-transport and the second is the a priori spherical averaging used to reduce the dimensionality of the solution space of the model, from wavevector to wavenumber space. DNS data are then used to gauge the relative importance of both possible deficiencies in the model.
Mitharwal, Rajendra
2015-01-01
This work presents a Boundary Element Method (BEM) formulation for contactless electromagnetic field assessments. The new scheme is based on a regularized BEM approach that requires the use of electric measurements only. The regularization is obtained by leveraging on an extension of Calderon techniques to rectangular systems leading to well-conditioned problems independent of the discretization density. This enables the use of highly discretized Huygens surfaces that can be consequently placed very near to the radiating source. In addition, the new regularized scheme is hybridized with both surfacic homogeneous and volumetric inhomogeneous forward BEM solvers accelerated with fast matrix-vector multiplication schemes. This allows for rapid and effective dosimetric assessments and permits the use of inhomogeneous and realistic head phantoms. Numerical results corroborate the theory and confirms the practical effectiveness of all newly proposed formulations.
Tests of Cosmological Inhomogeneity Using WMAP
Shubert, Richard; Tatineni, Mahidhar
2016-06-01
This paper reports on the latest results obtained from studies of the calibrated Time-Ordered Data of the Wilkinson Microwave Anisotropy Probe (9-yr) mission that has in the past been used to determine the anisotropy of the Cosmic Microwave Background Radiation, although with a novel objective. The purpose of this work has been to examine what can be inferred from these data about the local inhomogeneity of the CMBR, which would be in this case an apparent radial variation of the brightness (or effective temperature) at the same point of the celestial sky as seen by the WMAP spacecraft instruments from the center of observation, namely the Sun. The usual studies of anisotropy normally have averaged the observed temperature of any given point on the celestial sky over one full annual orbit of the WMAP spacecraft around the Sun to produce the well-known maps. Inhomogeneity of the kind being sought here, however, would manifest itself as a systematic variation of the apparent temperature at that point as a function of the orbital position of the spacecraft. The detection of such inhomogeneity, if it could be confirmed by subsequent observations, could significantly impact the standard cosmological paradigm. The computational approach used thus far in that search, over the last four years of study by supercomputer facilities at UCSD, has been to examine the differences of temperature seen of the same points on the sky, taken in pairs corresponding to the pointing directions of the A and B radiometer horns of the instrument, from different orbital positions of the spacecraft. From those observed differences of temperature and the corresponding angular separations of the respective orbital positions — here limited to values greater than or equal to 44 degrees out of a maximum available range of 1 - 45 degrees — an apparent radial gradient of temperature could be computed with lowest uncertainties. A small but significant gradient of temperature tentatively has been
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
Inhomogeneous calcium alginate ion cross-linking gel microspheres, a novel ion absorbent, were prepared by dropping a sodium alginate solution to a calcium chloride solution via an electronic droplet generator. Calcium alginate microspheres have uniform particle sizes, a smooth surface and a microporous structure. The electrode probe reveals the inhomogeneous distribution of calcium ions with the highest concentration on the surface, and the lowest concentration in the cores of the spheres. As a novel ion adsorbent, calcium alginate gel microspheres have a lower limiting adsorption mass concentration, a higher enrichment capacity and a higher adsorption capacity for Pb2+ than usual ion exchange resins. The highest percentage of the adsorption is 99.79%. The limiting adsorption mass concentration is 0.0426 mg/L. The adsorption capacity for Pb2+ is 644 mg/g. Calcium alginate gel microspheres have a much faster ion exchange velocity than D418 chelating resin and D113 polyacrylate resin. The moving boundary model was employed to interpret the ion exchange kinetics process, which indicates that the ion exchange process is controlled by intraparticle diffusion of adsorbable ions. So the formation of inhomogeneous gel microspheres reduces the diffusion distance of adsorbable ions within the spheres and enhances the ion exchange velocity. Alginate has a higher selectivity for Pb2+ than for Ca2+ and the selectivity coefficient KPbCa is 316. As an ion cross-linking gel, calcium alginate inhomogeneous microspheres can effectively adsorb heavy metal Pb2+ at a higher selectivity and a higher adsorption velocity. It is a novel and good ion adsorbent.
Jajodia, Sushil; Swarup, Vipin; Wang, Cliff; Wang, X Sean
2011-01-01
Moving Target Defense: Creating Asymmetric Uncertainty for Cyber Threats was developed by a group of leading researchers. It describes the fundamental challenges facing the research community and identifies new promising solution paths. Moving Target Defense which is motivated by the asymmetric costs borne by cyber defenders takes an advantage afforded to attackers and reverses it to advantage defenders. Moving Target Defense is enabled by technical trends in recent years, including virtualization and workload migration on commodity systems, widespread and redundant network connectivity, instr
Inhomogeneous waves in lossy metamaterials and negative refraction
Fedorov, Vladimir Yu
2013-01-01
We study the formation of inhomogeneous waves at the interface of a lossy metamaterial. We show that negative refraction can be interpreted as the formation of an inhomogeneous wave with the obtuse angle between equiamplitude and equiphase planes. Additionally we show that the refractive index and attenuation coefficient of a lossy metamaterial depend on an incident angle even if this metamaterial is isotropic.
Measurements of weak localization of graphene in inhomogeneous magnetic fields
DEFF Research Database (Denmark)
Lindvall, N.; Shivayogimath, Abhay; Yurgens, A.
2015-01-01
Weak localization in graphene is studied in inhomogeneous magnetic fields. To generate the inhomogeneous field, a thin film of type-II superconducting niobium is put in close proximity to graphene. A deviation from the ordinary quadratic weak localization behavior is observed at low fields. We...
Collapse arresting in an inhomogeneous quintic nonlinear Schrodinger model
DEFF Research Database (Denmark)
Gaididei, Yuri Borisovich; Schjødt-Eriksen, Jens; Christiansen, Peter Leth
1999-01-01
Collapse of (1 + 1)-dimensional beams in the inhomogeneous one-dimensional quintic nonlinear Schrodinger equation is analyzed both numerically and analytically. It is shown that in the vicinity of a narrow attractive inhomogeneity, the collapse of beams in which the homogeneous medium would blow up...
MRI intensity inhomogeneity correction by combining intensity and spatial information
Energy Technology Data Exchange (ETDEWEB)
Vovk, Uros; Pernus, Franjo; Likar, Bostjan [Faculty of Electrical Engineering, University of Ljubljana, Trzaska 25, 1000 Ljubljana (Slovenia)
2004-09-07
We propose a novel fully automated method for retrospective correction of intensity inhomogeneity, which is an undesired phenomenon in many automatic image analysis tasks, especially if quantitative analysis is the final goal. Besides most commonly used intensity features, additional spatial image features are incorporated to improve inhomogeneity correction and to make it more dynamic, so that local intensity variations can be corrected more efficiently. The proposed method is a four-step iterative procedure in which a non-parametric inhomogeneity correction is conducted. First, the probability distribution of image intensities and corresponding second derivatives is obtained. Second, intensity correction forces, condensing the probability distribution along the intensity feature, are computed for each voxel. Third, the inhomogeneity correction field is estimated by regularization of all voxel forces, and fourth, the corresponding partial inhomogeneity correction is performed. The degree of inhomogeneity correction dynamics is determined by the size of regularization kernel. The method was qualitatively and quantitatively evaluated on simulated and real MR brain images. The obtained results show that the proposed method does not corrupt inhomogeneity-free images and successfully corrects intensity inhomogeneity artefacts even if these are more dynamic.
Direct optical imaging of structural inhomogeneities in crystalline materials.
Grigorev, A M
2016-05-10
A method for optical imaging of structural inhomogeneities in crystalline materials is proposed, based on the differences in the optical properties of the structural inhomogeneity and the homogeneous material near the fundamental absorption edge of the crystalline material. The method can be used to detect defects in both semiconductors and insulators.
Quantum electrodynamics of inhomogeneous anisotropic media
Lopez, Adrian E Rubio
2014-01-01
In this work we calculate the closed time path (CTP) generating functional for the electromagnetic (EM) field interacting with inhomogeneous anisotropic matter. For this purpose, we first find a general expression for the electromagnetic field's influence action from the interaction of the field with a composite environment consisting in the quantum polarization degrees of freedom in each point of space, at arbitrary temperatures, connected to thermal baths. Then, we evaluate the generating functional for the gauge field, in the temporal gauge, by implementing the Faddeev-Popov procedure. Finally, through the point-splitting technique, we calculate closed expressions for the energy, the Poynting vector and the Maxwell tensor in terms of the Hadamard propagator. We show that all the quantities have contributions from the field's initial conditions and also from the matter degrees of freedom. Throughout the whole work we discuss and give insights about how the gauge invariance must be treated in the formalism w...
Dielectric Fluid in Inhomogeneous Pulsed Electric Field
Shneider, M N
2013-01-01
We consider the dynamics of a compressible fluid under the influence of electrostrictive ponderomotive forces in strong inhomogeneous nonstationary electric fields. It is shown that if the fronts of the voltage rise at a sharp, needle-like electrode are rather steep (less than or about nanoseconds), and the region of negative pressure arises, which can reach values at which the fluid loses its continuity with the formation of cavitation ruptures. If the voltage on the electrode is not large enough or the front is flatter, the cavitation in the liquid does not occur. However, a sudden shutdown of the field results in a reverse flow of liquid from the electrode, which leads to appearance of negative pressure, and, possibly, cavitation.
Casimir Torque in Inhomogeneous Dielectric Plates
Long, William
2013-01-01
In this work, we consider a torque caused by the well known quantum mechanical Casimir effect arising from quantized field fluctuations between plates with inhomogeneous, sharply discontinuous, dielectric properties. While the Casimir effect is a relatively well understood phenomenon, systems resulting in lateral or rotational forces are far less developed; to our knowledge, a theoretical study of discontinuous dielectric variants of such systems has not been attempted. We utilize a Proximity Force Approximation in conjunction with the Lifshitz dielectric formula to perform theoretical analyses of resultant torques in systems with bisected and quadrisected dielectric regions. We also develop a high precision Monte Carlo type numerical integrator to approximate our derived expressions. Our calculations of an energy density linear with the alignment angle result in a constant torque and have implications in NEMS (nano electromechanical systems) and MEMS (micro electromechanical systems), including a postulated ...
Creating Statistically Anisotropic and Inhomogeneous Perturbations
Armendariz-Picon, C
2007-01-01
In almost all structure formation models, primordial perturbations are created within a homogeneous and isotropic universe, like the one we observe. Because their ensemble averages inherit the symmetries of the spacetime in which they are seeded, cosmological perturbations then happen to be statistically isotropic and homogeneous. Certain anomalies in the cosmic microwave background on the other hand suggest that perturbations do not satisfy these statistical properties, thereby challenging perhaps our understanding of structure formation. In this article we relax this tension. We show that if the universe contains an appropriate triad of scalar fields with spatially constant but non-zero gradients, it is possible to generate statistically anisotropic and inhomogeneous primordial perturbations, even though the energy momentum tensor of the triad itself is invariant under translations and rotations.
Origin of Inhomogeneity in Glass Melts
DEFF Research Database (Denmark)
Jensen, Martin; Keding, Ralf; Yue, Yuanzheng
The homogeneity of a glass plays a crucial role in many applications as the inhomogeneities can provide local changes in mechanical properties, optical properties, and thermal expansion coefficient. Homogeneity is not a single property of the glass, instead, it consists of several factors...... such as bubbles, striae, trace element concentration, undissolved species, and crystallised species. As it is not possible to address all the factors in a single study, this work focuses on one of the major factors: chemical striae. Up to now, the quantification of chemical striae in glasses, particularly......, in less transparent glasses, has been a challenge due to the lack of an applicable method. In this study, we have established a simple and accurate method for quantifying the extent of the striae, which is based on the scanning and picture processing through the Fourier transformation. By performing...
The past attractor in inhomogeneous cosmology
Uggla, C; Wainwright, J; Ellis, G F R; Uggla, Claes; Elst, Henk van; Wainwright, John; Ellis, George F R
2003-01-01
We present a general framework for analyzing spatially inhomogeneous cosmological dynamics. It employs Hubble-normalized scale-invariant variables which are defined within the orthonormal frame formalism, and leads to the formulation of Einstein's field equations with a perfect fluid matter source as an autonomous system of evolution equations and constraints. This framework incorporates spatially homogeneous dynamics in a natural way as a special case, thereby placing earlier work on spatially homogeneous cosmology in a broader context, and allows us to draw on experience gained in that field using dynamical systems methods. One of our goals is to provide a precise formulation of the approach to the spacelike initial singularity in cosmological models, described heuristically by Belinski\\v{\\i}, Khalatnikov and Lifshitz. Specifically, we construct an invariant set which we conjecture forms the local past attractor for the evolution equations. We anticipate that this new formulation will provide the basis for ...
Inhomogeneous All-Dielectric Magnetic Metamaterials
Sun, Jingbo; Zhou, Ji; Kudyshev, Zhaxylyk; Litchinitser, Natalia M
2015-01-01
Anomalous field enhancement accompanied by resonant absorption phenomenon was originally discussed in the context of plasma physics and in applications related to radio-communications between the ground and spacecraft returning to Earth. Indeed, there is a critical period of time when all communications are lost due to the reflection/absorption of electromagnetic waves by the sheath of plasma created by a high speed vehicle re-entering the atmosphere. While detailed experimental studies of these phenomena in space are challenging, the emergence of electromagnetic metamaterials enables researchers exceptional flexibility to study them in the laboratory environment. Here, we experimentally demonstrated the localized field enhancement of the electromagnetic wave obliquely incident on a Mie-resonance-based inhomogeneous metamaterials with magnetic permeability gradually changing from positive to negative values.
Measurable inhomogeneities in stock trading volume flow
Cortines, A. A. G.; Riera, R.; Anteneodo, C.
2008-08-01
We investigate the statistics of volumes of shares traded in stock markets. We show that the stochastic process of trading volumes can be understood on the basis of a mixed Poisson process at the microscopic time level. The beta distribution of the second kind (also known as q-gamma distribution), that has been proposed to describe empirical volume histograms, naturally results from our analysis. In particular, the shape of the distribution at small volumes is governed by the degree of granularity in the trading process, while the exponent controlling the tail is a measure of the inhomogeneities in market activity. Furthermore, the present case furnishes empirical evidence of how power law probability distributions can arise as a consequence of a fluctuating intrinsic parameter.
Supernova Feedback in an Inhomogeneous Interstellar Medium
Martizzi, Davide; Quataert, Eliot
2014-01-01
Supernova (SN) feedback is one of the key processes shaping the interstellar medium (ISM) of galaxies. SNe contribute to (and in some cases may dominate) driving turbulence in the ISM and accelerating galactic winds. Modern cosmological simulations have sufficient resolution to capture the main structures in the ISM of galaxies, but are typically still not capable of explicitly resolving all of the small-scale stellar feedback processes, including the expansion of supernova remnants (SNRs). We perform a series of controlled three-dimensional hydrodynamic (adaptive mesh refinement, AMR) simulations of single SNRs expanding in an inhomogeneous density field with statistics motivated by those of the turbulent ISM. We use these to quantify the momentum and thermal energy injection from SNe as a function of spatial scale and the density, metallicity, and structure of the ambient medium. Using these results, we develop an analytic sub-resolution model for SN feedback for use in galaxy formation simulations. We then...
Monodromy of Inhomogeneous Picard-Fuchs Equations
Jefferson, Robert A
2013-01-01
We study low-degree curves on one-parameter Calabi-Yau hypersurfaces, and their contribution to the space-time superpotential in a superstring compactification with D-branes. We identify all lines that are invariant under at least one permutation of the homogeneous variables, and calculate the inhomogeneous Picard-Fuchs equation. The irrational large volume expansions satisfy the recently discovered algebraic integrality. The bulk of our work is a careful study of the topological integrality of monodromy under navigation around the complex structure moduli space. This is a powerful method to recover the single undetermined integration constant that is itself also of arithmetic significance. The examples feature a variety of residue fields, both abelian and non-abelian extensions of the rationals, thereby providing a glimpse of the arithmetic D-brane landscape.
Inhomogeneous reheating scenario with DBI fields
Li, Sheng
2010-08-01
We discuss a new mechanism which can be responsible for the origin of the primordial perturbation in inflationary models, the inhomogeneous DBI reheating scenario. Light DBI fields fluctuate during inflation, and finally create the density perturbations through modulation of the inflation decay rate. In this note, we investigate the curvature perturbation and its non-Gaussianity from this new mechanism. Presenting generalized expressions for them, we show that the curvature perturbation not only depends on the particular process of decay but is also dependent on the sound speed cs from the DBI action. More interestingly we find that the non-Gaussianity parameter fNL is independent of cs. As an application we exemplify some decay processes which give a viable and detectable non-Gaussianity. Finally we find a possible connection between our model and the DBI-Curvaton mechanism.
Inhomogeneity of the $\\Lambda$LTB models
Sundell, Peter
2016-01-01
The Lema\\'itre-Toman-Bondi (LTB) models have reported to suffer from incompatibility with cosmological observations and fine-tuning of the observer's location. Further analysis of these issues indicates that they could be resolved by models that are compatible with the supernova Ia data, but less inhomogeneous than those that have been presented in the literature so far. We study if such models exist by employing the degrees of freedom of the LTB models in a novel manner. We discovered two scenarios which may meet the expectations, but extensive numerical and analytical investigation showed them inviable. We extended our studies to the $\\Lambda$LTB models, which generalizes the LTB models by including a non-zero cosmological constant $\\Lambda$ in Einsteins equations. This adds an additional degree of freedom for the earlier scenarios and introduces a new scenario capable of meeting the expectations. However, extensive numerical and analytical investigation reveals that inclusion of $\\Lambda$ does not enhance ...
Inhomogeneous thermal conductivity enhances thermoelectric cooling
Directory of Open Access Journals (Sweden)
Tingyu Lu
2014-12-01
Full Text Available We theoretically investigate the enhancement of thermoelectric cooling performance in thermoelectric refrigerators made of materials with inhomogeneous thermal conductivity, beyond the usual practice of enhancing thermoelectric figure of merit (ZT of materials. The dissipation of the Joule heat in such thermoelectric refrigerators is asymmetric which can give rise to better thermoelectric cooling performance. Although the thermoelectric figure of merit and the coefficient-of-performance are slightly enhanced, both the maximum cooling power and the maximum cooling temperature difference can be enhanced significantly. This finding can be used to increase the heat absorption at the cold end. We further find that the asymmetric dissipation of Joule heat leads to thermal rectification.
Origin of Inhomogeneity in Glass Melts
DEFF Research Database (Denmark)
Jensen, Martin; Keding, Ralf; Yue, Yuanzheng
The homogeneity of a glass plays a crucial role in many applications as the inhomogeneities can provide local changes in mechanical properties, optical properties, and thermal expansion coefficient. Homogeneity is not a single property of the glass, instead, it consists of several factors...... such as bubbles, striae, trace element concentration, undissolved species, and crystallised species. As it is not possible to address all the factors in a single study, this work focuses on one of the major factors: chemical striae. Up to now, the quantification of chemical striae in glasses, particularly......, in less transparent glasses, has been a challenge due to the lack of an applicable method. In this study, we have established a simple and accurate method for quantifying the extent of the striae, which is based on the scanning and picture processing through the Fourier transformation. By performing...
The thermoelectric properties of inhomogeneous holographic lattices
Donos, Aristomenis
2014-01-01
We consider inhomogeneous, periodic, holographic lattices of D=4 Einstein-Maxwell theory. We show that the DC thermoelectric conductivity matrix can be expressed analytically in terms of the horizon data of the corresponding black hole solution. We numerically construct such black hole solutions for lattices consisting of one, two and ten wave-numbers. We numerically determine the AC electric conductivity which reveals Drude physics as well as resonances associated with sound modes. No evidence for an intermediate frequency scaling regime is found. All of the monochromatic lattice black holes that we have constructed exhibit scaling behaviour at low temperatures which is consistent with the appearance of $AdS_2\\times\\mathbb{R}^2$ in the far IR at T=0.
Inhomogeneous Reheating Scenario with DBI fields
Li, Sheng
2010-01-01
We discuss a new mechanism which can be responsible for the origin of the primordial perturbation in inflationary models, the inhomogeneous DBI reheating scenario. Light DBI fields fluctuate during inflation, and finally create the density perturbations through modulation of the inflation decay rate. In this note, we investigate the curvature perturbation and its non-Gaussianity from this new mechanism. Presenting generalized expressions for them, we show that the curvature perturbation not only depends on the particular process of decay but is also dependent on the sound speed $c_s$ from the DBI action. More interestingly we find that the non-Gaussianity parameter $f_{NL}$ is independent of $c_s$. As an application we exemplify some decay processes which give a viable and detectable non-Gaussianity. Finally we find a possible connection between our model and the DBI-Curvaton mechanism.
Quantizing polaritons in inhomogeneous dissipative systems
Drezet, Aurélien
2017-02-01
In this article we provide a general analysis of canonical quantization for polaritons in dispersive and dissipative electromagnetic inhomogeneous media. We compare several approaches based either on the Huttner-Barnett model [B. Huttner and S. M. Barnett, Phys. Rev. A 46, 4306 (1992), 10.1103/PhysRevA.46.4306] or the Green function, Langevin-noise method [T. Gruner and D.-G. Welsch, Phys. Rev. A 53, 1818 (1996), 10.1103/PhysRevA.53.1818] which includes only material oscillators as fundamental variables. We show that in order to preserve unitarity, causality, and time symmetry, one must necessarily include with an equal footing both electromagnetic modes and material fluctuations in the evolution equations. This becomes particularly relevant for all nanophotonics and plasmonics problems involving spatially localized antennas or devices.
Resistance switching in oxides with inhomogeneous conductivity
Institute of Scientific and Technical Information of China (English)
Shang Da-Shan; Sun Ji-Rong; Shen Bao-Gen; Wuttig Matthias
2013-01-01
Electric-field-induced resistance switching (RS) phenomena have been studied for over 60 years in metal/dielectrics/metal structures.In these experiments a wide range of dielectrics have been studied including binary transition metal oxides,perovskite oxides,chalcogenides,carbon-and silicon-based materials,as well as organic materials.RS phenomena can be used to store information and offer an attractive performance,which encompasses fast switching speeds,high scalability,and the desirable compatibility with Si-based complementary metal--oxide-semiconductor fabrication.This is promising for nonvolatile memory technology,i.e.,resistance random access memory (RRAM).However,a comprehensive understanding of the underlying mechanism is still lacking.This impedes faster product development as well as accurate assessment of the device performance potential.Generally speaking,RS occurs not in the entire dielectric but only in a small,confined region,which results from the local variation of conductivity in dielectrics.In this review,we focus on the RS in oxides with such an inhomogeneous conductivity.According to the origin of the conductivity inhomogeneity,the RS phenomena and their working mechanism are reviewed by dividing them into two aspects:interface RS,based on the change of contact resistance at metal/oxide interface due to the change of Schottky barrier and interface chemical layer,and bulk RS,realized by the formation,connection,and disconnection of conductive channels in the oxides.Finally the current challenges of RS investigation and the potential improvement of the RS performance for the nonvolatile memories are discussed.
Problem of time in slightly inhomogeneous cosmology
Anderson, Edward
2016-07-01
The problem of time (PoT) is a multi-faceted conceptual incompatibility between various areas of Theoretical Physics. While usually stated as between GR and QM, in fact 8/9ths of it is already present at the classical level. Thus we adopt a ‘top-down’ classical and then quantum approach. I consider a local resolution to the PoT that is Machian, which was previously realized for relational triangle and minisuperspace models. This resolution has three levels: classical, semiclassical and combined semiclassical-histories-records. This article’s specific model is a slightly inhomogeneous cosmology considered for now at the classical level. This is motivated by how the inhomogeneous fluctuations that underlie structure formation—galaxies and CMB hotspots—might have been seeded by quantum cosmological fluctuations, as magnified by some inflationary mechanism. In particular, I consider the perturbations about {{{S}}}3 case of this involving up to second order, which has a number of parallels with the Halliwell-Hawking model but has a number of conceptual differences and useful upgrades. The article’s main features are that the elimination part of the model’s thin sandwich is straightforward, but the modewise split of the constraints fail to be first-class constraints. Thus the elimination part only arises as an intermediate geometry between superspace and Riem. The reduced geometries have surprising singularities influenced by the matter content of the Universe, though the N-body problem anticipates these with its collinear singularities. I also give a ‘basis set’ of Kuchař beables for this model arena.
Effects of nanoscale density inhomogeneities on shearing fluids
DEFF Research Database (Denmark)
Ben, Dalton,; Peter, Daivis,; Hansen, Jesper Schmidt
2013-01-01
It is well known that density inhomogeneities at the solid-liquid interface can have a strong effect on the velocity profile of a nanoconfined fluid in planar Poiseuille flow. However, it is difficult to control the density inhomogeneities induced by solid walls, making this type of system...... systems. Using the sinusoidal transverse force method to produce shearing velocity profiles and the sinusoidal longitudinal force method to produce inhomogeneous density profiles, we are able to observe the interactions between the two property inhomogeneities at the level of individual Fourier components....... This gives us a method for direct measurement of the coupling between the density and velocity fields and allows us to introduce various feedback control mechanisms which customize fluid behavior in individual Fourier components. We briefly discuss the role of temperature inhomogeneity and consider whether...
Detection of Moving Targets Using Soliton Resonance Effect
Kulikov, Igor K.; Zak, Michail
2013-01-01
The objective of this research was to develop a fundamentally new method for detecting hidden moving targets within noisy and cluttered data-streams using a novel "soliton resonance" effect in nonlinear dynamical systems. The technique uses an inhomogeneous Korteweg de Vries (KdV) equation containing moving-target information. Solution of the KdV equation will describe a soliton propagating with the same kinematic characteristics as the target. The approach uses the time-dependent data stream obtained with a sensor in form of the "forcing function," which is incorporated in an inhomogeneous KdV equation. When a hidden moving target (which in many ways resembles a soliton) encounters the natural "probe" soliton solution of the KdV equation, a strong resonance phenomenon results that makes the location and motion of the target apparent. Soliton resonance method will amplify the moving target signal, suppressing the noise. The method will be a very effective tool for locating and identifying diverse, highly dynamic targets with ill-defined characteristics in a noisy environment. The soliton resonance method for the detection of moving targets was developed in one and two dimensions. Computer simulations proved that the method could be used for detection of singe point-like targets moving with constant velocities and accelerations in 1D and along straight lines or curved trajectories in 2D. The method also allows estimation of the kinematic characteristics of moving targets, and reconstruction of target trajectories in 2D. The method could be very effective for target detection in the presence of clutter and for the case of target obscurations.
Galactic r-process production: The inhomogeneous approach
Wehmeyer, B; Thielemann, F -K
2015-01-01
The origin of elements made by the rapid neutron-capture process (r-process) is not fully understood. Different sources have been proposed, e.g., core-collapse supernovae and neutron star mergers. Old metal-poor stars carry the signature of the astrophysical r-process source(s). Europium is the most indicative element to trace the r-process production, since it is mostly made by the r-process and it is easy to observe compared to other heavy r-process elements. In this work we simulate the evolution of europium in our Galaxy with the inhomogeneous chemical evolution model ICE, and we compare our results with spectroscopic observations. We test the most important parameters affecting the chemical evolution of the r-process element Eu: (a) for neutron star mergers the coalescence time scale of the merger and the probability to experience a neutron star merger event after two supernova explosions occurred and formed a double neutron star system ) and (b) for the sub-class of magneto-rotationally driven Supernova...
Moving a House by Moved Participants
DEFF Research Database (Denmark)
Axel, Erik
? The participant observer believed it was a matter of changing coordinates, but the engineers immediately saw it was an issue of pipes in the ground, could they be moved and still function as planned? To decide the possibility of this suggestion the engineer was given the task of investigating the consequences......The author performed an investigation of how a house was designed. He participated mainly in meetings, in which the house was engineered. The meetings proceeded in an agreeable atmosphere. While the architect was mostly concerned with integrating the functionality of the house, the engineer engaged...... of moving the house with respect to its servicing pipes. It was immediately underlined that this task was a surplus task and would therefore trigger an extra payment. When I interviewed the participants and asked them how they understood the function of the engineer, they revealed some irritation, since...
Embodied affectivity: On moving and being moved
Directory of Open Access Journals (Sweden)
Thomas eFuchs
2014-06-01
Full Text Available There is a growing body of research indicating that bodily sensation and behaviour strongly influences one’s emotional reaction towards certain situations or objects. On this background, a framework model of embodied affectivity is suggested: we regard emotions as resulting from the circular interaction between affective qualities or affordances in the environment and the subject’s bodily resonance, be it in the form of sensations, postures, expressive movements or movement tendencies. Motion and emotion are thus intrinsically connected: one is moved by movement (perception; impression; affection and moved to move (action; expression; e-motion. Through its resonance, the body functions as a medium of emotional perception: it colours or charges self-experience and the environment with affective valences while it remains itself in the background of one’s own awareness. This model is then applied to emotional social understanding or interaffectivity which is regarded as an intertwinement of two cycles of embodied affectivity, thus continuously modifying each partner’s affective affordances and bodily resonance. We conclude with considerations of how embodied affectivity is altered in psychopathology and can be addressed in psychotherapy of the embodied self.
Shajahan, T. K.; Sinha, Sitabhra; Pandit, Rahul
2007-01-01
Every sixth death in industrialized countries occurs because of cardiac arrhythmias such as ventricular tachycardia (VT) and ventricular fibrillation (VF). There is growing consensus that VT is associated with an unbroken spiral wave of electrical activation on cardiac tissue but VF with broken waves, spiral turbulence, spatiotemporal chaos and rapid, irregular activation. Thus spiral-wave activity in cardiac tissue has been studied extensively. Nevertheless, many aspects of such spiral dynamics remain elusive because of the intrinsically high-dimensional nature of the cardiac-dynamical system. In particular, the role of tissue heterogeneities in the stability of cardiac spiral waves is still being investigated. Experiments with conduction inhomogeneities in cardiac tissue yield a variety of results: some suggest that conduction inhomogeneities can eliminate VF partially or completely, leading to VT or quiescence, but others show that VF is unaffected by obstacles. We propose theoretically that this variety of results is a natural manifestation of a complex, fractal-like boundary that must separate the basins of the attractors associated, respectively, with spiral breakup and single spiral wave. We substantiate this with extensive numerical studies of Panfilov and Luo-Rudy I models, where we show that the suppression of spiral breakup depends sensitively on the position, size, and nature of the inhomogeneity.
The spin Hall effect of light in moving medium
Li, Hehe; Li, Xinzhong; Wang, Jingge
2017-01-01
In this paper, we investigate the spin Hall effect of light in moving inhomogeneous medium using the Gordon metric and the Maxwell’s equations in the gravitational field. Light experiences a moving medium as a gravitational field by means of the Gordon metric. It is shown that the spin Hall effect of light is modified by the motion of medium, and the deflection of the ray trajectory is dependent on the polarization and the motion of the medium. It is interesting that there is no coupling of the spin angular momentum of light and the effective gravitational field when the medium is moving along the direction of the gradient ∇n(r). The results provide a potential method for controlling the spin Hall effect of light in medium.
Effect of Tissue Inhomogeneity on Nonlinear Propagation of Focused Ultrasound
Institute of Scientific and Technical Information of China (English)
LIU Zhen-Bo; FAN Ting-Bo; GUO Xia-Sheng; ZHANG Dong
2010-01-01
@@ We study the influence of tissue inhomogeneity on the focused ultrasound based on the phase screen model and the acoustic nonlinear equation.The inhomogeneous tissue is considered as a combination of a homogeneous medium and a phase aberration screen.Six polyethylene(PE)plates with various correlation lengths and standard deviations are made to mimic the inhomogeneity induced by the human body abdominal.Results indicate that the correlation length affects the side lobe structure of the beam pattern; while the standard deviation is associated with the focusing capability.This study provides a theoretical and experimental basis for the development of a precise treatment plan for high intensity focused ultrasound.
Evolution of Vacuum Bubbles Embeded in Inhomogeneous Spacetimes
Pannia, F A Teppa
2016-01-01
As a first step in the analysis of the influence of inhomogeneities in the evolution of an inflating region, we study the propagation of bubbles of new vacuum in a radially inhomogeneous background filled with dust or radiation, and including a cosmological constant. For comparison, we also analyse the cases with homogeneous dust and radiation backgrounds. We show that the evolution of the bubble in the radiation environments is always slower than in the dust cases, both for homogeneous and inhomogeneous ambients, and leads to appreciable differences in the evolution of the proper radius of the bubble.
Resonance linewidth and inhomogeneous broadening in a metamaterial array
Jenkins, Stewart D
2012-01-01
We examine the effect of inhomogeneous broadening on the collective response of a planar metamaterial consisting of asymmetric split ring resonators. We show that such a response leads to a transmission resonance that can persist when the broadening of individual meta-atom resonance frequencies is roughly one half the frequency characterizing the split ring asymmetry. We also find that larger degrees of inhomogeneous broadening can drastically alter the cooperative response, destroying this resonance. The reduced effect of cooperative response due to inhomogeneous broadening may find applications in producing metamaterial samples that more closely mimic homogeneous magneto-dielectric medium with well-defined susceptibility and permittivity.
Entanglement in Ising Chain with Inhomogeneous Magnetic Field
Institute of Scientific and Technical Information of China (English)
Cenk Akyüz; Ekrem Aydmer
2008-01-01
We have numerically calculated the thermal entanglement of a two-qubit system at low temperatures in a isotropic Ising chain under an inhomogeneous magnetic field.It is shown that in the homogeneous magnetic field,the twoqubit system has entangled states.It is concluded that the presence of the inhomogeneity in the magnetic field plays an effective role on the entangled states.Finally,it is suggested that the inhomogeneity in the magnetic field can be used to create two separated entangled formations in a two-qubit system.
Jeans instability of an inhomogeneous streaming dusty plasma
Indian Academy of Sciences (India)
B P Pandey; B Van Der Holst; J Vranješ; S Poedts
2003-07-01
The dynamics of a self-gravitating unmagnetized, inhomogeneous, streaming dusty plasma is studied in the present work. The presence of the shear ﬂow causes the coupling between gravitational and electrostatic forces. In the absence of self-gravity, the ﬂuctuations in the plasma may grow at the expense of the density inhomogeneity and for certain wavelengths, such an unstable mode may dominate the usual streaming instability. However, in the presence of self-gravity, the plasma inhomogeneity causes an overlap between Jeans and streaming modes and collapse of the grain will continue at all wavelengths.
Spatiotemporal Compression Techniques for Moving Point Objects
Meratnia, N.; de By, R.A.; Bertino, E.
2004-01-01
Moving object data handling has received a fair share of attention over recent years in the spatial database community. This is understandable as positioning technology is rapidly making its way into the consumer market, not only through the already ubiquitous cell phone but soon also through small,
First artificial periodic inhomogeneity experiments at HAARP
Hysell, D. L.; McCarrick, M. J.; Fallen, C. T.; Vierinen, J.
2015-03-01
Experiments involving the generation and detection of artificial periodic inhomogeneities have been performed at the High Frequency Active Auroral Research Program (HAARP) facility. Irregularities were created using powerful X-mode HF emissions and then probed using short (10 μs) X- and O-mode pulses. Reception was performed using a portable software-defined receiver together with the crossed rhombic antenna from the local ionosonde. Echoes were observed reliably between about 85 and 140 km altitude with signal-to-noise ratios as high as about 30 dB. The Doppler shift of the echoes can be associated with the vertical neutral wind in this altitude range. Small but persistent Doppler shifts were observed. The decay time constant of the echoes is meanwhile indicative of the ambipolar diffusion coefficient which depends on the plasma temperature, composition, and neutral gas density. The measured time constants appear to be consistent with theoretical expectations and imply a methodology for measuring neutral density profiles. The significance of thermospheric vertical neutral wind and density measurements which are difficult to obtain using ground-based instruments by other means is discussed.
Optimality of Spatially Inhomogeneous Search Strategies.
Schwarz, Karsten; Schröder, Yannick; Qu, Bin; Hoth, Markus; Rieger, Heiko
2016-08-05
We consider random search processes alternating stochastically between diffusion and ballistic motion, in which the distribution function of ballistic motion directions varies from point to point in space. The specific space dependence of the directional distribution together with the switching rates between the two modes of motion establishes a spatially inhomogeneous search strategy. We show that the mean first passage times for several standard search problems-narrow escape, reaction partner finding, reaction escape-can be minimized with a directional distribution that is reminiscent of the spatial organization of the cytoskeleton filaments of cells with a centrosome: radial ballistic transport from the center to the periphery and back, and ballistic transport in random directions within a concentric shell of thickness Δ_{opt} along the domain boundary. The results suggest that living cells realize efficient search strategies for various intracellular transport problems economically through a spatial cytoskeleton organization that involves radial microtubules in the central region and only a narrow actin cortex rather than a cell body filled with randomly oriented actin filaments.
Inhomogeneous field theory inside the arctic circle
Allegra, Nicolas; Dubail, Jérôme; Stéphan, Jean-Marie; Viti, Jacopo
2016-05-01
Motivated by quantum quenches in spin chains, a one-dimensional toy-model of fermionic particles evolving in imaginary-time from a domain-wall initial state is solved. The main interest of this toy-model is that it exhibits the arctic circle phenomenon, namely a spatial phase separation between a critically fluctuating region and a frozen region. Large-scale correlations inside the critical region are expressed in terms of correlators in a (euclidean) two-dimensional massless Dirac field theory. It is observed that this theory is inhomogenous: the metric is position-dependent, so it is in fact a Dirac theory in curved space. The technique used to solve the toy-model is then extended to deal with the transfer matrices of other models: dimers on the honeycomb and square lattice, and the six-vertex model at the free fermion point (Δ =0 ). In all cases, explicit expressions are given for the long-range correlations in the critical region, as well as for the underlying Dirac action. Although the setup developed here is heavily based on fermionic observables, the results can be translated into the language of height configurations and of the gaussian free field, via bosonization. Correlations close to the phase boundary and the generic appearance of Airy processes in all these models are also briefly revisited in the appendix.
Optimality of Spatially Inhomogeneous Search Strategies
Schwarz, Karsten; Schröder, Yannick; Qu, Bin; Hoth, Markus; Rieger, Heiko
2016-08-01
We consider random search processes alternating stochastically between diffusion and ballistic motion, in which the distribution function of ballistic motion directions varies from point to point in space. The specific space dependence of the directional distribution together with the switching rates between the two modes of motion establishes a spatially inhomogeneous search strategy. We show that the mean first passage times for several standard search problems—narrow escape, reaction partner finding, reaction escape—can be minimized with a directional distribution that is reminiscent of the spatial organization of the cytoskeleton filaments of cells with a centrosome: radial ballistic transport from the center to the periphery and back, and ballistic transport in random directions within a concentric shell of thickness Δopt along the domain boundary. The results suggest that living cells realize efficient search strategies for various intracellular transport problems economically through a spatial cytoskeleton organization that involves radial microtubules in the central region and only a narrow actin cortex rather than a cell body filled with randomly oriented actin filaments.
Intercepting accelerated moving targets: effects of practice on movement performance.
Fialho, João V A P; Tresilian, James R
2017-02-14
When performing a rapid manual interception, targets moving under constant motion are often intercepted with greater accuracy when compared to targets moving under accelerated motion. Usually, accelerated targets are timed too late and decelerating ones too early. The present experiment sought to investigate whether these differences in performance when intercepting targets moving under constant and accelerated motions change after a short period of practice. The task involved striking targets that moved along a straight track by moving forward a manipulandum that moved along a slide perpendicular to the target's motion. Participants were allocated to one of the three experimental groups, defined according to the type of motion of the moving targets: constant speed, constant acceleration, and constant deceleration. Results showed that after some practice participants were able to intercept (positive and negative) accelerating moving targets as accurately as constant speed targets. These results suggest that people might be able to learn how to intercept accelerating targets, corroborating the results of some recent studies.
PARALLEL MOVING MECHANICAL SYSTEMS
Directory of Open Access Journals (Sweden)
Florian Ion Tiberius Petrescu
2014-09-01
Full Text Available Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 Moving mechanical systems parallel structures are solid, fast, and accurate. Between parallel systems it is to be noticed Stewart platforms, as the oldest systems, fast, solid and precise. The work outlines a few main elements of Stewart platforms. Begin with the geometry platform, kinematic elements of it, and presented then and a few items of dynamics. Dynamic primary element on it means the determination mechanism kinetic energy of the entire Stewart platforms. It is then in a record tail cinematic mobile by a method dot matrix of rotation. If a structural mottoelement consists of two moving elements which translates relative, drive train and especially dynamic it is more convenient to represent the mottoelement as a single moving components. We have thus seven moving parts (the six motoelements or feet to which is added mobile platform 7 and one fixed.
Energy Technology Data Exchange (ETDEWEB)
Ayala, R.E.; Gupta, R.P.; Chuck, T.
1995-12-01
The objective of this program is to develop mixed-metal oxide sorbent formulations that are suitable for moving-bed, high-temperature, desulfurization of coal gas. Work continues on zinc titanates formulations and Z-sorb III sorbent.
DEFF Research Database (Denmark)
Hansen, Lennard Højbjerg
2014-01-01
Every day we are presented with bodily expressions in audiovisual media – by anchors, journalists and characters in films for instance. This article explores how body language in the moving image has been and can be approached in a scholarly manner.......Every day we are presented with bodily expressions in audiovisual media – by anchors, journalists and characters in films for instance. This article explores how body language in the moving image has been and can be approached in a scholarly manner....
DEFF Research Database (Denmark)
Hansen, Lennard Højbjerg
2014-01-01
Every day we are presented with bodily expressions in audiovisual media – by anchors, journalists and characters in films for instance. This article explores how body language in the moving image has been and can be approached in a scholarly manner.......Every day we are presented with bodily expressions in audiovisual media – by anchors, journalists and characters in films for instance. This article explores how body language in the moving image has been and can be approached in a scholarly manner....
The formation of composite chaotic multiattractors containing inhomogeneities
Prokopenko, V. G.
2017-08-01
Two methods for introducing inhomogeneities into composite chaotic multiattractors have been proposed. The first method makes it possible to change the mutual arrangement of multiattractor elements. The second method allows one to preset differences between chaotic attractors forming a multiattractor.
Spectroscopic properties of inhomogeneously broadened spin ensembles in a cavity
DEFF Research Database (Denmark)
Kurucz, Zoltan; Wesenberg, Janus; Mølmer, Klaus
2011-01-01
The enhanced collective coupling to weak quantum fields may turn atomic or spin ensembles into an important component in quantum information processing architectures. Inhomogeneous broadening can, however, significantly reduce the coupling and the lifetime of the collective excitation...
Capacity analysis of inhomogeneous hybrid wireless networks using directional antennas
Institute of Scientific and Technical Information of China (English)
WU Feng; ZHU Jiang; TIAN Yi-long; ZOU Jian-bin
2016-01-01
Most of studies on network capacity are based on the assumption that all the nodes are uniformly distributed, which means that the networks are characterized by homogeneity. However, many realistic networks exhibit inhomogeneity due to natural and man-made reasons. In this work, the capacity of inhomogeneous hybrid networks with directional antennas for the first time is studied. By setting different node distribution probabilities, the whole network can be devided into dense cells and sparse cells. On this basis, an inhomogeneous hybrid network model is proposed. The network can exhibit significant inhomogeneity due to the coexistence of two types of cells. Then, we derive the network capacity and maximize the capacity under different channel allocation schemes. Finally, how the network parameters influence the network capacity is analyzed. It is found that if there are plenty of base stations, the per-node throughput can achieve constant order, and if the beamwidth of directional antenna is small enough, the network capacity can scale.
An oscillation criterion for inhomogeneous Stieltjes integro-differential equations
Directory of Open Access Journals (Sweden)
M. A. El-Sayed
1994-01-01
Full Text Available The aim of the paper is to give an oscillation theorem for inhomogeneous Stieltjes integro-differential equation of the form p(tx′+∫atx(sdσ=f(t. The paper generalizes the author's work [2].
The Absorption Characteristics of Inhomogeneous Double-Clad Fibers
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
The absorption characteristics of radially inhomogeneous double-clad fiber (DCF) are investigated firstly with the method of caustic radius, combined with the method of WKBJ. The results are significant for double-clad optical fiber lasers and amplifiers.
Perfect fluids coupled to inhomogeneities in the late Universe
Zhuk, Alexander
2016-01-01
We consider the Universe at the late stage of its evolution and deep inside the cell of uniformity. At such scales, the Universe is highly inhomogeneous and is filled with inhomogeneities in the form of galaxies and the groups of galaxies. We also suggest that the Universe is filled with a perfect fluid, and its fluctuations have peculiar velocities of the same (non-relativistic) order of magnitude as for the inhomogeneities. In this sense, the inhomogeneities (e.g. galaxies) and fluctuations of perfect fluids are coupled with each other. We clarify some important points of this approach and present a brief review of previous studies (e.g. CPL model and Chaplygin gas). We demonstrate that considered perfect fluids which satisfy our approach are really coupled to galaxies concentrating around them. The averaged (over the whole Universe) value of their fluctuations is equal to zero.
Minimal sets of Reidemeister moves
Polyak, Michael
2009-01-01
It is well known that any two diagrams representing the same oriented link are related by a finite sequence of Reidemeister moves O1, O2 and O3. Depending on orientations of fragments involved in the moves, one may distinguish 4 different versions of each of the O1 and O2 moves, and 8 versions of the O3 move. We introduce a minimal generating set of oriented Reidemeister moves, which includes two moves of types O1 and O2, and only one move of type O3. We then consider other sets of moves and show that only few of them generate all Reidemeister moves.
Breakdown of an Inhomogeneous Scale- Free Network Under Intentional Attack
Institute of Scientific and Technical Information of China (English)
LIN Guo-Ji; CHENG Xiang; OU-YANG Qi
2003-01-01
Using a recently introduced network model with node and connection diversity, we study the breakdown of different scale-free networks under intentional attacks. Our simulation results show that inhomogeneous networks are more sensitive to intentional attack than the homogeneous ones and that the centralization of the networks is an important variable, reflecting the characteristics of the network under intentional attack. Using a recently introduced method we can theoretically develop the critical point of the inhomogeneous networks.
Asymptotic properties of the inhomogeneous Lotka-Von Foerster system.
Inaba, H
1988-01-01
"In this paper, we investigate an extension of the multistate stable population model, which makes allowances for migration. The model is formulated as an inhomogeneous system of first order partial differential equations with integral boundary conditions. First, we construct its classical solution. Next, we reformulate the system as an abstract inhomogeneous Cauchy problem on a Banach space, and give its mild solution by using the population semigroup. Our main purpose is to investigate the asymptotic behavior of the mild solution." (SUMMARY IN FRE)
Minimum weight design of inhomogeneous rotating discs
Energy Technology Data Exchange (ETDEWEB)
Jahed, Hamid [Department of Mechanical Engineering, Iran University of Science and Technology, Tehran 16844 (Iran, Islamic Republic of); Farshi, Behrooz [Department of Mechanical Engineering, Iran University of Science and Technology, Tehran 16844 (Iran, Islamic Republic of)]. E-mail: farshi@iust.ac.ir; Bidabadi, Jalal [Department of Mechanical Engineering, Iran University of Science and Technology, Tehran 16844 (Iran, Islamic Republic of)
2005-01-01
There are numerous applications for gas turbine discs in the aerospace industry such as in turbojet engines. These discs normally work under high temperatures while subjected to high angular velocities. Minimizing the weight of such items in aerospace applications results in benefits such as low dead weights and lower costs. High speed of rotation causes large centrifugal forces in a disc and simultaneous application of high temperatures reduces disc material strength. Thus, the latter effects tend to increase deformations of the disc under the applied loads. In order to obtain a reliable disc analysis and arrive at the corresponding correct stress distribution, solutions should consider changes in material properties due to the temperature field throughout the disc. To achieve this goal, an inhomogeneous disc model with variable thickness is considered. Using the variable material properties method, stresses are obtained for the disc under rotation and a steady temperature field. In this paper this is done by modelling the rotating disc as a series of rings of different but constant properties. The optimum disc profile is arrived at by sequentially proportioning the thicknesses of each ring to satisfy the stress requirements. This method vis-a-vis a mathematical programming procedure for optimization shows several advantages. Firstly, it is simple iterative proportioning in each design cycle not requiring involved mathematical operations. Secondly, due to its simplicity it alleviates the necessity of certain simplifications that are common in so-called rigorous mathematical procedures. The results obtained, compared to those published in the literature show agreement and superiority. A further advantage of the proposed method is the independence of the end results from the initially assumed point in the iterative design routine, unlike most methods published so far.
Can we remove the systematic error due to isotropic inhomogeneities?
Negishi, Hiroyuki; Nakao, Ken-ichi
2017-01-01
Usually, we assume that there is no inhomogeneity isotropic in terms of our location in our Universe. This assumption has not been observationally confirmed yet in sufficient accuracy, and we need to consider the possibility that there are non-negligible large-scale isotropic inhomogeneities in our Universe. The existence of large-scale isotropic inhomogeneities affects the determination of cosmological parameters. In particular, from only the distance-redshift relation, we cannot distinguish the inhomogeneous isotropic universe model from the homogeneous isotropic one, because of the ambiguity in the cosmological parameters. In this paper, in order to avoid such ambiguity, we consider three observables—the distance-redshift relation, the fluctuation spectrum of the cosmic microwave background radiation, and the scale of the baryon acoustic oscillation—and compare these observables in two universe models. One is the inhomogeneous isotropic universe model with the cosmological constant, and the other is the homogeneous isotropic universe model with dark energy other than the cosmological constant. We show that these two universe models cannot predict the same observational data of all three observables but the same ones of only two of three, as long as the perturbations are adiabatic. In principle, we can distinguish the inhomogeneous isotropic universe from the homogeneous isotropic one through the appropriate three observables, if the perturbations are adiabatic.
A sodar for profiling in a spatially inhomogeneous urban environment
Directory of Open Access Journals (Sweden)
Stuart Bradley
2015-11-01
Full Text Available The urban boundary layer, above the canopy, is still poorly understood. One of the challenges is obtaining data by sampling more than a few meters above the rooftops, given the spatial and temporal inhomogeneities in both horizontal and vertical. Sodars are generally useful tools for ground-based remote sensing of winds and turbulence, but rely on horizontal homogeneity (as do lidars in building up 3-component wind vectors from sampling three or more spatially separated volumes. The time taken for sound to travel to a typical range of 200 m and back is also a limitation. A sodar of radically different design is investigated, aimed at addressing these problems. It has a single vertical transmitted sound pulse. Doppler shifted signals are received from a number of volumes around the periphery of the transmitted beam with microphones which each having tight angular sensitivity at zenith angles slightly off-vertical. The spatial spread of sampled volumes is therefore smaller. By having more receiver microphones than a conventional sodar, the effect of smaller zenith angle is offset. More rapid profiling is also possible with a single vertical transmitted beam, instead of the usual multiple beams.A prototype design is described, together with initial field measurements. It is found that the beam forming using a single dish antenna and the drift of the sound pulse downwind both give rise to reduced performance compared with expectations. It is concluded that, while the new sodar works in principle, the compromises arising in the design mean that the expected advantages have not been realized
MOVING TARGETS PATTERN RECOGNITION BASED ON THE WAVELET NEURAL NETWORK
Institute of Scientific and Technical Information of China (English)
Ge Guangying; Chen Lili; Xu Jianjian
2005-01-01
Based on pattern recognition theory and neural network technology, moving objects automatic detection and classification method integrating advanced wavelet analysis are discussed in detail. An algorithm of moving targets pattern recognition on the combination of inter-frame difference and wavelet neural network is presented. The experimental results indicate that the designed BP wavelet network using this algorithm can recognize and classify moving targets rapidly and effectively.
Effects of inhomogeneity at stagnation in 3D simulations of ICF implosions
Appelbe, Brian
2016-10-01
The stagnation phase of an ICF implosion is characterized by a hotspot and dense fuel layer that are spatially and temporally inhomogeneous. Perturbation growth during the implosion results in significant asymmetry at stagnation while the hotspot size, density and temperature change rapidly, even in non-igniting capsules. Diagnosing these inhomogeneities is necessary to increase yield in ICF experiments. In this work, 3D radiation hydrodynamic simulations of perturbed indirect drive ICF capsules are carried out using the CHIMERA code. During the stagnation phase a suite of novel and computationally efficient simulation tools are used to produce synthetic time-resolved neutron spectra and images. These tools allow a detailed study of the effects of hotspot inhomogeneities on diagnostic signals. Results show that the burn-averaged ion temperature drops rapidly during thermonuclear burn as the hotspot evolves from a localised, shock-heated region to a more massive, non-uniform plasma. Primary DD and DT neutron spectra show that there is significant residual bulk fluid motion at stagnation, complicating the measurement of ion temperature. Different perturbation modes cause different levels of anisotropic spectra shifts and broadening. However, in all cases the discrepancies between the DD and DT spectra are a reliable indicator of residual motion at stagnation. The simulations are used to examine the relationship between neutron scattering and areal density (ρR). Three measures of areal density are simulated: downscattered neutron ratio, attenuated primary neutron yield and nT backscatter edge. Each of these diagnoses the magnitude and anisotropy of the ρR with varying success, with accuracy decreasing for higher mode perturbations. Contributions to the neutron energy spectra from T +T reactions, secondary DT reactions and deuteron break-up are also evaluated.
Moving Spatial Keyword Queries
DEFF Research Database (Denmark)
Wu, Dingming; Yiu, Man Lung; Jensen, Christian S.
2013-01-01
Web users and content are increasingly being geo-positioned. This development gives prominence to spatial keyword queries, which involve both the locations and textual descriptions of content. We study the efficient processing of continuously moving top-k spatial keyword (MkSK) queries over spatial...... text data. State-of-the-art solutions for moving queries employ safe zones that guarantee the validity of reported results as long as the user remains within the safe zone associated with a result. However, existing safe-zone methods focus solely on spatial locations and ignore text relevancy. We...
BOYLE, PAUL J.; KULU, HILL; COOKE, THOMAS; GAYLE, VERNON; MULDER, CLARAH.
2008-01-01
This paper examines the effect of migration and residential mobility on union dissolution among married and cohabiting couples. Moving is a stressful life event, and a large, multidisciplinary literature has shown that family migration often benefits one partner (usually the man) more than the other. Even so, no study to date has examined the possible impact of within-nation geographical mobility on union dissolution. We base our longitudinal analysis on retrospective event-history data from Austria. Our results show that couples who move frequently have a significantly higher risk of union dissolution, and we suggest a variety of mechanisms that may explain this. PMID:18390300
Autonomous Landing on Moving Platforms
Mendoza Chavez, Gilberto
2016-08-01
This thesis investigates autonomous landing of a micro air vehicle (MAV) on a nonstationary ground platform. Unmanned aerial vehicles (UAVs) and micro air vehicles (MAVs) are becoming every day more ubiquitous. Nonetheless, many applications still require specialized human pilots or supervisors. Current research is focusing on augmenting the scope of tasks that these vehicles are able to accomplish autonomously. Precise autonomous landing on moving platforms is essential for self-deployment and recovery of MAVs, but it remains a challenging task for both autonomous and piloted vehicles. Model Predictive Control (MPC) is a widely used and effective scheme to control constrained systems. One of its variants, output-feedback tube-based MPC, ensures robust stability for systems with bounded disturbances under system state reconstruction. This thesis proposes a MAV control strategy based on this variant of MPC to perform rapid and precise autonomous landing on moving targets whose nominal (uncommitted) trajectory and velocity are slowly varying. The proposed approach is demonstrated on an experimental setup.
Feng, Liqiang; Li, Wenliang
2017-01-01
Spatial distribution of the molecular harmonic spectra from \\text{H}\\text{2}+ in the presence of inhomogeneous field has been theoretically investigated. It shows that (i) the harmonic intensities from the negative-H nucleus play the dominating role in harmonic emission spectra. (ii) Through the investigations of the nuclear signature effect on the spatial distribution of the molecular harmonic spectra, the differences of the harmonic intensities between the negative-H nucleus and the positive-H nucleus can be enhanced and reduced with the introduction of the higher vibrational state and the heavy nucleus (i.e. \\text{D}2+ ), respectively. The time-frequency analyses of the harmonic spectra, the time-dependent wave function and the electron localization have been shown to explain the harmonic spatial distribution and the electron motion. (iii) Due to the plasmon-resonance-enhancement near the metallic nanostructure, the harmonic cutoff can be remarkably enhanced as the spatial position of the inhomogeneous field moving away from the gap center. The ionization probabilities have been shown to explain the harmonic cutoff extension.
SECTIONING METHOD APPLICATION AT ELLIPSOMETRY OF INHOMOGENEOUS REFLECTION SYSTEMS
Directory of Open Access Journals (Sweden)
A. N. Gorlyak
2014-05-01
Full Text Available The paper deals with investigation of application peculiarities of ellipsometry methods and UF spectrophotometry at mechanical and chemical processing of optical engineering surface elements made of quartz glass. Ellipsometer LEF–3M–1, spectrophotometer SF–26 and interferometer MII–4 are used as experiment tools; they obtain widely known technical characteristics. Polarization characteristics of reflected light beam were measured by ellipsometry method; spectrophotometry method was used for measuring radiation transmission factor in UF spectrum area; by interference method surface layer thickness at quartz glass etching was measured. A method for HF–sectioning of inhomogeneous surface layer of polished quartz glass is developed based on ellipsometry equation for reflection system «inhomogeneous layer – inhomogeneous padding». The method makes it possible to carry out the measuring and analysis of optical characteristics for inhomogeneous layers system on inhomogeneous padding and to reconstruct optical profile of surface layers at quartz glass chemical processing. For definition of refractive index change along the layer depth, approximation of experimental values for polarization characteristics of homogeneous layers system is used. Inhomogeneous surface layer of polished quartz glass consists of an area (with thickness up to 20 nm and layer refractive index less than refractive index for quartz glass and an area (with thickness up to 0,1 μm and layer refractive index larger than refractive index for quartz glass. Ellipsometry and photometry methods are used for definition of technological conditions and optical characteristics of inhomogeneous layers at quartz glass chemical processing for optical elements with minimum radiation losses in UF spectrum area.
David-Tabibi, Omid
2008-01-01
In this article we review standard null-move pruning and introduce our extended version of it, which we call verified null-move pruning. In verified null-move pruning, whenever the shallow null-move search indicates a fail-high, instead of cutting off the search from the current node, the search is continued with reduced depth. Our experiments with verified null-move pruning show that on average, it constructs a smaller search tree with greater tactical strength in comparison to standard null-move pruning. Moreover, unlike standard null-move pruning, which fails badly in zugzwang positions, verified null-move pruning manages to detect most zugzwangs and in such cases conducts a re-search to obtain the correct result. In addition, verified null-move pruning is very easy to implement, and any standard null-move pruning program can use verified null-move pruning by modifying only a few lines of code.
Rennie, Richard
2015-01-01
The history of the moving image (the cinema) is well documented in books and on the Internet. This article offers a number of activities that can easily be carried out in a science class. They make use of the phenomenon of "Persistence of Vision." The activities presented herein demonstrate the functionality of the phenakistoscope, the…
Maximilien Brice
2002-01-01
DELPHI (DEtector for Lepton, Photon and Hadron Identification) was one of four experiments at CERN's Large Electron-Positron collider (LEP). Following LEP's decommissioning, the DELPHI detector has been moved within the cavern at Point 8, and now awaits permanent display.
DEFF Research Database (Denmark)
Leitheiser, Erin
two, fell short of increased expectations. This is significant because it demonstrates how external factors alone can change notions and attributions of responsibility (move the goalpost) as well as the effort needed to meet these new expectations. Overall, this shift illustrates the further...
DEFF Research Database (Denmark)
Mortensen, Kristian; Hazel, Spencer
2014-01-01
Opening an interaction is a crucial step in establishing and maintaining social relationships. In this paper we describe how participants in an institutional setting, a help desk counter for exchange students at an international university, literally move into interaction. This is accomplished...
DEFF Research Database (Denmark)
Christensen, Mark Schram; Grünbaum, Thor
2017-01-01
In this chapter, we assume the existence of a sense of “movement activity” that arises when a person actively moves a body part. This sense is usually supposed to be part of sense of agency (SoA). The purpose of the chapter is to determine whether the already existing experimental paradigms can...
Geertzen, Jan H. B.
2008-01-01
Moving beyond Disability was the theme of the 12th World Congress of the International Society for Prosthetics and Orthotics. This paper is a reflection of one of the keynote lectures discussing the International Classification of Functioning, Disability and Health (ICF). Multicultural aspects in di
DEFF Research Database (Denmark)
Simonsen, Gunvor
2008-01-01
as characterized by cultural diversity and variation. Moreover, the field has been haunted by a tendency of moving to easily from descriptive evidence to conclusions about African identity in the Americas. A promising way to overcome these problems, it is suggested, is to develop research that focuses on single...
Ainscow, Mel; Hopkins, David
1992-01-01
In many countries, education legislation embodies contradictory pressures for centralization and decentralization. In the United Kingdom, there is growing government control over policy and direction of schools; schools are also being given more responsibility for resource management. "Moving" schools within Improving the Quality of Education for…
Inhomogeneity in microstructure and mechanical properties during twist extrusion
Energy Technology Data Exchange (ETDEWEB)
Noor, Sh. Vakili [School of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Eivani, A.R., E-mail: aeivani@iust.ac.ir [School of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Jafarian, H.R. [School of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Mirzaei, M. [Material Engineering Group, Islamic Azad University, Kermanshah (Iran, Islamic Republic of)
2016-01-15
In the present paper, the effect of twist extrusion (TE) on the variations of hardness and tensile properties in commercial pure copper is investigated. It is found that hardness, yield and ultimate tensile strength of the alloy increased by increasing distance from the center of the sample after one pass TE. Similar consequences are observed when the second pass of deformation is considered. This is attributed to inhomogeneity of deformation and the higher strain imposed on the material at the peripheral regions. It should be noted that the inhomogeneity is increased at the second pass when route A of deformation is utilized and reduces by utilization of route D. This has as a well-established effect on the development of microstructure throughout the cross section of the samples. In fact, it is found that the microstructure at the peripheral regions is more significantly deformed leading to higher dislocation density and extensive subgrain formation. In addition, it is found that at the second pass using route A, inhomogeneity of deformation and microstructure increases. However, less inhomogeneity is observed when route D is utilized which is in line with the hardness and tensile test results. In the end, it is concluded that depending on the aim of the SPD process, if more homogeneous deformation and microstructure is required, route D is recommended and route A should be utilized in case if maximum inhomogeneity is desirable.
A study of low-dimensional inhomogeneous systems
Energy Technology Data Exchange (ETDEWEB)
Arredondo Leon, Yesenia
2009-01-15
While the properties of homogeneous one-dimensional systems, even with disorder, are relatively well-understood, very little is known about the properties of strongly interacting inhomogeneous systems. Their high-energy physics is determined by the underlying chemistry which, in the atomic scale, introduces Coulomb correlations and local potentials. On the other hand, at large length scales, the physics has to be described by the Tomonaga-Luttinger liquid (TLL) model. In order to establish a connection between the low-energy TLL and the quasi-one-dimensional systems synthesized in the laboratory, we investigate the density-density correlation function in inhomogeneous one-dimensional systems in the asymptotic region. To investigate homogeneous as well as inhomogeneous systems, we use the density-matrix renormalization group (DMRG) method. We present results for ground state properties, such as the density-density correlation function and the parameter K{sub c}, which characterizes its decay at large distances. (orig.)
Double-electron ionization driven by inhomogeneous fields
Chacón, A; Cucchietti, F; Suárez, N; Pérez-Hernández, J A; Ciappina, M F; Landsman, A S; Lewenstein, M
2016-01-01
Electron-electron correlation effects play an instrumental role in our understanding of sequential (SDI) and non-sequential double ionization (NSDI) mechanisms. Here, we present a theoretical study of NSDI driven by plasmonic-enhanced spatial inhomogeneous fields. By numerically solving the time-dependent Schr\\"odinger equation for a linear reduced model of He and a double-electron time-evolution probability analysis, we provide evidence for the enhancement effects in NSDI showing that the double ionization yield at lower laser peak intensities is increased due to the inhomogeneity of the laser field. Furthermore, our quantum mechanical model, as well as classical trajectory Monte Carlo simulations, show that inhomogeneous fields are a useful tool for splitting the binary and recoil processes in the rescattering scenario.
Flux and polarization signals of spatially inhomogeneous gaseous exoplanets
Karalidi, T; Guirado, D
2013-01-01
We present numerically calculated, disk--integrated, spectropolarimetric signals of starlight that is reflected by vertically and horizontally inhomogeneous gaseous exoplanets. We include various spatial features that are present on Solar System's gaseous planets: belts and zones, cyclonic spots, and polar hazes, to test whether such features leave traces in the disk--integrated flux and polarization signals. Broadband flux and polarization signals of starlight that is reflected by gaseous exoplanets are calculated using an efficient, adding--doubling radiative transfer code, that fully includes single and multiple scattering and polarization. The planetary model atmospheres are vertically inhomogeneous and can be horizontally inhomogeneous, and contain gas molecules and/or cloud and/or aerosol particles.
Inhomogeneous stationary and oscillatory regimes in coupled chaotic oscillators.
Liu, Weiqing; Volkov, Evgeny; Xiao, Jinghua; Zou, Wei; Zhan, Meng; Yang, Junzhong
2012-09-01
The dynamics of linearly coupled identical Lorenz and Pikovsky-Rabinovich oscillators are explored numerically and theoretically. We concentrate on the study of inhomogeneous stable steady states ("oscillation death (OD)" phenomenon) and accompanying periodic and chaotic regimes that emerge at an appropriate choice of the coupling matrix. The parameters, for which OD occurs, are determined by stability analysis of the chosen steady state. Three model-specific types of transitions to and from OD are observed: (1) a sharp transition to OD from a nonsymmetric chaotic attractor containing random intervals of synchronous chaos; (2) transition to OD from the symmetry-breaking chaotic regime created by negative coupling; (3) supercritical bifurcation of OD into inhomogeneous limit cycles and further evolution of the system to inhomogeneous chaotic regimes that coexist with complete synchronous chaos. These results may fill a gap in the understanding of the mechanism of OD in coupled chaotic systems.
On the accuracy of wave equations for inhomogeneous media
Xiang, Zhihai
2014-01-01
Homogeneous media is a very ideal assumption to establishing wave equations. Compared to the interested wave length, most materials in reality are inhomogeneous. To investigate the accuracy of electromagnetic, acoustic and elastic wave equations for inhomogeneous media, this paper checks their form-invariance in global Cartesian coordinate system by transforming them from arbitrary spatial geometries, in which they must be form-invariant according to the definition of tensor. In this way, it shows that form-invariant or not is an intrinsic property of wave equations, which is independent with the relation between field variables before and after coordinate transformation. With this approach, one can prove that Maxwell equations and acoustic equations are locally accurate to describe the wave propagation in inhomogeneous media, but Navier equations are not. In addition, new elastodynamic equations can be naturally obtained as the local versions of Willis equations, which are verified by some numerical simulati...
Phonon-plasmon interaction in magnetized inhomogeneous semiconductor quantum plasmas
Ghosh, S.; Muley, Apurva
2016-12-01
The phonon-plasmon interaction in a magnetized inhomogeneous semiconductor quantum plasma is reported using a quantum hydrodynamic model. A quantum modified dispersion relation is employed, which leads to an evolution expression for the gain coefficient of the acoustic wave. In the present study, quantum effects and inhomogeneity are taken into account through non-dimensional quantum parameter-H and scale length of density variation parameter-L, respectively. The effects of these parameters, as well as propagation distance z, angular frequency ω, and orientation of magnetic field θ, on gain characteristics of the acoustic wave are investigated. These investigations are made for linearly and quadratically varying density structures in the presence and the absence of the magnetic field. The results infer that the magnetic field and linearly or quadratically varying density structures would play a decisive role in deciding the gain characteristics of the acoustic wave in the inhomogeneous semiconductor quantum plasma.
Solutions of the chemical kinetic equations for initially inhomogeneous mixtures.
Hilst, G. R.
1973-01-01
Following the recent discussions by O'Brien (1971) and Donaldson and Hilst (1972) of the effects of inhomogeneous mixing and turbulent diffusion on simple chemical reaction rates, the present report provides a more extensive analysis of when inhomogeneous mixing has a significant effect on chemical reaction rates. The analysis is then extended to the development of an approximate chemical sub-model which provides much improved predictions of chemical reaction rates over a wide range of inhomogeneities and pathological distributions of the concentrations of the reacting chemical species. In particular, the development of an approximate representation of the third-order correlations of the joint concentration fluctuations permits closure of the chemical sub-model at the level of the second-order moments of these fluctuations and the mean concentrations.
Inclusion of matter in inhomogeneous loop quantum cosmology
Blas, Daniel Martín-de; Marugán, Guillermo A Mena; 10.1063/1.4734461
2013-01-01
We study the hybrid quantization of the linearly polarized Gowdy $T^3$ model with a massless scalar field with the same symmetries as the metric. For simplicity, we quantize its restriction to the model with local rotational symmetry. Using this hybrid approach, the homogeneous degrees of freedom of the geometry are quantized \\`a la loop, leading to the resolution of the cosmological singularity. A Fock quantization is employed both for the matter and the gravitational inhomogeneities. Owing to the inclusion of the massless scalar field this system allows us to modelize flat Friedmann-Robertson-Walker cosmologies filled with inhomogeneities propagating in one direction, providing a perfect scenario to study the quantum back-reaction of the inhomogeneities on the polymeric homogeneous and isotropic background.
Control of inhomogeneous atomic ensembles of hyperfine qudits
Mischuck, Brian E; Deutsch, Ivan H
2011-01-01
We study the ability to control d-dimensional quantum systems (qudits) encoded in the hyperfine spin of alkali-metal atoms through the application of radio- and microwave-frequency magnetic fields in the presence of inhomogeneities in amplitude and detuning. Such a capability is essential to the design of robust pulses that mitigate the effects of experimental uncertainty and also for application to tomographic addressing of particular members of an extended ensemble. We study the problem of preparing an arbitrary state in the Hilbert space from an initial fiducial state. We prove that inhomogeneous control of qudit ensembles is possible based on a semi-analytic protocol that synthesizes the target through a sequence of alternating rf and microwave-driven SU(2) rotations in overlapping irreducible subspaces. Several examples of robust control are studied, and the semi-analytic protocol is compared to a brute force, full numerical search. For small inhomogeneities, < 1%, both approaches achieve average fide...
Symmetry Analysis of Thermoelectric Energy Converters with Inhomogeneous Legs
Korzhuev, M. A.
2010-09-01
Symmetry analysis has been applied to thermoelectric energy converters [thermoelectric generators (TEG), coolers (TEC), and heaters (TEH)] with inhomogeneous legs. The features of the crystallographic symmetry of thermoelectric materials and the symmetry of legs, thermocouples, and modules are studied. The effect of symmetry on the figure of merit Z of thermoelectric energy converters is considered. A general rule for proper placement of legs in thermoelectric converters is developed. A modified tetratomic classification for thermoelectric energy converters with inhomogeneous legs (TEGa, TEGb, TEC, and TEH) is proposed. An increase in Z for thermoelectric energy converters with inhomogeneous legs is due to the bulk thermoelectric effect. An increase in Z gives the reduction of irreversible processes in the modules (Joule heating and thermal conductivity), accompanying breaking of the symmetry of the legs. It is found that violations of the symmetry requirements can lead to significant energy losses in converters.
A method for longitudinal relaxation time measurement in inhomogeneous fields
Chen, Hao; Cai, Shuhui; Chen, Zhong
2017-08-01
The spin-lattice relaxation time (T1) plays a crucial role in the study of spin dynamics, signal optimization and data quantification. However, the measurement of chemical shift-specific T1 constants is hampered by the magnetic field inhomogeneity due to poorly shimmed external magnetic fields or intrinsic magnetic susceptibility heterogeneity in samples. In this study, we present a new protocol to determine chemical shift-specific T1 constants in inhomogeneous fields. Based on intermolecular double-quantum coherences, the new method can resolve overlapped peaks in inhomogeneous fields. The measurement results are in consistent with the measurements in homogeneous fields using the conventional method. Since spatial encoding technique is involved, the experimental time for the new method is very close to that for the conventional method. With the aid of T1 knowledge, some concealed information can be exploited by T1 weighting experiments.
Boyle, P.J.; Kulu, H.; Cooke, T.; Gayle, V.; Mulder, C.H.
2008-01-01
This paper examines the effect of migration and residential mobility on union dissolution among married and cohabiting couples. Moving is a stressful life event, and a large, multidisciplinary literature has shown that family migration often benefits one partner (usually the man) more than the other. Even so, no study to date has examined the possible impact of within-nation geographical mobility on union dissolution. We base our longitudinal analysis on retrospective event-history data from ...
Directory of Open Access Journals (Sweden)
Ana M. González Ramos
2013-07-01
Full Text Available The special issue Women on the Move that the reader holds in their hands is the result of the hard work of very creative specialists in gender and mobility. Research on mobility and gender has progressively advanced from traditional, non-gender-specific literature on migration or mobility of highly skilled people. And, as these authors prove, the topic is already quantitatively and qualitatively relevant.
2012-01-01
As part of the "Move! Eat better" campaign, Novae’s nutrition adviser, Irène Rolfo, will give a talk on the subject of everyday good nutrition. This will be held in the main building auditorium at 12:30 on Thursday, 20 September 2012. Don’t miss this informative event. For more information, go to http://cern.ch/bpmm
2005-01-01
The Transport Service pulled out all the stops and, more specifically, its fleet of moving and lifting equipment for the Discovery Monday on 6 June - a truly moving experience for all the visitors who took part ! Visitors could play at being machine operator, twiddling the controls of a lift truck fitted with a jib to lift a dummy magnet into a wooden mock-up of a beam-line.They had to show even greater dexterity for this game of lucky dip...CERN-style.Those with a head for heights took to the skies 20 m above ground in a telescopic boom lift.Children were allowed to climb up into the operator's cabin - this is one of the cranes used to move the LHC magnets around. Warm thanks to all members of the Transport Service for their participation, especially B. Goicoechea, T. Ilkei, R. Bihery, S. Prodon, S. Pelletier, Y. Bernard, A. Sallot, B. Pigeard, S. Guinchard, B. Bulot, J. Berrez, Y. Grandjean, A. Bouakkaz, M. Bois, F. Stach, T. Mazzarino and S. Fumey.
Inhomogeneous Reionization and the Polarization of the Cosmic Microwave Background.
Weller
1999-12-10
In a universe with inhomogeneous reionization, the ionized patches create a second-order signal in the cosmic microwave background polarization anisotropy. This signal originates in the coupling of the free-electron fluctuation to the quadruple moment of the temperature anisotropy. We examine the contribution from a simple inhomogeneous reionization model and find that the signal from such a process is below the detectable limits of the Planck Surveyor mission. However, the signal is above the fundamental uncertainty limit from cosmic variance, so that a future detection with a high-accuracy experiment on subarcminute scales is possible.
Nonlinear Waves in an Inhomogeneous Fluid Filled Elastic Tube
Institute of Scientific and Technical Information of China (English)
DUAN Wen-Shan
2004-01-01
In a thin-walled, homogeneous, straight, long, circular, and incompressible fluid filled elastic tube, small but finite long wavelength nonlinear waves can be describe by a KdV (Korteweg de Vries) equation, while the carrier wave modulations are described by a nonlinear Schrodinger equation (NLSE). However if the elastic tube is slowly inhomogeneous, then it is found, in this paper, that the carrier wave modulations are described by an NLSE-like equation. There are soliton-like solutions for them, but the stability and instability regions for this soliton-like waves will change,depending on what kind of inhomogeneity the tube has.
A novel method for evaluating tissue inhomogeneity in elastography
Institute of Scientific and Technical Information of China (English)
BAI Peirui; WAN Mingxi; WANG Supin; ZHANG Dachun; DANG Jun
2006-01-01
Based on the detection of differential Rényi information (DRI) of segmented pre- and post-compression radio-frequency (RF) echo signals, a novel method for evaluating tissue inhomogeneity in elastography prior to the cross-correlation operation is proposed.In vitro experiments were carried out to corroborate the performance of the DRI method. Experimental results illustrate that valuable insights into local tissue inhomogeneity can be obtained through analyzing the DRI curves of the echo segments, which can provide information to aid the study of strain estimation algorithm in elastography.
Baryon inhomogeneities in a charged quark gluon plasma
Energy Technology Data Exchange (ETDEWEB)
Ray, Avijeet [Indian Institute of Technology Roorkee, Uttarakhand, 247667 (India); Sanyal, Soma, E-mail: sossp@uohyd.ernet.in [School of Physics, University of Hyderabad, Gachibowli, Hyderabad, 500046 (India)
2013-10-07
We study the generation of baryon inhomogeneities in regions of the quark gluon plasma which have a charge imbalance. We find that the overdensity in the baryon lumps for positively charged particles is different from the overdensity due to the negatively charged particles. Since quarks are charged particles, the probability of forming neutrons or protons in the lumps would thus be changed. The probability of forming hadrons having quarks of the same charges would be enhanced. This might have interesting consequences for the inhomogeneous nucleosynthesis calculations.
Transdimensional imaging of random velocity inhomogeneities in Nankai subduction zone
Takahashi, T.; Obana, K.; Yamamoto, Y.; Kaiho, Y.; Nakanishi, A.; Kodaira, S.; Kaneda, Y.
2014-12-01
The Nankai trough in southwestern Japan is a convergent margin where the Philippine Sea plate is subducting beneath the Eurasian plate. We have conducted five seismic observations with ocean bottom seismograms (OBSs) from 2008 to 2012 to elucidate detailed seismic structures and its relations with fault segments of large earthquakes. These observations covered the entire area of the Nankai trough, but quantity and quality of data are not spatially uniform because of different observing lengths and various noises. Waveform data of OBSs suggests variously-sized anomalies of random velocity inhomogeneity (i.e., scattering strength) in this subduction zone. To clarify details of random inhomogeneity structures, we conducted a transdimensional imaging of random inhomogeneities by means of the reversible jump Markov Chain Monte Carlo (rjMCMC) without assuming smooth spatial distributions of unknown parameters. We applied the rjMCMC for the inversion of peak delay times of S-wave envelopes at 4-8, 8-16, and 16-32 Hz, where the peak delay time is defined as the time lag from the S-wave onset to its maximal amplitude arrival. This delay time mainly reflects the accumulated multiple forward scattering effect due to random inhomogeneities. We assumed the von Karman type power spectral density function (PSDF) for random velocity fluctuation, and estimated two parameters related with the PSDF at large wavenumber. Study area is partitioned by discrete Voronoi cells of which number and spatial sizes are variable. Estimated random inhomogeneities show clear lateral variations along the Nankai trough. The strongest inhomogeneity on the Nankai trough was found near the subducted Kyushu-Palau ridge that is located at the western margin of the fault segments. We also find a horizontal variation of inhomogeneity along the non-volcanic tremor zone. Relatively strong inhomogeneities in this tremor zone were imaged beneath west Shikoku and Kii-Peninsula. These anomalies were not clearly
Possible effect of subsurface inhomogeneities on the lunar microwave spectrum
Fisher, A. D.; Staelin, D. H.
1977-01-01
Inhomogeneities beneath the lunar surface could alter the average microwave emission spectrum of the moon in a fashion generally consistent with observations, even in the absence of an average heat flux or density gradients with depth. The lunar subsurface was modeled as an inhomogeneous lossy dielectric with three-dimensional refractive-index fluctuations characterized by independent horizontal and vertical correlation lengths. The model suggests that attempts to infer the physical properties of the moon from the lunar microwave spectrum could be significantly inaccurate if subsurface scattering were neglected.
Inhomogeneous helicity effect in the solar angular-momentum transport
Yokoi, Nobumitsu
2017-04-01
Coupled with mean absolute vorticity Ω∗ (rotation and mean relative vorticity), inhomogeneous turbulent helicity is expected to contribute to the generation of global flow structure against the linear and angular momentum mixing due to turbulent or eddy viscosity. This inhomogeneous helicity effect was originally derived in Yokoi & Yoshizawa (1993) [1], and recently has been validated by direct numerical simulations (DNSs) of rotating helical turbulence [2]. Turbulence effect enters the mean-vorticity equation through the turbulent vortexmotive force ⟨u'×ω'⟩ [u': velocity fluctuation, ω'(= ∇× u'): vorticity fluctuation], which is the vorticity counterpart of the electromotive force ⟨u'× b'⟩ (b': magnetic fluctuation) in the mean magnetic-field induction. The mean velocity induction δU is proportional to the vortexmotive force. According to the theoretical result [1,2], it is expressed as δU = -νT∇×Ω∗-ηT(∇2H)Ω∗, where ηT is the transport coefficient, H = ⟨u'ṡω'⟩ the turbulent helicity, and Ω∗ the mean absolute vorticity. The first term corresponds to the enhanced diffusion due to turbulent viscosity νT. The second term expresses the large-scale flow generation due to inhomogeneous helicity. Since helicity is self-generated in rotating stratified turbulence [3], an inhomogeneous helicity distribution is expected to exist in the solar convection zone. A rising flow with expansion near the surface of the Sun generates a strongly negative helicity there [4]. This spatial distribution of helicity would lead to a positive Laplacian of turbulent helicity (∇2H > 0) in the subsurface layer of the Sun. In the combination with the large-scale vorticity associated with the meridional circulation, the inhomogeneous helicity effect works for accelerating the mean velocity in the azimuthal direction. The relevance of this inhomogeneous helicity effect in the solar convection zone is discussed further. References [1] Yokoi, N. and
Energy Density Inhomogeneities with Polynomial $f(R)$ Cosmology
Sharif, M
2015-01-01
In this paper, we study the effects of polynomial $f(R)$ model on the stability of homogeneous energy density in self-gravitating spherical stellar object. For this purpose, we construct couple of evolution equations which relate the Weyl tensor with matter parameters. We explore different factors responsible for density inhomogeneities with non-dissipative dust, isotropic as well as anisotropic fluids and dissipative dust cloud. We find that shear, pressure, dissipative parameters and $f(R)$ terms affect the existence of inhomogeneous energy density.
Dose inhomogeneities at various levels of biological organization
Energy Technology Data Exchange (ETDEWEB)
Bond, V.P.
1988-01-01
Dose inhomogeneities in both tumor and normal tissue, inherent to the application of boron neutron capture therapy (BNCT), can be the result not only of ununiform distribution of /sup 10/B at various levels of biological organization, but also of the distribution of the thermal neutrons and of the energy depositions from more energetic neutrons and other radiations comprising the externally-applied beams. The severity of the problems resulting from such inhomogeneities, and approaches to evaluating them, are illustrated by three examples, at the macro, micro and intermediate levels.
A Model of Emergent Universe in Inhomogeneous Space-Time
Bhattacharya, Subhra
2016-01-01
A scenario of an emergent universe is constructed in the background of an inhomogeneous space-time model which is asymptotically (at spatial infinity) FRW space-time. The cosmic substratum consists of non-interacting two components, namely {\\bf a)} homogeneous and isotropic fluid but dissipative in nature and {\\bf b)} an inhomogeneous and anisotropic barotropic fluid. In non-equilibrium thermodynamic prescription (second order deviations), particle creation mechanism is considered the cause for the dissipative phenomena. It is found that for constant value of the particle creation rate parameter there exists a scenario of emergent universe.
Optical coherent control in semiconductors: Fringe contrast and inhomogeneous broadening
DEFF Research Database (Denmark)
Østergaard, John Erland; Vadim, Lyssenko; Hvam, Jørn Märcher
2001-01-01
Optical coherent control experiments in semiconductors reveal how inhomogeneous broadening must be taken into account in contrast to previous coherent control experiments in atomic and molecular systems. With spectral resolution elf the coherent control signal, the optical phases involved...... is observed in the four-wave mixing spectra as a function of phase-delay representing coherent control in the spectral domain. The spectral phase change of this modulation provides a spectroscopic tool to analyze contributions of inhomogeneous broadening to electronic resonances in semiconductor structures....
Nonlinear acoustic waves in micro-inhomogeneous solids
Nazarov, Veniamin
2014-01-01
Nonlinear Acoustic Waves in Micro-inhomogeneous Solids covers the broad and dynamic branch of nonlinear acoustics, presenting a wide variety of different phenomena from both experimental and theoretical perspectives. The introductory chapters, written in the style of graduate-level textbook, present a review of the main achievements of classic nonlinear acoustics of homogeneous media. This enables readers to gain insight into nonlinear wave processes in homogeneous and micro-inhomogeneous solids and compare it within the framework of the book. The subsequent eight chapters covering: Physical m
Energy Technology Data Exchange (ETDEWEB)
Han, Ga Jin; Lee, Nam Kyung; Kim, Suk [Dept. of Radiology, Biomedical Research Inst., Pusan National Univ. Hospital, Pusan National Univ. School of Medicine, Busan (Korea, Republic of)], e-mail: kimsuk@medimail.co.kr; Kim, Tae Un [Dept. of Radiology, Pusan National Univ. Yangsan Hospital, Pusan National Univ. School of Medicine, Yangsan (Korea, Republic of); Song, Sang Heon [Dept. of Internal Medicine, Biomedical Research Inst., Pusan National Univ. Hospital, Pusan National Univ. School of Medicine, Busan (Korea, Republic of); Kim, Hyun Sung; Jo, Hong Jae [Dept. of Surgery, Biomedical Research Inst., Pusan National Univ. Hospital, Pusan National Univ. School of Medicine, Busan (Korea, Republic of)
2013-10-15
Background: CT scans of patients with febrile illness occasionally show hepatobiliary changes, although infection does not originate in the hepatobiliary system. These findings may cause radiologists and clinicians to misrecognize hepatobiliary diseases and initiate an inappropriate treatment. Thus, it is important to recognize hepatobiliary CT findings in cases of extrahepatobiliary infectious disease. Purpose: To evaluate extrarenal CT manifestations in patients with acute pyelonephritis and to determine the correlation between these extrarenal CT findings and septic liver based on laboratory parameters of sepsis. Material and Methods: This study included 157 retrospectively identified patients with confirmed acute pyelonephritis based on CT imaging and urine test, and who had also undergone multi-phase dynamic contrast-enhanced CT scan. Two radiologists reviewed CT findings including early inhomogeneous enhancement of the liver, periportal low density and gallbladder edema, which were correlated with laboratory data including liver function enzymes, albumin, C-reactive protein, white blood cell count, and results of a blood culture by using the Fisher's exact test and Mann-Whitney U test. Results: Forty-six patients (29.3%) showed early inhomogeneous enhancement of the liver, which was associated with increased C-reactive protein (P < 0.001), a positive blood culture (P < 0.005), and decreased albumin level (P < 0.002). The periportal low density and gallbladder wall edema were noted in 15 patients (9.6%) and six patients (3.8%), respectively. These two CT findings were significantly associated with only decreased albumin level (P < 0.001 and P < 0.040). Conclusion: Early inhomogeneous enhancement of the liver in patients with acute pyelonephritis was significantly associated with increased CRP level, a positive blood culture and decreased albumin level, reflecting sepsis and sepsis-associated liver dysfunction, requiring rapid and appropriate intensive
Dokgo, Kyunghwan; Woo, Minho; Choi, Cheong-Rim; Min, Kyoung-Wook; Hwang, Junga
2016-09-01
Generation of coherent ion acoustic solitary waves (IASWs) in inhomogeneous plasmas by an odd eigenmode (OEM) of electron holes (EHs) is investigated using 1D electrostatic particle-in-cell (PIC) simulations. The OEM oscillates at a frequency comparable to the trapped electron bouncing frequency, as also demonstrated by Lewis' theoretical formalism about the linear eigenmode in Bernstein-Greene-Kruskal (BGK) equilibrium. The density gradient in the inhomogeneous plasmas causes asymmetry in the EH potential structure associated with the OEM, whose amplitude grows rapidly as it propagates through the density gradient region. As the ions interact with this asymmetric potential, which oscillates slowly enough for the ions to respond, they are ejected to the lower density side with a larger potential amplitude, forming a chain of IASWs coherently with the oscillation of the OEM.
Nonlocal inhomogeneous broadening in plasmonic nanoparticle ensembles
DEFF Research Database (Denmark)
Tserkezis, Christos; Maack, Johan Rosenkrantz; Liu, Z.
Nonclassical effects are increasingly more relevant in plasmonics as modern nanofabrication techniques rapidly approach the extreme nanoscale limits, for which departing from classical electrodynamics becomes important. One of the largest-scale necessary corrections towards this direction...... is to abandon the local response approximation (LRA) and take the nonlocal response of the metal into account, typically through the simple hydrodynamic Drude model (HDM), which predicts a sizedependent deviation of plasmon modes from the quasistatic (QS) limit. While this behaviour has been explored for simple...... averaging through both HDM and the recent Generalized Nonlocal Optical Response (GNOR) theory, which apart from the resonance frequency shifts accounts successfully for size-dependent damping as well. We examine NPs made of either ideal Drude-like metals [of plasmon frequency (wavelength) ωp (λp...
Moving related to separation : who moves and to what distance
Mulder, Clara H.; Malmberg, Gunnar
2011-01-01
We address the issue of moving from the joint home on the occasion of separation. Our research question is: To what extent can the occurrence of moves related to separation, and the distance moved, be explained by ties to the location, resources, and other factors influencing the likelihood of movin
1999-01-01
Many people live away from their homes and communities. Worldwide, about 125 million people are migrant workers, immigrants, or refugees in search of education, employment, or safety, making them vulnerable to sexually transmitted infections (STIs), including HIV. Some practical approaches to HIV prevention with people on the move are delineated. These include: 1) the project in Niger describing its work with migrant peer educators; 2) a national program improving health services; 3) a program in India providing STI treatment and health information for truck drivers; 4) a South African HIV program, which includes activities within communities; and 5) HIV prevention programs for refugees in Tanzania and Mozambique.
Nucleation in the chiral transition with an inhomogeneous background
Taketani, B G; Taketani, Bruno G.; Fraga, Eduardo S.
2007-01-01
We consider an approximation procedure to evaluate the finite-temperature one-loop fermionic density in the presence of a chiral background field which systematically incorporates effects from inhomogeneities in the chiral field through a derivative expansion. Modifications in the effective potential and their consequences for the bubble nucleation process are discussed.
Inhomogeneous generalizations of Bianchi type VIh models with perfect fluid
Roy, S. R.; Prasad, A.
1991-07-01
Inhomogeneous universes admitting an Abelian G2 of isometry and filled with perfect fluid have been derived. These contain as special cases exact homogeneous universes of Bianchi type VIh. Many of these universes asymptotically tend to homogeneous Bianchi VIh universes. The models have been discussed for their physical and kinematical behaviors.
Tracking inhomogeneity in high-capacity lithium iron phosphate batteries
Paxton, William A.; Zhong, Zhong; Tsakalakos, Thomas
2015-02-01
Energy-dispersive x-ray diffraction (EDXRD) is one of the few techniques that can internally probe a sealed battery under operating conditions. In this paper, we use EDXRD with ultrahigh energy synchrotron radiation to track inhomogeneity in a cycled high-capacity lithium iron phosphate cell under in-situ and operando conditions. A sequence of depth-profile x-ray diffraction spectra are collected with 40 μm resolution as the cell is discharged. Additionally, nine different locations of the cell are tracked independently throughout a second discharge process. In each case, a two-peak reference intensity ratio analysis (RIR) was used on the LiFePO4 311 and the FePO4 020 reflections to estimate the relative phase abundance of the lithiated and non-lithiated phases. The data provide a first-time look at the dynamics of electrochemical inhomogeneity in a real-world battery. We observe a strong correlation between inhomogeneity and overpotential in the galvanic response of the cell. Additionally, the data closely follow the behavior that is predicted by the resistive-reactant model originally proposed by Thomas-Alyea. Despite a non-linear response in the independently measured locations, the behavior of the ensemble is strikingly linear. This suggests that effects of inhomogeneity can be elusive and highlights the power of the EDXRD technique.
Ventilation inhomogeneity in children with primary ciliary dyskinesia
DEFF Research Database (Denmark)
Green, Kent; Buchvald, Frederik F; Marthin, June Kehlet
2012-01-01
The lung clearance index (LCI) derived from the multiple breath inert gas washout (MBW) test reflects global ventilation distribution inhomogeneity. It is more sensitive than forced expiratory volume in 1 s (FEV(1)) for detecting abnormal airway function and correlates closely with structural lun...
Stress engineering and the applications of inhomogeneously polarized optical fields
Institute of Scientific and Technical Information of China (English)
Thomas G. BROWN; Amber M. BECKLEY
2013-01-01
Spatial inhomogeneities in the polarization of a light field can show fascinating effects in focusing, propagation, illumination, and imaging. This paper provides examples of these effects and describes how deterministic stress on the periphery of an optical element can be used in fundamental studies of beam propagation, as well as applications such as polarimetry.
ON FINITE ELEMENT METHODS FOR INHOMOGENEOUS DIELECTRIC WAVEGUIDES
Institute of Scientific and Technical Information of China (English)
Zhiming Chen; Jian-hua Yuan
2004-01-01
We investigate the problem of computing electromagnetic guided waves in a closed,inhomogeneous, pillared three-dimensional waveguide at a given frequency. The problem is formulated as a generalized eigenvalue problem. By modifying the sesquilinear form associated with the eigenvalue problem, we provide a new convergence analysis for the finite element approximations. Numerical results are reported to illustrate the performance of the method.
Multiwavelength erbium-doped fiber laser exploiting intracavity polarization inhomogeneity
Institute of Scientific and Technical Information of China (English)
孙军强; 丘军林; 黄德修
2000-01-01
Simultaneous multiwavelength lasing is demonstrated exploiting intracavity polarization in-homogeneity in an erbium-doped fiber laser. Experiments indicate that polarization hole burning can be enhanced by the changes of optical MQW waveguide bias current and the polarization states in the laser cavity. Ten wavelengths with 0.9 nm spacing are generated at room temperature.
Scattering of acoustic waves by macroscopically inhomogeneous poroelastic tubes.
Groby, J-P; Dazel, O; Depollier, C; Ogam, E; Kelders, L
2012-07-01
Wave propagation in macroscopically inhomogeneous porous materials has received much attention in recent years. For planar configurations, the wave equation, derived from the alternative formulation of Biot's theory of 1962, was reduced and solved recently: first in the case of rigid frame inhomogeneous porous materials and then in the case of inhomogeneous poroelastic materials in the framework of Biot's theory. This paper focuses on the solution of the full wave equation in cylindrical coordinates for poroelastic tubes in which the acoustic and elastic properties of the poroelastic tube vary in the radial direction. The reflection coefficient is obtained numerically using the state vector (or the so-called Stroh) formalism and Peano series. This coefficient can then be used to straightforwardly calculate the scattered field. To validate the method of resolution, results obtained by the present method are compared to those calculated by the classical transfer matrix method in the case of a two-layer poroelastic tube. As an example, a long bone excited in the sagittal plane is considered. Finally, a discussion is given of ultrasonic time domain scattered field for various inhomogeneity profiles, which could lead to the prospect of long bone characterization.
Higher dimensional inhomogeneous dust collapse and cosmic censorship
Ghosh, S G
2001-01-01
We investigate the occurrence and nature of a naked singularity in the gravitational collapse of an inhomogeneous dust cloud described by higher dimensional Tolman-Bondi space-times. The naked singularities are found to be gravitationally strong in the sense of Tipler. Higher dimensions seem to favour black holes rather than naked singularities.
Acoustic Force Density Acting on Inhomogeneous Fluids in Acoustic Fields
DEFF Research Database (Denmark)
Karlsen, Jonas Tobias; Augustsson, Per; Bruus, Henrik
2016-01-01
We present a theory for the acoustic force density acting on inhomogeneous fluids in acoustic fields on time scales that are slow compared to the acoustic oscillation period. The acoustic force density depends on gradients in the density and compressibility of the fluid. For microfluidic systems...
An algorithm of computing inhomogeneous differential equations for definite integrals
Nakayama, Hiromasa; Nishiyama, Kenta
2010-01-01
We give an algorithm to compute inhomogeneous differential equations for definite integrals with parameters. The algorithm is based on the integration algorithm for $D$-modules by Oaku. Main tool in the algorithm is the Gr\\"obner basis method in the ring of differential operators.
Non-parametric Bayesian inference for inhomogeneous Markov point processes
DEFF Research Database (Denmark)
Berthelsen, Kasper Klitgaard; Møller, Jesper
With reference to a specific data set, we consider how to perform a flexible non-parametric Bayesian analysis of an inhomogeneous point pattern modelled by a Markov point process, with a location dependent first order term and pairwise interaction only. A priori we assume that the first order term...
Multiwavelength erbium-doped fiber laser exploiting intracavity polarization inhomogeneity
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
Simultaneous multiwavelength lasing is demonstrated exploiting intracavity polarization inhomogeneity in an erbium-doped fiber laser. Experiments indicate that polarization hole burning can be enhanced by the changes of optical MQW waveguide bias current and the polarization states in the laser cavity. Ten wavelengths with 0.9 nm spacing are generated at room temperature.
Inhomogeneous magnetic field in AdS/CFT superconductor
Wen, Wen-Yu
2008-01-01
We study the holographically dual description of superconductor in (2+1)-dimensions in the presence of inhomogeneous magnetic field and observe that there exists type I and type II superconductor. A new feature of type changing is observed for type I superconductor near critical temperature.
A time inhomogeneous Cox-Ingersoll-Ross diffusion with jumps
Hoepfner, Reinhard
2009-01-01
We consider a time inhomogeneous Cox-Ingersoll-Ross diffusion with positive jumps. We exploit a branching property to prove existence of a unique strong solution under a restrictive condition on the jump measure. We give Laplace transforms for the transition probabilities, with an interpretation in terms of limits of mixtures over Gamma laws.
Rate-optimal Bayesian intensity smoothing for inhomogeneous Poisson processes
E. Belitser; P. Serra; H. van Zanten
2015-01-01
We apply nonparametric Bayesian methods to study the problem of estimating the intensity function of an inhomogeneous Poisson process. To motivate our results we start by analyzing count data coming from a call center which we model as a Poisson process. This analysis is carried out using a certain
Material inhomogeneities and their evolution a geometric approach
Epstein, Marcelo
2007-01-01
Presents a unified treatment of the inhomogeneity theory using some of the tools of modern differential geometry. This book deals with the geometrical description of uniform bodies and their homogeneity conditions. It also develops a theory of material evolution and discusses its relevance in various applied contexts.
Coherent excitonic nonlinearity versus inhomogeneous broadening in single quantum wells
DEFF Research Database (Denmark)
Langbein, Wolfgang Werner; Borri, Paola; Hvam, Jørn Märcher;
1998-01-01
The coherent response of excitons in semiconductor nanostructures, as measured in four wave mixing (FWM) experiments, depends strongly on the inhomogeneous broadening of the exciton transition. We investigate GaAs-AlGaAs single quantum wells (SQW) of 4 nm to 25 nm well width. Two main mechanisms...
Multiple solutions for inhomogeneous nonlinear elliptic problems arising in astrophyiscs
Directory of Open Access Journals (Sweden)
Marco Calahorrano
2004-04-01
Full Text Available Using variational methods we prove the existence and multiplicity of solutions for some nonlinear inhomogeneous elliptic problems on a bounded domain in $mathbb{R}^n$, with $ngeq 2$ and a smooth boundary, and when the domain is $mathbb{R}_+^n$
Matrix algorithms for solving (in)homogeneous bound state equations.
Blank, M; Krassnigg, A
2011-07-01
In the functional approach to quantum chromodynamics, the properties of hadronic bound states are accessible via covariant integral equations, e.g. the Bethe-Salpeter equation for mesons. In particular, one has to deal with linear, homogeneous integral equations which, in sophisticated model setups, use numerical representations of the solutions of other integral equations as part of their input. Analogously, inhomogeneous equations can be constructed to obtain off-shell information in addition to bound-state masses and other properties obtained from the covariant analogue to a wave function of the bound state. These can be solved very efficiently using well-known matrix algorithms for eigenvalues (in the homogeneous case) and the solution of linear systems (in the inhomogeneous case). We demonstrate this by solving the homogeneous and inhomogeneous Bethe-Salpeter equations and find, e.g. that for the calculation of the mass spectrum it is as efficient or even advantageous to use the inhomogeneous equation as compared to the homogeneous. This is valuable insight, in particular for the study of baryons in a three-quark setup and more involved systems.
Phase Diagram of Inhomogeneous Percolation with a Defect Plane
Iliev, G. K.; Janse van Rensburg, E. J.; Madras, N.
2015-01-01
Let be the -dimensional hypercubic lattice and let be an -dimensional sublattice, with . We consider a model of inhomogeneous bond percolation on at densities and , in which edges in are open with probability , and edges in open with probability . We generalize several classical results of (homogeneous) bond percolation to this inhomogeneous model. The phase diagram of the model is presented, and it is shown that there is a subcritical regime for and (where is the critical probability for homogeneous percolation in ), a bulk supercritical regime for , and a surface supercritical regime for and . We show that is a strictly decreasing function for , with a jump discontinuity at . We extend the Aizenman-Barsky differential inequalities for homogeneous percolation to the inhomogeneous model and use them to prove that the susceptibility is finite inside the subcritical phase. We prove that the cluster size distribution decays exponentially in the subcritical phase, and sub-exponentially in the supercritical phases. For a model of lattice animals with a defect plane, the free energy is related to functions of the inhomogeneous percolation model, and we show how the percolation transition implies a non-analyticity in the free energy of the animal model. Finally, we present simulation estimates of the critical curve.
Ekman Spiral in Horizontally Inhomogeneous Ocean with Varying Eddy Viscosity
2015-01-01
1 Ekman Spiral in Horizontally Inhomogeneous Ocean with Varying Eddy Viscosity...Oceanography Naval Postgraduate School, Monterey, California, USA Manuscript Click here to download Manuscript: Ekman -chu-pageoph-rev.docx 1...currently valid OMB control number. 1. REPORT DATE 2015 2. REPORT TYPE 3. DATES COVERED 00-00-2015 to 00-00-2015 4. TITLE AND SUBTITLE Ekman Spiral
One-dimensional diffusion model in an Inhomogeneous region
CSIR Research Space (South Africa)
Fedotov, I
2006-01-01
Full Text Available A one-dimensional model is developed to describe atomic diffusion in a graphite tube atomizer for electrothermal atomic adsorption spectrometry. The underlying idea of the model is the solution of an inhomogeneous one-dimensional diffusion equation...
Spatial Inhomogeneity of Kinetic and Magnetic Dissipations in Thermal Convection
Hotta, H.
2017-08-01
We investigate the inhomogeneity of kinetic and magnetic dissipations in thermal convection using high-resolution calculations. In statistically steady turbulence, the injected and dissipated energies are balanced. This means that a large amount of energy is continuously converted into internal energy via dissipation. As in thermal convection, downflows are colder than upflows and the inhomogeneity of the dissipation potentially changes the convection structure. Our investigation of the inhomogeneity of the dissipation shows the following. (1) More dissipation is seen around the bottom of the calculation domain, and this tendency is promoted with the magnetic field. (2) The dissipation in the downflow is much larger than that in the upflow. The dissipation in the downflow is more than 80% of the total at maximum. This tendency is also promoted with the magnetic field. (3) Although 2D probability density functions of the kinetic and magnetic dissipations versus the vertical velocity are similar, the kinetic and magnetic dissipations are not well correlated. Our result suggests that the spatial inhomogeneity of the dissipation is significant and should be considered when modeling a small-scale strong magnetic field generated with an efficient small-scale dynamo for low-resolution calculations.
Control of inhomogeneous atomic ensembles of hyperfine qudits
DEFF Research Database (Denmark)
Mischuck, Brian Edward; Merkel, Seth T.; Deutsch, Ivan H.
2012-01-01
We study the ability to control d-dimensional quantum systems (qudits) encoded in the hyperfine spin of alkali-metal atoms through the application of radio- and microwave-frequency magnetic fields in the presence of inhomogeneities in amplitude and detuning. Such a capability is essential...
An inhomogeneous wave equation and non-linear Diophantine approximation
DEFF Research Database (Denmark)
Beresnevich, V.; Dodson, M. M.; Kristensen, S.;
2008-01-01
A non-linear Diophantine condition involving perfect squares and arising from an inhomogeneous wave equation on the torus guarantees the existence of a smooth solution. The exceptional set associated with the failure of the Diophantine condition and hence of the existence of a smooth solution...... is studied. Both the Lebesgue and Hausdorff measures of this set are obtained....
An inhomogeneous Lax representation for the Hirota equation
Fioravanti, Davide
2016-01-01
Motivated by recent work on quantum integrable models without U(1) symmetry, we show that the sl(2) Hirota equation admits a Lax representation with inhomogeneous terms. The compatibility of the auxiliary linear problem leads to a new consistent family of Hirota-like equations.
Apparent horizons in Clifton-Mota-Barrow inhomogeneous universe
Vitagliano, Vincenzo; Sotiriou, Thomas P; Liberati, Stefano
2013-01-01
We analyze the apparent horizon dynamics in the inhomogeneous Clifton-Mota-Barrow solution of Brans-Dicke theory. This solution models a central matter configuration embedded in a cosmological background. In certain regions of the parameter space we find solutions exhibiting dynamical creation or merging of two horizons.
Inhomogeneous Absorption of Laser Radiation : Trigger of LIPSS Formation
Skolski, J. Z. P.; Romer, G. R. B. E.; Obona, J. V.; Ocelik, V.; in 't Veld, A. J. Huis; De Hosson, J. Th. M.
2013-01-01
The finite-difference time-domain method is used to study the inhomogeneous absorption of linearly polarized laser radiation below a rough surface. The results are analyzed in the frequency domain. It is shown that laser-induced periodic surface structures, with a periodicity larger than the laser w
Spherically symmetric inhomogeneous bianisotropic media: Wave propagation and light scattering
DEFF Research Database (Denmark)
Novitsky, Andrey; Shalin, Alexander S.; Lavrinenko, Andrei
2017-01-01
We develop a technique for finding closed-form expressions for electromagnetic fields in radially inhomogeneous bianisotropic media, both the solutions of the Maxwell equations and material tensors being defined by the set of auxiliary two-dimensional matrices. The approach is applied to determine...... the scattering cross-sections by spherical particles, the fields inside which correspond to the Airy-exponential waves....
Electron-Bernstein Waves in Inhomogeneous Magnetic Fields
DEFF Research Database (Denmark)
Armstrong, R. J.; Frederiksen, Å.; Pécseli, Hans
1984-01-01
The propagation of small amplitude electron-Bernstein waves in different inhomogeneous magnetic field geometries is investigated experimentally. Wave propagation towards both cut-offs and resonances are considered. The experimental results are supported by a numerical ray-tracing analysis. Spatial...... enhancements of the wave amplitude are interpreted as a result of caustic formation....
Energy Technology Data Exchange (ETDEWEB)
Fenoglietto, P.; Ailleres, N.; Simeon, S.; Dubois, J.B.; Azria, D. [CRLC Val d' Aurelle, 34 - Montpellier (France)
2010-10-15
An institution possesses three accelerators which have been identically parameterized as far as energies and collimators are concerned, to deliver equivalent intensity-modulated conformational radiotherapy. The RapidArc methodology has been implemented on a first machine, and then on a second one. The authors report tests performed to check whether a treatment could be optimized on a specific accelerator, and then performed on another one. Six patients suffering from ORL cancers have been selected. Dose computation and optimization has been performed with Eclipse. Half of treatments have been optimized on one accelerator, and the other half on the other one. According to the comparison between measured and computed doses, it appears that, in an institution possessing twin machines, patients may pass from one accelerator to the other without performing a new dosimetry. Short communication
DEFF Research Database (Denmark)
Agarwal, Pankaj K.; Arge, Lars Allan; Erickson, Jeff
2003-01-01
also describe an indexing scheme in which the number of I/Os required to answer a query depends monotonically on the difference between the query time stamp t and the current time. Finally, we develop an efficient indexing scheme to answer approximate nearest-neighbor queries among moving points.......We propose three indexing schemes for storing a set S of N points in the plane, each moving along a linear trajectory, so that any query of the following form can be answered quickly: Given a rectangle R and a real value t, report all K points of S that lie inside R at time t. We first present...... an indexing structure that, for any given constant >0, uses O(N/B) disk blocks and answers a query in O((N/B)1/2+ +K/B) I/Os, where B is the block size. It can also report all the points of S that lie inside R during a given time interval. A point can be inserted or deleted, or the trajectory of a point can...
Anaïs Schaeffer
2012-01-01
This year, the CERN Medical Service is launching a new public health campaign. Advertised by the catchphrase “Move! & Eat Better”, the particular aim of the campaign is to encourage people at CERN to take more regular exercise, of whatever kind. The CERN annual relay race is scheduled on 24 May this year. The CERN Medical Service will officially launch its “Move! & Eat Better” campaign at this popular sporting event. “We shall be on hand on the day of the race to strongly advocate regular physical activity,” explains Rachid Belkheir, one of the Medical Service doctors. "We really want to pitch our campaign and answer any questions people may have. Above all we want to set an example. So we are going to walk the same circuit as the runners to underline to people that they can easily incorporate movement into their daily routine.” An underlying concern has prompted this campaign: during their first few year...
Kennedy, K.D.; Vries, E.T. de; Koorevaar, P.
1998-01-01
This paper presents results obtained from two different Dynamic Channel Allocation (DCA) algorithms, namely the Timid and Persistent Polite Aggressive (PPA) algorithms, simulated under both static homogeneous and dynamic inhomogeneous traffic. The dynamic inhomogeneous traffic is modelled upon real
Analyses of Inhomogeneities in Radiosonde Temperature and Humidity Time Series.
Zhai, Panmao; Eskridge, Robert E.
1996-04-01
Twice daily radiosonde data from selected stations in the United States (period 1948 to 1990) and China (period 1958 to 1990) were sorted into time series. These stations have one sounding taken in darkness and the other in sunlight. The analysis shows that the 0000 and 1200 UTC time series are highly correlated. Therefore, the Easterling and Peterson technique was tested on the 0000 and 1200 time series to detect inhomogeneities and to estimate the size of the biases. Discontinuities were detected using the difference series created from the 0000 and 1200 UTC time series. To establish that the detected bias was significant, a t test was performed to confirm that the change occurs in the daytime series but not in the nighttime series.Both U.S. and Chinese radiosonde temperature and humidity data include inhomogeneities caused by changes in radiosonde sensors and observation times. The U.S. humidity data have inhomogeneities that were caused by instrument changes and the censoring of data. The practice of reporting relative humidity as 19% when it is lower than 20% or the temperature is below 40°C is called censoring. This combination of procedural and instrument changes makes the detection of biases and adjustment of the data very difficult. In the Chinese temperatures, them are inhomogeneities related to a change in the radiation correction procedure.Test results demonstrate that a modified Easterling and Peterson method is suitable for use in detecting and adjusting time series radiosonde data.Accurate stations histories are very desirable. Stations histories can confirm that detected inhomogeneities are related to instrument or procedural changes. Adjustments can then he made to the data with some confidence.
Astrocyte signaling in the presence of spatial inhomogeneities
Stamatakis, Michail; Mantzaris, Nikos V.
2007-09-01
Astrocytes, a special type of glial cells, were considered to have just a supporting role in information processing in the brain. However, several recent studies have shown that they can be chemically stimulated by various neurotransmitters, such as ATP, and can generate Ca2+ and ATP waves, which can propagate over many cell lengths before being blocked. Although pathological conditions, such as spreading depression and epilepsy, have been linked to abnormal wave propagation in astrocytic cellular networks, a quantitative understanding of the underlying characteristics is still lacking. Astrocytic cellular networks are inhomogeneous, in the sense that the domain they occupy contains passive regions or gaps, which are unable to support wave propagation. Thus, this work focuses on understanding the complex interplay between single-cell signal transduction, domain inhomogeneity, and the characteristics of wave propagation and blocking in astrocytic cellular networks. The single-cell signal transduction model that was employed accounts for ATP-mediated IP3 production, the subsequent Ca2+ release from the ER, and ATP release into the extracellular space. The model is excitable and thus an infinite range of wave propagation is observed if the domain of propagation is homogeneous. This is not always the case for inhomogeneous domains. To model wave propagation in inhomogeneous astrocytic networks, a reaction-diffusion framework was developed and one-gap as well as multiple-gap cases were simulated using an efficient finite-element algorithm. The minimum gap length that blocks the wave was computed as a function of excitability levels and geometric characteristics of the inhomogeneous network, such as the length of the active regions (cells). Complex transient patterns, such as wave reflection, wave trapping, and generation of echo waves, were also predicted by the model, and their relationship to the geometric characteristics of the network was evaluated. Therefore, the
Move Ordering using Neural Networks
Kocsis, L.; Uiterwijk, J.; Van Den Herik, J.
2001-01-01
© Springer-Verlag Berlin Heidelberg 2001. The efficiency of alpha-beta search algorithms heavily depends on the order in which the moves are examined. This paper focuses on using neural networks to estimate the likelihood of a move being the best in a certain position. The moves considered more like
DEFF Research Database (Denmark)
Morris, Tim; Manley, David; Northstone, Kate;
2016-01-01
A large literature exists suggesting that residential mobility leads to increased participation in risky health behaviours such as cannabis use amongst youth. However, much of this work fails to account for the impact that underlying differences between mobile and non-mobile youth have on this re......A large literature exists suggesting that residential mobility leads to increased participation in risky health behaviours such as cannabis use amongst youth. However, much of this work fails to account for the impact that underlying differences between mobile and non-mobile youth have...... regression models (log odds: 0.94, standard error: 0.42), indicating that children who move houses are more likely to use cannabis than those who remain residentially stable. However, decomposing this relationship into within- and between-child components reveals that the conventional model is underspecified...
Banichuk, Nikolay; Neittaanmäki, Pekka; Saksa, Tytti; Tuovinen, Tero
2014-01-01
This book deals with theoretical aspects of modelling the mechanical behaviour of manufacturing, processing, transportation or other systems in which the processed or supporting material is travelling through the system. Examples of such applications include paper making, transmission cables, band saws, printing presses, manufacturing of plastic films and sheets, and extrusion of aluminium foil, textiles and other materials. The work focuses on out-of-plane dynamics and stability analysis for isotropic and orthotropic travelling elastic and viscoelastic materials, with and without fluid-structure interaction, using analytical and semi-analytical approaches. Also topics such as fracturing and fatigue are discussed in the context of moving materials. The last part of the book deals with optimization problems involving physical constraints arising from the stability and fatigue analyses, including uncertainties in the parameters. The book is intended for researchers and specialists in the field, providin...
Institute of Scientific and Technical Information of China (English)
CHRIS; DEVONSHIRE-ELLIS
2008-01-01
Central China, initially overlooked by many foreign investors as being too far from the ports in Tianjin, Shanghai and Shenzhen, is emerging as an essential destination for multinationals in China.The Future of Central China: A Provincial Roadmap There is a huge manufacturing drive in central China. Businesses are moving inland to set up projects, investments and operations here, primarily due to lower labor and land costs as well as preferential policies for manufacturers. Multinational companies also are starting to view the region as the next step toward an integrated China strategy, and the consumer population in the second-and third-tier cities in central China represents a growing, largely untapped domestic market for foreign products and services.
2013-01-01
Are you curious to know whether you’re doing enough daily exercise…? Test yourself with a pedometer! Through the Move! Eat better campaign, launched in May 2012, the CERN medical service is aiming to improve the health of members of the personnel by encouraging them to prioritise physical activity in conjunction with a balanced diet. Various successful activities have already taken place: relay race/Nordic walk, Bike2work, Zumba and fitness workshops, two conferences (“Physical activity for health” and “Good nutrition every day”), events in the restaurants, as well as posters and a website. Although everyone has got the message from our various communications that physical activity is good for your health, there is still a relevant question being asked: “What is the minimum amount of exercise recommended?” 10,000 steps per day is the ideal figure, which has been demonstrated as beneficial by scientific studies ...
DEFF Research Database (Denmark)
Rai, Sudhanshu
In this article I discuss the Indian outsourcing phenomena and ask the question now what? Using data from the Euro-India project I demonstrate that a small but significant part of the Indian IT entities are moving beyond outsourcing, to co-creation where Innovation and the desire to create new...... markets is the key driver. This does not imply that outsourcing will disappear but it does mean that firms will engage in globalization using innovative mix of business models and technical platforms. We discuss the implication of this slow transformation to co-creation of innovation for the global...... outsourcing industry. The key thesis of this paper is to discuss co-creation as a form of innovation and how such a form of innovation is likely to bring Indian companies rich dividends....
Role of moving planes and moving spheres following Dupin cyclides
Jia, Xiaohong
2014-03-01
We provide explicit representations of three moving planes that form a μ-basis for a standard Dupin cyclide. We also show how to compute μ-bases for Dupin cyclides in general position and orientation from their implicit equations. In addition, we describe the role of moving planes and moving spheres in bridging between the implicit and rational parametric representations of these cyclides. © 2014 Elsevier B.V.
Large-scale flow generation by inhomogeneous helicity
Yokoi, Nobumitsu
2015-01-01
The effect of kinetic helicity (velocity--vorticity correlation) on turbulent momentum transport is investigated. The turbulent kinetic helicity (pseudoscalar) enters into the Reynolds stress (mirrorsymmetric tensor) expression in the form of a helicity gradient as the coupling coefficient for the mean vorticity and/or the angular velocity (axial vector), which suggests the possibility of mean-flow generation in the presence of inhomogeneous helicity. This inhomogeneous helicity effect, which was previously confirmed at the level of a turbulence- or closure-model simulation, is examined with the aid of direct numerical simulations of rotating turbulence with non-uniform helicity sustained by an external forcing. The numerical simulations show that the spatial distribution of the Reynolds stress is in agreement with the helicity-related term coupled with the angular velocity, and that a large-scale flow is generated in the direction of angular velocity. Such a large-scale flow is not induced in the case of hom...
A dynamical system approach to inhomogeneous dust solutions
Sussman, Roberto A
2007-01-01
We examine numerically and qualitatively the Lema\\^\\i tre--Tolman--Bondi (LTB) inhomogeneous dust solutions as a 3--dimensional dynamical system characterized by six critical points. One of the coordinates of the phase space is an average density parameter, $$, which behaves as the ordinary $\\Omega$ in Friedman-Lema\\^\\i tre--Robertson--Walker (FLRW) dust spacetimes. The other two coordinates, a shear parameter and a density contrast function, convey the effects of inhomogeneity. As long as shell crossing singularities are absent, this phase space is bounded or it can be trivially compactified. This space contains several invariant subspaces which define relevant particular cases, such as: ``parabolic'' evolution, FLRW dust and the Schwarzschild--Kruskal vacuum limit. We examine in detail the phase space evolution of several dust configurations: a low density void formation scenario, high density re--collapsing universes with open, closed and wormhole topologies, a structure formation scenario with a black hol...
An automatically generated code for relativistic inhomogeneous cosmologies
Bentivegna, Eloisa
2016-01-01
The applications of numerical relativity to cosmology are on the rise, contributing insight into such cosmological problems as structure formation, primordial phase transitions, gravitational-wave generation, and inflation. In this paper, I present the infrastructure for the computation of inhomogeneous dust cosmologies which was used recently to measure the effect of nonlinear inhomogeneity on the cosmic expansion rate. I illustrate the code's architecture, provide evidence for its correctness in a number of familiar cosmological settings, and evaluate its parallel performance for grids of up to several billion points. The code, which is available as free software, is based on the Einstein Toolkit infrastructure, and in particular leverages the automated-code-generation capabilities provided by its component Kranc.
TRANSMISSION AND ABSORPTION OF MICROWAVES BY AN INHOMOGENEOUS SPHERE PLASMA
Institute of Scientific and Technical Information of China (English)
SONG Falun; CAO Jinxiang; WANG Ge
2004-01-01
The numerical calculation of the transmission and absorption of microwaves at an arbitrarily incident angle to the inhomogeneous spherically symmetric plasma is presented.The nonuniform sphere is modeled by a series of concentric spherical shells, and the electron density is constant in each shell. The overall density profile follows any given distribution function. By using the geometrical optics approximation and considering the propagation coefficient is complex, as well as the attenuation and phase coefficients are vectors, the detailed evaluation shows that the transmission and absorption of microwaves in the inhomogeneous spherically symmetric plasma depend on the electron and neutral particle collision frequency, central density, incident angle of the microwaves and density distribution profiles.
Effect of inhomogeneities on high precision measurements of cosmological distances
Peel, Austin; Ishak, Mustapha
2014-01-01
We study exact relativistic effects of inhomogeneities on distance measures, focusing on the distance modulus, in a Swiss-cheese model of the universe with $\\Lambda$CDM background dynamics, and where the `holes' are non-symmetric structures described by the Szekeres metric. The Szekeres exact solution of Einstein's equations, which is inhomogeneous and anisotropic, allows us to capture potentially relevant effects on light propagation due to nontrivial evolution of structures. Unlike Swiss-cheese model studies with spherically symmetric holes, we find a net shift in the distance modulus $\\mu$ to distant sources even when we average over many lines of sight with randomized hole orientations and impact parameters. The light also need not propagate strictly through underdense regions to result in an overall bias, which is an accumulated effect associated with the evolution of the anisotropic holes. We find the average shift $\\langle\\Delta\\mu\\rangle$ relative to a pure $\\Lambda$CDM model to increase with redshift...
Generation of indirect combustion noise by compositional inhomogeneities
Magri, Luca; O'Brien, Jeff; Ihme, Matthias
2016-11-01
The generation of indirect combustion noise in nozzles and turbine stages is commonly attributed to temperature inhomogeneities and vorticity fluctuations. Here, compositional inhomogeneities in a multi-component gas mixture are shown to produce indirect noise both theoretically and numerically. The chemical potential function is introduced as an additional acoustic source mechanism. The contribution of the compositional noise is compared to the entropy noise and direct noise by considering subsonic, supersonic and shocked nozzles downstream of the combustor exit. It is shown that the compositional noise is dependent on the local mixture composition and can exceed entropy noise for fuel-lean conditions and supersonic/shocked nozzle flows. This suggests that compositional indirect combustion noise may require consideration with the implementation of advanced combustion concepts in gas turbines, including low-emissions combustors, high-power-density engine cores, or compact burners.
Spin diffusion from an inhomogeneous quench in an integrable system
Ljubotina, Marko; Žnidarič, Marko; Prosen, Tomaž
2017-07-01
Generalized hydrodynamics predicts universal ballistic transport in integrable lattice systems when prepared in generic inhomogeneous initial states. However, the ballistic contribution to transport can vanish in systems with additional discrete symmetries. Here we perform large scale numerical simulations of spin dynamics in the anisotropic Heisenberg XXZ spin 1/2 chain starting from an inhomogeneous mixed initial state which is symmetric with respect to a combination of spin reversal and spatial reflection. In the isotropic and easy-axis regimes we find non-ballistic spin transport which we analyse in detail in terms of scaling exponents of the transported magnetization and scaling profiles of the spin density. While in the easy-axis regime we find accurate evidence of normal diffusion, the spin transport in the isotropic case is clearly super-diffusive, with the scaling exponent very close to 2/3, but with universal scaling dynamics which obeys the diffusion equation in nonlinearly scaled time.
Determination of critical exponents of inhomogeneous Gd films
Energy Technology Data Exchange (ETDEWEB)
Rosales-Rivera, A., E-mail: arosalesr@unal.edu.co [Laboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia); Salazar, N.A. [Laboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia); Hovorka, O.; Idigoras, O.; Berger, A. [CIC nanoGUNE Consolider, Tolosa Hiribidea 76, E-20018 Donostia-San Sebastian (Spain)
2012-08-15
The role of inhomogeneity on the critical behavior is studied for non-epitaxial Gd films. For this purpose, the film inhomogeneity was varied experimentally by annealing otherwise identical samples at different temperatures T{sub AN}=200, 400, and 500 Degree-Sign C. Vibrating sample magnetometry (VSM) was used for magnetization M vs. T measurements at different external fields H. A method based upon the linear superposition of different sample parts having different Curie temperatures T{sub C} was used to extract the critical exponents and the intrinsic distribution of Curie temperatures. We found that this method allows extracting reliable values of the critical exponents for all annealing temperatures, which enabled us to study the effects of disorder onto the universality class of Gd films.
Enhancement of photoacoustic detection of inhomogeneities in polymers
Grondona, P; Iriarte, D I; Pomarico, J A; Ranea-Sandoval, Héctor F; Bilmes, G M
2013-01-01
We report a series of experiments on laser pulsed photoacoustic excitationin turbid polymer samples addressed to evaluate the sound speed in the samples and the presence of inhomogeneities in the bulk. We describe a system which allows the direct measurement of the speed of the detected waves by engraving the surface of the piece under study with a fiduciary pattern of black lines. We also describe how this pattern helps to enhance the sensitivity for the detection of an inhomogeneity in the bulk. These two facts are useful for studies in soft matter systems including, perhaps, biological samples. We have performed an experimental analysis on Grilon(R) samples in different situations and we show the limitations of the method.
Two-step estimation for inhomogeneous spatial point processes
DEFF Research Database (Denmark)
Waagepetersen, Rasmus; Guan, Yongtao
2009-01-01
The paper is concerned with parameter estimation for inhomogeneous spatial point processes with a regression model for the intensity function and tractable second-order properties (K-function). Regression parameters are estimated by using a Poisson likelihood score estimating function and in the ......The paper is concerned with parameter estimation for inhomogeneous spatial point processes with a regression model for the intensity function and tractable second-order properties (K-function). Regression parameters are estimated by using a Poisson likelihood score estimating function...... and in the second step minimum contrast estimation is applied for the residual clustering parameters. Asymptotic normality of parameter estimates is established under certain mixing conditions and we exemplify how the results may be applied in ecological studies of rainforests....
Twisted inhomogeneous Diophantine approximation and badly approximable sets
Harrap, Stephen
2010-01-01
For any real pair i, j geq 0 with i+j=1 let Bad(i, j) denote the set of (i, j)-badly approximable pairs. That is, Bad(i, j) consists of irrational vectors x:=(x_1, x_2) in R^2 for which there exists a positive constant c(x) such that max {||qx_1||^(-i), ||qx_2||^(-j)} > c(x)/q for all q in N. Building on a result of Kurzweil, a new characterization of the set Bad(i, j) in terms of `well-approximable' vectors in the area of `twisted' inhomogeneous Diophantine approximation is established. In addition, it is shown that Bad^x(i, j), the `twisted' inhomogeneous analogue of Bad(i, j), has full Hausdorff dimension 2 when x is chosen from the set Bad(i, j).
Stability analysis for bad cavity lasers with inhomogeneously broadened gain
Kazakov, Georgy A
2016-01-01
Bad cavity lasers are experiencing renewed interest in the context of active optical frequency standards, due to their enhanced robustness against fluctuations of the laser cavity. The gain medium would consist of narrow-linewidth atoms, either trapped inside the cavity or intersecting the cavity mode dynamically. A finite velocity distribution, atomic interactions, or interactions of realistic multilevel atoms with external field leads to an inhomogeneous broadening of the atomic gain profile. This can bring the bad cavity laser to operate in unstable regimes characterized by complex temporal patterns of the field amplitude. We present a new and efficient method for the stability analysis of bad cavity lasers with inhomogeneously broadened gain. We apply this method to identify the steady-state solutions for the metrology-relevant case of spin-1/2 atoms interacting with an external magnetic field.
Potential generated by a massive inhomogeneous straight segment
Institute of Scientific and Technical Information of China (English)
Nour-Eddine Najid; El Haj Elourabi; Mohamed Zegoumou
2011-01-01
The discoveries of binary asteroids have opened an important new field of research concerning the calculation of potential generated by irregular bodies. Some of them have an elongated shape. A simple model to describe the motion of a test parficle in that kind of potential requires consideration of a finite homogeneous straight segment. We construct this model by adding an inhomogeneous distribution of mass.To be consistent with the geometrical shape of the asteroid, we explore a parabolic profile of the density. We establish the closed analytical form of the potential generated by this inhomogeneous massive segment. The study of the dynamical behavior is fulfilled by the use of Lagrangian formulation, which allows us to calculate some two and three dimensional orbits.
Geometric spin Hall effect of light with inhomogeneous polarization
Ling, Xiaohui; Zhou, Xinxing; Yi, Xunong
2017-01-01
The spin Hall effect of light originates from spin-orbit interaction of light, which manifests two types of geometric phases. In this paper, we report the observation of a geometric spin Hall effect by generating a light beam with inhomogeneous polarization distribution. Unlike the previously reported geometric spin Hall effect observed in a tilted beam-detector system, which is believed to result from an effective spin-redirection Berry geometric phase, the geometric spin Hall effect demonstrated here is attributed to an effective, spatially varying Pancharatnam-Berry geometric phase generated by the inhomogeneous polarization geometry. Our further experiments show that the geometric spin Hall effect can be tuned by tailoring the polarization geometry of light, demonstrating the spin states of photons can be steered with a great flexibility.
Glauber theory and the quantum coherence of curvature inhomogeneities
Giovannini, Massimo
2016-01-01
The curvature inhomogeneities are systematically scrutinized in the framework of the Glauber approach. The amplified quantum fluctuations of the scalar and tensor modes of the geometry are shown to be first-order coherent while the interference of the corresponding intensities is larger than in the case of Bose-Einstein correlations. After showing that the degree of second-order coherence does not suffice to characterize unambiguously the curvature inhomogeneities, we argue that direct analyses of the degrees of third and fourth-order coherence are necessary to discriminate between different correlated states and to infer more reliably the statistical properties of the large-scale fluctuations. We speculate that the moments of the multiplicity distributions of the relic phonons might be observationally accessible thanks to new generations of instruments able to count the single photons of the Cosmic Microwave Background in the THz region.
Acoustic Wavefront Manipulation: Impedance Inhomogeneity and Extraordinary Reflection
Zhao, Jiajun; Chen, Zhining; Li, Baowen
2013-01-01
Optical wavefront can be manipulated by interfering elementary beams with phase inhomogeneity. Therefore a surface allowing huge, abrupt and position-variant phase change would enable all possibilities of wavefront engineering. However, one may not have the luxury of efficient abrupt-phase-changing materials in acoustics. This motivates us to establish a counterpart mechanism for acoustics, in order to empower the wide spectrum of novel acoustic applications. Remarkably, the proposed impedance-governed generalized Snell's law (IGSL) of reflection is distinguished from that in optics. Via the manipulation of inhomogeneous acoustic impedance, extraordinary reflection can be tailored for unprecedented wavefront manipulation while ordinary reflection can be surprisingly switched on or off. Our results may power the acoustic-wave manipulation and engineering. We demonstrate novel acoustic applications by planar surfaces designed with IGSL.
Glauber theory and the quantum coherence of curvature inhomogeneities
Giovannini, Massimo
2017-02-01
The curvature inhomogeneities are systematically scrutinized in the framework of the Glauber approach. The amplified quantum fluctuations of the scalar and tensor modes of the geometry are shown to be first-order coherent while the interference of the corresponding intensities is larger than in the case of Bose–Einstein correlations. After showing that the degree of second-order coherence does not suffice to characterize unambiguously the curvature inhomogeneities, we argue that direct analyses of the degrees of third- and fourth-order coherence are necessary to discriminate between different correlated states and to infer more reliably the statistical properties of the large-scale fluctuations. We speculate that the moments of the multiplicity distributions of the relic phonons might be observationally accessible thanks to new generations of instruments able to count the single photons of the Cosmic Microwave Background in the THz region.
Phase conjugation by four-wave mixing in inhomogeneous plasmas
Williams, Edward A.; Lininger, Diana M.; Goldman, Martin V.
1989-01-01
The effects of density, temperature, and velocity gradients on four-wave mixing (FWM) in a plasma are investigated. A fluid model is used in which the stimulated Brillouin terms are included, but pump depletion is neglected. The steady state phase conjugate reflectivity and signal transmission coefficients are calculated and discussed for both degenerate and resonant FWM. The substantial effects of inhomogeneity on the use of FWM as a plasma diagnostic are discussed.
Integration of inhomogeneous cosmological spacetimes in the BSSN formalism
Mertens, James B; Starkman, Glenn D
2015-01-01
We present cosmological-scale numerical simulations of an evolving universe in full general relativity (GR) and introduce a new numerical tool, {\\sc CosmoGRaPH}, which employs the Baumgarte-Shapiro-Shibata-Nakamura (BSSN) formalism on a 3-dimensional grid. Using {\\sc CosmoGRaPH}, we calculate the effect of an inhomogeneous matter distribution on the evolution of a spacetime. We also present the results of a set of standard stability tests to demonstrate the robustness of our simulations.
Two-step estimation for inhomogeneous spatial point processes
DEFF Research Database (Denmark)
Waagepetersen, Rasmus; Guan, Yongtao
This paper is concerned with parameter estimation for inhomogeneous spatial point processes with a regression model for the intensity function and tractable second order properties (K-function). Regression parameters are estimated using a Poisson likelihood score estimating function and in a second...... step minimum contrast estimation is applied for the residual clustering parameters. Asymptotic normality of parameter estimates is established under certain mixing conditions and we exemplify how the results may be applied in ecological studies of rain forests....
Characterization of residual stresses generated during inhomogeneous plastic deformation
DEFF Research Database (Denmark)
Lorentzen, T.; Faurholdt, T.; Clausen, B.;
1998-01-01
Residual stresses generated by macroscopic inhomogeneous plastic deformation are predicted by an explicit finite element (FE) technique. The numerical predictions are evaluated by characterizing the residual elastic strains by neutron diffraction using two different (hkl) reflections. Intergranular...... residual elastic strains between subsets of grains are predicted numerically and verified by neutron diffraction. Subsequently, the measured residual strain profiles in the test samples are modified by the intergranular strains and compared to the engineering predictions of the FE technique. Results...
Polarized beam splitting effect in inhomogeneously magnetized magnetooptic films.
Waring, M
1989-10-15
Linearly polarized light passing through a several micron thick magnetooptic film in the inhomogeneous magnetization state is split into a linearly polarized central beam and linearly polarized first and higher order diverging rings. The polarization of the central output beam lies in the same direction as the linearly polarized input, while the polarization of the diverging rings lies in a direction orthogonal to the input plane of polarization. The effect is described, and applications of the effect are discussed.
Investigation of effects of inhomogeneous exchange within ferrites
Energy Technology Data Exchange (ETDEWEB)
Kuetche, Victor K., E-mail: vkuetche@yahoo.fr [National Advanced School of Engineering, University of Yaounde I, P.O. Box 8390 (Cameroon); Centre d' Excellence en Technologies de l' Information et de la Communication (CETIC), University of Yaounde I, P.O. Box 812 (Cameroon); Department of Physics, Faculty of Science, University of Yaounde I, P.O. Box 812 (Cameroon); The Abdus Salam International Centre for Theoretical Physics (ICTP), Strada Costiera, 11-I-34151 Trieste (Italy); Nguepjouo, Francis T., E-mail: nguepjouofrancis@yahoo.fr [National Advanced School of Engineering, University of Yaounde I, P.O. Box 8390 (Cameroon); Centre d' Excellence en Technologies de l' Information et de la Communication (CETIC), University of Yaounde I, P.O. Box 812 (Cameroon); Department of Physics, Faculty of Science, University of Yaounde I, P.O. Box 812 (Cameroon); Kofane, Timoleon C., E-mail: tckofane@yahoo.com [Centre d' Excellence en Technologies de l' Information et de la Communication (CETIC), University of Yaounde I, P.O. Box 812 (Cameroon); Department of Physics, Faculty of Science, University of Yaounde I, P.O. Box 812 (Cameroon); The Abdus Salam International Centre for Theoretical Physics (ICTP), Strada Costiera, 11-I-34151 Trieste (Italy)
2015-01-15
In this paper, we investigate the effects of inhomogeneous exchange on the magnetization dynamics within a ferromagnetic slab of 0.5 mm thickness from the viewpoint of the Landau–Lifshitz–Gilbert phenomenological theory of damping in ferromagnets. As a result, we unearth a new coupled system of magnetization dynamics in which structural analysis reveals the existence of soliton propagation in the above ferrite.
Energy Density Inhomogeneities with Polynomial $f(R)$ Cosmology
Sharif, M.; Yousaf, Z.
2014-01-01
In this paper, we study the effects of polynomial $f(R)$ model on the stability of homogeneous energy density in self-gravitating spherical stellar object. For this purpose, we construct couple of evolution equations which relate the Weyl tensor with matter parameters. We explore different factors responsible for density inhomogeneities with non-dissipative dust, isotropic as well as anisotropic fluids and dissipative dust cloud. We find that shear, pressure, dissipative parameters and $f(R)$...
NQR Spin Diffusion in an Inhomogeneous Internal Field
Energy Technology Data Exchange (ETDEWEB)
Furman, Gregory B., E-mail: gregoryf@bgu.ac.il; Goren, Shaul D. [Ben Gurion University, Physics Department (Israel)
2004-12-15
The theory of NQR spin diffusion is extended to the case of spin lattice relaxation and spin diffusion in an inhomogeneous field. Two coupled equations describing the mutual relaxation and the spin diffusion of the nuclear magnetization and dipolar energy were obtained by using the method of nonequilibrium state operator. The equations were solved for short and long times approximation corresponding to the direct and diffusion relaxation regimes.
Robust Manipulation and Computation for Inhomogeneous Quantum Ensembles
2013-07-01
IEEE Transactions on Automatic Control (accepted). 2. A. Zlotnik, Y. Chen, I. Z. Kiss, H.-A. Tanaka...Dasanayake, and J. Ruths, “Control and Synchronization of Neuron Ensembles”, IEEE Transactions on Automatic Control (in press). 4. D. Stefanatos and J.-S...J.-S. Li, “Optimal Control of Inhomogeneous Ensembles”, IEEE Transactions on Automatic Control : Special Issue on Control of Quantum Mechanical
Della Mussia, S
2004-01-01
The first large active detector component was lowered into the ATLAS cavern on 1st March. It consisted of the 8 modules forming the lower part of the central barrel of the tile hadronic calorimeter. The work of assembling the barrel, which comprises 64 modules, started the following day. Two road trailers each with 64 wheels, positioned side by side. This was the solution chosen to transport the lower part of the central barrel of ATLAS' tile hadronic calorimeter from Building 185 to the PX16 shaft at Point 1 (see Figure 1). The transportation, and then the installation of the component in the experimental cavern, which took place over three days were, to say the least, rather spectacular. On 25 February, the component, consisting of eight 6-metre modules, was loaded on to the trailers. The segment of the barrel was transported on a steel support so that it wouldn't move an inch during the journey. On 26 February, once all the necessary safety checks had been carried out, the convoy was able to leave Buildi...
Institute of Scientific and Technical Information of China (English)
撒哈拉
2005-01-01
还怀念当年跳舞毯风靡的时光吗？左脚、右脚向前．向后，在不经意间展示你炫目的舞步。而最近PS2平台上的《EyeToy》让我们又接触到了一种需要游戏者舞动身体来参与的摄像头游戏．既玩了游戏又锻炼了身体．而昂达Eyebob摄像头让PC用户也能参与其中。想要玩玩摄像头游戏．现在不用转投Ps2的阵营．也不用改造你的硬件．只要你拥有一款摄像头．你就可以和家人与朋友轻松享受游戏的乐趣。来吧！Come on! Move your body now!
2012-01-01
CERN has many traditions, but in a week that’s seen the launch of the Medical Service’s ‘Move & eat better’ campaign, it’s refreshing to note that among the oldest is a sporting one. The CERN relay race dates back to 15 October 1971 when 21 pioneering teams set off to pound the pavements of CERN. Back then, the Focus users group came in first with a time of 12 minutes and 42 seconds. Today’s route is slightly different, and the number of teams has risen to over 100, with a new category of Nordic Walking introduced, as part of the campaign, for the first time. The relay has provided some memorable events, and perhaps one of the longest-standing records in the history of sport, with the UA1 strollers’ 10 minutes and 13 seconds unbeaten for thirty years. In the women’s category, the UN Gazelles set the fastest time of 13 minutes and 16 seconds in 1996, while in the veterans category, you wi...
Magnetostatic modes in ferromagnetic samples with inhomogeneous internal fields
Arias, Rodrigo
2015-03-01
Magnetostatic modes in ferromagnetic samples are very well characterized and understood in samples with uniform internal magnetic fields. More recently interest has shifted to the study of magnetization modes in ferromagnetic samples with inhomogeneous internal fields. The present work shows that under the magnetostatic approximation and for samples of arbitrary shape and/or arbitrary inhomogeneous internal magnetic fields the modes can be classified as elliptic or hyperbolic, and their associated frequency spectrum can be delimited. This results from the analysis of the character of the second order partial differential equation for the magnetostatic potential under these general conditions. In general, a sample with an inhomogeneous internal field and at a given frequency, may have regions of elliptic and hyperbolic character separated by a boundary. In the elliptic regions the magnetostatic modes have a smooth monotonic character (generally decaying form the surfaces (a ``tunneling'' behavior)) and in hyperbolic regions an oscillatory wave-like character. A simple local criterion distinguishes hyperbolic from elliptic regions: the sign of a susceptibility parameter. This study shows that one may control to some extent magnetostatic modes via external fields or geometry. R.E.A. acknowledges Financiamiento Basal para Centros Cientificos y Tecnologicos de Excelencia under Project No. FB 0807 (Chile), Grant No. ICM P10-061-F by Fondo de Innovacion para la Competitividad-MINECON, and Proyecto Fondecyt 1130192.
The magnitude-redshift relation in a realistic inhomogeneous universe
Hada, Ryuichiro
2014-01-01
The light rays from a source are subject to a local inhomogeneous geometry generated by inhomogeneous matter distribution as well as the existence of collapsed objects. In this paper we investigate the effect of inhomogeneities and the existence of collapsed objects on the propagation of light rays and evaluate changes in the magnitude-redshift relation from the standard relationship found in a homogeneous FRW universe. We give the expression of the correlation function and the variance for the perturbation of apparent magnitude, and calculate it numerically by using the non-linear matter power spectrum. We use the lognormal probability distribution function for the density contrast and spherical collapse model to truncate the power spectrum in order to estimate the blocking effect by collapsed objects. We find that the uncertainties in $\\Omega_m$ is $\\sim 0.02$, and that of $w$ is $\\sim 0.04$. We also discuss a possible method to extract these effects from real data which contains intrinsic ambiguities assoc...
Classical scattering of charged particles confined on an inhomogeneous helix
Zampetaki, A V; Krönke, S; Schmelcher, P
2013-01-01
We explore the effects arising due to the coupling of the center of mass and relative motion of two charged particles confined on an inhomogeneous helix with a locally modified radius. It is first proven that a separation of the center of mass and the relative motion is provided if and only if the confining manifold represents a homogeneous helix. In this case bound states of repulsively Coulomb interacting particles occur. For an inhomogeneous helix, the coupling of the center of mass and relative motion induces an energy transfer between the collective and relative motion, leading to dissociation of initially bound states in a scattering process. Due to the time reversal symmetry, a binding of the particles out of the scattering continuum is thus equally possible. We identify the regimes of dissociation for different initial conditions and provide an analysis of the underlying phase space via Poincar\\'e surfaces of section. Bound states inside the inhomogeneity as well as resonant states are identified.
A Level Set Approach to Image Segmentation With Intensity Inhomogeneity.
Zhang, Kaihua; Zhang, Lei; Lam, Kin-Man; Zhang, David
2016-02-01
It is often a difficult task to accurately segment images with intensity inhomogeneity, because most of representative algorithms are region-based that depend on intensity homogeneity of the interested object. In this paper, we present a novel level set method for image segmentation in the presence of intensity inhomogeneity. The inhomogeneous objects are modeled as Gaussian distributions of different means and variances in which a sliding window is used to map the original image into another domain, where the intensity distribution of each object is still Gaussian but better separated. The means of the Gaussian distributions in the transformed domain can be adaptively estimated by multiplying a bias field with the original signal within the window. A maximum likelihood energy functional is then defined on the whole image region, which combines the bias field, the level set function, and the piecewise constant function approximating the true image signal. The proposed level set method can be directly applied to simultaneous segmentation and bias correction for 3 and 7T magnetic resonance images. Extensive evaluation on synthetic and real-images demonstrate the superiority of the proposed method over other representative algorithms.
Dispersion properties of helical waves in radially inhomogeneous elastic media.
Syresin, D E; Zharnikov, T V; Tyutekin, V V
2012-06-01
In this paper, a method describing dispersion curve calculation for waves propagating in radially layered, inhomogeneous isotropic elastic waveguides is developed. Particular emphasis is placed on the helical waves with noninteger azimuthal wavenumbers, which can be potentially applied in such fields as nondestructive evaluation, acoustic tomography, etc., stipulating their practical importance. To solve the problem under consideration, the matrix Riccati equation is formulated for an impedance matrix. The use of the latter yields a simple form of the dispersion equation. Numerical computation of dispersion curves can encounter difficulties, which are due to potential singularities of the impedance matrix and the necessity to separate roots of the dispersion equation. These difficulties are overcome by employing the Cayley transform and invoking the parametric continuation method. The method developed by the authors is demonstrated by calculating dispersion diagrams in support of helical waves for several models of practical interest. Such computations for an inhomogeneous layer and its approximation by a set of homogeneous layers using a transfer matrix and Riccati equation methods revealed higher computational accuracy of the latter. Dispersion curves calculated for layers with different types of inhomogeneity demonstrated significant discrepancies at low frequencies.
Fluorescence-lifetime-based sensors using inhomogeneous waveguiding
Draxler, Sonja; Kieslinger, Dietmar; Trznadel, Karolina; Lippitsch, Max E.
1996-12-01
Most intrinsic fiberoptic sensors are based on the evanescent-wave scheme, where the evanescent field of modes guided in a fiber reaches out into a chemically sensitive coating. In the commonly used multimode waveguides, the evanescent field contains only a small part of the total energy, however, thus making evanescent-wave sensors rather insensitive. Combining a transparent substrate and a transparent sensing layer of rather similar refractive index into a common waveguiding structure produces an inhomogeneous waveguide, where a large portion of the total energy transverses the sensing layer. This yields much superior sensor performance. The transmission through a waveguide is subject to various disturbing influences. Thus it is advantageous to combine the inhomogeneous waveguiding approach with a measuring scheme that is not prone to those disturbances. Such a scheme is available with fluorescence lifetime-based sensors. The fluorescence lifetime of an indicator incorporated into the sensing layer is changed by the presence of the respective analyte. This lifetime is independent of the transmission through the waveguide. Thus inhomogeneous waveguiding together with fluorescence lifetime measurement paves the way for optical chemical sensors with high analyte sensitivity and immunity to external disturbances.
Inhomogeneous chiral symmetry breaking in dense neutron-star matter
Energy Technology Data Exchange (ETDEWEB)
Buballa, Michael; Carignano, Stefano [Technische Universitaet Darmstadt, Theoriezentrum, Institut fuer Kernphysik, Darmstadt (Germany)
2016-03-15
An increasing number of model results suggests that chiral symmetry is broken inhomogeneously in a certain window at intermediate densities in the QCD phase diagram. This could have significant effects on the properties of compact stars, possibly leading to new astrophysical signatures. In this contribution we discuss this idea by reviewing recent results on inhomogeneous chiral symmetry breaking under an astrophysics-oriented perspective. After introducing two commonly studied spatial modulations of the chiral condensate, the chiral density wave and the real kink crystal, we focus on their properties and their effect on the equation of state of quark matter. We also describe how these crystalline phases are affected by different elements which are required for a realistic description of a compact star, such as charge neutrality, the presence of magnetic fields, vector interactions and the interplay with color superconductivity. Finally, we discuss possible signatures of inhomogeneous chiral symmetry breaking in the core of compact stars, considering the cases of mass-radius relations and neutrino emissivity explicitly. (orig.)
Laser pulse propagation in inhomogeneous magnetoplasma channels and wakefield acceleration
Energy Technology Data Exchange (ETDEWEB)
Sharma, B. S., E-mail: bs-phy@yahoo.com; Jain, Archana [Government College Kota, Kota 324001 (India); Jaiman, N. K. [Department of Pure and Applied Physics, University of Kota, Kota 324010 (India); Gupta, D. N. [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Jang, D. G.; Suk, H. [Department of Physics and Photon Science, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Kulagin, V. V. [Sternberg Astronomical Institute of Moscow State University, Moscow 119992 (Russian Federation)
2014-02-15
Wakefield excitation in a preformed inhomogeneous parabolic plasma channel by an intense relativistic (≃10{sup 19} W/cm{sup 2}) circularly polarized Gaussian laser pulse is investigated analytically and numerically in the presence of an external longitudinal magnetic field. A three dimensional envelope equation for the evolution of the laser pulse is derived, which includes the effect of the nonparaxial and applied external magnetic field. A relation for the channel radius with the laser spot size is derived and examines numerically to see the external magnetic field effect. It is observed that the channel radius depends on the applied external magnetic field. An analytical expression for the wakefield is derived and validated with the help of a two dimensional particle in cell (2D PIC) simulation code. It is shown that the electromagnetic nature of the wakes in an inhomogeneous plasma channel makes their excitation nonlocal, which results in change of fields with time and external magnetic field due to phase mixing of the plasma oscillations with spatially varying frequencies. The magnetic field effect on perturbation of the plasma density and decreasing length is also analyzed numerically. In addition, it has been shown that the electron energy gain in the inhomogeneous parabolic magnetoplasma channel can be increased significantly compared with the homogeneous plasma channel.
COMMENT: Comment on `Inhomogeneities and birefringence in quartz'
Saint-Grégoire, P.; Luk'yanchuk, I.
1999-10-01
We comment on the role of the novel incommensurate elongated-triangle (ELT) phase in the huge light scattering in quartz at small angles that was observed more than 40 years ago at the icons/Journals/Common/alpha" ALT="alpha" ALIGN="TOP"/>-icons/Journals/Common/beta" ALT="beta" ALIGN="TOP"/> phase transition and was associated with optical inhomogeneities of unknown nature. The relation of these inhomogeneities with the differently oriented ferroelastic blocks of the ELT phase proposed by us and co-workers in a previous publication was misinterpreted and criticized in a recent article by Aslanyan et al (Aslanyan T E, Shigenari T and Abe K 1998 J. Phys.: Condens. Matter 10 4577), who claimed also that the lock-in occurs at qicons/Journals/Common/neq" ALT="neq" ALIGN="TOP"/>0. Responding to their criticism, we claim that the ELT blocks do have ferroelastic properties which induce the inhomogeneities of optical indices and that the lock-in occurs at q = 0.
Impact of cloud inhomogeneity on bi-directional reflectance
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
This paper uses SHDOM(Spherical Harmonics Discrete Ordinate Method)to calculate the nadir bidirectionaI reflectanee distribution function(BRDF)of the cumulus and stratocumulus fields at the wavelengths of 0.67 μm and 2.13 μm,and discusses the impact of cloud inhomogeneity on BRDF.The cloud fields are adopted from 13RC Phase Ⅱ.which are used to compare 3D radiative transfer models.The simulation results show that the cu field has 6% abnormal BRDF values(BRDF＞1)with the increase of solar zenith angle.Further analyses show that grid cells whose BRDF is greater than one gather together at the locaI trough of the top of cloud.These regions can receive not only the direct incident solar beam,but also the beam scattered by the higher cloud of its neighborhood.Hence,the BRDF of those regions is enhanced.The abnormal BRDF phenomenon shows that the cloud inhomogeneity can result in inconsistency between satellite observation and plane parallel theory,implying that the reflectance observed by high resolution satellite is maybe enhanced by the cloud 3D effects.Thus one should take this fact into account when using the product retrieved by these data.The dominant solar zenith angles are quite large in the mid-high altitude area,and the impact of cloud inhomogeneity on these areas may be more significant.
Large Scale Cosmological Anomalies and Inhomogeneous Dark Energy
Directory of Open Access Journals (Sweden)
Leandros Perivolaropoulos
2014-01-01
Full Text Available A wide range of large scale observations hint towards possible modifications on the standard cosmological model which is based on a homogeneous and isotropic universe with a small cosmological constant and matter. These observations, also known as “cosmic anomalies” include unexpected Cosmic Microwave Background perturbations on large angular scales, large dipolar peculiar velocity flows of galaxies (“bulk flows”, the measurement of inhomogenous values of the fine structure constant on cosmological scales (“alpha dipole” and other effects. The presence of the observational anomalies could either be a large statistical fluctuation in the context of ΛCDM or it could indicate a non-trivial departure from the cosmological principle on Hubble scales. Such a departure is very much constrained by cosmological observations for matter. For dark energy however there are no significant observational constraints for Hubble scale inhomogeneities. In this brief review I discuss some of the theoretical models that can naturally lead to inhomogeneous dark energy, their observational constraints and their potential to explain the large scale cosmic anomalies.
Modelling the inhomogeneous SiC Schottky interface
Gammon, P. M.; Pérez-Tomás, A.; Shah, V. A.; Vavasour, O.; Donchev, E.; Pang, J. S.; Myronov, M.; Fisher, C. A.; Jennings, M. R.; Leadley, D. R.; Mawby, P. A.
2013-12-01
For the first time, the I-V-T dataset of a Schottky diode has been accurately modelled, parameterised, and fully fit, incorporating the effects of interface inhomogeneity, patch pinch-off and resistance, and ideality factors that are both heavily temperature and voltage dependent. A Ni/SiC Schottky diode is characterised at 2 K intervals from 20 to 320 K, which, at room temperature, displays low ideality factors (n 8), voltage dependent ideality factors and evidence of the so-called "thermionic field emission effect" within a T0-plot, suggest significant inhomogeneity. Two models are used, each derived from Tung's original interactive parallel conduction treatment of barrier height inhomogeneity that can reproduce these commonly seen effects in single temperature I-V traces. The first model incorporates patch pinch-off effects and produces accurate and reliable fits above around 150 K, and at current densities lower than 10-5 A cm-2. Outside this region, we show that resistive effects within a given patch are responsible for the excessive ideality factors, and a second simplified model incorporating these resistive effects as well as pinch-off accurately reproduces the entire temperature range. Analysis of these fitting parameters reduces confidence in those fits above 230 K, and questions are raised about the physical interpretation of the fitting parameters. Despite this, both methods used are shown to be useful tools for accurately reproducing I-V-T data over a large temperature range.
Study of homogeneity and inhomogeneity phantom in CUDA EGS for small field dosimetry
Yani, Sitti; Rhani, Mohamad Fahdillah; Haryanto, Freddy; Arif, Idam
2017-02-01
CUDA EGS was CUDA implementation to simulate transport photon in a material based on Monte Carlo algorithm for X-ray imaging. The objective of this study was to investigate the effect of inhomogeneities in inhomogeneity phantom for small field dosimetry (1×1, 2×2, 3×3, 4×4 and 5×5 cm2). Two phantoms, homogeneity and inhomogeneity phantom were used. The interaction in homogeneity and inhomogeneity phantom was dominated by Compton interaction and multiple scattering. The CUDA EGS can represent the inhomogeneity effect in small field dosimetry by combining the grayscale curve between homogeneity and inhomogeneity phantom. The grayscale curve in inhomogeneity phantom is not asymmetric because of the existence of different material in phantom.
Inhomogeneous dephasing masks coherence lifetimes in ensemble measurements.
Pelzer, Kenley M; Griffin, Graham B; Gray, Stephen K; Engel, Gregory S
2012-04-28
An open question at the forefront of modern physical sciences is what role, if any, quantum effects may play in biological sensing and energy transport mechanisms. One area of such research concerns the possibility of coherent energy transport in photosynthetic systems. Spectroscopic evidence of long-lived quantum coherence in photosynthetic light-harvesting pigment protein complexes (PPCs), along with theoretical modeling of PPCs, has indicated that coherent energy transport might boost efficiency of energy transport in photosynthesis. Accurate assessment of coherence lifetimes is crucial for modeling the extent to which quantum effects participate in this energy transfer, because such quantum effects can only contribute to mechanisms proceeding on timescales over which the coherences persist. While spectroscopy is a useful way to measure coherence lifetimes, inhomogeneity in the transition energies across the measured ensemble may lead to underestimation of coherence lifetimes from spectroscopic experiments. Theoretical models of antenna complexes generally model a single system, and direct comparison of single system models to ensemble averaged experimental data may lead to systematic underestimation of coherence lifetimes, distorting much of the current discussion. In this study, we use simulations of the Fenna-Matthews-Olson complex to model single complexes as well as averaged ensembles to demonstrate and roughly quantify the effect of averaging over an inhomogeneous ensemble on measured coherence lifetimes. We choose to model the Fenna-Matthews-Olson complex because that system has been a focus for much of the recent discussion of quantum effects in biology, and use an early version of the well known environment-assisted quantum transport model to facilitate straightforward comparison between the current model and past work. Although ensemble inhomogeneity is known to lead to shorter lifetimes of observed oscillations (simply inhomogeneous spectral
Ghosh, Pranoy
2017-01-01
``A problem with defining force as rate of change of linear momentum'': Let us consider a body of mass m, moving with velocity u initially, in the next time interval it is acted by a force in the direction of motion, and at instant t + its mass is M and velocity v. F .t =Mv-mu or,v = m/M.u +F/M.t or,v =B.u +A.t where A =F/M,B =m/M. So other eqn of motion are: dS =vdt or dS =(B.u +A.t)dt or S =B.u.t +A/2.t2 Andv2 =B2 u2 +2A .B .u .t +A2 t2 or,v2 =B2 u2 +2A.S However, defining acceleration as rate of change of velocity, we have established an identity v =u +a.t which is independent of choice of v, u. M>>m, B is very small, product B.u or its higher power always tend to be negligible, even in cases when u is finitely large.In cases v ->c,F,M -> ∞ , thus A becomes indeterminate.There is inconvenience as A, B are not predetermined and are functions of u, v and thus the definition goes in circle. Hence we conclude, our hypothesis that force =rate of change of linear momentum is not sufficient; we would now find trial solutions to define force in most convenient way.
Enhancement and stabilization of traffic flow by moving in groups.
Kurata, S; Nagatani, T
2001-07-01
We study the traffic behavior of vehicles moving in groups analytically and numerically. A car-following model of traffic is extended to take into account a binary mixture of vehicles. It is shown that the movement in groups stabilizes the traffic flow. The jamming transition among the free traffic, the inhomogeneous traffic, and the homogeneous congested traffic occurs at a higher density than the threshold of the original model. The traffic current is highly enhanced at a high-density region by keeping a short headway without jam. The jamming transition is analyzed by using the linear stability method. It is found that the theoretical neutral stability curve agrees with the transition line obtained by the simulation.
Repetition priming from moving faces.
Lander, Karen; Bruce, Vicki
2004-06-01
Recent experiments have suggested that seeing a familiar face move provides additional dynamic information to the viewer, useful in the recognition of identity. In four experiments, repetition priming was used to investigate whether dynamic information is intrinsic to the underlying face representations. The results suggest that a moving image primes more effectively than a static image, even when the same static image is shown in the prime and the test phases (Experiment 1). Furthermore, when moving images are presented in the test phase (Experiment 2), there is an advantage for moving prime images. The most priming advantage is found with naturally moving faces, rather than with those shown in slow motion (Experiment 3). Finally, showing the same moving sequence at prime and test produced more priming than that found when different moving sequences were shown (Experiment 4). The results suggest that dynamic information is intrinsic to the face representations and that there is an advantage to viewing the same moving sequence at prime and test.
Congestion and residential moving behaviour
DEFF Research Database (Denmark)
Larsen, Morten Marott; Pilegaard, Ninette; Van Ommeren, Jos
2008-01-01
we study how congestion and residential moving behaviour are interrelated, using a two-region job search model. Workers choose between interregional commuting and residential moving, in order to live closer to their place of work. This choice affects the external costs of commuting, due...
Scattering of a spherical pulse from a small inhomogeneity: Dilation and rotation
Indian Academy of Sciences (India)
M D Sharma
2001-09-01
Perturbations in elastic constants and density distinguish a volume inhomogeneity from its homogeneous surroundings. The equation of motion for the first order scattering is studied in the perturbed medium. The scattered waves are generated by the interaction between the primary waves and the inhomogeneity. First order scattering theory is modified to include the source term generating the primary waves. The body force equivalent to the scattering source is presented in a convenient form involving the perturbations in wave velocities and gradient of density perturbation. A procedure is presented to study the scattering of a spherical pulse from a small inhomogeneity, in time domain. The size of inhomogeneity is assumed small as compared to its distance from source and receiver. No restrictions are placed on the positions of source, receiver and inhomogeneity. The dilatation and rotations are calculated for a pulse scattered from an arbitrary point in a spherical volume. The aggregate of the scattered phases from all the points of the inhomogeneity, reaching at a fixed receiver, gives the amount of scattering from the inhomogeneity. The interaction of both P and S waves with inhomogeneity are considered. Dilatation and rotations for scattering are obtained as integral expressions over the solid angle of inhomogeneity. These expressions are computed numerically, for hypothetical models. The effects of source (unit force) orientations, velocity and density perturbations, and size of inhomogeneity, on the scattered phases, are discussed.
Institute of Scientific and Technical Information of China (English)
LU Ming-Zhu; LIU Xue-Jin; SHI Yu; KANG Yan-Ni; GUAN Yu-Bo; WAN Ming-Xi
2012-01-01
We concentrate on the nondissipative mechanism induced shear wave in inhomogenous tissue.The shear wave equation of radiation force in inhomogeneous media is solved numerically with a finite-difference time-domain method.A rarely studied nondissipative mechanism of shear displacement due to a smooth medium inhomogeneity is evaluated.It is noted that unlike the dissipative effect,the nondissipative action on a localized inhomogeneity with its hardness parameter changing smoothly along the beam axis,compresses or stretches the focus area.The shear waves in nondissipative inhomogeneous media remain the property of sharp turn with 100％ peak positive displacement and 64％ peak negative displacement.This action is useful in discerning the water-like lesion.%We concentrate on the nondissipative mechanism induced shear wave in inhomogenous tissue. The shear wave equation of radiation force in inhomogeneous media is solved numerically with a finite-difference time-domain method. A rarely studied nondissipative mechanism of shear displacement due to a smooth medium inhomogeneity is evaluated. It is noted that unlike the dissipative effect, the nondissipative action on a localized inhomogeneity with its hardness parameter changing smoothly along the beam axis, compresses or stretches the focus area. The shear waves in nondissipative inhomogeneous media remain the property of sharp turn with 100% peak positive displacement and 64% peak negative displacement. This action is useful in discerning the water-like lesion.
Energy Technology Data Exchange (ETDEWEB)
Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2017-04-15
It is generally accepted that in order to describe the dynamics of relativistic particles in the laboratory (lab) frame it is sufficient to take into account the relativistic dependence of the particle momenta on the velocity. This solution of the dynamics problem in the lab frame makes no reference to Lorentz transformations. For this reason they are not discussed in particle tracking calculations in accelerator and plasma physics. It is generally believed that the electrodynamics problem can be treated within the same ''single inertial frame'' description without reference to Lorentz transformations. In particular, in order to evaluate radiation fields arising from charged particles in motion we need to know their velocities and positions as a function of the lab frame time t. The relativistic motion of a particle in the lab frame is described by Newton's second law ''corrected'' for the relativistic dependence of momentum on velocity. It is assumed in all standard derivations that one can perform identification of the trajectories in the source part of the usual Maxwell's equations with the trajectories vector x(t) measured (or calculated by using the corrected Newton's second law) in the lab frame. This way of coupling fields and particles is considered since more than a century as the relativistically correct procedure.We argue that this procedure needs to be changed, and we demonstrate the following, completely counterintuitive statement: the results of conventional theory of radiation by relativistically moving charges are not consistent with the principle of relativity. In order to find the trajectory of a particle in the lab frame consistent with the usual Maxwell's equations, one needs to solve the dynamic equation inmanifestly covariant form by using the coordinate-independent proper time τ to parameterize the particle world-line in space-time. We show that there is a difference between &apos
NMR, MRI, and spectroscopic MRI in inhomogeneous fields
Demas, Vasiliki; Pines, Alexander; Martin, Rachel W; Franck, John; Reimer, Jeffrey A
2013-12-24
A method for locally creating effectively homogeneous or "clean" magnetic field gradients (of high uniformity) for imaging (with NMR, MRI, or spectroscopic MRI) both in in-situ and ex-situ systems with high degrees of inhomogeneous field strength. THe method of imaging comprises: a) providing a functional approximation of an inhomogeneous static magnetic field strength B.sub.0({right arrow over (r)}) at a spatial position {right arrow over (r)}; b) providing a temporal functional approximation of {right arrow over (G)}.sub.shim(t) with i basis functions and j variables for each basis function, resulting in v.sub.ij variables; c) providing a measured value .OMEGA., which is an temporally accumulated dephasing due to the inhomogeneities of B.sub.0({right arrow over(r)}); and d) minimizing a difference in the local dephasing angle .phi.({right arrow over (r)},t)=.gamma..intg..sub.0.sup.t{square root over (|{right arrow over (B)}.sub.1({right arrow over (r)},t')|.sup.2+({right arrow over (r)}{right arrow over (G)}.sub.shimG.sub.shim(t')+.parallel.{right arrow over (B)}.sub.0({right arrow over (r)}).parallel..DELTA..omega.({right arrow over (r)},t'/.gamma/).sup.2)}dt'-.OMEGA. by varying the v.sub.ij variables to form a set of minimized v.sub.ij variables. The method requires calibration of the static fields prior to minimization, but may thereafter be implemented without such calibration, may be used in open or closed systems, and potentially portable systems.
Energy Technology Data Exchange (ETDEWEB)
Hamrin, J.G.
1980-01-01
Solar energy programs are entering a critical transitional period as we move from the initial marketing of solar technologies into a phase of widespread commercialization. We face the dual challenge of trying to get enough solar systems in place fast enough to prove solar is a viable alternative, while trying to ensure the systems are designed and installed properly, proving the energy savings as promised. This is a period of both great opportunity and high risk as the field becomes crowded with new solar cheerleaders and supporters but seldom enough competent players. The status of existing and proposed programs for the accelerated commercialization of solar energy in California is described.
Iorio, Lorenzo
2010-01-01
We, first, analytically work out the long-term, i.e. averaged over one orbital revolution, perturbations on the orbit of a test particle moving in a local Fermi frame induced therein by the cosmological tidal effects of the inhomogeneous Lemaitre-Tolman-Bondi (LTB) model. The LTB solution has recently attracted attention, among other things, as a possible explanation of the observed cosmic acceleration without resorting to dark energy. Then, we phenomenologically constrain both the parameters K_1 = -\\ddot R/R and K_2 = -\\ddot R^'/R^' of the LTB metric in the Fermi frame by using different kinds of solar system data. The corrections $\\Delta\\dot\\varpi$ to the standard Newtonian/Einsteinian precessions of the perihelia of the inner planets recently estimated with the EPM ephemerides, compared to our predictions for them, yield K_1 = (4+8) 10^-26 s^-2, K_2 = (3+7) 10^-23 s^-2. The residuals of the Cassini-based Earth-Saturn range, compared with the numerically integrated LTB range signature, allow to obtain K_1/2...
Kuchma, Anatoly; Shchekin, Alexander
2013-01-01
An analytical description of nucleation stage in a supersaturated vapor with instantly created supersaturation is given with taking into account the vapor concentration inhomogeneities arising as a result of depletion due to non-stationary diffusion onto growing droplets. This description suggests that the intensity of the nucleation of new droplets is suppressed in spherical diffusion regions of a certain size surrounding previously nucleated droplets, and remains at the initial level in the remaining volume of the vapor-gas medium. The value of volume excluded from nucleation depends on the explicit form of the vapor concentration profile in the space around the growing droplet, and we use for that the unsteady self-similar solution of time-dependent diffusion equation with a convective term describing the flow of the gas-vapor mixture caused by moving surface of single growing droplet. The main characteristics of the phase transition at the end of the nucleation stage are found and compared with those in t...
Wexler, Adam D; Drusová, Sandra; Woisetschläger, Jakob; Fuchs, Elmar C
2016-06-28
In this experiment liquid water is subject to an inhomogeneous electric field (∇(2)Ea≈ 10(10) V m(2)) using a high voltage (20 kV) point-plane electrode system. Using interferometry it was found that the application of a strong electric field gradient to water generates local changes in the refractive index of the liquid, polarizes the surface and creates a downward moving electro-convective jet. A maximum temperature difference of 1 °C is measured in the immediate vicinity of the point electrode. Raman spectroscopy performed on water reveals an enhancement of the vibrational collective modes (3250 cm(-1)) as well as an increase in the local mode (3490 cm(-1)) energy. This bimodal enhancement indicates that the spectral changes are not due to temperature changes. The intense field gradient thus establishes an excited subpopulation of vibrational oscillators far from thermal equilibrium. Delocalization of the collective vibrational mode spatially expands this excited population beyond the microscale. Hindered rotational freedom due to electric field pinning of molecular dipoles retards the heat flow and generates a chemical potential gradient. These changes are responsible for the observed changes in the refractive index and temperature. It is demonstrated that polar liquids can thus support local non-equilibrium thermodynamic transient states critical to biochemical and environmental processes.
Fault Induced Delayed Voltage Recovery in a Long Inhomogeneous Power Distribution Feeder
Stolbova, Irina; Chertkov, Michael
2014-01-01
We analyze the dynamics of a distribution circuit loaded with many induction motor and subjected to sudden changes in voltage at the beginning of the circuit. As opposed to earlier work \\cite{13DCB}, the motors are disordered, i.e. the mechanical torque applied to the motors varies in a random manner along the circuit. In spite of the disorder, many of the qualitative features of a homogenous circuit persist, e.g. long-range motor-motor interactions mediated by circuit voltage and electrical power flows result in coexistence of the spatially-extended and propagating normal and stalled phases. We also observed a new phenomenon absent in the case without inhomogeneity/disorder. Specifically, transition front between the normal and stalled phases becomes somewhat random, even when the front is moving very slowly or is even stationary. Motors within the blurred domain appears in a normal or stalled state depending on the local configuration of the disorder. We quantify effects of the disorder and discuss statisti...
Uncovering edge states and electrical inhomogeneity in MoS2 field-effect transistors.
Wu, Di; Li, Xiao; Luan, Lan; Wu, Xiaoyu; Li, Wei; Yogeesh, Maruthi N; Ghosh, Rudresh; Chu, Zhaodong; Akinwande, Deji; Niu, Qian; Lai, Keji
2016-08-02
The understanding of various types of disorders in atomically thin transition metal dichalcogenides (TMDs), including dangling bonds at the edges, chalcogen deficiencies in the bulk, and charges in the substrate, is of fundamental importance for TMD applications in electronics and photonics. Because of the imperfections, electrons moving on these 2D crystals experience a spatially nonuniform Coulomb environment, whose effect on the charge transport has not been microscopically studied. Here, we report the mesoscopic conductance mapping in monolayer and few-layer MoS2 field-effect transistors by microwave impedance microscopy (MIM). The spatial evolution of the insulator-to-metal transition is clearly resolved. Interestingly, as the transistors are gradually turned on, electrical conduction emerges initially at the edges before appearing in the bulk of MoS2 flakes, which can be explained by our first-principles calculations. The results unambiguously confirm that the contribution of edge states to the channel conductance is significant under the threshold voltage but negligible once the bulk of the TMD device becomes conductive. Strong conductance inhomogeneity, which is associated with the fluctuations of disorder potential in the 2D sheets, is also observed in the MIM images, providing a guideline for future improvement of the device performance.
Dynamics of optical rogue waves in inhomogeneous nonlinear waveguides
Institute of Scientific and Technical Information of China (English)
Zhang Jie-Fang; Jin Mei-Zhen; He Ji-Da; Lou Ji-Hui; Dai Chao-Qing
2013-01-01
We propose a unified theory to construct exact rogue wave solutions of the (2+1)-dimensional nonlinear Schr(o)dinger equation with varying coefficients.And then the dynamics of the first-and the second-order optical rogues are investigated.Finally,the controllability of the optical rogue propagating in inhomogeneous nonlinear waveguides is discussed.By properly choosing the distributed coefficients,we demonstrate analytically that rogue waves can be restrained or even be annihilated,or emerge periodically and sustain forever.We also figure out the center-of-mass motion of the rogue waves.
Hunting Local Mixmaster Dynamics in Spatially Inhomogeneous Cosmologies
Berger, B K
2004-01-01
Heuristic arguments and numerical simulations support the Belinskii et al (BKL) claim that the approach to the singularity in generic gravitational collapse is characterized by local Mixmaster dynamics (LMD). Here, one way to identify LMD in collapsing spatially inhomogeneous cosmologies is explored. By writing the metric of one spacetime in the standard variables of another, signatures for LMD may be found. Such signatures for the dynamics of spatially homogeneous Mixmaster models in the variables of U(1)-symmetric cosmologies are reviewed. Similar constructions for U(1)-symmetric spacetimes in terms of the dynamics of generic $T^2$-symmetric spacetime are presented.
Photon propagation in slowly varying inhomogeneous electromagnetic fields
Karbstein, Felix
2015-01-01
Starting from the Heisenberg-Euler effective Lagrangian, we determine the photon current and photon polarization tensor in inhomogeneous, slowly varying electromagnetic fields. To this end, we consider background field configurations varying in both space and time, paying special attention to the tensor structure. As a main result, we obtain compact analytical expressions for the photon polarization tensor in realistic Gaussian laser pulses, as generated in the focal spots of high-intensity lasers. These expressions are of utmost importance for the investigation of quantum vacuum nonlinearities in realistic high-intensity laser experiments.
Tailoring diffuse reflectance of inhomogeneous films containing microplatelets
Energy Technology Data Exchange (ETDEWEB)
Slovick, Brian A., E-mail: brian.slovick@sri.com; Baker, John M.; Flom, Zachary; Krishnamurthy, Srini [Applied Optics Laboratory, SRI International, Menlo Park, California 94025 (United States)
2015-10-05
We develop an analytical model for calculating the diffuse reflectance of inhomogeneous films containing aligned microplatelets with diameters much greater than the wavelength. The scattering parameters are derived by modeling the platelets as one-dimensional thin films, and the overall diffuse reflectance of the slab is calculated using the Kubelka-Munk model. Our model predicts that reflection minima and maxima arising from coherent interference within the platelets are preserved in the diffuse reflectance of the disordered slab. Experimental validation of the model is provided by reflectance measurements (0.3–15 μm) of a solid aerosol film of aligned hexagonal boron nitride platelets.
Motoneuron membrane potentials follow a time inhomogeneous jump diffusion process
DEFF Research Database (Denmark)
Jahn, Patrick; Berg, Rune W; Hounsgaard, Jørn
2011-01-01
Stochastic leaky integrate-and-fire models are popular due to their simplicity and statistical tractability. They have been widely applied to gain understanding of the underlying mechanisms for spike timing in neurons, and have served as building blocks for more elaborate models. Especially...... models can only be applied over short time windows. However, experimental data show varying time constants, state dependent noise, a graded firing threshold and time-inhomogeneous input. In the present study we build a jump diffusion model that incorporates these features, and introduce a firing...
Investigating inhomogeneous Szekeres models and their applications to precision cosmology
Peel, Austin Chandler
Exact solutions of Einstein's field equations that can describe the evolution of complex structures in the universe provide complementary frameworks to standard perturbation theory in which to analyze cosmological and astrophysical phenomena. The flexibility and generality of the inhomogeneous and anisotropic Szekeres metric make it the best known exact solution to explore nonlinearities in the universe. We study applications of Szekeres models to precision cosmology, focusing on the influence of inhomogeneities in two primary contexts---the growth rate of cosmic structures and biases in distance determinations to remote sources. We first define and derive evolution equations for a Szekeres density contrast, which quantifies exact deviations from a smooth background cosmology. Solving these equations and comparing to the usual perturbative approach, we find that for models with the same matter content, the Szekeres growth rate is larger through the matter-dominated cosmic era. Including a cosmological constant, we consider exact global perturbations, as well as the evolution of a single extended structure surrounded by an almost homogeneous background. For the former, we use growth data to obtain a best fit Szekeres model and find that it can fit the data as well as the standard Lambda-Cold Dark Matter (LCDM) cosmological model but with different cosmological parameters. Next, to study effects of inhomogeneities on distance measures, we build an exact relativistic Swiss-cheese model of the universe, where a large number of non-symmetric and randomly placed Szekeres structures are embedded within a LCDM background. Solving the full relativistic propagation equations, light beams are traced through the model, where they traverse the inhomogeneous structures in a way that mimics the paths of real light beams in the universe. For beams crossing a single structure, their magnification or demagnification reflects primarily the net density encountered along the path
Inhomogeneous critical current in nanowire superconducting single-photon detectors
Energy Technology Data Exchange (ETDEWEB)
Gaudio, R., E-mail: r.gaudio@tue.nl; Hoog, K. P. M. op ' t; Zhou, Z.; Sahin, D.; Fiore, A. [COBRA Research Institute, Eindhoven University of Technology, P.O. Box 513, NL-5600MB Eindhoven (Netherlands)
2014-12-01
A superconducting thin film with uniform properties is the key to realize nanowire superconducting single-photon detectors (SSPDs) with high performance and high yield. To investigate the uniformity of NbN films, we introduce and characterize simple detectors consisting of short nanowires with length ranging from 100 nm to 15 μm. Our nanowires, contrary to meander SSPDs, allow probing the homogeneity of NbN at the nanoscale. Experimental results, endorsed by a microscopic model, show the strongly inhomogeneous nature of NbN films on the sub-100 nm scale.
Gaussian beam diffraction in weakly anisotropic inhomogeneous media
Energy Technology Data Exchange (ETDEWEB)
Kravtsov, Yu.A., E-mail: kravtsov@am.szczecin.p [Institute of Physics, Maritime University of Szczecin, Szczecin 70-500 (Poland); Space Research Institute, Russian Academy of Science, Moscow 117 997 (Russian Federation); Berczynski, P., E-mail: pawel.berczynski@ps.p [Institute of Physics, West Pomeranian University of Technology, Szczecin 70-310 (Poland); Bieg, B., E-mail: b.bieg@am.szczecin.p [Institute of Physics, Maritime University of Szczecin, Szczecin 70-500 (Poland)
2009-08-10
Combination of quasi-isotropic approximation (QIA) of geometric optics with paraxial complex geometric optics (PCGO) is suggested, which allows describing both diffraction and polarization evolution of Gaussian electromagnetic beams in weakly anisotropic inhomogeneous media. Combination QIA/PCGO reduces Maxwell equations to the system of the ordinary differential equations of the first order and radically simplifies solution of various problems, related to microwave plasma diagnostics, including plasma polarimetry, interferometry and refractometry in thermonuclear reactors. Efficiency of the method is demonstrated by the example of electromagnetic beam diffraction in a linear layer of magnetized plasma with parameters, modeling tokamak plasma in the project ITER.
Ion-acoustic solitons in multispecies spatially inhomogeneous plasmas
Indian Academy of Sciences (India)
Tarsem Singh Gill; Harvinder Kaur; Nareshpal Singh Saini
2006-06-01
Ion-acoustic solitons are investigated in the spatially inhomogeneous plasma having electrons-positrons and ions. The soliton characteristics are described by Korteweg-de Vries equation which has an additional term. The density and temperature of different species play an important role for the amplitude and width of the solitons. Numerical calculations show only the possibility of compressive solitons. Further, analytical results predict that the peak amplitude of soliton decreases with the decrease of density gradient. Soliton characteristics like peak amplitude and width are substantially different from those based on KdV theory for homogeneous plasmas.
Generation of auroral kilometric radiation in inhomogeneous magnetospheric plasma
Burinskaya, T. M.; Shevelev, M. M.
2017-01-01
The generation of auroral kilometric radiation in a narrow 3D plasma cavity, in which a weakly relativistic electron flow is propagated along the magnetic field against a low-density cold background plasma, is studied. The time dynamics of the propagation and intensification of waves are analyzed using geometric optics equations. The waves have different wave vector components and start from the cavity center at an altitude of about the Earth's radius at plasma parameters typical for the auroral zone at this altitude. It is shown that the global inhomogeneity of the Earth's magnetic field is of key importance in shaping the auroral kilometric radiation spectra.
Estimation of geometrically undistorted B(0) inhomogeneity maps.
Matakos, A; Balter, J; Cao, Y
2014-09-01
Geometric accuracy of MRI is one of the main concerns for its use as a sole image modality in precision radiation therapy (RT) planning. In a state-of-the-art scanner, system level geometric distortions are within acceptable levels for precision RT. However, subject-induced B0 inhomogeneity may vary substantially, especially in air-tissue interfaces. Recent studies have shown distortion levels of more than 2 mm near the sinus and ear canal are possible due to subject-induced field inhomogeneity. These distortions can be corrected with the use of accurate B0 inhomogeneity field maps. Most existing methods estimate these field maps from dual gradient-echo (GRE) images acquired at two different echo-times under the assumption that the GRE images are practically undistorted. However distortion that may exist in the GRE images can result in estimated field maps that are distorted in both geometry and intensity, leading to inaccurate correction of clinical images. This work proposes a method for estimating undistorted field maps from GRE acquisitions using an iterative joint estimation technique. The proposed method yields geometrically corrected GRE images and undistorted field maps that can also be used for the correction of images acquired by other sequences. The proposed method is validated through simulation, phantom experiments and applied to patient data. Our simulation results show that our method reduces the root-mean-squared error of the estimated field map from the ground truth by ten-fold compared to the distorted field map. Both the geometric distortion and the intensity corruption (artifact) in the images caused by the B0 field inhomogeneity are corrected almost completely. Our phantom experiment showed improvement in the geometric correction of approximately 1 mm at an air-water interface using the undistorted field map compared to using a distorted field map. The proposed method for undistorted field map estimation can lead to improved geometric
Sensitivity of resistive and Hall measurements to local inhomogeneities
DEFF Research Database (Denmark)
Koon, Daniel W.; Wang, Fei; Petersen, Dirch Hjorth
2014-01-01
We derive exact, analytic expressions for the sensitivity of sheet resistance and Hall sheet resistance measurements to local inhomogeneities for the cases of nonzero magnetic fields, strong perturbations, and perturbations over a finite area, extending our earlier results on weak perturbations. We...... simulations on both a linear four-point probe array on a large circular disc and a van der Pauw square geometry. Furthermore, the results also agree well with Náhlík et al. published experimental results for physical holes in a circular copper foil disc....
Anomalous excitation facilitation in inhomogeneously broadened Rydberg gases
Letscher, Fabian; Niederprüm, Thomas; Ott, Herwig; Fleischhauer, Michael
2016-01-01
When atomic gases are laser driven to Rydberg states in an off resonant way, a single Rydberg atom may enhance the excitation rate of surrounding atoms. This leads to a facilitated excitation referred to as Rydberg anti-blockade. In the usual facilitation scenario, the detuning of the laser from resonance compensates the interaction shift. Here, we discuss a different excitation mechanism, which we call anomalous facilitation. This occurs on the "wrong side" of the resonance and originates from inhomogeneous broadening. The anomalous facilitation may be seen in experiments of attractively interacting atoms on the blue detuned side, where facilitation is not expected to appear.
The turbulent flow generated by inhomogeneous multiscale grids
Zheng, Shaokai; Bruce, Paul J. K.; Graham, J. Michael R.; Vassilicos, John Christos
2015-11-01
A group of inhomogeneous multiscale grids have been designed and tested in a low speed wind tunnel in an attempt to generate bespoke turbulent shear flows. Cross-wire anemometry measurements were performed in different planes parallel to the grid and at various streamwise locations to study turbulence development behind each of the different geometry grids. Two spatially separated single hot wires were also used to measure transverse integral length scale at selected locations. Results are compared to previous studies of shearless mixing layer grids and fractal grids, including mean flow profiles and turbulence statistics.
Sensitivity of charge transport measurements to local inhomogeneities
DEFF Research Database (Denmark)
Koon, Daniel; Wang, Fei; Petersen, Dirch Hjorth;
We derive analytic expressions for the sensitivity of resistive and Hall measurements to local variations in a specimen's material properties in the combined linear limit of both small magnetic fields and small perturbations, presenting exact, algebraic expressions both for four-point probe...... in the arbitrary case and of order N2 in the handful of cases that can be solved exactly, putting a powerful tool for inhomogeneity analysis in the hands of the researcher:calculation of the sensitivities requires little more than the solution of Laplace's equation on the specimen geometry....
Energy Imparted by Gravitational Waves in Inhomogeneous Space-times
Aydogdu, O; Aydogdu, Oktay; Salti, Mustafa
2006-01-01
In this paper, considering Einstein, Bergmann-Thomson and Landau-Lifshitz's energy-momentum definitions in both general relativity and teleparallel gravity, we compute the total energy distribution (due to matter and fields including gravitation) of the universe based on generalized inhomogeneous space-times. We obtain that Einstein and Bergmann-Thomson definitions of the energy-momentum complexes give the same results, while Landau-Lifshitz's energy-momentum definition does not provide same results for these type of metric. However, it is shown that the results obtained are reduced to the energy-momentum density of the Robertson-Walker space-times already available in the literature.
Inhomogeneous atomic Bose-Fermi mixtures in cubic lattices.
Cramer, M; Eisert, J; Illuminati, F
2004-11-05
We determine the ground state properties of inhomogeneous mixtures of bosons and fermions in cubic lattices and parabolic confining potentials. For finite hopping we determine the domain boundaries between Mott-insulator plateaux and hopping-dominated regions for lattices of arbitrary dimension within mean-field and perturbation theory. The results are compared with a new numerical method that is based on a Gutzwiller variational approach for the bosons and an exact treatment for the fermions. The findings can be applied as a guideline for future experiments with trapped atomic Bose-Fermi mixtures in optical lattices.
Dynamic modeling of presence of occupants using inhomogeneous Markov chains
DEFF Research Database (Denmark)
Andersen, Philip Hvidthøft Delff; Iversen, Anne; Madsen, Henrik
2014-01-01
on inhomogeneous Markov chains with where the transition probabilities are estimated using generalized linear models with polynomials, B-splines, and a filter of passed observations as inputs. For treating the dispersion of the data series, a hierarchical model structure is used where one model is for low presence......Occupancy modeling is a necessary step towards reliable simulation of energy consumption in buildings. This paper outlines a method for fitting recordings of presence of occupants and simulation of single-person to multiple-persons office environments. The method includes modeling of dependence...
MODELING OF NONLINEAR DEFORMATION AND BUCKLING OF ELASTIC INHOMOGENEOUS SHELLS
Directory of Open Access Journals (Sweden)
Bazhenov V.A.
2014-06-01
Full Text Available The paper outlines the fundamentals of the method of solving static problems of geometrically nonlinear deformation, buckling, and postbuckling behavior of thin thermoelastic inhomogeneous shells with complex-shaped mid-surface, geometrical features throughout the thickness, and multilayer structure under complex thermomechanical loading. The method is based on the geometrically nonlinear equations of three-dimensional thermoelasticity and the moment finiteelement scheme. The method is justified numerically. Comparing solutions with those obtained by other authors and by software LIRA and SCAD is conducted.
Numerical Research of Mode Conversion in an Inhomogeneous Plasma
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
The linear mode conversion of electromagnetic waves in the hot, unmagnetized inhomogeneous plasma is studied numerically for different density profiles, and the dependence of the absorption coefficient on the incident angles and the wave frequencies are obtained for different electrons' temperature. The results show that the shapes of the density profiles and the electron's temperature create a certain effect on the coefficients of absorption, which reaches its peak value (about 50%) for appropriate parameters. Effective absorption occurs in a limited range of parameter q.
The inhomogeneity expansion for planar QED in a magnetic background
Gat, G; Ray, R; Gat, Gil; Raval, Alpan; Ray, Rashmi
1994-01-01
The effective action for Q.E.D in external magnetic field is constructed using the method of inhomogeneity expansion. We first treat the non-relativistic case where a Chern-Simons like term is generated. We then consider the full relativistic theory and derive the effective action for the A_{\\mu} fields. In the non-relativistic case we also add a 4-fermi type interaction and show that under certain circumstances, it corresponds to a Zeeman type term in the effective action.
Optical bistabilities of higher harmonics: Inhomogeneous and transverse effects
Energy Technology Data Exchange (ETDEWEB)
Hassan, S.S., E-mail: Shoukryhassan@hotmail.com [Department of Mathematics, College of Science, University of Bahrain, P.O. Box 32038 (Bahrain); Manchester Metropolitan University, Dept. of Computing, Maths. and Digital Technology, Manchester M1 5GD (United Kingdom); Sharaby, Y.A., E-mail: Yasser_Sharaby@hotmail.com [Department of Physics, Faculty of Science, Suez Canal University, Suez (Egypt); Ali, M.F.M., E-mail: dr.mona.fathy@hotmail.com [Department of Mathematics: Faculty of Science, Ain Shams University, Cairo (Egypt); Joshi, A., E-mail: ajoshi@eiu.edu [Department of Physics, Eastern Illinois University, Charleston, IL 61920 (United States)
2012-10-15
The steady state behavior of optical bistable system in a ring cavity with transverse field variations and inhomogeneousely broadened two-level atoms is investigated outside the rotating wave approximation (RWA). Analytical and numerical investigation is presented for different cases of transverse field variations with Lorentzian or Gaussian line widths. When both (transverse and inhomogeneous) features taken into account, the first harmonic output field component outside the RWA exhibits a one-way switching down processes (butterfly OB) or reversed (clockwise) OB behavior, depending on the atomic linewidth shape.
Inhomogeneous broadening in non-interacting nonlocal plasmonic ensembles
DEFF Research Database (Denmark)
Tserkezis, Christos; Maack, Johan Rosenkrantz; Liu, Z.
2016-01-01
The importance of inhomogeneous broadening due to the size dependence of plasmon resonances in few-nm metallic particle ensembles is investigated through different models describing the nonlocal optical response of plasmonic nanospheres. Modal shifts and plasmon line broadening are shown to become...... important within the first-order correction to classical electrodynamics provided by the hydrodynamic Drude model, but turn out to be less prominent once additional single-particle size-dependent damping mechanisms are accounted for through the recently developed Generalized Nonlocal Optical Response theory...
Inhomogeneous phase shifting: an algorithm for nonconstant phase displacements
Energy Technology Data Exchange (ETDEWEB)
Tellez-Quinones, Alejandro; Malacara-Doblado, Daniel
2010-11-10
In this work, we have developed a different algorithm than the classical one on phase-shifting interferometry. These algorithms typically use constant or homogeneous phase displacements and they can be quite accurate and insensitive to detuning, taking appropriate weight factors in the formula to recover the wrapped phase. However, these algorithms have not been considered with variable or inhomogeneous displacements. We have generalized these formulas and obtained some expressions for an implementation with variable displacements and ways to get partially insensitive algorithms with respect to these arbitrary error shifts.
A New Look at Simple Inhomogeneous Chemical Evolution
Oey, M. S.
2000-01-01
A rudimentary, one-zone, closed-box model for inhomogeneous chemical evolution is offered as an alternative reference than the Simple model in the limit of no mixing. The metallicity distribution functions (MDFs) of Galactic halo and bulge stars can be matched by varying a single evolutionary parameter, nQ. Q is the filling factor of contaminating regions and n is the number of star-forming generations. Therefore, Q and n have equivalent roles, and combinations of n and Q yield systems with d...
Modelling the inhomogeneous SiC Schottky interface
Gammon, P. M.; Pérez-Tomás, Amador; Shah, V A; Vavasour, O.; Donchev, E.; J.S. Pang; Myronov, Maksym; Fisher, Craig A.; Jennings, M. R.; Leadley, D. R.; Mawby, P. A. (Philip A.)
2013-01-01
For the first time, the I-V-T dataset of a Schottky diode has been accurately modelled, parameterised, and fully fit, incorporating the effects of interface inhomogeneity, patch pinch-off and resistance, and ideality factors that are both heavily temperature and voltage dependent. A Ni/SiC Schottky diode is characterised at 2 K intervals from 20 to 320 K, which, at room temperature, displays low ideality factors (n 8), voltage dependent ideality factors and evidence of the so-called "thermio...
Accelerating expansion of the universe may be caused by inhomogenities
Bene, G; Vasuth, M; Bene, Gyula; Czinner, Viktor; Vasuth, Matyas
2003-01-01
We point out that, due to the nonlinearity of the Einstein equations, a homogeneous approximation in cosmology leads to the appearance of an additional term in the Friedmann equation. This new term is associated with the spatial inhomogenities of the metric and can be expressed in terms of density fluctuations. Although it is not constant, it decays much slower (as t^(-2/3)) than the other terms (like density) which decrease as t^(-2). The presence of the new term leads to a correction in the scaling factor that is proportional to t^2 and may give account of the recently observed accelerating expansion of the universe without introducing a cosmological constant.
Rf-inhomogeneity compensation using method of Fourier synthesis
Khaneja, Navin
2017-04-01
In this paper, we propose a new method for design of composite pulses that are robust to rf-amplitude (rf-inhomogeneity). We call this, the method of Fourier synthesis. The method is general enough to design excitation, inversion, refocusing or arbitary flip angle pulses that are robust to rf-amplitude. The method can be tailored to have amplitude selective excitation. We experimentally show rf-compensation over a order of magnitude (20 db) variation in rf-amplitude. The method is expected to find use in invivo NMR studies using surface coils, where there is large dispersion in rf-amplitude over the sample.
Kaur, Paramjit; Wasan, Ajay
2015-01-01
We present a theoretical model, using density matrix approach, to study the effect of weak as well as strong probe field on the optical properties of an inhomogeneously broadened multilevel V-system of the $^{87}$Rb D2 line. We consider the case of stationary as well as moving atoms and perform thermal averaging at room temperature. The presence of multiple excited states results in asymmetric absorption and dispersion profiles. In the weak probe regime, we observe the partial transparency window due to the constructive interference occurs between transition pathways at the line center. In a room temperature vapour, we obtain an increased linewidth of the transparency window and steep positive dispersion. For a strong probe regime, the transparency window with normal dispersion switches to enhanced absorption with anomalous dispersion at the line center. Here, we show how the electromagnetically induced transparency (EIT) depends on the polarizations of the applied fields. We also discuss the transient behavi...
Ammari, Habib; Seo, Jin Keun; Zhang, Tingting
2016-10-01
We are aiming to identify the thin insulating inhomogeneities and small conductive inhomogeneities inside an electrically conducting medium by using multi-frequency electrical impedance tomography. The thin insulating inhomogeneities are considered in the form of a tubular neighborhood of a curve and small conductive inhomogeneities are regarded as circular disks. Taking advantage of the frequency dependent behavior of insulating objects, we give a rigorous derivation of the potential along thin insulating objects at various frequencies. Asymptotic formula is given to analyze relationship between inhomogeneities and boundary potential at different frequencies. In numerical simulations, spectroscopic images are provided to visualize the reconstructed admittivity at various frequencies. For the view of both kinds of inhomogeneities, an integrated reconstructed image based on principal component analysis is provided. Phantom experiments are performed by using Swisstom EIT-Pioneer Set.
Gaussian moving averages and semimartingales
DEFF Research Database (Denmark)
Basse-O'Connor, Andreas
2008-01-01
In the present paper we study moving averages (also known as stochastic convolutions) driven by a Wiener process and with a deterministic kernel. Necessary and sufficient conditions on the kernel are provided for the moving average to be a semimartingale in its natural filtration. Our results...... are constructive - meaning that they provide a simple method to obtain kernels for which the moving average is a semimartingale or a Wiener process. Several examples are considered. In the last part of the paper we study general Gaussian processes with stationary increments. We provide necessary and sufficient...
Video Vortex reader II: moving images beyond YouTube
Lovink, G.; Somers Miles, R.
2011-01-01
Video Vortex Reader II is the Institute of Network Cultures' second collection of texts that critically explore the rapidly changing landscape of online video and its use. With the success of YouTube ('2 billion views per day') and the rise of other online video sharing platforms, the moving image
Video Vortex reader II: moving images beyond YouTube
Lovink, G.; Somers Miles, R.
2011-01-01
Video Vortex Reader II is the Institute of Network Cultures' second collection of texts that critically explore the rapidly changing landscape of online video and its use. With the success of YouTube ('2 billion views per day') and the rise of other online video sharing platforms, the moving image h
Lie Algebraic Discussions for Time-Inhomogeneous Linear Birth-Death Processes with Immigration
Ohkubo, Jun
2014-10-01
Analytical solutions for time-inhomogeneous linear birth-death processes with immigration are derived. While time-inhomogeneous linear birth-death processes without immigration have been studied by using a generating function approach, the processes with immigration are here analyzed by Lie algebraic discussions. As a result, a restriction for time-inhomogeneity of the birth-death process is understood from the viewpoint of the finiteness of the dimensionality of the Lie algebra.
On the large-scale inhomogeneous Universe and the cosmological constant
Palle, D
2002-01-01
We study the large-scale inhomogeneity of the Universe based on the averaging procedure of Buchert and Ehlers. The generalized Dyer-Roeder equation for the angular diameter distance of the inhomogeneous Universe is derived and solved for different cosmological models. We make a comparison of certain cosmic observables, such as the Hubble function, angular diameter distance,cosmological correction factor of homogeneous and inhomogeneous cosmological models, which are crucial ingredients in galaxy number counts and gravitational lenses.
Behaviour of light transmission channels in random media with inhomogeneous disorder
Xu, Yuchen; ZHANG Hao; Lin, Yujun; Zhu, Heyuan
2016-01-01
We present a numerical study on the light transport properties and statistics of transmission channels in random media with inhomogeneous disorder. For the case of longitudinal inhomogeneity of disorder we find that the statistics of the transmission channels is independent of the inhomogeneity and the system can be equivalent to a counterpart with homogeneous disorder strength, both of which have the same statistical distribution of the transmission channels. However, for the case of transve...
Green's function for a prestressed thermoelastic half-space with an inhomogeneous coating
Belyankova, T. I.; Kalinchuk, V. V.
2016-09-01
A mathematical model is developed for an inhomogeneous thermoelastic prestressed half-space consisting of a stack of homogeneous or functionally graded layers rigidly attached to a homogeneous base. Each component of the inhomogeneous medium is subjected to initial mechanical stresses and temperature. Successive linearization of the constitutive relations of the nonlinear mechanics of a thermoelastic medium is performed using the theory of superposition of small deformations on finite deformations with the inhomogeneity of the medium taken into account. Integral formulas are derived to explore dynamic processes in inhomogeneous prestressed thermoelastic media.
How Rapid is Rapid Prototyping? Analysis of ESPADON Programme Results
Directory of Open Access Journals (Sweden)
Ian D. Alston
2003-05-01
Full Text Available New methodologies, engineering processes, and support environments are beginning to emerge for embedded signal processing systems. The main objectives are to enable defence industry to field state-of-the-art products in less time and with lower costs, including retrofits and upgrades, based predominately on commercial off the shelf (COTS components and the model-year concept. One of the cornerstones of the new methodologies is the concept of rapid prototyping. This is the ability to rapidly and seamlessly move from functional design to the architectural design to the implementation, through automatic code generation tools, onto real-time COTS test beds. In this paper, we try to quantify the term Ã¢Â€ÂœrapidÃ¢Â€Â and provide results, the metrics, from two independent benchmarks, a radar and sonar beamforming application subset. The metrics show that the rapid prototyping process may be sixteen times faster than a conventional process.
Rehabilitation Counselor Certification: Moving Forward
Saunders, Jodi L.; Barros-Bailey, Mary; Chapman, Cindy; Nunez, Patricia
2009-01-01
This article provides a brief history of the Commission on Rehabilitation Counselor Certification and presents recent changes and strategic goals for moving forward. Challenges and opportunities for the profession in relation to certification are also discussed. (Contains 3 tables.)
Minimum Delay Moving Object Detection
Lao, Dong
2017-01-08
We present a general framework and method for detection of an object in a video based on apparent motion. The object moves relative to background motion at some unknown time in the video, and the goal is to detect and segment the object as soon it moves in an online manner. Due to unreliability of motion between frames, more than two frames are needed to reliably detect the object. Our method is designed to detect the object(s) with minimum delay, i.e., frames after the object moves, constraining the false alarms. Experiments on a new extensive dataset for moving object detection show that our method achieves less delay for all false alarm constraints than existing state-of-the-art.
Transient heating of moving objects
Directory of Open Access Journals (Sweden)
E.I. Baida
2014-06-01
Full Text Available A mathematical model of transient and quasistatic heating of moving objects by various heat sources is considered. The mathematical formulation of the problem is described, examples of thermal calculation given.
The Optimal Inhomogeneity for Superconductivity: Finite Size Studies
Energy Technology Data Exchange (ETDEWEB)
Tsai, W-F.
2010-04-06
We report the results of exact diagonalization studies of Hubbard models on a 4 x 4 square lattice with periodic boundary conditions and various degrees and patterns of inhomogeneity, which are represented by inequivalent hopping integrals t and t{prime}. We focus primarily on two patterns, the checkerboard and the striped cases, for a large range of values of the on-site repulsion U and doped hole concentration, x. We present evidence that superconductivity is strongest for U of order the bandwidth, and intermediate inhomogeneity, 0 < t{prime} < t. The maximum value of the 'pair-binding energy' we have found with purely repulsive interactions is {Delta}{sub pb} = 0.32t for the checkerboard Hubbard model with U = 8t and t{prime} = 0.5t. Moreover, for near optimal values, our results are insensitive to changes in boundary conditions, suggesting that the correlation length is sufficiently short that finite size effects are already unimportant.
Functional integral approach to the kinetic theory of inhomogeneous systems
Fouvry, Jean-Baptiste; Chavanis, Pierre-Henri; Pichon, Christophe
2016-10-01
We present a derivation of the kinetic equation describing the secular evolution of spatially inhomogeneous systems with long-range interactions, the so-called inhomogeneous Landau equation, by relying on a functional integral formalism. We start from the BBGKY hierarchy derived from the Liouville equation. At the order 1 / N, where N is the number of particles, the evolution of the system is characterised by its 1-body distribution function and its 2-body correlation function. Introducing associated auxiliary fields, the evolution of these quantities may be rewritten as a traditional functional integral. By functionally integrating over the 2-body autocorrelation, one obtains a new constraint connecting the 1-body DF and the auxiliary fields. When inverted, this constraint allows us to obtain the closed non-linear kinetic equation satisfied by the 1-body distribution function. This derivation provides an alternative to previous methods, either based on the direct resolution of the truncated BBGKY hierarchy or on the Klimontovich equation. It may turn out to be fruitful to derive more accurate kinetic equations, e.g., accounting for collective effects, or higher order correlation terms.
The effect of large scale inhomogeneities on the luminosity distance
Brouzakis, Nikolaos; Tetradis, Nikolaos; Tzavara, Eleftheria
2007-02-01
We study the form of the luminosity distance as a function of redshift in the presence of large scale inhomogeneities, with sizes of order 10 Mpc or larger. We approximate the Universe through the Swiss-cheese model, with each spherical region described by the Lemaitre Tolman Bondi metric. We study the propagation of light beams in this background, assuming that the locations of the source and the observer are random. We derive the optical equations for the evolution of the beam area and shear. Through their integration we determine the configurations that can lead to an increase of the luminosity distance relative to the homogeneous cosmology. We find that this can be achieved if the Universe is composed of spherical void-like regions, with matter concentrated near their surface. For inhomogeneities consistent with the observed large scale structure, the relative increase of the luminosity distance is of the order of a few per cent at redshifts near 1, and falls short of explaining the substantial increase required by the supernova data. On the other hand, the effect we describe is important for the correct determination of the energy content of the Universe from observations.
Modelling of the inhomogeneous interior of polymer gels
Shew, Chwen-Yang; Iwaki, Takafumi
2006-04-01
A simple model has been investigated to elucidate the mean squared displacement (MSD) of probe molecules in cross-linked polymer gels. In the model, we assume that numerous cavities distribute in the inhomogeneous interior of a gel, and probe molecules are confined within these cavities. The individual probe molecules trapped in a gel are treated as Brownian particles confined to a spherical harmonic potential. The harmonic potential is chosen to model the effective potential experienced by the probe particle in the cavity of a gel. Each field strength is corresponding to the characteristic of one type of effective cavity. Since the statistical distribution of different effective cavity sizes is unknown, several distribution functions are examined. Meanwhile, the calculated averaged MSDs are compared to the experimental data by Nisato et al (2000 Phys. Rev. E 61 2879). We find that the theoretical results of the MSD are sensitive to the shape of the distribution function. For low cross-linked gels, the best fit is obtained when the interior cavities of a gel follow a bimodal distribution. Such a result may be attributed to the presence of at least two distinct classes of cavity in gels. For high cross-linked gels, the cavities in the gel can be depicted by a single-modal uniform distribution function, suggesting that the range of cavity sizes becomes smaller. These results manifest the voids inside a gel, and the shape of distribution functions may provide the insight into the inhomogeneous interior of a gel.
Inhomogeneous Chemical Evolution of the Galaxy in the Solar Neighbourhood
Indian Academy of Sciences (India)
S. Sahijpal
2013-12-01
-body numerical simulations of an inhomogeneous Galactic Chemical Evolution (GCE) of the solar neighbourhood with a high temporal resolution are presented. The solar annular ring is divided into distinct spatial grids of area ∼ 1–2 kpc2. Each grid evolves distinctly in terms of star formation and nucleosynthetic yields from numerous generations of stars. The evolution of the galaxy is simulated by considering discrete episodes of star formation. Subsequent to the evolution of the simulated stars within each grid the stellar nucleosynthetic yields are homogenized within the grid rather than the traditionally adopted criteria of homogenizing over the entire solar annular ring. This provides a natural mechanism of generating heterogeneities in the elemental abundance distribution of stars. A complex chemical evolutionary history is inferred that registers episodes of time-dependent contributions from SN II+Ib/c with respect to SN Ia. It was observed that heterogeneities can remerge even after episodes of large scale homogenizations on scales larger than the grid size. However, a comparison of the deduced heterogeneities with the observed scatter in the elemental abundances of the dwarf stars suggest only a partial match, specifically, for [Fe/H] > -0.5. The deduced heterogeneities in the case of carbon, oxygen, magnesium, silicon, sulphur, calcium and titanium can explain the observed heterogeneities for [Fe/H] < -0.5. It may not be possible to explain the entire observed spread exclusively on the basis of the inhomogeneous GCE.
Spatial Inhomogeneity of Luminescence in III-Nitride Compounds
Directory of Open Access Journals (Sweden)
Gintautas TAMULAITIS
2011-11-01
Full Text Available The band gap of III-nitride semiconductors cover a wide range from 0.77 eV (band gap of InN to 6.2 eV (AlN. Thus, light-emitting diodes emitting from infrared to deep into ultraviolet can be fabricated using ternary III-nitrides InGaN, AlGaN, and AlInN with appropriate composition. However, growing the compounds with any desirable composition often encounters substantial difficulties due to phase separation, structural quality of the epilayers, impurities and extended defects, etc. The spatial inhomogeneity of emission properties in III-nitride epilayers and quantum well structures provides an informative insight into carrier migration, localization, and recombination and is important for development of light-emitting devices. In this paper, we introduce the techniques for luminescence study with spatial resolution (microphotoluminescence, confocal microscopy, scanning near field optical microscopy and cathodoluminescence, discuss material properties leading to emission inhomogeneity and review results on spatial distribution of photoluminescence and cathodoluminescence in InGaN and AlGaN, which are the most important ternary III-nitride compounds for application in light-emitting devices.http://dx.doi.org/10.5755/j01.ms.17.4.768
Enhancement of photoacoustic detection of inhomogeneities in polymers
Directory of Open Access Journals (Sweden)
P. Grondona
2013-01-01
Full Text Available We report a series of experiments on laser pulsed photoacoustic excitationin turbid polymer samples addressed to evaluate the sound speed inthe samples and the presence of inhomogeneities in the bulk. We describea system which allows the direct measurement of the speed of the detectedwaves by engraving the surface of the piece under study with a fiduciarypattern of black lines..We also describe how this pattern helps toenhance the sensitivity for the detection of an inhomogeneity in the bulk. These two facts are useful for studies in soft matter systems including, perhaps, biological samples. We have performed an experimental analysis on Grilon® samples in differentsituations and we show the limitations of the method. Received: 7 December 2012, Accepted: 19 June 2013; Reviewed by: V. Lakshminarayanan, Waterloo University, Canada; Edited by: J. J. Niemela; DOI: http://dx.doi.org/10.4279/PIP.050005Cite as: P. Grondona, H. O. Di Rocco, D. I. Iriarte, J. A. Pomarico, H. F. Ranea-Sandoval, G. M. Bilmes, Papers in Physics 5, 050005 (2013
Nanodomain structures with hierarchical inhomogeneities in PMN-PT.
Kurushima, Kosuke; Kobayashi, Keisuke; Mori, Shigeo
2012-09-01
The nanometric domain configuration of (1 - x) Pb(Mg(1/3)Nb(2/3))O(3-x)PbTiO(3) [(1 - x)PMN-xPT] single crystals in the monoclinic phase around a morphotropic phase boundary (MPB) has been examined thoroughly by means of transmission electron microscopy (TEM). Domain structures with hierarchically inhomogeneous configuration were found in the monoclinic phase near the MPB region around x ~ 0.32, which are characterized as nanoscaled lamella-type domain structures with ~10 nm width inside macroscopic-sized banded domains with 100 to 200 nm width. To elucidate formation processes of the domain structures with hierarchically inhomogeneous configuration, an in situ TEM observation of changes of the domain structures in the temperature window between 298K and 500K was carried out. It is revealed that these nanoscaled lamella-type domain structures with ~10 nm width appear inside the banded domains as a result of the tetragonal structure and are inherent to the monoclinic phase.
The perceived transmittance of inhomogeneous surfaces and media.
Anderson, Barton L; Singh, Manish; Meng, Jeanette
2006-06-01
A series of experiments was performed to determine how the visual system computes the transmittance of inhomogeneous surfaces and media. Previous work (Anderson, B. L. (1999) Stereoscopic surface perception. Neuron, 26, 919-928; Anderson, B. L. (2003) The role of occlusion in the perception of depth, lightness, and opacity. Psychological Review, 110, 762-784) has suggested that the visual system employs a transmittance anchoring principle in determining when transparency is perceived. This principle states that the visual system interprets the highest contrast region along contours and surfaces as a region in plain view and uses this anchor as a reference point for transparency computations. In particular, recent work has shown that the transmittance of homogeneous transparent surfaces is well described by a ratio of contrasts model (Singh, M., & Anderson, B. L. (2002). Toward a perceptual theory of transparency. Psychological Review, 109, 492-519). In this model, the transmittance of a transparent surface is determined by the contrast of a transparent image region normalized by the contrast of the region in plain view. Here, a series of experiments is reported that assesses this model for inhomogeneous transparent surfaces that vary in both space and time. The results of these experiments reveal that transmittance anchoring has both a spatial and temporal component, and that the perceived transmittance of transparent surfaces is well described by a ratio of perceived contrasts model.
Optical inspection of liquid crystal variable retarder inhomogeneities.
Vargas, Javier; Uribe-Patarroyo, Néstor; Antonio Quiroga, Juan; Alvarez-Herrero, Alberto; Belenguer, Tomás
2010-02-01
Liquid crystal variable retarders (LCVRs) are starting to be widely used in optical systems because of their capacity to provide a controlled variable optical retardance between two orthogonal components of incident polarized light or to introduce a known phase shifting (PS) between coherent waves, both by means of an applied voltage. Typically, the retardance or PS introduced by an LCVR is not homogeneous across the aperture. On the one hand, the LCVR glass substrates present a global bend that causes an overall variation of the retardance or PS. On the other hand, in the manufacturing process of an LCVR, there sometimes appears a set of micro-air bubbles that causes local retardance or PS inhomogeneities. In this work, we present an interferometric technique based on a Mach-Zehnder interferometer that is insensitive to vibrations and capable of inspecting and characterizing the LCVR's retardance or PS inhomogeneities. The feasibility of the proposed method is demonstrated in the experimental results, where the LCVR retardance is measured with an error of about 0.2 rad. The thickness of possible micro-air bubbles is obtained with a resolution of about 50 nm.
Inhomogeneous Deformation of Brain Tissue During Tension Tests
Rashid, Badar; Gilchrist, Michael D; 10.1016/j.commatsci.2012.05.030
2013-01-01
Mechanical characterization of brain tissue has been investigated extensively by various research groups over the past fifty years. These properties are particularly important for modelling Traumatic Brain Injury (TBI). In this research, we present the design and calibration of a High Rate Tension Device (HRTD) capable of performing tests up to a maximum strain rate of 90/s. We use experimental and numerical methods to investigate the effects of inhomogeneous deformation of porcine brain tissue during tension at different specimen thicknesses (4.0-14.0 mm), by performing tension tests at a strain rate of 30/s. One-term Ogden material parameters (mu = 4395.0 Pa, alpha = -2.8) were derived by performing an inverse finite element analysis to model all experimental data. A similar procedure was adopted to determine Young's modulus (E= 11200 Pa) of the linear elastic regime. Based on this analysis, brain specimens of aspect ratio (diameter/thickness) S < 1.0 are required to minimise the effects of inhomogeneous...
On parallel electric field generation in transversely inhomogeneous plasmas
Tsiklauri, David
2007-01-01
The generation of parallel electric fields by the propagation of ion cyclotron waves in the plasma with a transverse density inhomogeneity was studied. It was proven that the minimal model required to reproduce the previous kinetic simulation results of E_{||} generation [Tsiklauri et al 2005, Genot et al 2004] is the two-fluid, cold plasma approximation in the linear regime. By considering the numerical solutions it was also shown that the cause of E_{||} generation is the electron and ion flow separation induced by the transverse density inhomogeneity. We also investigate how E_{||} generation is affected by the mass ratio and found that amplitude attained by E_{||} decreases linearly as inverse of the mass ratio m_i/m_e. For realistic mass ratio of m_i/m_e=1836, such empirical scaling law, within a time corresponding to 3 periods of the driving ion cyclotron wave, is producing E_{||}=14 Vm^{-1} for solar coronal parameters. Increase in mass ratio does not have any effect on final parallel (magnetic field a...
Uniqueness of Petrov type D spatially inhomogeneous irrotational silent models
Apostolopoulos, P S; Apostolopoulos, Pantelis S; Carot, Jaume
2006-01-01
The consistency of the constraint with the evolution equations for spatially inhomogeneous and irrotational silent (SIIS) models of Petrov type I, demands that the former are preserved along the timelike congruence represented by the velocity of the dust fluid, leading to an infinite set of non-trivial constraints. This fact has been used to conjecture that the resulting models correspond to the spatially homogeneous (SH) models of Bianchi type I, at least for the case where the cosmological constant vanish. By exploiting the full set of the constraint equations as expressed in the 1+3 covariant formalism and using elements from the theory of the spacelike congruences, we provide a direct and simple proof of this conjecture for vacuum and dust fluid models, which shows that the Szekeres family of solutions represents the most general class of SIIS models. The suggested procedure also shows that, the uniqueness of the spatially inhomogeneous and irrotational models of Petrov type D is not affected by the prese...
The physical mechanism of "inhomogeneous" magnetization transfer MRI
Manning, Alan P.; Chang, Kimberley L.; MacKay, Alex L.; Michal, Carl A.
2017-01-01
Inhomogeneous MT (ihMT) is a new magnetic resonance imaging technique that shows promise for myelin selectivity. Materials with a high proportion of lipids, such as white matter tissue, show a reduced intensity in magnetic resonance images acquired with selective prepulses at positive and negative offsets simultaneously compared to images with a single positive or negative offset prepulse of the same power. This effect was initially explained on the basis of hole-burning in inhomogeneously broadened lines of the lipid proton spin system. Our results contradict this explanation. ihMT in lipids can be understood with a simple spin-1 model of a coupled methylene proton pair. More generally, Provotorov theory can be used to consider the evolution of dipolar order in the non-aqueous spins during the prepulses. We show that the flip-angle dependence of the proton spectrum of a model lipid system (Prolipid-161) following dipolar order generation is in quantitative agreement with the model. In addition, we directly observe dipolar order and ihMT signals in the non-aqueous components of Prolipid-161 and homogeneously-broadened systems (hair, wood, and tendon) following ihMT prepulses. The observation of ihMT signals in tendon suggests that the technique may not be as specific to myelin as previously thought. Our work shows that ihMT occurs because of dipolar couplings alone, not from a specific type of spectral line broadening as its name suggests.
Lyman-alpha Damping Wing Constraints on Inhomogeneous Reionization
Mesinger, Andrei
2007-01-01
One well-known way to constrain the hydrogen neutral fraction, x_H, of the high-redshift intergalactic medium (IGM) is through the shape of the red damping wing of the Lya absorption line. We examine this method's effectiveness in light of recent models showing that the IGM neutral fraction is highly inhomogeneous on large scales during reionization. Using both analytic models and "semi-numeric" simulations, we show that the "picket-fence" absorption typical in reionization models introduces both scatter and a systematic bias to the measurement of x_H. In particular, we show that simple fits to the damping wing tend to overestimate the true neutral fraction in a partially ionized universe, with a fractional error of ~ 30% near the middle of reionization. This bias is generic to any inhomogeneous model. However, the bias is reduced and can even underestimate x_H if the observational sample only probes a subset of the entire halo population, such as quasars with large HII regions. We also find that the damping ...
Efficient vector radiative transfer calculations in vertically inhomogeneous cloudy atmospheres
van Diedenhoven, Bastiaan; Hasekamp, Otto P.; Landgraf, Jochen
2006-08-01
Accurate radiative transfer calculations in cloudy atmospheres are generally time consuming, limiting their practical use in satellite remote sensing applications. We present a model to efficiently calculate the radiative transfer of polarized light in atmospheres that contain homogeneous cloud layers. This model combines the Gauss-Seidel method, which is efficient for inhomogeneous cloudless atmospheres, with the doubling method, which is efficient for homogeneous cloud layers. Additionally to reduce the computational effort for radiative transfer calculations in absorption bands, the cloud reflection and transmission matrices are interpolated over the absorption and scattering optical thicknesses within the cloud layer. We demonstrate that the proposed radiative transfer model in combination with this interpolation technique is efficient for the simulation of satellite measurements for inhomogeneous atmospheres containing one homogeneous cloud layer. For example, the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) measurements in the oxygen A band (758-773 nm) and the Hartley-Huggins ozone band (295-335 nm) with a spectral resolution of 0.4 nm can be simulated for these atmospheres within 1 min on a 2.8 GHz PC with an accuracy better than 0.1%.
Evolution of electron hole propating in inhomogeneous plasma
Dokgo, K.; Woo, M.; Choi, C.; Min, K. W.; Hwang, J.
2014-12-01
The evolution of electron hole (EH) propagation in the presence of plasma density inhomogeneity is investigated by both particle-in-cell (PIC) simulation and theory. At the beginning of simulation, EH is generated by plasma blob injection. When EH passes inhomogeneous plasma region, the EH potential (1st order) increases monotonically in proportion to the background plasma density (0th order). With this 1st order growth, 2nd order back and forth oscillations of the potential are observed in faster time scale compared to EH propagation time scale. A bulk motion of trapped electrons due to density gradient produces these potential oscillations and the frequency of 2nd order oscillation is found to be comparable to the bouncing frequency of these trapped particles. Using the theoretical technique introduced by Schwarzmeier, we discovered a normal mode localized in the 1st order EH potential with frequency comparable to average bounce frequency of trapped particle. Such mode has an odd symmetry that is exactly consistent with simulation result. Furthermore, ions are pushed backward in coherence with 2nd order potential in simulation. These coherent ions form into a train of backward propagating ion acoustic solitary waves (IASWs) that evolve to ion hole in simulation. Finally, EH starts to dissipate by nonlinear Landau damping and converge to another stable EH as it reaches high-density, homogenous region.
EBL Inhomogeneity and Hard-Spectrum Gamma-Ray Sources
Abdalla, Hassan; Böttcher, Markus
2017-02-01
The unexpectedly hard very-high-energy (VHE; E > 100 GeV) γ-ray spectra of a few distant blazars have been interpreted as evidence of a reduction of the γγ opacity of the universe due to the interaction of VHE γ-rays with the extragalactic background light (EBL) compared to the expectation from current knowledge of the density and cosmological evolution of the EBL. One of the suggested solutions to this problem involves the inhomogeneity of the EBL. In this paper, we study the effects of such inhomogeneity on the energy density of the EBL (which then also becomes anisotropic) and the resulting γγ opacity. Specifically, we investigate the effects of cosmic voids along the line of sight to a distant blazar. We find that the effect of such voids on the γγ opacity, for any realistic void size, is only of the order of ≲1% and much smaller than expected from a simple linear scaling of the γγ opacity with the line-of-sight galaxy underdensity due to a cosmic void.
Spectral Model of Non-Stationary, Inhomogeneous Turbulence
Bragg, Andrew D; Clark, Timothy T
2015-01-01
We compare results from a spectral model for non-stationary, inhomogeneous turbulence (Besnard et al., Theor. Comp. Fluid. Dyn., vol. 8, pp 1-35, 1996) with Direct Numerical Simulation (DNS) data of a shear-free mixing layer (SFML) (Tordella et al., Phys. Rev. E, vol. 77, 016309, 2008). The SFML is used as a test case in which the efficacy of the model closure for the physical-space transport of the fluid velocity field can be tested in a flow with inhomogeneity, without the additional complexity of mean-flow coupling. The model is able to capture certain features of the SFML quite well for intermediate to long-times, including the evolution of the mixing-layer width and turbulent kinetic energy. At short-times, and for more sensitive statistics such as the generation of the velocity field anisotropy, the model is less accurate. We present arguments, supported by the DNS data, that a significant cause of the discrepancies is the local approximation to the intrinsically non-local pressure-transport in physical...
Autowaves in moving excitable media
Directory of Open Access Journals (Sweden)
V.A.Davydov
2004-01-01
Full Text Available Within the framework of kinematic theory of autowaves we suggest a method for analytic description of stationary autowave structures appearing at the boundary between the moving and fixed excitable media. The front breakdown phenomenon is predicted for such structures. Autowave refraction and, particulary, one-side "total reflection" at the boundary is considered. The obtained analytical results are confirmed by computer simulations. Prospects of the proposed method for further studies of autowave dynamics in the moving excitable media are discussed.
Institute of Scientific and Technical Information of China (English)
Zhongliang Zu; Qi Liu; Yanming Yu; Song Gao; Shanglian Bao
2008-01-01
Driven equilibrium single pulse observation of T1(DESPOT1)is a rapid spin-lattice relaxation constant(T1)mapping technique in magnetic resonance imaging(MRI).However,DESPOT1 is very sensitive to flip angle(FA)inhomogeneity,resulting in T1 inaccuracy.Here,a five-point DESPOTl method is proposed to reduce the sensitivity to FA inhomogeneity through FA measurement and calibra-tion.Phantom and in vivo experiments are performed to validate the technique.As a result.a rapid and accurate T1 mapping is acquired by using the proposed five-point DESPOT1 method.
Transient inhomogeneous contrast enhancement of the spleen on arterial phase of spiral CT
Energy Technology Data Exchange (ETDEWEB)
Kim, Taik Kun; Kang, Hyo Jun; Lee, Ki Yeol; Park, Cheol Min; Chung, Kyoo Byung [Korea Univ. College of Medicine, Seoul (Korea, Republic of)
1997-02-01
To assess the relationship between splenic transient inhomogeneous contrast enhancement(CE) on the arterial phase of spiral CT, and splenic volume, and to classify the CE pattern in liver cirrhosis. We measured the splenic volume of 120 patients, 60 showed inhomogeneous splenic CE on arterial phase, and 60 showed homogeneous splenic CE. CT scans with intrinsic splenic pathology were excluded. Sixteen patients with clinically confirmed liver cirrhosis were included. Splenic volumes of the inhomogeneous and homogeneous CE group were compared. The inhomogeneous group was divided into grades according to areas of non-enhanced portion (grade 1, focal geographic; grade 2, multifocal patchy; grade 3, extensive serpentine inhomogeneous CE), and these were correlated with splenic volume. Among the 60 inhomogeneous CE scans, 23 cases (38.3%) showed splenomegaly (spleen volume > 220cm{sup 3}); in contrast, this applied to only 8 cases (13.3%) of the 60 homogeneous CE scans. Mean splenic volume in the inhomogeneous CE group (226.74 {+-} 129.78cm{sup 3}) was greater than in the homogeneous CE group (184.56 {+-} 77.44cm{sup 3}) (p < 0.033). A larger splenic volume and extensive inhomogeneous CE (grade 3) were noted, and most liver cirrhosis patients(14/16) were grade 3. Three such patients who had shown inhomogeneous splenic CE on arterial phase showed inhomogeneous CE even on portal phase. Inhomogeneous splenic CE on arterial phase was more common in cases of an enlarged spleen, and more extensive in liver cirrhosis. These findings suggest hemodynamic change of the spleen may be a contributory factor.
Acceleration of near-field scattering from an inhomogeneous spherical shell
Indian Academy of Sciences (India)
M D Sharma
2005-08-01
The three dimensional scattering of near-field, from a point source, is studied for acceleration in the time domain. The perturbation method is applied to define the acceleration for the first order scattering from a weak inhomogeneity in a homogeneous surrounding. A body force, arising from the interaction between the primary waves and the inhomogeneity, acts as the source generating the scattered motion. The acceleration of scattered waves is related to the velocity and density fluctuations of the inhomogeneity. No restrictions are placed on the inhomogeneity size or locations of the source and receiver. Decoupling of scattered motion enables the identification of different phases. Integral expressions are derived for the scattering acceleration due to the incidence of near-field wave (from an impulsive point force) at a radially inhomogeneous volume element. These integrals are solved further for scattering from an inhomogeneous spherical shell. The accelerations for back scattering are obtained as a special case. These accelerations are simple analytically solvable expressions in closed form. Only spherical asymmetry of wave velocity inhomogeneity can affect the scattered acceleration. Scattered acceleration is affected by the gradient of wave velocity inhomogeneity. The back scattering of near-field from a spherical shell, is independent of radial inhomogeneity of wave velocity. Inhomogeneity with smoothly perturbed wave velocity does not back-scatter any acceleration. Accelerations are computed numerically for scattering from a part of inhomogeneous spherical shell. Hypothetical models are considered to study the effects of the distances of spherical shell from source, receiver, its thickness and its position relative to the direction of impulsive force.
Moving Shadows, Moving Sun. Early Modem Sundials Restaging Miracles.
Mersmann, Jasmin
2015-01-01
Irrespective of geo- or heliocentric presuppositions, the functioning of sundials is based on the observation of moving shadows or light spots. Even though the cast shadow was often simply used to indicate the time, it could also remind the users of the ephemerality of earthly things or function as an index of planetary movements. This article examines the various ways in which early modem sundials visually interpret the moving shadow or light spot. The instruments address the shadow in inscriptions, integrate it into their design (e.g., in cruciform dials) or even manipulate its course (as in the so-called Horologium Ahaz). Both the crucifix and the Ahaz dials not only refer to astronomical miracles but actually restage them. Even though by means of the horologium it was not possible to explain the Old Testament miracle of the shadow moving backward, adepts were able to recreate it on a terrestrial scale.
Minimum Delay Moving Object Detection
Lao, Dong
2017-05-14
This thesis presents a general framework and method for detection of an object in a video based on apparent motion. The object moves, at some unknown time, differently than the “background” motion, which can be induced from camera motion. The goal of proposed method is to detect and segment the object as soon it moves in an online manner. Since motion estimation can be unreliable between frames, more than two frames are needed to reliably detect the object. Observing more frames before declaring a detection may lead to a more accurate detection and segmentation, since more motion may be observed leading to a stronger motion cue. However, this leads to greater delay. The proposed method is designed to detect the object(s) with minimum delay, i.e., frames after the object moves, constraining the false alarms, defined as declarations of detection before the object moves or incorrect or inaccurate segmentation at the detection time. Experiments on a new extensive dataset for moving object detection show that our method achieves less delay for all false alarm constraints than existing state-of-the-art.
Fitts, Charles R.
1991-05-01
Analytic functions are superimposed to model three-dimensional steady groundwater flow in regions containing one or more Inhomogeneities shaped like prolate or oblate ellipsoids of revolution. Each function and the sum of such functions are solutions of Laplace's equation, the governing differential equation for steady groundwater flow. The functions are implemented in a manner that provides exact continuity of flow across the entire boundary of each inhomogeneity. In general, continuity of head is provided at specified control points on the boundary and is approximated between control points. For the case of one inhomogeneity in a uniform flow field, it turns out that there is exact continuity of head across the entire surface of the inhomogeneity. The method is implemented in a computer program written by the author. Two applications are demonstrated: (1) flow to a gravel-packed well and (2) flow through a series of lens-shaped inhomogeneities. The examples demonstrate that the approximation of continuity of head can be made acceptable for many problems. A possible application of the technique would be testing various theories regarding contaminant migration and dispersion by simulating flow and chemical diffusion through large numbers of lens-shaped inhomogeneities.
Analysis and manipulation of field inhomogeneity effects in magnetic resonance imaging
de Leeuw, H.
2012-01-01
In the thesis the effects of macroscopic field inhomogeneities in MR imaging are analyzed and manipulation. Field inhomogeneities disturb the signal phase and invoke image distortions. Phase images are shown to serve as an effective means to generate and manipulate image contrast. In chapter 2 the
Stirring and mixing effects on oscillations and inhomogeneities in the minimal bromate oscillator
Dutt, A. K.; Menzinger, M.
1999-04-01
Stirring and mixing effects on the oscillations and inhomogeneities in the bromate-bromide-cerous system (minimal bromate oscillator) have been investigated in a continuously fed stirred tank reactor (CSTR). A movable microelectrode is used to monitor the inhomogeneities inside the CSTR in an oscillating phase. The results are explained in terms of the theory of imperfect mixing.
Collapse arresting in an inhomogeneous two-dimensional nonlinear Schrodinger model
DEFF Research Database (Denmark)
Schjødt-Eriksen, Jens; Gaididei, Yuri Borisovich; Christiansen, Peter Leth
2001-01-01
Collapse of (2 + 1)-dimensional beams in the inhomogeneous two-dimensional cubic nonlinear Schrodinger equation is analyzed numerically and analytically. It is shown that in the vicinity of a narrow attractive inhomogeneity, the collapse of beams that in a homogeneous medium would collapse may...
Inhomogeneity of the grain size of aircraft engine turbine polycrystalline blades
Directory of Open Access Journals (Sweden)
J. Chmiela
2011-10-01
Full Text Available The determination of the behaviour of inhomogeneous materials with a complex microstructure requires taking into account the inhomogeneity of the grain size, as it is the basis for the process of designing and modelling effective behaviours. Therefore, the functional description of the inhomogeneity is becoming an important issue. The paper presents an analytical approach to the grain size inhomogeneity, based on the derivative of a logarithmic-logistic function. The solution applied enabled an effective evaluation of the inhomogeneity of two macrostructures of aircraft engine turbine blades, characterized by a high degree of diversity in the grain size. For the investigated single-modal and bimodal grain size distributions on a perpendicular projection and for grains with a non-planar surface, we identified the parameters that describe the degree of inhomogeneity of the constituents of weight distributions and we also derived a formula describing the overall degree of inhomogeneity of bimodal distributions. The solution presented in the paper is of a general nature and it can be used to describe the degree of inhomogeneity of multi-modal distributions. All the calculations were performed using the Mathematica® package.
Granule fraction inhomogeneity of calcium carbonate/sorbitol in roller compacted granules
DEFF Research Database (Denmark)
Bacher, Charlotte; Olsen, P.M.; Bertelsen, P.;
2008-01-01
The granule fraction inhomogeneity of roller compacted granules was examined on mixtures of three different morphologic forms of calcium carbonate and three particle sizes of sorbitol. The granule fraction inhomogeneity was determined by the distribution of the calcium carbonate in each of the 10...
Some Plane Symmetric Inhomogeneous Cosmological Models in the Scalar-Tensor Theory of Gravitation
Ali, Ahmad T; Mahmoud, S R
2014-01-01
The present study deals with the inhomogeneous plane symmetric models in scalar - tensor theory of gravitation. We used symmetry group analysis method to solve the field equations analytically. A new class of similarity solutions have been obtained by considering the inhomogeneous nature of metric potential. The physical behavior and geometrical aspects of the derived models are also discussed.
Energy Technology Data Exchange (ETDEWEB)
Light, Max Eugene [Los Alamos National Laboratory
2017-04-13
This report outlines the theory underlying electromagnetic (EM) wave propagation in an unmagnetized, inhomogeneous plasma. The inhomogeneity is given by a spatially nonuniform plasma electron density n_{e}(r), which will modify the wave propagation in the direction of the gradient rn_{e}(r).
Numerical Analysis of Inhomogeneous Dielectric Waveguide Using Periodic Fourier Transform
Directory of Open Access Journals (Sweden)
M. Moradian
2007-01-01
Full Text Available A general method is introduced to obtain the propagation constants of the inhomogeneous dielectric waveguide. The periodic Fourier transform is applied to the normalized Maxwell's equations and makes the field components periodic. Then they are expanded in Fourier series. Finally, the trapezoidal rule is applied to approximate the convolution integral which leads to a set of coupled second-order differential equations that can be solved as an eigenvalue-eigenvector problem. The normalized propagation constant can be obtained as the square roots of the eigenvalues of the coefficient matrices. The proposed method is applied to the dielectric waveguide with a two-layered dielectric profile in the transverse direction, and the first four-confined TE modes are obtained. The propagation constants for the mentioned dielectric waveguide are also derived analytically and are then compared with those derived by the proposed method. Comparison of results shows the efficacy of the proposed method.
Diffusive Limits of the Master Equation in Inhomogeneous Media
Sattin, F; Salasnich, L
2015-01-01
In inhomogeneous environments several expressions for the flux of a diffusing quantity may apply--from Fick-Fourier's to Fokker-Planck's--depending upon the system studied. The integro-differential Master Equation (ME) provides a fairly generic framework for describing the dynamics of arbitrary systems driven by stochastic rules. Diffusive dynamics does arise as long-wavelength limit of the ME. However, while it is straightforward to obtain a diffusion equation with Fokker-Planck flux, its Fick-Fourier counterpart has never been worked out from the ME. In this work we show under which hypothesis the Fick's flux can actually be recovered from the ME. Analytical considerations are supported by explicit computer models.
Deflection of Rotating Symmetric Molecules by Inhomogeneous Fields
Gershnabel, Erez
2011-01-01
We consider deflection of rotating symmetric molecules by inhomogeneous optical and static electric fields, compare results with the case of linear molecules, and find new singularities in the distribution of the scattering angle. Scattering of the prolate/oblate molecules is analyzed in detail, and it is shown that the process can be efficiently controlled by means of short and strong femtosecond laser pulses. In particular, the angular dispersion of the deflected molecules may be dramatically reduced by laser-induced molecular pre-alignment. We first study the problem by using a simple classical model, and then find similar results by means of more sophisticated methods, including the formalism of adiabatic invariants and direct numerical simulation of the Euler-Lagrange equations of motion. The suggested control scheme opens new ways for many applications involving molecular focusing, guiding, and trapping by optical and static fields.
Effective Gap Equation for the Inhomogeneous LOFF Superconductive Phase
Casalbuoni, R; Gatto, R; Mannarelli, M; Nardulli, G; Ruggieri, M
2004-01-01
We present an approximate gap equation for different crystalline structures of the LOFF phase of high density QCD at T=0. This equation is derived by using an effective condensate term obtained by averaging the inhomogeneous condensate over distances of the order of the crystal lattice size. The approximation is expected to work better far off any second order phase transition. As a function of the difference of the chemical potentials of the up and down quarks, $\\delta\\mu$, we get that the octahedron is energetically favored from $\\delta\\mu=\\Delta_0/\\sqrt 2$ to $0.95\\Delta_0$, where $\\Delta_0$ is the gap for the homogeneous phase, while in the range $0.95\\Delta_0-1.32\\Delta_0$ the face centered cube prevails. At $\\delta\\mu=1.32\\Delta_0$ a first order phase transition to the normal phase occurs.
Inhomogeneous deformation in INCONEL 718 during monotonic and cyclic loadings
Worthem, D. W.; Robertson, I. M.; Socie, D. F.; Altstetter, C. J.; Leckie, F. A.
1990-01-01
The paper concentrates on the relation between microstructural observations of the dislocation structures and the macroscopic deformation responses of both aged and homogenized precipitate-hardened alloys at room temperature. The deformation responses are compared to the cyclic deformation response of an aged precipitate-hardened alloy. Early in the deformation, one deformation band per grain and little evidence of work hardening are observed; with increased deformation, work hardening begins, more bands nucleate, and their spacing becomes similar to that in the aged material. It is pointed out that the degree of coarseness of inhomogeneous deformation is not a result of a softening process within the bands due to precipitate shearing, but it is a function of the amount of work hardening within the bands.
Detecting Inhomogeneity in Daily Climate Series Using Wavelet Analysis
Institute of Scientific and Technical Information of China (English)
YAN Zhongwei; Phil D.JONES
2008-01-01
A wavelet method was applied to detect inhomogeneities in daily meteorological series,data which are being increasingly applied in studies of climate extremes.The wavelet method has been applied to a few well-established long-term daily temperature series back to the 18th century,which have been "homogenized" with conventional approaches.Various types of problems remaining in the series were revealed with the wavelet method.Their influences on analyses of change in climate extremes are discussed.The results have importance for understanding issues in conventional climate data processing and for development of improved methods of homogenization in order to improve analysis of climate extremes based on daily data.
A dynamical system connected with inhomogeneous 6-vertex model
Korepanov, I G
1994-01-01
A completely integrable dynamical system in discrete time is studied by means of algebraic geometry. The system is associated with factorization of a linear operator acting in a direct sum of three linear spaces into a product of three operators, each acting nontrivially only in a direct sum of two spaces, and the following reversing of the order of factors. There exists a reduction of the system interpreted as a classical field theory in 2+1-dimensional space-time, the integrals of motion coinciding, in essence, with the statistical sum of an inhomogeneous 6-vertex free-fermion model on the 2-dimensional Kagomé lattice (here the statistical sum is a function of two parameters). Thus, a connection with the "local", or "generalized", quantum Yang-Baxter equation is revealed.
Damping of Slow Magnetoacoustic Waves in an Inhomogeneous Coronal Plasma
Indian Academy of Sciences (India)
Nagendra Kumar; Pradeep Kumar; Shiv Singh; Anil Kumar
2008-03-01
We study the propagation and dissipation of slow magnetoacoustic waves in an inhomogeneous viscous coronal loop plasma permeated by uniform magnetic field. Only viscosity and thermal conductivity are taken into account as dissipative processes in the coronal loop. The damping length of slow-mode waves exhibit varying behaviour depending upon the physical parameters of the loop in an active region AR8270 observed by TRACE. The wave energy flux associated with slow magnetoacoustic waves turns out to be of the order of 106 erg cm-2 s-1 which is high enough to replace the energy lost through optically thin coronal emission and the thermal conduction belowto the transition region. It is also found that only those slow-mode waves which have periods more than 240 s provide the required heating rate to balance the energy losses in the solar corona. Our calculated wave periods for slow-mode waves nearly match with the oscillation periods of loop observed by TRACE.
Photoacoustic monitoring of inhomogeneous curing processes in polystyrene emulsions
Energy Technology Data Exchange (ETDEWEB)
Vargas-Luna, M.; Gutierrez-Juarez, G.; Rodriguez-Vizcaino, J.M.; Varela-Nsjera, J.B.; Rodriguez-Palencia, J.M.; Bernal-Alvarado, J.; Sosa, M. [Instituto de Fisica, Universidad de Guanajuato, Leon, Guanajuato (Mexico); Alvarado-Gil, J.J. [Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Merida, Antigua Carretera a Progreso, Merida, Yucatan (Mexico)
2002-07-07
The time evolution of the inhomogeneous curing process of polystyrene emulsions is studied using a variant of the conventional photoacoustic (PA) technique. The thermal effusivity, as a function of time, is determined in order to monitor the sintering process of a styrene emulsion in different steps of the manufacturing procedure. PA measurements of thermal effusivity show a sigmoidal growth as a function of time during the curing process. The parameterization of these curves permits the determination of the characteristic curing time and velocity of the process. A decreasing of the curing time and an increasing curing velocity for the final steps of the manufacturing process are observed. The feasibility of our approach and its potentiality for the characterization of other curing process are discussed. (author)
Laser photon merging in an electromagnetic field inhomogeneity
Gies, Holger; Shaisultanov, Rashid
2014-01-01
We study the effect of laser photon merging, or equivalently high harmonic generation, in the quantum vacuum subject to inhomogeneous electromagnetic fields. Such a process is facilitated by the effective nonlinear couplings arising from charged particle-antiparticle fluctuations in the quantum vacuum subject to strong electromagnetic fields. We derive explicit results for general kinematic and polarization configurations involving optical photons. Concentrating on merged photons in reflected channels which are preferable in experiments for reasons of noise suppression, we demonstrate that photon merging is typically dominated by the competing nonlinear process of quantum reflection, though appropriate polarization and signal filtering could specifically search for the merging process. As a byproduct, we devise a novel systematic expansion of the photon polarization tensor in plane wave fields.
Wave scattering in a multiscale random inhomogeneous medium
Tinin, Mikhail V.
2004-04-01
In this paper, using the Fock method of the fifth parameter and weighted Fourier-transform with respect to the coordinates of the source and observer, an integral representation is obtained for the wave field in a randomly inhomogeneous medium without invoking the assumption about small-angle propagation. Random trajectory variations to a first approximation are taken into account in calculating the partial wave phase (the expression under the integral sign). The expressions for the field in a medium with different-scale irregularities and for the scintillation index, obtained using this integral representation, are compared with known results. The good agreement with results from the theory of single scattering in a medium with background irregularities, and with investigations of the scintillation index made in terms of Rytov's method and path integrals, indicates that it is possible to use the approach developed in this study to describe the effects of simultaneous influence of different-scale irregularities.
AN ADAPTIVE INVERSE ITERATION FEM FOR THE INHOMOGENEOUS DIELECTRIC WAVEGUIDES
Institute of Scientific and Technical Information of China (English)
Jianhua Yuan
2007-01-01
We introduce an adaptive finite element method for computing electromagnetic guided waves in a closed, inhomogeneous, pillared three-dimensional waveguide at a given frequency based on the inverse iteration method. The problem is formulated as a generalized eigenvalue problems. By modifying the exact inverse iteration algorithm for the eigenvalue problem, we design a new adaptive inverse iteration finite element algorithm. Adaptive finite element methods based on a posteriori error estimate are known to be successful in resolving singularities of eigenfunctions which deteriorate the finite element convergence.We construct a posteriori error estimator for the electromagnetic guided waves problem.Numerical results are reported to illustrate the quasi-optimal performance of our adaptive inverse iteration finite element method.
A Hybrid Method with Deviational Particles for Spatial Inhomogeneous Plasma
Yan, Bokai
2015-01-01
In this work we propose a Hybrid method with Deviational Particles (HDP) for a plasma modeled by the inhomogeneous Vlasov-Poisson-Landau system. We split the distribution into a Maxwellian part evolved by a grid based fluid solver and a deviation part simulated by numerical particles. These particles, named deviational particles, could be both positive and negative. We combine the Monte Carlo method proposed in \\cite{YC15}, a Particle in Cell method and a Macro-Micro decomposition method \\cite{BLM08} to design an efficient hybrid method. Furthermore, coarse particles are employed to accelerate the simulation. A particle resampling technique on both deviational particles and coarse particles is also investigated and improved. The efficiency is significantly improved compared to a PIC-MCC method, especially near the fluid regime.
High-order harmonic generation from inhomogeneous fields
Ciappina, M F; Quidant, R; Lewenstein, M
2011-01-01
We present theoretical studies of high-order harmonic generation (HHG) produced by non-homogeneous fields as resulting from the illumination of plasmonic nanostructures with a short laser pulse. We show that the inhomogeneity of the local fields plays an important role in the HHG process and lead to the generation of even harmonics and a significantly increased cutoff, more pronounced for the longer wavelengths cases studied. In order to understand and characterize the new HHG features we employ two different approaches: the numerical solution of the time dependent Schr\\"odinger equation (TDSE) and the semiclassical approach known as Strong Field Approximation (SFA). Both approaches predict comparable results and show the new features, but using the semiclassical arguments behind the SFA, we are able to fully understand the reasons of the cutoff extension.
Diffuse spreading of inhomogeneities in the ionospheric dusty plasma
Energy Technology Data Exchange (ETDEWEB)
Shalimov, S. L., E-mail: pmsk7@mail.ru [Russian Academy of Sciences, Schmidt Institute of Physics of the Earth (Russian Federation); Kozlovsky, A. [Sodankylä Geophysical Observatory (Finland)
2015-08-15
According to results of sounding of the lower ionosphere at altitudes of about 100 km, the duration of radio reflections from sufficiently dense ionized meteor trails, which characterizes their lifetime, can reach a few tens of seconds to several tens of minutes. This is much longer than the characteristic spreading time (on the order of fractions of a second to several seconds) typical in meteor radar measurements. The presence of dust in the lower ionosphere is shown to affect the ambipolar diffusion coefficient, which determines the spreading of plasma inhomogeneities. It is found that the diffusion coefficient depends substantially on the charge and size of dust grains, which allows one to explain the results of ionospheric sounding.
Spatial structure of a collisionally inhomogeneous Bose-Einstein condensate
Energy Technology Data Exchange (ETDEWEB)
Li, Fei, E-mail: wiself@gmail.com [Hunan First Normal University, Department of Education Science (China); Zhang, Dongxia; Rong, Shiguang; Xu, Ying [Hunan University of Science and Technology, Department of Physics (China)
2013-11-15
The spatial structure of a collisionally inhomogeneous Bose-Einstein condensate (BEC) in an optical lattice is studied. A spatially dependent current with an explicit analytic expression is found in the case with a spatially dependent BEC phase. The oscillating amplitude of the current can be adjusted by a Feshbach resonance, and the intensity of the current depends heavily on the initial and boundary conditions. Increasing the oscillating amplitude of the current can force the system to pass from a single-periodic spatial structure into a very complex state. But in the case with a constant phase, the spatially dependent current disappears and the Melnikov chaotic criterion is obtained via a perturbative analysis in the presence of a weak optical lattice potential. Numerical simulations show that a strong optical lattice potential can lead BEC atoms to a state with a chaotic spatial distribution via a quasiperiodic route.
A note on generalized hydrodynamics: inhomogeneous fields and other concepts
Doyon, Benjamin
2016-01-01
Generalized hydrodynamics (GHD) was proposed recently as a formulation of hydrodynamics for integrable systems, taking into account infinitely-many conservation laws. In this note we further develop the theory in various directions. By extending GHD to all commuting flows of the integrable model, we provide a full description of how to take into account weakly varying force fields, temperature fields and other inhomogeneous external fields within GHD. We expect this can be used, for instance, to characterize the non-equilibrium dynamics of one-dimensional Bose gases in trap potentials. We also show that the GGE equations of state, and thus GHD, emerge uniformly in free particle models under the condition that the space-time variation scale of hydrodynamic observables grows unboundedly with time. We further show how the equations of state at the core of GHD follow from the continuity relation for entropy, and we show how to recover Euler-like equations and discuss possible viscosity terms.
Sensitivity of resistive and Hall measurements to local inhomogeneities
Koon, Daniel W.; Wang, Fei; Hjorth Petersen, Dirch; Hansen, Ole
2013-10-01
We derive exact, analytic expressions for the sensitivity of resistive and Hall measurements to local inhomogeneities in a specimen's material properties in the combined linear limit of a weak perturbation over an infinitesimal area in a small magnetic field. We apply these expressions both to four-point probe measurements on an infinite plane and to symmetric, circular van der Pauw discs, obtaining functions consistent with published results. These new expressions speed up calculation of the sensitivity for a specimen of arbitrary shape to little more than the solution of two Laplace equation boundary-value problems of the order of N3 calculations, rather than N2 problems of total order N5, and in a few cases produces an analytic expression for the sensitivity. These functions provide an intuitive, visual explanation of how, for example, measurements can predict the wrong carrier type in n-type ZnO.
Edge Vortex Flow Due to Inhomogeneous Ion Concentration
Sugioka, Hideyuki
2017-04-01
The ion distribution of an open parallel electrode system is not known even though it is often used to measure the electrical characteristics of an electrolyte. Thus, for an open electrode system, we perform a non-steady direct multiphysics simulation based on the coupled Poisson-Nernst-Planck and Stokes equations and find that inhomogeneous ion concentrations at edges cause vortex flows and suppress the anomalous increase in the ion concentration near the electrodes. A surprising aspect of our findings is that the large vortex flows at the edges approximately maintain the ion-conserving condition, and thus the ion distribution of an open electrode system can be approximated by the solution of a closed electrode system that considers the ion-conserving condition rather than the Gouy-Chapman solution, which neglects the ion-conserving condition. We believe that our findings make a significant contribution to the understanding of surface science.
Oscillator model for dissipative QED in an inhomogeneous dielectric
van Wonderen, A J
2004-01-01
The Ullersma model for the damped harmonic oscillator is coupled to the quantised electromagnetic field. All material parameters and interaction strengths are allowed to depend on position. The ensuing Hamiltonian is expressed in terms of canonical fields, and diagonalised by performing a normal-mode expansion. The commutation relations of the diagonalising operators are in agreement with the canonical commutation relations. For the proof we replace all sums of normal modes by complex integrals with the help of the residue theorem. The same technique helps us to explicitly calculate the quantum evolution of all canonical and electromagnetic fields. We identify the dielectric constant and the Green function of the wave equation for the electric field. Both functions are meromorphic in the complex frequency plane. The solution of the extended Ullersma model is in keeping with well-known phenomenological rules for setting up quantum electrodynamics in an absorptive and spatially inhomogeneous dielectric. To esta...
Inhomogeneous spatial point processes with hidden second-order stationarity
DEFF Research Database (Denmark)
Hahn, Ute; Jensen, Eva B. Vedel
correlation function g(u, v) is a function of u −˘ v, where −˘ is a generalized subtraction operator. For the reweighted second-order stationary processes, the subtraction operator is simply u −˘ v = u − v. The processes in the extended class are called hidden second-order stationary because, in many cases......Modelling of inhomogeneous spatial point patterns is a challenging research area with numerous applications in diverse areas of science. In recent years, the focus has mainly been on the class of reweighted second-order stationary point processes that is characterized by the mathematically...... attractive property of a translation invariant pair correlation function. Motivated by examples where this model class is not adequate, we extend the class of reweighted second-order stationary processes. The extended class consists of hidden second-order stationary point processes for which the pair...
Inhomogeneous Quantum Mixmaster: from Classical toward Quantum Mechanics
Montani, R B G
2006-01-01
Starting from the Hamiltonian formulation for the inhomogeneous Mixmaster dynam- ics, we approach its quantum features through the link of the quasi-classical limit. We fix the proper operator-ordering which ensures that the WKB continuity equation overlaps the Liouville theorem as restricted to the configuration space. We describe the full quantum dynamics of the model in some details, providing a characterization of the (discrete) spectrum with analytic expressions for the limit of high occupation number. One of the main achievements of our analysis relies on the description of the ground state morphology, showing how it is characterized by a non-vanishing zero-point energy associated to the Universe anisotropy degrees of freedom
Density functional theory for inhomogeneous associating chain fluids.
Bryk, P; Sokołowski, S; Pizio, O
2006-07-14
We propose a nonlocal density functional theory for associating chain molecules. The chains are modeled as tangent spheres, which interact via Lennard-Jones (12,6) attractive interactions. A selected segment contains additional, short-ranged, highly directional interaction sites. The theory incorporates an accurate treatment of the chain molecules via the intramolecular potential formalism and should accurately describe systems with strongly varying external fields, e.g., attractive walls. Within our approach we investigate the structure of the liquid-vapor interface and capillary condensation of a simple model of associating chains with only one associating site placed on the first segment. In general, the properties of inhomogeneous associating chains depend on the association energy. Similar to the bulk systems we find the behavior of associating chains of a given length to be in between that for the nonassociating chains of the same length and that for the nonassociating chains twice as large.
Non-Hermitian spin chains with inhomogeneous coupling
Energy Technology Data Exchange (ETDEWEB)
Bytsko, Andrei G. [Rossijskaya Akademiya Nauk, St. Petersburg (Russian Federation). Inst. Matematiki; Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Gruppe Theorie
2009-11-15
An open U{sub q}(sl{sub 2})-invariant spin chain of spin S and length N with inhomogeneous coupling is investigated as an example of a non-Hermitian (quasi-Hermitian) model. For several particular cases of such a chain, the ranges of the deformation parameter {gamma} are determined for which the spectrum of the model is real. For a certain range of {gamma}, a universal metric operator is constructed and thus the quasi-Hermiticity of the model is established. The constructed metric operator is non-dynamical, its structure is determined only by the symmetry of the model. The results apply, in particular, to all known homogeneous U{sub q}(sl{sub 2})-invariant integrable spin chains with nearest-neighbour interaction. In addition, the most general form of a metric operator for a quasi-Hermitian operator in finite dimensional space is discussed. (orig.)
Consistent regularization and renormalization in models with inhomogeneous phases
Adhikari, Prabal
2016-01-01
In many models in condensed matter physics and high-energy physics, one finds inhomogeneous phases at high density and low temperature. These phases are characterized by a spatially dependent condensate or order parameter. A proper calculation requires that one takes the vacuum fluctuations of the model into account. These fluctuations are ultraviolet divergent and must be regularized. We discuss different consistent ways of regularizing and renormalizing quantum fluctuations, focusing on a symmetric energy cutoff scheme and dimensional regularization. We apply these techniques calculating the vacuum energy in the NJL model in 1+1 dimensions in the large-$N_c$ limit and the 3+1 dimensional quark-meson model in the mean-field approximation both for a one-dimensional chiral-density wave.
Consistent regularization and renormalization in models with inhomogeneous phases
Adhikari, Prabal; Andersen, Jens O.
2017-02-01
In many models in condensed matter and high-energy physics, one finds inhomogeneous phases at high density and low temperature. These phases are characterized by a spatially dependent condensate or order parameter. A proper calculation requires that one takes the vacuum fluctuations of the model into account. These fluctuations are ultraviolet divergent and must be regularized. We discuss different ways of consistently regularizing and renormalizing quantum fluctuations, focusing on momentum cutoff, symmetric energy cutoff, and dimensional regularization. We apply these techniques calculating the vacuum energy in the Nambu-Jona-Lasinio model in 1 +1 dimensions in the large-Nc limit and in the 3 +1 dimensional quark-meson model in the mean-field approximation both for a one-dimensional chiral-density wave.
Theory of Radio Propagation in Inhomogeneous Media (The Eikonal Method)
Bianchi, S; Settimi, A
2010-01-01
The Istituto Nazionale di Geofisica e Vulcanologia has been involved since its foundation in the forecast of the conditions in which a radio link that makes use of propagation by means of ionospheric wave takes place. In the last times it gained interest also the precise forecast of the trajectory covered by a radio wave propagating into the atmosphere, specifically into the ionosphere, which can be considered, at first approximation, as an inhomogeneous medium, defined by a refraction index slowly varying in time. This work describes the theoretical bases to study a trajectory; they substantially make use of the methods of the geometrical optics. Such theoretical bases find applications in numerical methods to calculate the trajectories, as quoted in references [Bianchi, 2009].
Quantifying classical entanglement using polarimetry: Spatially-inhomogeneously polarized beams
Samlan, C T
2015-01-01
Generation of spatially inhomogeneously polarized (SIP) beams due to polarization spatial mode nonseparability is demonstrated using a polarization Sagnac interferometer. Counter propagating horizontal (H) and vertical (V) polarized Laguerre Gaussian beams of opposite topological charges(LG01)corresponding to the two binary degrees of freedom (DoF) are coherently superposed in the interferometer. Quantum inspired entanglement witness and quantification such as Bell state measurement, violation of CHSH form of Bells inequality and concurrence measurements are experimentally measured to establish nonseparability between the two DoF. As the SIP beams are equivalent to bipartite pure states, point wise Stokes polarimetry measurements are used to calculate the reduced coherency matrix corresponding to polarization DoF. Using these we calculate the linear entropy and maximized Bells measure to quantify the degree of entanglement of the SIP beams.
Superconductivity in an Inhomogeneous Bundle of Metallic and Semiconducting Nanotubes
Directory of Open Access Journals (Sweden)
Ilya Grigorenko
2013-01-01
Full Text Available Using Bogoliubov-de Gennes formalism for inhomogeneous systems, we have studied superconducting properties of a bundle of packed carbon nanotubes, making a triangular lattice in the bundle's transverse cross-section. The bundle consists of a mixture of metallic and doped semiconducting nanotubes, which have different critical transition temperatures. We investigate how a spatially averaged superconducting order parameter and the critical transition temperature depend on the fraction of the doped semiconducting carbon nanotubes in the bundle. Our simulations suggest that the superconductivity in the bundle will be suppressed when the fraction of the doped semiconducting carbon nanotubes will be less than 0.5, which is the percolation threshold for a two-dimensional triangular lattice.
Cosmological background torsion inhomogeneities and Lorentz violation in QED
Garcia de Andrade, L C
2003-01-01
A non-minimal photon-torsion axial coupling in the quantum electrodynamics (QED) framework is considered. The geometrical optics in Riemann-Cartan spacetime is considering and a plane wave expansion of the electromagnetic vector potential is considered leading to a set of the equations for the ray congruence. Since we are interested mainly on the torsion effects in this first report we just consider the Riemann-flat case composed of the Minkowskian spacetime with torsion. It is also shown that in torsionic de Sitter background the vacuum polarisation does alter the propagation of individual photons, an effect which is absent in Riemannian spaces. It is shown that the cosmological torsion background inhomogeneities induce Lorentz violation and massive photon modes in this QED.
Traveltime approximations for transversely isotropic media with an inhomogeneous background
Alkhalifah, Tariq
2011-05-01
A transversely isotropic (TI) model with a tilted symmetry axis is regarded as one of the most effective approximations to the Earth subsurface, especially for imaging purposes. However, we commonly utilize this model by setting the axis of symmetry normal to the reflector. This assumption may be accurate in many places, but deviations from this assumption will cause errors in the wavefield description. Using perturbation theory and Taylor\\'s series, I expand the solutions of the eikonal equation for 2D TI media with respect to the independent parameter θ, the angle the tilt of the axis of symmetry makes with the vertical, in a generally inhomogeneous TI background with a vertical axis of symmetry. I do an additional expansion in terms of the independent (anellipticity) parameter in a generally inhomogeneous elliptically anisotropic background medium. These new TI traveltime solutions are given by expansions in and θ with coefficients extracted from solving linear first-order partial differential equations. Pade approximations are used to enhance the accuracy of the representation by predicting the behavior of the higher-order terms of the expansion. A simplification of the expansion for homogenous media provides nonhyperbolic moveout descriptions of the traveltime for TI models that are more accurate than other recently derived approximations. In addition, for 3D media, I develop traveltime approximations using Taylor\\'s series type of expansions in the azimuth of the axis of symmetry. The coefficients of all these expansions can also provide us with the medium sensitivity gradients (Jacobian) for nonlinear tomographic-based inversion for the tilt in the symmetry axis. © 2011 Society of Exploration Geophysicists.
Quantum-orbit analysis of above threshold ionization by intense spatially inhomogeneous field
Shaaran, T; Lewenstein, M
2013-01-01
We perform a detailed analysis of above threshold ionization (ATI) in atoms within the strong field approximation (SFA) by considering spatially inhomogeneous monochromatic laser fields. The locally enhanced field induced by resonance plasmons is an example for such inhomogeneous fields. We investigate how the individual pairs of quantum orbits contribute to the photoelectron spectra and the angular electron momentum distributions. We demonstrate that the quantum orbits have a very different behavior in the spatially inhomogeneous field when compared to the homogeneous field. In the case of inhomogeneous fields, the ionization and rescattering times differ between neighboring cycles, despite the field being monochromatic. Indeed, the contributions from one cycle may lead to a lower cutoff, while another may develop a higher cutoff. Within our model, we show that the ATI cutoff extends far beyond the semiclassical cutoff, as a function of inhomogeneity strength. Furthermore, the angular momentum distributions ...
The Effect of Habitat Inhomogeneities and Fragmentation on Population Density and Time to Extinction
Energy Technology Data Exchange (ETDEWEB)
Kostova, T; Carlsen, T
2003-12-22
We present a study, based on simulations with SERDYCA, a spatially-explicit individual based model of rodent dynamics, on the connection between population persistence and the presence of inhomogeneities in the habitat. We are specifically interested on the effect that inhomogeneities that do not fragment the environment, have on population persistence. Our results suggest that a certain percentage of inhomogeneities can increase the average time to extinction of the population. Inhomogeneities decrease the population density and can increase the ratio of juveniles in the population thus providing a better chance for the population to restore itself after a severe period with critically low population density. We call this the ''inhomogeneity localization effect''.